JP4469797B2 - The manufacturing method of a resin composition, and the manufacturing method of the woody formation manufactured using this. - Google Patents

Description

The present invention relates to a urethane resin recycling technique, and more particularly to a resin composition using a urethane resin decomposition product and a woody molded body produced using the resin composition.

  With increasing interest in environmental problems in recent years, waste disposal technologies including urethane resins, which are frequently used for refrigerators, building materials, cushion materials, and the like, are being studied. Since this urethane resin is a thermosetting resin having a three-dimensional network structure, it is difficult to recycle, and at present, disposal such as landfill and incineration has been performed. However, since these processing means waste resources, development of a technique for disassembling them and reusing them as resin materials is required.

As a method of chemically decomposing a urethane resin, a method is known in which a urethane resin is decomposed with monoethanolamine and then distilled to isolate a polyol and a polyamine (see, for example, Patent Document 1). Moreover, as a method for producing a resin using the urethane resin decomposition product thus obtained, a method of regenerating the urethane decomposition product by mixing it with a urethane raw material (see, for example, Patent Document 2), or curing of an epoxy resin A method of reusing as an agent (for example, see Patent Document 3) is known.

JP-A 42-10634 JP-A-10-152578 JP 2004-75721 A

In the conventional regeneration methods shown in Patent Documents 2 and 3 above, the urethane resin decomposition product and isocyanate or epoxy are cross-linked by polyaddition reaction, so that after mixing them, the reaction between the urethane resin decomposition product and these compounds Gradually progressed, and there was a problem that the usable time after mixing (hereinafter referred to as pot life) was short.
Therefore, in the present invention, when producing a recycled resin using a urethane resin decomposition product, an object is to provide a resin composition using a urethane resin decomposition product with a long pot life and a wood molded product produced using the resin composition. It is what.

  When the present inventors regenerate a urethane resin decomposition product obtained by decomposing a urethane resin, the polycondensation of the urethane resin decomposition product and a compound having formaldehyde and / or a methylol group gives a resin composition. By adopting the route, the present invention has been completed by paying attention to the fact that it can be stably stored until the dehydration by heating or the condensation reaction by deformaldehyde is started.

The first aspect of the present invention is a step of chemically decomposing a urethane resin to obtain a urethane resin decomposed product having an OH group or NH ₂ group at the end, and the urethane decomposed product with formaldehyde or a compound that generates formaldehyde by heating. a method for producing a resin composition characterized in that it comprises a step of reacting.

The second of the present invention is to decompose the urethane resin chemically, and step ends to obtain a urethane resin decomposed substance of OH groups or NH ₂ groups, the urethane resin decomposed substance, with a compound having a methylol group A process for producing a resin composition.

A step of chemically decomposing a urethane resin to obtain a urethane resin decomposed product having a terminal OH group or an NH ₂ group, a compound that generates formaldehyde by heating with formaldehyde and heating , and a compound having a methylol group. A method for producing a wooden molded body , comprising: a step of reacting at least one to obtain a resin composition; and a step of mixing and adhering the resin composition and a wooden material .

As described above, the resin composition of the present invention has a long pot life and is economical. Moreover, the wood molding using this has good mechanical characteristics.

[First Embodiment]
Hereinafter, embodiments of each component of the resin composition and the method for producing the resin composition according to the present invention will be described.

(Urethane resin decomposition product)
The urethane resin decomposition product of the present embodiment is a product obtained by chemically decomposing a urethane resin, that is, reducing the molecular weight. Specific examples of urethane resins to be decomposed include foamed rigid urethane (rigid foam), isocyanurate materials having a nurate bond, foamed semi-rigid urethane (semi-rigid foam), foamed flexible urethane (soft foam), urethane Examples thereof include elastomers and RIM molded bodies, and these are used as heat insulating materials, structural materials, bedding, automobile seats, bumpers and the like.

  The method for chemically decomposing the urethane resin is not particularly limited as long as it generates a hydroxyl group and an amino group in the urethane resin decomposition product. Specifically, at least one of heat and a decomposing agent is allowed to act. And chemical decomposition methods (see Japanese Patent Publication No. S42-10634, Japanese Patent Application Laid-Open No. 6-184513, etc.).

(1-1) As a method of performing decomposition by heat, the urethane resin can be decomposed by heating the urethane resin at a temperature of 300 ° C. to 500 ° C. for 1 to 20 minutes.
Under these conditions, when the heating temperature falls below the above range, the decomposition rate of the urethane resin is insufficient, and it takes a long time to decompose, which is not practical. On the other hand, when the heating temperature exceeds the above range, the molecular weight of the decomposition product is too low, and the production conditions for the recycled resin become severe. In addition, when the heating time is less than the above range, the thermal decomposition is not sufficiently performed, the molecular weight is not sufficiently lowered, and it is inappropriate as a recycled resin material. On the other hand, when the heating time exceeds the above range, the molecular weight of the decomposed product is too low, and the production conditions for the recycled resin become severe.
This pyrolysis can be carried out by placing the urethane resin under normal pressure or under pressure. Further, as the atmosphere, it is desirable to perform nitrogen substitution or an oxygen-free atmosphere in order to prevent an undesired by-product of the urethane resin decomposition product from increasing.
In this thermal decomposition method, it is preferable that the urethane resin which is a decomposition target is broken into fine particles and decomposed. Further, the decomposition treatment can be performed while mechanically pulverizing. For this, a screw feeder such as an extruder is suitable.

(1-2) Next, a method for decomposing by applying a decomposing agent to urethane resin will be described below.
In this method, a decomposing agent is mixed with urethane resin to chemically decompose. Examples of the decomposing agent used in this method include amine decomposing agents, polyol decomposing agents, and hydrolysis catalysts. Among them, the amine decomposing agent contains a lot of amino groups in the decomposition product, so that the reaction with formaldehyde and / or methylol group described later becomes good, and a high-strength recycled resin can be obtained. Therefore, it is particularly preferable.

  Examples of the amine decomposing agent include primary amine, secondary amine, and tertiary amine. Monoethanolamine, diethanolamine, triethanolamine, tetramethylenediamine, propanediamine, isopropanolamine, 2- (2-aminoethylamino) ) Ethanol, 2-amino-2-hydroxymethyl-1,3-propanediol, ethylaminoethanol, aminobutanol, n-propylamine, di-n-propylamine, n-amylamine, isobutylamine, methyldiethylamine, cyclohexylamine Piperazine, piperidine, aniline, toluidine, benzylamine, phenylenediamine, xylylenediamine, chloroaniline, pyridine, picoline, N-methylmorpholine, ethylmorpholine, pyrazole, , 2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 12-aminododecanoic acid, 2-ethylhexylamine, 2-hydroxyethylaminopropylamine, 3- (2-ethylhexyloxy) propylamine, 3- (diethylamino) propylamine, 3- (dibutylamino) propylamine, 3- (dimethylamino) propylamine, 3- (methylamino) propylamine, 3,3′-iminobis (propylamine), 3-amino- 1-propanol, methyl 3-aminocrotonate, 3-methoxypropylamine, N- (2-aminoethyl) ethanolamine, N, N, N ′, N′-tetramethyl-1,6-hexamethylenediamine, N , N-diisopropylethylamine, N, N-diethylethanolamine N, N-dimethylethanolamine, N, N-butylethanolamine, N-ethylethylenediamine, n-hexylamine, N-methyl-3,3′-iminobis (propylamine), N-methylethanolamine, N- Methyldiethanolamine, sec-butylamine, t-butylamine, allylamine, isopropylamine, ethylamine, ethylenediamine, di-2-ethylhexylamine, di-n-octylamine, diallylamine, diisobutylamine, diisopropanolamine, diisopropylamine, diethylamine, diethylhydroxyl Amine, diethylenetriamine, cyclohexylamine, dicyclohexylamine, dibutylamine, dimethylamine, tetraethylenepentamine, tetramethyl-1,3-dia Minopropane, tetramethylethylenediamine, tri-n-octylamine, triallylamine, triisopropanolamine, triethylamine, triethylenetetramine, tributylamine, trimethylamine, propylamine, hexamethylenediamine, pentaethylenehexamine, pentamethyldiethylenetriamine, monoisopropanolamine, Examples include monobutylamine and monomethylamine. There is no problem even if a mixture of two or more of these compounds is used.

The degree of decomposition of the urethane resin is arbitrary as long as amino groups and hydroxyl groups remain in the decomposition product. The decomposition product can be decomposed to any molecular weight, but it is preferable to reduce the molecular weight with a decomposition agent less than the amount necessary to decompose all the urethane bonds in the urethane resin before decomposition. It is preferable to make a state in which some urethane bonds remain. If the urethane bond remains, the properties of the original urethane resin can be imparted to the regenerated resin. Moreover, as a preferable average molecular weight, although it changes with uses, what is necessary is just to decompose | disassemble so that the average molecular weight of polystyrene conversion may be 500-5000.
In order to obtain such a decomposed state, although depending on the structure of the original urethane resin, the decomposition agent is 1 part by weight to 100 parts by weight, preferably 2 to 25 parts by weight with respect to 100 parts by weight of the urethane resin as the decomposition target. What is necessary is just to mix | blend and decompose | disassemble in a part.
The decomposition temperature is preferably 150 to 300 ° C, and preferably 200 to 280 ° C. If the temperature is lower than this, the decomposition rate is slow, which is not economically preferable. If the temperature is higher than this, thermal decomposition increases, and a stable quality decomposition product cannot be obtained.

  These decomposition agents and urethane resin are put into a decomposition apparatus to obtain a urethane resin decomposition product. Any known cracking apparatus can be used as the cracking apparatus, but it is particularly desirable to use an extruder that can simultaneously perform heating, mixing, and compression. If the decomposition is carried out in a batch system such as a kettle, the thermal conductivity of urethane is poor, so there is a large difference in the start time of urethane decomposition. For this reason, since the part decomposed | disassembled earlier has a low molecular weight, and the thing decomposed | disassembled later becomes high molecular weight, it will become a decomposition product with a wide molecular weight.

As an example of the reaction between the amine decomposing agent and the urethane resin, the decomposition reaction with the urethane bond and urea bond in the urethane resin using diethanolamine is shown in the following chemical formula 1. In the following chemical formulas (1) to (4), R, R1, R2, and R3 all represent any divalent group, and may be the same or different. An SO ₂ group, a saturated or unsaturated alkylene group, an aromatic group and the like are represented. These contain what is contained in the urethane resin which is to-be-processed resin.

  When the urethane resin is decomposed in this way, the components contained in the decomposed product of the urethane resin are the polyol that is the raw material of the urethane resin to be decomposed, amines in which the end of the isocyanate of the raw material is replaced with an amino group, and the isocyanate end. It becomes amines or polyols added with the agent, and oligomers thereof. Specific examples of the components are listed below.

  First, as amines contained in the urethane resin decomposition product, raw material 4-4 ′ diphenylmethane diisocyanate and its polymer-derived diaminodiphenylmethane (MDA) and its polymer, toluylene diisocyanate (TDI) -derived toluylenediamine (TDI) ( TDA) and the like are listed as main amines. In addition, NDI (1,5-naphthalene diisocyanate), TODI (tolidine diisocyanate), HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), XDI (xylylene diisocyanate), H6XDA (hydrogenated MDI), LDI ( Lysine diisocyanate), triphenylmethane triisocyanate, tris (isocyanate phenyl) thiophosphate, TMXDI (tetramethylxylene diisocyanate), lysine ester triisocyanate, etc. The thing which the terminal of the prepolymer converted into the amino group is also mentioned.

  Examples of the polyols in the decomposed urethane resin include polyols generally used as a urethane resin raw material, and are roughly classified into polyether polyols, polyester polyols, and polyether ester polyols. Ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, hexanetriol, triethanolamine, pentaerythritol ethylenediamine, tolylenediamine, diphenylmethanediamine, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose Specific examples include those obtained by addition reaction of propylene oxide, ethylene oxide or the like with saccharides.

(Method of producing resin composition from urethane resin decomposition product)
As a method of obtaining a resin composition from a urethane resin decomposition product, (2-1) a method of reacting a urethane resin decomposition product with formaldehyde, (2-2) a method of reacting a urethane resin decomposition product with a compound having a methylol group There is. Hereinafter, these methods will be sequentially described.

(2-1) Method of reacting with a formaldehyde-based compound To obtain a resin composition by reacting a urethane resin decomposition product with formaldehyde, the urethane resin decomposition product and formaldehyde are mixed and then heated to obtain a urethane resin. It can be carried out by causing a polycondensation reaction between the decomposition product and the formaldehyde compound.

As the formaldehyde, formaldehyde or a compound that generates formaldehyde by heating can be used. Examples of the compound that generates formaldehyde by heating include hexamethylenetetramine (hexamine) and 1,3-dioxane (formal).
As a mixing ratio of the urethane resin decomposition product and the formaldehyde compound, it is preferable to use 0.05 to 1 part by weight of the formaldehyde compound with respect to 1 part by weight of the urethane resin decomposition product. When the blending ratio is outside this range, the resin to be regenerated is not sufficiently cured and a practical regenerated resin cannot be obtained.

  Urethane resin degradation product is a complex mixture, and its reaction with formaldehyde is not accurately determined, but the chemical formula shown below is between the main component (compound having amino group and hydroxyl group) in the urethane resin decomposition product and formaldehyde compound. It is considered that the reaction shown in 2 has occurred.

  That is, the amino group in the urethane resin decomposition product and formaldehyde are subjected to an addition reaction to form a methylol group (reaction A), and a condensation reaction between these methylol groups (reaction B) and an amino group (reaction C) hydroxyl group The resin is formed by a condensation reaction with (Reaction D). In some cases, the reaction product obtained in this reaction A becomes a solid at room temperature, but when heated, it melts, and during the heating, a condensation reaction of reaction B, reaction C, and reaction D occurs to form a resin composition. This reaction hardly proceeds in the presence of moisture, and it is preferable to cure by heating. As heating conditions, it is highly efficient and it is economically preferable to set it as the range of 150-200 degreeC.

(2-2) Method of reacting with a compound having a methylol group In order to obtain a resin composition by reacting a urethane resin decomposition product and a compound having a methylol group, the urethane resin decomposition product and a compound having a methylol group are mixed. Then, by heating, the polycondensation reaction can be performed between the amino group and hydroxyl group of the urethane resin decomposition product and a compound having a methylol group.

  As the compound having a methylol group in this embodiment, a substance represented by the following chemical formula 3 can be used.

  The compound having a methylol group shown in Chemical Formula 3 is not particularly limited as long as it has two or more methylol groups in the molecule. For example, a compound having a phenolic hydroxyl group (for example, phenol, Cresol, xylinol, p-alkylphenol, p-phenylphenol, chlorophenol, bisphenol, phenolsulfonic acid, resorcin, etc.) or those having an amino group (for example, urea, melamine, guanamine, aniline, For example, sulfoamides and amines used for the above-mentioned decomposed urethane resin) may be reacted with formaldehyde. There is no problem even if these are partially condensed. As these compounds, those obtained by using phenol, urea, or melamine as a raw material and reacting with formaldehyde are preferable because they are compatible with the urethane resin decomposition product.

  The reaction between the compound having a methylol group and the urethane resin decomposition product is estimated as shown in the following chemical formula 4. That is, a resin is formed by a condensation reaction between a methylol group and an amino group (reaction E) and a condensation reaction with a hydroxyl group (reaction F).

  The mixing ratio of the urethane resin decomposition product and the compound having a methylol group is not particularly limited, but when the number of hydroxyl groups / amino groups and the number of methylol groups in the urethane resin decomposition product are the same or in an excessive methylol group mixture Resin with high strength can be made. The preferred mixing ratio varies depending on the hydroxyl group / amino group content in the urethane resin decomposition product, but it is generally preferable to add a compound having 20 to 500 parts by weight of a methylol group to 100 parts by weight of the urethane resin decomposition product. More preferably, it is 50-300 weight part. If the amount of the compound having a methylol group is less than this, it may not be cured, and if it is too much, the amount of the urethane resin decomposed product contained in the recycled resin decreases, making it difficult to utilize the characteristics of the urethane resin decomposed product in the recycled resin. . After mixing these, it is heated and condensed by dehydration and deformaldehyde to form a resin.

  In any of the methods described in (2-1) and (2-2) above, alcohols, polyols, organic acids, amines, emulsifiers (anionic surfactants, Cationic surfactants, amphoteric surfactants, nonionic surfactants, etc.), compatibilizers, solvents and the like may be added. In order to proceed with the condensation reaction, ammonium sulfate, ammonium chloride or the like may be added.

Furthermore, it is preferable to add an alkaline substance to the resin composition of the present embodiment. By making the resin composition alkaline, the mechanical properties of the recycled resin can be improved. As the alkaline substance, a compound such as a salt of a weak acid strong base such as sodium acetate or sodium carbonate can be used.
The addition amount of the alkaline substance is preferably in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the urethane resin decomposition product. When the addition amount of the alkaline substance is below the above range, the effect of adding the alkaline substance cannot be expected. On the other hand, exceeding the above range is not preferable because these substances remain in the cured resin to lower the physical properties.

  Like the general thermosetting resin composition, the resin composition can be injected into a mold and heat-cured to produce a recycled resin molded body, or a pigment can be added to form a thermosetting paint. You can also. It can also be used as a thermosetting adhesive.

  Since the recycled resin using the resin composition contains a long-chain polyol or a urethane bond in the cured resin, it has more flexibility than a resin obtained by condensation of methylol groups such as urea, melamine, and phenol. In addition, by introducing a urethane bond into the cured resin, by using a decomposing agent that decomposes the urethane bond, the molecular weight can be reduced again and reused.

[Second Embodiment]
(Manufacturing method of the wooden molding)
A wood molding can be produced by adhering a wood material using the above resin composition. In this production method, the resin composition is mixed with a crushed piece of a wood material, and is heated and cured with a mold to form a molded body, or a plurality of thin plates of wood material are laminated, and the resin composition It can be carried out by using a product as an adhesive and heating it to form plywood.
Examples of the woody material include wood, straw, rice husk, sugar cane, plant-derived fiber, and the like. In the case of using crushed pieces of wood material, the size of the preferred wood material is not particularly limited, but generally, the crushed pieces having a maximum diameter of about 0.5 to 100 mm are used, and these are laminated and used. Is preferred. 99-70 parts by weight of these wood materials and 1-30 parts by weight of the resin composition are mixed in a mixer while spraying the resin composition, and press-molded. If the resin content is higher than this, the molded body may be ruptured by water vapor generated by the reaction, and if it is less than this, the adhesion is insufficient and it is difficult to make the molded body. Although the molding conditions and the like vary depending on the conditions, the molding time is generally 10 to 100 kg / cm ² , 100 to 200 ° C., and 10 minutes or less. The molding temperature is preferably 150 ° C. or higher. Since the reaction of the present invention is a dehydration reaction, the reaction is accelerated by removing water from the reaction system.

Since the recycled resin obtained as described above contains a long-chain polyol or urethane bond in the cured resin, it is more flexible than a resin obtained by condensation of methylol groups such as urea, melamine, and phenol, As a result, the wood molded body using this can be made into a molded body which is excellent in flexibility and does not impair the characteristics of the wood material.

  Hereinafter, it demonstrates in detail based on an Example.

[Example 1]
(Decomposition of urethane resin)
A urethane resin (mainly composed of a polyol having a hydroxyl value of 450 mgKOH / g and polymeric MDI: hereinafter urethane resin A) was synthesized as a heat insulating material for refrigerators. The synthesized urethane resin A: monoethanolamine = 4: 1 was introduced into a single-screw extruder at 250 ° C. to obtain a decomposed urethane resin liquid at room temperature.

(Manufacture of recycled resin)
When 80 parts by weight of this urethane resin decomposition product and 40 parts by weight of 33% formaldehyde solution were placed in a disposable cup and mixed, after a while, an ocherous solid was formed. (Hereinafter, solidified product) When placed in a mold and molded at 150 ° C., this solid substance was once melted and then cured to produce a resin plate using a urethane resin decomposition product. Further, after placing this solid at room temperature for one day, it was similarly molded with a mold at 150 ° C., and it was cured after melting to produce a resin plate.

[Example 2]
40 parts by weight of the urethane resin decomposition product decomposed in Example 1 was mixed with 50 parts by weight of a 65% aqueous solution of a melamine derivative having a methylol group at the terminal by reacting melamine with formaldehyde. After mixing, it was a brown liquid (hereinafter referred to as resin mixture A). When this was heated on a hot plate at 150 ° C., it was cured in 2 minutes. In addition, after this resin mixture A was left at room temperature for one day and similarly heated on a hot plate at 150 ° C., it was found that it cured in 2 minutes and could be stored for 1 day or longer.

[Example 3]
40 parts by weight of the urethane resin decomposition product decomposed in Example 1 and 50 parts by weight of a 65% aqueous solution of a urea derivative having a methylol group at the terminal by reacting formaldehyde with urea were mixed at room temperature. After mixing, it was a cream-colored liquid (hereinafter referred to as resin mixture B). When this was heated on a hot plate at 150 ° C., it was cured in 2 minutes. In addition, after this resin mixture B was left at room temperature for one day and similarly heated on a hot plate at 150 ° C., it was found that it cured in 2 minutes and could be stored for one day or more.

[Comparative Example 1]
50 parts by weight of the urethane resin decomposition product decomposed in Example 1 and 50 parts by weight of polymeric MDI (manufactured by Mitsui Takeda Chemical Co., Ltd., M-200) were mixed at room temperature. After a while after mixing, heat was generated and both reactions started, and after 2 minutes, they were cured. Since this cured product was not melted even when heated on a hot plate at 150 ° C., a resin plate could not be produced by a method such as molding. The storage time with this resin composition was 2 minutes or less.

[Comparative Example 2]
50 parts by weight of the urethane resin decomposition product decomposed in Example 1 and 50 parts by weight of a bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin, Epicoat 828) were mixed at room temperature. Immediately after mixing, it was placed in a mold and heated at 100 ° C. for about 2 hours to cure and obtain a resin plate. However, when this mixture was placed at room temperature for 6 hours, the viscosity increased so much that it became difficult to use, and it was cured after one day. Since this cured product was not melted even when heated on a hot plate at 150 ° C., a resin plate could not be produced by a method such as molding. From the above, it was found that the storage period with this resin composition was 6 hours.

  From the above, since the resin composition of the present invention is mixed with a urethane resin decomposition product and a regenerating agent (formaldehyde or a compound having a methylol group), the crosslinking reaction hardly proceeds unless it is heated. It was confirmed that the shelf life was excellent.

[Example 4] (Manufacture of wood board)
80 parts by weight of the decomposed urethane resin decomposed in Example 1, 100 parts by weight of a 65% aqueous solution of a melamine derivative having a methylol group at the end by reacting formaldehyde with melamine, and 20 parts by weight of a 15% aqueous solution of ammonium sulfate were mixed. Mixed with sawdust. When this mixture was put into a mold and molded at 150 ° C. for 10 minutes, a wood board using a urethane resin decomposition product as a part of the adhesive was obtained.

[Example 5]
80 parts by weight of the decomposed urethane resin decomposed in Example 1, 100 parts by weight of a 65% aqueous solution of a urea derivative having a methylol group at the end by reacting formaldehyde with urea, and 20 parts by weight of a 15% aqueous solution of ammonium sulfate were mixed. Mixed with sawdust. When this mixture was put into a mold and molded at 150 ° C. for 10 minutes, a wood board using a urethane resin decomposition product as a part of the adhesive was obtained.

[Example 6]
(Decomposition of urethane)
A urethane resin (mainly composed of a polyol having a hydroxyl value of 450 mgKOH / g and polymeric MDI: hereinafter urethane resin A) was synthesized as a heat insulating material for refrigerators. Synthesized urethane resin: diethanolamine = 10: 1 was mixed into a single screw extruder at 280 ° C. to obtain a urethane resin decomposition product. This urethane decomposition product had a softening point of 70 ° C. and was solid at room temperature.

(Manufacture of wood board)
60 parts by weight of this urethane resin decomposition product and 40 parts by weight of hexamethylenetetramine were mixed well in a pulverizer, 10 parts by weight of this mixture and 90 parts by weight of sawdust were mixed and placed in a mold and molded at 150 ° C. for 10 minutes. However, a wood board using a urethane resin decomposition product as a part of the adhesive was obtained.
The elastic modulus of this board was measured by the method of JIS A 5908.
The result was 2.01 GPa.

[Comparative Example 3]
A wood board was produced in the same manner as in Example 4 except that diphenylmethane diisocyanate was used as the agent to be reacted with the urethane resin decomposition product. The elastic modulus of this wood board was measured by the same method as in Example 6.
The result was 3.42 GPa, which was harder and less flexible than Example 6.

Claims (4)

A step of chemically decomposing a urethane resin to obtain a urethane resin decomposition product having an OH group or an NH ₂ group at the end , and a step of reacting formaldehyde or a compound that generates formaldehyde by heating with the urethane resin decomposition product The manufacturing method of the resin composition characterized by the above-mentioned. Characterized in that it comprises a step of chemically decomposing a urethane resin to obtain a urethane resin decomposition product having an OH group or an NH ₂ group at the end , and a step of reacting a compound having a methylol group with the urethane resin decomposition product. A method for producing a resin composition. 3. The compound according to claim 2, wherein the compound having a methylol group is a compound obtained by addition reaction of at least one of phenol, urea, and melamine with formaldehyde, or a compound obtained by partial condensation reaction thereof. A method for producing a resin composition. A step of chemically decomposing a urethane resin to obtain a urethane resin decomposition product having a terminal OH group or NH ₂ group , at least one of formaldehyde, a compound generating formaldehyde by heating and a compound having a methylol group, and the urethane resin A method for producing a wooden molded article , comprising: a step of reacting a decomposition product to obtain a resin composition; and a step of mixing and adhering the resin composition and a wooden material .