Dissolution and processing of cellulose

Abstract

The invention relates to a method for dissolving the components of gel forming materials suitable for use in wound care comprising the steps of admixing said components with an ionic liquid. The ionic liquid may be selected from the group of tertiary amine N-oxides, N,N-dimethyl formamide/nitrogen tetroxide mixtures, dimethyl sulphoxide/paraformaldehyde mixtures and solutions of limium chloride in N,N-dimethyl acetamide or N-methyl pyrrolidone.

Claims

1. A solution consisting of a chemically modified cellulose dissolved in an ionic liquid wherein the chemically modified cellulose is carboxymethylcellulose, and the ionic liquid consists essentially of a liquid ionic compound which is liquid below 150 C., the liquid ionic compound having: (i) a cation with a structure selected from: ##STR00002## wherein R.sup.1 and R.sup.2 are independently C.sub.1-C.sub.6 alkyl or C.sub.1-C.sub.6 alkoxyalkyl; and R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, and R.sup.9 are independently H, C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6 alkoxyalkyl, or C.sub.1-C.sub.6 alkoxy; and (ii) an anion selected from halogen, pseudohalogen, or C.sub.1-C.sub.6 carboxylate.

2. The solution of claim 1, wherein the carboxymethylcellulose prior to dissolution comprises a powder.

3. The solution of claim 1, wherein the dissolved carboxymethylcellulose is capable of being processed into a fiber, a nanofiber, a film, a coating, a foam, or a sponge.

4. The solution of claim 1, wherein the dissolved carboxymethylcellulose is capable of being processed into a fiber.

5. The solution of claim 4, wherein the fiber is sodium carboxymethyl cellulose fiber.

6. The solution of claim 5, wherein the sodium carboxymethyl cellulose fiber has a degree of substitution of at least 0.05 carboxymethyl groups per glucose unit and a tenacity of at least 10 cN/tex.

7. The solution of claim 1, wherein the carboxymethylcellulose is suitable for use in the treatment of wounds.

Description

EXAMPLE 1

(1) An ionic liquid, 1-butyl-3-methylimidazolium chloride was placed in a 70 C water bath to melt. Approximately 0.1 gram of degree of fiber as described in patent WO 93/12275 or Aquasorb (manufactured by Hercules Inc) were weighed out into a 20 ml scintillation vial. Sufficient molten ionic liquid was added to the vials to give a final concentration of polymer of 1% by weight. The vials without lids were placed in a microwave oven and heated at maximum power for 5 seconds. The vials were removed and the solution mixed. This was repeated until total dissolution of the polymer was achieved.

(2) The solution was spun by extruding a sample of the solution from a syringe with a 21 guage needle into an excess of IMS, a nonsolvent for the polymer. The coagulated fibres were recovered by filtration.

(3) It was also found that fibres could be electrospun by feeding a sample of the solution through a flat ended 25 guage needle and applying a positive 20 kV charge to the needle. The distance to the ground plate was 15 cm.

(4) A sample of the extruded fibre was hydrated with solution A (sodium/calcium chloride solution BP) and showed similar properties to the starting polymer.

EXAMPLE 2

(5) An ionic liquid, 1-ethyl-3-methylimidazolium acetate was used to make a 2% w/w solution of fiber as described in patent WO 93/12275 and sold under the trademark Aquacel. The flock of fibres were dispersed in the solvent at ambient temperature but required heating to form a solution.

(6) The solution was spun by extruding a sample of the solution through a Spinneret in the form or either a 400 jet 74 micron diameter parallel sided capillary or the same capillary with a straight sided conical inlet, or the same capillary with a hyperbolically curved inlet cone. The dope velocity was 2 m/min to 10 m/min spun into an excess of ethanol, a non solvent for the polymer. The coagulated fibres were recovered by filtration.

(7) The resulting fibres had a dry fibre average diameter of 15 microns and a hydrated average diameter of 38 microns.

EXAMPLE 3

(8) An ionic liquid, 1-ethyl, 3-methyl imidazolium acetate was used to make a 2% w/w solution of Hercules Aqualon A-500. The powder Was dispersed in the solvent at ambient temperature but required heating to form a solution.

(9) The solution was spun by extruding a sample of the solution through a Spinneret in the form or either a 400 jet 74 micron diameter parallel sided capillary or the same capillary with a straight sided conical inlet, or the same capillary with a hyperbolically curved inlet cone. The dope velocity was 2 m/min to 10m/min and was spun into an excess of ethanol, a non solvent for the polymer. The coagulated fibres were recovered by filtration.

(10) The resulting fibres had a dry fibre average diameter of 29 microns and a hydrated average diameter of 189 microns.