Radical curable resin composition, molding material, and molded article using the same

Abstract

To provide: a radically curable resin composition capable of obtaining a molded product having excellent handleability including film peelability and tackiness and excellent moldability of a molding material and excellent physical properties such as bending strength while suppressing a change in viscosity with time; a molding material; and a molded product using the same.SOLUTION: There is provided a radically curable resin composition which comprises a vinyl ester resin (A), an unsaturated monomer (B), a polycarbodiimide compound having an isocyanate group (C), a polyisocyanate compound (D) other than the polycarbodiimide compound (C) and a polymerization initiator as essential raw materials, wherein the isocyanate group content ratio (NCO%) of the polycarbodiimide compound (C) is in the range of 1% or more and 10% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a radically curable resin composition, a molding material, and a molded article using the same. [Background technology]

[0002] Fiber-reinforced resin composites, which use carbon fiber as a reinforcing fiber and reinforce thermosetting resins such as epoxy resins and unsaturated polyester resins, have attracted attention for their lightweight yet excellent heat resistance and mechanical strength. Their use is expanding in a variety of structural applications, including automobile and aircraft housings and various components. For these fiber-reinforced resin composites, the autoclave process, in which a prepreg material is heated and cured in a pressurized autoclave, is a well-known molding method for epoxy resins. For unsaturated polyester resins, intermediate materials such as sheet molding compound (SMC) and bulk molding compound (BMC) are used, followed by curing and molding using techniques such as press molding and injection molding. In particular, in recent years, there has been active development of materials with excellent productivity.

[0003] As such a molding material, for example, a carbon fiber reinforced sheet molding material containing unsaturated polyester, vinyl monomer, thermoplastic polymer, polyisocyanate, filler, conductive carbon black, and wide carbon fiber bundles as essential components is known (Patent Document 1). Although molded articles with excellent appearance can be obtained from such a molding material, the use of highly volatile styrene monomer results in a strong odor, which creates problems in the working environment during molding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 195607 Brochure [Patent Document 2] International Publication No. 2018 / 070076 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] To address the above-mentioned problems, a fiber-reinforced molding material has been proposed that contains, as essential raw materials, a vinyl ester resin, an unsaturated monomer having a flash point of 100°C or higher, a polyisocyanate (thickener), a polymerization initiator, and carbon fiber (Patent Document 2).

[0006] However, the fiber-reinforced molding material described in Patent Document 2 has a problem in that it has poor storage stability because its viscosity changes relatively greatly over time.

[0007] The problem to be solved by the present invention is to provide a radical-curable resin composition, a molding material, and a molded article using the same, which are excellent in handleability and moldability, including film peelability and tackiness, of the molding material while suppressing changes in viscosity over time, and which can give a molded article that is excellent in various physical properties such as bending strength. [Means for solving the problem]

[0008] The present invention relates to a radical-curable resin composition containing, as essential raw materials, a vinyl ester resin (A), an unsaturated monomer (B), a polycarbodiimide compound (C) having an isocyanate group, a polyisocyanate compound (D) other than the polycarbodiimide compound (C), and a polymerization initiator (E), wherein the polycarbodiimide compound (C) has an isocyanate group content (NCO%) in the range of 1% or more and 10% or less.

[0009] The present invention also relates to a molding material containing the radically curable resin composition.

[0010] The present invention also relates to a molded product using the molding material. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a radical-curable resin composition, a molding material, and a molded article using the same, which are excellent in handleability and moldability, including film peelability and tackiness, of the molding material while suppressing changes in viscosity over time, and which can give a molded article that is excellent in various physical properties such as bending strength. DETAILED DESCRIPTION OF THE INVENTION

[0012] The radically curable resin composition of this embodiment comprises, as essential ingredients, a vinyl ester resin (A), an unsaturated monomer (B), a polycarbodiimide compound (C) having an isocyanate group, a polyisocyanate compound (D) other than the polycarbodiimide compound (C), and a polymerization initiator (E). The polycarbodiimide compound (C) has an isocyanate group content (NCO%) ranging from 1% to 10%. The radically curable resin composition of this embodiment suppresses changes in viscosity over time, while providing excellent molding material handling and formability, including film peelability and tackiness, and producing molded articles with excellent physical properties such as flexural strength. While the reason why the radically curable resin composition of this embodiment exhibits these effects is unclear, the following is believed to be the case.

[0013] A composition thickened by reacting a vinyl ester resin with a polyisocyanate compound is hydrolyzed by acids, moisture in the air, and the like, resulting in a decrease in viscosity. It is believed that the radical-curable resin composition of this embodiment can suppress hydrolysis of the composition and suppress changes in viscosity by the carbodiimide groups contained in a specific amount of the polycarbodiimide compound (C) capturing acids such as carboxylic acids, and the isocyanate groups contained in the polycarbodiimide compound (C) capturing moisture. Furthermore, the presence of carbodiimide groups and isocyanate groups in the same molecule can prevent the carbodiimide groups from reacting with the isocyanate groups, thereby effectively capturing acids by the carbodiimide groups and capturing moisture by the isocyanate groups.

[0014] The radically curable resin composition of this embodiment contains the vinyl ester resin (A). The vinyl ester resin (A) is not particularly limited, and known vinyl ester resins can be used. The vinyl ester resin (A) can be obtained, for example, by reacting an epoxy resin (a1) with a (meth)acrylic acid (a2). To achieve a better balance between handling properties, such as film peelability and tackiness during molding, and fluidity, it is preferable to react the epoxy resin (a1) with the carboxyl group (COOH) of the (meth)acrylic acid (a2) in a molar ratio (COOH / EP) of 0.6 to 1.1. From the same viewpoint, the epoxy equivalent of the epoxy resin (a1) is preferably 180 to 500, more preferably 180 to 370, and even more preferably 180 to 250.

[0015] In this specification, "(meth)acrylic acid" refers to either or both of acrylic acid and methacrylic acid, and "(meth)acrylate" refers to either or both of acrylate and methacrylate.

[0016] In this specification, the epoxy equivalent is a value obtained based on a method in accordance with JIS K-7236:2001.

[0017] Examples of the epoxy resin (a1) include bisphenol type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol fluorene type epoxy resins, and biscresol fluorene type epoxy resins; novolac type epoxy resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins; oxodoridone-modified epoxy resins; brominated epoxy resins of these resins; and glycidyl ethers of polyhydric alcohols such as dipropylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether of alkylene oxide adduct of bisphenol A, and diglycidyl ether of hydrogenated bisphenol A. Examples of epoxy resins include alicyclic epoxy resins such as bisphenol A, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, and 1-epoxyethyl-3,4-epoxycyclohexane; glycidyl esters such as phthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, diglycidyl-p-oxybenzoic acid, and dimer acid glycidyl ester; glycidyl amines such as tetraglycidyldiaminodiphenylmethane, tetraglycidyl-m-xylenediamine, triglycidyl-p-aminophenol, and N,N-diglycidylaniline; and heterocyclic epoxy resins such as 1,3-diglycidyl-5,5-dimethylhydantoin and triglycidyl isocyanurate. Among these, bifunctional aromatic epoxy resins are preferred because of their superior strength of molded products, ease of handling of molding materials, and fluidity of molding materials during molding. Bisphenol A epoxy resins and bisphenol F epoxy resins are more preferred. These epoxy resins can be used alone or in combination of two or more.

[0018] The epoxy resin (a1) may be used after being made to have a high molecular weight with a dibasic acid such as bisphenol A in order to adjust the epoxy equivalent.

[0019] The reaction between the epoxy resin and (meth)acrylic acid is preferably carried out using an esterification catalyst at a temperature ranging from 60° C. to 140° C. A polymerization inhibitor or the like may also be used.

[0020] The radical curable resin composition of this embodiment contains the unsaturated monomer (B). The unsaturated monomer (B) is not particularly limited, and known unsaturated monomers can be used. Examples of the unsaturated monomer (B) include alkyl styrenes such as styrene, p-methylstyrene, p-ethylstyrene, p-propylstyrene, p-isopropylstyrene, p-butylstyrene, p-tert-butylstyrene, o-methylstyrene, o-ethylstyrene, o-propylstyrene, o-isopropylstyrene, m-methylstyrene, m-ethylstyrene, m-propylstyrene, m-isopropylstyrene, m-butylstyrene, mesitylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, and 4-butenylstyrene, and p-chlorostyrene. styrene-based compounds such as halogenated styrenes such as m-chlorostyrene, o-chlorostyrene, p-bromostyrene, m-bromostyrene, o-bromostyrene, p-fluorostyrene, m-fluorostyrene, o-fluorostyrene, and o-methyl-p-fluorostyrene; alkoxystyrenes such as p-methoxystyrene, o-methoxystyrene, and m-methoxystyrene; hydroxystyrenes, cyanostyrenes, and vinyl benzoates; divinylbenzene-based compounds such as 1,3-divinylbenzene, 1,4-divinylbenzene, 1,3-diisopropenylbenzene, and 1,4-diisopropenylbenzene;Methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, isotridecyl (meth)acrylate, n-stearyl (meth)acrylate, tetrahydrofurfuryl methacrylate, benzyl (meth)acrylate, methylbenzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, methylphenoxyethyl (meth)acrylate, morpholine (meth)acrylate, phenylphenoxyethyl acrylate, phenylbenzyl (meth)acrylate, phenyl methacrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl oxy Examples of suitable (meth)acrylate compounds include monofunctional (meth)acrylate compounds such as diethyl (meth)acrylate, dicyclopentanyl methacrylate, polyethylene glycol (meth)acrylate alkyl ether, and polypropylene glycol (meth)acrylate alkyl ether; hydroxyl group-containing (meth)acrylate compounds such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; and di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol di(meth)acrylate, and 1,4-cyclohexanedimethanol di(meth)acrylate. These compounds can be used alone or in combination of two or more.

[0021] The unsaturated monomer (B) preferably has a flash point of 100°C or higher, since this can suppress odor during molding and enables high-temperature, short-time molding. Among these, unsaturated monomers having an aromatic group are more preferred, since they can produce molding materials with higher strength, and benzyl methacrylate and phenoxyethyl methacrylate are even more preferred.

[0022] In this specification, the flash point is a flash point measured by the Cleveland Open Method specified in JIS K2265-4:2007.

[0023] The mass ratio ((A) / (B)) of the vinyl ester resin (A) to the unsaturated monomer (B) is in the range of 40 / 60 or more and 85 / 15 or less, but a range of 50 / 50 or more and 70 / 30 or less is preferred because this further improves the balance between handleability (film peelability and tackiness) and curability.

[0024] The radically curable resin composition of this embodiment contains the polycarbodiimide compound (C). The polycarbodiimide compound (C) is not particularly limited as long as it is a polycarbodiimide compound having an isocyanate group, and known compounds can be used. An example of the polycarbodiimide compound (C) is a compound obtained by subjecting the polyisocyanate compound (D) to a decarboxylation condensation reaction to form a carbodiimide. An example of a commercially available product of the polycarbodiimide compound (C) is Carbodilite V-05 (manufactured by Nisshinbo Chemical Inc.).

[0025] The isocyanate group content (NCO%) of the polycarbodiimide compound (C) is 1% or more, preferably 5% or more, from the viewpoint of suppressing changes in viscosity over time, and is 10% or less, from the viewpoint of suppressing the reaction between the carbodiimide groups and the isocyanate groups in the polycarbodiimide compound (C) to suppress the formation of uretonimine and more effectively capturing acid by the carbodiimide groups and water by the isocyanate groups. For these reasons, the isocyanate group content of the polycarbodiimide compound (C) is in the range of 1% or more to 10% or less, preferably in the range of 5% or more to 10% or less. The isocyanate group content (NCO%) of the polycarbodiimide compound (C) can be measured by potentiometric titration in accordance with JIS K1603-1:2007.

[0026] The carbodiimide equivalent of the polycarbodiimide compound (C) is preferably 800 or less, more preferably 500 or less, and even more preferably 300 or less, from the viewpoint of suppressing changes in viscosity over time, and is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more, from the viewpoint of suppressing crystallization of the polycarbodiimide compound. For these reasons, the carbodiimide equivalent of the polycarbodiimide compound (C) is preferably in the range of 100 or more to 800 or less, more preferably 150 or more to 500 or less, and even more preferably 200 or more to 300 or less. The carbodiimide group content of the polycarbodiimide compound (C) is 13 It can be measured by C-NMR.

[0027] The amount of the polycarbodiimide compound (C) added is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the total of the vinyl ester resin (A) and the unsaturated monomer (B), from the viewpoint of suppressing a decrease in viscosity due to hydrolysis, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoint of suppressing a reaction between the hydroxyl groups of the vinyl ester resin (A) and the isocyanate, thereby suppressing an increase in viscosity. For these reasons, the amount of the polycarbodiimide compound (C) added is preferably in the range of 1 part by mass or more to 10 parts by mass or less, more preferably 2 parts by mass or more to 8 parts by mass or less, relative to 100 parts by mass of the total of the vinyl ester resin (A) and the unsaturated monomer (B).

[0028] The radically curable resin composition of this embodiment contains the polyisocyanate compound (D). The polyisocyanate compound (D) is not particularly limited as long as it is a polyisocyanate compound other than the polycarbodiimide compound (C), and known compounds can be used. Examples of the polyisocyanate compound (D) include diphenylmethane diisocyanate (4,4'-isomer, 2,4'-isomer, or 2,2'-isomer, or a mixture thereof), diphenylmethane diisocyanate modified compounds such as nurate modified compounds, biuret modified compounds, uretonimine modified compounds, and polyol modified compounds modified with a polyol having a number average molecular weight of 1,000 or less, such as diethylene glycol or dipropylene glycol, tolylene diisocyanate, tolidine diisocyanate, polymethylene polyphenyl polyisocyanate, and xylylene diisocyanate. Examples of suitable polyisocyanates include one or more selected from the group consisting of aromatic polyisocyanates such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and norbornene diisocyanate; alicyclic polyisocyanates such as hexamethylene diisocyanate, nurate-modified hexamethylene diisocyanate, biuret-modified hexamethylene diisocyanate, and adducts thereof, and aliphatic polyisocyanates such as dimer acid diisocyanate. Among these, aromatic polyisocyanates are preferred because they provide molding materials with excellent handleability (film peelability and tackiness).

[0029] The molar ratio (NCO / OH) of the total of the isocyanate groups (NCO) of the polycarbodiimide compound (C) and the polyisocyanate (D) in the radical curable resin composition to the hydroxyl groups (OH) of the vinyl ester resin (A) is preferably 0.50 or more, more preferably 0.55 or more, and even more preferably 0.75 or more, from the viewpoint of film peelability and tackiness when made into a sheet material; and is preferably 0.95 or less, more preferably 0.90 or less, and even more preferably 0.85 or less, from the viewpoint of flexibility when made into a sheet material. For these reasons, the molar ratio (NCO / OH) of the total number of isocyanate groups (NCO) of the polycarbodiimide compound (C) and the polyisocyanate (D) in the radical-curable resin composition to the hydroxyl groups (OH) of the vinyl ester resin (A) is preferably in the range of 0.50 or more and 0.95 or less, more preferably in the range of 0.55 or more and 0.90 or less, and even more preferably in the range of 0.75 or more and 0.85 or less.

[0030] The polymerization initiator (E) is not particularly limited, but is preferably an organic peroxide, such as a diacyl peroxide compound, a peroxyester compound, a hydroperoxide compound, a ketone peroxide compound, an alkyl perester compound, a percarbonate compound, a peroxyketal, etc., which can be appropriately selected depending on the molding conditions. These polymerization initiators (E) can be used alone or in combination of two or more.

[0031] Among these, it is preferable to use a polymerization initiator having a temperature of 70°C or higher and 110°C or lower to obtain a 10-hour half-life in order to shorten the molding time. A temperature range of 70°C or higher and 110°C or lower is preferable because the molding material has a long shelf life at room temperature and can be cured in a short time by heating, resulting in a better balance between curability and moldability. 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-butylperoxydiethyl acetate, t-butylperoxyisopropyl carbonate, t-amylperoxyisopropyl carbonate, t-hexylperoxyisopropyl carbonate, di-tert-butylperoxyhexahydroterephthalate, and t-amylperoxytrimethylhexanoate.

[0032] The content of the polymerization initiator (E) is preferably in the range of 0.3 to 3 parts by mass per 100 parts by mass of the total amount of the vinyl ester resin (A) and the unsaturated monomer (B), since this provides excellent curing characteristics and storage stability.

[0033] The radical curable resin composition may use, as a raw material, materials other than the vinyl ester resin (A), the unsaturated monomer (B), the polycarbodiimide compound (C), the polyisocyanate compound (D), and the polymerization initiator (E). For example, the radical curable resin composition may contain a thermosetting resin other than the vinyl ester resin (A), a thermoplastic resin, a polymerization inhibitor, a curing accelerator, a filler, a low shrinkage agent, a mold release agent, a thickener, a viscosity reducer, a pigment, an antioxidant, a plasticizer, a flame retardant, an antibacterial agent, an ultraviolet stabilizer, a reinforcing material, a photocuring agent, and the like.

[0034] Examples of the thermosetting resin include vinyl urethane resin, unsaturated polyester resin, acrylic resin, epoxy resin, phenol resin, melamine resin, furan resin, etc. These thermosetting resins can be used alone or in combination of two or more.

[0035] Examples of the thermoplastic resin include polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polycarbonate resin, urethane resin, polypropylene resin, polyethylene resin, polystyrene resin, acrylic resin, methacrylic resin, polybutadiene resin, polyisoprene resin, and resins obtained by modifying these by copolymerization, etc. These thermoplastic resins can be used alone or in combination of two or more.

[0036] Examples of the polymerization inhibitor include hydroquinone, trimethylhydroquinone, pt-butylcatechol, t-butylhydroquinone, toluhydroquinone, p-benzoquinone, naphthoquinone, hydroquinone monomethyl ether, phenothiazine, copper naphthenate, copper chloride, 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, etc. These polymerization inhibitors can be used alone or in combination of two or more.

[0037] The content of the polymerization inhibitor is preferably in the range of 0.02 to 0.50 parts by mass per 100 parts by mass of the total amount of the vinyl ester resin (A) and the unsaturated monomer (B), from the viewpoint of a balance between material filling property during molding and short molding time.

[0038] Examples of the curing accelerator include metal soaps such as cobalt naphthenate, cobalt octenate, vanadyl octenate, copper naphthenate, and barium naphthenate, and metal chelate compounds such as vanadyl acetylacetate, cobalt acetylacetate, and iron acetylacetonate. Examples of 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 can be used alone or in combination.

[0039] The fillers include inorganic compounds and organic compounds, and can be used to adjust the physical properties of the molded product, such as strength, elastic modulus, impact strength, and fatigue durability.

[0040] Examples of the inorganic compound include calcium carbonate, magnesium carbonate, barium sulfate, mica, talc, kaolin, clay, celite, asbestos, barite, baryta, silica, silica sand, dolomite limestone, gypsum, aluminum fine powder, hollow balloons, alumina, glass powder, aluminum hydroxide, kansuiite, zirconium oxide, antimony trioxide, titanium oxide, molybdenum dioxide, and iron powder.

[0041] Examples of the organic compounds include powders of natural polysaccharides such as cellulose and chitin, and synthetic resin powders. Examples of synthetic resin powders include organic powders composed of hard resins, soft rubbers, elastomers, or polymers (copolymers), and particles having a multilayer structure such as a core-shell type. Specific examples include particles composed of butadiene rubber and / or acrylic rubber, urethane rubber, silicone rubber, polyimide resin powder, fluororesin powder, and phenolic resin powder. These fillers can be used alone or in combination of two or more.

[0042] Examples of the release agent include zinc stearate, calcium stearate, paraffin wax, polyethylene wax, carnauba wax, etc. Preferred examples include paraffin wax, polyethylene wax, carnauba wax, etc. These release agents can be used alone or in combination of two or more.

[0043] Examples of the thickener include metal oxides and hydroxides such as magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide, and acrylic resin-based fine particles, and can be appropriately selected depending on the handleability of the molding material of the present invention. These thickeners can be used alone or in combination of two or more.

[0044] The viscosity of the radically curable resin composition is preferably in the range of 200 mPa·s to 8000 mPa·s (25° C.) in order to further improve the resin impregnation into the reinforcing fibers.

[0045] The molding material of this embodiment contains the radical-curable resin composition, and the molding material can be provided with excellent working environment during molding, excellent handling properties (including film peelability and tackiness), and excellent moldability, while suppressing changes in viscosity, and capable of producing molded products with excellent physical properties such as bending strength.

[0046] The molding material may be a fiber-reinforced molding material containing carbon fiber, from the viewpoint of improving the mechanical properties of the molded article. As the carbon fiber, carbon fiber cut to a length in the range of 2.5 mm or more and 50 mm or less is preferred, and carbon fiber cut to a length in the range of 5 mm or more and 40 mm or less is more preferred, because this further improves the flowability in the mold during molding, the appearance and mechanical properties of the molded article.

[0047] As the carbon fiber, various types such as polyacrylonitrile, pitch, and rayon can be used, but among these, polyacrylonitrile-based fibers are preferred because high-strength carbon fibers can be easily obtained.

[0048] The number of filaments in the fiber bundle used as the carbon fiber is preferably in the range of 1,000 or more and 60,000 or less, since this further improves resin impregnation and the mechanical properties of the molded product.

[0049] The content of the carbon fiber in the components of the molding material is preferably in the range of 25% by mass or more and 80% by mass or less, and more preferably in the range of 40% by mass or more and 70% by mass or less, since this further improves the mechanical properties of the resulting molded product.

[0050] When the carbon fibers are contained in the molding material, the carbon fibers are impregnated into the resin with their fiber directions random.

[0051] From the viewpoints of excellent productivity and moldability with design diversity, the fiber reinforced molding material is preferably a sheet molding compound (hereinafter abbreviated as "SMC") or a bulk molding compound (hereinafter abbreviated as "BMC").

[0052] Examples of methods for producing the SMC include mixing and dispersing the vinyl ester resin (A), unsaturated monomer (B), polycarbodiimide compound (C), polyisocyanate compound (D), and polymerization initiator (E) using a mixer such as a conventional mixer, intermixer, planetary mixer, roll, kneader, or extruder. The resulting resin composition is then uniformly coated onto upper and lower carrier films. The carbon fiber is sandwiched between the resin compositions on the upper and lower carrier films. The entire assembly is then passed through impregnation rolls to apply pressure to impregnate the carbon fiber with the resin composition, and the assembly is then wound into a roll or folded zigzag. Further, aging is preferably performed at a temperature of 25 to 60°C. Examples of suitable carrier films include polyethylene film, polypropylene film, polyethylene-polypropylene laminate film, polyethylene terephthalate, and nylon.

[0053] The BMC can be produced in the same manner as in the SMC production method, by mixing and dispersing the vinyl ester resin (A), the unsaturated monomer (B), the polycarbodiimide compound (C), the polyisocyanate compound (D), the polymerization initiator (E), and other components using a mixer such as a conventional mixer, intermixer, planetary mixer, roll, kneader, or extruder, and then mixing and dispersing the carbon fiber in the resulting resin composition. Also, as in the SMC production method, it is preferable to age the BMC at a temperature of 25 to 60°C.

[0054] The molded article of the present invention can be obtained from the above molding material, and from the viewpoints of excellent productivity and design versatility, the molding method is preferably heat compression molding of SMC or BMC.

[0055] The heat compression molding method involves, for example, weighing a predetermined amount of molding material such as SMC or BMC, placing it in a mold preheated to 110-180°C, clamping the mold with a compression molding machine, shaping the molding material, maintaining a molding pressure of 0.1-30 MPa to cure the molding material, and then removing the molded product to obtain a molded product. Specific molding conditions are preferably a mold temperature of 120-160°C and a molding pressure of 1-15 MPa maintained for 1-5 minutes per mm of molded product thickness, and more preferably a mold temperature of 140-160°C and a molding pressure of 1-15 MPa maintained for 30-90 seconds per mm of molded product thickness, as this further improves productivity.

[0056] The molded articles obtained from the molding material of the present invention have excellent bending strength, bending modulus, etc., and can therefore be suitably used for automobile components, railway vehicle components, aerospace components, ship components, housing equipment components, sports components, light vehicle components, construction and civil engineering components, housings for office automation equipment, etc. [Example]

[0057] The present invention will be described in more detail below with reference to specific examples. The hydroxyl value was measured by measuring the number of milligrams of potassium hydroxide (mgKOH / g) required to neutralize the acetic acid produced when 1 g of a resin sample was reacted with an acetylating agent at a specified temperature and time according to the method specified in JIS K-0070. The acid value was measured by measuring the number of milligrams of potassium hydroxide (mgKOH / g) required to neutralize the free fatty acids, resin acids, etc. contained in 1 g of the resin sample according to the method specified in JIS K-0070.

[0058] [Synthesis Example 1: Synthesis of vinyl ester resin (A1)] A 2-L flask equipped with a thermometer, nitrogen inlet tube, and stirrer was charged with 725 parts by mass of epoxy resin (DIC Corporation's "Epiclon 860," a bisphenol A-type epoxy resin with an epoxy equivalent of 220), 284 parts by mass of methacrylic acid, and 0.28 parts by mass of t-butylhydroquinone. The flask was heated to 90°C under a 1:1 nitrogen / air mixture. 0.60 parts by mass of 2-methylimidazole was added, the temperature was raised to 110°C, and the reaction was continued for 10 hours. The acid value reached 6 or less, and the reaction was terminated. After cooling to approximately 60°C, the mixture was removed from the reactor, yielding a vinyl ester resin (A1) with a hydroxyl value of 215 mgKOH / g.

[0059] Example 1 (Preparation of radically curable resin composition (1)) 55 parts by mass of the vinyl ester resin (A1) obtained in Synthesis Example 1 was dissolved in 45 parts by mass of phenoxyethyl methacrylate to prepare a resin solution of 100 parts by mass. 1.0 part by mass of a polycarbodiimide compound ("Carbodilite V-05" manufactured by Nisshinbo Chemical Inc. (carbodiimide equivalent: 262, isocyanate group content: 8.2%), hereinafter abbreviated as "polycarbodiimide compound (C1)"), and 1.0 part by mass of liquid monomeric diphenylmethane diisocyanate (BASF INOAC A radical curable resin composition (1) was obtained by mixing 22 parts by mass of "Lupranate MI" manufactured by Polyurethane Co., Ltd. (hereinafter abbreviated as "polyisocyanate (D1)"), 1.2 parts by mass of a polymerization initiator ("Kayacarvone AIC-75" manufactured by Kayaku Akzo Co., Ltd., an organic peroxide (hereinafter abbreviated as "polymerization initiator (E)"), and 0.04 parts by mass of a polymerization inhibitor (parabenzoquinone (hereinafter abbreviated as "polymerization inhibitor (F)").

[0060] (Production of fiber-reinforced molding material (1)) The radical curable resin composition (1) was applied to a laminate film of polyethylene and polypropylene in an amount of 0.5 kg / m on average. 2 Onto this, carbon fibers cut into 25 mm pieces from a carbon fiber roving ("T700SC-12000-50C" manufactured by Toray Industries, Inc.) were uniformly dropped from the air so that the fibers had no fiber directionality, were of uniform thickness, and had a carbon fiber content of 50 mass %, and the radical curable resin composition (1) was applied at 0.5 kg / m in the same manner as above. 2 The carbon fibers were sandwiched between the films coated with the resin so that the resin was impregnated into the carbon fibers, and then the carbon fibers were packed and sealed in an aluminum vapor deposition film and left in a 40°C incubator for 20 hours to obtain a sheet-shaped fiber-reinforced molding material (1). The basis weight of this sheet-shaped fiber-reinforced molding material (1) was 2 kg / m 2 and the thickness was 2 mm.

[0061] [Examples 2 and 3, and Comparative Examples 1 and 2] (Preparation of radically curable resin compositions (2) to (5)) A radical curable resin composition (2) according to Example 2, a radical curable resin composition (3) according to Example 3, a radical curable resin composition (4) according to Comparative Example 1, and a radical curable resin composition (5) according to Comparative Example 2 were obtained in the same manner as in Example 1, except that the amount of the carbodiimide compound (C1) was changed to the amount shown in Table 1 below. In Table 1, carbodiimide compound (C2) refers to the carbodiimide compound "Carbodilite V-02B" manufactured by Nisshinbo Chemical Inc., carbodiimide compound (C3) refers to the carbodiimide compound "Carbodilite V-04PF" manufactured by Nisshinbo Chemical Inc., and polyisocyanate (D2) refers to the polyisocyanate "Cosmonate LL" manufactured by Mitsui Chemicals, Inc.

[0062] (Production of fiber-reinforced molding materials (2) to (5)) A sheet-shaped fiber reinforced molding material (2) (Example 2) containing the radical curable resin composition (2), a sheet-shaped fiber reinforced molding material (3) containing the radical curable resin composition (3) (Example 3), a sheet-shaped fiber reinforced molding material (4) containing the radical curable resin composition (4) (Example 4), and a sheet-shaped fiber reinforced molding material (5) (Example 5) containing the radical curable resin composition (5) were obtained in the same manner as in Example 1, except that the radical curable resin composition (1) was changed to the radical curable resin compositions (2) to (5).

[0063] <Evaluation> [Evaluation of handling (film peelability)] The fiber reinforced molding materials (1) to (5) were peeled from a polypropylene film at 25° C. and evaluated for releasability according to the following criteria. ○: The molding material is not sticky and no deposits remain on the film. △: The molding material is sticky and some of the material remains on the film. ×: The molding material and the film are in close contact with each other, and a large amount of adhesion remains on the film.

[0064] [Evaluation of handling (tackiness)] The fiber reinforced molding materials (1) to (5) were peeled from the film at 25° C., and then the tackiness was evaluated according to the following criteria. ○: No molding material adhered to fingers △: A little molding material adhered to the finger ×: Molding material is stuck to fingers

[0065] [Evaluation of storage stability] The viscosity of each of the radically curable resin compositions (1) to (5) was measured using a flow tester. The same radically curable resin compositions (1) to (5) were then left in an incubator at 40°C for 7 days, and the viscosity of each was also confirmed using the flow tester. The rate of viscosity change from the viscosity before storage at 40°C was calculated, and storage stability was evaluated based on the following criteria. The rate of viscosity change was calculated using the following formula: Viscosity change rate (%) = (viscosity before storage at 40°C (mPa·s) - viscosity after storage at 40°C (mPa·s)) / (viscosity before storage at 40°C (mPa·s)) × 100 ○: Viscosity change rate is less than ±30% △: Viscosity change rate is ±30% or more, but less than 50% ×: Viscosity change rate is ±50% or more The viscosity was measured under the following conditions. Measurement device: Shimadzu Flow Tester CFT-500D (Shimadzu Corporation) Die hole diameter: 1 mm Die length: 1mm Measurement temperature: 30℃ Test force: 125 kgf

[0066] [Flexibility evaluation] The ease of operation when placing the fiber reinforced molding materials (1) to (5) in the molding die was evaluated based on the following indexes. ◯: Can be easily set along the shape of the mold during molding. △: There is some elasticity (repulsion) during molding, but it can be set to fit the shape of the mold. ×: The elasticity is strong during molding, and it is not possible to set the sheet along the shape of the mold.

[0067] [Evaluation of bending strength and bending modulus] The fiber reinforced molding material (1) was peeled off from the film and cut into pieces of 260 mm x 260 mm. Two pieces were stacked together to form a 30 x 30 cm 2 The molded product was placed in the center of a flat plate mold and molded at a mold temperature of 150°C for 3 minutes under a pressure of 12 MPa, yielding a 2 mm thick flat plate-shaped molded product (1). The same procedure was carried out for the fiber-reinforced molding materials (2) to (5), yielding molded products (2) to (5) corresponding to the fiber-reinforced molding materials (2) to (5), respectively. Four samples were cut out from each of the molded products (1) to (5) in the horizontal and vertical directions, and a three-point bending test was carried out in accordance with JIS K7074 to evaluate the bending strength and bending modulus according to the following criteria. (bending strength) ○:350MPa or more ×: Less than 350 MPa (flexural modulus) ○: 25GPa or more ×: Less than 25GPa

[0068] The results of the evaluation are shown in Table 1.

[0069] [Table 1]

[0070] As is clear from the results in Table 1, the radically curable resin compositions of Examples 1 to 3 suppress changes in viscosity over time, while providing excellent handling properties, including film peelability and tackiness, of the molding material, and moldability, and can produce molded articles with excellent physical properties such as bending strength. On the other hand, for Comparative Examples 1 and 2, the polycarbodiimide compound (C2) and the polycarbodiimide compound (C3) do not have an isocyanate group, and therefore do not have sufficient hydrolysis resistance and are poor in storage stability.

Claims

1. A radical curable resin composition containing, as essential raw materials, a vinyl ester resin (A), an unsaturated monomer (B), a polycarbodiimide compound (C) having an isocyanate group, a polyisocyanate compound (D) other than the polycarbodiimide compound (C), and a polymerization initiator (E), the isocyanate group content (NCO%) of the polycarbodiimide compound (C) is in the range of 1% or more and 10% or less, a radical curable resin composition, wherein the amount of the polycarbodiimide compound (C) added is in the range of 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total amount of the vinyl ester resin (A) added and the unsaturated monomer (B) added.

2. The radical curable resin composition according to claim 1, further comprising a polymerization inhibitor as a raw material.

3. A molding material comprising the radical curable resin composition according to claim 1.

4. The molding material according to claim 3 , which contains carbon fibers.

5. A molded product using the molding material according to claim 3 or 4.

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