KR20090077369A - Expandable Styrene Polymer Resin Containing Carbon Black Particles - Google Patents

Abstract

The present invention provides an expandable styrene polymer resin including carbon black particles having a size of 30 to 140 nm. The expandable styrene polymer resin according to the present invention is formed by kneading by a twin screw extruder having a special screw combination, thereby foaming it to obtain an expanded styrene polymer resin foam having high thermal insulation at low density.

Description

Expandable Styrenic Polymer Resin Containing Carbon Black Particles}

The present invention relates to an expandable styrene polymer resin containing carbon black particles, and more particularly, to an expandable styrene polymer resin containing carbon black particles capable of forming a foam having excellent heat insulating properties even at a low density. .

The expandable styrene polymer resin is molded into a thermal insulation board, and the foam formed generally has a density of 30 g / l. This is because the foam of styrene polymer resin has a minimum value of thermal conductivity at the density. Therefore, in the case of a general foamable styrene polymer resin, there is a problem that the heat insulating performance is reduced when molded into a heat insulating board of a density lower than the density in order to save material and space.

In order to solve this problem, it is known that the thermal insulation performance can be maintained or increased at low density by adding organic and inorganic materials such as graphite, metal oxide, carbon black, and metal oxide to the expandable styrene polymer resin.

However, in the case of manufacturing a foam by mixing carbon black with polystyrene resin, difficulties in processing and resulting product quality problems occur. International Patent Publication No. 94/13721 proposes a solution to this problem. That is, the patent describes a method for producing a foam by mixing a polystyrene and a carbon black concentrate using an extruder and then adding a blowing agent to the mixture.

However, the patent requires a carbon black concentrate containing carbon black (thermal black) having a particle size of 150 nm or more to easily achieve the purpose of foam production. The patented manufacturing method has a limitation in that the carbon black concentrate must be used because the function of dispersing the carbon black in the manufacturing process is poor, and the use of carbon black also requires the use of a carbon black having a large particle size such as thermal black. There is this. Accordingly, the patent only solves the above-mentioned problems in the related art. Accordingly, there is still a need for improvement in processing and product quality in producing foams in which styrene polymer resin and carbon black are mixed.

It is an object of the present invention to provide an expandable styrene polymer resin containing carbon black, which can be formed to form expanded styrene polymer resin foam having high thermal insulation at low density and having excellent physical and flame retardant properties.

It is also an object of the present invention to provide expanded styrene polymer resin foams having high thermal insulation at low density.

The expandable styrene copolymer resin of the present invention comprises 0.05 to 25% by weight of carbon black particles, 1 to 15% by weight of blowing agent and the remaining amount of styrene polymer. At this time, the carbon black particles are characterized by having an average particle size of 30 ~ 140 nm. More preferably, the carbon black particles have an average particle size of 30 ~ 100 nm. Such expandable styrene copolymer resin of the present invention has excellent thermal insulation at low density when foamed. That is, the expandable styrene polymer resin of the present invention has a thermal conductivity of 29 to 30 mW / mK when foamed at a density of 19 to 20 g / l, and 34 mW / m when foamed at a density of 15 g / l. It has a thermal conductivity of K or less. In addition, the carbon black particles in the expandable styrene polymer resin of the present invention may have a bulk density of 0.03 to 0.5 g / ml.

The present invention also provides a styrene polymer foam formed by foaming the above expandable styrene polymer resin. The density of the foam is characterized in that 10 to 30 g / l.

The expandable styrene polymer resins of the present invention can form expanded styrene polymer resin foams having high thermal insulation at low density by foaming. In addition, the expandable styrene polymer resin of the present invention may not only contain carbon black particles having a low bulk density, but also contain carbon black particles having a high bulk density and may have high thermal insulation at low density.

The inventors have made considerable studies to incorporate carbon black particles into the expandable styrene polymer resins so that the expandable styrene polymer resins have excellent thermal insulation at low density. This object is an optimized melt mixing process of the styrene polymer resin and the carbon black. It has been found that this can be achieved by (compounding).

In order to obtain the expandable styrene polymer resin of the present invention, an important point in the melt mixing process of the styrene polymer and the carbon black particles is to use a twin screw extruder to improve the dispersibility of the carbon black. The inventors have found that twin screw extruders are easier to achieve this object compared to single screw extruders. In this method, styrene polymer resin is introduced into a twin screw extruder hopper, and carbon black is introduced into the hopper together with the styrene polymer resin described above or into another inlet of a twin screw extruder other than the hopper. In the present invention, the styrene polymer resin is uniformly kneaded with the carbon black in the molten state. The mixture of the styrene polymer resin and the carbon black particles kneaded uniformly in this manner is formed of the expandable styrene polymer resin by incorporating a blowing agent therein.

More specifically, the inventors have found that carbon black of any size can be dispersed by designing the screw combination to allow sufficient dispersion kneading in a twin screw extruder. This eliminates the need for carbon black concentrates, making it a more convenient and economical way.

FIG. 1 shows a schematic structure of an extruder used for producing the expandable styrene polymer resin of the present invention, and FIG. 2 shows a configuration of a kneading block of the extruder used for producing the expandable styrene polymer resin of the present invention. In the present invention, a twin screw extruder is used, but only one shaft is shown in the drawing for simplicity.

As shown in FIG. 1, the shaft of the extruder used in the present invention may be largely divided into a screw zone (or section) and a kneading block (a section). The screw section mainly serves to push the resin and carbon black particles introduced into the hopper in the direction of the screw, and the kneading block plays an important role in melting and kneading. The mixture of the resin and carbon black particles formed by kneading by the kneading block is again pushed in the advancing direction by the screw section.

As shown in FIG. 2, a general kneading block is composed of several disks, and the design elements of the kneading block are 1) staggered angle, 2) number of disks, and 3) thickness of disks. Generally, the thickness of the disc used is not more than 0.25 * D (D: outer diameter of the extruder barrel; *: multiplication mark). Like the illustrated screw combination, the plastic material introduced into the hopper is in a solid state, and plasticization (melting) occurs in the section ('ga') where the first encountering kneading block (s) are present after being introduced.

The inventors have found that carbon black disperses well when the thickness of the kneading disks in this section is greater than 0.3 * D, which is greater than the usual value, and in particular, two or more kneading blocks having a thickness of 0.3 * D to 0.4 * D in succession When arranged, it was found that no problems occurred with the dispersion of carbon black and subsequent foaming processes. It was also found that the effect was further amplified when the length of 'I', the distance from the hopper to the first kneading block, was shorter than 8 × D.

In order to manufacture the expandable styrene polymer resin of the present invention, if the thickness of the disk of the kneading block and the length of the screw section are as described above, the number of disks of the kneading block may be any number, but the number of disks of the kneading block is shown in FIG. 2. As shown in, it is preferred that there are five or more.

In the present invention, the operating conditions of the extruder applied to smoothly melt and knead the styrene polymer resin and the carbon black may be generally set, and may be appropriately selected according to the type and state of the base material and the additive. Typically, the rotational speed of the shaft is suitable about 150 to 300 rpm, the temperature of the barrel is suitable for about 120 to 250 ℃.

Next, the present invention contains a blowing agent in the mixture of the styrene polymer resin and the carbon black particles. In the present invention, the blowing agent is introduced into the mixture of the styrene polymer resin and the carbon black in two ways. The blowing agent is directly introduced into an extruder in which a mixture of styrene polymer resin and carbon black is in a molten state and then quenched at the exit of the extruder to form a foamable styrene polymer resin. Another method of injecting a blowing agent is to obtain a mixture of carbon black and styrene polymer resin in the extrusion process without adding a blowing agent, injecting the mixture into a pressure vessel, and impregnating the foam in the mixture at a constant temperature and pressure to expand the foamed styrene. It is a method of making a polymer resin.

In the expandable styrene polymer resin prepared according to the present invention, carbon black is 0.05 to 25% by weight, preferably 2 to 8% by weight, blowing agent 1 to 15% by weight and styrene polymer may be included in the remaining amount. In addition, the expandable styrene polymer resin of the present invention may further include additives such as a flame retardant, a flame retardant aid, a foamed nucleating agent, etc. in addition to the above.

The expandable styrene polymer resin formed by the present invention may be prepared in the form of a spherical bead having an average diameter of 0.2 to 2 mm or a cylindrical pellet having a diameter of 0.2 to 2 mm and a length of 0.2 to 3 mm.

The average particle size of the carbon black particles used in the present invention may be 30-140 nm, preferably 30-100 nm. In the expandable styrene polymer resin of the present invention, when the carbon black particles are 140 nm or more, it is disadvantageous to form uniform foaming when foaming. Particularly, when the carbon black particles are considerably large, the foam itself of low density may not be obtained. have. The expandable styrene polymer resin of the present invention contains smaller than the particle size of carbon black disclosed in International Patent Publication No. 94/13721, but has better thermal insulation when foamed at the same density, and also has carbon black particles having the same particle size. Even if it contains a foam having the same density has a better thermal insulation. In addition, the expandable styrene polymer resin of the present invention exhibits better thermal insulation performance at the same density as compared to other conventional expandable styrene polymer resins.

In addition, the carbon black used in the present invention may have a bulk density of 0.03-0.5 g / ml. In general, when the bulk density is large, handling is easy. However, in the case of containing the carbon black particles in the expandable styrene polymer resin, in the case of containing the carbon black having a large bulk density in the past, uniform kneading was difficult and the foamability and thermal insulation property of the expandable styrene polymer resin thus formed were not good. . On the contrary, in the present invention, even when using carbon black particles having a high bulk density, there is an additional advantage that uniform kneading is possible to obtain excellent foamability and heat insulation.

Carbon black particles used in the present invention may have a specific surface area of 30-1000 m ² / g.

As the blowing agent used in the present invention, blowing agents conventionally used for the preparation of the expandable resin may be applied. For example, hydrocarbons having 3 to 6 carbon atoms may be used. Examples of such hydrocarbons include n-butane, isobutane, cyclobutane, n-pentane, isopentane, neopentane, cyclopentane, n-hexane, cyclohexane and the like.

The styrene polymer resin used in the present invention may be a styrene homopolymer or a copolymer of styrene and other comonomers. In this case, as the styrene monomer, not only a styrene compound but also a styrene derivative may be used, and the comonomer copolymerizable with the styrene monomer is not particularly limited.

The foamed styrene polymer resin containing carbon black particles prepared as above is foamed to form a styrene polymer resin foam having a density of 5 to 35 g / l, preferably 10 to 30 g / l and especially 10-15 g / l. can do. Such foams exhibit very good thermal insulation at low densities. In particular, the styrene polymer resin foams produced according to the invention have a thermal conductivity of 29 to 30 mW / m · K at a density of 19 to 20 g / l, in particular 34 mW / m · K at a density of 15 g / l or less. Excellent heat insulation. Such thermal insulation performance has never been achieved in the past at the same density and particle size of the same carbon black.

The method of foaming the resin in the present invention is commonly known.

Hereinafter, the present invention is specifically illustrated by way of examples. However, the scope of the present invention should not be understood as being limited by the following examples.

<Example 1>

20.0 kg of polystyrene (LG Chemical Products GPPS 24HRE) and 0.8 kg of carbon black (Mitsubish Chemical Co., Ltd., Ketjen black EC-300J) having an average particle size of 36.5 nm were mixed at room temperature, and then carbon was Mixture pellets were prepared in which the black was uniformly mixed in polystyrene. After the prepared pellets were put in a pressurized container, isopentane was impregnated into the mixture at a temperature of 130 degrees Celsius and a maximum pressure of 6 kgf / cm ² to obtain a expandable styrene polymer containing carbon black. The polymer can be foamed to 21.9 g / l density by foaming with steam. The thermal conductivity was measured according to DIN 52 612 and the value was 29 mW / m · K.

<Example 2>

The foamed styrene polymer prepared in Example 1 was foamed to a density of 18.5 g / l, and the thermal conductivity of the foam was 31 mW / m · K.

Comparative Example 1

It carried out similarly to Example 1 except not adding carbon black. When foamed at a density of 21.0 g / l, the thermal conductivity of the foam was 34 mW / m · K, and when foamed at a density of 18.1 g / l, the thermal conductivity was 37 mW / m · K.

<Example 3>

Example 1 was repeated replacing the carbon black (Korea Carbon Black Co., Ltd., HIBLACK 170) having an average particle size larger than that of the carbon black used in Example 1, that is, having an average particle size of 58 nm. It was foamed to a density of 21.2 g / l, and the thermal conductivity of the foam was 30 mW / m · K.

Comparative Example 2

Example 1 was repeated replacing the carbon black (Severgazprom Co., Ltd., N991) having an average particle size larger than that of carbon black used in Example 1, that is, having an average particle size of 200 nm. Under the same foaming conditions as in Example 1, a foam having a density of 28 g / l or less could not be obtained.

1 shows a schematic structure of an extruder used to prepare the expandable styrene polymer resin of the present invention.

Figure 2 shows the configuration of the kneading block of the extruder used to prepare the expandable styrene polymer resin of the present invention.

Claims (8)

A foamable styrene polymer resin comprising 0.05 to 25% by weight of carbon black particles, 1 to 15% by weight of blowing agent and the remaining amount of styrene polymer, wherein the carbon black particles have an average particle size of 30 to 140 nm. Expandable styrene polymer resin. The method of claim 1, The carbon black particles have a foamed styrene polymer resin, characterized in that having an average particle size of 30 ~ 100 nm. The method according to claim 1 or 2, The expandable styrene polymer resin is formed of a styrene polymer resin foam having a thermal conductivity of 29 to 30 mW / m · K when foamed at a density of 19 to 20 g / l. The method according to claim 1 or 2, The expandable styrene polymer resin is formed of a styrene polymer resin foam having a thermal conductivity of 34 mW / m · K or less when foamed at a density of 15 g / l. The method according to claim 1 or 2, The carbon black particles are foamed styrene polymer resin, characterized in that the bulk density is 0.03 ~ 0.5 g / ml. The method according to claim 1 or 2, The expandable styrene polymer resin is in the form of a spherical bead having an average diameter of 0.2 to 2 mm or a cylindrical pellet form having an average diameter of 0.2 to 2 mm and an average length of 0.2 to 3 mm. The method according to claim 1 or 2, The foaming agent is a foamable styrene polymer resin, characterized in that the hydrocarbon compound or a mixture thereof having 3 to 6 carbon atoms. A styrene polymer foam formed by foaming the expandable styrene polymer resin according to any one of claims 1 to 7, wherein the density of the foam is 10 to 30 g / l.

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