JP3427157B2 - Expandable styrene resin particles and expanded styrene resin molded article - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expandable styrene resin particles used for foam molding and expanded styrene resin moldings obtained by molding.

[0002]

2. Description of the Related Art Acrylonitrile (AN) content is 25
A foam obtained by adding a volatile foaming agent to an acrylonitrile-styrene copolymer having a high acrylonitrile content of not less than 50% by weight and not more than 50% by weight (hereinafter referred to as a high AN-containing AS resin) is When a material having excellent chemical properties and having excellent thermal conductivity characteristics is selected as the foaming agent, the thermal conductivity can be kept low for a long time due to the gas barrier property of the high AN-containing AS resin. Therefore, the present inventors have found that it can be used as a very excellent heat insulating material, and the present inventors have previously disclosed in Japanese Patent Laid-Open No. 8-598.
Proposed 77.

However, if an attempt is made to increase the content of acrylonitrile, the molecular weight of the styrene portion in the AS resin is lowered, and, in addition to the plasticization phenomenon of the foaming agent contained in the expandable resin particles, the conventional high AN content is included. The expandable resin particles of the AS resin are very sensitive to the heat (generally steam is used) during foam molding, so if the steam pressure is changed to some extent, they melt on the surface of the foam molded body. Experienced the occurrence of a condition (a so-called melting phenomenon). In addition, if the vapor pressure during molding is low, the internal fusion of the molded body and the surface elongation may be partially defective, or conversely, if the high pressure is used, the molten state may partially occur on the surface of the foamed molded body. was there.

[0004]

[Problems to be Solved by the Invention]
The expandable resin particles that use N-containing AS resin as the base resin may have insufficient heat resistance, and may be molded into a large size or have a complicated shape or a large number of molded products with the same mold. In such a case, it becomes difficult to uniformly heat the entire die with steam, and it may be difficult to obtain a foamed molded product having a good internal fusion state and appearance as a whole. In addition, when the molten state is generated on the surface of the foamed molded product, not only the commercial value is lowered, but also the other characteristic of the foamed molded product is excellent in thermal conductivity, that is, excellent heat insulating performance. It will not be able to exhibit its characteristics. From the present situation, the present invention provides heat-resistant, expandable resin particles capable of easily responding to changes in heating conditions by steam at the time of foam molding, and the internal fusion state and surface state of the resulting foam molded article. It is an object of the present invention to provide an excellent foamed molded article which is excellent in heat conductivity and has a small thermal conductivity.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned object, the present inventors have found that a high AN-containing AS resin is kneaded with a specific N-phenylmaleimide-modified resin to improve the heat resistance of the resin. As a result, the range of vapor pressure that can be molded is widened, so that the obtained foamed molded product has an excellent internal fusion state and stabilizes the foamed molded product having no molten state on the surface. The present invention has been completed by finding out that the foamed molded product can be obtained by the above, and that the obtained foamed molded product has a low thermal conductivity and an excellent heat insulating property.

In the present invention, the vinyl cyanide compound unit is 3
0 to 50% by weight and aromatic vinyl compound unit 70 to 5
0 wt% and comprising a copolymer and (A), N-phenyl-Ma <br/> Reimido units 20 to 60 wt%, the aromatic vinyl compound units and 75 to 10 wt%, the vinyl cyanide compound unit 5 to 30% by weight of the copolymer (B) is mixed with a base resin obtained by adding a volatile foaming agent to the expandable styrene resin particles, wherein the base resin Is 85 to 98% by weight of the copolymer (A), and the copolymer (B) is
2 to 15% by weight of the expandable styrene resin particles, and 5 to 25% by weight of a volatile foaming agent in the expandable styrene resin particles. These are resin particles and have excellent heat resistance.
It is possible to provide expandable styrenic resin particles that can easily cope with changes in heating conditions due to steam during foam molding. Further, the foamed styrene-based resin molded body characterized by having a closed cell ratio obtained by foaming and molding the above-mentioned foamable resin is 85 to 100%, and both the internal fusion state and the surface state are excellent, and It is possible to obtain an excellent foamed styrene resin molded product having a small thermal conductivity.

Examples of the monomer constituting the vinyl cyanide compound unit used in the present invention include acrylonitrile and methacrylonitrile, and acrylonitrile is particularly preferable. Moreover, these can be used individually or in mixture of 2 or more types. Also,
Examples of the monomer constituting the aromatic vinyl compound unit used in the present invention include styrene, α (alpha) -methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, divinylbenzene,
It is a styrene derivative such as vinylnaphthalene, and styrene and α-methylstyrene are particularly preferable. Moreover, these can be used individually or in mixture of 2 or more types.

Examples of the monomer constituting the N-substituted maleimide unit used in the present invention include N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide and N-methylmaleimide.
-Phenylmaleimide, N-cyclohexylmaleimide, N-orthochlorophenylmaleimide, N-orthomethylphenylmaleimide, N-orthomethoxyphenylmaleimide and the like. Particularly, N-phenylmaleimide and N-cyclohexylmaleimide are preferable. Moreover, these can be used individually or in mixture of 2 or more types.

The copolymer (A), which is one of the base resins for the expandable styrenic resin particles of the present invention, contains 30 to 50% by weight of a vinyl cyanide compound unit and 70 to 50% of an aromatic vinyl compound unit. A copolymer which is 50% by weight is used. The content of the above vinyl cyanide compound unit is preferably 32 to 45% by weight, more preferably 3% by weight.
5 to 41% by weight. The reason for this is that if the amount is less than 30% by weight, a good foamed molded product can be obtained without mixing the copolymer (B), but since the gas barrier property is low, low thermal conductivity can be maintained for a long period of time. It is not preferable because it cannot be done. Further, when it exceeds 50% by weight, the viscosity of the resin becomes high and it becomes difficult to produce the copolymer (A), which is not preferable.

On the other hand, the copolymer (B) has an N-substituted maleimide compound unit of 20 to 60% by weight, an aromatic vinyl compound unit of 75 to 10% by weight, and a vinyl cyanide compound unit of 5 to 30% by weight. A copolymer consisting of and is used.
More preferably, the N-substituted maleimide compound unit is 3
0-40% by weight, aromatic vinyl compound unit 65-40
%, And the vinyl cyanide compound unit is 5 to 20% by weight. The reason why the above ratio is necessary is that when the content of the N-substituted maleimide compound unit is less than 20% by weight, the effect of improving heat resistance becomes insufficient, and when it exceeds 60% by weight, the fluidity of the polymer deteriorates. In addition, the compatibility with the copolymer (A) also deteriorates, which is not preferable.

If the amount of the aromatic vinyl compound unit exceeds 75% by weight, the effect of improving the heat resistance becomes insufficient, and if it is less than 10% by weight, the mechanical strength becomes low, which is not preferable. Vinyl cyanide compound unit 5% by weight
When it is less than the above range, the compatibility with the copolymer (A) is lowered and the heat resistance as the base resin cannot be sufficiently exhibited, which is not preferable. On the other hand, when it exceeds 30% by weight, the N-substituted maleimide compound unit is relatively decreased, and the effect of improving heat resistance is reduced, or the aromatic vinyl compound unit is reduced, and mechanical strength is reduced, which is preferable. Absent.

The base resin of the expandable styrenic resin particles of the present invention comprises the copolymer (A) and the copolymer (B).
It is necessary that the compounding ratio of is in the range of 2 to 15% by weight. The preferred blending ratio of the copolymer (B) is 3 to
13% by weight, more preferably 4 to 9% by weight. If the amount of the copolymer (B) is less than 2% by weight, the effect of improving the heat resistance at the time of molding will be small, and if it exceeds 15% by weight, the compatibility will be poor. This is because the elongation of the surface of the molded body is deteriorated, which is not preferable.

The means for mixing the copolymer (A) and the copolymer (B) is not particularly limited, but these copolymers are mixed in a predetermined blending ratio in advance with a V blender or a Nauta. After mixing using a mixer such as a mixer or a super mixer, the mixture is put into an extruder and sufficiently heated and melted to form a base resin, or a copolymer (A)
And a copolymer (B) are heated and melted by separate extruders, and then heated and melted and mixed so that a predetermined blending ratio can be obtained.

The base resin thus obtained was passed through an extruder and the expandable styrene resin particles had a diameter of about 0.
It can be extruded to have a diameter of 3 to 2.0 mm and cut into pellets or the like to obtain base resin particles for expandable styrene resin particles. The extruder that can be used here includes a single-screw extruder with a vent, a twin-screw extruder, and the like, but is not particularly limited.

The base resin of the expandable styrenic resin particles of the present invention has a methanol-soluble content of 3% by weight contained in the resin.
The following is preferable. This is because when the amount of methanol-soluble components is large, the heat resistance during foam molding is lowered, and a molten state is likely to occur on the surface of the foam molded body. The term "methanol-soluble component" as used herein means that the copolymer is dissolved in methyl ethyl ketone, and then the insoluble component when reprecipitated with a large amount of methanol is filtered through a glass filter, and the result of precise weighing after drying indicates the methanol-soluble component. It is obtained by measuring the weight fraction. The methanol-soluble component is a low molecular weight component mainly composed of N-substituted maleimide and aromatic vinyl compound.

The MFR of the base resin of the expandable styrenic resin particles of the present invention is preferably 0.1 to 5 g / 10 minutes, more preferably 0.1 to 2 g / 10 minutes.
More preferably, it is 0.15 to 1.1 g / 10 minutes. This is because when the MFR exceeds 5 g / 10 minutes, the molecular weight of the resin is lowered, so that it is not suitable as a resin for foam molding.

The expandable styrenic resin particles of the present invention are dispersed in an aqueous medium containing a dispersion aid such as an inorganic dispersant in a pressure vessel equipped with a stirrer, in which the above-mentioned base resin particles are sealed. Then, add a predetermined amount of volatile foaming agent, 60 ~ 1
It can be obtained by stirring at 30 ° C. to impregnate the base resin particles with the foaming agent, cooling and depressurizing, and then separating from the aqueous medium. As another method, a foaming agent is added during heating, melting and mixing of the copolymer (A) and the copolymer (B) to impregnate the base resin particles with the foaming agent and cool the mixture to a predetermined size. A method of cutting may be used.

As the inorganic dispersant of the present invention, it is possible to use an inorganic fine powder which is poorly soluble in water, such as metathesis method magnesium pyrophosphate, magnesium oxide and tricalcium phosphate. As the dispersion aid, an anionic surfactant such as sodium dodecylbenzene sulfonate can be used in combination. The amount of the inorganic dispersant used is preferably 0.05 to 5.0% by weight.

The expandable styrenic resin particles of the present invention may also contain various additives such as foaming aids (toluene, cyclohexane, ethylbenzene, etc.), fillers (silica, alumina, titanium oxide, talc, etc.) as required. Clay, calcium carbonate, etc.), lubricant (liquid paraffin, fatty acid ester, metal soap, etc.), flame retardant, flame retardant aid, antistatic agent, etc. can be added as appropriate.

Examples of the blowing agent used in the present invention include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane and hexane, cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane, methylene chloride, Halogenated hydrocarbons such as ethyl chloride, monochlorodifluoroethane (F-142b), dichlorofluoroethane (F-141b), trichlorofluoromethane, dichlorodifluoromethane, dichlorotrifluoroethane (F-123), dichlorotetrafluoromethane, etc. Halogenated fluorocarbons, tetrafluoromethane (F-134a), pentafluoroethane (F-12
5), difluorobutane (F-245fa, F-245
ca), trifluorobutane (F-236ea) and the like 2
The above-mentioned fluorine-containing hydrocarbon having 2 to 6 carbon atoms substituted with a fluorine atom, or a mixture thereof may be mentioned. Of these, fluorine-containing halogenated hydrocarbons and fluorine-based hydrocarbons are particularly preferable in that the heat insulating performance can be improved.

The foaming agent is preferably contained in the expandable resin particles in an amount of 5 to 25% by weight, more preferably 10 to 2%.
It is 0% by weight. This is because if it is less than 5% by weight, a sufficient foaming force cannot be obtained, and it is difficult to impregnate a foaming agent exceeding 25% by weight.

The expanded styrene resin molded article of the present invention is prepared by heating the expandable styrene resin particles with a heating medium such as steam to a temperature not lower than the softening temperature of the expandable resin to obtain pre-expanded particles having a desired bulk density. The pre-expanded particles can be obtained by filling the pre-expanded particles in a mold that can be sealed but not sealed, heat-foamed with a heating medium such as steam, cooled, and taken out from the mold. The pre-expanded particles and the foamed molded product may be subjected to an aging step, if necessary.

The bulk density of the expanded styrene resin molding of the present invention must be 0.10 to 0.017 (g / cm ³ ). The bulk density of the foamed molded article as referred to herein is a value obtained by dividing the weight of the foamed article by its volume, and this expression is used below unless otherwise specified. Bulk density is 0.10 (g /
This is because, when it is cm ³ ) or more, the fusion of the expanded particles becomes very bad, and when it is 0.017 (g / cm ³ ) or less, the thermal conductivity of the molded body becomes large and the heat insulating performance deteriorates.

The closed cell ratio of the expanded styrene resin molding of the present invention is preferably 85 to 100%. The reason for this is that if the closed cell rate is less than 85%, the physical properties, particularly the thermal conductivity, are adversely affected, and the closed cell rate is preferably 85% or higher. When molding is carried out by the conventional method, the heat of steam at the time of molding cannot be endured, the bubbles of the foam are broken, and the closed cell ratio decreases. In such a state, the volatile foaming agent with a small thermal conductivity remaining in the bubbles dissipates and, conversely, it is replaced by air with a large thermal conductivity, etc. Is expected to decrease. The foam obtained by the method according to the present invention has a high closed cell rate and can maintain excellent thermal conductivity.

The molding conditions for obtaining the expanded styrene resin molding of the present invention depend on the heating time, but the pressure of the steam introduced into the mold is 0.3 to 1.0 (Kgf / c).
m ² gauge pressure) is preferred, more preferably 0.4 to
It is 0.8 (Kgf / cm ² gauge pressure). 0.3 (K
If the pressure is less than gf / cm ² gauge pressure), a molten state is unlikely to occur in the appearance of the molded product, but the degree of fusion in molding is reduced and mechanical properties are poor. Above 1.0 (Kgf / cm ² gauge pressure),
It is difficult to control the molten state of the foamed molded product. As mentioned above, even if a large-sized molded product or a molded product with a complicated shape, or if multiple molded products are molded with the same mold, the range of molding conditions can be widened, so internal fusion It is possible to stably and reproducibly obtain a good molded product having an excellent appearance and a high closed cell rate.

The expandable resin particles obtained by adding the volatile foaming agent to the resin particles made of only the copolymer (A) not containing the copolymer (B) are 0.4 (kgf / cm ² Even with a vapor pressure of (gauge pressure), a part of the foamed molded product is melted, so that the bubbles of the molded product are broken and the closed cell ratio is lowered, and as a result, various physical properties are deteriorated. In particular, the thermal conductivity increases and the heat insulating performance decreases.

The present invention is excellent in that the heat resistance during foam molding can be increased without deteriorating the various physical properties, particularly the thermal conductivity, and also the heat resistance of the foam can be improved. For example, in the present invention, 5% of the copolymer (B)
The expanded styrene resin molded product obtained from the added expandable resin particles had a dimensional change of 0.5% or less when left in a constant temperature bath at a temperature of 80 ° C. for one week. On the other hand, a styrenic foamed resin molded product composed of only the copolymer (A) without the addition of the copolymer (B) shows a dimensional change of 0.5% when left in a constant temperature bath at a temperature of 75 ° C for one week. It was beyond. Thus, the heat resistant temperature of the foamed molded product obtained by the present invention can be improved by 5 to 10 ° C.

Since the expanded styrene resin molded product of the present invention has excellent thermal conductivity characteristics, this molded product is used as it is or in a structure in which it is sandwiched between other unfoamed resins, wood, concrete and the like. As a result, a very excellent heat insulating structure can be obtained. Further, since the AS component is included, oil adheres to other substances in contact with the foam, and even if the substance contains a plasticizer or the like, the molded body is not corroded by them, and therefore chemical resistance is high. It can be used as an excellent heat insulating structure that also has properties.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples and Comparative Examples. Example 1. Copolymer (A) having an acrylonitrile (AN) content of 40% by weight and a styrene (ST) content of 60% by weight (AS-4C, manufactured by Nippon Steel Chemical Co., Ltd.)
P: hereinafter referred to as AS-4CP) 95% by weight, styrene content 50% by weight, N-phenylmaleimide (PM
I) content 40% by weight, acrylonitrile content 1
5% by weight of the copolymer (B) (hereinafter referred to as N-phenylmaleimide modified resin) in a proportion of 0% by weight was previously blended in a V blender, and then kneaded in an extruder with a vent,
Pellets having a diameter of 0.5 mm and a length of 1.2 mm were obtained. MFR of the obtained pellets is 0.73 g
/ 10 minutes, the methanol-soluble content was 1.1% by weight.
The pellets were transparent and free of cloudiness.

Next, 1500 g of the obtained pellets and 25 parts of water were placed in an autoclave with a stirrer having an internal volume of 5 liters.
00 g and 30 g of magnesium oxide were added and stirred to disperse the resin in water. Next, with stirring, Freon HCF
C-123 225g and Freon HCFC-142b 1
After charging with 50g, the internal temperature of the autoclave is 110
The temperature was raised to ℃. The internal pressure of the autoclave at this time was 14 kgf / cm ² . After maintaining at 110 ° C. for 6 hours, it was cooled to 25 ° C. and separated from the aqueous medium to obtain expandable resin particles. The expandable resin particles were spherical particles. The expandable resin particles obtained contained 17% by weight of a foaming agent.

The expandable styrene resin particles obtained were steamed to obtain pre-expanded particles having a bulk density of 0.05 g / cm ³ . After leaving the pre-expanded particles at room temperature for 24 hours, the pre-expanded particles are filled in a mold having a content size of (500 × 300 × 15 mm), and 0.5 kg / cm ² of steam is introduced into the mold to carry out secondary Foaming was performed to obtain a foamed styrene resin molding. The obtained molded body had no melting on the surface and had a good appearance. This molded body was superior in heat resistance during molding and the appearance of the molded product to the case where the conventional AS resin was used. In addition, when the physical properties, especially the thermal conductivity, were measured, it was superior to when the conventional AS resin was used,
It was not aggravated by kneading the phenylmaleimide. The physical properties of the obtained foamed molded product are shown in Table 1.

[0032]

[Table 1]

Various physical properties were measured according to the following methods. 1. The thermal conductivity was measured according to JIS A1412. Device: AUTO-Λ HC-072 (Eihiro Seiki Co., Ltd.)
Manufacturing) Method: Heat flow meter method 1 Temperature measurement (20 ° C.) Test piece: 200 × 200 × 25 t (mm) 2. The closed cell ratio was measured according to ASTM D2856. Apparatus Air-comparison hydrometer (manufactured by Tokyo Science Co., Ltd.) Method: 1-1 / 2-1 Atmospheric pressure method Test piece: 28 × 28 × 23t (mm) Resin density: 1.05 g / cm ³ 3. MFR was performed according to JIS K 7210. Apparatus: Melt indexer conditions: Temperature; 200 ° C., load: 5 kg, sample weight: 5 g 4. The surface condition of the molded product was evaluated by the following method and evaluated according to the following criteria. Molding apparatus: ACE-11 molding machine (manufactured by Sekisui Machinery Co., Ltd.) Criteria: ⊚ does not show melting or elongation defects on the molding surface. ◯ indicates that the melting or elongation of the molded surface is less than 5% of the entire surface. △ indicates that the melting or elongation of the molding surface is 5-1 of the entire surface.
It is 0%. ×: defective melting or elongation of the molding surface is 10% of the entire surface
Greater than

Example 2. Expandable styrenic resin particles were obtained in the same manner as in Example 1 except that the mixing ratio of the N-phenylmaleimide-modified resin as the copolymer (B) was changed as shown in Table 2, and the expandable styrene-based resin particles had a bulk density of 0. It was pre-expanded particles of 0.05 g / cm ³ .

[0035]

[Table 2]

After filling the obtained pre-expanded particles in the same manner as in Example 1, the steam pressure introduced into the mold was 0.3 to 0.
It was molded by changing to 8 kgf / cm ² . The evaluation of the obtained molded body is shown in Table 2. As the amount of N-phenylmaleimide-modified resin increased, the degree of improvement in moldability increased, and a wide molding width could be provided.

Comparative Example 1. Copolymer (A) (AS-4C
Example 2 was repeated except that P) was 100% by weight and the copolymer (B) was not used. The results are shown in Table 2. When the N-phenylmaleimide-modified resin was 0%, the moldable range was extremely narrow and practical use was difficult. Comparative example 2. The same procedure as in Example 2 was carried out except that the mixing ratio of the copolymer (A) (AS-4CP) and the copolymer (B) was changed to 80/20. The results are shown in Table 2. When the N-phenylmaleimide-modified resin was 20% by weight, no molten state was generated on the surface of the foamed molded product, but the elongation was poor as a whole.

Example 3. Example 1 was carried out in the same manner as in Example 1 except that the copolymer (A) was changed to 30% by weight of acrylonitrile and 70% by weight of styrene. The obtained pellets had an MFR of 1.05 g / 10 minutes and a methanol-soluble content of 1.
It was 4% by weight. As a result of impregnating the obtained pellets in the same manner as in Example 1 and performing foam molding, a good molded product could be obtained. The physical properties of the obtained foamed molded product are shown in Table 1.

Example 4. Example 1 was carried out in the same manner as in Example 1 except that the copolymer (A) was changed to a resin containing 50% by weight of acrylonitrile and 50% by weight of styrene. The obtained pellets had an MFR of 0.16 g / 10 minutes and a methanol-soluble content of 1.6% by weight. As a result of impregnating the obtained pellets in the same manner as in Example 1 and performing foam molding, a good molded product could be obtained. The physical properties of the obtained foamed molded product are shown in Table 1.
It was shown to.

Example 5. Copolymer (A) (AS-4C
Example 1 was repeated except that the ratio of P) was changed to 90% by weight and the ratio of the copolymer (B) was changed to 10% by weight. The obtained pellets had an MFR of 0.66 g / 10 minutes and a methanol-soluble content of 1.3% by weight. When foam molding was performed in the same manner as in Example 1, a good molded product could be obtained, and the heat resistance during molding was higher than when 5% was added, and molding with a good appearance even at a higher steam pressure. I got the goods. The physical properties of the obtained foamed molded product are shown in Table 1.

Example 6. Copolymer (A) (AS-4C
Example 1 was repeated except that the proportion of P) was changed to 85% by weight and that of the copolymer (B) was changed to 15% by weight. The obtained pellets had an MFR of 0.46 g / 10 minutes and a methanol-soluble content of 1.3% by weight. There was slight clouding on the pellets, but there was no problem in producing the pellets. When foam molding was carried out in the same manner as in Example 1, the elongation was not as good as in Example 4, but there was no sink, and it was possible to mold at a higher water vapor pressure than conventional AS resin, and molding with a good appearance I got the goods. The thermal conductivity was also unchanged and good. The physical properties of the obtained foamed molded product are shown in Table 1.

Comparative Example 3. Copolymer (A) as base resin
(AS-4CP) was used in the same manner as in Example 1 except that 100% by weight was used. The obtained pellets had an MFR of 0.65 g / 10 minutes and a methanol-soluble content of 1.2% by weight.
Met. When foam molding was carried out in the same manner as in Example 1, melting occurred on the surface of the molded product, and a good molded product could not be obtained. It is considered that the heat resistance of the resin was not sufficient. In addition, melt shrinkage also occurred inside the foamed molded product, and the closed cell ratio decreased, so that the thermal conductivity characteristics deteriorated. The physical properties of the obtained foamed molded product are shown in Table 1.

Comparative Example 4. Copolymer (A) (AS-4C
Example 1 was repeated except that P) was 80% by weight and the copolymer (B) was 20%. The obtained pellets had an MFR of 0.40 g / 10 minutes and a methanol-soluble content of 1.
It was 2% by weight. The pellet was cloudy. When foam molding was carried out in the same manner as in Example 1, the surface elongation of the foam molded article was poor and a good foam molded article could not be obtained. It is considered that this is because the range of the compatibility of the AS resin and the phenylmaleimide modified resin was exceeded. The physical properties of the obtained foamed molded product are shown in Table 1.

Comparative Example 5. As the copolymer (A), AS-
The same procedure as in Example 1 was carried out except that a copolymer containing 25% by weight of acrylonitrile and 75% by weight of styrene was used instead of 4CP. The obtained pellets had an MFR of 1.22 g / 10 minutes and a methanol-soluble content of 1.4% by weight.
Met. As a result of foam molding in the same manner as in Example 1,
It was possible to obtain a good foamed molded product, but it was not possible to maintain a low thermal conductivity for a long period of time because of its poor gas barrier property. The physical properties of the obtained foamed molded product are shown in Table 1.

[0045]

As described above, the expandable styrenic resin particles of the present invention contain 30 to 50 vinyl cyanide compound units.
70% to 50% by weight of aromatic vinyl compound unit
And a copolymer (A) consisting of 20 to 60% by weight of an N-substituted maleimide unit, 75 to 10% by weight of an aromatic vinyl compound, and 5 to 30% by weight of a vinyl cyanide compound ( The heat resistance can be improved by mixing with B) in a specific range where these are compatible regions. Furthermore, since a foaming agent is contained in these base resins, the range of vapor pressure that can be molded is wide, and the resulting foamed molded article has an excellent internal fusion state, and there is no molten state on the surface. A foamed molded product can be stably obtained. Further, since the obtained foamed molded product can be obtained by containing a foaming agent having a low thermal conductivity, a foamed product excellent in oil resistance, solvent resistance, weather resistance and long-term maintenance of low thermal conductivity. Can be

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeharu Akishima 1-2-8-8, Chiyogaoka, Aso-ku, Kawasaki City, Kanagawa Prefecture (72) Koji Kito 1-2-8-102, Chiyogaoka, Aso-ku, Kawasaki City, Kanagawa Prefecture (56) References JP-A-4-345639 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 9/16-9/22 C08L 25/00-25/18

Claims (3)

(57) [Claims] 1. A copolymer (A) comprising 30 to 50% by weight of a vinyl cyanide compound unit and 70 to 50% by weight of an aromatic vinyl compound unit, and 20 to 60% by weight of an N-phenylmaleimide unit. %, Aromatic vinyl compound unit is 75
Foamable styrene-based resin containing a volatile foaming agent in a base resin obtained by mixing a copolymer (B) composed of 10 to 10% by weight and a vinyl cyanide compound unit of 5 to 30% by weight. Resin particles, wherein the base resin contains 85 to 98% by weight of the copolymer (A) and 2 to 15% of the copolymer (B).
Expandable styrenic resin particles characterized by being mixed by weight. 2. The expandable styrenic resin particles according to claim 1, wherein the volatile foaming agent is contained in the resin particles in an amount of 5 to 25% by weight. 3. A foamed styrene-based resin molded product, which has a closed cell ratio of 85 to 100% obtained by foaming the expandable resin particles according to claim 1 or 2.