JPS61163943A - Medium to high expansion ratio expandable polystyrene bead of small particle diameter - Google Patents

Abstract

PURPOSE:The titled polystyrene beads small in a change in moldability with time, obtained by impregnating polystyrene beads with a blowing agent in the presence of a specified aqueous medium. CONSTITUTION:An aqueous medium is obtained by adding 1-3wt%, based on PS beads, aromatic hydrocarbon (e.g., toluene), 0.1-2wt%, based on PS beads, high-boiling plasticizer (e.g., dioctyl adipate), 0.1-2wt%, based on PS beads, medium-boiling plasticizer (e.g., butyl methacrylate), 0.1-2wt%, based on PS beads, (alpha-methyl)styrene monomer and a dispersant such as an alkylbenzenesulfonate salt to water placed in a reaction vessel and thoroughly mixed to obtain asuspension. This aqueous medium in this reaction vessel is charged with PS beads of a small particle diameter and agitated and pressurized with a volatile blowing agent such as butane, and the temperature in the vessel is increased and then decreased by cooling to obtain the titled PS beads.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing thermoplastic bead beads that are expandable to medium and high times in ultra-small particles with little change in moldability over time in foam molding. @ of plastics polyfoam used in law! This invention relates to the YSA method for medium- to high-expandable thermoplastic resin beads of extremely small particles suitable for No. 4.

[Technical Background and Explanation of Prior Art 3 Expandable plastic beads with small particle size are easy to charge into molds, but when the expansion ratio is increased for those using a volatile foaming agent, Due to the remarkable decrease in foaming ratio due to daily changes, the particle size is currently 0.47
Expandable polystyrene beads with extremely small particles of ~0.14 m are used as a raw material for cup manufacturing at an expansion ratio of about 5 to 15 times.

On the other hand, in the full mold casting method, a model is made from plastic foam, buried in molding sand, and molten metal is injected in that state.The heat of the molten metal burns off the plastic foam model. At the same time, molten metal enters the hollow part and the shape becomes 5llIa, which is the same as the model.
It is a method of waving things.

1. To make a plastic foam model using the full mold method, use a plastic foam containing at least 50% (! amount) of methacrylic acid ester (equity 11849-23).
458 Publication), and polymer particles obtained by adding styrene monomer to polyethylene tfI resin particles and polymerizing them in order to make expandable plastic beads used in the production of plastic foam models in the full mold method. impregnation with a foaming agent (Japanese Patent Publication No. 57-18972)
No. 2) is known.

The present inventors have noticed that expandable plastic beads with small particle diameters have good filling properties into molds and are suitable for manufacturing plastic foam models using the above-mentioned full mold method. We conducted tests and found that the foamable plastic beads with small particle diameters known so far have a low expansion ratio, and that the full mold method using a foamed plastic model made using these beads was difficult. So,
Unable to obtain a product with a clean surface,
Also, I repeatedly encountered difficulty in flowing the molten metal during casting.

Therefore, we continued our research and developed a foamable plastic with small particle size.
1. If you use durable beads with a high expansion ratio, the molten metal will flow easily at 1111 m.
It was also discovered that a SaW product with a clean surface could be obtained, and based on this knowledge, the present invention was achieved.

[Object of the invention and summary of the invention]

An object of the present invention is to provide expandable plastic beads that do not reduce the expansion ratio due to changes over time during storage even if the particle size is small. The purpose of the present invention is to provide foamable plastic speed with a small particle size suitable for manufacturing models.

The present invention involves impregnating polystyrene beads with a foaming agent,
When producing expandable polystyrene beads, 1-3% aromatic hydrocarbons for polystyrene beads, 0.1-2% high boiling point plasticizer for polystyrene beads, 0.1% for polystyrene beads. Characterized by impregnating polystyrene beads with a blowing agent in the presence of an aqueous medium with ~2% of a medium-boiling plasticizer and 0.1-2% of styrene monomer or α-methylstyrene added to the polystyrene beads. This is a method for producing medium- to high-expandable polystyrene beads with small particle sizes.

In the present invention, the aromatic hydrocarbon can be selected from the group consisting of toluene, xylene and mixtures thereof, and the high boiling plasticizer is dioctyl adipate, dioctyl phthalate, dibutyl phthalate,
It can be selected from the group consisting of dibutyl sebacate, butyl benzyl phthalate, diisodecyl phthalate and mixtures thereof, and the medium boiling plasticizer can be butyl methacrylate, butyl acrylate and mixtures thereof.

The expandable polystyrene beads made into l1m according to the present invention are extremely small particles with a particle size of about 0.47 to 0.24, and even though they have an expansion ratio of 40 times or more, they do not change over time during storage. No decrease in foaming ratio was observed, nor was there any decrease in moldability.

[Detailed description of the invention]

According to the present invention, expandable polystyrene beads are aa-treated as follows.

Pour water into a reaction vessel, add a dispersant, aromatic hydrocarbon, high boiling point plasticizer, medium boiling point aJ111i115, and monomer, stir well to form an aqueous suspension, add polystyrene beads to this, and stir. Meanwhile, a volatile blowing agent is forced into the reaction vessel. After press-fitting a predetermined amount of volatile foaming agent,
After the temperature inside the reaction vessel is raised and the reaction is carried out for a predetermined period of time, the inside of the reaction vessel is cooled and the expandable polystyrene beads impregnated with the volatile blowing agent are taken out.

The dispersant can be anything that can disperse the aromatic hydrocarbon, high-boiling plasticizer, medium-boiling plasticizer, and monomer in water, such as sodium linear alkylbenzene sulfonate. Preferably, phosphates such as alkylbenzene sulfonates and magnesium pyrophosphate are used.

Aromatic hydrocarbons can be used as high-boiling point plasticizers, medium-boiling point plasticizers, and 7-mer solvents, and can also be used as agents for volatile blowing agents. For example, any solvent can be used, but toluene or xylene is preferably used.

As high-boiling plasticizers, preference is given to using dioctyl adipate, 9-octyl phthalate, dibutyl phthalate, dibutyl sebacate, butylbenzyl phthalate or diisodecyl phthalate.

As medium-boiling plasticizer it is preferred to use butyl methacrylate or butyl acrylate.

As the monomer, it is preferable to use styrene monomer or α-methylstyrene monomer.

The particle size of the expandable polystyrene beads produced according to the present invention is determined by the polystyrene beads charged into the reaction vessel, but due to impregnation with the volatile blowing agent, the particle size is slightly larger than that of the raw material polystyrene beads, but the difference is It's not that big.

In addition, volatile foaming agents are used to foam the drumsticks.
1. Any usable material may be used, but propane, butane, pentane, etc. are preferably used.

The expansion ratio of expandable polystyrene beads is determined by the volatile blowing agent with which the polystyrene beads are impregnated.

In the following, the present invention will be explained in more detail by an example of implementation and a comparative example.

Example 1 20001rL7I of water was placed in a 5L reaction vessel, and 1.0ml of sodium linear alkylbenzenesulfonate was added thereto. Oy
311 parts of magnesium 1-birophosphate, 301 parts of toluene, 8 g of butyl methacrylate, 8 g of α-methylstyrene, and 6 g of dioctyl adipate were added and stirred well to obtain an aqueous suspension. This has an average particle size of 0.47 to 0-31.
Add 2000y of styrene polymer particles of 180rpm.
While stirring (2), 414 cc of butane gas was gradually introduced under pressure. After the injection is complete, the temperature inside the reaction vessel is set to 70°C.
After continuing the reaction for 4 hours, the temperature inside the reaction vessel was cooled and the styrene electrolyte particles impregnated with the blowing agent were taken out at a temperature below 30°C.

Actual Example 2 In Example 1, the amount of butyl methacrylate was changed to 14.
Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Example 1, except that the amount of α-methylstyrene was 141.

Example 3 Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Example 1, except that 8 g of styrene monomer was used instead of α-methylstyrene.

Comparative Example 1 Put 2000 rrLl of water into a 5L reaction container, and add 1.01ml of sodium linear alkylbenzenesulfonate to it.
, 3 g of magnesium pyrophosphate, 301 g of toluene, 8 g of butyl methacrylate, and 8 g of α-methylstyrene were added and thoroughly stirred to obtain an aqueous suspension. To this, 20 styrene polymer particles with an average particle size of 0.47 to Q, 31 m were added.
0019 was added, and 414 CC of butane gas was gradually injected under stirring while stirring at 180 rpm. After 1,000 people, the temperature inside the reaction vessel was raised to 70°C, and after continuing the reaction for 4 hours, the first grade inside the reaction vessel was cooled, and the styrene polymer particles impregnated with the blowing agent were heated at 30°C or below. I took it out.

Comparative Example 2 Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Comparative Example 1, except that α-methylstyrene was not used.

Comparative Example 3 Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Comparative Example 1, except that α-methylstyrene was not used and 6 g of dioctyl adipate was used.

Comparative Example 4 Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Comparative Example 1, except that butyl methacrylate was not used and 6 g of dioctyl adipate was used.

Comparative Example 5 Comparative Example 1 except that butyl methacrylate was not used, α-methylstyrene was not used, and 6 g of dioctyl adipate was used.
In the same manner as above, styrene polymer particles impregnated with a blowing agent were obtained.

Comparative Example 6 Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Comparative Example 1, except that butyl methacrylate was not used.

Comparative Example 7 In Comparative Example 1, the amount of toluene was 46 g,
Styrene polymer particles impregnated with a blowing agent were obtained in the same manner as in Comparative Example 1, except that butyl methacrylate and α-methylstyrene were not used.

Test example! Using the expandable polystyrene beads prepared in Examples and Comparative Examples and stored for the period shown in Table 1,
In molding Im (manufactured by Sekisui Koki, ACE-3), the counterfeit was made by heating at steam pressure o and 7sK9/cd.
(Shaped.

The results of molding at a foaming ratio of 50 times were as shown in table 1.

Molding condition ○ in Table 1: The molding condition was good, and the surface elongation and appearance of the molded product were fully satisfactory.

Δ: The molding condition was not good, and the surface elongation and appearance of the molded product were unsatisfactory.

×: Molding condition is poor.

(Leaving space below) Table 1 Molding condition test example 2 at an expansion ratio of 50 times Expandable polystyrene beads made in Examples and Comparative Examples that had been stored for the period shown in Table 2 were used.
In the molding machine (ACE-3 manufactured by Sekisui Koki), the steam pressure is 0.
．． A counterfeit was molded by heating at 75 Ky/d.

The changes in foaming ratio over time during the foaming time shown in Table 2 are as follows:
It was as shown in Table 2.

(Leaving space below) Table 2-1 Change in expansion ratio over time (Example) Table 2-2 Change in expansion ratio over time (Comparative example) Table 2-3 Change in expansion ratio over time (Comparative example) Test According to the results of Example 1 and Test Example 2, when polystyrene beads are impregnated with butane gas, toluene, α-methylstyrene,
Products to which butyl methacrylate and dioctyl adipate are added have better molding conditions in foam molding than those to which either of these is not added, and there is almost no decrease in expansion ratio during oral changes during storage, and the particle size is Although it is small, it can be used for manufacturing foamed plastic models using the full mold method.

xylene was used instead of toluene, styrene monomer was used instead of alpha-methylstyrene, butyl acrylate was used instead of butyl methacrylate, and dioctyl phthalate was used instead of dioctyl adipate,
Expandable polystyrene beads were made using dibutyl phthalate, J dibutyl sebacate, butyl benzyl phthalate, or diisodecyl phthalate and similar tests were conducted, with results similar to those described above.

〔Effect of the invention〕

The expandable polystyrene beads produced according to the present invention use a volatile foaming agent, and even if the particle size is small, the foaming ratio does not decrease over time during storage, and the foaming Since no deterioration in the molding condition is observed during molding, it can be used for manufacturing plastic foam models using the full mold method.

Claims (3)

[Claims] (1) When manufacturing expandable polystyrene beads by impregnating polystyrene beads with a foaming agent, the amount of aromatic hydrocarbons is 1 to 3% to the polystyrene beads, and the high content is 0.1 to 2% to the polystyrene beads. In the presence of an aqueous medium with the addition of a boiling point plasticizer, 0.1-2% of a medium-boiling plasticizer relative to the polystyrene beads and 0.1-2% of styrene monomer or α-methylstyrene relative to the polystyrene beads. A method for producing polystyrene beads with small particle size and medium to high expandability, which comprises impregnating polystyrene beads with a foaming agent. (2) the aromatic hydrocarbon is selected from the group consisting of toluene, xylene and mixtures thereof, and the high boiling point plasticizer is dioctyl adipate, dioctyl phthalate, dibutyl phthalate, dibutyl sebacate,
selected from the group consisting of butyl benzyl phthalate, diisodecyl phthalate and mixtures thereof, and the medium boiling point plasticizer is butyl methacrylate,
2. The method for producing medium to high expandable polystyrene beads with small particle size according to claim 1, characterized in that the beads are selected from the group consisting of butyl acrylate and mixtures thereof. (3) The granules according to claim 2, wherein the aromatic hydrocarbon is toluene, the high-boiling plasticizer is dioctyl adipate, and the medium-boiling plasticizer is butyl methacrylate. A method for manufacturing small-diameter, medium- and high-expandable polystyrene beads.