CN119895006A

CN119895006A - Adhesive agent

Info

Publication number: CN119895006A
Application number: CN202380067083.3A
Authority: CN
Inventors: D·斯坦森斯; R·加勒; H·德库克莱
Original assignee: Insolek LLC
Current assignee: Insolek LLC
Priority date: 2022-09-19
Filing date: 2023-09-15
Publication date: 2025-04-25
Also published as: EP4590778A1; BE1030889A1; BE1030889B9; WO2024061769A1; BE1030889B1

Abstract

The invention relates to an adhesive, a method for the production thereof and a product obtained by means of the adhesive. The binder contains at least powder, water glass and a cross-linking agent. The powder contains carbohydrates and proteins. The ratio of the mass of the powder to the mass of the solid of the water glass is between 50:1 and 2:1.

Description

Adhesive agent

The present invention relates to adhesives for bonding particles, fibers, layers, strands or components (par), for example for producing engineered wood products, and to methods of making the adhesives. The invention also relates to products bonded with the adhesive, and to methods of bonding such products with the adhesive.

In engineered wood products, adhesives are used to join wood particles, wood fibers, wood strands, wood layers, and/or other wood ingredients or components. Examples of such engineered wood products are chipboard, wood fiberboard (e.g., MDF-medium density fiberboard and HDF-high density fiberboard, OSB-oriented strand Board (Or IENTED STRAND Board)), and laminates.

It is also possible to combine cellulose fibres or cellulose products into a board. Non-limiting examples are bamboo, straw, hemp or hemp bundles, kenaf.

The most common binders used in the production of engineered wood products are aminoplast polymers, produced via polycondensation of urea and formaldehyde to form urea formaldehyde resins (UF resins). Optionally, melamine is added and melamine urea formaldehyde resin (MUF resin) is obtained, or melamine and phenol are added to form melamine urea formaldehyde resin (MUPF resin). The main advantages of formaldehyde-based binders are their low cost (due to the use of inexpensive raw materials in their preparation) and their high reactivity. A disadvantage of such binders in engineered wood products is that they emit formaldehyde during and after polymerization. As a result, more and more people are looking for ways to limit formaldehyde emissions or even reduce formaldehyde emissions to zero. This is why formaldehyde-free binders for the production of engineered wood products have been sought after.

US2006/0163769 describes the use of water glass as a binder in the production of fire-resistant engineered wood products.

Known formaldehyde-free binders for use in the production of engineered wood products consist of the polymer methylene diphenyl diisocyanate (pMDI). These pMDI adhesives result in wood products with high strength and good water resistance. However, these adhesives have a number of drawbacks. First, they are much more expensive than the conventionally used aminoplasts, which results in a significant increase in the cost of the engineered wood product. On the other hand, such adhesives have lower stability than classical aminoplasts, have a strong tendency to stick to process equipment (which furthermore leads to the need for frequent cleaning of the process equipment) and can lead to release of isocyanate monomers upon application. This has an adverse effect on the efficiency of the production process of the engineered wood product.

The pMDI adhesive has better adhesive strength than conventionally used aminoplasts, so that less adhesive is required. However, this may be disadvantageous because a smaller amount of adhesive may result in an insufficient distribution of adhesive over the substrate.

US4190459a describes a process for producing mineral fibre mats (mat) for use as insulation. The mineral fibres are connected together by means of a binder, which is applied in the form of a so-called emulsion of water glass and isocyanate. Water glass having a solids content of between 40 and 55 mass% is proposed in US 4190459A. The so-called emulsion mentioned in US4190459a has an initial viscosity of 10000 mpa.s. However, such so-called emulsions are unstable, since the viscosity increases rapidly over time.

CA2019382A1 mentions in its prior art section US4190459A and states that the emulsion described in US4190459A has limited stability. CA2019382A1 describes the use of a mixture of isocyanate and sufficient metal soap as a binder in the product of worker Cheng Mu. The metal soap is used as a blocking compound to prevent the reaction between water and isocyanate, so that a sufficient amount of the metal soap is required. In addition, CA2019382A1 describes that water glass can also be blended into a mixture of isocyanate and sufficient metal soap to form an emulsion.

WO2022/049513A1 describes adhesives for engineered wood products. The binder is an emulsion of isocyanate in water. The isocyanate contains one or more of a diisocyanate, a polyisocyanate, a derivative of a diisocyanate, or a derivative of a polyisocyanate. The emulsion also contains water glass. The ratio of the combined mass of water and water glass on the one hand to the isocyanate mass on the other hand in the emulsion is preferably between 1.2 and 6.

It is an object of the present invention to provide formaldehyde-free binders which are suitable for bonding natural substrates and which can be readily used as binders in the production of industrial Cheng Mu products, such as wood veneer boards, wood fiber boards (e.g. MDF-boards and HDF-boards), OSB-boards and laminates.

To achieve this object, the invention has various aspects.

A first aspect of the invention is an adhesive. The binder is characterized in that the binder at least comprises powder, water glass and a cross-linking agent, wherein the powder comprises carbohydrate and protein. The water glass is a combination of Na ₂ O and SiO ₂ in water. The ratio of the mass of powder to the mass of solids of the waterglass is between 50:1 and 2:1, preferably between 30:1 and 3:1.

In the context of the present invention, the terms "binder" and "adhesive" are synonymously used with respect to a compound having a degree of adhesive properties, essentially providing the ability to bond between two or more sheets of material. Also, the terms "bond" and "bonding" are synonymously used with respect to the act of providing a bond between two or more sheets of material.

The binder is formaldehyde-free, stable, easy to produce and can be easily used as a binder in the production of industrial Cheng Mu products such as particleboard, wood fiber board (e.g. MDF-board and HDF-board), OSB-board and laminates.

The ratio of the mass of the powder of the binder of the first aspect of the invention to the mass of the solids of the water glass provides better stability of the binder, giving the binder good workability.

As mentioned above, water glass is a combination of Na ₂ O and SiO ₂ in water. The (molar) ratio between SiO ₂:Na₂ O and the mass of solids of the water glass (in water) can be varied. For example, the SiO ₂:Na₂ O molar ratio of water glass 2.0 is 2.0:1. Thus, 1 gram of water glass 2.0 (having a solids content of 40 mass%) contained 0.13 gram of solid Na ₂ O. For example, the SiO ₂:Na₂ O molar ratio of water glass 3.4 is 3.4:1. Thus, 1 gram of water glass 3.4 (having a 37 mass% solids content) contained 0.084 grams of solid Na ₂ O. Solid sodium silicate typically has a high Na ₂ O content, which dissolves in water, corresponding to a water glass of 1.0 to 1.5, or in other words a SiO ₂:Na₂ O molar ratio of 1.0:1 to 1.5:1.

In the context of the present invention, "solids content" refers to the mass percent of solids, unless otherwise indicated.

A preferred embodiment of the first aspect of the invention is characterized in that the ratio of the mass of the powder to the mass of solid Na ₂ O of the waterglass is between 140:1 and 6:1, preferably between 80:1 and 10:1, more preferably between 60:1 and 15:1.

The ratio of the mass of the powder according to this embodiment of the invention to the mass of solid Na ₂ O of the water glass also ensures good water resistance of the engineered wood product bonded with this binder.

In the first aspect of the invention, the powder preferably consists essentially of protein and carbohydrate. The powder may also contain an amount of water, i.e. the powder feels dry on its own.

Typically, powders have only limited solubility in water. As a result, a suspension having a sufficiently low viscosity and a sufficiently high solids content can be obtained. An adhesive having a low viscosity may be sufficiently distributed over the substrate, for example by spraying or sprinkling the adhesive. In principle, the adhesive can always have a sufficiently low viscosity by adding sufficient water, but excessive water leads to an excessively high pressure build-up when pressing the bonded substrate, which can cause cracks in the cured substrate.

The use of carbohydrates (e.g. starch) and proteins as binders is known each separately. Prior to the development of formaldehyde-based binders, proteins (e.g., gelatin) were typically used as binders. Starch is also commonly used as an adhesive in, for example, the paper industry where different paper layers are bonded together. However, first the starch is boiled, so that the crystalline phase of the starch is destroyed and the adhesion of the starch is improved. In all these cases, adhesives with low solids content and high viscosity are obtained.

It is the object of the present invention to prepare adhesives in which the carbohydrates present maintain their crystal structure. Furthermore, the presence of proteins in the powder ensures further insolubility of the powder in water at temperatures below 50 ℃. At higher temperatures (preferably greater than 60 ℃) the crystalline structure of the carbohydrate may be destroyed and the affinity of the powder for water is increased, with a significant increase in viscosity.

The binder may be produced by initially placing the powder in an aqueous suspension, preferably by high shear or turbulence. Because powders have limited solubility in water due to their composition, suspensions with high solids content can be obtained, while the viscosity is limited. As mentioned previously, low viscosity is important to be able to distribute the resulting adhesive sufficiently over the substrate, for example by spraying the adhesive.

In the next stage of producing the adhesive according to the invention, water glass may be added to the aqueous suspension of powder. The water glass interacts with the powder. This results in a gentle increase in viscosity and activation of the powder. This activation also ensures an improved dispersing ability of the powder and the addition of the cross-linking agent at a later stage results in a homogeneous and stable suspension.

In the next process step, a cross-linking agent capable of reacting with both the substrate and the powder may be added to the aqueous suspension of powder and water glass. Preferably, a crosslinker containing isocyanate, epoxy groups, azetidinium (azet idinium) and/or cyclic anhydride groups is used.

An important advantage of the present invention is that a stable suspension of the crosslinking agent (e.g. isocyanate) in water is obtained. The combination of powder and water glass thus acts as a crosslinker dispersant.

The addition of water glass provides improved adhesive strength of the powder. After the adhesive is applied, pressure is applied at an elevated temperature. At this elevated temperature, the proteins of the powder denature and the carbohydrates lose their crystallinity. At this elevated temperature, functional groups are also released mainly on the protein, as a result of which the water glass connected to the powder undergoes a hardening reaction. These functional groups are therefore hidden at low temperatures and are only expressed when the adhesive is heated to a temperature of greater than 50 ℃.

Since inexpensive water glass will also contribute to the adhesive strength, the amount of expensive crosslinking agent can remain limited. The amount of water glass is therefore preferably chosen such that the water glass functions not only as a dispersant but also to a large extent as a binder component. This allows less cross-linking agent to be used and thus a cheaper adhesive (and cheaper engineered wood products produced using such an adhesive) to be obtained which can be dosed and distributed evenly.

An important advantage of the present invention is that the cross-linking agent not only acts as a chain extender for the powder, but also reacts with hydroxyl groups of the substrate (e.g. wood) to improve the adhesive strength.

Water glass can furthermore lead to an improvement in the reactivity of the hydroxyl groups of the wood on the one hand and the crosslinking agent (e.g. isocyanate) on the other hand. The water glass thus functions not only as an emulsifier for the crosslinking agent (e.g. isocyanate). When using the binder and at the same time raising the temperature and after evaporation of the water, the suspension is destroyed and the water glass can act as a catalyst for the reaction of the crosslinking agent (e.g. isocyanate) with the hydroxyl groups of the wood.

A preferred embodiment of the first aspect of the invention is characterized in that the carbohydrate and protein containing powder is obtained by milling a plant material such as cereal (e.g. wheat, rye, barley, millet, rice or oat), maize, sugar beet, nuts (e.g. palm nut or coconut), seeds (e.g. rapeseed, linseed or sunflower seed) or beans (e.g. soybean, pea, lentil, broad bean), or the carbohydrate and protein containing powder is a combination of two or more of these.

These are readily available raw materials from which the powder can be extracted. An important advantage is also that different raw materials can be used. The production of the adhesive according to the invention is therefore not limited to one specific raw material.

A more preferred embodiment of the first aspect of the invention is characterized in that the powder is obtained by grinding beans (beans) such as soybeans, peas, lentils, fava beans.

A preferred embodiment of the first aspect of the invention is characterized in that the powder is a starch and/or flour, such as cereal starch and/or flour (e.g. wheat, rye, barley, millet, rice or oat), low-grade flour, corn starch and/or flour, beet starch and/or flour, nut starch and/or flour (e.g. palm nut or coconut), seed starch and/or flour (e.g. from rapeseed, linseed or sunflower) or legume starch and/or flour (e.g. from soybean, pea, lentil, broad bean), or a combination of two or more of these.

As is generally known, the terms "starch" and "flour" are used interchangeably with respect to powders obtained from grinding plant materials.

A more preferred embodiment of the first aspect of the invention is characterized in that the powder is soy starch and/or flour, such as soy flour, pea starch, broad bean starch, or a combination of two or more of these.

Flour and starch are readily available. An important advantage is also that different types of flour and/or starch can be used. The production of the binder according to the invention is thus not limited to one specific raw material or flour and/or starch type.

A particularly interesting class of flours for use in the present invention is the so-called "low-grade flours", which are residual materials of wheat flour production. Because of the relatively brown color of low-grade flour, this product has been declared unsuitable for producing wheat bread and is processed into animal feed. The low-grade flour has a higher protein to carbohydrate ratio than the grain from which the low-grade flour is obtained. Without wishing to be bound by any theory, the inventors suspect that a higher protein to carbohydrate ratio may result in better adhesive properties.

A preferred embodiment of the first aspect of the invention is characterized in that the powder in water is obtained by a process of fermenting a plant material.

This allows the preparation of powders from residual streams of the agricultural industry and thus improves the value of these residual streams. During such fermentation, microorganisms (e.g., fungi or bacteria) convert the natural raw materials into powders in aqueous suspension. These powders have a homogeneous combination of carbohydrates and proteins.

A preferred embodiment of the first aspect of the invention is characterized in that the ratio of the mass of protein to the mass of carbohydrate in the powder is between 2:1 and 1:30, preferably between 1.5:1 and 1:15, more preferably between 1:2 and 1:10.

A preferred embodiment of the first aspect of the invention is characterized in that the viscosity of the adhesive is less than 1000mpa.s, preferably less than 500mpa.s, at 25 ℃.

Adhesives having such viscosity values ensure good distribution of the adhesive over the products to be bonded. Due to its low viscosity, the adhesive can also be applied by spraying. These viscosity values also ensure good penetration of the adhesive into the pores of the product to be bonded. The workability of the adhesive is thus better due to the low viscosity.

A preferred embodiment of the first aspect of the invention is characterized in that the powder, water glass and the cross-linking agent are uniformly distributed in the binder.

This embodiment has the advantage that the adhesive can be used as a one-component system. The adhesive can be stored and used easily without further limitation.

A preferred embodiment of the first aspect of the invention is characterized in that the adhesive is a two-component adhesive having a first component and a second component. Wherein the first component is different from the second component in the presence of the powder and the cross-linking agent, respectively.

The first component may contain no water glass, or a portion of water glass or the entire amount of water glass. If the first component contains a portion of water glass or the entire amount of water glass, this facilitates dispersing the powder.

The second component may contain no water glass, or a portion of water glass or the entire amount of water glass. If the second component contains a portion of water glass or the entire amount of water glass, this promotes emulsification of the crosslinking agent in the second component.

In the case of two-component adhesives, the two components may be stored separately and mixed when an adhesive is desired, or applied separately to the product to be bonded. The separate storage of the two components of the (two-component) adhesive provides an extended shelf life of the adhesive.

A preferred embodiment of the first aspect of the invention is characterized in that the solids content in the binder is between 10 and 40 mass%, preferably between 15 and 35 mass%.

The adhesive according to this embodiment is easy to process and does not have to transport too much water when transporting the adhesive.

A preferred embodiment of the first aspect of the invention is characterized in that the crosslinker is a product comprising at least two isocyanate groups, preferably wherein the crosslinker comprises one or more of a diisocyanate, a polyisocyanate, a derivative of a diisocyanate or a derivative of a polyisocyanate.

Such a crosslinking agent is readily available. Furthermore, a limited amount of such a crosslinking agent is sufficient.

A preferred embodiment of the first aspect of the invention is characterized in that the cross-linking agent is a derivative or polymer of methylene diphenyl diisocyanate (MDI), preferably a polymer of methylene diphenyl diisocyanate (pMDI).

Such cross-linking agents are also readily available and again a limited amount of such cross-linking agents is sufficient.

In principle, various types of isocyanates can be used in the present invention. However, the polymer methylene diphenyl diisocyanate (pMDI) is preferred. Unlike many other isocyanates, the polymer methylene diphenyl diisocyanate (pMDI) is less or even not compatible with water. In many types of isocyanates, water reacts with isocyanate groups, resulting in the release of carbon dioxide. Because polymeric methylene diphenyl diisocyanate (pMDI) and water show little or no compatibility, there is only a limited reaction when water and polymeric methylene diphenyl diisocyanate (pMDI) are contacted. This is caused by the fact that when water and polymeric methylene diphenyl diisocyanate (pMDI) are mixed and the mixing is stopped, the water and polymeric methylene diphenyl diisocyanate (pMDI) are separated from each other. However, the suspension is stabilized using the powder according to the invention and water glass.

In addition, the polymer methylene diphenyl diisocyanate (pMDI) has a large number of reactive groups per molecule. This is advantageous for the adhesive strength, since a crosslinked dense network is obtained. The polymer methylene diphenyl diisocyanate (pMDI) is furthermore the cheapest choice for the commercially available isocyanate.

Because of these aspects, the polymer methylene diphenyl diisocyanate (pMDI) allows the advantages of the suspension according to the invention to be obtained in an optimal manner, wherein the cost of the adhesive and the product to be combined with the adhesive is low.

A preferred embodiment of the first aspect of the invention is characterized in that the cross-linking agent is a product containing at least two epoxide groups, or at least two cyclic anhydride groups, or at least two azetidinium functions, or a mixture of two or more of these products.

These crosslinking agents are products containing functional groups that are highly reactive with hydroxyl and/or carboxyl groups.

Examples of crosslinking agents which contain at least two epoxide groups and which can therefore be used in the present invention are bisphenol a (BPA) diepoxide, glycidyl cyclohexene oxide, epoxidized soybean oil or linseed oil, multifunctional glycidyl ethers or esters. Examples of azetidinium-containing crosslinkers are those used in the paper industry to make paper stronger mainly under wet conditions, such as Kymene 557H. Examples of crosslinking agents containing cyclic anhydrides are maleated oils such as those from soybean oil or linseed oil.

The advantage is that different types of crosslinking agents can be used. The present invention is not limited to the use of one type of crosslinker.

A preferred embodiment of the first aspect of the invention is characterized in that the ratio of the mass of the cross-linking agent to the mass of the powder is between 1:15 and 2:1, preferably between 1:10 and 1:1, more preferably between 1:8 and 1:1.25, even more preferably between 1:2.5 and 1:1.5.

The amount of cross-linking agent used in the adhesive may thus be limited. This reduces the price of the adhesive, as the crosslinker represents the most expensive of the adhesives.

A preferred embodiment of the first aspect of the invention is characterized in that the adhesive comprises a thermoplastic adhesive component, preferably a biorenewable thermoplastic adhesive component, such as an aqueous dispersion of natural latex or polylactic acid.

The adhesive may be tailored for a particular application. The use of a thermoplastic adhesive component allows for a reduced amount of cross-linking agent. In addition, the use of a biorenewable thermoplastic adhesive component ensures the "natural" nature of the adhesive.

A preferred embodiment of the first aspect of the invention is characterized in that the molar ratio of SiO ₂ to Na ₂ O in the water glass is between 4 and 1.5, preferably between 3.8 and 2.0, more preferably between 3.5 and 2.5, even more preferably between 3.5 and 2.8.

It appears that the use of the adhesive according to this embodiment results in a higher water fastness of the combined product. A relatively small amount of Na ₂ O in the water glass, relative to the amount of SiO ₂, appears to achieve this feature.

A preferred embodiment of the first aspect of the invention is characterized in that the adhesive contains one or more of a water repellent additive, a catalyst, a dye, a pigment, a flame retardant, a cold tack improver (cold tack improver), or a foaming agent.

The adhesive may contain such additives to impart specific properties to the bonded product and/or to improve the workability of the adhesive. Examples of water repellents which can be used are wax emulsions (for example based on paraffin waxes or hydrogenated vegetable oils), olefin-ketene dimers and alkyl succinic anhydrides. Preferably, these waterproofing agents are added in the form of an emulsion. Examples of catalysts that accelerate and improve the reaction between the hydroxyl groups of wood and isocyanate crosslinkers (e.g. pMDI) are tertiary amines and tin derivatives, which are well known in the polyurethane industry.

A preferred embodiment of the first aspect of the invention is characterized in that the D ₅₀ value of the particle size distribution by volume of the powder measured by laser diffraction (Beckman coulter laser diffraction device LS13 320) in the aqueous dispersion is less than 200 microns, preferably less than 100 microns, more preferably less than 50 microns, even more preferably less than 30 microns. The D ₅₀ value is the particle size (in microns) where 50% of the particles are smaller than this value.

These embodiments provide better adhesive stability and good adhesive efficiency.

A preferred embodiment of the first aspect of the invention is characterized in that the D ₉₀ value of the particle size distribution by volume of the powder measured by laser diffraction in the aqueous dispersion is less than 200 microns, preferably less than 100 microns. The D ₉₀ value is the particle size (in microns) where 90% of the particles are smaller than this value.

In a further aspect, the present invention provides a method of preparing an adhesive as described herein, the method comprising the steps of:

-mixing the powder and water to obtain a first aqueous suspension;

adding water glass and a cross-linking agent to the first aqueous suspension, and

-Further mixing the resulting suspension to obtain a binder;

Wherein the powder contains carbohydrates and proteins, wherein the water glass contains a combination of Na ₂ O and S iO ₂, and wherein the ratio of the mass of the powder to the mass of the solids of the water glass is between 50:1 and 2:1, preferably between 30:1 and 3:1.

A preferred embodiment of the method for preparing the adhesive of the invention is characterized by mixing the powder and water by high shear or turbulence.

A preferred embodiment of the method for producing the adhesive according to the invention is characterized in that water glass is first added to and mixed with the first aqueous suspension before the crosslinking agent is added.

As mentioned above, the affinity of the powder may be increased at elevated temperatures, e.g. 60 ℃ or higher, resulting in an increase in viscosity. In order to avoid or minimize the increase in viscosity, it may be preferred to maintain the temperature during the process steps below 60 ℃, e.g. below 50 ℃, below 40 ℃, and even below 30 ℃. The temperature may be maintained by any suitable means known in the art, such as cooling means.

A preferred embodiment of the method for preparing the adhesive according to the invention is characterized in that the temperature during the preparation of the first aqueous suspension and/or the adhesive is maintained below 60 ℃, preferably below 50 ℃, more preferably below 40 ℃ and even more preferably below 30 ℃.

It may be advantageous for the adhesive strength of the adhesive if the adhesive is applied to or mixed with the substrate shortly after the crosslinker has been added to the powder, water glass and water (e.g. within 1 hour, within 50 minutes, within 40 minutes, within 30 minutes, even within 10 minutes after the crosslinker has been added to the other components of the adhesive). By using the binder shortly after the crosslinker has been added to the powder, water glass and water, less crosslinker may have reacted with the powder and thus more crosslinker may still be available to react with the hydroxyl groups of the substrate (e.g., wood).

In yet another aspect, the invention provides an adhesive prepared according to the method as defined herein.

In yet another aspect, the invention provides a product. The product comprising particles, fibres, layers, bundles or components, wherein the particles, fibres, layers, bundles or components are bonded together using a binder according to any of the embodiments of the first aspect of the invention in a compression process at an elevated temperature, wherein water evaporates from the binder and the binder provides a combination of particles, fibres, layers, bundles or components. In the product, the mass ratio of the total amount of particles, fibers, layers, bundles or ingredients to the solids content of the binder is between 99:1 and 92:8, preferably between 98:2 and 95:5.

A preferred embodiment of the product according to the invention is characterized in that the mass ratio of the solids of the cross-linking agent in the binder to the total amount of particles, fibers, layers, bundles of the product is between 0.5 and 2 mass%, preferably between 0.75 and 1.75 mass%, more preferably between 1 and 1.5 mass%.

As previously mentioned, inexpensive water glass contributes to the adhesive strength, which allows the use of smaller amounts of expensive cross-linking agents in the adhesive relative to the total amount of particles, fibers, layers, bundles in the product.

The binder does not contain formaldehyde. Bonding may be achieved using a small amount of adhesive.

Preferably, the product is a board, such as a wood fibre board (e.g. MDF board or HDF board), a particleboard, an OSB (oriented strand board) board or a laminate. The product may also be a moulding in which the bonded wood components are pressed in a mould to a desired shape, for example for the preparation of pallet blocks.

In a preferred embodiment of the invention, the particles, fibers, layers, bundles or ingredients are wood-based or cellulose-based, such as bamboo, straw, reed, hemp, palm, miscanthus, bagasse, molasses, or agricultural waste streams.

It appears that the adhesive is particularly suitable for bonding wood components, such as wood chips, strands or wood fibers together.

A final aspect of the invention relates to a method of preparing a product. The method comprises the following steps:

-providing a quantity of particles, fibers, layers, bundles or components;

-applying a binder according to any of the embodiments of the first aspect of the invention to the particles, fibres, layers, bundles or components;

Shaping the mixture of particles, fibres, layers, bundles or components and binder, for example in the form of a sheet;

-curing the binder at an elevated temperature and under pressure, wherein water evaporates from the binder, and wherein curing of the binder results in a product wherein the particles, fibers, layers, bundles or components are bound together by the binder.

In principle, the product is obtained by pressing the bonded wood components with a heated press plate, but for thicker products or molded parts additional heating can be used via injection of steam.

The binder is formaldehyde free and can be easily used in the process.

Preferably, the particles, fibers, layers, bundles or ingredients are wood-based or cellulose-based, such as bamboo, straw, reed, hemp, palm, miscanthus, bagasse, molasses, or agricultural waste streams.

A preferred embodiment of the method for preparing the product according to the invention is characterized in that the mass ratio of the total amount of particles, fibres, layers, bundles or components to the solids content of the binder in the product is between 99:1 and 92:8, preferably between 98:2 and 95:5.

It is thus possible to work with a limited amount of adhesive with respect to the mass of the components to be bonded together.

A preferred embodiment of the method for producing the product according to the invention is characterized in that the product is a board, such as a wood fibre board (e.g. MDF board or HDF board), a particleboard, an OSB (oriented strand board) board or a laminate.

Adhesives are particularly suitable for such products. The obtained boards have good mechanical properties and are also water-resistant.

As mentioned above, if the adhesive is applied to or mixed with the substrate shortly after the crosslinker has been added to the powder, water glass and water, it may be advantageous for the adhesive strength of the adhesive, and subsequently the tensile strength of the bonded product.

A preferred embodiment of the method of preparing the product according to the invention is characterized in that the binder is applied to the particles, fibres, layers, bundles or ingredients within 1 hour, preferably within 50 minutes, more preferably within 40 minutes, even more preferably within 30 minutes after the cross-linking agent has been added to the powder, water glass and water.

The materials used

Water glass 2.0 (solids content 40 mass%) was obtained from PQ CHEMICA L S and had an SiO ₂:Na₂ O molar ratio of 2.0:1. Water glass 3.4 (solids content 37 mass%) was also obtained from PQ CHEMICA L S and had a molar ratio of sio ₂:Na₂ O of 3.4:1. I-Bond PB PM 4350 (pMDI) was obtained from Huntsman. 40% wax emulsion Vivas tar 9061,9061 was obtained from Netherlands H & R.

Examples

Example 1

In a first embodiment according to the invention, the suspension is obtained by mixing 10 g of rye flour (solids content 90% by mass) with 60 g of water under high shear. Then 2.5g of water glass 2.0 (solids content 40 mass%) corresponding to 0.33 g of Na ₂ O solids and 5.5 g of pMDI were added to the suspension and mixed. The resulting adhesive (suspension) has good physical stability and a viscosity of 150mpa.s (measured at 25 ℃).

7.5 Grams Vivas tar 9061 were first added to 450 grams wood chips and mixed, and then the suspension as described above was added and mixed. After the entire mixture had been mixed for 2 minutes, the bonded chips were placed in a molded article and the resulting mat was pressed at 200 ℃ for 2 minutes to form a plate having a thickness of 13mm and a density of 680kg/m ³. The sheet had an internal tensile strength of 0.50N/mm ² and a degree of swelling of 10% after 2 hours of immersion in water.

Example 2

In a second example according to the invention, the bonded crumb as described in example 1 was first stored at 25 ℃ for 30min and then pressed according to the same conditions as in example 1. The tensile strength measured was 0.48N/mm ² and the degree of swelling after 2 hours of immersion in water was 11%.

Example 3

In a third example according to the invention, the procedure of example 1 was repeated, but 10 g of pea starch E1370D was used instead of rye flour. The resulting adhesive (suspension) has good physical stability and a viscosity of 130mpa.s (measured at 25 ℃).

For a plate having a density of 700kg/m ³ and a thickness of 12mm, the tensile strength and the degree of swelling were measured as 0.52N/mm ² and 6%, respectively.

The powder used in the third example has a particle size distribution by volume in the aqueous dispersion measured by laser diffraction with a D ₅₀ value of 29.8 microns. The powder used in the third example has a particle size distribution by volume in the aqueous dispersion measured by laser diffraction with a D ₉₀ value of 67.4 microns.

Example 4

In a fourth example according to the invention, the procedure of example 1 is repeated, but 10 g of pea starch F70D are used instead of rye flour and 80 g of water are used instead of 60 g. The resulting adhesive (suspension) has good physical stability and a viscosity of 400mpa.s (measured at 25 ℃). For a plate having a density of 680kg/m ³ and a thickness of 13mm, the tensile strength and the degree of swelling were measured to be 0.58N/mm ² and 6%, respectively.

Comparative example 5

In comparative example 5, the procedure of example 1 was repeated, but no water glass was added. The resulting suspension has poor physical stability. After a few minutes, the pMDI droplets became visible in the suspension indicating phase separation. For a plate having a density of 680kg/m ³ and a thickness of 13mm, the tensile strength and the degree of swelling were measured to be 0.15N/mm ² and 20%, respectively.

Example 6

In a sixth example according to the invention, the procedure of example 1 was repeated, but the first component of the adhesive was obtained by mixing 10 g of rye flour (solids content 90%) with 35 g of water under high shear. The second component of the adhesive was obtained separately by mixing 25 grams of water, 2.5 grams of water glass 2.0 and 5.5 grams of pMDI under high shear to provide an emulsion.

After the wax emulsion was added to the wood chips as in example 1, the first and second components were dosed separately onto the wood chips and thoroughly mixed for 2 minutes. For a board having a density of 710kg/m ³ and a thickness of 12mm, the measured tensile strength and the degree of swelling of the wood veneer obtained were 0.45N/mm ² and 14%, respectively.

Example 7

In a seventh example according to the invention, the procedure of example 1 was repeated, but a suspension was obtained by mixing 10 g of broad bean starch with 60 g of water under high shear. Then 4.0 g of water glass 3.4 (37 mass% solids) corresponding to 0.34 g of Na ₂ O solids and 4.5 g of pMDI were added to the suspension and mixed. The resulting adhesive (suspension) has good physical stability and a viscosity of 160mpa.s (measured at 25 ℃).

For a board having a density of 610kg/m ³ and a thickness of 12mm, the measured tensile strength and the degree of swelling of the wood veneer obtained were 0.46N/mm ² and 7%, respectively.

The powder used in the seventh example has a particle size distribution by volume as measured by laser diffraction in an aqueous dispersion with a D ₅₀ value of 28.4 microns. The powder used in the seventh example has a particle size distribution by volume in the aqueous dispersion measured by laser diffraction with a D ₉₀ value of 87.9 microns.

Example 8

In an eighth example according to the invention, the procedure of example 1 was repeated, but using 6g of water glass 2.0 (40% solids) and 4.5 g of pMDI corresponding to 0.79 g of Na ₂ O solids. The resulting adhesive (suspension) has good physical stability and a viscosity of 140mpa.s (measured at 25 ℃). For a plate having a density of 680kg/m ³ and a thickness of 12mm, the tensile strength and the degree of swelling were measured to be 0.45N/mm ² and 15%, respectively.

Examples 9 to 10

In the ninth and tenth embodiments according to the present invention, the procedure of example 1 was repeated, but low grade flours having different particle sizes were used as powders.

For this purpose, 10 grams of low grade flour (1 or 2) was suspended in 60 grams of water, and then 4.0 grams of water glass 3.4 and 4.5 grams of pMDI were added. The two mixtures have good physical stability.

10 Grams Vivas tar 9061,901 were first added to 450 grams of wood chips and mixed, and then the suspension as described above was added and mixed. The bonded crumb was pressed at 200 ℃ for 2 minutes. The resulting wood veneer pieces having a thickness of 13mm all showed a degree of swelling of 6% after 2 hours of immersion in water. The tensile strength of the wood veneer with low-grade flour 1 was 0.38N/mm ², while the tensile strength of the wood veneer with low-grade flour 2 was 0.58N/mm ². The density of the two plates was 615kg/m ³.

The following table gives an overview of the adhesives, the many parameters of composition and viscosity of the adhesives, and the tensile strength and swelling of the products made with the adhesives according to the different examples.

Summary of the embodiments

Claims

1. The adhesive is characterized by comprising at least powder, water glass and a cross-linking agent, wherein the powder comprises carbohydrate and protein, and the water glass comprises a combination of Na ₂ O and SiO ₂;

Wherein the ratio of the mass of the powder to the mass of the solid of the water glass is between 50:1 and 2:1, preferably between 30:1 and 3:1.

2. Binder according to claim 1, characterized in that the ratio of the mass of the powder to the mass of solid Na ₂ O of the waterglass is between 140:1 and 6:1, preferably between 80:1 and 10:1, more preferably between 60:1 and 15:1.

3. The binder according to any of the preceding claims, characterized in that the powder is obtained by grinding plant raw materials such as cereals (e.g. wheat, rye, barley, millet, rice or oats), maize, sugar beet, nuts (e.g. palm nuts or coconuts), seeds (e.g. rapeseed, linseed or sunflower seeds) or beans (e.g. soybeans, peas, lentils, fava beans), or a combination of two or more of these.

4. The binder according to any of the preceding claims, characterized in that the powder is flour, such as cereal flour (e.g. wheat, rye, barley, millet, rice or oat), low-grade flour, corn flour, beet flour, nut flour (e.g. palm nut or coconut), seed flour (e.g. from rapeseed, linseed or sunflower seed) or legume flour (e.g. from soybean, pea, lentil, broad bean), or the powder is a combination of two or more of these.

5. The adhesive according to any of the preceding claims, characterized in that the powder in water is obtained by a process of fermenting plant material.

6. Binder according to any one of the preceding claims, characterized in that in the powder the ratio of the mass of the protein to the mass of the carbohydrate is between 2:1 and 1:30, preferably between 1.5:1 and 1:15, more preferably between 1:2 and 1:10.

7. Adhesive according to any one of the preceding claims, characterized in that the viscosity of the adhesive is less than 1000mpa.s, preferably less than 500mpa.s, at 25 ℃.

8. The adhesive according to any of the preceding claims, characterized in that the powder, the water glass and the cross-linking agent are uniformly distributed in the adhesive.

9. The adhesive according to any of the preceding claims 1-7, characterized in that the adhesive is a two-component adhesive;

Wherein the first component contains the powder, a portion of the water, and the entire amount of the water glass or a portion of the water glass or no water glass;

wherein the second component contains the cross-linking agent, a portion of the water and the entire amount of the water glass or a portion of the water glass or no water glass.

10. Adhesive according to any one of the preceding claims, characterized in that the solids content in the adhesive is between 10 and 40 mass%, preferably between 15 and 35 mass%.

11. Adhesive according to any one of the preceding claims, characterized in that the crosslinker is a product containing at least two isocyanate groups, preferably wherein the crosslinker contains one or more of a diisocyanate, a polyisocyanate, a derivative of a diisocyanate or a derivative of a polyisocyanate.

12. Adhesive according to any one of the preceding claims, characterized in that the cross-linking agent is a derivative or polymer of methylene diphenyl diisocyanate (MDI), preferably a polymer methylene diphenyl diisocyanate (pMDI).

13. The adhesive according to any of the preceding claims, characterized in that the crosslinking agent is a product containing at least two epoxy groups, or at least two cyclic anhydride groups, or at least two azetidinium functional groups, or a mixture of two or more of these products.

14. Binder according to any one of the preceding claims, characterized in that the ratio of the mass of the cross-linking agent to the mass of the powder is between 1:15 and 2:1, preferably between 1:10 and 1:1, more preferably between 1:8 and 1:1.25, even more preferably between 1:2.5 and 1:1.5.

15. Adhesive according to any one of the preceding claims, characterized in that the adhesive contains a thermoplastic adhesive component, preferably a biorenewable thermoplastic adhesive component, such as an aqueous dispersion of natural latex or polylactic acid.

16. Binder according to any one of the preceding claims, characterized in that the molar ratio of SiO ₂ to Na ₂ O in the water glass is between 4 and 1.5, preferably between 3.8 and 2.0, more preferably between 3.5 and 2.5, even more preferably between 3.5 and 2.8.

17. The adhesive according to any of the preceding claims, characterized in that the adhesive contains one or more of a water-repellent additive, a catalyst, a dye, a pigment, a flame retardant, a cold tack improver, or a foaming agent.

18. The adhesive according to any of the preceding claims, characterized in that the adhesive is a liquid and the powder is suspended in the adhesive.

19. The adhesive according to any of the preceding claims, characterized in that the D ₅₀ value of the particle size distribution of the powder by volume measured by laser diffraction in an aqueous dispersion is less than 200 microns, preferably less than 100 microns, more preferably less than 50 microns, even more preferably less than 30 microns.

20. The adhesive according to any of the preceding claims, characterized in that the D ₉₀ value of the particle size distribution of the powder by volume measured by laser diffraction in an aqueous dispersion is less than 200 microns, preferably less than 100 microns.

21. Wherein the particles, fibers, layers, bundles or components are bonded together in a pressing process at an elevated temperature using the binder according to any one of the preceding claims, wherein water evaporates from the binder and the binder provides a combination of the particles, fibers, layers, bundles or components;

Wherein the mass ratio of the total amount of particles, fibers, layers, bundles or ingredients to the solids content of the binder in the product is between 99:1 and 92:8, preferably between 98:2 and 95:5.

22. The product according to claim 21, wherein the mass ratio of solids of the cross-linking agent in the binder to the total amount of particles, fibers, layers, bundles of the product is between 0.5 and 2 mass%, preferably between 0.75 and 1.75 mass%, more preferably between 1 and 1.5 mass%.

23. Product according to any of the preceding claims 21-22, characterized in that the product is a board, such as a wood fibre board (e.g. MDF board or HDF board), chipboard, OSB (oriented strand board) board or laminate.

24. Product according to any of the preceding claims 21-22, characterized in that the product is a moulding, such as a pallet block.

25. The product according to any of the preceding claims 21-24, characterized in that the particles, fibres, layers, bundles or ingredients are wood-based or cellulose-based, such as bamboo, straw, reed, hemp, palm, miscanthus, bagasse, molasses, or agricultural waste streams.

26. A method of preparing a product, wherein the method comprises the steps of

-Providing a quantity of particles, fibers, layers, bundles or components;

-applying the binder according to any of the preceding claims 1-20 to the particles, fibers, layers, bundles or components;

-shaping the mixture of particles, fibres, layers, bundles or components and the binder, for example in the form of a sheet;

-curing the binder at elevated temperature and under pressure, wherein water evaporates from the binder, and wherein the curing of the binder results in a product in which the particles, fibres, layers, bundles or components are bound together by the binder.

27. The method according to claim 26, characterized in that the particles, fibers, layers, bundles or components are wood-based or cellulose-based, such as bamboo, straw, reed, hemp, palm, miscanthus, bagasse, molasses, or agricultural waste streams.

28. The method according to any of the preceding claims 26-27, characterized in that in the product the mass ratio of the total amount of particles, fibres, layers, bundles or ingredients to the solid content of the binder is between 99:1 and 92:8, preferably between 98:2 and 95:5.

29. The method according to any of the preceding claims 26-28, characterized in that the product is a board, such as a wood fibre board (e.g. MDF board or HDF board), a chipboard, an OSB (oriented strand board) board or laminate, or a moulding, such as a pallet board.