JP2007217848A - Press felt for papermaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a felt for papermaking having high compressibility and exhibiting excellent stain-proofing property. <P>SOLUTION: The felt for papermaking is equipped with a first bat layer formed on the surface of wet paper side of a base layer, a second bat layer formed on the surface of press side and a wet paper contact fiber layer formed on the surface of wet paper side of the first bad layer, and the wet paper contact fiber layer comprises a core-sheath conjugate fiber consisting of a core component having ≥80 mPa s absolute viscosity and composed of a high molecular weight nylon and a sheath component composed of a nylon having a melting point lower than that of the core component. Since the first bat layer is composed of a layer of nylon not containing the core-sheath conjugate fiber, the press felt has smoothness, resistance to hair loss/abrasion property, resistance to compressive fatigue and water-squeezing property in good balance. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a papermaking press felt (hereinafter simply referred to as “press felt”) used in a papermaking machine.

  Conventionally, a press apparatus has been used in order to squeeze water from wet paper in a papermaking process. In the press apparatus, the wet paper on which the paper layer has been formed is squeezed through a press felt at the press nip. In general, a press apparatus is composed of a plurality of press nips.

FIG. 5 is a schematic view of a press nip in the press apparatus.
The press nip is composed of a pair of press rolls P ′ and P ′ and a pair of press felts 11 ′ and 11 ′ that sandwich the wet paper web W ′. A pressure is applied to 11 ′, 11 ′ and the wet paper W ′, and water is squeezed out of the wet paper W ′ and absorbed by the press felts 11 ′, 11 ′.

  However, since the pressure applied to the wet paper web W ′ and the press felts 11 ′ and 11 ′ is suddenly released from the center (nip part) of the pressurizing part to the outlet, the press felts 11 ′ and 11 are in this part. The volume of 'expands rapidly. As a result, a negative pressure is generated in the press felts 11 ′ and 11 ′, and further, since the wet paper W ′ is made of fine fibers, a capillary phenomenon is also added, so that the moisture absorbed in the press felts 11 ′ and 11 ′ is again obtained. A phenomenon of shifting to the wet paper side, that is, a re-wetting phenomenon occurs.

  As a felt for preventing this rewetting phenomenon, for example, there is a press felt disclosed in Patent Document 1. This is a felt composed of a base layer, a wet web side batt layer, and a press side batt layer, in which a hydrophilic nonwoven fabric is arranged in the wet paper side batt layer, and the hydrophilic action of this hydrophilic nonwoven fabric results in a hydrophilic nonwoven fabric. It is said that the re-wetting phenomenon can be effectively suppressed because the water transfer action and the retention action of the transferred water are exhibited.

In addition, in press felt for papermaking, to maintain the function of squeezing water from wet paper (water squeezing), the function of recovering felt compressed without pressure flattening during compression (compression fatigue resistance) In addition, the function (smoothness) of improving wet paper smoothness by smoothing the felt, hair removal resistance, wear resistance, and the like are also regarded as important.
As a felt having such a function, for example, a press felt including a fiber having a core-sheath structure made of a two-component material is disclosed in Patent Document 2.
In this press felt, a two-component material comprising a sheath material having a low melting point and a core material having a high melting point is used as a fiber for the bat layer, and the sheath material having a low melting point is softened by heat curing treatment of the press felt. It is said that by forming a matrix, it is possible to improve the dewatering performance of the press felt and to enhance the compression resistance.
Furthermore, press felt using a woven fabric excellent in water squeezing and smoothness is used to support recent high-speed paper machines. In this woven fabric, warp yarn (felt CMD direction yarn) and driving yarn (also MD direction yarn) are both woven with a monofilament single yarn (see Patent Document 3).

JP 2004-143627 A Japanese Patent Laid-Open No. 8-302584 Japanese Patent Laid-Open No. 2000-170086

However, the press felts of Patent Documents 1 and 2 have a problem that they are easily subjected to repeated compression fatigue by a press device.
In addition, when a two-component material is used for the batt layer as in the press felt of Patent Document 2, the mechanical strength of the core material is reduced or chemically deteriorated due to the influence of the hot press during the manufacture of the felt. During the use of the felt, the fiber was cut, hair removal and wear progressed, and replacement was often required at an early stage.
Further, in the press felt of Patent Document 3, it is known that the felt hair removal / wearing property is remarkably poor because the sticking property between the bat fiber and the woven fabric by needle punching is worse than the felt using the conventional twisted yarn. Yes.
Accordingly, a press felt that suppresses the rewetting phenomenon and at the same time has a good balance of functions such as compression fatigue resistance, smoothness, hair removal / wear resistance, and water squeezability.

  In view of the above problems, an object of the present invention is to provide a press felt for papermaking that suppresses the rewetting phenomenon and is excellent in smoothness, wear resistance, compression fatigue resistance, and water squeezability.

The present invention provides a base layer, a first butt layer formed on the surface of the base layer on the wet paper side, a second butt layer formed on the surface on the press side, and a surface of the first butt layer on the wet paper side. A core component made of high molecular weight nylon having an absolute viscosity of 80 mPa · s or more, and a sheath component made of nylon having a melting point lower than that of the core component. The above-mentioned problems have been solved by a press felt for papermaking, wherein the first batt layer is made of a layer of nylon that does not contain the core-sheath composite fiber.
Here, the absolute viscosity of 80 mPa · s or more is an absolute viscosity measured at a temperature of 25 ° C. by dissolving nylon with 100 ml of 0.5 g / 95% sulfuric acid, and can be measured with a vibration viscometer. .
The content of the core-sheath composite fiber in the wet paper contact fiber layer is preferably 25% to 75%.
The wet paper web contact fiber layer may have a multilayer structure, and the content of the core-sheath composite fiber may be increased stepwise from the press side of the wet paper web contact fiber layer toward the wet paper web. The base layer is preferably a woven fabric in which warp yarn (felt CMD direction yarn) and driving yarn (also MD direction yarn) are both woven with a monofilament single yarn.

According to the present invention, the sheath component of the core-sheath composite fiber melts, and the wet paper web contact fiber layer becomes dense. As a result, the moisture in the press side layer becomes difficult to move to the wet paper web side because the wet paper web contact fiber layer serves as a barrier, so that the rewetting phenomenon can be suppressed.
Further, by making the core component of the core-sheath composite fiber highly viscous, that is, by using high molecular weight nylon, the hair removal / wear resistance and compression fatigue resistance of the felt are improved. As a result, the life of the felt ( Life) is extended, the number of felt exchanges is reduced, hair loss due to hair removal and wear is less likely to adhere to the wet paper, improving the papermaking quality, and maintaining the smoothness of the wet paper contact surface.
Further, the wet paper web contact fiber layer is composed of a core-sheath composite fiber, and the first bat layer formed on the surface of the base layer on the wet paper web side is composed of a nylon layer that does not contain the core-sheath composite fiber. The hair removal / wear resistance, compression fatigue resistance, and water squeezing resistance are well-balanced.
Furthermore, since the water permeability of the woven fabric is improved by using a woven fabric woven with monofilament single yarn as the base layer, a felt excellent in water squeezing can be configured.

The papermaking press felt of the present invention will be described in detail below.
FIG. 1 is a sectional view in the CMD direction of a press felt 10 according to the present invention.
The “machine direction (MD)” is the warp direction in which the paper machine moves the press felt, and the “machine crossing direction (CMD)” is the weft direction across the direction in which the paper machine moves the press felt.
As shown in FIG. 1, the press felt 10 includes a base layer 30, a first butt layer 22 formed on the surface of the base layer on the wet paper web, and a second butt layer 23 formed on the surface on the press side. The wet paper web side batt layer 21 disposed on the wet paper side surface of the first batt layer.
The first butt layer 22 formed on the surface of the base layer on the wet paper side and the second bat layer 23 formed on the surface of the press side are composed of staple fibers, and are respectively formed on the wet paper side of the base layer 30 by needle punching. The wet web contact side batt layer 21 is intertwined and integrated with the first batt layer 22 by needle punching.

In the press felt 10 of the present invention, the wet paper web side batt layer 21 is made of a core component made of high molecular weight nylon having an absolute viscosity of 80 mPa · s or more at a temperature of 25 ° C., and nylon having a melting point lower than that of the core component. The first batt layer 22 formed on the surface of the base layer on the wet paper web side includes the staple fiber of the core-sheath composite fiber 41 composed of the sheath component, and the conventional nylon fiber 42 not including the core-sheath composite fiber 41. Composed of staple fiber.
Here, the absolute viscosity at a temperature of 25 ° C. of 80 mPa · s or more is an absolute viscosity measured at a temperature of 25 ° C. by dissolving nylon with 100 ml of 0.5 g / 95% sulfuric acid. Can be measured.
In FIG. 1, the core-sheath composite fiber 41 is exaggerated for convenience.

  Conventionally, when a fiber having a core-sheath structure made of a two-component material is used for a butt layer of a press felt, the viscosity of the core component, that is, the molecular weight has not been considered. In the present invention, the core component has a higher viscosity than before, that is, high molecular weight nylon is used, and the layer made of the core-sheath composite fiber is formed on the surface of the base layer on the wet paper side of the first bat layer. By arranging on the surface, smoothness, hair removal / wear resistance, and compression fatigue resistance are provided in a well-balanced manner.

  The nylon used for the core component of the core-sheath composite fiber 41 is a high molecular weight nylon having an absolute viscosity of 80 mPa · s or higher at a temperature of 25 ° C., and has a higher melting point than the sheath component. By making the core component nylon have a high viscosity (80 mPa · s or more), the hair removal / wear resistance and compression fatigue resistance of the felt are improved. This is presumably because the molecular weight of the high molecular weight nylon becomes longer, so that mechanical properties (strength, durability such as friction and wear) due to the entanglement effect between the molecular chains are improved. When nylon having an absolute viscosity of less than 80 mPa · s (medium viscosity) is used, the effect of hair removal / wear resistance and compression fatigue resistance cannot be sufficiently obtained.

  Nylon preferably used for the core component is preferably high molecular weight nylon 6, high molecular weight nylon 66, high molecular weight nylon 46, high molecular weight nylon 610, high molecular weight nylon 612, or the like. Specifically, polymerization of ε-caprolactam (nylon 6), polycondensation of hexamethylenediamine and adipate (nylon 66), polycondensation of 1,4-diaminobutane and adipate (nylon 46), hexamethylenediamine and sebacine Nylon obtained by polycondensation of a nylon salt, such as polycondensation of an acid salt (nylon 610) or polycondensation of hexamethylenediamine / dodecanedioate (nylon 612), is preferred, and by DSC (differential scanning calorimetry) Mention may be made of aliphatic nylons having a melting point of 200 ° C. or higher. The absolute viscosity of these polymer nylons at 100 ml of 0.5 g / 95% sulfuric acid is preferably 80 mPa · s or more. These high molecular weight nylons are known polymerization methods, or a method of solid-phase polymerization in which nylon flakes once polymerized are placed in an inert gas atmosphere containing no oxygen and at 120 to 200 ° C. (for example, Special Table 2002). No. -529604) is used.

  The nylon used for the sheath component of the core-sheath composite fiber 41 is nylon having a lower melting point than that of the core component. As nylons preferably used for the sheath component, binary copolymer nylons such as nylon 6/12, nylon 6/610, nylon 66/6, nylon 66/12, nylon 66/610, nylon 6/66/12, nylon Mention may be made of terpolymer nylons such as 6/66/610. It is well known that the melting point of these copolymer nylons varies depending on the composition (% by weight of the copolymer component), but the copolymer nylon that can be used in the present invention has a melting point of 180 ° C. or less. Limited to.

When the sheath component melts during the hot pressing in the press felt manufacturing process, fiber shrinkage of the core-sheath composite fiber 41 occurs, and accordingly, the wet paper web side batt layer 21 becomes dense, and the felt surface is smooth. Will improve.
When the wet paper web side batt layer 21 becomes dense, when the press felt 10 is removed from the nip under pressure, the base layer, the first batt layer formed on the wet paper side surface of the base layer, and the press side surface Moisture in the second bat layer formed in this manner becomes difficult to move due to the dense layer as a barrier, and the rewetting phenomenon is effectively suppressed.

  In the present invention, the first bat layer 22 formed on the surface of the base layer on the wet paper side does not include the core-sheath composite fiber 41, is composed of normal nylon fibers 42, and the core is formed only on the wet paper web-side butt layer 21. The sheath composite fiber 41 was included. Thereby, smoothness, depilation / wear resistance, compression fatigue resistance, and water squeezability are provided in a well-balanced manner. When the first bat layer 22 includes the core-sheath composite fiber 41, the sheath component melts, and the entire bat layer formed on the surface of the base layer on the wet paper web becomes incompressible. However, it is inferior to the water squeezing ability in a press.

The wet paper web-side batt layer 21 is preferably made of a fiber in which a core-sheath composite fiber 41 and a normal nylon fiber 42 are mixed at a certain ratio, thereby smoothness, wear resistance, and compression fatigue resistance. Can have a more balanced sex. In this case, the blended cotton ratio is preferably 75% to 25% of the core-sheath composite fiber 41 and 25% to 75% of the nylon fiber 42.
When the content ratio of the core-sheath composite fiber 41 is less than 25%, the denseness of the wet paper web side batt layer 21 is lowered, so that the smoothness of the felt surface is deteriorated and the effect of suppressing the rewetting phenomenon is sufficiently obtained. Absent.
On the other hand, when the content of the core-sheath composite fiber 41 exceeds 75%, the felt is excellent in smoothness and wear resistance, and the rewetting phenomenon can be effectively suppressed. No. 21 tends to fatigue compression and tends to flatten.

Alternatively, the wet paper web side batt layer 21 may have a multilayer structure, and the content of the core-sheath composite fiber 41 may be increased stepwise from the press side of the wet paper web side batt layer 21 toward the wet paper web side. Thereby, smoothness and wear resistance can be further improved.
FIG. 2 shows an embodiment in which the wet paper web side batt layer 21 has a two-layer structure of a first layer 21a and a second layer 21b. The first layer 21a is formed by the second layer 21b. However, the content of the core-sheath composite fiber 41 is increased.
By setting it as such a structure, the wet paper web side batt layer 21 can be made into a structure with a good balance between rewetting and water squeezing. That is, since the first layer 21a having a high content of the core-sheath composite fiber 41 becomes dense, the rewetting and smoothness can be maintained, and the first layer 21b having a low content of the core-sheath composite fiber 41 has a low density. However, since compressibility is contributed, water squeezing improves and the wet paper web side batt layer 21 can provide re-wetability and water squeezing simultaneously. From this, compared with the case where the wet paper web side batt layer 21 is a single layer, the wettability is further improved because the dense layer is composed of two layers while maintaining smoothness and hair removal and wear. In addition, it has a synergistic effect that water squeezing is also improved.
On the contrary, when the content of the core-sheath composite fiber 41 is decreased stepwise from the press side of the wet paper contact side batt layer 21 toward the wet paper side, the structure is opposite to the above structure. Therefore, compared with the case where the wet paper web side batt layer 21 is a single layer, the smoothness, hair removal / wear properties, and rewetting properties are deteriorated.
In FIG. 2, the wet paper web side batt layer 21 is formed in two layers, but it may be formed of three or more layers.

  The volume ratio of the core portion to the sheath portion of the core-sheath composite fiber 41 is not particularly limited, but is in the range of 5: 1 to 1: 5, preferably 1: 1.

  Further, nylon 6, nylon 66, nylon 46, nylon 610, which is mixed with the wet paper web side batt layer 21, the nylon fiber 42 constituting the press side batt layer 23, and the core-sheath composite fiber 41, are used. Nylon 612 or the like is preferable.

As shown in FIGS. 1 and 2, the base layer 30 is made of a woven fabric obtained by weaving a warp yarn 31 (felt CMD direction yarn) and a driving yarn 32 (also MD direction yarn) with a monofilament single yarn. Although preferably used, as a woven structure, a double structure or a triple structure such as (2/1, 1/2), (3/1, 1/3), (5/1, 1/5), or (single Laminated structures such as (tissue + double structure) and (double structure + double structure) can be used. The thickness of the monofilament single yarn is 0.1 mm to 0.6 mm in diameter, and the yarn density of the structure can be 10 to 100/25 mm.
In addition, this invention is not limited to this, The structure which piled up the MD direction thread material and the CMD direction thread material without weaving, the film, the knitted fabric, and the thin strip | belt body wound spirally, and obtained the wide strip | belt body For example, various configurations can be adopted as appropriate. Further, as the material of the base layer 30, natural fibers such as wool, synthetic fibers such as polyester, nylon 6, nylon 66, etc. excellent in abrasion resistance, fatigue resistance, stretch characteristics, antifouling properties, etc. are used.

In addition, the fineness of the core-sheath composite fiber 41 is about 15 to 25 dtex for a pickup felt used in the front stage of the paper machine press part, and the second press used in the middle stage of the paper machine press part. In the felt for No. 3 press or the like, it is preferable to use a felt of about 10 to 20 dtex.
Moreover, it is good to use about 5-20 dtex (dtex) about the felt for No. 4 press and shoe press used in the back | latter stage of the press part of a paper machine.

Further, the fineness of the nylon fiber 42 is about 10 to 25 dtex for the wet paper side batt layer 20 of the pick-up felt used in the front stage of the press part of the paper machine, and 15 to 25 for the press side batt layer 23. What is about decitex (dtex) may be used.
Further, the wet paper side butt layer 20 of the felt for No. 2 press or No. 3 press used in the middle part of the press part of the paper machine has about 10 to 15 dtex, and 10 to the press side butt layer layer 23. A fineness of about 20 dtex may be used.
Further, the wet paper side butt layer 32 of the No. 4 press or shoe press felt used in the subsequent stage of the press part of the paper machine has about 5 to 15 decitex (dtex), and the press side butt layer 23 has 5 to 20 decitex. It is good to use a fineness of about (dtex).

  The press felt for papermaking of the present invention will be specifically described by the following examples. However, the present invention is not limited to these examples.

(Manufacture of core-sheath composite fiber)
Refined nylon 6 (caprolactam: melting point 220 ° C.) and copolymer nylon 6/12 (caprolactam / laurolactam: melting point 140 ° C.) were prepared, and each was individually fed into an extruder with a devolatilization port, followed by extrusion. Volatiles were removed in the machine, and melted core material nylon 6 and sheathed copolymer nylon 6/12 were quantified in a molten state with a quantitative gear pump and supplied to each core-sheath composite spinning nozzle. The core-sheath composite fiber spun through the core-sheath composite spinning nozzle is oiled while being cooled by a chimney, wound up at a natural stretch ratio, then stretched, then crimped, cut at a fixed length, and stapled with a core-sheath composite fiber. Fiber was manufactured.
For production of the core-sheath conjugate fiber, a “MODEL-EMF manufactured by Toyo Seimitsu Kogyo” spinning device can be used. In this apparatus, an extruder, a Nelson type multistage stretching machine, and a winder can be used.

In this example, high molecular weight nylon 6 (absolute viscosity 85 mPa · s at 25 ° C., melting point 220 ° C.) and medium molecular weight nylon 6 (absolute viscosity 70 mPa · s at 25 ° C., melting point 220 ° C.) are used as core materials. Copolymer nylon 6/12 (melting point: 140 ° C.) was used as the type and sheath material, and two types of staple fiber of core-sheath composite fiber having a volume ratio of the core part to the sheath part of 1: 1 were produced. The one using high molecular weight nylon 6 as the core material is referred to as composite fiber A, and the one using medium molecular weight nylon 6 as composite fiber B.
In addition, when the numerical values of the absolute viscosity of 85 mPa · s and the absolute viscosity of 70 mPa · s in this example are expressed by the relative viscosity (ηr eater) in a general-purpose measuring means (Ubbelohde viscosity method), ηr = 4.5 and 3 .0. Incidentally, the absolute viscosity of 80 mPa · s corresponds to ηr = 4.0.

(Manufacture of press felt for papermaking)
In order to make the conditions common to the examples and comparative examples, the basic configuration of all felts was as follows.
-Base layer: Woven Cloth A [twisted (primary twisted) two nylon monofilaments of 240 dtex, and twisted (supertwisted) two strands of the lower twisted yarn into MD direction yarn material and CMD direction yarn material Woven (3/1, 1/3) double structure]: basis weight 300 g / m ²
: Woven Cloth B [Double structure of (3/1, 1/3) of 1100 dtex nylon monofilament single yarn woven with MD direction yarn material and CMD direction yarn material]: Basis weight 300 g / m ²
・ Batt layer: Wet paper contact side batt layer (first layer) (17 dtex nylon 6 fiber and 17 dtex composite fiber A or B staple fiber) with a total basis weight of 120 g / m ²
: Wet paper contact side batt layer (second layer) (17 dtex nylon 6 fiber and 17 dtex composite fiber A staple fiber) with a total basis weight of 120 g / m ²
: The first batting layer (17 dtex nylon 6 fiber and 17 dtex composite fiber A staple fiber) has a total basis weight of 120 g / m ²
: The second batting layer (17 dtex nylon 6 fiber staple fiber) with a total basis weight of 100 g / m ²
・ Needle density: 700 times / cm ²
Hot press: The felt after needle punching is repeatedly passed through a pair of heat calender rolls (roll temperature: 160 ° C., press pressure: 30 kg / cm) at a speed of 5 m / min 5 times, 0.5 g / cm ³ A felt with the above density was obtained.
Tables 1 and 2 show the configurations of the felts of Examples 1 to 8 and Comparative Examples 1 to 6.

  Using the paper felt press felts of the above examples and comparative examples, the following conditions and methods were used to evaluate the rewetting phenomenon and squeezing resistance, and the compression fatigue resistance, hair loss / wear resistance, and smoothness. .

(Evaluation of rewetting phenomenon and water squeezing)
The rewetting phenomenon and water squeezing were evaluated by the apparatus shown in FIGS.
First, in the apparatus shown in FIG. 3 and FIG. 4, P is a press roll, 110 is a top felt, 10 is a bottom felt, SC is a suction tube, and SN is a shower nozzle.
In addition, the said Example and comparative example are used as the bottom side felt 10 also in any apparatus. In this case, a press felt similar to that shown in Comparative Example 2 was used as the top felt.
3 and 4 both have a felt travel speed of 800 m / min and a press pressure of 80 kg / cm.

The apparatus shown in FIG. 3 has a structure in which wet paper that has been released from the nip pressure is placed on the bottom felt 10 and conveyed. Accordingly, when the wet paper wetness at the position (press outlet 1) placed and transported on the bottom felt 10 is measured after the nip pressure is removed, the moisture content data of the wet paper in which the rewetting phenomenon occurs is obtained. Obtainable.
On the other hand, the apparatus shown in FIG. 4 has a large area where the bottom-side felt 10 comes into contact with the press roll, and the time when the wet paper released from the nip pressure comes into contact with the felt 10, 110 is very short. . Here, when the wetness of the wet paper at the position immediately after the release of the nip pressure (press outlet 2) is measured, the moisture content data of the wet paper that does not cause much rewetting is obtained.

  Here, the moisture content data by the apparatus of FIG. 3 and the same data by the apparatus of FIG. For the evaluation of water squeezing, in the water content data at the press outlet 1 by the apparatus of FIG. And the thing of 49% or more of water | moisture content was set to (water extraction evaluation "poor"). Regarding the evaluation of the rewetting phenomenon, the difference between the water content data by the apparatus of FIG. 3 and the same data by the apparatus of FIG. (Evaluation “good”). On the other hand, when the difference between the two is 0.5% or more and less than 1.0%, a re-wetting phenomenon occurs (evaluation is “OK”), and when the difference is 1.0% or more, a re-wetting phenomenon occurs. (Evaluation “bad”).

(Repeated compression fatigue test)
A compression fatigue test was conducted by repeatedly applying a 5 Hz pulse load at 120 kg / cm ² and 300,000 times. Compressive fatigue is expressed as a ratio (density after test / finished density), where “less than” 1.30 is “excellent”, 1.30 or more and 1.39 or less is “good”, and 1.40 or more “bad”. It was.

(Taper hair removal and wear test)
Hair removal resistance and abrasion resistance were evaluated by measuring the amount of fibers dropped from the papermaking felt using a taper polishing tester based on JIS1023-1992. A disk-shaped test piece was placed on a rotating turntable, and a rotating roll with high resistance was brought into contact with the test piece to measure the amount of fiber falling off (hair removal / wear amount). (Load: 0.5 kg, Wheel: CS-17, Number of revolutions: 3000 times, Unit: mg)
A hair removal / wear amount of 40 mg or less was evaluated as “good”, and a hair loss / wear amount exceeding 40 mg was determined as “bad”.

(Measurement of surface roughness)
The smoothness of the felt surface was evaluated by measuring the ten-point average roughness Rz (μm) (JIS-B0601) of the finished felt before the taper hair removal / wear test.
A sample having a surface roughness of less than 60 μm was defined as “excellent”, a sample having a surface roughness of 60 μm to 99 μm was defined as “good”, and a sample having a surface roughness of 100 μm or greater was defined as “bad”.
Table 3 shows the measurement results and evaluation of each test.

  As shown in Examples 1 to 8 in Table 3, the press felt for papermaking of the present invention suppresses the rewetting phenomenon, and at the same time has the functions of compression fatigue resistance, hair removal / wear resistance, smoothness and water squeezing function. It was confirmed that it was well-balanced.

It can be seen that Comparative Example 1 in which the first batt layer is composed of the core-sheath composite fiber has good compression fatigue resistance and anti-hair removal / wear resistance, but is inferior in the felt surface smoothness.
Further, in Example 3 and Comparative Example 3 in which the content of the core-sheath composite fiber in the wet paper web side batt layer is less than 25% and Comparative Example 2 not including the core-sheath fiber, the function of compression fatigue resistance is achieved. However, it can be seen that the rewetting phenomenon is not suppressed.
Further, Comparative Example 4 in which the content of the core-sheath composite fiber was decreased stepwise from the press side of the wet paper contact side batt layer toward the wet paper side has a function of resistance to compression fatigue and rewetting. However, the smoothness is poor. This is considered because the core-sheath composite fiber layer (second layer) containing less core-sheath composite fiber constitutes the felt surface.
In addition, Comparative Example 5 using medium molecular weight nylon as the core component of the core-sheath composite fiber has worse compression fatigue resistance, hair removal resistance, and wear resistance than Example 1 using high molecular weight nylon. I understand. Furthermore, since Example 8 uses a woven fabric woven with a monofilament monofilament as the base layer B as the base layer B, it is more pressed than Example 1 using a woven fabric woven with the monofilament twisted yarn of the base layer A. It was confirmed that the water content at the outlet (1 and 2) was both low and water squeezed was excellent.

Sectional drawing of embodiment of the press felt of this invention. Sectional drawing of another embodiment of the press felt of this invention. The schematic diagram of the apparatus for confirming the effect of the press felt of this invention. The schematic diagram of the apparatus for confirming the effect of the press felt of this invention. Schematic explanatory drawing of the press apparatus of a papermaking machine.

Explanation of symbols

10: Press felt for papermaking 21: Wet paper contact side butt layer (core-sheath composite fiber layer)
21a, 21b: wet paper web side batt layer (core-sheath composite fiber layer)
22: 1st butt layer 23: 2nd butt layer 30: Base layer 31: Warp yarn 32: Driving yarn 41: Core-sheath composite fiber 42: Nylon fiber

Claims (4)

A base layer, a first butt layer formed on the wet paper web surface of the base layer, a second bat layer formed on the press paper surface, and a wet paper web surface formed on the wet paper web surface of the first bat layer. A paper contact fiber layer,
The wet paper contact fiber layer includes a core / sheath composite fiber composed of a core component made of high molecular weight nylon having an absolute viscosity of 80 mPa · s or more, and a sheath component made of nylon having a lower melting point than the core component,
The first batt layer is made of a layer of nylon that does not contain the core-sheath conjugate fiber,
Press felt for papermaking.   The press felt for papermaking of Claim 1 whose content rate of the said core-sheath composite fiber in the said wet paper contact fiber layer is 25%-75%.   The papermaking according to claim 1 or 2, wherein the wet paper contact fiber layer has a multilayer structure, and the content of the core-sheath composite fiber is increased stepwise from the press side of the first batt layer toward the wet paper side. Press felt.   The press felt for papermaking according to any one of claims 1 to 3, wherein the base layer is a woven fabric woven from a warp yarn and a driving yarn of a monofilament single yarn.

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