US2091970A - Cellulose ester products and materials made therefrom - Google Patents

Description

Patented Sept. 7, 1937 UNITED STATES CELLULOSE ESTER PRODUCTS AND MA- TERIALS MADE THEREFROM Henry Dreyfus, London, England No Drawing. Application January 4, 1935, Serial I No. 329. lln Great Britain .lanuary 13,1934

, 9' Claims.

This invention relates to the manufacture or treatment of organic esters of cellulose, and is particularly concerned with the saponification of filaments, threads, yarns, ribbons and the like having a basis of cellulose acetate or other organic esters of cellulose.

I have nowfound that materials of the type referred to above may be very advantageously saponified by treating the materials in a bath containing methylamine, ethylene diamine or other non-metallic base and a swelling agent for the organic ester of cellulose under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

' By the process of the invention the materials can be saponified to a considerable depth below the surface in a relatively short time, and even substantially complete removal of the acidyl content of the materials can be effected quickly. The process can be carried out without damage to the materials and indeed may actually improve their serimetric properties. Thus, by the process of the invention there may be obtained materials of high tenacity and extensibility,

free from harshness, and having a high safeironing point and an afiinity for cotton dyes which may or may not be accompanied by an afinity ror cellulose ester dyes.

The organic ester of cellulose treated may be of normal or low viscosity, for example in the case of cellulose acetate the viscosity may be of the order of 30 to 50, 100, 200 or even higher, these figures being obtained by comparison of a 6% solution of the ester in acetone at 25 C. with glycerine at the same temperature taken as a standard of 100. Such esters of high viscosity may readily be made by methods in which degradation of the cellulose molecule is substantially avoided during acidylation. On the other hand, the viscosity of the cellulose acetate employed may be of the order of 10-20 or even lower, or between 20 and 30, measured on the scale referred to above.

The invention is of particular importance in connection with the saponification of filaments, threads, ribbons, fabrics and like materials having a basis of cellulose acetate and will be described with special reference to the treatment of such materials.

The materials treated may be made by any suitable dry or wet spinning method. Where high tenacity is required in the final products, it is of particular advantage to produce the filaments and the like by wet spinning methods-in (Ci. 8----2ll) the course of which they are stretched to a considerable extent, or to soften and stretch the materials after their production whether by a Wet or a dry spinning process. By applying the process of the invention to materials which have 5 been stretched considerably, for example to 200% of their original length or even more, ma-

terialsof particularly valuable serimetric properties are obtainable,

Particularly good results are obtained by the 10 use of saponifying baths, containing methylamine and a swelling agent for the base of the materials. Other strong aliphatic organic bases, for example ethylamine, propylamine, amylarnine and triethylamine, may also be employed. Again, 15 somewhat weaker bases of the same'series, for example trimethylamine and allylamine, may be used. Further, considerably stronger bases of thesame series may be employed, even very strong bases such as tetramethyl ammonium hydroxide, 20 provided care be taken to avoid damaging the materials. Amines containing more than one amino group, and particularly aliphatic diamines of relatively low molecular weight, for example ethylene diamine, symmetrical dimethyl ethylene 25 diamine, monomethyl ethylene diamine, and propylene diamine may also be used. Preferably at least one of the amino groups of such amines should be unsubstituted or mono-substituted.

Amines containing more than two amino groups 30 may also be employed, for example 1.2.3-triamino .i propane. The effect of one or more hydroxy groups in the amine appears to be to favour the penetration of the materials by the saponifying agent, and with this-object in view substances 35 of the type of wy-diamino-B-hydroxy propane may be used with advantage. Theuse of bases of the heterocyclic series, for example piperidine, is not excluded.

As indicated above, saponification is prefer- 40 ably effected by subjecting the materials to an aqueous bath containing methylamine or a like acting base and the swelling agent. Generally speaking concentrations of non-metallic base of about ill-30%, for instance 15-25% will be found 45 suitable. Although it may be of advantage in some cases to work at atmospheric temperature, or even at a lower temperature, somewhat higher temperatures are in general to be preferred, for example from 25 or 30 C. to 40, 50 or even 50 C. or higher. With a view to preventing excessive evaporation of the bath it is of ad vantage, particularlywhen working at relatively high temperatures, to cover the surface of the saponifying bath with a layer. of an oil, wax

or like substance which is immiscible with the bath.v The time during which the materials are in contact with the bath 'will naturally vary according to the amount of saponification to be effected, the nature of the bath and the temperature of treatment. Thus the time of treatment may vary from less than one minute, for instance 15-30 or 45 seconds to two or three minutes or even longer where a relatively 'slow acting base is employed. The material should not be allowed to remain in the bath after saponification is complete.-

The swelling agents employed may or may not contain hydroxy groups. As examples of non-hydroxy substances mention may be made of acetone, methyl ethyl ketone, dioxane, or methylene ethylene ether and their homologues or similar cyclicethers, cyclohexanone and the dimethyl ether of ethylene glycol. Examples of suitable substances containing hydroxy groups are diacetone alcohol, glycerol, glycol and its mono-methyl ether, benzyl alcohol and cyclohexanol. Alcoholic compounds may also be employed which, while not solvents for the organic esters of cellulose, yet possess latent solvent powers or which become solvents at higher temperatures or in the presence of small quantities of other substances. Thus, for example, methyl, ethyl, propyl and other lower alcohols may be employed with the greatest advantage at temperatures above atmospheric or in the pres-- ence of substances such as ethylene chloride and other chlorinated hydrocarbons capable of forming with the alcohols solvent mixtures for the cellulose esters. Although the saponifying medium will in general contain water, saponification may be effected in a suitable' non-aqueous medium, for example the organic base may be applied in a medium of alcohol in the substantial absence of water. The invention also ineludes the use of inorganic solvents or swelling agents, for example the thiocyanates of sodium. potassium or ammonium. The concentration in which the swelling agent or solvent is employed will naturally depend to some ,extentupon its nature. In the saponifica tion of cellulose acetate by means of methylvamine in the presence of acetone, concentrations of acetone of the order of 3 or 5 to '7 or even 10% have been found suitable. In similar circumstances using dioxane as the solvent, a concentration of about 0.5 to 1% or 2% has given satisfactory results. Concentrations of ammonium thiocyanate of the same order are re- 68 commended, and in general it is found that in the case of substances of well developed solvent power a concentration between 1 and 5% -is suitable. Higher concentrations, for example 10 to 15 or 20% or even higher, may in some cases 00 adversely affect the tenacity of the resulting products. rOn the other hand, substances such as alcohol for instance may, as already indicated, be employed in very much higher concentration. The saponifying medium may contain substances adapted to accelerate the saponification, for example small quantities of strong alkalies such as caustic soda or of heavy metals such as copper, silver, nickel or zinc as described in I}. S. applications S. Nos. 'l56,282, 756,284 and 756,255 filed'December 6, 1934, and 326 filed January 4, 1935. v A When the materials are treatedin the form of filaments, threads, yarns and the like, it is of advantage to eflectsaponiflcation in warp formation", i. c. by drawing a'large number of ends through the bath in substantially parallel relationship one to another and in the same plane. Thus, yarn may be drawn from a creel by means of rollers or like devices extending across the entire assembly of ends or so-called warp and immersed or partially immersed in a bath containing, the s'aponifying agent, through a reed into the bath, and after passing through the bath the materials may be drawn by a second roller, pair, of rolls or the like, situated outside the bath, through a reed and out of. the bath, whence they are forwarded to suitable collecting means or to means for eifecting any subsequent treatment to be applied. Preferably the materials are washed and dried before being wound.

The saponifying medium may however be applied by other means. Thus, for example, the ma terials in hank form may be suspended from rods which are caused to' .traverse the length of the bath, and at the same time to rotate so as to expose each portion of the yarnto the same depth in the bath for the same period. Again, the materials may be treated in the form of bobbins,

cheeses or like packages, or in the form of cakes fromcentrifugal spinning boxes. Any suitable means may infact be adopted in applying the saponifying agent to the materials. Materials in yarn or like form may be treated continuously with their, production and/or with a stretching step. Again, in the caseof such materialsTprovided saponification has not been carried too far, stretching may be effected after saponification as described in U. s. application s. No. 755,232,

filed November 28, 1934. The saponification process of the present invention is particularly adapted to enable yarns and like materials to iujndergo a stretching treatment after saponificaon. x

As indicated above, the materials may be saponified in fabric form. This may conveniently be effected by passing the fabric continuously through a bath containing the saponifying medium, for example in an apparatus of the t of the winch dyeing machine.

The materials prior to saponification may be subjected to a treatment adapted to facilitate penetration of the saponifying agent. This may comprise the application of water to the materials, or they may 'be treated with aqueous wetting agents, for example soaps.

The degree of saponification eflected may be sufllcient to reduce the original acidyl content of the ester by 8%, 10% or even less, but isipreferably somewhat higher, for example sufficientto remove 20-25 or 30% of the acidyl content.

Considerably higher degrees of saponification may be effected, for instance so as to remove 35 or 4,0 to 50 or 55% of the acidyl content or more,

even up to complete saponification, according to the particular purpose in view. The saponification may be suflicient to render cellulose acetate insoluble in substantially anhydrous acetone but soluble in acetone containing a considerable percentage, for example 25-30%, of water. Or saponiflcatipn may render the material insoluble in such mixtures as well as in anhydrous acetone. The saponification may raise the safe ironing point considerably. The material may gain an amnity for cotton dyes and may or may not retain its aflinity for cellulose ester dyes. Materla'ls saponified according to the invention may have, in addition to the valuable properties referred to above a tenacity, good memillllty then through a washing bath and over a series of steam heated drying rolls to suitable collecting means. The saponifying bath contains a 15-30% aqueous solution of mono-methylamine in which is dissolved 0.5-1.0% of ammonium thiocyanate. The temperature and speed of the materials are such that the desired degree of saponification is efiected by the time the materials leave the bath.

Example 2 The process is carried out as in Example 1, except that the ammonium thiocyanate is replaced by a similar quantity of dioxane and also contains 0.05-0.57}, of copper in solution.

Example 3 The process is carried out as in Example 2, except that the dioxane is replaced by 1-5% of acetone.

Although the invention has been described with particular reference to the treatment of materials having a basis of cellulose acetate, it is also applicable to the treatment of other materials containing saponifiable esters of cellulose, for example cellulose formate, propionate, butyrate, ethyl cellulose acetate, oxyethyl cellulose acetate and nitrocellulose acetate.

What I claim and desire to secure by Letters Patent is ments, threads, ribbons and like materials having a basis of cellulose acetate in an aqueous bath containing an organic base and in addition a nonhydroxy swelling agent for the cellulose acetate under such conditions that the materials are swollen without incipient solution and are saponifled in the swollen condition.

3. Process for the manufacture of artificial materials of improved extensibility and unimpaired tenacity, which comprises treating filaments,

threads, ribbons and like materials having a basis of organic ester of cellulose in an aqueous bath containing a lower aliphatic amine and in addition a swelling agent for the organic ester of cellulose under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

4. Process for the manufacture of artificial materials of improved extensibility and unimpaired tenacity, which comprises treating filaments, threads, ribbons and like materials having a basis of cellulose acetate in an aqueous bath containing methylamine and in addition a. swelling agent for the cellulose acetate under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

5. Process for the manufacture of artificial materials of improved extensibility and unimpaired tenacity, which comprises treating filaments,

threads, ribbons and like materials having a basis,

of organic ester of cellulose in an aqueous bath containing mono-methylamine and dioxane under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

6. Process for the manufacture of artificial materials of improved extensibility and unimpaired tenacity, which comprises treating filaments, threads, ribbons and like materials having a basis of organic ester of cellulose in an aqueous bath containing monomethylamine and acetone under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

'7. Process for improving the properties of filaments, threads, ribbons and like materials having a basis of organic ester of cellulose, which comprises saponifying the materials by treatment in an aqueous bath containing an organic base, a

metal capable of accelerating the saponification and in addition 'a swelling agent for the organic ester of cellulose, under such conditions that the materials are swollen with-out incipient solution and are saponified in the swollen condition.

8. Process for improving the properties of filaments, threads, ribbons and like materials having a basis ,of cellulose acetate, which comprises saponifying the materials by treatment in an aqueous bath containing methylamine, copper and in addition a non-hydroxy swelling agent for the cellulose acetate, under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

9. Process for the manufacture of artificial mabath containing an organic base and in addition a swelling agent for the organic ester of cellulose under such conditions that the materials are swollen without incipient solution and are saponified in the swollen condition.

HENRY DREYFUS.