US1947463A - Manufacture and treatment of cellulose esters - Google Patents

Description

Patented F eb. 20, 1934 UNITED STATES MANUFACTURE AND TREATMENT OF CELLULOSE ESTERS Henry Dreyfus,

London, England No Drawing. Application March 21, 1929, Serial No. 348,980, and in 1928 Claims.

This invention relates to the manufacture of cellulose esters of hydroxy aliphatic acids.

The cellulose derivatives are manufactured according to the present invention by the treatment I 5. of cellulose or cellulose-containing material with anhydrides of hydroxy aliphatic acids. .For convenience the cellulose derivatives thus obtained will be termed hereinafter hydroxyalkacyl derivatives of cellulose. The hydroxy groups thereof '10 may be esterified, for instance with acetic anhydride, so as to form acidyloxyalkacyl derivatives of I cellulose.

The acylation with the anhydrides of the hydroxy aliphatic acids may be carried to the mono-, 15 di-, or tri-acyl stage or to any intermediate stage, but the most valuable products are obtained if the reaction with the cellulose or cellulose-containing material is carried to the tri-acyl stage or to between the diand tri-acyl stage.

The anhydrides tobe used in the acylation may be derived from any convenient hydroxy aliphatic acids, for example glycollic acid, lactic acid, hydracrylic acid etc. and may be prepared by any convenient method. For example they may be prepared from the sodium, potassium, or other metallic salts of the acids or mixtures thereof by treatment with thionyl chloride.

As initial materials for acylation according to the present invention cotton or any other celluloses or near conversion products thereof may be employed, or bamboo, esparto or wood pulps from which the lignin, pentosan, resin and like constituents have been substantially removed, as for example in sulphite pulp, soda pulp and sulphate pulp.

The cellulosic materials may be treated, prior to the acylation, with organic acids in large or small quantities, and particularly with lower fatty acids, such as formic or acetic acid, or with 10 hydroxy-aliphatio acids, to increase their reactivity. Chemical pulps are preferably subjected to an alkaline purifying treatment, as described in my U. S. Patent No. 1,711,110, followed by the treatment with organic acids, prior to the acylation. The alkaline purifying treatment may for example be performed with caustic alkali of low concentration, such as 3% or under, with heating or boiling, or with caustic alkali of high concentration, such as 540% or more, in the cold or with only slig it heating.

The pretreatment with organic acids may be carried out in any convenient manner. For example, the cellulosic materials may be pretreated with concentrated or dilute acids, particularly formic or acetic acid, as described in my French Patent No. 565,654, or, where feasible, with the vapours of the acids, as described in my British Patent No. 263,938, the vapours being employed alone or mixed with air or other inertgas. After the treatment-with organic acids, the cellulosic Great Britain April 18,

materials may be subjected to a stream of air or other inert gas or to suction or vacuum to remove the organic acids wholly or partially. Formic acid, except when employed in small quantitiea,v

should be substantially removed. If for the pre-' treatment an acid, such as acetic acid, is used which will serve as a solvent diluent in the subsequent acylation its removal is of course unnecessary. However, in pretreating with organicacids alone I have found that the best results are obtained by employing either formic acid, such as 80-10()% formic acid, or a mixture of formic acid with another acid, such as acetic'acid and removing it before acylation.

Another type of pretreatment, which I have found very efficacious for rendering the cellulosic material more reactive, is that described in my British Patent No. 312,998. The cellulosic'material is treated with hydrochloric or other hydrohalide acid or with mixtures thereof. The acid is most advantageously employed in a proportion of 510% (corresponding to about l5-3il% of commercial acid'in the case of hydrochloric acid).

The aqueous acids may be distributed evenly over the'cellulosic material, for instance by spraying the material in a drum or mixer, the cellulosic material being allowed to stand with occasional turning to ensure uniform impregnation until a prodnot capable of rapid acylation is obtained. This type of pretreatment is most valuable when hyment with other mineral acids for example sulphuric acid.

The actual acylation of the cellulose or cellulose-containing material with the anhydrides may be carried out in any convenient manner. For example it may be conducted in presence of a solvent or mixture of solvents for the cellulose derivative produced. Acetic acid or other lower fatty acids (with the exception of formic acid) may for example be employed. The invention is however not limited to the use of any particular solvent. The solvent or solvent mixture may be present in any desired quantity such as 4 to 6 times the weight of the cellulose or celluloseoontaining material, but cellulose derivatives of especially high viscosity can be obtained if the solvent or solvent mixture be present in an hours.

amount greater than 6 times, say 8 to 20 times or more the weight of the cellulose or cellulosecontaining material.

Again the acylation may be conducted in suspension in non-solvent liquid diluents. If desired solvents may be present in addition to the non-solvent diluents. As in the acylation carried out in presence of a solvent so that the cellulose derivative is produced in solution, the acetic acid or equivalent solvent may be used in quantities in excess of 6 times the weight of the cellulose, for example, 8 to 20 times or more to obtain cellulose derivatives of high viscosity. In all such cases of using solvents in addition in carrying out the acylation in suspension, the diluent should be present in suincient quantity to prevent solution of the cellulose derivative produced.

Fibres, fabrics or the like made of or containing cotton or other cellulosic material may be acylated by means of the processes of the present invention by carrying out the acylation in suspension in presence of liquid diluents.

The treatment with the anhydrides of the hydroxy aliphatic acids is preferably conducted in presence of a suitable catalyst or condensing agent. For example, sulphuric acid or organically substituted sulphuric acids such as benzene sulphonic acid, bisulphates, e. g. sodium bisulphate, phosphoric acid, sulphuryl chloride, zinc chloride or the like may be employed. Metallic halides, for example the chlorides, of iron (fer- .ric),.tin (stannic), manganese, copper, nickel or cobalt, used in conjunction with hydrochloric or other hydrohalide acids give useful results. Fer- .ric and stannic chlorides may be used without hydrohalide acid. The quantity of catalyst to be employed will vary with the catalyst selected and with the type of cellulosic material to be treated.

Sulphuric acid should preferably be employed in proportions under 15% calculated on the weight of the cellulose and especially in proportions of 1 to 10%, while the ferric chloride, stannic chloride, or other halides given above should preferably be employed in a proportion of 5 to 20% on the weight of the cellulose, or if used in conjunction with hydrochloric or other hydrohalide acid both the halide itself and the hydrohalide acid should preferably be present in proportionsof between 5 and 15% on the weight of the cellulose.

In order to avoid degradation of the cellulose molecule the acylation is conducted at as low a temperature as possible. Temperatures not substantially exceeding 50 0., for example 20-30 C., atmospheric temperatures, or temperatures below atmospheric, e. g. 0-l0 C., are preferable. Ferric chloride .or other of the halide catalysts given above do however permit of the acylation being conducted with moderate heating without subsantially impairing the qualities of the products obtained.

The following examples illustrate the invention but are not to be considered as limiting it in any way Example 1 100 parts by weight of cotton cellulose are pretreated with formic acid, for example by treatment with 500-1000 parts of formic acidof about 85% strength, allowing to stand for some hours in the cold and hydro-extracting or by impregnating with about 15 parts of formic acid of '75.85% strength and allowing to stand for 8-12 The material is then washed, centrifuged and dried. The pretreated cellulose is then introduced into a mixture of 600 parts of acetic acid, 500 parts of glycollic anhydride and 10 to 12 parts of sulphuric acid. If necessary slight heating may be applied to initiate the reaction but throughout the acylation the temperature should not be allowed to rise much above 50 C. When solution is complete, the cellulose glycollatemay be separated from its solution by addition of a non-solvent, for example by addition of excess ofwater. It is soluble in diluted chloroform-alcohol and in aqueous acetone.

Example 2 100 parts by weight of cotton cellulose are pretreated as in Example 1 and are then introduced into a mixture of 500 parts of acetic acid, 400 parts of glycollic anhydride and 25 to 30 parts of sulphuryl chloride. Here again initial heating may be necessary. The temperature of the mixture is maintained at fill- C. until solution is complete.

Example 3 100 parts by weight of cotton cellulose are impregnated with a mixture of 20 parts of ferric chloride and 20 parts of 35% aqueous hydrochloric acid and allowed to stand in the cold for as hours. The cellulose is then-introduced into a mixture of 600 parts of acetic acid and 450parts or" glycollic anhydride. The acylation is effected at 4050 C. until solution is complete, when water may be added to destroy the remaining anhydride.

While the invention has been described above more particularly with reference to the produc tion of cellulose derivatives of glycollic acid, it is also applicable to the production of derivatives of higher hydroxy-aliphatic acids. Furthermore mixed derivatives may be produced by employing another anhydride, e. g. anhydrides of acetic acid and its homologues, in addition to the hydroxyaliphatic anhydrides. The mixed derivatives may, for example, be produced by treating first with a hydroxy-aliphatic acid anhydride and then with a fatty acid anhydride.

As stated above the hydroxyalkacyl derivatives or mixed alkacyl-hydroxyalkacyl derivatives of cellulose produced according to the present invention may be treated with esterifying agents, for example acetic anhydride, to produce derivatives in which the hydroxy groups have been wholly or partially converted into ester groups. Such derivatives may be termed acidyloxyalkacyl derivatives or mixed alkacyl-acidyloxyalkacyl derivatives of cellulose. For example the cellulose derivative of acetylglycollic acid may be obtained by treating the glycollic derivative of cellulose with acetic anhydride. If in treating a lower cellulose glycollate with acetic anhydride, as referred to above, the anhydride be employed in sufficient quantity, a mixed cellulose acetateacetylglycollate results directly.

Example 4 100 parts of cotton cellulose pretreated as in acetylglycollate is very similar in solubility and other properties to cellulose acetate.

I have further found that the cellulose derivatives made according to the present invention whether they be hydroxyalkacyl or acidyloxyalkacyl derivatives or the mixed derivatives containing in addition alkacyl groups may be subjected to secondary treatments or reactions for the purpose of changing their solubilities. The secondary treatments or reactions may, for example, be carried out in presence of inorganic or organic acids or acid salts, the treatment being arrested when the required solubility has been reached. In carrying out the secondary treatments in the primary acylation solutions or suspensions, the acylation catalysts themselves are in most cases sufficient to effect any desired change in solubility properties.

Example The primary acylation solution of Example 1 (i. e. the solution obtained before any separation of cellulose glycollate) is treated with -80 parts of water at a temperature of about 35 C. The cellulose glycollate becomes progressively soluble in organic solvents, e. g. acetone, containing more and more water. The treatment is stopped when the required solubility has been reached.

While the secondary or further treatments of the primary products may with advantage be conducted at ordinary or moderate temperatures, the reaction may, if desired, be quickened by heating up to relatively high or high temperatures, even up to or 100 C. but in such cases the presence of free mineral acids is preferably avoided.

What I claim and desire to secure by Letters Patent is:-

1. Process for the production of' cellulose esters containing hydroxyalkacyl groups, comprising treating materials consisting essentially of cellulose with hydroxyaliphatic acid anhydrides.

2. Process for the productionof cellulose esters containing hydroxyalkacyl groups, comprising treating materials consisting essentially of cellulose with hydroxyaliphatic acid anhydrides in presence of acylation catalysts.

, 3. Process for the productionof cellulose esters containing hydroxyalkacyl groups, comprising treating materials consisting essentially of cellulose with hydroxyaliphatic acid anhydrides in presence of sulphuric acid.

4. Process for the production of cellulose esters containing glycollyl groups, comprising treating materials consisting essentially of. cellulose with glycollic anhydride in presence of acylation catalysts.

5. Process for the production of cellulose esters containing glycollyl groups, comprising treating materials consisting essentially of cellulose with glycollic anhydride in-presence of sulphuric acid.

6. Process for the production of cellulose esters containing glycollyl groups, comprising treating materials consisting essentially of cellulose with glycollic anhydride in presence of acylation catalysts and a liquid acylation medium.

7. Process for the production of cellulose esters containing glycollyl groups, comprising treating materials consisting essentially of cellulose with organic acids and then with glycollic anhydride in presence of acylation catalysts.

8. Process for the production of cellulose esters containing glycollyl groups, comprising treating materials consisting essentially of cellulose with organic acids and then with glycollic anhydride in presence of acylation catalysts and a liquid of acylation catalysts and a liquid acylation medium.

10. A cellulose ester in which part of the cellulose nuclear'hydroxyl groups are esterified by alkacyl groups and part by hydroxy-alkacyl groups.

11. A cellulose acetate-glycollate in which part of the cellulose nuclear hydroxyl groups are esterified by acetyl groups and part by glycollyl groups.

12. Process for the manufacture of cellulose esters containing hydroxyalkacyl groups, comprising treating materials consisting essentially of cellulose with hydroxy aliphatic acid anhydrides and subjecting the resulting primary hydroxyalkacyl esters to the action of acidic substances for the purpose of changing their solubility characteristics.

13. Process for the manufacture of mixed cellulose esters containing hydroxyalkacyl and alkacyl groups, comprising treating materials consisting essentially of cellulose separately with an hydroxy aliphatic acid anhydride and a simple aliphatic acid anhydride both in the presence of acylation catalysts and a liquid acylation medium. and subjecting the resulting mixed primary cellulose esters to the action of acidic substances for the purpose of changing their solubility characteristics.

14. Process for the manufacture of cellulose esters containing hydroxyalkacyl groups, comprising treating materialsconsisting essentially of cellulose with hydroxy aliphatic acid anhydrides and subjecting the resulting primary hydroxyalkacyl esters to the action of the substances having mineral acidity for the purpose of changing their solubility characteristics.

15. Process for the manufacture of cellulose glycollates comprising treating materials consisting essentially of cellulose with glycollic anhydride and subjecting the resulting primary.

cellulose glycollates to the action of acidic substances for the purpose of changing theirsolubility characteristics.

16. Process for the manufacture of mixed cellulose esters containing glycollyl and acetyl groups, comprising treating materials consisting essentially of cellulose separately with glycollic anhydride and acetic anhydride both in the presence of acylation catalysts and a liquid acylation medium, and subjecting the resulting mixed primary cellulose esters to the action of acidic substances for the purpose of changing their solubility characteristics.

17. Partially hydrolyzed hydroxyallsacyl esters of cellulose.

18. Partially hydrolyzed cellulose glycollates.

l9. Partially hydrolyzed mixed cellulose esters in which part of the nuclear hydroxyl groups are esterified by alkacyl groups and part by hydroxyalkacyl groups. v

20. Partially hydrolyzed mixed cellulose esters in which part of the nuclear hydroxyl groups are esterified by acetyl groups and part by glycollyl groups.

HENRY DREYFUS.