JP3433275B2 - Dryer canvas for papermaking - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dryer canvas for papermaking, and more particularly, to a dimensional stability after heat setting of a canvas using a polyester monofilament yarn having a flat cross section and a large size, and a heat shrinkage ratio of the polyester monofilament yarn. The present invention relates to a dryer canvas which is improved by setting the value in an appropriate range.

[0002]

2. Description of the Related Art Dryer canvases for papermaking, which are used in the dry part of a paper machine, can be used as a dry part by increasing the ratio of waste paper as a raw material in the recent papermaking process and by using a filler for neutral papermaking. Since the amount of dirt attached to the canvas is increasing, for this reason, it is becoming more and more common to produce monofilaments having antifouling properties and excellent cleaning properties.

Further, in order to improve the surface smoothness, for example, monofilament yarns having a flat cross section have been used as warp yarns as shown in JP-A-54-77704. As the material of the monofilament yarn, a synthetic fiber yarn of polyethylene terephthalate (PET), which is a kind of polyester, is usually used.

By the way, recently, with the speeding up of paper machines and the promotion of energy-saving measures, the trend of the airtightness of the hood and the operation of high dew point has been further strengthened, and the atmosphere condition of the dryer part is more and more severe. Is becoming. That is, the steam pressure of the dryer part is set to be higher with the increase in the speed of the paper machine, and the dryer canvas for papermaking is exposed to high-temperature steam, which causes thermal deterioration in a relatively short period of time. There is a problem. In particular, the ears on both edges of the dryer canvas do not have wet paper intervening on the surface and are in direct contact with the surface of the heated dryer and are directly exposed to high-temperature steam, so the wet paper intervenes at the center. It was unavoidable that the rate of progress of heat deterioration was much faster than that of the main body. For this reason, it has been proposed that the material for forming the ear portion is made of polyethylene terephthalate (PET) and monofilament yarn such as aromatic aramid fiber or polyphenylene sulfide (PPS) fiber having a higher resistance to moist heat. For example, Japanese Utility Model No. 63-60499 and Japanese Utility Model No. 2-
No. 53997, a monofilament made of a highly heat resistant synthetic resin such as polyphenylene sulfide (PPS) or polyethylene ether terketone (PEEK) is used for at least a part of the warp forming the selvage of the dryer for papermaking. Have been described. Since these high heat resistant synthetic resins are more expensive than ordinary polyester resins, they are usually used only in the ears where there is a risk of thermal deterioration.

[0005]

When the dryer canvas is woven, the dryer canvas undergoes large expansion and contraction in the length and width directions due to the influence of heat, moisture, or canvas tension when used on a paper machine. In order to prevent dimensional changes as much as possible, heat setting is applied after weaving to give dimensional stability.

Generally, this heat setting process has a temperature of about 1
60 ° C to 180 ° C, and the size of the tension is 3 kg / cm to 1 kg /, depending on the tension used on the canvas.
It is selected from the range of cm.

When a polyester monofilament yarn having a flat cross section is used as a warp and the weaving is not relatively large in cross section, the heat shrinkage rate is 160 to 180 ° C.
There is no problem in terms of dimensional stability and the like even when weaving and heat-setting an ordinary polyester monofilament yarn having a ratio of about 3 to 6% under the conditions described in JP-A-54-77704.

However, when the cross-sectional dimension of the polyester monofilament yarn having a flat cross section becomes about 0.4 mm or more on the short side and / or about 0.6 mm or more on the long side, the dimension may be even after heat setting after weaving. It was found that sufficient stability could not be imparted.

This is because when the polyester monofilament yarn having a flat cross section has a normal heat shrinkage ratio as shown in FIG. 1, a monofilament yarn having a large cross sectional dimension is sufficient for the yarn even after heat setting. It was found that the reason is that it is difficult to attach such a crimp and dimensional stability is not obtained.

In order to provide a sufficient crimp, it is necessary to make the heat shrinkage rate of the polyester monofilament yarn having a flat cross section used for the warp higher than the usual value.

An object of the present invention is to optimize dimensional stability by heat-setting a polyester monofilament yarn having a flat cross section with a short side of about 0.4 mm or more and / or a long side of about 0.6 mm or more. To find the heat shrinkage.

[0012]

[Means for Solving the Problems] For the above-mentioned purpose, various examinations were conducted to find out how high the heat shrinkage ratio needs to be, and a trial weaving of canvas was performed. As a result, the cross section is flat and the short side is 0.
For the polyester monofilament yarn having a length of 58 mm and a long side of 0.88 mm, it was found that the one having the characteristic of the heat shrinkage ratio shown in FIG. This characteristic curve is 1
It exhibits a heat shrinkage ratio of about 9% or more between 60 ° C and 180 ° C.
Taking into consideration the air permeability and flexibility of the canvas, there is a problem in setting a too large heat shrinkage ratio. For example, a polyester monofilament yarn having a flat cross section with a short side of about 0.58 mm and a long side of about 0.88 mm is used. In case of about 160 ℃
It has also been found that it is desirable to have a heat shrinkage ratio of about 9% or more and about 14% or less between ˜180 ° C. However, the upper limit of this heat shrinkage ratio may be increased corresponding to the larger cross-sectional dimension of the monofilament yarn, and it is therefore desirable to determine the specific situation individually.

Incidentally, for polyester monofilament yarns having other short-side lengths of about 0.4 mm or more and / or long-side lengths of about 0.6 mm or more, it is sufficient in practice to use yarns having substantially the same characteristics. I was also able to confirm that I could attach a crimp.

That is, the warp of the dryer canvas is woven using a polyester monofilament yarn having a flat cross section and having a high heat shrinkage, and heat set to improve the surface property, and the dimensional stability is also sufficiently improved. I knew what to do.

Next, as described in Japanese Utility Model Laid-Open No. 63-60499 and Japanese Utility Model Laid-Open No. 2-53997, it was examined to use polyphenylene sulfide (PPS) monofilament yarn to reinforce the thermal deterioration of the ear portion. But,
When the polyester monofilament yarn having a flat cross section used for the warp of the canvas central body has a high heat shrinkage, the heat shrinkage of the PPS monofilament used for the selvage warp is related to this high heat shrinkage. Normal value (4.0% (160 ° C), 4.3% (180 ° C) when the cross-sectional flat dimension is 0.30 mm x 0.56 mm. When the cross-sectional flat dimension is 0.58 mm x 0.88 mm When the weaving is performed as it is and the heat setting process is performed, the selvage portion compresses in the running direction due to the relatively high heat shrinkage rate of the polyester monofilament yarn in the central body. In response, unevenness, wrinkles or streaks occur in the ears, and the central body and ears are shaped as a canvas.
It was found that there was a problem as a product because it was not uniform in terms of dimensions.

In that case, the heat shrinkage rate of the PPS monofilament yarn should be determined, and a canvas weaving or the like was conducted to further study.

As a result, in the case where the cross section is flat as in the case of the polyester monofilament yarn and the dimension is 0.58 mm in the short side and 0.88 mm in the long side, the one having the characteristic of the heat shrinkage ratio shown in FIG. 2 is optimal. It turned out to be 2 shows the characteristic of the heat shrinkage rate of the polyester monofilament yarn having a flat cross section, which has the same characteristic curve as that of FIG. As is clear from FIG. 2, when the heat-setting temperature is 160 ° C. to 180 ° C., the heat shrinkage rate of the polyphenylene sulfide (PPS) monofilament yarn having a flat cross section used for the warp of the selvage is The heat shrinkage ratio of flat polyester monofilament yarn is not lower than that.

In this case, it was also found that the heat shrinkage rate of the PPS monofilament yarn should be 9% or more between about 160 ° C and 180 ° C. This is about 1
This is because if it is less than 9% at 60 ° C to 180 ° C, it is difficult to obtain crimp even after heat setting and dimensional stability cannot be obtained. Further, when the heat shrinkage ratio of the PPS monofilament yarn is about 14% or more between 160 ° C. and 180 ° C., the heat shrinkage at the ears becomes large, and there is a problem in obtaining a uniform surface property of the entire canvas. , Preferably about 160 ° C
It has also been found that it is desirable that the heat shrinkage ratio of the PPS monofilament yarn between 180 ° C. is about 9% or more and 14% or less.

Next, the strength of the PPS monofilament yarn used for the selvage warp was examined. Generally, PPS monofilament yarn has a tenacity retention rate of 10 with respect to steam resistance.
Almost no deterioration occurs at 0%. On the other hand, the polyester monofilament yarn has a low tenacity retention rate depending on the use conditions. Therefore, the strength of the PPS monofilament thread at the time of manufacturing the product is not necessarily required as much as the strength of the polyester monofilament thread. Therefore, I first investigated what the strength was like when I finished using the canvas. As a result, the strength of the ears is 100k on average, judging from the service life of the canvas (about half a year to about one year).
It has been found that g / 3 cm or more is sufficient.

When the case where the warp density is 29.0 yarns / 2.54 cm (same as the example described later) is examined, the required strength per PPS monofilament yarn is 2.94 kg, and the cross-sectional dimension is 0.58 mm × 0. 88mm,
The required strength is 0.48 g / d (denier). However, if the strength is too low, weaving may not be successful. As a result of trial weaving and so on, we found that at least 2 g / d (denier) was required for weaving without causing problems.

As a result, the strength of the PPS monofilament yarn should be 2 g / d or more.

On the other hand, the strength of the polyester monofilament yarn used for the central body of the canvas is generally about 4.45 g / d (denier). Therefore, considering the strength ratio of the PPS monofilament yarn having a flat cross section used for the warp of the selvage and the polyester monofilament yarn having a flat cross section used for the warp of the central body, the PPS monofilament yarn is calculated based on the above numerical values. The strength of the polyester monofilament yarn is (2.0 g / d ÷ 4.45 g / d) × 100
(%) = 45%. In other words, it is sufficient that the PPS monofilament yarn of the selvage warp is 45% or more of the warp yarn of the central body.

In summary, in order to solve the above-mentioned problems, the present invention firstly requires that the cross-sectional dimensions of the polyester monofilament yarns in a paper-making dryer canvas are woven using polyester monofilament yarns having flat cross-sections as warp yarns. The short side was set to 0.4 mm or more and / or the long side was set to 0.6 mm or more, and the heat shrinkage ratio of the polyester monofilament yarn was set to 9% or more and 14% or less between 160 and 180 ° C.

Secondly, in the ear-reinforced dryer canvas, a part or all of the warp yarns of the ear portion is made of a polyphenylene sulfide monofilament yarn having the same flat cross-sectional dimension as the polyester monofilament yarn and the polyphenylene. the thermal shrinkage rate of the sulfide monofilament yarn, between 1 60 to 180 ° C, equal to or thermal shrinkage of the polyester monofilament yarn, or a polyester monofilament yarn heat shrinkage or more.

Thirdly, the strength of the polyphenylene sulfide monofilament yarn having a flat cross section used for the warp of the selvage is set to 45% or more of the strength of the polyester monofilament yarn used for the warp of the central body.

[0026]

[Action] the thermal shrinkage of the polyester monofilament yarn
1 60 to 180 of the high-rate than conventional in between ° C to about 9
Since it is set to be not less than%, the crimp due to the heat setting process is sufficiently imparted and the shape stability is enhanced.

When a polyphenylene sulfide monofilament yarn, which is a moist heat resistant fiber, is used in the canvas ear as a measure against heat deterioration, the heat shrinkage ratio of this yarn is not lower than the heat shrinkage ratio of the polyester monofilament yarn in the central body of the canvas. Due to the heat setting process, the compression force in the canvas traveling direction does not act on the ears, and the uniformity of the shape and dimensions of the entire canvas can be secured.

Further, it has been found that the strength of the polyphenylene sulfide monofilament yarn having a flat cross section used for the warp of the selvage should be 45% or more of the strength of the polyester monofilament yarn. It is possible to have the minimum strength, and it is possible to reduce the material cost.

[0029]

Embodiments of the present invention will be described with reference to the drawings.

The heat shrinkage rate and air permeability of the raw yarns in the examples were measured according to the following methods.

Thermal shrinkage

Five samples obtained by cutting the raw yarn into a length of 30 cm are treated in a hot air dryer for 20 minutes.

The sample taken out was in a standard state (temperature 20 ° C.,
It is left in a room with relative humidity of 65%) for about 30 minutes or more, and then its length is measured, and it is represented by an average value of five samples obtained by the following formula.

Thermal shrinkage (%) = {(300 (mm) -length after treatment (mm)) / 300 (mm)} × 100%

Air permeability

It was measured by the Frazier method of JIS L-1096.

FIG. 3 is a plan view of a double weave canvas showing an embodiment of the present invention, and FIG. 4 shows its structure. Figure 3
In FIG. 1, 1 is a canvas, 2 is a central body portion, and 3 is an ear portion. As shown in FIG. 4, the canvas 1 includes a central body 2
Is a flat polyester monofilament (“TM”)
Is abbreviated. ), The short side is 0.58 mm and the long side is 0.8
A warp yarn 4 of 8 mm and a weft yarn 5 made of a polyester monofilament (TM) of 0.8 φmm were respectively used to have a warp yarn density of 29.0 (pieces / 2.54 cm) and a weft yarn density of 12.7 ×.
It is woven with 2 (books / 2.54 cm). The ear 3 is a polyphenylene sulfide (PPS) monofilament having a flat cross section, with a short side of 0.58 mm and a long side of 0.88 m.
It is woven with a warp yarn 4 of m and a weft yarn 5 made of 0.8 mm polyester monofilament (TM). After weaving the entire canvas 1, the tension is 3 kg / cm → 1
Heat set processing is performed under hot air of 160 ° C. in kg / cm.

A polyester monofilament (TM) having a flat cross section used for the warp 4 of the central body 2,
The heat shrinkage rate of the raw yarn having the short side of 0.58 mm and the long side of 0.88 mm is as shown in FIG. Also, the warp 4 of the ear 3
Polyphenylene sulfide with a flat cross section (P
PS) monofilament with a short side of 0.58 m
The heat shrinkage rate of the raw yarn having a length m and a long side of 0.88 mm is as shown in FIG.

A polyester monofilament (TM) yarn used for the weft yarn 5 and having a 0.8 mm diameter raw yarn has a normal heat shrinkage of 2% at 160 ° C.
It may be about 4% at 0 ° C., and it is not always necessary to use a yarn having a high heat shrinkage ratio.

As can be seen from FIG. 2, polyphenylene sulfide (PP) having a flat cross section between 160 ° C. and 180 ° C.
S) The heat shrinkage rate of the monofilament thread exceeds that of the polyester monofilament thread having a flat cross section.

By weaving according to the specifications shown in FIG. 4 and heat-setting, a canvas having the specifications of the ears and the central body shown in FIG. 4 was obtained.

As a result, it is possible to obtain a product in which the central body and the ears are uniform, without the unevenness of the canvas, wrinkles or streaks.
As a result of the test, it was confirmed that the dimensional stability was also good.

The warp yarns 4 of the selvage 3 may be polyphenylene sulfide (PPS) monofilament yarns having a flat cross section, but some of the warp yarns 4 are PPS monofilament yarns, and the rest are polyester monofilaments having a flat cross section. May be. The proportion of PPS monofilament yarn having a flat cross section can be appropriately selected according to the application of the canvas.

The characteristic curve of the heat shrinkage ratio shown in FIG. 2 is an example for carrying out the present invention, and is not necessarily limited to this characteristic curve, and other characteristic curves can be used as long as they are in accordance with the gist of the present invention. Of course, a characteristic curve can be used.

Regarding the material of the polyphenylene sulfide (PPS) monofilament yarn having a flat cross section used for the warp of the selvage, not only polyphenylene sulfide alone but also polyphenylene sulfide and various additives such as heat-stabilized nylon 66 are added. It also includes those manufactured from things.

For the canvas of the example, a product having a width of 5 m and a length of 30 cm and a length of 50 m shown in FIG. 5 was tested to confirm the effect of heat shrinkage.

The test method and test results are shown in Table 1 below.
It shows in Table 2. In the table, the value in parentheses indicates the dimensional change rate of the ear when the central body is used as a reference.

[0048]

[Table 1]

[0049]

[Table 2]

The comparative example shown in Table 1 has a temperature of 160.
The dimensional change rate of the running method (longitudinal direction) at the end of the 1 ° C / tension 1 kg / cm set is + 0.4% in the ear compared to the central body, and the length of the ear is longer than the body It turns out that the whole is not uniform.

On the other hand, in the embodiment of Table 2, the running direction (length direction) between the ear and the central body is the same as the above.
It can be seen that there is no difference in size, and that it is uniform over the entire canvas.

[0052]

The heat shrinkage rate of the polyester monofilament yarn having a relatively large flat cross section having a short side of 0.4 mm or more and / or a long side of 0.6 mm or more is set to be higher than the conventional value by a predetermined amount. Dimensional stability can be improved by heat setting of a papermaking dryer canvas using the same yarn as the warp.

As a countermeasure against thermal deterioration of the ear of the canvas, polyphenylene sulfide (PP) which is a heat and heat resistant fiber is used.
Since the heat shrinkage rate of the polyphenylene sulfide (PPS) monofilament thread when the S) monofilament thread is used does not fall below the heat shrinkage rate of the polyester monofilament thread, the direction in which the canvas runs in the ear running direction due to the heat setting process. The compression force does not act and the uniformity of the shape and dimensions of the entire canvas can be maintained.

Further, it has been found that the strength of the PPS monofilament thread used for the selvage portion should be at least 45 (%) of that of the polyester monofilament thread of the central body portion, so that the material cost of the selvage warp threads can be reduced. .

[Brief description of drawings]

FIG. 1 is a dry heat shrinkage rate diagram of a canvas warp.

FIG. 2 is a dry heat shrinkage ratio diagram of the warp threads of the central body portion and the ear portion of the canvas.

FIG. 3 is a plan view of a canvas.

FIG. 4 is a diagram showing the organizational structure of a canvas.

FIG. 5 is a plan view of a canvas used for a stretch amount test.

[Explanation of symbols]

1 canvas 2 Central body 3 ears 4 warp 5 weft

Claims (3)

(57) [Claims] 1. A dryer canvas for papermaking woven using a polyester monofilament yarn having a flat cross-section as a warp, wherein the polyester monofilament yarn has a cross-sectional dimension of 0.4 mm or more and / or a long side of 0.6 m.
while more than m, the thermal shrinkage of the polyester monofilament yarn, Te smell between 1 60 to 180 ° C 9
% To 14% or less , a dryer canvas for papermaking. 2. The dryer canvas for papermaking according to claim 1, wherein a part or all of the warp yarns at both side edges of the dryer canvas has the same flat cross sectional dimension as the polyester monofilament yarn. And the heat shrinkage of the polyphenylene sulfide monofilament yarn ,
1. A dryer canvas for papermaking, wherein the heat shrinkage is equal to or more than the heat shrinkage of the polyester monofilament yarn between 160 and 180 ° C. 3. The dryer canvas for papermaking according to claim 2, wherein the strength of the polyphenylene sulfide monofilament yarn having a flat cross section used for the warp yarn of the selvage is 45% or more of the strength of the polyester monofilament yarn. Dryer canvas for papermaking.