CS240705B1 - Mixture on polystyrene base - Google Patents

Abstract

Polystyrene-based blend with improved processing properties, wholesome, composed of 100 wt. tough parts polystyrene prepared by block polymerization and 50 to 130 wt. standard parts polystyrene. Block polystyrene is softened by high viscosity an oil having a viscosity of 50 to 110 mPa. with in an amount of 0.5 to 5% by weight. Standard polystyrene is softened with mineral oil with a viscosity of 5 to 30 mPa. with. The total amount of oil in the mixture is the most 5% by weight.

Description

The present invention relates to a polystyrene-based composition with improved processing properties, which is harmless to health and suitable for the manufacture of moldings in contact with foodstuffs. Said mixture is a modification of the basic component of the impact polystyrene.

Tough polystyrenes are divided into extrusion and injection types according to processing technology. According to their properties and workability, they are further divided into:

medium tough - very workable, high tough - well workable and super tough - with special properties.

[Characteristics and technical parameters are given in ČSN 64 3062. The present mixture belongs to the category of medium-impact polystyrenes. It is known that medium-impact polystyrenes can be prepared directly by suspension by graft polymerization or block prepolymerization of styrene in the presence of dissolved rubber, followed by completion of the polymerization by the suspension process.

It is also known to blend tough polystyrene beads with standard polystyrene beads.

In new block technology, direct polymerization processes are also developed for the production of medium tough types where a tough polystyrene granulate emerges at the end of the line.

In these technologies continuous block grafting polymerization is used. This polymerization is conducted to only about 75% conversion and the remaining monomer is removed by high vacuum degassing.

If a block process is given below, it is a continuous graft polymerization carried out to incomplete conversion.

To compare the pelymerization processes, a ratio index was chosen, which indicates the cost-effectiveness ratio of the technology compared to the technology of toughened polystyrene block polymerization with suspension finish, for which an index of 100 was chosen.

If we compare, on the one hand, the procedure using suspension technology or block suspension with the block method, on the other hand, the relative indices are as follows:

Process

Raw materials suspension block styrene ilOO 95 rubber Γ00 111 plasticizer , 100 145 chemicals ilOO 72 total 100 ALIGN! 98 Energy electricity 1O0 80 steam 100 ALIGN! 10 cooling water 100 ALIGN! 60 fuel - 100 ALIGN! total 100 ALIGN! 82

The comparison shows that the block processes are advantageous mainly due to their low energy consumption, nor is the better use of raw materials negligible. However, it can also be seen from the comparative table that the continuous method of conducting block polymerization also results in poorer utilization of rubber and plasticizer, which is given by the statistical distribution of rubber particles in continuous polymerization.

The plasticizer during block polymerization is subject to high demands, especially in terms of stability, viscosity and the presence of volatiles. The plasticizers used in the suspension or block suspension polymerization are unsatisfactory since there will be a block in the degassing section. technology has caused the pump to overload.

In order to obtain good workability of the medium tough type, the production by the block process requires the dosage of 5 to 6.5% by weight. mineral oil, which is both economical and non-economic.

Also, the processes of blending the beads of tough standard polystyrene have numerous disadvantages, besides the low polymerization performance already mentioned, there are also demands for complex separation of the bead dust equipment, relatively low extrusion line performance and higher energy consumption.

The above disadvantages are overcome by the use of the composition according to the invention, characterized in that it consists of 100 parts by weight of blocky polystyrene prepared by block polymerization containing from 0.5 to 5 percent by weight of paraffin oil with a 240703 viscosity of 50 to 110 mPa. s at 40 ° C and 50 to 130 wt. % of standard polystyrene containing 4 to 7 wt. mineral oil having a viscosity of from 5 to 30 mPa. s at 40 ° C, the total amount of oil in the mixture being at most 5% by weight.

The mineral oil content is generally in the range of 0.5 to 5% by weight. The pellets prepared in a block manner completely without plasticizer have deteriorated properties, which are related to the dispersion and shape of the rubber particles, their size and the anchoring method in a homogeneous phase.

However, it is not necessary to use as viscous oil as the block process in the preparation of the standard polystyrene modification additive, whereby a hygienic directive with a maximum permissible plasticizer content of not more than 5% by weight can be observed with improved processability. The composition may further comprise dyes, pigments, antioxidants, interior and surface lubricants as possible and common in polystyrene plastics.

100 wt. parts by weight of polystyrene produced by block polymerization with a molecular weight of 22ΟΌΟΟ and a plasticizer content of 5% by weight. The plasticizer was paraffin oil having a viscosity of 85 mPa. at 40 ° C. Standard polystyrene beads were added to the pallets in an amount of 82% by weight. parts with the following characteristics:

Molecular weight 150,000, melt index 35 with a plasticizer content of 4.5% by weight. The plasticizer was a white oil having a viscosity of 13 mPa. s at 40 ³ C. The mixture was blended 'and zgranulována on a laboratory extruder having a diameter of 45 mm and a screw length of 28 D.

The flow properties of the material were evaluated on a high pressure capillary rheometer. Viscosities at a shear rate of 100 to 1000 ^-1 s, which are typical of the extrusion and injection process, were selected for evaluation. The rate of change of viscosity with increasing gradient is illustrated by the value of the flow exponent N.

He did

The invention was followed. To Fri a b u 1 k a 1

Medium-tough Medium-tough polystyrene produced by block polystyrene according to the invention by suspension technology

160 ° C 100 (Pa.sj 1000 (Pa.s)

N

180 [deg.] C. 100 (Pa.s) 1000 (Pa.s)

N

200 ° C 100 (Pa.s) 1000 (Pa.s)

N

1820

450

2.5

1020

210

3.2

610

140

2.8

620 360

2.9

930

180

3.5

570

120

3.1

220 [deg.] C. 100 (Pa.s) 1000 (Pa.s)

N

410

110

2.3

360

2.7

Example 2

The invention was followed. In a belt mixer, 100 wt. parts houž. polystyrene block with 54 wt. parts of standard polystyrene according to Example 1. The mixture was granulated on a laboratory ₍ extruder. After granulation, the mixture was evaluated. The results are shown in Table 2.

Example 3

The procedure was as in Example 2, and the same raw materials as in Example 1 were used except that 100 wt. parts of block polystyrene pellets with 122 wt. parts of standard polystyrene beads. The mixture was granulated and evaluated. The results are shown in Table 2.

Example 4

The invention was followed. In a belt mixer, 100 wt. parts by weight of pellet block polystyrene pellets having a molecular weight of 260,000 and containing 2 wt. mineral oil having a viscosity of 85 mPa. at 40 [deg.] C., a mass of approx. parts of standard polystyrene beads according to the preceding 240705 examples. The mixture was granulated on a laboratory extruder. After granulation, the mixture was evaluated. The results are shown in Table 2.

Example 5

The procedure was as in Example 1, except that the oil used in the preparation of the block polystyrene had a viscosity of 55 mPa. 40 ° C. The properties of the granulate produced are given in Table 2.

Table 2- Example Melt flow index Impact toughness Vicat heat resistance number CSN 64 0861 200 ° C load 49 N g / lQ min CSN 64 0612 J / cm ² ČSN 64 0521 method A ° C il 14 8.5 65 2 11 8.5 85 3 16 4,5 83 '4 6 8.0 86 5 13 6.0 84

All samples meet Hygiene conditions with a higher symbol, i. symbol N - General Directive 49/1978 for the classification of the lowest use.

Claims (1)

Polystyrene-based blend with improved processing properties, harmless, characterized in that it consists of 100 parts by weight of tough polystyrene prepared by block polymerization containing from 0.5 to 5% by weight of paraffin oil having a viscosity of from 50 to 50 VYNALEZU 110 mPa. at 40 and 50 to 130 parts by weight of standard polystyrene containing from 4 to 7% by weight of polystyrene; mineral oil having a viscosity of from 5 to 30 mPa. at 40 ° C, the total amount of oil in the mixture being at most 5% by weight.