WO2007018313A1

WO2007018313A1 - Press felt for papermaking

Info

Publication number: WO2007018313A1
Application number: PCT/JP2006/316060
Authority: WO
Inventors: Takashi Ohuchi
Original assignee: Ichikawa Co., Ltd.
Priority date: 2005-08-10
Filing date: 2006-08-09
Publication date: 2007-02-15
Also published as: EP1944411A1; JP2007046196A; EP1944411A4

Abstract

A press felt (10) which comprises a base (20) and batt layers (30), these layers being entangled by needle punching. The batt layers (30) comprise a wet-web-side layer (32), an interlayler (34), and a pressing-side layer (36). The interlayer (34) disposed as a wet-web-side batt layer (30) is constituted of either a mixture of staple fibers (50) and hollow fibers (52) in a given proportion or hollow fibers (52) only. The hollow fibers (52) of the interlayer (34) get squashed flat under nip pressing. When the nip pressing is relieved, however, the hollow fibers recover their original shapes and absorb the water present in the press felt (10) through the ends thereof and hold it in the hollows, earlier than the water transfers to the wet web. Namely, the hollow fibers (52) have the effect of preventing rewetting.

Description

Specification

Press felt for papermaking

Technical field

The present invention relates to a felt used for a papermaking press part, and more particularly to a papermaking press felt (hereinafter simply referred to as “press felt”) capable of improving water squeezability.

Background art

'' Traditionally, press equipment has been used to squeeze water from wet paper in the papermaking process.

In the press device, the wet paper on which the paper layer has been formed is squeezed through a press felt in a press two-pipe. In general, a press device is composed of a plurality of press nips.

FIG. 5 is a schematic view of press dip in the press apparatus.

The press nip is composed of a pair of press rolls P 'and P' and a pair of press felts 11 'and 11 that sandwich the wet paper web W'. In the press part of the press rolls P 'and P, Pressure is applied to the felts 11 ′ and 11 ′ and the wet paper W ′, and water is squeezed from the wet paper W ′ and absorbed by the press felts 11 ′ and 11 ′.

However, the pressure applied to the wet paper web W ′ and the press felts 11 ′ and 11 ′ is suddenly released from the center of the pressurizing section to the outlet.

Along with this, negative pressure is generated in the press felts 11 ′ and 11 ′ due to the rapid expansion of the volumes of the press felts 11 ′ and 11 ′ and the wet paper web W ′ from the center of the pressurizing section to the outlet. In addition, because the wet paper W 'consists of fine fibers, capillarity is also added.

As a result, the moisture absorbed in the press felt 1 1 ′, 11 ′ is transferred to the wet paper side again, that is, a phenomenon that is regarded as a problem among those skilled in the art as a rewetting phenomenon. .

In order to prevent such a re-wetting phenomenon, there is one in which an ultrafine fiber or a hydrophilic nonwoven fabric is provided on the batt layer (see, for example, JP-A-2004-143627). FIG. 6 is a sectional view in the CMD direction of a conventional press felt 10 '.

In FIG. 6, a conventional press felt 10 'is composed of a base body 20', a batt layer 30 ', and a hydrophilic nonwoven fabric 40', and these are intertwined and integrated by needle punching. Has been.

The batt layer 3 0 ′ is composed of a wet paper web side layer 3 1 ′ and a press side layer 3 2 ′. The batt layer 3 0 ′ has a structure in which staple fibers 5 0 ′ are punched on a base 2 20 ′ for 21 dollars. Therefore, the staple fiber 1 5 0 ′ is also arranged in the substrate 2 0 ′.

The hydrophilic nonwoven fabric 40 0 ′ is disposed in the wet paper web side layer 3 1 ′.

As the hydrophilic nonwoven fabric 40 ′, a spunbond nonwoven fabric composed of hydrophilic nylon fibers having a fineness of 4 dtex or less is used. The hydrophilic nonwoven fabric 40 'has a higher density and lower water permeability than vat fibers. Therefore, the moisture in the second wet paper side layer 3 l b ′ and the press side layer 3 2 ′ is difficult to permeate the hydrophilic nonwoven fabric 40 0 ′ and is difficult to return to the wet paper.

Further, since the fineness of the hydrophilic nonwoven fabric 40, is lower than that of the vat layer 30 ', the moisture retained in the first wet paper web side layer 3la' by the capillary phenomenon is reduced to the hydrophilic nonwoven fabric 4 It becomes easier to move to 0 '.

According to this conventional press felt 10 ', it is said that by placing a hydrophilic non-woven fabric in the wet paper side layer of the vat layer, it is possible to provide a press felt for paper making that has an excellent anti-wetting effect. ing.

In addition, warp yarns or weft yarns used for press felt base materials are constituted by hollow filament yarns (see, for example, US Pat. No. 6,179,965). Thus, if the hollow fiber is used for the base material, the contact area to be nip-pressed can be increased by increasing the elastic force of the base material. Along with this, it is said that the press felt can be squeezed to prevent wet paper rewetting.

Disclosure of the invention

However, in the conventional press felt, for example, the press felt of Patent Document 1, the hydrophilic non-woven fabric is provided in the wet paper web side layer, but the hydrophilic non-woven fabric is placed in an appropriate position in the wet paper web layer. Or evenly placed so that they do not overlap There was a problem that advanced technology was necessary.

Further, in the case where the press felt base material is constituted by a hollow filament yarn, since the hollow filament yarn is a long fiber filament, the end thereof is not located inside the felt, so that the hollow filament yarn has a hollow portion. Since there is no effect of absorbing moisture in the felt, there is a problem that the use of hollow filament yarn is not sufficient from the viewpoint of preventing rewetting.

Therefore, the present invention relates to moisture transfer to the wet paper side (re-wetting) accompanying the pressure release of the fuel bottle after passing through the two cups. Therefore, an object of the present invention is to provide a papermaking press fridge that can reduce rewetting.

The present invention relates to a papermaking press felt comprising a base and a butt layer comprising a wet paper side layer and a press side layer.

The above problem has been solved by a press felt for papermaking, wherein an intermediate layer including a staple fiber of a hollow fiber is disposed on the wet paper side batt layer. According to the present invention, as the hollow shape of the hollow fiber is recovered in the process of releasing the press felt from under pressure, water remaining inside the press felt is transferred to the hollow portion at the end of the hollow fiber. Can be sucked. As a result, it is possible to prevent water from migrating to the surface layer and effectively suppress the rewetting phenomenon. Staple fibers are usually short fibers (cut cotton) of 50 to 150 mm, so that the end of such staple fibers can be placed in large amounts in the butt layer of the press felt. You can.

Furthermore, according to the present invention, rewetting prevention is achieved by a relatively simple configuration in which an intermediate layer including a hollow fiber stable fiber (hereinafter simply referred to as “hollow fiber”) is disposed in the wet paper web batt layer. It is possible to provide a papermaking press felt that is highly effective.

Brief Description of Drawings

FIG. 1 is a cross-sectional view of an embodiment of a press felt according to the present invention.

FIG. 2 is a cross-sectional view of another embodiment of the press felt of the present invention.

FIG. 3 is a schematic diagram of an apparatus for confirming the effect of the press felt of the present invention. FIG. 4 is a schematic diagram of an apparatus for confirming the effect of the press ferrule of the present invention. FIG. 5 is a schematic explanatory diagram of a press device of a papermaking machine.

Fig. 6 is a cross-sectional view of a conventional press felt.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the press felt 10 of the present invention will be described with reference to FIGS. 1 and 2. FIG.

1 and 2 are cross-sectional views in the CMD direction of a press felt 10 used in the present invention.

“Machine direction (MD)” is the warp direction in which the paper machine moves the press felt, and “Cross machine direction (CMD)” is the weft direction across the direction in which the paper machine moves the press felt. It is.

In FIG. 1, a press felt 10 is composed of a substrate 20 and a base layer 30, which are entangled by dollar punching to form a papermaking press felt. The substrate 20 is provided to develop the strength of the press felt 10. Various materials are proposed by those skilled in the art, such as a woven fabric or a structure in which yarn materials are stacked without being woven, a film, and the like. What is currently used can be used suitably.

Suitable materials for the substrate 20 include natural fibers such as wool and synthetic fibers such as polyester, nylon 6 and nylon 6 6 which are excellent in abrasion resistance, fatigue resistance, stretch properties, antifouling properties, etc. .

The vat layer 3.0 includes a wet paper side layer 3 2, a middle layer 3 4, and a press side layer 3 6. The staple fiber 50 used in the butt layer 30 is a pick-up felt used in the front stage of the paper machine press spar. The wet paper side layer 32 has a 10 to 25 decitex (dtex). The press side layer 36 should have a fineness of about 15 to 25 decitex (dtex).

Also, in the felt for No. 2 press and No. 3 press used in the middle part of the press part of the paper machine, the wet paper side layer 3 2 should have a fineness of about 10 to 15 dtex. It is recommended that the press side layer 36 has a fineness of about 10 to 20 decitex (dtex). In the felt for No. 4 press press used in the latter part of the press part of the paper machine, the wet paper side layer 32 has a fineness of about 5 to 15 dtex (dte X), and the press side Layer 36 should have a fineness of about 5-20 decitex (dtex).

The configuration of the press part in the paper machine press is well known to those skilled in the art. For example, JP 2004-143627 A (paragraphs 0002 to 000 5 and FIG. 1, and paragraphs 0037 to 0038 and FIG. 14). The detailed description in this specification will be omitted.

In the vat layer 30 on the wet paper web side, an intermediate layer 34 including hollow fibers 52 is disposed. The middle layer 34 is composed of a staple formed by mixing staple fibers 50 and hollow fibers 52 at a certain ratio, or only hollow fibers 52.

In the case of the hollow fiber 52 alone, the middle layer 34 is preferably provided with a basis weight of 100 to 300 g / m ² , and a basis weight of about 200 g / m ² is preferable. Further, the intermediate layer 34, 2 5-75 constituted by hollow fibers 52 weight ^_0/0, it may also be so compensated staples file I bar 50 the rest les.

Examples of the hollow fiber 52 include those having a round hollow shape, a square hollow shape, a star hollow shape, or a porous hollow shape. However, the shape is not limited to these shapes, and the hollow fiber 52 may be hollow. Further, as the hollow fiber 52, a fiber having a fineness of 3 to 25 dtex (dtex) made of a synthetic fiber such as polyester or nayton can be used. A fiber having a fiber length of 50 to 15 mm can be used. For example, when a hollow hollow fiber is used as the hollow fiber 52, the hollow fiber 52 is flattened under the nip pressure and easily restored to the original shape when released from the pressure. The hollow fiber 52 has high durability against repeated pressurization.

As the hollow fiber 52, the pick-up felt used in the front stage of the press part of the paper machine, the middle layer 34 has a fineness of about 15 to 25 dtex (dtex), and the paper machine For felts for No. 2 press and No. 3 press used in the middle part of the press part, the middle layer 34 should have a fineness of about 10-20 dtex, and the press part of the paper machine Use later In the felt for No. 4 press used for press, it is recommended to use a medium layer 3 4 having a fineness of about 5 to 20 dtex.

As the base body 20 and the butt layer 30 are punched for 21 dollars, the stable fiber 50 and the hollow fiber 52 are also entangled in the base body 20. Is firmly integrated as a press felt.

Next, the operation of the press felt 10 shown in FIG. 1 will be described.

Conventionally, when the press felt 10 progresses in the machine direction under nip pressurization with a press roll and the nip pressurization is removed, the moisture transferred from the wet paper into the press felt 10 is transferred to the wet paper again. The so-called rewet phenomenon occurred. However, in the press felt 10 of the present invention, since the middle layer 34 is provided with hollow fibers that are easily flattened under the nip pressure, the density of the middle layer 34 is increased, but the effect of the pressure is increased. Therefore, moisture moves to the base and press side layer 36 located on the roll side of the middle layer 34. In particular, when pressurization works effectively, moisture is discharged from the press side layer 36 to the roll side.

Further, when the press felt 10 is released from the two-ply pressure, the hollow fiber 52 is gradually restored to the hollow shape as it is released from the pressure. At this time, before the moisture remaining in the press felt 10, particularly in the substrate 20 and the press side layer 36, is transferred again to the wet paper, the moisture is transferred to the hollow fiber 5 2 disposed in the middle layer 34. Can be absorbed into the hollow fiber 52 from the end.

As a result, the press felt 10 of the present invention can reduce the amount of moisture that moves to the wet paper web side layer 32 when it is removed from under the nip pressure, thereby effectively suppressing the rewetting phenomenon. Can do.

Further, when the ratio of the hollow fibers 52 in the wet paper side layer 3 4 is increased in order to reduce the amount of moisture transferred from the wet paper side layer 3 2 to the wet paper, a larger amount of the vat layer 30 Water can be absorbed by the hollow fiber 52 and the amount of moisture transferred from the wet paper web side layer 32 to the wet paper can be reduced.

In FIG. 2, the wet paper web butt layer 30 includes a plurality of first wet paper web side layers 3 2 a on the side in contact with the wet paper and second wet paper web side layers 3 2 b on the base 20 side. It consists of layers. In the first wet paper web side layer 32a, a plurality of middle layers 34a, 34b, 34c are arranged on the substrate 20 side with respect to the wet paper web contact layer 320a in contact with the wet paper web. The middle layer 34 is arranged as the second wet paper web side layer 32 b.

In FIG. 2, in the middle layers 34, 34a, 34b, 34c, the ratio of the hollow fibers 52 blended becomes higher as the distance from the wet paper web contact layer 320a increases. Therefore, while maintaining the smoothness of the wet paper web contact layer 320a with respect to the wet paper web, and by allowing the hollow fiber 52 to absorb more water in the vat layer 30, the wet paper web contact layer 320a is transferred to the wet paper web. Can reduce the amount of moisture transferred

In addition, in order to compare the effect of the present invention with a conventional press felt, an experiment was conducted with a simple configuration of the butt layer 30. In the experiment, the fineness of the hollow fiber 52 used for the middle layer 34 was specifically 7 dtex. The basis weight of the middle layer 34 was 200 gZm ² .

The basis weights of the wet paper web contact layer 320a and the middle layers 34a, 34b, 34c are each set to 50 gXm, and the wet paper web contact layer 320a uses only the stable fiber 50, In the middle layer 34a, 75% of the basis weight was composed of the staple fibers 50, and 25% of the basis weight was composed of the hollow fibers 52. In the middle layer 34b, 50% of the basis weight was composed of the stable fiber 50, and 50% of the basis weight was composed of the hollow fiber 52. In the middle layer 34c, 25% of the basis weight was composed of staple fibers 50, and 75% of the basis weight was composed of hollow fibers 52.

(Example)

The following experiment was conducted to confirm the effect of the press-felding paper for papermaking of the present invention.

Note that the basic configuration of all felts was as follows in order to make the conditions common to the examples and comparative examples. Substrate (Nylon monofilament twisted plain weave): Basis weight 300 g / m Batt layer (Nylon 6 and hollow fiber stable fiber): Total basis weight 550 g / ni Needle punch density: 700 times / cm ²

Except for the comparative example, an intermediate layer made of hollow fibers is disposed in the wet paper web side layer of the bag layer, and the wet paper web side layer (first wet paper web side layer, second wet paper web side layer) as a bat layer; It has a press side layer. Here, Examples and Comparative Examples shown in Table 1 were obtained for the material, fineness, and basis weight of the bat layer in the Examples and Comparative Examples.

Using the papermaking press felts of the above examples and comparative examples, experiments were conducted using the apparatus shown in FIGS.

First, in the apparatus shown in Fig. 3 and Fig. 4, in the figure, P is a press roll, 1 1 0 is a top felt, 1 0 is a bottom felt, SC is a succession tube, and SN is a shower nozzle .

The above examples and comparative examples are used as the bottom felt 10 in both apparatuses. In this case, a press felt similar to that shown in Comparative Example 1 was used as the top felt.

3 and 4 both have a felt traveling speed of 50 O m / min and a press pressure of 100 kgg cm.

The apparatus shown in FIG. 3 has a structure in which wet paper that has been released from the two-pipe pressure is placed on the bottom felt 10 and conveyed. Therefore, when the wet paper wetness at the position (press exit 1) placed and transported on the felt felt 10 is measured after the two-pipe pressure is removed, the wet paper that has undergone the rewetting phenomenon is measured. Moisture content data can be obtained.

On the other hand, the apparatus shown in FIG. 4 has a large area where the bottom felt 10 is in contact with the press roll, and the wet paper released from the two-push contact comes into contact with the ferrules 10 and 110. Time is very short. Here, when the wetness of the wet paper is measured at the position (press outlet 2) immediately after the release of the two-pipe pressure, the moisture content data of the wet paper that does not cause much rewetting is obtained.

Here, the difference between the moisture content data by the device of Fig. 3 and the same data by the device of Fig. 4 was obtained, and the rewetting phenomenon was evaluated. At this time: If the difference between the two is less than 0.5%, the rewetting phenomenon does not occur (evaluation is “good”). On the other hand, if the difference between the two is 0.5% or more and less than 1.0%, a re-wetting phenomenon occurs (evaluation is "OK"), and if it is 1.0% or more, a re-wetting phenomenon occurs. (Evaluation is “No”).

Table 1 summarizes the results. table 1

Rewetting evaluation → Moisture at press outlet 1 Moisture at press outlet 2

Less than 0.5 = good

0.5 or more to less than 1.0 = possible

1.0 or more = Impossible

As shown in Table 1, it was confirmed that the press felt for papermaking of the present invention can effectively suppress the rewetting phenomenon and exhibits an excellent effect.

Here, in particular, the effect that the middle layer including the hollow fiber is disposed in the wet paper web side layer of the vat layer could be confirmed by comparing the example and the comparative example.

In addition, the vat layer has a multilayer structure in order from the wet paper side, and the first layer is made of a layer of naïve without hollow fibers, and the second and subsequent layers have a nayton content. It was confirmed from Examples 2 to 3 that it was preferable that the hollow fiber content was 25% to 75% and the hollow fiber content was 75% to 25%.

Industrial applicability

As described above, according to the present invention, it is possible to provide a papermaking press felt excellent in rewetting prevention effect by a relatively simple configuration in which an intermediate layer containing hollow fibers is arranged in a bat layer on the wet paper side. it can.

Claims

The scope of the claims

1. In a press felt for papermaking comprising a substrate and a butt layer comprising a wet paper web side layer and a press side layer,

An intermediate layer containing hollow fiber staple fibers is arranged on the wet paper web side batt layer,

Press felt for papermaking.

2. The vat layer has a multilayer structure, and in order from the wet paper web side layer of the vat layer, the first layer is made of a nylon layer not including the staple fiber of the hollow fiber, and the second layer and thereafter are made of nylon. The press felt for papermaking according to claim 1, wherein the felt is blended at a content rate of 25% to 75% and a content rate of the hollow fiber of 75% to 25%.