Title of Invention

TREE RESISTANT INSULATION COMPOSITIONS

Abstract Insulation compositions for electric power cables having a polyolefin base polymer and an additive comprising either low molecular weight wax or polyethylene glycol (PEG) and optionally further comprising one or more hindered amine light stabilizers, amine antioxidants and other antioxidant blends are disclosed. Also disclosed are insulation compositions comprising a C2 to C8 alpha olefin in combination with a polyethylene homopolymer together with, optionally, one or more hindered amine light stabilizer and a liquid cresol antioxidant.
Full Text TREE RESISTANT INSULATION COMPOSITIONS
CLAIM OF PRIORITY
[0001] This application claims priority to U.S. Provisional Patent Application Nos.
60/953,309, filed August 6, 2007, and 60/018,625, filed January 2,2008, the disclosures of
which are hereby incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The invention relates to insulation compositions for electric power cables having
a polyolefin base polymer and an additive comprising either low molecular weight wax or
polyethylene glycol (PEG) and optionally further comprising one or more hindered amine light
stabilizers, amine antioxidants and other antioxidant blends. The invention also relates to an
insulation composition comprising a C2 to C8 alpha olefin in combination with a polyethylene
homopolymer together with, optionally, one or more hindered amine light stabilizer and a liquid
cre$ol antioxidant.
BACKGROUND OF THE INVENTION
[0003] Typical power cables generally have one or more conductors in a core that is
surrounded by several layers that can include: a first polymeric semiconducting shield layer, a
polymeric insulating layer, a second polymeric semiconducting shield layer, a metallic tape
shield and a polymeric jacket
[0004] Polymeric materials have been utilized in the past as electrical insulating and
semiconducting shield materials for power cables. In services or products requiring long-term
performance of an electrical cable, such polymeric materials, in addition to having suitable
dielectric properties, must be durable. For example, polymeric insulation utilized in building
wire, electrical motor or machinery power wires, or underground power transmitting cables,
must be durable for safety and economic necessities and practicalities.
[0015] One major type of failure that polymeric power cable insulation can undergo is
the phenomenon known as treeing. Treeing generally progresses through a dielectric section
under electrical stress so that, if visible, its path looks something like a tree. Treeing may occur
and progress slowly by periodic partial discharge. It may also occur slowly in the presence of
moisture without any partial discharge, or it may occur rapidly as the result of an impulse
voltage. Trees may form at the site of a high electrical stress such as contaminants or voids in the
body of the insulation-semiconductive screen interface. In solid organic dielectrics, treeing is the
most likely mechanism of electrical failures which do not occur catastrophically, but rather
appear to be the result of a more lengthy process. In the past, extending the service life of
polymeric insulation has been achieved by modifying the polymeric materials by blending,
grafting, or copolymerization of silane-based molecules or other additives so that either trees are
initiated only at higher voltages than usual or grow more slowly once initiated.
[0006] There are two kinds of treeing known as electrical treeing and water treeing.
Electrical treeing results from internal electrical discharges that decompose the dielectric. High
voltage impulses can produce electrical trees. The damage, which results from the application of
high alternating current voltages to the electrode/insulation interfaces, which can contain
imperfections, is commercially significant. In this case, very high, localized stress gradients can
exit and with sufficient time can lead to initiation and growth of trees. An example of this is a
high voltage power cable or connector with a rough interface between the conductor or
conductor shield and the primary insulator. The failure mechanism involves actual breakdown of
the modular structure of the dielectric material, perhaps by electron bombardment In the past
much of the art has been concerned with the inhibition of electrical trees.
[0007] In contrast to electrical treeing, which results from internal electrical discharges
that decompose the dielectric, water treeing is the deterioration of a solid dielectric material,
which is simultaneously exposed to liquid or vapor and an electric field. Buried power cables are
especially vulnerable to water treeing. Water trees initiate from sites of high electrical stress such
as rough interfaces, protruding conductive points, voids, or imbedded contaminants, but at lower
voltages than that required for electrical trees. In contrast to electrical trees, water trees have the
following distinguishing characteristics; (a) the presence of water is essential for their growth;
(b) no partial discharge is normally detected during their growth; (c) they can grow for years
before reaching a size that may contribute to a breakdown; (d) although slow growing, they are
initiated and grow in much lower electrical fields than those required for the development of
electrical trees.
[0008] Electrical insulation applications are generally divided into low voltage insulation
(less than 1 K volts), medium voltage insulation (ranging from 1 K volts to 69 K volts), and high
voltage insulation (above 69 K volts). In low voltage applications, for example, electrical cables
and applications in the automotive industry treeing is generally not a pervasive problem. For
medium-voltage applications, electrical treeing is generally not a pervasive problem and is far
less common than water treeing, which frequently is a problem. The most common polymeric
insulators are made from either polyethylene homopolymers or ethylene-propylene elastomers,
otherwise known as ethylene-propylene-rubber (EPR) or ethylene-propylene-diene ter-polymer
(EPDM).
[0000] Polyethylene is generally used neat (without a filler) as an electrical insulation
material. Polyethylenes have very good dielectric properties, especially dielectric constants and
power factors. The dielectric constant of polyethylene is in the range of about 2.2 to 2.3. The
power factor, which is a function of electrical energy dissipated and lost and should be as low as
possible, is around 0.0002 at room temperature, a very desirable value. The mechanical
properties of polyethylene polymers are also adequate for utilization in many applications as
medium-voltage insulation, although they are prone to deformation at high temperatures.
However, polyethylene homopolymers are very prone to water treeing, especially toward the
upper end of the medium-voltage range.
[0010] There have been attempts to make polyethylene-based polymers that would have
long-term electrical stability. For example, when dicumyl peroxide is used as a crosslinking
agent for polyethylene, the peroxide residue functions as a tree inhibitor for some time after
curing. However, these residues are eventually lost at most temperatures where electrical power
cable is used. U.S. Pat. No. 4,144,202 issued Mar. 13,1979 to Ashcraft, et al. discloses the incorporation into polyethylenes of at least one epoxy containing organo-silane as a treeing
inhibitor. However, a need still exists for a polymeric insulator having improved treeing
resistance over such silane containing polyethylenes.
[0011] Unlike polyethylene, which can be utilized neat, the other common medium-
voltage insulator, EPR, typically contains a high level of filler in order to resist treeing. When
utilized as a medium-voltage insulator, EPR will generally contain about 20 to about SO weight
percent filler, most likely calcined clay, and is preferably crosslinked with peroxides. The
presence of the filler gives EPR a high resistance against the propagation of trees. EPR also has
mechanical properties, which are superior to polyethylene at elevated temperatures. EPR is also
much more flexible than polyethylene which can be an advantage for tight Space or difficult
installation.
[0012] Unfortunately, while the fillers utilized in EPR may help prevent treeing, the
filled EPR will generally have poor dielectric properties, i.e. a poor dielectric constant and a poor
power factor. The dielectric constant of filled EPR is in the range of about 2.3 to about 2.8. Its
power factor is on the order of about 0.002 to about 0.005 at room temperatjure, which is
approximately an order of magnitude worse than polyethylene.
[00131 Thus, both polyethylenes and EPR have serious limitations as an electrical
insulator in cable applications. Although polyethylene polymers have good electric properties,
they have poor water tree resistance. While filled EPR has good treeing resistance and good
mechanical properties, it has dielectric properties inferior to polyethylene polymers.
[0014] Hindered amine light stabilizers or "HAL"s are primarily used in clear plastic
film, sheets or coatings to prevent degradation by light. HALs are used in unfilled polyethylene
insulations. They are thought to prevent degradation caused by light emitted by tiny electrical
discharges. US Patent No. 5,719,218 discloses an optically transparent polyethylene insulation
formulation with a HALs where it is stated that the HALs are useful for the prevention of
degradation of the insulation by water trees.
[Of 15] U.S. Patent No. 4,302,849 to Kawasaki et al proposes the use of high molecular
weight polyethylene glycol as a solution to electrical insulation deterioration in polyolefin
polymers. This technology has become widely used in the electrical cable industry, however, it is
over 25 years old and the need for more improved performance in additives for treeing resistance
exists.
[0016] Numerous methods to improve the performance of cross linked polyethylene
(XLPE) insulation against dielectric deterioration by water tree generation and growth have been
described in the literature. U.S. Pat No. 4,144,202 issued Mar. 13,1979, tolAshcraft et al relates
to the inhibition of water tree growth by use of certain organosilane compounds. U.S. Pat. No.
4,206,260 describes compositions containing an effective mount of an alcohol containing 6-24
carbon atoms as being an efficient water and electrical tree retardant insulation. German patent
2,737,430 discloses that certain alkoxysilanes act as tree retardant additives in polyethylene
insulation. European patent 0,166,781, published Jan. 8,1986 to Sumitomo Electric Industries
Limited describes a blend of ethylene and vinyl acetate copolymer as a water tree retardant
material. Certain aliphatic carboxylic acid derivatives when incorporated in suitable mounts in
XIPE are also reported to suppress water tree growth. Japanese application 63-226,814
published Sep. 21,1988 and Canadian application 2,039,894 published Oct* 6,1992 to Sarma et
al disclose an insulation composition comprising a low density PE in admixture with an
ethylene-vinyl acetate-vinyl alcohol copolymer as a possible water tree retardant composition.
[0O17J U.S. Patent No. 5,719,218 to Sarma proposes for improved water tree resistance
for an electrically insulating cross-linked polyethylene composition for use in high voltage
electrical cables, the cross-linked polyethylene being obtained by cross-linking a composition
consisting essentially of 98% of a low density, peroxide cross-linkable polyethylene, 1-2% of a
terpolymer of ethylene, vinyl acetate and vinyl alcohol and at least 0.15% of a stoically hindered
amine stabilizer. Commercial acceptance of this formulation has been limited.
[0018] Polymers containing peroxides are vulnerable to scorch, i.e., premature cross-
linking occurring during the polymer extrusion process. Scorch causes the formation of
discolored gel-like particles in the resin and leads to an undesired build up pf extruder pressure
duritg extrusion. A good stabilizer package for peroxide cross-linked polyethylene for medium
and high voltage cable insulation should protect the polymer against scorch during cable
extrusion and provide long term stability after the cable has been produced, i Additionally, the
cable quality would be negatively affected.
[00191 Consequently, a suitable stabilizer system should provide low scorch. In addition
to protection from scorch, the stabilizer system has an additional function. Alter the cable is
produced, it is in service for an extended period of time (service life; long term stability). Often,
the service life exceeds the intrinsic maximum stability of the polymer. Consequently, stabilizers
need to be added in order to assure a suitable service life. During the cross-linking step, the
interaction of the stabilizer with the peroxide should be as low as possible to ensure an optimum
cross-link density resulting in optimal mechanical properties. Cross-linking assists the polymer
in meeting mechanical and physical requirements, such as improved thermal aging and reduced
deformation under pressure. Consequently, the stabilizer system, while suppressing scorch
during the compounding step (and counteracting the effect of peroxides), should also have as few
interactions as possible with the peroxide in later stage of the cable manufacturing process. An
excess of organic peroxide may be used to achieve the desired level of cure, but, as described in
EP 1088851, this leads to a problem known as sweat out Sweat out dust is an explosion hazard,
may foul filters, and causes slippage and instability in the extrusion process.
[0010] Other properties, such as the solubility of the antioxidant in (he polymer matrix,
are also important A high solubility of the antioxidants ensures a low level! of blooming.
Blooming may result in the generation of dust on the pellets, which can lead to health and
environmental concerns. Additionally, additives that bloomed to the surfact might physically be
lost and become unavailable in the polymer matrix for their intended purpose. Consequently, a
suitable stabilizer package should have sufficient solubility with the polymef jmatrix. Further, a
low enough melting point is required. A low melting point ensures a good dispersion of the
antioxidant in the polymer matrix. Insufficient dispersion leads to decreased) performance of the
additive in the polymer matrix. An additive with a melting point above the ijaximum processing
temperature of the polymer (as determined by the peroxide) would result in jaj very poor
dispersion of the additive in the polymer matrix. This is considered a substantial drawback. The
most appropriate way to incorporate additives into the polymer would be in a liquid form. While
the stabilizer system does not necessarily need to be a liquid at room temperature, it needs to
melt at a low enough temperature to be easily filtered and added to the polymer in a liquid form.
A liquid addition will have the further advantage in that the additive can be filtered, thereby
increasing cleanliness. Increased cleanliness of the additive will further improve the cable
quality. Consequently, it is desirable that the stabilizing system have a sufficiently low melting
temperature and desired properties.
[0021J U.S. Patent No. 3,954,907 discloses that vulcanizable ethylene polymer-based
compositions, which are susceptible to scorching when processed at elevated temperatures, prior
to vulcanization, and in the presence of certain organic peroxide compounds, can be protected
against such scorching by the incorporation therein of monomelic vinyl compounds having a
defined structure.
(00221 U.S. Patent No. 5,530,072 discloses a process that is said to improve the
modification efficiency of peroxides through the proper selection of anti-o*idant additives and
control of the extrusion environment.
[00231 U.S. Patent No. 6,103,374 (EP 0965999 Al) discloses a composition comprising:
(a) polyolefin; (b) as a scorch inhibitor, 4,4'-thiobis(2-methyl-6-t-butyl pheiol); 2j2'-thiobis(6-t-
buryl-4-methylphenol); or mixtures thereof; (c) hydroquinone; a substituted hydroquinon; or
mixtures thereof in an amount sufficient to control color formation; and (d) pn organic peroxide.
[0024] U.S. Patent No. 6,180,231 (EP 1041582) discloses a composition comprising: (a)
polyethylene; (b) as a first scorch inhibitor, a substituted hydroquinone or 4J4 -thiobis(2-t-butyl-
5-methyl phenol); (c) as a second scorch inhibitor, distearyl disulfide; and (d) an organic
peroxide.U.S. Patent No. 6,180,706 (EP 0965998 Al) discloses a composition comprising: (a) a
low density homopolymer of ethylene prepared by a high pressure process; (b) a scorch inhibitor
selected from the group consisting of a substituted hydroquinone; 4,4MhiobU(2-methyl-6-t-
butylphenol); 2,2'-uiiobis(6-t-butyl-4-methylphenol); and 4,4'-thiobis(2-t-butyl-5-methylphenol)
in an amount of about 0.02 to about 0.07 part by weight of scorch inhibitor per 100 parts by
weight of homopolymer; (c) a cure booster, and (d) an organic peroxide.
[0025) U.S. Patent No. 6,187,858 discloses a composition comprising: (a) polyethylene;
(b) as a first antioxidant, a thiobisphenol; (c) as a second antioxidant, a compound containing 3-
(3»di-t-butyl-4-hydroxyphenyl)propionate in the molecule; (d) as a third antioxidant, distearyl
thiodipropionate; and (e) an organic peroxide, with the proviso that each antioxidant is present in
an amount of about 0.01 to the about 0.2 part by weight and the organic peroxide is present in an
amount of about 0.5 to about 3 parts by weight, all per 100 parts by weight of polyethylene.
[0026] U.S. Patent No. 6,191,230 discloses a masterbatch composition comprising: (a) a
copolymer of ethylene and 1-octene prepared with a metallocene catalyst; (b) a scorch inhibitor
of a substituted hydroquinone; 4,4'-thiobis(2-methyl-6-t-butylphenot); 4,4'-thiobis(2-t-butyI-5-
methylphenol); or mixtures thereof; (c) a cure booster, triallyl trimellitate; 3,9-divinyl-2,4,8,10-
tetra-oxaspiro[5.5]undecane; triallylcyanurate; triallyl isocyanurate; or mixtures thereof; and (d)
an organic peroxide.
[0027] U.S. Patent No. 6,869,995 discloses a composition comprising: (i) polyethylene,
and, based on 100 parts by weight of component (i), (ii) about 0.3 to about 0.6 part by weight of
4,4Mbiobis(2-methyl-6-t-butylphenol)
butyt-4-methylphenol)-, or a mixture of said compounds, and (iii) about 0.4 to about 1 part by
weight of a polyethylene glycol having a molecular weight in the range of about 1,000 to about
100,000.
[0028] U.S. Published Patent Application No. 2005/0148715 discloses a process for
preparing a composition comprising the step of selecting a composition for preparing a moldable,
test plaque having (1) a MDRtsl at 150 degrees Celsius of at least about 20, (2) a MDRtsl at 140
degrees Celsius of at least about 50, (3) a retention of tensile strength of at least about 75% after
two weeks of aging at 150 degrees Celsius, (4) a retention of elongation of at least about 75%
after two weeks of aging at 150 degrees Celsius, (5) water tree resistance less than about 45%,
and (6) sweatout of less than about 100 ppm of the thiobis phenolic antioxidant and (b) imparting
water tree resistance to the insulation of cables, the composition comprising: (i) polyethylene,
and based on 100 parts by weight of component (i), (ii) about 0.3 to about 0.6 part by weight of a
thiobis phenolic antioxidant selected from the group consisting of 4,4'-thiobis(2-methyl-6- -t-
butylphenol); 4,4,-thiobis(2-t-butyl-5-methylphenol); 2'-thiobis(6-t-butyl-4-meuiylphenol); or a
mixture of said compounds; and (iii) about 0.4 to about 1 part by weight of a polyethylene glycol
having a molecular weight in the range of about 1000 to about 100,000.
[0029] EP 1074580 discloses the use of [ 1 ,3,5-tris(4-tert-butyl-3-hiydroxy-2,6-
dimethylbenzyl)-l,5-triazine-2,4,6-(lHH,5H)-trione] as a scorch inhibitor in the technical
field of preparation of cable insulation, semi-conductive shields, and jackets. EP 1088851
discloses the use of a-tocopherol as a scorch inhibitor.
[00301 EP 1249845 discloses the use of 2,4-bis (n-octylthiomethyl)-&methylphenol as an
antioxidant for a peroxide crosslinked polyethylene composition used as insulating material for
medium and high voltage cables. EP 1249845 also discloses the combination of: a polyethylene;
a scorch inhibitor having a melting point below 50 C at atmospheric pressure; and an organic
peroxide. The use of 4,6-bis(octyltfiiomethyl)o-cresol, as a scorch inhibitor Is disclosed along
with other structurally related compounds. JP 57-126833 discloses related compounds.
[00311 WO 00/02207 discloses peroxide cross-linked polyethylene as an insulating layer
for wire and cable purposes mat can be stabilized by a two component system based on
2odiethylenebis[3(3>5-di-butyl-4-hydroxyphenyl)propionate] (IT) and djstearyl 3,3'-
thiopropionate (JE), usually at a total loading of about 0.4% total in a 1:1 ratio. It is also
disclosed that a single stabilizer approach can be used, more particularly one with combined
phenol and sulfur functionality, such as 4,4T-thiobis(2-t-butyl-5-methylphenol).
[0032] The use of antioxidant combinations is possible, but only a few of these
combinations can meet the desired combination of properties that are required for an insulating
material for medium voltage and high voltage power cable comprising, good anti-scorch, limited
interaction with the peroxide during cross-linking, good long term stability, good solubility, a
low melting point, and good color.
[00331 A good overview of the various polyethylene types is given in "Handbook of
Polyethylene" by A. J. Peacock (Marcel Dekker Publishers, 2000). A more specific description
of suitable polyethylenes is given in U.S. Published Patent Application No. 2005/0148715 Al
(page 2 paragraph [0017] to page 3 paragraph [0023]).
[00341 Therefore, a need exists in the electrical cable industry for an additive system mat
improves the tree resistance performance of polyolefin polymers as an electrical insulation
composition.
SUMMARY OF THE INVENTION
[0035] The invention provides an insulation composition for electric! cable comprising (a)
a base polymer comprising polyolefin, (b) an additive comprising a blend or} (i) at least one
amine antioxidant, and (ii) at least one hindered amine light stabilizer, and (hi) polyethylene
glycol. In further embodiments of the present invention, the composition may optionally
comprise an antioxidant mixture of (i) at least one fast radical scavenger selected from the group
consisting of: low hindered phenols, low hindered thiophenols, low hindered thiobisphenols,
aliphatic amines, aromatic amines, NOR HALS, hydroxylamines, and mixtiiites thereof, and (ii)
at least one long term stabilizer selected from the group consisting of low hindered phenols,
highly hindered phenols, thiosynergists, aliphatic amines, aromatic amines, HALS,
hydroxylamines, and mixtures thereof. Surprisingly these antioxidants and radical scavengers
give improved tree resistance over other combinations known in the art.
[0036] In other embodiments the invention provides an insulation composition for
electric cable comprising: (a) abase polymer comprising polyolefin; (b) an additive comprising;
(i) a low molecular weight EVA wax and optionally at least one hindered aijnine light stabilizer
and/or at least one amine antioxidant alone or in combination with the above antioxidant
mixtures.
[0037] In preferred embodiments of the invention the base polymer i comprises Zeigler
Natta low density polyethylene, and/or Zeigler Natta linear low density pot Ethylene. The
additive may be from about 0.5% to about 4.0% by weight of said compositujn preferably from
about 1.0% to about 2.5% by weight of said composition.
[0038} In still further embodiments, the invention provides an insulation composition for
an electric cable comprising: a base polymer comprising a C2 to Cg alpha olefin in combination
with a polyethylene homopolymer together with, optionally, one or more hindered amine light
stabilizers and other processing additives.
DETAILED DESCRIPTION OF THE DRAWING
[0039] Figure 1 shows a schematic for a peroxide injection system.
DETAILED DESCRIPTION OF THE INVENTION
[00401 The invention particularly relates to polymeric compositions utilizing polyoleflns,
which compositions have a unique combination of good mechanical properties, good dielectric
properties, and good water treeing resistance. The products are extremely useful as insulation
compositions tor electric power cables.
[0041] The polymers utilized in the protective jacketing, insulating, Conducting or
semiconducting layers of the inventive cables of the invention may be made by any suitable
process which allows for the yield of the desired polymer with the desired physical strength
properties, processability and electrical properties.
Base Polymer
[0042) The base polymer in accordance with the invention compris&j at least one
polyolefin polymer.
[0043) In embodiments of the invention the polyolefin base polymer is prepared using a
conventional Ziegler-Natta catalyst. In preferred embodiments of the invention the polyolefin
base polymer is selected from the group consisting of a Ziegler-Natta polyethylene, a Ziegler-
Natta polypropylene, a copolymer of Ziegler-Natta polyethylene and Ziegler-Natta
polypropylene, and a mixture of Ziegler-Natta polyethylene and Ziegler-Natta polypropylene. In
more preferred embodiments of the invention the base polymer polyolefin is a Ziegler-Natta low
density polyethylene (LDPE) or a Ziegler-Natta linear low density polyethylene (LLDPE) or a
combination of a Ziegler-Natta LDPE and a Ziegler-Natta LLDPE,
[0044] In other embodiments of the invention the polyolefin base polymer is prepared
using a metallocene catalyst. Alternatively, the polyolefin base polymer is a mixture or blend of
Ziegler-Natta base polymer and metallocene base polymer.
[0045] The base polymer utilized in the insulation composition for electric cable in
accordance with the invention may also be selected from the group of polymers consisting of
ethylene polymerized with at least one co-monomer selected from the group consisting of C3 to
C20 alpha-olefins and C3 to C20 polyenes. Generally, the alpha-olefins suitable for use in the
invention contain in the range of about 3 to about 20 carbon atoms. Preferably, the alpha-olefins
contain in the range of about 3 to about 16 carbon atoms, most preferably in the range of about 3
to about 8 carbon atoms. Illustrative non-limiting examples of such alpha-olefins are propylene,
1-butene, 1-pentene, 1-hexene, 1-octeneand 1-dodecene.
[0046( The base polymer utilized in the insulation composition for electric cables in
accordance with the invention may also be selected from the group of polymers consisting of
either ethylene/alpha-olefin copolymers or ethylene/alpha-olefin/diene terpjojlymers. The polyene
utilized in the invention generally has about 3 to about 20 carbon atoms. Preferably, the polyene
has in the range of about 4 to about 20 carbon atoms, most preferably in fee range of about 4 to
about 15 carbon atoms. Preferably, the polyene is a diene, which can be a straight chain,
branched chain, or cyclic hydrocarbon diene. Most preferably, the diene is a oon conjugated
diene. Examples of suitable dienes are straight chain acyclic dienes such as: 1,3-butadiene, 1,4-
hexadiene and 1,6-octadiene; branched chain acyclic dienes such as: 5-methyl-1,4-hexadiene,
3,7-dimethyl-1 ,6-octadiene, 3,7 -dimethyl-1,7-octadiene and mixed isomers of dihydro myricene
and dihydroocinene; single ring alicyclic dienes such as: 1,3-cyclopentadieae, 1,4-
cylcohexadiene, 1,5-cyclcoctadiene and 1,5-cyclododecadiene; and multi-ring alicyclic fused
and bridged ring dienes such as: tetrahydroindene, methyl tetrahydroindene, dicylcopentadiene,
bicyclo-(2,2,1)-hepta-2-5-diene; alkenyl, alkylidene, cycloalkenyl and cycloalkylidene
norbomenes such as 5-methylene-2morbornene (MNB). 5-propenyl-2-norb0mene, 5-
isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2-norbomene, 5-cyclohefcylidene-2-
norbomene, 5-vinyl-2-norbornene and norbornene. Of the dienes typically Used to prepare
EPR's, the particularly preferred dienes are 1,4-hexadiene, 5-emylidene-2-ni>|rbornene, 5-
vinyllidene-2-norbornene, 5-methylene-2-norbornene and dicyclopentadiene. The especially
preferred dienes are S-ethylidene-2-norbornene and 1,4-hexadiene.
[0047] As an additional polymer in the base polymer composition, a non-metallocene
base polymer may be used having the structural formula of any of the polyolefins or polyolefin
copolymers described above. Ethylene-propylene rubber (EPR), polyethylene, polypropylene
may all be used in combination with the Zeigler Natta and/or metallocene polymers in the base
polymer.
[0048] In embodiments of the invention, the insulation composition fcase polymer
comprises 30% to 50% by weight Zeigler Natta polymer or polymers and 50% to 70% by weight
mcUllocene polymer or polymers The total amount of additives in the treeing resistant "additive
package" are from about 0.5% to about 4.0% by weight of said composition* preferably from
about 1.0% to about 2.5% by weight of said compositioa
Zeigler Natta Polymers
[0049] A number of catalysts have been found for the polymerization of olefins. Some of
the earliest catalysts of this type resulted from the combination of certain transition metal
compounds with organometalric compounds of Groups I, II, and III of the Periodic Table. Due to
the extensive amounts of early work done by certain research groups many of the catalysts of
mat type came to be referred to by those skilled in the area as Ziegler-Natta type catalysts. The
moat commercially successful of the so-called Ziegler-Natta catalysts have heretofore generally
been those employing a combination of a transition metal compound and an organoaluminum
compound.
Metallocene Polymers
[0050] Metallocene polymers are produced using a class of highly active olefin catalysts
known as metallocenes, which for the purposes of this application are generally defined to
contain one or more cyclopentadienyl moiety. The manufacture of metallocene polymers is
described in U.S. Patent No. 6,270,856 to Hendewerk, et al, the disclosure of which is
incorporated by reference in its entirety.
[0051] Metallocenes are well known especially in the preparation of polyethylene and
copolyethylene-alpha-olefins. These catalysts, particularly those based on group IV transition
metals, zirconium, titanium and hafnium, show extremely high activity in ethylene
polymerization. Various forms of the catalyst system of the metallocene type may be used for
polymerization to prepare the polymers used in this invention, including but not limited to those
of (he homogeneous, supported catalyst type, wherein the catalyst and cocatalyst are together
supported or reacted together onto an inert support for polymerization by a gas phase process,
high pressure process, or a slurry, solution polymerization process. The metallocene catalysts are
also highly flexible in that, by manipulation of the catalyst composition and reaction conditions,
they can be made to provide polyolefins with controllable molecular weight from as low as
about 200 (useful in applications such as lube-oil additives) to about 1 million or higher, as for
example in ultra-high molecular weight linear polyethylene. At the same tune, the MWD of the
polymers can be controlled from extremely narrow (as in a polydispersity of about 2), to broad
(as in a polydispersity of about 8).
[0052] Exemplary of the development of these metallocene catalysts for the
polymerization of ethylene are U.S. Pat. No. 4,937,299 and EP-A-0 129 368 to Ewen, et al., U.S.
Fat No. 4,808,561 to Welborn, Jr., and U.S. Pat. No. 4,814,310 to Chang, which are all hereby
are fiilly incorporated by reference. Among other things, Ewen, et al. teaches that the structure of
the metallocene catalyst includes an alumoxane, formed when water reacts with trialkyl
aluminum. The alumoxane complexes with the metallocene compound to farm the catalyst
Welborn, Jr. teaches a method of polymerization of ethylene with alpha-olefins and/or diolefins.
Chang teaches a method of making a metallocene alumoxane catalyst system utilizing the
absorbed water in a silica gel catalyst support Specific methods for making ethylene/alpha-
olefin copolymers, and ethylene/alpha-olefin/diene terpolymers are taught in U.S. Pat. Nos.
4,871,705 (issued Oct. 3,1989) and 5,001,205 (issued Mar. 19,1991) to Hod, et al., and in EP-
A-0 347 129 published Apr. 8,1992, respectively, all of which are hereby fully incorporated by
reference.
Tree Resistant Additives or "Additive Package"
[0053] As described above, the additive or "additive package" in accordance with the one
embodiment of the invention comprises a blend of, (i) at least one amine antioxidant, (ii) at least
one hindered amine light stabilizer, and (iii) PEG.
[0054] In alternate embodiments of the invention, the additive or additive package in
accordance with the invention comprises (i) a low molecular weight copolymer wax selected
from the group consisting of ethylene vinyl acetate copolymers, ethylene alky! acrylate
copolymers wherein the alkyl group is selected from C1 to C6 hydrocarbons, ethylene alkyl
metbacrylate copolymers wherein the alkyl group is selected from C1 to C6 hydrocarbons and
ethylene alkyl acrylate alkyl methacrylate terpolymers wherein the alkyl group is independently
selected from CI to C6 hydrocarbons. The copolymer wax will have a weight average molecular
weight greater than about 10,000 daltons, preferably greater than about 12,000, and more
preferably greater than about 15,000. A preferred ethylene vinyl acetate copolymer will have a
weight average molecular weight from about 15,000 to about 50,000 and an even more preferred
EVA copolymer will have a weight average molecular weight from about 20,000 to about
40,000. The low molecular weight EVA wax additive package may further comprise
antioxidants and stablizers. In a preferred embodiment the additive package may comprise
(ii) at least one hindered amine light stabilizer and/or (iii) at least one an amine antioxidant
Hindered Amine Light Stabilizer
[0055] Any suitable hindered amine light stabilizer may be used in accordance with the
invention, for example, Bis (2,2,6,6 -tetramethyl-4-piperidyi) sebaceate (tinuvin 770); Bis
(1,2,2,6,6 -tetramemyl-4-piperidyl) sebaceate + methyl 1,2,2,6,6-tetramethyl-4-piperidyl
sebaceate (tinuvin 765); 1,6-Hexanediamine, N, N' -Bis (2,2,6,6 -tetramethyl-4-piperidyl)
polymer with 2,4,6 trichloro-l,3,5-triazine, reaction products with N-butyl :i,2,6,6-tetramethyl-4-
piperidmamine (Chimassorb 2020); Decanedioic acid, Bis (2,2,6,6 -tetramcthyl-M0ctyloxy)-4-
piperidyl)ester, reaction products with 1,1-dimethylethylhydroperoxide and octane (Tinuvin
123X Triazine derivatives (tinuvin NOR 371); Butanedioic acid, dimethylestdr 4 hydroxy -
2,2,6,6 -tetramethyl-piperidine ethanol (Tinuvin 622), l,3,5-Triazme-2,4,6MrkmneJN,N1,,-[l,2-
ethane-diyl-bis [[[4,6-bis-[butyl(l ,2,2,6,6pentamemylpipenmiyl)amino]-l .S-triazine-ylj
imino]-3,l-propanediyl]] bis [rN" - dibutyl-N\N" bis(2,2,6,6-tetramethy!Jpiperidyl)
(Chimassorb 119). Chimassorb 944 LD and Tinuvin 622 LD are preferred hindered amine light
stabilizers.
Amine Antioxidant
(0056] Any suitable amine antioxidant may be used in accordance with the invention, for
example, l,2-dihydro-2-2-4, octylated diphenylamine, diphenyl-p-phenylcne*diamine,
trimethylquinoline, 4,4'-di(l,l-dimethylbenzyl)-diphenylamine, ethoxy-l,2*dihydro-2-2-4
trimcthylquinoline, p,p'-dioctyldiphenylamine, 2-tert-butylhydroquinone 127C melting point &
166 MW, N-(l,3-dimethyl butyl)-N*-phenyl-p-phenylene diamine, N-phcnyl-N'isopropyl-p-
phcnylcne diamine, p-phenylene diamine, Agerite MA, Agerite D, Flectol TMQ, Agerite Stelite
257 TGA onset, Stalite S 299 TGA onset, Vulcanox OCD, Agerite DPPD 276 TGA onset &
150C melting point, Ethanox 703, Naugard PAN6, liquid Santaflex AW, Wbgstay 29, Vanox
12, Vulcanox 4020 melting point 45C, Dusantox 6PPD, Permanax 6PPD, Vulcanox 4010
melting point 75C, Rhenogran IPPD-80, Flexzone 3-C, Uniroyal A/O PD-1, Dusantox IPPD,
Wingstay 100 and Wingstay 200. Trimethylquinoline is a preferred amine antioxidant
PEG
10657] The use of high-molecular weight polyethylene glycol ("PEG**) as an additive to
prevent treeing in polyolefin insulation compounds is disclosed in U.S. Patent No. 4305,849,
which is incorporated herein by reference. In embodiments of the invention the polyethylene
glycol has more than 44 carbon atoms and has a molecular weight from about 1,000 to about
30,000 daltons.
Fillers
[0058] The insulating composition the invention may contain filler. An illustrative
example of a suitable filler is clay, talc (aluminum silicate or magnesium silicate), magnesium
aluminum silicate, magnesium calcium silicate, calcium carbonate, magnesium calcium
carbonate, silica, ATH, magnesium hydroxide, sodium borate, calcium borate, kaolin clay, glass
fibers, glass particles, or mixtures thereof. In accordance with the invention, the weight percent
range for fillers is from about 10 percent to about 40 percent, preferably from about 20 to about
30 weight percent filler.
Low Molecular Weight Wax
(0059] In alternate embodiments of the invention, the additive or additive package in
accordance with the invention comprises (i) a low molecular weight copolymer wax selected
from the group consisting of ethylene vinyl acetate copolymers, ethylene alkyl acrylate
copolymers wherein the alkyl group is selected from CI to C6 hydrocarbons, ethylene alkyl
methacrylate copolymers wherein the alkyl group is selected from CI to C6 hydrocarbons and
ethylene alkyl acrylate alkyl methacrylate terpolymers wherein the alkyl group is independently
selected from CI to C6 hydrocarbons. The copolymer wax will have a weight average molecular
weight greater than about 10,000 daltons, preferably greater than about 12,000, and more
preferably greater than about 15,000. A preferred ethylene vinyl acetate copolymer will have a
weight average molecular weight from about 15,000 to about 50,000 and an even more preferred
EVA copolymer will have a weight average molecular weight from about 20000 to about
40,000. and is a measure of the distribution of the molecular weights of the polymer chains. The
proportion of vinyl acetate in the low molecular weight EVA wax compounds of the invention
should be about 5 to 20 percent, preferably about 8 to 18 and even more preferably about 12 to
15 percent vinyl acetate. Suitable commercially available material includes AC 400, a 12 percent
vinyl acetate wax available from Honeywell Inc. of Monistown, N.J.
Other Antioxidant Mixtures
[0060] In certain embodiments of the present invention, the insulation compositions may
contain an antioxidant mixture comprising at least one fast radical scavenger and at least one
long term stabilizer. When present, it is preferable that the load level of fast radical scavengers,
is 100 to 5,000 ppm, more preferably 500 to 4,000 ppm, based on the weight of the polyolefin.
When present, it is preferable that the load level of the long term stabilizers), is 100 to 8,000
ppm, more preferably 500 to 6,000 ppm, based on the weight of the polyolefin. Most preferably,
the total load level of the mixture of antioxidants is in the range of 200 to 10,000 ppm. preferably
2,000 to 6,000 ppm, based on the weight of the polyolefin.
(0061) Preferably, the last radical scavengers), is (are) selected from the following
groups:
[0062] [1] a-tocopherol, P~ tocopherol, y- tocopherol, 5- tocopherol, derivatives and
mixtures thereof;
[0063] [2] sulfur containing phenolics, such as 4,6-bis(octylthiomethyl)-o-cresol, 2,4-
bis(alkylthiomethyl)-6-methylphenols, 2,6-d1alkyl-4-alkylthiomethylphenolB(B), 4-alkyl-2,6-
bis(alkylthic>memyl)phenols.4,6-bis(o thereof,
[0064] [3] 4,4t-thiobis(2-methyl-6-t-butylphenol), 4,4'-tiiiobis(2-t-butyl-5-methylphenol);
2,2'miobis(6-t-butyi-4methylphenol); 2,2'-thiobis 4-octyl phenol; and mixtures thereof;
[0065] [4] mixtures of 4,4-thiobis(2-t-butyl-5-me(hylphenol) with trijejthylene glycol bis
[3-[3,5-t-butyl-4-hydroxy-5-methylphenyl)propionate;
[0066] [5] l,3>tris(4-tertutyl-3-hydtoxy-2,6Kiimethylbenzyl)-l3,-triazine-2,4,6-
(HUH,5H)-trione;
[0067] [6] 2,5-4i-t-amyIhydroquinone;
[0068] [7] reaction products of 4-methyiphenol with dicyclopentadiene and isobutylene;
[0069] [8] oxidized bis(hydrogenated tallow alkyl amines and derivatives thereof;
[0070] [9] bis-O-octyloxy-2,6,6 tetramethyl-4-piperidinyl)sebacate;
[0071] [10] 4,4'-bis(a,a-dimethylbenzyl) diphenylamine, N-phenyl-styrenated
benzcnamine, diphenyiamine/acetone reaction product, p-(p-toluene-sulfonylamido)-
diphenylarnine. and mixtures thereof.
[0072] [11] 2,2-thiodiethylene bis[3(3-t-butyl-4-hydroxy-5 methylphenyl)propionate];
2-thiodiethylenebis[3(3,5-di-methyl-4-hydroxyphenyl)propionate]; and derivatives and
mixtures thereof with the long term stabilizers of group 1 below ; and
[0073] [12] degradation and fragmentation products containing functional phenolic
groups of 1 to 6 or 10. It is also contemplated that mixtures of any of the foregoing can also be
used. Further fist radical scavengers are listed in "Rubber Technology Handbook" by W.
Hoftnarm, Hanser Publishers (1989).
[0074] Preferably, the long term stabilizers), is (are) selected from the following groups:
[0075] [1] 2-1mdiemylenebis[3(3,5Hh-t-butylhydroxyphenyl)propionate];
[0076] [2] tetraldsmemylene(3,5-di-t-butyM-hydroxyhydrocinnama;te)methane;
[00T7] [3] octadecyl 3-(3',5'-di-t-butyl-4-hydroxy-phenyl)propionat C9-C21 linear and
branched alkyi esters of S-CS'jS'-di-t-butyl--hydroxyphenyOpropionic acid; Cn-Cis linear and
branched alkyi esters of 3-(3',5,-di-t-butyl-4-hydroxyphenyl) propionic acid;
[00781 [4] 1,3,5-tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate; U,5-trimethyl-2,4,6-
tris(3$5-di-t-butyl-4-hydroxybenzyl)benzene; N,N'-hexamethylene bis[3-(3,5Kh-t-butyl-4-
hydroxy-phenyl)-propioijanude];r4>is(3
[0079] [5] Sterically hindered amines, as well as the N compounds thereof (e.g., N-alkyl,
N-hydroxy, N-alkoxy, and N-acyl), such as bis(2,2,6,6-tetramethylpiperidmr4-yl)sebacate,
bis(2,6,6-tetramethylpiperidinyl)succinate, bisQ ,2,2,656-pentameihylp5ieridin-4-
yl)sebacate, bis( 1 pentamethylpiperidiji-4-yl) n-butyl 3,5-tert-butyl-44iydVoxybenzylmalonate, the condensate of
H2«hydroxyethyl)-2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, the condensate of
Nis(2,2J6,6-tetramethylpiperidin-4-yl)hexamethylenediamine and 4-tertoctylamino-2,6-
dichloro-1 ,3,5-triazine, txis(2,2,6,6-tetramethylpiperidin-4- yl)nitrilotriac«tete, tetrakis(2,6,6-
tetramcthylpiperidin-4-yl)-l,2,3,4-butanetetracarboxylate, 1- l'-(l ,2-ethanediyl)bis(3,3,5,5-
tetrtmethylpiperazinone), 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-
tetramethylpiperidme, bisO ,2,2,6,6-pentamethylpipe
butylbenzyl)malonate, 3-n-octyl-7,7,9 ,9-tetramethyl-l,3,8-triazaspiro[4.5]decan-2,4-dione, bis(l-
octyloxy-2,2,6,6- tetramethylpiperidyl)sebacate, bis(l -octyltetramethylpiperidyl-O-succinate, the
condensate of N J4,-bis(2,2,6,6-tetramethylpiperidin-4-yl) hexamethylenediamine and 4-
motpholino-2,6-dichloro-l, 3,5-triazine, the condensate of 2-chloro-4,6-bis(4-n- butyiamino-
2j6,6-tetramettiylpiperidyl)-l,3,5-triazine and l,2-bis(3-aminopropylamind)ethane, the
condensate of 2-chloro-4,6-bis(4-n-butylamino- 1,2,2,6,6-pentamethylpiperidyI)-l,3,5-triazine
and |,2-bis-(3-ammopropylanimo)ethane, 8-acetyl-3- dodecyl-7,7,9,9-tetramethyl- 1,3 ,8-
triaz£spiro[4.5]decane-2,4-dione, 3-dodecyl-1 -(l-ethanoyl-2,2,6,6-tetramethylpip«idiii-4-
i
yl)pyrolidin-2,5-dione, 3-dodecyI-l -(2,2,6,64etreme1hylpiperidinyl)pyrrolJdin-2,5-dione, 3-
dodcyl-l-0,2,2A6-pentamefl»ylpiperidin-yl)pyrrolidine-2,5-dione, a mixture of 4-
hexdecyloxy- and 4-stearyloxy-2,2,6,6-teteamethylpiperidine, the condensate of N,N*-
bis(J,6,6-tetitraiethylpiperidinyl)hexamethylenediamine and 4-cyclohexylamino-2,6-
dich}oro-l,3,5-triazine, the condensate of l-bis(3-aminopropylamino)ethan«, 2,4,6-dichloro-
U.-triazine and 4-butylaniino-2,6,6-teteamethylpiperidine (CAS Reg. Na 1136504-96-6]), N-
(2\6-tetramethyl piperidine-4-yl)-n-dodecylsucciniinide, A0AAj6j6-pentamethylpiperidinA-yA-
n-d oxo4piperanzinyl-triazines or so called PIP-T HALS, e.g., GOODRTTE® 30$4, 3150, and 3159
comjnercially available firom BF Goodrich Chemical Co. of Akron, Ohio, and similar materials
disclosed in U.S. Patent No. 5,071,981, photobondable HALS such as SANDUVOR® PR-31
AND PR-32 commercially available from Clariant Corp. of Charlotte, N.C., and similar
materials disclosed in GB-A-2269819, the reaction product of 7,7,9,9-tetramethyl-2-
cycf>undecyI-l-oxa-3,8-diaza-4-oxospiro[4,5]decane and epichlorohydrin. Examples of
thetttramethylpiperidine derived HALS include CYASORB® UV-3346 Light Stabilizer,
confcnercially available from CYTEC INDUSTRIES, SANDUVOR® 3055 HALS,
SANDUVOR® 3056 HALS, and SANDUVOR® 3058 HALS, commercially available from
SAWDOZ Corporation of Charlotte, N.C., CHMASORB® 944 Stabilizer, TTNUVTN® 622
Stabilizer, and TINUV1N® 144 Stabilizer, each commercially available fropi CIBA
SPECIALTIES, and mixtures raereof. See also generally U.S. Patent Nos. 5106,891,4,740,542,
4,619,956,4,426,471,4,426,472,4,356,307,4,344,876,4,314,933; GB-A-2269819. EP-A-
309400, EP-A-309401, EP-A-309402 and EP-A-0434608, each of which incorporated herein
hy reference in their entirety;
(0086) [6] thio type antioxidants, such as Dilauryl (hiodiopropionate,: Distearyi
thiodiopropionate, 2,3>5-trimethyl-4-[(3,7-dimethyl-6-octenyl)thio]-1 1,2,3#-rrimethyl-4-[(3,7-
dimethyl-6-octenyl)thio]-, (S)-Phenol, 2,5-trimethyl-4-[(3,7-dimethyl-6-optenyl)thio]-,
distearyi 3'-tbiopropionate, dilauryl 3,3f-thiopropionate, ditridecylthiodiprppionate, mixed
lauryN+stearylthiopropionate, esters of propanoic acid, tmobis[2,-(14-dime&emyl-5-methyl~
44-phcnylene], (ADK stab AO 23 (CAS number 66534-05-2,71982-66-6), jpWaerytritol tetrakis
(beta-lauryltbiopropionate); and
|00811 [7] polymerized l,2-dihydro-2,2,4- trimethylquinoline, 2,4-bis|(n-octylthio)-6-(4-
hvdjoxy-3,5-di-t-butylamlmo)-l,3s5-triazine} 4,4'-bis(a,a-dimethylbenzyi) diphenyiamine, N-
pheoyl-styrenated benzenamine, diphenylamine/acetone reaction product, p-(p-toluene-
sulfDnylamido)- diphenyiamine; and mixtures thereof.
[0082] Further long term stabilizers are listed in the 3rd edition (1990) and 5th edition
(2001) of "Plastics Additive Handbook," Hanser Publishers. Additionally, the "Rubber
Technology Handbook" by W. Hofinann, Hanser Publishers (1989), describes selected efficient
long term stabilizers.
[0083] Other contemplated antioxidants for use in the compositions of the present
invention include phenolic ester antioxidants such as benzenepropanoic acid, 3-(l,l-
dimediylethyl)-4-hydroxy-5-methyl-, l,2-ethanediylbis(oxy-2,l-ethanediyl) ester, and full or
partial esters of apoly(vinylphenol) and a 3,5-di-tert-butylhydroxybenzoic acid.
[0084] A specific embodiment of the invention is a composition wherein the fast radical
scavenger, is 4,6-bis(octylthiomethyl)o-cresol or derivatives thereof and is jl tended with a long
term stabilizer of a highly hindered phenol, thiosynergist, aromatic amine, aliphatic amine,
HALS, hydroxylamine, or mixtures thereof. For a structure derived from 4,6-
bis(octylthiomethyl)o-cresol, see EP 1249845 A2.
(0085] The most preferred derivative is 2,4-bis (n-docecylthiomethyl)-6-methylphenol.
Another preferred embodiment of the invention is a composition comprising the fast radical
scavenger 4,6-bis(octylmiomefliyl)o-cresol blended with the long term stabilizer 2,2'-
thiodiethylene bis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]. Another preferred embodiment
of the invention is a composition comprising the fast radical scavenger 4,6-
bis(octylthiomethvl)o-cresol blended with a long term stabilizing mixture comprising 2,2-
thiodi ethylene bis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate] and distearyl 3,3'-
thiopropionate or ditridecyl thiodipropionate. Another preferred embodiment of the invention is a
composition comprising the fast radical scavenger 4,6-bis(octylthiomethyI)o-cresol blended with
a long term stabilizer that comprises C13-C15 linear and branched alkyl esters of 3-(3\5'-di-t-
butyW-hydroxyphenyl) propionic acid. Another preferred embodiment of the invention is a
composition comprising the fast radical scavenger 4,6-bis(octylthiomethyl)o-cresol blended with
a long term stabilizer comprising a mixture of Q3-C1S linear and branched alkyl esters of 3-(3',5*-
di-t-butyl-4'- hydroxyphenyl) propionic acid and distearyl 3,3'-thiopropionate or ditridecyl
thiodipropionate. Another preferred embodiment of the invention is a composition comprising
the fast radical scavenger 4,6-bis(octylthiomethyl)o-cresol blended with a long term stabilizer
selected from the group consisting of propanoic acid, 3-(tetradecylthio}-, thiobis[2,-(l,l-
dimethylethyl)-5-methyl-4,l-phenylene] ester or propanoic acid, 3-(dodecylthio)-, thiobis[2,-(l,l-
dimethylethyl)-5-methyl-4,l-phenylene]ester, and mixtures thereof (ADK stab AO 23 (CAS
number 66534-05-2,71982-66-6)). Another preferred embodiment of the invention is a
composition comprising the fast radical scavenger 4,6-bis(octylthiomethyl)o-cresol a long term
stabilizer selected from the group consisting of propanoic acid, 3-(tetradecyltisio)-,tiiiobis[2,-(14-
dimethylethyl)-5- methyl-4,l-phenylene] ester or propanoic acid, 3-(dodecytthio)-, thiobis[2,-(l,l-
dimethylethyl-5-methyl-4,1 -phenylene]ester, and mixtures thereof (ADK stab AO 23) blended
with, distearyl 3,3'-thiopropionate or ditridecyl thiodipropionate. Another preferred embodiment
of the invention is a composition comprising the fast radical scavenger 4,6
bis(octylthiomethyl)o-cresol blended with a long term stabilizer comprising a blend of ADK stab
AO 23 and distearyl S'-thiopropionate or ditridecyl thiodipropionate. Another preferred
embodiment of the invention is a composition comprising the fast radical scavenger 4,6-
bis(octylthiomethyl)o-cresol blended with a long term stabilizer comprising 4,4'-bis(a,a
dimethylbenzyl) diphenylamine. Another preferred embodiment of the invention is a
composition comprising the fast radical scavenger 4,6-bis(octylthiomethyl)o-cresol blended with
a loeg term stabilizer comprising a mixture of 4,4'-bis(a,a-dimethylbenzyl) diphenylamine and
distearyl 3,3'-thiopropionate or ditridecyl thiodipropionate. Another preferred embodiment of the
invention is a composition comprising the fast radical scavenger 4,6-bis(octylthiomethyl)o-cresol
blended with a long term stabilizer comprising a mixture of 4,4'-bis(a,a-dimethyIbenzyl)
diphenylamine and 2,2 -thiodiethylenebis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate].
Another preferred embodiment of the invention is a composition comprising the fast radical
scavenger 4,6-bis(octylthiomethyl)o-cresol blended with a long term stabilizer comprising a
mixture of 4,4'-bis(a,a-dimethylbenzyl) diphenylamine and ADK stab AO 23. Another preferred
embodiment of the invention is a composition comprising the fast radical scavenger 4,6-
bis(octylthiomethyl)o-cresol blended with a long term stabilizer comprising NOR HALS with,
but not limited to, examples as Tinuvin 123 or Tinuvin 116.
[0086] The present invention also includes the use of a stabilized peroxide cross-linked
polyolefin composition as described herein as insulation media for medium fluid high voltage
wire and cable. (For a description of a similar composition wherein the polyolefin is
polyethylene, see EP 1074S80 A2 and EP 0966000 Al.) The organic peroxides useful as cross-
linking agents are those well known in the art, e.g., dialkyl peroxides such as idicumyl peroxide.
The load level range for the peroxide is usually 0.5 to 5% by weight. (For a description of such a
peroxide, see EP 1074580 A2 and EP 0966000 Al.)
[0097] The antioxidant blend can be added to the polymer as separate components, or as
a pre-mixed powder blend, or as a pre-mixed no-dust blend (prepared by any process known in
the art), or as a pre-dispersed blend in a polymer masterbatch or as premixed liquid blend. (For a
description of appropriate processing equipment, see EP 1074580 A2 and EP 0966000 Al.).
[0088] The blending of different types of antioxidants results in a tailor-made antioxidant
system for peroxide cross-linked polyethylene having excellent scorch resistance, minimal
peroxide interaction, sufficient long term properties to meet industry standards, a high solubility,
and low melting behavior. It is to be noted that some of the antioxidants mentioned as being
suitable components for the present invention have multi-functional properties, for example: (i)
4,6-bis(octylthiomethyl)o-cresol is classified for purposes of the invention as a fast radical
scavenger because it is a low hindered phenol. However, it also contains sulphur, which
contributes to the long term properties, (ii) 2,2'-thiodiethylene bis[3,(3,5-di-t-butyl-4-
hydroxyphenyl)propionate] is a highly hindered phenol that also contains sulphur. However, in
this case both contribute mainly to the long term stabilizer properties, (iii) The highly hindered
phenols and thiosynergists are actually two different classes of antioxidant but both exhibit the
concept of the present invention in that they both contribute mainly to the long term stabilizer
properties of the cross-linked polyethylene and somewhat to the anti-scorch property. Taking the
above into account, for purposes of the present invention, the fast radical scavengers can be
regarded as anti-scorch agents, and the highly hindered phenols and thiosynergists can be
regarded as having the main function of long term stabilizers (even though they might also
contribute to the anti-scorch properties).
Other Ingredients
[0089) Other additives commonly employed in the polyolefin compositions utilized in
the invention can include, for example, crosslinking agents, processing aids, pigments, dyes,
colorants, metal deactivators, oil extenders, stabilizers, and lubricants.
Processing
[0090] All of the components of the compositions utilized in the invention are usually
blended or compounded together prior to their introduction into an extrusion device from which
they are to be extruded onto an electrical conductor. The polymer and the other additives and
fillers may be blended together by any of the techniques used in the art to blend and compound
such mixtures to homogeneous masses. For instance, the components may be fluxed on a variety
of apparatus including multi-roll mills, screw mills, continuous mixers, compounding extruders
and Banbury mixers.
[0091] In a preferred embodiment of the invention the additives are premixed with a
small amount of polymer in a master batch. This master batch is added at the cable making
extruder such that for example 10% master batch is added with 90% base polymer such that the
resulting 100% mixture contains the additives in the desired quantity. In this way the cost of
mixing is only attached to about 10% of the total composition.
[0092] In tins embodiment or other embodiments preferably the orgjahic peroxide is not
premixed with the polymer. The peroxide is injected into the cable making extruder in the
desired quantity and it mixes with the polymers and or master batches while they are melted and
extruded. This avoids a second costly and time consuming mixing or absorbing step with the
polymers and or master batches before cable making.
[0099] After the various components of the composition are uniformly admixed and
blended together, they are further processed to fabricate the cables of the invention. Prior art
methods for fabricating polymer insulated cable and wire are well known, and fabrication of the
cable of the invention may generally be accomplished any of the various extrusion methods.
[0094] In a typical extrusion method, an optionally heated conducting core to be coated is
pulled through a heated extrusion dies, generally a cross-head die, in which layers of melted
polymer are applied to the conducting core. Upon exiting the dies, the conducting core with the
applied polymer layers is passed through a heated vulcanizing section, or continuous vulcanizing
section and then a cooling section, generally an elongated cooling bath, to cool. Multiple
polymer layers may be applied by consecutive extrusion steps in which an additional layer is
added in each step, or with the proper type of die, multiple polymer layers may be applied
simultaneously.
[0095] The polyolefin compositions can be vulcanized using traditional curing
procedures, such as chemical, thermal and radiation procedures. The curing agent can be a
hydrolysable silane compound such as vinyl tri-methoxy silane grafted to the polymer backbone
with an organic peroxide or grafted during polymerization of the polymer. The curing agents
employed in the present invention can be organic peroxides, dicumyl peroxide and
bis(terbutylperoxy) diisopropylbenzene. The peroxides act by decomposing at the cure
temperature to form free radicals which then abstract a hydrogen from adjacent polymer
molecules allowing the polymers to bond covalently to each other. To select the curing agents it
is necessary to take into account the decomposition temperatures of said agents, in order to avoid
undesirable problems during me mixture and extrusion processes. The curing agent amounts
and/or ratios to be used will be defined based on the type of application. They are also based on
theif compatibility with and or interference with the additive system.
[0096) The conductor of the invention may generally comprise any suitable electrically
conducting material, although generally electrically conducting metals such has copper or
aluminum.
EXAMPLES
Example 1 - Description of Master Batches and Formulas
[0097] The manufacturing of masterbatches or formulas was done hi two steps:
rarmixing additives with polyethylene pellets, dispersing additives into molten polyethylene, and
pelletizing. At the premixing stage, antioxidant, PEG and Hals were premixed in a 55 gallon
tumble-blender for 30 minutes, and then polyethylene LD 419 pellets were added to the mixture
and all ingredients were mixed for another 30 minutes. The premixing composition was fed to an
L/D 24:1 intermeshing co-rotating twin-screw extruder to make the insulation materials. The
melting temperature was maintained at 324 °F, and the screw speed maintained 150-180 rpm.
The finished insulation compounds was pelletized through a 24 hole strand Pelletier die.
The following materials were used:
Polymers
[0098] ExxonMobil LDPE, LD 419.MV, a polyethylene homopolyiirier, CAS number
9002-88-4, melt index 2.25g/10 min, density 0.921 g/cro3, peak melting temperature 228°F
(109°C). LD 419.MV is designed for wire and cable applications and suitatyIje for making
crosslinkable compounds for medium voltage insulation. Manufactured by ExxonMobil
Chemical, Baton Rouge, LA.
[0099] Petrothene NA951 080, a natural, low density, medium molecular weight
polyethylene homopolymer resin containing no additives. CAS number 9002-88-4, Melt index
2.2 g/10 nun, density 0.919 g/cm3, melting point 280°F (138°C). It provides excellent
processability over a wide range of extrusion conditions, including the low melt temperature
requirements of specialty applications like crosslinkable or foam extrusion. Manufactured by
Equistar Chemicals, Houston, TX.
[00100] Exact 4049, an ethylene-olefin copolymer, odorless opague white pellets, melt
index 4.5 g/10 min, density 0.873 g/cm3, peak melting temperature 131°F (55°Q, crystallization
point 106°F (41 °C). It provides good performance like excellent elastic recbVery/snap back, low
stress relaxation, low thermal bonding temperatures. Manufactured by ExxonMobil Chemical,
Baton Rouge, LA
Antioxidants
[00101] Irganox 1035, Thiodiethylene bis(3,5-di-(tert)-butyl-4-hydroxyhydrocinnamate
(CAS number 41484-35-9), melting range 63-78°C, bulk density 530-630 g/l Irganox 1035 is
an antioxidant and heat stabilizer for wire and cable applications. It is a sulfur containing primary
(phenolic) antioxidant and heat stabilizer used for the process stabilization of polyethylene wire
and cable resins. Manufactured by Ciba Specialty Chemicals Corp., Tarrytown, NY.
[00102] Irganox 245, Emylenebis(oxyethylene)bis-(3-(5-tert-butyl-4-nydroxy-m-tolyl)-
propionate), CAS number 36443-68-2. melting range 76-79 °C, specific gravity (20 °C) 1.14
g/cm3. Irganox 245 is a sterically hindered phenolic antioxidant particularly suitable for organic
substrates. It protects substrates against thermo-oxidative degradation during manufacturing,
processing and end-use. Irganox 245 is odorless, of low volatility, has a good; color stability and
exhibits high extraction resistance. Manufactured by Ciba Specialty Chemicals Corp.,
Tarrytown, NY.
[00103] Agerite resin D, Quinoline, 1,2-dihydrc-2,2,4-trimethyl homopolymer. CAS
number 26780-96-1. Melting point 82-102 °C, specific gravity 1.06. Agerite fesin D is a non-
blooming antioxidant, it retards oxidation and heat deterioration under even the most severe
conditions and increases curing activity of CR. R.T. Manufactured by Vand&bilt Company, Inc.,
Norwalk, Connecticut, CT.
[001O4] Irganox PS 802, Dioctadecyl 3,3' -thiodipropionate. CAS number 693-36-7.
Melting range 64-67°C, bulk density (FL form) 400-450 g/1. Irganox PS 802 \s used as a heat
stabilizer in combination with a primary phenolic antioxidant as thiosynergijst heat stabilizer. It
improves the long-term heat stability of polymers at the levels of 0.05-1 %. Manufactured by
Ciba Specialty Chemicals Corp., Tarrytown, NY.
[00105] Irgastab cable KV 10,4,6-bis(octylthiomethyl)-o-cresol. CAS number 110553-
27-0, melting range -14 °C, density (20 °Q 0.98 g/cm3. Irgstab Cable KV 10 is a liquid,
sulphur-containing, high performance primary (phenolic) antioxidant and heat stabilizer for the
base stabilization of polyethylene wire and cable resins. It improves processability of MV/HV
power cable compounds and extends performance of the cable insulation. It enables
simultaneous additiviation of peroxide and antioxidant as a liquid. Manufactured by Ciba
Specialty Chemicals Corp., Tarrytown, NY.
[00106] Vestowax AV 5012, Ethylene-vinylacetate copolymer wax. Drop point 99 - 104
°C, Viscosity at 140 °C, vinylacetate content 12 - 14%, density (20 °C) 0.$7-1.0 g/cm3, thermal
decomposition 250-300 °C. Manufactured by Degusa Corporation, Parsippjaby, NJ.
[00107] PoIyglyKol 20000, polyethylene glycol, is a white waxy solid $t room
temperature. Its two hydroxy! end groups as well as its ether groups mainly control the physical
and chemical properties. Manufactured by Clariant Corporation, Mount Holly, NC.
HALS
[00108] Chimassorb 944 LD, Poly[[6-[(l ,1,3,3-tetramemylbutyl)amirjq]-13,5-triazine-
2,4HUyl][2,6,6-trtram€4hylpiperidinyl)imino]-1,6-hexanediyl[2,2,6,6-teirRmethyl-4-
pipcridinyl)iiriino]]), CAS number 71878-19-8, molecular weigh Mn = 2000-3100 g/mol,
melting range 100-135 °C, specific gravity (20 °C) 1.01 g/cm3, bulk density 1450-550 g/1.
Chimassorb 944 is a high molecular weight hindered amine light stabilizer (flALS). It shows
excellent compatibility, high resistance to extraction and low volatility. It is highly effective as a
long-term thermal stabilizer in thin and thick articles and shows good extraction resistance.
Manufactured by Ciba Specialty Chemicals Corp., Tarrytown, NY.
Peroxide
[00109] Di-cup, dicumyl peroxide, is a white to pale yellow granular solid. Melting point
100°F (38°C), specific gravity 1.02 (at 25 °C). It is used as high temperature crosslinking agent
Manufactured by GEO Specialty Chemicals, Inc., Gibbstown, NJ.
[00110] Trigonox 101,2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, CAS number 78-63-
7, melting temperature 46.4°F (8°C), Density 0.865 (at 25 °C). Trigonox 101 is a clear, light-
yellow liquid with a faint odor. Manufactured by Akzo Nobel Polymer Chemicals LLC, Chicago,
IL.
Example 2 - Description of peroxide injection process
[00111] The peroxide injection system is shown in Figure 1. If solid dicumyl peroxide is
used, it must be melted in peroxide container in a 130 °F hot bath prior to injection. Melt
dicutayl peroxide or liquid trigonox 101 peroxide with or without liquid Lrgastab Cable KV10 is
dosed to polyethylene, if no masterbatch is added, by pumping them directly into the hopper by
means of stroke head, located in the bottom part of the hopper. The peroxide injection speed is
automatically adjusted by injection control panel based on the primary insulation extruder speed.
The spray method provides good mixing of the liquid additives with polyethylene at an early
stage. Coarse mixing takes place when the additives are directly introduced Into the hopper,
followed by intensive mixing in the melting zone and especially in the mixing zone of the
extruder.
Example 3 - Square Wire Tests
[00112] Square 14 gauge copper conductor wires with 30 mils of insulation were extruded
with a 20:1 LB Davis standard extruder and a crosshead the and cured in steam at 400°F, Eight
to ten 25 inch samples of these insulated square conductor wires were placed in a 75°C water
bath and energized with 7500 volts. Time to short circuit was recorded. The purpose of the
square conductor is to create an electrical stress concentration at each comet and accelerate time
to failure.
Accelerating Cable Life Test (ACLT)
[00113] The power cables tested were prepared in accordance with the formulations listed in
Table 1. The cables had a 1/0 19 wire stranded aluminum conductor surrounded by 15 mils of a
conductor shield, surrounded by either 60 or 175 mils of polyethylene insulation as specified in
Table 1 (representing the parts by weight) surrounded by 35 mils, of semicooductive insulation
shield. A copper mesh was then wrapped around the insulation shield to provide the ground path
for the shortout in the test The conductor shield was extruded first and then the insulation and
outer shield components were extruded over the conductor at one time on a Davis standard
tandem extruder and dry cured under pressurized nitrogen in a continuous catenary vulcanization
tubq and water cooled. Table 1 provides the composition of the insulation materials in each of
the tested cables.
[0014] The Comparative Example cables and samples of cables made according to the
invention were prepared for the test Samples were preconditioned for 72 hours at a 90 °C
conductor temperature in free air. The center of each sample was immersed in SO °C water. The
cable conductor temperature in me water was maintained at 75 °C for 8 hows each 24 hour
period. For the remaining 16 hours, the heating current was turned off. The samples were
energized at four times normal voltage stress (34.6 kv) until all test samples failed.
[00115] The failure times were analyzed using extreme value distribution statistics (Weibull) to
assess comparative mean life equivalency or enhancements versus control(s). For the Weibull
distribution, the distribution parameters are ETA (a), the scale parameter and data (P), the shape
parameter. The scale parameter measures the relative scope or largeness of the variable in
question (life in days) while the shape parameters measures the variation (or range min. to max.)
in the individual data (failure times) results of the population is sample. Both parameters of the
test population best fit distribution were compared to a controlled population Results of the
ACLT are shown in Table 2.
[00116] Comparative example Formula 1 contains PEG tree retardant and an improved
antioxidant known in the art to be suitable for tree retardant polyethylene. Comparative example
Formula 2 contains PEG tree retardant and an antioxidant combination known in the art to be
suitable for tree retardant polyethylene. Comparative example Formula DF42102 is a commercial
PEG tree retardant polyethylene from the Dow chemical company. Comparative example
XLWC085 is a "co polymer" tree retardant polyethylene from the Equistar chemical company.
[00117] Example of the invention Formula 3 contains PEG and an inventive antioxidant
combination. While it is known in the art to use this combination in electrical insulation it is not
know to use them with PEG to achieve electrical performance better than is known in the art.
[00118] Example of the invention formulas 5 and 5 A contain PEG and an inventive
antioxidant combination. While it is known in the art to use HALS in electrical insulation it is
not know to use it with an amine antioxidant with PEG to achieve electrical tree resistant
performance better than is known in the art. It is known in the art that HALS and an amine
antioxidant can reduce dissipation factor of certain polymers.
[00119] Example of the invention formulas 6 and 9 contain a copolymer wax and an
inventive antioxidant combination. "Co-polymer" insulations containing various polar polymers
are know but they have drawbacks such as higher dissipation factor, high adhesion to the outer
semiconductive shield and opacity when heated (in cable production the outer semiconductive
shield is removed and the cable is heated to melt and make transparent the insulation to observe
the quality of the inner semiconductive layer). The inventive copolymer wax advantageously
gives lower adhesion of the outer semiconductive screen, is transparent and gives electrical
performance better than is known in the art.
[00120] Example of the invention formula 9 gives electrical performance equal to than is
known in the art but has several advantages. It is more flexible than even EPR. The composition
requires no separate compounding or master batching step. The polymer, KV10 antioxidant and
cross linking agent can be added directly at the cable making extruder. This reduces cost and
also chances for contamination at compounding or master batching.
[00121] While the present invention has been described and illustrated by reference to
particular embodiments thereof, it will be appreciated by those of ordinary skill in me art that the
invention lends itself to variations not necessarily illustrated herein.
[00122] For this reason, then, reference should be made solely to the appended claims for
the purposes of determining the true scope of this invention.
What is claimed is:
1. An insulation composition for an electric cable comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising a blend of.
(i) at least one amine antioxidant, and
(ii) at least one hindered amine light stabilizer, and
(iii) polyethylene glycol.
2. The insulation composition according to claim 1 wherein said base polymer is
manufactured by a Zeigler Natta catalysis method.
3. The insulation composition according to claim 2 wherein said base polymer comprises
low density polyethylene.
4. The insulation composition according to claim 2 wherein said base polymer comprises
linear low density polyethylene.
5. The insulation composition according to claim 1 wherein said additive is from about
0.5% to about 10.0% by weight of said composition.
6. The insulation composition according to claim 1 wherein said additive is from about
1.0% to about 6.0% by weight of said composition.
7. The insulation composition according to claim 1 wherein said additive is from about
2.0% to about 5.0% by weight of said composition.
8. The insulation composition according to claim 1 in an electrical cable wherein said cable
has an characteristic time to failure in a square wire test of at least about 850 hours.
9. The insulation composition according to claim 1 in an electrical cable wherein said cable
has an characteristic time to failure in a square wire test of at least about 1000 hours.
10. The insulation compound according to claim 1, wherein said additive further comprises a
sulfur containing phenolic antioxidant.
11. An insulation composition for an electric cable comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising a blend of:
(i) at least one fast radical scavenger selected from the group consisting of
low hindered phenols, low hindered thiophenols, low hindered
thiobisphenols, aliphatic amines, aromatic amines, NOR HALS,
hydroxylamines, and mixtures thereof;
(ii) at least one long term stabilizer selected from the group consisting of
low hindered phenols, highly hindered phenols, thiosynergists, aliphatic
amines, aromatic amines, HALS, hydroxylamines, and tnixtures thereof,
and
(iii) polyethylene glycol.
12. An insulation composition for an electric cable comprising:
(a) a base polymer comprising polyolefin,
(b) a sulfur containing phenolic antioxidant, and
(c) polyethylene glycol.
13. The insulation composition of claim 12, wherein the adhesion of the composition is less
than 17 lbs. per ½ inch.
14. An insulation composition for an electric cable comprising:
(a) a base polymer comprising polyolefin;
(b) an additive comprising;
(i) a low molecular weight wax.
15. The insulation composition according to claim 14, wherein said additive further
comprises:
(ii) at least one amine antioxidant; and
(iii) at least one hindered amine light stabilizer.
16. The insulation composition according to claim 14 wherein said additive further comprises
a sulfur containing phenolic antioxidant
17. The insulation composition according to claim 14, wherein said additive further
comprises:
(ii) a phenolic ester antioxidant, and
(iii) at least one hindered amine light stabilizer.
18. The insulation composition according to claim 14, wherein said additive further
comprises at least one amine antioxidant.
19. The insulation composition according to claim 14 wherein said base polymer is
manufactured by a Zeigler Natta catalysis method.
20. The insulation composition according to claim 14 wherein said base polymer comprises
low density polyethylene,
21. The insulation composition according to claim 20 wherein said base polymer comprises
linear low density polyethylene.
22. The insulation composition according to claim 14 wherein said additive is from about
0.5% to about 10.0% by weight of said composition.
23. The insulation composition according to claim 14 wherein said additive is from about
1.0% to about 6.0% by weight of said composition.
24. The insulation composition according to claim 14, wherein said additive is from about
2.0% to about 5.0% by weight of said composition.
25. The insulation composition according to claim 14 in an electrical cable, wherein said
cablje has an characteristic time to failure in a square wire test of at least about 850 hours.
26. The insulation composition according to claim 14 in an electrical cable, wherein said
cable has an characteristic time to failure in a square wire test of at least about 1000 hours.
27. An insulation composition for an electric cable comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising;
(i) a low molecular weight wax, and
(ii) an antioxidant mixture comprising:
(a) at least one fast radical scavenger selected from the group consisting of
low hindered phenols, low hindered thiophenols, low hindered
thiobisphenols, aliphatic amines, aromatic amines, NOR HALS,
hydroxylamines, and mixtures thereof; and
(b) at least one long term stabilizer selected from the group consisting of
low hindered phenols, highly hindered phenols, thiosynergists, aliphatic
amines, aromatic amines, HALS, hydroxylamines, and mixtures thereof.
28. An insulation composition for an electric cable, comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising;
(i) a thio type antioxidant; and
(ii) a low molecular weight wax.
29 The insulation composition of claim 28, wherein the adhesion of the composition is less
than 17 lbs. per ½ inch.
30. An insulation composition for electric cable comprising:
(a) a base polymer comprising from about 50% to about 70%, based upon the
weight of the entire composition, of a C2 to C8 alpha olefin blended with a low density
polyethylene homo polymer base polymer,
(b) a non ionic surfactant, and
(c) a (i) sulfur containing phenolic antioxidant and (ii) an organic peroxide or
hydrolysable silane group;
wherein said base polymer, said non ionic surfactant, said sulfur containing phenolic
antioxidant and said peroxide or silane group are added at a cable making extruder.
31. The insulation composition according to claim 30 wherein said additive father comprises
at least one hindered amine light stabilizer.
32. The insulation composition according to claim 30 wherein said sulfur containing phenolic
antioxidant comprises 4,6-bis(octylthiomemyl)-o-cresol.
33. The insulation composition according to claim 30, wherein said additive further
comprises a phenolic ester antioxidant and at least one hindered amine stabilizer.
34. The insulation composition according to claim 30, wherein said additive further
comprises at least one amine antioxidant and at least one hindered amine light stabilizer.
35. The insulation composition according to claim 30, wherein said additive further
comprises a low molecular weight wax.
36 A process for making an electric cable having an insulation composition comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising a blend of:
(i) at least one amine antioxidant, and
(ii) at least one hindered amine light stabilizer, and
(iii) polyethylene glycol;
the process comprising:
forming a masterbatch of the additives and a first amount of the polyolefin;
adding the masterbatch to a second amount of polyolefin at a cable making extruder, and
adding peroxide at the cable making extruder at a temperature less than the
decomposition temperature of the peroxide.
37. The process for making an electric cable of claim 36, wherein the first amount of
polyolefin is about 10% of the total amount of polyolefin used in making the cable.
38. The process for making an electric cable of claim 36, wherein the peroxide is selected
from the group consisting of. organic peroxides, dicumyl peroxide and bis(terbutylperoxy)
diisopropylbenzene.
39 A process for making an electric cable having an insulation composition comprising:
(a) a base polymer comprising polyolefin,
(b) a sulfur containing phenolic antioxidant, and
(c) polyethylene glycol;
the process comprising:
forming a masterbatch of the sulfur containing phenolic antioxidant, the polyethylene
glycol and a first amount of the polyolefin;
adding the masterbatch to a second amount of polyolefin at a cable making extruder; and
adding peroxide at the cable making extruder at a temperature less than the
decomposition temperature of the peroxide.
40. The process for making an electric cable of claim 36, wherein the first amount of
polyolefin is about 10% of the total amount of polyolefin used in making the; cable.
41. The process for making an electric cable of claim 36, wherein the peroxide is selected
from the group consisting of: organic peroxides, dicumyl peroxide and bis(terbutylperoxy)
diisopropylbenzene.
47 A process for making an electric cable having an insulation composition comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising;
(i) a thio type antioxidant; and
(ii) a low molecular weight wax;
the process comprising:
forming a masterbatch of the additives and a first amount of the polyolefin;
adding the masterbatch to a second amount of polyolefin at a cable making extruder, and
adding peroxide at the cable making extruder at a temperature less than the
decomposition temperature of the peroxide.
43. The process for making an electric cable of claim 36, wherein the first amount of
polyolefin is about 10% of the total amount of polyolefin used in making the cable.
44. The process for making an electric cable of claim 36, wherein the peroxide is selected
front the group consisting of: organic peroxides, dicumyl peroxide and bis(terbutylperoxy)
diisopropylbenzene.
45. A process for making an electric cable having an insulation composition comprising:
(a) a base polymer comprising polyolefin; and
(b) an additive comprising a blend of:
(i) at least one phenolic ester antioxidant, and
(ii) at least one hindered amine light stabilizer, and
(iii) polyethylene glycol;
the process comprising:
forming a masterbatch of the additives and a first amount of the polyolefin;
adding the masterbatch to a second amount of polyolefin at a cable making extruder; and
adding peroxide at the cable making extruder at a temperature less than the
decomposition temperature of the peroxide.
46. The process for making an electric cable of claim 36, wherein the first amount of
polyolefin is about 10% of the total amount of polyolefin used in making the cable.
47. The process for making an electric cable of claim 36, wherein the peroxide is selected
from the group consisting of: organic peroxides, dicumyl peroxide and bis(terbutylperoxy)
diisopropylbenzene.

Insulation compositions for electric power cables having a polyolefin base polymer and an additive comprising
either low molecular weight wax or polyethylene glycol (PEG) and optionally further comprising one or more hindered amine light
stabilizers, amine antioxidants and other antioxidant blends are disclosed. Also disclosed are insulation compositions comprising a
C2 to C8 alpha olefin in combination with a polyethylene homopolymer together with, optionally, one or more hindered amine light
stabilizer and a liquid cresol antioxidant.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=fcaHxb7IXYYX7Zm6BRA92g==&loc=wDBSZCsAt7zoiVrqcFJsRw==


Patent Number 268904
Indian Patent Application Number 630/KOLNP/2010
PG Journal Number 39/2015
Publication Date 25-Sep-2015
Grant Date 22-Sep-2015
Date of Filing 18-Feb-2010
Name of Patentee GENERAL CABLE TECHNOLOGIES, CORP.
Applicant Address 4 TESSENEER DRIVE, HIGHLAND HEIGHTS, KENTUCKY 41076, UNITED STATES OF AMERICA
Inventors:
# Inventor's Name Inventor's Address
1 EASTER, MARK R. 4020 NORTH PENNSYLVANIA STREET, INDIANAPOLIS, INDIANA 46206 UNITED STATES OF AMERICA
PCT International Classification Number C08L 23/00,H01B 3/44
PCT International Application Number PCT/US2008/072351
PCT International Filing date 2008-08-06
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 61/018,625 2008-01-02 U.S.A.
2 60/935,309 2007-08-06 U.S.A.