JP2008202198A - Shoe press belt for papermaking - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt (shoe press belt) for papermaking, which has good water-squeezing property of wet paper, stable paper quality (wet paper smoothness and mark property) and scarcely causing damage (crack and wear) on the outer peripheral surface of a belt in use. <P>SOLUTION: In shoe press belt for papermaking, which is arranged between a press roll and a shoe, provided with a felt for receiving squeezed water from wet paper and pressed under high pressure toward the press roll, at least two kinds of shapes which are different in cross direction of paper-making machine are selected as shapes of drainage ditches extended on the side surface of the felt. The cross section shape of ditches may be U-shaped or trapezoidal and the shape of ditch bottoms may be flat bottom or round bottom or the combination thereof. As a result, functions of the shoe press belt can be shared in two kinds of ditches and improvement of draining ability and improvement of paper quality and surface smoothness of wet paper can simultaneously be satisfied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a shoe press belt used for improving water squeezing from wet paper and felt in a press part of a paper machine and other similar machines, and in particular, extends on the felt side surface of the shoe press belt. It relates to the groove shape.

  In papermaking, a major problem is how to increase moisture from wet paper in a press part that dehydrates moisture from wet paper in order to improve productivity. As a means of increasing the amount of press dewatering in order to achieve the purpose of reducing the moisture content of wet paper as much as possible, pressurization time is increased by increasing the press roll pressure, increasing the press roll hardness, or interposing a shoe press belt. In order to increase the pressurization time between the roll and the felt during pressing and improve the dewatering effect, a method of interposing a shoe press belt has been increasing in recent years.

  Further, recently, shoe press belts have increased in number of grooves extending on the felt side surface in order to efficiently drain the squeezed water. For example, the thing of patent document 1 aims at the improvement of wet paper squeezing by providing a some drainage groove in the outer peripheral surface of the belt used for a wide nip press (what is called a shoe press).

Conventionally, the groove shape is almost rectangular from the viewpoint of ease of processing, productivity, cost, etc., but the groove bottom is curved (Patent Documents 2 and 3), or the land is recessed. The thing which provided the curved top surface (patent document 4) is proposed.
The thing of patent document 2 provides a belt with good dewaterability (water squeezing) and strength sustainability of the shoe press by making the cross section U-shaped, and the end of the land part of the drainage groove is chamfered. The groove width is 0.5 to 4 mm, the depth is 0.5 to 5 mm, and the distance between adjacent drain grooves is 1 to 4 mm. Patent Document 3 also shows a case where the side wall of the groove is curved outward, in addition to the curved bottom portion.
In addition, the press jacket (press belt) described in Patent Document 4 has a plurality of webs (land portions) on the outer surface thereof, and grooves are interposed between these webs, and each web is concavely bent. It has a top surface.

The groove shape in each of the above documents is fixed to one shape (groove width, groove depth, land width, number of grooves) for reasons of productivity. In order to improve water squeezing, a belt having a so-called belt void volume (drainage capacity) with a large groove width and groove depth has been used.
However, when a belt having a single shape and an increased void volume is used, cracks in the groove and damage / abrasion of the land portion tend to occur. In addition, the paper quality and wet paper surface smoothness due to pressing tend to deteriorate (the ratio of the groove-shaped transfer mark appearing on the wet paper tends to increase). There is a problem that the wet paper drying energy after pressing increases because the aqueous property decreases.

Microfilm of Japanese Utility Model No. 57-147931 (Japanese Utility Model Publication No. 59-54598) Utility Model Registration No. 3104830 JP 2001-95484 A Japanese Patent Application Laid-Open No. 64-61591

  The present invention has been made in view of the above problems, and in a papermaking machine belt (shoe press belt), the wet paper wettability is good, the paper quality (wet paper smoothness and mark property) is stable, and the belt in use. An object of the present invention is to provide a belt with less damage (cracks and wear) on the outer peripheral surface.

  The present inventors have found that the above-mentioned problems can be solved by using two types of groove shapes, which has been one type in the past, and have reached the present invention. That is, the present invention is characterized in that a drain groove having two types of shapes, a main groove shape that shares drainage capacity and a secondary groove shape that shares paper quality and wet paper surface smoothness, is provided on the outer peripheral surface of the belt. This relates to the shoe press belt.

  The present invention is basically an invention relating to a shoe press belt for papermaking having two types of groove-shaped drainage grooves, and is based on the following technologies.

(1) In a belt for shoe press for papermaking, which is placed between a press roll and a shoe and receives felt from wet paper and is pressed against the press roll at high pressure. A drainage groove extending on the surface has at least two different groove shapes in the transverse direction of the papermaking machine.

(2) The shoe press belt for papermaking according to (1), wherein the shape of the drainage groove is of two types: a deep groove depth and a shallow groove shape.

(3) The shoe press belt for papermaking according to (2), wherein the drainage groove has a groove shape having a deep groove depth and a shallow groove shape arranged substantially alternately.

(4) The shoe press belt for papermaking according to any one of (1) to (3), wherein the shape of the drainage groove includes at least one of a rectangle, a trapezoid, and a U-shape.

(5) The groove shape of the drainage groove is any one of (2) to (4), wherein the groove having a deep groove depth is U-shaped and the groove having a shallow groove depth is trapezoidal. Shoe press belt for papermaking.

  According to the present invention, since the groove shape having good drainage and the groove shape having good paper mark property are arranged in parallel in the paper machine crossing direction, each function can be shared by each groove shape. Thus, it is possible to provide a papermaking shoe press belt that satisfies the improvement of drainage capacity and the improvement of paper quality and wet paper surface smoothness at the same time.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view of an apparatus 1 for forming (cutting) drainage grooves of a shoe press belt for papermaking according to the present invention.

  First, the endless base body 2 is hung between two rolls 3 and 3 and tensioned with a predetermined tension. The roll 3 is rotatable, and the base 2 advances in the rotation direction of the roll 3. Under such circumstances, the polyurethane layer is formed over the entire circumference of the substrate 2 by applying and curing the liquid polyurethane from above the substrate 2. Thereafter, drainage grooves 7 are formed on the outer peripheral surface 5 of the substrate 2 on which the polyurethane layer 4 is provided, using a grooving device 6.

  As shown in FIG. 2, the grooving device 6 is provided with a cutting blade in which cutting blades 8a and 8b for groove cutting are arranged.

  The groove shape is composed of two types (the deep groove (deep groove) 7a) and the shallow groove (sub groove 7b) (FIGS. 3 and 4). It is arranged side by side in a pattern.

  The groove dimensions are adopted such that the groove width is 0.5 to 2 mm, the groove depth is 0.5 to 2 mm, and the distance between the land portions to the adjacent drainage grooves is 1 to 5 mm. The distance (clearance) between the outer peripheral surface 5 of the belt and the cutting blades 8a and 8b is adjusted as appropriate so that the gap amount becomes a predetermined relative ratio. The relative ratio of the void amount (void volume) per groove is 10 to 70, preferably 25 to 50, with respect to the main groove 100.

As for the combination pattern of grooves, if the groove depth is d and the shallow groove is s,
Pattern I: ds-ds (in which one sub-groove is incorporated next to one main groove)
Pattern II: d-ss-d-ss (in which two sub-grooves are incorporated next to one main groove)
Pattern III: dd-s-dd-s (in which one sub-groove is incorporated next to two main grooves)
Pattern IV: dd-ss-dd-ss (in which two sub-grooves are incorporated next to two main grooves)
and so on.
In the case of Pattern I, the balance of crack property, water squeezing property, and wet paper mark property is the best. The water squeezing is slightly reduced, but if the emphasis is on cracking and wet paper mark properties, select Pattern II. Conversely, if the cracking property and wet paper mark property are slightly declining, select Pattern III if emphasizing water squeezing .

  Moreover, the cross-sectional shape may be either rectangular or trapezoidal, the groove bottom may be flat bottom or round bottom, or a combination thereof. The cross-sectional U-shape is a groove bottom having a round bottom. FIG. 4 shows that the main groove 7a (groove having a deep groove depth) is U-shaped, that is, the cross-sectional shape is U-shaped and the bottom of the groove is round bottom, and the auxiliary groove 7b (groove having a shallow groove depth) is trapezoidal ( This is an example in which the cross-sectional shape is a trapezoid and the groove bottom is a flat bottom.

In the combination of the cross-sectional shapes of the main groove and the sub-groove, the rectangles have the best balance of crackability, water squeezability, and wet paper mark property. Emphasizing water squeezing, when the main groove is rectangular and the sub-groove is trapezoid, the wet paper mark property is slightly lowered. The emphasis is placed on cracking and water squeezing, and the wet paper mark property is slightly lowered when the main groove is trapezoidal and the sub-groove is rectangular.
In the combination of the groove bottom shapes, when the main groove is a round bottom and the sub-groove is a flat bottom, the workability is good while maintaining the crack property, and the combination of the round bottoms is the best.

By chamfering the end portion of the land portion where there is no groove cutting, the end portion can be prevented from being chipped or missing.
The groove depth can be adjusted by appropriately adjusting the distance between the belt outer peripheral surface and the cutting blade.

  When the grooves are formed on the belt surface by a single cutting process, metal saws (cutting blades) having different radii are arranged alternately or according to a predetermined combination pattern (FIG. 2). Alternatively, when two cutting processes are performed, first, a metal saw (cutting blade) with a small radius is arranged to cut a secondary groove (shallow groove), and then a metal saw (cutting blade) with a large radius is arranged to form a secondary groove. The main groove (deep groove) is cut in the gap (shallow groove).

<Performance evaluation method>
About the manufactured shoe press belt, the performance is evaluated by the following tests, and the overall order is assigned with the order of functions.

<Crack test>
The apparatus shown in FIG. 5 is used. In this apparatus, both ends of the test piece S are clamped by the clamp hands CH and CH, and the clamp hands CH and CH are configured to reciprocate in the left and right directions in conjunction with each other. At this time, the tension applied to the test piece S is 3 kg / cm, and the reciprocating speed is 40 cm / sec. Then, the test piece S is pressed by the press roll RR and the press shoe PS. At this time, the test piece S is pressurized as the press shoe PS moves in the direction of the press roll RR. This pressure is 36 kg / cm ² . With this device, the number of reciprocations until a crack occurs is measured. In addition, the evaluation surface in the test piece is directed to the press roll RR side.
Evaluation point A: The number of times (unit: 10,000 times) until crack generation was 260,000 times or more.
Evaluation point B: One in the range of 120,000 times to 260,000 times.
Evaluation point C: 120,000 times or less.

<Water extraction test>
A wet paper squeezing test is performed using the apparatus shown in FIG. In this test apparatus, a belt body B is disposed at a position facing the press roll PR, and a press shoe PS is disposed so as to press the belt body B against the press roll PR from the inner peripheral side thereof. Further, between the press roll PR and the belt main body B, a top-side felt formed by implanting 11 dtex short fibers of nylon 6 on a base fabric by a needle punch method so that the basis weight is 1500 g / m ^2. Ft and bottom felt Fb are arranged. Now, the belt body B is run at a running speed of 1000 m / min when the nip pressure between the press roll PR and the press shoe PS is 1000 kN / m. Then, a water flow W is jetted at a pressure of 3 kg / cm ² from the nozzle N installed above the press roll PR at 15 liters / minute. At this time, the top roll is covered with the film of the water flow W, and the water flow W is impregnated in the top-side felt Ft and the bottom-side felt Fb and then supplied to the belt body B as well. In such a state, a wet paper sheet WS containing 70% of moisture is placed on the bottom-side felt Fb, passed through the nip, and the moisture of the wet paper sheet WS after passing is measured.
Evaluation point A: Wet paper moisture was 45% or less.
Evaluation point B: 45% to 53%.
Evaluation point C: 53% or more.

<Wet paper mark property test>
(1) The wet paper squeezed in the above squeeze test is stored in a dryer at 50 ° C. for 24 hours and dried, and then the surface of the dry paper is photographed.
(2) Read the image into the computer with the scanner. At this time, an operation for sharpening the image is performed as appropriate. Note that Adobe Photoshop "Photoshop 5" is used as the image reading software.
(3) The image processing software calculates the groove area (groove mark) transferred to the dry paper. At this time, “NIH image” of National Institutes of Health is used as image processing software.
(4) Using such image processing software, the ratio of the groove area (groove mark) transferred to the dry paper is calculated as a ratio to the groove area of the belt outer surface.
Evaluation points A: 50% or less Evaluation points B: 50 to 75% or less Evaluation points C: 75% or more

<Function order>
About a test result, comprehensive evaluation is performed based on each evaluation point of each above-mentioned examination, and the following functional rank is given.
All grades are A → Rank 1st Grade 2 grades A and others are B → Rank 2nd Grade 1 grade A and others are B → Rank 3 Even one grade is C There is a → ranking 4th

  About the shoe press belt by the said structure, Examples 1-9 and Comparative Examples 1 and 2 were created by the process specifically shown below.

Step 1: Using the apparatus shown in FIG. 1, an endless substrate is put between two rolls and is tensioned with a predetermined tension.
Process 2: A liquid polyurethane is arrange | positioned from the top of a base | substrate, and a polyurethane layer is formed over the perimeter of a base | substrate by making it harden | cure.
Step 3: The cutting blade 8a for cutting the main groove and the cutting blade 8b for cutting the minor groove are respectively installed in the grooving device. The shape and cutting conditions of this cutting blade were in accordance with Table 1. The groove dimensions are adjusted as appropriate so that the distance between the outer peripheral surface of the belt and the cutting blade (clearance) is such that the gap between the main groove and the sub-groove has a relative ratio described in the table.

The shapes of the main groove and the sub groove are adjusted in the following range.
Main groove (deep groove); groove width ... 0.8-1.2mm
Groove depth 0.8-1.8mm
The distance between the land and the adjacent drainage groove 2mm
(When the main groove and the sub groove are alternately arranged, the main groove interval is 4 mm.)
Minor groove (shallow groove); groove width: 0.5 to 1.2 mm
Groove depth ... 0.1-1.5mm
The distance between the land and the adjacent drainage groove 2mm
(When the main groove and the sub groove are alternately arranged, the main groove interval is 4 mm.)
Cutting to the outer peripheral surface of the belt is performed by appropriately adjusting the distance between the outer peripheral surface of the belt and the cutting blade with respect to the papermaking machine direction.

  The shoe press belts according to Examples 1 to 9 and Comparative Examples 1 and 2 were subjected to a crack test, a squeezing test, and a wet paper mark property test to evaluate performance. The results are shown in Table 2.

  According to the results in Table 2, the relative ratio between the main groove and the sub-groove is 100/25, the main groove and the sub-groove are alternately arranged in parallel, the cross-sectional shape is U-shaped, the groove bottom In the three evaluation tests, those having a round bottom had the best balance, and the best balance was obtained.

  Since the shoe press belt according to the present invention can satisfy both the drainage capacity and the paper quality improvement at the same time, the shoe press used for improving the water squeezing from wet paper and felt in the press part of the paper machine and other similar machines. It is extremely useful as an industrial belt.

It is an apparatus which forms the drainage groove | channel of the shoe press belt of this invention. It is a figure explaining arrangement | positioning of the cutting blade used for the groove | channel formation of this invention. It is a figure which shows the groove shape of the shoe press belt of this invention. It is a figure which shows the other groove shape of the shoe press belt of this invention. It is a figure which shows the apparatus used for a crack test. It is a figure which shows the outline | summary of a squeezing test.

Explanation of symbols

1: Drainage forming device
2: Substrate 3: Roll 4: Polyurethane layer
5: Outer peripheral surface
6: Groove cutting device 7: Drain groove 7a: Main groove 7b: Sub groove 8a: Cutting groove for main groove 8b: Cutting blade for sub groove S: Test piece CH: Clamp hand PR: Press roll PS: Press shoe B: Belt Body N: Nozzle W: Water flow Ft: Top felt Fb: Bottom felt WS: Wet paper sheet

Claims (5)

  In a shoe press belt for papermaking, which is placed between a press roll and a shoe and is placed with a felt for receiving water from wet paper and pressed against the press roll at a high pressure, it is extended on the felt side surface. The papermaking shoe press belt is characterized in that the drainage groove has at least two different groove shapes in the transverse direction of the papermaking machine.   2. The shoe press belt for papermaking according to claim 1, wherein the shape of the drainage groove is of two types: a deep groove depth and a shallow groove shape.   3. The shoe press belt for papermaking according to claim 2, wherein a groove shape of the drainage groove is substantially alternately arranged with a shallow groove depth and a shallow groove shape.   The shoe press belt for papermaking according to any one of claims 1 to 3, wherein a groove shape of the drainage groove includes at least one of a rectangle, a trapezoid, and a U-shape.   5. The papermaking shoe press according to claim 2, wherein a groove shape of the drainage groove is a U-shaped groove having a deep groove depth and a trapezoidal groove having a shallow groove depth. belt.