CA2173038C - Tree resistant cable - Google Patents
Tree resistant cableInfo
- Publication number
- CA2173038C CA2173038C CA002173038A CA2173038A CA2173038C CA 2173038 C CA2173038 C CA 2173038C CA 002173038 A CA002173038 A CA 002173038A CA 2173038 A CA2173038 A CA 2173038A CA 2173038 C CA2173038 C CA 2173038C
- Authority
- CA
- Canada
- Prior art keywords
- range
- weight
- polyethylene
- cable
- copolymer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
- H01B7/2813—Protection against damage caused by electrical, chemical or water tree deterioration
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
- H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
- H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes
- H01B3/44—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins
- H01B3/441—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes vinyl resins; acrylic resins from alkenes
Landscapes
- Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Organic Insulating Materials (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Communication Cables (AREA)
- Insulated Conductors (AREA)
- Flexible Shafts (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
A cable comprising one or more electrical conductors, each, or a core of one or more electrical conductors, surrounded by an insulating composition comprising:
(i) a homogeneous polyethylene having a polydispersity in the range of about 1.5 to about 3.5 and an essentially uniform comonomer distribution; and, based on 100 parts by weight of component (i), (ii) about 0.1 to about 20 parts by weight of a polyethylene glycol having a molecular weight in the range of about 1000 to about 30,000.
(i) a homogeneous polyethylene having a polydispersity in the range of about 1.5 to about 3.5 and an essentially uniform comonomer distribution; and, based on 100 parts by weight of component (i), (ii) about 0.1 to about 20 parts by weight of a polyethylene glycol having a molecular weight in the range of about 1000 to about 30,000.
Description
D~17270 21 73038 rr~T~ R~T~TA~r C.~RT,T~
Terhn;cal ~ield This invention relates to electric power cable insuwated with a polyethylene composition having an i~ ved resistance to water trees.
R~r.lr~rolln~l T..f~~ tion A typical electric power cable generally comprises one or more contlllctors in a cable core that is ~w~owlded by several layers of polymeric material that include a first sçmicon~lucting shield layer, an ins~ ;ng layer, a second ~emicon~lllct;ng shield layer, a metallic tape or wire shield, and a jacket.
These insuwated cables are known to suffer from shortened life when installed in an envil~)..m~nt where the inslll~*on is exposed to water, e.g., undel ~ l owld or loc~t;on~ of high hnmitlity. The shortened life has been attributed to the form~t;on of water trees, which occur when an organic polymeric material is subjected to an electrical field over a long period of time in the presence of water in liquwd or vapor form. The net result is a reduction in the dwelectric strength of the insulation.
Many solutions have been proposed for increasing the reRiFt~nce of organic ins~ *ng m~tsri~l~ to degradation by water treeing. The most recent solutions invoive the ~ it;on of polyethylene glycol, as a water tree growth inhihitor, to a heterogeneous low density polyethylene such as described in United States Patents 4,305,849;
4,612,139; and 4,812, 505. Another solution is the use of a homogeneous polyethylene per se as the organic ins~ ;ng material, i.e., without the adwition of a water tree growth inhibit~r. See United States Patent 5,246,783. Both of these solutions appear to be steps in the right direction, but there is a continuous industrial ~3em~n-1 for rove~l~ent partially because power cable is incre~ingly exposed to harsher ell-vi~ çnt~ and partially bec~ e consumers are more concerned with cable longevity, e.g., a service life of 30 to 40 years.
nicclosllre of ~a T~ .l.;on - An object of this v~t;~m~ thelefole, is to provide an insulated cable which exhibits a much i~ roved resistance to water trees. Other objects and advantages will becnme apparent hereinafter.
Acco,.li,lg to the invçntion~ an insulated cable has been discc,veled which meets the above object.
The cable comprises one or more electrical conductors, each, or a core of one or more electrical conductors, ~ loullded by an inslll~tinF co...l,osil ;on comprising (i) a homogeneous polyethylene having a polydispersity in the range of about 1.5 to about 3.5 and an essenti~lly ullifolll- csm()nomer distribution; and, based on 100 parts by weight of component (i), (ii) about 0.1 to about 20 parts by weight of a polyethylene glycol having a molecular weight in the range of about 1000 to about 30,000.
nescr~ti- n of the 1~,,~ mho~l;mant(s) Homogeneous polyethylenes are copolymers of ethylene, one or more alpha-olefins, and, optionally, a diene. The alpha-olefins can have 3 to 12 carbon atoms, and ~lerc.~bly have 3 to 8 carbon atoms.
FYs~ les ofthe alpha-olefins are propylene, l-butene, l-hPYçne, 4-methyl-l-pçnt^ e, and l-octene. Aæ noted above, they have a polydispersity (Mw/Mn) in the range of about 1.5 to about 3.5 and an essant;~lly ul~irwl~l comonom~r distribution. The homogeneous polyethylenes are characterized by single and relatively low DSC
melting points. Heterogeneous polyethylenes (the more common of the two), on the other hand, have a polydispersity (Mw/~In) greater than 3.5 and do not have a u~ l~ comonomer distribution. Mw is defined as weight average molecular weight and Mn is defined as number D-17270 2 ~ 73038 average moleclll~r weight. The homogeneous polyetLylenes can have a density in the range of 0.86 to 0.93 gram per cubic cçntimeter~ and ~.efelably have a density in the range of 0.87 to about 0.92 gram per cubic cçnt;meter. They also can have a melt index in the range of about 0.5 to about 30 grams per 10 minll~E, and l"ef~lably have a melt index in the range of about 0.5 to about 5 grams per 10 minutes.
Homogeneous polyethylenes can be ~ ed, for ~mple, with vanadium based catalysts such as those described in United States Patentæ 5,332,793 and 5,342,907, and they can also be 1,l el,aled with single site metallocene catalysts such as those described in United States Patents 4,937,299 and 5,317,036.
Generally, the polyethylene glycol is defined by its molecular weight, which can be in the range of about 1000 to about 30,000, and is l.lefelably in the range of about 5000 to about 25,000. The ol.l;...~-...
molecular weight is 20,000. Polyethylene glycol i& a polar compound, which can be repres~nterl by the formulas HOCH2(CH2OCH2)nCH2OH or HO(C2H4O)nH wherein, for ç~mple, n can be 225 to 680. This tr~n~l~t~s into a m~lec~ r weight in the range of about 10,000 to about 30,000. The amount of polyethylene glycol that can be in the inslll~ting composition can be in the range of about 0.1 to about 20 parts weight based on 100 parts by weight of the polyethylene component, and is ~,efe,ably in the range of about 0.1 to about 1 part by weight, and can even be as low as about 0.05 part by weight.
Collv~-.t ~ additives, which can be introduced into the polyethylene formlll~*on, are ey~mrlifie~l by ~ntio~ nt~, coupling agents, ultraviolet absorbers or st~hili7çrs, antistatic agents, ri~nent dyes, nnrle~t;ng agents, reinforcing fillers or polymer additives, slip agents, pl~sct;ri7ers~ processinF aids, lubricants, viscosity control agents, tackifiers, anti-blocking agents, surf~ nt~, çYt~nller oils, metal deactivators, voltage st~hili7çrs, flame retardant llers and additives, crosalinking agents, boosters, and catalysts, and smoke su~ ess~ntQ. Fillers and additives can be added in amounts r~n~ing from less than about 0.1 to more than about 200 parts by weight for each 100 parts by weight of the base resinj in this case, polyetLylene.
~ .Y~ .lçs of ~nt;nYili~n~s are: hindered rhçnolQ such as tetrakistmethylene(3,5-di-tert- butyl-4-hyLo~yllyL~o~ n~m~te)]methane, bis[(beta-(3,5-ditert-butyl-4-hyL~o~yl,enzyl)-methylcarbogyethyl)]slllrhi~e, 4,4'-thiobis(2-methyl-6-tert butylrh~nol), 4,4'-thiobis(2-tert-butyl-5-methylrhçnol), 2,2'-thiobis(4-methyl-6-tert-butylph~nol), and thiodiethylene bis(3,5-di-tert-butyl-4-hyL~I~y)hydrocinn~m~te; phosphites and phosphonites such as tns(2?4-di-tert-butylphenyl)phosphite and di-tert-butylphenyl-phosphonite; thio compounds such as dilau~yl~l,o li~l ol ionate, dimyristylthio.l;~,lol,ion~te, and distearylthiodi~lo~ionate; various siloxanes; and various ~min~s such as polymerized 2,2,4-trimethyl-1,2-dihydroqllinoline~ AntioYi~n~ can be used in amounts of about 0.1 to about 5 parts by weight per 100 parts by weight of polyethylene.
The resin can be crosslink~ by a~ ing a cros~linkin~ agent to the comrosition or by m~king the resin hydrolyzable, which is z~ccomrlicherl by ~rlinF hydrolyzable groups such as -Si(OR)3 wherein R is a Ly~Loc~byl radical to the resin structure through copolymeri7~t;r.n or ~ g.
Suitable cros~linking agents are organic peroYides such as dicumyl perogide; 2,5-dimethyl- 2,5-di(t-butylperogy)h~Y~ne; t-butyl cumyl perogide; and 2,5-dimethyl-2,5-di(t-bulyl~ y)h~Y~ne-3.
Dicumyl perogide is ~.~f~ d.
Hydrolyzable groups can be added, for ~YAmple, by copolymeri7in~ ethylene with an ethylenically lm~ . aled co ~oulld having one or more -Si(OR)3 groups such as villyll~ethogy- silane, vinyltriethogysilane, and ~mm~-meth~rylo~y~l o~yl~;~ethogysilane or grafting these silane compounds to the resin in the presence of the D.17270 2173038 a~ Pntioned organic peroxides. The hydrolyzable resins are then crosslinkP-l by moisture in the presence of a silanol a n(lçnc~stion catalyst such as dibulyllill dilaurate, dio~ lyllill maleate, dibulylli ~lisCetst~, stannous ~scet-s-~e, lead nsphtllPnste, and zinc caprylate.
DibulylLill dilaurate is l.le~lled.
F~gmples of hydrolyzable copolymers and hydrolyzable grafted copolymers are ethylenelvinyltrim-p-tllo~y silane copolymer, ethylene/gsmms.- methacrylo~yl,rol.ylllllllethogy silane copolymer, vinyltrimethoxy silane grafted ethylene/ethyl acrylate copolymer, vinyltrimethogy silane grafted linear low density ethylene/1-butene copolymer, and vinyltrimethoxy silane grafted low density polyethylene.
The cable of the invention can be l.lel.aled in vanous types of extruders, e.g., single or twin screw types. Compollntlin~ can be effecte-l in the extruder or prior to extrusion in a coll~/elltional mixer such as a BrabenderTM mixer or a BanburyTM mixer. A description of a convPntionsl extruder can be found in United States patent 4,857,600.
A typical extruder has a hopper at its upstream end and a die at its downstream end. The hopper feeds into a barrel, which contsin~ a screw. At the down~L,a~ end, between the end of the screw and the die, is a screen pack and a breaker plate. The screw portion of the extruder is consi-lared to be divided up into three sections, the feed section, the cc ~lession sect;on, and the metering section, and two zones, the back heat zone and the front heat zone, the sections and zones rllnning from upstream to downstream. In the alternative, there can be multiple hes.1;ng zones (more than two) along the axis r mning from upstream to down~LIe~. If it has more than one barrel, the barrels are connects-l in series. The length to diameter ratio of each barrel i8 in the range of about 15:1 to about 30:1. In wire cost;ng~
where the msteri sl is crosslinke-l after extrusion, the die of the cros~hes-l feeds directly into a hest;n~ zone, and this zone can be mAint~ine~ at a tempe~alula in the range of about 130C to about 260C, and ~lefelably in the range of about 170C to about 220C.
The advantage of the invention lies in the much improved water tree ~l~JWLIl rate. The pAtnnts m~nt;one~l in this specificAt;on are incol~ola~ed by lerel~llce herein. The iLlv~llLion is illustrated by the following çYAmrles.
..wles 1 to 8 The resistance of inslllAt;ng compositions to water treeing is determined by the method described in United States Patént 4,144,202. This measurement leads to a value for water tree resistance relative to a st~n~i~rd polyethylene inslllAt;ng material. The term used for the value is "water tree growth rate" (WTGR). From experience in laboratory tests of materials and for Accelçrated tests of cables, it has been est~hlichetl that the value for WTGR should be equal to or less than about 20 percent, preferably 10 percent, of the standard to provide a useful i~ vement in cable performAnce, i.e., in the life of a cable, which is in service and in contact with water during the period of the service.
Parts are by weight.
100 parts of each of the polyethylenes described below are com~ou,,ded with 0.61 part of polyethylene glycol (PEG) having a m~lleclllAr weight of 20,000 (if the PEG is used); 0.76 part of p-oriented styrçnAte~l rlirhenylAmin~; and 0.4 part of vinyl mo~ified polytlimethyl ~iloYAne in a two roll mill operating at 24 revolutions per minute (rpm) on the front roll and 36 rpm on the back roll and a tempeld~ule of 125 to 130 degrees C on the two rolls for a period of time (minutes). The procedure involves preh~At;nF the resin to 70 degrees C in an oven;
fllllring the resin as quickly as possible on the two roll mill (about 3 to 4 minn~eS); A~llling all of the non-peroxide additives and fluxing for an additional 3 to 4 minlltes; and then A~-ling the peroxide and fluxing, peeling, and folding until well mixed. Sufficient dicumyl peroxide is introduced into each composition to provide an osci~ ng disk rheQmeter (5 degree arc at 360 degrees F) reading of 48 inch-pound.
Each composition is then removed from the two roll mill as a crepe and diced and mol~e~i into one inch discs which are 0.25 inch thick in a press in two steps:
initial step final ~tep pressure (psi) low high tempe~d~e (C) 120 175 residencetime 9 15 to 20 - (minlltes) Each plaque is tested for WTGR and the results comp~red with a control polyethylene composition, which e~hibits 100 percent WTGR.
Variables and results are set forth in the following Table:
~able PEG WTGR
~nlrle polyethylene incorporated?(pelc&~t) *
A No 40.5 2 A Yes 16.4 3 B No 81.0 4 B Yes 6.2 C No 179.2 6 C Yes 12.5 7 D No 68.5 8 D Yes 10.8 $The lower value reflects the im~roved WTGR in the ~y~m~les in which the PEG is incorporated.
2 ~ 73038 A description of the polyethylenes follows (each polyethylene is prepared with a single site metallocene catalyst):
A = a copolymer of ethylene and 1-octene having an Mw/Mn ratio of about 2; a narrow comon~mPr distribution; 9.5 percent by weight l-octene; a melt index of 3.5 gr~mR per 10 minlltçs; and a density of 0.910 gram per cubic cenll;meter.
B = a copolymer of ethylene and l-octene having an Mw/Mn ratio of about 2; a narrow comonom~r distribution; 12 percent by weight 1-octene; a melt index ofl gram per 10 minlltçs; and a density of 0.902 gram per cubic centimeter.
C = a copolymer of ethylene and l-octene having an Mw/Mn ratio of about 2; a narrow comonom~r distribution; 24 percent by weight l-octene; a melt index ofl gram per 10 minutes; and a density of0.870 gram per cubic cçnl';meter.
D = a copolymer of ethylene and l-octene having an Mw/Mn ratio of about 2; a narrow comon~m~r distribution; 24 percent by weight l-octene; a melt index of 5 grams per 10 minlltes; and a density of0.870 gram per cubic centimeter.
Terhn;cal ~ield This invention relates to electric power cable insuwated with a polyethylene composition having an i~ ved resistance to water trees.
R~r.lr~rolln~l T..f~~ tion A typical electric power cable generally comprises one or more contlllctors in a cable core that is ~w~owlded by several layers of polymeric material that include a first sçmicon~lucting shield layer, an ins~ ;ng layer, a second ~emicon~lllct;ng shield layer, a metallic tape or wire shield, and a jacket.
These insuwated cables are known to suffer from shortened life when installed in an envil~)..m~nt where the inslll~*on is exposed to water, e.g., undel ~ l owld or loc~t;on~ of high hnmitlity. The shortened life has been attributed to the form~t;on of water trees, which occur when an organic polymeric material is subjected to an electrical field over a long period of time in the presence of water in liquwd or vapor form. The net result is a reduction in the dwelectric strength of the insulation.
Many solutions have been proposed for increasing the reRiFt~nce of organic ins~ *ng m~tsri~l~ to degradation by water treeing. The most recent solutions invoive the ~ it;on of polyethylene glycol, as a water tree growth inhihitor, to a heterogeneous low density polyethylene such as described in United States Patents 4,305,849;
4,612,139; and 4,812, 505. Another solution is the use of a homogeneous polyethylene per se as the organic ins~ ;ng material, i.e., without the adwition of a water tree growth inhibit~r. See United States Patent 5,246,783. Both of these solutions appear to be steps in the right direction, but there is a continuous industrial ~3em~n-1 for rove~l~ent partially because power cable is incre~ingly exposed to harsher ell-vi~ çnt~ and partially bec~ e consumers are more concerned with cable longevity, e.g., a service life of 30 to 40 years.
nicclosllre of ~a T~ .l.;on - An object of this v~t;~m~ thelefole, is to provide an insulated cable which exhibits a much i~ roved resistance to water trees. Other objects and advantages will becnme apparent hereinafter.
Acco,.li,lg to the invçntion~ an insulated cable has been discc,veled which meets the above object.
The cable comprises one or more electrical conductors, each, or a core of one or more electrical conductors, ~ loullded by an inslll~tinF co...l,osil ;on comprising (i) a homogeneous polyethylene having a polydispersity in the range of about 1.5 to about 3.5 and an essenti~lly ullifolll- csm()nomer distribution; and, based on 100 parts by weight of component (i), (ii) about 0.1 to about 20 parts by weight of a polyethylene glycol having a molecular weight in the range of about 1000 to about 30,000.
nescr~ti- n of the 1~,,~ mho~l;mant(s) Homogeneous polyethylenes are copolymers of ethylene, one or more alpha-olefins, and, optionally, a diene. The alpha-olefins can have 3 to 12 carbon atoms, and ~lerc.~bly have 3 to 8 carbon atoms.
FYs~ les ofthe alpha-olefins are propylene, l-butene, l-hPYçne, 4-methyl-l-pçnt^ e, and l-octene. Aæ noted above, they have a polydispersity (Mw/Mn) in the range of about 1.5 to about 3.5 and an essant;~lly ul~irwl~l comonom~r distribution. The homogeneous polyethylenes are characterized by single and relatively low DSC
melting points. Heterogeneous polyethylenes (the more common of the two), on the other hand, have a polydispersity (Mw/~In) greater than 3.5 and do not have a u~ l~ comonomer distribution. Mw is defined as weight average molecular weight and Mn is defined as number D-17270 2 ~ 73038 average moleclll~r weight. The homogeneous polyetLylenes can have a density in the range of 0.86 to 0.93 gram per cubic cçntimeter~ and ~.efelably have a density in the range of 0.87 to about 0.92 gram per cubic cçnt;meter. They also can have a melt index in the range of about 0.5 to about 30 grams per 10 minll~E, and l"ef~lably have a melt index in the range of about 0.5 to about 5 grams per 10 minutes.
Homogeneous polyethylenes can be ~ ed, for ~mple, with vanadium based catalysts such as those described in United States Patentæ 5,332,793 and 5,342,907, and they can also be 1,l el,aled with single site metallocene catalysts such as those described in United States Patents 4,937,299 and 5,317,036.
Generally, the polyethylene glycol is defined by its molecular weight, which can be in the range of about 1000 to about 30,000, and is l.lefelably in the range of about 5000 to about 25,000. The ol.l;...~-...
molecular weight is 20,000. Polyethylene glycol i& a polar compound, which can be repres~nterl by the formulas HOCH2(CH2OCH2)nCH2OH or HO(C2H4O)nH wherein, for ç~mple, n can be 225 to 680. This tr~n~l~t~s into a m~lec~ r weight in the range of about 10,000 to about 30,000. The amount of polyethylene glycol that can be in the inslll~ting composition can be in the range of about 0.1 to about 20 parts weight based on 100 parts by weight of the polyethylene component, and is ~,efe,ably in the range of about 0.1 to about 1 part by weight, and can even be as low as about 0.05 part by weight.
Collv~-.t ~ additives, which can be introduced into the polyethylene formlll~*on, are ey~mrlifie~l by ~ntio~ nt~, coupling agents, ultraviolet absorbers or st~hili7çrs, antistatic agents, ri~nent dyes, nnrle~t;ng agents, reinforcing fillers or polymer additives, slip agents, pl~sct;ri7ers~ processinF aids, lubricants, viscosity control agents, tackifiers, anti-blocking agents, surf~ nt~, çYt~nller oils, metal deactivators, voltage st~hili7çrs, flame retardant llers and additives, crosalinking agents, boosters, and catalysts, and smoke su~ ess~ntQ. Fillers and additives can be added in amounts r~n~ing from less than about 0.1 to more than about 200 parts by weight for each 100 parts by weight of the base resinj in this case, polyetLylene.
~ .Y~ .lçs of ~nt;nYili~n~s are: hindered rhçnolQ such as tetrakistmethylene(3,5-di-tert- butyl-4-hyLo~yllyL~o~ n~m~te)]methane, bis[(beta-(3,5-ditert-butyl-4-hyL~o~yl,enzyl)-methylcarbogyethyl)]slllrhi~e, 4,4'-thiobis(2-methyl-6-tert butylrh~nol), 4,4'-thiobis(2-tert-butyl-5-methylrhçnol), 2,2'-thiobis(4-methyl-6-tert-butylph~nol), and thiodiethylene bis(3,5-di-tert-butyl-4-hyL~I~y)hydrocinn~m~te; phosphites and phosphonites such as tns(2?4-di-tert-butylphenyl)phosphite and di-tert-butylphenyl-phosphonite; thio compounds such as dilau~yl~l,o li~l ol ionate, dimyristylthio.l;~,lol,ion~te, and distearylthiodi~lo~ionate; various siloxanes; and various ~min~s such as polymerized 2,2,4-trimethyl-1,2-dihydroqllinoline~ AntioYi~n~ can be used in amounts of about 0.1 to about 5 parts by weight per 100 parts by weight of polyethylene.
The resin can be crosslink~ by a~ ing a cros~linkin~ agent to the comrosition or by m~king the resin hydrolyzable, which is z~ccomrlicherl by ~rlinF hydrolyzable groups such as -Si(OR)3 wherein R is a Ly~Loc~byl radical to the resin structure through copolymeri7~t;r.n or ~ g.
Suitable cros~linking agents are organic peroYides such as dicumyl perogide; 2,5-dimethyl- 2,5-di(t-butylperogy)h~Y~ne; t-butyl cumyl perogide; and 2,5-dimethyl-2,5-di(t-bulyl~ y)h~Y~ne-3.
Dicumyl perogide is ~.~f~ d.
Hydrolyzable groups can be added, for ~YAmple, by copolymeri7in~ ethylene with an ethylenically lm~ . aled co ~oulld having one or more -Si(OR)3 groups such as villyll~ethogy- silane, vinyltriethogysilane, and ~mm~-meth~rylo~y~l o~yl~;~ethogysilane or grafting these silane compounds to the resin in the presence of the D.17270 2173038 a~ Pntioned organic peroxides. The hydrolyzable resins are then crosslinkP-l by moisture in the presence of a silanol a n(lçnc~stion catalyst such as dibulyllill dilaurate, dio~ lyllill maleate, dibulylli ~lisCetst~, stannous ~scet-s-~e, lead nsphtllPnste, and zinc caprylate.
DibulylLill dilaurate is l.le~lled.
F~gmples of hydrolyzable copolymers and hydrolyzable grafted copolymers are ethylenelvinyltrim-p-tllo~y silane copolymer, ethylene/gsmms.- methacrylo~yl,rol.ylllllllethogy silane copolymer, vinyltrimethoxy silane grafted ethylene/ethyl acrylate copolymer, vinyltrimethogy silane grafted linear low density ethylene/1-butene copolymer, and vinyltrimethoxy silane grafted low density polyethylene.
The cable of the invention can be l.lel.aled in vanous types of extruders, e.g., single or twin screw types. Compollntlin~ can be effecte-l in the extruder or prior to extrusion in a coll~/elltional mixer such as a BrabenderTM mixer or a BanburyTM mixer. A description of a convPntionsl extruder can be found in United States patent 4,857,600.
A typical extruder has a hopper at its upstream end and a die at its downstream end. The hopper feeds into a barrel, which contsin~ a screw. At the down~L,a~ end, between the end of the screw and the die, is a screen pack and a breaker plate. The screw portion of the extruder is consi-lared to be divided up into three sections, the feed section, the cc ~lession sect;on, and the metering section, and two zones, the back heat zone and the front heat zone, the sections and zones rllnning from upstream to downstream. In the alternative, there can be multiple hes.1;ng zones (more than two) along the axis r mning from upstream to down~LIe~. If it has more than one barrel, the barrels are connects-l in series. The length to diameter ratio of each barrel i8 in the range of about 15:1 to about 30:1. In wire cost;ng~
where the msteri sl is crosslinke-l after extrusion, the die of the cros~hes-l feeds directly into a hest;n~ zone, and this zone can be mAint~ine~ at a tempe~alula in the range of about 130C to about 260C, and ~lefelably in the range of about 170C to about 220C.
The advantage of the invention lies in the much improved water tree ~l~JWLIl rate. The pAtnnts m~nt;one~l in this specificAt;on are incol~ola~ed by lerel~llce herein. The iLlv~llLion is illustrated by the following çYAmrles.
..wles 1 to 8 The resistance of inslllAt;ng compositions to water treeing is determined by the method described in United States Patént 4,144,202. This measurement leads to a value for water tree resistance relative to a st~n~i~rd polyethylene inslllAt;ng material. The term used for the value is "water tree growth rate" (WTGR). From experience in laboratory tests of materials and for Accelçrated tests of cables, it has been est~hlichetl that the value for WTGR should be equal to or less than about 20 percent, preferably 10 percent, of the standard to provide a useful i~ vement in cable performAnce, i.e., in the life of a cable, which is in service and in contact with water during the period of the service.
Parts are by weight.
100 parts of each of the polyethylenes described below are com~ou,,ded with 0.61 part of polyethylene glycol (PEG) having a m~lleclllAr weight of 20,000 (if the PEG is used); 0.76 part of p-oriented styrçnAte~l rlirhenylAmin~; and 0.4 part of vinyl mo~ified polytlimethyl ~iloYAne in a two roll mill operating at 24 revolutions per minute (rpm) on the front roll and 36 rpm on the back roll and a tempeld~ule of 125 to 130 degrees C on the two rolls for a period of time (minutes). The procedure involves preh~At;nF the resin to 70 degrees C in an oven;
fllllring the resin as quickly as possible on the two roll mill (about 3 to 4 minn~eS); A~llling all of the non-peroxide additives and fluxing for an additional 3 to 4 minlltes; and then A~-ling the peroxide and fluxing, peeling, and folding until well mixed. Sufficient dicumyl peroxide is introduced into each composition to provide an osci~ ng disk rheQmeter (5 degree arc at 360 degrees F) reading of 48 inch-pound.
Each composition is then removed from the two roll mill as a crepe and diced and mol~e~i into one inch discs which are 0.25 inch thick in a press in two steps:
initial step final ~tep pressure (psi) low high tempe~d~e (C) 120 175 residencetime 9 15 to 20 - (minlltes) Each plaque is tested for WTGR and the results comp~red with a control polyethylene composition, which e~hibits 100 percent WTGR.
Variables and results are set forth in the following Table:
~able PEG WTGR
~nlrle polyethylene incorporated?(pelc&~t) *
A No 40.5 2 A Yes 16.4 3 B No 81.0 4 B Yes 6.2 C No 179.2 6 C Yes 12.5 7 D No 68.5 8 D Yes 10.8 $The lower value reflects the im~roved WTGR in the ~y~m~les in which the PEG is incorporated.
2 ~ 73038 A description of the polyethylenes follows (each polyethylene is prepared with a single site metallocene catalyst):
A = a copolymer of ethylene and 1-octene having an Mw/Mn ratio of about 2; a narrow comon~mPr distribution; 9.5 percent by weight l-octene; a melt index of 3.5 gr~mR per 10 minlltçs; and a density of 0.910 gram per cubic cenll;meter.
B = a copolymer of ethylene and l-octene having an Mw/Mn ratio of about 2; a narrow comonom~r distribution; 12 percent by weight 1-octene; a melt index ofl gram per 10 minlltçs; and a density of 0.902 gram per cubic centimeter.
C = a copolymer of ethylene and l-octene having an Mw/Mn ratio of about 2; a narrow comonom~r distribution; 24 percent by weight l-octene; a melt index ofl gram per 10 minutes; and a density of0.870 gram per cubic cçnl';meter.
D = a copolymer of ethylene and l-octene having an Mw/Mn ratio of about 2; a narrow comon~m~r distribution; 24 percent by weight l-octene; a melt index of 5 grams per 10 minlltes; and a density of0.870 gram per cubic centimeter.
Claims (8)
1. A cable comprising one or more electrical conductors, each, or a core of electrical conductors, surrounded by an insulating composition comprising (i) a homogeneous polyethylene having a polydispersity in the range of about 1.5 to about 3.5 and an essentially uniform comonomer distribution; and, based on 100 parts by weight of component (i),(ii) about 0.1 to about 20 parts by weight of a polyethylene glycol having a molecular weight in the range of about 1000 to about 30,000.
2. The cable defined in claim 1 wherein the polyethylene is a copolymer of ethylene, one or more alpha-olefins, each having 3 to 12 carbon atoms, and, optionally, a diene.
3. The cable defined in claim 1 wherein the polyethylene is made with a single site metallocene based catalyst.
4. The cable defined in claim 1 wherein the polyethylene has a density in the range of 0.86 to 0.93 gram per cubic centimeter and a melt index in the range of about 0.5 to about 30 grams per 10 minutes.
5. The cable defined in claim 1 wherein the alpha-olefin is 1-butene, 1-hexene, 4-methyl-1-pentene, or 1-octene.
6. The cable defined in claim 1 wherein the polyethylene glycol has a molecular weight in the range of about 5000 to about 25,000.
7. The cable defined in claim 1 wherein the polyethylene glycol is present in an amount of about 0.1 to about 1 part by weight.
8. A cable comprising one or more electrical conductors, each, or a core of one or more electrical conductors, surrounded by an insulating composition comprising:
(i) a homogeneous copolymer of a mixture comprising ethylene and one or more alpha-olefins, each having 3 to 8 carbon atoms, said copolymer having a polydispersity in the range of about 1.5 to about 3.5; an essentially uniform comonomer distribution; a density in the range of 0.87 to 0.92 gram per cubic centimeter; and a melt index in the range of about 0.5 to about 5 grams per 10 minutes, said copolymer having been prepared with a single site metallocene based catalyst; and, based on 100 parts by weight of component (i), (ii) about 0.1 to about 1 part by weight of a polyethylene glycol having a molecular weight in the range of about 5000 to about 25,000.
(i) a homogeneous copolymer of a mixture comprising ethylene and one or more alpha-olefins, each having 3 to 8 carbon atoms, said copolymer having a polydispersity in the range of about 1.5 to about 3.5; an essentially uniform comonomer distribution; a density in the range of 0.87 to 0.92 gram per cubic centimeter; and a melt index in the range of about 0.5 to about 5 grams per 10 minutes, said copolymer having been prepared with a single site metallocene based catalyst; and, based on 100 parts by weight of component (i), (ii) about 0.1 to about 1 part by weight of a polyethylene glycol having a molecular weight in the range of about 5000 to about 25,000.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41323695A | 1995-03-30 | 1995-03-30 | |
| US08/413,236 | 1995-03-30 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2173038A1 CA2173038A1 (en) | 1996-10-01 |
| CA2173038C true CA2173038C (en) | 1999-08-10 |
Family
ID=23636415
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002173038A Expired - Lifetime CA2173038C (en) | 1995-03-30 | 1996-03-29 | Tree resistant cable |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0735545B1 (en) |
| KR (1) | KR100271686B1 (en) |
| AT (1) | ATE181453T1 (en) |
| AU (1) | AU708233B2 (en) |
| BR (1) | BR9601205A (en) |
| CA (1) | CA2173038C (en) |
| DE (1) | DE69602872T2 (en) |
| DK (1) | DK0735545T3 (en) |
| ES (1) | ES2135169T3 (en) |
| GR (1) | GR3030891T3 (en) |
| TW (1) | TW403916B (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5731082A (en) * | 1996-06-24 | 1998-03-24 | Union Carbide Chemicals & Plastics Technology Corporation | Tree resistant cable |
| JPH10168298A (en) | 1996-12-10 | 1998-06-23 | Elf Atochem Japan Kk | Thermoplastic resin composition and molded product |
| US5919565A (en) * | 1997-03-20 | 1999-07-06 | Union Carbide Chemicals & Plastics Technology Corporation | Tree resistant cable |
| ATE303650T1 (en) * | 1997-06-20 | 2005-09-15 | Union Carbide Chem Plastic | CABLE RESISTANT TO DENDRITE FORMATION |
| US5962362A (en) | 1997-12-09 | 1999-10-05 | Union Carbide Chemicals & Plastics Technology Corporation | Unbridged monocyclopentadienyl metal complex catalyst and a process for polyolefin production |
| US6159889A (en) * | 1997-12-09 | 2000-12-12 | Union Carbide Chemicals & Plastics Technology Corporation | Unbridged monocyclopentadienyl metal complex catalyst and a process for polyolefin production |
| US6127302A (en) * | 1997-12-09 | 2000-10-03 | Union Carbide Chemicals & Plastics Technology Corporation | Unbridged monocyclopentadienyl metal complex catalyst and a process for polyolefin production |
| US6203907B1 (en) | 1998-04-20 | 2001-03-20 | Union Carbide Chemicals & Plastics Technology Corporation | Tree resistant cable |
| TWI224607B (en) * | 1998-06-16 | 2004-12-01 | Union Carbide Chem Plastic | Tree resistant cable |
| EP0989139A1 (en) * | 1998-09-25 | 2000-03-29 | Union Carbide Chemicals & Plastics Technology Corporation | Unbridged monocyclopentadienyl metal complex catalyst for olefin polymerization by reacting with particulate solids with functional groups |
| CA2351428C (en) * | 1998-11-20 | 2009-11-17 | Union Carbide Chemicals & Plastics Technology Corporation | A process for controlling water trees |
| SE516260C2 (en) * | 1999-07-01 | 2001-12-10 | Borealis Polymers Oy | Insulating composition for an electric power cable |
| US6191230B1 (en) * | 1999-07-22 | 2001-02-20 | Union Carbide Chemicals & Plastics Technology Corporation | Polyethylene crosslinkable composition |
| EP1564261B1 (en) | 2004-02-09 | 2016-05-25 | Merck Patent GmbH | Interference pigments |
| JP6437448B2 (en) | 2012-12-21 | 2018-12-12 | ダウ グローバル テクノロジーズ エルエルシー | Compound of polyolefin cable compounds for improved foamability and improved processability |
| WO2019178747A1 (en) | 2018-03-20 | 2019-09-26 | Dow Global Technologies Llc | Polyolefin-and-polyvinylpyrrolidone formulation |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5628231A (en) * | 1979-08-16 | 1981-03-19 | Nippon Yunikaa Kk | Polyolefin composition for electrical insulation |
| JPS57126004A (en) * | 1981-01-30 | 1982-08-05 | Nippon Unicar Co Ltd | Semiconductive polyolefin composition and cable using same |
| CA1181940A (en) * | 1982-03-31 | 1985-02-05 | Robert J. Turbett | Compositions of hydrocarbon-substituted diphenyl amines and high molecular weight polyethylene glycols; and the use thereof as water-tree retardants for polymers |
| US4812505A (en) * | 1987-05-18 | 1989-03-14 | Union Carbide Corporation | Tree resistant compositions |
| JPS63310517A (en) * | 1987-06-11 | 1988-12-19 | Sanyo Electric Co Ltd | Manufacture of superconductor wire material |
| US5246783A (en) * | 1991-08-15 | 1993-09-21 | Exxon Chemical Patents Inc. | Electrical devices comprising polymeric insulating or semiconducting members |
-
1996
- 1996-03-07 TW TW085102785A patent/TW403916B/en not_active IP Right Cessation
- 1996-03-15 ES ES96301806T patent/ES2135169T3/en not_active Expired - Lifetime
- 1996-03-15 EP EP96301806A patent/EP0735545B1/en not_active Expired - Lifetime
- 1996-03-15 AT AT96301806T patent/ATE181453T1/en not_active IP Right Cessation
- 1996-03-15 DE DE69602872T patent/DE69602872T2/en not_active Expired - Lifetime
- 1996-03-15 DK DK96301806T patent/DK0735545T3/en active
- 1996-03-26 KR KR1019960008291A patent/KR100271686B1/en not_active IP Right Cessation
- 1996-03-29 CA CA002173038A patent/CA2173038C/en not_active Expired - Lifetime
- 1996-03-29 BR BR9601205A patent/BR9601205A/en not_active IP Right Cessation
- 1996-03-29 AU AU50382/96A patent/AU708233B2/en not_active Ceased
-
1999
- 1999-07-30 GR GR990401972T patent/GR3030891T3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE69602872D1 (en) | 1999-07-22 |
| EP0735545B1 (en) | 1999-06-16 |
| DK0735545T3 (en) | 1999-11-22 |
| KR100271686B1 (en) | 2000-11-15 |
| CA2173038A1 (en) | 1996-10-01 |
| EP0735545A2 (en) | 1996-10-02 |
| AU5038296A (en) | 1996-10-10 |
| ATE181453T1 (en) | 1999-07-15 |
| GR3030891T3 (en) | 1999-11-30 |
| TW403916B (en) | 2000-09-01 |
| AU708233B2 (en) | 1999-07-29 |
| ES2135169T3 (en) | 1999-10-16 |
| EP0735545A3 (en) | 1997-04-16 |
| KR960035666A (en) | 1996-10-24 |
| DE69602872T2 (en) | 1999-10-21 |
| BR9601205A (en) | 1998-01-06 |
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