JPH07116335B2 - 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, these conventional flame-retardant compositions are required to be flame-retarded to a higher degree from the viewpoint of disaster prevention. Also, depending on the application, they tend to be obligatory. From this point of view, there is no generation of harmful gas during combustion, and inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide as low-smoke and non-pollution flame retardants meet the needs and rapidly increase demand. (For example, those techniques are disclosed in JP-A-51-132254 and JP-A-56-1368.
32, 60-13832, etc.)

On the other hand, one of the important characteristics of the resin used for the outer cover of the power cable is that it has excellent crosslinkability.

However, 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. The improvement of is eagerly awaited.

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.

(Means for Solving the Problem) The present invention includes (a) substantially ethylene and an unsaturated carboxylic acid or its ester or vinyl ester 2.5 to 20.
60% to 99.7% by weight of a copolymer consisting of mol%, (b) substantially ethylene, 0.005 to 2.0% mol of vinyl (meth) acrylate or allyl (meth) acrylate and an unsaturated carboxylic acid or its ester, or Vinyl ester 0
The crosslinkable flame retardant composition contains 20 to 200 parts by weight of the inorganic flame retardant (c) with respect to 100 parts by weight of the resin component composed of 20 to 20 mol% of the copolymer of 40 to 0.3% by weight.

Substantially ethylene in the above components (a) and (b) may include other α-olefins in addition to ethylene, and the α-olefins include propylene and butene-
1, pentene 1, hexene-1, 4-methyl-pentene-1, octene-1, decene-1, etc., and mixtures thereof can be exemplified.

Examples of the unsaturated carboxylic acid or its ester in the component (a) or (b) in the above copolymer include methacrylic acid, acrylic acid, ethyl methacrylate, di (glycidyl methacrylate), methyl acrylate, ethyl acrylate. Unsaturated carboxylic acids such as isopropyl acrylate, phenyl acrylate, maleic acid, fumaric acid, crotonic acid, itaconic acid, and citraconic acid, or esters thereof can be exemplified. Examples of the vinyl ester in component (a) or (b) include vinyl esters of saturated aliphatic carboxylic acids such as vinyl formate, vinyl acetate and vinyl butyrate.

The content of unsaturated carboxylic acid or its ester or vinyl ester in the component (a) is 2.5 to 20 mol%,
The content is preferably 5 to 15 mol%, and when the content is less than 2.5 mol%, the inorganic flame retardant such as magnesium hydroxide has poor 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.

Of the above unsaturated carboxylic acids or their esters, ethyl acrylate is particularly preferable in terms of electrical properties and the like.

Examples of the comonomer in the component (b) include allyl methacrylate, vinyl methacrylate, allyl acrylate, vinyl acrylate, and the content thereof is 0.00
5 to 2.0 mol%. It is preferably 0.01 to 1 mol%.

When the comonomer content is less than 0.005 mol%, almost no effect of modifying the crosslinkability of the ethylene copolymer is observed, and when it exceeds 2.0 mol%, it becomes economically expensive and the polymerization Gelation occurs at the time of molding
Molding becomes difficult or appearance is poor.

Further, the unsaturated carboxylic acid or its ester or vinyl ester is contained in the component (b) in an amount of 0 to 20 mol%.
Can be copolymerized up to the range of, preferably 0 to 10 mol%.

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 (c) of the present invention, an inorganic flame retardant is used, but other flame retardants such as halogen-based and phosphorus-based flame retardants can be used together with the inorganic flame retardant. As the halogen-based flame retardant, tetrabromobisphenol A
(TBA), hexabromobenzene, decabromodiphenyl ether, tetrabromoethane (TBE), tetrabromobutane (TBB), hexabromocyclodecane (HBCD)
And chlorinated paraffins, chlorinated polyphenyls, chlorinated polyethylenes, diphenyl chlorides, perchloropentacyclodecane, chlorinated naphthalenes, and other chlorine-based compounds, and more effective when used in combination with antimony trioxide. Exert.

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.

Examples of the inorganic flame retardant of the present invention include aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, basic magnesium carbonate, dolomite, hydrotalcite, calcium hydroxide, barium hydroxide, tin oxide hydrate, and borax. Inorganic metal compound hydrate, 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 Etc. 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 inorganic flame retardant is 20 to 200 parts by weight, preferably 40 parts by weight or more based on 100 parts by weight of the resin. When combined with other flame retardants, the total amount of flame retardants should not exceed 200 parts by weight. If the amount of the flame retardant is less than 20 parts by weight, the flame retarding effect is small, and if it exceeds 200 parts by weight, the mechanical strength and elongation are reduced, 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 a copolymer of unsaturated carboxylic acid or its ester or vinyl ester, (b) substantially ethylene, and (meth) vinyl acrylate or ( A Banbury mixer, a pressure kneader, a kneading extruder, a twin-screw extruder, a resin component comprising a copolymer with (meth) allyl acrylate and (c) a flame retardant, and optionally an inorganic filler and additives. It is usually melt-kneaded by a kneading machine commonly used such as rolls, pelletized, etc., and usually provided as a molded product or a master batch, etc., but the above resin component, flame retardant, additives and the like are dry blended. Good.

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 neutralizing agent, a foaming agent, a plasticizer, an air bubble inhibitor, a flowability improver, and the like 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 comprises a copolymer of substantially ethylene, which is the component (a), and an unsaturated carboxylic acid or its ester or vinyl ester. ,
(B) a resin component consisting essentially of ethylene and a copolymer of vinyl (meth) acrylate or allyl (meth) acrylate and optionally an unsaturated carboxylic acid or its ester or vinyl ester, c)
A composition containing a flame retardant, which has good filler acceptability, can achieve a high degree of flame retardancy, is rich in crosslinkability, and can significantly improve mechanical strength and heat resistance. be able to. 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, the composition of the present invention, in particular, the composition comprising an ethylene copolymer using ethyl acrylate as an unsaturated carboxylic acid or its ester, which is one of the comonomer of the component (b), has excellent electrical characteristics. Since it is excellent, it can be used as an electric material such as an electric wire, a cable, or an outer covering material. In particular, it requires a high level of flame resistance such as cables for various power plants such as the Nuclear Research Institute, which regulates the amount of corrosive gas, cables for chemical, steel, petroleum, and other plants, fire-resistant wires, and general household wiring. It is preferably used in places where it is used.

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 In a metal autoclave equipped with a stirrer, which was sufficiently substituted with nitrogen and ethylene, each of (a) component, (b) component and n-hexane as a chain transfer agent was charged. Further, by injecting the polymerization initiator, Jittershire-butyl peroxide, pressure 1600 kg / cm ² , polymerization temperature 170 ° C.,
Polymerization was carried out under the condition of a polymerization time of 60 minutes to prepare each ethylene copolymer shown in Table 1.

Examples 1 to 9 As the component (a), ethylene-acrylic copolymer, (EA
Content of 6.5 mol% and 4.7 mol%, manufactured by Nippon Petrochemical Co., Ltd.), ethylene-vinyl acetate copolymer (trade name: Nisseki Lexron V270, manufactured by Nippon Petrochemical Co., Ltd.),
Using the above ethylene copolymer as the component (b), the following (c) flame retardant and dicumyl peroxide (trade name:
Park Mill D, manufactured by Nippon Oil & Fats Co., Ltd., 2.0 wt%, Thiobis (trade name: Nocracsk 300, manufactured by Ouchi Shinko Co., Ltd.) 0.2 wt%
%, And the composition kneaded with a roll at a temperature of 120 ° C. was measured for tensile strength, elongation, heat resistance (heat deformation rate), gel fraction, oxygen index, volume resistivity, etc. The results are shown in Table 1. (However, the gel fraction was measured without adding a flame retardant). Example 7 is a reference example other than the present invention.

(C) 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 4M, Showa Light Metal Co., Ltd.) Comparative Examples 1 to 6 Low density polyethylene (Product name: Sun) Ishi Lexulon W2000, manufactured by Nippon Petrochemical Co., Ltd.), ethylene-ethyl acrylate copolymer (EA content 4.7 mol%, manufactured by Nippon Petrochemical Co., Ltd.), ethylene-vinyl acetate copolymer (trade name: Table 1 shows the results of evaluations made in the same manner as in Example 1 using each resin of Nisseki Lexron V270, manufactured by Nippon Petrochemical Co., Ltd.). (Comparative Examples 1 to 3) Table 1 shows the results of evaluation of the composition outside the scope of the present invention in the same manner as in Example 1 using the ethylene copolymer. (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 speed 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, made by Ouchi Shinko Co., Ltd.) 0.2 wt% and the composition at 120 ° C.
The sample obtained by kneading with a roll of No. 1 and thermally crosslinked for 30 minutes with a press molding machine at 160 ° C. was crushed within 35 to 20 mesh and extracted with xylene at 120 ° C. for 10 hours to obtain the residual rate.

4. Enzyme index It was performed according to JIS K 7201.

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

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location // H01B 3/44 FM

Claims (4)

[Claims] 1. (a) Substantially ethylene and unsaturated carboxylic acid or its ester or vinyl ester 2.5 to 2
60 to 99.7 wt% of 0 mol% copolymer, (b) substantially ethylene, 0.005 to 2.0 mol% of vinyl (meth) acrylate or allyl (meth) acrylate and unsaturated carboxylic acid or ester thereof Alternatively, with respect to 100 parts by weight of a resin component comprising 0 to 20 mol% of a vinyl ester and 40 to 0.3 wt% of a copolymer, (c) an inorganic flame retardant of 20 to 200
A crosslinkable flame-retardant composition containing parts by weight. 2. The crosslinkable flame-retardant composition according to claim 1, wherein the copolymer (a) is ethylene-ethyl acrylate or ethylene-vinyl acetate. 3. The crosslinkable flame retardant composition according to claim 1, wherein the inorganic flame retardant comprises magnesium hydroxide, aluminum hydroxide or a mixture thereof. 4. The crosslinkable flame-retardant composition according to any one of claims 1 to 3, wherein the ethylene copolymer is an ethylene copolymer obtained by a radical polymerization method.