WO2002042559A1

WO2002042559A1 - Multi-ply wiping product comprising absorbing material

Info

Publication number: WO2002042559A1
Application number: PCT/EP2001/013326
Authority: WO
Inventors: Thomas Heilemann; Bernd Lofink; Harald Harlacher
Original assignee: Sca Hygiene Products Gmbh
Priority date: 2000-11-21
Filing date: 2001-11-16
Publication date: 2002-05-30
Also published as: DE10057518A1; AU2002216044A1

Abstract

The invention relates to a multi-ply wiping product comprising two or more plies of tissue paper. Discrete liquid-absorbing zones (4) of an absorbing material (7) are added to the wiping product. These absorbing zones are located between at least two adjoining plies (5, 6). The absorbing material may be selected from the following materials, such as an absorbent clay, e.g. bentonite; superabsorber, e.g. hydrogel; natural cellulose fiber material, e.g. chemical pulps, mechanical pulps; CTMP, such as DFR and chemi-mechanical pulp. The absorbing material (7) is inserted in pockets (8) formed by ply bonding between adjoining plies. Ply bonding is achievable either by embossing or gluing. The absorbing material (7) is able to bond to at least one of the adjoining plies by means of the adhesive. This multi-ply product has a substantially improved absorptive capacity for liquids.

Description

MULTI-PLY WIPING PRODUCT COMPRISING ABSORBING MATERIAL

Technical Field

The invention relates to a multi-ply wiping product consisting of tissue paper, be it kitchen towels, toilet paper, facial cleansing wipes, paper handkerchiefs, etc.

Prior Art

Such a wiping product is used as a variety of tissue paper products. Various kinds of such products are available on the market, for example, in the form of kitchen towels, toilet paper, facial cleansing wipes, paper handkerchiefs, etc. Wipes of this kind are highly versatile in use and are suitable for a wealth of applications, from coarse wiping to wiping in highly demanding environments such as in printing and paint shops or in clean-room environments.

One disadvantage of the tissue paper products and wipes available on the market is their limited absorbency. Good multi- ply tissue paper products currently on the market absorb approx.

400 to 500 g water/m^ absolutely or approx. 9 to 11 g water/g fiber material. Both values apply for two- to three-ply products (measured as per DIN 54 540 Part 4 of June 1989) .

Diverse efforts have been made to improve the absorbency of a tissue paper product or of a wipe. Originally this involved attempts to produce a thicker paper or multi-ply product.

EP 0 851 950 Al describes a multi-ply tissue paper product including at least three plies, the middle ply of which consisting mainly of highly absorbing mechanical pulp incorporating no wet-strong means. This product has a relative water absorbency of but 5.2 g/g fiber material.

US-PS-A-4, 360, 021 concerns an absorbent article and not wiping products. The absorbent article is made up of discrete zones of absorbent material which is enclosed between two tissue sheets. The problem to be solved with this subject matter is how to split a single big absorbent zone into many discrete smaller zones. With such an absorbent article the purpose is to be able to distribute and absorb a large amount of liquid which is deposited on a small area of the product. Thereby the absorbent article does need a high concentration of absorbent material on a quite small area. Such a product will be quite bulky, stiff and inflexible.

Summary of the Invention

The invention is based on the problem (object) of providing a multi-ply wiping product consisting of tissue paper having an improved liquid absorbency.

This object is achieved by a multi-ply wiping product of tissue paper in which between at least two adjoining plies of tissue paper discrete liquid-absorbing zones of an absorbing material are located which has a higher liquid absorbency than the adjoining plies. Preferably only tissue paper plies are present, between which the zones are provided.

The size, distribution density and spacing of the absorbing zones need to be adapted to the particular application of the product. If the zones are too big and/or are arranged too dense or close one to another, the sheet product becomes too stiff and inflexible so that, for example, satisfactory wiping is no longer assured. On the other hand, if the zones are too small less liquid can be absorbed.

"Size" in this context is understood to mean both the area (A) taken up by the individual absorbing zones between the plies and the height (H) of the individual zones. "Distribution density" is understood to be the number of absorbing zones per area unit of the sheet product . The spacing (L) of the absorbing zones from each other is measured between the nearest edges of two zones .

An advantageous area (A) of the absorbing zones is in the range

0.01 cm² to 6 cm², preferably 0.01 cm² to 4 cm² and most preferred 0.05 cm² to 1 cm². These zones may take various shapes, e.g. in the shape of a rectangle, a square, a circle, a triangle or a polygon. The zones may also be irregular in shape. The height (H) is in the range 0.01 cm to 2 cm, preferably 0.05 cm to 1 cm and most preferred 0.1 cm to 0.5 cm. The sheet product may also contain absorbing zones differing in size. The flexibility of the absorbing material also plays a role in the possible size of the absorbing zones. If the absorbing material is relatively flexible, for example in making use of mechanical pulp, larger zones may be employed without the web losing elasticity or flexibility. The situation is different when the zones consist of hard-compressed bentonite.

In accordance with one preferred embodiment the area of all absorbing zones amounts to max. 30%, preferably 20% and most preferred 10% of the area of the sheet product.

The absorbing zones consist of a liquid-absorbing material which may be organic or inorganic. The absorbing material can, but need not have a higher relative absorption capacity (g absorbed liquid/g absorbing material) than the tissue paper and/or the non-woven fabrics . It is favourable for the absorbing material to have a relative absorption capacity, which is 20 %, preferably 50 % and most preferably 100 % higher than the relative absorption capacity of the tissue paper and/or the non- woven fabrics. Suitable inorganic material is an absorbent clay such as e.g. bentonite. Suitable organic materials are natural, cellulose fiber materials such as chemical pulp, mechanical pulp, CTMP, HTCTMP and chemi-mechanical pulp. DFR, a substance of SCA Hygiene Products, Ostrand, Sweden is an example of a suitable absorbent cellulose fiber material having a high absorptive capacity. DFR is a compressed web having a basis weight in the range 30 to 2000 g/m² and a density of 0.2 to 1.0 g/cm³. DFR is further described in WO 94/10956. Superabsorbers having suitable properties may likewise be used, such as, for example, Saalsorb 88 made by Allid Colloids GmbH.

Advantageously, the absorbing material may be put to use pelletized. The pellet may consist of agglomerated powdery or fibrous material compressed into a pellet. The absorbing material may also be achieved by size-reduction of larger components. The absorbing material may also quite naturally correspond to the shape of a pellet. The pellets can be adapted in size and shape to an embossing design. The size of said pellets corresponds to the aforementioned values for the absorbing zones. The flexibility of the absorbing material also plays a role in the possible size of the pellets. In case the absorbing material is relatively flexible, i.e. when it is, for example, mechanical pulp, larger pellets may be used without the web losing flexibility. The situation is different with pellets of hard-compressed bentonite.

One advantageous area (A) of the absorbent pellet is in the range 0.01 cm² to 6 cm², preferably 0.01 cm² to 4 cm² and most preferred 0.05 cm² to 1 cm². The pellets may be of any known shape e.g. in the shape of a rectangle, a square, a circle, a triangle or a polygon. The pellets may also be irregular in shape. The height (H) is advantageously 0.01 cm to 2 cm, preferably 0.05 cm to 1 cm and most preferred 0.1 cm to 0.5 cm.

In accordance with another advantageous embodiment the absorbing material may be powdery or fibrous .

In accordance with yet another preferred embodiment the absorbing material may be arranged in pockets between adjoining or superposed plies. These pockets are preferably formed by portions having ply bonding enclosing a portion having no ply bonding. The ply bonding may be achieved either purely mechanically by compression, e.g. by embossing or knurling, or chemimechanically by embossing and gluing or purely chemically by gluing. The portions of the ply bonding may either form a smooth transition or be discontinuous. The discontinuous ply bonding portions may consist of dotted or solid lines.

In producing the ply bonding by gluing, an adhesive as used conventionally in paper processing may be employed, such as for example starch or polyvinyl alcohol (WO 97/11226) . According to this document polyvinyl acetate and carboxymethyl cellulose may also be put to use. When using polyethylene as the tissue adhesive, it needs to be melted (US 4,867,831) . Such hot melts may also be applied by spraying.

The invention is compatible with all kinds of embossing. Preferably, however, an embossing is used in which the protuberances of the embossing pattern may form the aforementioned pockets. However, embossing must not negatively affect the absorbing material. This is the reason why foot-to- foot, or punta punta, embossing or embossing by an embossing roll having protuberances against a hard, smooth roll is preferred. Nested (or DESL (DERW) ) embossing may also be used when the embossing pattern is suitable therefor.

Advantageously, the absorbing material may be affixed by gluing one or both plies. In this case an adhesive may be applied, for example, in a specific pattern to one ply. The absorbing material is then applied to this bonding substance before the second ply is brought together with the first ply.

In accordance with a further advantageous embodiment the absorbing material may be secured by a combination of direct gluing to one or both plies and enclosing the absorbing material in the pockets by the ply bond.

Tissue paper consists in general and for example here of plant fibers, i.e. cellulose fibers. The tissue paper is formed on a fabric by dewatering an aqueous fiber suspension. The thus formed fiber web is then dried (DIN 6730, May 1996) . Tissue paper is a porous absorbing paper which is normally elastic due to wet or dry creping or rush-transfer of the paper web. For the invention all conventional kinds of multi-ply tissue papers having a basis weight in the range 8 to 60 g per ply may be used. The various plies may be the same or differ, for example, they may differ by the following properties: method of production, e.g. tissue dried by conventional methods or by through-air drying (TAD); basis weight; fiber composition or wet and/or dry strength.

Brief Description of the Drawings

The invention will now be detailed purely by way of examples with reference to the drawing in which:

Fig. 1 is a schematic view of a prior-art tissue paper product ;

Fig. 2 is a schematic view of a preferred embodiment of the invention; and

Fig. 3 is a schematic section view taken along the section line III-III in Fig. 2.

Detailed Description of Example Embodiments of the Invention

Referring now to Fig. 1 there is illustrated a schematic view of an embossed web of tissue paper 1 known from prior art. The circles 2 and 3 indicate the embossing pattern, each circle representing a protuberance thereof.

Referring now to Fig. 2 there is illustrated an embossed two-ply web 1 of two-ply tissue paper 5,6 in accordance with the invention. An embossing pattern is represented schematically on the web by small circles 2, 3. The shaded larger circles identify the location of absorbing zones 4 for absorbing liquid or water. The zones 4 may have a color different to the remainder of the product, but not necessarily so. When, e.g. the absorbing material in the absorbing zones is colorless or white, the absorbing material is hardly discernible from the outer side of the product. However, if the absorbing material is colored, the color may be made use of for decorative purposes. The absorbing zones may also be characterized by the use of colored adhesive for gluing the absorbing material. However, characterizing the absorbing zones may also be achieved by a pattern printed on the web. The absorbing zones cover roughly 1.5% of the area of the two-ply web.

Referring now to Fig. 3 there is illustrated the web as shown in Fig. 2 as taken along the section line III-III. The absorbing material 7 of the absorbing zones 4 is enclosed by two tissue plies 5, 6 by means of protuberances of the individual plies which are connected with each other foot-to-foot.

In the following tests the absolute water absorption and the relative water absorption were measured in accordance with DIN 54 540 Part 4 of June 1989.

1. Comparative Test:

The water absorption of a normal, three-ply tissue paper was measured. The tissue paper concerned is a normal "Zewa Wisch und Weg" 1997 product of SCA Hygiene Products GmbH having a basis weight of 53 g/m² and an embossing pattern the same as that show in Fig. 1. Ply bonding is by foot-to-foot embossing with gluing. The results are listed in Table 1.

Test 1

A multi-ply web in accordance with the invention was produced manually by inserting pellets of bentonite into pockets 8. The pockets were formed between two plies of the three-ply tissue paper surrounded by protuberances (see Fig. 2) . The same tissue paper was used as in the comparative test. One side of the pockets was cut open in a paper ply sufficiently so that one pellet of bentonite per pocket could be inserted. Before the pellets were inserted they were taped with a water-soluble double-sided adhesive produced by Nitto Tape. The inserted bentonite pellets had an area of approx. 0.08 cm², a height of 0.1 cm and covered roughly 0.8 to 0.9% of the area of the multiply tissue paper. The spacing between the edges of the nearest pellets was approx. 2.6 cm. The multi-ply web consists of 38 % by weight bentonite relative to dry paper. The water absorption is listed in Table 1.

The pellets were produced by compressing dried bentonite made by Roth Vetriebsgesellschaft . The bentonite was compressed at 500 kPA into round wafers of approx. 10 mm diameter. These wafers were then pelletized to produce pellets of approx. 4 mm diameter. Test 2 :

A multi-ply web in accordance with the invention was produced manually by applying between two plies pellets of superabsorber Salsorb 88 made by Allid Colloids GmbH in pockets 8. The pockets were formed between two plies of the three-ply tissue paper by being surrounded by embossed protuberances (see Fig. 2). The same tissue paper was used as in the comparative test. One side of the pockets was cut open sufficiently so that one pellet of superabsorber per pocket could be inserted. The superabsorber pellets were secured by a water-soluble double- sided adhesive tape produced by Nitto Tape.

The inserted superabsorber pellets had an area of 0.2 cm² and a height of 0.03 cm. The spacing between the edges of the nearest pellets was approx. 2.5 cm. The tissue paper product consists of 9 % by weight superabsorber relative to dry paper. The water absorption is listed in Table 1. Table 1:

As evident from the Table the absolute water absorption was significantly increased by making use of the absorbing material in additional discrete absorbing zones. The low relative water absorption of the product employing pellets of bentonite is explained by the high density of the bentonite pellets. However, the consumer is more interested in the absolute water absorption since it is primarily the absorbency per sheet of tissue paper that is experienced.

Claims

Patent Claims

1. A multi-ply wiping product comprising two or more plies of tissue paper, characterized in that discrete liquid-absorbing zones (4) are located between at least two adjoining plies (5, 6) of tissue paper, with the zones consisting of an added absorbing material (7) .

2. Multi-ply wiping product as set forth in claim 1, characterized in that the material of the absorbing zones is selected from the following materials, such as an absorbent clay, e.g. bentonite; superabsorber, e.g. hydrogel; natural cellulose fiber material, e.g. chemical pulps, mechanical pulps;

CTMP, such as DFR and che i-mechanical pulp.

3. Multi-ply wiping product as set forth in at least one of the claims 1 to 2 , characterized in that the absorbing material (7) is present in the form of pellets .

4. Multi-ply wiping product as set forth in at least one of the claims 1 to 2 , characterized in that the absorbing material (7) is powdery or fibrous.

5. Multi-ply wiping product as set forth in at least one of the claims 1 to 4, characterized in that the absorbing material (7) is arranged in pockets (8) formed by ply bonding between adjoining plies.

6. Multi-ply wiping product as set forth in claim 5, characterized in that the ply bonding is produced by- mechanical compression.

Multi-ply wiping product as set forth in claim 5, characterized in that the ply bonding is produced by an adhesive.

Multi-ply wiping product as set forth in at least one of the claims 2 to 4 , characterized in that the absorbing material (7) bonds to at least one of the plies by means of an adhesive.

9. Multi -ply wiping product as set forth in at least one of the claims 1 to 8 , characterized in that said absorbing zone (4) takes up an area in the range 0.01 cm² to 6 cm², preferably 0.01 cm² to 4 cm² and most preferred 0.05 cm² to 1 cm .

10. Multi-ply wiping product as set forth in at least one of the claims 1 to 9, characterized in that said absorbing zones (4) take up max 30%, preferably 20% and most preferred 10% of the area of the multi-ply product.

11. Multi-ply wiping product as set forth in at least one of the claims 1 to 10, characterized by said spacing (L) between two absorbing zones (4) being in the range 0.1 cm to 20 cm, preferably 0.5 cm to 15 cm and most preferred 1 cm to 10 cm.

12. Multi-ply wiping product as set forth in at least one of the claims 1 to 11, characterized in that the absorbing material has a relative absorption capacity which is 20 %, preferably 50 % and most preferably 100 %, higher than the relative absorption capacity of the tissue paper .

13. Multi-ply wiping product as set forth in at least one of the claims 1 to 12, characterized in that said tissue paper consists only of cellulose fibers

14. Multi-ply wiping product as set forth in at least one of the claims 1 to 13, characterized in that only tissue paper plies are given.