KR20060004384A - Expandable polystyrene resin, process for preparing thereof and expanded product produced by using said resin particules - Google Patents

Abstract

The present invention relates to a method for producing a foamable polystyrene resin having self-extinguishing resistance excellent in impact resistance and chemical resistance, a foamable polystyrene resin produced thereby, and a foamed molded article made of the resin particles. The method for preparing the expandable polystyrene resin of the present invention is characterized in that an acrylonitrile-styrene copolymer is added at the beginning of suspension polymerization, and carbon black is used as a flame retardant aid instead of reducing the amount of halogen-based flame retardants used. The foamed polystyrene-based resin thus prepared has improved impact resistance and chemical resistance, and at the same time, can maintain almost the same self-extinguishing property as when a large amount of halogen-based flame retardants are used.

Suspension polymerization, flame retardant, expandable polystyrene, carbon black, acrylonitrile-styrene copolymer

Description

Expandable Polystyrene Resin, Process for Preparing and Expanded Product Produced by Using Said Resin Particules

The present invention is a method for producing a foamed polystyrene resin having a self-extinguishing resistance excellent in impact resistance and chemical resistance compared to the general foamed styrene resin (EPS, Expanded Poly-Styrene), and the resulting foamed polystyrene resin and the resin particles It relates to a foam molded article produced.

Expandable styrene resins are generally prepared by suspension polymerization with water by containing a polymerization initiator and a blowing agent (for example, a hydrocarbon gas or a halogenated hydrocarbon-based blowing agent such as pentane or butane) in styrene. The expandable styrene resin obtained from this has the form of 0.2-3.0 mm spherical particle (bead, bead). At this time, the beads are washed and dried and then sieved to form a foamed article.

The foamed molded article of the expandable styrene resin particles is obtained by heating the expandable styrene resin particles impregnated with a styrene resin such as polystyrene with a blowing agent at a softening point or higher by steam or the like to obtain particulate prefoamed particles having independent bubbles therein. Subsequently, the prefoamed particles may be further heated by steam or the like in a closed mold capable of heating the inside with a vapor or the like from a small hole or a slit to mutually fuse by the volume expansion of the expanded particles to obtain a foamed molded article.

The foam molded article is a resource-saving material in which 98% of the volume is air and the remaining 2% is resin. Foamed molded articles of foamable styrene resin are excellent in cushioning, waterproofing, thermal insulation, and heat insulation, and are used as packaging materials for household appliances, agricultural product boxes, aquaculture rich, home insulation materials, and the like.

On the other hand, the foam molded article excellent in strength is characterized in that the impact mitigation effect is greater as a packaging material than the existing product. Therefore, there is an advantage that the amount of resin used can be reduced.

Conventionally, as a method for increasing the strength of the expandable styrene resin, a method of adding NaCl, a method of increasing the molecular weight of the polymer, a method of adding an acrylonitrile monomer, and the like have been used. However, when NaCl is used, particle formation is unstable, and the method of increasing the molecular weight improves the strength but the foaming power of the product is low. Finally, when acrylonitrile monomer is used, it is difficult to maintain polymerization stability. have.

Therefore, in order to solve the conventional problems as described above, the present inventors have intensively studied, and as a result, an acrylonitrile-styrene copolymer is introduced at the initial stage of the polymerization reaction of the expandable styrene resin, and the amount of halogen-based flame retardant used in the past is used. It has been found that by using carbon black as a flame retardant aid instead of reducing the amount, a foamable polystyrene resin having high strength and chemical resistance while having almost the same self-extinguishing property as when a large amount of halogen-based flame retardant is used is found.

The present invention has been completed based on these findings, and an object of the present invention is to provide a foamable polystyrene resin having excellent impact resistance and chemical resistance while having the same foaming and self-extinguishing properties as conventional products when preparing a foamable polystyrene resin by suspension polymerization. And to provide a method for producing the same.

It is an object of the present invention to provide a method for producing a expandable polystyrene resin having self-extinguishing superior in impact resistance and chemical resistance.

The method for producing a self-extinguishing expandable polystyrene resin according to the present invention is characterized by adding an acrylonitrile-styrene copolymer at the beginning of suspension polymerization of the expandable polystyrene resin and using carbon black as a flame retardant aid.

The impact resistance and chemical resistance of the expandable polystyrene-based resin may be improved by introducing an initial acrylonitrile-styrene copolymer.

The acrylonitrile-styrene copolymer is used in an amount of 20 to 30 parts by weight based on 100 parts by weight of the styrene monomer, wherein the acrylonitrile content in the acrylonitrile-styrene copolymer is 20 to 40% by weight, preferably 28 to 28 parts by weight. 36% by weight. When the acrylonitrile-styrene copolymer is used in less than 20 parts by weight, the strength improvement of the final product is insignificant, and when used in excess of 30 parts by weight, the polymerization stability is lowered. In the acrylonitrile-styrene copolymer, when the acrylonitrile content is less than 20%, the strength improvement is insignificant, and when the acrylonitrile-styrene copolymer is more than 40%, problems in polymerization stability occur.

In addition, in the prior art, the halogen-based flame retardant was used in the range of 0.4 to 0.8 parts by weight based on 100 parts by weight of the styrene monomer in the preparation of the expandable polystyrene resin, but the amount of the present invention may be reduced to about 0.1 to 0.4 parts by weight.

When the halogen-based flame retardant is added in the same amount to maintain the same self-extinguishing styrene resin as the existing self-extinguishing styrene resin, there is a problem in the polymerization stability of the polystyrene-based resin, thereby reducing the amount of halogen flame retardant and flame retardant The self-extinguishing property of the resin produced | generated by adding carbon black as an adjuvant can be maintained. The use of less halogen-based flame retardants has the advantage of reducing mechanical corrosion or adverse effects on humans or peripherals due to hydrogen halide generation.

The halogen-based flame retardant used in the present invention may be hexabromocyclododecane, tetrabromocyclooctane, tetrabromobisphenol A and the like, but hexabromocyclododecane is particularly preferable.

In the method of the present invention, the carbon black may be used in an amount of 1 to 8 parts by weight based on 100 parts by weight of the styrene monomer. If it is less than 1 part by weight, the flame retardancy improvement of the expanded polystyrene is insignificant, and if it is more than 8 parts by weight, the polymerization stability is inferior.

When producing the self-extinguishing expandable polystyrene resin of the present invention, the monomer (s) serving as a raw material of the styrene resin is suspended and polymerized in an aqueous medium.

It is preferable to use a polymerization initiator in the suspension polymerization, and as an initiator, without limitation, benzoyl peroxide, t-butyl peroxy benzoate, dicumyl peroxide, tert-amyl peroxy 2-ethylhexyl carbonate, lauryl per One or more compounds selected from the group consisting of oxides, tert-butyl peroxy isopropyl carbonate and cumene hydroxy peroxide are used. As for the usage-amount of a polymerization initiator, 0.01-0.7 weight part is preferable with respect to 100 weight part of monomers.

In addition, it is preferable to use a dispersant in the suspension polymerization, and a dispersant may include, but is not limited to, poorly water-soluble inorganic salts such as polyvinyl alcohol, methyl cellulose, polyvinyl pyrrolidone, tricalcium phosphate and magnesium pyrophosphate. have. As for the usage-amount of a dispersing agent, 0.3-1.0 weight part is preferable with respect to 100 weight part of monomers.

In addition, it is preferable to use a dispersing aid in order to impart stability to the dispersion system in the suspension polymerization, and the dispersing aid is, but is not limited to, hydroxypertite, ammonium persulfate, potassium persulfate, magnesium sulfate hydrate, calcium hydroxide And two or more selected from the group consisting of sodium dodecyl benzene sulfonate. As for the usage-amount of a dispersal auxiliary agent, 0.001-0.005 weight part is preferable with respect to 100 weight part of monomers.

The blowing agents used in the present invention include, but are not limited to, n-butane, isobutane, cyclobutane, n-pentane, isopentane, cyclopentane, neopentane, cyclohexane and the like as hydrocarbon compounds having 3 to 6 carbon atoms, It is also possible to use a mixture of two or more thereof.

As for the usage-amount of a blowing agent, 3-10 weight part is preferable with respect to 100 weight part of monomers.

In the polymerization reaction of the present invention, additives such as a cell size regulator and a molecular weight regulator can be added. For example, as the cell size regulator, polyethylene wax is 0.001 to 0.1 parts by weight based on 100 parts by weight of the monomer, and n- as the molecular weight regulator. Octyl mercaptan can be used at 0.05 to 0.5 parts by weight.

During suspension polymerization, the reaction temperature was maintained at about 90 ℃ for 2-4 hours at the beginning of the reaction, and then increased to about 100 ℃, maintained at about 2-4 hours, and finally raised to about 125 ℃ for 3 hours. Maintain the temperature to complete the reaction.

It is also an object of the present invention to provide an expandable polystyrene resin prepared by the above production method and a foam molded article made of the resin particles.

The expandable polystyrene resin prepared by the above production method preferably has a weight average molecular weight in the range of 150,000 to 400,000, and in this range, the strength of a molded article produced using the same is remarkably improved. Especially, the molded article manufactured from resin of the range of 150,000-350,000 is especially preferable at the point which is excellent in the balance of impact resistance and fusion resistance.

The particle size of the expandable polystyrene resin particles is appropriate in the range depending on the use of the molded article, but is preferably 0.5 to 1.5 mm. The particle diameter range of 0.5 mm or less is insufficient in impact resistance, and 1.5 mm or more is unpreferable because the filling property to a molding dry mold worsens.

Although the process of obtaining a molded article from the expandable styrene resin particle of this invention is performed by the method currently performed, it is not limited to this. For example, the foamed styrene resin particles are heated and foamed at a magnification of 20 to 100 times with water vapor of 85 to 110 ° C. in a foaming machine to prepare pre-expanded particles (preliminary foaming step), and the air is permeated into the pre-expanded particles in the air. After removing the moisture adhering to the (maturation step), the pre-expanded particles which have undergone this aging step are filled into a mold of a closed mold provided with a small hole or a slit, and further heated by steam, thereby fusion and integration of the individual particles. To make a molded article.

Examples of the foamed molded article manufactured in this way include various cushioning materials, heat insulating materials, packaging containers, and the like.

In the following Examples, the present invention will be described in more detail, but the present invention is not limited by the following Examples.

EXAMPLE

The monomers used for the polymerization according to the invention comprise 40 to 60% by weight in the mixture.

Example  One

8 kg of styrene monomer, 2 kg of acrylonitrile-styrene copolymer (36% by weight of acrylonitrile) and 10 kg of ionized water were added to a 40-l dissolution tank while stirring, 12 g of benzoyl peroxide as an initiator, 2 g of t-butylperoxybenzoate, and dicumyl peroxide. 35 g is added, and 35 g of sodium pyrophosphate and 35 g of magnesium sulfate are added as a dispersant. As other additives, 1 g of poly-wax, 30 g of hexabromocyclododecane, and 300 g of carbon black were added. 10 g of n-octyl mercaptan was added as a molecular weight regulator.

After the reactor was sealed, the temperature was raised to 90 ° C. over 1 hour, then maintained at this temperature for 2 hours, and then raised to 100 ° C. over 1 hour. The temperature was kept at 100 ° C. for 2 hours and then raised to 125 ° C. over 1 hour. During the temperature increase, 4 g of sodium dodecylbenzenesulfonate 10% aqueous solution is added. Thereafter, 900 g of pentane, a blowing agent, was added at the same time at 125 ° C. and maintained at this reaction temperature for 3 hours, and then cooled to 45 ° C. to obtain a polymer.

After the polymerization was completed, dehydration and drying process to obtain the final product. The final product thus obtained was foamed at an 80-fold rate using a foaming machine, and then maintained at room temperature for 4 hours, and then molded again using a vacuum molding machine (air machine PKB-306VS) to obtain a final molded product. After that, the foamed molded article was cut to 60 mm x 45 mm x 5 mm, and then the compressive strength was measured. The self-extinguishing property was tested by the KSM-3808 test method (sample specification: 10 mm x 200 mm x 25 mm). The temperature at the test site shall be maintained at 23 ± 5 ° C and the relative humidity at 50 ± 20%. The number of test specimens shall be five and the average number of extinguishing seconds is less than three seconds is called self-extinguishing pass.

Comparative example  One

The same procedure as in Example 1 except that acrylonitrile-styrene copolymer was not added during polymerization and 10 kg of styrene monomer was used instead.

Comparative example  2

It is the same as Example 1 except adding 1 kg of acrylonitrile-styrene copolymers at the time of superposition | polymerization, and using 9 kg of styrene monomers.

Comparative example  3

It is the same as Example 1 except the acrylonitrile content is 15% by weight in the acrylonitrile-styrene copolymer during polymerization.

Comparative example  4

The polymerization was the same as in Example 1 except that acrylonitrile-styrene copolymer and carbon black were not added, 10 kg of styrene monomer was used, and 50 g of hexabromododecane was used as a flame retardant.

Comparative example  5

It is the same as Example 1 except not adding carbon black at the time of superposition | polymerization.

◆ Measuring method: JIS A9511 (Density: 25g / l)                     

◆ Measurement method: KSM-38-8 combustion test

The expandable polystyrene resin prepared by the production method of the present invention is excellent in impact resistance and chemical resistance, and has the same degree of self-extinguishing as in the case of using a large amount of halogen-based flame retardant.

Claims (9)

A method for producing a foamable polystyrene resin by suspension polymerization, wherein the acrylonitrile-styrene copolymer is added to the initial stage of polymerization and carbon black is used as a flame retardant aid. The method according to claim 1, wherein the acrylonitrile-styrene copolymer is used in an amount of 20 to 30 parts by weight based on 100 parts by weight of the styrene monomer. The method according to claim 1 or 2, wherein the content of acrylonitrile in the acrylonitrile-styrene copolymer is 20 to 40% by weight. The method according to claim 3, wherein the acrylonitrile-styrene copolymer has an acrylonitrile content of 28 to 36% by weight. The method according to claim 1, wherein the carbon black is used in an amount of 1 to 8 parts by weight based on 100 parts by weight of the styrene monomer. The method according to claim 1, wherein the halogen-based flame retardant is used as a flame retardant in an amount of 0.1 to 0.4 parts by weight based on 100 parts by weight of the styrene monomer. 7. A process according to claim 6, wherein the halogen flame retardant is hexabromocyclododecane. The foamable polystyrene resin produced by the manufacturing method of Claims 1-7. A foamed molded article produced from the expandable polystyrene resin particles according to claim 8.