JP2001164055A - Polyolefin-based resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyolefin-based resin composition having excellent flexibility at a normal temperature, exhibiting sufficient mechanical characteristics at a high temperature, having excellent heat resistance. SOLUTION: A polyolefin polymer such as an ethylene vinyl acetate copolymer, etc., in an amount of 100 pts.wt. is compounded with 0.3-20 pts.wt. of a crosslinking auxiliary such as zinc methacrylate, triallyl isocyanurate, etc. Pseudo crosslinking is formed by addition of the crosslinking auxiliary and improvement in heat resistance is estimated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin composition, in which a polyolefin polymer is improved in heat resistance without crosslinking.

[0002]

2. Description of the Related Art Many insulators and sheaths of electric wires and cables are made of polyolefin polymers such as polyethylene from the viewpoint of electrical insulation. However, the heat resistance of the polyolefin polymer is not sufficient, and a cross-linked polyolefin polymer obtained by cross-linking the polyolefin polymer is used at a high temperature.

As a cross-linked polyolefin polymer such as cross-linked polyethylene, a cross-linking agent composed of an organic peroxide such as dicumyl peroxide (DCP) is added to a polyolefin polymer, and this is heated to a high temperature and chemically cross-linked. Known are those crosslinked by irradiation with an electron beam or those crosslinked with silane using a silane coupling agent. However, these cross-linked polyolefin polymers have high heat resistance due to cross-linking and can be used at a high temperature above the melting point or softening point, but have the disadvantage that the flexibility at room temperature is reduced and the flexibility is poor. There is also. In addition, in consideration of recycling, if it is cross-linked, it is difficult to perform molding again with the current technology, and there is no choice but to discard or incinerate.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyolefin-based material having good flexibility at normal temperature, sufficient mechanical properties even at high temperature, good heat resistance and recyclable. It is to obtain a resin composition.

[0005]

This problem is solved by a resin composition in which 0.3 to 20 parts of a crosslinking aid is blended with 100 parts (parts by weight, hereinafter the same) of a polyolefin polymer. Among them, a metal-containing monomer is preferable as the crosslinking aid, and an excellent effect can be obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
As the polyolefin polymer used in the present invention,
Ethylene ethyl acrylate copolymer (EEA), ethylene vinyl acetate copolymer (EVA), ethylene propylene rubber (EPR), polypropylene (PP), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE), Low density polyethylene (LDPE),
One or more blended polymers such as polyethylene such as high density polyethylene (HDPE) are used.

The crosslinking aid used in the present invention includes, for example, polyfunctional acrylates such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate, polyhydric alcohol methacrylate, N, N
'-M-phenylenedimaleimides, ammonium benzoate-based compounds, monomers containing silica filler, triallyl isocyanurate, metal-containing monomers such as zinc methacrylate, magnesium methacrylate, zinc dimethacrylate, magnesium dimethacrylate, 2 , 4,6-trimercapto S-triazine, N, N'-bis (2-methyl-2-nitropropyl) -1,6-hexadiamine, isocyanuric acid, thiadiazole derivative, cationic activator or the like, or 2 Mixtures of more than one species are used.

Among these crosslinking aids, monomers containing a metal in the molecule, for example, metal-containing monomers represented by zinc methacrylate and zinc dimethacrylate are preferred.
This is because the molecules of the polyolefin polymer are expected to be coordinated with the metal atoms of the metal-containing monomer, thereby increasing the effect of pseudo-crosslinking described later.

The compounding amount of this crosslinking aid is 0.3 to 20 parts per 100 parts of the polyolefin polymer.
If the amount is less than 3 parts, the effect of the composition cannot be obtained, and if the amount exceeds 20 parts, the increase in the effect levels off and the cost also increases. Also,
In the polyolefin resin composition of the present invention, non-halogen flame retardants such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, silicone powder,
Silicon gum, maleimide compound, carbon black,
Flame retardant aids such as red phosphorus and molybdenum compounds such as ammonium molybdate, an antioxidant, and a coloring agent can be appropriately blended.

The mixing of the polyolefin polymer and the crosslinking aid is carried out by mixing with a usual high-speed mixer or kneading with a kneader or an extruder. In this case, there is no need to add a crosslinking agent such as an organic peroxide. is there.

In such a polyolefin resin composition, the heat resistance is improved and the melting point or softening point of the polyolefin polymer is improved even though the molecules of the polyolefin polymer as the base polymer are not crosslinked. Even if it is heated to a temperature exceeding this, it will not be softened or deformed, and can be used at this temperature. Although the reason for this effect is unclear, it is presumed that pseudo-crosslinking is formed between the polymer molecules via a compound serving as a crosslinking aid.

Further, the polyolefin resin composition is thermoplastic because it does not form an original crosslink, and can be molded and processed in the same manner as a normal thermoplastic polymer.
It can be formed into a desired shape by extrusion molding, calendar molding, injection molding or the like. Further, the flexibility at room temperature does not decrease even by the addition of the crosslinking aid, and exhibits the same flexibility as the polyolefin polymer itself. For this reason, the polyolefin-based resin composition of the present invention can be used widely, for example, for electric wires, cable insulators, sheaths, etc., and also for electric wires, cable accessories, electric conduits, wiring ducts, and the like.

Hereinafter, the working effects will be clarified by showing specific examples. (Experimental Example 1) A resin composition having the composition shown in Table 1 was prepared, kneaded and molded by an extruder to form a sheet having a thickness of 2 mm, and a test piece was prepared. The heat resistance of this test piece was evaluated according to a heat deformation test specified in JIS C3005. The measurement temperature was set to 75 ° C., and those having a heating deformation rate of 10% or less passed. The ethylene-vinyl acetate copolymer of the polyolefin polymer used here has a vinyl acetate content of 25% by weight and a melting point of 72 ° C. Table 1 shows the results.

[0014]

[Table 1]

From the results shown in Table 1, it can be seen that by adding 0.3 parts or more of zinc methacrylate as a crosslinking aid, the heat deformation rate is greatly reduced and the heat resistance is improved. Also,
It can be seen that the result reaches a plateau when the content is 20 parts or more.

(Experimental Example 2) A resin composition having the composition shown in Table 2 was prepared, and the heating deformation ratio was measured in the same manner as in Experimental Example 1. The ethylene acetic acid copolymer used was the same as that in Experimental Example 1. Table 2 shows the results.

[0017]

[Table 2]

From the results shown in Table 2, it can be seen that the effect of improving the heat resistance can be similarly obtained with the crosslinking aid other than zinc methacrylate.

[0019]

As described above, in the polyolefin-based resin composition of the present invention, the heat resistance is improved and the melting point of the polyolefin polymer as the base polymer is obtained even though the original cross-link is not formed. Alternatively, use above the softening point is possible. In addition, despite its high heat resistance, the flexibility at room temperature is equivalent to that of the polyolefin polymer as the base polymer, and also has good flexibility.

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Claims (3)

[Claims] 1. A polyolefin resin composition comprising 0.3 to 20 parts by weight of a crosslinking aid per 100 parts by weight of a polyolefin polymer. 2. The polyolefin resin composition according to claim 1, wherein the crosslinking aid is a metal-containing monomer. 3. An electric wire using the polyolefin resin composition according to claim 1 or 2 as a coating material.