KR100753388B1 - Manufacturing Method of Expanded Polystyrene with Ethylenebisstearamide - Google Patents

Abstract

The present invention relates to a process for producing expandable polystyrene beads, and more particularly, to a process for forming expandable polystyrene beads having a uniform and fine cell structure. In order to control the size of a cell, A process for producing expanded polystyrene beads having a high mechanical strength and a low thermal conductivity by using a combination of ethylenebisstearamide and peroxide with a reoxidation initiator and using an inorganic dispersant to have a more uniform and very fine cell structure .

Expanded polystyrene, nucleating agent, thermal conductivity, cell

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing expanded polystyrene beads using ethylene bisstearamide,

1 is an optical microscope photograph of a cell according to Example 1 of the present invention.

2 is an optical microscope photograph of a cell according to Example 2 of the present invention.

3 is an optical microscope photograph of a cell according to Comparative Example 1 of the present invention.

More particularly, the present invention relates to a process for producing expanded polystyrene beads by using a nucleating agent having a specific size and a specific component and reacting with a specific initiator and a dispersant to produce uniform expanded polystyrene beads, Structure of the foamed polystyrene.

A bead-shaped polystyrene resin containing a blowing agent such as propane, pentane, butane, methyl chloride and the like and a nucleating agent is generally called expanded polystyrene bead, and a polystyrene foam can be produced by using it.

In general, the production of a foam which is widely used is carried out by first heating expanded polystyrene beads with steam, expanding the foams (primary foaming), leaving them for a predetermined time (aging), filling the molds with metal, And then cooling the metal mold to wait for the reduction of the foaming pressure inside the molded body, opening the mold and lifting the foamed mold.

The factor that greatly affects the physical properties of the molded article during the production of the foamed molded product is the size of the cell produced upon foaming. That is, as the cell becomes finer, it exhibits good physical properties. The larger the cell, the higher the thermal conductivity and the lower the strength. In addition, the surface of the molded article shines visually, or the adhering force with the adhesive is lowered .

Conventionally, a lot of studies have been made on a cell regulator for the production of expanded polystyrene beads capable of forming fine cells. Generally, when a polystyrene foam is prepared, a nucleating agent is used as a cell regulator. In the polymerization of the foam, the styrene resin melted at high temperature and high pressure in the reactor and the foam gas are dispersed around the nucleating agent to form polystyrene particles, It forms foams around the nucleating agent to form high quality uniform cells.

Ethylene vinyl acetate copolymer, polyethylene wax, calcium stearate, talc, magnesium carbonate, calcium silicate and the like were used as the most widely used nucleating agent for the production of expanded polystyrene beads. However, the nucleating agents are physically mixed with polystyrene matrix and mixed as an additive agent during polymerization, and foam gas and styrene resin are gathered to form cells around the nucleating agent during foaming. Since the nucleating agent is difficult to uniformly distribute in the polymer matrix, the foaming agent locally flocculates and thus it is difficult to form a fine and uniform cell, resulting in poor heat insulation and compressibility. Due to these disadvantages, the cellulosic material and the size of the cellulosic material to be manufactured by the conventional nucleating agents so far are uneven, and it is necessary to compensate for the physical properties.

The present invention has been accomplished by using ethylenebisstearamide (EBS) having an average particle diameter of 10 mu m or less as a nucleating agent and improving the dense and uniform structure of the cell . Accordingly, it is an object of the present invention to provide a method for producing expanded polystyrene beads having a uniform size by using ethylenebisstearamide (EBS) having an average particle size of 10 탆 or less as a nucleating agent.

Another object of the present invention is to provide a process for producing a foamed polystyrene foam having excellent heat insulation property, small cell diameter at the time of foaming, uniformity, and smooth and uniform surface.

The present invention also provides a polymerization system that utilizes a combination of a new initiator and a suspending agent that uses EBS as a nucleophilic agent.

The present invention relates to a process for preparing expanded polystyrene beads, and more particularly, to a process for producing expandable polystyrene beads using ethylenebisstearamide having an average particle size of 10 m or less EBS) and uniformly distributed in the resin by suspension polymerization using a peroxide and a redox-based initiator and an inorganic dispersant, thereby obtaining a foamed polystyrene having a high mechanical strength, a low thermal conductivity and a beautiful appearance And a manufacturing method for manufacturing the same.

In addition, the present invention adopts a combination of a redox initiator and a peroxide initiator in order to solve the phenomenon that when the EBS is used as a nucleating agent, the miscibility of EBS with the styrene monomer is insufficient to produce a foamed polystyrene having a poor cell shape , An inorganic dispersant having a specific composition was employed to produce a foamed polystyrene having a dense and uniform cell shape for the purpose of the present invention.

According to another aspect of the present invention, there is provided a method of manufacturing expanded polystyrene,

1) adding a dispersant to water as a dispersion medium in a reactor and uniformly dispersing the dispersion;

2) pulverizing ethylene bisstearamide to be used as a nucleating agent to a size of 10 μm or less;

3) adding styrene monomer, a polymerization initiator and pulverized ethylene bisstearamide to the reactor, heating the mixture to 50 to 90 ° C, and performing polymerization while stirring for 6 hours or more;

4) when the polymerization rate of the styrene monomer is 60 to 90% by weight in the polymerization step, the foaming agent is gradually introduced into the reactor while the temperature is gradually increased to 120 ° C;

5) cooling the reactor to a temperature of 20 to 30 DEG C, and removing excess foaming agent;

6) recovering and washing the foamed polystyrene beads manufactured;

7) drying;

.

The foamed polystyrene beads produced by the production method of the present invention are prepared by first expanding the expandable beads by steam and expanding them 50 to 90 times, filling the expanded beads in a mold, and molding the extruded beads to produce a molded product of polystyrene .

Ethylene bisstearamide used as a nucleating agent in this reaction has a melting temperature of 144 to 146 ° C and is usually sold in a bead shape of 840 μm or less. In the present invention, such ethylene bisstearamide is used as a nucleating agent, Of the average particle diameter. Preferably 0.1 to 10 mu m, and when it is 10 mu m or more, the foamed cells are not uniform and not formed densely. The pulverizing method may be pulverized using a conventional ball mill, a jet mill or a pulverizer, and is not limited in the present invention.

In the present invention, the reason why the average particle diameter of ethylenebisstearamide is limited to 10 mu m or less is because the melting temperature is from 144 to 146 DEG C, so that it is not melted during the polymerization reaction and participates in the reaction. This is because the cell is uniformly dispersed evenly on the surface of the styrene bead produced by the suspension polymerization and prevents the cells from being unevenly foamed at the time of foaming. Since the particle size of the nucleating agent of the present invention is as small as 10 탆 or less, it is distributed evenly inside the styrene beads produced by the suspension polymerization at a high dissolution rate. In the case of producing the foam, When the foaming gas is poured around the nucleus agent and steam is applied to the foaming agent, the foaming takes place around the nucleus agent to form an excellent cell having a small particle size and a uniform size.

In the present invention, the stability of the foamed cell formation according to the size of the nucleating agent is remarkable as an unexpected result, and compared with the case of using a commercially available size EBS, EBS having an average particle diameter of 10 탆 or less It is found that the density and uniformity of the cell are remarkably different from each other, and the inventor of the present invention has found that this phenomenon is a very unusual phenomenon, which is also a feature of the present invention.

Generally, the nucleating agent is physically mixed with the polystyrene matrix, but is not chemically bonded, so that the nucleating agent is likely to be unevenly distributed in the matrix. In this case, the foaming agent locally flocculates and is difficult to form fine and uniform cells. Increasing the amount of nucleating agent also reduces the compatibility with the polymer matrix. However, when the EBS having an average particle diameter of 10 mu m or less according to the present invention is used, the dispersibility is excellent, and uniform cells can be formed by uniform distribution.

In the present invention, the nucleating agent is used in an amount of 0.01 to 5% by weight based on the styrene monomer. When the content is less than 0.01% by weight, the cell serves as a cell regulator insufficient to form a uniform cell, and it is difficult to control the cell size to a fine state. When the cell content exceeds 5% by weight, And it is not economical since an effect of an excess amount of addition can not be expected.

In the present invention, the dispersion medium may be ordinary purified water, and purified water of the same amount as the styrene monomer may be used.

As described above, the foamed cell having the above-mentioned density and uniformity can be obtained only by using the EBS of 10 탆 or less as described above. However, in the present invention, when the combination of the specific initiator and the suspension is adopted, do.

As a result of solving the above problems, the polymerization initiator that can be used in the present invention includes benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, 5-di (oxyperbenzoate) -hexane-3,1,3-bis (tert-butylperoxide isopropyl) -benzene, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, Butyl peroxyacetate, t-butyl peroxyisobutylate, t-butyl peroxy (2-ethylhexanoate), peroxyisophthalate, peroxides such as t-butyl benzoate, methyl ethyl ketone peroxide, methyl cyclohexa peroxide and the like; Azo type compounds such as azobisisobutylonitrile and dimethyl azodiisobutylate, and ammonium persulfate as the redox initiator, and the like can be used. It is most preferable to use a mixed initiator in which benzoyl peroxide, t-butyl peroxybenzoate, ammonium persulfate and dicumyl peroxide are mixed. The weight ratio of the initiator is preferably 50 to 60:20 to 30: 8 to 12: 8 to 12 to give a total of 100, and more preferably 55: 25: 10: 10 by weight, the most dense and uniform cells could be formed. The amount of the mixing initiator varies depending on the type of the monomer used and the molecular weight of the polymer, and it is preferable to use 0.1 to 4 wt% based on the styrene monomer. If it is more than 4% by weight, the polymerization reaction is promoted at a low temperature to form cells, and when it is used at 0.1% by weight or less, the polymerization rate is slow and it is not economical.

The dispersing agent for suspension polymerization of the present invention is not limited as long as the dispersing agent used in ordinary suspension polymerization can maintain the stability of the particles. For example, a dispersing agent such as insoluble phosphate or water-soluble high-polymer protective colloid can be used. Examples of the insoluble phosphate include tricalcium phosphate, trisodium phosphate, magnesium phosphate and the like. Examples of the water- At least one water-soluble cellulose derivative selected from vinyl pyrrolidone, methyl cellulose, polyvinyl alcohol-co-vinyl acetate, hydroxyalkyl cellulose and carboxyalkyl cellulose, and sodium polyacrylate. However, in the present invention, when tricalcium phosphate, trisodium phosphate or the like is used as an inorganic suspension agent, expanded polystyrene having more excellent foamed cells can be produced. The content thereof is preferably 0.01% by weight or more based on the total amount of the substances present in the polymerization system.

The flame retardant of the present invention may be selected from decabromodiphenyl oxide, octabromodiphenyl oxide, brominated polystyrene, bis (tribromophenoxy) ethane, tetrabromobisphenol A, hexabromocyclododecane, brominated epoxy It is obvious that any one or more selected organic bromine flame retardants may be used, but not limited thereto, chlorine-based flame retardants and the like can be used. The content thereof is preferably 1 to 10% by weight based on the styrene monomer. When it is used in an amount of less than 1% by weight, the desired effect can not be expected. When it exceeds 10% by weight, other properties are deteriorated remarkably. It is also clear that the flame retardancy grade can be controlled according to the content of the flame retardant.

Examples of the foaming agent usable in the present invention include aliphatic hydrocarbons such as propane, butane, pentane and the like; Aliphatic cyclic hydrocarbons such as cyclobutane, cyclopentane and the like; Halogenated hydrocarbons such as methylene chloride, dichlorodifluoromethane, trichloromethane, trichloroethane, trichlorethylene, and the like. These solvents may be used alone or in combination. The content thereof is not particularly limited and may be generally used in the art Use quantity.

In addition, additives such as an inorganic antibacterial agent, a surfactant, a UV stabilizer, and an antioxidant may be further used as needed.

An inorganic antimicrobial substance may be added to impart the antimicrobial activity to the foam, and the content thereof is preferably 0.001 to 5% by weight in the polystyrene foam resin composition, and when it is used in an amount of 0.001% by weight or less, And it is undesirable because it may affect the nucleating agent when it is used in an amount exceeding 5% by weight. Examples of the antimicrobial material include metal oxides in which silver or zinc is supported on gamma alumina; Wherein the silver oxide is selected from at least one of ceramics selected from zinc oxide, aluminum oxide, and magnesium oxide, primary calcium phosphate, secondary calcium phosphate, tertiary calcium phosphate, calcium phosphite, calcium phosphate, calcium pyrophosphate Any one or more calcium phosphate type inorganic substances; Natural or synthetic aluminosilicate containing at least one metal selected from silver, zinc and copper may be used.

Surfactants may also be used in the polymerization, for example, sodium salts of alkylbenzenesulfonates, sodium salts of alpha olefinsulfonates having 6 to 12 carbon atoms, sodium salts of laurylsulfonate, dodecylbenzenesulfo Sodium salt of dodecylbenzenesulfonate, calcium salt of dodecylbenzenesulfonate, and mixtures thereof.

Further, a UV stabilizer may be further added to improve the weather resistance. For example, a benzophenone, benzotriazole or hindered amine compound may be used, and the heat stability of the resin and the synergistic effect with the stabilizer An antioxidant may be used. For example, at least one selected from a hydroxyphenyl-based, a tinarate-based, a tin-mercapto-based, and a perspate-based compound can be used.

In addition, as the above-mentioned reaction mixture in the present invention, styrene monomers, dispersion media, dispersants and initiators are all widely used in the production of expanded polystyrene to such an extent that can be easily understood by those skilled in the art of making expanded polystyrene It will be obvious that one can use.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

The thermal conductivity of the present invention was measured using TCA-8 manufactured by Anacon Co. The size of the sample was 200 x 200 x 25 cm, the temperature of the hot plate was 36.5 ° C, and the temperature of the low temperature plate was 10 ° C.

The flexural strength and compressive strength were measured using a Shimadzu Autograph AG-2000A. The feeds for the compressive strength measurements were 5 × 5 × 5 cm and the flexural strengths were 30 × 7.5 × 2.5 cm.

[Example 1]

While the reactor was being stirred slowly, 40 kg of water and 210 g of tricalcium phosphate (BUDENHEIM), 55 g of polyvinyl alcohol (KURARAY) and 30 g of trisodium phosphate (TAIYO NOBEL) were dispersed as a dispersion medium and dispersed uniformly. 110 g of benzoyl peroxide (AKZO NOBEL) as initiator, 50 g of t-butyl peroxybenzoate (AKZO NOBEL), 40 g of ammonium persulfate (Mitsubishi GAS Co.) as initiators were added to 40 kg of styrene monomer (Hyundai Petrochemical Co., ) And 20 g of dicumyl peroxide (GAO QIAO, Inc.) were dissolved in 60 g of ethylene bisstearamide (LEOCHEMICAL) having an average particle diameter of 10 mu m and 4 kg of hexabromocyclododecane (flame retardant) (GREAT LAKES CHEMICAL Co.) , The temperature of the reactor was gradually raised, and the reaction was carried out at 90 DEG C for 6 hours.

0.5 g of the reaction product was completely dissolved in 20 g of dichloromethane containing 0.001% by weight of n-butylbenzene as an internal standard substance, and the content of residual monomer was measured using gas chromatography to determine the polymerization rate to 75% by weight , 3500 g of pentane was fed into the reactor at a constant rate using a metering pump while slowly raising the temperature to 120 ° C. After maintaining the reaction for 6 hours, the polymerization temperature was cooled to 30 DEG C and unnecessary pentane gas was removed. The expanded polystyrene beads were recovered by using a wire net, washed with water and dried to obtain final expanded polystyrene beads.

The molecular weight and molecular weight distribution of the obtained expanded polystyrene beads were measured by a gel permeation chromatography method, and as a result, beads of uniform size having a weight average molecular weight of 280,000, a molecular weight distribution of 2.5, and an average particle size of 0.9 mm were prepared.

The foamed expanded polystyrene beads were foamed with steam to obtain expanded foam particles having a magnification of 50 times, and after 24 hours, the foamable particles were filled in a molding mold and molded to form a molded polystyrene product. The thermal conductivity, compressive strength and flexural strength of the thus-obtained molded article were measured. The results are shown in Table 1. The results are shown in Fig. 1, in which the molded article was thinly cut and magnified 100 times by using an optical microscope.

[Example 2]

The procedure of Example 1 was repeated except that 40 g of ethylene bistostearamide having an average particle diameter of 10 탆 was used as the nucleating agent in Example 1.

As a result, uniformly sized expanded polystyrene beads having a weight average molecular weight of 278,000, a molecular weight distribution of 2.5, and an average particle diameter of 0.8 mm were prepared.

The foamed expanded polystyrene beads were foamed with steam to obtain expanded foam particles having a magnification of 50 times, and after 24 hours, the foamable particles were filled in a molding mold and molded to form a molded polystyrene product. The thermal conductivity of the thus-prepared molded article was measured for compressive strength and flexural strength. The results are shown in Table 1. The results are shown in Fig. 2, where the molded product was cut into thin pieces and magnified 100 times using an optical microscope to observe the cells.

[Comparative Example 1]

Except that 12 g of polyethylene wax (number average molecular weight: 1000) was used as the nucleating agent in Example 1.

As a result, expanded polystyrene beads having a weight average molecular weight of 291,000, a molecular weight distribution of 2.7, and an average particle size of 0.92 mm were produced.

The foamed expanded polystyrene beads were foamed with steam to obtain expanded foam particles having a magnification of 50 times, and after 24 hours, the foamable particles were filled in a molding mold and molded to form a molded polystyrene product. The compressive strength and flexural strength of the molded article thus obtained were measured. The results are shown in Table 1. The results of observing the cells are shown in Table 1, in which the molded article is cut thinly and magnified 100 times by using an optical microscope.

[Comparative Example 2]

Except that the nucleating agent was not used in Example 1 above. As a result, expanded polystyrene beads having a weight average molecular weight of 310,000, a molecular weight distribution of 2.7, and an average particle diameter of 1.13 mm were produced, and their sizes were uneven.

The foamed expanded polystyrene beads were foamed with steam to obtain expanded foam particles having a magnification of 50 times, and after 24 hours, the foamable particles were filled in a molding mold and molded to form a molded polystyrene product. The thermal conductivity, the compressive strength and the flexural strength of the thus-obtained molded article were measured, and the results are shown in Table 1.

[Comparative Example 3]

Except that only 110 g of benzoyl peroxide (AKZO NOBEL) was used as the initiator in Example 1. As a result, uneven-sized beads having a weight average molecular weight of 285,000, a molecular weight distribution of 2.5, and an average particle size of 0.9 mm were produced.

The foamed expanded polystyrene beads were foamed with steam to obtain expanded foam particles having a magnification of 50 times, and after 24 hours, the foamable particles were filled in a molding mold and molded to form a molded polystyrene product. The thermal conductivity, the compressive strength and the flexural strength of the thus-obtained molded article were measured, and the results are shown in Table 1.

[Table 1]

As shown in the table, Examples 1 and 2 according to the present invention have low thermal conductivity and excellent insulation properties, and exhibit excellent compressive strength and flexural strength. As can be seen from Figs. 1 to 3, in the case of the expanded polystyrene of Example 1 and Example 2 using ethylene bistostearamide having a size of 10 탆 or less, which is a feature of the present invention, and the inorganic dispersant, As shown in FIG. 3, in the case of Comparative Example 1 using polyethylene wax as a nucleating agent, the cell size was not dense and the cell size was not uniform .

Also, although not shown in the figure, in Comparative Example 3 prepared using only one peroxide initiator as an initiator, the cell size was uneven, and it was found that the cells were not dense as compared with Example 1, and the thermal conductivity and compressive strength And the flexural strength was low.

According to the production method of the present invention, expanded polystyrene beads prepared using ethylene bisstearamide having a size of 10 탆 or less as a nucleating agent and a mixed initiator and an inorganic dispersant in which peroxide and redox initiator are mixed, Or less and has a uniform average particle diameter of less than or equal to the average particle diameter of the beads, and when the molded product is produced by foaming using the beads, the cells are uniform in size, cells of a very small size are formed, the heat insulating property is excellent, Was excellent in mechanical properties.

Claims (5)

1) adding a dispersant to water as a dispersion medium in a reactor and uniformly dispersing the dispersion; 2) pulverizing ethylene bisstearamide to be used as a nucleating agent to a size of 10 μm or less; 3) adding styrene monomer, a polymerization initiator and pulverized ethylene bisstearamide to the reactor, heating the mixture to 50 to 90 ° C, and performing polymerization while stirring for 6 hours or more; 4) when the polymerization rate of the styrene monomer is 60 to 90% by weight in the polymerization step, the foaming agent is gradually introduced into the reactor while the temperature is gradually increased to 120 ° C; 5) cooling the reactor to a temperature of 20 to 30 DEG C, and removing excess foaming agent; 6) recovering and washing the foamed polystyrene beads manufactured; 7) drying; ≪ / RTI > wherein the foamed polystyrene beads have an average particle size of less than about < RTI ID = The method according to claim 1, Wherein the nucleating agent is used in an amount of 0.01 to 5% by weight based on the weight of the styrene monomer. 3. The method of claim 2, The dispersant may be at least one selected from the group consisting of tricalcium phosphate, trisodium phosphate, magnesium phosphate, polyvinyl alcohol, polyvinylpyrrolidone, methylcellulose, polyvinyl alcohol-co-vinyl acetate, hydroxyalkylcellulose, carboxyalkylcellulose, sodium polyacrylate Wherein at least one selected from the group consisting of polypropylene and polypropylene is used. The method of claim 3, The initiator may be at least one selected from the group consisting of benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, 2,5-di (oxyperbenzoate) , 3-bis (tert-butylperoxide isopropyl) -benzene, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, stearoyl peroxide, 3,3,5-trimethylhexanoyl peroxide, t Butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy (2-ethylhexanoate), peroxyisophthalate, t-butyl benzoate, methyl ethyl ketone peroxide, One or more peroxides selected from oxides; At least one azo compound selected from azobisisobutylonitrile, and dimethyl azodiisobutylate; And a redox initiator such as ammonium persulfate, either singly or in combination. 5. The method of claim 4, The initiator is a mixture initiator obtained by mixing benzoyl peroxide, t-butyl peroxybenzoate, ammonium persulfate and dicumyl peroxide at a weight ratio of 50: 60: 20 to 30: 8 to 12: 8 to 12 Wherein the foamed polystyrene beads have an average particle size of less than about 5 占 퐉.

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