KR101242744B1 - Method for producing expandable polystyrene beads with expandable seed particles - Google Patents

Abstract

The present invention relates to a method for producing expandable polystyrene particles using expandable seed particles containing a blowing agent. More specifically, (1) forming an aqueous dispersion comprising selectively the expandable seed particles, the dispersant, and the surfactant, and (2) the styrene monomers in which the initiator and the additive are dissolved under pressure conditions so as not to foam the expandable seed particles. Seed polymerization, and (3) the polymerization is completed, and a blowing agent is added to obtain expandable polystyrene particles.
Such a method for producing expandable polystyrene particles provides a novel method for efficiently repolymerizing and normalizing non-popular products or extraneous products containing a blowing agent generated during suspension polymerization of conventional expandable polystyrene particles.

Description

Method for producing expandable polystyrene particles using expandable seed particles {Method for producing expandable polystyrene beads with expandable seed particles}

The present invention relates to a method for producing expandable polystyrene particles using expandable seed particles containing a blowing agent. More specifically, (1) forming an aqueous dispersion comprising selectively the expandable seed particles, the dispersant, and the surfactant, and (2) the styrene monomers in which the initiator and the additive are dissolved under pressure conditions so as not to foam the expandable seed particles. Seed polymerization, and (3) a polymerization method is completed, and a blowing agent is added thereto to obtain expandable polystyrene particles.

In general, suspension polymerization is widely known as a commercial method for producing expandable polystyrene particles.

The suspension polymerization method is a method of producing polymer particles using water as a dispersion medium and using monomers insoluble in water in the presence of dispersion stabilizers such as dispersants and surfactants. However, this polymerization method is prepared by dispersing the monomer present in the aqueous solution by a mechanical force, the resulting polymer particles have a very wide distribution of 0.1mm ~ 2mm, in the case of the expandable polystyrene particles for commercial use, Among them, 0.5mm ~ 1.5mm size particles are selected and subjected to the processing of foaming and molding, and then variously used as building insulation, agricultural and marine product packaging materials, and consumer electronics packaging buffers. This is because, for the resin particles of less than 0.5mm and more than 1.5mm, the volatilization of the impregnated blowing agent is too fast or too late to control the foaming and molding properties. Particularly, small particles of 0.5mm or less are not easily foamed and cause a significant decrease in mechanical properties. Therefore, they are classified as extraneous products and sold at low cost, or by reusing the extraneous products in styrene monomer during suspension polymerization. have.

In order to overcome this disadvantage, Korean Patent Publication No. 199-0010062, Korean Patent Publication No. 2000-0008971 and the like disclose a method for producing expandable polystyrene particles having a narrow particle size distribution.

Alternatively, the seed polymerization method is known as disclosed in Korean Patent Laid-Open Publication No. 2002-0000556 and Korean Patent Laid-Open Publication No. 2003-0070951.

Seed polymerization is a method of producing particles of a desired size by using a particle having a narrow particle size distribution as a seed, or using a uniform cylindrical pellet as a seed, into a suspension, and increasing the seed size while gradually adding a monomer. As such, the seed polymerization method is cumbersome to prepare in two steps, but there is an advantage that only particles of a desired size can be obtained. However, seed polymerization of foamable particles containing a blowing agent has a problem of foaming during the polymerization process.

It is therefore an object of the present invention to provide a novel process for producing expandable polystyrene particles which seed polymerizes expandable particles containing a blowing agent.

It is another object of the present invention to provide a novel method for producing expandable polystyrene particles which efficiently repolymerizes and commercializes non-popular products and extraneous expandable small particles that occur during suspension polymerization of commercial expandable polystyrene.

It is still another object of the present invention to provide a new method for producing economically expandable polystyrene particles by efficiently repolymerizing and normalizing non-popular products and extraneous expandable small particles that occur during suspension polymerization of commercially expandable polystyrene.

In the present invention, the principle of foaming of the expandable polystyrene particles is that the particles are expanded by the pushing force when the inside pressure of the expandable polystyrene particles is greater than the outside pressure, so that the particles are expanded outside the inside pressure of the particles by pressurizing during seed polymerization. A high pressure was maintained to produce expandable polystyrene particles.

By the method of the present invention in which the foamed seed particles are not foamed, under the pressurized conditions, the styrene monomers in which the initiator and the additive are dissolved are successively seeded and seed polymerized, and the non-popular products and extraneous foams, which are generated during suspension polymerization, can be efficiently recycled. It is possible to manufacture a product having good foaming and molding characteristics.

Figure 1 is a schematic diagram showing the foaming region according to the temperature, pressure of the expandable polystyrene particles by foaming agent type.

The present invention relates to a method for producing expandable polystyrene particles using expandable seed particles comprising a blowing agent. More specifically, (1) forming an aqueous dispersion comprising selectively the expandable seed particles, the dispersant, and the surfactant, and (2) the styrene monomers in which the initiator and the additive are dissolved under pressure conditions so as not to foam the expandable seed particles. Seed polymerization, and (3) the polymerization is completed, and a blowing agent is added to obtain expandable polystyrene particles.

In the practice of the present invention, in the step of (1) forming an aqueous dispersion, optionally comprising an effervescent seed particle, a dispersant, and a surfactant, the effervescent seed particle has the form of conventional spherical particles, cylindrical pellets, and amorphous forms. Granules, and the content of the blowing agent is not particularly limited.

The foamable seed particles are styrene made of polystyrene resin; Alkyl styrenes such as ethyl styrene, dimethyl styrene and para-methyl styrene; Alpha-alkylstyrenes such as alpha-methylstyrene, alpha-ethylstyrene, alpha-propylstyrene and alpha-butylstyrene; Halogenated styrenes such as chlorostyrene, and bromostyrene; And polymers and / or copolymers of styrene monomers composed of vinyl toluene, monomers copolymerizable with the styrene monomers, for example acrylonitrile, butadiene, alkyl acrylates, for example methyl acrylate, alkyl methacrylates, for example Copolymers with methyl methacrylate, isobutylene, vinyl chloride, isoprene and mixtures thereof.

The foamed seed particles may be selectively introduced into various additives such as graphite, carbon black, carbon nanotubes, flame retardants, or by using functional resin seeds such as high impact and high heat resistance, such as thermal insulation performance, antistatic ability, nonflammability, and high heat resistance. Various functionalities can be given.

The dispersant and the surfactant may be used in the conventional foamable polystyrene polymerization, in the present invention, the suspension was used as the inorganic dispersant, the surfactant was used anionic surfactant.

The dispersant may be prepared using all dispersants used in conventional expandable polystyrene polymerization, for example, an inorganic dispersant; Tricalcium phosphate, magnesium pyrophosphate, organic dispersants; Polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone and the like can be used, and in the present invention, 0.3 to 1.0 parts by weight of tricalcium phosphate is used based on 100 parts by weight of expandable polystyrene particles.

As the anionic surfactant, sodium laurylsulfonate, sodium alkylbenzenesulfonate, sodium oleinsulfonate, and the like are used. In the present invention, 0.01 to 0.2 parts by weight of sodium alkylbenzenesulfonate is used based on 100 parts by weight of the expandable polystyrene particles.

In the practice of the present invention, (2) in the step of seed polymerization by sequencing the styrene-based monomer in which the initiator and the additive are dissolved under pressurized conditions so that the foamable seed particles are not foamed, the pressurized conditions are that the foamed seed particles are not foamed, that is, foamable The conditions for maintaining the external pressure larger than the internal pressure of the particles above the softening point of the polystyrene particles are different depending on the blowing agent, as shown in FIG. 1.

The initiator used two kinds of initiators having different starting temperatures, and all initiators usually used in effervescent polystyrene polymerization may be used. In the practice of the present invention, benzoyl peroxide (BPO) and t-butyl peroxy benzoate may be used. 0.1-0.5 weight part is used with respect to 100 weight part of styrene monomers which injected two types of initiators, such as (TBPB).

Examples of the additives include conventional flame retardants used to impart various functionalities of the expandable polystyrene particles, solvents such as ethylbenzene and toluene, and foam control agents such as waxes.

The styrene monomer may be styrene, alkyl styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-alkyl styrene, alpha- methyl styrene, alpha- propyl styrene and alpha- butyl styrene, the amount of the monomer used is effervescent It is preferably in the range of 10 to 90 parts by weight based on 100 parts by weight of polystyrene particles, and can produce a variety of products with high functionality and physical properties depending on the type and content.

In the practice of the present invention, (3) in the step of completing the polymerization and at the same time adding a blowing agent to obtain the expandable polystyrene particles, the blowing agent may be used a blowing agent C4 ~ C6 hydrocarbons used in the production of general expandable polystyrene, for example Butane, i-butane, n-pentane, i-pentane, neo-pentane, cyclopentane and halogenated hydrocarbons may be used, and preferred blowing agents in the present invention include n-pentane and i-pentane in 100 parts by weight of expandable polystyrene particles. It is used at 15 parts by weight or less.

In the present invention, the method for producing expandable polystyrene particles using expandable seed particles is as follows.

In the practice of the present invention, to introduce a more accurate process, ultrapure water, foamable particle seeds, dispersants and surfactants are introduced into the reactor to maintain dispersion. When this process is complete, close the inlet of the reactor and raise / maintain the temperature between 60 ° C. and 80 ° C. under nitrogen under pressurized conditions (pressure is maintained at 2 atm if the foamable seed particles contain pentane), , Styrene-based monomer dissolved in an additive is gradually added while swelling while maintaining the chain pump for 2 hours or more. Thereafter, the pressure was further adjusted (if the foamable seed particles contained pentane, the pressure was maintained at 4 atm) and the polymerization was carried out while raising the temperature from 60 ° C. to 80 ° C. to 100 ° C. to 120 ° C. for 2 to 5 hours. After that, the impregnation is carried out simultaneously with the blowing agent. Impregnation may be carried out at 100 ° C. to 120 ° C. for 3 to 6 hours after adding the blowing agent, thereby preparing expandable polystyrene particles.

The step of foaming and molding the expandable polystyrene particles thus obtained may use conventional foaming and molding conditions, and there is no particular limitation.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1 Preparation of Expandable Polystyrene Particles Under Pressurized Conditions Using Expandable Seed Particles

Effervescent seed particles having a particle size of 0.3 mm to 0.5 mm and a pentane content of 5 parts by weight with respect to 100 parts by weight of the expandable seed particles were used. 0.2 kg of a dispersant (tricalcium phosphate; Dubon emulsifier) and 0.04 g of a surfactant (sodium alkylbenzene sulfonate; LGH) were added to a 100 L reactor with 40 kg of ultrapure water, and 16 kg of the expandable seed particles were added thereto. Thereafter, the reactor was closed and the reactor temperature was raised to 75 ° C. while maintaining the pressure at 2 atm using nitrogen, and the low temperature initiator (benzoyl peroxide; Hansol Chemical) 0.10 was added to 6 kg of styrene monomer (Styrene Monomer; SK). kg and 0.02 kg of a high temperature initiator (t-butyl peroxy benzoneate; Hosung Chemex) were dissolved and added for 3 hours. Thereafter, 18 kg of the styrene monomer was slowly added while heating at 75 ° C. to 110 ° C. for 3.5 hours while maintaining the additional pressure at 4 atm to proceed with polymerization. After this was completed, 2 kg of blowing agent (pentane; SK) was introduced into the reactor at 110 ° C. under nitrogen pressure, and impregnation was performed for 6 hours while maintaining a final reactor pressure of 13 kg _f / cm ² . After cooling below 30 ℃ and the product was discharged to the reactor. The product was washed with water, dried, foamed and molded to show in Table 1.

Example 2 Preparation of Expandable Polystyrene Particles Under Pressurized Conditions Using Expandable Seed Particles

In the step of seed polymerization by adding a styrene-based monomer in which an initiator and an additive are dissolved under pressure conditions so that the foamable seed particles are not foamed, 0.2 kg of a flame retardant (hexabromocyclododecane; Albemarle) is further dissolved as an additive together with the initiator. Except for 3 hours, foamed polystyrene particles were prepared in the same manner as in Example 1, washed with water, dried, foamed, and molded.

Comparative Example 1 Preparation of Expandable Polystyrene Particles at Normal Pressure Using Expandable Seed Particles

In the step of seed polymerization by sequencing the styrene-based monomers in which the initiator and the additive are dissolved under pressurized conditions so that the expandable seed particles are not foamed, except that the reactor inlet is closed and then pressurized with nitrogen, the process is carried out at atmospheric pressure. Was carried out in the same manner as in Example 1 and the results are shown in Table 1.

In Table 1 below, a method for evaluating foamability, molded article appearance, and fusion for 5 minutes was specifically performed as follows.

1) 5-minute effervescent: foamed drainage (fold) when foamed for 5 minutes at 0.3kg _f / cm ² steam pressure

2) Appearance of molded product: 50 times of pre-expanded foam, and the appearance is observed after molding by using a mold for measuring properties of 40cm × 30cm × 10cm.

3) Fusion: It shows the state in which the foamed granules of the molded products are in close contact with each other, and the percentage of the broken particles inside the molded product fractured surface (%)

 Property Item Example 1 Example 2 Comparative Example 1 5 minutes effervescent
(Drainage) 60 65 In the step of seed polymerization by sintering a styrene-based monomer in which the initiator and the additive are dissolved under unpressurized conditions, the foamed seed particles are foamed to cause deformation particles and dispersion instability to stop the polymerization. Molded product appearance Good Good Fusion (%) 60 70

As can be seen from the results of Table 1 above, the foamed seed particles were foamed in the same manner as in Examples 1 and 2 by seed polymerization of a styrene-based monomer in which an initiator and an additive were dissolved under pressurized conditions. It was possible to manufacture a product having good molding characteristics.

Although the present invention has been described in detail in the above embodiments, the above embodiments are not described to limit the scope of the present invention, but are described for illustrative purposes only.

Those skilled in the art will recognize that modifications of the invention are possible without departing from the scope and spirit of the invention, and the scope of the invention is determined by the following claims.

Claims (8)

(1) forming an aqueous dispersion comprising an expandable seed particle, a dispersant, and a surfactant; (2) seed polymerization by concatenating a styrene monomer in which an initiator and an additive are dissolved under pressurized conditions so that the expandable seed particle is not foamed; (3) A method for producing expandable polystyrene particles comprising completing the polymerization and simultaneously adding a blowing agent to obtain expandable polystyrene particles. The method of claim 1, wherein the pressurization condition is a condition in which the external pressure is kept larger than the internal pressure of the particle above the softening point of the expandable polystyrene particles. The method of claim 1, wherein the foamed seed particles comprise conventional spherical particles, cylindrical pellets, or amorphous granules. The method of claim 1, wherein the foamed seed particles are styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha-ethyl styrene, alpha-propyl styrene, alpha-butyl styrene, chloro styrene, and bromo A polymer of a monomer selected from the group consisting of styrene or at least one monomer selected from the group consisting of vinyl toluene, acrylonitrile, butadiene, methylacrylate, methylmethacrylate, isobutylene, vinyl chloride and isophorene; Method for characterized in that the copolymer of. The method of claim 1, wherein the expandable seed particle comprises an additive selected from graphite, carbon black, carbon nanotubes, and a flame retardant. The method of claim 1, wherein the expandable seed particles are high impact or high heat resistant functional resin seeds. The method of claim 1, wherein the weight ratio of the expandable seed particle and the styrene monomer is 10 to 90: 90 to 10. The method according to claim 1, wherein the step (3) is performed by adding a blowing agent, and the amount of the blowing agent is 15 parts by weight or less based on 100 parts by weight of the expandable polystyrene particles.

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