JPH0776292B2 - Crosslinkable flame retardant composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crosslinkable flame-retardant composition having excellent mechanical strength and heat resistance.

(Prior Art) Polyolefin is excellent in physical properties and chemical properties, and is molded into films, sheets, pipes, containers, etc. by various molding methods such as extrusion molding, injection molding and rotational molding, and is used for household use. It is the most popular general-purpose resin used in many industrial applications.

Since the above polyolefin is flammable, various methods for making it flame-retardant have been conventionally proposed.

The most general method is to add flame retardant containing halogen, phosphorus or the like to the polyolefin to make it flame-retardant. The degree of flame retardancy increases with the amount of flame retardant added. However, the increase in the amount of addition thereof not only brings about a decrease in mechanical strength, workability, etc., but also has a drawback that flexibility, cold resistance, etc. are significantly impaired. Further, from the viewpoint of disaster prevention, these conventional flame-retardant compositions are required to be flame-retarded to a higher degree, and they tend to be obligatory depending on the application. From this point of view, there is no generation of harmful gas at the time of combustion, inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide as low smoke and non-pollution flame retardants meet the needs, and the demand is rapidly increasing. (For example, those techniques are disclosed in JP-A-51-132254 and JP-A-56-1368.
32, 60-13832, etc.)

On the other hand, as an electrically insulating material, for example, excellent cross-linking property is required as one of important characteristics of resins for power cables.

However, for example, in conventional polyethylene for electric power cables, unless the amount of the cross-linking agent is increased, the gel fraction is not improved, and the heat distortion rate at a temperature higher than the melting point is remarkably increased. It is earnestly desired to improve the sex.

Further, in the conventional commercially available polyethylene,
Poor acceptance of inorganic flame retardants and low flame retardant effect. Also,
When the filling amount is increased, the mechanical strength, flexibility, workability, etc. are deteriorated and there is a drawback that it cannot be put to practical use.

(Problems to be Solved by the Invention) An object of the present invention is to solve the above-mentioned problems of the prior art,
In particular, it is to provide a crosslinkable flame retardant composition which has good acceptability for fillers, can obtain a high degree of flame retardancy, is rich in crosslinkability, and has improved heat resistance. Another object of the present invention is to provide a composition exhibiting a remarkable effect as an electrically insulating material.

(Means for Solving the Problem) The present invention includes (a) substantially 88 to 97.495 mol% ethylene;
(B) 0.005 to 2.0 mol% of vinyl (meth) acrylate or allyl (meth) acrylate and (c) unsaturated carboxylic acid or its ester or vinyl ester 2.5
A crosslinkable flame-retardant composition containing (d) 10-200 parts by weight of a flame retardant with respect to 100 parts by weight of an ethylene copolymer of 20 mol%.

The above-mentioned (a) component, substantially ethylene, means ethylene ethylene alone or ethylene as a main component and may also contain other α-olefin as a minor component, and the α-olefin includes propylene, butene- 1, pentene 1, hexene-1, 4-methyl-pentene-1, octene-1, decene-1, etc., and mixtures thereof can be exemplified.

Component (b) in the above copolymer is vinyl methacrylate, vinyl acrylate, allyl methacrylate, allyl acrylate, the content of which is 0.005 to 2.0 mol%,
It is preferably 0.01 to 1 mol%.

When the amount of the above monomer is less than 0.005 mol%, the effect of modifying the crosslinkability of the ethylene copolymer is hardly seen, and 2.0 mol%
If it exceeds the above range, it will be economically expensive, and further, gelation will occur during polymerization or during molding process, which makes molding difficult or causes poor appearance.

Examples of the unsaturated carboxylic acid or its ester which is the component (c) in the above copolymer include methacrylic acid, acrylic acid, ethyl methacrylate, glycidyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid. Phenyl, maleic acid, fumaric acid,
Examples thereof include unsaturated carboxylic acids such as crotonic acid, itaconic acid, and citraconic acid, or esters thereof.
Examples of the vinyl ester as the component (c) include vinyl esters of saturated aliphatic carboxylic acids such as vinyl formate, vinyl acetate and vinyl butyrate.

The content of the unsaturated carboxylic acid or its ester or vinyl ester as the component (c) is 2.5 to 20 mol%, preferably 3 to 15 mol%, and when the content is less than 2.5 mol%, magnesium hydroxide and the like are contained. The inorganic flame retardant becomes poor in acceptability and becomes fragile, resulting in deterioration of mechanical strength and flame retardancy. Also, when it exceeds 20 mol%, the strength of the resin is weak and the mechanical strength is lowered.

Among the above-mentioned component (c), ethyl acrylate is preferable in terms of electrical properties and the like.

The ethylene copolymer of the present invention is preferably produced by a conventional high pressure radical polymerization method.

The high-pressure radical polymerization method is a polymerization pressure of 500 to 4000 kg / cm.
² , preferably 1000 to 3500 kg / cm ² , reaction temperature 50 to 400 ° C.,
Preferably, under conditions of 100 to 350 ° C., ethylene and the comonomer are simultaneously or stepwise in a tank or tube reactor in the presence of a free radical catalyst, a chain transfer agent and, if necessary, an auxiliary agent. A method of contacting and polymerizing.

Examples of the above free radical catalyst include hydrogen, propylene, butene-
1, C ₁ -C ₂₀ or more saturated aliphatic hydrocarbons and halogen-substituted hydrocarbons such as methane, ethane, propane, isobutane, n-hexane, n-heptane, cycloparaffins, chloroform and carbon tetrachloride, C ₁ ~
C ₂₀ or higher saturated aliphatic alcohols and isopropanol, C _{1 to} C ₂₀ or higher saturated aliphatic carbonyl compounds such as carbon dioxide, acetone and methyl ethyl ketone and aromatic compounds such as toluene, ethylbenzene and xylene. Etc.

As the flame retardant which is the component (d) of the present invention, an addition type flame retardant such as a halogen flame retardant, a phosphorus flame retardant, or an inorganic flame retardant is used. Examples of the halogen-based flame retardant include tetrabromobisphenol A (TBA), hexabromobenzene, decabromodiphenyl ether, tetrabromoethane (TBE), tetrabromobutane (TBB), hexabromocyclodecane (HBCD), etc. Chlorine compounds such as brominated and chlorinated paraffins, chlorinated polyphenyls, chlorinated polyethylenes, diphenyl chlorides, perchloropentacyclodecane, chlorinated naphthalenes are listed, and more effective when used in combination with antimony trioxide. To do.

Further, as the phosphorus-based flame retardant, tricresyl phosphate, tri (β-chloroethyl) phosphate, tri (dichloropropyl) phosphate, tri (dibromopropyl) phosphate, 2,3-dibromopropyl-2,3-chloropropyl A phosphoric acid ester such as phosphate or a halogenated phosphoric acid ester is mainly mentioned.

Further, as the inorganic flame retardant of the present invention, aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, basic magnesium carbonate, dolomite, hydrotalcite,
Calcium hydroxide, barium hydroxide, tin oxide hydrate, hydrates of inorganic metal compounds such as borax, zinc borate, zinc metaborate, barium metaborate, zinc carbonate, magnesium calcium carbonate, calcium carbonate, barium carbonate , Magnesium oxide, molybdenum oxide, zirconium oxide, tin oxide, antimony oxide, red phosphorus and the like. These may be used alone or in combination of two or more. Among these, particularly, at least one selected from magnesium hydroxide and aluminum hydroxide has a good flame retardant effect and is economically advantageous. The particle size of these flame retardants varies depending on the type, but in magnesium hydroxide, aluminum hydroxide and the like, the average particle size is preferably 20 μm or less, more preferably 5 μm or less.

The amount of the flame retardant is in the range of 10 to 200 parts by weight, preferably 20 to 150 parts by weight, based on 100 parts by weight of the resin. Especially when using only the inorganic flame retardant, 40 parts by weight to 20 parts by weight
It is preferably used in the range of 0 parts by weight. If the amount of the flame retardant is less than 10 parts by weight, the flame retarding effect is small, and if it exceeds 200 parts by weight, the mechanical strength and elongation are lowered, the flexibility is lost, the material becomes brittle, and the low temperature characteristics are deteriorated.

In the composition of the present invention, at least one of the above-mentioned addition type flame retardants is used, but as described above, magnesium hydroxide, aluminum hydroxide and the like are particularly preferable, and they may be used in combination with a halogen-based flame retardant. preferable. Further, in the present invention, by using the inorganic filler and the flame retardant in combination, the amount of the flame retardant added can be reduced, and further, other characteristics can be imparted.

The inorganic filler used as an optional component in the present invention includes calcium sulfate, calcium silicate, clay, diatomaceous earth, talc, alumina, silica sand, glass powder, iron oxide, metal powder, graphite, silicon carbide, silicon nitride, silica. , Powdered and granular filler such as boron nitride, aluminum nitride, carbon black, mica, glass plate, metal foil such as sericite, pyroflight, aluminum flake, flat plate or scale-like filler such as graphite, shirasu balloon, metal Examples include balloons, glass balloons, hollow fillers such as pumice, glass fibers, carbon fibers, graphite fibers, whiskers, metal fibers, silicon carbide fibers, mineral fibers such as asbestos and wollastonite.

The addition amount of these is 1 part with respect to 100 parts by weight of the composition of the present invention.
It is applied up to about 00 parts by weight.

If the above-mentioned addition amount exceeds 100 parts by weight, mechanical strength such as impact strength of the molded product decreases, which is not preferable.

Examples of the method for crosslinking the composition of the present invention include crosslinking with an organic peroxide, silane crosslinking, or irradiation crosslinking such as electron beam irradiation.Examples of commonly used organic peroxides include dicumyl peroxide and tert- Butyldicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxine) hexyne-3, etc. It is usually 0.1 to 5 parts by weight, preferably 0.4 to 2 parts by weight, based on 100 parts by weight of the composition of the present invention. In addition, in silane crosslinking, vinylalkoxysilane (vinyltrimethoxysilane or the like) is grafted to the composition and then water-crosslinked.
Further, for the irradiation cross-linking, an irradiation source such as a high energy electron beam or X-ray is appropriately adopted.

Among the above crosslinking methods, crosslinking with an organic peroxide is particularly preferable.

The composition of the present invention comprises (a) substantially ethylene and (b)
An ethylene copolymer comprising vinyl (meth) acrylate or allyl (meth) acrylate, (c) unsaturated carboxylic acid or its ester or vinyl ester,
(D) A flame retardant, and optionally an inorganic filler and additives are melt-kneaded with a Banbury mixer, a pressure kneader, a kneading extruder, a twin-screw extruder, a roll, or other commonly used kneader to form pellets. It is usually used as a molded product or a master batch, but the above resin component may be dry blended with a flame retardant, an additive and the like.

Further, the composition of the present invention includes other synthetic resins, antioxidants, lubricants, various organic / inorganic pigments, ultraviolet inhibitors, dispersants,
Additives such as a copper damage inhibitor, a neutralizer, a foaming agent, a plasticizer, an anti-foaming agent, a flowability improver and a nucleating agent may be added within a range that does not significantly impair the effects of the present invention.

(Effects of the Invention) As described above, the crosslinkable flame-retardant composition of the present invention is substantially ethylene which is the component (a) and (meth) which is the component (b).
A composition obtained by adding a flame retardant as a component (d) to an ethylene copolymer comprising vinyl acrylate or allyl (meth) acrylate and an unsaturated carboxylic acid as a component (c) or its ester or vinyl ester, The composition has good filler acceptance, can achieve a high degree of flame retardancy, is rich in crosslinkability, and can significantly improve mechanical strength and heat resistance. By using an inorganic flame retardant as a flame retardant, for example, aluminum hydroxide, magnesium hydroxide, etc., no harmful gas is generated during combustion, and a low smoke, pollution-free flame-retardant composition is obtained, which is highly flame-retardant. This will meet the needs of today that are required to be realized.

In addition, since the composition of the present invention, in particular, the composition comprising an ethylene copolymer using ethyl acrylate as a comonomer of the component (c) has excellent electrical characteristics, an electric wire,
It can be used as an electric insulating material such as a cable or an electric material such as a jacket material. In particular, cables for various power plants such as the Nuclear Research Institute, which regulates the amount of corrosive gas,
It is preferably used in places where high flame retardancy is required, such as plant cables for chemicals, iron and steel, petroleum, fireproof electric wires, and wiring for general homes.

It is also used for molding applications such as extrusion molded products such as films, sheets and pipes, injection molded products, and as master batches, and is used in various fields such as textiles, electricity, electronics, automobiles, ships, aircraft, construction, civil engineering, etc. Used as packaging materials, furniture, household items, etc.

(Example) Method for producing ethylene copolymer A predetermined amount of ethylene was added to a metal autoclave equipped with a stirrer, which was sufficiently replaced with nitrogen and ethylene, and the following (b),
Component (c) and n-hexane which is a chain transfer agent are charged, and further, a polymerization initiator, zeta-searly butyl peroxide, is injected, the pressure is 1600 kg / cm ² , the polymerization temperature is 170 ° C.,
Polymerization was carried out under a polymerization condition of a polymerization time of 60 minutes to prepare various ethylene copolymers as shown in Table 1.

(B) Component Allyl Methacrylate (AMA) Vinyl Methacrylate (VMA) Allyl Acrylate (AA) (c) Component Ethyl Acrylate (EA) Vinyl Acetate (VA) Examples 1-8 In the above ethylene copolymer The following (d) flame retardant and dicumyl peroxide (trade name: Park Mill D, manufactured by NOF CORPORATION) 2 wt%, 4,4'-thiobis- (6-tert-butyl-4-methylphenol) (hereinafter (Thiobis) (Product name: Nokuratsukku 300, Ouchi Shinko Co., Ltd.)
The results of measuring the tensile strength, elongation, heat resistance (heat deformation rate), gel fraction, oxygen index, volume specific resistance, etc. of the composition blended with 0.2 wt% and kneaded with a roll at a temperature of 120 ° C. Is shown in Table 1. (However, the gel fraction was measured without adding a flame retardant).

(D) Flame retardant 1) Tetrabromobisphenol A derivative (Brand name: Fireguard 3003, Teijin Chemicals Ltd.) 2) Magnesium hydroxide (Mg (OH) ₂ ) (Brand name: Kisuma 5B, Kyowa Chemical Industry Co., Ltd. 3) Aluminum hydroxide (Al (OH) ₃ ) (Product name: Heidilite 42M, Showa Light Metal Co., Ltd.) Comparative Examples 1-6 Low density polyethylene (Product name: Sun) Ishi Lexulon W2000, Nippon Petrochemical Co., Ltd.), ethylene-ethyl acrylate copolymer (EA content 4.7 mol%, Nippon Petrochemical Co., Ltd.), ethylene-vinyl acetate copolymer (VA content 5.3) Table 1 shows the results of evaluation in the same manner as in Example 1 using each resin of mol%, manufactured by Nippon Petrochemical Co., Ltd.). Comparative Examples 1 to 3 In addition, ethylene-AMA-EA terpolymers outside the scope of the present invention were produced and evaluated in the same manner as in Example 1. The results are shown in Table 1. (Comparative Examples 4 to 6) The test methods are as follows.

<Test Method> 1. Tensile Strength and Elongation A test piece obtained by punching out a No. 3 dumbbell from a sheet having a thickness of 1 m / m was measured using Tensilon at a tensile strength of 200 mm / min.

2. Heating deformation rate It was performed according to JIS C 3005. It was measured at a temperature of 120 ° C. and a weight of 1 kg.

3. Gel Fraction Dicumyl peroxide (trade name: Park Mill D, manufactured by NOF Corporation) 2.0 wt%, thiobis (trade name: Nokratsk 3
00, manufactured by Ouchi Shinko Co., Ltd.) 0.2 wt% and the ethylene copolymer are kneaded with a roll at 120 ° C., and then press-molded at 160 ° C.
Crush the sample heat-crosslinked for 30 minutes to within 35 to 20 mesh,
The residual rate after extraction with xylene at 120 ° C for 10 hours was obtained.

4. Oxygen index Measured according to JIS K 7201.

5. Specific volume resistivity Conducted in accordance with JIS K 6723.

Claims (6)

[Claims] 1. A substantially 88 to 97.495 mol% of ethylene, (b) 0.005 to 2.0 mol% of vinyl (meth) acrylate or allyl (meth) acrylate, and (c) an unsaturated carboxylic acid or the same. Ester or vinyl ester
A crosslinkable flame retardant composition containing (d) 10 to 200 parts by weight of a flame retardant with respect to 100 parts by weight of an ethylene copolymer composed of 2.5 to 20 mol%. 2. The crosslinkable flame-retardant composition according to claim 1, wherein the unsaturated carboxylic acid or its ester or vinyl ester of (c) is ethyl acrylate or vinyl acetate. 3. The crosslinkable flame retardant composition according to claim 1 or 2, wherein the flame retardant is an inorganic flame retardant. 4. The crosslinkable flame retardant composition according to claim 3, wherein the inorganic flame retardant comprises magnesium hydroxide, aluminum hydroxide or a mixture thereof. 5. A halogen-based flame retardant and an inorganic flame retardant are used in combination as flame retardants.
The crosslinkable flame-retardant composition according to any one of item 4. 6. The crosslinkable flame-retardant composition according to any one of claims 1 to 5, wherein the ethylene copolymer is an ethylene copolymer obtained by a radical polymerization method.