JPH054479B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for effectively removing water from wet sheets of fibrous material in the press section of a paper machine. In particular, the present invention relates to the manufacture of belts for wide nip presses and methods of making the same.

BACKGROUND OF THE INVENTION The effective removal of water from wet sheets of fibrous material (dewatering) in the press sections of modern paper machines is an important factor in the economical production of paper. In the past, various approaches have been taken to this dewatering process, and various press designs and improvements have been made to the press fabrics or felts used to absorb water from the wet sheet. The goal of the above approach is to remove as much water as possible from the sheet before it reaches the drying section of the paper machine. In the drying section, heat is applied to the sheet to remove residual moisture. Therefore, the more water is removed in the press section, the less residual moisture will have to be removed by heating and evaporation in the drying section. In this way, the cost associated with the heating is reduced, and the production equipment can be operated economically to produce paper.

The press section of a paper machine consists of a series of double rolls between which the wet fibrous sheet is passed either supported on one absorbent felt or sandwiched between two absorbent felts. I am forced to do it. The area between the two rolls is called the nip, where the felt and wet fibrous sheet are compressed together so that the water squeezed from the sheet is absorbed into the felt.

Because of the limited size of the nip, dwell time, or time spent by the felt and wet fibrous sheet, is low. Accordingly, the press section of many paper machines generally consists of a series of banks of press rolls, which remove a sufficient amount of water from the sheet before it reaches the drying section.

Additionally, methods to improve dewatering include punching holes or forming grooves in the surface of the press roll to provide passageways for water from the felt. This method reduces rewetting of the sheet exiting the nip. Another improvement is that suction can be drawn from within the perforated press rolls to further increase the amount of water removed from the felt and sheet. This device is called a suction press.

Another approach to removing large amounts of water in the press section is to increase the dwell time in the press nip. This is done by coating the press rolls with an elastic compressible material, which causes the nip to widen slightly when the two press rolls are compressed. Since the length of the wet sheet to cover this slightly larger distance becomes longer, the dwell time becomes longer.

However, the greatest increase in dwell time is achieved through the use of a wide nip press. Here, one of the two rolls in the conventional press is replaced by a pressure shoe. This shoe is typically wider than the press roll in the cross-machine direction. The side of the shoe facing the press roll is a concave cylindrical surface and has approximately the same radius as the roll. As the shoe approaches the roll, a narrow gap is formed between the spinning roll surface and the fixed concave surface of the shoe. By using a suitably sized shoe, the length of this gap is significantly greater than in the nip of a conventional two roll press. Therefore, by passing the felt and wet fibrous sheet through this gap, a greater dwell time is obtained and more water is removed from the sheet.

However, there are potential problems with this press. Since the surface of the shoe is not movable, friction between the surface and the felt results in felt wear. To alleviate this problem and reduce damage to the felt due to friction, special belts are run between the surface of the shoe and the felt. This belt is lubricated on the side in contact with the shoe and has a surface running in the same direction as the felt. Since the felt moves along the nip with this belt and does not slide against the shoe, there is little wear and tear on the felt due to friction.

SUMMARY OF THE INVENTION The present invention provides a special belt for use in wide nip presses and a method for making the belt. It is an object of the present invention to make this special belt economical, requiring fewer steps than previously required, and making it possible to use previously unused polymeric materials as impregnating agents in the base fabric. The object of the present invention is to provide a means for manufacturing the above-mentioned special belt by a method. The base fabric is impregnated to prevent the lubricating liquid on the side of the belt that contacts the surface of the shoe from penetrating and staining the wet sheet and felt.

The present invention uses a large heated platen press consisting of two opposing platens and a special insert plate. The base fabric of the belt is provided in endless form and is arranged like a sleeve around the insert plate. The insert plate has at least the same width as the base fabric, and has approximately the same length and width as the upper and lower platens.

A sheet of uncured thermoset or thermoplastic polymer is placed between the inside of the base fabric sleeve and the insert plate. Pressure and heat are then applied by closing the platen press, thereby impregnating the base fabric with the polymer. If necessary, the polymer is further cured in this state.

After a suitable time, the platen press is opened and the fabric sleeve is rotated around the insert plate until the non-polymer impregnated areas of the fabric are located above and below the insert plate. A sheet of uncured polymer is then inserted in the same manner as above, and the process is repeated until the entire inner surface of the fabric sleeve is treated.

The above steps can be modified as appropriate. for example,
If a high degree of quality control is required, only one side of the insert plate is used. In this case, heat and pressure are applied to one of the two platens and the other platen is not heated. Alternatively,
The polymer sheet can be applied not only to the inner surface of the base fabric, but also to both sides.

There are many advantages to the belt and method of making it. By using a platen press and insert plate to produce the special belt, the final product can be obtained without having to rework the internal surfaces during production. In addition, coatings apply polymers to the surface of the base fabric (this
This eliminates the need for subsequent hardening and polishing, which is done in conventional methods. As a result, equipment costs are saved, process times are reduced, and a belt is obtained that is superior to conventional belts. The uniformity of the resulting belt thickness can be easily controlled by maintaining constant spacing between the insert plate and the upper and lower platens. Also, by using insert plates and/or platens with non-smooth surfaces, it is possible to produce belts with non-smooth ridges, grooves, or other surface features.

[Examples] Examples of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a heated platen press having an upper platen 1 and a lower platen 2 is used in the method for manufacturing the special belt of the present invention. An insert plate 3 is arranged in the space between the upper platen 1 and the lower platen. In this embodiment, the surfaces of these platens have linear dimensions and areas.
The upper and lower surfaces of the insert plate 3 facing the platen have the same dimensional parameters. Furthermore, both the platens 1, 2 and the insert plate 3 have a width at least equal to the width of the belt to be manufactured.

The base fabric 4 for the belt is supplied in endless form and is attached to the insert plate 3 and the upper platen 1.
and the lower platen 2 in a sleeve-like manner around the insert plate. The base fabric 4 is a single layer or multilayer weave of polyester monofilament, woven in a pattern with sufficient openings to allow complete impregnation and coverage. This eliminates the formation of voids where the lubricant used between the belt and the shoe permeates through the belt and contaminates the felt and fibrous web. Furthermore, in the method of the invention, the base fabric 4 can be supplied in any desired length and no mandrel is required.

A roll 5 driven by a suitable means is positionally adjustable in the direction shown by an arrow 6, and the base fabric 4
is kept under tension and rotated intermittently. Uncured polymers (e.g. polyurethane)
No. 7 sheets are placed between both sides of the insert plate 3 and the upper and lower base fabric portions of the insert plate 3. The platen press is then closed by bringing the upper platen 1 and lower platen 2 closer together to compress the base fabric 4, polymer sheet 7 and insert plate 3 together. The pressure and heat from the platen press melts the polymer sheet 7 and transfers this liquefied material into and around the textile structure of the base fabric 4. In this process,
Curing of the polymer also takes place.

Thereafter, the platen press is opened by separating the upper platen 1 and the lower platen 2.
Next, the base fabric 4 is advanced using the roll 5 so that the areas of the base fabric 4 to which the polymer sheet 7 is not attached are located above and below the insert plate 3. Then, a new polymer sheet 7 is inserted between the upper and lower sides of the insert plate 3 and the portions of the base fabric 4 above and below it. At this time, the sheet has been properly and quickly joined with the pressed sheet, and the above pressing process is repeated.

The above steps are repeated until the inner surface of the base fabric 4 has been completely treated to produce the special belt of the invention.

As mentioned above, it is also possible to produce wide nip press belts with grooved, uneven, or other surface textures that are not completely smooth. This can be achieved by using corresponding surface textures as insert plates and/or platens. FIG. 2a shows a plan view of a smooth insert plate or platen for manufacturing smooth belts, and FIG. 3a shows a cross-sectional view thereof. A grooved belt is manufactured by using a grooved insert plate and/or platen with grooves 8, as shown in plan view in Figure 2b and in cross-section in Figure 3b. The uneven belt is also manufactured by using an insert plate and/or platen having protrusions 9, as shown in plan view in FIG. 2c and in cross-section in FIG. 3c. A variety of other surface textures are possible through the use of appropriate insert plates and/or platens in belt manufacture.

Those skilled in the art will appreciate that various modifications in the belt and its manufacture are possible without departing from the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the process of manufacturing a wide nip (shoe) press belt according to the present invention.
Figures 2a, 2b and 2c are top views of smooth, grooved and curved insert plates or platens, respectively;
Figures a, 3b and 3c are respectively
Figure 2b is a cross-sectional view of the insert plate or platen shown in Figures 2a, 2b and 2c; 1, 2: platen, 3: insert plate,
4: Base fabric, 5: Roll, 7: Polymer sheet,
8: Groove, 9: Protrusion.

Claims (1)

[Claims] 1. A method for manufacturing a belt used in a wide nip press of a paper manufacturing machine, which includes: (a) disposing a base fabric and an insert plate in a space between an upper platen and a lower platen of a platen press; (b) inserting a polymer sheet into a platen press having said insert plate and said base fabric; (c) closing said platen press onto said insert plate, polymer sheet and base fabric; (d) inserting said polymer (e) opening the platen press after a sufficient time to allow the polymer to melt and penetrate in liquid form into the base fabric structure; (f) inserting a polymer sheet into the platen press and splicing it with the previously pressed polymer sheet; (g) the entire length of the fabric belt being coated and impregnated with the polymer; A method for manufacturing a belt for a wide nip press, characterized in that the above steps (c) to (f) are repeated until the belt is 2. The method of claim 1, wherein said base fabric is supplied in endless form and is sleeved around said insert plate. 3 The base fabric is the first fabric on both sides of the platen press.
2. The method of claim 1, wherein the insert plate is maintained under tension by a roll and a second roll. 4. The manufacturing method according to claim 3, wherein the first roll and the second roll advance the base fabric. 5. The method of claim 2, wherein the polymer sheet is inserted between the upper and lower surfaces of the insert plate and the base fabric. 6. The method of claim 2, wherein the polymer sheet is inserted into a platen press on both sides of the base fabric. 7. The method of claim 1, wherein the base fabric is woven in an open pattern from polyester monofilament. 8. The method of claim 7, wherein the base fabric is a single layer weave. 9. The method of claim 7, wherein the base fabric is a multilayer weave. 10. The method of claim 1, wherein the polymer is polyurethane. 11. The method of claim 1, wherein the insert plate has a smooth surface. 12. The method of claim 1, wherein said upper and lower platens have smooth surfaces. 13. Claim 1, wherein the surface of the insert plate has a pattern that is pressed onto the surface of the belt.
manufacturing method. 14. The method of claim 1, wherein the surfaces of the upper and lower platens have a pattern that is pressed onto the surface of the belt.