ROLL COVER AND ROLL

Abstract

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.

Claims

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.

2. The roll cover according to claim 1, wherein the roll cover is configured for the roll which is configured for being used in a machine line 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, and wherein the Poisson's ratio is between 0.45 and 0.5.

3. The roll cover according to claim 1, wherein a polyurethane is used as the elastomer material.

4. The roll cover according to claim 3, wherein the polyurethane includes or is made from at least one polycarbonate polyol.

5. The roll cover according to claim 1, wherein a polyurethane is used as the elastomer material, the polyurethane including or being made from at least one of (a) at least one 0-tolidine diisocyanate (TODI) and (b) one paraphenylene diisocyanate (PPDI).

6. 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.

7. The roll cover according to claim 6, wherein the ratio of the groove width to the groove depth is less than or equal to 0.5.

8. 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.

9. The roll cover according to claim 8, wherein the ratio of the bore diameter to the bore depth is less than or equal to 0.5.

10. The roll cover according to claim 1, wherein a hardness of the radial outer functional layer is greater than 10 P&J.

11. The roll cover according to claim 10, wherein the hardness of the radial outer functional layer is between 15 P&J and 50 P&J.

12. The roll cover according to claim 1, wherein a tensile stress value of the elastomer material changes by less than 20%, at 10% elongation (module 10, measured in a tensile test on an S2 strip according to DIN 53504) during 96 hours of storage at 110? C. in water pH=7.

13. The roll cover according to claim 12, wherein the tensile stress value of the elastomer material changes by less than 10%.

14. 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.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0047] The present invention is further explained below, with reference to examples.

[0048] The examples specify some examples of elastomers suitable for use in a roll cover according to one aspect of the present invention. These are different polyurethanes. However, the present invention is not limited to these exemplary formulations.

[0049] The following table shows examples of 4 different types of polyurethanes. The first PU_PC is a PU on the basis of a polycarbonate polyol with an MDI as an isocyanate.

[0050] The other three PUs (TODI 1, 2 and 3) each use TODI and the same crosslinking agent as isocyanate but differ in the polyol used.

TABLE-US-00001 PU PC PU TODI 1 PU TODI 2 PU TODI 3 Isocyanate MDI TODI TODI TODI Polyol Polycarbonate Polyether Polycarbonate Polycaprolactone polyol polyol polyol Crosslink MCDEA 1.4-Butanediol 1.4-Butanediol 1.4-Butanediol Agent

[0051] The following table shows the measured module 10 values before and after storage and

[0052] compares them with a standard PU.

[0053] For all materials used, the Poisson's ratio is between 0.45 and 0.5.

TABLE-US-00002 Before storage After storage Loss [%] Standard PU 4.3 2.2 48.8% PU PC 3.4 2.8 17.0% PU TODI 1 4.9 4.5 8.3% PU TODI 2 4.9 4.5 7.9% PU TODI 3 4.1 3.9 5.6%

[0054] As the comparison of the PU PC with the standard PU shows, use of polycarbonate polyols is advantageous for Module 10 stability. Instead of a loss of almost 50% for standard PU, the loss for PU PC is significantly less than 20%.

[0055] It is also clear that the samples in which TODI were used as isocyanate show excellent results, almost regardless of the polyol used. The loss is less than 10% respectively. All these materials with a module 10 loss of less than 20%, especially less than 10%, are very beneficial for use in a roll cover according to one aspect of the present invention!

[0056] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.