DE102023120631A1 - Process for joining, casting or coating substrates and curable mass therefor - Google Patents

Abstract

The invention relates to a method for joining, casting or coating substrates using a curable mass, a curable mass and a use of the curable mass for joining, casting or coating substrates. The curable mass comprises a first curable component (A) and a second curable component (B), a first photoinitiator (C) for the first curable component (A), which can be activated when irradiated with actinic radiation of a first wavelength λ ₁ , a second photoinitiator (D) for the second curable component (B), which can be activated when irradiated with actinic radiation of a second wavelength λ ₂ , the second wavelength λ ₂ being different from the first wavelength λ ₁ , and at least one radical-scavenging inhibitor (E) for scavenging radicals generated when the curable mass is irradiated with actinic radiation of the first wavelength λ ₁ . In the process, the curable mass is dosed onto a first substrate and activated by irradiation with actinic radiation of the first wavelength λ _1. The activated curable mass is then fixed by irradiation with actinic radiation of the second wavelength λ ₂ .
Furthermore, a hardenable mass and a use of a hardenable mass are specified.

Description

FIELD OF THE INVENTION

The invention relates to a method for joining, casting or coating substrates using a curable mass which can be activated by irradiation with actinic radiation, a curable mass and the use of such a curable mass.

TECHNICAL BACKGROUND

The EP 3 894 458 B1 discloses cationically polymerizable masses with two photoinitiators that can release an acid at different wavelengths. The masses can be activated by irradiation with a first wavelength and fixed by irradiation with a second wavelength. However, the achievable light fixation strengths are low. In one embodiment, the cationically polymerizable mass contains one or more acrylates, which, however, already lead to solidification of the mass when irradiated with the first wavelength, so that the mass can no longer be dosed without restriction.

In the scientific article von Kostanski et al.: “Cationic polymerisation using mixed cationic photoinitiator systems” (Designed Monomers and Polymers 2007, Vol. 10, No. 4, pages 327-345, doi: 10.1163/156855507781505110 ) describes mixtures of sulfonium or iodonium salts with ferrocenium salts. The ferrocenium salts serve as sensitizers for the photoinitiator based on the sulfonium or iodonium salt. A high-pressure mercury vapor lamp is used for irradiation. However, the various photoinitiators of the mixtures are not activated sequentially at specific wavelengths.

The US 4 849 320 A describes a photolithographic process using a mass that includes two photoinitiators and a mixture of radically and cationically polymerizable components. First, the mass is irradiated with radiation of a wavelength that is suitable for activating the radical photoinitiator in order to initially solidify the mass. The solidified mass is then irradiated with actinic radiation of a wavelength that is suitable for activating the cationic photoinitiator in order to create a structure in defined areas. In a subsequent washing process, the mass outside these areas, which was only partially hardened radically in the first step, is removed. The photoinitiators are selected so that their absorption ranges do not overlap and can be specifically activated separately by different wavelengths. Activation of the radical photoinitiator in the first exposure step immediately leads to solidification of the mass.

The US 5 707 780 A also describes masses that comprise mixtures of radically and cationically polymerizable components that can be activated simultaneously by irradiation with an argon laser at different wavelengths. The masses are characterized by a high initial strength after curing, which can be achieved by adjusting the ratio of the extinction coefficients of the radical and cationic photoinitiators to one another. The described masses can be used in additive manufacturing. Sequential exposure is not disclosed. After exposure, the mass solidifies immediately.

The US 5 472 991 A discloses a process for the two-stage hardening of a dental mass based on acrylates. The dental masses used contain at least two different photoinitiators that can be sequentially excited by light of different wavelengths. After the first exposure to a wavelength of 450 nm or greater, the dental mass is already solidified to such an extent that it can be brought into its final shape by mechanical modeling. Complete hardening is achieved by irradiation at a second wavelength that is shorter than the first wavelength.

In the JP 2017 149 813 A describes radiation-curable acrylate compositions which contain at least one (meth)acrylate and two photoinitiators for radical polymerization. Furthermore, the use of styrene-based compounds for targeted control of the molecular weight is disclosed. Despite the use of two initiators, separate activation and fixation is not provided.

The US 11 518 087 B2 describes a process for additive manufacturing in which curable masses with at least two different types of monomers and at least two photoinitiators that have different excitation wavelengths are used. Selective exposure with a first wavelength already leads to at least partial hardening of the mass. The mechanical behavior of the systems described can be adjusted by specifically controlling the excitation wavelengths. However, the masses do not have an open time and are not suitable for joining processes.

The WO 2001 092 362 A1 describes photoactivatable coatings based on polyisocyanates, thiols and a photolatent base. After irradiation or exposure, these can be cured within minutes to form a polythiourethane network.

In the EP 3 789 416 A1 describes radiation-curable compositions which comprise at least one polythiol, one polyisocyanate, one ethylenically unsaturated compound and one photolatent base. Additives such as a photoinitiator for radical polymerization can also be included. Curing of the compositions by exposure to different wavelengths is not provided for. A process using the composition provides for immediate solidification of the composition upon exposure for the layer-by-layer construction of additively manufactured structures.

SUMMARY OF THE INVENTION

The invention is based on the object of avoiding the above-described disadvantages of the methods and compositions known from the prior art and of providing curable materials which can advantageously be activated in a first irradiation step and fixed in a further irradiation step. In particular, the materials should enable a method with which the strength build-up can be controlled in a targeted manner by means of light fixation and at the same time reliable curing in shadow zones is ensured, in particular in the case of substrates which cannot be penetrated by radiation.

According to the invention, this object is achieved by a method according to claim 1 using a curable mass, by a curable mass according to claim 7 and the use of such a mass according to claim 10.

Further embodiments of the invention are specified in the subclaims, which can optionally be combined with one another.

1. a) Bereitstellen der härtbaren Masse, wobei die härtbare Masse folgende Komponenten umfasst:
   1. (A) eine erste härtbare Komponente ausgewählt aus der Gruppe bestehend aus kationisch polymerisierbaren Verbindungen, additionsvernetzbaren Verbindungen, durch Feuchtigkeit vernetzbaren Verbindungen und Kombinationen davon,
   2. (B) eine zweite härtbare Komponente bestehend aus mindestens einer radikalisch strahlungshärtbaren Verbindung,
   3. (C) einen ersten Photoinitiator für die erste härtbare Komponente (A), der bei Bestrahlung mit aktinischer Strahlung einer ersten Wellenlänge λ₁ aktivierbar ist, wobei der erste Photoinitiator eine photolatente Säure oder eine photolatente Base ist,
   4. (D) einen zweiten Photoinitiator für die zweite härtbare Komponente (B), der bei Bestrahlung mit aktinischer Strahlung einer zweiten Wellenlänge λ₂ aktivierbar ist, wobei die zweite Wellenlänge λ₂ von der ersten Wellenlänge λ₁ verschieden ist, und wobei der zweite Photoinitiator ein Radikalbildner ist, und
   5. (E) mindestens einen radikalfangenden Inhibitor zum Abfangen von bei Bestrahlung der härtbaren Masse mit aktinischer Strahlung der ersten Wellenlänge λ₁ erzeugten Radikalen;
2. b) Dosieren der härtbaren Masse auf ein erstes Substrat und Aktivieren der härtbaren Masse durch Bestrahlen mit aktinischer Strahlung der ersten Wellenlänge λ₁;
3. c) wahlweise Zuführen eines zweiten Substrats zur aktivierten härtbaren Masse auf dem ersten Substrat unter Bildung eines Substratverbunds; und
4. d) Fixieren der aktivierten härtbaren Masse durch Bestrahlen mit aktinischer Strahlung der zweiten Wellenlänge λ₂.

The method according to the invention for joining, casting or coating substrates using a curable mass comprises the following steps:

1. a) Providing the hardenable mass, wherein the hardenable mass comprises the following components:
   1. (A) a first curable component selected from the group consisting of cationically polymerizable compounds, addition-curable compounds, moisture-curable compounds, and combinations thereof,
   2. (B) a second curable component consisting of at least one radically radiation-curable compound,
   3. (C) a first photoinitiator for the first curable component (A) which is activatable upon irradiation with actinic radiation of a first wavelength λ ₁ , wherein the first photoinitiator is a photolatent acid or a photolatent base,
   4. (D) a second photoinitiator for the second curable component (B) which is activatable upon irradiation with actinic radiation of a second wavelength λ ₂ , wherein the second wavelength λ ₂ is different from the first wavelength λ ₁ , and wherein the second photoinitiator is a radical former, and
   5. (E) at least one radical-scavenging inhibitor for scavenging radicals generated upon irradiation of the curable composition with actinic radiation of the first wavelength λ ₁ ;
2. b) dosing the curable mass onto a first substrate and activating the curable mass by irradiation with actinic radiation of the first wavelength λ ₁ ;
3. c) optionally adding a second substrate to the activated curable mass on the first substrate to form a substrate composite; and
4. d) Fixing the activated curable mass by irradiation with actinic radiation of the second wavelength λ ₂ .

The method according to the invention is characterized by a precisely controllable process for activating and hardening the mass by means of irradiation at different wavelengths, which on the one hand by (pre-)activating the first curable component (A), reliable curing is also possible in shadow areas - while at the same time allowing the activated mass to be processed during an open time. On the other hand, the use of the second curable component (B) based on at least one radically radiation-curable compound creates the possibility of fast and reliable fixing of the curable mass by irradiation at a second wavelength, with the irradiation taking place in a separate step.

Here and in the following, "activation" of the mass means that the activated mass hardens after a specified period of time without any further energy input, even in shadow zones where the mass cannot be irradiated with actinic radiation of the second wavelength λ _2. The specified period of time is in particular a maximum of 24 hours. Within this period of time, the mass exceeds the gel point and changes to the solid state. The final hardening of the mass does not have to be completed at this point, however.

Final curing refers to a state at which the maximum strength build-up of the mass is complete. This means that the mechanical properties of the mass essentially no longer change. In particular, there is no further increase in the elastic modulus of the mass. Final curing is completed in particular within a maximum of seven days, preferably within three days, particularly preferably within one day, i.e. within 24 hours.

In the sense of the method according to the invention, “fixation” or “fixing” refers to the build-up of a strength of the mass beyond which no more flow of the mass can take place, or the level of strength beyond which joined parts, in particular substrates, can be handled in subsequent processes without causing destruction of the adhesive bond, in particular the substrate bond.

The use of the radical-scavenging inhibitor (E) ensures that radicals generated in the curable mass during irradiation with actinic radiation of the first wavelength λ ₁ , i.e. during activation of the mass in step b), do not lead to polymerization of the second curable component (B), which is undesirable at this time. This prevents further handling of the activated mass during the open time from being made difficult or impossible, and thus provides a particularly flexible process for joining, casting or coating. This is also possible in particular without having to rely on formulations of the curable mass in separate packaging units.

The multi-stage process is further made possible by a targeted activation of the first photoinitiator (C) and the second photoinitiator (D) at different wavelengths. In other words, the second wavelength λ ₂ is different from the first wavelength λ ₁ .

Preferably, the second wavelength λ ₂ is shorter than the first wavelength λ ₁ .

The difference between the wavelength λ ₁ used for irradiating and activating the first photoinitiator (C) and the wavelength λ ₂ used for irradiating and activating the second photoinitiator (D) is in particular at least 20 nm, preferably at least 30 nm.

The same applies to the emission maxima of the radiation sources used for irradiation. The difference between the wavelengths λ ₁ and λ ₂ is preferably chosen so that there is no overlap between the emission spectra of the radiation sources.

Monochromatic laser light can be used to irradiate the mass. However, radiation sources that have a singular emission maximum at the respective predetermined wavelength λ ₁ or λ ₂ are preferably used.

The radiation source is preferably an LED curing lamp, as is commercially available.

The first wavelength λ ₁ lies in particular in a range from 380 to 750 nm, while the second wavelength λ ₂ lies in particular in a range from 200 to 400 nm.

After the first irradiation with the first wavelength λ ₁ in step b), the mass remains liquid until the end of the open time, as described below. At the same time, the irradiation with the first wavelength λ ₁ , i.e. the activation of the first photoinitiator (C), ensures that a polymerization reaction is initiated in the first curable component (A), which also ensures reliable curing in shadow areas. Final curing is possible even if the shadow zones may no longer be accessible during subsequent irradiation.

Accordingly, step d) can be carried out in one embodiment within a processing time which preferably corresponds at most to the open time of the curable mass after activation of the curable mass by irradiation with actinic radiation of the first wavelength λ _1. This enables a particularly flexible process control without having to accept disadvantages with regard to the strength build-up during the final curing.

The molar ratio of inhibitor (E) to first photoinitiator (C) in the curable mass is in particular in a range from 0.4:1 to less than 20:1, preferably in a range from 0.4:1 to less than 10:1 or 1:1 to 10:1, particularly preferably in a range from 1:1 to 5:1.

A molar fraction of the inhibitor (E) in relation to the first photoinitiator (C) that is too low can lead to masses that become at least partially solid after the first irradiation, i.e. the irradiation of the mass with actinic radiation of the first wavelength λ ₁ , and are no longer joinable, in particular due to a polymerization of the second curable component (B) that is undesirable at that time.

If, however, the inhibitor (E) is used in too high a proportion or in too large an excess of the amount of substance, this can lead to the curable mass not being able to build up sufficient fixing strength when irradiated with actinic radiation of the second wavelength λ ₂ , since the radicals generated by the second photoinitiator (D) are intercepted to too great an extent by the inhibitor (E) and are thus not available for the polymerization of the second curable component (B).

In order to achieve a particularly high fixing strength after irradiation with actinic radiation of the second wavelength λ ₂ , the molar ratio of inhibitor (E) to second photoinitiator (D) in the curable composition can be 1:2 or less, preferably 1:5 or less, particularly preferably 1:10 or less.

In step b), the curable mass is dosed onto the first substrate and activated by irradiation with actinic radiation of the first wavelength λ _1. The order of dosing and activation in step b) depends only on the dosing and exposure device used in the respective process. Thus, the curable mass can first be dosed onto the first substrate and then activated by irradiation with actinic radiation of the first wavelength λ _1. When using a so-called flow apparatus, the activation of the curable mass can take place before dosing onto the first substrate. Suitable dosing devices for flow activation of the curable mass by irradiation are described in the DE 3 702 999 A1 and the DE 10 2007 017 842 A1 described.

Between steps b) and d), the second substrate can optionally be added to the activated hardenable mass on the first substrate as step c). In particular, the two substrates are then aligned with each other. In the process according to the invention, the substrates to be joined can thus be aligned precisely with each other within the open time. This is particularly important for joining processes for the manufacture of electro-optical components, for example camera modules. The activated mass is then fixed in place by the second irradiation step d) and thus converted into a dimensionally stable state.

Other particularly suitable substrates for bonding are displays, sensors, electronic components and housings.

The method according to the invention also makes it possible to achieve reliable curing or fixing of the activated mass at room temperature without additional heat input. However, this does not exclude the possibility that curing can be accelerated by heating the fixed mass.

• e) Erwärmen der fixierten härtbaren Masse auf dem ersten Substrat oder in dem Substratverbund.

In one variant, the method therefore further comprises the following step:

• e) heating the fixed curable mass on the first substrate or in the substrate composite.

In other words, the method according to the invention can optionally comprise an additional tempering step, which serves in particular for faster curing or for accelerated achievement of the final strength of the mass.

It may also be advantageous to heat the curable mass when providing it in step a) and/or to heat one or more of the substrates before dosing the curable mass in step b) and/or before joining in step c), which can also accelerate the final curing.

It is also possible for steps d) and e) to be carried out simultaneously, i.e. the activated curable mass is fixed by irradiation with actinic radiation of the second wavelength λ ₂ , while the curable mass is heated on the substrate or in the substrate composite.

The invention further relates to a curable mass which can be used in particular in the above-described method according to the invention for joining, casting or coating substrates.

The above-described statements regarding the process according to the invention apply accordingly to the curable composition according to the invention and vice versa.

1. (A) eine erste härtbare Komponente ausgewählt aus der Gruppe bestehend aus kationisch polymerisierbaren Verbindungen, additionsvernetzbaren Verbindungen, durch Feuchtigkeit vernetzbaren Verbindungen und Kombinationen davon,
2. (B) eine zweite härtbare Komponente bestehend aus mindestens einer radikalisch strahlungshärtbaren Verbindung,
3. (C) einen ersten Photoinitiator für die erste härtbare Komponente (A), der bei Bestrahlung mit aktinischer Strahlung einer ersten Wellenlänge λ₁ aktivierbar ist, wobei der erste Photoinitiator eine photolatente Säure oder eine photolatente Base ist,
4. (D) einen zweiten Photoinitiator für die zweite härtbare Komponente (B), der bei Bestrahlung mit aktinischer Strahlung einer zweiten Wellenlänge λ₂ aktivierbar ist, wobei die zweite Wellenlänge λ₂ von der ersten Wellenlänge λ₁ verschieden ist, und wobei der zweite Photoinitiator ein Radikalbildner ist, und
5. (E) mindestens einen radikalfangenden Inhibitor zum Abfangen von bei Bestrahlung der härtbaren Masse mit aktinischer Strahlung der ersten Wellenlänge λ₁ erzeugten Radikalen.

The curable composition according to the invention for joining, casting or coating substrates comprises the following components:

1. (A) a first curable component selected from the group consisting of cationically polymerizable compounds, addition-curable compounds, moisture-curable compounds, and combinations thereof,
2. (B) a second curable component consisting of at least one radically radiation-curable compound,
3. (C) a first photoinitiator for the first curable component (A) which is activatable upon irradiation with actinic radiation of a first wavelength λ ₁ , wherein the first photoinitiator is a photolatent acid or a photolatent base,
4. (D) a second photoinitiator for the second curable component (B) which is activatable upon irradiation with actinic radiation of a second wavelength λ ₂ , wherein the second wavelength λ ₂ is different from the first wavelength λ ₁ , and wherein the second photoinitiator is a radical former, and
5. (E) at least one radical-scavenging inhibitor for scavenging radicals generated upon irradiation of the curable composition with actinic radiation of the first wavelength λ ₁ .

Compared to the prior art, the compositions according to the invention are characterized in that they enable a high light-fixing strength and light-fixing speed, while at the same time they are suitable for a controlled curing process that can be controlled by irradiating the curable compositions in a multi-stage process.

The invention further relates to the use of the curable mass as described above for joining, casting or coating substrates.

DETAILED DESCRIPTION OF PREFERRED

EMBODIMENTS

The invention is described in detail and by way of example below using preferred embodiments, which, however, should not be understood in a limiting sense.

“One-component” or “one-component mass” means in the sense of the invention that the said components of the mass are present together in one packaging unit.

In the sense of the invention, “liquid” means that at 23 °C the loss modulus G'' determined by viscosity measurement is greater than the storage modulus G' of the mass in question.

The “open time” refers to the time after the first irradiation of the curable mass, i.e. after irradiation with actinic radiation of the first wavelength λ ₁ , during which the activated mass has not yet exceeded its gel point. During this time, the mass only changes its properties in terms of viscosity and adhesion insignificantly. It is possible to join a second substrate within the open time.

The open time is limited by the time at which a thread is pulled and/or at the latest by the time until a skin is formed, which can be determined by haptic measurement. Within the open time, the method according to the invention can be carried out reliably.

However, it is also possible that the activated masses remain at least partially joinable beyond the specified open time before they solidify to such an extent that no further flow or pressing onto another substrate is possible.

In order to enable a robust process, the feeding of a second substrate in step c) of the method according to the invention, if carried out, is preferred within the open time.

In addition to the composition of the curable mass, the open time can be influenced by the irradiated energy dose as well as by the temperature.

Where the indefinite article “a” or “an” is used, this also includes the plural form “one or more”, unless it is expressly excluded.

“At least difunctional” means that each molecule contains two or more units of the respective functional group.

Unless otherwise stated, all weight proportions listed below refer to the total weight of the mass.

In the following, the equivalents refer to 1 equivalent of the functional group and are given in relation to each other.

In a first embodiment, the curable composition for carrying out the process according to the invention contains, in addition to components (B) to (E), at least one cationically polymerizable compound (A1) as the first curable component (A). The first photoinitiator (C) of the curable composition of the first embodiment is preferably a photolatent acid (C1).

In a second embodiment, the curable composition for carrying out the process according to the invention contains, in addition to components (B) to (E), at least one addition-crosslinkable compound (A2) as the first curable component (A). The first photoinitiator (C) of the curable composition of the second embodiment is preferably a photolatent base (C2).

In a third embodiment, the curable composition for carrying out the process according to the invention contains, in addition to components (B) to (E), as the first curable component (A), at least one moisture-crosslinkable compound (A3). The first photoinitiator (C) of the curable composition of the third embodiment is preferably a photolatent acid (C1).

The individual components of the curable mass, which can be used in particular in the process according to the invention, are described in more detail below.

Component (A): First curable component

The curable composition comprises a first curable component (A) selected from the group consisting of cationically polymerizable compounds (A1), addition-crosslinkable compounds (A2), moisture-crosslinkable compounds (A3) and combinations thereof.

The components described below can therefore be used alone or in combination with each other as component (A).

The first curable component (A), through its respective components used in interaction with the first photoinitiator (C) matched to the first curable component (A), provides a curing mechanism which enables a time-delayed final curing of the curable mass even in shadow zones.

Suitable cationically polymerizable compounds (A1) preferably comprise one or more at least difunctional epoxy-containing compounds. At least “difunctional” means that the epoxy-containing compound contains at least two epoxy groups.

Component (A1) may comprise, for example, cycloaliphatic epoxides, aromatic and aliphatic glycidyl ethers, glycidyl esters or glycidyl amines and mixtures thereof.

Difunctional cycloaliphatic epoxy resins are known in the art and include compounds that carry both a cycloaliphatic group and at least two oxirane rings. Examples of representatives are 3-cyclohexenylmethyl-3-cyclohexylcarboxylate diepoxide, 3,4-epoxycyclohexylalkyl-3`,4`-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-6-methylcyclohexanecarboxylate, vinylcyclohexene dioxide, bis(3,4-epoxycyclohexylmethyl)adipate, dicyclopentadiene dioxide and 1,2-epoxy-6-(2,3-epoxypropoxy)hexahydro-4,7-methanindane and mixtures thereof.

Aromatic epoxy resins can also be used. Examples of aromatic epoxy resins are bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolak epoxy resins, cresol novolak epoxy resins, biphenyl epoxy resins, 4,4'-biphenyl epoxy resins, divinylbenzene dioxide, 2-glycidylphenyl glycidyl ether, naphthalenediol diglycidyl ether, glycidyl ether of tris(hydroxyphenyl)methane and glycidyl ether of tris(hydroxyphenyl)ethane and mixtures thereof. Furthermore, all fully or partially hydrogenated analogues of aromatic epoxy resins can also be used.

Isocyanurates and other heterocyclic compounds substituted with epoxy groups can also be used in the curable mass.

Examples include triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate.

In addition, polyfunctional epoxy resins of all the resin groups mentioned, toughly elasticized epoxy resins and mixtures of different epoxy resins can also be used in the composition according to the invention.

Also within the meaning of the invention is a combination of several epoxy-containing compounds, of which at least one is di- or higher functional.

In addition to the at least difunctional epoxy-containing compounds, monofunctional epoxides can also be used as reactive diluents.

Examples of commercially available epoxy-containing compounds are products sold under the trade names CELLOXIDE™ 2021P, CELLOXIDE™ 8000 by Daicel Corporation, Japan, as EPlKOTE™ RESIN 828 LVEL, EPlKOTE™ RESIN 166, EPlKOTE™ RESIN 169 by Momentive Specialty Chemicals B.V., the Netherlands, as Epilox™ resins of the product series A, T and AF by Leuna Harze, Germany, or as EPICLON™ 840, 840-S, 850, 850-S, EXA850CRP, 850-LC by DIC K.K., Japan, Omnilane 1005 and Omnilane 2005 by IGM Resins B.V., Syna Epoxy 21 and Syna Epoxy 06 by Synasia Inc., TTA21, TTA26, TTA60 and TTA128 from Jiangsu Tetra New Material Technology Co. Ltd., and THI-DE, DE-102 and DE-103 from Nippon Oil.

Instead of or in addition to epoxy-containing compounds, oxetane-containing compounds can also be used as cationically polymerizable compound (A1) in the curable mass. Processes for the preparation of oxetanes are known in particular from US 2017/0198093 A1 known.

Examples of commercially available oxetanes are bis(1-ethyl-3-oxetanylmethyl)ether (DOX), 3-allyloxymethyl-3-ethyloxetane (AQX), 3-ethyl-3-[(phenoxy)methyloxetane (POX), 3-ethyl-3-hydroxymethyloxetane (OXA), 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene (XDO), 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane (EHOX). The above-mentioned oxetanes are commercially available from TOAGOSEI CO., LTD.

The epoxides and/or oxetanes of the composition according to the invention, in particular for use in the process according to the invention, are preferably curable by a cationic photoinitiator (C1), which will be described in more detail later.

Instead of or in addition to epoxides or oxetanes, vinyl ethers can also be used as cationically polymerizable component (A1) in the composition according to the invention. Suitable vinyl ethers are trimethylolpropane trivinyl ether, ethylene glycol divinyl ether and cyclic vinyl ethers and mixtures thereof. Vinyl ethers of polyfunctional alcohols can also be used.

Finally, the cationically polymerizable component (A1) can comprise one or more alcohols that are used as reactive flexibilizers. In particular, higher molecular weight polyols can be used to flexibilize masses with at least one cationically polymerizable compound. Suitable polyols are available, for example, based on polyethers, polyesters, polycaprolactones, polycarbonates or (hydrogenated) polybutadienediols.

Examples of commercially available higher molecular weight polyols are products sold under the trade names ETERNACOLL UM-90 (1/1), Eternacoll UHC50-200 from UBE Industries Ltd., Capa™ 2200, Capa™ 3091 from Perstorp, Liquiflex H from Petroflex, Merginol 901 from HOBUM Oleochemicals, Placcel 305, Placcel CD 205 PL from Daicel Corporation, Priplast 3172, Priplast 3196 from Croda, Kuraray Polyol F-3010, Kuraray Polyol P-6010 from Kuraray Co., Ltd., as Krasol LBH-2000, Krasol HLBH-P3000 from Cray Valley or as Hoopol S-1015-35 or Hoopol S-1063-35 available from Synthesia Internacional SLU.

The list of cationically polymerizable compounds (A1) is to be seen as exemplary and not exhaustive. A mixture of the cationically polymerizable compounds (A1) mentioned is also within the meaning of the invention.

Instead of component (A1), the composition according to the invention can also contain addition-crosslinkable compounds (A2).

Preferably, the addition-crosslinkable compound (A2) comprises an isocyanate (A2-1), together with an isocyanate-reactive compound.

The group of suitable isocyanates (A2-1) includes aliphatic, cycloaliphatic, heterocyclic and aromatic isocyanates.

Preferably, the isocyanate (A2-1) is at least difunctional.

Examples of suitable polyisocyanates are: dimeric 2,4-diisocyanatotoluene, dimeric 4,4'-diisocyanatodiphenylmethane, 3,3'-diisocyanato-4,4'-dimethyl-N,N'-diphenylurea, the isocyanurate of isophorone diisocyanate, hexamethylene diisocyanate and its isocyanurate, pentamethylene diisocyanate and its isocyanurate, 1,4-phenylene diisocyanate, naphthalene-1,5-diisocyanate and addition products of diisocyanates with short-chain diols such as 1,4-butanediol or 1,2-ethanediol.

Furthermore, addition products of diisocyanates with polyethers, polyesters, polycarbonates, polybutadienes or other alcohols, amines or thiols can be used.

Preferred are isocyanurates of hexamethylenediamine, pentamethylenediamine or isophoronediamine as well as addition products of hexamethylenediamine or isophoronediamine with OH-terminated polymers.

The isocyanates (A2-1) can be used alone or in a mixture of two or more of the isocyanates.

The addition-crosslinkable compound (A2) can comprise at least one thiol (A2-2) as an isocyanate-reactive compound. The thiol (A2-2) is preferably an at least difunctional thiol.

Preferably, the at least difunctional thiol is selected from the group consisting of ester-based thiols, polyethers with reactive thiol groups, polythioethers, polythioether acetals, polythioether thioacetals, polysulfides, thiol-terminated urethanes, thiol derivatives of isocyanurates and glycoluril, and combinations thereof.

Examples of commercially available ester-based thiols based on 2-mercaptoacetic acid include trimethylolpropane trimercaptoacetate, pentaerythritol tetramercaptoacetate and glycol dimercaptoacetate, which are available under the brand names Thiocure™ TMPMA, PETMA and GDMA, respectively, from Bruno Bock.

Other examples of commercially available ester-based thiols include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutylate), glycol di(3-mercaptopropionate) and tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate, which are available under the brand names Thiocure™ TMPMP, PETMP, GDMP and TEMPIC from Bruno Bock.

Examples of commercially available (thio)ether-based thiols include DMDO (1,8-dimercapto-3,6-dioxaoctane), available from Arkema S.A., DMDS (dimercaptodiethyl sulfide) and DMPT (2,3-di((2-mercaptoethyl)thio)-1-propane-thiol), both available from Bruno Bock.

With regard to increased resistance of the cured mass to temperature and humidity, the use of ester-free thiols is particularly preferred. Examples of ester-free thiols can be JP 2012 153 794 A which is incorporated into the description by reference.

The preferred use in the composition is tris(3-mercaptopropyl)isocyanurate (TMPI) as a trifunctional ester-free thiol. This thiol has been shown to provide good hydrolytic stability and also improve adhesion to various substrates.

According to a particularly preferred embodiment, the at least difunctional thiol of component (A2-1) therefore comprises tris(3-mercaptopropyl)isocyanurate, alone or in admixture with other at least difunctional thiols.

Ester-free thiols based on a glycoluril compound are from the EP 3 075 736 A1 These can also be used in the compositions of the invention as further addition-crosslinkable resin components, alone or in a mixture with other at least difunctional thiols.

Ester-free thiols based on olefins or terpenes are in the US 9 340 716 B2 These can also be used in the compositions of the invention as further addition-crosslinkable resin components, alone or in a mixture with other at least difunctional thiols.

Higher functional thiols, which are obtainable, for example, by oxidative dimerization processes of at least difunctional thiols, can also be used.

Furthermore, at least difunctional thiols can be synthesized by reaction of at least difunctional thiiranes with a thiol.

It is known to those skilled in the art that primary thiols react more quickly with isocyanates than secondary or tertiary thiols. Depending on the process design, primary thiols may be advantageous because they enable faster curing, while in processes that require a longer open time, secondary or tertiary thiols may be preferred.

Instead of components (A1) and (A2), the composition according to the invention can also contain moisture-crosslinkable compounds (A3).

Preferably, the moisture-crosslinkable compound (A3) is selected from the group of silanes.

Suitable silanes include monofunctional, particularly low molecular weight silanes, di- or higher functional silane-modified oligomers and/or polymers. These are not further restricted structurally.

Examples of silane-modified polymers used are polyethers or polyacrylates with terminal alkoxysilane groups. Preferably, at least difunctional γ-alkoxysilanes are used. Their production is described, for example, in the US 5 364 955 A and the writings mentioned therein are described in detail.

γ-Alkoxysilanes with at least two alkoxysilane-containing end groups are available commercially, for example from Kaneka Belgium NV under the names Kaneka MS Polymer or Kaneka Silyl. Polyether-based γ-Alkoxysilanes are also available from Wacker Chemie AG under the names Geniosil STP-E15 and STP-E35.

Instead of or in addition to the γ-alkoxysilanes, so-called α-alkoxysilane compounds can also be used. Preferably, at least difunctional α-alkoxysilane compounds are used. The production of α-alkoxysilane-terminated compounds is, among other things, in the WO 03/014226 A1 described in detail. In addition, many of the preferred α-silanes based on polyethers or polyurethanes are commercially available from Wacker Chemie AG. These are sold commercially under the brand name GENIOSIL STP-E. Examples include the types Geniosil STP-E10 and STP-E30.

In addition to the polymeric compounds that can be crosslinked with moisture, monofunctional low-molecular alkoxysilane compounds can also be used. These alkoxysilanes contain a monovalent organic residue and are generally used to increase storage stability and to improve adhesion or flexibility.

Suitable monofunctional γ-alkoxysilanes with different organic radicals are available, for example, under the trade names Dynasylan VTMO, Dynasylan GLYMO, Dynasylan MEMO, Dynasylan MTMS from Evonik Industries AG.

Examples of commercially available monofunctional α-alkoxysilanes are products from Wacker Chemie AG. Corresponding methacrylate- or carbamate-functionalized α-alkoxysilanes are available under the names GENIOSIL XL 32, XL 33, XL 63 or XL 65. Higher molecular weight monofunctional alkoxysilanes can also be used. Such compounds are usually used to increase flexibility and can be purchased from Wacker Chemie AG under the names Geniosil XM 20 and XM25, for example.

Partially condensed monofunctional alkoxysilanes can also be used. Such products are commercially available, for example, under the name Dynasylan 6490 or Dynasylan 1146 from Evonik Industries AG.

In the present compositions, one or more of the alkoxysilanes mentioned can be used as moisture-crosslinkable compound (A3).

Mixtures of the above-mentioned α-alkoxysilanes and/or γ-alkoxysilanes can also be advantageously used for compositions for use in the process according to the invention.

The first curable component (A) is present in the composition, based on the total weight of the composition, in particular in a proportion of 5 to 90 wt.%, preferably in a proportion of 10 to 85 wt.%.

Component (B): Second curable component

The compositions according to the invention comprise a second curable component (B) consisting of at least one radically radiation-curable compound.

The second curable component (B) serves in particular to enable rapid, precise, controllable and reliable fixing of the already activated mass by irradiation with actinic radiation of the second wavelength λ ₂ , in particular at the latest as soon as the end of the open time of the activated mass is reached.

The radically radiation-curable compound (B) is not further restricted structurally as long as it contains ethylenically unsaturated double and/or triple bonds.

Suitable examples include (meth)acrylates, allyl compounds, vinyl compounds, methallyl compounds, isoprenes, butadienes and propargyles.

The compositions preferably contain at least one difunctional radically radiation-curable compound.

Preferably, radiation-curable compounds based on (meth)acrylates are used. For example, both aliphatic and aromatic (meth)acrylates can be used.

Here and in the following, (meth)acrylates refer to both the derivatives of acrylic acid and methacrylic acid as well as combinations and mixtures thereof.

The following radiation-curable compounds are suitable, for example: isobornyl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, 3,3,5-trimethylcyclohexanol acrylate, behenyl acrylate, 2-methoxyethyl acrylate and other mono- or polyalkoxylated alkyl acrylates, isobutyl acrylate, isooctyl acrylate, lauryl acrylate, tridecyl acrylate, isostearyl acrylate, 2-(o-phenylphenoxy)ethyl acrylate, acryloylmorpholine, N,N-dimethylacrylamide, 4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,10-decanediol diacrylate, tricyclodecanedimethanol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polybutadiene diacrylate, cyclohexanedimethanol diacrylate, diurethane acrylates of monomeric, oligomeric or polymeric Diols and polyols, trimethylolpropane triacrylate (TMPTA), and dipentaerythritol hexaacrylate (DPHA), and combinations thereof. Higher-functional acrylates derived from multiply branched or dendrimeric alcohols can also be used advantageously

The analogous methacrylates are also within the meaning of the invention.

Radiation-curable compounds with allyl groups are also suitable, such as 1,3,5-triallyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, which is commercially available as TAICROS® from Evonik. Compounds containing allyl groups lead to rapid fixing processes when irradiated with the second wavelength λ ₂ , particularly in the presence of thiols.

Unhydrogenated polybutadienes with free double bonds, such as the Poly BD® types, can also be used as radiation-curing compounds.

Urethane acrylates based on polyesters, polyethers, polycarbonate diols and/or (hydrogenated) polybutadiene diols can be used as higher molecular weight radiation-curable compounds in the second curable component (B).

Furthermore, radiation-curable hybrid compounds can be used which have both radically polymerizable groups and cationically polymerizable epoxy groups.

Examples of commercially available products that have both radically polymerizable groups and cationically polymerizable epoxy groups include 3,4-epoxycyclohexyl methyl methacrylate (TTA15) from Jiangsu Tetra New Material Technology Co., Ltd., UVACURE 1561 from UCB, Solmer SE 1605 from Melrob Ltd. and Miramer PE210HA from Miwon Europe GmbH.

The radiation-curable hybrid compounds mentioned can be used advantageously in particular in curable compositions according to the first embodiment.

Furthermore, radiation-curable hybrid compounds can be used which have both radically polymerizable groups and addition-crosslinkable groups.

Examples of suitable hybrid compounds further include hydroxy(meth)acrylates, isocyanato(meth)acrylates, epoxy(meth)acrylates, vinyl ether(meth)acrylates or oxetane(meth)acrylates.

Examples of commercially available products that contain both radically polymerizable groups and addition-crosslinkable groups include Karenz MOI and Karenz AOI from Resonac, Laromer PR 9000 from BASF, glycidyl methacrylate, Ebecryl 4141 and Ebecryl 4596 from Allnex.

The radiation-curable hybrid compounds mentioned can be used advantageously in particular in masses according to the second embodiment.

A combination of several radiation-curable compounds is also within the scope of the invention.

The second curable component (B) is present in the composition according to the invention in particular in a proportion of 5 to 50% by weight, preferably in a proportion of 10 to 40% by weight, in each case based on the total weight of the curable composition.

Component (C): First photoinitiator

The curable composition comprises a first photoinitiator (C), which is a photolatent acid (C1) or a photolatent base (C2).

The first photoinitiator (C) can be activated upon irradiation with actinic radiation of a first wavelength λ ₁ and initiates a polymerization reaction in the curable mass, which enables reliable final curing even in shadow zones.

In this context, the first photoinitiator (C) is particularly matched to the first curable component (A). This means that the polymerization reaction of the first curable component (A) is determined in particular by the activation of the first photoinitiator (C).

The photolatent acid (C1) preferably comprises at least one photolatent acid generator which releases an acid upon irradiation with actinic radiation of a first wavelength λ ₁ , and in particular a photolatent acid generator based on a metallocenium compound for cationic polymerization.

An overview of various metallocenium salts is given in the EP 0 542 716 B1 disclosed. Examples of different anions of the metallocenium salts are HSO ₄ ^- , PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , Cl ^- , Br, I ^- , ClO ₄ ^- , PO ₄ ^- , SO ₃ CF ₃ ^- , tosylate, aluminates or a borate anion, such as BF ₄ ^- and B(C ₆ F ₅ ) ₄ ^- .

Preferably, the photolatent acid (C1) based on a metallocenium compound is selected from the group of ferrocenium salts.

Examples of suitable ferrocenium salts are cumenylcyclopentadienyliron(II) hexafluorophosphate (Irgacure 261); naphthalenylcyclopentadienyliron(II) hexafluorophosphate, benzylcyclopentadienyliron(II) hexafluorophosphate and cyclopentadienylcarbazoleiron(II) hexafluorophosphate.

The photolatent acid (C1) preferably absorbs in the visible region of the electromagnetic spectrum. This means that the photolatent acid (C1) can preferably be activated at a first wavelength λ ₁ ≥ 380 nm. The photolatent acid (C1) can preferably be activated by radiation with a wavelength of λ ₁ ≥ 400 nm, preferably λ ₁ ≥ 460 nm.

Particularly preferably, the first wavelength λ ₁ , i.e. the activation wavelength of the curable mass, is in a range from 400 to 750 nm.

Suitable photolatent bases (C2) preferably comprise one or more compounds and derivatives derived from the group of cyclic amidine bases, cyclic guanidine bases, alpha-aminoacetophenones, dihydropyridines, imidazolium compounds, carbamates, biguanidinium compounds and mixtures thereof. The corresponding salts of the substance classes mentioned are also suitable as photolatent bases (C2).

Cyclic amidine bases include compounds based on 1,5-diazabicyclo[4.3.0]nonene, 1,8-diazabicyclo[5.4.0]undecene, 1,11-diazabicyclo[8.4.0]tetradecene, such as 1,8-diazabicyclo[5.4.0]undec-7-ene-anthracene-tetraphenylborate.

Structural analogues such as 2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidin-1-ium tetraphenylborate, 1-(anthracen-9-ylmethyl)-2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepin-1-ium tetraphenylborate or 1-(anthracen-9-ylmethyl)-2,3,4,6,7,8-hexahydropyrrolo[1,2-a]pyrimidin-1-ium tetraphenylborate can also be used advantageously.

Examples of cyclic guanidine bases can be selected from the group of bicyclic guanidine compounds and include, for example, 1,5,7-triazabicyclo[4.4.0]dec-5-ene-H-tetraphenylborate, 1-(anthracen-9-ylmethyl)-9-ethyl-3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-ium tetraphenylborate and 3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidin-1-ium tetraphenylborate.

Suitable alpha-aminoacetophenones are, for example, 2-benzyl-2-(dimethylamino)-1-(4-methoxyphenyl)butan-1-one, 2-benzyl-2-dimethylamino-4'-morpholinobutyrophenone and 2-dimethylamino-2-(4-methyl- benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one. Other compounds can be EP 0 284 561 B1 be taken.

Examples of photolatent bases based on dihydropyridine are N-methylnifedipine, N-butyl-2,6-dimethyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid diethyl ester and N-methyl-2,6-dimethyl-4-(4,5-dimethoxy-2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylic acid diethyl ester.

A suitable photolatent base based on an imidazolium compound is 3-(anthracen-9-ylmethyl)-1-methyl-1H-imidazol-3-ium tetraphenylborate.

A suitable photolatent base based on a carbamate is anthracen-9-ylmethyldiethylcarbamate.

Examples of photolatent bases based on biguanidinium compounds are 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium n-butyltriphenylborate, (Z)-([bis(dimethylamino)methylidene]amino)-N-cyclohexyl(cyclohexylamino)methaniminium tetrakis(3-fluorophenyl)borate and 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidium 2-(3-benzoylphenyl)propionate.

The compounds mentioned are commercially available under the name CGI 277 from BASF SE, Irgacure 369, Irgacure 907, Irgacure 379 each from IGM Resins and WPBG-345, WPBG-300, WPBG-266, WPBG-018 from Wako Chemicals Europe GmbH.

The decomposition products of the photolatent base (C2) preferably have a pKs of greater than 7 after irradiation with actinic radiation of the first wavelength λ _1. By activation of the photolatent base (C2), the pKs changes by at least one.

The photolatent base (C2) preferably absorbs in the visible region of the electromagnetic spectrum. This means that the photolatent base (C2) can preferably be activated at a first wavelength λ ₁ ≥ 380 nm. The photolatent base (C2) can preferably be activated by radiation with a wavelength of λ ₁ ≥ 400 nm.

The first photoinitiator (C), i.e. the photolatent acid (C1) or the photolatent base (C2), is contained in particular in a proportion of 0.01 to 5 wt.%, based on the total weight of the curable mass, but preferably in proportions of 0.05 to 3 wt.%.

Component (D): Second photoinitiator

In addition to components (A), (B) and (C), the composition, in particular for use in the process according to the invention, contains a second photoinitiator (D) for the radical polymerization of component (B). The second photoinitiator (D) is accordingly a radical former.

In the process according to the invention, the second photoinitiator (D) enables the mass previously activated in step b) to be fixed by irradiation with actinic radiation of the second wavelength λ ₂ . In other words, the second photoinitiator (D) forms radicals under the action of the actinic radiation of the second wavelength λ ₂ , which result in a polymerization of the second curable component (B) or trigger a polymerization of the second curable component (B).

All customary, commercially available compounds can be used as the second photoinitiator (D), such as, for example, α-hydroxy ketones, benzophenone, α,α'-diethoxyacetophenone, 4,4-diethylaminobenzophenone, 2,2-dimethoxy-2-phenylacetophenone, 4-isopropylphenyl-2-hydroxy-2-propyl ketone, 1-hydroxycyclohexylphenyl ketone, isoamyl p-dimethylaminobenzoate, methyl 4-dimethylaminobenzoate, methyl o-benzoylbenzoate, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-isopropylthioxanthone, dibenzosuberone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bisacylphosphine oxides, the compounds mentioned being used alone or in combination with two or more of the mentioned compounds can be used as a second photoinitiator (D).

As a second photoinitiator (D), which can be activated by UV radiation, the IRGACURE™ types from BASF SE can be used, such as the types IRGACURE 184, IRGACURE 500, IRGACURE 1179, IRGACURE 2959, IRGACURE 745, IRGACURE 651, IRGACURE 369, IRGACURE 907, IRGACURE 1300, IRGACURE 819, IRGACURE 819DW, IRGACURE 2022, IRGACURE 2100, IRGACURE 784, IRGACURE 250, IRGACURE TPO, IRGACURE TPO-L. The DAROCUR™ types from BASF SE can also be used, such as the types DAROCUR MBF, DAROCUR 1173, DAROCUR TPO and DAROCUR 4265.

The above lists are to be seen as examples for the second photoinitiator (D) and are in no way to be understood as limiting.

The second photoinitiator used as component (D) in the compositions according to the invention can preferably be activated by actinic radiation having a wavelength of from 200 to 400 nm, particularly preferably from 250 to 380 nm.

The second photoinitiator (D) is preferably selected such that it is not activated upon irradiation of the curable mass with the first wavelength λ ₁ .

According to the invention, the second photoinitiator (D) is activated in the process according to the invention by irradiating the mass at the second wavelength λ ₂ .

If required, the second photoinitiator (D) can be combined with a suitable sensitizer.

The difference between the wavelength λ ₁ used for irradiating and activating the first photoinitiator (C) and the wavelength λ ₂ used for irradiating and activating the second photoinitiator (D) is in particular at least 20 nm, preferably at least 30 nm.

The second photoinitiator (D) is present in the compositions in particular in a proportion of 0.01 to 5 wt.%, preferably 0.5 to 3 wt.%, in each case based on the total weight of the composition.

The sum of the proportions of the first photoinitiator (C) and the second photoinitiator (D), based on the total weight of the mass, is in particular at most 10 wt.%, preferably at most 5 wt.%.

Component (E): Inhibitor

In addition to components (A) to (D), the curable composition, in particular for use in the process according to the invention, contains as an essential constituent at least one inhibitor (E) for intercepting radicals generated when the curable composition is irradiated with actinic radiation of the first wavelength λ ₁ .

Thus, the inhibitor (E) ensures that the curable mass has an open time when irradiated with actinic radiation of the first wavelength λ ₁ , within which the activated mass remains dosable or joinable.

This effect is attributed in particular to the fact that the inhibitor (E) ensures that any radicals formed in the mass during irradiation with the first wavelength λ ₁ do not lead to a significant increase in the viscosity of the curable mass, in particular as a result of polymerization reactions of the second curable component (B) which are still undesirable at this point in time in the process according to the invention.

The inhibitor is further selected with respect to its proportion in the curable mass such that when the already activated mass is irradiated with the second wavelength λ ₂ in step d) by the second photoinitiator (D), a sufficient amount of radicals is formed which enable the polymerization of the second curable component (B) and thus lead to a fixation of the mass.

The inhibitor (E) can therefore be regarded as a radical scavenger which, on the one hand, protects the radiation-curable component (B) from premature conversion at the time of activation of the first curable component (A), and, on the other hand, is consumed by the radicals formed when the second photoinitiator (D) is activated, thus enabling the targeted conversion of the radiation-curable component (B) at the desired time. In other words, the inhibitor (E) ensures that the radiation-curable component (B) does not cure for at least the period of the open time. The open time can therefore be controlled via the proportion and type of inhibitor (E).

Depending on the proportion of the inhibitor (E) in the mass, the irradiation dose for activating the first photoinitiator (C) and/or its proportion in the mass can be varied, and vice versa.

Preferably, the irradiation dose, the proportion of the first photoinitiator (C) and the proportion of the inhibitor (E) are coordinated in such a way that the mass remains liquid during the open time after activation of the first photoinitiator (C).

Furthermore, the curing behavior of the mass can be further controlled via the ratio of the proportions of the inhibitor (E) and the second photoinitiator (D) and/or the irradiation dose for activating the second photoinitiator (D), since the consumption of the inhibitor (E) occurs more quickly the more radicals are generated from the second photoinitiator (D) in this step.

The inhibitor (E) is not further restricted structurally. For example, the inhibitor (E) comprises one or more compounds selected from the group consisting of hindered phenols, thioethers, phosphites, hindered amines (HALS), optionally substituted styrenes, nitrous acid esters, alkyl nitrites, dithiocarbamates, and combinations thereof.

Examples of suitable inhibitors (E) are 2,6-di-tert-butyl-4-methylphenol, 4-methoxyphenol, 1,4-dihydroxybenzene, 1,4-benzoquinone, (2,2,6,6-tetramethylpiperidinyl-1-1)oxyl, isoeugenol, α-tocopherol, 4-tert-butylcatechol, 1,2,3-trihydroxybenzene, 3,4,5-trihydroxybenzoic acid, lauryl gallate (dodecyl gallate), triphenyl phosphite, phenylphosphonic acid, tris(2,4-di(tert-butyl)-phenyl)phosphite, 2,2-diphenyl-1-picryl-hydrazyl, phenothiazine, 2-methylpropyl nitrite, 2-propyl nitrite, bis(1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, sebacic acid bis-(2,2,6,6-tetramethyl-4-piperidyl ester), 3,5-dimethylperhydro-1,3,5-thiadiazine-2-thione and N-nitroso-N-phenylhydroxylaminato)-aluminium salts.

Furthermore, 1,1-diphenylethylene, α-methylstyrene, tert-butyl nitrite, tetraethylthiuram disulfide and 2,4-diphenyl-4-methyl-1-pentene can advantageously be used in the curable composition, in particular for carrying out the process according to the invention.

Furthermore, CTA reagents (“chain transfer agents”), which are typically used for RAFT polymerizations, can be used as inhibitors (E). Examples are dithiobenzoates such as benzyl benzodithioate, trithiocarbonates such as S,S-dibenzyl trithiocarbonate and dithiocarbamates such as tetraethylthiuram disulfide (TEDS) and tetramethylthiuram disulfide.

In some cases, the inhibitor (E) may also comprise hexaarylbiimidazoles (HABI) or derivatives thereof. Typical commercially available hexaarylbiimidazoles are 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole (BCIM HABI), 2,2'-bis(2-methoxyphenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2-(2-ethoxyphenyl)-1-[2-(2-ethoxyphenyl)-4,5-diphenyl-2H-imidazol-2-yl]-4,5-diphenyl-1H-imidazole (LEDCUR 110), 2,2',4-tri(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenyl-1,1'-biimidazole (TCDM HABI).

The inhibitor (E) is present in the curable mass in particular in a proportion of 0.01 to 1.5 wt.%, based on the total weight of the mass, preferably in proportions of 0.1 to 1.5 wt.%.

The molar ratio of inhibitor (E) to first photoinitiator (C) in the curable composition is in particular in a range from 0.4:1 to 20:1, preferably in a range from 0.4:1 to 10:1 or 1:1 to 10:1, particularly preferably in a range from 1:1 to 5:1.

The molar ratio of inhibitor (E) to second photoinitiator (D) in the curable composition can be 1:2 or less, preferably 1:5 or less, particularly preferably 1:10 or less.

Component (F): Additives

The compositions according to the invention may further contain optional constituents as additives (F).

The additives (F) are preferably selected from the group of fillers, dyes, photosensitizers, pigments, anti-aging agents, fluorescent agents, accelerators (F1), adhesion promoters, drying agents, crosslinkers, flow improvers, wetting agents, thixotropic agents, diluents, non-reactive flexibilizers, non-reactive polymeric thickeners, flame retardants, corrosion inhibitors, plasticizers, tackifiers and combinations thereof.

Accelerator (F1):

In particular, in the case that the first curable component (A) contains a cationic polymerizable compound (A1), an accelerator (F1) for curing the mass by cationic polymerization can be added to the curable mass.

Peroxy compounds of the perester, diacyl peroxide, peroxydicarbonate and/or hydroperoxide type can be used as accelerators (F1). Hydroperoxides are preferably used. Cumene hydroperoxide in a 70 to 90% (v/v) solution in cumene is used as a particularly preferred accelerator.

By using peroxy compounds, the skin formation of the curable mass is accelerated after irradiation and activation of the first photoinitiator (C1) with the first wavelength λ ₁ .

The proportion of peroxy compounds is selected so that a sufficient open time remains in the process according to the invention for joining and optionally aligning a second substrate. The length of the open time required depends on the processing process carried out in each case.

The accelerator (F1), in particular the peroxy compound, is contained in particular in a proportion of 0 to 5 wt.%, based on the total weight of the mass.

The mass ratio between the first photoinitiator (C1), for example ferrocenium hexafluoroantimonate, and the peroxy compound, for example cumene hydroperoxide, can be varied within wide limits. Preferably, a mass ratio of 1:0.1 to 1:6 is used, particularly preferably from 1:2 to 1:4.

formulation of the curable masses

A formulation of the compositions according to the invention, in particular for use in the process according to the invention, comprises at least the components (A) to (E) described above.

1. (A) 5 bis 90 Gew.-% der ersten härtbaren Komponente,
2. (B) 5 bis 50 Gew.-% der zweiten härtbaren Komponente,
3. (C) 0,01 bis 5 Gew.-% des ersten Photoinitiators,
4. (D) 0,01 bis 5 Gew.-% des zweiten Photoinitiators,
5. (E) 0,01 bis 1,5 Gew.-% des Inhibitors, und
6. (F) 0 bis 80 Gew.-% an Zusatzstoffen.

Preferably, the mass consists of the following components, each based on the total weight of the mass:

1. (A) 5 to 90 wt.% of the first curable component,
2. (B) 5 to 50 wt.% of the second curable component,
3. (C) 0.01 to 5 wt.% of the first photoinitiator,
4. (D) 0.01 to 5 wt.% of the second photoinitiator,
5. (E) 0.01 to 1.5 wt.% of the inhibitor, and
6. (F) 0 to 80 wt.% of additives.

The inhibitor is preferably selected from the group consisting of hindered phenols, thioethers, phosphites, hindered amines (HALS), optionally substituted styrenes, nitrous acid esters, alkyl nitrites, dithiocarbamates and combinations thereof. More preferably, the inhibitor comprises 1,1-diphenylethylene, α-methylstyrene, tert-butyl nitrite, tetraethylthiuram disulfide and 2,4-diphenyl-4-methyl-1-pentene and combinations thereof.

• (A) 10 bis 85 Gew.-% einer kationisch polymerisierbaren Verbindung (A1) umfassend mindestens ein difunktionelles Epoxid als erste härtbare Komponente,
• (B) 5 bis 50 Gew.-% mindestens einer radikalisch strahlungshärtbaren Verbindung als zweite härtbare Komponente,
• (C) 0,1 bis 3 Gew.-% einer photolatenten Säure (C1) als ersten Photoinitiator,
• (D) 0,5 bis 3 Gew.-% eines radikalischen Photoinitiators als zweiten Photoinitiator,
• (E) 0,1 bis 1,5 Gew.-% des Inhibitors, und
• (F) 0 bis 80 Gew.-% an Zusatzstoffen.

According to a first embodiment, the mass preferably comprises or consists of the following components, each based on the total weight of the mass:

• (A) 10 to 85 wt.% of a cationically polymerizable compound (A1) comprising at least one difunctional epoxide as the first curable component,
• (B) 5 to 50 wt.% of at least one radically radiation-curable compound as a second curable component,
• (C) 0.1 to 3 wt.% of a photolatent acid (C1) as first photoinitiator,
• (D) 0.5 to 3 wt.% of a radical photoinitiator as a second photoinitiator,
• (E) 0.1 to 1.5 wt.% of the inhibitor, and
• (F) 0 to 80 wt.% of additives.

• (A) 20 bis 85 Gew.-% einer additionsvernetzbaren Verbindung (A2) umfassend mindestens ein mindestens difunktionelles Isocyanat (A2-1) und ein mindestens difunktionelles Thiol (A2-2) als erste härtbare Komponente,
• (B) 5 bis 50 Gew.-% mindestens einer radikalisch strahlungshärtbaren Verbindung als zweite härtbare Komponente,
• (C) 0,1 bis 3 Gew.-% einer photolatenten Base (C2) als ersten Photoinitiator,
• (D) 1 bis 5 Gew.-% eines radikalischen Photoinitiators als zweiten Photoinitiator,
• (E) 0,01 bis 1,5 Gew.-% des Inhibitors, und
• (F) 0 bis 80 Gew.-% an Zusatzstoffen.

According to a second embodiment, the mass preferably comprises or consists of the following components, each based on the total weight of the mass:

• (A) 20 to 85% by weight of an addition-crosslinkable compound (A2) comprising at least one at least difunctional isocyanate (A2-1) and at least difunctional thiol (A2-2) as the first curable component,
• (B) 5 to 50 wt.% of at least one radically radiation-curable compound as a second curable component,
• (C) 0.1 to 3 wt.% of a photolatent base (C2) as first photoinitiator,
• (D) 1 to 5 wt.% of a radical photoinitiator as a second photoinitiator,
• (E) 0.01 to 1.5 wt.% of the inhibitor, and
• (F) 0 to 80 wt.% of additives.

The at least difunctional isocyanate (A2-1) can be completely or partially replaced by a hybrid compound of component (B) which carries radically radiation-curable groups together with isocyanate groups.

Suitable inhibitors (E) in the compositions of the second embodiment are particularly substituted styrenes, nitrous acid esters or alkyl nitrites and dithiocarbamates.

The masses of the second embodiment form a polythiourethane network in the cured state. This is characterized by high media resistance.

• (A) 15 bis 85 Gew.-% einer durch Feuchtigkeit vernetzbaren Verbindung (A3) umfassend mindestens ein Silan als erste härtbare Komponente,
• (B) 5 bis 50 Gew.-% mindestens einer radikalisch strahlungshärtbaren Verbindung als zweite härtbare Komponente,
• (C) 0,05 bis 3 Gew.-% einer photolatenten Säure (C1) als ersten Photoinitiator,
• (D) 0,1 bis 3 Gew.-% eines radikalischen Photoinitiators als zweiten Photoinitiator,
• (E) 0,01 bis 1,5 Gew.-% des Inhibitors, und
• (F) 0 bis 80 Gew.-% an Zusatzstoffen.

According to a third embodiment, the mass preferably comprises or consists of the following components, each based on the total weight of the mass:

• (A) 15 to 85 wt.% of a moisture-crosslinkable compound (A3) comprising at least one silane as the first curable component,
• (B) 5 to 50 wt.% of at least one radically radiation-curable compound as a second curable component,
• (C) 0.05 to 3 wt.% of a photolatent acid (C1) as first photoinitiator,
• (D) 0.1 to 3 wt.% of a radical photoinitiator as a second photoinitiator,
• (E) 0.01 to 1.5 wt.% of the inhibitor, and
• (F) 0 to 80 wt.% of additives.

The compositions according to the invention of all embodiments are preferably provided as one-component compositions.

Use of the hardenable mass

The curable mass described above is particularly suitable for use in joining, casting or coating substrates. This also includes gluing, molding or sealing substrates.

The curable masses are particularly suitable for applications in which the strength build-up is to be controlled in a targeted manner by fixing light and at the same time reliable curing in shadow zones is to be ensured, especially in the case of non-transparent substrates. This property profile is particularly required in the production of electro-optical components, such as camera modules, the joining of displays or encapsulations with complex geometries, for example sensor encapsulations.

Housing bonding or application in fuel cells are also conceivable with the previously described masses, especially when using cationically polymerizable compounds (A1) with 1,1-diphenylethylene, tert-butyl nitrite and/or 2,4-diphenyl-4-methyl-1-pentene as inhibitor (E).

According to one embodiment of the method according to the invention, the masses can be activated by irradiation with the first wavelength λ ₁ in the flow. This means that the liquid mass is irradiated with actinic radiation, for example during dosing, before leaving the dosing device and is thereby activated. Dosing devices which have a penetrable zone and suitable LED irradiation devices are commercially available from DELO Industrie Klebstoffe GmbH & Co. KGaA under the trade name DELO-ACTIVIS and can be found, for example, in the DE 10 2021 133 731 A1 described. The use of such a flow activation device offers the advantage that the dosing and activation of the mass can take place in a single process step. This reduces the equipment required and saves installation space in industrial plants.

The dosing pressure of the mass in a flow activation apparatus is preferably 15 bar or less. The dosing pressure is particularly preferably below 10 bar in order to ensure process-safe and reliable activation of the mass. Typical dosing rates have volume flows of 1 to 15 cm ³ /min, preferably 2 to 10 cm ³ /min. Dosing rates that are too low can lead to premature hardening within the apparatus. Dosing rates that are too high, on the other hand, can lead to incomplete activation of the mass at a given irradiation power.

After activation of the mass by actinic radiation with the first wavelength λ ₁ , it has an open time during which the activated mass remains liquid and does not yet exceed the gel point. The subsequent process steps, in particular the feeding and joining of another substrate (step c), can be carried out reliably within the open time.

However, it is also possible for the activated mass to remain at least partially joinable beyond the specified open time before it solidifies to such an extent that no further flow or pressing onto another substrate is possible. In order to enable a robust process, the addition of a second substrate in step c) of the method according to the invention, if this is carried out, is preferred within the open time.

The open time of the activated masses is preferably at least 0.1 minute, and up to 30 minutes, more preferably up to 15 minutes or up to 5 minutes. Shorter open times of 0.1 to 1 minute are particularly suitable for fast industrial production processes. When using a flow activation apparatus, however, a longer open time can be advantageous for reasons of process reliability, in particular an open time of 1 minute or more, preferably an open time in the range of more than 5 to 30 minutes.

There is usually a correlation between the open time and the curing time, i.e. a shorter open time is not advantageous per se but can offer advantages for the overall process due to the faster curing of the mass.

However, hardenable masses with very short open times of less than one minute can only be processed to a limited extent in a joining process after activation and are also not suitable for flow activation.

After fixing by actinic radiation with the second wavelength λ ₂ , the mass has at least a so-called "green strength" or handling strength. This means that after fixing, no more flowing occurs. Components in joints remain fixed relative to one another and can thus be fed into further production steps, for example manually.

The mass activated and fixed according to the method according to the invention typically hardens completely within 7 days at room temperature, preferably within 3 days, particularly preferably within one day, i.e. within 24 hours. For faster hardening or to accelerate the final hardening of the mass, the mass can be heated either during or after the light fixation in step d).

Measurement methods and definitions used

radiation

To activate the curable mass with actinic radiation of the first wavelength λ ₁ and to fix it with actinic radiation of the second wavelength λ _2, the masses were each irradiated with a DELOLUX 20 LED lamp from DELO Industrie Klebstoffe GmbH & Co. KGaA. Different lamps were used for different wavelengths. The respective exposure times, intensities and wavelengths can be found in the tables below for the test examples.

room temperature

Room temperature is defined as 23 ± 2 °C.

curing

"Crosslinking" or "curing" is defined as a polymerization reaction beyond the gel point. The gel point is the point at which the storage modulus G' becomes equal to the loss modulus G''.

open time

The determination is carried out using a haptic test using a toothpick on glue drops (10 mg) on a glass slide. A triplicate determination is carried out and the arithmetic mean of the measured values obtained gives the open time. The glue drops are activated with an LED surface emitter (DELOLUX 20) under predefined conditions depending on the intended application. The activation conditions such as intensity, duration and wavelength of the irradiation can be found in the tables below for the test examples. At the end of the irradiation, a stop watch is started.

Using the toothpick, the expected increase in viscosity is assessed haptically in comparison to a non-activated reference sample of the same size and geometry. At intervals of approx. 5 s, the geometry of the activated adhesive drop is manipulated with the toothpick in a vertical movement by pulling the tip of the toothpick upwards from the center of the adhesive drop, with the toothpick held at an angle of approx. 45° to the slide. If the activated adhesive drop does not return to its original geometry within 1 s of manipulation with the tip of the toothpick, the stopwatch is stopped and the end of the adhesive's open time is reached.

In the event that a mass remains liquid or has an open time of less than 0.1 min and can no longer be reliably determined using the method described, it is marked as undetermined with “n.a.”.

assessment of light fixation

To assess the light fixation (solid vs. liquid), the mass is subjected to an optical assessment after irradiation with actinic radiation of the second wavelength λ _2. The intensity, duration and wavelength of the irradiation can be found in the following tables for the test examples. Optionally, the haptic test is carried out using a plastic spatula.

Masses that have a skin after irradiation and no longer flow are classified as “yes” in terms of their light fixation. Masses that have no skin after irradiation or that continue to flow are classified as “no” in terms of their light fixation.

Photo DSC measurements

DSC measurements of the reactivity of radiation-induced curing are carried out in a dynamic differential scanning calorimeter (DSC) of the type DSC3+ from Mettler Toledo. For this purpose, 6 to 10 mg of the liquid sample are weighed into an open aluminum crucible (40 µL) and exposed to light at 30 °C for 5 minutes. The intensity and wavelength can be found in the tables below for the test examples.

The peak time is evaluated after subtracting the energy input caused by the LED lamp.

Production of hardenable masses

To produce the curable masses used in the following examples, the liquid and soluble components are first mixed and then the fillers and optionally other solids are incorporated using a laboratory stirrer, laboratory dissolver or a speed mixer (Hauschild) until a homogeneous mass is formed.

Masses containing photoinitiators that are sensitive to visible light must be prepared under light outside the excitation wavelength of the respective photoinitiators or sensitizers.

The following list contains all the compounds used to produce the hardenable masses and their abbreviations:

Component (A): First curable component

• (A1) Cationically polymerizable compounds:
  • (A1-1): Epikote™ Resin 169 (mixture of bisphenol A and bisphenol F glycidyl ethers, available from Hexion)
  • (A1-2): 3,4-Epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, available under the trade name Celloxide 2021 P from Daicel
  • (A1-3): Eternacoll UM 90 (1/1) (aliphatic polycarbonate diol), available from UBE Industries Ltd.
  • (A1-4): Bis[1-Ethyl(3-oxetanyl)]methyl ether], available from DKSH
• (A2) Addition-crosslinkable compounds:
  • (A2-1): Isocyanates
    • (A2-1-1): Desmodur Ultra N3600 Aliphatic polyisocyanate (HDI isocyanurate), available from Covestro
  • (A2-2) Thiols
    • (A2-2-1): Tris(3-mercaptopropyl)isocyanurate (trifunctional thiol)
• (A3) Moisture-crosslinkable compounds
  • (A3-1): Geniosil STP-E15; at least difunctional γ-alkoxysilane compound, available from Wacker
  • (A3-2): Dynasylan VTMO; monofunctional γ-alkoxysilane compound, available from Evonik

Component (B): Second curable component

• (B-1): Sartomer SR833S (tricyclodecanedimethanol diacrylate), available from Sartomer
• (B-2): Photomer 4006 (trimethylolpropane triacrylate), available from iGM Resins
• (B-3): Epoxy Acrylate Solmer E 1605, available from Solmer Soltech Ltd.
• (B-4): Taicros ^® (triallyl isocyanurate), available from Evonik
• (B-5): Laromer PR9000 (hybrid compound isocyanate and acrylate), available from BASF SE

Component (C): Initiator for the first wavelength λ ₁

• (C-1): R-Gen 262 (η ⁵ -2,4-cyclopentadien-1-yl)[(1,2,3,4,5,6-η)-(1-methylbenzyl)benzene]-iron(I) hexafluoroantimonate; 50% in propylene carbonate, available from Chitec Technology
• (C-2): CGI-277 (2-benzyl-1-(3,5-dimethoxyphenyl)-2-(dimethylamino)butan-1-one), available from BASF

Component (D): Initiator for the second wavelength λ ₂

• (D-1): Omnirad BDK (2,2-dimethoxy-1,2-diphenylethan-1-one), available from IGM Resins
• (D-2): Omnirad 184 (1-hydroxycyclohexyl)phenylmethanone), available from IGM Resins
• (D-3) Omnirad 127 D (1,1'-(Methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone]), available from IGM Resins

Component E: Inhibitors

• (E-1): Nofmer MSD (1,1'-(1,1-dimethyl-3-methylene-1,3-propanediyl)bisbenzene), available from NOF Corporation
• (E-2):1,1-Diphenylethylene, available from TCI Germany
• (E-3): tert-butyl nitrite > 90%, available from Merck
• (E-4): 2,6-Di-tert-butyl-4-methylphenol >99%, available from Merck

Component F: Additives

• (F-1): Trigonox K-90 (cumene hydroperoxide 90%, other ingredients: 2-phenylisopropanol, cumene, acetophenone), available from AkzoNobel
• (F-2): Dodecylbenzenesulfonic acid > 95%, available from TCI
• (F-3): Trioctyl trimellitate Oxsoft TOTM LE, available from Krahn
• (F-4) Bluesil Photoinitiator 2074 (4-(-1-methylethyl)phenyl)-(4-methylphenyl)iodonium tetrakis(pentafluorophenylborate), available from Bluestar Silicones

The composition of the respective curable masses is given in the following tables 1 to 3. All weight proportions listed below refer to the total weight of the curable masses. Table 1: Examples according to the first embodiment. E1 E2 E3 E4 E5 E6 V1* V2* E7 V3* (A) 52.30% A1-1 87.18% A1-1 87.23% A1-1 87.18% A1-1 43.63% A1-2 68.15% A1-2 72.96% A1-2 87.40% A1-1 87.37% A1-1 85.95% A1-1 43.57% A1-3 8.50% A1-4 9.05% A1-4 (B) 44.88% B-3 10.00% B-1 10.00% B-1 10.00% B-2 10.00% B-1 20.00% B-1 15.00% B-1 10.00% B-1 10.00% B-1 10.00% B-1 (C) 0.30% C-1 0.30% C-1 0.30% C-1 0.30% C-1 0.48% C-1 0.48% C-1 0.48% C-1 0.30% C-1 0.30% C-1 0.30% C-1 (D) 2.00% D-1 2.00% D-1 2.00% D-1 2.00% D-1 2.00% D-2 2.00% D-3 2.00% D-3 2.00% D-1 2.00% D-1 2.00% D-1 (E) 0.22% E-1 0.22% E-1 0.17% E-2 0.22% E-1 0.22% E-1 0.36% E-1 0 0 0.03% E-1 1.75% E-1 (F) 0.30% F-1 0.30% F-1 0.30% F-1 0.30% F-1 0.10% F-1 0.51% F-4 0.51% F-4 0.30% F-1 0.30% F-1 molar ratio (E) : (C) 2.9:1 2.9:1 2.9:1 2.9:1 1.9:1 3.0:1 0 0 0.4:1 23.5:1 molar ratio (E) : (D) 1 : 8.3 1 : 8.3 1 : 8.3 1 : 8.3 1 : 10.5 1 : 6.1 0 0 1 : 60 1:1.1 Habitus after irradiation with λ ₁ = 460 nm, 10 s: 200 mW/cm ² fluid fluid fluid fluid fluid fluid firmly firmly fluid fluid Assessment of light fixation after irradiation with λ ₂ = 365 nm, 10 s: 200 mW/cm ² firmly firmly firmly firmly firmly firmly firmly firmly firmly fluid Open time [min] after irradiation with λ ₁ = 460 nm, 10 s: 200 mW/cm ² 1.5 8.0 10.0 7.5 3.5 22.0 nb nb 1.0 nb Habitus after irradiation with λ ₁ = 460 nm, 10 s: 200 firmly firmly firmly firmly firmly firmly firmly firmly firmly fluid mW/cm ² and 24 h waiting time at room temperature Peak time [s] Irradiation with 460 nm, 5 min, 200 mW/cm ² at 30 °C 3.4 4.2 4.6 3.5 4.7 nb 4.2 2.8 nb nb *: Comparison example Table 2: Examples according to the second embodiment. E8 E9 E10 E11 E12 E13 V4* V5* V6* V7* (A) 42.64% 42.70% 42.50% 41.53% 42.70% - 42.70% 43.90% 42.79% 42.05% A2-1-1 A2-1-1 A2-1-1 A2-1-1 A2-1-1 A2-1-1 A2-1-1 A2-1-1 A2-1-1 43.22% 43.30% 43.10% 42.40% 43.20% 29.00% 43.27% 44.60% 43.37% 42.62% A2-2-1 A2-2-1 A2-2-1 A2-2-1 A2-2-1 A2-2-1 A2-2-1 A2-2-1 A2-2-1 A2-2-1 (B) 10.66% 10.70% 10.60% 12.60% 10.65% 3.38% 10.67% 11.00% 10.70% 10.51% B-4 B-4 B-4 B-2 B-4 B-4 B-4 B-4 B-4 B-4 64.3% B-5 (C) 0.12% 0.12% 0.12% 0.12% 0.12% 0.08% - 0.13% 0.12% 0.12% C-2 C-2 C-2 C-2 C-2 C-2 C-2 C-2 C-2 (D) 3.00% 3.00% 2.99% 3.00% 3.00% 3.00% 3.00% - 3.00% 3.00% D-3 D-3 D-3 D-3 D-3 D-3 D-3 D-3 D-3 (E) 0.34% 0.16% 0.67% 0.33% 0.33% 0.23% 0.34% 0.35% - 1.68% E-1 E-3 E-1 E-1 E-1 E-1 E-1 E-1 E-1 (F) 0.02% 0.02% 0.02% 0.02% - 0.01% 0.02% 0.02% 0.02% 0.02% F-2 F-2 F-2 F-2 F-2 F-2 F-2 F-2 F-2 molar ratio (E) : (C) 4.0:1 4.0:1 8.0:1 4.0:1 4.0:1 4.0:1 - 4.0:1 - 20.0:1 molar ratio (E) : (D) 1 : 6.1 1 : 6.1 1 : 3.1 1 : 6.3 1 : 6.1 1 : 9.1 1 : 1.6 - - 1 : 1.2 Habitus after irradiation with λ ₁ = 400 nm, 5 s: 200 mW/cm ² fluid fluid fluid fluid fluid fluid fluid fluid firmly fluid Assessment of light fixation after irradiation with λ ₂ = 365 nm, 5 s: 1000 mW/cm ² firmly firmly firmly firmly firmly firmly firmly fluid firmly fluid Open time [min] after irradiation with λ ₁ = 400 nm, 5 s: 200 mW/cm ² 1.5 3 2 2 1.5 3.5 nb 2 nb 2.5 Habitus after irradiation with λ ₁ = 400 nm, 5 s: 200 mW/cm ² and 24 h firmly firmly firmly firmly firmly firmly fluid firmly firmly firmly waiting time at room temperature Peak time [s] Irradiation with 365 nm, 5 min, 200 mW/cm ² at 30 °C 5.9 nb nb 9.0 nb nb nb nb nb nb *: Comparison example Table 3: Examples according to the third embodiment. E14 V8* E901627 901629 (A) 45.00% 45.00% A3-1 A3-1 1.00% 1.00% A3-2 A3-2 (B) 15.40% 15.40% B-1 B-1 (C) 0.50% 0.50% C-1 C-1 (D) 2.00% 2.00% D-2 D-2 (E) 0.37% 0 E-1 (F) 0.10% 0.10% F-1 F-1 35.63% 36.00% F-3 F-3 molar ratio (E) : (C) 3.0:1 0 molar ratio (E) : (D) 1 : 6.0 0 Habitus after irradiation with λ ₁ = 460 nm, 10 s: 200 mW/cm ² fluid firmly Assessment of light fixation after irradiation with λ ₂ = 365 nm, 10 s: 200 mW/cm ² firmly firmly Open time [min] after irradiation with λ ₁ = 460 nm, 10 s: 200 mW/cm ² 12 nb Habitus after irradiation with λ ₁ = 460 nm, 10 s: 200 mW/cm ² and 24 h waiting time at room temperature firmly firmly *: Comparison example

Examples E1 to E7 in Table 1 show compositions of the first embodiment based on at least one cationically polymerizable compound (A1) for use in the process according to the invention. The compositions contain a photolatent acid (C-1) as the first photoinitiator (C) for the first curable component (A).

The activated masses of examples E1 to E6 initially remain liquid after irradiation with light of the first wavelength λ ₁ and have open times in the range of 1.5 to 22 minutes. They are therefore suitable for pre-activation. In particular, masses with a longer open time, such as example E6, can be used reliably in a flow-through activation apparatus. Shorter open times are suitable for bonding processes in which components are joined within a short time. Even if no fixing by irradiation with light of the second wavelength λ ₂ takes place according to step d) of the described process, the masses become solid and harden after 24 hours at the latest. Conversely, this means that the masses of examples E1 to E7 are suitable for reliably hardening after activation with light of the first wavelength λ ₁ even in shadow zones that are not accessible to irradiation with light of the second wavelength λ ₂ in step d).

Furthermore, all examples E1 to E7 can be fixed by irradiation with light of the second wavelength λ _2. During the open time, the viscosity of the masses is preferably at most 500 Pas.

Different open times can be set by the proportion of inhibitor (E) or the molar ratio of inhibitor (E) to the first photoinitiator (C), which can be activated when irradiated with the first wavelength λ _1. For example, a smaller proportion of inhibitor (E) with a molar ratio of components (E) to (C) reduced by a factor of 7 in example E7 leads to an open time of 1 minute, in direct comparison to an otherwise analogous formulation according to example E2. However, fixing of the mass according to example E7 after irradiation with light of the second wavelength λ ₂ remains possible, since there is an excess of the second photoinitiator (D) in relation to inhibitor (E), which can be activated when irradiated with light of the second wavelength λ ₂ .

Comparative example V3 has a high proportion of the inhibitor (E) of over 1.5% by weight with a molar ratio of the inhibitor (E) to the first photoinitiator (C) of 23.5:1. The mass cannot be activated by irradiation with light of the first wavelength λ ₁ under the selected conditions, but remains liquid even after 24 hours. Light fixation by irradiating the mass with light of the wavelength λ ₂ is also not possible under the conditions of comparative example V3.

Example E3 shows the use of an alternative inhibitor (E-2). With the same molar ratio (E) to (D) and (E) to (C) compared to example E2, a similar open time can be achieved after activation by irradiation with the first wavelength λ ₁ .

In contrast to examples E1 to E4 based on a glycidyl ether, example E5 shows a formulation using an alternative resin system comprising a cycloaliphatic epoxide and a polyol. The composition can also be used advantageously in the process according to the invention.

Comparative example V1 shows a formulation based on the state of the art according to EP 3 894 458 B1 The mass does not contain any inhibitor (E) and solidifies immediately after irradiation with light of the first wavelength λ ₁ and is therefore unsuitable for use in the process according to the invention due to the lack of an open time.

In contrast, the mass according to example E6, which is comparable to the mass of comparative example V1 and additionally contains an inhibitor (E-1) based on a methylstyrene dimer, can be activated by irradiation with light of the first wavelength λ ₁ without the mass immediately solidifying. After activation, the mass has an open time of 22 minutes and can be fixed by irradiation with light of the second wavelength λ ₂ .

The process according to the invention can be carried out independently of the resin system used and can be made possible solely by the addition of the inhibitor (E). Thus, the composition according to comparative example V2, which contains a cationically polymerizable compound based on a glycidyl ether (A1-1), does not have a sufficient open time in the sense of the invention in the absence of component (E). The comparable composition of example E3, on the other hand, can be activated, has an open time of about 10 minutes and can be fixed in a further step by irradiation with light of the second wavelength λ _2. The proportion of the inhibitor (E) in the curable composition is determined as a function of the amount of the photoinitiator. (C) and the irradiation dose are selected so that curing of the activated mass can occur within 24 hours.

Examples E8 to E13 in Table 2 show compositions of the second embodiment based on at least one addition-crosslinkable compound (A2) for use in the process according to the invention. The compositions contain a photolatent base (C-2) as the first photoinitiator (C) for the first curable component (A).

Acrylates (B-2; Example E11), allyl compounds (B-4; Example E8) or hybrid compounds comprising an acrylate and isocyanate functionality (B-5; Example E13) are used as the second curable component (B) in the compositions of the second embodiment. The hybrid compound (B-5) can replace the isocyanate compound of component (A2) in whole or in part. All of the substance classes mentioned can be fixed by irradiation with light of the second wavelength λ ₂ .

Examples E8 to E13 are suitable for carrying out the process according to the invention and, after activation by irradiation with light of the first wavelength λ _1, cure reliably even in shadow zones.

The masses have open times of 1.5 to 3.5 minutes and can be fixed by irradiation with light of the second wavelength λ ₂ .

Comparative example V4 does not use the first photoinitiator (C). The mass can be fixed by irradiation with light of the second wavelength λ ₂ , but cannot be activated. This means that the mass remains liquid even after 24 hours after irradiation with light of the first wavelength λ ₁ and has no measurable open time. It is therefore not suitable for curing in shadow areas.

If, however, the second photoinitiator (D) is omitted, as in comparative example V5, the masses do indeed cure after 24 hours after irradiation with light of the first wavelength λ ₁ without any further energy input. However, fixation in accordance with step d) of the process according to the invention is not possible.

Omitting the inhibitor (E) leads, as shown in Comparative Example V6, to masses which have no open time and solidify immediately after irradiation with light of the first wavelength λ ₁ .

The composition of comparative example V7 has a high proportion of the inhibitor (E) of over 1.5% by weight. However, such a high proportion of the inhibitor (E), based on the total weight of the composition, can lead to compositions that can no longer be activated in accordance with the invention, even if the molar ratio of the inhibitor (E) to the first photoinitiator (C) is in a range that is otherwise suitable for carrying out the process according to the invention.

Example E14 in Table 3 shows a composition of the third embodiment based on at least one moisture-crosslinkable compound (A3) comprising a γ-alkoxysilane compound. The composition of Example E14 has a proportion of inhibitor (E) of 0.37% by weight with a molar ratio of inhibitor (E) to first photoinitiator (C) of 3:1. The molar ratio of inhibitor (E) to second photoinitiator (D) is 1:6. The composition can be activated by irradiation with light of the first wavelength λ ₁ and fixed by irradiation with light of the second wavelength λ _2. The open time after the first irradiation is 12 minutes. The composition is suitable for use in the process according to the invention.

Comparative example V8, on the other hand, does not add an inhibitor (E). Without the addition of component (E), it is not possible to ensure that the process can be carried out step by step or that the build-up of strength can be controlled. Irradiation with light of the first wavelength λ ₁ as well as with light of the second wavelength λ ₂ leads directly to a solidification of the mass. The mass of comparative example V8 cannot therefore be used in the process according to the invention.

The cured masses of all described embodiments of the invention achieve a compressive shear strength of at least 1 MPa on aluminum after their final curing.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 3 894 458 B1 [0002, 0238]
• US 4 849 320 A [0004]
• US 5 707 780 A [0005]
• US 5 472 991 A [0006]
• JP 2017 149 813 A [0007]
• US 11 518 087 B2 [0008]
• WO 2001 092 362 A1 [0009]
• EP 3 789 416 A1 [0010]
• DE 3 702 999 A1 [0033]
• DE 10 2007 017 842 A1 [0033]
• US 2017/0198093 A1 [0075]
• JP 2012 153 794 A [0095]
• EP 3 075 736 A1 [0098]
• US 9 340 716 B2 [0099]
• US 5 364 955 A [0106]
• WO 03/014226 A1 [0108]
• EP 0 542 716 B1 [0141]
• EP 0 284 561 B1 [0150]
• DE 10 2021 133 731 A1 [0208]

Cited non-patent literature

• von Kostanski et al.: “Cationic polymerisation using mixed cationic photoinitiator systems” (Designed Monomers and Polymers 2007, Vol. 10, No. 4, pages 327-345, doi: 10.1163/156855507781505110 [0003]
• Kuraray Polyol P-6010 from Kuraray Co., Ltd., as Krasol LBH-2000, Krasol HLBH-P3000 from Cray Valley or as Hoopol S-1015-35 [0080]
• Hoopol S-1063-35 [0080]

Claims (11)

Method for joining, casting or coating substrates using a curable mass, the method comprising the following steps: a) providing the curable mass, the curable mass comprising the following components: (A) a first curable component selected from the group consisting of cationically polymerizable compounds, addition-crosslinkable compounds, moisture-crosslinkable compounds and combinations thereof, (B) a second curable component consisting of at least one radically radiation-curable compound, (C) a first photoinitiator for the first curable component (A), which can be activated upon irradiation with actinic radiation of a first wavelength λ ₁ , the first photoinitiator being a photolatent acid or a photolatent base, (D) a second photoinitiator for the second curable component (B), which can be activated upon irradiation with actinic radiation of a second wavelength λ ₂ , the second wavelength λ ₂ being different from the first wavelength λ ₁ , and wherein the second photoinitiator is a radical former, and (E) at least one radical-scavenging inhibitor for scavenging radicals generated upon irradiation of the curable mass with actinic radiation of the first wavelength λ ₁ ; b) dosing the curable mass onto a first substrate and activating the curable mass by irradiation with actinic radiation of the first wavelength λ ₁ ; c) optionally supplying a second substrate to the activated curable mass on the first substrate to form a substrate composite; and d) fixing the activated curable mass by irradiation with actinic radiation of the second wavelength λ ₂ . procedure according to claim 1 , where the second wavelength λ ₂ is shorter than the first wavelength λ ₁ . procedure according to claim 1 or 2 , wherein steps b) to d) are carried out within a processing time which corresponds at most to an open time of the curable mass after activation of the curable mass by irradiation with actinic radiation of the first wavelength λ ₁ . Process according to one of the preceding claims, wherein the inhibitor (E) is present in a proportion of 0.01 to 1.5 wt.%, based on the total weight of the mass. Method according to one of the preceding claims, wherein a molar ratio of inhibitor (E) to the first photoinitiator (C) in the curable mass is in a range from 0.4:1 to 20:1. Method according to one of the preceding claims, wherein a molar ratio of inhibitor (E) to second photoinitiator (D) in the curable mass is less than 1:2. Method according to one of the preceding claims, wherein the activation of the curable mass is carried out by irradiation with actinic radiation of the first wavelength λ ₁ in the flow. Method according to one of the preceding claims, wherein the method further comprises the following step: e) heating the fixed curable mass on the first substrate or in the substrate composite. Curable mass for joining, casting or coating substrates, wherein the curable mass comprises the following components: (A) a first curable component selected from the group consisting of cationically polymerizable compounds, addition-crosslinkable compounds, moisture-crosslinkable compounds and combinations thereof, (B) a second curable component consisting of at least one radically radiation-curable compound, (C) a first photoinitiator for the first curable component (A), which can be activated upon irradiation with actinic radiation of a first wavelength λ ₁ , wherein the first photoinitiator is a photolatent acid or a photolatent base, (D) a second photoinitiator for the second curable component (B), which can be activated upon irradiation with actinic radiation of a second wavelength λ ₂ , wherein the second wavelength λ ₂ is different from the first wavelength λ ₁ , and wherein the second photoinitiator is a radical former, and (E) at least one radical-scavenging inhibitor for scavenging radicals generated upon irradiation of the curable composition with actinic radiation of the first wavelength λ ₁ . Hardenable mass according to claim 9 , wherein the curable mass consists of the following components, each based on the total weight of the mass: (A) 5 to 90 wt. % of the first curable component, (B) 5 to 50 wt. % of the second curable component, (C) 0.01 to 5 wt. % of the first photoinitiator, (D) 0.01 to 5 wt. % of the second photoinitiator, (E) 0.01 to 1.5 wt. % of the inhibitor, and (F) 0 to 80 wt. % of additives. Use of the hardenable mass after claim 9 or 10 for joining, casting or coating substrates.