Electrically insulating compositions of dielectric polymer, mica flakes and silicone resin

{
  "publication_number": "US3655565A",
  "country": "US",
  "kind": "A",
  "title": "Electrically insulating compositions of dielectric polymer, mica flakes and silicone resin",
  "abstract": "Compositions suitable as electrical insulation comprised of synthetic dielectric polymer, mica flakes having specific surface area of about 7 square meters per gram or greater and a minor amount of a silicone resin that is substantially compatible but not reactive with the polymer. The compositions can withstand high electrical voltages over extended periods of time (being extremely resistant to corona breakdown) and also have good mechanical properties (e.g., toughness, strength and flexibility).",
  "claims": [
    "2. A composition according to claim 1 wherein the synthetic dielectric polymer is a polyimide. from about five to 80 parts of mica flakes having a specific surface area of about 7 square meters per gram or greater dispersed in the polymer, from about 40 to 60 parts of mica flakes having a specific surface area of about 7 square meters per gram or greater dispersed in the polymer, from about 45 to 50 parts of mica flakes having a specific surface area of 10 to 100 square meters per gram dispersed in the polymer,",
    "3. from about 4.5 to 5.5 parts of a silicone resin that a. is substantially compatible with the polymer of (1), b. is substantially not reactive with the polymer of (1) under processing conditions used for the composition, c. has on the average at least five silicon atoms in each resin molecule, d. has on the average at least 0.1 branch for each silicon atom in the resin molecule, and e. has the formula where R is a monovalent hydrocarbon radical, X is a hydroxyl or alkoxy radical, the sum of n and m is less than 3, and m is less than 1. provided that components (1), (2) and (3) total 100 parts. from about five to 10 parts of a silicone resin that a. is substantially compatible with the polymer of (1), b. is substantially not reactive with the polymer of (1) under processing conditions used for the composition, c. has on the average at least five silicon atoms in each resin molecule, d. has on the average at least 0.1 branch for each silicon atom in the resin molecule, and e. has the formula where R is a monovalent hydrocarbon radical, X is a hydroxyl or alkoxyl radical, the sum of n and m is less than 3, and m is less than 1. provided that components (1), (2) and (3) total 100 parts. from about one to 20 parts of a silicone resin that a. is substantially compatible with the polymer of (1), b. is substantially not reactive with the polymer of (1) under processing conditions used for the composition, c. has on the average at least five silicon atoms in each resin molecule, d. has on the average at least 0.1 branch for each silicon atom in the resin molecule, and e. has the formula where R is a monovalent hydrocarbon radical, X is a hydroxyl or alkoxyl radical, the sum of n and m is less than 3, and m is less than 1. provided that components (1), (2) and (3) total 100 parts. A composition according to claim 2 wherein the mica has a specific surface area of from 10 to 100 square meters per gram.",
    "4. A composition according to claim 1 wherein the mica has a specific surface area of from 10 to 100 square meters per gram.",
    "5. A composition according to claim 1 in sheet form.",
    "6. An electrically insulating composition having high corona resistance comprising",
    "7. An electrically insulating composition having high corona resistance comprising",
    "8. A composition according to claim 7 wherein the polyimide is a reaction product of pyromellitic dianhydride and 4,4''-diaminodiphenyl ether."
  ],
  "cpc": [
    "H01B 3/04",
    "H01B 3/30",
    "H01B 3/306",
    "H01B 3/46",
    "Y10T 428/2911"
  ],
  "assignees": [
    "MINNESOTA MINING & MFG"
  ],
  "filing_date": "1970-01-07",
  "publication_date": "1972-04-11",
  "grant_date": "1972-04-11",
  "priority_date": "1970-01-07",
  "application_number": "US-3655565D-A",
  "family_id": "21695244",
  "citations": [
    "US2568004A",
    "US2809952A",
    "US2997776A",
    "US3440207A",
    "US3464950A",
    "US3487123A",
    "US3520845A"
  ]
}