Patent Application
20070042209
The invention relates to multi-ply planar absorbent products and especially 3-plies products made of plies of tissue paper and non-wovens.
The term non-woven (ISO 9092, DIN EN 29092) is applied to a wide range of products which, in terms of their properties, are located between those of paper (cf. DIN 6730, May 1996) and cardboard (DIN 6730) on the one hand, and textiles on the other hand. As regards non-woven a large number of extremely varied production processes are used, such as the air-laid and spun-laced techniques as well as wet-laid techniques. The non-woven includes mats, non-woven fabrics and finished products made thereof. Non-wovens may also be called textile-like composite materials, which represent flexible porous fabrics that are not produced by the classic methods of weaving warp and weft or by looping. In fact, non-wovens are produced by intertwining, cohesive or adhesive bonding of fibres, or a combination thereof. The non-woven material can be formed of natural fibres, such as cellulose or cotton fibres, but can also consist of synthetic fibres, such as Polyethylene (PE), polypropylene (PP), polyurethane (PU), polyester, nylon or regenerated cellulose, or a mix of different fibres. The fibres may, for example, be present in the form of endless fibres of pre-fabricated fibres of a finite length, as synthetic fibres produced in situ, or in the form of staple fibres. The nonwovens according to the invention may thus consist of mixtures of synthetic and cellulose fibrous material, e.g. natural vegetable fibres (see ISO 9092, DIN EN 29092).
A tissue paper is defined as a soft absorbent paper having a low basis weight. One generally selects a basis weight of 8 to 30 g/m2, especially 10 to 25 g/m2 per ply. The total basis weight of multiple-ply tissue products is preferably equal to a maximum of 65 g/m2, more preferably to a maximum of 50 g/m2. Its density is typically below 0.6 g/cm3, preferably below 0.30 g/cm3 and more preferably between 0.08 and 0.20 g/cm3.
The production of tissue is distinguished from paper production by the its extremely low basis weight and its much higher tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5). Paper and tissue paper also differ in general with regard to the modulus of elasticity that characterizes the stress-strain properties of these planar products as a material parameter.
A tissue's high tensile energy absorption index results from the outer or inner creping. The former is produced by compression of the paper web adhering to a dry cylinder as a result of the action of a crepe doctor or in the latter instance as a result of a difference in speed between two wires (“fabrics”). This causes the still moist, plastically deformable paper web to be internally broken up by compression and shearing, thereby rendering it more stretchable under load than an uncreped paper.
Moist tissue paper webs are usually dried by the so-called Yankee drying, the through air drying (TAD) or the impulse drying method.
The fibers contained in the tissue paper are mainly cellulosic fibres, such as pulp fibers from chemical pulp (e.g. Kraft sulfite and sulfate pulps), mechanical pulp (e.g. ground wood), thermo mechanical pulp, chemo-mechanical pulp and/or chemo-thermo mechanical pulp (CTMP). Pulps derived from both deciduous (hardwood) and coniferous (softwood) can be used. The fibers may also be or include recycled fibers, which may contain any or all of the above categories. The fibers can be treated with additives—such as fillers, softeners, such as quaternary ammonium compounds and binders, such as conventional dry-strength agents or wet-strength agents used to facilitate the original paper making or to adjust the properties thereof. The tissue paper may also contain other types of fibers, e.g. regenerated cellulosic fibres or synthetic fibers enhancing, for instance, strength, absorption, smoothness or softness of the paper.
Tissue paper may be converted to the final tissue product in many ways, for example, by embossing or laminating it into a multi-ply product, rolled or folded.
If tissue paper is to be made out of pulp, the process essentially comprises
Paper can be formed by placing the fibers, in an oriented or random manner, on one or between two continuously revolving wires of a paper making machine while simultaneously removing the main quantity of water of dilution until dry-solids contents of usually between 12 and 35% are obtained.
Drying the formed primary fibrous web occurs in one or more steps by mechanical and thermal means until a final dry-solids content of usually about 93 to 97%. In the case of tissue making, this stage is followed by the crepe process which crucially influences the properties of the finished tissue product in conventional processes. The conventional dry crepe process involves creping on a usually 4.5 to 6 m diameter drying cylinder, the so-called yankee cylinder, by means of a crepe doctor with the aforementioned final dry-solids content of the raw tissue paper (wet creping can be used if lower demands are made of the tissue quality). The creped, finally dry raw tissue paper (raw tissue) is then available for further processing into the paper product or tissue paper product according to the invention.
Instead of the conventional tissue making process described above, the use of a modified technique is possible in which an improvement in specific volume is achieved by a special kind of drying within process section b and in this way an improvement in the bulk softness of the thus made tissue paper is achieved. This process, which exists in a variety of subtypes, is termed the TAD (through air drying) technique. It is characterized by the fact that the “primary” fibrous web (like a non-woven) that leaves the forming and sheet making stage is pre-dried to a dry-solids content of about 80% before final contact drying on the yankee cylinder by blowing hot air through the fibrous web. The fibrous web is supported by an air-permeable wire or belt (or TAD-fabric) and during its transport is guided over the surface of an air-permeable rotating cylinder drum (TAD-cylinder). Structuring the supporting wire or belt makes it possible to produce any pattern of compressed zones broken up by deformation in the moist state, also named moulding, resulting in increased mean specific volumes and consequently leading to an increase in bulk softness without decisively decreasing the strength of the fibrous web. Such a pattern is fixed in the area of the TAD-cylinder. Thereafter the pattern is further imprinted between the TAD-fabric and the Yankee-cylinder.
Creping may be conducted also during transfer of the paper sheet from the forming wire directly to the TAD-fabric or via a transfer fabric. For this creping the formingfabric runs faster than the following fabric receiving the sheet (rush transfer). For example, when applying the TAD technique for the production of raw tissue and the usual double-screen sheet formation in c-wrap configuration, for example, the so-called inner sheet-forming screen can thus be operated at a speed that is up to 40% faster than that of the next fabric or that of the subsequent felt, the initially formed and already pre-drained paper web being transferred to the next TAD fabric. This causes the still moist and as a result plastically deformable paper web to be internally broken up by compression and shearing, thereby rendering it more stretchable under load than a paper that has undergone neither “internal” nor external creping. This transfer of still plastically deformable paper web at a differential speed that simultaneously takes effect may also be brought about in other embodiments between a transfer fabric and the so-called TAD imprinting fabric or between two transfer fabrics.
Another possible influence on the softness and strength of the raw tissue lies in the production of a layering in which the primary fibrous web to be formed is built up by a specially constructed headbox in the form of physically different layers of fibrous material, these layers being jointly supplied as a pulp strand to the sheet making stage.
When processing the raw fibrous web or raw tissue paper into the final product (third process section), the following procedural steps are normally used individually or in combination: cutting to size (longitudinally and/or cross cutting), producing a plurality of plies, producing mechanical ply adhesion, volumetric and structural embossing, ply adhesion, folding, imprinting, perforating, application of lotions, smoothing, stacking, rolling up.
To produce multi-ply tissue paper products, such as handkerchiefs, toilet paper, towels or kitchen towels, an intermediate step preferably occurs with so-called doubling in which the raw tissue in the finished product's desired number of plies is usually gathered on a common multiply master roll.
The processing step from the raw tissue that has already been optionally wound up in several plies to the finished tissue product occurs in processing machines which include operations such as repeated smoothing of the tissue, edge embossing, to an extent combined with full area and/or local application of adhesive to produce ply adhesion of the individual plies (raw tissue) to be combined together, as well as longitudinal cut, folding, cross cut, placement and bringing together a plurality of individual tissues and their packaging as well as bringing them together to form larger surrounding packaging or bundles. The individual paper ply webs can also be pre-embossed and then combined in a roll gap according to the foot-to-foot or nested methods.
Hygiene or wiping products primarily include all kind of dry-creped tissue paper, wet-creped paper and cellulose or pulp wadding or all kinds of non-wovens, or combinations, laminates or mixtures thereof. Typical properties of these hygiene and wiping products include the ready ability to absorb tensile stress energy, their drapability, good textile-like flexibility, properties which are frequently referred to as bulk softness, a high surface softness, and a high specific volume with a perceptible thickness. As high a liquid absorbency as possible and, depending on the application, a suitable wet and dry strength as well as an appealable visual appearance of the outer product surface is desired. These properties, among others, allow these hygiene and wiping products to be used, for example, as cleaning wipes such as paper or non-woven wipes, windscreen cleaning wipes, industrial wipes, kitchen paper, or the like; as sanitary products such as for example toilet paper, paper or non-woven handkerchiefs, household towels, towels, and the like; as cosmetic wipes such as for example facials and as serviettes or napkins, just to mention some of the products that can be used. Furthermore, the hygiene and wiping products can be dry, moist, wet or pre-treated in any manner. In addition, the hygiene and wiping products may be folded, interleaved or individually placed, stacked or rolled, connected or not, in any suitable manner.
Due to the above description, the products can be used for personal and household use as well as commercial and industrial use. They are adapted to absorb fluids, for decorative purposes, for packaging or even just as supporting material, as is common for example in medical practices or in hospitals. In terms of their wide variety, hygiene and wiping products are now considered to be everyday products.
From WO 01/36188 A is known a multi-ply absorbent disposable surgical textile, especially a multi-ply absorbent wipe, comprising at least a first and a second outer non-woven ply, and at least one inner film bonded together with adhesive means. The inner film is a thermoplastic copolyester elastomer and a first pattern of discrete adhesive deposits is present on one side of the inner film and a second pattern of discrete adhesive deposits is present on the other side of the inner film, wherein said second pattern at least partly does not coincide with the first pattern. In this document is well described a method of making such multi-ply absorbent structure in which the patterns of discrete adhesive deposits are applied on each side of the inner film, followed by placing the outer plies on said inner film and pressing them.
From WO 96/24485 A1 multi-ply paper laminates are known using controlled adhesive strike-through. A carrier sheet of synthetic spunbond non-woven having suitable airflow characteristics is covered on each side with the less open paper without strike-through. The adhesive is applied in a pattern on one side of the carrier sheet. This laminate is a especially suited for paper products such as disposable table napkins.
U.S. Pat. No. 3,958,055 A1 teaches adhesive bonding of isotropic fiber webs to form pattern bonded composites. The process for manufacturing a non-woven fabric in a single path involves printing the adhesive on one web of cellulosic tissue in a clearly defined fine line pattern, laying the fiber web on the adhesive bearing surface of the tissue web, disposing a second cellulosic tissue web on the fiber web, and hot calendering the three layer composite so as to force the adhesive through the fiber web into the second tissue web while bonding the fibers of reinforcing web in place.
From U.S. Pat. No. 3,650,882 A1 is known a multi-ply paper towel comprising for example three tissue plies. The adhesive is applied either to the inner surface of the outer plies or on both sides of the inner ply in order to achieve ply-bonding between the inner ply and each of the outer plies.
Furthermore, from EP 0679122 B1, EP 0564319 B1 and EP 1017563 B1 a laminated fibrous structure is known comprising at least three tissue plies, wherein the adhesive is applied on each inner surface of the outer plies in order to achieve ply-bonding between each of the outer plies and the inner ply.
It is the technical problem of the invention to provide a multi-ply planar absorbent product and especially a toilet paper or household towel and the like with good ply-bonding especially when an inner ply is used, which is made of a material of low-adhesion ability. “Adhesion Ability” is the ability of a material to bind with another one using a given adhesive and resulting in a ply bonding of an acceptable level. A ply bonding of an acceptable level for tissue products is in a range between 0.08 and 0.3 N/50 mm (measured on a dry material, on the machine direction/mean value of the peaks above the total mean value).
This problem is solved by a multi-ply planar absorbent product, which comprises at least a first and a second outer tissue ply and at least one inner non-woven ply bonded together, with an adhesive, wherein the inner ply is a material of no or low adhesion ability. A first adhesive is present on one side of the inner ply in a first pattern of discrete adhesive deposits and a second adhesive is present on the other side of the inner ply in a second pattern of discrete adhesive deposits, wherein said second pattern at least partly does not coincide with the first pattern. Each of the first and second adhesive penetrates through the inner ply thereby bonding together the inner ply and at least the outer ply on the side opposite to the side where the adhesive is applied.
Preferably at least one of the plies is embossed either separately or in unison. Especially both of the outer plies are embossed and the embossment can be such that sandwiching the inner ply, the outer plies are in “foot-to-foot” contact wherein the adhesive is present at least in some of the “foot-to-foot” areas. If steel rolls are used for embossing in these “foot-two-foot” areas, the necessary pressure is achieved and applied on the adhesive.
According to a further improvement the embossment is such that sandwiching the inner ply, the outer plies are in “nested” contact wherein the adhesive is present in at least some of the “nested” areas. Preferably the adhesive surrounds mechanically fibers of the inner ply according to an interlocking grip. Together therewith the material of the non-woven inner ply can be a hydrophilic material. Especially the material is hydrophilic spunbond of low grammage. Therewith the tissue of the outer plies may be a through-air-dried (TAD) paper of about 18 g/m2 and the material of the inner ply then might be a hydrophilic spunbond non-woven of low grammage of about 9 gsm.
Furthermore, the problem is solved by a process for manufacturing a multi-ply planar absorbent product, which comprises at least a first and a second outer tissue ply and at least one inner non-woven ply made of a material of low adhesion ability bonded together, with an adhesive, said process comprising the steps of applying adhesive on one side of the inner ply in a first pattern of discrete adhesive deposits, applying adhesive on the other side of the inner ply in a second pattern of discrete adhesive deposits wherein said second pattern at least partly does not coincide with the first pattern. Then the first and the second tissue plies are placed on those sides of the inner ply carrying the first second pattern of adhesive respectively. Afterwards the plies are pressed together at least in those areas carrying the discrete adhesive deposits to cause them to penetrate through the inner ply thereby bonding together at least the inner ply and the ply lying opposite to the application side of the respective adhesive deposit.
By the invention a product is achieved in which in an easy manner, an appropriate ply bonding can be achieved when the inner ply is of no or low adhesion ability.
The invention is described hereafter on the basis of the following drawings illustrating some embodiments according to the present invention.
a to
As an example a three-ply product is described. These are the plies A, B and C. The plies A and C are named the outer plies and the ply B the inner ply. As an example the outer plies are made of a material being 18 g/m2 TAD (through air-dried) tissue paper. The material of the inner ply B is for example spunbond hydrophilic low grammage non-woven of 9 gsm. Such a non-woven has a low adhesion ability especially when the fiberes are covered by a surfactant. For instance as non-woven is used a 100% Polypropylene based hydrophilic spunbond (supplied from Supplier Union, 9 gsm, reference S0900PPW).
For example the non-woven is hydrophilic due to application of a surfactant while producing it.
In the following description an embodiment is shown where an adhesive is used for ply-bonding.
In
The manufacturing process as a principle is illustrated in
By the pressure exerted on the adhesive the adhesive penetrates through inner ply B in order to be fixed there so that the adhesive penetrated through the inner ply B causes ply-bonding with the adjacent outer ply being of tissue paper having a high adhesion ability.
The adhesive used herein may be for instance BVOH adhesive of high dry content (Atesin 1900, 16% for instance, Henkel-Polyvinyl Acetate Dispersion). Another adhesive is Polyvinyl alcohol and Plyethylenglycol based (SWIFT L998/4). It has a viscosity of 18.000 mPas at 26° C.
The manufacturing principle is more detailed illustrated in three embodiments shown in
Embodiments different from the one illustrated in
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP04/02077 | Mar 2004 | US |
| Child | 11513024 | Aug 2006 | US |
