Wet paper web transfer belt

Abstract

The object of the present invention is to reduce the wear of the doctor blade applied to the wet paper web transfer belt and the wear of the guide rolls supporting the wet paper web transfer belt while maintaining the wear resistance of the wet paper web contacting surface and the machine contacting surface of the wet paper web transfer belt together with the adhesive and releasing properties of the wet paper web on the wet paper web contacting surface of conventional wet paper web transfer belts. This is achieved by a wet paper web transfer belt in which a polyurethane is integrated with a reinforcing base material comprising a wet paper web-side surface and a machine-side surface, at least the wet paper web-side surface of the reinforcing base material is embedded in the polyurethane, an outer circumferential layer comprising a wet paper web contacting surface is constituted by some of the polyurethane; wherein, at least the outer circumferential layer comprises a spherical filler.

Claims

1. A wet paper web transfer belt in which a reinforcing base material comprising a wet paper web-side surface and a machine-side surface and a thermosetting polyurethane are integrated with each other, at least the wet paper web-side surface of the reinforcing base material is embedded in the polyurethane, an outer circumferential layer comprising a wet paper web contacting surface is constituted by some of the polyurethane; wherein at least the outer circumferential layer comprises a spherical filler having a roundness of 0.7 or more, and the spherical filler comprising a plurality of spherical fillers selected from inorganic fillers.

2. The wet paper web transfer belt according to claim 1, wherein the specific surface area of the spherical filler is 10 m.sup.2/g or less.

3. The wet paper web transfer belt according to claim 1, wherein the spherical filler is only comprised in the outer circumferential layer.

4. The wet paper web transfer belt according to claim 1, wherein the content of the spherical filler is 10 wt % or more in relation to the total weight of the outer circumferential layer (the total weight of the polyurethane, the filler(s) and other additives).

5. The wet paper web transfer belt according to claim 1, wherein an average particle diameter of the spherical filler is 1.0 to 100 m.

6. The wet paper web transfer belt according to claim 1, wherein two or more types of fillers of different average particle diameter are combined.

7. The wet paper web transfer belt according to claim 1, wherein the reinforcing base material is a composite reinforcing base material in which short fibers have been intertwiningly integrated by needle punching with at least the machine-side surface of the reinforcing base material.

8. The wet paper web transfer belt according to claim 7, wherein an inner circumferential layer comprising a machine contacting surface is constituted by some of the short fibers integrated with the machine-side surface.

9. The wet paper web transfer belt according to claim 1, wherein an inner circumferential layer comprising a machine contacting surface is constituted by some of the polyurethane.

10. A wet paper web transfer belt in which a reinforcing base material comprising a wet paper web-side surface and a machine-side surface and a thermosetting polyurethane are integrated with each other, at least the wet paper web-side surface of the reinforcing base material is embedded in the polyurethane, an outer circumferential layer comprising a wet paper web contacting surface is constituted by some of the polyurethane; wherein at least the outer circumferential layer comprises a spherical filler having a roundness of 0.7 or more, and wherein the specific surface area of the spherical filler is 10 m.sup.2/g or less.

11. A wet paper web transfer belt in which a reinforcing base material comprising a wet paper web-side surface and a machine-side surface and a thermosetting polyurethane are integrated with each other, at least the wet paper web-side surface of the reinforcing base material is embedded in the polyurethane, an outer circumferential layer comprising a wet paper web contacting surface is constituted by some of the polyurethane; wherein at least the outer circumferential layer comprises a spherical filler having a roundness of 0.7 or more, and wherein two or more types of fillers of different average particle diameter are combined.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a sectional view showing a wet paper web transfer belt according to the present invention.

(2) FIG. 2 is a sectional view showing another embodiment of a wet paper web transfer belt according to the present invention.

(3) FIG. 3 is a sectional view showing another embodiment of a wet paper web transfer belt according to the present invention.

(4) FIG. 4 is a sectional view showing another embodiment of a wet paper web transfer belt according to the present invention.

(5) FIG. 5 is a sectional view showing another embodiment of a wet paper web transfer belt according to the present invention.

(6) FIG. 6 is a sectional view showing another embodiment of a wet paper web transfer belt according to the present invention.

(7) FIG. 7 are schematic diagrams showing a method for impregnating and layering a wet paper web transfer belt according to the present invention with polyurethane.

(8) FIG. 8 is a schematic diagram showing an example of the press part of a papermaking machine.

(9) FIG. 9 is a schematic diagram relating to a test device for evaluating wear.

BEST MODES FOR CARRYING OUT THE INVENTION

(10) Hereinafter, the embodiments of the present invention will be explained in detail while referring to the drawings. The present invention is a wet paper web transfer belt 1 used in the press part of the papermaking machine shown in FIG. 8. The wet paper web transfer belt 1 is an endless belt supported by guide rollers 8.

(11) FIG. 1 is a sectional view in the width direction (in the Cross Machine Direction: CMD) of the wet paper web transfer belt 1 according to the present invention. The wet paper web transfer belt 1 is constituted by integrating a reinforcing base material 24 and a polyurethane 25 by impregnating with the polyurethane 25 and by layering and curing the polyurethane 25 so that the reinforcing base material 24 comprising a wet paper web-side surface 22 and a machine-side surface 23 is embedded in the thermosetting polyurethane 25, and so that an outer circumferential layer 27 comprising a wet paper web contacting surface 26 and an inner circumferential layer 28 comprising a machine contacting surface 30 are formed by some of the water-impermeable resin 25. A spherical filler 29 is included in the polyurethane 25 constituting the outer circumferential layer 27.

(12) FIGS. 2 to 6 are sectional views in the width direction showing another embodiment of the wet paper web transfer belt 1 according to the present invention. A wet paper web transfer belt 1 shown in FIG. 2 is constituted by integrating a reinforcing base material 24 and a polyurethane 25 by impregnating with the polyurethane 25 and by layering and curing the polyurethane 25 so that the reinforcing base material 24 comprising a wet paper web-side surface 22 and a machine-side surface 23 is embedded in the polyurethane 25, and so that an outer circumferential layer 27 comprising a wet paper web contacting surface 26 and an inner circumferential layer 28 comprising a machine contacting surface 30 are formed by some of the polyurethane 25. A spherical filler 29 is included in the polyurethane 25 constituting the outer circumferential layer 27 and the inner circumferential layer 28 and the polyurethane 25 impregnating the reinforcing base material 24. In this way, due to the filler contained in the inner circumferential layer 28, it is possible to improve the wear resistance of the machine contacting surface 30 while also improving the crack resistance of the polyurethane.

(13) A wet paper web transfer belt 1 shown in FIG. 3 is constituted by integrating a reinforcing base material 24 and a polyurethane 25 by impregnating with the polyurethane 25 and by layering and curing the polyurethane 25 so that the reinforcing base material 24 comprising a wet paper web-side surface 22 and a machine-side surface 23 is embedded in the polyurethane 25, and so that an outer circumferential layer 27 comprising a wet paper web contacting surface 26, an intermediate layer 31 formed between the outer circumferential layer 27 and the wet paper web contacting surface 22 of the reinforcing base material 24, and an inner circumferential layer 28 comprising a machine contacting surface 30 are formed by some of the polyurethane 25. A spherical filler 29 is included in the polyurethane 25 constituting the outer circumferential layer 27. In this way, it is possible to prevent the wear of the reinforcing base material 24 due to a filler by not including a filler in the polyurethane 25 impregnating the reinforcing base material 24, the inner circumferential layer 28 and the intermediate layer 31 adjacent to the reinforcing base material 24.

(14) A wet paper web transfer belt 1 shown in FIG. 4 is constituted by integrating a composite reinforcing base material 32, in which short fibers 33 have been intertwiningly integrated by needle punching in a machine-side surface 23 of a reinforcing base material 24 comprising a wet paper web-side surface 22 and a machine-side surface 23, and a polyurethane 25 by impregnating with the polyurethane 25 and by layering and curing the polyurethane 25 so that the composite reinforcing base material 32 is embedded in the polyurethane 25, and so that an outer circumferential layer 27 comprising a wet paper web contacting surface 26 and an inner circumferential layer 28 comprising a machine contacting surface 30 are formed by some of the polyurethane 25. A spherical filler 29 is included in the polyurethane 25 constituting the outer circumferential layer 27. In this way, by using the composite reinforcing base material 32, it is possible to improve the strength of the wet paper web transfer belt, adjust the impregnation speed of the polyurethane during manufacturing and also improve operability.

(15) A wet paper web transfer belt 1 shown in FIG. 5 is constituted by integrating a composite reinforcing base material 32, in which short fibers 33 have been intertwiningly integrated by needle punching in a machine-side surface 23 of a reinforcing base material 24 comprising a wet paper web-side surface 22 and a machine-side surface 23, and a polyurethane 25 by impregnating with the polyurethane 25 and by layering and curing the polyurethane 25 so that at least the wet paper web-side surface 22 of the composite reinforcing base material 32 is embedded in the polyurethane 25, and so that an outer circumferential layer 27 comprising a wet paper web contacting surface 26 is formed by some of the polyurethane 25, and the inner circumferential layer 28 comprising a machine contacting surface 30 is formed by some of the short fibers 33. A spherical filler 29 is included in the polyurethane 25 constituting the outer circumferential layer 27. In this way, due to the use of short fibers in the inner circumferential layer 28, the flexibility of the wet paper web transfer belt is improved; the installation of the belt in a papermaking machine is made easy, while the wear of the guide rollers 8 is reduced.

(16) A wet paper web transfer belt 1 shown in FIG. 6 is constituted by integrating a reinforcing base material 24 and a polyurethane 25 by impregnating with the polyurethane 25 and by layering and curing the polyurethane 25 so that the reinforcing base material 24 comprising a wet paper web-side surface 22 and a machine-side surface 23 is embedded in the polyurethane 25, and so that an outer circumferential layer 27 comprising a wet paper web contacting surface 26 and an inner circumferential layer 28 comprising a machine contacting surface 30 are formed by some of the polyurethane 25. Two types of spherical fillers 29, 29 of different average particle diameter are included in the polyurethane 25 constituting the outer circumferential layer 27. In this way, by including two or more types of a spherical filler of different average particle size in the outer circumferential layer 27, it is possible to adjust with greater accuracy the surface wear properties and the wear of the doctor blade and the guide rolls together with the adhesive and releasing properties of the wet paper web on the wet paper web contacting surface 26.

(17) The reinforcing base material 24 is generally a fabric woven with a weaving machine, or the like, from warp and weft yarns; however, a grid-like structure made by superposing warp and weft columns can also be used.

(18) Examples of materials for the reinforcing base material 24 and the short fibers 33 include polyester (polyethylene terephthalate, polybutylene terephthalate, and the like), aliphatic polyamide (polyamide 11, polyamide 12, polyamide 612, and the like), aromatic polyamide (aramid), polyvinylidene fluoride, polypropylene, polyether ether ketone, polytetrafluoroethylene, polyethylene, wool, cotton, metal, and the like.

(19) Examples of alternative materials for the polyurethane 25 include thermosetting resins such as epoxy, acrylic, and the like, or thermoplastic resins such as polyamide, polyarylate, polyester, and the like; preferably urethane resin is used.

(20) The roundness (X) of the filler particles can be expressed by formula (1) below; wherein, A and C are respectively the particle projected area and the perimeter measured on an image taken of a filler particle by an electron microscope, B is the area of a perfect circle corresponding to the perimeter C, r is the particle radius, and is the circular constant.
X=A/B=A/(r.sup.2)=A/{(C/2).sup.2}=A/C.sup.2(1)

(21) The fillers 29, 29 according to the present invention have a roundness of 0.7 or more.

(22) Examples of materials for the spherical fillers 29, 29 include inorganic fillers such as silica, glass, calcium carbonate, iron, stainless steel, alumina, aluminum, zinc, tin, titanium and the like. The average particle diameter of the spherical fillers 29, 29 can be in the range from 1.0 m to 100 m. The specific surface area of the spherical filler 29 can be 10 m.sup.2/g or less.

(23) The amount of spherical filler varies according to the type of paper to be made and according to the papermaking conditions; however, in order to ensure the sheet adhesion properties, it is preferred to introduce, into the outer circumferential layer 27, 10 wt % or more of the filler in relation to at least the total weight of the outer circumferential layer (the total weight of the polyurethane, the filler(s) and other additives). Moreover, in order to prevent contamination in parts where lipophilic contaminants (from pitch, sizing agents, and the like) are abundant, it is necessary to make the surface hydrophilic by introducing a relatively large amount of filler; however, if the amount of spherical filler exceeds 60% of the total weight (the total weight of the polyurethane, the filler(s) and other additives), the wet paper web transfer belt becomes too hard and there is the risk of cracks occurring. Further, in parts where fine pulp fibers with high adhesiveness are used, there is the risk of malfunctioning occurring in which the fine pulp fibers adhere to the surface of the wet paper web transfer belt if too much filler is introduced. Consequently, the total amount of the spherical fillers 29, 29 in each layer is preferably 10 wt % to 60 wt % of the total weight of the layer (the total weight of the polyurethane, the fillers and other additives). Other additives such as pigments and anti-foaming agents can be appropriately added according to design.

(24) Thus, by adopting the above-described constitution in the wet paper web transfer belt 1, it is possible to reduce the wear of the guide rolls supporting the wet paper web transfer belt and the wear of the doctor blade applied to the wet paper web transfer belt, while maintaining the adhesive and releasing properties of the wet paper web on the wet paper web contacting surface of conventional wet paper web transfer belts together with the wear resistance of the wet paper web contacting surface and the machine contacting surface of the wet paper web transfer belt.

(25) Hereinafter, a specific example of a production method of a wet paper web transfer belt according to the present invention will be explained.

(26) FIG. 7 is a schematic diagram showing the layering of polyurethane of the wet paper web transfer belt 1 shown in FIG. 1. As shown in FIG. 7 (a), the reinforcing base material 24 is installed so that the machine-side surface 23 of the reinforcing base material 24 is in contact with the rolls 40, which are arranged in parallel. Then, the inner circumferential layer 28 of the wet paper web transfer belt 1 can be formed by coating polyurethane from a resin discharge opening 42 onto the wet paper web-side surface 22 of the reinforcing base material 24 while rotating the rolls 40, and by allowing the polyurethane to penetrate by a coater bar 41 from the wet paper web-side surface 22 of the reinforcing base material 24 to the machine-side surface 23 thereof and by curing the polyurethane (FIG. 7 (b)). The semi-finished product obtained in this step is installed so that the wet paper web-side surface 22 of the reinforcing base material 24 is in contact with the two rolls 40, which are arranged in parallel; then, the inner circumferential layer 28 of the wet paper web transfer belt 1 can be formed by coating polyurethane from the resin discharge opening 42 onto the machine-side surface 23 of the reinforcing base material 24 while rotating the rolls 40, and by layering the polyurethane onto the machine-side surface 23 of the reinforcing base material 24 by the coater bar 41 and by curing the polyurethane; it is also possible to perform this process by inversing the front and the back.

(27) Next, the outer circumferential layer 27 of the wet paper web transfer belt 1 can be formed by again coating polyurethane from the resin discharge opening 42 onto the wet paper web-side surface 22 of the reinforcing base material 24 while rotating the rolls 40, and by layering the polyurethane by the coater bar 41 and by curing the polyurethane (FIG. 7 (c)). Now, the wet paper web transfer belt 1 shown in FIG. 1 can be obtained by including the spherical filler 29 in the polyurethane constituting the outer circumferential layer 27. Further, the wet paper web contacting surface 26 and the machine contacting surface 30 of the wet paper web transfer belt 1 can be polished according to need and the desired surface roughness can be obtained.

(28) Moreover, the wet paper web transfer belts 1 shown in FIGS. 2 to 6 can be obtained by optionally setting the use of a polyurethane comprising the spherical fillers 29, 29, the constitution of the intermediate layer 31 not comprising the spherical fillers 29, 29, and the use of the composite reinforcing base material 32 as substitute for the reinforcing base material 24.

(29) Hereinafter, the present invention will be described by means of the Examples and Comparative Examples.

(30) The Reinforcing Base Material

(31) The reinforcing base materials of the wet paper web transfer belts according to Examples 1 to 6 and Comparative Examples 1 to 3 used the following constitution. Upper warp yarn: twisted monofilament of 2000 dtex made from polyamide 6 Lower warp yarn: twisted monofilament of 2000 dtex made from polyamide 6 Weft yarn: twisted monofilament of 1400 dtex made from polyamide 6 Weave: double warp weave of 40 upper/lower warp yarns/5 cm and 40 weft yarns/5 cm

(32) The Polyurethane

(33) The polyurethane of the wet paper web transfer belts of Examples 1 to 6 and Comparative Examples 1 to 3 was obtained by reacting a mixture of tolylenediisocyanate (TDI) and polytetramethylene glycol (PTMG), as urethane prepolymer, with dimethylthiotoluenediamine (DMTDA), as curing agent.

(34) In Examples 1 to 6, the wet paper web transfer belt shown in FIG. 1 was obtained by using the above-described reinforcing base material and polyurethane. Moreover, in Comparative Examples 1 to 3, the wet paper web transfer belt was produced by changing the filler shown in FIG. 1. The polyurethane curing conditions were identical for all wet paper web transfer belts; after curing the polyurethane, the wet paper web contacting surface was polished and the surface roughness Ra (arithmetic average surface roughness) of the wet paper web contacting surface was fixed at 3 m for all belts.

(35) The conditions of the spherical fillers included in the outer circumferential layer of the wet paper web transfer belts of Examples 1 to 6 and the conditions of the fillers included in the outer circumferential layer of Comparative Examples 1 to 3 are shown in Table 1.

(36) High-density polyethylene bar wear tests were carried out with the wet paper web transfer belts of Examples 1 to 6 and Comparative Examples 1 to 3 by using the device shown in FIG. 9. The amount of wear of the high-density polyethylene bars was evaluated by the weight loss of the high-density polyethylene bar and the samples were indexed by using the amount of wear of Comparative Example 3 as 100. The tests were carried out at a test speed of the device of 1400 m/min, a test duration of 12 hours, and a pushing pressure of 300 N/m of a square high-density polyethylene bar of 20 mm20 mm. The evaluated results of the wear test are shown in Table 1.

(37) TABLE-US-00001 TABLE 1 Wear Filler Percent- Average age of particle Comparative Mate- Round- diameter Amount Wear Examples rial ness (m) (wt %) index (%) Example 1 Silica 0.7 2.5 60 86 28-86 Example 2 Silica 0.7 2.5 30 60 19-60 Example 3 Silica 0.7 2.5 10 22 7.1-22 Example 4 Silica 0.7 1.0 10 23 7.4-23 Example 5 Silica 0.7 100 10 24 7.7-24 Example 6 Silica 0.7 2.5:25 = 10 24 7.7-24 1:1 Comparative Silica 0.6 2.5 60 310 Example 1 Comparative Silica 0.6 2.5 30 193 Example 2 Comparative Silica 0.6 2.5 10 100 Example 3

(38) As shown in Table 1, the wet paper web transfer belts of Examples 1 to 6 are transfer belts which can reduce the wear of a member brought into contact with the surface thereof and which reduce the wear of the doctor blade.

EXPLANATION OF THE REFERENCE CHARACTERS

(39) W: wet paper web, 1: wet paper web transfer belt, 2: closed-draw papermaking machine, 3: press part, 4: dryer part, 5, 6: press felt, 7: dryer fabric, 8: guide rolls, 9: shoe, 10: press roll, 11: shoe press belt, 12: press section, 13: shoe press mechanism, 14: suction roll, 22: wet paper web-side surface, 23: machine-side surface, 24: reinforcing base material, 25: polyurethane, 26: wet paper web contacting surface, 27: outer circumferential layer, 28: inner circumferential layer, 29, 29: spherical filler, 30: machine contacting surface, 31: intermediate layer, 32: composite reinforcing base material, 33: short fibers, 40: rolls, 41: coater bar, 42: resin discharge opening, 43: top roll, 44: bottom roll, 45: guide rolls, 46: high-density polyethylene bar, 47: shower