CS239716B1

CS239716B1 - A method for producing a high-liquid propylene-ethylene copolymer

Info

Publication number: CS239716B1
Application number: CS84595A
Authority: CS
Inventors: Ladislav Pospisil; Jiri Pac; Jaroslav Petruj; Karel Sula; Jiri Ottis; Zdenek Sulc
Original assignee: Ladislav Pospisil; Jiri Pac; Jaroslav Petruj; Karel Sula; Jiri Ottis; Zdenek Sulc
Priority date: 1984-01-26
Filing date: 1984-01-26
Publication date: 1986-01-16
Also published as: CS59584A1

Abstract

Vynález se týká výroby vysokotekutých kopolymerů propylenu s etylenem připraveného degradaci iniciovanou organickým peroxidem za přítomnosti stabilizačního systému obsahujícího fenolická antioxidanty nebo jejich kombinaci s estery kyseliny thiodipropionové nebo s estery kyseliny fosforité. Pro odbourání se vychází z kopolymeru proplyenu s etylenem termlnálně blokového typu obsahující alespoň 1 % hmotnostní ethylenu a alespoň 20 % hmotnostních materiálů s indexem toku nižším než 0,5 g/10 minut, přičemž z celkového množ styl fenolických antloxidantů tvoří alespoň 1/3 stabilizátory na bázi stericky nebráněného fenolu, například 2,6-dimethyl-4-dodekakis (propenyl) fenolu.The invention relates to the production of high-flow copolymers of propylene with ethylene prepared by degradation initiated by organic peroxide in the presence of a stabilizing system containing phenolic antioxidants or their combination with thiodipropionic acid esters or with phosphorous acid esters. For the degradation, a copolymer of propylene with ethylene of the terminal block type containing at least 1% by weight of ethylene and at least 20% by weight of materials with a flow index lower than 0.5 g/10 minutes is used, with at least 1/3 of the total amount of phenolic antioxidants being stabilizers based on sterically unhindered phenol, for example 2,6-dimethyl-4-dodecakis (propenyl) phenol.

Description

(54) Process for producing a high-flow copolymer of propylene with ethylene •

The invention relates to the production of high-flow copolymers of propylene with ethylene prepared by degradation initiated by organic peroxide in the presence of a stabilizing system containing phenolic antioxidants or a combination thereof with thiodipropionic acid or phosphorous acid esters.

For degradation, a thermally-block-type copolymer of proplyene with ethylene containing at least 1% by weight of ethylene and at least 20% by weight of materials having a flow index of less than 0.5 g / 10 minutes is used, the total amount of phenolic antloxidant based on sterically unhindered phenol, for example 2,6-dimethyl-4-dodecakis (propenyl) phenol.

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239716 ₂

The invention relates to copolymers of propylene with increased flowability of ethylene, particularly suitable for injection molding of complex and dimensional parts with a long melt flow path.

For some applications, typical of which are thin-walled large-area products, it is necessary to use types of polypropylene (FP denoted) with a high flowability, which may be a melt index (the abbreviation II will be used for longer).

Typically, types with II in the range of 10 to 50 g / 10 minutes are used (unless otherwise stated, these are measured according to ČSN 64 0861, condition 12). These are prepared both by direct synthesis, which, however, is not accessible by the hox boundary II and by controlled molecular weight reduction.

This molecular reduction can be initiated both thermally, as described, for example, in Japanese patent JA 5 1135 996 or in the presence of degradants, e.g. trilauryltrithiophosphite (JA 4 9038 960), at temperatures of 350 to 400 ° C.

Another possibility is the use of organic peroxides as a degradation initiator.

Such a process is described, for example, in Belgian patent BE 606 669. The temperatures at which PP degradation takes place can then be reduced by up to 100 ° C compared to the previous processes.

Particularly preferred is the use of organic peroxides in the degradation of high molecular weight types where extreme thermal stress would otherwise be required.

Due to the high initiation efficiency of organic peroxides, their effect is usually moderated by a stabilizing system. This ae usually consists of old defended pheniiles, often sulfides and phosphites.

In addition to the moderating effect, of course, these ingredients also provide the thermo-oxidative stability of the final product.

The process of degradation of PP by the initiation system organic peroxide - stabilization system takes place in a short time interval. To achieve a uniform IT product, the degradation process needs to be homogeneous throughout the volume of material being processed.

This can be achieved either by a suitable choice of an organic peroxide, as for example disclosed in German patent DR 311 882, or by using stabilizers having excellent miscibility with the polymer. Such stabilizers are described in U.S. Pat. AO 185 959 and are based on 2,6-dimethyl-4-dodecakis (propenyl) phenol (I).

As has been previously found and described in the description of the invention to MS. No. 229,766, the stabilizing component (I) can be advantageously used in the preparation of controlled degraded PP types for fibers.

Other components of the respective stabilizing systems and their synergistic mixtures, i.e. sulfides, phosphites and light stabilizers, are described in detail in the aforementioned document.

With the appropriate choice of starting materials and preparation technology, FP types can be obtained by controlled degradation which are characterized not only by high flowability but also by good mechanical properties.

Such types of PP are then particularly suitable for injection molding of complex shapes and long wires of molten material flow. They have been described in the description of the invention to U.S. Pat. A0 No. 233 523, including their preparation.

However, homopolymers of propylene are not suitable for many applications requiring increased shock resistance. It is then necessary to apply copolymers of propylene with other olefinic monomers, the most common being ethylene. The injectable propylene / ethylene copolymers typically have a structure termed a terminal block.

A process for preparing a low embrittlement temperature material based on a two-step synthesis of so-called terminal block copolymers (abbreviated as TBC) is described in US 365045.

In a direct synthesis, a homopolymeric polypropylene block is prepared in a first step, followed by a second step in which a random propylene-ethylene copolymer is prepared. The concentration of hydrogen in the polymerization reactor is controlled so that the resulting resulting polymer has the desired flow index.

The polymerization itself can be carried out in a discontinuous or continuous manner. In this case, the comonomer is incorporated at the end of the polypropylene backbone, where the methylene units (-CHg-) are then triads (-CHg-CHg-CHg-> or longer blocks).

The comonomer usually used in amounts of less than 10 parts by weight per 100 parts by weight of copolymers substantially alters the physical properties (as compared to homopolymerization of the same IT).

The yield strength and flexural modulus of copolymers are substantially reduced. On the other hand, toughness, both impact, notch and impact, are considerably increased. It has now been found that propylene copolymers with other olefinic monomers, in particular ethylene, can serve as a starting material for the preparation of degraded polymers which, while substantially increasing the melt flow, largely maintain the level of mechanical properties of copolymers prepared directly by polymerization, raw materials and the whole additive system provide a precondition for the creation of a material of suitable utility properties.

However, the mechanical properties of the product are not only due to the resulting material flow index but are also significantly influenced by the characteristics (usually the comonomer content and the flow index) of the input material.

The preparation of degraded types of propylene copolymers, without taking into account the influence of the starting material, was previously described in U.S. Patent 4,061,694. It was also stated in this document that the degraded material has (with the same comonomer content) higher toughness than the polymerization type of the same index. flow.

Japanese Patent JA 5 8076-444 describes the preparation of degraded propylene-ethylene copolymers wherein the feedstock is a mixture of block and alternating copolymers. Controlled degradation is also used in the two-step production of propylene copolymers prepared by polymerization in liquid monomer, as described in EP-74-194. This process prepares in the first stage an alternating copolymer of propylene with ethylene.

SUMMARY OF THE INVENTION The present invention provides a process for the production of high-flow copolymers of propylene with ethylene-controlled degradation initiated by organic peroxide in the presence of a stabilizing system containing phenolic antioxidates or a combination thereof with thiodipropionic acid or phosphorous acid esters. and at least 20 parts by weight of materials having a Flow Index of less than 0.5 g / 10 min. in the presence of phenolic antioxidants, of which at least one third are stabilizers based on sterically unhindered phenols, such as 2,6 dimethyldodecakis (propenyl) phenol.

For the preparation of high-flow propylene copolymers it is necessary to use raw materials (in the form of powder or granules) whose 1T is less than 0.5 g / 10 min, or a mixture of raw materials in which the material with 1T less than 0.5 g / 10 min at least 20 parts by weight of the feedstock (the whole material being 100 parts by weight) in which the comonomer content is at least 1 part by weight.

The preparation of said type of degraded propylene copolymer can be carried out on single-wall 61 multi-screw extruders designed to guarantee the necessary homogeneity of the material being processed.

The starting material, if it is a granulate, can contain either all or part of the stabilizing system, the remaining components of the stabilizing system being fed into the machine together with the peroxide concentrate.

In the case of using the starting material in the form of a powder, the additives are metered either as a separate stream or together with the peroxide concentrate stream. The extruder temperatures range from 160 to 260 ° C.

The organic peroxide used as a source of free radicals initiating controlled degradation must meet the conditions of adequate volatility and reasonable half-life, as described in detail in DE 2311 682.

For example, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane (II) or 2,5-dimethyl-2,5-di-tert-butylperoxyhexin (III) or cumyl peroxide (IV) meet these requirements. The organic peroxide is used in an amount of 0.01 to 0.2 parts by weight, depending on the starting material and the desired flow properties of the product.

The examples below illustrate specific preparation procedures and working conditions. The initiator, stabilizer and processing additive forces are given relative to the propylene copolymer (propylene copolymer 100 parts) and are by weight.

Example 1

A mixture consisting of 100 parts propylene copolymer (IT = 0.2 g / min), ethylene content 1.4 parts), 0.14 parts phenolic stabilizer II (2,6-di-tert-butyl-4-methylphenol) was prepared on a fluidic mixer. 0.07 parts of phenolic stabilizer 11,6,6-dimethyl-4-dodecakis (propenyl) phenol, 0.1 parts of secondary sulfur antioxidant (distearylthiodipropionet) and 0.09 parts of organic peroxide (2,5-dimethyl-2,6- (di-tert-butylperuxyl) hexane).

The resulting mixture was fed into a single-wall extruder with a cylinder diameter of 19.1 mm and a distance ratio (L) to a diameter (D) of 20. The screw compression ratio was 4/1. In three adjustable zones of the machine, the temperatures were 220 ° C, 250 ° C and 200 ° C. The screw speed was 45 rpm. The resulting product had an IT-15.2 g / 10 min. Its mechanical properties will be presented in Table 1.

Example 2 *

It was processed under the conditions of Example 1, except that the feedstock (copolymer of propylene with ethylene; 1.4 parts of ethylene) mSl IT 3.2 g / 10 minutes and the initiator concentration was 0.032 parts. The resulting product had an IT = 17.4 g / 10 min. Its mechanical properties will be presented in Table 1.

Example 3

The conditions were as in Example 1, except that 0.116 parts of the initiator were used. The resulting product had an IT of 24.8 g / 10 min. Its mechanical properties will be given in Tab. 6. 1.

He did

The conditions were as in Example 1, except that 0.07 parts of initiator was used. The resulting product had an IT of 10.2 g / min. Its mechanical properties will be presented in Tab. 2.1.

Example 5

The operating conditions were as in Example 1, except that the temperature in the 2nd zone of the extruder was 280 ° C. The resulting product had an IT = 16.9 g / 10 min. Its mechanical properties will be presented in Tab. S. 1.

When k 1 ad, 6

The conditions were as in Example 1, except that the temperature in the first zone of the extruder was 180 ° C. The resulting product had an IT = 14.8 g / 10 min. Its mechanical properties will be presented in Tab. E. 1.

Example 7

A mixture was prepared containing 80 parts of the mixture used in Example 1 and 20 parts used in Example 2. Extrusion was carried out under the conditions described in Example 1. The resulting product had IT ³ 14.9 g / 10 min. Its mechanical properties will be presented in Tab. £. 1.

Example 8

A mixture was prepared comprising 20 parts of the mixture used in Example 1 and 80 parts of the mixture used in Example 2. Extrusion was carried out under the conditions described in Example 1. The resulting product had IT ³ 15.7 g / 10 min. Its mechanical properties will be presented in Tab. S. 1.

Example 9

The conditions were as in Example 1, except that a stabilization system consisting of 0.1 part phenolic stabilizer I, 0.05 part pentaerythrityl-tetrakis-3- (3,5 di-tert-butyl-4-) was used. hydroxyphenyl (propionate and 0.1 parts of the phosphite stabilizer (tris-4- (1'-phenyl) ethyl phenyl phosphorous). the resulting product had IT ³ 15.5 g / 10 min. the mechanical properties are shown-in tab. no. 1.

He did

The working conditions were as in Example 1, except that a stabilizing system consisting of 0.1 parts of phenolic stabilizer I, 0.1 parts of phosphite stabilizer (tris-4- (1'-phenyl) ethylphenyl phosphoric acid ester) was used. ) and 0.1 part of secondary sulfur antioxidant (distearylthiodipropionate). The resulting product had an IT = 15.7 g / 10 minutes. Its mechanical properties will be presented in Table 1.

They did

The procedure was as in Example 2, except that no initiator was introduced into the system. The resulting material had an IT = 3.4 g / 10 minutes. Its mechanical properties are given in Tab. no. 1.

Bodies for measuring mechanical properties were prepared from the materials prepared according to the procedures of Examples 1-11. The bodies were prepared by pressing at 230 ° C and conditioned for 14 days at 21 + 1 ° C before measurement. The measurements were performed according to the following Czechoslovak standards:

ČSN 64 0605 - Tensile test of plastics.

Specification: molded body, test speed 50 mm / min., Type of test body δ. 2 (1/5 reduction, 1 mm thick).

ČSN 64 0612 - Determination of impact and notch toughness of plastics by Charpy method

Specification: test specimen No. 3, notch type A, pendulum velocity at the moment of impact 2.9 m / s.

Tensile impact strength RHT - the test is carried out according to DIN 53 448 - Schlagzugversuch modified as follows:

1) Test specimen as for the tensile test of plastics (see above);

2) Dinstat tester (modified), hammer stroke 90 ° C.

Table δ. 1

Example number Yield strength MPa Tensile strength MPa Elongation% RHT kJm ^-2 Notch toughness »2 kJm Flow index

Claims

SUBJECT OF THE INVENTION

A process for the preparation of a volatile copolymer of propylene with ethylene-controlled degradation initiated by organic peoxide in the presence of a stabilizing system containing phenolic antioxidants or a combination thereof with thiodipropinic acid or phosphorous acid esters, characterized in that at least 20 parts by weight of a material with a flow index of less than 0.5 g / 10 min. in the presence of phenolic antioxidants of which at least one third are sterically unhindered 2,6 dimethyldodecakis (propenyl) phenol stabilizers.