JPH0359189A - Dryer canvas for papermaking - Google Patents

Abstract

PURPOSE:To provide the title resistant-to-stain canvas causing little reduction in its air permeability after washing, so designed that among the warp and weft, at least such weft as to occur on the paper side consist of specific coated yarns prepared by coating the peripheral surfaces of filament yarns as the core yarns with a synthetic resin. CONSTITUTION:Among the warp and weft making up the objective dryer canvas, at least such weft 3 as to occur on the paper side consist of coated yarns prepared by coating the peripheral surfaces of filament yarns (e.g. polyester ones) as the core yarns 1 with a synthetic resin (e.g. nylon 66). The coated yarns have the following characteristics: (1) sectional area ratio of the coating part 2 to core part 1=(1:1)-(1:3);(2) thickness of the coating part 2: 0.1-0.3mm; and (3) the ratio of the minor axis to major axis for the section of the coated yarns: (1:1.2)-(1:2).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a dryer canvas for papermaking that is resistant to staining during use.

(Prior art) Dryer canvas for papermaking uses
j1! Due to the dirt and pitch, there is a lot of dirt during use,
In particular, multifilament, which is often used for weaving dry canvas, is prone to dirt, which reduces air permeability and partially changes drying efficiency, resulting in uneven moisture content on the paper surface. Various countermeasures have been taken, such as applying silicone coating to the surface of the fibers to make them water- and oil-repellent and to make them less likely to get dirty. The coating is easily removed by steam, and the effect is not long-lasting.

In addition, dryer canvas (
JP-A No. 6 O-80313) is also known, but this canvas is susceptible to stains on the thread surface.Although the stain-proofing performance is long-lasting, stains cannot be avoided due to long-term use, and stain prevention is also known. Increasing the amount of polysiloxane in order to increase the effect has the drawbacks of decreasing the strength of the monofilament and worsening its dimensional stability.

(Problems to be Solved by the Invention) As a result of a detailed study by the present inventors on stains caused by the use of dryer canvases for papermaking, they found that there are roughly two types of stains. One type is dirt that adheres to the thread surface and is mainly adhered to by the pitch in the bulb. This stain can be improved by modifying the surface of the fiber to make it less likely to stain as described above.

However, it has been discovered that another major cause of stains on the dryer canvas is the texture formed by the warp and warp yarns that make up the surface, as well as the pitch that gets between the multifilament yarns that make up the surface and the single fibers that make up the spun yarn. did. This pitch attracts various impurities from the paper surface due to the pressure during the drying process, and gradually becomes a large stain.

This dirt is pushed into the weave and interstices of single fibers by the contact pressure with the cylinder and grows until it becomes a clump with roots inside, causing variations in the moisture content of the paper surface and making it easy to wash. This is something that cannot be prevented by the above-mentioned conventional technology.

(Means for Solving the Problems) The present invention is a dryer canvas that is resistant to stains, has a monofilament-like surface, has no fiber gaps, and has a cross-sectional shape that is deformed by the fluid pressure during weaving, making it difficult to form a weave. This prevents pitch from entering the weave during the drying process.

That is, in the present invention, among the warp and weft yarns constituting the canvas, at least the weft yarns appearing on the paper side are made of a coated yarn in which the peripheral surface of the filament of the core is coated with a synthetic resin, and the core of the coated yarn is coated with a synthetic resin. and the cross-sectional area ratio of the covering part is 1:1 to 1:3, and the thickness of the covering part is 0.1 to 0.3.
mm, and the coated yarn has a cross-sectional minor axis to major axis ratio of 1:1.2 to 1:2.

The above-mentioned coated yarn is a multifilament or spun yarn whose outer periphery is coated with a synthetic resin. Examples of the synthetic resin include polyamide, polypropylene, polytetrafluoroethylene, polyhexafluoropropylene, and the like.

The core filament is a multifilament or spun yarn of synthetic fibers such as polyester, polyamide, and polypropylene, which are used in common dryer canvases for papermaking.

Some kinds of such coated yarns are commercially available, such as Multiplast (trade name, Bayer Japan Co., Ltd.), which uses polyester multifilament as the core and polyamide, polypropylene, tetrafluoroethylene, etc. as the covering part. There is.

Coated yarns are flexible because the covering part does not have a fiber structure, and the core part is multifilament or spun yarn, so it is easily deformed by the pressure of the reed during weaving and the tension of the warp threads. In addition, during the finishing process, tension is applied in the warp direction and heated, which causes it to be sandwiched between the warp threads and pressure is applied from above and below, causing it to deform into a flatter shape.

FIG. 1 is a cross-sectional view of the coated yarn used in the present invention. The core (1) is a multifilament or a large group of short fibers of spun yarn, and the covering part is formed by coating or melting the synthetic resin and extruding it together with the core through a nozzle and cooling.

This Koterad yarn is woven as a canvas weft,
When finished, it deforms into a flat shape as shown in Figure 2, and expands in the weft direction so as to close the weave between the warp and weft threads.

The cross-sectional area ratio of the core part (1) and the covering part (2) is 1:1 to 1:3
It is. If the cross-sectional area of the covering part is smaller than the cross-sectional area of the core part and the thickness of the covering part is less than 0.1 inch, it will not easily deform. Conversely, if the covering part is larger than three times the core part and the thickness is less than 0.1 square centimeters, it will not be easily deformed. If it is thicker than 31 m, the deformation of the weft yarns will be too large and the surface of the canvas will become uneven, which will have a negative effect on the paper surface during the papermaking process.

The cross-sectional areas of the core and the covering are S1 and S2, respectively, and the radius from the center of the core yarn is r! , r2, then S! =
When S, St/Sz□ff(rz2-rt")/πr+"l
-...-11). Now, the thickness of the covering part is 0.1
If mm, r2=rl+0.1
-- (2), so from (1) and (2) rl・0.
24. r2·0.34 is obtained, that is, the diameter of the core yarn at this time is 0.68 ml+.

Also, when S2/51=3, the thickness of the covering part is 0.3 mm.
If so, rl''o, 3.r2·0.6 can be obtained in the same way, and the diameter of the core yarn will be 1.211+a.

(Effect of the invention) In the dryer canvas of the present invention using such a core yarn, the weft on the side that touches the paper surface spreads out flatly, closing the weave, and the surface of the weft itself is smooth, making it difficult to get dirty. .

(Example) Example 1 A triple-weave dryer canvas shown in Fig. 3 was fabricated using a polyester multifilament (only the surface layer weft (3)) and a polyester multifilament (core).
(2,000 denier) coated yarn was woven using nylon 66 coated yarn. Coated yarn outer diameter 0
．． , 82 mm, a core diameter of 0.56 mm, and a coating thickness of 0.13 mm. Polyester multifilament (2,000 denier) was used for the other weft and warp yarns.

After weaving, the coated yarn was finished with a high tension of 5 kg/cm and a roll temperature of 180°C, and the major diameter was 0.
．． It was deformed into a flat shape with a length of 98a1m and a short axis of 0.73a+m.

Example 2 A dryer canvas was produced in the same manner as in Example 1 except for the coated yarn. The core of the coated yarn is polyester multifilament (1,000 denier), the coating is polytetrafluoroethylene, and the outer diameter is 0.
．． The diameter of the core was 0.4+am, and the thickness of the covering was 0.11 mm. The coated yarn after finishing similar to Example 1 has major diameters of 0.74 mm and 0.55 mm.
It was deformed into a flat shape.

Example 3 A triple weft dryer canvas shown in FIG. 4 was woven using coated yarns for the warp (4) of the surface layer and the weft (3) of the surface layer. The warp (4) had a core made of polyester multifilament (1,100 denier) and a covering part made of polyamide, with an outer diameter of 0.62 mm, a core diameter of 0.4 mm, and a covering part thickness of 0.11++v. The core of the weft (3) is polyester multifilament (2,000 denier)
The covering part is made of polytetrafluoroethylene with an outer diameter of 0.82mm, a core diameter of 0.6mm, and a thickness of the covering part of 0.11*m.
Met. Polyester multifilament (1,250 denier) was used for the other warps and wefts. After the same finishing process as in Example 1, the weft coated yarn has a length f! 0
0-98I1, it had been deformed into a flattened shape with a minor axis of 0.65.

Comparative Example 1 The same weft triple weave dryer canvas as in Example 1 was woven, except that polyester multifilament (1,200 denier) was used instead of the coated yarn. Even after the same finishing process as in Example 1, the weft cross section was hardly deformed.

A triple weave dryer canvas identical to that of Example 3 was woven except that polyester multifilament (1,250 denier) was used instead of the coated yarn. Even in the same finishing process as in Example 1, the weft cross section was hardly deformed.

Next, in order to compare the stain prevention effects of the dryer canvases of each of the above Examples and Comparative Examples, the dryer canvases were actually used in the drying process of the paper manufacturing process, and were tested at the initial stage, after 3 months of use, and after cleaning by high-pressure spraying of hot water. The air permeability of each was measured. The results are shown in Table-1.

Table 1 (Effects of the Invention) As is clear from the air permeability measurement results of the above examples, the dryer canvas according to the present invention shows less deterioration after 3 months of use and less adhesion of pitch and impurities during the papermaking process. It can also be seen that the air permeability after washing is close to that of the initial one, and that dirt can be easily removed.Especially, Example 2 using polytetrafluoroethylene has a good effect on dirt and washing. It shows.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an example of a coated yarn used in the present invention, and FIGS. 2, 3, and 4 are schematic cross-sectional views showing the structure of a dryer canvas according to an embodiment of the present invention. In the figure, (1) core section, (2) covering section, (3) surface layer weft, (4> surface layer warp).

Claims (1)

[Claims] Of the warp and weft yarns constituting the canvas, at least the weft yarns that appear on the paper side are coated yarns in which the peripheral surface of the filamentous body of the core is coated with synthetic resin, and the cross-sectional area ratio of the core portion and the coated portion of the coated yarn is is 1:1 to 1:3,
The thickness of the coating portion is 0.1 to 0.3 mm, and the ratio of the short axis to the long axis of the cross section of the coated yarn is 1:1.2 to 1.
: A dryer canvas for paper making characterized by: 2.