DISPOSABLE WIPING ARTICLE AND ITS MANUFACTURING PROCESS

DESCRIPTION

OBJECT OF THE INVENTION

The present invention belongs to a group of disposable wiping articles used normally for hygiene and personal care, or for domestic cleaning, for example.

The purpose of the invention is to develop a multi-layered wipe, soft to the touch, which allows for water absorption, while avoiding the breakdown and loss of the cellulose fibres and optimizing cost factors and the reduction of the volume of the product and its breaking up when wet.

It is also an aim of the invention that patterns and words can be printed easily and are clearly visible and lasting.

The other aim of the invention is its processing and manufacture.

BACKGROUND TO THE INVENTION

Demand for nonwoven materials has increased considerably in recent years and its use is widespread in various fields, especially in the manufacture of diapers and wipes to name two examples.

Nonwoven production is a three stage process: layer formation, bonding of the layer and final finish.

In the first stage different techniques can be employed, such as carding.

Another method is known as "airlaid" which comprises passing the fibres

through an air current and then through a perforated drum in order to produce a very soft layer. Another technique is that known as "spunlaid" in which polymeric melted fibres are extruded and cooled when laid on a belt thereby forming a uniform layer. "Wetlaid" is yet another method which consists of mixing water with the fibres which cross a filtered screen, eliminating the water and dried by the pressure of rollers.

The layers obtained in this way are very fine and need to be made more substantial by being joined together by means of chemical, thermal or mechanical adhesion. One mechanical method which deserves mention is that of "hydroentanglement", normally employed in carded and wetlaid layers and consists in the use of water under high pressure to join the fibres.

Finally, finishing methods depend on customer needs and the properties required in each layer, such as so they are conductors, flame retardant, absorbent etc.

Patent US 2005/0129897 refers to a cleaning product which consists of multiple abrasive layers, an absorbent underlayer and are structured in such a way that they stay together until worn out when they come apart. In this case the absorbent layer normally consists of cellulose and the abrasive layer preferably includes a layer of "meltspun".

It is worth pointing out that a common problem in disposable wiping articles and tissues is that the fibres come apart as much when wet as when dry, sticking to things they are applied to and once wet, breaking up easily due to their low mechanical resistance when wet.

In the case of paper, carded layers were used to provide softness and then airlaid layers were used to speed up the process in the ongoing development of wipes, in the case of paper.

In addition, many attempts have been made to improve the appearance of these nonwovens by means of designs drawn on their surface.

Spunbonded layers do not take dye readily due to their polymeric content, in particular polypropylene, which is a hydrophobic material which repels dye, requiring that the material be treated first to facilitate their adhesion.

DESCRIPTION OF THE INVENTION

The present invention has as its aim the resolution of the afore-mentioned problems, and is made up of three layers, two layers of nonwoven, which could be spunlaid or spunbonded and an inner layer of tissue between them, forming a structure which prevents the loss of cellulose fibres from the tissue layer.

The nonwoven layers provide softness and allow water to pass through, being therefore, ideal for this application.

The tissue layer provides absorption and facilitates the production of wet wipes (with added lotion) or dry wipes (with absorbency).

In a preferred embodiment of the invention the tissue layer would have a number of perforations which facilitate the adhesion between the spunlaid or spunbonded layers.

It is thought that these perforations can have various shapes such as stars, logos, teddy bears etc. which confer a decorative character on the final product, as they can be seen through the nonwoven layers of low grammage. It has been demonstrated that the quality of the impression on the tissue layer is excellent, much better than that seen in other materials, for which reason the invention suggests that the tissue layer takes a dyed image in

combination with the use of spunbonded or spunlaid layers of very low grammage which allow the impressions reflected in the tissue layer to be seen through the spunbonded or spunlaid layer. It is thought that the ideal grammage of the spunbonded or spunlaid layer would be between 4 and 16 g/m2, preferably between 5 and 13g/m2.

These imprints could be made in different colours and could be logos, pictures, etc.

In this way the product gains an attractive appearance with imprints which are normally hidden by the outer layers of spunbonded or spunlaid nonwoven. In addition, as the dye does not come into contact with the skin, they can be of a lower quality than those used in other cases, apart from making for easier adhesion to the tissue layer. The resulting impression is therefore more economical than that of a composite.

The solution provided by this invention is more economical than other hitherto known solutions of joining layers, such as that of adding synthetic fibres to the tissue layer so that it bonds better to the external layer which has the negative effect of reducing its absorption capacity in comparison with the present invention for a wipe of the same weight. This is due to the need to reduce the number of cellulose fibres when synthetic fibres are added.

As the present invention of a perforated tissue layer provides equal absorption in a lighter wipe it is clearly a satisfactory, cost-effective solution.

The wipe which is the aim of this invention does not rule out the possibility of joins between three layers using additional adhesives, synthetic easy bonding fibres, polymeric fibres like those of the spunbonded or spunlaid layer, or other methods.

Another aspect of the present invention concerns its manufacturing procedure in which it is worth noting the different adhesion methods used to join the three layers, like calandering, hydroentanglement, and lamination.

The calandering method consists in passing the three layers through a calander together resulting in the bonding of the fibres of each layer through the perforations in the tissue layer. The temperature of the calander can vary between around 135 C and 175 C depending on the speed employed, the grammage, material, the degree of crystallisation of the fibres, and others.

By means of this procedure satisfactory results are obtained in terms of absorption capacity and non-breakdown of fibres.

Another method is that of hydroentanglement which involves using fine jets of water at high pressure to tangle the fibres around each other and in so doing bonding the three layers together.

This last method has certain advantages over calandering and achieves a low-cost, highly absorbent product which is greater in volume, while protecting the tissue layer and avoiding linting and the breakdown of fibres.

At the same time it is thought that the procedures described could include the addition of an adhesive on both sides of the tissue layer to facilitate its bonding.

The tissue layer could include low melting-point material fibres, such as copolymer EVA or polyethylene, or synthetic fibres like those from which the spunlaid or spunbonded is manufactured, normally polypropylene. Another bonding method would be that of lamination in which an adhesive might be applied to both sides of the tissue layer, as might also be applied synthetic or polymeric fibres to the tissue layer.

The manufacturing procedure of the three layer structure disposable wiping article using spunlaid nonwoven around a tissue layer, either perforated or non-perforated, is produced on-line and has certain phases:

- the supply of spunlaid fibres from respective beams and that of a sheet of perforated or non-perforated tissue from one roll in order to form a multilayer structure with the sheet of tissue in between two separate spunlaid sheet,

- a compact bonding of the multilayer structure to obtain a wipe formed by a tissue layer in between two spunlaid layers, by means of one of the methods previously described of calandering, hydroentanglement, or lamination.

The manufacturing procedure of the three layer structure disposable wiping article using spunbonded nonwoven around a tissue layer is produced on line and has certain phases:

- the supply of spunbonded sheets from respective unwinders and that of a perforated or non-perforated tissue sheet from one roll in order to form a sandwich structure with the tissue in between two separate spunbonded sheets,

- a compact bonding of the sandwich structure to obtain a wipe formed by a tissue layer in between two spunbonded layers, by means of one of the methods previously described of calandering, hydroentanglement, or lamination.

DESCRIPTION OF THE DRAWINGS

In order to achieve a better understanding of the features of the invention and

in accordance with a preferred example of it, the description includes a set of drawings which illustrate the following:

Figure 1 - Shows a schematic view of the manufacturing procedure of the wipe produced by calandering in line in order to obtain a perforated tissue • layer between two spunlaid layers.

Figure 2 - Shows a schematic view of the manufacturing procedure of the wipe by means of hydroentanglement in order to obtain a perforated tissue layer between two spunbonded layers.

Figure 3 — Shows a schematic view of the manufacturing procedure of the wipe by means of calandering in order to obtain a perforated tissue layer between two spunbonded layers.

Figure 4 - Shows a schematic view of the manufacturing procedure of the wipe by lamination using adhesive in order to obtain a perforated tissue layer between two spunbonded layers.

Figure 5 - Shows a schematic view of the manufacturing procedure of the wipe by lamination using adhesive in order to obtain a non-perforated tissue layer between two spunbonded layers.

PREFERRED EMBODIMENT OF THE INVENTION

The following description in conjunction with the figures describes some examples of the manufacturing procedures of composite wipes, object of the present invention.

In figure 1 the means used to obtain the wipe made with spunlaid layers can be seen. In the same figurei it can be seen that the separate spunlaid fibres (1) are taken to a conveyor belt (2) from respective beams (3) to both sides

of a roll (4) from which a sheet of tissue is supplied (5) featuring perforations (7).

The conveyor belt (2) moves a sandwich structure formed by the tissue sheet (5) featuring perforations (7) and the fibres located under and over the tissue sheet (5) towards a calander (6) where said sandwich structure is pressed and heated forming bonds between the fibres through the perforations (7') pressing together the whole.

The material so obtained is made up of two layers of spunlaid (1 ') with a layer of tissue (5') with perforations (7') in between, across which the spunlaid layers (1') are found.

In figure 2 the means used to obtain the wipe made with spunbonded layers can be seen. It is seen that the fibres are taken to a conveyor belt (2) from unwinders (8) in the form of spunbonded sheets (9) previously calandered, between which a sheet of tissue (5), featuring perforations (7), is supplied from a roll (4) forming a multilayer structure.

The conveyor belt (2) moves the multilayer structure towards a water jet terminal (12) which impels fine jets of water at high pressure so that they cross the fibres bonding and compacting them into a final product which is made up of two layers of spunbonded (9') between which is found a layer of tissue (5') featuring perforations (7').

In figure 3 , as in the previous figure, fibres are taken to a conveyor belt (2) from the winders (8) in the form of spunbonded sheets (9) previously calandered, between which a sheet of tissue (5) is supplied featuring perforations (7) from a roll (4), leading to its bonding, in this case by calendering in order to obtain a final product made up of two layers of spunbonded (9') between which a layer of tissue (5') featuring perforations

(7 ¹ ) is found.

In figures 4 and 5 the lamination procedure can be seen, in which two unwinders (8) supply sheets of spunbonded (9) previously calandered, between which a sheet of tissue (5) is supplied, in figure 4 it is featuring perforations (7) and in figure 5 without perforations, to which an adhesive (14) is applied on both sides, leading to its bonding by lamination performed by lamination rolls (15), in order to obtain a final product made up of two layers of spunbonded (9') between which a layer of tissue (5') is found.

The procedures represented in figures 2, 3, 4 and 5 for the making of wipes with spunbonded layers (9') would be equally valid for the making of wipes with spunlaid (1 '), substituting winders (8) for beams (3) supplying separate spunlaid fibres (1).