Thermoplastic resin composition for foam molding and foamed molded product thereof

Abstract

To provide a thermoplastic resin composition for foam molding which enables molding of a foam molded article that has a uniform and fine foam cell structure and is also excellent in surface appearance.SOLUTION: A thermoplastic resin composition for foam molding contains 0.1-5 pts.mass of the following component (D), with respect to 100 pts.mass of the total of 1-20 pts.mass of the following component (A), 0-50 pts.mass of the following component (B), and 40-90 pts.mass of the following component (C). Component (A): rubber-reinforced styrenic resin (A) obtained by polymerizing a vinyl monomer (b1) containing an aromatic vinyl compound in presence of a rubbery polymer (a). Component (B): styrenic resin (B) obtained by polymerizing a vinyl monomer (b2) containing an aromatic vinyl compound. Component (C): aromatic polycarbonate resin. Component (D): tetrafluoroethylene-based polymer (D) having a number average molecular weight by DSC method of 100,000 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermoplastic resin composition for foam molding that can form a foam-molded product that exhibits a fine foam cell structure, has a uniform cell size regardless of the part of the foam-molded product, has excellent mechanical properties, and also has an excellent surface appearance in injection foam molding, and a foam-molded product using this thermoplastic resin composition for foam molding.

Background Art

[0002] In an injection molding method using a thermoplastic resin, in order to reduce the amount of resin components used and achieve weight reduction, etc., injection foam molding in which a foaming agent is added to a resin material and injection molding is known. As a foaming agent used in injection foam molding, thermally decomposable chemical foaming agents such as azodicarbonamide are known (Patent Document 1). Also, instead of chemical foaming, physical foaming agents using nitrogen gas, carbon dioxide, etc. as foaming agents are known. Furthermore, a method using a physical foaming agent in a supercritical state has also been proposed.

[0003] Also, the following have been proposed as thermoplastic resin compositions for foam molding. (1) 5 to 90% by mass of a rubber-reinforced styrene resin (A) obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another vinyl monomer (b1) copolymerizable with the aromatic vinyl compound in the presence of a rubbery polymer (a), and having a thermal cyclohexane solubility of 1 to 99% by mass based on the rubbery polymer (a), 0 to 85% by mass of a styrene resin (B) obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another vinyl monomer (b2) copolymerizable with the aromatic vinyl compound, Aromatic polycarbonate resin (C) 10 to 90% by mass, Consisting of 0.1 to 5 parts by mass of a chemical foaming agent (D) with respect to 100 parts by mass in total of the above components (A) to (C), A thermoplastic resin composition for foam molding characterized in that the ratio of the rubbery polymer (a) to the total of the above components (A) to (C) is 3 to 50% by mass (Patent Document 2).

[0004] (2) A rubber-reinforced styrene resin (A) is obtained by polymerizing an aromatic vinyl compound or another vinyl monomer copolymerizable with an aromatic vinyl compound (b1) in the presence of a rubbery polymer (a), and the amount of thermal cyclohexane solubility is 1 to 99% by mass based on the rubbery polymer (a), and is present in an amount of 5 to 90% by mass. A styrene-based resin (B) obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another vinyl monomer copolymerizable with the aromatic vinyl compound (b2) in an amount of 0 to 85% by mass, Aromatic polycarbonate resin (C) 10-90% by mass, The mixture consists of 100 parts by mass of the above components (A) to (C) in total, 0.1 to 5 parts by mass of a chemical blowing agent (D), 0.5 to 18 parts by mass of talc (E), and 0.5 to 25 parts by mass of a fibrous filler (F). A thermoplastic resin composition for foam molding characterized in that the proportion of rubbery polymer (a) in the total of 100% by mass of the above components (A) to (C) is 3 to 50% by mass (Patent Document 3). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-133485 [Patent Document 2] Japanese Patent Publication No. 2010-254833 [Patent Document 3] Japanese Patent Publication No. 2011-37925 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] For foamed molded products obtained by injection foam molding of thermoplastic resin compositions for foam molding, (i) It exhibits a high foaming ratio, a fine foam cell structure, uniform foam cell size regardless of the part of the foamed molded product, and excellent mechanical performance (especially rigidity). (ii) The surface appearance is good, free from defects such as swirl marks and surface irregularities caused by uneven foaming, which result from the transfer of gas released during foam molding onto the unfoamed skin layer formed on the surface of the molded product, thereby degrading the surface quality. This is required. From this perspective, further improvements are desired in the thermoplastic resin compositions for foam molding described in Patent Documents 2 and 3.

[0007] The present invention has been made in view of the above-mentioned conventional problems, and aims to provide a thermoplastic resin composition for foam molding and a foam molded product using the same, which can be used in injection foam molding to produce a foam molded product that exhibits a fine foam cell structure, has uniform foam cell size regardless of the part of the foam molded product, has excellent mechanical performance and excellent surface appearance. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive research to solve the above problems and have found that by blending a high molecular weight tetrafluoroethylene polymer (D) with a resin component consisting of a rubber-reinforced styrene resin (A) and an aromatic polycarbonate resin (C), or a rubber-reinforced styrene resin (A), a styrene resin (B), and an aromatic polycarbonate resin (C), the leakage of foaming gas during injection foam molding is suppressed, resulting in stable foam moldability and solving the above problems. This led to the completion of the present invention. In other words, the gist of this invention is as follows:

[0009] [1] A thermoplastic resin composition for foam molding containing 1 to 20 parts by mass of component (A), 0 to 50 parts by mass of component (B), and 40 to 90 parts by mass of component (C) to total 100 parts by mass, and containing 0.1 to 5 parts by mass of component (D) with respect to the total of 100 parts by mass of components (A) to (C). Component (A): A rubber-reinforced styrene resin (A) obtained by polymerizing an aromatic vinyl compound or another vinyl monomer copolymerizable with an aromatic vinyl compound (b1) in the presence of a rubbery polymer (a). Component (B): A styrene resin (B) obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another vinyl monomer (b2) copolymerizable with the aromatic vinyl compound Component (C): An aromatic polycarbonate resin (C) Component (D): A tetrafluoroethylene-based polymer (D) having a number-average molecular weight of 100,000 or more by the DSC method

[0010] [2] The thermoplastic resin composition for foam molding according to [1], further comprising 0.1 to 5 parts by mass of a chemical foaming agent (E) with respect to 100 parts by mass in total of the components (A) to (C).

[0011] [3] The thermoplastic resin composition for foam molding according to [1] or [2], further comprising 0.1 to 20 parts by mass of an inorganic filler (F) with respect to 100 parts by mass in total of the components (A) to (C).<00,00076>

[0012] [4] The thermoplastic resin composition for foam molding according to any one of [1] to [3], which is used for core-back injection foam molding.

[0013] [5] A foam-molded article obtained by molding the thermoplastic resin composition for foam molding according to any one of [1] to [4].

[0014] [6] A foam-molded article obtained by core-back injection foam molding of the thermoplastic resin composition for foam molding according to any one of [1] to [4].

Effects of the Invention

[0015] According to the thermoplastic resin composition for foam molding of the present invention, in injection foam molding, a fine foam cell structure is developed, the size of the foam cells is uniform regardless of the part of the foam-molded article, and the foam-molded article has excellent mechanical properties and excellent surface appearance can be provided.

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail.

[0017] [Thermoplastic resin composition for foam molding] The thermoplastic resin composition for foam molding of the present invention contains 1 to 20 parts by mass of component (A), 0 to 50 parts by mass of component (B), and 40 to 90 parts by mass of component (C) to total 100 parts by mass, and contains 0.1 to 5 parts by mass of component (D) with respect to the total of 100 parts by mass of components (A) to (C). Component (A): A rubber-reinforced styrene resin (A) obtained by polymerizing an aromatic vinyl compound or another vinyl monomer copolymerizable with an aromatic vinyl compound (b1) in the presence of a rubbery polymer (a), Component (B): Styrene resin (B) obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another vinyl monomer (b2) copolymerizable with the aromatic vinyl compound. Ingredients (C): Aromatic polycarbonate resin (C) Component (D): Tetrafluoroethylene polymer (D) with a number-average molecular weight of 100,000 or more as determined by DSC method.

[0018] In this invention, "(co)polymerization" means both homopolymerization and copolymerization, and "(meth)acrylate" means at least one of acrylate and methacrylate. The same applies to "(meth)acrylic acid." Furthermore, the thermoplastic resin composition for foam molding of this invention may be simply abbreviated as "thermoplastic resin composition."

[0019] [Component (A): Rubber-reinforced styrene resin (A)] Component (A) is a rubber-reinforced styrene resin (A) obtained by polymerizing an aromatic vinyl compound or another vinyl monomer (b1) copolymerizable with an aromatic vinyl compound in the presence of a rubbery polymer (a).

[0020] Examples of rubbery polymers (a) include conjugated diene rubbers such as polybutadiene, polyisoprene, butadiene-styrene copolymer, and butadiene-acrylonitrile copolymer; olefin rubbers such as ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, ethylene-butene-1 copolymer, and ethylene-butene-1-non-conjugated diene copolymer; acrylic rubber; silicone rubber; polyurethane rubber; silicone-acrylic IPN rubber; natural rubber; conjugated diene block copolymer; hydrogenated conjugated diene block copolymer; and the like.

[0021] The above-mentioned olefin-based rubber is not particularly limited, but examples include ethylene-α-olefin-based rubber containing ethylene and α-olefins having 3 or more carbon atoms. The ethylene content is calculated as 100% by mass of the total amount of monomers constituting the above-mentioned ethylene-α-olefin-based rubber. In that case, the amount is preferably 5 to 95% by mass, more preferably 50 to 90% by mass, and even more preferably 60 to 88% by mass.

[0022] Examples of α-olefins having 3 or more carbon atoms include propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methylbutene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, and 1-undecene. These α-olefins may be included individually or in combination of two or more. Of the above α-olefins, propylene and 1-butene are preferred.

[0023] The α-olefin content is preferably 95-5% by mass, more preferably 50-10% by mass, and particularly preferably 40-12% by mass, when the total amount of monomers constituting the ethylene-α-olefin rubber is taken as 100% by mass.

[0024] Ethylene-α-olefin rubber may be a binary copolymer composed of ethylene and α-olefin, or it may be a polymer (terpolymer, quaternary copolymer, etc.) composed of these and other compounds. Examples of other compounds include non-conjugated diene compounds.

[0025] Examples of non-conjugated diene compounds used in olefin-based rubbers include alkenyl norbornenes, cyclic dienes, and aliphatic dienes, with dicyclopentadiene and 5-ethylidene-2-norbornene being preferred. These non-conjugated diene compounds can be used individually or in combination of two or more. The content of non-conjugated diene compound units in ethylene-α-olefin-based rubber is usually less than 30% by mass, preferably less than 15% by mass.

[0026] The above-mentioned acrylic rubber is not particularly limited, but a (co)polymer of an alkyl (meth)acrylate compound having 1 to 8 carbon atoms in the alkyl group, or a copolymer of this alkyl (meth)acrylate compound with a vinyl monomer copolymerizable thereto is preferred.

[0027] Specific examples of alkyl acrylate compounds with 1 to 8 carbon atoms in the alkyl group used here include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, i-butyl acrylate, amyl acrylate, hexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate. Specific examples of alkyl methacrylate compounds include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, amyl methacrylate, hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate. Of these compounds, n-butyl acrylate and 2-ethylhexyl acrylate are preferred. These can be used individually or in combination of two or more.

[0028] Furthermore, vinyl monomers copolymerizable with the above-mentioned alkyl (meth)acrylate compounds include, for example, polyfunctional vinyl compounds, aromatic vinyl compounds, and vinyl cyanide compounds.

[0029] Polyfunctional vinyl compounds are monomers having two or more vinyl groups in a single monomer molecule, and they function to crosslink (meth)acrylic rubbers and act as reaction initiation points during graft polymerization. Specific examples of polyfunctional vinyl monomers include polyfunctional aromatic vinyl compounds such as divinylbenzene and divinyltoluene; (meth)acrylic acid esters of polyhydric alcohols such as (poly)ethylene glycol dimethacrylate and trimethylolpropane triacrylate; and diallyl malate, diallyl fumarate, triallyl cyanurate, triallyl cyanurate, diallyl phthalate, and allyl methacrylate. These polyfunctional vinyl compounds can be used individually or in combination of two or more.

[0030] All of the aromatic vinyl compounds and vinyl cyanide compounds described below can be used. Furthermore, other copolymerizable monomers include acrylamide, methacrylamide, vinylidene chloride, alkyl vinyl ethers with 1 to 6 carbon atoms in the alkyl group, alkyl esters of (meth)acrylates with 9 or more carbon atoms in the alkyl group, (meth)acrylic acid, etc. These can be used individually or in combination of two or more.

[0031] The preferred monomer composition of the above acrylic rubber is 80 to 99.99% by mass, more preferably 90 to 99.95% by mass, of alkyl (meth)acrylate ester compound units with 1 to 8 C1 alkyl groups; 0.01 to 5% by mass, more preferably 0.05 to 2.5% by mass, of polyfunctional vinyl compound units; and 0 to 20% by mass, more preferably 0 to 10% by mass, of other vinyl monomer units copolymerizable therewith. However, the monomer composition shall total 100% by mass.

[0032] As described below, the rubber-reinforced styrene resin (A) preferably has a thermal cyclohexane solubility of 1 to 99% by mass, based on the rubber polymer (a). In order to make the thermal cyclohexane solubility of the rubber-reinforced styrene resin (A) 1% by mass or more, based on the rubber polymer (a), when using a polyfunctional vinyl compound in the production of the above acrylic rubber, it is preferable to carry it out in a later stage of polymerization. That is, it can be produced by polymerizing an alkyl (meth)acrylate compound and, if necessary, another copolymerizable vinyl monomer (b1) in the initial stage of polymerization, and then polymerizing the alkyl (meth)acrylate compound and the polyfunctional vinyl compound, and, if necessary, another copolymerizable vinyl monomer (b1) in the later stage of polymerization.

[0033] The present invention relates to a method for producing acrylic rubber, which includes (1) a method of polymerizing by adding various vinyl monomers all at once, (2) a method of polymerizing by adding a specific vinyl monomer all at once and then adding the remaining vinyl monomers in a later stage of polymerization, (3) a method of polymerizing by adding a portion of various vinyl monomers and then continuously adding the remaining vinyl monomers, and (4) a method of polymerizing by dividing the various vinyl monomers into two or more stages. Method (4) is preferred, and method (4) is even more preferred, in which a polyfunctional vinyl compound is used in the second and later stages. Emulsion polymerization is particularly preferred as the polymerization method.

[0034] The volume-average particle size of the acrylic rubber is preferably 50 to 1000 nm, more preferably 40 to 700 nm, and particularly preferably 50 to 500 nm.

[0035] Specifically, the conjugated diene block copolymer is a copolymer comprising at least one of the following block A or block C and at least one of the following block B or block A / B, or a polymer of block B or A / B. These can be produced by known anionic polymerization methods, for example, by methods disclosed in Japanese Patent Publication No. 47-28915, Japanese Patent Publication No. 47-3252, Japanese Patent Publication No. 48-2423, Japanese Patent Publication No. 48-20038, etc.

[0036] The specific structure of the conjugated diene block copolymer is: A; Aromatic vinyl compound polymer block, B; Conjugated diene polymer block, A / B; Random copolymerization pairs of aromatic vinyl compounds / conjugated dienes. C; Consists of a copolymer of a conjugated diene and an aromatic vinyl compound, and is a tapered block in which the aromatic vinyl compound gradually increases. If we define them as such, the following structures can be cited.

[0037] AB (1) ABA (2) ABC (3) A-B1-B2 (4) (Here, B1 is a conjugated diene polymer block or a conjugated diene with an aromatic vinyl compound) The copolymer block has a preferably 20% or more vinyl bond content in the conjugated diene portion, while B2 is a conjugated diene polymer block or a copolymer block of a conjugated diene and an aromatic vinyl compound, with a preferably less than 20% vinyl bond content in the conjugated diene portion. AA / B (5) AA / BC (6) AA / BB (7) AA / BA (8) B2-B1-B2 (9) (Here, B1 and B2 are the same as above.) CB (10) CBC (11) CA / BC (12) CAB (13)

[0038] Furthermore, copolymers having these basic skeletons repeated can be cited, and these may also be conjugated diene block copolymers obtained by coupling them. A copolymer with the structure of formula (4) is shown in Japanese Patent Publication No. 2-133406, and copolymers with the structures of formulas (5) and (6) are shown in Japanese Patent Publication No. 2-305814 and Japanese Patent Publication No. 3-72512, respectively.

[0039] Examples of conjugated dienes used here include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, and chloroprene. However, to obtain a conjugated diene-based block copolymer that is industrially usable and has excellent physical properties, 1,3-butadiene, isoprene, and 1,3-pentadiene are preferred, and 1,3-butadiene is more preferred.

[0040] Furthermore, examples of aromatic vinyl compounds used here include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, hydroxystyrene, vinylxylene, monochlorostyrene, dichlorostyrene, monobromstyrene, dibromstyrene, fluorostyrene, pt-butylstyrene, ethylstyrene, vinylnaphthalene, divinylbenzene, 1,1-diphenylstyrene, N,N-diethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, and others, with styrene and α-methylstyrene being preferred, and styrene being particularly preferred.

[0041] The ratio of aromatic vinyl compound to conjugated diene in a conjugated diene block copolymer is 0-70 / 100-30 by mass ratio, preferably 0-60 / 100-40, more preferably 0-50 / 100-50, and when the aromatic vinyl compound is essential, it is preferably 10-70 / 90-30. Here, if the content of aromatic vinyl compound exceeds 70% by mass, it becomes resinous, and its effect as a rubber component is inferior, which is undesirable. Furthermore, the amount of vinyl bonding in the conjugated diene portion of a conjugated diene block is typically in the range of 5-80%.

[0042] The number-average molecular weight of conjugated diene block copolymers is typically 10,000 to 1,000,000, preferably 20,000 to 500,000, and more preferably 20,000 to 200,000. Of these, the number-average molecular weight of part A of the above structural formula is preferably in the range of 3,000 to 150,000, and the number-average molecular weight of part B is preferably in the range of 5,000 to 200,000. Here, the number-average molecular weight is the value measured by gel permeation chromatography (GPC).

[0043] The amount of vinyl bond in conjugated diene compounds can be adjusted using N,N,N',N'-tetramethylethylenediamine, trimethylamine, triethylamine, and diazocyclo(2,2,2)octa This can be done using amines such as amines, ethers such as tetrahydrofuran, diethylene glycol dimethyl ether, and diethylene glycol dibutyl ether, thioethers, phosphines, phosphoamides, alkylbenzene sulfonates, potassium or sodium alkoxides, etc.

[0044] Examples of coupling agents used in the present invention include diethyl adipate, divinylbenzene, methyldichlorosilane, silicon tetrachloride, butyltrichlorosilicon, tetrachlorotin, butyltrichlorotin, dimethylchlorosilicon, tetrachlorogermanium, 1,2-dibromoethane, 1,4-chloromethylbenzene, bis(trichlorosilyl)ethane, epoxidized linseed oil, tolylene diisocyanate, and 1,2,4-benzenetriisocyanate.

[0045] The hydrogenated conjugated diene block copolymer is a partially hydrogenated or fully hydrogenated product in which at least 30%, preferably 50%, of the carbon-carbon double bonds of the conjugated diene portion of the above-mentioned conjugated diene block copolymer are hydrogenated, and more preferably 90% or more are hydrogenated.

[0046] The hydrogenation reaction of conjugated diene block copolymers can be carried out by known methods. Furthermore, by adjusting the hydrogenation rate by known methods, the desired hydrogenated conjugated diene block copolymer can be obtained. Specific methods include those disclosed in Japanese Patent Publication No. 42-8704, Japanese Patent Publication No. 43-6636, Japanese Patent Publication No. 63-4841, Japanese Patent Publication No. 63-5401, Japanese Patent Application Publication No. 2-133406, Japanese Patent Application Publication No. 1-297413, and others.

[0047] The rubbery polymer (a) used in the present invention preferably has a gel content of 70% by mass or less from the viewpoint of foaming properties of the thermoplastic resin composition for foam molding, more preferably has a gel content of 50% by mass or less, and even more preferably 10% by mass or less. The gel content can be determined by the following method. 1 g of rubbery polymer (a) is placed in 100 ml of toluene and left to stand at room temperature for 48 hours. Then, the toluene-insoluble matter and the toluene-insoluble material, filtered through a 100-mesh wire mesh (with a mass of W1 gram), are vacuum-dried at 80°C for 6 hours and weighed (with a mass of W2 grams). Substitute W1 and W2 into the following formula (14) to obtain the gel content. Note that some ethylene-propylene rubbery polymers contain ethylene crystals; in such cases, the gel content should be determined by dissolving the polymer at 80°C. Gel content = [[W2(g) - W1(g)] / 1(g)] × 100 (14)

[0048] The gel content can be adjusted during the production of the rubbery polymer (a) by appropriately setting the type and amount of crosslinkable monomer used, the type and amount of molecular weight regulator used, the polymerization time, the polymerization temperature, the polymerization conversion rate, etc.

[0049] Preferred rubbery polymers (a) used in the present invention include polybutadiene, butadiene-styrene copolymer, ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, acrylic rubber, silicone rubber, conjugated diene block copolymer, and hydrogenated conjugated diene block copolymer. More preferably, ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, acrylic rubber, conjugated diene block copolymer, and hydrogenated conjugated diene block copolymer. Particularly preferred are acrylic rubber, ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, conjugated diene block copolymer, and hydrogenated conjugated diene block copolymer. Most preferred is acrylic rubber with a gel content of 10% by mass or less and a volume-average particle diameter of 50 to 500 nm, particularly 50 to 300 nm.

[0050] The rubbery polymer (a) can be obtained by known methods such as emulsion polymerization, solution polymerization, bulk polymerization, and suspension polymerization. Among these, acrylic rubber is preferably produced by emulsion polymerization, ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene copolymer, conjugated diene block copolymer, and hydrogenated conjugated diene block copolymer are preferably produced by solution polymerization, and polybutadiene and butadiene-styrene copolymer are preferably produced by solution polymerization.

[0051] Component (A) is obtained by polymerizing an aromatic vinyl compound or another vinyl monomer (b1) that can copolymerize with an aromatic vinyl compound in the presence of the above-mentioned rubbery polymer (a). That is, the vinyl monomer (b1) may be an aromatic vinyl compound alone, or a mixture of an aromatic vinyl compound and another vinyl monomer that can copolymerize with the aromatic vinyl compound. Furthermore, component (A) is preferably obtained by polymerizing 80 to 30 parts by mass of an aromatic vinyl compound or another vinyl monomer (b1) that can be copolymerized with an aromatic vinyl compound in the presence of 20 to 70 parts by mass of the above-mentioned rubbery polymer (a) (however, the total of the rubbery polymer (a) and the vinyl monomer (b1) shall be 100 parts by mass). More preferably, this ratio is 30 to 60 parts by mass of the rubbery polymer (a) and 70 to 40 parts by mass of the vinyl monomer (b1).

[0052] All of the aromatic vinyl compounds described in rubbery polymer (a) above can be used as aromatic vinyl compounds. Styrene and α-methylstyrene are particularly preferred, and these can be used individually or in combination of two or more.

[0053] Other vinyl monomers copolymerizable with aromatic vinyl compounds include vinyl cyanide compounds, (meth)acrylic acid ester compounds, maleimide compounds, and various other functional group-containing unsaturated compounds. Other functional group-containing unsaturated compounds include unsaturated acid compounds, epoxy group-containing unsaturated compounds, hydroxyl group-containing unsaturated compounds, acid anhydride group-containing unsaturated compounds, oxazoline group-containing unsaturated compounds, and substituted or unsubstituted amino group-containing unsaturated compounds. These other vinyl monomers can be used individually or in combination of two or more.

[0054] Examples of vinyl cyanide compounds include acrylonitrile and methacrylonitrile, which can be used individually or in combination of two or more. Chemical resistance is imparted by the use of vinyl cyanide compounds. The amount of vinyl cyanide compound used is usually 0 to 60% by mass, preferably 5 to 50% by mass, as a percentage of the total amount of vinyl monomer (b1).

[0055] Examples of (meth)acrylic acid ester compounds include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate, which can be used individually or in combination of two or more. The use of (meth)acrylic acid ester compounds improves surface hardness. The amount of (meth)acrylic acid ester compound used is usually 0 to 80% by mass as a percentage of the total amount of vinyl monomer (b1).

[0056] Examples of maleimide compounds include N-aryl maleimides such as N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-hydroxyphenyl)maleimide, and N-chlorophenylmaleimide, and N-cycloalkyl maleimides such as N-cyclohexylmaleimide. These can be used individually or in combination of two or more. In addition, maleimide units may be introduced by copolymerizing maleic anhydride before imidation. Heat resistance is imparted by the use of maleimide compounds. The amount of maleimide compound used is usually 1 to 60% by mass as a percentage of the total amount of vinyl monomer (b1).

[0057] Examples of unsaturated acid compounds include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, and cinnamic acid, which can be used individually or in combination of two or more.

[0058] Examples of epoxy group-containing unsaturated compounds include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether, which can be used individually or in combination of two or more.

[0059] Examples of hydroxyl group-containing unsaturated compounds include 3-hydroxy-1-propene, 4-hydroxy-1-butene, cis-4-hydroxy-2-butene, trans-4-hydroxy-2-butene, 3-hydroxy-3-methyl-1-propene, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, and N-(4-hydroxyphenyl)maleimide. These can be used individually or in combination of two or more.

[0060] Examples of oxazoline group-containing unsaturated compounds include vinyl oxazolines, which can be used individually or in combination of two or more.

[0061] Examples of unsaturated compounds containing acid anhydride groups include maleic anhydride, itaconic anhydride, and citraconic anhydride, which can be used individually or in combination of two or more.

[0062] Examples of substituted or unsubstituted amino group-containing unsaturated compounds include aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, phenylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, acrylamine, N-methylacrylamine, acrylamide, N-methylacrylamide, and p-aminostyrene. These can be used individually or in combination of two or more.

[0063] When the above-mentioned other functional group-containing unsaturated compounds are used, the compatibility between the rubber-reinforced styrene resin (A) and the styrene resin (B) and aromatic polycarbonate resin (C) may be improved when these two are blended. The amount of the above-mentioned other functional group-containing unsaturated compounds used is usually 0.1 to 20% by mass, preferably 0.1 to 10% by mass, relative to the total amount of components (A) and (B).

[0064] The content of monomers other than aromatic vinyl compounds in vinyl monomer (b1) is usually 80% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less, when the total amount of vinyl monomer (b1) is taken as 100% by mass.

[0065] More preferred combinations of monomers constituting the vinyl monomer (b1) are styrene alone, styrene / acrylonitrile, styrene / methyl methacrylate, styrene / acrylonitrile / methyl methacrylate, styrene / acrylonitrile / glycidyl methacrylate, styrene / acrylonitrile / 2-hydroxyethyl methacrylate, styrene / acrylonitrile / (meth)acrylic acid, styrene / N-phenylmaleimide, styrene / methyl methacrylate / cyclohexylmalemide, etc., and even more preferably, styrene alone, styrene / acrylonitrile = 65 / 45~90 / 10 (mass ratio), styrene / methyl methacrylate = 80 / 20~20 / 80 (mass ratio), and combinations of styrene / acrylonitrile / methyl methacrylate, where the amount of styrene is any in the range of 20~80% by mass, and the total amount of acrylonitrile and methyl methacrylate is any in the range of 20~80% by mass.

[0066] The rubber-reinforced styrene resin (A) can be produced by known polymerization methods, such as emulsion polymerization, bulk polymerization, solution polymerization, suspension polymerization, and polymerization methods combining these. If the rubbery polymer (a) is obtained by emulsion polymerization, component (A) can also be produced by emulsion polymerization. Furthermore, if the rubbery polymer (a) is obtained by solution polymerization, component (A) is generally and preferably produced by bulk polymerization, solution polymerization, and suspension polymerization. However, even if the rubbery polymer (a) is produced by solution polymerization, component (A) can be produced by emulsion polymerization if the rubbery polymer (a) is emulsified using a known method. Also, even if the rubbery polymer (a) is produced by emulsion polymerization, component (A) can be produced by bulk polymerization, solution polymerization, and suspension polymerization after coagulation and isolation.

[0067] When manufactured by emulsion polymerization, polymerization initiators, chain transfer agents, emulsifiers, etc., are used, and all known ones can be used. Examples of polymerization initiators include cumene hydroperoxide, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, tetramethylbutyl hydroperoxide, tert-butyl hydroperoxide, potassium persulfate, and azobisisobutyronitrile. Furthermore, it is preferable to use redox-based materials such as various reducing agents, sugar-containing iron pyrophosphate formulations, and sulfoxylate formulations as polymerization initiator aids.

[0068] Examples of chain transfer agents include octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexyl mercaptan, and terpinolenes. As emulsifiers, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, aliphatic sulfonates such as sodium lauryl sulfate, higher fatty acid salts such as potassium laurylate, potassium stearate, potassium oleate, potassium palmitate, and rosinates such as potassium rosinate can be used.

[0069] In emulsion polymerization, the rubbery polymer (a) and vinyl monomer (b1) may be used in the following ways: the vinyl monomer (b1) may be added all at once in the presence of the entire amount of rubbery polymer (a) and polymerized; or it may be added in stages or continuously. Furthermore, a portion of the rubbery polymer (a) may be added during the polymerization process.

[0070] After emulsion polymerization, the obtained latex is usually coagulated with a coagulant. Then, the latex is washed with water and dried to obtain the powder of component (A). At this stage, two or more latex components (A) obtained by emulsion polymerization may be blended as appropriate before coagulation, or latex components (B) may be blended as appropriate before coagulation. As coagulants, inorganic salts such as calcium chloride, magnesium sulfate, and magnesium chloride, or acids such as sulfuric acid, acetic acid, citric acid, and malic acid can be used. Alternatively, the powder of component (A) can be obtained by spray-drying the latex.

[0071] The solvents that can be used when producing component (A) by solution polymerization are inert polymerization solvents used in ordinary radical polymerization, such as aromatic hydrocarbons like ethylbenzene and toluene, ketones like methyl ethyl ketone and acetone, acetonitrile, dimethylformamide, and N-methylpyrrolidone.

[0072] The polymerization temperature is typically in the range of 80 to 140°C, preferably 85 to 120°C. Polymerization may be carried out using a polymerization initiator, or it may be carried out by thermal polymerization without the use of a polymerization initiator. Suitable polymerization initiators include organic peroxides such as ketone peroxides, dialkyl peroxides, diacyl peroxides, peroxyesters, hydroperoxides, azobisisobutyronitriles, and benzoyl peroxides. When using chain transfer agents, for example, mercaptans, turpin-lenes, and α-methylstyrene dimers can be used.

[0073] Furthermore, when producing component (A) by bulk polymerization or suspension polymerization, polymerization initiators, chain transfer agents, etc., as described in the section on solution polymerization can be used.

[0074] The amount of residual monomer in component (A) obtained by each of the above polymerization methods is usually 10,000 ppm or less, preferably 5,000 ppm or less.

[0075] Component (A), obtained by polymerizing a vinyl monomer (b1) in the presence of a rubbery polymer (a), includes a copolymer in which the vinyl monomer (b1) is graft copolymerized with the rubbery polymer (a), and an ungrafted component (a (co)polymer of vinyl monomer (b1)) that is not grafted onto the rubbery polymer (a).

[0076] The grafting rate of the rubber-reinforced styrene resin (A) is usually adjusted to 5 to 100% by mass, preferably 10 to 90% by mass, more preferably 15 to 85% by mass, and most preferably 20 to 80% by mass. The grafting rate can be changed by various factors such as the type and amount of polymerization initiator used, the type and amount of chain transfer agent used, the polymerization method, the contact time between the vinyl monomer (b1) and the rubbery polymer (a) during polymerization, the type of rubbery polymer (a), and the polymerization temperature. Generally, increasing the grafting rate reduces the amount of components that dissolve from component (A) in hot cyclohexane, but the absence of these dissolved components worsens the foaming properties of the thermoplastic resin composition of the present invention. The graft ratio can be calculated using the following formula (15). Graft rate (mass%) = {(TS) / S} × 100 (15)

[0077] In the above formula (15), T is the mass (g) of the insoluble matter obtained by separating the insoluble matter from the soluble matter by adding 1 g of rubber-reinforced styrene resin (A) to 20 ml of acetone, shaking it with a shaker for 2 hours, and then centrifuging it with a centrifuge (rotation speed: 23,000 rpm) for 60 minutes, and S is the mass (g) of the rubbery polymer (a) contained in 1 g of rubber-reinforced styrene resin (A). If only aromatic vinyl compounds are used as the vinyl monomer (b1), methyl ethyl ketone is used instead of acetone for the measurement.

[0078] Furthermore, the intrinsic viscosity [η] of the acetone-soluble component of the rubber-reinforced styrene resin (A) (measured at 30°C using methyl ethyl ketone as the solvent) is typically 0.15 to 1.2 dl / g, preferably 0.2 to 1.0 dl / g, and more preferably 0.2 to 0.8 dl / g.

[0079] The average particle size of the grafted rubbery polymer particles dispersed in the rubber-reinforced styrene resin (A) is typically 50 to 3,000 nm, preferably 40 to 2,500 nm, and particularly preferably 50 to 2,000 nm. When the rubber particle size is less than 50 nm, the impact resistance tends to be poor, and when it exceeds 3,000 nm, the surface appearance of the molded product tends to be poor.

[0080] Furthermore, a transparent component (A) can be obtained by substantially matching the refractive index of the copolymer of the rubbery polymer (a) and the vinyl monomer (b1) used and / or by substantially making the particle size of the dispersed rubbery polymer (a) substantially below the wavelength of visible light (usually 1,500 nm or less), and these transparent resins can also be used as component (A) of the present invention.

[0081] Component (A) may be used alone, or two or more components with different copolymerization compositions or physical properties may be mixed and used.

[0082] [Component (B): Styrene resin (B)] Component (B) is a styrene resin (B) obtained by polymerizing an aromatic vinyl compound, or an aromatic vinyl compound and another vinyl monomer (b2) copolymerizable with the aromatic vinyl compound. That is, the vinyl monomer (b2) may be the aromatic vinyl compound alone, or a mixture of the aromatic vinyl compound and another vinyl monomer copolymerizable with the aromatic vinyl compound. All of the aromatic vinyl compounds and other vinyl monomers copolymerizable with the aromatic vinyl compound described above can be used. Furthermore, the vinyl monomer (b2) may be the same as or different from the vinyl monomer (b1) described above.

[0083] The content of monomers other than aromatic vinyl compounds in vinyl monomer (b2) is usually 80% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less, when the total amount of vinyl monomer (b2) is taken as 100% by mass.

[0084] Preferred component (B) is a homopolymer of styrene, a styrene-acrylonitrile copolymer, a styrene-methyl methacrylate copolymer, a styrene-acrylonitrile-methyl methacrylate copolymer, a styrene-maleimide compound copolymer, and copolymers of these with the above-mentioned functional group-containing unsaturated compounds.

[0085] Component (B) can be produced by known polymerization methods described in the production method of component (A) above, such as emulsion polymerization, bulk polymerization, solution polymerization, suspension polymerization, and combinations thereof.

[0086] The weight-average molecular weight of styrene resin (B) is typically 40,000 to 300,000, preferably 60,000 to 150,000. Mechanical strength and moldability are further improved when the weight-average molecular weight of styrene resin (B) is within the above range. Here, the weight-average molecular weight of styrene resin (B) is the value on a standard polystyrene basis, measured by gel permeation chromatography (GPC).

[0087] Component (B) may be used alone, or two or more components with different copolymerization compositions or physical properties may be mixed and used.

[0088] [Ingredients (C): Aromatic polycarbonate resin (C)] Aromatic polycarbonate resin (C) can be any known polymerization method, such as interfacial polycondensation between a dihydroxyaryl compound and phosgene, or transesterification (melt polycondensation) between a dihydroxyaryl compound and a carbonate compound such as diphenyl carbonate.

[0089] Examples of the above-mentioned dihydroxyaryl compounds include bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-t-butylphenyl)propane, 2,2-bis(4-hydroxy-3-t-butylphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 4,4'-dihydroxyphenyl ether, 4,4'-dihydroxyphenyl sulfide, 4,4'-dihydroxyphenyl sulfone, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone, hydroquinone, resorcinol, and the like. Furthermore, there are polyorganosiloxanes with hydroxyaryloxy-terminated structures (see, for example, U.S. Patent No. 3,419,634). These can be used individually or in combination of two or more. Among these, 2,2-bis(4-hydroxyphenylpropane (bisphenol A) is preferred.

[0090] The viscosity-average molecular weight of the polycarbonate resin (C) is preferably 12,000 to 40,000, more preferably 15,000 to 35,000, and particularly preferably 18,000 to 30,000. A higher molecular weight results in higher mechanical strength of the resulting foamed molded product, but reduces fluidity, making it difficult to obtain uniform cells and tending to degrade the appearance of the foamed molded product. Two or more aromatic polycarbonate resins (C) with different molecular weights can also be used as component (C).

[0091] Here, the viscosity-average molecular weight of aromatic polycarbonate resin (C) can usually be calculated by substituting the specific viscosity (ηsp), measured using methylene chloride as the solvent at 20°C and a concentration of [0.7 g / 100 ml (methylene chloride)], into the following equation (17). Viscosity average molecular weight=([η]×8130) 1.205 (17) Here, [η] = [(ηsp × 1.12 + 1)] 1 / 2-1] / 0.56C. Note that C represents concentration.

[0092] Aromatic polycarbonate resin (C) obtained by interfacial polycondensation may contain various chlorine compounds, which may adversely affect the durability of the thermoplastic resin composition of the present invention. For this reason, the chlorine compound content of aromatic polycarbonate resin (C) is usually 300 ppm or less, preferably 100 ppm or less, as chlorine atoms.

[0093] [Content of ingredients (A) to (C)] In the thermoplastic resin composition for foam molding of the present invention, the content of component (A) is 1 to 20 parts by mass, preferably 3 to 18 parts by mass, and more preferably 5 to 15 parts by mass, in 100 parts by mass of the total of components (A) to (C). When the content of component (A) is less than 1 part by mass, the impact strength decreases, and when it exceeds 20 parts by mass, the moldability decreases.

[0094] Furthermore, in the thermoplastic resin composition for foam molding of the present invention, the content of component (B) is 0 to 50 parts by mass, preferably 0 to 40 parts by mass, and more preferably 0 to 30 parts by mass, in 100 parts by mass of the total of components (A) to (C). Component (B) is used as needed to impart various functionalities to the thermoplastic resin composition of the present invention or to improve compatibility with other resins by changing the copolymerization components of the styrene resin (B). However, if its content exceeds 50 parts by mass, the foaming properties are impaired, and the appearance of the resulting foamed molded product deteriorates. In particular, component (B) is preferable because it provides a good balance between mechanical strength and fluidity when the content of rubbery polymer (a) in the total 100% by mass of component (A) and component (B) is 3 to 50% by mass.

[0095] Furthermore, in the thermoplastic resin composition for foam molding of the present invention, the content of component (C) is 40 to 90 parts by mass, preferably 45 to 85 parts by mass, and more preferably 50 to 80 parts by mass, in 100 parts by mass of the total of components (A) to (C). If the content of component (C) is less than 40 parts by mass, it becomes difficult to obtain a foamed molded product with a uniform cell diameter, and 90 parts by mass is used. exceed This results in a decrease in the appearance of the resulting foamed molded product.

[0096] [Component (D): Tetrafluoroethylene polymer (D)] The thermoplastic resin composition for foam molding of the present invention is characterized by containing, in addition to the above components (A) to (C), component (D): a tetrafluoroethylene polymer (D) having a number average molecular weight of 100,000 or more by the DSC method. By including such a high molecular weight tetrafluoroethylene polymer (D) in a predetermined proportion, the problems of the present invention are solved.

[0097] Examples of tetrafluoroethylene polymers (D) include polytetrafluoroethylene polymers and acrylic polymer-modified tetrafluoroethylene polymers.

[0098] The tetrafluoroethylene polymer may be a tetrafluoroethylene homopolymer, or a copolymer of tetrafluoroethylene with vinylidene fluoride, hexafluoropropylene, etc. Preferably, it is a tetrafluoroethylene homopolymer.

[0099] Acrylic polymer-modified tetrafluoroethylene polymers are obtained by modifying tetrafluoroethylene polymers with acrylic polymers. Various modification methods are possible, such as blending (meth)acrylic acid ester polymers with polytetrafluoroethylene polymers, polymerizing (meth)acrylic acid ester monomers in the presence of an aqueous dispersion of polytetrafluoroethylene particles, or polymerizing monomers having ethylenically unsaturated bonds in a mixture of an aqueous dispersion of polytetrafluoroethylene particles and an aqueous dispersion of (meth)acrylic acid ester polymers. Commercially available acrylic polymer-modified tetrafluoroethylene polymers can be used, such as Metabren A3000 manufactured by Mitsubishi Chemical Corporation.

[0100] The molecular weight of the tetrafluoroethylene polymer (D) is 100,000 or more, as measured by differential scanning calorimeter (DSC). A molecular weight of 100,000 or more effectively improves the appearance of the foamed molded product and makes the foam cells finer and more uniform. From these viewpoints, the molecular weight of the tetrafluoroethylene polymer (D) is preferably 200,000 or more, and more preferably 300,000 or more. On the other hand, if the molecular weight of the tetrafluoroethylene polymer (D) is excessively large, the thermoplastic resin composition for foamed molding of the present invention becomes non-uniform; therefore, the molecular weight of the tetrafluoroethylene polymer (D) is preferably 20,000,000 or less, and more preferably 15,000,000 or less. The measurement method using the DSC method and the calculation method for the number-average molecular weight are as described in the Examples section below.

[0101] In the thermoplastic resin composition for foam molding of the present invention, the content of component (D) is 0.1 to 5 parts by mass, preferably 0.3 to 4 parts by mass, and more preferably 0.5 to 3 parts by mass, based on 100 parts by mass of the total of components (A) to (C). If the content of component (D) is less than 0.1 parts by mass, the effects of the present invention resulting from the incorporation of component (D) cannot be fully obtained, and if it exceeds 5 parts by mass, the moldability decreases and the appearance of the resulting molded product is impaired.

[0102] Furthermore, the thermoplastic resin composition of the present invention may use only one type of component (D), or it may contain two or more types with different copolymerization compositions and physical properties.

[0103] [Ingredients (E): Chemical foaming agent (E)] The thermoplastic resin composition for foam molding of the present invention preferably further contains a chemical blowing agent (E) (hereinafter sometimes referred to as "component (E)"). There are no particular limitations on the chemical blowing agent (E), but since the thermoplastic resin composition of the present invention contains an aromatic polycarbonate resin (C), amine-based blowing agents that degrade the aromatic polycarbonate resin (C) are undesirable. Preferred examples include, for example, thermal decomposition type inorganic blowing agents that decompose to generate carbon dioxide (such as sodium bicarbonate), thermal decomposition type blowing agents that decompose to generate nitrogen gas, and known thermal decomposition type blowing compounds such as 4,4'-oxybis(benzenesulfonyl hydrazide) (OBSH), azobisisobutyronitrile, p-toluenesulfonyl hydrazide, and 5-phenyltetrazole.

[0104] The amount of chemical blowing agent (E) is appropriately selected depending on the type of chemical blowing agent (E) and resin used to obtain the desired foaming ratio. Typically, the amount of chemical blowing agent (E) is 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass, and more preferably 0.3 to 3 parts by mass, per 100 parts by mass of the total of components (A) to (C). If the amount of chemical blowing agent (E) is less than 0.1 parts by mass, the amount of chemical blowing agent (E) is too low, making it difficult to make the diameter of each foam cell uniform. On the other hand, if the amount of chemical blowing agent (E) exceeds 5 parts by mass, the amount of chemical blowing agent (E) is too high, causing mold contamination by residue of the chemical blowing agent (E), making it difficult to obtain a foamed molded product with a good appearance.

[0105] [Ingredients (F): Inorganic Filler (F)] The thermoplastic resin composition for foam molding used in the present invention may optionally contain an inorganic filler (F) (hereinafter sometimes referred to as "component (F)"). By incorporating an inorganic filler (F), it may be possible to stably obtain a foamed molded product having fine and uniform foam cells, and the rigidity, heat resistance, and dimensional stability of the foamed molded product may be improved.

[0106] Examples of inorganic fillers (F) used in the present invention include talc, wollastonite, calcium carbonate, mica, silica, titania, and other inorganic compound powders, as well as glass fibers. In the present invention, talc is particularly preferred in terms of foaming properties and improved rigidity. Talc is generally known as hydrated magnesium silicate (4SiO2·3MgO·H2O) and is a mineral mainly composed of approximately 60% by mass of SiO2 and approximately 30% by mass of MgO. Surface-treated talc may also be used.

[0107] When inorganic filler (F) is incorporated, the amount of inorganic filler (F) in the thermoplastic resin composition of the present invention is preferably 0.1 to 20 parts by mass, more preferably 3 to 10 parts by mass, and even more preferably 5 to 15 parts by mass, based on 100 parts by mass of the total of components (A) to (C). By incorporating inorganic filler (F) in such proportions, the rigidity, heat resistance, and dimensional stability of the resulting foamed molded product can be improved.

[0108] The particle size of the inorganic filler (F) is not particularly limited, but the central particle size of the volume cumulative particle size measured by laser diffraction or the like, i.e., the 50% average particle size (hereinafter also referred to as "D50"), is preferably 0.5 to 50 μm, and particularly preferably 2 to 20 μm. If the particle size is less than 0.5 μm, it becomes difficult to obtain the effect of a nucleating agent, and the foam cell diameter becomes large, which is undesirable. On the other hand, if the particle size exceeds 50 μm, the foam cells become coarse and few in number, resulting in inferior strength and appearance of the foamed molded product, which is undesirable.

[0109] [Other ingredients] <Heat aging inhibitor> The thermoplastic resin composition of the present invention may contain a heat aging inhibitor. Examples of heat aging inhibitors include phenol-based, phosphorus-based, and sulfur-based agents, and preferably a mixture of these three types. Using this mixture of three types as a heat aging inhibitor provides the effect of maintaining tensile elongation when exposed to high temperatures for a long period of time.

[0110] Among the heat aging inhibitors, phenol-based examples include 2,6-di-t-butylphenol derivatives, 2-methyl-6-t-butylphenol derivatives, octadecyl 3(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 4,4'-butylidene-bis(6-t-butyl-m-cresol), and pentaerythrityl tetrakis[3-(3,5-di- Examples include t-butyl-4-hydroxyphenyl)propionate, 2[1-(2-hydroxy-3,5-di-t-pentylphenyl)-ethyl]-4,6-di-t-pentylphenyl acrylate, and 2-t-butyl-6(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate.

[0111] Examples of phosphorus-based phosphates include tris(2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetraylbis(2,4-di-t-butylphenyl phosphite), distearyl pentaerythritol diphosphite, sodium dihydrogen phosphate, and disodium monohydrogen phosphate.

[0112] Examples of sulfur-based compounds include didodecyl 3,3'-thiobispropionate, dioctadecyl 3,3'-thiobispropionate, pentaerythritol-tetrakis(3-laurylpropionate), and dilauryl 3,3'-thiodipropionate.

[0113] The content of the thermal aging inhibitor in the thermoplastic resin composition of the present invention is usually 0 to 5% by mass, preferably 0 to 3% by mass. In the thermoplastic resin composition of the present invention, the thermal aging characteristics of rubber-reinforced styrene resin (A) and styrene resin (B), other than aromatic polycarbonate resin (C), are improved by adding a thermal aging inhibitor. However, in the case of aromatic polycarbonate resin (C), the thermal aging inhibitor may act as a catalyst that promotes hydrolysis, and there is a tendency for degradation to be suppressed by not adding a thermal aging inhibitor. Considering these conflicting effects, an optimal thermal aging prevention effect can be obtained by adding the above thermal aging inhibitor up to a maximum of 5% by mass.

[0114] <Other additives> The thermoplastic resin composition of the present invention may contain known additives such as weathering agents, lubricants, colorants, flame retardants, flame retardant additives, antistatic agents, and silicone oils. Of these, benzotriazole-based, triazine-based, and benzophenone-based weathering agents are preferred. Ethylene bisstearylamide and hydrogenated castor oil are preferred as lubricants. Carbon black and red iron oxide are examples of colorants. Polyethers and alkyl group-containing sulfonates are examples of antistatic agents.

[0115] <Other resins> The thermoplastic resin composition of the present invention may contain other thermoplastic resins other than components (A) to (C), for example, in an amount of 20 parts by mass or less per 100 parts by mass of the total of components (A) to (D) and the other resin, as long as it does not impair the performance intended for the present invention. Examples of thermoplastic resins that can be incorporated into the thermoplastic resin composition of the present invention include rubber-reinforced styrene resins (except for component (A)), polyolefin resins, vinyl chloride resins, acrylic resins, polyester resins, polyamide resins, polyacetal resins, polyphenylene ether resins, and polyarylene sulfide resins. These thermoplastic resins can be used individually or in combination of two or more.

[0116] [Manufacturing of thermoplastic resin compositions for foam molding] The thermoplastic resin composition for foam molding of the present invention can be manufactured by kneading each component using various extruders, Banbury mixers, kneaders, rolls, etc. For example, pellets of the thermoplastic resin composition for foam molding of the present invention can be obtained by kneading components (A) to (D) and, if necessary, a chemical blowing agent (E), an inorganic filler (F), and other additives. Specifically, this can be done by melting components (A) to (D) and other additives as necessary using a twin-screw extruder. The heating temperature during this melt kneading is appropriately selected depending on the formulation of the thermoplastic resin composition for foam molding, but is usually 220 to 260°C.

[0117] Furthermore, a preferred method for blending a chemical blowing agent (E) into a molten plastic resin is to dry blend the thermoplastic resin composition pellets and the blowing agent masterbatch pellets, then supply the mixture to a molding machine, where the resin is plasticized and foamed in the mold. A physical blowing agent may also be used in combination. Specific examples of physical blowing agents include propane, butane, water, and carbon dioxide.

[0118] [Foam molded products] The foamed molded product of the present invention is obtained by foaming and molding the thermoplastic resin composition for foam molding of the present invention.

[0119] As a method for molding a foamed molded product of the present invention using the thermoplastic resin composition for foam molding of the present invention, known methods such as injection foam molding and extrusion foam molding can be used.

[0120] In the injection foam molding method, the thermoplastic resin composition of the present invention is injected into a cavity space formed in the mold of an injection molding machine. Immediately, or after a predetermined time has elapsed, a movable mold, or a movable core installed inside the movable mold, is retracted to a predetermined position at a predetermined speed, thereby expanding the cavity space and causing foaming. A foamed molded product can be obtained by this so-called core-back injection molding method. Since the temperature of the injection molding mold is usually considerably lower than the temperature of the thermoplastic resin composition at the time of injection, a dense skin layer that is hardly foamed is formed on the surface of the foamed molded product that is in contact with the surface of the cavity.

[0121] The foamed molded product of the present invention can also be integrally formed so as to be in contact with the surface of a substrate such as a resin. Such a laminate can be formed by first placing the substrate in the cavity space and injecting the thermoplastic resin composition for foam molding of the present invention onto its surface. Alternatively, using an injection molding machine equipped with two injection units, the substrate can be formed by first injecting a resin or the like to be the substrate, then retracting a movable core installed inside the movable mold to form a cavity space for injecting the thermoplastic resin composition for foam molding of the present invention, then injecting the thermoplastic resin composition for foam molding of the present invention, and then further retracting the movable core to expand the cavity space and foam it to form a laminate in which a foamed molded layer is laminated on the surface of the substrate.

[0122] In injection foam molding according to the present invention, the retraction speed of the movable mold, or the retraction speed of the movable core installed inside the movable mold, i.e., the "mold opening speed," is preferably 0.05 to 20 mm / second. More preferably, this mold opening speed is 0.1 to 10 mm / second. By using such a mold opening speed, a homogeneous foamed molded product with an average cell diameter of 50 to 500 μm can be produced. If the mold opening speed is less than 0.05 mm / second, cooling will proceed too quickly, resulting in insufficient foaming and potentially causing surface irregularities. On the other hand, if the mold opening speed exceeds 20 mm / second, the resulting foamed molded product may have a large cell diameter and be uneven.

[0123] Furthermore, the temperature of the injected thermoplastic resin composition for foam molding is preferably 200 to 280°C, more preferably 220 to 270°C. If this temperature is below 200°C, the fluidity of the thermoplastic resin composition for foam molding will be insufficient, and filling defects may occur, especially at the end portions. On the other hand, if the temperature exceeds 280°C, thermal degradation may occur depending on the composition of the thermoplastic resin composition for foam molding.

[0124] Furthermore, the mold temperature is preferably 20 to 80°C, and particularly preferably 30 to 70°C. If this temperature is below 20°C, the thermoplastic resin composition for foam molding that is in contact with the inner surface of the mold will cool rapidly, making it impossible to produce a homogeneous foamed molded product, and filling defects may occur at the ends. On the other hand, if the temperature exceeds 80°C, a homogeneous skin layer may not be formed in the portion that is in contact with the surface of the cavity of the foamed molded product, which is undesirable.

[0125] Furthermore, the time from the injection of the thermoplastic resin composition for foam molding until the start of retraction of the movable mold, or the movable core installed inside the movable mold (mold retraction delay time), is preferably 3 seconds or less, although this depends on the mold opening speed. Retraction may also start immediately after the completion of injection. This mold retraction delay time is preferably 0.1 to 2.5 seconds, and particularly preferably 0.1 to 1.5 seconds. If the mold retraction delay time exceeds 3 seconds, cooling may progress too much, making it impossible to obtain a homogeneous foamed molded product.

[0126] The amount of mold retraction can be set according to a predetermined foaming ratio and is not limited, but in particular, for machine frames and the like, it is preferable to retract the mold, i.e., open the mold, so that the final wall thickness of the foamed molded product is 1.1 to 3.0 times the initial wall thickness of the material filling the cavity space inside the mold. If this ratio of wall thickness is called the foaming ratio, the foaming ratio is preferably 1.1 to 3 times, more preferably 1.5 to 2 times, and considering that many foamed molded products have a wall thickness of 5 to 30 mm, and especially 5 to 25 mm, the amount of mold retraction is usually 2.5 to 30 mm.

[0127] The cooling time depends on the dimensions of the foamed molded product and the cooling method, but it is sufficient if the temperature of the foamed molded product drops to around 40-80°C at the time of demolding. Generally, 30 seconds or more is sufficient, and even for large products, 100 seconds is enough.

[0128] In the method for molding foamed products of the present invention, a fabric or film may be inserted into the mold during injection filling.

[0129] The foamed molded product of the present invention exhibits a fine foam cell structure, and the size of the foam cells is uniform regardless of the part of the foamed molded product, resulting in a foamed molded product with excellent mechanical performance. Specifically, the average diameter of the foam cells is preferably 50 to 500 μm, more preferably 70 to 450 μm, and even more preferably 100 to 400 μm, with uniform foam cell diameters and a narrow particle size distribution being preferable. In particular, it is preferable that the foamed molded product is a uniform foamed molded product in which the majority of the foam cells have a diameter of 400 μm or less.

[0130] The foamed molded product of the present invention can further be expanded to a desired expansion ratio of 1.01 to 3.0 times, preferably 1.1 to 2.7 times, and more preferably 1.5 to 2.5 times.

[0131] The shape of the foamed molded product of the present invention can be selected according to the purpose, application, etc., and can be plate-shaped (sheet-shaped), cylindrical, semi-cylindrical, rod-shaped, wire-shaped, lump-shaped, etc.

[0132] [Application] The foamed molded products of the present invention can be used as civil engineering and construction-related materials such as signboards, concrete panels, roof insulation materials, tatami core materials, sliding doors, wood substitutes for system kitchens, bath lids, and table tops; interior and exterior materials for vehicles such as side moldings, sound-absorbing materials, bumpers, door handles, console boxes, ceiling materials, pillars, center low cluster finish panels, cowl side trims, center outlets, door linings, ashtrays, footrests, steering column covers, lower inserts, lower handle panels, wheel caps, and spoilers; daily necessities such as containers, trays, and returnable boxes; electrical and electronic components such as housings for televisions, video players, and air conditioners, parabolic antennas, and air conditioner outdoor units; sports equipment such as kickboards and protectors; interior and exterior materials for houses and offices such as walls, floors, machine frames, furniture, decorative sheets, partitions, lattices, fences, rain gutters, sizing boards, and carports; machine frames for toys and amusement machines, cushioning materials, reinforcing materials, insulation materials, core materials, and alternative plywood. Furthermore, depending on the application, the foamed molded product of the present invention can be used as an article formed by integrating and compounding it with other molded products, components, etc. [Examples]

[0133] The present invention will be described more specifically below by way of examples and comparative examples. However, the present invention is not limited to the following examples in any way as long as the gist thereof is not exceeded. In the following, "parts" means "parts by mass" and "%" means "% by mass".

[0134] [Raw Materials] In the following examples and comparative examples, the raw materials of the thermoplastic resin composition were the resin components produced by the following methods and the following commercially available products.

[0135] [Production of Component (A): ABS Resin (Butadiene-Based Rubber Polymer / Styrene / Acrylonitrile Copolymer) (A-1)] In a stainless steel autoclave equipped with a ribbon-type stirring blade, 15 parts of polybutadiene [manufactured by JSR Corporation, "BR51", high cis type, Mooney viscosity (ML 1+4 , 100 °C) 33, gel content 0%], 64 parts of styrene, 21 parts of acrylonitrile, and 140 parts of toluene were charged. The internal temperature was raised to 75 °C, and the contents of the autoclave were stirred for 1 hour to obtain a homogeneous solution. Then, 0.45 parts of t-butylperoxyisopropyl monocarbonate was added, the internal temperature was further raised, and after reaching 100 °C, the polymerization reaction was carried out at a stirring rotation speed of 100 rpm while maintaining this temperature.

[0136] After the start of the polymerization reaction, the internal temperature was raised to 120 °C at the 4th hour, and the reaction was further carried out for 2 hours while maintaining this temperature to complete. After cooling the internal temperature to 100 °C, 0.2 parts of octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenol)-propionate was added. The polymerization conversion rate was 95%. The reaction mixture was withdrawn from the autoclave, and the unreacted substances and the solvent were distilled off by steam distillation. The cylinder temperature was adjusted to 220 °C and the vacuum degree was adjusted to 770 mmHg with a 40 mmφ extruder equipped with a vacuum vent to substantially devolatilize the volatile components and pelletize to obtain ABS resin (A-1). The polymerization conversion rate of ABS resin (A-1) was 91%, the grafting rate was 68%, the intrinsic viscosity [η] of the acetone-soluble portion was 0.39 dl / g, the amount of thermal cyclohexane dissolved was 2%, and the weight-average molecular weight was 48,000.

[0137] [Production of component (B): AS resin (styrene / acrylonitrile copolymer) (B-1)] Two stainless steel autoclaves equipped with ribbon blades were connected and purged with nitrogen. 75 parts styrene, 25 parts acrylonitrile, and 20 parts toluene were continuously added to the first reaction vessel. A solution of 0.16 parts tert-dodecyl mercaptan and 5 parts toluene was continuously supplied as a molecular weight modifier, and a solution of 0.1 parts 1,1'-azobis(cyclohexane-1-carbonnitrile) and 5 parts toluene was continuously supplied as a polymerization initiator. The polymerization temperature in the first vessel was controlled to 110°C, with an average residence time of 2.0 hours and a polymerization conversion rate of 57%. The resulting polymer solution was continuously drawn from the first reaction vessel using a pump installed outside the first vessel, in the same amounts as the supplied styrene, acrylonitrile, toluene, molecular weight modifier, and polymerization initiator, and supplied to the second reaction vessel. The polymerization temperature in the second reaction vessel was 130°C, and the polymerization conversion rate was 75%. The copolymer solution obtained in the second reaction vessel was directly defoliated using a twin-screw, three-stage vented extruder to obtain AS resin (B-1) with an intrinsic viscosity [η] of 0.64 dl / g and a weight-average molecular weight of 122,000.

[0138] [Component (C): PC resin (C-1)] Aromatic polycarbonate resin: As PC resin (C-1), we used "Novarex 7022PJ" (viscosity-average molecular weight: 20,900) manufactured by Mitsubishi Engineering Plastics Corporation.

[0139] [Component (D): Tetrafluoroethylene polymer (D)] The following commercially available products were used as tetrafluoroethylene polymers (D). The number-average molecular weights of these tetrafluoroethylene polymers (D) were determined by the following method. (D-1): Tetrafluoroethylene homopolymer "Polyflon MPA FA-500H" (number average molecular weight: 500,000) manufactured by Daikin Industries, Ltd. (D-2): Acrylic-modified tetrafluoroethylene polymer "Metablend A-3800" (number average molecular weight: 12,000,000) manufactured by Mitsubishi Chemical Corporation (D-3): Tetrafluoroethylene homopolymer "Fluon L172JE" (number average molecular weight: 20,000) manufactured by AGC, Inc.

[0140] <Measurement by DSC method and calculation of number average molecular weight> The heat of crystallization ΔHc (cal / g) was determined using a differential scanning calorimeter DSC (Q200 manufactured by TA Instruments) and calculated by the following formula. Number average molecular weight = 2.1×10 10 ΔHc -5.16

[0141] [Component (E): Chemical blowing agent (E)] As the chemical blowing agent (E), "Polystyrene EB106", a masterbatch (ADCA / ABS = 10 / 90 (mass ratio)) manufactured by Yonghe Chemical Industry Co., Ltd. was used. The blending amount of the chemical blowing agent was 0.35 parts by mass with respect to 100 parts by mass of the resin components (total of components (A) to (C)).

[0142] [Component (F): Inorganic filler (F)> (F-1): Micronized talc "MICRO ACE SG-200" manufactured by Nippon Talc Co., Ltd. (D50 by laser diffraction method: 1 μm) (F-2): Wollastonite "NYGLOS 4W" manufactured by IMERYS (Average particle diameter 7 μm by electron microscope observation) (F-3): Glass fiber "CSF3PE-332ST" manufactured by Nitto Boseki Co., Ltd. (Average particle diameter 13 μm by electron microscope observation)

[0143] [Examples 1 to 9, Comparative Examples 1 to 9] [Manufacture of thermoplastic resin composition for foam molding] The raw materials shown in Tables 1 and 2 were mixed in the proportions shown in Tables 1 and 2. These were then blended in a Henshel mixer, and extruded at 250°C using a twin-screw extruder TEX44 manufactured by Japan Steel Works to obtain thermoplastic resin pellets before foam molding.

[0144] [Injection foam molding] A 110(t) electric molding machine (J110AD) manufactured by Japan Steel Works was used as the foam molding machine. The obtained thermoplastic resin pellets and foaming agent masterbatch (chemical foaming agent (E)) were dry blended and supplied to the foam molding machine to perform core-back type injection foam molding, and foam molded products (plate-shaped products measuring 100 mm x 100 mm x 3.7 mm thick) were obtained as evaluation test specimens. In injection foam molding, the filling time was 1 second, the mold opening speed was 0.5 mm / second, the injection temperature was 250°C, the mold temperature was 80°C, the mold retraction delay time was 0 seconds, and the foaming ratio was 1.5 times.

[0145] [Evaluation of foamed molded products] The obtained foamed molded products were evaluated as follows, and the results are shown in Tables 1 and 2.

[0146] <External observation> (Swirl mark) The outer surface of the foamed molded product was visually inspected, and the degree of surface deterioration due to swirl marks was evaluated according to the following criteria. ◎: Has almost no swirl marks and excellent surface appearance. ○: Slight swirl marks are present, but the surface appearance is good. △: Swirl marks are present, and the surface appearance is slightly inferior. ×: Swirl marks are prominent, resulting in a poor surface appearance.

[0147] (Surface unevenness) The outer surface of the foamed molded product was visually inspected, and the degree of surface deterioration due to the occurrence of surface dents was evaluated according to the following criteria. ◎: The surface is completely free of dents and has an excellent appearance. ○: Although slight surface indentations are observed, the overall surface appearance is good. △: Surface indentations are observed, resulting in a slightly inferior surface appearance. ×: The surface has noticeable indentations, resulting in an inferior surface appearance.

[0148] <Cross-sectional observation> (bubble breakage) The foamed molded product was cut in the thickness direction, and the cross-section was observed. The degree of cell rupture and the degree of cell bonding due to rupture were evaluated according to the following criteria. ◎: There is absolutely no rupture of the foam cells or cell bonding due to rupture, and the cells are uniform across the entire cross-section. ○: Slight rupture of foam cells and bonding of cells due to rupture are observed, but the cells are relatively uniform across the entire cross-section. △: Rupture of foam cells and cell bonding due to rupture are observed, and there are slight non-uniform areas of cells in the cross-section. ×: Non-uniform areas of the cells are observed in many parts of the cross-section due to rupture of the foam cells and the subsequent bonding of cells after rupture.

[0149] (Cell shape) The foamed molded product was cut in the thickness direction, and the cell shape of the cross-section was observed. The fineness of the cells was evaluated according to the following criteria. ◎: Fine foam cells with a diameter of approximately 100 μm are uniformly present, resulting in excellent cell shape. ○: Most are fine foamed cells with a cell diameter of about 100 μm, and have excellent cell shape. △: A small number of foam cells with a diameter of 100-300 μm are present among the fine foam cells with a diameter of approximately 100 μm, resulting in slightly inferior uniformity. ×: The cell diameter of the foamed cells is non-uniform, ranging from 100 to 300 μm, resulting in poor uniformity.

[0150] [Table 1]

[0151] [Table 2]

[0152] [Consideration] As is clear from Tables 1 and 2, in Examples 1 to 9, in which the tetrafluoroethylene polymer (D) of component (D) was incorporated into the thermoplastic resin composition for foam molding, excellent foamed molded products were obtained with good surface appearance and a fine and uniform foam cell structure. In contrast, Comparative Examples 1, 3, and 4, which do not contain tetrafluoroethylene polymer (D), and Comparative Example 2, which contains tetrafluoroethylene polymer (D) but whose number-average molecular weight is lower than the specified range of the present invention, are particularly inferior in terms of foamed cell structure. Comparative Examples 5-8 used the tetrafluoroethylene polymer (D) according to the present invention, but due to the high amount of polymer used, the appearance was inferior. Comparative Example 9 satisfies the scope of the present invention in terms of the amount of tetrafluoroethylene polymer (D), but because there is a large amount of styrene resin (B) of component (B) and a small amount of aromatic polycarbonate resin (C) of component (C), the foamed cell structure is inferior.

Claims

1. A thermoplastic resin composition for foam molding containing 1 to 15 parts by mass of component (A), 50 parts by mass or less of component (B), and 40 to 80 parts by mass of component (C) in a total of 100 parts by mass, and with respect to the total of 100 parts by mass of components (A) to (C), it contains 1 to 5 parts by mass of component (D) and 0.1 to 5 parts by mass of a chemical blowing agent (E). Component (A): A rubber-reinforced styrene resin (A) obtained by polymerizing an aromatic vinyl compound or another vinyl monomer (b1) copolymerizable with an aromatic vinyl compound in the presence of a rubbery polymer (a). Component (B): Styrene resin (B) obtained by polymerizing an aromatic vinyl compound or an aromatic vinyl compound and another vinyl monomer copolymerizable with the aromatic vinyl compound (b2). Ingredients (C): Aromatic polycarbonate resin (C) Component (D): Tetrafluoroethylene polymer (D) with a number-average molecular weight of 100,000 or more as determined by DSC method.

2. The thermoplastic resin composition for foam molding according to claim 1, further comprising 0.1 to 20 parts by mass of an inorganic filler (F) per 100 parts by mass of the total amount of components (A) to (C).

3. A thermoplastic resin composition for foam molding according to claim 1 or 2, used in core-back type injection foam molding.

4. A foamed molded article obtained by molding a thermoplastic resin composition for foam molding according to any one of claims 1 to 3.

5. A foamed molded article obtained by core-back injection foam molding of a thermoplastic resin composition for foam molding according to any one of claims 1 to 3.

Images