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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing atoms other than carbon or hydrogen
  • C08L23/0892—Copolymers of ethene with unsaturated hydrocarbons containing atoms other than carbon or hydrogen with monomers containing atoms other than carbon, hydrogen or oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L43/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and containing boron, silicon, phosphorus, selenium, tellurium or a metal; Compositions of derivatives of such polymers
  • C08L43/04—Homopolymers or copolymers of monomers containing silicon
• • 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
  • H01B3/28—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances natural or synthetic rubbers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms
  • C08L23/0815—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms with aliphatic 1-olefins containing one carbon-to-carbon double bond
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene
  • C08L23/14—Copolymers of propene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2312/00—Crosslinking
  • C08L2312/08—Crosslinking by silane

Definitions

• This invention generally relates to silane moisture curable polymer resin compositions and more particularly, to such compositions having increased low temperature flexibility.
• the majority of polyethylene insulated low voltage cables are cured or crosslinked by a moisture cure process whereby an alkoxy silane attached to the polyethylene chain is hydrolyzed and then cures under the influence of a suitable catalyst.
• the alkoxy silane may be attached to the polyethylene chain by two methods. Either vinyl trialkoxy silane is copolymerized with ethylene to yield a silane copolymer or the vinyl alkoxy silane is grafted onto the polyethylene, polymer backbone by peroxide initiated reactive extrusion.
• the resulting copolymer is similar to LDPE and is a semi-rigid insulation material (flexural modulus of about 200 MPa).
• more flexible resin systems can be produced by blending in an elastomer with the polyethylene during a reactive extrusion step.
• special extrusion equipment e.g., silane dosing equipment, designed barrier screw, etc.
• elastomers that degrade or scission in the presence of peroxide or other free-radical sources cannot be used.
• existing moisture-cured resins tend to become brittle or stiff at low temperatures, such as can be encountered in outdoor use during the winter.
• the invention is a composition
• a composition comprising: (1) at least about 60 weight percent, based on the total weight of polymer resins, of at least one silane crosslinkable polyolefin polymer resin: and, (2) up Io about 40 weight percent, based on the total weight of polymers, of at least one polyolefin polymer elastomer resin, wherein the polyolefin polymer elastomer resin has a density of less than or equal to about 0.89 g/cm 3 and a melt index, I 2 , of less than about 50 g/10 min and which has been prepared using at least one metallocene calalyst
• the invention is a cable comprising: (1) a conductive core: and, (2) a layer of an insulating material outside of the conductive core, wherein the insulating material comprises a composition comprising (a) at least about 60 weight percent, based on the total weight of polymer resins, of at least one silane crosslinkabie polyolefin polymer resin; and, (b) up to about 40 weight percent, based on the total weight of polymers, of at least one polyolefin polymer elastomer resin, wherein the polyolefin polymer elastomer resin has a density of less than or equal to about 0.89 g/cm 3 and a melt index, I 2 , of less than about 50g10 min. and which has been prepared using at least one metallocene catalyst.
• the insulating material comprises a composition comprising (a) at least about 60 weight percent, based on the total weight of polymer resins, of at least one silane crosslinkabie polyolefin polymer resin; and,
• Moisture curable polymers with silane functional groups are well-known in the field. Such polymers can be made either by copolymerization with a vinyl silane monomer or by one of many methods for grafting a silane-eontaining molecule to the backbone of a polymer chain. Examples of such techniques are disclosed in U.S. Pat. Nos. 3,646,155; 6,420,485; 6,331 ,597; 3,225,018; or 4,574,133, all of which are incorporated herein by reference. Polymers with silane functional groups are also commercially available, for example, SI-LINK.TM ethylene-vinyltrimethoxysilane copolymers available from Dow Chemical Co. or VISICOTM polymers from Borealis
• the silane-functionalized polymers usable in the present invention may be cured by contact with, or exposure to, water (moisture), preferably in the presence of a condensation catalyst (also called " moisture-cure” catalyst herein).
• a condensation catalyst also called " moisture-cure” catalyst herein.
• Suitable catalysts include metal carboxylates, such as dibutyltin dilaurate, stannous octoate, stannous acetate, lead naphthcnatc and zinc octoate; organic metal compounds, such as titanium esters and chelates such as tetrabutyl titanate; organic bases, such as ethylamine, hexylamine and pipcridine; and acids, such as mineral acids and fatty acids.
• Ambient or accelerated cure systems typically use fast acting condensation catalysts, such as aromatic sulphonic acids.
• Preferred catalysts are organic tin compounds such as dibutyltin dilaurate, dibutyl dimethoxy tin, dibutyltin bis(2,4-pcntanedionate), stannous octoate, and aromatic sulphonic acids.
• Such moisture-cure condensation catalysts and catalyst systems are readily commercially available.
• suitable commercial catalysts in niasterbatch form include, without limitation, DFDB 5480NT (a tin catalyst system), DFDA 5488NT (a fast ambient cure catalyst niasterbatch) from DOW Plastics, or the Borealis AMBICATTM system LE 4476.
• the amount of catalyst sufficient to cure the silane-functionalized polymer will generally depend on the specific type selected but will preferably range from about 0.01 to 0.1 parts by weight per 100 parts by weight of the silane polymer. If added in the form of a commercial polymer masterbatch as above the catalyst masterbatch is added in the ratio 5 parts to 95 parts of silane copolymer.
• the moisture cure may be done in a steam chamber, a continuous steam vulcanization tunnel, a hot water sauna, or simply by exposure to air (ambient cure) or any other convenient means.
• the silane-functionalized polymers Prior to moisture curing, are blended with low density metallocene polyolefin elastomers, a particular combination which leads to a crosslinked flexible compound.
• the polyolefin elastomers are ethylene copolymers. These polyolefin elastomers should have a density of less than or equal to about 0.89 g/cm , more preferably less than or equal to about 0.885 g/mm 3 . All polymer density values in the specification and claims are as measured by ASTM D-792.
• the polyolefin elastomers have a melt index, I 2 , of less than about 50 g/10 min, more preferably between about 1 and about 40/10 min, and more preferably, of between about 1 to about 30/10 min. All melt indexes in the specification and claims are as measured by ASTM D- 1238, Condition 190 C/2.16 kg,
• the polyolefin elastomer preferably composes at least about 20, more preferably at least about 30, most preferably about 40 weight percent of the total weigh of polymer resins in the composition
• the polyolefin elastomers are prepared with at least one metallocene catalyst.
• the elastomer resin may also be prepared with more than one metallocene catalyst or may be a blend of multiple elastomer resins prepared with different metallocene catalysts.
• the elastomer is a substantially linear ethylene polymer (SLEP).
• SLEPs and other metallocene catalyzed elastomers are known in the art, for example, US 5,272,236 incorporated herein by reference.
• These elastomer resins are also commercially available, for example, as ENGAGETM elastomer resins available from Dow Chemical Co. or EXACTTM polymers from Exxon or TAFMER TM polymers from Mitsui Chemicals.
• the polyolefin elastomer should be incompatible (i.e., immisicibie) with the silane-functionalized polymer. This is in contrast to prior art systems that either rely on a radical grafting process or cover blends of silane copolymer with crystalline polyethyienes which are mutually compatible.
• the inventors speculate that the incompatibility of the silane copolymer and the polyolefin elastomer allows the silane copolymer to still form a crosslinked network even in the presence of high (up to 40% or so) amounts of the elastomer. Consequently, the final blend has excellent cure performance, mechanicals and flexibility.
• the composition can contain other flame retardants and fillers including metal hydrates (such as aluminum trihydroxide and magnesium hydroxide), talc, calcium carbonate, organoclay, glass fibers, marble dust, cement dust, feldspar, silica or glass, fumed silica, silicates, alumina, various phosphorus compounds, ammonium bromide, antimony trioxide, antimony trioxide, zinc oxide, zinc borate, barium sulfate, silicones, aluminum silicate, calcium silicate, titanium oxides, glass microspheres, chalk, mica, clays, wollastonite, ammonium octamolybdate, intumescent compounds, expandable graphite, and mixtures thereof.
• metal hydrates such as aluminum trihydroxide and magnesium hydroxide
• talc such as aluminum trihydroxide and magnesium hydroxide
• calcium carbonate such as aluminum trihydroxide and magnesium hydroxide
• organoclay such as aluminum trihydroxide and magnesium hydroxide
• the fillers may contain various surface coatings or treatments, such as silanes, fatty acids, and the like.
• Halogenated organic compounds including halogenated hydrocarbons such as chlorinated paraffin, halogenated aromatic compounds such as pentabromotoluene, decabromodiphenyl oxide, decabromodiphenyl ethane, ethylene- bis(tetrabromophthalimide), dechlorane plus, and other halogen-containing flame retardants.
• halogenated hydrocarbons such as chlorinated paraffin
• halogenated aromatic compounds such as pentabromotoluene, decabromodiphenyl oxide, decabromodiphenyl ethane, ethylene- bis(tetrabromophthalimide), dechlorane plus, and other halogen-containing flame retardants.
• One skilled in the art would recognize and select the appropriate halogen agent depending on the desired performance of the composition.
• the composition can further comprise various other additives. Per
• the composition can contain other additives such as, for example, antioxidants (e.g., hindered phenols such as, for example, IRGANOXTM 1010 a registered trademark of CibaSpecialty Chemicals), phosphites (e.g., IRGAFOSTM 168 a registered trademark of CibaSpecialty Chemicals), U.V.
• antioxidants e.g., hindered phenols such as, for example, IRGANOXTM 1010 a registered trademark of CibaSpecialty Chemicals
• phosphites e.g., IRGAFOSTM 168 a registered trademark of CibaSpecialty Chemicals
• additives are employed in functionally equivalent amounts known to those skilled in the art. generally in amounts of up to about 65 percent by weight, based upon the total weight of the composition.
• composition of the invention can be made by simply dry blending or melt blending the individual components and additives.
• certain of the ingredients may be premixed, such as by melt processing, into master batches, Such master batches are useful in aiding uniform dispersion of the ingredients and minimizing the number of components that need to be blended at the end-user's facilities.
• the compositions of the present invention can be processed to fabricated articles by any suitable means known in the art.
• the compositions can be processed to films or sheets or to one or more layers of a multi layered structure by know processes, such as calendering, blowing, casting or (co-)extrusion processes.
• compositions of the present invention can also be prepared from the compositions of the present invention.
• the compositions can be processed to foams or fibers or extruded into wire and cable coatings such as jacketing and insulation.
• Curing and cure rate procedure The plate is placed immediately in a water bath at 60C and cure time noted. Hot set performance at 200oC with 0.2MPa weight as per specification is measured as a junction of cure time in the water bath.
• Test procedures On the fully cured samples (i.e., when hot set is at the minimum) tensile and flexural modulus properties are measured. Results are summarized in Table 2 below.

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• Chemical & Material Sciences (AREA)
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• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Organic Insulating Materials (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Insulated Conductors (AREA)

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