US2395396A - Thermal stretching of cellulose derivative yarn - Google Patents

Description

Patented Feb. 26, 1946 THERMAL STRETCIHNG F CELLULOSE DERIVATIVE YARN Rollin F. Conaway, Wilmington, Dcl., asslgnor to E. I. du Pont de Nemours & Company, Wilmington, Bet, a corporation of Delaware Ne Drawing. Application September 25, 1942, Serial No. 459,739

12 Claims.

This invention relates to a process for the prevention of adherence of filaments of artificial thermoplastic material to each othe while in the plastic state, and still more particularly to a process operative to prevent filaments sticking during the preparation of high tenacity yarns from thermoplastic cellulose derivatives by stretching yarns rendered plastic by a heat treatment, and to the filament treated according to the process.

This application is a continuation-in-part of application Serial No. 387,551, filed April 8, 1941.

In the field of artificial textiles there is an increasing interest in yarns of much lighter tenacity than have heretofore been available. A method widely employed for preparing high tenacity yarns consists in stretching the preformed filaments of the yarn which have been rendered plastic by an additional treatment such as the applicatlon of solvents and/or of heat. when this method is'employed, there is a tendency for the individual filaments of the yarn to adhere to each other while in the plastic state and thereby form coarse monofils which are generally undesirable in the textile industry. One of the important problems, therefore, in the preparation of high tenacity yarns by the stretching of yarns in a plastic state is to prevent the sticking oi filaments during the stretching operation. This problem is particularly acute in the stretching of thermoplastic yarns of cellulose derivatives, the filaments of which are softened by the thermal process by heat alone, as in Niogret, U. 8. Patent No. 1,921,426.

An object of this invention is to provide a process which will serve to overcome the difilculty oi sticking filaments encountered during the stretching of yarns of thermoplastic cellulose derivatives. A further object is in the provision of filaments of thermoplastic cellulose derivatives, which have been treated to prevent sticking during the stretching thereof. A still further object resides in a process for forming high tenacity yarns of thermoplastic cellulose derivatives which yarns are free of stuck filaments. A still further obiect is to provide a. process for preparing high tenacity yarn free of stuck filaments, from heat-softened yarn comprised of preformed iilaments of cellulose acetate. These and other obiects will more clearly appea hereinafter.

The objects of this invention are accomplished by applying to yarns of preformed filaments of thermoplastic cellulose derivatives, 9. liquid composition containing essentially a dissolved or dispersed inert solid having a melting or softenin point above the thermal stretching temperature of the yarns, said composition being substantially inert to the cellulose derivatives under the operating conditions, that is, having no softening action on the yarn either at low or elevated temperatures. The treated yarn is then optionally conditioned to remove all or a portion of the liquid and is heat-softened, and then stretched while in the softened state. Finally the composition is removed from the high tenacity yarn by any convenient method, as by washing, for example.

For purposes of this invention there may be employed any solid substance, or potentially solid substance, the melting or softening point of which is above the thermal stretching temperature of the yarn undergoing treatment, and which in addition does not, under the operating conditions. have a softening or dissolving effect on, and is otherwise chemically inert with respect to, the cellulose derivative of which the yarn is comprised. Preferred inert solids are the water-soluble salts of inorganic and organic acids such as the sodium, potassium, and lithium sulfates. chlorides. and bromides; sodium suliocyanate, magnesium sulfate, calcium chloride, barium nitrate, sodium and potassium alums, beryllium chloride, copper sulfate, calcium acetate. sodium formate, sodium propionate, sodium lactate, and sodium glycolate, which are applied in aqueous solution. Substantially water-insoluble solids such as talc, bentonite, chalk, fullers earth, starch, carbon black, synthetic resins, and the like can also be employed, and are applied most conveniently a aqueous dispersions. Solventand dispersing media other than water, which do not have a softening eil'ect on thermoplastic cellulose derivatives, can likewise be employed, either singly, in homogeneous mixture, or in the form of emulsions.

In most instances, the addition to the liquid composition of a binding agent which is inert, that is, does not exert a softening action on the cellulose derivatives, improves the process by enabling more uniform tretching to be carried out and by providing a protective covering for the yarn. It is preferred to use those colloidal binding and protective agents which also function as crystallization inhibitors for the watersoluble salts employed. Examples of suitable colloidal binding agents, yarn protective agents and/or crystallization inhibitors are glucosldes such as saponin, naturally occurring gums such gum arable, protein materials such as glue and gelatin, polyvinyl alcohol, water-soluble cellulose derivatives such as water-soluble methyl and hydroxyethyl cellulose, and pectin.

The preferred antisticking compositions of this invention are prepared by dissolving the watersoluble salt and the colloidal binding agent in water to form a homogeneous solution. A small amount of a wetting agent, such as the sodium salt of long chain alkyl sulfates, may also be added to the solution in order to improve the uniformity of wetting of the yarn by the solution. The concentration of constituents in the solution varies with the type of yarn, nature of stretching conditions, extent of stretching, composition of the constituents in the solution of antisticking composition, and method of applying the finish to the yarn. In general, the optimum conditions are obtained with aqueous solutions containing from 0.5 to of the salt, 0.1 to 2% of water-soluble colloidal binding agent, and 0.01 to 1% of a wetting agent.

The drying or conditioning of the yarn prior to stretching by the thermal procedure is optional and depends on the type of thermal stretching unit employed. In most cases more uniform yarn properties are obtained with dry yarn, whereas in a few cases wet or moist yarn produces more uniform stretching conditions and stretched yarns with improved physical properties.

The following examples illustrate the invention. Parts are by weight.

Example I This example illustrates the use of sodium chloride and saponin as the antisticking composition for cellulose acetate yam when the speeds and extent of stretching are relatively low.

An aqueous solution of sodium chloride and saponin was prepared by dissolving 1 part of sodium chloride and 1 part of purified saponin in 98 parts of water at room temperature. The resulting homogeneous solution was applied to 150 denier-100 filament cellulose acetate yarn having 3 turns/inch twist by means of a size roll at a linear yarn speed of l5 ft./min., and dried. The resulting dry yarn, which contained 3% of antisticking composition on a dry basis. was stretched 1000% by passing the yarn into a heated chamber maintained at a temperature of 218 C. and stretching the heat-softened yarn at a wind-up speed of 110 ftJmin. The resulting stretched yarn possessed a tenacity of 2.3 g./den., and was free from filament sticking. When the yarn was stretched under the same conditions without applying an antisticking finish, the resulting stretched yarn was stuck badly and possessed the characteristics of a monofil.

Example II This example illustrates the use of the sodium chloride-saponin size on fine denier cellulose acetate yarn at rapid stretching rates.

An aqueous solution containing 2 parts of sodium chloride and 2 parts of saponin in 96 parts of water was prepared and applied to 300 denier- 100 filament cellulose acetate yarn having 3 turns/inch twist by means of a size roll at a linear speed of 60 ft./mm. The yarn. containing 1.0% antisticking composition. was dried at room temperature and passed into an electrically heated chamber maintained at a temperature of approximately 225" C. The heat-softened yarn was stretched 1070% at a wind-up speed of 200 ftJmin. The 28 denier-100 filament stretched yarn possessed a tenacity or 3.8 g./den.. and had a soft, pleasant hand indicating the absence of asaasoe filament sticking. The filaments of the yarn separated completely from one another on breaking, indicating the absence of filament sticking. Cellulose acetate yarn stretched under the same conditions in the absence of an antisticking finish was stuck badly and in general possessed the properties of a monofil.

Example III This example illustrates the use of the sodium chloride-saponin antisticking composition on cellulose acetate yarn stretched in a liquid medium in which the sizing and stretching operations were carried out continuously without an intermediate drying operation.

An aqueous solution containing 8 parts of sodium chloride and 2 parts of saponin dissolved in parts of water was prepared and applied to 300 denierfilament cellulose acetate yarn possessing 3 turns/inch twist by means of a size roll at a linear speed of 25 ft./min. The wet yarn, containing 3.4% antisticking composition on a dry basis, was then passed into a liquid bath of molten solder composed of equal parts of tin and lead, maintained at a temperature of 238 C., and the yarn stretched 515% at a wind-up speed of 130 it./min. Theresulting washed and dried 58 denier-100 filament yarn possessed a tenacity of 3.2 g./den., a soft and pleasant hand, and separated completely into filaments on breaking.

Example IV This example illustrates the use of the sodium chloride-saponin antisticking composition on large denier cellulose acetate yarn stretched in hot liquid media at high stretching ratios.

An aqueous solution containing 12 parts of sodium chloride, 2 parts of saponin, and 86 parts of water was prepared and applied to 660 denier- 66 filament cellulose acetate yarn containing 3 turns/inch twist by means of a sizing roll at a linear speed of 20 ft./min. The wet yarn, containing 5.0% of antisticking composition, was passed into a hot liquid bath of solder (50% tin- 50% lead) maintained at a temperature of approximately 245 C. under a yarn tension of 8 grams. The heat-softened yarn was stretched 1250% at a wind-up speed of 250 i't./min. The washed and dried 53 denier yarn possessed a tenacity of 3.1 g. /den., and was free from filament sticking since the filaments separated on rubbing or breaking the yarn.

Example V This example illustrates the use of the sodium chloride-saponin antisticking composition containing a small amount of a wetting agent in the stretching of large denier cellulose acetate yarn with hot liquid baths at high stretching ratios.

An aqueous solution containing 10 pans of sodium chloride. 2 parts of saponin, 0.1 part of "Lorol" sodium sulfate ("Lorol" refers to the residue of commercially available mixed primary alcohols containing 10 to 18 carbon atoms), and 87.9 parts of water was prepared and placed in conventional sizing equipment. 2400 denierfilament cellulose acetate yarn containing 3.

turns/inch twist was passed over the size roll coated with the composition at a linear speed of 3 ft./min. The wet yarn containing 7.0% antisticking composition was passed into a hot liquid bath of molten solder (50% tin-50% lead) at a temperature of approximately 240 C. under a tension of 20-25 grams. The heat-softened yarn was stretched 15'70% at a wind-up speed of aseasce ftJmin. The washed and dried 150-denier yarn possessed a tenacity of 2.2 g./den. It possessed a soft, pleasant hand and the filaments separated completely on breaking the yarn.

Example VI This example illustrates the use or the sodium chloride-saponin antisticking composition on cellulose acetate propionate yarn.

A 150 denier-38 filament mixed ester yarn prepared i'rom cellulose acetate propionate containing approximately 2.5% of combined propionic acid and 52% of combined acetic acid was passed over a size roll containing the same antisticking composition as employed in Example V, at a linear speed of 22 it./min. The wet yam, containing 6.0% of antisticklng composition, was passed into a hot liquid (50% tin-50% lead solder) bath maintained at a temperature or 240 c. The heat-softened yarn was stretched 600% at a wind-up speed or 132 ft.,/min. The resulting stretched yarn possessed a tenacity of 2.5 g./den., and a soft, pleasant hand indicating that the filaments were not stuck to each other.

Example VII This example illustrates the use oi the sodium chloride-saponin antisticking composition on cellulose nitrate yarn.

An aqueous solution containing 8 parts of sodium chloride, 2 parts of saponin. and 90 parts of water was prepared and placed in the sizing equipment. A 550 denier-60 filament cellulose nitrate yarn spun from cellulose nitrate with a nitrogen content of 11.06% was passed over the size roll coated with antisticking solution, at a linear speed 01' 50 it./min. The yarn was allowed to dry at room temperature before stretching. The dry yarn was passed through a hot air stretching chamber maintained at a temperature of 186 C. at an in-put speed of 19 it./min. and a wind-up speed of 100 it./min. The resulting 105 denier stretched yam possessed a tenacity or 2.65 g./den. and a soft, pleasant hand indicating that the filaments of the yarn had not been (used to each other during the stretching operation.

Example VIII This example illustrates the use of glue in the antisticking composition in place oi saponin as the water-soluble colloid.

An aqueous solution containing 20 parts sodium chloride, 6 parts of hide glue, and 74 parts oi water was prepared and placed in the sizing equipment. A 300 denier-100 filament cellulose acetate yarn was passed over the size roll at a linear speed of 50 it./min. The yarn containing 14% of antisticking composition was dried at room temperature and stretched 500% by passing the dry yarn through a heated air chamber maintained at a temperature of 222 C. at an in-put speed oi it./min. and a wind-up speed 01' 50 it./min. The resulting purified yarn had a tenacity of 2.9 g./den. and a very soft hand. The filaments in this yarn could be separated by merely untwisting the yarn, indicating the absence oi stuck filaments.

Example IX This example illustrates the use of gelatin as the water-soluble colloid in the antisticlring composition.

An antisticking solution containing 4 parts of ,sodium chloride, 4 parts of gelatin, and 92 parts of water was prepared and placed in the sizing equipment. A 300 denier-100 filament cellulose acetate yarn was passed over the size roll coated with the antisticking solution at a linear speed of 50 itJmin. The yarn, containing 9.0% of antisticking composition, was dried at room temperature and stretched 600% by passing the dry yarn through a heated chamber maintained at a temperature of 228 C. in which the in-put speed was 20 ft./min. and the out-put speed 120 itJmin. The resulting stretched yarn, after washing to remove the finish, possessed a tenacity oi 2.9 g./den., and was free from stuck filaments.

Example X This example illustrates the use of gum arable as the water-soluble colloid in the antlsticking composition.

An antisticking composition containing 20 parts of sodium chloride, 4 parts of gum arable, and 76 parts of water was prepared and placed in the sizing equipment. A sample of 300 denierfilament cellulose acetate yarn was passed over the size roll at a linear speed of i0 ft./min. The wet yarn containing 10% of antisticking composition was passed through a heated chamber maintained at a temperature of 222 C. at an in-put speed of 10 ft./min. and a wind-up speed of 50 it./min. The resulting yarn, which had been stretched 500%, possessed a very soft hand and a tenacity of 3.0 g./den. The filaments in the yarn could be separated by untwisting the yarn. indicating the absence of filament sticking.

Example XI This example illustrates the use of sodium sulfate in the antisticking composition in place of sodium chloride.

An antlsticking composition containing 15 parts of anhydrous sodium sulfate, 1 part of saponin, and 84 parts of water was prepared and placed in the sizing equipment. A 300 denier-100 filament cellulose acetate yarn was passed over the sizing roll and into a heated stretching chamber maintained at a temperature of 220 C., at a rate of 10 ft./min. The yarn. containing 8.6% ant-isticking composition, was stretched 500% in the chamber and wound on a positively-driven bobbin at a speed of 50 ft./min. The stretched yarn had a tenacity of 2.8 g./den. and was very soft and free from stuck filaments.

Example XII This example illustrates the use of an antisticking finish in the stretching of delustered cellulose acetate yarn.

An aqueous solution containing 10 parts of sodium chloride, 2 parts of saponin, 0.1 part of "Lorol sodium sulfate, and 87.9 parts of water was prepared and placed in the pan of the sizing equipment. A 300 denier-104 filament cellulose acetate yarn delustered with titanium oxide pigment was passed over the size roll at a linear speed of 22 it./min The wet yarn, containing 5.8% antisticking composition, was stretched 600% while passing through a hot liquid solder (50% tin-50% lead) bath maintained at a temperature of 240 C. The resulting stretched yarn possessed a soft hand and a tenacity of 3.0 8./den. The filaments of the yarn separated completely on breaking, indicating the absence of stuck filaments.

Example XIII This example illustrates an antisticking composition containing calcium acetate and saponin. An aqueous solution of calcium acetate and saponin was prepared by dissolving 6 parts of calcium acetate and 2 parts of saponin in 92 parts of water at room temperature. The resulting homogeneous solution was applied to 300 denier-100 filament cellulose acetate yarn by passing the yarn continuously through approximately 4 inches of the solution in a size pan at a linear speed of 36 itJmin. The resulting wet yarn was stretched 555% by passing into an 18- inch molten solder bath heated to a temperature of 238 C. and winding the heat-softened yarn on a bobbin at a wind-up speed of 200 ftJmin. under a tension of 6 grams. The resulting 55 denier yarn had a tenacity of 3.0 g./den., elongation of 5.5%, and fibrillated completely on breaking, indicating the absence oi filament sticking.

Example XIV This example illustrates an antisticking composition containing calcium acetate and polyvinyl alcohol.

An aqueous solution of calcium acetate and polyvinyl alcohol was prepared by dissolving 1.2 parts of calcium acetate and 0.1 part of watersoluble polyvinyl alcohol in 98.7 parts of water at room temperature. The resulting homogeneous solution was applied to 300 denier-100 filament cellulose acetate yam by passing the yarn continuously through approximately 4 inches of the solution in a size pan at a linear speed of 40 ft./min. The wet yarn was passed over the surface of a pre-drier 36 inches in length, heating by steam to a temperature of 116 C. in order to dry the impregnated yarn. The dry yarn was passed continuously into a vertical heated tube 36 inches in length heated to a temperature of 245 C. The heat-softened yarn was stretched 555% in the heated air column under a tension of 6 grams and wound on a bobbin at a wind-up speed of 225 ft./rnin. The resulting stretched 55 denier yarn, after washing possessed a tenacity of 3.1 g./den., an elongation of 5.0%, and a soft, pleasant hand indicating the absence of filament sticking.

Example XV This example illustrates the use of an antisticking composition containing sodium formate and saponin.

An aqueous solution sodium formats and saponin was prepared by dissolving 6 parts of sodium formate and 1 part of saponin in 93 parts of water at room temperature. The resulting homogeneous solution was applied to 300 denier- 100 filament cellulose acetate yarn containing 3 turns per in h twist by passing the yarn continuously through 4 inches of the solution in a size pan at a linear speed of 39 it./mln. The wet yarn was dried by passing over a steam heated drier and the dry yarn was stretched 770% by passing through a vertical air-type stretching unit heated to a temperature of approximately 245 C. under a stretching tension of 6 grams and a wind-up speed of 240 ft/min. The resulting 40 denier yarn had a tenacity of 3.4 g./den., an elongation of and a. soft, pleasant hand indicating the absence of filament sticking.

Example XVI This example illustrate the use of an antisticking composition containing sodium propiomate and saponin.

An aqueous solution of sodium propionate and saponin was prepared by dissolving 9 parts of sodium propionate and 1 part of saponin in 90 parts of water at room temperature. The resulting homogeneous solution was applied to 300 denierfilament cellulose acetate yarn by passing the yarn continuously through approximately 4 inches or the solution at a linear speed 01 36 ft./min. The resulting wet yarn was passed into an 18- inch molten solder bath, the same as in Example XIII above, heated to a temperature of 242 C. and stretched 555% under a tension of 9 grams and a wind-up speed of 200 rtJmin. The resulting high tenacity yarn had a yery soft and pleasant hand, indicating the absence of filament sticking.

Example XVII This example illustrates the use 01' an aqueous dispersion of talc as the antisticking composition.

An aqueous dispersion containing 2 parts of saponin. 8 parts of finely divided tale in which a major portion of the particles had a particle size of 1 to 15 microns, 0.5 part of Gar-dine? WA (sodium salt of technical sulfated dodecanol-i) and 89.5 parts 01' water was prepared by adding the tale to the aqueous solution oi the other constituents with rapid agitation. The resulting dispersion was applied to 300 denier- 100 filament cellulose acetate yarn by passing the yarn continuously through approximately 4 inches of the dispersion in a size pan at a linear speed of 36 ft./min. The wet impregnated yarn was passed into an 18-inch solder bath at a temperature of 242 C., and the heat-softened yarn stretched 555% under a tension of 8 grams and a wind-up speed of 200 i't./min. The resulting 55 denier yarn possessed a tenacity of 3.0 g./den., an elongation of 5.5%, a soft hand, and an open structure indicating the absence of filament sticking.

Example XVIII This example illustrates the use of an aqueous dispersion of finely divided chalk as the antisticking composition.

The same conditions were employed as in the preceding example, except that the aqueous dispersion contained 8 parts 01' finely divided chalk in place of 8 parts of talc.

Example XIX This example illustrates the use of an aqueous dispersion of fuller's earth as the antisticking composition.

The same conditions were employed in this example as in Example XVII above. except that 4 parts of fullers earth was employed in the dispersion in place of 8 parts of talc. The resulting stretched yarn was harsh prior to washing, but after washing was soft and open indicating the absence of filament sticking.

Example XX This example illustrates the use of an aqueous dispersion of fulier's earth and bentonite as the antisticking composition.

In this example the same conditions were employed as in Example XVII above, except that 8 parts of fullers earth and 1 part of bentonite were employed in the aqueous dispersion in place of the tale. The resulting stretched and washed yarn was soft and open indicating the absence of filament sticking.

Example XXI This example illustrates the use of a solution of Gardinol WA (sodium salt of sulfated technical dodecanol-l) in a commercial mixture oi butyl stearate and palmitate.

A composition containing 4 parts of Gardinol" WA and 96 parts of a mixture of butyl palmitate and stearate was prepared by adding the asoasee "Gardinol" WA to the synthetic oil mixture with rapid stirring at room temperature. Approximately one-half of the GardinoP' WA dissolved in the oil so that the resulting composition was a dispersion of "GardinoP WA in a solution of Gardinoi WA and butyl stearate and paimitate. This oil dispersion was applied to 300 denier-100 filament cellulose acetate yarn by passing the yarn over a size roll coating with the dispersion at a linear speed of 36 ft./min. The coated yarn was passed into an 18-inch bath of molten solder at a temperature of 242 C. The heat-softened yarn was stretched 555%, under a stretching tension of 8 grams and a wind-up speed of 200 ft./min. The resulting stretched yarn, after scouring, possessed a soft hand and open structure indicating the absence of filament sticking.

Example XXII This example illustrates the use of an aqueousoil emulsion as an antisticking composition.

An aqueous solution containing 2 parts of "Gardinol" WA, 1 part of saponin, 2 parts of sodium propionate, dissolved in 25 parts of water was added at room temperature, with rapid stirring, to 25 parts of a commercial mixture of butyl stearate and palmitate. The resulting emulsion was applied to 300 denier-100 filament cellulose acetate yarn by the size-r011 technique, and the coated yarn stretched in the molten solder bath under the same conditions as in Example XXI above. The stretched 55 denier yarn, after scouring in an 0.5% soap solution, washing and conditioning, possessed a tenacity of 3.0 g./den., an elongation of 4%, a soft hand, and open structure, indicating the absence of filament sticking.

It is understood that the above examples are by way of illustration only and that the invention is susceptible to wide variation from'the exact materials and conditions set forth in the examples. Thus, the anti-sticking composition of this invention is applicable to all thermoplastic yarns and to those types of stretching procedures where there is a tendency for the surface of the individual filaments to become suiliciently soft or plastic to cause them to adhere to one another.

The concentration of the inert solid employed may vary between wide limits and is determined by the type of yarn employed, the conditions of sizing and stretching, and the extent of stretching. If the rate and extent of stretching of cellulose acetate yarn is low, a concentration of 1% of solid, such as sodium chloride, may be sufllclent. On the other hand, if the rate of stretching is high, which necessitates the use of higher temperatures in the stretching chamber, and the extent of stretching is high, such as in the order' of 800-2000%, it may be necessary to increase the concentration of the solid to as much as 20%. Concentrations of solid in the range of 0.5% to 5% are in most cases preferable.

The concentration of binding agent employed in the composition depends on the concentration of salt which in turn is governed by the factors mentioned above. With concentrations of the inert solid in the order of 0.5% to 5%, concentrations of binding agent in the order of 0.1% to 2% are sufiicient. When the concentration of solid is increased to it may be necessary to increase the concentration of binding agent to as much as 6%. The preferable concentration of binding agent is in the range of 0.01% to 2%, but the concentration may be increased to 5.0% or higher without deleterious effects.

The wetting agent added to the solution may be any of th standard types of surface-active agents that meet the basic requirements of the other ingredients in the composition. The materials which have been found to be most eifective are the sodium salts of the long-chain aliphatic acids, such as stearlc acid, and the salts of the sulfonates and sulfates of the corresponding alcohols of these acids, such as Lorol" sodium sulfate. The concentration of surface-active agents employed depends on the efliciency of the material as well as th type of antisticking composition, yarn, and sizing conditions employed. In general, a concentration in the order of 0.01% to 1.0% is most desirable but can be increased to higher values without deleterious effects.

Any of the standard methods of sizing, such as by passing the yarn through the solution or over a sizing roll, can be employed to apply the antisticking solution to the yarn. The concentration of antlsticking finish on the yarn, calculated on a dry basis, may vary between wide limits, depending on the chemical and physical nature of the yarn and the stretching conditions. When the extents and rates of stretching of cellulose acetate yarn are low, a solids concentration of 1% of the antlsticking finish on the yarn may be adequate to prevent the fusing of filaments. Under more drastic conditions in which large denier yarns are stretched in the order of 2000% at rapid rates and high temperatures, concentrations of the antisticklng finish on the yarn, calculated on a dry basis, may be as high as 10% in order to prevent sticking of filaments during the stretching operation; If the concentration of finish on the yarn becomes too high and the uniformity of application is not adequate, diiiiculty is encountered with non-uniform stretching conditions so that, for" most operating conditions, concentration of finish in the order of 1% to 10% on the yarn is preferred.

The treated yarn can be passed into the stretching chamber in either a wet, moist, or dry condition. When the yarn enters the stretching medium in a wet state, the application of the antisticking composition and the stretching procedure is preferably carried out in one continuous operation. When the yarn is dry or moist, the operation may be either continuous or discontinuous. If the operation is continuous, the yarn is passed through conditioner or drier to lower the moisture content tothe desired extent prior to passing through the stretching chamber. If the application of the antlsticking composition is carried out separately, the yarn can be dried or conditioned in suitable ovens or chambers prior to stretching. The advisability of using the continuous or discontinuous process depends on a number of factors, among which the most important are the type of yarn employed and the conditions of stretching. Under some conditions of stretching, better results are obtained with moist or wet yarn, whereas under other conditions, the uniformity of stretching is improved by the use of essentially dry yarns.

The antisticking finish may be removed from the stretched yarn by suitably washing either immediately following the stretching operation or after some subsequent textile operation.

The procedure of coating the yarn with the composition of this invention prior to stretching in order to prevent the sticking of filaments produces stretched yarns with high tenacities and.

proved yarn properties, such as higher knot strength, which are highly desirable and, in most cases, essential in yarns for general textile use. The procedure is also useful in the thermal treatment of yarns composed of multiple filaments of thermoplastic materials, such as polystyrene, Vinyon, vinyl esters, vinyl ethers, methacrylates and nylon, in addition to the cellulose derivatives. The thermoplastic cellulose derivatives may be classified broadly as esters, ethers, mixed esters, mixed ethers, and mixed ether-esters, such as cellulose acetate, nitrate, propionate, butyrate, acetate propionate, acetate butyrate, ethyl cellulose, benzyl cellulose, ethyl lauryl cellulose, ethyl cellulose acetate, and methyl cellulose propionate.

I claim:

1. In the process for producing high tenacity filaments, yarns, and threads of thermoplastic cellulose derivatives wherein preformed filaments of thermoplastic cellulose derivatives are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating a liquid composition comprising an inert solid having a melting or softening point above the thermal stretching temperature of the filaments, and heat-treating the filaments to soften the same while retaining said inert solid thereon whereby to prevent sticking of the filaments while in the softened condition.

2. In the process for producing high tenacity filaments, yarns, and threads of thermoplastic cellulose derivatives wherein preformed filaments of thermoplastic cellulose derivatives are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating a liquid composition comprising an inert solid having a melting or softening point above the thermal stretching temperature of the filaments, and an inert water-soluble binding agent, and heattreating the filaments to soften the same while retaining said inert solid and binding agent thereon whereby to prevent sticking of the filaments while in the softened condition.

3. In the process for producing high tenacity filaments, yarns, and threads of cellulose acetate wherein preformed filaments of cellulose acetate are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating a liquid composition comprising an inert solid having a melting or softening point above the thermal stretching temperature of the filaments, and heat-treating the filaments to soften the same while retaining said inert solid thereon whereby to prevent sticking of the filaments while in the softened condition.

4. In the process for producing high tenacity filaments, yarns, and threads, of cellulose acetate wherein preformed filaments of cellulose acetate are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating a liquid composition comprising an inert solid having a melting or softening point above the thermal stretching temperature of the filaments, and an inert water-soluble binding agent, and heat-treating the filaments to soften the same while retaining said inert solid and binding agent thereon whereby to prevent sticking of the filaments while in the softened condltion.

5. In the process for producing high tenacity filaments, yarns, and threads, of thermoplastic cellulose derivatives wherein preformed filaments of thermoplastic cellulose derivatives are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating an aqueous liquid composition comprising an inert water-soluble salt having a melting point above the thermal stretching temperature of the filaments, and heat-treating the filaments to soften the same while retaining said inert solid thereon whereby to prevent sticking of the filaments while in the softened condition.

6. In the process for producing high tenacity filaments, yarns, and threads, of thermoplastic cellulose derivatives wherein preformed filaments of thermoplastic cellulose derivatives are softened by heat and stret... :d while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating an aqueous liquid composition comprising an inert water-soluble salt having a melting point above the thermal stretching temperature of the filaments, and an inert water-soluble binding agent, and heat-treating the filaments to soften the same while retaining said inert solid and binding agent thereon whereby to prevent sticking of the filaments while in the softened condition.

'7. In the process for producing high tenacity filaments, yarns, and threads, of cellulose acetate wherein preformed filaments of cellulose acetate are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating an aqueous liquid composition comprising an inert water-soluble salt having a melting point above the thermal stretching temperature of the filaments, and heat-treating the filaments to soften the same while retaining said inert solid thereon whereby to prevent sticking of the filaments while in the softened condition.

8. In the process for producing high tenacity filaments, yarns, and threads, of cellulose acetate wherein preformed filaments of cellulose acetate are softened by heat and stretched while in the softened condition, the improvement which comprises applying to the filaments prior to heat treating an aqueous liquid composition comprising an inert water-soluble salt having a melting point above the thermal stretching temperature of the filaments, and an inert water-soluble binding agent, and heat-treating the filaments to soften the same while retaining said inert solid and binding agent thereon whereby to prevent sticking of the filaments while in the softened conditlon.

9. In the process for producing high tenacity filaments, yarns, and threads, of cellulose acetate wherein preformed filaments of cellulose acetate are softened by heat and stretched while in the softened condition, the improvements which comprise applying to the filaments prior to heat treating an aqueous liquid composition comprising an inert water-soluble salt having a melting point above the thermal stretching temperature of the filaments, an inert water-soluble binding agent, and a wetting agent, heat-treating the filament to soften the same while retaining said inert solid, binding agent and wetting agent thereon whereby to prevent sticking of the softened filaments, and removing the composition from the filaments after stretching.

10. In the process for producing high tenacity filaments, yarns, and threads, of thermoplastic cellulose derivatives wherein preformed filaments of thermoplastic cellulose derivatives are softened by heat and stretched while in the softened con.

a,sos,seo

dition, the improvement which comprises app ying to the filaments prior to heat treating an aqueous liquid composition comprising from about 0.5% to about 10% by weight of an inert water-soluble salt having a melting or softening point above the thermal stretch temperature of the filaments, and Iron 0.l% to about 2% by weight of an inert water-soluble binding agent, and heat-treating the filaments to soften the same while retaining said inert solid and bindin; agent thereon whereby to prevent sticking of the filaments while in the softened condition,

11. In the process for producing high tenacity filaments, yarns, and threads, of cellulose acetate wherein preformed filaments oi cellulose acetate are softened by heat and stretched while in the softened condition, the improvement which comrises applying to the filaments prior to heat treating an aqueous liquid composition compris- ROE-IN F. CONAWAY.

Certificate of Correction Patent No. 2,395,396.

February 26, 1946.

ROLLIN F. CON AWAY It is hereby certified that errors appear in the printed s ecification of the above numbered patent requiring correction as follows: Pa e 1, hghter" read higher; page 2, first column, line 67,

mt column, line 14, for xample II, for 60 ft./mm.

read 60fi.lm'in.; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofice.

Signedand sealed this 14th day of May, A. D. 1946.

[BELL] LESLIE FRAZER,

First Assistant C'ommissiomr of Patents.

a,sos,seo

dition, the improvement which comprises app ying to the filaments prior to heat treating an aqueous liquid composition comprising from about 0.5% to about 10% by weight of an inert water-soluble salt having a melting or softening point above the thermal stretch temperature of the filaments, and Iron 0.l% to about 2% by weight of an inert water-soluble binding agent, and heat-treating the filaments to soften the same while retaining said inert solid and bindin; agent thereon whereby to prevent sticking of the filaments while in the softened condition,

11. In the process for producing high tenacity filaments, yarns, and threads, of cellulose acetate wherein preformed filaments oi cellulose acetate are softened by heat and stretched while in the softened condition, the improvement which comrises applying to the filaments prior to heat treating an aqueous liquid composition compris- ROE-IN F. CONAWAY.

Certificate of Correction Patent No. 2,395,396.

February 26, 1946.

ROLLIN F. CON AWAY It is hereby certified that errors appear in the printed s ecification of the above numbered patent requiring correction as follows: Pa e 1, hghter" read higher; page 2, first column, line 67,

mt column, line 14, for xample II, for 60 ft./mm.

read 60fi.lm'in.; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofice.

Signedand sealed this 14th day of May, A. D. 1946.

[BELL] LESLIE FRAZER,

First Assistant C'ommissiomr of Patents.