Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Reexamination Certificate
1999-11-30
2001-07-24
Dawson, Robert (Department: 1712)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
C525S477000, C525S478000, C524S492000, C264S176100, C528S024000
Reexamination Certificate
active
06264865
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to a silicone rubber base compound for electrical wire coating, silicone rubber composition for electrical wire coating, and a process for the production of silicone rubber coated electrical wires.
Due to its superior heat resistance, cold resistance, weatherability, electrical characteristics, etc., silicone rubber has found many uses as a material for extrusion molding used for making tubing, tape, sheets, electrical wire coating, and the like. In the past, chlorinated organoperoxides, such as 2,4-dichlorobenzoyl peroxide and chlorobenzoyl peroxide, have been used as the curing agents for curing silicone rubber compositions using in such extrusion molding materials. However, the problem with silicone rubber compositions produced by adding these chlorinated organoperoxides is that they emit offensive odors in the process of curing and cause blooming on the surface of the moldings made of silicone rubber after curing. Blooming is a phenomenon where due to the gradual exudation of curing agent decomposition products on the surface of a molding its surface turns white. Silicone rubber compositions containing added bis(orthomethylbenzoyl) peroxide (Japanese Kokai (Unexamined) Patent Publication No. Sho 59{1984}-18758) and silicone rubber compositions containing added bis(paramethylbenzoyl) peroxide (Japanese Kokai (Unexamined) Patent Publication No. Sho 62{1987}-185750) as the curing agent have been suggested as a means to eliminate such problems. However the problem with these silicone rubber compositions is that their cure rate is slow and voids are liable to be generated in the silicone rubber and when these silicone rubber compositions are used as materials for electrical wire coating they have inferior electrical insulating properties, such as the increased frequency of arcing at high voltages. Although such problems are eliminated to a certain degree if the rate of output of the silicone rubber composition from the extruding machine is lowered and the heat curing time is made longer, the rate of production of silicone rubber coated electrical wires decreases resulting in the disadvantage of increased production cost.
The present inventors have arrived at the present invention as a result of in-depth investigations aimed at eliminating the above described problems. Namely, it is an object of the present invention to provide a silicone rubber base compound for electrical wire coating suitable for use as the main ingredient of a silicone rubber composition for electrical wire coating which is a silicone rubber coating material superior in moldability prior to curing and superior in electrical insulating properties after curing, a silicone rubber composition for electrical wire coating which is a silicone rubber coating material superior in moldability prior to curing and superior in electrical insulating properties after curing, and a process for the production of silicone rubber coated electrical wires.
SUMMARY OF INVENTION
A silicone rubber base compound for electrical wire coating such that when it is extruded using an extruding machine having a variable screw with an L/D=10 and a die with a diameter of 1 mm attached thereto at a barrel and head temperature of 70° C., the per-minute extruder output rate at a screw rotation speed of 100 rpm is not less than 1.2 times the extruder output rate at a screw rotation speed of 50 rpm, a silicone rubber composition for electrical wire coating obtained by compounding diacyl organic peroxide consisting of carbon atoms, hydrogen atoms, and oxygen atoms with the silicone rubber base compound for electrical wire coating, and a process for the production of silicone rubber coated electrical wire using the silicone rubber composition for electrical wire coating.
DESCRIPTION OF INVENTION
The present invention is a silicone rubber base compound for electrical wire coating, which is characterized in that when it is extruded using an extruding machine having a variable screw with an L/D=10 and a die with a diameter of 1 mm attached thereto at a barrel and head temperature of 70° C., the per-minute extruder output rate at a screw rotation speed of 100 rpm is not less than 1.2 times the extruder output rate at a screw rotation speed of 50 rpm, to a silicone rubber composition for electrical wire coating obtained by compounding a diacyl organic peroxide consisting of carbon atoms, hydrogen atoms, and oxygen atoms with said silicone rubber base compound, and to a process for the production of silicone rubber coated electrical wires.
The silicone rubber base compound for electrical wire coating of the present invention is the main ingredient of a silicone rubber composition for electrical wire coating and when it is extruded using an extruding machine having a variable screw with an L/D=10 and a die with a diameter of 1 mm attached thereto at a barrel and head temperature of 70° C., the per-minute extruder output rate at a screw rotation speed of 100 rpm is not less than 1.2 times, and, preferably, not less than 1.2 times and not more than 10 times, the extruder output rate at a screw rotation speed of 50 rpm. Here, if the per minute output rate at a screw rotation speed of 100 rpm becomes less than 1.2 times the output rate at a screw rotation speed of 50 rpm, a silicone rubber coating material superior in electrical insulating properties is not obtained. In addition, the extruding machine having a variable screw with an L/D of 10 and a die with a diameter of 1 mm attached thereto can be a device used in the testing or manufacture of silicone rubber coated electrical wires and may be either a testing device or a piece of production equipment.
The silicone rubber base compound of the present invention should satisfy the above described conditions and although there are no particular limitations concerning its type and such, it is preferable for it to have the composition described hereinbelow: (A) 100 parts by weight of an organopolysiloxane composition consisting of about 25 to 100 parts by weight of (A-1) organopolysiloxane polymer with a weight average molecular weight of less than 550,000 represented by the average unit formula R
a
SiO
(4-a)
/2, where R is a substituted or non-substituted monovalent hydrocarbon group, and a is a number of about 1.8 to 2.3, and 0 to about 75 parts by weight of (A-2) organopolysiloxane polymer with a weight average molecular weight of not less than 550,000 represented by the average unit formula: R
a
SiO
(4-a)
/2, where R is a substituted or non-substituted monovalent hydrocarbon group, and a is a number of about 1.8 to 2.3, and (B) about 10 to 100 parts by weight of fumed silica have a BET specific surface area of not more than 150 m
2
/g.
To explain the preceding in greater detail, the organopolysiloxane composition of component (A) is the main component of the base composition of the present invention, and the organopolysiloxane polymer comprising component (A-1) forming part of component (A) must have a weight average molecular weight of less than 550,000, and, preferably, within a range of 250,000 to less than 550,000. Such organopolysiloxane polymers are represented by the average unit formula: R
a
SiO
(4-a)
/2, where R is a substituted or non-substituted monovalent hydrocarbon group exemplified by alkyl groups such as methyl, ethyl, and propyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, butenyl, and hexenyl; aryl groups such as phenyl and tolyl; 3,3,3-trifluoropropyl, 2-phenylethyl, and 2-cyanoethyl. Also, a is a number of about 1.8 to 2.3. The molecular structure of this component is, preferably, substantially linear, but may be a structure having some branching. The weight average molecular weight of the organopolysiloxane polymer can be easily determined, for example, by gel permeation chromatography.
The organopolysiloxane polymer comprising component (A-2) must have a weight average molecular weight of not less than 550,000. In the same manner as the above described component
Baba Katsuya
Ota Kenji
Boley William F.
Cesare James L. De
Dawson Robert
Dow Corning Toray Silicone Company, Ltd.
Peng Kuo-Liang
LandOfFree
Silicone rubber base compound for electrical wire coating,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silicone rubber base compound for electrical wire coating,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silicone rubber base compound for electrical wire coating,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2548444