NL8301474A - FLAME-RETARDANT CROSS-BAND POLYALKENE INSULATION MATERIAL. - Google Patents

Description

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Flame retardant cross-linked polyolefin insulating material.

The invention relates to cross-linkable polymeric mixtures containing moisture; are heat and flame resistant and suitable for the manufacture of insulated wire and insulated cables as well as molded products. More particularly, it relates to an ethylene-vinyl acetate copolymer blend having a high degree of flame retardancy.

One of the most important areas in which fire resistant polymer blends are applied is in an electrical environment, where both insulating or fire retardant properties are pursued, more particularly in the field of conductor insulation.

There was a time when extrudable blends available in the wire and cable flame retardant range required that they contain halogenated polymers such as chlorinated polyethylene, polyvinyl chloride, chlorobutadiene, chlorinated paraffin, etc., together with, antimony, trioxide both components being present in temporally large amounts. Alternatively, a chlorosulfonated polyethylene paint coating was applied to a non-flame retardant insulating compound, which involved an additional operation.

For certain types of dry transformers, especially high voltage transformers, a problem was that electrical errors occurred due to surface creep of the organic insulating compound used. The problem was solved by the addition of hydrated alumina to mixtures whose organic binder consisted of butyl rubber, epoxy resins or polyester resins. However, these blends do not have a balance of excellent extrudability properties, physical and electrical properties, heat resistance and flame retardancy. Such blends are disclosed in U.S. Pat. Nos. 2,997,526; 2,997,527 and 2,997,528. The disclosed blends for such use have poor tensile strength, elongation 30 and percent permanent elongation after aging.

Fire-retardant polymeric mixtures which, inter alia, exhibit improved moisture and heat resistance and mainly consist of an intimate mixture of at least one crosslinkable polymer, the main component of which is an ethylene-vinyl acetate copolymer, one or more silanes and one or more hydrated inorganic fillers have found wide acceptance in the wire and cable field. Such blends are disclosed in U.S. Pat. Nos. 3,832,326 and 3,922,442.

These patents disclose mixtures containing from 80 to 400, preferably 5, 125 to 140 parts of filler per 100 parts of polymer and 0.5 to 5.0 parts of silane per 100 parts of filler. No specific concentration range of lubricant has been disclosed, although 2 parts of calcium stearate per 100 parts of polymer are used in all fourteen blends of the examples.

The known polymeric blends of the latter US patents show a balance of improved physical and electrical properties combined with a high degree of flame and fire retardancy. These highly desirable results are achieved without the use of halogenated polymers such as polyvinyl chloride and chlorosulfonated polyethylene, removing hydrogen chloride vapors; without soot allowing use as colored insulations; without any flame retardant coatings as usually required thereby eliminating an additional process step when the blends are used, for example, as insulating compounds extruded on a conductor.

Such blends are used in particular as white (an inherent property) and colored uni-insulation which can be extruded over metal, eg copper or aluminum, conductors, to provide single layer insulation or mantle that according to ü.L. standards for 90 ° C operation are judged and in some cases to temperatures of up to 125 ° C and up to 600 volts.

The insulating blends of US patents have proved particularly useful for insulating switchboard wire, gear wire, and wires related to motorized vehicles. a unique combination of superior electrical properties combined with resistance to the decomposing effects of heat and fire are essential and where low smoke density and non-corrosive vapors are desired.

In the latter two US patents, ethylene-vinyl acetate copolymers are cross-linked in their mixtures by irradiation with high energy sources or by chemical cross-linking agents. As observed with other radiation-cured polymer mixtures, the radiation-cured mixtures prepared in accordance with said U.S. patents have poorer physical strength properties than the corresponding mixtures cured with peroxide. The reasons for this are not fully understood, although the exact nature and amount of the major and minor components in the mixture are believed to contribute to this. Various modifications were tested with the peroxide cured product to obtain the radiation cured equivalents. The copolymer in the radiation cured product has a high vinyl acetate content and aluminum stearate has replaced the calcium stearate lubricant. Although this has improved the physical strength of the radiation cured mixtures beyond what it would be, it is still significantly lower than the peroxide cured product.

U.S. Patent 4,349,605 describes a radiation cross-linked polymer blend having improved physical strength properties substantially similar to a chemically cross-linked. corresponding polymer blend. The improved physical strength properties are obtained by using increased amounts of slitting and the substitution of the mold Wiz lubricant for the aluminum stearate lubricant.

In addition to the three essential components, other additives may be included in the blends of U.S. Pat. Nos. 3,832,326 and 3,922,442 to achieve certain desirable properties. Among these additives are pigments, antioxidants and stabilizers.

Antioxidants are included to slow down polymer degradation due to oxidation that takes place according to a free radical chain mechanism. The antioxidants work either by binding the peroxy radicals so that free radicals are unable to propagate the chain of reaction, or by decomposing the hydroperoxides in such a way that carbonyl groups and additional free radicals are not formed. The former chain-breaking antioxidants called free radical cleaners or retarders are usually hindered phenols, amines and the like. The latter, referred to as peroxide decomerers, are generally sulfur compounds (viz. Mercaptans, sulfides, 8301474 [4] disulfides, sulfoxides, sulfones, thiodipropionic acid esters and the like), or metal complexes of dithiocarbamates and dithiophosphates.

The prior art also describes stabilizers for synthetic resins such as in U.S. Patent 4,279,805, which describes an alkylene bis-thioalkanecarboxylic acid amide as a stabilizer and as corrosion retardants, for example, in U.S. Patent 4,124,549.

U.S. Patent 4,255,303 discloses a blend for electrical applications with electrical resistance, tensile strength and elongation comprising ethylene-vinyl acetate, a halogenated flame retardant, antimony trioxide, peroxide and zinc stearate. US Patent 4,035,325 discloses a combination in which the effectiveness of flame retardant combinations of antimony trioxide and halogen containing compounds such as hexabromocyclododecane (HBCD), chlorinated paraffins, tetrabromophthalic anhydride (TBPA) and tetrabromoterphalic acid (TBTA) is deliberately increased by the addition of certain organometallic compounds which have the chemical structure of either substituted hydrazines or substituted 3-amino-1,2,4-triazole amides.

According to the present invention there is provided a polymer blend with a lubricant system that also significantly improves the flame retardancy of the blend.

According to the invention it has been found that a significant flame retardant property can be obtained in ethylene copolymer (in particular ethylene-vinyl acetate copolymers) mixtures containing silane-treated hydrated inorganic fillers using a lubricant mixture consisting of a fatty acid of 8 to 25 carbon atoms and an alkylene bisamide wherein the alkylene group has from 2 to 8 carbon atoms and the amide component has from 8 to 25 carbon atoms, said lubricant being preferably used in combination with antimony trioxide and a halogenated flame retardant additive except for the normally flame retardant hydrated alumina. More specifically, the present blend comprises the use of the above-described lubricant mixture in place of the normal calcium stearate-lubricant normally used in the above-described combinations. More particularly, the invention is directed to a cross-linkable polymer mixture comprising: a) a copolymer of ethylene and a vinyl ester of a C 1 -C 8 aliphatic carboxylic acid, a C 1 -C 6 alkyl acrylate or C 1-6 CLalkyl-2. o 1 o 1 o methacrylate, 5 b) 80 - 400 parts of hydrated inorganic filler per 100 parts of copolymer, c) 0.4 to 8 and preferably 0.8 to 4 parts of an alkoxysilane per 100 parts of hydrated inorganic filler and d) an anti-flame component containing a halogenated flame retardant, antimony trioxide in addition to the normal flame retardant, hydrated inorganic filler and quite surprisingly a two-component lubricant system comprising a fatty acid of 8 to 25 carbon atoms and an alkylene bisamide in which the alkylene group has 2 to 8 carbon atoms and the amide group has 8 to 25 carbon atoms.

The present invention can also be described as relating to an improvement in a crosslinkable polymer mixture of the type a) a copolymer of ethylene and a vinyl ester of a C 2 -C 8 aliphatic carboxylic acid, alkyl acrylate or a C 1 -C 8 alkyl- methacrylate and b) a silane-treated hydrated inorganic filler, wherein the concentration of said filler is 80 to 40 parts of filler per 100 parts of copolymer, c) halogenated flame retardants and anti-mononoxide, which is used as an unusually effective flame retardant. a two-component lubricant system comprising a fatty acid of 8 to 25 carbon atoms and an alkyl 30-leen bisamide in which the alkylene group contains 2 to 8 carbon atoms and the amido group contains 8 to 25 carbon atoms.

The invention also relates to an electrical conductor coated with a single insulating layer containing these crosslinkable polymeric mixtures.

The invention relates to cross-linkable polymeric mixtures comprising copolymers of ethylene and a vinyl ester of an 8301474

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6-fatal carboxylic acid, an alkyl acrylate or an alkyl methacrylate and a silane-treated hydrated inorganic filler which, when used with a two-component lubricant system as described above in combination with antimony trioxide and halogenated and non-halogenated flame retardants, has very strong flame retardant properties. These mixtures are used in particular for wire and cable insulation.

Mixtures according to the invention contain, in addition to a special lubricant combination, one or more halogenated flame retardants and optionally antimony trioxide, one or more cross-linkable or curable ethylene copolymers, one or more silanes and one or more hydrated inorganic fillers. The copolymers, silanes and inorganic fillers include those disclosed in US Pat. Nos. 3,832,326 and 3,922,442, which are considered to be incorporated herein.

The terms cross-linkable or cross-link have their normal meaning in the present description, i.e., they indicate the formation of primary valence bonds between polymer molecules.

Cross-linking can be carried out by any of the known methods, such as chemical, including peroxide cross-linking. irradiation using cobalt-60, accelerators, 8-rays, γ-rays, electrons, X-rays, etc. or by thermal cross-linking. The basic methods of cross-linking polymers are particularly well known in the art and need not be described in detail here.

The polymeric component of the present blend is a copolymer of ethylene and a copolymer, which can be a vinyl ester, an acrylate or a methacrylate. The vinyl ester can be a vinyl lester of a C2 "Cgaliphatic carboxylic acid, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pentanoate or vinyl hexanoate. The acrylates and methacrylates can be any of the C 1 -C 6 alkyl esters including, for example, methyl, ethyl, propyl, butyl, pentyl or hexyl acrylate or methacrylate.

The preferred copolymer comprising the polymeric component of the invention is an ethylene-vinyl acetate copolymer that is about 6 to about 90%, preferably about 90 to about 40%, most preferably about 9 to about 28% vinyl acetate and the balance contains ethylene.

Although little recovery and some properties 8301474 # 7 are even impaired, it is possible to include minor amounts of other crosslinkable polymers or copolymers in the mixture of the invention. However, ethylene copolymers, preferably ethylene-vinyl acetate copolymers as described above, should make up at least about 66% of the total polymers present. Representative of such minor polymeric components that can be used in such non-preferred embodiments are polyethylene, copolymers of ethylene with propylene, butene, the acrylates and maleates, polydimethylsiloxane and polymethylphenylsiloxane, copolymers of vinyl acetate with the acrylates, etc. Of course, blends of these minor polymeric components are used.

Terpolymers of ethylene and vinyl acetate derived from, for example, any of the corresponding monomeric materials as mentioned above (other than ethylene or vinyl acetate) can be used. A representative terpolymer is an ethylene-vinyl acetate-vinyl maleate terpolymer.

The ethylene-vinyl acetate copolymers used in the invention preferably have a melt index of from about 1.0 to about 20.0.

The polyethylenes useful in the present invention essentially include all high, medium and low density polyethylenes as well as mixtures thereof. The most preferred polyethylenes for blending for use as a single layer insulation for electrical wires and cables generally have a density of from about 0.900 to about 0.950 g / cm3 and a melt index of from about 1.0 to about 10.0.

More specifically, the blends of the invention surprisingly provide a very strong flame-retardant blend using a two-component lubricant, retaining other desirable properties including an unexpected balance of: 1. low temperature brittleness, ie the blend does not will tear easily during low temperature movement (ASTM D 746).

35 2. Heat resistance after aging, i.e. an excellent stretch after extensive use at 90 ° C and even 125 ° C.

8301474 8 3. Resistance to arcing and breakdown resistance up to 5 kV, while even porcelain has a surface breakdown of 4 kV. However, this property is not often required, in the preferred environment of below 600 volts service.

5 4. moisture resistance, ie low mechanical absorption of water, resulting in an increased dielectric constant.

5. Resistance to industrial chemicals.

6. Resistance to oil and petrol or diesel fuels.

It is not known why the mixtures according to the invention exhibit such a superior balance of properties. There may be some synergistic relationship between the ethylene-vinyl acetate copolymer, silane and hydrated inorganic filler, but the applicant does not wish to commit to such a theory.

15 However, it has been determined that for low voltage environments, less than 5000 volts. even more particularly for less than 600 volts the mixtures according to the invention are particularly suitable for use as sole insulation, uni-insulation is a term accepted in this field by which an insulation is indicated, whereby a layer is placed around the conductor. extruded and this single layer serves as electrical insulation and as a jacket for providing physical and flame protection. The present blends are particularly suitable for use as uni-isolation in the below 5000 volts range, and more particularly in the below 600 volts range, where only a single extruded coating is used and in this environment superior balance of properties required. Furthermore, it has been found that ethylene-vinyl acetate copolymers will retain very large amounts of fillers and nevertheless exhibit a high flexibility and a high degree of cross-linking. Simultaneously obtaining high filler loading, flexibility and crosslinking is very surprising since high flexibility and high crosslinking were generally considered incompatible as well as high crosslinking and high filler loading (implying low crosslinkable polymer content). Ethylene-vinyl acetate copolymers further provide improved flame retardancy to the polymer blends of the invention.

The above-described ethylene-vinyl acetate copolymers can be cross-linked by irradiation with high energy electron beams or using chemical cross-linking additives. Fully cross-linked, these polymers are thermally cured in behavior. In the preferred mixtures of the invention, chemical cross-linking is preferred, especially where improved physical strength is required.

Chemical cross-linking is accomplished by adding a cross-linking agent, for example dicumyl peroxide or a, a'-bis (t-butyl peroxy) diisopropyl benzene to the ethylene-vinyl acetate copolymer.

The peroxide is later activated during processing to join the ethylene-vinyl acetate polymer chains into a three-dimensional network (and other minor amounts of cross-linkable polymer, if any).

The chemical cross-linking is carried out according to the methods known in the art and changes in the general cross-linking conditions as set forth below will be apparent to those skilled in the art. Moreover, the present invention is not limited to the use of tertiary organic peroxides for chemical cross-linking and other kind of recognized materials which decompose while providing free radicals. Of course, such crosslinkers should not decompose during the mixing of the mixture, but the selection of acceptable crosslinkers will be apparent to those skilled in the art.

In general, it can be said that as the amount of cross-linking agent used increases, the degree of polymer cross-linking increases. Usually no more than 10% (based on the polymer) of the organic tertiary peroxides need to be used, with 3 to 6% being more typical values. Other cross-linking agents may require different amounts, but these can be easily determined. It is often recommended to avoid very small amounts of cross-linking agents as some loss of resistance to deformation under sudden or continuous pressure may result. Cross-linking coagents such as triallyl cyanurate and the like may also be included to increase the cross-linking agent's effectiveness.

The tertiary organic peroxides, like most other chemical cross-linking agents, are activated by heating to above their activation temperature after which decomposition takes place. Any of the known methods can be used for this activation, for example treating the mixture with high pressure steam.

The technique of cross-linking by irradiation is so strongly developed that nothing needs to be said with regard to these methods. When higher total radiation doses are used, the degree of cross-linking generally increases, and for preferred cross-links a total radiation dose of about 5 to 25 megarads will be used.

Cross-linking generally takes place at superatmospheric pressures, for example of the order of 14 to 28 kg / cm 2, although higher or lower pressures may be used. Pressure is needed when steam cured to achieve the required activation temperature of the peroxide catalyst. When curing with high temperature gas, pressure is desired to avoid porosity in the insulation. Porosity is highly undesirable in electrical insulation as it lowers electrical insulating properties and can cause premature corona breakage.

In general, it can be said that the higher the degree of cross-linking, the more resistant the polymer mixture to heat, moisture, chemical reagents, aging changes and environmental conditions, etc., and usually is wear. At lower degrees of cross-linking, there is also some loss of heat resistance as well as a pronounced effect on the percent stretch after. aging. The precise degree of cross-linking can, of course, be changed to take into account the above factors and their effect on the final product. Although higher or lower values can be used for wire and cable insulation, a crosslinking rate of the order of about 85-95% for ethylene-vinyl acetate is generally preferred determined by the extraction weight of soluble components in the cross-linked polymer.

One or more substituted silanes are the second essential component of the polymer blends of the invention.

Any silane can be used in the present invention that does not adversely affect the desired balance of properties.

And that helps promote the bond between the polymer and the inorganic filler according to the invention provided that the silane does not make the mixture incombustible and does not interfere or degrade the polymer cross-linking during the processing of the polymer, for example, alkoxy and amine Cocks .

The silanes which are preferred in forming the insulating mixtures according to the invention are the alkoxy silanes, for example lower alkyl, alkenyl, alkynyl and arylalkoxy silanes as well as the lower alkyl, alkenyl, alkynyl, and arylalkoxyalkoxy or aryloxy- alkyl silanes. Specific examples of such silanes are methyl-triethoxy, methyltris (2-methoxyethoxy), dimethyldiethoxyalkyl-trimimex-10-vinyl, tris (2-methoxyethoxy), phenyl-tris (2-methoxyethoxy), vinyltrimethoxy- and vinyltriethoxysilane .

For best results, it is recommended to use the vinyl silanes, and of the vinyl silanes, the following are particularly preferred: 15-methacryloxypropyltrimethoxysilane (formula 1 of the formula sheet) and vinyl tris (2-methoxyethoxy) silane (formula 2 of the formula sheet).

The fillers used in the invention are the hydrated inorganic fillers, for example hydrated aluminum oxides (Al 2 O 3. 3 ^ 0 or Al (QH) 3), hydrated magnesium oxide, and hydrated calcium silicate. Of these compounds, the hydrated alumina is most preferred.

To achieve the described superior balance of properties, it is required that a hydrated inorganic filler be used to formulate the polymer blends.

It is emphasized that large amounts of another type of filler, whether or not inert, cannot be incorporated into the blends while still achieving the superior balance of properties.

The water of hydration of the inorganic filler must be released during the addition of heat sufficient to cause combustion or ignition of the ethylene-vinyl acetate copolymer. The water of hydration chemically bonded to the inorganic filler is released endothermically. It has been found that the hydrated inorganic filler increased flame retardancy in a manner far superior to other fillers previously used in this field for 8301474

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12 to provide flame retardant insulation, for example, carbon black, clays, titanium dioxide, etc. Even more surprising is that flame retardancy is combined with excellent electrical insulating properties at the high filler loadings employed, since at these loadings the copolymer mixture contains a large amount of bound water. contains.

The filler size should be consistent with those used in the prior art.

An antioxidant mixture which may also be included as a component of the polymeric blends of the invention includes a diester of thiodipropionic acid, wherein the preferred diester is distearyl-3,3'-thiodipropionate (DSTDP). It has been found that the use of two different types of antioxidants provides an effective oxidation delay. Thus, a mixture of a chain-breaking type antioxidant and a peroxide decomposer provides a highly effective antioxidant mixture. Therefore, with DSTDP, which is a known peroxide decomposer, an amine or a hindered phenol can be used effectively as an antioxidant mixture. Among these free radical cleaners, the sterically hindered phenols are particularly effective. Suitable phenols include the alkylated phenols, the alkylidene bis-alkylated phenols and the polyphenols. Specific examples thereof include 2,6-ditertiary butyl-pararcresol, octadecyl 3,5-di-t-butyl-4-hydroxy-hydrocinnamate, 2,2'-methylene-bis (6-t-butyl-4-methylphenol ), 4,4'-butyl-idene-bis (6-t-butyl-3-methylphenol), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl- 4-hydroxybenzyl) benzene and tetrakis (methylene (3,5-di-t-25-butyl-4-hydroxy-hydrocinnamate) methane, the latter being particularly preferred.

When polymeric insulation is formed on conductors by extrusion, it is preferred that a lubricant form part of the insulating mixture. Such lubricants such as a fatty acid soap or a metal derivative thereof have hitherto been used. The lubricant not only promotes the extrusion process, but also improves the stripping properties of wire insulation, facilitating the task of the end user.

The lubricant component is an essential component of the polymer blends of the invention. It has been found that the combination of antimony trioxide and a halogenated flame retardant in addition to the hydrated filler in the required concentration, plus a special two-component lubricant mixture, provides a lubricant-effective amount. unexpectedly provides the crosslinked mixtures according to the invention with exceptionally good flame retardant properties.

Calcium stearate has thus been used quite frequently as a lubricant for polymeric blends such as those according to U.S. Pat. Nos. 3,832,326 and 3,922,442. However, it has now been found that a lubricant mixture comprising a fatty acid such as lauric acid and an alkyl amis such as ethylene bis stearamide, especially when used in combination with antimony trioxide and halogenated non-halogenated flame retardants, provides a cross-linked mixture with strong increased flame retardant properties.

The two-component lubricant mixture according to the invention comprises a fatty acid with 8 to 25 carbon atoms and an alkylene bisamide 15 of the general formula 3 of the formula sheet, wherein R is a divalent alkylene radical of 2 to 8 carbon atoms and R 'is the group

O

2 -C-R

2 wherein R is an aliphatic radical of 5 to 25 carbon atoms, in an amount from about 1: 1 to about 1: 6 of fatty acid to 20 alkylene bisamide, and preferably in a ratio of about 1: 3 from acid to alkylene - bisamide. Preferably, the two-component lubricant mixture comprises 25% lauric acid and 75% ethylene bis-stearamide. The total amount of the lubricant blend should be from about 0.01 to about 10% by weight of the total polymer blend, and preferably from about 0.5 to about 3%.

The two-component lubricant blend has been found to be particularly effective in a peroxide hard hair polymer blend when used in combination with antimony trioxide and halogenated flame retardants such as ethylene bis-tetra-bromo-phthalimide, decabromodiphenyloxide, etc. The antimony trioxide incorporated in an amount from about 2 to about 20 wt%, and preferably from about 4 to about 8 wt%, and the halogenated flame retardant is included in an amount from about 50 to about 30 wt%, and preferably from about 8 up to about 14% by weight of the total polymeric mixture.

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The amounts of polymer and filler in the mixture according to the invention can be varied within wide limits. The silane percentage should be in the range of about 0.5 to 5.0 parts per 100 parts of polymer. Lower amounts may be insufficient to provide a suitable surface treatment, while large amounts may adversely affect some of the physical properties, ie the stretch, of an extruded insulating mixture after cross-linking.

Best results are obtained in coating, for example extruding on electrical wires and cables when 80 to 400 or more parts by weight of filler (preferably at least 125 to 150 parts by weight), 0.5 to 5.0 parts by weight of silane and 100 parts by weight of polymer are present.

The mixture according to the invention can be formed in a number of ways. However, it is always necessary that the filler and polymer be intimately mixed with the silane when dispersion of the filler into the polymer is started. This can be done in one. internal mixer, such as a Banbury or WemerSt_Pfleiderer extruder.

Any known processing equipment that ensures an intimate mixture of the essential components can be used provided that the silane couples the hydrated inorganic filler to the polymeric component.

It will be clear that in addition to the essential components of the mixture according to the invention, other additives may be present, for example pigments, stabilizers, provided that they do not interfere with the cross-linking, if desired, or damage desired properties. Such materials are present in very minor amounts ranging from less than 10% of the polymer and usually in amounts less than 5%. There are two reasons why amounts of other components are not desired; first of all, the present mixture 30 has superior properties per se; second, some significant amounts of, for example, other fillers only result in the balance of properties being reduced or disturbed.

To form insulation on conductors by extrusion, a lubricant such as a fatty acid soap or metal derivative thereof has been used successfully in the past. Such materials have also improved the stripping properties of wire insulation and thereby made it possible. the insulation can be easily stripped from the wire by the user to facilitate splitting and eleven closings. Practice has been to use acceptable soaps such as the alkaline earth metal fatty acid soaps with preferred soap being calcium stearate 5. Further representative examples of such lubricants include the alkaline earth metal salts and aluminum salts of stearic, oleic, palmitic and other fatty acids used for this purpose, silicone oil, long chain aliphatic amides, waxes, etc.

However, it has now been discovered that the two-component lubricant system of the invention is not only an effective lubricant, but also promotes flame retardant properties especially when used with a halogenated flame retardant, antimony trioxide and a non-halogenated flame retardant agent in a peroxide-hard-hair polymer blend.

The following examples further illustrate certain aspects of the invention.

A number of crosslinkable polymeric blends are shown in Table. - & is prepared where the lubricant used was calcium stearate.

(The numbers in the tables indicate parts by weight).

Each of these blends was extruded on 14 AWG wire and subjected to Underwriters Laboratories flame retardant VW-1 (Vertical-Wire) test (UL FR-1).

The results of the UL FR-1 tests performed with the samples containing calcium stearate are shown in Table B.

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μοίΜ ^ ν ^ p- οο ο & .So * * ^ ^ η> Η 8301474 21

As can be seen from the results of the tests, only two samples, namely, Nos 5 and 19 / containing calcium stearate passed the UI »FR-1 flame retardancy test. This is not considered satisfactory. Although the two materials passed the test, their similarity to compositions of other materials indicates that a reproducible answer to the FR-1 test would be very poor and not acceptable for commercial use.

Further samples were prepared using a two-component lubricant in combination with the halogen-containing flame retardant and antimony trioxide as shown in Table C.

8301474 22 ιΛ m in in

ΟΟΟ Ο (Ν 04 tf> Ο · * Ο CM p ^ fNO

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8301474 23

The HL FR-1 test was performed with the samples containing the two-component lubricant system, the results of which are shown in Table D.

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H 0>> 0 13 W G 0

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From these results, it can be seen that even under the stringent FR-1 test, the samples with compositions are those. the two-component lubricant system comprising more than 50% passed the test, while the samples without this lubricant system even passed 18%.

In addition, when comparing samples 22-30 containing the two-component lubricant system of the invention with samples 18 and 19 containing calcium stearate as a lubricant, it can be seen that they retain other desirable properties such as physical strength and elongation, as shown in table E.

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S ^ «&« «8301474

Claims (13)

A crosslinkable polymer mixture with improved flame retardancy comprising: a) a copolymer of ethylene and a vinyl ester of a ^ 2 ~ or aliphatic carboxylic acid, a C 1 -C 6 alkyl acrylate or C 1 -C 8 alkyl methacrylate, b) 80 to 400 parts of hydrated inorganic filler per 100 parts of copolymer, c) 0.4 to 8 parts of an alkoxysilane per 100 parts of hydrated inorganic filler and 10 d) a flame retardant component comprising a two-component lubricant system comprising a fatty acid with 8 to 25 carbon atoms and an alkylene bis-stearamide of the general formula 3 of the formula sheet, wherein R is a divalent alkylene radical having 2 carbon atoms and R ' O "2 -C-R, 2 wherein R is an aliphatic radical of 8 to 25 carbon atoms, a halogenated flame retardant and optionally antimony trioxide. 2. Mixture according to claim 1, characterized in that the two-component lubricant system is present in an amount from about 0.1 to about 10% by weight of the total polymer mixture. Blend according to claim 2, characterized in that the two-component lubricant system is present in an amount of from about 0.5 to about 3.0% by weight of the total polymer blend. Mixture according to claims 2-3, characterized in that the ratio of said fatty acid to said alkylene bisamide is about 1: 1 to about 1: 6. Mixture according to claim 4, characterized in that the ratio is about 1: 3. Mixture according to claims 1-5, characterized in that the fatty acid is lauric acid. 8301474 Mixture according to claims 1-6, characterized in that the alkylene bisamide is ethylene bis stearamide. Mixture according to claims 6-7, characterized in that the ratio of the lauric acid to the ethylene bis-stearamide is about 1: 3. Mixture according to claims 1-8, characterized in that said halogenated flame retardant is present in an amount of about 5 to about 30% by weight based on the total polymer mixture. A mixture according to claims 1-9, characterized in that the halogenated flame retardant is selected from ethylene bis-tetrabromophthalimide and decabromobiphenyloxide. Mixture according to claims 1-10, characterized in that the antimony trioxide is present in an amount of about 2 to about 20% by weight of the total polymer mixture. Electric conductor coated with a uni-insulating layer containing the cross-linked polymer mixtures according to claims 1-11. - ·· - · i1- "ill 8301474 J \ - · CH_ O 13 II H2-C == C-C-0 (CH2) 3Si (0CH3) 3 H2C = CHSi (OCH2CH2OCH3) 3 II N-R-N ^^ III National Distillers & Chemical Corporation 8301474