Cake meal isolated protein-based adhesive as well as preparation method and application thereof

Abstract

The invention discloses a cake meal isolated protein-based adhesive as well as a preparation method and application thereof. Relates to the technical field of adhesives. The raw materials of the adhesive comprise the following components: trifuran formaldehyde diimine; a carbonyl compound; separating protein from the cake meal; furfuryl amine; an ester compound; a curing agent; an initiator; and water. The adhesive disclosed by the invention is an adhesive which is good in mechanical property, strong in water resistance and capable of being rapidly cured.

Description

Technical Field

[0001] The invention relates to the technical field of adhesives, and in particular to a cake protein-separated adhesive and a preparation method and application thereof. Background Art

[0002] Cake protein isolate refers to the protein component extracted from the cake of vegetable oil crops, mainly from soybeans, peanuts, rapeseed and other oil crops. After the oil is extracted from these vegetable oils, the remaining material is the cake, which itself contains a certain proportion of plant protein. Traditional cake is usually used as feed or fertilizer, but with the advancement of science and technology, the protein in the cake has begun to be widely studied and applied in industrial production due to its unique biochemical properties and excellent bonding properties, especially in the field of adhesives. Cake protein isolate is not only a renewable biological resource, but also has degradability and high environmental friendliness, which meets the current society's demand for green environmental protection.

[0003] Adhesives, as the name implies, are materials used to bond two or more substances together. They achieve the bonding of substances through physical adsorption, chemical reaction, or a combination of both. There are many types of adhesives, which can be divided into natural adhesives, synthetic adhesives, and bio-based adhesives according to their sources. Among them, bio-based adhesives have gradually gained popularity in recent years, especially in terms of environmental protection and sustainable development. Bio-based adhesives are usually composed of polymers from natural plants or animals. These adhesives not only have good bonding properties, but also can be naturally degraded after use, avoiding the pollution of the environment by traditional synthetic adhesives.

[0004] However, despite the wide variety of adhesives currently on the market, there is still the problem of insufficient bonding strength, especially in some applications that need to withstand greater mechanical pressure or high temperature and high humidity environments. The bonding strength of adhesives is directly related to their reliability and durability in practical applications. Although many natural adhesives and bio-based adhesives have advantages in environmental protection, they usually show lower bonding strength due to the characteristics of their molecular structure, especially in extreme environments such as moisture or high temperature, and are prone to lose their bonding effect. Therefore, improving the bonding strength of adhesives and enhancing their temperature and humidity resistance has become an important technical problem in adhesive research.

[0005] Artificial boards are man-made materials made of wood fibers, plant fibers or other non-wood raw materials after physical and chemical processing and bonded with adhesives. They are widely used in furniture manufacturing, construction, decoration and other fields. The emergence of artificial boards solves the problem of shortage of wood resources, and also provides the construction and home furnishing industries with more abundant and low-cost material options. Common artificial boards include particleboards, density boards, plywood, etc. In the production process of artificial boards, adhesives play a vital role. Adhesives are not only used to bond the fibers inside the board, but also to ensure the stability, strength and durability of the board. The quality of the adhesive directly determines the comprehensive performance of the artificial board, especially in terms of compressive strength, bending strength and impact resistance.

[0006] With the increasing attention paid to environmental protection and sustainable development, bio-based adhesives have gradually become the research focus of the wood-based panel industry. In the production of traditional wood-based panels, most of the adhesives used are chemically synthesized. Although these adhesives can provide sufficient bonding strength, they usually contain harmful volatile organic compounds (VOCs). These chemical components will affect air quality and human health during production and use. Therefore, the development of low-VOC emission, non-toxic and high-performance bio-based adhesives has become a technical demand of the current wood-based panel industry.

[0007] As a new type of bio-based adhesive, cake separation protein-based adhesive has environmental advantages such as low toxicity, low VOC emissions, and biodegradability. At the same time, it can effectively meet the requirements of bonding strength for wood-based board production. The protein molecules in cake have certain adhesion and can form a strong bond with other materials under appropriate conditions. This protein adhesive can not only greatly reduce the pollution to the environment during the production of wood-based boards, but also reduce dependence on petroleum-based chemicals, thereby reducing the consumption of non-renewable resources.

[0008] At present, there are still challenges in the practical application of cake protein isolate-based adhesives. First, although cake protein isolate has certain bonding properties, in order to achieve high strength comparable to traditional synthetic adhesives, it still needs to be improved through modification and optimization of the formula. Summary of the invention

[0009] The object of the present invention is to provide an adhesive with good mechanical properties, strong water resistance and rapid curing.

[0010] A first aspect of the present invention is:

[0011] An adhesive is provided.

[0012] A second aspect of the present invention is:

[0013] Provided is a method for preparing an adhesive.

[0014] The third aspect of the present invention is:

[0015] Application of the adhesive.

[0016] The invention also provides a man-made board.

[0017] Specifically, the technical solution adopted according to the first aspect of the present invention is:

[0018] An adhesive, the raw materials of which include the following components:

[0019] Trifurancarboxaldehyde diimide;

[0020] Carbonyl compounds;

[0021] Cake protein isolate;

[0022] Furfurylamine;

[0023] Ester compounds;

[0024] Curing agent;

[0025] Initiator;

[0026] water.

[0027] According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0028] The adhesive of the present invention is an adhesive with good mechanical properties, strong water resistance and the ability to cure quickly.

[0029] The trifuran carboxaldehyde diimide has three branches in its molecular structure, and can effectively extend the chain in a condensation reaction to form a cross-linked network structure. In addition, the trifuran carboxaldehyde diimide has high reactivity and can react with carbonyl compounds to quickly generate a polymer modifier with high reactivity through a condensation reaction. The polymer modifier can react with active groups on the cake protein isolate macromolecules and subsequent related substances to form a unique molecular network structure.

[0030] As a small molecule compound, the furfural amine can undergo free radical polymerization reaction with itself, the lignin component in the bamboo and wood components, the hydroxyl groups on the macromolecular chain of the cake and meal separated protein, the heterocycles in the ester compounds, and the oxygen heterocycles in the structure of the polymer modifier in the present invention, so as to covalently connect multiple components, thereby improving the curing speed of the adhesive; in addition, the furfural amine itself can undergo a certain condensation to form multiple cross-linked network interpenetrating structures, so as to fully fix multiple components that are easily degraded and easily hydrolyzed in the cross-linked network interpenetrating structures, thereby improving the mechanical properties of the adhesive.

[0031] By initiating an olefin condensation reaction between the ester compound and other raw material components through an initiator, a plurality of different interpenetrating cross-linked network structures are formed through a variety of different condensation and polymerization reactions. Several structures are interpenetrating with each other and connected to each other by covalent bonds. In addition, the hydrophilic groups are significantly consumed and reduced through the reaction formed by covalent bonds. While enhancing the mechanical properties, the hydrophilic properties of the adhesive can be significantly reduced, thereby improving the water resistance of the adhesive.

[0032] According to one embodiment of the present invention, the raw materials of the adhesive include the following components in parts by weight:

[0033] Trifurancarboxaldehyde diimide;

[0034] Carbonyl compounds;

[0035] Cake protein isolate;

[0036] Furfurylamine;

[0037] Ester compounds;

[0038] Curing agent;

[0039] Initiator;

[0040] water.

[0041] According to one embodiment of the present invention, the carbonyl compound includes glyoxal.

[0042] According to one embodiment of the present invention, the ester compound includes at least one of tetrahydrofurfuryl methacrylate and furfuryl methacrylate.

[0043] According to one embodiment of the present invention, the initiator includes a peroxide initiator.

[0044] According to one embodiment of the present invention, the initiator includes at least one of ammonium persulfate and potassium persulfate.

[0045] According to one embodiment of the present invention, the cake protein isolate comprises at least one isolated protein of tung oil cake, camellia oil cake, soybean cake and litsea cubeba cake.

[0046] According to one embodiment of the present invention, the cake protein isolate is a modified cake protein isolate, which is obtained by subjecting the cake protein to urea and / or alkaline agent modification treatment. Preferably, the modified cake protein isolate is obtained by subjecting the cake protein to urea modification treatment.

[0047] According to one embodiment of the present invention, the preparation method of the modified meal protein isolate comprises the following steps: mixing 2-3% urea and 25-30% meal vegetable protein in water, stirring continuously for 0.5-1h, and obtaining the modified meal protein isolate. Preferably, the preparation method of the modified meal protein isolate comprises the following steps: mixing 2% urea and 25% meal vegetable protein in water, stirring continuously for 0.5-1h, and obtaining the modified meal protein isolate.

[0048] According to one embodiment of the present invention, the curing agent includes GY-051 condensation amine curing agent.

[0049] Specifically, the technical solution adopted according to the second aspect of the present invention is:

[0050] A method for preparing the adhesive comprises the following steps:

[0051] S1: mixing trifuran formaldehyde diimide and a carbonyl compound in water, and heating the mixture to react to obtain a modifier;

[0052] S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator to obtain the adhesive.

[0053] According to one embodiment of the present invention, in step S1, the temperature of the heating reaction is 60-80°C.

[0054] According to one embodiment of the present invention, in step S1, the heating reaction time is 1-2 hours.

[0055] According to one embodiment of the present invention, in step S1, the step of heating the reaction includes heating and refluxing.

[0056] According to one embodiment of the present invention, step S2 further includes the following steps: after mixing the modifier, meal protein isolate, furfurylamine, ester compound, curing agent and initiator, a mixture is obtained, and the pH of the mixture is adjusted to 3-5, and the adhesive is obtained through reaction. The pH value affects the curing ability of the adhesive. When the pH value is an alkaline environment, the components of the adhesive cannot initiate a reaction during the heating process and cannot be cured to form a cross-linked network structure; when the pH value is an acidic environment but is not within the range of 3-5, the components cannot be cured to form a cross-linked network structure.

[0057] Another aspect of the present invention further provides an artificial board, including the adhesive as described in the embodiment of the first aspect. Since the application adopts all the technical solutions of the above adhesive, it has at least all the beneficial effects brought by the technical solutions of the above embodiment.

[0058] According to one embodiment of the present invention, the artificial board comprises a bamboo particle board.

[0059] According to one embodiment of the present invention, the bamboo particle board is a board with a thickness of 2 to 8 mm. The raw material is shavings, the length of the shavings is 0.8 to 4 mm, the thickness is 0.2 to 0.25 mm, and the aspect ratio is about 15 mm.

[0060] According to one embodiment of the present invention, the bamboo particle board can replace plywood and be used as a furniture bottom board, a partition board, and can also be used as a core board of plywood.

[0061] According to one embodiment of the present invention, the preparation of the bamboo particleboard includes the steps of mixing the adhesive of the present invention with the shavings and performing hot pressing.

[0062] According to one embodiment of the present invention, the hot pressing temperature is 100-110°C.

[0063] According to one embodiment of the present invention, the hot pressing time is 100 to 180 seconds.

[0064] According to one embodiment of the present invention, the hot pressing pressure is 0.8-1.2 MPa.

[0065] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0066] The words "preferred", "more preferred" and the like in the present invention refer to embodiments of the present invention that can provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0067] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0068] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0069] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0070] The meal protein isolate in the embodiments and comparative examples is a modified meal protein isolate. The preparation method of the modified meal protein isolate comprises the following steps: mixing 2% by mass of urea and 25% by mass of meal vegetable protein in water, and continuously stirring for 1 hour to obtain the modified meal protein isolate.

[0071] In the examples and comparative examples, the initiator is potassium persulfate.

[0072] Example 1

[0073] An adhesive, wherein the raw materials of the adhesive include the following components in parts by weight:

[0074] Trifurancarboxaldehyde diimide, 12 parts;

[0075] Carbonyl compounds, 10 parts;

[0076] Cake protein isolate, 30 parts;

[0077] Furfurylamine, 6 parts;

[0078] ester compounds, 10 parts;

[0079] Curing agent, 2 parts;

[0080] Initiator, 1 part;

[0081] Water, 60 parts.

[0082] The above-mentioned ester compound is tetrahydrofurfuryl methacrylate;

[0083] The above carbonyl compound is glyoxal.

[0084] The method for preparing the above adhesive comprises the following steps:

[0085] S1: trifuran formaldehyde diimide and glyoxal are mixed in water, and reacted under heating reflux stirring at 80°C for 1 hour to obtain a modifier;

[0086] S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator, adjusting the pH value to 3, and obtaining the adhesive.

[0087] Example 2

[0088] The difference between Example 2 and Example 1 is that the ester compound in Example 2 is furfuryl methacrylate.

[0089] Specific:

[0090] An adhesive, wherein the raw materials of the adhesive include the following components in parts by weight:

[0091] Trifurancarboxaldehyde diimide, 12 parts;

[0092] Glyoxal, 10 parts;

[0093] Cake protein isolate, 30 parts;

[0094] Furfurylamine, 6 parts;

[0095] Carbonyl compounds, 10 parts;

[0096] Curing agent, 2 parts;

[0097] Initiator, 1 part;

[0098] Water, 60 parts.

[0099] The above-mentioned ester compound is furfuryl methacrylate;

[0100] The above carbonyl compound is glyoxal.

[0101] The method for preparing the above adhesive comprises the following steps:

[0102] S1: trifuran formaldehyde diimide and glyoxal are mixed in water, and reacted under heating reflux stirring at 80°C for 1 hour to obtain a modifier;

[0103] S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator, adjusting the pH value to 3, and obtaining the adhesive.

[0104] Example 3

[0105] The difference between Example 3 and Example 1 is that the carbonyl compound is malondialdehyde.

[0106] Specific:

[0107] An adhesive, wherein the raw materials of the adhesive include the following components in parts by weight:

[0108] Trifurancarboxaldehyde diimide, 12 parts;

[0109] Carbonyl compounds, 10 parts;

[0110] Cake protein isolate, 30 parts;

[0111] Furfurylamine, 6 parts;

[0112] ester compounds, 10 parts;

[0113] Curing agent, 2 parts;

[0114] Initiator, 1 part;

[0115] Water, 60 parts.

[0116] The above-mentioned ester compound is tetrahydrofurfuryl methacrylate;

[0117] The above carbonyl compound is malondialdehyde.

[0118] The method for preparing the above adhesive comprises the following steps:

[0119] S1: trifuran formaldehyde diimide and malondialdehyde are mixed in water, and reacted under heating reflux stirring at 80°C for 1 hour to obtain a modifier;

[0120] S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator, adjusting the pH value to 3, and obtaining the adhesive.

[0121] Example 4

[0122] The difference between Example 4 and Example 1 is that the amount of trifuran formaldehyde diimide used is different, that is, 5 parts.

[0123] Specific:

[0124] An adhesive, wherein the raw materials of the adhesive include the following components in parts by weight:

[0125] Trifurancarboxaldehyde diimide, 5 parts;

[0126] Carbonyl compounds, 10 parts;

[0127] Cake protein isolate, 30 parts;

[0128] Furfurylamine, 6 parts;

[0129] ester compounds, 10 parts;

[0130] Curing agent, 2 parts;

[0131] Initiator, 1 part;

[0132] Water, 60 parts.

[0133] The above-mentioned ester compound is tetrahydrofurfuryl methacrylate;

[0134] The above carbonyl compound is glyoxal.

[0135] The method for preparing the above adhesive comprises the following steps:

[0136] S1: trifuran formaldehyde diimide and glyoxal are mixed in water, and reacted under heating reflux stirring at 80°C for 1 hour to obtain a modifier;

[0137] S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator, adjusting the pH value to 3, and obtaining the adhesive.

[0138] Example 5

[0139] The difference between Example 5 and Example 1 is that the amount of furfurylamine used is different, which is 15 parts.

[0140] Specific:

[0141] An adhesive, wherein the raw materials of the adhesive include the following components in parts by weight:

[0142] Trifurancarboxaldehyde diimide, 12 parts;

[0143] Carbonyl compounds, 10 parts;

[0144] Cake protein isolate, 30 parts;

[0145] Furfurylamine, 15 parts;

[0146] ester compounds, 10 parts;

[0147] Curing agent, 2 parts;

[0148] Initiator, 1 part;

[0149] Water, 60 parts.

[0150] The above-mentioned ester compound is tetrahydrofurfuryl methacrylate;

[0151] The above carbonyl compound is glyoxal.

[0152] The method for preparing the above adhesive comprises the following steps:

[0153] S1: trifuran formaldehyde diimide and glyoxal are mixed in water, and reacted under heating reflux stirring at 80°C for 1 hour to obtain a modifier;

[0154] S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator, adjusting the pH value to 3, and obtaining the adhesive.

[0155] Comparative Example 1

[0156] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, trifuran formaldehyde diimide is replaced by furfural.

[0157] Comparative Example 2

[0158] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, furfurylamine is replaced by phenylethylamine.

[0159] Comparative Example 3

[0160] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, glyoxal is replaced by ethylene glycol.

[0161] The difference between Comparative Example 4 and Example 1 is that in Comparative Example 4, the ester compound is methacrylate.

[0162] Comparative Example 5

[0163] The difference between Comparative Example 5 and Example 1 is that in Comparative Example 5, the pH value of the adhesive is not 3, but 8.

[0164] Performance Test:

[0165] This test example tests the performance of the bamboo engineering material obtained in the comparative example of the embodiment, and the test results are shown in Table 1. Preparation of lightweight bamboo engineering material. Lightweight bamboo engineering material refers to a material with a density of less than 1.0 g / cm 3 The density of reconstructed bamboo board is greater than 1.0g / cm 3 , up to 1.2g / cm 3 Too high density seriously affects the convenience of transportation, installation and use of the board. This paper maintains the stability of the board performance under the premise of significantly reducing the density of the board.

[0166] Table 1

[0167]

[0168]

[0169] In Comparative Example 1, trifuran formaldehyde diimide is replaced with furfural, both of which contain oxygen heterocyclic structure and aldehyde structure. Furfural itself is also a curing agent and can self-condense, but furfural and glyoxal have weak reactivity, so it is impossible to obtain modifier A, resulting in that subsequent reactions cannot be fully carried out. The subsequent product adhesive obtained cannot be fully cured during the hot pressing process, and cannot form a multi-linked interpenetrating network cross-linked network structure through the reaction between the components, resulting in the need for higher pressure hot pressing, resulting in higher density, and poor mechanical properties, longer curing time, and water absorption thickness expansion can only reach T15.0 level (≤15%).

[0170] In Comparative Example 2, furfural amine is replaced by phenylethylamine. Both contain amino groups, but the reactivity is quite different. This is because furfural amine reacts with other components through the amino group and the C on the heterocycle to form a covalent bond, while phenylethylamine only has an amino group and has a very low reactivity with other components. The components are only blended and cannot be cured to form a cross-linked network structure. The subsequent product adhesive cannot be cured during the hot pressing process, resulting in the inability to hot press the sheet, and the density, mechanical properties, and water absorption thickness expansion cannot be detected.

[0171] In Comparative Example 3, glyoxal is replaced by ethylene glycol. The reactivity of the two is quite different. Glyoxal undergoes aldehyde-ammonia condensation, aldol condensation and other reactions with the components through its own aldehyde group to form covalent bonds, while ethylene glycol cannot participate in the reaction. The components are only blended and cannot be cured to form a cross-linked network structure. The subsequent product adhesive cannot be cured during the hot pressing process, resulting in the inability to hot-press the sheet, and the density, mechanical properties, and water absorption thickness expansion cannot be detected.

[0172] The ester compound in Comparative Example 4 is methacrylate, and the chemical structure of the methacrylate in Comparative Example 4 is significantly different from that of tetrahydrofurfuryl methacrylate or furfuryl methacrylate selected in the embodiment. Tetrahydrofurfuryl methacrylate and furfuryl methacrylate contain tetrahydrofurfuryl and furfuryl groups, and have two reactive groups. In the curing reaction, they can react with other components through two reactive groups to form a multi-linked interpenetrating network structure, and can also achieve their own chain extension reaction, thereby improving the physical properties of the adhesive and reducing the density of the sheet. Methacrylate can only undergo self-polymerization reaction and cannot fully participate in the chemical reaction of other substances. It only contains monofunctional active groups, and has poor chain extension performance, resulting in the need for high pressure hot pressing, resulting in high density, poor mechanical properties, long curing time, and actual water absorption thickness expansion test exceeding 15%.

[0173] The pH value of the adhesive in Comparative Example 5 is not 3, but 8. The pH value affects the curing ability of the adhesive. When the pH value is 8, in an alkaline emulsion environment, the components of the adhesive cannot initiate a reaction during the heating process, and cannot be cured to form a cross-linked network structure. The subsequent product adhesive cannot be cured during the hot pressing process, resulting in the inability to hot press the sheet, and the density, mechanical properties, and water absorption thickness expansion cannot be detected.

[0174] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An adhesive, characterized in that: The raw materials of the adhesive include the following components: Trifurancarboxaldehyde diimide; Carbonyl compounds; Cake protein isolate; Furfurylamine; Ester compounds; Curing agent; Initiator; water.

2. An adhesive according to claim 1, characterized in that: The raw materials of the adhesive include the following components in parts by weight: Trifuranformaldehyde diimide, 5-12 parts; Carbonyl compound, 3 to 10 parts; Cake protein isolate, 20-40 parts; Furfurylamine, 5-15 parts; Ester compounds, 10 to 18 parts; Curing agent, 2 to 5 parts; Initiator, 0.5-2 parts; Water, 50-80 parts.

3. An adhesive according to claim 1, characterized in that: The carbonyl compound includes at least one of glyoxal and malondialdehyde.

4. An adhesive according to claim 1, characterized in that: The ester compound includes at least one of tetrahydrofurfuryl methacrylate and furfuryl methacrylate.

5. The adhesive according to claim 1, characterized in that: The initiator includes a peroxide initiator.

6. An adhesive according to claim 1, characterized in that: The cake protein isolate is a modified cake protein isolate, which is obtained by subjecting the cake protein to modification treatment with urea and / or alkaline reagent.

7. A method for preparing an adhesive as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: S1: mixing trifuran formaldehyde diimide and a carbonyl compound in water, and heating the mixture to react to obtain a modifier; S2: mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator to obtain the adhesive.

8. A method according to claim 7, characterized in that: In step S1, the temperature of the heating reaction is 60-80°C.

9. A method according to claim 7, characterized in that: Step S2 also includes the following steps: after mixing the modifier, cake protein isolate, furfural amine, ester compound, curing agent and initiator, a mixture is obtained, and the pH of the mixture is adjusted to 3-5, and the adhesive is obtained through reaction.

10. A wood-based panel, characterized in that: The artificial board comprises an adhesive as claimed in any one of claims 1 to 6.

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