USRE14338E - Hekry deeyfus - Google Patents

Description

HENRY DREYFUS, or rasnn; swrrznanann.

cEnLU osE ecn'ra'rns AND PROCESS or MAKING SAME.

No Drawing. Original 110.

T all whom it may concern Be it known that I, HENRY Dnnrrtrs, a

citizen of the Republic of Switzerland, re-

' siding at Basel, Switzerland, have invented .certam new, and useful Improvements in Cellulose Acetates and Processes of Making Same, of which the following description is a specification.

The present invention relates to'cellulose acetates having special properties; and the methods whereby such acetates are produced.

The known processes of making cellulose acetates mostly depend upon the selection of the particular condensing agent to be employed. The greater part of the patents assume thatsulfuric acid is highly injurious on accountof its great splitting action on cellulose. Accordingly various substitutes therefor have been proposed, such as hydro- ;chloric, nitric, nitrosulfuric acids, or salts such as zinc chlorid, sodium bisulfate, sulfonic acids, chloracetic acid, etc. In some of these processes,'either cellulose or hydrocellulose may be employed, e. 9. that produced by the Girard process, using sulfuric acid. of 3% strength, or by using sulfuric 'and glacial acetic acid. Other processes use moist cellulose .to avoid splitting of the cellulose Each of these processes is said to have its own special advantages,and with the rocess usin sulfuric acid, etc., and

glacial acetic acid, solutions are obtained WhlCl]. have more or less vlscosity, or hm- .pidity, according to the exact procedure followed.

The. products heretofore produced, have been in nearly allcases soluble in chloroform, and in glacial acetic acid. Films made therefrom havebeen either stretchy,

brittle or otherwise objectionable, rendering them practically useless for most purposes.

In my present invention I have found a process for the. direct manufacture, by a direct acetylization processv of cellulose ace-r tates insolublein chloroform, but soluble in a mixture .of'chloroform and alcohol, which "acetates are also insoluble in diluted or concentrated alcohol. Some of these products are soluble in pure acetone,'o'thers are distinguished by acharacteristic behavior upon treating them with pure acetone. Th come transparent or semi-fluid and .p astic therein, and'by the addition of a small quan-' Specification of Reissued Letters Patent. Reissued J 1y 31, 1917,

1,181,857, dated May 2, 1916,:Serial No. 652,442, filed October 2, 1911. Application for reissue filed October 19, 1916. Serial No. 126,502.

tity of water, they produce viscous solutions. In carrying out this process, there is no intermediate stage, in which the cellulose acetates become soluble in chloroform. I have found that the manufacture of these products depends upon a series of conditions, which must be present in carrying out the reaction. Thus the production of this result depends upon the simultaneous control, relatively to each other, of the temperature employed in'the reaction, the humidity or amount of moisture present in the cellulosic material employed, the amount of condensing agent employed, and the quantity of acetylating agent relatively to the weight of cellulose used. These are some of the factors which arein mutual depend-. ence with each other, and which determine the properties of the cellulose acetates produced in carrying out the process.

I have found that, in the preparation of such acetates, sulfuric acid as the condensing agent, is perfectly satisfactory, provided that certain precautions are observed, as follows :-1, in carrying out the process at a temperature not above 40 C., and pref erably at ordinary room temperature, or by cooling to. a lower temperature; 2, in employing the proper quantityof the acetylizing agent; 3, in employing the proper quantity of the condensing agent; l, the selection of a cellulosic material (cellulose,

hydrocellulose or partially acetylized cellulose) containing the proper amount of moisture. v

My: new process depends (amongv other conditions) upon carryingout the process of acetylation at or below ordinary room temperature, that is up to about 30 (3., and

upon employing particular proportions of acetic anhydrid or acetyl chlorid, and of sulfuric acid or other condensing agent; both as compared with the amount of cellulose, and also depending upon theamount of moisture present in the cellulose, or other cellulosic body. These conditions'depend upon each other, and determine the properties of the resulting products; If 10% of' sulfuric acid, based on the weight of cellulose, is used, the amount of acetic anhydrid used can be varied between'about' 1.5 and 3 (preferably 1.8 kg. to 3 kg.) to each kilo'of celluloseor cellulose derivatives. If

more than 10% of sulfuric acid, say up to 20%, be employed, then (in addition to the ferred to, per kg.-bf cellulosic material) there will be used an additional quantity of acetic anhydrid, up to about four times the excess of sulfuric acid used, over and above the above mentioned. These figures are based on using sulfuric acid 95 to 100% strength, pure acetic anhydrid, and

I tained. If-20% or more of cellulose containing 5 to 6% of moisture, and working at ordinary room temperature. If the cellulose used contain more or less thanthis amount of moisture, the amount of acetic anhydridwill be increased or diminished accordingly. I

b Using 110% of sulfuric acid, and 3 kg. of acetic anhydrid, per kilo of cellulose containing 5 to6% of moisture and keeping the reacting materials at or below ordinary room temperature, products extremely soluble in alcohol-chloroform, but insoluble in chloroform alone, will be produced, I have also found that if it is desired to use alarger amount of sulfuric acid, the amount of moisture in thecellulose to be employed should be" decreased, otherwise, insoluble, pasty or mucilaginous products will be obsulfuric acid is to be] used the cellulose should preferably be dry, for example cellulose having been dried at -25to 50 (3., in a dry room, and this is especially to be followed, if the cellulose,be-'

- fore acetylization, is treated with a mixture acetylization to take place in a regular manv capable of sulfuric and'glacial acetic acid. It is not advisable to too much hydrolyze thecellulose before the introduction of acetic an-' hydrid or other acetylizing agents. Using cellulose containing 5% of moisture it is preferable to introduce it directly into a mixture of glacial acetic acid, acetic anhydrid and sulfuric acid.

If as much as 25% of sulfuric acid is to be used, dry cellulose should preferably be used, and it should be directly added to the above described mixture, otherwise a gelatinous product more or less easily soluble in dilute alcohol or hot water will be produced. I have found, thatin order to cause the ner, it is preferable to add the acetic anhydrid, or other acetylizing agent, to the mixture of "glacial acetic acid, sulfuric acid and cellulose, while constantly stirring the reacting mass. For the manufacture, in one operation, of products having a very great solubility, the amount of sulfuric acid should be between about 10 and 20% of the weight of the cellulose used, and the above proportions between the sulfuric acid, moisture content of the cellulose and aceticanhydrid should be rather closely followed. In this manner one can obtain products which are of producing very concentrated solutions of cellulose acetates in alcohol-chloroform or alcohol-tetrachlorethane and which 65.

can be used directly in the manufacture of In order to carry out my process, dry cellulose, or cellulose with a moisture content of say about 5%, or cellulose reviously treated with diluted sulfuric acid and dried down to about 5% of moisture,) or with ami'xture of glacial acetic and sulfuric acids, or a hydro-cellulose (provided the latter is not too much decomposed), may be used. It is evident that the afore-mentioned proportions between the moisture content, amount of sulfuric acid, the amount of acetylizing agent and temperature must be closely followed. By this energetic hydration, that is to sayby the preceding hydrolyzation at low temperatures-for example by the treatment with sulfuric and glacial acetic acids, it is ti) be noted that the cellulose molecule will not be destroyed or depolymerize'd no danger of depolymerization of the cellulose molecule during the acetylization step.

Also the low temperature at the commence-' ment of the acetylization does not have any disadvantageous effect, apparently since the entering acetyl groups have a protecting influence upon 'the cellulose molecule. That I the hydration at low temperatures does have a protecting effect is apparently due to the fact that in the hydration or treatment during and after the introduction of the cellulose into the acetylizing mixture-at, or preferably below, ordinary the temperature does not rise much above this point. In accordance with myinvention, however, I have found that only those room temperature,

cellulose acetates which are substantially insoluble in chloroform, but which become readily soluble by the addition thereto of more or less acetates are readily soluble in acetone, and others of which are very solublein diluted acetone containing a small amount of water,).

are of value for the production, (by further transformation) of products having useful solubilities, and other useful properties.

These are produced in the present invention,

in observing the conditions of temperature, quantity of. sulfuric acid, quantity of acetic anhydri'd' and the like,*rela'tive to each other.

I alcohol, (some ofwhich cellulose In accordance with my invention, by directly' introducing the cellulose, and maintaining the materials at or below ordinary room temperature, unless observing the conditions above pointed out, there will be obtained only syrupy products, which contain cellulose acetates readily soluble in chloroform, and which also contain a large quantity of unchanged fibers. Such products are not of value for the production of celluloid and films.

In order to obtain valuable products, the temperature during the llltI'OdllCtlOIl'Of the cellulose, and up to the completion of the reaction, must in every case be kept down.

.In operating in this manner, syrupy liquids are not obtained, but solutions of the highest viscosity, which do not contain a law quantity of unchanged fibers, and accordingl the products produced inaccordance w1th my process are transparent, and give in the acetylating solution, very viscous products which may even approach a stiff or gelatinous mass. These products and especially their transformation products, give solutions of the highest viscosity, which products can therefore be employed in the celluloid and film industries. 1 I j I In order to obtain rapidly a highly viscous solution, approaching in consistency a clear, stiff gelatinous mass, in accordance with my present invention, it is necessary to use very low temperatures. A product insoluble in chloroform, together with a high viscosity can be obtained (while using sulfuric acid alone as the condensing agent) if the temperature is not allowed, even in approaching the end of the acetylation to approach 40 C., and the temperature uring the entire process is preferably kept at or below ordinary room temperature to secure the'best results. But in connection with this, I call attention to the fact that the roducts of the presentiinvention are not intermediate products produced in the processes heretofore employed for the production of chloroform-soluble cellulose acetates, since in observing the conditions above stated to be necessary in my process, syrupy solutions will never be obtained. .In many instances, at the end of the acetylizing reaction,there will be present clear, very VlS- cous solutions, or clear gelatinous masses, of

such a high viscosity that they are scarcely movable or are wholly immovable, that is to say they congeal from their acetylationsolutions,'so that'they can be pulverized. Such products can not be produced if, the cellulose is introduced into an acetylizing mixture of which the temperature is above ordinary room temperature, and if sulfuric acid is used as'the condensing agent. 7

I again call attention to the fact that the present invention does not depend upon the temperature and the quantity of sulfuric acid alone, but upon these factors in connection with the amount of moisture in the cellulose employed, and this latter has to be taken in consideration. In a general way 10% and 20% of the greater the amount of moisture present in the cellulose employed, the smaller must be the quantity of condensing agent to be employed, and all the above factors must be kept in mutual dependence one upon the other. In using a cellulose containing about 5 to 6% of molsture, better results are secured than with a dry cellulose, since with a dry cellulose the reaction goes on much more slowly, and in connection therewith other inconveniences result, for example that the viscosity of the solution does not appear until the last moment, when aa clear solution or clear mass is obtained.

In accordance with my invention it is further necessary to use a quantity of an acetylating agent, such as acetic ,anhydrid, preferably not more than three times, and it is best to use only about two and one-half times the weight of the cellulose employed, since the excess of acetylating agent makes it more difiicult to observe the preferable tem-" and makes it also more difficult perature, to interrupt the reaction at the proper time. If smaller quantities of sulfuric acid as a condensing agent havee been used, it is easier to regulate the temperature but the reaction does not go on so energetically. ways necessary mum quantity of sulfuric acid, relatively to the weight of cellulose used, in order to obtain technically valuable products. Accordingly the quantity of sulfuric acid can not arbitrarily be changed, but can be changed. onlyaccording to the other conditions present in the reaction, (a. 9. amount of moisture, etc). The most favorable results for-obtaining these cellulose acetates, I insoluble in chloroform are obtained espe-.

cially by the direct introduction of the cel lose into the acetylating mixture of for example glacial acetic acid, aceticanhydrid, and sulfuric acid, if one employs between sulfuric acid (andwith advantage not under 5%) calculated upon the weight of the cellulose employed. In

this case one obtains products, some of which are easily soluble in such solvents as concentrated acetone, and others in; somewhat dilutedacetone, which products, by their further transformation (for example in a precipitated form'.) give other solubilities- The products, obtained by my process are distinguished in that while they are insoluble in chloroform, or in tetrachlorethane they can be dissolved to produce very concentrated solutions in alcohohchloroform, or 'in alcohol-tetrachlorethane, etc., which was not possible with the products heretofore produced by any direct process.

The products obtained in myprocess are especially distinguished from those previously produced, by their great stability which is also true of the articles made therefrom, by their being substantially insoluble It is al- 7 to employ a certain miniin chloroform, and bytheir property of being able to give highly concentrated and viscous solutions of cellulose acetates, in alcohol-chloroform or in alcohol-tetrachlorethane (mixtures of, say, equal volumes of alcohol and chloroform,'or alcohol and tetra chlorethane, respectively).

Those products which are completely or partially soluble in alcohol-benzin and other solvents, are of particular interest.

In order to illustrate my invention I give the following examples, the parts being by I ane, etc., (these solvents for example being weight, but it is to be noted that the in- Yention'is not limited to these examples.

Example I: 200 parts of cellulose, for example cotton containing about 5% of moisture, are treated with a mixture of 800 parts of glacial acetic acid and 20 parts of concentrated sulfuric acid. Into this mixture while constantly stirring, and at ordinary room temperature, or by cooling, 400 parts of acetic anhydrid'are slowly added. This addition may be made at once or after 2 or 3 hours or more. As soon as the material dis solves, water may be added, while constantly stirring, to precipitate the cellulose acetate which is then washed, pressed, and-dried.

This product is insoluble in chloroform but swells therein, it is soluble giving highly concentrated and viscous solutions in alcohol-chloroform or in alcohol-tetrachlorethcomposed of equal volumes of the two liquids). The product shrinks in pure acetone and forms a transparent, semifluid mass which by the addition of asmall amount of water roduces a viscous solution. Without precipltation by water the solution obtained by acetylization can also be employed directly or after neutralization of the mineral acid for the manufacture of artificial silk,

or other threads or for other purposes,

Example II: 200 parts ofcotton having a moisture content of about 5% are treated in the same manner with the mixture of, 800 parts of glacial acetic acid and 20 parts of concentrated sulfuric acid. Directly, or after two to threehours approximately 600 parts of acetic anhydrid are added, while constantly stirring and while preventing any substantial rise in temperature, the product is a viscous solution similar to that produced and after 2 or 3 hours 650 to 700 parts of acetic anhydrid are introduced, preferablyv while the mixture is maintained at or below ordinary room temperature, andwhile stirring. A product is obtained similar tothat of Example II, and is worked up in the same manner.

In these examples, the cotton orpaper may be replaced by other forms of cellulose, or by their products of transformation. Commercial sulfuric acid, glacial acetic acid, and acetic anhydridcan be used, of which the strength varies more or less or other acetylizing or diluting agents may be employed'.

The proportions of sulfuric acid," glacial acetic acid, acetic anhydrid, and cellulose should not be greatly varied. The amount ofmoisture in the cellulose may vary somewhat. The cellulose esters may be separated or precipitated from their solutions in any appropriate manner.

In a very advanced reaction with acetylation solutions, being more movable or more fluid, the precipitated acetate after drying, becomes fluid in chloroform, with out dissolving therein. The samecremarks. applyfgenerally to tetrachlorethane, as to chloroform, but upon addition of; more or less alcohol, either to the chloroform or the tetrachlorethane, the cellulose acetate readily dissolves to produce a viscous solution, according to the duration of the reaction, and it becomes increasingly soluble in concentrated or diluted acetone. v

The solubilities of the product, during this secondreactionwill successively change, depending upon the conditions present. The product, at the end of the acetylation reaction being soluble in a mixture of alco: hol and chloroform (equal parts, for example), the solubility in such solvent successlve ly lncreases; in relatively concentrated acetone, the solubility increases up to acer- .tain maximum, and then commences ,to decrease, while the solubility in any more dilute acetone continues to increase up to a certain'maximum (coming later thani'the maximum solubility in more concentratedacetone). A solubility in chloroform alone may be developed, reach a maximum of ready solubility, and decrease, before reaching the maximum solubility in. acetone, or the solubility iu'chloroform may notvbe de veloped at any stage of the process so that the product remains always insoluble in chloroform depending upon the particular conditions and procedure. A solubility in a mixture of alcohol and benzene and'in diluted alcohol will begin, approach a maxiinum and then begin to fall, beforethe maximum solubility in concentrated acetone is reached.

Theprocess of altering the solubilities by the further treatment with acid solutions,

and the products of such treatment, are

claimed in my copending applications 7 82,- 530 filed August 1 1912 Patent No. 1,217,- 722, dated Feb. 2'7, 1917 and 73,496 filed January 21, 1916.

What I claim is:-'

1. A process of directly producing cellulose acetates substantially insoluble in chloroform, and insoluble in alcohol, but readily soluble in alcohol-chloroform, which comprises reactin acid and acetlc anhydrid in proportions of about 10 parts of cellulose, not more than 2 1; parts of sulfuric acid, and about 15 to parts of acetic anhydrid, at a temperature not above 40 C. r

2. A- process of directly producing cellulose acetates, insoluble in chloroform and in alcohol, but soluble'in chloroform-alcohol,

which comprises reacting upon .cellulose with sulfuric acid and acetate anhydridin proportions of about 10 parts of moist cellulose, about 1 part of sulfuric acid, and about 15 to 30 parts of acetic anhydrid, at "a temperature not above room temperature.

3. A process of directly producing cellulose acetate substantially insoluble in chloroform which comprises treating 200 parts of cellulosic material containing about 5% of moisture with a mixture of glacial acetic acid and about 20 parts of sulfuric acid, then adding,.while stirring, and while not above'ordinary room temperature about 400 parts of acetic anhydrid, then after the cellulose has been transformed into acetates which have gone into solution, precipitating by adding the reaction mixture to water while stirring, separating the precipitated cellulose acetates, and drying the same;

4:. A process of directly preparing"cellulose acetates substantially insoluble in chloroform and in alcohol but readily soluble in alcohol-chloroform, which comprises treating a cellulosic material containing about 5 to 6% of moisture with not, less than 1% times its weight of an acetylizing agent, at

a temperature belowabout 40 0., in the presence of not more than about 10% of its weight of sulfuric acid as a condensin agent. j

5. A process of directly preparin a class of cellulose esters which are inso uble J in i chloroform and insoluble in alcohol, but

which are readily soluble in chloroform-alcohol, which comprises treating 100 parts of a cellulosic material with a mixture including from 150 to 300 parts of acetic anhydrid and a condensing agent corresponding to about 10 parts of sulfuric acid, said reaction being tained ower than 40 C. I I v 6. A process of making cellulose acetates which com rises reacting upon cellulose with sulfurlc acid and acetic anhydrid in proportions of about 10 parts of cellulose,

upon cellulose with sulfuric performed at a temperature main-.

concentrated sulfuric acid, and allowing the materials to react, and thereafter introducing an acetylizing agent, while the mixture containing the sulfuric and glacial acetic acids and the acetylizing agent are at a temperature not above ordinary room temper- 1 ature.

8. A process of. producing cellulose acetates, substantially insoluble in chloroform and in alcohol, in a direct manner, which comprises mixin together 800 parts of glacial acetic aci and 20 parts of concen trated sulfuric acid, and introducing thereinto about 200 parts of cellulose containingabout 5% of moisture, and thereafter adding, while maintaining the mixture at not above ordinary room temperature, about 400 parts of acetic anhydrid.

9. A processof directly producing cellulose acetates substantially insoluble'in chloroform and in alcohol, but readily soluble in chloroform-alcohol, which comprises reacting upon'cellulose containing not more than about 6% of moisture with about double its vweight of acetic anhydrid, in the presence of not more than about 25%. of sulfuric cid as a condensmg gent, at not above ordinary room temperatur 10. A cellulose acetate which is 'substantially insoluble .in alcohol alone and in chloroform alone, but which is readily soluble in alcohol-chloroform and in alcohol tetrachlorethane, said product being also soluble "in acetone .of a relatively high concentration, said product being further characterized in that upon bein treated, with an acid material, with or wit out the addition of water, its solubility in acetone of various concentrations is successively changed accordin to the duration of the reaction.

11.15 cellulose acetate'which is substantially-insoluble-in alcohol alone and in chloroform alone, but which is readily soluble in alcohol-chloroform, and in alcohol-tetrachlorethane, said product being also soluble 1D. acetone of a relatively high concentration, said product being further character- 'ized in that upon being treated with an acid material, with or w thout the addition of water, its solubility in an acetone of various conoentrationsis successively changed according to the duration of the reaction, and

that by further it produc continuing, said treatment, es a product soluble in water.

12. A cellulose acetate which is insoluble 5 in chloroform alone, and

but soluble in concentrated acetone.

(1 readily soluble in a mixture ofalone, alone, an

insoluble in aldohol chloroform-and alcohol, said product being further characterized in that upon being treated with an acid material, a product is 10 produced having a ditferent behavior toward acetone of various concentrations than has the product of departure.

- HENRY DREYFUS.