JP2017122148A - Adhesive and molded sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive capable of shortening a curing time while ensuring high adhesive strength, and a molded plate using the same. An adhesive contains a sugar-based mixture containing a sugar and an organic sulfonic acid and an isocyanate, and contains 0.1 to 75 parts by mass of the organic sulfonic acid with respect to 100 parts by mass of the sugar. The molded plate includes the above-mentioned adhesive and a plurality of plant pieces bonded by the adhesive. The adhesive can shorten the curing time while ensuring high adhesive strength. Then, by using the adhesive, a molded plate having high strength and water resistance can be obtained. [Selection diagram] Fig. 6

Description

  The present invention relates to an adhesive and a molded plate using the same. Specifically, the present invention relates to an adhesive having excellent adhesiveness, and a molded plate using the adhesive.

  Wood-based boards such as particle boards and fiberboards can be manufactured using particles and fine fibers obtained from waste materials and building waste materials produced during lumber production. And the production amount of the wooden board is increasing worldwide because the material is cheaper than the plywood.

  In addition, a board using plant pieces is also known as a wooden board. As plant pieces, herbaceous plants such as bamboo, kenaf and flax, rice straw, wheat straw, oil palm fiber, bagasse, beet pulp and the like are used in addition to wood. Oil palm fiber is the fiber after extracting the oil, bagasse is the pomace after collecting sugarcane sugar, and beet pulp is the pomace after collecting sugar beet sugar. It is possible to produce a wooden board using particles and fine fibers obtained from these agricultural wastes as raw materials.

  Conventionally, wood-based boards have used biomass-derived adhesives such as casein, soybean glue, and glue. However, since biomass-derived adhesives have poor physical properties such as adhesiveness, petroleum-derived thermosetting adhesives such as urea resins, melamine resins, and phenol resins have been used in recent years. However, the thermosetting adhesive may contain components harmful to the human body such as formaldehyde. Therefore, when using a wood-based board using such a thermosetting adhesive as an interior material for a house, harmful components such as formaldehyde may volatilize from the board and adversely affect the health of residents. Also, in preparation for the future depletion of fossil resources, adhesion technology using natural substances derived from non-fossil resources is attracting attention again.

  Therefore, there is a strong demand for the development of a board that does not use petroleum-derived thermosetting adhesives but uses particles or fine fiber materials themselves or naturally derived substances as adhesive components. However, an adhesive using a naturally derived substance generally requires a long time for curing, and it is necessary to add more adhesive.

  Patent Document 1 discloses a manufacturing method of a chipboard or a fiberboard. Specifically, it is disclosed that the production method includes a step of adding a polycarboxylic acid to a plant-derived material and a step of adding a small amount of a compound having an isocyanate group to the plant-derived material and / or the polycarboxylic acid. Yes.

International Publication No. 2012/098749

  However, even in the manufacturing method of Patent Document 1, it takes a long time to secure practically necessary adhesive strength, and thus further shortening of the curing time is required.

  The present invention has been made in view of such problems of the prior art. And the objective of this invention is providing the adhesive agent which can shorten hardening time, and a shaping | molding board using the same, ensuring high adhesive strength.

  In order to solve the above problems, the adhesive according to the first aspect of the present invention includes a sugar-based mixture containing sugar and organic sulfonic acid, and isocyanate. And 0.1-75 mass parts of organic sulfonic acids are included with respect to 100 mass parts of sugars.

  The molded board which concerns on the 2nd aspect of this invention contains the above-mentioned adhesive agent and the some plant piece adhere | attached with an adhesive agent.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive which can shorten hardening time can be obtained, ensuring high adhesive strength. Moreover, the molded board which has high intensity | strength and water resistance can be obtained by using the said adhesive agent.

Regarding Examples 1-1 to 1-4 and Comparative Examples 1-1 and 1-2, the ratio of isocyanate in the total solid content of the adhesive and the hot water insolubility (curing rate) of the obtained cured product It is a graph which shows a relationship. Regarding Examples 2-1 to 2-4 and 3-1 to 3-4 and Comparative Examples 2-1 to 2-2 and 3-1 to 3-2, the ratio of isocyanate in the total solid content of the adhesive, It is a graph which shows the relationship with the hot water insoluble rate (curing rate) of the obtained hardened | cured material. It is a graph which shows the relationship between the ratio of the isocyanate in the total solid of an adhesive agent, and the hot water insoluble rate (curing rate) of the obtained hardened | cured material regarding the comparative examples 4-1 to 4-6. It is a graph which shows the relationship between the ratio of the isocyanate in the total solid of an adhesive agent, and the hot water insoluble rate (curing rate) of the obtained hardened | cured material regarding the comparative examples 5-1 to 5-6. It is a graph which shows the relationship between the water absorption thickness expansion coefficient of the particle board of Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-8, and the ratio of isocyanate in the total solid content of the adhesive. It is a graph which shows the relationship between the peeling strength of the particle board of Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-8, and the ratio of isocyanate in the total solid content of the adhesive. It is a graph which shows the relationship between the bending strength of the particle board of Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-8, and the ratio of isocyanate in the total solid content of the adhesive. It is a graph which shows the relationship between the bending strength at the time of the particle board of Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-8, and the ratio of isocyanate in the total solid content of the adhesive.

  Hereinafter, the adhesive according to the present embodiment and a molded plate using the adhesive will be described in detail.

[adhesive]
The adhesive according to the present embodiment is a thermosetting adhesive that is cured by heating and pressing. Specifically, the adhesive according to this embodiment includes a sugar-based mixture containing sugar and organic sulfonic acid, and isocyanate.

(sugar)
As described above, the sugar-based mixture contains sugar. As the sugar, at least one selected from the group consisting of monosaccharides, disaccharides, oligosaccharides and polysaccharides can be used. Examples of the monosaccharide include glucose, fructose, ribose, arabinose, rhamnose, xylulose, deoxyribose and the like. Examples of the disaccharide include sucrose, maltose, cellobiose, trehalose, and tulanose. Examples of the oligosaccharide include fructooligosaccharide, galactooligosaccharide, mannan oligosaccharide, stachyose and the like. The oligosaccharide may be, for example, a sugar in which 10 or less sugar chains are linked. Examples of the polysaccharide include starch, agarose, alginic acid, glucomannan, inulin, chitin, chitosan, hyaluronic acid, glycogen, and cellulose. As the sugar, one or a combination of the above compounds can be used.

  Moreover, it is preferable that sugar is 1 type, or 2 or more types chosen from monosaccharide and disaccharide. The monosaccharide is preferably at least one of glucose and fructose. The disaccharide is preferably at least one selected from the group consisting of sucrose, maltose and cellobiose. Furthermore, sucrose can be more preferably used as the sugar. Sucrose is obtained by extracting and purifying from plants such as sugar cane and sugar beet. However, crude sucrose containing impurities other than sucrose obtained in the process until sucrose is refined, waste molasses discharged without crystallization, bagasse, which is squeezed, also contains a lot of sucrose. . These crude sugars, molasses and bagasse can also be used as sugars.

(Organic sulfonic acid)
The sugar-based mixture contains an organic sulfonic acid in addition to the sugars described above. As the organic sulfonic acid, at least one of alkyl sulfonic acid and aromatic sulfonic acid can be used. Of these, the organic sulfonic acid is preferably an aromatic sulfonic acid, and more preferably a sulfonic acid having a benzene ring. Further, as the organic sulfonic acid, it is preferable to use at least one selected from the group consisting of p-toluenesulfonic acid, benzenesulfonic acid, metaxylenesulfonic acid and methanesulfonic acid. Of these, p-toluenesulfonic acid is particularly effective, and the reaction between low-molecular-weight modified products proceeds to polymerize and contribute to adhesion. Benzene sulfonic acid and meta-xylene sulfonic acid are also suitable as a molding plate material because they are highly effective and the reaction between the low-molecular modified products proceeds to polymerize and contribute to adhesion. Therefore, it is preferable to use at least one selected from the group consisting of p-toluenesulfonic acid, benzenesulfonic acid and metaxylenesulfonic acid as the organic sulfonic acid.

(Isocyanate)
The adhesive of this embodiment contains an isocyanate in addition to the sugar-based mixture described above. As the isocyanate, for example, (poly) isocyanate having two or more isocyanate groups in one molecule can be used. Various polyfunctional aliphatic, alicyclic and aromatic isocyanates can be used as the (poly) isocyanate. Examples of (poly) isocyanate include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 4,4-dicyclohexylmethane diisocyanate (H12MDI), tolylene diisocyanate (TDI), crude tolylene diisocyanate, modified tolylene diisocyanate, 2,4′-diphenylmethane diisocyanate (2,4′-MDI), 2,2′-diphenylmethane diisocyanate (2,2′-MDI), 4,4′-diphenylmethane diisocyanate (4,4′-MDI), polymethylene Polyphenylene polyisocyanate (polymeric MDI), modified diphenylmethane diisocyanate (carbodiimide modification, prepolymer modification, etc.), o-tolidine diisocyanate (TODI), naphthylene Diisocyanate (NDI), xylylene diisocyanate (XDI), and the like lysine diisocyanate (LDI). Isocyanates may be used alone or in admixture of two or more. The isocyanate may be water-dispersed or non-water-dispersed.

  From the viewpoint of handling and working environment, and from the viewpoint of increasing the strength of the molded plate more effectively, 2,4′-MDI, 2,2′-MDI, 4,4′- A mixture of MDI and polymeric MDI having 3 or more benzene rings is preferred.

(Content ratio of sugar and organic sulfonic acid and reaction mechanism)
In the sugar-based mixture, the organic sulfonic acid is preferably contained in an amount of 0.1 to 75 parts by mass with respect to 100 parts by mass of the sugar. When the sugar is 100 parts by mass, when the organic sulfonic acid content is 0.1 parts by mass or more, the effect as a reaction catalyst is easily obtained. In addition, when the sugar is 100 parts by mass, when the content of the organic sulfonic acid is 75 parts by mass or less, the hydrolysis reaction of the sugar is not excessively promoted, and the polymerization may be inhibited. Less. Moreover, it can suppress that an acid remains and the intensity | strength of a shaping | molding board falls. Furthermore, when the molded plate is produced, the contact ratio between the press machine and the organic sulfonic acid is reduced during pressurization, so that the metal corrosion of the press machine is difficult to proceed.

  The content ratio of sugar to organic sulfonic acid in the sugar mixture is such that the content of organic sulfonic acid is 0.15 parts by mass to 20 parts by mass when sugar is 100 parts by mass. preferable. Furthermore, when the sugar is 100 parts by mass, the content of the organic sulfonic acid is more preferably 0.2 parts by mass to 15 parts by mass.

  The reaction mechanism of sugar and organic sulfonic acid is presumed as follows. The sugar is hydrolyzed in the presence of the organic sulfonic acid, temporarily reduced in molecular weight and modified, and then modified into a low molecular compound having a furan ring or the like. Furthermore, the organic sulfonic acid serves as a catalyst, the polymerization reaction between the low molecular compounds is promoted, and polymerized. For this reason, the polymerized compound contributes to adhesion. In addition, since organic sulfonic acid has lower reactivity with metal than inorganic acid, it is difficult to adversely affect metal facilities during molding. Further, the reaction system of sugar and organic sulfonic acid does not contain an organic solvent or formaldehyde, and does not contain a tertiary amine that generates formaldehyde by decomposition. Therefore, it becomes easy to suppress the emission of organic solvents and formaldehyde. This action can also be caused by the reaction of a saccharide with an acid such as a carboxylic acid. However, the combination of a saccharide and an organic sulfonic acid has a higher reactivity of polymerization. Therefore, the adhesive of this embodiment has a sugar-based mixture obtained by mixing sugar and organic sulfonic acid as an essential component.

  It should be noted that sugar can undergo a reaction of low molecular weight by hydrolysis and subsequent high molecular weight even in the presence of carboxylic acid. However, in the reaction between a saccharide and a carboxylic acid, a sugar containing a fructose residue reacts quickly, but a sugar containing a glucose residue tends to react slowly. On the other hand, it was found that in the reaction between sugar and organic sulfonic acid, the reaction was fast even with a sugar containing no fructose residue.

  The sugar not containing a fructose residue can be obtained by saccharification of starch produced from corn, potato, sweet potato, tapioca and the like with an enzyme. Specifically, maltose as a disaccharide is obtained by the action of amylase, and glucose (glucose) is obtained by the action of glucoamylase. Cellobiose can be obtained by saccharifying cellulose. These sugars do not contain fructose residues as they are, and the reaction rate is slow in the reaction with carboxylic acids. However, in the reaction between sugar and organic sulfonic acid, the reaction rate can be increased regardless of the presence or absence of fructose residues. Therefore, the range of sugar selection can be expanded, and a wide variety of sugars can be used, so that an excellent thermosetting adhesive utilizing natural resources can be obtained.

(Content ratio of sugar-based mixture and isocyanate and reaction mechanism)
In the adhesive of this embodiment, it is preferable that 4-400 mass parts of isocyanate is included with respect to 100 mass parts of sugar-type mixtures. Moreover, it is more preferable that 4-400 mass parts of isocyanate is included with respect to a total of 100 mass parts of saccharide | sugar and organic sulfonic acid.

  When the isocyanate is 4 parts by mass or more with respect to 100 parts by mass of the sugar-based mixture, the next reaction is likely to proceed. First, sugar hydroxyl groups react with isocyanate to form urethane bonds. A part of the generated urethane bond is decomposed into amine and carbon dioxide. However, since carbon dioxide is released out of the system, the decomposition reaction of the urethane bond becomes an irreversible reaction, and the elimination of carbon dioxide is promoted. On the other hand, the produced amine reacts with isocyanate to form a urea bond, thereby improving adhesion. As described above, in the adhesive of the present embodiment, a modified product of sugar generated by the reaction of sugar and organic sulfonic acid reacts with isocyanate to form a urethane bond or a urea bond, thereby exhibiting excellent adhesiveness. Is possible.

  Here, even when isocyanate exceeds 400 parts by mass with respect to 100 parts by mass of the sugar-based mixture, the effect of the present embodiment can be obtained. However, when the isocyanate exceeds 400 parts by mass, the reaction between the sugar and the organic sulfonic acid becomes difficult to proceed, and the reaction between the isocyanate, the sugar and the plant piece becomes dominant. May be reduced. Furthermore, when the reaction of isocyanate becomes dominant, since isocyanate has high binding property with a metal, sticking with a press device or the like may occur, and productivity may be lowered. Further, since the cost increases when a large amount of isocyanate is used, even if sugar is used, the cost advantage may be reduced. Therefore, it is preferable that isocyanate is 400 mass parts or less with respect to 100 mass parts of sugar-type mixtures.

  In the adhesive of this embodiment, sugar, organic sulfonic acid, and isocyanate are the main components. A main component is a component which contributes to adhesiveness in the component in an adhesive agent.

  As will be described later, the molded plate of this embodiment can be obtained by heating and pressurizing the obtained mixture after mixing the adhesive and the plant pieces. That is, for example, a molded plate can be formed by compressing the mixture from above and below with a heated hot platen. However, when the mixture of the adhesive and the plant piece is compressed with a hot platen, the reaction between the sugar and the organic sulfonic acid may not easily proceed in the core layer that is far from the hot plate and does not easily rise in temperature. However, since the adhesive of the present embodiment contains isocyanate in addition to the sugar-based mixture, even if an unreacted product of sugar and organic sulfonic acid is present in the core layer, the adhesive is more adhesive due to the reaction product of isocyanate. Is obtained. Therefore, even a molded plate having a large thickness can ensure high adhesion and water resistance while shortening the time required for curing.

(Carboxylic acid content and reaction mechanism)
In the adhesive of this embodiment, it is preferable that the sugar-based mixture further contains a carboxylic acid, and 0.1 to 600 parts by mass of the carboxylic acid with respect to 100 parts by mass of the sugar. Since the sugar-based mixture contains carboxylic acid, in addition to the reaction between sugar and organic sulfonic acid, the reaction between sugar and carboxylic acid can coexist, thus increasing the reactivity and improving the adhesion Can do. In addition, when carboxylic acid is contained, the bondability of the cured product is increased, so that the water resistance can be improved.

  The carboxylic acid is preferably contained in an amount of 0.1 to 600 parts by mass with respect to 100 parts by mass of the sugar. When the sugar is 100 parts by mass, the effect of the carboxylic acid is further enhanced when the content of the carboxylic acid is 0.1 parts by mass or more. Further, when the saccharide content is 100 parts by mass, when the carboxylic acid content is 600 parts by mass or less, unreacted carboxylic acid hardly remains and the curability can be improved. More preferably, when the sugar is 100 parts by mass, the carboxylic acid content is 0.2 to 200 parts by mass. More preferably, when the sugar is 100 parts by mass, the content of carboxylic acid is 2 parts by mass to 30 parts by mass. The content of carboxylic acid may be less than the content of organic sulfonic acid. For example, the content of carboxylic acid may be half or less than the content of organic sulfonic acid.

  As the carboxylic acid, at least one of a monovalent carboxylic acid and a polyvalent carboxylic acid can be used. The polyvalent carboxylic acid is preferably an organic carboxylic acid having a plurality of carboxyl groups (COOH) in one molecule.

  Examples of the monovalent carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, lactic acid, benzoic acid and the like. As the polyvalent carboxylic acid, at least one selected from the group consisting of a divalent carboxylic acid, a trivalent carboxylic acid, a tetravalent carboxylic acid, and a pentavalent or higher carboxylic acid can be used. Of these, divalent to tetravalent carboxylic acids are preferable because they are easy to use. Examples of the polyvalent carboxylic acid include citric acid, itaconic acid, malic acid, tartaric acid, succinic acid, oxalic acid, adipic acid, malonic acid, phthalic acid, sebacic acid, maleic acid, fumaric acid, glutaric acid (pentanedioic acid). ), Gluconic acid, glutaconic acid, pentenedioic acid and the like. These monovalent carboxylic acids and polyvalent carboxylic acids may be anhydrides. Among these, the polyvalent carboxylic acid preferably contains at least one of citric acid and itaconic acid. Citric acid and itaconic acid can be produced from plants. In this case, since the use of fossil resources can be suppressed, the load on the environment is reduced, which is preferable.

  The polyvalent carboxylic acid may have a hydroxyl group. In that case, it becomes possible to improve adhesiveness. The polyvalent carboxylic acid preferably has a molecular weight of 500 or less, more preferably 300 or less. When the molecular weight of the polyvalent carboxylic acid is small, the catalytic efficiency for sugar can be increased.

  It is preferable that the adhesive of this embodiment does not contain excess polyvalent carboxylic acid. Multivalent carboxylic acids may react slowly with sugars. Moreover, when polyhydric carboxylic acid is contained excessively, progress of reaction with saccharide | sugar and organic sulfonic acid may be prevented. Therefore, the adhesive of this embodiment does not need to contain polyvalent carboxylic acid.

  When the adhesive contains a carboxylic acid, the reaction between the sugar and the carboxylic acid is slower than the reaction between the sugar and the organic sulfonic acid, so the carboxylic acid may remain as an unreacted material left behind in the reaction. . If carboxylic acid remains after curing, the curing reaction may not proceed sufficiently. Therefore, it is preferable that no carboxylic acid remains after curing. In order to prevent carboxylic acid from remaining after curing, the adhesive only needs to contain carboxylic acid to such an extent that carboxylic acid does not remain after curing. In particular, polyvalent carboxylic acids are expected to react with sugars, but if they remain, the adhesiveness may not be sufficiently exhibited. Therefore, it is preferable that no polycarboxylic acid remains after curing.

(Adhesive form)
The adhesive of this embodiment may be a powder or a liquid. Since many of the above components are solid, a powdery adhesive can be obtained by mixing with powder. The liquid adhesive can be obtained by dissolving or dispersing the above components in a solvent. Although it does not specifically limit as a solvent, For example, water, alcohol, etc. are illustrated.

  Here, sugar, organic sulfonic acid, and carboxylic acid can be easily made into an aqueous solution. Many isocyanates are liquid at room temperature. Therefore, an aqueous solution of sugar, organic sulfonic acid and carboxylic acid and liquid isocyanate can be treated as separate liquids and separately dispersed in plant pieces to be described later.

  When the adhesive of this embodiment is a liquid, it is preferably an aqueous dispersion. Thereby, the adhesive can be easily prepared and the handling becomes easy. Moreover, application | coating or dispersion | spreading to a to-be-adhered material becomes easy by making an adhesive agent into an aqueous dispersion. Furthermore, since no organic solvent is used, the human body is safe and environmentally friendly.

  Sugar, organic sulfonic acid, and carboxylic acid are easily dissolved in water, but isocyanate is difficult to dissolve. Therefore, isocyanate can be dispersed in water. In addition, although isocyanate reacts with water, since it becomes an acidic liquid with organic sulfonic acid, reaction at normal temperature is slow and can be made into a dispersion. In addition, when a sugar and an organic sulfonic acid are mixed with water at a concentration higher than the saturation concentration, an aqueous dispersion can be obtained. Because sugar and organic sulfonic acid are in a compatible state, when heated and pressurized, the modification of sugar and organic sulfonic acid is promoted, forming a polymer cured product, and exhibiting excellent adhesiveness be able to.

  When the adhesive is an aqueous solution or an aqueous dispersion, the amount of water is appropriately set depending on the shape and surface properties of the adherend and is not particularly limited. The adhesive of the aqueous solution or aqueous dispersion preferably contains 15 to 500 parts by mass of water with respect to 100 parts by mass in total of sugar and organic sulfonic acid. When the water content is 15 parts by mass or more, water does not decrease too much and mixing becomes easy, so a more uniform adhesive can be obtained. In order to make the adhesive more uniform, the water content is more preferably 25 parts by mass or more when the total amount of sugar and organic sulfonic acid is 100 parts by mass. On the other hand, when the content of water is 500 parts by mass or less, the amount of water does not increase excessively, and the adhesiveness of the adhesive can be exhibited better. This is because excessive penetration of the adhesive is less likely to occur, and a slow increase in temperature due to evaporation during heat curing is suppressed, and curability is improved. From that viewpoint, it is more preferable that the content of water is 400 parts by mass or less when the total amount of sugar and organic sulfonic acid is 100 parts by mass.

  When the adhesive is an aqueous solution or an aqueous dispersion and further contains a carboxylic acid, the amount of water may be based on the total amount of sugar, organic sulfonic acid and carboxylic acid. The amount of water added is preferably 15 parts by mass or more, and more preferably 25 parts by mass or more when the total amount of sugar, organic sulfonic acid and carboxylic acid is 100 parts by mass. The amount of water is preferably 500 parts by mass or less, and more preferably 400 parts by mass or less, when the total amount of sugar, organic sulfonic acid and carboxylic acid is 100 parts by mass.

  In the case where the adhesive is an aqueous solution or an aqueous dispersion and does not contain a carboxylic acid, the amount of water may be further reduced. For example, in this case, the blending amount of water may be 300 parts by mass or less or 250 parts by mass or less when the total amount of sugar and organic sulfonic acid is 100 parts by mass.

  In the adhesive of the present embodiment, sugar, organic sulfonic acid, and isocyanate are the main components of adhesion. And when carboxylic acid is added, carboxylic acid becomes a component which assists adhesion | attachment.

  Note that the adhesive may contain an additive. Examples of the additive include a stabilizer, a colorant, a thickener, a reaction accelerator, and the like.

  In the above adhesive, the reaction system does not need to contain an organic solvent or formaldehyde. Therefore, it is possible to suppress the diffusion of the organic solvent derived from the adhesive and the diffusion of formaldehyde.

(Adhesion with adhesive)
The adhesive of the present embodiment can exhibit adhesiveness and adhere the adherend by heating and pressurizing it between the adherend and the adherend. The heating and pressing are preferably a press. According to the press, the adhesiveness can be easily expressed. The adherend may be two or more solid members having an adhesive surface, or may be a plurality of small pieces formed by an adhesive. In the case of bonding two solid members, for example, an adhesive is disposed between the members by application or spraying, and then the members are pressed in a direction approaching each other to be heated and pressurized. Thereby, the curing reaction of the adhesive proceeds and the members can be bonded. Moreover, when shape | molding by adhere | attaching a some small piece with an adhesive agent, for example, after mixing a some small piece with an adhesive agent, this mixture is arrange | positioned to a shaping | molding die, and is heated and pressurized. As a result, the curing reaction of the adhesive proceeds, and a small plate can be bonded to form a molded plate.

  The adhesive can be used for bonding various members and small pieces. Moreover, an adhesive agent can be used for adhesion | attachment of a metal, for example, can adhere a stainless steel block. Further, the adhesive can be used for bonding wood or glass.

  Thus, the adhesive of this embodiment contains a sugar-based mixture containing sugar and organic sulfonic acid and isocyanate. And 0.1-75 mass parts of organic sulfonic acids are included with respect to 100 mass parts of sugars. Since the polymerization reaction is promoted by the coexistence of the organic sulfonic acid and the isocyanate and becomes a strong adhesive component, an adhesive having excellent adhesiveness can be obtained. Further, even when a molded plate having a large thickness is manufactured, the time required for curing is shortened, so that practical production efficiency and cost can be achieved.

[Molded plate]
Next, the molded plate according to the present embodiment will be described in detail. The molded board of this embodiment includes the above-described adhesive and a plurality of plant pieces that are bonded by the adhesive.

  In this embodiment, a molded board can be formed by using the above-mentioned adhesive and a plurality of plant pieces. Since a plant piece becomes an element in a shaping | molding board, you may call it an element piece. And since the adhesiveness of this embodiment exhibits adhesiveness by heating and pressurization, it can be used suitably for formation of a shaping | molding board. In addition, the adhesive may not contain an organic solvent or formaldehyde in the reaction system, and may not contain a tertiary amine that generates formaldehyde by decomposition. Therefore, it is possible to suppress the diffusion of the organic solvent derived from the adhesive and the diffusion of formaldehyde.

(Plant fragment)
Examples of plants used as raw materials for plant fragments include woody plants such as conifers and broad-leaved trees, annual or biennial herbaceous plants, or agricultural waste after harvesting grains, vegetable oils, plant sugars, and the like. Specific examples of agricultural waste include herbs such as kenaf, rice, bamboo, and flax, bagasse, beet pulp, rice straw, wheat straw, and oil palm fiber. By using these, effective use of resources can be achieved. In particular, the utilization of resources can be promoted by using annual or biennial herbaceous plants or agricultural waste.

  Woody plants such as conifers and hardwoods are rich in cellulose, hemicellulose, and lignin. In addition, herbaceous plants have cellulose, hemicellulose, and lignin as main constituents, the same as woody plants. Furthermore, herbaceous plants are characterized by a high content of low-molecular components such as hemicellulose components and hot water-soluble components as compared with woody plants, and rich in components that denature into adhesive components under heat and pressure. Therefore, it is suitable for the material of the forming plate.

  Specific examples of the hemicellulose component include arabinoglucuronoxylan, glucomannan, and glucuronoxylan. Arabinoglucuronoxylan and glucomannan are components that are mainly contained in conifers. Glucuronoxylan and glucomannan are components that are mainly contained in hardwoods. The plant piece may contain these components or components similar thereto.

  The plant piece may be obtained by cutting a plant, etc., and may be a small piece, a fiber, a single plate, or a powder. Good. The molded board obtained by the plant piece and the adhesive can be a wooden board. Here, the term “woody” refers to a molded product having a woody texture, and even a material obtained from a plant other than wood is included in the wooden board.

(Plant pieces containing sugar)
As described above, the plant piece preferably contains at least one selected from the group consisting of a cellulose component, a hemicellulose component, and lignin. In that case, since adhesiveness can be expressed by the component derived from a plant piece, adhesiveness can be improved. Moreover, the plant piece may contain sugar. In that case, since the sugar derived from a plant piece reacts with an organic sulfonic acid and expresses adhesiveness, adhesiveness can be improved.

  As the plant piece, a wood piece obtained by cutting wood can be used. Examples of the wood pieces include a saw board, a single board, a wood strand, a wood chip, and a wood fiber. A material obtained by bonding a wood piece with an adhesive can be a wood-based board such as a laminated board, plywood, fiber board, oriented strand board (OSB), particle board, medium density fiber board (MDF). And when the adhesive agent of this embodiment is used, since adhesive agent forms the polymeric hardened | cured material, the outstanding adhesiveness and a moldability can be expressed. Although it does not specifically limit as wood, Appropriate materials, such as a cedar, a cypress, a hiba, a pine, a moth, and a drill, may be sufficient.

  A herbaceous plant can also be used as the plant piece. As the herbaceous plant, at least one of sugar cane and sugar beet can be used. These can utilize residual sugar and improve physical properties. Further, since the remaining sugar can be reduced in the molded plate, the physical properties can be improved. In particular, bagasse, which is a pomace of sugarcane, can be used effectively.

(Adhesion mechanism of plant fragments)
Low molecular components such as hemicellulose components, sugars, and hot water soluble components contained in plant fragments are modified into adhesive components under heat and pressure, but the reaction is accelerated and coherent due to the coexistence of organic sulfonic acid and isocyanate. Become an ingredient. That is, the hemicellulose component and sugar are hydrolyzed by the presence of the organic sulfonic acid and temporarily reduced in molecular weight, and then the organic sulfonic acid serves as a catalyst to promote the polymerization reaction between the low molecular compounds. Moreover, components having a hydroxyl group such as hemicellulose components, sugars, and lignin react with isocyanate. Therefore, when these components are contained in the plant piece, the adhesiveness is increased. In addition, if low-molecular components such as hemicellulose and sugar remain in the molding plate, this component may cause mold generation. However, by adding organic sulfonic acid and isocyanate, molding of low-molecular components such as hemicellulose and sugar is possible. Residual amount in the plate can be reduced. Therefore, it is possible to obtain a molded plate in which generation of mold is suppressed.

  Moreover, when an organic sulfonic acid and isocyanate coexist with a plant piece, a shaping | molding board can be shape | molded in a short time. On the other hand, if organic sulfonic acid and isocyanate are not present, the reaction between the modified low molecular compounds is delayed, which may cause deterioration of physical properties. In addition, since organic sulfonic acid has a lower reactivity with metals than inorganic acids, it is difficult to adversely affect metal facilities during molding.

(Shape of plant fragment)
The plant piece used as the raw material of a shaping | molding board can be processed into the granular particle | grains with a diameter of several hundred micrometers-several cm by a grinding process. Moreover, the plant used as the raw material of the molded plate has a diameter (fiber diameter) of about 50 μm to 2 mm and a length (fiber length) of about 100 μm to 20 mm by defibrating the bast portion and stem core portion. It can be processed into fine fibers. Using these particles and fine fibers as plant pieces (fine pieces), a molded plate can be produced.

(Mixing ratio of plant fragment and adhesive)
The mixing ratio of the plant piece and the adhesive is appropriately set depending on the raw materials to be used, molding conditions, use of the resulting molded plate, necessary physical properties, and the like, and is not particularly limited. For example, the solid content of the adhesive is preferably 4 to 20 parts by mass with respect to 100 parts by mass of the dry mass of the plant pieces. If the amount of the adhesive is too small, the adhesive force may be reduced, and even if the amount of the adhesive is too large, an adhesive layer may be formed so that the interfacial adhesion may be reduced. Is preferably blended. As for the solid content amount of an adhesive agent, it is more preferable that it is 8 mass parts or more with respect to 100 mass parts of dry mass of a plant piece. In this case, the adhesiveness is further increased. The solid content of the adhesive is more preferably 15 parts by mass or less with respect to 100 parts by mass of the dry mass of the plant piece. In this case, a decrease in interfacial adhesion can be further suppressed.

(Adhesive conditions during molding plate production)
As mentioned above, it is preferable that the adhesive of this embodiment contains 0.1-75 mass parts of organic sulfonic acids with respect to 100 mass parts of sugars. Here, when using the plant piece containing sugar, the sugar in a plant piece contributes to adhesiveness as mentioned above. This is because the sugar in the plant piece reacts with the organic sulfonic acid. Therefore, in the adhesive of the present embodiment, the organic sulfonic acid can sufficiently exhibit adhesiveness even when the amount is more than 75 parts by mass with respect to 100 parts by mass of the sugar in the adhesive. For example, the organic sulfonic acid may be 100 parts by mass or more, or 200 parts by mass or more with respect to 100 parts by mass of the sugar in the adhesive. In this case, the upper limit of the content of the organic sulfonic acid is not particularly limited, but the organic sulfonic acid is preferably 10000 parts by mass or less, and 1000 parts by mass with respect to 100 parts by mass of the sugar in the adhesive. It is more preferable that the amount is not more than part.

  When bonding plant pieces, the adhesive preferably contains a carboxylic acid. When the carboxylic acid is used, the carboxylic acid supplements the catalytic reaction of the organic sulfonic acid to exert a catalytic action, and the adhesiveness can be improved. Moreover, when the reaction of the organic sulfonic acid and the reaction of the carboxylic acid are mixed, a stronger cured product can be formed and a molded plate having high strength can be obtained. The carboxylic acid is particularly preferably a polyvalent carboxylic acid. The addition of carboxylic acid improves the physical properties.

(Shape of molded plate)
The thickness and density of the molded plate of the present embodiment are not particularly limited, and are set as appropriate depending on the application, but the thickness is preferably 2 mm or more and 40 mm or less. A thickness of 2 mm or more is preferable because physical properties such as strength of the molded plate are secured. When the thickness is 40 mm or less, the amount of heat that cures the adhesive is transmitted to the center of the molded plate within a practically possible molding time by heating and pressurizing, so the cured product of the adhesive reaches the center. Can be formed. In addition, since a physical property can be ensured if the density is the density prescribed | regulated to the fiber board and particle board in Japanese Industrial Standard, and the wood panel in Japanese agricultural and forestry standard, it is preferable.

(Layer structure of molded plate)
When the molded board is a particle board, a layer structure is often formed. Since the surface layer and the back layer of the molded plate are often required to be dense and smooth, fine plant pieces are often used. Further, the surface layer and the back layer are often added with a large amount of adhesive or a water-repellent component such as wax in order to suppress entry of moisture and the like. On the other hand, as the core layer in the molded plate, plant pieces having a size larger than that of the front layer and the back layer may be used for securing the strength of the board.

  When the molded plate is composed of at least three layers of a surface layer, a core layer, and a back layer, the composition of the adhesive used for the surface layer and the back layer and the adhesive used for the core layer may be different. That is, the surface layer and the back layer are close to the hot platen at the time of molding and the temperature rises rapidly, so that the content of isocyanate that cures at a low temperature may be small. On the other hand, when molding, the core layer, which is far from the hot platen and has a slow temperature rise, can be molded into a board whose strength is ensured in a short time if the content of isocyanate is larger than the surface layer and the back layer. Therefore, it is preferable. In addition, the thickness of each layer and the shape of a plant piece can be suitably set according to a use.

  The adhesive used for the front layer and the back layer preferably has a mass ratio of sugar and organic sulfonic acid to isocyanate of 100: 0 to 150 (sum of sugar and organic sulfonic acid: isocyanate). Moreover, it is preferable that the mass ratio of the sum total of saccharide | sugar and organic sulfonic acid and isocyanate is 100: 40-150 (total of saccharide | sugar and organic sulfonic acid: isocyanate) as for the adhesive agent used for a core layer. Within this range, it is preferable because a board having physical properties can be formed in a short time.

(Adhesive dispersion method)
The method of dispersing the sugar-based mixture containing sugar and organic sulfonic acid and the isocyanate on the surface of the plant piece is not particularly limited. Many sugars and organic sulfonic acids are powders, and many are water-soluble. Most of isocyanate is liquid at room temperature, and when it is dispersed in water or alcohol, the reaction proceeds with time and insoluble matter is likely to be produced. However, since isocyanate reacts slowly under acidic conditions such as organic sulfonic acid and carboxylic acid, it is possible to prepare an adhesive as an aqueous dispersion and disperse it in plant pieces by spraying or coating. Moreover, it can also disperse | distribute separately with respect to a plant piece, without mixing a sugar-type mixture and isocyanate.

(Conditions for heating and pressurizing when manufacturing molded plates)
The molded plate can be produced by mixing a small piece, which is an adherend, and the above-mentioned adhesive, and heating and pressing the mixture. When using a plant piece, the plant piece used as a raw material may be a dry raw material. Thereby, handling becomes easy. Moreover, the ground material which grind | pulverized the shaping | molding board using a plant piece can also be used as a plant piece. In that case, the plant piece can be reused. In addition, in this embodiment, since the saccharide | sugar mixture containing saccharide | sugar and organic sulfonic acid and isocyanate are used together, heat press molding can be performed efficiently. For this reason, heating and pressing can be performed in a shorter time.

  The molded plate can be obtained by attaching an adhesive to the above-mentioned plant pieces and then heat-pressing the plant pieces to which the deposits are attached. In this case, for example, it is preferable to obtain the mixture by attaching an adhesive of an aqueous solution or an aqueous dispersion to the plant piece and heating and pressing the mixture. By using water as a dispersion solvent for the sugar-based mixture and the isocyanate, the adhesive can be efficiently attached to the surface of the plant piece. In addition, although an organic solvent may be used as a dispersion solvent instead of water, water is more advantageous from the viewpoint of environmental protection.

  By heat and pressure molding, the adhesive can react to obtain a molded plate. In the case of using plant pieces, the plant pieces are bonded together with an adhesive component generated by denaturing the components contained in the plant pieces themselves.

  As a method of attaching the adhesive to the plant piece, an appropriate attachment method can be used. For example, it can be made to adhere by spraying aqueous solution toward a plant piece with a spray. Moreover, it can be made to adhere by immersing a plant piece in aqueous solution. Furthermore, it can also be made to adhere by apply | coating with a roll, a brush, etc. Further, components other than isocyanate can be adhered by using a powder adhesive instead of an aqueous solution or water dispersion and spraying this powder directly on plant pieces.

  The conditions for heat and pressure molding, such as molding pressure, molding temperature, molding time, etc., can be appropriately set depending on the type and shape of the plant piece, its surface condition, the thickness of the molding plate, and the like. The molding temperature is preferably 140 ° C. or higher and 240 ° C. or lower. When the molding temperature is 240 ° C. or lower, the deterioration of the components hardly proceeds, so that the physical properties as a molded plate are hardly lowered. In addition, when the molding temperature is 140 ° C. or higher, the reaction rate is difficult to decrease and curing is likely to be sufficient. The molding temperature is more preferably 200 ° C. or lower. In this case, deterioration of the adherend can be suppressed. The molding temperature is preferably 160 ° C. or higher. In this case, the reaction rate is less likely to decrease, and curing is likely to be further sufficient.

  The molding pressure is appropriately set depending on the thickness, specific gravity and the like of the molded plate, but is preferably 0.5 MPa or more and 4 MPa or less. When the molding pressure is 0.5 MPa or more, it is possible to sufficiently press-bond, and it is easy to improve the strength of the molded plate. When the molding pressure is 4 MPa or less, the molding pressure is not too high and the molded plate is hardly broken. The molding pressure is more preferably 3 MPa or less. In this case, it is possible to make the molded plate more difficult to break. The molding pressure is more preferably 0.7 MPa or more. In this case, the adhesive and the adherend can be sufficiently bonded, and the strength of the molded plate can be further increased.

  With respect to the molding time, for example, it can be in the range of 1 minute to 60 minutes, preferably 2 minutes to 30 minutes, more preferably 3 minutes to 15 minutes. Thereby, a favorable molded board can be manufactured efficiently.

  In addition, it is preferable that sugar is not left as much as possible on the obtained molded plate. Thereby, while improving adhesiveness, water resistance can be improved. In addition, when no sugar remains, the generation of mold can be suppressed. That is, the sugar in the adhesive is modified by the organic sulfonic acid, but it is preferable that the total amount of the sugar is modified. Moreover, when a plant piece contains saccharide | sugar, it is preferable to also modify | denature the saccharide | sugar in a plant piece. For example, the ratio of the sugar obtained by extracting the molded plate with hot water at 90 ° C. for 3 hours is preferably less than 5% by mass, and more preferably 1% by mass or less. Moreover, it is more preferable that the ratio of the said saccharide | sugar is 0.5 mass% or less in a dry component, and it is especially preferable that it is 0.1 mass% or less. In addition, a dry component means the component when it becomes constant weight when a shaping | molding board is heated at 105 degreeC, ie, a component when it becomes constant weight.

  It is better that the resulting molded plate contains as little carboxylic acid derived from the adhesive as possible. That is, the carboxylic acid in the adhesive is used for the reaction with the sugar, but it is preferable that the entire amount of the carboxylic acid is used for the reaction and does not remain. Thereby, while improving adhesiveness, water resistance can be improved. For example, the ratio of the carboxylic acid obtained by extracting the molded plate with hot water at 90 ° C. for 3 hours is preferably less than 5% by mass, and more preferably 1% by mass or less. . Further, the ratio of the carboxylic acid is more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less in the dry component.

(Surface material)
The molded plate may be provided with a surface material on one surface or both surfaces thereof. By providing the surface material, the strength of the molded plate can be increased. The surface material may be a board shape, a sheet shape, or the like. In this case, the molded plate becomes a part of the composite molded plate made of the composite material. The surface material may be provided by being adhered to the molded plate after molding, or may be provided by being overlapped at the time of molding the molded plate and adhered by a component in the adhesive. As surface material, board, such as wood, particle board, fiberboard, veneer made by thinly slicing wood, decorative sheet made of plastic or paper, sheet-like material such as moisture-proof sheet, etc. Can be used.

  Hereinafter, the present embodiment will be described in more detail with reference to examples, comparative examples, and reference examples, but the present embodiment is not limited to these examples.

[Examples 1-1 to 1-4, and Comparative Examples 1-1 and 1-2]
Evaluation of curability of adhesives (sugar mixtures consisting of sugar and organic sulfonic acid, and isocyanate) alone

(Sample preparation)
First, 95 parts by mass of sucrose (manufactured by Wako Pure Chemical Industries, Ltd.), 5 parts by mass of metaxylenesulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.), and 100 parts by mass of water were mixed and dissolved. As a result, an aqueous solution containing sugar and organic sulfonic acid and having a solid content ratio of 50% was prepared.

  Next, the obtained aqueous solution and isocyanate were mixed in the proportions shown in Table 1 (sugar mixture: isocyanate = 100: 0, 95: 5, 75:25, 50:50, 25:75, 0: 100). The total solid mass was weighed so as to be 2 g. Then, the weighed aqueous solution and isocyanate were mixed in a 110 mL glass sample tube bottle. This sample tube bottle was heated in a dryer at 180 ° C. for 60 minutes to obtain a cured sample of each example. As the isocyanate, Soflan-R MIC-K (polymethylene polyphenylene polyisocyanate (polymeric MDI) 100% single substance, liquid with a solid content of 100%) manufactured by Soflan With Co., Ltd. was used.

(Hot water extraction)
100 mL of distilled water was added to a 110 mL glass sample tube bottle containing the cured sample of each example, and hot water extraction was performed. In addition, hot water extraction was performed by heating the mixture of a sample and distilled water at 95 degreeC for 4 hours. And the mixture after hot water extraction was filtered, and it isolate | separated into the hot water insoluble material and the hot water soluble material.

(Drying and mass measurement)
The hot water insoluble material was dried with a dryer at 105 ° C. to obtain a constant weight, and then mass measurement was performed. And the hot water insoluble rate (hardening rate) was computed from the following numerical formula 1 from the mass of the hot water insoluble matter and the mass of the sample before hot water extraction. The hot water insolubility (curing rate) is shown in Table 1. In addition, about the result of a hot water insoluble rate, the graph which made the ratio (mass%) of the isocyanate in the total solid of an adhesive the horizontal axis, and made the hot water insoluble rate (curing rate) the vertical axis | shaft is shown in FIG.
[Equation 1]
[Hot water insoluble rate (%)] = [Mass of hot water insoluble matter] / [Mass of cured sample] × 100

  As shown in Table 1, when the mixing ratio is sugar-based mixture: isocyanate = 0: 100, it is a water-insoluble component before curing, so the curing rate is high. On the other hand, when the mixture ratio is sugar-based mixture: isocyanate = 100: 0, since all are water-soluble components before curing, the curing rate is low.

  Here, the hot water insolubility when the sugar-based mixture and the isocyanate are mixed at 50:50 is 64%, which is the hot water insolubility of only the sugar-based mixture, if both components cause curing inhibition. It becomes lower than 79% which is an intermediate between 94% which is the hot water insolubility of only isocyanate. Moreover, when both components accelerate | stimulate hardening, it becomes higher than 79%, and when both components do not inhibit hardening, it becomes about 79% of the middle. That is, as shown in FIG. 1, when creating a graph in which the ratio of isocyanate in the total solid content of the adhesive is on the horizontal axis and the hot water insolubility is on the vertical axis, if both components cause curing inhibition, The graph is considered to have a downwardly convex shape. Moreover, when both components accelerate | stimulate hardening, it is thought that a graph becomes an upward convex shape. When both components do not inhibit or accelerate curing, it is considered that they are connected by a straight line such as the dotted line shown in FIG.

  As shown in Table 1, when the sugar-based mixture and the isocyanate were mixed at 50:50, the hot water insolubility was 84%, which was higher than the middle 79%. From this result, it is considered that curing is accelerated by mixing the sugar-based mixture and the isocyanate as compared with the case of single use. Moreover, as shown in FIG. 1, it is considered that the sugar-based mixture: isocyanate = 0: 100 and 100: 0 have a convex shape upward, and both components are more accelerated than when alone. . In particular, the promoting effect at 180 ° C. is remarkable.

  Thus, it turns out that sclerosis | hardenability improves by hardening in presence of the sugar-type mixture containing sugar and organic sulfonic acid, and isocyanate as an adhesive agent.

[Examples 2-1 to 2-4 and 3-1 to 3-4, and Comparative Examples 2-1 to 2-2 and 3-1 to 3-2]
Evaluation of curability of adhesives (sugar, organic sulfonic acid and carboxylic acid mixture, and isocyanate) alone

(Sample preparation)
First, 107 parts by mass of sugarcane molasses, 25 parts by mass of citric acid (manufactured by Wako Pure Chemical Industries, Ltd.), 1 part by mass of p-toluenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.), and 68.1 parts by mass of water Were mixed and dissolved. As a result, an aqueous solution containing sugar, organic sulfonic acid and carboxylic acid and having a solid content ratio of 50% was prepared. The sugarcane waste molasses is from Hayashi Shokai Co., Ltd., and has a solid content ratio of 70%, a sugar content ratio of 62%, and a sucrose content ratio of 29.5%.

  The obtained aqueous solution and isocyanate were mixed in the proportions shown in Tables 2 and 3 (sugar mixture: isocyanate = 100: 0, 95: 5, 75:25, 50:50, 25:75, 0: 100). ) And the total solid mass was weighed to 2 g. Then, the weighed aqueous solution and isocyanate were mixed in a 110 mL glass sample tube bottle. The sample tube bottle was heated in a drier at 200 ° C. or 160 ° C. for 60 minutes to obtain a cured sample of each example. Isocyanate is a mixture of 55% by mass of Oshika Resin B-1605 (polymethylene polyphenylene polyisocyanate (polymeric MDI)) manufactured by Oshika Co., Ltd. and 45% by mass of 4,4′-diphenylmethane diisocyanate (4,4′-MDI). It was used. The isocyanate mixture was a liquid having a solid content of 100%.

(Hot water extraction)
100 mL of distilled water was added to a 110 mL glass sample tube bottle containing the cured sample of each example, and hot water extraction was performed. In addition, hot water extraction was performed by heating the mixture of a sample and distilled water at 95 degreeC for 4 hours. And the mixture after hot water extraction was filtered, and it isolate | separated into the hot water insoluble material and the hot water soluble material.

(Drying and mass measurement)
The hot water insoluble material was dried with a dryer at 105 ° C. to obtain a constant weight, and then mass measurement was performed. And from Formula 1, the hot water insoluble rate (curing rate) was calculated from the mass of the hot water insoluble material and the mass of the sample before hot water extraction. Table 2 shows the hot water insolubility (curing rate) of Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-2. Moreover, the hot water insoluble rate (curing rate) of Examples 3-1 to 3-4 and Comparative Examples 3-1 to 3-2 is shown in Table 3. In addition, about the result of a hot water insoluble rate, the graph which made the ratio (mass%) of the isocyanate in the total solid of an adhesive the horizontal axis and made the hot water insoluble rate (curing rate) the vertical axis | shaft is shown in FIG.

  As shown in Table 2 and Table 3, since the mixture ratio of sugar-based mixture: isocyanate = 0: 100 is a water-insoluble component before curing, the curing rate is both 160 ° C. and 200 ° C. high. On the other hand, those having a mixture ratio of sugar-based mixture: isocyanate = 100: 0 are all water-soluble components before curing, and therefore the curing rate is as low as 59% at a curing temperature of 160 ° C., which is 200 ° C. By doing so, the curing rate is improved to 81%.

  Here, as described above, when creating a graph with the horizontal axis representing the ratio of isocyanate in the total solid content of the adhesive and the vertical axis representing the hot water insolubility, if both components cause curing inhibition, The graph is considered to have a downwardly convex shape. Moreover, when both components accelerate | stimulate hardening, it is thought that a graph becomes an upward convex shape. When both components do not inhibit or accelerate curing, it is considered that they are connected by a straight line such as the dotted line shown in FIG.

  As shown in FIG. 2, both the curing temperature of 160 ° C. and 200 ° C. has a convex shape between the sugar-based mixture: isocyanate = 0: 100 and 100: 0. It is thought that the component accelerates curing.

  In Table 4, from the ratio of isocyanate in the total solid content of the adhesive and the estimated curing rate (simple mixed curing rate) when the sugar-based mixture and isocyanate do not inhibit or accelerate curing when the curing temperature is 160 ° C. The relationship with the value which the hardening rate is rising was shown.

  As shown in Table 4, the acceleration effect at 160 ° C. is remarkable when the proportion of isocyanate is between 4 and 80% by mass. Thus, it turns out that sclerosis | hardenability improves by hardening in the presence of sugar-type mixture containing sugar, organic sulfonic acid, and carboxylic acid, and isocyanate as an adhesive agent.

[Comparative Examples 4-1 to 4-6]
Evaluation of curability of adhesives (sugar-based mixture consisting of sugar and carboxylic acid, and isocyanate) alone

(Sample preparation)
First, 95 parts by mass of sucrose (manufactured by Wako Pure Chemical Industries, Ltd.), 5 parts by mass of citric acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a carboxylic acid, and 100 parts by mass of water were mixed and dissolved. As a result, an aqueous solution containing sugar and carboxylic acid and having a solid content ratio of 50% was prepared.

  Next, the obtained aqueous solution and isocyanate were mixed at the ratio shown in Table 5 (sugar mixture: isocyanate = 100: 0, 95: 5, 75:25, 50:50, 25:75, 0: 100). The total solid mass was weighed so as to be 2 g. Then, the weighed aqueous solution and isocyanate were mixed in a 110 mL glass sample tube bottle. This sample tube bottle was heated in a dryer at 180 ° C. for 60 minutes to obtain a cured sample of each example. In addition, the same isocyanate as Example 1-1 was used.

(Hot water extraction)
100 mL of distilled water was added to a 110 mL glass sample tube bottle containing the cured sample of each example, and hot water extraction was performed. In addition, hot water extraction was performed by heating the mixture of a sample and distilled water at 95 degreeC for 4 hours. And the mixture after hot water extraction was filtered, and it isolate | separated into the hot water insoluble material and the hot water soluble material.

(Drying and mass measurement)
The hot water insoluble material was dried with a dryer at 105 ° C. to obtain a constant weight, and then mass measurement was performed. And from Formula 1, the hot water insoluble rate (curing rate) was calculated from the mass of the hot water insoluble material and the mass of the sample before hot water extraction. Table 5 shows the hot water insolubility (curing rate). In addition, about the result of a hot water insoluble rate, the graph which made the ratio (mass%) of the isocyanate in the total solid of an adhesive the horizontal axis, and made the hot water insoluble rate (curing rate) the vertical axis | shaft is shown in FIG.

  As shown in Table 5, when the mixing ratio is sugar-based mixture: isocyanate = 0: 100, the curing rate is high because it is a water-insoluble component before curing. On the other hand, those having a mixture ratio of sugar-based mixture: isocyanate = 100: 0 are all water-soluble components before curing, and further contain no organic sulfonic acid that promotes curing. Low.

  Here, as described above, when creating a graph with the horizontal axis representing the ratio of isocyanate in the total solid content of the adhesive and the vertical axis representing the hot water insolubility, if both components cause curing inhibition, The graph is considered to have a downwardly convex shape. Moreover, when both components accelerate | stimulate hardening, it is thought that a graph becomes an upward convex shape. When both components do not inhibit or accelerate curing, it is considered that they are connected by a straight line such as the dotted line shown in FIG.

  As shown in FIG. 3, it is considered that the sugar-based mixture: isocyanate = 0: 100 and 100: 0 are almost linearly connected, and both components are neither cured nor inhibited. Thus, as an adhesive. It can be seen that even when cured in the presence of a sugar-based mixture containing a sugar and a carboxylic acid and an isocyanate, it does not promote curability.

[Comparative Examples 5-1 to 5-5]
Evaluation of curability of adhesive (sugar and isocyanate) alone

(Sample preparation)
First, 100 parts by mass of sucrose (manufactured by Wako Pure Chemical Industries, Ltd.) and 100 parts by mass of water were mixed and dissolved. Thus, an aqueous solution containing sugar and having a solid content ratio of 50% was prepared.

  Next, the obtained aqueous solution and isocyanate were mixed in the proportions shown in Table 6 (sugar mixture: isocyanate = 100: 0, 95: 5, 75:25, 50:50, 25:75, 0: 100). The total solid mass was weighed so as to be 2 g. Then, the weighed aqueous solution and isocyanate were mixed in a 110 mL glass sample tube bottle. This sample tube bottle was heated in a dryer at 180 ° C. for 60 minutes to obtain a cured sample of each example. In addition, the same isocyanate as Example 1-1 was used.

(Hot water extraction)
100 mL of distilled water was added to a 110 mL glass sample tube bottle containing the cured sample of each example, and hot water extraction was performed. In addition, hot water extraction was performed by heating the mixture of a sample and distilled water at 95 degreeC for 4 hours. And the mixture after hot water extraction was filtered, and it isolate | separated into the hot water insoluble material and the hot water soluble material.

(Drying and mass measurement)
The hot water insoluble material was dried with a dryer at 105 ° C. to obtain a constant weight, and then mass measurement was performed. And from Formula 1, the hot water insoluble rate (curing rate) was calculated from the mass of the hot water insoluble material and the mass of the sample before hot water extraction. Table 6 shows the hot water insolubility (curing rate). In addition, about the result of a hot water insoluble rate, the graph which made the ratio (mass%) of the isocyanate in the total solid of an adhesive the horizontal axis, and made the hot water insoluble rate (curing rate) the vertical axis | shaft is shown in FIG.

  As shown in Table 6, when the mixing ratio is sugar-based mixture: isocyanate = 0: 100, the curing rate is high because it is a water-insoluble component before curing. On the other hand, those having a mixture ratio of sugar-based mixture: isocyanate = 100: 0 are all water-soluble components before curing, and further contain no organic sulfonic acid that promotes curing. Low.

  Here, as described above, when creating a graph with the horizontal axis representing the ratio of isocyanate in the total solid content of the adhesive and the vertical axis representing the hot water insolubility, if both components cause curing inhibition, The graph is considered to have a downwardly convex shape. Moreover, when both components accelerate | stimulate hardening, it is thought that a graph becomes an upward convex shape. When both components do not inhibit or accelerate curing, it is considered that they are connected by a straight line such as the dotted line shown in FIG.

  As shown in FIG. 4, it is considered that the sugar-based mixture: isocyanate = 0: 100 and 100: 0 are almost linearly connected, and both components are neither cured nor inhibited. Thus, even if it hardens | cures in presence of sugar and isocyanate as an adhesive agent, it turns out that sclerosis | hardenability is not accelerated | stimulated.

[Examples 6-1 to 6-6 and Comparative Examples 6-1 to 6-8]
Evaluation of physical properties of wood particle board

(Setting common conditions)
A softwood chip having a thickness of 2 mm to 10 mm and a length of 20 mm to 100 mm was produced as a plant piece, and then the chip was separated into a rough chip for the core layer and a fine chip for the front and back layers. At this time, the average particle diameter of the coarse chips was about 5 mm to 100 mm, and the average particle diameter of the fine chips was about 1 mm to 5 mm.

Moreover, in Examples 6-1 to 6-6 and Comparative Examples 6-1 to 6-8, the thickness of the obtained board was 12 mm, and the target density was 700 to 750 kg / m ³ . Furthermore, the ratio of the solid content of the adhesive to the dry mass of the plant pieces (solid content addition rate) was 15% by mass for both the core layer and the front and back layers. The thickness ratio of the surface layer, core layer, and back layer was 3: 6: 3.

(Example 6-1)
As the adhesive for the core layer and the front and back layers, the following sugar-based mixture and isocyanate were used.
Sugar mixture: Sucrose as sugar (Wako Pure Chemical Industries, Ltd.), p-toluenesulfonic acid (made by Wako Pure Chemical Industries, Ltd.) as organic sulfonic acid, and citric acid (made by Wako Pure Chemical Industries, Ltd.) as carboxylic acid ) Was used. Then, by mixing at a mass ratio of sugar: organic sulfonic acid: carboxylic acid: water = 75: 1: 24: 50, a sugar mixture was prepared.
Isocyanate: a mixture of 55% by mass of Oshika Resin B-1605 (polymethylene polyphenylene polyisocyanate (polymeric MDI)) manufactured by Oshika Co., Ltd. and 45% by mass of 4,4′-diphenylmethane diisocyanate (4,4′-MDI) It was used. The isocyanate mixture was a liquid having a solid content of 100%.

  First, a plant piece for a core layer or front and back layers was put into a drum blender, and a sugar-based mixture was sprayed on the plant piece by spraying. Under the present circumstances, it mixed so that a sugar type mixture might be 95 mass% among 15 mass% which is the solid content addition rate of an adhesive agent. Then, after drying with an 80 degreeC dryer until the moisture content of the plant piece became 2%, the isocyanate was sprayed with the spray with respect to the plant piece further using the drum blender. Under the present circumstances, it mixed so that isocyanate might be 5 mass% among 15 mass% which is the solid content addition rate of an adhesive agent.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Example 6-2)
A particle board of this example was obtained in the same manner as in Example 6-1 except that the ratio of the sugar-based mixture to the isocyanate was 50:50 (mass%).

(Example 6-3)
A particle board of this example was obtained in the same manner as in Example 6-1 except that the ratio of the sugar mixture to the isocyanate was 25:75 (mass%).

(Example 6-4)
As the adhesive for the core layer and the front and back layers, the following sugar-based mixture and isocyanate were used.
Sugar mixture: Fructose (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the sugar, and metaxylene sulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the organic sulfonic acid. Then, a powdered sugar-based mixture was prepared by mixing using a mixer at a mass ratio of sugar: organic sulfonic acid = 80: 20.
Isocyanate: Soflan-R MIC-K manufactured by Soflanwiz Co., Ltd. (polymethylene polyphenylene polyisocyanate (polymeric MDI) 100% single substance, liquid with a solid content of 100%) was used.

  Next, the plant pieces for the core layer or the front and back layers were put into a drum blender, and a sugar-based mixture was sprayed on the plant pieces by spraying. Under the present circumstances, it mixed so that sugar-type mixture might be 50 mass% among 15 mass% which is the solid content addition rate of an adhesive agent. Then, after drying with an 80 degreeC dryer until the moisture content of the plant piece became 2%, the isocyanate was sprayed with the spray with respect to the plant piece further using the drum blender. Under the present circumstances, it mixed so that isocyanate might be 50 mass% among 15 mass% which is the solid content addition rate of an adhesive agent.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Example 6-5)
Using the same sugar-based mixture and isocyanate as in Example 6-4, the composition of the adhesive was changed between the core layer and the front and back layers to produce boards.

  First, plant pieces for front and back layers were put into a drum blender, and a sugar-based mixture was sprayed on the plant pieces by spraying. Under the present circumstances, it added so that the solid content addition rate of a sugar-type mixture might be 15 mass% with respect to the dry mass of a plant piece. And it dried with the 80 degreeC dryer until the moisture content of the plant piece became 2%.

  Moreover, the plant piece for core layers was thrown into the drum blender, and also the sugar-type mixture was sprayed with the spray with respect to the said plant piece. Under the present circumstances, it mixed so that sugar-type mixture might be 50 mass% among 15 mass% which is the solid content addition rate of an adhesive agent. Then, after drying with an 80 degreeC dryer until the moisture content of the plant piece became 2%, the isocyanate was sprayed with the spray with respect to the plant piece further using the drum blender. Under the present circumstances, it mixed so that isocyanate might be 50 mass% among 15 mass% which is the solid content addition rate of an adhesive agent.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat, and this laminated mat is heated at a surface pressure of 2.5 MPa while being heated by a heating press device having a board surface temperature of 200 ° C. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Example 6-6)
After forming a laminated mat in the same manner as in Example 6-5, the laminated mat was pressed with a surface pressure of 2.5 MPa for 5 minutes with a heating press apparatus having a board surface temperature of 230 ° C. Obtained. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

  Table 7 shows the raw material ratios of the core layer adhesive and the front and back layer adhesives in Examples 6-1 to 6-6, and the composition and molding conditions of the adhesive.

(Comparative Example 6-1)
As the adhesive for the core layer and the front and back layers, a urea melamine resin binder widely used for general wood boards was used. As the urea melamine resin-based binder, one obtained by dissolving 1.2 parts by mass of ammonium chloride with respect to 100 parts by mass of Oshika Resin (registered trademark) TB103 (liquid having a solid content of 64%) manufactured by Oshika Co., Ltd. was used.

  First, plant pieces for a core layer or front and back layers were put into a drum blender, and further urea melamine resin binder was sprayed on the plant pieces. Under the present circumstances, it added so that the solid content addition rate of a urea melamine resin-type binder might be 15 mass% with respect to the dry mass of a plant piece. And it dried with the 80 degreeC dryer until the moisture content of the plant piece became 2%.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Comparative Example 6-2)
First, plant pieces for a core layer or front and back layers were put into a drum blender, and further, the same urea melamine resin binder as in Comparative Example 6-1 was sprayed on the plant pieces. Under the present circumstances, it mixed so that a urea melamine resin-type binder might be 95 mass% among 15 mass% which is the solid content addition rate of an adhesive agent. Then, after drying with an 80 degreeC dryer until the moisture content became 2%, the isocyanate was sprayed with the spray with respect to the plant piece using the drum blender. Under the present circumstances, it mixed so that isocyanate might be 5 mass% among 15 mass% which is the solid content addition rate of an adhesive agent. As the isocyanate, Oshika Resin B-1605 (polymethylene polyphenylene polyisocyanate (polymeric MDI)) manufactured by Oshika Co., Ltd. was used.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat, and this laminated mat is heated at a surface pressure of 2.5 MPa while being heated by a heating press device having a board surface temperature of 200 ° C. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Comparative Example 6-3)
A particle board of this example was obtained in the same manner as in Comparative Example 6-2 except that the ratio of the urea melamine resin-based binder and the isocyanate was 50:50 (mass%).

(Comparative Example 6-4)
As the adhesive for the core layer and the front and back layers, only the following sugar-based mixture without using organic sulfonic acid was used.
Sugar mixture: Sucrose (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the sugar, and citric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the carboxylic acid. Then, by mixing at a mass ratio of sugar: carboxylic acid: water = 75: 25: 50, a sugar-based mixture was prepared.

  First, a plant piece for a core layer or front and back layers was put into a drum blender, and a sugar-based mixture was sprayed on the plant piece by spraying. Under the present circumstances, it added so that the solid content addition rate of a sugar-type mixture might be 15 mass% with respect to the dry mass of a plant piece. And it dried with the 80 degreeC dryer until the moisture content of the plant piece became 2%.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat, and this laminated mat is heated at a surface pressure of 2.5 MPa while being heated by a heating press device having a board surface temperature of 200 ° C. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Comparative Example 6-5)
As the adhesive for the core layer and the front and back layers, the same sugar-based mixture not using the organic sulfonic acid as in Comparative Example 6-4 and the following isocyanate were used.

Isocyanate: a mixture of 55% by mass of Oshika Resin B-1605 (polymethylene polyphenylene polyisocyanate (polymeric MDI)) manufactured by Oshika Co., Ltd. and 45% by mass of 4,4′-diphenylmethane diisocyanate (4,4′-MDI) It was used. The isocyanate mixture was a liquid having a solid content of 100%.

  First, a plant piece for a core layer or front and back layers was put into a drum blender, and a sugar-based mixture was sprayed on the plant piece by spraying. Under the present circumstances, it mixed so that a sugar type mixture might be 95 mass% among 15 mass% which is the solid content addition rate of an adhesive agent. Then, after drying with an 80 degreeC dryer until the moisture content became 2%, the isocyanate was sprayed with the spray with respect to the plant piece using the drum blender. Under the present circumstances, it mixed so that isocyanate might be 5 mass% among 15 mass% which is the solid content addition rate of an adhesive agent.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat, and this laminated mat is heated at a surface pressure of 2.5 MPa while being heated by a heating press device having a board surface temperature of 200 ° C. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Comparative Example 6-6)
A particle board of this example was obtained in the same manner as in Comparative Example 6-5 except that the ratio of the sugar-based mixture not using the organic sulfonic acid and the isocyanate was 50:50 (mass%).

(Comparative Example 6-7)
As the adhesive for the core layer and the front and back layers, only the following sugar mixture was used.
Sugar mixture: Sucrose as sugar (Wako Pure Chemical Industries, Ltd.), p-toluenesulfonic acid (made by Wako Pure Chemical Industries, Ltd.) as organic sulfonic acid, and citric acid (made by Wako Pure Chemical Industries, Ltd.) as carboxylic acid ) Was used. Then, by mixing at a mass ratio of sugar: organic sulfonic acid: carboxylic acid: water = 75: 1: 24: 50, a sugar mixture was prepared.

  First, a plant piece for a core layer or front and back layers was put into a drum blender, and a sugar-based mixture was sprayed on the plant piece by spraying. Under the present circumstances, it added so that the solid content addition rate of a sugar-type mixture might be 15 mass% with respect to the dry mass of a plant piece. And it dried with the 80 degreeC dryer until the moisture content of the plant piece became 2%.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

(Comparative Example 6-8)
The same isocyanate as Example 6-1 was used as the adhesive for the core layer and the front and back layers.

  First, plant pieces for a core layer or front and back layers were put into a drum blender, and isocyanate was sprayed onto the plant pieces by spraying. Under the present circumstances, it added so that the solid content addition rate of isocyanate might be 15 mass% with respect to the dry mass of a plant piece.

Thereafter, the plant pieces to which the adhesive is attached are laminated in the order of the surface layer, the core layer, and the back layer to form a laminated mat, and this laminated mat is heated at a surface pressure of 2.5 MPa while being heated by a heating press device having a board surface temperature of 200 ° C. The particle board was obtained by pressing for 3 minutes. The particle board had a thickness of 12 mm and an air dry density of 700 to 750 kg / m ³ .

  Table 8 shows the raw material ratios of the adhesive for core layer and the adhesive for front and back layers, the composition of the adhesive, and the molding conditions in Comparative Examples 6-1 to 6-8.

(Evaluation)
About the particle board obtained in Examples 6-1 to 6-6 and Comparative Examples 6-1 to 6-8, the water absorption thickness expansion coefficient, peel strength, bending according to Japanese Industrial Standard JIS A5908 (Particle Board) Strength and bending strength after wetness (B test, measurement after boiling) were measured. The results are shown in Table 7 and Table 8.

  Comparative Example 6-1 uses a general wood adhesive. And with this adhesive alone, the board physical properties are as low as the U type level specified in JIS, and it is necessary to secure the M type level by adding wax or the like to improve water resistance. In Comparative Example 6-2, physical properties such as water resistance and hot water resistance are improved by adding isocyanate to the urea melamine resin binder. As shown in Table 8, the physical properties are improved by adding a small amount of isocyanate, but remain small.

  In Comparative Example 6-3, 50% by mass of isocyanate is added to 50% by mass of the urea melamine resin-based binder. Thereby, the obtained particle board has secured the physical property which conforms to JIS18P. However, since formaldehyde is contained in the adhesive, a measure for reducing formaldehyde is required. Further, when a higher level of quality than JIS 18P is required, it is difficult to achieve.

  Comparative Example 6-4 is a plant-based adhesive that has been developed in recent years. If long-time molding is possible, the physical properties are improved. However, the physical properties could not be improved sufficiently under these conditions. In Comparative Example 6-5, physical properties such as water resistance and hot water resistance are improved by adding isocyanate to the plant adhesive. As shown in Table 8, the physical properties are improved by adding a small amount of isocyanate, but remain small.

  In Comparative Example 6-6, 50% by mass of isocyanate is added to 50% by mass of the plant adhesive. As a result, the obtained particle board can ensure physical properties conforming to JIS 18M, but it is difficult to ensure the P type level specified in JIS.

  Moreover, Comparative Example 6-7 accelerates | stimulates reaction rather than Comparative Example 6-4 by adding a sulfonic acid to the sugar-type mixture of Comparative Example 6-4, without adding isocyanate. However, the physical properties of the obtained particle board are insufficient. That is, when the thickness is 12 mm, the heating temperature is 200 ° C., and the heating time is 3 minutes, the temperature of the core layer at the time of pressing is about 110 ° C. Therefore, even when an adhesive in which sulfonic acid is added to a sugar-based mixture is used, the reaction of sugar, sulfonic acid, and carboxylic acid does not proceed sufficiently, resulting in insufficient generation of a cured product and reduced physical properties.

  In Comparative Examples 6-8, only the isocyanate was used, and high physical properties conforming to JIS 18P were obtained. However, the higher the price of isocyanate and the higher the proportion of isocyanate, the higher the price of the resulting particle board.

  In contrast to these comparative examples, each example has superior characteristics. Specifically, the physical properties of Example 6-1 are significantly improved as compared with Comparative Examples 6-7, and the board physical properties of 18U level can be ensured although it does not reach the 18M level specified by JIS. . This is presumably because sugar and sulfonic acid are contained in the sugar mixture, and the use of isocyanate further promotes the modification of the sugar and improves the adhesiveness.

  In Example 6-2, 50% by mass of isocyanate is added to Example 6-1. Thereby, the physical property of the obtained particle board is greatly improved. Furthermore, in Example 6-2, compared with Comparative Example 6-3 and Comparative Example 6-6, water resistance is greatly improved, and it is possible to ensure a water absorption thickness expansion rate of a level below 10%. is there.

  In Comparative Example 6-3, formaldehyde is added to the urea melamine resin-based binder, and a formaldehyde reduction measure is required. On the other hand, since Example 6-2 does not add a urea melamine resin-based binder, a formaldehyde reduction measure becomes unnecessary.

  Example 6-3 also has high physical properties, and can ensure the 18P level specified in JIS. However, the higher the isocyanate ratio and the higher the isocyanate ratio, the higher the price of the resulting particle board. Therefore, in terms of cost reduction by using a low-cost sugar-based mixture, the advantage is low.

  Example 6-4 differs from Example 6-2 in the composition of the sugar-based mixture and does not contain carboxylic acid. However, Example 6-4 also has high physical properties, and in terms of adhesiveness, physical properties higher than those of Example 6-2 are obtained, and the 18P level specified in JIS can be secured.

  In Example 6-5, the adhesive for the core layer is the same as that of Example 6-4, but the adhesive for the front and back layers is different. By using only the sugar mixture as the adhesive for the front and back layers as in Example 6-5, it is possible to ensure the physical properties of the 18M level specified in JIS while reducing the cost. In addition, isocyanate may adhere to a metal hot platen, but the adhesive trouble can be reduced by using only a sugar-based mixture as the front and back layer adhesive.

  5 to 8, the ratio (mass%) of isocyanate in the total solid content of the adhesive and the physical properties of the particle boards of Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-8. The relationship is shown. As shown in FIG. 5 to FIG. 8, when the addition ratio of isocyanate is between 4 and 80% by mass, the sugar-based mixture containing sulfonic acid is superior to the sugar-based mixture not containing sulfonic acid with respect to the physical properties of the particle board. Met. Moreover, when the saccharide-based mixture containing sulfonic acid is compared with the urea melamine resin-based binder, it can be seen that the saccharide-containing mixture containing sulfonic acid is superior or equivalent. However, the sugar-based mixture has an advantage over the urea melamine resin-based binder because it does not require a formaldehyde reduction measure.

  In addition, when the addition ratio of isocyanate exceeds 80% by mass, the advantage in terms of cost is reduced, and therefore the addition ratio is preferably 80% by mass or less. Moreover, when the addition ratio of isocyanate is less than 4% by mass, the effect of improving physical properties is limited, and the overall superiority is lowered. Therefore, the addition ratio is preferably 4% by mass or more.

  Next, although an isocyanate is not contained, a reference example is shown in order to show an appropriate quantitative ratio of sugar, organic sulfonic acid and carboxylic acid. In any case, when an isocyanate is further added, the hydroxyl group of the sugar reacts with the isocyanate to form a urethane bond and a urea bond, so that the physical properties are improved.

[Reference Examples 7-1 to 7-4, Reference Comparative Examples 7-1 to 7-7]
A kenaf stalk core chipboard (thickness 5 mm) was produced.

(Reference Example 7-1)
As plant material, kenaf stalk, which is a herbaceous plant, was used. Specifically, the kenaf stem core after removing the bast fiber that is the outer skin portion of the kenaf stem was used. A kenaf stem core chip was obtained by cutting the kenaf stem core to a length of about 5 cm and crushing the kenaf stem core using a pulverizer (ring flaker). The dimensions of this chip were an average length of 15 mm, an average width of 5 mm, and an average thickness of 2 mm. When the kenaf stalk core chip was extracted with hot water at 90 ° C. for 3 hours, the soluble component ratio was 5.8% by mass in the dry matter.

  Sucrose was used as the sugar, and p-toluenesulfonic acid was used as the organic sulfonic acid. These were mixed with water to prepare an adhesive having a mixing ratio of sucrose: p-toluenesulfonic acid: water = 10: 5: 15.

With respect to 100 parts by mass of the kenaf stalk core chip, the adhesive was sprayed so that the solid content addition rate was 15 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Example 7-2)
Glucose (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the sugar, and benzenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the organic sulfonic acid. These were mixed with water to prepare an adhesive having a mixing ratio of glucose: benzenesulfonic acid: water = 18: 0.02: 20.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 18.02 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Example 7-3)
Maltose (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the sugar, and p-toluenesulfonic acid was used as the organic sulfonic acid. These were mixed with water to prepare an adhesive with a mixing ratio of maltose: p-toluenesulfonic acid: water = 16: 4: 20.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 20 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press device at 200 ° C. at a surface pressure of 2 MPa for 5 minutes to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Example 7-4)
Sucrose was used as the sugar, p-toluenesulfonic acid was used as the organic sulfonic acid, and citric acid was used as the polyvalent carboxylic acid. These and water were mixed to prepare an adhesive having a mixing ratio of sucrose: p-toluenesulfonic acid: citric acid: water = 4.7: 0.3: 15: 20.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 20 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Comparative Example 7-1)
With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, water was sprayed so that the addition rate was 20 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained. However, since the strength of the board was very weak, a relatively strong portion was used for the test.

  In addition, 100 mass parts of kenaf stalk core chips used in Reference Example 7-1 were laminated as they were to form a laminated mat, and this laminated mat was heated to 200 ° C. with a heating press device at a surface pressure of 2 MPa and 10 to 60. Attempts were made to form a compact by pressing to minutes. However, they could only be broken by hand.

(Reference Comparative Example 7-2)
With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, water was sprayed so that the addition rate was 20 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 20 minutes while being heated to 250 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Comparative Example 7-3)
P-Toluenesulfonic acid was used as the organic sulfonic acid, and this was mixed with water to prepare an adhesive having a mixing ratio of p-toluenesulfonic acid: water = 0.3: 0.5.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 0.3 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Comparative Example 7-4)
Benzenesulfonic acid was used as the organic sulfonic acid, and this was mixed with water to prepare an adhesive having a mixing ratio of benzenesulfonic acid: water = 18: 30.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 18 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Comparative Example 7-5)
P-Toluenesulfonic acid was used as the organic sulfonic acid, and lactic acid (manufactured by Wako Pure Chemical Industries, Ltd., commercially available as an aqueous solution) was used as the monovalent carboxylic acid. These were mixed with water to prepare an adhesive having a mixing ratio of p-toluenesulfonic acid: lactic acid: water = 2: 5: 7 in a substantial mass ratio.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 7 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Comparative Example 7-6)
Benzenesulfonic acid was used as the organic sulfonic acid, and itaconic acid (manufactured by Iwata Chemical Industry Co., Ltd.) was used as the polyvalent carboxylic acid. These were mixed with water to prepare an adhesive having a mixing ratio of benzenesulfonic acid: itaconic acid: water = 0.1: 19.9: 20 by mass ratio.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 20 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Reference Comparative Example 7-7)
P-Toluenesulfonic acid was used as the organic sulfonic acid, and malic acid (manufactured by Fuso Chemical Industries, Ltd.) was used as the polyvalent carboxylic acid. These were mixed with water to prepare an adhesive having a mixing ratio of p-toluenesulfonic acid: malic acid: water = 3: 12: 15 by mass ratio.

With respect to 100 parts by mass of the kenaf stalk core chip used in Reference Example 7-1, the adhesive was sprayed so that the solid content addition rate was 15 parts by mass. Thereafter, kenaf stalk core chips were laminated to form a laminated mat, and this laminated mat was pressed with a heating press apparatus at a surface pressure of 2 MPa for 10 minutes while being heated to 200 ° C. to form a molded body. As a result, a kenaf stalk core chipboard having a thickness of 5 mm and an air-drying density of 0.6 g / cm ³ was obtained.

(Evaluation)
About the molded body (board) obtained in Reference Examples 7-1 to 7-4 and Reference Comparative Examples 7-1 to 7-7, peel strength test (strength according to Japanese Industrial Standard JIS A5905 (fiberboard)) Test) and water absorption thickness expansion coefficient test (water resistance test), and the peel strength and water absorption thickness expansion coefficient were measured. Further, as a hot water resistance test, a hot water absorption thickness expansion coefficient was measured when a 200 mm square sample was immersed in warm water at 80 ° C. for 5 minutes. Tables 9 and 10 show the board configuration, bonding conditions, board molding conditions, and evaluation results.

In Reference Comparative Example 7-1, only a board with low physical properties was obtained. In Reference Comparative Example 7-2, molding was performed at a higher temperature and longer time than Reference Comparative Example 7-1, but the water resistance and hot water resistance were low. In Reference Comparative Examples 7-3 and 7-4, the board could be produced by adding organic sulfonic acid, but the water resistance and hot water resistance were low. In Reference Comparative Example 7-5, a board could be prepared by adding organic sulfonic acid and monovalent carboxylic acid, and the water resistance and hot water resistance were improved, but the strength was low. In Reference Comparative Examples 7-6 and 7-7, it was possible to produce a board by adding organic sulfonic acid and polyvalent carboxylic acid, and the water resistance and hot water resistance were further improved, but the strength did not increase much, It was lower than 1 N / mm ² .

  On the other hand, in Reference Examples 7-1 to 7-4, a board having high physical properties could be produced by adding sugar and organic sulfonic acid.

In Reference Examples 7-1 to 7-3, when the sugar and the organic sulfonic acid were added in different types and amounts, the physical properties were all improved. Comparing Reference Example 7-1 and Reference Comparative Example 7-7, the total amount of organic sulfonic acid and sugar in Reference Example 7-1 was the same as that in Reference Comparative Example 7-7. Is the same as the total amount. However, the physical properties of Reference Example 7-1 were higher than those of Reference Comparative Example 7-7, and the strength was particularly improved. In Reference Example 7-2, although the physical properties tended to decrease when the amount of the organic sulfonic acid was decreased, the strength was high at 1 N / mm ² or more. In Reference Example 7-3, although the molding time was shortened, the strength was as high as 1 N / mm ² or more. In Reference Example 7-4, physical properties were improved by further adding a polyvalent carboxylic acid.

[Reference Examples 8-1 to 8-4, Reference Comparative Examples 8-1 to 8-6]
A cedar fiber board (thickness 2 mm) was produced.

(Reference Example 8-1)
Chips were obtained by pulverizing cedar wood obtained from cedar, which is a woody conifer, using a pulverizer (hammer mill). This chip was defibrated with a defibrator (refiner) to obtain a cedar fiber having a fiber diameter of 20 to 200 µm and a length of 2 to 5 mm.

  Cellobiose (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the sugar, and p-toluenesulfonic acid was used as the organic sulfonic acid. These and water were mixed to prepare an adhesive having a mixing ratio of cellobiose: p-toluenesulfonic acid: water = 18: 0.05: 20.

With respect to 100 mass parts of said cedar fiber, said adhesive agent was sprayed by spray so that the solid content addition rate might be 18.05 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 6 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Example 8-2)
Glucose was used as sugar, and benzenesulfonic acid was used as organic sulfonic acid. These were mixed with water to prepare an adhesive having a mixing ratio of glucose: benzenesulfonic acid: water = 18: 5: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the above-described adhesive was sprayed so that the solid content addition rate was 23 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 2 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Example 8-3)
Sucrose was used as the sugar, and p-toluenesulfonic acid was used as the organic sulfonic acid. These were mixed with water to prepare an adhesive having a mixing ratio of sucrose: p-toluenesulfonic acid: water = 18: 2: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 20 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 3 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Example 8-4)
Sucrose was used as the sugar, p-toluenesulfonic acid was used as the organic sulfonic acid, and citric acid was used as the polyvalent carboxylic acid. These and water were mixed to prepare an adhesive having a mixing ratio of sucrose: p-toluenesulfonic acid: citric acid: water = 9.8: 0.4: 9.8: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 20 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 3 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Comparative Example 8-1)
Water was sprayed on the cedar fiber used in Reference Example 8-1 with a spray so that the addition rate was 20 parts by mass. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed at a surface pressure of 2 MPa for 20 minutes while being heated to 230 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

  The above-mentioned cedar fibers to which water has been added are laminated to form a laminated mat, and this laminated mat is pressed with a heating press apparatus at 200 ° C. at a surface pressure of 2 MPa for 3 to 6 minutes. Attempts were made to form, but only those with weak strength were produced.

(Reference Comparative Example 8-2)
Sucrose was used as the sugar, and this was mixed with water to prepare an adhesive with a mixing ratio of sucrose: water = 20: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 20 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 3 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Comparative Example 8-3)
Citric acid was used as the polyvalent carboxylic acid, and this was mixed with water to prepare an adhesive having a mixing ratio of citric acid: water = 20: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 20 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 3 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Comparative Example 8-4)
Sucrose was used as the sugar, and citric acid was used as the polyvalent carboxylic acid. These were mixed with water to prepare an adhesive having a mixing ratio of sucrose: citric acid: water = 10: 10: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 20 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 3 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Comparative Example 8-5)
P-Toluenesulfonic acid was used as the organic sulfonic acid, and this was mixed with water to prepare an adhesive having a mixing ratio of p-toluenesulfonic acid: water = 18: 30.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 18 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 6 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Reference Comparative Example 8-6)
P-Toluenesulfonic acid was used as the organic sulfonic acid, and citric acid was used as the polyvalent carboxylic acid. These and water were mixed to prepare an adhesive having a mixing ratio of p-toluenesulfonic acid: citric acid: water = 0.2: 19.8: 20.

With respect to 100 mass parts of cedar fibers used in Reference Example 8-1, the adhesive was sprayed so that the solid content addition rate was 20 mass parts. Thereafter, cedar fibers were laminated to form a laminated mat, and this laminated mat was pressed for 3 minutes at a surface pressure of 2 MPa while being heated to 200 ° C. with a heating press device to form a molded body. As a result, a cedar fiber board having a thickness of 2 mm and an air-drying density of 0.8 g / cm ³ was obtained.

(Evaluation)
About the molded body (board) obtained in the above Reference Examples 8-1 to 8-4 and Reference Comparative Examples 8-1 to 8-6, peel strength test (strength test) according to JIS A5905, water absorption thickness The expansion coefficient test (water resistance test) was performed, and the peel strength and the water absorption thickness expansion coefficient were measured. In addition, as a hot water resistance test, a hot water absorption thickness expansion coefficient was measured when a 75 mm square sample was immersed in warm water at 70 ° C. for 4 hours. Tables 11 and 12 show the board configuration, bonding conditions, board molding conditions, and evaluation results.

  In Reference Comparative Example 8-1, only a board with low physical properties was obtained. In Reference Comparative Example 8-2, sugar was added, but the physical properties were not sufficiently improved. In Reference Comparative Examples 8-3 and 8-4, water resistance and hot water resistance were improved by adding carboxylic acid, but the strength was low. In Reference Comparative Example 8-5, organic sulfonic acid was added, but the strength was low. In Reference Comparative Example 8-6, organic sulfonic acid and polyvalent carboxylic acid were added, but the strength was low.

  On the other hand, in Reference Examples 8-1 to 8-4, a board having high physical properties could be produced by adding sugar and organic sulfonic acid.

  In Reference Examples 8-1 to 8-3, when sugar and organic sulfonic acid were added in different types and amounts, the physical properties were improved, and particularly high values were obtained in strength. In particular, in Reference Example 8-2, high physical properties were secured despite shortening the molding time. In Reference Example 8-4, the physical properties were improved by the addition of polyvalent carboxylic acid.

  The reason why the strength was increased in each of the reference examples is considered to be that the denaturation of the components in the plant pieces progressed by the combined use of sugar and organic sulfonic acid. The denaturation is considered to be caused by the esterification and crosslinking of the hydroxyl groups in the plant pieces.

  From the above results, it was found that high-quality adhesives and boards can be obtained by a simple process using sugar and organic sulfonic acid. In Reference Examples 7-1 to 7-4, when a board having a thickness of 5 mm is formed at 200 ° C., it takes 5 minutes or 10 minutes. However, it is clear from Examples 6-1 to 6-6 that the molding time can be shortened by adding isocyanate to the adhesives of Reference Examples 7-1 to 7-4.

From the above results, sugars, organic sulfonic acids and carboxylic acids have appropriate quantitative ratios, and the following can be understood.
-It is preferable that the organic sulfonic acid is contained at 0.1 to 75 parts by mass with respect to 100 parts by mass of the sugar.
-It is an embodiment of the present invention that no carboxylic acid is contained.
-Carboxylic acid is contained and it is preferable to contain by 0.1-600 mass parts with respect to 100 mass parts of saccharides.

  As described above, the contents of the present embodiment have been described according to the examples. However, the present embodiment is not limited to these descriptions, and it is obvious to those skilled in the art that various modifications and improvements are possible. is there.

Claims (4)

A sugar-based mixture containing sugar and organic sulfonic acid;
Isocyanate,
Including
An adhesive comprising 0.1 to 75 parts by mass of the organic sulfonic acid with respect to 100 parts by mass of the sugar. The sugar-based mixture further includes a carboxylic acid,
The adhesive according to claim 1, comprising 0.1 to 600 parts by mass of the carboxylic acid with respect to 100 parts by mass of the sugar.   The adhesive according to claim 1 or 2, comprising 4 to 400 parts by mass of the isocyanate with respect to 100 parts by mass of the sugar-based mixture. The adhesive according to any one of claims 1 to 3,
A plurality of plant pieces adhered by the adhesive;
Including molded plate.

Images