JP2012153826A - Polystyrene resin foam, foaming polystyrene resin particle, and method for manufacturing the polystyrene resin foam and the foaming polystyrene resin particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polystyrene resin foam which has excellent foam molding property at the high foaming time, and has high bending strength.SOLUTION: The polystyrene resin foam contains 1 to 20 mass% of scale-like silicate having an average particle diameter of 5 to 200 μm and an aspect ratio of 30 or more.

Description

  The present invention relates to a polystyrene resin foam, expandable polystyrene resin particles, and a method for producing the same. More specifically, the present invention relates to a polystyrene resin foam excellent in foam moldability at the time of high foaming and excellent in bending strength, expandable polystyrene resin particles usable for the production of the foam, and a method for producing the same.

Polystyrene resin foams are generally foamed by heating and foaming expandable polystyrene resin particles with steam or the like to form pre-expanded particles, which are then filled into a closed mold having a large number of small holes, and heated again with pressurized steam or the like. It is manufactured by foaming, filling gaps between the foamed particles, and fusing the foamed particles together, then cooling and taking out from the mold.
The expandable polystyrene resin particles are usually produced by suspending and polymerizing a styrene monomer in water and impregnating with a foaming agent, or as disclosed in Japanese Patent Publication No. 49-2994 (Patent Document 1). The polystyrene resin particles are produced by suspending polystyrene resin particles in water, supplying a styrene monomer continuously or intermittently thereto to polymerize the resin, and impregnating with a foaming agent (seed polymerization method). Furthermore, it is manufactured by melting a polystyrene resin in an extruder, kneading the foaming agent, and then extruding it into a heated heating medium from a mold having small holes and cutting it into particles.
Polystyrene resin foams are used, for example, as packing materials such as fish boxes, heat insulation containers, and heat insulating materials for building materials. In particular, recently, high foaming has been demanded from the viewpoint of environment and cost.

Japanese Patent Publication No.49-2994

  However, when the foaming is increased, there is a problem that the mechanical strength of the foam is lowered. Therefore, a highly foamed foam that can be used for packing heavy materials or structural materials has been desired.

The inventor of the present invention has found that a polystyrene-based resin foam having sufficient mechanical strength can be provided even with high foaming by containing scaly silicate having an average particle diameter and an aspect ratio within a specific range. The present invention has been reached.
Thus, according to the present invention, there is provided a polypolystyrene-based resin foam characterized by containing 1 to 20% by mass of flaky silicate having an average particle size of 5 to 200 μm and an aspect ratio of 30 or more. .

Further, according to the present invention, in a dispersion obtained by dispersing polystyrene resin seed particles containing scaly silicate having an average particle diameter of 5 to 200 μm and an aspect ratio of 30 or more in water, a styrene monomer A monomer impregnation step for impregnating the polystyrene resin seed particles with
A polymerization step of polymerizing the styrenic monomer simultaneously with or after impregnation;
There is provided a method for producing expandable polystyrene resin particles characterized by including a foaming agent impregnation step of impregnating a foaming agent simultaneously with polymerization or after polymerization.
Furthermore, according to this invention, the expandable polystyrene resin particle obtained by the said method is provided.

ADVANTAGE OF THE INVENTION According to this invention, even if it is highly foamed, the foam which can contribute to resource saving with sufficient mechanical strength, the expandable polystyrene resin particle which can manufacture a foam, and its manufacturing method can be provided. For example, when the density is 20.0 kg / m ³ , a foam having a bending strength of 0.4 MPa or more can be provided.

Furthermore, when the scaly silicate is mica or sericite, a foam having more sufficient mechanical strength can be provided even with high foaming.
In addition, when the flaky silicate has an aspect ratio of 10 to 1000 and the polystyrene resin foam has a density of 10 to ³⁰ kg / m ³ , the foam moldability is excellent even when the density is lowered, and the bending strength is higher. It is possible to provide an excellent polystyrene resin foam.
Furthermore, since the scaly silicate is surface-treated with a surface treatment agent, expandable polystyrene resin particles having improved familiarity with polystyrene resin particles can be provided.

The inventor of the present invention reviewed the structure of the foam as described below in order to increase the foaming and the strength of the polystyrene resin foam (hereinafter also referred to as a foam).
That is, the strength of the foam is generally greatly influenced by the bubble diameter, the bubble film thickness, the bubble density, the open cell ratio, and the foam density forming the foam. Among them, it has been conventionally considered that increasing the number of bubble films by reducing the bubble diameter (making fine bubbles) is effective in improving the strength.
However, when the bubble diameter is reduced, the bubble film thickness is reduced, and the bubbles are torn by heating during molding, so that the moldability and strength are easily lowered. Thus, it was very difficult to achieve both low density and high strength.

Therefore, as a result of investigation by the present inventor, by containing 1 to 20% by mass of scaly silicate having an average particle diameter of 5 to 200 μm and an aspect ratio of 30 or more, the strength is reduced even when the foam is highly foamed. It was determined that fewer foams could be obtained. For example, a foam having a density of 20.0 kg / m ³ and a bending strength of 0.4 MPa or more can be provided. Further, for example, a bending strength of 0.3 MPa or more can be obtained with a foam having a density of 10.0 kg / m ³ , and a bending strength of 0.6 MPa or more can be obtained with a foam having a density of 30.0 kg / m ³ .

(Foam)
The foam of the present invention contains 1 to 20% by mass of flaky silicate having an average particle diameter of 5 to 200 μm and an aspect ratio of 30 or more.
The foam preferably has a density of 10 to ³⁰ kg / m ³ . By having the density in this specific range, a foam having higher bending strength can be provided. A more preferable density is 12.5 to 20.0 kg / m ³ .
The foam can be suitably used as a packaging material such as a fish box, a heat insulating container, and a heat insulating material for building materials.

(1) Scale-like silicate Scale-like silicate can realize high magnification and high strength by having an average particle size of 5 to 200 μm. When the average particle size is less than 5 μm, sufficient strength improvement may not be observed. On the other hand, when the average particle size is larger than 200 μm, the bubble film is likely to be broken at the time of foaming, and the foam moldability and strength may be reduced. A preferable average particle diameter is 10 to 150 μm.
Furthermore, scaly silicate has an aspect ratio of 30 or more. If the aspect ratio is less than 30, sufficient strength cannot be obtained, and foam moldability may be deteriorated. A preferred aspect ratio is 50 or more, and a more preferred aspect ratio is 70 or more. The upper limit of the aspect ratio is preferably 1000 from the viewpoint of reducing the tearing of the bubble film during foam molding.

The content of scaly silicate is 1 to 20% by mass. If it is less than 1 mass%, the heat insulation of a foam may fall. If the amount is more than 20% by mass, the foam film may be easily broken when the expandable polystyrene resin particles are expanded, and it may not be possible to increase the expansion ratio of the foam. The content is preferably 3 to 20% by mass, and more preferably 5 to 15% by mass.
Examples of scaly silicate include mica (for example, natural mica and synthetic mica), sericite, and the like. Unlike natural mica, synthetic mica is an artificially produced mica having a composition in which all —OH groups in the crystal structure of natural mica are substituted with —F groups, and KMg ₃ AlSi ₃ O ₁₀ F ₂ is the ideal composition.

The surface of the scaly silicate may be coated with a metal oxide. Examples of such metal oxides include titanium oxide and iron oxide. Specific examples of the scaly silicate having a surface coated include natural mica or synthetic mica whose surface is coated with titanium oxide, and natural mica or synthetic mica whose surface is coated with iron oxide.
The content of the metal oxide is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and particularly preferably 30 to 60% by mass in the scale-like silicate whose surface is coated with the metal oxide.

Furthermore, the surface of the scaly silicate is preferably treated with a silane coupling agent, a titanium coupling agent, or another surface treatment agent for the purpose of improving compatibility with the polystyrene resin.
This surface treatment is preferably performed at the stage of producing expandable polystyrene resin particles. Conventionally, the compatibility with the resin component is improved by the surface treatment of scaly silicate, but this is not preferable because the operation becomes complicated. By performing the surface treatment in the seed particles as in the present invention, the operation is simplified and the surface treatment agent can be used effectively.

(2) Polystyrene resin The foam contains a polystyrene resin. The polystyrene resin is not particularly limited, and for example, a styrene monomer such as styrene, α-methylstyrene, paramethylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromostyrene, or the like. Examples thereof include a polymer or a copolymer thereof. The polystyrene resin preferably contains 50% by mass or more of a component derived from styrene, and more preferably consists of polystyrene.

  The polystyrene resin may be a copolymer of a styrene monomer and a vinyl monomer copolymerizable with the styrene monomer. In the case of a copolymer, it is preferable that a component derived from a styrene monomer occupies a main component (50% by mass or more, preferably 80% by mass or more, more preferably 99.8 to 99.9% by mass). Examples of such vinyl monomers include alkyl (meth) acrylates having 1 to 8 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate, (meth) In addition to acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate, maleic anhydride, N-vinylcarbazole and the like can be mentioned.

(3) Manufacturing method of foam A foam can be manufactured with the following method, for example. First, polystyrene resin particles are impregnated with a foaming agent to obtain expandable polystyrene resin particles. Next, the expandable polystyrene resin particles are pre-expanded to obtain pre-expanded particles. Then, a foam can be manufactured by filling pre-expanded particles in a mold and heating and foaming.

Expandable polystyrene resin particles are, for example,
(I) Polystyrene resin seed particles (hereinafter referred to as seed particles) are dispersed in an aqueous medium, and a styrene monomer is continuously or intermittently supplied thereto, and suspension polymerization is performed in the presence of a polymerization initiator. Particles obtained by so-called seed polymerization method, or (ii) a styrenic monomer is continuously or intermittently supplied into an aqueous medium and subjected to suspension polymerization in the presence of a polymerization initiator, and a foaming agent The particle | grains obtained by the method of impregnating, what is called suspension polymerization method, etc. can be used.
In particular, the seed polymerization method is preferable for obtaining the foam of the present invention because the bubble diameter is easier to adjust than that obtained by the suspension polymerization method.

The expandable polystyrene resin particles obtained by the seed polymerization method can be manufactured through the following steps, for example.
(A) Polystyrene type by impregnating a polystyrene resin seed particle containing scale-like silicate dispersed in an aqueous medium in a reaction vessel with a styrene monomer, or polymerizing while impregnating. Step of obtaining resin particles (B) Step of impregnating polystyrene resin particles with foaming agent or impregnating foaming agent during polymerization of styrene monomer

(A) Seed particles As the monomer for obtaining seed particles, any of the styrenic monomers and vinyl monomers mentioned in the section of the foam can be used. When the polystyrene-based resin constituting the seed particles has a small styrene-converted weight average molecular weight, the mechanical strength of the foam obtained by foaming the expandable polystyrene-based resin particles may be lowered. On the other hand, if it is large, the foamability of the expandable polystyrene resin particles may decrease. A preferable average molecular weight is 120,000 to 600,000.
The seed particles can be produced by a general-purpose method. For example, seed particles can be produced by supplying a predetermined amount of polystyrene-based resin and scaly silicate to an extruder, melt-kneading, extruding into a strand form from the extruder, and cutting at predetermined lengths. It can also be produced by suspension polymerization, emulsion polymerization, bulk polymerization, or the like.

  If the particle size of the seed particles is within a narrow range, the particle size of the expandable polystyrene resin particles can be well aligned. In view of this, it is possible to use, as seed particles, particles prepared by once sieving the particles obtained by the suspension polymerization method so that the particle diameter is in the range of ± 20% of the average particle diameter. When seed particles are obtained by the bulk polymerization method, pellets having a desired particle size can be used. According to the seed polymerization method, expandable polystyrene resin particles having a desired particle size range according to the application can be produced with a yield of almost 100%. For example, particles classified as 0.3 to 0.5 mm, 0.5 to 0.7 mm, 0.7 to 1.2 mm, 1.2 to 1.5 mm, 1.5 to 2.5 mm are desired. It can select according to the average particle diameter of the expandable polystyrene-type resin particle to do.

The seed particles preferably contain a polystyrene-based resin and a scaly silicate.
It is preferable to use the scaly silicate contained in the seed particles in a range of 3 to 10 parts by mass with respect to 100 parts by mass of the polystyrene resin particles obtained from the seed particles. It is preferable to adjust the amount of seed particles used and the total amount of styrenic monomer supplied to the dispersion so as to fall within this range.
Furthermore, it is preferable that content of the scale-like silicate in a seed particle is 6.0-50.0 mass%. When there is little content of the scale-like silicate in a seed particle, the heat insulation of a foam may fall. On the other hand, when the foamable polystyrene resin particles are foamed, the foam film may be broken due to the scale-like silicate, and it may be difficult to obtain a foam having a high expansion ratio. A more preferable content is 10 to 40% by mass, and further preferably 15 to 25% by mass.

  The seed particles preferably contain 0.1 to 0.7% by mass of a polyolefin wax. When the content of the polyolefin wax is less than 0.1% by mass, the dispersion of the scaly silicate may be deteriorated. On the other hand, when it exceeds 0.7 mass%, the dissipation of the foaming agent from the expandable polystyrene resin particles may become too fast. More preferable content is 0.1-0.6 mass%, and still more preferable content is 0.1-0.5 mass%.

(B) Aqueous medium Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol).
(C) Styrenic monomer As the styrenic monomer, the styrenic monomer mentioned in the column of the foam can be used. Moreover, you may add the vinyl monomer quoted in the column of the said foam to the styrene-type monomer. As this vinyl monomer, divinylbenzene and alkylene glycol dimethacrylate are preferred. In addition, as the usage-amount of a vinyl monomer, 0.01-0.02 mol% is preferable with respect to the total amount of a styrene-type monomer and a vinyl monomer.

(D) Polymerization initiator As the polymerization initiator, any radical-generating polymerization initiator used in usual suspension polymerization of styrene can be used. For example, benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2,2-bis Organic peroxides such as (t-butylperoxy) butane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, azobisisobutyronitrile, Examples include azo compounds such as azobisdimethylvaleronitrile. These polymerization initiators may be used alone or in combination of two or more. In order to adjust the molecular weight and reduce the residual monomer, it is preferable to use a plurality of polymerization initiators having a decomposition temperature in the range of 80 to 120 ° C. in order to obtain a half-life of 10 hours.

(E) Use amount of seed particles The use amount of seed particles is preferably 10 to 90 mass%, more preferably 15 to 80 mass%, and particularly preferably 15 to 70 mass% with respect to the total amount of resin particles at the end of polymerization. %, Most preferably 15-50% by weight. If the amount of the seed particles used is less than 10% by mass, it becomes difficult to control the amount of the styrene monomer impregnated in the seed particles within a predetermined range, or the polystyrene resin constituting the polystyrene resin particles has a high molecular weight or A large amount of fine powder particles may be generated and the production efficiency may decrease. Moreover, when it exceeds 90 mass%, the scale-like silicate contained in seed particles will be in the state contained uniformly in the expandable polystyrene resin particle, and moldability may fall.

(F) Other components A suspension stabilizer may be used to stabilize the dispersibility of the styrene monomer droplets and seed particles.
Examples of the suspension stabilizer 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. Here, when a poorly soluble inorganic compound is used, an anionic surfactant is usually used in combination.
The anionic surfactant functions as an auxiliary stabilizer for stabilizing the dispersion by the suspension stabilizer, and a foam obtained by being partially dissolved or entrained in the polystyrene resin particles. May affect the size of air bubbles in the body. Therefore, what is necessary is just to select the kind of anionic surfactant so that it may fall in the range of a desired bubble film thickness.

  Examples of the anionic surfactant include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzenesulfonates such as calcium dodecylbenzenesulfonate and sodium dodecylbenzenesulfonate, alkyls Sulfonates such as naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, higher alcohol sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, polyoxy Examples thereof include sulfuric acid ester salts such as ethylene alkylphenyl ether sulfate, and phosphoric acid ester salts such as alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

  Furthermore, in order to adjust the average cell diameter of the foam, 5-10 minutes before the end of the seed polymerization, immediately after the end of the seed polymerization, or after impregnating the polystyrene resin particles with the foaming agent, You may add so that it may become 0.01-0.8 mass% in a polystyrene-type resin particle. Examples of such foam preparation agents include stearates such as ethylene bis stearic acid amide, triglycerin fatty acid esters, and the like.

(G) Polymerization conditions The polymerization is usually carried out by maintaining heating at 60 to 150 ° C for 1 to 10 hours, although it varies depending on the monomer species, polymerization initiator species, polymerization atmosphere species, and the like.
Examples of the polymerization atmosphere include an atmosphere in which the oxygen concentration in the reaction vessel during the polymerization reaction is maintained at 15% by volume or more. This particular oxygen concentration is useful when the foam contains scaly acid salts. That is, when the oxygen concentration is less than 15% by volume, a large amount of scaly silicate tends to be contained on the surface of the expandable polystyrene resin particles. Therefore, when the pre-expanded particles are secondarily expanded, bubbles on the surface of the pre-expanded particles may be broken by scaly silicate. As a result, high foaming magnification of the foam may be hindered. In addition, it is impossible to obtain a foaming pressure for sufficiently preliminarily fusing the pre-expanded particles by fusing, resulting in inadequate heat fusing integration between the expanded particles. The mechanical strength of the resulting foam may be reduced. A more preferable oxygen concentration is in the range of 15 to 21% by volume.
The amount of seed particles used and the total amount of styrenic monomer supplied to the dispersion are prepared so that the scale-like silicate contained in the seed particles is in the range of 1 to 20% by mass in the resulting foam. Is preferred.

  The styrene monomer is preferably supplied into the aqueous medium so that the amount of the styrene monomer in the seed particles from the beginning of impregnation of the styrene monomer to the end of polymerization is 60% by mass or less. By maintaining this amount of styrene monomer during polymerization, the styrene monomer is polymerized near the center of the seed particles, and as a result, the surface of the resulting expandable polystyrene resin particles contains a lot of scaly silicate. Can be prevented. The amount of styrenic monomer is preferably 40% by mass or less, and more preferably 30% by mass or less.

(H) Polystyrene resin particles The particle diameter of the polystyrene resin particles is preferably 0.3 to 2.0 mm from the viewpoint of filling into the mold of pre-expanded particles described later, More preferably, it is 1.4 mm.
Furthermore, if the polystyrene-based resin constituting the polystyrene-based resin particles has a small styrene-equivalent weight average molecular weight (Mw), the mechanical strength of the foam may decrease. On the other hand, if it is large, the foamability of the expandable polystyrene resin particles is lowered, and a foam with a high expansion ratio may not be obtained. The preferred weight average molecular weight is in the range of 120,000 to 600,000 suitable for ordinary foam molding. Moreover, it is preferable to prepare the weight average molecular weight of the seed particles in a range suitable for the above foam molding.

  In order to adjust the weight average molecular weight to a range suitable for ordinary foam molding, it is important to make the polymerization initiator work efficiently, and to prevent unnecessary decomposition and generate radicals throughout the polymerization process, In the distribution, polymerization temperature program, and seed polymerization method, it is preferable to further adjust and control the monomer supply rate, the polymerization rate during polymerization, and the like.

(I) Impregnation step The impregnation with the foaming agent may be performed on the particles after the polymerization of the styrene monomer, or the growing particles may be impregnated with the foaming agent. Impregnation during the polymerization can be performed by a method of impregnation in an aqueous medium (wet impregnation method). The impregnation after polymerization can be carried out by a wet impregnation method or a method of impregnation in the absence of a medium (dry impregnation method). Moreover, it is preferable to perform the impregnation in the middle of polymerization normally in the latter stage of polymerization.

As the foaming agent, a gaseous or liquid organic compound having a boiling point equal to or lower than the softening point of the polystyrene resin and normal pressure is suitable. For example, hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, petroleum ether, ketones such as acetone and methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, etc. Low boiling ether compounds such as alcohols, dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, halogen-containing hydrocarbons such as HCFC-141b, HCFC-142b, HCFC-124, HFC-134a, HFC-152a, carbonic acid Inorganic gases such as gas, nitrogen and ammonia can be used. These foaming agents may be used alone or in combination of two or more. Among these, it is preferable to use hydrocarbons from the viewpoint of preventing the destruction of the ozone layer, and from the viewpoint of quickly replacing with the air and suppressing the change with time of the foam. Among the carbon hydrogens, hydrocarbons having a boiling point of −45 to 40 ° C. are more preferable, and propane, n-butane, isobutane, n-pentane, isopentane and the like are more preferable.
The amount of the foaming agent used is preferably 1 to 10% by mass and more preferably 2 to 7% by mass with respect to 100 parts by mass of the expandable polystyrene resin particles.

(J) Expandable polystyrene resin particles The expandable polystyrene resin particles are particles obtained by the above method.
If the content of the foaming agent in the expandable polystyrene resin particles is small, it may be difficult to increase the expansion ratio of the foam, and the heat-sealing between the pre-expanded particles is insufficient. The appearance of may deteriorate. On the other hand, when the amount is large, the foam may shrink, or it may take time to adjust the foaming gas in the pre-foamed particles or foam molding, and the production efficiency may be reduced. The preferable content is 2.0 to 9.0% by mass of the total amount of the expandable polystyrene resin particles, and the more preferable content is 3.0 to 7.0% by mass. The content of the foaming agent in the expandable polystyrene resin particles was measured after being left in a thermostatic chamber at 13 ° C. for 5 days immediately after production.

(K) Others A solvent or a plasticizer may be added to the expandable polystyrene resin particles.
Examples of the solvent include aromatic organic compounds such as styrene, toluene, ethylbenzene, and xylene, cyclic aliphatic hydrocarbons such as cyclohexane and methylcyclohexane, ethyl acetate, and butyl acetate.
Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate, and diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.

When the content of the solvent and the plasticizer in the expandable polystyrene resin particles is small, the effect of adding the solvent and the plasticizer may not be exhibited. On the other hand, when the content is large, the foam obtained using the expandable polystyrene resin particles may be contracted or melted to deteriorate the appearance. A preferable content is 0.1 to 1.5% by mass of the total amount of the expandable polystyrene resin particles, and more preferably 0.2 to 1.0% by mass.
The impregnation with the solvent and the plasticizer can be performed on the particles after the polymerization of the styrene monomer or the seed particles during the styrene monomer impregnation. Further, a solvent or a plasticizer may be added to the seed particles in advance.

  When the impregnation temperature of the solvent and plasticizer into the polystyrene resin particles, seed particles or seed particles during impregnation with the styrene monomer is low, the impregnation takes time and the production efficiency of the expandable polystyrene resin particles may decrease. is there. On the other hand, when it is high, a large amount of coalescence between the expandable polystyrene resin particles may occur. The impregnation temperature is preferably 60 to 120 ° C, more preferably 70 to 100 ° C.

Furthermore, the expandable polystyrene resin particles of the present invention contain other additives such as a foamed cell nucleating agent, a filler, a flame retardant, a flame retardant aid, a lubricant, and a colorant as long as the physical properties are not impaired. You may go out. Other additives can be included in the expandable polystyrene resin particles in the same manner as the solvent and plasticizer.
Examples of the flame retardant include tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, and the like. And when there is little content of the flame retardant in an expandable polystyrene resin particle, the flame retardance of a foam may become inadequate. On the other hand, if it is large, the moldability of the foam may be lowered. The content of the flame retardant is preferably 0.5 to 1.5% by mass.
Moreover, as a flame retardant adjuvant, the organic peroxide like a dicumyl peroxide is mentioned, for example. And when there is little content of the flame retardant adjuvant in an expandable polystyrene-type resin particle, the effect which added the flame retardant adjuvant may not express. On the other hand, if it is large, the moldability of the foam may be lowered. The content of the flame retardant aid is preferably 0.05 to 0.5% by mass.

(L) Pre-expanded particles The expandable polystyrene resin particles are pre-expanded with water vapor using a pre-foaming machine to form pre-expanded particles having a large number of small holes. The bulk density of the pre-expanded particles is preferably in the range of 0.01 to 0.03 g / cm ³ . When the bulk density of the pre-expanded particles is smaller than 0.01 g / cm ³ , the resulting foam may shrink and the appearance may be deteriorated. In addition, the thermal insulation performance and mechanical strength of the foam may decrease. On the other hand, when the bulk density is larger than 0.03 g / cm ³ , not only the lightweight property of the foam is lowered, but also the effect of adding scaly silicate may be reduced.

(M) Molding of foam The pre-expanded particles are filled into a closed mold having a large number of small holes, and again heated and foamed with pressurized steam or the like to fill the gaps between the pre-expanded particles and A foam can be manufactured by integrating by fusing. At that time, the density of the foam can be adjusted, for example, by adjusting the filling amount of the pre-expanded particles in the mold.
The pre-expanded particles may be aged, for example, at normal pressure before molding the foam. The aging temperature of the pre-expanded particles is preferably 20 to 60 ° C. When the aging temperature is low, the aging time of the pre-expanded particles may be long. On the other hand, if it is high, the foaming agent in the pre-expanded particles may be dissipated and the moldability may be lowered.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples. Various measurement methods in the examples are described below.
<Average particle size and aspect ratio of scaly silicate>
Examples of the method for measuring the average particle size of the flaky silicate include a method for obtaining an average particle size by a microtrack laser diffraction method or a micro sieve mesh sieve method, a method for obtaining by observation with an electron microscope, and the like. Although the numerical value of the particle size varies depending on the measurement method, the micro sieve screen sieve method and the electron microscope are close to the actual particle size, and the micro track laser diffraction method is slightly larger than the actual value. The average particle diameter in the present specification is measured by a microtrack laser diffraction method from the viewpoint of ease of measurement and high reproducibility.

  The aspect ratio of the scaly silicate is measured under observation with a scanning electron microscope (Hitachi High-Technologies scanning electron microscope S-2400, hereinafter referred to as SEM). Specifically, the sample fixed on the SEM sample stage is increased from the direction of the cleaved surface (smooth surface) or laminated cross section (fracture surface) by increasing the observation magnification up to the maximum when one particle enters the field of view. Capture images (shoot). Next, the sample stage is rotated to capture (capture) an image from a direction different from the previous direction. From the image (photograph) thus obtained, the maximum length of the cleavage plane and the thickness of the laminated section are measured. Divide the measured value of the cleavage plane by the measured value of the laminated cross section to obtain the aspect ratio for each sample. This operation is performed on 100 mica flakes arbitrarily extracted. The average value of 100 aspect ratios is defined as the aspect ratio of the present specification.

<Styrene monomer amount>
The method for measuring the amount of styrene monomer in seed particles impregnated with styrene monomer (hereinafter referred to as growing particles) refers to that measured in the following manner.
That is, the growing particles are taken out from the dispersion, and the water adhering to the surface is wiped off with gauze. 0.08 g of the growing particles are collected, and the collected growing particles are dissolved in 24 ml of toluene to prepare a toluene solution. Next, 10 ml of the Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to the toluene solution. The result obtained by titrating the obtained solution with an N / 40 sodium thiosulfate solution is defined as a titration constant (milliliter) of the sample. The Wis reagent is obtained by dissolving 8.7 g of iodine and 7.9 g of iodine trichloride in 2 liters of glacial acetic acid.

On the other hand, without dissolving the growing particles, 10 ml of Wis reagent, 30 ml of 5% by weight potassium iodide aqueous solution and 30 ml of 1% by weight starch aqueous solution are added to 24 ml of toluene. The resulting solution was titrated with a N / 40 sodium thiosulfate solution to give a blank titration (in milliliters).
From the obtained droplet constant, the amount of styrene monomer in the growing particles is calculated based on the following formula.
Amount of styrenic monomer in the growing particles (% by mass)
= 0.1322 × (blank drop constant−sample drop constant) / sample drop constant

<Weight average molecular weight>
A weight average molecular weight means the styrene conversion weight average molecular weight measured in the following ways.
That is, 30 mg of polystyrene resin is dissolved in 10 ml of chloroform. The resulting solution is filtered through a non-aqueous 0.45 μm chromatographic disk, and the average molecular weight is measured under the following conditions using a chromatograph.
Gas chromatograph: Product name “Detector 484, Pump 510” manufactured by Water
Column: Showa Denko Corporation trade name “Shodex GPC K-806L (φ8.0 × 300 mm)” Column temperature: 40 ° C.
Carrier gas: Chloroform Carrier gas flow rate: 1.2 ml / min injection / pump temperature: room temperature detection: UV254 nm
Injection amount: Standard polystyrene for 50 microliter calibration curve: Trade name “shodex” manufactured by Showa Denko KK Weight average molecular weight: 1030000 Polystyrene

<Scaly silicate content>
The expandable polystyrene resin particles are treated at 150 ° C. for 3 hours to dissipate the foaming agent. Place 1.0 g (mass of sample before ashing) of the residue after dissipation into a magnetic crucible with a capacity of 30 mL. The residue is incinerated by heating at 550 ° C. for 5 hours in an electric furnace (muffle furnace STR-15K (made by Isuzu)). The magnetic crucible is allowed to cool to room temperature (25 ° C.) in a desiccator. The mass of the sample after ashing in the magnetic crucible after standing to cool is measured. By substituting the mass of the sample before and after ashing into the following equation, the scaly silicate content (parts by mass) relative to 100 parts by mass of the polystyrene resin is calculated.
Scale-like silicate content (parts by mass) = Sample mass after ashing / Sample mass before ashing

<Bulk density>
The bulk magnification of the pre-expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using pre-expanded particles as a measurement sample, and this measurement sample is naturally dropped into a measuring cylinder. The volume Vcm ³ of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. By substituting Wg and Vcm ³ into the following formula, the bulk density of the pre-expanded particles is calculated.
Bulk density of pre-expanded particles (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Foam density>
The mass (a) and the volume (b) of a test piece (example 75 × 300 × 35 mm) cut out from a foam (after molding and dried at 40 ° C. for 20 hours or more) are 3 significant digits or more, respectively. And the density of the foam (kg / m ³ ) is determined by the formula (a) / (b).

<Maximum bending strength>
The maximum bending strength of the foam is measured in accordance with the method described in JIS K9511: 1999 “Foamed plastic heat insulating material”. Specifically, a rectangular parallelepiped test piece having a length of 75 mm, a width of 300 mm, and a thickness of 30 mm is cut out from a foam having a density of 20 kg / m ³ . Thereafter, the maximum bending strength of the test piece was measured using a bending strength measuring device (trade name “UCT-10T” manufactured by Orientec Co., Ltd.), a compression speed of 10 mm / min, a distance between fulcrums of 200 mm, a pressure wedge 10R, and a support. The measurement is performed under the condition of the table 10R. Three test pieces are prepared, the maximum bending strength is measured for each test piece as described above, and the arithmetic average is defined as the maximum bending strength.
Evaluation: Maximum bending strength is 0.40 MPa or more: ○
Less than 0.40 MPa: ×

[Example 1]
7975 g of polystyrene resin having a weight average molecular weight of 180,000 (polystyrene manufactured by Sekisui Plastics Co., Ltd.), 2000 g of natural mica having an average particle diameter of 20 μm and an aspect ratio of 85, and 25 g of polyethylene wax (polywax 1000 manufactured by Baker Petrolite) Were fed to a twin screw extruder. The feed was melt kneaded at 230 ° C. and extruded from an extruder into a strand. This strand was cut into predetermined lengths to produce cylindrical seed particles (diameter: 0.8 mm, length: 0.8 mm).
Next, 2000 g of water, 500 g of seed particles, 6 g of magnesium pyrophosphate and 0.3 g of calcium dodecylbenzenesulfonate were supplied to a polymerization vessel equipped with a stirrer. The feed was heated to 75 ° C. with stirring to make a dispersion.

Subsequently, 3.0 g of a silane coupling agent (3-methacryloxypropylmethyldimethoxysilane), 9.0 g of benzoyl peroxide and 1.0 g of t-butylperoxybenzoate were dissolved in 200 g of styrene monomer. All of the styrene monomer-containing solution was fed into the dispersion with stirring.
And 60 minutes after finishing supplying a styrene monomer containing solution in a dispersion liquid, the dispersion liquid was made into 90 degreeC. Thereafter, seed polymerization was carried out while further supplying 1300 g of styrene monomer at a constant supply rate over 150 minutes. The seed polymerization was performed with the reaction vessel open to the atmosphere. The oxygen concentration in the void of the reaction vessel was 19.8%. Subsequently, the reaction vessel was sealed, heated to 125 ° C. and left at a constant temperature for 2 hours, and then cooled to room temperature (about 25 ° C.) to obtain polystyrene resin particles.

Next, the dispersion liquid in which the polystyrene resin particles were dispersed was kept at 90 ° C. Subsequently, 162 g of butane was injected into the reaction vessel and then held for 6 hours to impregnate the polystyrene resin particles with butane. Thereafter, the inside of the reaction vessel was cooled to 25 ° C. to obtain expandable polystyrene resin particles.
After applying polyethylene glycol as an antistatic agent to the surface of the expandable polystyrene resin particles, zinc stearate and hydroxystearic acid triglyceride were applied to the surface of the expandable polystyrene resin particles. The coating amounts of zinc stearate and hydroxystearic acid triglyceride were adjusted to 0.05 mass% in the expandable polystyrene resin particles, respectively.

Thereafter, the expandable polystyrene resin particles were left in a thermostatic chamber at 13 ° C. for 5 days. The butane content in the expandable polystyrene resin particles after standing was measured by gas chromatography to be 5.8% by mass.
Then, the expandable polystyrene resin particles were heated and pre-expanded to a bulk density of 0.019 g / cm ³ to obtain pre-expanded particles. The pre-expanded particles were aged at 20 ° C. for 24 hours.

Next, the pre-expanded particles were filled in a mold and heated and foamed to obtain a foam having a length of 400 mm × width of 300 mm × thickness of 30 mm. After the foam was dried in a drying room at 50 ° C. for 6 hours, the density of the foam was measured and found to be 20 kg / m ³ . This foam was excellent in appearance without shrinkage.
The scaly silicate content of the foam and the maximum bending strength of the polystyrene resin foam were measured. As a result, the content of mica was 4.9% by mass, and the maximum bending strength was 0.48 MPa.

[Example 2]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle size of 8 μm and an aspect ratio of 80 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 4.8% by mass, and the maximum bending strength was 0.47 MPa.

[Example 3]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle size of 15 μm and an aspect ratio of 84 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 5.0% by mass, and the maximum bending strength was 0.48 MPa.

[Example 4]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle size of 55 μm and an aspect ratio of 89 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 4.9% by mass, and the maximum bending strength was 0.48 MPa.

[Example 5]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle size of 100 μm and an aspect ratio of 90 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 4.8% by mass, and the maximum bending strength was 0.47 MPa.

[Example 6]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle size of 155 μm and an aspect ratio of 87 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 5.1% by mass, and the maximum bending strength was 0.46 MPa.

[Example 7]
A foam was obtained in the same manner as in Example 1 except that sericite having an average particle diameter of 15 μm and an aspect ratio of 80 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 4.8% by mass, and the maximum bending strength was 0.46 MPa.

[Example 8]
A silane-based cup using 8584 g of polystyrene resin having a weight average molecular weight of 180,000, 1400 g of natural mica having an average particle diameter of 20 μm and an aspect ratio of 85, and 16 g of polyethylene wax (manufactured by Baker Petrolite: Polywax 1000) A foam was obtained in the same manner as in Example 1 except that 2.1 g of a ring agent (3-methacryloxypropylmethyldimethoxysilane) was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 2.8% by mass, and the maximum bending strength was 0.43 MPa.

[Example 9]
A polymerization vessel equipped with a stirrer was supplied with 2000 g of water, 1000 g of cylindrical seed particles obtained in the same manner as in Example 1, 6 g of magnesium pyrophosphate and 0.3 g of calcium dodecylbenzenesulfonate, and heated to 75 ° C. while stirring. A dispersion was prepared.
Subsequently, 6.0 g of a silane coupling agent (3-methacryloxypropylmethyldimethoxysilane), 9.0 g of benzoyl peroxide and 1.0 g of t-butyl peroxybenzoate were dissolved in 200 g of styrene monomer. All of the styrene monomer-containing solution was fed into the dispersion with stirring.

And 60 minutes after finishing supplying a styrene monomer containing solution in a dispersion liquid, the dispersion liquid was made into 90 degreeC. Thereafter, seed polymerization was carried out while 200 g of styrene monomer was further fed into the dispersion at a constant feed rate over 60 minutes. The seed polymerization was performed with the reaction vessel open to the atmosphere. The oxygen concentration in the void of the reaction vessel was 19.8%. Subsequently, the reaction vessel was sealed, heated to 125 ° C. and left at a constant temperature for 2 hours, and then cooled to room temperature to obtain polystyrene resin particles.
Next, a foam was obtained from the polystyrene resin particles in the same manner as in Example 1.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 14.3% by mass, and the maximum bending strength was 0.44 MPa.

[Comparative Example 1]
A polystyrene resin having a weight average molecular weight of 180,000 was supplied to a twin screw extruder. The feed was melt kneaded at 230 ° C. and extruded from an extruder into a strand. This strand was cut into predetermined lengths to produce cylindrical seed particles (diameter: 0.8 mm, length: 0.8 mm). A foam was obtained in the same manner as in Example 1 except that these seed particles were used. As in Example 1, the maximum bending strength of the foam was measured. The maximum bending strength was 0.37 MPa.
Since the foam obtained in Comparative Example 1 did not contain scaly silicate, it was inferior in mechanical strength.

[Comparative Example 2]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle diameter of 3 μm and an aspect ratio of 70 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 4.9% by mass, and the maximum bending strength was 0.38 MPa.
The foam obtained in Comparative Example 2 had a small flaky silicate particle size and was inferior in bending strength.

[Comparative Example 3]
A foam was obtained in the same manner as in Example 1 except that natural mica having an average particle size of 300 μm and an aspect ratio of 85 was used.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 4.9% by mass, and the maximum bending strength was 0.33 MPa.
The foam obtained in Comparative Example 3 was inferior in foam moldability due to the large particle size of the scaly silicate, and was insufficient in strength.

[Comparative Example 4]
Example 1 was used except that seed particles obtained from 9784 g of polystyrene resin having a weight average molecular weight of 180,000, 200 g of natural mica having an average particle diameter of 20 μm and an aspect ratio of 85, and 16 g of polyethylene wax were used. To obtain a foam.
As in Example 1, the flaky silicate content in the expandable polystyrene resin particles and the maximum bending strength of the foam were measured. The content of natural mica was 0.5% by mass, and the maximum bending strength was 0.37 MPa.
The foam obtained in Comparative Example 4 was inferior in bending strength.

Claims (8)

  A polystyrene-based resin foam comprising 1 to 20% by mass of flaky silicate having an average particle diameter of 5 to 200 μm and an aspect ratio of 30 or more.   The polystyrene resin foam according to claim 1, wherein the scaly silicate is mica or sericite. The polystyrene resin foam according to claim 1 or 2, wherein the polystyrene resin foam has a bending strength of 0.4 MPa or more when the density is 20.0 kg / m ³ . In a dispersion obtained by dispersing polystyrene resin seed particles containing scaly silicate having an average particle diameter of 5 to 200 μm and an aspect ratio of 30 or more in water, a styrene monomer is used as the polystyrene resin seed particles. A monomer impregnation step for impregnation;
A polymerization step of polymerizing the styrenic monomer simultaneously with or after impregnation;
A method for producing expandable polystyrene resin particles, comprising a foaming agent impregnation step of impregnating a foaming agent simultaneously with polymerization or after polymerization. The monomer impregnation step
The surface of the scaly silicate is treated with the surface treating agent by impregnating the polystyrene resin seed particles with the surface treating agent of the scaly silicate and the polymerization initiator together with the first styrene monomer, and then polymerizing. And a process of
The second styrene monomer is added to the polystyrene-based resin seed particles containing the surface-treated scale-like silicate, and the second styrene monomer is contained in the polystyrene-based resin seed particles in a reaction vessel in which an oxygen concentration is maintained at 15% or more. The method for producing expandable polystyrene resin particles according to claim 4, further comprising a step of impregnating so that the amount of the styrene monomer of 2 is 60% by weight or less.   The method for producing expandable polystyrene resin particles according to claim 4 or 5, wherein the scaly silicate is mica or sericite.   Expandable polystyrene resin particles obtained by the method according to any one of claims 4 to 6.   Polystyrene resin foam particles obtained by foaming the expandable polystyrene resin particles according to claim 7.