KR20070053953A - Method for manufacturing expandable polystyrene particles with excellent thermal insulation capability - Google Patents

Abstract

The present invention relates to a method for producing expandable polystyrene particles comprising graphite particles. It is obtained by suspending expandable polystyrene particles in the form of suspended mini-pellets containing graphite particles, followed by heating with blowing agent and C 6 -C 10 aromatic hydrocarbons. Suspended mini pellets are polystyrene particles in the form of mini pellets containing graphite and having an L / D of 1.5-2.5 mm / 0.5-1.0 mm or a volume of 2 mm ³ or less. The expandable polystyrene particles obtained by this method have a good thermal conductivity improvement effect and form fine bubbles upon foaming to provide expandable polystyrene particles having excellent thermal insulation properties.

Thermal Conductivity, Graphite, Bubbles, Heat Insulation, Foaming, Polystyrene, Particles, Mini Pellets

Description

Method for manufacturing expandable polystyrene particles with excellent thermal insulation capability}

The present invention relates to a method for producing expandable polystyrene particles containing graphite, and more particularly, comprising suspending a suspending mini pellet containing graphite, followed by heating by adding a blowing agent and a C6-C10 aromatic hydrocarbon. It relates to a method for producing expandable particles.

Polystyrene foams are generally pre-expanded foamable polystyrene particles to obtain pre-foamed granules, which are filled into a closed mold having a plurality of small holes, and then heated and foamed by pressurized steam to fill the voids between the foamed granules, After fusion to each other, it is produced by cooling and releasing from the mold.

The polystyrene foam is mainly used as a heat insulating material, and is sandwiched between panels and used for building walls, and so on, such as low thermal conductivity, low water absorption, and high strength are required. In particular, in order to obtain the same insulation performance, the improvement of the insulation material can reduce the production cost by reducing the amount of expanded polystyrene particles, or the outer wall can be slimmed by reducing the thickness of the insulation, thereby increasing the living space. Because of this, the demand for improvement has continued.

As one method for improving the performance of the heat insulating material, a method of identifying and improving the heat transfer mechanism of the resin foam has been proposed. In general, the thermal conductivity of a plastic foam can be divided from its conduction mechanism into (a) conduction in solid phase, (b) conduction in gas phase, (c) radiation between bubble membranes, and (d) convection of gas in bubbles. In the case of a high foaming body, the volume occupied by resin by high foaming is very small, and the ratio of the conductivity of the solid phase (resin) of (a) to the thermal conductivity is small. The conduction of the gas phase in (b) is advantageous in reducing the thermal conductivity when using a high molecular weight freon-based gas in the foam, but gradually decreases the effect on the thermal conductivity as the gas is dispersed and replaced with air from the foam. Convection of the gas in the bubble of (d) is confirmed when the bubble diameter is 4 mm or more and can be ignored in a conventional resin foam. Therefore, the highest degree of influence on the thermal conductivity is radiation between the bubble films of (c). Radiation refers to heat transfer that occurs between two opposing surfaces at different surface temperatures and has a great effect of attenuating radiant heat transfer due to the solid (resin) surface constituting the bubbles in the foam. Therefore, the bubble diameter of the foam is closely related to the blocking of radiant heat, and the smaller the bubble diameter, the more the number of heat flow blockages per unit thickness increases, and as a result, the thermal conductivity decreases.

As another way to improve the thermal conductivity of polystyrene foam, a method of introducing an inorganic heatless material has been proposed. EP-A-620 246 describes moldings of expanded polystyrene foams containing particulate heatless materials, in particular carbon black and graphite. The incorporation of the particulate heatless material into the molding is preferably carried out by coating the surface of the prefoamed polystyrene foam granules or by embedding them in polystyrene particles which have not yet been foamed. However, this method makes it difficult to distribute the graphite uniformly in the polystyrene foam, greatly impairs the adhesion of the prefoamed foam granules, causing a low quality foam, and causes the problem of the graphite particles peeling off the surface of the molding. do.

Korean Patent Laid-Open Publication No. 2001-0012557 discloses a foamed styrene polymer having polymerization with a styrene monomer in the presence of graphite particles, introducing graphite into the expandable polystyrene particles to improve thermal conductivity, and having good processing and physical properties. However, the product obtained by incorporating graphite during polymerization may cause allelicity and non-uniformity of bubbles, leading to deterioration of important physical properties such as absorption and strength.

In addition, patent applications WO 98/51734, 98/51735, 99/16817, US 3,072,584, European Patent Application No. 072536, and the like, and heat-free materials such as graphite or carbon black are added together with a blowing agent to form polystyrene foam through extrusion foaming. A method of preparing is reported. However, there is a disadvantage in that the dispersion efficiency of the additives including graphite and foam non-uniformity of the foam, resulting in a foam having a low density of 20 kg / m ³ or less.

Therefore, there is a continuing demand for a heat insulating material having a low thermal conductivity by including an inorganic heatless material without deterioration of the heat insulating material properties such as water absorption or strength.

It is an object of the present invention to provide a novel process for producing expandable polystyrene particles containing graphite particles.

It is an object of the present invention to provide a process for producing expandable polystyrene particles containing graphite using suspended polystyrene particles comprising graphite.

Another object of the present invention is to provide a polystyrene expandable polystyrene in the form of mini pellets containing graphite particles having excellent thermal insulation properties such as thermal conductivity, water absorption and strength.

Another object of the present invention is to provide a novel foam obtained by the foaming of expandable polystyrene in the form of mini pellets containing graphite particles having excellent thermal insulation properties such as low thermal conductivity, water absorption and strength.

The present invention for achieving the above object

Aqueous suspension of suspendable polystyrene mini pellets comprising graphite; And

Heating by adding a blowing agent and a C6-C10 hydrocarbon;

It consists of a method for producing a expandable polystyrene polymer containing graphite particles comprising a.

In the present invention, the susceptible polystyrene minipellet means a particle having a size that can be stably suspended by conventional aqueous suspension or the like, and preferably L / D is 1.5-2.5 mm / 0.5-1.0 mm or It refers to polystyrene particles in the form of mini pellets having a volume of 2 mm ³ or less.

In one embodiment of the present invention, extrusion is carried out using a single screw extruder or a twin screw extruder to obtain particles in the form of suspended mini pellets, including graphite and other additives, and under water cutting or water cooling. Mini pellets of this size can be obtained by cutting by use of a die-face pelletizer.

In the practice of the present invention, the polystyrene particles used for the production of mini pellets are styrene; 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.

In the present invention, graphite used in the production of mini pellets is introduced for lowering the thermal conductivity. As the graphite used, natural graphite or synthetic graphite may be used, and in order to reduce the appropriate thermal conductivity, the particle size is preferably 1 μm to 50 μm, particularly preferably 2 μm to 10 μm, and the bulk density is 100 g / l to 500 g / l and specific surface area from 5 m ² / g to 20 m ² / g. In the present invention, the graphite particles are preferably used 0.05 to 20% by weight, more preferably 0.5 to 10% by weight based on the styrene polymer.

In the present invention, the blowing agent used for the foaming of the polystyrene particles can be used a conventional blowing agent used for the expandable styrene polymer, preferably the blowing agent is added in 3 to 10% by weight based on the polystyrene polymer. Suitable blowing agents may use aliphatic hydrocarbons having 4 to 6 carbon atoms, preferably a mixture of pentane and cyclopentane.

In the present invention, C6-C10 aromatic hydrocarbon is used to facilitate the solubility of the blowing agent to the polystyrene particles, to stabilize the foaming polystyrene particles over time and to improve the foamability, and to facilitate the spheroidization of the polystyrene particles in the form of mini-pellets, Preference is given to using 0.1-1.0% by weight as standard. When the amount of C6-C10 aromatic hydrocarbon is small, the foamability of the expandable polystyrene particles is reduced, it is difficult to be spherical when using the mini-pellet polystyrene particles, and if the amount of the aromatic hydrocarbon is too large, the heat resistance of the final molded product is reduced. Can cause. The C6-C10 aromatic hydrocarbon may include benzene, toluene, p-xylene, o-xylene, m-xylene, ethylbenzene, propyl benzene, isopropylbenzene, and the like, preferably toluene, ethyl benzene .

The polystyrene foam according to the present invention may include a bubble control agent to control the size of the bubble at the time of foaming. In polystyrene foam, bubble size plays an important role in mechanical properties and thermal insulation performance, and more specifically, when the bubble size is 300 μm or more, the thermal conductivity increases and the strength decreases due to gas convection inside the bubble. In a preferred embodiment of the present invention, the bubble control agent can be used in the process of extruding suspendable polystyrene mini pellets containing graphite or in the impregnation process according to the present invention. In one preferred embodiment of the present invention, as the bubble control agent, ethylene bis strate, calcium carbonate, talc, clay, silica, barium strate, diatomaceous earth, citric acid and sodium bicarbonate content can be used, 5 wt% or less, Preferably it is 3 weight% or less.

The polystyrene foam according to the invention can be introduced in the process of extruding susceptible polystyrene mini pellets containing graphite or in the impregnation process according to the invention for the purpose of improving flame retardancy. In one preferred embodiment of the present invention, the flame retardant is hexabromo cyclododecane, tetrabromo cyclooctane, tetrabromo vinylcyclohexane, 2,2- (4-allyloxy-3,5-dibromo Bromine flame retardants such as phenyl) propane and tribromophenyl allyl ether and conventional chlorine flame retardants can be used, and hexabromo cyclododecane is preferable.

In the present invention, the step of aqueous suspension of the suspendable polystyrene mini pellets containing graphite can be made using a conventional suspension method, there is no particular limitation. In one embodiment of the invention, the mini-pellets and suspending agent may be added to water and stirred. Suspensions may be used conventional suspensions used in the polystyrene polymerization process, there is no particular limitation.

In the present invention, the step of heating the blowing agent and the C6-C10 hydrocarbon is preferably heated by heating for about 3-7 hours at a temperature of 100-130 ℃. When the heating temperature is lowered, the softening capacity of polystyrene is lowered, which makes it difficult to add a blowing agent into the polystyrene. May cause degradation.

Foams of expandable polystyrene containing graphite particles having excellent thermal insulation properties such as low thermal conductivity, water absorption, and strength according to the present invention are expanded polystyrene obtained by heating graphite, a blowing agent, and a C6-C10 aromatic hydrocarbon into aqueous suspended polystyrene particles. It can be obtained by foaming the particles. The foaming conditions may use the conventional conditions used for the foaming of the expandable polystyrene, there is no particular limitation. Foams containing foamed graphite can be foamed by those skilled in the art to have a diameter of 70-200 microns, and have the advantage of excellent properties such as absorption and strength, including thermal conductivity.

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 >

100% by weight of polystyrene (Kumho Petrochemical; HIPS 490FB) and 5% by weight of impression graphite (KOMA; HCN-908) were blended and melted at a biaxial molding machine at 220 ° C., using an underwater water cutting machine. Polystyrene containing graphite was extruded to obtain mini pellets having an average volume of 1.5 mm ³ to 2 mm ³ . Next, 100% by weight of polystyrene particles in the form of mini pellets containing graphite, 100% by weight of pure water, 0.24% by weight of a suspending agent (tricalcium phosphate, Dubon; DET-10), a flame retardant (hexabromocyclododecane, GLC; CD75P ^™ ) 0.35% by weight was inserted into the reactor at room temperature, the temperature was reacted at 70 ° C. for 1 hour and 30 minutes, and after completing the temperature increase at 120 ° C., 7% of a blowing agent (pentane, SK) was added and maintained for 5 hours. The expanded polystyrene particles containing graphite thus obtained were dehydrated and dried, and then coated with a blending agent to perform physical property evaluation.

< Example 2 >

To understand the effect of the bubble control agent, 2% by weight of ethylenebisstearate (predecessor chemical) was introduced, 100% by weight of polystyrene (Kumho Petrochemical; HIPS 490FB) and 5% by weight of graphite graphite (KOMA; HCN-908) blending% by melting in the biaxially shaper 220 ℃ and underwater pelletizer (Under water Cutting) extruded polystyrene to obtain a pellet of the Mini-the average volume of 1.5 mm ³ to about 2mm ³ containing graphite using. Next, the impregnation process was the same as in <Example 1>, and the foamed polystyrene particles containing graphite were dehydrated and dried, followed by coating a blending agent, and the physical properties were evaluated.

< Example 3 >

Using the same mini-pellet polystyrene particles as in <Example 2>, impregnated in the same manner, and the foaming agent was changed in 7% by weight of pentane (SK) 6% by weight of pentane (SK), cyclopentane (SK) 1 wt% was used. Next, after dewatering and drying the expandable polystyrene particles containing graphite, the blending agent was coated, and the physical properties were evaluated.

< Example 4 >

Using the same mini-pellet polystyrene particles as in <Example 2>, it was prepared in the same manner as in <Example 2> except that 0.5% by weight of toluene (SK) was introduced in the impregnation process. Next, after dewatering and drying the expandable polystyrene particles containing graphite, the blending agent was coated, and the physical properties were evaluated.

< Comparative Example 1 >

100% by weight of polystyrene (Kumho Petrochemical; HIPS 490FB) was melted at a biaxial molding machine at 220 ° C. and extruded using an Under Water Cutting machine to have an average volume of 1.5 mm ^3. Mini pellets of 2 mm ³ were obtained. Next, 100% by weight of polystyrene particles in the form of Mini-pellet containing graphite, 100% by weight of pure water, 0.24% by weight of a suspending agent (tricalcium phosphate, Dubon; DET-10), a flame retardant (hexabromocyclododecane, GLC) CD75P ^TM ) 0.35% by weight was inserted into the reactor at room temperature, and the temperature was reacted at 70 ° C for 1 hour and 30 minutes. After completion of the temperature increase at 120 ° C, 7% of a blowing agent (pentane, SK) was added and maintained for 5 hours. The expanded polystyrene particles containing graphite thus obtained were dehydrated and dried, and then coated with a blending agent to perform physical property evaluation.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 5 minutes effervescent 40 40 40 60 40 Foam lip appearance Oval Oval Oval Fully spherical Oval Foam Density (kg / m ³ ) 0.030 0.030 0.030 0.030 0.030 Thermal Conductivity (W / m-K) 0.312 0.0309 0.0304 0.0305 0.0342 Bubble size (mm) 200-400 70-100 70-100 70-100 100-120 Absorption rate (g / 100cm ² ) 0.95 0.39 0.38 0.40 0.52

Physical property evaluation in Table 1 was performed specifically as follows.

1.5 minutes effervescent: foamed drainage (doubled) when foamed for 5 minutes at 0.3 K steam pressure

2.Density: Gross weight (kg) / Molded product volume (m3)

3.Thermal conductivity: It is the value measured by the plate heat flow meter method among the methods of measuring the thermal conductivity of the thermal insulation material specified in Korean Industrial Standard KS L 9016 (W / m-K).

4. Bubble size: Average diameter (mm; measured under microscope) between cell wall and cell

5. Absorption rate: The surface area divided by the amount of water absorbed according to the absorption method of the expanded polystyrene insulation according to KS M 3808, Korean Industrial Standard (g / 100cm ² ).

From the results of Table 1, it can be seen that the introduction of graphite into the expandable polystyrene particles has a noticeable effect of improving the thermal conductivity, and the decrease in physical properties due to the increase in the bubble size due to the introduction of graphite was able to control the appropriate bubble size by the addition of a bubble regulator. .

In addition, the selection of a blowing agent having a high boiling point such as cyclopentane and excellent solubility in polystyrene in the introduction of the blowing agent positively improves the thermal conductivity, and the introduction of a solvent such as toluene and ethylbenzene increases the solubility of the blowing agent in polystyrene. It was confirmed that temporal stabilization and foamability of the expandable polystyrene particles, and the spheronization of the polystyrene particles in the form of mini pellets were facilitated.

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.

According to the present invention, a novel method for producing polystyrene particles containing graphite is provided. By foaming the polystyrene particles, it was possible to adhere to the bubble diameter of the existing polystyrene foam to significantly lower the thermal conductivity while maintaining the physical properties such as absorption, strength, etc. to produce a foam having excellent thermal insulation properties.

Claims (12)

Aqueous suspension of suspendable polystyrene mini pellets comprising graphite; And Heating by adding a blowing agent and a C6-C10 hydrocarbon; Method for producing a expandable polystyrene polymer containing graphite particles comprising a. The method of claim 1 wherein the polystyrene mini pellets have an L / D of 1.5-2.5 mm / 0.5-1.0 mm or a volume of 2 mm ³ or less. The method of claim 1 wherein the polystyrene particles are styrene, ethylstyrene, dimethylstyrene, para-methylstyrene, alpha-methylstyrene, alpha-ethylstyrene, alpha-propylstyrene, alpha-butylstyrene, chlorostyrene, bromostyrene and vinyl. A polymer or copolymer of monomers of toluene, a copolymer of monomers with acrylonitrile, butadiene, methylacrylate, methylmethacrylate, isobutylene, vinyl chloride, isophorene and mixtures thereof. The method according to claim 1, which is heated to a temperature of 100 to 130 ° C. for 3-7 hours. The method of claim 1, wherein the graphite particles contained in the polystyrene minipellets have a size of 1 µm to 50 µm. The method of claim 5, wherein the graphite particles are 0.05 wt% to 25 wt% based on the polystyrene particles. The method of claim 1, wherein the minipellet further comprises an infrared absorber and other additives selected from the group consisting of carbon black, aluminum, glass fiber, carbon fiber, clay, loess. The method of claim 1 further comprising an additive in addition to the blowing agent and the C6-C10 aromatic hydrocarbon. The method of claim 1, wherein the blowing agent is used together with at least one selected from the group consisting of cyclopentane alone or aliphatic hydrocarbons, halogenated hydrocarbons, halogen-free hydrocarbons except cyclopentane. 10. The method of claim 9, wherein the blowing agent uses 1-15 parts by weight based on 100 parts by weight of the polystyrene polymer. The method of claim 1, wherein the C6-C10 aromatic hydrocarbon is selected from the group consisting of toluene, ethylbenzene and mixtures thereof. The method of claim 1, wherein the aromatic hydrocarbon is used in an amount of 0.1 wt% to 1 wt% based on the polystyrene polymer.