HK1162561A - Fire resistant expansible polystyrene resin particle - Google Patents

Description

Flame-retardant expandable polystyrene resin particles

Technical Field

The present invention relates to flame-retardant expandable polystyrene resin particles. More specifically, the present invention relates to flame-retardant expandable polystyrene resin particles using tetrabromocyclooctane as a flame retardant.

Background

Expandable polystyrene resin particles are used in a wide range of applications, and are used in the fields of agricultural and aquatic products, household electrical appliances, building materials and civil engineering. In particular, in the field of building materials, a polystyrene-based foam molded article used as a heat insulating material for walls and floors is strongly desired to have a foam molded article excellent in heat insulating performance from the viewpoint of energy saving, and is also required to have flame retardant performance.

In the above-mentioned method for producing expandable polystyrene-based resin particles, a method of adding a flame retardant together with a styrene-based monomer at the time of polymerization, a method of adding a flame retardant at the time of impregnating polystyrene-based resin particles with a foaming agent, and the like are employed. The former method is described in 2003-335891 (patent document 1) and the latter method is described in 2007-246606 (patent document 3).

Patent document 1: japanese patent laid-open publication No. 2003-335891

Patent document 2: japanese laid-open patent publication No. 2002-194130

Patent document 3: japanese laid-open patent publication No. 2007-246606

Disclosure of Invention

In the former method, Hexabromocyclododecane (HBCD) is mainly used as a flame retardant. HBCD is a substance that is considered to be accumulated in the living body, and is not desired to be used. In the latter method, Tetrabromocyclooctane (TBCO) is mainly used, but the TBCO monomer is in a powder form, and there is a problem that the TBCO adheres to each other in a pellet form due to the storage state. The TBCO is formed in a pellet shape, and the dispersion of the flame retardant becomes uneven, and as a result, the absorption of the powdery flame retardant by the resin particles becomes uneven, and there is a problem that a part of the resin particles absorb the flame retardant in a large amount. Further, since the flame retardant is formed into a pellet shape, there is a problem that the workability in the production process is poor.

An object of the present invention is to provide flame-retardant expandable polystyrene resin particles which, even when powdered Tetrabromocyclooctane (TBCO) is used as a flame retardant, can prevent the TBCO from being unevenly absorbed by the resin particles and can prevent the TBCO from being formed into a pellet shape, thereby improving the workability in the production process.

The present inventors have found that by using a specific amount of a flame retardant which is not accumulated in a living body and which is excellent in handling properties in a production process, expandable polystyrene resin particles which are excellent in heat-fusion properties between particles when expanded and which can give an expanded molded article having excellent flame retardancy can be provided, and have completed the present invention.

The flame-retardant expandable styrene-based resin particles of the present invention are characterized in that: before or during impregnation of a foaming agent into polystyrene resin particles dispersed in an aqueous suspension, tetrabromocyclooctane as a powdery flame retardant dispersed by silica fine powder is impregnated, and the flame-retardant foamable polystyrene resin particles are taken out from the aqueous suspension, wherein 0.45 to 2.0 parts by weight of the tetrabromocyclooctane is added to 100 parts by weight of the polystyrene resin, and the flame retardant contains 0.3 to 1.5 parts by weight of the silica fine powder to 98.5 to 99.7 parts by weight of the tetrabromocyclooctane.

The method for producing flame-retardant expandable polystyrene resin particles of the present invention is characterized by comprising: before or during impregnation of a foaming agent into polystyrene resin particles dispersed in an aqueous suspension, 0.45-2.0 parts by weight of tetrabromocyclooctane dispersed by silicon dioxide fine powder as a powdery flame retardant is impregnated into the polystyrene resin particles, and the flame-retardant foamable polystyrene resin particles are obtained by taking out the polystyrene resin particles from the aqueous suspension, wherein the powdery flame retardant contains 0.3-1.5 parts by weight of the silicon dioxide fine powder relative to 98.5-99.7 parts by weight of tetrabromocyclooctane.

Effects of the invention

Thus, the flame-retardant expandable polystyrene particles of the present invention are characterized in that: the flame retardant is uniformly absorbed in the expandable polystyrene-based particles. The added flame retardant is prepared by adding silicon dioxide micro powder into tetrabromocyclooctane, and the dispersibility of the tetrabromocyclooctane is obviously improved by adding the silicon dioxide micro powder. Therefore, flame-retardant expandable polystyrene resin particles which have extremely good workability in production, can uniformly absorb a flame retardant into expandable polystyrene resin particles, and have good heat-fusion properties during molding can be provided.

Further, since tetrabromocyclooctane is uniformly and stably dispersed in the fine silica powder, the tetrabromocyclooctane does not cause secondary aggregation and sedimentation, and the problem of clogging of piping lines and the like due to the tetrabromocyclooctane does not occur.

In addition, since all the fine silica powder added to the flame retardant flows out in the drainage water in the production process, only the flame retardant is absorbed in the obtained expandable polystyrene resin particles. Further, since the fine silica powder is not absorbed, the flame retardancy of the foam obtained from the flame-retardant expanded polystyrene particles is not lowered.

Further, since the expanded polystyrene resin is a foam obtained from a flame-retardant expanded polystyrene resin containing no HBCD flame retardant, expandable polystyrene resin particles which are not accumulated in a living body and can be molded into a product having excellent heat insulation properties and flame retardancy can be obtained.

Detailed Description

The method for producing flame-retardant expandable polystyrene resin particles is characterized in that before or during impregnation of a foaming agent into polystyrene resin particles dispersed in an aqueous suspension, 0.45-2.0 parts by weight of a powdery flame retardant tetrabromocyclooctane is impregnated into the polystyrene resin particles to obtain flame-retardant expandable polystyrene resin particles, wherein the flame retardant comprises 98.5-99.7 parts by weight of tetrabromocyclooctane and 0.3-1.5 parts by weight of a silica fine powder. However, if tetrabromocyclooctane is added after impregnation with a blowing agent, there is a problem that the obtained flame-retardant expandable polystyrene resin particles are cured.

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

Polystyrene resin particles produced by a known method can be used as the polystyrene resin particles in the present invention, and examples thereof include the following methods:

(1) a suspension polymerization method in which an aqueous medium, a styrene monomer and a polymerization initiator are supplied into an autoclave, and the styrene monomer is suspension-polymerized while being heated and stirred in the autoclave to produce polystyrene resin particles;

(2) a seed polymerization method comprising supplying an aqueous medium and polystyrene resin seed particles into an autoclave, dispersing the polystyrene resin seed particles in the aqueous medium, heating and stirring the autoclave while continuously or intermittently supplying a styrene monomer to allow the polystyrene resin seed particles to absorb the styrene monomer, and polymerizing the styrene monomer in the presence of a polymerization initiator to produce polystyrene resin particles. Among them, polystyrene resin seed particles can be produced and classified by the suspension polymerization method of the above (1).

Among them, examples of the polystyrene-based resin of the present invention include homopolymers of styrene-based monomers such as styrene, α -methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, and bromostyrene, and copolymers thereof.

The polystyrene resin may be a copolymer of the above-mentioned styrene monomer as a main component and a vinyl monomer copolymerizable with the styrene monomer, and examples of such vinyl monomer include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and hexadecyl (meth) acrylate, alkyl (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, and ethyl fumarate, and besides, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate.

In addition, the average particle diameter of the polystyrene resin particles is preferably 0.3 to 2.0mm, more preferably 0.6 to 1.4mm, from the viewpoint of filling the cavity with pre-expanded particles obtained by pre-expanding the flame-retardant expandable polystyrene resin particles when the flame-retardant expandable polystyrene resin particles are used for in-mold foam molding.

Further, 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 flame-retardant polystyrene-based resin foamed molded article obtained by foaming the flame-retardant expandable polystyrene-based resin particles is lowered, while if it is large, the expandability of the flame-retardant expandable polystyrene-based resin particles is lowered, and there is a tendency that a flame-retardant polystyrene-based resin foamed molded article having a high expansion ratio cannot be obtained, and therefore, it is preferably from 20 to 50 ten thousand, and more preferably from 24 to 40 ten thousand.

The polymerization initiator used in the suspension polymerization method and the seed polymerization method is not particularly limited, and examples thereof include benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, isopropyl carbonate, t-butyl peroxyacetate, 2-bis (t-butyl peroxy) butane, t-butyl peroxy-3, 3, 5-trimethylhexanoate, di-t-butyl peroxyhexahydroterephthalate and other organic peroxides, and azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile and the like, and these may be used alone or in combination of two or more.

The aqueous suspension obtained by dispersing the polystyrene resin particles in an aqueous medium may be an aqueous suspension obtained by using a reaction solution after polymerization by the suspension polymerization method or the seed polymerization method, or an aqueous suspension obtained by separating the polystyrene resin particles obtained by the suspension polymerization method or the seed polymerization method from the reaction solution and suspending the polystyrene resin particles in a separately prepared aqueous medium. The aqueous medium is not particularly limited, and examples thereof include water and ethanol (alcohol), with water being preferred.

In the suspension polymerization method or seed polymerization method, a suspension stabilizer may be used in order to stabilize the dispersibility of the styrene monomer droplets or polystyrene resin seed particles in the polymerization of the styrene monomer, and examples of such a suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyacrylamide, and polyvinylpyrrolidone, and water-insoluble inorganic salts such as tricalcium phosphate and magnesium pyrophosphate.

Examples of the anionic surfactant include alkyl sulfates such as sodium dodecyl sulfate, alkyl benzene sulfonates such as sodium dodecyl benzene sulfonate, higher fatty acid salts such as sodium oleate, and β -tetrahydroxynaphthalene sulfonate, with alkyl benzene sulfonates being preferred.

In the method for producing flame-retardant expandable polystyrene resin particles of the present invention, the polystyrene resin particles dispersed in the aqueous suspension are impregnated with the blowing agent in a known manner. As such a blowing agent, organic compounds having a boiling point of not higher than the softening point of the polystyrene resin and being gaseous or liquid under normal pressure are suitable, and examples thereof include hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, and petroleum ether, ketones such as acetone and methyl ethyl ketone, alcohols such as methanol, ethanol, and isopropanol, low-boiling ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether, inorganic gases such as carbon dioxide gas, nitrogen gas, and ammonia gas, and hydrocarbons having a boiling point of-45 to 40 ℃ are preferred, and propane, n-butane, isobutane, n-pentane, and isopentane are more preferred. The blowing agent may be used alone or in combination of two or more.

In the method for producing flame-retardant expandable polystyrene resin particles of the present invention, before or during impregnation of a foaming agent into polystyrene resin particles dispersed in an aqueous suspension, tetrabromocyclooctane as a powdery flame retardant is supplied to the aqueous suspension, and the polystyrene resin particles are impregnated with the powdery flame retardant under pressure. The aqueous medium is not particularly limited as long as it is compatible with the aqueous suspension in which the polystyrene resin particles are dispersed, and examples thereof include water and ethanol (alcohol), with water being preferred.

In order to improve the dispersibility, fine silica powder is added to the powdery flame retardant tetrabromocyclooctane. The method of adding the fine silica powder to tetrabromocyclooctane is preferably mixing in a mixer such as a henschel mixer for a certain time.

The fine silica powder added to the powder flame retardant tetrabromocyclooctane has a specific surface area of 170 to 330m²(ii)/g, good hydrophilicity and hydrophobicity, more preferably 200m in specific surface area²(ii) in terms of/g. In addition, if the specific surface area is less than 170m²The dispersibility of tetrabromocyclooctane cannot be improved, and as a result, the tetrabromocyclooctane undergoes secondary aggregation. In addition, if the specific surface area is more than 330m²The amount of fine silica powder scattered increases, which results in a problem of poor workability in production.

The amount of the fine silica powder added to tetrabromocyclooctane is preferably 0.3 to 1.5 parts by weight of the fine silica powder based on 98.5 to 99.7 parts by weight of tetrabromocyclooctane, and the lower limit is more preferably 0.5 part by weight. If it is less than 0.3 part by weight, the dispersibility of tetrabromocyclooctane is not improved, and as a result, secondary aggregation of tetrabromocyclooctane occurs. On the other hand, if it exceeds 1.5 parts by weight, the amount of fine silica powder scattered increases, and there is a problem that the workability in production is deteriorated.

The content of tetrabromocyclooctane is preferably adjusted to 0.45 to 2.0 parts by weight, more preferably 0.6 to 1.5 parts by weight, and particularly preferably 0.7 to 1.0 part by weight, based on 100 parts by weight of polystyrene resin particles. When the amount is less than 0.45 part by weight, the flame retardancy of the resulting flame-retardant expandable polystyrene-based resin molded article is lowered. On the other hand, if it exceeds 2.00 parts by weight, the production cost increases, while the amount of blocking during the pre-expansion increases, and the filling property of the pre-expanded beads into the mold of the molding machine deteriorates.

After flame-retardant expandable polystyrene resin particles are produced by impregnating polystyrene resin particles dispersed in an aqueous suspension with a blowing agent and a powdery flame retardant, the flame-retardant expandable polystyrene resin particles are taken out from the aqueous suspension, and if necessary, the flame-retardant expandable polystyrene resin particles may be subjected to a washing treatment and a drying treatment.

In addition, from the viewpoint of filling the cavity with pre-expanded beads obtained by pre-expanding the flame-retardant expandable polystyrene resin beads during in-mold expansion molding, the average particle diameter of the flame-retardant expandable polystyrene resin beads is preferably 0.3 to 2.0mm, more preferably 0.6 to 1.4 mm.

In addition, in the flame-retardant expandable polystyrene resin particles, additives such as a bubble control agent, a filler, a flame-retardant auxiliary, a lubricant, a colorant, and a solvent may be added as necessary within a range not to impair physical properties in addition to the powdery flame retardant, and when these additives are added to the flame-retardant expandable polystyrene resin particles, the additives may be added to an aqueous suspension in which the polystyrene resin particles are dispersed.

Next, a description will be given of a method for producing a flame-retardant polystyrene resin foamed molded article by using the flame-retardant expandable polystyrene resin particles. As a method for producing a flame-retardant polystyrene resin foamed molded article using the flame-retardant expandable polystyrene resin particles, a known method can be used, and specifically, the flame-retardant expandable polystyrene resin particles can be pre-expanded by heating to have a bulk density of 0.01 to 0.05g/cm³The left and right polystyrene resin pre-expanded beads are filled in the cavity of the mold and heated to expand the beads, whereby a flame-retardant polystyrene resin foamed molded article can be obtained.

When the density of the above-mentioned flame-retardant polystyrene-based resin foam molded article is low, the independent cell ratio of the flame-retardant polystyrene-based resin foam molded article is lowered, and the heat insulating property and mechanical strength of the flame-retardant polystyrene-based resin foam molded article are lowered, while when the density is high, the time required for one cycle of the foam molded article in the mold is prolonged, and the production efficiency of the flame-retardant polystyrene-based resin foam molded article is lowered, and therefore, it is preferable that the density is 0.01 to 0.05g/cm³。

Examples

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

(example 1)

Production example 120g of tricalcium phosphate (produced by Daping chemical Co., Ltd.), 2.4g of sodium dodecylbenzenesulfonate, 140g of benzoyl peroxide (purity: 75% by weight), 30g of t-butylperoxy-2-ethylhexyl monocarbonate, 40kg of ion-exchanged water, and 40kg of styrene monomer were put into an autoclave having an internal volume of 100 liters and equipped with a stirrer, and stirred with a stirring paddle rotating at 100rpm to form an aqueous suspension.

Subsequently, while the stirring paddle was rotated at 100rpm to stir the aqueous suspension, the temperature in the autoclave was raised to 90 ℃ and maintained at 90 ℃ for 6 hours, and the temperature in the autoclave was raised to 120 ℃ and maintained at 120 ℃ for 2 hours, thereby suspension-polymerizing the styrene monomer.

Then, the temperature in the autoclave was cooled to 25 ℃, polystyrene particles were taken out from the autoclave, washed and dehydrated repeatedly for many times, and after the drying process, the polystyrene particles were classified to obtain polystyrene particles having a particle diameter of 0.6 to 0.85mm and a weight average molecular weight of 30 ten thousand.

Next, 30kg of ion-exchanged water, 4g of sodium dodecylbenzenesulfonate and 100g of magnesium pyrophosphate were charged into a separate 100-liter autoclave equipped with a stirrer, and 11kg of the above polystyrene beads were charged into the autoclave as seed particles, followed by stirring to uniformly disperse the seed particles in water.

Further, 2g of sodium dodecylbenzenesulfonate and 20g of magnesium pyrophosphate were dispersed in 6kg of ion exchange water to prepare a dispersion, 88g of benzoyl peroxide (purity: 75%) as a polymerization initiator and 50g of t-butylperoxy-2-ethylhexyl monocarbonate were dissolved in 5kg of a styrene monomer to prepare a styrene monomer solution, and the styrene monomer solution was added to the dispersion and stirred with a homomixer to emulsify the styrene monomer solution to obtain an emulsion.

Then, the autoclave was heated to 75 ℃ and held, then the above emulsion was added to the autoclave and held for 30 minutes so that the styrene monomer and benzoyl peroxide were smoothly absorbed into the polystyrene seed particles, and then 28kg of the styrene monomer was continuously dropped into the autoclave over 160 minutes while the autoclave was heated from 75 ℃ to 108 ℃ at a heating rate of 0.2 ℃/minute, and then 20 minutes after completion of dropping of the styrene monomer, the autoclave was heated to 120 ℃ at a heating rate of 1 ℃/minute and held for 90 minutes, and the polystyrene particles were obtained by seed polymerization. In addition, all styrene monomers were used for polymerization.

(example 1)

2.24g of silica (trade name "AEROSIL 200", manufactured by AEROSIL CORPORATION, Japan) was added as a fluidizing agent to 440g of tetrabromocyclooctane (trade name "ピロガ - ド FR-200", manufactured by first Industrial pharmaceutical Co., Ltd.) as a flame retardant, and the mixture was dry-mixed (for example, Henschel mixer) to prepare flame retardant A.

Subsequently, the autoclave was cooled to 90 ℃ at a cooling rate of 1 ℃/min, 132g of dicumyl peroxide was added to the autoclave as a flame retardant aid, and the flame retardant A was added to the autoclave.

After 30 minutes, the autoclave was closed, and then, 2640g of butane (isobutane/n-butane (weight ratio) 30/70) and 1100g of pentane (isopentane/n-pentane (weight ratio) 20/80) were introduced into the autoclave as blowing agents under pressure with nitrogen for 30 minutes, and the mixture was held in this state for 3 hours.

Then, the autoclave was cooled to 25 ℃ and the flame-retardant expandable polystyrene particles were taken out from the autoclave, washed and dehydrated repeatedly for a plurality of times, and subjected to a drying step, and then the flame-retardant expandable polystyrene particles were classified to obtain flame-retardant expandable polystyrene particles having a particle diameter of 0.85 to 1.2mm, an average particle diameter of 1.1mm, and a weight average molecular weight of 30 ten thousand.

The powdery flame retardant of the flame retardant a was entirely impregnated with polystyrene particles.

(example 2)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that the amount of tetrabromocyclooctane was changed to 220g in the preparation of flame retardant A.

(example 3)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that the amount of tetrabromocyclooctane was changed to 660g in the preparation of flame retardant A.

(example 4)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that the amount of tetrabromocyclooctane was 880g in the preparation of flame retardant A.

(example 5)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1, except that 4.48g of hydrophilic silica was used instead of 2.24g of hydrophilic silica in the preparation of the flame retardant A.

(example 6)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1, except that 6.72g of hydrophilic silica was used instead of 2.24g of hydrophilic silica in the preparation of the flame retardant A.

(example 7)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that hydrophilic silica (product name "AEROSIL 300" manufactured by AEROSIL corporation, Japan) was used as a fluidizing agent in the preparation of the flame retardant A.

(example 8)

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that hydrophobic silica (product name "AEROSILR 974" available from AEROSIL corporation, Japan) was used as a fluidizing agent in the preparation of the flame retardant A.

Comparative example 1

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that the amount of tetrabromocyclooctane was 88g in the preparation of the flame retardant A.

Comparative example 2

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that the amount of tetrabromocyclooctane used in the preparation of flame retardant A was 1320 g.

Comparative example 3

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1, except that hydrophilic silica was not used for the preparation of the flame retardant a.

Comparative example 4

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1, except that 0.22g of hydrophilic silica was used instead of 2.24g of hydrophilic silica in the preparation of the flame retardant A.

Comparative example 5

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1, except that 8.96g of hydrophilic silica was used instead of 2.24g of hydrophilic silica in the preparation of the flame retardant A.

Comparative example 6

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that hydrophilic silica (product name "AEROSIL 130" of japan AEROSIL) was used as a fluidizing agent in the preparation of the flame retardant a.

Comparative example 7

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that hydrophilic silica (product name "AEROSIL 380" from aesosil corporation, japan) was used as a fluidizing agent in the preparation of the flame retardant a.

Comparative example 8

Flame-retardant expandable polystyrene particles were obtained in the same manner as in example 1 except that 88.0g of tetrabromobisphenol A-bis (2, 3-dibromopropylether) was used in place of 2.24g of hydrophilic silica in the preparation of flame retardant A.

The following evaluations were made for the above examples and comparative examples as shown in tables 1 and 2.

[ method for measuring specific surface area of silica ]

The method for measuring the specific surface area of the fine silica powder used in the present invention is entirely based on the BET method.

[ blocking evaluation of flame retardant A ]

100g of flame retardant was added to a polyethylene bag, the mixture was packed into a 50mm diameter tube, and a 1.1kg weight was placed thereon, and the tube was kept in an oven at 40 ℃ for 1 month, and then taken out, observed and evaluated.

In a very hard state, the flame retardant solidified without disintegrating even with hand.

In the hard state, the flame retardant sets but disintegrates if held in the hand.

Have a tight feel, but do not coagulate, in a loose state.

[ Molding of polystyrene foam molded article ]

40kg of the obtained flame-retardant expandable polystyrene particles, 20g of polyethylene glycol as a surface treatment agent, 60g of zinc stearate, 40g of fatty acid triglyceride (product of Rakan ビタミン, trade name: リケマ - ル VT-50) and 20g of fatty acid monoglyceride (product of Rakan ビタミン, trade name: リケマ - ル S-100P) were charged into a tumbler mixer, and stirred for 30 minutes to coat the surface of the flame-retardant expandable polystyrene particles with the surface treatment agent.

Subsequently, after the flame-retardant expandable polystyrene particles were kept in a refrigerator at 15 ℃ for 48 hours, 5.8kg of flame-retardant expandable polystyrene particles were added to 1 liter of the cylindrical batch pressure pre-expander having a volume of 350 liters up to the upper surface of the foamed layer as described in Japanese patent publication 57(1982) -133[3347] publicly known and conventional technical group (foam molding) on page 39, and the mixture was heated with steam for 2 minutes to obtain polystyrene pre-expanded particles.

Then, the polystyrene pre-expanded beads were left to stand for 24 hours in an atmosphere of room temperature, and a block molding machine (trade name "PEONY. 205 DS", manufactured by Sasa veitchii industries, Ltd.) having a mold with a rectangular parallelepiped cavity having a length of 840X a width of 930mm X a height of 530mm was prepared, the polystyrene pre-expanded beads were filled in the cavity of the mold, 0.07MPa (gauge pressure) of water vapor was injected into the cavity of the mold for 20 seconds to secondarily expand the polystyrene pre-expanded beads, and then the mold was cooled until the mold internal pressure became-0.01 MPa, to obtain a rectangular parallelepiped flame-retardant polystyrene expanded molded article. Thereafter, the flame-retardant polystyrene foam-molded article was stored in a dry room at 70 ℃ for 3 days.

[ binding of Pre-expanded particles ]

Preparation of W₁(g) The polystyrene pre-expanded beads obtained in the above-mentioned manner were sieved using a sieve having a mesh opening of 1cm, and the weight W of the polystyrene pre-expanded beads remaining on the sieve was measured₂(g) The degree of binding of the pre-expanded particles was calculated based on the following formula, and the results are shown in tables 1 and 2. In addition, 1 wt% or less was evaluated as "o", and more than 1 wt% was evaluated as "x".

The binding degree (wt%) of the pre-expanded particles is 100 xW₂/W₁

[ flammability test ]

From the flame-retardant polystyrene foam molded body obtained, 5 test pieces in a rectangular parallelepiped shape having a length of 200mm × a width of 25mm × a height of 10mm were cut out by a vertical cutter, and after being left in an oven at 60 ℃ for 1 day, the average value of 5 test pieces was determined by measurement method a according to JIS a9511-2006 to obtain a flame-out time, and the results were comprehensively evaluated according to the following criteria and shown in tables 1 and 2 as self-extinguishing properties. In the JIS standard, the flame-out time is required to be 3 seconds or less, preferably 2 seconds or less, more preferably 1 second or less.

Flame out time greater than 3 seconds, or even 1 test strip was defective or burned past the burn limit indicator line.

Flame out time greater than 1 second within 3 seconds, 5 samples were intact, without defects, and did not burn beyond the burning limit indicator line.

Flame out time was within 1 second, 5 samples were intact, no incomplete, and did not burn beyond the burning limit indicator.

[ evaluation of appearance of foamed molded article ]

The appearance of the foamed molded article was visually observed and evaluated based on the following criteria.

The welded portions of the foamed particles to each other were smooth.

The welded portions of the foamed particles to each other generate unevenness.

[ Heat weldability ]

A cutting line of 5mm depth was cut along the short side direction at the center in the longitudinal direction of the top surface of the 6 th sliced product (1840 mm in length × 980mm in width × 50mm in thickness) cut from the bottom by a nickel-chromium alloy, and the sliced product was manually divided into 2 parts along the cutting line to obtain cut pieces of 920mm in length × 930mm in width × 50mm in thickness.

The number of particles (a) broken in the expanded particles and the number of particles (b) broken at the interface between the expanded particles were counted in the cut surface of the obtained divided piece, and the fusion ratio was calculated based on the following formula. The results are shown in tables 1 and 2. Further, 70% or more of the fusion ratio was-.

Welding ratio (%): 100 × number of particles (a)/(number of particles (a) + number of particles (b))

From table 1, it was confirmed that the examples containing 0.45 to 2.0 parts by weight of the tetrabromocyclooctane based on 100 parts by weight of the polystyrene resin and 0.3 to 1.5 parts by weight of the silica fine powder based on 98.5 to 99.7 parts by weight of the tetrabromocyclooctane as a powdery flame retardant were excellent in the blocking evaluation, bonding of pre-expanded beads, flammability test (self-extinguishing property), flammability test evaluation, appearance evaluation of foam molded articles, and heat fusion property.

On the other hand, in Table 2, the combustion test (self-extinguishing property) was deteriorated and the combustion test was evaluated as X in comparative example 1 containing 0.2 parts by weight of tetrabromocyclooctane based on 100 parts by weight of the polystyrene resin. In addition, relative to 100 parts by weight of polystyrene resin, containing 3.0 parts by weight of the tetrabromocyclooctane of comparative example 2, its blocking evaluation is x and heat fusion is x. In comparative example 3 containing no hydrophilic silica, blocking was evaluated as x, and the bonding of the pre-expanded beads was also evaluated as x. In comparative example 4 in which the amount of the fine silica powder was 0.05 part by weight, blocking was evaluated as "x" and the bonding of the pre-expanded beads was also evaluated as "x". In addition, comparative example 5 in which the silica fine powder was 2 parts by weight had a problem in the evaluation of the appearance of the foam molded article. In addition, the silicon dioxide powder is scattered greatly. In addition, in comparative example 6 in which the fluidizing agent was changed to tetrabromobisphenol A-bis (2, 3-dibromopropylether), the binding of the pre-expanded particles was X, the flammability test (self-extinguishing property) was also deteriorated, and the flammability test evaluation was X.

Industrial applicability

The flame-retardant expandable polystyrene particles of the present invention are used in a wide range of applications, including the fields of agricultural and aquatic products, household electrical appliances, and building materials and civil engineering. Particularly, in the field of building materials, the thermal insulating material is used for walls and floors.

Claims (5)

1. A flame-retardant expandable polystyrene resin particle characterized in that:

before or during impregnation of a foaming agent into polystyrene resin particles dispersed in an aqueous suspension, tetrabromocyclooctane as a powdery flame retardant dispersed by silica fine powder is impregnated, and the flame-retardant expandable polystyrene resin particles are obtained by taking out the particles from the aqueous suspension,

adding 0.45-2.0 parts by weight of the tetrabromocyclooctane to 100 parts by weight of the polystyrene resin,

the fine silica powder is contained in an amount of 0.3 to 1.5 parts by weight based on 98.5 to 99.7 parts by weight of the tetrabromocyclooctane as the powdery flame retardant.

2. The flame-retardant expandable polystyrenic resin particles according to claim 1, wherein: the specific surface area of the fine silica powder is 170 to 330m²/g。

3. A method for producing flame-retardant expandable polystyrene resin particles, characterized by comprising: before or during impregnation of a foaming agent into polystyrene resin particles dispersed in an aqueous suspension, 0.45 to 2.0 parts by weight of tetrabromocyclooctane as a powdery flame retardant dispersed in silica fine powder is impregnated into the polystyrene resin particles, and the polystyrene resin particles are taken out from the aqueous suspension to obtain the flame-retardant expandable polystyrene resin particles,

the powdery flame retardant contains the fine silica powder in an amount of 0.3 to 1.5 parts by weight based on 98.5 to 99.7 parts by weight of tetrabromocyclooctane.

4. A pre-expanded particle, characterized in that:

the flame-retardant expandable polystyrene resin particles according to claim 1 or 2, which are obtained by pre-expanding the particles.

5. A foamed molded body, characterized in that:

the method for producing a thermoplastic resin composition, which comprises filling the mold with the pre-expanded particles according to claim 4 and expanding the pre-expanded particles.