JP2017071669A - Manufacturing method of expandable styrene resin particle to which flame retardancy is added - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method capable of obtaining an expandable polystyrene resin particle having flame retardant performance by suspension polymerization while reducing the used amount of a flame retardant.SOLUTION: There is provided a manufacturing method of an expandable polystyrene resin particle having a process of dispersing a flame retardant and a styrene monomer in an aqueous medium, the particle contains a brominated polymer as the flame retardant of 0.3 pt.wt. to 2.0 pts.wt. based on 100 pts.wt. of the styrene monomer, the flame retardant assistant of 0.2 pt.wt. to 1.1 pts.wt., has a ratio of the flame retardant to the flame retardant assistant of 0.4 to 3.0 and total amount of the flame retardant and the flame retardant assistant of 1.1 pts.wt. or more.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing expandable polystyrene resin particles having a step of dispersing a flame retardant and a styrene monomer in an aqueous medium.

  Polystyrene resin foam is widely used for construction and civil engineering applications, but it is often required to have flame retardant performance when used for housing-related materials, etc., and expandable polystyrene resin foam containing flame retardant etc. Is often used.

  The more the flame retardant is contained, the more the flame retardant performance is improved.However, when the flame retardant is present in the suspension polymerization system, the flame retardant inhibits the progress of the polymerization, and the residual amount of monomer in the foam increases. Concerns increase. In addition, the EPS production method by suspension polymerization is characterized by its low cost and easy adjustment of molecular weight, etc., but the current mainstream polymer-type flame retardant has a high molecular weight, so suspension stability There was also a problem that the sex deteriorated.

  Therefore, in recent years, there has been an increasing demand for methods for reducing the amount of flame retardant as much as possible. As a method for producing expandable styrene resin particles having flame retardancy, for example, in Patent Document 1, 100 parts of styrene, 1 part of brominated butadiene / styrene copolymer and 0.2 part of flame retardant aid are charged. A method for producing expandable polystyrene resin particles having a flame retardant performance with a residual styrene amount of 230 to 280 ppm, which includes a step of polymerizing in water, has been proposed. However, the amount of the flame retardant, the amount of the flame retardant aid, and the ratio of the flame retardant / flame retardant aid cannot be optimized, and there is a problem that a large amount of the flame retardant is required.

  Moreover, in patent document 2, the expandable polystyrene-type resin which has a process which emulsifies and polymerizes the seed particle | grains containing a brominated butadiene-styrene block copolymer, a flame retardant adjuvant, and styrene in water. A method for producing particles has been proposed. However, since there is no step of dispersing the flame retardant and the styrene monomer in the aqueous medium from the initial stage of polymerization, there are many steps until obtaining EPS resin particles, and productivity is poor. Moreover, in order to knead PS and a flame retardant using an extruder, a flame retardant decomposes and requires a flame retardant more than necessary. Further, the molecular weight of PS is reduced by passing through the extrusion process, and the molecular weight cannot be easily adjusted even in the subsequent polymerization operation. Therefore, the final molecular weight tends to be low and the strength tends to deteriorate.

  In Patent Document 3, expandable polystyrene having a step of polymerizing by stirring 100 parts of styrene, 0.62 part of hexabromocyclododecane (flame retardant) and 0.21 part of dicumyl peroxide (flame retardant aid) in water. A method for producing resin particles has been proposed. However, since the flame retardant used is hexabromocyclododecane, there is an environmental problem.

  Moreover, in patent document 4, with respect to 100 mass parts of resin components, 0.1-1.0 mass part of flame retardants and 0.1-0.5 mass part of flame retardant adjuvants are flame retardant: flame retardant adjuvant = The modified polystyrene-type expandable resin particle contained in the ratio of 1: 0.12-0.63 (mass ratio) is proposed. However, there is a problem in that productivity is poor because a flame retardant is not added from the beginning but a step of impregnating resin particles with a foaming agent after preparation is required.

JP2015-117282A JP, 2015-101702, A Japanese Patent Laid-Open No. 06-025456 JP 2014-189769 A

  The objective of this invention is providing the manufacturing method which can reduce the usage-amount of a flame retardant conventionally and can obtain the expandable polystyrene-type resin particle which has a flame retardance performance by suspension polymerization.

  As a result of intensive studies, the inventors of the present invention have focused on the fact that the flame retardant decomposes during combustion and promptly releases a halogen-based molecule or the like to the gas layer portion in order to exhibit flame retardancy. In order to accelerate the decomposition of flame retardants, peroxides have been conventionally included in resin particles as flame retardant aids. It wasn't. In this invention, it discovered that a flame retardant could be reduced rather than before by making a flame retardant / flame retardant adjuvant = 0.4 or more and 3.0 or less.

  In addition, brominated polymers are currently the mainstream as flame retardants, but suspension polymerization has been difficult due to the large molecular weight, but the amount of flame retardants has been revised by reviewing the ratio of flame retardants and flame retardant aids. As a result, the present invention has been completed.

  That is, the first of the present invention is a method for producing an expandable polystyrene resin particle having a step of dispersing a flame retardant and a styrene monomer in an aqueous medium, and is based on 100 parts by weight of the styrene monomer. The flame retardant contains a brominated polymer of 0.3 part by weight or more and 2.0 parts by weight or less, and a flame retardant aid contains 0.2 part by weight or more and 1.1 parts by weight or less of the flame retardant and the flame retardant. The ratio of the auxiliary agent is flame retardant / flame retardant auxiliary = 0.4 or more and 3.0 or less, and the total amount of the flame retardant and the flame retardant auxiliary is 1.1 parts by weight or more. A method for producing expandable polystyrene resin particles.

  A second aspect of the present invention is the method for producing expandable polystyrene resin particles according to the first aspect, wherein the brominated polymer is a brominated butadiene-styrene copolymer.

  The third of the present invention is the method for producing expandable polystyrene resin particles according to the first or second invention, wherein the amount of residual styrene monomer is 300 ppm or less.

  A fourth aspect of the present invention is the expandable polystyrene system according to any one of the first to third aspects, wherein the expandable polystyrene resin particles have a weight average molecular weight (Mw) of 250,000 to 400,000. A method for producing resin particles.

  5th of this invention is described in any one of 1st-4th invention characterized by including 0.05 to 0.6 weight part of compounds shown by General formula (1) as a polymerization initiator. Method for producing expandable polystyrene resin particles.

(In the formula, R ₁ represents an alkyl group, and R ₂ represents a branched or straight chain alkyl group.)
According to a sixth aspect of the present invention, the R ₁ structure of the general formula (1) as a polymerization initiator is a methyl group or an ethyl group, and the R ₂ structure is a 2-ethylhexyl group or an isopropyl group. 5. A process for producing expandable polystyrene resin particles according to any one of the inventions.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method which can reduce the usage-amount of a flame retardant conventionally and can obtain the expandable polystyrene-type resin particle which has a flame retardance performance by suspension polymerization can be provided.

  The present invention relates to a method for producing expandable polystyrene resin particles having a step of dispersing a flame retardant and a styrene monomer in an aqueous medium, and as a flame retardant with respect to 100 parts by weight of a styrene monomer. Containing 0.3 to 2.0 parts by weight of a brominated polymer, 0.2 to 1.1 parts by weight of a flame retardant aid, and the ratio of the flame retardant to the flame retardant aid is Flame retardant / flame retardant aid = 0.4 or more and 3.0 or less, and the total amount of the flame retardant and the flame retardant aid is 1.1 parts by weight or more. This is a method for producing resin particles.

  The flame retardant used in the present invention is a brominated polymer. Brominated styrene, brominated butadiene-vinyl aromatic copolymer, brominated novolak resin allyl ether, brominated poly (1,3-cycloalkadiene) and brominated poly (4-vinylphenol allyl ether).

  Of these, a brominated butadiene / vinyl aromatic copolymer is preferred because it is easy to obtain flame retardancy. Among brominated butadiene / vinyl aromatic copolymers, brominated butadiene / styrene copolymers are more preferable because high flame retardancy is easily obtained. The styrene-butadiene copolymer before bromination is diblock copolymer (for example, styrene / butadiene block copolymer), triblock copolymer (for example, styrene / butadiene / styrene block copolymer), tetrablock copolymer The polymer may be a polymer (for example, styrene / butadiene / styrene / butadiene block copolymer) or a multi-block copolymer (for example, styrene / butadiene / styrene / butadiene / styrene block copolymer). The styrene / butadiene copolymer may be prepared by any known method including random polymerization, but is preferably prepared by continuous anionic polymerization or a coupling reaction. Of these, brominated triblock copolymers such as brominated styrene / butadiene / styrene block copolymers are particularly preferred.

  Other flame retardants include low molecular weight compounds such as polyglycerin dibromopropyl ether, tetrabromobisphenol A, tetrabromobisphenol-A-bis (2,3-dibromo-2-methylpropyl ether) and the like. Even if a flame retardant is used, the effect of lowering the amount of residual styrene in the expandable polystyrene resin particles of the final product can be obtained, but the molecular weight is lowered due to a decrease in the polymerization efficiency of the styrene monomer.

  The addition amount of the flame retardant in the present invention is 0.3 parts by weight or more and 2.0 parts by weight or less, preferably 0.5 parts by weight or more and 1.0 parts by weight or less with respect to 100 parts by weight of the styrene monomer. It is. If the amount is less than 0.3 parts by weight, sufficient flame retardancy cannot be obtained. On the other hand, when the amount exceeds 2.0 parts by weight, the resulting foamable polystyrene resin particles may be deteriorated in molding processability and the surface property of the molded article, and the stability during styrene polymerization is impaired.

  Examples of the flame retardant aid used in the present invention include high temperature decomposition type organic substances such as cumene peroxide, dicumyl peroxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane. . In particular, dicumyl peroxide and 2,3-dimethyl-2,3-diphenylbutane are preferred because they are less decomposed during polymerization and have less influence on dispersion during suspension polymerization.

  The addition amount of the flame retardant aid in the present invention is 0.2 parts by weight or more and 1.1 parts by weight or less, preferably 0.4 parts by weight with respect to 100 parts by weight of the styrene monomer. More than 0.8 parts by weight. If the amount is less than 0.2 parts by weight, sufficient flame retardancy cannot be obtained. Moreover, when it exceeds 1.1 weight part, in order to plasticize an expandable polystyrene-type resin particle, it exists in the tendency for the moldability in high temperature and the surface property of a molded object to be impaired especially.

  The total amount of the flame retardant and the flame retardant aid in the present invention is 1.1 parts by weight or more. If it is less than 1.1 parts by weight, the flame retardancy tends to deteriorate.

  The ratio of the flame retardant to the flame retardant aid in the present invention is flame retardant / flame retardant aid = 0.4 to 3.0, more preferably 0.5 to 2.0. When the ratio of the flame retardant and the flame retardant auxiliary is 0.4 or less, the flame retardant is too small to obtain sufficient flame retardancy. On the other hand, if it exceeds 3.0, the amount of radicals generated by the flame retardant aid is smaller than that of the flame retardant, so that sufficient flame retardancy cannot be obtained as well. Or the surface properties of the molded body tend to deteriorate.

  The expandable polystyrene resin particles of the present invention are produced by a so-called suspension polymerization method having a step of dispersing a flame retardant and a styrene monomer in an aqueous medium from the initial stage of polymerization. The suspension polymerization method is more preferable than so-called seed polymerization in which styrene is added as seed particles obtained by kneading PS and a flame retardant in advance with an extruder in terms of productivity and molecular weight adjustment.

  Suspension polymerization is a manufacturing method as follows, for example. In a predetermined amount of aqueous suspension medium, in addition to the general polymerization initiator used for the polymerization of polystyrene, together with the compound represented by the general formula (1), a styrene monomer, brominated butadiene / vinyl aromatic copolymer Polymerization and other additives are added, and polymerization is performed at a predetermined temperature, preferably 90 ° C. or more and less than 100 ° C. for a certain period of time. When the conversion rate of the styrene monomer reaches 80% or more and 95% or less, Complete. After the polymerization step, a foaming agent is added, and the foaming agent impregnation step is performed at a predetermined temperature, preferably 110 ° C. or higher and 120 ° C. or lower for a predetermined time. After cooling, foamable styrene resin particles are obtained.

  When the temperature of the blowing agent impregnation step is 110 ° C. or more and 120 ° C. or less, in particular, since a compound having a 10-hour half-life temperature of the general formula (1) of 96 ° C. or more and 110 ° C. or less is used efficiently, Polymerization proceeds in a stable manner. However, when the temperature is less than 110 ° C., radical generation of the compound of the general formula (1) is reduced, and the productivity is lowered. Is required.

  When the polymerization conversion rate is less than 80%, after adding the foaming agent, the polymerization system becomes unstable in the foaming agent impregnation step of 110 ° C. or more and 120 or less, the cell structure of the foamed particles of the final product changes, and the foaming property When the polymerization conversion rate exceeds 95%, the polymerization time becomes longer and the productivity is lowered.

  The expandable polystyrene resin particles of the present invention obtained as described above have a residual styrene monomer amount of 300 ppm or less, preferably 250 pm or less. The lower limit is practically less than 0 ppm, so it is 1 ppm or more if dare to display.

  The weight average molecular weight Mw of the expandable styrene resin particles in the present invention is preferably 250,000 or more and 400,000 or less, more preferably 260,000 or more and 350,000 or less. When the weight average molecular weight Mw of the expandable styrene resin particles is less than 250,000, not only the strength when formed into a foamed molded product is lowered, but the surface of the molded product tends to melt and the appearance tends to be deteriorated. If it is too high, the foamability will be low and the moldability will be deteriorated (the heating temperature necessary to obtain pre-expanded particles with the desired expansion ratio and the molding temperature necessary to obtain a molded article with excellent fusion properties will be high. The surface properties of the molded body also deteriorate.

  The weight average molecular weight Mw can be controlled by a combination of the amount of the initiator used for polymerizing the styrene resin particles and the polymerization temperature. For example, Mw can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

  Here, the weight average molecular weight Mw of the expandable thermoplastic resin particles in the present invention is a value measured under the conditions described later using a gel permeation chromatograph (hereinafter sometimes abbreviated as “GPC”). It is a numerical value in terms of polystyrene.

  Examples of the styrene monomer used in the present invention include styrene and styrene derivatives such as α-methyl styrene, paramethyl styrene, t-butyl styrene, chlorostyrene, and components capable of copolymerization with styrene. For example, esters of acrylic acid and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, cetyl methacrylate, various monomers such as acrylonitrile, dimethyl fumarate, ethyl fumarate, divinylbenzene, alkylene glycol dimethacrylate Bifunctional monomers such as are also included. One or more of these copolymerizable components may be used for copolymerization.

  Phenylacetylene produced as a by-product in the process of producing styrene monomer acts as a polymerization inhibitor, and when the amount of phenylacetylene is 100 ppm or more, the amount of residual styrene in the foamable styrene resin particles of the final product increases. . On the other hand, if the amount of phenylacetylene is less than 100 ppm, the amount of residual styrene in the expandable polystyrene resin particles of the final product decreases, but a step for removing phenylacetylene is required, and the cost of the styrene monomer itself increases. The upper limit of the amount of phenylacetylene is 400 ppm with styrene called general purpose.

  Examples of the dispersant used in the present invention include dispersants generally used for suspension polymerization, 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.

The polymerization initiator used in the present invention is a compound represented by the general formula (1), R ₁ is an alkyl group, R ₂ has a branched or straight chain alkyl group structure, and specifically, T-butylperoxy-2-ethylhexyl monocarbonate, t-amylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, and the like.

(In the formula, R ₁ represents an alkyl group, and R ₂ represents a branched or straight chain alkyl group.)
In particular, among the compounds of the general formula (1), the R ₁ structure is a methyl group or an ethyl group, the R ₂ structure is an ethylhexyl group or an isopropyl group, and the 10-hour half-life temperature is 96 ° C. or higher and 110 ° C. or lower. A certain compound is preferable because it can reduce the amount of residual styrene in the expanded styrene resin particles as the final product. Examples thereof include t-butyl peroxy-2-ethylhexyl monocarbonate (10 hour half-life temperature 99 ° C.), t-amyl peroxy-2-ethylhexyl monocarbonate (98.5 ° C.), and the like.

  The amount of the compound represented by the general formula (1) varies depending on the molecular weight of the foamable styrene resin particles to be obtained, but is 0.05 parts by weight or more and 0.6 parts by weight with respect to 100 parts by weight of the styrene monomer. Or less, preferably 0.1 parts by weight or more and 0.5 parts by weight or less, more preferably 0.2 parts by weight or more and 0.4 parts by weight or less. When the amount of the compound represented by the general formula (1) is within the above range, a resin having an appropriate molecular weight can be obtained and the amount of residual styrene can be reduced. Even if it is less than 0.05 parts by weight, the effect of reducing the amount of residual styrene is exhibited, but a long reaction time may be required. Moreover, although an upper limit is 0.6 weight part, the effect of reducing the amount of residual styrene-type monomers does not change, but there exists a tendency for the molecular weight of resin to fall and cost becomes high.

  In the present invention, when a compound having a 10-hour half-life temperature of 96 ° C. or higher and 110 ° C. or lower is used in the general formula (1), the amount of residual styrene can be further reduced while suppressing a decrease in molecular weight. Is possible. For this compound, it is important that the 10-hour half-life temperature is 96 ° C. or higher and 110 ° C. or lower. The amount of residual styrene can be reduced. A 10-hour half-life temperature of less than 95 ° C. is not preferable because the amount of cleavage during polymerization increases and the molecular weight of the resin decreases. As a solution to this problem, it is possible to lower the polymerization temperature. However, in this case, the polymerization time is extended, which is not preferable for industrial production. Conversely, when the 10-hour half-life temperature exceeds 110 ° C., the amount of initiator that cleaves during heat treatment or foaming agent impregnation is insufficient, and the amount of residual styrene cannot be reduced sufficiently.

  In the production of expandable styrenic resin particles, generally, an initiator mainly for forming a resin and an initiator mainly for reducing the amount of residual styrene are generally used in combination. 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. Therefore, also in the present invention, the polymerization temperature, the polymerization time, the molecular weight of the resin, etc. can be selected by using one or more commonly used other polymerization initiators in combination with the compound represented by the general formula (1). Since it is possible to obtain a good product in which the amount of residual styrene is reduced while further widening the width, it is a very preferable embodiment to use in combination. Examples of other commonly used polymerization initiators include organic oxides such as benzoyl peroxide, t-butyl peroxybenzoate, isopropyl t-butyl peroxycarbonate, butyl perbenzoate, and azobisisobutyrate. Examples include azo compounds such as ronitrile.

  Examples of the blowing agent used in the present invention include aliphatic hydrocarbons such as hydrocarbons having 3 to 5 carbon atoms such as propane, isobutane, normal butane, isopentane, normal pentane and neopentane, and ozone such as difluoroethane and tetrafluoroethane. Examples thereof include volatile blowing agents such as fluorinated hydrocarbons having a destruction coefficient of zero. Moreover, these foaming agents can also be used together. The amount used is preferably 3 parts by weight or more and 12 parts by weight or less, more preferably 5 parts by weight or more and 9 parts by weight or less, with respect to 100 parts by weight of the styrene resin particles.

  As the additive used in the present invention, a plasticizer, a bubble regulator, an external additive, and the like can be used depending on the purpose. Examples of the plasticizer include stearic acid triglyceride, palmitic acid triglyceride, lauric acid triglyceride, stearic acid diglyceride, stearic acid monoglyceride and other fatty acid glycerides, palm oil, palm oil, palm kernel oil and other vegetable oils, dioctyl adipate, dibutyl sebacate And aliphatic hydrocarbons such as liquid paraffin, cyclohexane and organic hydrocarbons such as cyclohexane. These may be used in combination.

  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.

  Specific examples of the external additive include, for example, fatty acid triglycerides such as lauric acid triglyceride, stearic acid triglyceride, linoleic acid triglyceride, lauric acid diglyceride, stearic acid diglyceride, linoleic acid diglyceride, and the like, lauric acid monoglyceride, stearic acid monoglyceride, and the like. , Fatty acid monoglycerides such as linoleic acid monoglyceride, fatty acid metal salts such as zinc stearate, calcium stearate, magnesium stearate, aluminum stearate, zinc laurate, calcium laurate, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxy Ethylene stearyl ether, polyoxyethylene laurate, polyoxye Renparumiteto, polyoxyethylene stearates, such as non-ionic surfactants such as polyoxyethylene oleate and the like. These external additives and attachments may be used alone or in combination of two or more. These external additives and attachments may be added to the aqueous system when impregnated with the foaming agent, or may be added and coated after dehydration or after drying, regardless of the coating method. A preferable coating method is a method of attaching by drying and coating by mixing and stirring.

  The expandable polystyrene resin particles of the present invention can be foamed by a known method to obtain a polystyrene resin foam molded article. For example, a method of once preparing pre-expanded particles and then filling the mold with the pre-expanded particles and then molding, or a method of directly filling the mold with expandable polystyrene resin particles and foam-molding can be used. The following method is mentioned as an example of the manufacturing method of a foaming molding. By heating the expandable styrene resin particles of the present invention at a temperature of about 80 to 110 ° C. using water vapor with a rotary stirring type prefoaming device, a prefoamed particle having a bulk ratio of about 30 to 100 ml / g is obtained and obtained. The obtained pre-expanded particles are filled in a mold having a desired shape, and heated at about 105 to 145 ° C. using water vapor or the like to obtain a polystyrene-based resin foam molded article. The thus obtained polystyrene resin foam molded article of the present invention has flame retardancy and a small amount of residual styrene monomer.

  Polystyrene-based resin foam moldings are widely used as containers for storing fresh food, heat insulating materials for construction and civil engineering, and buffer materials for automobiles.

  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.

(Molecular weight measurement method)
Gel foam permeation chromatograph is obtained by dissolving 0.02 g of expandable thermoplastic resin particles in 20 ml of tetrahydrofuran (hereinafter sometimes abbreviated as “THF”) with respect to the obtained expandable thermoplastic resin particles. Using (GPC), GPC measurement was performed under the following conditions to obtain a GPC measurement chart, a weight average molecular weight (Mw), and a number average molecular weight (Mn). The obtained value is a relative value in terms of polystyrene.
Measuring device: manufactured by Tosoh Corporation, high-speed GPC device HLC-8220
Column used: Tosoh Corporation, SuperHZM-H x 2, SuperH-RC x 2 Column temperature: 40 ° C, mobile phase: THF (tetrahydrofuran)
Flow rate: 0.35 ml / min, injection volume: 10 μl
Detector: RI.

(Residual styrene measurement method)
The expandable styrene resin particles are dissolved in methylene chloride (internal standard cyclopentanol), and the amount of residual styrene (ppm) contained in the expandable styrene resin particles is measured under the following conditions using gas chromatography (GC). Quantified.
Measuring apparatus: Gas chromatography GC-2014 manufactured by Shimadzu Corporation
Column: Capillary column (GL Science Rtx-1)
Column temperature conditions: 50 → 80 ° C. (3 ° C./min), then 80 → 180 ° C. temperature increase (10 ° C./min),
Carrier gas: helium.

(Measurement method of phenylacetylene in styrene monomer)
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.

Internal standard cyclopentanol was dissolved in styrene, and the amount of phenylacetylene (ppm) in styrene was quantified under the following conditions.
Measuring apparatus: Gas chromatography GC-2014 manufactured by Shimadzu Corporation
Column: Capillary column (GL Science Rtx-1)
Column temperature condition: After raising the temperature to 50 → 70 ° C. (3 ° C./min) and holding at 70 ° C. for 30 minutes. Temperature rising from 70 to 170 ° C. (10 ° C./min) Carrier gas: helium.

(Surface property evaluation)
The expandable polystyrene resin particles are heated with water vapor in a pressure type prefoaming machine (manufactured by Daikai Kogyo Co., Ltd.) to obtain prefoamed granules having a bulk magnification of 55 ml / g. Next, after this pre-foamed grain was cured at room temperature for 1 day, a flat foam was formed with a KR-57 molding machine manufactured by Daisen Industries.

The surface state of the obtained thermoplastic resin foam was visually observed, and the surface property was evaluated according to the following criteria.
A: There is no melting of the surface, no intergranularity, and it is very beautiful.
○: Melting of the surface, little intergranularity, and beautiful.
Δ: Surface melted, intergranular, appearance somewhat poor.
X: Surface melting, intergranularity, and poor appearance.

(Evaluation of flame retardancy)
The flame retardancy of the obtained foamed molded product was evaluated according to the following criteria.
○: The oxygen index is 26 or more and the self-extinguishing property is less than 3 seconds.
X: The oxygen index is less than 26 and / or the self-extinguishing property is 3 seconds or more.

(1) Oxygen index measurement A test piece obtained by cutting a foamed molded article into 10 × 10 × 150 mm is cured in an oven at 60 ° C. for 12 hours, and then conforms to JIS K7201-2: 2007 (Test method for flammability by oxygen index). The oxygen index was measured.

(2) Self-extinguishing evaluation Five test pieces cut out from a foamed molded article to 10 mm × 25 mm × 200 mm were cured in a 60 ° C. oven for 12 hours, and then measured according to measurement method A of JIS A9511: 2006R. The average value of the test piece was calculated | required and it was set as the flame-out time.

Example 1
The amount of phenylacetylene in styrene was 50 ppm. The polymerization method was carried out by a suspension polymerization method in which a flame retardant and a styrenic monomer were added from the beginning to an aqueous medium as follows.

  In a 6 L autoclave with a stirrer, 96 parts by weight of water, 0.15 part by weight of tribasic calcium phosphate, 0.005 part by weight of sodium α-olein sulfonate, 0.08 part of benzoyl peroxide, t-butylperoxy-2-ethylhexyl mono Carbonate (10 hour half-life temperature 99 ° C) 0.38 parts, Brominated butadiene / styrene copolymer ("EMERALD 3000" bromine content 64% by Chemtura) 1.0 part, Dicumylper as flame retardant aid After adding 0.4 part of oxide and 1.0 part of palm oil as an additive, 100 parts by weight of styrene was added, the temperature was raised, and polymerization was carried out at 98 ° C. for 5 hours. Thereafter, 0.5 parts by weight of cyclohexane and 8 parts by weight of normal rich butane (normal / iso = 70/30) were charged as additives, the temperature was raised to 120 ° C., and foaming agent impregnation polymerization was performed for 4 hours. Then, it cooled to 40 degreeC, taken out the expandable styrene-type resin particle, and dried.

  When the molecular weight of the obtained expandable styrene resin particles was measured by GPC, it was 270,000, and when the residual styrene content was measured by gas chromatography, it was 170 ppm.

  Moreover, the obtained expandable styrene resin particles were sieved, and particle diameters of 0.6 mm to 1.2 mm were collected. The foamed thermoplastic resin particles thus obtained were prefoamed at a bulk magnification of 50 times using a pressure prefoaming machine [manufactured by Daikai Kogyo Co., Ltd., BHP] under a blowing vapor pressure of 0.1 MPa. Then, it was left to stand at room temperature for 1 day, and curing drying was performed.

  The obtained styrene resin pre-expanded particles are filled into a flat plate mold using a molding machine [manufactured by Daisen Co., Ltd., KR-57] and molded in-mold under molding conditions of blowing vapor pressure of 0.06 MPa. The foamed molded product was obtained.

  The flame retardancy was 29% with an oxygen index and a flame extinguishing time of 0.9 seconds. The results are shown in Table 1.

(Examples 2 to 12, Comparative Examples 1 to 7)
As shown in Table 1, except that the type and amount of flame retardant and flame retardant aid were changed, expandable styrenic resin particles, pre-expanded particles, and foamed molded article were obtained in the same manner as in Example 1. A similar evaluation was performed.

(Comparative Example 8)
<Manufacture of polystyrene resin seed particles>
Using a φ50 mm single screw extruder, 95 parts by mass of polystyrene resin, 5 parts by mass of brominated butadiene / styrene copolymer as a flame retardant, and a stabilizer were melt-kneaded at a temperature of 170 to 230 ° C. Subsequently, it extruded from the die | dye which has a small hole in strand shape, and after quenching in water, it cut | disconnected with the pelletizer, and obtained the cylindrical styrene-type resin particle.

<Manufacture of expandable styrene resin particles>
In the polymerization of thermoplastic resin particles, 92 parts by weight of water in a 6 L autoclave, 0.6 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium α-olefin sulfonate, and 20 parts by weight of the resulting polystyrene resin seed particles , 0.4 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate and 0.4 parts of dicumyl peroxide were suspended, and the aqueous suspension was heated to 90 ° C.

  Further, while maintaining at 90 ° C. and stirring, 80 parts by weight of styrene monomer and 0.25 parts by weight of benzoyl peroxide were dropped into the reaction system over 5 hours to perform polymerization, and then cyclohexane was added as an additive. 0.5 part by weight and 8 parts by weight of normal rich butane (normal / iso = 70/30) were charged, the temperature was raised to 120 ° C., and foaming agent impregnation polymerization was performed for 4 hours. Then, it cooled to 40 degreeC, taken out the expandable styrene-type resin particle, and dried. Thereafter, pre-expanded particles and a foam-molded product were obtained in the same manner as in Example 1. Each evaluation result is shown in Table 1.

  In the seed polymerization, there is a problem that the flame retardancy is deteriorated as compared with the suspension polymerization of the same amount of the flame retardant (Example 1). Furthermore, since the molecular weight is low, the strength is likely to be low. This is presumably because the flame retardant must be kneaded in advance with PS and an extruder to obtain seed particles, so that the flame retardant decomposes and the molecular chain of PS becomes shorter.

Claims (6)

A method for producing expandable polystyrene resin particles comprising a step of dispersing a flame retardant and a styrene monomer in an aqueous medium, wherein the brominated polymer is used as a flame retardant with respect to 100 parts by weight of the styrene monomer. 0.3 part by weight or more and 2.0 parts by weight or less, flame retardant aid is contained by 0.2 part by weight or more and 1.1 parts by weight or less, and the ratio of the flame retardant to the flame retardant assistant is flame retardant / difficult Production of expandable polystyrene resin particles, characterized in that the flame retardant is 0.4 or more and 3.0 or less, and the total amount of the flame retardant and the flame retardant aid is 1.1 parts by weight or more. Method. The method for producing expandable polystyrene resin particles according to claim 1, wherein the brominated polymer is a brominated butadiene-styrene copolymer. The method for producing expandable polystyrene resin particles according to claim 1 or 2, wherein the amount of residual styrene monomer is 300 ppm or less. 4. The method for producing expandable polystyrene resin particles according to claim 1, wherein the expandable polystyrene resin particles have a weight average molecular weight (Mw) of from 250,000 to 400,000. The expandable polystyrene resin particles according to any one of claims 1 to 4, wherein the polymerization initiator contains 0.05 parts by weight or more and 0.6 parts by weight or less of the compound represented by the general formula (1). Production method.

(In the formula, R ₁ represents an alkyl group, and R ₂ represents a branched or straight chain alkyl group.) 6. The polymerization initiator according to claim 1, wherein the R ₁ structure of the general formula (1) is a methyl group or an ethyl group, and the R ₂ structure is a 2-ethylhexyl group or an isopropyl group. Method for producing expandable polystyrene resin particles.