WO2001002159A1

WO2001002159A1 - Method and calender device for calendering an absorbent layer formed from fiber material by means of a dry-forming technique

Info

Publication number: WO2001002159A1
Application number: PCT/US2000/018819
Authority: WO
Inventors: Juha Sorvari; Paavo Hyvarinen; Seppo FÖHR
Original assignee: Bki Holding Corporation
Priority date: 1999-07-07
Filing date: 2000-07-07
Publication date: 2001-01-11
Also published as: AU6084400A

Abstract

Disclosed is a method and calender device for calendering an absorbent layer formed from fiber material by means of a dry-forming technique. The calender device (1) comprises at least two opposing calender rolls (6a and 6b), forming a nip (7) into which the dry-formed material web (3) can be fed, and one endless transfer wire (8) on one side of the dry-formed material web (3). The endless transfer wire (8) includes felt material. One of the calender rolls is an embossed calender roll (6a), and the material web (3) can be calendered against the endless transfer wire (8) by means of the embossed calender roll (6a) so that an embossed pattern corresponding to the patterning of the embossed calender roll (6a) is formed on the material web (3).

Description

METHOD AND CALENDER DEVICE FOR CALENDERING AN ABSORBENT LAYER FORMED FROM FIBER MATERIAL BY MEANS OF A DRY-FORMING TECHNIQUE

Background of the invention

5 The object of the present invention is a method for calendering an adsorbent layer

formed from fibre material by means of a dry- forming technique, in which method the dry-

formed material web is conveyed on an endless transfer wire to a nip formed by calender rolls

and calendered by means of the calender rolls against the endless transfer wire.

The object of the invention also comprises a calender device for calendering an

0 absorbent layer formed from fibre material by means of a dry-forming technique, the said

calender device comprising at least two opposite calender rolls, forming a nip into which the dry-formed material web can be fed, and one endless transfer wire on one side of the dry-

formed material web.

In the manufacture of non- woven hygiene products, for example, an absorption layer

5 is first formed by a dry-forming technique, to the said layer being added a binder or bonding

fibres which bind the material web formed into a porous material layer due to the effect of

heat. The absorption layer may also consist of several layers placed on top of one another,

depending on the desired thickness.

Material layers made in this way are used for the manufacture of various types of

0 nappies, feminine sanitary towels, and surgical dressings for hospitals. Hygiene products to which a superabsorbent agent has been added locally in order to improve absorbency are also known.

Different products usually serve to provide the desired end result as regards the

functioning of the product. However, producing, for example, areas of varying absorbency

in the same product usually requires various process stages, such as the addition of

superabsorbent particles, additional calendering, etc. The easiest way to produce areas of

poorer absorbency is to compact them by separate calendering, and the advantage of such

areas is that they convey liquid better and more quickly to the different parts of the product.

On the other hand, as dry-formed products become more common in the home, too,

for example, in the form of paper towels and napkins, attention must also be paid to other

properties of the products than just absorbency. Among other things, the outward appearance,

"feel" and identifϊability of the products are important properties in products aimed at

consumers. Currently known dry-formed products intended for end users are not - despite

their good properties - sufficiently distinguishable from conventional paper products to justify

their higher price.

The aim of this invention is to achieve a method and device for manufacturing the type

of absorbent layer by means of which both absorption layers patterned in a useful manner, e.g.

for hygiene products, and individualised products differing from conventional products in

outward appearance, feel and properties, can easily be produced from dry-formed fibre

material.

There are various previously known methods and devices for calendering an absorbent

layer formed from fibre material by a dry-forming technique.

From U.S. Patent 4,668,322, hereby incorporated by references a method and device

are known for embossing a dry roll of, for example, kitchen toweling. The dry fibre web on the forming wire is embossed while the web is in the unsized state and while it travels through the two rolls which effect the embossing, supported by the pressure-resistant support wire,

which means that the said wire also travels through the rolls. The said support wire may, for

example, be a woven belt made of steel or hard plastic.

The problem with the arrangement described above is that the fibre web is pressed by means

of a hard embossed roll against a hard support wire, as a result of which at least one of the

hard components, either the embossed roll or the support wire, will wear out.

Summary of the Invention

The object of the invention is a method and calender device which will eliminate the

above problem.

The aims of the invention are achieved by a method which is characterised by the fact

that the patterning of the material web is formed with the help of an endless transfer wire

comprising felt material and two opposite calender rolls, one of the calender rolls being

embossed, and that the dry-formed material web is pressed by means of the embossed

calender roll against the endless transfer wire comprising felt material so that an emboss

pattern corresponding to the patterning of the embossed calender roll is formed on the surface

of the calendered material web.

The aims of the invention are achieved by means of a calender device which is

characterised by the fact that the endless transfer wire comprises felt material, that one of the

calender rolls is an embossed calender roll, and that the material web can be calendered

against the endless transfer wire by means of the embossed calender roll so that an embossed

pattern corresponding to the patterning of the embossed calender roll is formed on the material web.

The invention is based on the fact that a dry- formed material web is pressed by means of a patterned calender roll against a transfer wire comprising felt material.

The advantage of the solution relating to the invention is that its application enables

a calender device with a long service to be obtained, since the patterned steel roll withstands

wear and the transfer wire comprising felt material withstands pressure and is at the same time

resistant to wear.

This type of solution gives an extremely good embossing result.

Brief Description of the Figures

The invention is now described in greater detail in relation to the preferred

embodiments, with reference to Fig. 1 which schematically depicts a dry-forming line

comprising the calender device relating to the invention.

Detailed Description of the Invention

Fig. 1 shows a dry-forming line which comprises the calender device 1 relating to the

invention.

In the dry-forming line relating to the Figure, a material web 3 is formed on the

forming web 2 in a manner known as such, in one or more stages by means of forming boxes

4a-4c, that is, formers. In conjunction with the forming wire 2 shown in the Figure suction

boxes 5a-5c are also arranged by means of which suction boxes the material web 3 is sucked

against the forming wire 2.

The Figure shows the type of dry- forming line which comprises three forming boxes

4a-4c and three suction boxes 5a-5c.

The fibres which form the material web 3 may be chemical pulp fibre and/or relatively

long-fibred mechanical pulp, which is bonded after calendering by latex and by heat. The fibres in the material web 3 may also consist partly, or even completely, of synthetic fibres, in which case the material web 3 is bonded after calendering by means of the so-called

thermobonding process. The plastic fibres may be of any suitable thermobonding type, for

example bicomponent fibres, with a core of polypropylene and a polyethylene sheath. The

material web 3 may comprise 15-85% wood fibre (chemical pulp fibre), 10-70% plastic fibre,

and 5-75% superabsorbent particles. The basis weight of the material web 3 formed may be in the order of 80 g/m2.

After the forming stage the material web 3 is transferred to the calender device 1

comprising at least two opposite calender rolls 6a and 6b, forming a nip 7 into which the dry-

formed material web 3 can be fed. The calender device 1 also includes an endless transfer

wire 8 on one side of the dry-formed material web 3. The transfer wire 8 comprises felt

material. The transfer wire 8 is preferably made of so-called paper machine press felt. One

of the calender rolls is an embossed calender roll 6a. The material web 3 can be calendered

against the embossed transfer wire 8 by means of the embossed calender roll 61, so that an

embossed pattern corresponding to the patterning of the embossed calender roll 6a is formed

on the material web 3.

The embossed calender roll 6a can preferably be heated, for example, to a temperature

ranging between 100 and 250°C, more preferably to a temperature ranging between 180 and

220°C. The embossed calender roll 6a has preferably at least a steel surface on which the

patterning (not shown) has been made.

The dry-forming line relating to the Figure also comprises a first drier wire 9 and a

second drier wire 10.

At the first drier wire 9 is the first binder station 11 , which has in conjunction with it

the first through-flow furnace 12. At the second drier wire 10 there is correspondingly a second binder station 13 , which has in conjunction with it a second through- flow furnace 14.

After the second drier web 10, the bonded material web 15 may be calendered by

means of the pair of rolls 16.

It is obvious to a person skilled in the art that as technology develops, the basic idea of the invention may be implemented in many ways. The invention and its embodiments are

thus not limited to the above examples, but may vary within the scope of the claims.

Claims

IN THE CLAIMS:

1. A method for calendaring an absorbent layer formed from fibre material by means of a dry-forming technique, in which method the dry-formed material web (3) is conveyed on an endless transfer wire (8) to a nip (7) formed by the calendar rolls (6a and 6b) and calendared by the calendar rolls (6a and 6b) against the endless transfer wire (8); characterized in that the patterning of the material web (3) is formed by means of the endless transfer wire (8) comprising felt material and two opposite calendar rolls (6a and 6b), one of the calendar rolls (6a) being embossed, and that the dry-formed material web (3) is pressed by means of the embossed calendar roll (6a) against the endless transfer wire (8) comprising felt material so that an embossed pattern corresponding to the patterning of the embossed calendar roll (6a) is formed on the surface of the calendered material web (3).

2. A method as claimed in claim 1 , characterized in that the embossed calendar roll (6a) is heated to a temperature ranging between 100 and 250°C, preferably to a temperature ranging between 180 and 220°C.

3. A calendar device for calendering an absorbent layer formed from fibre material by means of a dry-forming technique, the said calendar device ( 1 ) comprising at least two opposite calendar rolls (6a and 6b), forming a nip (7) into which the dry-formed material web (3) can be fed, and one endless transfer wire (8) on one side of the dry-formed material web (3), characterized in that the endless transfer wire (8) comprises felt material, that one of the calendar rolls is an embossed calendar roll (6a), and that the material web (3) can be calendared against the endless transfer wire (8) by means of the embossed calendar roll (6a) so that an embossed pattern corresponding to the patterning of the embossed calendar roll (6a) is formed on the material web (3).