KR20090051670A - Expandable polystyrene bead and method for preparing the same - Google Patents

Abstract

It is an object of the present invention to provide a novel expandable polystyrene bead containing a new flame retardant material which has never been used in conventional expandable polystyrene beads and a process for producing the same. Expandable polystyrene beads provided in the present invention, styrene-based polymer particles; A blowing agent impregnated in the styrene polymer particles; And expanded vermiculite powder dispersed in the styrene-based polymer particles.

Effervescent Polystyrene Beads

Description

Expandable polystyrene bead and manufacturing method thereof {EXPANDABLE POLYSTYRENE BEAD AND METHOD FOR PREPARING THE SAME}

 FIELD OF THE INVENTION The present invention relates to "expandable polystyrene beads" and methods of making the same, and more particularly to foamable polystyrene beads having improved flame retardancy and methods of making the same.

"Moulded parts made of expanded polystyrene" is widely used as a building material or the like because of its excellent thermal insulation. Polystyrene foam moldings can be obtained by foaming a large number of expandable polystyrene beads. Conventional polystyrene foam moldings have a disadvantage of being excellent in insulation and workability, but poor in flame retardancy, and thus have been difficult to be widely used as building materials.

Thus, various efforts have been made to improve the flame retardancy of polystyrene foam moldings, one of which is to provide expandable polystyrene beads containing a flame retardant. In this case, it is not easy to find an effective flame retardant that does not inhibit the properties of the foamed polystyrene beads and at the same time allows the foamed polystyrene beads to exhibit excellent flame retardancy. In the case of expandable polystyrene beads containing a conventional flame retardant, the use of a flame retardant such as halogen-based flame retardant, phosphorus-based flame retardant, expanded graphite powder and the like has been proposed.

For example, US Pat. No. 6,444,714 discloses a method for producing expandable styrene polymer bead-type particles by polymerizing styrene in an aqueous suspension, optionally with at least one comonomer, based on the monomers. Carrying out the polymerization in the presence of from about 50% by weight of "expanded graphite" and from 2 to 20% of a phosphorus-based flame retardant, and at least one aliphatic hydrocarbon blowing agent having from 4 to 6 carbon atoms prior to the polymerization. A method of providing expandable styrene bead-shaped particles is disclosed which includes adding to, during, or after, and wherein the average diameter is from 0.2 to 2.0 mm. U. S. Patent No. 6,444, 714 also discloses polymers of styrene and optionally at least one comonomer; 5 to 50% by weight of expanded graphite as a uniformly dispersed flame retardant; And at least one aliphatic hydrocarbon blowing agent having 4 to 6 carbon atoms; wherein the expanded graphite has an average particle size of 20 to 100 μm, and the styrene polymer particles are 0.2 to 2.0 mm A foamable styrene polymer particle powder having an average diameter of is disclosed.

SUMMARY OF THE INVENTION The basic object of the present invention is to provide a foamed polystyrene bead and a method for manufacturing the same, which can obtain a polystyrene foam molded article exhibiting improved flame retardancy and excellent thermal insulation. It is a specific object of the present invention to provide a novel expandable polystyrene bead containing a new flame retardant material which has never been used in conventional expandable polystyrene beads and a method for producing the same.

Expandable polystyrene beads provided in the present invention,

Styrene polymer particles;

A blowing agent impregnated in the styrene polymer particles; And

And expanded vermiculite powder dispersed in the styrene-based polymer particles.

Expandable polystyrene bead first production method of the present invention,

Proceeding with suspension polymerization of styrene monomer or suspension polymerization of styrene monomer and at least one comonomer, optionally in the presence of an auxiliary flame retardant or inorganic filler, on an aqueous reaction medium in which the expanded vermiculite powder is dispersed; And

And adding a blowing agent before the start of the suspension polymerization, during the suspension polymerization, or after the suspension polymerization.

Expandable polystyrene bead second production method of the present invention,

Compounding the styrene-based polymer and the expanded vermiculite powder and cutting it while extruding to produce styrene-based polymer particles in which the vermiculite powder is dispersed; And

And adding a blowing agent to the styrene-based polymer particles in which the expanded vermiculite powder is dispersed.

Expanded vermiculite, which is used as a main flame retardant in the expandable polystyrene beads of the present invention, is a clay mineral having an inset layered structure, and generally refers to a hydrous mica that is a modified product of gold mica and biotite. Vermiculite has the form M _x (Mg, Fe) ₆ (Si _{- x} Al _x ) 0 ₂ 0 (OH) _y H ₂ O, where x is 1 to 1.4, y is about 8, and M is Is an exchangeable cation such as Mg ⁺⁺ , Ca ⁺⁺ and the like. These vermiculite is similar to biotite. Unique to minerals, vermiculite is a unique mineral that contains three waters: absorbed water, interlaminar water, and crystalline water. Vermiculite is sufficiently hydrated at room temperature, and there are two layers of water and a small amount of exchangeable ions, and the interlayer distance is 14.2Å. Such vermiculite has properties such as leeches due to peeling expansion phenomenon due to the pressure of water vapor generated in the crystal during heating.

When the vermiculite is expanded by heat treatment, it expands by about 6 to 20 times depending on the condition of the heat treatment and the properties of the raw material. "Expanded vermiculite" peeled and expanded by heat has a low specific gravity, excellent heat insulating properties and sound insulation, and is used as a heat insulating material, aggregate of lightweight concrete, sound absorbing material, and the like. In addition, it is used as a filler (filler), weighting agent, etc. of paper, plastic, paint, and also used as a packing material for packaging.

However, such expanded vermiculite has never been used in expandable polystyrene beads as a flame retardant as well as an inorganic filler. Nevertheless, it has been found in the present invention that polystyrene foam moldings produced using expandable polystyrene beads containing expanded vermiculite powder have been found to exhibit very good flame retardancy. In addition, it has been found that the expanded vermiculite powder does not inhibit the foaming performance of the expandable polystyrene beads and other physical properties of the expanded polystyrene beads. Moreover, expanded vermiculite is very inexpensive compared to flame retardant materials such as expanded graphite which have been used in the past, thereby making it possible to make very economical production of highly flame retardant expandable polystyrene beads.

Hereinafter, the expandable polystyrene beads of the present invention will be described in more detail.

Expandable polystyrene beads of the present invention,

Styrene polymer particles;

A blowing agent impregnated in the styrene polymer particles; And

And expanded vermiculite powder dispersed in the styrene-based polymer particles.

The styrenic polymer particles may be polystyrene. Alternatively, the styrene polymer particles may be made of a polymer of styrene and at least one comonomer. Examples of the comonomer include "ethylenically unsaturated monomers", alkylstyrenes, divinylbenzenes, acrylonitriles, alphamethylstyrenes, At least one compound selected from methyl methacrylate and vinyl acrylate monomers may be used.

The styrenic polymer particles preferably have physical properties such that the density of the entire foamed particles after foaming can be in the range of about 5 g / l to about 20 g / l. In this case, the foamed styrenic polymer particles can exhibit more excellent heat insulating properties. As the styrenic polymer having a physical property in which the density of the whole particle after foaming may be in the range of about 5 g / l to about 20 g / l, specific examples include polystyrene having a weight average molecular weight of about 100,000 to about 400,000. Can be.

The shape and size of the styrene polymer particles are not particularly limited. Typically, the average particle size of the styrenic polymer particles may be about 0.3 to about 3.0 mm. The styrenic polymer particles may typically be in the form of spherical or elliptical particles.

The blowing agent is impregnated in the styrenic polymer particles, and in a later foaming process, serves to promote the foaming of the styrenic polymer particles. As the blowing agent, for example, an aliphatic hydrocarbon compound having 4 to 6 carbon atoms can be used. The content of the blowing agent may be, for example, about 3 to about 8 parts by weight based on 100 parts by weight of the styrenic polymer particles. Preferably, the content of blowing agent may be adjusted such that the foamed styrenic polymer particles have a density in the range of about 5 g / l to about 20 g / l.

Expanded vermiculite powder is dispersed in styrene polymer particles. If the particle size of the expanded vermiculite powder is too small, it may be difficult to obtain satisfactory levels of insulation, flame retardancy and self-extinguishing ability because of poor absorption and ion exchange capacity. In addition, during foaming of the expandable polystyrene beads, a decrease in strength and dimensional stability due to shrinkage of the product may occur.

On the other hand, if the particle size of the expanded vermiculite powder is too large, in the process of preparing the expandable polystyrene beads based on the suspension polymerization method, the stability of the suspension reaction solution is lowered, and the internal water content of the prepared polystyrene particles is too high, so that in the subsequent foam molding process Difficulties can arise. In addition, vermiculite is not smoothly introduced into the polystyrene particles, causing holes in the polystyrene particles, thereby preventing the polystyrene particles from having an appropriate blowing agent content, and the shape of the polystyrene particles may become unrounded. . In this case, foaming of the expandable polystyrene beads may not be easy, and even if foamed, workability, strength, dimensional stability, and the like may be reduced.

Thus, for example, the average particle size of the expanded vermiculite powder is preferably about 30 to about 150 μm, more preferably about 40 to about 50 μm.

If the content of the expanded vermiculite powder is too small, the effect of improving the flame retardancy may be weak. In addition, strength and dimensional stability of the core material may be lowered after molding, and the flame retardancy and self-extinguishing property may be insufficient because the fire extinguishing role may not be automatically performed.

On the other hand, if the content of the expanded vermiculite powder is too large, the size of the polymerized polystyrene particles may be excessively small when preparing expandable polystyrene beads by suspension polymerization in the presence of the expanded vermiculite powder. In addition, the polymerized polystyrene particles have the form of needles having a high aspect ratio, and in severe cases, the polymerization itself may fail. In addition, during foaming, the adhesion between the foamed polystyrene beads may be excessively lowered. In such a case, the polystyrene foam molded article suffers from shrinkage due to low fusion, not only maintaining the original shape of the product, but also causing agglomeration of expanded vermiculite powder, so that the quality of the polystyrene foam molded article may be greatly degraded.

Thus, for example, the content of the expanded vermiculite powder is preferably about 0.1 to about 50 parts by weight, more preferably about 1 to about 12 parts by weight based on 100 parts by weight of the styrene polymer.

Another embodiment of the expandable polystyrene beads of the present invention may further comprise an auxiliary flame retardant. Secondary flame retardants are used to further enhance the flame retardant effect of the expanded vermiculite powder.

As the auxiliary flame retardant, for example, a phosphorus flame retardant, a bromine flame retardant, expanded graphite, or a combination thereof may be used. As the phosphorus flame retardant, for example, inorganic or organic phosphate, phosphite or phosphonate, red phosphorus, or a combination thereof can be used. Specific examples of the phosphorus flame retardant include diphenyl phosphate, triphenyl phosphate, diphenyl cresyl phosphate, ammonium polyphosphate, resorcinol diphenyl phosphate, melamine phosphate, dimethyl phenyl phosphonate and dimethyl methyl phosphonate. One or more compounds may be used. As the bromine flame retardant, for example, hexabromocyclododecane (HBCD), decabromo diphenyloxide (DBDPO), or a combination thereof may be used.

If the content of the auxiliary flame retardant is too small, the synergistic effect of flame retardancy may be weak. When the content of the auxiliary flame retardant is too excessive, in the production of expandable polystyrene beads by suspension polymerization in the presence of expanded vermiculite powder, the dispersion stability of the suspension may be lowered, and also the adhesion may be lowered during the foam molding process. . For example, the content of the auxiliary flame retardant is preferably about 0.1 to about 30 parts by weight, more preferably about 1 to about 10 parts by weight based on 100 parts by weight of the styrenic polymer.

Another embodiment of the expandable polystyrene beads of the present invention may further comprise an inorganic filler. Through the additional use of inorganic fillers, the strength and dimensional safety of the foamed polystyrene foam molded articles can be further improved.

As the inorganic filler, for example, talc, aluminum hydroxide, magnesium hydroxide, calcium carbonate, graphite, metal powder (e.g., spherical or plate aluminum powder), metal oxide powder (e.g., silicon oxide), or these Combinations can be used.

If the content of the inorganic filler is too small, the addition effect may be weak. When the content of the inorganic filler is too excessive, the dispersion stability of the suspension may be lowered when preparing expandable polystyrene beads by suspension polymerization in the presence of expanded vermiculite powder, and also the adhesion may be lowered during the foaming process. have. For example, the content of the inorganic filler is preferably about 0.1 to about 30 parts by weight, more preferably about 1 to about 10 parts by weight based on 100 parts by weight of the styrene polymer.

The expandable polystyrene beads of the present invention can be prepared, for example, by suspension polymerization in the presence of expanded vermiculite powder, or by compounding.

Hereinafter, the first manufacturing method of the expandable polystyrene beads of the present invention will be described in detail.

Expandable polystyrene bead first production method of the present invention,

Subjecting the expanded vermiculite powder to an aqueous reaction medium in which the expanded vermiculite powder is dispersed, optionally in the presence of an auxiliary flame retardant or inorganic filler, or suspension polymerization of styrene monomer or suspension polymerization of at least one comonomer; And

And adding a blowing agent before the start of the suspension polymerization, during the suspension polymerization, or after the suspension polymerization.

In the first production method of the present invention, in the process of growing the styrene polymer particles through suspension polymerization of the styrene monomer, the expanded vermiculite powder dispersed on the aqueous reaction medium is incorporated into the styrene polymer particles.

In the suspension polymerization process, the polymerization of only the styrene monomer can be progressed by only adding the styrene monomer. Alternatively, copolymerization of the styrene monomer and the comonomer may be carried out by introducing the styrene monomer and the at least one comonomer together. In this case, the polymerized styrene polymer particles become a styrene copolymer in which vermiculite powder is mixed.

Further, in the suspension polymerization process, for example, conventional additives such as peroxide initiators, suspension stabilizers, chain transfer agents, nucleating agents, plasticizers, or combinations thereof may be used. As the peroxide initiator, for example, BPO (benzoylperoxide), TBP (t-butylperoxide), N3M ((1,1-Di (tert-butylperoxy) -3,3,5-trimethyl cyclohexane)), A117 (tert-Butylperoxy 2-ethylhexyl carbonate), and the like can be used. As the suspension stabilizer, for example, magnesium pyrophosphate, calcium phosphate or the like can be used. As the chain transfer agent, toluene, ethylbenzene, alphamethylstyrene dimer, and the like can be used, for example. As the nucleating agent, for example, polyethylene wax, Fisher Trosch wax, EBS (ethylene-bis-stearic amide), or the like can be used. As a plasticizer, ethylbenzene, toluene, mineral oil, paraffin oil, etc. can be used, for example.

In the suspension polymerization process, the expanded vermiculite powder may be a sealant coupling agent, a phosphorus surface treatment agent, or a thermoplastic resin solution (for example, a styrene polymer, a (meth) acrylate polymer, a vinyl acetate resin, or a polyvinyl chloride). It can be added after surface treatment. As such, when the expanded vermiculite powder is surface treated, the vermiculite powder can be more reliably adhered to the growing styrene polymer particles without being separated into the water layer during suspension polymerization.

In addition, in the suspension polymerization process, by adding an auxiliary flame retardant, an inorganic filler, or a combination thereof, it is possible to produce expanded polystyrene beads further comprising an auxiliary flame retardant and / or inorganic filler in addition to vermiculite powder. Auxiliary flame retardants or inorganic fillers may also be surface treated with a sealant coupling agent, a phosphorus surface treatment agent, or a thermoplastic solution (e.g., styrene polymer, (meth) acrylate polymer, vinyl acetate resin, polyvinyl chloride, etc.). It may be added later.

Hereinafter, the second method for producing expandable polystyrene beads of the present invention will be described.

Expandable polystyrene bead second production method of the present invention,

Adding styrene-based polymer and expanded vermiculite powder, optionally by adding an auxiliary flame retardant or inorganic filler, and then cutting it while compounding and extruding to produce styrene-based polymer particles in which the expanded vermiculite powder is dispersed; And

And adding a blowing agent to the styrene-based polymer particles in which the expanded vermiculite powder is dispersed.

The second production method of the present invention is based on the compounding of conventional plastic materials. Therefore, further detailed description of the second manufacturing method of the present invention will be omitted. The second production method of the present invention can easily achieve the expanded vermiculite powder content range that is difficult to easily implement in the first production method of the present invention based on the suspension polymerization method.

Another embodiment of the second production method of the present invention, the styrene-based polymer, expanded vermiculite powder and blowing agent, and optionally additional auxiliary flame retardant or inorganic filler, comprising the step of compounding and cutting while extruding Can be. In this embodiment, polystyrene bead formation and blowing agent injection can be accomplished in one process.

In the first and second production methods of the present invention, specific examples and amounts of expanded vermiculite powder, auxiliary flame retardant, inorganic filler, foaming agent and the like are as described above.

Hereinafter, the expandable polystyrene beads of the present invention and the manufacturing method of the present invention will be described in more detail with reference to Examples.

<Example>

Example  One

In this example, expandable polystyrene beads were prepared based on the suspension polymerization method in the presence of expanded vermiculite powder. The expanded vermiculite powder used had a density of 64 to 160 kg / m ³ , a particle size of 40 to 50 μm, an acidity of 6 to 9, a melting point of 1200 to 1320 ° C., and an ion exchange capacity of 50 to 150 g / meq.

First, 45 kg of deionized water and 150 g of polyvinyl alcohol (PVA) were previously added to a 100 liter CSTR reactor, followed by stirring. Thereafter, in a polystyrene solution obtained by dissolving 3 kg of polystyrene beads (Dongbu HiTek F551) in 27 kg of styrene monomer, 200 g of BPO and N3M ((1,1-Di (tert-butylperoxy) -3,3, 45 g of 5-trimethyl cyclohexane)) and 30 g of A117 (tert-Butylperoxy 2-ethylhexyl carbonate) were added, and 1.8 kg of expanded vermiculite powder was added and homogenized by stirring. Then, suspension polymerization was performed at 90 degreeC for 5 hours, stirring at 200 rpm.

Then, the temperature was raised to 100 ° C. and 2.5 kg of normal pentane was added as a blowing agent for 1 hour. Subsequently, the mixture was heated to 120 ° C., further subjected to suspension polymerization for 2 hours, cooled to 30 ° C., and dehydrated to obtain expandable polystyrene beads having a particle size distribution ranging from 0.3 mm to 3.0 mm.

Example  2

In this example, expandable polystyrene beads were prepared based on suspension polymerization in the presence of expanded vermiculite powder and auxiliary flame retardant. The expanded vermiculite powder used had a density of 64 to 160 kg / m ³ , a particle size of 40 to 50 μm, an acidity of 6 to 9, a melting point of 1200 to 1320 ° C., and an ion exchange capacity of 50 to 150 g / meq. Secondary flame retardants used were red (particle size 7-20 μm), RDP (resorcinol bis (diphenyl phosphate)), HBCD, expanded graphite (density 2.2 g / cm3, particle size 180-200 μm, expansion rate 50-80 times) It was.

First, 45 kg of deionized water and 150 g of polyvinyl alcohol (PVA) were previously added to a 100 liter CSTR reactor, followed by stirring. Thereafter, in a polystyrene solution obtained by dissolving 3 kg of polystyrene beads (Dongbu HiTek F551) in 27 kg of styrene monomer, 200 g of BPO and N3M ((1,1-Di (tert-butylperoxy) -3,3, 45 g of 5-trimethyl cyclohexane)) and 30 g of A117 (tert-Butylperoxy 2-ethylhexyl carbonate) were added, 1.8 kg of expanded vermiculite powder, 240 g of enemy, 120 g of RDP, 360 g of HBCD, and 120 g of expanded graphite. Homogenization by stirring. Then, suspension polymerization was performed at 90 degreeC for 5 hours, stirring at 200 rpm.

Then, the temperature was raised to 100 ° C. and 2.5 kg of normal pentane was added as a blowing agent for 1 hour. Subsequently, the mixture was heated to 120 ° C., further subjected to suspension polymerization for 2 hours, cooled to 30 ° C., and dehydrated to obtain expandable polystyrene beads having a particle size distribution ranging from 0.3 mm to 3.0 mm.

Example  3

In this example, expandable polystyrene beads were prepared based on the expanded vermiculite powder and suspension polymerization in the presence of an auxiliary flame retardant and an inorganic filler. Vermiculite powder used was a density of 64 ~ 160kg / m ³ , particle size 40 ~ 50 ㎛, acidity 6 ~ 9, melting point 1200 ~ 1320 ℃, ion exchange capacity of 50 ~ 150 g / meq. The secondary flame retardants used were red (particle size 7-20 μm), RDP (resorcinol bis (diphenyl phosphate)), HBCD, expanded graphite (density 2.2 g / cm3, particle size 180-200 μm, expansion rate 50-80 times). . The inorganic filler used was talc (particle size 1-3 μm) and aluminum hydroxide (particle size 1-3 μm) surface-treated with Seallan.

First, 45 kg of deionized water and 150 g of polyvinyl alcohol (PVA) were previously added to a 100 liter CSTR reactor, followed by stirring. Thereafter, in a polystyrene solution obtained by dissolving 3 kg of polystyrene beads (Dongbu HiTek F551) in 27 kg of styrene monomer, 200 g of BPO and N3M ((1,1-Di (tert-butylperoxy) -3,3, 45 g of 5-trimethyl cyclohexane)) and 30 g of A117 (tert- Butylperoxy 2-ethylhexyl carbonate) were added, 1.8 kg of expanded vermiculite powder, 240 g of red, 120 g of RDP, 360 g of HBCD, 120 g of expanded graphite, talc 120 g and 60 g of aluminum hydroxide were added and homogenized by stirring. Then, suspension polymerization was performed at 90 degreeC for 5 hours, stirring at 200 rpm.

Then, the temperature was raised to 100 ° C. and 2.5 kg of normal pentane was added as a blowing agent for 1 hour. Subsequently, the mixture was heated to 120 ° C., further subjected to suspension polymerization for 2 hours, cooled to 30 ° C., and dehydrated to obtain expandable polystyrene beads having a particle size distribution ranging from 0.3 mm to 3.0 mm.

Comparative example  One

In this comparative example, expandable polystyrene beads containing only a blowing agent were produced based on the suspension polymerization method.

First, 45 kg of deionized water and 150 g of polyvinyl alcohol (PVA) were previously added to a 100 liter CSTR reactor, followed by stirring. Thereafter, in a polystyrene solution obtained by dissolving 3 kg of polystyrene beads (Dongbu HiTek F551) in 27 kg of styrene monomer, 200 g of BPO and N3M ((1,1-Di (tert-butylperoxy) -3,3, 45 g of 5-trimethyl cyclohexane)) and 30 g of A117 (tert-Butylperoxy 2-ethylhexyl carbonate) were added and stirred. Then, suspension polymerization was performed at 90 degreeC for 5 hours, stirring at 200 rpm.

Then, the temperature was raised to 100 ° C. and 2.5 kg of normal pentane was added as a blowing agent for 1 hour. Subsequently, the mixture was heated to 120 ° C., further subjected to suspension polymerization for 2 hours, cooled to 30 ° C., and dehydrated to obtain expandable polystyrene beads having a particle size distribution ranging from 0.3 mm to 3.0 mm.

Comparative example  2

In this comparative example, based on the suspension polymerization method, expandable polystyrene beads containing only a blowing agent and an auxiliary flame retardant were prepared. As auxiliary flame retardant, red (particle size 7 ~ 20 ㎛), RDP (resorcinol bis (diphenyl phosphate)), HBCD, expanded graphite (density 2.2 g / cm3, particle size 180 ~ 200 ㎛, expansion rate 50 ~ 80 times) It was.

First, 45 kg of deionized water and 150 g of polyvinyl alcohol (PVA) were previously added to a 100 liter CSTR reactor, followed by stirring. Thereafter, in a polystyrene solution obtained by dissolving 3 kg of polystyrene beads (Dongbu HiTek F551) in 27 kg of styrene monomer, 200 g of BPO and N3M ((1,1-Di (tert-butylperoxy) -3,3, 45 g of 5-trimethyl cyclohexane)) and 30 g of A117 (tert-Butylperoxy 2-ethylhexyl carbonate) were added, followed by homogenization by adding 240 g of red, 120 g of RDP, 360 g of HBCD, and 120 g of expanded graphite. Then, suspension polymerization was performed at 90 degreeC for 5 hours, stirring at 200 rpm.

Then, the temperature was raised to 100 ° C. and 2.5 kg of normal pentane was added as a blowing agent for 1 hour. Subsequently, the mixture was heated to 120 ° C., and further subjected to suspension polymerization for 2 hours, cooled to 30 ° C., and then dehydrated to obtain expandable polystyrene beads having a particle size distribution ranging from 0.3 mm to 3.0 mm.

Comparative example  3

In this comparative example, expandable polystyrene beads containing only a blowing agent, an auxiliary flame retardant, and an inorganic filler were prepared based on the suspension polymerization method. As auxiliary flame retardants, red (particle size 7 ~ 20 ㎛), resorcinol bis (diphenyl phosphate), HBCD, expanded graphite (density 2.2 g / cm 3, particle size 180 ~ 200 ㎛, expansion rate 50 ~ 80 times) were used. As the inorganic filler, talc (particle size of 1 to 3 μm) and aluminum hydroxide (particle size of 1 to 3 μm) surface-treated with Seallan were used.

First, 150 g of PVA (polyvinyl alcohol) was previously added to 45 kg of deionized water and stirred in a 100 liter CSTR reactor. Thereafter, in a polystyrene solution obtained by dissolving 3 kg of polystyrene beads (Dongbu HiTek F551) in 27 kg of styrene monomer, 200 g of BPO and N3M ((1,1-Di (tert-butylperoxy) -3,3, 45 g of 5-trimethyl cyclohexane)) and 30 g of A117 (tert-Butylperoxy 2-ethylhexyl carbonate) were added, 240 g of red, 120 g of RDP, 360 g of HBCD, 120 g of expanded graphite, 120 g of talc, 60 g of aluminum hydroxide. After the addition, the mixture was homogenized by stirring. Then, suspension polymerization was performed at 90 degreeC for 5 hours, stirring at 200 rpm.

Then, the temperature was raised to 100 ° C. and 2.5 kg of normal pentane was added as a blowing agent for 1 hour. Subsequently, the mixture was heated to 120 ° C., and further subjected to suspension polymerization for 2 hours, cooled to 30 ° C., and then dehydrated to obtain expandable polystyrene beads having a particle size distribution ranging from 0.3 mm to 3.0 mm.

<Evaluation Result>

Table 1 summarizes the evaluation results of the flame retardancy of the polystyrene foam molded blocks obtained by foaming the foamed polystyrene beads obtained in Examples 1 to 3 and Comparative Examples 1 to 3 at 25 g / l and molding at 27 g / l. ONI and PA III were used as evaluation items.

In the ONI method, five specimens of 125 mm x 12.7 mm x 12.7 mm are prepared and the specimen is burned while adjusting the ratio of nitrogen gas and oxygen gas (21% at room temperature). If it was judgment and 2/3 or more remained, it was judged as pass. The ONI index of each specimen is expressed as the minimum oxygen concentration determined as pass. It is determined that the higher the ONI index, the higher the flame retardancy. In the PA III method, five specimens of 200 mm × 10 mm × 25 mm were prepared and the specimens were burned, and then the flame marks were observed while observing whether the flame mark reached or not and whether or not the paper was ignited. The length reached was measured. It is determined that the shorter the length that the flame mark is reached without the occurrence of ignition, the better the flame retardancy is.

Example Evaluation item Comparative example Evaluation item ONI PA III (mm) ONI PA III (mm) Example 1 23 150 Comparative Example 1 21 200 Example 2 24 130 Comparative Example 2 22 170 Example 3 26 108 Comparative Example 3 24 150

As shown in Table 1, in the case of Example 1 (polystyrene + foaming agent + expandable vermiculite powder), a higher ONI index and a lower PA III index were measured compared to that of Comparative Example 1 (polystyrene + foaming agent). In addition, also in Examples 2 and 3 using expanded vermiculite powder, higher ONI index and lower PA III index were measured as compared with Comparative Examples 2 and 3 without using expanded vermiculite powder. From this fact, it can be seen that the flame retardancy of the polystyrene foam is greatly improved due to the expanded vermiculite powder.

Claims (7)

Styrene polymer particles; A blowing agent impregnated in the styrene polymer particles; And Expanded polystyrene beads comprising; expanded vermiculite powder dispersed in the styrene-based polymer particles. The expanded polystyrene bead according to claim 1, wherein the expanded vermiculite powder has an average particle size of 30 to 150 mu m. The expanded polystyrene bead according to claim 1, wherein the expanded vermiculite powder has a content of 0.1 to 50 parts by weight based on 100 parts by weight of the styrenic polymer. 2. The expandable polystyrene bead of claim 1 wherein said expandable polystyrene bead further comprises an auxiliary flame retardant. 2. The expandable polystyrene beads according to claim 1, wherein the expandable polystyrene beads further comprise an inorganic filler. Subjecting the expanded vermiculite powder to an aqueous reaction medium in which the expanded vermiculite powder is dispersed, optionally in the presence of an auxiliary flame retardant or inorganic filler, or suspension polymerization of styrene monomer or suspension polymerization of at least one comonomer; And Adding a blowing agent before the start of the suspension polymerization, during the suspension polymerization, or after the suspension polymerization; foamable polystyrene beads manufacturing method comprising a. Adding styrene-based polymer and expanded vermiculite powder, optionally by adding an auxiliary flame retardant or inorganic filler, and then cutting it while compounding and extruding to produce styrene-based polymer particles in which the expanded vermiculite powder is dispersed; And And adding a blowing agent to the styrene-based polymer particles in which the expanded vermiculite powder is dispersed.