CN112063203A

CN112063203A - Coating composition for generating silicon dioxide film coating

Info

Publication number: CN112063203A
Application number: CN202010963284.XA
Authority: CN
Inventors: 张红生
Original assignee: Zhejiang Shichuang Optics Film Manufacturer Co ltd
Current assignee: Zhejiang Shichuang Optics Film Manufacturer Co ltd
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2020-12-11

Abstract

A coating composition for forming a silica film coating, the coating composition comprising (in parts by mass): 0.5-20 parts of polyalkoxysiloxane, 60-100 parts of organic solvent and 0.5-20 parts of water; wherein the polyalkoxysiloxane is:

wherein x > 0 and n is an integer > 1 and the R group is an alkyl group. In the present invention, the coating materialThe composition is based on polyalkoxysiloxane, and the polyalkoxysiloxane is catalyzed and hydrolyzed by using an acid catalyst, so that the obtained coating is stable in performance and can be stored for a long time, uniform, excellent-performance and strong-adhesion silicon dioxide-like coatings can be formed on the surfaces of different substrates, and the coating is strong in remodelability, wide in application range and high in application prospect.

Description

Coating composition for generating silicon dioxide film coating

Technical Field

The invention belongs to the technical field of coatings, and particularly relates to a coating composition for generating a silicon dioxide film coating.

Background

Sol-Gel functional coatings based on low molecular alkoxysilanes (e.g., tetraethoxysilane) are widely used in the glass industry, Electronics, Specialty packaging, solar cells, and construction (Sol-Gel technologies for Thin Films, Fibers, perforers, Electronics, and Specialty Shapes, eds Lisa C. Klein, published by Noyes Publications, 1988). Alkoxysilanes are used as binders in scratch-resistant coatings, and such coatings can greatly increase the surface hardness of polymers such as polycarbonates or polymethacrylates. Another use of alkoxysilanes is for antireflective coatings. WO2006/129973A1 describes a low refractive index coating with an antireflection effect, which coating consists of an alkoxysilane binder and porous nanoparticles. US6777069B2, in turn, discloses a method of forming an anti-reflective coating using an alkoxy group-containing silicone material to produce a low refractive index. Another use of alkoxysilane-based coating formulations is in water and oxygen barrier coatings on polymeric films. For example, the article Thin Solid Films 2005, 473, 351-356 reports barrier coatings prepared by condensation of different alkoxysilanes. Another use of alkoxysilanes is in the preparation of electroactive coatings, for example by adding electroactive compounds to coating solutions containing alkoxysilanes to impart antistatic and even conductive properties to the coating. Alkoxysilanes can also be used to prepare coatings with specific wetting properties, such as stain resistance (Accounts of Chemical Research 2014, 47, 2, 678-. Another important use of alkoxysilanes is primer coatings, by means of which good adhesion of organic coatings on inorganic substrates and vice versa can be achieved (e.g. US 5869140).

Coating by low molecular alkoxysilane solutions presents a number of problems. First, low molecular weight compounds have poor film forming properties, resulting in cracks, opacity, and gel particles in the film. This problem can be solved by multiple coating as suggested in US7157529B2, but this necessarily increases the production costs. The second is the aging problem. The hydrolytic condensation of the alkoxysilane during storage is continued, which tends to change the properties of the coating liquid with the passage of time. US2006/0286813A1 describes the preparation of a silica-like film by first coating a polyalkoxysiloxane film and subsequently curing it in an ammonia atmosphere. Although film formation and coating stability are improved by this method, ammonia gas is required in the coating process, which is expensive and highly equipment demanding. In addition, the use of non-reactive polyalkoxysiloxanes leads to dewetting on many substrates.

Disclosure of Invention

In view of the above problems, it is an object of the present invention to provide a coating composition for forming a silica thin film coating, which is based on polyalkoxysiloxane and is catalytically hydrolyzed by the polyalkoxysiloxane using an acid catalyst, and which can form a silica-like coating having uniform, excellent properties and strong adhesion on the surface of various substrates, wherein the coating composition is stable in performance and can be stored for a long period of time; and various functional coatings can be further prepared by adding different functional compounds based on the coating composition.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a coating composition for forming a silica thin film coating, comprising (in parts by mass): 0.5-20 parts of polyalkoxysiloxane, 60-100 parts of organic solvent and 0.5-20 parts of water; wherein the polyalkoxysiloxane is:

，（1）；

in formula (1), x > 0 and n are integers > 1, and the R group is an alkyl group.

In the invention, polyalkoxysiloxane is used to replace alkoxysilane, firstly, compared with alkoxysilane, polyalkoxysiloxane has a plurality of alkoxy groups, and the hydrolytic condensation activity is higher, so that the polymerization conversion rate of polyalkoxysiloxane liquid under acid catalysis is higher, and the stability of the coating is better; the molecular weight is higher, the degree of crosslinking of the polymer film is higher, and the film forming effect of the coating is good; finally, because the film-forming performance of the polyalkoxysiloxane is good, no coupling agent or only a small amount of coupling agent needs to be added, so that the phenomenon that the added coupling agent generates self-polymerization reaction to cause the increase of the coating particle size, the narrowing of the distribution and even the occurrence of the side effect of gel particles is avoided. The invention adopts the polyalkoxysiloxane with excellent self-film-forming property and stability, so the components of the coating composition are simplified, the control of the process flow is simple, the used production equipment is easy to obtain, and the invention has higher production and application prospects.

As a further preferred aspect of the present invention, the polyalkoxysiloxane is activated by hydrolysis with an acid catalyst, and the acid catalyst is one of a liquid protonic acid and a solid acid.

In the invention, the parameters such as the dosage, the time and the like of the solid acid are more controllable, so the solid acid is further preferably selected, particularly the cation exchange resin, and the molar concentration of the acid is controlled to be 0.001-1 mol/L.

As a further preferable aspect of the present invention, the molar ratio of the acid catalyst to the silicon atom in the coating composition is 0.0001 to 0.1: 1.

as a further preferred of the present invention, the organic solvent is one or more of alcohol, ketone, ether or ester; further preferably, the alcohol may be preferably methanol, ethanol, propanol, isopropanol, isobutanol, diethylene glycol, benzyl alcohol, phenethyl alcohol, and the ketone is preferably acetone, methyl ethyl ketone, methyl isobutyl ketone.

As a further preference of the present invention, the coating composition further comprises an adhesion-enhancing compound which is:

，（2）；

in the formula (2), n is an integer which is more than 1, and m is an integer which is more than 0; the Y group is a non-hydrolyzable organic group and the Z group is a hydrolyzable group.

In a further preferred embodiment of the present invention, the Y group includes one of an unsaturated vinyl group, an epoxy group, an amino group, a carboxylic acid group, a phosphoric acid group, a hydroxyl group, an isocyanate group, and a succinimide group, and the Z group includes one of an alkoxy group, a carboxyl group, a halogen atom, and an amino group.

As a further preferred of the present invention, the coating composition further comprises a light-effect agent, wherein the light-effect agent is one of a metal oxide, a nanoparticle having a mesoporous or hollow structure, an aromatic group-containing silane, and a perfluoroalkylsilane.

In the present invention, the metal oxide may be tin oxide, antimony-doped tin oxide, indium-doped tin oxide, fluorine-doped tin oxide, zinc-doped tin oxide, indium-doped zinc oxide, germanium oxide, cerium oxide, aluminum oxide, zinc oxide, zirconium oxide, titanium oxide, silicon nitride, or the like; these compound particles can impart compatibility with a coating material by surface adsorption or chemical grafting of an organic or inorganic group; nanoparticles having a mesoporous or hollow structure, preferably mesoporous silica particles; the aromatic group-containing silane can be 1-naphthyl trimethoxysilane or 9-anthryl trimethoxysilane; the perfluoroalkylsilane is preferably one of 1H,1H,2H, 2H-perfluorodecyltrimethoxysilane and 1H,1H,2H, 2H-perfluorooctyltrimethoxysilane.

As a further preferred of the invention, the coating composition further comprises a wetting agent, wherein the wetting agent is one of perfluoroalkane silanes, in particular one of 1H,1H,2H, 2H-perfluorodecyltrimethoxysilane and 1H,1H,2H, 2H-perfluorooctyltrimethoxysilane.

In a further preferred embodiment of the present invention, the adhesion-enhancing compound is one of methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, mercaptopropyltrimethoxysilane and mercaptopropyltriethoxysilane.

In a further preferred embodiment of the present invention, the liquid protonic acid is one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and the solid acid is a cation exchange resin.

In the present invention, an antioxidant, an antistatic agent, a light stabilizer, an inhibitor, a leveling agent, a non-reactive polymer, a surfactant, a lubricant, and the like may be further added to the coating composition for imparting more properties to the coating, for example, zirconia particles are added to increase hardness to prepare an abrasion resistant coating, and a compound having a layered structure, such as synthetic hectorite, graphene, is added to increase barrier properties to prepare a protective coating.

In the present invention, the coating composition is not particularly limited to the substrate, and the substrate may be metal, ceramic, glass, plastic, wood, slate, or the like. Among them, the plastic substrate may include polycarbonate, polymethylmethacrylate, polystyrene/polymethylmethacrylate copolymer, polystyrene, polyester, polyolefin, triacetyl cellulose resin, allyl diglycol dicarbonate, ABS resin, styrene-acrylonitrile copolymer, polyamide, epoxy resin, melamine resin, cyclic polyolefin resin, and the like.

In the present invention, the coating composition can be applied by various existing coating methods, such as meniscus (blade) coating, spin coating, spray coating, dip coating, roll coating, slit coating, and the like. The wet film thickness of the coating is dependent on the content of the constituents of the coating composition obtained according to the invention and the desired dry film thickness after drying and curing.

In the present invention, the condensation of the activated polyalkoxysiloxane can be carried out at room temperature, or can be accelerated by heating; and the secondary crosslinking process can be realized by using an ultraviolet free radical polymerization method.

In conclusion, the invention has the following beneficial effects:

the coating prepared by the coating composition has the characteristics of high hardness, good toughness, strong adhesive force and transparency.

In the invention, the synergist and the reinforcing agent which can be used conventionally can be directly added into the polyalkoxysiloxane liquid, so that the coating has new functional characteristics, can be highly modified and can be suitable for different substrates or application fields.

The composition has wide raw material source and lower cost.

The equipment used in the preparation method of the coating composition is simpler, the whole process flow is basically consistent with the prior art, and the preparation method can be directly replaced into the prior art.

Drawings

FIG. 1 is a scanning electron micrograph of example 2 of the present invention.

Detailed Description

Example 1

Connecting a 500ml three-necked flask with a Vickers fractionating column and a distillation device, introducing nitrogen for protection, and sequentially adding 139.2g of tetraethoxysilane and 64g of absolute ethyl alcohol under magnetic stirring (500 rmp); cooling in ice water bath for 10min, and slowly adding mixed solution of 6.9g concentrated hydrochloric acid (37%) and 10g deionized water; then heating to 80 ℃ for reaction for 5h, keeping the temperature, vacuumizing by using a film pump, and slowly evaporating free ethanol; then heating to 135 ℃ under the high vacuum degree of an oil pump (1 multiplied by 10 < -3 > mbar) for further hydrolytic condensation, and distilling out residual low molecular compounds; after 2h the reaction was complete and a clear viscous liquid was obtained. The complete hydrolytic condensation of 10g of this compound gives 4.6g of silica and the formula of this compound is calculated as:

；

the weight average molecular weight of the product was 830 g/mol as determined by gel chromatography with chloroform as the eluate and polystyrene calibration.

Example 2

2.1g of polyethoxysiloxane synthesized in example 1 was dissolved in 18g of isopropanol, 0.3g of hydrochloric acid with a concentration of 0.15 mol/L was then added, and the resulting solution was stirred at room temperature for 8 hours to give a stable, transparent solution; and (3) rolling the transparent solution onto the surface of a polyethylene terephthalate (PET) film through a 300-line/inch anilox roller, drying the film for 2min at room temperature, sending the film into a blast oven, and continuously drying the film for 2min at 80 ℃ to obtain a transparent high-adhesion silicon dioxide film on the surface of the PET. The scanning electron microscope result is shown in figure 1, and the surface of the film is flat, uniform and free of cracks.

Example 3

2.1g of polyethoxysiloxane synthesized in example 1 is dissolved in 18g of isopropanol, 0.3g of deionized water and 0.2g of cation exchange resin (Amberlyst 15) are added, the obtained system is shaken for 8h at room temperature, and then the ion exchange resin is removed by filtration to obtain a stable transparent solution; the solution is coated on the surface of a PET film by a roller through a 300-line/inch reticulate pattern, the film is sent into a blast oven after being dried for 2min at room temperature, and the film is continuously dried for 2min at 80 ℃, so that a transparent, high-adhesion and uniform silicon dioxide film is obtained on the surface of the PET film.

Comparative example 1

Comparative example 1 was set up to differ from example 3 in that the polyethoxysiloxane prepared in example 1 was replaced with a tetraalkoxysilane.

Comparative example 2 was set up, differing from example 3 in that the polyethoxysiloxane prepared in example 1 was replaced with a mixture of tetraalkoxysilanes and trialkoxysilanes.

Comparative example 3 was set up, except that the polyethoxysiloxane prepared in example 1 was replaced with a mixture of ethyl orthosilicate, methyltrimethoxysilane, gamma-methacryloxypropyltrimethylsilane.

The solutions prepared in examples 2 and 3, and comparative examples 1 to 3, and the obtained silica films were subjected to performance tests:

viscosity: placing the transparent solution in an environment of 25 ℃ for 24 hours, and testing the viscosity at the environment of 25 ℃ by using a rotary viscometer;

thickness of the silicon dioxide film layer: testing according to GB 1767-1979;

hardness: testing the pencil hardness according to GB/T6739-2006;

adhesion force: tested according to GB/T9286-1998, the grade 0 is the best, and the grade 5 is the worst;

toughness: impact resistance was tested according to GB/T1732-1993 at 50cm, 1 kg.

The results of the above tests are shown in the following table:

according to the data, the coating composition prepared by the invention has the advantages that the thickness of a formed film layer is small, the hardness can reach 2H, the toughness is high, and the adhesive force is good; in comparative examples 1 and 2, only the most basic alkoxysilane or a mixture thereof had a poor film-forming effect without adding a reinforcing agent such as a coupling agent; in contrast, in comparative example 3, the currently popular mixture of ethyl orthosilicate, methyltrimethoxysilane and gamma-methacryloxypropyltrimethylsilane is used, and the effects of hardness, toughness and the like of the prepared film are not yet met.

The inventors further studied coating compositions having special functionality based on examples 1 to 3:

example 4

2.1g of polyethoxysiloxane synthesized in example 1 and 0.2g of methacryloxypropyltrimethoxysilane are dissolved in 18g of isopropanol, 0.4g of deionized water and 0.3g of ion exchange resin (Amberlyst 15) are added, the obtained system is shaken for 8 hours at room temperature, then the ion exchange resin is removed by filtration, and a stable and transparent solution is obtained; the solution was roll coated onto the surface of the silicon nitride film coated PET film by a 300 line/inch screen. After drying at room temperature for two minutes, the film was fed into a forced air oven and allowed to dry at 80 ℃ for an additional 2 minutes, after which a further 300 line/inch cross-hatch was applied to the surface of the coating by means of a roll coating of an acrylate UV-curable hard coating WS-1050 (Khalada industries, Ltd.). The adhesion of the hard coating on the substrate can reach 0 grade due to the base coating containing the activated polyalkoxysiloxane, and the performance is further enhanced.

Example 5

2.1g of polyethoxysiloxane synthesized in example 1 is taken and dissolved in 18g of isopropanol, then 0.3g of hydrochloric acid with the concentration of 0.15 mol/L is added, the obtained system is stirred for 8 hours at room temperature to obtain a stable transparent solution, then 0.2g of aminopropyltriethoxysilane is added and the stirring is continued for 4 hours to obtain a solution; the obtained solution was roll-coated on the surface of a silicon nitride film-coated PET film through a 300-line/inch anilox roll, and after drying at room temperature for 2min, the film was sent to a forced air oven, and further dried at 80 ℃ for 2min, and then a polyurethane thermosetting hard coating SAU1501 (west ampere space triple chemical limited) was further coated on the surface of the coating through a 300-line/inch anilox roll. The adhesion of the hard coating on the substrate is greatly improved and can reach the best grade due to the base coating containing the activated polyalkoxysiloxane.

Example 6

The method is suitable for preparing the glass surface anti-reflection coating and the surface anti-reflection coating thereof: 2.1g of polyethoxysiloxane synthesized in example 1 was dissolved in 10g of isopropanol, 0.8g of hydrochloric acid with a concentration of 0.15 mol/L was then added, and the resulting solution was stirred at room temperature for 8 hours to give a stable, transparent solution; then adding isopropanol to adjust the solid content of the solution to 4.2%; an isopropanol dispersion (Ningpott particle technologies, Inc.) of hollow silica particles having an average particle diameter of 55nm and an average wall thickness of 6nm was diluted with isopropanol to a solid content of 2.8%; the obtained mixture was mixed with an activated polyalkoxysiloxane paint having a solid content of 4.2% by mass to obtain the desired anti-reflective paint. The coating is coated on the surface of glass in a dip-coating mode, the pulling speed is 2.7mm/s, and the coated glass is dried for 5min at room temperature and then cured for 5min at 500 ℃. The average reflectivity of the obtained glass in the wavelength range of 380-760nm is 2.0 percent, and the haze is less than 0.8 percent.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

1. A coating composition for forming a silica film coating is characterized by comprising the following components in parts by mass: 0.5-20 parts of polyalkoxysiloxane, 60-100 parts of organic solvent and 0.5-20 parts of water; wherein the polyalkoxysiloxane is:

，（1）；

2. A silica film coating forming coating composition as claimed in claim 1 wherein said polyalkoxysiloxane is activated by hydrolysis with an acid catalyst, said acid catalyst being one of a liquid protonic acid and a solid acid.

3. The silica thin film coating forming coating composition of claim 2, wherein the molar ratio of the acid catalyst to the silicon atoms in the coating composition is 0.0001 to 0.1: 1.

4. the silica film coating forming coating composition of claim 1, wherein the organic solvent is one or more of an alcohol, a ketone, an ether, or an ester.

5. A silica film coating forming coating composition according to claim 2, further comprising an adhesion enhancing compound, said adhesion enhancing compound being:

，（2）；

6. The silica film coating forming coating composition of claim 5 wherein said Y group comprises one of an unsaturated vinyl group, an epoxy group, an amino group, a carboxylic acid group, a phosphoric acid group, a hydroxyl group, an isocyanate group, and a succinimide group, and said Z group comprises one of an alkoxy group, a carboxyl group, a halogen atom, and an amino group.

7. The coating composition for forming a silica thin film coating according to any one of claims 2 to 6, further comprising a photo-effective agent, wherein the photo-effective agent is one of metal oxide, nano-particles having a mesoporous or hollow structure, silane containing an aromatic group, and perfluoroalkylsilane.

8. A silica film coating forming coating composition as claimed in any one of claims 2 to 6 further comprising a wetting agent which is one of perfluoroalkylsilanes.

9. The silica film coating forming coating composition of claim 6, wherein the adhesion enhancing compound is one of methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, aminopropyltriethoxysilane, aminopropyltrimethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane.

10. A silica film coating forming coating composition as claimed in claim 2 wherein said liquid protonic acid is one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and said solid acid is a cation exchange resin.