Method of manufacturing non-woven fabrics

Abstract

 Method of manufacturing non-woven fabrics by forming a fabric with three layers (known as CSC): a first card layer (C layer), a second spun layer (S layer) and a third card layer (C layer), characterised in that it comprises a stage wherein the continuous filaments (18) of the unconsolidated spun web (7) are placed directly on a first card web (3), to subsequently deposit the second card web (11) on the spun web (7). The spun web (7) is fed on the first card web (3) by means of a transport apron (17) that forms a certain angle (a) with the surface of the first card web (3), which is preferably maintained in the horizontal position.

Description

Technical sector of the invention

[0001] This invention relates to the manufacturing of non-woven fabrics within the technical textile sector; more specifically, the manufacturing of fabrics for wet wipes. Specifically, this invention relates to a method of manufacturing non-woven fabrics, by forming a fabric with three layers (known as CSC): a first card layer (C layer), a second spun layer (S layer) and a third card layer (C layer).

Background of the invention

[0002] The product whereto this invention relates is a non-woven fabric, with interlaced fibres, designed to produce wet wipes to be used on the human skin. For this reason, the fabric must be absorbent and soft to the touch.

[0003] In the current state of the art, there is a method of producing these fabrics: with production lines formed by two or three cards and, starting from short fibres of between 30 and 50 mm, made of viscose fibre (absorbent), mixed with artificial fibres. Another methodology to produce these fabrics is by the so-called spunbond technique, which consists of producing continuous PP (polypropylene) or PET (polyethylene terephthalate) filaments (spun) that are consolidated by means of bond calendering by thermofusion. However, these fabrics are not absorbent.

[0004] Currently, there is a technical limitation in the spunlace product and the spunlace process using carded fibres, which does not make it possible to manufacture products with viscose, polyester and/or polypropylene fibres with grammages of less than 40 g/m2 at productive speeds and with the physical characteristics required by the current market (weak product in the transverse direction and with low thickness). There have been attempts to resolve it by means of fabrics with three layers (known as CSC), a first card layer (C layer), a second spun layer (S layer) and a third card layer (C layer),

[0005] Patent EP1192306 discloses a CSC fabric wherewith the necessary absorption and feel are obtained, by adding the spun's greater resistance, making it possible to create products that have the same or better characteristics than the previous conventional products. According to this patent, a first carded web is introduced in the spun machine's apron, inside it, wherein the spun layer is deposited by the action of a strong vacuum. The two-layer fabric is subsequently coated by a third card layer, which creates problems upon feeding the webs and extracting the compound web. According to this patent, the layers are then compacted by means of cold pinch rollers, which leads to the problem of excessively reducing the thickness, which must remain within an adequate range.

[0006] Patent application US2005/0215156A1 proposes to pre-consolidate the spun web by means of a first water jet, to subsequently complete the consolidation by means of a second water jet; it mentions that, prior to the second jet, layers of other types of webs made of continuous polymer filaments may be added. This preconsolidation of the spun web may entail problems and requirements that are not always justified by the quality of the final product obtained.

[0007] Also worth citing are patents US6430788 and US6321425, wherein the spun web is consolidated by means of a calender, which entails the disadvantage of excessively reducing the thickness and adversely affecting the final product's feel.

[0008] Finally, another CSC process proposal worth mentioning is that disclosed in patent EP1275764, which describes the introduction, between two card webs, of spunbonded fabric from a spool with the fabric that has previously been produced in another spunbond line. The spunbonded product is subject to calendering, which once again entails the problem caused by calendering, which adversely affects the feel, thickness and bulking characteristics. Moreover, since it is not manufactured in-line, but in two independent lines, it is a much less efficient method.

[0009] The existing CSC process proposals do not make it possible to obtain a product with the required thickness values and necessary transverse tractions. Furthermore, there is the problem of lamination between CSC layers and of linting of fibres and/or filaments on the surface, since they are not capable of efficiently bonding the layers of the different products.

Explanation of the invention

[0010] The purpose of this invention is to join the two production methodologies explained above, by forming a fabric with three layers (known as CSC), a first card layer (C layer), a second spun layer (S layer) and a third card layer (C layer), which produces the necessary absorption and feel, but free from the above-mentioned problems and disadvantages of the state of the art, by adding the spun's greater resistance, making it possible to create products with the same or better characteristics than current products, even having greater thickness, greater bulking capacity and better feel characteristics, much more suitable for the intended use.

[0011] To this end, the object of this invention is a new method of manufacturing non-woven fabrics, of the type specified, which, in essence, is characterised by a stage wherein the continuous filaments of the unconsolidated spun web are placed directly on the first card web, to subsequently deposit the second card web on the spun web.

[0012] According to another characteristic of the invention, the spun web is fed on the first card layer by means of a transport apron that forms a certain angle with the surface of the card layer, which is preferably maintained in the horizontal position.

[0013] Said angle is preferably less than or equal to 35 degrees.

[0014] The method also considers a stage of impregnation with a surfactant in order to hydrophilise it, thereby compensating for the spun product's (continuous PP filaments) hydrophobic properties.

[0015] According to another characteristic of the method of the invention, both the spun web and the first card web coated by the spun web are made to go through weed rollers with a breathable surface and a (vacuum) suction section.

[0016] Currently, the various stages of the method are performed in an "in-line" production plant.

[0017] Moreover, this invention discloses the non-woven fabric product manufactured by means of the method as claimed in the preceding claims, as well as a wet wipe manufactured from the above-mentioned non-woven fabric product.

[0018] Although it may seem anti-intuitive and contrary to usual practise for a person skilled in the art, the application of the unconsolidated spun web makes it possible to optimise the final characteristics of the final products obtained by means of the method of the invention, specifically, albeit not exclusively, wet wipes. One possible explanation is that, since the S layer is not pre-consolidated, a stronger bond is obtained between the C-S-C layers when they are consolidated in the Jet, thus obtaining a cohesive product with the required tractions and thickness. In this manner, the "barrier" effect caused by the S layer placed in the middle of the product is also reduced.

[0019] In sum, the essence of the invention consists of allowing for good coupling of the spun web (continuous filaments) between the two card webs (short fibres).

Brief description of the drawings

[0020] Below we offer a detailed description of preferred, albeit not exclusive, embodiments of the method of this invention; for a better understanding thereof, we attach drawings that are provided merely as non-limiting examples; the only Figure (Fig. 1) is a schematic view representing an installation for the implementation of the method of this invention.

Detailed description of the drawings

[0021] Fig. 1 shows that the production line for the implementation of the method of the invention comprises a card 1, which produces a first card web 3 that is transported on a first card apron 2, and on a second card apron 8, which passes beneath a spun production station 4. At this point, some terminological precisions must be made: in the state of the art, "web" is understood to mean the formation of fibres in a uniform, unconsolidated (there is no dimensional stability) layer on an apron, and "fabric" is understood to mean an already-consolidated web, that is, one having stable dimensions and a high level of cohesion between the fibres or filaments that compose it.

[0022] An unconsolidated spun web 7, formed from continuous filaments 18 (e.g., of PP or PET), leaves spun station 4 and is transported, between the aprons, by a weed roller 5. Weed roller 5 is a roller with a breathable surface and a (vacuum) suction section designed to transport unconsolidated web 7. Spun web 7 descends on an apron 17 and is deposited on the first card web 3, transported by a second apron 8 and carried by weed roller 6, from apron 17 to apron 8, being deposited on card web 3. Thus, a compound web 9 is formed which is made of the first card web 3 and the superimposed spun web 7.

[0023] Apron 17, which transports spun 7, forms a certain angle a with the surface of the first card web layer 3, which is preferably maintained in the horizontal position. Angle a is preferably between 0 and 35°.

[0024] A second card web 11 is produced on a second card 10 and deposited on compound web 9, which advances on the second apron 8, forming the CSC compound web 16, which constitutes the object of the invention; following entanglement by a water jet 12, a hydrophiliser 13 and a drier 14, the non-woven fabric is formed and, after being spooled in a winder 15, the final product, that is, the fabric designed for manufacturing wet wipes and other uses, is obtained.

[0025] Regarding hydrophiliser 13, it is important to mention that it is necessary to impregnate the product with a surfactant in order to hydrophilise it, so as to achieve the standard values of absorption, wicking rate and sinking time in the wet wipe market. This addition is\ necessary to overcome the spun product's (continuous PP filaments) hydrophobic properties.

[0026] The method of the invention leads to a product 16 (wet wipe) with good thickness, transverse traction capacity, absorption capacity and product dimensional stability (linting, lamination) characteristics.

[0027] The product may be imprinted by means of thermoprinting or hydroprinting and may be subject to already-known finishes or coatings.

[0028] The method of the invention makes it possible to obtain a product with the following characteristics:
Surface density (grammage): between 18 g/m2 and 50 g/m2.

[0029] Card webs made of Vs/PES, Vs/PP or Vs with fibres between 0.9 dtex and 5 dtex, and lengths between 30 and 70 mm.

Spun with continuous PP filaments between 1 dtex and 3 dtex.

Spun webs 7: between 6 and 20 g/m2.

Card webs 3 and 11: between 6 and 30 g/m2.

Final thickness of product 16: between 0.5 and 1.2 mm.

Product's transverse tractions: between 10 and 40 N/50 mm.

Product absorption greater than 400%.

Having sufficiently described the nature of this invention, as well as how to implement it, we specify that anything that does not alter, change or modify the main principle thereof is subject to detail variations.

Claims

1. Method of manufacturing non-woven fabrics by forming a fabric with three layers (known as CSC): a first card layer (C layer), a second spun layer (S layer) and a third card layer (C layer), characterised in that it comprises a stage wherein the continuous filaments (18) of the unconsolidated spun web (7) are placed directly on a first card web (3), to subsequently deposit the second card web (11) on the spun web (7).

2. Method, as claimed in claim 1, characterised in that the spun web (7) is fed on the first card web (3) by means of a transport apron (17) that forms a certain angle (a) with the surface of the first card web (3), which is preferably maintained in the horizontal position.

3. Method, as claimed in claim 2, characterised in that said angle (a) is preferably less than or equal to 35 degrees.

4. Method, as claimed in claim 1, characterised in that it comprises a stage of impregnation with a surfactant, in a hydrophiliser (13), in order to hydrophilise the spun web (7).

5. Method, as claimed in any of the preceding claims, characterised in that both the spun web (7) and the first card web (8) coated by the spun web (7), are made to go through weed rollers (5; 6) with a breathable surface and a (vacuum) suction section.

6. Method, as claimed in any of the preceding claims, characterised in that the different stages thereof are performed in an "in-line" production plant.

7. Non-woven fabric product (16), which is manufactured by means of a method as claimed in the preceding claims.

Amended claims

Amended claims in accordance with Rule 137(2) EPC.

1. Method of manufacturing non-woven fabrics by forming a fabric with three layers (known as CSC): a first card layer (C layer), a second spun layer (S layer) and a third card layer (C layer), comprising a first stage of forming a unconsolidated spun web (7) in a spun station (4) and a second stage of placing the continuous filaments (18) directly on a first card web (3), to subsequently deposit the second card web (11) on the spun web (7), characterised in that it comprises, between the first and the second stages, the intermediate stage of feeding the unconsolidated spun web (7) out of the spun station (4), the second stage of placing being performed in the exterior of the spun station.

2. Method, as claimed in claim 1, characterised in that the spun web (7) is fed on the first card web (3) by means of a transport apron (17) that forms a certain angle (a) with the surface of the first card web (3), which is preferably maintained in the horizontal position.

3. Method, as claimed in claim 2, characterised in that said angle (a) is preferably less than or equal to 35 degrees.

4. Method, as claimed in claim 1, characterised in that it comprises a stage of impregnation with a surfactant, in a hydrophiliser (13), in order to hydrophilise the spun web (7).

5. Method, as claimed in any of the preceding claims, characterised in that both the spun web (7) and the first card web (8) coated by the spun web (7), are made to go through weed rollers (5; 6) with a breathable surface and a (vacuum) suction section.

6. Method, as claimed in any of the preceding claims, characterised in that the different stages thereof are performed in an "in-line" production plant.

Drawing