JP3221019B2 - Low-density fused expanded resin molded article of polystyrene resin expanded particles and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-density fused foamed resin molded article of rubber-modified polystyrene resin foamed particles and a method for producing the same. According to the present invention, electronic components, audio equipment, and the like are significantly reduced in size and weight, and the demand for cushioning packaging materials for lighter objects is increasing. Since the density of plastics is much lower than that of conventional products due to the handling of industrial waste, the weight used can be greatly reduced as compared with conventional buffer materials. As a result, the amount of industrial waste generated can be reduced.

[0002]

2. Description of the Related Art Conventionally, when a light-weight packaged article is cushioned and packaged with a cushioning material made of a fused foamed molded article of foamed polystyrene resin particles having a low elasticity and poor elasticity (hereinafter referred to as a foamed molded article), it is too hard. Thus, there is a problem that a sufficient buffer absorption effect cannot be obtained. As a solution to this, a rubber-modified rubber in which a butadiene-based polymer rubber in which polystyrene is encapsulated in one or more small particles in a continuous phase of polystyrene, commonly called a high-impact polystyrene resin, is dispersed in the form of particles. It is known to obtain expanded molded articles by obtaining expanded particles using a polystyrene resin.

[0003] For example, Japanese Patent Publication No. 51-46536 discloses that the elasticity of a foamed molded article obtained by adding a butadiene component to a polystyrene resin can be enhanced. , The average rubber particle diameter is 0.1.
It is disclosed that the impact resistance can be further improved by adjusting the thickness to 7 μm or less. However, the "impact destruction performance" referred to in the above invention is a performance mainly for preventing the foamed molded article from being broken or broken by a drop impact, and the foam film in the present invention is very thin. This is clearly different from the “bubble-resistant puncture-preventing performance” of preventing bubbles that are a phenomenon peculiar to a certain low-density foam molded article from bursting as if they were punctured.

[0004] Although the elasticity of the foamed article obtained by adding the butadiene component can be improved, the high foaming performance is inferior, and foaming, which is an important factor in increasing the elasticity, is more important than the addition of the butadiene component. There has been a problem that the density of the molded article has not been sufficiently reduced, and when the resulting foam molded article is used as a lightweight cushioning packaging material, a sufficient cushioning effect cannot be obtained.

[0005]

Generally, when a light-weight product such as an electronic component or an audio device is subjected to cushioning and packaging, a pressure-receiving load applied to a foamed molded article serving as a cushioning material is small (that is, low stress).
Therefore, there is a problem that the compression deformation of the foamed molded article is small in response to a drop impact, and it is difficult to sufficiently obtain an impact absorbing effect. There is a strong demand for a highly economical lightweight cushioning packaging material using a resin foam molded article.

By adding a rubber component to a polystyrene resin, the inventors of the present invention have shown a "compression strain recovery performance" which shows the continuity of shock absorption performance, which is the basic buffering performance.
In addition to having the "puncture resistance of air bubbles" that prevents the rupture of the foam film that constitutes the foam molded article caused by the drop impact, commonly called the "puncture phenomenon", and adding a rubber component In this way, it is possible to improve the property that the high foaming performance is remarkably reduced, and to obtain a foam molded article with a higher density than conventional products, a level that was thought to be impossible with polystyrene resin foam molded articles so far. However, it is intended to complete a foamed molded article having high elasticity.

[0007]

According to the present invention, a butadiene polymer rubber in which polystyrene is encapsulated in small particles is dispersed in a continuous phase of polystyrene in the form of particles. Expanded rubber-modified polystyrene resin particles having a content of 5 to 15 % by weight and a weight average particle diameter of the butadiene polymer rubber particles of 0.05 to 1.0 μm and a particle diameter distribution of 1.5 or less. A molded article having a density of 0.009 to 0.014 g
/ Cm ³ , and 80% or more of the cells have a closed cell structure, and a low-density fusion-foamed resin molded article of polystyrene-based resin expanded particles, and polystyrene is contained in small particles in a continuous phase of polystyrene. Butadiene-based polymer rubber is dispersed in the form of particles, the content of the butadiene component in the whole is 5 to 15% by weight, and the weight-average particle size of the butadiene-based polymer rubber particles is 0.05 to 1%. 0.0μ
m, a volatile organic blowing agent is impregnated with 0.07 to 0.25 gmol in an amount of 100 g of a rubber-modified polystyrene resin having a particle size distribution of 1.5 or less to obtain expandable resin particles. The foamable resin particles are foamed with steam in a foaming machine, and the bulk density is 0.009 to 0.1 in one foaming.
014 g / cc of foamed particles were obtained, and then the foamed particles were introduced into a mold, heated with steam to fuse and form the foamed particles, and the density was 0.009 to 0.014 g / cm.
³ , and 80% or more of the cells are a method for producing a low-density fused foamed resin molded article of polystyrene resin foamed particles having a closed cell structure, and the above object can be easily achieved by the present invention.

[0008] Rubber-modified polystyrene in the present invention, Poributaji et emissions or butadiene as the butadiene-based polymer - a styrene copolymer was dissolved in styrene monomer, the polymerization solution and eggplant, then stirring heating the polymer solution It is obtained by polymerizing butadiene-based polymer in the form of rubber particles dispersed in a continuous phase of polystyrene.

A solvent may be added during the polymerization reaction, and the solvent may be an aromatic hydrocarbon, for example, toluene, xylene, ethylbenzene, or a mixture of two or more thereof. The polymerization solution can be polymerized at a temperature of 100 to 180 ° C, and a polymerization initiator is used to improve the quality.

Peroxy ketals such as 1,1-bis (t-butylperoxy) cyclohexane and 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane as usable polymerization initiators; Di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t
Dibutyl peroxides such as -butylperoxy) hexane; dialpoxides such as benzoyl peroxide and m-toluoyl peroxide; peroxydicarbonates such as dimyristyl peroxydicarbonate; t-butylperoxyisobromide There are peroxyesters such as bicarbonate, ketone peroxides such as cyclohexanone peroxide, and hydroperoxides such as p-mentha hydroperoxide.

The polymerization reaction is carried out at a temperature of 50 to 150 ° C., preferably 90 to 135 ° C., at a constant temperature or gradually raised . The rubber particle diameter specified in the present invention is 0.0
Uniform and fine special rubber particles having a particle size distribution of 5 to 1.0 μm and a particle size distribution of 1.5 or less increase the affinity of the butadiene-based polymer to polystyrene, adjust the viscosity of the polymerization solution, and stir speed. It can be obtained according to many manufacturing requirements such as adjusting the time and using a homogeneous stirring device (for example, JP-A-60-130613).

As shown in FIGS. 4 and 5, the structure of such rubber particles is a so-called core-shell structure in which a single polystyrene small particle is contained inside polybutadiene particles, or as shown in FIGS. 6 and 7. A plurality of polystyrene small particles are included inside the polybutadiene particles,
It is formed into a so-called salami structure. The rubber-modified polystyrene having the core-shell structured particles can be efficiently obtained by using a type 2 or type 3 block copolymer comprising one polybutadiene block and one or two polystyrene blocks as a butadiene-based polymer.

The content of the polystyrene block in the block copolymer is preferably in the range of 20 to 45% by weight. Examples of such a butadiene-based polymer are disclosed in, for example, JP-A-64-74208. Have been. The structure of the rubber particles can be confirmed by a transmission electron micrograph taken by an ultra-thin section method of the resin composition.

The method for obtaining the foamed molded article of the present invention is as follows. The rubber-modified polystyrene resin is continuously supplied to the extruder, extruded into a thread form from the holes provided in the die of the extruder while being heated and melted in the extruder, and immediately cooled up and down by a cooling bath containing water. The resin is cut in the length direction by a rotary cutter while being picked up by two driving rolls to obtain resin particles.

Next, a volatile organic foaming agent such as isopentane, normal pentane, isobutane, normal butane, hexane or the like is used in an amount of 0.07 to 0.
The impregnating resin is impregnated with 25 gmol to obtain foamable resin particles. The method of impregnating the volatile organic foaming agent is, for example, putting the resin particles in an autoclave, adding the volatile organic foaming agent to the resin particles, sealing the container, and then impregnating by heating and pressing or After the resin particles are melted under pressure in an extruder, a volatile organic foaming agent is press-fitted through a foaming agent supply line that is separately connected to the extruder, sufficiently mixed with the resin in a molten state, and then provided in a die portion of the extruder. Extruded into a thread from the pores provided,
A method is used in which foaming resin particles are obtained by cutting in a length direction with a rotary cutter while sandwiching and being taken up by two upper and lower drive rolls while being cooled by a cooling bath storing water directly.

Next, these expandable resin particles are highly expanded by steam using a known molding machine for polystyrene expanded beads, and the target bulk density is 0.009 to 0.014 g / c.
c to form expanded particles. From the viewpoint of obtaining a low-density foamed molded article having a closed cell structure with the target performance of the present invention using the foamed particles, a so-called one-stage foaming process in which the foam is foamed to a target bulk density in one step It is desirable to use a foaming method.

Although the reason is not always clear, according to the so-called multi-stage foaming method in which foaming is carried out to a target bulky by foaming several times, since the density is extremely low,
It is considered that the foam film of the foamed particles having a very thin film shape is greatly damaged by repeated steam heating. The foamed resin particles thus obtained can be fused into one body by a known automatic molding machine for polystyrene foam beads to obtain a foam molded body.

[0018]

FIG. 1 is an experimental view showing the significance of the amount occupied by the butadiene component in the rubber-modified polystyrene resin of the present invention.
That is, the horizontal axis in FIG. 1 shows the content of the butadiene component in% by weight, and the vertical axis shows the evaluation from two viewpoints: [load at which puncturing occurs in the bubble film] and [low stress buffering coefficient].

That is, the density of the foamed molded article is 0.011 g /
When evaluated in conformity with cm ³ , it is shown that the [puncture load of the bubble film] decreases with a decrease in the amount of the component, and remarkably worsens when the butadiene component amount is less than 5% by weight.
On the other hand, the content of the butadiene component is 7.
It shows the best value around 5% by weight, and further shows that the butadiene component content is significantly worse when the amount exceeds 15% by weight. It can be seen that a composition with improved characteristics can be obtained according to the target. From the viewpoint of simultaneously satisfying two factors, that is, the puncture load of the bubble film and the low stress buffering coefficient, which exhibit properties that are contradictory in relation to the butadiene component amount, the dotted line shown in FIG. , That is, a composition in which the butadiene component amount is in the range of 5 to 15% by weight.

FIG. 2 is an experimental view showing the significance of butadiene polymer rubber particles of the rubber-modified polystyrene resin of the present invention. That is, the horizontal axis in FIG. 2 shows the average rubber particle diameter (μm), and the vertical axis shows the evaluation of [closed cell rate]. A plurality of diagrams in FIG. 2 each show the distribution of the rubber particle diameter.

First, it is shown that as the average rubber particle diameter increases, the closed cell ratio of the obtained foamed molded article decreases, and when the average rubber particle diameter exceeds 1.0 μm, it significantly deteriorates. Secondly, even if the average rubber particle diameter is less than 1.0 μm, if the rubber particle diameter distribution exceeds the value of 1.5, it is also shown that the closed cell ratio of the obtained foamed molded article is significantly reduced. That is, in order to obtain a foam having a high closed-cell structure, which is most important from the viewpoint of enhancing the properties of the obtained foam, a rubber particle diameter represented by a weight average value must be 1.0 μm.
m or less, more specifically 0.05 to 1.0 μm, which can be obtained practically industrially, and the distribution of the rubber particles is 1.5 or less, preferably the rubber particle diameter is It shows that the distribution is 0.05 to 0.7 μm and the distribution is 1.2 or less.

FIG. 3 is an experimental view showing the significance of the density of the foam molded article of the present invention. That is, the horizontal axis in FIG. 3 shows the density (g / cm ³ ) of the foamed molded product, and the vertical axis shows the evaluation from two viewpoints of [low stress buffering coefficient] and [compression recovery].

According to FIG. 3, as the density of the foamed article increases, the "recovery amount of compression strain" decreases, and when the density of the foamed article exceeds 0.014 g / cm ³ , it rapidly deteriorates. Is shown. On the other hand, the [low stress buffering coefficient] deteriorated when the density of the foamed molded article was reduced, and was significantly deteriorated when the density of the foamed molded article was less than 0.009 g / cm ³ , and the characteristics were improved according to the target. It can be seen that a foam molded article is obtained.

As described above, from the viewpoint of simultaneously satisfying [low stress buffering coefficient] and [compression strain recovery amount], which show contradictory properties in relation to the density of the foamed molded article, FIG. It is desirable to select the range of the dotted line shown in FIG. 3, that is, the range of the density of the foam molded article of 0.009 to 0.014 g / cm ³ . Next, Table 2 summarizes the results of the respective experiments and comprehensively summarizes and displays the performance evaluation results.

That is, according to the foamed molded article of the present invention, all the evaluation items were evaluated as inferior (× and 中 in the table).
No.) are shown and show excellent performance. From the above, the content of the butadiene component of the rubber-modified polystyrene resin to be used, the distribution of the rubber particle size thereof, and the density and closed cell rate of the obtained foamed molded article are all specified, and the object of the present invention is the first [low stress It can be seen that a buffer wrapping material that can simultaneously satisfy the three requirements of "buffer absorption performance", "compression strain recovery performance", and "bubble resistance puncture prevention performance" can be obtained.

As described above, according to the foamed molded article of the rubber-modified polystyrene resin of the present invention, a high density can be achieved at a high level, and the "low stress buffering performance" required for a lightweight cushioning packaging material is excellent. In addition, the effect of obtaining a cushioning material for lightweight articles having both the basic cushioning performances of “compression strain recovery performance” and “air bubble resistance puncture prevention performance” was obtained.

The mechanism of action that produces such an effect is not necessarily clear, but is considered as follows. That is, in the rubber-modified polystyrene resin used in the present invention, (a) a rubber component dispersed and present in the form of particles inside a cell membrane forming a foamed molded article is relieved of internal stress caused by a drop impact. Effectively preventing the destruction of the bubble film, which is referred to as the "puncture phenomenon."

(B) The rubber component which is very permeable to the foaming agent and easily escapes has an average particle diameter which is a value sufficiently smaller than the thickness of the highly foamed and extremely thin foam film. By dispersing in the form of particles having a particle size of 1.0 μm or less, the rubber particles can be sufficiently covered with the polystyrene phase in the thickness direction of the cell membrane, and the property that the foaming agent of the polystyrene resin is not easily dissipated can be utilized. That

(C) The large distribution of the rubber particle diameter means that the composition, structure, etc., of the cross section of the extremely thin cell membrane is very inhomogeneous, the cells expand, the cell membrane expands in the plane direction, and tends to grow. It is considered that when this occurs, a phenomenon of non-uniform growth or partial growth difficulty is induced, and the bubble film is easily broken. Accordingly, the use of uniform rubber particles having a distribution of the rubber particle diameter of 1.5 or less, preferably 1.2 or less in the present invention enhances the formation of the closed cell structure of the obtained foamed molded article. It is considered.
It is believed that the mechanism of action described above produces a synergistic effect to achieve the targeted performance of the present invention.

[Measurement method] 1) Average particle diameter Butadiene rubber particles 500 to 500 in a transmission electron micrograph taken of a rubber-modified polystyrene resin by an ultra-thin section method.
The particle diameter of 1000 particles is measured and calculated by the following equation.

[0031]

(Equation 1)

[0032]

(Equation 2)

2) Particle size distribution Calculated by the following equation.

[0034]

(Equation 3)

3) Bulk density The expanded particles are weighed in a measuring container having an internal volume of 1000 cc so that the bulk volume becomes exactly 1000 cc. Then, the weight of the total amount of the weighed expanded particles is measured and calculated by the following equation.

[0036]

(Equation 4)

4) Density Weight (Wg) The volume (Vcm ³ ) of a known foam is measured by a submersion method, and the value obtained by dividing the weight by the volume is the density (g / cm).
³ ).

5) Closed cell ratio The true volume of about 24 cm ³ of a foam having a known density (g / cm ³ ) was measured by using an air comparison type hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. The bubble rate [S, (%)] is calculated.

[0039]

(Equation 5)

6) Low stress buffering coefficient According to JIS-Z-0235, a drop impact test was performed under the conditions of a drop height of 80 cm, a test specimen thickness of 5 cm, and a static stress value of 0.03 kg / cm ² , Decrease) Find the speed,
The data was the number of times of the first drop, and based on this data, it was determined as follows.

[0041]

(Equation 6)

7) Amount of recovery of compressive strain Vertical X according to JIS K-6767 repeated compression set test method
Specimens each measuring 50 mm × 50 mm × 50 mm in width × thickness were subjected to a 25% compression test and determined as follows.

[0043]

Equation 7] R: recovered amount of compression set (mm) R _1: 25% -compression of the thickness (mm) R _2: thickness after recovery _{(mm) R = R 2 -R} 1
.

8) Weight of puncture of air bubbles Vertical × horizontal × according to JIS-Z-0235, drop impact test method
A flat weight having a weight of 50 g is dropped from a height of 80 cm from the upper surface on the entire upper surface of the test specimen having a thickness of 100 mm x 100 mm x 50 mm from the upper surface to the lower surface in order to reduce impact and compressive strain. The weight of the weight when bursting starts to occur in the foam film of the foamed molded article as the test specimen is determined, and is defined as the weight of punctured bubbles. It should be noted that the test specimen once subjected to the drop impact test shall be replaced with a new test specimen without using again, and the next drop impact test shall be performed.

[Evaluation method] (1) Low stress impact absorption performance The low stress shock absorption coefficient is determined by the following evaluation scale based on the value determined in the section of the low stress buffer coefficient.

[0046]

[Table 1]

(2) Compressive strain recovery performance The following evaluation scale was used to determine the amount of compressive strain recovery (mm) obtained in the section on the method of measuring the amount of recovery of compressive strain.

[0048]

[Table 2]

(3) Puncture Prevention Performance of Air Bubble Resistance The puncture generation weight (kg) of the bubble obtained in the section of the method of measuring the puncture generation weight of the bubble was determined by the following evaluation scale.

[0050]

[Table 3]

[0051]

[Table 4]

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described below in detail with reference to embodiments. [Adjustment of Rubber-Modified Polystyrene] A butadiene-based polymer was dissolved in a styrene monomer at a compounding ratio shown in Tables 5, 6, and 7, and ethylbenzene 5 was added to 100 parts of the dissolved solution.
And 1,1-bis (t-butylperoxy) cyclohexane are added to adjust the polymerization raw material liquid. Each of the raw material liquids was separately fed into a continuous three-stage polymerization vessel to perform polymerization. Each polymerizer has a volume of 1.2 liters and is equipped with stirring blades.

The polymerization temperature was varied between 105 ° C. and 145 ° C., and was polymerized to a solid content of about 80% in the final polymerization reactor. Ethylbenzene is removed, the strand is drawn from the die, cooled with water, and cut into pellets. After measuring the content of the butadiene component in the pellet, if necessary, use a polystyrene resin (Stylon 683, manufactured by Asahi Kasei Kogyo Co., Ltd.).
It was diluted using a 0 mmφ single screw extruder and adjusted to the respective butadiene component amounts shown in Tables 5, 6, and 7. In the course of the polymerization, the temperature conditions of the polymerization, the conditions of the stirring, and the like were adjusted to finally obtain rubber-modified polystyrene resins (HIPS 1 to 20) shown in Tables 5, 6, and 7.

Examples and Comparative Example 1 Each of the above rubber-modified polystyrene resins was separately provided with a pressure-supplying device for a foaming agent, and a connection line from the pressure-supplying device was connected to a melt-kneading section in a cylinder of an extruder. To the extrusion impregnating device, which is equipped with a resin cooling device and a die device having a large number of outlet holes for the resin in the forehead, and pressurizes and supplies the foaming agent while melting and kneading in the extruder. Is pumped at a constant rate of 0.15 gram mole per 100 g of resin, and cooled to an appropriate temperature with a cooling device while kneading and mixing with the resin. And immediately cut in the length direction with a rotary cutter while taking it through a cooling bath storing cooling water to obtain each expandable resin particle.

EXPERIMENTAL EXAMPLE 1 Expandable resin particles obtained from rubber-modified polystyrene and HIPS-1 by the above-mentioned method were subjected to a single-stage expansion method called a one-stage expansion method using a steam expander to achieve a target bulk density. 0.011 g / cm ³ of foamed resin particles were obtained. Then, after the foamed resin particles are aged in a room at 20 ° C. for 24 hours, a molding machine for styrene foam (manufactured by Kasahara Kogyo; PION)
(Y-75 type) and each thickness, length and width are 5
A 0 mm × 300 mm × 300 mm plate-like foamed resin molded product was obtained. Next, the plate-like foamed resin molded product was dried in a drying room at a humidity of 50 ° C. for 3 hours and then taken out.
After aging for 0.01 hour, the bulk density was measured to be 0.011 g
/ Cm ³ and the results of evaluation are shown in Tables 8 and 9.

EXPERIMENTAL EXAMPLES 2 to 22 Rubber-modified polystyrene resins corresponding to the experimental numbers shown in Tables 8 and 9 (described in detail in Tables 5, 6, and 7) were used in the same manner as in Experimental Example 1. The obtained expandable resin particles,
Similarly, the foaming and molding were performed in the same manner as in Experimental Example 1 to obtain a foamed molded product corresponding to the experiment number, and the evaluation results are shown in Tables 8 and 9.

Comparative Example 2 Rubber-modified polystyrene obtained by the above method, HIPS-2
In addition, foaming resin particles were obtained in exactly the same manner as in Example 1, except that isopentane was supplied under a constant pressure by a pump at a ratio of 0.05 gram mole per 100 g of resin. Then, the foamed resin was foamed with a steam foaming machine to obtain foamed resin particles having a bulk density of 0.033 g / cc. Next, the foamed resin particles are allowed to stand in a room for 24 hours, and after aging, are foamed again by the steam foaming machine to obtain foamed resin particles having a target bulk density of 0.011 g / cc and are aged in a room at 20 ° C. for 24 hours. Tables 8 and 9 show the results of evaluation obtained by molding a foamed article having a density of 0.011 g / cm ³ by molding in the same manner as in Experimental Example 1.

[0058]

[Table 5]

[0059]

[Table 6]

[0060]

[Table 7]

[0061]

[Table 8]

[0062]

[Table 9]

[0063]

As has been described in detail above, the low-density foamed resin molded article of the present invention has the above-described structure, and thus has an impact absorption performance, a compression strain recovery performance, and an impact fracture resistance. Combined, has the advantage of excellent foam molded article for buffer packaging applications, for example, can be used for buffer packaging of lightweight and easily breakable contents such as electronic components, audio equipment or communication equipment, and because of low density It is an excellent invention that plays a major role in the industry where the weight used can be reduced and the amount of industrial waste generated can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is an experimental diagram showing the significance of the amount occupied by a butadiene component in a rubber-modified polystyrene resin of the present invention.

FIG. 2 is an experimental diagram showing the significance of butadiene-based polymer rubber particles of the rubber-modified polystyrene resin of the present invention.

FIG. 3 is an experimental view showing the significance of the density of the foam molded article of the present invention.

FIG. 4 is a sketch drawing in which a cross section of a rubber particle of the rubber-modified polystyrene resin of the present invention is enlarged.

FIG. 5 is an enlarged cross-sectional sketch showing a dispersion state of rubber particles of the rubber-modified polystyrene resin of the present invention.

FIG. 6 is a sketch drawing in which a cross section of a rubber particle of a comparative product is enlarged.

FIG. 7 is an enlarged cross-sectional sketch showing a dispersion state of rubber particles of a comparative product.

[Explanation of symbols]

 1 of FIG. 1 Buffer coefficient FIG. 2 of FIG. 2 Impact fracture initiation load 1 of FIG. 2 Particle size distribution of 1.2 FIG. 2 2 Particle size distribution of 1.5 FIG. Stress buffering coefficient Fig. 3-2 Recovery of compressive strain Fig. 4 1 polybutadiene Fig. 4 2 polystyrene Fig. 6 1 polybutadiene Fig. 6 2 polystyrene

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Claims (2)

(57) [Claims] 1. A polystyrene continuous phase in which a butadiene polymer rubber in which polystyrene is encapsulated in small particles is dispersed in the form of particles, and the content of the butadiene component in the whole is 5 to 15% by weight. And the weight average particle diameter of the butadiene polymer rubber particles is 0.05 to 1.0 μm.
m, a molded article comprising foamed particles of a rubber-modified polystyrene resin having a particle size distribution of 1.5 or less, having a density of 0.009 to 0.014 g / cm ³ and 80% of the cells The above is a low-density fused foamed resin molded article of polystyrene resin foamed particles having a closed cell structure. 2. A butadiene polymer rubber in which polystyrene is encapsulated in small particles in a continuous phase of polystyrene is dispersed in the form of particles, and the content of the butadiene component in the whole is 5 to 15% by weight. The volatile organic blowing agent is added in an amount of 100 grams of a rubber-modified polystyrene resin having a butadiene-based polymer rubber particle having a weight average particle size of 0.05 to 1.0 μm and a particle size distribution of 1.5 or less.
After obtaining foamable resin particles by impregnating the foamable resin particles in an amount of 07 to 0.25 gmol, the foamable resin particles are foamed by steam in a foaming machine, and the bulk density is 0.009 to 0.014 by one foaming.
The resulting foamed particles of g / cc, then the density fused molded foamed particles each other and heated with steam introduced expanded beads in the mold is in 0.009~0.014g / cm ^3, and the bubbles A method for producing a low-density fused foamed resin molded article of expanded polystyrene resin particles in which 80% or more of the polystyrene-based resin has a closed cell structure.