U.S. patent application number 13/822114 was filed with the patent office on 2013-07-25 for polymeric compositions with voltage stabilizer additive.
The applicant listed for this patent is Timothy J. Person. Invention is credited to Timothy J. Person.
Application Number | 20130186670 13/822114 |
Document ID | / |
Family ID | 44736102 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130186670 |
Kind Code |
A1 |
Person; Timothy J. |
July 25, 2013 |
Polymeric Compositions with Voltage Stabilizer Additive
Abstract
Disclosed are polymeric compositions with improved breakdown
strength. The polymeric compositions contain a polyolefin and a
voltage stabilizing agent. The voltage stabilizing agent is a
diphenoxybenzene and/or a benzanilide. The present polymeric
compositions exhibit improved breakdown strength when applied as an
insulating layer for power cable.
Inventors: |
Person; Timothy J.;
(Freehold, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Person; Timothy J. |
Freehold |
NJ |
US |
|
|
Family ID: |
44736102 |
Appl. No.: |
13/822114 |
Filed: |
September 23, 2011 |
PCT Filed: |
September 23, 2011 |
PCT NO: |
PCT/US11/52916 |
371 Date: |
March 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61388260 |
Sep 30, 2010 |
|
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|
Current U.S.
Class: |
174/110SR ;
524/226; 524/342 |
Current CPC
Class: |
C08K 5/20 20130101; H01B
7/02 20130101; C09D 123/06 20130101; C09D 7/63 20180101; H01B 3/441
20130101; H01B 3/307 20130101; C08K 5/06 20130101; C08K 5/06
20130101; C08L 23/02 20130101; C08K 5/20 20130101; C08L 23/02
20130101 |
Class at
Publication: |
174/110SR ;
524/342; 524/226 |
International
Class: |
H01B 3/30 20060101
H01B003/30 |
Claims
1. A polymeric composition comprising: a polyolefin; and a
diphenoxybenzene of the structure (I) ##STR00005## wherein
R.sub.1-R.sub.14 are the same or different, each of
R.sub.1-R.sub.14 is selected from the group consisting of hydrogen,
a C.sub.1-C.sub.20 hydrocarbyl group, a substituted
C.sub.1-C.sub.20 hydrocarbyl group, and combinations thereof.
2. The polymeric composition of claim 1 wherein the polyolefin is a
polyethylene.
3. The polymeric composition of claim 1 wherein the polyolefin is a
crosslinked polyethylene.
4. The polymeric composition of claim 1 wherein at least one of
R.sub.1-R.sub.14 is a C.sub.1-C.sub.20 hydrocarbyl group.
5. The polymeric composition of claim 1 wherein each of
R.sub.1-R.sub.14 is hydrogen.
6. The polymeric composition of claim 1 comprising from about 0.1
wt % to about 3 wt % of the diphenoxybenzene.
7. A polyolefin composition comprising: a polyolefin; and a
benzanilide of the structure (II) ##STR00006## wherein
R.sub.1-R.sub.10 are the same or different, and each of
R.sub.1-R.sub.10 is selected from the group consisting of hydrogen,
a C.sub.1-C.sub.20 hydrocarbyl group, a substituted
C.sub.1-C.sub.20 hydrocarbyl group, and combinations thereof.
8. The polymeric composition of claim 7 wherein the polyolefin is a
polyethylene.
9. The polymeric composition of claim 7 wherein the polyolefin is a
crosslinked polyethylene.
10. The polymeric composition of claim 7 wherein at least one of
R.sub.1-R.sub.10 is a C.sub.1-C.sub.20 hydrocarbyl group.
11. The polymeric composition of claim 7 wherein each of
R.sub.1-R.sub.10 is hydrogen.
12. The polymeric composition of claim 7 comprising from about 0.1
wt % to about 3 wt % of the benzanilide.
13. A coated conductor comprising: a conductor; and a coating on
the conductor, the coating comprising the polymeric composition of
claim 1.
14. The coated conductor of claim 13 wherein the coating is an
insulating layer.
15. The coated conductor of claim 13 wherein the coating is a
shielding layer.
16. A coated conductor comprising: a conductor; and a coating on
the conductor, the coating comprising the polymeric composition of
claim 7.
17. The coated conductor of claim 16 wherein the coating is an
insulating layer.
18. The coated conductor of claim 16 wherein the coating is a
shielding layer.
Description
BACKGROUND
[0001] A typical power cable includes one or more conductors in a
cable core surrounded by one or more layers of polymeric material.
Medium voltage (6 to 36 kV) and high voltage (higher than 36 kV)
and extra high voltage (greater than 220 kV) cable typically
includes a core surrounded by an inner semiconducting layer,
followed by an insulating layer, and then an outer semiconducting
layer.
[0002] The load-carrying capacity of a cable system is limited, in
part, by the heat transfer away from the conductor. Polyolefins,
such as polyethylene, are frequently utilized in the insulating
layer and/or in the semiconducting layer. Polyethylene has a low
dielectric permittivity and a relatively high electrical breakdown
strength.
[0003] Known are voltage stabilizing agents for polyolefin
compositions that increase electrical breakdown strength of
insulating layers in power cable. Conventional voltage stabilizing
agents, however, have poor compatibility with polyolefins. The art
recognizes the continuous need for voltage stabilizing agents
compatible with polyolefins for (i) increased electrical breakdown
strength of cable insulation material, (ii) increased reliability
with existing cable designs and/or (iii) provision of high-stress
designs that are able to deliver increased amounts of energy.
SUMMARY
[0004] The present disclosure is directed to polymeric compositions
with improved electrical breakdown strength. The present polymeric
compositions are composed of (i) a polymeric component and (ii) a
voltage stabilizing agent (VSA) and exhibit improved electrical
breakdown strength and increased endurance to high electrical
stress. The present voltage stabilizing agent can be melt-mixed
with polyolefin and can be functionalized via established
chemistries to further improve compatibility with polyolefin, and
increase electrical breakdown strength to the polyolefin, while
imparting little impact on crosslinking chemistry typically
practiced in power cable insulating compositions. The present
polymeric compositions find use as an insulating layer in wire and
cable applications and power cable in particular.
[0005] In an embodiment, a polymeric composition is provided and
includes a polymeric component and a voltage stabilizing agent. The
polymeric component is a polyolefin. The voltage stabilizing agent
is a diphenoxybenzene. The diphenoxybenzene has the structure
(I).
##STR00001##
[0006] R.sub.1-R.sub.14 are the same or different. Each of
R.sub.1-R.sub.14 is selected from hydrogen, a C.sub.1-C.sub.20
hydrocarbyl group, a substituted C.sub.1-C.sub.20 hydrocarbyl
group, and combinations thereof.
[0007] In an embodiment, another polymeric composition is provided
and includes a polymeric component and a voltage stabilizing agent.
The polymeric component is a polyolefin. The voltage stabilizing
agent is a benzanilide. The benzanilide has the structure (II).
##STR00002##
[0008] R.sub.1-R.sub.10 are the same or different. Each of
R.sub.1-R.sub.10 is selected from hydrogen, a C.sub.1-C.sub.20
hydrocarbyl group, a substituted C.sub.1-C.sub.20 hydrocarbyl
group, and combinations thereof.
[0009] In an embodiment, the polymeric composition includes a
polyolefin and a voltage stabilizing agent that is a mixture of the
diphenoxybenzene (I) and the benzanilide (II).
[0010] The present disclosure provides a coated conductor. In an
embodiment, a coated conductor is provided and includes a conductor
and a coating on the conductor. The coating includes any of the
foregoing polymeric compositions. In other words, the coating
contains a (i) polyolefin and (ii) a voltage stabilizing agent that
is a diphenoxybenzene of structure (I) and/or a benzanilide of
structure (II).
[0011] An advantage of the present disclosure is a polymeric
composition with improved breakdown strength.
[0012] An advantage of the present disclosure is a voltage
stabilizing agent with improved compatibility with polyolefin.
[0013] An advantage of the present disclosure is a voltage
stabilizing agent that reduces electrical treeing in a polymeric
composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of a power cable in accordance
with an embodiment of the present disclosure.
[0015] FIG. 2 is a Weibull analysis for LDPE prepared at different
mix temperatures.
DETAILED DESCRIPTION
[0016] The present disclosure provides a polymeric composition. The
polymeric composition includes (i) a polymeric component, (ii) a
voltage stabilizing agent, and (iii) optionally other
additives.
[0017] The polymeric component may include thermoplastics and/or
thermoset material (such as silicone rubber). The polymeric
component may be crosslinked or may be non-crosslinked. Nonlimiting
examples of suitable thermoplastics include, polyurethanes,
polyolefins, polyacetals, polycarbonates, vinyl polymers,
polyamides, polyimides, acrylics, polystyrenes, polysulfones,
polyetherketones, cellulosics, polyesters, polyethers,
fluoropolymers, and copolymers thereof such as olefin-vinyl
copolymers, olefin-allyl copolymers and copolymers of polyethers
and polyamides. Examples of vinyl polymers include polyvinyl
chloride, polyvinyl acetate, vinyl chloride/vinyl acetate
copolymers, polyvinyl alcohol and polyvinyl acetal.
[0018] When it is desired to use a crosslinked polymeric component,
crosslinking can be accomplished by one or more of the following
nonlimiting procedures: free radical crosslinking (i.e., peroxide
cross-linking); radiation cross-linking (electron accelerators,
gamma-rays, high energy radiation, such as X-rays, microwaves,
etc.); thermal crosslinking, and/or moisture cure crosslinking
(i.e., silane-graft).
[0019] In an embodiment, the polymeric component is a polyolefin.
Nonlimiting examples of suitable polyolefins are homopolymers and
copolymers containing one or more C.sub.2-C.sub.20 .alpha.-olefins.
For purposes of this disclosure, ethylene is considered an
.alpha.-olefin. Nonlimiting examples of suitable .alpha.-olefins
include ethylene, propylene, isobutylene, 1-butene, 1-pentene,
1-hexene, 4-methyl-1-pentene, and 1-octene. Nonlimiting examples of
suitable polyolefins include ethylene-based polymer,
propylene-based polymer, and combinations thereof. An
"ethylene-based polymer", or "polyethylene" and like terms is a
polymer containing at least 50 mole percent (mol %) units derived
from ethylene. A "propylene-based polymer," or "polypropylene" and
like terms is a polymer containing at least 50 mole percent units
derived from propylene.
[0020] In an embodiment, the polymeric component is an
ethylene-based polymer. The ethylene-based polymer may be ethylene
homopolymer or an ethylene/.alpha.-olefin interpolymer. The
.alpha.-olefin content is from about 5, or about 10, or about 15,
or about 20, or about 25, wt % to less than 50, or less than about
45, or less than about 40, or less than about 35, wt % based on the
weight of the interpolymer. The .alpha.-olefin content is measured
by .sup.13C nuclear magnetic resonance (NMR) spectroscopy using the
procedure described in Randall (Rev. Macromol. Chem. Phys., C29
(2&3)). Generally, the greater the .alpha.-olefin content of
the interpolymer, the lower the density and the more amorphous the
interpolymer, and this translates into desirable physical and
chemical properties for the protective insulation layer.
[0021] The .alpha.-olefin is a C.sub.3-20 linear, branched or
cyclic .alpha.-olefin. Nonlimiting examples of suitable of
C.sub.3-20 .alpha.-olefins include propene, 1-butene,
4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene,
1-tetradecene, 1-hexadecene, and 1-octadecene. The .alpha.-olefins
also can contain a cyclic structure such as cyclohexane or
cyclopentane, resulting in an .alpha.-olefin such as
3-cyclohexyl-1-propene (allyl cyclohexane) and vinyl cyclohexane.
Although not .alpha.-olefins in the classical sense of the term,
for purposes of this disclosure certain cyclic olefins, such as
norbornene and related olefins, particularly
5-ethylidene-2-norbornene, are .alpha.-olefins and can be used in
place of some or all of the .alpha.-olefins described above.
Similarly, styrene and its related olefins (for example,
.alpha.-methylstyrene, etc.) are .alpha.-olefins for purposes of
this disclosure. Nonlimiting examples of suitable ethylene-based
polymers include the following copolymers: ethylene/propylene,
ethylene/butene, ethylene/1-hexene, ethylene/1-octene,
ethylene/styrene, ethylene-vinyl acetate, ethylene-vinyl
propionate, ethylene-vinyl isobutyrate, ethylene-vinyl alcohol,
ethylenemethyl acrylate, ethylene-ethyl acrylate, ethylene-ethyl
methacrylate, ethylene/butyl-acrylate copolymers (EBA),
ethylene-allyl benzene, ethylene-allyl ether, and
ethylene-acrolein; ethylene-propylene (EPR) or
ethylene-propylene-diene (EPDM) rubbers; natural rubbers; butyl
rubbers and the like.
[0022] Nonlimiting examples of suitable terpolymers include
ethylene/propylene/1-octene, ethylene/propylene/butene,
ethylene/butene/1-octene, ethylene/propylene/diene monomer (EPDM)
and ethylene/butene/styrene. The copolymers/interpolymers can be
random or blocky.
[0023] The ethylene-based polymer can be high density polyethylene
(HDPE), medium density polyethylene, (MDPE), low density
polyethylene, (LDPE), linear low density polyethylene (LLDPE),
and/or very low density polyethylene (VLDPE). The ethylene-based
polymers used in the practice of this disclosure can be used alone
or in combination with one or more other ethylene-based polymers,
e.g., a blend of two or more ethylene-based polymers that are
"different from one another," which means the ethylene-based
polymers are uncommon by way of at least one property such as:
monomer/comonomer composition and content, melt index, melt
temperature, degree of branching, catalytic method of preparation,
etc. If the ethylene-based polymer is a blend of two or more
ethylene-based polymers, then the ethylene-based polymers can be
blended by any in-reactor or post-reactor process. The reactors can
be charged with the same catalyst but operated at different
conditions, e.g., different reactant concentrations, temperatures,
pressures, etc, or operated at the same conditions but charged with
different catalysts.
[0024] Examples of ethylene-based polymers made with high pressure
processes include (but are not limited to) low density polyethylene
(LDPE), ethylene vinyl acetate copolymer (EVA), ethylene ethyl
acrylate copolymer (EEA), and ethylene silane acrylate
terpolymers.
[0025] Nonlimiting examples of ethylene-based polymers include very
low density polyethylene (VLDPE) (e.g., FLEXOMER.RTM.
ethylene/1-hexene polyethylene made by The Dow Chemical Company),
homogeneously branched, linear ethylene/.alpha.-olefin copolymers
(e.g., TAFMER.RTM. by Mitsui Petrochemicals Company Limited and
EXACT.RTM. by Exxon Chemical Company), homogeneously branched,
substantially linear ethylene/.alpha.-olefin polymers (e.g.,
AFFINITY.RTM. and ENGAGE.RTM. polyethylene available from The Dow
Chemical Company), and ethylene block copolymers (e.g., INFUSE.RTM.
polyethylene available from The Dow Chemical Company).
Substantially linear ethylene copolymer is described in U.S. Pat.
Nos. 5,272,236, 5,278,272 and 5,986,028.
[0026] Voltage Stabilizing Agent
[0027] In addition to the polymeric component, the polymeric
composition also includes a voltage stabilizing agent (or VSA). A
"voltage stabilizing agent," as used herein, is a compound which
reduces the damage to a polymeric material when exposed to an
electric field. It has been considered that a VSA may trap or
deactivate electrons to inhibit electrical treeing in an insulation
material, or otherwise to provide effective screening of high
localized fields (near defects or contaminants) to thereby reduce
the energy and/or frequency of injected electrons which may impart
damage to the polyolefin. Blending the VSA with the polymeric
component inhibits or otherwise retards treeing. Bounded by no
particular theory, it is believed the VSA fills and/or surrounds
defects in the polymeric component, the defects being points of
tree initiation. Defects include voids and/or impurities present in
the polymeric component.
[0028] In an embodiment, the polymeric composition includes a (i)
polyolefin, (ii) a voltage stabilizing agent that is a
diphenoxybenzene, and (iii) optional additives. Diphenoxybenzene
has the structure (I) below.
##STR00003##
[0029] R.sub.1-R.sub.14 are the same or different. Each of
R.sub.1-R.sub.14 is selected from hydrogen, a C.sub.1-C.sub.20
hydrocarbyl group, a substituted C.sub.1-C.sub.20 group, and
combinations thereof. The hydrocarbyl group may be substituted or
unsubstituted.
[0030] As used herein, the term "hydrocarbyl" or "hydrocarbon" is a
substituent containing only hydrogen and carbon atoms, including
branched or unbranched, saturated or unsaturated, cyclic,
polycyclic, fused, or acyclic species, and combinations thereof.
Nonlimiting examples of hydrocarbyl groups include alkyl-,
cycloalkyl-, alkenyl-, alkadienyl-, cycloalkenyl-,
cycloalkadienyl-, aryl-, aralkyl, alkylaryl-, and
alkynyl-groups.
[0031] As used herein, the term "substituted hydrocarbyl" or
"substituted hydrocarbon" is a hydrocarbyl group that is
substituted with one or more nonhydrocarbyl substituent groups. A
nonlimiting example of a nonhydrocarbyl substituent group is a
heteroatom. As used herein, a "heteroatom" is an atom other than
carbon or hydrogen. The heteroatom can be a non-carbon atom from
Groups IV, V, VI, and VII of the Periodic Table. Nonlimiting
examples of heteroatoms include: halogens (F Cl, Br, I), N, O, P,
B, S, and Si. A substituted hydrocarbyl group also includes a
halohydrocarbyl group and a silicon-containing hydrocarbyl group.
As used herein, the term "halohydrocarbyl" group is a hydrocarbyl
group that is substituted with one or more halogen atoms.
[0032] In an embodiment, the polyolefin is a polyethylene.
[0033] In an embodiment, the polyolefin is a crosslinked
polyethylene.
[0034] In an embodiment, at least one of R.sub.1-R.sub.14 is a
C.sub.1-C.sub.20 hydrocarbyl group.
[0035] In an embodiment, each of R.sub.1-R.sub.14 is hydrogen.
[0036] In an embodiment, the polymeric composition contains from
about 0.1 wt %, or about 0.2 wt % to about 3 wt %, or about 1 wt %
of the diphenoxybenzene. Weight percent is based on total weight of
the polymeric composition.
[0037] The disclosure provides another polymeric composition
composed of (i) a polymeric component and (ii) a VSA that is a
benzanilide and (iii) optional additives. The polymeric component
may be any polymeric component as disclosed above.
[0038] In an embodiment, the polymeric composition includes a
polyolefin and the VSA is a benzanilide with the structure (II)
below.
##STR00004##
[0039] R.sub.1-R.sub.10 are the same or different. Each of
R.sub.1-R.sub.10 is selected from hydrogen, a C.sub.1-C.sub.20
hydrocarbyl group, a substituted C.sub.1-C.sub.20 hydrocarbyl
group, and combinations thereof. The hydrocarbyl group may be
substituted or unsubstituted.
[0040] In an embodiment, the polyolefin is a polyethylene.
[0041] In an embodiment, the polyolefin is a crosslinked
polyethylene.
[0042] In an embodiment, at least one of R.sub.1-R.sub.10 is a
C.sub.1-C.sub.20 hydrocarbyl group.
[0043] In an embodiment, each of R.sub.1-R.sub.10 is hydrogen.
[0044] In an embodiment, the polymeric composition contains from
about 0.1 wt % to about 3 wt % of the benzanilide. Weight percent
is based on total weight of the polymeric composition.
[0045] The foregoing VSAs unexpectedly improve electrical breakdown
strength in insulating layers containing the present polymeric
compositions. The improvement in electrical breakdown strength can
be seen in the increased breakdown voltages exhibited in Examples 1
and 2 described hereafter.
[0046] Moreover, the present VSAs exhibit good solubility in the
polyolefin matrix and a low migration tendency. The present VSAs
may also be effectively utilized with regard to other components of
the polyolefin composition, and are compatible with cross-linking
agents.
[0047] Additives
[0048] Any of the foregoing polymeric compositions may optionally
contain one or more additives. Nonlimiting examples of suitable
additives include antioxidants, stabilizers, processing aids,
scorch retarders, and/or cross-linking boosters. As antioxidant,
sterically hindered or semi-hindered phenols, aromatic amines,
aliphatic sterically hindered amines, organic phosphates, thio
compounds, and mixtures thereof, can be mentioned. Typical
cross-linking boosters may include compounds having a vinyl or an
allyl group, e.g. triallylcyanurate, triallylisocyanurate, and di-,
tri- or tetra-acrylates. As further additives, flame retardant
additives, acid scavengers, inorganic fillers, water-tree
retardants and other voltage stabilizers can be mentioned
[0049] A "scorch retarder," as used herein is a compound that
reduces the formation of scorch during extrusion of a polymer
composition, at typical extrusion temperatures used, when compared
to the same polymer composition extruded without said compound.
Besides scorch retarding properties, the scorch retarder may
simultaneously result in further effects like boosting, i.e.
enhancing cross-linking performance during the cross-linking
step.
[0050] The polymeric composition may comprise two or more
embodiments disclosed herein.
[0051] Coated Conductor
[0052] The present disclosure provides articles containing the
present polymeric compositions. In an embodiment, the article
includes a conductor and a coating on the conductor. This forms a
coated conductor. The conductor may be a single cable or a
plurality of cables bound together (i.e., a cable core, or a core).
The coated conductor may be flexible, semi-rigid, or rigid.
Nonlimiting examples of suitable coated conductors include flexible
wiring such as flexible wiring for consumer electronics, a power
cable, a power charger wire for cell phones and/or computers,
computer data cords, power cords, appliance wiring material, and
consumer electronic accessory cords.
[0053] A coating is located on the conductor. The coating may be
one or more inner layers such as an insulating layer and/or a
semiconducting layer. The coating may also include an outer layer
(also referred to as a "jacket" or a "sheath"). The coating
includes any of the present polymer compositions as disclosed
herein. As used herein, "on" includes direct contact or indirect
contact between the coating and the conductor. "Direct contact" is
a configuration whereby the coating immediately contacts the
conductor, with no intervening layer(s) and/or no intervening
material(s) located between the coating and the conductor.
"Indirect contact" is a configuration whereby an intervening
layer(s) and/or an intervening structure(s) or material(s) is/are
located between the conductor and the coating. The coating may
wholly or partially cover or otherwise surround or encase the
conductor. The coating may be the sole component surrounding the
conductor. Alternatively, the coating may be one layer of a
multilayer jacket or sheath encasing the metal conductor.
[0054] In an embodiment, the coated conductor includes an
insulating layer containing the present polymeric composition.
[0055] In an embodiment, the coated conductor is a power cable
operating at a voltage greater than 1 kV, or greater than 6 kV, or
greater than 36 kV. FIG. 1 shows an insulated power cable 10 which
includes a metallic conductor 12, an internal shielding layer 14,
an insulating layer 16, an external shielding layer 18, a metallic
screen 20 of wound wires or conducting bands, and an outermost
layer, with a sheath 22.
[0056] In an embodiment, the internal shielding layer 14 and/or the
insulating layer 16 and/or the external shielding layer 18 are/is
composed of a polymeric composition containing polyethylene and
diphenoxybenzene of the structure (I).
[0057] In another embodiment, the internal shielding layer 14
and/or the insulating layer 16 and/or the external shielding layer
18 contains a polymeric composition containing polyethylene and the
benzanilide of the structure (II).
[0058] The present coated metal conductor may comprise two or more
embodiment disclosed herein.
DEFINITIONS
[0059] All references to the Periodic Table of the Elements herein
shall refer to the Periodic Table of the Elements, published and
copyrighted by CRC Press, Inc., 2003. Also, any references to a
Group or Groups shall be to the Groups or Groups reflected in this
Periodic Table of the Elements using the IUPAC system for numbering
groups. Unless stated to the contrary, implicit from the context,
or customary in the art, all parts and percents are based on
weight. For purposes of United States patent practice, the contents
of any patent, patent application, or publication referenced herein
are hereby incorporated by reference in their entirety (or the
equivalent US version thereof is so incorporated by reference),
especially with respect to the disclosure of synthetic techniques,
definitions (to the extent not inconsistent with any definitions
provided herein) and general knowledge in the art.
[0060] Any numerical range recited herein, includes all values from
the lower value to the upper value, in increments of one unit,
provided that there is a separation of at least 2 units between any
lower value and any higher value. As an example, if it is stated
that the amount of a component, or a value of a compositional or a
physical property, such as, for example, amount of a blend
component, softening temperature, melt index, etc., is between 1
and 100, it is intended that all individual values, such as, 1, 2,
3, etc., and all subranges, such as, 1 to 20, 55 to 70, 197 to 100,
etc., are expressly enumerated in this specification. For values
which are less than one, one unit is considered to be 0.0001,
0.001, 0.01 or 0.1, as appropriate. These are only examples of what
is specifically intended, and all possible combinations of
numerical values between the lowest value and the highest value
enumerated, are to be considered to be expressly stated in this
application. In other words, any numerical range recited herein
includes any value or subrange within the stated range. Numerical
ranges have been recited, as discussed herein, reference melt
index, melt flow rate, and other properties.
[0061] The term "alkyl," as used herein, refers to a branched or
unbranched, saturated hydrocarbon radical. Nonlimiting examples of
suitable alkyl radicals include, for example, methyl, ethyl,
n-propyl, i-propyl, n-butyl, t-butyl, i-butyl (or 2-methylpropyl),
etc. The alkyls have 1 to 20 carbon atoms.
[0062] The term "aryl" or "aryl group," as used herein, is a
substituent derived from an aromatic hydrocarbon compound. An aryl
group has a total of from six to twenty ring atoms, and has one or
more rings which are separate or fused, and may be substituted with
alkyl and/or halo groups. The aromatic ring(s) may include phenyl,
naphthyl, anthracenyl, and biphenyl, among others.
[0063] The term "arylalkyl" or "arylalkyl group," as used herein,
is a compound containing both aliphatic and aromatic structures.
The term "arylalkyl group" includes "aralkyl groups" (an alkyl
group substituted by at least one aryl group) and/or "alkylaryl
groups" (an aryl group substituted by at least one alkyl
group).
[0064] The terms "blend" or "polymer blend," as used herein, is a
blend of two or more polymers. Such a blend may or may not be
miscible (not phase separated at molecular level). Such a blend may
or may not be phase separated. Such a blend may or may not contain
one or more domain configurations, as determined from transmission
electron spectroscopy, light scattering, x-ray scattering, and
other methods known in the art.
[0065] The "breakdown voltage" of an insulator is the minimum
voltage that causes a portion of an insulator to become
electrically conductive.
[0066] "Cable" and like terms is at least one wire or optical fiber
within a protective insulation, jacket or sheath. Typically, a
cable is two or more wires or optical fibers bound together,
typically in a common protective insulation, jacket or sheath. The
individual wires or fibers inside the jacket may be bare, covered
or insulated. Combination cables may contain both electrical wires
and optical fibers. The cable, etc. can be designed for low, medium
and high voltage applications. Typical cable designs are
illustrated in U.S. Pat. Nos. 5,246,783, 6,496,629 and
6,714,707.
[0067] The term "composition," as used herein, includes a mixture
of materials which comprise the composition, as well as reaction
products and decomposition products formed from the materials of
the composition.
[0068] "Composition" and like terms mean a mixture or blend of two
or more components.
[0069] The term "comprising," and derivatives thereof, is not
intended to exclude the presence of any additional component, step
or procedure, whether or not the same is disclosed herein. In order
to avoid any doubt, all compositions claimed herein through use of
the term "comprising" may include any additional additive,
adjuvant, or compound whether polymeric or otherwise, unless stated
to the contrary. In contrast, the term, "consisting essentially of"
excludes from the scope of any succeeding recitation any other
component, step or procedure, excepting those that are not
essential to operability. The term "consisting of" excludes any
component, step or procedure not specifically delineated or listed.
The term "or", unless stated otherwise, refers to the listed
members individually as well as in any combination.
[0070] A "conductor" is an element of elongated shape (wire, cable,
fiber) for transferring energy at any voltage (DC, AC, or
transient). The conductor is typically at least one metal wire or
at least one metal cable (such as aluminum or copper) but may
include optical fiber.
[0071] "Crosslinked," "cured" and similar terms mean that the
polymer, before or after it is shaped into an article, was
subjected or exposed to a treatment which induced crosslinking and
has xylene or decalene extractables of less than or equal to 90
weight percent (i.e., greater than or equal to 10 weight percent
gel content).
[0072] An "insulating layer" is a layer having a volume resistivity
greater than 10.sup.10 ohm-cm, or greater than 10.sup.12
ohm-cm.
[0073] A "layer," as used herein, is polymer based layer
surrounding the conductor, for example, an electrically insulating
layer, a semiconductive layer, a sheath, a protective layer, a
water blocking layer, or a layer performing combined functions, for
example, a protective layer charged with a conductive filler.
[0074] The term "medium voltage" generally means a voltage of
between 6 kV and about 36 kV, whereas "high voltage" means voltages
higher than 36 kV, and "extra high voltage" generally means
voltages greater than 220 kV. The skilled artisan understands that
these general voltage ranges may be different outside of the United
States.
[0075] The term "polymer" is a macromolecular compound prepared by
polymerizing monomers of the same or different type. "Polymer"
includes homopolymers, copolymers, terpolymers, interpolymers, and
so on. The term "interpolymer" is a polymer prepared by the
polymerization of at least two types of monomers or comonomers. It
includes, but is not limited to, copolymers (which usually refers
to polymers prepared from two different types of monomers or
comonomers, terpolymers (which usually refers to polymers prepared
from three different types of monomers or comonomers),
tetrapolymers (which usually refers to polymers prepared from four
different types of monomers or comonomers), and the like.
[0076] A "shielding layer" may be semiconductive or resistive. A
shielding layer having semiconductive properties has a volumetric
resistivity value, of less than 1000 .OMEGA.-m, or less than 500
.OMEGA.-m, when measured at 90.degree. C. A shielding layer having
resistive properties has a volumetric resistivity value greater
than a semiconductive shielding layer. A shielding layer having
resistive properties typically has a dielectric constant greater
than about 10.
[0077] Test Methods
[0078] Melt index (MI) is measured in accordance with ASTM D
1238-01 test method at 190.degree. C. with a 2.16 kg weight for
ethylene-based polymers.
[0079] By way of example, and not by limitation, examples of the
present disclosure are provided.
EXAMPLES
[0080] 1. Sample Preparation
[0081] Polyethylene homopolymer (0.92 g/cc, MI 2.0 g/10 min) is
melt fluxed in a Brabender mixing bowl, after which voltage
stabilizing agent is melt-compounded into the polyethylene at a
target mix temperature and 30 rpm for 5 minutes to insure adequate
incorporation. The polymeric composition is removed from the mixing
bowl and compression molded into a slab that is 0.25 inches thick.
Compression molding is achieved using a pressure of 300-500 psi and
a temperature of 140.degree. C. for 3 minutes, after which the
pressure is increased above 2000 psi while maintaining the sample
at 140.degree. C. for an additional 3 minutes. The high pressure is
then maintained while the sample cools.
[0082] 1 inch square specimens are die-cut from the slab and
pre-drilled to a depth of 0.5 inches along one of the major axes.
Steel needles (60.degree. cone, 3 micron tip radius) are inserted
into the pre-drilled holes and placed into a jig to complete the
insertion at elevated temperature. The entire jig is conditioned in
a circulating air oven for 1 hour at 105.degree. C., after which
the needle is advanced into the softened polymer at a rate of
approximately 1 mm every 5 minutes while remaining in the
105.degree. C. oven. The needles are advanced to a stop which
produces a point-to-plane distance of approximately 1.9 mm.
[0083] A series of specimens are energized to an applied 6 kV 60 Hz
voltage for 30 minutes, followed by an increase in the applied
voltage of 1 kV every 30 minutes up to a maximum 18 kV test
voltage. The breakdown voltage for each specimen is recorded for
evaluation of the characteristic voltage as the scale parameter of
a fitted Weibull failure distribution.
[0084] Example 1 is LDPE containing 2.9 wt % diphenoxybenzene
(molar equivalent to 2 wt % of anthracene), available from Sigma
Aldrich, prepared with a mix temperature of 140.degree. C.
[0085] Example 2 is LDPE containing 2.2 wt % benzanilide (molar
equivalent to 2 wt % of anthracene), available from Sigma Aldrich,
prepared with a mix temperature of 190.degree. C.
[0086] Comparative Sample A is LDPE with no voltage stabilizing
agent mixed at a temperature of 140.degree. C.
[0087] Comparative Sample B is LDPE containing no voltage
stabilizing agent, compounded at 225.degree. C.
[0088] Comparative Sample C is LDPE containing 2 wt % anthracene,
mixed at a temperature of 225.degree. C.
[0089] Comparative Sample A
[0090] A series of 18 specimens of Comparative Sample A are fit to
a 2-parameter Weibull failure distribution. The data exhibits
significant non-linearity leading to poor correlation (r 2 of
0.75). A 3-parameter Weibull failure distribution is found to be
better suited to describe the failure distribution (r 2 of 0.88),
with an offset t0=8.8 kV. A 3-parameter Weibull characteristic
voltage of 11.7 kV is determined for Comparative Sample A, with a
90% confidence interval which spanned 10.7 to 13.7 kV, as shown in
FIG. 2.
[0091] Comparative Sample B
[0092] As a means to demonstrate any impact of performance on mix
temperature, Comparative Sample B includes the evaluation of 11
specimens prepared with elevated mix temperature (225.degree. C.
compared to 140.degree. C. used in Comparative Sample A). As shown
in FIG. 2, the 3-parameter Weibull distribution (r 2=0.77) yields a
characteristic voltage of 10.2 kV (90% confidence interval of 9.6
to 11.4 kV) with an offset of t0=8.5 kV. The characteristic voltage
appears to have been reduced slightly by the elevated mix
temperature, yet the difference is not statistically significant.
However, it does suggest that Comparative Sample A represents a
conservative baseline for the determination of potential
improvements to the characteristic voltage for any materials
compounded at temperatures between 140 and 225.degree. C.
[0093] Comparative Sample C
[0094] Comparative Sample C is LDPE containing 2 wt % anthracene,
which has been prepared using a mix temperature of 225.degree. C.
Eight specimens were evaluated to determine the characteristic
voltage of 16.3 kV (90% confidence interval ranging from 15.3 to
17.2 kV), which is well above the characteristic voltage of
Comparative Examples A and B. This performance is consistent with
expectations, as anthracene is a known voltage stabilizing
agent.
Example 1
[0095] A series of 7 specimens of Example 1 are evaluated, yet four
of the seven specimens survived the entire test program through the
maximum 18 kV applied voltage. (None of the LDPE samples survived
the entire program through 18 kV). When fit to a similar
3-parameter Weibull distribution (the three failures of course
achieve a perfect fit), a characteristic voltage of nearly 47 kV is
estimated. Using a more reasonable 2-parameter model (r 2=0.94),
the characteristic voltage for Example 1 is estimated to be 23.9 kV
(90% confidence interval of 16.4-51.3 kV).
[0096] A comparison of the lower confidence bound of Example 1
(16.4 kV) with the upper confidence bound of Comparative Sample A
(13.7 kV) indicates the voltage stabilizing nature of the present
composition.
Example 2
[0097] Example 2 is LDPE containing 2.2 wt % benzanilide (molar
equivalent to 2 wt % of anthracene), available from Sigma Aldrich,
prepared with a mix temperature of 190.degree. C. Eight specimens
are evaluated, and three survived the maximum voltage step of 18
kV. The 3-parameter Weibull distribution (r 2=0.92) yields a
characteristic voltage of 29 kV and an offset of t0=9.8 kV, with a
90% confidence interval spanning 13.5 to 77 kV.
[0098] The improved characteristic voltage performance of Example 2
relative to Comparative Samples A and B is clear. Although the
conservative comparison of Example 2 with Comparative Sample A does
indicate slight overlap between the 90% confidence intervals, it is
clear that statistically significant separation would exist at just
under a 90% confidence level with the data generated.
[0099] While significant overlap exists between the failure
distributions of Example 2 and Comparative Sample C, it should be
noted that none (0 of 8) of the specimens from Comparative Sample C
survived the entire duration of the needle test through the 18 kV
maximum test voltage. However, three (3 of 8) of Example 2 survived
the test protocol throughout the maximum 18 kV test voltage.
[0100] None of the specimens from Comparative Sample A (0 of 18)
survived the test protocol throughout the maximum 18 kV test
voltage.
[0101] It can be concluded that the inventive composition, Example
2, therefore, provides increased breakdown strength over that of
Comparative Samples A and B.
[0102] It is specifically intended that the present disclosure not
be limited to the embodiments and illustrations contained herein,
but include modified forms of those embodiments including portions
of the embodiments and combinations of elements of different
embodiments as come within the scope of the following claims.
* * * * *