DE2039093B2 - Process for converting the unstable tetragonal crystal modification II into the stable hexagonal crystal modification in molded bodies made of isotactic polybutene- (l) - Google Patents

Description

further external compressive and tensile stresses is about 50 hours, it is below that according to the invention Conditions depending on temperature and stretching only a few seconds to minutes. Hence lets through a post-processing stretching process, e.g. in the production of Pipes, make modification I directly from modification II, which then immediately produces the desired has optimal physical and technical values such as module, strength and dimensional stability.

In addition, the present invention provides
a valuable lesson for technical action, there
it allows it, depending on the type of molded body, its
Stretchability, the time available up to winding and the possible cooling before grooving after the action of the mechanical tension has set the technically optimal process parameters or stretching, can be largely freely combined with differential meters.

Surprisingly, it has been shown that - compared with the prior art - by no means high elongations are required in order to achieve a high degree of conversion II to I in a very short time or to achieve a high conversion speed.

Rather, even with small elongations of up to 50%, preferably from 5 to 30%, a niche load of 50%> of modification II have converted into the more than 50 percent conversion within modification I. In table 1 Reach 5 minutes. The prerequisite for this is only

Stretch sion in a separate operation by z. B. clamped on one side and stretches with a pulling device. It is also possible to inflate the tubes biaxially.

In the manufacture of plates, for example, the thick film emerging from the extruder is left behind of modification II for further stretching over different fast running defined tempered Rollers run.

To explain these relationships, it makes sense to introduce a characteristic elongation in which a certain proportion of modification II has passed into modification I within 5 minutes. The degree of conversion from II to I, which is 5

thermoanalytically, radiographically or by means of determine a density determination.

Example 1 The 50% value elongation

The 50 _{% elongation ε 05} is defined as the elongation in% at which 5 minutes after the mechanical

Lich that the stretching process at temperatures below 50 ^c C, for example between +30 and -30 ⁰ C, preferably between +30 and 0 ° C, is carried out.

Polybutene- (I) is understood to be one which polymerizes with catalysts of the Ziegler-Natta type and its tacticity is so high that it can crystallize. For example, a is suitable Polybutene- (l) a tacticity with which one can obtain degrees of crystallization > 10% can reach. The polybutene (l) can contain low-molecular substances such as conventional plasticizers (e.g. butyl stearate) or low-molecular substances Polyolefins (polyethylene, polypropylene) with molecular weights of about 300 to 3000 also contain Pigments or dyes and similar additives that are common with thermoplastics. It can also (up to 50 percent by weight) other high molecular weight substances, e.g. B. polypropylene with molecular weights above 10,000 contain without the conversion according to the invention is disturbed.

Shaped bodies are understood as meaning those end or intermediate products that can be obtained without significant Allow to stretch impairment of their usability, for example profiles of all kinds, hoses, Tubes, plates and films.

The invention is explained in more detail in the following description.

the values for ε _{0 5} for seven different temperatures between -30 and + 50 ⁰ C are shown.

Polybutene- (l) used: Reduced specific viscosity 3.82 deciliter / gram, c = 0.1 gram / Deciliter decahydronaphthalene, 135 ° C: ether extract = 0.67%; Degree of crystallization of modification I: 0.35.

Table 1

50 ^o / o elongation _{£ ()} . temperature • / 0 (Elongation at the 50 ⁰ O ( ⁰ C) the Mod. H are converted) 50 50 25th 14th 7th 11 0 5 O 7.5 -15 10 -30 11

As you can see, one must at 5O ⁰ C stretch even by 50%> the PoIybuten- (l) to within 5 minutes of a 50 percent conversion of II

The stretching of modification II of polybutene- (l) 55 according to I. On the other hand, you need can be done in several ways and depends on lower temperatures, especially below

even only 5 ° / o (minimum) to 50% of the modification to convert from about 30 ° C, only elongations under 15%, at 0 ⁰ C II. These expansions are so small that they can be easily implemented technically and, in particular, do not produce any disruptive anisotropy effects in the material. It must also be mentioned that at temperatures above 50 ° C., in addition to the high elongations required

also be rollers running at different speeds, over 65 for II-to-I conversion no uniform result the plastic part is pulled. Stretching can be achieved, since the

One can also - especially with larger di- material constricting locally (so-called cold-stretched dimensions Pipes - the pipes after extrusion).

depends on which items are to be crafted. For example, when making Profiles, hoses or pipes through the corresponding extrudates immediately after the extrusion Stretch the pull-off devices until the desired elongations and the associated modification conversion is reached. The pull-off devices can be commercially available pullers or

Example 2

The 90% value calculation

In practice, depending on the type of manufacturing conditions, it may be more sensible to use, _{for example, the 90% value elongation £ 0 g instead of the 50% value elongation.} ε _{0 9} is the elongation in% at which 90% of modification II is converted into modification I within 5 minutes. Table 2 gives f _O9 values for various temperatures between -30 and + 7 ° C.

The polybutene- (I) used is the same as in Example I.

Table 2

90 »/« - value expansion _{8 <t} . temperature % (Elongation at which 90 ° / o ( ⁰ C) of Mod. II are converted) -30 23 -15 22nd -6 32 0 37 7th 50

Naturally, the 90% value elongations are greater than the 50% value elongations at the same temperatures. The influence of temperature can again be clearly seen. The minimum of 90% -Wertsdehnung is shifted compared to 5O ° / o value of elongation at lower temperatures and the expansion process is approximately -15 ° C. To achieve a practically instantaneous 90prozentrigen conversion should therefore be approximately between +10 and - 20 ⁰ C take place.

Above 50 ° C and below - 30 ⁰ C is a drawing for the aforementioned Einschnürerscheinungen not useful.

Example 3

Hoses and pipes made of plastics are often placed on drums immediately after extrusion wound up and stored. In the case of polybutene- (I), difficulties arise in this process in that the tube is rolled up in the course

ίο converts to modification I from 5 to 7 days. As a result of this transformation, the pipe is later difficult to unwind and it arises difficult to handle, rigid »helix«. The spiral formation can be avoided if the

Pipes stretched before winding. Thus, 15 m long tubes of 1.5 "/" carbon black filled polybutene (l) (reduced specific viscosity of 4.4 deciliters / gram, c = 0.1 grams / deciliter decahydronaphthalene, 135 ⁰ C; degree of crystallization of the

Mod. I: 0.33) stretched by 14% immediately after extrusion at 8 and 22 ° C with a chain hoist. The undrawn pipe still consists of more than 95% of the 15 minutes after the extrusion Modification II. The pipes stretched at 8 and 22 ° C. are 80 minutes after extrusion or 50% converted into modification I.

The stretched tubes are then wound up together with an undrawn tube and unrolled again after 14 days of storage to determine the spiral formation. With the 8 and 22 ° C stretched pipes, the helix formation is negligibly small, i.e. H. of the same Order of magnitude, as is usually the case with other plastics such as polyvinyl chloride, polyethylene or polypropylene also occurs and does not have a disruptive effect. The unstretched tube, however, can Do not lay in a straight pipe after unwinding.

Claims (3)

1 2 Now it is known that the modification patent claims: Conversion of polybutene- (l) from II to I can be accelerated by referring to modification II 1. Process for converting the unstable tensile stresses can act; through 200- to tetragonal crystal modification II in the stable 5,300 percent elongation at room temperature hexagonal crystal modification I with shaped body modification II quickly changes into modification I. pern, especially in extruded form (J. Makromol. Sci. B, Physics 1, 1967, p. 309 bis bodies, made of isotactic polybutene- (l) under 334). Exposure of mechanical tensile stresses to US Pat. No. 3,468,862 teaches that extruded, Strain, characterized in that io-quenched films of polybutene-1 in one or Temperadie molded body at temperatures below doors 25-110 ⁰ C to 150 ⁰ C to about 50 multiaxially overall by up to 50% mono- or biaxially 700% under training to be stretched. Modification I stretched to the physical 2. The method according to claim 1, characterized by verker.nzeich properties and the clarity of the films, that the moldings improve at temperature. ratures between +30 and -30 ⁰ C stretched Meanwhile, elongations and deformations of will. 200 to 300% in practice to achieve one 3. The method according to claim 1 and 2, characterized in that rapid modification conversion in general, that the moldings are undesirable and disadvantageous at temperature and, moreover, technically stretched between - ¹ - 30 and ^{0 0} C are difficult to achieve, especially if the. large-sized parts such as hoses, pipes or Panels made of polybutene (l) stretched or deformed should be. Also, by the high Strains strong anisotropy effects occur that 25 has a negative impact on the mechanical properties The invention relates to a method for converting. It is therefore desirable to have a technical realization the unstable tetragonal crystal modification to create severe conditions under which in short 11 into the stable hexagonal crystal modification I at no time "a high degree of conversion of II Molded bodies, especially extruded according to I, is achieved. Molded bodies made of isotactic polybutene- (l) under 30 From US Pat. No. 2,920,352 it is known to have a Effect of mechanical tensile stresses through film made of amorphous polyethylene terephthalate, whose Strain. Middle part is stronger than the outer zone, at 80 bi. Polybutene- (l) is known to stretch various Kn- 90 ° C uniform thickness, with stall modifications (J. Appl. Phys., Vol. 35, No. 11, at the same time by aligning a molecular November 1964, pp. 3241 to 3248) . Solidification occurs from the melting orientation; the acceleration, ie after granulation and in particular the reduction of a crystal transformation in another after thermoplastic processing, the substance is initially formed by slight stretching at lower temperatures, modification II, which cannot be deduced from this at room temperatures. Ullmanns temperature and without the influence of mechanical tension Encyklopadie der technischen Chemie, Vol. 14, 1963, changes to stable modifications in about 5 to 7 days, p. 179 and 180, only teaches in general that cation I is rearranged. The tetragonal modification II, the rate of conversion of form II into that of polybutene- (l), has poor mechanical form I in the case of isotactic polybutene-1 due to me properties and, for example, can increase mechanical stress at room temperature and that the flow strength of only 30 to 40 kp / cm ² compared to thermal pretreatment and the crystal ^{orientation-200 kp / cm 2 of} the hexagonal modification I. 4.5 influence on the properties of the substance. This means that especially large-sized Saechtling-Zebrowski, plastic molded parts, obtained from polybutene- (l), Taschenbuch, Munich, 1967, pp. 180 and 181, so within the first time practically not mechanically like Kunststoffe, Vol. 55, H. 11, 1965, pp. 822 to 827, claimed, in some cases not even go beyond this general state of the art are not stored, transported or processed further and leave the influence of temperature on can. the crystal transformation brought about by elongation This disadvantage can be avoided by keeping the technical meaning completely open,
Semifinished product solidified from the melt within the object of the invention is to provide a 30 minutes after cooling to indicate the final procedure, which is under technical custom form cold deformed and then 0.5 to 55 bar conditions high conversion speed 12 hours without the action of major forces, d. H. high degree of conversion from II to I, the molding stores (FR-PS 1595010); in cases, scored. in which this mode of operation is not possible, this object is achieved according to the invention the modification conversion is solved by adding the moldings at temperatures to polybutene- (l) considerably accelerate 60 to 50 ° C uniaxially or multi-axis by up to 50% (DT-OS 1 938 913). be stretched. However, it is sometimes associated with difficulties. The advantages achieved with the invention exist the, the shaped body after its production in the in the practically momentarily produced crystal structure final Form to be stored force-free, e.g. if the unstable modification II is rearranged into the one extruded pipes, the modification I stable in stretched form by stretching. While wants to wind on reels, and not the half-life of the modification rearrangement of the It is always desirable to incorporate the polybutene- (l) additives polybutene- (l) from modification II to I in the case of room, temperature and atmospheric pressure without influence