SE445081B - HARDENABLE COMPOSITION FOR ELECTRIC COATING BASED ON ETHEN-ALKYL ACRYLATE COPOLYMES CONTAINING HYDRATIZED ALUMINUM OXIDE FILLER AND ELECTRIC WIRE OR CABLE INSULATED WITH THE COMPOSITION - Google Patents

Description

7806929-1 2 at high temperatures and extruding them, again at high temperatures, onto the electrical conductor. When certain fillers are used in combination with ethylene copolymer-based compositions, the entire curable composition is sensitive to vulcanization during its high temperature processing prior to the vulcanization of composite fl xem on the electrical conductor. Vulcanization is in fact the premature vulcanization of the insulating composition.

This premature vulcanization usually occurs, when it occurs, in the cylinder or nozzle head of the extruder in which the insulating composition is processed, at elevated temperatures, before it is extruded on an electrical conductor, and before its intended vulcanization. When an insulating composition is vulcanized in the extruder, the extruder composition will have defects in the form of discontinuity and unevenness in the surface of the insulation and lumps or surface waves caused by gel particles in the body of the extrudate. In addition, excessive vulcanization can cause a sufficient pressure build-up in the extruder to require a complete cessation of the extrusion process.

Another important property that an insulated appliance or car cable possesses is also that it must be clamp-resistant.

This means that when a cable is surrounded by a clamp, the insulation around the cable must withstand the clamping force of the clamp.

Ethylene-vinyl acetate polymer-based compositions and certain ethylene-alkyl acrylate-copolymer-based compositions containing more than 18% by weight of ethyl acrylate are susceptible to squeezing.

It has now been found that curable ethylene-alkyl acrylate copolymer-based compositions having 2: 5 to: E18 weight percent ethyl acrylate, utilizing hydrated alumina fillers treated with at least one silane, provide clamp resistant coatings.

An object of the present invention is to provide scorch-resistant, curable compositions based on filled ethylene-alklacrylate copolymer-based compositions containing 25 to 18% by weight of ethyl acrylate.

Another object of the present invention is to provide a flexible, clamp-resistant insulation for electrical wire and cable, primarily apparatus and car cables.

Another object of the present invention is to provide fouling-resistant insulation for electrical wire and cable, primarily apparatus and car cables.

A further object of the invention is to provide a flexible insulation for electrical wire and cable while maintaining tensile strength, elongation, brittleness temperature, machining and fire retardancy properties.

These and other objects of the present invention are achieved by the use of hydrated alumina filler treated with at least one silane in an ethylene-alkyl acrylate copolymer based composition containing 1.58% by weight of ethyl acrylate.

The adhesive composition of the present invention comprises: an ethylene-alkyl acrylate copolymer containing inne15 to fi18% by weight of ethyl acrylate and from about 80 to about 400 parts, preferably about 100 to 150 parts, per 100 parts of ethylene-alkyl acrylate copolymer, of hydrated alumina treated with 0.5 to about 5.0 parts, preferably from about 1.0 to about 3.0 parts, per 100 parts of filler, of at least one silane.

The copolymers used in the present invention comprise units corresponding to ethylene and an alkyl ester of an acrylic acid. By alkyl acrylic acid ester for the purpose of the present invention is meant an alkyl ester of an acrylic acid as defined in Acrylic Resins, by Milton B. Horn, page 15f, under the subheading "Monomer Chemistry", which includes alkyl esters of both unsubstituted acrylic acid (CH 2 = CH-COOH) a ls simple alpha-substituted acrylic acids such as those acrylic acids having a lower alkyl substituent, for example methacrylic acid (CH2 = (11-- COOH) CH3 Special acrylic acid esters suitable for the preparation of the copolymers include those such as methyl, ethyl, propyl , isopropyl, butyl, isobutyl, hexyl, t-butyl, 2-ethylhexyl, decyl, lauryl and stearyl esters of acrylic or methacrylic acids.

It will be apparent to those skilled in the art that the alkyl moiety of the alkyl acrylate may, if desired, also have certain simple substituents which do not substantially interfere with the formation of the copolymers nor deviate from their desirable properties without departing from the scope and spirit of the present invention. the present invention. At present, the preferred alkyl esters are the lower alkyl esters of simple acrylic acids, for example methyl, ethyl and butyl acrylates and methacrylates.

The preferred copolymer is ethylene-ethyl acrylate copolymer containing è.5 to 18% by weight of ethyl acrylate. A suitable copolymer contains 14-16% by weight of ethyl acrylate. The most preferred copolymer is ethylene-ethyl acrylate copolymer containing 5% by weight of ethyl acrylate.

The ethylene-alkyl copolymers typically have a density (test procedure ASTM 1505 with conditioning in the same manner as in ASTM D-147-72) of about 0.92 to 0.94 and a melt index (ASTM D-1238 at 3.08 kp / cmz test pressure) of about 1 to about 50 decigrams per minute.

The ethylene polymers can be cured by irradiation with high energy electron beams or by using chemical hardeners.

The technology with electron beam networking is so highly developed that a person skilled in the art is very familiar with this procedure. The chemical hardener is preferably an organic peroxide. The organic peroxide hardener that can be used in the present invention includes all organic peroxides that are capable of providing free radicals for crosslinking the ethylene polymer under the crosslinking conditions used for the compositions.

The organic peroxide compounds can be used individually or in combination with each other.

The preferred organic peroxide compounds that can be used in the compositions of the present invention can also be broadly classified as those in which each oxygen atom of each peroxide group is directly attached to a tertiary carbon atom whose remaining valences are attached to hydrocarbon groups selected from alkyl, cycloalkyl, aryl and aralkyl. Peroxides of this type are generally described in U.S. Patent No. 2,888,424. Examples of the organic peroxide compounds that can be used in the vulcanizable compositions of the present invention include di-alpha-cumyl peroxide 2,5-dimethyl-2,5-di ( t-butylperoxy) -hexyn-3 2,5-dimethyl-2,5-di (t-butylperoxy) -hexane t-butylcumyl peroxide di-t-butylperoxide alpha, alpha'-bis (t-butylperoxy) -p-di- isopropylbenzene 2,5-dimethyl-2,5-di (benzoyl peroxy) -hexane t-butyl peroxyisopropyl carbonate.

In addition, organic hydroperoxide compounds, as described in U.S. Pat. Nos. 3,954,907 and 4,018,852, which are incorporated herein by reference, are suitable for use in the present invention. In addition, crosslinking aids (or promoters) for peroxides, such as allyl compounds, such as triallyl cyanurate, can be used.

The organic peroxide compounds are used in crosslinking effective amounts in the compositions of the present invention, which may range from about 0.1 to 8.0 and preferably from about 0.3 to 5.0 of organic peroxide compound per part by weight of ethylene polymer in such compositions.

The nitrated alumina filler of the present invention is commercially available in various forms and grades. The hydrated alumina filler may have an average particle size of between 0.5 and 50 microns. For maximum resistance to counter-ignition and for optimal dispersion, it is generally desired to be within this range.

The silane that can be used in the present invention is characterized by the following formula: RaSiX4_a wherein R is selected from lower alkyl, lower alkenyl or lower alkynyl; X is an alkoxy group having 1 to 20 carbon atoms and a is an integer of 1 or 2. The term "lower" as used herein refers to 1 to 4 carbon atoms.

Particular examples of such silanes include methyltriethoxy, methyltris (2-methoxyethoxy), dimethyldiethoxy, alkyltrimethoxy, vinyltris (2-methoxyethoxy), vinyltrimethoxy and vinyltriethoxysilane.

The preferred silanes are as follows: gamma-methacryloxypropyltrimethoxy-silane CH 3 O H - H 2 C = C - C-O (CH 2) 3 S 1 (OCH 3) 3 and vinyl-tris (betamethoxyethoxy) silane H C = CHSi (OCH CH 2 OCH 3) 3. The compositions of the present invention also advantageously comprise from about 0.1 to about 3.0 and preferably from 0.05 to about 1.0 parts of one or more suitable high temperature antioxidants for the ethylene polymer per 100 parts of the ethylene polymer.

These antioxidants are preferably sterically blocked phenols or amines. Such compounds include 1,3,5-trimethyl-2,4,6-tris (3,5-ditertiary butyl-4-hydroxybenzyl) benzene; 1,3,5-tris (3,5- ditertiary butyl-4-hydroxobenzyl) -5-triazine-2,4,6- (1H, 3H, 5H) trione; tetrakis- [methylene-3- (3 ', 5-di-t-butyl-4' -hydroxyphenyl) -propionate: methane; 7 and di (2-methyl-4-hydroxy-5-t-butylphenyl) Sulfyl-Polymerized 1,2-dihydro-2,2,4-trimethylquinoline can also be used.

The antioxidants can be used individually or in combination with each other.

In addition to the ethylene-alkyl acrylate copolymer and the silane-treated hydrated alumina filler, the compositions of the present invention may also contain other adjuvants of the types normally used in curable electrical insulation compositions.

These other aids include hardeners; antioxidants, other fillers; flow agents; nucleating agents for fermented systems; UV stabilizers; dyes and dyes; voltage stabilizers; metal deactivators, coupling agents and lubricants, such as fatty acid soap or metal derivatives thereof. Such a material is also important for improving the peeling properties for wire insulation and thus for allowing the insulation to be easily peeled from the wire by the user to facilitate spüisnnr; and for the production of terminations. Acceptable soaps are the alkaline earth metal fatty acid soaps.

A preferred soap is calcium stearate. Additional examples of suitable lubricants include the alkaline ferrous metal salts and aluminum salts of stearic acid, oleic acid, palmetic acid and other fatty acids used in the art for this purpose, silicone oil, etc.

These aids shall be used in amounts adapted to provide the intended effect in the resulting composition.

The compositions of the present invention may also be extended, or filled, with polymers other than the ethylene-alkyl acrylate copolymer, which are compatible, i.e., may be physically blended or alloyed with the ethylene-alkyl acrylate copolymer. The resulting compositions shall contain at least 30% by weight of ethylene-alklacrylate copolymers in all the polymers which may be present in the composition based on the total weight of the resulting composition. Some of the other polymers that can be used include polyvinyl chloride and polypropylene.

The total amount of excipients used will vary from 0 to about 60 weight percent based then the total weight of the composition.

All the components of the present invention are usually mixed together before their introduction into the stranded device from which they are to be stranded. Then an electrical conductor. The ethylene-alkyl acrylate copolymer and other desired components can be blended together by any of the methods used in the art to blend and compound thermoplastics into homogeneous pulps.

The specified silane and hydrated alumina can be mixed so that the silane is intimately coated on the surface of the alumina.

Then the silane / filler and the other additional components were added to the polymer and mixed with it. Care was taken to control the temperature increase during mixing so that the peroxide was not activated prior to completion of the mixing. Alternatively, a stock mixture containing the polymer and the alumina filler and, if desired, some or all of the other components may be added to the mass of polymer. However, it is important in this method to prevent the addition of stearate to allow preferential coating of the filler with the silane. The introduction of silane and stearate at the same time will lead to poorer overall mechanical properties. When the ethylene-alkyl acrylate copolymer is not available in powder form, the compositions can be prepared by introducing the polymer into the rolling mill, kneading it until it forms a band around the roll, then adding a mixture of the remaining components and continuing the rolling until an intimate mixture is obtained. The rollers are preferably maintained at a temperature which is in the range of 80-150 ° C and which is below the decomposition temperatures of the peroxide compound (s). The composition, in the form of a mat, is removed from the rolling mill and then brought into a mold, usually grit-like pieces, which are suitable for subsequent processing.

After the various components of the compositions of the present invention are uniformly mixed and blended together, they are further processed, in accordance with the process of the present invention, in a conventional extruder at about 120 DEG-16 DEG.

After being extruded onto a wire or cable, or other substrate, the compositions of the present invention are cured at elevated temperatures of about 180 ° C and preferably at 215-230 ° C using conventional curing methods.

The invention is further illustrated by the following examples.

Examples 1-3 The compositions in these examples are prepared by mixing all the components (except stearate) in a Banbury mixer. The components were mixed intimately and after softening the resin, calcium stearate was added to the mixture. The stearate was finally added to allow preferential coating of the hydrated alumina filler with the silane.

The compositions of the compositions are set forth in Table I. Table I - 9 _12 E Ethylene-vinyl acetate copolymer (a) 43.65 ----- ----- Ethylene-ethyl acrylate copolymer (b) --- - 41.85 41.85 Hydrated alumina 55.00 54.40 54.40 Vinyl tris (beta-methoxyethoxy) silane 0.50 1.50 1.50 Antioxidant (c) 0.85 0.85 --- Calcium stearate ----- 0.90 0.90 Triallyl cyanurate ----- 00.50 0.50 Antioxidant (d) - - ~ - - - - - - 0.85 Peroxide (e) 0.65 0.50 0.45 Peroxide (f) - - - - - - - - - 0.19 100 100 100 (a) 18% by weight vinyl acetate; melt index 2.5; (b) 17.6% by weight of ethyl acrylate, melt index 1.2; (c) polymerized 1,2-dihydro-2,2,4-trimethylquinoline; (d) tetrakis [methane-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane; (E) alpha, alpha'-bis (t-butylperoxy) diisopropylbenzene; (f) di-alpha-cumyl peroxide.

The compositions in Table I were processed into test specimens as required by the following test procedures and subjected to the following tests: tensile strength and elongation, ASTM-D412-68; Shore D Hardness ASTM-D2240-75; secant module, ASTM-D882-758; density, ASTM-D1505-68; brittleness temperature, ASTM-D746-73; tensile strength and elongation (as above, under heat aging conditions).

Fire tests as described Monsantoreometer Curing This test method is described in more detail in U.S. Patent 4,018,852, which is hereby incorporated by reference. In summary, Fig. 1 of said patent specification shows the typical Monsantoreometer curve. The optimum cure level (highest crosslink density) is referred to as H.

It is measured in cm-kg of torque on the rheometer test equipment. A higher value for H corresponds to a higher crosslink density.

The time, in minutes, required to achieve 90% of the maximum cure (H) is denoted as Ct. Anvulking time reached, when a rheometer level of 11.5 cm-kg of torque on the rise- is defined as the time, in minutes, at which the curve the part of the curve.

In general, one is interested in getting to the maximum cure (H) as soon as possible. In other words, a short Ct is desirable. At the same time, one would like St to be as long as possible because a longer St means that the vulcanizable composition is desired to be processed at a higher speed or at a higher temperature, ie it would be less susceptible to vulcanization.

Brabender setting time A constant amount of weight of material is added to a Brabender mixer which is kept at 150 ° C and 40 rpm and which is suitably adjusted so that a torque can be continuously measured on the material.

When the material reaches l35 ° C, torque measurement begins determined by means of a Brabender Plastograph Recorder. The torque continues to decrease until a significant degree of crosslinking occurs at which time the torque measured value begins to increase. At the time when the torque curve intersects the zero point, scorching is considered to have occurred. The width of a bowl-shaped curve described by Plastogra fl v fi k flflfifl ïlar the vulcanization time measurement in minutes. The wider the bowl at this curve, the smaller the indentation.

The results of these tests are reported in Table II. 7806929-1 12 Table II Exemooi 1 '2 g Physical properties nragnåiifastnet, kp / omz _ 170.8 142.7 153.9 clearing, 5 253 233 220 Shore D-hardness 47 47 49 sokananodui, kp / omz 1336 1223 1256 Density , g / omz, 1406 1398 1419 Brittleness temperature, OC -55.0, 52.0 -50.5 Heat aging Tensile strength, kp / cm2 / elongation,% 7 days, 15s ° c is3 / zoo 159/233 16a / 2oo Monsantoreometer H (cure level) cm / kg, 128.3 139.8 140.3 ST (wetting time) min 1.05 1.30 1.38 CT (cure time), min HS 5.65 5.15 5.55 s ofoctivity factor = í -fS- 13.65 20.53 26.19 TT Brabender evaporation time minutes 4.1 6.0 8.2 Fire tests sAr J refers to 15111 approved approved approved UL 788 device - “- -“ - - “- CSA device brammæst -“ - - “- -“ - l These tests are performed on an 18 guage copper twisted conductor (16 strands) with 0.762 mm insulation.

A comparison of the results shows similar physical properties with both copolymer systems with the exception of a slightly lower tensile strength and elongation with the ethylene-ethyl acrylate copolymer system (Examples 2 and 3). However, the compositions of the present invention (Examples 2 and 3) exhibit greater flexibility as shown by the lower Secant Module values.

The Monsantoreometer values and the Brabender vaporization time values show that the compositions of the present invention (Examples 2 and 3) are superior to an ethylene-vinyl acetate copolymer system (Example 1) in scorch resistance. Heat aging data and flammability data are comparable between the two resin systems.

Example Gel 4 ~ 5 The compositions of these examples were prepared by the methods of Examples 1-3.

The compositions of the compositions are reported in Table III.

Table III in ethylene-ethyl acrylate copolymer (a) 41.85 ----- Ethylene-ethyl acrylate copolymer (b) ----- 41.85 Hydrated alumina 54.40 54.40 Vinyl-tris (beta-methoxyethoxy) silane 1 , 50 1.50 Antioxidant (c) 0.85 0.85 Calcium stearate 0.90 0.90 Trial lyl cyanurate Û. 50 0.50 Peroxia (a) 0.50 ojso 100 100 (a) 20.35% by weight ethyl acrylate, melt index 4.8; (b) 17.60% by weight of ethyl acrylate, melt index 1.2; (c) Polymerized 1,2-dihydro-2,2,4-trimethylquinoline; (d) alpha, alpha'-bis (t-butylperoxy) diisopropylbenzene.

The compositions in Table III were subjected to a clamping test (according to SAE J 8a) as follows: a 91.4 cm cable was placed tensioned over a 3.8 mm steel bar and subjected to the force of a weighted steel anvil applying an increasing force at a speed of 2, 27 kg / min. The moment the insulation is squeezed through, the 3.18 mm rod comes into contact with the test conductor and the test is interrupted. For an 18 guage wire with a conductor diameter of approximately 1,016 mm and an insulation thickness of 0.762 mm, the minimum durability required to pass this test is 220.8 kpcn. 7806929-1 14 The results of this test are reported in Table IV.

Table IV Example 5 å Clamp Resistance, bpcm 193.2-200.1 248.4-255.3 From the values in the table it appears that a composition containing 518% ethyl acrylate in the ethylene-acrylic copolymer is more clamp resistant than a copolymer containing more than 18% ethyl acrylate.

Claims (6)

'7806929-1 15 PATENT REQUIREMENTS 1. A curable composition for electrical coating is characterized in that it comprises ethylene-alkyl acrylate copolymer containing 25 to 318% by weight of ethyl acrylate and from about 80 to about 400 parts per 100 parts of the ethylene-alkyl acrylate copolymer of hydrated alumina treated with at least a silane having the following formula: RaS1X4_a wherein R is selected from lower alkyl, lower alkenyl or lower alkynyl, X is an alkoxy group having 1 to 20 carbon atoms and a is an integer of 1 or 2, the silane being present in an amount of from 0, 5 to about 5.0 parts of silane per 100 parts of hydrated alumina. 2. A composition according to claim 1, characterized in that R is lower alkenyl and a is 1. 3. A composition according to claim 2, characterized in that the silane is vinyl-tris (beta-methoxyethoxy) silane. Composition according to any one of Claims 1 to 3, characterized in that the ethylene-alkyl acrylate copolymer consists of ethylene-ethyl acrylate copolymer. 5. A composition according to claim 4, characterized in that the ethylene-ethyl acrylate copolymer contains gß to 510% by weight of ethyl acrylate. Electric wire or cable characterized in that it is insulated with a composition comprising ethylene-alkyl acrylate copolymer containing ¿5 to 318% by weight of ethyl acrylate and from about 80 to about 400 parts per 100 parts of the ethylene-alkyl acrylate copolymer of hydrated alumina treated with at least one silane of the following formula: R SiX a 4 7806929-1 1 CW wherein R is selected from lower alkyl, lower alkenyl or lower alkynyl, X is an alkoxy group having 1-20 carbon atoms and a is an integer of 1 or 2, the silane being present in an amount of from 0.5 to about 5.0 parts of silane per 100 parts of hydrated alumina.