JP3461728B2 - Styrene resin foam and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a styrene resin foam and a method for producing the same. More specifically, produced by extruding and foaming using carbon dioxide,
The present invention relates to a styrene resin foam having a low density (that is, a high expansion ratio) and a good thickness, and a method for producing the same.

[0002]

2. Description of the Related Art At present, as a foaming agent used for producing a plate-shaped styrene resin foam, for example, butane,
Hydrocarbons such as propane and methyl chloride (hereinafter M
C), ethyl chloride (hereinafter referred to as EC),
1-monochloro-difluoroethane (hereinafter referred to as 142b) and the like are known, and these are used alone or in combination.

Since the above-mentioned foaming agent has excellent solubility in the raw styrene resin, the styrene resin is sufficiently impregnated with the foaming agent, and as a result, it has a high expansion ratio and a good thickness. A plate-shaped styrene resin foam is obtained.

However, since these foaming agents are relatively expensive and their properties are flammable,
It costs money to ensure safety. Further, 142b is known as a so-called CFC-based gas, and has a problem of depleting the ozone layer and causing a global warming phenomenon. Considering the currently increasing environmental problems,
Not preferred to use.

In view of these problems, a method for producing a styrene resin foam using carbon dioxide, which is more environmentally friendly and cheaper than the above-mentioned foaming agent, as a foaming agent is described ( JP-A-1-209120 and JP-A-3-81346).

[0006]

However, when the present inventors actually used the above carbon dioxide as a blowing agent, the solubility in styrene resin was poor as compared with the above-mentioned conventional blowing agents, Moreover, since the vapor pressure is high, the expansion ratio is at most about 10 to 20 times and the thickness is 1
The limit is to obtain a styrene resin foam of about 0 mm,
It was difficult to manufacture a plate-shaped styrene resin foam having a higher expansion ratio and a thickness.

The object of the present invention is to overcome the drawbacks of these conventional techniques and to provide a styrene resin foam having a high expansion ratio and good thickness by using carbon dioxide as a foaming agent, and a method for producing the same. Is to provide.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have paid attention to the physical properties (melt flow rate and melt tension) of styrene resin used as a raw material, However, it was thought that it might affect the expansion ratio and thickness of the foam to be produced, and further research was conducted.Surprisingly, as the raw material resin, the above-mentioned melt flow rate and melt tension were When the styrene resin represented by the relational expression (1) is used,
The inventors have found the new fact that a styrene resin foam having a high expansion ratio and a good thickness can be produced, and completed the present invention.

That is, the present invention is an extruded foam of styrene resin containing only carbon dioxide as a foaming agent, the density of which is 0.030 to 0.047 g / cm ³ , and the thickness is 1.
5 to 120 mm and an average bubble diameter of 0.05 to
The present invention relates to a styrene resin foam having a size of 0.50 mm.

As for the styrene-based resin, when the melt flow rate is X (g / 10 minutes) and the melt tension is Y (g · f), the relationship between X and Y is expressed by the formula (1):

[0011]

## EQU00003 ## A styrene resin represented by Y> -0.65X + 11.6 (where 2 <X <10) is used .

The method for producing a styrenic resin foam having the above-mentioned predetermined density, thickness and average particle diameter is the same as the method for producing an extruded styrene resin foam using only carbon dioxide as a blowing agent. When the melt flow rate is X (g / 10 minutes) and the melt tension is Y (g · f) as the raw material styrene-based resin, the relationship between X and Y is expressed by the formula (1):

[0013]

(4) Y> -0.65X + 11.6 (where 2 <
X <10. ) Is extruded and foamed using a styrene resin represented by

According to the present invention, carbon dioxide, which is inexpensive and is cleaner than conventional foaming agents, is used as the foaming agent, and the styrene resin foam produced is the same as the above-mentioned conventional foaming agents. Similar to the case where it is used, it has a high expansion ratio and a good thickness.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The styrenic resin foam of the present invention having the above-mentioned predetermined density, thickness and average particle diameter is a raw material in a method for producing an extruded foam of a styrene resin using carbon dioxide as a foaming agent. As a styrene resin, the melt flow rate is X (g / 10 minutes) and the melt tension is Y.
(G · f), the relation between X and Y is
(1):

[0016]

(5) Y> −0.65X + 11.6 (where 2 <
X <10. ) Is produced by extruding and foaming using a styrene resin represented by

The raw material styrene resin used in the present invention includes a melt flow rate (MFR),
As long as the relationship with the melt tension is represented by the above formula (1), it can be used without any limitation. In addition to a styrene homopolymer, a copolymer with butadiene, acrylonitrile or methyl methacrylate, or a mixture thereof (ABS resin). Etc.)

The MFR referred to in the present invention is a value obtained by measuring the raw styrene resin under the measurement conditions (temperature: 200 ° C., load: 5 kgf / cm ² ) described in JIS K7210.

The melt tension as used in the present invention means that Capirograph PMD-C manufactured by Toyo Seiki Seisaku-sho, Ltd. is used, the test temperature is 200 ° C., the preheating time is 5 minutes, the capillary shape is 1.00 mm in diameter, 10 mm in length, and inflowing. Using an angle of 45 °, extrusion speed 100 mm / min, winding speed 12
The value measured in mm / min.

The relationship between the MFR and the melt tension in the raw styrene resin is specified for the following reasons.

As is well known, when carbon dioxide is used as a foaming agent, the carbon dioxide is not sufficiently impregnated into the styrene resin because of its low affinity with styrene resin and poor solubility. It is difficult to produce a styrene-based resin foam that is fine (small cell diameter), thick, and has a high expansion ratio.

Therefore, carbon dioxide is used as a foaming agent, a styrene resin is extruded and foamed, and at a high expansion ratio,
In order to produce a styrene resin foam having a good thickness, how to dissolve the carbon dioxide necessary for high foaming in the styrene resin becomes a problem. Factors that affect the solubility include pressure and temperature during production.

Further, the above-mentioned styrene resin is required to have a high melt tension to withstand the high foaming.

However, in the case of using a styrene resin having a high melt tension that can withstand the high foaming, the MFR is generally lowered and the proper foaming temperature is increased, so that the styrene resin is increased. The amount of carbon dioxide dissolved in the resin decreases, and the expansion ratio does not increase.

On the contrary, when a styrene resin whose foaming proper temperature is lowered to increase the amount of carbon dioxide dissolved in the styrene resin is used, the MFR is high and the melt tension is low. I can't stand it.

From the above, in the present invention, by using the styrene resin represented by the following formula (1), which has a high MFR and a high melt tension, the carbon dioxide required for high foaming can be converted into styrene resin. It is possible to lower the foaming temperature to a level at which it can be dissolved in the resin, and the high melt tension at that foaming temperature enables high foaming.

[0027] In the present invention uses only carbon dioxide as a blowing agent in consideration of environmental issues.

In the present invention, as the raw material styrene resin,
The melt flow rate is X (g / 10 minutes) and the melt tension is Y (g.
f), the relationship between X and Y is expressed by the formula (1):

[0029]

## EQU6 ## Y> -0.65X + 11.6 (where 2 <
X <10. ) The styrene resin represented by is used.

More specifically, for example, when the melt flow velocity X is 3 (g / 10 minutes), the right side of the equation (1) is 9.65, so 9.65 (g · f) It must be a styrenic resin with a higher melt tension Y.

By using the raw material styrenic resin represented by the above formula (1), the foaming temperature range can be lowered despite the high melt tension, and since the melt tension at the time of foaming is high, carbon dioxide can be used. It is possible to obtain a foam having a good thickness and a high expansion ratio without the possibility of internal foaming immediately after foaming.

Particularly in the present invention, the relationship between X and Y is represented by the formula (1 '):

[0033]

## EQU7 ## It is preferable to use a styrene resin represented by -0.65X + 15>Y> -0.65X + 11.6 (provided that 2 <X <10).

Here, when a raw material styrene resin having an MFR of more than 10, that is, a low melt tension is used, the foaming temperature range becomes low. Therefore, a large amount of carbon dioxide should be dissolved in the styrene resin. But you can
It does not have a melt tension that can withstand high foaming, and because the foaming temperature region is low, when it is foamed and cooled, it immediately falls below the Vicat softening point, and it is not possible to increase the expansion ratio.

On the other hand, when a raw material styrene resin having an MFR of less than 2, that is, a high melt tension is used, the foaming temperature region becomes high, and the amount of carbon dioxide dissolved in the styrene resin becomes small. However, the expansion ratio cannot be increased.

Further, the relation between X and Y is expressed by the formula (2):

[0037]

(8) Y <−0.65X + 11.6 (where 2 <
X <10. When using a styrene resin represented by
However, since the melt tension is low, internal foaming occurs immediately after foaming, and it is not possible to obtain the styrene resin foam of the present invention having a high expansion ratio and a thickness.

The carbon dioxide used as the blowing agent in the present invention may be in a gas or liquid state,
Considering solubility, permeability, diffusibility, etc. in styrene resin, it is preferable to use carbon dioxide maintained at a critical temperature or higher and a critical pressure or higher.

The method of dissolving carbon dioxide in the resin in the extruder is not particularly limited, and a conventionally known method can be used.
For example, a method of injecting carbon dioxide in a gas state under pressure, a method of injecting carbon dioxide in a liquid state with a blanker pump or the like can be mentioned. At that time, the carbon dioxide is usually 2.
0 to 5.0 parts by weight, preferably 3.0 to 4.0 parts by weight, should be dissolved.

When the amount of the foaming agent used is less than the above range, it is impossible to obtain a fine foam having a high expansion ratio. On the contrary, when the amount of the foaming agent used exceeds the above range, internal foaming occurs,
A styrene resin foam having a high expansion ratio cannot be obtained.

In the present invention, since carbon dioxide is used as the foaming agent, the bubbles can be sufficiently miniaturized. However, a foam nucleating agent or the like may be added to the raw styrene resin in order to further miniaturize the bubbles.

Examples of the foam nucleating agent include talc, carbon dioxide, calcium carbonate, clay, magnesium oxide,
Inorganic fine powders such as zinc oxide, glass beads, glass powder, titanium oxide, carbon black, anhydrous silica, calcium silicate and the like can be mentioned. Among them, it is preferable to use titanium oxide, talc, calcium carbonate and anhydrous silica.

The particle size of the foam nucleating agent is preferably 50 μm or less, and more preferably 10 to 30 μm, in consideration of reducing the cell diameter of the obtained foam and reducing the thermal conductivity thereof.

In the present invention, in addition to the above-mentioned components, plasticizers, pigments, stabilizers, fillers, flame retardants, etc. may be used for the purpose and applications, provided that they do not impair the quality (discoloration, coloring, etc.) of the foam produced. You may add suitably according to.

As the extruder used when the styrene resin having the above-mentioned specific physical properties is extruded and foamed by using only carbon dioxide as a foaming agent, either a single screw type or a twin screw type is used. can do.

In the present invention, as a method for extruding and foaming, for example, a tandem type extrusion method in which two extruders are directly connected in a vertical direction (steps consisting of the following (1) to (3)) is adopted. (1) In the raw material styrene resin heated and melted in the first extruder, carbon dioxide as a foaming agent is supplied, and after sufficiently kneading, carbon dioxide is supplied while maintaining the critical state of carbon dioxide. The raw material styrene resin (hereinafter, referred to as a resin composition) is fed into the second extruder. (2) The resin composition fed into the second extruder is cooled to a temperature suitable for foaming while maintaining the critical pressure of carbon dioxide or higher. (3) Next, the resin composition cooled to a temperature suitable for foaming,
By extruding through the die of the die connected to the outlet side of the second extruder, the pressure drops below the critical pressure of carbon dioxide to form a foam.

In the step (1), the heating and melting temperature of the raw material styrene resin is usually 180 to 220 ° C., preferably 190 to 210 ° C.

Carbon dioxide, which is a foaming agent, is preferably in a critical state when kneading with the raw material styrene resin in order to improve the solubility and dispersibility in the raw styrene resin.

The carbon dioxide may be heated and pressurized in the extruder to be in a critical state, or may be heated and pressurized before being supplied to the extruder to be in a critical state.

Further, in order to improve the kneading property of the raw material styrene resin and carbon dioxide, a kneading part such as a static mixer or a pin mixer is connected to a connecting part between the first extruder and the second extruder. Good.

In the step (2), the resin composition is cooled to a temperature suitable for foaming, that is, 130 to 150 ° C, preferably 135 to 145 ° C. If the cooling here is not sufficient, continuous and stable extrusion foaming may not be possible.

When the resin composition can be cooled to the temperature within the above range by only the first extruder, it is not necessary to use the second extruder and only the first extruder is used. It is possible to produce a styrene resin foam.

In the step (3), the shape of the die of the die connected to the outlet side of the second extruder is not particularly limited,
Examples include parallel grooves and square shapes.

The pressure applied to the resin composition at the die die (die pressure) is 60 to 120 kg / cm ² , preferably 80 to 110 kg / cm ² .

The temperature of the resin composition during foaming is usually 1
The temperature is 30 to 150 ° C, preferably 135 to 145 ° C.

By employing a die having such a die shape and extrusion conditions, it is possible to stably perform extrusion molding without causing extrusion unevenness.

The styrene resin foam obtained by the production method of the present invention has a density of 0.030 to 0.047 g / c.
m ³ , thickness 15-120 mm, preferably 25-10
0 mm and the average bubble diameter is 0.05 to 0.50 m
m, preferably 0.2 to 0.40 mm.

The average cell diameter in the present invention is AST.
According to MD-2842-69 and using a scanning electron microscope JSM T-300 (manufactured by JEOL Ltd.) as a measuring device, MD (flow direction), TD (width direction) and VD ( A value (mm) obtained by measuring bubble diameters in each of three directions (thickness direction) and arithmetically averaging these bubble diameters.
Is.

The reason for defining the average bubble diameter in the above range is as follows.

The styrene resin foam obtained by extruding and foaming with carbon dioxide is vaporized during foaming, carbon dioxide (gas) escapes from the bubbles, and only air is present in the bubbles after foaming. The thermal conductivity is usually higher than when using a conventional foaming agent (such as fluorocarbon gas or hydrocarbon).

Therefore, there is a possibility that the regulation of the extruded polystyrene foam heat insulating plate described in JIS A 9511 may not be satisfied.

Therefore, in the present invention, the radiation component (that is, the average bubble diameter), which is one of the factors of the thermal conductivity, is reduced so that the thermal conductivity satisfies the thermal conductivity described in JIS A 9511. The average bubble diameter is within the above range.

If the thickness of the styrene resin foam is less than the above range, it may not be possible to mold a high expansion ratio (low density). On the contrary, if the thickness of the styrene resin foam exceeds the above range, molding itself may be difficult.

The extruded shape of the styrenic resin foam is not particularly limited, and examples thereof include a plate shape and a square bar shape, and a plate shape is particularly preferable.

Since the styrene resin foam of the present invention uses only carbon dioxide as a foaming agent, carbon dioxide diffuses from the styrene resin foam at the time of foaming, and only air is contained in the bubbles of the foam. Since it is included, it is less harmful and less expensive than the case of using a conventional foaming agent.

Therefore, since it has the same thickness and high expansion ratio as when the conventional foaming agent is used, it can be used as a core material for tatami mats, a heat insulating material for walls, floors and the like.

[0067]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. In the following, "parts" means parts by weight. Example 1 Polystyrene as a resin (G-13-50A, MF manufactured by Nippon Steel Chemical Co., Ltd.
R = 4.0 (g / 10 min), melt tension = 11.0 (g · f)) 100 parts, and talc powder as a foam nucleating agent was added to this resin in an amount of 0.1.
075 parts, hexabromocyclododecane (H
2.0 parts of BCD) was added and the resulting mixture was fed to the extruder. A tandem type extruder was used.

Then, the mixture was melt-kneaded in the first tandem type extruder, and 3.8 parts of carbon dioxide (gas) was injected as a foaming agent under pressure. After press-fitting, kneading with a screw, 200 ° C, 60 rpm, mixing pressure 2
The foaming agent and the mixture were thoroughly kneaded with a pin mixer under the condition of 00 kg / cm ² to obtain a resin composition.

After the kneading, the resin composition was cooled in the second extruder to a resin temperature suitable for foaming, and then the resin composition was attached to the tip (outlet side) of the second extruder. From (lip: width w = 90 mm, t = 1.2 mm),
It was extruded and foamed at 35 kg per hour. The die pressure is 7
It is 9.8 kg / cm ² .

Then, the extruded foam was molded by passing it through a molding device, which was closely attached to the tip of the die and made by facing two plates, and was cooled at the same time as the molding.

As a result, the width is 172 mm and the thickness is 28.5.
mm plate-like foam was obtained. Moreover, when the density (measured using an electronic densitometer) and the average cell diameter of the obtained foam were measured, the density was 0.040 g / cm ³ , and the average cell diameter was 0.26 mm.

The flammability satisfied the standard of JIS A 9511, and the thermal conductivity hardly changed with time, and satisfied the standard (1 type) of JIS A 9511. Example 2 Polystyrene as a resin (G-13-50A, MF manufactured by Nippon Steel Chemical Co., Ltd.)
R = 4.0 (g / 10min), melt tension = 11.0 (gf)),
Company's G-13-50B (MFR = 6.0 (g / 10min), melt tension = 7.6
Extrusion foaming and molding were performed in the same manner as in Example 1 except that (g.f)) was used.

As a result, the width is 170 mm and the thickness is 27.5.
mm plate-like foam was obtained. When the density and the average cell diameter of the obtained foam were measured in the same manner as in Example 1, the density was 0.041 g / cm ³ and the average cell diameter was 0.25 mm. In addition, both flammability and thermal conductivity (1 type) satisfied the requirements of JIS A 9511. Comparative Example 1 Polystyrene (G-13-50A, MF manufactured by Nippon Steel Chemical Co., Ltd.)
R = 4.0 (g / 10min), melt tension = 11.0 (gf)),
Electrochemical HRM-3 (MFR = 0.7 (g / 10min), melt tension =
Extrusion foaming and molding were carried out in the same manner as in Example 1 except that 19.2 (gf)) was used.

As a result, the width is 150 mm and the thickness is 25.0.
mm plate-like foam was obtained. When the density and the average cell diameter of the obtained foam were measured in the same manner as in Example 1, the average cell diameter was 0.30 mm, which was satisfactory.
The density was 0.052 g / cm ^3, and only a high-density heavy molded product could be produced, and a low-density product could not be produced. Comparative Example 2 Polystyrene as a resin (G-13-50A, MF manufactured by Nippon Steel Chemical Co., Ltd.)
R = 4.0 (g / 10min), melt tension = 11.0 (gf)),
Asahi Kasei Stylon 679 (MFR = 20.0 (g / 10min
), Melt tension = 1.4 (g · f)), and extrusion foaming and molding were carried out in the same manner as in Example 1.

As a result, the width is 150 mm and the thickness is 25.0.
mm plate-like foam was obtained. When the density and the average cell diameter of the obtained foam were measured in the same manner as in Example 1, the average cell diameter was 0.32 mm, which was satisfactory.
The density was 0.052 g / cm ^3, and only a high-density heavy molded product could be produced, and a low-density product could not be produced. Comparative Example 3 Polystyrene as a resin (G-13-50A, MF manufactured by Nippon Steel Chemical Co., Ltd.)
R = 4.0 (g / 10min), melt tension = 11.0 (gf)),
Company's G-13-55S (MFR = 2.3 (g / 10min), melt tension = 9.5
(g.f)) was used, and extrusion foaming and molding were carried out in the same manner as in Example 1 except that 4.2 parts of carbon dioxide was pressed.

As a result, the width is 165 mm and the thickness is 25.5.
mm plate-like foam was obtained. When the density and the average cell diameter of the obtained foam were measured in the same manner as in Example 1, the average cell diameter was 0.28 mm, which was satisfactory.
The density was 0.049 g / cm ^3, and only a high-density heavy molded product could be manufactured, and a low-density product could not be manufactured.

[0077]

INDUSTRIAL APPLICABILITY In the present invention, carbon dioxide is used as a foaming agent .
It is possible to produce a styrenic resin foam having a high expansion ratio and a good thickness by using the slag.

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Claims (2)

(57) [Claims] 1. A measuring article described in JIS K 7210.
Set the melt flow rate depending on the situation to X (g / 10 minutes),
Using a rograph, test temperature 200 ℃, preheating time 5 minutes,
Capillary shape, diameter 1.00mm, length 10m
m, inflow angle 45 °, extrusion speed 100 mm /
melt measured at min and winding speed of 12 mm / min
When the melt tension is Y (g · f), the relationship between X and Y is
(1) Y> −0.65X + 11.6 (where 2 <X <10
is there. Made of a styrene-based resin represented by), there only is to that press out the foam and blowing agent of carbon dioxide, the density of 0.0
30-0.047 g / cm ³ , thickness 15-120 mm
And a styrene resin foam having an average cell diameter of 0.05 to 0.50 mm. 2. A method for producing an extruded foam of a styrene resin using only carbon dioxide as a foaming agent, which is described in JIS K 7210 as a raw material styrene resin.
The melt flow rate and X (g / 10 min) according to the measurement conditions
, Using a capillograph, test temperature 200 ℃, preheat
5 minutes, 1.00 mm diameter as capillary shape,
Extrusion speed of 1 with a length of 10 mm and an inflow angle of 45 °
00 mm / min, winding speed 12 mm / min
Assuming that the measured melt tension is Y (g · f), the relationship between X and Y is expressed by the formula (1): Y> −0.65X + 11.6 (where 2 <X <10 It is characterized in that it is extruded and foamed using a styrene resin represented by
^{3. A} method for producing a styrene resin foam having a thickness of 15 to 120 mm and an average cell diameter of 0.05 to 0.50 mm.