JP2015101670A - Foam resin sheet, fiber reinforced thermosetting resin composite formed body using the same, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam resin sheet for manufacturing fiber reinforced thermosetting resin composite formed body that is light in weight and has high rigidity, can easily form a three-dimensional formed article and has an excellent surface quality, and to provide a fiber reinforced thermosetting resin composite formed body by using the foam resin sheet, and a manufacturing method thereof.SOLUTION: The problem is solved by blending, into a thermosetting resin composition, a thickening particle that increases the viscosity of the thermosetting resin composition by being heated to a predetermined temperature as well as by blending a foam particle that foams the thermosetting resin composition by expanding at a predetermined temperature.

Description

  The present invention relates to a foamed resin sheet, a fiber-reinforced thermosetting resin composite molded body using the foamed resin sheet, and a method for producing the same.

  In recent years, fiber reinforced resin composite materials have been adopted for OA equipment, personal computer casings, automobile interiors and outer panels in terms of light weight, high strength, and high rigidity. In addition, sandwich molded bodies in which a honeycomb structure or a lightweight foam material is sandwiched between fiber reinforced resin layers are extremely lightweight and highly rigid, and therefore their applications are expanding rapidly. Such a molded body is formed by thinly slicing an acrylic resin foam material, a polypropylene resin foam material, a urethane resin foam material, etc. to form a core layer, and a prepreg impregnated with a thermosetting resin on the surface of the core layer. It is used to form a skin layer, which is molded by a hot press molding method or an autoclave method (Patent Document 1).

  However, since these core layers are used by thinly slicing them from the foamed material, there is a problem that time and cost are required for slicing. Further, since the foam material does not follow the three-dimensional shape, the foam material is cut to produce a three-dimensional shape. Therefore, the yield of the material is poor and the processing cost is quite expensive (Patent Document 1).

  In Patent Documents 2 and 3, the production of a fiber-reinforced thermosetting resin sandwich molded body that uses a foamable resin and a liquid molding resin and simultaneously molds a foam core and a surface layer portion made of a resin containing a fibrous reinforcing material. A method is disclosed. In this method, a molded article having a three-dimensional shape can be obtained efficiently. However, when the foamable resin is foamed, the viscosity of the matrix resin is low, and the resin flows by entraining bubbles. Therefore, many voids are formed on the surface of the sandwich molded body, and there is a problem that the surface appearance is inferior.

  Patent Document 4 discloses a carbon fiber reinforced thermoplastic resin sandwich molded body obtained by expanding a foamed particle in a thermoplastic resin layer after obtaining a thermoplastic resin layer containing unfoamed foamed particles. However, since the matrix resin is a thermoplastic resin, the molding temperature is high and the molding equipment is expensive.

International Publication No. 2006/028107 Pamphlet JP-A-4-27532 JP-A-6-143441 JP 2012-196899 A

  The conventional method of obtaining a core material by thinly slicing a foam material and the method of obtaining a three-dimensional core material by cutting a foam material have a poor material yield and a considerably high processing cost. This technique is not suitable for manufacturing a low-cost FRP composite molded body. Moreover, the surface appearance of the molded product was insufficient in the method using a foamable resin and a liquid molding resin.

  An object of the present invention is to provide a foamed resin sheet used for manufacturing a fiber-reinforced thermosetting resin composite molded body that is lightweight and highly rigid, can easily form a three-dimensional shape, and has excellent surface quality. is there. Furthermore, the other subject of this invention is providing the fiber reinforced thermosetting resin composite molded object produced using this foamed resin sheet, and its manufacturing method.

  The inventor mixes a thickening resin that increases the viscosity of the thermosetting resin composition by heating to a predetermined temperature in the thermosetting resin composition, and expands by heating to the predetermined temperature. Thus, the present inventors have found that the above problems can be solved by blending foamed particles for foaming the thermosetting resin composition, and have completed the present invention.

  The present invention for solving the above problems is as follows.

[1] a thermosetting resin composition comprising an epoxy resin and a curing agent;
A thickening resin that increases the viscosity of the thermosetting resin composition by heating to a temperature equal to or higher than the thickening start temperature;
Foamed particles for foaming the thermosetting resin composition by heating to a temperature equal to or higher than the foaming start temperature;
A foamed resin sheet comprising:
The foamed resin sheet, wherein the foaming start temperature is higher than the thickening start temperature.

  The invention [1] includes the following inventions [2] to [5].

  [2] The foamed resin sheet according to [1], wherein a foaming start temperature of the foamed particles is 90 to 140 ° C.

  [3] The foamed resin sheet according to [1], wherein the thickening resin is polymethyl methacrylate.

  [4] The foamed resin sheet according to [1], wherein the thickening resin is a curing agent that starts curing at a lower temperature than the curing agent.

  [5] The foamed resin sheet according to [1], wherein a reinforcing fiber base is provided in the foamed resin sheet.

  The invention [5] includes the following inventions [6] to [7].

  [6] The foamed resin sheet according to [5], wherein the reinforcing fiber base is made of organic fibers.

  [7] The foamed resin sheet according to [5], wherein the reinforcing fiber base is made of inorganic fibers.

[8] A foamed core layer formed by foaming the foamed resin sheet according to [1];
A skin layer made of a fiber reinforced thermosetting resin, formed on at least one surface of the foam core layer;
A fiber-reinforced thermosetting resin composite molded body having a density of 0.4 to 1.0 g / cm ³ .

[9] The foamed resin sheet according to [1],
A prepreg for skin layer preparation that obtains the fiber-reinforced thermosetting resin by heating to a temperature equal to or higher than the curing start temperature;
Placed in the mold,
The fiber-reinforced heat according to [8], wherein the foamed resin sheet is foamed by heating to a temperature 20 to 80 ° C. higher than the foaming start temperature, and the prepreg for preparing the skin layer is cured. A method for producing a curable resin composite molded article.

  [10] The method for producing a fiber-reinforced thermosetting resin composite molded article according to [9], wherein the skin layer-preparing prepreg contains polymethyl methacrylate.

  The foamed resin sheet of the present invention is suitably used to obtain a high-quality FRP composite molded body that is foamed and cured in a short time during high-temperature press molding to suppress poor appearance and poor performance. When the foamed resin sheet of the present invention is used, a highly accurate FRP composite molded body can be obtained under low pressure conditions. Therefore, the surface quality of the FRP composite molded body is excellent, and it can be applied to parts that require design.

1 (a) to 1 (b) in FIG. 1 are explanatory views schematically showing the foamed resin sheet of the present invention. 2 (a) to 2 (b) in FIG. 2 are explanatory views schematically showing a molding process of the FRP composite molded body of the present invention.

1. Foamed resin sheet The foamed resin sheet of the present invention is
A thermosetting resin composition comprising an epoxy resin and a curing agent;
A thickening resin;
Unfoamed expanded particles,
Comprising.

  Unexpanded expanded particles expand by being heated to a temperature higher than the foaming start temperature, and foam the thermosetting resin composition constituting the expanded resin sheet. When the thickening resin is heated above the thickening start temperature, the viscosity of the thermosetting resin composition is increased to maintain the form of the foamed resin sheet, and the bubbles formed by foaming of the foamed particles are foamed resin. Suppresses movement to the surface of the sheet. As a result, the foamed resin sheet in which the expanded particles are expanded has an apparent volume. The foamed resin sheet of the present invention contains foamed particles in an unfoamed state, but part of the foamed particles may start to foam.

  The thermosetting resin composition containing the thickening resin is thickened by heating to 30 to 130 ° C. In the foamed resin sheet of the present invention, it is preferable that the foamed particles are in an unfoamed state and the thermosetting resin composition is thickened by the thickening resin.

  Fig.1 (a)-1 (b) is explanatory drawing which shows typically the foamed resin sheet of this invention. 1 (a) and 1 (b), reference numeral 100 denotes an unfoamed foamed resin sheet, which includes a thermosetting resin composition 51 and unfoamed foamed particles 53. When the foamed particle 53 is heated to a temperature higher than the foaming start temperature of the foamed particle 53, the foamed particle 53 becomes the foamed foamed particle 53a. Thereby, as shown in FIG.1 (b), the apparent volume of the foamed resin sheet 100 increases, and it becomes the foamed foamed resin sheet 101. FIG. This foamed foamed resin sheet 101 constitutes a core layer of an FRP composite molded body described later.

1-1. Thermosetting resin composition In the present invention, the thermosetting resin composition is a resin composition containing an epoxy resin and a curing agent.

1-1-1. Epoxy resin The epoxy resin used in the present invention is not particularly limited, but bisphenol type epoxy resin, alcohol type epoxy resin, biphenyl type epoxy resin, hydrophthalic acid type epoxy resin, dimer acid type epoxy resin, alicyclic epoxy resin, etc. Bifunctional epoxy resin; glycidyl ether type epoxy resin such as tetrakis (glycidyloxyphenyl) ethane, tris (glycidyloxyphenyl) methane; glycidylamine type epoxy resin such as tetraglycidyldiaminodiphenylmethane; naphthalene type epoxy resin; novolak type Examples thereof include phenol novolac type epoxy resins which are epoxy resins; cresol novolac type epoxy resins.

  Furthermore, polyfunctional epoxy resins, such as a phenol type epoxy resin, etc. are mentioned. Furthermore, various modified epoxy resins such as urethane-modified epoxy resin and rubber-modified epoxy resin can also be used.

  Especially, it is preferable to use the epoxy resin which has an aromatic group in a molecule | numerator, and the epoxy resin which has either a glycidylamine structure or a glycidyl ether structure is more preferable. Moreover, an alicyclic epoxy resin can also be used suitably.

  Examples of the epoxy resin having a glycidylamine structure include N, N, N ′, N′-tetraglycidyldiaminodiphenylmethane, N, N, O-triglycidyl-p-aminophenol, N, N, O-triglycidyl-m-. Various isomers of aminophenol, N, N, O-triglycidyl-3-methyl-4-aminophenol, and triglycidylaminocresol are exemplified.

  Examples of the epoxy resin having a glycidyl ether structure include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins.

  These epoxy resins may have a non-reactive substituent in the aromatic ring structure or the like as necessary. Examples of non-reactive substituents include alkyl groups such as methyl, ethyl and isopropyl, aromatic groups such as phenyl, alkoxyl groups, aralkyl groups, and halogen groups such as chlorine and bromine.

  Examples of the bisphenol type epoxy resin include bisphenol A type resin, bisphenol F type resin, bisphenol AD type resin, bisphenol S type resin and the like. Specifically, jER815 (trade name), jER828 (trade name), jER834 (trade name), jER1001 (trade name), jER807 (trade name), and Mitsui Petrochemical's Epomic R-710 manufactured by Mitsubishi Chemical Corporation. (Trade name), Dainippon Ink and Chemicals EXA1514 (trade name), and the like are exemplified.

  Examples of the alicyclic epoxy resin include Araldite CY-179 (trade name), CY-178 (trade name), CY-182 (trade name), and CY-183 (trade name) manufactured by Huntsman. .

  Examples of the phenol novolac type epoxy resin include jER152 (trade name), jER154 (trade name) manufactured by Mitsubishi Chemical Corporation, DEN431 (trade name), DEN485 (trade name), DEN438 (trade name), and DIC manufactured by Dow Chemical. As cresol novolac type epoxy resins such as Epicron N740 (trade name) manufactured by Huntsman, Araldite ECN1235 (trade name), ECN1273 (trade name), ECN1280 (trade name), Nippon Kayaku EOCN102 (trade name), EOCN103 (Product name), EOCN104 (Product name), etc. are exemplified.

  Examples of the various modified epoxy resins include Adeka Resin EPU-6 (trade name) and EPU-4 (trade name) manufactured by Asahi Denka as urethane-modified bisphenol A epoxy resins.

  These epoxy resins can be appropriately selected and used alone or in combination. Among these, bifunctional epoxy resins represented by bisphenol type include various grades of resins from liquid to solid depending on the difference in molecular weight. Therefore, these resins are conveniently blended for the purpose of adjusting the viscosity of the thermosetting resin composition.

1-1-2. Curing Agent Examples of the curing agent used in the present invention include dicyandiamide, various isomers of aromatic amine curing agents, and imidazole compounds. From the viewpoint of excellent curability and physical properties after curing, dicyandiamide (DICY) and an imidazole compound which are amide-based curing agents are preferable.

  Specific examples of dicyandiamide (DICY) include jER cure DICY7 and DICY15 manufactured by Mitsubishi Chemical Corporation.

  Moreover, when using DICY, it is more preferable to use together with a urea type hardening | curing agent. DICY is not very soluble in epoxy resin and needs to be heated to a high temperature of 160 ° C. or higher for sufficient dissolution, but the dissolution temperature can be lowered by using it together with a urea-based curing agent. .

  Examples of urea-based curing agents include phenyldimethylurea (PDMU) and toluenebisdimethylurea (TBDMU).

  The usage-amount of the hardening | curing agent in a thermosetting resin composition is 5-30 mass parts with respect to 100 mass parts of epoxy resins. If the usage-amount of a hardening | curing agent is 5 mass parts or more, a crosslinking density will become enough and sufficient hardening speed will be obtained. If the epoxy curing agent is 30 parts by mass or less, problems such as a decrease in mechanical properties of the cured resin and turbidity of the cured resin due to the excessive presence of the curing agent can be suppressed.

  When using DICY and a urea-type curing agent (PDMU, TBDMU, etc.) together as an epoxy curing agent, the amount of use is 4 to 15 parts by mass of DICY and 100% of urea-based curing agent for 100 parts by mass of the epoxy resin. It is preferably 3 to 10 parts by mass (however, the total amount of DICY and urea-based curing agent is 7 to 20 parts by mass).

  Examples of imidazole compounds include 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-paratoluyl Such as -4-methyl-5-hydroxymethylimidazole, 2-methatoruyl-4-methyl-5-hydroxymethylimidazole, 2-methatoruyl-4,5-dihydroxymethylimidazole, 2-paratoluyl-4,5-dihydroxymethylimidazole, etc. Examples include imidazole compounds in which hydrogen at the 5-position of 1H-imidazole is substituted with a hydroxymethyl group, and hydrogen at the 2-position is substituted with a phenyl group or a toluyl group. Among these, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-paratoluyl-4-methyl-5-hydroxymethylimidazole, 2-methatoruyl-4-methyl -5-Hydroxymethylimidazole, 2-methatoruyl-4,5-dihydroxymethylimidazole, and 2-paratoluyl-4,5-dihydroxymethylimidazole are more preferable.

  Further, 1- (2-hydroxy-3-phenoxypropyl) -2-methylimidazole and adduct compounds obtained by reacting glycidyl ether type epoxy resin with 2-methylimidazole can be mentioned. Among them, an adduct compound obtained by reacting an aryl glycidyl ether type epoxy resin with 2-methylimidazole is preferable because the properties of the cured product of the resin composition can be improved. When using an imidazole compound as a hardening | curing agent, it is preferable that an imidazole compound is 2-30 mass parts with respect to 100 mass parts of epoxy resins, and it is preferable that it is 3-15 mass parts.

1-2. Thickening resin The thickening resin used in the present invention is blended in the thermosetting resin composition and heated to a temperature higher than the thickening start temperature to dissolve or swell and react in the thermosetting resin composition. Increase viscosity. Examples of the thickening resin include thickening particles made of polymethylmethacrylate and the like, and a curing agent that starts curing at a lower temperature than the curing agent.

1-2-1. Thickened particles Examples of the thickened particles used in the present invention include particles obtained by copolymerizing one or more unsaturated compounds and a crosslinkable monomer. Although not particularly limited, it is desirable to include a resin having a monomer unit of at least one of an acrylic ester compound, a methacrylic ester compound, and a vinyl compound.

  The acrylate ester compound used for the thickening particles refers to a compound having an acrylate structure and derivatives thereof, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, Examples thereof include sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate and the like.

  The methacrylic acid ester compound used for the thickening particles refers to a compound having a methacrylic acid ester structure and a derivative thereof, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, n-hexyl methacrylate. And cyclohexyl methacrylate.

  The vinyl compound used for the thickening particles refers to a compound having a polymerizable vinyl structure. For example, styrene, α-methylstyrene, divinylbenzene, and these aromatic rings are various functional groups such as alkyl groups and halogen atoms. Examples include substituted compounds.

  Further, the thickening particles may be a polymer composed of one kind or plural kinds of polymerization units of a methacrylic ester compound, an acrylic ester compound and a vinyl compound, and a plurality of kinds of resins having different structures are mixed. Resin may be used. Furthermore, (1) a polymer comprising at least one of an acrylate ester compound, a methacrylic ester compound, and a diene compound, and (2) an acrylic ester compound or a methacrylic ester compound and a radical polymerizable unsaturated compound. (3) A composite resin that is ion-crosslinked by adding metal ions to a polymer composed of a carboxylic acid.

  As the thickening particles, commercially available products made of polymethylmethacrylate having no core-shell structure, such as Zefiac F325 and Zefiac F320 (both manufactured by Aika Industry Co., Ltd.) can also be used. Polymethyl methacrylate having a core-shell structure is not preferable because it hardly swells in the thermosetting resin composition and has a low effect of increasing the viscosity.

  The particle diameter of the thickening particles is not particularly limited, but the average particle diameter is preferably 0.3 to 10 μm, and preferably 0.5 to 8 μm. The thickening particles swell to 1 to 50 μm by heating. The content of the thickening particles is preferably 5 to 40 parts by mass with respect to 100 parts by mass of the epoxy resin, more preferably 6 to 30 parts by mass, and particularly preferably 8 to 20 parts by mass. .

1-2-2. Low-temperature curing agent As the curing agent used as the thickening resin in the present invention, among the above-mentioned curing agents, a curing agent that starts curing at a lower temperature than the curing agent blended in the thermosetting resin composition (hereinafter referred to as “low temperature”). It is also referred to as “curing agent”. Examples include aliphatic amines, alicyclic amines, modified aliphatic amines, modified alicyclic amines, aromatic amines, polyamide amines, mercaptans, acid anhydrides, tertiary amine catalysts, latent curing agents, and the like. Although it will not specifically limit if it is a hardening | curing agent which reacts at low temperature rather than the above-mentioned hardening | curing agent, An aliphatic amine, an alicyclic amine, a modified aliphatic amine, a modified alicyclic amine, and a tertiary amine catalyst are preferable.

  1-15 mass parts is preferable with respect to 100 mass parts of epoxy resins, and, as for content of a low temperature hardening | curing agent, 1-10 mass parts is more preferable.

1-3. Expanded particle The expanded particle used in the present invention is a thermally expandable expanded particle in which the expanded particle expands when heated to the foaming start temperature or higher. The expanded particles are preferably expanded particles of thermally expandable microcapsules. Examples of the expanded particles of the thermally expandable microcapsule include thermally expandable thermoplastic polymer particles containing a foaming agent composed of a volatile liquid. It is particularly preferable for the purpose of the present invention that the particles are fine particles.

  The volatile liquid blowing agent is not particularly limited, but ethane, ethylene, propane, propylene, butane, butene, isobutene, n-pentane, neopentane, hexane, heptane and other aliphatic hydrocarbons, dichlorotetrafluoroethane, Various halogenated aliphatic hydrocarbons such as 1,1-dichlorodifluoroethylene can be used. The expanded particles are not limited to a solid, and may be fine droplets of a volatile liquid dispersed in a resin composition.

  Commercially available products are “Matsumoto Microsphere (registered trademark)” manufactured by Matsumoto Yushi Seiyaku Co., Ltd. and “EXPANCEL (registered trademark)” manufactured by Nippon Philite.

  Content of the expanded particle in a foamed resin sheet is 5-20 mass%, and 7-15 mass% is preferable. The foaming start temperature of the foamed particles is usually 90 to 140 ° C, and preferably 90 to 130 ° C.

1-4. Reinforcing fiber base material provided in the foamed resin sheet The foamed resin sheet of the present invention preferably has a reinforcing fiber base material provided for the purpose of improving strength and rigidity. The reinforcing fiber substrate is composed of organic fibers such as aromatic polyamide fibers, aromatic polyester fibers, and high-strength polyethylene fibers; inorganic fibers such as carbon fibers, graphite fibers, glass fibers, alumina fibers, and boron fibers. It is preferable. These reinforcing fiber base materials can be used in the form of a woven fabric, a knitted fabric, a braid, a non-woven sheet.

The thickness of the reinforcing fiber substrate is not particularly limited, and is appropriately adjusted according to the thickness and use of the foamed resin sheet. The content of the reinforcing fiber substrate to be provided inside the foamed resin sheet is preferably ^{30~500g / m 2, 30~300g / m} 2 is more preferable. In this range, the handleability of the foamed resin sheet is high.

1-5. Other Additives In the present invention, the thermosetting resin composition may contain a phosphorus-based flame retardant as a flame retardant. The phosphorus-based flame retardant is not particularly limited as long as it contains a phosphorus atom in the molecule, and examples thereof include organic phosphorus compounds such as phosphate esters, condensed phosphate esters, phosphazene compounds, and polyphosphates, and red phosphorus. Can be mentioned.

  Phosphate ester refers to an ester compound of phosphoric acid and an alcohol compound or a phenol compound. In the present invention, flame retardancy can be imparted to the fiber-reinforced composite material by blending a phosphate ester.

  Specific examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri (2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris (isopropylphenyl) Phosphate, tris (phenylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl (2-ethylhexyl) phosphate, di (isopropylphenyl) phenyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl Acid phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl 2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, melamine phosphate, dimelamine phosphate, melamine pyrophosphate, triphenylphosphine oxide, tricresylphosphine oxide, diphenyl methanephosphonate, diethyl phenylphosphonate, resorcinol poly Mention may be made of condensed phosphates such as phenyl phosphate, resorcinol poly (di-2,6-xylyl) phosphate, bisphenol A polycresyl phosphate, hydroquinone poly (2,6-xylyl) phosphate and condensates thereof.

  Examples of the condensed phosphate ester include resorcinol bis (di2,6-xylyl) phosphate, resorcinol bis (diphenyl phosphate), bisphenol A bis (diphenyl phosphate), and the like. As a commercial product of resorcinol bis (di2,6-xylyl) phosphate, PX-200 (manufactured by Daihachi Chemical Industry Co., Ltd.) can be mentioned. Examples of commercially available resorcinol bis (diphenyl phosphate) include CR-733S (manufactured by Daihachi Chemical Industry Co., Ltd.). Examples of commercially available products of bisphenol A bis (diphenyl phosphate) include CR-741 (manufactured by Daihachi Chemical Industry Co., Ltd.). Among these, resorcinol bis (di2,6-xylyl) phosphate is preferably used from the viewpoint of excellent curability and heat resistance.

  The phosphazene compound can impart flame retardancy to FRP by containing a phosphorus atom and a nitrogen atom in the molecule. The phosphazene compound is not particularly limited as long as it does not contain a halogen atom and has a phosphazene structure in the molecule. Commercially available phosphazene compounds include SPR-100, SA-100, SPB-100, SPB-100L (above, manufactured by Otsuka Chemical Co., Ltd.), FP-100, FP-110 (above, manufactured by Fushimi Pharmaceutical). Can be mentioned.

  The flame retardant effect of phosphorus atoms is considered to be due to the promoting effect of phosphorus carbide formation, and is affected by the phosphorus atom content in the thermosetting resin composition. In this invention, it is preferable that the content rate of the phosphorus atom in a thermosetting resin composition is 1.2-4.0 mass%, and it is further more preferable that it is 1.4-4.0 mass%. When the phosphorus atom content is less than 1.2% by mass, the flame retardant effect may not be sufficiently obtained. When it exceeds 4.0% by mass, the heat resistance and mechanical properties of FRP, particularly the rigidity and Charpy impact The value may decrease. The phosphorus content (mass%) here is determined by the mass of phosphorus atoms (g) / the mass of the total resin composition (g) × 100. The phosphorus atom content in the thermosetting resin composition can be obtained by the above-described calculation method, or by organic element analysis of the thermosetting resin composition or FRP, ICP-MS (inductively coupled plasma mass spectrometry), or the like. You can ask for it.

  Among the phosphorus-based flame retardants, a phosphoric ester and a phosphazene compound are preferably used since the handleability is good and a transparent resin cured product is obtained.

1-6. Method for Producing Foamed Resin Sheet The foamed resin sheet of the present invention is obtained by forming a sheet of a mixture of a thermosetting resin composition containing an epoxy resin and a curing agent, a thickening resin, and unfoamed foam particles. Can be manufactured.

  First, an epoxy resin, a curing agent, unfoamed expanded particles, and a thickening resin are kneaded at a predetermined temperature to prepare a resin composition.

  When thickening particles are used as the thickening resin, the temperature during kneading is preferably 40 to 120 ° C, more preferably 50 to 100 ° C, and particularly preferably 50 to 90 ° C. When exceeding 120 degreeC, the curing reaction of an epoxy resin and a hardening | curing agent may advance, and the storage stability of the foamed resin sheet obtained may fall. When it is less than 40 ° C., the viscosity of the resin composition is high, and it may be difficult to knead substantially.

  When a low-temperature curing agent is used as the thickening resin, the temperature during kneading is preferably 30 to 80 ° C, more preferably 30 to 70 ° C. When it exceeds 80 degreeC, hardening reaction of an epoxy resin and a hardening | curing agent may advance, and the storage stability of the foamed resin sheet obtained may fall. When it is less than 30 ° C., the viscosity of the resin composition is high, and it may be difficult to knead substantially.

  The kneading needs to be performed under the condition that the expanded particles do not start expansion, and is preferably performed at a temperature lower by 5 ° C. or more than the expansion start temperature of the expanded particles, and more preferably performed at a temperature lower by 10 ° C. or more.

  Kneading can be performed using a conventionally known apparatus. Specific examples include a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing vessel provided with a stirring blade, and a horizontal mixing vessel. Each component can be kneaded in the air or in an inert gas atmosphere. When kneading is performed in the air, an atmosphere in which temperature and humidity are controlled is preferable.

  The resin mixture thus obtained is processed into a sheet by a known method. The sheet processing method is not particularly limited, and any conventionally known method can be adopted. Specifically, a hot melt method can be suitably employed. The hot melt method is a method for producing a resin sheet by applying a resin mixture in a thin film form on a support such as release paper or release film. The method for applying the resin mixture in the form of a film is not particularly limited, and any conventionally known method can be used. Specifically, a foamed resin sheet can be produced by casting and casting a resin mixture on a support using a die extrusion, an applicator, a reverse roll coater, a comma coater, or the like. The temperature of the resin mixture at the time of producing the foamed resin sheet is appropriately determined according to the composition of the resin mixture, the viscosity, and the foaming start temperature of the foamed particles.

Although the resin amount of the foamed resin sheet is not particularly defined, it is preferably 100 to 2000 g / m ² , and more preferably 100 to 1000 g / m ² in order to improve the handleability.

  When producing a foamed resin sheet in which a reinforcing fiber base is installed, the resin sheet prepared above is laminated on the reinforcing fiber base and heated under pressure to impregnate the reinforcing fiber base with the resin mixture. It is manufactured by.

  The foamed resin sheet of the present invention preferably thickens the resin mixture after sheet processing. Heating is preferred as a method for thickening. The heating temperature is equal to or higher than the temperature at which the thickening resin swells, dissolves and reacts (thickening start temperature) and is lower than the foaming start temperature of the foamed particles, and is 5 ° C. or more lower than the foaming start temperature of the foamed particles. It is preferable that the temperature is lower by 10 ° C. or more.

1-7. Method for Using Foamed Resin Sheet In the foamed resin sheet of the present invention, the foamed particles expand in the sheet by heating to a temperature equal to or higher than the foaming start temperature of the foamed particles. Since the resin in the foamed resin sheet is thickened by the thickening particles, the foamed particles that have expanded in the sheet remain inside the sheet and are difficult to separate out of the sheet. Therefore, when the foamed resin sheet is heated to the foaming start temperature or higher, the apparent volume increases. The apparent volume of the foamed resin sheet after foaming is preferably 1.5 to 10 times that of the foamed resin sheet before foaming, and more preferably 2 to 5 times.

  The foamed resin sheet of the present invention can produce an FRP composite molded body having a foamed core layer at the core by forming a skin layer made of a fiber reinforced thermosetting resin (FRP) on the surface thereof.

2. FRP composite molded article The FRP composite molded article of the present invention comprises a foam core layer formed by foaming the foamed resin sheet, and a skin layer made of FRP formed on at least one surface of the foam core layer. . A skin layer made of FRP is usually produced using a prepreg for producing a skin layer.

2-1. Skin Layer Preparation Prepreg In the present invention, the skin layer preparation prepreg is not particularly limited, and a conventionally known prepreg can be used. In particular, a prepreg for press molding that can be cured in a short time during high-temperature press molding and the resin flow is controlled is preferable. Hereinafter, a preferred prepreg for preparing a skin layer will be described.

  The prepreg for skin layer preparation is composed of a reinforcing fiber substrate and an epoxy resin composition [A]. The epoxy resin composition [A] is partly or wholly impregnated in the reinforcing fiber base material and integrated with the reinforcing fiber base material. The epoxy resin composition [A] includes an epoxy resin, a curing agent, and thickening particles.

  The prepreg for preparing the skin layer uses a resin composition having a low original viscosity, and the viscosity of the resin composition is increased by using thickening particles in a predetermined temperature range. Therefore, a region (temperature zone) in which the viscosity change of the epoxy resin composition [A] is moderate is formed, and high resin impregnation property can be obtained by press molding in the region, and the prepreg for skin layer preparation Resin flow from the inside can be suppressed. As a result, FRP produced using a prepreg is unlikely to cause molding defects such as resin wilt. On the other hand, in the case of a method of appropriately selecting an epoxy resin to be used and increasing the viscosity of the resin composition itself, or a conventional method of increasing the viscosity of the resin composition using a thixotropic agent or the like, The viscosity increases overall. In this case, the resin flow can be suppressed, but the impregnation property of the resin composition is lowered. As a result, the prepreg produced using the resin composition having an increased viscosity in this way has many unimpregnated portions of the resin, and the FRP produced using the prepreg has many voids.

  The content (RC) of the epoxy resin composition [A] is preferably 15 to 60% by mass, more preferably 20 to 50% by mass based on the total mass of the prepreg for skin layer preparation, It is especially preferable that it is 25-45 mass%. When the content is less than 15% by mass, voids and the like are generated in the obtained fiber-reinforced composite material, and mechanical properties and the like may be deteriorated. When the content exceeds 60% by mass, the reinforcing effect by the reinforcing fibers becomes insufficient, and the mechanical properties and the like may be deteriorated.

  Here, the content (RC) of the epoxy resin composition is determined by immersing the prepreg in sulfuric acid and eluting the resin composition impregnated in the prepreg. Specifically, it is obtained by the following method.

  First, a prepreg is cut out to 100 mm × 100 mm to produce a test piece, and its mass is measured. Next, this prepreg test piece is immersed in sulfuric acid and boiled as necessary. Thereby, the resin impregnated in the prepreg is decomposed and eluted in sulfuric acid. Thereafter, the remaining fibers are filtered off, washed with sulfuric acid, dried, and the mass of the fibers is measured. The content rate of the epoxy resin composition [A] is calculated from the mass change before and after the decomposition operation with sulfuric acid.

  The form of the prepreg for preparing the skin layer is as follows: a reinforcing fiber layer comprising a reinforcing fiber and an epoxy resin composition [A] impregnated between the reinforcing fibers, and a resin coating layer coated on the surface of the reinforcing fiber layer. Preferably it consists of. The thickness of the resin coating layer is preferably 2 to 50 μm. When the thickness of the resin coating layer is less than 2 μm, the tackiness becomes insufficient, and the molding processability of the prepreg may be significantly lowered. When the thickness of the resin coating layer exceeds 50 μm, it is difficult to wind the prepreg into a roll with a uniform thickness, and the molding accuracy may be significantly reduced. The thickness of the resin coating layer is more preferably 5 to 45 μm, and particularly preferably 10 to 40 μm.

2-1-2. Reinforced fiber substrate Reinforced fiber substrate includes carbon fiber, glass fiber, aramid fiber, silicon carbide fiber, polyester fiber, ceramic fiber, alumina fiber, boron fiber, metal fiber, mineral fiber, rock fiber and slug fiber. Examples are materials. Among these reinforcing fibers, carbon fibers, glass fibers, and aramid fibers are preferable. Carbon fiber is more preferable in that it has good specific strength and specific elastic modulus, and provides a lightweight and high-strength FRP. Polyacrylonitrile (PAN) -based carbon fibers are particularly preferable in terms of excellent tensile strength.

  When PAN-based carbon fiber is used as the reinforcing fiber, the tensile elastic modulus is preferably 100 to 600 GPa, more preferably 200 to 500 GPa, and particularly preferably 230 to 450 GPa. The tensile strength is 2000 to 10000 MPa, preferably 3000 to 8000 MPa. The diameter of the carbon fiber is preferably 4 to 20 μm, and more preferably 5 to 10 μm. By using such a carbon fiber, the mechanical properties of the obtained FRP can be improved.

  The reinforcing fiber substrate is preferably used in the form of a sheet. Examples of the reinforcing fiber base sheet include, for example, a sheet in which a large number of reinforcing fibers are aligned in one direction, bi-directional woven fabrics such as plain weave and twill weave, multiaxial woven fabric, non-woven fabric, mat, knit, braid, and reinforcing fibers. And the like.

In general, multiaxial woven fabric is a sheet of a bundle of reinforcing fibers aligned in one direction and laminated at different angles (multiaxial woven fabric substrate) such as nylon yarn, polyester yarn, glass fiber yarn, etc. It refers to a woven fabric that is stitched through the laminated body in the thickness direction with a stitch yarn and reciprocated along the surface direction between the front surface and the back surface of the laminated body. In the case of a multiaxial woven fabric, a carbon fiber bundle of 400 to 2000 TEX is preferably used and woven so that the fiber weight between each layer is 50 to 1000 g / m ² .

  Examples of preferred carbon fiber multiaxial fabrics include [+ 45 / −45], [−45 / + 45], [0/90], [0 / + 45 / −45], [0 / −45 / + 45], [ 0 / + 45/90 / −45] and the like. 0, ± 45, 90 represents the lamination angle of each layer constituting the multiaxial woven fabric, and the fiber axis directions of the reinforcing fibers aligned in one direction are 0 °, ± 45 ° with respect to the length direction of the woven fabric. , 90 °. The stacking angle is not limited to these angles, and can be any angle.

  The thickness of the sheet-like reinforcing fiber base is preferably 0.01 to 3 mm, and more preferably 0.1 to 1.5 mm. These reinforcing fiber bases may contain a known sizing agent in a known content.

2-1-3. Epoxy resin composition [A]
The epoxy resin composition [A] of the prepreg for skin layer preparation comprises an epoxy resin, a curing agent, and thickening particles. The types and amounts of these components are as described in the above (1-1-1), (1-1-2), and (1-2-1). As the thickening particles used in the present invention, polymethyl methacrylate is preferable, and commercially available products made of polymethyl methacrylate having no core-shell structure, such as Zefiac F325 and Zefiac F320 (both are Aika Industry Co., Ltd.), should be used. You can also.

2-1-4. Production method of epoxy resin composition [A] The epoxy resin composition [A] can be produced by mixing an epoxy resin, a curing agent, and thickening particles.

  The method for producing the epoxy resin composition [A] is not particularly limited, and any conventionally known method may be used. Examples of the kneading temperature include a range of 40 to 120 ° C. When the temperature exceeds 120 ° C., the curing reaction partially proceeds, and the storage stability of the resulting resin composition and the prepreg produced using the resin composition may decrease. When the temperature is lower than 40 ° C., the viscosity of the epoxy resin composition is high, and it may be difficult to knead substantially. Preferably it is 50-100 degreeC, More preferably, it is the range of 50-90 degreeC.

  As a kneading apparatus, the same apparatus as described in the method for producing a (1-6) foamed resin sheet can be used.

2-1-5. Manufacturing method of prepreg for skin layer preparation The manufacturing method of the prepreg for skin layer preparation of this invention does not have a restriction | limiting in particular, Any conventionally well-known method is employable. Specifically, the solvent method and the above-described hot melt method can be suitably employed.

  The impregnation temperature when the reinforcing fiber base material is impregnated with the epoxy resin composition [A] by the hot melt method is preferably in the range of 50 to 120 ° C. When the impregnation temperature is less than 50 ° C., the epoxy resin composition [A] has a high viscosity and may not be sufficiently impregnated into the reinforcing fiber base. When the impregnation temperature is 120 ° C. or higher, the curing reaction of the epoxy resin composition [A] proceeds, and the storage stability of the resulting prepreg may be reduced, or the drapeability may be reduced. The impregnation temperature is more preferably 60 to 110 ° C, particularly preferably 70 to 100 ° C.

  The impregnation pressure when the reinforcing fiber base material is impregnated with the resin sheet of the epoxy resin composition by the hot melt method is appropriately determined in consideration of the viscosity and the resin flow of the resin composition.

2-2. Manufacturing method of FRP composite molded body The FRP composite molded body of the present invention is obtained by laminating a prepreg for preparing a skin layer on one side or both sides of an unfoamed foamed resin sheet, and heating the foamed particles in the foamed resin sheet. And the prepreg for preparing the skin layer is cured. That is,
(I) After obtaining a foamed resin sheet containing unfoamed foamed particles,
(Ii) Laminating a prepreg for preparing a skin layer on one or both sides of a foamed resin sheet,
(Iii) Place in the mold and expand the expanded particles in the expanded resin sheet by heating to a temperature 20 to 80 ° C. higher than the expansion start temperature of the expanded particles,
(Iv) A method of molding by integrally heat-curing the prepreg for preparing the skin layer and the epoxy resin of the foamed resin sheet.

  2 (a) to 2 (b) are explanatory views schematically showing a molding process of the FRP composite molded body of the present invention. 2A and 2B, reference numeral 50 denotes a foamed resin sheet, which includes a resin composition 51 and unfoamed foam particles 53. 55a and 55b are prepregs for preparing the skin layer, and are laminated on both surfaces of the foamed resin sheet 50. When the foamed resin sheet 50 and the prepregs 55a and 55b for skin layer preparation disposed in the molds 57a and 57b are heated to a temperature higher than the foaming start temperature of the foamed particles 53, the foamed particles 53 expand and 53a (foamed) Finished foamed particles). As a result, as shown in FIG. 2B, the foamed resin sheet 50 increases its apparent volume to become the foamed resin sheet 52, and the prepregs 55a and 55b for skin layer preparation are deformed along the mold. . Further, by heating the foamed resin sheet 50 and the prepregs 55a and 55b for preparing the skin layer to the curing temperature or higher, the epoxy resin inside the foamed resin sheet 50 and the prepregs 55a and 55b for preparing the skin layer is cured. Thereby, a FRP compound molded object is shape | molded.

The density of the FRP composite molded body of the present invention is 0.4 to 1.0 g / cm ³ , and the thickness of the foamed core layer after curing is preferably 0.5 to 3.0 mm, preferably 0.5 to 2.0 mm. Is more preferable.

  The curing time in the production method of the present invention is preferably 1 to 20 minutes. Thereby, it is possible to produce an FRP composite molded body having high productivity and excellent quality.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to an Example. The components and test methods used in the examples and comparative examples are described below.

(Carbon fiber)
"Tenax (registered trademark)" HTS40-12K (tensile strength 4.2 GPa, tensile elastic modulus 240 GPa, manufactured by Toho Tenax Co., Ltd.)
(Fiber reinforced base material)
Carbon fiber paper BP-1030A-ES (manufactured by Toho Tenax Co., Ltd., weight 30 g / m ² )

[Thermosetting resin composition]
(Epoxy resin)
"JER (registered trademark)" 154 (semi-solid phenol novolac type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
・ "JER (registered trademark)" 828 (liquid bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
"JER (registered trademark)" 834 (Liquid bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
"JER (registered trademark)" 1001 (solid bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation)
"JER (registered trademark)" 1256 (solid bisphenol A type phenoxy resin, manufactured by Mitsubishi Chemical Corporation)
(Curing agent)
・ Dicy7 (Dicyandiamide, manufactured by Mitsubishi Chemical Corporation)
"OMICURE (registered trademark)" 24 (2,4'-toluenebis (3,3-dimethylurea), manufactured by PTI Japan)
DCMU-99 (3,4-dichlorophenyl-1,1-dimethylurea, manufactured by Hodogaya Chemical Co., Ltd.)
・ "Amicure (registered trademark)" VDH (hydrazide compound, manufactured by Ajinomoto Fine Techno Co., Ltd.)

(Thickening particles)
"Zefiac (registered trademark)" F320 (alkyl methacrylate polymer), average polymerization degree 30,000, manufactured by Aika Industry Co., Ltd.)
"Zephiac (registered trademark)" F325 (alkyl methacrylate polymer), average polymerization degree 4,000, manufactured by Aika Industry Co., Ltd.)

(Epoxy resin curing agent that reacts at low temperatures)
・ "Ancamine K-54" (Tris-2,4,6-dimethylaminomethylphenol), manufactured by PTI Japan Ltd.)

(Other flame retardants)
PX-200 (resorcinol bis (di2,6-xylyl) phosphate, phosphorus content 9.0%, manufactured by Daihachi Chemical Industry Co., Ltd.)
SPB-100 (Phosphononitrile acid phenyl ester, phosphorus content 13.4%, manufactured by Otsuka Chemical Co., Ltd.)

(Foamed particles)
・ "Matsumoto Microsphere (registered trademark)" F-48 (manufactured by Matsumoto Yushi Seiyaku Co., Ltd., foaming start temperature 100 ° C)
・ "Matsumoto Microsphere (registered trademark)" F-100M (Matsumoto Yushi Seiyaku Co., Ltd., foaming start temperature 130 ° C)

(1) Preparation of thermosetting resin composition for foamed resin sheet Addition of a predetermined amount of epoxy resin into a kneader, kneading and raising the temperature to 150 ° C. to completely dissolve the solid components A viscous liquid was obtained. While continuing kneading, the temperature was lowered to a temperature of 50 to 60 ° C., and a thermosetting resin composition was obtained by stirring for 30 minutes so that a predetermined amount of a curing agent, a thickener and foamed particles were added and dispersed uniformly. .

(2) Production of Foamed Resin Sheet Using a reverse roll coater, the temperature of the thermosetting resin composition is maintained at 60 ° C., and the thermosetting resin composition obtained above is applied onto release paper to give 600 g / m ² to prepare a resin sheet having a unit weight. Next, it heat-processed for 2 minutes at the temperature described in Table 1, the resin sheet was thickened, and the foamed resin sheet was produced.

(3) Preparation of prepreg for skin layer preparation In a kneader, 4 kg of jER154, 4 kg of jER834, and 2 kg of jER1001 were added and heated to a temperature of 150 ° C. while kneading to completely dissolve the solid components. A viscous liquid was obtained. While continuing kneading, the temperature was lowered to 60 ° C., and 0.5 kg of Dicy7, 0.4 kg of Omicure 24 and 1.5 kg of Zefiac F320 were added and stirred for 30 minutes so as to disperse uniformly. Obtained. Using the reverse roll coater, the epoxy resin composition obtained above was applied onto release paper to prepare a resin film with a weight of 50 g / m ² . Next, the above resin film is laminated on both sides of the carbon fiber aligned in a sheet shape so that the carbon fiber mass per unit area is 200 g / m ^2, and the temperature is 95 ° C. and the pressure is 0.2 MPa. And impregnated with the epoxy resin composition to produce a unidirectional prepreg with a Wf of 67%.

(4) Manufacture of CFRP composite molded body The foamed resin sheet obtained in (2) is cut into one sheet having a length of 299 mm and a width of 299 mm, and the skin layer preparation prepreg obtained in (3) is formed into a length of 299 mm and a width of 299 mm. Four sheets were cut. Next, two prepregs for preparing the skin layer were laminated on both sides of the foamed resin sheet so that they were plane-symmetrical so that 0 ° and 90 ° were alternated to prepare a preform. Next, the preform prepared above is set in a plate forming mold of length 300 mm × width 300 mm × thickness 2 mm heated to 16050 ° C., and the thickness is controlled with a spacer so that the thickness of the molded product becomes 2 mm. The mold was clamped at a surface pressure of 1.0 MPa. After holding at 160 ° C. for 10 minutes, the mold was opened to obtain a CFRP composite molded body having a thickness of 2 mm.

(5) Appearance determination of CFRP composite molded body The appearance of the CFRP composite molded body obtained above was evaluated according to the following criteria. The voids were visually observed and the number of φ0.2 mm or more was measured.
Appearance determination ◎ Molded state is very good: surface void 0.10 pieces / cm ² or less ○ Molded state is good: surface void 0.11 to 0.20 pieces / cm ²
Δ: There is a problem in the molding state: Surface voids 0.21 to 0.30 / cm ²
X Molding state is poor: Surface void 0.31 piece / cm ² or more

(6) Density measurement of CFRP composite molded body The CFRP composite molded body was cut into a size of 50 mm in length and 50 mm in width, and then density measurement was performed by a water displacement method. At this time, the water temperature is also measured at the same time and calculated using the density of water at the measured water temperature. From these measured values, the density of the cured resin was calculated using the following formula.
Density of CFRP composite molded body (g / cm ³ ) = [(W1 / (W1-W2)] × d
W1: Mass of the CFRP composite molded body in the atmosphere (g)
W2: Mass of CFRP composite molded body in water (g)
d: Density of water at the measured water temperature (g / cm ³ )

(Examples 1-5, Comparative Examples 1-3)
The thermosetting resin composition was manufactured by the method as described in (1) at the ratio described in Table 1. Using the obtained thermosetting resin composition, a foamed resin sheet was produced by the method described in (2). Moreover, the CFRP composite molded body was produced by the method described in (3) to (6), and various performances were evaluated. The evaluation results are shown in Table 1.

(Example 6)
The thermosetting resin composition was manufactured by the method as described in (1) at the ratio described in Table 1. Using the obtained thermosetting resin composition, a foamed resin sheet was produced by the method described in (2). The foamed resin sheet is laminated on the reinforcing fiber base, and heated (100 ° C.) under pressure (pressure 0.2 MPa) to impregnate the resin into the reinforcing fiber base. A foamed resin sheet was manufactured. Moreover, the CFRP composite molded body was produced by the method described in (3) to (6), and various performances were evaluated. The evaluation results are shown in Table 1.

(Example 7)
The thermosetting resin composition was manufactured by the method as described in (1) at the ratio described in Table 1. Using the obtained thermosetting resin composition, a foamed resin sheet was produced by the method described in (2). Further, a CFRP composite molded body was produced by the method described in (3) to (6) except that the thickness was controlled with a spacer so that the thickness of the molded product of (4) was 2.5 mm, and various performances were obtained. Evaluated. The evaluation results are shown in Table 1.

(Example 8)
The thermosetting resin composition was manufactured by the method as described in (1) at the ratio described in Table 1. Using the obtained thermosetting resin composition, a foamed resin sheet was produced by the method described in (2). Further, cut the two prepregs for preparing the skin layer obtained in (3) into a length of 299 mm and a width of 299 mm, and then set the prepreg for preparing the skin layer to 0 ° so that both sides of the foamed resin sheet are symmetrical. A CFRP composite molded body was produced by the method described in (3) to (6) except that one upper and lower layers were laminated, and various performances were evaluated. The evaluation results are shown in Table 1.

  Since Comparative Example 1 did not contain a thickener, the resin viscosity was low, resulting in poor molding. In Comparative Example 2, the foaming start temperature of the foamed particles is lower than the thickening start temperature of the thickener. Therefore, foaming started prior to the thickening of the resin, making it impossible to use as a foamed resin sheet. Since the comparative example 3 was used without increasing the viscosity of the resin, the resin viscosity was low and the molding was poor.

  The FRP composite molded body obtained from the present invention can be widely used in general industrial applications such as automobile applications, marine applications, sports applications, electronic equipment parts, personal computer housings and the like.

DESCRIPTION OF SYMBOLS 50 ... Foamed resin sheet 51 ... Thermosetting resin composition 53 ... Unexpanded expanded particle 53a ... Expanded expanded particle 55a, 55b ... Prepreg for skin layer preparation 57a, 57b ... -Mold 52 ... Foamed resin sheet 100 ... Unfoamed foam resin sheet 101 ... Foamed foam resin sheet.

Claims (10)

A thermosetting resin composition comprising an epoxy resin and a curing agent;
A thickening resin that increases the viscosity of the thermosetting resin composition by heating to a temperature equal to or higher than the thickening start temperature;
Foamed particles for foaming the thermosetting resin composition by heating to a temperature equal to or higher than the foaming start temperature;
A foamed resin sheet comprising:
The foamed resin sheet, wherein the foaming start temperature is higher than the thickening start temperature.   The foamed resin sheet according to claim 1, wherein a foaming start temperature of the foamed particles is 90 to 140 ° C.   The foamed resin sheet according to claim 1, wherein the thickening resin is polymethyl methacrylate.   The foamed resin sheet according to claim 1, wherein the thickening resin is a curing agent that starts curing at a lower temperature than the curing agent.   The foamed resin sheet according to claim 1, wherein a reinforcing fiber base is provided in the foamed resin sheet.   The foamed resin sheet according to claim 5, wherein the reinforcing fiber base is made of an organic fiber.   The foamed resin sheet according to claim 5, wherein the reinforcing fiber base is made of inorganic fibers. A foam core layer formed by foaming the foamed resin sheet according to claim 1;
A skin layer made of a fiber reinforced thermosetting resin, formed on at least one surface of the foam core layer;
A fiber-reinforced thermosetting resin composite molded body having a density of 0.4 to 1.0 g / cm ³ . A foamed resin sheet according to claim 1;
A prepreg for skin layer preparation that obtains the fiber-reinforced thermosetting resin by heating to a temperature equal to or higher than the curing start temperature;
Placed in the mold,
The fiber-reinforced heat according to claim 8, wherein the foamed resin sheet is foamed by heating to a temperature 20 to 80 ° C. higher than the foaming start temperature, and the skin layer preparation prepreg is cured. A method for producing a curable resin composite molded article.   The method for producing a fiber-reinforced thermosetting resin composite molded body according to claim 9, wherein the prepreg for preparing the skin layer contains polymethyl methacrylate.

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