JP5571403B2 - Papermaking felt and method for producing the same - Google Patents

Description

  The present invention relates to a papermaking felt in which a batt fiber layer is integrated with a base fabric layer by needling, and a method for producing the same.

  In felts for papermaking, a bat fiber layer of the required thickness is laminated and integrated on the base fabric layer, but on its surface, relatively small irregularities due to the bat fiber itself, spots on the bat fiber, and the needling method There are various large and small irregularities, such as relatively large irregularities generated by. If the unevenness of the surface of the bat fiber layer is remarkable, the surface property of the wet paper pressed together with the felt by the press roll on the paper making machine will also deteriorate. In addition, it is known among felt manufacturers for papermaking that the surface property of felt has a great influence on the water squeezing ability. The larger the irregularity of the felt surface, the more uneven the pressure state under pressure by the press roll. As a result, the felt watering performance decreases. For this reason, it is required to improve the surface property, that is, to make the surface of the bat fiber layer smoother with less irregularities on the papermaking surface side.

  In general, surface roughness parameters such as arithmetic average roughness Ra defined in JIS B0601 are used for evaluation of surface properties, and these parameters may be applied to papermaking tools (for example, , See Patent Document 1). Patent Document 1 discloses a paper transport belt, and since the surface is a resin layer, the surface state does not change greatly even when pressed. However, in the felt for papermaking, the felt surface is an aggregate in which bat fibers, which are short fibers, are entangled with each other. When pressed, the bat fibers move and the aggregate state of the bat fibers on the felt surface changes. Therefore, the surface roughness parameters such as arithmetic mean roughness Ra, which is a measurement under non-pressurization, evaluate the surface properties of the felt under non-pressurization and use parameters such as pressure uniformity that are measured under pressure. It is preferable to do.

  In order to smooth the surface of the bat fiber layer, for example, a method using bat fibers having a small fineness is applied. Reducing the fineness of the bat fiber reduces the relatively small irregularities caused by the diameter of the bat fiber, and also increases the number of bat fibers when using the same weight of bat fiber, so it depends on the local fiber state The surface roughness to be reduced can be reduced. As another method for smoothing the surface of the bat fiber layer, a technique is disclosed in which a papermaking felt is pressed during finishing to form a flat surface. By pressing the felt for papermaking, the surface roughness and pressure uniformity can be reduced (see, for example, Patent Documents 2 to 5).

Japanese Patent No. 3264461 JP 2006-9188 A Japanese Patent No. 3360145 Special table 2007-532785 gazette Japanese Patent No. 2649044 Patent No. 4064930

  However, it is not easy to reduce the uniformity of the pressure depending on the fiber spots and tangling spots only by the method using bat fibers having a small fineness. Furthermore, depending on the stage of the papermaking process, the felt for papermaking requires dehydration, dirt prevention, hair removal prevention, etc. in addition to surface properties, and reducing the fineness of the bat fiber can cause dirt depending on the stage of the papermaking process. There is a risk of causing new problems such as easy clogging.

  In addition, since the bat fibers of the bat fiber layer are intertwined in a complicated manner, there are portions having local variations in hardness and spotted spots on the surface of the bat fiber layer. When pressing papermaking felt during finishing, the pressure during pressing is generally set to 60 kN / m or less so as not to impair the various performances of papermaking felt after pressing. Even by such a method, local variations in hardness and spotted spots have not been completely eliminated.

  The present invention has been devised based on such inventor's knowledge, and its main purpose is to provide a papermaking felt configured to improve the surface property of paper and a method for producing the same. It is to provide.

In order to solve such problems, the present invention is a papermaking felt comprising at least a base fabric layer and a surface layer in which bat fibers are entangled and integrated with the base fabric layer by needling. The papermaking surface is a polished surface, the coefficient of variation of the felt surface pressure distribution under the average pressure of 0.1 MPa of the polished surface is 0.25 or less, and the arithmetic average roughness Ra is 10 to 10. It is in the range of 38 μm.

  According to the said structure, the surface property of a felt surface layer can be improved by using the felt felt surface layer, without using felt with a small fineness, and pressing a felt with an excessive pressure. Moreover, the felt concerning the said structure can improve the surface property of a felt surface layer, without impairing dehydrating property, stain | pollution | contamination prevention property, and hair loss prevention property by selecting suitably the batt fiber with which a surface layer is equipped. Further, by polishing the felt, the bat fiber is polished to flatten the fiber, and fine scratches and burrs are generated on the fiber surface. The flattening of the fibers and the formation of fine scratches and burrs increase the surface area of the fibers, thereby improving the hydrophilicity of the felt and improving the “familiarity” to the wet paper.

  The evaluation of the polished felt surface may use both the coefficient of variation of the surface pressure distribution that can evaluate the felt surface under pressure and the arithmetic average roughness that can evaluate the felt surface under non-pressure. Is preferred. According to the above configuration, the felt surface property in a state where the felt is used on the paper machine can be accurately evaluated by processing the felt surface in the above range using these two parameters in combination, and a desired surface. The state can be obtained.

  Here, the variation coefficient is obtained by calculating the standard deviation of the measured pressure distribution on the surface based on the definition of JISZ8101-1-1.15, and then dividing the standard deviation by the average value of the pressure. This coefficient of variation relatively represents variations in pressure distribution. The arithmetic average roughness is defined in JIS B 0601: 2001 “Product Geometrical Specification (GPS) —Surface Properties: Contour Curve Method—Terminology, Definition, and Surface Property Parameters”.

  The pressure at the time of measuring the pressure on the felt surface is optimally 0.1 MPa. The reason is as follows. That is, the pressure uniformity of the felt can be divided into pressure uniformity mainly caused by the base fabric layer and pressure uniformity caused by the surface bat layer (= surface pressure uniformity). In order to reduce pressure spots caused by the base fabric layer, it is necessary to change the base fabric design. However, if the base fabric design is changed, other performance changes besides pressure uniformity. It is difficult to improve only the pressure uniformity while maintaining the performance required for other felts. On the other hand, by performing surface polishing, the surface pressure uniformity can be improved while maintaining the performance required for other felts. And since the pressure spot resulting from a base fabric layer does not generate | occur | produce under the pressure of about 0.1 MPa (it is not measured), only a felt surface pressure uniformity can be evaluated by the pressure measurement of 0.1 MPa.

  In the polished felt surface, the coefficient of variation of the pressure distribution on the felt surface is preferably 0.27 or less, more preferably 0.25 or less, and the arithmetic average roughness Ra of the polished surface is preferably The thickness is preferably 10 to 45 μm or less, more preferably 10 to 38 μm or less. According to this configuration, it is possible to improve the machine operation efficiency by improving the felt water squeezing and also to improve the surface property of the paper produced by the paper machine.

  However, if the arithmetic average roughness is less than 10 μm, the transfer of the wet paper from the felt to the roll or the transfer of the wet paper from the felt to the felt is not performed smoothly, and the wet paper is attached to the felt before the transfer. There is a risk of causing “paper being picked”. In order to prevent the occurrence of “paper scraping”, the above configuration realizes the above-described coefficient of variation and arithmetic surface roughness to achieve the optimum felt surface for the conditions of the place where the felt is used. The degree of polishing is adjusted.

  In the above configuration, it is preferable that the average fineness of the bat fiber in the surface layer is 17 dtex or more and 24 dtex or less.

  The fineness represents the thickness of the fiber and is expressed as a ratio of mass to a certain length of the fiber. Here, the average fineness is set to 17 dtex or more because the bat fiber having a fineness of 17 dtex or less has a weak force because the fibers are entangled with each other, that is, the strength of one fiber and the pulling resistance of the fiber are weak. This is because a lot of fluffing and hair loss occurs, and the polishing workability may be deteriorated. The occurrence of fluffing and hair loss during polishing was the reason why it was thought that the effect of polishing was not sufficiently obtained even if surface polishing was performed on paper felts.Therefore, felt makers for papermaking felt No surface polishing was performed. However, the present inventor has repeatedly studied the cause of hair loss and fluffing during polishing, enabling felt surface polishing, and without sacrificing other requirements required for felt. It is possible to improve the pressure uniformity. If the vat fineness is 24 dtex or more, the distance between the fibers on the felt surface becomes too wide, so that the arithmetic average roughness and the variation coefficient of the pressure distribution cannot be sufficiently improved by surface polishing. However, according to the said structure, while being able to grind | polish to desired surface property, polishing workability | operativity can be improved.

In the above configuration, it is preferable that the density of the papermaking felt is 0.390 g / cm ³ or more. In a papermaking felt having a density of 0.390 g / cm ³ or less, since the fibers are not sufficiently intertwined, the surface layer may become fluffed by polishing. The fluffing of the surface layer tends to cause hair loss of the fibers, and thus the anti-hair removal resistance is lowered. However, the above-described configuration can suppress such a decrease in performance.

  The said structure WHEREIN: The said batt fiber of a surface layer can consist of a core-sheath-type composite fiber which is a polymeric material softened and fuse | melted by heat processing. Here, the core-sheath type composite fiber includes a core part made of a first polymer material and a sheath part made of a second polymer material having a melting point different from that of the first polymer covering at least a part of the core part. The melting point temperature of the second polymer material can be lower than the melting point temperature of the first polymer material. The surface layer was heated to a temperature lower than the melting point temperature of the first polymer and higher than the melting point temperature of the second polymer, and then cooled to a temperature lower than the melting point temperature of the second polymer. It is preferable to form the surface by polishing it later.

  The said structure applies the core-sheath type | mold composite fiber which applied two types of polymers from which melting | fusing point differs to a core part and a sheath part to a bat fiber. In this configuration, the polymer of the sheath part has a lower melting point than the polymer of the core part. Therefore, by placing the surface layer in a temperature environment lower than the melting point of the core part and higher than the melting point of the sheath part, The sheath portion can be melted while maintaining the portion.

  According to the above configuration, by melting the second polymer material of the sheath portion once before the polishing process, it becomes possible to efficiently perform the polishing even when the bond due to the entanglement between the bat fibers is weak, It is possible to achieve a desired felt surface property. Also, by melting the sheath after polishing and then curing it, the bonding between the bat fibers becomes strong, and it is possible to prevent the bat fibers on the surface layer from being removed when the felt is used on the paper machine. it can. As described above, the timing for melting the sheath may be determined before or after the polishing process, based on the use conditions of the felt, the workability of the polishing process, and the like.

  In the configuration in which the core-sheath type composite fiber is applied, the surface layer includes an outer bat layer disposed on the surface side and an inner bat layer disposed on the inner side of the outer bat layer, The outer bat layer is preferably constructed of the core-sheath composite fiber. According to this configuration, by arranging the core-sheath type composite fiber on the surface layer, it is possible to limit the region where the polymer is melted and cured, while taking advantage of the characteristics of the bat fiber other than the core-sheath type composite fiber, Abrasiveness and hair removal prevention can be improved.

  In the configuration to which the core-sheath composite fiber is applied, it is preferable that the average fineness of the outer bat fiber is 2.5 dtex or more and 17 dtex or less. That is, in the case where the bat fiber has a bat fineness of 17 dtex or less as in the configuration in which the above-described core-sheath composite fiber is not applied, it is difficult to polish efficiently because the entanglement force between the bat fibers is weak. However, the joint force between the bat fibers can be improved by using the core-sheath type composite fiber. If the bat fibers are 2.5 dtex or more, the bonding force between the bat fibers can be improved to a level sufficient for polishing. Further, as described above, a normal bat fiber of 17 dtex or more has a sufficient bonding force between bat fibers for polishing without using a core-sheath type composite fiber, but for reasons other than improving the polishing workability, Mixing and using the sheath-type composite fiber with the vat fiber having such a fineness is not a problem in polishing.

  In addition, it is disclosed by patent document 6 to grind | polish with respect to resin processing felt. By coating the felt with resin, the bonding force between the bat fibers is certainly improved and surface polishing becomes possible. However, the maximum size of the papermaking felt is over 10 m, and the length (loop length) is 15 m or more, sometimes 100 m or more. Such a large product is subjected to resin processing only for the purpose of polishing. That is very inefficient considering its energy cost and working time. Moreover, the viscosity of the aqueous resin solution of the water-dispersed resin as disclosed in Patent Document 6 is very small, and tends to gather in a dense portion of bat fibers due to capillary action during resin processing. The portion where the bat fiber is dense is harder than the portion where the bat fiber is dense, and is hard to be compressed. If more resin adheres to such a portion, that portion becomes more difficult to be compressed. Even if the felt according to the prior art in such a state is subjected to surface polishing, the arithmetic average roughness can be reduced, but not much improvement in surface pressure uniformity can be expected.

Further, if the viscosity of the resin liquid is increased in order to avoid such a partial increase in hardness due to the collection of the resin liquid, the resin amount of the resin processing felt is usually only a few tens g / m ² , It becomes difficult to uniformly adhere to the entire felt. Furthermore, if the amount of resin used for resin processing is increased in order to uniformly apply a resin solution having a relatively high viscosity, other results required for felt, such as a decrease in air permeability, may be deteriorated. .

  On the other hand, the viscosity when the low melting point portion of the core-sheath type composite fiber is melted is much larger than the viscosity of the aqueous resin solution of these water-dispersed resins, and does not move greatly when melted. Further, since the second polymer material having a low melting point used for reinforcing the bonding strength between fibers exists as a sheath portion of the bat fiber, a small amount of the fiber bonding strength improving component is uniformly distributed over the entire felt surface. It is possible. Therefore, using a core-sheath type composite fiber when the surface bat fineness is relatively small, such as an average of 17 dtex or less, improves the polishing efficiency while maintaining other required performance, and produces a felt having an excellent surface. It is effective in. Thus, the said structure is excellent also in cost and performance compared with the prior art.

  The said structure WHEREIN: The said surface layer can be made to contain the said core-sheath-type composite fiber of 20% or more and 80% or less. According to this configuration, it is possible to improve the bonding force between the bat fibers and efficiently perform polishing while maintaining the breathability of the bat fibers on the surface layer.

Another aspect of the present invention is a method for producing a felt for papermaking comprising a base fabric layer and a surface layer in which bat fibers are entangled and integrated with the base fabric layer by needling, wherein the paper surface of the surface layer is The polished and batt fiber includes a core-sheath type composite fiber that is a polymer material that is softened and melted by heat treatment, and the core-sheath type composite fiber includes a core portion made of a first polymer material, and the core. Before the paper surface of the surface layer is polished, as a sheath comprising a second polymer material covering at least a part of the first polymer material and having a melting point temperature lower than the melting point temperature of the first polymer. Furthermore, it is characterized by being heated and cooled at a temperature lower than the melting point temperature of the first polymer and higher than the melting point temperature of the second polymer material.

  According to the above configuration, a method for producing a felt for papermaking that improves the surface property of the felt surface layer by polishing the felt surface layer without using felt with a small fineness or pressing the felt with an excessive pressure is provided. be able to.

  In the above configuration, by melting the second polymer material of the sheath portion once before the polishing process, it becomes possible to efficiently perform the polishing even when the bond due to the entanglement between the bat fibers is weak, Felt surface properties can be realized.

  Thus, according to this invention, the surface property of a felt surface layer can be improved by grind | polishing a felt surface layer, without using a felt with small fineness and pressing a felt with an excessive pressure.

It is typical sectional drawing which shows an example of the felt for paper manufacture concerning one Embodiment of this invention. It is typical sectional drawing which shows the comparative example concerning a prior art. It is an electron micrograph which shows the felt surface after the grinding | polishing process of the Example concerning one Embodiment of this invention. It is a typical side view which shows an example of the grinding | polishing process of the felt for paper manufacture concerning one Embodiment of this invention. It is explanatory drawing of surface roughness. It is a drawing substitute photograph which shows the measurement result of the pressure measurement film before the grinding process of the Example concerning one Embodiment of this invention. It is a drawing substitute photograph which shows the measurement result of the pressure measurement film after the grinding process of the Example concerning one Embodiment of this invention.

  Hereinafter, an embodiment according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of a papermaking felt according to an embodiment of the present invention. This felt 10 has a multi-layer structure in which a batt fiber layer 2 as a surface layer is laminated and integrated on a base fabric layer 1 by needling. The base fabric layer 1 can be a monofilament yarn or a fabric woven from a plurality of filaments twisted by a loom, but is not limited to this, and only a multilayer fabric, a width direction or a length direction yarn can be used. A formed cloth, a resin sheet, or the like can also be applied.

  The plane 3 opposite to the base fabric layer 1 of the batt fiber layer 2 is the side on which the wet paper (not shown) contacts. The surface of the flat surface 3 is polished so as to have a predetermined “arithmetic average roughness” and “coefficient of variation of surface pressure distribution” that do not cause “paper removal”.

  On the other hand, referring to the comparative example according to the prior art of FIG. 2, the comparative example also has a multilayer structure in which the batt fiber layer 12 is laminated and integrated on the base fabric layer 11 by needling. However, the surface 13 on the opposite side of the base fabric layer 11 of the bat fiber layer 12 is in a state in which the irregularities generated during the needling remain. Thus, when the unevenness | corrugation of the surface 13 is remarkable, the surface property of the wet paper pressed with a felt with a press roll on a papermaking machine will also fall. Further, the surface property of the felt has a great influence on the water squeezing ability, and the greater the unevenness of the felt surface, the more uneven the pressure state under pressure by the press roll, and the felt water squeezing performance decreases. Even when the papermaking felt is pressed during the finishing process to form a flat surface, the bat fibers of the bat fiber layer are intertwined in a complex manner, so there is local variation in hardness on the surface of the bat fiber layer. There was a portion having spotted spots, and this variation and spots reduced the surface properties of the wet paper.

  In this embodiment, the flat surface 3 shown in FIG. 1 is formed by polishing the batt fiber layer 12 up to the polishing line 14 shown by a broken line in FIG. FIG. 3 shows an electron micrograph showing the felt surface after polishing (corresponding to plane 3). Referring to FIG. 3, the batt fiber layer on the felt surface in contact with the wet paper is polished and is in a state similar to the fiber layer of the flat fiber. However, when deformed bat fibers such as flat fibers are used, normal bat fibers other than deformed fibers may be exposed to the surface that contacts the wet paper by needling from the bat layer inside the felt, improving the flatness. Was difficult. On the other hand, in this embodiment, since the surface polishing is performed after the needling step, the surface property can be improved without being affected by the needling.

  Further, by polishing the felt, as shown in FIG. 3, the bat fiber is polished to flatten the fiber, thereby causing fine scratches and burrs on the fiber surface. The flattening of the fibers and the formation of fine scratches and burrs increase the surface area of the fibers, thereby improving the hydrophilicity of the felt and improving the “familiarity” to the wet paper.

  Next, an example of the surface polishing process will be described with reference to FIG. The felt 10 is formed in a loop shape with the bat fiber layer 12 (see FIG. 2) on the outside, and is spanned between a pair of transport rolls 21 and 21 installed at a predetermined interval so that a constant tension is applied. Yes. The transport rolls 21 and 21 rotate clockwise, and the felt 10 rotates clockwise. A polishing roll 22 is disposed between the transport rolls 21 and 21, and the polishing roll 22 is arranged so that the bat fiber layer 12 is brought into contact with the bat fiber layer 12 of the felt 10 (see FIG. 2) with a certain pressure. It is energizing upward.

  The polishing roll 22 is provided with a polishing cloth on the outer surface, and the width of the polishing roll is appropriately selected according to the width of the felt 10. The polishing process is not limited to the case where a polishing roll is used, and polishing paper, a polishing belt, a polishing plate, and the like can also be applied.

  The polishing roll 22 rotates clockwise while in contact with the bat fiber layer 12 at a predetermined pressure. Since the felt 10 also rotates in the clockwise direction, the polishing cloth of the polishing roll 22 and the bat fiber layer 12 (see FIG. 2) abut against each other so that the bat fiber layer 12 is polished. In the configuration of FIG. 4, the surface 13 is polished to the polishing line 14 as shown in FIG. 2 by appropriately setting the pressure for biasing the batt fiber layer 12 and the polishing time, and the polishing is performed as shown in FIG. A flat plane 3 is formed. In such a polishing process, in order to make the burr of the bat fiber generated by polishing lie in a certain direction, the wet paper is set by setting the traveling direction of the felt in a direction in which the burr is suppressed in the paper making process. It can be prevented from being caught and dragged by the burr on the felt surface layer. In addition, the process of polishing so that the polishing cloth of the polishing roll 22 and the batt fiber layer 12 (see FIG. 2) face each other is provided at least in the final stage of the polishing process, and the previous polishing process is performed. It can also be set as the structure which does not specifically limit the direction which both contact | abut in a process.

  In the evaluation of the polished felt surface in this embodiment, the variation coefficient of the surface pressure distribution that can evaluate the felt surface under pressure and the arithmetic average roughness that can evaluate the felt surface under non-pressurization Are used together.

  Here, with reference to FIG. 5, “surface roughness” which is a surface state in which undulations of peaks and valleys continue at small intervals will be briefly described. “Surface roughness” is defined as “arithmetic average roughness Ra” in JIS B 0601: 2001 “Product Geometric Specification (GPS) —Surface Properties: Contour Curve Method—Terminology, Definitions and Surface Properties Parameters”. .

  Fig.5 (a) is a schematic diagram of the cross-sectional curve of the surface 13 (refer FIG. 2) of the bat fiber layer 12 used as the measuring object measured by the surface roughness measuring device (not shown). FIG. 5A reproduces the surface property shown in FIG. 2 as a cross-sectional curve.

  If the horizontal axis in FIG. 5A is x and the vertical axis is z, the cross-sectional curve is Z (x). The “arithmetic average roughness Ra” can be obtained by gradually integrating the Z (x) with the evaluation length L by the evaluation length L, and has a cross-sectional curve shown in FIG. In the examples described below, “arithmetic mean roughness Ra” in accordance with JIS B 0601: 2001 is shown.

  On the other hand, the variation coefficient of the surface pressure distribution is obtained by calculating the standard deviation of the measured surface pressure distribution based on the definition of JISZ8101-1-1.15, and then dividing this standard deviation by the average value of the pressure. . This coefficient of variation relatively represents variations in pressure distribution.

  The variation coefficient of the surface pressure distribution can be easily obtained by analyzing the pressure data measured by the pressure measurement film on the polished surface. For example, pressure spots are measured with a pressure measurement film (prescale for fine pressure (4LW) 0.05 MPa-0.2 MPa: manufactured by Fuji Film), and the measurement result is a pressure image analysis system (manufactured by Fuji Film: FPD-9210). It is possible to obtain a variation coefficient of pressure distribution by taking out the pressure data in each part using the export function and statistically processing this data with Microsoft Excel CEL.

  The pressure at the time of measuring the pressure on the felt surface is optimally 0.1 MPa. That is, the pressure uniformity of the felt can be divided into the pressure uniformity mainly due to the base fabric layer and the pressure uniformity due to the surface bat layer (= surface pressure uniformity). Since the pressure spots do not occur under the pressure of about 0.1 MPa (not measured), only the felt surface pressure uniformity can be evaluated by the pressure measurement of 0.1 MPa.

  Next, Example 1 of the present embodiment will be described. In Example 1, a base material layer formed by weaving warps and wefts with a loom is needling nylon bat fibers, which are polyamide synthetic fibers as a surface layer. The fiber materials and finenesses of Examples 1-1 and 1-2 and Reference Examples 1-1 to 1-4 are shown in Table 1. Here, the fineness of Examples 1-1 and 1-2 is 17 dtex or more and 24 dtex or less. Reference Examples 1-1 and 1-2 are batt fiber layers having a fineness of 24 dtex or more, and Reference Examples 1-3 and 1-4 are batt fiber layers having a fineness of 17 dtex or less. In Example 1-2 and Reference Example 1-1, the batt fiber layer is formed of two types of fibers having different finenesses.

  In the examples and reference examples, the surface shown in FIG. 1 is subjected to the polishing process shown in FIG. 4, and the “roughness” after the needling shown in FIG. 2 and the uneven pressure distribution remain. Is in a polished state. Table 2 shows the results of measuring the density, polishing amount, and air permeability before and after polishing of the examples and reference examples before and after polishing. In addition, the felt of an Example and a reference example is press-processed before grinding | polishing by the pressure which is 10-60 kN / m different according to the conditions used, respectively.

Referring to Table 2, there is no significant change in air permeability before and after polishing in both the examples and the reference examples. As described above, the polishing process in the present example and the reference example does not change the ventilation characteristics of the bat fibers themselves in the examples and the reference examples provided for the process. The density of Examples 1-1 and 1-2 and Reference Examples 1-1 to 1-4 is 0.390 g / cm ³ or more, and neither of them shows fuzz on the felt surface after polishing.

  Table 3 shows the difference (percentage) between the measured values of the surface pressure distribution variation coefficient before and after polishing and the measured values before and after polishing for the examples and reference examples. Table 4 shows the difference (percentage) between the measured value of arithmetic average roughness Ra before and after polishing and the measured value before and after polishing for the examples and reference examples.

  Referring to Table 3, the “variation coefficient of the surface pressure distribution” decreases in both the examples and the reference examples, that is, a more uniform pressure distribution than before the polishing process is realized. Referring to Examples 1-1 and 1-2 and Reference Examples 1-2, 1-3, and 1-4, the surface pressure distribution coefficient of variation (JISZ8101-1) was polished to be 0.25 or less. Yes. Thus, polishing can reduce the non-uniform pressure distribution on the felt surface. Further, the difference between the measured values before and after the polishing process expressed as a percentage is larger than that of the reference example, which indicates that the polishing process effect of reducing the non-uniform pressure distribution is high. However, even in the reference example, in Reference Examples 1-2, 1-3, and 1-4, the coefficient of variation of the pressure distribution is reduced by 15% or more due to polishing, and for example, Reference Example 1-2 is a 27 dtex bat Although the fineness is used, it is possible to obtain a surface pressure distribution superior to the pressure distribution before polishing of Example 1-1 using a 17 dtex bat by polishing, which is practically useful. From these facts, when felt is used, it is preferable to reduce the coefficient of variation of the surface pressure distribution by 15% or more by polishing, and further reduce it by 22% or more as in Examples 1-1 and 1-2. Is particularly preferred.

  Next, when the arithmetic average roughness Ra is viewed with reference to Table 4, it is included in the range of the arithmetic average roughness Ra of the polished surface of 10 to 38 μm in the example, and 10 in the reference examples 1-2 to 1-4. It is included in the range of ˜45 μm. The arithmetic average roughness Ra of the polished surface is preferably 10 to 45 μm or less in order to improve machine operation efficiency by improving felt water squeezing and also to improve the surface property of paper produced by a paper machine. More preferably, the thickness is 10 to 38 μm or less. As described above, according to the present invention, even in Reference Examples 1-2 to 1-4, an improvement in machine operation efficiency by improving felt water squeezing and an improvement in surface properties of paper produced by a paper machine are realized. I can do it.

  Moreover, when the difference of the measured value before and behind grinding | polishing process is seen, compared with a reference example, it turns out that the reduction | decrease of arithmetic average roughness before and behind grinding | polishing process is 25% or more and is very large. On the other hand, when the fineness is small as in Reference Examples 1-3 and 1-4, the polishing workability is poor, and in Reference Example 1-4, the effect of reducing the roughness by polishing was not obtained.

  The measurement results of the pressure measurement film before and after polishing in the examples are shown in FIGS. 6 and 7, respectively. The pressure measurement film develops a color at a pressurized portion. When the pressure is high, the color is deep, when the pressure is low, the color is thin. Comparing the surface texture of FIG. 6 before the polishing process and the surface texture of FIG. 7 after the polishing process, many white and light portions are seen before the polishing process of FIG. It can be seen. On the other hand, after the polishing process of FIG. 7, there is a part with a light color, but there is no white part, and the whole color is developed almost uniformly, and no needling meridian is seen.

  According to the present embodiment, by polishing the felt surface layer, it is possible to improve the surface properties of the felt surface layer without using a felt having a small fineness or pressing the felt with an excessive pressure. Moreover, the felt concerning the said structure can improve the surface property of a felt surface layer, without impairing dehydrating property, stain | pollution | contamination prevention property, and hair loss prevention property by selecting suitably the batt fiber with which a surface layer is equipped. Further, polishing the felt causes the batt fibers to be polished to flatten the fibers, thereby causing fine scratches and burrs on the fiber surface. The flattening of the fibers and the formation of fine scratches and burrs increase the surface area of the fibers, thereby improving the hydrophilicity of the felt and improving the “familiarity” to the wet paper.

Next, a water squeezing test was performed in order to confirm the water squeezing improvement effect brought about by the felt surface smoothness improvement and the felt pressure uniformity improvement by polishing. The squeezing test was conducted by the following method. That is, wet paper and an aluminum plate, whose moisture has been adjusted in advance and whose weight has been measured, are placed on the felt at the press entrance, passed through the press, and the weight of the wet paper in the wet paper receiver is measured. And the amount of squeezing in a press is calculated from the wet paper weight change before and after the pressing of the wet paper, and the water squeezing between the felts is compared. This water squeezing test was performed using the samples before and after polishing in Example 1. The test was performed under the conditions of a felt running speed of 200 m / min, a felt moisture of 500 ± 25 g / m ² , a wet paper basis weight of 50 ± 2.5 g / m ² , and a wet paper web moisture before press of 60 ± 1.0%. The test was performed under the condition of the number of samples n = 20, and the squeezed water was compared with the average value.

  The results are shown in Table 5. Referring to Table 5, the sample after polishing is squeezed 1.5% more than the sample before polishing, and the felt surface smoothness and pressure uniformity are improved by the polishing process. Can be improved.

  Next, Example 2 of the present embodiment will be described. In Example 2, a base fabric layer formed by weaving warps and wefts with a loom, a normal nylon layer (simply referred to as “nylon” in the table) and a core-sheath type composite fiber (simply referred to as “core sheath in the table”). )) And is needling. In Example 2, two types of samples in which vat fibers having different fineness were needled were used. Table 6 shows the material and fineness of the fibers of Example 2. Here, the fineness of Example 2 is in the range of 2.5 dtex or more and 17 dtex or less. Moreover, Example 2 is configured to include 20% or more and 80% or less of the core-sheath type composite fiber. In Example 2-2, the bat raw material 3 is the outer bat layer.

  In the core-sheath type composite fiber, two kinds of polymers having different melting points are applied to the core part and the sheath part. Since the polymer of the sheath part has a lower melting point than the polymer of the core part, the core part was maintained by placing the surface layer in a temperature environment lower than the melting point of the core part and higher than the melting point of the sheath part. The sheath part can be melted as it is. For example, a high melting point (200 ° C. or higher) polyamide synthetic fiber can be applied to the core portion, and a low melting point (140 ° C. to 160 ° C.) polyamide synthetic fiber can be applied to the sheath portion.

  In this configuration, the sheath layer is melted after polishing the surface layer, and then cured, thereby strengthening the bonding between the bat fibers and curing the surface layer, thus preventing the bat fibers on the surface layer from being removed. To do. In addition, about the timing which melt | dissolves a sheath part, it judges based on the use conditions of felt, workability | operativity of grinding | polishing processing, etc., You may carry out before grinding | polishing processing or before and after grinding | polishing processing without being limited after the above-mentioned grinding | polishing processing. That is, by melting the second polymer material of the sheath portion once before polishing, it becomes possible to perform polishing efficiently even when the entanglement force between the bat fibers is weak, and the desired felt surface property can be obtained. It can be realized.

  In the second embodiment, the polishing process shown in FIG. 4 is performed in the same manner as the first embodiment, and the “roughness” and the non-uniform pressure distribution after the needling shown in FIG. The surface shown is polished. Table 7 shows the results of measuring the density, polishing amount, and air permeability before and after polishing of the examples before and after polishing.

Referring to Table 7, Example 2 shows no significant change in air permeability before and after polishing. As described above, the polishing process in this example does not change the ventilation characteristics of the bat fiber itself of the example used for the process. The density of the example is 0.390 g / cm ³ or more, and no fuzz or the like is observed on the felt surface after polishing.

  Table 8 shows the difference between the measured value of the surface pressure distribution variation coefficient before and after the polishing process and the measured value before and after the polishing process, and the difference (percentage) between the measured value of the arithmetic average roughness Ra and the measured value before and after the polishing process. .

  Referring to Table 8, the coefficient of variation of the surface pressure distribution is lowered, and polishing can be performed so that the coefficient of variation of the surface pressure distribution (JISZ8101-1) is 0.25 or less. Thus, polishing can reduce the non-uniform pressure distribution on the felt surface. Further, the difference between the measured values before and after the polishing process shown as a percentage of the example is larger than that of the reference example shown in Table 3, and in the example, the effect of the polishing process for reducing the non-uniform pressure distribution is high. It is shown that.

  Next, when the arithmetic average roughness Ra is seen, it is included in the range of the arithmetic average roughness Ra of 10 to 38 μm of the polished surface. As described above, the present embodiment can realize improvement in machine operation efficiency by improving felt water squeezing and improvement in surface properties of paper produced by a papermaking machine. Further, in this example, it can be seen that the roughness is remarkably reduced before and after polishing. In Reference Example 1-4 described above, there was almost no change in roughness before and after polishing, but in Examples where the core-sheath composite fiber was applied, a reduction in roughness could be realized.

  The preferred embodiments of the present invention have been described above. The present invention is not limited to what is described in the specification and drawings, and design changes can be made without departing from the spirit of the invention. For example, a water-soluble polymer adhesive such as polyvinyl alcohol glue or starch glue may be applied to the surface fiber before polishing the batt fiber, and the adhesive may be removed after polishing. By such a procedure, the polishing process can be facilitated by fixing the surface layer.

  The felt for papermaking according to the present invention has an effect of improving the surface property of paper, and the felt for papermaking in which bat fiber layers are integrated on the surface or both front and back surfaces of a base fabric layer having a multilayer structure, In particular, it is useful as a press felt used in a press part (squeezing part) of a paper machine.

DESCRIPTION OF SYMBOLS 1,11 Base fabric layer 2,12 Butt fiber layer 3 Plane 10 Felt 13 Surface 21 Transport roll 22 Polishing roll

Claims (8)

A papermaking felt comprising at least a base fabric layer and a surface layer in which bat fibers are entangled and integrated with the base fabric layer by needling,
Papermaking surface of the surface layer, Ri polished surface der,
A coefficient of variation in felt surface pressure distribution under an average pressure of 0.1 MPa on the polished surface is 0.25 or less, and an arithmetic average roughness Ra is in the range of 10 to 38 μm. Felt for. 2. The papermaking felt according to claim 1 , wherein an average fineness of the batt fiber of the surface layer is 17 dtex or more and 24 dtex or less. The papermaking felt according to claim 1 or 2 , wherein the density of the papermaking felt is 0.390 g / cm3 or more. The batt fiber of the surface layer includes a core-sheath type composite fiber that is a polymer material that is softened and melted by heat treatment,
The core-sheath-type conjugate fiber includes a core portion made of a first polymer material, and a sheath portion covering at least a part of the core portion and made of a second polymer material different from the first polymer material. Become
The papermaking felt according to claim 1, wherein the melting point temperature of the second polymer material is lower than the melting point temperature of the first polymer material. The surface layer is composed of an outer bat layer arranged on the surface side and an inner bat layer arranged on the inner side of the outer bat layer,
5. The papermaking felt according to claim 4 , wherein the outer bat layer includes the core-sheath composite fiber. The papermaking felt according to claim 5 , wherein the average fineness of the bat fiber of the outer bat layer is 2.5 dtex or more and 17 dtex or less. The felt for papermaking according to any one of claims 4 to 6, wherein the surface layer includes 20% or more and 80% or less of the core-sheath type composite fiber. A method for producing a felt for papermaking, comprising: a base fabric layer; and a surface layer in which batt fibers are entangled and integrated with the base fabric layer by needling,
The surface papermaking surface is polished ,
The batt fiber includes a core-sheath type composite fiber that is a polymer material that is softened and melted by heat treatment,
The core-sheath type composite fiber includes a core portion made of a first polymer material and a second polymer material that covers at least a part of the core portion and has a melting point temperature lower than the melting point temperature of the first polymer. And a sheath part consisting of
Before the surface papermaking surface is polished, it is heated and cooled at a temperature lower than the melting point temperature of the first polymer and higher than the melting point temperature of the second polymer material . Felt manufacturing method.