KR101153150B1 - Method for Preparing Expandable Styrenic Polymer Resin Containing Carbon Black Particles - Google Patents

Abstract

The present invention provides a foamed styrene polymer resin comprising melting and kneading a styrene polymer resin and carbon black particles in an extruder to form a mixture of the styrene polymer resin and the carbon black particles and incorporating a blowing agent in the mixture. Provide a method. At this time, the extruder is a twin screw extruder, the disk thickness of the kneading block of the twin screw extruder is 0.3 x D or more, where D is the outer diameter of the barrel of the extruder. Foaming such expandable styrene polymer resins yields expanded styrene polymer resin foams having high thermal insulation at low density.

Styrene polymer, carbon black, foam, twin screw extruder, kneading block, disc thickness

Description

Method for preparing expandable styrene polymer resin containing carbon black particles {Method for Preparing Expandable Styrenic Polymer Resin Containing Carbon Black Particles}

The present invention relates to a method for producing 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. It relates to a manufacturing method.

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, when the carbon black is mixed with the polystyrene resin to prepare a foam, difficulties in processing and a problem in product quality 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. Therefore, the patent only solves the above-mentioned problems in the prior 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 a process for preparing expandable styrene polymer resins containing carbon black which can be formed to form expanded styrene polymer resin foams with high thermal insulation at low density and to have good physical and flame retardant properties. .

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

It is also an object of the present invention to provide a kneading method in an extruder in which inorganic particles can be uniformly dispersed in a thermoplastic resin.

The present invention provides a foamed styrene polymer resin comprising melting and kneading a styrene polymer resin and carbon black particles in an extruder to form a mixture of the styrene polymer resin and the carbon black particles and incorporating a blowing agent in the mixture. Provide a method. At this time, the extruder is a twin screw extruder, the disk thickness of the kneading block of the twin screw extruder is 0.3 x D or more, where D is the outer diameter of the barrel of the extruder. Here, the length of the screw section of the extruder disposed before the kneading block is preferably shorter than 8 x D. It is preferable that two or more kneading blocks are arranged continuously in the said extruder. The kneading block may be composed of five or more disks.

In another aspect, the present invention provides a method for producing a styrene polymer resin foam comprising the step of foaming the expandable styrene polymer resin prepared according to the above method. At this time, the density of the foam is preferably 10 to 30 g / l.

The present invention also provides a kneading method comprising the step of melting and kneading the thermoplastic polymer resin and the inorganic particles in an extruder to form a mixture of the thermoplastic polymer resin and the inorganic particles. At this time, the extruder is a twin screw extruder, the disk thickness of the kneading block of the twin screw extruder is 0.3 x D or more, where D is the outer diameter of the barrel of the extruder. Here, the length of the screw section of the extruder disposed before the kneading block is preferably shorter than 8 x D. It is preferable that two or more kneading blocks are arranged continuously in the said extruder. The kneading block is generally composed of five or more disks. The inorganic particles preferably have an average particle size of 30 to 500 nm, a bulk density of 0.03 to 0.5 g / ml, and a specific surface area of 30 to 1000 m ² / g.

The expandable styrene polymer resins produced by the present invention can form expanded styrene polymer resin foams having high thermal insulation at low density by foaming. In addition, the kneading method of the present invention can uniformly disperse the inorganic particles, particularly carbon black, which is difficult to be uniformly blended in the thermoplastic resin, in the thermoplastic resin so that processing problems and product quality problems do not occur.

The inventors have found that this object is achieved by an optimized melt mixing process (compounding) of styrene polymer resin and carbon black.

An important point in the production method of the expandable styrene polymer resin containing the carbon black particles by the melt mixing process provided by the present invention 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 the method of the present invention, 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.

Figure 1 shows a schematic structure of an extruder used in the present invention, Figure 2 shows the configuration of the kneading block of the extruder used in 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. In general, the thickness of the disk 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 the solid state, and plasticization (melting) occurs in the section ('ga') where the first encountering kneading block (s) are placed after the injection.

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. In addition, it was found that the effect is further amplified when the length of 'I', which is the distance from the hopper to the first kneading block, is shorter than 8 × D.

According to 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 the disks of the kneading block may be five or as shown in FIG. It is preferable that it is more than that.

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 then impregnating the foam in the mixture at a constant temperature and pressure to expand the foamed styrene polymer. How to make a 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 to the above, 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. as necessary.

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 is preferably 30 to 500 nm, particularly 35 to 200 nm, bulk density of 0.03 to 0.5 g / ml, and specific surface area of 30 to 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 to 15 g / l. can do. Such foams exhibit very good thermal insulation at low densities. In particular, the styrene polymer resin foams prepared 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 at a density of 15 g / l or less to 34 mW / m? K. Excellent heat insulation. The method of foaming the resin in the present invention is commonly known.

The present invention can provide a kneading method in which the thermoplastic polymer resin and the inorganic particles are melted and kneaded in an extruder to form a mixture by applying the requirements of the twin screw extruder described above. Here, the thermoplastic polymer resin may include not only styrene polymer resins but also generally known thermoplastic polymer resins, and also the inorganic particles include not only carbon black particles but also inorganic particles which generally need to be uniformly kneaded with the thermoplastic polymer resin. can do. If such inorganic particles meet the requirements of particle size, bulk density, or specific surface area mentioned above for carbon black particles, in particular the process of the present invention will greatly contribute to its uniform dispersion. Thus, the kneading method of the present invention can be applied for a mixture of 0.05 to 30% by weight of inorganic particles and the remaining amount of thermoplastic polymer resin. Of course, the mixture may comprise further additives.

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 Chemicals GPPS 24HRE) and 0.8 kg of carbon black (Mitsubish Chemical Co., Ltd., Ketjen black EC-300J) were mixed at room temperature and carbon black was uniformly mixed in polystyrene using a twin screw extruder. Mixture pellets were prepared. After the prepared pellets were put in a pressurized container, isopentane was impregnated into the mixture at a temperature of 130 ° C. and a maximum pressure of 6 kgf / cm ² to obtain a foamed 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 carbon black (Korea Carbon Black Co., Ltd., HIBLACK 170) having an average particle size larger than the carbon black used in Example 1. It was foamed to a density of 21.2 g / l, and the thermal conductivity of the foam was 30 mW / m? K.

1 shows a schematic structure of an extruder used in the present invention.

Figure 2 shows the configuration of the kneading block of the extruder used in the present invention.

Claims (17)

In the method for producing a foamable styrene polymer resin comprising melting and kneading a styrene polymer resin and carbon black particles in an extruder to form a mixture of the styrene polymer resin and the carbon black particles and incorporating a blowing agent in the mixture. , The carbon black particles satisfy an average particle size of 30 to 500 nm and a specific surface area of 30 to 1000 m ² / g, The extruder is a twin screw extruder, the disk thickness of the kneading block of the twin screw extruder is 0.3 x D or more, the length of the screw section of the extruder disposed before the kneading block is shorter than 8 x D, where D is the extruder Characterized in that the outer diameter of the barrel Method for producing expandable styrene polymer resin. The method of claim 1, The disk thickness of the kneading block of the twin screw extruder is characterized in that the range of 0.3 x D ~ 0.4 x D Method for producing expandable styrene polymer resin. delete The method of claim 1, In the extruder, the kneading block is characterized in that two or more consecutively arranged Method for producing expandable styrene polymer resin. The method of claim 1, The kneading block is characterized by consisting of five or more disks Method for producing expandable styrene polymer resin. The method of claim 1, The expandable styrene polymer resin is characterized in that it comprises 0.05 to 25% by weight of the carbon black, 1 to 15% by weight of the blowing agent and the remaining amount of the styrene polymer. Method for producing expandable styrene polymer resin. The method of claim 1, 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. Method for producing expandable styrene polymer resin. delete The method of claim 1, The carbon black particles have a bulk density of 0.03 to 0.5 g / ml. Method for producing expandable styrene polymer resin. The method of claim 1, The step of incorporating the blowing agent is characterized in that the blowing agent is directly added to the extruder in the molten state of the mixture of styrene polymer and carbon black and then quenched at the outlet of the extruder to mix the blowing agent. Method for producing expandable styrene polymer resin. The method of claim 1, The step of incorporating the blowing agent is characterized in that the mixture of the styrene polymer and carbon black obtained in the extruder in a pressure vessel and then impregnating the blowing agent in the mixture Method for producing expandable styrene polymer resin. The method of claim 1, The blowing agent is characterized in that the hydrocarbon compound or a mixture thereof having 3 to 6 carbon atoms Method for producing expandable styrene polymer resin. Claim 1 to 2, 4 to 7, 9 to 12 comprising the step of foaming the expandable styrene polymer resin according to any one of the foam to obtain a foam, the density of the foam is 10 To 30 g / l Process for the preparation of foams of styrene polymers. delete delete delete Obtained by the method of claim 13, in the form of a spherical bead having an average diameter of 0.2 to 2 mm or in the form of a cylindrical pellet having an average diameter of 0.2 to 2 mm and an average length of 0.2 to 3 mm, at a density of 15 to 29 g / l. When foamed is characterized in that it is formed of a styrene polymer resin foam having a thermal conductivity of 32 ~ 34 mW / m? K Expandable Styrene Polymer Resin.

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