DE1803432A1 - Manufacture of high strength polyamide or polyester - Google Patents

Abstract

Manufacture of high strength polyamide (nylon 66) or polyester yarns by the after-polymerisation of chips of polymer of normal relative viscosity (40-50) to give a polymer of relative viscosity of 80 or more, in which the polymer chips are allowed to fall through an ascending current of hot dry nitrogen directly into a screw extruder, in which they are melted and from which the melt passes via a metering pump to a spinneret to be melt spun in the normal way. Very high tenacity yarns can be produced with constant mechanical properties suitable for use as tyre cord or as reinforcement for high pressure tubing or the like.

Description

"Process and device for the production of high-strength polyamide or polyester yarns "Priority: October 16, 1967 / Italy registration no .: 53369-A / 67 (Italian Patent No. 820,373) The invention relates to a method and a Device for the production of high-strength polyamide and polyester yarns.

As is well known, must for the production of polyamide and polyester yarns highly viscous polymers with good mechanical properties are used, whereby the required high viscosities are not achieved by means of conventional polycondensation can be achieved in the autoclave. Rather, the polymer must be in the solid state in the form of chips with a gas stream, especially superheated steam, Mixtures of water vapor and nitrogen, practically pure nitrogen or carbon dioxide heat treated: Such a treatment is called "post-condensation in solid State ". For example, by post-condensation of 6,6-polyamide chips (6,6-polyamide = polycondensation product from hexamethylenediamine and Adipic acid) with a relative viscosity of 40 to 50 with a polycondensate a relative viscosity of 80 and above.

However, it has been found that the post-condensation by means of superheated Steam is completely useless because the schnitzel is then melted In spinning, the viscosity gradually decreases and the yarn obtained is entirely conventional Properties that are far from the desired high values.

On the other hand, the post-condensation of the schnitzel does not occur once in a nitrogen or carbon dioxide stream using conventional methods to produce results, that one would normally expect. Namely, it was found that the results can be completely different and depend, among other things, on how dio post-condensed Schnitzels are stored before remelting and spinning and how the remelting and the task in the spinning head can be carried out. Particularly The effects of oxygen and the air in the surrounding area seem to be detrimental Atmosphere, even if it only lasts for a short time. Although it turned out that the post-condensation in the nitrogen or carbon dioxide stream does not, like the ii Superheated steam flow achieved can be referred to as "temporary". However, the "Zuverlesiglceitefaktorw not exactly satisfactory with this method, since certain mechanical Properties of the yarns obtained cannot be predicted within acceptable tolerances permit. It follows that the problem of Production see B. of tire cord or reinforcement threads with consistent quality for hoses for hydraulic fluids can not be solved reliably.

The present invention therefore aims primarily to provide a method and make a device available, by means of which high-strength polyamide and polyester yarns with predetermined constant mechanical properties can be reliably manufactured. Other purposes and advantages of the present invention are described below.

The invention thus provides a method for producing High-strength polyamide and polyester yarns through post-condensation of the prepolymers in the solid state in a hot stream of nitrogen or carbon dioxide and melt spinning the mass, which is characterized in that it is the prepolymer in the form a descending column of cookies or chips in hot nitrogen or Feeds carbon dioxide stream into a screw extruder and the post-polymer with With the help of the screw extruder, which feeds a metering pump of a spinneret, spins.

An embodiment of the device for carrying out the invention Method is explained with reference to the drawing in the diagram.

The spinning head 10 is via the screw extruder 14, in which the polymer chips are melted, and a metering pump 12 is supplied with the melted polymer.

A filling funnel 19 is arranged at the top of the post-condensation tower 18 The bottom of the tower is gastight at 17 to the feed hopper 16 of the extruder 14 flanged. A double-walled tower is used, the two walls of which have a heating jacket 20th form, which has an inlet 22 and an outlet 21 for a heating medium, such as water vapor, Is provided 0 Inside the heating jacket 20 eats a pipe sole length 23 coaxially to the Tower arranged so that a heat exchange between the through the heating jacket or media flowing through the coil takes place 0 The upper end 24 of the coil is connected to the storage tank for that gas (nitrogen or carbon dioxide), with which the Naohkon.densation is carried out 0 The lower end 25 of the pipe coil 23 has a nozzle on the tower sump, which in an axial direction upwards into the tower opens and through which the gas preheated in the coil 23 into the interior 26 of the tower in countercurrent to the polymer chips flowing down through the tower is directed. To improve the heat exchange and the trickling down of the schnitzel For example, a suitable stirrer (not shown) can be arranged in the interior 26 of the tower.

The tower 18 can also be heated in other ways than shown, e.g. Devices are replaced and the gas directed to the nozzle 25 can be separated by means of be heated in a self-contained facility, provided, of course, that the temperature inside the tower can be adjusted to the desired value can, In the borderline case, the heating jacket 20 can become an insulating cladding, if the proportion of the total amount of heat supplied via the heating jacket for heating the amount of heat required inside the tower decreases; this is the gas supply above the nozzle 25 is increased accordingly, so that it alone supplies the heat for heating the Polymerisatsohnitzel inside the tower takes over the post-condensation temperature.

When the system is in operation, dry nitrogen is produced through the nozzle 25 or dry carbon dioxide supplied at high temperature, the temperature in the tower and the dwell time of the schnitzel in the tower in a manner known per se be set that the desired degree of polycondensation of the initiated in the tower Polymers is obtained. When using 6,6-polyamide or polyethylene terephthalate the temperature of the gas stream is 140 to 250 ° C, preferably 180 to 24,000, but in any case less than the melting temperature of the polymer. It understands of itself that the heating jacket 10 has substantially the same temperature.

The degree of polycondensation is generally determined by a polyamide the relative viscosity and, in the case of a polyester, the intrinsic molar viscosity expressed. For 6,6 polyamide the initial maximum relative viscosity is the polymer chips fed into the hopper 19 are about 40 to 50, in the case of polyethylene terephthalate, the initial maximum intrinsic molar viscosity is about 0.68 to 0.70.

The values given here for the relative viscosity were obtained using obtained an Ostwald viscometer at 25 ° C and denote the outflow time of a 8.4% by weight solution of the polymer in 90% formic acid, based on the outflow time of the pure solvent.

The values for the intrinsic viscosity were represented by a diagram obtained, in dom the concentration plotted against aie relative viscosity at 2500 using o-chlorophenol as a solvent.

In the device according to the invention, the number of revolutions of the extruder screw is 14 and the task of the schnitzel in the filling funnel 15 tailored to the required Dwell time of the Schnl4.zel in. Tower 18. For this purpose, the metering device 28 for the chips and the extruder screw, expediently by means of a device 30 coupled, whereby the Eüilhöhe of the tower 18 to the different working speeds of the extruder 14 can be set and the selected filling level throughout Spinning process is maintained.

When the schnitzel reaches the desired degree of polycondensation they trickle through the tower into the extruder via the feed hopper 16 and are melted and spun immediately without interruption. The dry, hot Gas that is blown upwards by means of the nozzle 25 not only causes post-condensation the schnitzel but also reduces the moisture content to the usual desired Value, makes special measures for degassing the extruder 14 superfluous and creates automatically a protective atmosphere. inside the extruder where the polycondensate is melted Consequently, there is no stage of treatment between the task of Schnitzel in the tower 18 and the spinning of the polycondensate by means of the spinning head 10 that is not under the control of the operator. It should also be noted that the pressure of the gas injected through the nozzle 25 is not critical is; However, the method is preferably carried out with the hopper 19 is freely open to the outside0 In the examples below, a device of the type shown in the drawing is used. The tower 18 had a length of 3 400 mm and a diameter of 127 mm and is heated with saturated steam. The screw of the extruder 14 has a diameter of 45 μm and its length is 24 times the diameter. The nitrogen blown through the nozzle 25 has in all cases an oxygen content of less than 2 parts by weight per million. on.

The tensile strength is in g / den (based on the original titer) and the elongation at break expressed in% and are measured using the SCOTT Mod IP-4 determined, whereby the load is increased in constant steps. The yarn is 24 hours in an atmosphere with a temperature of 240C and a relative Humidity of 72% conditioned. The length of the sample is 200 mm inclusive of the sections that lie on the clamping plates.

Example 1 There are 6,6-polyamide chips with a relative viscosity of 45 and a moisture content of 0.6% by weight is used to 220 ° C. Through the nozzle 25, 0.5 Nm3220 ° C. is achieved per kilogram of polymer hot @ dry nitrogen supplied. The dwell time of the schnitzel in tower 18 is 3 hours.

Pulled off the tower sump during operation of the device rehearse have a relative viscosity of 88 and a moisture content of 0.02 o / on. The molten mass obtained in the extruder 14 is passed through the spinning nozzle 10 pressed with 140 openings. The thread bundle obtained is made by means of a drawing pin and a heated platen of 18,000 at a speed of 280 m / min. and stretched in a stretching ratio of 5.20 t 1. A thread yarn is obtained with a total denier of 840 denier that has a relative viscosity of 86, a tensile strength of 9.4 g / den and an elongation at break of 18.5%.

Example 2 The experiment of Example 1 is repeated, however instead of dry nitrogen, superheated steam with a temperature of 2200C used, the through the nozzle 25 in a Xenge of 1.6 kg / kg polymer 0 Samples withdrawn from the tower sump during operation of the device have a relative viscosity of 62.5 and a moisture content of 0.15 % on.

All the end product is a 140-ply yarn with a total denier of 840 denier and a relative viscosity of only 48.9, a tensile strength of 8.6 g / denier and a gross elongation of 16%.

Example 3 The experiment of Example 1 is repeated, but is the temperature 210 ° C. Removed during operation of the device sm the tower sump Schnitzel have a relative viscosity of 70 and a moisture content of 0R025 wt% aut0 The end product obtained is a 140-thread yarn with a total denier of 840 denier, a relative viscosity of 69.2, a tensile strength of 9.2 g / denier and an elongation at break of 18.3% o Example 4 6,6-polyamide chips with similar properties as in the previous examples, tower 18 treated with dry nitrogen of 22,000 in an amount of 0.18 Nm3 / kg of polymer. The residence time is 2.25 hours.

The samples taken from the tower sump have a relative viscosity of 68.1 and a moisture content of 0.03%. The end product is obtained a 140-thread yarn with a total denier of 840 denier with a relative viscosity of 67.3, a tensile strength of 9.3 g / den and an elongation at break of 18.3%.

Example 5 The apparatus used in the previous examples is operated with polyethylene terephthalate, which means 0.05 wt .-% titanium dioxide was matted and had an intrinsic viscosity of 0.679 and a moisture content of 0.015 s. The tower 18 is operated at a temperature of 22,000 and a nitrogen stream is used in an amount of 1 Nm3 / kg polymer. The residence time is 4 hours.

The polymer melted in the extruder 14 is passed through a spinneret with 192, openings extruded the thread bundle obtained is heated by means of a Stretching pin of 90 ° C and a heated platen of 18000 at one speed from 150 m / min. stretched. The draw ratio is 5.2 : 1.

Those withdrawn from the tower sump during operation of the device Samples have an intrinsic viscosity of 0.763 and a moisture content of less than 0.005%. The thread yarn obtained (total denier 1,000 denier) has an intrinsic viscosity of 0.745, a tensile strength of 8.3 g / den and a Bruohdehnung from 12 91 to, Example 6 The procedure of Example 5 is repeated, however, the amount of nitrogen is increased to 5 m3 / kg of polymer and the residence time 10 hours increased.

Those withdrawn from the tower sump during operation of the device Samples have an intrinsic viscosity of 0.925 and a moisture content of less than 0.005%. The thread yarn obtained (total denier 1,000 denier) has an intrinsic viscosity of 0.910, a tensile strength of 9 g / den and an elongation at break of 12%.

Example 7 Schnitzel aue poly - # - caprolactam with a relative Viako appearance clay 40, an aomer content of 0.2% and a moisture content of 0.3% by weight are in the device according to the invention with dry nitrogen at 200 ° C treated, which is fed in an amount of 0.35 Nm3 / kg polymer. The dwell time is 3 hours

The relative viscosity and moisture content of the during the Operations of samples withdrawn from the tower sump is 70 br, 0.02%.

Dae in the extruder 14 geachmolzene polymer is through a Spinneret extruded with 140 openings and treated as in Example 1. A yarn is obtained with a total titer of 840 den, a relative viscosity of 69.3, a draw strength of n15 g / den and an elongation at break of 17 0 Example 8 To the "reliability factor" To determine the method according to the invention, the procedure is as follows: After Example 1, 3 and 4 each produce a total of 150 kg of yarn, a sample is drawn after every 10 kg of yarn and its relative viscosity is determined will. For each 15 viscosity values obtained in this way, the average value becomes and the coefficient of variation achieved. The results are shown in the table below given table I example avg. relat. Viscosity coefficient of variation i @ nt coefficient,% "1 87.0 0.31" 3 69.6 0.33 "4 67w1 0.34 Beyond that, schnitzel the same type of polymer in tower 18 under the same conditions as in example 1, 3 and 4 are post-condensed up to a total amount of 200 kg each, however in these tests, hereinafter referred to as tests A, B and C, the post-condensate discharged from the tower sump was not melted and spun immediately, but removed and stored for different periods of time, after storage the post-condensate is made by means of the extruder 14, the pump 12 and the spinning head 10, as described in Example 1, melted or spun and drawn, a total of 150 kg of yarn is used for each experiment The measured values for the relative viscosity (which are similar to those in Table I) are given in Table II below, Table II Experiment Average relative viscosity coefficient of variation,% A 81.9 2.23 B 64.1 3.38 is a 63.4 3.06 Taking the results of Table II with indentations from Table I compares, one will immediately find that the averages for the relative Viscosity are much lower than that in Table I, in addition, the The coefficients of variation given in Table II are incomparably higher than those in Table From this it is clear that a yarn can produce whose relative viscosity is higher and where the relative viscosity remains essentially constant.

Claims (4)

P a t e n t a n s p r ü c h e 1. Process for the production of high strength Polyamide and polyester yarns through post-condensation of the prepolymers in solid State in hot nitrogen or carbon dioxide stream and melt spinning of the mass, characterized in that the prepolymer is in the form of a descending column from placeholes or chips in a hot stream of nitrogen or carbon dioxide into one The screw extruder and the post-polymerizate with the help of the screw extruder, who feeds a metering pump of a spinneret, spins 20 device for implementation of the method according to claim 1, consisting of a spinning head and a dosing pump, which is fed by a screw extruder, by gekennzeichn @ t that the post-condensate the son corner extruder (14) directly by means of a vertical post-condensation tower (18) is supplied, in the interior (26) of which at least one nozzle (25) is arranged through which the hot gas flows in 3. Device according to claim 27, characterized in that that the tower (18) has a heating jacket (20) in which a pipe coil (23) is arranged through which the gas flows to the nozzle (25) and which in heat exchange with the heating medium flowing through the heating jacket (20). 4. Apparatus according to claim 29, characterized in that the tower (18) is provided with an insulating cladding and the gas is separated by means of a self-contained device is heated0