Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1983-08-30
1984-12-04
Griffin, Ronald W.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C08B 1506
Patent
active
044865856
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a procedure for producing soluble cellulose derivatives. In particular the invention relates to a procedure for producing cellulose compounds which can be dissolved in alkali and therefrom precipitated in the form of film or fibre.
When producing regenerated cellulose, most often the so-called viscose method is applied towards cellulose dissolving, in said method first being prepared alkali cellulose and this is reacted with carbon disulphide to obtain cellulose xanthogenate. The cellulose xanthogenate may be dissolved in a alkali solution and regenerated by precipitation in film or fibre form to become cellulose again. The carbon disulphide used in the method is an extremely toxic substance. Endeavours have been made to find a substituting chemical to replace it which would be economical enough in use and which would not cause similar environmental and health detriments as are caused by carbon disulphide. No commercial methods or processes to replace the viscose method are in use to date.
Finnish Pat. No. 61033 and our copending patent application Ser. No. 341,133, filed Jan. 20, 1982, now U.S. Pat. No. 4,404,369, disclose procedures for manufacturing alkali soluble cellulose carbamate from cellulose and urea. When urea is heated to the melting point or to a higher temperature, it begins to decompose, forming isocyanic acid and ammonia. Isocyanic acid in itself is not a particularly stable compound: it tends to become trimerized into isocyanuric acid. Further, isocyanic acid tends to react with urea, whereby biuret is formed. Isocyanic acid also reacts with cellulose, producing an alkali soluble cellulose compound, which is called cellulose carbamate. The reaction may be written as follows ##STR1## The compound thus produced, that is cellulose carbamate, may be dried after washing and stored even for prolonged periods or it may be directly dissolved in alkali solution. From this solution may be manufactured cellulose carbamate fibres by spinning, in like manner as in the viscose fibre manufacturing process. The keeping quality of cellulose carbamate and its transportability in dry state afford a very great advantage compared with the cellulose xanthogenate in the viscose method, which cannot be stored nor transported, not even in solution form.
The degree of polymerisation of the cellulose that is used as the starting material in the procedures described in Finnish Pat. No. 61033 and U.S. Pat. No. 4,404,369 has a great significance regarding the end product. The higher the degreee of polymerisation of the staring cellulose, the higher the viscosity of the alkaline solution of the end product, and correspondingly, the lower the cellulose carbamate content of the solution obtained in dissolving the end product. As regards the solubility of the end product, it is also essential that the degree of polymerisation of the cellulose starting material is as uniform as possible. A suitable DP of the cellulosic starting material is between 800 and 400.
For decreasing the polymerisation degree of cellulose, an alkali treatment has been applied in traditional methods. This involves treating the cellulose in sheet or fibre form with an 18% alkali solution. Through the effect of air or oxygen, depolymerisation of the cellulose is achieved. If the cellulose is in sheets, it is shredded at this phase in order to enhance the effect of air. If desired, the alkali treatment may be discontinued at the polymerisation degree desired by washing with water and drying. Cellulose which has been treated in this manner and dry-comminuted is suitable for use as starting material in manufacturing cellulose carbamate.
On the other hand, the alkali treatment mentioned is a process involving several steps and conducive to higher cost and it includes quite many drawbacks. In the method, it is necessary to add water and alkali to the cellulose. Before the next step, the substances mentioned have to be removed from the cellulose by the aid of a washing and drying process, which causes considerable extra costs.
REFERENCES:
patent: 2134825 (1938-11-01), Hill et al.
patent: 3352773 (1967-11-01), Schwartz et al.
patent: 4404369 (1983-09-01), Huttunen et al.
Chemical Abstracts, Ninth Collective Index, vols. 76-85, 1972-1976, pp. 10320cs and 10321cs, "Cellulose [9004-34-6], Reactions--Degrdn. of".
Eklund Vidar
Ekman Kurt
Huttunen Jouko
Mandell Leo
Turunen Olli
Griffin Ronald W.
Neste Oy
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