LYOCELL STAPLE FIBER

Abstract

The present invention relates to Lyocell staple fiber consisting of a plurality of cut filaments, which is characterized in that at least part of said cut filaments exhibit an overall cross-sectional shape which is a bi- or multi-filar cross-sectional shape resulting from notionally partially overlapping two or more fiber cross-sectional shapes.

Claims

1-44. (canceled)

45. A process for the manufacture of a Lyocell staple fiber, comprising the steps of: extruding a solution of cellulose dissolved in an aqueous tertiary amine-oxide through a spinneret exhibiting a plurality of spinneret orifices whereby filaments are formed; conducting said filaments via an air gap into a precipitation bath; drawing said filaments in said air gap; blowing air on said filaments in said air gap; precipitating said filaments in said precipitation bath; cutting said precipitated filaments in order to form cut filaments, wherein at least part of said spinneret orifices consists of an assembly of two or more holes being located adjacent such that when the solution is extruded through said holes, the filaments extruded from said holes are partially fused to form one fused filament, said process being characterized in that said air blown on said filaments in the air gap is directed onto said filaments; in case of a row arrangement of said holes, essentially parallel to the direction of said row; in case of a triangle arrangement of said holes, essentially parallel to the direction of one of the base lines of said triangle; in case of a square arrangement of said holes, essentially parallel to the direction of one of the base lines of said square; and in case of other geometrical arrangement of said holes, essentially parallel to the direction of the main orientation axis of said arrangement.

46. The process according to claim 45, wherein all of said holes have a circular shape.

47. The process according to claim 46, wherein all of said holes have the same diameter.

48. The process according to claim 46, wherein at least one or more of said holes has/have a higher diameter than the rest of said holes.

49. The process according to claim 48, wherein the ratio of the cross-sectional area of the hole(s) with the higher diameter to the cross-sectional area of the hole(s) with a smaller diameter is from more than 1:1 to 16:1.

50. The process according to claim 45, wherein all of said spinneret orifices consist of an identical assembly of holes in terms of the geometrical arrangement, the shape and the size of said holes.

51. The process according to claim 50, wherein said spinneret orifices are positioned in a plurality of parallel rows and in that, within each of said rows, all assemblies of holes are oriented essentially parallel to each other.

52. The process according to claim 45, wherein the diameter of said holes in said hole assembly is from 35 to 200 m.

53. The process according to claim 45, wherein the distance from the centre of one hole to the centre of the next adjacent hole in said hole assembly is from 100 to 500 m, preferably 150 to 250 m.

54. The process according to claim 45, wherein at least one of said holes has a non-circular shape.

55. The process according to claim 54, wherein said non-circular shape is a multilobal, preferably trilobal, or triangular shape.

56. A Lyocell staple fiber consisting of a plurality of cut filaments, obtainable by a process according to claim 46, wherein at least part of said cut filaments exhibit an overall cross-sectional shape which is a bi- or multi-filar cross-sectional shape resulting from notionally partially overlapping two or more fiber cross-sectional shapes and wherein all of said partially overlapped cross-sectional shapes are essentially circular shapes.

57. The Lyocell staple fiber according to claim 56, wherein said two or more partially overlapped circular shapes have essentially the same diameter.

58. The Lyocell staple fiber according to claim 56, wherein one or more of said partially overlapped circular shapes has/have a higher diameter than the rest of said overlapped circular shapes.

59. The Lyocell staple fiber according to claim 56, wherein said overall cross-sectional shape is a bi-filar cross-sectional shape resulting from notionally overlapping two essentially circular shapes.

60. The Lyocell staple fiber according to claim 56, wherein said overall cross-sectional shape is a tri-filar cross-sectional shape resulting from notionally overlapping three essentially circular shapes.

61. The Lyocell staple fiber according to claim 60, wherein said three overlapped circular shapes are arranged in a row.

62. The Lyocell staple fiber according to claim 60, wherein that said three overlapped circular shapes are arranged in the form of a triangle.

63. The Lyocell staple fiber according to claim 56, wherein said overall cross-sectional shape is a quadri-filar cross-sectional shape resulting from notionally overlapping four essentially circular shapes.

64. The Lyocell staple fiber according to claim 63, wherein said four overlapped circular shapes are arranged in a row.

65. The Lyocell staple fiber according to claim 63, wherein said four overlapped circular shapes are arranged in the form of a square, a parallelogram, or a rhombus.

66. The Lyocell staple fiber according to claim 63, wherein said four overlapped circular shapes are arranged in the form of a triangle, with one of said circular shapes forming the centre of said triangle.

67. The Lyocell staple fiber according to claim 56, wherein said filaments exhibit a decitex of from 0.5 to 8 dtex.

68. The Lyocell staple fiber according to claim 56, wherein said overall cross-sectional shape is a multi-filar cross-sectional shape resulting from notionally overlapping five or more essentially circular shapes.

69. The Lyocell staple fiber according to claim 56, wherein essentially all of the cut filaments exhibit essentially the same overall cross-sectional shape.

70. The Lyocell staple fiber according to claim 56, wherein said overall cross-sectional shape is hollow.

71. The Lyocell staple fiber according to claim 56, wherein the fiber exhibits a fiber tenacity in conditioned state which is higher by at least 15% than the fiber tenacity of a comparison Lyocell staple fiber of the same decitex, wherein all cut filaments of said comparison Lyocell staple fiber exhibit an essentially round cross-section.

72. The Lyocell staple fiber according to claim 56, wherein the fiber exhibits a decitex-related flexural rigidity of at least 0.5 mN.mm.sup.2/tex.sup.2.

73. A product comprising the staple fiber according to claim 56 wherein said product is selected from the group consisting of medical-, hygiene-, household textiles, technical- and apparel applications, such as wound dressings, laparotomy pads, bed pads, tampons, sanitary towels, wipes, incontinence products, pillows, duvets, towels, carpets, pile fabrics, damask, satin, insulation materials, reinforcement fiber for polymers, paper or concrete, textile articles, such as knitted or woven textile articles, shirtings, velour, chinos, cotton-like hand fabrics and garments made thereof.

74. The process according to claim 49, wherein the ratio of the cross-sectional area of the hole(s) with the higher diameter to the cross-sectional area of the hole(s) with a smaller diameter is from more than 1.6 to 1 to 2.7 to 1.

75. The Lyocell staple fiber according to claim 67, wherein said filaments exhibit a decitex of from 0.5 to 4 dtex.

76. The Lyocell staple fiber according to claim 68, wherein said overall cross-sectional shape is a multi-filar cross-sectional shape resulting from notionally overlapping five or seven essentially circular shapes.

77. The Lyocell staple fiber according to claim 72, wherein the fiber exhibits a decitex-related flexural rigidity of more than 0.6 mN.mm.sup.2/tex.sup.2.

78. The Lyocell staple fiber according to claim 71, wherein the fiber exhibits a fiber tenacity in conditioned state which is higher by at least 20% than the fiber tenacity of a comparison Lyocell staple fiber of the same decitex.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] FIG. 1 shows schematically a spinneret orifice suitable for the production of filaments with a bi-filar cross-sectional shape, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifice.

[0079] FIGS. 2A) and 2B) show schematically two different spinneret orifices suitable for the production of filaments with tri-filar cross-sectional shapes, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifices.

[0080] FIGS. 3A) to 3C) show schematically three different spinneret orifices suitable for the production of filaments with a quadri-filar cross-sectional shape, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifices.

[0081] FIGS. 4A) to 4B) show schematically two further spinneret orifices suitable for the production of filaments with a quadri-filar cross-sectional shape, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifices.

[0082] FIGS. 5A) to 5B) show schematically two different spinneret orifices suitable for the production of filaments with a cross-sectional shape composed of five fiber cross-sectional shapes, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifices.

[0083] FIGS. 6A) to 6B) show schematically two further spinneret orifices suitable for the production of filaments with a cross-sectional shape composed of five fiber cross-sectional shapes, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifices.

[0084] FIGS. 7A) to 7B) show schematically two different spinneret orifices suitable for the production of filaments with a cross-sectional shape composed of seven fiber cross-sectional shapes, the preferable direction of blowing air, and possible overall cross-sectional shapes of filaments spun from said spinneret orifices.

[0085] FIGS. 8A) to 8D) show two embodiments of producing staple fiber according to the invention with a tri-filar cross-sectional shape.

[0086] FIGS. 9A) to 9B) show a further embodiment of producing staple fiber according to the present invention with a tri-filar cross-sectional shape.

[0087] FIG. 10 shows the tri-filar cross-sectional shape of a Lyocell staple fiber according to the present invention.

[0088] FIG. 11 shows the tri-filar cross-sectional shape of a further Lyocell staple fiber according to the present invention

[0089] FIG. 12 shows the quadri-filar cross-sectional shape of a Lyocell staple fiber according to the present invention with a hollow structure.

[0090] According to FIG. 1, a spinneret orifice for the production of Lyocell staple fiber with a bi-filar cross-sectional shape consists of two spinneret holes (left side). The holes may be of the same or different diameter. An optionally smaller hole diameter is indicated by a smaller circle, and vice versa (this applies for all FIGS. 1 to 7).

DETAILED DESCRIPTION OF THE INVENTION

[0091] The shaded structures shown on the right side of FIG. 1 show the two potential overall cross-sectional shapes of a fused filament spun through the spinneret orifice at the left side. In the case of two holes with the same large diameter, a bi-filar cross-section composed of two partially overlapping comparatively large circles results. In case that one of the two holes has a smaller diameter, a cross-sectional shape such as the shaded structure shown at the right end of FIG. 1 results, wherein one larger circle is partially overlapping with a smaller circle.

[0092] The arrow in FIG. 1 indicates the preferred direction in which blowing air should be directed onto the extruded filaments such as to achieve the best results in terms of reproducibility and uniformity of the cross-sectional shapes of the fused filaments.

[0093] FIGS. 2 to 7 are based on the same principal structure as FIG. 1: On the left side, the geometrical arrangement of a spinneret structure is shown. Right therefrom, several possible fiber cross-sectional shapes are shown (shaded structures), in dependence on the respective hole diameters (small or large). Furthermore, in each of these figures, the preferred direction of the blowing air is indicated.

[0094] Therefore, in the following only a few comments are to be made with regard to FIGS. 2 to 7:

[0095] With regard to FIG. 2A), this shows a tri-filar cross-sectional shape in a row form, if holes of the same diameter are used. The blowing direction preferably is essentially parallel to the row.

[0096] FIG. 2B) shows possible tri-filar cross-section shapes in a triangular configuration. Especially if the hole in the intersection point of the two equal sides of the isosceles triangle is bigger (this is indicated by bold lines in the triangular hole configuration on the left side in FIG. 2B), a teddy-bear-like shape (the shaded structure in the middle) results. The blowing direction preferably is essentially parallel to the base line of the triangle of the spinning holes.

[0097] FIGS. 3A to 3C) show various embodiments of overall quadri-filar cross-sectional shapes. The preferred blowing direction, indicated by the arrow, is preferably the same for all the shown embodiments 3A) to 3C). In the case of FIG. 3A) (hole arrangement in a column), the blowing direction is preferably essentially parallel to the row. In the case of FIG. 3B) (hole arrangement in a square), the blowing direction is preferably essentially parallel to one of the base lines of the square. In the case of FIG. 3C), the preferred blowing direction is essentially parallel to the main orientation axis of the geometrical arrangement of the spinneret holes. Alternatively, the preferred blowing direction may be essentially parallel to the main diagonal of the square of FIG. 3B), or, in the case of FIG. 3C), may be essentially parallel to the axis defined by the connection between the uppermost and the lowermost of the holes.

[0098] In FIGS. 4A) and 4B) the respective main orientation axis of the geometrical arrangements shown is indicated with a dotted line. The cross-sectional shapes which are obtainable from the hole arrangement shown depending on the respective hole diameters are self-explaining The shaded structure according to Figure A) shows a hollow cross-sectional structure which is obtainable by suitably choosing the respective distances of the four spinneret holes.

[0099] The preferred blowing direction with regard to both FIGS. 4A) and 4B) is essentially parallel to the main orientation axis as indicated therein.

[0100] The same applies to FIGS. 5A) and 5B), showing cross-sectional shapes resulting from spinning the solution through a spinneret orifice with five adjacent spinneret holes.

[0101] FIGS. 6 and 7 show further embodiments, including cross-sectional shapes resulting from spinning the solution through a spinneret orifice with seven adjacent spinneret holes (FIG. 7) and including hollow cross-sectional shapes.

EXAMPLES

Example 1

[0102] FIGS. 8 and 9 demonstrate the influence of the direction of blowing air on the obtainable cross-sectional shape of the staple fiber of the invention.

[0103] In each case, a spinneret with various spinneret orifices each consisting of three holes, arranged in the form of a triangle, were used. In each orifice, two of the holes had a diameter of 80 m, and one of the holes had a diameter of 120 m. The distance from the center of the bigger hole to the center of the adjacent holes was 250 m each.

[0104] FIGS. 8A, 8B, and 9A, respectively, show the respective spinneret configuration and the direction of the blowing air employed.

[0105] All other spinning parameters being constant, the only variation resided in the direction of the blowing air (indicated by the arrows in FIGS. 8A), 8B) and 9A), respectively).

[0106] As apparent from FIG. 8C) (showing the result of the experiment according to FIG. 8A) and FIG. 8D) (showing the result of the experiment according to FIG. 8B), as compared with FIG. 9B) (showing the result of the experiment according to FIG. 9A), the best uniformity in fiber cross-sectional shape and reproduction of the original spinneret hole configuration is achieved with the test arrangement according of FIG. 9A), i.e. where the air is blown onto the filaments in a direction essentially parallel to the base line of the triangle defined by the two smaller holes, respectively.

Example 2

[0107] FIGS. 10 and 11 show the cross-sectional shapes of Lyocell staple fiber according to the present invention, produced from a spinneret configuration as described above with regard to FIGS. 8 and 9.

[0108] A standard spinning solution of 13% cellulose in NMMO was spun at 110 C. through the spinneret configuration as described, and was led through an air gap with a length of around 20 mm.

[0109] Blowing air was directed onto the extruded filaments. The blowing direction was essentially parallel to the base line of the triangle defined by the two smaller spinneret holes (cf. FIG. 9A).

[0110] Both FIGS. 10 and FIGS. 11 show very uniform cross-sectional shapes of the filaments obtained, and good reproduction of the teddy-bear-like configuration of the spinning holes.

Example 3

[0111] For the production of the staple fiber depicted in FIG. 12, spinneret orifices having four holes each were employed. Each hole had a diameter of 100 m. The distance from the center of one hole to its neighboring hole was 500 m. The holes were arranged in the form of a rhomboid. The blowing air was directed onto the spun filaments essentially parallel to the main orientation axis of the rhomboid (cf. FIG. 4A). A standard spinning solution of 12.3% cellulose in NMMO was spun at 120 C. through the spinneret configuration as described, and was led through an air gap with a length of around 20 mm.

[0112] As apparent from FIG. 12, the resulting staple fiber shows excellent uniform cross-sectional shape and has a remarkably reproducible hollow structure.

Example 4

[0113] Applying a constant set of spinning parameters, standard Lyocell staple fiber with an essentially round cross-section and Lyocell staple fiber with a tri-filar cross-sectional shape (spun from a spinneret with orifices as described with regard to example 1 and FIGS. 8 and 9, respectively) with varying decitex were produced. The following table compares the fiber tenacities of the fibers obtained:

TABLE-US-00001 TABLE 1 Fiber tenacity Fiber elongation Spinneret Pulp Decitex (conditioned (conditioned configuration employed (dtex) state) cN/dtex state (%) Fiber type Round Bacell* 3.3 35.5 14.5 Lyocell-standard Cf. Bacell 3.3 40.2 9.9 Lyocell trifilar - Example 1 teddy-bear Round Bacell 6.7 31.3 12.4 Lyocell-standard Cf. Bacell 6.7 36.5 11.0 Lyocell trifilar - Example 1 teddy-bear Round KZO3** 6.7 23.7 9.60 Lyocell-standard Cf. KZO3 6.7 30.7 11.20 Lyocell trifilar - Example 1 teddy-bear Cf. KZO3 18.7 23.3 9.8 Lyocell trifilar - Example 1 teddy-bear *Bacell is a TCF-bleached eucalyptus sulfite pulp produced by Bahia Brasil. **KZO3 is a TCF-bleached beech sulfite pulp produced by Lenzing AG.

[0114] It can easily be seen that the Lyocell staple fiber according to the invention has a significantly higher fiber tenacity than a standard Lyocell staple with the same decitex.

Example 5

[0115] Lyocell staple fiber according to the present invention produced with a spinneret configuration as described with regard to example 1 and FIGS. 8 and 9, respectively, was compared with various other types of cellulosic fibers in terms of its decitex-related flexural rigidity. The results are shown in table 2:

TABLE-US-00002 TABLE 2 Fiber Type Pulp Decitex Flexural (mN mm.sup.2/tex.sup.2) employed (dtex) rigidity Viscose - Standard KZO3 1.7 0.29 Viscose - Standard KZO3 1.9 0.24 Viscose - Standard KZO3 1.7 0.29 Modal fiber - produced from a KZO3 6.2 0.41 spinneret with trilobal holes Modal fiber - produced from a KZO3 6.4 0.34 spinneret with trilobal holes Modal fiber - produced from a KZO3 6.5 0.44 spinneret with trilobal holes Modal fiber - produced from a KZO3 6.6 0.35 spinneret with trilobal holes Lyocell trifilar - teddy-bear KZO3 16.7 0.51 Lyocell trifilar - teddy-bear KZO3 16.7 0.5 Lyocell trifilar - teddy-bear Bacell 3.6 0.91 Lyocell trifilar - teddy-bear KZO3 6.4 0.54 Lyocell trifilar - teddy-bear KZO3 6.5 0.69 Lyocell trifilar - teddy-bear Saiccor* 6.8 0.63 Lyocell trifilar - teddy-bear Bacell 6.5 0.65 Lyocell trifilar - teddy-bear Bacell 6.5 0.68 Lyocell trifilar - teddy-bear Bacell 6.5 0.63 Lyocell trifilar - teddy-bear Bacell 6.5 0.62 Lyocell trfilar - teddy-bear Bacell 6.4 0.69 Lyocell - Standard Bacell 6.1 0.37 *Saiccor is a TCF-bleached eucalyptus sulfite pulp, produced by Saiccor South Africa.

[0116] The Modal fiber in the above example was produced according to the teaching of PCT/AT/000493 (not pre-published).

[0117] From table 2, it is apparent that the Lyocell staple fiber with a tri-filar teddy-bear-like cross-sectional shape has a significantly higher decitex-related flexural rigidity than the other cellulosic fibers observed. Especially the decitex-related flexural rigidity of the staple fiber according to the invention was higher than 0.5 mN mm.sup.2/tex.sup.2 in all of the examples.