US2249175A - Preparation of solutions of heatripened cellulose xanthate - Google Patents

Description

g upwards of mi i um, mi e. o ter temperature was maintained for 4 minutes emu-dialer 2,249,115

-- UNITED sTATEs PATE OFFICE s nus-ll a No Drawing Application October 17 1,88,

seminarians v scum-(cumin r v This invention relates to the preparation of ripening treatment oi the process hereof. they solutions of heat-ripened cellulose xanthate. It may be dissolved in relatively cold or reirigdeals with a process by which cellulose xanthate erated caustlc soda solution at a temperature 4 .is ripened quickly under heat and is then put into sufliciently low to arrest the heat-ripening reacthe form of a finished cellulose xanthate or vis- 5 tron quickly or practically instantaneously and cose solution 01 the desired characteristics. into yield a xanthate or viscose solution or the decluding cellulose content, causticity, degree 01 sired stability or keeping quality. The amount ripeness, ripeness-stabilitmetc for the particoi-the cold or refrigerated caustic soda solution ularp rpose in view, to: instance. for spinning thus used for dissolving the heat-ripened zaninto rayon filaments or casting into films. o thate crumbs and the causticity'o't such solution 4 In accordance with the present invention, celmay be such as to yield a finished xa'nthate or v I lose xanthate or viscose solution to be produced for spinning into rayon filaments. is heated to much higher than room temper- While not limited thereto, the present invenature until the xanthate has acquired substan- -tion now be descrihed in terms oi particular tially the degree of ripeness desired, whereupon examples 0! procedure designed to yield finished the heated xanthate is admixed with relatively cellulose xanthate or viscose solutions'of a comcold or refrigerated aqueous medium in amount position and other characteristics ordinarily desufilcient to dilute the cellulose content oi the sired for spinning into rayon filaments. Accordxanthate to that of thefinal solution to be proing to one procedure, which involves reparingduced. .The aqueous medium thus admixed with from wood pulp or low solution viscosity a celluripening reaction in the xanthatei Its admixture No; 2,112 7 8 cellulOse l a r V cose soluwith the xanthate is eii'ected in the presence oi, tionwas prepared at cellulose and caustic soda in amount to promote substantially comconcentrations much higher than desired in the,

plete dissolution of the xanthate in the aqueous finished viscose solution. peciflcally, the solumedium, thereby conducing to the desired tion thus prepared had a cellulose content of finished cellulose xanthate or viscose solution. so, 12% and a caustic soda content of 10.86%. Such" The cellulose xanthate to be heat-ripened purcomparatively concentrated viscose solution was I suant to the present invention may be a cellue promptly after preparation'heated ind r t y n lose xanthate solution of distinctly higher cela tank, which was jacketed by aiheating medium,

lulose content than that 01' the final solution and stirred or mixed constantiyas it was being desired iorinstance. a finished solution such h dfate f heating was such that the subjected to the heat-ripening treatment hereof of the refrigerated diluting water and cellulose maybe in the form oi'- the usual xanthated xanthate solution: and it was noted that, when crumbs such as undergoes dissolution in weak the diluted solution had acquired substantial caustic soda. solution in the customary viscoseuniiormity throughout, its temperature had making process. Once such crumbs-have been dropped to 4 C. The ripeness value of the di-. heat-ripened to the desireddegree by the heat- I5 luted solution at 4' 0., as determinedby astandmanufacture; and

, cose and at the same cellulose and,

minutes to 42 C., in

continuous mixing were consumed before a monium chloride test, was 10.8 In other words,-

the diluted viscose-solution had been practically stabilized in its ripeness and could be kept for a substantial period of time, that is, for many hours, with practically no] change'in its degree of ripeness. The normal or satisfactory ripeness value of viscose solution for spinning :into

rayon filaments ranges from 9 to'11,such valuebeing determined by the same 334 in the 1926 edition of Hottenroth.

A heat-ripened viscose solution prepared and standard ammonium chloride test, which is described on page Die Kunstseide-' by V.

stabilized by the procedure just described is quite suitable for spinning into rayon filamen clear and its ripeness Thus, the solution-resulting from such. procedure is falls into the range usually considered satisfactory for rayon manufacture. I

Again, the composition of such solution comports with that considered satisfactoryfor usual rayon the ripeness-stability of such solution is such as to enable its storage or keeping for such substantial periods of time as "are customary in usual viscose-rayon manufacture. It is thus seen that the present invention makes possible an accelerated or heat-ripening of vistimethe attainment of a finished viscose solution as satisfactory in practically every respect for viscose-rayon manufacture as the ripened viscose syrup heretofore prepared by prolonged ripening of a freshly prepared viscose solution at the final or adiusted caustic soda concentrations. Another example of procedure performed accordant with the present invention involved the heat-ripening of cellulose xanthate crumbs prepared asordinarily by xanthating soda-cellulose crumbs with carbon bisulphide in the usual xanthating drum. It might be mentioned, however, that the soda-cellulose crumbs thus xanthated were produced from a hardwood sulphite pulp rather than a spruce sulphite pulp. The xanthated crumbs, which were of characteristic orange color, were tumbled in a closed container submerged in a liquid heating medium maintained at a temperature of 50 0. As the tumbling of the solid xanthate crumbs continued, their temperature, which was initially 27 C., gradually rose in 10 minutes to 37 C., in

in 50 minutes to The container was then opened and its content of heat-ripened xanthate 35 minutes to 48 C., and

; over a substantial period of time.

ammonium chloride ripeness test made on the solution after overnight standing showed a value of 10.8, which value means that the solution had the desired ripeness-stability or keeping quality 7 w *The resulting viscose solution was thus of a ripeness and of a composition normal for spinning into rayon filaments. In saying that its ripeness or maturity was normal, it is meant that itsripeness value, as determined by the standard ammonium chloride test, fell within a range of 9 to 11; and in saying that its composition was normal, it is meant that its cellulose content fell within a range of about 6 to 8% and that its caustic soda content was approximately equal to, or in the neighborhood of, its cellulose content.

The practice of the present invention lends itself to various changes or modifications, including the incorporation into the cellulose xanthate or viscose solution of substances that increase the rate of the heat-ripening. reaction and/or of substances that decrease the rate of the heatripening reaction. Thus, we have found that the addition of glycerine to a viscose solution accelerates its ripening even in the absence of heating and that the addition to a viscose solution of a very small amount of glycerine before it undergoes the heat-ripening and dilution treatcrumbs discharged into a caustic soda solution of 4.89%,caustic soda content and refrigerated to 2 C., which solution was used in amount calculated to yield a finished xanthate or viscose solution of 7.4% cellulose content and 6.7% caustic soda content. The mixing of the crumbs and the solution was effected in a high-speed mixing vessel, which quickly yielded a mixture at a temperature of 2 C. The crumbs went into solution gradually and about 90 minutes of clear solution, that is, one practically devoid of visible undissolved residue, was realized. The resulting solution, which at 2 C. was found to have an ammonium chloride ripeness value of 10.9, was mixed for another 30 minutes and then permitted to stand overnight while exposed to a surrounding atmosphere at 10 to 15 C. An

. cellulose content and erated water.

ments hereof permits a given degree of ripeness to be attained in a distinctly shorter period of time than otherwise possible. On the other hand, we have found that neutral sodium sulphite decreases the rate of the ripening reaction and that the addition to a viscose solution of a very small amount of sodium sulphite prior to the heat-ripening and dilution treatments hereof may be desirable in order to decelerate the heat-ripening reaction to some extent. Again, sodium sulphite may to advantage be added to the refrigerated diluting water or caustic soda solution used to arrest the ripening reaction in the heat-ripened viscose solution or in-the heat-ripened xanthate crumbs; or a very small amount of sodium sulphite .may be added in crystalline or concentrated solution form to the heat-ripened viscose solution before its dilution with the refrig- In all such cases, the sodium sulphite serves to supplement the action of the cold aqueous medium in arresting quickly the ripening reaction in the viscose or cellulose xanthate solution and in enabling the realization of a finished viscose or cellulose xanthate solution of the desired ripeness-stability. In some instances,

the glycerine may be added to .the initial viscose solution in order to increase the rate of the heatripening reaction thereupon, whereupon, when the heat-ripening reaction in the solution is to .be arrested, sodium'sulphite may be used, as

hereinbefore described, in addition to the refrigerated aqueous medium to arrest the ripening reaction quickly at the desired stage of ripeness. Assuming that a finished viscose solution of 7 .4% 6.7% caustic soda content is to be prepared, as hereinbeforedescribed, one may, ifdesired, use, say, about: 1% of glycerine in "the heat-ripening treatment and use in addition to the refrigerated aqueous medium, say, about 0.2%to 0.5% of sodium sulphite for the purpose of arresting the heat-ripening reaction in the xanthate solution and thus stabilizing the ripeness of the solution,--the percentages of the glycerine and sodium sulphite being basedon the finished viscose solution.

In speaking in the foregoing specification and in theappended claims about heating cellulose xanthate of a cellulose content greater than that of the finished solution desired or to be produced by the process hereof, we mean that the cellulose xanthate is heated either in the form of a solution more concentrated in cellulose than the finished solution or in the form of cellulose xanthate crumbs. When the cellulose xanthate is heat-ripened in the form of a viscose solution comparatively concentrated in cellulose, its caus-.

ticity may be and preferably is such as to furnish all the caustic soda necessary for the finished solution; or some caustic soda may be supplied along with the refrigerated diluting water when the heat-ripened viscose solution is stabilized in its ripeness and brought to the desired final composition. On the other hand, when the cellulose xanthate is heat-ripened in the form of crumbs, practically all of the caustic soda necessary for dissolving the crumbs and furnishing a finished viscose solution of the desired composition may be supplied along with the refrigerated water used to arrest the heat-ripening reaction in the crumbs. In any event, the aqueous medium used to arrest quickly any further substantial ripening reaction in the xanthate, whether in the form of a heat-ripened viscose solution or of crumbs, is admixed with the xanthate in the presence of suflicient caustic soda or equivalent alkali to permit the desired substantially complete dissolution of the'xanthate and to yield a finished xanthate solution of the desired composition and ripeness-stabilit Irrespective of whether comparatively concentrated viscose solutions or cellulose xanthate crumbs are subjected .to the heat-ripening treatment thereof, it is usually desirable for such purposes as manufacturing rayon filaments and films that the finished solution to be spun into rayon filaments or cast into films be of a cellulose content of about 6 to 8%, that is, that the ripened solution be of a cellulose content of about 6 to 8% after it has been diluted with refrigerated aqueous medium and cooled thereby to a temperature, say, downwards of about 15 0., at which substantial ripeness-stability of solution prevails over a substantial period of time, namely, a period of greater than, say, about 12 hours. So, too, the causticity of the finished viscose solution should be such as to promote or maintain substantially complete solution of the cellulose xanthate. A caustic soda content or causticity in the finished viscose solution approximately equal to, or in the neighborhood of, that of the cellulose content of the solution makes possible the realization of the last-named desideratum. It is, howevento beunderstood that the process hereof, although advantageously applicable to the preparation of finished viscose solutions designed especially for such purposes as manufacturing rayon filaments and films, may be extended to the preparation of finished viscose or cellulose xanthate solutions of a cellulose content above or below the range of about 6% to 8% and of a causticity or caustic soda content preferably approximating the cellulose content and in any event sufllcient to promote or maintain substantially complete solution of the cellulose xanthate.

We claim:

o 1. A process of producing a solution of heatmedium in amount ripened cellulose xanthate having a desired degree of ripeness, which comprises heating to much higher than room temperature and in admixture with glycerine a cellulose xanthate of a cellulose content greater than that of said solution to be produced, said glycerine amounting to about 1%, based on said solution, continuing such heating until said xanthate has acquired substantially the degree of ripeness desired, and mixing with said heated xanthate and refrigerated aqueous sufiicient, to dilute the cellulose content of said xanthate to that of the solution to be produced and about 0.2% to 0.5% sodium sulphite, based on said solution, said aqueous medium being sufiiciently refrigerated to arrest quickly further substantial ripening reaction in said xanthate and to cool the mixture to a temperature at which said xanthate has substantial ripeness-stability over a substantial period of time and said aqueous medium being mixed with said xanthate in the presence of sufficient alkali to promote substantially complete dissolution of said xanthate in said aqueous medium.

2. A process of producing a heat-ripened viscose solution having a desired degree of ripeness, which comprises heating to much higher than room temperature a viscose solution containing glycerine and having a cellulose content greater than that of said solution to be produced, said glycerine amounting to about 1%, based on said solution, continuing such heating until said solution has acquired substantially the degree of ripeness desired, and mixing with said heated solution refrigerated water in amount sufiicient to dilute the cellulose content of said solution to that of the solution to be produced, said water being sufiiciently refrigerated to arrest quickly further substantial ripening reaction in said solution and to cool said solution to a temperature at which it has substantial ripeness-stability over asubstantial period of time and said water being mixed with said viscose solution in the presence. of sufficient alkali to maintain the viscose substantially completely dissolved.

3. A process of producing a heat-ripened viscose solution having a desired degree of ripeness, which comprises heating to-much higher than room temperature a viscose solution of a cellulose content greater than that of the solution to be produced, continuing such heating until said solution has acquired substantially the degree of ripeness desired, and mixing with said heated solution refrigerated aqueous medium in amount sufficient to dilute the cellulose content of said solution to that of the solution to be produced and about 0.2% to 0.5% sodium sulphite, based on said solution, said water being sufiiciently refrigerated to arrest quickly further substantial ripening reaction in said solution and to cool said solution to a temperature at which it has substantial ripeness-stability over a. substantial period of time and said water being mixed with said viscose solution in the presence of suflicient alkali to maintain the viscose substantially completely dissolved.

GEORGE A. RICHTER. HAROLD P. VANNAH.