JP2008075051A - Method for producing self fire-extinguishing foamable polystyrene-based resin particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a self fire-extinguishable foamable polystyrene-based resin particle that can incorporate a flame retardant uniformly, and can be used for producing a foamed molded article that gives a good cutting plane when being cut by nichrome wire heating. <P>SOLUTION: The method for producing the self fire-extinguishable foamable polystyrene-based resin particle comprises impregnating a 100 pts.wt. polystyrene-based resin with a 0.3-2 pts.wt. powdered flame retardant and a foaming agent in a state of an aqueous suspension, wherein, the impregnation of the flame retardant is performed before or during the impregnation of the foaming agent through adding a dispersion, that is prepared by dispersing a 5-40 pts.wt. flame retardant and a 2-10 pts.wt. slightly water soluble inorganic salt to a 100 pts.wt. aqueous medium, to the aqueous suspension. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for producing self-extinguishing polystyrene-based resin particles used for producing a self-extinguishing polystyrene-based resin foam molded article used in the field of building materials, particularly for building materials.

In general, as a method of producing a polystyrene resin foam molded article having a desired shape such as a block shape, bead-like expandable polystyrene resin particles are heated and pre-foamed, and the resulting pre-foamed particles are obtained in a desired shape. A manufacturing method is employed in which a mold having a cavity is filled into the cavity, then foam-molded in the mold, and the molded body is taken out of the mold after cooling.
In addition, polystyrene resin foam moldings used for building materials are cut into molded shapes using energized and heated nichrome wires after molding into a predetermined shape such as a block shape in order to match the desired dimensions and shape. (Hereinafter referred to as block cut or nichrome cut).
Furthermore, polystyrene-based resin foam moldings used for building materials are required to have self-extinguishing properties that meet certain standards (hereinafter sometimes abbreviated as self-extinguishing properties). In order to clear the property standard, self-extinguishing expandable polystyrene resin particles to which a flame retardant is added when producing expandable polystyrene resin particles are provided. As the flame retardant, a brominated flame retardant such as hexabromocyclododecane is used.

In recent years, the use of self-extinguishing polystyrene resin foam molded products that have been block-cut for building materials has been increasing for panels for building materials, and the quality required for the nichrome cut surface has increased accordingly. The expandable styrene resin particles used for building materials contain a flame retardant in order to impart flame retardancy. One method of incorporating a flame retardant into the resin particles is to add a powdery flame retardant directly to a reaction kettle (autoclave). In this method, the flame retardant causes secondary agglomeration in the liquid, resulting in non-uniform dispersion, resulting in non-uniform absorption of the flame retardant into the resin particles, and some particles containing a large amount of flame retardant. Absorb. Because the particles are inferior in heat resistance, they cannot withstand the heating during molding, shrink and become hardened grains, and when the nichrome is cut, the nichrome wire bounces off the hardened grains, and uneven stripes are generated on the nichrome cut surface. , Significantly reduce the value of the product. In addition, sufficient adhesion strength with the panel may not be obtained.
Conventionally, for example, techniques disclosed in Patent Documents 1 to 3 have been proposed for self-extinguishing polystyrene resin foam molded products to which a flame retardant is added.

  In Patent Document 1, (a) 100 parts by mass of vinyl aromatic polymer particles, about 50 to 500 parts by mass of water, an effective amount of a suspending agent, and about 0.1 to 2. Forming an aqueous suspension of 5 parts by weight of hexabromocyclododecane, about 3 to 20 parts by weight of a C4-C6 aliphatic hydrocarbon blowing agent; (b) the suspension at a temperature of about 40-140 ° C. Heat for about 0.5-15 hours to incorporate hexabromocyclododecane and blowing agent into the polymer particles to form refractory, expandable thermoplastic beads, and (c) separate the beads from water A process for the production of refractory and expandable thermoplastic beads is disclosed.

  In Patent Document 2, tetrafluorobisbisphenol A diallyl ether having an average particle size of 120 μm or less in an expandable styrene resin particle obtained by adding a foaming agent to a styrene resin particle main body, a styrene resin particle main body and tetrabromo Expandable styrene resin particles having flame retardancy, which are impregnated within a range of 1.0 to 5.0% by mass with respect to the total amount with bisphenol A diallyl ether, are disclosed.

In Patent Document 3, tetrabromobisphenol A diallyl ether is dispersed in the presence of a surfactant so that the particle diameter is 50 μm or less, and then a polystyrene resin particle together with a softener, a flame retardant aid, a plasticizer and a foaming agent. A method for producing self-extinguishing foamed polystyrene resin particles, characterized by impregnating in a resin, is disclosed.
JP-A-4-132746 JP 11-255946 A JP-A-11-130898

However, the conventional techniques disclosed in Patent Documents 1 to 3 have the following problems.
Although the method for producing thermoplastic beads described in Patent Document 1 does not clearly show the manner in which the flame retardant is charged, it is considered that powder is charged as it is based on the description. When the flame retardant is added in the form of powder, the absorption into the beads becomes non-uniform, and secondary fine aggregation tends to occur in the liquid by further miniaturization. In addition, many flame retardants tend to be present near the surface, and this flame retardant tends to cause so-called blocking in which foamed particles are fused and bonded during pre-foaming.

  In the prior art described in Patent Document 2, the flame retardant having a large specific gravity can be dispersed in the liquid under stirring with water and surfactant, but the liquid is sent from the tank to the reaction kettle (autoclave). At times, there is a risk that the flame retardant settles in the lower part of the tank or the piping line, and the piping line is blocked. In addition, many flame retardants tend to exist in the vicinity of the surface. For this reason, there is a tendency that so-called blocking, in which foamed particles are fused and bonded during the preliminary foaming by the flame retardant, tends to occur.

  In the prior art described in Patent Document 3, there is a step of removing glass beads used for miniaturization, which is disadvantageous in production. Flame retardants with large specific gravity can be dispersed in liquid in water and surfactant under stirring, but when there is no stirring, that is, when liquid is sent from the tank to the reaction kettle, the bottom of the tank and piping Risk of sinking into the line and plugging. In addition, many flame retardants tend to exist in the vicinity of the surface. For this reason, there is a tendency that so-called blocking, in which foamed particles are fused and bonded during the preliminary foaming by the flame retardant, tends to occur.

  The present invention has been made in view of the above circumstances, and is capable of uniformly adding a flame retardant into a particle, and manufacturing a foam molded body that can obtain a good cut surface when a foam molded body obtained by foam molding is Nichrome cut. An object is to provide a self-extinguishing foamable polystyrene resin particle capable of extinguishing.

  In order to achieve the above-mentioned object, the present invention impregnates a powdered flame retardant with 0.3-2 parts by mass and a foaming agent with respect to 100 parts by mass of polystyrene resin particles in an aqueous suspension. In the method for producing expandable polystyrene-based resin particles, before or during the impregnation of the foaming agent, 5 to 40 parts by mass of the flame retardant and 2 to 10 parts by mass of the hardly water-soluble inorganic salt with respect to 100 parts by mass of the aqueous medium. Provided is a method for producing self-extinguishing expandable polystyrene resin particles, wherein the dispersed flame retardant dispersion is added to the aqueous suspension, and the resin particles are impregnated with the flame retardant.

  In the method for producing self-extinguishing foamable polystyrene resin particles of the present invention, the total content of aromatic organic compounds composed of styrene monomer, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, and toluene is preferably less than 2000 ppm. .

  In the method for producing self-extinguishing foamable polystyrene resin particles of the present invention, it is preferable to make the average particle diameter of the flame retardant in the flame retardant dispersion liquid smaller than 100 μm.

  In the method for producing self-extinguishing foamable polystyrene resin particles of the present invention, it is preferable to add a surfactant to the flame retardant dispersion.

The method for producing self-extinguishing foamable polystyrene resin particles according to the present invention comprises 5 to 40 parts by mass of a flame retardant and a hardly water-soluble inorganic salt 2 with respect to 100 parts by mass of an aqueous medium before or during impregnation with a foaming agent. By adding a flame retardant dispersion in which 10 parts by mass is dispersed to the aqueous suspension and impregnating the resin particles with the flame retardant, the flame retardant can be uniformly added to the particles. Moreover, since the secondary aggregation and sedimentation which generate | occur | produce when a flame retardant is added to the autoclave for resin particle manufacture can be prevented, the malfunction which the piping line by a flame retardant obstruct | occludes can be prevented.
Further, since the flame retardant can be uniformly added to the particles, the impregnation (absorption) efficiency of the flame retardant into the resin particles is increased, the waste of the flame retardant is reduced, and the amount of the flame retardant used can be reduced.
Further, since the hardly water-soluble inorganic salt can be uniformly added to the particles together with the flame retardant, it is possible to suppress the occurrence of so-called blocking, in which the foamed particles are fused and bonded at the time of preliminary foaming.
In addition, according to the method for producing self-extinguishing foamable polystyrene resin particles of the present invention, a flame retardant can be uniformly added to the particles, so that it is good when Nichrome cutting is performed on a foam molded product obtained by foam molding. Self-extinguishing foamable polystyrene resin particles capable of producing a foamed molded product that can provide a simple cut surface can be produced.
In addition, by making the total content of aromatic organic compounds consisting of styrene monomers, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, and toluene less than 2000 ppm, low volatile organic compounds that can cope with environmental problems such as recent sick houses (Low VOC) compatible building materials can be provided.
Further, by making the average particle diameter of the flame retardant in the flame retardant dispersion liquid smaller than 100 μm, uniform absorption into the resin particles and impregnation efficiency can be further improved.
Further, by adding a surfactant to the flame retardant dispersion, the dispersion of the flame retardant in the liquid is improved, and the flame retardant can be more uniformly added to the particles.

  The method for producing self-extinguishing foamable polystyrene resin particles of the present invention comprises 0.3 to 2 parts by mass of a powdered flame retardant and a foaming agent with respect to 100 parts by mass of polystyrene resin particles in an aqueous suspension. In the method of impregnating and producing self-extinguishing foamable polystyrene resin particles, before or during impregnation of the foaming agent, 5 to 40 parts by mass of a flame retardant and a hardly water-soluble inorganic salt with respect to 100 parts by mass of the aqueous medium A dispersion in which 2 to 10 parts by mass are dispersed is added to the aqueous suspension and impregnated with a flame retardant.

In the production method of the present invention, the method for producing the main polystyrene resin particles is not limited, but a method for producing polystyrene resin particles by polymerizing a styrene monomer in an aqueous medium, for example,
(1) A suspension polymerization method in which a styrene monomer is placed in an autoclave together with an aqueous medium and a polymerization initiator, and a polystyrene resin particle is produced by performing a polymerization reaction of the styrene monomer while heating and stirring in the autoclave.
(2) Polystyrene resin seed particles and an aqueous medium are dispersed in an autoclave, and a styrene monomer is continuously or intermittently supplied while being heated and stirred in the autoclave, and the styrene monomer is supplied to the polystyrene resin seed particles. A seed polymerization method in which polystyrene resin particles are produced by polymerizing in the presence of a polymerization initiator.
It is preferable that

  In the production method of the present invention, the polystyrene-based resin is not particularly limited. For example, styrene-based resins such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene. Examples include monomer homopolymers or copolymers thereof, and polystyrene-based resins containing 50% by mass or more of styrene are preferable, and polystyrene is more preferable.

  Further, the polystyrene resin may be a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, the main component of which is the styrene monomer. As, for example, alkyl (meth) acrylate such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl In addition to fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.

  The average particle diameter of the polystyrene resin particles is the point of filling of the polystyrene resin pre-expanded particles into the mold when performing in-mold foam molding using the self-extinguishing foam polystyrene resin particles of the present invention. From 0.3 to 2.0 mm, preferably from 0.6 to 1.4 mm. Furthermore, if the polystyrene-based weight average molecular weight of the polystyrene-based resin constituting the polystyrene-based resin particles is small, the mechanical strength of the polystyrene-based resin foam molded article obtained by foaming the expandable polystyrene-based resin particles may decrease. On the other hand, if it is large, the foamability of the expandable polystyrene resin particles is lowered, and there is a possibility that a polystyrene-based resin foam molded article having a high expansion ratio cannot be obtained, so 200,000 to 500,000 are preferable, and 240,000 to 400,000 is more preferable.

  Examples of the flame retardant used in the production method of the present invention include brominated aliphatic hydrocarbon compounds such as hexabromocyclododecane, tetrabromocyclooctane, tetrabromobutane, hexabromocyclohexane, tetrabromobisphenol A, and tetrabromobisphenol F. Brominated phenols such as 2,4,6-tribromophenol, brominated phenol derivatives such as tetrabromobisphenol A-bis (2,3-dibromopropyl ether), tetrabromobisphenol A-diglycidyl ether, etc. Of these, tetrabromocyclooctane is more preferable.

  The usage-amount of a flame retardant shall be 0.3-2.0 mass parts with respect to 100 mass parts of polystyrene-type resin particles. When the proportion of the flame retardant used is less than 0.3 parts by mass, a sufficient flame retardant effect cannot be expected. There is a fear. More preferably, it is 0.5-1.5 mass part, More preferably, it is 0.7-1.0 mass part.

  In the step of preparing the flame retardant dispersion, the amount of the flame retardant added to 100 parts by mass of the aqueous medium is 5 to 40 parts by mass. When the amount of the flame retardant added is less than 5 parts by mass, water necessary for dispersion increases, which is disadvantageous in cost. Moreover, when it exceeds 40 mass parts, refinement | miniaturization of a flame retardant will become difficult and it will become difficult to obtain the flame retardant dispersion liquid which the flame retardant disperse | distributed uniformly. More preferably, it is 10-30 mass parts.

  Examples of the poorly water-soluble inorganic salt used in the production method of the present invention include tricalcium phosphate, hydroxyapatite, magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, magnesium phosphate, magnesium carbonate, and the like. More preferred.

  In the step of preparing the flame retardant dispersion, the amount of the hardly water-soluble inorganic salt added to 100 parts by mass of the aqueous medium is 2 to 10 parts by mass. When the addition amount of the hardly water-soluble inorganic salt is less than 2 parts by mass, a sufficient anti-settling effect of the flame retardant cannot be obtained, and when it exceeds 10 parts by mass, the viscosity of the flame retardant dispersion increases and the flame retardant is uniform. It becomes difficult to obtain a liquid dispersed in More preferably, it is 3-7 mass parts.

  As the foaming agent used in the production method of the present invention, a gaseous or liquid organic compound having a boiling point equal to or lower than the softening point of a polystyrene resin and suitable at normal pressure is suitable. For example, propane, n-butane, isobutane. N-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, hydrocarbons such as petroleum ether, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol and isopropyl alcohol, dimethyl ether, diethyl ether, Low boiling point ether compounds such as dipropyl ether and methyl ethyl ether, inorganic gases such as carbon dioxide, nitrogen and ammonia are used. These foaming agents may use only 1 type and may use 2 or more types together. Among these, preferable blowing agents are hydrocarbons having a boiling point of −45 to 40 ° C., and propane, n-butane, isobutane, n-pentane, isopentane and the like are preferable.

  In the (1) suspension polymerization method or (2) seed polymerization method, the polymerization initiator used when polymerizing the styrene monomer is not particularly limited, and examples thereof include benzoyl peroxide, lauryl peroxide, t- Butyl peroxybenzoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-bis (t-butylperoxy) butane, t- Organic peroxides such as butylperoxy-3,3,5 trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile These may be used alone or in combination.

  In the above (1) suspension polymerization method or (2) seed polymerization method, a suspension stabilizer is used to stabilize the dispersibility of the styrene monomer droplets and the polystyrene resin seed particles when polymerizing the styrene monomer. Examples of such suspension stabilizers include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate and magnesium pyrophosphate. In the case of using a poorly soluble inorganic compound, an anionic surfactant is usually used in combination.

  In the step of preparing the flame retardant dispersion, it is preferable to refine the average particle size of the flame retardant in the flame retardant dispersion to less than 100 μm. If the average particle diameter of the flame retardant in the flame retardant dispersion exceeds 100 μm, the absorption of the flame retardant into the resin particles may be uneven. As for the average particle diameter of the flame retardant in a flame retardant dispersion liquid, 50 micrometers or less are more preferable, and the range of 1 micrometer-30 micrometers is further more preferable.

  As a method of refining the flame retardant in the flame retardant dispersion to an average particle diameter of less than 100 μm, it can be achieved by using a pre-refined flame retardant, but in the step of preparing the flame retardant dispersion, in the aqueous medium It is desirable to refine the liquid obtained by adding a flame retardant or a flame retardant and a hardly soluble inorganic compound using a conventionally known emulsification / dispersion apparatus such as a homomixer or a milder. In this case, a uniform flame retardant dispersion can be prepared simultaneously with the miniaturization of the flame retardant.

  In addition to the flame retardant and the hardly water-soluble inorganic compound, it is preferable to add a surfactant to the flame retardant dispersion. As the surfactant, an anionic surfactant is preferable. For example, alkyl sulfates such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, higher fatty acid salts such as sodium oleate, β-tetrahydroxy Examples thereof include naphthalene sulfonate, and alkylbenzene sulfonate is more preferable. The addition amount of the surfactant to the flame retardant dispersion is preferably in the range of 0.005 to 0.10 parts by mass with respect to 100 parts by mass of the aqueous medium. If the addition amount of the surfactant is less than the above range, the effect of improving the dispersibility of the flame retardant in the flame retardant dispersion may be difficult to obtain. On the other hand, if the above range is exceeded, foaming by the surfactant becomes excessive and the productivity may be lowered.

  The timing of adding the flame retardant dispersion to the aqueous suspension in which the polystyrene resin particles are suspended may be before or during the impregnation of the foaming agent. In addition, at the time of this addition, the entire amount of the flame retardant dispersion may be added at once, or may be added in a plurality of times, or may be added in small portions continuously.

  After adding the flame retardant dispersion and the foaming agent to the aqueous suspension in which the polystyrene resin particles are suspended, the self-extinguishing foamable polystyrene resin particles are taken out from the autoclave and separated from the aqueous suspension. If necessary, wash and dry the product.

  In the production method of the present invention, in the self-extinguishing foamable polystyrene resin particles, in addition to the flame retardant, within the range where the physical properties are not impaired, a bubble regulator, filler, flame retardant aid, lubricant, colorant Additives such as solvents and plasticizers can be added as necessary.

In the method for producing self-extinguishing foamable polystyrene resin particles of the present invention, the total content of aromatic organic compounds composed of styrene monomer, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, and toluene is preferably less than 2000 ppm. . The total content of aromatic organic compounds consisting of styrene monomers, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, and toluene is preferably less than 2000 ppm, and it is less than 2000 ppm to cope with environmental problems such as recent sick houses. The building material corresponding to the low volatile organic compound (low VOC) which can be provided can be provided. 750 ppm or less is more preferable. In addition, the measuring method of an aromatic organic compound is mentioned later.
In order to make the total content of the aromatic organic compound in the self-digestible expandable polystyrene resin particles less than 2000 ppm with respect to the total weight of the expandable polystyrene resin particles, the production of expandable polystyrene resin particles Sometimes it is preferred not to add the above-mentioned aromatic organic compound separately as a plasticizer.
However, in the production of self-digestible expandable polystyrene resin particles, the aromatic organic compound is not separately added as a plasticizer, but in the styrene monomer used as a raw material for expandable polystyrene resin particles. As impurities, ethyl benzene, isopropyl benzene, normal propyl benzene, xylene and toluene are contained in a large amount, or a large amount of unreacted styrenic monomer remains in the expandable polystyrene resin particles. There exists a possibility that the said aromatic organic compound may be contained exceeding the said range in a polystyrene-type resin particle.
Therefore, select a styrene monomer with few impurities so that the total content of the above-mentioned aromatic organic compound in the self-digestible expandable polystyrene resin particles is less than 2000 ppm with respect to the total weight of the expandable polystyrene resin particles. In addition, it is necessary to adjust the production conditions of the expandable polystyrene resin particles. Examples of methods for adjusting the production conditions of expandable polystyrene resin particles for suppressing the total content of the aromatic organic compound within a predetermined range include, for example, polymerization initiation used for suspension polymerization and seed polymerization of polystyrene resins. Two types of polymerization initiators with different decomposition temperatures are used as the agent. First, suspension polymerization of a polystyrene resin is performed using a polymerization initiator with a low decomposition temperature, and then polystyrene with a polymerization initiator with a high decomposition temperature is used. And a method of continuously performing suspension polymerization of a resin. In the above method, among the two types of polymerization initiators having different decomposition temperatures, the polymerization initiator having a high decomposition temperature is preferably a polymerization initiator having a half-life of 10 hours at a temperature of 90 to 120 ° C. Examples of such a polymerization initiator include t-butyl peroxybenzoate, t-butyl peroxybivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t- Examples include butyl peroxyacetate and 2,2-t-butylperoxybutane.

Self-extinguishing expandable polystyrene resin particles obtained by the production method of the present invention are molded into a desired shape by a conventionally well-known in-mold foam molding method, and suitable for self-extinguishing polystyrene resin foam molding in the field of building materials. The body can be manufactured. In this in-mold foam molding method, self-extinguishing foam polystyrene resin particles are heated to form pre-expanded particles having a bulk density of about 0.01 to 0.05 g / cm ³ , and then a mold having a cavity having a desired shape. A conventionally well-known method can be used in which the pre-expanded particles are filled into the cavities, foam-molded in-mold, and the foam-molded product is released after cooling. The density of the foam molded product obtained by this in-mold foam molding method is not limited, but is preferably about 0.01 to 0.05 g / cm ³ . If the density is less than the above range, the closed cell ratio of the foamed molded product may be reduced, and the heat insulation and strength may be reduced. On the other hand, when the density exceeds the above range, the molding cycle at the time of in-mold foam molding becomes long, and the productivity may be lowered.

The production method of the present invention comprises a flame retardant in which 5 to 40 parts by mass of a flame retardant and 2 to 10 parts by mass of a water-insoluble inorganic salt are dispersed with respect to 100 parts by mass of an aqueous medium before or during the impregnation of the foaming agent. By adding the dispersion to the aqueous suspension and impregnating the resin particles with the flame retardant, the flame retardant can be uniformly added to the particles. Moreover, since the secondary aggregation and sedimentation which generate | occur | produce when a flame retardant is added to the autoclave for resin particle manufacture can be prevented, the malfunction which a piping line obstruct | occludes with a flame retardant can be prevented.
Further, since the flame retardant can be uniformly added to the particles, the impregnation (absorption) efficiency of the flame retardant into the resin particles is increased, the waste of the flame retardant is reduced, and the amount of the flame retardant used can be reduced.
In addition, according to the method for producing self-extinguishing foamable polystyrene resin particles of the present invention, a flame retardant can be uniformly added to the particles, so that it is good when Nichrome cutting is performed on a foam molded product obtained by foam molding. Self-extinguishing foamable polystyrene resin particles capable of producing a foamed molded product that can provide a simple cut surface can be produced.
Hereinafter, the effects of the present invention will be demonstrated by examples.

(Example 1)
[Suspension polymerization]
In an autoclave with a stirrer having an internal volume of 100 liters, 120 g of tricalcium phosphate (manufactured by Ohira Chemical Co., Ltd.), 4 g of sodium dodecylbenzenesulfonate, 140 g of benzoyl peroxide (purity 75%), t-butylperoxy-2-ethylhexyl monocarbonate 30 g, 40 kg of ion-exchanged water and 40 kg of styrene monomer were added, and then dissolved and dispersed under stirring at 100 rpm to form a suspension.
Subsequently, the temperature in the autoclave was raised to 90 ° C. while stirring the stirring blade at 100 rpm, and then held at 90 ° C. for 6 hours.
After that, the temperature inside the autoclave is further raised to 120 ° C. and held at 120 ° C. for 2 hours, then the temperature inside the autoclave is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified. Styrenic resin particles having a diameter of 0.6 to 0.85 mm and a weight average molecular weight of 300,000 were obtained.
In addition, any of the raw materials and additives used in the above process may be added first.
In addition, the raw materials and additives used in the above steps may be added as they are, or may be diluted and dissolved.

[Seed polymerization]
Next, 30 kg of pure water, 4 g of sodium dodecylbenzenesulfonate and 100 g of magnesium pyrophosphate are placed in a 100 liter autoclave equipped with a stirrer, and polystyrene having a particle size of 0.60 to 0.85 mm and a weight average molecular weight of 300,000 as described above. 11 kg (25 parts by mass) of core particles were added and stirred at 120 rpm to be dispersed in the liquid.
The previously prepared emulsion was then added to the reactor maintained at 75 ° C. This emulsion was prepared by dispersing 88 kg of benzoyl peroxide (purity 75%) as a polymerization initiator in a dispersion of 6 kg of pure water, 2 g of sodium dodecylbenzenesulfonate and 20 g of magnesium pyrophosphate, t-butylperoxy-2-ethylhexyl mono 5 kg of styrene in which 50 g of carbonate was dissolved was added, and the mixture was stirred and emulsified with a homomixer. Thereafter, the styrene resin particles are held for 30 minutes so that the styrene and the polymerization initiator are well absorbed, and then 28 kg of styrene is added to the inside of the autoclave at 0.2 ° C./min from 75 ° C. to 108 ° C. over 160 minutes. It was dripped continuously while raising the temperature. (At the end of dropping, the amount of styrene added to the reactor is 33 kg, that is, 75 parts by mass, and the total amount of styrene-based resin particles and added styrene is 100 parts by mass.) Twenty minutes after the completion of dropping, the temperature was raised to 120 ° C. at a rate of 1 ° C./min and held for 90 minutes.

[Preparation of flame retardant dispersion]
To 2 kg of pure water, 0.7 g of sodium dodecylbenzenesulfonate as a surfactant and 60 g of magnesium pyrophosphate as a hardly water-soluble inorganic salt are added, and a homomixer (made by Tokushu Kika Kogyo Co., Ltd., product name: TK homomixer MARKII fmodel, While stirring at a rotational speed of 12000 rpm, 440 g of tetrabromocyclooctane (hereinafter referred to as TBCO; manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: trade name Piroguard FR-200) is added as a flame retardant and stirred for 20 minutes to flame retardant. Was finely dispersed to prepare a dispersion, which was allowed to stand for 30 minutes.

[Preparation of emulsion]
To a dispersion of 2 kg of warm water and 0.8 g of sodium dodecylbenzenesulfonate, 308 g of diisobutyl adipate (trade name: DI4A, manufactured by Taoka Chemical Co., Ltd.) and 132 g of flame retardant aid dicumyl peroxide (DCP) are added, The emulsion was prepared by stirring with a mixer.

[Impregnation]
Thereafter, the autoclave was cooled to 90 ° C. at a rate of 1 ° C./min, and the previously prepared emulsion was added to the reactor. Thirty minutes after the addition of this emulsion, the previously prepared flame retardant dispersion was added and sealed, and 2640 g of butane (isobutane / normal butane = 30/70) and pentane (isopentane) as the blowing agent. / Normal pentane = 20/80) 1100 g of nitrogen was pressurized into the autoclave for 30 minutes, held in that state for 3 hours, the temperature in the autoclave was cooled to 25 ° C., and the contents were taken out of the autoclave. Then, dehydration, drying and classification were performed to obtain self-extinguishing foamable styrene resin particles having a particle diameter of 0.85 to 1.2 mm and a weight average molecular weight of 300,000.

(Example 2)
The same procedure as in Example 1 was performed except that the amount of magnesium pyrophosphate used in the flame retardant dispersion was changed to 100 g.

(Example 3)
The same procedure as in Example 1 was performed except that the magnesium pyrophosphate used in the flame retardant dispersion was changed to tricalcium phosphate.

Example 4
The same procedure as in Example 1 was performed except that 440 g of the flame retardant TBCO used for the flame retardant dispersion was changed to 330 g.

(Example 5)
Example 1 except that the flame retardant TBCO used in the flame retardant dispersion was changed to tetrabromobisphenol A-bis (2,3-dibromopropyl ether) (trade name Pyroguard SR-720, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) The same method was used.

(Example 6)
After the seed polymerization step of Example 1, the temperature in the autoclave is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified, and the particle size is 0.85 to 1.2 mm and the weight average molecular weight is 30. Ten million polystyrene particles were obtained.
Subsequently, 36 kg of pure water, 6 g of sodium dodecylbenzenesulfonate and 150 g of magnesium pyrophosphate were added to a 100 liter autoclave equipped with a stirrer, and 44 kg of the polystyrene core particles described above were further added and stirred at 120 rpm and dispersed in the liquid. The temperature inside the autoclave was kept at 30 ° C. Subsequently, the same emulsion as previously prepared Example 1 was added to the reactor. 30 minutes after the addition of this emulsion, the same flame retardant dispersion as previously prepared Example 1 was added and sealed, and the temperature in the autoclave was increased to 90 ° C. at a rate of 1 ° C./min. Warm, 2640 g of butane (isobutane / normal butane = 30/70) and 1100 g of pentane (isopentane / normal pentane = 20/80) as a blowing agent were pressurized with nitrogen and pressed into the autoclave for 30 minutes. After holding for a period of time, the temperature in the autoclave is cooled to 25 ° C., the contents are taken out from the autoclave, dehydrated, dried and classified, and a foaming property having a particle size of 0.85 to 1.2 mm and a weight average molecular weight of 300,000. Styrene resin particles were obtained.

(Comparative Example 1)
The same procedure as in Example 1 was performed, except that the flame retardant TBCO was directly charged into the autoclave in a powder state without preparing the flame retardant dispersion.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the amount of magnesium pyrophosphate used in the flame retardant dispersion was 0 g. In Comparative Example 2, after preparing the flame retardant dispersion, the flame retardant immediately precipitated and separated, so the flame retardant dispersion was added again with stirring immediately before the addition of the autoclave.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that the amount of magnesium pyrophosphate used in the flame retardant dispersion was changed to 300 g.

(Comparative Example 4)
The flame retardant used in the flame retardant dispersion was changed to tetrabromobisphenol A-bis (2,3-dibromopropyl ether) (Daiichi Kogyo Seiyaku Co., Ltd., trade name Piroguard SR-720), and directly in powder form The same method as in Example 1 was carried out except that it was put in an autoclave.

[Blend process]
40 kg of self-extinguishing foamable styrene resin particles produced in Examples 1 to 6 and Comparative Examples 1 to 4, 20 g of polyethylene glycol as a surface treatment agent and 60 g of zinc stearate, fatty acid triglyceride (product of Riken Vitamin Co., Ltd.) Name: Riquemar VT-50) 40 g, fatty acid monoglyceride (product name: Rikemar S-100P, manufactured by Riken Vitamin Co., Ltd.) 20 g was put into a tumbler mixer, stirred for 30 minutes, and surface-treated to self-extinguishing foam polystyrene resin particles. The agent was coated.

[Pre-foaming process]
The self-extinguishing foamable polystyrene resin particles after the blending step are stored in a 15 ° C. cool box for 48 hours, and then published by JPO Gazette 57 (1982) -133 [3347], well-known and commonly used technology (foam molding) p. 5.8 kg per shot was put into a cylindrical batch type pressure pre-foaming machine with a volume of 350 liters up to the foam layer upper surface detector described in 39, and heated with steam for 2 minutes to obtain pre-foamed particles.

[Molding process]
The pre-expanded particles are allowed to stand at room temperature for 24 hours, and then 0.07 MPa (gauge pressure) on a block molding machine [PEONY-205DS manufactured by Kasahara Kogyo Co., Ltd.] having a mold size: height 1840 mm, width 930 mm, and depth 530 mm. ) At a vapor pressure of 20) for 20 seconds, and then cooled until the internal pressure of the mold became -0.01 MPa, and released from the mold to obtain a block foam molded article. Thereafter, it was stored in a 70 ° C. drying room for 3 days.

[Nichrome cutting process]
Place the block molding on the base of the nichrome cutting machine with the fixed side (length 1840mm, width 930mm plane) down, and stretch ten 0.4mm diameter nichrome wires in parallel at 50mm intervals. Nichrome cutting was performed under the conditions of 600 mm / min and current of 3 A / line to obtain a flat sliced product.

  About the said Examples 1-6 and Comparative Examples 1-4, it measured about each measurement item of sedimentation of a flame retardant, the coupling | bonding at the time of foaming, the number of stripe generation | occurrence | production, self-extinguishing measurement, and block fusion. The measurement method and evaluation criteria for each item were as follows.

<Evaluation of settling of flame retardant>
After preparing the flame retardant dispersion, after standing for 30 minutes, it was visually determined whether or not there was sedimentation of the flame retardant at the bottom of the container before adding it to the autoclave.

<Measurement of bond during pre-foaming>
All the pre-expanded particles are passed through a sieve having an opening of 1 cm, the mass of the foam particles not passing through the sieve is measured, and the ratio to the mass of all the expandable styrene resin particles (beads) used for the pre-expansion ( %).
Bonding during pre-expansion (%) = mass of mass of foam particles not passing through sieve / mass of all expandable styrene resin particles (beads) × 100
As the evaluation criteria, a case where the bond at the time of foaming exceeds 1.0% is judged as poor (x), and a case where the bond is 1.0% or less is judged as good (◯).

<Measurement of the number of streaks on the nichrome cut surface>
The number of streaks (uneven lines) generated on all the cut surfaces obtained by the nichrome cut was measured by visual observation and converted to the number of streaks generated per square meter.

<Self extinction measurement>
Five test samples of 200 mm x 25 mm x 10 mm in size are cut out from the foamed molded article with a vertical cutter, cured in a 60 ° C oven for 1 day, measured according to the combustion test A method of JIS A9511, and self-extinguishing time ( Seconds). In this JIS standard, the self-extinguishing time needs to be within 3.0 seconds, more preferably within 2.0 seconds, and even more preferably within 1.0 seconds.
Evaluation criteria for self-extinguishing are as follows: self-extinguishing time exceeding 3.0 seconds is rejected (x), 3.0 seconds or less is acceptable (○), 1.0 seconds or less is good (◎ ).

<Fusion rate>
After making a cut line with a depth of about 5 mm with a cutter knife along the center of the sixth block molded body (length 1840 mm, width 930 mm, thickness 50 mm) obtained by Nichrome cutting, along this cut line The foamed molded body is divided into two by hand (length: 920 mm, width: 930 mm, thickness: 50 mm), and the number of particles broken within the particle in an arbitrary range of 100 to 150 with respect to the expanded particles in the fracture surface ( a) and the number of particles broken at the interface between the particles (b) are counted, and the values obtained by substituting them into the formula [(a) / ((a) + (b))] × 100 are fused. The arrival rate (%). A fusion rate of 70% or higher was evaluated as good (◯), and less than 70% was evaluated as defective (×).

  The measurement results are summarized in Table 1.

  From the result of Table 1, in Examples 1-6 which concern on the manufacturing method of this invention, there is no sedimentation of a flame retardant, a flame retardant can be added smoothly in aqueous suspension, and the dispersibility of a flame retardant is also favorable. there were. Furthermore, the foam molded body obtained by foam molding of the self-extinguishing foam polystyrene resin particles produced in Examples 1 to 6 is bonded at the time of foaming, the number of streaks, self-extinguishing measurement, and block fusion. Good results were obtained for each measurement item.

On the other hand, the comparative example 1 which added the flame retardant in the powder state was inferior about the coupling | bonding at the time of foaming, and the number of streaks generating.
In Comparative Example 2 in which a flame retardant dispersion was prepared without using a hardly water-soluble inorganic salt (magnesium pyrophosphate), the flame retardant immediately settled and separated after adjusting the flame retardant dispersion. The flame retardant dispersion was stirred and added with stirring. In Comparative Example 2, the number of streaks was greater than in Examples 1-6.
In Comparative Example 3, a flame retardant dispersion could not be prepared.
In Comparative Example 4 in which a flame retardant different from that in Comparative Example 1 was added in a powder state, as in Comparative Example 1, the number of bonds and streaks generated during foaming was poor.

Furthermore, about the self-extinguishing foaming polystyrene-type resin particle each manufactured in Examples 1-6 and Comparative Examples 1-4, the aromatic organic compound containing total amount was measured with the following measuring method.
<Total aromatic organic compound content>
After precisely weighing 1 g of self-extinguishing expandable polystyrene 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 weighed expandable polystyrene resin particles. Further, dimethylformamide was added to a dimethylformamide solution to prepare a measurement solution of 25 mL, and 1.8 μL of this measurement solution was supplied to a 230 ° C. sample vaporization chamber and gas chromatograph (manufactured by Shimadzu Corporation, trade name) The chart of each aromatic organic compound detected by “GC-14A” was obtained, and the amount of the aromatic organic compound was determined from each chart based on the calibration curve of each aromatic organic compound measured in advance. By calculating, the total amount of aromatic organic compounds in the expandable polystyrene resin particles was calculated.

Detector: FID
Column: GL Sciences (3mmφ × 2.5m)
Liquid phase: PEG-20M PT 25%
Carrier: Chromosorb W AW-DMCS
Mesh: 60/80
Column temperature: 100 ° C
Detector temperature: 230 ° C
DET temperature: 230 ° C
Carrier gas (nitrogen)
Carrier gas flow rate (40ml / min)

  The evaluation criteria for the total amount of aromatic organic compounds were evaluated as good (◯) when less than 2000 ppm and poor (×) when 2000 ppm or more. The measurement results are shown in Table 1.

Claims (4)

In a method for producing self-extinguishing expandable polystyrene resin particles by impregnating 0.3 to 2 parts by mass of a powdered flame retardant and a foaming agent with respect to 100 parts by mass of polystyrene resin particles in an aqueous suspension. ,
Before or during impregnation of the foaming agent, an aqueous suspension of a flame retardant dispersion in which 5 to 40 parts by weight of a flame retardant and 2 to 10 parts by weight of a water-insoluble inorganic salt are dispersed with respect to 100 parts by weight of an aqueous medium. A method for producing self-extinguishing foamable polystyrene resin particles, which is added to a liquid and impregnated with a flame retardant into resin particles.   The self-extinguishing expandable polystyrene resin particle according to claim 1, wherein the total content of aromatic organic compounds comprising styrene monomer, ethylbenzene, isopropylbenzene, normal propylbenzene, xylene, and toluene is less than 2000 ppm. Manufacturing method.   The method for producing self-extinguishing expandable polystyrene resin particles according to claim 1 or 2, wherein the average particle size of the flame retardant in the flame retardant dispersion is refined to less than 100 µm.   The method for producing self-extinguishing foamable polystyrene resin particles according to any one of claims 1 to 3, wherein a surfactant is added to the flame retardant dispersion.