FI116690B - Coating of fibrous web involves applying layer(s) of coating material to surface on side(s) of web by using curtain coater, and subjecting still moist coating of applied layers of coating material to hot compression contact - Google Patents

Abstract

A fibrous web is coated with coating layer(s) by applying layer(s) of a coating material to the surface on side(s) of a fibrous web (W) by using a curtain coater (21). A still moist coating of the applied layers of coating material is subjected to a hot compression contact by means of a hot contact surface or contact surfaces. The coating is bonded to the fibrous web's surface, and dried. The web's surface became smooth and glazed. An independent claim is also included for an apparatus (2) for coating a fibrous web, comprising curtain coater for applying layer(s) of coating material onto a surface of the fibrous web, as well as a treatment unit (22) immediately downstream of the curtain coater in the fibrous web's traveling direction for treating the fibrous web in a hot compression contact.

Description

116690

Method and apparatus for coating a fibrous web

The invention relates to a method and an apparatus for coating a fibrous web, wherein the fibrous web is pre-calendered before the coating step and the final calender is after the coating step.

Many current calendering processes consist of several individual sub-steps, such as, for example, a two-nip soft calender and a multi-nip calender with several similar nips in a row. It is an object of the invention to utilize a calender comprising a use-10 screening step in a process for coating a fibrous web so as to provide a coating method in which the most compact equipment can be used. To accomplish this object, the method of the invention is characterized in that the process comprises applying a fiber web to be coated to a single nip or treatment zone of the calender for pre-calendering, a pre-calendering to a fiber web coating step, and a subsequent The device according to the invention, in turn, is characterized in that the device comprises a calender with a pre-calendering step, a coating step and a final calendering step comprising at least one nip or processing zone of the calender, the final calendering step comprising in connection with the point between the pre-calendering step and the end-calendering step, the device includes a calender with a pre-calendering 1 «•. ' : the calendering step (Ni), the coating step (15; 15a-15d) and the final calendering step (N;

• I

•, · | N2), the pre-calendering step comprising at least one nip or processing zone of the calender, the final calendering step comprising at least one other of the same calender; "; the nip or processing zone and the coating step (15; 15a-15d) is followed by the same calender .

30 f »'!' The calender used in the method may be selected from the group consisting of at least - t; '· · A soft calender, a machine calender, a super calender, a multi-nip calender or a belt calender comprising two nips or a processing step. The belt calender as a special embodiment; na is a metal belt calender comprising at least two processing steps.

35 116690 2

The invention will now be further described with reference to the accompanying drawings, in which:

Figures 1-3 schematically illustrate some metal belt calendars suitable for carrying out the method according to the invention, Fig. 4 schematically illustrates a two-nip soft calender suitable for implementing the method according to the invention, and Figures 5-6 schematically depict some multilip calendars suitable for implementing the method according to the invention.

Figure 1 shows an arrangement based on a metal belt calender for carrying out the method according to the invention. The arrangement comprises two separate metal belts 2a and 2b which rotate around the guide rollers 3 and form, by means of a roller 5 acting as an interposed member, two processing areas Νχ and N2 of the fibrous web W1r W2. At least a portion of the inner guide rollers 3 of the belt turns are made movable to adjust the tension of the belts 2a and 2b and their movement as desired. As the fibrous web passes through each treatment area, it is subjected to a desired pressure pulse and thermal effect as a function of time. Inside the belt passage 2a, the nip roll 6 shown in Figure 1 for interrupted butter may be provided for forming an additional nip against the roll 5 to provide an increased pressure effect on the fibrous web. The counter roll 5 as well as the nip roll 6 can

«IMI

be a deflection-compensated roll or not, and is selected from the group consisting of:

• <I

'··' · 'trembling roll such as polymer coated roll, rubber coated roll or elastic; '; sea roll, shoe roll, thermal roll and fiber roll.

25 ('When using the device of Figure 1, the fibrous web Wi is first passed through a treatment area:' to pre-calender the fibrous web. The fibrous web is then introduced into the casings I.

to step 15, where it is coated by an appropriate coating process.:. selected from the group consisting of dry coating, cast coating, curtain. · *, 30 Coating, Blade Coating, Spray Coating, Micro Jet Coating or Film Coating.

'! 'After the coating step, the coated fibrous web designated as W2, i t:' is passed through a second treatment area N2 to adhere the coating and the end of the fibrous web. · Grooming.

»* T ·>

• I

3 1 1 6691)

The device embodiment 20 of Fig. 2 also has two belt turns 2a, 2b and a counter roll 5 between them, thereby forming two processing areas N1 and N2, as in the case of Fig. 1. Optionally, there are more than one coating step, whereby, for example, in the coating step 15a, one side of the web can be coated and in the coating step 15b, the other side of the web 5 can be coated. Step 15b The coating may also be implemented in such a way that it is used for coating the same side as the coating step 15a to provide a multi-layer coating. The fibrous web W: is first introduced into the pre-calendering step Ni and then into the coating step 15a, after which it is passed through a roller 7 to an optional second coating step 15 and from there to the anchoring / final calendering step N2.

The device embodiment 30 of Figure 3 has a first metal belt wrap 2a and a first counter roll 5a forming a first treatment area Nt between them, and a second metal belt wrap 2b and a second counter roll 5b forming a second treatment area N 2 between them. The counter rolls 5a, 5b are disposed such that they form with each other a coating attachment nip N, which is preferably heated. This device implementation allows the fibrous web to be processed in various ways, e.g. by passing the fibrous web Wi first through the treatment area Ni for pre-calendering and then through the coating step 15a and further through the roller 7 further through the second coating step 15b from which it is applied to for final calendering. After this step, the coated slag W2 may be removed from the device for further processing, such as winding. Coating steps 15a and 15b with each other may be optional or may utilize either :: Head, either one side of the web to coat more layers or web 25 to coat the different sides. Optionally, after the fastening nip N, the web may have:; ': a third coating step 15c from which the web may be passed through one of the turning rolls 7a.

• · · I

•: · Processing area N2 for fastening / final calendering processing. The device can. · ·. there may also be a fourth coating step 15d, which may function e.g. as a pre-coating step prior to the actual coating step 15a and / or 15b and / or 15c. The coating steps 15a to 30d may optionally be applied one or more at a time to the same fibrous web '; for treating so as to form a single or multiple layer coating; · On one or both sides of the turain. In addition, the direction of travel of the fibrous web may be: * .. opposite to the above, e.g., a treatment area N2 or an attachment nip; '* *; pi N can serve as a precalender and processing area Ni as a final calender.

* * · • i · 35 4 116690

In the device embodiment 40 of Figure 4, the coating station 15 is disposed between the two nipples N1 and N2 of the soft calender, whereby the same compact device provides pre-calendering and final calendering after coating.

In the device embodiment 50 of Figure 5, the coating step 15 is connected to the position between the two nips of the multi-nip calender, and in the device embodiment 60 of Figure 6, the coating step 15 is located between the two rows of rollers. In the embodiments of Figures 5 and 6, the fibrous web passes through a plurality of nips before and after coating for efficient pre-calendering and final calendering.

The coating step 15,15a, 15b shown in the device embodiment of Figures 1, 2 and 3 includes the application or transfer of a coating material to the surface of the web. The coating step may further include drying, heating and fixing if necessary.

15

Particularly preferably, the proposed process is suitable for coating in dry form (dry coating).

• * »• I> • * • · t> · I | )

Claims (12)

A method of coating a fibrous web, in which the fibrous web is pre-coated before the coating step and finalized after the coating step, characterized in that in the method the web to be coated is added to a nip in the calender or a post-processing zone for pre-calendering; after the pre-calendering, the fiber web coating step is performed, and after the coating step, the fiber web is passed to the second nip of the same calender or the final calendering treatment zone. 10 A method according to claim 1, characterized in that the calendering is performed with a soft calender, machine calender, super calender, multi-type calender or band calender comprising Itminstone two nip or a treatment step. 3. A method according to claim 1, characterized in that the calendering is carried out with an at least two processing steps comprising metal strip calender. Method according to Claim 1, characterized in that the calendering is performed with a multi-type calender (60) having at least two roll systems. 20 5. A method according to any one of claims 1 to 4, characterized in that the coating method is selected from the group consisting of dry coating, cast coating,:: ridging coating, knife coating, spray coating, microjet coating or film coating. coating. »« • * * »· *> t <25 Process according to any of the preceding claims, characterized in that, the pre-calendering, coating and final calendering step of the fiber web coating treatment is carried out as an on-line process on the fiber web production line. Process according to any of claims 1-5, characterized in that the pre-coating, coating and final calendering step for the fiber web coating treatment is carried out as an off-line process on the fiber web production line. [8. Apparatus (10,20,30,40,50,60) for pre-calendering, coating and final peeling of a fibrous web, characterized in that the apparatus has a calender 35 with a pre-calendering step (NO, a coating step (15; 15a)). -15d) and a final calendering step (N; N2), which pre-calendering step comprises the calender at least one roll nip or a treatment zone, the final calendering step comprises the same calender's at least a second roll nip or a treatment zone and the coating step (15); arranged in conjunction with the same calender in a position between the pre-calender stage and the final calender stage. Device according to claim 8, characterized in that the calender is a soft calender, machine calender, super calender, multi-type calender or band calender. 10. Device according to claim 8, characterized in that calender is a metal band calender. 11. Device according to claim 9, characterized in that the metal strip scales have two separate metal strip runs (2a, 2b) between which a counter roll (5) is arranged sl, that two treatment zones (Nu N2) for the fiber web (Wt, W2) are formed. and that a coating step (15) is placed at a point between the treatment zones (Ni, N2) such that the fiber web can be passed over a first treatment zone (Ni) acting as the pre-calendering step into the coating step (15) and thence to a second one, which calendering step functioning zone (N2). 20 Device according to claim 8, characterized in that the calender is a multi-type calender (60) having at least two separate roll systems. »