ROLL AND ITS USE

Abstract

The present invention relates to a roll for use in a manufacture of a fibrous web comprising cellulosic fibers. The roll comprises a roll body with a cylindrical surface, and a roll cover, which is arranged to cover the cylindrical surface of the roll body. The cover comprises a functional layer, which comprises a polymer matrix and filler particles embedded in the polymer matrix. The filler particles comprise hollow spherical particles of aluminium oxide, titanium oxide, zirconium oxide and/or silicon carbide, which hollow particles have a particle size of 200 m.

Claims

1. A paper or board machine roll for use in the manufacture of a paper or board web comprising cellulosic fibres, the roll comprising: a roll body with a cylindrical surface; a roll cover covering the cylindrical surface of the roll body; wherein the cover comprises a functional layer which comprises a polymer matrix and filler particles embedded in the polymer matrix; wherein the filler particles comprise hollow spherical particles made of a material selected from the group consisting of: aluminium oxide, titanium oxide, zirconium oxide and silicon carbide; and wherein the hollow spherical particles have a particle size of less than or equal to 200 micrometers.

2. The paper or board machine roll of claim 1, wherein at least 50 to 90% of the filler particles are hollow spherical particles.

3. The paper or board machine roll of claim 2 wherein at least 80% of the filler particles of the filler particles are hollow spherical particles.

4. The paper or board machine roll of claim 3 wherein at least 90% of the filler particles of the filler particles are hollow spherical particles.

5. The paper or board machine roll of claim 1 wherein the hollow spherical particles comprise a shell wall surrounding an internal closed cavity, wherein the shell wall has a thickness in the range of 1-50 m.

6. The paper or board machine roll of claim 5 wherein the shell wall has a thickness in the range of 2-25 m.

7. The paper or board machine roll of claim 1 wherein the hollow spherical particles have a particle size in a range of 5-40 m.

8. The paper or board machine roll of claim 1 wherein the hollow spherical particles have a hardness of greater than or equal to 7 Moh.

9. The paper or board machine roll of claim 8 wherein the hollow spherical particles have a hardness of greater than 8 Moh.

10. The paper or board machine roll of claim 1 wherein the hollow spherical particles are particles of aluminium oxide.

11. The paper or board machine roll of claim 1 wherein the polymer matrix of the functional layer is rubber, or thermosetting or thermoplastic polymer.

12. The paper or board machine roll of claim 11 wherein the polymer matrix of the functional layer is rubber, and wherein the functional layer comprises at maximum 40 weight-percent of hollow spherical particles.

13. The paper or board machine roll of claim 12 wherein functional layer comprises at maximum 25 weight-percent of hollow spherical particles.

14. The paper or board machine roll of claim 13 wherein the functional layer comprises at maximum 7.5 weight-percent of hollow spherical particles.

15. The paper or board machine roll of claim 11 wherein the polymer matrix of the functional layer is epoxy resin, and wherein the functional layer comprises at maximum 50 weight-percent of hollow spherical particles, embedded into the matrix.

16. The paper or board machine roll of claim 16 wherein the roll is a calender roll.

17. The paper or board machine roll of claim 11, wherein the polymer matrix of the functional layer is polyurethane resin and wherein the functional layer comprises at maximum 10 weight-percent of hollow spherical particles, embedded into the matrix.

18. The paper or board machine roll of claim 11 wherein the roll is a press roll, suction roll, sizer roll or a coater roll.

19. The paper or board machine roll of claim 1 wherein the polymer matrix of the functional layer further comprises at least one of, additional filler particles and additives.

20. The paper or board machine roll of claim 1 wherein the hollow spherical particles are surface modified.

21. The paper or board machine roll of claim 1 wherein in addition to the functional layer the roll cover comprises a base layer, which is arranged in contact with the roll surface and an optional intermediate layer, which is arranged between the functional layer and the base layer.

22. A roll in a paper machine, board machine, tissue machine or in a converting machine for a fibrous cellulosic web, the roll comprising: a roll body with a cylindrical surface; a roll cover covering the cylindrical surface of the roll body; wherein the cover comprises a functional layer which comprises a polymer matrix and filler particles embedded in the polymer matrix; wherein the filler particles comprise hollow spherical particles made of a material selected from the group consisting of: aluminium oxide, titanium oxide, zirconium oxide and silicon carbide; and wherein the hollow spherical particles have a particle size of less than or equal to 200 micrometers.

23. A method of forming or converting a fibrous cellulosic web comprising engaging a roll with a web within a paper machine, a board machine, a tissue machine or in a converting machine, the roll comprising: a roll body with a cylindrical surface; a roll cover covering the cylindrical surface of the roll body; wherein the cover comprises a functional layer which comprises a polymer matrix and filler particles embedded in the polymer matrix; wherein the filler particles comprise hollow spherical particles made of a material selected from the group consisting of: aluminium oxide, titanium oxide, zirconium oxide and silicon carbide; and wherein the hollow spherical particles have a particle size of less than or equal to 200 micrometers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Some embodiments of the invention are explained more closely in the following schematical non-limiting drawings.

[0045] FIG. 1 shows a nip roll arrangement in a paper or board machine.

[0046] FIG. 2 shows a more detailed view of a roll and roll cover.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] FIG. 1 shows a nip roll arrangement in a paper or board machine. Two parallel rolls 10, 20 are located adjacent to each other and form a nip N between them. One or both of the rolls 10, 20 may be loadable against each other. Rolls 10, 20 may be rolls of a calender, a press, a coater or a sizer. A web W of a paper or board is running through the nip N either unsupported or supported by a belt or felt. Both of the rolls have a metal body or shell 1 and at least one of them has a roll cover 2, made of polymer and arranged to enclose the metal body or shell 1.

[0048] FIG. 2 shows a more detailed view of a roll and roll cover. The cover 2 comprises at least a functional layer 3 which is the outermost layer of the cover 2 and provides the surface of the metal body 1 of the roll. During the manufacture of paper or board the functional layer 3 is in contact either with a fibrous web or a fabric supporting the fibrous web, and thus the functional layer is exposed to wear and the stress from the environment. The functional 3 layer comprises at least one filler and optionally reinforcing fibers.

[0049] Beneath the functional layer 3 there may be one or more intermediate layer(s) 4, which provide an adhering layer between the metal body 1 and the functional layer 3. The intermediate layer(s) 4 may further provide other tailored properties for the cover 2, for example in terms of grading hardness, thermal conductivity, etc. The intermediate layer(s) 4 may comprise fiber reinforcement. The one or more of the intermediate layer(s) 4 may further comprise at least one filler. The filler in the intermediate layer(s) may be the same as or different from the filler in the functional layer 3. In case of two or more intermediate layers, the filler in the individual intermediate layers may be the same or different. The amount of the filler in the intermediate layer 4 is preferably lower than the amount of the filler in the functional layer 3.

EXPERIMENTAL

[0050] Some embodiments of the invention are described in the following non-limiting examples, where cover compositions for calender rolls or sizer rolls were tested using varying filler compositions.

Examples 1-3

[0051] Three samples simulating calender roll covers were prepared. A resin composition comprising bisphenol-F epoxy resin, diethyl toluene diamine hardener and a filler was made. The resin composition was the same in all examples 1-3, only the filler type was varied as shown in Table 1.

[0052] Example 1 represents an embodiment according to the invention, while examples 2 and 3 represent comparative embodiments. In Example 1 the used filler comprised hollow aluminium oxide spheres having particle size of 5-40 m (supplied by Kit-Stroy SPb, Russia). In Comparative Example 2 the used filler comprised silica having a D50 particle size of 3 m (supplied by Sibelco, Finland) and in Comparative Example 3 the used filler comprised silicon carbide having a D50 particle size of 3 m (supplied by Saint-Gobain).

[0053] Each resin composition thus obtained was applied to aramide fiber sheet and laminate plates with thickness of 12 mm was built. The laminate plates were cured at a temperature of 150 C. for 8 hours. Several mechanical tests were performed to the laminate plates. The wear test was performed as a rubber wheel wear test slightly modified from standard ASTM G65 giving material loss in mm.sup.3/Nm. Other tests performed were hardness (H), measured as Shore D hardness, tensile strength (TS), elongation at break (E) and impact strength (IS), measured as Charpy impact test. The measured value for the embodiment according to the invention (Example 1) is given in Table 1 as an absolute value, while the values for the comparative examples 2 and 3 are given as a percentage in relation to Example 1. A positive percentage value for wear indicates that the surface is more prone to wear, which is undesired. Negative percentage values for hardness, tensile strength, elongation and impact strength indicate that the surface has lower strength properties, which is undesired.

Examples 4-5

[0054] Examples 4-5 compare the effect of material and hardness of the microsphere filler in a composite. Epoxy composition comprising bisphenol A epoxy resin, diethyl toluene diamine hardener and filler was applied on aramid fiber sheets in a similar way as described in examples 1-3.

[0055] Example 4 represents an embodiment according to the invention while Example 5 represents a comparative example. The laminate plate in Example 4 contains 25 w-% hollow aluminium oxide spheres with a particle size of 5-40 m (supplied by Kit-Stroy SPb, Russia). In Example 5 the hollow aluminium oxide spheres of Example 4 were replaced with the same amount of alkali aluminosilicate microspheres having a D50 particle size of 5 m and hardness of 7 Mohs Scale (supplied by 3M).

[0056] Surprisingly it was found that Example 4, i.e. an embodiment according to the invention, gave better performance over the comparative Example 5 for all tested properties. Thus, it may be assumed without wishing to be bound by a theory that it is not the spherical form of the particles alone which provides the improved performance for the roll cover. It seems that due to the hollow morphology of the particles the properties of the roll cover were improved.

Examples 6-8

[0057] Three samples simulating a sizer roll cover were prepared. A polyurethane composition was made by mixing PPDI-terminated polyether prepolymer, an amine hardener and a filler. The polyurethane composition was the same in all examples 6-8, only the filler type was varied as shown in Table 1.

[0058] Example 6 represents a comparative example, while Example 7 and Example 8 represent embodiments according to the invention. In comparative Example 6 the filler was calcined alumina with particle size of 3 m (supplied by Almatis). In Examples 7 and 8 the calcined alumina filler of Example 6 was replaced by hollow aluminium oxide spheres having particle size of 5-40 m (supplied by Kit-Stroy SPb, Russia). The obtained resin compositions with filler were mold-cast and post-cured at 130 C. for 20 hours. The wear test was performed as a rubber wheel wear test slightly modified from ASTM G65 giving material loss as mm.sup.3/Nm. The measured value for the comparative test is given as an absolute value in Table 1 while the values for the Examples 7 and 8 according to the invention are given as percentage in relation to Comparative Example 6. A negative percentage value for wear indicates that the surface is more resistant to wear, which is desired.

Examples 9-10

[0059] Acrylonitrile butadiene rubber with a carbon black content of about 70 phr and cured hardness of 85 Shore A was used as the test matrix for hollow aluminium oxide spheres having particle size of 5-40 m (supplied by Kit-Stroy SPb, Russia). By adding 5 w-% of hollow aluminium oxide spheres into the rubber composition the abrasion loss decreased by 30%. In Examples 9-10 the test method for wear was DIN 53516, giving abrasion loss in mm.sup.3.

[0060] It can be seen from the results in Table 1 that the improvements which are obtained by roll cover compositions comprising hollow aluminium oxide particles are on a surprisingly high level in all aspects. Especially, abrasive wear values showed good and unexpected improvement with all tested polymer types. It can be seen that the obtained improvement in abrasive wear was over 20%.

TABLE-US-00001 TABLE 1 Polymers, filler details and results for Examples 1-10. Alkali Standard Al.sub.2O.sub.3, alumino calcined hollow Silicate Wear, Polymer Al.sub.2O.sub.3, spheres SiO.sub.2, SiC, spheres, [mm.sup.3/ H, TS, E, IS, Example type [weight-%] [weight-%] [weight-%] [weight-%] [weight-%] Nm]/[mm.sup.3]* [ShD] [MPa] [%] [N/mm] 1 Epoxy 14 0.016 87 57.2 2.7 10.7 2(C) Epoxy 14 +32% 1% 19% 33% 30% 3(C) Epoxy 14 +23% 0% 17% 30% 36% 4 Epoxy 25 0.0072 89 104 2.8 28.4 5(C) Epoxy 25 +70% 2% 13% 7% 27% 6(C) PU 2.5 0.0067 7 PU 2.5 38% 8 PU 5.0 61% 9(C) Rubber 195* 10 Rubber 5.0 30% (C) = comparative example *= DIN abrasion

Examples 11-14

[0061] Four samples simulating a calender roll cover were prepared using an epoxy composition comprising bisphenol epoxy resin, diethyl toluene diamine hardener and a filler. The filler used was silicon carbide, hollow aluminium microsperes or their mixture. Used fillers and their amounts in Examples 11-14 are given in Table 2. In Comparative Example 11 only SiC was used as a filler. In Examples 12-14 SiC filler was gradually replaced by the hollow aluminium spheres, in portions of 50%, 75% and 100%.

[0062] The mechanical tests were performed in the same manner as for Examples 1-3, and the results are given in the same manner as for Examples 6-8, using the measured value for the Comparative Example 11 as an absolute value.

TABLE-US-00002 TABLE 2 Filler details and results for Examples 11-14. Al.sub.2O.sub.3 SiC, spheres, Wear Resin % of % of [mm.sup.3/ H, TS, E, IS, Example type the filler the filler Nm] [ShD] [MPa] [%] [N/mm] 11(C) Epoxy 100 0 0.0075 89.8 68.7 1.6 9.68 12 Epoxy 50 50 16% +1.6% 0% +6% +8% 13 Epoxy 25 75 19% +2.9% 12% 0% +1% 14 Epoxy 0 100 35% +2.0% +45% 38% +91% (C) = Comparative Example

[0063] It can be seen from the results in Table 2 that improvements may be obtained by roll cover compositions comprising hollow aluminium oxide particles almost in all aspects. Especially, abrasive wear values showed good and unexpected improvement.

[0064] When testing dynamic behavior in terms of tan-delta as a function of temperature it was found that a roll cover according to the invention and comprising hollow aluminium spheres behaved very similarly, almost identically to the SiC filled roll cover. Based on all the tests performed it can be concluded that all the basic properties of a roll cover were improved without compromises, which is rarely achieved by a single raw material alone.

[0065] Even if the invention was described with reference to what at present seems to be the most practical and preferred embodiments, it is appreciated that the invention shall not be limited to the embodiments described above, but the invention is intended to cover also different modifications and equivalent technical solutions within the scope of the enclosed claims.