DE1150804B - Thermoplastic molding compound made primarily from polypropylene - Google Patents

Description

GERMAN

PATENT OFFICE

M 41528IV c / 39b

REGISTRATION DATE: MAY 15, 1959

NOTICE THE REGISTRATION AND ISSUE OF THE EDITORIAL: JUNE 27, 1963

The invention relates to thermoplastic materials based on polypropylene with high degree of polymerization and high crystallinity as well as improved strength properties at low Temperatures compared to pure polypropylene.

It is known that olefin polymers of crystalline structure, and particularly polypropylene, are extremely beneficial have good physical properties, such as B. high tensile strength, a high modulus of elasticity and good mechanical properties at high temperatures. But polypropylene has other than these very good properties has a brittleness point between 0 and 20 ° C, depending on the average Molecular weight of the polymer, which makes processing quite difficult in special cases and the use of the polymer is not possible where it has good mechanical properties lower temperatures are required.

Numerous attempts have been made to eliminate these poor properties by adding other polymers with a lower brittleness point. In general, however, the results were hardly satisfactory. Thus it was found, for example, with the use of polyethylene, that this, although there is a brittle point of - 72 ° C has, must be added to the polypropylene in amounts of more than 70% to a low brittle point of about -15 to -2O ⁰ C to obtain.

The additives also change all other properties of the original polymer, so that their application can hardly be described as favorable.

From U.S. Patent 2,631,954 is the addition known from natural rubber, butadiene-styrene rubber or polyisobutylene to polyethylene, whereby although the flexibility of the polyethylene is improved, its brittleness point is worsened. That there are opposing relationships between the flexibility and the brittleness point of polyethylene, goes from table LXXXIII, p. 344, of the book "Polyethylene" by Raff and Allison (Interscience Publishers, Inc., New York). The table values given there clearly show that the brittleness point of polyethylene worsens with increasing addition of polyisobutylene while the flexibility is improved.

It is all the more surprising that in the molding composition according to the invention, which contains polypropylene as the base material, the additives used in the prior art as additives to improve the flexible thermoplastic molding composition
mainly made of polypropylene

Applicant:

Montecatini Soc. Gen. per l'Industria
Mineraria e Chimica, Milan (Italy),

and Dr. Karl Ziegler,
Mülheim / Ruhr, Kaiser-Wilhelm-Platz 1

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald

and Dr.-Ing. Th. Meyer, patent attorneys,

Kohl 1, Deichmannhaus

Claimed priority:
Italy of May 20, 1958 (No. 7819)

Franco Ranalli, Milan (Italy),
has been named as the inventor

Polyethylene are known to improve the brittleness of polypropylene.

Indeed, it has surprisingly been found that a considerable decrease in the brittleness point can be achieved with a thermoplastic molding compound from 80 to 95 percent by weight a highly crystalline, high molecular weight polypropylene and 20 to 5 percent by weight of one Butadiene-styrene rubber or a natural rubber and optionally customary stabilizers. The resulting reduction in the brittleness point is more than satisfactory while on the other hand, the mechanical and thermal properties of polypropylene have little effect will.

In order to obtain satisfactory results in the preparation of the mixtures, it is advantageous to use the Polypropylene rubber mixtures at a temperature above the melting point of polypropylene (from about 180 ° C and above) to mix homogeneously. It is also useful to start with the Melt polypropylene before adding the rubber. Mixing can be done according to the usual Homogenization process in a roller mixer

309 61S / 287

or in a Banbury mixer, provided that the aforesaid suitable Conditions regarding temperature and treatment can be met.

In this way, products are obtained which are after deformation or after extrusion show very good impact resistance values down to temperatures below 0 ° C.

In the case of mixtures of polypropylene with natural rubber, the amounts are between 5 and 20% satisfactory values of the brittleness point, while with mixtures of polypropylene with Butadiene-styrene rubber amounts between 5 and 10% are sufficient; this gives the obvious one Advantage that the other mechanical and thermal properties of the polypropylene do not can be significantly influenced.

The invention is illustrated in the following examples.

example 1

2 g of 2,6-di-tert-butyl-p-cresol become 900 g solid propylene polymer with a molecular weight of approximately 200,000 (calculated from the Value of the intrinsic viscosity in tetrahydronaphthalene according to the formula for polyethylene of Harris) and added with 85% residue after extraction with n-heptane and the polymer in melted on a roller mixer. Then 100 g of butadiene-styrene rubber are added in successive portions. That The whole thing is calendered for 20 minutes at 180 to 190 ° C. and the skin obtained in a plate press for 5 minutes formed into a plate at 200 ° C, from which

ίο Samples to determine the brittleness point be cut off.

In the same way, plates for the preparation of the sample pieces for the determination of del other mechanical properties molded; the results of these tests are given in Table 1.

Example 2

A mixture of polypropylene and butadiene-styrene rubber with a rubber content of 20% is produced as described in Example 1.

The sample pieces obtained are compared with those obtained in Example 1 and with those from pure polypropylene tested; the following results are obtained:

Tabel

properties ASTM Polypropylene
without additives Polypropylene
+ 10 «/ 0 butadiene
Styrene rubber Polypropylene
+ 20% butadiene
Styrene rubber Brittleness point
Vicat (5 kg)
Vicat (1 kg)
Flexural modulus E, kg / em ² D 746-52T
D 747-50D + 1 ⁰ C
74 ° C
above 150 ° C
8700 ± 200 ° C -18 ° C
65 ° C
145 ° C
7600 ± 700 ° C -18 ° C
58 ° C
141 ° C
62001140 ° C

Example 3

Two blends of polypropylene with a 40 as described in Example 1, prepared. The following Content of 10 or 20% natural rubber, results were obtained:

Tabel

properties ASTM Polypropylene
without additives Polypropylene
+ 10% nature
rubber Polypropylene
+ 20% nature
rubber Brittleness point
Vicat (5 kg)
Vicat (1 kg)
Flexural modulus E, kg / cm ² D746-52T
D 747-50 + 1 ° C
74 ° C
above 150 ° C
8700+ 200 ° C -7 ⁰ C
61 ⁰ C
142 ⁰ C
7700 + 300 ⁰ C -14 ° C
54 ⁰ C
138 ° C
7050 + 250 ⁰ C

Claims (1)

PATENT CLAIM: Thermoplastic molding compound consisting mainly of polypropylene and a second polymer, characterized in that it contains 80 to 95 percent by weight of a highly crystalline, high molecular weight polypropylene and 20 to 5 percent by weight of a butadiene-styrene rubber or a natural rubber and optionally customary stabilizers. Documents considered: German Patent No. 959 327. © 309 618/287 6.