Wood fiberboard, binder composition for wood fiberboard, and method for manufacturing wood fiberboard.

Abstract

The present invention provides a wood-based board that can be manufactured using a binder composition that has high strength and good applicability to wood chips. [Solution] The wood-based board of the present invention is a wood-based board in which a plurality of wood pieces are molded and integrated with a binder. The binder contains a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine. The polymer has a composition in which, based on 100% by mass of the total amount of constituent units derived from monomer components constituting the polymer, 50 to 100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0 to 3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0 to 50% by mass of other constituent units, and the neutralization rate of the carboxyl group by the metal salt is 20% or less. The alkanolamine has two or more hydroxyl groups in one molecule.

Description

Technical Field

[0001] The present invention relates to a wood board, a binder composition for a wood board, and a method for manufacturing a wood board. More specifically, the present invention relates to a wood board in which a plurality of wood pieces are integrally molded with a binder, a binder composition suitable for manufacturing a wood board, and a method for manufacturing the above wood board.

Background Art

[0002] As a method for manufacturing a wood board, a method of integrally molding a plurality of wood pieces with a binder is known. As the above binder, generally, a thermosetting resin produced by a condensation reaction with formaldehyde, such as water-soluble urea, melamine resin, and phenol resin, is used alone or in combination of a plurality. However, these binders cause problems in terms of work and health in use due to the gas and irritating odor of free formaldehyde released from the binder, and are cited as one of the causes of sick house syndrome indoors.

[0003] Therefore, in recent years, wood boards using binders that do not generate a formaldehyde odor have been developed (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the wood-based boards disclosed in Patent Documents 1 and 2 had the problem of being weaker in strength compared to conventional wood-based boards using binders that generate formaldehyde. Furthermore, in order to obtain wood-based boards that are superior in appearance, strength, and productivity, the binders must also have excellent applicability to wood chips.

[0006] Therefore, an object of the present invention is to provide a wood-based board that can be manufactured using a binder composition that has high strength and good applicability to wood chips. Another object of the present invention is to provide a binder composition that has good applicability to wood chips and can be used to manufacture a wood-based board with high strength. Yet another object of the present invention is to provide a method for manufacturing a wood-based board that is highly productive and has high strength. [Means for solving the problem]

[0007] The present invention is a wood-based board in which multiple wood pieces are molded and integrated with a binder. The above binder includes a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine. The above polymer has a composition where, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer, 50-100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0-3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0-50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The above alkanolamine provides a wood-based board having two or more hydroxyl groups in one molecule.

[0008] The weight-average molecular weight of the above polymer is preferably between 1,000 and 100,000.

[0009] The amount of structural components derived from the alkanolamine in the above binder is preferably 5 to 70 mol% relative to 100 mol% of the constituent units derived from the carboxylic acid (salt) of the above polymer.

[0010] The above unsaturated monocarboxylic acid (salt) preferably includes (meth)acrylic acid (salt).

[0011] The above alkanolamine preferably contains diethanolamine.

[0012] The pH of the binder composition forming the above-mentioned binder is preferably 3.5 or higher.

[0013] The solid content concentration of the binder composition forming the above-mentioned binder is preferably 15% by mass or more.

[0014] The moisture content of the above wood chips is preferably 1% by mass or more.

[0015] Furthermore, the present invention includes a polymer having a structure in which a carboxyl group is neutralized with an alkanolamine. The above polymer has a composition where, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer, 50-100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0-3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0-50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The above alkanolamine provides a binder composition for wood-based boards having two or more hydroxyl groups in one molecule.

[0016] Furthermore, the present invention relates to a method for producing a wood-based board by press-molding a mixture containing a binder composition and a plurality of wood chips. The above binder composition comprises a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine, The above polymer has a composition where, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer, 50-100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0-3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0-50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. Provided is a method for manufacturing a wood board, wherein the alkanolamine has two or more hydroxy groups in one molecule.

Advantages of the Invention

[0017] The wood board of the present invention has high strength and can be manufactured using a binder composition with good coating properties for wood chips. Therefore, the wood board of the present invention can have high strength, good appearance, and excellent productivity. Further, the binder composition for the wood board of the present invention has good coating properties for wood chips and can manufacture a wood board having high strength. Moreover, according to the manufacturing method of the present invention, a wood board having excellent productivity and high strength can be manufactured.

Modes for Carrying Out the Invention

[0018] [Wood Board] The wood board of the present invention is formed by integrally molding a plurality of wood chips with a binder.

[0019] (Binder) The above binder contains at least a polymer having a structure in which a carboxy group is neutralized with an alkanolamine.

[0020] More specifically, the polymer has a structure in which a carboxy group and / or a carboxylate group in a polymer having a carboxy group and / or a carboxylate group is neutralized with an alkanolamine. In this specification, the above carboxy group and / or carboxylate group may be referred to as "carboxylic acid (salt)", and the same applies to other cases where "(salt)" is appended. Further, the polymer having a carboxy group and / or a carboxylate group, that is, the polymer having a carboxylic acid (salt) may be referred to as a "precursor polymer". On the other hand, the polymer having a structure in which the carboxy group is neutralized with an alkanolamine may be referred to as a "polymer of the present invention". The above binder may contain only one kind of the polymer of the present invention or may contain two or more kinds.

[0021] The polymer of the present invention contains at least a structural unit derived from an unsaturated monocarboxylic acid (salt). The polymer of the present invention may contain only one kind or two or more kinds of structural units derived from an unsaturated monocarboxylic acid (salt).

[0022] Examples of the unsaturated monocarboxylic acid in the above-mentioned unsaturated monocarboxylic acid (salt) include (meth)acrylic acid (acrylic acid and / or methacrylic acid), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, etc. Further, examples of the unsaturated monocarboxylic acid also include unsaturated monocarboxylic acids having a hydroxy group such as α-hydroxyacrylic acid and α-hydroxymethylacrylic acid. Among them, from the viewpoint of a high curing rate during molding, a high crosslink density after molding, and higher strength, (meth)acrylic acid is preferable. That is, as the above-mentioned unsaturated monocarboxylic acid (salt), (meth)acrylic acid and / or its salt ((meth)acrylic acid (salt)) is preferable.

[0023] Examples of the salt in the unsaturated monocarboxylic acid salt include monovalent metal salts such as alkali metal salts (lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt, etc.); divalent metal salts such as alkaline earth metal salts (calcium salt, magnesium salt, etc.); quaternary ammonium salts, amine salts, substituted amine salts or double salts thereof, etc.

[0024] The content ratio of the structural unit derived from the unsaturated monocarboxylic acid (salt) in the polymer of the present invention is 50 to 100% by mass, preferably 60 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, particularly preferably 90 to 100% by mass, based on 100% by mass of the total amount of the structural units derived from the monomer components constituting the polymer of the present invention.

[0025] The polymer of the present invention may or may not contain a structural unit derived from an unsaturated dicarboxylic acid (salt). The polymer of the present invention may contain only one kind or two or more kinds of structural units derived from an unsaturated dicarboxylic acid (salt).

[0026] Examples of unsaturated dicarboxylic acids in unsaturated dicarboxylic acids (salts) include itaconic acid, maleic acid, fumaric acid, crotonic acid, and their acid anhydrides. Examples of salts in unsaturated dicarboxylic acid salts include those exemplified and described above in the section on unsaturated monocarboxylic acid salts.

[0027] The content of constituent units derived from unsaturated dicarboxylic acid (salt) in the polymer of the present invention is 0 to 3% by mass, preferably 0 to 2% by mass, more preferably 0 to 1% by mass, and even more preferably 0 to 0.5% by mass, based on 100% by mass of the total amount of constituent units derived from monomer components constituting the polymer of the present invention. It is presumed that crosslinking by alkanolamine does not proceed well in constituent units derived from unsaturated dicarboxylic acid (salt) because the distance between the two carboxylic acid (salt) is close, and a high proportion of constituent units derived from unsaturated dicarboxylic acid (salt) tends to result in inferior bending strength of the wood-based board.

[0028] The polymer of the present invention may contain other constituent units other than those derived from unsaturated monocarboxylic acids (salts) and unsaturated dicarboxylic acids (salts) (i.e., constituent units derived from monomer components other than unsaturated monocarboxylic acids (salts) and unsaturated dicarboxylic acids (salts)). The polymer of the present invention may contain only one of the above-mentioned other constituent units, or it may contain two or more.

[0029] Other monomer components include, for example, sulfonic acid monomers such as 3-allyloxy-2-hydroxypropanesulfonic acid, (meth)allylsulfonic acid, isoprenesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, and their salts; amino group-containing monomers such as vinylpyridine, vinylimidazole, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diallylamine, diallyldimethylamine, and their quaternary derivatives and salts; N-vinyl monomers such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N-vinyl-N-methylformamide, N-vinyl-N-methylacetamide, and N-vinyloxazolidone; and amide group-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide. Examples of monomers include: unsaturated alcohol monomers such as 3-(meth)allyloxy-1,2-dihydroxypropane, 3-allyloxy-1,2-dihydroxypropane, (meth)allyl alcohol, and isoprenol; polyalkylene glycol monomers having a structure in which alkylene oxide is added to the above unsaturated alcohol monomers; alkyl (meth)acrylate monomers such as butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and dodecyl (meth)acrylate; hydroxyl group-containing alkyl (meth)acrylate esters such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; vinylaryl monomers such as styrene, indene, and vinylaniline; alkenes such as isobutylene and octene; and vinyl carboxylates such as vinyl acetate and vinyl propionate.

[0030] Among the other monomer components mentioned above, alkyl (meth)acrylates containing hydroxyl groups are preferred, from the viewpoint of forming an esterification reaction with carboxylic acids during molding, resulting in a higher crosslink density and greater strength after molding.

[0031] The content of the above-mentioned other constituent units in the polymer of the present invention is 0 to 50% by mass, preferably 0 to 40% by mass, more preferably 0 to 30% by mass, even more preferably 0 to 20% by mass, and particularly preferably 0 to 10% by mass, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer of the present invention.

[0032] The polymer of the present invention may contain phosphorus. The phosphorus may be derived from a phosphorus-containing compound used, for example, as a chain transfer agent when synthesizing the precursor polymer described later, which is a precursor of the polymer of the present invention. In other words, in this case, the phosphorus is contained in the residues of the phosphorus-containing compound bound to the polymer of the present invention or the precursor polymer. When the polymer of the present invention contains phosphorus, it is preferable because the curing reaction of the binder is promoted.

[0033] Examples of the phosphorus-containing compounds mentioned above include phosphorus oxoacids or salts such as hypophosphorous acid (salt), phosphorous acid (salt), phosphoric acid (salt), pyrophosphate (salt), polyphosphate (salt), and organophosphate (salt). The phosphorus element content in the polymer of the present invention is preferably 0 to 10% by mass, more preferably 0.1 to 6% by mass, and even more preferably 0.5 to 4% by mass, based on the phosphorus-containing compound, relative to 100% by mass of the total amount of the polymer of the present invention. The residues of the phosphorus-containing compounds that may be contained in the polymer of the present invention may be one or more.

[0034] The alkanolamine that neutralizes the carboxylic acid (salt) in the above-mentioned precursor polymer has two or more hydroxyl groups in one molecule. The number of hydroxyl groups is preferably 2 to 4, more preferably 2 to 3, and even more preferably 2. One type of alkanolamine may be used, or two or more types may be used.

[0035] Examples of the above-mentioned alkanolamines include alkanolamines having two hydroxyl groups, such as diethanolamine, diisopropanolamine, methyldiethanolamine, and methyldiisopropanolamine; alkanolamines having three hydroxyl groups, such as triethanolamine, triisopropanolamine, diethanolisopropanolamine, diisopropanolethanolamine, and tris(2-hydroxybutyl)amine; and alkanolamines having four hydroxyl groups, such as tetrahydroxyethylethylenediamine and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine. In addition, alkanolamines in which some of these alkanolamines are bonded to a polymer (for example, polymers having a triisopropanolamine backbone) are also included.

[0036] Among the above alkanolamines, diethanolamine is preferred from the viewpoint of having a fast curing rate during molding, a high crosslink density after molding, and higher strength.

[0037] The amount of structural components derived from the alkanolamine in the above-mentioned binder is preferably 5 to 70 mol%, more preferably 10 to 60 mol%, even more preferably 15 to 50 mol%, and particularly preferably 20 to 45 mol%, based on 100 mol% of the constituent units derived from the carboxylic acid (salt) of the polymer of the present invention. When the above amount is 5 mol% or more, the flexural strength is further increased. When the above amount is 70 mol% or less, the flexural strength is further increased, and the applicability of the binder composition is also improved.

[0038] The polymer of the present invention has a neutralization rate of carboxyl groups by metal salts of 20% or less, preferably 10% or less, more preferably 5% or less, even more preferably 1% or less, and particularly preferably 0%. Since the structure neutralized by the metal salt (e.g., -COONa) does not contribute to the crosslinking of the polymer, the above neutralization rate of 20% or less facilitates the crosslinking of the polymer by alkanolamines, resulting in a high crosslink density after molding and enabling high flexural strength. The above neutralization rate is a ratio (mol%) to the total amount of constituent units derived from the above carboxylic acid (salt) of 100 mol%.

[0039] Examples of the above-mentioned metal salts include monovalent metal salts such as alkali metal salts (lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, etc.) and divalent metal salts such as alkaline earth metal salts (calcium salts, magnesium salts, etc.).

[0040] The weight-average molecular weight of the polymer of the present invention is preferably 1,000 to 100,000, more preferably 1,500 to 60,000, even more preferably 2,000 to 30,000, even more preferably 2,500 to 20,000, even more preferably 3,000 to 15,000, and particularly preferably 3,500 to 10,000. When the weight-average molecular weight is 1,000 or more, the flexural strength is higher. When the weight-average molecular weight is 100,000 or less, the flexural strength is higher, and the coatability of the binder composition is also better. The weight-average molecular weight can be measured using GPC with polyacrylic acid as the standard substance, and specifically can be measured by the method described in the examples.

[0041] The content of the polymer of the present invention in the binder is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the total amount of the binder. The binder may also contain the above-mentioned precursor polymer and free alkanolamine, in which case it is preferable that the total proportion of the polymer of the present invention, the above-mentioned precursor polymer, and the free alkanolamine is within the above range.

[0042] The above-mentioned binder may contain other components besides the polymer of the present invention. Examples of these other components include known or conventional components used in binders for wood-based boards, such as resin components other than the polymer of the present invention, and crosslinking agents, curing accelerators, neutralizing agents, plasticizers, inorganic or organic fillers, colorants (pigments, dyes), thickeners, dispersants, wetting agents, defoaming agents, antiseptics and antifungal agents, rust inhibitors, and water repellents, other than alkanolamines. Each of these other components may consist of only one or two or more.

[0043] The content of the polymer of the present invention is preferably 50% by mass or more, and may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, with 95% by mass or more being preferred, based on 100% by mass of the total amount of resin components in the binder (i.e., the sum of the polymer of the present invention and resin components other than the polymer of the present invention).

[0044] The content of the above alkanolamine is preferably 50% by mass or more, and may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, with 95% by mass or more being preferred, based on 100% by mass of the total amount of the above crosslinking agents (i.e., the sum of the alkanolamine and other crosslinking agents).

[0045] The pH of the binder composition forming the above binder is preferably 3.5 or higher, more preferably 4.0 or higher, even more preferably 4.2 or higher, and particularly preferably 4.4 or higher. When the pH is 3.5 or higher, the bending strength is increased. Furthermore, deterioration of the wood chips and corrosion of the molding machine can be suppressed. The pH is, for example, 7.0 or lower, preferably 6.5 or lower, and more preferably 5.5 or lower. When the pH is 7.0 or lower, the bending strength is increased, and the applicability of the binder composition is improved.

[0046] The solid content concentration of the above binder composition is preferably 15% by mass or more, more preferably 17% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more. When the solid content concentration is 15% by mass or more, the bending strength is higher. From the viewpoint of superior coatability of the binder composition, the solid content concentration is preferably 50% by mass or less, and more preferably 40% by mass or less.

[0047] (wood chips) The wood chips (wood fragments) can be any known or conventional wood fragments used for wood-based boards. Examples of wood fragment materials include coniferous trees such as pine, cedar, and cypress, and broad-leaved trees such as lauan, kapur, and poplar. One type of wood fragment may be used, or two or more types may be used.

[0048] Wood chips are obtained by grinding the wood chip material into granules using a known grinding device (chipper), such as a hammer mill, pin mill, or jet mill. The particle size (maximum diameter) of the wood chips is, for example, 0.5 to 5 mm.

[0049] The shape of the wood fragments is not particularly limited, but examples include chips, flakes, wafers, strands, and fibers.

[0050] The moisture content of the wood chips is preferably 1% by mass or more, and more preferably 3% by mass or more, based on 100% by mass of the total amount of wood chips. When the moisture content is 1% by mass or more, the applicability of the binder composition is superior. From the viewpoint of ease of removal during molding, the moisture content is preferably 20% by mass or less, and more preferably 15% by mass or less. The moisture content can be determined from the formula (m1-m0)×100 / m0 in accordance with JIS A 5905 (2003) 6.4. Here, m1 is the mass (g) of the wood chips before drying, and m0 is the mass (g) of the wood chips when they reach a constant weight after being placed in an air dryer at 103°C.

[0051] The bending strength of the wood-based board of the present invention is preferably 4.0 MPa or higher, more preferably 5.0 MPa or higher, and even more preferably 6.0 MPa or higher. The higher the bending strength, the better the strength, and there is no particular upper limit. The upper limit of the bending strength is, for example, 20 MPa. The bending strength can be measured by a three-point bending test using a universal material testing machine with a test piece span of 50 mm and a deformation speed of 1.5 mm / min on a wood-based board measuring 80 mm in length and 20 mm in width.

[0052] The wood-based board of the present invention can be manufactured using a binder composition that has high strength and good applicability to wood chips. Therefore, the wood-based board of the present invention may have high strength, a good appearance, and excellent productivity.

[0053] [Manufacturing method for wood fiberboard] The method for manufacturing wood-based boards of the present invention (sometimes simply referred to as "the manufacturing method of the present invention") is a method for manufacturing wood-based boards by press-molding a mixture containing a binder composition and a plurality of the above-mentioned wood pieces. The binder composition contains at least the polymer of the present invention. That is, the binder composition is a composition that forms a binder for binding a plurality of wood pieces together in the wood-based board (a binder composition for wood-based boards). The binder composition for wood-based boards has good applicability to wood pieces and can be used to manufacture wood-based boards with high strength. Furthermore, the manufacturing method of the present invention can be used to manufacture the wood-based boards of the present invention.

[0054] (Binder composition) The above-mentioned binder composition may contain, in addition to the polymer of the present invention, other components exemplified and described as components that may be included in the binder for the wood-based board of the present invention, as well as a solvent. As the solvent, an aqueous medium is preferred, and more preferably water, from the viewpoint of excellent environmental suitability, excellent solubility and dispersibility of the polymer of the present invention, and excellent coatability. One solvent may be used alone, or two or more solvents may be used.

[0055] The content of the polymer of the present invention in the above binder composition is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on 100% by mass of the total amount of solids in the above binder composition. The above binder composition may also contain the above precursor polymer and free alkanolamine, in which case it is preferable that the total proportion of the polymer of the present invention, the above precursor polymer, and free alkanolamine is within the above range.

[0056] The content of the polymer of the present invention is preferably 50% by mass or more, and may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, and preferably 95% by mass or more, based on 100% by mass of the total amount of resin components in the binder composition (i.e., the sum of the polymer of the present invention and resin components other than the polymer of the present invention).

[0057] The amount of structural components derived from the alkanolamine in the above-mentioned binder composition is preferably 5 to 70 mol%, more preferably 10 to 60 mol%, even more preferably 15 to 50 mol%, and particularly preferably 20 to 40 mol%, based on 100 mol% of the constituent units derived from the carboxylic acid (salt) of the polymer of the present invention. When the above amount is 5 mol% or more, the flexural strength is further increased. When the above amount is 70 mol% or less, the flexural strength is further increased, and the applicability of the binder composition is also improved.

[0058] The content of the above alkanolamine is preferably 50% by mass or more, and may be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, with 95% by mass or more being preferred, based on 100% by mass of the total amount of the above crosslinking agents (i.e., the sum of the alkanolamine and other crosslinking agents).

[0059] The pH of the above binder composition is preferably 3.5 or higher, more preferably 4.0 or higher, even more preferably 4.2 or higher, and particularly preferably 4.4 or higher. When the pH is 3.5 or higher, the bending strength is increased. Furthermore, deterioration of the wood chips and corrosion of the molding machine can be suppressed. The pH is, for example, 7.0 or lower, preferably 6.5 or lower, and more preferably 5.5 or lower. When the pH is 7.0 or lower, the bending strength is increased, and the applicability of the binder composition is improved.

[0060] The solid content concentration of the above binder composition is preferably 15% by mass or more, more preferably 17% by mass or more, even more preferably 20% by mass or more, and particularly preferably 25% by mass or more. When the solid content concentration is 15% by mass or more, the bending strength is higher. From the viewpoint of superior coatability of the binder composition, the solid content concentration is preferably 50% by mass or less, and more preferably 40% by mass or less.

[0061] The viscosity of the above binder composition is preferably 100 mPa·s or less, more preferably 80 mPa·s or less, even more preferably 60 mPa·s or less, even more preferably 38 mPa·s or less, and particularly preferably 30 mPa·s or less. When the viscosity is 100 mPa·s or less, the coatability of the binder composition is superior. From the viewpoint of excellent handling, the viscosity is, for example, 1 mPa·s or more. The viscosity is the viscosity at 25°C and can be measured using a B-type viscometer. The rotor and rotation speed are appropriately selected according to the viscosity range.

[0062] (Manufacturing method) The above-mentioned binder composition can be prepared by mixing the polymer of the present invention with the other components and solvents as needed. Alternatively, the polymer of the present invention can be produced in the binder composition by adding and mixing the above-mentioned precursor polymer and the above-mentioned alkanolamine in a solvent. The above mixing can be carried out by conventional methods.

[0063] The above-mentioned precursor polymer is the same as the polymer of the present invention, except that it has not been neutralized with an alkanolamine. That is, the above-mentioned precursor polymer is a polymer having a carboxylic acid (salt), and the content of constituent units derived from unsaturated monocarboxylic acid (salt) is 50 to 100% by mass, the content of constituent units derived from unsaturated dicarboxylic acid (salt) is 0 to 3% by mass, and the content of the other constituent units is 0 to 50% by mass, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the precursor polymer. The preferred range of the content of these various constituent units is the same as the preferred range in the polymer of the present invention.

[0064] The weight-average molecular weight of the above-mentioned precursor polymer is preferably 1,000 to 100,000, more preferably 1,500 to 60,000, even more preferably 2,000 to 30,000, even more preferably 2,500 to 20,000, even more preferably 3,000 to 15,000, and particularly preferably 3,500 to 10,000. When the weight-average molecular weight is 1,000 or more, the flexural strength is higher. When the weight-average molecular weight is 100,000 or less, the flexural strength is higher, and the coatability of the binder composition is also better. The weight-average molecular weight can be measured using GPC with polyacrylic acid as the standard substance, and specifically can be measured by the method described in the examples.

[0065] In the manufacturing method of the present invention, first, the binder composition and a plurality of the wood chips are mixed to impregnate the wood chips with the binder composition and prepare the mixture. The wood chips may be dried before mixing to adjust their moisture content as needed. After mixing, the solvent that may be contained in the binder composition may be evaporated as needed to adjust the solid content concentration and prepare the mixture. The mixing ratio of the binder composition and the wood chips is not particularly limited, but the mass ratio of wood chips to the solid content of the binder composition [wood chips / solid content of binder composition] is preferably 70 / 30 to 99 / 1, more preferably 75 / 25 to 98 / 2, even more preferably 80 / 20 to 97 / 3, even more preferably 85 / 15 to 96 / 4, and particularly preferably 90 / 10 to 95 / 5. When the mass ratio is 70 / 30 or higher, the wood texture is good, the appearance is good, and the workability tends to be excellent. When the mass ratio is 99 / 1 or lower, the bending strength tends to be excellent.

[0066] Next, the above mixture is subjected to press molding. Specifically, the above mixture is spread into a mold for wood fiberboard, and then heated and pressurized to form a board, thereby manufacturing the wood fiberboard. The following description will explain the manufacturing method as an example when the wood fiberboard is fiberboard (when the wood pieces are fibrous wood pieces). When molding the above mixture by heating and pressurizing, the above mixture is first formed into a mat-like material. The forming method is not particularly limited, but examples include wet forming and dry forming (air forming). When using the wet forming method, it is necessary to thoroughly dry the mat-like material before molding.

[0067] Examples of equipment used in the wet forming method include long-wire papermaking machines (Ford linear machines) and cylinder papermaking machines. On the other hand, examples of equipment used in the dry forming method include forming machines equipped with gravitational or suction filters, or Levanite filters.

[0068] The molding conditions for forming a mat-like material into a plate are not particularly limited, but the molding temperature is preferably 130 to 270°C, more preferably 150 to 250°C, the molding pressure is preferably 1 to 6 MPa, more preferably 3 to 5 MPa, and the molding time is preferably 1 to 20 minutes, more preferably 5 to 15 minutes. If the molding temperature is 130°C or higher, sufficient durability and water resistance are achieved. If the molding temperature is 270°C or lower, deterioration of the wood fragments can be suppressed, a decrease in strength can be suppressed, and sufficient durability and water resistance are achieved. If the molding pressure is 1 MPa or higher, sufficient durability and water resistance are achieved. If the molding pressure is 6 MPa or lower, high fiber strength can be maintained. If the molding time is 1 minute or more, sufficient durability and water resistance are achieved. If the molding time is 20 minutes or less, deterioration of the wood fragments can be suppressed, a decrease in strength can be suppressed, and sufficient durability and water resistance are achieved.

[0069] Examples of equipment used for molding include hot presses equipped with a pressurizing section, a heating plate, etc. After the molding process, further treatments such as heat treatment or oil immersion may be performed to improve physical properties such as water resistance.

[0070] According to the manufacturing method of the present invention, it is possible to manufacture wood-based boards that have excellent productivity and high strength.

[0071] Since glass does not have reaction sites with carboxyl groups, when using a polymer having a carboxylic acid (salt), such as the polymer of the present invention, as a binder, a reaction site with glass can be formed by using a silane coupling agent in combination. On the other hand, wood chips have hydroxyl groups derived from cellulose and are reactive with carboxyl groups. For this reason, the polymer of the present invention can be used as a binder in wood-based boards without using a silane coupling agent in combination. The resulting wood-based board of the present invention has high flexural strength. For this reason, the above binder and the above binder composition do not need to contain a silane coupling agent, and the content of the silane coupling agent in the binder (or binder composition) may be, for example, 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less, or 0.05% by mass or less, based on 100% by mass of the total amount of solids in the binder (or binder composition). Furthermore, it is preferable that the wood-based board of the present invention has a chemical bond between the above binder (particularly the polymer of the present invention) and the wood chips.

[0072] Furthermore, since glass is an inorganic material, it is less susceptible to degradation by heating. Therefore, even if there is a large amount of moisture in the binder composition, the water can be sufficiently evaporated by applying heat, allowing it to harden. On the other hand, since wood chips are organic materials, they degrade when heated. Therefore, if there is a large amount of moisture in the binder composition, a long heating time is required for water evaporation and hardening of the binder, resulting in the wood chips degrading easily. In contrast, the binder composition using the polymer of the present invention has high curability and can be hardened in a relatively short heating time. In particular, when the solid content concentration is 15% by mass or more, it can efficiently evaporate water, making it a suitable binder composition for wood-based boards.

[0073] Furthermore, since glass does not absorb water, the glass substrate can be used regardless of its moisture content. In fact, glass contains almost no water, so its moisture content is always approximately 0%. On the other hand, wood chips readily absorb water, so the applicability of the binder composition changes depending on the moisture content of the wood chips used. For this reason, when the moisture content of the wood chips is adjusted to be 1% by mass or more per 100% by mass of the total amount of wood chips, the technical significance of the present invention, which is that the binder composition using the polymer of the present invention has excellent applicability to wood chips, is more efficiently demonstrated. [Examples]

[0074] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "percent mass".

[0075] <Measurement conditions (GPC) for weight-average molecular weight (10,000 or less)> Equipment: HLC-8320GPC manufactured by Tosoh Corporation Detector: RI Column: TSK-GEL G3000PWXL manufactured by Tosoh Corporation (2 connected in series) Column temperature: 40℃ Flow rate: 0.5mL / min. Sample solution injection volume: 10 μL (sample concentration: 0.5% by mass) Calibration curve: Created using a cubic equation based on Mp and elution time, using polyacrylic acid standards (Mp=1250, 2925, 7500, 16000, 36200, 43100) and sodium acetate (Mp=94) from Polymer Standards Service. Eluent: A solution obtained by diluting a mixture of sodium dihydrogen phosphate dodecahydrate and disodium hydrogen phosphate dihydrate (34.5g / 46.2g) with pure water to 5000g.

[0076] <Measurement conditions for weight-average molecular weight (when it exceeds 10,000) (GPC)> Equipment: HLC-8320GPC manufactured by Tosoh Corporation Detector: RI Column: TSKgel GMPWXL manufactured by Tosoh Corporation (connected in series, 2 columns) Column temperature: 40 °C Flow rate: 1 mL / min Sample solution injection volume: 20 μL (sample concentration: 0.5 mass%) Calibration curve: Prepared using polyacrylic acid standards (Mp = 1200, 2925, 7500, 16000, 36200, 43100, 73600, 115000, 143000, 321000, 532000, 724000, 1020000, 1390000) manufactured by Polymer Standards Service, and created as a cubic equation based on Mp and elution time Eluent: (60.84 mM sodium carbonate aqueous solution + 60.84 mM sodium hydrogen carbonate aqueous solution) / acetonitrile = 83.74 / 16.26 (mass ratio)

[0077] <pH measurement> The pH of the binder composition was measured under the following conditions Apparatus: "pH METER D-52" manufactured by Horiba, Ltd. Electrode: Glass electrode Temperature: 25 °C

[0078] <Viscosity measurement> The viscosity of the binder composition was measured under the following conditions Apparatus: B-type viscometer Temperature of the aqueous solution during measurement: 25 °C Rotor and rotation speed: Appropriately selected according to viscosity

[0079] <Measurement of solid content concentration> Weighed 1.0 g of the sample into an aluminum dish, diluted it with 1.0 g of pure water, and spread it evenly. This was dried in an oven at 130 °C for 1 hour, cooled in a desiccator, and then the mass after drying was measured. The solid content (non-volatile content) concentration was calculated from the mass difference before and after drying. Unless otherwise specified, the solid content concentration measured by the above procedure was used as the concentration of the precursor polymer solution and the binder composition

[0080] <Production Example 1> 720.0 g of pure water (hereinafter referred to as initial water) was pre-charged into a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, and the temperature was raised to the boiling point under stirring. Then, under stirring, 1000.0 g of 80% acrylic acid (hereinafter referred to as AA) aqueous solution, 56.9 g of 45% sodium hypophosphate monohydrate (hereinafter referred to as SHP) aqueous solution, and 53.3 g of 15% sodium persulfate (hereinafter referred to as NaPS) aqueous solution were added dropwise separately to the system under reflux at the boiling point. The entire amounts of the 80% AA aqueous solution, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate from 0 to 180 minutes. After all dropwise addition was complete, the mixture was matured for another 30 minutes under reflux conditions to complete the polymerization. By adjusting with pure water, a precursor polymer solution with a solid content of 45% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 10,000 was obtained.

[0081] <Manufacturing Example 2> In a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, 720.0 g of pure water and 24.0 g of maleic anhydride (hereinafter referred to as MA) were pre-charged and heated to the boiling point under stirring. After confirming that the MA had dissolved, 970.0 g of 80% AA aqueous solution, 56.9 g of 45% SHP aqueous solution, and 53.3 g of 15% NaPS aqueous solution were then separately added dropwise to the system under stirring and reflux at the boiling point. The entire amounts of the 80% AA aqueous solution, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate from 0 to 180 minutes. After all additions were completed, the system was matured for another 30 minutes under reflux at the boiling point to complete the polymerization, and then adjusted with pure water to obtain a precursor polymer solution with a solid content of 45% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 10,000.

[0082] <Manufacturing Example 3> 720.0 g of pure water was pre-charged into a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, and heated to the boiling point under stirring. Then, under stirring, 500.0 g of 80% AA aqueous solution, 400.0 g of 2-hydroxyethyl methacrylate (hereinafter referred to as HEMA), 56.9 g of 45% SHP aqueous solution, and 53.3 g of 15% NaPS aqueous solution were added dropwise, separately, to the system under reflux at the boiling point. The entire amounts of the 80% AA aqueous solution, HEMA, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate from 0 to 180 minutes. After all additions were completed, the system was matured for another 30 minutes under reflux at the boiling point to complete the polymerization, and then adjusted with pure water to obtain a precursor polymer solution with a solid content of 45% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 10,000.

[0083] <Manufacturing Example 4> In a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, 720.0 g of pure water and 24.0 g of MA were pre-charged and heated to the boiling point under stirring. After confirming that the MA had dissolved, 500.0 g of 80% AA aqueous solution, 376.0 g of HEMA, 56.9 g of 45% SHP aqueous solution, and 53.3 g of 15% NaPS aqueous solution were then added dropwise, separately, to the system under stirring and reflux at the boiling point. The entire amounts of 80% AA aqueous solution, HEMA, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate from 0 to 180 minutes. After all additions were completed, the system was matured for another 30 minutes under reflux at the boiling point to complete the polymerization, and then adjusted with pure water to obtain a precursor polymer solution with a solid content of 45% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 10,000.

[0084] <Manufacturing Example 5> 720.0 g of pure water was pre-charged into a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, and heated to the boiling point under stirring. Then, under stirring, 1000.0 g of 80% AA aqueous solution, 142.2 g of 45% SHP aqueous solution, and 53.3 g of 15% NaPS aqueous solution were added dropwise separately to the system under reflux at the boiling point. The entire amounts of the 80% AA aqueous solution, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate from 0 to 180 minutes. After all additions were completed, the system was matured for another 30 minutes under reflux at the boiling point to complete the polymerization, and then adjusted with pure water to obtain a precursor polymer solution with a solid content of 45% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 1,500.

[0085] <Manufacturing Example 6> 720.0 g of pure water was pre-charged into a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, and heated to the boiling point under stirring. Then, under stirring, 1000.0 g of 80% AA aqueous solution, 8.9 g of 45% SHP aqueous solution, and 49.6 g of 15% NaPS aqueous solution were added dropwise, separately, to the system under reflux at the boiling point. The entire amounts of the 80% AA aqueous solution, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate from 0 to 180 minutes. After all additions were completed, the system was matured for another 30 minutes under reflux at the boiling point to complete the polymerization, and then adjusted with pure water to obtain a precursor polymer solution with a solid content of 40% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 90,000.

[0086] <Manufacturing Example 7> In a 2.5 L stainless steel separable flask equipped with a stirrer, reflux condenser, and thermometer, 720.0 g of pure water and 320.0 g of maleic anhydride (hereinafter referred to as MA) were pre-charged and heated to the boiling point under stirring. After confirming that the MA had dissolved, 600.0 g of 80% AA aqueous solution, 56.9 g of 45% SHP aqueous solution, and 53.3 g of 15% NaPS aqueous solution were then separately added dropwise to the system under stirring and reflux at the boiling point. The entire amounts of the 80% AA aqueous solution, 45% SHP aqueous solution, and 15% NaPS aqueous solution were added continuously at a constant dropping rate over 0 to 180 minutes. After all additions were completed, the system was matured for another 30 minutes under reflux at the boiling point to complete the polymerization, and then adjusted with pure water to obtain a precursor polymer solution with a solid content of 45% containing a polymer (carboxyl group-containing polymer) with a weight-average molecular weight of 10,000.

[0087] <Examples 1-10, Comparative Example 1> A binder composition was obtained by mixing each component according to the formulation composition shown in Table 1. The pH and viscosity of the obtained binder composition were measured and summarized in Table 1. The obtained binder composition formed a polymer in which the carboxyl group was neutralized by diethanolamine due to the blending of a carboxyl group-containing polymer and diethanolamine. Since the molecular weight of diethanolamine is negligibly small compared to the molecular weight of the polymer before neutralization, the weight-average molecular weight of the polymer with the neutralized structure is judged to be about the same as before neutralization. Furthermore, since carboxylic acids have a higher pKa than hypophosphorous acid and persulfate, the possibility of the carboxyl group being substituted with Na derived from sodium hypophosphorous acid or sodium persulfate is low, and Na derived from sodium hypophosphorous acid or sodium persulfate does not contribute to the neutralization rate of the carboxyl group and does not need to be considered. In addition, since no metal salts were added in the examples and comparative examples, the neutralization rate of the polymer by metal salts was judged to be 0%. Then, wood-based boards were manufactured using the obtained binder composition according to the "Method for Manufacturing Wood-Based Boards" described below and evaluated according to the "Evaluation Method" described later. The results are shown in Table 1. In the table, "carboxyl group-containing polymer" indicates the mass of the precursor polymer solution obtained in each manufacturing example. Also, "80% diethanolamine" in the table refers to diethanolamine diluted with pure water to adjust to 80%.

[0088] (Manufacturing method for wood-based boards) Wood chips were placed in a hot air dryer at 80°C for 24 hours to obtain wood chips with a moisture content of 5-10%. The moisture content of the wood chips can be calculated using the formula (m1-m0)×100 / m0, in accordance with JIS A 5905 (2003) 6.4. Here, m1 is the mass (g) of the wood chips before drying, and m0 is the mass (g) of the wood chips when they reach a constant weight after being placed in an air dryer at 103°C.

[0089] Next, 15 parts of the binder composition obtained in each example were added to 45 parts of dried wood chips while stirring, impregnating the wood chips with the binder composition. The chips impregnated with the binder composition were laid out in a 100 x 100 mm mold and heated and compressed using a hot press at a pressure of 3 MPa and a temperature of 200°C for 10 minutes, resulting in a density of approximately 0.5-0.6 g / cm³. 3 We also fabricated wood-based boards with a thickness of 8-10 mm.

[0090] (Bending strength test of wood-based boards) After cutting the fabricated wood-based boards to a length of 80 mm and a width of 20 mm, a three-point bending test was performed using a universal material testing machine (manufactured by Instron) under the conditions of a specimen span of 50 mm and a deformation speed of 1.5 mm / min to obtain the bending strength. The boards were then evaluated based on the following evaluation criteria. [Evaluation Criteria] ◎: 6.0 MPa or higher ○: 5.0 MPa or higher, less than 6.0 MPa △: 4.0 MPa or higher, less than 5.0 MPa ×: Less than 4.0 MPa

[0091] (Applicability of the binder composition) The applicability of the binder composition was evaluated based on numerical values ​​obtained by viscosity measurement of the binder composition, according to the evaluation criteria below. [Evaluation Criteria] ◎: No problems whatsoever with actual use. ○: While there are no problems with practical use, it may affect productivity. ×: Unacceptable level in practical use

[0092] [Table 1]

[0093] As shown in Table 1, the binder compositions of the examples were judged to have high flexural strength and excellent coatability. In particular, when the weight-average molecular weight of the polymer was relatively small (Examples 1-5, 7), coatability was judged to be even better. Furthermore, when the solid content concentration was high (Examples 1-9), and among these, when the [alkanolamine / carboxyl group] and pH were within a specific range (Examples 1-6), flexural strength was judged to be higher. On the other hand, when the proportion of constituent units derived from unsaturated dicarboxylic acid (salt) was high (Comparative Example 1), flexural strength was evaluated to be inferior.

[0094] The following describes variations of the invention relating to this disclosure. [Note 1] This is a wood-based board in which multiple wood pieces are molded together with a binder. The binder comprises a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine. The polymer is characterized in that, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer, 50-100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0-3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0-50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The aforementioned alkanolamine has two or more hydroxyl groups in one molecule, and is a wood-based board. [Note 2] The weight-average molecular weight of the polymer is 1,000 to 100,000, as described in Note 1. [Note 3] The amount of structural components derived from the alkanolamine in the binder is 5 to 70 mol% relative to 100 mol% of the constituent units derived from the carboxylic acid (salt) of the polymer, as described in Note 1 or 2. [Note 4] The wood-based board described in any one of Notes 1 to 3, wherein the unsaturated monocarboxylic acid (salt) includes (meth)acrylic acid (salt). [Note 5] The wood-based board according to any one of Notes 1 to 4, wherein the alkanolamine includes diethanolamine. [Note 6] The wood-based board according to any one of Notes 1 to 5, wherein the pH of the binder composition forming the binder is 3.5 or higher. [Note 7] The wood-based board according to any one of Notes 1 to 6, wherein the solid content concentration of the binder composition forming the binder is 15% by mass or more. [Note 8] The wood-based board described in any one of Notes 1 to 7, wherein the moisture content of the wood chips is 1% by mass or more. [Note 9] Contains polymers having a structure in which the carboxyl group is neutralized with an alkanolamine, The polymer is characterized in that, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer, 50-100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0-3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0-50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The aforementioned alkanolamine is a binder composition for wood-based boards having two or more hydroxyl groups in one molecule. [Note 10] The weight-average molecular weight of the polymer is 1,000 to 100,000, the binder composition for wood-based boards as described in Note 9. [Note 11] The amount of structural components derived from the alkanolamine is 5 to 70 mol% relative to 100 mol% of the constituent units derived from the carboxylic acid (salt) of the polymer, as described in Note 9 or 10. [Note 12] The wood-based board binder composition according to any one of Notes 9 to 11, wherein the unsaturated monocarboxylic acid (salt) comprises (meth)acrylic acid (salt). [Note 13] The wood-based board binder composition according to any one of Notes 9 to 12, wherein the alkanolamine comprises diethanolamine. [Note 14] A binder composition for wood-based boards as described in any one of Notes 9 to 13, wherein the pH is 3.5 or higher. [Note 15] A binder composition for wood-based boards according to any one of Notes 9 to 14, wherein the solid content concentration is 15% by mass or more. [Note 16] A method for producing a wood-based board by press-molding a mixture containing a binder composition and multiple wood chips. The binder composition comprises a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine. The polymer is characterized in that, based on 100% by mass of the total amount of constituent units derived from the monomer components constituting the polymer, 50-100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0-3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0-50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The method for producing wood-based boards, wherein the alkanolamine has two or more hydroxyl groups in one molecule. [Note 17] The method for producing wood-based boards as described in Note 16, wherein the weight-average molecular weight of the polymer is 1,000 to 100,000. [Note 18] The method for producing wood-based board according to Note 16 or 17, wherein the amount of structural components derived from the alkanolamine in the binder composition is 5 to 70 mol% relative to 100 mol% of the constituent units derived from the carboxylic acid (salt) of the polymer. [Note 19] The method for producing wood-based board according to any one of Notes 16 to 18, wherein the unsaturated monocarboxylic acid (salt) includes (meth)acrylic acid (salt). [Note 20] The method for producing wood-based board according to any one of Notes 16 to 19, wherein the alkanolamine includes diethanolamine. [Note 21] The method for producing a wood-based board according to any one of Notes 16 to 20, wherein the pH of the binder composition is 3.5 or higher. [Note 22] The method for producing wood-based board according to any one of Notes 16 to 21, wherein the solid content concentration of the binder composition is 15% by mass or more. [Note 23] The method for manufacturing a wood-based board according to any one of Notes 16 to 22, wherein the moisture content of the wood chips is 1% by mass or more.

Claims

1. It is a wood-based board in which multiple pieces of wood are molded together with a binder. The binder comprises a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine. The polymer is characterized in that, based on 100% by mass of the total amount of constituent units derived from monomer components constituting the polymer, 50 to 100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0 to 3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0 to 50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The aforementioned alkanolamine has two or more hydroxyl groups in one molecule, and is a wood-based board.

2. The wood-based board according to claim 1, wherein the weight-average molecular weight of the polymer is 1,000 to 100,000.

3. The wood-based board according to claim 1 or 2, wherein the amount of structural components derived from the alkanolamine in the binder is 5 to 70 mol% with respect to 100 mol% of the constituent units derived from the carboxylic acid (salt) of the polymer.

4. The wood-based board according to claim 1 or 2, wherein the unsaturated monocarboxylic acid (salt) comprises (meth)acrylic acid (salt).

5. The wood-based board according to claim 1 or 2, wherein the alkanolamine comprises diethanolamine.

6. The wood-based board according to claim 1 or 2, wherein the pH of the binder composition forming the binder is 3.5 or higher.

7. The wood-based board according to claim 1 or 2, wherein the solid content concentration of the binder composition forming the binder is 15% by mass or more.

8. The wood-based board according to claim 1 or 2, wherein the moisture content of the wood chips is 1% by mass or more.

9. The polymer contains a structure in which the carboxyl group is neutralized with an alkanolamine. The polymer is characterized in that, based on 100% by mass of the total amount of constituent units derived from monomer components constituting the polymer, 50 to 100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0 to 3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0 to 50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The aforementioned alkanolamine is a binder composition for wood-based boards having two or more hydroxyl groups in one molecule.

10. This is a method for producing a wood-based board by press-molding a mixture containing a binder composition and multiple wood chips. The binder composition comprises a polymer having a structure in which the carboxyl group is neutralized with an alkanolamine. The polymer is characterized in that, based on 100% by mass of the total amount of constituent units derived from monomer components constituting the polymer, 50 to 100% by mass of constituent units derived from unsaturated monocarboxylic acid (salt), 0 to 3% by mass of constituent units derived from unsaturated dicarboxylic acid (salt), and 0 to 50% by mass of other constituent units, and the neutralization rate of carboxyl groups by metal salts is 20% or less. The method for producing wood-based boards, wherein the alkanolamine has two or more hydroxyl groups in one molecule.

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