JPS581126B2 - Polystyrene Polystyrene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high impact polystyrene with improved impact strength, tensile strength and flowability.

The three physical properties of high-impact polystyrene are particularly important: impact strength, tensile strength, and flowability, and various studies have been conducted to improve these properties.

For example, increasing the amount of rubber components such as polybutadiene added during styrene polymerization to improve impact strength, increasing the molecular weight of the polymer to improve tensile strength, or improving flowability. For this reason, there is a method of adding a lubricant such as liquid paraffin.

However, in these methods, as the amount of rubber components such as polybutadiene increases, the tensile strength and flowability decrease significantly, and as the molecular weight of the polymer increases, the flowability deteriorates.

Furthermore, the tensile strength is reduced by adding a lubricant such as liquid paraffin.

In this way, while conventional methods can improve one of the target physical properties such as impact resistance, they also prevent deterioration of other physical properties other than the target physical properties such as flowability or tensile strength. I couldn't.

Resins that are excellent only in specific physical properties have extremely limited uses and are extremely disadvantageous in terms of industrial production.

The present invention is not an invention that improves only one of these physical properties, but an impact resistance invention that simultaneously improves three physical properties that are particularly important properties of high-impact polystyrene: impact strength, tensile strength, and flowability. This invention is aimed at producing polystyrene.

That is, the present invention provides a method for producing high-impact polystyrene by dissolving a butadiene-based rubber elastomer in an aromatic vinyl monomer and polymerizing it. The ratio of the low molecular weight polymer to the rubber elastomer is 50~
The present invention provides a method for producing high-impact polysterene, which is characterized in that it is added in an amount of 100% by weight and bulk polymerized in the presence or absence of a low grafting initiator.

In addition to styrene, which is the most typical aromatic vinyl monomer (1) used in the present invention, there are also core and/or side chain substituted styrenes (for example those substituted with lower alkyl groups or halogens, especially chlorine), Examples include paramethylstyrene, α-methylstyrene, parachlorstyrene, and others.

Although these styrene derivatives may occupy the entire amount of the aromatic vinyl monomer, it is generally preferable to limit the amount to about 30% by weight of the total monomer raw material.

The butadiene rubber elastomer (2) mixed with the aromatic vinyl monomer (1) is an elastomer containing a butadiene monomer such as polybutadiene or sterene-butadiene rubber, and the mixing ratio is aromatic. The amount is about 2 to 30% by weight, preferably 5 to 15% by weight, based on the vinyl monomer (1).

In general, if it is less than 2% by weight, it will not be possible to obtain a higher impact strength than ordinary high-impact polystyrene, and if the
If the amount exceeds % by weight, it is practically impossible to dissolve polybutadiene in the monomer, and the present invention cannot be carried out.

Furthermore, the low molecular weight polymer obtained mainly from isobutylene to be mixed with the above two components is isobutylene, or a low molecular weight polymer having an average molecular weight of 200 to 1000 obtained by polymerizing isobutylene and monoolefin or diolefin, and It is also possible to use a hydrogenated version of this.

If the average molecular weight of this low molecular weight polymer is less than 200, the resulting polymer will scatter during granulation or molding, reducing the effect and making it impractical.
If it is larger, the impact strength will not improve.

Generally, this low molecular weight polymer is produced by low-polymerizing a mixed gas containing mainly isobutylene from the butane-butene fraction produced by essential oil gas or naphtha cracking in the presence of a Friedel-Crafts type catalyst. , is a copolymer material in which isoptylene is reacted with a small amount of butene, and in the present invention, a low molecular weight substance having a molecular weight of 200 to 1000 is used.

However, even if liquid paraffin, dioctyl phthalate, etc., which are commonly used as lubricants, are used instead of this low molecular weight polymer, no improvement in impact strength is observed.

The low molecular weight polymer is 50 to 100% by weight, preferably 50 to 80% by weight, based on the butadiene rubber elastomer.
Used in weight percentages.

When used in an amount less than 50% by weight, the effect of improving impact strength is small, and when used in an amount greater than 100% by weight, tensile strength decreases.

Polymerization is carried out in the presence of the three components mentioned above, and although the purpose of the present invention can be achieved by simply carrying out thermal polymerization without using an initiator, it is preferable to use an initiator in order to facilitate polymerization. .

However, if an initiator is used, an initiator with low grafting property,
For example, radical polymerization initiators must be used, such as aliphatic diacyl peroxides such as lauroyl peroxide, octanol peroxide, or azo compounds such as azobisisobutyronitrile, azobiscyclohexanenitrile.

The low molecular weight polymer obtained mainly consisting of the butadiene rubber elastomer and isoprene is dissolved in the aromatic vinyl monomer, and bulk polymerization is carried out in the presence or absence of the low grafting initiator. The bulk polymerization is carried out until the polymerization is completed, or until the particles (microgel) of the rubbery material portion are substantially uniformly dispersed in a size of 1 to 10 μm, and then the polymerization is carried out by suspension polymerization. There are two ways to complete it.

In the case of polymerization using an initiator in the above polymerization method, it is particularly important to use an initiator with low grafting property during bulk polymerization, and an initiator with high grafting property can be used during suspension polymerization.

Therefore, two types of initiators, a low-temperature decomposable low-grafting initiator and a high-temperature decomposable high-grafting initiator, can be used together.

Bulk polymerization is generally carried out at a temperature of about 40 to 120°C, preferably 6°C.
Polymerization is carried out at a polymerization temperature of 0 to 100°C, and if suspension polymerization is subsequently carried out, it is continued until the conversion rate during bulk polymerization reaches 15 to 40% by weight, and then transferred to suspension polymerization and carried out at 40 to 40% by weight.
It is preferable to continue the polymerization at a polymerization temperature of about 180°C, preferably 80 to 160°C.

Polymerization is generally carried out in the presence of an inert gas, such as nitrogen gas, under a pressure of usually 0.5 to 10 kg/cm<2>.

Example 1 6 parts of polybutadiene rubber (Diene 35A manufactured by Asahi Kasei Co., Ltd.) and 5 parts of polyptene LV-10 (manufactured by Nisseki Jushi Kagaku Co., Ltd. average molecular weight = 310) were dissolved in 94 parts of styrene monomer, and 0.18 parts of lauroyl peroxide, Add 0.15 parts of tertiary butyl peroxybenzoate and polymerize in bulk at 70°C for 5 hours with stirring. Add this solution to 100 parts of water containing 1 part of calcium phosphate, and further polymerize at 90°C for 5 hours and at 130°C for 2 hours. Suspension polymerization was carried out for a period of time.

The bead-shaped polymer thus obtained was washed with hydrochloric acid and water, dried, and granulated using an extruder with a diameter of 40 mm.

After granulation, predetermined test pieces were produced using an injection molding machine and their physical properties were measured.

The results are shown in Table-1.

Comparative Example 1 Example 1 except that polybutene LV-10 was not used.
Polymerization was carried out under the same conditions.

The results are shown in Table 1.

Example 2 Polybutene HV-35 (
Table 1 shows the results of an experiment conducted in the same manner as in Example 1 except that 5 parts of Nisseki Jushi Kagaku Co., Ltd., average molecular weight 750) were used.

Comparative Example 2 Polybutene HV-300 instead of polybutene LV-10
(manufactured by Nisseki Jushi Kagaku Co., Ltd., average molecular weight 1,260) was used, but the experiment was conducted in the same manner as in Example 1.

The results are shown in Table 1.

Example 3 An experiment was carried out in the same manner as in Example 1 except that styrene-butadiene rubber (SBR1502 manufactured by Japan Synthetic Rubber Co., Ltd.) was dissolved instead of polybutadiene rubber.

The results are shown in Table 1.

Example 4 The same experiment as in Example 1 was carried out except that the amount of polybutene LV-10 was reduced to 3 parts.

The results are shown in Table 1. Comparative Example 3 An experiment was conducted in the same manner as in Example 1 except that the amount of holybutene LV-10 was reduced to 1 part.

The results are shown in Table 1. Comparative Example 4 Example 1 by increasing the amount of polybutene LV-10 to 10 parts
I conducted the same experiment.

The results are shown in Table 1. Comparative Example 5 An experiment was carried out in the same manner as in Example 1, except that benzoyl peroxide was used as an initiator instead of lauroyl peroxide.

The results are shown in Table 1.

Reference example 1 Dioctyl phthalate (instead of polybutene LV-10)
The experiment was conducted in the same manner as in Example 1, except that the solution (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved.

The results are shown in Table 1. Reference Example 2 An experiment was conducted in the same manner as in Example 1 except that liquid paraffin (P-300 manufactured by Matsumura Sekiyu Co., Ltd.) was dissolved instead of polybutene LV-10.

The results are shown in Table 1. Example 5 A solution of styrene-polybutadiene rubber and polybutene LV-10 dissolved in the proportions of Example 1 was thermally polymerized in bulk at 110°C for 4 hours and at 120°C for 2 hours, and then tertiary butyl peroxybenzo Suspension polymerization was carried out under the same conditions as in Example 1 by adding 0.15 part of Ade.

The results are shown in Table 1. The polymer was measured under the following conditions.

Impact strength: Measured at a temperature of 20°C according to ASTM D-256. Tensile strength: Measured at a temperature of 20°C and a tensile speed of 30 mm/min on a test piece press-formed into the shape of a JIS dumbbell No. 2.

Claims (1)

[Claims] 1 In a method for producing impact-resistant polystyrene by dissolving a butadiene-based rubber elastomer in an aromatic vinyl monomer and polymerizing it, a low molecular weight polymer obtained mainly of isobutylene with an average molecular weight of 200 to 1000 is added to the rubber elastomer. A method for producing high-impact polystyrene, which comprises bulk polymerizing the polystyrene in the presence or absence of a low-grafting initiator.