JP2013216912A - Resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin foam which has excellent flowability of a resin upon foaming, is safe, and has little adverse impact on environment, high foaming, and excellent flexibility.SOLUTION: A resin foam is produced by dissolving gas in a polymer under high pressure, then releasing the pressure, and forming gas bubbles, wherein the gas is carbon dioxide in a supercritical state or nitrogen in a supercritical state. The resin foam contains the following components (a) and (b'): (a) a thermoplastic polymer and (b') surface-treated aluminum hydroxide or magnesium hydroxide.

Description

  The present invention relates to a resin foam excellent in flexibility and flame retardancy. This resin foam is suitably used for applications requiring softness and cushioning properties such as internal insulators for electronic devices, cushioning materials, sound insulation materials, heat insulating materials, food packaging materials, clothing materials, and building materials. .

  In the case of foams used as internal insulators for electronic devices, cushioning materials, sound insulation materials, heat insulating materials, clothing materials, building materials, etc., softness and cushioning from the viewpoint of their sealing properties when incorporated as parts Characteristics such as excellent heat resistance and heat insulation are required. Various resin foams having such characteristics have been proposed so far.

  However, since the resin foam is composed of a thermoplastic polymer, it has a drawback that it easily burns. For this reason, the above-mentioned problems have been addressed by blending various flame retardants, particularly in applications where imparting flame retardancy is essential, such as electronic equipment. Conventionally, for example, brominated resins, chlorinated resins, phosphorus-based and antimony-based flame retardants are used as the flame retardant.

  However, there are the following problems with respect to the flame retardancy imparting technology. That is, flame retardants such as chlorine and bromine generate gases that are harmful to the human body and corrosive to equipment during combustion. In addition, phosphorous and antimony flame retardants have problems such as toxicity and explosiveness.

  In order to solve the above problems, a method has been proposed in which a metal hydroxide that is non-halogen-nonantimony is added as an inorganic flame retardant. However, this method requires the use of a large amount of metal hydroxide, resulting in new problems. That is, in such a system, since the fluidity of the resin (thermoplastic polymer) is lowered at the time of foaming, the growth of bubbles is hindered and a sufficient foaming ratio cannot be obtained.

Accordingly, an object of the present invention is to provide a resin foam excellent in flexibility and flame retardancy.
Another object of the present invention is to exhibit excellent flame retardancy, excellent fluidity of the resin during foaming, high foaming and excellent flexibility, and safety and environmental impact. The object is to provide a resin foam having a small amount.

  As a result of intensive studies to achieve the above object, the present inventors have not only been able to exhibit excellent flame retardancy when using a specific metal compound as a flame retardant, but also the fluidity of the resin during foaming. As a result, it was found that a resin foam having high foaming and excellent flexibility was obtained, and the present invention was completed.

That is, this invention provides the resin foam characterized by containing the following (a) and (b) component.
(B) Thermoplastic polymer (b) Surface-treated metal hydroxide

  In the present invention, the metal element in the metal hydroxide of the component (b) is at least one selected from the group consisting of aluminum, magnesium, calcium, nickel, cobalt, tin, zinc, copper, iron, titanium, and boron. A metal element is preferred. The metal hydroxide as the component (b) may be a composite metal hydroxide.

  In the resin foam of the present invention, the surface treatment of the component (b) is performed using an aluminum compound, a silane compound, a titanate compound, an epoxy compound, an isocyanate compound, a higher fatty acid or a salt thereof, and a phosphate ester. It is preferable that the surface treatment with at least one surface treatment agent selected from the group consisting of the above.

  In the present specification, the term “thermoplastic polymer” is used in a broad sense including not only ordinary thermoplastic resins but also rubber elastomers and thermoplastic elastomers. Boron (B) is also included in the metal element.

  Since the resin foam of the present invention uses a surface-treated metal hydroxide as a flame retardant, the resin foam has excellent flame retardancy, and is highly foamed and excellent in flexibility. In addition, it is safe and has a low environmental impact.

[(A) Thermoplastic polymer]
The thermoplastic polymer constituting the resin foam of the present invention is not particularly limited as long as it is a polymer capable of forming a foam. Examples of such a thermoplastic polymer include polyolefin polymers such as low density polyethylene, medium density polyethylene, linear polyethylene, high density polyethylene, polypropylene, a copolymer of ethylene or propylene and other α-olefins; Polystyrene polymers such as polystyrene and ABS resin; polymethyl methacrylate; polyvinyl chloride; polyvinyl fluoride; alkenyl aromatic resin; polyamide such as 6-nylon, 66-nylon, 12-nylon; polyethylene terephthalate, polybutylene terephthalate, etc. Polyester; Polycarbonate such as bisphenol A-based polycarbonate; Polyacetal; Polyphenylene sulfide; Ethylene and vinyl acetate, acrylic acid, acrylic ester, methacrylic acid, Copolymers with acrylate, vinyl alcohol, etc. (ethylene copolymers); ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, polyisobutylene, chlorine Olefin-based elastomers such as fluorinated polyethylene; styrene-based thermoplastic elastomers such as styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-isoprene-butadiene-styrene copolymers, and hydrogenated polymers thereof And various thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, acrylic-based thermoplastic elastomers, and polyolefin-based thermoplastic elastomers. These thermoplastic polymers can be used alone or in admixture of two or more.

  Among these, (i) a thermoplastic elastomer, (ii) a polyolefin-based polymer (for example, polypropylene), (iii) a rubber (elastomer) or a thermoplastic polymer containing a thermoplastic elastomer (for example, an ethylene-propylene copolymer) A mixture of an olefin elastomer and a polyolefin polymer such as polypropylene is preferred.

[(B) Surface-treated metal hydroxide]
(Metal hydroxide)
(B) As metal elements in the surface-treated metal hydroxide, aluminum (Al), magnesium (Mg), calcium (Ca), nickel (Ni), cobalt (Co), tin (Sn), zinc (Zn ), Copper (Cu), iron (Fe), titanium (Ti), boron (B) and the like. Of these, aluminum, magnesium and the like are preferable.

  The metal hydroxide may be composed of one kind of metal element or may be composed of two or more kinds of metal elements. In the present invention, as the metal hydroxide composed of one kind of metal element, for example, aluminum hydroxide, magnesium hydroxide or the like is preferably used.

In this invention, the composite metal hydroxide which is a metal hydroxide comprised by 2 or more types of metal elements can also be used suitably. Specific examples of such composite metal hydroxides include sMgO. (1-s) NiO.cH ₂ O [0 <s <1, 0 <c ≦ 1], sMgO. (1-s ) ZnO.cH ₂ O [0 <s <1, 0 <c ≦ 1], sA1 ₂ O _3. (1-s) Fe ₂ O ₃ .cH ₂ O [0 <s <1, 0 <c ≦ 3 ] Etc. are mentioned.

Among these, a composite metal hydroxide composed of magnesium, nickel, and zinc is optimal. Specifically, a composite represented by sMgO. (1-s) Q ¹ O.cH ₂ O [Q ¹ represents Ni or Zn, and 0 <s <1, 0 <c ≦ 1]. Metal hydroxides, for example, magnesium oxide / nickel oxide hydrate and magnesium oxide / zinc oxide hydrate are particularly preferably used.

  The composite metal hydroxide may have a polyhedral shape or a thin flat plate shape. When a polyhedral composite metal hydroxide is used, a highly foamed resin foam can be obtained.

  The average particle diameter (average particle diameter) of the metal hydroxide is, for example, about 0.5 to 10 μm, preferably about 0.6 to 6 μm. The average particle size can be measured by, for example, a laser particle size measuring device. When the average particle size exceeds 10 μm, it becomes difficult to obtain a highly foamed resin foam.

(surface treatment)
In the present invention, the metal hydroxide is surface-treated. As the surface treatment method, a surface treatment method using a surface treatment agent conventionally used for metal hydroxides can be employed. As such a surface treating agent, for example, aluminum compounds, silane compounds, titanate compounds, epoxy compounds, isocyanate compounds, higher fatty acids or salts thereof, and phosphate esters are preferably used. A surface treating agent can be used individually or in mixture of 2 or more types.

  As the aluminum compound, an aluminum coupling agent can be used. Examples of the aluminum coupling agent include acetoalkoxyaluminum diisopropylate, aluminum ethylate, aluminum isopropylate, mono sec-butoxyaluminum diisopropylate, aluminum sec-butyrate, ethyl acetoacetate aluminum diisopropylate, aluminum tris ( Ethyl acetoacetate), aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum tris (acetylacetonate), cyclic aluminum oxide isopropylate, cyclic aluminum oxide isostearate and the like.

  A silane coupling agent can be used as the silane compound. As silane coupling agents, vinyl group-containing silane coupling agents, (meth) acryloyl group-containing silane coupling agents, amino group-containing silane coupling agents, epoxy group-containing silane coupling agents, mercapto group-containing Examples include silane coupling agents, carboxyl group-containing silane coupling agents, and halogen atom-containing silane coupling agents. Specifically, examples of the silane coupling agent include vinyltrimethoxysilane, vinylethoxysilane, dimethylvinylmethoxysilane, dimethylvinylethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, vinyl-tris (2 -Methoxy) silane, vinyltriacetoxysilane, 2-methacryloxyethyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxy-propylmethyldimethoxysilane, 3-aminopropyl Trimethoxylane, 3-aminopropyltriethoxysilane, 2-aminoethyltrimethoxysilane, 3- [N- (2-aminoethyl) amino] propyltrimethoxysilane, 3- (2-amino Til) amino] propyltriethoxysilane, 2- [N- (2-aminoethyl) amino] ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxy (Cyclohexyl) ethyltriethoxysilane, 3-glycidoxy-propyltrimethoxysilane, 3-glycidoxy-propylmethyldiethoxysilane, 2-glycidoxy-ethyltrimethoxysilane, 2-glycidoxy-ethyltriethoxysilane, 3-mercaptopropyltrimethoxy Examples include silane, carboxymethyltriethoxysilane, 3-carboxypropyltrimethoxysilane, and 3-carboxypropyltriethoxysilane.

  The titanate compound includes a titanate coupling agent. Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, isopropyl tridecylbenzenesulfonyl titanate, tetraisopropyl bis ( Dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate Titanate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylate Isostearoyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri (dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, dicumyl phenyloxy acetate titanate, etc. diisostearoyl ethylene titanate.

  An epoxy resin can be used as the epoxy compound. Examples of the epoxy resins include glycidyl ether type epoxy resins such as bisphenol A type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, and alicyclic epoxy resins. In addition, as the epoxy compound, for example, monoepoxy compounds such as styrene oxide, glycidyl phenyl ether, allyl glycidyl ether, glycidyl (meth) acrylate, 1,2-epoxycyclohexane, epichlorohydrin, and glycidol are used. Also good.

  A polyisocyanate compound can be used as the isocyanate compound. Polyisocyanate compounds include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate; cycloaliphatic diisocyanates such as isophorone diisocyanate and 4,4'-dicyclohexylmethane diisocyanate; diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2 Aromatic diisocyanates such as 1,6-tolylene diisocyanate, phenylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, toluylene diisocyanate; polymers having free isocyanate groups by reaction of these diisocyanate compounds with polyol compounds, etc. Is included. Moreover, as an isocyanate type compound, monoisocyanate type compounds, such as phenyl isocyanate and a stearyl isocyanate, may be sufficient, for example.

  Examples of the higher fatty acids or salts thereof include higher fatty acids such as oleic acid, stearic acid, palmitic acid, and lauric acid, and salts of the higher fatty acids (for example, metal salts). Examples of the metal atom in the higher fatty acid metal salt include alkali metal atoms such as sodium atom and potassium atom, alkaline earth metal atoms such as magnesium atom and calcium atom.

  As the phosphoric acid esters, phosphoric acid partial esters are preferably used. Examples of the phosphoric acid partial esters include phosphoric acid partial esters in which phosphoric acid (such as orthophosphoric acid) is partially esterified (mono or diesterified) with an alcohol component (such as stearyl alcohol), or the phosphoric acid partial esters. (For example, metal salts with alkali metals).

  As the surface treatment agent, aluminum compounds (such as aluminum coupling agents) and titanate compounds (such as titanate coupling agents) are suitable.

  The usage-amount of a surface treating agent can be selected from the range of about 0.1-10 weight part (preferably 0.3-8 weight part) with respect to 100 weight part of metal hydroxides, for example.

  As a surface treatment method for the metal hydroxide, a conventional surface treatment method (for example, a dry method, a wet method, an integral blend method, etc.) can be appropriately selected and applied.

  The surface-treated metal hydroxide can be used alone or in combination of two or more.

  In such a surface-treated metal hydroxide, since the surface of the metal hydroxide is covered with an organic group or the like, flame retardancy due to the metal hydroxide is suppressed or prevented while preventing a decrease in the fluidity of the resin. It is thought that the effect of crystallization can be demonstrated.

  The content of the surface-treated metal hydroxide is, for example, about 10 to 90% by weight, preferably about 20 to 70% by weight of the entire resin foam. If the content is too small, the flame retarding effect is reduced, while if the content is too large, it is difficult to obtain a highly foamed resin foam.

  The resin foam of the present invention includes, in addition to the components (A) and (B), as necessary, a vulcanizing agent, a pigment, a dye, a surface treatment agent, an anti-aging agent, an ultraviolet absorber, an antistatic agent, An appropriate amount of a lubricant, a nucleating agent, a surfactant, a plasticizer, and the like may be included.

[Production of resin foam]
As a method for producing the resin foam of the present invention, a method usually used for foam molding such as a physical method and a chemical method can be employed. A common physical method is to form bubbles by dispersing a low boiling point liquid (foaming agent) such as chlorofluorocarbons or hydrocarbons in a polymer and then heating to volatilize the foaming agent. The chemical method is a method of obtaining a foam by forming cells with a gas generated by thermal decomposition of a compound (foaming agent) added to the polymer base. In view of recent environmental problems, a physical method is preferable. In particular, since a foam with a small cell diameter and high cell density can be obtained, a gas such as nitrogen or carbon dioxide is dissolved in the polymer at high pressure, and then the pressure is released, for example, the glass transition temperature or softening of the polymer. A method of forming bubbles by heating to the vicinity of the point is preferable. In this case, it is preferable to use a gas such as carbon dioxide in a supercritical state.

The resin foam obtained in this way has a sufficient foaming ratio because the fluidity of the resin is ensured at the time of foaming and the growth of bubbles is not inhibited compared to the case of using a metal hydroxide that has not been surface-treated. Obtained, and high flexibility is imparted. For example, a resin foam having a relative density of about 0.01 to 0.20, preferably about 0.01 to 0.10 is obtained. The relative density is a value calculated by the following formula.
Relative density (-) = (density of foam) ÷ [density of sheet (resin molded body) before foaming]

  In addition, the resin foam of the present invention has higher safety and less burden on the environment than conventional foams containing flame retardants such as chlorinated resins and antimony.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Preparation Example Surface treatment was performed by a wet treatment method using aluminum hydroxide (average particle size: 1.0 μm) as an aluminum-based coupling agent (acetoalkoxyaluminum diisopropylate) as a surface treatment agent. Specifically, with respect to 100 parts by weight of aluminum hydroxide, 2 parts by weight of an aluminum coupling agent and 200 parts by weight of isopropyl alcohol (IPA) are added and stirred and mixed for another 10 minutes. After ultrasonic stirring, the mixture was allowed to stand for 1 hour. Thereafter, centrifugation and washing with IPA were each carried out twice, followed by drying at 80 ° C. for 4 hours to obtain a surface-treated metal hydroxide.

Example Surface-treated metal hydroxide (aluminum hydroxide) obtained by the above preparation example: Polypropylene having a density of 0.9 g / cm ³ and a melt flow rate of 4 at 230 ° C. with respect to 100 parts by weight. 50 parts by weight and ethylene propylene-based elastomer having a JIS-A hardness of 69: 50 parts by weight were kneaded at a temperature of 170 ° C. by a lab plast mill (manufactured by Toyo Seiki Seisakusho) equipped with roller-type blades. Using a hot plate press heated to 180 ° C., it was molded into a sheet having a thickness of 0.5 mm and φ80 mm. This sheet was placed in a pressure vessel and impregnated with carbon dioxide by holding it in an atmosphere of 150 ° C. under a pressure of 15 MPa for 10 minutes. Subsequently, the foam was obtained by reducing pressure rapidly. The relative density of the foam was 0.091. The oxygen index of the sheet was 22.8.

Comparative Example Aluminum hydroxide without surface treatment (average particle size: 1.0 μm): 100 parts by weight, polypropylene having a density of 0.9 g / cm ³ and a melt flow rate of 4 at 230 ° C .: 50 parts by weight And 50 parts by weight of an ethylene propylene elastomer having a JIS-A hardness of 69: kneaded at a temperature of 170 ° C. by a Laboplast mill (manufactured by Toyo Seiki Seisakusho) equipped with roller-type blades, and then heated to 180 ° C. Using a hot plate press, the sheet was molded into a sheet having a thickness of 0.5 mm and φ80 mm. This sheet was placed in a pressure vessel and impregnated with carbon dioxide by holding it in an atmosphere of 150 ° C. under a pressure of 15 MPa for 10 minutes. Subsequently, the foam was obtained by reducing pressure rapidly. The relative density of the foam was 0.423. The oxygen index of the sheet was 22.4.

  As is clear from the above results, the resin foams of the examples corresponding to the present invention ensure fluidity at the time of foaming, the relative density is extremely small, and the high foaming compared to the resin foams of the comparative examples. It is understood that it exhibits excellent flexibility and excellent flame retardancy. It is also safe and has little environmental impact.

Claims (6)

A resin foam produced by forming gas bubbles by dissolving a gas in a polymer at high pressure and then releasing the pressure, wherein the gas is carbon dioxide in a supercritical state or nitrogen in a supercritical state A resin foam comprising the following components (A) and (B '):
(B) Thermoplastic polymer (b) Surface-treated aluminum hydroxide or magnesium hydroxide The (b ′) component surface treatment is at least selected from the group consisting of aluminum compounds, silane compounds, titanate compounds, epoxy compounds, isocyanate compounds, higher fatty acids or salts thereof, and phosphate esters The resin foam according to claim 1, which is a surface treatment with one surface treatment agent. The resin foam according to claim 1 or 2, wherein an average particle diameter of aluminum hydroxide or magnesium hydroxide as the component (b ') is 0.5 to 10 µm. The resin foam according to any one of claims 1 to 3, wherein a proportion of the (b ') component of aluminum hydroxide or magnesium hydroxide in the entire resin foam is in the range of 10 to 90% by weight. . (A) The component thermoplastic polymer is at least one polymer selected from (i) a thermoplastic elastomer, (ii) a polyolefin-based polymer, and (iii) a thermoplastic polymer containing rubber or a thermoplastic elastomer. Item 5. The resin foam according to any one of Items 1 to 4. The resin foam according to any one of claims 1 to 5, having a relative density of 0.01 to 0.20.