JP2002356576A - Polystyrene resin pre-foamed particle, production method and foamed molded material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polystyrene resin foamed molded material, containing little of a volatile organic compound, and stable in dimension even used at a high temperature for a long term. SOLUTION: The polystyrene resin pre-foamed particles have many island-like indeterminated projections on the surface of the foamed particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pre-expanded styrene resin particle, a method for producing the same, and an expanded molded article.
More specifically, the content of the volatile organic compound is extremely low, and the dimensions are very stable over a long period of time even in a high-temperature atmosphere, and the molding time is short. The present invention relates to a styrene-based resin foam molded article having strength, a styrene-based resin pre-expanded particle capable of providing the molded article, and a method for producing the same. The styrenic resin foam molded article of the present invention is particularly suitable as a heat insulating building material.

[0002]

2. Description of the Related Art When expandable styrene resin particles containing 1 to 15% by weight of a foaming agent are heated to a softening point or higher by steam or the like, particulate pre-expanded particles having closed cells are obtained. The pre-expanded particles are filled into a closed mold having small holes and slits, and then heated inside with so-called in-mold molding in which the pre-expanded particles expand to fill gaps between the particles. While being fused together, the desired foam molded article is obtained. Such a foamed molded article is widely used as a heat insulating building material for houses and the like because of its excellent properties such as heat insulation, freedom of shape, light weight, and water resistance.

In recent years, in detached houses and condominiums,
Floor heating devices that directly heat the floor with hot water, electric heat, or other heating means have become widespread. In this device, heat is prevented from escaping from the heating means to the lower outdoor area, and the room (from the floor surface) is made more efficient. It has been practiced to incorporate the above-mentioned heat-insulating building material for the purpose of heating.

[0004]

The heat-insulating building materials used in this floor heating device include a high-temperature environment during operation (approximately 70
℃), the dimensions are stable for a long period of time, and it is not only desired that a gap between the floor material and the like does not easily occur due to thermal expansion or thermal contraction, but it is particularly concerned with a sick house (indoor air pollution) recently. It has been strongly required that the content of volatile organic compounds is extremely low.

The volatile organic compounds include not only aromatic organic compounds such as styrene monomer, toluene, ethylbenzene and xylene but also those having 16 carbon atoms (normal pressure boiling point of 287).
C), cycloaliphatic hydrocarbons such as cyclohexane and methylcyclohexane, methyl acetate,
Acetates such as butyl acetate are mentioned as targets. And since all of these organic compounds have the effect of increasing the foaming ability and the fusing property of the expandable polystyrene resin particles, when the content thereof is reduced, the foamability is reduced and the density is reduced. Not only becomes difficult, but also the fusion-bonding property of the foamed molded article is deteriorated, so that there is a problem that its mechanical strength is also reduced.

As a method for solving this problem, for example, Japanese Patent Application Laid-Open No. H11-106548 discloses that the molecular weight is 220,000 to 200,000.
In 350,000 polystyrene particles, residual styrene is 1 to 3
Expandable styrene-based resin particles containing a plasticizer and a foaming agent having an ppm value of 00 ppm and an SP value of 7 to 10 have been proposed. However, these expandable styrenic resin particles use a volatile substance (a kind of volatile organic compound) such as butane or pentane as a blowing agent, and a large amount of the blowing agent is present in the obtained foamed molded article. However, there is a drawback that it evaporates gradually. In addition, the foam molded article obtained here is, for example, 4
Even when a treatment of dissipating the volatile organic compound by heating at 0 to 60 ° C. is performed, the content of the volatile organic compound is 1000
It is difficult to reduce the content to less than ppm, and the dimensional stability under a high temperature environment is poor.

Therefore, the present inventor has studied a method of using an inorganic gas such as nitrogen or carbon dioxide instead of an aliphatic hydrocarbon having a low boiling point as a blowing agent. JP-A-4-3
No. 51646 discloses a method for producing highly foamed pre-expanded particles using an inorganic gas. Further, Japanese Patent Application Laid-Open No. Hei 5-310986 discloses that styrene-based resin particles having a flame retardant adhered to the surface are pressurized with an inorganic gas to form expandable resin particles, and then contacted with steam to form pre-expanded particles. A method is disclosed in which the pre-expanded particles are placed in a mold, and steam is blown into the mold to form a foamed molded article.

However, in these methods,
The following disadvantages were found. That is, irregularities are formed on the surface of the used pre-expanded particles by embossing the shape of the air bubbles. In order to use the pre-expanded particles to form an expanded molded article with good fusion, the pre-expanded particles are heated to a very high temperature. (Eg, at 130 ° C. or higher), it is necessary to take a method such as molding by heating or extending the heating time.

However, there remain problems such as a long molding time including a cooling step and a high manufacturing cost. Further, such a problem becomes more remarkable as the amount of the styrene-based monomer remaining in the styrene-based resin particles decreases, and it was not possible to obtain a foamed molded article satisfying these problems by the conventional technology.

[0010]

Means for Solving the Problems The present inventors heat-treat expandable styrene-based resin particles containing carbon dioxide gas at a temperature at which substantially no foaming occurs, thereby obtaining the surface of the expandable styrene-based resin particles. It was surprisingly found that irregular-shaped island-like projections were formed on the surface of the pre-expanded particles obtained by dissipating the gas and then pre-expanding. It has been found that when the pre-expanded particles are subjected to heat molding, the vapor pressure is low or the time required for molding is reduced, and furthermore, a foam molded article having excellent mechanical strength can be obtained even if the internal fusion rate is low. It led to. Furthermore, the volatile organic compound in the foamed molded product is extracted and removed by carbon dioxide gas in the process of pre-foaming and molding, and is extremely reduced to 1000 ppm or less. It also has the feature of being very stable.

Thus, according to the present invention, there are provided styrene resin pre-expanded particles characterized in that a large number of irregular island-shaped projections are formed on the surface of the expanded particles.

Further, according to the present invention, there is provided a foamed styrene-based resin article obtained by subjecting the styrene-based resin pre-expanded particles to foam molding.

According to the present invention, foamable styrene resin particles containing carbon dioxide gas are added to styrene resin particles having a residual styrene monomer content of not more than 500 ppm at a temperature of 40 to 100 ° C. A method for producing styrene-based resin pre-expanded particles, comprising a step of producing styrene-based pre-expanded particles by heating for 90 seconds and then heating.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Styrene resin particles (hereinafter, referred to as "resin particles") constituting the expandable styrene resin particles (hereinafter, referred to as "expandable resin particles") used in the present invention.
As such, a generally known granular material of a styrene resin can be used. Specifically, such resin particles include styrene, α-methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene,
Homopolymer particles of styrene-based monomers such as divinylbenzene (bifunctional monomer) or copolymer particles obtained by combining two or more of these monomers, methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, cetyl Esters of acrylic acid and methacrylic acid such as methacrylate, or acrylonitrile,
Copolymer particles with monomers other than styrene-based monomers such as dimethyl fumarate, ethyl fumarate, and alkylene glycol dimethacrylate (bifunctional monomer) are included. Further, resin particles obtained by extruding and blending with a resin other than the styrene resin within a range where the styrene component in these styrene resin particles exceeds 50% by weight may be used. Examples of the resin other than the styrene resin include a polyphenyl ether resin, a polyolefin resin, and a rubber component. In particular, polystyrene resin particles are preferable as the styrene resin particles.

The particle size of the resin particles can be appropriately selected according to the application, and for example, a particle having a particle size of 0.2 to 5 mm can be used.

Furthermore, since it is said that volatile organic compounds are involved in sick houses (indoor air pollution), which have recently become a particular problem, it is desired to reduce the content thereof as much as possible. In this respect, it is preferable that the amount of the residual styrene monomer in the resin particles is as small as possible, and it is particularly preferable that the amount of the resin particles be 0 to 500 ppm in the resin particles. 500 pp residual styrene monomer content
If foaming and molding are carried out by including carbon dioxide in resin particles exceeding m, the content of volatile organic compounds containing residual styrene-based monomers in the resulting molded article may increase. In addition, when the content of the residual styrene monomer is large, the dimensional change rate is apt to increase, which is not preferable.

The volatile organic compounds in the resin particles include
Not only residual styrene-based monomers but also aromatic hydrocarbons such as toluene, ethylbenzene, cumene, and propylbenzene contained in the raw material styrene. More specifically, in a chromatograph obtained by measuring by gas chromatography, a hydrocarbon-based organic compound which appears in a shorter time than n-hexadecane (normal pressure boiling point: 286 ° C.) which is an aliphatic hydrocarbon having 16 carbon atoms And hydrocarbons such as aromatic hydrocarbons such as toluene and styrene, aliphatic hydrocarbons such as butane and pentane, and cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane.

In order to reduce the amount of the residual styrenic monomer in the resin particles, for example, a high-temperature-initiated polymerization catalyst of 0.05% by weight or more based on styrene is used in suspension polymerization, The polymerization temperature is preferably set to 115 ° C. or higher. Examples of the high temperature initiation type polymerization catalyst include t-butyl peroxybenzoate, t-butyl peroxypivalate,
The temperature for obtaining a half-life of 10 hours such as -butylperoxyisopropyl carbonate, t-butylperoxyacetate, 2,2-t-butylperoxybutane is 1
Those having a temperature of 00 to 115 ° C are particularly preferred. However, if these high-temperature-initiated polymerization catalysts are used more than necessary, decomposition by-products such as t-butanol are contained, which is not preferable.

The molecular weight of the resin particles is preferably from 200,000 to 400,000 in terms of weight average molecular weight by GPC (gel permeation chromatography). If it is less than 200,000, the strength of the foamed molded article is reduced, and if it is more than 400,000, it is difficult to obtain sufficient foamability, which is not preferable. Foamable resin particles are obtained by adding carbon dioxide as a foaming agent to the above resin particles. The carbon dioxide gas as the foaming agent may be 100% carbon dioxide gas, but other foaming agents may be added as long as the effects of the present invention are not impaired. As other blowing agents,
Air, inorganic gases such as nitrogen, aliphatic hydrocarbons such as propane, butane, pentane, and hexane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane;
An organic gas such as a fluorocarbon may be mixed. As the fluorinated hydrocarbon, it is preferable to use difluoroethane, tetrafluoroethane, or the like having an ozone depletion potential of zero. Here, the organic gas is preferably used within a range not exceeding 20% by weight of the total amount of the foaming agent.

When carbon dioxide is contained in the resin particles,
It is preferable to apply various surface treatment agents on the surface of the resin particles, and examples of such surface treatment agents include a binding inhibitor that prevents the bonding of the pre-expanded particles during heating and foaming,
Examples include a fusion promoter during molding, an antistatic agent, and a spreading agent.

Examples of the binding inhibitor include talc, calcium carbonate, silica, zinc stearate, aluminum hydroxide, ethylenebisstearic acid amide, tribasic calcium phosphate, dimethyl silicon and the like. Examples of the fusion promoter include stearic acid, triglyceride stearic acid, triglyceride hydroxystearate, sorbitan stearate, and polyethylene wax.

Examples of the antistatic agent include polyoxyethylene alkylphenol ether and stearic acid monoglyceride. Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil. In the resin particles, if necessary, bubbles such as a flame retardant such as hexabromocyclododecane and tetrabromocyclooctane, a methacrylic acid ester-based copolymer, ethylene bisstearic acid amide, polyethylene wax, and an ethylene-vinyl acetate copolymer may be used. An adjusting agent or the like may be contained in advance.

The content of carbon dioxide in the expandable resin particles is preferably 1 to 15% by weight. In order to make the resin particles contain carbon dioxide gas, for example, after putting the resin particles in a pressure-tight container, the carbon dioxide gas is press-fitted, and the resin particles are brought into contact with the pressurized carbon dioxide gas. The content temperature may be as high as a temperature at which the resin particles do not coalesce and agglomerate with each other, but are usually about 0 to 40 ° C.

The pressure at which the resin particles are contained carbon dioxide gas is usually, 10 kg / cm ² G or more, preferably 15~40kg / cm ² G. The content time is appropriately adjusted so that the resin particles have the above-mentioned carbon dioxide content, and is usually about 1 to 20 hours, preferably 2 to 8 hours. The expandable resin particles containing carbon dioxide gas are taken out of the pressure-resistant closed container and subjected to a heat treatment at a temperature at which the expandable resin particles do not substantially expand. By this treatment, the gas near the surface of the expandable resin particles is selectively dissipated and then pre-expanded to obtain styrene-based resin pre-expanded particles (hereinafter, referred to as “pre-expanded particles”).
Irregular island-like projections can be formed on the surface of the “pre-expanded particles”. Here, the irregular island-shaped protrusion does not mean an uneven state in which the shape of air bubbles is raised on the surface of the pre-expanded particles, but means an uneven structure as shown in the photographs of FIGS. In the present invention, it has been surprisingly found that when the in-mold molding is performed using the pre-expanded particles of the present invention having such projections, the pre-expanded particles are likely to be firmly thermally fused to each other. This means that if the molding time is the same as the conventional one, a molded body having more excellent mechanical strength can be obtained. In addition, when the same mechanical strength as that of the prior art is desired, the mechanical strength can be obtained in a shorter heating time in which the pre-expanded particles can be internally fused to a degree generally referred to as good. It is possible to shorten the manufacturing time of the molded body including the molded article. By shortening the manufacturing time, heat energy and the like can be reduced, so that the manufacturing cost can be significantly reduced.

The heat treatment of the expandable resin particles is usually conveniently performed in a foaming machine, but may be performed in an openable container separate from the foaming machine. The temperature of the heat treatment is 40 to 10
0 ° C, preferably 60 to 100 ° C. Examples of the heating medium at this time include hot air or a mixture of steam and air. The heating time is 3 to 90 seconds, preferably 5 to 60 seconds. If the treatment time is less than 3 seconds or the temperature is less than 40 ° C., only irregularities derived from the shape of bubbles appear on the surface of the pre-expanded particles, and the irregular island-shaped projections of the present invention are hardly obtained. It is not preferable because the effect of improving the strength cannot be expected. On the other hand, if the treatment time is 90 seconds or the temperature exceeds 100 ° C., it is difficult to obtain low-density pre-expanded particles, which is not preferable.

The expandable resin particles from which carbon dioxide gas has escaped near the particle surface are subjected to a preliminary foaming treatment in a foaming machine. As a heating medium at this time, for example, steam is used.

The bulk density of the obtained pre-expanded particles is usually about 0.015 to 0.5 g / cm ³ .

The above-mentioned pre-expanded particles are molded in a mold to produce an expanded molded article. Specifically, the pre-expanded particles are filled in a molding die, and steam is blown into the die to heat the pre-expanded particles. When the pre-expanded particles are heated by contact with steam, the pre-expanded particles expand, but the space in which the foam can be expanded by the molding die is limited. The body is obtained.

Furthermore, the foamed molded article thus obtained has a very low content of volatile organic compounds of 1000 ppm or less, and a dimensional change rate of ± 0.2% when heated at 70 ° C. for 1200 hours. Within and extremely small. Therefore, it is particularly suitable for use as a heat insulating building material such as a floor heating heat insulating material used in a high temperature environment.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the evaluation method of the foam molding obtained by the Example and the comparative example is shown below.

<Content of Volatile Organic Compound> The content obtained by the following three kinds of measurement methods is determined by summing up the values. [Measurement of hydrocarbon compound having 5 or less carbon atoms] The foamed molded article was placed in a pyrolysis furnace at 150 ° C, and volatile hydrocarbons were measured by gas chromatography. Gas chromatography (GC): GC manufactured by Shimadzu Corporation
-14B Pyrolysis furnace: PYR-1A manufactured by Shimadzu Corporation Column: Polapack Q 80/100 (3 mmφ × 1.
5m) Column temperature: 100 ° C Detector (FID) temperature: 120 ° C

[Measurement of hydrocarbons having 6 or more carbon atoms up to the peak of styrene appearing in the gas chromatogram] The foamed product was dissolved in dimethylformamide, and an internal standard solution (cyclopentanol) was added. It was measured by GC. However, peaks that could not be identified were quantified by conversion to the amount of toluene detected. GC: Shimadzu GC-14A Column: PEG-20M PT25% 60/80
(2.5m) Column temperature: 105 ° C Detector (FID) temperature: 220 ° C

(Measurement of Hydrocarbons Containing C16 (n-hexadecane) from the Next Peak of Styrene Appearing in Gas Chromatogram) The foamed product was dissolved in chloroform and measured by gas chromatography / mass spectrometry (GCMS). . However, a blank test was performed using only a solvent that did not dissolve the test piece, and the detected substance amount in the blank test was subtracted. Further, unspecified peaks were quantified in terms of the amount of toluene detected. GCMS: Shimadzu QP5000 Column: J & W Scientific DB-1
(1 μm × 60 m 0.25 mmφ) Measurement conditions: column temperature (after holding at 60 ° C. for 1 minute, 10
(The temperature is raised to 300 ° C at a rate of ° C / min.) Split ratio: 10 Carrier gas: He (1 ml / min) Interface temperature: 260 ° C

<Surface State of Pre-expanded Particles> The surface state of the pre-expanded particles is confirmed by forming a substantially irregular island-like projection in a magnified photograph of 30 times the size of the pre-expanded particles.

<Internal fusion ratio> A cut line having a depth of about 5 mm was made on the surface of the foamed molded product with a cutter knife, and then the foamed molded product was divided into two along this line by hand. For the particles, the number (a) of the particles broken in the particles and the number (b) of the particles broken at the interface between the particles are counted, and the equation [(a) / ((a) + (b)] is obtained. )] ×
The value obtained by substituting 100 was used as the internal fusion rate (%).

<Dimensional change rate> The foamed molded product taken out of the molding die was left in a thermo-hygrostat at a temperature of 23 ° C and a relative humidity of 50% (standard temperature and humidity according to JIS-K7100) for 24 hours. Square plate with upper and lower surfaces parallel to each other (150 mm long, 150 mm wide, 30 m thick)
m) was cut out, and three straight lines parallel to each other in the vertical and horizontal directions were written in the center thereof at 50 mm intervals to obtain a test piece according to JIS-K6767. The test piece was placed horizontally in a hot air circulating drier maintained at 70 ° C., subjected to a heating test for 1200 hours, taken out, and left again in a constant temperature and humidity chamber for 1 hour.

Dimension measurement before and after the heating test is based on JIS
The dimensional change was determined according to the following equation. Dimensional change rate (%) = (L2−L1) × 100 / L1 (where L1 is the dimension of the foam molded article left at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours after molding in the mold, L2
Is the dimension of the foam molded article after heating the foam molded article at 70 ° C. for 1200 hours.) The dimension is the average value of the length of three straight lines in each of the vertical and horizontal directions written on the foam molded article. .

<Bending strength> The bending strength was measured by a method according to JIS A9511. That is, the obtained measured values were substituted into the following formula, and the average value was calculated. Flexural strength (kgf / cm ² ) = 3FL / 2bh ² F: Maximum point load Distance between fulcrums (L): 20 cm Specimen width (b): 7.5 cm Specimen height (h): 2.5 cm Test Piece length: 30cm Measurement number: 3 Test speed: 10mm / min

Example 1 A 100-liter reactor was charged with 40 kg of pure water, 2.2 g of sodium dodecylbenzenesulfonate, and 60 g of magnesium pyrophosphate, and used as an aqueous medium. Then, 176 g of styrene in which 176 g of benzoyl peroxide (purity: 75%), 30 g of t-butylperoxybenzoate and 22 g of polyethylene wax (molecular weight: 1000) were dissolved.
g was added with stirring and suspended, and the temperature was raised to 90 ° C. to initiate polymerization. When the polymerization progressed to a polymerization conversion rate of 95% by weight as measured by a specific gravity method, the temperature of the reactor was raised to 125 ° C. and maintained for 2 hours, and then cooled to room temperature to take out styrene resin particles. When the amount of the residual styrene monomer in the obtained styrene-based resin particles was measured by gas chromatography, it was 430 ppm, and the content of volatile organic compounds other than styrene was 1,174 ppm in total.
Met. The weight average molecular weight measured by the GPC method was 246,000.

Of the styrene resin particles, a particle size of 0.7 to
After putting 15 kg of 1.0 mm into a rotary pressure-resistant container having a content of 30 liters, 7.5 g of polyethylene glycol 300 as a spreading agent, 7.5 g of glycerin monostearate, and carbonic acid as a binding inhibitor are used. 30 g of calcium was added, and the container was rotated to adhere to the surface of the resin particles. Next, after stopping the rotation, carbon dioxide gas was injected into the container, and kept at 25 ° C. and 30 kg / cm ² G for 6 hours to contain carbon dioxide gas in the resin particles.

The expandable styrene resin particles thus obtained were taken out of the pressure-resistant container, immediately put into a foaming machine equipped with a stirrer maintained at a temperature of 60 ° C. in a can with a mixed gas of steam and air, and heated for 80 seconds. Next, steam was introduced into the foaming machine, and the foamed resin particles were brought into contact with the steam and prefoamed to obtain styrene resin prefoamed particles. Further, the surface of the pre-expanded particles was confirmed in a 30-times enlarged photograph. This enlarged photograph is shown in FIG.

Six hours after the pre-expansion, the pre-expanded particles are filled into a molding die having a mold cavity of 400 mm in length × 300 mm in width × 30 mm in thickness, and 1.0 k
At a heating steam pressure of g / cm ² G, steam is blown for 40 seconds (time during which the peak temperature of heating is maintained: heating time) to expand the styrene resin foam molded article having a bulk density of 0.025 g / cm ^3. Obtained. At this time, the molding production time (total time from the start of heating to the end of cooling) was 105 seconds. After the obtained foam molded article was dried in a constant temperature room at 50 ° C. for 7 days, the content of the volatile organic compound was measured by gas chromatography, and the internal fusion rate, bending strength, and dimensional change rate were evaluated. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article.

Example 2 Pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1, except that the pre-expanded particles were pre-expanded so that the bulk density of the particles was 0.05 g / cm ³ . Table 1 shows the evaluation results of the obtained pre-expanded particles and the foamed molded article. Also, the surface of the pre-expanded particles was confirmed in enlarged photographs of 30 times and 300 times. Fig. 2 shows this 30 times enlarged photograph.
FIG. 3 shows an enlarged photograph of 300 times.

Example 3 Except that the expandable resin particles were taken out of the pressure-resistant container and immediately introduced into a foaming machine equipped with a stirrer whose internal temperature was kept at 95 ° C. by a mixed gas of steam and air, and heat-treated for 10 seconds, Pre-expanded particles and an expanded molded article were obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article.

Example 4 The pre-expanded particles obtained in Example 1 were filled in a molding die.
And 0.9kg / cm ^TwoMolded with heated steam pressure of G
Except for the above, the pre-expanded particles and
A foam molded article was obtained. Obtained pre-expanded particles and expanded foam
Table 1 shows the evaluation results of the shapes. The bulk density of the foam
The degree is 0.025 g / cm^ThreeMet.

Example 5 A 100-liter reactor was charged with 40 kg of pure water, 2.2 g of sodium dodecylbenzenesulfonate, and 60 g of magnesium pyrophosphate, and used as an aqueous medium. Next, styrene 4 in which 148 g of benzoyl peroxide (purity 75%), 30 g of t-butylperoxybenzoate and 22 g of polyethylene wax (molecular weight 1000) were dissolved.
1.8 kg and 2.2 kg of butyl acrylate were added with stirring and suspended, and the temperature was raised to 85 ° C. to initiate polymerization. When the polymerization conversion reached 95% by weight as measured by the specific gravity method, the reactor was heated to 120 ° C.
After holding for a time, the mixture was cooled to room temperature, and styrene resin particles were taken out. The amount of residual styrene monomer in the resin particles obtained here was measured by gas chromatography, and was 392 ppm, and the content of volatile organic compounds other than styrene was 992 ppm in total. The weight average molecular weight measured by the GPC method (in terms of polystyrene) is 29.
7000.

Among the styrene-based resin particles, a particle size of 0.
After putting 15 kg of 7 to 1.0 mm into a rotary pressure-resistant container having a content of 30 liters, 7.5 g of polyethylene glycol 300, 7.5 g of glycerin monostearate as a spreading agent, and a binding inhibitor Was added and 30 g of calcium carbonate was added, and the container was rotated to adhere to the surface of the resin particles. Then, after stopping the rotation, carbon dioxide gas was injected into the container, and kept at 25 ° C. and 30 kg / cm ² G for 4 hours to contain carbon dioxide gas in the resin particles.

The expandable styrene-based resin particles thus obtained are taken out of the pressure-resistant container, immediately put into a foaming machine equipped with a stirrer whose inside temperature is maintained at 60 ° C. by a mixed gas of steam and air, and placed for 10 seconds. Heat treated. Next, steam was introduced into the foaming machine, the particles were brought into contact with the steam, and pre-foamed to obtain styrene-based resin pre-foamed particles.

6 hours after prefoaming, 400 m long
The pre-expanded particles are filled in a molding die having a mold cavity of mx 300 mm wide x 30 mm thick, and 0.9 k
Steam was blown in at a heating steam pressure of g / cm ² G for 40 seconds, and the mixture was expanded again to obtain a foamed styrene-based resin having a bulk density of 0.025 g / cm ³ . After the obtained foam molded article was dried in a constant temperature chamber at 50 ° C. for 7 days, the content of the volatile organic compound was measured by gas chromatography, and the internal fusion rate, bending strength, and dimensional change rate were evaluated. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article.

Example 6 Melted at 200 ° C. by a single screw extruder to a diameter of 0.6 m.
high impact polystyrene resin particles (butadiene content 8%) in the form of pellets having a length of 1.0 mm and a length of 15 k
g in a rotary pressure-resistant container having a content of 30 liters, and then polyethylene glycol 300 as a spreading agent.
5 g, glycerin monostearate 7.5
g, 30 g of calcium carbonate was added as a binding inhibitor, and the container was rotated to adhere to the surface of the resin particles. Next, the rotation was stopped, and then carbon dioxide gas was injected into the container, and 25
° C., kept 30kg / cm ² 6 h G is contained carbon dioxide gas into the resin particles, to obtain a foamed styrene resin particles.
The residual styrene in the obtained styrene-based resin particles was measured by gas chromatography to be 450 ppm, and the total amount of volatile organic compounds other than the styrene-based monomer was 1252 ppm.

The expandable styrene resin particles thus obtained are taken out of the pressure-resistant container and immediately put into a foaming machine equipped with a stirrer whose inside temperature is maintained at 60 ° C. by a mixed gas of steam and air. Heat treatment was performed for seconds. next,
Steam was introduced into a foaming machine, and the foamed resin particles were brought into contact with steam to foam the particles, thereby obtaining styrene-based resin pre-expanded particles.

Six hours after prefoaming, 400 m long
The pre-expanded particles are filled in a molding die having a mold cavity of mx 300 mm wide x 30 mm thick, and 0.9 k
Steam was blown in for 40 seconds at a heated steam pressure of g / cm ² G for expansion to obtain a foamed styrene-based resin having a bulk density of 0.025 g / cm ³ . 50 ° C.
After drying in a constant temperature room for 7 days, the content of volatile organic compounds was measured by gas chromatography, and the internal fusion rate, bending strength and dimensional change rate were evaluated. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article.

[0053]

[Table 1]

From the above results, by using styrene-based resin particles having an amount of residual styrene monomer of 500 ppm or less and containing carbon dioxide gas and foaming to obtain pre-expanded particles, the styrene-based monomer was included. The content of volatile organic compounds is 1
It was possible to obtain an extremely small foam molded article of 000 ppm or less. Moreover, as a result of molding the pre-expanded particles having irregular island-shaped projections on the surface at a low temperature, it was found that a foam molded article having sufficient mechanical strength was obtained even if internal fusion was small. In addition, these foamed molded articles had a very small change in heating dimension at high temperatures.

Comparative Example 1 Pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1, except that the expandable styrene resin particles obtained in Example 1 were pre-expanded without heat treatment. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article. The surface of the pre-expanded particles was confirmed in a 30-times enlarged photograph. This enlarged photograph is shown in FIG. According to this comparative example, when the surface of the pre-expanded particles to be used has an uneven shape derived from bubbles therein, the internal fusion of the molded article is reduced, and as a result, the mechanical strength is also significantly reduced. I understand.

Comparative Example 2 The expandable styrene resin particles obtained in Example 1 were prefoamed without heat treatment. Further, the internal fusion ratio of the molded product obtained by molding the pre-expanded particles in the mold was determined in Example 1.
Pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1 except that the molding heating conditions were changed to 80%, which is the same as in Example 1. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article. According to this comparative example, the internal fusion rate becomes equal to that of Example 1. However, in order to make the mechanical strength equal, the heating steam pressure must be higher than that of Example 1, and the molding manufacturing time Was found to be significantly longer than in Example 1.

Comparative Example 3 The expandable styrene resin particles obtained in Example 1 were taken out of the pressure-resistant container and immediately put into a foaming machine equipped with a stirrer whose internal temperature was maintained at 60 ° C. by a mixed gas of steam and air. Then, heat treatment was performed for 120 seconds. Further, pre-expanded particles and a foamed molded product were obtained in the same manner as in Example 1, except that the molding heating conditions obtained by molding the pre-expanded particles in a mold were changed. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article. Surface of the pre-expanded particles obtained by the comparative example shows a state in which in a state of resinification is not bubbles formed, the bulk density was as high as 0.05 g / cm ^3. Furthermore, when the pre-expanded particles were molded in a mold, it was found that the internal fusion of the molded body was low, and as a result, the mechanical strength was significantly reduced.

Comparative Example 4 Pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1, except that the amount of t-butyl peroxybenzoate used was changed to 10 g. Table 1 shows the evaluation results of the obtained pre-expanded particles and the expanded molded article. According to this comparative example, when the content of the residual styrene monomer in the styrene-based resin particles used is large, the internal fusing property of the foamed molded article is improved,
The dimensional change rate is significantly inferior. Further, it was found that the molding production time at this time was significantly longer than that of Example 1.

From Table 1, it can be seen that, in Comparative Example 1, the pre-expanded particles having no irregular island-like projections formed on the surface not only have poor internal fusion but also have a significant decrease in mechanical strength. all right. Further, in Comparative Example 2, in order to impart sufficient mechanical strength to the molded body, it is necessary to increase the heating steam pressure, which leads to an increase in heat energy, and furthermore, the molding production time becomes longer, so that the production cost is increased. Was found to be higher. In Comparative Example 3, it was found that the surface of the obtained pre-expanded particles was resinified and no cell membrane was formed, so that not only internal fusion was inferior, but also mechanical strength was significantly reduced. .

In Comparative Example 4, the content of the residual styrene monomer in the styrene resin particles was 1892 ppm, and the content of the volatile organic compound other than the styrene monomer was 10%.
Since it was as high as 93 ppm, the dimensional change rate of the obtained foamed molded article was inferior.

[0061]

The foamed styrenic resin article of the present invention has an extremely low content of volatile organic compounds and a moderate mechanical strength even if the internal fusion rate is low. Further, it is possible to reduce the heat energy in the production and the molding production time, and the product value is very high. This foamed molded product is particularly suitable for use as a heat insulating material for buildings used at relatively high temperatures, such as a gas hot water type or electric type heat insulating material for floor heating used in condominiums and detached houses. .

[Brief description of the drawings]

FIG. 1 is an electron micrograph of the surface of pre-expanded particles obtained in Example 1.

FIG. 2 is an electron micrograph of the surface of pre-expanded particles obtained in Example 2.

FIG. 3 is an electron micrograph of the surface of the pre-expanded particles obtained in Example 2.

4 is an electron micrograph of the surface of the pre-expanded particles obtained in Comparative Example 1. FIG.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Yamagata 10-5-462, Nishiojimachi, Kusatsu-shi, Shiga Prefecture (72) Ikuo Morioka 659-15, Nakakomori-cho, Omihachiman-shi, Shiga Prefecture F-term (reference) 4F074 AA32 AC20 AC26 AC31 AC32 AD10 AD17 AG07 AG10 AG11 BA32 BC11 BC15 CA30 CA32 CA49 CA51

Claims (7)

[Claims] 1. A pre-expanded styrene-based resin particle comprising a large number of irregularly shaped island-shaped projections formed on the surface of an expanded particle. 2. The styrenic pre-expanded particles are prepared by heating carbon dioxide-containing expandable styrenic resin particles at 40 to 100 ° C.
The styrene-based resin pre-expanded particles according to claim 1, which is obtained by pre-expanding the expandable styrene-based resin particles after heating for 3 to 90 seconds. 3. The styrene resin according to claim 1, wherein the expandable styrene resin particles are particles obtained by adding carbon dioxide to styrene resin particles having a residual styrene monomer content of 500 ppm or less. Pre-expanded particles. 4. A foamed styrene-based resin article obtained by foam-forming the styrene-based resin pre-expanded particles according to claim 1. 5. The styrenic resin foam according to claim 4, wherein a dimensional change rate represented by the following equation is within ± 0.2% when heated at 70 ° C. for 1200 hours. Dimensional change rate (%) = (L2−L1) × 100 / L1 (where L1 is the dimension of the styrene-based resin foam molded article left at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours after in-mold molding, L2 Is obtained by heating the foamed styrene resin to 70 ° C.
Is the size of the foamed styrene resin when heated for 1200 hours at 6. The content of the volatile organic compound is 1000 p.
The styrenic resin foam according to claim 4 or less. 7. The amount of the residual styrene monomer is 500 pp.
m or less, and expandable styrene-based resin particles containing carbon dioxide gas in styrene-based resin particles
A method for producing styrene-based resin pre-expanded particles, comprising a step of producing styrene-based pre-expanded particles by heating for 90 seconds and then heating.