IL25230A - Polyester drawing process - Google Patents

Description

Patents Form No. 3 PATENTS AND DESIGNS ORDINANCE.

SPECIFICATION.

"POLYESTER DRAWING PROCESS" I / WE , MONSANTO COMPANXf a corporation organized and existing under the.laws of the State of Delaware, United States of America, of 800.North Lindbergh Boulevard, St. Louis, Missouri,. United States of Amerioa, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement : - This invention relates to a process for drawing polyester filaments. More particularly, this invention relates to a process for drawing polyester filaments in the form of a tow to impart uniform orientation throughout the filaments in the tow.

In the commercial production of staple fiber, it is desirable for economic reasons to combine several hours of production from one or more spinning machines into a large tow containing on the order of thousands of filaments and draw this large bundle of filaments simultaneously. A number of methods have been used to facilitate the drawing of the unorlented filaments by applying heat prior to or during the orientation step, e.g., by passing the yarn over or between hot plates or between hot zones or around hot pins and the like. These procedures have proved satisfactory for drawing textile or industrial denier polyester continuous filament yarns, but are unsatisfactory for the drawing of large tows needed to produce staple fiber. Uniform heating of all the filaments within a large tow is difficult to aohleve using hot surfaces or zones and non-uniform drawing normally results. Such poorly drawn fibers have varying physical properties and since the unorlented and partially oriented fibers dye to much darker shades than the oriented ones, they are particularly undesirable when the staple is intended for dyed goods.

These dark-dyed fibers appear In fabrics as flecks of dark color. The use of wet drawing processes has been reported to yield more uniformly drawn fibers than do the heated dry processes and are generally preferred in In the accompanying drawings Figures I and II illustrate schematically front elevations of convenient apparatus for drawing polyester tow In accordance with the present invention.

It Is an object of this invention to provide a novel process for drawing tow composed of substantially unoriented polyester filaments.

Another object of this invention Is to provide a novel process for drawing large tows of substantially unoriented polyester filaments in which the drawn tow Is very uniform and possesses excellent physical properties.

Other objects and advantages of this invention will become readily apparent from the detailed description thereof immediately following.

The objects of this invention are accomplished by passing a tow of substantially unoriented polyester filaments through a first inert bath maintained at about 80 to 100°C, cooling said filaments to a temperature of from about ij.0 to 60°C, and thereafter drawing the tow at a draw ratio of at least 2 times Its original length while passing the tow through a second inert bath maintained at about 80 to 100°C. Preferably, the first inert bath is maintained at about 80°C, then the tow is cooled to about 55°C.t and then drawn at a draw ratio of from about 2 to 6 times its original length while being passed through a second inert bath maintained at about 90°C, When the drawing process is carried out In the manner described above, a uniform draw is imparted to the filaments In the tow and excellent physical properties are obtained. process of this invention, any fluid harmless to the filaments may be used. Preferably, aqueous baths are used in that they are economical to use and give satisfactory results.

Dwell times for the filaments in the baths may vary as long as the filaments are thoroughly wetted and the temperature of the filaments reach approximately the desired temperature. If desired, finishing agents may be incorporated in either of these baths or they may be applied to the filaments at some later point. These finishing agents may include anti-static agents, wetting agents, plasticizers, stabilizers and the like.

The accompanying drawings illustrate convenient methods for practicing the present invention. In Fig. 1 , the tow which is to be oriented is passed over rolls 1 through 8 , and 11 through 18, respectively, rolls I to 8 being maintained at a given uniform poripherial speed while rolls 11 through 18 have a uniform peripheral speed at least 2 times greater. Between rolls 2 and 3 the tow passes through a vessel 9, which contained the first inert liquid bath maintained at a temperature at a range of about 80 to 100°C. Rolls 1 , 2 and 3 are neither heated nor cooled. Rolls I4. , 5 , 6, 7, and 8 are maintained at a temperature of from about lj.0 to 60°C. Between rolls 7 and II the tow passes through a second vessel 10, which contains a second inert liquid bath maintained at a temperature in the range of about 80 to 100°C. The second inert liquid bath may be in the form of a liquid spray if desired.

Using the Pig. 2 version of the apparatus, the tow is passed over rolls 1 through 16 and 19 through 26 peripherlal speed while rolls 19 through 26 have a uniform peripherlal speed at least 2 times greater. Between rolls 6 and 7 the tow passes through a vessel 17, which contains the first Inert liquid bath maintained at a temperature at a range of about 80 to 100°C. Rolls 1 to 7 are neither heated nor cooled. Rolls 8 to 16 are maintained at a temperature of from about lj.0 to 60°C. Between rolls 16 and 19 the tow passes through a second vessel l8 , which contains a second inert liquid bath maintained at a temperature in the range of about 80 to 100°C. The second inert liquid bath may be in the form of a liquid spray if desired.

The apparatus described is convenient to carry out the process of this invention. However, it should be pointed out that other apparatus may be used equally as well. The number and arrangement of the rolls in the apparatus used may be varied, although it is desirable to employ a plurality of feed rolls and a plurality of draw rolls.

The tow cooling step between the two aqueous baths is required to prevent filaments breaking at draw ratios required to develop desirable high fiber tenacity and low fiber elongation. The combination of high preheat bath temperature, medium temperature between the two baths and high temperature in the draw bath gives the optimum fiber properties.

The process of the present invention is used to its greatest advantage in drawing large tows comprised of substantially unoriented polyester filaments. have a small degree of orientation introduced during the spinning operation. The draw ratio applied to the tow will vary depending upon the character of the product desired and upon the degree of orientation introduced into the filaments during spinning. Generally, a draw ratio of at least 2 times the original length of the filaments may be used for the purposes of this invention. Preferably, the draw ratio used will be from about 2 to about 6 times the original length of the filaments. Drawing speeds of up to about 500 yards per minute may be used.

The polyester filaments suitable for drawing according to the process of this invention are those formed from dicarboxylic acids and glycols, and copolyesters or modifications of these polyesters and copolyesters. The polyesters and copolyesters specifically useful in the instant invention are those resulting from heating one or more of the glycols of the series, H0(CR-, )n0H, in which n is an integer from 2 to 10, with one or more dicarboxylic acids or ester-forming derivatives thereof. The process of this invention is particularly useful in the drawing of polyethylene terephthalate filaments which are the poly-condensation product of ethylene glycol and terephthalic acid or an ester-forming derivative thereof.

The drawing of polyester filaments using the process of this invention produces highly uniform oriented filaments. Attempts to draw polyester tows under process conditions outside the scope of this Invention result in a less desirable product. An important factor in determining the quality of the drawn tow is the frequency filament segmentd accept dye much more readily than drawn filaments and therefore show up in dyed fabrics as undesirable deeply dyed flecks. Drawing filament according to the process of this invention produce drawn filament exhibiting very few of these deeply dyed flecks.

To further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that these are merely intended to be illustrative and not limitative. The values reported in the examples for dyeing defects were determined by cutting the tow to staple fibers, carding and blending the staple fibers, and dyeing samples of the blended fibers with Latyl Blue PLW dye (C.I. Disperse Blue 27)· The dyeing defects are reported as the number of dark-dyed fibers per 100 grains of card sliver. Dyeing defect values in excess of about 20 are usually regarded as being too high for commercial acceptability; and average values lower than 10 are desired in order that occasional samples will not exceed the value 20.

EXAMPLE 1 Polyester yarn was prepared by extruded molten polyethylene terephthalate through a 280 hole spinneret in a conventional manner. The yarn was collected at a speed of 1,100 yards per minutes and wound on bobbins. Yarn denier was II.3O. Fiber birefringence average O.OOij.7, Ninety- six ends of this yarn were plyed to form a tow of approximately 28,880 filaments and 137,000 undrawn denier. This tow was drawn on the apparatus shown in Pig. 1. The first aqueous bath was maintained at f>5°C., rolls I4.-8 at at 90°C. The tow was fed in the form of a flat sheet two inches wide over feed rolls 1-8 at 27.8 yards per minute and taken up on draw rolls 11- 18 at 125 yards per minute. The draw ratio was 1±. . Prom the draw rolls the tow passed into a conventional stuffing box crimper and then into a hot air oven where it was dried at 1-.50C. for nine minutes in a free to relax condition. The filaments in the dried tow averaged 1.1+9 denier, l+.l grams per denier tenacity and I .3 percent elongation. The tow was found to have a dyeing defect count of 22 per 100 grains card sliver.

The experient was repeated using the same yarn bobbins but raising the first aqueous bath temperature to 80°C. and changing the temperature of rolls 3- 8 to I4.O-1+50C. Tow drawing performance was equally good. Filament denier was slightly lower at 1..+5 » tenacity significantly higher at 5· 0 grams per denier, and elongation lower at 3I . percent. The tow was uniformly drawn as proved by a dyeing defect count of 10 per 100 grains card sliver.

EXAMPLE 2 Polyester yarn was prepared by extruding molten polyethylene terephthalate through a 280 hole spinneret in a conventional manner. The yarn was collected at a speed of 1100 yards per minute and wound on bobbins. Yarn denier was 1270. Fiber birefringence was in a 0.006 to 0.010 range. One hundred and forty ends of this yarn were plyed to form a tow of approximately 39,200 filaments and 177 , 000 undrawn denier. This tow was drawn on the apparatus shown in Fig. 1. The first aqueous bath was maintained at 80°C, rolls 1+ through 8 at 55°C. and the of a flat sheet 2 1/2 Inches wide over feed rolls 1- 8 at 52.7 yards per minute and taken up on draw rolls 11- 18 at 215 yards per minute. The draw ratio was I4.. O8. From the draw rolls the tow passed into a conventional stuffing box crimper and then into a hot air oven where it was dried at Hj.5°C. for 9 minutes in a free to relax condition. The filaments In the dried tow averaged 1.56 denier, 50 percent elongation, and 5.3 grams per denier tenacity. The tow was uniformly drawn as shown by a dyeing defect count of 3« The experiment was repeated raising rolls 1+- 8 to 80°C. Tow drawing performance was very poor. The tow broke and wrapped on the draw rolls three times in a 60 minute run. Filament properties were 1.57 denier, 51 percent elongation, and 1+.6 grams per denier tenacity, a considerable drop in strength from the previous run. The tow was uniformly drawn as proved by a dyeing defect count of zero.

EXAMPLE 3 Polyester yarn was prepared by extruding molten polyethylene terephthalate through a 280 hole spinneret in a conventional manner. The yarn was collected at a speed of 1 ,120 yards per minute and wound on bobbins. Yarn denier was 1310. Fiber birefringence was in a 0.001+ to 0.010 range. One hundred and forty-four ends of this yarn were plyed to form a tow of approximately 1+0, 300 filaments and 187 , 000 undrawn denier. This tow was drawn on the apparatus shown in Fig. 2. The first aqueous bath was maintained at 55°C., rolls 8-16 at 55°C. and the second aqueous bath, in the form of a spray, at 90°C. The tow was rolls 1-16 at 55.3 yards per minute and taken up on draw rolls 19-26 at 215 yards per minute. The draw ratio was 3.93. Prom the draw rolls the tow passed into a conventional stuffing box crimper and then into a hot air oven where the tow was dried at ll50C. for 12 minutes in a free to relax condition. The filaments in the dried tow averaged 1.5 denier, 5.16 grams per denier tenacity, 30 percent elongation, and 35 modulus. The tow was uniformly drawn as proved by a dyeing defect count of 13 er 100 grains card sliver.

The experiment was repeated using the same yarn bobbins but raising the first aqueous bath temperature to 80°C. The drawing performance was equally good. Filament denier was the same at 1.5^1·, tenacity slightly higher at 5.19 grams per denier, elongation 3 percent and modulus higher at 3* The tow was uniformly drawn as proved by a dyeing defect count of 19 per 100 grains card sliver.

Claims (9)

95230 / 9.

1. A process for orienting polyester filaments characterized by passing a tow containing a plurality of substantially unorlented filaments through an inert fluid bath maintained at a temperature from about 80 to 100?C, cooling said tow to a temperature from about 40 to 60aC, and thereafter drawing said tow at least 2 times its original length while passing it through a second inert fluid bath maintained at a temperature from about 80 to 100°C.

2. The process of Claim 1, characterized in that said tow is drawn from about 2 to 6 times its original length.

3. The process of Claim 2, characterized in that said polyester is polyethylene terephthalate.

4. The process of Claim 3, characterized in that said inert bath is an aqueous bath.

5. The process of Claim , characterized in that the first aqueous bath is at a temperature of 80eC. and the second aqueous bath is at a temperature of 90°C.

6. The process of Claim 5, characterized in that said tow is cooled to a temperature of from about 40-45°C.

7. The process of Claim 5, characterized in that said tow is cooled to a temperature of about 55°C.

8. A process for orienting polyester filaments substantially as described in the herein Examples.

9. Polyester filaments whenever produced by the process claimed in any one of the preceding claims. \ A. E. MULFORD Attorney for Applicants.