US2092008A - Saponification of cellulose ester material - Google Patents

Description

Patented Sept. 7, 1937 UNITED STATES SAPONIFICATION 0F CEDLULOSE ESTER MATERIAL Robert Wighton Moncrleif, Frank Brentnall Hill, and Thomas Barnard Frearson, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application December'ii, 1934, Se-

rial No. 756,284. ,In Great Britain December 12 Claims.

This invention relates to the treatment 01' cel-- lulose acetate and other organic esters of cellulose and particularly to a process for reducing the acidyl content of such esters. The invention 5 is specially applicable to the saponification of filaments, threads, yarns, ribbons and the like made of or containing such esters.

It has been discovered that organic esters .of cellulose can be saponified by means of nonmetallic bases, for example methylamine, ethylene diamine and other aliphatic amines, particularly those of low molecular weight in the liquid phase, with particular advantage and that by treating threads of cellulose acetate and like materials in this way speciallydesirable proper ties maybe imparted to' the materials. We have now found that the 'saponification of materials having a basis of cellulose acetate or other or- .ganic ester of cellulose by means of non-metallic saponifying agents and in particular methylamine and similar bases may be accelerated to a considerable extent by the presence during the saponification of heavy metals, 1. e. metals other than the alkali and alkaline earth metals.

It is to be understood that the term metal is used in a sense broad enough to include compounds of the metal. It appears that the metals which are most suitable for use in the process of lic bases is claimed in our co-pending U. S. appli-.

cation S. No. 756,285 filed December 6, 1934.

The metal is preferably added to the saponifying bath in the form of'a soluble salt but may also be employed in other forms, forexample in some cases it is convenient to add the metal in the form of an oxide or hydroxide. Preferably the metal is added in such a form that it readily dissolves in the saponifying bath, and the saponitying bath may as a result contain a double, compound of the metal with the particular base employed. The saponifying bath may contain two or more heavy metals capable of accelerating the saponification. Other accelerating agents may also be present, for example small quantities 01' caustic soda or other strong mineral base, as 'claimed in our co-pending U. S. application S.

No; 756,282, filed December 6, 1934.

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 glycerlneat 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 cellulosemolecule is substantially avoided during acidylation, for example-f the methods of U. S. .Patent No. 1,708,787. 0n the other hand, the viscosity of the cellulose acetate employed may beer the order of 10-20 or even lower, or between 20 and 30, measured on the scale referred to above. v

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 andthe like by wet spinning methods in the.

course of which they are stretched to a considerf able 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 been stretched considerably, for example to 200% of'their original length or even more, materials of particularly valuable serimetric properties are obtainable.-

Particularly good results are obtained by the use of saponifying baths containing methyl- ,amine or ethylene diamine and silver, nickel or zinc. Other strong aliphatic organic bases, for example ethylamine, propylamine, amylamine and triethylamine, may also be employed,- Again, somewhat weaker bases of the same series, for example trimethylamine and allylamine, may be used. Further, considerably stronger bases of the same series may be employed, even very strong bases such as tetramethyl ammonium hydroxide, provided carebe taken to avoid damaging the materials. Again, amines other than ethylene diamine containing more than one amino group, and particularly aliphatic diamines of relatively low molecular weight, for

i example symmetrical dimethyl ethylene diamlne,

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 may also be employed, for example 1.2.3-triamino propane. The eifect 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 of the type of wy-diaflliDO-fl-llYdl'OXY propane may be used with advantage. Again, bases of the heterocyclic series, for example piperidine.

may be used.

saponification is preferably effected by subjecting the materials to an aqueous bath containing methylamine or a like acting-base and the metal in solution. Generally speaking it is advantageous to employ the base in a concentration of 10-30%, and particularly 15-25%. The temperature of the bath may range from below atmospheric temperature to the neighbourhood of the boiling point of the solution. It is often convenient to work at temperatures between 15 or 20 C. and 25 or 30 C. but when a high degree of saponification is to be effected it is preferable to work at a somewhat higher temperature, e. g. -60 C. or 70 C. or even higher, depending on the boiling point of the solution. With a view to preventing excessive evaporation of the base it is of advantage, particularly when 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. The concentrations and temperatures employed in particular cases will naturally depend upon the properties of the particular base employed. In general, the conditions may be chosen so that the desired degree of saponification may be effected by means of a treatment lasting from 1-2 minutes or less up to 3 or 4 minutes. On the other hand the treatment may be more protracted.

When the saponifying agent is applied to the materials in the form of an aqueous solution, it is convenient to incorporate the metal, for

. example in the form of the oxide or hydroxide or of a water-soluble salt, in the saponifying medium itself. It is not, however, essential that the metal should be introduced in this way. It may, for instance, be applied to the materials prior to the application of the saponifying agent, or even introduced into the spinning solution from which they are made.

A very considerable acceleration of the saponifying process may be effected by the presence in the saponifying bath of quite small concentrations of the metal, e. g. 0.01-0.05% on the weight of the bath or even less. On the other hand somewhat higher concentrations may be employed, e. g. 0.1% or 0.5%. Since it is undesirable that the final product should contain substantial quantities of the metal it is preferable to work with the smallest quantities capable of giving the desired result.

The saponifying medium may also contain swelling agents, solvents or latent solvents for the cellulose ester, for example cyclohexanol, methyl cyclohexanol, glycerol, ethylene glycol and its mono methyl and dimethyl ethers, diacetone alcohol, benzyl alcohol, acetone, dioxane or methylene ethylene ether.

When the materials are treated in the form of filaments, threads, yarns and the like, it is of adopted for this purpose.

advantage to effect saponification "in warp formation, i. e. 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 saponifying 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 foreffecting any subsequent treatment to be applied. Preferably the materials are washed and dried before being wound.

The saponifying agent may be applied by other means. Thus, for example, the materials in hank form may be suspended from rods which arecaused to traverse the length of the bath, and at the same time to rotate so as to expose each portion of the yarn to the same depth in the bath for the same period. Again, the materials may be treated in the form of bobbins, cheeses or other packages. Any suitable means may in fact 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 case of such materials, stretching may be effected during saponification or, provided saponification has not been carried too far, after saponification. In general it is necessary to soften the materials to enable them to be stretched to the desired extent, and in choosing a suitable softening agent due regard should be had to the extent to which the materials have been saponifled.

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

It is generally advisable to treat the materials after saponification so' as to remove any metal remaining therein. Any suitable means may be A convenient means comprises washing the materials with a dilute acid with which the particular metal forms a soluble salt.

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 maybe treated with aqueous wetting agents, for example soaps.

The degree of saponification effected may be sufi'icient to reduce the acidyl content of the ester by 23-10% or even less, but is preferably somewhat higher, for example suflicient to reduce the acidyl content by 20-25% or 30%. Considerably higher degrees of saponification may be effected sufficient to remove 35 or 40 to 50 or 55% of the acidyl content or more, even up to complete saponification, according to the particular purpose in view. Generally speaking, a loss in acidyl content of 20-25 or 30% is capable of rendering the cellulose acetate material insoluble insoluble in substantially anhydrous acetone but may be soluble in acetone containing a considerable percentage, e. g. 25-30%, of water. Or saponiilcation may render the material insoluble in such mixtures as well as in anhydrous acetone. The saponification may raise the safe ironing point considerably. Materials saponifled according to the invention may have, in addition to the valuable properties referred to above, a high tenacity and elasticity and a good extensibility.

Such materials are of particular value for use in the manufacture of high twist yams. Thus, high twist yarns partially saponified according to the invention have been found particularly useful as weft in the manufacture of crepe fabrics. Again, by the process of the invention, it is possible to obtain completely saponified materials of excellent tensile properties.

The following examples illustrate the inve n-' tion:

Example 1 Cellulose acetate yarn is drawn in warp formation through an aqueous bath containing 15-30% of monomethylamine and 0.05-0.05% of silver, I I which is introduced into the bath in the form of silver nitrate. The temperature of the bath is maintained between 50 and 60 C. and the rate of travel of the materials is adjusted so that the yarn is in contact with the bath for 1-3 minutes.

Example 2 The process is carried out as described in-Example 1 except that the bathcomprises a"'l5-30% aqueous solution of ethylene diamine containing 0.05-0.5% ofnickel which is introduced into the bath in the form of nickel sulphate.

Similarly other non-metallic bases, for example propylamine, di-methylamine or others of the bases referred to above may be applied.

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 othermaterials containing other saponifiable esters of celluloss, for example cellulose formate, propionate, butyrate, ethyl cellulose acetate, oxy-ethyi cellulose acetate and nitrocellulose acetate.

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

1. Process for reducing the acidyl content oi an organic ester of cellulose, which comprisessaponii'ying the ester by means oi? a saponifying agent therefor which is a water-soluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from .said nitrogen atom, in the presence in solution of metal selected from the group consisting ct nickel, zinc, and silver.

2. Process for saponifying filaments, threads, ribbons and like materials having a basis of organic ester 'of cellulose, which comprises treating the materials with an aqueous solution of a 5 saponifying agent therefor which is a water-soluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom, in the presence in 7 solution of a metal selected from the group consisting of nickel, zinc and silver.

3. Process for saponiiying filaments, threads.

, ribbons and like materials having a basis of cellulose acetate, which comprises treating the ma- 76 terials with an aqueous solution of a saponlfyins agent therefor which is a water-soluble"'nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is I directly attached to three other atoms apart from said nitrogen atom, in the presence in solution of a metal selected-from the group consisting of nickel, zinc and silver.

4. Process for saponifying illaments threads, ribbons and like materials having a basis of cellulose acetate, which comprises treating the materials with an aqueous bath containing a watersoluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom which is a saponifying agent for the organic ester of cellulose and a double compound of said base with a metal selected from the group consisting oi nickel,

zinc and silver.

5. Process for saponifying filaments, threads, ribbons and like materials having a basis of organicester of cellulose, which comprises treating the materials with an aqueous solution of a saponifying agent therefor which is a water-soluble nitrogeneous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen'atom, in the presence of nickel in solution. I

6. Process for saponifying filaments, threads, ribbons .and like materials having a basis of organic ester ofceilulose, which comprises treating the materials with an aqueous solution of a saponifying agent therefor which is a watersoluble nitrogenous organic base in which each carbon atom that is directly attached to a nitrogen atom is directly attached to three other atoms apart from said nitrogen atom, in the presence of I atom is directly attached to three otheratoms apart from said nitrogen atom, in the presence of silver in solution.

8. Process for saponifying filaments, threads,

ribbons and like materials having a basis of cellulose acetate, which comprises treating the materials with an aqueous solution of an amine selected from the group consisting of monomethylamine, mono-ethylamine and ethylene diamine, in the presence of nickel in solution.

9. Process for saponifying filaments, threads,

ribbons and like materialshaving a basis of cellulose acetate, which comprises treating the materials with an aqueous solution of an amine selected from the group consisting of monomethyiamine, mono-ethylamine and ethylene diamine, in the presence of zinc in solution.

10. Process for saponiiying filaments, threads, ribbons and likematerials having a basis of cellulose acetate, which comprises treating the materials with an aqueous-solution of an amine select .ed from the group consisting of mono-methylamine, mono ethylamine and ethylene diamine, in the presence 02 silver in solution.

11. Process for saponifyingdllaments, threads, ribbons and like materials having a basis of organic ester of cellulose, which comprises treating vthe materials with an aqueous medium contain-- in: in solution an amine oi relatively low molecusolution anamine of relatively low molecular weight which is a saponifying agent for cellulose acetate and a metal selected from the group consisting ofnickel, zinc and silver.

ROBERT WIGHTON MONCRIEFF. FRANK BRENTNALL HILL. THOMAS BARNARD FREARSON.