Non-flammable resin composition and non-flammable crosslinked resin foam

Abstract

To provide a non-halogen incombustible crosslinked resin foam that exhibits incombustibility, achieves a sufficiently high foaming rate, and also offers a sufficiently improved compressive stress value, and an incombustible resin composition suitable for obtaining the incombustible crosslinked resin foam.SOLUTION: An incombustible resin composition includes the following components (A)-(E): (A) an ethylene-vinyl acetate copolymer, (B) a metal hydrate, (C) red phosphorus, (D) a processing aid, and (E) a foaming agent. Relative to 100 pts.mass of the content of component (A), the content of component (B) is 100-300 pts.mass, the content of component (C) is 2-25 pts.mass, and the content of component (D) is 0.1-50 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a nonflammable resin composition and a nonflammable crosslinked resin foam. [Background technology]

[0002] Resin foams are generally obtained by forming a crosslinked structure (a three-dimensional network structure) in a resin composition and then foaming it. Because resin foams are in a foamed state, they are excellent in light weight, heat insulating properties, compressive stress, etc., and can also have desired water resistance, chemical resistance, etc., and are widely used in fields such as building materials, electrical appliances, automobiles, and energy equipment. Since resin foams are generally flammable, when non-flammable or flame-retardant properties are required for the resin foam, the desired non-flammable or flame-retardant resin foam is produced by foaming a resin composition containing a flame retardant while forming a crosslinked structure.

[0003] Halogen-based flame retardants have traditionally been used as the flame retardant. Halogen-based flame retardants have a high flame retardant effect, and even a small amount can be added to sufficiently enhance the non-flammability of the resulting resin foam. However, non-flammable resin foams using halogen-based flame retardants have the problem of generating harmful corrosive gases (halogen gases) when exposed to high temperatures. For this reason, development of non-flammable resin foams using non-halogen flame retardants is underway.

[0004] Red phosphorus is known as a non-halogen flame retardant. Patent Document 1, for example, discloses a flame-retardant or non-flammable resin foam using red phosphorus. The flame-retardant polyolefin resin foam is characterized by comprising 100 parts by weight of a resin component consisting of an ethylene-acrylic acid alkyl ester copolymer alone or a mixture of the copolymer with another polyolefin resin, 50 to 200 parts by weight of a hydrated metal oxide, 5 to 100 parts by weight of ammonium polyphosphate, 0.1 to 50 parts by weight of red phosphorus, and a blowing agent, the weight ratio of which is ammonium polyphosphate:red phosphorus=1:0.01 to 10, and the resulting flame-retardant polyolefin resin composition is crosslinked with ionizing radiation and then foamed by heating to a temperature equal to or higher than the decomposition temperature of the blowing agent. Patent Document 2 discloses a halogen-free flame-retardant resin foam, characterized in that it is obtained by crosslinking and foaming using a resin composition containing 100 parts by mass of a resin component (A) containing an ethylene-vinyl acetate copolymer (A1) and / or an ethylene-ethyl acrylate copolymer (A2), 151 to 300 parts by mass of (B) magnesium hydroxide and / or surface-treated aluminum hydroxide as a metal hydrate, 2 to 25 parts by mass of (C) red phosphorus, 5 to 100 parts by mass of (D) titanium oxide, and 10 to 40 parts by mass of (E) a thermally decomposable blowing agent, wherein the total content of vinyl acetate and ethyl acrylate, which are copolymer components of the ethylene-vinyl acetate copolymer (A1) and / or ethylene-ethyl acrylate copolymer (A2), in the resin component (A) is 14 to 50% by mass. Furthermore, Patent Document 3 discloses a non-halogen flame-retardant resin foam characterized by being obtained by heating and foaming a resin composition comprising 100 parts by weight of polyethylene resin, 50 to 130 parts by weight of magnesium hydroxide, 5 to 50 parts by weight of zinc borate and / or antimony trioxide, 2 to 20 parts by weight of red phosphorus, 0.5 to 5 parts by weight of a lubricant, as well as a foaming agent and a crosslinking agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-235402 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-001572 [Patent Document 3] Japanese Patent Application Publication No. 2-296841 Summary of the Invention [Problem to be solved by the invention]

[0006] Although non-halogen flame retardants have the advantage of not emitting harmful substances even when exposed to high temperatures, their blending amount in resin foam to impart non-combustibility needs to be larger than that in the case of blending halogen-based flame retardants. However, blending a large amount of non-halogen flame retardant increases the open cell ratio of the resulting resin foam, resulting in the resulting resin foam having inferior compressive strength, etc.

[0007] An object of the present invention is to provide a non-halogen-based non-flammable crosslinked resin foam that is non-flammable, has a sufficiently high expansion ratio, and has a sufficiently increased compressive stress value, as well as a non-flammable resin composition that is suitable for obtaining this non-flammable crosslinked resin foam. [Means for solving the problem]

[0008] As a result of intensive research aimed at solving the above problems, the present inventors have found that by preparing a resin composition by blending an ethylene-vinyl acetate copolymer, a metal hydrate, red phosphorus, a processing aid, and a blowing agent in a specific ratio, a crosslinked resin foam obtained from the resin composition exhibits nonflammability, achieves a sufficiently high expansion ratio, and also has a sufficiently high compressive stress value. Based on these findings, the present inventors have conducted further research and have now completed the present invention.

[0009] That is, the above problems were solved by the following means. <1> It contains the following components (A) to (E): (A) ethylene-vinyl acetate copolymer, (B) metal hydrate, (C) Red phosphorus, (D) processing aids; (E) a foaming agent, A non-flammable resin composition, wherein the content of the component (B) is 100 to 300 parts by mass, the content of the component (C) is 2 to 25 parts by mass, and the content of the component (D) is 0.1 to 50 parts by mass, relative to 100 parts by mass of the component (A). <2> The component (D) is an acrylic processing aid. <1> The non-flammable resin composition according to claim 1. <3> The above-mentioned composition contains the following component (F): <1> or <2> The non-flammable resin composition according to claim 1. (F) Flame retardant synergist <4> The aforementioned <1> ~ <3> 1. A nonflammable crosslinked resin foam obtained by forming a crosslinked structure in the nonflammable resin composition according to any one of claims 1 to 9, and then subjecting the crosslinked product to a foaming treatment simultaneously with or after the formation of the crosslinked structure. <5> It contains the following components (a) to (d): (a) ethylene-vinyl acetate copolymer, (b) metal hydrate; (c) red phosphorus; (d) processing aids; A non-flammable crosslinked resin foam, wherein the content of the component (b) is 100 to 300 parts by mass, the content of the component (c) is 2 to 25 parts by mass, and the content of the component (d) is 0.1 to 50 parts by mass, relative to 100 parts by mass of the component (a). <6> In the compressive stress-strain test of JIS K 6767 (1999), the compressive stress at 25% strain is 10 kPa or more. <4> or <5> The non-flammable crosslinked resin foam according to claim 1. [Effects of the Invention]

[0010] The nonflammable resin composition of the present invention can be subjected to a foaming treatment simultaneously with or after the formation of the crosslinked structure by introducing a crosslinked structure thereinto, thereby obtaining a crosslinked resin foam that is nonflammable, has a sufficiently high expansion ratio, and has a sufficiently high compressive stress value. The nonflammable crosslinked resin foam of the present invention is nonflammable, has a sufficiently high expansion ratio, and has a sufficiently high compressive stress value. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present invention and this specification, "non-flammable" means that, in the case of a resin composition, a crosslinked resin foam obtained by crosslinking and foaming the resin composition has a total heat release value of 8 MJ / m when heated for 20 minutes in a heat release test (in accordance with ISO 5660-1:2002). 2 For cross-linked resin foam, the total heat release rate after 20 minutes of heating is 8MJ / m in the heat release test (based on ISO 5660-1:2002). 2 This means that:

[0012] [Nonflammable resin composition] The non-flammable resin composition of the present invention (hereinafter also referred to as "the resin composition of the present invention") contains (A) an ethylene-vinyl acetate copolymer (also referred to as component (A)), (B) a metal hydrate (also referred to as component (B)), (C) red phosphorus (also referred to as component (C)), (D) a processing aid (also referred to as component (D)), and (E) a foaming agent (also referred to as component (E)). Components (A) to (E) and the optional components described below may each be used alone or in combination of two or more. The resin composition of the present invention preferably does not contain a halogen-based flame retardant (a flame retardant containing a halogen element). The components contained in the resin composition of the present invention will be described below.

[0013] <(A) Ethylene-vinyl acetate copolymer> The resin composition of the present invention contains (A) an ethylene-vinyl acetate copolymer (EVA) as a resin component constituting the base resin. The polymerization form of the ethylene-vinyl acetate copolymer used in the present invention may be any of random, alternating, block, and graft polymerization.

[0014] In the ethylene-vinyl acetate copolymer, the content of the vinyl acetate component, which is a constituent component, is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, in terms of the balance between the elongational viscosity due to filler dispersion in the resin and the strain hardening due to elongational flow. From the same viewpoint as above, the content of the vinyl acetate component is preferably 10% by mass or more, more preferably 15% by mass or more. A preferred range for the content of the vinyl acetate component is 10 to 40% by mass, more preferably 15 to 35% by mass, and even more preferably 15 to 30% by mass. The content of the vinyl acetate component can be determined from the amounts of each monomer used in synthesizing the ethylene-vinyl acetate copolymer.

[0015] The melt flow rate (hereinafter simply referred to as MFR) of the ethylene-vinyl acetate copolymer used in the present invention is preferably 0.1 to 100 g / 10 min, more preferably 0.1 to 50 g / 10 min, and even more preferably 0.5 to 30 g / 10 min. The MFR is measured in accordance with JIS K 7210:1999 under conditions of a load of 2.16 kg and a temperature of 190°C. By adjusting the MFR of the ethylene-vinyl acetate copolymer to fall within the above preferred range, the resin and metal hydrate can be mixed more uniformly.

[0016] The ethylene-vinyl acetate copolymer can be synthesized by a conventional method, or a commercially available product such as EVAFLEX (registered trademark) EV460 (product name) manufactured by Dow Mitsui Polychemicals can be used.

[0017] In the resin composition of the present invention, the content of the component (A) is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of expansion ratio. Furthermore, from the viewpoint of non-flammability, the content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. The content of the component (A) is preferably in the range of 10 to 50% by mass, more preferably 15 to 45% by mass, and even more preferably 20 to 40% by mass.

[0018] <(B) Metal hydrate> The resin composition of the present invention contains (B) a metal hydrate. The metal hydrate is a so-called filler, and various shapes, such as needle-shaped, block-shaped, scaly powder, granular, and block-shaped, can be used. The metal hydrate functions as a flame retardant (non-halogen flame retardant) together with red phosphorus in the resin composition of the present invention or in a crosslinked resin foam obtained by crosslinking and foaming the resin composition. Examples of this metal hydrate include aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, and barium hydroxide. Among these, metal hydroxides are preferred, and the use of magnesium hydroxide and / or aluminum hydroxide is preferred from the viewpoint of achieving higher non-flammability.

[0019] The metal hydrate may be surface-treated or untreated. Examples of surface-treated products include those surface-treated with a fatty acid such as stearic acid or oleic acid, those surface-treated with a phosphate ester, and those surface-treated with a silane coupling agent having a vinyl group or an epoxy group at the terminal. In the present invention, it is more preferable that the metal hydrate is surface-treated with a fatty acid or a combination of a fatty acid and a silane coupling agent.

[0020] The component (B) is commercially available, and examples thereof include magnesium hydroxide under the trade name MAGNIFIN (registered trademark) H-5MV (trade name, manufactured by HUBER) and aluminum hydroxide under the trade name B703S (trade name, manufactured by Nippon Light Metal Co., Ltd.).

[0021] The resin composition of the present invention contains 100 to 300 parts by mass of component (B) per 100 parts by mass of component (A). By setting the content of component (B) in the resin composition of the present invention within the above range, the expansion ratio of a crosslinked resin foam obtained by crosslinking and foaming the resin composition can be further increased. Furthermore, in combination with the action of red phosphorus, this crosslinked resin foam can be imparted with sufficiently high non-flammability (flame retardancy). From the viewpoint of further improving non-flammability, the content of component (B) is preferably 125 parts by mass or more, more preferably 150 parts by mass or more, per 100 parts by mass of component (A). Furthermore, from the viewpoint of further improving the expansion ratio, the content is preferably 250 parts by mass or less, more preferably 200 parts by mass or less. The content of component (B) is preferably 125 to 250 parts by mass, more preferably 150 to 200 parts by mass, per 100 parts by mass of component (A).

[0022] <(C)Red phosphorus> The resin composition of the present invention contains (C) red phosphorus. Red phosphorus is also a type of filler. Red phosphorus undergoes thermal decomposition when exposed to high temperatures, such as during combustion, and promotes char formation through its strong dehydration action, thereby exhibiting flame retardant properties through its air-blocking effect. The red phosphorus used in the present invention can be any of those commonly used as flame retardants. From the standpoints of safety and ease of handling (moisture resistance, etc.), red phosphorus particles whose surfaces have been treated with a resin or the like are particularly preferred.

[0023] Component (C) is commercially available, for example, as Novaled (registered trademark) 120 (product name) manufactured by Rinkagaku Kogyo Co., Ltd.

[0024] The resin composition of the present invention contains 2 to 25 parts by mass of component (C) per 100 parts by mass of component (A). By setting the content of component (C) within the above range, in combination with the effects of the other components, it is possible to impart the desired non-flammability to a crosslinked resin foam obtained from the resin composition and further increase the expansion ratio of the crosslinked resin foam. From the viewpoint of further improving non-flammability, the content of component (C) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of component (A). Furthermore, from the viewpoint of further improving foamability, the content is preferably 23 parts by mass or less, more preferably 20 parts by mass or less. The content of component (C) is preferably 5 to 23 parts by mass, more preferably 7 to 23 parts by mass, and even more preferably 10 to 20 parts by mass, per 100 parts by mass of component (A).

[0025] <(D) Processing aids> The resin composition of the present invention contains (D) a processing aid. From the viewpoint of further improving the expansion ratio of the crosslinked resin foam obtained from the resin composition of the present invention, the processing aid is preferably an acrylic processing aid. The acrylic processing aid may contain a component derived from an acrylic monomer, such as acrylic acid, methacrylic acid; Acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate; Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and 2-ethylhexyl methacrylate Preferably, the polymer contains a constituent component derived from a monomer selected from the following and has a weight average molecular weight greater than that of component (A): The weight average molecular weight of component (D) is preferably 400,000 to 5,000,000. By using the acrylic processing aid as the processing aid in the specific amount specified in the present invention, it is possible to further increase the affinity with the component (A), thereby further increasing the expansion ratio and non-flammability, and further increasing the compressive stress.

[0026] Component (D) is commercially available, for example, as Metablen (registered trademark) P-1050 (product name) manufactured by Mitsubishi Chemical Corporation.

[0027] The resin composition of the present invention contains 0.1 to 50 parts by mass of component (D) per 100 parts by mass of component (A). By setting the content of component (D) within the above range, even when a relatively large amount of a non-halogen flame retardant is blended, the crosslinked resin foam obtained from the resin composition can have a fine closed-cell structure and excellent elasticity, while suppressing the generation of open cells. From the viewpoint of further improving the compressive stress of the crosslinked resin foam obtained from the resin composition, the content of component (D) is preferably 1 part by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of component (A). Furthermore, from the viewpoints of improving the expansion ratio and non-flammability of the resin foam, the content is preferably 45 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less. The content of component (D) is preferably in the range of 1 to 45 parts by mass, more preferably 10 to 40 parts by mass, and even more preferably 15 to 35 parts by mass, per 100 parts by mass of component (A).

[0028] <(E) Foaming Agent> The resin composition of the present invention contains (E) a foaming agent. The foaming agent is preferably a thermally decomposable foaming agent. A thermally decomposable foaming agent is a foaming agent that decomposes upon heating to generate gas. Examples of the thermally decomposable foaming agent include azodicarbonamide (ADCA), p,p'-oxybisbenzenesulfonylhydrazide (OBSH), N,N'-dinitrosopentamethylenetetramine (DPT), p-toluenesulfonylhydrazide, benzenesulfonylhydrazide, diazoaminobenzene, N,N'-dimethyl-N,N'-dinitroterephthalamide, and azobisisobutyronitrile.

[0029] Component (E) is commercially available, for example, Uniform AZ VI50ST (trade name) manufactured by Otsuka Chemical Co., Ltd.

[0030] From the viewpoint of increasing the expansion ratio, the resin composition of the present invention preferably contains 10 parts by mass or more of component (E) per 100 parts by mass of component (A), more preferably 12 parts by mass or more, and even more preferably 15 parts by mass or more. Furthermore, from the viewpoint of reducing compressive stress due to cell breakdown, the content is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less. The content of component (E) is preferably within a preferred range, preferably 10 to 50 parts by mass, more preferably 12 to 45 parts by mass, and even more preferably 15 to 40 parts by mass, per 100 parts by mass of component (A).

[0031] <(F) Flame retardant synergist> The resin composition of the present invention may contain (F) a flame retardant aid (also referred to as component (F)) to the extent that the effects of the present invention are not impaired. The flame retardant aid is also a type of filler. Examples of the flame retardant aid include magnesium oxide, aluminum oxide, titanium oxide, silicon oxide, cobalt oxide, vanadium oxide, chromium oxide, manganese oxide, iron oxide, nickel oxide, zinc oxide, silica, clay, hindered amines, antioxidants, antimony trioxide, and zinc borate. In particular, it is preferable to contain titanium oxide as component (F). When the resin composition of the present invention contains component (F), it preferably contains 5 to 30 parts by mass, and more preferably 10 to 25 parts by mass, of component (F) per 100 parts by mass of component (A).

[0032] <(G) Crosslinking Agent> The resin composition of the present invention may contain (G) a crosslinking agent (also referred to as component (G)) to the extent that the effects of the present invention are not impaired. Examples of the crosslinking agent include radical generators, and organic peroxides are preferably used. For example, organic peroxides such as dicumyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexyne-3, α,α'-bis(t-butylperoxydiisopropyl)benzene, t-butylperoxycumene, 4,4'-di(t-butylperoxy)valeric acid n-butyl ester, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-di(t-butylperoxy)cyclohexane are preferably used. The radical generator thermally decomposes to generate radicals, which can abstract hydrogen from resin components and other components to create reactive sites and form crosslinked structures. Furthermore, by using the radical generator in combination with a crosslinking aid (described below), the generated radicals can cause an addition reaction of carbon-carbon unsaturated bonds to form crosslinked structures. When the resin composition of the present invention contains component (G), it preferably contains 0.003 to 2.0 parts by mass of component (G) per 100 parts by mass of component (A), more preferably 0.05 to 2.0 parts by mass, even more preferably 0.3 to 1.8 parts by mass, and even more preferably 0.6 to 1.6 parts by mass.

[0033] <(H) Crosslinking Coagent> The resin composition of the present invention may contain (H) a cross-linking aid (also referred to as component (H)) to the extent that the effects of the present invention are not impaired. Examples of the cross-linking aid include polyfunctional vinyl compounds, and among these, polyfunctional acrylate compounds and / or polyfunctional methacrylate compounds and / or polyfunctional vinyl ether compounds are preferred. Specific examples include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and divinylbenzene. The polyfunctional vinyl compound preferably has two or more vinyl groups (including cases where vinyl groups are contained as acryloyl groups or methacryloyl groups) in one molecule, more preferably three or more, and even more preferably three to six. When the resin composition of the present invention contains component (H), it preferably contains 0.1 to 1.5 parts by mass, and more preferably 0.2 to 1.0 part by mass, of component (H) per 100 parts by mass of component (A).

[0034] <Other ingredients> In addition to the above components (A) to (H), the resin composition of the present invention may contain other components such as a foaming aid, a dispersant, a filler, a pigment, a light stabilizer, a heat stabilizer, a lubricant, etc. As described below, a silane coupling agent for forming a crosslinked structure may also be contained in the resin composition, provided that the effects of the present invention are not impaired.

[0035] [Method of producing resin composition] The resin composition of the present invention can be obtained by melt-kneading and homogenizing the above-mentioned components (A) to (E) and, if necessary, the above-mentioned optional components, using a commonly used kneading device such as a batch kneader, a roll, a kneader, or a Banbury mixer, or a twin-screw extruder.

[0036] The resin composition of the present invention may be formed into a molded article by molding the melt-kneaded product, which may be formed by various molding methods such as extrusion molding or press molding.

[0037] [Non-flammable cross-linked resin foam] The non-flammable crosslinked resin foam of the present invention (hereinafter also referred to as "the resin foam of the present invention") can be obtained by forming a crosslinked structure in the resin composition of the present invention and subjecting the crosslinked body to a foaming treatment either simultaneously with the formation of the crosslinked structure or after the formation of the crosslinked structure. Therefore, the resin foam of the present invention contains the following components (a) to (d): (a) ethylene-vinyl acetate copolymer, (b) metal hydrate; (c) red phosphorus; (d) processing aids; With respect to 100 parts by mass of the component (a), the content of the component (b) is 100 to 300 parts by mass, the content of the component (c) is 2 to 25 parts by mass, and the content of the component (d) is 0.1 to 50 parts by mass. In the present invention, the resin foam may have, as a specific feature, that it is obtained by forming a crosslinked structure in the resin composition of the present invention and then subjecting the crosslinked body to a foaming treatment simultaneously with or after the formation of the crosslinked structure, as described above, but this simply specifies the state of the resin foam. In other words, this specific feature further clarifies the structure or properties of the resin foam.

[0038] The components contained in the resin foam of the present invention, such as the (a) ethylene-vinyl acetate copolymer, (b) metal hydrate, (c) red phosphorus, and (d) processing aid, are basically the same as those described in the resin composition of the present invention, and the contents thereof are also substantially the same. On the other hand, the resin foam of the present invention differs from the resin composition of the present invention in that the resins and the like form a crosslinked structure. That is, in the resin foam of the present invention, the terms (a) ethylene-vinyl acetate copolymer, (d) processing aid, and the above-mentioned crosslinking aid are used to mean the presence of components derived from these resins (polymers) or monomers as components of the crosslinked product formed by the crosslinking reaction.

[0039] The shape of the resin foam of the present invention is, for example, 2 to 20 mm in thickness and 200 kg / m 3 It can be made into the following sheet form. Apparent density is 35 to 150 kg / m 3 More preferably, it is 50 to 140 kg / m 3 The "apparent density" of the resin foam of the present invention is a value measured by dividing the mass of a test piece of the foam cut into a predetermined size (e.g., 10 cm × 10 cm) by the volume of the foam (volume including the air bubbles).

[0040] Examples of methods for producing the resin foam of the present invention include a method in which the formation of a crosslinked structure in the resin composition of the present invention and the foaming treatment are carried out simultaneously (in parallel), and a method in which a crosslinked structure is formed in the resin composition and then the foaming treatment is carried out. An example of these methods will be described below.

[0041] -Method for simultaneously forming a crosslinked structure and foaming treatment- The resin composition of the present invention is prepared by adding the above-mentioned (G) crosslinking agent and, if necessary, (H) crosslinking aid. The kneading during preparation is carried out at a temperature (approximately 100 to 130°C) at which the (G) crosslinking agent and (E) foaming agent are unlikely to decompose. The resin composition can be in the form of pellets. The resulting resin composition is fed into an extruder and extrusion-molded at a resin temperature of approximately 100 to 130°C to obtain an unfoamed sheet having the desired thickness and width. This unfoamed sheet is placed in a heating and foaming furnace adjusted to approximately 180 to 230°C to cause a crosslinking reaction and foaming, thereby producing a resin foam sheet of the present invention.

[0042] - A method of foaming after forming a crosslinked structure - A silane coupling agent is added to the resin composition of the present invention, and the resin components (e.g., (A) ethylene-vinyl acetate copolymer and (D) processing aid) in the resin composition are reacted with the silane coupling agent to introduce graft chains into the resin components. The functional groups of the graft chains are then reacted with each other to form a crosslinked structure, yielding a crosslinked product of the desired shape (e.g., sheet-like). The foam is then heated to decompose the blowing agent and generate gas, thereby obtaining the resin foam of the present invention. Suitable silane coupling agents include vinyltrialkoxysilanes. The above-mentioned component (G) can also be used as a radical generator to introduce graft chains. It is also preferable to add a silanol condensation catalyst, such as dibutyltin dilaurate, to the resin composition. Alternatively, the resin foam of the present invention can be obtained by irradiating the resin composition of the present invention in a desired shape (e.g., a sheet) with ionizing radiation to form a crosslinked structure, and then heating the composition to decompose the blowing agent and generate a gas. The ionizing radiation that can be irradiated includes α-, β-, or γ-rays, electron beams, neutron beams, etc.

[0043] Each of the above methods may be used alone, or two or more of them may be used in combination. In any of the methods, the above-mentioned (H) crosslinking aid may be blended into the resin composition as needed to form a stronger crosslinked structure.

[0044] The resin foam of the present invention preferably has a closed-cell structure. The open-cell ratio (ratio of open cells to all cells) is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. The open-cell ratio is a value measured using an air comparison hydrometer Model 1000 (manufactured by Tokyo Science Co., Ltd.) in accordance with the method described in ASTM D-2856-87, and can be determined by the following formula (1): Open cell rate (%) = [(apparent volume - volume measured with air comparison hydrometer) / apparent volume] × 100 (Equation 1)

[0045] The average cell diameter of the cells contained in the resin foam of the present invention is preferably 400 μm or less, more preferably 250 μm or less. In the present invention, the average cell diameter is calculated by the following formula (2) using the average cell area S obtained by dividing the total area of ​​the cells by the number of the cells in an observed cross section of the resin foam of the present invention. Average bubble diameter = 2×√(S / π) (Formula 2)

[0046] The resin foam of the present invention is non-flammable, achieves a desired high expansion ratio, and is excellent in elasticity (compressive stress). For example, when the resin foam of the present invention is stacked to a thickness of 25 mm and the compressive stress (kPa) at 25% strain is measured in accordance with JIS K 6767 (1999), it is preferable that the measured value is 10 kPa or more. When the resin foam of the present invention is stacked to a thickness of 25 mm or more, it can be adjusted by appropriately shaving it down to a thickness of 25 mm. [Example]

[0047] The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these.

[0048] [Examples 1 to 15 and Comparative Examples 1 to 5] The materials used to prepare the resin foams of Examples 1 to 15 and Comparative Examples 1 to 5 are shown in Table 1 below. Details of the materials used are as follows.

[0049] <Raw materials used> Ethylene-vinyl acetate copolymer (EVA) (vinyl acetate content 19% by mass, MFR 2.5 g / 10 min, trade name: EVAFLEX (registered trademark) EV460, manufactured by Dow Mitsui Polychemicals) Metal hydrate-1 (Magnesium hydroxide, fatty acid-treated, product name: MAGNIFIN H-5MV, manufactured by HUBER) Metal hydrate-2 (aluminum hydroxide, fatty acid-treated, product name: B703S, manufactured by Nippon Light Metal Co., Ltd.) Red phosphorus (product name: Novaled (registered trademark) 120, manufactured by Rinkagaku Kogyo Co., Ltd.) Processing aid (acrylic processing aid, product name: Metablen (registered trademark) P-1050, manufactured by Mitsubishi Chemical Corporation) Foaming agent (product name: Uniform AZ VI50ST, manufactured by Otsuka Chemical Co., Ltd.) Flame retardant synergist-1 (silica, product name: S0-C2, manufactured by Admatechs Co., Ltd.) Flame retardant synergist-2 (hindered amine, trade name: Adekastab LA-77Y, manufactured by ADEKA Corporation) Flame retardant aid-3 (titanium oxide, trade name: Ti-Pure (registered trademark) R-103, manufactured by Chemours) Foaming aid (product name: Zinc Oxide No. 1, manufactured by Mitsui Mining & Smelting Co., Ltd.) Dispersant (glycerin monostearate, product name: Rikemal S-100, manufactured by Riken Vitamin Co., Ltd.) Crosslinking agent-1 (organic peroxide: dicumyl peroxide, trade name: Percumyl D, manufactured by Nippon Oil & Fats Co., Ltd.) Crosslinking agent-2 (organic peroxide: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, trade name: PERHEXA (registered trademark) C, manufactured by NOF Corporation) Crosslinking aid (trifunctional triacrylate compound: trimethylolpropane triacrylate, product name: NK Ester TMPT, manufactured by Shin-Nakamura Chemical Co., Ltd.)

[0050] <Production of resin foam> The raw materials were mixed according to the composition shown in Table 1 below, melt-kneaded at 120°C using a 1-liter kneader, and the kneaded mixture was formed into a sheet using an open roll. After cooling, the sheet was cut and granulated using a pelletizer to obtain resin compositions (pellets) of Examples 1 to 15 and Comparative Examples 1 to 5. The obtained pellets were fed into an extruder set at a temperature of 100 to 130°C, molded into a sheet with a thickness of 3 mm, and then cut into a square with a width and length of 10 cm to produce the unfoamed sheets of Examples 1 to 15 and Comparative Examples 1 to 5. These unfoamed sheets were then introduced into a hot air oven adjusted to 220°C, and the crosslinking reaction and foaming treatment were carried out simultaneously at this high temperature to produce the resin foams of Examples 1 to 15 and Comparative Examples 1 to 5.

[0051] [Performance evaluation] The resin foams (Examples 1 to 15, Comparative Examples 1 to 5) produced as described above were subjected to the following performance evaluations.

[0052] (Foaming test) The density of each of the unfoamed sheets of Examples 1 to 15 and Comparative Examples 1 to 5, and each of the resin foams obtained by crosslinking and foaming the sheets, was measured, and the expansion ratio was calculated using the following formula 3. The calculated expansion ratios were evaluated according to the following evaluation criteria. Expansion ratio = density of unfoamed sheet / apparent density of resin foam (Equation 3) -Evaluation criteria- ○: Expansion ratio is 25 times or more △: Expansion ratio is 20 times or more but less than 25 times ×: Expansion ratio less than 20 times The apparent density of each of the resin foams in Examples 1 to 15 was 35 to 80 kg / m 3 was within the range.

[0053] (Compression stress-strain test) Resin foams of 5 cm square (7 mm thick, 5 cm wide, and 5 cm long) were cut out from the resin foams of Examples 1 to 15 and Comparative Examples 1 to 5. The resulting 5 cm square resin foams were stacked in the thickness direction to a thickness of 25 mm. The compressive stress (kPa) at 25% strain of each 25 mm thick sample was measured at 25°C in accordance with JIS K 6767 (1999). Three independent tests were performed, and the average compressive stress value was calculated and evaluated according to the following evaluation criteria. -Evaluation criteria- ○: The average value of 25% compressive stress is 10 kPa or more △: Average value of 25% compressive stress is 7.5kPa or more and less than 10kPa ×: The average value of 25% compressive stress is less than 7.5 kPa

[0054] (Pyrophoresis test: cone calorimeter test) The resin foams of Examples 1 to 15 and Comparative Examples 1 to 5 were prepared into 10 cm squares (thickness: 7 mm, width: 10 cm, length: 10 cm). Each resin foam was heated for 20 minutes in accordance with ISO 5660-1:2002, and the total calorific value was measured and evaluated based on the following evaluation criteria. A rating of ◯ indicates that the foam is non-flammable. -Evaluation criteria- ○: Total calorific value is 8MJ / m 2 below ×: Total calorific value is 8MJ / m 2 Overcoming

[0055] The results of each test are shown in Table 1. The amounts listed in the table below are in parts by mass.

[0056] [Table 1]

[0057] As is clear from Table 1, the resin foam of Comparative Example 1, which did not contain the processing aid component (D), had an average compressive stress value of less than 10 kPa and was poor in elasticity. The resin foam of Comparative Example 4, in which the content of component (D) exceeded the specified range, was poor in foamability and was not non-flammable. The resin foam of Comparative Example 2, in which the content of component (C) was lower than the specified range, was not non-flammable, and the resin foam of Comparative Example 5, in which the content of component (C) was higher than the specified range, was poor in foamability. Furthermore, the resin foam of Comparative Example 3, in which the content of component (B) was lower than the specified range, was poor in foamability and was not non-flammable. In contrast, all of the resin foams (Examples 1 to 15) that satisfied all of the requirements of the present invention were excellent in foaming properties, non-flammability, and elasticity.

Claims

1. It contains the following components (A) to (E): (A) ethylene-vinyl acetate copolymer, (B) metal hydrate, (C) red phosphorus, (D) acrylic processing aids, (E) a blowing agent, A nonflammable resin composition, wherein the content of the component (B) is 100 to 300 parts by mass, the content of the component (C) is 5 to 25 parts by mass, and the content of the component (D) is 1 to 50 parts by mass, relative to 100 parts by mass of the component (A).

2. The non-flammable resin composition according to claim 1, further comprising the following component (F): (F) Flame retardant synergist

3. A non-flammable crosslinked resin foam obtained by forming a crosslinked structure in the non-flammable resin composition according to claim 1 or 2, and then subjecting the crosslinked product to a foaming treatment simultaneously with or after the formation of the crosslinked structure.

4. It contains the following components (a) to (d): (a) ethylene-vinyl acetate copolymer; (b) metal hydrate, (c) red phosphorus, (d) acrylic processing aids; A non-flammable crosslinked resin foam, wherein the content of the component (b) is 100 to 300 parts by mass, the content of the component (c) is 5 to 25 parts by mass, and the content of the component (d) is 1 to 50 parts by mass, relative to 100 parts by mass of the component (a).

5. The nonflammable crosslinked resin foam according to claim 4, which has a compressive stress of 10 kPa or more at 25% strain in the compressive stress-strain test of JIS K 6767 (1999).

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