Paper Transporting Felt and Press Apparatus of Paper Machine Having the Paper Transporting Felt

Abstract

A paper transporting felt includes a base layer, a first batt layer formed on a wet paper side surface of the base layer, a second batt layer formed on a press side surface of the base layer, a wet paper contacting fibrous layer including a plurality of split fibers split into fine fibers and a high polymer elastic material impregnating gaps between the fine fibers, and formed on a wet paper side surface of the first batt layer so as to allow the fine fibers and the high polymer elastic material to come into direct contact with the wet paper, and a hydrophilic nonwoven fabric layer disposed between the first batt layer and the wet paper contacting fibrous layer. In a surface of the wet paper contacting fibrous layer which comes into direct contact with the wet paper, the fine fibers are partially covered with the high polymer elastic material.

Description

TECHNICAL FIELD

The present invention relates to a paper transporting felt and a press apparatus of a paper machine having the paper transporting felt, and more particularly to a paper transporting felt for use in a press mechanism having a shoe press and a press apparatus of a shoe press type paper machine having the paper transporting felt.

BACKGROUND ART

Generally, a paper machine has a wire part, a press part, and a drier part. The wire part, the press part, and the drier part are disposed in that order of arrangement along a transporting direction of a wet paper. The wet paper is transported while being consecutively delivered to paper transporting tools disposed respectively in the wire part, the press part, and the drier part, and has its water squeezed out (i.e., dewatered), and is finally dried in the drier part. A press apparatus disposed in the press part has a plurality of press mechanisms disposed in series along the transporting direction of the wet paper. Each press mechanism has a pair of endless belt-shaped paper transporting felts as well as a pair of rolls (i.e., a roll press) or a roll and a shoe (i.e., a shoe press) which serve as a press disposed in such a manner as to vertically oppose each other to nip respective portions of the paper transporting felts therebetween. As the wet paper being transported by the paper transporting felts which travel at substantially the same speed in the same direction is pressurized by the pair of rolls or the roll and the shoe together with the paper transporting felts, water in the wet paper is absorbed by the paper transporting felts while the wet paper is being dewatered. It should be noted that such paper machines include a roll press type paper machine in which a press apparatus for nipping and pressurizing portions of the paper transporting felts sandwiching the wet paper by means of the pair of rolls is provided in the press part, a shoe press type paper machine in which a press apparatus for nipping and pressurizing portions of the paper transporting felts sandwiching the wet paper by means of the roll and the shoe is provided in the press part, and so on.

In particular, according to the shoe press type paper machine, in comparison with the more popular roll press type paper machine, the press zone of a pressing portion (i.e., a nip formed by the roll and the shoe) can be made wider. Since the pressing time can thereby be made long, the dewatering characteristic excels further. However, at a portion extending from a center of the pressing portion between the roll and the shoe to an exit, the pressure applied to the wet paper and the paper transporting felts is suddenly released, the volumes of the paper transporting felts and the wet paper suddenly expand in this portion. As a result, negative pressure occurs in the paper transporting felts and the wet paper, and since the wet paper consists of fine fibers, the capillary phenomenon is further added. Therefore, the so-called re-wetting phenomenon occurs in which the water absorbed in the paper transporting felts is moved back to the wet paper. Thus, the portion extending from the center of the pressing portion between the roll and the shoe to the exit constitutes a major factor causing the dewatering performance of the press apparatus of the paper machine to decline.

The wet paper needs to be delivered to a paper transporting tool (e.g., a drier canvas) of an ensuing process between the wire part and the press part, between press mechanisms such as a first press area and a second press area of the press apparatus, and between the press part and the drier part. Accordingly, particularly in the paper transporting felt in the press apparatus, not only a wet paper dewatering function and a wet paper transporting function but also a paper releasing function for allowing the wet paper to be smoothly released from the paper transporting felt at the time of delivering the wet paper to the ensuing process (i.e., for facilitating the release of the wet paper from the paper transporting felt) is required. Moreover, a smoothing function for smoothing the wet paper surface, in particular, is further required for the paper transporting felt of the press mechanism disposed on the downstream side in the transporting direction of the wet paper in the press part.

As the paper transporting felt adapted to prevent the re-wetting phenomenon of the paper transporting felt and blowing and the like at the time of pressing, one is known which is impregnated with emulsion resin and in which some contrivance is made in the wet paper side portion (refer to U.S. Pat. No. 4,500,588.). More specifically, in the paper transporting felt, a batt layer formed on the surface of a base layer is impregnated with emulsion resin, and the wet paper side surface of the batt layer is calendered such that the wet paper side surface of the batt layer becomes a dense and chamois-like smooth surface, thereby forming a barrier layer. Alternatively, a coarse-fibered layer formed on the surface of the base layer is impregnated with emulsion resin, a barrier layer (a nonwoven fabric layer) is provided on the coarse-fibered layer, and a fine fibered-layer is formed on the barrier layer (the nonwoven fabric layer). The arrangement provided is such that the emulsion resin is prevented from penetrating up to the wet paper side surface of the paper transporting felt by the barrier layer. Therefore, the re-wetting and blowing of the paper transporting felt are prevented, thereby making it possible to increase the papermaking speed.

As a paper transporting felt in which an attempt is made to improve the paper releasing function at the time of the delivering of the wet paper, one is known in which a hydrophobic material is disposed in a portion of its wet paper placing surface for placing the wet paper thereon and transporting the wet paper (refer to JP-A-2001-89990.). More specifically, in this paper transporting felt, either one material of a high polymer elastic member having a wet paper placing surface and a surface-layer forming material disposed in the high polymer elastic member is made hydrophobic, and portions for repelling water and portions for condensing water are thus provided on the wet paper placing surface in a dispersed manner so as to break water films formed between the wet paper placing surface and the wet paper. An attempt is thereby made to improve the paper releasing function.

In addition, a paper transporting felt is also known in which a fibrous material is caused to project from the wet paper side surface of the paper transporting felt so as break water films formed between the wet paper side surface and the wet paper, thereby making an attempt to improve the paper releasing function (refer to JP-A-2004-124274.). More specifically, this paper transporting felt consists of a substrate, machine side layer, and a wet paper side layer having a high polymer elastic portion such as urethane resin, and as the surface of the high polymer elastic portion is subjected to processing such as polishing, portions of a fibrous material mixed in the high polymer elastic portion are made to project from the wet paper side surface.

With the press apparatus of the paper machine, water is squeezed out by applying a very large pressure to the paper transporting felts at the pressing portion (i.e., the nip), so that stains (specifically, components of such as additives and paste contained in the wet paper) are likely to attach to the paper transporting felts. Accordingly, with the press apparatus of the paper machine, since the life of the paper transporting felt (i.e., the usable period of the paper transporting felt) is short, maintenance is required to replace the paper transporting felt with a new one whenever necessary. It should be noted that it goes without saying that the frequency of the replacement of such paper transporting felts is greater in the case of the press apparatus of the shoe press type paper machine than in the case of the press machine of the roll press type paper machine.

Moreover, with the press apparatus of the type paper machine, the falling off and cutting off of fibers (the so-called loss of fibers) on the surface of the batt layer of the paper transporting felt which comes into direct contact with the wet paper occur noticeably due to the very large pressure or friction at the pressing portion (i.e., the nip). Most of the fallen-off fibers and the cut-off fibers are discharged to the outside of the press apparatus by a cleaning means consisting of a water shower, a suction box, and the like. However, there are cases where slight portions of them are attached to the surface of the wet paper. Since the fallen-off fibers and the cut-off fibers are thicker and harder than the fibers of the wet paper, the paper which has been manufactured with such fibers attached to its surface is inferior in printability in some cases (more specifically, decoloration or the like can occur when printing is effected). Thus, the loss of fibers on the batt layer surface of the paper transporting felt which comes into direct contact with the wet paper deteriorates the quality of paper products such as printed matter. Meanwhile, the surface of the batt layer constitutes a factor causing the surface smoothness of the wet paper to decline noticeably since the surface becomes coarse due to the loss of fibers.

However, the fibers forming the surface of the batt layer of the paper transporting felt which comes into direction contact with the wet paper are difficult to simply replace with monofilaments. A specific reason is as follows: Fiber masses (i.e., masses of fibers) are likely to be produced if the monofilaments are carded in a preliminary stage of a needling process (carding is present in the preliminary stage of the needling process, and the fibrous paper sheet after the carding is implanted by needling), which is one of the processes for manufacturing the paper transporting felt. These fiber masses are implanted in the felt in the needling immediately after the carding, and relatively large irregularities are formed on the surface of the paper transporting felt, so that the surface smoothness of the wet paper undesirably declines.

The paper transporting felt which is disclosed in U.S. Pat. No. 4,500,588 and whose wet paper side surface has been calendered is a paper transporting felt which has excellent surface smoothness and is water impermeable (i.e., water is impermeable from the wet paper side surface to the press side surface). However, since this paper transporting felt is inferior in the wet paper dewatering performance and the paper releasing performance, this paper transporting felt is unsuitable for the press apparatus of a paper machine in which the wet paper dewatering function and a high paper releasing function are required for the paper transporting felt. With such a paper transporting felt, thin water films are likely to be formed between the smooth wet paper side surface and the wet paper, and the water films act like an adhesive, so that there is a high possibility that the wet paper adheres to the wet paper side surface. In addition, the paper transporting felt which is disclosed in U.S. Pat. No. 4,500,588 and in which a nonwoven fabric layer is interposed between the coarse-fibered layer on the base layer side and the fine-fibered layer on the wet paper side capable of including fiber masses is also unsuitable for the press apparatus of a paper machine in which the wet paper dewatering function and a high smoothing function are required for the paper transporting felt.

In addition, in the case of the paper transporting felts disclosed in JP-A-2001-89990 and JP-A-2004-124274, although improvements are made to some extent in the paper releasing function, since the entire batt layer consisting of ordinary fibers is formed by including a high polymer elastic member in both cases, the compressing and recovering performance of the paper transporting felt at the time of pressing is low. Moreover, since the paper transporting felt is water impermeable (i.e., water is impermeable from the wet paper side surface to the press side surface), it is impossible to expect the wet paper dewatering characteristic. Furthermore, since the size of the fibers projecting from the high polymer elastic member toward the wet paper side is relatively large, irregularities on the wet paper side surface of the paper transporting felt also become large.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a paper transporting felt in which stains can be easily removed, an excellent paper releasing function at the time of delivery of the wet paper is performed, and the function of smoothing the wet paper surface is enhanced, as well as a press apparatus of a paper machine having the paper transporting felt.

The invention provides a paper transporting felt which is at least one paper transporting felt of a pair of paper transporting felts for a shoe press, which are disposed in a press apparatus provided in a press part of a paper machine, form a press mechanism together with a shoe press having a roll and a shoe in the press apparatus, and are pressurized by the roll and the shoe while sandwiching a wet paper, to absorb water squeezed from the wet paper, having:

a base layer;

a first batt layer which is formed on a wet paper side surface of the base layer;

a second batt layer which is formed on a press side surface of the base layer;

a wet paper contacting fibrous layer which includes a plurality of split fibers split into fine fibers and a high polymer elastic material impregnating gaps between the fine fibers, and is formed on a wet paper side surface of the first batt layer so as to allow the fine fibers and the high polymer elastic material to come into direct contact with the wet paper; and

a hydrophilic nonwoven fabric layer which is disposed between the first batt layer and the wet paper contacting fibrous layer,

wherein, in a surface of the wet paper contacting fibrous layer which comes into direct contact with the wet paper, the fine fibers are partially covered with the high polymer elastic material.

In the paper transporting felt, the wet paper contacting fibrous layer contains 1 wt. % to 10 wt. % of the high polymer elastic material.

In the paper transporting felt, fibers for forming the wet paper contacting fibrous layer contains 15 wt. % to 100 wt. % of the split fibers and nonsplit fibers as remains.

In the paper transporting felt, each size of the split fibers prior to splitting is 3.3 dtex or smaller.

In the paper transporting felt, each size of the split fibers prior to splitting is 1.9 dtex.

The invention also provides a press apparatus of a paper machine having the paper transporting felt.

The invention also provides a press apparatus of a paper machine having a plurality of press mechanisms each having the paper transporting felt, wherein the plurality of press mechanisms are disposed in series along a transporting direction of the wet paper being transported by the paper transporting felts.

In the press apparatus of a paper machine, each size of the split fibers prior to splitting is 3.3 dtex or smaller.

In the press apparatus of a paper machine, each size of the split fibers prior to splitting is 1.9 dtex.

The press apparatus of a paper machine is a press machine of a closed draw type.

In the press apparatus of a paper machine, the press apparatus is a press apparatus of a shoe press type paper machine, and a press of the press apparatus is a shoe press having a roll and a shoe for pressurizing the paper transporting felt.

In the press apparatus of a paper machine, the press apparatus is a press apparatus of a roll press type paper machine, and a press of the press apparatus is a roll press having a pair of rolls for pressurizing the paper transporting felt.

According to the paper transporting felt, the wet paper contacting fibrous layer, which has been formed by splitting the plurality of split fibers into fine fibers and by subsequently impregnating gaps between the fine fibers with the high polymer elastic material, is formed on the wet paper side surface of the first batt layer of the paper transporting felt so as to be brought into direct contact with the wet paper. Therefore, it is possible to improve the surface smoothness of the wet paper contacting fibrous layer, thereby making it possible to manufacture high-quality paper having a smooth surface. In addition, the surface of the wet paper contacting fibrous layer is formed as a surface in which the fine fibers formed by the splitting of the split fibers are partially covered with the high polymer elastic material. Since the surface of the wet paper contacting fibrous layer has slight irregularities caused by the projection of these infinitesimal fine fibers, water films between the wet paper contacting fibrous layer and the wet paper are likely to be broken or are difficult to be formed. Hence, the paper releasability from the paper transporting felt is excellent, so that the wet paper can be easily delivered to the drier canvas in the ensuing process.

In addition, since the fine fibers formed by the splitting of the split fibers are combined to some extent and are partially covered by the high polymer elastic material, the so-called capillary phenomenon is difficult to occur, and the falling off of these fine fibers from the paper transporting felt is prevented. Consequently, as for the paper manufactured by the paper machine using the paper transporting felts, its surface becomes extremely smooth. Moreover, since the life of the paper transporting felt (i.e., the usable period of the paper transporting felt) is long, it is possible to decrease the frequency of maintenance for replacing the paper transporting felt with a new one.

In addition, since the hydrophilic nonwoven fabric layer is disposed between the first batt layer and the wet paper contacting fibrous layer, the high polymer elastic material with which the wet paper contacting fibrous layer is impregnated from its surface side is blocked by the hydrophilic nonwoven fabric layer, and layers deeper than the hydrophilic nonwoven fabric layer (i.e., the first batt layer, the base layer, and the second batt layer) are not impregnated with the high polymer elastic material. Thus, the high polymer elastic material is disposed only in the wet paper contacting fibrous layer (e.g., by 0.5 mm or thereabouts from the surface).

Accordingly, since the paper transporting felt has water permeability and appropriate compressing and recovering functions (cushionability), the paper transporting felt is able to exhibit its dewatering characteristic effectively. In addition, stains (specifically, components of such as additives and paste contained in the wet paper W) which are temporarily attached to the wet paper contacting fibrous layer including the high polymer elastic material are likely to be exfoliated from the surface of the wet paper contacting fibrous layer and are moved to the wet paper by virtue of the appropriate compressing and recovering functions (cushionability) of the paper transporting felt. Namely, the paper transporting felt has a high self-cleaning function. Consequently, stains are difficult to remain on the paper transporting felt, and since the stains which are moved to the wet paper are originally contained in the wet paper as its components, no effect is exerted on the quality of the wet paper. In addition, the movement of the water temporarily absorbed from the wet paper by the paper transporting felt back to the wet paper (i.e., the so-called re-wetting phenomenon) is prevented by the hydrophilic nonwoven fabric layer.

It should be noted that wet paper contacting fibrous layer of the paper transporting felt in accordance with the invention is formed such that after the split fibers of the wet paper contacting fibrous layer are split into fine fibers, the gaps between these fine fibers are impregnated with the high polymer elastic material. The splitting of the split fibers is preferably effected in the needling process which if one of the processes of manufacturing the paper transporting felt. Fiber masses (i.e., masses of fibers) are likely to be produced if the split fibers are split into fine fibers by carding in a preliminary stage of a needling process. These fiber masses are implanted by needling, and relatively large irregularities are formed on the surface of the paper transporting felt, so that the surface smoothness of the wet paper declines. The splitting of the split fibers may be effected, for instance, by needling using small-gauge needles in the needling process, by rubbing the implanted split fibers with a brush (commonly called a teasel) of a raising machine after the needling process, or by refining (hot water rinsing) the paper transporting felt after the needling process. Namely, the splitting of the split fibers may be effected in any process insofar as the process is carried out after carding, which is the preliminary stage of the needling process, and before the impregnation with the high polymer elastic material. Then, after the splitting of the split fibers into fine fibers, the gaps between the fine fibers are impregnated with the high polymer elastic material.

The impregnation with the high polymer elastic material is performed as follows: After the plurality of split fibers are split into fine fibers, a synthetic resin such as water-based urethane resin, water-based acrylic resin, water-based epoxy resin, water-based synthetic rubber (i.e., water-based emulsion resin), or the like is applied with a roller or sprayed with a sprayer at ordinary temperature to impregnate the gaps between the fine fibers, and is subsequently cured on heating.

According to the paper transporting felt, since the wet paper contacting fibrous layer contains 1 wt. % to 10 wt. % of the high polymer elastic material, not all the pores between the fibers are filled with the high polymer elastic material, and appropriate porosity is maintained between the fibers. In other words, the structure is made porous. Therefore, water films formed between the wet paper contacting fibrous layer and the wet paper are dispersed, and appropriate cushionability is provided. Consequently, it is possible to obtain a paper transporting felt the paper releasability from which is excellent, which absorbs water squeezed from the wet paper by stretching by being pressurized by the press in each press mechanism, and which has a smooth surface. In addition, by appropriately changing the impregnation ratio of the high polymer elastic material, the paper transporting felts can be provided with optimal characteristics (paper releasability, surface smoothing characteristic, dewatering characteristic, etc.) for the respective press mechanisms. It should be noted that the reason the ratio of the high polymer elastic material for impregnation is set to 1 wt. % or greater is that if the ratio of the high polymer elastic material is less than 1 wt. %, it is practically impossible to expect for the effect of the high polymer elastic material. Also, the reason the ratio of the high polymer elastic material for impregnation is set to 10 wt. % or smaller is that if the ratio of the high polymer elastic material is more than 10 wt. %, the cushionability and the water permeability of the paper transporting felt are lost, causing a decline in the wet paper dewatering characteristic.

According to the paper transporting felt, since fibers for forming the wet paper contacting fibrous layer contain 15 wt. % to 100 wt. % of the split fibers and the nonsplit fibers as remains, the wet paper contacting fibrous layer may be formed by the split fibers. Alternatively, it is possible to change the characteristics of the paper transporting felt by appropriately changing the mix spinning ratio between the split fibers and the nonsplit fibers. Here, the weight ratio of mix spun fibers is defined by “weight of the split fibers 15A/(weight of the split fibers 15A+weight of the nonsplit fibers)×100.” It should be noted that the nonsplit fibers refer to ordinary monofilaments which are not split even at the time of carding or at the time of needling or even in the process of manufacturing the paper transporting felt following the needling process.

The surface smoothness and the dewatering characteristic, which are the characteristics required for the paper transporting felt, are inversely correlated. Hence, if the density of the paper transporting felt is increased to improve the performance of smoothing the surface of the wet paper, the dewatering characteristic tends to deteriorate. Meanwhile, the plurality of press mechanisms disposed from the upstream side in the transporting direction of the wet paper being transported to the downstream side respectively require subtly different functions. Priority is placed on the dewatering characteristic in the case of the paper transporting felt of the press mechanism disposed on the upstream side, while the performance of smoothing the surface of the wet paper is required for the paper transporting felt of the press mechanism disposed on the downstream side. Accordingly, by appropriately changing the mix spinning ratio between the nonsplit fibers and the split fibers, the paper transporting felts can be provided with optimal characteristics (surface smoothing characteristic, dewatering characteristic, etc.) for the respective press mechanisms.

According to the paper transporting felt, since each size of the split fibers prior to splitting is 3.3 dtex or smaller, even if the size of the split fiber prior to splitting was 3.3 dtex, the size of the fine fibers formed by the splitting of the split fibers becomes smaller than 3.3 dtex. Thus, if the wet paper contacting fibrous layer including the slit fibers, which become fine fibers of a size which is practically as close to the size of the fibers of the wet paper as possible by being split, is formed, it is possible to manufacture high-quality paper extremely excelling in the surface smoothness. In addition, as the gaps between such fine fibers are impregnated with the high polymer elastic material, the surface of the wet paper contacting fibrous layer can be made a smoother surface excelling in the paper releasability. Even in a case where fine fibers fallen off or cut off from the wet paper contacting fibrous layer (i.e., fine fibers formed by the splitting of the split fibers) due to the so-called loss of fibers are slightly attached to the surface of the wet paper, since these fine fibers are extremely slender, the quality of the wet paper is not caused to decline.

In addition, according to the paper transporting felt, since each size of the split fibers prior to splitting is 1.9 dtex, it is more preferable. It should be noted that, as for the nonsplit fibers, those having a size of, for example, 1.9 dtex (the same value as the size prior to splitting of the split fibers) to 6 dtex are preferable.

According to the press apparatus of a paper machine, since it has the paper transporting felt, excellent operation and effects are exhibited, as described above.

As in the press apparatus of a paper machine which is a press apparatus of a paper machine having a plurality of press mechanisms each having the paper transporting felt, if the plurality of press mechanisms are disposed in series along the transporting direction of the wet paper being transported by the paper transporting felts, it is suitable in effectively squeezing water from the wet paper and delivering the wet paper to the ensuing paper transporting felts with excellent paper releasability. Namely, according to the press apparatus of a paper machine, it is possible to effectively squeeze water from the wet paper containing a large amount of water, and the wet paper can be delivered reliably to the ensuing paper transporting felts, thereby permitting high-speed papermaking operation.

In particular, if the paper transporting felt impregnated with a relatively large amount of (within the range of 1 wt. % to 10 wt. %) high polymer elastic material is disposed in the press mechanism disposed on the downstream side in the transporting direction of the wet paper among the plurality of press mechanisms, it is conceivable that the water permeability may slightly decline as compared with the paper transporting felt in which the amount of impregnation with the high polymer elastic material is small. However, since the paper transporting felt has not only the function of smoothing the wet paper surface but also high paper releasability, the wet paper being transported at high speed can be reliably delivered to the drier canvas in the ensuing process, and high-speed papermaking becomes possible.

According to the press apparatus of a paper machine, since each size of the split fibers prior to splitting is 3.3 dtex or smaller, even if the size of the split fiber prior to splitting was 3.3 dtex, the size of the fine fibers formed by the splitting of the split fibers becomes smaller than 3.3 dtex. Thus, if the wet paper contacting fibrous layer including the slit fibers, which become fine fibers of a size which is practically as close to the size of the fibers of the wet paper as possible by being split, is formed, it is possible to manufacture high-quality paper extremely excelling in the surface smoothness.

In addition, according to the press apparatus of a paper machine, since each size of the split fibers prior to splitting is 1.9 dtex, it is more preferable.

According to the press apparatus of a paper machine, since it is a press apparatus of a closed draw type, the wet paper is transported in a state of being sandwiched by the pair of paper transporting felts. Consequently, the wet paper can be transported at an extremely high speed without applying a force to the wet paper which has weak strength and is likely to be cut off. Accordingly, efficient papermaking is made possible.

According to the press apparatus of a paper machine, since the press apparatus is a press apparatus of a shoe press type paper machine, the press zone of a pressing portion (i.e., a nip formed by the roll and the shoe) can be made wider. Since the pressing time can thereby be made long, the dewatering characteristic excels further. Moreover, since the so-called re-wetting phenomenon can be prevented, the dewatering performance is high in the portion extending from the center of the pressing portion between the roll and the shoe to the exit.

According to the press apparatus of a paper machine, even if the press apparatus is a press apparatus of a roll press type paper machine, benefits of the above-described outstanding operation and effects based on the invention can be obtained.

Consequently, it is possible to provide a paper transporting felt in which stains can be easily removed, an excellent paper releasing function at the time of delivery of the wet paper is performed, and the function of smoothing the wet paper surface is enhanced, as well as a press apparatus of a paper machine having the paper transporting felt.

A brief description of the invention has been given above. Further, the details of the invention will be come more apparent by perusing the best mode for carrying out the invention described below, by referring to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a vertical cross-sectional view of an embodiment of a paper transporting felt in accordance with the invention;

FIG. 2 is an enlarged cross-sectional view of a split fiber for forming a wet paper contacting fibrous layer of the paper transporting felt shown in FIG. 1; and

FIG. 3 is a plan view illustrating a schematic construction of an embodiment of a press apparatus of a paper machine in accordance with the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, a detailed description will be given of an embodiment of the invention in accordance with the invention with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of a paper transporting felt 100 in accordance with the invention. FIG. 2 is an enlarged cross-sectional view of a split fiber for forming a wet paper contacting fibrous layer of the paper transporting felt shown in FIG. 1. FIG. 3 is a plan view illustrating a schematic construction of an embodiment of a press apparatus of a paper machine in accordance with the invention.

As shown in FIG. 1, the paper transporting felt 100 has a base layer 11, a batt layer 13 (a first batt layer 13A and a second batt layer 13B), a hydrophilic nonwoven fabric layer 23, and a wet paper contacting fibrous layer 15. More specifically, the first batt layer 13A is formed on the wet paper side surface of the base layer 11, the second batt layer 13B is formed on the press side surface (more specifically, one side of the pair of rolls or one side of the roll and the shoe) of the base layer 11, and the hydrophilic nonwoven fabric layer 23 is formed on the wet paper side surface of the first batt layer 13A. The wet paper contacting fibrous layer 15 is formed on the wet paper side surface of the hydrophilic nonwoven fabric layer 23 so as to come into direct contact with a wet paper. The base layer 11, the bat layer 13 (the first batt layer 13A and the second batt layer 13B), the hydrophilic nonwoven fabric layer 23, and the wet paper contacting fibrous layer 15 are entangled and integrated by needling.

The base layer 11 is for imparting strength to the paper transporting felt 100, and it is possible to appropriately use, for instance, woven fabrics using as basic materials those synthetic fibers such as Nylon 6 and Nylon 66 or natural fibers such as wool that excel in such as wear resistance, fatigue resistance, elongation characteristics, or fabrics formed by overlapping yarns without weaving them or those which have been formed into films by using such materials. In this embodiment, a woven fabric is adopted as the base layer 11.

The batt layer 13 (the first batt layer 13A and the second batt layer 13B) is a nonsplit fiber layer formed by staple fibers 17 having a size of 6 decitex (dtex) or greater (generally, 17 dtex or thereabouts). As the material for forming the batt layer 13, a material similar to that of the base layer 11 is appropriately used. It should be noted that the second batt layer 13B may be omitted in accordance with the characteristics required for the paper transporting felt 100.

The hydrophilic nonwoven fabric layer 23 is formed by a hydrophilic nonwoven fabric constructed with a high density by laminating non-split fibers which are finer than the fibers forming the batt layer 13 and which have, for example, a size of 4 dtex or smaller. As examples of the hydrophilic nonwoven fabric for forming the hydrophilic nonwoven fabric layer 23, it is possible to cite nonwoven fabrics formed by laminating fibers obtained by melting a resin such as nylon and by forming it into yarn, e.g., spunbonded nonwoven fabrics obtained by laminating continuous filaments, nonwoven fabrics obtained by drawing a molten polymer by hot air into ultra-fine fibers and forming them into sheet form, and so on.

To effectively prevent re-wetting, it is preferred that the hydrophilic property of the hydrophilic nonwoven fabric layer 23 be such that the angle of contact with water becomes 30° when the moisture percentage of the hydrophilic nonwoven fabric layer 23 is controlled so as to become 30 to 50%. It should be noted that the moisture percentage of the hydrophilic nonwoven fabric layer 23 is determined from (water/total weight)×100.

Fibers for forming the wet paper contacting fibrous layer 15 contain split fibers 15A (i.e., the split fibers 15A account for 100 wt. % of the fibers for forming the wet paper contacting fibrous layer 15). As shown in FIG. 2, each of the split fibers 15A for forming the wet paper contacting fibrous layer 15 is a composite fiber having a structure in which it is split into a plurality of fine fibers (petal portions 19 and a stem portion 21 which will be described later) by the pressing pressure, friction, hot water rinsing, or the like. Split fibers 15A having a size of 3.3 dtex or smaller are preferable, and fibers with circular sections having a size of 1.9 dtex and a length of 51 mm are used in this embodiment. The split fiber 15A consists of seven portions including the six petal portions 19 with sector-shaped sections and one stem portion 21 with a substantially asterisk-shaped section for joining adjacent ones of the petal portions 19. These portions are combined in a circular section and are formed in a splittable manner.

In terms of its material, the split fiber 15A is formed of, for instance, Nylon 6 (i.e., N6), and the stem portion 21 is formed of, for instance, polybutylene terephthalate (i.e., PBT). As a specific example of such a split fiber 15A, it is possible to cite ‘PA31’ (tradename; manufactured by Toray Industries, Inc.) or the like. I should be noted that the reason the size of the split fiber 15A is set to 3.3 dtex or smaller is mainly to facilitate the formation of the wet paper contacting fibrous layer 15, and specifically to ensure that the split fibers 15A are not split when subjected to carding in a preliminary stage of a needling process which is a manufacturing process of the paper transporting felt 100 itself, but are effectively split at the time of the splitting process (e.g., needling, a raising process using a raising machine, hot water rinsing by refining, etc.) which is effected prior to the impregnation with the high polymer elastic material.

It should be noted that the fibers for forming the wet paper contacting fibrous layer 15 may not be formed by the split fibers 15A alone. Specifically, the fibers for forming the wet paper contacting fibrous layer 15 may contain 15 wt. % to 100 wt. % of the split fibers 15A and the nonsplit fibers as remains. The nonsplit fibers are monofilaments which are not split even at the time of carding or needling or even in the process of manufacturing the paper transporting felt after the needling process. In addition, as the nonsplit fibers, stable fibers having a size of, for instance, 1.9 dtex (i.e., the same value as the size persisting prior to splitting of the split fiber) to 6 dtex are preferable.

Gaps between the fine fibers formed by the splitting of the plurality of split fibers 15A are impregnated with a high polymer elastic material 25 from the wet paper surface side of the wet paper contacting fibrous layer 15. Specifically, the wet paper contacting fibrous layer 15 contains 1 wt. % to 10 wt. % of the high polymer elastic material 25. As for the high polymer elastic material 25, after the plurality of split fibers 15A are split into fine fibers, a synthetic resin such as water-based urethane resin, water-based acrylic resin, water-based epoxy resin, water-based synthetic rubber (i.e., water-based emulsion resin), or the like is applied with a roller or sprayed with a sprayer at ordinary temperature to impregnate the gaps between the fine fibers, and is subsequently cured on heating. At this time, since the hydrophilic nonwoven fabric layer 23 is disposed in the layer beneath the wet paper contacting fibrous layer 15 (i.e., the wet paper side surface of the first batt layer 13A), further impregnation with the high polymer elastic material 25 is hampered by the hydrophilic nonwoven fabric layer 23, so that the first batt layer 13A, the base layer 11, and the second batt layer 13B are not impregnated.

As for the basis weight of the respective constituent elements in a typical example of the paper transporting felt 100 thus constructed, the basis weight of the wet paper contacting fibrous layer 15 is 400 g/m2; the basis weight of the hydrophilic nonwoven fabric layer 23 is 40 g/m2; the basis weight of the first batt layer 13A is 400 g/m2; the basis weight of the base layer 11 is 650 g/m2; and the basis weight of the second batt layer 13B is 100 g/m2. In addition, 5 wt. % (10 g/m2) of the high polymer elastic material 25 is contained in the wet paper contacting fibrous layer 15.

In addition, as for the basis weight of the respective constituent elements in one example in which the paper transporting felt 100 is made lightweight, the basis weight of the wet paper contacting fibrous layer 15 is 100 g/m2; the basis weight of the hydrophilic nonwoven fabric layer 23 is 40 g/m2; the basis weight of the first batt layer 13A is 200 g/m2; the basis weight of the base layer 11 is 200 g/m2; and the second batt layer 13B is omitted. In addition, 1 wt. % (1 g/m2) of the high polymer elastic material 25 is contained in the wet paper contacting fibrous layer 15.

In addition, as for the basis weight of the respective constituent elements in one example in which the paper transporting felt 100 is made heavyweight, the basis weight of the wet paper contacting fibrous layer 15 is 300 g/m2; the basis weight of the hydrophilic nonwoven fabric layer 23 is 40 g/m2; the basis weight of the first batt layer 13A is 800 g/m2; the basis weight of the base layer 11 is 1500 g/m2; and the basis weight of the second batt layer 13B is 300 g/m2. In addition, 10 wt. % (30 g/m2) of the high polymer elastic material 25 is contained in the wet paper contacting fibrous layer 15.

A brief description will be given of the method of manufacturing the paper transporting felt 100. First, a sheet in which the batt layer 13 has been integrated on both surfaces of the woven base layer 11 by needling and the like is prepared. Then, after the hydrophilic nonwoven fabric layer 23 and a paper sheet of the split fibers 15A after carding are placed on the surface of the first batt layer 13A, the paper sheet of the split fibers 15A, the hydrophilic nonwoven fabric layer 23, the batt layer 13, and the base layer 11 are entangled and integrated by needling therethrough. It should be noted that since the split fibers 15A are able to maintain their size of 1.9 dtex the time of the carding process, it is possible to prevent the occurrence of fiber masses produced when carding is effected in a state in which, for example, the split fibers 15A are each split into fine fibers (the petal portions 19 and the stem portion 21).

Next, the wet paper contacting fibrous layer 15 having a smooth wet paper side surface covered with the fine fibers and in a state of being not yet impregnated with the high polymer elastic material 25 is formed by splitting the split fibers 15A into fine fibers (the petal portions 19 and the stem portions 21) by needling, friction with a brush of the raising machine, or the splitting operation of such as hot water rinsing in the refining process. Then, the high polymer elastic material 25 is applied to its wet paper side surface with a roller or sprayed with a sprayer to impregnate the gaps between the fine fibers, and is subsequently cured on heating. At this time, since the hydrophilic nonwoven fabric layer 23 is disposed in the layer beneath the wet paper contacting fibrous layer 15, further impregnation with the high polymer elastic material 25 into the layer below the hydrophilic nonwoven fabric layer 23 is hampered, so that the first batt layer 13A, the base layer 11, and the second batt layer 13B are not impregnated. As the high polymer elastic material 25 which can be used, it is possible to cite synthetic resins including, for example, water-based urethane resin, water-based acrylic resin, water-based epoxy resin, water-based synthetic rubber (i.e., water-based emulsion resin), and the like. The impregnation ratio of the high polymer elastic material 25 is appropriately selected in the range of 1 wt. % to 10 wt. % in correspondence with the characteristics required for the press mechanism in which the paper transporting felt 100 is installed.

In the paper transporting felt 100 for, for example, pickup (the paper transporting felt disposed at an entrance of the press apparatus of the paper machine) thus manufactured, the basis weight of the wet paper contacting fibrous layer 15 is 150 g/m2; the impregnation ratio of the high polymer elastic material 25 is 1 wt. %; the density of the entire fibers forming the paper transporting felt 100 is 0.420 g/cm3; and the air permeability is 25 cc/cm2/sec (this value is a mean value of the values measured by applying a pressure of 125 Pa to test pieces of the paper transporting felt 100 in accordance with the Frazir method on the basis of JIS L 1096). In addition, in the paper transporting felt 100 installed in, for instance, a third press mechanism of a multi-stage press apparatus, the basis weight of the wet paper contacting fibrous layer 15 is 200 g/m2; the impregnation ratio of the high polymer elastic material 25 is 3 wt. %; the density of the entire fibers forming the paper transporting felt 100 is 0.450 g/cm3; and the air permeability is 15 cc/cm2/sec. In addition, in the paper transporting felt 100 installed in, for instance, a fourth press mechanism, the basis weight of the wet paper contacting fibrous layer 15 is 250 g/m2; the impregnation ratio of the high polymer elastic material 25 is 5 wt. %; the density of the entire fibers forming the paper transporting felt 100 is 0.500 g/cm3; and the air permeability is 5 cc/cm2/sec.

It should be noted that, in order to form the paper transporting felt 100 having optimal characteristics in correspondence with the type of paper to be made, the kinds of fibers for respectively forming the base layer 11, the batt layer 13, the hydrophilic nonwoven fabric layer 23, and the wet paper contacting fibrous layer 15, as well as the type of the high polymer elastic material 25 and the impregnation ratio, are selected, as required, by taking into account such as the respective characteristics or the characteristics when combined. (Modification of the Paper Transporting Felt 100)

As a preferred modification of the paper transporting felt 100, it is possible to cite one which has a wet paper contacting fibrous layer having mixed-spun fibers containing 30 wt. % of the split fibers 15A of 1.9 dtex and the nonsplit fibers of 3.3 dtex as remains (i.e., 70 wt. %). In this case, the average size of the fibers forming the wet paper contacting fibrous layer is approx. 2.9 dtex. It should be noted that the base layer 11, the batt layer 13, the hydrophilic nonwoven fabric layer 23, and the high polymer elastic material 25 are similar to the ones described above. Since the wet paper contacting fibrous layer contain nonsplit fibers which are not split into fine fibers, the surface of the wet paper contacting fibrous layer is prevented from becoming too dense, and appropriate water permeability and an irregular surface is ensured, so that water can be effective squeezed from the wet paper W, and satisfactory paper releasability can be ensured.

Next, referring to FIG. 3, a description will be given of a press apparatus 300 of a shoe press type paper machine in which the paper transporting felts 100 each formed in the shape of an endless belt (annularly) are installed.

As shown in FIG. 3, the press apparatus 300 of the shoe press type paper machine is a so-called closed draw type press apparatus 300 in which two press mechanisms including a first press mechanism 51 and a second press mechanism 53 are disposed in series along a transporting direction of the wet paper W (the direction of arrow A). As the paper machine is constructed as the shoe press type paper machine of the closed draw type in which the wet paper W is transported and pressurized in the state of being sandwiched by two pairs of the paper transporting felts 100 for a shoe press, the wet paper W can be transported stably at a high speed of, for instance, 1200 to 1400 m/min. Consequently, papermaking is made possible at an extremely high efficiency in comparison with the shoe press type paper machine of the open draw type and the like.

The first press mechanism 51 includes the pair of the paper transporting felts 100 (100A) for a shoe press, as well as a first shoe 55 and a first roll 57 (i.e., a first shoe press) which are disposed in face-to-face relation so as to form a first nip (i.e., a first pressing portion) therebetween. The second press mechanism 53 includes the pair of the paper transporting felts 100 (100B) for a shoe press, as well as a second shoe 59 and a second roll 61 (i.e., a second shoe press) which are disposed in face-to-face relation so as to form a second nip (i.e., a second pressing portion) therebetween. It should be noted that, by taking into consideration the wet-paper dewatering function and the function of smoothing the wet paper surface, the amount of impregnation with the high polymer elastic material 25 in the paper transporting felt 100A installed in the first press mechanism 51 is normally set to be smaller than the amount of impregnation with the high polymer elastic material 25 in the paper transporting felt 100B installed in the second press mechanism 53. Specifically, the paper transporting felt 100A installed in the first press mechanism 51 is impregnated with 3 wt. % of the high polymer elastic material 25, and the paper transporting felt 100B installed in the second press mechanism 53 is impregnated with 5 wt. % of the high polymer elastic material 25. Namely, as the paper transporting felts installed in the second press mechanism 53 disposed on the downstream side, the paper transporting felts 100B in which priority is placed on the function of smoothing the wet paper surface rather than the wet-paper dewatering function are used.

It should be noted that although, as shown in FIG. 3, the paper transporting felts 100 (100A; 100B) may be adopted as the upper and lower paper transporting felts of the first press mechanism 51 and the second press mechanism 53, the paper transporting felts 100 (100A; 100B) may alternatively be adopted as either the upper paper transporting felts or the lower paper transporting felts of the first press mechanism 51 and the second press mechanism 53. In the case where the paper transporting felts 100 (100A; 100B) are installed as either the upper paper transporting felts or the lower paper transporting felts of the first press mechanism 51 and the second press mechanism 53, it suffices if arbitrary paper transporting felts are adopted in correspondence with the papermaking characteristics as the other paper transporting felts. Still alternatively, only the paper transporting felts 100A or only the paper transporting felts 100B may be adopted as the paper transporting felts of the first press mechanism 51 and the second press mechanism 53.

As shown in FIG. 3, the wet paper W carried out from a wire part (not shown) and delivered to the first press mechanism 51 is transported while being sandwiched by the pair of the paper transporting felts 100A, and water is squeezed out by being pressurized by the first shoe 55 and the first roll 57. The squeezed water is absorbed from the porous wet paper contacting fibrous layer 15 to the first batt layer 13A and the like of each paper transporting felt 100A. Next, the wet paper W is delivered to the second press mechanism 53 and is transported while being sandwiched by the pair of the paper transporting felts 100B, and water is further squeezed out by being pressurized by the second shoe 59 and the second roll 61. The squeezed water is absorbed from the porous wet paper contacting fibrous layer 15 to the first batt layer 13A and the like of each paper transporting felt 100B.

It should be noted that the wet paper contacting fibrous layer w 15, with which the wet paper W comes into contact when the wet paper W is delivered from the first press mechanism 51 to the second press mechanism 53, is porous, and since an appropriately irregular surface is formed on its surface, the paper releasability is excellent, so that the wet paper W is easily released from the paper transporting felts 100A and is reliably delivered to the paper transporting felts 100B. In addition, since the surface of the wet paper contacting fibrous layer 15, which is brought into direct contact with the wet paper W, is formed as a smooth surface by being covered with the split fine fibers of the split fibers 15A and the high polymer elastic material 25 (plus nonsplit fibers in the case where the wet paper contacting fibrous layer 15 contains the nonsplit fibers), the wet paper W having a smooth surface is pressurized and is delivered to the drier part (not shown) to dry.

It should be noted that when the pressure acting on the wet paper W and the paper transporting felts 100A and 100B in a zone extending from the first pressing portion formed by the first shoe 55 and the first roll 57 or the second pressing portion formed by the second shoe 59 and the second roll 61 to the exit is released, the re-wetting phenomenon tends to occur in which the moisture in the paper transporting felts 100A and 100B is transferred to the wet paper W side. However, since the hydrophilic nonwoven fabric layer 23 is higher in density and lower in water permeability than the batt layer 13, the moisture in the batt layer 13 is difficult to permeate through the hydrophilic nonwoven fabric layer 23 and move to the wet paper contacting fibrous layer 15. As a result, the occurrence of the re-wetting phenomenon is suppressed.

It should be noted that although, as described above, a description has been given of the press apparatus 300 having two-stage press mechanisms 51 and 53 by way of one example as an embodiment of the press apparatus of the shoe press type paper machine in accordance with the invention. However, it goes without saying that the press apparatus may be a press apparatus having one press mechanism or a press apparatus in which a multiplicity of press mechanisms are disposed in series (i.e., disposed).

Here, to deepen an understanding of the invention, a brief description will be given of the construction of the embodiment of the paper transporting felt in accordance with the invention and the construction of the embodiment of the press apparatus of the shoe press type paper machine having the paper transporting felt.

A paper transporting felt 100 which is at least one paper transporting felt 100 of a pair of paper transporting felts for a shoe press, which are disposed in a press apparatus 300 provided in a press part of a shoe press type paper machine, form a press mechanism (51; 53) together with a shoe press having a roll (57; 61) and a shoe (55; 59) in the press apparatus 300, and are pressurized by the roll (57; 61) and the shoe (55; 59) while sandwiching a wet paper W, to absorb water squeezed from the wet paper W.

The paper transporting felt 100 has:

a base layer 11;

a first batt layer 13A which is formed on a wet paper W side surface of the base layer 11;

a second batt layer 13B which is formed on a roll (57; 61) side surface or a shoe (55; 59) side surface of the base layer 11;

a wet paper contacting fibrous layer 15 which includes a plurality of split fibers 15A split into fine fibers and a high polymer elastic material 25 impregnating gaps between the fine fibers, and is formed on a wet paper W side surface of the first batt layer 13A so as to allow the fine fibers and the high polymer elastic material 25 to come into direct contact with the wet paper W; and

a hydrophilic nonwoven fabric layer 23 which is disposed between the first batt layer 13A and the wet paper contacting fibrous layer 15,

wherein, in a surface of the wet paper contacting fibrous layer 15 which comes into direct contact with the wet paper W, the fine fibers are partially covered with the high polymer elastic material 25.

The wet paper contacting fibrous layer 15 contains 1 wt. % to 10 wt. % of the high polymer elastic material 25. The fibers for forming the wet paper contacting fibrous layer 15 may contain 15 wt. % to 100 wt. % of the split fibers 15A and the nonsplit fibers as remains.

The press apparatus 300 of a shoe press type paper machine is a press apparatus of a shoe press type paper machine having a plurality of press mechanisms each having the pair of paper transporting felts 100 (100A; 100B), wherein the plurality of press mechanisms (51, 53) are disposed in series (i.e., disposed) along the transporting direction A of the wet paper W transported by the paper transporting felts 100A and 100B.

Each size of the split fibers 15A prior to splitting in the paper transporting felt 100 (100A; 100B) is 3.3 dtex or smaller, more preferably 1.9 dtex.

The press apparatus 300 of a shoe press type paper machine is a press machine of a closed draw type.

As described above, according to the paper transporting felt 100, the wet paper contacting fibrous layer 15, which has been formed by splitting the plurality of split fibers 15A into fine fibers and by subsequently impregnating gaps between the fine fibers with the high polymer elastic material 25, is formed on the wet paper side surface of the first batt layer 13A of the paper transporting felt 100 so as to be brought into direct contact with the wet paper W. Therefore, it is possible to improve the surface smoothness of the wet paper contacting fibrous layer 15, thereby making it possible to manufacture high-quality paper having a smooth surface. In addition, the surface of the wet paper contacting fibrous layer 15 is formed as a surface in which the fine fibers formed by the splitting of the split fibers 15A are partially covered with the high polymer elastic material 25. Since the surface of the wet paper contacting fibrous layer 15 has slight irregularities caused by the projection of these infinitesimal fine fibers, water films between the wet paper contacting fibrous layer 15 and the wet paper W are likely to be broken or are difficult to be formed. Hence, the paper releasability from the paper transporting felt 100 is excellent, so that the wet paper W can be easily delivered to the drier canvas in the ensuing process.

It should be noted that the wet paper contacting fibrous layer 15 is formed as one having mixed-spun fibers of the split fibers 15A and nonsplit fibers, gaps between the fine fibers (those obtained by the splitting of the split fibers 15A), gaps between the fine fibers and the nonsplit fibers, and gaps between the nonsplit fibers are impregnated with the high polymer elastic material 25. In the surface of such a wet paper contacting fibrous layer 15 which is brought into direct contact with the wet paper W, the fine fibers and the nonsplit fibers are partially covered with the high polymer elastic material 25, and the surface of the wet paper contacting fibrous layer 15 has slight irregularities caused by the projection of these infinitesimal fine fibers, water films between the wet paper contacting fibrous layer and the wet paper W are likely to be broken or are difficult to be formed. Hence, the paper releasability from the paper transporting felt 100 is excellent, so that the wet paper W can be easily delivered to the drier canvas in the ensuing process.

In addition, since the fine fibers formed by the splitting of the split fibers 15A are combined to some extent and are partially covered by the high polymer elastic material 25, the so-called capillary phenomenon is difficult to occur, and the falling off of these fine fibers from the paper transporting felt 100 is prevented. Consequently, as for the paper manufactured by the shoe press type paper machine using the paper transporting felts 100, its surface becomes extremely smooth. Moreover, since the life of the paper transporting felt 100 (i.e., the usable period of the paper transporting felt 100) is long, it is possible to decrease the frequency of maintenance for replacing the paper transporting felt 100 with a new one.

In addition, since the hydrophilic nonwoven fabric layer 23 is disposed between the first batt layer 13A and the wet paper contacting fibrous layer 15, the high polymer elastic material 25 with which the wet paper contacting fibrous layer 15 is impregnated from its surface side is blocked by the hydrophilic nonwoven fabric layer 23, and layers deeper than the hydrophilic nonwoven fabric layer 23 (i.e., the first batt layer 13A, the base layer 11, and the second batt layer 13B) are not impregnated with the high polymer elastic material 25. Thus, the high polymer elastic material 25 is disposed only in the wet paper contacting fibrous layer 15 (e.g., by 0.5 mm or thereabouts from the surface).

Accordingly, since the paper transporting felt 100 has water permeability and appropriate compressing and recovering functions (cushionability), the paper transporting felt 100 is able to exhibit its dewatering characteristic effectively. In addition, stains (specifically, components of such as additives and paste contained in the wet paper W) which are temporarily attached to the wet paper contacting fibrous layer 15 including the high polymer elastic material 25 are likely to be exfoliated from the surface of the wet paper contacting fibrous layer 15 and are moved to the wet paper W by virtue of the appropriate compressing and recovering functions of the paper transporting felt 100. Namely, the paper transporting felt 100 has a high self-cleaning function. Consequently, stains are difficult to remain on the paper transporting felt 100, and since the stains which are moved to the wet paper W are originally contained in the wet paper W as its components, no effect is exerted on the quality of the wet paper W. In addition, the movement of the water temporarily absorbed from the wet paper W by the paper transporting felt 100 back to the wet paper W (i.e., the so-called re-wetting phenomenon) is prevented by the hydrophilic nonwoven fabric layer 23.

In addition, according to the press apparatus 300 of a shoe press type paper machine, if the plurality of press mechanisms 51 and 53 each having the pair of paper transporting felts 100 (100A; 100B) are disposed in series along the transporting direction A of the wet paper W being transported by the paper transporting felts 100 (100A and 100B), it is suitable in effectively squeezing water from the wet paper W and delivering the wet paper W to the ensuing paper transporting felts with excellent paper releasability. Namely, it is possible to effectively squeeze water from the wet paper W containing a large amount of water, and the wet paper W can be delivered reliably to the ensuing paper transporting felts, thereby permitting high-speed papermaking operation. In particular, if the paper transporting felt 100B impregnated with a relatively large amount of (within the range of 1 wt. % to 10 wt. %) high polymer elastic material 25 is disposed in the press mechanism 53 disposed on the downstream side in the transporting direction of the wet paper W among the plurality of press mechanisms 51 and 53, it is conceivable that the water permeability may slightly decline as compared with the paper transporting felt 100A in which the amount of impregnation with the high polymer elastic material 25 is small. However, since the paper transporting felt 100B has not only the function of smoothing the wet paper surface but also high paper releasability, the wet paper W being transported at high speed can be reliably delivered to the drier canvas in the ensuing process, and high-speed papermaking becomes possible.

In addition, it is possible to change the characteristics of the paper transporting felt 100 by appropriately changing the mix spinning ratio between the split fibers 15A and the nonsplit fibers in the wet paper contacting fibrous layer 15. Here, the weight ratio of the mixed-spun fibers is defined by “weight of the split fibers 15A/(weight of the split fibers 15A+weight of the nonsplit fibers)×100.” The surface smoothness and the dewatering characteristic, which are the characteristics required for the paper transporting felt 100, are inversely correlated. Hence, if the density of the paper transporting felt 100 is increased to improve the performance of smoothing the surface of the wet paper W, the dewatering characteristic tends to deteriorate. Meanwhile, the plurality of press mechanisms 51 and 53 disposed from the upstream side in the transporting direction of the wet paper W being transported to the downstream side respectively require subtly different functions. Priority is placed on the dewatering characteristic in the case of the paper transporting felt 100A of the press mechanism 51 disposed on the upstream side, while the performance of smoothing the surface of the wet paper W is required for the paper transporting felt 100B of the press mechanism 53 disposed on the downstream side. Accordingly, by appropriately changing the mix spinning ratio between the nonsplit fibers and the split fibers 15A, the paper transporting felts 100 can be provided with optimal characteristics (surface smoothing characteristic, dewatering characteristic, etc.) for the respective press mechanisms 51 and 53.

In addition, according to the paper transporting felt 100, since the wet paper contacting fibrous layer 15 contains 1 wt. % to 10 wt. % of the high polymer elastic material 25, not all the pores between the fibers are filled with the high polymer elastic material 25, and appropriate porosity is maintained between the fibers. In other words, the structure is made porous. Therefore, water films formed between the wet paper contacting fibrous layer 15 and the wet paper W are dispersed, and appropriate cushionability is provided. Consequently, it is possible to obtain a paper transporting felt 100 the paper releasability from which is excellent, which absorbs water squeezed from the wet paper W by stretching by being pressurized by the roll 57 or 61 and the shoe 55 or 59 in each press mechanism 51 or 53, and which has a smooth surface. In addition, by appropriately changing the impregnation ratio of the high polymer elastic material 25, the paper transporting felts 100 can be provided with optimal characteristics (paper releasability, surface smoothing characteristic, dewatering characteristic, etc.) for the respective press mechanisms 51 and 53.

In addition, according to the paper transporting felt 100, since the size of each of the split fibers 15A prior to splitting is 3.3 dtex or smaller, even if the size of the split fiber 15A prior to splitting was 3.3 dtex, the size of the fine fibers formed by the splitting of the split fibers 15A becomes smaller than 3.3 dtex. Thus, if the wet paper contacting fibrous layer 15 including the slit fibers 15A, which become fine fibers of a size which is practically as close to the size of the fibers of the wet paper W as possible by being split, is formed, it is possible to manufacture high-quality paper extremely excelling in the surface smoothness. In addition, as the gaps between such fine fibers are impregnated with the high polymer elastic material 25, the surface of the wet paper contacting fibrous layer 15 can be made a smoother surface excelling in the paper releasability. Even in a case where fine fibers fallen off or cut off from the wet paper contacting fibrous layer 15 (i.e., fine fibers formed by the splitting of the split fibers 15A) due to the so-called loss of fibers are slightly attached to the surface of the wet paper W, since these fine fibers are extremely slender, the quality of the wet paper W is not caused to decline. In addition, it is more preferable if the size of each of the split fibers 15A prior to splitting is a small value such as 1.9 dtex.

It should be noted that the paper transporting felt 100 is such that after the split fibers 15A of the wet paper contacting fibrous layer 15 are split into fine fibers, the gaps between these fine fibers are impregnated with the high polymer elastic material 25. The splitting of the split fibers 15A is preferably effected in the needling process which if one of the processes of manufacturing the paper transporting felt. Fiber masses (i.e., masses of fibers) are likely to be produced if the split fibers 15A are split into fine fibers by carding in a preliminary stage of a needling process. These fiber masses are implanted by needling, and relatively large irregularities are formed on the surface of the paper transporting felt, so that the surface smoothness of the wet paper declines. The splitting of the split fibers 15A may be effected, for instance, by needling using small-gauge needles in the needling process, by rubbing the implanted split fibers 15A with a brush (commonly called a teasel) of a raising machine after the needling process, or by refining (hot water rinsing) the paper transporting felt 100 after the needling process. Namely, the splitting of the split fibers 15 may be effected in any process insofar as the process is carried out after carding, which is the preliminary stage of the needling process, and before the impregnation with the high polymer elastic material 25. Then, after the splitting of the split fibers 15A into fine fibers, the gaps between the fine fibers are impregnated with the high polymer elastic material 25.

The impregnation with the high polymer elastic material 25 is performed as follows: After the split fibers 15A are split into fine fibers, a synthetic resin such as water-based urethane resin, water-based acrylic resin, water-based epoxy resin, water-based synthetic rubber (i.e., water-based emulsion resin), or the like is applied with a roller or sprayed with a sprayer at ordinary temperature to impregnate the gaps between the fine fibers, and is subsequently cured on heating.

In addition, according to the press apparatus 300 of a shoe press type paper machine, since it is a press apparatus of a closed draw type, the wet paper W is transported in a state of being sandwiched by the pair of paper transporting felts 100. Consequently, the wet paper W can be transported at an extremely high speed without applying a force to the wet paper W which has weak strength and is likely to be cut off. Accordingly, efficient papermaking is made possible.

It should be noted that the invention is not limited to the above-described embodiment and modifications, and alterations, improvements, and the like are possible, as required. In addition, the materials, shapes, dimensions, numerical values, forms, numbers, places of disposition, and the like are arbitrary and are not limited, insofar as they are capable of attaining the invention.

For example, effective operation can be similarly obtained even if the paper transporting felt 100 is installed in a shoe press type paper machine of an open draw type having a portion where the wet paper W is independently transported in the course of being transported. Still alternatively, benefits of the above-described outstanding operation and effects based on the invention can be obtained even if the paper transporting felt 100 is installed in a press apparatus of a roll press type paper machine of the closed draw type or the open draw type.

This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2004-284264 filed on Sep. 29, 2004, the entire contents of which are incorporated herein by reference.

Claims

1. A paper transporting felt comprising:

a base layer;

a first batt layer which is formed on a wet paper side surface of the base layer;

a second batt layer which is formed on a press side surface of the base layer;

a wet paper contacting fibrous layer which includes a plurality of split fibers split into fine fibers and a high polymer elastic material impregnating gaps between the fine fibers, and is formed on a wet paper side surface of the first batt layer so as to allow the fine fibers and the high polymer elastic material to come into direct contact with the wet paper; and

a hydrophilic nonwoven fabric layer which is disposed between the first batt layer and the wet paper contacting fibrous layer,

wherein, in a surface of the wet paper contacting fibrous layer which comes into direct contact with the wet paper, the fine fibers are partially covered with the high polymer elastic material.

2. The paper transporting felt according to claim 1,

wherein the wet paper contacting fibrous layer contains 1 wt. % to 10 wt. % of the high polymer elastic material.

3. The paper transporting felt according to claim 1,

wherein fibers for forming the wet paper contacting fibrous layer contain 15 wt. % to 100 wt. % of the split fibers and nonsplit fibers as remains.

4. The paper transporting felt according to any one of claims 1 to 3,

wherein each size of the split fibers prior to splitting is 3.3 dtex or smaller.

5. The paper transporting felt according to claim 4,

wherein each size of the split fibers prior to splitting is 1.9 dtex.

6. A press apparatus of a paper machine comprising the paper transporting felt according to claim 1.

7. A press apparatus of a paper machine comprising a plurality of press mechanisms each having the paper transporting felt according to claim 1,

wherein the plurality of press mechanisms are disposed in series along a transporting direction of the wet paper transported by the paper transporting felts.

8. The press apparatus of a paper machine according to claim 7,

wherein each size of the split fibers prior to splitting is 3.3 dtex or smaller.

9. The press apparatus of a paper machine according to claim 8,

wherein each size of the split fibers prior to splitting is 1.9 dtex.

10. The press apparatus of a paper machine according to claim 6,

wherein the press apparatus is a press machine of a closed draw type.

11. The press apparatus of a paper machine according to claim 7,

wherein the press apparatus is a press machine of a closed draw type.

12. The press apparatus of a paper machine according to claim 6,

wherein the press apparatus is a press apparatus of a shoe press type paper machine, and a press of the press apparatus is a shoe press having a roll and a shoe for pressurizing the paper transporting felt.

13. The press apparatus of a paper machine according to claim 7,

wherein the press apparatus is a press apparatus of a shoe press type paper machine, and a press of the press apparatus is a shoe press having a roll and a shoe for pressurizing the paper transporting felt.

14. The press apparatus of a paper machine according to claim 6,

wherein the press apparatus is a press apparatus of a roll press type paper machine, and a press of the press apparatus is a roll press having a pair of rolls for pressurizing the paper transporting felt.

15. The press apparatus of a paper machine according to claim 7,

wherein the press apparatus is a press apparatus of a roll press type paper machine, and a press of the press apparatus is a roll press having a pair of rolls for pressurizing the paper transporting felt.