CS257334B1 - Mixture of elastomeres for continual production of tough polystyrenes - Google Patents

Abstract

Polybutadiene elastomer blend for continuous production of tough polystyrenes block technology containing besides polybutadiene polybutadiene an elastomer that is branched. Amount branched polybutadiene in the mixture is 10 to 50 parts by weight of the elastomer mixture.

Description

The invention relates to a mixture of elastomers for the continuous production of tough polystyrenes by block technology.

The technical specification requirements for polybutadiene elastomers used for the production of tough polystyrenes by continuous flow technology differs from the requirements for elastomers for batch technology (suspension or block suspension). In continuous technology, the addition of solvent (ethylbenzene, toluene, etc.) is used, which results in a different mode of conducting the prepolymerization of the rubber solution, in principle a polybutadiene elastomer with a higher Mooney value is used.

As is known, the butadiene molecule polymerizes in three stereospecific configurations:

cis trans vinyl

All polybutadiene elastomers contain a mixture of the three basic structures in varying proportions.

Of the wide range of products, polybutadiene rubbers with a low or medium cis content of 1,4 structures, predominantly containing 35 to 55% cis, are most commonly used for tough polymers.

For economic reasons, possibly to highlight some properties, it is known to use an elastomeric blend of polybutadiene having a low cis-1,4 structure, with polybutadiene containing more than 95% cis-1,4 structures being added as the second elastomer.

Furthermore, during the preparation of polybutadiene by polymerization, a different degree of chain branching occurs.

In practice, branching is often expressed by the ratio of the measured intrinsic viscosity to the intrinsic viscosity calculated in the Mark-Houwink equation of molecular weight distribution.

branching index measured intrinsic viscosity calculated intrinsic viscosity

According to this criterion, linear elastomeric polybutadiene has an index equal to 1. Elastomers with an index of 0.7 and below are highly branched.

Another less accurate indicator of branching is the ratio of solution viscosity (5 wt% in styrene) to Mooney viscosity. The advantage is that it relies only on measured data.

It has been found that the use of branched polybutadiene elastomers brings about an improvement in the physico-mechanical properties of tough polystyrenes, especially notch toughness.

These disadvantages of the prior art are overcome by the elastomer blend for the continuous production of the impact-resistant polystyrenes according to the invention, which is composed of 50 to 90 wt. % polybutadiene rubber base with a polydispersity coefficient Mw / Mn = 1.8 to 3.5 with a solution viscosity of 90 to 180 m Pa, a carbon black of 10 to 50 wt. % polybutadiene rubber having a branching index of 0.7 to 0.95, a polydispersity coefficient of 2.5 to 5.5 and a solution viscosity of 40 to 100 m Pa. with.

The use of this composition according to the invention primarily improves the impact and notch toughness, as documented by the following examples.

Comparative example

In the model unit for the production of block tough polystyrene in a continuous process, tough polystyrene - a type suitable for injection molding containing 7% by weight of polybutadiene rubber - was produced. The rubber of the following specification was used:

polydispersity coefficient Mw _ _n

Mn ^{of 2, for} solution viscosity 165 mPas, for Mooney 53

The following temperature and conversion profile was maintained in the reactor section:

Table

Temperature Conversion

prepolymerization boiler 125 to 128 Noc: 2 ° C 29 to 32 % wt. 45 rpm I. horizontal reactor 136 to 138 ° c 44 to 47 % wt. 17 rpm II. horizontal reactor 153 to 156 ° c 54 to 56 % wt. 12 rpm III. horizontal reactor 159 to 160 ° c 67 toŽ 70 % wt. 7 rpm

After degassing to 0.05 wt. Free styrene, extrusion and granulation test specimens were prepared and the physical-mechanical properties listed in Table I were measured.

Example 1

An elastomeric composition according to the invention having the following composition was used:

wt. parts of the elastomer as specified in the comparative case by weight of the elastomer. parts of polybutadiene elastomer with branching index = 0.7 polydispersity coefficient 3.7 solution viscosity 60 mPas

The elastomeric mixture of the above composition was dissolved in styrene monomer on 7 wt% solutions. The elastomer solution was processed in a continuous unit to produce block tough polystyrene with the same temperature and conversion profile as in the comparative case.

After degassing, extrusion and granulation, physical-mechanical properties were measured on the prepared samples. The measured data are shown in Table I.

Example 2

An elastomeric composition according to the invention having the following composition was used:

wt. parts of the elastomer as specified in the comparative case by weight of the elastomer. parts of polybutadiene elastomer with branching index = 0.95 polydispersity coefficient = 2.6 viscosity 42 mPas

For further processing, the same procedure was used as in the comparative example.

Test specimens were prepared from the tough polystyrene obtained and the physico-mechanical properties were measured. The results are shown in Table I.

Example 3

An elastomeric composition according to the invention having the following composition was used:

wt. Polybutadiene elastomer parts specifications:

viscosity 180 mPas polydispersity Mw _, _

Mn ^3.5 wt. parts of butadiene elastomer with branching index = 0.8 with polydisper rye coefficient = 5.5 with viscosity 98 mPas

In the further processing, the same procedure was used as in the comparative example.

Test specimens were prepared from the tough polystyrene obtained and the physico-mechanical properties were measured. The results are shown in Table I.

Example 4

An elastomeric composition according to the invention having the following composition was used:

wt. parts of basic polybutadiene elastomer the following specifications:

polydispersity coefficient ^Mw - 1 0

Mn 'solution viscosity 90 mPas wt. parts of polybutadiene elastomer with branching index = 0.8 polydispersity coefficient Mw θ

Mn 'with a viscosity of 72 mPas

In the further processing, the same technological procedure as in the comparative example was used.

Test specimens were prepared from the tough polystyrene obtained and the physico-mechanical properties were measured. Results - in Table X.

Table 1

Quality indicator Method Units Cf. Example Example Example Example example 1 2 3 4 Notch toughness of Charpy CSN 64 0612 Trial body No 2 r 2 J.cm 1.06 1.17 1.39 1.24 1.56 Charpy impact strength CSN 64 0612 Trial body No 2 J.cm 10.3 10.7 12.0 11.2 12.5 Contractual shrinkage CSN 64 0209 Ϊ 30 í 5 í 30-5 4 30% 5% 30% 5% 30 - 5%

Continuation table

Quality indicator Method Units Cf. example Example 1 Example 2 Example 3 Example 4 Melt flow index CSN 64 0861 200 C load 49 N g / 10min 8.1 7.9 7.8 8.2 8.0 Ductility CSN 64 0605 34 37 42 39 44

SUBJECT OF THE INVENTION

Claims (1)

Blend of elastomers for the continuous production of tough polystyrenes by block technology, characterized in that it consists of 50 to 90 wt. % of polybutadiene rubber having a polydispersity coefficient Mw / Mn of 1.8 to 3.5, a solution viscosity of 90 to 180 mPas and of from 10 to 50 wt. polybutadiene rubber having a branching index of 0.7 to 0.95, a polydispersity coefficient of 2.5 to 5.5, and a solution viscosity of 40 to 100 mPas.