KR20190086837A - A method for manufacturing expandable polystyrene beads having excellent thermal stability - Google Patents

Abstract

One aspect of the present invention provides a method for manufacturing expandable polystyrene particles, comprising the steps of: (a) manufacturing seed particles comprising styrene resin, graphite powder, and titanium oxide powder; (b) manufacturing an emulsion comprising the seed particles, styrene monomer, dispersant, initiator and water; (c) further adding a styrene monomer to the emulsion to induce a reaction; and (d) obtaining particles by adding a blowing agent to the product of step (c).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing expanded polystyrene particles having excellent thermal stability,

The present invention relates to a method for producing expandable polystyrene particles, and more particularly to a method for producing expandable polystyrene particles having excellent thermal stability.

Expandable polystyrene (EPS) is excellent in strength, buffering property and heat insulation property, and is used for household electric appliances packaging materials, agricultural and marine products boxes, building insulation materials, sandwich panels and the like. As methods for producing such expandable polystyrene particles, a suspension polymerization method, an extrusion method, and a seed polymerization method are known.

The suspension polymerization method is a method of preparing polymer particles by using water as a dispersion medium and using monomers insoluble in water in the presence of a dispersion stabilizer such as a dispersant or a surfactant. However, since the monomers existing in the aqueous solution are dispersed by the suspension polymerization mechanical force, the obtained polymer particles have a very wide distribution of 0.1 to 1,000 mu m in size, leading to the generation of non-ionic grades and outcrops Which requires a stepwise fractionation operation through a separator in order to obtain a genuine product. In order to overcome such shortcomings, Korean Patent Publication No. 1993-0010062 and Korean Patent Publication No. 2000-0008971 disclose a method for producing expandable polystyrene particles having a narrow particle size distribution.

Korean Patent Laid-Open No. 2005-0024330 discloses another method of producing expandable polystyrene particles by an extrusion method so as to have a uniform particle size according to the hole size of a die. However, in the process of impregnating the foaming agent with polystyrene, it is necessary to control the dispersion and the generated heat of the melt, which may lead to problems such as a decrease in molecular weight upon extrusion, degradation of additives, and deterioration in quality including foaming of the final product. In order to overcome such a problem, Korean Patent No. 0703828 and Korean Patent No. 0801275 disclose a method of impregnating a foaming agent in a separate reactor after extruding polystyrene or impregnating the extruded pellets simultaneously with seed polymerization .

As another method, Korean Patent Publication No. 2002-0000556 and Korean Patent Publication No. 2003-0070951 disclose a seed polymerization method. In the seed polymerization method, a bead having a narrow particle size distribution is fractionated by fractionation of beads obtained by the suspension polymerization method, or pellets or particles of a uniform cylindrical pellet are extruded into a suspension using a seed, and the monomer is gradually added It is the process of obtaining seed particles of desired size by growing the seed size. However, such a seed polymerization method is a two-step process, which is inconvenient and can not produce particles smaller than the seed since it is essentially a method of growing the seed of the particle into an allele.

Korean Patent No. 1099028 discloses a method for producing expandable polystyrene beads using an allergen seed. However, this method regulates the amount of monomers injected in the swelling step to induce sub-fraction due to over-swelling of the allergic seed, And the amount of the monomer to be added is the same or larger than the amount of the seed.

On the other hand, as the government's energy saving policy in the construction materials market has been steadily strengthened, the thickness of the thermal insulation material has become thicker, and research and development on the process and method for introducing graphite powder excellent in heat insulation property into expandable polystyrene particles have been actively carried out .

Korean Patent Laid-Open Publication No. 2014-0105823 discloses a method for producing expandable polystyrene particles by dispersing graphite powder in styrene in which polystyrene is dissolved in an amount of 1 to 30% by weight based on the suspension polymerization. Korean Patent Publication No. 2014-0105845 and Korean Patent No. 0801275 Discloses a process for producing graphite powder-containing particles or seeds in the form of micropellets by firstly using suspension polymerization or extruder and additionally adding graphite to the expanded polystyrene particles by seeding addition while continuously adding styrene. do. Korean Patent No. 0703823 discloses a method for producing expanded polystyrene particles by preparing a polystyrene pellet in which graphite powder is dispersed by using an extruder and injecting a blowing agent in a suspension reactor.

However, the heat insulating material prepared from the expandable polystyrene particles containing graphite powder is superior in heat insulating property to a general white product. On the other hand, when exposed to direct sunlight in summer or used as core material of sandwich panel and exposed to high temperature of steel plate, There is a possibility that the heat insulating material is melted as shown in Fig.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art and it is an object of the present invention to provide a heat- And a method for producing the expandable polystyrene particles.

According to an aspect of the present invention, there is provided a method for producing a seed particle, comprising: (a) preparing seed particles comprising a styrene resin, a carbon-based powder, and a titanium oxide powder; (b) preparing an emulsion comprising the seed particles, the styrenic monomer, the dispersant, the initiator and water; (c) adding a styrene-based monomer to the emulsion to react; And (d) introducing a blowing agent into the product of step (c) to obtain particles. The present invention also provides a method for producing expandable polystyrene particles.

In one embodiment, the styrenic resin is selected from the group consisting of styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha-propyl styrene, alpha-butyl styrene, chlorostyrene, bromostyrene, Or a mixture of the first monomer and a second monomer selected from the group consisting of vinyl toluene, acrylonitrile, butadiene, methyl acrylate, methyl methacrylate, isobutylene, vinyl chloride, isoprene, and combinations thereof. And a second monomer selected from the group consisting of a combination of two or more of the monomers.

In one embodiment, the carbon-based powder may be one selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene, fullerene, carbon fiber, and combinations of two or more thereof.

In one embodiment, the styrenic monomer is selected from the group consisting of styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha-propyl styrene, alpha-butyl styrene, chlorostyrene, bromostyrene, And combinations thereof.

In one embodiment, the amount of the carbon-based powder may be 1 to 10 parts by weight based on 100 parts by weight of the styrene-based resin in the step (a).

In one embodiment, the amount of the titanium oxide powder may be 1 to 10 parts by weight based on 100 parts by weight of the styrene resin in the step (a).

In one embodiment, the amounts of the styrenic monomers introduced in steps (b) and (c) may be S _b and S _c , respectively, and S _b : S _c = 100 parts by weight: 100 to 500 parts by weight.

In one embodiment, the foaming agent may be selected from the group consisting of butane, i-butane, n-pentane, i-pentane, neo-pentane, cyclopentane, halogenated hydrocarbons and combinations of two or more thereof.

In one embodiment, the amount of the blowing agent may be 3 to 20 parts by weight based on 100 parts by weight of the seed particles.

Another aspect of the present invention provides a heat insulating material comprising expandable polystyrene particles produced according to the above method.

In one embodiment, the thermal conductivity of the insulation may be less than or equal to 32 mW / mK at a density of 25 kg / m < ³ >.

According to one aspect of the present invention, by allowing the expandable polystyrene particles to contain a certain amount of the graphite powder and the titanium oxide powder, it is possible to make the thermal conductivity, that is, the heat insulating property, Can be remarkably improved.

It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be deduced from the description of the invention or the composition of the invention set forth in the claims.

FIG. 1 is a photograph showing a phenomenon in which a heat insulating material made from expandable polystyrene particles containing graphite powder is melted when exposed to direct sunlight during the summer.
FIG. 2 is a photograph of the degree of thermal deformation of the heat insulating material specimen according to Examples and Comparative Examples of the present invention when evaluating thermal stability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

According to an aspect of the present invention, there is provided a method for producing a seed particle, comprising: (a) preparing seed particles comprising a styrene resin, a carbon-based powder, and a titanium oxide powder; (b) preparing an emulsion comprising the seed particles, the styrenic monomer, the dispersant, the initiator and water; (c) adding a styrene-based monomer to the emulsion to react; And (d) introducing a blowing agent into the product of step (c) to obtain particles. The present invention also provides a method for producing expandable polystyrene particles.

In the step (a), seed particles containing a styrene resin, a carbon-based powder, and a titanium oxide powder can be produced. The seed particles may have a variety of shapes including conventional cylindrical pellets, spherical beads, or other indefinite particles.

Wherein the styrenic resin is selected from the group consisting of styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha-propyl styrene, alpha-butyl styrene, chlorostyrene, bromostyrene, A homopolymer or copolymer of the first monomer or a copolymer of the first monomer and a monomer selected from the group consisting of vinyltoluene, acrylonitrile, butadiene, methyl acrylate, methyl methacrylate, isobutylene, vinyl chloride, isoprene, , And preferably a homopolymer of styrene, that is, polystyrene, but is not limited thereto.

Since the carbon-based powder absorbs infrared rays, the thermal conductivity of the low-density polystyrene-based insulating material produced from the carbon-based powder is lowered, thereby providing improved heat insulation. The carbon-based powder may be, for example, one selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene, fullerene, carbon fibers and combinations of two or more thereof, , But is not limited thereto. In the step (a), the amount of the carbon-based powder may be 1 to 10 parts by weight, preferably 3 to 6 parts by weight, based on 100 parts by weight of the styrene-based resin.

However, when the insulation material made of expandable polystyrene particles containing carbon-based powder is excellent in heat insulation as compared with a general white insulation material, when exposed to direct sunlight in summer or used as a core material of a sandwich panel and exposed to high temperature of the steel plate, There is a possibility that a phenomenon that the heat insulating material is melted as shown in Fig. 1 due to the increase of the surface temperature due to the absorption of the radiant heat of the system powder may occur, so that it is necessary to adequately reduce, offset and reflect the radiant heat.

The titanium oxide powder can remarkably offset or reduce the amount of radiant heat absorbed by the carbon-based powder powder by reflecting the radiant heat, so that the thermal stability of the heat-insulating material made of expandable polystyrene particles containing the titanium oxide powder is remarkably improved . In the step (a), the amount of the titanium oxide powder may be 1 to 10 parts by weight, preferably 3 to 6 parts by weight, based on 100 parts by weight of the styrene resin.

In the case where the seed particles include both the carbon-based powder and the titanium oxide powder in a certain amount, the heat insulating property and the thermal stability of the heat insulating material made from the seed particles can be balanced at the same time, Climate constraints can be overcome. However, if the total amount of the carbon-based powder and the titanium oxide powder is more than 15 parts by weight based on 100 parts by weight of the styrene-based resin, mechanical properties such as strength and buffering property derived from the styrene- May be adjusted to 5 to 15 parts by weight, preferably 5 to 9 parts by weight.

In the step (b), an emulsion including the seed particles, the styrene-based monomer, the dispersant, the initiator and water may be prepared.

Wherein the styrenic monomer is selected from the group consisting of styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha -propyl styrene, alpha-butyl styrene, chlorostyrene, bromostyrene, And preferably, it may be styrene, but is not limited thereto.

The dispersant may be any dispersant used in the polymerization of conventional expandable polystyrene, and may be, for example, an inorganic dispersant such as tetrasodium pyrophosphate, tricalcium phosphate, magnesium pyrophosphate, magnesium chloride, polyvinyl alcohol, methylcellulose, Organic dispersants such as polyvinyl pyrrolidone. The amount of the dispersant may be 0.1 to 5 parts by weight, preferably 0.5 to 2 parts by weight based on 100 parts by weight of the seed particles.

The initiator may be any initiator used in the polymerization of conventional expandable polystyrene, and in particular, two types of initiators having different starting temperatures may be used. For example, a combination of benzoyl peroxide (BPO) and t-butyl peroxybenzoate (TBPB) or a combination of benzoyl peroxide (BPO) and 1,1-bis (t-butyl peroxycyclohexane) The initiator may be used in an amount of 0.1 to 1 part by weight, preferably 0.1 to 0.5 part by weight based on 100 parts by weight of the seed particles.

The emulsion may further comprise a surfactant. The surfactant may be selected from the group consisting of sodium alkyl sulphonate, sodium lauryl sulphonate, sodium alkyl benzene sulphonate, sodium oleate sulphonate, and combinations of two or more thereof. The amount of the surfactant may be 0.1 to 1 part by weight based on 100 parts by weight of the seed particles.

In addition, the emulsion may further include additives capable of imparting various properties to the seed particles, for example, a flame retardant agent, a bubble modifier, and the like.

When the emulsion is heated to a predetermined temperature, for example, 50 to 80 ° C, preferably 60 to 70 ° C, the seed particles may be swollen by polymerizing the styrene-based monomer in the presence of the initiator . As used herein, the term "swelling" can be understood as a concept involving the phenomenon or process in which the seed particle is polymerized with the styrene-based monomer to grow the seed particle.

In the step (c), a styrene-based monomer may be further added to the emulsion for reaction. Specifically, the swollen seed particles contained in the emulsion can be polymerized with the styrene-based monomer added further under the condition that the temperature is raised to 100 to 150 ° C, preferably 120 to 135 ° C in the step (c) have.

The amounts of the styrenic monomers introduced in steps (b) and (c) may be S _b and S _c , respectively, and S _b : S _c = 100 parts by weight: 100 to 500 parts by weight. In the production of the expandable polystyrene particles, the expandable polystyrene particles whose sizes and size distributions are adjusted to a necessary range by dividing the styrene-based monomer into a predetermined range in the steps (b) and (c) Can be manufactured.

In the step (d), the foamed polystyrene particles can be obtained by impregnating the product of step (c) with a foaming agent.

The foaming agent may be one selected from the group consisting of butane, i-butane, n-pentane, i-pentane, neo-pentane, cyclopentane, halogenated hydrocarbons and combinations of two or more thereof, / I-pentane, but is not limited thereto. The amount of the blowing agent may be 3 to 20 parts by weight, preferably 10 to 16 parts by weight based on 100 parts by weight of the seed particles.

Another aspect of the present invention provides a heat insulating material comprising expandable polystyrene particles produced according to the above method.

In the case of the heat insulating material made of the expandable polystyrene particles, a thermal conductivity of 32 mW / mK or less, preferably 30 mW / mK or less can be realized based on the density of 25 kg / m ^{3 in} the KS standard.

Hereinafter, embodiments of the present invention will be described in detail.

Example 1

6 kg of graphite powder and 3 kg of titanium oxide (TiO ₂ ) powder were added to 100 kg of polystyrene and mixed. The mixture was melted at 230 ° C in a twin-screw extruder and then subjected to an underwater cutting to obtain an average volume including graphite and titanium oxide Micro] pellets of 2.0 mm < ³ > or less were obtained.

In a 100 L reactor, 0.2 kg of tricalcium phosphate as a dispersant was added to 40 kg of ultrapure water and stirred, and 20 kg of micropellets containing graphite and titanium oxide were added. The temperature of the reactor was raised to 60 DEG C, and 1 kg of hexabromocyclododecane as a flame retardant, 0.05 kg of benzoyl peroxide as a low temperature initiator, and 0.03 kg of t-butyl peroxybenzoate as a high temperature reagent were dissolved in 5 kg of styrene for 2 hours Lt; / RTI >

The inlet of the reactor was closed, and 15 kg of styrene was slowly added thereto while being heated from 60 ° C to 125 ° C for 3.5 hours to conduct polymerization. After completion of the polymerization, 3 kg of pentane, which is a foaming agent, was introduced into the reactor at a pressure of nitrogen at 125 ° C. and impregnation was carried out for 5 hours while maintaining the final pressure of the reactor at 13 kgf / cm ² .

Thereafter, the temperature of the reactor was cooled to 30 DEG C or less and the product was discharged to the reactor. The product was dried, foamed, and molded to produce a heat insulator having the same density, and the thermal conductivity and thermal stability were evaluated.

Example 2

Polystyrene 100kg 3kg graphite powder and titanium oxide to the (TiO ₂₎ was added a powder 6kg were mixed, melted in the twin-screw molding machine into 230 ℃ the following, the average volume of 2.0mm ³ or less particle with a water pelletizer (Under water cutting) uniform A micropellet containing a graphite was obtained.

Thereafter, the same method as in Example 1 was used to produce a heat insulator, and thermal conductivity and thermal stability were evaluated.

Comparative Example 1

9 kg of graphite powder was added to 100 kg of polystyrene and mixed. The mixture was melted in a twin-screw extruder at 230 ° C. and then subjected to underwater cutting to obtain a micropellet containing uniform graphite particles having an average volume of 2.0 mm ³ or less .

Thereafter, the same method as in Example 1 was used to produce a heat insulator, and thermal conductivity and thermal stability were evaluated.

Comparative Example 2

9 kg of titanium oxide (TiO ₂ ) powder was added to 100 kg of polystyrene and mixed. The mixture was melted in a twin-screw extruder at 230 ° C., and particles having an average volume of 2.0 mm ³ or less were uniformly contained in graphite using an underwater cutting machine To obtain micropellets.

Thereafter, the same method as in Example 1 was used to produce a heat insulator, and thermal conductivity and thermal stability were evaluated.

Experimental Example

The density, thermal conductivity, thermal stability and surface temperature of the heat insulators prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were measured. The results are shown in Table 1 and FIG. 2, respectively.

Generally, it is recommended that the temperature of the heat insulating material processed by expandable polystyrene particles is 70 ° C or less. However, in order to induce thermal melting under severe conditions, the same size specimen of 20 cm * 15 cm * 1 cm is kept in the drier at 90 ° C for 5 hours The thermal stability of each specimen was relatively evaluated. Here,?,? And? Indicate cases where the thermal deformation of the specimen is excessive, and, when the thermal deformation of the specimen is good, the case is excellent. The surface temperature is a value obtained by measuring the surface temperature of each specimen when evaluating the thermal stability of each specimen.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Density (kg / m ³ ) 25 25 25 25 Thermal conductivity (mW / mK) 30 31 30 33 Thermal stability ○ ○ △ ◎ Surface temperature (℃) 96.3 96.3 97.0 96.0

Referring to Table 1 and FIG. 2, the heat insulating material of Comparative Example 1 containing only the conventional graphite powder has a low thermal conductivity, but an excessive thermal deformation.

On the other hand, in the heat insulating materials of Examples 1 and 2 including a certain amount of graphite powder and titanium oxide powder, thermal deformation was remarkably reduced while keeping the thermal conductivity low.

Comparative Example 2, which contains titanium oxide powder only on the basis of the same content, contains only graphite powder. However, since the titanium oxide powder reflects radiant heat, the heat insulating property of the heat insulating material can be improved. The thermal stability was improved while the heat insulating property was lowered as compared with Comparative Example 1 in which

According to the KS standard, a thermal conductivity of 32 mW / mK or less is required based on the density of 25 kg / m ³ in the case of a heat insulating material made of expandable polystyrene particles. According to the above results, when a graphite powder and a titanium oxide powder are mixed, It is possible to obtain a heat insulating material having excellent heat stability while satisfying the heat insulating property of the heat insulating material.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (11)

(a) preparing seed particles comprising a styrene-based resin, a carbon-based powder, and a titanium oxide powder;
(b) preparing an emulsion comprising the seed particles, the styrenic monomer, the dispersant, the initiator and water;
(c) adding a styrene-based monomer to the emulsion to react; And
(d) adding a foaming agent to the product of step (c) to obtain particles. The method according to claim 1,
Wherein the styrenic resin is selected from the group consisting of styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha-propyl styrene, alpha-butyl styrene, chlorostyrene, bromostyrene, A homopolymer or copolymer of the first monomer or a copolymer of the first monomer and a monomer selected from the group consisting of vinyltoluene, acrylonitrile, butadiene, methyl acrylate, methyl methacrylate, isobutylene, vinyl chloride, isoprene, Wherein the second monomer is a copolymer selected from the group consisting of ethylene, propylene, butadiene, isobutylene, and propylene. The method according to claim 1,
Wherein the carbon-based powder is one selected from the group consisting of graphite, carbon black, carbon nanotubes, graphene, fullerene, carbon fiber, and combinations of at least two of the foregoing. The method according to claim 1,
Wherein the styrenic monomer is selected from the group consisting of styrene, ethyl styrene, dimethyl styrene, para-methyl styrene, alpha-methyl styrene, alpha -propyl styrene, alpha-butyl styrene, chlorostyrene, bromostyrene, Wherein the method comprises the steps of: The method according to claim 1,
Wherein the amount of the carbon-based powder is 1 to 10 parts by weight based on 100 parts by weight of the styrene-based resin in the step (a). The method according to claim 1,
Wherein the amount of the titanium oxide powder is 1 to 10 parts by weight based on 100 parts by weight of the styrene-based resin in the step (a). The method according to claim 1,
In the steps (b) and (c), the input amounts of the styrenic monomers are S _b and S _c ,
S _b : S _c = 100 parts by weight: 100 to 500 parts by weight. The method according to claim 1,
Wherein the foaming agent is one selected from the group consisting of butane, i-butane, n-pentane, i-pentane, neo-pentane, cyclopentane, halogenated hydrocarbons and combinations of two or more thereof. The method according to claim 1,
Wherein the amount of the blowing agent is 3 to 20 parts by weight per 100 parts by weight of the seed particles. A heat insulating material comprising expandable polystyrene particles produced according to any one of claims 1 to 9. 11. The method of claim 10,
Wherein the thermal conductivity of the heat insulator is 32 mW / mK or less at a density of 25 kg / m ³ .

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