EP0173200A2 - High-strength filaments for a sewng-yarn, and process for manufacturing those filaments - Google Patents

Abstract

1. A multifilament feed yarn from filament-forming polyesters for preparing high-strength multiply sewing yarns, which has a heat shrinkage S200 of 5 to 7 % and a reference extension (D45 ) at 45 cH/tex of less than 10 % and wherein the filament-forming polyester has a high average molecular weight corresponding to a relative solution viscosity (1.0 g of polymer in 100 ml of dichloroacetic acid at 258C) of more than 2.0.

Description

The present invention relates to high-strength multifilament polyester supply threads for the production of sewing threads and a method for their manufacture.

Sewing threads are to be understood in this patent as sewing threads. For the production of these threads with a corresponding machine, supply threads are required, which in the present case should consist of endless polyester threads. Sewing threads of this type must have high strength, be easy to sew, provide good seam strength and be low-shrinkage in order to prevent the seams from warping during washing or during thermal treatment.

From German Auslegeschrift 1 288 734 it can be seen that for the production of high-strength yarns, the spinning conditions must be selected so that the tensions acting on the solidifying thread are unusually low and the spun thread produced has only a very slight pre-orientation, for example a birefringence of equals less than 0.003. Spinning take-off speeds of 600 to 800 m / min have proven themselves in this connection.

These low delivery rates per spinneret are unsatisfactory. The obvious measure of increasing the throughput per nozzle by increasing the spinning take-off speed, as is shown, for example, in FIG. 1 of German Offenlegungsschrift 2 207 849, does not lead to success, since all attempts to produce high-strength yarns by fast spinning have low strength and the high elongation of such threads failed. The textile values manufactured in this way threads can already be found in US Pat. No. 2,604,667.

A method is described in German Auslegeschrift 22 54 998, in which the freshly spun threads are first to be fanned and twisted and only then to the stretched cord thread obtained. The application of a twisted cord before stretching is relatively complex, but particularly prone to failure. For these reasons, the method has probably not gained any practical importance.

An attempt to produce high-strength polyester yarns by rapid spinning is described in Japanese Laid-Open Application 51-53019. The birefringence of the supply yarn should be greater than 0.030, the drawing should be at least 70% of the maximum possible drawing ratio. This process uses a shrinking stage with up to 11% shrinkage approval. The yarns produced in this way have a high tensile strength with values of up to 7.0 g / den, their hot air shrinkage at 150 ° C. is between 0.8 and 2.7% in the examples. Despite these generally favorable textile technology data, sewing threads made from them do not have satisfactory sewing properties. This is particularly evident in the small sewing lengths of such sewing threads. It is suspected that the disadvantages of the polyester yarns described in Japanese Patent Application Laid-Open No. 51-53019 could be based at least in part on the low molecular weight of these yarns. However, the use of thread-forming polyesters with a relatively low molecular weight is widespread in the production of high-strength yarns, since polyesters with a higher average molecular weight should have a lower modulus of elasticity and, in particular, high shrinkage values. This dependency is mentioned, for example, in the German interpretation 23 32 720, column 2, lines 41 to 46.

There was therefore still the task of producing high-strength polyester supply yarns which had a hot air shrinkage of 5 to 7% at a temperature of 200 ° C. and which could be processed into sewing yarns with excellent sewing properties. In addition, these supply threads should have the highest possible strength.

It has now been found that such supply threads are obtained in a modified rapid spinning process if, contrary to the teaching of the prior art, thread-forming polyesters are used which have a high average molecular weight corresponding to a high relative viscosity of over 2.0. The relative viscosity is determined on solutions of 1 g of polymer in 100 ml of dichloroacetic acid at 25 ° C. with the aid of capillary viscometers. It is surprising that such rapidly spun threads with a high molecular weight are suitable at all for the production of sewing threads. By increasing the spinning speed or the winding speed and the associated preorientation of the threads reduce the strength of the threads obtained even after a corresponding additional drawing, as was already to be expected according to the teaching of German designation 12 88 734. Surprisingly, however, such supply threads with significantly reduced tensile strength show after Twisting process and a corresponding dyeing a smaller decrease in strength, the substance utilization of the dyed thread is much better than with corresponding twists made of slowly spun material, but in particular the threads according to the invention show their processing into a sewing thread an unexpected high seam strength and an unexpectedly improved processing ability. The so-called sewing length is used as a measure.

The process according to the invention consists of high-speed spinning of high molecular weight polyester, whereby measures known per se, such as, for example, nozzle heating, are intended to minimize the molecular weight degradation during the spinning process. The fixing temperature of 225'C and below allows the production of the yarns according to the invention on conventional stretching devices. The draw ratio must of course be adapted to the higher pre-orientation of the supply yarns. The advantages which can be achieved when using the supply threads according to the invention are best illustrated in the examples. Various supply threads were used there and processed into sewing threads by twisting. The mean molecular weight of the thread-forming polyester and the pre-orientation or winding speed of the threads during spinning were varied. In this description, the birefringence of the threads serves as a measure of the pre-orientation. The reference elongation (D ₄₅ ), ie the elongation _/ which is measured at 45 cN / tex, is a measure of the elasticity of the threads. In contrast to the initial module, the reference elongation is also influenced by the possible presence of a "shrink saddle" in the force-elongation diagram (KD diagram). The KD diagram shows a greater or lesser degree of elongation of the material in the case of thermo-mechanically shrunk threads after a usual steep increase even with relatively low tensile stresses. Only at higher elongation values does the curve continue to rise and then end at possibly similar values to the corresponding but unshrunk material. In the case of a shrunk material, however, the elongation at break is also significantly higher. The hot air shrink S ₂₀₀ or S ₁₈₀ was determined according to DIN 53866 at temperatures of 200 or 180 ° C.

The proximity properties were determined using a specially developed test method, for which patent protection is sought in the same day's application. A sewing test with the help of an industrial sewing machine under standardized conditions served as the measured variable. The suitability of a sewing thread can be concluded from the length of the seam produced. An industrial sewing machine from Pfaff was used with a Nm 90 needle, sewing was done with a double lockstitch with 5 stitches per centimeter and normally a sewing speed of 4000 stitches per minute. The thread tension of the upper thread is 175 to 180 cN, the lower thread consists of a good sewing thread made of cotton. The tension of the lower thread is adjusted so that the loops in the material disappear (perfect seam appearance). A 5-ply layer of cotton twill with a basis weight of 185 g / m ² is sewn, which has 95 warp and 50 weft threads per centimeter. A standard fabric for work suits from Nadler & Sohn, Augsburg, item no. 13960-80 / 2, dark-colored construction was dyed and sanforized. The measured value "sewing length" indicates the length of the seam in centimeters until the thread breaks and is an average of 10 sewing attempts per test spool. The test process is interrupted if a sewing length greater than 1000 cm is found during a measurement, since experience has shown that sewing lengths over 1000 cm can in any case be described as very good sewing behavior.

The requirements for the sewing test can be made more difficult. The above-mentioned conditions are met in the difficult sewing test, but with a thread tension the upper thread of 220 cN worked and with a stitch count of 5000 stitches / minute.

Seam strength is another parameter for assessing the properties of sewing threads. It is determined by using an industrial sewing machine e.g. from the Pfaff company. Machine setting: lockstitch 5 stitches per centimeter seam length, 4000 stitches / minute. The upper and lower threads are the same in this test and consist of the sample. The thread tension is optimally adjusted for a good seam appearance, a double layer of cotton twill is sewn. The same material that was used for the sewing length determination was used as the cotton twill. The seam strength is the maximum tensile strength of a 5 cm wide strip. This pulling force is determined in a pulling device with a working speed of 10 cm per minute. The value found is converted to the individual thread.

Also suitable for characterizing the properties of sewing threads is the so-called "knife abrasion number", which was determined using a modified abrasion tester from Zweigle with the designation G 550 S, the rotating test specimen having a hard metal profile abrasion bar. For each measurement, 20 thread loops are placed on the device and each loaded with a weight such that the thread tension is 0.135 cN / dtex. The number of scrubbing tours is determined, which is necessary until one of the 20 test loops used is worn through.

The following examples are intended to explain the invention further. Unless stated otherwise, percentages and parts refer to amounts by weight.

Examples

The threads were spun out by melting suitable polyethylene terephthalate materials in an extruder (whereby when using highly viscous polyester materials the spin pack temperature was kept at 290 ^* C, but the die temperature was kept at 315 ^* C. In contrast, spinning with a lower viscosity was carried out with a spin pack and Nozzle temperature of 295 ° C. In each case, nozzles with 32 holes were used After the threads had cooled in the spinning shaft, the threads were wound up at 800 or 1000 or, according to the invention, at 3000 m per minute, for example.

The spinning bobbins obtained were then presented to so-called three-pallet machines, for example an SZ 26 from Barmag. The threads are drawn off from the spinning bobbin and heated to the drawing temperature of usually 87 ° C. on a first godet, which is looped 6 times, for example, and then passed on to a second heated godet, which is heated to the fixing temperature. The stretching takes place between the first and second godets. The draw ratio used depends on the pre-orientation of the filaments. It is detailed in the table below. After the fixing godet, which the yarn rotates 10 times, for example, the thread is passed onto a third godet, which is usually not heated. The thread material can be relaxed between the second and third godets. The stretched threads are then wound onto cops. The thread material received only a protective twist of about 10 turns per meter under these conditions. Working speed when using SZ 26 machines 610 m / min. The thread material thus obtained represents the supply threads for the production of a sewing thread. The supply threads must be rewound on supply spools. They are then submitted to a LEZZENI twine-type twister type TBR to test their properties. This machine operated at a speed of 10 m / min and produced a triple thread of 138 dtex f 32 S 840 x 3 Z 540. The threads obtained were subjected to HT dyeing at 135 ° C. for 120 minutes. The dyed thread was then examined for its textile properties and in particular its suitability as a sewing thread. The measured values obtained are shown in the table below.

Aus der Tabelle der Beispiele ist zu entnehmen, daß die erfindungsgemäß hergestellten Zulieferfäden des Beispiels 1 eine deutlich geringere Festigkeit aufweisen als die nach dem Stande der Technik, d.h. insbesondere nach Beispiel 3. Aber nicht nur die Festigkeitswerte der Zulieferfäden, sondern auch die daraus hergestellten Zwirne nach der Färbung zeigen noch eine geringere Feinheitsfestigkeit als der Stand der Technik. Auffallend ist allerdings, daß bei den erfindungsgemäßen Fäden die Abnahme der Festigkeitswerte geringer ist als nach dem Stand der Technik. Dies wird besonders deutlich bei Betrachtung der Substanzausnutzung, die sich wie folgt errechnet:

From the table of examples it can be seen that the supply threads of Example 1 produced according to the invention have a significantly lower strength than that according to the prior art, ie in particular according to Example 3. But not only the strength values of the supply threads, but also the threads produced therefrom after dyeing show a lower tenacity than the prior art. It is striking, however, that the decrease in the strength values of the threads according to the invention is less than according to the prior art. This becomes particularly clear when considering the substance utilization, which is calculated as follows:

The difference in substance utilization of 97% for threads according to the invention compared to 88% according to the prior art is remarkable. It is even more astonishing, however, that the sewing threads produced from the supply threads according to the invention have better seam strength, but in particular a significantly improved sewing length, particularly under difficult conditions. This surprising improved serviceability was in no way to be expected, in particular it could not be derived from the values of the supply threads or the physical values of the sewing threads produced therefrom.

Claims (4)

1. Multi File supplier filaments of fiber-forming polyesters for preparing high-strength, twisted threads, characterized in that the supply yarns that a heat shrinkage S ₂₀₀ of 5 to 7% at a Bezugsdeh- _nu ng _(D45) at ₄₅ cN / _t ex of less than 10% and the thread-forming polyester has a high average molecular weight corresponding to a relative solution viscosity (1.0 g of polymer in 100 ml of dichloroacetic acid at 25 ° C.) of more than 2.0. 2. Supplying threads according to claim 1, characterized in that the thread-forming substance consists of polyethylene terephthalate or a copolymer of polyethylene terephthalate with up to ₅ % by weight of copolymer building blocks. 3. A process for the production of supply threads according to one of the preceding claims, characterized in that a high molecular thread-forming polyester is melt-spun according to known methods with the lowest possible molecular weight reduction so that the threads obtained still have a relative solution viscosity of more than 2.0, The threads are given a pre-orientation due to high winding speeds, which corresponds to a birefringence of more than 0.030 and the multifilament threads obtained are stretched and fixed at temperatures up to 225 ^° C. 4. The method according to claim 3, characterized in that the stretching and fixing of the multifilament threads is carried out on a godet machine with heatable godets.