JP2001002821A - Styrene-based resin foam and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-density, thick-walled foam with uniform foam structure by subjecting a styrene-based resin to extrusion foam molding by using carbon dioxide and water as foaming agents with a nonionic surfactant having a specific HLB. SOLUTION: A nonionic surfactant having an HLB of 12-18 is used. Carbon dioxide and water as foaming agents and the nonionic surfactant having an HLB of 12-18 are added to a styrene-based resin in a molten state, mixed, and subjected to extrusion foam molding to prepare this styrene-based foam. Preferably, 2.0-6.0 pts.wt. of carbon dioxide, 0.5-2.0 pts.wt. of water (with the proviso that carbon dioxide is present more than water) and 0.1-1.0 pts.wt. of the nonionic surfactant are blended with 100 pts.wt. of the styrene-based resin. The foam preferably has a density of 0.025-0.050 g/cm3, especially 0.040 g/cm3 or less, a thickness of 10-120 mm, especially 15 mm or more and an average bubble diameter of 0.10-0.80 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-density styrene resin foam having a low density, that is, a high expansion ratio, and a method for producing the same.

[0002]

2. Description of the Related Art Using an extruder, a styrene resin is extruded into the atmosphere through a die of a mold while foaming agent is pressed into a styrene resin in a heat-melted state, and foamed. When producing a foam, the foaming agent may be a hydrocarbon such as butane or propane, or methyl chloride, ethyl chloride,
Halogenated hydrocarbons such as monochloro-difluoroethane are generally used.

[0003] All of these foaming agents have good compatibility with the styrene resin and are uniformly and largely impregnated in the resin, so that the density thereof is about 0.050 g / c.
A thick foam having a low density of not more than m ³ and a high expansion ratio and a thickness of not less than 10 mm can be easily produced by the extrusion foaming method. But,
Among the above foaming agents, hydrocarbons have flammability, so there is a problem that handling is difficult. Some of the halogenated hydrocarbons affect the ozone layer.

Therefore, the use of a gas such as nitrogen or carbon dioxide has been studied as a so-called environmentally-friendly foaming agent which is safe because it does not have flammability or the like and has no risk of affecting the environment. However, among the above, nitrogen is extremely low in compatibility with the styrene-based resin, and cannot be uniformly and largely impregnated into the resin.
It is substantially impossible to extrude and foam a foam having a low density and a sufficient thickness like the above-mentioned conventional product.

[0005] That is, as a method of using a nitrogen as a foaming agent to increase the expansion ratio of a foam produced by the extrusion foam molding method and reduce the density, the pressure inside the extruder is increased and nitrogen is added to the resin. It is conceivable to forcibly impregnate it. However, in order to obtain a low-density and thick-walled foam such as a conventional product by this method, even at the die mouth of the extruder, an extremely high pressure which cannot be obtained with the current extruder can be obtained. It is necessary to develop a special extruder that can generate such a high pressure, and it is difficult to put it to practical use at present.

On the other hand, carbon dioxide has a better compatibility with styrene-based resins than nitrogen, but its value is still insufficient compared with hydrocarbons and the like. It is not possible to extrude and foam a dense and thick foam. Therefore, it is conceivable to increase the amount of carbon dioxide injected into the resin, but in this method, the bubbles of the foam become finer as the amount of carbon dioxide increases, and the strength of the film constituting the bubbles decreases. Therefore, heat shrinkage is likely to occur during extrusion, and the degree to which the density and thickness of the foam are prevented from increasing is increased.

[0007] Therefore, the effect of this method is limited, and it is difficult to produce a foam having a low density and a sufficient thickness like conventional products.

[0008]

SUMMARY OF THE INVENTION The present inventors used water in combination with the above-mentioned system using carbon dioxide as a blowing agent,
It was studied to obtain a low-density, high-expansion-ratio, and thick-walled foam. That is, water has a high foaming power when used as a foaming agent for a resin, and has the characteristic that the foam immediately after foaming can be quickly cooled and its heat shrinkage and the like can be suppressed. Utilizing the high foaming power of, prevents bubbles from becoming too fine,
By utilizing the cooling effect of the latter, the foam immediately after foaming is quickly cooled to suppress thermal shrinkage, and then the amount of carbon dioxide and water is adjusted to obtain a low-density and thick-walled foam. I thought it could be manufactured.

However, in a temperature range of 150 ° C. or less, which is considered to be most suitable for extrusion foaming of a styrene resin,
Water has a remarkably low dispersibility in styrene resins and the like, and when the water is added in an amount sufficient to exert the above-mentioned effects, the foamed structure becomes non-uniform due to uneven dispersion of water, and It became clear that foaming and the like occurred, and it was not possible to obtain the desired low-density and thick-walled foam.

In order to solve this problem, for example, as disclosed in Japanese Patent Publication No. 10-506858, carbon dioxide and water are sequentially injected into a resin in a heated and molten state, and then immediately before extrusion foaming. We studied to adopt a method of sufficiently dispersing by dynamic stirring method. However, even if this method is adopted, the problem that the foamed structure still becomes uneven and internal foaming occurs cannot be solved.

An object of the present invention is to provide a safer and more environmentally friendly hydrocarbon and halogenated hydrocarbon.
A new styrene-based resin foam that is manufactured using carbon dioxide and water as blowing agents, and has a low density, thick wall, and a uniform foaming structure as low as when using hydrocarbons, etc. , An efficient and simple manufacturing method thereof.

[0012]

Means for Solving the Problems In order to solve the above problems,
The present inventors have added a compatibilizer that mainly improves the compatibility between styrene resin and water to a system composed of styrene resin, carbon dioxide and water, and in an extruder, in a melt-mixed state. It was studied to improve the compatibility of each of the above components.

As a result, when a nonionic surfactant having an HLB of 12 to 18 is used as the compatibilizer,
By the action of the nonionic surfactant, particularly suitable for extrusion foam molding of styrene resin as described above.
Since the compatibility of water with a styrenic resin or the like in a temperature range of 0 ° C. or less is improved, the problem of uneven foaming due to uneven dispersion of water is solved. The inventors have found that a styrene resin foam having a low density of not more than 0.050 g / cm ³ , a high expansion ratio, a thickness of not less than 10 mm, and a uniform foam structure can be obtained, and the present invention has been completed. Was.

That is, the styrenic resin foam of the present invention is prepared by extruding a styrenic resin by using carbon dioxide and water in combination as a blowing agent, and using a nonionic surfactant having an HLB of 12 to 18. It is characterized by being formed by foam molding. The method for producing a styrene-based resin foam of the present invention is characterized in that carbon dioxide and water as blowing agents and a nonionic surfactant having an HLB of 12 to 18 are added to a styrene-based resin in a molten state, and mixed. It is characterized by extrusion foaming.

In the present invention, the HLB of the nonionic surfactant is limited to 12 to 18 because the nonionic surfactant whose HLB is out of this range is obtained from the results of Examples and Comparative Examples described later. As is apparent, the effect of increasing the compatibility of water with the styrene resin or the like cannot be obtained, and a uniform foam without internal foaming or the like cannot be produced.

It should be noted that among the inventors, Nimura and the other inventors first used water alone as a foaming agent, or used water and a supplementary amount of nitrogen in combination to form a styrene-based compound. It has been proposed to add a nonionic surfactant to a system for extrusion-molding a resin (Japanese Patent Laid-Open No. 8-41236). According to this method, the density is 2.6 × 10 ⁻¹ g / g, as described in column 0014 of the publication.
cm ³ or more (0.26 g / cm ³ or more), thickness 3.0 m
m or less, and it is possible to produce a thinner foam sheet compared to the present invention, but a low-density and thick-walled foam having a uniform foam structure as in the present invention is obtained. I couldn't do that.

The reason is the same as above. In other words, in order to obtain a low-density and thick-walled foam, it is necessary to inject a large amount of a foaming agent. However, both water and nitrogen have poor compatibility with the styrene-based resin as described above. Even if a surfactant is added, the foamed structure becomes non-uniform, and a low-density, thick-walled foam having a uniform foamed structure cannot be obtained.

HLB (Hydrophile-Lipophile Balanc)
e) is an index indicating the balance between the hydrophilic group and the lipophilic group in the surfactant.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. As described above, the present invention uses carbon dioxide and water in combination as a foaming agent for extrusion foam molding, and uses H.sub.2 as a compatibilizer.
Except that a nonionic surfactant having an LB of 12 to 18 is used, it is carried out in the same manner as ordinary extrusion foam molding.

That is, carbon dioxide and water as a foaming agent and a nonionic surfactant as a compatibilizer are added to a styrene-based resin in a heat-melted state, mixed, and extruded into the atmosphere through a die portion of a mold. The styrene-based resin foam is produced by foaming. As an apparatus for carrying out such a manufacturing method, for example, a tandem extruder in which a first extruder and a second extruder are connected via a mixer 60 as necessary as shown in FIG. 1 is preferably used. Is done.

The tandem extruder heats the styrene resin charged into the hopper 11 as shown by a white arrow in the figure, first in the first extruder 10 at a temperature higher than a temperature suitable for extrusion foam molding. While being melted, carbon dioxide (nozzle 12a) and water (nozzle 12b) as foaming agents were press-fitted from nozzles 12a and 12b provided in the middle of the extruder 10 as shown by solid arrows in the figure. While mixing in the presence of a nonionic surfactant as a compatibilizer, the mixture is continuously supplied to a mixer 60 as shown by a dashed line arrow in the figure. While the mixture is further sufficiently melted and mixed, the mixture is continuously supplied to the second extruder 20;
After adjusting the temperature to a predetermined temperature suitable for extrusion foaming while further mixing by rotating, the extrusion foaming into the atmosphere is continuously performed through the mouth portion 31 of the mold 3 connected to the tip of the second extruder 20. This is for continuously producing a styrene resin foam.

In the figure, reference numeral 4 denotes cooling of the styrene-based resin 5 extruded from the base 31 of the mold 3 while cooling the resin 5 while restricting expansion in the thickness direction due to foaming. It is a pair of plate-shaped forming tools for forming a styrene-based resin foam into a predetermined thickness. Nonionic surfactant is used in hopper 1 together with styrene resin.
Although it may be introduced from the beginning, it is more preferable to press-in the solution dissolved in water together with the water from the nozzle 12b.

When such an extruder is used, for example, carbon dioxide and water are successively pressed into a resin in a heat-melted state and immediately before extrusion foaming, as disclosed in Japanese Patent Publication No. Hei 10-506858. Compared to a method of sufficiently dispersing by a dynamic stirring method, there is an advantage that not only the foamed structure becomes uniform as described above, but also the productivity of the styrene resin foam is improved.

That is, in the method disclosed in Japanese Patent Application Laid-Open No. 10-506858, the resin, which has been cooled to a temperature suitable for extrusion foaming and has a high viscosity, is dynamically stirred using a mixer or the like. A great deal of energy and time are required for stirring. On the other hand, in the present invention, in the first extruder 10, or in the first extruder 10 and the subsequent mixer 60, a step of cooling at a higher temperature and lower viscosity before cooling to a temperature suitable for extrusion foaming. Therefore, the components are sufficiently mixed, so that less energy is required, and the time required for stirring is short, and the productivity of the styrene resin foam is improved.

The conditions for extrusion foaming using the tandem extruder shown in FIG. 1 are not particularly limited, but the amount of water added as a blowing agent is preferably smaller than the amount of carbon dioxide added. That is, it is preferable that W _C > W _H expressed in terms of the added amount of carbon dioxide W _C (parts by weight) and the added amount of water W _H (parts by weight) with respect to 100 parts by weight of the styrene resin.

If this condition is not satisfied and W _C ≦ W _H , water cannot be uniformly dispersed in the styrene resin even though a nonionic surfactant is added. In addition, the foamed structure may be non-uniform, and a low-density and thick-walled foam having a uniform foamed structure may not be obtained. Others are not particularly limited, but the addition amounts of the carbon dioxide and water and the nonionic surfactant are preferably within the following ranges with respect to 100 parts by weight of the styrene resin.

Carbon dioxide: added amount W _C = 2.0 to 6.0
Parts by weight Water: added amount W _H = 0.5 to 2.0 parts by weight Nonionic surfactant: added amount W _S = 0.1 to 1.0 parts by weight [However, carbon dioxide and water are added in the above. Quantity W _C , W _H
Is preferably W _C > W _H as described above,
If the addition amount W _C of the carbon dioxide is 2.0 parts by weight is preferably added amount W _H of water is less than 2.0 part by weight, the addition amount W _H of water conversely 2.0 when parts by weight, the addition amount W _C of the carbon dioxide is preferably in the range of more than 2.0 parts by weight. ] Fear The amount W _H of the addition amount W _C and / or water of carbon dioxide is less than this range, not to insufficient amount of overall blowing agents, are to give a foam of low density is and thick There is. Conversely, when the amount W _C and / or amount W _H of water carbon dioxide exceeds this range, to the expansion ratio of the internal foaming caused by the foam does not rise again at low density Moreover, there is a possibility that a thick foam cannot be obtained.

It should be noted, of low density is and thick, yet considering that the foam structure to obtain a homogeneous foam, the amount W _C of the carbon dioxide, especially in the range of above 2.0 to 4.
It is preferably about 0 parts by weight. Also for the same reason,
The added amount W _{H of the} water is preferably in the range of 1.0 to 1.0.
It is preferably about 2.0 parts by weight. Further, it is less than the range amount W _S of nonionic surfactant of the, the nonionic surfactant effect is insufficient due to the addition, non-uniform foam structure by dispersion unevenness of water May occur. Conversely, even beyond the amount W _S is the range of nonionic surfactant, not only is more additives effect not obtained, the discharge variation in the extrusion caused by an excess of nonionic surfactant Thus, extrusion molding may be difficult.

The addition amount W of the nonionic surfactant
_S is preferably in the above range, particularly preferably about 0.1 to 0.5 parts by weight. The melting, mixing temperature, extrusion temperature, etc. of the resin may be adjusted to the same level as in the past. The styrene resin foam thus produced has, for example, a density of 0.025 to 0.050 g / cm ³ , particularly 0.040 g / cm ³ .
g / cm ³ or less, thickness 10 to 120 mm, especially 15
mm or more, and the average bubble diameter is 0.10 to 0.80 mm
That is, it is low-density, thick, and has a uniform foam structure.

As described above, nonionic surfactants having an HLB of 12 to 18 are used. Such nonionic surfactants include, among various surfactants classified as polyethylene glycol type or polyhydric alcohol type nonionic surfactants, H
Any of various compounds having an LB of 12 to 18 can be used.

Specific examples thereof include, for example, alkyl and alkyl allyl polyoxyethylene ethers [more specifically, single-chain polyoxyethylene ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene Sterol ethers, polyoxyethylene lanolin derivatives, etc.), alkyl allyl formaldehyde condensed polyoxyethylene ethers (more specifically, ethylene oxide derivatives of alkyl phenol formalin condensates, etc.), polyoxyethylene polyoxypropylene block copolymers, polyoxyethylene polyoxy Ether-type surfactants such as propylalkyl ether, and polyoxyethylene ethers of glycerin esters (more specifically, polyoxyethylene ethers). Serine fatty acid ester, polyoxyethylene castor oil and hardened castor oil, etc.), ether ester surfactants such as polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan Any of ester-type surfactants such as fatty acid esters, propylene glycol fatty acid esters, and sucrose fatty acid esters, and nitrogen-containing surfactants such as fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkylamines, and amine oxides. And a compound having an HLB of 12 to 18 as described above is preferably used.

In consideration of the function as a compatibilizer, the HLB of the nonionic surfactant is preferably about 14 to 16 in the above range. As the styrene resin, polystyrene, that is, a homopolymer of styrene is most preferably used, and a copolymer of styrene with another vinyl monomer can also be used.

Examples of other vinyl monomers copolymerized with styrene include α-methylstyrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylate, methacrylate, and maleic anhydride. Examples of the styrene resin include diene rubbery polymers such as polybutadiene, styrene-butadiene copolymer, and ethylene-propylene-nonconjugated diene terpolymer in order to improve the impact resistance and the like of the foam. A rubber-modified styrene resin to which coalesced is added, so-called high-impact polystyrene may be used.

These styrenic resins can be used alone or in combination of two or more. As the styrene resin, in order to favorably foam a foam, a melt flow rate R ₁ (g / 10
Min) and the melt tension T ₁ (g · f) are represented by the following equation (1) (2): 2 ≦ R ₁ ≦ 10 (1) T ₁ ≧ −0.65R ₁ +11.6 (2) It is preferable to use those that are related.

[0035] here, the melt flow rate of at 200 ° C. (melt flow rate: MFR) and R _1, the test of Shosai the styrenic resin, "Flow testing method of thermoplastics" Japanese Industrial Standard JIS K7210 According to the method, condition 8 (test temperature: 200 ° C,
Test load: refers to a value measured at 5.00 kgf). The melt tension T ₁ is a value measured using Capillograph PMD-C manufactured by Toyo Seiki Seisakusho under the following conditions.

Test temperature: 200 ° C. Preheating time: 5 minutes Extrusion speed: 100 mm / min Winding speed: 12 mm / min Capillary: 1.00 mm in diameter, 10 mm in length, 45 ° inflow angle As described above, the styrene resin is Since it has low affinity with carbon dioxide and water as a foaming agent and poor compatibility, it is not easy to produce a foam having a uniform cell structure, a thickness and a high expansion ratio.

However, when a styrene-based resin having a relationship between the melt flow rate at 200 ° C. and the melt tension represented by the formulas (1) and (2) is used, the resin has a high melt tension. Since the foaming temperature range is relatively low and the melt tension during foaming is high, the occurrence of internal foaming can be reliably prevented. Therefore, as described above, a styrene resin foam having a low density, a high expansion ratio, a thick wall, and a uniform cell structure can be favorably manufactured.

When a resin having a melt flow rate R ₁ of more than 10 g / 10 minutes, that is, a resin having a low melt tension T _1, is used as the styrene resin, the foaming temperature range becomes low. Although the carbon can be dissolved in a larger amount, the resin does not have a melting tension enough to withstand high foaming, or because the foaming temperature range is low, the foaming temperature is immediately below the Vicat softening point when cooled. Therefore, there is a possibility that the expansion ratio of the foam cannot be increased as described above.

Conversely, when the melt flow rate R ₁ is 2 g / 10
When the styrene-based resin having a melt tension T _{1 of} less than ₁ minute is used, the foaming temperature range is increased, and the amount of carbon dioxide dissolved in the resin is reduced. There is. Further, when the melt flow velocity R ₁ and the melt tension T ₁ do not satisfy the above formula (2), and T ₁ <−0.65R ₁ +11.6, the melt tension is higher than the melt flow velocity. Since it is low, internal foaming easily occurs immediately after foaming. Therefore, also in this case, there is a possibility that a thick styrene resin foam having a high expansion ratio cannot be produced.

The melt flow rate R of the styrene resin
₁ is preferably within the range of the above formula (1), particularly preferably within the range of 4 to 7 g / 10 minutes. Further, the melt tension T ₁ is preferably in the range of the above formula (2), and particularly preferably T ₁ ≦ −0.65R ₁ +15. A foam nucleating agent (cell regulator) may be added to the styrene-based resin in order to further improve the uniformity of the cell structure. Examples of the foam nucleating agent include talc, calcium carbonate, clay, magnesium oxide, zinc oxide, glass beads, glass powder, titanium oxide,
Inorganic fine powders such as carbon black, anhydrous silica and calcium silicate can be used. The particle size of the foam nucleating agent is 50 μm
Hereinafter, the thickness is particularly preferably about 10 to 30 μm. Further, the addition amount of the foam nucleating agent is preferably about 0.1 to 1 part by weight based on 100 parts by weight of the styrene resin.

Styrene resins include, for example, colorants, flame retardants, lubricants (various waxes such as hydrocarbons, fatty acids, fatty acid amides, esters, alcohols, etc., metallic soaps, silicone oils, low molecular weights). Various additives such as polyethylene (eg, polyethylene), spreading agents (eg, liquid paraffin, polyethylene glycol, and polybutene) and dispersants may be added. These additives are added in a range that does not hinder the production of the foam and does not affect the properties of the produced foam.

As a mold 3 for extrusion foam molding, FIG.
As shown in FIG. 2A, the resin extrusion channel 30 and the base 31 are arranged in communication with each other, and the resin extrusion channel 30 corresponds to the thickness direction of the styrene resin foam. use what is in the range of _{40 ≦ S 2 / S 1 ≦} 100: the width S ₂ direction, of the base portion 31, ratio S ₂ / S ₁ between the width S ₁ in the same direction, the formula (3) In such a case, the amount of the foam nucleating agent is reduced from the above-mentioned range, or the same good It is possible to produce a suitable foam, and there is an advantage that ash content at the time of incineration can be reduced.

That is, when the mold 3 having such a dimension is used, the width S ₁ , which is disposed at the end of the resin extrusion flow path 30 and is smaller than the width S ₂ of the flow path 30, has a predetermined length. Since the pressure inside the extruder 20 is maintained at a high pressure required for dissolving carbon dioxide up to the tip of the die portion 31 by the die portion 31 having the length (land length) L ₁ ,
By increasing the amount of carbon dioxide dissolved in the resin, the expansion ratio of the foam can be increased, and the cell structure can be made uniform.

Further, as is apparent from the above-described effects, by adjusting the width S ₁ of the mouth portion 31 and the land length L ₁ , the pressure inside the second extruder 20 can be freely adjusted. is there. Further, the width S _{2 of} the resin extrusion flow path 30 provided in front of the base 31 is such that the styrene-based resin in the flow path 30 is extruded from the base 31 into the atmosphere, and then the thickness is increased as described above. Like foaming, it also functions to retain shape memory.

Therefore, by using the above-mentioned mold 3, the cell structure is as uniform as the case where a predetermined amount of the foam nucleating agent is added, and the low density, the high foaming ratio and the thick The styrene resin foam of the meat can be favorably produced without reducing the amount of the foam nucleating agent added or adding the foam nucleating agent at all.

When the ratio S ₂ / S ₁ exceeds 100 in the above-mentioned mold 3, a portion where the resin does not flow in the mold 3 is generated, and there is a possibility that an unfoamed resin is generated. . When the ratio S ₂ / S ₁ is less than 40, a thick styrene resin foam may not be produced satisfactorily, as is apparent from the above description. The ratio S ₂ / S ₁ is preferably within the above range, particularly within the range of 60 to 80, in consideration of performing good molding while avoiding these problems.

The mold 3 in the example shown in FIG.
The base 31 and the base 31 are connected by a tapered surface 32. For example, as shown in FIG. 2B, the resin extrusion channel 30 and the base 31 may be connected by a vertical surface 33.

[0048]

The present invention will be described below based on examples and comparative examples. The densities of the plate-like styrene resin foams manufactured in the following Examples and Comparative Examples were calculated by actually measuring the weight per unit volume. The average bubble diameter was measured using a scanning electron microscope [JSM T-300 manufactured by JEOL Ltd.] in accordance with the measurement method described in ASTM D2842-69. That is, the cell diameter of each of the extruded and foamed foam in the resin flow direction (MD), width direction (TD) and thickness direction (VD) is measured, and the measured values are arithmetically averaged to obtain an average cell diameter. The diameter was determined.

Example 1 A mixture was prepared by dry blending the following components. 100 parts by weight of polystyrene [G-13-50A (trade name, manufactured by Nippon Steel Chemical Co., Ltd., melt flow rate R ₁ = 4.0 g / 10 min, melt tension T ₁ = 11.0 g · f)] Foam nucleating agent) 0.075 parts by weight Hexabromocyclododecane (flame retardant) 2.0 parts by weight Next, this mixture was connected to a first and a second extruder via a pin mixer. The tandem extruder is supplied to a hopper of a first extruder, and melted and mixed at a mixing temperature of 200 ° C. in the first extruder.
From the two nozzles provided in the middle of the extruder,
Carbon dioxide as a blowing agent and a solution of polyoxyethylene lauryl ether (HLB = 16) as a compatibilizer in water as a blowing agent were press-fitted into an extruder and added.

The amounts of the above components were 3.8 parts by weight of carbon dioxide and 100 parts by weight of polystyrene.
Water was 1.5 parts by weight and polyoxyethylene lauryl ether was 0.3 parts by weight. Next, the molten mixture after the injection was melted and mixed for a while in the first extruder, and then continuously supplied to a pin mixer. In the pin mixer, the mixing temperature was 180 ° C., and the mixing pressure was 200 kg / c.
m ² , more fully melted under the condition of a rotation speed of 60 rpm,
Mixed.

Then, the molten mixture is continuously supplied from a pin mixer to a second extruder, and in the second extruder,
After uniformly cooling to 130 ° C., which is a temperature suitable for extrusion foaming, the lip width W connected to the tip of the second extruder
= 50 mm, and continuously extruded into the atmosphere through a slit-shaped mold having a thickness t = 1.4 mm to foam, and the thickness of the above-mentioned molding tool is passed through a pair of plate-like molding tools arranged at an interval of 30 mm. The styrene-based resin foam was produced by cooling while correcting it to 30 mm, which is the same as the interval of the styrene resin foam.

The density of the obtained foam was 0.030 g / c.
m ³ , and the average bubble diameter was 0.6 mm. Example 2 A 30 mm thick styrene resin foam was produced in the same manner as in Example 1 except that 0.3 parts by weight of polyoxyethylene lauryl ether having an HLB of 12.6 was used as a compatibilizer. .

The density of the obtained foam was 0.032 g / c.
m ³ , and the average bubble diameter was 0.5 mm. Comparative Example 1 An attempt was made to produce a styrenic resin foam in the same manner as in Example 1 except that a nonionic surfactant as a compatibilizer was not added. A uniform foam could not be obtained.

Comparative Example 2 A styrene resin foam was produced in the same manner as in Example 1 except that 0.3 parts by weight of polyoxyethylene octyl phenyl ether having an HLB of 9.0 was used as a compatibilizer. However, internal foaming occurred, and a foam having a uniform internal structure could not be obtained.

Table 1 summarizes the above results.

[0056]

[Table 1]

[0057]

As described in detail above, according to the present invention,
Safer and more environmentally friendly than hydrocarbons and halogenated hydrocarbons, using carbon dioxide and water as blowing agents, and as low density as when using hydrocarbons, A new styrene-based resin foam having a thick wall and a uniform foam structure can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of an extruder for performing a production method of the present invention.

FIGS. 2A and 2B are cross-sectional views each showing an example of a mold used in the extruder.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 105: 04 F term (Reference) 4F074 AA08D AA25D AA32 AA32A AA32D AA47A AA48A AA49A AA51A AB02 BA32 BA34 BA95 BC02 CA22 CC22X CC32Y DA02 DA03 DA23 4F207 AA13 AB02 AB10 AG20 KA01 KA11 KK23 KK30 4F212 AA13 AB02 AB10 AB16 AG20 UA10 UB02 UC05 UC06 UC06 UC10 UF06 UF21 4J002 BC031 BC041 BC061 BC071 BH011 FD062 FD 012141 BN061 FD

Claims (8)

[Claims] An extruded foam molding of a styrene resin using carbon dioxide and water as a foaming agent and a nonionic surfactant having an HLB of 12-18. Characterized styrene resin foam. 2. A density of 0.025 to 0.050 g / c.
m ^3, a thickness of at 10～120Mm, and an average cell diameter is 0.10~0.80mm claim 1 styrene resin foam according. 3. The styrene resin foam according to claim 2, wherein the density is 0.040 g / cm ³ or less and the thickness is 15 mm or more. 4. A method for producing a styrenic resin foam according to claim 1, wherein the styrenic resin in a molten state contains carbon dioxide and water as blowing agents and HLB of 12 to 12.
18. A method for producing a styrenic resin foam, comprising adding, mixing and extrusion-molding a nonionic surfactant of No. 18. 5. Using a tandem extruder in which first and second two extruders are connected, first, in the first extruder, a styrene-based material in a molten state at a temperature higher than a temperature suitable for extrusion foaming. Carbon dioxide and water as a foaming agent were added to the resin, mixed uniformly in the presence of a nonionic surfactant, and then the mixture was adjusted in a second extruder to a temperature suitable for extrusion foaming. The method for producing a styrenic resin foam according to claim 4, wherein the foaming is carried out by extrusion foaming. 6. A mixer is provided between the first extruder and the second extruder, and the mixture obtained by the first extruder is further melted and mixed by the mixer and then supplied to the second extruder. Item 6. The method for producing a styrene resin foam according to Item 5. For 7. 100 parts by weight of a styrene resin, in the range of the addition amount W _C of the carbon dioxide is 2.0 to 6.0 parts by weight, the addition amount W _H of water is 0.5 to 2.0 parts by weight , W _C > W _H , and the addition amount W of the nonionic surfactant to 100 parts by weight of the styrene resin.
_The method for producing a styrenic resin foam according to claim 4, wherein _S is in the range of 0.1 to 1.0 part by weight. 8. A styrene-based resin having a melt flow rate R ₁ (g / 10 minutes) at 200 ° C. and a melt tension T ₁ (g · f) of the formula (1) (2): 2 ≦ R _{1 ≦ 10 (1) T 1 ≧} -0.65R 1 +11.6 method according to claim 4 styrene resin foam according to use styrene resin are in a relationship represented by (2).