US1938176A

US1938176A - Manufacture of mixed cellulose esters

Info

Publication number: US1938176A
Application number: US315356A
Authority: US
Inventors: Dreyfus Camille; George W Miles
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1928-10-26
Filing date: 1928-10-26
Publication date: 1933-12-05
Anticipated expiration: 1950-12-05

Description

Patented Dec. 5, 1933 UNITED STA Camille Dreyfus, New York, N. Y., and George W. Miles, Boston, Mass, assignors to Celanese Corporation of America, a corporation of Delaware i No Drawing. Application October 26, 1928 Serial No. 315,356

11 Claims. (01. 2601-101) ployed catalysts or by using only very small amounts of such catalysts.

Still another object or" our invention is to devise a process for making mixed inorganic-organic esters of cellulose inone operation.

Still another object of our invention is to devise a process for making mixed esters of cellulose wherein the esterifying agents em ployed act as dehydrating agents, the one for the other. a

Still another object of our invention is to produce mixed cellulosenitrate and acetatewhich is esterified to a greater degree than has heretofore been considered possible.

Still another object of our invention is to produce mixed nitrate-acetate cellulose which is very stable even when the nitrogen content of such compound is very high; Other objects and advantages will appear from the following detailed description.

Heretofore in producing mixed esters .of cellulose it has been thought necessary to first esterify the cellulose with one esterifying agent and to replace part of these ester groups by treatment with another esterifying medium. In other in- I stances where cellulose ester products containing more than one species of acid radicals were de-, sired, these were obtained by physically mixing the different cellulose esters in the desired proportions. Theproducts of the latter processes were not true chemical compounds but were in fact merely mixtures of the different ingredients. We'have found that it is unnecessary to follow these long and expensive procedures in order to obtain mixed esters of cellulose. We havediscovered a process whereby two different species of ester groups can be introduced into the cellulose molecule in'one operation. Thismakes it possible to obtain variousmixed cellulose esters at a greatly reduced cost] and -in a very much shorter time than is required under the present ractice. I

)Our invention also enables'us to; procure mixed esters containing the diiierent ester groups in any desired ratio, one to another. We have also been "able to-obtain, by virtue of our process, a

- much 'higher degree of- 'esterification thanha's heretofore been obtainable or considered possible. Our invention is of particular value in the manufacture of mixed nitrate and acetate of cellulose, since it permits the nitration and acetylation of'the cellulose in one operation and in a single bath. In addition to the savingof time, this improvement hasother beneficial results. Nitrate-acetates of cellulose have been obtained which have a high nitrogen contentfbut are nevertheless very stable and which at the same time possess the valuable properties of the respective esters.

-We have also discovered that it is possible to make these mixed nitrate-acetates of cellulose without the use of "catalysts such as are usually employed in the manufacture of cellulose esters. We may dispense with the use of sulphuric acid as a c'atalystgthereby avoiding the-formation of the sulpho compounds to which the unstable properties of nitro cellulose are usually attributed.

The cellulosic material treate din accordance with our process may be any suitable cellulose or its derivatives. It may be cotton, cottonlinters,

' wood pulp or other forms of cellulose. The cellu- TESI PATENT OFFICE losic material may be pretreated in any. known manner in order to promote and facilitate its cellulosic material, such as cotton linters, with acetic anhydride, glacial acetic acid and fuming nitric acid at or below, preferably below, room temperatures. can beeifected in the absence of glacial acetic acid. Also phosphoric acid (H3PO4 or HPOs) can be added to the esterifying bath with beneficial results especially where it is desired to esterify the cellulose without the use of acetic anhydride. In some instances, small amounts of sulphuric acid may be used as a catalyst for the reaction. I

Although this description is largely. concerned with the manufacture of nitrate-acetate of cellulose, this invention is not tobe considered as limited thereto. Other mixed esters can also be madeby our process, for example, nitrate proe pionate of cellulose, nitrate butyrate of cellulose, etc. .In like manner the amounts of reagents given in the examples which follow are not limitative. The amounts of the various reagents will vary with the final product which is desired.

These end products can be of such infinite variety Where desired the esterification.

to utilize in order to obtain the various producta The products obtained by the process herein disclosed have an unlimited number of applications in the arts and in industry. Thus the products containing a comparatively high nitrogen content can be employed. in the explosive field. The acetyl content of the mixed ester has only a beneficial effect on the compound, increasing its stability without having any appreciable deterrent effect on its combustibility. Such high nitrogen content esters can also be used in the plastic arts where heretofore only low nitrogen content nitro cellulose could be employed. This is due to the fact that although the combustibility of the mixed ester has not been reduced, its stability during processing has been materially improved.

These mixed esters, due to their excellent properties, therefore are of great utility in all branches of theplastic art. They also furnish excellent bases for lacquers, varnishes and films. They can also be used in manufacturing laminated glass. In short these mixed esters afford excellent substitutes for the respective individual esters, usually excelling the single esters in their adaptability. t

For obtaining greater reactivity of the cellulosic material and thus inreasing the rate of the esterification process and also to obtain a mixed cellulose ester of higher clarity, we prefer first to subject the celluloseto a preliminary treat ment which may include either a pretreatment process or a prehydrolysis process or both a pretreatment or a prehydrolysis process.

The pretreatment process comprises the treatment of the, cellulosic material with a relatively small proportion of a lower fatty acid such as propionic acid, formic acid or acetic acid, and in the presence or in the absence of a small amount of a catalyst such as sulphuric acid. The propionic, formic or acetic acid may be applied to the cellulosic material in any suitable manner either in the form of a liquid, or in the form of a vapor.

As illustrations of a few methods of carrying out our invention, the following examples are given. The parts as indicated are by weight unless otherwise indicated.

Example I 1100 parts of acetic anhydride are mixed with about 400 parts of fuming nitric acid, both liquids Example II 100 parts of cellulose (cotton linters) are introduced into approximately 1000 parts of glacial acetic acid and allowed to stand about 15 hours at room temperatures. The mass is then cooled with ice water and to this cool mass is added a cold mixture of about 400 parts of fuming nitric acid, 400 parts of acetic anhydride and 400 parts of glacial acetic acid. The mass is well stirred,

cooled and allowed to stand about 16 hours at room temperatures. The reaction mass is then subjected to the hereinafter described secondary treatment. The final product on analysis showed a nitrogen content of 7.96% and an acetyl value of 16.52%.

Example III Example IV 1100 parts of 95% H3PO4 are mixed with 450 parts of fuming nitric acid and cooled in ice water. To this cool mixture is added 325 parts of acetic anhydride and parts of cotton linters, and the mixture kept in ice water for about two hours. The reaction mixture is then allowed to stand for about 18 hours in a water bath at about 20 C. The mass was then subjected to an after treatment as hereinafter described. Upon analysis the final product was found to have a nitrogen value of 13.39% and an acetyl value of 25.52%.

Example V 100 parts of cellulose are introduced into 630 parts of glacial acetic acid and allowed to stand for one hour in ice water. 60 parts of fuming nitric acid in 150 parts of cold glacial acetic acid is then added and finally 325 parts of acetic anhydride containing 10 parts of sulphuric acid are introduced into the mixture. The reaction mixture was allowed to stand for about 16 hours after which time it was subjected to thehereinafter described secondary treatment. The final product had a nitrogen content of 5.59% ,and an acetyl value of 42.0%. I

Example VI 100 parts of cotton linters are put in a bath of 630 parts of glacial acetic acid and allowed to stand over night. This is then cooled with ice water and to it is added about 380 parts of acetic anhydride containing 40 parts of sulphuric acid. There is then added 100 parts of cold glacial acetic acid containing 60 parts of fuming nitric acid. The reaction was completed in half an hour and the product washed. On analysis it showed a nitrogen content of 3.75% and an acetyl value of 34.44%.

It is to be understood that the above examples and the foregoing detailed description are given merely by way of illustration and our invention is not to be considered as limited thereto. Many variations from the above specific examples may be made without departing from the spirit of our invention.

It will be seen from the above examples that the cellulose is esterified to a remarkably high degree-in fact to a degree hitherto unattainable and considered impossible. The nitrogen and acetyl figures given are based on the esterified cellulose and a nitrogen value of 13.79%, for example, is in fact comparable to a nitrogen content of between 15 and 16% in a straight nitrocellulose. The same is also true of the acetyl;

value.

is the fact that the esterifying agents also act as dehydrating agents. The acetic anhydride acts as a dehydrating agent for the nitration and the fuming nitric acid acts as a dehydrating agent for the acetylation.

The reaction masses resulting from the above examples are then subjected to an after-treatment. The masses are tested for free anhydride and the latter is then hydrolized by the addition of the requisite amount of water. A slight excess of water is added and the mass allowed to ripen for a period of twenty four hours at about to C. A sample taken from the mass at the end of this time is precipitated by water, washed free of acid and dried and should show the solubility in acetone desired. When this test shows the proper solubility in acetone or other solvent used as guide, the mass proper is similarly precipitated. and washed until free of acid.

The precipitated product is then placed in about twenty times its weight of water containing less than .05% of sulphuric acid and boiled for a period of four hours or until a sample of the above materiahwhen dried, shows the desired solubility in acetone, ethyl acetate, etc. This treatment with boiling water containing a trace of mineral acid serves the double purpose of splitting up the sulfo esters of cellulose formed during the reaction when sulphuric acid is used as catalyst, thus increasing the thermo stability of the product, and at the same time, completing the hydrolysis of the product, the main portion of which is accomplished during the ripening process, so that the product is soluble in the solvents desired, which comprises those enumerated above.

Having described our invention what we claim and desire to secure by Letters Patent is:

1. Method of producing mixed nitrate-acetate of cellulose which comprises treating material consisting substantially of cellulose with acetic anhydride and fuming nitric acid in one bath.

2. Method of producing mixed nitrate-acetate of cellulose which comprises treating material consisting substantially of cellulose with acetic anhydride, glacial acetic acid and fuming nitric acid in one bath.

3. Method of producing mixed nitrate-acetate of cellulose which comprises treating material consisting substantially of cellulose with acetic anhydride, phosphoric acid and fuming nitric acid in one bath.

4. Method of preparing mixed nitrate-acetate of cellulose which comprises treating material consisting substantially of cellulose with acetic anhydride and fuming nitric acid simultaneously in one bath between about 0 C. and room tem-- peratures. v

5. Method of preparing mixed nitrate-acetate of cellulose which comprises treating material consisting substantially of cellulose with acetic anhydride, glacial acetic acid and fuming nitric acid simultaneously in one bath between about 0 C. and room temperatures until a nitrogen content of over 3.75% is obtained.

6. Method of producing mixed nitrate-acetate of cellulose which comprises pretreating material consisting substantially of cellulose With a lower aliphatic acid and then treating the pretreated material with acetic anhydride and fumingnitric acid in one bath.

7. Method of producing mixed nitrate-acetate of cellulose which comprises pretreating material consisting substantially of cellulose with a relatively small proportion of acetic acid and then treating the pretreated material with acetic anhydride and fuming nitric acid in one bath.

- 8. Mixed nitrate-acetate of'cellulose whose nitrate and acetate radicles are introduced in the cellulose molecule simultaneously, said nitrateacetate of cellulose having a nitrogen content of at least 13.28%.

9. Mixed nitrate-acetate of cellulose whose nitrate and acetate radiclesare introduced in the cellulose molecule simultaneously, said nitrateacetate of cellulose having a nitrogen content of at least 13.28%, being free of catalysts and having a high degree of stability and combustibility.

10. Mixed nitrate-acetate of cellulose whose nitrate and acetate radicals are introduced in the cellulose molecule simultaneously, said hitrate-acetate of cellulose having a nitrogen content of 13.79% and an acetyl value of 32.34%.

11. Mixed nitrate-acetate of cellulose whose nitrate and acetate radicals are introduced in the cellulose molecule simultaneously, said nitrate-acetate of cellulose having a nitrogen content of 13.79% and an acetyl value of 32.34%, being free of catalyst and having a high degree of stability and combustibility.

CAMILLE DREYFTUS. GEORGE W. MILES.