Method for sizing a multi-ply fiber web and a forming section for a multi-ply fiber web

Patent metadata

Field	Value
Publication number	US-11299857-B2
Application number	US-201916601171-A
Country	US
Kind code	B2
Filing date	Oct 14, 2019
Priority date	Oct 15, 2018
Publication date	Apr 12, 2022
Grant date	Apr 12, 2022

Abstract

A method for forming a multi-ply fiber web in which least part of the sizing of the multi-ply fiber web is provided by applying sizing agent in the form of foam by a curtain type application device (C10, C20) in between at least two layers of the multi-ply fiber web in the forming section. The invention also relates to a forming section for a multi-ply fiber web having at least one twin-wire forming part formed between a wire (10) for the bottom layer and a wire (20) for the top layer of the multi-ply fiber web, where the layers are joined, and the treated layers combined. The forming section has a curtain type application device (C10, C20) for applying sizing agent in the form of foam in between two layers of the multi-ply fiber web in the forming section of a multi-ply fiber web production line.

First claim

We claim:

1. A method for forming a multi-ply fiber paper or board web, comprising the steps of:
forming a first fiber layer of the paper or board web on a first wire in a fiber web former so the first fiber layer has a first side in contact with the first wire, and a second side opposite the first side;
forming a second fiber layer of the paper or board web on a second wire in the fiber web former so the second fiber layer has a first side in contact with the second wire, and a second side opposite the first side;
applying a sizing agent, at least part of which forms a foam, by at least one curtain application device to at least one of the second side of the first fiber layer and the second side of the second fiber layer;
forming a multi-ply fiber web in a twin-wire forming part of the former by bringing the second side of the first fiber layer on the first wire into engagement with the second side of the second fiber layer on the second wire so that the sizing agent is between the first fiber layer and the second fiber layer and the first wire and the second wire form the twin-wire forming part of the former; and
conveying in the twin-wire forming part of the former the sizing agent from one of the first fiber layer of the paper or board web and the second fiber layer of the paper or board web over a boundary therebetween into the other of the first fiber layer of the paper or board web and the second fiber layer of the paper or board web so that the sizing agent enhances ply-bond strength.

2. The method of claim 1 wherein the step of applying the sizing agent by at least one curtain application device is done such that the at least one curtain application device does not contact the first fiber layer and does not contact the second fiber layer.

3. The method of claim 2 wherein the step of applying the sizing agent comprises passing the sizing agent through a slot in the at least one curtain application device.

4. The method of claim 1 wherein at least one device for removing water is positioned below at least one of the first wire and the first side of the first fiber layer and the second wire and the first side of the second fiber layer at a location below the at least one curtain application device.

5. The method of claim 1 wherein conveyance and penetration of the sizing agent into the multi-ply fiber web over a boundary formed between the first fiber layer and the second fiber layer is guided by a suction device at a beginning of the twin-wire forming part.

6. The method of claim 1 further comprising the step of using an air guide to turn a boundary air flow off a running direction of at least one of the first fiber layer second side and the second fiber layer before the step of applying a sizing agent by said at least one curtain application device.

7. The method of claim 1 wherein conveyance and penetration of the sizing agent into the multi-ply fiber web over the boundary formed between the first fiber layer and the second fiber layer is by a combining roll at the beginning of the twin-wire forming part positioned inside the second wire which forms an upper wire loop, the combining roll being positioned after the application of the sizing agent in the form of foam by the curtain application device.

8. The forming section of claim 7 wherein conveyance and penetration of the sizing agent into the multi-ply fiber web over the boundary formed between the first fiber layer and the second fiber layer is guided by a sleeve roll positioned inside the first wire which forms a lower wire loop.

Assignees

• Valmet Technologies Inc

Inventors

• Pietikäinen Reijo
• Poikolainen Antti
• Cecchini Juan
• Virkkunen Teuvo

Classifications

• D21H21/56

  Foam · CPC title

• D21F11/002

  by using a foamed suspension · CPC title

• D21H23/48 Primary

  Curtain coaters · CPC title

• D21H21/16 Primary

  Sizing or water-repelling agents · CPC title

• D21H21/28

  Colorants {; Pigments or opacifying agents} · CPC title