FI104435B - A method of film transfer coating and a method of implementing a film press - Google Patents

Abstract

The invention concerns a method in film transfer coating in a film press, in which press the nip (N) of the film press is formed out of two faces placed against each other and moving in the same direction so that said moving faces are pressed against each other in the nip. A coating agent or surface size is applied as a film (F1, F2) onto at least one of the moving faces that form the film press nip (N) and that are subjected to pressing, in which connection the coating agent or surface size is transferred in the nip (N) between the moving faces onto the paper or board web (W) running through the nip. After the nip the web is separated either directly from the nip or so that it follows one or the other of the moving faces. The web is separated from the nip so that, at least at one side of the web, the curve radius of the opening geometry is larger than 0.75 metre. The invention also concerns a film press intended for carrying out the method.

Description

104435

Method for Film Transfer Coating and Implementation of the Method in a Film Press Förfarande vid filmöverföringsbeläggning och * filmpress avsedd att genomföra förfarandet 5

The invention relates to a method of film transfer coating in a film press, whereby two opposing surfaces moving in the same direction are formed into a film press nip against said movable surfaces in a nip against one another, and wherein is transferred in a nip between the moving surfaces to a paper or board web passing through the nip, and after the nip is removed either directly from the nip or following either of the moving surfaces.

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The invention also relates to a film press for carrying out the method, comprising two opposing movable surfaces, a nip formed by pressing said movable surfaces against each other, through which a paper or board web has been passed, and the film press 20 is provided with a coating applicator: film to at least one of the pressed movable surfaces forming the film press nip, wherein the coating material or surface adhesive in the film press nip is · · arranged to move to a paper or cardboard web, the web being adapted to be detached either directly from the nip or

Using film transfer technology in film adhesive presses, the application of adhesive or paste to the paper is accomplished by applying the desired coating thickness to one or both rolls of the film adhesive, depending on whether one or both sides of the film are to be coated. formed by a nip formed by the paper web passing through said nip. Generally, the film rolls of the 2 104435 film adhesive presses are provided with a flexible coating and the application to the roll surface may be accomplished using a known blade coating, a bar coating with a smooth or grooved rod or similar nozzle apparatus.

Nowadays, paper machines and hence the associated film adhesive presses * 5 are aiming for ever higher speeds, whereby increasing this speed in particular in film adhesive presses has introduced a new problem, namely, when spraying large quantities of coating material there is spray coating on the back side. The misting is due to cracking of the coating film in the film press when the film is removed from the film roll. Thus, the coating film splits so that most of the film remains on the paper while a smaller portion remains on the surface of the film roll. Excessive fogging in itself can be quite a problem, which is reflected in the degraded quality of the coating on the coated paper. The problem also arises from the fact that even less mist builds up on the machine structures and drips onto the paper web, ruining the quality of the paper, or that the mist spreads to the room air. Another significant problem in film presses is how to control the web release line from the film press roll, which is followed by the web after the nip. In known solutions, the release point of the web from the roll does not remain the same, but the release point "walks" along the roll surface. There may have been fluttering in the web, which in turn may have resulted in web breaks and their known harmful consequences.

In addition, the machine direction and also the transverse direction of the web release point cause a serious fogging problem.

Since the problems described above have not become significant until the increase of the web speeds, the prior art contains very few solutions to eliminate these problems or even to solve them; , that could be reduced.

There are, of course, some earlier solutions and of these, for example, U.S. Patent No. 90,266, which attempts to prevent fog formation by using a special coat structure. Similarly, Finnish Patent No. 93,243 discloses a solution in which fog formation is not prevented per se, i i Ί 3 104435 but this mist is collected by means of mechanical devices arranged on the back side of the nip, or at least it is sought to be collected, Therefore, the prior art does not provide a solution for fog formation itself. Finnish Patent No. 101092 further seeks 5 improvements to the solutions of the above-mentioned patents, and thus the process described in this patent addresses the formation of the coating mist itself, in that the patented solution seeks to prevent the formation of

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In the prior art, reference is also made to U.S. Patent No. 5,496,406, in which, in a film press, the web is supported after the nip by air support beams disposed so that the bar closer to the nip supports the web on the side of the roll followed by the web.

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It is an object of the present invention to provide a novel improved solution for controlling the release line of a web and problems related to the formation of a coating agent or surface adhesive and the application of a mist. To achieve this object, the method according to the invention is essentially characterized in that the web 20 is detached from the nip so that the opening geometry at least on one side of the web has a radius of curvature greater than 0.75 m.

The film press according to the invention, in turn, is characterized in that the opening geometry of the film press after the nip at least on one side of the web 25 has a radius of curvature of more than 0.75 m.

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The major advantages of the invention over the prior art solutions are that the invention seeks to keep the web release from the film press nip as controlled as possible by the selection of the post press nip opening geometry according to the invention. In particular, thanks to this opening geometry, the invention as such is not only intended to

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4 104435 completely prevent fog formation. Therefore, when there is no mist at all, it is not a problem either. The post-nip opening film geometry of the film press according to the invention provides control over the cleavage geometry of the coating, stabilizes the web release, and maintains a low film burst rate.

Thus, fog formation is substantially eliminated and runnability is improved. Other advantages and features of the invention will become apparent from the following detailed description of the invention.

The invention will now be described, by way of example, with reference to Figures 10 of the accompanying drawings.

Figure 1 is a full schematic side view of a film press for both sides of the web or for surface sizing utilizing the method of the invention.

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Figure 2 is a view similar to Figure 1 of a film press for single-sided coating or surface sizing of the web utilizing the method of the invention.

Figure 3 is a view similar to Figures 1 and 2 of a film press of the invention for single-sided coating or surface sizing of the web as a belt application.

In Figure 1, the film press is generally denoted by the reference numeral 10. The film press 10 comprises a film press pin N formed between the first and second film press rolls 1,2. The paper or board web W is guided to said nip N in Fig. 1 t, guided by a guide roll 5. The film press 10 of Figure 1 is a coating or surface sizing agent on both sides of the web W and thus each film press roll 1,2 is provided with applicator devices 3,4 for applying the coating material or surface adhesive to film F1, F2 30 on each roll surface Γ, 2 '. in the film clamp nip N to the web W and the coated or surface-glued web W is led out of the nip N in FIG. The radii of the film press rolls 1,2 are designated by the designations R1 and R2.

Figure 2 illustrates a film press generally designated 10A.

The film press 10A comprises, as in Fig. 1, a film press pin N formed between the first and second film press rolls 1A, 2A. The paper or board web W is guided to said nip N in Fig. 2, guided by a guide roll 5.

The film press 10A of Figure 2 differs from the solution shown in Figure 1 in that the film press 10A of Figure 2 is a coating or surface sizing agent on one side of the web W and thus only one of the roll pair rolls of the film press 10A, the first film press roll IA having a film the second roll 2A of the film press 10A serves merely as a counter roll to provide the desired line pressure to the nip N in FIG. The film F, in the film clamp nip N moves to the web W and the coated or surface-glued web W '15 on one side is led out of the nip N in Figure 2 following the surface 2A' of the second film clamp roll 2A. Also in Fig. 2, the radii of the film press rollers 1A, 2A are denoted by reference R 1 and R 2.

Fig. 3 illustrates a film press designated 10B. The film press 20 1 OB comprises a film press nip N formed between the first and second film press rollers 1B, 2B by way of FIGS. 1 and 2 such that in the embodiment shown in this figure, the first film press roll IB is passed through a nip N - a belt IB '. formed by end folding rollers 6,7,8 to form an endless belt loop.

The paper or board web W is guided to said nip N in Fig. 3, guided by a guide roll 5 25. The film press 10B according to Fig. 3 is a coating or surface sizing on one side of the web W and for this purpose the belt press IB 'of the film press 10B ...

an applicator 3B for applying a coating material or a surface adhesive to a film Fj j on a belt IB '. The second roll 2B of the film press 1 OB functions in a manner similar to Figure 2 merely as a counter roll to provide the desired line pressure to the nip N. Film F, 30 in film clamp nip N moves from strap IB 'to web W, and on one side coated 6 104435 or surface-glued web W is led out of nip N in Fig. 3, following strip IB' from which it is removed after nip N.

Figures 1-3 are merely examples of how the coating and / or surface sizing of the film press 5 can be performed and how the film press nip geometry can be controlled without limiting the invention to these examples.

From the starting points which led to the invention, it can be briefly stated that, as described above, in the film presses, the fogging after the nip increases as the speed 10 increases. During trial runs, it has been found that if web W 'is taken out of nip N out of the belt; With the help of the tangent, the fogging is substantially less than without the belt. The belt situation can be approached by increasing the diameters of the rolls forming the nip N of the film press. This dependence largely follows the normal-acceleration formula: 15 v = V 2 * (1 / R 1 + 1 / R 2), where v = normal acceleration V = speed "20 Rt and R 2 = radii of the rolls.

The solution according to the invention uses a pair of rolls which exceeds the value 1.33 of 1.5 m + 1.5 m of the largest known roll presses calculated from formula 1 / RX + 1 / R2. It is most advantageous to increase the diameter of the hard surface counter roll as this roll 25 is very rarely replaced. This can be achieved by using a counter roll over 1.5 m in diameter. However, it is possible that at least one of the nip forming rolls is more than 1.5 m in diameter.

] «When using a belt, it is advantageous to arrange the web outlet in the direction of the tangent j of the film roll either directly along the nip or following the film roll. In the case of two straps, that is to say, where there is a strap on each side of the nip, stripping would take place! 7 104435 according to the size requirements of the above roll diameters or by removing the belts at a constant angle from the film of the other belt. Prior to detaching the web from the second film belt, it would be advantageous to dry the coating on the belt to increase the filter layer formed by the coating, which is known to reduce fogging.

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Thus, in the method according to the invention, the nip N of the film press is formed by two opposing surfaces moving in the same direction (roll surface / belt) which are pressed against each other in the nip. The coating agent or surface adhesive is applied as film F 1, F 2 to at least one of the movable surfaces under compression of the film press nip N, whereby the coating agent or surface adhesive is transferred between the moving surfaces N through a nip W or through a nip W According to the invention, the opening geometry is always detached so that the opening geometry at least on one side of the web has a radius of curvature greater than 15 0.75 m. Thus, in the case of a roll nip, at least one roll is more than 1.5 m in diameter.

In single-sided coating or surface sizing of the web, the web is placed after the nip to follow the compressed moving surface on the opposite side of the web to be coated or bonded before being released from the film press.

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At least one (cf. Fig. 3) or both of the nip-forming pressed movable surfaces may be formed by an endless loop formed through the nip. On the other hand, either or both of the nip forming movable surfaces may be formed by a roll surface.

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In a one-sided coating or surface sizing of the web, the movable surface pressed against the surface to be coated or adhered to the surface may be hard, especially a metal surface, or on the other hand may consist of a soft coating, particularly a polymeric coating.

8 104435

Further, in a one-sided coating or surface sizing of the web, a pressurized movable surface on the opposite side of the web to be coated or bonded may be water-scraped or moistened with water spray or steam to facilitate release of the web. Further, said surface may comprise * 5 coating or surface adhesive-repellent coating.

Where the nip of the film press is formed of two movable belts under compression, the coating may be dried after the nip prior to removal of the web from the belt to increase the layer of sequins formed by the coating.

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The invention has been described above by way of example with reference to the preferred embodiments shown in the accompanying drawings. However, the invention is not limited to the examples shown in the figures, but different embodiments of the invention may vary within the scope of the inventive idea as defined in the appended claims.

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Claims (18)

A method of film transfer coating in a film press, wherein two opposing surfaces moving in the same direction are formed into a film press nip 5 (N) by pressing said movable surfaces against each other in a nip, and wherein the coating material or surface adhesive is applied to the film (F, N2) forming pressed moving surfaces, whereby the coating material or surface adhesive is transferred to a paper or board web (W) passing through the nip (N) between the movable surfaces and the web is removed either directly from the 10 nip or following one of the moving surfaces, pinch such that the opening geometry has a radius of curvature of at least 0.75 m, at least on one side of the web. A method according to claim 1, characterized in that in single-sided coating or surface sizing of the web 15, the web is after the nip to follow the pressed moving surface on the opposite side of the web before the film press: out of the film press. Method according to Claim 1 or 2, characterized in that at least one or both of the nip-forming pressed movable surfaces are formed by an endless loop formed through the nip. Method according to claim 1 or 2, characterized in that at least one or both of the nip-forming pressed movable 4 · surfaces are formed by a roller. i The method according to any one of the preceding claims, characterized in that in the unilateral coating or surface sizing of the web or the surface to be bonded to the surface of 104435, the movable surface under pressure is hard, in particular metal surface. Method according to one of Claims 1 to 4, characterized in that, in the unilateral coating or surface sizing of the web, the pressurized movable surface on the opposite side of the web to be coated or surface sizing consists of a soft coating, in particular a polymer coating. 10 A method according to any one of the preceding claims, characterized in that in the unilateral coating or surface sizing of the web, a pressurized movable surface on the opposite side of the web to be coated or surface-squeezed is dewatered or moistened with water mist or vapor to facilitate stripping. . 15 A method according to any one of the preceding claims, characterized in that, in the unilateral coating or surface sizing of the web, the pressurized moving surface on the opposite side of the web to be coated or surface sizing consists of a coating which repels the coating material or surface sizing. • · A method according to any one of the preceding claims, wherein the film press nip is formed of two movable belts under compression, characterized in that after the nip is removed from the belt, the coating 25 is dried to increase the filter layer formed by the coating. J » A film press for carrying out the method according to any one of the preceding claims, comprising two opposed surfaces moving in the same direction, squeezing against said movable surfaces a nip (N) of a film press through which a paper or board web (W) is inserted. | and the film press being provided with coating means for applying a coating agent or a 104435 surface adhesive to a film (F ,, F2) on at least one of the pressed movable surfaces forming the film press n (N), the coating material or surface adhesive being wherein, after the nip, the web is adapted to be detached either directly from the nip 5 or one of its movable surfaces, characterized in that the opening geometry of the film press after the nip is at least on one side of the web having a radius of curvature of more than 0.75 m. A film press according to claim 10, characterized in that, in a single-sided or surface sizing film press, the web is placed after the nip to follow the pressed moving surface on the opposite side of the web to be coated or surface-squeezed before being removed from the film press. Film press according to Claim 10 or 11, characterized in that at least one or both of the nip forming movable pressed surfaces comprises a continuous loop formed through the nip. A film press according to claim 10 or 11, characterized in that at least one or both of the nip forming movable surfaces käsittää comprises a film press roll surface. : Film press according to one of Claims 10 to 13, characterized in that the movable surface on the side opposite to the surface to be coated or surface-bonded in the single-sided or surface-sizing film press 25 is a hard surface, in particular a metal surface. v * Film press according to one of Claims 10 to 13, characterized in that the movable pressurized surface on the opposite side of the web to be coated or surface-bonded in the film press 30 or the surface sizing agent comprises a soft coating, in particular a polymeric coating. , Film press according to one of Claims 10 to 15, characterized in that the movable surface on the opposite side of the web to be coated or superimposed on the single-sided or surface-sizing film press is provided with means for dewatering or dewatering said surface. s 10 A film press according to any one of claims 10 to 16, characterized in that! that the pressurized movable surface on the opposite side of the web to be coated or superimposed on the single-sided or surface-sizing film press is provided with a coating that repels the coating material or the surface-adhesive. A film press according to any one of claims 10 to 17, wherein the film press nip is formed of two movable moving belts, wherein the film press is provided with means for drying the coating after the nip before removing the web from the belt to increase the filter layer formed by the coating. • f • -; Λ »J 104435 J {%