POLYSACCHARIDE FILM AND METHOD FOR THE PRODUCTION THEREOF

Abstract

The present invention relates to a method for the production of films made of polysaccharides which, as a fiber-forming substance, contain (1.fwdarw.3)-glucan, as well as to the films made thereof and to their use.

Claims

1. A method for the production of a polysaccharide film, wherein the finished spinning solution for the extrusion comprises an amine oxide, at least 23% by weight of water, related to the total quantity of the spinning solution, and, as a polysaccharide, (1.fwdarw.3)-glucan.

2. The method according to claim 1, wherein the amine oxide is N-methylmorpholine-N-oxide.

3. The method according to claim 1, wherein at least 90% of the (1.fwdarw.3)-glucan consist of hexose units and at least 50% of the hexose units are linked via (1.fwdarw.3)-glycosidic bonds.

4. The method according to claim 1, wherein the extrusion is carried out by means of a straight slot die or an annular slot die.

5. The method according to in claim 1, wherein the spinning solution is stretched following the extrusion.

6. A polysaccharide film comprising a film-forming substance, wherein the film-forming substance consists substantially of (1.fwdarw.3)-glucan.

7. (canceled)

8. (canceled)

Description

DESCRIPTION OF THE INVENTION

[0017] The above described object is solved by a method for the production of a polysaccharide film, wherein the finished spinning solution for the extrusion comprises an amine oxide, at least 23% by weight, preferably at least 26% by weight, of water, related to the total quantity of the spinning solution, and (1.fwdarw.3)-Glucan as a polysaccharide. This makes it possible to do without the use of a combined evaporation and dissolution unit, e.g., a filmtruder or thick layer kneader (LIST Discotherm or the like).

[0018] For the purposes of the present invention, the terms film and sheet shall be used as being synonymous.

[0019] The method for the preparation of the inventive film consists of the following steps: [0020] 1. Preparation of a spinning solution containing aqueous amine oxide and (1.fwdarw.3)-glucan. For this purpose, using the above mentioned methods that are generally known for the production of cellulose amine oxide solutions is possible. [0021] 2. Extruding the spinning solution through a die, via an air gap under stretching, and into a spinning bath containing an aqueous amine oxide, washing the regenerated film for removal of amine oxide, and drying.

[0022] The concentration of the (1.fwdarw.3)-glucan substance in the spinning solution may be between 5 and 20% by weight, preferably between 8 and 15% by weight.

[0023] Preferably, the amine oxide is N-methylmorpholine-N-oxide.

[0024] The (1.fwdarw.3)-glucan used according to the invention can be prepared by bringing an aqueous solution of saccharose into contact with GtfJ glucosyltransferase isolated from Streptococcus salivarius (Simpson et al. Microbiology, vol. 41, pp 1451-1460 (1995)).

[0025] In a preferred embodiment of the method according to the invention, at least 90% of the (1.fwdarw.3)-glucan are hexose units and at least 50% of the hexose units are linked via (1.fwdarw.3)-glycosidic bonds.

[0026] The degree of polymerization of the (1.fwdarw.3)-glucan employed in the method according to the invention, expressed as weight average DP.sub.w, may be between 200 and 2000; values between 500 and 1000 are preferred.

[0027] Surprisingly, it was also discovered that the method according to the invention not only permits the use of dry (1.fwdarw.3)-glucan. Also the use of water-containing, especially of initially moist (1.fwdarw.3)-glucan which was never dried after having been produced, is possible. This procedural variant only requires the appropriate adaptation of the water content of the amine oxide to be added. This further reduces the total energy to be used for the evaporation of water. This variant is of great economic interest especially if the plant for the production of the (1.fwdarw.3)-glucan is located directly adjacent the plant for the production of the inventive film.

[0028] The extrusion and shaping, respectively, of the spinning mass according to the invention can be performed by means of generally known methods: either in a flat film process by means of a straight slot die or by means of an annular slot die in a tubular film process as is known, e.g., from WO 98/42492 A2, or in a blown film process known, e.g., from WO 95/35340 A1 or WO 00/23250 A1.

[0029] Typically, the spinning solution is stretched following the extrusion. This may either take place only in one direction, i.e., axially, or both in the machine direction and transversely to it, i.e., biaxially. Preferably, the relevant stretching is carried out in the air gap prior to entry into the spinning bath.

[0030] A polysaccharide film characterized in that the film-forming substance consists substantially of (1.fwdarw.3)-glucan is also subject-matter of the present invention.

[0031] In a preferred embodiment, at least 90% of the (1.fwdarw.3)-glucan are hexose units and at least 50% of the hexose units are linked via (1.fwdarw.3)-glycosidic bonds.

[0032] The degree of polymerization of the (1.fwdarw.3)-glucan employed in the method according to the invention, expressed as weight average DP.sub.w, may be between 200 and 2000; values between 500 and 1000 are preferred.

[0033] In a preferred embodiment, the inventive polysaccharide film is oriented in at least one dimension. In another preferred embodiment, the inventive polysaccharide film is oriented in two dimensions perpendicular to one another. The orientation is carried out by suitable stretching, preferably in the air gap prior to entry into the spinning bath.

[0034] 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

[0035] In the following, the percentage values are always stated in percent by weight, unless otherwise specified.

Example 1

[0036] The (1.fwdarw.3)-glucan is first suspended in aqueous NMMO 50%, and then converted with NMMO 78% into a spinning solution containing 10% (1.fwdarw.3)-glucan, 29.9% water, 60% NMMO, and 0.1% propyl gallate as a stabilizer. The propyl gallate was stirred in in 2155 g of aqueous NMMO 50%, then 567 g of (1.fwdarw.3)-glucan were mixed in slowly and stirred for 15 minutes using an Ultraturrax T50, 2559 g of aqueous NMMO 78% were added to this suspension, and 106 g of water were removed.

[0037] The spinning solution was extruded at 100 C. through a 60 mm long film die having a 350 m wide slot, with an output of 26.9 g of spinning mass per minute, subjected to a draft of 1:2, coagulated in a precipitation bath, washed with water to remove the NMMO completely, dried, and wound up.

[0038] The produced film had the following characteristics: film thickness: 11 um, longitudinal strength: 87 Mpa, transverse strength: 41 Mpa, longitudinal elongation at break: 5.2%.

Example 2 (Reference Example)

[0039] Pulp is converted with aqueous NMMO 78% into a spinning solution containing 10% cellulose, 11.9% water, 78% NMMO, and 0.1% propyl gallate as a stabilizer.

[0040] The GPE was stirred in in 5000 g of aqueous NMMO 78%, then 532 g of cellulose were mixed in, followed by the removal of 532 g of water under vacuum from this suspension.

[0041] The spinning solution was extruded at 100 C. through a 60 mm long film die having a 350 m wide slot, subjected to a draft of 1:2, the shaped body was coagulated in a precipitation bath, washed with water to remove the NMMO completely, dried, and wound up.

[0042] The produced film had the following characteristics: film thickness: 11 um, longitudinal strength: 173 Mpa, transverse strength: 84 Mpa, longitudinal elongation at break: 7.1%.