JP2016164213A - Foamable resin particle and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam molded body excellent in fire resistance, heat resistance and thermal insulation property and small in the content of a volatile organic compound by using a styrenic monomer containing a phenylacetylene amount of 50 ppm or more.SOLUTION: There is provided a foamable resin particle containing a foaming agent in a copolymer containing 60 wt.% or more and 75 wt.% or less of a styrene monomer containing a phenylacetylene amount of 50 ppm or more, 21 wt.% or more and 27 wt.% or less of an acrylonitrile monomer and 3 wt.% or more and 15 wt.% or less of an alpha methylstyrene monomer and a fire retardant of 1.5 pts.wt. or more and 3.0 pts.wt. or less based on 100 pts.wt. of the foamable resin particle and having weight average molecular weight in terms of polystyrene of 150,000 or more and 250,000 or less.SELECTED DRAWING: None

Description

  The present invention uses a styrene monomer containing 50 ppm or more of phenylacetylene, is excellent in flame retardancy and heat resistance, and has a low content of volatile organic compounds, production method, pre-foaming The present invention relates to particles and a foamed molded product.

  Expandable polystyrene resin particles are well known as expandable resin particles. Expandable polystyrene resin particles are generally widely used because they can be easily obtained by in-mold foam molding and are inexpensive. Expandable polystyrene resin particles are excellent in light weight and heat insulation performance, but due to the low heat resistance of polystyrene, comparison of heat insulation materials for piping, heat insulation materials for roofs, automotive materials, solar system heat insulation materials, water heater insulation materials, etc. There was a problem with dimensional stability during long-term use under high temperatures.

  In order to solve the above problems, Patent Documents 1 and 2 describe heat-resistant styrene resin particles obtained by copolymerizing alphamethylstyrene and styrene. Although these heat-resistant styrene resin particles are excellent in heat resistance and flame retardancy, copolymerization of alphamethylstyrene and styrene makes it difficult to reduce residual styrenic monomers due to polymerization problems, and it is necessary to carry out reactions at high temperatures. was there.

  Patent Documents 3, 4, and 5 introduce styrene / acrylonitrile / alpha-methylstyrene heat-resistant styrene resin particles. In this invention, the flame retardancy and heat resistance are excellent, and the residual styrene monomer is reduced, but a large amount of flame retardant is used to obtain flame retardancy. Was not enough.

  On the other hand, phenylacetylene produced as a by-product in the production process of styrene acts as a polymerization inhibitor in the polymerization of styrene, and if there is a large amount of phenylacetylene, the amount of residual styrene in the final product increases. In a member that requires a light volatile organic substance, in order to reduce the amount of residual styrene, styrene having a low concentration of phenylacetylene is used as a raw material. Although there is no description about expandable resin particles using styrene containing a phenylacetylene amount of 50 ppm or more, various methods for reducing the residual styrene amount are disclosed.

  For example, Patent Document 6 and Patent Document 7 describe expandable styrene resin particles that change the plasticizer to a non-volatile one and reduce the amount of residual styrene contained in the expandable styrene resin particles. The purpose is achieved by increasing the polymerization temperature or extending the polymerization time. However, in a polymerization system using a hydrocarbon-based blowing agent or a polymerization system using a halogen-based flame retardant for imparting flame retardancy, for example, the primary radical of the initiator is a hydrocarbon-based blowing agent or a halogen-based flame retardant. In contrast, since the hydrogen abstraction reaction is performed, the amount of residual styrene is difficult to decrease even when polymerization is performed at a high temperature for a long time, which is a general method.

  Patent Document 8 describes a method for reducing the amount of residual styrene to 300 ppm or less. However, after adding butane as a foaming agent, the reaction is carried out at 120 ° C. for 6 hours. doing.

  Patent Document 9 uses a low-temperature polymerization initiator having a 10-hour half-life temperature of 50 ° C. to 80 ° C. and n-butyl-4,4-bis (t-butylperoxy) valerate to prevent water leakage. A method for producing excellent expandable styrenic resin particles is disclosed. However, there is no description regarding the amount of residual styrene, and particularly in a system containing a flame retardant, there is a problem that the amount of residual styrene is not sufficiently lowered by the method disclosed in the patent literature.

  Patent Document 10 discloses a method for producing styrene resin particles by bulk polymerization using styrene having a phenylacetylene content of 200 ppm or less, but expandable styrene resin particles produced by aqueous suspension polymerization. The field of use is different.

JP 2012-77149 A Patent No. 5080226 JP 2007-246666 A JP 2003-335891 A JP 2001-181433 A JP 2002-356575 A Japanese Patent Laid-Open No. 10-17698 JP-A-11-106548 Japanese Patent No. 3597109 JP-A-5-222125

  The object of the present invention is to use a styrene monomer having a phenylacetylene content of 50 ppm or more, and to provide a foamed molded article having excellent flame retardancy, heat resistance and heat insulation properties, and having a low content of volatile organic compounds. Is to provide.

  As a result of intensive studies, the present inventors have completed the present invention. That is, the present invention is as follows.

  (1) Styrene monomer having a phenylacetylene content of 50 ppm or more 60 wt% or more and 75 wt% or less, acrylonitrile monomer 21 wt% or more and 27 wt% or less, alphamethylstyrene monomer 3 wt% or more 15 A foaming resin particle comprising a foaming agent in a copolymer consisting of not more than wt%, wherein the flame retardant is 1.5 parts by weight or more and 3.0 parts by weight or less with respect to 100 parts by weight of the foaming resin particles. A foamable resin particle containing and having a polystyrene-equivalent weight average molecular weight of 150,000 to 250,000.

  (2) The expandable resin particle according to (1), wherein the flame retardant is a bromine-containing organic compound having a 2,3-dibromo-2-alkylpropyl group.

  (3) The bromine-containing organic compound having a 2,3-dibromo-2-alkylpropyl group is tetrabromobisphenol-A-bis (2,3-dibromo-2-methylpropyl) ether ( Expandable resin particles according to 1) or (2).

  (4) The expandable resin particles according to any one of (1) to (3), wherein the content of residual styrene monomer is 300 ppm or less.

  (5) An alkyl perester-based bifunctional polymerization initiator is used in an amount of 0.1 part by weight or more and 0.5 part by weight or less, and 85 ° C. in the presence of a chain transfer agent of 0.5 part by weight or more and 1.0 part by weight or less. When the monomer is polymerized at 94 ° C. or lower and the conversion rate of the monomer reaches 90% or higher and 99% or lower, a foaming agent is introduced, and then the temperature of the polymerization system is 106 ° C. or higher and 120 ° C. or lower. The method for producing expandable resin particles according to any one of (1) to (4), wherein the foaming agent is impregnated.

  (6) The expandable resin according to (5), wherein the alkyl perester-based bifunctional polymerization initiator is di-t-butylperoxyhexahydroterephthalate and the chain transfer agent is α-methylstyrene dimer. Particle production method.

  (7) Pre-expanded particles obtained by pre-expanding the expandable resin particles according to any one of (1) to (6).

  (8) A foam-molded product obtained by molding the pre-expanded particles according to (7) in a mold.

  In the present invention, using a styrene monomer having an amount of phenylacetylene of 50 ppm or more, using a specific flame retardant, and an expandable styrene-based resin particle produced by a production method, the flame retardant has excellent flame retardancy even with a small amount of flame retardant. It is possible to provide a foamed molded article having excellent heat resistance and heat insulation heat retention and low content of volatile organic compounds.

  Hereinafter, embodiments of the present invention will be described in more detail.

  The expandable resin particles of the present invention are composed of a styrene monomer having a phenylacetylene content of 50 ppm or more, 60 wt% or more and 75 wt% or less, an acrylonitrile monomer 21 wt% or more and 27 wt% or less, and an alpha methyl styrene monomer. Monomers selected from 3% by weight or more and 15% by weight or less of the body are copolymerized so that the total amount becomes 100% by weight, and the foaming resin particles include a foaming agent, and 100 parts by weight of the foamable resin particles In contrast, it is characterized by containing 1.5 to 3.0 parts by weight of a brominated flame retardant and having a polystyrene-equivalent weight average molecular weight of 150,000 to 250,000.

  The styrene monomer used in the present invention is preferably 65% by weight to 75% by weight, and more preferably 70% by weight to 73% by weight. When the styrene monomer component is large, heat resistance cannot be obtained, and when it is small, the moldability tends to be inferior.

  In addition, when a styrene monomer having a phenylacetylene content of less than 50 ppm is used, the residual styrene content in the foamable resin particles of the final product is reduced, but the process of removing phenylacetylene in the process of producing the styrene monomer This increases the cost of the styrene monomer itself. The amount of phenylacetylene of a styrene monomer called general-purpose styrene is 50 to 400 ppm, and the styrene monomer used in the present invention contains 50 ppm or more of phenylacetylene.

  The acrylonitrile monomer is preferably 23% by weight or more and 25% by weight or less. When there are many acrylonitrile monomers, a moldability will deteriorate, and when too large, polymerization stability will deteriorate. If the amount of acrylonitrile is small, the heat resistance deteriorates and the residual styrene monomer tends to be difficult to reduce.

  The alpha methyl styrene monomer is preferably 4% by weight or more and 10% by weight or less, and more preferably 4 parts by weight or more and 7 parts by weight or less. When the amount of alphamethylstyrene monomer is small, heat resistance cannot be obtained, and when it is large, flame retardancy deteriorates and residual styrene monomer tends to remain.

  In order to obtain flame retardancy, the expandable resin particles of the present invention are not particularly limited as a flame retardant, but are preferably bromine-containing organic compounds having a 2,3-dibromo-2-alkylpropyl group. . As a flame retardant, a bromine-based organic compound is contained in an amount of 1.5 to 3.0 parts by weight, preferably 1.8 to 2.5 parts by weight. When there are few brominated flame retardants, sufficient flame retardancy cannot be obtained, and when there are many brominated flame retardants, a residual monomer will remain easily and a moldability will also deteriorate.

  Examples of bromine-containing organic compounds having a 2,3-dibromo-2-alkylpropyl group include tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl) ether, tetrabromobisphenol S-bis (2, 3-dibromo-2-methylpropyl) ether, tetrabromobisphenol F-bis (2,3-dibromo-2-methylpropyl) ether, etc., among which tetrabromobisphenol A-bis (2,3-dibromo- 2-methylpropyl) ether is preferable because it effectively exhibits flame retardancy.

  As the flame retardant, a flame retardant aid may be used in combination. As the flame retardant aid, a radical generator such as peroxide is used, and dicumyl peroxide, t-butyl peroxybenzoate, 2,3-dimethyl- 2,3-diphenylbutane, 3,4-dialkyl-3,4-diphenylhexane, and the like. Among them, in order to obtain a good flame retardancy with little influence on polymerization, a one-hour half-life temperature Is preferably a peroxide of 130 ° C. or higher and 150 ° C. or lower, and particularly preferably dicumyl peroxide. The flame retardant aid is preferably used in an amount of 0.3 to 1.5 parts by weight based on 100 parts by weight of the expandable resin particles. When the amount of the flame retardant aid is small, the flame retardancy is deteriorated, and when the amount is large, the heat resistance tends to be deteriorated.

  The polymerization initiator used in the present invention is generally a polymerization initiator mainly for forming a resin (polymerization step) and a polymerization initiator for reducing the amount of residual styrene (foaming agent impregnation step). It is usually performed to use together. The selection of these initiators is appropriately determined in consideration of the polymerization temperature, the polymerization time, and the required molecular weight of the resin.

  As a polymerization initiator mainly for forming a resin (polymerization step), a radical-generating polymerization initiator generally used for the production of thermoplastic polymers can be used. Benzoyl oxide, lauroyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperpivalate, t-butylperoxyisopropyl carbonate, di-t-butylperoxyhexahydroterephthalate, 1,1- Organic peroxides such as di (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, di-t-butylperoxyhexahydroterephthalate, azo Examples include azo compounds such as bisisobutyronitrile and azobisdimethylvaleronitrile.These polymerization initiators may be used alone or in combination of two or more. In particular, in the monomer composition of the present invention, using an initiator having a 10-hour half-life temperature of 85 ° C. or higher and 94 ° C. or lower, and performing the first stage polymerization at 85 ° C. or higher and 95 ° C. or lower controls the polymerization reaction. Among them, an alkyl perester-based bifunctional polymerization initiator is preferable because it is easy to adjust the polymerization rate and the molecular weight. In particular, it is preferable to use di-t-butylperoxyhexahydroterephthalate (10-hour half-life temperature 83 ° C.). The amount of the polymerization initiator used in the first stage polymerization is preferably 0.1 part by weight or more and 0.5 part by weight or less, and more preferably 0.2 part by weight or less 0.4 part by weight. If the amount of the polymerization initiator is small, the polymerization may not proceed sufficiently. If it is too large, the polymerization reaction may proceed rapidly and it may be difficult to control the polymerization.

  The polymerization initiator for reducing the amount of residual styrene (foaming agent impregnation step) is preferably one having a 10-hour half-life temperature of 90 ° C. or more and 100 ° C. or less, and 1,1-bis (t-amyl par Oxy) -3,3,5-trimethylcyclohexane (10-hour half-life temperature 92 ° C.), 1,1-bis (t-butylperoxy) cyclohexane (10-hour half-life temperature 97 ° C.), t-butyl peroxy- 2-ethylhexyl monocarbonate (10-hour half-life temperature 99 ° C), t-amylperoxy-2-ethylhexyl monocarbonate (10-hour half-life temperature 98.5 ° C), and the like.

  These initiators are preferably 0.1 parts by weight or more and 0.5 parts by weight or less, more preferably 0.15 parts by weight or more and 0.3 parts by weight or less. When the amount of the polymerization initiator is small, the residual styrene monomer tends to remain, and when it is large, it is difficult to adjust the molecular weight.

  Examples of the chain transfer agent used in the present invention include α-methyl which is generally used for polymerization of mercaptan chain transfer agents such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and acrylonitrile-styrene resins. Styrene dimer or the like can be used as a polymerization regulator. The amount used is preferably 0.5 parts by weight or more and 1.0 parts by weight or less, and the polymerization rate and molecular weight can be easily adjusted. Among them, the use of α-methylstyrene dimer is preferable because the odor of the foam does not occur.

  The molecular weight of the expandable resin particles of the present invention can be adjusted by combining the polymerization initiator and chain transfer agent with polymerization conditions. The weight average molecular weight is 150,000 to 250,000, preferably 170,000 to 220,000. If the weight average molecular weight is 150,000 or less, the strength and flame retardancy of the obtained foamed molded product tend to be low, and if it is 250,000 or more, the moldability tends to deteriorate.

  As the additive used in the invention, a plasticizer, a bubble regulator or the like can be used depending on the purpose. Examples of the plasticizer include high-boiling plasticizers having a boiling point of 200 ° C. or higher. Examples include vegetable oils such as palm kernel oil, aliphatic esters such as dioctyl adipate and dibutyl sebacate, and organic hydrocarbons such as liquid paraffin and cyclohexane, but they are not used because they tend to deteriorate the heat resistance. It is preferable.

  Examples of the air conditioner include aliphatic bisamides such as methylene bis stearic acid amide and ethylene bis stearic acid amide, polyethylene wax, and the like.

  The method for producing expandable resin particles of the present invention is carried out by a suspension polymerization method carried out in an aqueous suspension. (1) Polymerization step, (2) Foaming agent charging step, (3) Foaming agent impregnation step, ( 4) Manufactured through a cooling and drying process.

(1) Polymerization step A bifunctional polymerization initiator for forming a resin in a predetermined amount of an aqueous suspension medium, a polymerization initiator for reducing the amount of residual styrene, a styrene monomer, an acrylonitrile monomer, α-methylstyrene A monomer, a chain transfer agent, and other additives are added, and polymerization is performed at a predetermined temperature, preferably 85 ° C. or more and less than 94 ° C. for a certain period of time, and the polymerization conversion rate of the styrene monomer is 90% or more and 99% or less. When reached, the polymerization process is completed.

  Examples of the dispersant for aqueous suspension polymerization of expandable styrene resin particles include commonly used dispersants such as poorly water-soluble inorganic salts such as calcium phosphate, hydroxyapatite, and magnesium pyrophosphate. When these poorly water-soluble inorganic salts are used, the use of an anionic surfactant such as α-olefin sodium sulfonate or dodecylbenzene sodium sulfonate is effective because the dispersion stability increases. Further, the hardly soluble inorganic salt may be added one or more times during the polymerization in order to adjust the particle diameter of the resulting expandable styrene resin particles for extruded foam board.

(2) Foaming agent charging step Next, when the monomer conversion rate reaches 90% or more and 99% or less, a blowing agent is added at a temperature of the polymerization step, preferably 85 ° C or more and less than 94 ° C, and styrene. Impregnation into the system resin particles. When a foaming agent is added at a polymerization conversion rate of less than 90%, radicals present in the polymerization system are chain-transferred to the foaming agent, and the amount of residual styrene in the final product tends to increase, and the polymerization conversion rate is 99%. Exceeding the amount of residual styrene makes the reaction time longer.

  As the blowing agent used in the present invention, at least one selected from the group consisting of propane, isobutane, normal butane, isopentane, normal pentane, and neopentane is used. The amount used is preferably 2 to 10 parts by weight, more preferably 4 to 8 parts by weight, with respect to 100 parts by weight of the resin particles.

(3) Foaming agent impregnation step After adding the foaming agent, the temperature in the polymerization system is raised to 106 ° C or higher and 120 ° C or lower, and the foaming agent is impregnated into the resin particles for a certain period of time. When the foaming agent impregnation temperature is 106 ° C. or more and 120 ° C. or less, the impregnation of the foaming agent proceeds efficiently, and even when styrene having a phenylacetylene content of 50 ppm or more is used, the polymerization of styrene proceeds and the residual styrene of the final product The amount is reduced. However, when the temperature is lower than 105 ° C., radical generation of the polymerization initiator that reduces the amount of residual styrene is reduced, productivity is lowered, and at the same time, the degree of impregnation of the foaming agent into the resin particles is poor, and the cell structure of the foamed particles is poor. It becomes uniform, and the surface of the resulting foamed molded product is damaged in appearance such as burrs. On the other hand, when the temperature exceeds 120 ° C., the impregnation with the foaming agent is improved, but the internal pressure of the polymerization machine becomes high, and a polymerization machine specification having a pressure resistance of heavy equipment may be required.

(4) Cooling / Drying Step When the predetermined time for impregnating the foaming agent is completed, the polymerization temperature is cooled and dried to obtain expandable polystyrene resin particles for the extruded foam board of the present invention. The amount of residual styrenic monomer in the final product is 300 ppm or less, preferably 300 pm or less. The lower limit is practically less than 0 ppm, so it is 1 ppm or more if dare to display.

  The obtained expandable resin particles can be made into pre-expanded particles by a general pre-expand method. Specifically, it is placed in a container equipped with a stirrer and heated by a heat source such as water vapor to perform preliminary foaming up to a desired foaming ratio.

  Further, the pre-expanded particles can be molded by a general in-mold molding method to form a foam molded body. Specifically, it is filled in a mold that can be closed but cannot be sealed, and heat-sealed with water vapor to obtain a foamed molded article.

  The foamed molded product of the present invention is pre-foamed at a foaming ratio of 50 times and has an oxygen index of 28 or more in order to exhibit sufficient flame retardancy when used as a heat insulating material or automobile interior material when molded. preferable.

  When the foamed molded product of the present invention is used as a heat insulating material, it is preferable that the heat resistance is small when it is used at 90 ° C. or more. Specifically, the molded product is prefoamed and molded at a foaming ratio of 50 times. The dimensional change rate of the body at 90 ° C. for 24 hours is preferably 0.5% or less.

  Examples and Comparative Examples are given below, but the present invention is not limited thereby. In addition, about the molecular weight of resin in an Example and a comparative example, the amount of residual styrene in resin, the amount of phenyl acetylene in a styrene monomer, and evaluation of a flame retardance, it measured with the following method. “Parts” and “%” are based on weight unless otherwise specified.

(Method for measuring phenylacetylene in styrene)
A calibration curve for the amount of phenylacetylene derived from the ratio of the amount of phenylacetylene and the amount of cyclopentanol was prepared using styrene having an amount of phenylacetylene of 0 ppm.

  The internal standard cyclopentanol is dissolved in styrene, and gas chromatography GC-2014 manufactured by Shimadzu Corporation (capillary column: Rtx-1 manufactured by GL Sciences, column temperature condition: 50 → 70 ° C. (3 ° C./min) After heating and holding at 70 ° C. for 30 minutes, the temperature was raised from 70 to 170 ° C. (10 ° C./min), and the amount of phenylacetylene (ppm) in styrene was quantified using a carrier gas: helium.

(Measurement of polymerization conversion rate at the end of the polymerization process)
The suspension slurry at the end of the polymerization step was collected, the slurry was filtered, and the resin particles were air-dried. 0.25 g of the obtained resin particles were dissolved in 20 cc of methylene chloride (internal standard cyclopentanol), and gas chromatography (GC-14B manufactured by Shimadzu Corporation, column: 3 m, filler: PEG-20M 25%, column temperature: 110 degreeC, carrier gas: helium), the amount of residual monomers contained in the resin particles was quantified from the calibration curve, and the polymerization conversion was measured.

(Molecular weight measurement method)
0.02 g of expandable resin particles were dissolved in 20 cc of tetrahydrofuran, and GPC (HLC-8020 manufactured by Tosoh Corporation, column: TSKgel Super HZM-H, column temperature: 40 ° C., flow rate: 0.35 ml / 1 min.) It was measured. The weight average molecular weight was determined as a converted value of standard polystyrene.

(Measurement of residual styrene monomer)
0.25 g of expandable resin particles were dissolved in 20 cc of methylene chloride (internal standard cyclopentanol), and gas chromatography (GC-14B, manufactured by Shimadzu Corporation), column: 3 m, packing agent: PEG-20M 25%, column temperature: 110 ℃, carrier gas: helium), the amount of residual styrene monomer contained in the expandable resin particles was quantified from the calibration curve, and the total value passed 0.03% or less of the expandable resin particles. It was. Those below the lower limit of detection were denoted as ND.

(Production of pre-expanded particles)
The expandable resin particles were sieved to obtain expandable resin particles having a particle diameter of 0.5 to 1.4 mm.

  The fractionated expandable resin particles were prefoamed to a bulk magnification of 50 times under the condition of a blowing vapor pressure of 0.09 to 0.10 MPa using a pressure type prefoaming machine “Daikai Kogyo Co., Ltd., BHP”. This was left for 1 day to obtain pre-expanded particles having a bulk magnification of 50 times.

(Manufacture of foam moldings)
The obtained pre-expanded particles are blown into a mold using a molding machine “Daisen, KR-57” at a blown vapor pressure of 0.05 MPa, thereby forming a flat-plate foam having a thickness of 20 mm, a length of 400 mm and a width of 350 mm. A molded body was obtained.

(Surface properties of molded products)
The state of the surface of the foamed molded product was evaluated by visual observation. The larger the numerical value, the more beautiful the surface state with few gaps between particles, and 3 or more expressed with a perfect score of 5 was regarded as acceptable.
5: Gaps are not found 4: There are some gaps, but I don't really know 3: There are some gaps, but it is acceptable as a whole 2: Gaps are conspicuous 1: There are many gaps

(Oxygen index)
A foamed molded product having a molded product magnification of 50 was dried at 60 ° C. for 12 hours. Then, the sample piece cut out to 10x10x200mm was measured based on JISK7201 (flammability test method by an oxygen index), and 28 or more was set as the pass.

(Dimension shrinkage at 90 ° C)
A foamed molded product having a molded product magnification of 50 was dried at 60 ° C. for 24 hours. Thereafter, the molded body was cut out to a length of 150, a width of 150, and a thickness of 20 (t) mm, and the initial dimension (A) was determined by measuring the length and width dimensions at three locations. Then, it was left to stand in a dryer at 90 ° C. for 168 hours, and after leaving it to stand, the same measurement was performed to determine the dimension (B). The dimensional shrinkage rate was calculated by the following formula, and 0.5% or less was accepted.
Dimensional shrinkage (%) = ((A)-(B)) / (A) × 100

(Examples 1-10, Comparative Examples 1-7)
In a 6 L autoclave with a stirrer, 110 parts by weight of water, 0.105 part by weight of tricalcium phosphate, 0.0075 part by weight of sodium α-olein sulfonate, and a polymerization initiator, a chain transfer agent in the amounts shown in Table 1, difficulty A flame retardant, a flame retardant aid, and a plasticizer were charged and deoxidized with a vacuum pump to a gauge pressure of -0.06 MPa. Thereafter, stirring with a stirrer was started, and styrene, alphamethylstyrene, and acrylonitrile in amounts shown in Table 1 were charged, and stirring was performed for 30 minutes. In addition, the styrene used the thing which measured the amount of phenyl acetylene in styrene, added the phenyl acetylene pure goods, and adjusted the quantity. Thereafter, the temperature was raised to 90 ° C. and held at 90 ° C. for 5 hours and 30 minutes to complete the first polymerization. The polymerization conversion at that time is shown in Table 1.

  Next, 4.6 parts by weight of normal rich butane (normal / iso = 70/30) was charged. Table 1 shows the impregnation temperature and impregnation time of the blowing agent. Thereafter, the foamed resin particles were taken out by cooling to 40 ° C., dehydration and drying. The molecular weight and residual styrene monomer were measured for the expandable resin particles. The results are shown in Table 1.

  The foamable resin particles obtained were prefoamed to obtain prefoamed particles having a bulk density of 50 times, and further molded in-mold to obtain a 50-fold foamed molded product.

  About the obtained foaming molding, surface property, an oxygen index, and 90 degreeC dimensional-change rate were evaluated. The results are shown in Table 1.

  Although the thing of Examples 1-10 which is the range of this invention passed the residual styrene-type monomer, the surface property of a molded object, an oxygen index, and 90 degreeC dimensional change rate, it is a thing of Comparative Examples 1-5 Is not acceptable because it deviates from the requirements of the present invention.

  In Comparative Example 6, the amount of phenylacetylene in styrene is ND, but the unit price of styrene is expensive.

Claims (8)

Styrene monomer having a phenylacetylene content of 50 ppm or more 60% to 75% by weight, acrylonitrile monomer 21% to 27% by weight, alphamethylstyrene monomer 3% to 15% by weight A foaming resin particle comprising a foaming agent in a copolymer comprising, containing 100 parts by weight of the foaming resin particle, 1.5 parts by weight or more and 3.0 parts by weight or less of a flame retardant, Expandable resin particles having a weight average molecular weight in terms of polystyrene of 150,000 to 250,000. 2. The expandable resin particle according to claim 1, wherein the flame retardant is a bromine-containing organic compound having a 2,3-dibromo-2-alkylpropyl group. 2. The bromine-containing organic compound having a 2,3-dibromo-2-alkylpropyl group is tetrabromobisphenol-A-bis (2,3-dibromo-2-methylpropyl) ether. 2. The expandable resin particle according to 2. The expandable resin particle according to any one of claims 1 to 3, wherein the content of the residual styrene monomer is 300 ppm or less. An alkyl perester-based bifunctional polymerization initiator is used in an amount of 0.1 to 0.5 parts by weight, and in the presence of 0.5 to 1.0 parts by weight of a chain transfer agent, 85 ° C to 94 ° C. The monomer is polymerized below, and when the conversion rate of the monomer reaches 90% or more and 99% or less, a foaming agent is introduced, and then the temperature of the polymerization system is 106 ° C or more and 120 ° C or less and foaming is performed. The method for producing expandable resin particles according to any one of claims 1 to 4, wherein the agent is impregnated. 6. The production of expandable resin particles according to claim 5, wherein the alkyl perester-based bifunctional polymerization initiator is di-t-butylperoxyhexahydroterephthalate, and the chain transfer agent is α-methylstyrene dimer. Method. Pre-expanded particles obtained by pre-expanding the expandable resin particles according to any one of claims 1 to 6. A foam-molded product obtained by molding the pre-expanded particles according to claim 7 in a mold.