DE1079788B - Process for the production of structures, such as threads or films, from linear polyesters - Google Patents

Description

GERMAN

In the production of shaped structures from linear, high-melting polyesters, in particular made of terephthalic acid polyesters, the polymers are deformed from the melt flow or from the solution. For example, threads are obtained by pressing them out of perforated nozzles and foils by pressing them out of slot nozzles. These shaped structures are drawn off from the nozzles that produce them and placed on spools or rollers or the like. Collected. Then they are in suitable at room temperature or at an elevated temperature Arrangements stretched to a multiple of their original dimensions, giving them a permanent, the high strength of the linear polyester is imparted molecular orientation.

When producing particularly thin shaped structures from linear polyesters, for example thinner Threads, tapes or foils, the economic efficiency of the manufacturing process described above decreases. It is not readily possible with the manufacturing speed beyond a certain point Limit value - with threads usually about 1000 m / min - go beyond, and it must therefore be the Number of production facilities running at the same time - for example the number of spinning positions - be greatly increased.

It is the aim of the invention described below to provide a method for simplified manufacture to indicate thinner formed structures made of linear polyester, in which, by transforming thicker ones, already formed structures into thinner ones, the number of shaping devices per unit of quantity is essential can be reduced. Furthermore, since thicker shaped structures are assumed, more simply constructed and easier-to-use shaping devices are used. Essentially permits such a process that is based on metamorphosis Relatively thick formed structures are based on thinner ones, produced in some way, especially formed thick structures - for example, ribbons, embossed foils or the like - in to convert thin, similarly shaped structures.

The French patent specification 726 031 describes the production of thin threads from thick threads. This is where the completely finished thick threads are used - these are cellulose threads - Softened by heating and pulled out while soft. This procedure prohibits polyesters because of their high melting point. For finished, stretched polyester threads if the melting point is above 250 ° C. Softening heating would cause molecular degradation and severe damage to strength at the same time even after being cooled down again.

The method according to the British patent process for the production of structures, such as threads or foils,
made of linear polyesters

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M., Brüningstr. 45

Dr. Herbert Kurzke and Dr. Helmut Sattler,

Bobingen via Augsburg,
have been named as inventors

695 567 applies the for threads made of linear polyester. Process step of softening by heating and stretching no longer occurs in this state the end product, but rather an intermediate state, namely on the undrawn, freshly spun, not yet molecularly oriented threads. To The process of this patent specification can be freshly formed structures made of linear polyesters at temperatures remains plastic from 20 to 60 ° C above the apparent minimum crystallization temperature stretch to many times their original dimensions without adopting a molecular orientation. The structures, which have been stretched in this way, are then still at temperatures between the Second-order conversion temperature of the polyester and 30 ° C. above its apparent minimum crystallization temperature stretched in the usual way with a permanent molecular orientation imprinted. The apparent minimum crystallization temperature denotes the lowest temperature at which there is substantial crystallization of the polyester begins. It is for most of the high-melting points that are suitable for the production of fibers Polyesters in the region of 100 ° C. The second order transition temperature is that temperature in which discontinuities occur in the dependence of thermodynamic quantities on the temperature. It is generally between 65 and 70 ° C. The permanent, plastic, non-molecular orientational elongation is therefore in this process at temperatures greater than 120 ° C and less than 160 ° C.

The conversion of thick molded structures into thinner ones using the method of the British patent specification 695 567 now has the following disadvantages:

909 770/420

1. The permanent, plastic, non-orienting deformation must be carried out there on freshly formed structures.

2. The plasticizing temperature is between 120 and 160 ° C, ie above 1.00 ° C ₁ and can therefore only be achieved with hot air, with selected liquid baths or with the help of hot contact surfaces. Heating with hot air is not easy to carry out with large amounts of material to be treated at the same time, and neither is contact heating on heated surfaces. When using liquid baths, the removal of the residual bath liquid from the end product creates additional inconveniences.

3. The main disadvantage of the already known conversion process is that it is proportionate low strength of the structures produced by this process. According to the patent mentioned In the examples included, values of up to 2.4 g / den were achieved for threads made of linear polyesters. These strengths are far below those of the normal manufacturing process.

A two step process for reducing the thickness of a molded article made from terephthalic acid polyester is in the French. Patent Specification 1,079,319. After that, slides are split in two oriented in directions perpendicular to one another, to make them the same in all directions to impart physical properties. Both stretching have a molecularly orienting effect and can therefore do not go beyond a certain level, 1: 3.25 according to the French patent specification mentioned. The change in thickness of the film after this process is only as great as that with the production of molded structures made of linear high-melting polyesters always linked molecularly orientational stretching is common.

Quite the opposite of what was known, it has now been found, surprisingly, that shaped as yet undrawn Structures made of linear polyesters change at temperatures between the transition point of the second order and the apparent minimum crystallization point in the presence of water or water vapor as plasticizing medium in at least one direction by a multiple of its original dimensions stretch plastically without molecular orientation. Those remaining after the method of the invention Structures stretched plastically without molecular orientation can then be cold in the usual way or hot-orientated stretching, resulting in end products that have their strength values at least not inferior to those obtained after the normal production process.

From British patent specification 603 842 it is already known that water is the deformation of polyester threads can promote. The cited patent only relates to the stretching process which the molecular chains are oriented. It is new and not previously known that water is in contact at elevated temperature makes the polyester so soft that it can be stretched without Molecular orientation occurs.

The temperature range of the process according to the invention lies between the transition point second order, 70 ° C, and the apparent minimum crystallization point, 100 ° C. It is technically extremely comfortable.

The method according to the invention is thus characterized in that the primarily formed structures at Temperatures between 70 and 100 ° C in the presence 7a of water or steam as a plasticizing medium in at least one direction many times over their original dimensions permanently stretched plastically and then in the usual way stretched in a molecularly orienting manner.

The advantages achieved by the method of the invention over the known one are very important. It is no longer necessary to use freshly formed structures. Rather, structures can also be used stretch plasticizing, which were obtained several months in advance from the shaping facilities. Finally, and this is especially important, the end products exhibit those for ordinary, without Polyester threads obtained by plasticizing stretching have the usual strength, for example for threads one from 5 to 6 g / den.

The process of permanent plastic expansion is determined by the duration of the dwell time in the hot medium. After a sufficiently long dwell time, the plastic expansion takes place without any molecular orientation of the structure. It even gets rid of the peeling from the forming device The resulting molecular pre-orientation of the structure is eliminated or at least considerably reduced.

The limit of the residence time in the plasticizing medium depends on the type and temperature of the Medium and the thickness of the structure. It is, for example, 15 seconds for a polyester thread of 50 the single titer in a water bath at 95 ° C as a plasticizing medium. When the temperature drops of the plasticizing medium, the limit of the residence time for non-orienting expansion increases. Man the temperature of the plasticizing medium is therefore advantageously close to the apparent minimum crystallization temperature Select.

It is also not necessary that the necessary for the actual stretching process, per se very low tensile stress acts on the structure during the entire dwell time. It is sufficient rather, a dwell time in the plasticizing medium without mechanical influence during the expansion at the end of this dwell time can still be carried out quickly in the medium.

The found possibility of converting thick, shaped structures made of linear polyesters into thin ones leads to the following manufacturing processes: B. threads, tapes or foils are formed in the usual manner by appropriate devices, usually nozzles, drawn off from these and optionally wound onto supply spools or rollers. In the further manufacturing process, the structures are placed in water or steam as a plasticizing medium, most simply in water, which can also contain a wetting agent, at a temperature of over 70 ° C _1, preferably 95 ° C, and then after a set residence time several times over their dimensions remain stretched without molecular orientation. This process can be carried out continuously because of the relatively short residence times. The stretched structures are then finally stretched in the manner customary for the production of shaped structures from linear polyesters, cold or hot, with molecular orientation.

The permanent orientation-free expansion in the plasticizing medium can be practically up to any Enlargement of the longitudinal dimension are driven, for example up to 15 times the initial lengths -and ■ more.

The method according to the invention allows manufacture thin, shaped structures made of thicker and

saves shaping facilities compared to the normal production process or leads to the same Number of shaping furnishing to increase the capacity according to the ratio of orientation-free plastic expansion. The shaping facilities can also be essential be made easier, since they only need to produce relatively thick structures. Another An essential advantage of the method according to the invention is that it is much easier to produce thin structures from being ίο special shape, such as B. ribbons, threads, films of varying thickness and the like., Are to be produced. Such Effects can be created relatively easily on thick structures, for example using Langlooh nozzles, while thin structures with such effects can hardly be produced directly. With the plastic one During the conversion process, the special shape of the starting material is retained.

The process of the invention is of practical importance for the processing of the polyterephthalic acid alkylene esters, in particular of polyethylene terephthalate, but can also be used in the same way are used on threads and fabrics made of other high-melting spinnable polyesters, e.g. B. the Polyester of pco-oxy-feutoxy-tienoic acid and the Polyester of oxypivalic acid. Of course, thread-forming polyesters are also included in addition to the main component or components, a minor amount of modifying bifunctional additional components included, like other dicarboxylic acids than terephthalic acid and glycols other than ethylene glycol.

example 1

A non-drawn, monofilament thread with a single titer 50 denier made of polyethylene terephthalate was in a water bath of 95 ° C with a residence time of 20 seconds to the ofache its original length Remaining orientation-free stretched and then cold-orientated to a final titre of 2.0 denier. The total stretching from the starting material was therefore 25 times. The end product had a strength of 5.6 g / den.

Example 2

A non-drawn spun thread made of polyethylene terephthalate with a total titer of 200 denier with 18 individual threads was continuously stretched four times in a water bath at 95 ° C. to remain orientation-free. During spinning or during removal from the spinneret to the thread a pre-orientation was issued, characterized by a birefringence of 3.8 x 10. ³ After the plastic expansion, the birefringence ^{had decreased to 1.5 · 10 -3} , and accordingly the pre-orientation. The stretched thread was cold orientated stretched four times. This gave a polyester silk with the final denier of 12.5 denier with 18 individual threads, that is to say an individual denier of 0.7 denier, with a strength of 6 g / denier.

Claims (1)

Claim: Process for the production of structures, such as threads or films, from polyesters, in which the shaped Structures drawn out to multiples at least in one direction without molecular orientation and then stretched in the same direction in a molecularly orienting manner, characterized in that that the warping is carried out in the presence of water or steam at temperatures of 70 to 100.degree. Considered publications: French patent specification No. 726 031,
1079 319; British Patent No. 603 842. © 909 770/420 4.60