Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-02
2002-10-22
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S223000, C524S224000, C524S194000
Reexamination Certificate
active
06469088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stabilizer mixtures, improved polyolefin compositions stabilized with said stabilizer mixtures and to articles of manufacture utilizing same. The stabilizer compositions are a mixture of a diacyl hydrazine compound wherein one or both of the acyl moieties contain a hindered phenolic substitutent and an alkylenebisacylamide wherein one or both of the acyl moieties contain a hindered phenolic substituent. These stabilizer combinations provide improved oxidative stability for polyolefins and particularly for polyolefin insulation utilized in applications where the insulation will be in contact with water-blocking fillers
2. Description of the Invention
Polyolefin resins, especially polyethylene and polypropylene, are widely used as primary insulation materials for wire. For example, telephone “singles” are produced by extrusion coating 19, 22, 24 or 26 AWG copper wire with solid and/or foamed resin. For the construction of telecommunication cables, these singles are uniformly twisted into pairs and up to 50 or more of these pairs are then typically bundled in a metallic or plastic sheath.
While the outer sheath or jacket provides mechanical protection for the individually insulated conductors, significant deterioration of the insulation, which ultimately results in cracking and necessitates replacement of the cable, has been observed in certain installations. Environmental factors, primarily moisture, heat, light, oxygen and physical stress, are known to accelerate this deterioration. Stabilizers have been used to inhibit deterioration caused by these factors.
Combinations of primary antioxidants and metal deactivators have been used to protect polyolefin compositions used to insulate copper conductors against thermooxidative degradation. Commercially, a combination of pentaerythrityl tetrakis(3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate) and N,N′-bis(3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionyl hydrazine has been demonstrated to be effective. A discussion of primary antioxidant/metal deactivator combinations can be found in Chapter 2 of the
Plastics Additive Handbook
, edited by R. Gachter and H. Muieller, Hanser Publishers (1987), and in an article by G. D. Brown,
International Wire and Cable Symposium Proceedings
1987, pp. 337-343.
A second type of degradation, referred to as “treeing,” is caused by moisture. To minimize the risk of water penetration, the jacket or sheath encasing the bundled insulated wires is filled with a water-blocking filler grease. These filler grease compounds, usually hydrocarbons of a heavy oil or waxy consistency, are forced under pressure into the cable to fill the voids and interstices therein. While these cable fillers have generally proven to be effective water-blocks, they have a tendency to extract the stabilizer(s). Thus, while the oxidative stability of the insulation may initially be adequate, after exposure to the water-blocking agent there is a significant decrease in the stabilizer protection which can lead to premature catastrophic failure. In one study comparing the stability of solid and cellular polyethylene insulation with and without contact with hydrocarbon filler reported at pages 85 and 86 of the above-referenced text of Gächter and Muieller, it was found that aging in the presence of petrolatum reduces the stability of solid polyethylene by 35 percent and of cellular polyethylene by 10-40 percent.
The choice of stabilizer is therefore even more critical where the insulated conductor is used in conjunction with a water-blocking cable filler. After evaluating numerous primary antioxidant/metal deactivator combinations in polyethylene, Brown in his above-referenced article reports he was unable to identify a cost effective primary antioxidant - alternative to pentaerythrityltetrakis(3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate) providing good melt processing stabilization and improved performance after cable filler exposure. Keogh, et al., in U.S. Pat. Nos. 5,380,591 and 5,575,952 utilize a mixture of one or more alkylhydroxyphenylalkanoyl hydrazines and one or more functionalized hindered amines as stabilizers to provide polyolefin insulation compositions which are resistant to extraction and premature degradation.
It would be highly advantageous if an improved stabilizer formulation were available which provided superior oxidative stability upon exposure to water-blocking grease fillers. It would be even more advantageous if the components of the stabilizer package were readily available. These and other advantages are provided by the formations of the present invention which will be described in more detail to follow.
SUMMARY OF THE INVENTION
The improved stabilizer compositions of the invention which provide superior oxidative stability when incorporated in polyolefin insulation compositions exposed to water-blocking fillers comprise a mixture of (a) a diacyl hydrazine compound wherein one or both of the acyl moieties contain a hindered phenolic substitutent and (b) an alkylenebisacylamide compound wherein one or both of the acyl moieties contain a hindered phenolic substituent, (a) and (b) respectively present in a weight ratio from about 1:1 to 8:1. The diacyl hydrazine compound has the formula
wherein R is a C
1-10
alkylene group, A is a hindered phenolic substituent corresponding to the formula
wherein R′ is a C
1-8
alkyl group and B is hydrogen or A and, in a preferred embodiment, is N,N′-bis(3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionyl)hydrazine. The alkylenebisacylamide compound has the formula
where AB and R are the same as defined for the diacyl hyrazine compound and, in a preferred embodiment is N,N′-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydro-cinnamide). The stabilizers of the invention are preferably employed with propylene polymers containing both amorphous and crystalline phases. Propylene polymers of this type can be either reactor-made or post-reactor produced blends of polypropylene homopolymer and ethylene-propylene copolymers. The diacyl hydrazine compound will constitute from 0.1 to 1.0 percent of the total composition and the alkylenebisacylamide compound will constitute from 0.05 to 0.8 percent of the total composition. Highly effective propylene polymer insulation compositions can additionally contain 5 to 20 percent high density polyethylene, 0.1 to 1 percent small particle size talc and 0.005 to 0.1 percent organic peroxide. Propylene polymer compositions formulated in accordance with the invention are particularly effective primary insulation for 20-26 AWG copper wire coated to a thickness of 7-15 mil and maintained in contact with a hydrocarbon filler grease within a jacketed assembly.
DETAILED DESCRIPTION
Stabilizer combinations utilized for the present invention are mixtures of diacyl hydrazine compounds wherein one or both of the acyl moieties contains a hindered phenolic substitutent and alkylenebisacylamides wherein one or both of the acyl moieties contains a hindered phenolic substituent. These stabilizer combinations are useful with a wide variety of polyolefins used for primary insulation and jacketing applications to improve oxidative stability. These polyolefins include &agr;-olefin homopolymers, copolymers and blends obtained by conventional polymerization methods known to the art. The stabilizer mixtures of the invention are particularly useful with polyethylene (PE) and polypropylene (PP).
As utilized herein, the terms polyethylene and polypropylene are intended to encompass both homopolymers and copolymers of ethylene and propylene, respectively. All percentages and ratios referred to herein are on a weight basis unless otherwise indicated. Percentages of components are given on a weight basis, based on the total weight of the composition.
Useful polyolefin compositions of the invention are formulated using polyethylene resins having densities in the range from about 0.92 g/cm
3
up to
Baracka Gerald A.
Equistar Chemicals LP
Heidrich William A.
Szekely Peter
LandOfFree
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