Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1983-08-30
1984-06-26
Griffin, Ronald W.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
264178R, 264178F, 264187, C08B 1506, C08B 328, C08B 1122
Patent
active
044567499
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a procedure for precipitating a cellulose derivative from an alkali solution. In particular the invention relates to a procedure for precipitating cellulose carbamate from its alkali solution, in the form of fibre or film.
In the Finnish patent applications Nos. 793226 and 810226 is disclosed a procedure for producing an alkali soluble cellulose derivative from cellulose and urea at elevated temperature. The procedure is based on the fact that when urea is heated to its melting point or to a higher temperature it begins to decompose into isocyanic acid and ammonia. Isocyanic acid in itself is no 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, cellulose carbamate, may be dried after washing and stored even over prolonged periods, or it may be dissolved in an aqueous alkali solution, for manufacturing fibre for instance. From this solution may be manufactured cellulose carbamate fibres or films by spinning or by extruding, in like manner as in the viscose manufacturing process. The keeping quality and transportability of cellulose carbamate in dry state afford a great advantage compared with the cellulose xanthate in the viscose process, which cannot be stored nor transported, not even in solution form.
If, for instance, continuous fibre or filament manufactured from cellulose carbamate suitable for textile use is required, it is necessary first to make a solution of carbamate in an aqueous solution of alkali, e.g. of sodium hydroxide. Thereafter, it is possible to precipitate from this solution fibre or film in like manner as in manufacturing viscose fibre cellulose is regenerated from a NaOH solution of cellulose xanthate. In the viscose process, xanthate solution is as a rule spun into a precipitation bath which contains dilute sulphuric acid and sodium sulphate.
Although the precipitation of cellulose carbamate in sulphuric acid resembles the precipitation process in the viscose method, it is a totally different matter in principle. Cellulose carbamate is stable in acid conditions and does not, therefore, decompose into cellulose on precipitating, as in the viscose process. However, contacting the alkaline solution of the carbamate with sulphuric acid induces precipitation of the cellulose carbamate, and at the same time sodium sulphate is formed as sodium hydroxide is neutralized.
When trying to apply, in the precipitation of cellulose carbamate from a solution of sodium hydroxide, similar precipitation solutions to those used in manufacturing viscose, it was found that the dry matter content of the precipitated carbamate fibre remained for lower than in the viscose process, which is far too low. This has the further consequence that the initial strength of the fibre product thus produced was not sufficent to tolerate the mechanical stresses involved in the treatment of the fibre. The low dry matter content of the fibre also implies that in the drying phase of the fibre much more water must be evaporated and more energy consumed.
The object of the present invention is a procedure in which in the precipitation of cellulose carbamate a high enough dry matter content is achieved. The procedure of the invention for precipitating cellulose carbamate from an alkali solution is characterized in that the solution is brought into contact with an aqueous solution of sulphuric acid containing one or several cations selected from the group: Na, Al, Mg, Zn and Ca cations.
Suitable sources for supplying Al, Mg, Ca or Zn cations are the corresponding sulphates, although also other salts, for instance chlorides, may be used. Differences exist between different cations: it appears as if trivalent cations were more powerful than bivalent or monovalent cations. A highly advisable ca
REFERENCES:
patent: 2129708 (1938-09-01), Schreiber
patent: 2134825 (1938-11-01), Hill et al.
patent: 4367191 (1983-01-01), Cuculo et al.
patent: 4404369 (1983-09-01), Huttunen et al.
Eklund Vidar
Ekman Kurt
Huttunen Jouko
Mandell Leo
Turunen Olli
Griffin Ronald W.
Neste Oy
LandOfFree
Procedure for precipitating cellulose derivative does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Procedure for precipitating cellulose derivative, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Procedure for precipitating cellulose derivative will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2233306