WO1993024935A1

WO1993024935A1 - Telephone cables

Info

Publication number: WO1993024935A1
Application number: PCT/US1993/004871
Authority: WO
Inventors: Michael John Keogh; Geoffrey David Brown
Original assignee: Union Carbide Chemicals & Plastics Technology Corporation
Priority date: 1992-05-26
Filing date: 1993-05-24
Publication date: 1993-12-09
Also published as: MX9303053A

Abstract

An article of manufacture comprising (i) a plurality of electrical conductors, each surrounded by one or more layers of a mixture comprising (a) one or more polyolefins and (b) the reaction product(s) of an anhydride of an unsaturated aliphatic diacid and one or more functionalized hindered amines and/or functionalized hindered phenols; and (ii) hydrocarbon cable filler grease within the interstices between said surrounded conductors.

Description

TELEPHONE CABLES

Technical Field

This invention relates to wire and cable and the insulation and jacketing therefor and, more particularly, to telephone cable.

Background Information

A typical telephone cable is constructed of twisted pairs of metal conductors for signal transmission. Each conductor is insulated with a polymeric material. The desired number of transmission pairs is assembled into a circular cable core, which is protected by a cable sheath incorporating metal foil and/or armor in combination with a polymeric jacketing material. The sheathing protects the transmission core against mechanical and, to some extent, environmental damage.

Of particular interest are the grease-filled telephone cables. These cables were developed in order to minimize the risk of water penetration, which can severely upset electrical signal transmission quality. A watertight cable is provided by filling the air spaces in the cable interstices with a hydrocarbon cable filler grease. While the cable filler grease extracts a portion of the antioxidants from the insulation, the watertight cable will not exhibit premature oxidative failure as long as the cable maintains its integrity.

In the cable transmission network, however, junctions of two or more watertight cables are required and this joining is often accomplished in an outdoor enclosure known as a pedestal (an interconnection box). Inside the pedestal, the cable sheathing is removed, the cable filler grease is wiped off, and the transmission wires are interconnected. The pedestal with its now exposed insulated wires is usually subjected to a severe environment, a combination of high temperature, air, and moisture. This environment together with the depletion by extraction of those antioxidants presently used in grease-filled cable can cause the insulation in the pedestal to exhibit premature oxidative failure. In its final stage, this failure is reflected in oxidatively embrittled insulation prone to cracking and flaking together with a loss of electrical transmission performance.

To counter the depletion of antioxidants, it has been proposed to add high levels of antioxidants to the polymeric insulation. However, this not only alters the performance characteristics of the insulation, but is economically unsound in view of the high cost of antioxidants. There is a need, then, for antioxidants which will resist cable filler grease extraction to the extent necessary to prevent premature oxidative failure and ensure the 30 to 40 year service life desired by industry.

Disclosure of the Invention

An object of this invention, therefore, is to provide a grease-filled cable construction containing antioxidants, which will resist extraction and be maintained at a satisfactory

stabilizing level. Other objects and advantages will become apparent hereinafter.

According to the invention, an article of manufacture has been discovered which meets the above object.

The article of manufacture comprises, as a first component, a plurality of electrical conductors, each surrounded by one or more layers of a mixture comprising (a) one or more polyolefins and (b) the reaction product(s) of an anhydride of an unsaturated aliphatic diacid and one or more functionalized hindered amines and/or functionalized hindered phenols; and, as a second component, hydrocarbon cable filler grease within the interstices between said surrounded conductors. In one other embodiment, the article of manufacture comprises first and second components; however, the mixture of the first component contains absorbed hydrocarbon cable filler grease or one or more of the hydrocarbon constituents thereof and, in another embodiment, the article of manufacture is comprised only of the first component wherein the mixture contains hydrocarbon cable filler grease or one or more of the hydrocarbon constituents thereof.

Description of the Preferred Embodiments

The polyolefins used in this invention are generally thermoplastic resins, which are crosslinkable. They can be homopolymers or copolymers produced from two or more comonomers, or a blend of two or more of these polymers, conventionally used in film, sheet, and tubing, and as jacketing and/or insulating materials in wire and cable applications. The monomers useful in the production of these homopolymers and copolymers can have 2 to 20 carbon atoms, and preferably have 2 to 12 carbon atoms. Examples of these monomers are alpha-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene; unsaturated esters such as vinyl acetate, ethyl acrylate, methyl acrylate, methyl methacrylate, t-butyl acrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, and other alkyl acrylates; diolefins such as 1,4-pentadiene, 1,3-hexadiene, 1,5-hexadiene, 1,4-octadiene, and ethylidene norbornene, commonly the third monomer in a terpolymer; other monomers such as styrene, p-methyl styrene, alpha-methyl styrene, p-chloro styrene, vinyl naphthalene, and similar aryl olefins; nitriles such as acrylonitrile,

methacrylonitrile, and alpha-chloroacrylonitrile; vinyl methyl ketone, vinyl methyl ether, vinylidene chloride, maleic anhydride, vinyl chloride, vinylidene chloride, vinyl alcohol, tetrafluoroethylene, and chlorotrifluoroethylene; and acrylic acid, methacrylic acid, and other similar unsaturated acids.

The homopolymers and copolymers referred to can be non-halogenated, or halogenated in a conventional manner, generally with chlorine or bromine. Examples of halogenated polymers are polyvinyl chloride, polyvinylidene chloride, and polytetrafluoroethylene. The homopolymers and copolymers of ethylene and propylene are preferred, both in the non-halogenated and halogenated form. Included in this preferred group are terpolymers such as ethylene/propylene/diene monomer rubbers.

Other examples of ethylene polymers are as follows: a high pressure homopolymer of ethylene; a copolymer of ethylene and one or more alpha-olefins having 3 to 12 carbon atoms; a homopolymer or copolymer of ethylene having a hydrolyzable silane grafted to their backbones; a copolymer of ethylene and a hydrolyzable silane; or a copolymer of an alpha-olefin having 2 to 12 carbon atoms and an unsaturated ester having 4 to 20 carbon atoms, e.g., an ethylene/ethyl acrylate or vinyl acetate copolymer; an ethylene/ethyl acrylate or vinyl acetate/hydrolyzable silane terpolymer; and ethylene/ethyl acrylate or vinyl acetate

copolymers having a hydrolyzable silane grafted to their

backbones.

With respect to polypropylene: homopolymers and copolymers of propylene and one or more other alpha-olefins wherein the portion of the copolymer based on propylene is at least about 60 percent by weight based on the weight of the copolymer can be used to provide the polyolefin of the invention. The polypropylene can be prepared by conventional processes such as the process described in United States patent 4,414,132. The alpha-olefins in the copolymer are preferably those having 2 or 4 to 12 carbon atoms.

The homopolymer or copolymers can be crosslinked or cured with an organic peroxide, or to make them hydrolyzable, they can be grafted with an alkenyl trialkoxy silane in the presence of an organic peroxide which acts as a free radical generator or catalyst. Useful alkenyl trialkoxy silanes include the vinyl trialkoxy silanes such as vinyl trimethoxy silane, vinyl triethoxy silane, and vinyl triisopropoxy silane. The alkenyl and alkoxy radicals can have 1 to 30 carbon atoms and preferably have 1 to 12 carbon atoms. The hydrolyzable polymers can be moisture cured in the presence of a silanol condensation catalyst such as dibutyl tin dilaurate, dioctyl tin maleate, stannous acetate, stannous octoate, lead naphthenate, zinc octoate, iron 2-ethyl hexoate, and other metal carboxylates.

The homopolymers or copolymers of ethylene wherein ethylene is the primary comonomer and the

homopolymers and copolymers of propylene wherein propylene is the primary comonomer may be referred to herein as polyethylene and polypropylene, respectively.

Anhydrides of unsaturated aliphatic diacids having 4 to 20 carbon atoms, and preferably 4 to 10 carbon atoms, can be used for the reaction with the hindered phenol and/or hindered amine. The reaction product can be formed in two ways. In situ formation can be accomplished by mixing the polyolefin, the anhydride, and the hindered phenol and/or hindered amine together at a temperature in the range of about 100°C to about 260°C. The second method is to first mix the anhydride with the hindered phenol and/or hindered amine at a temperature in the range of about 100°C to about 260°C and then compound the reaction product with the polyolefin. The mole ratio of anhydride to hindered phenol and/or hindered amine can be in the range of about 1 to about 10 moles of anhydride per mole of total hindered phenol and hindered amine and is preferably in the range of about 1 to about 5 moles of anhydride per mole of total hindered phenol and hindered amine. For each 100 parts by weight of polyolefin, the other components of the insulation mixture can be present in about the following proportions:

Component Parts by Weight

Broad Range Preferred

Range

(i) Total reaction 0.01 to 5 0.1 to 1 product of

anhydride and

hindered phenol

and/or hindered

amine

(ii) Grease 3 to 30 5 to 25

The term "anhydride" shall be considered to include acyclic and cyclic anhydrides and dianhydrides, which can be saturated or unsaturated. Examples are maleic anhydride, itaconic anhydride, nadic anhydride, succinic anhydride, methylsuccinic anhydride, phthalic anhydride, hexahydrophthalic anhydride, 4-methylphthalic anhydride, hexahydro-4-methylphthalic anhydride; methyl-5-norbornene-2,3-dicarboxylic anhydride; 1,2,4-benzene-tricarboxylicanhydride; and 1,2,4,5-benzenetetracarboxylic anhydride (pyromellitic anhydride). Excess anhydride, if present after reaction, can be removed by devolatilization at temperatures in the range of about 200°C to about 250°C using a vacuum, if necessary.

The reaction product of anhydride and hindered phenol and/or hindered amine can have the following structural formulas:

wherein R is:

—

Y is -N(R⁴)C(=0)-R⁵-C(=0)-N(R⁴);

R⁴ is hydrogen or methyl;

R⁵ is a direct bond or a diradical having 1 to 4 carbon atoms;

R² and R³ are independently tert-butyl or tert-amyl;

a is an integer from 0 to 4;

X is 1,2 ethyl; 1,2 propyl; 1,2-cyclohexyl; 4-methyl-1,2 cyclohexyl;

1,2-ethylene; or 5-methyl-2,3-norbornyl; and

Z is hydrogen, methyl, -C(=0)OH, or -(C(=0)-0)_bM

wherein M is an alkali metal or an alkaline earth metal and b is 1 or 2.

It is preferred that, in the above formulas, R⁴ is hydrogen, R⁵ is a direct bond, and a is an integer from 0 to 2.

Hydrocarbon cable filler grease is a mixture of hydrocarbon compounds, which is semisolid at use temperatures. It is known industrially as "cable filling compound". A typical requirement of cable filling compounds is that the grease has minimal leakage from the cut end of a cable at a 60 °C or higher temperature rating. Another typical requirement is that the grease resist water leakage through a short length of cut cable when water pressure is applied at one end. Among other typical requirements are cost competitiveness; minimal detrimental effect on signal transmission; minimal detrimental effect on the physical characteristics of the polymeric insulation and cable sheathing materials; thermal and oxidative stability; and cable fabrication processability.

Cable fabrication can be accomplished by heating the cable filling compound to a temperature of approximately 100°C. This liquefies the filling compound so that it can be pumped into the multiconductor cable core to fully impregnate the interstices and eliminate all air space. Alternatively, thixotropic cable filling compounds using shear induced flow can be processed at reduced temperatures in the same manner. A cross section of a typical finished grease-filled cable transmission core is made up of about 52 percent insulated wire and about 48 percent interstices in terms of the areas of the total cross section. Since the interstices are completely filled with cable filling compound, a filled cable core typically contains about 48 percent by volume of cable filling compound.

The cable filling compound or one or more of its hydrocarbon constituents enter the insulation through absorption from the interstices. Generally, the insulation absorbs about 3 to about 30 parts by weight of cable filling compound or one or more of its hydrocarbon constituents, in toto, based on 100 parts by weight of polyolefin. A typical absorption is in the range of a total of about 5 to about 25 parts by weight per 100 parts by weight of polyolefin. It will be appreciated by those skilled in the art that the combination of resin, cable filling compound constituents, and antioxidants in the insulation is more difficult to stabilize than an insulating layer containing only resin and antioxidant, and no cable filling compound constituent.

Examples of hydrocarbon cable filler grease (cable filling compound) are petrolatum; petrolatum/polyolefin wax mixtures; oil modified thermoplastic rubber (ETPR or extended thermoplastic rubber); paraffin oil; naphthenic oil; mineral oil; the aforementioned oils thickened with a residual oil, petrolatum, or wax; polyethylene wax; mineral oil/rubber block copolymer mixture; lubricating grease; and various mixtures thereof, all of which meet industrial requirements similar to those typified above.

Generally, cable filling compounds extract insulation antioxidants and, as noted above, are absorbed into the polymeric insulation. Since each cable filling compound contains several hydrocarbons, both the absorption and the extraction behavior are preferential toward the lower molecular weight hydrocarbon wax and oil constituents. It is found that the insulation composition with its antioxidant not only has to resist extraction, but has to provide sufficient stabilization (i) to mediate against the copper conductor, which is a potential catalyst for insulation oxidative degradation; (ii) to counter the effect of residuals of chemical blowing agents present in cellular and cellular/solid (foam/skin) polymeric foamed insulation; and (iii) to counter the effect of absorbed constituents from the cable filling compound.

Functionalized hindered phenols, useful in the invention, can be, among others, hydrazides, hydrazones, semicarbazides, oxamides, carbazates, or ami no and amine compounds. The following are examples of the above:

2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-aminopropane

2,6-di-t-butyl-4-aminophenol, 2,6-di-t-amyl-4-aminophenol

2 ,6-di-t-hexyl-4-aminophenol

2,6-bis(1,1-dimethylpentyl)-4-aminophenol

2,6-bis(1,1,3,3-tetramethylbutyl)-4-aminophenol

2-t-butyl-6-t-amyl-4-aminophenol

2-t-butyl-6-(1,1-dimethylbutyl)-4-aminophenol

2-t-amyl-6-(1,1-dimethylbutyl)-4-aminophenol

2-t-butyl-6-(1,1-dimethylpentyl)-4-aminophenol

2-t-butyl-6-(1,1,3,3-tetramethylbutyl)-4-aminophenol

2-t-butyl-6-methyl-4-aminophenol

2-t-amyl-6-methyl-4-aminophenol

3,5-di-t-butyl-4-hydroxybenzylamine

3,5-di-t-amyl-4-hydroxybenzylamine

3,5-di-t-hexyl-4-hydroxybenzylamine

3-t-butyl-5-methyl-4-hydroxybenzylamine

2-(3,5-di-t-butyl-4-hydroxyphenyl)ethylamine

2-(3,5-di-t-amyl-4-hydroxyphenyl)ethylamine

2-(3-t-butyl-5-methyl-4-hydroxyphenyl)ethylamine

3-(3,5-di-t-butyl-4-hydroxyphenyl)propylamine

3-(3,5-di-t-amyl-4-hydroxyphenyl)propylamine

3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propylamine

3-(3,5-di-t-butyl-4-hydroxyphenyl)propionhydrazide

3-(3,5-di-t-amyl-4-hydroxyphenyl)propionhydrazide

3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionhydrazide

3-(3-t-butyl-4-hydroxyphenyl)propionhydrazide

3-(3,6-di-t-hexyl-4-hydroxyphenyl)propionhydrazide

3,5-di-t-butyl-4-hydroxybenzhydrazide

3,5-di-t-amyl-4-hydroxybenzhydrazide

3-t-butyl-5-methyl-4-hydroxybenzhydrazide

3-(3,5-di-t-butyl-4-hydroxyphenyl)acrylic acid hydrazide

4-(3,5-di-t-butyl-5-hydroxyphenyl)semicarbazide

1-methyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionhydrazide

(3,5-di-t-butyl-4-hydroxyphenyl)acetylhydrazide N-(3,5-di-t-butyl-4-hydroxyphenyl)-N'-aminooxamide

2,5-di-t-butyl-4-hydroxyphenylcarbazate

3,5-di-t-butyl-4-hydroxybenzylcarbazate

(3,5-di-t-butyl-4-hydroxyphenylmercapto)acetylhydrazide

(3-t-butyl-5-methyl-4-hydroxyphenylmercapto)acetylhydrazide

3-(3,5-di-t-butyl-4-hydroxyphenylmercapto)propionhydrazide

3-(3-t-butyl-5-methyl-4-hydroxyphenylmercapto)propionhydrazide

(3,5-di-t-butyl-4-hydroxybenzylmercapto)acetylhydrazide

(3-t-butyl-5-methyl-4-hydroxybenzylmercapto)acetylhydrazide

3-(3,5-di-t-butyl-4-hydroxybenzylmercapto)propionhydrazide

3-(3-t-butyl-5-methyl-4-hydroxybenzylmercapto)propionhydrazide

The preferred hindered phenol is 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionhydrazide.

Functionalized hindered amines, useful in the invention, can be, among others, piperidines functionalized with amines, hydrazines, hydrazides, carboxamides, oxamides, succinamides, or malonamides. The following are examples of the above:

4-amino-2,2,6,6-tetramethylpiperidine

4-amino-1-benzyl-2,2,6,6-tetramethylpiperidine

4-amino-1,2,2,6,6-pentamethylpiperidine

4-amino-1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine

4-amino-1-(2-cyanoethyl)-2,2,6,6-tetramethylpiperidine

4-amino-1-butyl-2,2,6,6-tetramethylpiperidine

4-amino-2,6-diethyl-2,3,6-trimethylpiperidine

4-amino-2,6-diethyl-1,2,3,6-tetramethylpiperidine

2,2,6,6-tetramethyl-4-piperidinylhydrazine

1,2,2,6,6-pentamethyl-4-piperidinylhydrazine

3-(2,2,6,6-tetramethyl-4-piperidinylamino)propionhydrazide (2,2,6,6-tetramethyl-4-piperidinylamino)acetylhydrazide

3-(1,2,2,6,6-pentamethyl-4-piperidinylamino)propionhydrazide N-(2,2,6,6-tetramethyl-4-piperidinyl)hydrazinecarboxamide N-(1,2,2,6,6-pentamethyl-4-piperidinyl)hydrazinecarboxamide N-(2,2,6,6-tetramethyl-4-piperidinyl)-N'-aminooxamide

N-(2,2,6,6-tetramethyl-4-piperidinyl)-N'-aminosuccinamide

N-(2,2,6,6-tetramethyl-4-piperidinyl)-N'-aminomalonamide

N-(1-acetyl-2,2,6,6-tetramethyl-4-piperidinyl)-N'aminooxamide

3-(1-acetyl-2,2,6,6-tetramethyl-4-piperidinylamino)propion- hydrazide

(2,2,6,6-tetramethyl-4-piperidinyloxy)acetyl hydrazide

(1,2,2,6,6-pentamethyl-4-piperidinyloxy)acetyl hydrazide

3-(2,2,6,6-tetramethyl-4-piperidinyloxy)propion hydrazide

3-(1,2,2,6,6-pentamethyl-4-piperidinyloxy)propion hydrazide N,N-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-N^,-aminooxamide 3-[N,N-bis(2,2,6,6-tetramethyl-4-piperidinyl)amino]-propion- hydrazide

N-(2,2,6,6-tetramethyl-4-piperidinyl)-N-butyl-N'aminooxamide

The preferred hindered amine is:

N-(2,2,6,6-tetramethyl-4-piperidinyl)-N'-aminooxamide.

The polyolefin can be one polyolefin or a blend of polyolefins. The reaction product can be one or a mixture of reaction products of anhydride and hindered phenol and/or hindered amine. The reaction product can be present in the mixture with free hindered phenol or free hindered amine and can also be used in combination with disulfides, phosphites or other non-phenolic or non-amine antioxidants in molar ratios of about 1:1 to about 1:2 for additional oxidative and thermal stability, but, of course, it must be determined to what extent these latter compounds are extracted by the grease since this could affect the efficacy of the combination.

The following conventional additives can be added in conventional amounts if desired: ultraviolet absorbers, antistatic agents, pigments, dyes, fillers, slip agents, fire retardants, stabilizers, crosslinking agents, halogen scavengers, smoke inhibitors, crosslinking boosters, processing aids, e.g., metal carboxylates, lubricants, plasticizers, viscosity control agents, and blowing agents such as azodicarbonamide. The fillers can include, among others, magnesium hydroxide and alumina trihydrate. As noted, other antioxidants and/or metal

deactivators can also be used, but for these or any of the other additives, resistance to grease extraction must be considered. 1,2-Bis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamoyl)hydrazine added as an adjunct metal deactivator and antioxidant is desirable.

Additional information concerning grease-filled cable can be found in Eoll, The Aging of Filled Cable with Cellular Insulation. International Wire & Cable Symposium Proceeding 1978, pages 156 to 170, and Mitchell et al, Development.

Characterization, and Performance of an Improved Cable Filling Compound. International Wire & Cable Symposium Proceeding 1980, pages 15 to 25. The latter publication shows a typical cable construction on page 16 and gives additional examples of cable filling compounds.

Additional examples of various polyolefins, hindered phenols, hindered amines, and anhydrides useful in the invention can be found in United States patents 4,801,749;

4,824,884; 4,857,596; 4,863,999; 4,866,136; 4,868,246; 4,874,803; and 4,927,891; and European patent application 434,080.

The patents, patent application, and other publications mentioned in this specification are incorporated by reference herein.

The invention is illustrated by the following

examples.

EXAMPLES 1 to 31

Various materials used in the examples are as follows:

Polyethylene I is a copolymer of ethylene and 1-hexene. The density is 0.946 gram per cubic centimeter and the melt index is 0.9 gram per 10 minutes. Antioxidant A is tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane.

Antioxidant B is 1,2-bis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamoyl)hydrazine

Antioxidant C is N-(2,2,6,6-tetramethyl-4-piperidinyD-N'aminooxamide

Antioxidant D is 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic hydrazide

(i) Preparation of N-[(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide]succinimide.

Into a 100 milliliter three-neck round bottom flask equipped with a magnetic stirrer are added 0.40 gram (0.004 mole) of succinic anhydride; 1.17 grams (0.0048 mole) of antioxidant D, and 50 milliliters of decalin. The mixture is heated with stirring under nitrogen to 180°C for two hours and then to 210°C for an additional 1/2 hour. After cooling to room temperature, an equal volume of hexane is added and the white crystals are filtered, washed repeatedly with hexane, and dried under vacuum at 60°C for 2 hours. The yield of white powdered crystalline material is 1.40 grams (93.3 percent by weight of theoretical yield) with a melting point of 205°C to 208°C.

This procedure is repeated for the anhydrides mentioned in examples 2 to 8 to yield the respective imides with melting points and in the yields set forth in the Table.

(ii) Preparation of N-(2,2,6,6-tetramethyl-4-piperidinyl)-N'-(succinimido)oxamide

Into a 100 milliliter three-neck round bottom flask equipped with a magnetic stirrer are added 1.0 gram (0.01 mole) of succinic anhydride, 2.0 grams (0.0082 mole) of antioxidant C, and 50 milliliters of decalin. The mixture is heated with stirring under nitrogen to 180°C for 4 hours and then to 210°C for an additional 1/2 hour. After cooling to room temperature, an equal volume of hexane is added and the resulting white crystals are filtered and washed repeatedly with hexane and dried at 60°C in a vacuum oven for 2 hours. The yield is 2.08 grams (78.3 percent by weight of theoretical yield) with a melting point of 219°C to 235°C.

This procedure is repeated for the anhydrides mentioned in examples 10 to 15 to yield the respective N-imidooxamides with the melting points and in the yields set forth in the Table.

(iii) In situ preparation of a mixture of resin and the N-imidooxamide prepared in paragraph (ii) above.

To a small Brabender™ mixer heated to 150°C are added 40 grams of polyethylene I, 0.133 gram (0.00055 mole) of antioxidant C, and 0.11 gram (0.0011 mole) of succinic anhydride. The contents are fluxed and mixed at 220°C for 5 minutes and then held at 220°C for 5 additional minutes before discharge.

For examples 16 to 31, 10 mil polyethylene plaques are prepared for oxidation induction time (OIT) testing. In examples 16 to 27 and 29, the plaques are prepared from a mixture of polyethylene I and the antioxidants mentioned in Table II. In examples 28, 30, and 31, the plaques are prepared from a mixture of polyethylene I and reaction products prepared in situ as in (iii) above, i.e., in example 28, a mixture of polyethylene I, antioxidant D, and maleic anhydride, and in examples 30 and 31, a mixture of polyethylene I, antioxidant C, and 4-methylphthalic anhydride and hexahydro-4-methylphthalic anhydride, respectively.

A laboratory procedure simulating the grease filled cable application is used to demonstrate performance. Resin samples incorporating specified antioxidants are prepared as above. The samples are first pelletized and then formed into approximately 10 mil (0.010 inch) thick test plaques using ASTM D-1928 methods as a guideline. There is a final melt mixing on a two roll mill or laboratory Brabender™ type mixer followed by preparation of the test plaques using a compressor molding press at 150°C. Initial oxygen induction time is measured on these test plaques.

A supply of hydrocarbon cable filler grease is heated to about 80°C and well mixed to insure uniformity. A supply of 30 millimeter dram vials are then each filled to approximately 25 millimeters with the cable filler grease. These vials are then cooled to room temperature for subsequent use. An oil extended thermoplastic rubber (ETPR) type cable filler grease is the hydrocarbon cable filler grease used in these examples. It is a typical cable filling compound.

Each ten mil test plaque is then cut to provide about twenty approximately one-half inch square test specimens. Before testing, each vial is reheated to about 70°C to allow for the easy insertion of the test specimens. The specimens are inserted into the vial one at a time together with careful wetting of all surfaces with the cable filler grease. After all of the specimens have been inserted, the vials are loosely capped and placed in a 70°C circulating air oven. Specimens are removed after 2 and 4 weeks, the surfaces are wiped dry with tissue, and the specimens are tested for OIT. In examples 27, 28, 32, and 33, after 4 weeks, the remaining specimens are removed, wiped dry, and placed in a static air chamber at 90°C. At various intervals, specimens are removed and tested for OIT.

OIT testing is accomplished in a differential scanning calorimeter with an OIT test cell. The test conditions are: uncrimped aluminum pan; no screen; heat up to 200°C under nitrogen, followed by a switch to a 50 milliliter flow of oxygen. Oxidation induction time (OIT) is the time interval between the start of oxygen flow and the exothermic

decomposition of the test specimen. OIT is reported in minutes; the greater the number of minutes, the better the OIT. OIT is used as a measure of the oxidative stability of a sample as it proceeds through the cable filler grease exposure and the oxidative aging program. Relative performance in the grease filled cable applications can be predicted by comparing initial sample OIT to OIT values after 70°C cable filler grease exposure and 90°C oxidative aging.

Variables and results are set forth in the following Tables I and II.

TABLE I

PRODUCT MELTING POINT

EXAMPLE ANHYDRIDE YIELD (%) (°C)

1 Succinic 93.3 205 to 208

2 Maleic 87.8 60 to 90

3 Methylsuccinic 87.5 146 to 166

4 Phthalic 95.3 175 to 182

5 Hexahydrophthalic 88.4 130 to 151

6 4-Methylphthalic 86.8 209 to 215

7 Hexahydro-4-methylphthalic 85.5 147 to 158

8 Methyl-5-norbornene-2,3-dicarboxylic 53.5 192 to 202

9 Succinic 78.3 219 to 235

10 Maleic 89.0 240 to 247

11 Methylsuccinic 84.7 240 to 269

12 Phthalic 93.7 290 to 304

13 Hexahydrophthalic 94.5 171 to 213

14 4-Methylphthalic 98.5 252 to 263

15 Hexahydro-4-methylphthalic 95.3 233 to 247

TABLE II

OIT INITIAL (MINUTES)

EXAMPLE ANTIOXIDANTS WT.% (0 WEEKS) 2 WEEKS 4 WEEKS 6 WEEKS

16 A 0.40 116 11 7 ╌ 17 B 0.15 51 19 14 ╌ 18 A/B 0.40/0.15 158 29 19 ╌ 19 D 0.40 35 9 8 ╌ 20 Reaction Product of Example 2 0.40 119 61 43 ╌ 21 Reaction Product of Example 1 0.40 76 51 53 ╌ 22 Reaction Product of Example 3 0.40 126 81 64 ╌ 23 B 0.15 51 19 14 ╌ 24 C/B 0.40/0.15 64 27 27 ╌ 25 Reaction Product of Example 14/B 0.40/0.15 125 57 54 ╌ 26 Reaction Product of Example 15/B 0.40/0.15 93 79 66 ╌ 27 D 0.40 35 8 8 3 28 Reaction Product of Example 2 0.40 101 47 47 43 29 C 0.40 13 13 13 ╌ 30 Reaction Product of Example 14 0.40 125 56 56 ╌ 31 Reaction Product of Example 15 0.40 90 50 50

Notes to Tables I and II:

1. In examples 1 to 8, the anhydride is reacted with antioxidant D, as in (i) above.

2. In examples 9 to 15, the anhydride is reacted with antioxidant C, as in (ii) above.

3. Product yield (%) is the percent by weight of actual product based on the theoretical yield.

4. wt. % is the percent by weight of antioxidant based on the weight of polyethylene I.

5. Examples 16 to 27 and 29 are conducted with a mixture of polyethylene I and antioxidant(s), which are not prepared in situ, and oil.

6. Examples 28, 30, and 31 are conducted with a mixture of polyethylene I and antioxidant(s), which are prepared in situ, as in (iii) above, and oil.

7. In examples 27 to 31, there is 0.40 percent by weight antioxidant based on the weight of polyethylene I.

EXAMPLE 32

A mixture of antioxidants C and D in a molar ratio of 1:1 is added to phthalic anhydride in a molar ratio of 1:1 under conditions favorable to produce a mixture of the reaction product of C and anhydride and D and anhydride. The composition of the mixture is controlled by adjusting the C/D stoichiometry. The antioxidants are mixed with polyethylene I in total amount of 0.40 percent by weight based on the weight of the resin 10 mil films are prepared, and the OIT testing procedure is followed as above. The results are as follows: OIT (minutes)

Weeks

Initial

(0 Weeks) 2 4 8 12 20

180 88 76 61 54 50

EXAMPLE 33

A mixture of antioxidants C and D in a molar ratio of 1:1 is added to 1,2,4,5-benzenetetra-carboxylic anhydride in a molar ratio of 1:1 under conditions favorable to produce three different products, C-anhydride-D, C-anhydride-C, and D-anhydride-D. The composition of the mixture is controlled by adjusting the C/D molar ratio. The antioxidants are mixed with polyethylene I in a total amount of 0.40 percent by weight based on the weight of the resin, 10 mil films are prepared, and the OIT testing procedure is followed as above. The results are as follows:

OIT (minutes)

Weeks

Initial

(0 Weeks) 2 4 8 12 20

111 79 69 66 58 50

Claims

1. An article of manufacture comprising (i) a plurality of electrical conductors, each surrounded by one or more layers of a mixture comprising (a) one or more polyolefins and (b) the reaction product(s) of an anhydride of an unsaturated aliphatic diacid and one or more functionalized hindered amines and/or functionalized hindered phenols; and (ii) hydrocarbon cable filler grease within the interstices between said surrounded conductors.

2. The article of manufacture defined in claim 1 wherein the reaction product has the following structural formula(s):

Y is -N(R⁴)C(=O)-R⁵-C(=O)-N(R⁴);

R⁴ is hydrogen or methyl;

R⁵ is a direct bond or a diradical having 1 to 4 carbon atoms;

R² and R³ are independently tert-butyl or tert-amyl;

a is an integer from 0 to 4;

X is 1,2 ethyl; 1,2 propyl; 1,2-cyclohexyl; 4-methyl-l,2 cyclohexyl;

1,2-ethylene; or 5-methyl-2,3-norbornyl; and

Z is hydrogen, methyl, -C(=O)OH, or -(C(=O)-O)_bM

wherein M is an alkali metal or an alkaline earth metal and b is 1 or 2.

3. The article of manufacture defined in claim 2 wherein R⁴ is hydrogen, R⁵ is a direct bond, and a is an integer from 0 to 2.

4. The article of manufacture defined in claim 2 wherein the hydrocarbon cable filler grease or one or more of the hydrocarbon constituents thereof is present in the mixture of component (i).

5. The article of manufacture defined in claim 4 wherein the amount of hydrocarbon cable filler grease or one or more of the hydrocarbon constituents thereof, in toto, present in the mixture of component (i) is in the range of about 3 to about 30 parts by weight based on 100 parts by weight of polyolefin.

6. An article of manufacture comprising one or more electrical conductors, each surrounded by one or more layers of a mixture comprising

(a) one or more polyolefins;

(b) one or more compounds having the following structural formula(s):

wherein R is:

Y is -N(R⁴)C(=0)-R⁵-C(=0)-N(R⁴);

R⁴ is hydrogen or methyl;

R⁵ is a direct bond or a diradical having 1 to 4 carbon atoms;

R² and R³ are independently tert-butyl or tert-amyl;

a is an integer from 0 to 4;

X is 1,2 ethyl; 1,2 propyl; 1,2-cyclohexyl; 4-methyl-1,2 cyclohexyl;

1,2-ethylene; or 5-methyl-2,3-norbornyl; and

Z is hydrogen, methyl, -C(=0)OH, or -(C(=0)-0)_bM

wherein M is an alkali metal or an alkaline earth metal and b is 1 or 2.

(c) a hydrocarbon cable filler grease or one or more of the hydrocarbon constituents thereof.

7. The article of manufacture defined in claim 6 wherein component (c) is present in an amount of about 3 to about 30 parts by weight based on 100 parts by weight of polyolefin.

8. The article of manufacture defined in claim 7 wherein for each 100 parts of weight of polyolefin, component (b) is present in an amount of about 0.01 to about 5 parts by weight.

9. An article of manufacture comprising (i) a plurality of electrical conductors, each surrounded by one or more layers of a mixture of (a) polyethylene, polypropylene, or mixtures thereof and (b) the reaction product(s) of an anhydride of an unsaturated aliphatic diacid and N-(2,2,6,6-tetramethyl-4-piperidinyl)-N'-aminooxamide and/or 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic hydrazide; and (ii) hydrocarbon cable filler grease within the interstices between said surrounded conductors, wherein the total reaction product(s) are present in an amount of about 0.01 to about 5 parts by weight based on 100 parts by weight of combined polyethylene and polypropylene.

10. The article of manufacture defined in claim 9 wherein 1,2-bis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamoyl)-hydrazine is included in the mixture.