US1700595A - Cellulose composition for esterification and process of preparing same - Google Patents

Description

Patented Jan. 29, 1929.

' UNITED STATES PATENT OFFICE.

GEORGE A. RICHTER, OF BERLIN, NEW HAMPSHIRE, ASSIGNOR T BROWN COMPANY OF BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE.

CELLULOSE comrosmon non ESTERIFICATION "AND rnocnss or PREPARING SAME.

No Drawing.

This invention relates to the preparation of a cellulose composition for esterification, being more especially related to the preparation of a composition for nitration, and has for its object the preparation of a composition which when nitrated has a low acid retention and gives a high yield of nitrocellulose.

One process of preparing cellulose fiber for nitration is disclosed and claimed in application, Serial No. 140,677, filed October 9, 1926. In accordance with that process, wood fiber, but more particularly a high alpha cellulose wood fiber, is mercerized prior to nitration. When high alpha cellulose wood fiber is mercerized in bulk form, particularly in the presence of a small quantity of an oxidant, and then nitrated, the resulting nitrocellulose yields solutions of lower viscosity and of markedly better color than those prepared from nitrated, unmercerized fiber.

When mercerized fiber is nitrated in bulk form, however, the acid retention is appreciably higher, and the yield appreciably lower 2 than when unmercenzed fiber is first made into thin paper or tissue, which is then mercerized and nitrated as disclosed and claimed in application, Serial No. 140,675, filed October 9, 1926, by Milton 0, Schur and Royal H. Rasch. The quality of nitrocellulose obtainable from mercerized bulk fiber, and the i hysical and mechanical characteristics "of aments, films, lacquers, and kindred products prepared from such nitrocellulose, are,

5' however, apparently as good as when similar 5 fiber in tissue form is nitrated. Apparently, the higher acid retention and lower yield accompanyingthe nitration of mercerized bulk fiber are imputable to the higher absorptivity I 40 of the bulkfiber. Thus, owing to the higher retention of acid by the bulk her, a greater loss of the fiber apparently takes place during nitration and when after centrifuging it is submerged in water,-"my theory being that the wash water'efiects a slower dilution and washing out of the acid in the bulk fiber than when tissue is washed, and that during such slower dilution acidconcentrations are roduced in the bulk fiber, which favor 'a ydrolysis of nitrocellulose. "If, however, it

is attempted to form thin paper from the ,gether by regenerated cellulose, which serves Application filed March 3, 1927. Serial lilo. 172,567.

fiber, preferably in beaten condition, with the mercerized fiber.

The object of the present invention is to produce a relatively strong, dense paper or tissue from mercerized cellulose fiber without the use of unmercerized fiber, whereby the desiderata of lower acid retention and higher yield may be realized; I have found that this object maybe attained by treating the mercerized fiber with a solution of nitrocellulose or with a cellulose derivative capable of being regenerated into cellulose, and then, if other than nitrocellulose be employed, regenerating the cellulose in situ on the fiber. For instance, a mercerized fiber paper may be formed, then passed'through a solution of cellulose xanthate, and the cellulose regenerated in' situ in the paper. The fibers thus become encased in and bonded togo to increase the strength and density of the paper. When a paper thus permeated with regenerated. cellulose is nitrated, it is found that the acid retention isappreciably lower, .and the nitrocellulose yield appreciably higher than when mercerized bulk pulp is nitrated.

The production of a mercerized fiber paper permeated with regenerated cellulose may be accomplished by several different procedures. Thus, one method of procedure may be substantially. as follows. Mercerized cellulose fiber is run out on a paper machine into thin sheets orrtissue. The paper thus formed is loose and bulky, but these characteristics may be made less pronounced by incorporating a small proportion of unmercerized fiber, either beaten or unbeaten but preferably the latter, intothe mercerized fiber. The paper is then saturated with a cellulose anthate solution of sufiicient cellulose concentration to yield about 2% to 5% regenerated cellulose, when regenerated in the paper. The paper is then partially or completely dried and immersed in a cellulose-regenerab ing reagent, e. g., a solution of sodium bisulphate and sulphuric acid, toeftect a regeneration of cellulose in situ in the paper. The paper may then be washed, steeped, if desired, in a sulphur-removing reagent, e. g., a

sodium sulphide solution, again washed, and

finally dried. Preferably, the dry paper is formed similarly to beater-sizing. In such case, cellulose xanthate solution is added to the mercerized fiber in the beater engine, and after it has been uniformly disseminated throughout the pulp, a regenerating reagent is added. The pulp may then be washed and run out on a paper machine into thin pa er, which is dried and preferably calendere The cellulose may also be regenerated from cellulose derivatives other than viscose. For

instance, the regeneration of cellulose may occur from other esters or from cuprammo-- nium cellulose, but cellulose xanthate is preferred, because it is less expensive and easier to treat successfully. When nitro-cellulose is employed as the cellulose derivative, its regeneration into cellulose need not be effected, as no acidgrouping which might afiect nitration or the quality of the nitrocellulose is present in the paper. In suchcase, the

" mercerized fiber is treated with a solution of cellulose nitrate in an ether-alcohol mixture, for example, and the solvent then evaporated and recovered, thus leaving the fibers encased and bonded together with cellulose nitrate,

which serves to strengthenand density the .paper. The paper is then preferably calendered, as previously. Where, however, it is undesirable to allow nitrocellulose to remain in the paper, asfor instance where. such paper is to be stored or shipped, the nitrocellulose may be regenerated into cellulose as is effected when cellulose derivatives other than nitrocellulose are employed. This may be accomplished, for example, by steeping the paper in a denitrating bath, e. g., a so dium sulphide solution, whereupon the paper may be washed and dried.

While fiber made into paper gives the best results upon nitration, nevertheless bulk mercerized fiber whichhas been treated with regenerated cellulose'or nitrocellulose when nitrated in bulk form gives improved results over bulk mercerized fiber alone. For incellulose fiber and a cellulose stance, bulk mercerized fiber which has been treated with regenerated cellulose or nitro cellulose maybe fluifed mechanically tore-v semble cotton linters, or may be formed as a relatively thick, loosely felted, uncompacted web on a Fourdrinier wire or a cylinder machine, and nitrated in. such form.

In any of the procedures hereinbefore' given, the mercerized fiber has been prepared for nitration without the introduction of foreign materials which would be nitrated along with the cellulose and contaminate the nitrocellulose. The utility of the process herein described is that the advantage of mercerizing fiber in bulk form, as well as theadvantage arising from a desirable physical condition of fiber.v

when nitration is being efl'ected,*are both I realized. In plant practice, it is more economical to mercerize and wash pulp in 19.1 e quantities in bulk form and to recovert e mercerizing solution, rather than to mercerize thin paper or tissue. By the process of the present invention, the economical advantages of mercerizing fiber in bulk form are enjoyed, and at the same time a paper of good nitrating characteristics may be manufactured therefrom. 1

Having thus described certain embodiments of this-invention, it is obvious that these may be varied without departing from the spirit or scope of invention'as set forth in the appended claims.

What I claim is;

1. A composition comprising merceriz cellulose fiber and regenerated cellulose deposited on' said fiber.

2. A composition comprisin mercerized erivative deposited. on said fiber.

' 3. A paper comprising mercerized cellulose fiber permeated with regenerated celluose.

4. A paper comprising mercerized cellulose fiber permeated with a cellulose derivaive.

5. A calendered paper comprising mercerized cellulose fiber permeated with regener-- ated cellulose.

6. A process which comprises runnin mercerized fiber out on a paper machine, an

permeating the paper with a cellulose derivaive.

7. A process which comprises running mercerized fiber out on a paper machine, permeating the paper with a cellulose 'derlvative, and regenerating cellulose in situ in the paper.

8. A process which comprises running meating the paper with a cellulose derivative, regenerating cellulose in situ in the paper, and nitrating the paper.

10. A process which comprises running mercerized fiber out on a paper machine, saturating the paper with a solution of cellulose xanthate, drying the paper, regenerating cellulose in situ in the paper, and nitrating'the paper.

11. A process step which comprises permeating paper composed of mercerized cellulose fiber, with a cellulose derivative.

12. A process which comprises permeating paper composed of mercerized cellulose fiber, with a cellulose derivative; and nitrating the same. Y 13. The process step which comprises permeating paper composed of mercerized cellulose fiber, with regenerated cellulose.

14. A process which comprises permeating 16. A process which comprises fixing regenerate-d cellulose on mercerized cellulose fiber, running the fiber out on a paper machine, and nitrating the paper.

17. A process which comprises incorporating a solution of cellulose xanthate into mercerized cellulose fiber, adding a regenerating reagent to the fiber, thereby regenerating cellulose on the fiber; and running the fiber out on a paper machine. 7 In testimony whereof I aflixed my signature.

GEORGE A. RICHTER;