NL8104162A - FLAME-RESISTANT POLYMERIC COMPOSITION. - Google Patents

Description

* j * -1- VO 2292

Flame-resistant polymeric composition

The invention relates to crosslinkable polymeric compositions which are resistant to moisture and heat and are further flame resistant, which are suitable for the formation of insulated wires and cables, as well as other mold products. In particular, the invention relates to a cross-linkable ethylene-vinyl acetate copolymer composition which complies with the procedure known as the CSA Verification Test.

Flame retardant polymer compositions are widely used in an electrical environment, i.e., where both insulating and flame retardant properties are desired, more particularly with regard to pipe insulation.

Extrudable compositions intended for the wire and cable technology were formerly flame-resistant by incorporating halogenated polymers such as chlorinated polyethylene, polyvinyl chloride, chlorine-15-butadiene, chlorinated paraffin, etc., together with anti-moon trioxide, with both compounds in measurable quantities were present. A coating of chlorosulfonated polyethylene dye was also applied to a non-flame resistant insulating compound, which meant an additional manufacturing step.

20 ...

For some types of dry transformers, especially high voltage transformers, the problem existed that electrical breakdowns arose due to surface shrinkage of the organic insulating component used. This problem was solved by adding hydrated alumina to compositions, the organic binder of which consisted of butyl rubber, epoxy resins or polyester resins. However, these compositions have no balanced properties, namely both excellent extrudability and physical and electrical properties; as well as heat and flame resistance. Such compositions are described in U.S. Pat. Nos. 2,997,526-8. The compositions described for such purpose have insufficient tensile strength, elongation and percent elongation after aging.

8104 162 V ί -2-

Flame-retardant polymeric compositions, which, inter alia, have improved resistance to moisture and heat, and essentially consist of a homogeneous mixture of at least one cross-linkable polymer, which contains as main component an ethylene-vinyl acetate copolymer, one or more silanes and one or more hydrated inorganic fillers , have found wide application in wire and cable technology. Such compositions are described in U.S. Pat. Nos. 3,832,326 and 3> 922.hk2. These polymeric compositions have an excellent combination (or balance) of improved physical and electrical properties along with a high degree of flame and fire resistance. These particularly desirable results are achieved without using halogenated polymers, such as polyvinyl chloride and chlorosulfonated polyethylene, resulting in hydrogen chloride vapors. are eliminated; without soot, so that they can be used as colored insulating materials; without any flame retardant coatings, as are usually required, thereby avoiding the additional manufacturing step when the compositions are used, for example, as insulating compounds, which are extruded on a conductor; and without antimony trioxide, whereby a very expensive component can be eliminated.

Such compositions are particularly used as white (an inherent property) and colored union insulating compositions, which can be extruded onto metal, such as copper or aluminum conductors, thereby providing a single layer insulating and jacket forming composition. which, according to US standards, is suitable for operation at 90 ° C and in some cases even at temperatures of 125 °, up to a maximum of 600 volts.

These insulating compositions of U.S. Pat. Nos. 3,382,326 and 3,922.1 * 22 have been found to be particularly suitable for insulating wires for switchboards, gear wire, and automotive wire, with an excellent combination of excellent electrical properties, combined with resistance to the decomposing influences of heat and fire essential and low smoke density.and non-corrosive vapors are desired.

In addition to the three necessary components, other additives such as pigments, stabilizers, lubricants and antioxidants can be included in the composition of the aforementioned patents 8104162 * 1-3. Polyethylated trimethyldihydroquinoline of the antioxidants shown in said patents has been found to provide effective oxidation inhibition.

In the CSA missing test, 3 samples of isolated polymer wire (1) are heated in an oven; (2) immersed in insulating varnish; .

(3) reheated in an oven * for a long period of time; (4) cooled and 10 (5) bent over a small diameter doom *

The tested polymeric composition will not suffice if the insulation of one of the 3 samples when bent over the doom tears open to the conductor. Compositions which are exemplified according to the aforementioned patents and in which polymerized trimethyldihydroquinoline is used as an antioxidant do not pass the CSA missing test.

Many polymers are subject to oxidation, which adversely affects their physical properties. This decomposition can be caused by heat, light or other forms of energy.

With most polymers, the oxidation proceeds via a free-radical chain mechanism. The free radicals are formed in the polymer under the influence of an internal energy source. These radicals react with oxygen to form a peroxy radical which in turn reacts with the polymer to form a hydro-peroxide and another radical which continues the chain reaction.

Anti-oxidants have been developed to prevent the decomposition of a polymer. They serve to bind the peroxy radicals so that these radicals are unable to continue the reaction chain; or to decompose the hydroperoxide in such a way that carbonyl groups and additional free radicals are not formed. The former chain-breaking antioxidants, called free radical sequestering agents or inhibitors, are usually hindered phenols or amines. The latter, called peroxide decomposers, are generally sulfur compounds (i.e., mercaptans, sulfides, disulfides, sulfoxides, sulfones, thiodipropionic acid esters) or metal complexes of dithiocarbamates or dithiophosphates.

The patent publication describes a number of oxidants, 8104162 t * * ..............

which have hitherto been used with olefinic resins.

U.S. Pat. Nos. 3,16Q,680 and 3,282,890 describe an antioxidant combination of a sterically hindered phenol and a diester of thiodipropionic acid for use in a-olefinic hydrocarbon polymers. U.S. Pat. No. 3,033,811+ discloses the use of a three component antioxidant consisting of a hindered phenol, a diester of thiopropionic acid and phenyl salicylate in a polymer of an α-olefinic hydrocarbon containing 2-10 carbon atoms. U.S. Patent 3,18-1,971 10 describes a combination of a phenolic antioxidant and a primary or secondary aromatic or aliphatic amino compound with propylene homopolymers or copolymers of propylene with other hydrocarbons. US Pat. No. 3,21 + 2,135 describes the combination of an ester of boric acid with a hindered phenol and a diester of thiodipropionic acid to inhibit oxidation for homopolymers and copolymers of α-olefinic hydrocarbons with 2-8 carbon atoms. U.S. Patent 3,21 + 5,9 ^ 9 is directed to homo- and copolymers of aliphatic olefinic hydrocarbons of 2-8 carbon atoms and mixtures thereof, the anti-oxidant being the combination of a phosphorus-containing polyphenolic compound and the dilauryl or distearyl ester of n dithiopropionic acid is used. None of these. Patents discloses or suggests that the antioxidant combinations can be suitably incorporated into non-hydrocarbon polymers, i.e., no use is proposed with a polymer containing a significant amount of an ethylene-vinyl acetate copolymer.

It is an object of the invention to provide a cross-linkable ethylene-vinyl acetate copolymer composition that complies with the CSA varnish test.

It is a further object of the invention to provide an ethylene-vinyl acetate copolymer composition containing a silane-treated hydrated inorganic filler which not only has excellent moisture and heat resistance, but also flame retardancy. -varnish test 35.

All percentages and parts in this description are by weight unless otherwise stated.

8104162 ♦> -5- »

The present invention has found that when the polymerized trimethyldihydroquinoline antioxidant in the ethylene vinyl acetate (EVA) compositions of U.S. Pat. Nos. 3,832,326 and 3,922, ½ is replaced by an antioxidant containing a dieter of thiodipropionic acid, the obtained compositions not only have substantially the same moisture and heat resistance, flame retardancy and oxidation inhibition as before, but also unexpectedly passed the CSA varnish test.

More particularly, the invention is directed to a crosslinkable polymer composition capable of passing the CSA verification test comprising: (a) a polymer component comprising at least 66 wt.% Of an ethylene copolymer and a vinyl ester of an aliphatic carboxylic acid of 2-6 carbon atoms, an alkyl acrylate of 1-6 carbon atoms or an alkyl methacrylate of 1-6 carbon atoms; (b) 80-100 parts of hydrated inorganic filler per 100 parts of the polymer component; (c) 0.5-5 ”parts of an alkoxy sila per 100 parts of hydrated inorganic filler and (d) an amount of an anti-oxidant composition containing at least 23% distearyl-3,3'-thiodipropionate and which is so effective that the polymeric composition can pass the CSA Verification test.

The invention is also directed to a cross-linkable polymer composition capable of passing CSA Verification Test comprising: a) a polymer component containing at least 66 wt.% Of an ethylene copolymer and a vinyl ester of an aliphatic carboxylic acid with 2-6 carbon atoms, an alkyl acrylate with 1-6 carbon atoms or an alkyl methacrylate with 1-6 carbon atoms; b) 80-400 parts of hydrated inorganic filler per 100 parts of the polymer component; c) 0.5-5 parts of an alkoxysilane per 100 parts of hydrated inorganic filler; d) 0.1-5 parts of distearyl-3,31-thiodipropionate per 100 parts of the polymer component.

The invention also relates to an improved cross-linkable polymer composition of the type, comprising: 8104 162 * * ~ -6- ....... "a) a polymer component containing at least 66% by weight of a copolymer of ethylene and a vinyl ester of an aliphatic carboxylic acid with 2-6 carbon atoms, an alkyl acrylate with 1-6 carbon atoms or an alkyl methacrylate with 1-6 carbon atoms; 5 b) 80-100 parts of hydrated inorganic filler per 100 parts of the polymer component and o) 0.5-5 parts of an alkoxysilane per 100 parts of hydrated inorganic filler, said polymer composition being mixed with an amount of an antioxidant composition comprising at least 23% distearyl-3,31-thiodipropionate and such .. is effective that the polymer composition can pass the CSA varnish test.

The invention also relates to an electrical conductor coated with a union insulating layer comprising one of the above-described crosslinkable polymeric compositions which pass the CSA varnish test.

The invention relates to cross-linkable polymer compositions comprising copolymers of ethylene and a vinyl ester of an aliphatic carboxylic acid, an alkyl acrylate or an alkyl methacrylate, as well as a silanes-treated hydrated inorganic filler and which pass the CSA varnish test. These compositions are particularly suitable as insulating materials for wires and cables.

In addition to a particular antioxidant composition, the compositions of the invention contain 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 as described in U.S. Pat. Nos. 3,832,326 and 3,922.

The terms cross-linkable or cross-linking have the normal meaning in this description, i.e. z. that they indicate the formation of primary valence bonds between polymer molecules.

Cross-linking can be accomplished by a known procedure, such as by chemical means including peroxide cross-linking; by radiation using cobalt-60, accelerators, 35 O-rays, gamma rays, electrons, X-rays, or by thermal cross-linking. The basic procedures for polymer cross-linking are known in the art and need not be more particularly herein 8104162 V * -7- to be described today - * The polymer component of the composition of the invention is a copolymer of ethylene and an eonomer, which may be a vinyl ester, an acrylate or methacrylate. aliphatic carbonic acid with 2-6 carbon atoms, such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pentanoate or vinyl hexanoate The acrylates and methacrylates can be any alkyl esters of 1-6 carbon atoms, including, for example, 10 methyl, ethyl Propyl, butyl, pentyl or hexyl acrylate or methacrylate. The preferred polymer comprising the polymer compound of the invention is an ethylene-vinyl acetate copolymer having about 9- 90% a, preferably about 9%, especially about 9-28% vinyl acetate, with ethylene as the balance.

Although it is of little advantage and some properties are even adversely affected, it is possible to include small amounts of other crosslinkable polymers or copolymer in the composition of the invention. However, ethylene copolymers, especially ethylene-vinyl acetate copolymers, as described above, should comprise at least about 66% of the total amount of polymers present. Examples of such minor polymeric components that can be used in these non-preferred embodiments include polybutylene, ethylene copolymers with propylene, butene, the acrylates and maleates, polydimethylsiloxane and poly-methylphenylsiloxane, copolymers of vinyl acetate with acrylates, etc.

Of course, mixtures of these minor polymeric components can also be used.

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

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

The polyethylenes suitable for use according to the invention essentially comprise all high, medim and low density polyethylenes, as well as mixtures thereof. Most preferred polyethylenes in blends for use as union insulation for electrical wires and 8104162 4 '. X) * -8- ..... "cables generally have a density of about 0.900-0.950 g / cc and a melt index of about 1.0-10.0.

More particularly, the compositions of the invention have an excellent and unexpected balance of: 5. - 1. low temperature brittleness, i.e. the composition. c— will not tear easily during low temperature weightings (ASTM D Ik6).

2. Heat resistance after aging, i.e. excellent elongation after extended use at 90 ° C and even 125 ° C.

10 3. Resistance to arc breakdown and current path formation, up to a height of 5 KV; (nb.even porcelain shows surface breakdown at k KV). This one. however, property is usually not required in the preferred environment where the voltage exceeds 600 Volts.

k. Flame retardancy and flame retardancy.

15 5 · Resistant to moisture, i.e. low mechanical absorption of water, providing an excellent dielectric constant.

6. Resistant to industrial chemicals.

It is not known why the compositions of the invention exhibit such a superior balance of properties.

It is possible that there is a synergistic relationship between the ethylene-vinyl acetate copolymer, silane and hydrated inorganic filler, but no such theory is binding. However, it has been found that the compositions of the invention in an environment of low voltage, less than 5000 volts, especially even less than 600 volts, are particularly suitable for use as uninsulating materials. Uni-insulation is a term accepted in the art, which denotes an insulation in which one layer is extruded around the conductor and this one layer serves as electrical insulation and jacket to provide physical and flame protection. The compositions of the invention are particularly suitable for use as uninsulating materials in a range of less than 5000 VoTt, especially less than 600 Volts, when only a single extruded coating is used, in an environment, where a superior balance of properties is required. Furthermore, it has been found that ethylene-vinyl acetate copolymers retain large amounts of filler and yet provide a high flexibility and a high degree of cross-linking. The fact that high filler loading, flexibility and 8104162-9 crosslinking can be achieved at the same time is very surprising, since it was generally assumed that high flexibility and a high degree of crosslinking were incompatible, as well as a high degree of crosslinking and a high degree of crosslinking. filler charge (meaning low crosslinkable polymer content) Ethylene-vinyl acetate copolymers further impart excellent flame retardancy to the polymer compositions of the invention.

The above-described ethylene-vinyl acetate copolymers can be cross-linked by irradiation with high energy electron beams or by using chemical cross-linking agents. After complete cross-linking, these polymers can exhibit a thermosetting behavior.

In the preferred compositions of the invention, chemical cross-linking is preferred, especially when excellent physical strength is required.

Chemical cross-linking is achieved by incorporating a cross-linking agent, such as dicumyl peroxide or α, a * -bis- (t-butyl peroxy) diisopropyl benzene in the ethylene-vinyl acetate copolymer. The peroxide is later activated during processing, thereby coupling the ethylene-vinyl acetate copolymer chain (and other minor amounts of cross-linkable polymer, if any) into a three-dimensional network.

The chemical cross-linking is carried out according to known procedures, whereby variations in the general cross-linking conditions, as described below, will not pose any problems in the art. Moreover, the invention is not limited to the use of tertiary organic peroxides for chemical cross-linking, and it is thus possible to use other materials known in the art which decompose to form free radicals. It goes without saying that such cross-linking agents should not decompose when the composition 30 is mixed; however, the choice of acceptable cross-linking agents can be left to the skilled person.

Generally speaking, as the amount of cross-linking agent is increased, the degree of polymer cross-linking will increase. Usually no more than 10% (based on the polymer) of the organic tertiary peroxides need to be used, with 3-6%. proposes a suitable route. Other cross-linking agents may require different amounts, but these can be easily determined. It is often advisable to avoid very low amounts of cross-linking agents, as this may result in some loss of resistance to deformation under sudden or continuous pressure. In order to increase the effectiveness of the cross-linking agent 5, cross-linking aids such as triallyl cyanurate may also be included. As is the case with most other chemical crosslinkers, the tertiary organic perozys are activated by heating to their activation temperatures above which decomposition occurs. Known procedures can be used to accomplish activation, for example, in. contacting the composition with high pressure steam.

The technique of radiation cross-linking has been developed to such an extent that little is required with regard to such procedures. As higher total radiation doses are used, the degree of cross-linking will generally increase, with preferred cross-links using a total radiation dose of about 5-25 megarads.

Cross-linking is generally carried out at superatmospheric pressures, for example of the order of 15-30 bar, although higher or lower pressures can also be used. Pressure is applied to avoid uncontrolled porosity in the polymer, which would be highly undesirable for electrical insulation.

Generally, at a higher degree of cross-linking, the polymer composition will be more resistant to moisture and chemical reagents and less resistant to abrasion. At lower degrees of cross-linking there is also some loss of heat resistance as well as a pronounced effect on the percentage elongation after aging. The exact degree of cross-linking can of course be varied, taking into account the aforementioned 30 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 95% for ethylene-vinyl acetate is generally most desired, which is determined by the extractable weight of 35 soluble components in the cross-linked polymer .

The second essential component of the polymeric composition of the invention is one or more substituted 8104162-11 silanes.

According to the invention, any silane can be used that will not adversely affect the desired balance of properties and will contribute to the binding of the polymer and the organic swelling agent, provided that the silane is non-flammable, for example, alkoxy and amine silanes and does not interfere or decompose cross-linking of the polymer during polymer processing.

The preferred silanes used to form the insulating master compositions are the alkoxy silanes, for example lower alkyl, alkenyl, alkynyl and arylalkoxy silanes, as well as the lower alkyl, alkenyl, alkynyl and arylalkoxyalkoxy or -aryloxyalkoxy silanes. Specific examples of such silanes are methyl triethoxy, methyl tris (2-methoxyethoxy}, dimethyldiethoxy, alkyl trimethoxyT, vinyl tris (2-methoxyethoxy), vinyl tris O 2 -methoxy ethoxy), vinyl trimetho-15-yl and vinyl triethoxysilane.

For optimal results, it is preferred to use vinylsilanes, of which gamma-methaeryloxypropyltrimethoxysilane and vinyltris (2-methoxyethoxy) silane are particularly preferred:

The fillers used according to the invention are the hydrated, inorganic fillers, for example hydrated aluminum oxides (ΑΙ ^ Ο ^ .ΒΗ ^ Ο or Al (OH) ^), hydrated magnesium, hydrated calcium silicate. Of these compounds, hydrated alumina is most preferred.

In order to obtain the excellent balance of properties, as described, it is necessary to use a hydrated inorganic filler for the formation of the polymeric compositions according to the invention. It should be emphasized here that it is not possible to add large amounts of other types of fillers, whether or not inert, to the compositions and yet achieve the excellent balance of properties.

The hydrate pad in the inorganic filler must be released sufficiently during heating to cause combustion or ignition of the ethylene-vinyl acetate copolymer. The hydrate water chemically bound to the inorganic filler is released endothermically. It has been found that the hydrated inorganic filler increases the flame retardancy much more strongly than is the case with the known fillers previously used for flame retardant insulating purposes, for example carbon black, clays and titanium dioxide. More surprisingly, the flame retardancy at the higher filler charges is associated with excellent electrical insulating properties, since the copolymer composition contains a large amount of bound water in these filler charges.

The filler size can be selected in known manner.

*

The fourth component of the polymeric compositions of the invention is the antioxidant composition, and it is also due to its influence. component, that the compositions can surprisingly pass the CSA missing test. An essential ingredient, this antioxidant is formed by a diester of thiodipropionic acid. The preferred diester is distearyl-3,3f-thiocli-propionate (DSTDP). Although this material is a known anti-oxidant, which functions as a peroxide decomposer, its influence is on the compositions of the invention, thereby rendering it. the CSA varnish test can pass, not entirely clear. The action of this particular diester is all the more surprising because a related diester, dilauryl-3,3'-thiodipropionate (DLTDP), although often used as an antioxidant mixture with or in combination with DSTDP, will not provide a polymeric composition, which will pass the CSA missing test when used in place of DSTDP in the compositions of the invention.

In addition to DSTDP, which is an essential component of the anti-oxidant composition, other anti-oxidants can be used in combination therewith. It has been found that the use of two different types of anti-oxidants gives rise to an effective oxidation inhibition. Thus, a mixture of an anti-oxidant of the chain-breaking type and of a peroxide-decomposer type will provide a very effective antioxidant composition. Thus, with the DSTDP, which is a known peroxide decomposer, an amine or a hindered phenol can be used effectively as an antioxidant composition.

Of these free radical sequestrants, 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-para-cresol, octadecyl-3,5-di-t-butyl-1-hydroxy-hydrocinnamate, 8104162 -13-2,2'-methylene-bis- (6-t -butyl-4-methylphenol), 4,4'-butylidene bis- (6-t-butyl-3-methylphenol), 1,3,5-trimethyl-2,4,6-tris- (3,5- di-t-butyl-4-hydroxybenzyl) benzene and tetratris (methylene) -3,5-di-t-butyl-4-hydroxyhydrocinnamate) methane, the latter being particularly preferred.

CSA Missing Test.

According to this test, developed by the Canadian Standard Association, de-insulation of wire windings (Section 6.7 of CSA Standard C22.2 No. 116) and electrical wires and cables (Section 4.25 CSA Standard 10 C22.2 No. 0.3) are evaluated. The tests applied to wire windings and electrical wires and cables are essentially the same. Insulated wire samples are heated in an air oven at 104-106 ° C for half an hour, then removed from the oven and immediately immersed in insulating varnish for 1 hour at room temperature. After removing the varnish, the sample is suspended at room temperature for 1 hour and then at 11 9-151 for 2 hours; 159-161 or 203-205 ° C in an oven, depending on the type of wire. After cooling to room temperature for 2 hours, each sample is bent once around a small diameter doom.

An insulated wire will not pass this test if the insulation of any of the three tested wire samples tears open to the conductor.

It is surprising that the compositions of the invention pass this rigorous test, while known compositions such as those disclosed in U.S. Pat. Nos. 3,832,326 and 3,922.41 (2 although having properties that make them suitable as excellent flame retardant wire and cable insulation materials cannot pass the CSA miss test The compositions of the invention not only pass the CSA miss test but also demonstrate the excellent fire retardant and moisture and heat resistance of the polymer compositions of the aforementioned patents.

The amounts of the polymer and filler in the compositions of the invention can be varied over a wide range. However, the silane percentage should be in the range of 055-530 parts / 100 parts filler. Lower amounts may be insufficient for effective surface treatment, while larger amounts may adversely affect some of the physical properties, such as elongation, of an extruded insulating compound after cross-linking.

Best results in coating, such as extrusion, on electrical wires and cables are obtained when 80-00 or more parts by weight of filler (preferably at least 125-150 parts by weight), 0.5-5 * 0 parts by weight of silane and 100 parts by weight of polymer are present.

The antioxidant composition must be used in an amount such that an effective oxidation inhibition is obtained and sufficient DSTDP must also be present for the polymeric composition to pass the CSA missing test. When DSTDP is the sole component of the anti-oxidant composition, meeting the CSA missing test will not present any particular problems. When other antioxidants are combined with the DSTDP, the DSTDP must form at least 25% of the antioxidant composition. The anti-oxidant composition, expressed in a specific amount, should be in the range of Q5-5-5, preferably 1.0-3.0 parts / 100 parts polymer.

The compositions of the invention can be formed in a number of different ways. It is always necessary, however, that the filler and the silane are brought into thorough contact with each other. The preferred method of filler treatment is to add the silane directly to the polymer, followed by addition of the filler, the antioxidant composition, and other additives, if desired. This can be done in an internal mixer, such as a Banbury or Werner and Pfleiderer mixer. At its option, the silane can be added directly to the filler, dispersed therein, then the polymer and the antioxidant composition are added.

Any known processing equipment ensuring a homogeneous mixture of the essential components can be used, provided that the silane is homogeneously and thoroughly dispersed on the surface of the hydrated inorganic filler.

It will be appreciated that in addition to the necessary components of the compositions of the invention, other additives may be present, such as pigments, stabilizers, provided that they do not interfere with cross-linking or adversely affect the desired properties. Such materials are present in very minor amounts, usually less than 10 # of the polymer and usually in amounts less than 5% There are two reasons why 5 amounts of other components are not desired: 1. The composition of the invention is itself all excellent properties; 2., any significant amounts of other fillers will easily disrupt the balance of properties.

Generally, for forming insulation on conductors by ertrusion, the preferred embodiment of the invention, another component is required, i.e. a lubricant, such as a fatty acid soap or metallic derivative thereof.

Such a material is also "important for improving the stripping properties of wire insulation, which also allows the insulation to be easily pulled off the wire by the user to facilitate connections and branching.

However, it is necessary to avoid soaps which influence the cross-linking reaction (free radical mechanism), such as zinc stearate, which reacts with organic peroxides. Acceptable soaps are the alkaline earth acid soaps. A preferred soap is calcium stearate.

Further representative examples of suitable lubricants include the alkaline earth salts and aluminum salts of stearic, oleic, palmitic and other fatty acids known in the art for this purpose, silicone oil, long aliphatic amides and waxes. A particularly suitable lubricant is a mixture of 15-35 # lauric acid and 85-65 # ethylene bis-stearami.

The following example serves to further illustrate some aspects of the invention.

A number of cross-linkable EVA copolymer compositions were prepared and subjected to the CSA loss test. Each of the samples contained the same copolymer, hydrated alumina, silane and cross-linking agent in the same amounts, viz.

17 Samples were prepared, each of which, except for the aforementioned 35 components, contained a one- or two-component antioxidant composition, and a lubricant. Four commercially available antioxidants have been evaluated, including two diesters of thiopropionic acid, 8104162-16, which due to their very similar antioxidant properties are often used interchangeably in the art. The other heath antioxidants were amines. phenol type antioxidants. The two lubricants tested were also commercially available products.

The silane, filler and the other components were added to the polymer and mixed therewith. Temperature rise during mixing was carefully counteracted so as not to activate the peroxide before mixing was completed. After mixing, the polymer composition was extruded onto a copper wire using a Brabender 10 Extruder and the temperature was elevated to high peroxide activation temperature by vulcanization in high pressure steam.

The compositions of these examples and the results of the CSA varnish test are listed in Table A.

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Sample No. 1 is an example of the compositions of U.S. Pat. Nos. 3,832,326 and 3,922.kk2. This sample did not pass the CSA missing test, as did six other samples.

Of the seven samples containing DSTDP, six were passed in Test 5 (samples 3, 7, 8, 1U and 16). Of the 18 types comprising these six DSTDP samples, only one showed a deep crack in the insulation. Each of the fifteen type samples containing the polymerized quinoline anti-oxidant exhibited deep cracks (samples 1, 2, 11, 12 and 13), as did all nine types out of 10 samples containing the DLTDP anti-oxidant (samples 12, 15 and 17).

It may also be significant that the only DSTDP sample (sample 11) that did not pass the test also contained the polymerized quinoline antioxidant, all of which. three samples showed deep cracks.

These tests demonstrate that DSTDP with the polymerized quinoline antioxidant. was not effective. Furthermore, DLGDP cannot be applied in place of DSTDP when the CSA missing test is required to be met.

From these tests it appears that of the additives tested, 20 is DSTDP, the most important candidate for satisfying the CSA missing test. Furthermore, the best anti-oxidant combination was DSTDP + the hydrocinnamate, while the most effective system contained this anti-oxidant system + the Mold Wiz lubricant. Samples of the latter system (samples 1Λ and 16) showed only minor cracks, if any.

8104162

Claims (6)

1. A cross-linkable polymer composition, which is able to pass the CSA varnish test, characterized in that it comprises the following components: (a) a polymer component with at least 66% by weight of a copolymer of ethylene and a vinyl ester of an aliphatic carboxylic acid with 2-6 carbon atoms, an alkyl acrylate with 1-6 carbon atoms or an alkyl methacrylate with 1-6 carbon atoms; (b) 80-100 parts of hydrated inorganic filler per 100 parts of the polymer component; (C) 0.5-5 parts of an alkoxysilane per 100 parts of hydrated inorganic filler and (d) such an effective amount of an antioxidant composition containing at least 25 # distearyl-3,3'-thiodipropionate, that the polymer composition complies with the CSA missing test. The composition according to claim 1, characterized in that the copolymer is an ethylene-vinyl acetate copolymer. Composition according to claims 1-2, characterized in that the composition contains 80-1 * 00 parts of hydrated inorganic filler per 100 parts of the polymer component, 0.5-5 parts of alkoxysilane per 100 parts of hydrated inorganic filler and 0.1 Contains 5 parts of distaryl 3,3'-thiodipropionate per 100 parts of the polymer component. 1 *. Composition according to claims 1-3, characterized in that the antioxidant composition of component (d) further contains a sterically hindered phenol. Composition according to claim 1 *, characterized in that 0.1-5 parts of the sterically hindered phenol are present per 100 parts of the polymer components. Composition according to claim 1 * or 5, characterized in that the phenol is trakis (methylene (3,5- <-tertiary-butyl-1-hydroxy-hydrocinna-30-measure)) methane. T. A composition according to claims 1-6, characterized in that it additionally contains a lubricating effective amount of a lubricant comprising lauric acid and ethylene bis-stearamide. 8. A composition according to claim J, characterized in that 8-104162 -22- 0.1-5 parts of a lubricant comprising lauric acid and ethylene bis-stearamide are present. Electric conductor, coated with a mi-insulating layer, containing the cross-linkable polymeric composition according to any one of claims 1 to 3. 8104162