CA2105896A1 - Isolation compositions in humidity reticulated polyethylene (xlpe) with contraction reduced at 130°c for use in low tension power cables - Google Patents
Isolation compositions in humidity reticulated polyethylene (xlpe) with contraction reduced at 130°c for use in low tension power cablesInfo
- Publication number
- CA2105896A1 CA2105896A1 CA 2105896 CA2105896A CA2105896A1 CA 2105896 A1 CA2105896 A1 CA 2105896A1 CA 2105896 CA2105896 CA 2105896 CA 2105896 A CA2105896 A CA 2105896A CA 2105896 A1 CA2105896 A1 CA 2105896A1
- Authority
- CA
- Canada
- Prior art keywords
- polyethylene
- compositions
- ethylene
- fact
- polypropylene
- 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.)
- Abandoned
Links
Classifications
-
- 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
Abstract
ABSTRACT
The current invention consists in the modification of the polyethylene that are usually employed for the application of the "Sloplas" reticulation process with polypropylene (PP). The polypropylene presents a softening point between 155 up to 165°C, which guarantees, up to 130°C, the dimensional stability of the extruded material. The mixture of the PP with low density poly-ethylene (LDPE) or low density linear polyethylene (LLDPE) or co-polymeric polyethylene of ethylene vinyl acetate (EVA) in an adequate concentration is the solution for the contraction prob-lem. The selection of the type of polypropylene and of the blendization process that are adequate is the solution for the formation of a polymeric fusion. The co-polymeric polypropylenes of ethylene, with a level of ethylene beginning at 6%, are usually adequate to promote the blendization.
The current invention consists in the modification of the polyethylene that are usually employed for the application of the "Sloplas" reticulation process with polypropylene (PP). The polypropylene presents a softening point between 155 up to 165°C, which guarantees, up to 130°C, the dimensional stability of the extruded material. The mixture of the PP with low density poly-ethylene (LDPE) or low density linear polyethylene (LLDPE) or co-polymeric polyethylene of ethylene vinyl acetate (EVA) in an adequate concentration is the solution for the contraction prob-lem. The selection of the type of polypropylene and of the blendization process that are adequate is the solution for the formation of a polymeric fusion. The co-polymeric polypropylenes of ethylene, with a level of ethylene beginning at 6%, are usually adequate to promote the blendization.
Description
2 1 ~ 3 ~ 9 ~
ISGLATION COMPOSITIONS IN HUMIDITY RETICULATED POLYETHYLENE (XLPE) WITH COMTRACTION REDUCED ~T 130C, FOR USE IN LOW TENSION POWER CABLES
The current inventlon refers to an electrlc cable, lsolated wlth composltlons o~ low denslty polyethylene, whlch are humldlty retlculate. More preclsely, lt refers to the appllcatlon of composltlons wlth a low denslty polyethylene base, and whlch are humldlty retlculate for lsolatlng and coverlng cables. The process ls known as "SIOPLAS". The commercial processes for obtalnlng the retlculate polyethylene ln the lndustry of cables are baslcally the followlng. The oldest one consists ln applylng addltlves to the polyethylene wlth organlc peroxldes, wlth an actlvatlng temperature above the temperature for softenlng the polyethylene used. These composltes are applled ln the case of cables manufactured through an extruslon process followed by a thermo-chemlcal retlculatlon process slmultaneously wlth the instant heatlng of the lsolated cable above the peroxlde actlva-tlng temperature, for lnstance, through saturated vapor heatlng or through radlant heat produced by electrlc reslstances, followed by ~0 a process correspondlng to water coollng. In both cases, the process ls done under pressure, slnce the decomposltlon gases generated by the chemlcal reactlons cause the exlstence of bubbles ln the extruded lsolatlon. Thls process ls stlll wldely used for the productlon of medlum/hlgh tenslon cables, because lt ls the only way to obtaln large extruded and retlculated lsolatlon sectlons wlthout empty spots. Thls process requlres hlgh cost lndustrlal lnstallatlons.
., , . . . , . , . . . ., . , . ~ ~, . .......... . . . . .. .
. ~ . . .. - .. ..
Another process for obtalnlng retlculate polyethylene isolatlon ls the radlatlon by means of electron beams or sources o gamma radlatlon. Through thls process, the cable ls lsolated by means of a normal extruslon process that may be applled to thermoplastlc polyethylene, followed by a retlculatlon process, and ln a subsequent phase, by means of hlgh energy electron beam radlatlon or gamma radlatlon sources. In thls case the process ls malnly used for cables wlth a small extruded section, since the penetratlon capaclty of the electrons ls llmlted. Both processes, the electronlc radlatlon and gamma sources, require hlgh cost lnstallatlons, malnly because of special protectlon needed for the operator and for the envlronment. The productlon speed of cables ls llmlted by the amount of energy that these sources can llberate and by the amount of material (lsolatlon) to be retlculated.
These processes are ùsually lndlcated and applled to speclal cables.
Another process ls the chemlcal retlculatlon done by means of humldlty. In thls process, an organo-sllane that can be hydrolysed ls lntroduced to the polyethylene molecule whlch stlll malntalns lts thermoplastlc characterlstlcs, belng applled on the cable by means of a usual extruslon that can be applled to the thermoplastlc polyethylene, where the extruslon speed ls only llmlted by the extruslon and the materlal characterlstlcs. The polyethylene retlculatlon ln the cable occurs ln the reel, depend-lng on the materlal ln the envlronmental temperature and humldlty condltlons or by exposlng the reel to a "sauna" type envlronment.
~;3~9g Thls ls a low cost process for the productlon of low tenslon cables, slnce lt only requlres usual process equlpment for thez-moplastlc materlals. And, above all, lt ls advantageous for the lsolatlon of conductors whlch have a non-round sectlon, as, for lnstance, sector conductors (shape of a shell), whlch are pre-vio~lsly twlsted. Thls process ls not advantageous for the produc-tlon of medlum/hlgh tenslon cables, slnce the dlffuslon of humldl-ty through large extruded sectlons ls slow and the humldlty ls one of the factors for the formatlon of arborescence ln polyethylene that are under electrlc "stress" of hlgh gradlent.
Thls last process for obtalnlng retlculated polyethylene as described above ls, nowadays, wldely used by the manufacturers of cables, malnly as lsolatlon of power cables for low tenslon.
The process i8 widely mastered by the manufacturers of cables, with at least t~o ways of obtalning the composlte for extruslon.
a) Composltes wlth organo-sllane that ls prevlousl~
lnserted lnto the polyethylene are commercially avallable or can be prepared locally by the manufacturer of cables. Here, two families of composites are identified~
a.l) Polyethylene wlth lnserted organo-silane applled to commerclal polyethylene (thls process may be done by any thermoplastlc processor that has adequate equlpment);
a.2) Polyethylene wlth organo-sllane that is co-polymerized during the ethylene polymerlzation process (obvlously, this process is only known to the :. . . . :
, . : :-210`~896 petrochemlcal lndustry whlch ls lnvolved ln the productlon of polyethylene).
b) Composltes wlth the organo-silane lnserted durlng the cable extruslon process. Usually, thls process ls known by the cable manufacturers. The varlatlons for this process are b.l) Humectatlon of the granules wlth organo-sllane and peroxlde lmmedlately before the extruslon;
b.2) Dosage and dlrect in~ection of the organo-sllane and peroxlde in the extrudlng material (Monosil Process);
b.3) Dosage and direct in~ectlon of the organo-silane and peroxide through "CTN" (Cavity Transfer Mlxer), connected to the head of the extruding material, known as Sllanox Process The reticulation process of the polyethylene through humldlty, as descrlbed above, has been widely accepted for the manufacture of power cables for low tension in relatlon to the other processes, due, malnly, to the cost savlng aspect of the process, that ls, the larger productlvlty, less consumptlon of energy, less lnvestment. On the other hand, the humidlty reticu-lation process presents technical advantages for the applicatlon process. The most lmportant ones are the posslbllity of extrusion for any conductor proflle and the possibillty of embossing during the extruslon.
The extruslon processes commonly used for isolating conductors differ according to the type of tools used for the formatlon of isolatlon ln the conductor. The keywords used to .... ,, . . ~ . . ~ . -- - - , - - - - -.. : . . . ~ . . .. . .
2 ~ 9 ~
dlffer the processes are "Extruslon under Pressure", "Extruslon under Seml-tubes" and "Extruslon under tubes". For the "Extrusion under Pressure", the tools used have, approxlmatelyl the flnal isolatlon dlmenslons ~the polyethylene ls placed over the conduc-tor wlthout stretching); for the "Extruslon under Seml-tubes", the tools are sllghtly blgger than the dlmenslons of lsolatlon and they are generally used when the composlte tends to flow backwards by the male; and for the "Extruslon under tubes", the male and female are, generally, much blgger than the isolatlon dlmenslon of ~he conductor, and they are used when the proflle of the conductor ls not round, which makes lt lmposslble to use tlght tools or ln the case of composites applled on very thln materlals (typlcal example, FEP "Teflon"). In thls case, the flnal shape of the lsolation ls obtalned by stretchlng the tube up to the flnal dl-mension.
A problem that ls always present in the extruslon of thermoplastlc materlals are the resldual tenslons left by the conformatlon process, slnce the thermoplastlc materlals are poly-merlc ~macro-molecules) whlch, ln the extrusion process, are Z0 squeezed and stretched. Usually, the polymerlc materlals requlre a relatlvely long tlme for relaxlng the tenslons stored durlng the passage through the tools. SInce the lsolatlon ls rapldly cooled, to obtaln productlvlty and to avold deformltles ln the reel, a large part of the tenslons ls stored.
The power cables for low tenslon are covered by lnter-national speclflcatlons, such as IEC 502183), NBR ABNT Pro~ect 3.20.3-026~90). Under the servlce condltlons, these cables are : ., :, :, . ~ .. . .. .
2~5896 classlfied for contlnuous servlce at a 90C temperature (ln the conductor), and at an overload process, durlng a short perlod of tlme, up to 130C, and under a short-clrcuit condltion up to 250C.
The retlculated polyethylene obtalned by the "Sloplas"
process, when heated above lts softenlng temperature (95 to 115C), tends to relax the tenslons left by the extruslon process, creatlng a contractlon, especlally ln the ends of the cable expos-lng the conductor. --To prevent accldents created by the contractlon agalnst the installatlons, the rules descrlbed above lnclude a quallflca-tlon test. Such a test conslsts in cuttlrlg 200mm from the central part of a sample that has at least 1200mm of the lsolated cable, then exposlng thls sample to heat ~or 1 hour at 130C ln an alr stove, and measuring the lsolation contractlon at both ends The value found mu~t not exceed 4~.
In practice, what was notlced was that for the poly-ethylene that were retlculated through the "Tu~e Extruded Sloplas", the contractlon can reach 20% causlng serlous lncon-veniences for the use of the cable.
~; The current lnventlon has the purpose of solvlng the current technlcal problems, through the modlflcatlon of the polyethylene that are usually employed ln the "Sloplas" process, wlth the addltlon of polypropylene (PP). The polypropylene has a softenlng temperature between 155 up to 165C, whlch guarantees, up to 130C, the dlmenslonal stablllty of the extruded materlal.
::
2~ ~S~96 ~7487-458 The mlxture of the PP with the low density polyethylene (LDI?E) or linear low denslty polyethylene (LLDPE) or co-polymeric pol~yethylene of vlnyl ethylene acetate (EVA) ln an adequate con-centratlon ls the solutlon for the contractlon problem.
The low denslty polyethylene (LDPE) ls a homopolymerlc or co-polymerlc vlnyl acetate (VA) or methylacrylate (MA) up to 10%. The llnear low denslty polyethylene (LLDPE) ls a butene or hexene co-polymerlc. The polypropylene ls a propylene-ethylene co-polymerlc wlth a co-monomerous level (ethylene) over 6%, belng used ln a preferred proportlon between 15 and 25%.
Below ls the descrlptlon of experlmental results obtaln- -ed wlth composltlons of the known technlque and of the current inventlon.
Exàmples 1, 2, 3 (wlth contractlon):
Usual compo~ltlon~ wlth polyethylene ba~e whlch can be retlculated through the "Sloplas" proces~.
Ingredient Example 1 Example 2 Example 3 LDPE (MFI 1,3) 100 LDPE (Co-polymerlc 9% Vlnyl Acetate) MFI 4 - - 100 LLDPE (MFI 4) - 100 Antl-oxldatlng 0.2 0.2 0.2 VIMO 1.5 1.5 1.5 Cumlla Peroxlde (96-100%~ 0.12 0.12 0.12 DBTL 0.05 0.05 0.05 NOTESs VIMO (Vlnyl Trlmethoxy Sllane), Organo Sllane wlth three methoxy radlcal~ to one vlnyl radlcal - DBTL (Dl-Butyl Tln .-. . . :.. :- : .:
~, . . . .
21 05~ 9 ~
Laurate) Organlc salt of tin used as a catalyzer for hydrolysis.
- These compositions can be easily reproduced in a laboratory uslng the technlque of humectation for the granulated polyethylene wlth the silane, peroxlde and DBTL. The above compositions were extruded with tube extrusion tools over a flat proflle conductor with a rate of section reduction of 2 (DDR - draw down ratio).
To enable the reaction of the lnsertlon of the silane to occur, a fuslon temperature (Melt) of 220C was used. After treatlng them ln waterbath at 70C for 16 hours, ln a contractlon controlled way, they became faded and a fracture in the flection occurred.
Pesults obtained Property Example 1: Example 2: Example 3 Contraction 13% 5.5% 19%
Fading none none none Fracture none none none Examples 4 and 5 (with fracture): Polyethylene compositions modlfied with homo-polymeric polypropylene.
Ingredient Example 4, Example 5:
LDPE (MFI 1,33 80 LLDPE (MFI 1,0) - 80 Homopolymeric PP tMFI 4,0 -KMT 6100 from Polibrasil) 20 20 Antloxldatlng 0.2 0.2 VTMO 1.5 1.5 Cumlla Peroxlde (96-100%) 0.12 0.12 :: .
. , ~ . .; . ., . ..... - , .. .. . .. .
.. ~ . ~ ~ ..... . . ..... ... . .
2~03~9~
~7487-458 Examples 4 and 5 were processed the same way as examples 1, 2, and 3.
Results obtained:
Property Example 4: Example 5 Contraction 1.5% 1.0%
Fadlng occurred occurred ~-Fracture occurred occurred Examples 6 and 7 (wlthout contractlon or fracture): :
Composltlons of polyethylene modlfled wlth co-polymerlc polypropylene.
Ingredlent Example 6: Example 7-LDPE (MFI 1,3) 80 - ~
LLDPE (MFI 1,0) - 80 ~-.
Copolymerlc PP (8% ethylene) MFI 4;
EPT30RSF Spheripol from Antloxldant 0.2 0.2 VTMO 1.5 1.5 Cumlla Peroxide Ig6-100~) 0.12 0.12 DBTL 0.05 0.05 Examples 6 and 7 were processed the same way as examples 1, 2, 3, 4, and 5.
Re ults obtalned:
Property Example 6, Example 7:
Contractlon 3.0% 3.0%
~:: Fadlng none none : : Fracture none none .~ , ; ~, 9 - 2~ 0~9~ -Examples 8, 9, and 10 aimed at estlmatlng the best PP/LDPE relatlon; the smaller PP level, the greater cost reductlon.
In~r.edlent Example 8: Example 9 Example 10 LDPE (MFI 1,3) 85.0 82.5 80.0 Copolymerlc PP ~8% ethylene) MFI 4;
EPT30RSF from HIMONT 15.0 17.5 20.0 Antloxldatlng 0.2 0.2 0.2 VTMO 1.5 1.5 1.5 Cumlla Peroxlde (96-100%) 0.12 0.12 0.12 DBTL 0.05 0.05 0.05 Examples 8, 9, and 10 were processed the same way as examples 1, 2, 3, 4, 5, 6, and 7.
Results obtalned:
Property Example 8- Example 9 Example 10:
Contraction 7.0% 4.5% 4.0~
Fadlng none none none Fracture none none none 502/83 ~3rd ISSUE 1991) AND ABNT 3.20.3-026/90 (REVISION NBR-6251/86): ~oth speclflcatlons have the same requlrements.
Propertles Unlt Requlrement Example 7 Example 9 I) Inltlal Tenslon and rupture MPa 12.5 21.9 16.6 Stretchlng and rupture ~ 200 480 480 2~ Oa89~
II) After aglng ln alr stove at 135C for 168 hours Varlatlon o~ tenslon and rupture % MAX 25 +4 +5 Varlatlon of stretchlng at rupture % MAX 25 -2 -3 Stretchlng at heat (200C) wlth load of 0.2MPa % MAX 175 60 60 Permanent deformlty after stretchlng test at heat % MAX 15 15 15 .- ~ . . : .
., ~ .... , . . ~ . .
- . . - . . . . . ..
ISGLATION COMPOSITIONS IN HUMIDITY RETICULATED POLYETHYLENE (XLPE) WITH COMTRACTION REDUCED ~T 130C, FOR USE IN LOW TENSION POWER CABLES
The current inventlon refers to an electrlc cable, lsolated wlth composltlons o~ low denslty polyethylene, whlch are humldlty retlculate. More preclsely, lt refers to the appllcatlon of composltlons wlth a low denslty polyethylene base, and whlch are humldlty retlculate for lsolatlng and coverlng cables. The process ls known as "SIOPLAS". The commercial processes for obtalnlng the retlculate polyethylene ln the lndustry of cables are baslcally the followlng. The oldest one consists ln applylng addltlves to the polyethylene wlth organlc peroxldes, wlth an actlvatlng temperature above the temperature for softenlng the polyethylene used. These composltes are applled ln the case of cables manufactured through an extruslon process followed by a thermo-chemlcal retlculatlon process slmultaneously wlth the instant heatlng of the lsolated cable above the peroxlde actlva-tlng temperature, for lnstance, through saturated vapor heatlng or through radlant heat produced by electrlc reslstances, followed by ~0 a process correspondlng to water coollng. In both cases, the process ls done under pressure, slnce the decomposltlon gases generated by the chemlcal reactlons cause the exlstence of bubbles ln the extruded lsolatlon. Thls process ls stlll wldely used for the productlon of medlum/hlgh tenslon cables, because lt ls the only way to obtaln large extruded and retlculated lsolatlon sectlons wlthout empty spots. Thls process requlres hlgh cost lndustrlal lnstallatlons.
., , . . . , . , . . . ., . , . ~ ~, . .......... . . . . .. .
. ~ . . .. - .. ..
Another process for obtalnlng retlculate polyethylene isolatlon ls the radlatlon by means of electron beams or sources o gamma radlatlon. Through thls process, the cable ls lsolated by means of a normal extruslon process that may be applled to thermoplastlc polyethylene, followed by a retlculatlon process, and ln a subsequent phase, by means of hlgh energy electron beam radlatlon or gamma radlatlon sources. In thls case the process ls malnly used for cables wlth a small extruded section, since the penetratlon capaclty of the electrons ls llmlted. Both processes, the electronlc radlatlon and gamma sources, require hlgh cost lnstallatlons, malnly because of special protectlon needed for the operator and for the envlronment. The productlon speed of cables ls llmlted by the amount of energy that these sources can llberate and by the amount of material (lsolatlon) to be retlculated.
These processes are ùsually lndlcated and applled to speclal cables.
Another process ls the chemlcal retlculatlon done by means of humldlty. In thls process, an organo-sllane that can be hydrolysed ls lntroduced to the polyethylene molecule whlch stlll malntalns lts thermoplastlc characterlstlcs, belng applled on the cable by means of a usual extruslon that can be applled to the thermoplastlc polyethylene, where the extruslon speed ls only llmlted by the extruslon and the materlal characterlstlcs. The polyethylene retlculatlon ln the cable occurs ln the reel, depend-lng on the materlal ln the envlronmental temperature and humldlty condltlons or by exposlng the reel to a "sauna" type envlronment.
~;3~9g Thls ls a low cost process for the productlon of low tenslon cables, slnce lt only requlres usual process equlpment for thez-moplastlc materlals. And, above all, lt ls advantageous for the lsolatlon of conductors whlch have a non-round sectlon, as, for lnstance, sector conductors (shape of a shell), whlch are pre-vio~lsly twlsted. Thls process ls not advantageous for the produc-tlon of medlum/hlgh tenslon cables, slnce the dlffuslon of humldl-ty through large extruded sectlons ls slow and the humldlty ls one of the factors for the formatlon of arborescence ln polyethylene that are under electrlc "stress" of hlgh gradlent.
Thls last process for obtalnlng retlculated polyethylene as described above ls, nowadays, wldely used by the manufacturers of cables, malnly as lsolatlon of power cables for low tenslon.
The process i8 widely mastered by the manufacturers of cables, with at least t~o ways of obtalning the composlte for extruslon.
a) Composltes wlth organo-sllane that ls prevlousl~
lnserted lnto the polyethylene are commercially avallable or can be prepared locally by the manufacturer of cables. Here, two families of composites are identified~
a.l) Polyethylene wlth lnserted organo-silane applled to commerclal polyethylene (thls process may be done by any thermoplastlc processor that has adequate equlpment);
a.2) Polyethylene wlth organo-sllane that is co-polymerized during the ethylene polymerlzation process (obvlously, this process is only known to the :. . . . :
, . : :-210`~896 petrochemlcal lndustry whlch ls lnvolved ln the productlon of polyethylene).
b) Composltes wlth the organo-silane lnserted durlng the cable extruslon process. Usually, thls process ls known by the cable manufacturers. The varlatlons for this process are b.l) Humectatlon of the granules wlth organo-sllane and peroxlde lmmedlately before the extruslon;
b.2) Dosage and dlrect in~ection of the organo-sllane and peroxlde in the extrudlng material (Monosil Process);
b.3) Dosage and direct in~ectlon of the organo-silane and peroxide through "CTN" (Cavity Transfer Mlxer), connected to the head of the extruding material, known as Sllanox Process The reticulation process of the polyethylene through humldlty, as descrlbed above, has been widely accepted for the manufacture of power cables for low tension in relatlon to the other processes, due, malnly, to the cost savlng aspect of the process, that ls, the larger productlvlty, less consumptlon of energy, less lnvestment. On the other hand, the humidlty reticu-lation process presents technical advantages for the applicatlon process. The most lmportant ones are the posslbllity of extrusion for any conductor proflle and the possibillty of embossing during the extruslon.
The extruslon processes commonly used for isolating conductors differ according to the type of tools used for the formatlon of isolatlon ln the conductor. The keywords used to .... ,, . . ~ . . ~ . -- - - , - - - - -.. : . . . ~ . . .. . .
2 ~ 9 ~
dlffer the processes are "Extruslon under Pressure", "Extruslon under Seml-tubes" and "Extruslon under tubes". For the "Extrusion under Pressure", the tools used have, approxlmatelyl the flnal isolatlon dlmenslons ~the polyethylene ls placed over the conduc-tor wlthout stretching); for the "Extruslon under Seml-tubes", the tools are sllghtly blgger than the dlmenslons of lsolatlon and they are generally used when the composlte tends to flow backwards by the male; and for the "Extruslon under tubes", the male and female are, generally, much blgger than the isolatlon dlmenslon of ~he conductor, and they are used when the proflle of the conductor ls not round, which makes lt lmposslble to use tlght tools or ln the case of composites applled on very thln materlals (typlcal example, FEP "Teflon"). In thls case, the flnal shape of the lsolation ls obtalned by stretchlng the tube up to the flnal dl-mension.
A problem that ls always present in the extruslon of thermoplastlc materlals are the resldual tenslons left by the conformatlon process, slnce the thermoplastlc materlals are poly-merlc ~macro-molecules) whlch, ln the extrusion process, are Z0 squeezed and stretched. Usually, the polymerlc materlals requlre a relatlvely long tlme for relaxlng the tenslons stored durlng the passage through the tools. SInce the lsolatlon ls rapldly cooled, to obtaln productlvlty and to avold deformltles ln the reel, a large part of the tenslons ls stored.
The power cables for low tenslon are covered by lnter-national speclflcatlons, such as IEC 502183), NBR ABNT Pro~ect 3.20.3-026~90). Under the servlce condltlons, these cables are : ., :, :, . ~ .. . .. .
2~5896 classlfied for contlnuous servlce at a 90C temperature (ln the conductor), and at an overload process, durlng a short perlod of tlme, up to 130C, and under a short-clrcuit condltion up to 250C.
The retlculated polyethylene obtalned by the "Sloplas"
process, when heated above lts softenlng temperature (95 to 115C), tends to relax the tenslons left by the extruslon process, creatlng a contractlon, especlally ln the ends of the cable expos-lng the conductor. --To prevent accldents created by the contractlon agalnst the installatlons, the rules descrlbed above lnclude a quallflca-tlon test. Such a test conslsts in cuttlrlg 200mm from the central part of a sample that has at least 1200mm of the lsolated cable, then exposlng thls sample to heat ~or 1 hour at 130C ln an alr stove, and measuring the lsolation contractlon at both ends The value found mu~t not exceed 4~.
In practice, what was notlced was that for the poly-ethylene that were retlculated through the "Tu~e Extruded Sloplas", the contractlon can reach 20% causlng serlous lncon-veniences for the use of the cable.
~; The current lnventlon has the purpose of solvlng the current technlcal problems, through the modlflcatlon of the polyethylene that are usually employed ln the "Sloplas" process, wlth the addltlon of polypropylene (PP). The polypropylene has a softenlng temperature between 155 up to 165C, whlch guarantees, up to 130C, the dlmenslonal stablllty of the extruded materlal.
::
2~ ~S~96 ~7487-458 The mlxture of the PP with the low density polyethylene (LDI?E) or linear low denslty polyethylene (LLDPE) or co-polymeric pol~yethylene of vlnyl ethylene acetate (EVA) ln an adequate con-centratlon ls the solutlon for the contractlon problem.
The low denslty polyethylene (LDPE) ls a homopolymerlc or co-polymerlc vlnyl acetate (VA) or methylacrylate (MA) up to 10%. The llnear low denslty polyethylene (LLDPE) ls a butene or hexene co-polymerlc. The polypropylene ls a propylene-ethylene co-polymerlc wlth a co-monomerous level (ethylene) over 6%, belng used ln a preferred proportlon between 15 and 25%.
Below ls the descrlptlon of experlmental results obtaln- -ed wlth composltlons of the known technlque and of the current inventlon.
Exàmples 1, 2, 3 (wlth contractlon):
Usual compo~ltlon~ wlth polyethylene ba~e whlch can be retlculated through the "Sloplas" proces~.
Ingredient Example 1 Example 2 Example 3 LDPE (MFI 1,3) 100 LDPE (Co-polymerlc 9% Vlnyl Acetate) MFI 4 - - 100 LLDPE (MFI 4) - 100 Antl-oxldatlng 0.2 0.2 0.2 VIMO 1.5 1.5 1.5 Cumlla Peroxlde (96-100%~ 0.12 0.12 0.12 DBTL 0.05 0.05 0.05 NOTESs VIMO (Vlnyl Trlmethoxy Sllane), Organo Sllane wlth three methoxy radlcal~ to one vlnyl radlcal - DBTL (Dl-Butyl Tln .-. . . :.. :- : .:
~, . . . .
21 05~ 9 ~
Laurate) Organlc salt of tin used as a catalyzer for hydrolysis.
- These compositions can be easily reproduced in a laboratory uslng the technlque of humectation for the granulated polyethylene wlth the silane, peroxlde and DBTL. The above compositions were extruded with tube extrusion tools over a flat proflle conductor with a rate of section reduction of 2 (DDR - draw down ratio).
To enable the reaction of the lnsertlon of the silane to occur, a fuslon temperature (Melt) of 220C was used. After treatlng them ln waterbath at 70C for 16 hours, ln a contractlon controlled way, they became faded and a fracture in the flection occurred.
Pesults obtained Property Example 1: Example 2: Example 3 Contraction 13% 5.5% 19%
Fading none none none Fracture none none none Examples 4 and 5 (with fracture): Polyethylene compositions modlfied with homo-polymeric polypropylene.
Ingredient Example 4, Example 5:
LDPE (MFI 1,33 80 LLDPE (MFI 1,0) - 80 Homopolymeric PP tMFI 4,0 -KMT 6100 from Polibrasil) 20 20 Antloxldatlng 0.2 0.2 VTMO 1.5 1.5 Cumlla Peroxlde (96-100%) 0.12 0.12 :: .
. , ~ . .; . ., . ..... - , .. .. . .. .
.. ~ . ~ ~ ..... . . ..... ... . .
2~03~9~
~7487-458 Examples 4 and 5 were processed the same way as examples 1, 2, and 3.
Results obtained:
Property Example 4: Example 5 Contraction 1.5% 1.0%
Fadlng occurred occurred ~-Fracture occurred occurred Examples 6 and 7 (wlthout contractlon or fracture): :
Composltlons of polyethylene modlfled wlth co-polymerlc polypropylene.
Ingredlent Example 6: Example 7-LDPE (MFI 1,3) 80 - ~
LLDPE (MFI 1,0) - 80 ~-.
Copolymerlc PP (8% ethylene) MFI 4;
EPT30RSF Spheripol from Antloxldant 0.2 0.2 VTMO 1.5 1.5 Cumlla Peroxide Ig6-100~) 0.12 0.12 DBTL 0.05 0.05 Examples 6 and 7 were processed the same way as examples 1, 2, 3, 4, and 5.
Re ults obtalned:
Property Example 6, Example 7:
Contractlon 3.0% 3.0%
~:: Fadlng none none : : Fracture none none .~ , ; ~, 9 - 2~ 0~9~ -Examples 8, 9, and 10 aimed at estlmatlng the best PP/LDPE relatlon; the smaller PP level, the greater cost reductlon.
In~r.edlent Example 8: Example 9 Example 10 LDPE (MFI 1,3) 85.0 82.5 80.0 Copolymerlc PP ~8% ethylene) MFI 4;
EPT30RSF from HIMONT 15.0 17.5 20.0 Antloxldatlng 0.2 0.2 0.2 VTMO 1.5 1.5 1.5 Cumlla Peroxlde (96-100%) 0.12 0.12 0.12 DBTL 0.05 0.05 0.05 Examples 8, 9, and 10 were processed the same way as examples 1, 2, 3, 4, 5, 6, and 7.
Results obtalned:
Property Example 8- Example 9 Example 10:
Contraction 7.0% 4.5% 4.0~
Fadlng none none none Fracture none none none 502/83 ~3rd ISSUE 1991) AND ABNT 3.20.3-026/90 (REVISION NBR-6251/86): ~oth speclflcatlons have the same requlrements.
Propertles Unlt Requlrement Example 7 Example 9 I) Inltlal Tenslon and rupture MPa 12.5 21.9 16.6 Stretchlng and rupture ~ 200 480 480 2~ Oa89~
II) After aglng ln alr stove at 135C for 168 hours Varlatlon o~ tenslon and rupture % MAX 25 +4 +5 Varlatlon of stretchlng at rupture % MAX 25 -2 -3 Stretchlng at heat (200C) wlth load of 0.2MPa % MAX 175 60 60 Permanent deformlty after stretchlng test at heat % MAX 15 15 15 .- ~ . . : .
., ~ .... , . . ~ . .
- . . - . . . . . ..
Claims (8)
1. Isolation compositions in humidity reticulated poly-ethylene (XLPE) with contraction reduced at 1300°C, for use in low tension power cables, characterized by the fact that they are compositions with polyethylene base modified by the addition of polypropylene.
2. Compositions, according to claim 1, characterized by the fact that the polypropylene is a co-polymeric of propylene-ethylene with a proportion of ethylene above 6%.
3. Compositions, according to claim 2, characterized by the fact that the proportion of the added polypropylene is between 15 and 25%.
4. Compositions, according to claim 1, characterized by the fact that the polyethylene has low density, medium density or high density.
5. Compositions, according to claim 4, characterized by the fact that the polyethylene is linear and has low density.
6. Compositions, according to claim 4, characterized by the fact that the low density polyethylene is a co-polymeric of vinyl acetate or methyl acrylate up to 10%.
7. Compositions, according to claim 5, characterized by the fact that the low density linear polyethylene is a co-polymeric of butene or hexene.
8. Compositions, according to claims 1 through 7, charac-terized by the fact that the isolation has its contraction below 4%, in compliance with rules IEC 502 from 1983 (3rd issue 1991), and ABNT Project 3.20.3-026/90 (revision NBR-6251/1986).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BRPI9203610 | 1992-09-11 | ||
| BR929203610A BR9203610A (en) | 1992-09-11 | 1992-09-11 | INSULATION COMPOSITIONS IN HUMIDITY-LINKED POLYETHYLENE (XLPE) WITH REDUCED CONTRACTION AT 130 C, FOR USE ON LOW VOLTAGE POWER SUPPLY CABLES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2105896A1 true CA2105896A1 (en) | 1994-03-12 |
Family
ID=4054935
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2105896 Abandoned CA2105896A1 (en) | 1992-09-11 | 1993-09-10 | Isolation compositions in humidity reticulated polyethylene (xlpe) with contraction reduced at 130°c for use in low tension power cables |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0587453A3 (en) |
| AU (1) | AU4626593A (en) |
| BR (1) | BR9203610A (en) |
| CA (1) | CA2105896A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6506842B1 (en) | 1997-01-29 | 2003-01-14 | Dupont Dow Elastomers L.L.C. | Rheology-modified thermoplastic elastomer compositions and articles fabricated therefrom |
| EP1672161B1 (en) * | 2004-12-20 | 2009-04-01 | Gabriel Pichler | Joint sealing and method of producing the same |
| US11837383B2 (en) | 2020-03-27 | 2023-12-05 | Prysmian S.P.A. | Cables with improved coverings to reduce shrinkback and methods of forming the same |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4857250A (en) * | 1984-04-13 | 1989-08-15 | Union Carbide Corporation | One-extrusion method of making a shaped crosslinkable extruded polymeric product |
| DE3520106C2 (en) * | 1985-06-05 | 1995-07-27 | Dynamit Nobel Ag | Process for the production of cross-linked molded articles with increased impact strength from ternary polyolefin molding compositions |
| ES8802623A1 (en) * | 1985-09-20 | 1988-09-01 | Kabelmetal Electro Gmbh | Elongated products |
| US4948669A (en) * | 1988-02-08 | 1990-08-14 | E. I. Du Pont De Nemours And Company | Flame retardant ethylene polymer blends |
| US5112919A (en) * | 1989-10-30 | 1992-05-12 | Union Carbide Chemicals & Plastics Technology Corporation | Solid feeding of silane crosslinking agents into extruder |
-
1992
- 1992-09-11 BR BR929203610A patent/BR9203610A/en not_active Application Discontinuation
-
1993
- 1993-09-09 AU AU46265/93A patent/AU4626593A/en not_active Abandoned
- 1993-09-10 CA CA 2105896 patent/CA2105896A1/en not_active Abandoned
- 1993-09-13 EP EP9393307197A patent/EP0587453A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| BR9203610A (en) | 1994-03-22 |
| EP0587453A3 (en) | 1994-08-24 |
| AU4626593A (en) | 1994-03-17 |
| EP0587453A2 (en) | 1994-03-16 |
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