JPS6076550A - Flame-retardant resin composition - Google Patents

Abstract

PURPOSE:A composition obtained by incorporating a resin component containing containing polyvinyl chloride, ethylene-vinyl acetate copolymer and chlorinated polyethylene with a zinc compound, and an acrylic or methacrylic acid compound, and capable of forming a firm expanded carbonized layer on contact with a flame. CONSTITUTION:A composition obtained by incorporating (A) a resin component polyvinyl chloride, ethylene-vinyl acetate copolymer and chlorinated polyethylene with (B) a zinc compound and (C) a compound of acrylic acid and/or methacrylic acid. A component obtained by incorporating 100pts.wt. polyvinyl chloride with >=30pts.wt. total of ethylene-vinyl acetate copolymer (with >=15wt% vinyl acetate content and <=15 melt index) and chlorinated polyethylene (with 35-45% chlorine content) is used as the component (A).

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objectives of the Invention] The present invention relates to a flame-retardant resin composition that is flame-retardant and foams and carbonizes when exposed to flame to form a heat insulating layer.

For example, in electric wires and cables, polyethylene, crosslinked polyethylene, ethylene-propylene copolymer rubber, and the like are used as insulators.

These insulators are flammable, and in order to impart flame retardancy, flame retardants such as halogen compounds have been incorporated into the insulators.

Addition of a flame retardant to a thermoplastic resin involves sacrificing the excellent electrical, mechanical, and chemical properties of the resin molded product, and is also unfavorable from the viewpoint of processability and economy.

For this reason, it is being considered to strengthen the flame retardancy of the retardant sheath by adding no or only a small amount of flame retardant to the insulator.

The properties required of such a protective sheath include not only flame retardancy, but also resistance to softening or melting due to the heat of a fire, and excellent heat insulation properties. It can be said that it is best to form a strong foamed carbonized layer by heat.

Various resin compositions have been proposed that form a foamed carbonized layer due to heat generated during a fire, but a resin composition that can form a foamed carbonized layer that can sufficiently protect the interior has not yet been obtained.

The present invention is based on the above, and aims to provide a fi-combustible resin that has flame retardancy and forms a strong foamed carbonized layer when exposed to flame.

[Summary of the Invention] The formation of foamed carbonized l- is especially important in electric wires and cables that are mainly composed of combustible materials.The formation of a foamed layer blocks heat and softens the combustible resin inside due to a rise in temperature. , prevent liquefaction, gasification, etc. This foamed carbonized layer must not develop cracks, cracks, etc. when exposed to flame.
Also, it cannot be lost due to falling. In order for the foamed carbonized layer to maintain its shape even after long-term contact with flame, it is important that it quickly turn into a carbide.

Thus, the present invention provides: (a) a resin component containing polyvinyl chloride, an ethylene-vinyl acetate copolymer, and chlorinated polyethylene, (b) a zinc compound, ~ (C) a compound of acrylic acid and/or methacrylic acid, The polyvinyl chloride used in the present invention provides a flame-retardant resin composition consisting of homopolymers as well as copolymers mainly composed of vinyl chloride, such as vinyl chloride and ethylene-vinyl acetate, ethylene - Graft copolymers with ethyl acrylate, chlorinated polyethylene, polyurethane, etc., or vinyl chloride and ethylene,
It may also be a copolymer with propylene, vinyl acetate, etc.

As the ethylene-vinyl acetate copolymer, one having a vinyl acetate content of 15% by weight or more and a melt index of 15 or less is particularly preferable. Of course, this also includes those based on ethylene-vinyl acetate, such as Levaloy, a trade name commercially available from DuPont.

As the chlorinated polyethylene, one having a chlorine content of 35 to 45% is particularly preferable.

Any combination of polyvinyl chloride, ethylene-vinyl acetate copolymer and chlorinated polyethylene may be used, but for example, the combination of ethylene-vinyl acetate copolymer and chlorinated polyethylene is 30 f for 100 parts by weight of polyvinyl chloride.
Fiffi part or more is preferable.

Moreover, it is preferable that 10 parts by weight or more of both the ethylene-vinyl acetate copolymer and the chlorinated polyethylene are contained.

The combination of these three types of polymers is achieved through a delicate balance of carbonization, melt viscosity, gasification, foamability, and retention properties of the polymers during contact with flame, and is essential for the formation of a foamed carbonized heat insulating layer. This is a different combination.

After the zinc compound has good dehydrochlorination of polyvinyl chloride,
That is, it has a carbonization catalytic effect, and the released hydrogen chloride functions effectively to impart flame retardancy and as a foaming gas, and at the same time carbonizes polyvinyl chloride and chlorinated polyethylene after dehydrochlorination.

Examples of the zinc compound include zinc carbonate, zinc borate, zinc phosphate, zinc pyromellit, etc., and the appropriate content thereof is 0.5 parts by weight or more based on 100 parts by weight of polyvinyl chloride.

The compound of acrylic acid and/or methacrylic acid is, for example, methyl methacrylate, and specifically, it is known under the trade name Metablane P1 Metablane L, which is commercially available from Mitsubishi Raylan Co., Ltd.

These metabrenes are widely recognized as processing aids and high molecular weight propellants for polyvinyl chloride, but the present inventor has discovered that these compounds exhibit extremely unique behavior in forming a foamed carbonized layer when exposed to flame. Admitted.

That is, it was found that there was a significant difference in the formation of foamed cells in the foamed carbonized layer formation stage at 200° C. or higher between when these compounds were added and when these compounds were not added.

The amount of acrylic acid and/or methacrylic acid added is not particularly limited;
．． A range of 5 to 20 parts by weight is particularly effective.

In the present invention, in addition to the various components mentioned above, plasticizers, stabilizers, lubricants, flame retardants, fillers, antioxidants, colorants, etc. may be added. Furthermore, it is also possible to add a polyfunctional monomer and crosslink three-dimensionally with a free radical generator or an energetic beam to improve heat deformation resistance and the like.

The compositions of the present invention are particularly effective as protectants for flammable insulation or sheaths of electric wires and cables, but can also be used as NO protection for other flammable products. When this composition is used as a shelf material, it may be formed directly onto the outer periphery of a combustible product by extrusion or the like, or it may be formed into a tape, tube, etc. and then applied to the combustible product.

[Examples and Comparative Examples] Compositions were prepared with the mixing ratios shown on each side of Table 1.

Next, a copper wire with a diameter of 511I11 was coated with crosslinked polyethylene as an insulator to a thickness of 1.2cm, and the above composition was extrusion coated on the outer periphery of the wire to a thickness of Jt 1111111. :, got the line.

The evaluation results for the obtained electric wires are as shown in the lower column of Table 1.

In the combustion test, the Mi wire was placed in the direct position, and the inner flame height was 50 II.
III+, 3 cycles were performed using a Bunsen burner flame with an external flame height of 100 mIm at a 45 degree angle, with 1 cycle of 30 seconds of flame application and 30 seconds of flame removal, and those that did not extinguish for 30 seconds or more in any cycle were rejected. .

Regarding the cracking of the sheath, the sheath was opened and the insulator was exposed, and there were cracks in the size (opening of 1 mm or less) and cracks (opening of 2 ml or more).

The thickness of the foamed carbonized layer was measured after 3 cycles of flame application and flame removal.

The state of the insulator was observed after three cycles of flame application and flame removal.

Table 1 (Blending amount unit: melon part) [Effects of the invention] As is clear from the above explanation, the flame-retardant resin composition of the present invention foams and carbonizes when exposed to flame, forming a strong heat insulating layer. It is now possible to form a combustible ash, and exhibits an extremely excellent protective effect against combustible ash.

Claims (1)

[Claims] (+) (a) a resin component containing polyvinyl chloride, an ethylene-vinyl acetate copolymer, and chlorinated polyethylene, (b) a zinc compound, (C) an acrylic acid and/or methacrylic acid A flame-retardant resin composition comprising a compound.