GB1586327A

GB1586327A - Flame-resistant composition and electrical product thereof

Info

Publication number: GB1586327A
Application number: GB20808/78A
Authority: GB
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1977-07-18
Filing date: 1978-05-19
Publication date: 1981-03-18
Also published as: JPS5654020B2; DK321778A; YU171178A; JPS5440842A; CA1121534A; JPS5696408A; DE2821652C2; DE2821652A1; YU39424B; FR2398372A1; SE7807903L; FR2398372B1; HU179188B

Description

(54) FLAME-RESISTANT COMPOSITION, AND ELECTRICAL PRODUCT THEREOF (7i) We, GENERAL ELECTRIC COMPANY, a Corporation organized and existing under the laws of the State of New York, United States of America, of 1 River Road, Schenectady, 12305, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The increased use of polymeric compositions, such as polyolefins, in many and diverse applications or products, and the combustibility of such polymeric materials, has greatly stimulated the investigation of flame-proofing measures for polymeric compositions.Moreover, the high costs of fire damage in lives and property, and the imposition of increasingly stringent safety regulations, have recently significantly intensified the pursuit of more effective or practical means of controlling or inhibiting combustion and the propagation thereof in many products and materials.

Notwithstanding prior developments of a great number of flame-proofing measures or additives resulting from this expanding effort, there remains a continuing need for improvements to meet current or new requirements in this area.

This invention comprises the discovery of the improved resistance to flame or combustion, and the propagation thereof, and other advantages attributable to the combination of decabromodiphenyl ether, silicone gum and dibasic lead phthalate with cross-linked polyolefins, such as polyethylene, and other ingredients. The invention thus relates to flame-resistant polyolefin compounds, and it has particular utility in flame-proofing electrical insulations comprising ethylenecontaining polymer compounds which have been cross-link cured.

The drawing comprises a perspective view of an insulated conductor comprising a metallic element having a cross-linked polyolefin insulation thereabout.

In accordance with this invention, a cured polymeric compound having a high level of resistance to flame and combustion, and deformation and flow at high or flame temperatures, among other improved and advantageous attributes, is provided by a polyolefin composition comprising cross-linked ethylene-containing polymers, decabromodiphenyl ether, silicone gum and dibasic lead phthalate.

This invention provides a flame-resistant, cross-link cured polyolefin composition which comprises Polyolefin (as hereinafter defined) 100 parts by weight Decabromodiphenyl ether 15--50 parts by weight Silicone gum 3-10 parts by weight Organic lead salt 3-10 parts by weight Antimony oxide 5-25 parts by weight Fumed silica 3-10 parts by weight This invention also provides a cross-linked product obtained by curing a composition as defined above with a peroxide curing agent or by irradiation and an electrical conductor comprising a metallic conductive element having thereon such a cross-linked polyolefin composition.

The polyolefin compositions used according to this invention are ethylenecontaining polymers such as polyethylene, copolymers of ethylene and other polymerizable materials, and blends of such polymers including copolymers.

Typical copolymers of ethylene and other polymerizable materials include, for example, ethylene-propylene copolymers and ethylene-propylene diene terpolymers, ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers, and ethylenebutene copolymers.

The flame-resistant, cross-link cured polyolefin compositions of this invention can comprise fillers, pigments, curing coagents, and other conventional additives including preservatives such as anti-oxidants, modifying agents, mold release ingredients, processing aids or lubricants such as lead or zinc stearates in minuscule amounts of 1 to 5 parts by weight, which are commonly compounded with polyolefins, in addition to the essential ingredients or basic components thereof set forth hereinafter, i.e. the decabromodiphenyl ether, silicon gum, organic lead salt, (e.g. dibasic lead phthalate), antimony oxide and fumed silica.

The invention applies to and includes all of the above-referred polyolefins when cross-link cured and thermoset by a heat-activated peroxide cross-linking agent such as disclosed in U.S. patents 2,888,424; 3,079,370; 3,086,966 and 3,214,422, or by irradiation. Suitable peroxide cross-link curing agents comprise organic tertiary peroxides characterized by at least one unit of the structure:

which decomposes at a temperature above 295"F and thereby provide free radicals. Peroxide curing agents can be used in amounts of 2 to 8 parts by weight per 100 parts of the polymer. A preferred peroxide is a di--cumyl peroxide, and other apt peroxides comprise the tertiary diperoxides such as 2,5-dimethyl-2,5-di (tbutyl peroxy) hexane and 2,5-dimethyl-2,5-di(t-butyl peroxy) hexyne-3, and the like diperoxy and polyperoxide compounds.Also a curing coagent such as triallyl cyanurate is preferably employed in amounts of up to 5 parts by weight per 100 parts of the polymer. Radiation cross-link curing can be produced by high energy electrons, X-ray and the like sources of irradiation.

The organopolysiloxane gum or elastomer used according to this invention, comprises gums or organopolysiloxanes which have been condensed to a high molecular weight polymer of a gummy elastic, substantially semi-solid state. For example a typical silicone elastomer for use in the composition of this invention is a class of dimethylpolysiloxanes having the chemical structure:

Another class of silicone elastomers for use in this invention comprises the methyl-phenyl polysiloxanes. Further examples of the type of silicone elastomer gums usable in obtaining the compositions of this invention comprise the organopolysiloxanes referred to in U.S. patents 2,888,424 and 2,888,419, and identified in detail in U.S. patents 2,448,556; 2,448,756; 2,457,668; 2,484,595; 2,490,357; 2,521,528; 2,541,137; 3,098,836; and 3,341,489.Such high molecular weight siloxane polymers normally have Brookfield viscosities in excess of 100,000 centipoise at 250C.

The lead component preferably comprises dibasic lead phthalate.

The fumed silica preferably comprises a form of silica described in U.S. patent 2,888,424, and a type which is sold under the trade designation of Cab-O-Sil MS7 of Godfrey L. Cabot, Inc., of Boston, Massachusetts ("Cab-O-Sil" is a Registered Trade mark).

The combination of decabromodiphenyl ether, silicone gum and dibasic lead phthalate and other ingredients of this invention can be mixed and combined with a polyolefin component by means of any conventional compounding method or apparatus, such as working in a Banbury mixer or on a two roll rubber mill.

Preferably the ingredients of the compound formulation, except those which are sensitive to the relatively moderate mixing temperatures of 300 F to 4000 F, such as a heat decomposable peroxide curing agent, are combined and initially admixed together or substantially uniformly dispersed with each other at a temperature sufficient to soften and plasticize- the particular polyolefin ingredient. Following the attainment of substantial uniformity of the admixed ingredients, the temperature of the admixed batch is reduced below the decomposition level of the particular peroxide curing agent, or other heat sensitive ingredient, and the curing agent or any other sensitive ingredient is then introduced and dispersed preferably uniformly in the mix.

The proportions of the flame-proofing combination of decabromodiphenyl ether, silicone gum, dibasic lead phthlate and the like ingredients admixed with the polyolefin compounds depend, of course, upon the desired or required degree of resistance to flame and combustion, and the content of polymeric or other combustible materials in the overall compound. The necessary amounts for effective flame resistance in polyolefins comprise 15 to 50 parts by weight of the decabromodiphenyl ether, 3 to 10 parts by weight of the silicone gum, and 3 to 10 parts by weight of the dibasic lead phthalate, per 100 parts by weight of the organic polymer content of the compound.

In accordance with this invention, the level of resistance to flame and deformation or flow at high or flame temperatures provided by the combination of decabromodiphenyl ether, silicone gum and organic lead salt, and other ingredients of this invention with a polyolefin compound is enhanced by the inclusion of an oxide of antimony, such as antimony trioxide, in the composition in amounts from 5 to 25 parts by weight per 100 parts by weight of the polyolefin.

Typical formulations for the practice of this invention comprise, in relative parts by weight, the following combinations of essential and preferred ingredients.

Ingredient Parts by Weight Polyolefin 100 Decabromodiphenyl ether 15-50 Silicone gum 3-10 Dibasic lead phthlate 3-10 Antimony oxide 5-25 Fumed silica 3-10 Clay 0--25 Antioxidants 1--10 Processing aid or molding lubricant Curing coagent 03 Organic peroxide curing agent 2-5 The following comprise examples of the novel and improved flame resistant polyolefin composition of this invention, with the ingredients given in relative parts by weight.

The test specimens for each example were compounded in a typical manner, comprising combining all ingredients, except the peroxide curing agent, at a temperature of 100"C+5"C for about 5 minutes, then adding and blending in the peroxide for another 5 minutes at the same temperature, and curing the sample specimens thereof at 1770C for 30 minutes in a press.The composition of the specific formulations and their properties after curing are set forth below: Ingredients Examples Parts By Weight I II Polyethylene 100 100 Decabromodiphenyl ether 40 25 Silicone gum 6.25 5 Dibasic lead phthalate 5 5 Antimony oxide 14 10 Fumed silica 5 5 Clay 15 Antioxidants Polymerized trimethyl dihydroquinoline, Agerite MA 1.5 - 4,4'-thiobis-(6 tert-butyl-m cresol), Santowhite Crystals* 0.25 Thioester bis hindered-phenol, Irganox 1035* 3 Thio dipropionate polyester, Poly TDP 2000 3 Processing aid Lead stearate 1 Vinyl silane - 1.25 Curing coagent-triallyl cyanurate 1 Peroxide curing agent-dicumyl peroxide 2.5 2.5 Properties Examples 1 11 Oxygen Index Value 28.4 27.2 UL-44 FR-I Flame Test passed passed Original Tensile strength, psi 2460 2233 Original Elongation, percent 400 376 Heat Treated 7 Day at 1509C Percent Retention-Tensile, psi 88 99 Percent Retention-Elongation 91 90 Heat Treated 30 Days at 1 360C Percent Retention-Tensile, psi 89 92 Percent Retention-Elongation 88 80 Heat Treated 60 Days at 1360C Percent Retention-Tensile, psi 89 99 Percent Retention-Elongation 82 82 Heat Treated 90 Days at 1360C Percent Retention-Tensile, psi 55 60 Percent Retention-Elongation 34 19 * "Santowhite" and "Irganox" are Registered Trade Marks The flame resisting properties of the examples of the compositions of this invention were all identically evaluated by the Oxygen Index Test (ASTM D2863-7-) which designates the fraction of oxygen by volume in nitrogen required to just maintain flaming of the material of the test sample. Thus, the higher the oxygen index for a composition, the better its resistance to combustion and flame.

Referring to the drawing, there is shown a typical construction for an insulated electrical wire or cable product 10, comprising a metallic conductive element 12 and an overlying body of cured polymeric insulation 14 extending thereabout or covering the conductor. In the drawing, the product 10 is illustrated as a short section with the insulation 14 removed from the end portion of the conductor 12.

According to one embodiment of this invention, the novel flame-resistant polyolefin thereof can be used to provide or form the insulation 14 on conductive element 12 of wire or cable product 10. It is to be understood from the foregoing, however, that the insulation can comprise a coating on any portion of a conductive element and that the insulation need not completely enclose the element where such is not necessary for a desired insulative effect.

Claims

WHAT WE CLAIM IS:

1. A flame-resistant, cross-link cured polyolefin composition which comprises Polyolefin (as hereinbefore defined) 100 parts by weight Decabromodiphenyl ether 15-50 parts by weight Silicone gum 3-10 parts by weight Organic lead salt 3-10 parts by weight Antimony oxide 5-25 parts by weight Fumed silica 3-10 parts by weight

2. A composition as claimed in Claim 1, wherein the polyolefin comprises polyethylene, a copolymer of ethylene and other polymerizable material, or a blend of such polymers.

3. A composition as claimed in Claim 1 which comprises Polyethylene 100 parts by weight Decabromodiphenyl ether 40 parts by weight Silicone gum 6.25 parts by weight Dibasic lead phthalate 5 parts by weight Antimony oxide 14 parts by weight Fumed silica 5 parts by weight Antioxidant 1.75 parts by weight Triallyl cyanurate curing coagent 1 parts by weight Organic tertiary peroxide curing agent 2.5 parts by weight

4. A composition as claimed in Claim 3, wherein the antioxidant comprises 1.5 parts by weight of polymerized trimethyl dihydroquinoline and 0.25 parts by weight of 4,4'-thiobis (6 tert-butyl-m-cresol).

5. A composition as claimed in Claim 1 which comprises Polyethylene 100 parts by weight Decabromodiphenyl ether 25 parts by weight Silicone gum 5 parts by weight Dibasic lead phthalate 5 parts by weight Antimony oxide 10 parts by weight Fumed silica 5 parts by weight Clay 15 parts by weight Antioxidants 6 parts by weight Vinyl Silane 1.25 parts by weight Triallyl cyanurate curing coagent I parts by weight Organic tertiary peroxide curing agent 2.5 parts by weight

6. A composition as claimed in Claim 5 wherein the antioxidant comprises 3 parts by weight of thioester bis hindered-phenol and 3 parts by weight of thio dipropionate polyester.

7. A cross-linked polyolefin composition which comprises the product of curing a composition according to any preceding Claim with a peroxide curing agent or by irradiation.

8. An electrical conductor comprising a metallic conductive element having thereon a flame-resistant, cross-link cured polyolefin as claimed in Claim 7.

9. A flame retardant polyolefin composition as claimed in Claim 1 and substantially as hereinbefore described with reference to Example I or II.

10. An electrical conductor as claimed in Claim 8 and substantially as hereinbefore described.