JPH07278338A - Foamed styrene resin and its production - Google Patents

Abstract

PURPOSE:To provide a foamed styrene resin having excellent heat-insulation performance and mechanical properties without using a chlorine-containing compound liable to generate an acid, etc., inducing the corrosion of mold by using a specific aliphatic foaming agent in combination with a specific evaporation-type foaming agent. CONSTITUTION:This foamed styrene resin having a thickness of 20-150mm is produced by mixing a styrene resin with (A) an aliphatic foaming agent composed of 25-70wt.% of propane and 75-30wt.% of a pentane (preferably n-pentane) and (B) an evaporation-type foaming agent consisting of 1,1-difluoro-1- chloroethane preferably at a weight ratio (A/B) of 15/85 to 60/40 by pressing the foaming agents into the resin or adding to the resin. The amount of the component B is 0.15-0.25mol based on 100g of the styrene resin and the foam contains the components A and B. Preferably, the foams are composed of foams having a foam diameter of <=0.25mm and foams having a foam diameter of 0.4-1mm and the areal ratio of the foam of <=0.25mm diameter is 10-80% per unit cross-section of the foamed material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a styrene resin foam and a method for producing the same. More specifically, it relates to a styrene resin foam which can be suitably used as a heat insulating material and a method for producing the same.

[0002]

2. Description of the Related Art Among styrene resin foams mainly used as a heat insulating material for construction, a method of using an evaporative foaming agent is mainly used as a method for producing an extruded foam.

The evaporative foaming agent used here not only serves as foaming energy, but also has a plasticizing function in the extrusion system, and also has a function of adjusting cell size and controlling cell growth rate in the foaming process. In addition, since it is greatly contained in the bubbles of the produced foam, it has a great influence on the performance of the foam, especially the thermal conductivity that governs the heat insulation property. The choice of foaming agent has always been a major research issue.

Conventionally, the evaporative foaming agents used in styrene resin extruded foams include a poorly permeable foaming agent that governs the performance of the foamed product after foaming, plasticization in the extruder, foaming energy and bubbles. The combination with an easily permeable foaming agent that affects growth rate control is often used. As a typical example, dichlorodifluoromethane is a group of easily permeable foaming agents from the group of hardly permeable foaming agents. Since then, methyl chloride is mainly used.

However, in recent years, research on the relationship between ozone layer depletion in the stratosphere and chlorine originating from CFCs has progressed, and the abolition of specific CFCs has been decided from the viewpoint of ozone layer protection. Japanese Patent Publication No. 57-7175 discloses 1,1-difluoro-1-chloroethane, which contains chlorine but has a smaller ozone depleting ability than specific CFCs in which all the substituents are replaced by chlorine and fluorine. A foaming agent has been proposed in which an easily permeable foaming agent such as methyl chloride or ethyl chloride is combined as an optional component.

From the viewpoint of occupational hygiene, it is required to protect the working environment of methyl chloride and ethyl chloride. Therefore, it is more preferable to use a foaming agent that is not restricted in use.

On the other hand, in the industry in which the refractory blowing agent was forced to be changed due to the total abolition of dichlorodifluoromethane, which had been handled as a representative of the refractory blowing agent, the performance was lower than that of dichlorodifluoromethane. For the purpose of preventing the above, for example, even when using 1,1-difluoro-1-chloroethane described in JP-B-57-7175, a non-permeable foaming agent in which the heat insulating performance is contained in the bubbles. The present inventors have developed a method for improving not only the above performance but also the cell structure of the foam (Japanese Patent Laid-Open No. 3-109445).

In the above method, 1,1-difluoro-1-chloroethane is used as an example of the hardly permeable foaming agent, and methyl chloride is used as an example of the easily permeable foaming agent, and the bubble diameter is mainly 0.25 mm or less. Bubbles and bubble diameter 0.4
Water is used together with an inorganic powder having a large number of hydroxyl groups on the surface and a water-absorbing polymer substance in order to obtain a foam having a cell structure composed of bubbles of 1 mm.

However, when such a method is adopted, since water is present, hydrochloric acid is generated due to the hydrolysis reaction of methyl chloride depending on the apparatus and manufacturing conditions adopted, and the hydrochloric acid causes the extrusion / foaming apparatus. May be corroded. In order to prevent such corrosion, it is possible to neutralize the generated hydrochloric acid by mixing an alkaline substance into the system, but such a neutralization reaction is not always sufficient, and a better solution is desired. There is.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and has a heat insulating property and various machines without using chlorine-containing compounds such as methyl chloride and ethyl chloride, which easily generate acid. The object is to provide a foam having excellent physical properties.

[0011]

That is, the present invention is
An aliphatic foaming agent consisting of 25 to 70% by weight of propane and 75 to 30% by weight of pentane and an evaporative foaming agent consisting of 1,1-difluoro-1-chloroethane are contained in the cells and have a thickness of 20 to Styrenic resin foam characterized by having a length of 150 mm, and 25 to 70% by weight of styrene and 75 to 75% of pentane on styrene resin.
30% by weight of an aliphatic foaming agent and an evaporative foaming agent consisting of 1,1-difluoro-1-chloroethane are press-fitted or added, and then extrusion foaming is performed, and a styrene-based resin having a thickness of 20 to 150 mm The present invention relates to a method for producing a resin foam.

[0012]

FUNCTION AND EXAMPLE As described above, the styrenic resin foam of the present invention is obtained by adding 25 to 30% of propane to styrene resin.
It is obtained by press-fitting or adding an aliphatic blowing agent consisting of 70% by weight and 75 to 30% by weight of pentane and an evaporative blowing agent consisting of 1,1-difluoro-1-chloroethane, followed by extrusion foaming.

In the present invention, hydrocarbons containing chlorine atoms such as methyl chloride and ethyl chloride are not used at all as the easily permeable blowing agent, and specific ones of the aliphatic hydrocarbons, that is, propane and pentane are used. And when such propane and pentane are mixed at a constant ratio, by combining with 1,1-difluoro-1-chloroethane, which is one of the hydrofluorocarbon-based blowing agents, the heat insulating property and the mechanical property are improved. A foam with excellent strength can be obtained.

The aliphatic blowing agent used in the present invention is composed of 25 to 70% by weight of propane and 75 to 30% by weight of pentane.

Thus, in the present invention, a mixture of propane and pentane is used because, when the mixture of propane and pentane is used, these hydrocarbons are dissolved in the molten resin in the extrusion system. Becomes easier,
This is because it is easy to uniformly disperse in the molten resin in the extruder and the extrusion state is stabilized.

For example, when propane is used alone as a hydrocarbon without using pentane together, a foam product which does not require a skin layer on its surface, such as a mechanical product such as sliced to a desired thickness. Although it can be used in the production of foam products produced by finishing, the plasticization of the molten resin becomes insufficient, and phenomena such as cracks occur in the skin layer. Is not suitable for. In addition, when pentane is used alone as a hydrocarbon without using propane in combination, there is a restriction that the foam after extrusion will shrink and the foam density cannot be made too small. Like

From this point of view, the aliphatic blowing agent is 25% by weight or more of propane, preferably 30% by weight or more, that is, 75% by weight or less of pentane, preferably 70% by weight.
Further, it is composed of 70% by weight or less of propane, preferably 60% by weight or less, that is, 30% by weight or more of pentane, preferably 40% by weight or more.

As pentane, normal pentane is particularly preferable because it has excellent compatibility with styrene resins such as polystyrene, but isopentane, neopentane and the like can also be used in the present invention.

The mixing ratio of the aliphatic foaming agent and 1,1-difluoro-1-chloroethane is such that the aliphatic foaming agent /
If the 1,1-difluoro-1-chloroene (weight ratio) is too small, it tends to be difficult to obtain the desired heat insulating performance of the foamed body, so 10/90 or more,
It is preferable to adjust it so that it is above 15/85, and if it is too large, 1,1-
Difluoro-1-chloroethane is less likely to volatilize from the cell, the cell internal pressure rises with the inflow of air, and the heat resistance of the foam tends to decrease, so it is 70/30 or less, especially 60/40 or less. It is preferable to adjust

In the present invention, if butane is further present in the evaporative blowing agent, the cause is not clear, but the combustion characteristics of the obtained foam become poor,
Not desirable depending on the application.

Examples of the styrene resin used in the present invention include polystyrene and, for example, styrene and α-
Examples thereof include copolymers of monomers capable of copolymerizing with styrene such as methylstyrene and maleic anhydride, and resins obtained by blending polystyrene with styrene-butadiene rubber.

In the present invention, the styrenic resin may optionally contain additives such as a nucleating agent, an inorganic powder having a large number of hydroxyl groups on its surface, and a water-absorbing polymer compound.

Examples of the nucleating agent include known nucleating agents used in extrusion foaming. Typical examples of the nucleating agent include talc powder and calcium carbonate powder, and these nucleating agents can be used alone or in combination of two or more kinds. The particle size of the nucleating agent is usually 3 to 100 μm, especially 5 to 20 μm.
Is preferably adjusted so that The nucleating agent is mainly used for adjusting the size of the bubbles having a bubble diameter of 0.4 to 1 mm in the obtained foam, and the compounding amount of the nucleating agent is 100 parts by weight of the styrene resin ( Parts by weight,
The same shall apply hereinafter) 0.05 to 5 parts, especially 0.1
It is preferable to adjust it to be about 2.5 parts. When the blending amount is less than the above range, the effect of blending the nucleating agent is not sufficiently exhibited, and the cell size tends to be enlarged, and if the above range is exceeded. In the meanwhile, although the cell size becomes small, it tends to be difficult to achieve the target density.

Further, in the present invention, a foam is obtained by the usual extrusion foaming using the nucleating agent, and in addition to the nucleating agent, an inorganic powder having a large number of hydroxyl groups on the surface or a water-absorbing polymer compound. With the presence of water in the extrusion system,
By mixing small cells, it is possible to obtain a foam having a more desirable cell structure.

A typical example of the inorganic powder having a large number of hydroxyl groups on the surface is A manufactured by Nippon Aerosil Co., Ltd.
Examples thereof include anhydrous silica having a silanol group on the surface such as EROSIL (average particle size 12 × 10 ⁻³ μm), and such inorganic powders can be used alone or in combination of two or more kinds. The average particle size of the inorganic powder having a large number of hydroxyl groups on the surface is usually 5 × 10 ⁻³ to 30 × 10 ⁻³ μ.
m, especially 5 × 10 ^{−3 to} 20 × 10 ⁻³ μm. The blending amount of the inorganic powder having a large number of hydroxyl groups on the surface is preferably adjusted to be 0.05 to 2 parts, particularly 0.1 to 0.5 parts, relative to 100 parts of the styrene resin. When the amount is less than the above range, the number of fine bubbles to be produced tends to decrease, and when it exceeds the range, fine bubbles tend to be less likely to be produced. .

Representative examples of the water-absorbing polymer compound include, for example, Nippon Shokubai Kagaku Kogyo Co., Ltd., Aqualic CA ML-10 (average particle size 10 μm), Sumitomo Seika Co., Ltd., Aquakeep 4S ( Examples thereof include polyacrylate-based resins having an average particle size of 20 μm), and such water-absorbing polymer compounds can be used alone or in admixture of two or more. It is preferable that the average particle diameter of such a water-absorbing polymer compound is usually adjusted to 5 to 70 μm, especially 5 to 20 μm. The blending amount of the water-absorbing polymer compound is 0.
It is preferable that the amount is adjusted to 05 to 2 parts, especially 0.1 to 0.8 parts. When the amount is less than the above range, the number of fine bubbles to be produced tends to decrease, and when it exceeds the range, fine bubbles tend to be less likely to be produced. .

Further, in the present invention, the nucleating agent,
In addition to inorganic powders having a large number of hydroxyl groups on the surface, water-absorbing polymer compounds, flame retardants such as hexabromocyclododecane, antioxidants such as polymeric hindered phenol compounds, barium stearate, magnesium stearate, etc. Other commonly used additives such as the above-mentioned lubricant can be blended by appropriately adjusting the blending amount.

The foamed product of the present invention can be obtained by adjusting a predetermined amount of the styrene-based resin and additives, heating and melting and kneading, and then press-fitting or adding an evaporative foaming agent to perform extrusion foaming.

The heating temperature, the melt-kneading time, and the melt-kneading means at the time of melt-kneading the styrene resin and the additive are not particularly limited, and the heating temperature is not lower than the melting temperature of the synthetic resin, usually 150 to 250. C., and the melt-kneading time cannot be unconditionally determined because it depends on the extrusion amount per unit time, the melt-kneading means, etc., but usually the styrene resin and the additive are uniformly dispersed. The time required can be selected, and examples of the melt-kneading means include a screw type extruder and the like, but there is no particular limitation as long as it is used for ordinary extrusion foaming.

If the amount of the evaporative foaming agent used is too small, not only the expansion ratio of the obtained styrene resin foam decreases but also the shrinkage of the foam after extrusion tends to increase. Therefore, it is preferable that the amount is adjusted to be 0.1 mol or more, particularly 0.15 mol or more with respect to 100 g of the styrene-based resin, and if it is too much, the dimensional stability of the foam tends to decrease. Therefore, 0.3m for 100g of styrene resin
It is preferably adjusted to be ol or less, especially 0.25 mol or less.

After press-fitting or adding the evaporative blowing agent,
For example, a foam having a bubble diameter of about 0.2 to 0.7 mm, usually about 0.3 to 0.5 mm, is produced by a usual method such as extrusion through a foaming device such as a slit die. . When, in addition to the nucleating agent, inorganic powder and / or water-absorbing polymer compound having a large number of hydroxyl groups on the surface and water are present, bubbles having a bubble diameter of 0.25 mm or less and a bubble diameter of 0 are mainly used. A foam in which large and small bubbles of 4 to 1 mm coexist can be suitably produced.

In order to obtain a foam having a cell structure in which large and small bubbles coexist, which characterizes the present invention, the styrene resin, the evaporative foaming agent and water are required.

The water used in the present invention is not particularly limited, and pure water or the like can be used. When the amount of water press-fitted or added to the obtained heat-melted and kneaded product is too small or too much, the thermal conductivity, bending strain, etc. of the styrene resin foam Bubble diameter 0.2 that can improve physical properties
Since it tends to be difficult to obtain a foam having a cell structure in which bubbles of 5 mm or less and bubbles of 0.4 to 1 mm in diameter are dispersed in a sea-island shape through a cell membrane, it is difficult to obtain 100 parts of styrene resin. On the other hand, it is preferably adjusted to 0.2 parts or more, particularly 0.3 parts or more, and 1.5 parts or less, and especially 0.7 parts or less. When the amount of water used is within the above range, a foam having a good cell structure, which is the object of the present invention, can be obtained.

The evaporative foaming agent and water may be press-fitted or added to the heat-melted and kneaded product at the same time, or may be press-fitted or added separately, and the present invention is limited by the press-fitting or adding method. Not something.

In order to allow the water to exist in the extrusion system,
As described above, an inorganic powder or a water-absorbing polymer compound having a large number of hydroxyl groups on the surface may be interposed, and in this case,
A part or all of the water adsorbed on the inorganic powder and / or the water-absorbing polymer compound can be pressed or added to the heat-melted and kneaded product.

When the evaporative blowing agent and water are press-fitted into the hot melt kneaded product, the pressure is not particularly limited as long as the pressure can be higher than the internal pressure of the extruder.

The heat-melted and kneaded product into which the evaporative foaming agent and a predetermined amount of water have been pressed or added is then passed through a commonly used foaming device such as a slit die to a low pressure region such as atmospheric pressure. Extruded. Thus, by extruding into the low pressure area, the bubble diameter is mainly 0.25 mm.
A styrene resin foam comprising the following cells and bubbles having a cell diameter of 0.4 to 1 mm is obtained.

The foam of the present invention has a cell size distribution of cells having a cell size of 0.25 mm or less and a cell size of 0.
Any bubbles having a peak of 4 to 1 mm may be used, but it is preferable that there are few bubbles having a bubble diameter between these two peaks. For example, the content of the bubbles contained in the foam having a diameter of more than 0.25 mm and less than 0.4 mm and the bubbles having a diameter of more than 1 mm is preferably 30% or less, more preferably 20% or less,
More preferably, it is 10% or less.

As described above, the foam of the present invention is mainly composed of bubbles having a bubble diameter of 0.25 mm or less and bubbles having a bubble diameter of 0.4 to 1 mm, and bubbles having a bubble diameter of 0.25 mm or less and a bubble diameter of 0. A bubble with a diameter of 0.4 to 1 mm does not form a layer, a bubble with a diameter of 0.4 to 1 mm mainly serves as an island, and a bubble with a diameter of 0.25 mm or less becomes the sea, a so-called sea-island structure or a diameter of 0.25 mm or less. The bubble size is 0.4 ~
It has a structure in which bubbles of 1 mm are dispersed so as to directly surround them through respective bubble films.

The low thermal conductivity of the foam of the present invention is due to
In the conventional synthetic resin foam having a uniform cell structure, the heat flow moving through the uniform cell structure causes the fine bubbles existing around the cells having a cell diameter of 0.4 to 1 mm in the foam of the present invention. It is presumed that this is because the bubbles are divided by bubbles having a diameter of 0.25 mm or less. Also, regarding bending strength and bending deflection, since stress applied to the cell membrane is dispersed by the fine bubbles having a bubble diameter of 0.25 mm or less existing in a sea-island shape as described above, suitable bending characteristics are exhibited. It is estimated to be.

Thus, the foam of the present invention is mainly composed of cells having a cell diameter of 0.25 mm or less and a cell diameter of 0.4 to 1 mm.
Bubbles are dispersed in a sea-island structure,
It is considered that the fine cells having a size of 0.25 mm or less bring about a decrease in thermal conductivity and an increase in the amount of bending deflection, and the bubbles having a bubble diameter of 0.4 to 1 mm maintain mechanical strength such as bending strength. The bubble diameter of the foam of the present invention is 0.25.
The bubbles having a diameter of less than or equal to mm and the bubbles having a diameter of 0.4 to 1 mm do not disperse unevenly from the viewpoint of lowering the thermal conductivity, increasing the amount of bending deflection, and imparting an appropriate bending strength. It is desirable that they are evenly dispersed.

As described above, the diameter of the fine cells of the foam of the present invention is preferably 0.25 mm or less,
If it is larger than 0.25 mm, the thermal conductivity tends to be high and the bending deflection amount tends to be low. Further, bubbles having a bubble diameter of 0.4 to 1 mm are more preferably 0.4
It is desirable to have a bubble diameter of 0.7 mm.

By the way, regarding the composition ratio of bubbles having a bubble diameter of 0.25 mm or less and bubbles having a bubble diameter of 0.4 to 1 mm,
If the ratio of the area of bubbles having a cell diameter of 0.25 mm or less to the cross-sectional area of the foam is too small, the flexibility tends to be small, so 10% or more, preferably 2
It is preferably 0% or more, and when it is too large, the mechanical strength such as bending strength and compressive strength tends to decrease, so 80% or less, preferably 70%.
It is desirable that the amount is below, and more preferably 50% or less. .

The thickness of the foam of the present invention is not particularly limited, but in order to impart preferable heat insulating property, bending strength and bending deflection, a normal plate-like material such as a sheet is used rather than a thin material. It is preferable to have a thickness such as, usually 20 to 150 mm, preferably 20 to 100 mm.
mm.

The density of the foam of the present invention is also not particularly limited, but in order to impart lightweight and excellent heat insulating property and bending strength, it is 15 to 50 kg / m ^3.
Is preferred.

As described above, the styrenic resin foam of the present invention has excellent heat insulating properties, and also has suitable bending strength and bending deflection property, so that it is a heat insulation material for a wooden house which requires a large bending deflection at the time of construction. And so on.

Next, the styrene resin foam of the present invention and the method for producing the same will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Polystyrene resin (manufactured by Nippon Steel Chemical Co., Ltd., trade name: Estyrene G-17, melt index (MI): 3.
1) 100 parts by weight, as a water-absorbing polymer compound, manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd., Aqualic CA ML-10
(Average particle diameter 10 μm) 0.2 part, talc 0.1 part as a nucleating agent and hexabromocyclododecane 3.0 part as a flame retardant were added, and the mixture was heated to 200 ° C. in an extruder while kneading. Evaporative foaming agent having the composition shown in Table 1 and 0.5 part of water are press-fitted, and after kneading, cooled to about 120 ° C., slits with a gap of 2.0 mm and channel surface are coated with fluororesin. It was extruded and foamed through the formed molding die to obtain a plate-shaped styrene resin foam having a thickness of 25 to 35 mm.

As the physical properties of the obtained foam, foam density, foam physical properties (heat conductivity, compressive strength, bending strength, self-extinguishing property), foam appearance, cell structure and corrosion resistance are determined by the following methods. Therefore investigated. The results are shown in Table 1.

(A) Foam density Determined by the following formula.

[Foam density] = [foam weight] / [foam volume] (b) Physical properties of foam (heat conductivity, compressive strength, bending strength, self-extinguishing property) Measured according to JIS A-9511. .

(C) Foam appearance The shape of the foam, the smoothness of the skin, and the presence of giant cells such as voids were visually observed.

(D) Cell structure The occupied area ratio of cells having a cell diameter of 0.25 mm or less per cross-sectional area of the foam was determined as follows.

A longitudinal section of the foam was photographed with a scanning electron microscope (manufactured by Hitachi, Ltd., product number: S-450) at a magnification of 30 times, and the photographed photograph was copied by a dry copying machine. .

In photocopying, cells having a diameter in the thickness direction (vertical direction in the photo) larger than 7.5 mm are filled with black ink (primary treatment).

The primary processed image is measured by an image processing device (manufactured by Pierce Co., Ltd., product number: PIAS-II).

Capture the primary processed image in pseudo color,
The image is binarized (shading is divided into two in a fixed area).

The dark color portion of the area of 750 pixels (corresponding to an area of 0.25 mm or less in cell diameter) or less is lightened.

"FPACTAR" in the image analysis calculation function
EA (area ratio) "is used to occupy the entire image 7.5 mm
The area of the following cell (light portion divided by light and shade) is calculated by the following formula.

[0060]

[Equation 1]

By measuring the occupied area ratio of the bubbles having a diameter of 0.25 mm or less per cross-sectional area of the foam, the diameter of the bubbles other than the bubbles having a diameter of 0.25 mm or less is 0.4 to 1 mm. It was confirmed that it was mainly composed of bubbles.

(E) Corrosion resistance About 50 g of evaporative foaming agent having the composition shown in Table 1 and 5 g of water
After adding about 1.5 g of iron piece as a test piece to the one to which was added, this was heated for 1 hour at 120 ° C. in a pressure-resistant ampoule containing a glass container and cooled, and then the weight of the test piece was measured. The weight loss due to corrosion was investigated.
When the weight loss of the test piece was 0.1% by weight or less, the test piece was judged to be acceptable (indicated by ◯ in the table), and when it was more than 0.1% by weight, it was determined as unacceptable (indicated by x in the table).

[0063]

[Table 1]

From the results shown in Table 1, the foams obtained in Examples 1 to 3 all have an appropriate foam density,
Excellent foam physical properties and foam appearance, cell diameter 0.25
It can be seen that the occupied area ratio of bubbles having a size of less than or equal to 30 mm is about 30%, which is excellent in corrosion resistance.

Example 4 A styrene resin foam was obtained in the same manner as in Example 1 except that 0.5 part of water was not pressed into the extruder.

The foam density, foam physical properties and foam appearance of the obtained foam were examined in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 8 A styrene resin foam was obtained in the same manner as in Comparative Example 1 except that the water absorbing polymer compound was not used.

The foam density, foam physical properties and foam appearance of the obtained foam were examined in the same manner as in Example 1. The results are shown in Table 2.

[0069]

[Table 2]

From the results shown in Table 2, it can be seen that the foam obtained in Example 4 has an appropriate foam density and is excellent in foam physical properties and foam appearance.

[0071]

According to the production method of the present invention, an eco-friendly type hydrofluorocarbon is used,
Methyl chloride, which limits the working environment during the production of foam
Foams with excellent heat insulation performance and various mechanical properties can be obtained without using chlorine-containing compounds such as ethyl chloride.

Further, according to the production method of the present invention, even when water is used in producing a foam having a cell structure in which large and small cells are mixed, conventional methods such as methyl chloride and ethyl chloride are used. Since a chlorine-containing compound is not required, an acidic substance is not generated by the reaction between water and the foaming agent, and therefore, there is an effect of solving a problem such as corrosion of the device.

Claims (7)

[Claims] 1. An air bubble containing an aliphatic blowing agent consisting of 25 to 70% by weight of propane and 75 to 30% by weight of pentane and an evaporative blowing agent consisting of 1,1-difluoro-1-chloroethane in the cells. 20-150m thick
m is a styrene-based resin foam. 2. An aliphatic blowing agent and 1,1-difluoro-
Weight ratio with 1-chloroethane (aliphatic foaming agent / 1,1
-Difluoro-1-chloroethane) 10/90 to 70
The styrene-based resin foam according to claim 1, which is / 30. 3. The foam constituting the foam is mainly composed of bubbles having a bubble diameter of 0.25 mm or less and bubbles having a bubble diameter of 0.4 to 1 mm, and the bubbles having a bubble diameter of 0.25 mm or less are cross-sectional areas of the foam. The styrene-based resin foam according to claim 1 or 2, which has an occupied area ratio of 10 to 80%. 4. An aliphatic foaming agent consisting of 25 to 70% by weight of propane and 75 to 30% by weight of pentane and an evaporative blowing agent consisting of 1,1-difluoro-1-chloroethane are press-fitted or added to a styrene resin. Then, a method for producing a styrene-based resin foam having a thickness of 20 to 150 mm, which is characterized by performing extrusion foaming. 5. An aliphatic blowing agent and 1,1-difluoro-
Weight ratio with 1-chloroethane (aliphatic foaming agent / 1,1
-Difluoro-1-chloroethane) 10/90 to 70
The method for producing a styrene-based resin foam according to claim 4, which is / 30. 6. The method for producing a styrene resin foam according to claim 4, wherein 0.2 to 1.5 parts by weight of water is present in the styrene resin with respect to 100 parts by weight of the styrene resin during extrusion foaming. . 7. The bubbles constituting the foam are mainly composed of bubbles having a bubble diameter of 0.25 mm or less and bubbles having a bubble diameter of 0.4 to 1 mm, and the bubbles having a bubble diameter of 0.25 mm or less are cross-sectional areas of the foam. The method for producing a styrene-based resin foam according to claim 4, 5 or 6, which has an occupied area ratio of 10 to 80%.