GB2153832A - Flame retardant polyolefin compositions - Google Patents

Abstract

Polyolefin compositions having superior mechanical properties, processability and flame retardancy can be obtained by blending polyolefin resin, a halogen-containing flame retardant, antimony trioxide, a crosslinking agent, a radical-generating agent and optionally a boron compound.

Description

SPECIFICATION Flame retardant polyolefin composition This invention relates to polyolefin compositions having high flame-retardancy. More particularly, it relates to polyolefin compositions having good mechanical properties, processability and flame retardancy.

On account of superiority in processability, chemical resistance, weatherability, electrical characteristics, etc, polyolefin resin is widely used in various products including electrical household appliances. On the other hand it has drawbacks in that it is extremely inflammable, liquefied by pyrolysis atthetime of combustion, forms liquid drops with flaming or without flaming combustion, and burnt pieces cut by fusion tend to fall away (hereinafterthe dropped or fallen materials will be referred to as "drip", and the tendencytoform drips as the "dripping property").

The existence or not of drip is one ofthe important factorsforevaluatingflame-retardancy. Even when a resin is superior in self-extinguishing property, its flame-retardancy is ranked in a lower grade if it has drip. Thus an impovement of dripping property is one of the important problems with regard to flameretarding techniques for such resins. Further, since polyolefin resin has a relatively higher crystallinity and non-polar properties, it is poor in compatibility with a flame-retardant, and shows a great reduction in physical properties upon addition of a flame-retar dant.Onthisaccount,forflame retarding or retardance of polyolefin resin, various proposals have been made.

As general methods for making aflame retardant polyolefin composition, a simultaneous use of an organic-halogen-containing flame-retardant with a certain kind of metal oxide (Japanese patent publication 25061 of 1976) and addition of a nitrogencontaining compound, a boron-containing compound or a water-containing inorganic compound, as a flame-retardant, have prevailed. However, an organic halogen-containing flame-retardant is superior in self-extinguishing property but has the drawback in that drip is formed atthetime of burning. Onthe other hand, an inorganic flame-retardant, e.g. magnesium hydroxide, is superior in dripping property, and has a certain extent of self-extinguishing property but has a drawback in that a high level of flame-retardancy requires a large addition of retardant.A polyolefin composition containing a large amount of incorporated inorganic compound suffers in deterioration of processing characteristics, due to the reduction in fluidity ofthe molten material and the reduction in machanical properties of formed articles made from such a composition. The range of addition is limitative in practical use, because this reduction of machanical strength of formed articles makes the attainment of a high level offlame-retardancy difficult.

In orderto overcome these drawbacks, it has been proposed to use simultaneously a bromine-contain inflame retardant and a borofluoride salt in polypropylene resin (Japanese laid open application No.

163937 of 1979); to mix ethylene-propylene rubber modified with a silane compound and a flame retardant with polyethylene resin, followed by cros slinking with an organic peroxide (Japanese laid open patent application No.110139 of 1980); to use simultaneously a silane coupling agent, ethylenepropylene rubber, chlorinated polyethylene and a flame-retardant in forming, followed by crosslinking with water (Japanese laid open patent application No.

45716 of 1980). However, according to the abovementioned Japanese laid open application No. 163937 of 1979, the improvement of dripping property is still not in the state which can be said to be sufficient. The processes of Japanese laid open patent application No.110139of1980andNo.457l6ofl980arethose which have been applied to polyethylene, which create crosslinking very easily in the presence of an organic peroxide.

The present inventors concentrated their effort in trying to solve the above-mentioned problem relating to flame-retardant polyolefin compositions. As a result, they succeeded in obtaining flame-retardant polyolefin compositions which typically have improved machanical strength innformed articles, greatly improved dripping property atthetime of burning, and further improved drawdown of burnt resin pieces through melting and falling of drops of burnt resin pieces.Such compositions are obtained for example by (a) incorporating a crosslinking agent and a radical generating agent in a polyolefin resin either in the presence of a halgen-containing flame-retardant and antimonytrioxide or in the presence of a halogencontaining flame-retardant, antimonytrioxide and a boron compound, and subjecting the resulting mixtureto melting and kneading treatment or(b) mixing either a halogen-containing flame-retardant and anti monytrioxide or a halogen-containing flame-retardant, antimonytrioxide and a boron compound, with a polyolefin resin having been, in advance, treated with a crosslinking agent and a radical generating agent and subjecting the resulting mixture to melting and kneading treatment.

As evident from the foregoing description, it is an object ofthe present invention to provide flameretardant polyolefin compositions which can provide formed articles typically having improved machanical strength, and greatly improved dripping property at the time of burning.

The compositions of the present invention have the following constitution: (1) Aflame retardant polyolefin composition obtained by blending various components, where the percentages are based upon the weight of the following (A) to (E) components, except where a different basis for the percentages is stated: (A) 0.1 to 15% by weight of a crosslinking agent, (B) 0.005 to 5% by weight of a radical-generating agent, (C) 5 to 60% by weight of a halogen-containing flame-retardant, (D) 100 to 10% by weight of antimony trioxide based upon the said halogen-containing flame retardant, (E) polyolefin resin.

(2) Aflame retardant polyolefin composition obtained by blending various components, where the percentages are based upon the total weight ofthe following (A) to (F) constituents, except where a different basis for the percentages is stated: (A) 0.1 to 15% by weight of a crosslinking agent, (B) 0.005 to 5% by weight of a radical generating agent, (C) Sto 60% by weight of a halogen-containing flame-retardant, (D) 100 to 10% by weight of an antimonytrioxide based upon the said halogen-containing flame-retardant, (E) polyolefin resin, and (F) 1 to 10% by weight of a boron compound.

The polyolefin resin is subjected to melting and kneading treatment with at least the crosslinking agent and the radical-generating agent in order to achieve the blended composition.

As polyolefin resins used in the pesent invention, a homopolymer of an α-olefin such as propylene, butylene orthe like, a random copolymer, a biock copolymer consisting selected two or more members of ethylene, propylene and butylene and ethylene vinylacetate copolymer, styrene - butadiene copolymer, ethylene - propylene rubber and a mixture of two or more of these members can be mentioned. Especially a polyolef,rì resin containing, as a main component, polypropylene resin, is preferable.

As a halogen-containing flame-retardant, an aormatic bromine compound having a melting point of 300 C or higher e.g. decabromodiphenyl oxide, ethylene bis -tetrabromophthalimide or the like is useful. Especially decabrornodiphenyl oxide is preferably used.

The amount of addition of said halogen-containing flame-retardant is in the range of 5#60% by weight, preferabl f 550% by weight, most preferably 7~30% by weight.

The amount of addition of antlmonytrioxide is in the range of 100#10% by weight based upon the abovementioned halogen-containing flame-retardant agent.

As crosslinking agent, polyfunctional monomers, monofunctional monomers, oxim nitroso compound, malemide compound, silane coupling agent, etc. are used.

As concrete examples, there are, for example, triallyl cyanurate, triallylisocyanu rate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, divinylbenzene, diallylphthalate, divinylpyridine, vinyltoluene, ethylvinylbenzene, styrene monomerquinonedioxime, benzoquinonedioxime, p-nitrosophenol, N,N' - m - phenylenebis - maleimide, vinyltriethoxysilane,y methacryloxypropyl -trimethoxysilane, y -aminopropyltriethoxysilane, etc.

The amount of addition of said crosslinking agent is in the range of 0.1 ~15% by weight, preferably 0.5~10% byweight, most preferably 16% by weight.

As radical generating agents, materials which generate a radical by thermal decomposition is useful.

For example, they are dicumyl peroxide; 2,5 - dimethyl - 2,5 - di(t - butyl peroxy)hexane, 2,5 - dimethyl - 2,5 di(t-butyl peroxy)hexyne - 3; 1,3 - bis(t -butylperox yisopropyl)benzene; 1,1,4,4,7,7 - hexamehtylcyclo 4,7 -diperoxynonane; cumenehydroperoxide; cumylperoxytrimethyl silane, etc.

The amount of addition of said radical generating agent varies according to the kind of it, and it is in the range of 0.0055% by weight, particularly 0.01 ~1 %byweight.

As boron compounds, borax, borofluoride salt, for example, sodium borofluoride, potassium borofluoride, ammonium borofluorode are useful.

The amount of addition is in the range of 1 ~10% by weight, preferably 18% by weight, most preferably 2~6% by weight.

In the present invention, various kinds of additives, for example, antioxidant, lubricant, pigment, inorga nicfiller (for example, calcium carbonate, talc, clay, mica, magnesium hydroxide, glass fibers, etc.) can be used simultaneously.

In the production ofthe present composition, there is no particular limitation in the order of addition of each component of the above-mentioned (A), (B), (C), (D) and (E). Any ofthe following methods i.e. a method of simultaneous mixing of (A), (B), (C), (D) and (E) followed by melting and kneading; a method in which (A) and (B) are added during the processing of melting and kneading of (C), (D) and (E) and a method in which after melting and kneading of (A), (B) and (E) in advance, (C) and (D) are mixed and melting and kneading are carried out subsequently. Further, there is also no particular limitation in the order of addition of each components of above-mentioned (A), (B), (C), (D), (E) and (F).Any one ofthefollowing methods i.e. a method in which (A), (B), (C), (D), (E) and (F) are simultaneously mixed and subjected to melting and kneading; a method in which after melting and kneading of (A), (B) and (F) in advance, (C), (D) and (E) are mixed and subjected to melting and kneading; or a method in which (A) and (B) are added during the processing of mixing, melting and kneading of (C), (D), (E) and (F) and furthersubjected to melting and kneading, is applicable.

As an apparatus for mixing the above-mentioned each components, a common mixing apparatus such as a mixer having an attached high speed stirrer e.g.

Henschel mixer (name of particle of trade) ribbon blender, tumbler may be useful. For melting and kneading, a common single ortwin screw extruder can be used. Melting and kneading temperature is in the range of 170 C-300 C, preferably200 C#260 C.

Retention time in the extruder of product mixed by melting will be sufficient if a retention time in a common extruder is used.

From the pellets of polyolefin composition, thus obtained, test specimen of predetermined dimension were molded and flame-retardancy and mechanical strength were measured. With regard to flame retardancy, extremely betterflame-proofness and dripping property were indicated, compared with comparative test specimens. Further, in mechanical strength, flexural modulus, flexural strength, tensile strength, Izod impact strength, the test specimen show higher numerical values in all these tests compared with comparative test specimen and it has been revealed that increase of mechanical strength of formed articles as well as improvement of a large extent of flame retardancy and dripping property can be attained.

The present invention will be more concretely illustrated by referring to specific examples and Comparative Examples. Burning tests in the specific examples and Comparative examples were carried out according to the following method. Furtherthe measurements of mechanical strength were carried out according to the method of JISK 6758-1981.

Burning test Test specimens having a length of 127 mm, a width of 12.7 mm and a thickness of 0.8 mm were vertically suspended by fixing at the top end in a room in which there is no movement of air. Aflame of Bunsen burner having been controlled to produce a 19 mm blue flame was applied to a test specimen from its lower end for 10seconds. After 10 seconds, the burner was removed and a time at which the test specimen continues to burn with flaming after removal ofthe burner, was measured and this is recorded as the first flaming combustion time.Immediately after extinguishment oftestspecimen,a blueflameofburnerwasapplied again to the test specimen at its lower end according to the same method for 10 seconds and a time elasped until extinguishment was attained again was measured and this is recorded as the second flaming combustion time. Subsequently a time during which the test specimen is burning with glowing combustion is also measured. This time are summed up with the above-mentioned second flaming combustion time and recorded as a glowtime. Further, cotton is placed atthe position 305 mm belowthe test specimens and observed whether it catches fire byflaming drip during the testing time and the result is recorded.

Foregoing tests were carried out by using 5test specimens and fire-retardancywas evaluated.

Specific examples 1#2 and Comparative examples 1#3 After definite amounts of a halogen-containing flame-retardant, antimony trioxide, a crosslinking agent, and a radical generating agent having the details described in Table 1 were mixed with, as polyolefin resin, ethylene-propylene block copolymer having a melt flow rate (M.F.R.) of 2.5 g/l 0 min. (the extruded amount of melted resin for 10 minutes at the time when 2.16 Kg of load is applied at 230 C) and ethylene content of 12% by weight or a propylene homopolymer having a M.F.R. of 2.0 g/l 0 min. the mixture was melted and kneaded (mean retention time of 25 sec.) at 230 C by using a twin screw extruder having a diameter of 45 mm (Brand PCM-45 of Ikegai Tekkosho K.K. to do pelletizing. As Comparative examples 1#3, each ofthe components described in Table 1 was mixed, melted, and kneaded according to the method the same as that of Examples 1#2 to do pelletizing. Resulting pellets were charged an injection molding machineto mold test specimen of definite dimension, which were subjected to the measurement offlammability and mechanical strength. The result are shown in Table i.

Table 1

Example Comparative Comparative Example Comparative Unit 1 example 1 example 2 2 example 3 Polyolefin resin El % by 67 70 40 - weight # E2 - - - 37 40 Halogen-containing Cl # 20 20 40 40 40 flame-retardant Antimony trioxide D .. 10 10 20 20 20 Crosslinking agent Al # 3 3 - 3 3 Radical generator Bl # 0.01 - - 0.01 First flaming combustion time Whether or not drip formed at the first - no yes no ?o no combustion time Second flaming sec. 1 @*1) *2) not clear 0.5 notclear*2) combustion time Whether or not drip formed at the second - no yes yes no yes combustion time Whether or not cotton - no yes no no no ignited Glow time sec. 45 not *3) not *3) 55 not *3) measurable measurable measurable Table 1 (continued)

Unit Example Compar. Compar. Example Compar.

1 ex. 1 ex. 2 2 ax. 3 Flexural modulus Egf/cm2 15,000 14,400 - - ~ 2 Flexural strength Eq f/cm 350 315 - - Tensile Tensile strength Kgf/cm2 275 225 - Ac Izod impact strength Kg f.cm/cni 6.3 6.0 - - (wi Lll 1l l Note:Al: trimethylolpropanetriacrylate, Blt 1,3-bis (t-butylperoxyisopropyl 1) benzene, C1: decabromodiphenyl oxide, D: antinlony trioxide, El: ethylene-pro-pylene block copolymer haviny 12% by weight of ethylene, E2: propylene homopolylller.

*1) "#" shows that test speclemen cont thued to burn with flaming.

*2) "not cleat" shows thdL combustion time could not be measured due to melt-falling at the time wlien d LU)llcT applied to the test specimen.

*3) "not medsulable" bis measuiement of glow time could not be done due to melt falling of the test specimen.

As evidenttrom Example 1, Comparative examples 1 2 those which did not use a crosslinking agent and a radical generating agent were not extinguished as in Comparative example and fall of drip with flaming combustion was observed. Further, those in which the amount of a flame-retardant and antimony trioxide were increased, were satisfactory in combustiontime but melting and falling of test specimens were observed by the second combustion. In contrast, Example 1 showed excellent extinguishment and dripping property in spite of its same amounts of addition of the flame-retardant and antimonytrioxide as in Comparative example 1. Particularly, at the second combustion time, notable difference in dripping property was observed.Further, as for mechanical strengths, higher numerical values were indicated in flexural modulus, flexs ray strength, tensile strength, Izod impact strength, etc. compared with those of Comparative example 1.

In specific example 2, a propylene homopolymer having a melt-flow rate 2.0 g/10 min. was used as a polyolefin resin and subjected to similartests but it was revealed that a great extent offlammability and dripping property were improved et the time ofthe second combustion as compared with those of Comparative example 3.

Examples 3#4 and Comparativeexamples 4#7 To polypropylene homopolymer having a M.f.r. of 2.0 g/l 0 min., as a polyolefin resin, a halogencontaining flame-retardant, antimony trioxide, a crosslinking agent a radical generating agent, and a boron compound, the details of which are described in Table 2, each in definite amounts were admixed in a Henschel mixer (FM-75C manufactured by Mitsui Miike Seisakusho), and thereafter by using a twin screw extruder having a diameter of 45 mm (PCM-45, of ikegai Tekko K.K.), melting and kneading were carried out at 230 C (mean retention time in the extruder 25 sec.) to effect pelletizing.As Comparative examples 4#7, each ofthe components described in Table 2 were mixed, melted and kneaded according to the method the same with those of Examples 3~4, to effect pelletizing. Resulting pellets were charged to an injection molding machineto mold into test specimen of definite dimension at a temperature of 250 C, and the molded test specimens were subjected to the measurementofflammabilityand mechanical strength. The results of these tests are shown in Table 2.

Examples 5#9 and Comparative examples 8#9 By using, as polyolefin resin, an ethylene-propyiene block copolymerhaving a M.F.R. of 2.5 g/10 min. and further using, in Examples 6~7, as inorganic filler, talc and wollastonite, definite amounts of each ofthe components the detail of which are described in Table 3, were mixed, melted and kneaded according to a method similartothatofspecificexamples 3#4 to effect pelletizing.

By using the resulting pellets, testspecimen of definite dimension were molded according to a method described in specific examples 3#4 and measurements offlammability and mechanical strength were conducted. The results of these tests are indicated in Table 3.

Table 2

Example Example Example Compar. Compar. Compar.

Unit 4 ox. 4 ox. 5 ox. 6 ox. 7 Polyolefin resin Fl %by 62 62 65 37 40 30 weight Halogen-containing Cl " 20 - 20 40 40 40 flame-retardant " C2 " - 20 - - - Antimony triuxide U " 10 10 10 20 20 20 Crosslinking agent Al " 3 3 (3 0 Radical generating Bl " 0.01 0.01 0 0.01 0 0 agent Boron compound LI " 5 5 5 0 0 10 First combustion time sec. 7 Whether or not drip is b present at the first - no no yes no no combustion time Second combustion Llr: sec. 5 5 5 @ 1) 1 5 8 Whether or not drip Is present at the second @ no no yes no yes yes combustion time Whether or not ignited - no no yes no no no the cotton due to drip Glow time sec. 25 55 unmeas-*2) 70 unmeas-*2) unmeas-*2) urable urable urable Table 2 (continued)

Ullit Example Example i~omp4ar. Compar. 6 ex. 7 3 4 ex. 4 ex. 5 ex. 6 ex. 7 Yi Flexural modulus Kg f/cn 22,500 - 19,400 - - riai Flexural strength Kg f/cnl 490 - 455 zrw Tensile strength Kg f/cm 320 - i00 ot J.6 3.6 zisi lzod impse strenyllr NOte Al: trimethylolprupanetriacrylate, Bl: 1,3-bis (t-butylperoxyisopropyl) behzene, Cl: decabromodiphenyloxide, C2: ethylenebistetrabromophthalimide, e1: sodium b, ri fluorlde, Fl: propylene homopolymer (M.F.P. 2.0 g/10 min.), *1) "" shows that d Lest specimen continued to burn.

*2) "unmeasurable" means that the measurement of glow time could not be measured due to the melt-falling of test specimen.

Table 3

Specific Comparative example Specific example Unit ex. 5 8 9 6 7 8 9 Polyolefin resin F1 t by 62 62 30 50 50 62 62 weight Halogen-containing flame retardant Cl " 20 20 20 20 20 20 20 Antimony trioxide D 10 10 20 10 10 10 10 Crosslinking agent Al 3 3 0 3 3 - 3 A2 " - - - - - 3 Radical generating Bl 0.01 0 0 0.01 0.01 0.01 0.01 agent Boron compound El ., 5 5 10 5 5 5 E2 " - - - - - - 5 Inorganic filler G1 " 0 0 0 12 0 0 0 " G2 ' 0 0 U 0 12 0 0 Pirst combustion time sec. 6 9 0.2 9 3 11 7 Whether or not drip is present at the first - no yes no no no no no combustion time Second conbustion time sec. 4 # 2 2 1 4 8 5 Whether or not drip is present at the second ~ no yes yes no no no no combustion time Whether or not ignited cotton is present or ~ no yes no no no no no not due to drip Glow tlme ser. 26 unmeas- unmeas- 40 35 50 30 urable urable Table 3 (continued)

Unit specific Comparative example Specific example ex. ex. 5 8 9 6 7 8 9 Flexural modulus Kgf/cm2 15.800 15.100 2 of elasticity Kgf/cm 15,800 15,700 - - - - 1 3 > Flexurdl stieigtli ' " 330 - - - 'I 4J ceec Tensile stiej,,1t1, 265 220 - - - - ma E a Izod /cm 6.1 t.cucm strength gl.cm/cm 6.1 5.8 - - - - Note: A2: pentaerythritol triacrylate E2: borax F2; ethylene-propylene block copolymer cont@@@ing 12% by weight of ethylene (M.F.R. 2.5 g/10 min.) Cl:Tdl k G2: WollastulultC Others are tlie same with the lute I Table 2.

As understandable from the description of Table 2, it can be seen that extinguishing property, glow time and dripping property are all greatly improved.

Namely, as indicated in Comparative example 6, simple increase of the amount of a halogen-contain ing flame-retardant and antimony trioxide provides good extinguishing property but melt-falling oftest specimen were observed and dripping property was not improved at all. It can be seen that those in which combination same with thatof specific example 3 was made except that a crosslinking agent and a radical generating agent as in Comparative example 4were not added, did not show extinguishment and melt fallen materiais were observed, and it is observed that neither extinguishing property nor dripping property was improved.Those in which addition of a halogencontaining flame retardant and antimonytrioxide was merely increased, relative to Comparative example 4 as in Comparative example 7 improves exting uishing propertybutmeltfallingoftestspecimenwas observed and dripping property was not improved.

Further, in a system in which a boron compound was removed from specific example 3, as in Comparative example 5, extinguishment property and dripping property showed satisfactory result but a glow time was considerably longer. The first goal of this glow time is 30 seconds or less and the second goal is 60 seconds or less but considering from these results, it cannot be said that this system is satisfactory.

Whereas it has been revealed that extinguishment property, glow time and dripping property were all improved. Further, specific example 4 is directed to a case where ethylene bis(tetra - bromophthalimide) was used as a halogen-containing flame-retardant but extinguishment property and dripping property are improved.

Referring nowTable3, specific example 5 is directedto a case where an ethylene propylene block copolymer having an ethylene content of 12% by weight (M.F.R. 2.5 g/l 0 min.) was used as a polyolefin resin and showed good extinguishment, glowtime and dripping property, similarilyas in specific example 3. Comparative example 8 is directed to a case where only a radical generating agent is removed from specific example 5 but it is seen that both extinguishment and dripping property were worse and the effectiveness of a crosslinking agent is not exhibited due to the non-existence of a radical generating agent.It is observed that simple increase ofthe amounts of a halogen-containing flame retardant, and antimonytrioxide, makes extinguishment bettersimilarily as in Comparative example 7, melt-falling oftest specimens were observed.

Further, specific examples 6~7 correspond to the cases where an inorganic filler are added to specific example 5. Self-extinguishmentand dripping proper ty were good but a glowtime is inferior to specific example 5to some extent. Specific example 8 is directed to a case where pentaerythritol triacrylate is used as a crosslinking agentandexample9is directed to a case where borax is used as a boron compound and it has been revealed that superior extinguishment, dripping property and glowtime were exhibited as in specific example 5.

Claims (10)

1. Aflame-retardant polyolefin composition com prising the following components (A), (B), (C), (D), (E) and optionally (F), where the percentages are based on the total weight ofthe components (A) to (E) or (A) to (F), except where a different basis is specified: (A) 0.1 to 15% byweightofcrosslinking agent; (B) 0.005 to 5% by weight of a radical-generating agent; (C) 5 to 60% by weight of a halogen-containing flame-retardant; (D) 100 to 10% by weight of antimonytrioxide relative to the halogen-containing flame-retardant; (E) polyolefin resin; and (F) optionally 1 to 10% byweightofa boron compound.

2. Aflame-retardant polyolefin composition according to Claim 1, wherein the polyolefin resin is at least one resin selected from propylene homopolymer; a random copolymer of two or three of ethylene, propylene and butylene; a block copolymer of two or three of ethylene, propylene and butylene; ethylene-vinylacetate copolymer; or ethylene-propylene rubber.

3. Aflame-retardant polyolefin composition according to Claim 1 or2wherein the crosslinking agent is at least one agent selected from triallyl cyanurate, triallyl isocyanu rate, diethyleneglycol dimethacrylate, trimethylol propanetriacrylate, trimethylol propane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, divinyl benzene, diallyl phthalate, divinyl pyridine,vinyl toluene, ethyl vinyl benzene, styrene monomer, quinone dioxime, benzoquinone dioxime, p-nitrosophenol N,N'-m-phenylene bis maleimide, vi nyltriethyoxysilane, y - metharyloxypropyltrimethoxysilane ory -aminopropyltriethyoxysilane.

4. Aflame-retardant polyolefin composition according to Claim 1,2 or 3 wherein the halogencontaining flame-retardant is at least one flame retardant selected from decabromodiphenyloxide and ethylene - bis - tetrabromophthalimide.

5. A flame-retardant polyolefin composition according to any preceding Claim wherein the radical generating agent is at least one agent selected from dicu myl peroxide, 2,5 - dimethyl -2,5 - di - (t butylperoxy)hexane,2,5- dimethyl - 2,5 - di(t butylperoxy)hexane --3; 1,3 -bis(t - butylperoxyisopropyl)benzene, 1,1,4,4,7,7 - hexamethylcyclo - 4,7 diperoxynonane, cumenehydroperoxide and cumyl peroxytrimethylsilane.

6. Aflame-retardant polyolefin composition according to any preceding claim wherein the boron compound is present and is at least one compound selected from borax, potassium borofluoride, sodium borofluoride and ammonium borofluoride.

7. Aflame-retardant polyolefin composition according to any preceding claim, when prepared by mixing the components (A) to (E) and also (F) when required, and melting and kneading the mixture.

8. Aflame-retardantpolyolefin composition according to any of claims 1 to 7, when prepared by mixing the components (A), (B) and (E), melting and kneading the mixture, and blending in the components (C) and (D) and also (F) when required.

9. Aflame-retardant polyolefin composition according to any preceding claim, wherein the percentage amountfor at least one of the following components is in ranges: (A) 0.5 to 10%; (B) 0.01 to 1% (C) 5 to 50%; or (F) 1 to 8%; where the basesforthe percentages are as in claim 1.

10. Aflame-retardant polyolefin composition according to any preceding claim and containing one or morefurthercomponents.