Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-05-18
2001-05-15
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S547000, C428S418000
Reexamination Certificate
active
06232376
ABSTRACT:
TECHNICAL FIELD
This invention relates to moisture curable polyolefin compositions and a masterbatch type composition therefor.
BACKGROUND INFORMATION
Polyolefins, particularly polyethylene, can be crosslinked by first making the resin hydrolyzable, which is accomplished by adding hydrolyzable groups to the resin structure through copolymerization or grafting. For example, ethylene can be copolymerized with an ethylenically unsaturated compound having one or more —Si(OR)
3
groups wherein R is a hydrocarbyl radical or the silane compound can be grafted to the resin in the presence of an organic peroxide. The hydrolyzable resins are then crosslinked by moisture in the presence of a silanol condensation catalyst.
The moisture curable polyethylene can be prepared by a single step process, which typically involves introducing all of the components, i.e., the resin, usually in the form of pellets; the unsaturated alkoxysilane; an organic peroxide; a silanol condensation catalyst; an antioxidant; and other additives, into an extruder; mixing the components together; heating until the hydrolyzable group is grafted to the resin; and extruding a molded product, such as a pellet, through the die.
Unfortunately, many of the present moisture curable resin compositions, when converted to typical end products such as power cable insulation, jacketing or semiconducting shields, suffer from inferior heat endurance, poor thermal aging resistance, and yellowing
DISCLOSURE OF THE INVENTION
An object of this invention, therefore, is to provide a moisture curable polyolefin composition, which, when converted to various end products, evinces much improved heat endurance, thermal aging resistance, and resistance to yellowing.
According to the invention, a moisture curable polyolefin composition has been discovered which meets the above object.
The composition comprises
(a) a polyolefin, and for each 100 parts by weight of component (a),
(b) 0.1 to 10 parts by weight of an unsaturated alkoxy silane;
(c) 0.01 to 2 parts by weight of an organic peroxide;
(d) 0.01 to 2 parts by weight of a silanol condensation catalyst;
(e) 0.02 to 2 parts by weight of a hindered amine stabilizer;
(f) 0.01 to 1 part by weight of a hindered phenol antioxidant; and
(g) 0.01 to 1 part by weight of an arylamine antioxidant.
In another embodiment of the invention, components (b) to (g) are combined in masterbatch form. This unsaturated alkoxy silane composition is found to have a high level of storage stability.
The composition comprises:
(a) an unsaturated alkoxy silane, and for each 100 parts by weight of component (a),
(b) 0.1 to 10 parts by weight of an organic peroxide;
(c) 0.1 to 10 parts by weight of a silanol condensation catalyst;
(d) 0.02 to 10 parts by weight of a hindered amine stabilizer;
(e) 0.01 to 10 parts by weight of a hindered phenol antioxidant; and
(f) 0.01 to 10 parts by weight of an arylamine antioxidant.
Finally, another embodiment of the invention displays the moisture curable composition in two parts, the first being the polyolefin portion and the second being the unsaturated alkoxy silane portion. The composition comprises:
(i) a polyolefin, and for each 100 parts by weight of component (i),
(ii) 0.2 to 20 parts by weight of an unsaturated alkoxy silane, and for each 100 parts by weight of component (ii),
(a) 0.1 to 10 parts by weight of an organic peroxide;
(b) 0.1 to 10 parts by weight of a silanol condensation catalyst;
(c) 0.02 to 10 parts by weight of a hindered amine stabilizer;
(d) 0.01 to 10 parts by weight of a hindered phenol antioxidant; and
(e) 0.01 to 10 parts by weight of an arylamine antioxidant.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Polyolefin, as that term is used herein, is a thermoplastic resin, which is crosslinkable. It can be a homopolymer or a copolymer produced from two or more comonomers, or a blend of two or more of these polymers, conventionally used in film, sheet, and tubing, and as jacketing and/or insulating materials in wire and cable applications. The polymers can be crystalline, amorphous, or combinations thereof. They can also be block or random copolymers. The monomers useful in the production of these homopolymers and copolymers can have 2 to 20 carbon atoms, and preferably have 2 to 12 carbon atoms. Examples of these monomers are alpha-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-i-pentene, and 1-octene; unsaturated esters such as vinyl acetate, ethyl acrylate, methyl acrylate, methyl methacrylate, t-butyl acrylate, n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, and other alkyl acrylates; diolefins such as 1,4-pentadiene, 1,3-hexadiene, 1,5-hexadiene, 1,4-octadiene, and ethylidene norbornene, commonly the third monomer in a terpolymer; other monomers such as styrene, p-methyl styrene, alpha-methyl styrene, p-chloro styrene, vinyl naphthalene, and similar aryl olefins; nitriles such as acrylonitrile, methacrylonitrile, and alpha-chloroacrylonitrile; vinyl methyl ketone, vinyl methyl ether, vinylidene chloride, maleic anhydride, vinyl chloride, vinylidene chloride, vinyl alcohol, tetrafluoroethylene, and chlorotri-fluoroethylene; and acrylic acid, methacrylic acid, and other similar unsaturated acids.
The homopolymers and copolymers referred to can be non-halogenated, or halogenated in a conventional manner, generally with chlorine or bromine. Examples of halogenated polymers are polyvinyl chloride, polyvinylidene chloride, and polytetra-fluoroethylene. The homopolymers and copolymers of ethylene and propylene are preferred, both in the non-halogenated and halogenated form. Included in this preferred group are terpolymers such as ethylene/propylene/diene monomer rubbers.
With respect to polypropylene: homopolymers and copolymers of propylene and one or more other alpha-olefins wherein the portion of the copolymer based on propylene is at least about 60 percent by weight based on the weight of the copolymer can be used to provide the polyolefin of the invention. Polypropylene can be prepared by conventional processes such as the process described in U.S. Pat. No. 4,414,132. Preferred polypropylene alpha-olefin comonomers are those having 2 or 4 to 12 carbon atoms.
Polyethylene, as that term is used herein, is a homopolymer of ethylene or a copolymer of ethylene and a minor proportion of one or more alpha-olefins having 3 to 12 carbon atoms, and preferably 4 to 8 carbon atoms, and, optionally, a diene, or a mixture or blend of such homopolymers and copolymers. The mixture can be a mechanical blend or an in situ blend. Examples of the alpha-olefins are propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The polyethylene can also be a copolymer of ethylene and an unsaturated ester such as a vinyl ester, e.g., vinyl acetate or an acrylic or methacrylic acid ester.
The polyethylene can be homogeneous or heterogeneous. The homogeneous polyethylenes usually have a polydispersity (Mw/Mn) in the range of about 1.5 to about 3.5 and an essentially uniform comonomer distribution, and are characterized by single and relatively low DSC melting points. The heterogeneous polyethylenes, on the other hand, have a polydispersity (Mw/Mn) greater than 3.5 and do not have a uniform comonomer distribution. Mw is defined as weight average molecular weight and Mn is defined as number average molecular weight. The polyethylenes can have a density in the range of 0.860 to 0.950 gram per cubic centimeter, and preferably have a density in the range of 0.910 to about 0.930 gram per cubic centimeter. They also can have a melt index in the range of about 0.1 to about 50 grams per 10 minutes, preferably 0.5 to 10 grams per 10 minutes. A granular polyethylene is also preferable.
The polyethylenes can be produced by low or high pressure processes. They are preferably produced in the gas phase, but they can also be produced in the liquid phase in solutions or slurries by conventional techniques. Low pressure processes are typically run at pressures below 1000 psi whereas high pressure processes are typically run at pressures above 15,000 psi.
T
Ishihara Koji
Nomura Yasuo
Ohki Ariyoshi
Okazawa Makoto
Tsukada Kiroku
Bresch Saul R.
Nippon Unicar Company Ltd.
Sanders Kriellion
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