BE568898A - - Google Patents

Description

       

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   The present invention relates to a new mixture of staple fibers and more particularly to a yarn of natural and synthetic fibers which is stronger and more resistant to abrasion.



   The use of two or more varieties of staple fibers to form blends, and yarns and fabrics made therefrom are known in the art. These blends are manufactured to obtain new and attractive fabrics with better physical and aesthetic properties. With the advent of recent synthetics, it had appeared that the strength of yarns of known and inexpensive natural fibers could be improved by the addition of small amounts of the new high tenacity materials. For example, it was expected that cotton yarns having a tenacity of 1-2 g / denier (gdp) could advantageously be reinforced by mixing chopped nylon fibers therein (tenacity 4-7 gdp). .



   In fact, this benefit could not be realized and much research has been done to establish the cause. The subject is discussed in an article by A. Kemp and J.D. Owen in Textile Institute Journal, Transaction, 46, 684-698 (1955). This article shows that cotton and nylon blends are less strong than 100% cotton yarns when less than about 80% nylon enters the blend. This behavior has been found to be due to a much greater elasticity of the nylon fiber; therefore at low loads, it is the cotton which supports the tensions.

   Due to its low elongation at break (about 7%), cotton would break before the nylon filaments could withstand a significant part of the load, especially in the case of compositions containing little Nylono.
It is also recognized in the art that the modulus of many synthetic fibers can be increased by a heat drawing operation. These operations are common in the manufacture of wires intended to serve as cables for tires, for example. However, these treatments are not suitable for improving staple fibers, since the improvement is not stable with aging, when the filaments can freely retract (i.e. when they are not envied. on a rigid winding). This shrinkage results in a loss of the modulus improvement gained by hot stretching.



  In addition, these treatments are unstable at boiling, which is a common treatment of textile fabrics, so that fabrics which contain these fibers suffer from excessive shrinkage.



   The object of the present invention is to provide a chopped fiber yarn which is composed of a mixture of natural and synthetic fibers, the synthetic fiber of which is a high tenacity linear condensing polymer having a load capacity equal to or greater than. that of the natural fiber to elongation at break of the latter.



   Synthetic linear condensation polymers suitable in the present invention are those which can be imparted a high orientation by a stretching operation and which can then be crystallized by a sufficiently thorough heat treatment to retain their orientation.



  Polymers which are particularly suitable are linear polyamides such as polyhexamethylene adipamide (Nylon 66) and polycaproamide (Nylon 6); Crystallizable copolymeric polyamides are also suitable when they comprise 85% or more of Nylon 66 or Nylon 6.



   Staple fibers of high load bearing synthetic polymers can also be prepared from filaments spun from linear condensation polyesters. Of these, the most interesting are polyesters of the terephthalate type and polyesters which comprise at least 85% of repeating structural groups of formula
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High modulus natural or naturally occurring short fibers which are particularly suitable in the present invention are fibers based on cellulose, cotton, cotton, rayon, viscose, acetate and other cellulose derivatives. lower modulus fibers, such as protein fibers (e.g. wool), and even some synthetic fibers such as polyacrylonitrile fibers,

   can be advantageously mixed with the linear high tenacity condensation polymers mentioned above.



  Likewise, blends of the polyamide and polyester fibers with any of the natural fibers or any of the blends of the natural fibers can be used.



   Synthetic condensation polymer fibers are suitable for the present invention (a) by stretching them to the maximum possible draw ratio and (b) by subjecting them to heat treatment under the draw tension for at least 1 second at the maximum possible temperature. For example, when processing polyamide filaments, the heat exposure under the draw tension should be about 1000 to 6000 degree-seconds, preferably 2000 to 5000 degree-seconds. This maximum temperature is usually on the order of or in the vicinity of the point of degradation of the polymer.



   The filaments thus treated are characterized both by a high degree of crystallinity and by a high degree of crystalline orientation. These characteristics make them stable to aging in a relaxed state, so that their load-bearing capacity is maintained at least until incorporation of the fiber into the fabric. The yarn resulting from these filaments does not exhibit high shrinkage which is detrimental to boiling. For example, in a preferred embodiment of the present invention, synthetic fibers are obtained which can be mixed with cotton fibers and which have a load capacity of at least 2.1 g per denier at an elongation of 7. % (elongation at break of the middlings) and a boiling shrinkage not exceeding about 6% after 9 days of relaxed aging.



   In the drawings, Fig. 1 schematically shows one form of a cable drawing machine suitable for manufacturing the high load capacity fiber of the present invention. Fig. 2 is a diagram showing the improvement in toughness resulting from the addition of the high load carrying capacity chopped nylon fibers of the present invention to combed cotton. 3 is a diagram which shows a similar relationship for blends of rayon and nylon, and FIG. 4 similarly shows the tenacity of nylon and wool blends. The curves for other blends of natural fibers such as wool with nylon and polyethylene terephthalate have the same general configuration.



   In the commissioning of the apparatus shown in FIG. 1, multiple strands of unstretched filaments from a spinning bench, rack or other similar device are combined into a high denier tow (power source not shown) and enter the machine stretching under the fcome of a strip of filaments in 1. The strip of filaments is pressed against the first of a series of feed rollers 3, 3, 3, by means of the nip roll 2, which prevents cable slippage. The feed rollers 3 are all driven at an identical and constant peripheral speed and serve to feed the cable to the drawing fingers 5.

   In the drawing zone, the cable follows a zig-zag path around the three fixed stainless steel drawing fingers 5 and thus undergoes a friction effect which locates the point of drawing.



  The strip of filaments is then driven, passing over a heated plate 6 (heater not shown) to the take-up cylinders 7, 7, 7. The take-off cylinders, which all operate at the same speed, rotate. at a peripheral speed greater than that of the feed rollers 3, 3, 3, and the wire is therefore drawn. The relative peripheral speed of the two sets of cylinders determines the draw ratio o The drawn cable leaves the machine at 8, from where it is led to a creping device, a cutting device in storage or to a

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 cable winding device.

   It should be noted that the hot plate 6 is relatively long, for example 9 feet (2.74 m) and it can be advantageously heated by electricity or by hot oil of water vapor under high pressure, etc., according to conventional methods. It is desirable that the tow which passes through this machine be laid out in a broad flat strip of filaments of uniform thickness, but small. When staple fiber sizes are added to the tow before drawing, this addition is usually done before the filaments reach nip roll 2.



   The apparatus shown in FIG. 1 is only one example of a suitable method of drawing cables; other arrangements may offer particular advantages. For example, it may be desirable to use feed or take-up cylinders which operate at different peripheral speeds, thereby reducing slip to a minimum. A greater number or a smaller number of drawing fingers made of various known abrasion resistant materials can be used.
The process of the present invention will be described with reference to cotton and nylon blends, because of their importance in industry.



  The application of the process to other fiber blends will be studied later.



   The elongation at break of the middlings is about 7% and their tensile strength is about 2.1 g per denier. At this stretch, nylon from polyhexamethylene adipamide and conventionally processed has a load capacity of about 0.5 to 1.0 9 / denier. For ease of nomenclature, herein is referred to as the load capacity of a filament at an elongation given by Tallong: for example, the load capacity (T) of the nylon fiber of the present invention. The invention should be at least 2.0 g denier at 7% elongation, which corresponds to the elongation at break of cotton, which is about 7% and has a tenacity of about 2 gdp.



  EXAMPLE 1.-
Nylon yarn spun by conventional methods from polyhexamethylene adipamide flakes is combined into a bundle of about 16,700 filaments to form a 63,000 denier tow. The cable (without the addition of aqueous finishes) is stretched in a machine shown schematically in Fig. 1 The machine is equipped with a hot plate with a length of 9 feet (2.74 m) and the ratio d is varied. stretching, the stretching speed and the contact time with the plate, as well as the temperature of the plate. The strip of filaments is braked by a 420 winding around three friction fingers which precede the heated plate. The temperature of the wire as it passes over the hot plate is determined by a contact thermocouple.

   The average values are given in Table 1. The extent of the heat treatment is calculated by multiplying the average temperature of the wire by the time during which the wire remains at this temperature. The result is therefore expressed in degree-seconds.



   Samples of yarns produced under these conditions are aged for nine days in the relaxed state at 78 F (26 C) and 72% relative humidity, before determining their tension-elongation characteristics. preparation of each sample are given in Table I below.



   TABLE I.



   Operating conditions.



   Heat treatment..
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  Sample <SEP> Stretching report <SEP> <SEP> seconds <SEP> Temperature <SEP> Degrees-seconds.
<tb>



  ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ <SEP> ¯¯¯¯¯¯ <SEP> C
<tb>
<tb> A <SEP> 3.01 <SEP> 2.0 <SEP> 30 <SEP> 60
<tb>
<tb> B <SEP> "<SEP> 0.15 <SEP> 190 <SEP> 29
<tb>
<tb> C <SEP> "<SEP> 1.8 <SEP> 180 <SEP> 320
<tb>
<tb> D <SEP> "<SEP> 12 <SEP> 175 <SEP> 2100 '<SEP>. <SEP>
<tb>
 

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   TABLE I.



  Operating conditions.
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  Thermal <SEP> treatment,
<tb>
<tb> Sample <SEP> Stretching report <SEP> <SEP> Seconds <SEP> Temperature <SEP> Degrees-seconds.,
<tb>
 
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 ¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯¯¯¯¯¯¯¯ ¯¯¯¯¯¯. r, 0 ¯¯¯¯¯¯¯¯¯¯¯¯ 3.01 joz 5100
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<tb> F <SEP> 3.62 <SEP> 2.0 <SEP> 30 <SEP> 60
<tb>
 
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 o o, 15 180 27 H fi, 8 175 320
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<tb> I <SEP> "<SEP> 12 <SEP> 170 <SEP> 2000
<tb>
 
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 1 30 $ 1 0 5400
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<tb> K <SEP> "<SEP> 45 <SEP> 170 <SEP> 7700
<tb>
<tb>
<tb>
<tb> L <SEP> "<SEP> 60 <SEP> 160 <SEP> 9600
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> M <SEP> 3.87 <SEP> 2.0 <SEP> 30 <SEP> 60
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> N <SEP> "<SEP> 0.15 <SEP> 180 <SEP> 27
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 01 <SEP> 4.07 <SEP> 2.0 <SEP> 30 <SEP> 60
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> P <SEP> "<SEP> 12,

  0 <SEP> 170 <SEP> 2000
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Q1 <SEP> 4.14 <SEP> 2.0 <SEP> 30 <SEP> 60
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> R <SEP> "<SEP> 0.15 <SEP> 180 <SEP> 27
<tb>
<tb>
<tb>
<tb>
<tb> s <SEP> "<SEP> 1, <SEP> 2 <SEP> 180 <SEP> 220
<tb>
<tb>
<tb>
<tb>
<tb> T <SEP> 6 <SEP> 195 <SEP> 1200
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> U <SEP> "<SEP> 30 <SEP> 175 <SEP> 5300
<tb>
<tb>
<tb>
<tb>
<tb> V <SEP> "<SEP> 45 <SEP> 170 <SEP> 7700
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> W <SEP> "<SEP> 60 <SEP> 165 <SEP> 9900
<tb>
 1 Draw ratio too high to be applicable; the thread breaks. We do not get a sample.



   The properties of the samples obtained under the conditions indicated in Table I are shown in Table 2. The T of each sample is determined from its stress-elongation curve using a conventional Instrono apparatus. The values are calculated. based on 1 g / denier. The boiling shrinkage is determined on one skein of the test wire; the length of the skein is measured before and after the 60 minutes of the boil treatment and the percent change is calculated (based on the length before boiling).



   The birefringence of the yarn, which is determined by the method of Heyn, Textile Research Journal, 22, 513 (1952), is a measure of crystal orientation. Density is measured using tubes of density gradients according to the method de Boyer, Spencer and Wiley, Journal Polymer Science, 1, 249, (1946). The density is proportional to the degree of crystallinity of the fiber.



   It is of course known that nylon filaments include crystalline regions and amorphous regions. The density of the amorphous regions is estimated to be about 1.069 and that of the crystalline regions to about 1.220 by infrared methods. This mode of determination is described by Stareather & Monynihan in Journal Polymer Science, 22, 363 (1956). On the basis of these data, it is possible to calculate a value which is proportional to the fraction of the crystal volume by using the formula
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 (mean yarn density - density of amorphous yarn x 100% (density of crystalline yarn at 10 = density of 100% amorphous yarn which gives a number proportional to the percent crystallinity.



   An examination of the data in Table 2 shows that acceptable T values are obtained when two criteria are satisfied: (a) the density is greater than about 1.139 and (b) the birefringence simultaneously exceeds 0.0590. These two parameters characterize the polyamide of the present invention and constitute a

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 minimum for an acceptable cotton blend. It is evident, of course, that at higher draw ratios, higher heating temperatures and longer contact times, a mixed yarn is obtained with correspondingly higher T7 value and toughness. .



   TABLE 2.



   Test results.
 EMI5.1
 
<tb>



  Tenacity <SEP> T <SEP> Withdrawal
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Sample <SEP> Tenacity <SEP> T72 <SEP> Birefringence <SEP> Density <SEP> Shrinkage
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> gdpl <SEP> 2
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> A <SEP> 3.7 <SEP> 0.98 <SEP> 0.0521 <SEP> 1.136 <SEP> 9.1
<tb>
<tb>
<tb>
<tb>
<tb> B <SEP> 3.6 <SEP> 1.04 <SEP> 0.0528 <SEP> 1.135 <SEP> 9.0
<tb>
<tb>
<tb>
<tb> C <SEP> 3.9 <SEP> 1.35 <SEP> 0.0527 <SEP> 1.136 <SEP> 8.5
<tb>
<tb>
<tb>
<tb>
<tb> D <SEP> 4.0 <SEP> 1.45 <SEP> 0.0564 <SEP> 1.141 <SEP> 5.1
<tb>
<tb>
<tb>
<tb>
<tb> E <SEP> 3.9 <SEP> 1.147 <SEP> 0.0567 <SEP> 1.142 <SEP> 5.6
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> F <SEP> 5.0 <SEP> 1.44 <SEP> 0.0573 <SEP> 1.137 <SEP> 8.1
<tb>
<tb>
<tb>
<tb>
<tb> G <SEP> 5.3 <SEP> 1.54 <SEP> 0.0583 <SEP> 1.138 <SEP> 8.2
<tb>
<tb>
<tb>
<tb> H <SEP> 5, <SEP> 7 <SEP> 1,

  81 <SEP> 0.0584 <SEP> 1.138 <SEP> 7.0
<tb>
<tb>
<tb>
<tb>
<tb> 5.9 <SEP> 2.19 <SEP> 0.0594 <SEP> 1.142 <SEP> 4.2
<tb>
<tb>
<tb>
<tb>
<tb> J <SEP> 5.5 <SEP> 2.11 <SEP> 0.0586 <SEP> 1.140 <SEP> 5, <SEP> 2 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb> K <SEP> 5.8 <SEP> 2.18 <SEP> 0.0589 <SEP> 1.141 <SEP> 4.6
<tb>
<tb>
<tb>
<tb>
<tb> L <SEP> 5, <SEP> 6 <SEP> 2.16 <SEP> 0.0602 <SEP> 1.143 <SEP> 4, <SEP> 4 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> M <SEP> 6.0 <SEP> 1.61 <SEP> 0.0547 <SEP> 1.139 <SEP> 7.5
<tb>
<tb>
<tb>
<tb>
<tb> N <SEP> 6, <SEP> 9 <SEP> 1.72 <SEP> 0.0568 <SEP> 1.139 <SEP> 8.1
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> P <SEP> 7.3 <SEP> 2.68.

   <SEP> 0.0612 <SEP> 1.143 <SEP> 4, <SEP> 7 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> s <SEP> 6.7 <SEP> 2.50 <SEP> 0.0602 <SEP> 1.140 <SEP> 5.6
<tb>
<tb>
<tb>
<tb>
<tb> T <SEP> 7.3 <SEP> 2.68 <SEP> 0.0622 <SEP> 1.142 <SEP> 4.9
<tb>
<tb>
<tb>
<tb>
<tb> U <SEP> 6.5 <SEP> 2, <SEP> 58 <SEP> 0.0606 <SEP> 1.141 <SEP> 6.0
<tb>
<tb>
<tb>
<tb> V <SEP> 6.5 <SEP> 2.61 <SEP> 0.0606 <SEP> 1.142 <SEP> 4.6
<tb>
<tb>
<tb>
<tb>
<tb> W <SEP> 6.4 <SEP> 2.59 <SEP> 0.0694 <SEP> 1.142 <SEP> 4.9
<tb>
 Tenacity after relaxed aging for 9 days at 78 F (26 C) and 72% relative humidity.



  2 Load at 7% elongation, 9 days of aging in the relaxed state o Shrinkage measured by boiling in water for 60 minutes a skein measured beforehand o
The data in Tables 1 and 2 show that satisfactory results are obtained at draw ratios greater than about 4.0 with high plate temperatures, a heating time of at least 1 second and exposure of the plate. wire of at least 200 degree-seconds. Best results are obtained, especially at relatively low draw ratios, when the yarn exposure is at least 1000 degree-seconds. Usually, higher T values and less boiling shrinkage are obtained with more heat exposure.



   It should be noted, however, that draw ratios which cause excessive breakage and processing temperatures which cause alteration of the color of the yarn should be avoided. For a polyamide free from the added antioxidant, some alteration in the color of the yarn, which may make it unsuitable for use in white fabrics, may be seen at exposure levels somewhat above about 50,000 degrees. -seconds.



   To the knowledge of the Applicant, nylon fibers cut from

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 high load capacity and having the physical properties of the fiber of the present invention have not been used previously. Some of the conditions listed in Table 1 are illustrative of those used in the routine processing of nylon yarns. For example, the conventional drawing process in which the yarn is stretched over a friction finger, substantially as described in U.S. Patent Babcock No. 2,289,232, is illustrated by Samples A, F and M for reports. stretching from 3.01 to 3.87. The wire does not receive any heat input apart from the heat produced by the friction on the drawing fingers. None of these samples has a T7 greater than 2.0 gdp.



  A T of at least 2.1 and preferably 2.5 gdp is extremely desirable. sample M has the minimum density of 1.139, but it does not have the minimum birefringence of 0.0590. 'Higher orientation (via increased draw ratio) cannot be achieved under these test conditions as shown by test condition 0, which is not achievable at a draw ratio of 4.07 . It should also be noted that these unacceptable threads are further characterized by a boiling shrinkage of greater than about 6.0%.



   Conventional drawing processes in which the wire comes into contact with a heated finger or plate during the drawing operation are characterized by samples B, G, N and R. None of these samples (see Table 2) has an acceptable T value, neither a birefringence nor a density greater than the prescribed minima. The test condition R shows that it is impossible to stretch the yarn at higher ratios (4.14) with short heating times, because the yarn breaks.



   It should be noted that the high load carrying capacity staple fiber of the present invention is not simply a product of higher tenacity obtained by a conventional increase in the draw ratio and / or temperature. This point is illustrated by the M and N samples (Tables 1 and 2) which have higher toughness resulting from a higher draw ratio than samples I to L, but unacceptable T7 values. Samples I to L are acceptable.



    EXAMPLE II The process of Example I is repeated with filaments spun from Nylon 6 (polymer derived from caprolactam) at 3-4% monomer, finished under vacuum.



  The draw ratio in this case is 4.00, and the filaments are held at a temperature of 165 ° C for 30 seconds under draw tension. The yarn obtained, after 9 days of aging in the relaxed state, has a tenacity of 6.3 gdp, an elongation at break of 19.1% and a T of 2.3 gdpo The yarn sample has a density greater than 1.139, and a birefringence greater than 0.0590.



   The greater tenacity of the yarns obtained from the high load-carrying capacity cut nylon of the present invention in blends with combed cotton is evident from FIG. 2 as compared to Conventionally Made Cut Nylon o The diagram shows that 70% or more Cut Nylon must be added to combed cotton yarns to achieve the tenacity of the original 100% cotton yarn. In contrast, the nylon-cotton blend yarn of the present invention gives greater tenacities even when the amounts of nylon added are small.



   The high load-carrying capacity cut nylon of the present invention can also be used with advantage to form blends with cut rayon yarns, as shown in FIG. 3. In this case, the critical parameter is the elongation at break of the rayon yarn, which is typically 14%. Cut nylon should therefore have a high T value. The cut nylon of the present invention shows a marked improvement in this over compared to conventional cut nylon; the curve of FIG. 3 shows that initial additions of conventional nylon, up to about 50%, result in a reduction in tenacity and that the initial tenacity of the rayon is only achieved in y

 <Desc / Clms Page number 7>

 adding more than about 65% Nylon.

   In contrast, the cut nylon of the present invention exhibits an increase in toughness without the initial additions.
The high load carrying capacity nylon of the present invention can also be added with advantage to natural low modulus fibers, such as wool, as shown in Fig. 4. For equivalent compositions, the staple fibers of the present invention. gives a stronger yarn than when blending with the wool of conventional nylon cut.



   Another measure of the improvement in the tenacity and the uniformity of the yarns obtained from the mixed fibers of the present invention is given by the skein breaking test (lea test), shown in Table 3, for blends with cotton, rayon and wool o The values from the test show a consistent improvement in strength with increasing additions of the staple fibers of the present invention, compared with a reduction in tenacity or with a degree less improvement for cut nylon, prepared in the conventional way.



     TABLE 3.



  Lea test values for nylon yarns and other fibers.



   Nylon, length 1¸ inch (38.1 mm) 3 den. filament.
 EMI7.1
 
<tb>



  <SEP> fiber <SEP> blend <SEP> Cotton <SEP> Rayon <SEP> Wool
<tb>
<tb>
<tb> n <SEP> of <SEP> yarn <SEP> 20/1 <SEP> 15/1 <SEP> 8/1
<tb>
<tb>
<tb> Type <SEP> of <SEP> Nylon <SEP> cut <SEP> T7 <SEP> C2 <SEP> T7 <SEP> C <SEP> T7 <SEP> C
<tb>
<tb>
<tb> Lea <SEP> test
<tb>
 Nylon added: 0% 2040 2040 1700 1700 1148 1148
20% 2150 1730 2200 1580 2240 1490
30% 2220 1610 2750 1540 2840 1830
100% 4300 3000
Nylon cut at high T7
Classic cut nylon.



   In addition to the improvement in the tenacity of cotton yarns made from blends containing the high load-carrying staple fiber of the present invention, there is a marked improvement in abrasion resistance, as shown by the data in Table 4. From High load-carrying capacity cut nylon of 29 2 denier per filament, 1 ½ inch (38.1 mm) is mixed in the quantities shown with 1 1/8 inch (28.6 mm) middlings and spun into a thread cotton number 20/1 which is then knitted into a fabric and subjected to a Stoll abrasion test at. flat, made according to the AoSoT.M standard. D-1175-55T. The fabrics are tested after boiling.



   TABLE 4.



   Effect of Nylon on abrasion resistance.
 EMI7.2
 
<tb>



  <SEP> abrasion cycles <SEP> to <SEP> flat <SEP> Stoll
<tb>
<tb>
<tb> Cotton, <SEP> middlings <SEP> of <SEP> 1 <SEP> 1/8 <SEP> inch <SEP> (28.6 <SEP> mm) <SEP> 425
<tb>
<tb>
<tb>
<tb>
<tb> Addition <SEP> of <SEP> 15% <SEP> of <SEP> Nylon <SEP> to <SEP> value <SEP> T7
<tb>
<tb>
<tb>
<tb> high <SEP> 1025
<tb>
<tb>
<tb>
<tb>
<tb> Addition <SEP> of <SEP> 30% <SEP> of <SEP> Nylon <SEP> to <SEP> value <SEP> T7
<tb>
<tb>
<tb>
<tb> high <SEP> 1433
<tb>
<tb>
<tb>
<tb>
<tb> Addition <SEP> of <SEP> 50% <SEP> of <SEP> Nylon <SEP> to <SEP> value <SEP> T7
<tb>
<tb>
<tb>
<tb> high <SEP> 1928
<tb>
 x Executed in accordance with A.S.T.M. standard D-1175-55T.

 <Desc / Clms Page number 8>

 



   The high load carrying capacity staple fiber of the present invention also has remarkable pilling resistance, either in admixture with another staple fiber or in the form of a 100% nylon fabric. "Pilling" is a defect often observed when fabrics woven from high tenacity synthetic fibers are subjected to abrasion. It forms on the surface of the fibers fibrous, ugly pellets, called "pills".



   What may be called a "heat treatment and stretching process" by which the high load capacity cut nylon of the present invention is prepared must be critically controlled. It is desirable to stretch the nylon yarns in the absence of added moisture; that is, if antistatic finishes are added to the wire prior to drawing, they must be of a non-aqueous type or, alternatively, the rope must be dried before being subjected to the drawing operations .

   If aqueous finishes are required, the heating operation should be carried out in such a way as to ensure sufficient time and heat capacity to vaporize the water in excess over that in equilibrium with the polymer at room temperature, as well as the water. conditions necessary to subject the fila. ing heat treatment to the required level of degree seconds. It is important to avoid exposing treated filaments to wet conditions (e.g. liquid water, water vapor at high humidity conditions or high humidity conditions and high temperature) after heat treatment and stretching.



   Obviously, if an antistatic or other type of staple fiber size is to be applied to the tow before heat treatment and drawing, that size must be stable at the hot plate temperatures that the filaments will encounter.



   As indicated above, the maximum possible draw ratio should be used on the sole condition of avoiding excessive breakage of the filaments. The cable can be heated advantageously in contact with a hot plate, the shape of which is not critical, as long as necessary to obtain good contact. It was established that the wire reaches the temperature of the plate within 1 to 1 second; during the remainder of the contact time with the plate, the filaments have been found to be at substantially the temperature of the plate. An alternative which may sometimes be desirable is to use radiant heat or a hot air furnace .

   Combinations of these processes are often of interest, because the hot plate heats the cable quickly, while the oven provides a very uniform heat treatment and prevents friction of the wire and the formation of charred deposits of wire finishes on the wire surfaces. heated contact.



   Nylon 66 cord can be heated to temperatures of 140 to 225 C, and preferably 165 to 200 C. The residence time at this temperature varies from 1 to 40 seconds, with shorter times requiring higher temperatures. high, as shown above. Very satisfactory results are obtained when the wire is heated in contact with the plate at 195 ° C., then in an oven at 185 ° C. for 20 seconds. Under these conditions, the wire is subjected to a heat treatment of 3800 degree-seconds, which constitutes an extremely suitable exposure; a draw ratio of 3.7 can be used for 2.2 denier filaments.

   As an indication, the following draw ratios are given which are suitable for different deniers of the filaments:
 EMI8.1
 
<tb> Denier <SEP> Stretch
<tb>
<tb> 1.2 <SEP> 3.2
<tb>
<tb> 2.2 <SEP> 3.7
<tb>
<tb> 4, <SEP> 3 <SEP> 4, <SEP> 5 <SEP>
<tb>
<tb> 10 <SEP> 5
<tb>
 
The heat treatment ranges apply to a wide range of deniers (eg 1.2 to 15 denier and more per filament). It may be desirable to raise processing temperatures by about 5 ° C for filaments.

 <Desc / Clms Page number 9>

 from 10 to 15 denier, but the processing times should not be changed.

   Generally, the heat exposure under the stretching tension should be about 1000 to 6000 degree-seconds and preferably 2000 to 5000 degree-seconds.
After the heat treatment, it is desirable to allow the filaments to cool somewhat before releasing the draw tension. Preferably, the cable will be cooled to 90 ° C or less.



   After drawing, nylon intended to serve as staple fibers is usually creped in a creping device (eg that described in US Pat. No. 2,311,174). This treatment has been found to lead to some relaxation of the yarn, especially when performed in the presence of moisture.



  This relaxation results in a significant drop in the T7 value and is therefore undesirable. For example, nylon is easily processed without creping at a T of 2.5 gdp. Under the same treatment conditions, but followed by a creping operation giving a creping index of 10%, the T is only 1.9 gdp; with further creping to achieve a creping index of 20.5% (normal for classic 3 denier cut nylon / filament), the T7 drops to 1.57 gdp.



     2 creping index is determined on individual filaments (a) by grinding a fiber to eliminate crimping without substantially extending it, (b) by measuring the length in the ground condition, (c) leaving the fiber freely retracting and measuring again; creping is calculated as follows: length (a) - length (c) X 100% = creping index length (a) Therefore, to obtain the maximum values of T, mechanical creping should be avoided. More satisfactory results are obtained by feeding the cable directly to a suitable cutting device. A suitable cutting device is described in U.S. Patent Hull No. 2,694,447.

   Preferably, the cut fiber is then passed through an opener, for example the Davis Furber opener for synthetic fibers. The cut fibers opened can then be baled under the usual pressure and in this way they acquire sufficient crimping to be able to be mixed satisfactorily with cotton or processed in conventional cotton spinning plants. Maximum retention of the high load-bearing capacity of the chopped fibers of the present invention is achieved if the fiber is chopped and baled as soon as possible after the stretching operation.



   The high load carrying capacity staple fiber of the present invention is suitable for blending into clusters, slivers for the preparation of 100% synthetic yarns.



   The high load carrying capacity staple fiber of the present invention can be prepared from polyethylene terephthalate filaments. The preparation is illustrated by the following example.



  EXAMPLE III.-
Spun filaments of polyethylene terephthalate (relative viscosity 26.7) are combined into a tow of about 50,000 denier, 120,000 filaments, which is drawn on a machine arranged in substance as shown in Figo 1, with the except that the friction fingers and the hot plate are removed. During the drawing operation, water heated to 95 C. is sprayed onto the cable. After the drawing operation in the machine shown in Fig. 1, the cable passes through a heat treatment furnace. and thence in a second set of draw rollers which keep the yarn under suitable tension.

   By adjusting the peripheral speed of the second set of drawing rolls relative to the first set, the cable can be relaxed, held at a constant length, or stretched while it is passing through the oven. Cable passes through the 8-foot (2.4 m) oven three times in an SO path Cable is exposed for approximately 20 seconds

 <Desc / Clms Page number 10>

 to circulating air at 190 C in the oven. The yarn is stretched by 1% as it passes through the oven. This treatment is sufficient to remove most of the water added during drawing, but it is even more remarkable that it imparts a high degree of crystallinity to the yarn.

   Due to the much lower sensitivity to water of the polyethylene terephthalate filaments (compared to nylon), it is unnecessary to keep the tow in a dry state.



  1 After this treatment, the cable is mechanically creped and cut into 1 inch (38.1 mm) sections. The sections are mixed with Egyptian cotton; the properties of the fibers and the values of the tests l1 (sample A) are given in Table 50. Table 5 also reproduces the similar results obtained for chopped fibers of conventionally prepared polyethylene terephthalate (sample B); the preparation is similar to that of the high T chopped fiber of the present invention except that the tow is heat treated in the heating oven while it is free to relax.



   TABLE 5.



   Physical properties of Dacron 1 cotton yarn blends.
 EMI10.1
 
<tb>



  Sample <SEP> A <SEP> B
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Dacron <SEP> to <SEP> high <SEP> Cotton <SEP> Dacron <SEP> classic
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> value <SEP> T7 <SEP> from Egypt
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Tenacity <SEP> (gpd) <SEP> 5.3 <SEP> 3-4 <SEP> 3.8
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> T7 <SEP> (gpd) <SEP> 4, <SEP> 8 <SEP> 3-4 <SEP> 1, <SEP> 0 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Withdrawal <SEP> to <SEP> the boil <SEP>% <SEP> 3 <SEP> 3 <SEP> 0
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Lea <SEP> test <SEP> mixture,

   <SEP> 65/352
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 13/1 <SEP> n <SEP> cotton <SEP> 4930 <SEP> 38603 <SEP> 2940
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 47/1 <SEP> n <SEP> cotton <SEP> 3670 <SEP> 35003 <SEP> 2060
<tb>
 Dacron is the trademark for Pont's polyester fiber made from polyethylene terephthalate 2 The blend consists of 65 parts Dacron and 35 parts cotton 3 The test value is for 100% cotton yarns.



   Table 5 shows that the test values for a mixture of 65 parts of polyethylene terephthalate filaments and 35 parts of cotton filaments indicate a substantial improvement in toughness when using the fiber of the present invention.



    EXAMPLE IV Filaments of polyethylene terephthalate are drawn as in Example III; they are then released at 3¸% in the heat treatment oven at 13000, then mechanically creped and cut into strands. These filaments are called sample Co A second batch of chopped fibers, called sample D, is prepared under similar conditions, except that the tow is subjected to 2% stretching in the oven at 140 C, followed by heat treatment at 140 ° C. 'released state at 140 C. The properties of the filaments are shown in Table VI.



   TABLE 6.
 EMI10.2
 
<tb>



  Sample <SEP> C <SEP> D
<tb>
<tb> Tenacity, <SEP> gpd <SEP> 5,2 <SEP> 5,2
<tb>
 

 <Desc / Clms Page number 11>

 TABLE 60
 EMI11.1
 
<tb> Elongation <SEP> at <SEP> the <SEP> break, <SEP>% <SEP> 20 <SEP> 25
<tb>
<tb> T7, <SEP> gpd <SEP> 3.5 <SEP> 1.5
<tb>
   Mixed with cotton in the weight ratio of 65 parts to 35 parts cotton, the yarn from sample D has a lower test value of 15%, which shows that it is the T value which determines the tenacity. of the mixture, rather than the toughness of polyethylene terephthalate,
By resuming the conditions for preparing sample C, except that the oven is maintained at 220 C, similar results are obtained.

   The serviceability is somewhat better at 220 C <. Maximum T values can be obtained when the polyethylene terephthalate yarn is stretched by about 1% in the furnace by proper adjustment of the speed of the second set of rolls d. 'call. This improvement comes, to a certain extent, at the expense of the dyeing rate and this way of acting is therefore not preferred for mixtures of staple fibers which are to be dyed; for such blends it is more desirable to provide about 4% relaxation, which is a satisfactory compromise.



  EXAMPLE V.-
By repeating the test under the conditions of sample A, but using filaments of high tinctorial affinity polyethylene terephthalate modified by sulfonates, filaments in which 2 mole percent of a sulfonated isophthalate radical replace an equivalent amount of a terephthalate radical, as described in US patent application Griffing and Remington n 622,811, the dye content is high enough to be able to use oven temperatures of the order of 180 C associated with an oven treatment to zero relaxation; under these conditions, high T7 values are obtained at the same time as a high tinctorial rate.



   The above examples are intended to illustrate the present invention and it is clear that modifications can be made in the nature of the staple fiber, time, temperature, stretch, etc., to obtain a finished yarn or ultimate fabric with desired properties. It should also be noted that the replacement of cotton by wool, or by other cellulosic fibers can be done when conditions permit.



   Slightly less desirable results can be obtained with polyethylene terephthalate filaments when the stretching is carried out without the addition of hot water using the arrangement of FIG. 1 and which has been found to be useful for nylon filaments. In addition, satisfactory results are obtained by dry drawing followed by heat treatment in an oven using superheated water vapors or air at 200 Co
The high load carrying capacity staple fiber of the present invention can contain the usual delustrants, dye modifiers, antistatic agents, antioxidants, heat stabilizers, and the like.

   Suitable sizes for staple fibers can be added before, during or after the stretching and heat treatment operation, provided that the conditions of heat stability and, for polyamides, absence of effects are observed. hygroscopic tending to raise the moisture content of the fiber above the equilibrium value (eg, about 4.1% in a relative humidity of 76%, to 74 F or 23 C).



   The present invention offers many advantages over the known methods. It allows the use of relatively inexpensive natural fibers or those derived from natural cellulosic materials with even small proportions of synthetic fibers to obtain a yarn which can be made into articles of clothing with better resistance to wear and abrasion. .

 <Desc / Clms Page number 12>

 



  Another advantage is that clothing items made from these blended fibers, such as sweaters and socks have better properties, such as less pilling and elongation, softer feel, better shape retention. and greater comfort. It is therefore evident that the fibers described herein constitute a significant economic improvement over known fibers.



   Although certain embodiments and details of execution have been described to illustrate the present invention, it is clear that many changes and modifications can be made to it without departing from its scope.



    CLAIMS.



   1.- Cut fiber yarn composed of a mixture of fibers of a natural polymer (or of natural origin) and fibers of a synthetic polymer, characterized in that the synthetic fiber is a fiber of a A high tenacity linear condensing polymer having a load capacity equal to or greater than that of natural fiber at elongation at break of natural fiber.


    

Claims (1)

2.- staple fiber yarn according to claim 1, characterized in that the synthetic fiber is a linear polyamide and preferably a polyamide which comprises 85% or more of polyhexamethylene adipamide or of polyca- proamideo 3. - Staple fiber yarn according to claim 1 or 2, characterized in that the synthetic fiber is a linear polyamide having a birefringence of at least 0.0590 and an average density greater than approximately 1.1390 4. A staple fiber yarn according to claim 1, characterized in that the synthetic fiber is a linear polyester of the terephthalate type. 5.- staple fiber yarn according to claim 1, characterized in that the synthetic fiber is a linear condensation polyester comprising at least 85% of recurring structural groups of formula: EMI12.1 60- staple fiber yarn according to claim 1, characterized in that the natural fiber is cotton. 70- staple fiber yarn according to claim 1, characterized in that the natural fiber is regenerated cellulose. 8. Chopped fibers of a synthetic linear condensing polymer suitable for blending with cotton fibers to form yarns according to claim 1, characterized by a load capacity of at least 2.1 g per denier to 7. % elongation and by boiling shrinkage not exceeding about 6%, these two properties being measured after 9 days of aging in the relaxed state. 90- Cut fibers according to claim 8, characterized in that the condensation polymer is a linear polyethylene terephthalate 100- Cut fibers according to claim 8, characterized in that the condensation polymer is a linear polyamide, such as polyhexamethylene adipamide or polycaproamide. 11. Chopped fibers according to claim 10, characterized by a birefringence of at least 0.0590 and by an average density greater than about 1.139. 120- A method of manufacturing staple fibers according to claim 10 or 11, characterized in that a bundle of filaments is stretched to practically the maximum possible draw ratio, while simultaneously heating the filaments, the product of the filament. heating time, in seconds, and temperature, er <Desc / Clms Page number 13> degrees centigrade, being about 1000 to 6000, and then, if desired, the drawn filaments are passed directly through a suitable short staple cutter. 13. A method according to claim 12, characterized in that the product of the heating time and the temperature is about 2000 to 5000.