Curable resin composition, fiber-reinforced molding material, molded part and polyol and process for their preparation

Abstract

[Problem] A curable resin composition using an amino acid as at least one raw material, a fiber-reinforced molding material, and a molded article are provided. Furthermore, a polyol compound using an amino acid as at least one raw material and a method for producing the same are provided. [Solution] A curable resin composition according to the present invention comprises a urethane (meth)acrylate resin (A), a (meth)acrylate monomer (B), and a polymerization initiator (C), and is characterized in that the urethane (meth)acrylate resin (A) is a reaction product of a polyisocyanate (a1), a polyol having an amino acid backbone (a2), and a hydroxyalkyl (meth)acrylate (a3), and characterized in that the polyol having an amino acid backbone (a2) is a reaction product of an amino acid and a cyclic carbonate compound. [Selected Figure] none

Description

TECHNICAL FIELDThe present invention relates to a curable resin composition, a fiber-reinforced molding material, a molding and a polyol, and a method for producing the same.BACKGROUND ARTFiber-reinforced molding materials containing a curable resin composition including, for example, a urethane (meth)acrylate resin and reinforcing fibers such as glass fibers and carbon fibers are conventionally known (see, for example, Patent Document 1). Such fiber-reinforced molding materials are attracting attention because of their properties such as excellent heat resistance, mechanical strength and durability under light weight, and their uses are being extended to various applications including automobile components, structural members such as home components, sports article components and office equipment casings, and the like.Recently, in view of the constitution of a sustainable society, for example, reduction of the amount of the petroleum-based raw materials used and conversion to chemical raw materials produced by non-petroleum-based processes are being demanded. Therefore, there is a demand for using amino acids for which a manufacturing process by fermentation has been established and which can be supplied widely as a raw material for the curable resin composition.For example, Non-Patent Document 1 discloses a technique for obtaining an ω-hydroxycarboxylic acid obtained from L-phenylalanine and ethylene carbonate. However, there is a disadvantage in that the use of the ω-hydroxycarboxylic acid as a raw material for the above curable resin composition including, for example, a urethane (meth)acrylate resin requires a further step of modifying a carboxyl group in the ω-hydroxycarboxylic acid. Moreover, for example, due to the large amounts of reagents used, the yield of only 17%, and the large amounts of waste produced, the process disclosed in Non-Patent Document 1 has the disadvantage of being unsuitable for industrial use.DOCUMENTS RELATED TO THE PRIOR ARTPATENT DOCUMENTWO 2021 / 131564 A1NON-PATENT DOCUMENTNon-Patent Document 1: Nobuhiro Kihara et al., "Polycondensation of ω-Hydroxy Carboxylic Acid Derived from L-Phenylalanine and Ethylene Carbonate", Journal of Polymer Science Part A: Polymer Chemistry, Vol. 34, Edition 9, pp. 1819-1822 (1996)SUMMARY OF THE INVENTIONPROBLEM TO BE SOLVED OF THE INVENTIONA problem to be solved by the present invention is to provide a curable resin composition using an amino acid as at least one raw material, a fiber-reinforced molding material, and a molded article. Another problem to be solved by the present invention is to provide a polyol compound using an amino acid as at least one raw material and a production method thereof.MEANS FOR ACHIEVING THE OBJECTA curable resin composition according to the present invention comprises a urethane (meth)acrylate resin (A), a (meth)acrylate monomer (B) and a polymerization initiator (C), and is characterized in that the urethane (meth)acrylate resin (A) is a reaction product of a polyisocyanate (a1), a polyol having an amino acid backbone (a2), and a hydroxyalkyl (meth)acrylate (a3), and in that the polyol having an amino acid backbone (a2) is a reaction product of an amino acid and a cyclic carbonate compound.A fiber-reinforced molding material according to the present invention is characterized by comprising the above curable resin composition and reinforcing fibers.A molded article according to the present invention is characterized in that the above fiber-reinforced molded material is used.A polyol according to the present invention is characterized by having an amino acid backbone and being a reaction product of an amino acid and a cyclic carbonate compound.A method for producing a polyol according to the present invention is characterized in that an amino acid and a cyclic carbonate compound are mixed and heated at a temperature of 100° C. to 150° C. without solvent until an acid value of 1 mgKOH / g or less is reached to obtain a polyol having an amino acid backbone.ADVANTAGES OF THE INVENTIONAccording to the present invention, a curable resin composition using an amino acid as at least one raw material, a fiber-reinforced molding material, and a molded part can be provided. Moreover, according to the present invention, a polyol using an amino acid as at least one raw material and a production method thereof can be provided.EMBODIMENT OF THE INVENTIONA curable resin composition according to an embodiment of the present invention is a curable resin composition comprising a urethane (meth)acrylate resin (A), a (meth)acrylate monomer (B) and a polymerization initiator (C), and is characterized in that the urethane (meth)acrylate resin (A) is a reaction product of a polyisocyanate (a1), a polyol having an amino acid backbone (a2), and a hydroxyalkyl (meth)acrylate (a3), and in that the polyol having an amino acid backbone (a2) is a reaction product of an amino acid and a cyclic carbonate compound. The curable resin composition may be a thermosetting resin composition or a photocurable resin composition; however, since, for example, a molded part having a freely adjustable thickness can be obtained and a molded part having a higher degree of curing can be obtained, a thermosetting resin composition is preferable.The urethane (meth)acrylate resin (A) is a reaction product of a polyisocyanate (a1), the polyol with an amino acid backbone (a2), and a hydroxyalkyl (meth)acrylate (a3).The polyisocyanate (a1) preferably contains a polyisocyanate having a cyclic backbone in order to further improve the heat resistance of a molded article. These polyisocyanates (a1) may be used alone, or two or more thereof may be used in combination.Examples of the polyisocyanate (a1) include aromatic polyisocyanates such as 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, carbodiimide-modified 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, nurate-modified diphenylmethane diisocyanate, biuret-modified diphenylmethane diisocyanate, urethaneimine-modified diphenylmethane diisocyanate, polyol-modified diphenylmethane diisocyanate modified with a polyol having a number average molecular weight of 1,000 or less such as diethylene glycol or dipropylene glycol, tolylene diisocyanate (TDI), toluidine diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate and tetramethylxylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate and norbornene diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate, nuerate-modified hexamethylene diisocyanate, biuret-modified hexamethylene diisocyanate, hexamethylene diisocyanate adducts and dimer acid diisocyanate. Among these, from the viewpoint of further improved heat resistance of a molded article, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, carbodiimide-modified 4,4'-diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate, norbornene diisocyanate, xylylene diisocyanate and isophorone diisocyanate (IPDI) are preferred. It is to be noted that these polyisocyanates (a1) may be used alone or two or more thereof may be used in combination.The polyol having an amino acid backbone (a2) is a reaction product of an amino acid and a cyclic carbonate compound.An amino acid is an organic compound having both a carboxyl group and an amino group and further having a side chain. Examples of amino acids include a variety of amino acids having, in the side chain, a carboxyl group, an amino group, an alkyl group, a hydroxyl group, an amide group, an imino group, an aromatic backbone, or the like. The amino acid may be any of α-amino acid, β-amino acid, γ-amino acid and δ-amino acid, and α-amino acids may be either L-body or D-body. Amino acids are not limited to naturally occurring amino acids, and may be amino acid derivatives in which a variety of groups are introduced into the side chains of naturally occurring amino acids.The amino acid is preferably one or more types of amino acids selected from the group consisting of: an amino acid having a hydrophobic side chain; an amino acid having a carboxyl group in a side chain, the carboxyl group in the side chain having a protecting group; an amino acid having an amino group in a side chain, the amino group in the side chain having a protecting group; an amino acid having an alcoholic hydroxyl group in a side chain, a hydroxyl group of the alcoholic hydroxyl group having a protecting group; and an amino acid having a phenolic hydroxyl group in a side chain, a hydroxyl group of the phenolic hydroxyl group having a protecting group. From curable resin compositions using these amino acids as a raw material, molded articles having excellent strength can be obtained as compared with those obtained from curable resin compositions using amino acids other than the above as a raw material.As for the amino acid having a hydrophobic side chain, examples of α-amino acids include glycine, alanine, valine, norvaline, leucine, isoleucine, proline, phenylalanine, methionine and tryptophan. Examples of β-amino acids include β-alanine. Examples of γ-amino acids include γ-aminobutyric acid (4-aminobutyric acid).Examples of the amino acid having a carboxyl group in a side chain, the carboxyl group in the side chain having a protecting group, include aspartic acid and glutamic acid each having a carboxyl group bearing a protecting group in a side chain. The protecting group is not particularly limited, and examples thereof may include an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 11 carbon atoms. Specifically, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a phenyl group, a benzyl group, a phenacyl group, and a cyclohexyl group are mentioned, and among these, an alkyl group having 1 to 4 carbon atoms is more preferred as the protecting group. Examples of alkyl groups having 1 to 4 carbon atoms include, in particular, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group and a tert-butyl group. Moreover, an aspartic acid having an α-carboxyl group carrying the protecting group may be used as the β-amino acid, and a glutamic acid having a similar protecting group may be used as the γ-amino acid.Examples of amino acids having an amino group in a side chain, the amino group in the side chain having a protecting group, include lysine and ornithine each having an amino group bearing a protecting group in a side chain. The protecting group is not particularly limited, and examples thereof include an acyl group and a urethane-type protecting group. Examples of the acyl group include an acetyl group, a propionyl group and a butanyl group. Examples of the urethane type protecting group include a 9-fluorenylmethyloxycarbonyl group, a benzyloxycarbonyl group, and a t-butoxycarbonyl group. Among them, as the protecting group, the acyl group such as an acetyl group, a propionyl group or a butanyl group is more preferred.Examples of the amino acid having an alcoholic hydroxy group in a side chain, wherein a hydroxy group of the alcoholic hydroxy group has a protecting group, include serine, threonine, and hydroxypropylrolin each having an alcoholic hydroxy group, wherein the alcoholic hydroxy group has a hydroxy group bearing a protecting group. The protecting group is not particularly limited, and examples thereof include an acyl group, an alkoxycarbonyl group, an alkyl group and an aralkyl group. Examples of the acyl group include acyl groups having 1 to 8 carbon atoms such as an acetyl group, an isobutyroyl group, a pivaloyl group, a benzoyl group, and a 4-tolyl group. Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group and a sec-butoxycarbonyl group. Examples of the alkyl group include alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a t-butyl group. Examples of the aralkyl group include aralkyl groups having 7 to 21 carbon atoms such as a benzyl group and a 4-monomethoxybenzyl group. In addition, there are mentioned protecting groups such as a methoxymethyl group, a methylthiomethyl group, a benzyloxymethyl group, a methoxyethoxymethyl group and a tetrahydropyranyl group.Examples of the amino acid having a phenolic hydroxy group in a side chain, wherein a hydroxy group of the phenolic hydroxy group has a protecting group, include tyrosine and DOPA each having a phenolic hydroxy group, wherein the phenolic hydroxy group has a hydroxy group bearing a protecting group. The protecting group is not particularly limited, and examples thereof include an alkyl group and an aralkyl group. For example, alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group and a t-butyl group are mentioned. Examples of the aralkyl group include aralkyl groups having 7 to 21 carbon atoms such as a benzyl group and a 4-monomethoxybenzyl group.Among the above amino acids, the amino acids having a hydrophobic side chain are particularly preferred. As the α-amino acid having a hydrophobic side chain, for example, alanine, valine, norvaline, leucine, isoleucine, proline, phenylalanine, methionine or tryptophan are preferred. Beta-alanine, i.e., the β-amino acid having a hydrophobic side chain, and γ-aminobutyric acid, i.e., the γ-amino acid having a hydrophobic side chain, are preferred. Moreover, in cases where a molded article requires high strength, the hydrophobic side chain is particularly preferably a short chain, and examples thereof include alanine, valine, norvaline, leucine, isoleucine, phenylalanine, β-alanine and γ-aminobutyric acid. Alpha-amino acids having an alkyl group or an aromatic backbone in a side chain are more preferred, and examples thereof are alanine, valine, norvaline, leucine, isoleucine and phenylalanine.As the cyclic carbonate compound, those having only one cyclic carbonate group in a molecule are preferable, and one or more types of carbonate selected from a group consisting of ethylene carbonate, propylene carbonate, and glycerin carbonate are preferable. Since a curable resin composition containing the polyol compound (a2) obtained by reacting such a cyclic carbonate compound with an amino acid can contain more amino acid backbone than those containing a polyol (a2) obtained using a cyclic carbonate compound other than the above, a molded article having a better strength can be obtained.The polyol having an amino acid backbone (a2) is a reaction product of an amino acid and a cyclic carbonate compound, and can be obtained by, for example, heat mixing. An organic solvent may be used during the heating mixing; however, in this case, the heating mixing is preferably performed without solvent because a step of removing the solvent is required after the heating mixing.More specifically, an amino acid and a cyclic carbonate compound are supplied to a reaction vessel at normal temperature. A catalyst may be added as needed. The temperature is gradually raised to a temperature of 100° C. to 150° C. Since carbonate gas is formed during heating, it is also possible, for example, to initially maintain the temperature at a temperature of 120° C. and, after the gas evolution has been reduced, to raise the temperature to a predetermined reaction temperature. The heating is maintained until the contents become clear and after the contents have become clear the acid number of the contents is measured. When the acid value is 1 mgKOH / g or less, heating is stopped, cooling to a temperature of 60° C. is performed, and the contents are taken out.A reaction is effected by heating an amino acid and a cyclic carbonate compound to form a polyol having an amino acid backbone (a2). The reaction mechanism is unclear, but it seems that a reaction as described below takes place.As an example, a case where L-valine and ethylene carbonate are heated will be explained.(1) Ethylene carbonate is added to the α-amino group of L-valine to produce N-(2-hydroxyethoxy)carbonyl-L-valine.(2) The product obtained above is dissolved in the system and, at the same time, the α-carboxyl group of the remaining L-valine is reacted with the remaining ethylene carbonate to cause an esterification reaction to produce carbon dioxide, resulting in the production of N-(2-hydroxyethoxy)carbonyl-L-valine (2-hydroxyethyl ester), that is, a polyol having an amino acid backbone (a2).A mixing ratio (molar ratio) of a cyclic carbonate compound to an amino acid is preferably 1.9 to 2.4, more preferably 2.0 to 2.3. When the molar ratio is less than 1.9, it takes a long time for an acid value of 1 mgKOH / g or less to be reached, and on the other hand, when the molar ratio exceeds 2.3, unreacted cyclic carbonate compounds remain, which may result in decreased strength properties of a molded article. In order to counteract the unreacted cyclic carbonate compounds remaining in a removed content, the unreacted cyclic carbonate compounds can also be removed by a decompression treatment after checking the acid number.As the catalyst, those used as catalysts for epoxy resins can be used. Specifically, there may be mentioned phosphines such as triphenylphosphine, quaternary phosphonium salts such as tetrabutylphosphonium bromide, quaternary ammonium salts such as tetrabutylammonium bromide, carbonates such as potassium carbonate, tertiary amines such as triethylamine and diazabicycloundecene, tin compounds such as dibutyltin oxide, dibutyltin diacetate, zinc compounds such as zinc octylate, titanium compounds such as tetrabutyl titanate, and germanium compounds such as germanium oxide. Among these, quaternary phosphonium capable of promoting a reaction in small amounts is preferred.During the heating, it is preferable to let an inert gas such as nitrogen gas, argon gas or xenon gas flow into the reaction vessel to counteract discoloration of the contents.Examples of the hydroxyalkyl (meth)acrylate (a3) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxy-n-butyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-n-butyl (meth)acrylate and 3-hydroxy-n-butyl (meth)acrylate. Among them, 2-hydroxyethyl (meth)acrylate is preferred from the viewpoint of the balance of strength properties. These hydroxyalkyl (meth)acrylates (a3) may be used alone, or two or more of them may be used in combination.In addition, as a raw material for the urethane (meth)acrylate resin (A), polyols other than the polyol having an amino acid backbone (a2) may be used in combination, if necessary. As other polyols, for example, polyester polyol, acrylic polyol, polyether polyol, polycarbonate polyol and polyalkylene polyol can be used.Regarding the isocyanate groups (NCO) in the isocyanate compound and the hydroxyl groups (OH) in the polyol having an amino acid backbone (a2) and the hydroxyalkyl (meth)acrylate (a3), wherein the isocyanate compound and the polyol are raw materials of the urethane (meth)acrylate resin (A), a molar ratio of NCO to OH (NCO / OH) is preferably 0.7 to 1.3, more preferably 0.8 to 1.1, and even more preferably 0.8 to 1.0, from the viewpoint of a balance in heat resistance and strength properties.Desirably, a biomass-derived compound is used as the (meth)acrylate monomer (B), but since the types of such biomass-derived compounds are limited, the compounds used as the (meth)acrylate monomer (B) are not particularly limited. Depending on the physical properties required for applications, compounds are selected accordingly. As examples, monofunctional (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, Tetrahydrofurfuryl(meth)acrylat furfuryl (meth)acrylate, benzyl (meth)acrylate, methylbenzyl (meth)acrylate, phenoxyethyl (meth)acrylate and methylphenoxyethyl (meth)acrylate are mentioned; di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, 1,3-propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, Tricyclodecandimethanoldi(meth)acrylat di(meth)acrylate of ethylene oxide adducts of isosorbide and Furandimethanoldi(meth)acrylat ; and glycerol (meth)acrylate compounds such as glycerol (meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, diglycerol tri(meth)acrylate and diglycerol tetra(meth)acrylate; and ethylene oxide-modified materials and propylene oxide-modified materials thereof. These may be used alone, or two or more thereof may be used in combination.Among them, from the viewpoint of volatility during use and handling hazardous substances as well as from the viewpoint of mechanical strength and heat resistance of molded articles, (meth)acrylates having a molecular weight of 150 to 400 are preferable, and isobornyl (meth)acrylate, Tetrahydrofurfuryl(meth)acrylat furfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, methylphenoxyethyl (meth)acrylate, benzyl (meth)acrylate, methylbenzyl (meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, and Furandimethanoldi(meth)acrylat are more preferable.Moreover, from the viewpoint of further improving the balance of the operability of resin compositions and molding materials, the quality of molded articles, and the productivity, the content of the (meth)acrylate monomer (B) in the sum of the urethane (meth)acrylate resin (A) and the (meth)acrylate monomer (B) (hereinafter abbreviated as "content (B)") is preferably 5 mass % to 50 mass %, more preferably 10 mass % to 40 mass %.The polymerization initiator (C) is not particularly limited, but an organic peroxide is preferred; for example, diacyl peroxide compounds, peroxyester compounds, hydroperoxide compounds, ketone peroxide compounds, alkyl perester compounds, percarbonate compounds and peroxyketals may be mentioned, and these may be suitably selected according to molding conditions. Moreover, these polymerization initiators (C) may be used alone, or two or more thereof may be used in combination.In addition, in order to shorten the molding time, it is preferable to use, among them, a polymerization initiator whose temperature is 60° C. or more and 110° C. or less to achieve a half-life of 10 hours. When a polymerization initiator whose temperature for attaining a half-life of 10 hours is 70° C. or more and 105° C. or less is used, the fiber-reinforced molding material has a long life at normal temperature and can be cured by heating in a short time (within five minutes), and therefore, such a polymerization initiator is preferable: By using such a polymerization initiator in the fiber-reinforced molding material according to the present invention, both excellent curability and moldability can be attained. Examples of such polymerization initiators include 1,6-bis(t-butylperoxycarbonyloxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-amylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, t-butylperoxyethyl acetate, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, t-amylperoxyisopropyl carbonate, t-amylperoxy-2-ethylhexyl carbonate, t-hexylperoxyisopropyl carbonate, di-tert-butylperoxyhexahydroterephthalate, t-amylperoxytrimethylhexanoate, t-amylperoxyisononanoate, t-hexylperoxy-2-ethylhexanoate and n-butyl-4,4-di(t-butylperoxy)valerate. According to the molding conditions, an optimum organic peroxide is selected and used.Depending on the types of resins to be used and the shapes of the molded articles to be produced, a photopolymerization initiator may be used in combination as the polymerization initiator (C). A photopolymerization initiator is a polymerization initiator that generates radicals by light irradiation, and known photopolymerization initiators can be used without particular limitation. As the photopolymerization initiator, alkylphenone-based radical initiators, benzophenone-based radical initiators, benzoin-based radical initiators, and acylphosphine oxide-based radical initiators are preferred because of their ready availability. A photopolymerization initiator alone without using an organic peroxide can be used and selected accordingly.An amount of the polymerization initiator (C) to be added is preferably in a range of 0.5 parts by mass to 5 parts by mass based on the sum of the urethane (meth)acrylate resin (A) and the (meth)acrylate monomer (B) being 100 parts by mass, from the viewpoint that both the curing properties and the storage stability are excellent.A curable resin composition of the present embodiment may contain components other than the above urethane (meth)acrylate resin (A), the above (meth)acrylate monomer (B) and the above polymerization initiator (C); for example, it may contain thermosetting resins, thermoplastic resins, polymerization inhibitors, curing accelerators, fillers, low profile additives, mold release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antimicrobial agents, ultraviolet stabilizers and reinforcing materials.Examples of thermosetting resins include vinyl ester resins, unsaturated polyester resins, phenol resins, melamine resins, furan resins and bismaleimide resins. These thermosetting resins may be used alone, or two or more thereof may be used in combination.Examples of thermoplastic resins include polyamide resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polycarbonate resins, polyurethane resins, polypropylene resins, polyethylene resins, polystyrene resins, acrylic resins, polybutadiene resins, polyisoprene resins, and resins obtained by modifying these resins, for example, by copolymerization. Among these, polyamide resins and polyurethane resins are preferred from the viewpoint of a high brittleness improving effect. Moreover, these thermoplastic resins may be used alone, or two or more thereof may be used in combination. Further, the thermoplastic resins may be used by adding them in the form of particles or by melting and mixing them. When the thermoplastic resins are used in the form of particles, the particle diameter is preferably 30 μm or less, more preferably 5 μm to 20 μm, from the viewpoint of dispersibility into fibers.Examples of polymerization inhibitors include hydroquinone, trimethylhydroquinone, p-t-butylcatechol, t-butylhydroquinone, toluhydroquinone, p-benzoquinone, naphthoquinone, hydroquinone monomethyl ether, phenothiazine, copper naphthenate, and copper chloride. These polymerization inhibitors may be used alone, or two or more thereof may be used in combination.Examples of the curing accelerators include metal soaps such as cobalt naphthenate, cobalt octoate, vanadyl octoate, copper naphthenate and barium naphthenate; and metal chelate compounds such as vanadyl acetyl acetate, cobalt acetyl acetate and iron acetylacetonate. In addition, examples of the amines include N,N-dimethylamino-p-benzaldehyde, N,N-dimethylaniline, N,N-diethylaniline, N,N-dimethyl-p-toluidine, N-ethyl-m-toluidine, triethanolamine, m-toluidine, diethylenetriamine, pyridine, phenylmorpholine, piperidine and diethanolaniline. These curing accelerators may be used alone, or two or more thereof may be used in combination.As the fillers, inorganic compounds and organic compounds can be used to adjust physical properties such as strength, modulus of elasticity, impact resistance and fatigue strength of molded articles.Examples of the inorganic compounds include calcium carbonate, magnesium carbonate, barium sulfate, mica, talc, kaolin, clay, celite, asbestos, barite, silica, silica sand, dolomite limestone, gypsum, aluminum fine powder, hollow balloons, alumina, glass powder, aluminum hydroxide, white limestone, zirconia, antimony trioxide, titanium oxide, molybdenum dioxide, and iron powder.Examples of the organic compounds include powders of natural polysaccharides such as cellulose and chitin, and powders of synthetic resins: As the powders of synthetic resins, powders of organic materials consisting of, for example, hard resins, soft rubbers, elastomers or polymers (copolymers), and particles having a multi-layered structure such as a core-shell structure may be used. Concrete examples include acrylic particles, polyamide particles and particles made of, for example, butadiene rubber and / or acrylic rubber, urethane rubber and silicone rubber, polyimide resin powder, fluororesin powder and phenol resin powder. These fillers may be used alone, or two or more thereof may be used in combination.Examples of the mold release agents include zinc stearate, calcium stearate, paraffin wax, polyethylene wax and carnauba wax. Paraffin wax, polyethylene wax and carnauba wax are preferably mentioned. These mold releasing agents may be used alone, or two or more thereof may be used in combination.Examples of the thickeners include metal oxides and metal hydroxides such as magnesium oxide, magnesium hydroxide, calcium oxide and calcium hydroxide, and acrylic resin-based fine particles. These may be appropriately selected according to the operability of the fiber-reinforced molding material of the present embodiment. These thickeners may be used alone, or two or more thereof may be used in combination.The fiber-reinforced molding material of the embodiment of the present invention is characterized by containing the above-mentioned curable resin composition and reinforced fibers (D). The fiber-reinforced molding material is preferably a prepreg.Examples of the reinforcing fibers (D) include carbon fibers, glass fibers, basalt fibers, silicon carbide fibers, aluminum oxide fibers, boron fibers, metal fibers, and organic fibers such as aramid fibers, vinylon fibers, tetroron fibers, and cellulose fibers. From the viewpoint that molded articles having higher strength and higher elasticity can be obtained, carbon fibers or glass fibers and basalt fibers are preferable, and carbon fibers are more preferable. These reinforcing fibers (D) may be used alone, or two or more thereof may be used in combination.As the carbon fibers, various types such as polyacrylonitrile-, pitch- and viscose-based carbon fibers can be used. Among these, polyacrylonitrile-based carbon fibers are preferred because high-strength carbon fibers are easily available.The shape of the reinforcing fibers (D) is not particularly limited. Examples thereof include reinforcing fiber strands in which reinforcing fiber filaments are bundled, unidirectional carbon fiber materials in which reinforcing fiber strands are arranged in parallel in one direction, woven fabrics or short cut reinforcing fibers, and nonwoven fabrics and paper formed of reinforcing fibers cut into short lengths. When unidirectional carbon fiber materials are used as the reinforcing fibers, high mechanical properties can be obtained by stacking and molding the unidirectional carbon fiber materials, which is preferable.In the case of using reinforcing fibers cut into short lengths, it is preferable to use carbon fibers cut into 2.5 mm to 50 mm pieces from the viewpoint of further improving the in-mold flowability during molding and the appearance of the molded articles.Examples of fabrics include plain fabrics, twill fabrics, satin fabrics, and sewn sheets such as non-crimping fabrics in which sheets of parallel unidirectional fiber bundles or sheets stacked at different stacking angles are sewn together to avoid separation.The basis weight of the reinforcing fibers (weight per square meter of fibers) is not particularly limited, but is preferably 10 g / m 2 to 650 g / m 2. When the basis weight is 10 g / m 2 or more, the variation in the fiber width becomes small, resulting in good mechanical properties, which is preferable. When the basis weight is 650 g / m 2 or less, the resin impregnation becomes good, which is preferable. The basis weight is more preferably 50 g / m 2 to 500 g / m 2 and particularly preferably 50 g / m 2 to 300 g / m 2.The content of the reinforcing fibers (D) in the fiber-reinforced molding material of the present embodiment is preferably in the range of 20 mass % to 85 mass %, and more preferably in the range of 40 mass % to 80 mass %, from the viewpoint of further improving the mechanical strength of the resultant molded articles.The fiber-reinforced molding material of the present embodiment is obtained, for example, by impregnating the reinforcing fibers (D) with a resin solution, the resin solution being obtained by mixing the polyisocyanate (a1), the polyol with an amino acid backbone (a2), the hydroxyalkyl (meth)acrylate (a3), the (meth)acrylate monomer (B), and the polymerization initiator (C) with a known mixer such as a planetary mixer or a kneader.Specifically, first, using a known mixer such as a planetary mixer or a kneader, the polyisocyanate (a1), the polyol are mixed with an amino acid backbone (a2), the hydroxyalkyl (meth)acrylate (a3), the (meth)acrylate monomer (B), and the polymerization initiator (C) to prepare a composition. The fiber-reinforced molding material of the present embodiment can be produced by Step 1 in which, on the upper surface of a polyethylene terephthalate film which has been subjected to a releasing treatment (hereinafter abbreviated as "PET releasing film"), the composition immediately after mixing and impregnating the reinforcing fibers (D) therewith, then, another PET releasing film is put over the upper surface thereof to nip the reinforcing fibers (D) therebetween, and then rolled with a rolling mill to obtain a sheet, and Step 2 in which the obtained sheet is allowed to stand at a normal temperature to 50°C to cause the isocyanate groups of the polyisocyanate (a1) to react with the hydroxyl groups of the polyol with an amino acid backbone (a2) and the hydroxyalkyl (meth)acrylate (a3) (urethanization reaction), In order to produce the urethane (meth)acrylate resin (A). As long as the impregnation effect on the reinforcing fibers (D) is not impaired in step 1, a resin solution in which the polyisocyanate (a1), the polyol having an amino acid backbone (a2), and the hydroxyalkyl (meth)acrylate (a3) could already be partially reacted beforehand may be used.The fiber-reinforced molding material of the present embodiment preferably has a thickness of 0.02 mm to 1.0 mm. The thickness of 0.02 mm or more facilitates handling in stacking and is preferable, and at the thickness of 1 mm or less, good impregnation with the resin is achieved and is preferable. Moreover, the thickness of 0.05 mm to 0.5 mm is more preferred.As a method for obtaining a molded part from the above-obtained fiber-reinforced molding material, for example, the following method is used: the PET releasing films are separated from the fiber-reinforced molding material, 8 to 30 sheets of the fiber-reinforced molding material are stacked, then the stacked sheets are placed in a mold preheated to 110° C. to 160° C., the fiber-reinforced molding material is clamped with a compression molding machine to mold it, a molding pressure of 0.1 MPa to 10 MPa is maintained to cure the fiber-reinforced molding material, and thereafter a molded part is obtained by extraction. In this case, preference is given to a manufacturing method in which compression molding is performed with heating in a mold having a shear edge at a molding temperature of 130° C. to 160° C. for a specified time of 1 minute to 3 minutes per millimeter of the thickness of the molded part while maintaining a molding pressure of 1 MPa to 8 MPa.Since molded articles obtained from the fiber-reinforced molded material of the present embodiment have excellent flexural strength, interlaminar shear strength and the like, they can be used, for example, in automobile components, rail vehicle components, aircraft and spacecraft components, ship components, residential components, sports article components, light vehicle components, civil engineering and office equipment enclosures.EMBODIMENTSThe present invention will be described in more detail below by way of concrete examples.(Synthesis Example 1: Preparation of a polyol having amino acid backbone (a2-1))In a 0.5 I flask equipped with a thermometer, a nitrogen inlet tube and a stirrer, 117 g of L-valine, 185 g of ethylene carbonate and 0.3 g of tetrabutylphosphonium bromide were placed, the temperature was raised by heating from room temperature to 80° C., and after checking the dissolution thereof, stirring was started. With the prevention of foaming, the temperature was raised to 120° C. and then held at this temperature for 2 hours. Thereafter, the temperature was raised to 130°C and then held at that temperature for 24 hours. After checking that the content of the flask was clear and contained no solids, the acid value was measured to be 0 mgKOH / g. Thereafter, it was cooled to a temperature of 60° C., and the content was taken out. The obtained compound was liquid at normal temperature and had a hydroxyl value of 561 mgKOH / g. The yield in percent based on the theoretical yield was 86%. As compared with the production method described in the above Non-Patent Document 1, it is seen from the yield in percent that the amount of waste is small.(Synthesis Example 2: Preparation of a polyol having amino acid backbone (a2-2))In the above-described 0.5-I flask, 165 g of L-phenylalanine, 185 g of ethylene carbonate and 0.35 g of tetrabutylphosphonium bromide were placed, the temperature was raised by heating from room temperature to 80°C, and stirring was started after checking the dissolution thereof. With the prevention of foaming, the temperature was raised to 120° C. and then held at this temperature for 2 hours. Thereafter, the temperature was raised to 130°C and then held at that temperature for 18 hours. After checking that the content of the flask was clear and contained no solids, the acid value was measured to be 0.5 mgKOH / g. Thereafter, it was cooled to a temperature of 60° C., and the content was taken out. The obtained compound was liquid at normal temperature and had a hydroxyl value of 426 mgKOH / g. The yield in percent based on the theoretical yield was 91%.(Synthesis Example 3: Preparation of a polyol having amino acid backbone (a2-3))In the above-described 0.5 I flask, 131 g of L-leucine, 185 g of ethylene carbonate and 0.32 g of tetrabutylphosphonium bromide were placed, the temperature was raised by heating from room temperature to 80°C, and stirring was started after checking the dissolution thereof. With the prevention of foaming, the temperature was raised to 120° C. and then held at this temperature for 2 hours. Thereafter, the temperature was raised to 130°C and then held at that temperature for 21 hours. After checking that the content of the flask was clear and contained no solids, the acid value was measured to be 0.8 mgKOH / g. Thereafter, it was cooled to a temperature of 60° C., and the content was taken out. The compound obtained was liquid at normal temperature and had a hydroxyl value of 510 mgKOH / g. The yield in percent based on the theoretical yield was 85%.(Synthesis Example 4: Preparation of a polyol having amino acid backbone (a2-4))In the above-described 0.5-liter flask, 103 g of 4-aminobutyric acid, 185 g of ethylene carbonate and 0.29 g of tetrabutylphosphonium bromide were placed, the temperature was raised by heating from room temperature to 80°C, and stirring was started after checking the dissolution thereof. With the prevention of foaming, the temperature was raised to 120° C. and then held at this temperature for 2 hours. Thereafter, the temperature was raised to 130°C and then held at that temperature for 6 hours. After checking that the content of the flask was clear and contained no solids, the acid value was measured to be 0 mgKOH / g. Thereafter, it was cooled to a temperature of 60° C., and the content was taken out. The compound obtained was liquid at ordinary temperature and had a hydroxyl value of 561 mgKOH / g. The yield in percent based on the theoretical yield was 90%.(Example 1: Preparation and evaluation of resin composition and prepreg (1))Twenty parts by mass of polyol having an amino acid backbone (a2-1) (a reaction product of L-valine and ethylene carbonate, hydroxyl equivalent: 100) obtained in Synthesis Example 1, 26 parts by mass of 2-hydroxyethyl (meth)acrylate (a3-1), 15 parts by mass of a (meth)acrylate monomer (isobornyl methacrylate) (B-1), 0.04 parts by mass of parabenzoquinone, and 1 part by mass of a polymerization initiator (C-1) ("Trigonox 122-C80" manufactured by Kayaku Akzo Corporation, organic peroxide) were mixed, and then 50 parts by mass of a polyisocyanate (a1-1) (2,4'-diphenylmethane diisocyanate) were mixed therewith to prepare a resin composition (X-1).The obtained resin composition (X-1) was applied to a surface of a PET release film, then carbon fibers (D-1) ("TRK979PQRW"manufactured by Mitsubishi Rayon Co., Ltd.) were laid on the resin composition (X-1) to impregnate it so that the carbon fiber content was 60 mass %. Over the upper surface thereof, another PET release film was laid to sandwich the carbon fibers (D-1) therebetween, then heated at a temperature of 45° C. for 24 hours, followed by standing and storing at room temperature for 3 days to obtain a prepreg (1) as a fiber-reinforced molding material. The obtained prepreg (1) had a thickness of 0.25 mm.[Production of Molded Article]The obtained prepreg (1) was cut into pieces each having a width of 298 mm and a length of 218 mm, then separated from the PET releasing sheets, and 8 sheets were stacked so that the fibers were oriented in the same direction to obtain a laminate. The obtained laminate was placed in the center of a flat plate shape to which a release agent had been once applied, and compression molding was performed with a compression molding machine under the conditions of a pressure of 4 MPa, an upper mold of 140° C., a lower mold of 135° C., and a molding time of 3 minutes. After opening the mold, the molded article was removed from the mold using a suction pad made of rubber having a diameter of 100 mm and blowing air into the mold, and after cleaning, the molded article was clamped between stainless steel plates each having a weight of 5 kg and cooled. Thereby, a molded article (1) in the form of a flat plate having a width of 300 mm, a length of 220 mm and a thickness of 2 mm was obtained. As a release agent, Daifree GW-251 (manufactured by Daikin) diluted 10-fold with distilled water was used.[Evaluation of Flexural Strength]From the obtained molded article (1), a test piece having a size of 15 mm width and 100 mm length was cut out, and the bending strength was measured according to JIS K7074, and evaluated according to the following criteria: A: 1,300 MPa or more B: 1,200 MPa or more and less than 1,300 MPa C: less than 1,200 MPa[Evaluation of Interlaminar Shear Strength]From the obtained molded article (1), a test piece having a size of 10 mm width and 22 mm length was cut out, and the interlaminar shear strength for this test piece was measured according to JIS K7078 and evaluated according to the following criteria: A: 80 MPa or more B: 70 MPa or more and less than 80 MPa C: less than 70 MPa[Evaluation of Heat Resistance]From the obtained molded article (1), a test piece having a size of 10 mm width and 55 mm length was cut out, and the dynamic viscoelasticity was measured using "RSA-G2" manufactured by TA Instruments, with a measurement frequency of 1 Hz and a temperature increase rate of 5° C. / min, in a three-point bending mode and a temperature range of 10° C. to 200° C. At a storage elastic modulus E', an intersection of an approximately straight line in a glass region and a tangent in a transition region was set to a glass transition temperature (Tg), and the heat resistance was evaluated according to the following criteria: A: 100°C or higher; B: 90°C or higher and lower than 100°C C: lower than 90°C(Example 2: Preparation and evaluation of resin composition and prepreg (2))In the present example, except for using 26 parts by mass of the polyol having an amino acid backbone (a2-2) obtained in Synthesis Example 2 instead of 20 parts by mass of the polyol having an amino acid backbone (a2-1), a resin composition (X-2) was prepared in the same manner as described in Example 1. Then, except for using the obtained resin composition (X-2), a prepreg (2) and a molded article (2) were prepared in the same manner as described in Example 1, and the evaluation described above was performed.(Example 3: Preparation and evaluation of resin composition and prepreg (3))In the present example, except for using 22 parts by mass of the polyol having an amino acid backbone (a2-3) obtained in Synthesis Example 3 instead of 20 parts by mass of the polyol having an amino acid backbone (a2-1), a resin composition (X-3) was prepared in the same manner as described in Example 1. Then, except for using the obtained resin composition (X-3), a prepreg (3) and a molded article (3) were prepared in the same manner as described in Example 1, and the evaluation described above was carried out.(Example 4: Preparation and evaluation of resin composition and prepreg (4))In the present example, except for using 20 parts by mass of the polyol having an amino acid backbone (a2-4) obtained in Synthesis Example 4 instead of 20 parts by mass of the polyol having an amino acid backbone (a2-1), a resin composition (X-4) was prepared in the same manner as described in Example 1. Then, except for using the obtained resin composition (X-4), a prepreg (4) and a molded article (4) were prepared in the same manner as described in Example 1, and the evaluation described above was performed.(Comparative Example 1: Production and Evaluation of Resin Composition (R1) and Prepreg (RX1))In the present comparative example, instead of the polyols having an amino acid backbone (a2-1) to (a2-4), a polyol having no amino acid backbone (ar-1) ("BA-3U" manufactured by Nippon Nyukazai Co., Ltd., ethylene oxide adduct of bisphenol A, hydroxyl equivalent: 178) is used. With a solution obtained by previously mixing 26 parts by mass of polyol having no amino acid backbone (ar-1) with 20 parts by mass of 2-hydroxyethyl (meth)acrylate (a3-1) at a temperature of 80° C. and cooling the mixture to normal temperature, 15 parts by mass of ethylenically unsaturated monomer (B-1), 0.03 parts by mass of parabenzoquinone, and 1.0 parts by mass of polymerization initiator (C-1) were mixed, and then 38 parts by mass of polyisocyanate (a1-1) was mixed therewith to prepare a resin composition (RX-1). Then, except for using the obtained resin composition (RX-1), a prepreg (R1) and a molded product (R1) were prepared in the same manner as described in Example 1, and the evaluation described above was performed.The results of the above evaluation of the obtained molded articles (1) to (4) and (R1) are shown in Table 1. [Table 1] Table 1] [Table 1] Table 1]Prepreg(1)(2)(3)(4)(R1)Resin compositionX-1X-2X-3X-4RX-1Amino acid usedL-valineL-phenylalanineL-leucine4-Aminobutyric acidPolyisocyanate (a1)a1-1a1-1a1-1a1-1a1-1Polyol with amino acid backbone (a2)a2-1a2-2a2-3a2-4Polyol without amino acid backbone (ar)ar-1Hydroxyalkyl (meth)acrylate (a3)a3-1a3-1a3-1a3-1a3-1(Meth)acrylic monomer (B)B-1B-1B-1B-1B-1Polymerization initiator (C)C-1C-1C-1C-1C-1JudgmentFlexural strength [MPa]A. AA. AA. AA. AC. C14801410146013101170Interlaminar shear strength [MPa]A. AA. AA. AB. BB. B9783897672Heat resistance [° C.]A. AA. AA. AA. AA. A113116110106115All the molded articles (1) to (4) of Examples 1 to 4 are molded articles produced using a prepreg containing a curable resin composition in which an amino acid was used as at least one raw material and reinforcing fibers. As shown in Table 1, the molded articles (1) to (4) of Examples 1 to 4 have not only excellent heat resistance but also excellent bending strength and interlaminar shear strength compared with those of the molded article (RX-1) of Comparative Example 1. Moreover, the molded articles (1) to (3) of Examples 1 to 3 have excellent interlaminar shear strength as compared with the molded article (4) of Example 4.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2021 / 131564 A1

[0005] Cited Non-Patent LiteratureNobuhiro Kihara et al., "Polycondensation of ω-Hydroxy Carboxylic Acid Derived from L-Phenylalanine and Ethylene Carbonate", Journal of Polymer Science Part A: Polymer Chemistry, Vol. 34, Edition 9, pp. 1819-1822 (1996

[0006]

Claims

A curable resin composition comprising a urethane (meth)acrylate resin (A), a (meth)acrylate monomer (B) and a polymerization initiator (C), wherein the urethane (meth)acrylate resin (A) is a reaction product of a polyisocyanate (a1), a polyol having an amino acid backbone (a2), and a hydroxyalkyl (meth)acrylate (a3), and wherein the polyol having an amino acid backbone (a2) is a reaction product of an amino acid and a cyclic carbonate compound.The curable resin composition according to claim 1, wherein the amino acid is one or more types of amino acids selected from a group consisting of: an amino acid having a hydrophobic side chain; an amino acid having a carboxyl group in a side chain, the carboxyl group in the side chain having a protecting group; an amino acid having an amino group in a side chain, the amino group in the side chain having a protecting group; an amino acid having an alcoholic hydroxyl group in a side chain, a hydroxyl group of the alcoholic hydroxyl group having a protecting group; and an amino acid having a phenolic hydroxyl group in a side chain, a hydroxyl group of the phenolic hydroxyl group having a protecting group.The curable resin composition according to claim 2, wherein the amino acid is the amino acid having a hydrophobic side chain, and wherein the amino acid having a hydrophobic side chain is an α-amino acid having an alkyl group or an aromatic backbone in a side chain.The curable resin composition according to claim 1 or 2, wherein the cyclic carbonate compound is one or more types of carbonate compounds selected from a group consisting of an ethylene carbonate, a propylene carbonate, and a glycerol carbonate.A fiber-reinforced molding material comprising the curable resin composition according to claim 1 or 2 and reinforcing fibers (D).A molded article using the fiber-reinforced molding material according to claim 5.A polyol having an amino acid backbone which is a reaction product of an amino acid and a cyclic carbonate compound.A method for producing a polyol, wherein an amino acid and a cyclic carbonate compound are mixed and heated without solvent at a temperature of 100°C to 150°C until an acid value of 1 mgKOH / g or less is reached, to obtain a polyol having an amino acid backbone.