POLYURETHANE ROLL COVER FOR CALENDER ROLL FOR PAPERMAKING MACHINE

1 . A calender roll for a papermaking machine, comprising:

a substantially cylindrical core; and

a cover circumferentially surrounding the core, the cover comprising:

a base layer circumferentially overlying the core; and

a topstock layer comprising polyurethane circumferentially overlying the base layer, the topstock layer being fiber-reinforced, the polyurethane having a glass transition temperature of between about 120 and 150° C., the topstock layer having a hardness of 70 to 90 ShD.

2 . The calender roll defined in claim 1 , wherein the polyurethane has a strain at failure of at least 7 percent.

3 . The calender roll defined in claim 1 , wherein the polyurethane is prepared from a mixture comprising an isocyanate, a catalyst and a hardener.

4 . The calender roll defined in claim 3 , wherein the isocyanate comprises MDI.

5 . The calender roll defined in claim 3 , wherein the isocyanate is included at a weight percent of between about 70 and 85 percent, and the catalyst is included at a weight prevent of between about 10 and 20 percent.

6 . The calender roll defined in claim 1 , wherein the topstock layer is reinforced with fiber selected from the group consisting of: glass, carbon, polyester, nylon, aramid, and combinations thereof.

7 . The calender roll defined in claim 6 , wherein the fiber comprises a filament or tape.

8 . The calender roll defined in claim 1 , in combination with a papermaking machine, wherein the calender roll is mounted in the calender section.

9 . A calender roll for a papermaking machine, comprising:

a substantially cylindrical core; and

a cover circumferentially surrounding the core, the cover comprising:

a base layer circumferentially overlying the core; and

a topstock layer comprising polyurethane circumferentially overlying the base layer, the topstock layer being fiber-reinforced, the polyurethane having a strain at failure of between about 7 and 12 percent, the topstock layer having a hardness of 70 to 90 ShD.

10 . The calender roll defined in claim 9 , wherein the polyurethane is prepared from a mixture comprising an isocyanate, a catalyst and a hardener.

11 . The calender roll defined in claim 10 , wherein the isocyanate comprises MDI.

12 . The calender roll defined in claim 10 , wherein the isocyanate is included at a weight percent of between about 70 and 85 percent, and the catalyst is included at a weight prevent of between about 10 and 20 percent.

13 . The calender roll defined in claim 9 , wherein the topstock layer is reinforced with fiber selected from the group consisting of: glass, carbon, polyester, nylon, aramid, and combinations thereof.

14 . The calender roll defined in claim 13 , wherein the fiber comprises a filament or tape.

15 . The calender roll defined in claim 9 , in combination with a papermaking machine, wherein the calender roll is mounted in the calender section.

16 . A calender roll for a papermaking machine, comprising:

a substantially cylindrical core; and

a cover circumferentially surrounding the core, the cover comprising:

a base layer circumferentially overlying the core; and

a topstock layer comprising polyurethane circumferentially overlying the base layer, the topstock layer being fiber-reinforced, wherein the polyurethane is prepared from a mixture comprising an isocyanate, a catalyst and a hardener, and wherein the isocyanate is included at a weight percent of between about 70 and 85 percent, and the catalyst is included at a weight percent of between about 10 and 20 percent; the polyurethane having a glass transition temperature of between about 120 and 150° C. and a strain at failure of between about 7 and 12 percent, the topstock layer having a hardness of 70 to 90 ShD.

17 . The calender roll defined in claim 16 , wherein the topstock layer is reinforced with fiber selected from the group consisting of: glass, carbon, polyester, nylon, aramid, and combinations thereof.

18 . The calender roll defined in claim 17 , wherein the fiber comprises a filament or tape.

19 . The calender roll defined in claim 16 , in combination with a papermaking machine, wherein the calender roll is mounted in the calender section.