NO873810L - IMPROVEMENTS OF YARN TEXTURING. - Google Patents

Description

The invention relates to improvements in and in the texturing of yarns, and it relates more particularly to improved polyester draw-texturing feed yarns having the ability to be draw-textured at high speeds without excess broken filaments and with other advantages such as high-speed draw-texturing process and a process for producing such feeding nets.

The manufacture of textured polyester multifilament yarns has been carried out commercially on a world scale for many years. The simultaneous draw-texturing by means of a false-twist texturing process of partially oriented feed yarn with low crystallinity produced by spin-orientation, i.e. drawing of melt-spun polyester filaments at high drawing rates of e.g.

2743 mpm, was described by Petrille in US patent 3,771,307,

and the feed yarns were described by Piazza and Reese in US Patent 3,772,872. The use of these spin-oriented feed yarns has made it possible to significantly increase texturing speeds. For about. in 1970, commercially available texturing machines (false-twist texturing) were suitable for maximum speeds of only on the order of approx. 200 mpm (meters per minute). Due to improvements in machine design, for several years now there have been commercially available draw texturing machines with the ability to operate at very high speeds of e.g. 1000 mpm or more. Despite the availability of such machines suitable for machine operation for such desirable, very high speeds, commercially available draw texturing polyester feed yarns (DTFY) have not been textured commercially at such high speeds as the machines are capable of. This is mainly due to a very large number of broken filaments produced at these very high speeds. Any broken filaments are undesirable as they can cause difficulties and even yarn breakage during subsequent processing and also textile defects. The number of broken filaments that can be tolerated in practice will depend on the desired application of the textured

yarn and any textile. In commercial practice, the ends of the spools are examined for broken filaments, and the number of protruding broken filaments is counted to give a measure of the likely number of broken filaments in the yarn in this lay-up unit. The total number of these counted broken filaments is then divided by the number of pounds (0.454 kg) in the layout unit and expressed as BFC. For certain end uses, the maximum that can be tolerated is between 0.5 and 0.6 BFC, i.e. between 5 and 6 broken filaments for every 4.54 kg of polyester yarn, it will be understood that one break is likely to be counted as two broken filaments . Thus, a texturizer having a texturing machine suitable for operation at 1000 mpm or more, if the polyester draw texturing feed yarns that are commercially available cannot be processed on this machine at more than approx.

850 mpm without significantly exceeding the desired maximum (ie approx. 0.5 BFC), in practice being forced to

operate this machine at this speed of 850 mpm instead of increasing the speed to the maximum performance of the machine.

Despite the clear commercial impulse to provide polyester draw-texturing feed yarns suitable to be draw-textured at speeds in excess of 1,000 mpm without excessive BFC, this problem of at-

bring about a commercially satisfactory feed net has not yet been solved.

I have found it possible to increase texturing speeds without causing an excess of broken filaments by increasing the draw speed used to achieve the desired spin orientation in the feed yarn. Such feed yarns, produced at relatively high draw rates of 4000 mpm, have not yet been textured commercially on a large scale because of the attendant disadvantages, mainly in that the resulting textured yarns have not become as voluminous as yarns already available commercially. Bulkiness was generally measured as CCA, a value of at least approx. 4 is considered desirable, or as TYT, a value of over 20 is generally considered desirable today.

The problem facing the industry has therefore been to provide a polyester multifilament draw-texturing feed yarn (DTFY) suitable to be draw-textured on existing commercial machines at a speed of at least 1000 mpm and even to provide

a layout unit of textured yarn, yarn with e.g. no more than approx. 0.5 BFC and over 20 TYT, as it is understood that such figures depend very much on economic and other commercial considerations and what competitors are prepared to offer at any given time. As time passes, the demand in any industry generally tends to increase.

The present invention provides a solution to this problem. In one aspect of the invention, a method has been provided by which an improved new polyester feed yarn can be draw-textured at high speeds to provide yarns with satisfactory texture without excessive BFC. In another aspect, improved new polyester feed yarns are provided, whereby this problem can be solved. In a further aspect, a method for the production of these improved, new feeding yarns is provided.

In a further aspect, the use of the feed yarn can provide other advantages, even when increased speed during texturing is not necessary or desirable.

According to one aspect of the invention, there is provided a continuous process for making polyester drawing texturing feed yarn, comprising the steps of first forming a molten polyester by reacting (a) ethylene glycol with terephthalic acid and/or

esters thereof, followed by polycondensation (b), these reaction steps are carried out in the presence of suitable catalysts therefore,

and then melt-spinning the resulting molten polyester into filaments and drawing them at a rate of approx. 3,000 to 4,000 mpm, preferably at speeds in the lower part of this range, such as approx. 3,000

to 3200 mpm, to produce partially oriented yarns of low crystallinity, in which the polyester is modified by introduction into the polymer, as a solution in ethylene glycol,

a substance selected from the group consisting of trimesic acid, trimellitic acid or an ester thereof in an amount indicated approximately by line AB in Figure 1 of the accompanying drawing.

According to another aspect of the invention is

it produced a partially oriented polyester multifilament draw texturing feed yarn with low crystallinity, as shown by a "boil-off" shrinkage of approx. 45% and an elongation at break of approx. 155%, consisting essentially of polymerized ethylene terephthalate residues chain-branched with trimellitate or trimesat residues in an amount of approx. 6 MEQ,

and with a relative viscosity of approx. 21 LRV. Alternatively, "boil-off" shrinkage can be approx. 20-25%, elongation at break approx. 133%, and the amount of trimesate or trimellitate residues approx. 4 MEQ. Elongation (of fracture) is a measure of orientation (which is birefringence), elongation is decreased as spin orientation is increased, while shrinkage is affected by crystallinity, as well as orientation, and is decreased as crystallinity increases. A multifilament drawing texturing feed yarn has thus been obtained which has been produced by polymerization of ethylene and terephthalate derivatives with trimesate or trimellitate residues which act as chain branchers and of spinning orientation at a drawing speed of at least approx. 3000 to 4000 mpm, preferably at a lower speed, such as approx. 3000 to 3200 mpm, and which is suitable to be texturized at a speed of at least 1000 mpm to provide a textured yarn layup unit of not more than approx.

0.5 BFC and a TYT of over 20.

According to a further aspect of the invention

there is provided a process for making a false-twist textured yarn, wherein a multifilament polyester feed yarn is subjected to simultaneous draw-texturing at a rate of at least 500 mpm, the feed yarn consisting essentially of polymerized ethylene ether phthalate residues and of trimesate or trimellitate residues which

acts as a warp generator, and the resulting texture unit of textured yarn has no more than approx. 0.5 BFC and over 20 TYT.

It will be apparent that the new feed yarn and its method make it possible to provide textured polyester yarn with increased color uptake and/or improved frizz compared to prior commercial polyester yarns textured under comparable conditions.

As will be explained below with reference

to the drawings, the amount of chain branching will depend on various considerations, especially spinning speed, as it will generally be desirable to use as much chain branching as possible to obtain greater advantages with regard to certain conditions, while the amount should not be so great that will cause spinning difficulties, and this will depend on the extraction speed in the sense that the desired amount of chain branching will decrease as the extraction speed is increased. An advantage in color uniformity of textured yarns (and textiles) has also been achieved by drawing filaments of feed yarn at a lower speed than the specified speed range. Fig. 1 is a graphical representation of the relationship between extraction speed in ypm and the amount of chain branching in MEQ. Fig. 2 is a graphical representation showing mug properties (TYT) against the amount of chain branching as used in example 2.

The production of the feed yarn is preferably carried out by a continuous process in which the steps of polymerization and spinning are linked together, as the alternative process that has been carried out in some plants by first producing the polyester and then extruding this in the form of silk ribbons which are cooled with water and cut to pellets or flakes which are then remelted for a separate process by spinning into filaments can introduce uncertainties and problems which can lead to unevenness in the resulting feed yarn filaments. It will be pointed out that evenness of polyester filaments in the feed yarn is of great importance in order to achieve high drawing-texturing speeds without too large a number of broken filaments.

An important element of the invention is believed to be the use of trimellitic acid, or trimesic acid, or a derivative thereof in small amounts (e.g. 4-6 MEQ) as a chain brancher in the process for producing the polyester, which is therefore a copolymer. It is believed that such chain branching has not previously been used commercially for the purpose of producing a feed yarn suitable for being drawn-textured at high speeds, e.g. at 1000 mpm, without excessive number of broken filaments, e.g. no more than approx. 0.5 BFC, which gives the desired voluminous yarn, e.g. with TYT over 20. However, it is nothing new to propose the use of chain splitters for other purposes. E.g. MacLean et al., U.S. Patent 4,092,299, proposes a high draw ratio polyester feed yarn and its draw texturing, and U.S. Patent 4,113,704 proposes a polyester filament-forming polymer and its method of manufacture. As the two patent descriptions are practically identical, only US patent 4,092,299 will be discussed.

MacLean et al., US Patent 4,092,299, suggests increased productivity by using a chain brancher in such an amount that the polyester has 1-15 or 2-14 microequivalents of reactive branching sites per grams of polymer (MEQ), and preferably 5-12 MEQ. The increased productivity is achieved by increasing the drawing ratio during the drawing texturing and/or increasing the drawing speed during the filament formation, as the orientation (birefringence) of the feed yarn is reduced by the use of chain branches. The optimal level of chain branching is discussed in column 11 and will depend on many factors. Pentaerythritol is suggested as the preferred chain brancher, but is not desirable according to the present invention as it evaporates during polymer manufacture.

We have found that the use of such evaporable chain brancher leads to problems and consequent lack of uniformity in the resulting filaments for drawing texturing feed yarns. Although a volatile chain former such as pentaerythritol may be perfectly adequate for operation at low texturing speeds and for MacLean's goal of increasing productivity, it is not a solution to the problem of providing a draw-texturing feed yarn suitable for draw-texturing at a speed of, f .ex. 1000 mpm, with no surplus of broken filaments,

e.g. no more than approx. 0.5 BFC which gives a desired voluminous yarn, e.g. over 20 TYT.

According to the present invention, we have found it desirable to use a chain brancher that is adequately stable (both in monomer form during processing and polymerization and in polymeric form during formation of the polymer and spinning into filaments and subsequent processing), not so volatile that it causes problems and unevenness during the preparation of the polymer, and that it is soluble in the catalyzed glycol to facilitate addition to the reaction. Trimellitic acid and its ester derivatives fulfill all these functions, and it is believed that trimesic acid and its ester derivatives will have similar functions and benefits. There are two main methods of preparing polyethylene terephthalate polyesters, namely ester exchange of dimethyl terephthalate (DMT) with ethylene glycol (EG) to form a prepolymer, followed by further polymerization, or reaction of terephthalic acid (TPA) with EG to form the prepolymer, followed by further polymerization. If the DMT method is used, an ester,

such as trimethyl trimellitate (TMTM), will be preferred, while trimellitic acid (TMA) will generally be preferred for the TPA process.

MacLean is not limited to the use of pentaerythritol, but covers other chain branching agents having a functionality greater than 2, i.e. containing more than 2 functional groups such as hydroxyl, carboxyl or ester. Accordingly, other polyhydroxy chain branchers are mentioned and are aromatic, polyfunctional acids or their esters (column 7). Trimesic acid, trimethyltrimesate and tetramethylpyromellitate are specifically mentioned in lines 41-42, but are not used in the examples. In Table IV, column 12, trimer acid has been used in amounts of 11,800 and 23,600 ppm (stated to be 6.5 and 12.9 MEQ, but instead calculated as 12.9 and 25.1 MEQ respectively), and mellitic acid (benzenehexa -carboxylic acid) is used in amounts of 9.8 and 14.7 MEQ. The only texturing speed mentioned by MacLean is 182.9 mpm (column 10, line 15). Draw (spin) speeds vary between 3,109.0 and 4,023.4 mpm in Examples 2 and 4, and are 5,029 and 5,486 mpm in Example 6, and are otherwise 3,109.0 mpm. Productivity (MacLean's measure) stated "increases decidedly with spinning speed over most of the range of speeds suitable for the apparatus employed" (column 11, lines 58-60), and it was impossible to determine whether the productivity curve continued to increase with spinning speed.

As will be shown in the following examples, where the DMT ester exchange process is used to prepare the polyester, the chain brancher is conveniently dissolved in the catalyzed EG solution used in an otherwise conventional ester exchange reaction between DMT and EG using suitable catalysts to prepare the prepolymer. Further polymerization (sometimes referred to as finishing) is carried out under vacuum with a suitable material such as phosphorus again in a conventional manner to produce a polymer of the required viscosity (measured as LRV). The resulting polymer is then preferably fed continuously to the spinning unit without intermediate conversion to flake and remelting, and is spun to produce partially oriented filaments of low crystallinity at draw rates of 3,000 mpm or more, with special care in spinning conditions to provide uniform filaments, to limit breakage during spinning or during subsequent high-speed draw-texturing operations.

TMTM has three reactive carboxyl groups, two of which are converted into the molecular chain. The second reacts to form a side chain which is referred to as a chain brancher. If and when these chain branchers react with another molecule, a cross-link is formed. There are clearly many more chain branchers than cross-links formed. Also, because there are only three of these (carboxyl) reactive sites in TMTM, there is only one chain branching. The equivalent weight and molecular weight are therefore the same. 0.15% by weight of TMTM (based on the weight of the polymer) is the same as

1,500 ppm and is almost 6 MEQ (5.95). 0.10% of TMTM

(1,000 ppm) is similarly almost 4 MEQ. Trimesic acid has the same molecular weight as trimellitic acid, so the same values apply.

As indicated above and elsewhere in the description, the amount of chain branching must be carefully adjusted, especially according to the rate of withdrawal, if the full benefit of the invention is to be obtained. Optimal values are indicated graphically as the line AB in fig. 1 in the attached drawings, where such optimal quantities (such as MEQ) are plotted against the extraction speeds (in mpm) for the equipment that I have used. It will be understood that some variation may be permitted, and the exact optimum value may well differ according to various factors such as ingredients used and equipment for producing the polymer and yarn and operational preferences. However, as the amount of chain branching increases, the melt viscosity generally increases, and this soon causes problems, especially in spinning, so that spinning is rendered impossible due to melt breakage.

However, it is generally desirable to use as much chain branching as possible, in accordance with the aforementioned, in order to achieve the stated advantages in the textured yarns, especially in increased mug and color absorption compared to yarns of unmodified polymer. There is thus a rather narrow area in the mix ratio of chain-branches in which I prefer to operate. As indicated, this range decreases with the draw speed used to make DTFY, as the melt viscosity increases, and spinning problems consequently increase with increased speeds. The color evenness of the textured yarn has further improved when lower drawing speeds have been used within the specified range. If this is important, an extraction speed that is relatively low within the operating range, i.e. less than 3,500 mpm, and especially approx. 3,000 to 3,200 mpm. This preferred, relatively low speed is surprising, contrary to what I have expected from my knowledge in this area and from what is taught in the subject. However, the speed should not be too low, as this will lead to filaments that are thermally unstable and may cause problems when fusing or melting on the (first) heating device of the texturing machine or when suspended. In this regard, the desired minimum draw rate is clearly greater than that taught by Petrille and Piazza and Reese in US Patents 3,771,307 and 3,772,872 for unmodified (homopolymer) PET yarns. As already indicated, and as is well known, the elongation (to break) generally decreases as the extraction speed increases, this is a measure (inverse) of the orientation. Thus, an increase in elongation (other parameters being held constant) generally indicates a tendency toward instability of the filaments for heating, while a decrease in elongation similarly indicates less color uniformity. It will be understood that all the specified numerical parameters will depend on ingredients, equipment and operational preferences to some extent. The preferred value for LRV is 21, as too high a value will increase the melt viscosity, and this leads to spinning problems as already explained. However, too low LRV contributes to reducing tensile values, especially the toughness of the filaments, and this leads to breakage during draw-texturing. If the shrinkage is too low, this similarly indicates too high crystallinity,

and this leads to irregularities which generally appear first as reduced color evenness, while insufficient

crystallinity (too high shrinkage) leads to variability at other conditions, and can produce filaments that are not sufficiently stable to heat, as indicated above. It will be understood that spinning conditions must be carefully monitored, and the desired amount of chain branching must be carefully selected and influenced by the draw-out rate which can be selected according to the desired values for the possibly textured yarns. If color uniformity is important, a lower speed of approx. 3,000 mpm be preferred. If better freezing values are more important, a higher extraction speed may be preferred. However, as the extraction rate increases, a point is reached where the presence of chain branchers does not continuously increase freezing values, although other benefits such as improved color uniformity will still be apparent.

The use of chain forks has been highlighted

to provide a significantly higher spinning stretch than unmodified polymer. This is believed to be a significant advantage of the method according to the invention.

As shown, a significant advantage of the resulting textured yarns obtained by draw-texturing the improved modified feed yarns of the present invention is the low number of broken filaments (BFC) obtained even when the texturing is carried out at very high speeds. The resulting textured yarns also have other advantages. As can be seen from the examples, the color capability, or color uptake, is improved. In retrospect, this may not seem so surprising, as there have been several previous proposals for the use of other trifunctional chain branching agents in polyester polymers in much larger amounts (0.5-0.7 mol%, i.e. approx. 10 times as much ) to achieve better dyeability, oil stain removal or low pilling, as discussed in column 1 of US patent 4,092,299. However, despite these general suggestions for improving such values according to the state of the prior art, no one is known to have previously actually produced a textured polyester fiber with improved dyeability by incorporating a trimellitate or trimesate chain brancher into the polymer.

used for the production of DTFY.

A further improvement in textured yarns believed to result from the chain branching of the invention is the improved crimp values as shown by the CCA and TYT values in the examples. This is an important commercial advantage. In practice, it is necessary to operate the draw-texturing process in this way in order to obtain textured yarns that have at least equal frizz values to those already available commercially. The crimp values can be adjusted to some extent by varying the draw-texturing conditions, and this may also depend on the skill and knowledge of the texturizer who may be forced to reduce the texturing speed to improve the crimp values of the resulting textured yarn. Thus, a desirable goal for the texturizer is to achieve or exceed the target mug values while reducing costs by operating at the maximum possible speed.

The invention is further illustrated in the following examples. The yarn values are measured as in US patent 4,134,882 (Frankfort and Knox) with the following exception.

BCD (Broken Filament Count) is measured as indicated below, by the number of broken filaments per pounds of yarn.

In practice, a representative number of yarn lay-up units are evaluated, and an average BFC is obtained by visually counting the total number of free ends on

both ends, and by dividing by the total weight of yarn in these layout units.

The TYT (Textured Yarn Tester) measures the ripple of a textured yarn continuously as follows. The instrument has two zones. In the first zone, the crimp contraction of the textured yarn is measured, while in the second zone residual shrinkage can be measured. But only the first zone (crush contraction) is of interest for the present purpose. In particular, the textured yarn is removed from its unit package and passed through a stretching device which increases the stretch to the desired level, 10 g for 160 denier yarn (0.06 gpd). The yarn is then directed to a first driven roll and its separator roll to isolate the incoming tension from the tension following this first roll. This roll is hereinafter referred to as the first roll. Next, in this first zone, the yarn is guided through a first tension sensor and through an insulated, hollow tube 164 cm long and 1.27 cm in diameter held at 160°C to a second set of rollers, a driven roller and a separator, which isolates the tension in the yarn in the first zone from that in the next zone, and to a third set of rollers, a driven roller and a separator roller, which further isolates the tension in zone 1 from the tension in zone 2. The peripheral speed to roll 3 is set sufficiently faster than that of roll 2 so that this roll imparts 2 g of tension to a 160-denier thread line (about 0.013 gpd), and rolls 2 and 3 are controlled by the first tension sensor at such speeds as to ensure that the tension in zone 1 is that desired (about 0.001 gpd). As the yarn leaves the third set of rollers, it is passed through a second sensor and then to a fourth set of rollers which isolates the tension in the second zone from winding tension or "waste jet". The speed of the fourth set of rollers is controlled by the second sensor, and this tension is set at 10 g for a 160-denier yarn or 0.0625 gpd. Naturally, the total tensions will change with a change in the denier of the textured yarn. As indicated, only the relative velocities in and out of the first zone are of interest in this example.

TYT is calculated as a percentage of the peripheral speeds V, to the first roll and V2 to the second roll:

The CCA (Crimp Contraction) of textured yarn is determined in the following way: A looped hook with a denier of 5,000 is produced by winding the textured yarn on a denier spool. The number of ties required on the spool is equal to 2,500 divided by the denier of the yarn. A 500g weight is hung on the looped rope for initial stretching of the rope. This weight is then replaced by a 25 g weight to provide a loading of 5.0 mg/denier in the hemp. The loaded hemp is then heated for 5 minutes in an oven supplied with air at 120°C, after which time it is removed from the oven and allowed to cool. While still under 5.0 mg/denier load, the length of the hespen, Lc, is measured. The lighter weight is then replaced by the 500 g weight, and the length of the rope, Lg, is measured again. Mug contraction is then expressed as a percentage which is calculated by the formula:

Color uptake - Each yarn was knitted into a sleeve using a Lawson Hemphill FAK knitting machine.

The knitted sleeve was rinsed, dyed at 129°C using Eastman polyester blue GLF (Dispersed Blue 27 No. 60767), rinsed again, dried, flattened, and then the light reflection coefficient is measured on different sections of the sleeve with a "Color Eye Instrument ", which is marketed by Macbeth Corporation. Values of the reflection coefficient are converted to K/S values by applying the Kubelka-Munk function, which is the theoretical expression for the reflection coefficient on dyed yarn (in this case in the sleeve), to the concentration of dye in the fiber. Sections of a "control yarn" are knitted in each sleeve so that all K/S values can be rationalized,

ie expressed in "% color absorption" against this control as standard.

Example 1

Copolymer for the new and improved feed yarn for drawing texturing (DTFY) is produced by copolymerizing dimethyl terephthalate (DMT), ethylene glycol (EG) and approx. 4.3 MEQ trimethyltrimellitate (TMTM) (approx. 4.3 microequivalents per g of DMT). 4.3 MEQ is 0.11% of TMTM per g of copolymer. TMTM is dissolved in and added with the catalyzed glycol. At the required concentration, TMTM is completely soluble in the catalyzed glycol and neither enhances nor suppresses the catalytic values of manganese and antimony salts used as catalysts. Catalyst contents are identical to those used for standard PET. The required amount of phosphorus, either as an acid or a salt, is added when the exchange is complete and before proceeding with polymerization to inactivate the manganese catalyst during polymerization. 0.3% TiO 2 calculated on DMT is added as a glycol suspension to the material, after the exchange is complete and before polymerization, to provide opacity in the resulting DTFYs. It has been found that the addition, exchange and polymerization process conditions used for standard PET are acceptable. The polymerization actually occurs faster for the new copolymer. In the compositions used here, both the copolymer and the standard (linear polymer) PET (used as a control) were prepared by a continuous polymerization process. It is found that the resulting new copolymer has an LRV slightly higher than that of the control, slightly more than 21 against the standard polymer by approx. 20.5. The new copolymer also has a slightly higher melt viscosity than the control. This increased melt viscosity was not sufficient to cause problems during polymer production, polymer transport or spinning. The polymer is pumped from the continuous polymerizer to the spinning machines where it is spun into the new and improved feed yarn for drawing texturing.

The new copolymer is pumped through a filter pack and then through a spin nozzle which has 34 capillaries, each 15 x 60 mils (diameter x length). Spinning temperatures are somewhat higher than those required for standard PET (approx. 300°C versus approx. 293°C for standard PET).

The extruded filaments are quenched by passing room temperature air across the filaments below the spinneret, using the same cross-flow system as for standard PET filaments. The amount of air flow across the filaments is adjusted to achieve the best operating conditions. The final treatment is carried out after the filaments have been quenched. Filaments are then allowed to run together into a thread direction and are then handled as such. This thread direction is fed at 3,600 mpm around the first pre-roll, called a feed roll, then a second pre-roll, called a let-down roll, through a coiling device and then to a suitable winding device at approx. 3,600 mpm. The peripheral speed of the lay-down pre-roll is set to provide the voltage between the feed and the lay-down pre-rolls that produces the best coherent spinning. These conditions were essentially the same as for standard yarns. Coherent spinning was found to be excellent. Plot units of the new DTFY were judged to be at least as good as those of the standard yarn.

DTFY has tensile properties and other physical properties

values acceptable to DTFY. These values are listed and compared with the standard PET control DTFY in Table IA.

As the new DTFY is spun at 3,600 mpm, but has orientation properties (elongation and birefringence) more similar to standard POY spun at 2,300 mpm, standard POY spun at the same speed was prepared and used as a control. The crystallinity of the new DTFY is greater than each control (density and C.I.).

Each DTFY is textured on a laboratory model, Barmag FK6-900 texturing machine, which is equipped for friction-forged texturing, with a Barmag T-6 arrangement as a disk array/using a 0-9-0 array of "Kyocera " ceramic discs with a gap of 0.75 mm. Texturing speed comparisons were made over the speed range from 750 to 1,150 mpm, divided into 100 mpm intervals. The draft ratio to avoid wave motion for each yarn is determined and applied. The temperatures of the first and second hot plates are set to 220°C and 190°C, conditions used by many in the art for PET yarn. During texturing, virtually no breakage occurred with the new yarn at any of these speeds. In contrast, there were more breaks for the control yarns, especially at higher speeds, such as at 950 mpm, more at 1,050 mpm, and none of the control yarns could be used at 1,150 mpm, i.e. it was not possible to draw-texture any control yarns at this speed . Stretch before the disc and after the disc was measured for each yarn at each texturing speed. The textured yarns were tested for broken filament textured yarn properties (BFC), and TYT and CCA mug properties and color uptake with the results set forth in Table IB.

These results show that the new DTFY has very significant advantages over each control yarn with the very important value of broken filaments (BFC), especially at higher texturing speeds of more than 1,000 mpm, higher frizz properties (TYT and CCA) and greater color uptake .

Example 2

Table IIB shows that the performance of DTFY decreases as the TMTM content is reduced below approx. 4 MEQ. Example 1 is repeated for the letters S, X, V and Y, except that the concentration of TMTM is changed as shown in Table IIA. No problems arise during the polymer production, polymer transport or spinning, with the exception of the letter Y, where almost 6 MEQ was used, so that the melt viscosity increased and this caused some problems during the spinning.

When the TMTM concentration is increased insignificantly further to

6.3 MEQ, the spinning continuity is so small with some filaments pulling away from the spinning nozzle that this either presupposes a break in the spinning thread line, or the free ends of the filament are reunited with the thread line and carried to the winding. Such free end filaments are very serious defects and cause problems during subsequent texturing and give rough fabric spots. When such fabric is dyed, these "free ends" dye more deeply and give a very serious and undesirable "mottled" appearance to the fabric. At these higher TMTM contents, filament "fall-out" becomes such a serious problem that spinning is called "impossible" due to "melt-fracture". Changes in spinning conditions, generally used to reduce or eliminate "melt fracture" in PET, do not correct the problem with TMTM copolymers where the content is approx. 6.3 MEQ. Similar problems with spinning continuity are found at 5.9 MEQ (letter Y), but filaments can be spun with poor continuity, and thus the values have been measured for letter Y.

Any such yarn is textured on a Barmag M-80, but otherwise as in example 1. Workability was excellent, even at 1,000 mpm. Each textured yarn was evaluated for textured yarn properties and compared to controls E and B spun at 3,200 mpm and 3,660 mpm without TMTM in Table IIB. Spent filaments are much less for the TMTM-containing yarns than for the control, but letter X (containing less than 1 MEQ of TMTM) gave some results bordering on acceptable. TYT mug properties of these yarns are best understood from the graphical representation of TYT versus TMTM content (MEQ) as shown in fig. 2. The preferred concentration is approx.

4 MEQ of TMTM at this extraction rate (3.6 60 mpm).

Example 3

This example shows the spinning of the new yarn at a spinning speed of 3,200 mpm, in the preferred range,

and the change in properties since the TMTM content is varied at this spinning speed, essentially following example 1 with respect to other conditions. At this speed of 3,200 mpm, it has been found that the concentration of TMTM can be increased to levels of 6.3 MEQ and even obtain feed yarn acceptable for drawing texturing. Polymers can be prepared without serious problems at concentrations even higher than approx. 6.3 MEQ, and even up to approx. 8 MEQ. Since the TMTM concentration increases from 3.9 MEQ to approx. 6.3 MEQ, the melt viscosity for the required "Relative Viscosity" increased substantially. However, this increase is easily compensated by the polymer production and spinning at 3,200 mpm at moderate and acceptable increases in temperature. But since TMTM concentration is increased from approx. 6.3 MEQ to approx. 8 MEQ, the melt viscosity increases rapidly for the desired relative viscosity, and I could not compensate for this increase in the melt viscosity by using higher temperatures in the polymer preparation, polymer transport and especially in spinning. Particularly during spinning, the higher melt viscosity rapidly increases the melt fracture in the filaments that are spun, with accompanying defects in the as-spun yarn and gives a very sharp increase in the number of spinning breaks. The usual corrective actions of adjusting spinning temperature, varying capillary dimensions and adjusting cooling do not overcome the problems, especially at a TMTM concentration of approx. 7.9 MEQ and higher.

Table III compares the applied spinning conditions and values of DTFY for the two TMTM chain branched yarns selected for further evaluation and a control without any TMTM. The best found spinning temperature for each polymer is listed in the table. The denier of each feed yarn was set during yarn manufacture to give approximately 150 denier textured yarn.

Each yarn was textured at texturing rates from 750 mpm to 1,050 mpm, divided into 100 mpm intervals, on the FK6-900 as in Example 1, and the results are tabulated. At the lowest texturing speed, BFC is not appreciably better for TMTM chain-branched yarns than for the control. However, as the texturing speed is increased to 850 mpm and above, both TMTM chain branched yarns show a much lower BFC level than the control, which is unacceptable. When the two TMTM branched yarns are compared, the higher level of TMTM chain branched yarn is much better in BFC than the lower level. It is thus clear that when doing optimal DTFY at these lower extraction rates, one must use more TMTM than is desired at a higher extraction rate (Example 2). It is also clear that more optimism is desirable to achieve e-t DTFY at this extraction rate which will yield less than 0.5 BFC. Regarding the crimp values of TYT and CCA, the TMTM cross-linked yarns are also better than the control; these higher mug values give higher volume and a more comfortable grip in the fabric. Again, the higher TMTM chain branched yarn has higher textured yarn curl values than the lower TMTM chain branched . Finally, in terms of color uptake, both TMTM chain branched yarns have higher color uptake than the control and again the one with a higher concentration of TMTM chain branched yarn has a higher color uptake. Significantly better color uniformity is noted at these lower preferred spin speeds, which is in contrast to the preference stated by MacLean which had an entirely different purpose.

As will be understood for a reasoned comparison, the operating conditions must be comparable. E.g. different results have been obtained with the same DTFY on two texturing machines of different types made by the same manufacturer. It is well known that better voluminousness can generally be achieved by expediently increasing the temperature of the (first) heating device during texturing when standard linear polymer such as DTFY is used. By using sufficient amounts of chain branchers according to the invention, I have achieved similar levels of bulkiness and color uniformity (under standard conditions at 129.5°C) at lower texturing temperatures (e.g. about 220°C) that I achieved at higher texturing temperatures (e.g. about 240°C) when using standard linear polymer such as DTFY, and then I have been able to obtain textured yarns that are improved in these respects by using higher texturing temperatures ( such as about 240°C) with the chain branched DTFY on the condition that sufficient chain branchers are used according to the invention.

I believe that if trimethyl trimesate is substituted for trimethyl trimellitate in the examples given above, substantially the same results will be obtained.

Claims (7)

1. Continuous process for the manufacture of polyester drawing texturing feed yarn, comprising the steps of first forming a molten polyester by reaction, in the presence of catalysts therefore, of (a) ethylene glycol with terephthalic acid and/or esters thereof, followed by (b) polycondensation and then melt-spinning the resulting molten polyester into filaments and drawing them at a rate of approx. 3,000 to 4,000 mpm to provide partially oriented yarns of low crystallinity, in which the polyester is modified by introducing into the polymer, as a solution in ethylene glycol, a substance selected from the group consisting of trimesic acid, trimellitic acid or an ester thereof, in an amount approximately as indicated of the line AB in fig. 1 in the accompanying drawings. 2. Method according to claim 1, characterized in that the filaments are extracted at a speed of approx. 3,000-3,200 mpm. 3. Partially oriented polyester multifilament draw texturing feed yarn with low crystallinity, as shown by a "boil-off" shrinkage of approx. 45% and a fracture elongation of approx. 155%, consisting essentially of polymerized ethylene terephthalate residues chain-branched with approx. 6 MEQ of trimesic or trimellitic acid residues, and with a relative viscosity (LRV) of approx. 21. 4. Yarn according to claim 3, but where the "boil-of f" shrinkage is approx. 20-25%, the elongation at break is approx. 133% and trimesic or trimellitic acid residues are in an amount of approx. 4 MEQ. 5. Multifilament drawing texturing feed yarn which has been produced by polymerization of ethylene and terephthalate derivatives with trimesic or trimellitic acid residues acting as chain branchers and by spinning orientation at a drawing speed of approx. 3,000 to 4,000 mpm, and which is suitable to be draw-textured at a speed of at least 1,000 mpm to provide a textured yarn layup unit of not more than approx. 0.5 BFC, and a TYT of over 20. 6. Yarn according to claim 5, characterized in that the filaments are pulled out at a speed of approx. 3,000-3,200 mpm. 7. Process for the production of false-twist textured yarn, in which a multifilament polyester feed yarn is subjected to simultaneous draw-texturing at a speed of at least 500 mpm, the feed yarn consists essentially of polymerized ethylene terephthalate residues and of trimesine or trimellitic acid residues which act as a chain brancher, and the resulting unit packing of textured yarn has no more than approx. 0.5 BFC, and over 20 TYT.