US2338641A - Method of making yarn - Google Patents

Description

Jan. 4, 1944. R. B. HlcKEY O METHOD OF MAKING YARN Filed Feb. '7, 1941 ,2a/R AND HEAT l oanfr VAR/AT/O/Y ON/IVERAGE /QoE/erH/CKEY INVENTOR 7% mi u gmk A TT NEYS Patented Jan. 4, 1944 METHOD F MAKING YARN Robert B. Hickey, Kingsport, Tenn., allignor to .Eastman Kodak Company, Rochester, N. Y., a

corporation of New Jersey Application February 7, 19411, Serial No. 377,874

12 Claims.

This invention relates to the method of making yarn consisting of a hydrolyzed cellulose ester containing acetyl groups and 1-6% of saturated fatty acid groups of 3-4 carbon atoms, which ester has a viscosity of 30-150 seconds, and to a process for preparing that yarn.

In the textile art there are instances where yarn of a bright luster is desired. Bright luster yam has been previously prepared from cellulose ester solutions, but the uniformity of the luster of that yarn has shown wide variation. Also, in many instances the ability oi the finished yarn to stretch has been poor. In addition, in processes by which the yarn was prepared, varous difficulties arose, such as breaking of the yarn during the spinning operation, stopping-up of the spinneret (blebbing), poor filter ability and the like, particularly if high spinning speeds were attempted. v

One of the objects of this invention is to make possible the preparation of a yarn having high uniformity of luster. Another object of the invention is to minimize the difilculties met with in prior yarn spinning processes, particularly in high speed spinning. A further object of my in; vention is to produce a yarn having a satisfactory inherent stretch or stretchability as compared with cellulose ester yarns generally.

I have found that yarns of high luster uniformity, whether of the bright luster type or of a lesser luster, may be prepared by spinning the yarn from a solution of an acetyl cel1ulose,hav ing a 1-6% propionyl or butyryl content and a viscosity of 30-150 seconds, in a volatile solvent, particularly acetone, in which the ester constitutes at least 25.5% of the spinning solution at a .speed of at least 450 meters per minute. I have found that, not only is it thus possible to obtain high luster uniformity, but also a product havingsatisfactory inherent stretch. I have also found that the use of a low viscosity, low propionyl cellulose acetate propionate (or corresponding acetate butyrate) and a high concentration of ester in the spinning solvent makes possible the use of high spinning speeds and a minimum of breaks and blebs.

Good stretch means that the finished filament may be subjected to considerable elongation without breaking. For instance, in the case of filaments of a 3 denier per filament yarn, the filament may be stretched 2326% of its original length before breaking of the lament occurs. With 1.5 denier filaments the yarn may be stretched 1.5-20% of its original length before breaking occurs. By good is meant stretchability of filaments commensurate with these values.

This application relates to yarns whether of the bright luster, the moderate luster, or the dull luster type. As uniformity of luster is of particular importance in the bright and moderate luster type yarns, my invention is particularly adapted to the making of those yarns. However, it is also adapted for the making of dull luster type yarns, such as are obtained by incorporating an opaquing agent in the spinning solution. In the case of the latter, the primary purpose of my invention is to make possible the spinning of the yarn at high speeds without appreciable danger from breaks or other interruptions in the spinning process and to obtain yarn having good stretch.

The cellulose esters which are suitable for use in my process, are preferably prepared in accordance with the process described and claimed in Malm Patent No. 2,097,464. This ester may be made, for example, by thoroughly wetting the cellulose with a mixture of acetic acid and a small amount of propionic acid followed by esterification induced by adding a mixture of an esterifying amount of acetic anhydride, sufllcient sulfuric acid to prompte the esteriflcation and, if needed, acetic acid or some other solvent as desired by the individual operator. After the esterication has occurred, as shown by the dissolving of the cellulose in the reaction mixture, aqueous acetic acid is added to the mass to convert it to a hydrolyzing mixture. It may also be desirable to neutralize a portion (such as half) of the catalyst at this time, such as described in Fletcher application Serial No. 299,151, filed Oct. 12, 1939, to moderate the rate at which the hydrolysis proceeds. After about hours or when the ester has a precipitation value of 81.5 to 85.5, it may be precipitated, Washed and dried, and employed for making yarn in accordance with my invention providing it has a viscosity within the range of 30-150 seconds If the product has a higher viscosity than desired, a higher temperature may be employed in the esterication to assist in lowering the viscosity and Vice versa The various conditions in my spinning process are adjusted so as to contribute to a high spinning speed and to do this a solids content in the spinning solution of at least 25.5% is generally required. A spinning speed of at least 450 meters per minute is made possible by various factors, one of which is maintaining the percentage of water in the solvent for the cellulose ester between 1.5 and 2.5%. 'I'he water, not only aids in the dissolving power of the solvent for the esters of the type employed for yarn, but also contributes to the economy of the process, as it is uneconomical to dry the ester and solvent down to the point where the water content of the spinning solution is less than 1.5%. On the other hand. limiting the percentage of water used in the spinning solution to not more than 2.5% is conducive to high speed spinning.

Another factor which contributes to high speed spinning is the use of cabinets o! from 20 to 30 feet length together with a rate o! now oi.' the evaporative medium in the spinning cabinet such that the concentration of the solvent in the eilluent air is from l2% by volume and heating the evaporative medium to a temperature of from '10 to 120 C. prior to introducing it into the spinning cabinet. A further factor contributing to a spinning speed of at least 450 meters per minute is the use of a spinning solution having a viscosity not to exceed 700 seconds. 'I'he viscosity of the spinning solution will usually have a 100 second minimum under the conditions given herein.v As will be pointed out herein, it is desirable that the viscosity of the spinning solution, prepared from the lower viscosity esters (such as of 30-80 sec.' viscosity), be not more than 400 seconds to obtain the best results.A A still further factor which contributes to the high speed spinning is the use of a spinning solution having a celluloseester content of at least 25.5%. As pointed out above. this solids content contributes to the continuity of spinning and also to the desirable properties obtained in the result ing product.

Obviously, to assure a spinning speed of at least 450 meters per minute, the spinning solution should be extruded at such a rate that the desired speed is attained. The length of spinning cabinet, (20-30 feet) the temperature and the rate of flow of the evaporating medium given contribute to the curing of the illaments when extruded at the rate of at least Y450 meters per minute. If a shorter spinning cabinet is used, under ordinary conditionathe temperature and rate of ow will be increased to assure the proper curing of the filaments. On the other hand, if a cabinet length much greater than 30 ft. is useci there is danger of the laments breaking in the formative stage unless some intermediateA support is provided.

A high spinning speed is desirable and is li ited only by the conditions of operation. For practical operation a` speed within the range-of 600-700 meters per minute is usually desirable.

My invention is susceptible of adaptation to various types of evaporative spinning. One type of spinning in which it may be employed is that in which a heated spinning solution is extruded into a zone of substantially immobile atmosphere at about the same temperature as the extruded spinning solution, for instance. 50-'10" C. and thence into a zone of evaporative medium, nowing counter-current-to the yarn, of progressively higher temperature, with the highest temperature being not more than about 120 C. Such a spinning process'is illustrated speciilcally in Figure I of the drawing. 'I'his type of spinning technique would ordinarily be preferable for the preparation of yarn in accordance with my invention.

Another type -of spinning process in which my invention is applicable is that in which a heated spinning solution is extruded into a zone in which evaporative medium is introduced into the spinning cell in the vicinity of the spinneret and ilows concurrently with the lament in the initial portion of the cell, this evaporative medium having a temperature of the order of -i0 C. The iilament in the spinning cell then passes into a zone of evaporative medium, ilowlng countercurrent to the yarn and encounters progressively higher temperatures with the highest tempera- Another method which may be employed for spinning yarn in which my invention may be used is that in which the heated spinning solution is extruded into a zone of substantially immobile atmosphere, whose temperature (025 C.) is considerably lower than that of the spinning solution and thence into a. zone of heated evaporative medium, flowing counter-current to the yarn, so as to encounter progressively higher temperatures with the highest temperature being not more than about C. In this type of spinning it is desirable that the zone of immobile atmosphere be approximately 12 feet in length.

The spinning cabinet employed should be of sufllcient length to provide for a spinning speed voi! at least 450 and preferably 600 meters per minute.` I have found cabinets of approximately 20 to 30- feet length to be satisfactory for this purpose. Obviously, if a shorter cabinet is employed, compensation will be necessary such as by speeding jup the rate of ilow of the evaporating medium or increasing its temperature.

The drawing is comped of Fig. I, a side elevation of a spinning machine which may be employed in producing'v artiiicial silk in accordance with my invention; Fig. II a graph comparing the yarn produced in accordance with my invention with other yarn of a similar nature.

Fig. I illustrates a spinning machine consisting of a pipe manifold I in which the supply of spinning solution is conducted which is then led into feed pipe 2 and passes by means of valve 3 to the pump 4. The pump steps up'the lpressure and forces the solution through the candle lter 5 located in the upper portion of spinning cabinet I'I. The tllter 5 is provided with a heating jacket 6 supplied with a heating fluid such as water which enters the bottom of the Jacket through the inlet 'I and passes out at the top through outlet 8. After passing through candle lter 5 the solution is extruded through fine orifices in the spinning dye or spinneret 9 in the form of fine filaments. As these nlaments proceed down the cabinet II the solvent is evaporated therefrom and the .finished filaments are brought together at the guide roll I0 over which they pass thence through a minute opening II in the wall of the cabinet to a draw roll I2. From the draw-roll the laments are conducted over guide I3 and through guide I4 to spinning pot or bobbin i5 where they are spun into the desired thread. The bobbin may be rotated by means of a motor I6. The walls of the spinning cabinet may be provided with any suitable heatinsulating material. Also it is desirable that a suitable gaseous evaporating medium be conducted atelevated temperature through the cabinet entering at the air and heat inlet and exiting at the outlet shown. Such gaseous media should be substantially inert and have no deleterious eiects on the elements being produced. Obviously various modications and alterations may be made in the described apparatus by the individual operator.

Fig. II of the drawing is a graph based upon actual experimental results of a very large number of instances. Curve A of the graph is based upon a large number o f bobbins obtained using a low propionyl cellulose ester having a viscosity of 250 seconds and being in solution in acetone of 23.9% concentration. Curve B is based on a large number of bobbins obtained by spinning a low propionyl ester having a viscosity of seconds dissolved in acetone at a concentration of 24.9%. Curve C is based upon a large number of bobbins of the same viscosity ester but the p of the 'amount of variation in luster uniformity allowed for the bobbins against the percentage of bobbins in a given batch which fall within the tolerance allowed.

A very satisfactory spinning solution consists of a solution of a hydrolyzed cellulose ester, the

vacyl of which consists of 38% acetyl and 1.5%

propionyl, which ester has a, precipitation value of BLS-85.5 and a viscosity of 125 seconds dissolved in acetone containing approximately 2% Water so that the cellulose ester constitutes approximately 26% of the solution and the viscosity of the solution is 600 seconds.

The spinning solution is conducted through the pipe I to the feed pipe 2 lthrough"which it passes by means of valve 3 to the pump 4. The pump is for the purpose of forcing the solution through the candle filter 5 located in the upper portion of the spinning cabinet I1. The filter 5 is provided with a jacket 6 having an inlet 1 and outlet 8 as shown.

After the solution passes through the candle filter 5, it is extruded through a spinneret 9 in the form of fine filaments of rounded cross section at a rate of approximately 600 meters per minute. These filaments first encounter a substantially immobile evaporative atmosphere of lower temperature than the spinning solution. As they reach a point adjacent to the air outlet I9 a current of warm air is encountered, the temperature progressively increasing as the filaments proceed from outlet I9 to the vicinity of air inlet I 8. The finished filaments come together at a common point on the guide roll I under which they pass, thence through a minute opening II in the wall of the cabinet to a draw roll I2. From the draw-roll the filaments are conducted over guide I3 and through guide I4 to a spinning pot or bobbin I where they are formed into the desired thread. The bobbin may be rotated by means of a motor I6 which may also be employed for reciprocating the guide I4 in any desired manner. This apparatus and its use are more fully described in U. S. Patent No. 2,000,048 of H. G. Stone, dated May 7, 1935.

Figure II of the drawing illustrates the superiority of the yarn prepared in accordance with my invention as regards luster uniformity over yarn prepared from cellulose esters of similar type. Luster uniformity was measured by taking 100 bobbins and determining their variation from the average luster value with a luster meter. The graph indicates the percentage of bobbins which varied not more than 2%, not more than 4%, etc.

In the graph of Figure II, the designated curves are based on the data shown by the following table the cellulose ester in each case being a hydrolyzed acetone-soluble ester containing 1.5% propionyl, the remainder of the acyl being acetyl:

The graph illustrates that the best uniformity of luster of a filament is obtained by,

1. Using an ester of a type with whichnmy invention is concerned having a viscosity within the range of 30-150 seconds, and

2. Having at least 25.5% ester in the spinning solution.

The running of the spinning process at a speed of at least 450 meters per minute will result in a yarn having a satisfactory uniformity of luster. It is preferred, to use a spinning speed in the vicinity of 600 meters a minute-in commercial operations. My observations lead me to believe that the uniformity of luster of the yarn increases with an increase in the spinning speed providing the other necessary conditions are present as pointed out herein.

Some conditions under my invention are also suitable for making low denier yarn, or in other words yarns made up of filaments having a denier of 1-21/2. In previous processes in which filaments of low denier have been prepared, breaks in the spinning process were not uncommon and the continuity of the process was adversely affected in other Ways such as by stopping-up of the spinnerets. I have found that yarn of high luster uniformity may be obtained by preparing low denier filaments using a cellulose ester, as defined herein, in the lower part of the inherent part of the viscosity range given, such as having a viscosity of 30-80 seconds. By using esters having this low a viscosity. the viscosityof the spinning solution may be low, such as approximately 100-400 seconds, which is conducive to making fine filaments, and yet the solids content may be at least 25.5%, the latter being necessary to obtain good luster, if that is desired.

The uniformity of luster of the various yarns referred to herein may be determined by taking a large number of samples (at least 100) of each kind of yarn and testing them on a standard luster-meter of which there are several on the market. The yarns having the highest uniformity of luster, obviously, have most of the luster values varying but little from the average value. The viscosity of the cellulose esters, as used throughout this application, is to be understood as'being the viscosity in seconds of a solution of one part of the ester in four parts of acetone. Although my process is adapted for use with any of the solvents which have been found to be suitable in practice for spinning cellulose acetate or low propionyl cellulose esters, it is primarily concerned with the preparing of yarn using acetone, this solvent having been found to be the most suitable for this purpose upy to the present time. The maximum solids content in the spinning solution is limited only by the percentage of the cellulose ester which can be dissolved therein, without exceeding the spinning solution viscosity indicated as the permissible maximum.

The rate of flow of the evaporative medium, usually heated air, through the spinning cabinet in my process has been given herein in 'terms of the acetone-in-air concentration in the eiiiuent from the spinning cabinet as this is the criterion which determines that rate. As was pointed out herein, the rate of flow of the evaporative mediurn varies with the variation of any one of a number of conditions of the spinning process, such as the length of the spirming cabinet, the denier of the filaments being spun and the speed at which the filaments are extruded or the spinning speed.

I claim:

1. A process for preparing yarn having a high luster uniformity and good stretch, which comprises extruding through e, spinneret at a speed of at least 450 meters per minute a solution essentially consisting of a volatile solvent, l.5-2.5% water and at least 25.5% of a hydrolyzed ac etone-soluble cellulose ester containing 1-6% of saturated fatty acid groups of 3.4 carbon atoms, the remainder of the acyl present being acetyl which ester has a viscosity of 30-150 seconds in a composition consisting of 1 part of the cellulose ester and 4 Darts of acetone.

2. A process for preparing yarn having a high luster uniformity and good stretch, which comprises extruding through a spinneret at a speed of approximately 600 meters per minute a solution essentially consisting of a volatile solvent, 1.5-2.5% water and at least 25.5% of a hydrolyzed acetone-soluble cellulose ester containing 16% of saturated fatty acid groups of 3-4 carbon atoms, the remainder of the acyl present being acetyl which ester has a viscosity of 30-150 seconds in a composition consisting of l part of the cellulose ester and 4 parts of acetone.

' 3. A process for preparing yarn having a high luster uniformity and good stretch, which comprises extruding through a spinneretl at a speed of at least 450 meters per minute a solution havingalviscosity of not more than '700 seconds es- 4. A process for preparing yarn having a higl'r luster uniformity and good stretch, which comprises extruding through a spinneret at a speed of at least 450 meters per minute into a spinning cabinet from 20 to 30 feet in -length through which an evaporative medium having an initial temperature of from 'l0-120 C. passes in such amounts as t give from 1 to 2% solvent by volume in the eiiluent evaporative medium a solution essentially consisting of a volatile solvent, l.5-2.5% water and at least 25.5% of a hydrolyzed acetone-soluble cellulose ester containing 1-6% of saturated fatty acid groups of 3-4 carbon atoms, the remainder of the acyl present being acetyl which ester has a viscosity of 30-150 seconds in a composition consisting of l part of the cellulose ester and 4 parts oi acetone.

5. A process for preparing yarn having a high luster uniformity and good stretch, which comprises extruding through a spinneret at a speed of at least 450-meters per minute a solution essentially consisting of acetone, 1.5-2.5% Water and at least 25.5% of a hydrolyzed acetone-soluble cellulose ester containing approximately 1.5% of saturated fatty acid groups of 3-4 carbon atoms, the remainder of the acyl present being acetyl which ester has a viscosity of 30-150 seconds in a composition consisting of l part of the cellulose ester and 4 parts of acetone.

6. A process for preparing yarn having a high luster uniformity and good stretch, which comprises extruding through a spinneret at a speed of at least 450 meters per minute a solution essentially consisting of acetone, 1.5-2.5% water and at least 25.5% of a hydrolyzed acetone-soluble cellulose ester containing l-6% of propionyl, the remainder of the acyl present being acetyl which ester has a viscosity of 30-150 seconds in a composition consisting of l part of the cellulose ester and 4 parts of acetone.

7. A process for preparing yarn having a. high luster uniformity'and good stretch, which comprises extruding through a spinneret at a speed of at least 450 meters per minute a solution essentially consisting of acetone,*1.52.5% water and at least 25.5% of a hydrolyzed acetone-soluble cellulose ester containing 1-6% of butyryl, the remainer of the acyl present. being acetyl which ester has a -viscosity of -150 seconds in a composition consisting or 1 part of the cellulose ester and 4 parts of acetone.

8. A process for preparing yarn made up of filaments of low denier having a high luster uniformity and good stretch, which comprises ex'- truding through a spinneret at a speed of at least 450 meters per minute a solution having a viscosity of -400 seconds essentially` consisting of acetone, 1.5-2.5% water and at least 25.5% of a hydrolyzed acetone-soluble cellulose ester containing 1.6% of saturated fatty acid groups of 3-4 carbon atoms, the remainder of the acyl present being acetyl which ester has a viscosity of 30-80 seconds in a composition consisting of 1 part of the cellulose ester and 4 parts of acetone.

9. A spinning solution essentially consisting of acetone, l.5-2.5% water and at least 25.5% of a hydrolyzed acetone soluble acetyl cellulose containing 1-6% of saturated fatty acid groups of 3-4 carbon atoms, which ester has a viscosity of 30450 seconds in a composition consisting of 1 part of the cellulose ester and 4 parts of acetone, the spinning solution being capable of being spun at a rate of at least 450 meters per minute and its constituents being in such proportions to each other that the spinning solution has a viscosity of no more than '700'seconds.

10. A spinning solution essentially consisting of acetone, 1.5-2.5% water and at least 25.5% of a hydrolyzed acetone soluble acetyl cellulose containing 1-6% of propionyl, which ester has a viscosity of 30-150 seconds in a composition consisting of 1 part of the cellulose ester and 4 parts of acetone, the spinning solution being capable of being spun at a rate of at least 450 meters per minute and its constituents being in such proportions to leach other that the spinning solution has a viscosity of no more than 100 seconds.

l1. A spinning solution essentially consisting of acetone, 1.5-2.5% Water and at least 25.5% of a hydrolyzed acetone soluble acetyl cellulose containing 1-6% of butyryl, which ester has a viscosity of 30-150 seconds, the spinning solution being capable of being spun at a rate of at least 450 meters per minute and its constituents being in such proportions to each other that the spinning solution has a viscosity of no more than 700 seconds.

12. A spinning solution essentially consisting of acetone, 1.5-2.5% water and approximately 26% of a hydrolyzed acetone-soluble cellulose ester containing approximately 1.5% propionyl, the remainder of acyl present being acetyl, which ester has an acetone viscosity approximately of seconds, the spinning solution being capable of being spun at a rate of at least 450 meters per minute and its constituents being in such proportions to each other that the spinning solution has a viscosity of no more than 700 seconds.

ROBERT B. HICKEY.

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