EP1957710A1

EP1957710A1 - Papermaking felt and shoe press apparatus

Info

Publication number: EP1957710A1
Application number: EP06811714A
Authority: EP
Inventors: Takashi Ouchi
Original assignee: Ichikawa Co Ltd
Current assignee: Ichikawa Co Ltd
Priority date: 2005-10-07
Filing date: 2006-10-06
Publication date: 2008-08-20
Also published as: WO2007043632A9; TW200728554A; JP4712508B2; JP2007100277A; WO2007043632A1; CN101268231A

Abstract

A papermaking felt (100) includes a base layer (11), a first batt layer (13A) formed on a surface of the base layer on a wet paper side, and a contacting layer (15) including formed on a surface of the first batt layer on a the wet paper side where the wet paper comes into contact. The contacting layer includes a hydrophilic fiber, and the hydrophilic fiber is fibrillated by being pressed by a roll and a shoe .

Description

DESCRIPTION

PAPERMAKING FELT AND SHOE PRESS APPARATUS

Technical Field

The present invention relates to a papermaking felt, especially for a shoe press, and a shoe press apparatus for a paper machine m which the papermaking felt is employed. Background Art

A press part of a shoe press type paper machine is provided with a press apparatus . The press apparatus includes a plurality of press mechanisms aligned in series along a direction of carrying a wet paper. Each press mechanism includes a pair of papermaking felts of an endless belt type, and a roll and a shoe (namely, a shoe press) arranged so as to face each other m a vertical direction and to interpose respective portions of the papermaking felts therebetween. The wet paper is carried by the papermaking felts which travels m the same direction substantially at equal speed, and is pressed by the roll and the shoe with the papermaking felts, thereby squeezing out water from the wet paper so as to be absorbed to the papermaking felts.

In such press mechanism having the shoe press, a press zone of a press portion (namely, a nip) formed between the roll and the shoe can be widely provided m comparison with a more general press mechanism having a roll press (namely, a press mechanism which employs a pair of rolls in place of a combination of a roll and a shoe) . Thus, a press time period can be prolonged and therefore, the above-described press mechanism is further excellent in a water squeeze out performance .

However, in an area between a center of the press portion and an outlet of the press portion, , volumes of the papermakmg felt and the wet paper expand rapidly since a pressure applied to the wet paper and the papermakmg felt is suddenly released. As a result, due to a negative pressure produced at the papermakmg felt and the wet paper as well as a capillary phenomenon m the wet paper including fine fibers, so-called a re-wettmg phenomenon occurs m which the water absorbed by the papermakmg felt shifts back to the wet paper. In this way, the area between the center of the press portion and the outlet of the press portion constitutes a significant factor of deteriorating a water squeeze out performance of the press apparatus of the shoe press type paper machine.

In order to improve a water squeeze out performance, JP-A-2004-143627 discloses a papermakmg felt having a hydrophilic nonwoven cloth disposed inside a batt layer so as to suppress the occurrence of the re-wettmg phenomenon batt layer. The hydrophilic nonwoven cloth may be, for example, a cloth constituted by laminating fibers formed by melting and spinning a resin, such as a span bond nonwoven cloth constituted by laminating continuous filaments, or a sheet-like nonwoven cloth formed by stretching a melted polymer with hot wind so as to be formed into fine fibers .

The hydrophilic nonwoven cloth has a higher density and a lower permeability relative to batt fibers. Therefore, in a papermakmg felt, it is difficult for water inside the batt layer arranged on a roll side (or a shoe side) of the hydrophilic nonwoven cloth to move to the batt layer on the the wet paper side or to the wet paper by permeating the hydrophilic nonwoven cloth. Therefore, by the hydrophilic nonwoven cloth, the water inside the batt fiber on the roll side (or the shoe side) is prevented from being returned to the wet paper. Further, a fineness of the hydrophilic nonwoven cloth is lower than a fineness of the batt layer. Therefore, it is easy for the water inside the batt layer arranged on the wet paper side of the hydrophilic nonwoven cloth to be shifted to the hydrophilic nonwoven cloth by the capillary phenomenon, thereby preventing the re-wetting phenomenon.

In a shoe press apparatus for a paper machine, m comparison with a roll press apparatus, water is squeezed out by applying a very large pressure on the papermakmg felt at the press portion (namely, the nip) . Therefore, the papermakmg felt easily becomes flattened, and result m having a high density. In accordance therewith, stain (specifically, components of an additive, a glue and the like included in the wet paper) adheres to and accumulates m the papermaking felt. Therefore, due to a short service life of the papermaking felt (namely, a time period capable of using the papermaking felt) , maintenances such as frequently interchanging the papermaking felt with a new one or cleaning the papermaking felt m the midst of papermaking are required for the shoe press apparatus for a paper machine.

Furthermore, m the shoe press apparatus for a paper machine, due to large pressure or friction at the press portion (namely, the nip) , there are significant fall offs or cut offs (so-called an unhaiπng) of fibers at a surface of the batt layer where the wet paper directly comes into contact. Although most of the fallen-off fibers or cut-off fibers are discharged outside the press apparatus by cleaning means such as a water shower and a suction box and the like, there is a case some of such fibers stick onto a surface of the wet paper. Because the fallen-off fibers or the cut-off fibers are bolder and harder than fibers of the wet paper, there is a case where the paper is made with such fibers being adhered on the surface thereof, and a printing adaptability becomes inferior. More specifically, there is a case where a decoloration occurs when printing. In such way, the unhainng of fibers at the surface of the batt layer where the wet paper directly comes into contact deteriorates a quality of a paper product such as a printed matter. On the other hand, the surface of the batt layer constitutes a factor of significantly deteriorating a smoothness of a surface of the wet paper since the surface of the batt layer is roughened by the unhainng of fibers.

As main functions required for the papermakmg felt for the shoe press, there are not only the a function of carrying the wet paper and the water squeeze out function, but also the function of smoothing the surface of the wet paper and an excellent paper separating function m delivering the wet paper, as is apparent from the above. The papermakmg felt disclosed in JP-A-2004-143627 is emphasized mainly on an improvement of the water squeeze out function, and it does not contribute to improvements m the smoothness of the surface of the wet paper or the paper separating performance which is required for a high quality paper.

Disclosure of the Invention

It is an object of the present invention to provide a papermakmg felt having excellent functions m smoothing a surface of a wet paper and m separating a wet paper therefrom when delivering, in which a stain is easy to be removed, and to further provide a shoe press apparatus for a paper machine m which such papermakmg felt is employed.

According to one or more embodiments of the invention, a papermakmg felt of a press apparatus for a paper machine, m which the paper making felt is disposed bet.wϊeen a roil ana a wet paper or between a shoe and the wet paper, the papermakmg felt includes: a base layer; a first batt layer formed on the base layer on the wet paper side; and a contacting layer formed on the first batt layer on the wet paper side where the wet paper directly comes into contact. The contacting layer includes a hydrophilic fiber, and the hydrophilic fiber is fibπllated when pressed by the roll and the shoe.

An amount of the hydrophilic fiber with respect to the contacting layer may be 15 % to 100 % by weight, and the rest of the contacting layer may be formed by a nonhydrophilic fiber .

The papermakmg felt may further include a hydrophilic nonwoven cloth layer between the base layer and the contacting layer.

The papermakmg felt may further include a second batt layer formed on the base layer on the roll side or the shoe side.

According to one or more embodiments of the invention, a shoe press apparatus for a paper machine includes: a shoe; a pair of papermakmg felts interposing a wet paper therebetween; and a roll disposed such that the pair of papermakmg felts is interposed between the shoe and the roll. At least one of the papermakmg felts includes: a base layer; a first batt layer formed on the base layer on the wet paper side; and a contacting layer formed on the first batt layer on the wet paper side where the wet paper direictlv comes into contact. The contacting layer includes a hydrαphilic fiber, and the hydrophilic fiber is fibπllated when ptessed by the roll and the shoe.

An amount of hydrophilic fiber with respect to the contacting layer may be between 15 % and 100 % by weight, and the rest of the contacting layer may be formed by a nonhydrophilic fiber.

At least one of the papermakmg felts may further include a hydrophilic nonwoven cloth layer between the base layer and the contacting layer.

At least one of the papermakmg felts may further include a second batt layer formed on the base layer on the roll side or the shoe side.

According to one or more embodiments of the invention, in a shoe press apparatus for a paper machine having a plurality of press mechanisms aligned in series along a direction of carrying a wet paper, each press mechanism include: a shoe; a pair of papermakmg felts interposing a wet paper therebetween; and a roll disposed such that the pair of papermakmg felts is interposed between the shoe and the roll. At least one of the papermakmg felts includes: a base layer, a first batt layer formed on the base layer on the wet paper side; and a contacting layer formed on the first batt layer on the wet paper side where the wet paper directly comes into contact. The contacting layer includes a hydrophilic fiber, and the hydrophilic fiber is fibπllated when pressed by the roll and the shoe.

At least one of the papermakmg felts of the press mechanism aligned at downstream side along the direction of carrying the wet paper may further include a hydrophilic nonwoven cloth layer between the base layer and the contacting layer .

According to one or more embodiments of the invention, the, contacting layer including the hydrophilic fiber fibriHated into micro fibers by being pressed by the shoe press (namely, the roll and the shoe) is formed on the surface of the first batt layer on the wet paper side of the papermakmg felt where the wet paper comes into contact. Therefore, when the contacting layer including the hydrophilic fiber which becomes a micro fiber having a extremely low fineness by being fibrillated is formed, a surface smoothness of the wet paper can be promoted. Further, stain (specifically, a component of an additive, a glue or the like included in the wet paper) temporarily adhered to the papermaking felt is fallen off from the papermaking felt along with the micro fiber by a so-called unharing phenomenon of the micro fiber formed by fibrillatmg the hydrophilic fiber. Therefore, the stain is difficult to remain at the papermaking felt. Even when a micro fiber (namely, the small fiber formed by fibrillatmg the hydrophilic fiber) fallen off or cut off from the contacting layer is more or less adhered to a surface of the wet paper, since the small fiber is extremely fine, quality of the wet paper is not deteriorated. Further, stain temporarily shifted to the wet paper along with falling off the small fiber formed by the fibrillation is inherently included m the wet paper as a component thereof. Therefore, the stain does not effect any influence on the quality of the wet paper. Thus, a surface of a paper fabricated by the shoe press type paper machine using the papermaking felt becomes extremely smooth, further, service life of the papermaking felt (namely, a time period capable of using the papermaking felt) is prolonged. Therefore, there can be reduced a frequency of maintenance of interchanging the papermaking felt by a new one or cleaning the papermaking felt in the midst of making paper or the like. Therefore, it is preferable that the hydrophilic fiber is included at least at a surface of the contacting layer brought into direct contact with the wet paper. Further, according to one or more embodiments of the invention, the fibrillation of the hydrophilic fiber of the contacting layer of the papermaking felt is carried out instantly in trial operation (namely, so-called running in operation) of the shoe press apparatus of the paper machine. Therefore, high quality paper can stably be fabricated from the beginning of paper making operation, and a time period until stabilizing the paper making operation can considerably be shortened. Meanwhile, it is preferable that the hydrophilic fiber used m the papermaking felt be a fiber fibrillated by being pressed by the shoe press, the fiber is not fibπllated but maintains a comparatively bold state at a carding step or a needling step during a process of manufacturing the papermaking felt. For example, when the hydrophilic fiber is fibrillated into a micro fiber is assumedly carded m carding, a fiber block (namely, block of fiber) is easy to be produced. The fiber block is implanted to the felt m the needling step to form recesses and projections at a surface of the papermaking felt. Therefore, a surface smoothness of the wet paper is deteriorated. Thus, by using the contacting layer including the hydrophilic fiber fibrillated into a micro fiber by being pressed by the shoe press, such a drawback can be overcome.

According to one or more embodiments of the invention, 15 % to 100 % of the contacting layer by weight is formed by the hydrophilic fiber and the rest of the contacting layer is formed by the' nonhydrophilic fiber . Therefore, by pertinently changing a weight rate of the hydrophilic fiber, a property of the papermaking felt for the shoe press can be changed. Here, the weight rate of the hydrophilic fiber is defined by "weight of hydrophilic fiber/ (weight of hydrophilic fiber + weight of nonhydrophilic fiber) x 100". Further, the nonhydrophilic fiber is a normal ordinary fiber which is not fibrillated even in the carding step or the needling step or even by being pressed by the shoe press (namely, roll and shoe) .

A surface smoothness and a water squeeze out property constituting properties requested for the papermaking felt are brought into an inversely proportional relationship, when a density of the papermaking felt is increased in order to promote the function of smoothing the surface of the wet paper, the water squeeze out property tends to be deteriorated. On the other hand, functions which differ from each other delicately are requested for a plurality of the press mechanisms arranged from upstream to downstream of a direction of carrying the wet paper to be carried, the water squeeze out property is emphasized m the papermaking felt of the press mechanism arranged on the upstream side, further, a function of smoothing the surface of the wet paper is requested for the papermaking felt of the press mechanism arranged on the downstream side. Therefore, the papermaking felts can be provided with properties (surface smoothness, water squeeze out property or the like) optimum for the respective press mechanisms by pertinently changing the weight rate of the hydrophilic fiber.

According one or more embodiments of the invention, the hydrophilic nonwoven cloth layer is provided between the base layer and the contacting layer and therefore, reshifting of moisture temporarily absorbed from the wet paper to the papermakmg felt (namely, so-called re-wettmg phenomenon) is hampered by the hydrophilic nonwoven cloth layer.

According one or more embodiments of the invention, the shoe press apparatus is provided with the papermakmg felt as described above. Therefore, excellent operation and effect are achieved as described above.

According one or more embodiments of the invention, when the plurality of press mechanisms are arranged m the shoe press apparatus to be aligned in series along with the direction of carrying the wet paper carried by the papermakmg felts, the arrangement is particularly preferable m view of squeezing out water efficiently from the wet paper. Namely, a large amount of water can effectively be squeezed out from the wet paper including much of the moisture, thereby, the papermakmg felt can be provided with an excellent paper separating function m delivering the wet paper and therefore, the paper making operation can be carried out at high speed.

According one or more embodiments of the invention, when at least one of the papermakmg felts of the press mechanism aligned at downstream side along the direction of carrying the wet paper includes a hydrophilic nonwoven cloth layer between the base layer and the contacting layer, a water permeating function may slightly be deteriorated m comparison with those of the papermaking felts without the hydrophilic nonwoven cloth layer. However, there can be provided not only a function of smoothing a surface of the wet paper but also a high function of preventing re-wettmg. Therefore, the press apparatus is particularly preferable in view of preventing the re-wettmg phenomenon and preferable in view of smoothing the surface of the wet paper.

According to one or more embodiments of the invention, there can be provided the papermaking felt from which stain is easy to be fallen off, and which is excellent m the function of smoothing the surface of the wet paper and in paper separating function when delivering the wet paper, and further, the shoe press apparatus of the paper machine having such papermaking felt can be provided.

Brief Description of the Drawings

A concise explanation has been given of the invention as described above. The advantages, nature, and various additional features of the invention will appear more fully upon consideration of the embodiments with reference to the following drawings. Fig.l is a vertical sectional view of a papermakmg felt according to a first embodiment of the invention.

Fig.2 is a vertical sectional view of a papermakmg felt according to a second embodiment of the invention.

Fig.3 is an outline view for explaining of a shoe press apparatus of a paper machine according to another embodiment the invention.

Description of the embodiments

Embodiments according to the invention will be explained below m details with ' reference to the drawings.

Fig.l is a vertical sectional view of a papermakmg felt 100 according to the first embodiment of the invention, Fig.2 is a vertical sectional view of a papermakmg felt 200 according to the second embodiment of the invention, Fig.3 is an outline view for explaining a shoe press apparatus of a paper machine accprdmg to another embodiment of the invention. First Embodiment

As shown m Fig.l, the papermakmg felt 100 includes a base layer 11, a batt layer 13 (a first batt layer 13A and a second batt layer 13B), and a contacting layer 15. More specifically, the first batt layer 13A is formed on a surface of the base layer 11 on a wet paper side, the second batt layer 13B is formed on the other surface of the base layer 11 on a roll side or a shoe side, and the contacting layer 15 is formed on a surface' of the first batt layer 13A on the wet paper side where the wet paper comes into contact. The base layer 11, the batt layer 13 (the first batt layer 13A and the second batt layer 13B) and the contacting layer 15 are entwined and integrated by needling.

The base layer 11 is for providing a strength to the papermakmg felt 100. For example, a woven cloth or a nonwoven string material that are laminated together or formed into a film-like shape may be used. As a material thereof, for example, a synthetic fiber such as nylon 6 and nylon 66 that are excellent m wear resistance, fatigue resistance, elongating property and stain proof, or a natural fiber such as wool. According to the embodiment, a woven cloth is adopted as the base layer 11. A basis weight of the base layer 11 is 550 g/m², a thickness of the base layer is 1.5 mm, and a density of a fiber forming the base layer 11 is 0.367 g/cm³.

The batt layer 13 (the first batt layer 13A and the second batt layer 13B) is an ordinary fiber layer formed with staple fiber 17 having a fineness of 6 decitex (dtex) or more (generally, about 17 dtex) . A basis weight of the batt layer 13 is 500 g/m². More specifically, a basis weight of the first batt layer 13A is 400 g/m², and a basis weight of the second batt layer 13B is 100 g/m². A thickness of the first batt layer 13A is 0.9 mm, and a density of staple fiber 17 forming the first batt layer 13A is 0.444 g/cm³. A thickness of the second batt layer 13B is 0.4 mm, and a density of staple fiber 17 forming the second batt layer 13B is 0.250 g/cm³. As a material which forms the batt layer 13, a material similar to the base layer mat be used. Further, the second batt layer 13B may be omitted m accordance with a property requested for the papermakmg felt 100.

The contacting layer 15 is made of a hydrophilic fiber

(m other words, the amount of the hydrophilic fiber with respect to the contacting layer 15 is 100 % by weight) . The hydrophilic fiber forming the contacting layer 15 is a fiber fibrillated into a plurality of small fibers by a press operation of a shoe press apparatus of the paper machine. It is preferable that a fineness of the hydrophilic fiber be 10 dtex or more. In the first embodiment, a fiber having a fineness of 6 dtex is used. A main reason for using the hydrophilic fiber having the fineness of 10 dtex or more is to facilitate the forming of the contacting layer 15, more specifically, to form the contacting layer 15 such that the hydrophilic fiber is not fibrillated m a carding step or a needling step during the manufacturing process of the papermakmg felt 100, and such that the hydrophilic fiber is fibrillated effectively by a press operation of a shoe press

(the roll and the shoe) when the papermakmg felt 100 is mounted on the press apparatus of the paper machine. A basis weight of the contacting layer 15 is 100 g/m², a thickness of the contacting layer 15 is 0.20 mm, and a density of the hydrophilic fiber forming the contacting layer 15 is 0.500 g/cm³. The fibrillation of the hydrophilic fiber will be described later in details Further, an amount of the hydrophilic fiber with respect to the contacting layer 15 may be 15 % to 100 % by weight, while the rest of the contacting layer 15 is formed by a nonhydrophlic fiber. Here, the nonhydrophlic fiber is an ordinary fiber that does not fibπllate in the carding step or the needling step, further, even when pressed by the shoe press (namely, the roll and the shoe) . Further, it is preferable that a staple fiber having a fineness of, for example, 6 dtex (namely, the same fineness as the fineness of the hydrophilic fiber before being fibπllated) to 20 dtex be used as the ordinary fiber. Further, the fibrillation is a phenomenon m which a fibril (a micro fiber) inside a fiber emerges on a surface of the fiber and fluffs and splits finely by a friction.

As the hydrophilic fiber, a cellulose series fiber such as rayon, polynogic, cupro, cotton, hemp, silk or the like is preferable, among these, rayon is particularly preferable. Here, the hydrophilic means having at least one of a water attracting property or a water holding property.

As a specific example of a hydrophilic fiber, there is a fiber having a hygroscopic property. In this case, when the fiber absorbs water, there is an affinity between the water and the fiber. Further, as one of the properties of the hydrophilic fiber that is suitable for the papermakmg felt 100 of the first embodiment, a standard moisture regain may be 4.0 % or more, preferably, 5.0 % or more. The standard moisture regains of the above-mentioned hydrophilic fibers are, rayon 11.0 %, polynogic 11.0 %, cupro 11.0 %, cotton 8.5 %, hemp 12.0 %, silk 12.0 %. Here, the standard moisture regain is a numerical value calculated based on a calculating equation of "standard moisture regain" described m JIS L0105 (rule of physical test method of fiber product) .

A method of manufacturing the papermakmg felt 100 will simply be explained. First, the woven base layer 11 with the batt layers 13 integrated on each surfaces thereof with by needling is prepared. Then, after mounting a web sheet of a hydrophilic fiber, on which the carding is performed, on a surface of the first batt layer 13A, the web sheet of the hydrophilic fiber, the batt layer 13 and the base layer 11 are penetrated by needles so as to be entwined and integrated so that the contacting layer 15 is formed. A needle used for needling is provided with, for example, a boldness of 36 count, a barb number of 2 edges 6 barbs, a depth of the barb of substantially 0.1 mm, a diameter of a boldness of a tip of the needle of 0.04 mm, and by using the needle, needling is carried out by a needle depth of 7 to 16 mm with 650 needles/cm².

In the carding step, the hydrophilic fiber can maintain the fineness of 6 dtex. Therefore, a fiber block which is produced when the carding is performed on a fibrillated fiber can be prevented. Further, The boldness of the needle tip portion (diameter of about 0.04 mm) and the depth of the barb (about 0.1 mm) are sufficiently larger relative to a diameter of the hydrophilic fiber of which is about 0.03 mm (a calculated value from the fineness of 6 dtex) , in other words, the hydrophilic fiber is very fine. Therefore, m piercing the needle m the needling step, the hydrophilic fiber is moved to escape from the needle tip and the needle is hardly pierced to the hydrophilic fiber. Further, the hydrophilic fiber, which contacts with the barb, moves around the barb that is sufficiently larger relative to the boldness of the hydrophilic fiber, and is hardly fibrillated by the barb. Therefore, the contacting layer 15 (or the hydrophilic fiber) is not fibrillated even by the needling, and the contacting layer 15 having a smooth surface is provided while most of the fiber is kept in a bold state (6 dtex) .

A basis weight of the papermakmg felt 100 manufactured m such way is 1150 g/m², a thickness of the papermakmg felt 100 is 3.00 mm, and a density of the fiber forming the papermakmg felt 100 as a whole is 0.383 g/cm³. Further, m the papermakmg felt 100, a density of a total of fibers of plural layers excluding the contacting layer 15 is 0.375 g cm³, and basis weight thereof is 1050 g/m². A permeability of the papermakmg felt 100 is 8 cc/cm²/sec (this is an average value of permeability measured by applying a pressure 125 Pa on a test piece of the papermakmg felt 100 by a fragile method based on JIS L 1096) .

The contacting layer 15 is fibrillated into micro fibers by being pressed by the press operation of the roll and the shoe (shoe press) when mounted to the shoe press apparatus of the paper machine to travel . In this way, the papermakmg felt 100 having the contacting layer 15, a surface of which is smooth and covered with micro fibers, is formed. Upon fibrillatmg the hydrophilic fiber of the contacting layer 15, it is preferable that the fibrillation be carried out in advance m a trial operation (so-called running in) of the shoe press apparatus of the paper maker such that the papermakmg felt 100 is pressed by the roll and the shoe (the shoe press) while spraying water to the papermakmg felt 100 with a shower (namely, cleaning means) and sucking the water soaked in the papermakmg felt 100 by a suction box (namely, cleaning means) so that the fibrillation of the hydrophilic fiber is finished before actually making a paper.

Further, in order to make the papermakmg felt 100 have an optimum characteristic in accordance with a kind of paper to be made, kinds of respective fibers for the base layer 11, the batt layer 13, and the contacting layer 15 are pertinently selected in consideration of properties of the fiber alone or fibers combined together.

Modified Example of the Papermakmg Felt 100

As one of the preferable modified examples of the papermakmg felt 100, there may be a papermakmg felt 100 having a contacting layer, m which an amount of a hydrophilic fiber of 6 dtex is 50 % by weight and is the rest (namely, 50 % of the weight) is a nonhydrophlic fiber of 10 dtex. In this case, an average boldness of the fibers forming the contacting layer becomes about 8 dtex. The base layer 11 and the batt layer 13 are similar to those described above. By including the nonhydrophlic fiber, Which is not fibrillated into micro fibers, in the contacting layer, a pertinent permeability is ensured without making a surface of the contacting layer excessively dense and therefore, water can effectively be squeezed out from the wet paper W. Second Embodiment

Next, the papermakmg felt 200 according to the second embodiment of the invention will be explained with reference to Fig.2. Features that are similar to those of the first embodiment (namely, the papermakmg felt 100) have already been explained are attached with the same notations or corresponding notations m the drawing and an explanation thereof will be simplified or omitted.

As shown by Fig.2, the papermakmg felt 200 includes the base layer 11, the batt layer 13 (the first batt layer 13A and the second batt layer 13B) and the contacting layer 15, similarly to the papermaking felt 100. The papermakmg felt 200 differs from the papermaking felt 100 m that the papermaking felt 200 includes a hydrophilic nonwoven cloth layer 23 inside the first batt layer 13A provided between the base layer 11 and the contacting layer 15.

More specifically, the second batt layer 13B is formed on the surface of the base layer 11 on the roll side or the shoe side, a first portion 13Aa of the first batt layer 13A is formed on the surface of the base layer 11 on the wet paper side, the hydrophilic nonwoven cloth layer 23 is formed on a surface of the first portion 13Aa of the first batt layer 13A on the wet paper side, a second portion 13Ab of the first batt layer 13A is formed on a surface of the hydrophilic nonwoven cloth layer 23 on the wet paper side, and the contacting layer 15 is formed on a surface of the second portion 13Ab of the first batt layer 13A on the wet paper side so as to be brought into direct contact with the wet paper. These layers are entwined and integrated by needling. A basis weight of the papermaking felt 200 is 1350 g/m², a thickness of the papermaking felt 200 is 3.50 mm, and a density of a total of fiber forming the papermaking felt 200 is 0.386 g/cm³. A basis weight of the hydrophilic nonwoven cloth layer 23 is 50 g/m², a thickness of the hydrophilic nonwovoen cloth layer 23 is 0.1 mm, and a density of a fiber forming the hydrophilic nonwoven cloth layer 23 is 0.500 g/cm³. Further, in the papermaking felt, a density of total fibers of plural layers excluding the contacting layer 15 is 0.379 g/cm³, and the basis weight thereof is 1100 g/m². A permeability of the papermaking felt 200 formed in this way is 4 cc/cm²/sec (this value is an average value of permeability measured by applying a pressure of 125 Pa on a test piece of the papermaking felt 200 by a fragile method based on JIS L 1096) . Further, the contacting layer 15 may be formed on the surface of the hydrophilic nonwoven cloth layer 23 on the wet paper side without forming the second portion 13Ab of the first batt layer 13A.

The hydrophilic nonwoven layer 23 is formed by a hydrophilic nonwoven cloth which is made to have a high density by laminating a fiber finer than a fiber forming the batt layer 13, for example, a fineness of 4 dtex or less. The hydrophilic nonwoven cloth forming the hydrophilic nonwoven cloth layer 23 may be, for example, a span bond nonwoven cloth formed by laminating a fiber made by melting and spinning a resin such as nylon. Such fiber may be, for example, a continuous filament. Further, he hydrophilic nonwoven cloth forming the hydrophilic nonwoven cloth layer 23 may be a nonwoven cloth formed into a sheet-like shape by forming fine fiber. Such fine fiber may be made by elongating a polymer melted by hot wind.

In order to effectively prevent re-wettmg, it is preferable that the hydrophilic property of the hydrophilic nonwoven cloth layer 23 is set such that a contact angle of the hydrophilic nonwoven cloth layer 23 with respect to water becomes 30° or less when a moisture rate of the hydrophilic nonwoven cloth layer 23 is adjusted to be 30 % to 50 %. Here, the moisture rate of the hydrophilic nonwoven cloth layer 23 is calculated from (water weight/total weight of the hydrophilic nonwoven cloth layer 23) x 100. Modified Example of Papermakmg Felt 200

In one of the preferable modified examples of the papermakmg felt 200, a basis weight of papermakmg felt is 1350 g/m², a thickness of the papermakmg felt is 3.56 mm, a density of a total of fiber forming the papermakmg felt is 0.379 g/cm³, a basis weight of the base layer is 650 g/m², a thickness of the base layer is 1.7 mm, a density of a fiber forming the base layer is 0.382 g/cm³, a basis weight of the batt layer formed by staple fiber 17 having a fineness of 3.3 dtex is 450 g/m² (more specifically, a basis weight of the first batt layer is 300 g/m², and a basis weight of the second batt layer is 150 g/m²) , a thickness of the first batt layer is 0.8 mm, a density of staple fiber 17 forming the first batt layer is 0.375 g/cm³, a thickness of the second batt layer is 0.6 mm, a density of the staple fiber 17 forming the second batt layer is 0.250 g/cm³, a basis weight of the contacting layer formed by a hydrophilic fiber of 3 dtex is 200 g/m², a thickness of the contacting layer xs 0.36 mm, a density of a hydrophilic fiber forming the contacting layer is 0.556 g/cm³, a basis weight of the hydrophilic nonwoven cloth layer is 50 g/m², a thickness of the hydrophilic nonwoven cloth layer is 0.1 mm, and a density of a fiber forming the hydrophilic nonwoven cloth layer is 0.500 g/cm³. In this modified example of the papermakmg felt 200, a density of total fibers of plural layers excluding the contacting layer is 0.359 g/cm³. Further, a permeability of the modified example of the papermakmg felt 200 is 3 cc/cm²/sec.

Next, with reference to Fig.3, an explanation will be given of a shoe press apparatus 300 of a paper machine mounted with the papermakmg felt 100 and the papermakmg felt 200, both formed m a shape of an endless belt (ring-like shape) .

As shown by Fig.3, the shoe press apparatus 300 of the paper machine is a press apparatus of a so-called closed draw type m which a first press mechanism 51 and a second press mechanism 53 are arranged in series along a direction of carrying wet paper W (along the direction of arrow A) . Further, by constituting the shoe press type paper machine of the closed draw type in which the wet paper W is carried and pressed m a state of being squeezed by a pair of the papermakmg felts 100 and a pair of the papermakmg felts 200, the wet paper W can stably be carried at high speed of, for example, 1200 m/mm to 1400 m/mm. Therefore, a paper can be made m an extremely high efficiency compared with, fo«r-example, a shoe press type paper machine of an open draw type.

The first press mechanism Sl includes a pair of the papermaking felts 100, and a first shoe 55 and a first roll 57 (in other words, a first shoe press) which are arranged so as to face each other so that a first nip (m other words, a first press portion) is formed therebetween. The second press mechanism 53 includes a pair of the papermaking felts 200, and a second shoe 59 and a second roll 61 (in other words, a second shoe press) which are arranged so as to face each other so that a second nip (in other words, a second press portion) is formed therebetween .

As shown m Fig.3, the papermaking felts 100 may be adopted as the upper and the lower papermaking felts of the first press mechanism 51. However, the papermaking felt 100 may be adopted for one of the upper papermaking felt or the lower papermaking felt. When the papermaking felt 100 is employed as one of the upper papermaking felt or the lower papermaking felt of the first press mechanism 51, an arbitrary papermaking felt may be adopted for the other papermaking felt m accordance with a characteristic of a paper.

Similarly, as shown m Fig.3, the papermaking felts 200 may be adopted as the upper and the lower papermaking felts of the second press mechanism 53. However, the papermaking felt 200 may be adopted for one of the upper papermaking felt or the lower papermakmg felt. When the papermakmg felt 100 is employed as one of the upper papermakmg felt or the lower papermakmg felt of the second press mechanism 53, an arbitrary papermakmg felt may be adopted for the other papermakmg felt in accordance with a characteristic of the paper.

Further, only the papermakmg felts 100 or only the papermakmg felts 200 may be adopted as the papermakmg felts of both the first press mechanism 51 and the second press mechanism 53.

Further, only the papermakmg felt 100 or only the papermakmg felt 200 may be adopted as the papermakmg felt of the second press mechanism 53. In this case, an arbitrary papermakmg felt may be adopted for the papermakmg felt of the first press mechanism 51 m accordance with a characteristic of the paper.

By a trial run of the shoe press apparatus 300 of the paper machine, the hydrophilic fibers of the contacting layer 15 of the papermakmg felt 100 and the hydrophilic fibers of the contacting layer 15 of the papermakmg felt 200 are fibrillated. That is, the respective contacting layers 15 (namely, the hydrophilic fibers) are fibrillated to become micro fibers by being pressed when passing between the first shoe 55 and the first roll 57, and further between the second shoe 59 and the second roll 61. Also, the surfaces of the papermakmg felts 100, 200 on the wet paper side become smooth. In the embodiment, a pressing condition of the papermaking felt 100 by the first shoe 55 and the first roll 57 is 800 kN/m, and a pressing condition of the paper carrying felt 200 by the second shoe 59 and the second roll 61 is 1050 kN/m. Further, a shoe width is 10 inches both for the first shoe 55 and the second shoe 59, and respective traveling speeds of the papermaking felt 100 and the papermaking felt 200 are 1700

As shown by Fig.3, the wet paper W carried out from a wire part (not illustrated) and delivered to the first press mechanism 51 is nipped' by the pair of papermaking felts 100 and carried, while water is squeezed out by pressing the wet paper W by the first shoe 55 and the first roll 57, and the squeezed-out water is absorbed by the papermaking felt 100. Next, the wet paper W is delivered to the second press mechanism 53 and nipped by the pair of papermaking felts 200 and carried, while water is further squeezed out by being pressed by the second shoe 59 and the second roll 61, and the squeezed-out water is absorbed by the papermaking felt 200. At this occasion, a surface of the wet paper W brought into contact with the contacting layer 15 is smoothed, and the wet paper W is delivered to a drier part (not shown) to be dried.

Further, when the wet paper W and the papermaking felt 200 are released from the pressure applied m the second press portion by the second shoe 59 and the second roll 61 at the outlet area, the re-wettmg phenomenon m which the water inside the papermakmg felt 200 moves to the wet paper W side may occur. However, the density of the hydrophilic nonwoven cloth layer 23 is higher than that of the batt layer 13, and a permeability thereof is lower than that of the batt layer 13. Therefore, the water contained in the second batt layer 13B arranged on the second shoe 59 side or the second roll 61 side of the hydrophilic nonwoven cloth layer 23 is difficult to be moved to the second portion 13Ab of the first batt layer 13A on the wet paper side by permeating the hydrophilic nonwoven cloth layer 23. Thus, the re-wettmg phenomenon is prevented from being brought about. Further, since the fineness of the hydrophilic nonwoven cloth layer 23 is lower than the fineness of the batt layer 13, the water contained m the second portion 13Ab of the first batt layer 13A arranged on the wet paper side of the hydrophilic nonwoven cloth layer 23 is moved to and held by the hydrophilic nonwoven cloth layer 23 by the capillary phenomenon. Therefore, the re-wetttmg phenomenon can effectively be prevented.

Although an explanation has been given of the press apparatus 300 having two stages of the press mechanisms 51, 53 as an example as one embodiment of the shoe press apparatus of the paper machine according to the invention, it is obvious that a press apparatus may include a single press mechanism or a press apparatus may include a plurality of press mechanisms aligned in series.

As explained above, according to the papermaking felt

(100; 200) , the contacting layer 15 including the hydrophilic fiber fibrillated into micro fibers by being pressed by the shoe presses (namely, rolls (57; 61) and shoes (55; 59)) is formed at the surface of the first batt layers 13A of the papermaking felts (100; 200) on the wet paper W side to be brought into direct contact with the wet paper W. Therefore, when there is formed the contacting layer 15 including the hydrophilic fiber of micro fibers having an extremely low fineness by being fibrillated, the smoothness of the surface of the wet paper W can be promoted. Furthermore, stain

(specifically, a component of an additive, a glue or the like) included in the wet paper W adhered temporarily to the papermaking felt (100; 200) is fallen off by a so-called unhairing phenomenon of micro fibers formed fibrillation of the_, hydrophilic fiber from the papermaking felt (100; 200) along with the micro fibers. Therefore, the stain is difficult to remain m the papermaking felt (100; 200) . Even when micro fibers (namely, small fibers formed by fibrillation of the hydrophilic fiber) are more or less adhered to the surface of the wet paper W by being fallen off or cut off from the contacting layer 15, since the micro fibers are extremely fine, the micro fibers do not deteriorate the quality of the wet paper W. Further, the stain partially shifted to the wet paper by falling off of the micro fibers formed by the fibrillation is included inherently in the wet paper W as a component thereof. Therefore, the stain does not affect any influence on the quality of the wet paper W at all. Thus, the surface of the paper fabricated by the shoe press type paper machine using the papermakmg felt (100; 200) become extremely smooth, and a service life of the papermakmg felt (100; 200), that is, a time period of capable of using the papermakmg felt is prolonged. Therefore, there can be reduced a frequency of maintenance of interchanging the papermakmg felt (100; 200) by a new one or cleaning the papermakmg felt in the midst of making the paper or the like. Therefore, it is preferable that the hydrophilic fiber is included at at least the surface of the press paper contact fiber layer 15 where the wet paper W comes into contact.

Further, according to the shoe press apparatus 300 of the paper machine, when the papermakmg felt 100 is arranged at the press mechanism 51 arranged on the upstream side in the direction A of carrying the wet paper W m the plurality of press mechanisms 51, 53, the arrangement is particularly preferable m view of squeezing out water efficiently from the wet paper W. That is, according to the shoe press apparatus 300 of the paper machine having such constitution, a large amount of water can effectively be squeezed out from the wet paper including much water, thereby, providing the papermakmg felt (100; 200) with an excellent paper separating function m delivering the wet paper. Therefore, paper making operation can be carried out at high speed.

Further, according to the papermakmg felt 200, the hydrophilic nonwoven cloth layer 23 is provided between the base layer 11 and the contacting layer 15. Therefore, reshifting of the water absorbed temporarily from the wet paper W to the papermakmg felt 200 (namely, so-called re-wetting phenomenon) is hampered by the hydrophilic nonwoven cloth layer 23. Further, according to the shoe press apparatus 300 of the paper machine, when the papermakmg felt 200 is arranged to the press mechanism 53 arranged on the downstream side m the direction A of carrying the wet paper W in the plurality of press mechanisms 51, 53, although there is conceivable a case m which a water permeating function becomes slightly lower than that of the papermakmg felt 100, since the papermakmg felt 200 is provided with not only the function of smoothing the surface of the wet paper but also function of highly preventing re-wetting, the papermakmg felt 200 is particularly preferable m view of preventing the re-wettmg phenomenon and m view of smoothing the surface of the wet paper .

Further, according to the papermakmg felts (100; 200), since the respective finenesses of the hydrophilic fibers before the fibrillation is 10 dtex more less, even when the fineness of' the hydrophilic fiber before fibrillation is assumedly 10 dtex, the fineness of the small fiber formed by subjecting the hydrophilic fiber to fibrillation becomes smaller than 10 dtex. Therefore, when there is formed the contacting layer 15 including the hydrophilic fiber for constituting the micro fiber having the fineness as proximate to the fineness of the fiber of the wet paper W as possible, high quality paper excellent in surface smoothness can bemanufactured. It is further preferable when the respective finenesses of the hydrophilic fibers before the fibrillation is smaller such as 6 dtex.

Further, when the contacting layer 15 is formed such that the amount of the hydrophilic fiber is 15 % to 100 % by weight and the rest is formed by the nonhydrophilic fiber, the property of the papermakmg felt (100; 200) can be changed by pertinently changing a weight rate of the hydrophilic fiber. Here, the weight rate of the hydrophilic fiber is defined by "weight of hydrophilic fiber/ (weight of hydrophilic fiber + weight of nonhydrophilic fiber) x 100". The surface smoothness and the water squeeze out property which are properties required for the papermakmg felt (100; 200) are in an inversely proportional relationship, and when a density of the papermakmg felt (100; 200) is increased in order to promote the function of smoothing the surface of the wet paper W, the water squeeze out property tends to be deteriorated. On the other hand, ' as for the plurality of press mechanisms 51, 53 arranged from the upstream to the downstream along the direction of carrying the wet paper W to be carried, respective functions that are slightly different are required such that the water squeeze out property is emphasized for the papermakmg felt 100 of the press mechanism 51 arranged on the upstream side, further, the function of smoothing the surface of the wet paper W is requested for the papermakmg felt 200 of the press mechanism 53 arranged on the downstream side. Therefore, by pertinently changing the weight rate of the hydrophilic fiber, the papermakmg felts 100, 200 can be provided with properties (surface smoothness, water squeeze out property, or the like) optimum for the respective press mechanisms 51, 53.

Further, according to the press apparatus 300 of the shoe press type paper machine, since the press apparatus 300 is the press apparatus of the closed draw type, the wet paper W is carried m the state of being squeezed by the pairs of the papermakmg felts (100; 200) for the shoe presses. Thereby, the wet paper W is not elongated (under no draw) , and the wet paper W can be carried at an extremely high speed. Therefore, paper can be made efficiently.

Further, it is preferable to fibrillate the hydrophilic fiber of the contacting layer 15 of the papermakmg felt (100_/ 200) in trial operation (so-called running in operation) of the shoe press apparatus for the paper machine. It is preferable that the hydrophilic fiber used in the papermaking felt (100; 200) be a fiber that is fibπllated by being pressed by the shoe press, but not fibrillated and maintains a comparatively bold state in the carding step or the needling step during the manufacturing of the papermaking felt. For example, a fiber block is easy to be produced when the hydrophilic fiber which is fibrillated into micro fibers is assumedly carded in carding. Such fiber block is implanted to the felt m the needling step and forms recesses and projections at the surface of the papermaking felt. Therefore, the surface smoothness of the wet paper is deteriorated. Such a drawback can be overcome by using the contacting layer 15 including the hydrophilic fiber which is fibrillated into micro fibers by being pressed by the shoe press.

Further, the invention is not limited to the embodiments and the modified examples but can pertinently be modified, improved or the like. Materials, shapes, dimensions, numerical values, modes, numbers, arranging locations and the like of respective constituents elements in the embodiments and the modified examples are arbitrary and not limited so far as the invention can be achieved thereby.

For example, even when the papermaking felt (100; 200) is mounted on a shoe press type paper machine of an open draw type having a portion in which a single one of the wet paper W is carried in the midst of carrying the wet paper W, the paperrdakmg felt (100; 200) is similarly operated effectively .

Further, although according to the embodiment, there is shown a case of applying the invention to the shoe press apparatus of the paper machine, the invention is not limited thereto, and the invention may be applied to a press apparatus of a roll press type paper machine having a pair of rolls for pressing the papermakmg felt.

While there has been described m connection with the embodiments of the present invention, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention. It is aimed, therefore, to cover m the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.

The present application is based on Japanese patent application no. 2005-295256, filed on October 7, 2005, the content' of which is incorporated herein by reference.

Industrial Applicability

The present invention provides a papermakmg felt from which stain is easy to fall off, and has an excellent function of smoothing a surface of wet paper and also an excellent paper separating function m delivering the wet paper, and further provides a shoe press apparatus of a paper machine having such papermaking 'felt.

Claims

1. A papermaking felt of a press apparatus for a paper machine, m which the paper making felt is disposed between a roll and a wet paper or between a shoe and the wet paper, the papermaking felt comprising: a base layer; a first batt layer formed on the base layer on the wet paper side; and a contacting layer formed on the first batt layer on the wet paper side where the wet paper directly comes into contact, wherein the contacting layer includes a hydrophilic fiber, and the hydrophilic fiber is fibrillated when pressed by the roll and the shoe.

2. The papermaking felt according to claim 1, wherein an amount of the hydrophilic fiber with respect to the contacting layer is 15 % to 100 % by weight, and the rest of the contacting layer is formed by a nonhydrophilic fiber.

3. The papermaking felt according to claim 1, further comprising a hydrophilic nonwoven cloth layer between the base layer and the contacting layer.

4. The papermaking felt according to claim 2, further comprising a hydrophilic nonwoven cloth layer between the base layer and the contacting layer.

5. The papermaking felt according to claim 1, further comprising a second batt layer formed on the base layer on the roll side or the shoe side.

6. A shoe press apparatus for a paper machine comprising: a shoe; a pair of papermaking felts interposing a wet paper therebetween; and a roll disposed such that the pair of papermaking felts is interposed between the shoe and the roll, wherein at least one of the papermaking felts comprises: a base layer; a first batt layer formed on the base layer on the wet paper side; and a contacting layer formed on the first batt layer on the wet paper side where the wet paper directly comes into contact, further wherein the contacting layer includes a hydrophilic fiber, and the hydrophilic fiber is fibrillated when pressed by the roll and the shoe.

7. The shoe press apparatus according to claim 6, wherein an amount of hydrophilic fiber with respect to the contacting layer is between 15 % and 100 % by weight, and the rest of the contacting layer is formed by a nonhydrophilic fiber .

8. The shoe press apparatus according to claim 6, wherein at least one of the papermakmg felts further comprises a hydrophilic nonwoven cloth layer between the base layer and the contacting layer.

9. The shoe press apparatus according to claim 7, wherein at least one of the papermakmg felts further comprises a hydrophilic nonwoven cloth layer between the base layer and the ,contacting layer.

10. The shoe press apparatus according to claim 6, wherein at least one of the papermakmg felts further comprises a second batt layer formed on the base layer on the roll side or the shoe side.

11. A shoe press apparatus for a paper machine having a plurality of press mechanisms aligned in series along a direction of carrying a wet paper, each press mechanism comprising : a shoe; a pair of papermaking felts interposing a wet paper therebetween; and a roll disposed such that the pair of papermaking felts is interposed between the shoe and the roll, wherein at least one of the papermaking felts comprises* a base layer; a first batt layer formed on the base layer on the wet paper side; 'and a contacting layer formed on the first batt layer on the wet paper side where the wet paper directly comes into contact, further wherein the contacting layer includes a hydrophilic fiber, and the hydrophilic fiber is fibrillated when pressed by the roll and the shoe.

12. The shoe press apparatus according to claim 11, wherein an amount of hydrophilic fiber with respect to the contacting layer is between 15 % and 100 % by weight, and the rest of the contacting layer is formed by a nonhydrophilic fiber .

13. The shoe press apparatus according to claim 11, wherein at least one of the papermakmg felts of the press mechanism aligned at downstream side along the direction of carrying the wet paper further comprises a hydrophilic nonwoven cloth layer between the base layer and the contacting layer .

14. The shoe press apparatus according to claim 12, wherein at least one of the papermakmg felts of the press mechanism aligned at downstream side along the direction of carrying the wet paper further comprises a hydrophilic nonwoven cloth layer between the base layer and the contacting layer.

15. The shoe press apparatus according to claim 11, wherein at least one of the papermakmg felts further comprises a second batt layer formed on the base layer on the roll side or the shoe side.