JPH11172593A - Functional epoxy silicone covering for clothing for paper-making machine and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart excellent stain-controlling performance to the cloth to be used in the paper making machine with a long-life durability that can retain staining prevention as long as the cloth is usable by coating the cloth with a silicone-epoxy resin. SOLUTION: Single-layer or multi-layer cloth of polyester which will be used in the steps of shape formation, pressing, drying and the like is coated with a resin composition containing an emulsion of silicone epoxy resin as a base and a curing agent or crosslinking agent by spraying or with a kiss-roll applicator in an amount of 0.1-10.0 wt.%, preferably 1.0-3.0 wt.% on the dry basis and is heat-treated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a woven fabric or cloth for papermaking machines, which has become less likely to become soiled by a durable coating. It has the durability until the life of the battery ends.

[0002]

BACKGROUND OF THE INVENTION Modern paper makers basically use very sophisticated paper machines for removing moisture from paper materials. Water or moisture is continuously removed in three parts or locations of the machine. In a first forming section, the paper material is placed on a moving forming cloth and the water is drained through the cloth to obtain a paper sheet or web containing about 18 to 25 weight percent solids. The web enters the fabric press section and passes over one or more nips (between rolls) on a moving press fabric to remove excess water and remove solids from about 36-50.
The sheet contains the weight percentage. The sheet is then transferred to the drying section of a papermaking machine, where the sheet is supported by a drying cloth in a steam-heated drying cylinder and contains about 92-96 percent solids. For a papermaking cloth for a papermaking machine, a different range of functions is required depending on where it is located on the papermaking machine, that is, whether it is located in a molding, pressing or drying portion.

[0003] The forming cloth used in the papermaking process is a papermaking cloth used in the sheet forming part of a papermaking machine. Molded fabrics are generally a combination, usually interwoven, of synthetic yarns, the woven structure being characterized by large open spaces between intersecting yarns. The forming fabric must retain large openings to remove moisture from the fiber slurry that overlies it.

[0004] Since the ability to remove moisture is an important function of the forming cloth, the forming cloth should have a large opening throughout its life. However, the openings in the cloth become smaller continuously over the lifetime. In addition to fiber slurries, paper pulp typically contains additives such as, for example, filter clay, pitch (resin content), and polymeric materials that close open fabric openings. Using recycled fibers, a significant amount of contaminants enter in the form of inks, adhesives, tars and polymeric materials, which also close the fabric openings. In addition, molded fabric designs now include multilayer fabrics, which are more susceptible to contamination issues.

[0005] Therefore, a cloth with higher resistance to contamination is desired. One solution is to use a yarn that is resistant to contamination in the structure of the fabric. However, the measures are not entirely satisfactory. The resistance to such yarn contamination is short-lived and poor. Another solution is to improve the resistance to contamination by coating or treating the papermaking cloth. This method is also not entirely satisfactory because of the short-lived resistance to contamination provided by the coating and the lack of advantage.

US Pat. Nos. 5,207,873 and 5,395,868 describe papermaking fabrics that are permanently resistant to soiling. The fabrics have been treated and coated with a solution containing tetrafluoroethylene, urethane copolymer and polyacrylamide as basic components. However, the coating as a whole is not effective for closing paper machines and is not permanent.

One problem with coatings or treatments is that the coating itself reduces the permeability of the fabric, thereby inhibiting the basic function of the molded fabric of removing moisture. Therefore, the coating applied to the molded fabric should be selected so as not to reduce the permeability as much as possible.

[0008]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a fabric for use in the forming, pressing and drying sections of a papermaking machine, wherein the resistance to contamination is maintained throughout its life. Those cloths (woven fabrics) are, for those skilled in the art, a closing for papermaking machines, and the terms are generally interchangeable. It is another object of the present invention to provide a durable coating that lasts for the life of the fabric. It is yet another object of the present invention to provide a coating that does not significantly affect the permeability of the fabric. The present invention further relates to a coating for a cloth for a papermaking machine, and aims at achieving the above-mentioned objects.

[0009]

SUMMARY OF THE INVENTION The present invention is a coated fabric for a papermaking machine which has very good resistance to contamination, which lasts for the life of the fabric. The present invention is also a method of coating a paper machine cloth to increase resistance to contamination. The coatings described herein can significantly improve the resistance of the fabric to contamination without significantly increasing the permeability of the fabric. That is, the present invention provides a thin, low weight coating that does not add extra weight to the fabric.

Investigations by the inventors have shown that a coating made of silicone-epoxy resin makes it possible to maintain the resistance to contamination for paper machine closings throughout the life of the fabric. As the silicone-epoxy coating (or coating material), a water-soluble mixture containing a silicon-epoxy resin is suitable. The silicone-epoxy resin is believed to adhere to the polyester or nylon threads that form the fabric. A suitable product of the silicone-epoxy resin composition is available from Deco Industries, Inc., Fort Edward, NY, USA under the trade name Weerron. Preferred is Wearlon 2020-98, a three component product comprising a silicone-epoxy based emulsion and a curing and cross-linking agent. These components can be mixed, applied to a cloth, or diluted if necessary, as the manufacturer states.

[0011] Fabrics having effective resistance to soiling have a coating containing from 5 to 50% solids by weight, the coating being from 0.1 to 10% by weight of the uncoated fabric.
Increase weight by 0%. The increasing weight percent is Is calculated.

In general, reducing the solids content of the coating or the weight added by the coating does not significantly impair the initial permeability of the coated fabric. Water is a preferred diluent for aqueous coating materials and can be used to reduce the solids content, ie, the weight gain. Solids content of 10-15% (weight percent,
(W / W) or fabrics with a 1 to 3% increase in weight retain much of the original permeability. That is, it is on the order of about 90-99% of the initial permeability, which is a preferable value. In other words, as a result of the coating, the permeability is only 1
Only a reduction of about 10%. The coating on the cloth is
It can be performed by the usual method, a method of dipping in a coating bath,
Coating by blade or bar, coating by squeegee, coating by transfer, spraying, contacting (kiss) or coating by roller, slot coating and brushing can be used. Contact roller (kiss roll)
The application according to 1) is effective. The coating may be a single application or a plurality of applications. Following the application, there is a step of removing excess material, followed by a step of drying or curing the coating based on the specifications of the manufacturer of the material. These methods and steps are well known to those skilled in the art. In addition, as a target of coating, any one-layer or multi-layer cloth can be applied.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples illustrate the invention and its applications.

Example 1 A three layer fabric consisting of polyester fibers was coated on its surface, but not all, with an aqueous solution of Wearon 2020-98. This aqueous solution is a silicon-epoxy coating material (49% solids by weight),
Available from Decora Industries of Fort Edward, New York, USA. The coating material was further applied by Binks # 7 spray gun (available from Binks Manufacturing Company, Franklin Park, Illinois, USA). The weight gain associated with the coating was 8.3% compared to the uncoated fabric. No parts of the belt were coated for control.

The fabric was mounted on a small paper machine and operated for three days. With this machine, old cardboard (OC
C) Paper made of 100% pulp. The machine speed is 460-670 m / min (1500-2200 f
t / min). A needle shower was used at 13.8 bar (200 psi) without any cleaning chemistry. After doing so, the cloth was removed and analyzed. The attached drawings relate to the appearance and condition of the removed fabric.

The cloth was cut and the sections were analyzed for contamination. FIGS. 1 and 3 are photographs of each section at 5 × magnification. Then, the photograph was subjected to a scanning operation by a computer to make it black and white. Convert the image to a bitmap file,
Image processing was performed using Microsoft Paintbrush, and the contaminated area was colored blue (FIGS. 2 and 4). Removing the black and white cloth image leaves only the blue color image.
The image is subjected to an image analysis program, the blue pixels are counted, and the percentage of the contaminated portion can be known. The results are as follows.

Sample% Contaminated Area 1 Uncoated 4.1 2 Coated 0.3 All areas of the coated fabric are more resistant to contamination than areas of the uncoated fabric. I understand.

Example 2 A wear-on 2020-98 silicone-epoxy coating material was applied to a plurality of fabrics at a solids content of 5-25% (wt%). The three coating materials were applied to the three layers of cloth with a kiss-roll applicator (roller applicator). Table 1 shows the composition of the coating material. The three samples separated from each other on the coated fabric were air permeable and weight gained before and after coating or application and averaged. For a coating material with a solids content of 15%, when dried, the weight gain due to coating is 11.18 g / m ² ,
It was equivalent to 2.7% of the weight of the uncoated fabric.

[0019]

Table 1% of solids 25% 15% 10% 5% Water (gallon) 48.98 69.39 79.59 89.80 Portion "A" (gallon) 40.82 24.49 16.33 8.16 Portion "X" (gallon) 2.04 1.22 0.82 0.41 Portion "B" (Gallon) 8.16 4.90 3.27 1.63 Total 100.00 100.00 100.00 100.00 One gallon is 3.7853 liters.

The coatings were left for a week to cure. Three samples were cut from each coated fabric for each coating and showered with high pressure shower for 8 hours (oscillating needle shower). The conditions are described below. Tables 2 and 3 show the data.
Shown in The mass in Table 2 is the weight of a 2 inch (0.0505 m) diameter sample taken from the cloth.

High Pressure Shower Condition Fabric Tension = 39 PLI 6.83 kN / m (PLI is pounds / inch) Fabric Size Tested = 107 "x 9" 27
2cm x 22.9cm Cloth speed on machine = 1500 feet / min 457
m / min Water pressure = 400 psig 27.6 bar (psi is pounds / square inch) Shower arm = 150 strokes / min The nozzles were separated by 1 inch along the shower arm length direction for uniform showering. . Demand for long lasting high pressure showers (in this case 8 psi at 400 psig)
Time), this test is a good measure of the durability of the coating.

Table 3 is based on the data of Table 2. Table 3 presents the data of Table 2 in terms of air permeability and weight gain for uncoated and coated fabrics. It includes data before and after high-pressure showering. When the coated fabric is showered, the coating may survive the high pressure shower, as the increase in air permeability and weight never returns to the original level of the uncoated fabric. I understand.

[0023]

Table 2 Belt Solids% Before Shower After Shower 0 Uncoated 544 544 7 5 532 529 5 10 523 526 3 15 519 521 1.25 125 512 512 Belt Solids% Before Shower After Shower 0 Uncoated 0.840 0.840 7 5 0.847 0.844 5 10 0.850 0.846 3 15 0.863 0.856 1 25 0.876 0.854

[0024]

[Table 3] Air permeability (decrease%) Belt Solid content% Before shower After shower 0 Uncoated --- --- 7.5 5 2.33% 2.82% 5 10 3.98% 3.37% 315 4.59% 4.35% 125.88% 3.49% Weight (increase%) Belt Solids% Before Shower After Shower 0 No Coating --------- 75 5 0.75% 0.44% 5 10 1.15% 0.71% 3 15 2.70% 1.90% 125 4.20% 1.59%

[Brief description of the drawings]

FIG. 1 is a photograph of an uncoated section showing the soiled cloth at 5 × magnification.

FIG. 2 shows an image of the FIG. 1 image processed to show contamination.

FIG. 3 is a photograph of a coated section showing the cloth contaminated at 5 × magnification.

FIG. 4 shows an image obtained by performing image processing on the image shown in FIG. 3 as in FIG. 2;

Claims (17)

[Claims] 1. A closing for a paper machine for use in any of the forming, pressing or drying parts of the paper machine, comprising at least one coating comprising a silicone-epoxy resin, said closing being resistant to contamination. Closing for paper machines. 2. The closing of claim 1 wherein said coating is a silicone-epoxy resin applied from a water-soluble mixture. 3. The closing of claim 1 wherein the weight gain of the coating when dried is 0.1 to 10.0% based on the weight of the closing. 4. The weight gain of the coating, when dried, is 1.0-3.0% based on the weight of the closing.
The closing of claim 1. 5. The closing of claim 1, wherein the coating is applied in at least two layers. 6. The closing of claim 1, wherein the coating applied to the closing is cured. 7. The closing is a one layer cloth.
The closing of claim 1. 8. The closing is a multilayer fabric.
The closing of claim 1. 9. A method of imparting resistance to contamination for a paper machine closing, comprising applying at least one layer of a silicone-epoxy resin to said closing. 10. The method of claim 9, wherein said coating is applied by spraying. 11. The method of claim 9 wherein said coating is applied with a kiss roll applicator. 12. The method of claim 9, wherein said coating is applied in at least two layers of application. 13. The method of claim 9, wherein said coating applied to said closing is cured. 14. The fabric of claim 9, wherein said fabric is a single layer fabric.
the method of. 15. The fabric of claim 9, wherein the fabric is a multilayer fabric.
the method of. 16. The method of claim 9, wherein the weight gain of the coating when dried is 0.1 to 10.0% based on the weight of the closing. 17. The method of claim 9, wherein the weight gain of the coating when dried is 1.0-3.0% based on the weight of the closing.