JPH08208870A - Flame-retardant foam - Google Patents

Abstract

PURPOSE: To obtain a highly blowing type flame-retardant foam useful as a heat insulating member, a sound insulating member and a cushioning member, generating no halogenated gas during combustion, having high safety, comprising a polyolefin resin containing a vinyl acetate residue, a metal hydroxide and carbon black. CONSTITUTION: This high blowing type polyolefinic foam is obtained by blending 100 pts.wt. polyolefin resin having 10-90wt.% vinyl acetate residue content (e.g. ethylene/vinyl acetate copolymer) with 50-300 pts.wt. metal hydroxide (e.g. magnesium hydroxide), 0.3-30 pts.wt. carbon black (e.g. oil furnace black), a cross- linking agent (e.g. dicumyl peroxide) and a blowing agent (e.g. azocarbonamide), melting, kneading to give a melted compound, extruding the melted compound into a sheetlike state and generates no hydrogen halide in combustion, has high safety and is useful as a heat insulating member, a sound insulating member and a cushioning member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly flame-retardant polyolefin flame-retardant foam which does not generate hydrogen halide during combustion and is highly safe.

[0002]

2. Description of the Related Art Polyolefin foams, especially high-foam polyethylene foams, have excellent properties such as heat insulation and cushioning. Therefore, they have been conventionally used in the form of sheets or pipes for electric appliances, automobiles, civil engineering. It is widely used as heat insulation, sound insulation, and cushioning material for construction and air conditioning equipment. However, this polyolefin foam is inherently flammable, which limits its field of application. Therefore, various flame retardant treatments are performed. Currently, the mainstream treatment method for making polyolefin foams flame-retardant is, for example, ethylene / vinyl acetate copolymer used as a base resin and a large amount of metal hydroxide added thereto, or a polyolefin resin. And a metal hydroxide, a halogen-based flame retardant, and antimony trioxide are used in combination.

[0003]

However, in the method of blending the metal hydroxide with the ethylene / vinyl acetate copolymer,
Sufficient flame retardant effect cannot be obtained unless an extremely large amount of metal hydroxide is added, and if a large amount of metal hydroxide is added to the extent that a sufficient flame retardant effect is obtained, outgassing occurs at the time of foaming. There is a problem that a high foam is not obtained. In addition, since metal hydroxides generally have relatively high thermal conductivity, adding a large amount of them will reduce the heat insulating properties of the foam, increase the specific gravity of the foam, and reduce the flexibility. There are also problems such as inconvenience. When a halogen-based flame retardant and antimony trioxide are used in combination, the above problem is solved because the amount of metal hydroxide compounded is relatively small, but the halogen-based flame retardant causes hydrogen halide during combustion. There is a problem of gas generation, and the use of antimony trioxide is also being considered from a toxicological point of view. The present invention has been made to solve the above problems, and therefore an object thereof is not to generate hydrogen halide during combustion, high safety, high foaming type, and sufficient flame retardancy. Another object of the present invention is to provide a polyolefin foam having the same.

[0004]

The above problems can be solved by providing a flame-retardant foam containing a polyolefin resin having a vinyl acetate residue, a metal hydroxide and carbon black. In this flame-retardant foam, the content of vinyl acetate residue in the polyolefin resin is in the range of 10% by weight to 90% by weight, and the content of metal hydroxide is 100 parts by weight of the polyolefin resin. On the other hand, it is in the range of 50 to 300 parts by weight, and the content ratio of carbon black is the above-mentioned polyolefin resin 1.
It is preferably in the range of 0.3 to 30 parts by weight with respect to 00 parts by weight.

[0005]

By adding carbon black to a mixture of a polyolefin resin having a vinyl acetate residue and a metal hydroxide, the amount of the metal hydroxide can be reduced while maintaining a sufficient flame retardant effect. .

Hereinafter, the polyolefin resin having a vinyl acetate residue used in the flame-retardant foam of the present invention is referred to as "base resin". This base resin may be a polymer having both an olefin residue and a vinyl acetate residue in the molecular chain, for example, an ethylene / vinyl acetate copolymer (EVA) simple substance. Further, a polymer having both an olefin residue and a vinyl acetate residue in its molecular chain, for example, EVA, or polyvinyl acetate which is a polymer mainly containing a vinyl acetate residue, and a polyolefin resin, for example, high-density polyethylene. (HDPE), low density polyethylene (LDPE) or linear low density polyethylene (L-LDPE), or a copolymer of an olefin and another monomer, for example, ethylene / ethyl acrylate copolymer (EEA), ethylene / It may be a mixture with a methyl acrylate copolymer (EMA), an ethylene / methyl methacrylate copolymer (EMMA), an ethylene / ethyl methacrylate copolymer (EEMA), or the like.

In any of the above base resins, the content of vinyl acetate residues contained in them is preferably within the range of 10% by weight to 90% by weight of the total amount of the base resin. When the content of vinyl acetate residue is less than 10% by weight, the flame retardant effect due to the synergistic effect with the metal oxide and carbon black becomes insufficient, and when it exceeds 90% by weight, the tackiness of the base resin during melting is insufficient. Becomes large, it tends to adhere to the support at the time of producing the foam, and it becomes difficult to obtain a high foam. From this viewpoint, the content of vinyl acetate residue in the base resin is more preferably within the range of 15% by weight to 50% by weight.

Examples of preferable metal oxides to be added to the above base resin include aluminum hydroxide and magnesium hydroxide. In particular, when manufacturing a foam, there is a step of heating to a high temperature of 200 ° C. or higher, and from this viewpoint, it is more preferable to use magnesium hydroxide that is stable at a high temperature.

The metal oxide content is preferably in the range of 50 to 300 parts by weight with respect to 100 parts by weight of the base resin. If it is less than 50 parts by weight, it is difficult to obtain a sufficient flame retardant effect, and if it exceeds 300 parts by weight, outgassing easily occurs in the foaming process, and it becomes difficult to obtain a high foam.

As the carbon black to be added to the flame-retardant foam of the present invention, oil furnace black, thermal black, lamp black, channel black, acetylene black and the like can all be used. Carbon black is 0.
It is preferable to mix within the range of 3 to 30 parts by weight. If it is less than 0.3 parts by weight, it becomes difficult to obtain a sufficient flame retardant effect, and if it exceeds 30 parts by weight, carbon black affects the crosslinking of the base resin in the foaming process, and it becomes difficult to obtain a sufficiently high foam.

In the flame-retardant foam of the present invention, the above-mentioned base resin, metal oxide and carbon black are preferably mixed in the above-mentioned proportions, and if necessary, an organic peroxide such as dicumylper. It is manufactured by adding a resin cross-linking agent such as oxide, a cross-linking aid such as a multi-sensitive monomer, a foaming agent such as azodicarbonamide, and melt-kneading to obtain a melt compound, which is then foam-molded by extrusion or casting. be able to. A long sheet-shaped foam or a long pipe-shaped foam can be easily obtained by using the extrusion molding method, and a foam having a complicated shape can be obtained by using the casting method. As another manufacturing method, the foam of the present invention can be obtained by, for example, crosslinking the above compound to which a foaming agent has been added by electron beam irradiation and the like, followed by heat foaming. Methods and apparatus for making these foams are generally known and used in the art.

The flame-retardant foam of the present invention may contain, in addition to the above components, an ultraviolet absorber, an antioxidant, a colorant, a small amount of a foam nucleating agent such as talc, and an additive such as a lubricant. .
Further, a small amount of a flame retardant such as a halogen-based flame retardant, antimony trioxide, and / or red phosphorus may be contained as long as the object of the present invention is not impaired.

[0013]

The present invention will be described in more detail with reference to the following examples. (Examples 1 and 2) An ethylene / vinyl acetate copolymer containing 20% by weight of a vinyl acetate residue was used as a base resin, magnesium hydroxide was used as a metal hydroxide, oil furnace black was used as carbon black, and diglyceride was used as a crosslinking agent. Mild peroxide (DCP) and azodicarbonamide (ADCA) as a foaming agent were added, and the melt compound obtained by melt-kneading was extruded into a sheet to produce each foam. Table 1 shows the blending ratio (weight ratio) of each component.

(Examples 3 to 4) In the same manner as in Example 1 except that a small amount of a halogen-based flame retardant (perchlorocyclopentadecane, "Dechlorane Plus" manufactured by Somar Corporation) and antimony trioxide were added in addition to the above components. To produce each foam. Table 1 shows the blending ratio (weight ratio) of each component.

Comparative Example 1 For comparison, an ethylene / vinyl acetate copolymer containing 20% by weight of vinyl acetate residue was used as a base resin, carbon black was not contained, magnesium hydroxide and a large amount of halogen-based flame retardant were used. A flame-retardant foamed product was prepared in the same manner as in Example 1 to obtain Comparative Example 1. Mixing ratio of each component (weight ratio)
Is shown in Table 1.

The foams of Examples 1 to 4 and Comparative Example 1 were tested for foaming ratio, flame retardancy (OI), and whether or not hydrogen halide gas was generated during combustion. The flame retardancy test was performed according to JIS K7201, and the hydrogen halide gas generation test during combustion was performed according to IEC754. The results are shown in Table 1. In the table, the presence or absence of generation of hydrogen halide gas is indicated by “No occurrence” = “Occurrence” = “X”.

[0017]

[Table 1]

From the results shown in Table 1, the foams of Examples 1 and 2 contained no halogen-based flame retardant and antimony trioxide,
It can be seen that good flame retardancy was exhibited, and a high expansion ratio was obtained, even though the compounding ratio of the metal hydroxide was relatively small (particularly in Example 1). It goes without saying that hydrogen halide gas is not generated. The foams of Examples 3 to 4 are examples containing an extremely small amount of a halogen-based flame retardant and antimony trioxide, but are good because they contain the base resin according to the constitution of the present invention, a metal hydroxide and carbon black. It can be seen that it exhibits excellent flame retardancy, a high expansion ratio, and virtually no generation of hydrogen halide gas. On the other hand, in the foam of Comparative Example 1 containing no carbon black, the flame retardancy equivalent to that of Examples 1 to 4 was obtained by adding an extremely large amount of the halogen-based flame retardant and antimony trioxide. However, as a matter of course, hydrogen halide gas was generated. The expansion ratio is also slightly lower.

[0019]

EFFECTS OF THE INVENTION Since the flame-retardant foam of the present invention contains a polyolefin resin having a vinyl acetate residue, a metal hydroxide and carbon black, it does not generate hydrogen halide during combustion and is safe. A highly flame-retardant, highly flame-retardant polyolefin-based flame-retardant foam is obtained.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tomohisa Watanabe 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Ltd.

Claims (2)

[Claims] 1. A flame-retardant foam containing a polyolefin resin having a vinyl acetate residue, a metal hydroxide, and carbon black. 2. The content of vinyl acetate residue in the polyolefin resin is in the range of 10% by weight to 90% by weight, and the content of metal hydroxide is 50 parts by weight based on 100 parts by weight of the polyolefin resin. 2. The flame-retardant foam according to claim 1, wherein the content of carbon black is in the range of 0.3 to 30 parts by weight with respect to 100 parts by weight of the polyolefin resin. body.