Resin foam and method for producing resin foam

Abstract

The object of the present invention is to provide a resin foam that is excellent in moldability even in a multi-cavity molding system in which multiple products are molded using one mold, and that also has excellent flame retardancy. [Solution] A resin foam obtained by foaming a base resin composition, wherein the base resin composition comprises (A) a resin, (B) a phosphorus-based flame retardant, and (C) a zinc compound, the (A) resin comprises (A-1) a polyphenylene ether-based resin, (A-2) a polystyrene-based resin, and (A-3) a resin having a carbon-carbon unsaturated double bond, and the resin foam contains 0.05 to 5.0 moles of zinc per mole of carbon-carbon unsaturated double bonds in the (A-3) resin having a carbon-carbon unsaturated double bond.

Description

[Technical Field]

[0001] The present invention relates to a resin foam and a method for producing a resin foam. [Background technology]

[0002] Flame-retardant plastics and metals have traditionally been used as materials for the internal components of automobiles and electronic devices. Because of their excellent flame retardancy and high strength, their use in automobile components and electronic devices is expanding. However, from the perspective of energy conservation, there is a demand for lighter materials that also have excellent physical properties such as flame retardancy, strength, and impact resistance. One such material is flame-retardant foam molded products. Known examples of flame-retardant foamed molded articles include those produced by adding a flame retardant to a blend resin of a polystyrene-based resin and a polyphenylene ether-based resin and foaming the blend (see, for example, Patent Documents 1 and 2). However, to achieve the same level of flame retardancy as injection-molded products, resin foams require the addition of more flame retardant than injection-molded products. This is because, when comparing samples of the same size, foams contain less resin per unit volume than unfoamed resins, making them less likely to form a char layer and resulting in a longer burning time. Furthermore, because foams contain less resin than unfoamed resins, they are more likely to soften due to the heat of combustion, resulting in increased resin dripping during combustion, which also contributes to reduced flame retardancy. Increasing the amount of flame retardant added to foams to improve flame retardancy improves flame retardancy, but also leads to reduced mechanical properties, heat resistance, and foamability. Patent Document 3 discloses a technique for adding a rubber component to achieve both foamability and flame retardancy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-95892 [Patent Document 2] International Publication No. 2003 / 004552 [Patent Document 3] Patent No. 4712914 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, in addition to the problem of reduced flame retardancy, there are also process issues in the production of foam molded products, such as the fact that the foam molding cycle takes longer than the injection molding cycle. Because the foam molding cycle takes time, there is a growing demand for multi-cavity molding, which allows multiple products to be molded in one cycle in order to make the molding process more efficient. However, with multi-cavity molding, the amount of resin foam filled per product is reduced, which causes a problem of reduced moldability.

[0005] Therefore, an object of the present invention is to provide a resin foam that is excellent in moldability even in a multi-cavity molding system in which multiple products are molded using one mold, and that also has excellent flame retardancy. Another object of the present invention is to provide a method for producing a resin foam that can produce a resin foam that has excellent moldability and excellent flame retardancy, even in a multi-cavity system in which multiple products are molded using a single mold. [Means for solving the problem]

[0006] The present invention is as follows.

[0007] [1] A resin foam obtained by foaming a base resin composition, The base resin composition is (A) resin, (B) phosphorus-based flame retardants, and (C) Zinc compounds Including, The (A) resin is (A-1) polyphenylene ether resin, (A-2) polystyrene resin, and (A-3) Resin having a carbon-carbon unsaturated double bond Including, A resin foam containing 0.05 to 5.0 moles of zinc per mole of carbon-carbon unsaturated double bonds in the (A-3) resin having carbon-carbon unsaturated double bonds.

[0008] [2] The resin foam according to [1], which is in the form of beads.

[0009] [3] The resin foam according to [1] or [2], having a flame retardancy of V-2 to V-0 as measured based on the UL94 vertical flame test of the UL standard.

[0010] [4] The resin foam according to any one of [1] to [3], comprising 5 to 25 parts by mass of the phosphorus-based flame retardant (B) per 100 parts by mass of the resin (A).

[0011] [5] relative to 1 mol of phosphorus contained in the base resin composition, The resin foam according to any one of [1] to [4], wherein the amount of the carbon-carbon unsaturated double bond is 0.001 to 0.2 mol.

[0012] [6] The resin foam according to any one of [1] to [5], comprising 40 to 94 parts by mass of the polyphenylene ether resin (A-1) per 100 parts by mass of the resin (A).

[0013] [7] The resin foam according to any one of [1] to [6], wherein the (A-2) polystyrene-based resin is contained in an amount of 1 to 59 parts by mass per 100 parts by mass of the (A) resin.

[0014] [8] The resin foam according to any one of [1] to [7], wherein the (A-3) resin having a carbon-carbon unsaturated double bond contains a structural unit derived from styrene, and the ratio of the structural unit derived from styrene to 100% by mass of the (A-3) resin having a carbon-carbon unsaturated double bond is 60 to 99% by mass.

[0015] [9] The resin foam according to any one of [1] to [8], wherein the (B) phosphorus-based flame retardant is at least one selected from the group consisting of phosphate esters and phosphazene compounds.

[0016]

[10] A granulation step of kneading the resin foam according to any one of [1] to [9] in an extruder and then pelletizing it to prepare pellets of a base resin composition; an impregnation step of impregnating the pellets with a foaming agent; a foaming step of foaming the pellets impregnated with the foaming agent to obtain a resin foam; A method for producing a resin foam, comprising:

[0017]

[11] a granulation step in which pellets of the base resin composition obtained by extrusion kneading, and / or fused pellets of the base resin composition generated during extrusion, and a resin mass discharged from the extruder or die are kneaded in an extruder and then pelletized to prepare pellets of the base resin composition; an impregnation step of impregnating the pellets with a foaming agent; a foaming step of foaming the pellets impregnated with the foaming agent to obtain a resin foam; A method for producing a resin foam, comprising: The base resin composition is (A) resin, (B) phosphorus-based flame retardants, and (C) Zinc compounds Including, The (A) resin is (A-1) polyphenylene ether resin, (A-2) polystyrene resin, and (A-3) Resin having a carbon-carbon unsaturated double bond Including, A method for producing a resin foam, comprising the step of: (A-3) containing 0.05 to 5.0 moles of zinc per mole of carbon-carbon unsaturated double bonds in the resin having carbon-carbon unsaturated double bonds. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a resin foam that is excellent in moldability even in a multi-cavity molding system in which a plurality of products are molded using one mold, and that has excellent flame retardancy. Furthermore, according to the present invention, a method for producing a resin foam can be provided that can produce a resin foam that has excellent moldability and excellent flame retardancy, even in a multi-cavity system in which multiple products are molded using a single mold. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of the gist thereof.

[0020] (Resin foam) The resin foam of this embodiment is A resin foam obtained by foaming a base resin composition, The base resin composition is (A) resin, (B) phosphorus-based flame retardants, and (C) Zinc compounds Including, (A) Resin, (A-1) polyphenylene ether resin, (A-2) polystyrene resin, and (A-3) Resin having a carbon-carbon unsaturated double bond Including, (A-3) The resin contains 0.05 to 5.0 moles of zinc per mole of the carbon-carbon unsaturated double bond of the resin having the carbon-carbon unsaturated double bond. The resin foam has excellent moldability even in a multi-cavity molding system in which a plurality of products are molded using one mold, and also has excellent flame retardancy.

[0021] The shape of the resin foam of the present embodiment may be, for example, a plate, a cylinder, a prism, or a bead, but is not limited to any of these shapes. The term "bead-shaped" refers to a spherical or approximately spherical shape. In this specification, the term "approximately spherical" includes a perfect sphere, an oval sphere such as a rugby ball, or shapes similar thereto.

[0022] The resin foam of the present embodiment is preferably, but not limited to, foamed beads. The foamed beads have a bead shape.

[0023] The resin foam of the present embodiment preferably has a flame retardancy of V-2 to V-0 as measured based on the UL94 vertical burning test of the UL standard. Furthermore, the flame retardancy of the resin foam measured based on the UL94 vertical burning test of the UL standard is particularly preferably V-0. The flame retardancy measured based on the UL94 vertical flame test of the UL standard can be specifically evaluated by the method described in the examples.

[0024] ((Base resin composition)) The resin foam of the present embodiment is produced by foaming a base resin composition, which contains (A) a resin, (B) a phosphorus-based flame retardant, and (C) a zinc compound. The base resin composition of the present embodiment is preferably a foaming base resin composition used to obtain a resin foam. The base resin composition of the present embodiment may be foamed to produce a resin foam for obtaining a foam molded article, or a foam molded article may be directly produced.

[0025] [(A) Resin] The resin (A) in the resin foam of this embodiment includes (A-1) a polyphenylene ether resin, (A-2) a polystyrene resin, and (A-3) a resin having a carbon-carbon unsaturated double bond.

[0026] <(A-1) Polyphenylene ether resin> (A-1) Polyphenylene ether resin refers to a polymer containing a structural unit represented by the following general formula (I), and examples thereof include a homopolymer consisting of a structural unit represented by the following general formula (I) and a copolymer containing a structural unit represented by the following general formula (I). [ka] In general formula (I), R 1 , R 2 , R 3 and R4 are each independently a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a phenyl group, or a haloalkyl group or haloalkoxy group having at least two carbon atoms between the halogen atom and the benzene ring in general formula (I) and not including the tertiary α-carbon atom. In general formula (I), n is an integer representing the degree of polymerization.

[0027] Specific examples of polyphenylene ether resins include poly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene) ether, poly(2-methyl-6-ethyl-1,4-phenylene) ether, poly(2-methyl-6-propyl-1,4-phenylene) ether, poly(2,6-dipropyl-1,4-phenylene) ether, poly(2-ethyl-6-propyl-1,4-phenylene) ether, poly(2,6-dibutyl-1,4-phenylene) ether, poly(2,6-dilauryl-1,4-phenylene) ether, poly(2,6-diphenyl-1,4-diphenylene) ether, and poly(2,6-dimethoxy-1,4-phenylene). ,4-phenylene) ether, poly(2,6-diethoxy-1,4-phenylene) ether, poly(2-methoxy-6-ethoxy-1,4-phenylene) ether, poly(2-ethyl-6-stearyloxy-1,4-phenylene) ether, poly(2,6-dichloro-1,4-phenylene) ether, poly(2-methyl-6-phenyl-1,4-phenylene) ether, poly(2,6-dibenzyl-1,4-phenylene) ether, poly(2-ethoxy-1,4-phenylene) ether, poly(2-chloro-1,4-phenylene) ether, poly(2,6-dibromo-1,4-phenylene) ether, etc., but are not limited to these. 1 and R 2 is an alkyl group having 1 to 4 carbon atoms, and R 3 and R 4 is preferably hydrogen or an alkyl group having 1 to 4 carbon atoms.

[0028] The polyphenylene ether resin can be produced by any known method without any particular limitation, and can be easily produced, for example, by oxidatively polymerizing 2,6-xylenol using, as a catalyst, a complex of cuprous salt and amine by Hay, as described in U.S. Patent No. 3,306,874. Other examples include methods described in U.S. Patent Nos. 3,306,875, 3,257,357, 3,257,358, JP-B-52-17880, JP-A-50-51197, and JP-A-63-152628.

[0029] In addition, in this embodiment, the polyphenylene ether resin may be a modified polyphenylene ether resin in which some or all of the structural units constituting the polyphenylene ether resin are modified with an unsaturated or saturated carboxylic acid or a derivative thereof. Examples of the modified polyphenylene ether resin include those described in JP-A-2-276823 (U.S. Pat. No. 5,159,027, U.S. Reissue Patent No. 35,695), JP-A-63-108059 (U.S. Pat. No. 5,214,109, U.S. Pat. No. 5,216,089), JP-A-59,724, etc. The modified polyphenylene ether resin is produced, for example, by melt-kneading a polyphenylene ether resin with an unsaturated or saturated carboxylic acid or a derivative thereof in the presence or absence of a radical initiator to cause a reaction. Alternatively, the modified polyphenylene ether resin is produced by dissolving a polyphenylene ether resin and an unsaturated or saturated carboxylic acid or a derivative thereof in an organic solvent in the presence or absence of a radical initiator and causing a reaction in the solution.

[0030] Examples of unsaturated carboxylic acids or derivatives thereof include maleic acid, fumaric acid, itaconic acid, halogenated maleic acids, cis-4-cyclohexene-1,2-dicarboxylic acid, endo-cis-bicyclo(2,2,1)-5-heptene-2,3-dicarboxylic acid, and the like, as well as acid anhydrides, esters, amides, imides, and the like of these dicarboxylic acids, as well as acrylic acid, methacrylic acid, and the like, as well as esters, amides, and the like of these monocarboxylic acids.

[0031] Examples of saturated carboxylic acids or derivatives thereof include compounds that undergo thermal decomposition at the reaction temperature during production of the modified polyphenylene ether resin to become derivatives of the modified polyphenylene ether resin. Specific examples of saturated carboxylic acids or derivatives thereof include malic acid and citric acid.

[0032] The polyphenylene ether resin may be composed solely of the polyphenylene ether resin described above, in which the polyphenylene ether resin is 100% by mass, or may be the polymer alloy described above. In the case of a polymer alloy, from the viewpoints of heat resistance and flame retardancy, the content of the polyphenylene ether resin in 100% by mass of the polymer alloy is preferably 30 to 99% by mass, more preferably 40 to 95% by mass, and even more preferably 50 to 75% by mass.

[0033] The weight-average molecular weight (Mw) of the (A-1) polyphenylene ether resin is preferably 20,000 to 90,000, more preferably 40,000 to 80,000, and even more preferably 50,000 to 75,000. When the (A-1) polyphenylene ether resin has a weight-average molecular weight of 20,000 or more, it is possible to sufficiently prevent the resin from breaking during foaming. Furthermore, when the (A-1) polyphenylene ether resin has a weight-average molecular weight of 90,000 or less, the melt viscosity of the resin does not become too high, and good granulation tends to be possible without the die pressure reaching the upper limit of the processing limit in the granulation step (production of base resin composition pellets) in the production of expanded beads described below. The weight average molecular weight (Mw) can be determined by measuring the resin by gel permeation chromatography (GPC) and using the molecular weight of the peak in the chromatogram to obtain a calibration curve (created using the peak molecular weight of the standard polystyrene) obtained from measurements of commercially available standard polystyrene.

[0034] The content of the (A-1) polyphenylene ether resin is preferably 30 to 99 mass %, more preferably 40 to 95 mass %, and even more preferably 50 to 75 mass %, relative to 100 mass % of the base resin composition.

[0035] Furthermore, the resin foam of this embodiment preferably contains 40 to 94 parts by mass, more preferably 50 to 90 parts by mass, and even more preferably 55 to 75 parts by mass of the (A-1) polyphenylene ether resin per 100 parts by mass of the (A) resin.

[0036] <(A-2) Polystyrene Resin> (A-2) polystyrene resin refers to a homopolymer of styrene and a styrene derivative, or a copolymer having styrene and a styrene derivative as the main component (a component contained in the polystyrene resin at 50% by mass or more). In the present invention, even if a copolymer has styrene and a styrene derivative as the main component, it is not included in (A-2) polystyrene resin, but is included in (A-3) resin having a carbon-carbon unsaturated double bond, as described below, if the copolymer has a carbon-carbon unsaturated double bond in a part other than the aromatic ring (for example, high impact polystyrene (HIPS) or styrene-butadiene copolymer). Examples of the styrene derivatives include o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, α-methylstyrene, β-methylstyrene, diphenylethylene, chlorostyrene, and bromostyrene.

[0037] Examples of the homopolymer polystyrene resin (A-2) include polystyrene, poly-α-methylstyrene, and polychlorostyrene. Examples of the copolymer (A-2) polystyrene resin include binary copolymers such as styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, styrene-maleimide copolymer, styrene-N-phenylmaleimide copolymer, styrene-N-alkylmaleimide copolymer, styrene-N-alkyl-substituted phenylmaleimide copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-n-alkyl acrylate copolymer, styrene-n-alkyl methacrylate copolymer, ethylvinylbenzene-divinylbenzene copolymer, and graft copolymers such as styrene-grafted polyethylene, styrene-grafted ethylene-vinyl acetate copolymer, (styrene-acrylic acid)-grafted polyethylene, and styrene-grafted polyamide. These may be used alone or in combination of two or more.

[0038] The content of the (A-2) polystyrene resin is preferably 1 to 70 mass %, more preferably 5 to 60 mass %, and even more preferably 10 to 50 mass %, relative to 100 mass % of the base resin composition.

[0039] Furthermore, the resin foam of this embodiment preferably contains 1 to 59 parts by mass, more preferably 3 to 40 parts by mass, and even more preferably 5 to 25 parts by mass of (A-2) polystyrene-based resin per 100 parts by mass of (A) resin.

[0040] The polystyrene resin may be produced by any conventionally known production method.

[0041] <(A-3) Resin Having a Carbon-Carbon Unsaturated Double Bond> In the resin foam of this embodiment, the resin (A-3) having a carbon-carbon unsaturated double bond is not particularly limited as long as it is a resin having a carbon-carbon unsaturated double bond, and examples thereof include high impact polystyrene (HIPS), styrene-butadiene copolymer, and ABS (acrylonitrile-butadiene-styrene resin). High impact polystyrene (HIPS) has fine rubber particles blended or graft-polymerized into a styrene polymer matrix. Examples of the rubber include polybutadiene, styrene-butadiene copolymer, polyisoprene, and ethylene-propylene copolymer. In the present invention, the term "resin having a carbon-carbon unsaturated double bond" refers to a resin having a carbon unsaturated double bond in a part other than an aromatic ring.

[0042] In the resin foam of this embodiment, from the viewpoint of improving foamability, the amount of carbon-carbon unsaturated double bonds per mole of phosphorus contained in the base resin composition is preferably 0.001 to 0.5 moles, more preferably 0.001 to 0.2 moles, and even more preferably 0.001 to 0.15 moles. Generally, the addition of a flame retardant reduces the melt viscosity of the base resin, making it more susceptible to membrane rupture during foaming, making it difficult to obtain a high-quality resin foam. However, by controlling the amount of carbon-carbon unsaturated double bonds per mole of phosphorus in the base resin component within the above range, it becomes easier to adjust the melt viscosity to an optimum level for foaming, making it easier to obtain a resin foam with an excellent closed cell ratio. The amount of carbon-carbon unsaturated double bonds per mole of phosphorus contained in the base resin composition was determined by measuring the amount of phosphorus by ICP-MS and the amount of carbon-carbon unsaturated double bonds by 1 It can be measured by H-NMR (ECS400, 400 MHz) and calculated by (amount of carbon-carbon unsaturated double bonds) / (amount of phosphorus). Details of the measurement method are described in the Examples.

[0043] In the resin foam of this embodiment, from the viewpoints of foamability and heat resistance, the amount of carbon-carbon unsaturated double bonds in the base resin composition is preferably 0.1 to 10 mass%, more preferably 0.2 to 7.0 mass%, and even more preferably 0.2 to 5.0 mass%, relative to 100 mass% of the base resin composition. The amount of carbon-carbon unsaturated double bonds in the base resin composition is 1 This is a value measured by H-NMR (ECS400, 400 MHz).

[0044] The (A-3) resin having a carbon-carbon unsaturated double bond preferably contains structural units derived from styrene. When the (A-3) resin having a carbon-carbon unsaturated double bond contains structural units derived from styrene, the proportion of structural units derived from styrene relative to 100% by mass of the (A-3) resin having a carbon-carbon unsaturated double bond is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 65% ​​by mass or more. Furthermore, the proportion of structural units derived from styrene relative to 100% by mass of the (A-3) resin having a carbon-carbon unsaturated double bond is preferably 99% by mass or less, preferably 50 to 99% by mass, and more preferably 60 to 99% by mass. The ratio of structural units derived from styrene is: 1 This is a value measured by H-NMR.

[0045] The resin foam of this embodiment preferably contains, per 100 parts by mass of the resin (A), 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 8 parts by mass or more of the resin (A-3) having a carbon-carbon unsaturated double bond. The resin foam of this embodiment preferably contains, per 100 parts by mass of the resin (A), 59 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less of the resin (A-3) having a carbon-carbon unsaturated double bond.

[0046] [(B) Phosphorus-based flame retardant] The phosphorus-based flame retardant (B) in this embodiment may contain a phosphorus compound, such as a phosphate ester, a phosphazene compound having a bond between a phosphorus atom and a nitrogen atom in the main chain, a trialkylphosphine oxide, or a triphenylphosphine oxide. The (B) phosphorus-based flame retardant is preferably at least one selected from the group consisting of phosphoric acid esters and phosphazene compounds.

[0047] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, tricyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, dimethyl ethyl phosphate, methyl dibutyl phosphate, ethyl dipropyl phosphate, hydroxyphenyl diphenyl phosphate, and resorcinol bisdiphenyl phosphate. Further examples include phosphate ester compounds obtained by modifying these with various substituents, various condensed phosphate ester compounds, and phosphate ester compounds having a cyclic structure. Among these, from the viewpoints of heat resistance, flame retardancy, and foaming property, phosphazene compounds, triphenyl phosphate, condensed type phosphate ester compounds, and phosphate ester compounds having a cyclic structure are preferred. These may be used alone or in combination of two or more.

[0048] The base resin composition preferably contains 5 to 25 parts by mass of (B) phosphorus-based flame retardant per 100 parts by mass of (A) resin, more preferably 10 to 25 parts by mass, and even more preferably 15 to 25 parts by mass, of (B) phosphorus-based flame retardant per 100 parts by mass of (A) resin.

[0049] [(C) Zinc compounds] Examples of zinc compounds include zinc chloride, zinc oxide, zinc sulfide, zinc sulfate, zinc chromate, zinc stearate, zinc stannate, zinc gluconate, and zinc phosphide (Zn3P2). These may be used alone or in combination of two or more.

[0050] The content of the zinc compound is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, per 100 parts by mass of the (A) resin, and is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the (A) resin.

[0051] The resin foam of this embodiment contains 0.05 to 5.0 moles of zinc per mole of carbon-carbon unsaturated double bonds in the resin (A-3) having a carbon-carbon unsaturated double bond. From the viewpoint of improving foamability, the resin preferably contains 0.1 to 4.0 moles of zinc per mole of carbon-carbon unsaturated double bonds in the resin (A-3) having a carbon-carbon unsaturated double bond, more preferably 0.2 to 3.5 moles, and even more preferably 0.3 to 3.0 moles. The reason why the amount of zinc is preferable within the above range is presumed to be as follows: Generally, when carbon-carbon unsaturated double bonds are heated, radicals are generated and a crosslinked structure is formed. If the crosslinking reaction proceeds excessively, the molecular weight increases and a foreign gel is present in the resin, which causes the extensional viscosity of the base resin to become non-uniform and makes the film more susceptible to rupture during foaming, making it difficult to obtain a high-quality foam. Furthermore, even if a foam with a high closed cell content is obtained, if an excessive crosslinked structure is formed, the extensional viscosity will be too high, resulting in insufficient expansion during molding and poor appearance of the molded product. However, by setting the zinc content per mole of carbon unsaturated double bonds in the base resin component within the above range, it is thought that the zinc appropriately suppresses the crosslinking reaction, making it easier to obtain a foam with excellent moldability.

[0052] [Other additives] In this embodiment, the base resin composition may contain other additives in addition to (A) the resin, (B) the phosphorus-based flame retardant, and (C) the zinc compound.

[0053] Examples of other additives include flame retardants other than the (B) phosphorus-based flame retardant, flame retardant aids, heat stabilizers, antioxidants other than those mentioned above, antistatic agents, inorganic fillers, anti-dripping agents, ultraviolet absorbers, light absorbers, plasticizers, release agents, dyes and pigments, rubber components, and resins other than the resins (A-1) to (A-3) mentioned above, and these can be added within a range that does not impair the effects of the present invention. The content of other additives is preferably 0 to 40 parts by mass, more preferably 0 to 20 parts by mass, and even more preferably 0 to 5 parts by mass, relative to 100 parts by mass of the (A) resin.

[0054] In order to achieve sufficient flame retardancy, it is preferable that the base resin composition further contains a flame retardant other than the (B) phosphorus-based flame retardant.

[0055] Other flame retardants include organic flame retardants and inorganic flame retardants. Organic flame retardants include halogen-based compounds such as bromine compounds, and non-halogen-based compounds such as phosphorus-based compounds and silicone-based compounds. Inorganic flame retardants include metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and antimony-based compounds such as antimony trioxide and antimony pentoxide. Among the above flame retardants, from an environmental perspective, non-halogen flame retardants are preferred, phosphorus-based and silicone-based flame retardants are more preferred, and phosphorus-based flame retardants are even more preferred.

[0056] [Method of manufacturing base resin composition] The method for producing the base resin composition is not particularly limited, and examples include a method in which (A) resin, (B) phosphorus-based flame retardant, (C) zinc compound, and optional components are mixed using a Henschel mixer, tumbler, V-shaped blender, or the like, and then kneaded using a kneading machine such as a single-screw or multi-screw extruder, a heated roll, a kneader, or a Banbury mixer. Among these, kneading using an extruder equipped with a vent pressure reduction device is preferred from the standpoint of productivity. Alternatively, each component can be continuously fed into the extruder, either individually or in batches, using a metering feeder or the like, without premixing. The kneading temperature may be in accordance with the preferred processing temperature of the base resin, and may be, for example, 140 to 350°C, and preferably 180 to 300°C.

[0057] In this embodiment, the base resin composition is preferably in the form of pellets (i.e., base resin composition pellets). The base resin composition pellets can be used to produce a resin foam. The base resin composition pellets of this embodiment may be expanded to produce a resin foam for obtaining a foamed molded article, or a foamed molded article may be produced directly. The base resin composition pellets can be used to obtain a resin foam with good moldability and expandability, as well as a foamed molded article with excellent flame retardancy and appearance.

[0058] The shape of the base resin composition pellet of this embodiment is preferably such that the cross section when cut perpendicular to the longitudinal direction is substantially circular, and examples of such shapes include substantially columnar and substantially spherical, with spherical being preferred. In this specification, "approximately circular" includes a perfect circle, an ellipse, or a similar rounded shape. "Approximately columnar" includes not only a columnar shape with a constant cross section, but also a shape with a varying cross section (such as a shape in which the cross section diameter decreases toward both ends in the longitudinal direction). "Approximately spherical" includes a perfect sphere, an oval sphere like a rugby ball, or a similar shape.

[0059] -Method of manufacturing base resin composition pellets- The method for producing the base resin composition pellets is not particularly limited, and examples thereof include methods of pelletizing the base resin composition by a hot cut method, an underwater cut method, a strand cut method, etc. Among these, the hot cut method and the underwater cut method are preferred as the pelletizing method because voids are less likely to occur near the pellet surface, and the underwater cut method is preferred because it is easy to efficiently produce nearly spherical pellets having the above-mentioned characteristics. When using the underwater cutting method, the water pressure of the circulating water is preferably 1.0 to 2.0 bar. This is thought to have the effect of suppressing the generation of cavities in the water by applying water pressure during cutting, preventing cutting errors, and making the pellets uniform in shape, and also to apply pressure to the molten resin emerging from the die, making the pellet shape more spherical. In this specification, pressure is expressed as gauge pressure. Furthermore, the higher the temperature of the circulating water for underwater cutting, the better, preferably at least 90° C., and more preferably at least 95° C. By keeping the circulating water temperature within the above range, the cooling rate of the molten resin is slowed down, reducing the temperature difference between the surface and interior of the resin, making it easier to suppress the generation of voids or to reduce the size of voids if they are generated.

[0060] (Resin foam) The resin foam of this embodiment is a resin foam obtained by foaming a base resin composition containing (A) a resin, (B) a phosphorus-based flame retardant, and (C) a zinc compound. The (A) resin, (B) the phosphorus-based flame retardant, and (C) the zinc compound may be the same as those contained in the base resin composition described above, and the contents thereof may also be the same. The resin foam of the present embodiment is obtained by foaming the above-described base resin composition, and may also be obtained by foaming pellets of the above-described base resin composition.

[0061] The expansion ratio of the resin foam of this embodiment is preferably 3 to 50 cc / g, more preferably 5 to 15 cc / g, and even more preferably 6 to 12 cc / g. When the expansion ratio of the resin foam is 50 cc / g or less, the closed cell ratio tends to be high and excellent moldability tends to be achieved. When the expansion ratio of the resin foam is 3 cc / g or more, the objective of reducing the weight of parts tends to be fully achieved. The expansion ratio of the resin foam is determined by measuring the weight W (g) of the resin foam, then measuring the volume V (cc) by a submersion method, and dividing the volume by the weight.

[0062] The closed cell ratio of the resin foam of the present embodiment is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. When the closed cell ratio of the resin foam is 80% or more, excellent moldability tends to be exhibited. The closed cell ratio of a resin foam can be determined by measuring the true volume (Vxp) of a resin foam with a known expansion ratio (cc / g) using an air comparison hydrometer manufactured by Beckman Co., Ltd., and calculating the closed cell ratio Sp (%) using the following formula. Sp(%)={(Vxp-Wp / ρp) / (Vap-Wp / ρp)}×100 Vxp: True volume of resin foam (cm 3 ) Vap: Volume of resin foam (expansion ratio x mass) (cc) Wp: Mass of resin foam (g) ρp: density of the base resin composition of the resin foam (g / cm 3 )

[0063] -Method of manufacturing resin foam- The method for producing the resin foam of this embodiment is not particularly limited, and examples thereof include extrusion foaming, in which a gas is injected into a molten resin in an extruder to foam it, and a method including a granulation step for producing pellets of a base resin composition, an impregnation step for impregnating the pellets of the base resin composition with a blowing agent, and a foaming step for foaming the pellets of the base resin composition to obtain a resin foam. Furthermore, the method for producing a resin foam may include a granulation step in which pellets of the base resin composition obtained by extrusion kneading, fused materials between base resin compositions generated during extrusion, resin mass discharged from an extruder or die, or a resin foam are fed back into the extruder to produce pellets of the base resin composition. Furthermore, the granulation step may be a granulation step in which the resin foam of this embodiment is kneaded in an extruder and then pelletized to produce pellets of the base resin composition.

[0064] The method for producing a resin foam of the present embodiment includes a granulation step of kneading the resin foam of the present embodiment in an extruder and then pelletizing the kneaded resin foam to produce pellets of a base resin composition; an impregnation step of impregnating the pellets with a foaming agent; and a foaming step of foaming the pellets impregnated with the foaming agent to obtain a resin foam.

[0065] In addition, a method for producing a resin foam according to another embodiment includes the steps of: a granulation step in which pellets of the base resin composition obtained by extrusion kneading, and / or fused pellets of the base resin composition generated during extrusion, and a resin mass discharged from the extruder or die are kneaded in an extruder and then pelletized to prepare pellets of the base resin composition; an impregnation step of impregnating the pellets with a foaming agent; a foaming step of foaming the pellets impregnated with a foaming agent to obtain a resin foam; A method for producing a resin foam, comprising: The base resin composition is (A) resin, (B) phosphorus-based flame retardants, and (C) Zinc compounds Including, (A) Resin, (A-1) polyphenylene ether resin, (A-2) polystyrene resin, and (A-3) Resin having a carbon-carbon unsaturated double bond Including, The resin composition is characterized by containing 0.05 to 5.0 moles of zinc per mole of unsaturated double bonds in the base resin composition. According to the above-described method for producing a resin foam, a resin foam having excellent moldability and excellent flame retardancy can be produced even in a multi-cavity molding method in which a plurality of products are molded using one mold.

[0066] <Granulation process> Examples of the granulation process include a granulation process in which the resin foam of this embodiment is kneaded in an extruder and then pelletized to produce pellets of a base resin composition, and a granulation process in which pellets of the base resin composition obtained by extrusion kneading, and / or fused base resin composition pellets generated during extrusion, or resin lumps discharged from the extruder or die, are kneaded in an extruder and then pelletized to produce pellets of a base resin composition.

[0067] In the granulation step, the method for kneading the components of the base resin composition is not particularly limited, and may be the same as the method described in the above-mentioned [Method for producing base resin composition], and the kneading temperature may also be the same. In the granulation step, the method for pelletizing the base resin composition after extrusion is not particularly limited, and may be the same as the method described in the above-mentioned [Method for producing base resin composition pellets], and when an underwater cut method is used, the conditions such as the water pressure and temperature of the circulating water may also be the same.

[0068] <Impregnation process> In the impregnation step, the method for incorporating a blowing agent into the base resin composition is not particularly limited, and any commonly used method can be applied. Examples of methods for incorporating a blowing agent include a method using an aqueous medium such as water as a suspension (suspension impregnation), a method using a thermally decomposing blowing agent such as sodium bicarbonate (blowing agent decomposition method), a method in which a gas is brought into an atmosphere above the critical pressure and brought into liquid phase and contacted with the base resin composition (liquid phase impregnation), and a method in which a gas is brought into contact with the base resin composition in a gas phase under a high-pressure atmosphere below the critical pressure (gas phase impregnation). Among these, the method for incorporating a blowing agent into the base resin composition is particularly preferably a gas phase impregnation method under a high-pressure atmosphere below the critical pressure.

[0069] The vapor-phase impregnation method provides better gas solubility in the resin than suspension impregnation, which is carried out under high-temperature conditions, making it easier to increase the foaming agent content. Therefore, it is easier to achieve a high expansion ratio and relatively uniform bubble size within the base resin composition. The foaming agent decomposition method is also carried out under high-temperature conditions, and since not all of the added thermal decomposition foaming agent becomes gas, the amount of gas generated tends to be relatively small. Therefore, vapor-phase impregnation has the advantage of making it easier to increase the foaming agent content. Furthermore, compared to liquid-phase impregnation, vapor-phase impregnation tends to require more compact equipment, such as pressure-resistant equipment and cooling equipment, making it easier to keep equipment costs low. The gas-phase impregnation conditions are not particularly limited, but the atmospheric pressure is preferably 0.5 to 6.0 MPa, more preferably 2.0 to 4.0 MPa. The atmospheric temperature is preferably 5 to 30°C, more preferably 7 to 20°C. The impregnation time is preferably 2.0 to 6.0 hours, more preferably 2.5 to 4.0 hours. When the atmospheric pressure, atmospheric temperature, and impregnation time are within the above ranges, gas dissolution into the base resin composition tends to proceed more efficiently. In particular, a low atmospheric temperature tends to increase the amount of impregnation but slow the impregnation rate, while a high atmospheric temperature tends to decrease the amount of impregnation but speed up the impregnation rate. Taking these factors into consideration, it is preferable to set the atmospheric temperature as described above to efficiently proceed with gas dissolution into the base resin composition.

[0070] The blowing agent is not particularly limited, and commonly used gases can be used. Examples thereof include inorganic gases such as air, carbon dioxide gas, nitrogen gas, oxygen gas, ammonia gas, hydrogen gas, argon gas, helium gas, and neon gas; fluorocarbons such as trichlorofluoromethane (R11), dichlorodifluoromethane (R12), chlorodifluoromethane (R22), tetrachlorodifluoroethane (R112), dichlorofluoroethane (R141b), chlorodifluoroethane (R142b), difluoroethane (R152a), HFC-245fa, HFC-236ea, HFC-245ca, and HFC-225ca; aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, and neopentane; dimethyl ether, diethyl ether, methyl ethyl ether, isopropyl ether, n-butyl ether, diisopropyl ether, furan, Examples of the carboxylic acid ester include ethers such as furfural, 2-methylfuran, tetrahydrofuran, and tetrahydropyran; ketones such as dimethyl ketone, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl i-butyl ketone, methyl n-amyl ketone, methyl n-hexyl ketone, ethyl n-propyl ketone, and ethyl n-butyl ketone; alcohols such as methanol, ethanol, propyl alcohol, i-propyl alcohol, butyl alcohol, i-butyl alcohol, and t-butyl alcohol; carboxylic acid esters such as methyl formate, ethyl formate, propyl formate, butyl formate, amyl formate, methyl propionate, and ethyl propionate; and chlorinated hydrocarbons such as methyl chloride and ethyl chloride. These may be used alone or in combination of two or more.

[0071] From the viewpoint of flame retardancy, it is preferable that the blowing agent is not flammable or flame-stimulating, and from the viewpoint of gas safety, inorganic gases are more preferable. Furthermore, inorganic gases are less soluble in resins than organic gases such as hydrocarbons, and are easily released from the base resin composition during the foaming process or after molding of the foamed molded article, which has the advantage of providing superior dimensional stability of the foamed molded article over time. Furthermore, inorganic gases are less likely to cause plasticization of the resin due to residual gas, and are therefore more likely to exhibit excellent heat resistance at an earlier stage after molding. Among inorganic gases, carbon dioxide is preferred from the viewpoints of solubility in resins and ease of handling.

[0072] The amount of the foaming agent to be impregnated is preferably 3 to 13 parts by mass, more preferably 3.5 to 10 parts by mass, per 100 parts by mass of the resin contained in the base resin composition. When the amount of the blowing agent impregnated is 3 parts by mass or more relative to 100 parts by mass of the resin contained in the base resin composition, a higher expansion ratio is easily achieved, and the variation in cell size within the base resin composition is suppressed, which tends to reduce the variation in expansion ratio between base resin compositions.When the amount of the blowing agent impregnated is 13 parts by mass or less relative to 100 parts by mass of the resin contained in the base resin composition, the cell size does not become too small, and excessive foaming is suppressed, which tends to make it easier to maintain the closed cell ratio.

[0073] <Foaming process> The method for expanding the expanded beads in the expansion step is not particularly limited, but examples include a method in which the pressure is suddenly reduced from a high-pressure condition to a low-pressure atmosphere to expand the blowing agent (gas, etc.) dissolved in the base resin composition, and a method in which the blowing agent (gas, etc.) dissolved in the base resin composition is heated with pressurized steam, hot air, etc. to expand the blowing agent. Among these, the method of heat foaming is particularly preferred, because the size of the bubbles inside the base resin composition tends to become uniform compared to the method of suddenly releasing the mixture from a high-pressure condition to a low-pressure atmosphere.

[0074] Pressurized steam, which has the advantage of facilitating control of the expansion ratio, particularly for products with a low expansion ratio, can be introduced, for example, through multiple steam holes at the bottom of the foaming furnace and the resin is stirred with a stirring blade, thereby enabling the base resin composition to be foamed more uniformly and efficiently. The rotation speed of the stirring blade is preferably 20 to 120 rpm, more preferably 50 to 90 rpm. When the rotation speed of the stirring blade is 20 rpm or higher, the pressurized steam is more easily applied to the resin, making foaming control easier and reducing the likelihood of problems such as blocking. Furthermore, when the rotation speed of the stirring blade is 120 rpm or lower, the resin foam is less likely to be damaged by the stirring blade during foaming, and problems such as a decrease in the closed cell ratio and an inability to achieve the desired expansion ratio tend to be less likely to occur. In addition, as a foaming method for the resin foam in the foaming step, a method of heating and foaming with high-temperature hot air (hot air foaming) is also preferred. This method is particularly effective when the glass transition temperature of the base resin composition (base resin composition pellets) is high. The hot air foaming method may be either a batch method or a continuous method.

[0075] When a resin foam is expanded to a desired expansion ratio, the expansion may be performed in a single step during the expansion process, or in multiple steps, such as secondary and tertiary expansion. In the case of multiple-step expansion, it is preferable to subject pre-expanded particles (e.g., expanded particles that have not yet been expanded in the final step) to a pressure treatment with an inorganic gas before each expansion step. The gas used for the pressure treatment is not particularly limited, but inorganic gases are preferred from the viewpoints of flame retardancy and gas safety. Examples of inorganic gases include air, carbon dioxide, nitrogen gas, oxygen gas, ammonia gas, hydrogen gas, argon gas, helium gas, and neon gas. From the viewpoints of ease of handling and economy, carbon dioxide and air are preferred, but are not limited thereto. The pressure treatment method is also not particularly limited, but examples include a method in which a pre-expanded resin foam is filled into a pressure tank and pressurized by supplying an inorganic gas into the tank.

[0076] If aliphatic hydrocarbon gases remain in a resin foam, the residual gas plasticizes the resin, lowering the glass transition temperature and making it difficult to achieve excellent heat resistance. Furthermore, if aliphatic hydrocarbon gases remain in the resin foam in the expanded beads, the gas gradually escapes over time, making the resulting foamed molded article more susceptible to dimensional changes. Therefore, the residual concentration (content) of the remaining aliphatic hydrocarbon gas is preferably 1,000 ppm by volume or less. The residual concentration of aliphatic hydrocarbon gases remaining in a resin foam can be reduced to 1000 ppm by volume or less, for example, by using an inorganic gas as a foaming agent, or by subjecting the resin foam to an "aging process" in which the foam is left under high-temperature conditions (which can be set at any temperature between 40°C and 80°C, for example) for a long period of time to release the remaining gases. In this specification, the residual concentration of the aliphatic hydrocarbon gas is the value (volume ppm) obtained by dividing the volume of the aliphatic hydrocarbon gas contained in the resin foam by the volume of the foam, and 1 volume ppm (hereinafter simply referred to as "ppm") corresponds to 0.0001 volume %.

[0077] (foam molded body) The foam molded article of the present embodiment is preferably made of the resin foam of the present embodiment. The foam molded article may also be obtained by adding a foaming agent to the base resin composition or base resin composition pellets and foaming them. The other foam molded article of this embodiment is produced using the above-described base resin composition or base resin composition pellets, which have good moldability and foamability, and therefore has excellent flame retardancy and appearance.

[0078] The expansion ratio of the foamed molded article of this embodiment is 3 to 50 cm 3 / g, and 5 to 15 cm 3 / g, and 9 to 12 cm 3 / g. It is more preferable that the expansion ratio of other foamed molded articles is 50 cm 3When the expansion ratio of the foamed molded article is 3 cm or less, excellent heat resistance, mechanical properties, and appearance tend to be exhibited. 3 / g or more, the objective of reducing the weight of parts tends to be sufficiently achieved. The expansion ratio is calculated by measuring the weight W (g) of the resin foam, measuring the volume V (cc) by a submersion method, and dividing the volume by the weight.

[0079] The closed cell ratio of the foamed molded article of this embodiment is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. When the closed cell ratio of the foamed molded article is 80% or more, it tends to be possible to exhibit excellent heat resistance, mechanical properties, and appearance. The closed cell content of the foamed molded product can be determined in the same manner as that for the closed cell content of the resin foam.

[0080] -Method of manufacturing foam molded products- Furthermore, the method for producing a foam molded article includes a molding step in which the resin foam of this embodiment is used for molding. The method for molding a foam molded article using a resin foam is not particularly limited, but examples include a method in which the resin foam is filled into the cavity of a molding die, heated to cause expansion and simultaneously heat-seal the resin foam pieces together, and then cooled to solidify the product and mold it. The method for filling the resin foam is not particularly limited, and known methods can be used. It is preferable to subject the resin foam to a gas pressure treatment before filling the cavity of a molding die. Applying a certain gas pressure to the cells of the resin foam firmly fuses the resin foams that make up the resulting foamed molded article, improving the rigidity and appearance of the foamed molded article. The gas used for the pressure treatment is not particularly limited, but air and inorganic gases are preferred from the standpoints of ease of handling and economy. The pressure treatment method is not particularly limited, but examples include a method in which the resin foam is filled into a pressure vessel, and then pressurized gas is introduced and the pressure is increased to a maximum pressure of 0.1 to 20 MPa over 10 minutes to 96 hours, thereby supplying the gas to the pressure vessel.

[0081] Examples of heating methods for forming the foamed molded article include heating using a heat medium such as water vapor, heating with a heater such as an IR heater, heating using microwaves, etc. When heating using a heat medium, a general-purpose heat medium may be used, and water vapor is preferred from the viewpoint of efficiently heating the resin. A molding method for foam molded products using water vapor (steam foam molding) generally uses a mold with steam holes and may include a process called one-way / reverse one-way heating, in which the air inside the mold and between the foam particles is replaced with steam, a process called double-sided heating, in which steam is introduced from both sides of the mold to sufficiently heat the resin foam and fuse the resin foam together, and a cooling process in which water is sprayed on the product after heating. In particular, the temperature tends to be the highest during the double-sided heating process, so the residual stress in the foam molded product can be controlled by controlling the temperature and time of the double-sided heating process.

[0082] When the heating temperature of the resin foam is high, the resin foams tend to fuse together and the residual stress in the foam-molded product is easily reduced, which tends to improve the moldability, heat resistance, and appearance. However, if the heating temperature is too high, the foam-molded product tends to shrink, warp, and the like. Furthermore, when the heating time of the resin foam is long, the resin foams tend to fuse together and the residual stress in the foam-molded product is easily reduced, which tends to improve the moldability, heat resistance, and appearance. However, if the heating time is too long, the foam-molded product shrinks, warps, and the like, or the cycle time is shortened, which deteriorates the moldability. From the above viewpoints, the heating temperature of the resin foam in the molding step is preferably at least Tg of the base resin composition - 30°C, and may be at least Tg - 20°C, at least Tg - 10°C, at least Tg, or may be higher than Tg. Furthermore, the heating temperature of the resin foam in the molding step is preferably at most Tg of the base resin composition + 50°C, and may be at most Tg + 30°C, or at most Tg + 20°C. From the above viewpoints, the heating time of the resin foam in the molding step is preferably 10 seconds or more, and may be 20 seconds or more, 40 seconds or more, or more than 40 seconds. The heating time of the resin foam in the molding step is preferably 180 seconds or less, and may be 120 seconds or less, or 90 seconds or less. For example, the forming step may involve heating at a high temperature above Tg or heating at or above Tg for an extended period of time greater than 40 seconds. [Example]

[0083] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0084] The measurement and evaluation methods used in the examples and comparative examples are explained below.

[0085] <Zinc content> Approximately 0.1 g of sample was weighed into a TFM digestion vessel, and sulfuric acid (Kanto Chemical Co., Ltd., ultra-high-purity sulfuric acid Ultrapur-100) and nitric acid (Kanto Chemical Co., Ltd., ultra-high-purity nitric acid (EL grade)) were added. The mixture was then subjected to acid digestion under pressure using a Milestone General microwave digestion device. The digested solution was adjusted to a constant volume of 50 mL and analyzed using an Agilent Technologies ICP-MS.

[0086] <Phosphorus content> Approximately 0.1 g of sample was weighed into a TFM digestion vessel, and sulfuric acid (Kanto Chemical Co., Ltd., ultra-high-purity sulfuric acid Ultrapur-100) and nitric acid (Kanto Chemical Co., Ltd., ultra-high-purity nitric acid (EL grade)) were added. The mixture was then subjected to acid digestion under pressure using a Milestone General microwave digestion device. The digested solution was adjusted to a constant volume of 50 mL and analyzed using an Agilent Technologies ICP-MS.

[0087] <Carbon-carbon unsaturated double bond amount> Approximately 25 mg of sample was dissolved in 0.7 mL of deuterated chloroform (containing the reference peak TMS, 0.00 ppm) by heating at 50°C. 1H-NMR (ECS 400, 400 MHz) was used to perform 512 integrated measurements. From the obtained spectrum, the integral values ​​of polyphenylene ether resin (-CH3 (6H), 2.09 ppm), polystyrene in the resin with double bonds (benzene ring (5H), 6.2-7.5 ppm), and butadiene (double bond (2H), 4.9-6.0 ppm) were calculated. Since the integral value of polystyrene overlaps with the integral value of the benzene ring of the polyphenylene ether resin, the value obtained by subtracting the integral value of the overlapping signal was used. The amount of carbon-carbon unsaturated double bonds in the resin with carbon-carbon unsaturated double bonds was calculated from these signal integral values ​​and the number of protons.

[0088] <Moldability> Using each foam molding method, foam moldings measuring 150 mm x 150 mm x 3 mm thick were produced under conditions of a cracking rate of 10%. When one foam molding was produced in one molding cycle using one mold, it was considered single-cavity molding, and when three foam moldings of the above dimensions were produced in one molding cycle using one mold, it was considered multi-cavity molding. The resulting foam moldings were visually inspected, and the appearance of the foam moldings was evaluated according to the following criteria. A: No defects in appearance were observed on either the surface or the edge of the foamed molded article. B: Poor appearance is observed on the surface or edge of the foamed molded article. C: Poor appearance was observed on the surface and edges of the foamed molded product, or a plate-shaped foamed molded product could not be obtained, making it impossible to judge the appearance.

[0089] <Expansion ratio of resin foam> After measuring the weight W (g) of the resin foam, the volume V (cc) was measured by the submersion method, and the volume was divided by the weight to obtain V / W (cc / g), which was used as the expansion ratio.

[0090] <Closed cell ratio of resin foam> The true volume (Vxp) of a resin foam with a known expansion ratio (cc / g) was measured using an air comparison type hydrometer manufactured by Beckman Co., Ltd., and the closed cell percentage Sp (%) was calculated using the following formula. Sp(%)={(Vxp-Wp / ρp) / (Vap-Wp / ρp)}×100 Vxp: True volume of resin foam (cm 3 ) Vap: Volume of resin foam (expansion ratio x mass) (cc) Wp: Mass of resin foam (g) ρp: density of the base resin composition of the resin foam (g / cm 3 )

[0091] <Flame retardancy> Flame retardancy was evaluated by conducting a test based on the UL94 vertical flame test of the US UL standard. The measurement method is as follows: The resulting resin foam was molded into test pieces measuring 125 mm in length, 13 mm in width, and 5 mm in thickness, and five of these molded pieces were used for evaluation. The test pieces were attached vertically to a clamp and exposed to a 20 mm flame for 10 seconds twice. The test pieces were rated as V-0, V-1, V-2, or non-compliant based on their combustion behavior. The criteria for V-0, V-1, V-2, and non-compliant are as follows: V-0: The duration of flaming combustion was within 10 seconds for both the first and second tests, the total duration of flaming combustion and flameless combustion for the second test was within 30 seconds, the total flaming combustion time for the five test specimens was within 50 seconds, no specimens burned up to the position of the fixing clamps, and no cotton was ignited by falling burning material. V-1: The duration of flaming combustion for both the first and second tests was within 30 seconds, and the total duration of flaming combustion and flameless combustion for the second test was within 60 seconds. The total flaming combustion time for the five test specimens was within 250 seconds. No specimens burned up to the position of the fixing clamps, and no cotton was ignited by falling burning material. V-2: The duration of flaming combustion was within 30 seconds for both the first and second tests, and the total duration of flaming combustion and flameless combustion for the second test was within 60 seconds. The total flaming combustion time for the five test specimens was within 250 seconds. No specimens burned up to the position of the fixing clamps, and the cotton was ignited by falling burning material. Non-compliant: Not applicable to V-0, V-1, or V-2.

[0092] The raw materials used in the examples and comparative examples are described below.

[0093] (A-1) Polyphenylene ether resin-1: Modified polyphenylene ether resin S201A (Made by Asahi Kasei Corporation) (A-2) Polystyrene resin-1: General-purpose polystyrene resin GP685 (manufactured by PS Japan Co., Ltd.) (A-3) Resin having carbon-carbon unsaturated double bonds-1: High-impact polystyrene resin HIPS 475D (manufactured by PS Japan Co., Ltd.) (A-3) Resin-2 having carbon-carbon unsaturated double bonds: Styrene-butadiene copolymer K-Resin (manufactured by INEOS Stylorution) (B) Phosphorus-based flame retardant-1: Condensed phosphate ester flame retardant CR-741 (manufactured by Daihachi Chemical Industry Co., Ltd.) (B) Phosphorus-based flame retardant-2: Phosphazene-based flame retardant Rabitol FP-110 (manufactured by Fushimi Pharmaceutical Co., Ltd.) (C) Zinc Compound-1: Zinc Oxide (C) Zinc Compound-2: Zinc Sulfide

[0094] Examples and comparative examples will be described below.

[0095] [Example 1 and Examples 3 to 5] (A-1) Polyphenylene ether resin-1, (A-2) Polystyrene resin-1, (A-3) Resin-1 with carbon-carbon unsaturated double bonds, (B) Phosphorus-based flame retardant-1, (B) Phosphorus-based flame retardant-2, (C) Zinc compound-1, and (C) Zinc compound-2 were mixed in the proportions shown in Table 1, and the mixture was heated, melted, and kneaded in an extruder. The mixture was then extruded to prepare base resin composition pellets. Following the method described in Example 1 of JP-A-4-372630, the base resin composition pellets were placed in a pressure-resistant container. The gas in the container was replaced with dry air, and carbon dioxide (gas) was injected as a blowing agent. The base resin pellets were impregnated with 7% by weight of carbon dioxide over 3 hours at a pressure of 3.0 MPa and a temperature of 10°C. The base resin composition pellets were then foamed with pressurized steam in a foaming furnace while rotating the stirring blade at 77 rpm to produce a resin foam. The expansion ratio and closed cell ratio of the resulting resin foam are shown in Table 1. This resin foam was pressurized to 0.4 MPa over 4 hours, then held at 0.4 MPa for 8 hours for pressure treatment. It was then filled into an internal molding die equipped with a steam vent and heated with pressurized steam to expand and fuse the resin foam together. It was then cooled and removed from the die to obtain a foamed molded article. The measurement and evaluation results for various physical properties of this foamed molded article are shown in Table 1.

[0096] [Example 2] Except for changing (A-3) Resin-1 having a carbon-carbon unsaturated double bond to (A-3) Resin-2 having a carbon-carbon unsaturated double bond, base resin composition pellets, a resin foam, and a foam-molded article were obtained in the same manner as in Example 1. The measurement and evaluation results of various physical properties are shown in Table 1.

[0097] [Example 6] After obtaining base resin composition pellets with the same composition as in Example 1, the pellets were fed into the extruder again to obtain base resin composition pellets, a resin foam, and a foam-molded product. The measurement and evaluation results of various physical properties are shown in Table 1.

[0098] [Comparative Example 1] Base resin composition pellets, a resin foam, and a foam-molded product were obtained in the same manner as in Example 1, except that (C) zinc compound was not added and (A-1) polyphenylene ether resin-1, (A-2) polystyrene resin-1, (A-3) resin having a carbon-carbon unsaturated double bond-1, and (B) phosphorus-based flame retardant-1 were mixed in the proportions shown in Table 1. Measurement and evaluation results of various physical properties are shown in Table 1.

[0099] Comparative Example 2 Base resin composition pellets, a resin foam, and a foam-molded product were obtained in the same manner as in Example 1, except that (A-3) resin having a carbon-carbon unsaturated double bond-1 was not blended, and (A-1) polyphenylene ether resin-1, (A-2) polystyrene resin-1, (B) phosphorus-based flame retardant-1, and (C) zinc compound were mixed in the proportions shown in Table 1. Measurement and evaluation results of various physical properties are shown in Table 1.

[0100] Comparative Example 3 Base resin composition pellets, a resin foam, and a foam-molded product were obtained in the same manner as in Example 1, except that (B) phosphorus-based flame retardant-1 was not added and (A-1) polyphenylene ether resin-1, (A-2) polystyrene resin-1, (A-3) resin having a carbon-carbon unsaturated double bond-1, and (C) zinc compound were mixed in the proportions shown in Table 1. Measurement and evaluation results of various physical properties are shown in Table 1.

[0101] Comparative Example 4 Base resin composition pellets, a resin foam, and a foam-molded article were obtained in the same manner as in Example 1, except that the amount of (C) zinc compound was changed to the ratio shown in Table 1. The results of measurement and evaluation of various physical properties are shown in Table 1.

[0102] [Table 1]

[0103] From Table 1, it can be seen that the resin foam of the present invention has excellent moldability even in a multi-cavity molding system in which multiple products are molded using one mold, and also has excellent flame retardancy. [Industrial Applicability]

[0104] According to the present invention, it is possible to provide a resin foam that has excellent flame retardancy and is excellent in multi-cavity performance for molding a plurality of products using one mold.

Claims

1. A resin foam obtained by foaming a base resin composition, The base resin composition is (A) a resin, (B) a phosphorus-based flame retardant, and (C) Zinc compounds Including, The (A) resin is (A-1) polyphenylene ether resin, (A-2) a polystyrene resin, and (A-3) Resin having a carbon-carbon unsaturated double bond Including, A resin foam containing 0.05 to 5.0 moles of zinc per mole of the carbon-carbon unsaturated double bond of the resin (A-3) having a carbon-carbon unsaturated double bond.

2. The resin foam according to claim 1 , which is in the form of beads.

3. The resin foam according to claim 1 or 2, which has a flame retardancy of V-2 to V-0 as measured based on the UL94 vertical flame test of the UL standard.

4. The resin foam according to claim 1 or 2, comprising 5 to 25 parts by mass of the phosphorus-based flame retardant (B) relative to 100 parts by mass of the resin (A).

5. relative to 1 mole of phosphorus contained in the base resin composition The resin foam according to claim 1 or 2, wherein the amount of the carbon-carbon unsaturated double bond is 0.001 to 0.2 mol.

6. The resin foam according to claim 1 or 2, comprising 40 to 94 parts by mass of the polyphenylene ether resin (A-1) per 100 parts by mass of the resin (A).

7. The resin foam according to claim 1 or 2, comprising 1 to 59 parts by mass of the (A-2) polystyrene-based resin per 100 parts by mass of the (A) resin.

8. 3. The resin foam according to claim 1, wherein the resin having a carbon-carbon unsaturated double bond (A-3) contains a structural unit derived from styrene, and the ratio of the structural unit derived from styrene to 100% by mass of the resin having a carbon-carbon unsaturated double bond (A-3) is 60 to 99% by mass.

9. The resin foam according to claim 1 or 2, wherein the (B) phosphorus-based flame retardant is at least one selected from the group consisting of phosphate esters and phosphazene compounds.

10. a granulation step of kneading the resin foam according to claim 1 or 2 in an extruder and then pelletizing the kneaded resin foam to prepare pellets of a base resin composition; an impregnation step of impregnating the pellets with a foaming agent; a foaming step of foaming the pellets impregnated with the foaming agent to obtain a resin foam; A method for producing a resin foam, comprising:

11. a granulation step in which pellets of the base resin composition obtained by extrusion kneading, and / or fused pellets of the base resin composition generated during extrusion, and a resin mass discharged from the extruder or die are kneaded in an extruder and then pelletized to prepare pellets of the base resin composition; an impregnation step of impregnating the pellets with a foaming agent; a foaming step of foaming the pellets impregnated with the foaming agent to obtain a resin foam; A method for producing a resin foam, comprising: The base resin composition is (A) a resin, (B) a phosphorus-based flame retardant, and (C) Zinc compounds Including, The (A) resin is (A-1) polyphenylene ether resin, (A-2) a polystyrene resin, and (A-3) Resin having a carbon-carbon unsaturated double bond Including, The method for producing a resin foam, wherein the resin (A-3) having a carbon-carbon unsaturated double bond contains 0.05 to 5.0 moles of zinc per mole of the carbon-carbon unsaturated double bond.

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