We Claim:
1. A rotor shaft supporting disc for a rotor-type open-end spinning machine, the rotor shaft supporting disc having a circumferential portion bonded and covered with a rubber member via an adhesive, wherein the rubber member comprises a rubber member that:
1) comprises a peroxide vulcanized rubber member obtained by subjecting one kind or
two or more kinds of rubbers or modified products thereof selected from the
following rubber materials (a) to (c) to peroxide vulcanization:
(a) a hydrogenated nitrile-butadiene rubber (HNBR) containing bound acrylonitrile at 18 to 44 wt%;
(b) a modified product having compounded therein 20 parts by weight or more to 120 parts by weight of zinc methacrylate and/or zinc acrylate with respect to 100 parts by weight of the hydrogenated nitrile-butadiene rubber (HNBR); and
(c) a modified product that comprises a hydrogenated carboxylated nitrile-butadiene rubber (HXNBR) obtained by subjecting a nitrile-butadiene rubber terpolymerized with 1 to 10 wt% of methacrylic acid and/or acrylic acid to hydrogenation; and
2) has Performance of being free frorn melting even at 400°C in a melting point
measurement method in conformity with one of JIS K0064: Test methods for melting
point and melting ränge of chemical products and melting point measurement
methods of United States Pharmacopeia (USP) and European Pharmacopoeia (EP),
and has a tan5, which is measured by a bending Vibration test mode in conformity
with one of JIS K7244-5 and ISO 6721-5 at an ambient temperature of 80°C and a
frequency of 60 Hz, of 0.15 or less.
2. The rotor shaft supporting disc for a rotor-type open-end spinning machine as claimed in claim 1, wherein the peroxide vulcanized rubber member has the following Performance in hardness:
a type A durometer hardness and a type D durometer hardness, each of which is
measured by a spring-type (durometer hardness) hardness measurement method in
conformity with one of JIS K6253, ISO 48, and ISO 7619 at 25°C, of 90° or more and 68°
or less, respectively. // n .

Claims:
4-T—A rotor shaft supporting disc for a rotor-type open-end spinning machine, the rotor shaft supporting disc having a circumferential portion bonded and covered with a rubber member via an adhesive,
Qr. Whereinf
-the rubber member comprises a rubber member that:
1) Comprises a peroxide vulcanized rubber member obtained by subjecting one kind or two or more kinds of nibbers or modified products thereof selected from the following rubber materials (a) to (c) to peroxide vulcanization:
(a) a hydrogenated nitrile-butadiene rubber (HNBR) containing bound acrylonitrile at 18 to
44wt%i
and/of
(b) a modified product having compounded therein 20 parts by weight or more to 120 parts by weight of zinc methacrylate and/or zinc acrylate with respect to 100 parts bv weight of the hydrogenated nitrile-butadiene rubber (HNBR); and
(c) a modified product that comprises a hydrogenated carboxylated nitrile-butadiene rubber (HXNBR) obtained by subjecting a nitrile-butadiene rubber terpolymerized with 1 to 10 wt% of methacrylic acid and/or acrylic acid to hydrogenation; and
(a) thereof to peroxide vulcanization; and
the rubber member is 2) has Performance of being free from melting even at 400°C in a melting point measurement method in conformity with one of JIS K0064: Test methods for melting point and melting ränge of chemical products and melting point measurement methods of United States Pharmacopeia (USP) and European Pharmacopoeia (EP), and has a tanS, which is measured by a bending Vibration test mode in conformity with one of JIS K7244-5 and ISO

6721-5 at an ambient temperature of 80°C and a frequency of 60 Hz, of 0.15 or less.
2^_A rotor shaft supporting disc according to claim 1, whcrcin thc modificd product comprises a rubber having compounded therein 20 parts by wcight or more to 120 parts by weight ofzinc methacrylate and/or zinc acrylate vvith respect to 100 parts by weight of the hydrogenated nitrile butadiene rubber.
3. A rotor shaft supporting disc according to claim 1, wherein the modified product comprises a hydrogenated carboxylated nitrile butadiene rubber (HXNBR) obtained by subjecting a nitrile butadiene rubber terpolymorized vvith 1 to 10 wt% of methacrylic aeid and/or acrylic aeid to hydrogenation.
2. The A rotor shaft supporting disc for a rotor-type open-end spinning machine as claimed in claim L according to any one of Claims 1 to 3, wherein the peroxide vulcanized rubber member has the following Performance in hardness: member has a type A durometer hardness and a type D durometer hardness, each of which is measured by a spring-type (durometer hardness) hardness measurement method in conformity with one of JIS K6253, ISO 48, and ISO 7619 at 25°C, of 90° or more and 68° or less, respectively.