WO1991016357A1

WO1991016357A1 - Cellulose derivatives

Info

Publication number: WO1991016357A1
Application number: PCT/AU1991/000151
Authority: WO
Inventors: Anthony Archelaou Sioumis
Original assignee: Commonwealth Scientific And Industrial Research Organisation
Priority date: 1990-04-23
Filing date: 1991-04-23
Publication date: 1991-10-31

Abstract

A process for the preparation of a derivative of cellulose and formic acid comprising reacting a cellulose-containing material with formic acid in the presence of an organic solvent and a catalyst. The organic solvent is preferably methylene chloride. The catalyst is preferably sulphuric acid. The resulting cellulose derivative may be used in the production of cellulose products, especially cellulose fibres.

Description

CELLULOSE DERIVATIVES

This invention relates to a process for the manufacture of cellulose esters and is particularly concerned with the production of cellulose formates. The invention is also concerned with a process for producing regenerated cellulose fibres.

Conventionally rayon (viscose) is produced from cellulose by the viscose process. In this prior art method, cellulose is reacted with concentrated caustic soda to produce soda cellulose which is then reacted with carbon disulphide to form sodium cellulose xanthate which is dissolved in dilute sodium hydroxide to form viscose solution also known as dope.

This viscose solution is ripened and then extruded through a spinneret into a sulphuric bath containing zinc sulphate, sodium sulphate and other chemicals such as glucose to control the coagulation rate and the properties of the resultant regenerated cellulose fibre which is known as viscose or rayon. The regenerated cellulose fibres produced by the viscose process are often bleached to eliminate the yellowing which occurs during the xanthation.

The viscose process is becoming environmentally unacceptable because of the pollution resulting from the use of carbon disulphide which is malodorous, highly volatile, flammable and toxic. The control of pollution in the viscose process is both difficult and expensive. A further disadvantage of the process is the long times (approximately 24 hours) required for the preparation and ripening of the viscose solution before it is ready for spinning. An alternative method for preparing spinnable material suggested in the prior art entails the formation of a cellulose ester. One such process involves the formation of a cellulose formate made from the reaction of cellulose and formic acid with the aid of a catalyst. As far as we are aware, none of these prior art processes have proved to be commercially feasible.

It is an object of the present invention to provide a process which overcomes, at least in part, one or more of the problems attending prior art processes, for instance, the environmental problems associated with the xanthation process.

Accordingly, in one aspect, the present invention provides a process for the preparation of a derivative of cellulose and formic acid comprising reacting a cellulose-containing material with formic acid in the presence of an organic solvent and a catalyst.

Examples of cellulose-containing material suitable for use in the present process include cotton linters, alpha cellulose and wood-derived chemical cellulose which is also known as dissolving pulp. It has also been found that chemical wood pulps, such as those intended for use in paper manufacturing, are also suitable for use in the present process.

The chemical wood pulp may be any pulp conventionally used for paper making, other than pulps produced by purely mechanical means. By the term "chemical wood pulp" we include full chemical pulps, semichemical pulps, chemithermomechanical and chemimechanical pulps. Preferably full chemical pulps are used. Examples of full chemical pulps are those produced using the soda, soda-anthraquinone, kraft, bisulphite and sulphite processes. The pulp may be bleached or unbleached.

HEET Examples of suitable catalysts are phosphoric acid and hydrogen chloride. Those catalysts that bind water are preferred. Sulphuric acid is particularly preferred.

The organic solvent may be any compound capable of breaking the hydrogen bonding within the cellulose. A chlorinated hydrocarbon solvent may be used. Methylene chloride is particularly preferred. Other solvents that may be used in the process include dichloroethylene, trichloroethylene and chloroform.

In a preferred form, the present invention provides a process for the preparation of a derivative of cellulose and formic acid comprising reacting a cellulose-containing material with formic acid in the presence of methylene chloride and a catalyst.

Preferably the catalyst is sulphuric acid, although, as indicated above, other catalysts may be used.

The cellulose product of the present invention is particularly suitable for use in the production of regenerated cellulose fibres with properties akin to those of rayon (viscose) .

Accordingly in yet a further form, the present invention provides a process for producing regenerated cellulose product comprising:

(a) reacting a cellulose-containing material with formic acid in the presence of an organic solvent and a catalyst to form a viscous solution; and

(b) contacting said solution with an aqueous medium to regenerate cellulose.

SUBSTITUTE SHEET The above process is especially suited for producing regenerated cellulose fibres by extruding the solution into the aqueous medium.

In an especially preferred form, vacuum is applied to the solution prior to extruding it into the aqueous medium. This is a technique that is commonly employed in the art of viscose spinning. The vacuum generally acts to remove any gases from the solution and improves the properties of the fibres produced from the solution.

The temperature of the aqueous medium used as the coagulation bath to regenerate the cellulose may range from about 10 to about 30°C.

Residual formyl groups in the product may be easily removed by hydrolysis with dilute sodium hydroxide at ambient temperatures.

The invention also includes the products of the process of the invention.

Advantages of the present invention over the conventional viscose process include:

speed of dissolution of the cellulose; the viscous solution (dope) is ready for spinning within 30 minutes

the use of carbon disulphide is eliminated, resulting in a substantial reduction in pollution; in the preferred process, methylene chloride and formic acid are readily recoverable, and the sulphuric acid may be recovered if desired.

SUBSTITUTE SHEET the coagulating bath may contain only water although additives such as ferric chloride may be used to control the properties of the fibre.

yellowing of the fibre does not occur so that the bleaching may be eliminated.

A further advantage of the process of the present invention is that the cellulose filaments initially formed in the coagulation bath are at least partially esterified with formic acid and can be stretched considerably more than those obtained by the viscose process. This provides flexibility in operation and allows fibres with a wide range of properties to be produced.

A particular advantage of the use of the preferred organic solvent, methylene chloride, is that a substantial portion of it separates from the clear viscous solution and is easily recovered by decantation.

The formylation reaction may be carried out in the temperature range from about 9 C to about 30 C. More preferably the reaction is carried out at around 15°C.

We have found it to be particularly advantageous to make up a stock mixture of formic acid and methylene chloride which can be mixed with the cellulose-containing material concurrently with sulphuric acid or prior to the addition of the sulphuric acid. This avoids significant reaction between the formic acid and sulphuric acid which results in the production of carbon monoxide. The formic acid, methylene chloride and sulphuric acid may be mixed together before addition to the cellulose, provided that the mixture is not allowed to stand too long before the addition. Hydrolysis of residual formyl groups in the regenerated fibre may be accomplished by treating the fibre with an alkaline medium. Preferably the treatment is carried out at around ambient temperature with about 1.5% sodium hydroxide solution. Ammonium hydroxide may also be used. Alternatively, if it is desired to avoid the use of alkali, the hydrolysis may be effected by other means for example by exposing the fibre to steam.

The relative proportions of cellulosic material, formic acid, organic solvent and catalyst may be selected so as to achieve the desired degree of polymerisation. For example where the cellulose-containing material is substantially alpha cellulose, we have found a ratio of sulphuric acid to cellulose material of 1.5:1 to be satisfactory. In the case of cotton linters a ratio of about 2.5:1 has been found to be satisfactory.The ratio of methylene chloride to formic acid may range up to about 10:7.

It should be clear to the reader, however, that the invention is not limited in this particular aspect and the ratios of the various components may be selected so as to achieve a product having the desired properties.

Conventional additives may be added to the dope. These additives include dyestuffs, fire retardants, pigments and lustre control agents.

Additives may be used in the coagulation step to alter the fibre properties. For example ferric chloride may be used to prevent self-adhesion of the fibres.

The invention will now be more fully described with reference to the accompanying examples. It should be understood however, that the description following is illustrative only and should not be taken in any way as a restriction of the generality of the invention described above.

Example 1

Cellulose pulp (30 g; Acetakraft from International Paper Company and CIP Inc) was stirred at approximately 14°C for 35 minutes with a mixture comprising 900 ml of methylene chloride : formic acid (10:7) (standard mixture) and 45 ml of sulphuric acid. 500 ml of liquid was decanted off and the clear viscous solution pumped through a 50-hole spinneret (hole diameter 64 micrometre) into a coagulant bath containing water to produce filaments. The filaments were then stretched in a water bath at 55 C.

Properties of the resultant fibres were: denier 4.68; tenacity 1.71 g/denier; strain 39% and modulus 49 g/denier.

Example 2

Nitration cellulose-Q pulp (20 g; product of ITT Rayonier) was added to a mixture of 600 ml of methylene chloride : formic acid (10:7) and 30 ml of sulphuric acid. The mixture was kept at approximately 14 C and stirred for 28 minutes. A further 110 ml of formic acid was then added and the mixture stirred for a further two minutes. The supernatant liquid (340 ml) was removed and the clear viscous solution transferred to a piston-driven pump and extruded through a 50-hole spinneret (hole diameter 64 micrometre) into a coagulation bath containing water. The resultant fibres were then air-stretched. The stretched fibres were immersed in a 1.5% solution of sodium hydroxide for 5 minutes and then washed with water to yield regenerated cellulose fibres with the following properties: denier 3.59; tenacity 1.35 g/denier; strain 38% and modulus 24.1 g/denier.

Example 3

900 ml of a mixture of methylene chloride : formic acid (10:7) and 45 ml of sulphuric acid were added to 30 g of a cellulose pulp (Nitration Cellulose-Q; product of ITT Rayonier) and the mixture stirred for 18 minutes with ice cooling. The temperature of the mixture varied from 24 to 12°C. After 510 ml of supernatant liquid was removed the residual clear viscous solution was extruded through a 50-hole spinneret (hole diameter 64 micrometre) into a coagulation bath containing water. The resultant fibres were then air-stretched and hydrolysed with a 1.5% sodium hydroxide solution as in Example 2.

The final product had the following properties: denier 4.56; tenacity 1.910 g/denier; strain 19% and modulus 42 g/denier.

Example 4

To cotton linters (30 g) standard mixture (900 ml) and H^SO. (69 ml) were added and stirred for 17 minutes with ice cooling. The temperature of the reaction varied from 23-12°C.

The supernatant solvent (420 ml) was decanted off and formic acid (140 ml) was added and the resultant mixture stirred for 3 minutes. A 500 holes (diameter 64 micrometre) spinneret was used. Water was used in the coagulation bath at 15 C and the fibres were stretched % in a water bath at 58 C.

The final product had the following properties: denier 1.2; tenacity 1.90 g/denier; strain 22% and modulus 14.7 g/denier.

Example 5

400 ml of a mixture of methylene chloride:formic acid (10:7 v/v) and 35 ml of sulphuric and were added to 20 g of unbleached Pinus radiata bisulphite pulp (Kappa No. 31.1; product of Apcel Pty Ltd) and the mixture stirred for 30 minutes at approximately 15 C. After 140 ml of supernatant liquid was removed the residual viscous solution was extruded through a 500-hole spinneret (hole diameter 64 micrometre) into a coagulation bath containing water. The resultant fibres were then air-stretched and hydrolysed with a 3% sodium hydroxide solution. The final product had the following properties: denier 2.1; tenacity 1.74 g/denier; elongation 18% and modulus 24.1 g/denier.

Example 6

P. radiata bisulphite pulp which had been bleached using the C/E/H bleaching sequence (20 g; Apcel Pty Ltd) was stirred at approximately 15 C for 25 minutes with a mixture comprising 400 ml of methylene chloride:formic acid (10:7 v/v) and 30 ml of sulphuric acid. 150 ml of liquid was decanted off and the viscous solution pumped through a 500-hole spinneret (hole diameter 64 micrometre) into a coagulant bath containing water to produce filaments. Pumping of the viscous solution through the spinneret commenced 40 minutes after the beginning of the experiment. The filaments were then air-stretched and treated with a 3% sodium hydroxide solution.

Properties of the resultant regenerated cellulose fibres were: denier 3.0; tenacity 2.08 g/denier; elongation 21% and modulus 21.8 g/denier.

It will be seen that the use of chemical wood pulps as described above provides excellent results in terms of the properties of the resultant fibre.

Example 7

Methylene chloride:formic acid (10:7 v/v) (1000 ml) were added to cotton linters (50g) . Sulphuric acid (100 ml) was added and the mixture was stirred for 22 minutes at 15 C. The supernatant liquid (600 ml) was decanted off and vacuum (20 mm Hg) was applied to the sample prior to spinning through a 500 hole (64 micrometre) spinneret.

Water was used in the coagulation bath and the temperature kept at 15 C. The sample was air stretched (50%) and the fibres were washed with 3% sodium hydroxide solution.

The regenerated cellulose fibres had the following properties: denier 2.1; tenacity 3038g/denier; elongation 18.4% and modulus 41.4 g/denier.

It will be clear to the reader that various modifications and alterations may be made to the particular aspects described above without departing from the spirit and scope of the present invention.

Claims

The claims defining the invention are as follows:

1. A process for the preparation of a derivative of cellulose and formic acid comprising reacting a cellulose-containing material with formic acid in the presence of an organic solvent and a catalyst.

2. A process as claimed in claim 1 wherein the cellulose containing material is selected from the group comprising cotton linters, alpha-cellulose, wood derived chemical cellulose, bleached chemical wood pulps and unbleached chemical wood pulps.

3. A process as claimed in claim 2 wherein the bleached chemical wood pulps and unbleached chemical wood pulps are produced by the soda process, soda-anthaquinone process, kraft process, bisulphite process or sulphite process.

4. A process according to any one of claims 1-3 wherein the catalyst is a catalyst that will bind water.

5. A process according to any one of claims 1 to 3 wherein the catalyst is selected from phosphoric acid or hydrogen chloride.

6. A process according to claim 4 wherein the catalyst is sulphuric acid.

7. A process according to any one of the preceding claims wherein the organic solvent is an organic compound that is capable of breaking hydrogen bonding within the cellulose-containing material.

8. A process according to claim 7 wherein the organic solvent comprises a chlorinated hydrocarbon.

SUBSTITUTE SHEET

9. A process according to claim 8 wherein the organic solvent is methylene chloride.

10. A process according to any one of the preceding claims wherein the process is carried out at a temperature of from about 9 C to about 30 C.

11. A process for producing regenerated cellulose products comprising:

a) reacting a cellulose-containing material with formic acid in the presence of an organic solvent and a catalyst to form a viscous solution; and b) contacting said solution with an aqueous medium to regenerate cellulose,

12. A process as claimed in claim 11 wherein the cellulose is regenerated by extruding the solution into the aqueous medium to produce cellulose fibres.

13. A process as claimed in claims 11 or 12 wherein the cellulose containing material is selected from the group comprising cotton linters, alpha-cellulose, wood derived chemical cellulose, bleached chemical wood pulps and unbleached chemical wood pulps.

14. A process as claimed in claim 13 wherein the bleached chemical wood pulps and unbleached chemical wood pulps are produced by the soda process, soda-anthaquinone process, kraft process, bisulphite process or sulphite process.

15. A process according to any one of claims 11 to 14 wherein the catalyst is a catalyst that will bind water.

HEET

16. A process according to any one of claims 11 to 14 wherein the catalyst is selected from phosphoric acid or hydrogen chloride.

17. A process according to claim 15 wherein the catalyst is sulphuric acid.

18. A process according to any one of claims 11 to 17 wherein the organic solvent is an organic compound that is capable of breaking hydrogen bonding within the cellulose-containing material.

19. A process according to claim 18 wherein the organic solvent comprises a chlorinated hydrocarbon compound.

20. A process according to claim 19 wherein the organic solvent is methylene chloride.

21. A process according to any one of claims 11 to 20 wherein step (a) is carried out at a temperature of from about 9°C to about 30°C.

22. A process according to any one of claims 11 to 21 wherein the aqueous medium is at a temperature in the range of about 10°C to about 30°C.

23. A process according to any one of claims 11 to 22 wherein a vacuum is applied to the solution prior to extruding the solution into the aqueous medium.

24. A cellulose derivative produced by the process as claimed in any one of claims 1 to 10.

25. A regenerated cellulose product produced by the process as claimed in any one of claims 11 to 23.

26. A process substantially as hereinbefore described with reference to any one of Examples 1 to 7.

27. A regenerated cellulose product produced substantially as hereinbefore described with reference to any one of Examples

1 to 7.