MXPA99001814A - Short press band and manufact method - Google Patents

Abstract

The present invention relates to a press shoe strip for papermaking, comprising a first endless resin layer formed on a polished surface of a mandrel, a base fabric layer comprising a sheet of woven fabric over the entire of the outer periphery of the first resin layer, at least one of the intersecting fiber assemblies of the fabric sheet are high strength fibers q > e extend axially along the mandrel, a coil layer comprising a high strength fiber wound circumferentially in a spiral on the outer periphery of the base fabric layer, and a second layer of endless resin on the outer periphery of the core. the coil layer, the second resin layer is in contact with the first layer through the base fabric layer and the coil layer. The shoe press band constructed in this way shows a high resistance in the machine direction as well as in the cross machine direction.

Description

SHOULDER PRESS BAND AND MANUFACTURING METHOD BRIEF SUMMARY OF THE INVENTION This invention relates to shoe press of the type used in papermaking, and more particularly to a band for use in a closed-type shoe press, and a method for making the band. The use of shoe presses in paper manufacturing has increased because it reduces the number of press units needed in the press area. The closed-type press shoe has been particularly popular because it requires only a relatively small space and minimizes wasted oil. However, in the papermaking process, a band for use in the closed-type shoe press experiences more severe working conditions as compared to a band for use in an open-type shoe press. The most severe working conditions include higher operating speeds and higher narrowing pressures. For these reasons, users require belts for closed-type shoe presses that have improved durability. To manufacture the closed type band, various manufacturing techniques using a mandrel are known. For example, Japanese Patent Publication No. 57236/1991 and the Japanese Patent Laid-Open No. 45889/1989 discloses methods of using an endless woven fabric for core material. However, with these methods, it is difficult to obtain alignment in the circumferential direction. Manufacturing methods which do not use woven cloth are described in International Patent Publication 503315/1989 and Japanese Patent Laid-open Publication No. 209578/1996. In these manufacturing methods, a high strength fiber is stretched at regular intervals over the entire periphery of a mandrel in the cross machine direction (CMD). These methods have the disadvantage that it requires a very long time to stretch the high strength fiber. In another known method of manufacture, a fibrous web in the form of a mat of a woven fabric, impregnated with an uncured resin, is wound in a spiral around a mandrel for curing. This method has been described in Japanese Patent Application Laid-Open No. 298292/1989 and International Patent Application No. 505428/1993. This method has the disadvantage that detachment may occur in the spiral line defining the union between successive turns of the spirally wound fibrous web or cloth. According to a conventional manufacturing method, although an endless woven fabric extends from a pair of rolls, its outer surface is impregnated and coated by a coating machine, with a first resin layer, which It cures. Subsequently, the endless woven fabric is removed on the rollers, turned through and returned to the rollers. The outer surface of the woven fabric turned upside down is impregnated and coated with a second layer of resin, which is also cured. The total thickness is adjusted and subsequently concave grooves are formed in the second resin layer to complete the band. The conventional method described above has two important drawbacks. First of all, to impregnate and coat the back part of the endless woven fabric with a second layer of resin, it is necessary to turn the band upside down. The process of flipping the band upside down produces tension within the band. Second, an inherent tension is released in the endless woven fabric as a result of the winding process, when the resin is cured. The release of the inherent tension that results from the rolling process may result in an unstable form, and flapping of the band may occur when used. Therefore, the conventional closed-type shoe press band has several inherent drawbacks. Further, when the web is produced by extending an endless woven fabric between the two rollers, and when tension is applied in the CMD direction in use, dimensional variations in the CMD direction readily occur. Such variations dimensions are the main cause of shortened band duration. The main objective of the invention is to correct the defects described above and to provide a shoe press band with excellent performance and durability, having a high resistance in the machine direction (MD) as well as in the CMD direction, and stability superior dimensional in the CMD direction. The shoe press band according to the invention comprises a first endless resin layer having a uniform or smooth internal surface in the form of a surface of revolution, for example, a cylinder. Preferably, the uniform internal surface is produced by forming the first resin layer on a polished surface of a rotatable mandrel. The web also includes a base fabric layer comprising a sheet of woven fabric positioned over the entire outer periphery of the first resin layer, at least one of the intersecting fiber assemblies of the fabric sheet being fibers of high strength that extend axially along the base fabric layer. The term "axially extending" means placed in a common plane with the axis, but not perpendicular to the axis. The shoe press band also includes a coil layer comprising a high strength fiber wound circumferentially in a spiral on the outer periphery of the base fabric layer and a second layer of endless resin on the outer periphery of the coil layer, the second resin layer is in contact with the first layer through the base fabric layer and the coil layer. The shoe press band constructed in this manner shows sufficient strength in the machine direction (MD) as well as in the cross machine direction (CMD). The method for manufacturing a shoe press band according to the invention comprises the steps of: forming a first endless resin layer on a polished surface of a rotatable mandrel; forming a base fabric layer by placing, over the entire outer periphery of the first resin layer, a woven fabric sheet, at least one of the intersecting fiber assemblies of which consist of high strength fibers, so that the fibers of one of the assemblies extend along the axial direction of the mandrel; forming a coil layer by winding the high strength fiber over the outer periphery of the base fabric layer circumferentially in a spiral; and subsequently forming a second endless resin layer on the outer periphery of the coil layer so as to contact the first resin layer through the base fabric layer and the coil layer. This simple construction method provides a shoe press band that has superior performance. Other objects and advantages of the invention will be apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partially enlarged cross-sectional view showing a band according to the invention; Figure 2 (a) and Figure 2 (b) are respectively side cross-sectional views, and a perspective view of a mandrel illustrating the formation of a first resin layer; Figure 3 is a perspective view showing a shoe press mechanism using a band according to the invention; Figure 4 is a partial plan view of a sheet of woven fabric for use in the base fabric layer; Figure 5 is a perspective view showing a process of laying a single woven fabric sheet, which becomes a base fabric layer, on the outer surface of a first resin layer formed on the mandrel surface; Figure 6 is a perspective view showing a multi-layered woven fabric, which becomes a base fabric layer; Figure 7 is a perspective view showing the formation of a coil layer; Figure 8 (a) is a cross-sectional, side view showing the conventional process for manufacturing a shoe press band; and Figure 8 (b) is a partial cross-sectional view, showing a shoe press obtained by the conventional method.

DETAILED DESCRIPTION As shown in Figure 2, a first resin layer 2 is formed on the polished surface of a mandrel M, the surface of the mandrel M is coated with a release agent (not shown), or alternatively, a mandrel is adhered to the mandrel. release sheet (not shown). At the top of the release layer or the release sheet, the resin layer is formed to a thickness preferably in the range of from about 0.5 mm to about 2.0 mm, using a coating machine such as a doctor's bar or a T coater bar, as shown in Figure 2 (a). As shown in Figure 3, a band is passed 1 between a press roll 101 and a shoe 102 in a shoe press mechanism 100. The first resin layer 2, which constitutes the innermost layer of the band 1, slides on the shoe 102 while it is in close contact with the shoe. Therefore, the inner surface of the band must have a high level of uniformity. Since this high level of uniformity results from the polished surface of the mandrel M, no further treatment of the web is required. The surface of the mandrel M is polished not only to ensure uniformity of the innermost layer of the web, but also to improve the release properties of the web.

The mandrel M is also preferably provided with a heating device (not shown) to promote curing of the resin layer 2 and also to promote curing of the subsequently applied resin layer. A layer 3 of base fabric is placed on the outer periphery of the first resin layer 2. With reference to Figure 4, the base fabric layer 3 is formed by a sheet P of woven fabric. The sheet P of fabric comprises intersecting sets of S and Y fibers. At least the S fibers are high strength fibers. Y fibers can be, but do not need to be, high strength fibers. As shown in Figure 5, the sheet P of woven fabric is placed over the entire outer periphery of the first resin layer 2, and is positioned so that the high strength fibers S extend along the length of the J axis direction of the mandrel M. The high strength fibers S of the woven fabric sheet extends along the axial direction of the mandrel, i.e., the direction of the width of the band. You can use fibers that are not high strength for intersecting Y fibers. Even high strength fibers are not used for both fibers that make up the sheet P of woven fabric, the high strength S fibers impart resistance to the web in the CMD direction. The sheet P of woven fabric may be a single woven fabric sheet, as shown in Figure 5, which extends around the outer periphery of the first resin layer 2 once and which covers the entire first layer 2 of resin, with the edges Pl and P2 of the sheet of cloth coinciding with each other, in opposite relation. Alternatively, the woven fabric sheet can be a multi-sheet sheet, as shown in Figure 6, covering the outer periphery of the first resin layer 2 with the edges Pl 'and P2"which coincide with each other, and with the edges P2 'and Pl' 'that coincide with each other, either the single sheet woven fabric sheet or the multiple sheet fabric sheet can be used, however, the multiple sheet fabric sheet is easier to Again, with reference to Figure 1, a coil layer 4 is formed on the outer periphery of the base fabric layer 3. The coil layer 4 comprises high strength SY fibers wound around the base fabric layer circumferentially in a spiral (in the case of a cylindrical mandrel, the spiral will be a helix.) As shown in figure 7, the layer of The coil is obtained by winding the high-strength fiber SY around the base fabric layer 3 in a spiral formed by the bobbin Bo while the mandrel is rotated M. The coil layer is wound on the total area of the layer 3 of the coil. base fabric. There are cases in which a plurality of coils can be used to wind a plurality of fibers to form the coil layer. The coil layer 4 is effective to impart resistance to the web 1 in the circumferential direction (MD direction). On the outer periphery of the coil layer 4 an endless layer 5 of a second resin is formed. The base fabric layer 3 and the coil layer 4 are impregnated with the second resin layer 5 so that the second resin layer is brought into contact with the outer surface of the first resin layer 2 to a contact surface 6 . At the contact surface 6, the first and second resin layers melt and become integral with each other. A sizing or adhesive can be used to improve integration, if necessary. The resin used for the first resin layer 2 and the second resin layer 5 can be selected from rubber and other elastomers. The polyurethane resin is preferred. As the polyurethane resin, thermoset urethane is preferable in view of its physical properties, and may be selected within a range of 80 to 98 ° hardness (JIS-A). The first resin layer 2 and the second resin layer 5 can be the same or different in terms of hardness.

The high strength fiber S, as shown in Figure 4, used for at least one of the sets of intersecting fibers in the woven fabric P of the base fabric layer 3, is a vertical fiber, comparatively thick, by example, monofilament yarn, multiple filament yarn corresponding to denier 800 to 6000, or twisted yarn. Such a thread imparts the necessary resistance to band 1 in the direction CMD. The Y fibers, which intersect the high strength S fibers, are able to support the fiber S so that the interval between the fibers S does not deviate. The texture of the sheet P of woven fabric is not important, but is preferably use double weft, triple weft or simple texture. The material for high strength S fiber is preferably a synthetic fiber having a high modulus and a high modulus of elasticity, such as nylon, polyester, aromatic polyamide, aromatic polyimide or high strength polyethylene. Inorganic fibers such as carbon fibers and glass fiber can also be used. The strength of the fiber material is preferably within a range of 120 to 250 kg / cm and the fiber material preferably is within a range of 10 to 40 kg / cm, in a 1% modulus. By placing the sheet P of woven fabric on the outer periphery of the first resin layer 2, the mandrel is caused to rotate little by little. The sheet P of woven cloth is placed Thus, the high strength fiber S is parallel to the axial direction of the mandrel, and is caused to compressively bond before the first resin layer 2 is cured, that is, while still retaining a glue-like property. In the case described above, when the woven cloth P is of a single sheet, its length is adjusted to 99.7% to 100% of the circumference of the first resin layer 2, and it is wound once around the first layer 2 of resin so that it covers the entire first layer of resin. The process of attaching the woven fabric layer to the first resin layer can be more easily accomplished by forming the fabric layer so that the circumferential Y fibers extend beyond the ends of the fabric sheet, and the fibers are combined. that extend among themselves. Further, when the woven sheet P is a sheet of multiple sheets, it is important to be careful not to excessively open the interval between the end portions and not to excessively overlap the end portions. As in the case of high strength S fiber, the material for the high strength SY fiber used for the coil layer 4 can be a monofilament yarn, a multi-filament yarn or twisted yarn, consisting of synthetic fibers having a high toughness, a high modulus and a modulus of high elasticity, such as nylon, polyester, aromatic polyamide, aromatic polyimide or high strength polyethylene.

It is preferable to produce the high strength SY fiber so that the final product has a resistance of 170 to 250 kg / cm when rolled in 20 pieces to 50 pieces / 5 cm for nylon or multiple filaments of PET (4500d), or by rolling in 10 pieces at 30 pieces / 5 cm for multiple filaments (3000d) consisting of aromatic polyamide. The second layer 5 can be formed, after the coil layer 4 is formed by winding the high strength fiber SY. Alternatively, the second layer 5 can be formed while winding the high strength fiber SY. After the second resin layer 5 is formed, the resin is cured, the surface is polished to obtain the desired thickness of the band, a concave groove 7 is formed on the surface, as required, to obtain the band 1. Alternatively , the slot can be a blind hole, that is, a recess with a circular cross section. The web is then removed from the mandrel M. The web can be easily removed from the mandrel by using a release agent or a release sheet provided in advance on the surface of the mandrel. Other techniques for removal include the use of a hydraulic press and make use of the expansion and shrinkage of the resin. An example of a shoe press band and a method for its manufacture according to the invention is as follows.

A polished surface of a mandrel having a diameter of 1500 mm, and which can be rotated by appropriate drive, is coated with a release agent (KS-61: produced by Shin-Etsu Chemical). The mandrel surface is coated with a thermosettable urethane resin comprising, as a prepolymer, Takenate L2395 produced by Takeda Chemical, and as a curing agent 3, 3'-dichloro-4,4'-diaminodiphenylmethane, to a thickness of 1 mm using a doctor's bar, and let it stand for 10 minutes. Then, a sheet P of woven fabric is wound around the outer periphery of the first resin layer. The knitted cloth sheet has a weft mesh of 30 pieces / 5 cm and a warp knit of 40 pieces / 5 cm. It comprises 800d polyester monofilament yarns like warp, and multiple filament yarn (high strength S fiber) of polyester 4500d as the weft. The yarns are wound on a double weave weaver, so that the multiple filament yarns (the high strength S fibers) extend along the axial direction of the mandrel. The woven fabric sheet and the first resin layer are joined compressively with the ends of the woven fabric sheet placed opposite one another. After the base fabric layer 3 is formed on the outer periphery of the first resin layer 2, a polyester 4500d multiple filament yarn (the high strength SY fiber) is wound around the outer periphery of the layer of base cloth, circumferentially in a spiral at a pitch of 30 pieces / 5 cm to form the winding layer 4. Subsequently, the coil layer is coated and impregnated with the same thermosettable urethane resin that is used for the first resin layer 2, up to a thickness of 5.5 mm above the coil layer 4, and heated and cured at 100. ° C for 5 hours to form the second layer 5 of resin. Subsequently, the surface of the second resin layer 5 is polished to obtain a total thickness of 5.2 mm and then a concave groove 7 is formed in the circumferential direction with a rotating blade to complete the formation of the band 1. For comparison, also a conventional shoe press band 1 'is formed, as shown in Figure 8 (b) by the process shown in Figure 8 (a). An endless woven fabric C (ie, a woven fabric produced by an endless weaver) was curled between two rollers A and B. The outer surface of the woven fabric C was impregnated and coated with a first layer of resin by a machine D coating, and the first resin layer is heated and cured, and then polished to form the E layer. Subsequently, the endless woven fabric C is removed from the rolls A and B, turned upside down, and curled again between rollers A and B. The outer surface of the woven fabric is then impregnated and coated with a second layer F of resin, and the second resin layer is heated and cured at 100 ° C for 5 hours to form the second layer F of resin. The second layer F of resin is polished to a total thickness of 5.2 mm, and then a concave groove G is formed in the circumferential direction using a rotating blade, to complete the band 1 '. Thermosettable urethane resin was used for both resin layers comprising, as a prepolymer, Takenate L2395 (produced by Takeda Chemical), and as a curing agent, 3, 3'-dichloro-4,4'-diaminodiphenylmethane. The physical properties and production time (between the formation of the first and second resin layers) were compared with the results shown in the following table.

The above table shows that the band of this application is superior in physical properties with respect to the conventional band with which it is compared. The endless woven fabric used as the base fabric layer for the conventional web has unstable web dimensions resulting from the internal tension in the woven fabric caused by irregularities in the arrangement of the weft, elongation or curl of the weft during weaving , or internal stress due to loads encountered in the process of flipping the band backwards between the steps of forming the first resin layer and forming the second resin layer. In contrast, since the band according to the invention has no such internal tension, it is dimensionally stable, particularly in the CMD direction. The above table also shows that the band of this invention can be manufactured in a shorter time compared to the conventional band. Since the conventional band uses an endless woven fabric, it is turned upside down to form the second resin layer after the first layer is formed of resin. Before the band is turned upside down, the first layer of resin must be heated and cured, and this requires at least 10 hours. In the band according to this invention, however, there is no need to flip the band upside down, or for similar steps, and the interval between the formation of the first resin layer and the formation of the second resin layer is only about 1 hour. Therefore, the band according to the invention has a shortened manufacturing time. The shoe press band according to the invention shows the following beneficial effects. Firstly, since the first resin layer constituting the innermost layer of the strip is formed on a polished surface of a mandrel, a uniform surface is formed without the need for further treatment. Secondly, since the base fabric layer of the web are woven fabric sheets having ends, it is easy to adjust the dimensions in the circumferential direction during the manufacture of the web, and therefore manufacturing costs are reduced. Third, since the base fabric layer uses high strength fibers that extend along the axial direction of the mandrel, the band exhibits sufficient strength in the CMD direction. Therefore, the band is dimensionally stable in operation and capable of generating a product that exceeds the high dimensional accuracy over a prolonged period. In fourth Instead, since the outer periphery of the base fabric layer of the web is formed with a coil layer made of high strength fiber, the web also shows sufficient strength in the MD direction. Fifth, since the base fabric layer and the coil layer are coated and integrated, and the second resin layer is in contact with the first resin layer, both resin layers become integral with each other. Accordingly, the destruction of the web and detachment of the resin layer as a result of stresses acting on the web during use is greatly reduced. Finally, in the manufacturing method of the invention, there is no need to polish the first resin layer or flip the first resin layer upside down, after its formation. The fact of avoiding the need to polish the first layer of resin and turn it upside down significantly improves the production efficiency.

Claims (4)

1. A shoe press band, characterized in that it comprises: a first endless resin layer having a uniform internal surface, in the form of a surface of revolution having an axis, the first resin layer having an outer periphery; a base fabric layer comprising a woven fabric sheet positioned over the entire outer periphery of the first resin layer, the fabric sheet comprises intersecting fiber assemblies, and at least one of the intersecting fiber assemblies is high strength fibers that extend in the axial direction along the base fabric layer; a coil layer comprising high strength fibers circumferentially wound in a spiral about the outer periphery of the base fabric layer; and a second endless resin layer on the outer periphery of the coil layer, the second resin layer is in contact with the first resin layer through the base fabric layer and the coil layer.

2. The shoe press band, according to claim 1, characterized in that the inner surface The uniform of the first endless resin layer is in the form of a cylinder, and in which the fibers of at least one of the sets of the intersecting fibers extend parallel to the axis.

3. The shoe press band, according to claim 1, characterized in that the first endless resin layer is a layer formed on a polished surface of a rotatable mandrel.

4. A method for manufacturing a shoe press band, manufacturing method which is characterized in that it comprises the steps of: forming a first layer of endless resin on a polished surface of a rotatable mandrel; forming a base fabric layer by placing, on the entire outer periphery of the first resin layer, a woven fabric sheet comprising sets of intersecting fibers, at least one of the assemblies being high strength fibers, so that the fibers of one of the assemblies extends along the axial direction of the mandrel; forming a coil layer by winding the high strength fiber over the outer periphery of the base fabric layer, circumferentially in a spiral; Y subsequently forming a second endless resin layer on the outer periphery of the coil layer, so as to contact the first resin layer through the base fabric layer and the coil layer.