DE2734071A1 - POLYAETHYLENE INSULATION MATERIAL - Google Patents

Description

Patent attorneys
Dr.-lng. Waiter Abitz Dr. Dieter F. M ο rf Dipl.-Fhys. M. Gritschneder 8 Munich 86, Pieiuftnauerstr. 28

JULY 28, 1977

AD 4839 A

EGG. DU PONT DE NEMORS AND COMPAIiY Wilmington »Delaware» V.St.A.

Polyethylene insulation material

709885/0997

The invention relates to electrical insulation or insulation materials, such as primary insulation, in particular suitable for high voltage cables. It concerns a polyethylene composition »containing an additive» which ensures resistance to the electrical breakdown of the cable. In a special way, that is Invention with the improvement of the resistance to electrical failure of a low density exhibiting polyethylene and crosslinked polyethylene.

Electrical failure of high voltage insulation often starts with contaminating particles. It's extreme difficult or even impossible »solid organic insulating materials (like polyethylene) to extrude onto a conductor without any flaws. Even if in the making extreme cleanliness of the polyethylene »can be used during the subsequent handling of the resin before the Final processing impurities are introduced. Another cause of electrical insulation failure consists in the presence of voids.

High-voltage cables insulated with polymers are subject to dielectric breakdown after an electrical "partial discharge channel formation" or "treeing" known mechanism. The tree formation represents one relative slowly progressing degradation of insulating materials caused by electron and ion bombardment of the insulation caused. The bombardment creates micro-channels or tubes with a tree-like or tuft-like appearance formed »from which the aforementioned designation is explained. Tree formation begins due to ionization (corona) during strong voltage increases at points with impurities or cavities, which are for the polymeric insulating material Represent premd structures. When the tree formation once has started »the ramifications usually spread

- 1 709885/0997

continues (especially during further sharp spikes), and at an indefinite time it can lead to a dielectric failure.

Various additives have already been used to solve this problem Suggested especially for polyethylene or other polyolefins that require tree formation only starts when a higher voltage is applied. With the help of an additive, an attempt is made to prevent the failure the isolation by preventing any tree formation.

US Pat. No. 3,499,791 describes a coating for a high-voltage cable made from a polyethylene resin which contains an inorganic ionic salt of a strong acid and a compound with pronounced zwitterion formation. The insulated cable is resistant to the electrical breakdown and stress cracking corona effect.

US Pat. No. 3,956,420 describes an insulating material with improved dielectric strength contains a polyolefin, a ferrocene compound and a substituted quinoline derivative. In the patent specification furthermore, the additional use of a small amount of polyhydric alcohol, dispersants, surface-active agents Agents or unsaturated polymers or mixtures thereof for further improving the dielectric strength described.

In US Pat. No. 3,795,646, an ethylene-containing polymer composition with improved ionization resistance under high voltage stress is described, which is obtained by adding a liquid silicone (silicone oil) to a crosslinked polyethylene.

709885/0997

AD 4839 A

The JA-PS 14348/75 describes wire cables with improved dielectric strength, which by a Polyethylene insulation with a content of O> 1 wt .- ^ of an aromatic ketone is achieved.

According to DT-OS 2 147 684, the dielectric strength is of polymers (especially polyethylene) by increasing the free path of charge carriers (electrons) changed by incorporating additional scattering centers or by reducing the crystallinity of the polymer .

Japanese patent application 7201988 describes an isolated Power cables with improved dielectric strength »which are made with the help of an insulating layer of polyethylene» Polypropylene, polycarbamate or polyester with a content of mica particles, which with a hydrophobic insulating material are coated from silicone oil, stearic acid, palmitic acid or oleic acid.

In Japanese Patent Application Laid-Open No. 49/119,937 there are electrical insulating resin compositions described, in which an increased dielectric strength is achieved that to a resin (such as polyethylene) a ferrocene-aldehyde or ketone polymer with ferrocene groups or a mixture of the mixed ferrocene-containing polymers and a higher alcohol.

The invention relates to a composition of matter and an electrical conductor having such a composition is coated, which consists essentially of polyethylene or crosslinked polyethylene and an effective amount of an alcohol with 6 to 24 carbon atoms, which is a building growth inhibitor capable of »for

- 3 709885/0997

at least a thousandfold increase in electrical resistance of polyethylene (measured after an electrical durability test).

Appropriate materials include

(a) a composition of polyethylene and a tree growth inhibitor in foiin at least one alcohol with 6 to 24 carbon atoms;

(b) the composition of (a) with a peroxide crosslinking agent ;

(c) the composition of (a) or (b) which has been crosslinked; and

(d) the composition of (a) »(b) or (c) as insulation on an electrical conductor.

A particularly suitable insulation for high-voltage cables Composition consists essentially of optionally crosslinked polyethylene and one that has electrical resistance improving higher alcohol. A rapid test (referred to here as "Test Method A") shows that the Presence of the alcohol inhibits electrical tree growth (but not tree formation) by at least a thousandfold Increase in the electrical resistance of polyethylene can be achieved. It is assumed »that the called test direct conclusions about the long-term electrical resistance of such an insulation on a Conductor »i.e. an extended service life of the insulation when used for the intended purpose is permitted.

Under "polyethylene" or "crosslinked polyethylene" are homopolymers or copolymers with at least 85 wt .- ^ ethylene units and at least 95 wt .- ^

- 4 -709885/0997

To understand olefin units. These polymers are consistent with the definition of "polyethylene plastics" ASTM Standards Yearbook 1976, 1976, Part 36, page ("Plastics or Resins Made by Polymerization of not less than 85% by weight of ethylene and not less as 95% by weight total olefins "). A preferred polyethylene or crosslinked polyethylene contains about 100% by weight of ethylene units.

Specific examples of olefins which can be used as comonomers are propylene, butene-1, hexene-1, octene-1 and decene-1. Specific Examples of other suitable comonomers are norbornene, butadiene, styrene, methacrylic acid, vinyl acetate, Ethyl acrylate, isobutyl acrylate and methyl vinyl ether.

With "polyethylene" in the present context only Polymers denotes that are practically free of crosslinking, while the term "crosslinked polyethylene" relates to polymers containing crosslinks. The cross-links can be by any mechanism, for example by irradiation or with the aid of a peroxide crosslinking agent.

Polyethylene or crosslinked low-density polyethylene can be used according to the invention. The polyethylene types with higher density are not suitable according to the invention, since in their Pail when an alcohol of the type defined here is added only a small or no (and certainly not a thousandfold) improvement in electrical durability or resistance is achieved. "Low density" means that the polyethylene in question, optionally crosslinked, has a density of up to about 0.92 g / cm '; for the definition of "low density" reference is also made to ASTM test standard D 1248-74.

- 5 -709885/0997

For certain applications, the stiffness of the insulation also plays a role in the choice of polyethylene; For example, overhead transmission cables require flexibility.

According to the invention, the polyethylene or crosslinked polyethylene The additive to be incorporated is an alcohol with 6 to 24 carbon atoms, preferably 8 to 12 carbon atoms. Aliphatic and / or monohydric alcohols are preferred. The alcohols can either be straight or be branched-chain. Specific examples of suitable alcohols are n-hexyl-, n-heptyl- »n-octyl-» n-decyl- » n-dodecyl, n-tetradecyl, stearyl, eicosyl and benzyl alcohol as well as 2-decanol, 4-decanol, cyclohexanol, 3-methylheptanol-3 » 2-methyloctanol-2 and 2-phenylpropanol-2; n-decyl alcohol and n-dodecyl alcohol are special among them preferred. The alcohols that can be used are also referred to in the present context as "tree growth inhibitors".

The alcohol can be any conventional polyethylene Method can be incorporated, for example by mixing with the solid polyethylene prior to compounding or extrusion, injection into the molten polyethylene, diffusion into the solid polyethylene or crosslinked Polyethylene by spraying, soaking or steam contacting or bringing into contact with a polyethylene or cross-linked polyethylene-containing object with liquid or vaporous alcohol.

The suitability of an additive to increase electrical Resistance by at least a thousandfold can be determined by a test method (test method A) in which (not crosslinked) polyethylene in the absence of a peroxide

- 6 709885/0997

wetting agent is used. Because the conversion of polyethylene in crosslinked polyethylene with the help of a peroxide crosslinking agent to increase the electrical resistance can lead »the improvement achieved with a tree growth inhibitor by adding a peroxide crosslinking agent to a certain extent obscured. A modification of test method A »in the networked Polyethylene is used instead of polyethylene »has proven itself as a rough test» with their help whether, in a rapid test, the incorporation of an additive improves the electrical resistance is achieved. However, this modified test method A is not sufficient for the determination in all cases » whether an at least a thousandfold improvement in electrical resistance is achieved.

With test method A, a tree formation must be triggered in an insulating material test body. If the polyethylene is cross-linked, the "tree" can be examined visually. On the other hand, (non-crosslinked) polyethylene is opaque and does not allow a visual determination of a "tree ¹ , ^1" without making an incision in the polyethylene. Therefore, when using test method A on polyethylene, one generally has to use several test specimens and destroy one test specimen determine whether tree growth has occurred under the initial stress conditions.

Although in test method A the determination »whether an additive is based on the electrical resistance of polyethylene a rapid test increased by at least a thousandfold »no peroxide crosslinking agent is used» extends the invention relates to a composition of matter which is im essentially made of polyethylene or crosslinked polyethylene (the crosslinking by any mechanism, e.g.

- 7 708885/0997

AO

with the help of a peroxide) and an alcohol, as well as the use of such a composition for an electrical conductor.

A concentration of alcohol required to increase the time to failure (as measured by Test Method A) by at least a thousand fold is called the "effective fraction". This concentration (based on the weight of the alcohol in relation to the weight of the polyethylene) leads directly to at least a thousand-fold increase in the useful life of non-crosslinked polyethylene. Purely cross-linked polyethylene means that an effective proportion of an alcohol is to be equated with the alcohol concentration that would be necessary to bring about an at least a thousand-fold improvement in (non-cross-linked) polyethylene. In general, the alcohol in a proportion of about 0.5 to about 10 wt. -Fi (preferably from about 1 to about 5 wt .- ^) of polyethylene or crosslinked polyethylene available.

It is also possible to use higher alcohol concentrations with advantage. However, such an addition can lead to an increase in the power factor or loss angle of the polyethylene or crosslinked polyethylene. You should therefore not use an excessively high proportion if a higher power factor is harmful (for example in the case of high-voltage transmission lines). In such an application, the insulating material preferably has a power factor of at most 1 i », preferably of at most 0.5%».

Appropriate materials include

(a) a composition of polyethylene and at least one alcohol containing 6 to 24 carbon atoms,

709885/0997

Ai

(b) the composition of (a) with a peroxide crosslinking agent »

(c) the composition of (a) or (b) that has been crosslinked, and

(d) the composition of (a), (b) or (c) as insulation or insulating material on an electrical Ladder.

A particularly preferred composition according to the invention contains polyethylene, a peroxide crosslinking agent and at least an alcohol containing 8 to 12 carbon atoms as a tree growth inhibitor. This composition is suitable as a starting material for insulations containing crosslinked polyethylene, which can be used for electrical conductors.

The conventional peroxide crosslinking agents used for polyethylene crosslinking are suitable for the purpose according to the invention, such as di-α-cumyl peroxide, 2,5-bis (tert-butylperoxy) -2,5-dimethylhexane or 2,5-dimethyl-2,5-di- (tert-butylperoxy) -hexyne-3.

If the peroxide crosslinking agent is soluble in alcohol, you can solve it in this and incorporate the solution into the polyethylene. The polyethylene containing these additives will normally not be crosslinked until after application to an electrical conductor.

To explain, and not to be bound by, any theory about the manner in which the alcohol consumes the Inhibits tree growth, it should be noted that the alcohol has the ability to cross-link through the polyethylene or Diffuse polyethylene through into voids in the insulation. The initial formation of microchannels in the iso-

- 9 709885/0997

AD 4839 A

The tree growth follows, resulting in a tree-like appearance results. Tree growth usually progresses to the point of dielectric failure of the insulation. Pure the In the present case, however, it is assumed that one of the inventive Definition of appropriate alcohol penetrates the cavities and the electron and ion bombardment prevented. The inhibition of tree growth after it has started leads to an increase in electrical resistance the insulation.

The test method is intended to be one causing the dielectric failure Mechanism to be mimicked. In practice, power cables generally begin to tree during strong voltage increases, which can be attributed to switching operations or lightning strikes, for example. Afterward it can occur under normal operating conditions and especially during additional strong voltage increases insulation failure. When using the composition according to the invention, the longer than Tree growth inhibitor added alcohol to the useful life of the insulation by preventing the growth of 'trees' after their Inhibits initiation and thereby prevents premature insulation failure.

In contrast to conventional test methods, which determine the dielectric strength of an insulation, test method A is intended to provide a measure of the service life of the insulation. In this test, a high AC voltage initially applied to electrodes within the insulation triggers tree formation without the insulation failing. This initial tree formation is followed by a recovery period during which no voltage is applied for at least about 24 hours. The time to failure of the insulation is then determined by applying a voltage of between the electrodes, which are 2 mm apart

- 10 709885/0997

12,000 V, i.e. an average electrical voltage gradient of 6,000 V / mm under the assumption a uniform field (see test method A). However, the field is due to the small diameter of the shaped ends of the electrodes are reinforced to a value of more than 6,000 V / mm.

It can be assumed that the rapid test for determining the electrical resistance is a useful standard for the service life of the insulation * which is used over long periods of time (e.g. at least 30 years) it is of course inexpedient to carry out such a long test. In addition, a long-term test would only be relative few test specimens actually fail, so that a statistical investigation would be necessary. In case of a A composition consisting essentially of polyethylene and containing the alcohol mentioned will be used in normal use failure due to dielectric breakdown of the polyethylene is unlikely to occur.

The following is the test to determine the increase in electrical resistance (test method A) explained.

Test method A

The polyethylene used for this test method is initially formed into a block, here called the "SPING test specimen" referred to as. "SPING" is the abbreviation for "plague phase inner needle spark gap" (solid phase internal needle gap). A SPING test specimen measures 25 mm square and is 6 mm thick and contains two longitudinally embedded, aligned electrodes that are equally spaced from the end faces and from the opposite edges. The tips of the electrodes are in the Block center at a distance of 2 mm from each other. The electric

- 11 709885/0997

each are about 30 mm long and each have one Diameter of about 0.6 mm. One electrode (the high-voltage electrode) has a conical tip with an included angle of 30 ° and a radius of 5 μια; the second electrode (ground electrode) is on one Ground hemispherical end (radius 0.3 mm).

At least five SPING test specimens are used for each of the tests used. Each SPING test specimen is placed under silicone oil to prevent creeping sparks. The high voltage electrode is connected to a high voltage rail, while the ground electrode is connected to a spaced pair of 6.25 cm spheres, the are grounded via a 1 megaohm resistor. A gap or distance is set between the balls that is sufficient that sufficient tension is achieved to trigger tree formation in the SPING test body. With in one Spheres set at a distance of 0.762 cm, for example, one at a speed of 500 V / sec. increasing Voltage (60 Hz) applied until a discharge takes place between the two balls. Before this rollover takes place, the stress imposed on the test specimen is practically zero. At the moment of collapse However, the air gap will give the specimen electrodes the applied voltage plus one from the arc developed radio frequency signal and maintained for 1 to 2 seconds, resulting in tree formation. The for The voltage required to induce tree formation will vary depending on the composition tested. Pure polyethylene, which contains an alcohol corresponding to the definition according to the invention, a voltage of 35 to 40 kV is required. For polyethylene containing other additives, the voltage required may be higher or lower; the however, the voltage to be applied in each case can easily be passed through

- 12 709885/0997

Visually inspect each test specimen for any tree formation that has begun.

After the tree has started to form »no voltage is applied to the test specimen for about 24 hours. Afterward a high voltage of 12,000 V (average 6000 V / mm) is applied between the electrodes. One determines until the failure of the middle test piece (e.g. the third test piece out of five test pieces or of the fifth specimen out of nine specimens in terms of time to failure) elapsed time; the received The value is the "electrical resistance".

Failure is indicated by dielectric breakdown. If a failure occurs "a tree ¹¹ connects the two electrodes and leads to a sudden amplification of the current (which can be displayed on a recording ammeter)" whereby the test on the test specimen in question is terminated.

The tree growth inhibitor used according to the invention has the effect the improvement in a different way than the traditional additives. The known additives are in the generally referred to as compounds »which when added to polyethylene or other suitable insulating materials require higher characteristic voltage to trigger tree formation at a needle tip (for the relevant Methods, a »sharp needle tip embedded in the test specimen is generally used; the second electrode is arranged in different ways). The characteristic tension is that tension »at the at the Half of the test specimens start to form after one hour. Investigated to determine the size mentioned you have several groups of specimens at some different voltages. If you determine the characteristic tension

- 13 709885/0997

Ah

has asked »the test is over.

In contrast, the tree growth inhibitor is used in the Invention not to prevent the beginning of tree formation, but exclusively to suppress growth of a tree after its initial formation.

Although the invention relates to a composition of polyethylene or crosslinked polyethylene with an alcohol » the composition may contain other conventional additives; such additives are usually present. Examples of such additives are antioxidants such as polymerized trimethyldihydroquinone, lubricants such as Calcium stearate, pigments such as titanium dioxide, fillers such as glass particles, and reinforcing agents such as fiber materials, e.g. asbestos or glass fibers.

Although an insulating material made of polyethylene or cross-linked polyethylene with a content of a tree growth inhibitor is particularly suitable for power cables in which the current is carried under a voltage of at least 15 kV (such as 15 to 220 kV), this material can also be used for purposes in which lower or higher voltages occur. In accordance with the prior art, a semiconductor layer can be arranged between the conductor and an insulating layer in a power cable. Such semiconductor layers usually contain an insulating composition which also contains carbon black.

The invention also provides objects (in particular power cables) made of an electrical conductor and an insulating layer "which consist of an inhibitor-containing polyethylene composition according to the invention" with a semiconductor layer optionally located between the insulating layer and the conductor.

- 14 -709885/0997

1+

The following examples illustrate the invention.

Insulating materials for Comparative Example A and Examples 1 to 4

A) Polyethylene: Homopolymer melt index (ASTM D-1238) 1.8 g / 10 min.

Density 0.918 g / cm ⁵

[determined according to ASTM D-1505-68 (renewed 1975)]

B) Antioxidant: 4 »4'-thio-bis- (6-tert-butyl-m-cresol),

1500 ppm

C) Tree growth inhibitor: n-dodecyl alcohol

(except for comparative example A)

Comparative example A (no tree growth inhibitor)

SPING test
body Degree of
Failure Test method A
Time to failure
Hours. 1 1 0.10 CVl 2 0.25 3 5 0.38 4th 4th 0.35 5 3 0.25 example 1 and 2

In Example 1, n-dodecyl alcohol is incorporated into polyethylene pellets by drum mixing and subsequent extrusion mixing. In Example 2, the n-dodecyl alcohol is injected into the molten polyethylene with the aid of a gear pump in the mixing zone of the extruder. In example 1 and

- 15 709885/0997

AD 4839 A 273407

the final concentration of n-dodecyl alcohol exceeds 3 wt -. $> of polyethylene (measured by IR spectrometry). Nine SPING test specimens are produced per example and tested using test method A.

The nine SPING test specimens from Examples 1 and 2 are removed from the test after 1960 and 1730 hours, respectively, without any Test specimen has failed. The electrical resistance is therefore more than 1960 hours or more than 1730 hours.

The test is then continued on the same SPING test specimens. The nine SPING test specimens from Examples 1 and 2 are then removed from the test after a total of 4000 hours, without that some specimen has failed. The electrical resistance is therefore more than 4000 hours in each case.

A comparison of examples 1 and 2 with the comparative example A shows that the electrical durability is increased by more than a thousand times.

Example 3 and 4

In these examples, n-dodecyl alcohol is also used as an additive in a concentration of about 3 wt .- ^ of the polyethylene (determined by IR spectrometry) was used. In Example 3, the polyethylene is mixed in a Banbury mixer with the alcohol while mixing in Example 4 is carried out in a Brabender mixer. There will be each nine SPING test specimens produced from the compositions of the examples and tested according to test method A. All SPING test specimens from Example 3 are removed from the test after 850 hours, while all SPING test specimens of Example 4 after 720 hours from the test. It shows

- 16 709885/0997

that none of the test specimens failed in either example 3 or example 4. The electrical resistance is thus more than 850 hours or more than 720 hours. The increase in electrical resistance to the Comparative Example A is more than a thousand times.

In the remaining examples (Examples 5 to 10) and in the Comparative Examples B to D, test method A is also used, but with the minor changes that the Electrodes each have a diameter of 1 mm (instead of 0 »6 mm) and the second electrode at one end is ground to a hemisphere with a radius of 0.5 mm (instead of 0.3 mm). These changes are only to facilitate machining when making the shape of the Electrode end made, since a thickness of 1 mm ensures less flexibility than a thickness of 0.6 mm. Carried out with the thicker and the thinner electrodes in SPING test specimens made from the same insulating material Parallel tests confirm that the same test results are achieved in each case. The one using the thicker one Test performed on electrodes will therefore continue to be referred to as "Test Method A".

Example 5 to 10

In these examples the insulating material corresponds to that of Examples 1 to 4. The polyethylene used is also a homopolymer with a density of 0.918, but has a melt index of 2.5 and contains about 750 ppm of the same antioxidant. Other tree growth inhibitors are also used. The tree growth inhibitor content of the polyethylene is 3% by weight in each case .

In Examples 5 to 10, the tree growth inhibitor is used

- 17 -

703885/0997

Polyethylene pellets by drum mixing and then Extrusion blending incorporated. There are four SPING test specimens prepared for each example and tested according to test method A (if you take four SPING test specimens to the test is subject to, the electrical resistance is higher than the time until the failure of the second SPING test body »however less than the time to failure of the third SPING test piece).

Example 5 uses n-dodecyl alcohol (primary alcohol) as the tree growth inhibitor. All SPING test specimens are removed from the test after 600 hours. It turns out that no test specimen has failed. The electrical resistance is therefore more than 600 hours.

In Example 6, the tree growth inhibitor used is cyclohexanol (primary alcohol). All SPING test specimens are made according to 768 hours removed from the test. It turns out that no test specimen has failed. The electrical resistance is thus more than 768 hours.

In Example 7, the tree growth inhibitor used is benzyl alcohol (primary alcohol). All SPING test specimens are removed from the test after 720 hours. It turns out that no Test specimen has failed. The electrical resistance is therefore more than 720 hours.

In Example 8 the tree growth inhibitor is 2-decanol (secondary alcohol). All SPING test specimens are made according to 552 hours removed from the test. It turns out that no Test specimen has failed. The electrical resistance is therefore more than 552 hours.

In Example 9, 4-decanol is used as the tree growth inhibitor (secondary alcohol). All SPING test specimens are made according to

- 18 -70 * 885/0997

31.

600 hours removed from the test. It turns out »that no Test specimen has failed. The electrical resistance is therefore more than 600 hours.

In Example 10 the tree growth inhibitor is 2-phenyl-2-propanol (tertiary alcohol). All SPING test specimens are removed from the test after 552 hours. It shows »that no test specimen has failed. The electrical resistance is therefore more than 552 hours.

In all examples 5 to 10, compared to the comparative example A achieves a more than a thousandfold increase in electrical resistance.

Comparative Examples B, C and D

In Comparative Examples B to D, polyethylene is tested with a higher density.

In comparative example B, polyethylene is used with a density of O »96O g / cm, the 100 ppm antioxidant" Irganox 10-10 " contains. The polyethylene pellets are made with 3 # n-dodecyl alcohol by drum mixing and subsequent extrusion mixing united.

In Comparative Example 0, 88.11 wt .- # pellets of the same polyethylene (density 0.960 g / cm ⁵ ) and 11.89 wt .- # pellets of polyethylene with a density of 0.918 g / cm ⁵ (the 700 ppm antioxidant "Sanotox B "contains) drum-mixed, further mixed by extrusion in a twin-screw press and processed into pellets. Comparative Example D corresponds to Comparative Example C with the exception that 52.38 wt.% Polyethylene with a density of 0.960 g / cm ⁵ and 47 »62 wt.% Polyethylene with a density of 0» 918 g / cm are used.

- 19 -70 * 885/0997

turns. In any case, the pellets from the mixture are then 3 fi n-dodecyl tumbled "followed by a Extrusionsvermisehen connects.

The materials are then used to create SPING test specimens manufactured. A small piece of polymer is then taken from a SPING test specimen for each composition Density determination (ASTM I) 1505-68) separated. The densities are:

Comparative Example B 0.957 g / cm '; Comparative Example C 0.949 g / cm '; and Comparative Example D 0.936 g / cm.

Five test specimens from each material are then used Subject to test method A. In Comparative Examples B, C and D, all five SPING test specimens fail before the end of a day. The electrical resistance is therefore less than 24 hours in each case.

End of description. / _t

- 20 -

70 * 885/0997

Claims (3)

E. I. DU PONT DE NEMORS AJID COMPANY AD 4839 A PATENT CLAIMS Composition of matter »essentially consisting of (a) optionally crosslinked low density polyethylene; and (b) an effective proportion of at least one alcohol with 6 to 24 carbon atoms »which is capable of» the electrical resistance of polyethylene (determined according to test method A) by at least a thousandfold. 2. Process for making a low density polyethylene and one in an alcohol having 6 to 24 carbon atoms Composition containing soluble peroxide as a crosslinking agent »characterized» that he (a) Dissolves the peroxide in the alcohol and (b) incorporating the peroxide and alcohol into the polyethylene. 3. Use of the composition according to claim 1 for the insulating layer of an electrical conductor or cable. - 1 709885/0997 ORIGINAL INSPECTED