JP2009298969A - Expandable polystyrene-based resin particle and polystyrene-based resin expansion-molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide expandable polystyrene-based resin particles slight in mutual blocking of pre-expanded particles in undergoing pre-expansion and excellent in mutual fusibility of expanded particles in undergoing in-mold expansion molding, expandable in a high expansion ratio, and also excellent in terms of the environment and safety. <P>SOLUTION: The expandable polystyrene-based resin particles are such as to be obtained by impregnating a foaming agent in polystyrene-based resin particles. The expandable polystyrene-based resin particles are characterized by containing 0.3-2.0 pts.wt. of a ≤11C fatty acid as a plasticizer based on 100 pts.wt. of the polystyrene-based resin particles. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an expandable polystyrene resin particle and a polystyrene resin foam molded article.

  Conventionally, polystyrene-based resin foam-molded products have been used in many fields such as food applications, home appliance fields, cushioning material applications, residential building materials, and civil engineering applications. This polystyrene-based resin foam-molded product is obtained by pre-expanding expandable polystyrene-based resin particles into pre-expanded particles, filling the pre-expanded particles into a mold of a foam molding machine, and supplying heated steam into the mold. Thus, the pre-expanded particles are heated and foamed so as to be fused and integrated with each other, so-called in-mold foam molding.

  In recent years, there has been a demand for a polystyrene-based resin foam molded article having a higher expansion ratio than before. Furthermore, polystyrene-based resin foam moldings used for food and building materials are required to have further safety, and the revised Occupational Safety and Health Law may cause dangers or health problems. However, it is necessary to describe the label, safety data sheet, etc. of the name, ingredients, properties, effects on the human body, handling precautions, first-aid measures, etc. It is stipulated that there is.

  As expandable polystyrene resin particles, Patent Document 1 discloses that an aliphatic hydrocarbon or a cycloaliphatic hydrocarbon having a boiling point lower than the softening point of the resin is contained in the thermoplastic resin particles. Expandable thermoplastic resin particles characterized by containing 1 to 15% by weight and 0.2 to 3.0% by weight of diisobutyl adipate are disclosed.

  Patent Document 2 discloses expandable polystyrene resin particles containing a predetermined amount of at least one ester compound selected from the group consisting of adipic acid esters and sebacic acid esters.

  However, the above expandable polystyrene resin particles use adipic acid ester such as diisobutyl adipate or sebacic acid ester as one of the plasticizers, and in order to obtain a polystyrene resin foam molded product with a high expansion ratio, It was necessary to use a large amount, and this was not preferable in terms of cost and environment.

  Further, Patent Document 3 includes a predetermined amount of a plasticizer that is made of polystyrene resin particles having a predetermined weight average molecular weight, contains a predetermined amount of isobutane as a foaming agent, is liquid at room temperature, and has a boiling point of 200 ° C. or higher. Expandable polystyrene resin particles contained therein are disclosed. In paragraph [0018], only phthalic acid esters, fatty acid esters, and phosphoric acid esters are disclosed as plasticizers, and in the examples, 2-ethylhexyl phthalate and dimethyl phthalate are used. It has only been done.

  However, the expandable polystyrene resin particles, like the expandable polystyrene resin particles described above, require a large amount of plasticizer and a phthalate ester in order to obtain a polystyrene resin foam molded product with a high expansion ratio. Has an environmental problem, and is not preferable in terms of both cost and environment.

Patent Document 4 discloses that when 100 parts by weight of expandable polystyrene resin particles are subjected to vacuum distillation under a pressure of 6.666 × 10 ⁻⁴ MPa (5 mmHg) at 350 to 1200 ppm of styrene monomer. Expandable polystyrene resin particles characterized by containing 0.1 to 2 parts by weight of a plasticizer that cannot be distilled at a temperature of 250 ° C. or less and a foaming agent are disclosed. In paragraph [0024], palm oil, palm kernel oil, palm oil, and rapeseed oil are exemplified as the plasticizer.

  However, the edible oil disclosed as a plasticizer is insufficient in fusion of the pre-expanded particles at the time of in-mold foam molding, and a good polystyrene-based resin foam molded product cannot be obtained.

  Furthermore, Patent Document 5 discloses expandable polystyrene resin particles obtained by adding predetermined amounts of two types of plasticizers to polystyrene resin particles.

  However, toluene has been disclosed as a plasticizer, and it cannot be used because of the recent stricter regulations on organic chemicals, environmental impact, and prohibition of use in food applications. However, there was a problem in the health of workers.

JP-A-9-52970 JP 2006-213850 A Japanese Patent Application Laid-Open No. 9-130036 JP 2003-64212 A JP 2004-307729 A

  The present invention has less fusing (blocking) between pre-expanded particles at the time of pre-foaming, and is excellent in the fusion property between the foamed particles obtained by foaming the pre-foamed particles at the time of in-mold foam molding. Polystyrene resin that can be used suitably in a wide range of fields such as food applications, home appliances, cushioning materials, residential building materials, civil engineering applications, especially in the food field. An expandable polystyrene resin particle capable of obtaining a foam molded article and a polystyrene resin particle foam molded article obtained using the same are provided.

  The expandable polystyrene resin particles of the present invention are expandable polystyrene resin particles obtained by impregnating polystyrene resin particles with a foaming agent, and have 11 carbon atoms as a plasticizer with respect to 100 parts by weight of the polystyrene resin particles. It contains 0.3 to 2.0 parts by weight of the following fatty acids.

  The polystyrene resin constituting the polystyrene resin particles is not particularly limited. For example, styrene, α-methylstyrene, vinyltoluene, ethylstyrene, i-propylstyrene, t-butylstyrene, dimethylstyrene, bromostyrene, Examples include homopolymers of styrene monomers such as chlorostyrene or copolymers thereof.

  The polystyrene resin may be a copolymer of the styrene monomer containing 50% by weight or more of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer. Examples of such vinyl monomers include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cetyl (meth) acrylate, (meth ) In addition to acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, difunctional monomers such as divinylbenzene, alkylene glycol dimethacrylate, polyethylene glycol di (meth) acrylate, and the like. In addition, 150,000 to 400,000 are preferable and the weight average molecular weight by GPC (gel permeation chromatography) method of the polystyrene resin is more preferably 250,000 to 350,000.

  The polystyrene resin particles are impregnated with a foaming agent to form expandable polystyrene resin particles. The foaming agent is not particularly limited as long as it is conventionally used for expandable polystyrene resin particles, and examples thereof include aliphatic hydrocarbons such as propane, butane, pentane, isopentane, hexane, and cyclopentane. 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 2-chloro-1,1,1,2- CFC-based blowing agents such as tetrafluoroethane (HCFC-124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), and aliphatic hydrocarbons Is preferred. In addition, a foaming agent may be used independently or may be used together.

  If the content of the foaming agent in the expandable polystyrene resin particles is small, the thermal fusion between the expanded particles obtained by foaming the expandable polystyrene resin particles becomes insufficient, and the mechanical strength of the foam molded product On the other hand, if the amount is too large, the size of the foamed particles obtained by foaming the expandable polystyrene resin particles becomes too large, the smoothness of the surface of the foamed molded product is impaired, and the appearance of the foamed molded product And the appearance when printing is performed on the surface of the foamed molded article may be reduced, so that 2 to 12 parts by weight is preferable and 3 to 9 parts by weight is more preferable with respect to 100 parts by weight of the polystyrene resin particles.

  Here, the content of the foaming agent in the expandable polystyrene resin particles refers to that measured in the following manner. That is, the foamable polystyrene resin particles are supplied to a heating furnace at 180 ° C. to obtain a chart of the foaming agent to be measured from the gas chromatograph, and based on the calibration curve of the foaming agent to be measured that has been measured in advance. Then, the amount of the foaming agent in the expandable polystyrene resin particles is calculated from the chart.

In addition, content of the foaming agent in an expandable polystyrene-type resin particle can be measured on condition of the following using a gas chromatograph (Shimadzu Corporation brand name "GC-14B").
Detector: FID
Heating furnace: Product name “PYR-1A” manufactured by Shimadzu Corporation
Column: Shinwa Kako Co., Ltd. (3mm diameter x 3m)
Liquid phase: Squalane 25% by weight
Carrier: Shimalite 60-80 NAW
Heating furnace temperature: 180 ° C
Column temperature: 70 ° C
Detector temperature: 110 ° C
Inlet temperature: 110 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 60 ml / min

  And the expandable polystyrene resin particle of the present invention contains a fatty acid having 11 or less carbon atoms as a plasticizer, and preferably contains a linear saturated fatty acid having 11 or less carbon atoms. Preferably, a linear saturated fatty acid having 8 to 10 carbon atoms is contained. Such fatty acids having 11 or less carbon atoms are not particularly limited, and include caprylic acid (linear saturated fatty acid having 8 carbon atoms), capric acid (linear saturated fatty acid having 10 carbon atoms), and the like. Caprylic acid is preferred.

  When the number of carbon atoms of the fatty acid is large, the plastic effect is weakened, and the foamability of the foamed particles obtained by foaming the pre-foamed particles becomes insufficient at the time of in-mold foam molding. If it is less, the odor of the fatty acid will become strong, and it will be difficult to use it especially for food applications.

  If the content of the fatty acid having 11 or less carbon atoms in the expandable polystyrene resin particles is small, the expandability of the expandable polystyrene resin particles is lowered, and a highly expanded polystyrene resin foam molded article is obtained. On the other hand, if the foamed polystyrene resin particles are pre-foamed, in-mold foam molding is performed using pre-foamed particles obtained by pre-foaming the expandable polystyrene resin particles. Therefore, since a good polystyrene resin foam molded article cannot be obtained, it is limited to 0.3 to 2.0 parts by weight with respect to 100 parts by weight of polystyrene resin particles, and 0.5 to 1.2 parts by weight. preferable.

  Furthermore, in addition to the above fatty acids, known plasticizers such as cyclohexane, diisobutyl adipate and coconut oil may be contained. The content of diisobutyl adipate is preferably 0.3 to 1.5 parts by weight, more preferably 0.3 to 1.2 parts by weight, with respect to 100 parts by weight of polystyrene resin particles, and 0.5 to 1.0 parts by weight. Part is particularly preferred.

  The cyclohexane content is preferably 0.3 to 1.5 parts by weight, more preferably 0.3 to 1.2 parts by weight, and more preferably 0.5 to 1.0 parts by weight based on 100 parts by weight of the polystyrene resin particles. Part by weight is particularly preferred.

  Since the expandable polystyrene resin particles of the present invention contain a fatty acid having 11 or less carbon atoms as a plasticizer as described above, it is possible to reduce the amount of the styrene monomer that has acted as a plasticizer. Specifically, the content of the styrene monomer in the expandable polystyrene resin particles is preferably 3000 ppm or less with respect to the total weight of the expandable polystyrene resin particles.

  In addition, content of the styrene-type monomer in an expandable polystyrene-type resin particle is measured in the following way. After precisely weighing 1 g of expandable styrene resin particles, 1 ml of a dimethylformamide solution containing 0.1% by volume of cyclopentanol was added as an internal standard solution to the accurately measured expandable styrene resin particles. Further, dimethylformamide is added to the above dimethylformamide solution to prepare a measurement solution of 25 ml, and 1.8 microliter of this measurement solution is supplied to a sample vaporization chamber at 230 ° C., and the styrene monomer to be measured from the gas chromatograph. The amount of styrene monomer is calculated from the above chart based on the calibration curve of the styrene monomer to be measured that has been measured in advance.

In addition, content of the styrene-type monomer in an expandable styrene-type resin particle can be measured on the following measurement conditions using a gas chromatograph (Shimadzu Corporation brand name "GC-14A").
Detector: FID
Column: GL Sciences Inc. (3mm diameter x 2.5m)
Liquid phase: PEG-20M PT 25% by weight
Carrier: Chromosorb W AW-DMCS
Mesh: 60/80
Column temperature: 100 ° C
Detector temperature: 230 ° C
Inlet temperature: 230 ° C
Carrier gas: Nitrogen Carrier gas flow rate: 40ml / min

  Further, the surface property of the polystyrene resin particle foam molded article obtained by coating the surface of the expandable polystyrene resin particles with metal soap, talc powder, wax, or the like and performing foam molding in the mold may be improved.

  Next, the manufacturing method of the expandable polystyrene resin particle of this invention is demonstrated. As a method for producing expandable polystyrene resin particles, first, polystyrene resin particles produced by a general-purpose production method are dispersed in an aqueous medium in a general-purpose manner to prepare a particle dispersion. In addition, it does not specifically limit as an aqueous medium, Water, alcohol, etc. are mentioned, Water is preferable.

  Here, as a method for producing polystyrene resin particles, for example, (1) a polystyrene resin particle is produced by supplying a styrene monomer into an aqueous medium and polymerizing the styrene monomer in the presence of a polymerization initiator. (2) A dispersion obtained by suspending polystyrene resin seed particles in an aqueous medium is prepared, and a styrene monomer is supplied into the dispersion to polymerize the styrene monomer on the polystyrene resin seed particles. A method for producing polystyrene resin particles by impregnation and polymerization in the presence of an initiator. (3) Supplying a polystyrene resin to an extruder, melt kneading and extruding into strands, and cutting the strands at predetermined intervals. The method of manufacturing a polystyrene-type resin particle etc. is mentioned, The manufacturing method of (1) is preferable.

  The polymerization initiator used for polymerizing the styrene monomer is not particularly limited, and examples thereof include benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, t-butyl peroxide, and t-butyl peroxide. Pivalate, t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butylperoxyacetate, 2,2-t-butylperoxybutane, 2,2-bis (t -Butylperoxy) butane, t-butylperoxy-3,3,5 trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate and other organic peroxides, azobisisobutyronitrile, azobisdimethyl Examples include azo compounds such as valeronitrile. , These may be used in combination may be used alone.

  In addition, when the polystyrene resin particles are produced by the production method of (1) and (2), the reaction liquid may be used as the particle dispersion liquid, or the polystyrene resin particles are once removed from the dispersion liquid. It may be separated and the polystyrene resin particles may be dispersed in a new aqueous medium to prepare a particle dispersion.

  Then, after supplying a fatty acid having 11 or less carbon atoms as a plasticizer to the particle dispersion, the particle dispersion is heated, and a foaming agent is pressed into the particle dispersion to have 11 or less carbon atoms in the polystyrene resin particles. It is possible to obtain expandable polystyrene resin particles by impregnating with a fatty acid and a foaming agent. In addition, after impregnating a polystyrene-type resin particle with a foaming agent, you may make it impregnate a polystyrene-type resin particle under a heating and pressurization with a C11 or less fatty acid.

  Further, in the above description, when the polystyrene resin particles are impregnated with a foaming agent and a fatty acid having 11 or less carbon atoms, or after the polystyrene resin particles are impregnated with a foaming agent, the fatty acid having 11 or less carbon atoms is converted into polystyrene. Although the case where the resin resin particles were impregnated was explained, a fatty acid having 11 or less carbon atoms was contained in the styrene monomer, and simultaneously with the production of the polystyrene resin particles, the number of carbon atoms in the resulting polystyrene resin particles May contain 11 or less fatty acids.

  Next, the point which manufactures a polystyrene-type resin particle foaming molded article by in-mold foaming using the expandable polystyrene-type resin particle of this invention is demonstrated. First, pre-expanded particles are produced by pre-expanding expandable polystyrene resin particles with a general-purpose pre-expander.

  Next, after filling the obtained pre-expanded particles in a mold of a foam molding machine, a heating medium such as steam is supplied into the mold to heat and expand the pre-expanded particles, and the pre-expanded particles expand. The foamed particles thus obtained can be thermally fused and integrated with each other by these foaming pressures to obtain a foam molded product.

  The expandable polystyrene resin particles of the present invention are expandable polystyrene resin particles obtained by impregnating polystyrene resin particles with a foaming agent, and have 11 carbon atoms as a plasticizer with respect to 100 parts by weight of the polystyrene resin particles. Since it contains 0.3 to 2.0 parts by weight of the following fatty acids, it is excellent in the plasticizing effect of the polystyrene resin by the above fatty acids, and the pre-expanded particles are expanded at the time of in-mold foam molding. In addition to being excellent in the fusing property between the expanded particles obtained, the pre-expanded particles are hardly bonded (blocked) even during the pre-expansion.

  Therefore, according to the expandable polystyrene resin particles of the present invention, it is possible to smoothly perform a series of steps from pre-foaming to in-mold foam molding, which is excellent in terms of environment and safety, and excellent in mechanical strength and appearance. Polystyrene resin particle foamed molded articles can be easily molded. And since the obtained polystyrene-type resin particle foam-molded article is excellent in safety | security, it can be used suitably especially for a food use or a building material use.

  And since the expandable polystyrene resin particle of the present invention contains the above-mentioned predetermined fatty acid and has an excellent plasticizing effect, the content of the styrene monomer is set to the total weight of the expandable polystyrene resin particle. And can be suppressed to 3000 ppm or less.

  Therefore, the polystyrene-based resin particle foam-molded product obtained by using the expandable polystyrene-based resin particles of the present invention has a reduced volatile component, and is particularly preferably used for food applications and building material applications that require safety. Can do.

(Example 1)
In an autoclave equipped with a stirrer, 40000 parts by weight of styrene monomer, 120 parts by weight of tricalcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 4 parts by weight of sodium dodecylbenzenesulfonate, 140 parts by weight of benzoyl peroxide (purity 75%), t -After supplying 30 parts by weight of butyl peroxy-2-ethylhexyl monocarbonate and 40000 parts by weight of ion-exchanged water, the stirring blade of the stirrer of the autoclave was rotated at a stirring speed of 80 rpm to stir the inside of the autoclave to obtain a suspension. Produced.

  Next, while rotating the stirring blade of the stirrer of the autoclave at 80 rpm, the temperature inside the autoclave was raised to 90 ° C. and held at 90 ° C. for 6 hours, and then the temperature inside the autoclave was raised to 120 ° C. The autoclave is cooled to 25 ° C. for 2 hours, and the suspension is taken out of the autoclave, dehydrated and washed repeatedly, and after a drying step and a classification step, a particle size of 0.7-1 Polystyrene particles having a diameter of 0.2 mm and an average particle diameter of 0.9 mm were obtained.

  Next, after supplying 100 parts by weight of water into an autoclave equipped with a stirrer, the stirring blades of the stirrer are rotated at a rotational speed of 120 rpm, and the inside of the autoclave is stirred to produce as a dispersant by a metathesis method. After supplying 0.6 parts by weight of magnesium pyrophosphate and 0.015 parts by weight of sodium dodecylbenzenesulfonate to prepare an aqueous medium, 100 parts by weight of the polystyrene particles were supplied into the aqueous medium.

  Thereafter, 1.0 part by weight of caprylic acid (trade name “Lunac 8-98” manufactured by Kao Corporation) was supplied as a plasticizer into the autoclave. Further, the temperature inside the autoclave was raised to 100 ° C. while rotating the stirring blade of the stirrer of the autoclave at a rotation speed of 120 rpm, and then butane (isobutane: 30% by weight, normal butane: 70% by weight) in the autoclave. ) 8 parts by weight were pressurized with nitrogen and pressed in over 30 minutes, held in that state for 2 hours, then the temperature in the autoclave was cooled to 25 ° C, the contents were taken out from the autoclave, dehydrated, dried and foamed Polystyrene particles were obtained. All caprylic acid was absorbed in the polystyrene particles. Thereafter, expandable polystyrene particles having a particle diameter of 0.7 to 1.2 mm and an average particle diameter of 0.9 mm were obtained through a classification step.

  Next, a surface treatment agent comprising 100 parts by weight of the obtained expandable polystyrene particles, 0.05 part by weight of polyethylene glycol and 0.15 part by weight of zinc stearate is supplied to a Laedige mixer and stirred for 10 minutes. Then, the entire surface of the expandable polystyrene particles was uniformly coated with the surface treatment agent. In addition, all the surface treating agents supplied in the Raedige mixer were adhered to the surface of the expandable polystyrene particles.

  The expandable polystyrene particles are allowed to stand for 24 hours in a 15 ° C. cool box, and then supplied to a cylindrical batch type pressure pre-foaming machine and heated by steam to be pre-foamed at a bulk magnification of 60 times. Pre-expanded particles were obtained.

  Subsequently, the pre-expanded particles obtained were allowed to stand for 24 hours in a room temperature atmosphere, and then the pre-expanded particles were filled into a mold having a rectangular parallelepiped shape of 1840 mm long × 930 mm wide × 530 mm high. After that, the inside of the mold cavity was heated with water vapor at a gauge pressure of 0.07 MPa for 20 seconds, and then cooled until the pressure in the mold cavity became −0.01 MPa. From the inside of the mold, a polystyrene foam molded product having a rectangular parallelepiped shape of 1840 mm in length, 930 mm in width, and 530 mm in thickness was obtained.

(Example 2)
In an autoclave equipped with a stirrer, 40000 parts by weight of styrene monomer, 120 parts by weight of tricalcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 4 parts by weight of sodium dodecylbenzenesulfonate, 140 parts by weight of benzoyl peroxide (purity 75%), t -After supplying 100 parts by weight of butyl peroxybenzoate, 1.0 part by weight of caprylic acid and 40000 parts by weight of ion-exchanged water as a plasticizer, the stirring blade of the stirrer of the autoclave is rotated at a stirring speed of 80 rpm, and the inside of the autoclave is stirred. In the same manner as in Example 1 except that no suspension was prepared and no caprylic acid was added to the autoclave when the polystyrene particles were impregnated with the foaming agent. Got.

Example 3
In an autoclave equipped with a stirrer, 40000 parts by weight of styrene monomer, 120 parts by weight of tricalcium phosphate (manufactured by Taihei Chemical Co., Ltd.), 4 parts by weight of sodium dodecylbenzenesulfonate, 140 parts by weight of benzoyl peroxide (purity 75% by weight), After supplying 30 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and 40000 parts by weight of ion-exchanged water, the stirring blade of the stirrer of the autoclave is rotated at a stirring speed of 80 rpm to stir the inside of the autoclave. It was created.

  Next, while rotating the stirring blade of the stirrer of the autoclave at 80 rpm, the temperature inside the autoclave was raised to 90 ° C. and held at 90 ° C. for 6 hours, and then the temperature inside the autoclave was raised to 120 ° C. The autoclave is cooled to 25 ° C. for 2 hours, and the suspension is taken out of the autoclave, dehydrated and washed repeatedly. After the drying step and the classification step, the particle size is 0.4 to 0. .7 mm polystyrene particles were obtained.

  Next, 300 parts by weight of the polystyrene particles, 700 parts by weight of ion-exchanged water, 0.1 part by weight of sodium dodecylbenzenesulfonate, and 3 parts by weight of magnesium pyrophosphate were supplied to the autoclave with an agitator.

  Also, a dispersion is prepared by dispersing 0.08 parts by weight of sodium dodecylbenzenesulfonate and 0.8 parts by weight of magnesium pyrophosphate in 300 parts by weight of ion-exchanged water, while benzoyl peroxide is added to 200 parts by weight of styrene monomer. A styrene monomer mixture is prepared by dissolving 3.5 parts by weight and 0.2 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate, and the styrene monomer mixture is added to the above dispersion and a homomixer is used. To obtain an emulsion.

  Thereafter, the inside of the autoclave was heated and maintained at 75 ° C., and then the emulsion was supplied. After holding for 20 minutes, the autoclave was heated from 75 ° C. to 108 ° C. at a rate of 0.2 ° C./min, and 10 parts by weight of caprylic acid (trade name “Lunac 8-98” manufactured by Kao Co., Ltd.) 510 parts by weight of the solution dissolved in parts by weight are continuously dropped into the autoclave over 160 minutes, and after 20 minutes from the end of dropping, the temperature inside the autoclave is raised to 120 ° C. and held for 90 minutes. Then, polystyrene particles were obtained by seed polymerization. All styrene monomers were used for polymerization.

  Thereafter, while rotating the stirring blade of the autoclave stirrer at a rotation speed of 120 rpm, the inside of the autoclave is kept at 100 ° C., and butane as a blowing agent in the autoclave (isobutane: 30 wt%, normal butane: 70 wt%) 80 parts by weight were pressurized with nitrogen for 30 minutes and held in that state for 2 hours, then the temperature in the autoclave was cooled to 25 ° C., the contents were taken out from the autoclave, dehydrated and dried, and foamed. Polystyrene particles were obtained. All caprylic acid was absorbed in the polystyrene particles. Thereafter, expandable polystyrene particles having a particle diameter of 0.7 to 1.2 mm and an average particle diameter of 0.9 mm were obtained through a classification step.

  Next, a surface treatment agent comprising 100 parts by weight of the obtained expandable polystyrene particles, 0.05 part by weight of polyethylene glycol and 0.15 part by weight of zinc stearate is supplied to a Laedige mixer and stirred for 10 minutes. Then, the entire surface of the expandable polystyrene particles was uniformly coated with the surface treatment agent. In addition, all the surface treating agents supplied in the Raedige mixer were adhered to the surface of the expandable polystyrene particles. Thereafter, pre-expanded particles and polystyrene foam-molded articles were obtained in the same manner as in Example 1.

(Example 4)
Expandable polystyrene particles and a polystyrene foam-molded article were obtained in the same manner as in Example 1 except that 100 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate was added instead of 30 parts by weight.

(Example 5)
Expandable polystyrene particles and a polystyrene foam-molded article were obtained in the same manner as in Example 1 except that caprylic acid was changed to 0.5 parts by weight instead of 1.0 part by weight.

(Example 6)
Expandable polystyrene particles and a polystyrene foam molded article were obtained in the same manner as in Example 1 except that caprylic acid was changed to 1.8 parts by weight instead of 1.0 part by weight.

(Example 7)
Expandable polystyrene particles and a polystyrene foam molded article were obtained in the same manner as in Example 1 except that capric acid (trade name “Lunac 10-98” manufactured by Kao Corporation) was used as a plasticizer instead of caprylic acid.

(Example 8)
Implemented except that caprylic acid was changed to 0.8 parts by weight instead of 1.0 parts by weight, and 0.5 parts by weight of cyclohexane (trade name “cyclohexane” manufactured by JOMO) was supplied as plasticizer together with caprylic acid in the autoclave. In the same manner as in Example 1, expandable polystyrene particles and a polystyrene foam molded article were obtained.

Example 9
Instead of 1.0 part by weight, 0.8 parts by weight of caprylic acid was used, and together with caprylic acid in the autoclave, 0.5 parts by weight of cyclohexane (trade name “cyclohexane” manufactured by JOMO) as a plasticizer and 0.3 parts of diisobutyl adipate Expandable polystyrene particles and a polystyrene foam-molded product were obtained in the same manner as in Example 1 except that parts by weight were supplied.

(Example 10)
Instead of 1.0 parts by weight, 0.8 parts by weight of caprylic acid is supplied, and 0.5 parts by weight of palm oil (trade name “Lunac L-50” manufactured by Kao Corporation) as a plasticizer is supplied with caprylic acid in the autoclave Except that, expandable polystyrene particles and a polystyrene foam molded article were obtained in the same manner as in Example 1.

(Example 11)
The caprylic acid was changed to 0.8 parts by weight instead of 1.0 part by weight, and 0.5 parts by weight of diisobutyl adipate (trade name “Lunac L-50” manufactured by Kao Corporation) as a plasticizer was supplied into the autoclave together with caprylic acid. Except that, expandable polystyrene particles and a polystyrene foam-molded article were obtained in the same manner as in Example 1.

(Comparative Example 1)
Expandable polystyrene particles and polystyrene foam-molded articles were obtained in the same manner as in Example 1 except that toluene (trade name “Toluene” manufactured by Mobil Inc.) was used instead of caprylic acid as a plasticizer.

(Comparative Example 2)
Expandable polystyrene particles and polystyrene foam molded articles were obtained in the same manner as in Example 1 except that cyclohexane was used in place of caprylic acid as a plasticizer.

(Comparative Example 3)
Expandable polystyrene particles and a polystyrene foam molded article were obtained in the same manner as in Example 1 except that palm oil was used instead of caprylic acid as a plasticizer.

(Comparative Example 4)
Expandable polystyrene particles and polystyrene foam-molded articles were obtained in the same manner as in Example 1 except that 0.8 parts by weight of coconut oil and 0.5 parts by weight of toluene were used instead of caprylic acid as a plasticizer. .

(Comparative Example 5)
Expandable polystyrene particles were obtained in the same manner as in Example 1 except that caprylic acid was changed to 2.5 parts by weight instead of 1.0 part by weight. An attempt was made to form a polystyrene resin foam-molded product using the expandable polystyrene particles in the same manner as in Example 1, but shrinkage occurred during the pre-expansion of the expandable polystyrene particles.

(Comparative Example 6)
Expandable polystyrene particles and a polystyrene-based resin foam molded article were obtained in the same manner as in Example 1 except that caprylic acid was changed to 0.1 parts by weight instead of 1.0 part by weight.

  The amount of residual styrene monomer in the obtained expandable polystyrene resin particles was measured in the above manner, and the foamability, blocking property and fusion property were measured in the following manner, and the results are shown in Table 1. In Comparative Example 5, since the shrinkage occurred during the preliminary foaming of the expandable styrene particles, the evaluation of foamability, blocking property, and fusing property was not performed.

(Foaming)
Expandable styrene particles were supplied to a foaming furnace and heated with steam of 690 kPa (0.7 kgf / cm ² ) for 3 minutes to foam to obtain expanded particles. 10 g of the obtained foamed particles were placed in a graduated cylinder, the volume was measured, and the volume was divided by the weight (10 g) to calculate the apparent foaming ratio (cm ³ / g).

(Blocking property)
The expanded styrene particles W ₁ g were pre-expanded 60 times in apparent volume. The blocking particles in which the pre-foamed particles were bonded together were separated using a sieve having an opening of 10 mm, and the weight W ₂ g of the blocking particles was measured. And blocking property was computed based on the following formula.
Blocking property (%) = 100 × W ₂ / W ₁

(Fusability)
The polystyrene foam molded product was divided into two by hand along the score line, and this divided cross section was visually observed. Then, in the divided cross section of the test sheet, the number of all the expanded particles (a) and the number of expanded particles (b) in which the expanded particles themselves were broken without breaking at the thermal fusion interface with each other were counted. The fusion rate was calculated based on the following formula.
Fusion rate (%) = 100 × b / a

Claims (5)

Expandable polystyrene resin particles obtained by impregnating polystyrene resin particles with a foaming agent, and 0.3 to 2.0 fatty acids having 11 or less carbon atoms as plasticizers with respect to 100 parts by weight of polystyrene resin particles. Expandable polystyrene resin particles characterized by containing parts by weight. The expandable polystyrene resin particles according to claim 1, wherein the plasticizer is a fatty acid having 8 to 10 carbon atoms. 3. The expandable polystyrene resin particle according to claim 1 or 2, wherein the fatty acid is caprylic acid. The expandable polystyrene resin particles according to any one of claims 1 to 3, wherein the amount of the styrene monomer is 3000 ppm or less with respect to the total weight of the expandable polystyrene resin particles. A polystyrene-based resin foam molded article obtained by in-mold foam molding of pre-expanded particles obtained by pre-expanding the expandable polystyrene resin particles according to any one of claims 1 to 4.