KR19990023136A - Papermaking Closing and Pollution Prevention Method - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a papermaker's fabric, and more particularly, to a papermaker's closure that maintains a desirable transmittance while being resistant to contamination by a coating having durability over the entire life of the fabric. The coating is made of silicone epoxy to provide antifouling over the life of the fabric.

Description

Papermaking Closing and Pollution Prevention Method

The present invention relates to a papermaking cloth (clothing) consisting of a fabric having a stain-proof function by a durable coating and a method for preventing the stain, the life of the coating is the same as the overall life of the fabric, while excessively limiting the permeability of the fabric. It doesn't.

Modern papermakers use highly precise paper machines, which are essentially a type of dehydrator that removes water from the paper feed. Water is removed sequentially in three stages or three sections in the paper machine. In the first section, the forming portion, the paper feed is laminated to a moving forming fabric and dewatered through the fabric to form a paper sheet or web having a solids of about 18-25% by weight. The web thus formed is conveyed to the next section, the press fabric portion, where sufficient dehydration is achieved by passing through one or more nip presses of the moving press fabric, resulting in a sheet having about 36-50% solids. This sheet is then returned to the drying section of the paper machine where the drying fabric holds the paper sheet in a heat or steam heat dryer to obtain about 92-96% by weight of solids.

The papermaker's fabric must perform a number of functions, namely forming, pressing and drying, depending on the position of the papermaker.

The forming fabric used in the papermaking process is a kind of papermaking fabric used in the forming portion of the papermaking machine. The forming fabric is generally composed of synthetic yarns that are joined together by weaving, and the construction of the fabric is characterized by a large degree of open space between the crossing yarns. The forming fabric must maintain great openness to facilitate dehydration from the laminated fiber slurry.

Dehydration capacity is an important function in forming fabrics, so it is necessary to maintain high openness until the end of life.

However, the opening of the fabric continues to decrease over time. In addition to fiber slurries, paper pulp typically contains additives such as filled clays, pitches, and polymeric materials, which serve to block the open space of the fabric. Even when using recycled fibers, significant amounts of contamination occur in the form of inks, deposits, tars, and polymers, which also act to block the open space of the fabric. In addition, the forming fabrics are currently designed in multiple layers and more susceptible to contamination.

Therefore, it is desirable to improve the antifouling force on the fabric. As a solution for this, a technique of using an antifouling yarn in the fabric structure has been proposed. However, this proved to be less than satisfactory overall in that the antifouling function provided by the yarn was too short and inefficient. Another solution proposed is to coat the papermaker's fabric to prevent contamination. However, this method is also undesirable in that the antifouling function provided by the coating is too short and inefficient.

US Pat. Nos. 5,207,873 and 5,395,868 disclose papermaking fabrics that have a permanent protection against adhesion of contamination. This fabric is coated with a solution consisting mainly of tetrafluoroethylene, urethane copolymer and polyacrylamide. However, this coating proved to be totally ineffective or permanent against paper machine closing.

In general, a fundamental problem that arises in coatings, or treatment techniques, is that the coating itself reduces the permeability of the fabric, as is known, and consequently inhibits the dehydration ability, which is the main function of the forming fabric. Therefore, all of the coatings applied to the forming fabric have the important problem of suppressing the reduction in permeability as much as possible.

It is an object of the present invention to provide a papermaking closing made of fabric and used in the forming, pressing and drying parts of the paper machine, with improved antifouling over the life of the fabric.

It is another object of the present invention to provide a coating that maintains durability over the entire life of the fabric.

Another object of the present invention is to provide a coating in which the fabric does not significantly affect the transmittance.

Another object of the present invention is to provide a coating which can be used for papermaking fabrics and attains all of the above objects.

FIG. 1-Photograph shows a 5x magnification of the uncoated portion of the contaminated fabric.

FIG. 2-Computational diagram excluding the fabric from FIG. 1 to indicate contamination.

3-photographic representation of a five-fold magnification of a coating of contaminated fabric.

FIG. 4-Computer synthesized diagram excluding the fabric from FIG. 3 to indicate contamination.

The present invention relates to a coated fabric for use in paper machines, which provides a consistently enhanced antifouling ability over its entire life. In another aspect, the present invention provides an antifouling method of coating a fabric used in a paper machine to enhance antifouling ability. The coating formulation disclosed in the present invention substantially improves the antifouling ability to the fabric while hardly reducing the transmittance of the fabric, and does not significantly increase the mass of the fabric. That is, the present invention can provide a thin, low weight papermaking coating that limits the added mass to the fabric as much as possible.

Applicants have discovered that coatings comprised of silicone epoxy resins provide antifouling to papermaking closing over the entire life of the fabric. Suitable silicone epoxy coatings are aqueous mixtures containing silicone epoxy resins. Silicone epoxy resins are believed to bond with polyester or nylon filaments forming a closing. A suitable silicone epoxy resin line is available from Wearlin ^R under the trade name Decora Industries, Fort Edwards, NY. A preferred formulation is Wearlon ^R 2020-98, which is a three component formulation of silicone-epoxy based emulsions, curing agents and crosslinking agents. These ingredients are mixed in situ and applied to the fabric at the manufacturer's recommendation and can be diluted as needed.

An effective antifouling fabric will have its coating formulation containing 5% -50% solids by weight to weight and an added mass of 0.1% -10% by weight of the uncoated fabric. The added mass% is as follows.

Generally, when the solids content of the coating or the added mass of the coating decreases, the inherent transmittance of the coated fabric is maintained higher. The use of water as the preferred diluent for coating of aqueous bases reduces the solids content and consequently the added mass. Fabrics having a solids content in the range of 10% -15% (w / w) or an additive mass of 1% -3% have been found to maintain high levels of intrinsic transmission. That is, it is preferable to maintain the intrinsic transmittance about 90% -99%. In other words, as a result of coating, only about 1% -10% transmittance is reduced. The application method may be any conventional method such as immersion in a coating bath, blade or bar coating method, squeeze coating, transfer coating, spraying, kiss or applicator roll, slow applicator, brush applicator, and double kiss roll application is effective. It was. The coating may be applied once, or may be applied multiple times. A series of treatments require the removal of excess material and subsequent drying or curing, depending on the manufacturing characteristics of the coating material. These methods are already known by those skilled in the art.

Example 1

A portion of the surface of the three-layer forming fabric consisting of polyester filaments was coated with a WEARLON ^R 2020-98 silicone-epoxy coating (49% solids w / w) from Decora Industries, Inc., Fort Edwards, NY. The coating formulation was applied to a single layer with a Binks # 7 spray gun (Binks Mfg. Co., Franklin Park, Ill.). The excess liquid was removed by vacuum method. The added mass was determined to be 8.3% based on the weight of the uncoated fabric. The belt portion was not coated for use as a control.

The fabric was installed in a pilot machine and run for 3 days. The instrument was treated with pulp consisting of 100% OCC (old corrugated container), and the instrument speed ranged from 460-670 m / min (1500-2200 ft / min). The needle shower is 13.8 bar (200 psi) and no cleaning chemical is used. The fabric was removed and analyzed after the experiment. After removal, the appearance and condition of the fabric showed the following characteristics.

That is, contamination analysis was performed on the fabric portion. 1 and 3 are photographs of 5 times magnification for each part. The picture was input in gray color to the computer through a scanner, and the image was then converted into a bitmap file (bitmap file, * .bmp) and displayed with a Microsoft paintbrush program (see FIGS. 2 and 4). The contaminants were then colored blue. The gray fabric was removed from the burn leaving only the blue part. The image was then transferred to an image analysis program to count the blue pixels to find a contaminated area of a%. The results are as follows.

Sample Contaminated%

1. Uncoated 4.1

2. Coated 0.3

All areas of the coated fabric show increased antifouling compared to the uncoated areas.

Example 2

A silicone epoxy coating formulation of WEARLON ^R was applied to the fabric at a solids content ranging from 5% -25% (w / w). Three coatings were applied to the three layered fabric via a kiss roll applicator. The formulation composition is as shown in Table 1.

Three separate samples were taken for the coated fabric and the average was calculated by measuring the added mass according to air permeability and coating results. For coating formulations with 15% solids the added mass on drying was determined to be 11.18 g / m ² or 2.7 wt% based on the weight of the uncoated fabric.

The coating had a curing period of one week. Three samples from each fabric were cut for a given coating and a high pressure shower (oscillating needle shower) was added for 8 hours under the conditions described below. Table 2 and Table 3 show the data. As shown in Table 2, mass is the mass of the two-diameter sample taken from the fabric.

--High Pressure Shower Settings--

Fabric Tension = 39 PLI 6.83 kN / m

Fabric size

Experimented = 107 × 9 272cm × 22.9cm

Speed on the device

= 1500 ft./min 457 m / min

Water pressure

= 400 psig 27.6 bars

Shauer cancer

= 150 strokes / min

The nozzles were evenly spaced at one interval across the length of the shower arm.

It was suitable as a test to measure coating durability due to the harsh environment and its duration (400 psig for 8 hours in this case) following the high pressure shower test.

Table 3 is based on Table 2. Table 3 shows the data in Table 2 for the items of air permeability change and added mass change between the uncoated fabric and the coated fabric exposed to both high pressure showers. It can be seen that after the exposure of the high pressure shower the coating remains intact since its air permeability and added mass do not return to the original level of the uncoated fabric in the coated fabric with the shower.

Solids% 25% 15% 10% 5% Water (gallons) 48.98 69.39 79.59 89.80 Part A (gallons) 40.82 24.49 16.33 8.16 Part X (gallons) 2.04 1.22 0.82 0.41 Part B (gallons) 8.16 4.90 3.27 1.63 Sum 100.00 100.00 100.00 100.00

belt Solid% After coating before shower 1 week after coating 0 Uncoated 544 544 7 5 532 529 5 10 523 526 3 15 519 521 One 25 512 525 belt Solid% After coating before shower 1 week after coating 0 Uncoated 0.840 0.840 7 5 0.847 0.844 5 10 0.850 0.846 3 15 0.863 0.856 One 25 0.876 0.854

Transmittance (% decrease) belt Solid% After coating before shower 1 week after coating 0 Uncoated --- --- 7 5 2.33% 2.82% 5 10 3.98% 3.37% 3 15 4.59% 4.35% One 25 5.88% 3.49%

Mass (% increase)

belt Solid% After coating before shower 1 week after coating 0 Uncoated --- --- 7 5 0.75% 0.44% 5 10 1.15% 0.71% 3 15 2.70% 1.90% One 25 4.20% 1.59%

According to the configuration as described above, the present invention can provide a papermaking fabric that can have a deterrent and optimal transmittance at the same time until the end of the fabric life is preferably maintained dehydration capacity.

Claims (17)

Anti-contamination papermaking closure consisting of fabric coated with one or more layers containing silicone epoxy resin, used for forming, pressing and drying parts of paper machine The method of claim 1, And the coating layer is a silicone epoxy resin applied from an aqueous mixture. The method of claim 1, The dry mass addition of the coating is 0.1% -10.0% based on the mass of the closing. The method of claim 1, The paper mass closing of the coating is 1.0% -3.0% based on the mass of the closing when dried. The method of claim 1, And the coating is applied to at least two layers. The method of claim 1, The coating applied to the closing is a paper machine closing that is cured. The method of claim 1, Closing is a paper machine closing that is a single layer fabric. The method of claim 1, Closing is a paper machine closing that is a multilayer fabric. As a pollution prevention method for imparting pollution prevention power to paper machine closing, Applying at least one layer of silicone epoxy resin to a papermaking closing. The method of claim 9 The coating is sprayed method of pollution prevention. The method of claim 9, A method for preventing contamination where the coating is applied by a kiss roll applicator. The method of claim 9, A method for preventing contamination wherein the coating is applied in two or more layers. The method of claim 9, The coating applied to the closing is a method for preventing contamination. The method of claim 9, The fabric is a single layer fabric, pollution prevention method. The method of claim 9, The fabric is a multilayer fabric prevention method. The method of claim 9, The dry mass addition of the coating is 0.1% -10.0% based on the mass of the closing. The method of claim 9, The paper mass closing of the coating is 1.0% -3.0% based on the mass of the closing when dried.