US2112275A - Saponification of cellulose esters - Google Patents

Description

Patented Mar. 29, 1938 2,112,275

UNITED STATES OFFICE SAPONIFICATION F CELLUILOSE ESTERS Henry Dreyfus, London, England No Drawing. Application January 4, 1935, Se-

rial No. 327. In Great Britain January 15, 1934 8 Claims. (Cl. 8-20) This invention relates to improvements in the adjusted so as to produce rapid saponification, or

treatment of filaments, threads, yarns, fabrics the type of process in which the material underand the like and is more particularly concerned going treatment is first impregnated with the apwith processes for the saponification of textile and propriate. amount of saponifying agent, for exother materials containing cellulose esters. ample in a bath or in a padding mangle or like I have found that it is of advantage in the impregnating machine andis subsequently heated,

saponification of materials of the type referred for example by passage over heated drums or to above, particularly when using strongly alkaother heated surfaces to effect a rapid saponificaline saponilying agents such for example as caustion. Similarly spinning box cakes, yarn wound 1o tic soda, to have present a small quantity of a on perforated bobbins or other foraminous suplo salt of the saponifying agent wtih an aromatic port may have the saponil'ying medium circulated substance of weakly acid reaction. Thus for ex-. through them. Travelling materials are preferample it is of advantage when saponifying such ably treated in warp formation, that is to say a materials by means of caustic soda to have present large number of yarns, threads or the like are small quantities of the sodium salt of phenol, aligned and carried together through the saponil5 salicylic acid, benzoic acid or other phenol or lying treatment with the aid of rollers or other aromatic carboxylic acid. In the presence of driving means operating upon the sheet of yarns small quantities of such substances saponification as a whole. In this Way great uniformity of can be carried out rapidly Without damaging the treatment can be obtained with resultant unimaterials or undesirably reducing their tenacity formity in the properties, and particularly in the or extensibility. dyeing properties of the materials treated.

The term phenols is intended to include not The invention includes'both partial and comonly phenol itself and its homologues such as plete saponification. For example in the case of cresol, but in addition diand polyhydric phenols treating cellulose acetate materials the saponifor example resorcinol, pyrocatechin, hydroquification may be such as to remove 10-20 or 30% none, phloroglucinol, pyrogallol and the like and of the original acidyl content of the ester and may substitution products of the phenolic bodies and be for the purpose of increasing the safe ironing especially carboxy substitution products such as point of the materials or generally increasing salicylic acid. The carboxy substitution products their resistance to heat treatments and/or for app-ear to give better results qua the textile propthe purpose of conferring thereon an affinity for erties of the saponified materials than the simple cotton colours, or may be such as to remove a phenols. much greater proportion of the original acidyl The saponifying agent preferably comprises an content such as 50-70 or 75%, or to produce comaqueous solution of caustic soda or caustic potash. plete saponification.

The solution may be of relatively low concentra- As indicated above the phenol or equivalent 5 tion, for instance from 1 or 2% or even less to 3 or substance or sodium phenate or other reaction 4%, or of considerably higher concentration, for product of the substance with the saponifying instance 5-10 or 15%. The bath may be at atmedium is preferably incorporated directly in an mospheric temperature or below atmospheric but aqueous solution of caustic alkali or other alkao for rapid saponification somewhat higher temperline substance so as to make up the saponifying 40 atures are preferable and the bath may even be medium. However, the yarns, threads, fabrics maintained at a temperature just short of the or other materials may if desired be impregnated boiling point. with the phenol or phenate prior to contact with The phenol or its equivalent is preferably disthe saponifying medium. In order to obtain a -15 solved in the saponifying medium, although othgood impregnation the phenolic substance may be er suitable methods of application are not exapplied in the free state rather than in the form eluded. The phenol or the like should be present :of a phenate. In such a preliminary impregnain'small' quantity, for example in a concentration tion care should be taken that the concentration of the order of 0.2-0.5% up to 1% based on the of the phenol in the pretreatment bath does not total saponifying medium. produce incipient solution of the cellulose ester The saponifying medium may be applied in any unless at the same time mutual adherence of fllasuitable manner. The invention includes simple ments to make for example a monofil or ribbon is treatments of hanks or other packages in a bath, desired. the treatment of travelling filaments in which The saponifying medium may contain in addicase the saponifying conditions are preferably tion to the saponifying agent and the phenolic 56 susbtance any other desired constituents, as for example swelling agents for the cellulose ester under treatment. For example, when cellulose acetate materials are treated the saponifying medium may contain ethylene methylene ether, dioxane or acetone.

The following example illustrates the invention:

Example Cellulose acetate yarn is drawn from a creel in warp formation through a saponifying bath, through a washing bath which removes residual alkali carried over from the saponifying bath, and over a series of steam heated drying rolls to suitable collecting means. The saponifying bath contains an aqueous solution of caustic soda of relatively low concentration, in which is dissolved a small quantity of sodium phenate.

Instead of phenol, other like acting substances may be employed, for example resorcinol, phloroglucinol or salicylic acid.

The process of the invention is particularly applicable to the treatment of cellulose acetate materials but may be applied to other organic esters of cellulose, for example cellulose formate, propionate, butyrate, oxy-ethyl acetate and the like. The tensile strength of the resulting products may be improved by stretching the materials, preferably before the saponifying treatment and either during or after the spinning of the materials, for example stretching them under the action of a softening agent, for instance the solvents mentioned above, to 200 to 300 or even 500% or more of their original length. Furthermore,

'it is advantageous to employ cellulose esters of high viscosity characteristics, for example, in the case of cellulose acetate, products having a viscosity of above 40 and preferably more than 50 to 100 or even 200 or more as measured by a comparison of the viscosity of a 6% solution of the cellulose acetate in acetone against that of r glycerin'e taken as a standard of 100.

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

1. Process of saponifying filaments, threads,

' ribbons and like materials composed substantially of organic esters of cellulose comprising treating the same with a bath containing an alkaline saponifylng agent and small quantities of a. salt of said agent with an aromatic substance of Weakly acid reaction selected from the group consisting of phenols and carboxylic acids.

2. Process of sapom'fying filaments, threads, ribbons and like materials composed substantially of organic esters of cellulose comprising treating the same in an aqueous caustic alkali bath containing small quantities of the salt of said alkali with a phenol.

3. Process of saponifying filaments, threads, ribbons and like materials composed substantially of organic esters of cellulose comprising treating the same in an aqueous caustic alkali bath containing small quantities of the salt of said alkali with an aromatic carboxylic acid.

4. Process for the treatment of filaments, threads, ribbons and like materials composed substantially of organic esters of cellulose which comprises subjecting the materials to substantially complete saponification by treatment with a bath containing caustic alkali and small quantities of a salt of said alkali with an aromatic substance of Weakly acid reaction selected from the group consisting of phenols and carboxylic acids.

kali and small quantities of a salt of said alkali with ordinary phenol.

6. Process of saponifying filaments, threads, ribbons and like materials composed substantially of cellulose acetate comprising treating the same with a bath containing aqueous caustic alkali and small quantities of a salt of said alkali with resorcinol.

7. Process of saponifying filaments, threads, ribbons and like materials composed substantially of cellulose acetate comprising treating the same with a bath containing aqueous caustic alkali and small quantities of a salt of said alkali with a phenolic carboxylic acid.

8. Process of saponifying filaments, threads, ribbons and like materials composed substantially of cellulose acetate comprising treating the same with a bath containing aqueous caustic alkali and small quantities of a salt of said alkali with salicylic acid.

HENRY DREYFUS.