KR950007089B1 - Shared articles of crosslinked polymers - Google Patents

Abstract

Electrical conductors which are insulated by an inner polymeric layer having little or no cross-linking and high elongation, and an outer polymeric layer having a relatively high level of cross-linking and low elongation. Preferably each of the components comprises a crystalline fluorocarbon polymer, especially an ethylene/tetrafluoroethylene copolymer. Such articles can be prepared by (1) melt-extruding a first polymeric composition which contains little or no cross-linking agent, and a second polymeric composition which contains a greater amount of cross-linking agent, (2) maintaining the two extrudates under conditions such that cross-linking agent migrates from the second to the first composition, and (3) cross-linking both compositions, preferably by radiation.

Description

Crosslinked polymer products

The present invention relates to an electrically insulating conductor.

It has been known that bridged polymer compositions are used as electrical insulators on wires or other conductors. Known insulated wires include radiation bridged fluorocarbon polymers, which are widely used as aircraft wires, in particular wires coated with a layer of ethylene / tetrafluoroethylene copolymer (sometimes referred to as ETFE polymer). Military publication MIL-W-22759 sets several standards for insulated wires. For example, United States Patent Nos. 3,763,222, 3,840,691, 3,894,118, 3,911,192, 3,970,770, 3,985,716, 3,995,091, 4,031,167, 4,155,823 and 4,353,961.

Such wires have significant drawbacks if the outer surface of the insulator is damaged and subsequently the availability of the wires propagates through the insulator, which is very undesirable. This disadvantage is particularly acute when the insulation wire is used in aircraft or other high performance situations where the consequences of insulation failure are too severe. Quantitative measurement of this drawback can be obtained with a notch transfer test as described below.

This drawback was found to be substantially mitigated by an insulator consisting of an inner layer of polymer with little or no bridging and an outer layer with relatively high levels of bridging. Moreover, this improvement is eliminated with little or substantially no degradation of other important properties of the insulation, such as rub abrasion resistance, twisted wire abrasion resistance and cutting resistance.

In one aspect, the present invention provides an electrically insulating conductor, in particular a wire, configured as follows.

(1) electrical conductors;

(2) (a) (i) the polymer consists of a first melted bridged polymer composition having a melting point of 200 ° C. or higher, and (ii) a first M ₁₀₀ value of 0 to 24.5 kg / cm 2 (0 to 350 spi). Internal electrical insulation layer having; And (b) (i) a second molten bridged polymer composition separated from the conductor by an inner layer, and (ii) the polymer has a melting point of at least 200 ° C., and (iii) at least 24.5 kg / cm 2 (350spi) ), and the at least 1M than ₁₀₀ value 3.5㎏ / ㎠ (insulating layer having a high value as ₁₀₀ 50spi claim 2M).

The M ₁₀₀ value herein is the modulus value measured at a temperature above the melting point of the polymer by the procedure detailed below, indicating the degree of crosslinking of the layer. A preferred method of making such an insulated conductor consists of the following steps.

(1) melt molding the first polymer composition to make a first layer;

(2) melt molding the second polymer composition to make a second layer by contacting the second composition containing the spin bridging agent with the first layer;

(3) maintaining contact between the first layer and the second layer with a portion of the spin bridging agent moving from the second layer to the first layer; And

(4) spinning the first layer and the second layer to cause bridge bonding of the first layer and the second layer.

In the polymerization composition used in the present invention, the polymer component preferably comprises a melt-formable crystalline polymer having a melting point of 200 ° C. or higher, more preferably 250 ° C. or higher, or a mixture of such polymers. will be. The term “melting point” is used to denote a temperature above that at which crystals do not appear in the polymer (or when the crystalline polymer mixture is used as the main crystalline component of the mixture). Particularly preferred polymers are fluorocarbon polymers.

The term “fluorocarbon polymer” has been used to denote a polymer or a polymer mixture in which fluorine contains at least 10% by weight, preferably at least 25% by weight. Thus, the fluorocarbon polymer is a single fluorine-containing polymer, a mixture of two or more fluorine-containing polymers, or a mixture of one or more fluorine-containing polymers with one or more fluorine-free polymers. The fluorocarbon polymer comprises at least 50% by weight, in particular at least 75% by weight, in particular 85% by weight, of at least 25% by weight of one or more thermoplastic crystalline polymers comprising at least 25% by weight of a homopolymer such as fluorine, preferably a crystalline polymer. It is desirable to. Such fluorocarbon polymers are, for example, fluorine-containing polymers and / or polyolefins, preferably crystalline polyolefins, in addition to crystalline fluorine-containing polymers or polymers. Fluorine-containing polymers are generally single- or copolymers of olefin unsaturated monomers containing one or more fluorine, or copolymers of one or more olefins with one or more such monomers. Fluorocarbon polymers have a melting point of at least 200 ° C. and sometimes a melting point of at least 250 ° C., such as about 300 ° C.

Preferably the polymerization composition has a viscosity of 10 ⁵ poise or less at a temperature no higher than 60 ° C. above its melting point. Preferred fluorocarbon polymers are copolymers of ethylene and tetra fluorethylene and optionally one or more other comonomers, in particular 35 to 60 mole percent ethylene, 35 to 60 mole percent tetra fluor ethylene and up to 10 mole percent Or a copolymer composed of more other comonomers.

Other specific polymers that may be used include ethylene and chlorotrifluoroethylene copolymers, copolymers of one or both of hexafluoropropylene and tetrafluoroethylene with vinylidene fluoride, or hexafluoroisobutylene and fluorine Copolymers of vinylidene sulfide and tetrafluoroethylene and hexafluoropropylene copolymers.

The polymerization composition may optionally include suitable additives such as pigments, sulfiding agents, heat stabilizers, acid acceptors and processing aids.

The first and second compositions preferably contain the same polymerization composition, more preferably are substantially the same in all respects except for the degree of bridge bonding.

The conductor is preferably a metal (eg copper) wire that is twisted or solid. The wire is for example 10 to 2 AWG in size. The first layer is preferably in contact with the conductor. The second member forms the ribbon cable in the form of a layer having the same general shape as the first layer or used to connect a plurality of wires each wire is surrounded by the first layer. The layers are preferably in direct contact but may be interconnected by an adhesive layer.

Preferably, the first and second members are molded by melt extrusion, in particular continuous extrusion, tubular extrusion or pressure extrusion so that these layers become hot when first contacted, in order to enhance the movement of the bridge binder.

Preferably the polymer composition should be selected such that at least the outer layer has a tensile strength of at least 3,000 psi (210 kg / cm 2). And because higher tensile strength is desirable in the bridged product, and there is often a decrease in tensile strength during the spinning step, higher initial tensile strength, for example 6,000 psi (420 kg / cm 2) or more, preferably 7,000 psi ( 490 kg / cm 2) or more, particularly 8,000 psi (56 kg / cm 2) or more is preferred.

The thickness of the inner layer is generally 0.0075 cm to 0.038 cm (0.003 inches to 0.015 inches), preferably 0.075 cm to 0.0225 cm (0.003 inches to 0.009 inches). The thickness of the outer layer is generally 0.01 cm to 0.063 cm (0.004 inches to 0.025 inches), preferably 0.01 cm to 0.023 cm (0.005 inches to 0.009 inches).

Preferred spinal bridge conjugates comprise at least 15 mole percent, preferably at least 20 mole percent, more preferably at least 25 mole percent carbon-carbon unsaturated groups. In most cases the crosslinker comprises at least two ethylene dipolymers such as allyl, metallyl, propargyl or vinyl groups. We have achieved good results with bridged binders comprising at least two allyl groups, in particular three or four allyl groups. Particularly preferred bridging agents are triallyl cyanurate (TAC) and triallyl isocyanurate (TAIC), and other specific bridging agents are triallyl trimellitate, triallyl trimesate, tetraallyl pyromellitate, 1 And diallyl ester of 1,3-trimethyl-5-carboxy-3- (p-carboxyphenyl) indane. Other bridging agents disclosed in the above-mentioned U.S. patents, which are known to be incorporated into the fluorocarbon polymer prior to molding, may also be used. Mixtures of crosslinkers may be used.

In a preferred method of making a product of the present invention wherein the bridge binder moves from the second member to the first member, the extruded first composition contains little or no other binder (eg 0 to 2% by weight, preferably Is 0%); The extruded second composition comprises at least as much as required during the bridging step, such as at least 5% by weight, preferably 5 to 25% by weight, in particular 7 to 12% by weight of the bridging agent. The time required to maintain the contact of the layers before bridging depends on the degree of movement required and the temperature during the contact and is between 5 and 150 above the melting point of the polymer (or lower melting point if there are two or more polymers in the layers). It is preferable to lower the temperature.

Upon spinning the inner layer preferably comprises 0 to 3% by weight of the bridge binder and the outer layer comprises 3 to 10% by weight of the bridge binder.

In general, the throwing dose used in the spinning step is 50 Mrad or less so that the polymer does not decompose due to excessive radiation, and the throwing dose is preferably balanced against the tendency of the polymer to decompose due to the high throwing of the radiation. It will depend on the degree of bridge engagement. Suitable projection amounts are generally in the range of 2 to 40 Mrads, for example 2 to 30 Mrads, preferably 3 to 20 Mrads, in particular 5 to 25 Mrads, in particular 5 to 15 Mrads. The ionizing radiation may be in the form of, for example, accelerated electrons or gamma rays. Spinning is generally carried out at about room temperature, although higher temperatures may also be used.

The inner layer need not be crosslinked at all, but is preferably crosslinked to have an M100 value of 2.8 to 17.5 kg / cm 2 (40 to 250 psi), particularly 3.5 to 10.5 kg / cm 2 (50 to 150 psi). The elongation of the inner layer is preferably at least 100%, in particular at least 125%, for example at least 150%, in particular from 200 to 300%.

The outer layer is preferably bridged to have an M100 value of at least 28 kg / cm 2 (400 psi), with at least 31.5 kg / cm 2 (45 psi) and in many cases a minimum of at least 42 kg / cm 2 (600 psi). This is more preferable. The elongation of the outer layer is preferably 40 to 150%, in particular 50 to 120%.

The various physical properties mentioned in this specification were measured as described below.

Notch propagation values are measured on one insulated wire, approximately 30 centimeters (12 inches) long. Using a laser blade perpendicular to the wire's axis, make a notch about 5 centimeters (2 inches) from one end of the insulator. The depth of the notch is such that the laser blade protrudes by 0.01 centimeter (0.004 inch) distance, or if the insulation consists of two layers and the outer layer has a thickness t less than 0.018 centimeter (0.007 inch), (t-0.0051) It is controlled by placing a laser blade between two metal blocks to protrude a distance of centimeters (t-0.002 inches). The end of the wire closer to the notch is secured to a horizontal core with a diameter equal to three times the outer diameter of the insulation. It is secured to the other end of an additional wire of 0.675 kg (1.5 lb) to suspend the wire vertically. The mandrel then rotates clockwise at about 60 revolutions per minute until most of the wire is wound around the mandrel. The mandrel is then rotated counterclockwise until the wire is unwound and most of the wire is wound around the mandrel again. Again, the mandrel rotates clockwise until the wire is unwound and most of the wire is rewound in the mandrel. This procedure is continued until the conductor is visible by visually observing the notched area. At this time, if the conductor breaks (or if some or all wires of the twisted wire conductor break), then the breakage is due to the breakage, not because the notch has propagated through the insulation. The number of cycles (half of the number of times the mandrel rotation was reversed) is recorded.

The M ₁₀₀ value is determined by a static modulus test conducted about 40 ° C. above the melting point of the polymer (eg at about 320 ° C. for the ETEE polymer), as described in US Pat. No. 4,353,961.

Tensile strength and elongation are determined by ASTM D 638-72 (ie at 23 ° C.) at a test rate of 50 mm (2 inches) per minute. The cross line wear value, cut resistance value, and rub wear value are determined by the test method described in US Pat. No. 4,353,961.

The invention is presented by the following examples, in which example 1 is a comparative test.

Example 1

Twisted tin-plated copper wire of 20AWG (19/32) is melt-extruded and continuously extruded thereon, so that the inner insulation layer is 0.01 to 0.0125 cm (0.004 to 0.005 inch) thick, and the outer insulation layer is 0.018 to 0.020 cm (0.007 to 0.008 inches) thick.

These layers consist of the following compositions.

Polymeric insulators were bridged by spinning 14 Mrads.

Example 2

The same procedure as in Example 1 was carried out except for the composition of the inner layer.

The various tests presented above for the products of the examples were carried out to obtain the following results (average values of the samples).

* In most specimens, breakage occurred due to breakage of conductor lines.

Claims (8)

An insulated electric wire comprising a metal wire and a polymerized electric insulator surrounding the wire, wherein the electrical insulation comprises (a) (i) a first molten bridged polymer composition having a melting point of 200 ° C. or higher. (Ii) an internal electrical insulation layer having a first M ₁₀₀ value of 0 to 24.5 kg / cm 2 (0 to 350 spi); And (b) (i) a second molten bridged polymer composition separated from the conductor by an inner layer, and (ii) the polymer has a melting point of at least 200 ° C., and (iii) at least 24.5 kg / cm 2 (350spi) ), and the at least 1M than ₁₀₀ value 3.5㎏ / ㎠ (electric wire insulation, characterized in that it comprises an insulating layer having a high value as ₁₀₀ 50spi claim 2M). The polymer of claim 1 wherein each of the polymers of each of the first and second polymer compositions is capable of one or more addition copolymerization with 35 to 60 mole percent units derived from ethylene, 35 to 60 mole percent units derived from tetrafluoro ethylene. Insulated electric wire, characterized in that consisting of 0 to 10 mole percent unit copolymer derived from the comonomer. The insulated electric wire according to claim 2, wherein the inner layer has an M ₁₀₀ value of 3.5 kg / cm 2 to 10.5 kg / cm 2, and the outer layer has an M ₁₀₀ value of at least 42 kg / cm 2. The insulated electric wire according to claim 3, wherein the inner layer has an elongation of 200% to 300% and the outer layer has an elongation of 50% to 120%. The thickness of the inner layer in contact with the wire is 0.0075 cm to 0.038 cm, has an elongation of at least 125%, and the thickness of the outer layer in contact with the inner layer is from 0.01 cm to 0.063 cm thick, 50%. Insulated electric wire, characterized in that having an elongation of to 120%. (1) melt molding the first polymer composition to make a first layer; (2) melt molding the second polymer composition for making a second layer by contacting the second composition containing the spin bridge binder with the first layer; (3) maintaining contact between the first layer and the second layer with a portion of the spinning bridge binder moving from the second layer to the first layer; And (4) radiating the first layer and the second layer so as to cause bridge bonding of the first layer and the second layer. The method of claim 6, wherein the first polymer composition is free of the spin bridge binder included when melt-molded, and the second polymer composition includes 5 wt% or more of the spin bridge binder immediately after the melt molding. 7. The polymer of claim 6 wherein each of the polymers of the first and second polymer compositions is capable of one or more addition copolymerizations with 35 to 60 mole percent units derived from ethylene, 35 to 60 mole percent units derived from tetrafluoroethylene. Characterized in that it consists of a copolymer of 0 to 10 mole percent units derived from the comonomer.