JP2005264005A - Method for producing flame-retardant conductive crosslinked polyolefin foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a highly flame-retardant nonhalogen/nonphosphorus conductive crosslinked polyolefin foam. <P>SOLUTION: The method for producing the nonhalogen/nonphosphorus flame-retardant conductive crosslinked polyolefin foam comprises putting a foamable crosslinkable composition prepared by mixing and kneading a polyolefin resin with conductive carbon, a blowing agent, and a crosslinking agent into a press mold, heating the composition in the mold under pressure to yield an intermediate foam, and heating and foaming the intermediate foam in a non-airtight mold to form a crosslinked polyolefin foam, wherein 2 to 30 pts. wt. melamine cyanurate is added to 100 pts. wt. polyolefin resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a method for producing a non-halogen / non-phosphorus flame retardant conductive crosslinked polyolefin foam based on a polyolefin resin.

    The present applicant has added and kneaded carbon, a foaming agent and a crosslinking agent to polyolefin, crosslinked in a mold under pressure, and then heated and foamed under normal pressure (Japanese Patent Publication No. 2). -29095). However, the above production method did not suggest imparting flame retardancy.

    Further, as a conventional method for producing a flame-retardant foam, a method of heating and foaming a polyolefin to which an inorganic filler is added (Japanese Patent Publication No. 60-26500), or a halogen-based or phosphorus-based foam is used. There is a method in which a flame retardant added is heated and foamed (Japanese Examined Patent Publication Nos. 48-9857, 48-29857 and 58-5930). However, since the flame retardant foam of the above prior art uses a halogen-based flame retardant, harmful halogen gas is generated at the time of combustion, which adversely affects the human body and the environment.

Non-halogen technology includes ethylene-vinyl acetate copolymer alone or a mixture of 50% by weight or more of ethylene-vinyl acetate copolymer and one or more other polyolefin resins, and the content of vinyl acetate. Is 5 to 20% by weight of polyolefin resin matrix 100 parts by weight, inorganic flame retardant 50 to 200 parts by weight, red phosphorus 5 to 50 parts by weight, melamine compound 5 to 50 parts by weight, polyhydric alcohol 1 to 15 parts by weight and A foamable flame retardant resin composition comprising 15 to 30 parts by weight of a foaming agent has been proposed (Japanese Patent No. 3308633).
Japanese Patent Publication No. 2-29095 Japanese Patent Publication No. 60-26500 Japanese Patent Publication No. 48-9487 Japanese Patent Publication No. 48-29857 Japanese Patent Publication No.58-5930 Japanese Patent No. 3308633

    However, since the above non-halogen flame retardant technology adds red phosphorus, it has an adverse effect on electronic equipment, and the amount of flame retardant added is large, so a large amount of conductive carbon is added and the foaming conditions are narrow. It has been a problem that it cannot be applied to a method for producing a conductive foam. Accordingly, an object of the present invention is a non-halogen / non-phosphorus flame-retardant conductive cross-linked polyolefin foam that has sufficient flame retardancy, does not generate harmful halogen gas during combustion, and does not adversely affect electronic equipment. It is in providing the manufacturing method of.

In order to achieve the above object, the first method of the present invention is to add 2 to 30 parts by weight of melamine cyanurate, conductive carbon, a foaming agent and a cross-linking agent to 100 parts by weight of a polyolefin resin, and to obtain the cross-linkability obtained. A method for producing a flame-retardant conductive cross-linked polyolefin-based foam, wherein the foamable composition is heated under pressure and then decompressed to form a foam.

The second method of the present invention is to add and knead 2 to 30 parts by weight of melamine cyanurate, conductive carbon, a foaming agent and a crosslinking agent to 100 parts by weight of a polyolefin resin, and pressurize the resulting crosslinkable foamable composition. The composition is cross-linked by heating to a temperature at which the foaming agent does not substantially decompose, and then the resulting crosslinkable foamable composition is removed from the mold under normal pressure so as not to expand or expand rapidly. A method for producing a flame-retardant conductive cross-linked polyolefin foam characterized by heating to a foaming agent.

In the production method of the present invention, when the melamine cyanurate and aluminum hydroxide are less than the above range, sufficient flame retardancy cannot be obtained, and when added beyond the above range, foam molding is inhibited and satisfactory foaming is achieved. I can't get a body.

    According to the method of the present invention, it has sufficient conductivity and flame retardancy, and does not contain halogen that adversely affects the human body or the environment, or phosphorus that adversely affects electronic equipment. Furthermore, the flame retardant performance is high, and the foam obtained by the method of the present invention can conform to UL94HBF.

    In the present invention, polyolefin is, for example, polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polytetrafluoroethylene, ethylene-propylene copolymer, poly-4-methyl-1-pentene, polyvinyl chloride, polyvinylidene chloride, Examples thereof include polyvinylidene fluoride, tetrafluoroethylene, and an ethylene copolymer.

The conductive carbon referred to in the present invention is furnace carbon black, acetylene carbon black, channel carbon black and the like, and these may be used alone or in combination of two or more. In particular, among carbon blacks, furnace black having a surface area (nitrogen adsorption method) of 900 m ² / g or more is a preferable conductive carbon black.

    The cross-linking agent as used in the present invention has a decomposition temperature at least equal to or higher than the flow start temperature of the polyolefin resin in the polyolefin-based resin, and is decomposed by heating to generate free radicals between or within the molecules. Organic peroxides that are radical generators that cause cross-linking, such as dicumyl peroxide, 1,1-ditertiary butyl peroxide, 1,1-ditertiary butyl peroxy-3,3,5-trimethylcyclohexane 2,5-dimethyl-2,5-ditertiary butyl peroxyhexane, 2,5-dimethyl-2,5-ditertiary butyl peroxyhexyne, α, α-ditertiary butyl peroxyisopropylbenzene, tertiary butyl per Oxyketone, tertiary butyl peru Although there are xylbenzoate, etc., the optimum organic peroxide must be selected according to the resin used at that time.

The foaming agent referred to in the present invention is a chemical foaming agent having a decomposition temperature equal to or higher than the melting temperature of the polyolefin resin. For example, azo compounds such as azodicarbonamide and barium azodicarboxylate; nitroso compounds such as dinitrosopenta Methylenetetramine, trinitrotrimethyltriamine, etc .; p, p′-oxybisbenzenesulfonyl hydrazide, etc. of hydrazide compounds; p, p′-oxybisbenzenesulfonyl semicarbazide, toluenesulfonyl semicarbazide of sulfonyl semicarbazide compounds, etc. There are Jid etc.

In the present invention, a foaming aid can be added depending on the type of foaming agent. Examples of the foaming aid include compounds mainly composed of urea, metal oxides such as zinc oxide and lead oxide, compounds mainly composed of salicylic acid and stearic acid, that is, higher fatty acids or higher fatty acid metal compounds.

In the present invention, for the purpose of improving the physical properties of the composition to be used or reducing the price, a compounding agent (filler) that does not significantly adversely affect the cross-linking, such as zinc oxide, titanium oxide, calcium oxide, magnesium oxide, oxidation Metal oxides such as silicon, carbonates such as magnesium carbonate and calcium carbonate, fiber materials such as pulp, various dyes, pigments, fluorescent materials, and other conventional rubber compounding agents can be added as necessary. .

Next, a method for producing the non-halogen / non-phosphorus flame retardant conductive crosslinked polyolefin foam of the present invention will be described.

First, in the first method, conductive carbon is preferably added in an amount of 13 to 30 parts by weight, melamine cyanurate 2 to 30 parts by weight, a foaming agent and a cross-linking agent are added to and kneaded with 100 parts by weight of polyolefin, and the obtained cross-linkage is obtained. The foamable composition is heated at 140-170 ° C. for a certain period of time under pressure and then depressurized to produce a foam.

  In the second method, 5 to 25 parts by weight of conductive carbon, 2 to 30 parts by weight of melamine cyanurate, a foaming agent, a foaming aid and a crosslinking agent are added and kneaded with respect to 100 parts by weight of polyolefin, and the obtained crosslinking is performed. The foamable composition is crosslinked by heating to a temperature at which the foaming agent does not substantially decompose in a mold under pressure, and then the resulting foamable crosslinkable composition is removed from the mold. It is characterized by foaming by heating under normal pressure so as not to foam or expand rapidly.

  The heating means under normal pressure includes placing the foamable cross-linking composition in a mold of a desired shape such as a rectangular parallelepiped type that is not a closed system, a metal bath using a rose alloy, a wood alloy, an oil bath, sodium nitrate, potassium nitrate, In a salt bath using one or more molten salts of potassium nitrite or the like, in a nitrogen stream, or a rectangular parallelepiped is provided with a heating medium conduit (heating medium: steam, etc.) on its outer wall After being heated for a predetermined time in a state covered with an expandable iron plate or the like, a foam is obtained by cooling. The heating temperature is 145 to 210 ° C., preferably 160 to 190 ° C., depending on the type of polyolefin used, and the heating time is 60 to 210 minutes, preferably 90 to 180 minutes.

    The conductive foam obtained by the production method of the present invention passed the horizontal combustion test defined in the United States UL (Underwriters Laboratories) 94HBF. Therefore, the obtained non-halogen flame-retardant conductive crosslinked polyolefin-based foam can be applied to a buffer material of an electronic device, a radio wave absorber and the like

Low-density polyethylene (trade name: Novatec LC-520, density 0.9226 g / cm ³ , melt flow rate 3.8 g / 10 min, manufactured by Mitsubishi Chemical Corporation) and 100 parts by weight of furnace carbon black (trade name: Ketsu Chen Black EC, manufactured by Mitsubishi Chemical Corporation) 10 parts by weight, melamine cyanurate (trade name: MC-610, manufactured by Nissan Chemical Industries, Ltd.) 20 parts by weight, azodicarbonamide (trade name: VINYHALL AC # 3, Eiwa Kasei) Kogyo Nouri Co., Ltd.) 4 parts by weight, zinc white 2 parts by weight, α, α′-bis (t-butylperoxy) diisopropylbenzene (trade name: Perkadox-14 / P40, manufactured by Kayaku Nouri Co., Ltd.) The composition consisting of parts is kneaded with a kneader at 110 ° C., and kneaded into a mold (18 × 300 × 300) in a press heated to 160 ° C. And heated under pressure for 50 minutes to obtain a foam.

The apparent density of the obtained foam was 80 kg / m ³ , and when the surface resistance value was measured, it was 3 × 10 ³ Ω. Moreover, as a result of conducting the horizontal combustion test of said UL94HBF about the obtained foam, all the requirements were satisfied and passed.

Low-density polyethylene (trade name: Novatec LC-520, density 0.9226 g / cm ³ , melt flow rate 3.8 g / 10 min, manufactured by Mitsubishi Chemical Corporation) and 100 parts by weight of furnace carbon black (trade name: Ketsu CHENBLACK EC, manufactured by Mitsubishi Chemical Corporation) 10 parts by weight, melamine cyanurate 20 parts by weight, azodicarbonamide (trade name: VINYHALL AC # 3, manufactured by Eiwa Kasei Kogyo Co., Ltd.) 9 parts by weight, α, α′-bis A composition comprising 0.8 parts by weight of (t-butylperoxy) diisopropylbenzene (trade name: Parkadox-14 / P40, manufactured by Kayaku Nouri Co., Ltd.) is kneaded with a 110 ° C. kneader and heated to 140 ° C. The mold (33 × 500 × 1025) in the pressed press is filled with the kneaded product, heated under pressure for 50 minutes, and then the foamable crosslinked composition is taken out. did.

Next, the primary foam is placed in the approximate center of a non-airtight openable metal mold (90 × 1070 × 2130 mm) provided with a flow path of heated steam, and 7.0 kg / cm ² of heated steam is added to the primary foam. The foam was obtained after flowing through the channel and heating for 180 minutes to decompose and cool the remaining foaming agent and crosslinking agent.

The apparent density of the obtained foam was 60 kg / m ³ , and the measured surface resistance value was 8 × 10 ³ Ω. Moreover, as a result of conducting the horizontal combustion test of said UL94HBF about the obtained foam, all the requirements were satisfied and passed.

Low-density polyethylene (trade name: Novatec LC-520, density 0.9226 g / cm ³ , melt flow rate 3.8 g / 10 min, manufactured by Mitsubishi Chemical Corporation) and 100 parts by weight of furnace carbon black (trade name: Ketsu A foam was obtained under the same formulation and foaming conditions as in Example 1 except that the amount was changed to 16 parts by weight (Chen Black EC, manufactured by Mitsubishi Chemical Corporation) and 2 parts by weight of melamine cyanurate.

The apparent density of the obtained foam was 55 kg / m ³ , and the surface resistance value measured was 500Ω. Moreover, as a result of conducting the horizontal combustion test of said UL94HBF about the obtained foam, all the requirements were satisfied and passed.
Comparative Example 1

In Example 1, except that melamine cyanurate was changed to 1 part by weight, a foam was obtained under the same composition and foaming conditions as in Example 1, and the result of a horizontal combustion test of UL94HBF was rejected.
Comparative Example 2

In Example 1, except that the melamine cyanurate was changed to 40 parts by weight, an attempt was made to mold a foam with the same composition and foaming conditions as in Example 1, but there were too many flame retardants added and a satisfactory foam Could not get.
Comparative Example 3

In Example 2, except that melamine cyanurate was changed to 1 part by weight, a foam was obtained with the same formulation and foaming conditions as in Example 1, and the result of a horizontal combustion test of UL94HBF was rejected.
Comparative Example 4

In Example 2, except that melamine cyanurate was changed to 40 parts by weight, an attempt was made to mold a foam with the same composition and foaming conditions as in Example 1, but there were too many flame retardants added and a satisfactory foam Could not get.

As described above, according to the method of the present invention, a non-halogen / non-phosphorus conductive cross-linked polyolefin-based foam excellent in flame retardancy and conductivity can be produced. The non-halogen / non-phosphorus flame-retardant conductive cross-linked polyolefin foam produced by the method of the present invention can be applied to a buffer material of an electronic device, a radio wave absorber, etc.

Claims (2)

Adding and kneading 2 to 30 parts by weight of melamine cyanurate, conductive carbon, a foaming agent and a crosslinking agent to 100 parts by weight of a polyolefin-based resin, heating the resulting crosslinkable foamable composition under pressure, then depressurizing, A method for producing a flame-retardant conductive cross-linked polyolefin-based foam characterized by producing a foam. Add and knead 2 to 30 parts by weight of melamine cyanurate, conductive carbon, foaming agent and crosslinking agent to 100 parts by weight of polyolefin resin, and the foaming agent does not substantially decompose under pressure in the resulting crosslinkable foamable composition. The composition is crosslinked by heating to a temperature, and then the resulting crosslinkable foamable composition is removed from the mold and heated under normal pressure so as not to expand or expand suddenly, thereby forming a foaming agent. A method for producing a flame-retardant conductive cross-linked polyolefin foam.