Liquid composition and fiber-reinforced composite material using said liquid composition

Abstract

To provide a liquid composition for a fiber-reinforced plastic intermediate substrate which is capable of suppressing void to a minimum, and has excellent mechanical properties and heat resistance properties.SOLUTION: A liquid composition for a fiber-reinforced plastic intermediate substrate contains a composition (A) which includes a compound (a) having two or more isocyanate groups, and a composition (B) which includes vinyl ester resin (b1) and ethylenic unsaturated group-containing mono-alcohol compound (b2). Further, in a preferable embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate, a polymerization inhibitor (C) is blended in the compositions (A) and / or (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a liquid composition for fiber-reinforced plastic intermediate substrates, a fiber-reinforced plastic intermediate substrate, and a method for producing the fiber-reinforced plastic intermediate substrate, and in particular to a liquid composition for fiber-reinforced plastic intermediate substrates that have excellent curing properties, a fiber-reinforced plastic intermediate substrate, and a method for producing the fiber-reinforced plastic intermediate substrate. [Background technology]

[0002] Fiber reinforced plastics (FRP) are lightweight and strong, and are used in a variety of structural components. These applications span a wide range of fields, including housing equipment, automobiles, ships, civil engineering, and sports equipment, but in recent years, the use of FRP has been increasing, particularly in the automobile and transportation-related equipment fields, where weight reduction is essential.

[0003] FRP manufacturing methods include Resin Transfer Molding (RTM), in which a concave mold containing reinforcing fibers is sealed with a convex mold and then resin is injected and pressure-impregnated; the SMC method, in which short fibers impregnated with resin are sandwiched between films and passed through rollers to form a continuous sheet (Sheet Molding Compound (SMC)), which is then cut and placed in a mold where it is heated and pressurized in a press; and the autoclave method, in which fibers or fabrics impregnated with resin and brought to a semi-cured state (prepreg) are layered in a mold, the entire laminate surface is covered with film or the like, airtightly sealed, bagged, degassed under reduced pressure, and placed in an autoclave (heat and pressure molding oven) where it is heated and pressurized to manufacture the product.

[0004] Methods for manufacturing intermediate substrates include the solvent method, in which a resin composition and a solvent are mixed, the mixture is impregnated into a fiber substrate, and the solvent is then dried and removed to obtain the intermediate substrate; and the hot melt method, in which the viscosity of the resin composition is reduced by heating to produce a film of the resin composition (resin film), which is then attached to the top and bottom of a fiber substrate in which continuous fibers are aligned in one direction, and the resin composition is impregnated into the fiber substrate by heating and pressurizing to obtain the intermediate substrate.

[0005] The matrix resin for the intermediate substrate is often a resin composition containing a thermosetting resin, which has excellent impregnation properties for reinforcing fibers and heat resistance after curing. Examples of thermosetting resins that can be used include unsaturated polyester resin, vinyl ester resin, epoxy resin, phenolic resin, melamine resin, and bismaleimide resin.

[0006] Urethane (meth)acrylate compounds have been known to have excellent adhesive properties with carbon fibers and are used as sizing agents for carbon fibers (Patent Document 1). In addition, because urethane (meth)acrylate compounds have good adhesive properties with reinforcing fibers, it has been proposed to use them in combination with resins that have poor adhesive properties with reinforcing fibers (Patent Document 2).

[0007] It has also been proposed to improve the impregnation of fiber substrates by using an epoxy resin that is liquid at room temperature as the matrix resin of a sheet molding compound (Patent Document 3).

[0008] Furthermore, it has been proposed to use a resin composition consisting of a vinyl ester resin and a diallyl phthalate resin as the matrix resin of the prepreg, thereby improving the toughness and heat resistance of the fiber-reinforced composite material (Patent Document 4). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 11-200252 [Patent Document 2] Japanese Patent Publication No. 62-292839 [Patent Document 3] Patent Publication No. 2021-91920 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-24787 Summary of the Invention [Problem to be solved by the invention]

[0010] However, conventional methods for manufacturing intermediate substrates, such as the solvent method, have the problem of insufficient solvent removal, resulting in the evaporation of residual solvent in the intermediate substrate during molding, resulting in the formation of voids in the fiber-reinforced composite material. Raising the drying temperature to sufficiently remove the solvent would result in the intermediate substrate, which is made of a resin composition containing a thermosetting resin, curing, making it difficult to sufficiently remove the solvent using this manufacturing method. Furthermore, with the hot-melt method, as the fiber substrate becomes thicker, the resin composition cannot be sufficiently impregnated in the thickness direction. This makes it difficult to produce thick intermediate substrates that are sufficiently impregnated with the resin composition.

[0011] The matrix resin for the intermediate substrate is typically a thermosetting resin composition prepared by diluting an epoxy resin composition, unsaturated polyester resin, or vinyl ester resin with styrene. While the former provides excellent mechanical properties and heat resistance in the cured product, it is difficult to achieve both rapid curing and B-stage stability. The latter has a very low viscosity, allowing for excellent impregnation into the fiber substrate during the production of the intermediate substrate. It also provides excellent rapid curing and B-stage stability, but its large cure shrinkage makes it difficult to obtain a fiber-reinforced composite material with high dimensional stability.

[0012] Furthermore, the fiber-reinforced composite materials using the urethane (meth)acrylate compounds described in Patent Documents 1 and 2 have the problem that they are unable to obtain sufficient mechanical properties.

[0013] Furthermore, in the invention described in Patent Document 3, the heat resistance of the fiber-reinforced composite material obtained by curing the sheet molding compound is low, at around 150°C, which is not satisfactory for practical use in applications that require heat resistance, such as around automobile engines.

[0014] Furthermore, in the invention described in Patent Document 4, the resin composition has a high viscosity, making it difficult to impregnate a thick fiber substrate. In addition, there is no mention of molding shrinkage or warpage of a fiber-reinforced composite material obtained by curing a prepreg using the resin composition.

[0015] Therefore, an object of the present invention is to provide a liquid composition for fiber-reinforced plastic intermediate substrates that solves the above problems, minimizes voids, and has excellent mechanical properties and heat resistance. [Means for solving the problem]

[0016] The present inventors have conducted extensive research into resin compositions from various perspectives, and as a result have come up with the liquid composition of the present invention.

[0017] That is, the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention contains a composition (A) containing a compound (a) having two or more isocyanate groups, and a composition (B) containing a vinyl ester resin (b1) and an ethylenically unsaturated group-containing monoalcohol compound (b2). A liquid composition for a fiber-reinforced plastic intermediate substrate, wherein a polymerization inhibitor (C) is blended into the composition (B). It is characterized by:

[0018] In a preferred embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention, a polymerization inhibitor (C) is added to the composition (A). too It is characterized by being blended.

[0019] In addition, in a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, a polymerization initiator (D) and / or a urethane catalyst (E) is blended into the composition (A) and / or (B).

[0020] In addition, in a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, the molar ratio (B / A) of the isocyanate-reactive groups in the composition (B) to the number of moles of isocyanate groups in the composition (A) is 0.8 to 1.2.

[0021] In addition, in a preferred embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention, the composition (A) and / or (B) is characterized by containing a polymerizable monomer (F) that does not have an isocyanate-reactive group.

[0022] In a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, the content of the polymerizable monomer (F) is 1 to 40% by weight relative to the total weight of the compositions (A) and (B).

[0023] In a preferred embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention, the viscosity measured with a Brookfield viscometer at 10 to 50° C. is 5 to 200 mPa·s.

[0024] In a preferred embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention, the liquid composition of the present invention is impregnated into a fiber material.

[0025] The fiber-reinforced composite material of the present invention is characterized by being obtained by curing the fiber-reinforced plastic intermediate substrate of the present invention.

[0026] The method for producing a fiber-reinforced plastic intermediate substrate of the present invention is characterized by comprising the steps of impregnating a fiber material with the liquid composition of the present invention at an arbitrary composition, and maturing the fiber-reinforced plastic intermediate substrate obtained by the impregnation.

[0027] In a preferred embodiment of the method for producing a fiber-reinforced plastic intermediate substrate of the present invention, the aging temperature is 30 to 80°C. [Effects of the Invention]

[0028] The liquid composition for fiber-reinforced plastic intermediate substrates of the present invention has the advantageous effect of providing an intermediate substrate with excellent impregnation into the substrate, minimal shrinkage during curing, and excellent dimensional stability. The resulting intermediate substrate also has the advantageous effect of providing a highly reliable composite material with excellent mechanical properties and heat resistance, and virtually no voids or unimpregnated areas. The intermediate substrate of the present invention also has the advantageous effect of providing excellent curing properties and storage stability.

[0029] Furthermore, the present invention has the advantageous effect of enabling the production of intermediate substrates with a large unit weight by using a liquid composition having a low viscosity and excellent impregnation properties. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following description in any way as long as it does not deviate from the gist of the present invention. In the present invention, "(meth)acrylate" refers to "acrylate" and "methacrylate". Similarly, "(meth)acrylic acid ester" refers to "acrylic acid ester" and "methacrylic acid ester".

[0031] The liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention is characterized by containing a composition (A) containing a compound (a) having two or more isocyanate groups, and a composition (B) containing a vinyl ester resin (b1) and an ethylenically unsaturated group-containing monoalcohol compound (b2). That is, the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention is characterized by being a blend of the following (A) and (B): composition (A) containing a compound (a) having two or more isocyanate groups, and composition (B) having the following (b1) and (b2) as essential components. (b1) Vinyl ester resin (b2) Ethylenically unsaturated group-containing monoalcohol compound

[0032] First, the composition (A) will be described. The composition (A) is a composition containing a compound (a) having two or more isocyanate groups.

[0033] Examples of the compound (a) having two or more isocyanate groups include aromatic isocyanate compounds such as 1,3-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and m-tetramethyl xylene diisocyanate; hydrogenated xylylene diisocyanate (1,3-bis(isocyanatomethyl)cyclohexyl) Examples of suitable isocyanate compounds include alicyclic isocyanate compounds such as isophorone diisocyanate, norbornene diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated methylene bisphenylene diisocyanate, and 1,4-cyclohexane diisocyanate; aliphatic isocyanate compounds such as 1,6-hexamethylene diisocyanate and trimethylene diisocyanate; trifunctional isocyanates having an isocyanurate ring obtained by trimerizing a bifunctional isocyanate compound; and polyol-modified isocyanate prepolymers. These isocyanate compounds can be used alone or in combination of two or more. Among these, aliphatic isocyanate compounds are particularly preferred from the viewpoints of viscosity and reactivity. Examples include isophorone diisocyanate and prepolymers having isocyanate groups obtained by reacting isophorone diisocyanate with a vinyl ester resin (b1) in an excess of isocyanate groups.

[0034] If the viscosity increases too quickly after mixing the compositions (A) and (B), it is possible to suppress the reaction by not adding the urethane catalyst (E), or to produce the intermediate base material at a low temperature at which the viscosity of the liquid composition does not exceed the range.

[0035] Next, composition (B) will be described. Composition (B) is a composition that can contain a vinyl ester resin (b1), an ethylenically unsaturated group-containing monoalcohol compound (b2), and a polymerization inhibitor (C) in any ratio. The vinyl ester resin (b1) and the ethylenically unsaturated group-containing monoalcohol compound (b2) are essential components of composition (B), and the polymerization inhibitor (C) can be added as needed. The vinyl ester resin (b1) and the ethylenically unsaturated group-containing monoalcohol (b2) added to composition (B) are preferably liquid at the fiber impregnation temperature (any temperature in the range of 10 to 50°C), but solid materials may also be used as long as they form a liquid composition for composition (B).

[0036] The vinyl ester resin (b1) is a reaction product (unsaturated monobasic acid epoxy ester) of an epoxy resin component and an unsaturated monobasic acid component.

[0037] The epoxy resin component is a compound having at least two epoxy groups per molecule, and examples thereof include diglycidyl ether type epoxy resins having a bisphenol compound such as bisphenol A, bisphenol F, or brominated bisphenol A as the main skeleton, polyglycidyl ether type epoxy resins having a polynuclear phenol compound such as phenol novolac, cresol novolac, or brominated phenol novolac as the main skeleton, polyglycidyl ester type epoxy resins having an organic polybasic acid such as dimer acid or trimellitic acid as the main skeleton, and glycidyl ether type epoxy resins having a diol compound such as an ethylene oxide or propylene oxide adduct of bisphenol A, glycol, or hydrogenated bisphenol A as the main skeleton. These epoxy resins may be used alone or in combination.

[0038] The unsaturated monobasic acid component is a monobasic acid having an ethylenically unsaturated group, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, sorbic acid, etc. These unsaturated monobasic acid components may be used alone or in combination.

[0039] The ethylenically unsaturated group-containing monoalcohol compound (b2) refers to a (meth)acrylic acid ester containing a hydroxyl group, and examples thereof include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, trimethylolpropane di(meth)acrylate, glycidyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, diacrylated isocyanurate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, and 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid.

[0040] These ethylenically unsaturated group-containing monoalcohol compounds (b2) can be used alone or in combination of two or more. Among these ethylenically unsaturated group-containing monoalcohol compounds (b2), 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoints of the viscosity of the liquid composition and the mechanical properties of the cured product. When heat resistance is required, pentaerythritol tri(meth)acrylate is preferred.

[0041] In a preferred embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention, a polymerization inhibitor (C) is blended into the composition (A) and / or (B). As described above, the polymerization inhibitor (C) can be blended into the composition (B), but it can also be blended into the composition (A), only into the composition (A), only into the composition (B), or both into the compositions (A) and (B).

[0042] As the polymerization inhibitor (C), for example, known polyhydric phenol-based polymerization inhibitors such as hydroquinone, parabenzoquinone, methylhydroquinone, trimethylhydroquinone, etc. can be used.

[0043] In addition, in a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, a polymerization initiator (D) and / or a urethane catalyst (E) are further blended into the composition (A) and / or (B).

[0044] In a preferred embodiment of the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention, the composition (A) and / or (B) contains a polymerizable monomer (F) that does not contain an isocyanate-reactive group.

[0045] First, the polymerization initiator (D), urethanization catalyst (E), and polymerizable monomer (F) not containing an isocyanate-reactive group will be described. Each of these components can be blended into either composition (A) or (B), or can be blended into both compositions (A) and (B). The polymerization initiator (D) can be an essential component when curing the intermediate substrate by radical polymerization in the production of a fiber-reinforced composite material, which will be described later.

[0046] The urethanization catalyst (E) and the polymerizable monomer (F) containing no isocyanate-reactive group may be blended as needed.

[0047] Examples of the polymerization initiator (D) include organic peroxides, such as ketone peroxides such as methyl ethyl ketone peroxide and acetylacetone peroxide, diacyl peroxides such as benzoyl peroxide, peroxy esters such as t-butyl peroxybenzoate, hydroperoxides such as cumene hydroperoxide, dialkyl peroxides such as dicumyl peroxide, and peroxydicarbonates such as bis(4-tert-butylhexyl)peroxydicarbonate.

[0048] Furthermore, when photocuring properties are to be imparted to the intermediate substrate, a photocuring initiator can be used, and examples thereof include acetophenone-based compounds such as acetophenone, p-dimethylaminoacetophenone, and p-dimethylaminopropiophenone; aminobenzophenone-based compounds such as α-alkylaminobenzophenone; benzophenone-based compounds such as benzophenone and 2-chlorobenzophenone; benzoin ether-based compounds such as benzoin methyl ether; benzil ketal-based compounds such as benzil dimethyl ketal; anthraquinone-based compounds such as 2-ethylanthraquinone and octamethylanthraquinone; organic peroxides such as cumene peroxide; thiol compounds such as 2-mercaptobenzimidazole; and o-acyloxime-based compounds such as acetophenone o-benzoyloxime.

[0049] These can be appropriately selected from the aging temperature, molding temperature and storage temperature of the intermediate substrate, and can be used alone or in combination of two or more.

[0050] The amount of polymerization initiator (D) added is 0.05 to 5 parts by weight per 100 parts by weight of the liquid composition. Although polymerization initiator (D) can be blended into composition (B), it is preferable to blend it into composition (A) in consideration of the storage stability of composition (B), since composition (B) contains a compound having an ethylenically unsaturated group.

[0051] The urethanization catalyst (E) can be an acidic catalyst or a basic catalyst, but highly active tin compounds such as dibutyltin dilaurate and dibutyltin diacetate are preferred. The amount of catalyst added varies depending on the other raw materials selected, but is 0 to 800 ppm based on the weight of the liquid composition from the viewpoints of heat generation during aging, the rate of urethane acrylate formation, the storage stability of the intermediate substrate, and the mechanical properties of the cured product.

[0052] The polymerizable monomer (F) that does not contain an isocyanate-reactive group is preferably one that does not react with an isocyanate group at room temperature, and examples of the polymerizable monomer (F) that does not react with an isocyanate group at room temperature include vinyl monomers, monofunctional (meth)acrylic acid esters, and polyfunctional (meth)acrylic acid esters. If a polymerizable monomer that reacts with an isocyanate group is added, the mixture may react during storage, increasing the viscosity, which may result in poor workability or insufficient mechanical properties.

[0053] Examples of vinyl monomers include styrene, vinyl toluene, α-methylstyrene, and vinyl acetate. Examples of monofunctional (meth)acrylic acid esters include methyl methacrylate, benzyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth). ) acrylate, and examples of polyfunctional (meth)acrylic acid esters include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tripropylene di(meth)acrylate, norbornene dimethanol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethylene oxide-added bisphenol A di(meth)acrylate, propylene oxide-added bisphenol A di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tris(2-(meth)acryloyloxyethyl)isocyanurate. These polymerizable monomers (E) can be used alone or in combination of two or more. From the viewpoints of tackiness and odor as an intermediate substrate, and the mechanical properties of the cured product, it is preferable to use diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene di(meth)acrylate, benzyl methacrylate, dicyclopentenyl (meth)acrylate, ethylene oxide-added bisphenol A di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and propylene oxide-added bisphenol A di(meth)acrylate.

[0054] In a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, the content of the polymerizable monomer (F) is 0 to 40% by weight relative to the total weight of the compositions (A) and (B). That is, the blending amount of the polymerizable monomer (F) in the liquid composition can be adjusted within the range of 0 to 40% by weight in accordance with the urethane acrylate obtained by aging to achieve the target viscosity characteristics and tackiness of the intermediate substrate. From the viewpoint of reducing cure shrinkage of the intermediate substrate, 0 to 20% by weight is preferred.

[0055] In addition, in a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, from the viewpoint of imparting better FRP mechanical properties, the composition is further characterized in that the molar ratio (B / A) of the isocyanate-reactive groups in composition (B) to the number of moles of isocyanate groups in composition (A) is 0.8 to 1.2, preferably 0.9 to 1.1.

[0056] In a preferred embodiment of the liquid composition for fiber-reinforced plastic intermediate substrates of the present invention, the viscosity of the liquid composition, which is a mixture of compositions (A) and (B), measured with a Brookfield viscometer at 10 to 50°C is 5 to 200 mPa·s. That is, the viscosity of the liquid composition of the present invention, at the time when compositions (A) and (B) are mixed, is preferably 5 to 200 mPa·s at 10 to 50°C, and although this depends on the unit area weight of the target intermediate substrate, a viscosity of 5 to 100 mPa·s is particularly preferred. If the viscosity exceeds 200 mPa·s, impregnation into substrates with large unit area weights will be poor, and there is a risk of unimpregnated areas being formed.

[0057] The liquid composition of the present invention changes into a urethane (meth)acrylate by aging, and the ethylenically unsaturated group equivalent of the urethane acrylate is not particularly limited, but is preferably less than 1000 g / eq. If it is 1000 g / eq or more, the balance of mechanical properties (flexural strength, tensile strength, compressive strength, interlaminar shear strength) will be poor, and the heat resistance of the molded product may be reduced.

[0058] The liquid composition of the present invention may contain inorganic particles or rubber particles for the purpose of adjusting viscoelasticity and improving mechanical properties. Examples of inorganic particles include, but are not limited to, calcium carbonate, alumina, talc, titanium oxide, and silica. Examples of rubber components include, but are not limited to, crosslinked rubber particles and core-shell rubber particles in which a rubber component is surrounded by a crosslinked polymer. The amount of these particles added varies depending on the viscosity of the liquid resin composition, but is 2 to 80% by weight, preferably 2 to 75% by weight.

[0059] Furthermore, carbon nanotubes can be blended into the liquid composition of the present invention to further improve the mechanical strength and impact resistance of the FRP. From the viewpoint of the viscosity and coatability of the liquid composition, single-walled carbon nanotubes are preferred, and the blending amount of single-walled carbon nanotubes in the FRP should be 0.05 to 0.5 wt %.

[0060] Furthermore, the liquid composition of the present invention may contain, as needed, a low shrinkage agent, an internal mold release agent, a dispersant, etc. These additives are preferably in liquid form from the viewpoint of solubility, but may also be in solid form if they are dissolved in the composition by application of heat.

[0061] The fiber-reinforced plastic intermediate substrate of the present invention is characterized by being obtained by impregnating a fiber material with the liquid composition for a fiber-reinforced plastic intermediate substrate of the present invention.

[0062] Fibers used in the intermediate substrate of the present invention include, but are not limited to, carbon fiber, glass fiber, aramid fiber, Zylon fiber, boron fiber, basalt fiber, cellulose, etc. Furthermore, the reinforcing fiber content is 10 to 90% by weight, and from the viewpoints of mechanical properties and moldability, it is preferably 30 to 80% by weight. There are no limitations on the surface treatment agent or shape of the reinforcing fiber (unidirectional, cross, NCF, nonwoven fabric, etc.). Furthermore, it is also possible to sandwich a core material between two fibrous substrates. Examples of core materials include foamed nonwoven fabric and honeycomb core mat.

[0063] The method for producing a fiber-reinforced plastic intermediate substrate of the present invention is characterized by comprising the steps of impregnating a fiber material with the liquid composition of the present invention at a desired composition and aging the fiber-reinforced plastic intermediate substrate obtained by the impregnation. In the present invention, the liquid composition can be impregnated into the fiber material at a desired composition at a temperature of, for example, 10 to 60°C, although this is not particularly limited. Furthermore, in the present invention, if necessary, the fiber material may be sandwiched between films and impregnated with the liquid composition using roller pressure to form a roll or a bound structure. The fiber-reinforced plastic intermediate substrate obtained by the impregnation can then be aged. That is, in the present invention, urethane acrylate can be formed while the liquid composition is impregnated into fibers or textiles during the aging process. Conventionally, urethane acrylate has been formed first and then impregnated into fibers, etc.; however, the present inventors surprisingly discovered that the liquid composition of the present invention can be impregnated into fibers, textiles, etc., through a aging process to form urethane acrylate. As a result, in the present invention, it is possible to more strongly bond the liquid composition and the fibers, and as will be apparent from the examples described below, this has the advantageous effect of enabling the development of better impregnation properties, curing properties, mechanical properties, and the like.

[0064] In a preferred embodiment, the aging temperature can be 30 to 80°C from the viewpoint of promoting urethanization and suppressing radical polymerization reactions. In this manner, the liquid composition can be coated onto a film, fibers or textiles placed on the coated surface, sandwiched between films, and pressure applied with rollers to impregnate the fibers or textiles with the liquid composition. It is preferable to use a breakwater-like jig to maintain a constant width of the coated material from the coating plant until it contacts the fibers or textiles. Alternatively, the liquid composition can be dripped or sprayed onto the fibers or textiles, sandwiched between films, and pressure applied with rollers to impregnate the fibers or textiles with the liquid composition. Materials impregnated by these methods can be formed into rolls or bundles and aged in an oven (30 to 80°C).

[0065] The fiber-reinforced composite material of the present invention is characterized by being obtained by curing the fiber-reinforced plastic intermediate substrate of the present invention.

[0066] The cured intermediate substrate of the present invention, in which urethane acrylate is formed on fibers, can be obtained by applying heat and pressure to heat-cure. That is, curing by radical polymerization can be performed. Molding methods that apply heat and pressure include autoclave molding, oven molding, sheet winding molding, and press molding. Depending on the type of polymerization initiator in the liquid composition, the molding temperature is preferably 70 to 180°C, preferably 100 to 150°C, the molding time is preferably 3 to 60 minutes, and the molding pressure is preferably 0.1 to 10 MPa. [Example]

[0067] Hereinafter, one embodiment of the present invention will be described in more detail using examples, but the present invention is not limited to these examples. In these examples, "parts" means parts by weight unless otherwise specified. In the examples, a prepreg was produced as an example of an intermediate substrate.

[0068] [Synthesis Example] Synthesis of vinyl ester resin (b1) (Synthesis of vinyl ester resin 1) A five-neck flask equipped with a thermometer, a stirrer, a gas inlet tube, and a reflux condenser was charged with 678.9 parts of bisphenol A epoxy resin (manufactured by DIC Corporation, product name: EPICLON 850), 316.9 parts of methacrylic acid (manufactured by Mitsubishi Gas Chemical Company, Inc.), 3.0 parts of triphenylantimony, 0.2 parts of methylhydroquinone, and 1.0 part of 2-methylimidazole, and the mixture was reacted for 5 hours under an air flow (0.1 L / min) while maintaining the temperature at 130°C, to obtain vinyl ester resin 1.

[0069] (Synthesis of vinyl ester resin 2) A five-neck flask equipped with a thermometer, stirrer, gas inlet tube, and reflux condenser was charged with 661.8 parts of bisphenol A epoxy resin (DIC Corporation, product name: EPICLON 850), 89.8 parts of bisphenol A (Nippon Steel Chemical & Material Co., Ltd.), and 0.4 parts of triphenylphosphine. The mixture was allowed to react for 0.5 hours under a nitrogen flow (0.2 L / min) at 150 °C, followed by molecular elongation. The mixture was then cooled to 125 °C, and 242.9 parts of methacrylic acid (Mitsubishi Gas Chemical Company, Inc.), 3.0 parts of triphenylantimony, 0.2 parts of methylhydroquinone, and 2.0 parts of 2-methylimidazole were added. The mixture was allowed to react for 2 hours under an air flow (0.1 L / min) at 130 °C, resulting in vinyl ester resin 2.

[0070] (Synthesis of vinyl ester resin 3) A five-neck flask equipped with a thermometer, a stirrer, a gas inlet tube, and a reflux condenser was charged with 671.5 parts of a phenol novolac epoxy resin (manufactured by DIC Corporation, product name: EPICLON N-740), 325.1 parts of methacrylic acid (manufactured by Mitsubishi Gas Chemical Company, Inc.), 0.7 parts of methylhydroquinone, and 2.7 parts of 2-methylimidazole, and the mixture was reacted under an air flow (0.1 L / min) at a temperature of 120°C for 3 hours to obtain vinyl ester resin 3.

[0071] [Preparation of Liquid Composition] Composition A and Composition B were prepared.

[0072] <Preparation of Composition A> Preparation of Liquid Composition A(x-1) (for preparing Composition (C-1) used in Examples 1 and 2) 959.5 parts of isophorone diisocyanate (manufactured by Evonik, product name: VESTANAT IPDI) and 40.5 parts of tert-butyl peroxybenzoate (manufactured by NOF Corporation, product name Perbutyl Z) were mixed in a container and stirred at room temperature until a homogeneous solution was obtained, thereby obtaining composition A(x-1).

[0073] Preparation of Liquid Composition A (x-2) (for preparing Composition (C-2) used in Example 3) 958.3 parts of isophorone diisocyanate (manufactured by Evonik, product name: VESTANAT IPDI) and 41.7 parts of tert-butyl peroxybenzoate (manufactured by NOF Corporation, product name Perbutyl Z) were mixed in a container and stirred at room temperature until a homogeneous solution was obtained, thereby obtaining composition A(x-2).

[0074] Preparation of Liquid Composition A (x-3) (for preparing Composition (C-3) used in Example 4) 956.1 parts of isophorone diisocyanate (manufactured by Evonik, product name: VESTANAT IPDI) and 43.9 parts of tert-butyl peroxybenzoate (manufactured by NOF Corporation, product name Perbutyl Z) were mixed in a container and stirred at room temperature until a homogeneous solution was obtained, thereby obtaining composition A(x-3).

[0075] <Preparation of Composition B> Preparation of Liquid Composition B(y-1) (for preparing Composition (C-1) used in Examples 1 and 2) 462.9 parts of the vinyl ester resin 1, 365.6 parts of 2-hydroxyethyl methacrylate (manufactured by Mitsubishi Gas Chemical Company, Inc.), 170.7 parts of diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: NK Ester 2G), 0.4 parts of dibutylhydroxytoluene, 0.1 parts of methylhydroquinone, and 0.3 parts of dibutyltin dilaurate were mixed in a container and stirred until a homogeneous solution was obtained, thereby obtaining composition B(y-1).

[0076] Preparation of Liquid Composition B (y-2) (for preparing Composition (C-2) used in Example 3) 350.8 parts of the vinyl ester resin 2, 434.8 parts of 2-hydroxyethyl methacrylate (manufactured by Mitsubishi Gas Chemical Company, Inc.), 213.6 parts of diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: NK Ester 2G), 0.4 parts of dibutylhydroxytoluene, 0.1 parts of methylhydroquinone, and 0.3 parts of dibutyltin dilaurate were mixed in a container and stirred until a homogeneous solution was obtained, thereby obtaining composition B(y-2).

[0077] Preparation of Liquid Composition B (y-3) (for preparing Composition (C-3) used in Example 4) 422.1 parts of the vinyl ester resin 3, 295.2 parts of 2-hydroxyethyl methacrylate (manufactured by Mitsubishi Gas Chemical Company, Inc.), 281.9 parts of diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: NK Ester 2G), 0.4 parts of dibutylhydroxytoluene, 0.1 parts of methylhydroquinone, and 0.3 parts of dibutyltin dilaurate were mixed in a container and stirred until a homogeneous solution was obtained, thereby obtaining composition B(y-3).

[0078] The prepared liquid compositions A and B were blended in the weight ratios shown in Table 1 and stirred for about 30 seconds until a uniform solution was obtained, yielding liquid compositions (C-1 to C-3) for intermediate substrates. Table 1 also lists the viscosity of the prepared liquid compositions, the molar ratio (B / A) of isocyanate-reactive groups in composition (B) to the number of moles of isocyanate groups in composition (A), and the theoretical ethylenically unsaturated group equivalent of the urethane (meth)acrylate formed after aging.

[0079] Comparative Example Resin Synthesis (Synthesis of vinyl ester resin 4) A five-neck flask equipped with a thermometer, a stirrer, a gas inlet tube, and a reflux condenser was charged with 689.9 parts of a bisphenol A epoxy compound (manufactured by Mitsubishi Chemical Corporation, product name: jER 1001), 127.6 parts of methacrylic acid (manufactured by Mitsubishi Gas Chemical Company, Inc.), 0.8 parts of monomethyl ether hydroquinone, and 1.6 parts of 2-methylimidazole, and the mixture was reacted for 10 hours under an air flow (0.2 L / min) at a temperature of 110 to 120°C. The mixture was then diluted with 180.0 parts of diethylene glycol dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: NK Ester 2G), to obtain vinyl ester resin 4.

[0080] [Preparation of Comparative Resin] As a comparative example, a resin was prepared.

[0081] Preparation of vinyl ester resin (VE-1) (composition (C-4) used in Comparative Example 1) 990.1 parts of the vinyl ester resin 4 and 9.9 parts of tert-butylperoxy 2-ethylhexyl monocarbonate (manufactured by NOF Corporation, product name: Perbutyl E) were mixed at 80°C and stirred until a homogeneous solution was obtained, to obtain a resin composition (C-4).

[0082] Preparation of Epoxy Composition (EP-1) (Composition (C-5) used in Comparative Example 2) 917.4 parts of a bisphenol A type epoxy resin blend (a 50:50 weight ratio blend of Mitsubishi Chemical Corporation's product name: jER 1001 and Mitsubishi Chemical Corporation's product name: jER 828) were blended with 45.9 parts of dicyandiamide and 36.7 parts of a urea derivative, and the mixture was stirred until a homogeneous solution was obtained, thereby obtaining a resin composition (C-5).

[0083] The viscosities of the resins prepared above are shown in Table 1. Table 1 shows the preparation of the liquid compositions.

[0084] [Table 1]

[0085] [Wet-through test] To evaluate the impregnation properties of the liquid composition and resin, two drops of the liquid composition (C-1) and resin compositions (C-2 to C-4) shown in Table 1 were applied to a sheet of carbon fiber fabric (manufactured by Mitsubishi Chemical Corporation, product name: TR3523M) using a dropper at each impregnation temperature, and the time required for the material to penetrate to the back side under normal pressure was measured. The test results are shown in Table 2. Table 2 shows the results of the wet-through test (evaluation of the impregnation properties of the liquid composition and resin).

[0086] [Table 2]

[0087] (Judgment method) ◎10 seconds or less 〇20 seconds or less △30 seconds or less ×30 seconds or more

[0088] [Shrinkage rate measurement] To evaluate the dimensional stability, the shrinkage rates of the cured products of the liquid compositions (C-1 to C-3) and resin compositions (C-4 and C-5) were measured. The shrinkage rates were calculated from the specific gravity of the liquid and the specific gravity of the cured product. The liquid compositions (C-1 to C-3) were cured after thickening was completed. The thickening conditions and the results of the shrinkage rate measurements are shown in Table 3.

[0089] [Table 3]

[0090] [Preparation of intermediate substrate] Preparation of prepregs (P-1 to P-6) Table 4 shows the conditions for preparing the intermediate substrate (prepreg) and the impregnation state of the prepreg.

[0091] [Table 4]

[0092] Ten sheets of carbon fiber fabric (manufactured by Mitsubishi Chemical Corporation, product name: TR3523M) cut into 33 cm squares were impregnated with the liquid compositions (C-1 to C-3) shown in Table 1 in the proportions shown in Table 4, and then aged under various conditions to obtain prepregs. The obtained prepregs contained approximately 60 wt% fiber.

[0093] In P-5 and P-6 (Comparative Examples 1 and 2), prepregs were obtained by the hot melt method.

[0094] [Molding of intermediate substrate] Prepreg molding The prepared prepregs (P-1 to P-6) were molded using a 100-ton hydraulic press (manufactured by Toho Press Manufacturing Co., Ltd.) to obtain molded plates (Examples 1 to 4 and Comparative Examples 1 to 2). The molding temperature was 130°C (Examples 1, 3, 4 and Comparative Examples 1 to 2) and 150°C (Example 2), the molding pressure was 10 bar, and the molding time was 7 minutes.

[0095] [Measurement of physical properties of formed plate] The obtained molded plates were subjected to a bending test, an interlaminar shear test, a dynamic viscoelasticity measurement, a moldability test, and an impregnation test.

[0096] Bending test Measurements were carried out according to the method compliant with JISK7018.

[0097] Interlaminar shear test Measurements were carried out according to JIS K7078.

[0098] Dynamic viscoelasticity measurement Measurements were carried out using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, product name: RSA-G2).

[0099] Formability and impregnation test (presence of voids and unimpregnated areas) To confirm impregnation and formability, the cross section of a test piece with a formed thickness of approximately 2.4 mm and a length of 30 cm was examined under a microscope to check the number of voids and unimpregnated areas. (Judgment method) Number of voids and unimpregnated areas per cross-sectional area 0~1 pieces〇 2~3 pieces△ 3 or more ×

[0100] Table 5 shows the results of the bending test, interlaminar shear test, dynamic viscoelasticity measurement, moldability and impregnation test for the prepreg molded plate.

[0101] [Table 5]

[0102] Tables 2 to 5 show that the liquid composition has excellent impregnation into the substrate, and produces an intermediate substrate with little shrinkage during curing and excellent dimensional stability. Furthermore, Table 5 shows that the intermediate substrate produces a highly reliable composite material with excellent mechanical properties and heat resistance and almost no voids or unimpregnated areas. The present invention, which uses the liquid composition with low viscosity and excellent impregnation, makes it possible to produce an intermediate substrate with a large unit weight per area, and to provide a liquid composition for producing an intermediate substrate with a large unit weight per area, as well as an FRP with high strength and excellent dimensional stability, which minimizes the number of laminations. [Industrial Applicability]

[0103] The radical polymerizable resin composition and intermediate substrate of the present invention are lightweight and have high strength, and therefore can be used in a wide range of applications, including, but not limited to, transportation equipment, industrial materials, civil engineering reinforcement materials, and sports equipment.

Claims

1. A liquid composition for a fiber-reinforced plastic intermediate substrate, comprising: a composition (A) containing a compound (a) having two or more isocyanate groups; and a composition (B) containing a vinyl ester resin (b1) and an ethylenically unsaturated group-containing monoalcohol compound (b2), wherein a polymerization inhibitor (C) is blended into the composition (B).

2. 2. The liquid composition according to claim 1, wherein a polymerization inhibitor (C) is also blended in said composition (A).

3. 3. The liquid composition according to claim 1, wherein a polymerization initiator (D) and / or a urethanization catalyst (E) is blended in the composition (A) and / or the composition (B).

4. The liquid composition according to any one of claims 1 to 3, wherein the molar ratio (B / A) of the isocyanate-reactive groups in the composition (B) to the molar number of isocyanate groups in the composition (A) is 0.8 to 1.

2.

5. The liquid composition according to any one of claims 1 to 4, characterized in that the composition (A) and / or (B) contains a polymerizable monomer (F) that does not have an isocyanate reactive group.

6. The liquid composition according to any one of claims 1 to 5, wherein the content of the polymerizable monomer (F) is 1 to 40 wt% based on the total weight of the compositions (A) and (B).

7. The liquid composition according to any one of claims 1 to 6, characterized in that the viscosity at 10 to 50°C measured with a Brookfield viscometer is 5 to 200 mPa·s.

8. A fiber-reinforced plastic intermediate substrate obtained by impregnating a fiber material with the liquid composition according to any one of claims 1 to 7.

9. A fiber-reinforced composite material obtained by curing the fiber-reinforced plastic intermediate substrate according to claim 8.

10. A method for producing a fiber-reinforced plastic intermediate substrate, comprising: a step of impregnating a fiber material with the liquid composition according to any one of claims 1 to 7 at an arbitrary composition; and a step of aging the fiber-reinforced plastic intermediate substrate obtained by the impregnation.

11. The method according to claim 10, wherein the aging temperature is 30 to 80°C.

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