Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-01-20
2001-05-15
Hoke, Veronica P. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S101000, C524S405000, C524S436000, C524S437000
Reexamination Certificate
active
06232377
ABSTRACT:
TECHNICAL FIELD
This invention relates to a flame retardant composition useful in cable construction.
BACKGROUND INFORMATION
Polyolefin resins are commonly used as a material for the insulation and the sheath layers of wires and cables. Recently a higher degree of flame retardance has been demanded in accordance with, for example, a vertical tray test, which can be referred to as the “70,000 Btu per hour” test. Flame retardants such as organic halogen compounds; flame retardant aids such as antimony trioxide; or flame retardant resins such as poly (vinyl chloride) and chlorinated polyethylene can be blended into polyolefins to render them flame retardant; however, these additives cause dripping, smoking, and/or the emission of harmful gases when subjected to burning, and can also cause metals to corrode.
To solve these problems, addition of inorganic flame retardants such as metal hydroxides to the polyolefin resins was proposed and the composition was applied as insulating and sheath layers to various wires and cables. This did not, however, solve the problem of drip or improve the vertical tray test to a commercially desirable extent.
DISCLOSURE OF THE INVENTION
An object of this invention, therefore, is to provide a flame retardant cable composition, which reduces drip and improves on the vertical tray test. Other objects and advantages will become apparent hereinafter.
According to the present invention, the above object is met by a flame retardant composition comprising
(A) about 50 to about 95 percent by weight of at least one polymer selected from the group consisting of ethylene/vinyl ester copolymer; ethylene/alpha, beta unsaturated carboxylate copolymer; and very low density ethylene/alpha-olefin copolymer; and
(B) about 5 to about 50 percent by weight of an ethylene/alpha-olefin copolymer having a melt flow rate of about of about 0.5 to about 50 grams per 10 minutes; a density of 0.860 to 0.935 gram per cubic centimeter; and a Mw/Mn ratio of up to about 3, said copolymer having been prepared with a single site catalyst, and, for each 100 parts by weight of component (A) and component (B) combined,
(C) about 2 to about 50 parts by weight of a polyethylene modified with a functional group containing compound;
(D) about 5 to about 250 parts by weight of a metal hydrate;
(E) about 1 to about 12 parts by weight of a triazine ring containing compound; and
(F) about 0.5 to about 5 parts by weight of a flame retardant compound selected from the group consisting of a boron compound, a molybdenum compound, and a silicone.
DESCRIPTION OF THE PREFERRED EMBODIMENTS(s)
The first component of the composition is (A) about 50 to about 95 percent by weight, preferably about 55 to about 75 percent by weight, of at least one polymer selected from the group consisting of ethylene/vinyl ester copolymer; ethylene/alpha, beta unsaturated carboxylate copolymer; and very low density ethylene/alpha-olefin copolymer.
The ethylene and vinyl ester copolymer is generally produced by a high-pressure radical polymerization process. Examples of vinyl esters, which can be used in the preparation of the copolymer are vinyl propionate, vinyl acetate, vinyl caprate, vinyl laurate, vinyl stearate, and vinyl trifluoroacetate. Vinyl acetate is preferred.
It is desirable that the ethylene/vinyl ester copolymer has a melt flow rate of about 0.5 to about 50 grams per 10 minutes, preferably about 0.5 to about 10 grams per 10 minutes, and a vinyl monomer content of about 5 to about 40 percent by weight, preferably about 10 to about 35 percent by weight.
The ethylene and alpha, beta unsaturated carboxylate copolymer is also generally produced by a high-pressure radical polymerization process. Examples of the unsaturated carboxylates are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, cyclohexyl acrylate, lauryl acrylate, stearyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, stearyl methacrylate, glycidyl methacrylate, monomethyl maleate, monoethyl maleate, diethyl maleate, and monoethyl fumarate. The alkyl acrylates are preferred, particulary ethyl acrylate.
It is desirable that the ethylene/unsaturated carboxylate copolymer has a melt flow rate of about 0.5 to about 50 grams per 10 minutes, preferably about 0.5 to about 10 grams per 10 minutes, and a monomer content of about 5 to about 40 percent by weight, preferably about 10 to about 35 percent by weight.
In the very low density ethylene/alpha-olefin copolymer, the alpha-olefin generally contains about 3 to about 12 carbon atoms. Examples of the alpha-olefins are propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene. The copolymer is linear.
It is desirable that the linear very low density ethylene/alpha-olefin copolymer has a melt flow rate of about 0.5 to about 50 grams per 10 minutes, preferably about 0.5 to about 10 grams per 10 minutes, and a density of 0.860 to 0.910 gram per cubic centimeter.
The linear very low density ethylene/alpha-olefin copolymer can be prepared by using a Ziegler type catalyst system, a Phillips type catalyst system, or other conventional transition metal catalyst systems.
A Ziegler type catalyst system can be comprised of a transition metal compound such as titanium or vanadium compounds; a cocatalyst, e.g., an organometallic compound such as an organoaluminum compound; and a catalyst support such as an oxide of silicon, titanium, or magnesium. A Phillips type catalyst system can be comprised of a chromium oxide and a catalyst support such as an oxide of aluminum. Other conventional transition metal catalyst systems can be exemplified by molybdenum oxide and a catalyst support such as an oxide of aluminum.
The very low density ethylene/alpha-olefin copolymers can be produced under high-pressure (at or above 50 Mpa), medium pressure (10 to 50 Mpa) or low pressure (normal pressure, about 10 Mpa). The polymerization process is not particularly limited, and can be carried out by solution, suspension, slurry, or vapor phase processes.
The second component of the composition is (B) about 5 to about 50 percent by weight, preferably about 25 to about 45 percent by weight, of an ethylene/alpha-olefin copolymer having a melt flow rate of about of about 0.5 to about 50 grams per 10 minutes; a density of 0.860 to 0.935 gram per cubic centimeter; and a Mw/Mn ratio of up to about 3, said copolymer having been prepared with a single site catalyst. This copolymer is also linear.
The linear ethylene/alpha-olefin copolymer can be prepared by co-polymerizing ethylene with an alpha-olefin having 3 to 12 carbon atoms by using a single site catalyst having a catalytic active species with a constrained geometric shape. Examples of the alpha-olefins are propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and 4-methyl-1-pentene. Among them, 1-octene is preferable with respect to mechanical properties and processability.
Linear in the linear ethylene/alpha-olefin copolymers means a small amount of long-chain branching can be present.
The linear ethylene-alpha-olefin copolymer desirably has a melt flow rate of about 0.5 to about 50 grams per 10 minutes, preferably about 0.5 to about 10 grams per 10 minutes; a density of 0.860 to 0.935 gram per cubic centimeter, preferably 0.860 to 0.910 gram per cubic centimeter; and a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) determined by size exclusion chromatography of not more than about 3.0, and preferably not more than about 2.5.
The single site catalyst to be used for the polymerization of the ethylene/alpha-olefin copolymer is called a single site because its active points are a single species (single site). It is also called as metallocene or Kaminsky catalyst. Examples of these catalysts follows.
A transition metal compound expressed by formula (i):
(Cp)
m
MR
n
R′
p
(i)
wherein Cp is an unsubstituted or
Hayashi Akio
Horita Katsuhiro
Ishihara Koji
Bresch Saul R.
Hoke Veronica P.
Nippon Unicar Company Ltd.
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