Polyurethane roll cover for calender roll for papermaking machine

Abstract

A calender roll for a papermaking machine includes: a substantially cylindrical core; and a cover circumferentially surrounding the core. The cover comprises: 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.

That which is claimed is: 
     
         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.