Sheet molding compound

Abstract

To provide a sheet molding compound which enables provision of a molded article that is excellent in flame retardancy, and is excellent in shape retention and electric characteristics even after being brought into contact with flame and becoming a high temperature.SOLUTION: A sheet molding compound is formed by impregnating a fiber reinforced base material with a resin composition containing a thermosetting resin, a polymerizable monomer, a shrinkage-reducing agent, a curing agent, a polymerization initiator and a filler, wherein the thermosetting resin contains at least one selected from the group consisting of an unsaturated polyester resin having a halogen atom, a vinyl ester resin having a halogen atom, and a urethane acrylate resin having a halogen atom, and the filler contains a silicon-based filler.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a sheet molding compound. [Background technology]

[0002] Sheet molding compounds are sheet-shaped molding materials obtained by impregnating a fiber base material such as glass fiber or organic fiber with a paste-like composition containing a thermosetting resin such as an unsaturated polyester resin and a vinyl monomer as a diluent. Molded products can be obtained by pressurizing and heating the sheet molding compounds. Sheet molding compounds are mainly used as molding materials for bathtubs, water tanks, septic tanks, etc., but are also used as materials for electrical parts such as plugs and lighting components for electrical appliances and breaker bases. Materials for electrical components need to have high flame retardancy from the viewpoint of fire safety, and therefore attempts have been made to obtain flame-retardant sheet molding compounds by adding flame retardants or the like. For example, Patent Document 1 discloses an unsaturated polyester resin composition that contains specific amounts of a resin component including an unsaturated polyester, a polymerizable monomer, and a shrinkage reducing agent which is polyvinyl acetate, as well as aluminum hydroxide and a flame retardant, for the purpose of improving flame retardancy in addition to low shrinkage and dimensional stability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 080412 Summary of the Invention [Problem to be solved by the invention]

[0004] When a fire breaks out and an electrical component comes into contact with the flame, there is a problem that the shape retention of the resin material used in the electrical component is reduced, which may expose the conductive parts, and there is a problem that the electrical insulation is reduced, which may cause an electric shock. The use of a resin material containing a flame retardant for an electrical component is also insufficient as a countermeasure against these problems. This is thought to be because, even in the case of a resin material containing a flame retardant, the flammable components become gas, making the molded product brittle and reducing the shape retention. In addition, when the material comes into contact with the flame, the surface layer is carbonized, which makes it easy to conduct electricity, and the electrical insulation is reduced. Therefore, an object of the present invention is to provide a sheet molding compound which is excellent in flame retardancy and which can give a molded article which has excellent shape retention and electrical properties even after coming into contact with a flame and becoming hot. [Means for solving the problem]

[0005] The present inventors have discovered that the above problems can be solved by using a specific thermosetting resin having a halogen atom and a silicon-based filler in a sheet molding compound. That is, the present invention relates to the following. [1] A sheet molding compound obtained by impregnating a reinforcing fiber substrate with a resin composition containing a thermosetting resin, a polymerizable monomer, a low shrinkage agent, a curing agent, a polymerization inhibitor, and a filler, wherein the thermosetting resin contains at least one selected from the group consisting of an unsaturated polyester resin having a halogen atom, a vinyl ester resin having a halogen atom, and a urethane acrylate resin having a halogen atom, and the filler contains a silicon-based filler. [2] The sheet molding compound according to the above item [1], wherein the total content of the unsaturated polyester resin having a halogen atom, the vinyl ester resin having a halogen atom, and the urethane acrylate resin having a halogen atom relative to the total amount of the thermosetting resin is 50 to 100 mass %, and the mass ratio of the sum of the thermosetting resin and the polymerizable monomer to the low shrinkage agent [thermosetting resin and polymerizable monomer / low shrinkage agent] is 60 / 40 to 90 / 10. [3] The sheet molding compound according to the above [1] or [2], wherein the content of the silicon-based filler is 5 to 50 parts by mass when the total content of the thermosetting resin, the polymerizable monomer, and the low shrinkage agent is 100 parts by mass. [4] The sheet molding compound according to any one of the above [1] to [3], wherein the content of the silicon-based filler is 15 to 40 parts by mass when the total content of the thermosetting resin, the polymerizable monomer, and the low shrinkage agent is 100 parts by mass. [5] The sheet molding compound according to any one of the above [1] to [4], wherein the silicon-based filler contains at least one selected from the group consisting of glass micro hollow sphere filler, silica micro hollow sphere filler, silica sand, diatomaceous earth, crystalline silica, amorphous silica, mica, and short glass fiber. [6] The sheet molding compound according to any one of the above [1] to [5], wherein the halogen atom is chlorine or bromine. [7] The sheet molding compound according to any one of the above [1] to [6], wherein the reinforcing fiber base material is made of glass fiber. [8] The sheet molding compound according to any one of the above [1] to [7], wherein the polymerizable monomer contains a styrene-based monomer. [9] A molded article for electrical parts obtained by molding the sheet molding compound according to any one of the above [1] to [8]. Effect of the Invention

[0006] According to the present invention, there is provided a sheet molding compound capable of obtaining a molded product having excellent flame retardancy, shape retention and electrical properties even after contact with a flame and reaching a high temperature. Therefore, the sheet molding compound is useful as a molding material for electrical parts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [Sheet molding compound] The sheet molding compound of the present invention is a sheet molding compound obtained by impregnating a reinforcing fiber substrate with a resin composition containing a thermosetting resin, a polymerizable monomer, a low-shrinkage agent, a curing agent, a polymerization inhibitor, and a filler, wherein the thermosetting resin contains at least one selected from the group consisting of unsaturated polyester resins having halogen atoms, vinyl ester resins having halogen atoms, and urethane acrylate resins having halogen atoms, and the filler contains a silicon-based filler. The sheet molding compound of the present invention has excellent flame retardancy and can give molded articles that have excellent shape retention and electrical properties even after coming into contact with flames and reaching high temperatures, making it useful as a molding material for electrical parts. The reason why the sheet molding compound of the present invention is able to exhibit the above-mentioned excellent effects is not clear, but is thought to be as follows. The thermosetting resin having halogen atoms and the silicon-based filler used in the sheet molding compound of the present invention exhibit flame retardancy and, even when exposed to flames, are able to suppress the formation of a carbonized layer, particularly on the surface of the molded article, and maintain the surface shape, so that the resulting molded article is believed to have good shape retention and electrical properties.

[0008] <Resin composition> The resin composition constituting the sheet molding compound of the present invention is a resin composition containing a thermosetting resin, a polymerizable monomer, a low shrinkage agent, a curing agent, a polymerization inhibitor and a filler, the thermosetting resin containing at least one selected from the group consisting of an unsaturated polyester resin having a halogen atom, a vinyl ester resin having a halogen atom, and a urethane acrylate resin having a halogen atom, and the filler containing a silicon-based filler.

[0009] (thermosetting resin) The thermosetting resin contained in the resin composition contains at least one selected from the group consisting of an unsaturated polyester resin having a halogen atom, a vinyl ester resin having a halogen atom, and a urethane acrylate resin having a halogen atom. Of these, the thermosetting resin is preferably an unsaturated polyester resin having a halogen atom.

[0010] The thermosetting resin may be composed of only one or more selected from the group consisting of unsaturated polyester resins having halogen atoms, vinyl ester resins having halogen atoms, and urethane acrylate resins having halogen atoms, but the thermosetting resin contained in the resin composition may contain resins other than unsaturated polyester resins having halogen atoms, vinyl ester resins having halogen atoms, and urethane acrylate resins having halogen atoms, within a range that does not impair the effects of the present invention. Such resins are preferably thermosetting resins having no halogen atoms, more preferably at least one selected from the group consisting of unsaturated polyester resins having no halogen atoms, vinyl ester resins having no halogen atoms, and urethane acrylate resins having no halogen atoms, and even more preferably unsaturated polyester resins having no halogen atoms. From the viewpoint of flame retardancy of a molded product, the total content of the unsaturated polyester resin having a halogen atom, the vinyl ester resin having a halogen atom, and the urethane acrylate resin having a halogen atom is preferably 40 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 60 to 100 mass%, still more preferably 70 to 100 mass%, and even more preferably 80 to 100 mass%, based on the total amount of the thermosetting resin. The halogen atom is preferably chlorine or bromine, more preferably bromine, and may include both chlorine and bromine.

[0011] The content of the thermosetting resin in the resin composition is preferably 7 to 40 mass %, more preferably 8 to 35 mass %, even more preferably 10 to 30 mass %, and still more preferably 15 to 25 mass %.

[0012] [Unsaturated polyester resin containing halogen atoms] The unsaturated polyester resin having a halogen atom is not particularly limited as long as it is a polyester having a halogen atom and an unsaturated bond, but it preferably contains a constituent unit derived from a saturated dicarboxylic acid, a constituent unit derived from an unsaturated dicarboxylic acid, and a constituent unit derived from a diol, and more preferably consists essentially of a constituent unit derived from a saturated dicarboxylic acid, a constituent unit derived from an unsaturated dicarboxylic acid, and a constituent unit derived from a diol. In addition, one or more of the structural units contains a halogen atom.

[0013] The saturated dicarboxylic acid that gives the constituent unit derived from a saturated dicarboxylic acid is preferably at least one selected from the group consisting of aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and aliphatic dicarboxylic acids, and more preferably aromatic dicarboxylic acids. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, and 4,4'-biphenyldicarboxylic acid. From the viewpoint of the balance between the availability of raw materials and the performance of the resulting unsaturated polyester, at least one selected from the group consisting of terephthalic acid, isophthalic acid, and phthalic acid is preferred. The aromatic dicarboxylic acid may be an anhydride. By using the aromatic dicarboxylic acid, an unsaturated polyester resin having excellent mechanical properties, water resistance, and chemical resistance can be obtained. Examples of the alicyclic dicarboxylic acid include 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and endomethylenetetrahydrophthalic anhydride. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, sebacic acid, azelaic acid, succinic acid substituted with an alkyl group having 16 to 18 carbon atoms, and dimer acid. The saturated dicarboxylic acids may be used alone or in combination of two or more kinds.

[0014] Examples of unsaturated dicarboxylic acids that provide structural units derived from unsaturated dicarboxylic acids include maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, etc., and are preferably at least one selected from the group consisting of maleic acid, maleic anhydride, and fumaric acid, more preferably at least one selected from the group consisting of maleic acid and maleic anhydride, and even more preferably maleic anhydride. The unsaturated dicarboxylic acids may be used alone or in combination of two or more kinds.

[0015] Examples of diols that provide diol-derived structural units include aliphatic diols, alicyclic diols, etherified diphenols, polyalkylene glycols, and the like, with aliphatic diols being preferred. Aliphatic diols include ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,4-butenediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 2-ethyl-2-methylpropane-1,3-diol, 2-butyl -2-Ethylpropane-1,3-diol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2,4-dimethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-hydroxy-2,2-dimethylpropyl-3-hydroxypropyl Examples of the glycol include 2,2-dimethylpropanoate, diethylene glycol, triethylene glycol, and dipropylene glycol. Of these, at least one selected from the group consisting of ethylene glycol, 1,2-propanediol (propylene glycol), dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,8-octanediol is preferred, at least one selected from the group consisting of neopentyl glycol, propylene glycol, and dipropylene glycol is more preferred, at least two selected from the group consisting of neopentyl glycol, propylene glycol, and dipropylene glycol is even more preferred, and neopentyl glycol, propylene glycol, and dipropylene glycol are even more preferred. The aliphatic diols may be used alone or in combination of two or more, and it is preferable to use two or more of them in combination.

[0016] Examples of the alicyclic diol include 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F. Examples of the etherified diphenol include bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct. Examples of the polyalkylene glycol include polyethylene glycol, polyalkylene glycol, and polytetramethylene glycol. The diols may be used alone or in combination of two or more kinds.

[0017] The unsaturated polyester resin may contain other structural units in addition to the structural units described above. Examples of components that provide other structural units include monocarboxylic acids, trivalent or higher polycarboxylic acids, monoalcohols, trivalent or higher polyhydric alcohols, and hydroxycarboxylic acids. As the carboxylic acid component (saturated dicarboxylic acid, unsaturated dicarboxylic acid, monocarboxylic acid, trivalent or higher polycarboxylic acid, hydroxycarboxylic acid), lower alkyl esters and anhydrides thereof may be used.

[0018] The unsaturated polyester resin having a halogen atom contains a halogen atom, and preferably contains at least one selected from the group consisting of a component consisting of a diol having a halogen atom and a component consisting of a dicarboxylic acid having a halogen atom, and more preferably contains a component consisting of a diol having a halogen atom. The diol having a halogen atom is preferably a diol containing bromine, more preferably at least one selected from the group consisting of brominated bisphenol A and its alkylene oxide adduct, brominated bisphenol F and its alkylene oxide adduct, brominated bisphenol S and its alkylene oxide adduct, and 2,2-bis(bromomethyl)-1,3-propanediol, still more preferably at least one selected from the group consisting of tetrabromobisphenol A and its alkylene oxide adduct, tetrabromobisphenol S and its alkylene oxide adduct, and 2,2-bis(bromomethyl)-1,3-propanediol, and even more preferably at least one selected from the group consisting of 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl]propane and 2,2-bis(bromomethyl)-1,3-propanediol. The dicarboxylic acid having a halogen atom is preferably at least one selected from the group consisting of dicarboxylic acids containing bromine and dicarboxylic acids containing chlorine, and more preferably dicarboxylic acids containing bromine. The bromine-containing dicarboxylic acid is preferably at least one selected from the group consisting of bromomaleic acid and bromophthalic acid. The chlorine-containing dicarboxylic acid is preferably at least one selected from the group consisting of chloromaleic acid, HET acid and HET acid anhydride.

[0019] The molar ratio [carboxy group / hydroxy group] of the total of the carboxy groups of the carboxylic acid components (saturated dicarboxylic acids, unsaturated dicarboxylic acids, monocarboxylic acids, tri- or higher carboxylic acid polycarboxylic acids, hydroxycarboxylic acids) to the total of the hydroxy groups of the alcohol components (dihydric alcohols, monoalcohols, tri- or higher carboxylic acid polyhydric alcohols, hydroxycarboxylic acids) is preferably 0.9 / 1.1 to 1.1 / 0.9, and more preferably 0.95 / 1.05 to 1.05 / 0.95. The ratio (mol) of the constituent units derived from unsaturated dicarboxylic acids in the constituent units derived from the carboxylic acid components (saturated dicarboxylic acids, unsaturated dicarboxylic acids, monocarboxylic acids, trivalent or higher polycarboxylic acids, and hydroxycarboxylic acids) is preferably 70 to 99 mol %, more preferably 80 to 99 mol %, even more preferably 90 to 99 mol %, and still more preferably 90 to 98 mol %, calculated in terms of the number of carboxy groups. The ratio (mol) of the constitutional units derived from a diol in the constitutional units derived from the alcohol component (diol, monoalcohol, trihydric or higher polyhydric alcohol, hydroxycarboxylic acid) is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 80 to 100 mol%, and still more preferably 90 to 100 mol%, calculated in terms of the number of hydroxyl groups, and the constitutional units derived from the alcohol component may be composed only of constitutional units derived from a diol.

[0020] The method for producing the unsaturated polyester resin is not particularly limited, but it can be obtained by reacting the carboxylic acid component and the alcohol component described above. In this case, an esterification catalyst may be used. The esterification catalyst may be at least one metal compound selected from antimony, germanium, titanium, tin, zinc, aluminum, and manganese. The amount of the esterification catalyst added is preferably 0.01 to 1.5 mol% based on the saturated carboxylic acid component. In order to suppress the reaction of unsaturated bonds, a polymerization inhibitor may be added as necessary. Examples of the polymerization inhibitor include polyhydric phenol-based polymerization inhibitors such as hydroquinone, toluhydroquinone, trimethylhydroquinone, and tertiary butylcatechol, and quinone-based polymerization inhibitors such as parabenzoquinone and toluquinone. The amount of the polymerization inhibitor added is preferably 0.002 to 1.0 part by mass, and more preferably 0.005 to 0.3 part by mass, based on 100 parts by mass of the total amount of the carboxylic acid component and the alcohol component. The reaction temperature is preferably 150 to 280°C, and more preferably 160 to 250°C. The end point of the reaction can be judged based on the acid value of the reaction mixture, the amount of condensation water (alcohol when a lower alkyl ester is used as the raw material) generated, the viscosity of the resulting polyester, and the like.

[0021] [Vinyl ester resin having halogen atoms] The vinyl ester resin having halogen atoms is not particularly limited, but may be a polymer obtained by subjecting an epoxy resin to an addition reaction with an unsaturated basic acid, and is also called an epoxy acrylate. The epoxy resin is not particularly limited, and examples of the epoxy resin that can be used include epi-bis-glycidyl ether, novolac-type glycidyl ether, brominated glycidyl ether, other glycidyl ethers, nitrogen-containing types, glycidyl esters, peracetic acid oxidized types, and glycol-type glycidyl ethers. These may be used alone or in combination of two or more. The vinyl ester resin having a halogen atom contains a halogen atom, and preferably contains a component made of an epoxy resin having a halogen atom. The epoxy resin having a halogen atom is preferably a brominated bisphenol type epoxy compound, more preferably at least one selected from the group consisting of a brominated bisphenol A type epoxy compound, a brominated bisphenol F type epoxy compound, and a brominated bisphenol S type epoxy compound, and further preferably a brominated bisphenol A type epoxy compound. The unsaturated basic acid is not particularly limited, and is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, sorbic acid, hydroxymethyl methacrylate maleate, hydroxyethyl acrylate maleate, hydroxypropyl methacrylate maleate, hydroxypropyl acrylate maleate, and dicyclopentadiene acrylate maleate, which may be used alone or in combination of two or more kinds.

[0022] The method for producing the vinyl ester resin having a halogen atom is not particularly limited, and may be a method known in the art. Specifically, the vinyl ester resin having a halogen atom can be produced by the method described in "Vinyl Ester Resin" (edited by the Vinyl Ester Resin Research Group, Chemical Daily, 1993).

[0023] [Urethane acrylate resin having halogen atoms] Although there are no particular limitations on the urethane acrylate resin having a halogen atom, it is a radically polymerizable compound having a urethane bond and a (meth)acrylate group in the molecule, and also having a halogen atom, and is molded and cured to form a molded article. In the present invention, the term "(meth)acrylate" refers to at least one selected from the group consisting of "acrylate" and "methacrylate".

[0024] The urethane acrylate resin used in the present invention is not particularly limited, and may be an adduct of a polyisocyanate and a (meth)acrylate having a hydroxyl group. An "adduct of a (meth)acrylate having a hydroxyl group of a polyisocyanate" refers to an adduct obtained by forming a urethane bond between the isocyanate group of a polyisocyanate and the hydroxyl group (hydroxyl group) of a (meth)acrylate having a hydroxyl group. The urethane acrylate resin used in the present invention may further contain a component made of a polyol or a polyester polyol, and preferably contains a component made of a polyol having a halogen atom. The halogen-containing urethane acrylate resin will be described in detail below. By using such a urethane acrylate resin, the molded article obtained will have excellent flame retardancy, shape retention and electrical properties even after coming into contact with flame and becoming hot.

[0025] Examples of the polyisocyanate include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds, and are preferably at least one selected from the group consisting of alicyclic isocyanate compounds and aliphatic isocyanate compounds, and more preferably both alicyclic isocyanate compounds and aliphatic isocyanate compounds. In addition, trifunctional isocyanates (nurate-type polyisocyanates) having an isocyanurate ring obtained by trimerizing a bifunctional isocyanate compound, and isocyanate prepolymers modified with polyols are also preferably used.

[0026] Examples of the aromatic isocyanate compound include 1,3-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and m-tetramethylxylene diisocyanate. Examples of the alicyclic isocyanate compound include hydrogenated xylylene diisocyanate (1,3-bis(isocyanatomethyl)cyclohexane), isophorone diisocyanate, norbornene diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated methylene bisphenylene diisocyanate, and 1,4-cyclohexane diisocyanate. Examples of the aliphatic isocyanate compound include 1,6-hexamethylene diisocyanate, trimethylene diisocyanate, etc. These isocyanate compounds can be used alone or in combination of two or more kinds.

[0027] Of the polyisocyanates, at least one selected from the group consisting of 1,6-hexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, and nurate-type polyisocyanates thereof is preferred, at least one selected from the group consisting of 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and nurate-type polyisocyanates thereof is more preferred, and isophorone diisocyanate and nurate-type polyisocyanates thereof are even more preferred.

[0028] The (meth)acrylate having a hydroxyl group is preferably a hydroxyalkyl (meth)acrylate. Examples of the hydroxyalkyl (meth)acrylate include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyphenoxypropyl (meth)acrylate. Hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate are preferred, and hydroxyethyl (meth)acrylate is more preferred.

[0029] When a component consisting of a polyol or a polyester polyol is contained, examples of usable polyols include aliphatic diols and etherified diphenols, and examples of polyester polyols include those obtained by polycondensation of at least one selected from the group consisting of unsaturated acids and saturated acids with at least one selected from the group consisting of aliphatic diols and etherified diphenols. The urethane acrylate resin having a halogen atom contains a halogen atom, and preferably contains a component made of a polyol having a halogen atom. The polyol having a halogen atom is preferably a glycol containing bromine, more preferably at least one selected from the group consisting of brominated bisphenol A and its alkylene oxide adduct, brominated bisphenol F and its alkylene oxide adduct, brominated bisphenol S and its alkylene oxide adduct, and 2,2-bis(bromomethyl)-1,3-propanediol, still more preferably at least one selected from the group consisting of tetrabromobisphenol A and its alkylene oxide adduct, tetrabromobisphenol S and its alkylene oxide adduct, and 2,2-bis(bromomethyl)-1,3-propanediol, and even more preferably at least one selected from the group consisting of 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl]propane and 2,2-bis(bromomethyl)-1,3-propanediol.

[0030] (Polymerizable monomer) The resin composition contains a polymerizable monomer. Before curing, the polymerizable monomer acts as a diluent to give fluidity to the resin composition and also functions as a solvent for the resin, and after curing, it acts as a crosslinked portion to improve the strength and hardness of the resulting molded product. The polymerizable monomer is preferably at least one selected from the group consisting of a styrene-based monomer, a (meth)acrylic acid-based monomer, and a vinyl acetate-based monomer, more preferably at least one selected from the group consisting of a styrene-based monomer and a (meth)acrylic acid-based monomer, and even more preferably a styrene-based monomer. The styrene-based monomer is preferably at least one selected from the group consisting of styrene, vinyltoluene, and α-methylstyrene, and more preferably styrene. Examples of (meth)acrylic acid monomers include methyl methacrylate, methacrylic acid, acrylic acid, benzyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, glycidyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and norbornyl (meth)acrylate. Examples of the acrylate include acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, acrylic (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, pentamethylpiperidyl (meth)acrylate, tetramethylpiperidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. The content of the polymerizable monomer in the resin composition is preferably 5 to 30 mass %, more preferably 6 to 25 mass %, even more preferably 7 to 20 mass %, and still more preferably 8 to 15 mass %.

[0031] (Low shrinkage agent) The resin composition contains a shrinkage reducing agent. The low shrinkage agent is preferably at least one of polystyrene, polyvinyl acetate, polystyrene / polyvinyl acetate block copolymer, polyethylene, polypropylene, polymethyl methacrylate, styrene-butadiene block copolymer, and saturated polyester.

[0032] The content of the low shrinkage agent is preferably 5 to 15 mass %, more preferably 6 to 13 mass %, even more preferably 6.5 to 11 mass %, and even more preferably 6.5 to 9 mass %, based on the total amount of the resin composition. By having the content of the low shrinkage agent in the above range, shrinkage during curing of the sheet molding compound can be effectively suppressed, and the shape retention of the molded product can also be improved. In addition, the mass ratio of the total of the thermosetting resin and the polymerizable monomer to the low shrinkage agent [thermosetting resin and polymerizable monomer / low shrinkage agent] is preferably 60 / 40 to 90 / 10, and more preferably 65 / 35 to 80 / 20, from the viewpoint of suppressing shrinkage and from the viewpoint of shape retention of a molded product.

[0033] (hardening agent) The resin composition contains a curing agent. The curing agent is used to quickly obtain a uniform cured product during molding. The type and amount of the curing agent used may vary depending on the application. The curing agent is preferably a peroxide. The peroxide is preferably at least one selected from the group consisting of ketone peroxides, diacyl peroxides, peroxy esters, hydroperoxides and dialkyl peroxides, and more preferably a peroxy ester. The content of the curing agent in the resin composition is preferably 0.05 to 5 mass %, more preferably 0.1 to 4 mass %, even more preferably 0.2 to 2 mass %, and still more preferably 0.3 to 1 mass %.

[0034] (Polymerization inhibitor) The resin composition contains a polymerization inhibitor. The polymerization inhibitor is blended to prevent gelation during production, ensure pot life during molding, and improve storage stability. Suitable polymerization inhibitors include polyhydric phenol-based polymerization inhibitors such as hydroquinone, toluhydroquinone, trimethylhydroquinone, and tertiary butylcatechol, and quinone-based polymerization inhibitors such as parabenzoquinone and toluquinone, with polyhydric phenol-based polymerization inhibitors being preferred. The content of the polymerization inhibitor is preferably 0.001 to 0.1% by mass, and more preferably 0.005 to 0.05% by mass, based on the total amount of the resin composition.

[0035] (filling material) The resin composition contains a filler, and the filler contains a silicon-based filler. By using a silicon-based filler as the filler, it is possible to obtain a sheet molding compound that can produce molded products that have high shape retention even when exposed to flames.

[0036] The silicon-based filler preferably contains at least one selected from the group consisting of glass micro hollow sphere filler, silica micro hollow sphere filler, silica sand, diatomaceous earth, crystalline silica, amorphous silica, mica, and short glass fibers, more preferably contains at least one selected from the group consisting of glass micro hollow sphere filler, silica micro hollow sphere filler, crystalline silica, amorphous silica, mica, and short glass fibers, and even more preferably contains at least one selected from the group consisting of glass micro hollow sphere filler and silica micro hollow sphere filler. The filler contained in the resin composition may contain a filler other than the silicon-based filler, as long as the effect of the present invention is not impaired.

[0037] As the filler other than the silicon-based filler, at least one selected from the group consisting of aluminum hydroxide and calcium carbonate is preferable, and aluminum hydroxide is more preferable. By including aluminum hydroxide as the filler, the flame retardancy can be further improved. When the resin composition contains aluminum hydroxide, the mass ratio of the silicon-based filler to aluminum hydroxide [silicon-based filler / aluminum hydroxide] is preferably 2 / 98 to 30 / 70, more preferably 3 / 97 to 30 / 70, and even more preferably 5 / 95 to 20 / 80. The content of the filler in the resin composition is preferably 30 to 80 mass %, more preferably 40 to 70 mass %, even more preferably 45 to 65 mass %, and still more preferably 50 to 60 mass %. From the viewpoint of improving shape retention, the content of the silicon-based filler is preferably 2 to 30 parts by mass, more preferably 3 to 25 parts by mass, even more preferably 5 to 20 parts by mass, and even more preferably 5 to 15 parts by mass, based on the total amount of the filler. From the viewpoint of improving shape retention, the content of the silicon-based filler is preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, even more preferably 15 to 40 parts by mass, and still more preferably 15 to 35 parts by mass, when the total content of the thermosetting resin, the polymerizable monomer, and the low shrinkage agent is 100 parts by mass.

[0038] (Other Ingredients) The resin composition may contain other components such as a thickener, a release agent, a wetting and dispersing agent, etc. Depending on the application, these may be added during the synthesis of the thermosetting resin, may be mixed when blending each component of the resin composition, or may be mixed immediately before use.

[0039] The thickener is used to make the resin composition viscous and gel-like. The type and amount of the thickener used may vary depending on the application. The thickener is preferably at least one selected from the group consisting of alkaline earth metal oxides and alkaline earth metal hydroxides, and more preferably an alkaline earth metal oxide. As the alkaline earth metal oxide, magnesium oxide is preferred. As the hydroxide of an alkaline earth metal, magnesium hydroxide and calcium hydroxide are preferred. The content of the thickener is preferably 0.1 to 5 mass %, more preferably 0.2 to 4 mass %, even more preferably 0.3 to 2 mass %, and still more preferably 0.5 to 1.5 mass %, based on the total amount of the resin composition.

[0040] The release agent is blended to improve the releasability of the molded product and to further increase moldability. As the release agent, at least one selected from the group consisting of fatty acids, fatty acid metal salts, polyolefin waxes, petroleum waxes, and animal / plant waxes is preferred, and fatty acid metal salts are more preferred. Examples of fatty acids include stearic acid and palmitic acid, and examples of fatty acid metal salts include metal salts of stearic acid and metal salts of palmitic acid. The polyolefin wax includes polyethylene wax and oxidized polyethylene wax. An example of the petroleum wax is paraffin wax. Examples of animal or vegetable waxes include carnauba wax and montan wax. The release agent may be used alone or in combination of two or more kinds. The content of the release agent is preferably 0.5 to 5 mass %, more preferably 1 to 3 mass %, based on the total amount of the resin composition.

[0041] The wetting and dispersing agent is added to the resin composition in order to adjust the viscosity of the resin composition. Examples of the wetting and dispersing agent include modified polyurethane, phosphate ester, and phosphate polyester. The wetting and dispersing agent may be used alone or in combination of two or more. The content of the wetting and dispersing agent is preferably 0.3 to 3.0 mass %, more preferably 0.5 to 2.5 mass %, based on the total amount of the resin composition.

[0042] <Reinforced fiber base material> The reinforcing fiber substrate contained in the sheet molding compound of the present invention is preferably a substrate made of glass fiber. The form of the reinforcing fiber substrate may be roving, cloth, mat, woven fabric, chopped roving, chopped strand, etc., and at least one selected from the group consisting of chopped roving and chopped strand is preferable. The fiber substrate may be used alone or in a suitable mixture of two or more types. The content of the reinforcing fiber base in the sheet molding compound is preferably 20 to 50 mass %, more preferably 20 to 45 mass %, even more preferably 20 to 40 mass %, and still more preferably 25 to 35 mass %.

[0043] <Method of manufacturing sheet molding compound and molded products for electrical parts> As described above, the sheet molding compound of the present invention is produced by impregnating a reinforcing fiber substrate with a resin composition containing a thermosetting resin, a polymerizable monomer, a low shrinkage agent, a curing agent, a polymerization inhibitor, and a filler. There are no particular limitations on the method for producing the compound, but it is preferable to produce the compound by the method described below. The resin composition is impregnated into a reinforcing fiber substrate to obtain a sheet-like compound, and both sides of the sheet are covered with films to improve handling. Specifically, the resin composition is applied to two films, a reinforcing fiber substrate is sprinkled on the resin composition, the resin composition sides of the two films are bonded together, and the laminated films are pressed from both sides to impregnate the reinforcing fiber substrate with the resin composition. After that, the laminated sheets are aged to obtain a laminated sheet-like product with the semi-solid compound as the intermediate substrate. During molding, the sheet-like material is cut, charged into a mold, pressurized and heated, and cured to obtain a molded product. Since the sheet molding compound of the present invention has the above-mentioned constitution, it is possible to obtain a molded article which has excellent flame retardancy, shape retention and electrical properties even after contact with flame and exposure to high temperatures.

[0044] The molded article for electrical parts of the present invention can be obtained by molding the above-mentioned sheet molding compound. The molded article for electrical parts of the present invention can be obtained by cutting the sheet molding compound, charging it into a mold, and curing it under pressure and heat. The molded article for electrical parts of the present invention has excellent flame retardancy, and is excellent in shape retention and electrical properties even after coming into contact with flame and becoming hot. EXAMPLES

[0045] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Measurements and evaluations in the examples were performed as follows. Table 1 shows the types of raw materials, the amounts of raw materials, the results of measurements, and the results of evaluations. The figures for the amounts of raw materials are in "parts by mass." Table 1 is divided into Table 1(1) and Table 1(2).

[0046] <Production of molded products> The sheet molding compounds obtained in the Examples and Comparative Examples were molded under the following conditions to obtain molded articles to be used in the following evaluations. The sheet molding compound was heated and compressed in a 300mm x 300mm flat mold. The molding conditions were a mold temperature of 140°C on both the front and back of the plate, a molding pressure of 8MPa, and a retention time in the mold of 300 seconds. The molded product was then removed from the mold and immediately cooled between iron plates to obtain a 2mm thick flat molded product.

[0047] <Flame retardancy evaluation (UL94 vertical flame test)> Flame retardancy tests were conducted and evaluated according to the UL94 vertical flame test method. The thickness of the test piece was 2 mm. The results were evaluated according to the following criteria. Among those that conform to the UL94 standard, V-0 is the best, followed by V-1 and V-2. (Evaluation Criteria) ◎:V-0 ○:V-1 △:V-2 ×: Not compliant with UL94 standards

[0048] <Evaluation of electrical characteristics (tracking resistance test)> The molded product (plate) cut into a 10 cm square was clamped and fixed with two clamps. Next, a 500 W gas burner was applied from below the plate and heated for 10 minutes. At this time, the distance from the gas burner nozzle to the plate was 90 mm. After 10 minutes, the gas burner was turned off and the plate was cooled. The flat plate heat-treated as described above was evaluated for tracking resistance according to JIS-C-2134. The larger the tracking index (TI), the better the electrical insulation and electrical properties. In this embodiment, a plate with a tracking index (TI) of more than 400V has excellent electrical insulation and good electrical properties.

[0049] <Evaluation of shape retention (hardness test)> The molded product (plate) cut into a 10 cm square was clamped and fixed with two clamps. Next, a 500 W gas burner was applied from below the plate and heated for 10 minutes. At this time, the distance from the gas burner nozzle to the plate was 80 mm. After 10 minutes, the gas burner was turned off and the plate was cooled. The hardness of the molded product after heat treatment was measured by pressing a Shore A hardness tester against the center of the heat-treated flat plate. A high hardness value indicates good shape retention.

[0050] Production Example 1 (Production of unsaturated polyester resin having bromine atoms) 3145 parts by mass of 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl]propane, 703 parts by mass of 1,2-propanediol, 42 parts by mass of phthalic anhydride, and 1366 parts by mass of maleic anhydride were charged into a glass reaction vessel equipped with a stirrer, a heater, a thermometer, a fractionator, and a nitrogen gas inlet tube, and polycondensation reaction was carried out for 8 hours at 190 ° C. while stirring under a nitrogen atmosphere. When the solid acid value reached 35 mg KOH / g (measured according to JIS K 6901: 2021. The same applies to the following manufacturing examples), the reaction was terminated by cooling to obtain an unsaturated polyester resin (UP-1) having bromine atoms.

[0051] Production Example 2 (Production of Unsaturated Polyester Resin) 713 parts by mass of dipropylene glycol, 1383 parts by mass of neopentyl glycol, and 441 parts by mass of isophthalic acid were charged into a glass reaction vessel equipped with a stirrer, a heater, a thermometer, a fractionator, and a nitrogen gas inlet tube, and polycondensation reaction was carried out at 210°C while stirring under a nitrogen atmosphere. When the solid acid value was 10 mgKOH / g or less, it was cooled to 150°C or less. Next, 647 parts by mass of 1,2-propanediol and 2343 parts by mass of maleic anhydride were further added, and polycondensation reaction was carried out at 210°C while stirring under a nitrogen atmosphere. When the solid acid value was 27 mgKOH / g or less, it was cooled to terminate the reaction, and an unsaturated polyester resin (UP-2) was obtained.

[0052] Production Example 3 (Production of Vinyl Ester Resin Having Bromine Atoms) 2961 parts by mass of tetrabromobisphenol A type epoxy resin, 657 parts by mass of methacrylic acid, 11 parts by mass of triphenylstibine, 1 part by mass of toluhydroquinone, and 4 parts by mass of 2-methylimidazole were charged into a glass reaction vessel equipped with a stirrer, a heater, a cooling tube, a thermometer, and a gas inlet tube, and an addition reaction was carried out at 130° C. while blowing in air and stirring. When the solid acid value reached 5.0 mg KOH / g, the reaction was terminated by cooling, and a vinyl ester resin (VE-1) having bromine atoms was obtained.

[0053] Production Example 4 (Production of urethane acrylate resin having bromine atoms) In a glass reaction vessel equipped with a stirrer, a heater, a cooling tube, a thermometer, and a gas inlet tube, 1152 parts by mass of isophorone diisocyanate and 0.7 parts by mass of dibutyltin dilaurate were charged, and the mixture was heated to 85°C while stirring and blowing in air. A mixture of 1696 parts by mass of 2,2-bis[3,5-dibromo-4-(2-hydroxyethoxy)phenyl]propane, 650 parts by mass of 2-hydroxyethyl methacrylate, and 1.4 parts by mass of dibutylhydroxytoluene was separately prepared. While maintaining the temperature in the glass reaction vessel at 85 to 95°C, one-third of the mixture was added every 30 minutes, and the reaction was carried out for a total of 90 minutes. The temperature was then maintained at 95 to 105°C. The reaction was monitored by IR, and the absorption of the isocyanate group (2250 cm -1When the temperature (around 1000° C.) became constant, the reaction was judged to be complete, and a urethane acrylate resin having bromine atoms (UA-1) was obtained.

[0054] Production Example 5 (Production of urethane acrylate resin having bromine atoms) In a glass reaction vessel equipped with a stirrer, a heater, a cooling tube, a thermometer, and a gas inlet tube, 1607 parts by mass of isophorone diisocyanate and 0.7 parts by mass of dibutyltin dilaurate were charged, and the mixture was heated to 85°C while stirring and blowing in air. Separately, a mixed solution of 1435 parts by mass of 2,2-bis(bromomethyl)-1,3-propanediol, 455 parts by mass of 2-hydroxyethyl methacrylate, and 1.4 parts by mass of dibutylhydroxytoluene was prepared. While maintaining the temperature in the glass reaction vessel at 85 to 95°C, one-third of the mixed solution was added every 30 minutes, and the reaction was allowed to proceed for a total of 90 minutes. The temperature was further maintained at 85 to 95°C. The reaction was monitored by IR, and the absorption of the isocyanate group (2250 cm -1 When the temperature (around 1000° C.) became constant, the reaction was judged to be complete, and a urethane acrylate resin having bromine atoms (UA-2) was obtained.

[0055] Example 1 (Production of Sheet Molding Compound) The resin composition was prepared as follows. Unsaturated polyester resin UP-1 47 parts by weight, styrene 28 parts by weight, 30% styrene solution of polystyrene / polyvinyl acetate block copolymer (product name: Modiper SV30B30, manufactured by NOF Corp.) 25 parts by weight, hydroquinone (manufactured by Seiko Chemical Co., Ltd.) 0.03 parts by weight, hexyl peracetate (product name: Perhexyl A, manufactured by NOF Corp.) 1.0 part by weight, zinc stearate (product name: ZNS-P, manufactured by ADEKA Corp.) 5 parts by weight, aluminum hydroxide (product name: B-333L, manufactured by Armolix Corp.) A resin composition was obtained by mixing and stirring 120 parts by mass of glass hollow micro sphere filler 1 (product name: Glass Bubbles K37, manufactured by 3M Japan Ltd.), 20 parts by mass of glass hollow micro sphere filler 1 (product name: Glass Bubbles K37, manufactured by 3M Japan Ltd.), and 2.5 parts by mass of a wetting dispersant (product name: BYK-W9010, manufactured by BYK-Chemie), and then adding and mixing 2.0 parts by mass of magnesium oxide paste (product name: Magmicron MD-4AM-2, manufactured by Mikuni Pigment Co., Ltd.) and 10 parts by mass of gray pigment paste (manufactured by Tokyo Ink Co., Ltd.).

[0056] Next, a sheet molding compound was prepared. The resin composition obtained as described above was applied to the upper and lower stretched polypropylene carrier films using a doctor blade to a thickness of about 1 mm. Glass fiber chops (glass roving equivalent to TEX4800 cut to a length of about 2.5 cm) were uniformly spread on the resin composition applied to the film placed below. The amount of glass fiber chops was 22 mass% with respect to the total amount of the sheet molding compound. The upper and lower resin compositions were laminated so as to sandwich the glass fiber chops, and then pressure was applied to the whole to impregnate the glass fiber chops with the resin composition, and the sheet molding compound was obtained by storing it at 35°C to 45°C for 24 hours.

[0057] Examples 2 to 17 and Comparative Examples 1 to 5 (Production of Sheet Molding Compounds) A sheet molding compound was obtained in the same manner as in Example 1, except that the raw materials of the resin composition were changed to the types and amounts shown in Table 1. The raw materials shown in Table 1 are as follows. Glass micro hollow sphere filler 2 Product name: Glass Bubbles S28HS, 3M Japan Ltd. Silica micro hollow sphere filler Product name: Marllite BA-15, manufactured by Marunaka Shirado Co., Ltd. Glass short fiber Product name: Milled fiber MF06JB1-20, manufactured by Asahi Fiberglass Co., Ltd. -Spherical silica particles Product name: Micron S4070, Nippon Steel Chemical & Material Co., Ltd. Mica powder Product name: Mica powder A-21, manufactured by Yamaguchi Mica Co., Ltd.

[0058] [Table 1]

[0059] [Table 2]

[0060] From Table 1, it can be seen that the molded article obtained by molding the sheet molding compound of the embodiment does not burn in the combustion test and has high combustibility. Furthermore, in the tracking resistance test after heat treatment, it can be seen that no tracking occurs and the electrical insulation is excellent. It can also be seen that the hardness after heat treatment is high and the shape is maintained. From these, it can be seen that the sheet molding compound of the present invention has excellent flame retardancy and can obtain a molded article that has excellent shape retention and electrical properties even after contact with a flame and reaching a high temperature. Since the sheet molding compound of the present invention has the above-mentioned excellent properties, it is useful as a molding material used for electrical parts.

Claims

1. A sheet molding compound obtained by impregnating a reinforcing fiber substrate with a resin composition containing a thermosetting resin, a polymerizable monomer, a shrinkage reducing agent, a curing agent, a polymerization inhibitor, and a filler, the thermosetting resin contains at least one selected from the group consisting of an unsaturated polyester resin having a halogen atom, a vinyl ester resin having a halogen atom, and a urethane acrylate resin having a halogen atom, The sheet molding compound, wherein the filler comprises a silicon-based filler.

2. a total content of the unsaturated polyester resin having a halogen atom, the vinyl ester resin having a halogen atom, and the urethane acrylate resin having a halogen atom relative to the total amount of the thermosetting resin is 50 to 100 mass %, 2. The sheet molding compound according to claim 1, wherein a mass ratio of the total of the thermosetting resin and the polymerizable monomer to the low shrinkage agent [thermosetting resin and polymerizable monomer / low shrinkage agent] is 60 / 40 to 90 / 10.

3. The sheet molding compound according to claim 1 or 2, wherein the content of the silicon-based filler is 5 to 50 parts by mass when the total content of the thermosetting resin, the polymerizable monomer, and the low shrinkage agent is 100 parts by mass.

4. The sheet molding compound according to claim 1 or 2, wherein the content of the silicon-based filler is 15 to 40 parts by mass when the total content of the thermosetting resin, the polymerizable monomer, and the low shrinkage agent is 100 parts by mass.

5. 3. The sheet molding compound according to claim 1, wherein the silicon-based filler comprises at least one selected from the group consisting of glass micro hollow sphere filler, silica micro hollow sphere filler, silica sand, diatomaceous earth, crystalline silica, amorphous silica, mica, and short glass fiber.

6. 3. The sheet molding compound of claim 1 or 2, wherein the halogen atom is chlorine or bromine.

7. 3. The sheet molding compound according to claim 1 or 2, wherein the reinforcing fiber substrate comprises glass fibers.

8. 3. The sheet molding compound according to claim 1, wherein the polymerizable monomer comprises a styrene-based monomer.

9. A molded article for electrical parts obtained by molding the sheet molding compound according to claim 1 or 2.

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