Polysaccharide fibers and method for producing same

Abstract

The present invention relates to a direct dissolving process for the production of polysaccharide fibers which contain α(1.fwdarw.3)-glucan as a fiber-forming substance, with aqueous sodium hydroxide solution as a solvent, as well as to the fibers made thereby, and to their use.

Claims

1. A non-woven product comprising a polysaccharide fiber whose fiber-forming substance is α(1.fwdarw.3)-glucan, wherein the α(1.fwdarw.3)-glucan has a weight average degree of polymerization between 200 and 2000.

2. The non-woven product of claim 1, wherein at least 90% of the α(1.fwdarw.3)-glucan are hexose units and at least 50% of the hexose units are linked via α(1.fwdarw.3)-glycosidic bonds.

3. The non-woven product of claim 1 or 2, wherein the polysaccharide fiber is a continuous filament.

4. The non-woven product of claim 1 or 2, wherein the polysaccharide fiber is a staple fiber.

5. The non-woven product of claim 1 or 2, wherein said fiber is produced using a direct dissolving process in aqueous sodium hydroxide solution.

6. The non-woven product of claim 1 or 2, wherein the weight average degree of polymerization is between 500 and 1000.

Description

DESCRIPTION OF THE INVENTION

(1) The above described object is solved by a new direct dissolving process for the production of a polysaccharide fiber whose fiber-forming substance is α(1.fwdarw.3)-glucan, the direct dissolving process being based on aqueous sodium hydroxide solution.

(2) Hence, the subject-matter of the present invention is, on the one hand, a method for the production of a polysaccharide fiber whose fiber-forming substance is α(1.fwdarw.3)-glucan, the method being a direct dissolving process and the solvent being aqueous sodium hydroxide solution.

(3) Surprisingly, it was found that standard spin baths as used in the viscose process (they contain about 100 g/l H.sub.2SO.sub.4 and about 250 g/l Na.sub.2SO.sub.4) yield very poor results, but that two other, very different spin bath compositions yield significantly better results.

(4) 1. High-acid spinning: it was discovered that filament formation and the stretchability of the regenerated filament improve significantly when increasing the concentration of sulfuric acid in the spin bath. The examined range with good spinning characteristics reaches from 200 to 500 grams of sulfuric acid per liter of spin bath.

(5) 2. Low-acid spinning: the second spinning range, which exhibited a significantly better spinning reliability, is at very low acid concentrations below 60 grams per liter of spin bath, preferably from 20-60 g/l. Good results were also obtained using a two-bath system, where the first bath has very high salt contents and a very low acid concentration, whereby the spun filament is only coagulated at first and is regenerated only in the second, acid regeneration bath.

(6) In a preferred embodiment of the inventive method, the H.sub.2SO.sub.4 concentration in the spin bath is therefore between 200 and 500 g/l.

(7) In a second preferred embodiment of the inventive method, the H.sub.2SO.sub.4 concentration in the spin bath is therefore between 20 and 60 g/l.

(8) In a preferred embodiment of the inventive method, the spun fiber is subsequently stretched in an acid regeneration bath.

(9) According to the invention, the NaOH concentration in the spinning solution is to be between 4.0 and 5.5% by weight, related to the total quantity of the spinning solution. Outside this range, the solubility of the glucan is not sufficiently ensured.

(10) For the purposes of the present invention, the term “fiber” shall comprise both staple fibers having a defined staple length and continuous filaments. All principles of the invention that are described hereinafter generally apply to both staple fibers and continuous filaments.

(11) The single fiber titer of the inventive fibers can be between 0.1 and 10 dtex. Preferably, it is between 0.5 and 6.5 dtex, and more preferably between 0.9 and 6.0 dtex. In the case of staple fibers, the staple length is usually between 0.5 and 120 mm, preferably between 20 and 70 mm, and more preferably between 35 and 60 mm. In the case of continuous filaments, the number of individual filaments in the filament yarn is between 50 and 10,000, preferably between 50 and 3,000.

(12) The α(1.fwdarw.3)-glucan can be prepared by bringing an aqueous solution of saccharose into contact with glucosyltransferase (GtfJ) isolated from Streptococcus salivarius (Simpson et al., Microbiology, vol. 41, pp 1451-1460 (1995)).

(13) In a preferred embodiment of the method according to the invention, at least 90% of the α(1.fwdarw.3)-glucan are hexose units and at least 50% of the hexose units are linked via α(1.fwdarw.3)-glycosidic bonds.

(14) The method for the production of the inventive fiber consists of the following steps:

(15) 1. Preparing an α(1.fwdarw.3)-glucan solution in diluted aqueous sodium hydroxide solution.

(16) 2. Extruding the α(1.fwdarw.3)-glucan-containing spinning solution through a spinneret into a sulfuric acid spin bath, stretching the fibers in an acid regeneration bath, and post-treatment.

(17) The concentration of the fiber-forming substance in the spinning solution can be between 4 and 18% by weight, preferably it is between 4.5 and 12% by weight.

(18) The degree of polymerization of the α(1.fwdarw.3) glucan employed in the method according to the invention, expressed as weight average DP.sub.w, can be between 200 and 2000; values between 500 and 1000 are preferred.

(19) In a preferred embodiment at least 90% of the α(1.fwdarw.3)-glucan of the polysaccharide fiber according to the invention are hexose units and at least 50% of the hexose units are linked via α(1.fwdarw.3)-glycosidic bonds.

(20) The above described polysaccharide fiber whose fiber-forming substance is α(1.fwdarw.3)-glucan and which was produced using the also above described direct dissolving process in aqueous sodium hydroxide solution is also the subject-matter of the present invention.

(21) The use of the inventive fibers for the production of textile products such as yarns, woven fabrics, or knitted fabrics as well as of various dry-laid and wet-laid papers, nonwovens, hygiene articles such as tampons, panty liners, and diapers, and of other nonwovens, especially absorbent nonwoven products, is also the subject-matter of the present invention.

(22) The invention will be described below with reference to examples. However, the invention is not expressly limited to these examples but also includes all other embodiments that are based on the same inventive concept.

EXAMPLES

(23) The degree of polymerization of the α(1.fwdarw.3)-glucans was determined by means of GPC in DMAc/LiCl. Subsequently, it is always the weight average of the degree of polymerization (DP.sub.w) that is specified.

Example 1

(24) An aqueous glucan solution containing 9% of α(1.fwdarw.3)-glucan with a DP.sub.W of 800 as well as 4.5% by weight of NaOH was cooled down to 3° C., filtered, and deaerated. By using a spinneret, the solution was extruded into a spin bath at 35° C., containing 300 g/l of sulfuric acid, and 50 g/l of sodium sulfate. The spinneret had 53 perforations with a diameter of 50 μm. In order to achieve adequate fiber strength, stretching in the regeneration bath (97° C., 25 g/l H.sub.2SO.sub.4) was carried out. The draw-off velocity was 30 m/min.

(25) The properties of the obtained fibers are listed in Table 1.

Example 2

(26) An aqueous glucan solution containing 9% of α(1.fwdarw.3)-glucan with a DP.sub.W of 1000 as well as 4.8% by weight of NaOH was cooled down to 0° C., filtered, and deaerated. By using a spinneret, the solution was extruded into a spin bath at 20° C., containing 35 g/l of sulfuric acid, 280 g/l of sodium sulfate, and 45 g/l of zinc sulfate. The spinneret had 53 perforations with a diameter of 40 μm. In order to achieve adequate fiber strength, stretching in the regeneration bath (92° C., 55 g/l H.sub.2SO.sub.4) was carried out. The draw-off velocity was 25 m/min. The properties of the obtained fibers are listed in Table 1.

(27) TABLE-US-00001 TABLE 1 titer FFk FDk example dtex cN/tex % ex. 1 1.7 15.3 11.1 ex. 2 1.7 19.1 9.2 FFk fiber strength, conditioned FDk fiber elongation, conditioned