DE1038273B - Process for the production of pipes and other molded articles, with the exception of foils made of ethylene-propylene copolymers, which have been produced by the low-pressure process - Google Patents

Description

GERMAN

To an increasing extent: Thermoplastics are used in the manufacture of a wide variety of products Profiles and! Shaped body used. They often serve as substitutes for those previously used Materials like metals, be it because they allow more efficient production, or because they improved properties. The range of thermoplastics that can be used in this way has grown continuously. This not only speaks of the desire to broaden or enrich the raw material base for the manufacture of numerous objects, but also the fact that each one has hitherto used Plastics still have considerable defects. A few examples are given to illustrate this:

In the hard state, polyvinyl chloride shows strong brittleness and therefore a risk of breakage, in plasticized State the known disadvantages caused by the plasticizer, e.g. B. plasticizer migration, and physiological hazards. Polystyrene and polymethacrylic acid methyl ester are also brittle. All three Groups are not boil-proof.

Polyethylene, which does not show the above-mentioned deficiencies, in turn has the disadvantage of only a minor one Tear resistance. In recent times it has now been successful gen to produce a modified polyethylene with only a low branching content, which shows significantly improved strength. Unfortunately, this advantage had some disadvantages themselves, the z. B. in a lower flexibility, combined with a deteriorated notched impact strength, passed. Another disadvantageous property compared to normal polyethylene is the so-called "Restriction of flow" that becomes clear when you put thick objects under rapid tensile stress subject. The properties described find their: Expression in the so-called tension-strain diagram. Normal high pressure polyethylene is shown in the diagram shown in Fig. I, labeled due to a low yield point (referred to as the »yield point« in Anglo-Saxon literature), good ones elastic elongation, but low tear strength. Low-pressure polyethylene (Fig. II) gives way considerably from it. It has a high yield strength, combined with a lower elastic elongation, however good tear resistance. The thicker the selected test bars, the more blatant the proportions will. These facts are discussed in the publication "A new polyethylene" by. Schulz and Mehne in "Kunststoffe" (1955), pp. 410 to 414, described in detail. With polypropylene (Fig. III) are the conditions essentially similar to with polyethylene. So the situation was as follows:

It is a process for the manufacture of pipes using the polymers mentioned

and other moldings, with the exception of films made of ethylene-propylene

copolymers, which after the

Low pressure process produced

have been

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly Master Lucius & Brüning,

Frankfurt / M., Brüningstr. 45

Dr. Erhard Grams,

Dr. Albert Gumboldt, Frankfurt / M.-Höchst,

and Dr. Kurt Rust, Frankfurt / M.-Sindlingen,

have been named as inventors

possible to obtain either good flexibility and flowability or high tear strength. It seemed impossible, however, to gain both advantages at the same time.

The subject of patent application F 18751 is Use of copolymers of ethylene with 3 to 20%, preferably 10 to 14%, of higher Olefins as a raw material for plastic films.

It has now been found that pipes and other shaped bodies with the exception of films can be made from Ethylene-propylene copolymers, which are produced by the low-pressure process, thereby produce can that they are made from ethylene-propylene copolymers whose propylene content is between 3 and 30% is produced in a manner known per se (cf. FIG. IV).

The low pressure polymers can be according to the Ziegler process, as it is, for. B. in the Belgian Patent 533 362 is described to produce.

In addition to tubes, plates, shells, angles, solid cylinders and any other shaped bodies can also be used getting produced.

The use of such copolymers for the stated purpose is an important technical one Progress.

An advantage of the proposed according to the invention Composition compared to other ethylene-propylene copolymers with regard to their

809 600/49?

it can be used to produce moldings to a considerable extent. While copolymers with a propylene content of less than 3 ° / o not to any appreciable extent of normal low-pressure polyethylene differ, mixed polymers with a proportion of about 30% upwards are soft, for the purposes mentioned are unusable products. Only the claimed polymers have at the same time high tear strength and good flexibility.

The optimal physical properties are best shown in the ¹ stress diagram of the ethylene / propylene 88:12 copolymer. For comparison, the curves of two further copolymers that lie outside the claimed range are shown in the following sketch.

kg / cm ¹ 400

300 4

I §200

100

200

400

600 600

Strain -

1000%

Tensile strain diagram of

A ethylene / propylene copolymer

B. C.

fl

88:12
99: 1

Only the claimed mixed polymer ratio shows the soft curve progression (as a characteristic for good flexibility and good resistance to jerky loads) nevertheless high tear resistance.

From US Pat. No. 2 691645, column 1, Lines 4 to 6, column 17, lines 11 to 20 and British Patent 722,250 are known to Copolymers of ethylene and propylene have been processed into various Fortr bodies.

Compared to this prior art, the subject of the invention is by a certain content of the copolymer used according to the invention. As from the description in detail can be seen, the technique is by the invention The copolymers used are considerably enriched.

example 1

There were 1 mm thick plates made of the following polymers in a known manner: normal high-pressure polyethylene, low-pressure polyethylene with a low content of CH _{3 end} groups, polypropylene, copolymer of ethylene and propylene in a ratio of 90:10. The following values were determined on such plates:

Testicular print Low pressure Polyethylene Polyethylene 30th 16 180 297 600 950 157 350 125 325

Polypropylene

Mixed polymer

Ethylene / propylene

90:10

Elongation at the yield point, ° / o.

Tear strength, kg / cm ² -

Elongation at break, ° / e

Ball indentation hardness, 10 "

kg / cm ² 60 "

20th
305
700
360
336

30th

290

1025

182

166

It is clear from the above values that Example 2

when using the invention in a manner known per se, low-

Copolymer not to include an expected pressure polyethylene, polypropylene and a mixed

between the two home polymers lying polymer 90:10 on the screw press 2-inch

Effect acts. 70 tubes with a wall thickness of 5 mm were produced.

The advantage of flexibility that the copolymer has over the homopolymers, becomes clear when one examines the reelability, which is important for transport and installation purposes. The pipe made from the copolymer can easily be reeled up to a diameter of 1.20 m, which is not the case with the pipes made from homopolymers because of their excessive rigidity the case is.

Claims (1)

Claim: Process for the manufacture of pipes and others Moldings, with the exception of films from ethylene-propylene copolymers, the after the Niederdruoky method are, characterized in that they are made from ethylene-propylene copolymers, their propylene content between 3 and 30% is produced in a manner known per se. Taken into consideration"! Publications: U.S. Patent No. 2,691,647;
British Patent No. 722 250. 1 sheet of drawings © «09 600/495 p. 58