Roll cover and roll
A roll cover and a roll in particular for use in a machine line for the production or processing of a fibrous web is provided, wherein the roll cover includes a radial outer functional layer which provides the surface of the roll cover in contact with the web, and wherein the functional layer has structural elements, in particular in the form of grooves and/or bores, wherein the functional layer is constructed of an elastomer material with a Poisson number greater than 0.4, between 0.45 and 0.5.
1 . A roll cover for a roll, the roll cover comprising:
a surface configured for being in contact with a web of fibrous material, the surface being formed by a radial outer functional layer, the radial outer functional layer including a plurality of structural elements and being composed of an elastomer material that has a Poisson's ratio greater than 0.4, a rubber material being used as the elastomer material, a hardness of the radial outer functional layer being greater than 10 Pusey & Jones (P&J) and less than 35 P&J, the rubber material having a rubber formulation based on hydrogenated acrylonitrile butadiene rubber (HNBR) or ethylene propylene diene rubber (EPDM).
2 . The roll cover according to claim 1 , wherein the roll cover is for the roll which is configured for being used in a machine for producing or processing the web of fibrous material, wherein the plurality of structural elements are at least one of a plurality of grooves and a plurality of bores.
3 . The roll cover according to claim 1 , wherein the plurality of structural elements includes a plurality of grooves each of which includes a groove width and a groove depth, and wherein a ratio of the groove width to the groove depth is less than or equal to 0.7.
4 . The roll cover according to claim 3 , wherein the ratio of the groove width to the groove depth is less than or equal to 0.5.
5 . The roll cover according to claim 1 , wherein the plurality of structural elements includes a plurality of bores each of which includes a bore diameter and a bore depth, and wherein a ratio of the bore diameter to the bore depth is less than or equal to 0.7.
6 . The roll cover according to claim 5 , wherein the ratio of the bore diameter to the bore depth is less than or equal to 0.5.
7 . The roll cover according to claim 1 , wherein the hardness of the radial outer functional layer is between 15 P&J and 50 P&J.
8 . The roll cover according to claim 1 , wherein the elastomer material is water-resistant, such that during 672 hours of storage at 70° C. in water with pH=7 a hardness of the elastomer material changes by a maximum of 5 P&J.
9 . The roll cover according to claim 8 , wherein the hardness of the elastomer material changes by 3 P&J or less.
10 . The roll cover according to claim 1 , wherein the elastomer material is acid-resistant, such that during 672 hours of storage at 70° C. in sulfuric acid (H 2 SO 4 ) with pH=1.5 a hardness of the elastomer material changes by a maximum of 5 P&J.
11 . The roll cover according to claim 10 , wherein the hardness of the elastomer material changes by 3 P&J or less.
12 . The roll cover according to claim 1 , wherein the elastomer material is alkali-resistant, such that during 672 hours of storage at 70° C. in caustic soda (NaOH) with pH=14 a hardness of the elastomer material changes by a maximum of 10 P&J.
13 . The roll cover according to claim 12 , wherein the hardness of the elastomer material changes by 5 P&J or less.
14 . The roll cover according to claim 1 , wherein a tensile stress value of the elastomer material changes by less than 10%, at 10% elongation (“module 10”, measured in a tensile test on an S1 or S2 strip according to DIN 53504) during 672 hours of storage at 70° C. in water with at least one of pH=7, 5 weight-% sulfuric acid, and 5 weight-% caustic soda.
15 . The roll cover according to claim 14 , wherein the tensile value of the elastomer material changes by less than 8%.
16 . A roll for a machine line for producing or processing a web of fibrous material, the roll comprising:
a roll core which is substantially cylindrical; and
a roll cover applied to the roll core, wherein the roll cover includes a surface configured for being in contact with the web of fibrous material, the surface being formed by a radial outer functional layer, the radial outer functional layer including a plurality of structural elements and being composed of an elastomer material that has a Poisson's ratio greater than 0.4, a rubber material being used as the elastomer material, a hardness of the radial outer functional layer being greater than 10 Pusey & Jones (P&J) and less than 35 P&J, the rubber material having a rubber formulation based on hydrogenated acrylonitrile butadiene rubber (HNBR) or ethylene propylene diene rubber (EPDM).