AU2012286157A1

AU2012286157A1 - Regenerated cellulose fiber

Info

Publication number: AU2012286157A1
Application number: AU2012286157A
Authority: AU
Inventors: Ingo Bernt; Matthew North; Walter Roggenstein; Reinhold Rothenbacher; Roland Scholz
Original assignee: Kelheim Fibres GmbH
Current assignee: Kelheim Fibres GmbH
Priority date: 2011-07-15
Filing date: 2012-06-26
Publication date: 2014-01-16
Also published as: KR20140037209A; US20140147616A1; CN103649388A; EP2732082A1; WO2013010761A1; BR112014000826A2; EP2546395A1; CA2839234A1; JP2014524987A

Abstract

The invention relates to a regenerated cellulose fiber (1"), the cross-section of which has a substantially flat elongated section (3). The fiber according to the invention is characterized in that at least one limb (4, 5, 6, 7) branches off from the elongated section, the length of said limb being maximally 40% of the length of the elongated section (3).

Description

1 Regenerated Cellulose Fibre The present invention relates to a regenerated cellulose fibre which is obtained by the viscose process. For sanitary applications such as, for example, tampons or absorbent bodies in general, fibres with a particularly high liquid storage capacity are desirable in order to thus allow an absorption capacity as high as possible of the sanitary product. Fibre materials according to the prior art which usually are used for the production of tampons are regular viscose fibres, so-called trilobal viscose fibres and cotton. The specific absorption capacity of said fibres according to the so-called Syngina test as described further below is about 4.0 g/g for cotton, 4.5 g/g for regular viscose and 5.2 g/g for trilobal viscose fibres. The aim of tampon producers is to achieve a particular degree of absorption with a minimum expenditure of fibre material and money. While cotton is slowly becoming obsolete as a fibre material for tampons because of its insufficient absorption capacity, trilobal fibres are much more expensive to produce and it is far more difficult to process them into tampons, as compared to regular viscose. Many different approaches for increasing the absorption capacity of cellulose fibres have been reported: 1. a chemical modification by grafting monomers onto the cellulose fibre 2. a chemical modification by incorporating absorbent polymers such as carboxymethyl cellulose, chitosan, cellulose carbamate, alginate or guaran into the cellulose fibre matrix 3. a physical modification of the fibres such as, e.g., hollow fibres or collapsed hollow fibres, as known, for example, from US-A 4,129,679, or 4. multi-limbed fibres (so-called ,,trilobal" fibres) which are obtained by using spinnerets having multi-limbed extrusion holes with at least 3 limbs having a length-to-width ratio of 2:1 to 10:1, as known, for example, from EP-Al 0 301 874. The disadvantage of a chemical modification of the cellulose fibre is that a costly and time consuming toxicological and physiological test procedure is necessary for very delicate 2 medical applications such as those of tampons and the occurrence of the toxic shock syndrome (TSS) keeps most tampon producers from using chemically modified fibre materials although the chemicals are possibly regarded as safe. The disadvantage of hollow fibres and collapsed hollow fibres is that they are difficult to produce because of their high water retention capacity, as a result of which the fibres swell strongly during washing and adhere to each other during drying because of the formation of hydrogen bonds, which makes them brittle in the dry state, soapy in the wet state and renders it difficult to break them up and process them into a carded fabric. In recent years, the use of multi-limbed, in particular trilobal fibres has experienced a steady increase. The production of multi-limbed viscose fibres has been described, for example, in the US patents 5,634,914 and 5,458,835 and in EP-Al 0 301 874. The process disclosed therein describes the spinning of a commonly used viscose, which may contain a certain amount of a modifier known from prior art, through extrusion holes of a multi-limbed shape, in particular a trilobal shape, into a conventional spinning bath. The essential feature of said process is that the shape of the multi-limbed extrusion holes in the spinneret is similar to the desired shape of the cross-section of the filaments. According to the teachings of those documents, the geometry of the spinneret hole determines the shape of the fibre cross-section, and a particular length-to-width ratio of the fibre cross-section can be obtained by designing the extrusion holes appropriately. Moreover, the prior art with regard to multi-limbed fibres teaches that such multi-limbed fibres have an absorption capacity which is enhanced in comparison to that of viscose fibres according to the prior art, namely in particular in tampons, and that such fibres must have at least 3 limbs and that each limb of those fibres must exhibit a length-to-width ratio of at least 2:1, most preferably of from 3:1 to 5:1. The larger the length-to-width ratio, the higher would be the proportion of free volume and the absorption capacity of the fibres, provided that the limbs are not so long and thin that they will bend back onto themselves. In those documents, it is also mentioned that, under the conditions of slow regeneration spinning, even higher absorption capacities of the multi-limbed fibres can be achieved, for example, by lowering the acid level and/or increasing the sulphate level and/or adding a viscose modifier.

3 The fact that hollow spaces in the cross-section of viscose fibres increase the absorption capacity of said fibres and of the products produced therefrom is furthermore known from US-A 4,362,159. From WO 2004/085720 A, a solid regenerated standard viscose fibre is known which has a cross-section the area of which is larger than the area of the largest equilateral triangle inscribed into said cross-section by a factor of less than 2.50 times, preferably less than 2.40 times, particularly preferably less than 2.25 times, and which exhibits a Syngina absorption capacity of more than 6.0 g/g fibre, as defined below. WO 2004/005595 A describes an absorbent standard viscose fibre having an irregularly lobed cross-section. Further viscose fibres with irregular cross-sections are described in US 4,129,679 and GB-A 1,333,047. US 6,403,217 BI describes a variety of die configurations for the production of fibres having modified fibre cross-sections according to the melt spinning process. Melt spinning processes differ fundamentally from the wet spinning process used in the viscose process. Conventional trilobal fibres as known from EP 0 301 874 A exhibit a high absorption capacity. One the one hand, this is attributable to the high stiffness caused by their geometrical structure, which stiffness increases the stability of the pores formed by trilobal fibres and thus enables the storage of large amounts of liquid. On the other hand, the Y structure also affects the packing density of the fibres: Because of their sterically demanding structure, hollow spaces are automatically formed which are larger than when, for example, a round fibre of the same structure is used. Due to the coarse pore structure, the capillarity in Y-fibres as known from prior art is relatively minor. For absorbent bodies with a faster absorption performance and a better distribution effect, the formation of a larger number of hollow spaces, which, in exchange, are smaller, would be advantageous. In order to overcome the above-mentioned disadvantages of known absorbent viscose fibres, according to the invention, a regenerated cellulose fibre is provided the cross-section of which comprises an oblong, essentially flat section and which is characterized in that at least one limb branches off from the oblong section, wherein the length of said limb is at most 40% of the length of the oblong section.

4 The object of the invention is also achieved by a fibre bundle which contains a plurality of cellulose fibres according to the invention. Further aspects of the present invention relate to a process for the production of the cellulose fibre according to the invention as well as to the use of the cellulose fibre according to the invention and of the fibre bundle according to the invention. SHORT DESCRIPTION OF THE FIGURES Fig. 1 shows the attachment of two trilobal cellulose fibres known, for example, from EP 0 301 874. Fig. 2 shows the attachment of several fibres having a flat cross-section. Fig. 3 shows the cross-section of a fibre according to the invention. Fig. 4 shows the attachment of several fibres according to the invention. Fig. 5 shows the retention of water by a fibre according to the invention. DETAILED DESCRIPTION OF THE INVENTION It has been found that, in case of a cellulose fibre the cross-section of which comprises an essentially flat, oblong section comprising at least one limb protruding therefrom, the pore size of products produced from a plurality of such fibres can be influenced favourably as compared to trilobal fibres. The limb is preferably arranged essentially at a right angle with respect to the oblong section. Particularly preferred are embodiments in which several branch-off limbs are provided. Advantageously, the limbs can thereby branch off from the oblong section in both directions. It is likewise preferred that the total length of the branch-off limbs does not exceed the length of the oblong section.

5 At least a portion of the limbs, preferably all the limbs, may have a ratio of length to width of from 2:1 to 10:1. At least a portion of the limbs, preferably all the limbs, may have a width which is smaller than the width of the flat section. The entire curvature of the flat section preferably has at most 1200. Even when the spinning is effected through dies with a flat spinning opening, a certain curvature may occur in the resulting flat fibres (or, respectively, in the flat section which is provided according to the invention). The angle defined by the endpoints of the flat section as well as the point of the flat section which is located farthest from the imaginary straight line through said endpoints is thereby regarded as the curvature. The fibre titre of the fibre according to the invention may range from 1.3 dtex to 10 dtex. The cellulose fibre according to the invention can be provided in the form of a staple fibre, a short-cut fibre or as a filament tow. The invention also relates to a fibre bundle containing a plurality of regenerated multi limbed cellulose fibres, wherein at least 10%, preferably at least 20%, particularly preferably at least 50%, of the multi-limbed cellulose fibres are provided in the form of a cellulose fibre according to the invention. In the fibre bundle according to the invention, also essentially all of the multi-limbed cellulose fibres contained therein may be provided in the form of a cellulose fibre according to the invention. A plurality of fibres can be understood as a "fibre bundle", for example, spun rayon (a plurality of staple fibres), a strand of continuous filaments or a bale of fibres. Preferably, essentially all of the multi-limbed cellulose fibres contained in the fibre bundle are provided in the form of the cellulose fibre according to the invention and, respectively, the cross-sections of the multi-limbed cellulose fibres contained in the fibre bundle are essentially equal. The fibre bundle may contain further fibres, for example, cellulose fibres which are not multi-limbed, but also fibres of a different origin, e.g., from other polymers.

6 The process according to the invention for the production of a regenerated cellulose fibre and, respectively, of a fibre bundle according to any of the preceding claims comprises the steps of - providing a viscose spinning mass - spinning the viscose spinning mass through at least one opening of a spinneret into a spinning bath, whereby filaments are formed, and is characterized in that the opening of the spinneret comprises a slot-shaped section from which at least one limb branches off the length of which is at most 40% of the length of the slot-shaped section. Optionally, the process according to the invention may comprise the step of mixing the fibres produced by the process with other fibres, for example, conventional multi-limbed fibres, fibres which are not multi-limbed and/or fibres of a different origin, e.g., from other polymers. Preferably, the smaller angle between the limb and the slot-shaped section has between 300 and 900, particularly preferably between 600 and 900. Preferably, the process according to the invention is configured such that the spinneret comprises several openings, with all the openings having essentially the same shape. In this way, the preferred configuration, namely that all fibres have essentially the same cross section, is achieved, for example, in a fibre bundle consisting of fibres according to the invention. The invention also relates to the use of the regenerated cellulose fibre according to the invention and, respectively, of the fibre bundle according to the invention in absorbent products, sanitary products, in particular tampons, incontinence products, sanitary pads and panty liners, filling materials for blankets, cushions and sleeping bags, packings for foodstuff, in particular for meat products, papers, in particular filter papers, flock, clothing, in particular inlay fleece and clothing textiles for moisture management, mixed with other fibres or as a multi-layered structure, and wound dressings. Examples: Y-Fibres for the production of absorbent bodies having a high absorption capacity are known from the prior art. By the wings existing in this case, the fibre centres are kept at a large 7 distance from each other so that structures with a large liquid storage capacity emerge. However, the capillarity is limited due to the size of the pores that are formed. Fig. 1 shows the attachment of two conventional Y-fibres 1, 2 and the pore structure produced in this way. The production of fibres having a flat cross-section is also known from the prior art. The sole use of flat fibres for absorbent bodies is not preferred since, due to their structure, they may be located very closely next to each other and the structures thus produced have only a minor absorption capacity, see Fig. 2, in which flat fibres 1', 2' (etc.) lying next to each other are depicted. A further problem of flat fibres is that they can be bent about their thinner axis with relative ease. Therefore, hollow spaces in liquid-charged absorbent bodies collapse easily. In the fibre according to the invention, a smaller pore size can now be achieved by appropriately arranging and dimensioning at least one, preferably several limbs diverging from the oblong section. Fig. 3 shows a preferred embodiment of a fibre 1," according to the invention comprising an oblong section 3 and several limbs 4, 5, 6, 7 diverging from the oblong section 3 essentially at a right angle, as is the case in Fig. 3. Said fibre can be produced by spinning a viscose spinning mass through a spinning opening having an appropriate configuration (i.e., a slot shaped section and limb-shaped sections branching off from said section). As shown in Fig. 3, the length of the limbs 4, 5, 6, 7 is in each case less than 40% of the length of the oblong section. The width of the limbs is in each case smaller than the width of the oblong section. During the fibre processing according to the prior art, the fibres are parallelized at a certain rate. Therefore, the following consideration initially takes parallelized fibres as a basis. The limbs of the structure produced from fibres according to the invention act as distance pieces which cause the formation of a large number of very fine capillaries when several such fibres are attached to each other (see Fig. 4). Simultaneously, the limbs also act as a reinforcement and as distance pieces, which prevents a bending of the fibre across the thinner axis of the flat fibre portion. In this manner, a high absorption capacity is ensured.

8 A further advantage of the fibre according to the invention is that water is stored particularly advantageously by adhesion forces in the large number of clearances between the limbs of a fibre, which is illustrated in Fig. 5. Thus, structures made of the fibres according to the invention exhibit a particularly high water retention capacity against pressure.

Claims

1. A regenerated cellulose fibre (1") the cross-section of which comprises an oblong, essentially flat section (3), characterized in that at least one limb (4, 5, 6, 7) branches off from the oblong section, wherein the length of said limb is at most 40% of the length of the oblong section.

2. A cellulose fibre according to claim 1, characterized that the limb (4, 5, 6, 7) is arranged essentially at a right angle with respect to the oblong section (3).

3. A cellulose fibre according to claim 1 or 2, characterized in that several branch-off limbs (4, 5, 6, 7) are provided.

4. A cellulose fibre according to claim 3, characterized in that the limbs (4, 5, 6, 7) branch off from the oblong section (3) in both directions.

5. A cellulose fibre according to claim 3 or 4, characterized in that the total length of the branch-off limbs (4, 5, 6, 7) does not exceed the length of the oblong section (3).

6. A cellulose fibre according to any of the preceding claims, characterized in that at least a portion of the limbs (4, 5, 6, 7), preferably all the limbs, have a ratio of length to width of from 2:1 to 10:1.

7. A cellulose fibre according to any of the preceding claims, characterized in that at least a portion of the limbs (4, 5, 6, 7), preferably all the limbs, have a width which is smaller than the width of the flat section (3).

8. A cellulose fibre according to any of the preceding claims, characterized in that the entire curvature of the flat section has at most 120'.

9. A cellulose fibre according to any of the preceding claims, characterized in that the fibre titre ranges from 1.3 dtex to 10 dtex.

10. A cellulose fibre according to any of the preceding claims, characterized in that it is provided in the form of a staple fibre, a short-cut fibre or as a filament tow. 10

11. A fibre bundle containing a plurality of regenerated multi-limbed cellulose fibres, wherein at least 10%, preferably at least 20%, particularly preferably at least 50%, of the multi-limbed cellulose fibres are provided in the form of a cellulose fibre according to any of the preceding claims.

12. A fibre bundle according to claim 11, characterized in that the cross-sections of the contained multi-limbed cellulose fibres are essentially equal.

13. A process for the production of a regenerated cellulose fibre and, respectively, of a fibre bundle according to any of the preceding claims, comprising the steps of - providing a viscose spinning mass - spinning the viscose spinning mass through at least one opening of a spinneret into a spinning bath, whereby filaments are formed, characterized in that the opening of the spinneret comprises a slot-shaped section from which at least one limb branches off the length of which is at most 4 0% of the length of the slot shaped section.

14. A process according to claim 12, characterized in that the spinneret comprises several openings, with all the openings having essentially the same shape.

15. The use of a regenerated cellulose fibre and, respectively, of the fibre bundle according to any of claims 1 to 9 in absorbent products, sanitary products, in particular tampons, incontinence products, sanitary pads and panty liners, filling materials for blankets, cushions and sleeping bags, packings for foodstuff, in particular for meat products, papers, in particular filter papers, flock, clothing, in particular inlay fleece, and wound dressings.