CN1659336A - The Method of Improving the Smoothness of Rolled Paper - Google Patents

Abstract

The present invention provides a method for improving the smoothness of a paper web surface by subjecting the paper web surface to the action of an untreated smooth roller moving at a different speed than the paper web, thereby causing frictional heat to plasticize the fibers at the uppermost portion of the paper surface. Surprisingly, the inventors have discovered that no abrasive is required to generate the heat required to improve smoothness.

Description

The Method of Improving the Smoothness of Rolled Paper

technical field

The present invention relates to a method for improving the smoothness of the surface of a fibrous web without compromising other properties such as thickness per weight, density, yield and quality. More particularly, the present invention relates to a method in which a web/board web is passed over a smooth, untreated roll in such a frictional manner that sufficient heat is generated to render the surface The fibers are plasticized or melted.

Background technique

For all printing jobs, the surface of the paper web/board should be as smooth and/or uniform as possible. A typical method for improving the smoothness of the web/board surface, before coating, as the final finishing process after coating the web/board substrate, or for uncoated web/board, involves extrusion. Press cardboard. This is called rolling. During the rolling process, the paper is subjected to a smooth finish under enormous pressure. The goal of rolling is to smooth the paper surface, or to plastically deform the paper and replicate the surface of the rolling rolls on the paper. This is accomplished by passing the web through one or more twin roll nips. In this way, the material is simultaneously compressed and rubbed to form a polished surface. The hardness of the rollers can be equal or unequal. The method can be enhanced by using more pressure or by heating or wetting the surface fibers to make them more flexible. For example, in one method, the web/board passes through one or more heated nip nips at a temperature higher than that of the web. The web/board surface to be finish-calendered is pressed against said heated rolls. The applied heat raises the surface temperature of the web/board to the glass transition temperature, which causes the fibers to soften and conform to the roll surface.

There are many types of rolling machines, but they all use mechanical extrusion or sliding forces to even out the surface. Conventional rolling suffers from considerable drawbacks. After re-wetting, the surface smoothed by rolling will recover all or part of its original shape. Paper is also known to lose up to 35-40% of its strength properties and 25-35% of its inherent opacity due to rolling. At the same time, the original toughness of the paper web will be significantly reduced. In addition, some kind of paper compression or densification occurs during the rolling process. Considering the problems associated with rolling, much work has been done to find different methods for smoothing surfaces.

US Patent No. 5,533,244 discloses a method of polishing paper with a canvas belt that slides over the web at a different speed than the web itself, creating friction. US Patent No. 4,089,738 discloses a soft rolling device which acts as a sliding friction device on the paper surface. The device will smooth the surface of the paper in the same way as the original Super Roller. US Patent No. 4,112,192 discloses the application of a heated rolling equipment.

It is well known in the papermaking field that different types of rolls are used for different purposes such as web conveying, coating and rolling. For example, in the drying process, the paper stock is fed into a dryer section where it is dried by passing over steam heated rolls. After drying, the paper is sent to a size press where it is passed through rolls, such as calender rolls, and additives are applied to produce the specific surface characteristics required for the final product.

U.S. Patent Nos. 6,468,133 and 6,497,793 disclose a method of grinding away the most protruding parts of the web with grinding devices such as grinding rollers or vibrating grinding devices or rotating grinding drums to remove high density short spots on the surface of the paper. fiber. US Patent No. 2,349,704 discloses a method of polishing the surface of a paper web with a cloth polishing roll. The surface of the roll includes a powdered abrasive bonded to the surface with a binder, the purpose of which is to compress and polish the paper to the same extent as it would be with a super-roller; and, according to the According to the patent specification, the density of the treated paper is the same as after superroller treatment and glazing, as measured by a Baush & Lomb gloss meter, and is 10 points higher than before treatment. US Patent No. 4,267,215 discloses a method of coating the surface of a web using an inverted roll technique in which the direction of motion of the application roll relative to the web is reversed. U.S. Patent No. 2,118,763 relates to a method of processing fiberboard by moving the board in one direction while subjecting the moving board to a pair of opposed, smooth-surfaced, highly heated rollers in contact with the surface of the board As a result, the rollers rotate at a higher rate in a direction opposite to the direction of motion of the plate.

None of the prior art methods provide a simple and economical method of smoothing the surface of a fibrous web. Furthermore, the strength properties of the paper are significantly degraded during the use of known methods. Increasing smoothness by rolling without increasing paper density can yield considerable economic benefits.

Contents of the invention

The inventors have found that considerable improvements in smoothness can be achieved by ignoring the prior art teachings of abrasive or insulating rolls to improve smoothness and instead using uncoated smooth rolls.

It is thus an object of the present invention to eliminate the disadvantages of the prior art and to provide a novel method of treating the surface of a fibrous web, especially the surface of the paper web/board, in order to improve its smoothness while at the same time sufficiently maintaining the web Paper thickness and mechanical properties.

Accordingly, it is an object of the present invention to provide a method for improving the surface smoothness of a fibrous web without compromising other properties such as basis weight thickness, density, yield and quality.

It is an object of the present invention to provide a method in which a fibrous web is passed over an uncoated smooth roll, wherein the rotational speed of the roll is different from the rotational speed of the web and is sufficient to generate sufficient friction to Heat is generated and melts the fiber surface.

Another object of the present invention is to provide a method wherein the fibrous web is passed over an uncoated smooth roll rotating in the same or opposite direction to the web's movement.

The present invention also includes an improved method wherein said uncoated smooth roll is a simple mild steel roll.

The present invention also includes an improved method wherein said uncoated smooth roll is a simple chrome plated mild steel roll.

Furthermore, the present invention also includes a method which may include a soft backing roll pushing the web/board towards said web.

The present invention also includes a method wherein said backup roll moves at the same speed and direction as said web.

The invention also provides a method in which the smoothing step is preferably carried out prior to coating, size press or rolling of the board.

It is an object of the present invention to provide a method for improving the smoothness of a fibrous web without causing a loss in thickness per unit weight due to rolling. The method involves passing the web/board through an uncoated smooth roll prior to rolling.

Another object of the present invention is to provide a method wherein said rolling step is only required to control the thickness in the transverse direction through the fiber. Therefore, its thickness loss per unit weight is minimal.

An advantage of the present invention is that many of the properties of paper can be achieved with fewer fibres, which can improve the smoothness of the surface without loss of paper thickness.

Another advantage of the present invention is that it separates two variables (smoothness and paper thickness) that are closely linked in standard rolling processes, thereby giving the papermaker the choice of either using increased surface smoothness without loss of thickness. For the paper, either increase the hardness, but the corresponding thickness of the paper will also increase, or remove the fiber, and obtain the same thickness as before.

Description of drawings

Figure 1 shows that a smooth, uncoated roll improves smoothness as much as a ground roll;

Figure 2 shows that smooth, uncoated rolls can improve smoothness as much as ground rolls; and

Figure 3 shows the smoothness that can be expected with a smooth, uncoated roll based on the prior art.

Detailed ways

In the paper industry, rolls are used for different purposes, such as conveying webs, coating and rolling, etc. The present invention is based on the surprising discovery that a smooth roll can be used to generate heat and thus considerably improve the smoothness of the web/board, which was previously thought to require an abrasive cover roll Completed. In particular, the present invention provides a method of improving the smoothness of the web surface by subjecting the web surface to an uncovered smooth roller moving at a different speed from the web, thereby due to The heat generated by the friction plasticizes the uppermost fibers on the paper. Surprisingly, the inventors have discovered that it is not necessary to add any abrasives to the steel rolls to generate the heat required to increase the smoothness.

The terms "paper/board", "paper" and "board" refer to products formed from sheets containing cellulosic or woody fibers. "Paperboard" is synonymous with "cardboard". The grammage of the paper or board can vary widely from about 30 to about 500 g/m.sup.2. Measured according to the Parker Print Surf method, the roughness of the web to be processed is about 0.1 to 30.mu.m, preferably about 1 to 15.mu.m. In the present invention, the roughness varies between about 100 and 400 units, preferably between 200 and 325 units, especially 125 units, as measured by the Sheffield roughness measurement method. The present invention can be used to treat any desired paper web or paperboard web. As a matter of practice, the terms "paper" or "web" are used herein to refer to "paper" and "board", "web", and "web of paperboard", respectively.

Within the scope of the present invention, the terms "cellulosic fibers" and "lignocellulosic fibers" are used to denote materials derived from cellulosic and lignocellulosic materials, respectively. In particular, "cellulosic fibers" refer to materials obtainable from chemical wood pulp and other plant raw materials. So, for example, webs containing "cellulosic fibers" may be made from kraft, sulfite or organosol pulps. "Lignofiber" means material obtainable from wood and other plant raw materials by mechanical defibration, such as by industrial refining processes, such as refiner mechanical pulp (RMP), pressure refiner pulp (PRMP), thermomechanical pulp (TMP), Ground wood pulp (GW) or pressure ground wood pulp (PGW) or thermo-mechanical pulp (CTMP) or any other method of producing fibrous material that can be formed into a web or coated.

The terms "fines", "fibrils" and "fibers" refer to material broken up into small particles with a cross-sectional diameter of approximately less than 10.mu.m, usually between 0.001 and 2.mu.m, "fibrils " and "fiber" are materials having a length to cross-sectional diameter ratio greater than about 6.

The term "web tension" means the tension caused by the friction created by uncovered smooth rolls, not just the external web tension obtained by forwarding the web means.

The paper web/board is produced on conventional paper machines, such as fourdrinier machines. On this machine, a furnish of papermaking raw material ("furnish" is primarily water and raw material ("stock") is virgin, recycled or blended virgin and recycled wood fiber pulp, filler, size and/or or dyes) from the headbox settles onto the papermaking wire (a fast-moving perforated conveyor belt or screen) that serves as the table on which the paper is formed. As the furnish moves forward, the gravity suction box under the papermaking wire draws the water out. Typically, after paper leaves the "wet end" of the paper machine it still contains a significant amount of moisture. Therefore, it is necessary to feed the paper into the extrusion section consisting of a series of heavy rotating drums, which squeeze out the moisture in the paper, and further compact and reduce the moisture in the paper. After extrusion the paper enters the dryer section. Hot air or steam heating cylinders come into contact with all sides of the paper, thereby evaporating the water to a lower level. The paper is optionally passed through a sizing liquid to reduce its porosity and to help the printing ink remain on the surface of the paper rather than penetrate it. The paper can also continue through an additional dryer to evaporate liquid during sizing and coating. Calenders or polished steel rolls smooth and compact the paper. At the same time as most roll mills are glazed, some rolls can be used for matting or matte finishing.

The process of the present invention involves subjecting the web to a smooth roll for processing, preferably after the web has been dried sufficiently to impair the reasonable mechanical strength of the web. The diameter of the rolls can be optional. The only condition is that the surface of the roller must be smooth. Rollers can be made of mild steel to a suitable shape. In the method according to the invention, the web may have two opposing surfaces and the method comprises subjecting both surfaces of the paper to an untreated smooth roll.

The smoothing operation of the present invention is achieved by bringing one or both surfaces of the web/board web into contact with an untreated smooth roll in such a way as to generate sufficient friction to generate heat and thus soften Surface fibers of paper web/board. In this way, the speed difference between the roll and the web/board to be smoothed should be sufficient to generate enough friction to generate heat. The best way to do this is to have the web move in the opposite direction to the web, or in the same direction as the web but at a different speed. The critical speed difference depends on the quality of the wood or pulp used to make the paper/board.

To ensure good, smooth surface contact with the smooth roll in the method of the present invention, it may be effective to use a backup roll on the side of the web opposite the smooth roll that moves at the speed and direction of the web. The pressure applied to the web can vary over a wide range as long as the web/board is not significantly compressed. Usually, the surface pressure is about 0.01 to 1000 kPa, preferably about 1 to 300 kPa. The speed and pressure should be kept at such a level that localized heating will soften the surface fibers. The heat generation naturally depends on the particular fiber web and said pressure. For example, to ensure that the rolls are not overheated, the temperature can be regulated by internal or external cooling.

The rotation of the roller adopts the traditional driving method. Thus, any transmission and running mechanism such as pneumatic and hydraulic cylinders and electric motors can be used to achieve the movement of the rollers. For example, a pulley conveyor system coupled with a prime mover, such as an electric motor, can provide a convenient, smooth variable speed drive for the rollers without the need for complex gearing.

Thus, the present invention is an improvement over existing equipment by driving paper machine rolls or dryer cylinders in a direction opposite to the direction of web motion. The invention can also be realized by having an untreated smooth roller connected to a frame, the shaft for the roller being pivotally mounted on rails and adapted to move the roller. By moving the rollers transversely relative to the web, the apparatus can be controlled and at the same time the web tension adjusted. The direction of motion of the rollers need not be transverse to the web, but the rollers may move, for example by tilting relative to the web or by turning the shaft along a circular path. Through the movement of the rollers it is also possible to adjust the distance, in other words how far the web travels on the roller lip. The smoothing force can be adjusted, for example, by bringing an uncoated smooth roll into contact with a web of pre-determined web tension, and by adjusting the position of the roll or changing the angle between the web and the roll to adjust the resulting Web tension.

The further web/board treatment process according to the invention is carried out either directly on the smooth surface or after sizing or coating the smooth surface. Further methods usually include smooth surface polishing, light rolling or re-drying, or a combination of these procedures. For coating, the web/board can be provided with a polymeric layer, barrier layer, varnish or with a normal paint color. These webs/boards are especially suitable for printing and writing and inkjet printing. The untreated optional gloss texture product is also suitable for wrapping, bagging and bagging.

In a preferred embodiment of the invention, the roll is an untreated smooth roll, ie the surface of the roll is untreated with abrasives. In another preferred embodiment, the untreated smooth roll is formed by treating a metal surface which has been smoothed by the standard production process for any roll intended for a paper machine. An untreated smooth roll can be a plain mild steel roll or a chrome plated roll. The preferred roll is a simple mild steel roll.

In a preferred embodiment according to the present invention, the speed difference between the untreated smooth roll and the fiber web should be sufficient to cause friction and thereby generate sufficient heat to melt the surface fibers of the web/board.

In another embodiment of the invention, the web/board may be coated web/board, uncoated fiber-free paper, light weight coated web/board, linerboard or other grades of uncoated Fiber covered material. Preferably, the method of the present invention is applied to the web/board prior to coating, size press treatment or rolling. In some cases, rolling may not be necessary.

In a preferred embodiment one or more rolls may be used to smooth a surface of the web/board. The rolls can rotate in the opposite or the same direction as the web/board travel. There must be a speed difference between the web and the uncoated smooth roll.

The present invention provides a simple and economical method for smoothing the web/board, in which an opportunity is created for simple smoothing of existing paper machine rolls or dryers by driving the paper machine rolls or dryers in the There are equipment improvements. The present invention thus does not require special grinding rolls and special dust extraction equipment to capture the dust and debris released during the buffing process. Also in previous methods using grinding rolls, low friction strength paper standards delaminated and weakened during handling. The present invention does not require higher surface strength. Moreover, the method of the present invention further reduces the steps required for rolling.

Several experiments were carried out to compare the effect of smooth and ground rolls. The paperboard used in these trials was a solid bleached sulfate (SBS) base stock used on paper machines in the southeastern United States. Paperboard is made with minimal rolling and is not coated. The test equipment used a 50 cm wide substrate. The grinding rolls were coated with tungsten carbide using the HVOF (High Velocity Oxygen Spray Technology) method with a final average roughness ( _Ra ) of approximately 175 microinches. A smooth roll is simply a steel roll manufactured to the standard tolerances of paper machine operation, without being over polished or coated with a functional coating. In such equipment, the web is held on functional or "live" rolls by backup rolls. The speed of the backup roller is the same as that of the web. The back-up rolls are made of very soft rubber, in this case with an HSA value of 50. The pressure used to deform the backup roll to achieve the desired result is very low, typically in the range of 3-10 pounds per linear inch (pli). These low pressures are well below what the paper is subjected to in a standard rolling train, and they do not cause the on-scale loss of thickness that can be seen on a rolling train. The speed of the web in the tests was typically between 300 and 400 meters per minute (mpm). Table 1 shows that a perfectly smooth roll can give almost the same smoothness as a ground roll. Figure 1 corresponds to the data in Table 1. Figure 2 shows that smooth uncoated rolls according to the invention can produce similar improvements in smoothness relative to ground rolls prior to coating on solid bleach sulphate (SBS). The whiskers represent the 95% confidence limit for the mean smoothness improvement of the nip pressure over the test, the squares and circles represent the mean value itself. Figure 3 shows the results that can be expected based on known techniques in the art, and the results that can be expected by those skilled in the art. That is, smoothing would not be expected to alter the surface roughness, so the difference in smoothness of the board before and after treatment was zero.

Table 1 source Sheffield base before processing type of roll Speed of movable roller (mpm) Gap Length(mm) Processed Sheffield, cardboard Δ Sheffield = smoothness improvement 1 SBS 274 grinding roller -650 25 220 54 2 SBS 274 grinding roller -650 20 213 61 3 SBS 274 grinding roller -650 25 197 77 4 SBS 274 grinding roller -650 30 192 82 5 SBS 274 grinding roller -1000 30 178 96 6 SBS 274 grinding roller -1000 25 178 96 7 SBS 274 grinding roller -1000 20 184 90 8 SBS 274 smooth roll -650 13.5 218 56 9 SBS 274 smooth roll -650 twenty one 218 56 10 SBS 274 smooth roll -650 31.5 209 65 11 SBS 267 smooth roll -650 31.5 198 69 12 SBS 267 smooth roll -650 twenty one 195 72 13 SBS 267 smooth roll -650 13.5 195 72 14 SBS 267 smooth roll -1000 13.5 202 65 15 SBS 267 smooth roll -1000 twenty one 192 75 16 SBS 267 smooth roll -1000 31.5 191 76

· Sheffield measures the smoothness of a surface. Higher numbers indicate a rougher surface, and lower numbers indicate a smoother surface.

• ΔSheffield is the difference between the initial smoothness value and the final smoothness value. It thus represents an improvement in smoothness, with higher values indicating more smoothness improvement and a better result.

• The speed of the rolls and the nip length are two variables referring to the process variables when we implement the method in this case. Roll speed is the speed of the roll surface in contact with the paper in meters per minute. The nip length is a measure of the pressure in the nip. Higher pressure causes greater deformation of the soft backing roll on the other side of the paper away from the grinding or smoothing roll,

Obviously, other changes and variants are possible in accordance with the invention. It is therefore to be understood that the various forms of the invention described above and shown in the accompanying drawings are illustrative only and do not limit the scope of the invention.

Claims (29)

1, a kind of method that is used to increase paper web or cardboard fiber roll coil paper surface smoothness comprises:

Make web surfaces be subjected to the effect of the roller of smooth unprocessed mistake, the speed discrepancy of wherein said roller and roll web is enough to frictional heat and thereby makes cardboard fiber plasticising topmost.

2, according to a kind of method of claim 1, it comprises 125 Sheffield units of the maximum reduction of the roughness of web surfaces.

3, according to a kind of method of claim 1, wherein roll web has two opposite surfaces, and described method comprises that two surfaces that make roll web all are subjected to the effect of smooth roll.

4, according to a kind of method of claim 1, wherein smooth undressed roller is simple steel rider.

5, according to a kind of method of claim 1, its central roll rotates along the direction the same with roll web.

6, according to a kind of method of claim 1, its central roll is along rotating in the opposite direction with roll web side.

7, according to a kind of method of claim 1, wherein paper web or cardboard can be used for printing, packing or packing.

8, according to a kind of method of claim 1, wherein roll web was subjected to the effect of smooth uncoated roller before coating, sizing applicator are handled or be rolling.

9, according to a kind of method of claim 1, this method use soft underprop roller.

10, according to a kind of method of claim 9, wherein the soft underprop roller rotates with speed identical with web velocity and direction and direction.

11, a kind ofly be used to handle printing, packing or the baling paper width of cloth or cardboard fiber roll coil paper surface, do not roll up the method for the density of roll web, comprising:

Make web surfaces be subjected to the effect of smooth undressed roller, the difference between the rotating speed of wherein said roller and the rotating speed of roll web is enough to frictional heat and thereby makes the fiber plasticising on cardboard top.

12,, comprise 125 Sheffield units of the maximum reduction of the roughness of web surfaces according to a kind of method of claim 11.

13,, comprise making web surfaces and of the smooth roll contact of a relative web surfaces, so that make the surface fiber fusing on the described web surfaces with enough speed motions according to a kind of method of claim 11.

14, according to a kind of method of claim 11, wherein roll web has two opposite surfaces, and described method makes two surfaces of roll web all be subjected to the effect of smooth roll.

15, according to a kind of method of claim 11, wherein smooth uncoated roller is simple steel rider.

16, according to a kind of method of claim 11, its central roll rotates along the direction identical with roll web.

17, according to a kind of method of claim 11, its central roll is along rotating in the opposite direction with roll web side.

18, according to a kind of method of claim 11, wherein roll web was subjected to the effect of smooth uncoated roller before coating, sizing applicator are handled or be rolling.

19, according to a kind of method of claim 11, this method is used the soft underprop roller.

20, according to a kind of method of claim 19, wherein the soft underprop roller is with speed identical with web velocity and direction and direction motion.

21, be used to increase paper web or cardboard fiber roll coil paper surface smoothness and do not lose the thick method of paper, comprising:

Make web surfaces be subjected to the effect of undressed smooth roll at dried state; With roll web is contacted with described roller, the speed discrepancy between wherein said roller and the roll web is enough to frictional heat and thereby makes the fiber plasticising on cardboard top.

22, according to a kind of method of claim 21, it comprises that the roughness with web surfaces reduces maximum 125 Sheffield units.

23,, comprise web surfaces is contacted with respect to the smooth roll of web surfaces with suitable speed motion with one, so that make the surface fiber fusing on the described roll web according to a kind of method of claim 21.

24, according to a kind of method of claim 21, wherein roll web has two opposite surfaces, and described method makes two surfaces of roll web all be subjected to the effect of smooth roll.

25, according to a kind of method of claim 21, wherein smooth uncoated roller is simple steel rider.

26, according to a kind of method of claim 21, its central roll rotates along the direction identical with roll web.

27, according to a kind of method of claim 21, its central roll is along rotating in the opposite direction with roll web side.

28, according to a kind of method of claim 21, wherein paper web or cardboard are used for printing, packing or packing.

29, according to a kind of method of claim 28, wherein roll web was subjected to the effect of smooth uncoated roller before coating, sizing applicator are handled or be rolling.

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