US2092802A - Textile materials and their treatment and manufacture - Google Patents

Description

Patented Sept. 14, 193 7 lTED STATES TEXTILE MATERIALS ANT) THEIR TREAT- MENT AND MANUFACTURE Henry Dreyfus, London, England No Drawing.

Application February 11, 1933,

Serial No. 656,369. In Great Britain March 4 Claims.

This invention relates to the treatment and manufacture of textile materials, and in particular to the manufacture of staple fibre for spun yarns. The invention also includes the 5 staple fibre itself and spun yarns and fabrics and other materials made therefrom.

It is well known that cellulose acetate or other cellulose esters or ethers are extremely liable to become electrified, so that when these fibres are employed in the manufacture of staple fibre for the production of spun yarns considerable difliculties occur in the various operations, such as opening, combing or carding, drawing and spinning. These difficulties militate considerably against the successful manufacture of spun yarns from cellulose acetate or like cellulose derivatives which are liable to electrification.

I have now found that if such materials are provided with an outer coating or layer of cellu- 20 lose or of cellulose derivatives which are-easily soluble or dispersible in water or at least have a high hygroscopicity, or a coating or layer of any other hygroscopic colloidal solid, electrification troubles are minimized and the manufacture can be carried out on the lines customarily adopted in the manufacture of cotton yarns or of spun yarns from the cellulosic type of artificial silk. Not only does the invention eliminate or decrease the electrification to which the materials are liable, but in addition the manufacture of the spun yarns from the staple fibre is very much facilitated, since it appears that the outer layer of cellulose or of the type of cellulose derivative or colloid referred to promotes adhesion and therefore facilitates the twisting operation and minimizes rupture of the spun product. 'The term hygroscopic is used in this specification to denote that the materials in question have a moisture regain of at least -20% of their 40 weight.

The coatings may be provided in any suitable manner; for instance the coating may be of a cellulose regenerated from viscose, from nitrocellulose or from a cellulose dissolved in ammoniacal copper solutions or metallic salt solutions. From the point of view of facilitating the actual coating operation, a point which is referred to in greater detail hereinafter, it is desirable to provide a coating of a cellulose which is somewhat degraded, as opposed to undegraded or a-cellulose. For example p-cellulose, &-cellu lose or other degraded celluloses which are more or less soluble in aqueous alkalies or even in water may be used. Such celluloses have the additional advantage that they are more easy to apply. They may be prepared for use in accordance with the invention by the direct degradation of cellulose, for example by treatment with alkalies, acids, or oxidizing agents, e. g. by heating with layer, cellulose derivatives which are easily soluble or dispersible in water or which have a high hygroscopicity may be employed. The hydrophile properties of such cellulose derivatives may be f due to the substitution groups or may be due to degradation of the cellulose molecule itself. Thus for example in the latter case cellulose esters, such as cellulose acetate, propionate and the like or cellulose ethers, such as methyl, ethyl or benzyl cellulose, may be employed in which either previous to, during or subsequent to the introduction of the substituent groups the cellulose molecule has been so degraded that the product is hydrophile in character, and is in consequence soluble in acetone or alcohol which is considerably diluted with water or even soluble in water itself. On the other hand, the hydrophile character may be due to hydrophile groups present in the substituent groups of the cellulose derivatives, as for example hydroxy or carboxy groups, which confer increased-solubility or dispersibility in water or dilute alkalies or other aqueous liquids. Thus for example I may employ for the purpose of the present invention cellulose esters or ethers containing free hydroxy groups or carboxy groups or carboxylic salt groups. In this connection reference is made to the various cellulose derivatives described in U. 8. Patent No. 1,502,379, U. S. applications S. Nos. 475,630 filed 15th August, 1930, and 492,085 filed 29th October, 1930, and British Patent No. 277,721. These specifications describe the manufacture of hydroxylated or carboxylated ethers or esters of cellulose, for example cellulose esters of oxalic or maleic acid, glycollic acid, lactic acid, malic acid, tartaric acid or glyceric acid, and also hydroxy and carboxy alkyl ethers of cellulose.

Any desired means may be adopted for producing the cellulose or cellulose derivative coatings upon the cellulose ester or ether threads treated in accordance with the invention. For example threads may be coated with solutions of a suitable cellulose or with solutions of suitable cellulose derivatives and the cellulose regenerated therefrom in situ. Even when using cellulose derivatives such as viscose, it is advantageous to employ a degraded cellulose. For instance a 'viscose solution may be ripened to beyond the usual degree of ripening adopted in the manu-. facture of viscose artificial silk. After coating with a viscose solution ripened to the desired degree the cellulose may be regenerated by treatment with an acid or salt or even by a simple drying and/or steaming. Nitro-cellulose coatings, 4

with sodium hydrosulphide or other saponifying agent.

Another method of producing a cellulosic coating on the outside of the cellulose derivative materials, which may be applied either instead of or in conjunction with the above'methods, is to reconvert the outer layer into cellulose. Thus for example cellulose ester materials may be subjected to a surface saponification, for example by .any of the processes described in U. S. Patents Nos. 1,884,620, 1,884,621, 1,884,622, and 1,884,623, and U. S. application S. No. 523,837 filed 19th March, 1931. The degree of saponification may vary within wide limits, but in general with cellulose acetate filaments a saponification to the extent of a loss of 20% on the total weight is sufficient for the purposes of the present invention.

The production of the cellulosic coatings may be effected at any convenient stage of the manufacture of the staple fibre prior to the opening, carding, drawing and spinning operations referred to above. It may be conducted prior to the cutting operation, since it is very convenient to apply the cellulosic coating whilst the filaments are in continuous form, but in addition the cutting operation may be very much facilitated by previous application of wet treatments. The invention does not, however, exclude the treatment of already cut fibres, which may, for example, be soaked in viscose solution and subsequently dried and/or steamed so as to decompose the viscose into cellulose. A previous conversion of the viscose into an ammonium viscose facilitates conversion to cellulose by simple drying or steaming.

It is desirable to effect the coating in such a way that the individual filaments or fibres are not caused to stick together. In the case of treating continuous filaments this may be effected very simply by employing combs, curved bars or other means by which the individual filaments are kept apart, or in the case of either continuous filaments or already cut fibres it may be achieved by using relatively dilute solutions of the coating material, for example solutions of viscose of 1 or 2 to 5%, and/or by hydroextracting or otherwise removing excess of the treating liquor before converting into cellulose or other desired coating. Thus, for example, already cut fibres may be treated with a dilute solution of viscose and allowed to drain or hydroextracted prior to treatment with an acid or an acid salt to convert the viscose into cellulose. If the filaments or fibres treated by the invention are allowed to steep for some considerable time in the treating liquor, the treated fibres may then be washed to remove excess liquor and still obtain a substantial deposit of cellulose or cellulose derivative.

Continuous filaments may receive cellulosic coatings while in any desired form, for example in the form of hanks or whilst traveling from bobbin to bobbin or during any other operation in which the threads travel to or from a. winding device. The filaments or threads may be treated continuously with their manufacture by a dry or wet spinning operation. It is 'convenient to treat the materials whilst they are in warp formation, and for this purpose the warp may be built up from a creel of bobbins or other packages or from the ends proceeding from a number of spinning machines. This applies quite broadly whatever method be adopted for producing the cellulosic coatings, i. e. application of a solution of cellulose followed by precipitation, or application of a cellulose derivative followed by conversion to cellulose, or superficial saponification of the existing cellulose ester thread. The threads may for example be carried through a bath containing the solution of cellulose or cellulose derivative, if necessary through a decomposing bath, and may be subsequently dried. It is preferred, however, to subject them to the cutting operation while they are still wet, since in this form the bundles of filaments are easy to handle and cutting is facilitated.

If desired hygroscopic bodies, other than the hygroscopic colloidal bodies of the invention, may be applied to the materials before, during or after the application of the cellulosic coating. Such hygroscopic bodies may for example be glycerine, glycols or other polyhydric alcohols or hygroscopic derivatives thereof or inorganic bodies, for example ammonium citrate, the chlorides of magnesium, calcium, zinc, iron and strontium, the nitrates of magnesium, calcium, zinc, iron and cobalt and nickel, the acetates and formates of ammonia, sodium and potassium, sodium and ammonium phosphates, amines and amides and their salts, e. g. acetamide and methylamine hydrochloride, and quaternary ammonium compounds and their salts. Such compounds may be applied separately or together with the application of the cellulose or cellulose derivative coating, or alternatively they may be formed on the material during the operation of applying the cellulosic coating or separately therefrom. For example it is easy to provide simultaneously an outer layer of cellulose and also an application of sodium or potassium acetate by simple superficial saponification of cellulose acetate threads without subsequent washing to remove the sodium or potassium acetate which results from the saponification treatment with caustic soda or caustic potash. Similarly if trisodium phos-v phate or ammonia be employed as the saponifying agent the resulting sodium phosphate or ammonium acetate may be retained upon the filaments or other materials so as to confer increased hygroscopic properties thereon. In this combined formation of a cellulosic outer layer with impregnation with another hygroscopic body it is particularly convenient to employ the rapid saponification process described in U. S. Patents Nos. 1,884,622 and 1,884,623 in which a definite amount of saponifying agent is applied to the materials, preferably whilst in warp formation, and the desired amount of saponification effected or completed by passage over heated drums or the like. In the case of the present invention it is not necessary that the heated drums shall completely dry the materials, since as previously stated it is convenient to retain a proportion of water upon the materials to facilitate the subsequent cutting operation.

The cutting of the continuous filaments or threads to form the required staple fibre may again be effected whilst the filaments or threads are travelling, but is most conveniently effected whilst they are in the form of hanks, either while still on the swift, reel or drum on which the hank is wound, or after removal therefrom. The

filaments or threads may for this purpose be arranged compactly, and if a large amount of liquid is retained due to the hygroscopic character of the coating and to impregnation with other hygroscopic bodies, the mass of filaments or threads acquires a firmness and consistency which is very advantageous in handling and cutting, while offering no inconvenience because of excess liquid. Thus for example the bundles of filaments containing a relatively large proportion of aqueous liquid, say about 100% based on their weight, may be cut into the desired lengths by means of a guillotine cutting machine. The invention is not of course limited to cutting the continuous filaments or threads while they are wet. When cutting has been conducted with the filaments or threads in the wet state, the dry! ing of the bulk of moisture from the masses of cut fibre may be carried out either by leaving the fibres on trays, conveyors or the like or in bags or other containers exposed to the open air or by placing them in suitable chambers and may be aided if desired by such means as air currents, vacuum or heat. In this manner the wet fibres may be made sufiiciently dry for effecting the spinning operation. Complete drying may if desired be effected, since the cellulosic outer layer aided, if desired, by the presence of another hygroscopic body promotes moisture regain from the humid atmosphere in which the spinning operation is preferably effected.

As previously stated the cellulosic outer layer itself tends to increase the friction between the fibres and so aids the spinning operation. However, if desired, roughening media,'such as silica, barytes, lithopone, and kieselguhr, or even soluble salts may be applied to the materials with a view to increasing the friction still more. roughening media may be applied separately or together with the cellulosic coating, or where other hygroscopic bodies are applied separately from the cellulosic coating, may be applied together with said hygroscopic bodies- If necessary or desirable the fibre may be lubricated, for example with olive oil, prior to winding or cutting, and again such application of lubricant may be conducted separately or together with any of the operations previously described.

When the cutting of the filaments -or threads is effected while they are in a wet condition, the fibres may tend to be somewhat matted, but

passage of the dried fibres through an opener' readily brings them into a suitable state for the carding operation.

After the formation of the spun yarns from the staple fibre, and before or after weaving, knitting or otherwise working up the spun yarns, into fabric form, the cellulose or cellulose derivative coating may if desired, andif feasible, be removed from the materials. This is readily possible if the outer layer is constituted by a cellulose, and particularly a highly degraded cellulose, or a cellulose derivative which is soluble or readily dispersible in water or other aqueous media, for example slightly alkaline medium. The coating may then be removed by a vigorous scouring operation.

The invention has been described above more particularly as involving the application to the filaments or fibres of an outer layer of cellulose or of a cellulose derivative which is of a hygroscopic character. It also includes, however, the application of a coating or outer layer of any other hygroscopic colloidal solid material, for example starch, polyvinyl alcohoL-or a partially esterified or etherified polyvinyl alcohol having the hygroscopic properties. Such bodies may be applied in aqueous solutions, particularly the polyvinyl alcohol or soluble derivative thereof or soluble starch, or may, where feasible, be applied in solution in a volatile organic solvent. In these Such cases it is not necessary to employ any subsequent conversion step, since the hygroscopic outer layer may be applied in the form of the actual substance having the desired hygroscopic properties. The following examples illustrate the invention but are not to be considered as limiting it in any way.

Example 1 Cellulose acetate. yarn in hank form is soaked for about 15 minutes in a viscose solution containing about 2-3% of cellulose and prepared from a cellulose which has been degraded, for example by treatment with mineral acids at relatively high temperatures. After soaking, the yarn is removed and treated in a suitable acid bath to decompose the viscose, for example a 25-35% solution of sodium bi-sulphate. The yarn is then de-sulphurized and washed, and after hydro-extracting is cut-intostaples. These are partially dried, if necessary, and are then put through the usual spinning processes, including opening, combing or carding, drawing and twisting, to form a spun yarn.

Example 2 other. On emerging from the bath the threads may be passed over a steam heated drum in order to dry or partially dry them and may then be out into suitable lengths for staple fibre.

' Example 3 A dry spun cellulose acetate thread is passed What I claim and desire to secure by Letters Patent is:

1. Process for the, manufacture of spun yarn, which comprises forming on filamentary ma terial comprising a water-insoluble organic derivative of cellulose an outer layer of degraded cellulose, converting said filamentary material into short lengths and subsequently spinning the short lengths into spun yarn. 1

2. Process for the manufacture of spun yarn, which comprises forming. on continuous filamentary material comprising cellulose acetate an outer layer of degraded cellulose, subsequently converting said filamentary material into short lengths and spinning the short lengths into spun yarn. i

3. Spunyarn comprising short lengths of filaments of an organic derivative of cellulose having an outer layer of degraded cellulose.

4. Spun yarn comprising short lengths of filaments of cellulose acetate having an outer layer of degraded cellulose.

- HENRY DREYFUS.