Extensible blanket

Abstract

The present invention relates to a stretchable blanket (20) formed as a continuous loop and comprising: a back cover (20B) having a back side (20BS), the back side (20BS) being an inner surface of the loop of the stretchable blanket (20); a cover (20F) having a front side (20FS), the front side (20FS) being an outer surface of a loop of the stretchable blanket (20) and being configured to provide a stretchable layer of the stretchable blanket (20); and a reinforcing layer (20R) between the back cover (20B) and the front cover (20F). At least the back cover (20B) of the stretchable blanket (20) comprises an elastomeric matrix and ultra-high molecular weight polyethylene (UHMWPE, UHMW) or high density polyethylene (HDPE) particles.

Description

Technical Field

[0001] The present invention relates to a stretchable blanket for fiber web production, in particular for producing impact-resistant, puncture-resistant and tear-resistant fiber web grades in a stretching processing unit. More specifically, the present invention relates to a stretchable blanket. Background Art

[0002] As is known, fiber webs, such as paper or board webs, are manufactured by a plurality of machines which together form a fiber web production line of up to several hundred meters. As is known from the prior art, a fiber web production line typically comprises an assembly formed by a plurality of devices arranged in succession in a processing line. A typical production and processing line for fiber webs comprises a headbox, a wire section and a press section and a subsequent drying section and a reel. The production and processing line may also comprise other sections and devices for processing and / or finishing the fiber web, such as a size press, a coating device, a calender. The production and processing line typically also comprises at least one slitter-winder for forming customer rolls and roll packaging equipment.

[0003] It is known from the prior art that impact-, puncture- and tear-resistant fiber web grades are produced in a fiber web production line in a stretching treatment unit by a method in which a stretchable rubber blanket, e.g. in an apparatus for producing uncreped stretchable paper, increases the elongation value of the fiber web to be produced, said rubber blanket crimping the fiber web at a micro level in the machine direction (MD), i.e. in the running and longitudinal direction of the fiber web.

[0004] Typically, a stretchable fiber web is produced in a stretching processing unit (often called Clupak unit) for providing impact, puncture and tear resistant fiber web grades, especially paper webs. The stretching processing unit is typically located in the dryer section of a fiber web production line, usually between two dryer sections or dryer groups, typically after about half of the dryer section of the fiber web production line, more typically after about 2 / 3 of the dryer section of the fiber web production line. When the moist fiber web enters the stretching processing unit, one of its surfaces comes into contact with the surface of the dryer cylinders and the other surface comes into contact with the front side of the front cover of the stretchable blanket. The front cover of the stretchable blanket is already in MD stretching. The tension of the stretchable blanket against the dryer cylinders and the pressure provided by the nip bar keep the incoming fiber web pinned to (slightly adhered to) the stretched cover of the stretchable blanket. After passing under the press bar, the cover of the stretch blanket starts to shrink in MD and the fibers of the fiber web shrink together with the stretch blanket, resulting in MD shrinkage of the fiber web. The shrinkage of the cover of the stretch blanket and the fiber web is mainly provided by sliding between the dryer surface and the fiber web. A steam film is formed between the dryer surface and the moist fiber web, creating conditions that allow sliding to occur. The reverse curvature of the dryer further enhances the sliding of the fiber web and the fiber compaction process. As a result, the fiber web produced by the stretch treatment unit is smooth and has improved strength and greater elongation compared to a fiber web not treated in the stretch treatment unit. As a result, an impact-, puncture- and tear-resistant fiber web is provided, which is particularly suitable for use as a paper grade for bag making, in particular cement bags, as a plastic or metal foil laminated paper grade and as a cable and insulation board or paper grade.

[0005] In the stretch processing unit, the back side of the stretch blanket is pressed against the rotating drying cylinder by a non-rotating bead. Therefore, the back side of the stretch blanket is typically wetted and slides against the bead. This sliding contact between the bead and the back side of the stretch blanket causes wear, even to the extent that parts of the rubber may come loose and thus be removed from the back side of the stretch blanket. This can also cause the back side of the stretch blanket to become sticky, which can make the situation worse.

[0006] It is known from the prior art that the roller rubber layer uses ultra high molecular weight polyethylene (UHMWPE, UHMW) material to improve the wear resistance in the case of rotating contact between the roller rubber layer and the fiber web. Therefore, it is under very different conditions compared to the technical problem of the stretching process, in which the contact is non-rotating and the materials of the layering strip and the fiber web are also very different.

[0007] An object of the present invention is to create a stretchable blanket which eliminates or at least minimizes the disadvantages and problems of the prior art.

[0008] In particular, the object of the present invention is to create an improved stretchable carpet, in particular with regard to the wear of the back side of the stretchable carpet. Summary of the invention

[0009] In order to achieve the above objects and objects that will become apparent later, the main features of the stretchable blanket according to the present invention are as follows.

[0010] According to an advantageous aspect of the invention, the stretchable blanket is formed as a continuous loop and comprises: a back cover having a back side, i.e. the inner surface of the stretchable blanket; a front cover having a front side, i.e. the outer surface of the stretchable blanket and forming a stretchable layer of the stretchable blanket; and a reinforcing layer located between and in close proximity to, i.e. in contact with, the back cover and the front cover. At least the back cover of the stretchable blanket comprises an elastomeric matrix, advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR), and ultra-high molecular weight polyethylene (UHMWPE, UHMW) particles or high-density polyethylene (HDPE) particles. The hardness of the back cover is 50-70 Shore A hardness. The reinforcing layer comprises longitudinal yarns and transverse yarns and may, for example, comprise carbon black or silica as reinforcing filler material. Typically, the width of the stretchable blanket is 1 meter to 8 meters, and the thickness of the stretchable blanket is 15mm to 40mm, advantageously 20mm to 35mm.

[0011] Ultra-high molecular weight polyethylene (UHMWPE, UHMW) is a subset of thermoplastic polyethylene, also known as high modulus polyethylene (HMPE). High-density polyethylene (HDPE) is a petroleum thermoplastic.

[0012] According to an advantageous aspect of the invention, in the back cover of the stretchable blanket, the average particle size of the ultra-high molecular weight polyethylene or high-density polyethylene particles in the elastomeric matrix (advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR)) is between 10 microns and 300 microns in diameter, and is generally less than 750 μm in diameter.

[0013] According to an advantageous aspect of the invention, in the back cover of the stretchable blanket, 5-40% of the total weight of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the weight of the ultra-high molecular weight polyethylene or high-density polyethylene particles.

[0014] According to an advantageous aspect of the invention, in the back cover of the stretchable blanket, 5.5-43% of the total volume of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the volume of the ultra-high molecular weight polyethylene or high-density polyethylene particles.

[0015] According to an advantageous aspect of the invention, the back cover of the stretchable blanket (the back side of which is the inner surface of the stretchable blanket) has a thickness of 1 to 5 mm and comprises an elastomeric matrix (advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR)) and ultra-high molecular weight polyethylene or high-density polyethylene particles. The hardness of the back cover is advantageously 50 to 70 Shore A.

[0016] According to an advantageous aspect of the invention, the cover of the stretchable blanket (whose front side is the outer surface of the stretchable blanket) has a thickness of 10 to 30 mm and comprises an elastomeric matrix (advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR)) and ultra-high molecular weight polyethylene or high-density polyethylene particles. The cover can also be made of a solid rubber composition. The hardness of the cover is advantageously 50 to 70 Shore A.

[0017] According to an advantageous aspect of the invention, in the cover of the stretchable blanket, the average particle size of the ultra-high molecular weight polyethylene or high-density polyethylene particles in the elastomeric matrix (advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR)) is between 10 microns and 300 microns in diameter, and is generally less than 750 μm in diameter.

[0018] According to an advantageous aspect of the invention, in the stretchable blanket cover, 0-20% of the total weight of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the weight of the ultra-high molecular weight polyethylene or high-density polyethylene particles.

[0019] According to an advantageous aspect of the invention, in the cover of the stretchable blanket, 0-22% of the total volume of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the volume of the ultra-high molecular weight polyethylene or high-density polyethylene particles.

[0020] According to an advantageous aspect of the invention, the reinforcement layer comprises a textile reinforcement layer which provides dimensional stability and structural integrity of the stretch blanket during operation. Typically, the reinforcement layer comprises two separate reinforcement layers: one layer having reinforcement yarns extending in the longitudinal (MD) direction and one layer having reinforcement yarns extending in the cross-machine direction (CD). The reinforcement yarns are synthetic fibers or natural fibers. Carbon black and / or silica are used as reinforcing filling materials in a matrix made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber, or in a matrix of natural rubber with ultra-high molecular weight polyethylene or high-density polyethylene particles, or in a matrix of natural rubber and styrene-butadiene rubber mixtures with ultra-high molecular weight polyethylene or high-density polyethylene particles. The thickness of the reinforcement layer is typically 2 mm-4 mm.

[0021] By means of the present invention and its advantageous features, several advantages are achieved: the wear resistance of the stretchable blanket is significantly improved and the friction with the wet metal surface of the bead is significantly reduced. The ultra-high molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE) particles provide the stretchable blanket with higher wear resistance by reducing the friction between the back side of the stretchable blanket and the bead. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] However, aspects of the present invention and further objects and advantages thereof will be best understood from the following description of certain exemplary embodiments when read in conjunction with the accompanying drawings, and hereinafter the invention will be described in more detail with reference to the accompanying drawings, in which:

[0023] exist Figure 1 , an example of a stretching processing unit having a stretchable blanket is schematically shown.

[0024] exist Figure 2 In FIG. 1 , a cross-sectional view of an advantageous example of an extendable blanket according to the present invention is schematically shown. Figure 3 , a graph indicating the wear loss in the test example is schematically shown.

[0025] Reference signs used in the drawings:

[0026] 10 extension processing units

[0027] 11A, 11B drying cylinder

[0028] 12 extension drying cylinder

[0029] 13 Carrying roll

[0030] 14 Bypass load roller

[0031] 15 Spreading roller

[0032] 16 Release agent sprayer

[0033] 17 Scraper blade

[0034] 20 Stretch Blanket

[0035] 20B Stretchable Blanket Back Cover

[0036] 20BS can stretch the back side of the blanket

[0037] 20F stretch blanket cover

[0038] 20FS can stretch the front side of the blanket

[0039] 20R Stretchable Blanket Reinforcement

[0040] 21 Carpet tension roller

[0041] 22I, 22U blanket bearing roller

[0042] 23 Blanket Lubrication Sprayer

[0043] 24 Blanket Atomizing Sprinkler

[0044] 25 Layering

[0045] 26 Pneumatic pressure rod for pressure strips

[0046] 27 Nip Pool

[0047] 28 air dam (air damping)

[0048] 29 Blanket grinding machine

[0049] N Nip

[0050] W Fiber Web DETAILED DESCRIPTION

[0051] In the course of this description, similar numerals and symbols will be used to identify similar elements according to different views showing the present invention. For the sake of clarity, some repeated reference numerals may have been omitted in the drawings.

[0052] exist Figure 1 In FIG. 1 , an example of a stretching processing unit 10 with a stretchable felt 20 is schematically shown. In the stretching processing unit 10, a stretchable fiber web W is produced. The stretching processing unit 10 is typically located in the dryer section of a fiber web production line, usually between two dryer sections or drying cylinder groups, typically after about half of the dryer section of the fiber web production line, more typically after about 2 / 3 of the dryer section of the fiber web production line. Figure 1In the example of FIG. 1 , the stretching processing unit 10 is positioned between the drying cylinders 11A and 11B. The first drying cylinder 11A is positioned before the stretching processing unit 10, and the second drying cylinder 11B is positioned after the stretching processing unit 10. The fiber web W is guided from the first drying cylinder 11A to the stretching processing unit 10 via the first carrier roller 13A and the first spreading roller 15A, and reaches the surface of the stretching drying cylinder 12 of the stretching processing unit 10. Accordingly, the fiber web W is guided from the surface of the stretching drying cylinder 12 of the stretching processing unit 10 to the surface of the second drying cylinder 11B after the stretching processing unit 10 via the second carrier roller 13B and the second spreading roller 15B. The stretching treatment unit 10 typically further comprises a release agent sprayer 16 configured to provide a release agent onto the surface of the stretching cylinder 12 of the stretching treatment unit 10 before the fiber web W is guided onto the surface of the stretching cylinder 12 of the stretching treatment unit 10, and a doctor blade 17 configured to clean the surface of the stretching cylinder 12 of the stretching treatment unit 10 after the fiber web W has been guided away from the surface of the stretching cylinder 12 of the stretching treatment unit 10. The stretching treatment unit 10 may also be provided with a bypass carrier roller 14 configured to guide the fiber web W through the stretching treatment unit 10 when stretching treatment is not required or available or for maintenance purposes of the stretching treatment unit 10.

[0053] In addition, if Figure 1As shown in the example of , the stretching processing unit 10 includes a stretchable blanket 20, which is formed into a continuous loop. The stretchable blanket 20 is guided by a blanket carrying roller 22I positioned inside the loop of the stretchable blanket 20 and a guide roller 22U positioned outside the loop of the stretchable blanket 20. The blanket tension roller 21 positioned inside the loop of the stretchable blanket 20 is used to control the tension of the stretchable blanket 20. A blanket grinder 29 associated with the stretchable blanket 20 may also be provided. The stretchable blanket 20 is configured to travel on the outer surface of the stretching cylinder 12 of the stretching processing unit 10 so that the fiber web W is positioned between the front side 20FS of the stretchable blanket 20 and the stretching cylinder 12 of the stretching processing unit 10. The pressure bar 25 is positioned inside the loop of the stretchable blanket 20. The pressure bar 25 forms a press zone N with the dryer 12 of the stretching processing unit 10. The pressure bar 25 provides the required pressure of the stretchable blanket 20 against the back side 20BS of the stretchable blanket 20 to stretch the fiber web W. The stretch treatment unit 10 further comprises: at least one blanket lubricating shower 23 positioned inside the ring of the stretchable blanket 20 for lubricating the back side 20BS of the stretchable blanket 20; and at least one blanket atomizing shower 24 positioned outside the ring of the stretchable blanket 20 for moisturizing the front side 20FS of the stretchable blanket 20. The bead 25 is provided with a bead pneumatic pressure link 26 for controlling the pressure provided by the bead 25 and its direction. Advantageously, a nip pool 27 is provided at the intersection of the stretchable blanket 20 and the bead 25 and is limited by an air dam 28 which is located before the nip pool 27 in the direction of travel of the stretchable blanket 20.

[0054] exist Figure 2An advantageous example of a stretchable blanket 20 is shown in a cross-sectional view in FIG. The stretchable blanket 20 comprises: a back cover 20B having a back side 20BS as an inner surface of the stretchable blanket; a front cover 20F having a front side 20FS as an outer surface of the stretchable blanket 20 and forming a stretchable layer of the stretchable blanket; and a reinforcing layer 20R, which is close to the back cover 20B toward the inside of the stretchable blanket 20. At least the back cover 20B of the stretchable blanket 20 comprises an elastomeric matrix (advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR)) and ultra-high molecular weight polyethylene or high-density polyethylene particles. The back cover 20B has a hardness of 50-70 Shore A hardness. The reinforcing layer 20R comprises longitudinal yarns and transverse yarns as reinforcing filling materials. The thickness of the back cover 20B of the stretchable blanket 20 is 1 mm to 5 mm. The cover 20F of the stretchable blanket 20 has a thickness of 10 mm to 30 mm and advantageously comprises an elastomeric matrix (advantageously made of natural rubber or a mixture of natural rubber and styrene-butadiene rubber (SBR)) and ultra-high molecular weight polyethylene or high-density polyethylene particles. The cover can also be made of a solid rubber composition. The hardness of the cover is advantageously 50 to 70 Shore A. The reinforcement layer 20R comprises a textile reinforcement layer, which provides dimensional stability and structural integrity of the stretchable blanket 20 during operation. Typically, the reinforcement layer comprises two separate reinforcement layers: one layer with reinforcement yarns extending in the longitudinal (MD) direction and one layer with reinforcement yarns extending in the transverse (CD) direction. The reinforcement yarns are reinforcing filling materials in a matrix of natural rubber or a mixture of natural rubber and styrene-butadiene rubber, or in a matrix of natural rubber with ultra-high molecular weight polyethylene or high-density polyethylene particles, or in a matrix of natural rubber with styrene-butadiene rubber particles with ultra-high molecular weight polyethylene or high-density polyethylene particles. The thickness of the reinforcement layer is typically 2 mm-4 mm.

[0055] refer to Figure 1-Figure 2In the embodiment of the present invention, a stretchable fiber web W is produced in a stretching processing unit 10, a wet fiber web W is guided to the stretching processing unit 10, and one surface of the fiber web W contacts one surface of a stretching cylinder 12, and the other surface contacts the front side 20FS of a cover 20F of a stretchable blanket 20. The cover 20F of the stretchable blanket 20 is already in an MD stretched state. The tension of the stretchable blanket 20 against the dryer 12 and the pressure provided by the pressure bar 25 keep the introduced fiber web W pressed to (slightly adhered to) the stretched cover 20F of the stretchable blanket 20. After passing under the pressure bar 25, the cover 20F of the stretchable blanket 20 starts to shrink in MD, and the fibers of the fiber web W shrink together with the stretchable blanket 20, resulting in MD shrinkage of the fiber web W. The shrinkage of the cover 20F of the stretchable blanket 20 and the fiber web W is mainly provided by the sliding between the surface of the stretching dryer 12 and the fiber web W. A film of steam forms between the surface of the stretch cylinder 12 and the surface of the moist fiber web W, creating conditions that allow slippage to occur. The reverse curvature of the stretch cylinder 12 further enhances the slippage of the fiber web W and the fiber compaction process.

[0056] Figure 3 A comparison chart of the wear of rubber not filled with ultra-high molecular weight polyethylene particles (unfilled rubber) and rubber filled with ultra-high molecular weight polyethylene particles (UHMWPE filled rubber) test examples is shown. In the test, the rubber filled with ultra-high molecular weight polyethylene particles has 20 weight percent (w-%) of particles. In the test, the wear loss (mm 3 ) is measured according to the wear rate of DIN 53516. In the diagram, lower values ​​mean less wear, so it can be concluded that the addition of UHMWPE particles significantly reduces the wear of the rubber.

[0057] Test examples related to friction values ​​are also given, and the static and dynamic friction values ​​of the same samples on wet metal surfaces were measured, see Table 1. Prior to the measurement, both test panels were smoothed with 800 grit sandpaper.

[0058] Material Static friction value Dynamic friction value UHMWPE filled rubber 0.42 0.18 No filling rubber 0.73 0.37

[0059] Table 1: Friction coefficient of UHMWPE filled rubber and unfilled rubber.

[0060] The lower the value, the lower the friction. It is easy to see from the test results in Table 1 that UHMWPE has a significant effect on reducing friction.

[0061] From the results it can be concluded that the addition of UHMWPE in the rubber mix capable of stretching the blanket reduces the drag and wear of the corresponding surface of the blanket. Reducing friction will also lead to reduced energy consumption.

[0062] In the foregoing description, although some functions have been described with reference to certain features, these functions may be performed by other features, whether described or not. Although features have been described with reference to certain embodiments or examples, these features may also be present in other embodiments or examples, whether described or not. The present invention has been described above only by reference to some advantageous examples, but the present invention is not narrowly limited to these examples. Many modifications and changes are possible within the present invention as defined in the appended claims.

Claims

1. A stretchable blanket (20), the stretchable blanket (20) being formed as a continuous loop and comprising: a back cover (20B) having a back side (20BS), the back side (20BS) being the inner surface of the loop of the stretchable blanket (20); A cover (20F) having a front side (20FS), wherein the front side (20FS) is the outer surface of the ring of the stretchable blanket (20) and is configured to provide a stretchable layer of the stretchable blanket (20); and a reinforcing layer (20R) between the back cover (20B) and the cover (20F), characterized in that at least the back cover (20B) of the stretchable blanket (20) includes an elastomeric matrix and ultra-high molecular weight polyethylene (UHMWPE, UHMW) or high-density polyethylene (HDPE) particles.

2. The stretchable blanket according to claim 1, characterized in that: The elastomeric matrix is ​​made of natural rubber or a mixture of natural rubber and styrene butadiene rubber (SBR).

3. The stretchable blanket according to claim 1 or 2, characterized in that: The hardness of the bottom cover (20B) of the stretchable blanket (20) is 50-70 Shore A hardness.

4. A stretchable blanket according to any one of the preceding claims, characterized in that In the back cover (20B) of the stretchable blanket (20), the average particle size of the ultra-high molecular weight polyethylene or high density polyethylene particles in the elastomer matrix is ​​between 10 and 300 microns in diameter, and is generally less than 750 microns in diameter.

5. The stretchable blanket according to any one of the preceding claims, characterized in that In the back cover (20B) of the stretchable blanket (20), 5-40% of the total weight of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the weight of the ultra-high molecular weight polyethylene or high-density polyethylene particles, and / or 5.5-43% of the total volume of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the volume of the ultra-high molecular weight polyethylene or high-density polyethylene particles.

6. A stretchable blanket according to any one of the preceding claims, characterised in that The back cover (20B) of the stretchable blanket (20) has a thickness of 1 mm to 5 mm and comprises an elastomeric matrix.

7. A stretchable blanket according to any one of the preceding claims, characterised in that The cover (20F) of the stretchable blanket has a thickness of 10 mm to 30 mm and comprises an elastomeric matrix.

8. A stretchable blanket according to any one of the preceding claims, characterised in that In the cover (20F) of the stretchable blanket (20), the average particle size of the ultra-high molecular weight polyethylene or high density polyethylene particles in the elastomer matrix is ​​between 10 microns and 300 microns in diameter, and is generally less than 750 microns in diameter.

9. A stretchable blanket according to any one of the preceding claims, characterised in that In the cover (20F) of the stretchable blanket (20), 0-20% of the total weight of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the weight of the ultra-high molecular weight polyethylene or high-density polyethylene particles, and / or in the cover (20F) of the stretchable blanket (20), 0-22% of the total volume of the elastomeric matrix and the ultra-high molecular weight polyethylene or high-density polyethylene particles is the volume of the ultra-high molecular weight polyethylene or high-density polyethylene particles.

10. The stretchable blanket according to any one of the preceding claims, characterized in that The reinforcing layer (20R) of the stretchable blanket (20) comprises longitudinal yarns and transverse yarns in an elastomeric matrix.

11. Application of a stretchable blanket in a stretching processing unit (10) for producing a stretchable fiber web (W), the stretchable blanket being a stretchable blanket (20) according to any one of the preceding claims, the stretching processing unit (10) comprising a stretching cylinder (12) and a pressure bar (25), a pressing area (N) being formed between the stretching cylinder (12) and the pressure bar (25), in the stretching processing unit (10), the stretchable blanket (20) and the fiber web (W) are configured to be guided through the pressing area (N), and in the pressing area (N), the back side (20BS) of the stretchable blanket (20) abuts against the pressure bar (25), and the front side (20FS) of the stretchable blanket (20) abuts against the stretching cylinder (12).

12. The use according to claim 11, characterized in that: The contact between the pressure strip (25) and the back side (20BS) of the stretchable blanket (20) is a sliding contact.

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