JP7632768B2 - LAMINATE, MANUFACTURING METHOD FOR LAMINATE, AND BATTERY CASE - Google Patents

Description

The present invention relates to a laminate that is lightweight and thin, yet has excellent flame resistance and strength, and can be suitably used for a variety of molded product applications, and a battery case using the same.

Since the lithium-ion batteries used in many electric vehicles have the risk of catching fire, their battery cases must be strong as well as highly flame-resistant and fire-resistant. At the same time, to realize cars with better fuel economy and a lower environmental impact, molding materials are needed that can further reduce the weight and space of the battery case itself while still fully maintaining the aforementioned performance.

As a lightweight and high-strength molding material, a so-called FRP sandwich molding is known, in which a resin foam is used as the core material and sandwiched between fiber-reinforced plastic (see, for example, Patent Document 1). However, the resin foam used as the core material in this sandwich molding is generally flammable, and in order to impart a certain degree of flame resistance, a resin foam with a sufficient thickness must be used, so it cannot be used for applications such as battery cases, which require both high flame resistance and fire resistance, as well as light weight and space saving.

JP 2022-80629 A

Therefore, the problem that the present invention aims to solve is to provide a molding material that is lightweight and thin-walled while having excellent flame resistance and strength, and that can be suitably used for molded products such as battery cases, and a battery case using the same.

As a result of extensive research, the inventors discovered that a laminate comprising a core layer (A) formed by compressing a foam in the thickness direction and an outer layer (B) made of fiber-reinforced plastic is lightweight and thin, yet has excellent flame resistance and strength, and can be used in a variety of molded product applications, including battery cases, and thus completed the present invention.

That is, the present invention relates to (I) a laminate comprising a core layer (A) formed by compressing a foam in the thickness direction and an outer layer (B) made of fiber-reinforced plastic.

The present invention further relates to (II) a laminate described in (I) above, in which the compression ratio of the core layer (A) is 40% or more in terms of thickness.

The present invention further relates to (III) a laminate described in (I) or (II) above, wherein the aspect ratio of the foam cells of the core layer (A) is 2 or more.

The present invention further relates to (IV) a laminate according to any one of (I) to (III) above, wherein the outer layer (B) is obtained by hot molding a prepreg containing reinforcing fibers (f) and a matrix resin (r), and the matrix resin is a resin composition (1) containing a polyisocyanate compound (r1) and a polyhydroxy(meth)acrylate compound (r2), or a resin composition (2) containing a polyisocyanate compound (r1), a monohydroxy(meth)acrylate compound (r3), and a polyhydroxy compound (r4).

The present invention further relates to a method for producing a laminate described in any one of (I) to (IV) above, comprising: (V) heating and molding a precursor having a core layer (a) made of a foam and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r) under conditions in which the core layer (a) is compressed.

The present invention further relates to (VI) a method for producing a laminate described in any of (I) to (IV), in which the core layer (A) and the outer layer (B) made of fiber-reinforced plastic are bonded together using an adhesive.

The present invention further relates to (VII) a method for producing a laminate described in any one of (I) to (IV) above, which comprises hot molding a precursor obtained by laminating the core layer (A) and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r).

The present invention further relates to (VIII) a battery case using a laminate described in any of (I) to (IV).

According to the present invention, it is possible to provide a laminate that is lightweight and thin, yet has excellent flame resistance and strength, and that can be suitably used for molded products such as battery cases, and a battery case using the laminate.

The present invention is described in detail below.

The laminate of the present invention is characterized by comprising a core layer (A) made of foam compressed in the thickness direction and an outer layer (B) made of fiber-reinforced plastic.

As the foam, foams made of various resin materials can be used without any particular restrictions. Examples of the resin materials include polyurethane resin, phenol resin, melamine resin, acrylic resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polystyrene resin, styrene acrylic resin, ABS resin, polyphenylene ether resin, polyetherimide resin, polymethyl methacrylate resin, polymethacrylimide resin, etc. The foaming method and foaming agent used for these resin materials are not particularly limited, and those foamed by publicly known and commonly used foaming agents and foaming methods can be used. Among them, bead foams are preferable because the resulting laminate has better flame resistance, and bead foams of polystyrene resin are more preferable.

The bead foam can be produced, for example, by injecting a foaming gas into particles made of the various resin materials, heating the particles to pre-expand, and then foaming the resulting foam beads under heat and pressure. The average particle size of the foam beads is preferably in the range of 0.5 to 5 mm, since the resulting laminate has better flame resistance and strength. Examples of the foaming gas include propane, butane, and pentane, and the amount of gas injected is preferably 5 to 7 mass% of the foam beads. The expansion ratio is preferably 40 to 70 times, since the resulting laminate has better flame resistance and strength. The density of the foam is preferably in the range of 0.01 to 0.07 g/cm ³ , since the laminate has a good balance of light weight, flame resistance, and strength.

In the bead foam, a functional coating agent can be applied to the surface of the foamable beads, which are the raw material, to impart the desired performance to the resulting foam. Examples of functional coating agents include flame-retardant coating agents and heat-resistant coating agents. Among these, a resin bead foam with a flame-retardant coating agent applied to the surface is preferred, since the resulting laminate has better flame resistance. Examples of the flame-retardant coating agent include those containing phosphorus atom-containing compounds, halogen atom-containing compounds, nitrogen atom-containing compounds, hydrated metal compounds, borates, metal oxides, silicone compounds, etc. as flame retardants.

The core layer (A) of the present invention is obtained by compressing the foam in the thickness direction. The compression ratio of the core layer (A) is preferably 40% or more, more preferably 60% or more, and particularly preferably 85% or more, in terms of thickness, since the resulting laminate is thin but has sufficient flame resistance. Also, it is preferably 97% or less, and more preferably 95% or less. Also, the aspect ratio of the foam cells of the core layer (A) is preferably 1.7 or more, more preferably 2.5 or more, and particularly preferably 6.7 or more, since the resulting laminate is thin but has sufficient flame resistance. Also, it is preferably 30 or less, and more preferably 20 or less. The aspect ratio of the foam cells may be either an actual value measured by observing the cross section of the foam with a microscope, or a calculated value calculated from the compression ratio.
Aspect ratio = 1/[1 - compression ratio (%)/100]

The thickness of the core layer (A) is preferably in the range of 0.5 to 5 mm, and more preferably in the range of 1 to 3 mm, since the resulting laminate has an excellent balance of flame resistance, strength, and light weight. The core layer (A) may be formed of only one layer, or may be multi-layered. When the core layer (A) is multi-layered, each layer may be formed of the same type of foam, or each layer may be formed of a different type of foam. Even when the core layer (A) is multi-layered, the total thickness of the core layer (A) is preferably in the range of 0.5 to 5 mm, and more preferably in the range of 1 to 3 mm.

The outer layer (B) made of the fiber-reinforced plastic is specifically obtained by hot molding a prepreg containing reinforcing fibers (f) and a matrix resin (r).

Examples of the reinforcing fibers (f) include carbon fibers, glass fibers, silicon carbide fibers, alumina fibers, boron fibers, metal fibers, and organic fibers such as aramid fibers, vinylon fibers, and tetron fibers. These may be used alone or in combination of two or more types. Among these, carbon fibers and glass fibers are preferred because they provide a laminate with higher strength.

Various types of carbon fiber can be used, such as polyacrylonitrile, pitch, and rayon. Among these, polyacrylonitrile-based fibers are preferred because they produce carbon fibers with higher strength.

The shape of the reinforcing fiber (f) is not particularly limited, and examples thereof include reinforcing fiber tows in which reinforcing fiber filaments are converged, unidirectional materials in which reinforcing fiber tows are aligned in one direction, woven fabrics, short-cut reinforcing fibers, and nonwoven fabrics or papers made of short-cut reinforcing fibers. When the reinforcing fiber (f) is a fabric, examples thereof include a plain weave, twill weave, satin weave, or non-crimped fabric, which is a sheet in which fiber bundles are aligned in one direction, or a sheet in which the fibers are stacked at different angles and stitched to prevent unraveling. When short-cut reinforcing fibers are used as the reinforcing fibers (f), it is preferable to use fibers cut to a length of 2.5 to 50 mm, since this improves the fluidity in the mold during molding and the appearance of the molded product. Among these, it is preferable to use unidirectional materials or woven fabrics as the reinforcing fibers, since this results in a stronger outer layer (B). When using a prepreg using unidirectional materials as reinforcing fibers, a stronger outer layer (B) can be obtained by stacking multiple sheets in a quasi-isotropic manner, for example, with the fiber directions alternating between 0° and 90°.

For the same reasons as above, the length of the short cut reinforcing fibers is more preferably 8 to 50 mm, and particularly preferably 10 to 30 mm.

The basis weight (weight per 1 ^m2 of fiber) of the reinforcing fiber (f) can be of various types without any particular limitation. The optimum value also differs depending on the reinforcing fiber (f). In general, the basis weight is preferably in the range of 30 to 650 g/ ^m2 , since it is excellent in balance between the uniformity of the fiber width of the reinforcing fiber (f) and the impregnation of the matrix resin (r). When the reinforcing fiber (f) is a glass fiber, the basis weight is preferably 50 g/ ^m2 or more, and more preferably 100 g/ ^m2 or more. Also, it is preferably 600 g/ ^m2 or less, and more preferably 350 g/ ^m2 or less. When the reinforcing fiber (f) is a carbon fiber, it is preferably 50 g/ ^m2 or more, and more preferably 80 g/ ^m2 or more. Also, it is preferably 300 g/ ^m2 or less, and more preferably 200 g/ ^m2 or less.

The basis weight of the short cut reinforcing fibers is preferably 250 to 1500 g/m ² , more preferably 300 to 1400 g/m 2, and particularly preferably 400 to 1300 g/m ² , from the viewpoint of achieving both favorable impregnation ^properties and high strength.

In addition, the content of the reinforcing fibers (f) in the prepreg is preferably 40% by mass or more, more preferably 50% by mass or more, since this results in a stronger outer layer (B). Also, the content is preferably 90% by mass or less, more preferably 80% by mass or less.

The matrix resin (r) can be impregnated into the reinforcing fiber (f) and can be molded by heating or the like, and a wide variety of resins can be used without particular restrictions. Among them, a thermosetting resin composition is preferable because of ease of handling. Furthermore, since the outer layer (B) obtained is a prepreg that is high in strength, easy to handle, and has excellent moldability into various shapes, it is preferable that the resin composition contains a urethane reaction component formed by an isocyanate group and a hydroxyl group, and that a polymerizable unsaturated group is present in the resin composition. Examples of such resin compositions include a resin composition (1) containing a polyisocyanate compound (r1) and a polyhydroxy(meth)acrylate compound (r2), and a resin composition (2) containing a polyisocyanate compound (r1), a monohydroxy(meth)acrylate compound (r3), and a polyhydroxy compound (r4).

In the present invention, a (meth)acrylate compound refers to a compound having either or both of an acryloyl group and a methacryloyl group, a (meth)acryloyl group refers to either or both of an acryloyl group and a methacryloyl group, and a (meth)acrylic acid refers to either or both of acrylic acid and methacrylic acid.

The polyisocyanate compound (r1) may be, for example, an aliphatic diisocyanate compound such as butane diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, or dimer acid diisocyanate; an alicyclic diisocyanate compound such as norbornane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, or hydrogenated diphenylmethane diisocyanate; tolylene diisocyanate, Examples of the isocyanate compound include aromatic diisocyanate compounds such as xylylene diisocyanate, tetramethyl xylylene diisocyanate, lysine diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate; and modified compounds of these isocyanate compounds, such as isocyanurate modified compounds, biuret modified compounds, allophanate modified compounds, carbodiimide modified compounds, urethane imine modified compounds, and polyol modified compounds modified with polyols such as diethylene glycol and dipropylene glycol. These compounds may be used alone or in combination. Among these, aromatic diisocyanate compounds and various modified compounds thereof are preferred because they provide an outer layer (B) with excellent heat resistance. When multiple types of polyisocyanate compounds (r1) are used in combination, the proportion of the aromatic diisocyanate compound and various modified products thereof relative to the total mass of the polyisocyanate compound (r) is preferably 50 mass% or more, more preferably 80 mass% or more, and particularly preferably 90 mass% or more.

The polyhydroxy(meth)acrylate compound (r2) may be, for example, a (meth)acrylate compound having epoxy resin and (meth)acrylic acid as reaction raw materials.

Examples of the epoxy resin include diglycidyloxybenzene, diglycidyloxynaphthalene, aliphatic epoxy resins, biphenol-type epoxy resins, bisphenol-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, glycidylamine-type epoxy resins, heterocyclic epoxy resins, glycidyl ester-type epoxy resins, triphenolmethane-type epoxy resins, phenol or naphthol aralkyl-type epoxy resins, phenylene or naphthylene ether-type epoxy resins, oxodilone-modified epoxy resins, and brominated epoxy resins thereof. The epoxy resin may be an epoxy resin obtained by extending the above-mentioned specific examples with an extender.

Examples of the aliphatic epoxy resin include various aliphatic polyol compounds and polyglycidyl ethers of one or more of these alkylene oxide adducts with epihalohydrin. Examples of the aliphatic polyol compounds include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methylpropanediol, 1,2,2-trimethyl-1,3-propanediol, 2,2-dimethyl-3-isopropyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1, Examples of the diol include aliphatic diol compounds such as 6-hexanediol, 1,4-bis(hydroxymethyl)cyclohexane, and 2,2,4-trimethyl-1,3-pentanediol; alicyclic diol compounds such as 2,2-bis(4-hydroxyphenyl)propane; and aliphatic polyol compounds with three or more functional groups such as trimethylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, ditrimethylolpropane, and dipentaerythritol.

Examples of the biphenol-type epoxy resin include biphenol compounds such as biphenol and tetramethylbiphenol, and polyglycidyl ethers of one or more of these alkylene oxide adducts with epihalohydrin.

Examples of the bisphenol type epoxy resin include bisphenol compounds such as bisphenol A, tetrabromobisphenol A, bisphenol F, bisphenol S, bisphenol fluorene, and biscresol fluorene, and alkylene oxide adducts of these compounds which are polyglycidyl etherified with epihalohydrin.

The novolac type epoxy resin is, for example, a novolac resin made of one or more phenolic compounds such as phenol, dihydroxybenzene, cresol, xylenol, naphthol, dihydroxynaphthalene, bisphenol, and biphenol, which is polyglycidyl etherified with epihalohydrin.

Examples of alicyclic epoxy resins include those obtained by hydrogenating the biphenol compounds or bisphenol compounds mentioned above, and those obtained by polyglycidyl etherifying one or more of these alkylene oxide adducts with epihalohydrin, as well as 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 1-epoxyethyl-3,4-epoxycyclohexane, etc.

Examples of the glycidylamine type epoxy resin include N,N-diglycidylaniline, triglycidylaminophenol, tetraglycidylxylenediamine, 4,4'-methylenebis[N,N-diglycidylaniline], etc.

Examples of the heterocyclic epoxy resin include 1,3-diglycidyl-5,5-dimethylhydantoin and triglycidyl isocyanurate.

Examples of the glycidyl ester type epoxy resin include diglycidyl ester of phthalic acid, diglycidyl ester of tetrahydrophthalic acid, diglycidyl-p-oxybenzoic acid, and glycidyl ester of dimer acid.

Examples of extenders for epoxy resins include the various biphenol compounds and their hydrogenated products, the various bisphenol compounds and their hydrogenated products, dibasic acid compounds, and acid group-containing polyester resins.

Among these, the bisphenol type epoxy resin is preferred because of its excellent impregnation into the reinforcing fiber (f) and the strength of the resulting outer layer (B). In this case, the epoxy equivalent of the epoxy resin is preferably in the range of 150 to 600 g/equivalent, and more preferably in the range of 200 to 450 g/equivalent.

The reaction between the epoxy resin and (meth)acrylic acid can be carried out by heating at a temperature of about 60 to 140°C in the presence of any esterification catalyst. If necessary, a reaction solvent or a polymerization inhibitor may be added. The reaction ratio between the epoxy resin and (meth)acrylic acid is preferably such that the molar ratio of the functional groups of both [carboxy group/epoxy group] is in the range of 0.6 to 1.1.

When the bisphenol-type epoxy resin is used as the epoxy resin, the hydroxyl value of the resulting (meth)acrylate compound is preferably 50 to 200 mg/KOH. In addition, the (meth)acryloyl group equivalent is preferably in the range of 300 to 600 g/equivalent.

The polyhydroxy(meth)acrylate compound (r2) may be used alone or in combination with multiple types. When multiple types of polyhydroxy(meth)acrylate compounds (r2) are used in combination, the ratio of the bisphenol type epoxy resin (meth)acrylate compound to the total mass of the polyhydroxy(meth)acrylate compound (r2) is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more.

Examples of the monohydroxy(meth)acrylate compound (r3) include hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, trimethylolpropane di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, (poly)oxyalkylene(meth)acrylate compounds having (poly)oxyalkylene chains such as (poly)oxyethylene chains, (poly)oxypropylene chains, and (poly)oxytetramethylene chains introduced into these molecular structures, and lactone-modified (meth)acrylate compounds having (poly)lactone structures introduced into these molecular structures. These compounds may be used alone or in combination.

Among them, monohydroxymono(meth)acrylate compounds are preferred, and hydroxyethyl(meth)acrylate is more preferred, because they provide an excellent balance between the impregnation of the reinforcing fiber (f) and the strength of the resulting outer layer (B). When multiple types of monohydroxy(meth)acrylate compounds (r3) are used in combination, the proportion of hydroxyethyl(meth)acrylate to the total mass of the monohydroxy(meth)acrylate compounds (r3) is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

Examples of the polyhydroxy compound (r4) include dihydroxybenzene, dihydroxynaphthalene, the various aliphatic polyols mentioned above, biphenol compounds, bisphenol compounds, their alkylene oxide adducts, and lactone-modified compounds. These may be used alone or in combination. Among these, alkylene oxide adducts of bisphenol compounds are preferred because they provide an excellent balance between the impregnation of the reinforcing fiber (f) and the strength of the resulting outer layer (B). In addition, the average number of moles of alkylene oxide added is preferably in the range of 2 to 10 moles.

When multiple types of polyhydroxy compound (r4) are used in combination, the ratio of the alkylene oxide adduct of the bisphenol compound to the total mass of the polyhydroxy compound (r4) is preferably 50 mass% or more, more preferably 80 mass% or more, and particularly preferably 90 mass% or more.

In the resin composition (1), the molar ratio (NCO/OH) of the isocyanate groups contained in the polyisocyanate compound (r1) to the hydroxyl groups contained in the polyhydroxy(meth)acrylate compound (r2) is preferably in the range of 0.3 to 1.2, more preferably in the range of 0.4 to 1.1, and particularly preferably in the range of 0.5 to 1.0, in order to provide excellent ease of handling and moldability of the prepreg.

In the resin composition (2), the molar ratio (NCO/OH) of the isocyanate group contained in the polyisocyanate compound (r1), the hydroxyl group contained in the monohydroxy(meth)acrylate compound (r3), and the sum of the hydroxyl groups contained in the polyhydroxy compound (r4) is preferably in the range of 0.7 to 1.3, more preferably in the range of 0.8 to 1.1, and particularly preferably in the range of 0.8 to 1.0, because the ease of handling and moldability of the prepreg are excellent. In addition, the molar ratio (r3/r4) of the monohydroxy(meth)acrylate compound (r3) to the polyhydroxy compound (r4) is preferably in the range of 40/60 to 80/20, and more preferably in the range of 50/50 to 70/30, because the heat resistance and curability are further improved.

The resin compositions (1) and (2) may contain other polymerizable unsaturated group-containing compounds other than the polyhydroxy(meth)acrylate compound (r2) and the monohydroxy(meth)acrylate compound (r3). Specific examples thereof include, for example, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, pentyl(meth)acrylate, hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, isodecyl(meth)acrylate, lauryl(meth)acrylate, isotridecyl(meth)acrylate, n-stearyl(meth)acrylate, ethylene glycol(meth)acrylate alkyl ether, propylene glycol(meth)acrylate ... Aliphatic mono(meth)acrylate compounds such as ricolin (meth)acrylate alkyl ether; alicyclic mono(meth)acrylate compounds such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl mono(meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and dicyclopentanyl methacrylate; heterocycle-containing mono(meth)acrylate compounds such as glycidyl (meth)acrylate and tetrahydrofurfuryl acrylate; benzyl (meth)acrylate, phenyl (meth)acrylate, and the like. aromatic ring-containing mono(meth)acrylate compounds such as phenylbenzyl (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, phenoxybenzyl (meth)acrylate, benzyl benzyl (meth)acrylate, and phenylphenoxyethyl (meth)acrylate; (poly)oxyalkylene-modified mono(meth)acrylate compounds in which a polyoxyalkylene chain such as a propylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain has been introduced; lactone-modified mono(meth)acrylate compounds in which a (poly)lactone structure has been introduced into the molecular structure of the above-mentioned various mono(meth)acrylate compounds; ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, aliphatic di(meth)acrylate compounds such as (meth)acrylate; alicyclic di(meth)acrylate compounds such as 1,4-cyclohexanedimethanol di(meth)acrylate, norbornane di(meth)acrylate, norbornane dimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and tricyclodecane dimethanol di(meth)acrylate; aromatic ring-containing di(meth)acrylate compounds such as biphenol di(meth)acrylate and bisphenol di(meth)acrylate; polyoxyalkylene-modified di(meth)acrylate compounds in which a (poly)oxyalkylene chain such as a (poly)oxyethylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain has been introduced into the molecular structure of the acrylate compound; lactone-modified di(meth)acrylate compounds in which a (poly)lactone structure has been introduced into the molecular structure of the above-mentioned various di(meth)acrylate compounds; aliphatic tri(meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate and glycerin tri(meth)acrylate; (Poly)oxyalkylene-modified tri(meth)acrylate compounds in which a (poly)oxyalkylene chain such as a (poly)oxyethylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain has been introduced into the molecular structure of an acrylate compound; lactone-modified tri(meth)acrylate compounds in which a (poly)lactone structure has been introduced into the molecular structure of the aliphatic tri(meth)acrylate compound; pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, penta ... Examples of such compounds include aliphatic poly(meth)acrylate compounds having 4 or more functional groups, such as tetrafunctional or higher functional poly(meth)acrylates, (poly)oxyalkylene-modified poly(meth)acrylate compounds having 4 or more functional groups in which a (poly)oxyalkylene chain such as a (poly)oxyethylene chain, a (poly)oxypropylene chain, or a (poly)oxytetramethylene chain has been introduced into the molecular structure of the aliphatic poly(meth)acrylate compounds, and lactone-modified poly(meth)acrylate compounds having 4 or more functional groups in which a (poly)lactone structure has been introduced into the molecular structure of the aliphatic poly(meth)acrylate compounds. These compounds may be used alone or in combination of two or more types.

Among these, bifunctional or higher (meth)acrylate compounds having a molecular weight in the range of 150 to 600 are preferred because they provide an excellent balance between the impregnation of the reinforcing fibers (f) and the strength of the resulting outer layer (B). When multiple types of other polymerizable unsaturated group-containing compounds are used in combination, the ratio of bifunctional or higher (meth)acrylate compounds having a molecular weight in the range of 150 to 600 to the total mass of the other polymerizable unsaturated group-containing compounds is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

When other polymerizable unsaturated group-containing compounds are used in the resin composition (1), the amount of the compounds is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the polyisocyanate compound (r1) and the polyhydroxy (meth)acrylate compound (r2), because it provides an excellent balance between the impregnation of the reinforcing fiber (f) and the strength of the resulting outer layer (B). Also, when other polymerizable unsaturated group-containing compounds are used in the resin composition (2), the amount of the compounds is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the polyisocyanate compound (r1), the monohydroxy (meth)acrylate compound (r3), and the polyhydroxy compound (r4).

The resin compositions (1) and (2) may contain a polymerization initiator. The polymerization initiator may be any of the general types without particular limitation, but is preferably an organic peroxide. Examples of organic peroxides include diacyl peroxide compounds, peroxyester compounds, hydroperoxide compounds, ketone peroxide compounds, alkyl perester compounds, percarbonate compounds, and peroxyketals. These may be used alone or in combination. Among them, those having a temperature of 60°C or higher for obtaining a 10-hour half-life are preferred because they shorten the molding time. In addition, when a laminate is manufactured by the manufacturing methods 1 and 3 described below, and particularly when the core layer (a) or the core layer (A) is a polystyrene foam, in order to avoid molding defects due to swelling of the polystyrene foam, those having a 10-hour half-life temperature of 90°C or lower are preferred, those having a temperature of 80°C or lower are more preferred, and those having a temperature of 70°C or lower are particularly preferred. 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-butylperoxy2-ethylhexyl carbonate, t-amylperoxyisopropyl carbonate, and t-amylperoxy2-ethylhexyl. Examples of the polymerization initiator include butyl peroxy isopropyl carbonate, di-tert-butyl peroxy hexahydroterephthalate, t-amyl peroxy trimethyl hexanoate, t-amyl peroxy isononaate, t-hexyl peroxy 2-ethyl hexanoate, n-butyl 4,4-di(t-butylperoxy)valerate, 1,1,3,3-tetramethyl butyl peroxy 2-ethyl hexanoate, t-butyl peroxy 2-ethyl hexanoate, and t-butyl peroxy pivalate. The amount of the polymerization initiator added is preferably in the range of 0.5 to 3% by mass based on the total mass of the polymerizable unsaturated group-containing compound in the resin composition.

The resin compositions (1) and (2) may contain other components in addition to the various compounds described above. Examples of other components include thermoplastic resins, polymerization inhibitors, curing accelerators, fillers, shrinkage reducing agents, release agents, thickeners, viscosity reducers, pigments, antioxidants, plasticizers, flame retardants, antibacterial agents, UV stabilizers, reinforcing materials, and photocuring agents.

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, polybutadiene resin, polyisoprene resin, and those modified by copolymerization, etc. These may be used alone or in combination of two or more types.

Examples of the polymerization inhibitor include hydroquinone, trimethylhydroquinone, p-t-butylcatechol, t-butylhydroquinone, toluhydroquinone, p-benzoquinone, naphthoquinone, hydroquinone monomethyl ether, phenothiazine, copper naphthenate, copper chloride, etc. These may be used alone or in combination of two or more.

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 may be used alone or in combination of two or more.

Fillers are broadly divided into inorganic compounds and organic compounds. Fillers are components added primarily to adjust the physical properties of molded products, such as strength, elastic modulus, impact strength, and fatigue durability.

Examples of the inorganic compounds 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, kansui stone, zirconium oxide, antimony trioxide, titanium oxide, molybdenum dioxide, and iron powder. Examples of organic compounds include natural polysaccharide powders 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 of synthetic resin powders include particles composed of butadiene rubber, acrylic rubber, urethane rubber, silicone rubber, and the like, polyimide resin powder, fluororesin powder, and phenolic resin powder. These may be used alone or in combination of two or more types.

Examples of the release agent include zinc stearate, calcium stearate, paraffin wax, polyethylene wax, carnauba wax, etc. Preferred are paraffin wax, polyethylene wax, carnauba wax, etc. These may be used alone or in combination of two or more.

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. These thickeners can be used alone or in combination of two or more.

Examples of the flame retardant include phosphorus atom-containing compounds, halogen atom-containing compounds, nitrogen atom-containing compounds, hydrated metal compounds, borates, metal oxides, silicone compounds, etc. These flame retardants can be used alone or in combination of two or more.

The method for producing the prepreg is not particularly limited, but examples include a method in which the components of the matrix resin (r) are mixed using a known mixer such as a static mixer, a power mixer, a planetary mixer, or a kneader, and then the matrix resin is impregnated into the reinforcing fiber (f), which is then sandwiched between release films and rolled using a rolling mill. When the matrix resin (r) is impregnated into the reinforcing fiber (f), it may be heated as appropriate.

When the resin compositions (1) and (2) are used as the matrix resin (r), the sheet after rolling can be left at room temperature to 50°C to cause a urethane reaction between the isocyanate groups and hydroxyl groups in the resin composition, thereby making it possible to obtain a prepreg with excellent storage stability and ease of handling. Furthermore, when the resin compositions (1) and (2) are used as the matrix resin (r), the resin composition may be one in which a partial urethane reaction has progressed during the preparation process.

The thickness of the prepreg is preferably 0.02 mm or more, more preferably 0.05 mm or more, because it is easy to handle and has excellent moldability. Also, it is preferably 1.0 mm or less, more preferably 0.5 mm or less.

The outer layer (B) can be obtained by hot molding the prepreg. One example of the hot molding method is, for example, a method in which a plurality of prepregs are laminated and placed in a mold preheated to 110°C to 160°C, clamped and molded with a compression molding machine, and cured while maintaining a molding pressure of 0.1 to 10 MPa. Furthermore, a manufacturing method is preferred in which a mold having a shear edge is used, a molding pressure of 1 to 8 MPa is maintained at a mold temperature of 130°C to 160°C, and hot compression molding is performed for 1 to 3 minutes per 1 mm thickness of the molded product. The number of prepregs can be arbitrarily set based on the balance between moldability and the strength of the obtained outer layer (B), but it is preferable that it is in the range of 1 to 20 sheets because it is excellent in light weight. In addition, the orientation of the prepregs when stacking the prepregs can be arbitrarily set taking into account the desired strength, but it is preferable to stack them so that they are quasi-isotropic. For example, it is preferable to stack them in order so that the fiber directions are alternated between 0° and 90°. The thickness of the outer layer (B) is preferably 0.1 mm or more, more preferably 0.4 mm or more, and particularly preferably 0.6 mm or more, in terms of the balance between the strength and lightness of the resulting laminate, and is preferably 2.0 mm or less, and more preferably 1.5 mm or less.

The laminate of the present invention may include the core layer (A) and the outer layer (B), and as described above, the core layer (A) may be multi-layered, or the outer layer (B) may be multi-layered. The laminate of the present invention may also have other layers other than these. The other layers may be arranged on both sides of the core layer (A) or only on one side. It is preferable that the other layers are located between the core layer (A) and the outer layer (B). Examples of the other layers include a metal layer, a resin layer, and an adhesive layer. In this case, it is preferable that the ratio of the thickness of the core layer (A) and the outer layer (B) to the total thickness of the laminate is 80% or more, and more preferably 85% or more.

The method for producing the laminate of the present invention is not particularly limited, and the laminate can be produced by a wide variety of methods depending on the application and desired shape of the laminate. As some specific examples, the following three production methods can be mentioned. These production methods will be described below.
(Manufacturing method 1) A method for manufacturing a laminate, in which a precursor obtained by laminating a core layer (a) made of a foam and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r) is heat-molded under conditions in which the core layer (a) is compressed. (Manufacturing method 2) A method for manufacturing a laminate, in which the core layer (A) and the outer layer (B) made of the fiber-reinforced plastic are bonded together using an adhesive. (Manufacturing method 3) A method for manufacturing a laminate, in which a precursor obtained by laminating a core layer (A) and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r) is heat-molded.

The manufacturing method 1 is a method of hot-molding a precursor in which a core layer (a) made of a foam and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r) are laminated under conditions in which the core layer (a) is compressed. As described above, the outer layer (b) is preferably a laminate of multiple prepregs, specifically 1 to 20 prepregs. The lamination direction when laminating the prepregs can be set arbitrarily taking into account the desired strength, but it is preferable to laminate them so that they are quasi-isotropic. For example, it is preferable to laminate them in order so that the fiber directions are staggered between 0° and 90°. The core layer (a) and the outer layer (b) may be laminated directly, or another layer such as an adhesive layer may be provided between them. Furthermore, when producing a laminate by Production Method 1, in order to prevent the foam constituting the core layer (a) from further foaming in the heat forming step, the moldable temperature of the prepreg constituting the outer layer (b) is preferably 140°C or lower, and more preferably 110°C or lower.

In the above-mentioned manufacturing method 1, the molding conditions are not particularly limited, but examples include a method in which molding is performed for several minutes to several tens of minutes at a temperature of 80 to 140°C and a pressure of 0.1 to 6 MPa. If necessary, a release agent may be applied to the mold, and the precursor is preferably filled in the center of the mold. In addition, the thickness of the laminate may be adjusted using a spacer or the like so that it has a predetermined thickness.

The manufacturing method 2 is a method of bonding the core layer (A) and the outer layer (B) made of the fiber-reinforced plastic with an adhesive. The core layer (A) and the outer layer (B) used in manufacturing method 2 are as described above. The adhesive used in manufacturing method 2 is not particularly limited and is selected according to the application and desired shape of the laminate, and examples of the adhesive include acrylic resin-based, urethane resin-based, rubber-based, polyester resin-based, epoxy resin-based, cyanoacrylate resin-based, silicone resin-based, and modified silicone resin-based adhesives. The adhesive may be in any form, such as one-component liquid, two-component liquid, sheet, or double-sided tape.

The manufacturing method 3 is a method of hot-molding a precursor obtained by laminating the core layer (A) and the outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r). The core layer (A) used in manufacturing method 3 is as described above. As described above, the outer layer (b) is preferably a laminate of multiple prepregs, specifically, 1 to 20 prepregs. The direction in which the prepregs are laminated can be set arbitrarily taking into account the desired strength, but it is preferable to laminate them so that they are quasi-isotropic. For example, it is preferable to laminate them in order so that the fiber directions are staggered between 0° and 90°. The core layer (A) and the outer layer (b) may be laminated directly, or other layers such as an adhesive layer may be provided between them. Furthermore, when producing a laminate by Production Method 3, in order to prevent the foam constituting the core layer (A) from further foaming in the heat forming step, the moldable temperature of the prepreg constituting the outer layer (b) is preferably 140°C or lower, and more preferably 110°C or lower.

In the above-mentioned manufacturing method 3, the molding conditions are not particularly limited, but examples include a method in which molding is performed for several minutes to several tens of minutes at a temperature of 80 to 140°C and a pressure of 0.1 to 6 MPa. If necessary, a release agent may be applied to the mold, and the precursor is preferably filled in the center of the mold. In addition, the thickness of the laminate may be adjusted using a spacer or the like so that the thickness is a predetermined thickness.

The laminate of the present invention is lightweight yet has excellent flame resistance and strength, and can therefore be suitably used for a variety of applications, including battery cases, aerospace aircraft components, railway vehicle components, housing equipment components, electronic equipment components, medical equipment components, home appliance components, and automotive components.

Next, the present invention will be described in detail with reference to examples and comparative examples. In the following, "parts" and "%" are by weight unless otherwise specified.

Production Example 1 Production of Prepreg (1) Into a 1 L flask equipped with a thermometer, nitrogen and air inlet tubes, a cooling condenser, and a stirrer, an epoxy resin ("Epicron 152" manufactured by DIC Corporation), 365 parts by mass of tetrabromobisphenol A type epoxy resin (epoxy equivalent 365 g/equivalent, bromine content 48.1% by mass), 84 parts by mass of methacrylic acid, and 0.18 parts by mass of t-butylhydroquinone as a polymerization inhibitor were charged, and the temperature was raised to 95° C. under a gas flow of a 1:1 mixture of nitrogen and air. 0.9 parts by mass of triphenylphosphine was added as a catalyst, the temperature was raised to 105° C., and the reaction was carried out for 12 hours. Since the acid value became 1 or less, the reaction was terminated. After cooling to about 80° C., the mixture was removed from the reaction vessel, and epoxy methacrylate (1) was obtained. The hydroxyl value of this resin was 135 mgKOH/g. The (meth)acryloyl group equivalent of this resin was 450 g/equivalent.

Diphenylmethane diisocyanate (BASFINOAC Polyurethanes, Ltd., "Lupranate MI") 13 parts by mass, epoxy (meth)acrylate resin (1) obtained above 80 parts by mass, ethylenically unsaturated monomer (butanediol dimethacrylate) 20 parts by mass, and polymerization initiator (KAYAKU Akzo Co., Ltd., "Trigonox 122-C80", organic peroxide, 10-hour half-life temperature 87°C) 11.3 parts by mass were mixed to obtain matrix resin (1). Using a prepreg manufacturing device, glass fiber (Nippon Electric Glass Co., Ltd., "ER1620F", glass fiber basis weight 162 g/m ² ) was impregnated with matrix resin (1) so that the resin mass content was 35%, and a prepreg (1) having a thickness of 0.13 mm was obtained.

Production Example 2 Production of Prepreg (2) 13 parts by mass of diphenylmethane diisocyanate ("Lupranate MI" manufactured by BASFINOAC Polyurethanes Co., Ltd.), 80 parts by mass of the epoxy (meth)acrylate resin (1) obtained in Production Example 1, 20 parts by mass of an ethylenically unsaturated monomer (butanediol dimethacrylate), and 18.1 parts by mass of a polymerization initiator ("Trigonox 421-70" manufactured by Kayaku Akzo Co., Ltd., organic peroxide, 10-hour half-life temperature 65°C) were mixed to obtain a matrix resin (2). Using a prepreg manufacturing device, glass fibers ("ER1620F" manufactured by Nippon Electric Glass Co., Ltd., glass fiber basis weight 162 g/m ² ) were impregnated with the matrix resin (2) so that the resin mass content was 35%, and a prepreg (2) having a thickness of 0.13 mm was obtained.

Production Example 3 Production of Prepreg (3) 100 parts by mass of a mixture of polymethylene polyphenyl polyisocyanate and diphenylmethane diisocyanate ("Millionate MR-200" manufactured by Tosoh Corporation, polymethylene polyphenyl polyisocyanate content of 55 to 65 mass), 59 parts by mass of hydroxyethyl methacrylate, 24 parts by mass of an ethylene oxide adduct of bisphenol A ("Newpol BPE-20" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl group equivalent of 164 g/equivalent), 31 parts by mass of an ethylene oxide adduct of bisphenol A ("Newpol BPE-40" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl group equivalent of 204 g/equivalent), and 2.1 parts by mass of a polymerization initiator ("Trigonox 122-C80" manufactured by Kayaku Akzo Co., Ltd., organic peroxide) were mixed to obtain a matrix resin (2). Using a prepreg manufacturing device, glass fibers ("ER1620F" manufactured by Nippon Electric Glass Co., Ltd., glass fiber basis weight 162 g/ ^m2 ) were impregnated with matrix resin (3) so that the resin mass content was 35%, and a prepreg (3) with a thickness of 0.13 mm was obtained.

Production Example 4 Production of Prepreg (4) 100 parts by mass of a mixture of polymethylene polyphenyl polyisocyanate and diphenylmethane diisocyanate ("Millionate MR-200" manufactured by Tosoh Corporation, polymethylene polyphenyl polyisocyanate content of 55 to 65% by mass), 59 parts by mass of hydroxyethyl methacrylate, 24 parts by mass of an ethylene oxide adduct of bisphenol A ("Newpol BPE-20" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl group equivalent of 164 g/equivalent), 31 parts by mass of an ethylene oxide adduct of bisphenol A ("Newpol BPE-40" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl group equivalent of 204 g/equivalent), and 2.1 parts by mass of a polymerization initiator ("Trigonox 122-C80" manufactured by Kayaku Akzo Co., Ltd., organic peroxide) were mixed to obtain a matrix resin (3). Using a prepreg production device, carbon fibers ("T700SC" manufactured by Toray Industries, Inc., carbon fiber basis weight 100 g/m ² ) were impregnated with matrix resin (4) so that the resin mass content was 34%, to obtain a prepreg (4) having a thickness of 0.1 mm.

Production Example 5 Production of Prepreg (5) 100 parts by mass of a mixture of polymethylene polyphenyl polyisocyanate and diphenylmethane diisocyanate ("Millionate MR-200" manufactured by Tosoh Corporation, polymethylene polyphenyl polyisocyanate content of 55 to 65% by mass), 59 parts by mass of hydroxyethyl methacrylate, 24 parts by mass of an ethylene oxide adduct of bisphenol A ("Newpol BPE-20" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl group equivalent 164 g/equivalent), 31 parts by mass of an ethylene oxide adduct of bisphenol A ("Newpol BPE-40" manufactured by Sanyo Chemical Industries, Ltd., hydroxyl group equivalent 204 g/equivalent), and 2.1 parts by mass of a polymerization initiator ("Trigonox 122-C80" manufactured by Kayaku Akzo Co., Ltd., organic peroxide) were mixed to obtain a matrix resin (3). Using an SMC manufacturing device, carbon fibers ("T700SC" manufactured by Toray Industries, Inc., carbon fiber basis weight 1150 g/ ^m2 ) cut into 1/2 inch pieces and randomly scattered were impregnated with matrix resin (4) so that the resin mass content was 43%, thereby obtaining a prepreg (5) having a thickness of 1.6 mm.

Examples 1 to 4 and Comparative Example 1
The laminates (1) to (9) and the laminate (1') were produced as follows, and various evaluation tests were carried out. The evaluation results of each laminate are shown in Tables 1 and 2.

Example 1: Production of laminate (1) The prepreg (1) obtained in Production Example 1 was cut into sizes of 298 mm x 218 mm and 298 mm x 218 mm, and eight sheets were laminated in order so that the fiber directions of the prepreg were alternated between the 0° direction and the 90° direction. This was filled into the center of a flat plate mold coated with a mold release agent, and compression molded under conditions of a pressure of 4 MPa, an upper mold temperature of 140°C, a lower mold temperature of 135°C, and a molding time of 3 minutes to obtain an outer layer (B1) of 300 mm x 220 mm x 1 mm. The flexural modulus of the outer layer (B1) measured in accordance with JIS K 7017 was 24.6 GPa.
A 4 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a foam of styrene beads with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut to a size of 298 mm x 218 mm, and then filled into the center of a flat plate mold and compression molded under conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A1) of 300 mm x 220 mm x 2 mm. The compression ratio in the thickness direction of the core layer (A1) was 50%, the specific gravity was 0.08 g/ ^m3 , and the aspect ratio of the foam cells calculated from the compression ratio was 2.
Using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko, thickness 0.15 mm), one sheet of the outer layer (B1) was attached to each side of the core layer (A1) to obtain a laminate (1).

Example 2: Production of laminate (2) The thermosetting prepreg (1) obtained in Production Example 1 was cut into sizes of 298 mm x 218 mm and 298 mm x 218 mm, and four sheets were laminated in order so that the fiber directions of the prepreg were alternated between the 0° direction and the 90° direction. This was filled into the center of a flat plate mold coated with a mold release agent, and compression molded under conditions of a pressure of 4 MPa, an upper mold temperature of 140°C, a lower mold temperature of 135°C, and a molding time of 3 minutes to obtain an outer layer (B2) of 300 mm x 220 mm x 0.5 mm. The flexural modulus of the outer layer (B2) measured in accordance with JIS K 7017 was 24.6 GPa.
A 10 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a foam of styrene beads with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut to a size of 298 mm x 218 mm, and then filled into the center of a flat plate mold and compression molded under conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A2) of 300 mm x 220 mm x 2 mm. The compression ratio in the thickness direction of the core layer (A2) was 80%, the specific gravity was 0.20 g/ ^m3 , and the aspect ratio of the foam cells calculated from the compression ratio was 5.
Using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko, thickness 0.15 mm), one sheet of the outer layer (B2) was attached to each side of the core layer (A2) to obtain a laminate (2).

Example 3: Production of laminate (3) The thermosetting prepreg (1) obtained in Production Example 1 was cut into sizes of 298 mm x 218 mm and 298 mm x 218 mm, and three sheets were laminated in order so that the fiber directions of the prepreg were alternated between the 0° direction and the 90° direction. The pieces were filled into the center of a flat plate mold coated with a release agent, and compression molded in a compression molding machine under conditions of a pressure of 4 MPa, an upper mold temperature of 140°C, a lower mold temperature of 135°C, and a molding time of 3 minutes to obtain an outer layer (B3) having a width of 300 mm x 220 mm x 0.35 mm. The flexural modulus of the outer layer (B3) measured in accordance with JIS K 7017 was 24.6 GPa.
A 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a foam of styrene beads with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut to a size of 298 mm x 218 mm, then filled into the center of a flat plate mold and compression molded under conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A3) of 300 mm x 220 mm x 2 mm. The compression ratio in the thickness direction of the core layer (A3) was 90%, the specific gravity was 0.40 g/ ^m3 , and the aspect ratio of the foam cells calculated from the compression ratio was 10.
Using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko, thickness 0.15 mm), one sheet of the outer layer (B3) was attached to each side of the core layer (A3) to obtain a laminate (3).

Example 4: Production of Laminate (4) A 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a styrene bead foam with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut into a size of 298 mm x 218 mm, and then filled into the center of a flat plate mold and compression molded under the conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A4) of 300 mm x 220 mm x 1.5 mm. The compression ratio of the core layer (A4) in the thickness direction was 92.5%, the specific gravity was 0.53 g/ ^m3 , and the aspect ratio of the foam cell calculated from the compression ratio was 13.3.
Using a flame-retardant double-sided tape (Nitto Denko Corporation's "No. 5011N", thickness 0.15 mm), one outer layer (B2) obtained in Example 2 was attached to each side of the core layer (A4) to obtain a laminate (4).

Example 5: Production of Laminate (5) The prepreg (2) obtained in Production Example 2 was cut into sizes of 298 mm x 218 mm and 298 mm x 218 mm, and eight sheets were laminated in order so that the fiber directions of the prepregs were alternated between the 0° direction and the 90° direction. This was then attached to both sides of a 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a styrene bead foam with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) cut into a size of 298 mm x 218 mm, and then filled into the center of a flat plate mold coated with a release agent. A 4 mm spacer was placed, and compression molded under conditions of a pressure of 4 MPa, an upper mold temperature of 105°C, a lower mold temperature of 100°C, and a molding time of 5 minutes to obtain a laminate (5) of 300 mm x 220 mm x 4 mm.
The flexural modulus of the outer layer measured in accordance with JIS K 7017 was 24.6 GPa.

Example 6 Production of Laminate (6) A 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a styrene bead foam with a flame retardant coated surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut into a size of 298 mm x 218 mm, and then packed into the center of a flat plate mold and compression molded under the conditions of an upper mold temperature of 30°C, a lower mold temperature of 30°C, and a molding time of 5 minutes to obtain a core layer (A4) of 300 mm x 220 mm x 4 mm. The prepreg (2) obtained in Production Example 2 was cut to sizes of 298 mm x 218 mm and 298 mm x 218 mm, and eight prepregs were laminated in order so that the fiber directions of the prepregs were alternately in the 0° direction and the 90° direction, and then the prepregs were loaded into the center of a flat plate mold to which a release agent had been applied, a 4 mm spacer was placed, and compression molded under conditions of a pressure of 4 MPa, an upper mold temperature of 105°C, a lower mold temperature of 100°C, and a molding time of 5 minutes to obtain a laminate (6) of 300 mm x 220 mm x 4 mm.
The flexural modulus of the outer layer measured in accordance with JIS K 7017 was 24.6 GPa.

Example 7: Production of laminate (7) The prepreg (3) obtained in Production Example 3 was cut into sizes of 298 mm x 218 mm and 298 mm x 218 mm, and eight sheets were laminated in order so that the fiber directions of the prepreg were alternated between the 0° direction and the 90° direction. This was filled into the center of a flat plate mold coated with a mold release agent, and compression molded under conditions of a pressure of 4 MPa, an upper mold temperature of 140°C, a lower mold temperature of 135°C, and a molding time of 3 minutes to obtain an outer layer (B4) of 300 mm x 220 mm x 1 mm. The flexural modulus of the outer layer (B4) measured in accordance with JIS K 7017 was 23.2 GPa.
A 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a foam of styrene beads with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut to a size of 298 mm x 218 mm, then filled into the center of a flat plate mold and compression molded under conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A3) of 300 mm x 220 mm x 2 mm. The compression ratio in the thickness direction of the core layer (A3) was 90%, the specific gravity was 0.40 g/ ^m3 , and the aspect ratio of the foam cells calculated from the compression ratio was 10.
Using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko Corporation), one sheet of the outer layer (B4) was attached to each side of the core layer (A3) to obtain a laminate (7).

Example 8: Production of laminate (8) The prepreg (4) obtained in Production Example 4 was cut into sizes of 298 mm x 218 mm and 298 mm x 218 mm, and eight sheets were laminated in order so that the fiber directions of the prepreg were alternated between the 0° direction and the 90° direction. This was filled into the center of a flat plate mold coated with a release agent, and compression molded under conditions of a pressure of 4 MPa, an upper mold temperature of 140°C, a lower mold temperature of 135°C, and a molding time of 3 minutes to obtain an outer layer (B5) of 300 mm x 220 mm x 1 mm. The flexural modulus of the outer layer (B5) measured in accordance with JIS K 7017 was 61.5 GPa.
A 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a foam of styrene beads with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut to a size of 298 mm x 218 mm, then filled into the center of a flat plate mold and compression molded under conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A3) of 300 mm x 220 mm x 2 mm. The compression ratio in the thickness direction of the core layer (A3) was 90%, the specific gravity was 0.40 g/ ^m3 , and the aspect ratio of the foam cells calculated from the compression ratio was 10.
Using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko Corporation), one sheet of the outer layer (B5) was attached to each side of the core layer (A3) to obtain a laminate (8).

Example 9: Production of laminate (9) The prepreg (5) obtained in Production Example 5 was cut to a size of 290 mm x 212 mm. One of these sheets was placed in the center of a flat plate mold coated with a release agent, and compression molded under conditions of a pressure of 10 MPa, an upper mold temperature of 145°C, a lower mold temperature of 145°C, and a molding time of 3 minutes to obtain an outer layer (B5) of 300 mm x 220 mm x 1.5 mm. The flexural modulus of the outer layer (B5) measured in accordance with JIS K 7017 was 29 GPa.
A 20 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a foam of styrene beads with a flame retardant coating on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut to a size of 298 mm x 218 mm, and then filled into the center of a flat plate mold and compression molded under conditions of upper mold temperature 30°C, lower mold temperature 30°C, and molding time 5 minutes to obtain a core layer (A3) of 300 mm x 220 mm x 2 mm. The compression ratio in the thickness direction of the core layer (A3) was 80%, the specific gravity was 0.20 g/ ^m3 , and the aspect ratio of the foam cells calculated from the compression ratio was 5.
Using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko Corporation), one sheet of the outer layer (B5) was attached to each side of the core layer (A3) to obtain a laminate (9).

Comparative Example 1: Production of Laminate (1') A 2 mm thick polystyrene foam plate ("Varishield" manufactured by Ushiomatex Co., Ltd., a styrene bead foam with a flame retardant coated on the surface, density 0.04 g/ ^cm3 , expansion ratio 60 times) was cut into a size of 300 mm x 220 mm to form a core layer (A1').
The outer layers (B1) obtained in Example 1 were attached to both sides of the core layer (A1') one by one using a flame-retardant double-sided tape (No. 5011N, manufactured by Nitto Denko, thickness 0.15 mm) to obtain a laminate (1').

Evaluation of the thickness of the laminate The total thickness of the core layer (A) and the outer layer (B) (two layers) was evaluated as the thickness of the laminate. In this evaluation, the thickness of the double-sided tape used in the manufacturing process of the laminate was not included in the thickness of the laminate.

Measurement of specific gravity of laminate The specific gravity was evaluated by dividing the total weight of the core layer (A) and the outer layer (B) (two layers) by the volume of the laminate. Note that in this evaluation, the weight and volume of the double-sided tape used in the manufacturing process of the laminate were not included in the weight and volume of the laminate.

Evaluation of flame resistance Using a gas burner, the center of one side of the laminate was exposed to a flame, and the laminate was heated for 6 minutes by adjusting the position of the flame so that the temperature of the direct flame in contact with the laminate was 1000° C. The surface temperature of the center of the side of the laminate not heated by the direct flame was measured, and the maximum temperature during heating was used for evaluation.

Evaluation of Strength of Laminate The bending stiffness (D) was calculated as an index showing the strength of the laminate and evaluated.
The bending stiffness (D) was calculated from the following formula.
D=((E1×t1)×(E2×t2)×(T+tc) ² )/4λ(E1×t1+E2×t2)
Here, E is the flexural modulus [kN/ ^mm2 ] of the outer layer (B) (upper layer E1, lower layer E2), t is the thickness [mm] of the outer layer (B) (upper layer t1, lower layer t2), tc is the thickness [mm] of the core layer (A), and T is the thickness [mm] of the laminate. λ is calculated as 1-(Poisson's ratio) ² , with 0.99 used as the coefficient for anisotropic materials.
Steel plates with a strength exceeding 4.5 kN ^mm2 , which is the average value for the steel plates, were rated as A, and steel plates with a strength below this were rated as B.

Claims (6)

The foamed foam has a core layer (A) compressed in the thickness direction and an outer layer (B) made of a fiber-reinforced plastic,
The foam is a polyethylene resin bead foam having a flame retardant coating applied to its surface,
A laminate in which the compressibility of the core layer (A) is 40% or more in terms of thickness, and the aspect ratio of foam cells of the core layer (A), represented by the following formula, is 2 or more.
Aspect ratio = 1/[1 - compression ratio (%)/100] The laminate according to claim 1, wherein the outer layer (B) is obtained by hot molding a prepreg containing reinforcing fibers (f) and a matrix resin (r), and the matrix resin is a resin composition (1) containing a polyisocyanate compound (r1) and a polyhydroxy(meth)acrylate compound (r2), or a resin composition (2) containing a polyisocyanate compound (r1), a monohydroxy(meth)acrylate compound (r3), and a polyhydroxy compound (r4). The method for producing the laminate according to claim 1 or 2, in which a precursor in which a core layer (a) made of a foam and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin (r) are laminated is heated and molded under conditions in which the core layer (a) is compressed. 3. The method for producing a laminate according to claim 1 or 2, wherein a core layer (A) obtained by compressing a foam in a thickness direction and an outer layer (B) made of a fiber-reinforced plastic are bonded together using an adhesive to obtain a laminate including the core layer (A) and the outer layer (B). 3. The method for producing a laminate according to claim 1 or 2, wherein a precursor is obtained by laminating a core layer (A) obtained by compressing a foam in a thickness direction and an outer layer (b) made of a prepreg containing reinforcing fibers (f) and a matrix resin ( r), and the precursor is heated and molded to obtain a laminate including the core layer (A) and the outer layer (B) made of a fiber-reinforced plastic. A battery case using the laminate according to claim 1 or 2.