Ramp for hard disc
A ramp having a surface hardness of 2.6 GPa or more, which is obtained by molding a polyacetal resin. Such a ramp made of a polyacetal resin is excellent in moldabilities, and an abrasion loss at the resin portion of the ramp is remarkably small when a hard disk is operated. Thus it is suitable as a ramp for housing and guiding a head within a hard disk drive.
1. A ramp which has a surface hardness of 2.6 GPa or more, and
which is obtained by molding a polyacetal resin, said polyacetal resin being selected from the group consisting of an oxymethylene homopolymer as obtained by the terminal stabilizing treatment of an oxymethylene homopolymer substantially comprising oxymethylene units, said oxymethylene homopolymer being produced by using as a raw material formic aldehyde monomer, or a cyclic oligomer; an oxymethylene copolymer as obtained by the terminal stabilizing treatment of an oxymethylene copolymer produced by using the above-mentioned raw material and a comonomer; an oxymethylene-oxyalcohol copolymer having a branched molecular chain structure; and an oxymethylene block copolymer comprising 50% by weight or more of polyoxymethylene (POM) blocks and 50% by weight or less of blocks of a polymer different from said POM.
2. A ramp according to claim 1 , wherein the polyacetal resin is a polyacetal copolymer.
3. A ramp according to claim 1 , having a shear stress of 1×10 6 to 1×10 7 when determined at a shear rate of 10,000(1/sec.) at a temperature of 210° C.
4. A ramp according to claim 2 , having a shear stress of 1×10 6 to 1×10 7 when determined at a shear rate of 10,000(1/sec.) at a temperature of 210° C.
5. A ramp according to claim 1 , having a shear stress of 1×10 6 to 6×10 6 when determined at a shear rate of 10,000(1/sec.) at a temperature of 210° C.
6. A ramp according to claim 2 , having a shear stress of 1×10 6 to 6×10 6 when determined at a shear rate of 10,000(1/sec.) at a temperature of 210° C.
7. A a ramp according to claim 2 , wherein the ramp is obtained by molding at a mold temperature of 75 to 135° C.
8. A a ramp according to claim 4 , wherein the ramp is obtained by molding at a mold temperature of 75 to 135° C.
9. A a ramp according to claim 6 , wherein the ramp is obtained by molding at a mold temperature of 75 to 135° C.
10. A ramp according to claim 1 , wherein the ramp has a surface hardness of 2.8 GPa or more.
11. A ramp according to claim 2 , wherein the ramp has a surface hardness of 2.8 GPa or more.
12. A ramp according to claim 6 , wherein the ramp has a surface hardness of 2.8 GPa or more.
13. A method according to claim 9 , wherein the ramp has a surface hardness of 2.8 GPa or more.
14. A ramp according to claim 1 , wherein the cyclic oligomer is trioxane or tetraoxane.
15. A ramp according to claim 1 , wherein the comononer is selected from the group consisting of ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,4-butanediol and a cyclic formal.
16. A ramp according to claim 15 , wherein the cyclic formal is a glycol formal or a diglycol formal.