EP0659924A1 - Non-woven composite which includes minimal two layers and process of manufacturing a non-woven - Google Patents

Abstract

According to the invention it is characterised in that it includes: - a first sheet carded from fibres of curled heat-fusible materials of fine titre, - a second sheet by direct spinning from straight filaments of extruded heat-fusible material, - multiple welding points produced vertically through the two sheets to consolidate each of the sheets and to bond them on a part of their area of contact, - multiple unwelded regions from which the curled material emerges, to increase the feeling of softness and of textile feel of the product. Application in the field of the manufacture of nonwoven products as a component of hygiene articles and hospital and medical products. <IMAGE>

Description

The present invention relates to a complex nonwoven consisting of at least two plies intended for hygiene and medical articles, as well as to its manufacturing process.

The invention will find its application in the field of the manufacture of nonwoven products which have many applications today as a component of hygienic articles such as diapers for babies, products for adult incontinence as well as hospital and medical products, for example surgical clothing.

The nonwoven in tablecloth is a product used in many applications because it has particularly sought-after qualities such as, for example, softness when there is contact with the skin in products such as baby diapers. The nonwoven web is used in particular as a covering material for cellulose wadding and as a finishing product for the layer in contact with the skin.

During the continuous manufacture of diapers for infants or incontinence, the nonwoven in tablecloth is worked with the polyethylene tape and the absorbent wadding at very high production rates and it is subjected to elongations in all directions. The nonwoven ply must therefore have qualities of mechanical resistance to tearing both in the longitudinal direction and in the transverse direction.

The nonwoven in tablecloth must also have, for this application to baby diapers, wettability qualities which allow it to be easily traversed by the liquid to allow this liquid to easily reach the absorbent mass constituted by the cellulose wadding and the super absorbent.

For other applications, a nonwoven web will be sought with hydrophilic qualities rather than hydrophobic.

For certain applications such as adult incontinence, double barrier and fecal barrier, hospital products, the nonwoven in tablecloth must have a barrier effect and be resistant. We can still try to color this nonwoven, which is not always easy today.

• un premier procédé utilisant la technique du cardage qui sera désigné dans la description par procédé cardé,
• un deuxième procédé utilisant la technique du filage direct qui sera désigné dans la présente description par procédé filage direct.

There are two processes for making nonwoven webs:

• a first process using the carding technique which will be designated in the description by carded process,
• a second method using the direct spinning technique which will be designated in the present description by direct spinning process.

For these two carded manufacturing and direct spinning processes, the raw material used must be hot-melt and it may for example be made of polypropylene. If the material is identical in the two processes, it however has a different origin since fibers will be used for the carded process while granules will be used for direct spinning.

Other hot-melt materials could naturally be used apart from polypropylene and it could for example be polyethylene and polyester and possibly more generally any other hot-melt material.

The choice of polypropylene is motivated today by its good value for money and its good machinability, that is to say that it is an easy material to work on machines.

Among the other advantages of polypropylene, one can cite a good dermatological quality because it has an almost harmlessness. This material also has good bacteriological qualities. When one seeks to make fibers, and in particular crimped fibers, polypropylene is easy to spin. The material also has good mechanical characteristics and tear resistance.

Polypropylene also has the advantage of being able to be worked at a lower temperature than polyester and therefore less energy is required to perform calendering and extrusion. Polypropylene is also easily incinerable.

The first known manufacturing method for producing nonwoven plies, known as the carded process, uses a card web made cold with polypropylene fibers.

The tablecloths produced are of a grammage which extends from 10 to 50 grams per square meter and the fibers used are generally crimped polypropylene fibers of fine titration (for example from 1.5 Dtex to 6 Dtex) and a cut of approximately 35 to 50 millimeters. In the known process, the sheet is formed cold on a card and the polypropylene fibers are slightly entangled, which gives a sheet whose fibers are very little linked with very low natural cohesion.

This tablecloth, for example a few millimeters thick, cannot be worked because it disintegrates as soon as one seeks to grasp it.

The known carded process therefore comprises, after the formation of the polypropylene fiber web, a second phase of consolidation of this web, which is done by thousands of welding spots by hot calendering and under pressure.

The nonwoven web thus produced by the carded process has very interesting qualities of textile feel, softness and bulkiness obtained by the crimped fibers and it has good uniformity. The wettability and rewetting characteristics of the product are good.

However, the carded process has a significant drawback because if the resistance of the ply in the longitudinal direction is good, it is entirely insufficient for certain applications in the transverse direction. This may indeed cause fragility during its use for the manufacture of hygiene articles such as baby diapers, period towels, adult incontinence or medical clothing.

The second known process for the manufacture of composite nonwoven consisting of at least two plies is the direct spinning process which consists in directly transforming polypropylene granules by means of a extruder. The straight filaments are extruded and they are brought together in a stream aerodynamically. Here again, the sheet does not have sufficient cohesion and it is necessary for it to be able to be used and worked to consolidate it. This is achieved by hot and press calendering and the consolidation of the web is done by thousands of welding spots which locally melt the filaments by making them adhere to each other. The operating conditions for this calendering are generally different from those used for the carded process.

The nonwoven fabricated by the direct spinning process is advantageous from the point of view of resistance and isotropy because good mechanical resistance and adequate elongation in the longitudinal or transverse direction of the web are obtained.

The most important drawback of nonwoven by direct spinning is its lack of softness and swelling since there is naturally no crimped fibers here which in the carded process gives this textile feel. In the direct spinning process, the continuous straight filaments give the whole a certain stiffness.

This stiffness, for certain other applications such as double barriers, faecal barriers or adult incontinence, can also have other advantages.

Another important drawback of the ply obtained by direct spinning is its irregular appearance. Indeed, the aerodynamic and random distribution of the filaments gives a sheet which lacks regularity.

The invention aims to remedy these drawbacks and for this purpose, one of the first objects of the nonwoven composite in at least two plies is to have qualities of softness and swelling necessary for applications in the field of hygiene or of the medical, which put the product in contact with the skin, sometimes very fragile of the new born.

Another object of the nonwoven composite in at least two plies according to the invention is to have simultaneously this softness, good mechanical strength and an adequate elongation in the longitudinal direction of the ply but also transverse which will facilitate the work of the tablecloth during the manufacture of hygienic or medical products.

It is indeed necessary, to manufacture these products, to implement very rapid rates.

Another advantage of the nonwoven composite in at least two plies according to the invention is that it can be produced either with hydrophilic or hydrophobic qualities depending on the applications, while retaining their softness and good mechanical resistance.

Another object of the nonwoven composite in at least two plies according to the invention is to improve the wettability, that is to say the property to be crossed by a liquid to quickly reach and disperse in the absorbent mass of wadding . The nonwoven in a baby diaper application must be rewettable several times over time according to the needs of the child. Thus the nonwoven has, vis-à-vis the liquid, important functions to be implemented, transport of liquid in one direction, rewetting when the liquid rises, dispersion and diffusion of the liquid.

Another advantage of the nonwoven composite in at least two plies according to the invention is to constitute a resistant barrier for other applications such as adult incontinence, double barrier and fecal barrier, hospital products.

Another object of the nonwoven composite in at least two plies according to the invention is to have a regular surface appearance, good uniformity and a balanced resistance in the longitudinal and transverse resistance: better isotropy.

Another object of the nonwoven composite in at least two plies according to the invention is to be able to be easily colored as is sometimes desired for certain applications. In this case, the carded tablecloth will be colored, the other tablecloth being able to remain white or vice versa.

• une première nappe cardée à partir de fibres de matières thermofusibles frisées de fin titrage,
• une deuxième nappe par filage direct à partir de filaments droits de matière thermofusible extrudée,
• de multiples points de soudure réalisés verticalement à travers les deux nappes pour consolider chacune des nappes et les liaisonner sur une partie de leur surface de contact,
• de multiples zones non soudées desquelles émerge la matière frisée,

pour augmenter la sensation de douceur et de toucher textile du produit.The invention relates to a composite nonwoven consisting of at least two plies intended for the manufacture of hygiene and medical articles, characterized in that that he understands:

• a first tablecloth carded from fibers of curly hot-melt materials of fine titration,
• a second ply by direct spinning from straight filaments of extruded hot-melt material,
• multiple weld points made vertically through the two plies to consolidate each of the plies and bond them over part of their contact surface,
• multiple non-welded areas from which the crimped material emerges,

to increase the feeling of softness and textile feel of the product.

• on forme une première nappe cardée à partir de fibres de matières thermofusibles frisées de fin titrage, lesdites fibres n'étant pas consolidées,
• on forme une deuxième nappe par filage direct à partir de filaments droits de matière thermofusible extrudée qui sont nappés de façon aérodynamique, lesdits filaments n'étant pas consolidés,
• on superpose les deux nappes,
• on réalise un seul calandrage à chaud et sous pression des deux nappes superposées pour assurer simultanément les fonctions suivantes :
  • consolidation de la nappe cardée par fusion des fibres frisées dans les multiples zones de soudure,
  • consolidation de la nappe par filage direct par fusion des filaments droits dans les mêmes zones de soudure,
  • liaison des deux nappes sur une partie de leur surface en contact,

pour fabriquer un produit à toucher textile doux et à résistance mécanique isotropique.The invention also relates to a method of manufacturing a composite nonwoven consisting of at least two plies intended for the manufacture of hygiene and medical articles, characterized in that:

• a first carded web is formed from fibers of curly hot-melt materials of fine titration, said fibers not being consolidated,
• a second ply is formed by direct spinning from straight filaments of extruded hot-melt material which are aerodynamically lapped, said filaments not being consolidated,
• we overlap the two layers,
• a single calendering is carried out hot and under pressure of the two superimposed layers to simultaneously perform the following functions:
  • consolidation of the carded web by fusion of the crimped fibers in the multiple welding zones,
  • consolidation of the sheet by direct spinning by melting straight filaments in the same welding zones,
  • bonding of the two plies on part of their contacting surface,

to make a product with soft textile feel and isotropic mechanical resistance.

• la figure 1 est une vue schématique du procédé selon l'invention,
• la figure 2 est une vue en coupe du produit après calandrage.

The invention will be better understood by referring to the following description of an embodiment illustrated by the accompanying drawings which form an integral part of the description:

• FIG. 1 is a schematic view of the method according to the invention,
• Figure 2 is a sectional view of the product after calendering.

Reference is made to FIG. 1 which shows a sheet (1) which is schematically superimposed on a sheet (2).

The ply (1) is obtained according to the carded process which therefore consists in making a card web with polypropylene fibers. The tablecloths produced have a grammage of the order of 10 to 50 grams per square meter and the fibers used will preferably be crimped polypropylene fibers of fine titration 1.5 Dtex to 6 Dtex and a cut of 35 to 60 millimeters . These crimped fibers have advantageous qualities when one seeks to obtain a nonwoven in a web which has a textile feel and a very good softness because this material will be in direct contact with the skin.

The tablecloth (1) is very little linked and it has a weak but existing natural cohesion which allows it to be superimposed on the tablecloth (2) but not worked in a machine for example for manufacturing baby diapers.

This ply (1) comes out of a card but is not exactly the product manufactured according to the carded process since, at the time when it is superimposed on the ply (2), it has not undergone any consolidation by calendering before the superposition with the tablecloth (2).

The same applies to the sheet (2) which is formed by direct spinning from straight filaments of extruded hot-melt material which are lapped in a known manner, for example aerodynamically. There too, the sheet (2) and its filaments have not been consolidated, that is to say that at the time when the sheet (2) is superimposed on the sheet (1), it has not no calendering or hot welding. If the cohesion of the two layers (1 and 2) is weak at the time of their superposition in the zone (3), it is nevertheless sufficient to be able to be worked. Naturally, this cohesion would be insufficient to manufacture hygiene articles, this is why it will be necessary after the zone (3) to calender the sheets (1 and 2) by means of the cylinders (4 and 5).

In the conventional carded process, the ply (1) would have been the subject only of a calendering around 150 ° C. and pressures between 20 and 100 bars.

On the other hand, in the conventional direct spinning process, the ply (2) would have been calendered at 130 ° C.

It can thus be seen that it would not have been possible to obtain good results by superimposing a ply (1) which would have undergone calendering with a ply (2) which would also have undergone calendering according to known methods. Indeed, a third calendering for bonding the webs by means of the cylinders (4 and 5) would not be bearable for the product because it would then lose many of its softness qualities and the crimped polypropylene fibers would all be completely crushed.

• consolidation de la nappe (1),
• consolidation de la nappe (2),
• liaison des nappes (1 et 2) en une seule nappe.

The invention in the original process which it implements therefore provides for superimposing the two plies (1 and 2) manufactured according to the carded process and according to the direct spinning process but before these plies have been consolidated. A single calendering will thus be carried out by the rollers (4 and 5) and this calendering will have the following three functions which will be carried out simultaneously:

• consolidation of the water table (1),
• consolidation of the water table (2),
• connection of the sheets (1 and 2) in a single sheet.

The process consists in bringing together the two types of carded web or by direct spinning, on which no consolidation has been carried out beforehand. It is only when the two plies are superimposed that they can be joined by calendering by proceeding to bond the two plies over part of their surface in contact (6). A calendering is carried out in a single operation which has three functions which, if they were carried out separately, would no longer allow between the welding points to define multiple non-welded zones from which the crimped material would emerge. These areas have been shown diagrammatically in (7) with the crimps (8). The welding points were produced by vertical calendering in the direction of the arrow (F) and they have a width (l) of very small dimension. Over this width (l) the first layer (1) was compressed and the calendering caused the formation of a groove (9), the bottom (10) of which can come, for example, below the contact zone (6) of the two layers. In the welding zones, the ply (2) is also consolidated in the small parts (11) following calendering. In this zone (11), the filaments of the sheet (2) are partially melted and stick to each other.

It is important that there is only one calendering by the rollers (4 and 5) so that the material of the web (1) does not lose its qualities of softness.

It should also be noted that the layers (1 and 2) must have sufficiently close melting points for this unique calendering with the three functions described to be carried out under good conditions.

In the area of the weld points, the material melted on the two layers will make it possible to consolidate the layers, that is to say to bond them over part of their surface in contact (6).

After calendering by the rollers (4 and 5), a composite nonwoven consisting of at least two plies (12) which can be worked and wound in (13) is obtained.

The process can be implemented with all hot-melt materials such as polypropylene, polyethylene or polyester.

By consolidating the plies (1 and 2) and bonding them with a single calendering, the material is not made to lose its softness qualities and a nonwoven in ply is obtained, the tear resistance of which is particularly good.

The tablecloths which are currently produced and manufactured in the hygiene industry are exclusively manufactured either from the carded process or from the direct spinning process and under these conditions have very specific advantages and disadvantages already described.

The present invention creates a new product which combines the advantages of the two methods, more efficient which will implement a single calendering instead of three.

We could naturally associate a tablecloth (1 and 2) in very different grammages depending on the applications from 10 to 100 grams per square meter.

It will also be possible to combine more than two layers, for example three, by placing them in very varied relative positions on the application that it is desired to obtain. If we are looking for softness, we will use two layers of carding and a layer of direct spinning, if we are looking for resistance, we will use two layers of direct spinning and a layer of carding.

In all cases, consolidation will be done by a single calendering which will make it possible to produce thousands of welding points, themselves spaced and separated by multiple non-welded zones from which the crimped material emerges.

In the carded process, the bonding temperature of the web is 150 ° C whereas it is normally 135 ° C in the direct spinning process. It will be necessary to implement a median temperature or seek to approximate these temperatures by playing on the raw materials.

The number of engraving points is different in the carded process and in the direct spinning process and again, a compromise will have to be found with regard to the drawings and the engraving of the cylinder (4). Good results have been obtained with 20 to 100 engraving points per square centimeter.

To obtain the structure shown in Figure 2, which leaves a lot of material (7), it is necessary to calender in one go the three layers and make sure that the distance (l) is quite small. A single weld zone releases a large amount of fiber material and keeps it soft.

The face (14) will be smooth and glazed because it will have been in contact with the smooth cylinder (5).

The composite nonwoven consisting of two carded plies and consolidated direct spinning has better resistance in the transverse direction and also makes it possible to produce a hydrophilic face and a hydrophobic face.

Better isotropy with regard to resistance to elongation will increase the productivity of machines for manufacturing hygienic and medical articles with regard to production rates.

The new nonwoven obtained in two layers will present a better uniformity and a more regular appearance. The wettability characteristics will also be improved. We can also obtain a different coloring on each side.

Applications of composite nonwoven in at least two layers will be numerous for hygiene and medical articles, baby diapers, feminine hygiene, adult incontinence, headdress, shoe covers, disposable medical clothing.

Naturally, other implementations of the present invention, within the reach of those skilled in the art, could also have been envisaged without departing from the scope thereof.

Claims (7)

Composite nonwoven for hygiene and medical articles, consisting of at least two plies, namely a first ply of fibers of hot-melt material of fine titration and a second ply of continuous filaments of extruded hot-melt material, characterized in that the first ply (1) is a carded ply of crimped fibers (8) and in that said nonwoven comprises multiple weld points (11) produced vertically through said two plies to consolidate each of the two plies (1,2) and bond them over part of their contact surface, so that the crimped material (8) emerges from the multiple non-welded zones. Nonwoven according to claim 1 characterized in that the first carded web of crimped fibers is towards the outside of the nonwoven. Nonwoven according to claim 1 characterized in that the imprint of the weld zones penetrates over the entire height of the first carded ply. Nonwoven according to one of claims 1 to 3 characterized in that the crimped fibers of the first carded ply are polypropylene fibers having a titration of between 1.5 and 6 dtex and a cut of 35 to 60 mm. Process for manufacturing a composite nonwoven, for hygiene and medical articles, with soft textile feel and isotropic mechanical resistance consisting of at least two plies, characterized in that: - two unconsolidated layers of hot-melt materials are formed simultaneously, the first (1) by carding crimped fibers of fine titration and the second (2) by direct spinning of extruded continuous filaments aerodynamically lapped, - the two unconsolidated layers are superimposed, - a single calendering is carried out, hot and under pressure, of the two plies thus superimposed according to multiple welding zones, thus simultaneously ensuring the consolidation of each of the plies and the connection of the two plies together over part of their contact surface, by melting the thermoplastic material constituting the crimped fibers and the continuous filaments in the multiple welding zones. A method according to claim 5 characterized in that the calendering temperature is determined so as to be median between the melting temperatures of crimped fibers and continuous filaments. Method according to one of claims 5 or 6 characterized in that the number of weld zones is between 20 and 100 per square centimeter.

Images