(19)
(11) EP 0 272 497 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
31.01.1990 Bulletin 1990/05

(43) Date of publication A2:
29.06.1988 Bulletin 1988/26

(21) Application number: 87117570.9

(22) Date of filing: 27.11.1987
(51) International Patent Classification (IPC)4: H01B 3/52, H01B 3/30
(84) Designated Contracting States:
CH DE GB LI SE

(30) Priority: 28.11.1986 JP 283301/86
12.12.1986 JP 295790/86
24.12.1986 JP 309750/86
22.07.1987 JP 180926/87

(71) Applicants:
  • MITSUBISHI PAPER MILLS, LTD.
    Chiyoda-ku Tokyo 100 (JP)
  • HITACHI, LTD.
    Chiyoda-ku, Tokyo 101 (JP)

(72) Inventors:
  • Hyodo, Kenji
    4-1,Higashikanamachi,Katsushika-ku,Tokyo (JP)
  • Nozaki, Masaoki
    4-1,Higashikanamachi,Katsushika-ku,Tokyo (JP)
  • Ishizuka, Humihiko
    4-2,Marunouchi 3-chome,Chiyoda-ku,Tokyo (JP)
  • Ooe, Etsuo
    4026,Kujicho,Hitachi-shi,Ibaragi-ken (JP)
  • Tsukioka, Hideo
    4026, Kujicho,Hitachi-shi,Ibaragi-ken (JP)
  • Tani, Ichitaro
    4026,Kujicho,Hitachi-shi,Ibaragi-ken (JP)
  • Kamata, Yuzuru
    4026,Kujicho,Hitachi-shi,Ibaragi-ken (JP)
  • Endo, Kaoru
    4026,Kujicho,Hitachi-shi,Ibaragi-ken (JP)

(74) Representative: VOSSIUS & PARTNER 
Postfach 86 07 67
81634 München
81634 München (DE)


(56) References cited: : 
   
       


    (54) Low-dielectric constant press board for oil impregnation insulation


    (57) The present invention is directed to a low-dielectric constant press board for oil impregnation insulation which comprises a poly(4-methylpentene-1) fiber and/or a poly(3-methylbutene-1) fiber and a kraft pulp. This press board may be formed by first laminating the mixed wet sheets of the poly(4-methylpentene-1) fiber and/or the poly(3-methylbutene-1) fiber and the kraft pulp, and then heating/pressing the laminate integrally. In this case, the wet sheets of the kraft pulp (2) alone may be disposed over and under the mixed wet sheets (1), or over, under and between the mixed wet sheets. Further, the press board may additionally contain at least one selected from polyethylene terephthalate fibers and polyphenylene sulfide fibers in an amount of less than 28 wt%.






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