JP2883780B2 - Method for producing synthetic resin foam 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 a method for producing a foamed synthetic resin article. More specifically, the present invention relates to foam molding in which an unfoamed synthetic resin sheet containing a foaming agent is used as a material, which is heated and foamed, and at the same time, is brought into close contact with a mold so that foaming and molding are simultaneously performed. The present invention relates to a method for producing a body.

[0002]

2. Description of the Related Art A method for producing a synthetic resin foam molded article is as follows.
It can be roughly divided into two. One is a bead molding method and the other is an extrusion foaming method. The bead molding method uses foamable beads made of synthetic resin particles containing a foaming agent, puts it into a mold, heats it with steam, foams the particles, and fuses them together to form a mold. This is a method for obtaining the same foamed molded article. In the extrusion foaming method, a synthetic resin is put into an extruder, heated and melted, and a foaming agent is contained in the extruder, extruded and foamed at the same time. This is a method in which a foamed molded article having a desired shape is formed by cutting and cutting.

The bead molding method is used to produce a thick molded body having a complicated shape. More specifically,
The bead molding method is used to produce a molded article having a thickness that differs greatly in some places, for example, a cushioning fixing material when an electric product is put in a cardboard box. Extrusion foaming has also been used to make molded articles of uniform thickness, especially thin containers, such as foamed trays and cups. Among them, the extrusion foaming method has been widely used because the foaming operation is easy and the product can be manufactured at low cost.

In the extrusion foaming method, it is theoretically possible to produce a foamed resin sheet by simultaneously pressing a foamed resin sheet into a molding die, but in most cases, the process of producing a foamed material and pressing it into the molding die are performed. It was performed separately from the step of forming a molded body. Further, in the process of forming a foam, it is common to include a foaming agent in a synthetic resin in an extruder, and extrude from the extruder and simultaneously foam to form a foamed sheet. However, there have been attempts to extrude a sheet containing a foaming agent in an extruder, and cool the extruded sheet without foaming to obtain an unfoamed foamable sheet.

[0005] Japanese Patent Publication No. Hei 1-550833 describes a method for continuously producing a foamed sheet by an extrusion foaming method. The method is to extrude a synthetic resin containing a foaming agent as a sheet from an extruder, immediately cool it to produce an unfoamed foamable sheet, and then heat it again to foam it. How to make it. However, the foamable sheet is only meant to be present temporarily in the series of continuous manufacturing equipment shown there. That is, the foamable sheet cannot be taken out of the manufacturing apparatus, stored in another place, and then subjected to foaming. Moreover, the foamable sheet is described as being able to be made of plastic in general. However, as an example, only the case of using a styrene-based resin as a material is shown. Only one example of a foamable sheet containing argon is shown.

[0006] Styrene resins have the advantages of good shape stability and electrical insulating properties, and are easy to foam and mold. However, it has a drawback that it cannot be used at a temperature of 90 ° C. or higher because of poor heat resistance. Therefore, the appearance of a heat-resistant foam molded article has been desired.

[0007]

SUMMARY OF THE INVENTION The present invention uses a resin having better heat resistance than styrene resin as a material.
An object of the present invention is to provide a method for producing a molded article foamed by an extrusion foaming method.

[0008]

Means for Solving the Problems The present inventor tried to select a thermoplastic resin having excellent heat resistance other than a styrene-based resin and extrude and foam it to obtain a foamed resin sheet. At this time, the present inventor has found that when a polyamide resin, a thermoplastic polyester resin, and a polycarbonate resin are used as the resin, these resins can be extruded and foamed, and the resin sheet thus foamed has sufficient heat resistance. It was confirmed that it became. In addition, the inventor of the present invention selects and uses a resin having a small gas permeability for these resins as a foaming agent, and rapidly cools a resin sheet containing a foaming agent obtained by extrusion to obtain an unfoamed foamable sheet. It was found that the foamed sheet obtained had foaming properties even after being left for a while. Further, the inventor of the present invention has obtained an unfoamed foamable sheet,
It has been found that when this is stored for a while and then heated and foamed, it becomes a very uniformly finely foamed sheet. Moreover, it has been found that the fineness of the foam when foamed in this way is much finer and more beautiful than the foam obtained by foaming simultaneously with extrusion. The present invention has been completed based on such knowledge.

According to the present invention, a polyamide, a thermoplastic polyester or a polycarbonate resin is supplied to an extruder, and a gas permeability at 25 ° C. and a relative humidity of 50% is 10 cc. mm / cm ² . sec. cmH
g × 10 ¹⁰ or less gas is injected into the resin in the extruder, and a resin composition containing gas in a ratio of 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the resin is not foamed from the extruder. And extrude the sheet immediately after 5
Guide into a liquid below 0 ° C and quench to keep it in an unfoamed state,
A method for producing a synthetic resin foam molded article characterized in that an unfoamed foamable resin sheet is taken out, stored for a while, then heated and brought into close contact with an appropriate mold to simultaneously perform foaming and molding. Is what you do.

In the present invention, the resin is selected from polyamide, thermoplastic polyester and polycarbonate resin. The polyamide resin is a resin generally called nylon, and is a chain polymer having an acid amide bond as a repeating unit in the molecule. The thermoplastic polyester resin is a high-molecular chain polyester obtained by reacting an aromatic dicarboxylic acid with a dihydric alcohol. Typical examples are polyethylene terephthalate and polybutylene terephthalate. Polycarbonate is a chain polymer having a carbonate bond as a repeating unit. A typical example is an aromatic polycarbonate resin made from bisphenol A and phosgene.

Although the polyamide resin and the thermoplastic polyester resin are crystalline, it is preferable to use an amorphous resin in the present invention. Preferred resins are amorphous polyamide resins, amorphous polyethylene terephthalate resins, polycarbonate resins, and polyamide resins called 6-nylon.

In the present invention, a gas having a small gas permeability for each resin is used as a foaming agent. The gas having a small gas permeability is defined as 25% for each resin.
At 10 ° C. and a relative humidity of 50%. m
m / cm ² . sec. Gas of cmHg × 10 ¹⁰ or less. The gas permeability differs depending on the type of gas and the type of resin even under the above temperature and humidity. For example, for an amorphous polyamide resin, nitrogen is 0.05 cc. mm /
cm ² . sec. It has a gas permeability of cmHg × 10 ¹⁰ and carbon dioxide of 0.4 cc. mm / cm ² . sec.
It has a gas permeability of cmHg × 10 ¹⁰ . Further, nitrogen was 0.4 cc. For amorphous polyethylene terephthalate resin. mm / cm ² . sec. cmHg × 10
^It has a gas permeability of ¹⁰ and 3.6 cc of carbon dioxide. mm
/ Cm ² . sec. It has a gas permeability of cmHg × 10 ¹⁰ . For polycarbonate resin, nitrogen was 3.0 cc. mm / cm ² . sec. cmHg × 10 ¹⁰
Gas permeability. For polyamide resin, nitrogen was 0.2 cc. mm / cm ² . sec. c
It has a gas permeability of mHg × 10 ¹⁰ and carbon dioxide of 1.
6cc. mm / cm ² . sec. It has a gas permeability of cmHg × 10 ¹⁰ . Gas permeability measurement method is AST
It is defined in MD 1434 and is based on JIS K71
Since a similar method is defined in 26, a value measured by this method is used.

With respect to the three resins used in the present invention, the blowing agents having a small gas permeability include carbon dioxide, nitrogen, butane, neon, argon, krypton, and xenon.

In the present invention, the resin is supplied to an extruder, and the gas is pressed into the resin in the extruder to cause the gas to act as a foaming agent. Although only one extruder can be used as the extruder, it is preferable to use a tandem extruder in which a plurality of extruders are connected in series.

If necessary, various auxiliaries conventionally used in the production of foams can be added to the above resin. For example, a small amount of talc powder is added as a cell regulator, and in the case of a thermoplastic polyester resin, an acid dianhydride such as pyromellitic anhydride is added to improve the melting properties. However, in the present invention, such a thing can be added. Further, a coloring agent, a heat stabilizer, an antioxidant, a flame retardant, a reinforcing agent, and the like can be added.

In the present invention, the above resin is supplied to the extruder, and after the resin is melted in the extruder, the above gas is injected into the resin. When a tandem extruder is used as the extruder, gas is injected into the resin melted in the first extruder constituting the tandem extruder. At this time, in the first extruder, the resin pressure is kept at 200 kg / cm ² or less.

According to the present invention, the above-mentioned gas is injected into the resin in the extruder, and the gas is fed into the resin in an amount of 0.01 to 100 parts by weight.
So as to be contained at ３3.0 parts by weight. Among them,
Preferably, 0.05 to 0.5 parts by weight of gas is contained with respect to 100 parts by weight of resin. This gas amount is a small amount as a foaming agent, and in order to include this small amount of gas in the molten resin in the extruder in a stable state, as described above, the pressure in the extruder is set to 200 kg / cm ² or less. It is necessary to hold. Of which 5 is preferred
The pressure is from 0 to 150 kg / cm ² .

Thus, the resin containing the foaming agent is:
The mixture is well kneaded in the extruder and sent as a uniform composition. When the extruder is a tandem extruder, the resin containing the foaming agent in the first extruder is sent to the next extruder, where the resin and the foaming agent are further kneaded.
The next extruder mentioned above is often the last extruder, but when three extruders are connected in series, the resin is further sent to a third extruder. Thus, when passing through multiple extruders, the resin is extruded from the last extruder at a higher pressure than the first extruder. The pressure when extruded from the last extruder is 100 kg / cm ² or more.
Among them, preferred is 150 kg / cm ² or more, and more preferred is 200 kg / cm ² or more.

The pressure of the last extruder must be higher than the pressure of the first extruder. The reason is that if the pressure of the last extruder is lower than the pressure of the first extruder, the resin will foam in the die attached to the tip of the last extruder, and it will be extruded in an unfoamed state Is not possible. Further, even if the resin sheet foamed and extruded in the die is cooled and then left for two hours or more and then heated again, it does not foam finely.

A die is attached to the tip of the extruder.
This die is provided with a sheet-shaped opening from which a molten resin containing a foaming agent is extruded in a sheet shape. This extrusion is usually performed downward, and the extruded resin sheet is immediately put into a cooling water tank. The resin sheet thus extruded is cooled and solidified in an unfoamed state. This is one of the major features of the present invention.

A cooling liquid at 50 ° C. or lower, preferably 30 ° C. or lower, more preferably 20 ° C. or lower is stored in the cooling water tank. A liquid at such a temperature is necessary to prevent the extruded resin sheet from foaming. In addition, the distance between the surface of the cooling liquid and the base opening is
Make it as small as possible. This is because the extruded resin sheet is not given a chance to foam. The distance is 5mm
It is desirable to make the following. In addition, as the cooling liquid, alcohol, liquid nitrogen, liquid carbon dioxide, or the like can be used in addition to water. The resin sheet that has been cooled to suppress foaming is taken out in an unfoamed state. The unfoamed resin sheet taken out is usually wound into a roll and stored. It is a major feature of the present invention that the foamable resin sheet is taken out and stored in an unfoamed state.

The storage of the foamable sheet is usually performed in the atmosphere. The temperature at that time is preferably equal to or lower than normal temperature. The storage is preferably performed for 2 hours or more. During this time, even if the foamable sheet is left undisturbed, the foaming agent does not volatilize significantly from the foamable sheet because the permeability of the gas used as the foaming agent is small. For example, if the thickness is 0.
In a foamable sheet in which a nitrogen gas as a foaming agent is contained at about 0.12% by weight in a 19 mm polyamide resin film,
Even after leaving it in air at 20 ° C. for 2 days, it still has sufficient foaming properties. When the storage temperature is lowered, foamability can be maintained for a longer period. Therefore, this foamable sheet can be sufficiently practically used as a foamable sheet even after storage.

When the foamable sheet is heated to a temperature higher than the softening point of the resin, the foamable sheet foams to generate fine bubbles, and the transparent sheet becomes opaque and the thickness increases. In this way, the sheet can be formed into an arbitrary shape by pressing the sheet against the forming mold by utilizing the softening of the sheet.

Heating can be performed in various ways. For example, heating can be performed by irradiating with far-infrared rays, blowing hot air, contacting water vapor, or contacting a heating plate. Among them, a preferable method for obtaining a finely foamed molded body with a beautiful surface is a method of irradiating with far infrared rays and a method of bringing a heating plate into contact. Further, the heating needs to be performed uniformly over the surface of the sheet.
This is because, if not uniform in the surface direction, only the heated portion foams and swells, so that the entire sheet is largely wavy. In order to suppress this, it is preferable to fix the periphery of the sheet with a frame.

The molding can be performed in various ways. For example, it can be formed into an arbitrary shape by vacuum forming, press forming, pressure forming, etc., which have been performed so far.
In particular, in this case, since the sheet is not already foamed and is in the state of foaming for the first time since it has not been foamed yet, it has a tendency to greatly undulate in the surface direction of the sheet. A molded article can be easily made. Therefore, this sheet is suitable for making containers such as cups and trays.

When the unfoamed foamable sheet is foamed by heating as described above, the obtained foam is foamed uniformly with fine bubbles, and the surface has no irregularities due to the bubbles. Has a glossy smooth surface. This point is completely different from a styrene resin foam obtained by foaming with extrusion. More specifically, the styrene-based resin foam obtained by extrusion foaming has an average cell diameter of 200 μm or more, even if it has fine cells, but was obtained from the foamed sheet of the present invention. The foam has an average cell diameter of 30 μ or less. Also, in the foamed sheet of the styrene resin obtained by extrusion foaming, the surface is wavy along the cells and is not a smooth surface, but the foam obtained from the foamable sheet of the present invention has a smooth surface. It has a glossy surface like a mirror surface. In addition, since the foam obtained from the foamable sheet according to the present invention is made of polyamide, thermoplastic polyester or polycarbonate resin, it is tough and has high mechanical strength in proportion to the thickness of the sheet. The foam thus obtained is foamed uniformly and finely and has a beautiful surface.

[0027]

According to the method of the present invention, the gas permeability is 10 cc. mm / cm ² . sec. Since a gas having a gas permeability of not more than cmHg × 10 ¹⁰ is contained in a ratio of 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the resin,
The resulting foamable sheet does not immediately lose foamability. Therefore, it can be taken out as an unfoamed foamable sheet. As we decided to store this foamable sheet for a while,
An unfoamed, low-bulk sheet is provided as a raw material, and is subjected to a conventional forming process to obtain a foamed body having a desired shape. Therefore, when the manufacturer of the foamable sheet and the processor of the foam molding are different from each other, it is advantageous because the cost of storing and transporting the sheet can be saved. In addition, since a foam molding and processing company can obtain foaming and molding all at once, it is possible to provide a foam molded article with high added value.

Further, according to the method of the present invention, since the polyamide, thermoplastic polyester or polycarbonate resin is used as the resin, the obtained foamable sheet and the foamed molded product obtained by further foaming the foamable sheet have sufficient strength. With sufficient heat resistance. Furthermore, since it was taken out as an unfoamed foamable resin sheet and stored for a while, and then heated and foamed, compared with a sheet immediately foamed by extrusion foaming,
It is possible to provide a beautiful foamed article in which bubbles are far finer and more uniformly foamed, and the surface is smooth and beautiful.

Further, in the case of using a tandem extruder for producing an unfoamed foamable sheet, a pressure of 200 kg / cm ² or less in the first extruder, preferably 50 kg / cm ² or less.
At a pressure of ~ 150 kg / cm ² , the resin is melt-kneaded, and a gas serving as a foaming agent is injected into the resin to form a mixture.
From the last extruder to a higher pressure than the first extruder and 1
Assuming that the resin is extruded under a pressure of 00 kg / cm ² or more, a gas as a foaming agent is contained in a proportion of 0.01 to 3.0 parts by weight with respect to 100 parts by weight of the resin to obtain a foamable resin. It becomes easier. The present invention provides the above benefits.

[0030]

The following is a detailed description of the advantages of the present invention with reference to Examples and Comparative Examples. Hereinafter, simply “%” means “% by weight”.

[0031]

Example 1 The first extruder had a diameter of 50 mm.
mm extruder, a subsequent extruder having a diameter of 65 mm was used, and a tandem extruder in which the two extruders were connected in series was used. A die was attached to the tip of the subsequent extruder, and the die was provided with an opening having a width of 150 mm and a thickness of 0.3 mm, and the resin was extruded from this opening. The opening was downward and the surface of the cooling water was located 5 mm below the opening.

As the resin, an amorphous polyamide resin was used, and the resin used was sold under the trade name of Sealer 3426 by Du Pont-Mitsui Polychemicals.
Nitrogen gas was used as a foaming agent. mm / cm ² . sec. cm
It had a gas permeability of Hg × 10 ¹⁰ .

The above resin is put into the first extruder at a rate of 10 kg per hour, and the temperature of each part of the barrel in the tandem extruder is appropriately adjusted within the range of 200 to 260 ° C.
A gas pressure inlet is provided in the middle of the barrel of the first extruder, the pressure in the first extruder is set to 90 kg / cm ² , and nitrogen gas is injected into the resin therein, and nitrogen gas occupies about 0.12%. I did it. The pressure in the subsequent extruder was increased to 250 kg /
cm ² , the temperature of the resin was 230 ° C., and the temperature at the outlet of the base was 220 ° C., which was 10 ° C. lower than that, and the resin was extruded from the opening of the base. The extruded sheet was immediately placed in cooling water at 25 ° C. to solidify the sheet in an unfoamed state, and the solidified sheet was wound around a roll. Thus, a foamable sheet having a thickness of 0.19 mm was obtained.

After leaving the foamable sheet in the air at 30 ° C. for 2 days, the periphery of the sheet is fixed with a frame, and the central portion of the sheet is heated by contacting with a heating plate at 130 ° C. for 5 seconds.
Foaming and vacuum forming were performed to make a shallow container 130 mm in width, 100 mm in width, and 30 mm in depth. The obtained container has fine bubbles uniformly dispersed therein, and has a size of about 2.3.
The foam was doubled, and the thickness of the container bottom was 0.38 mm. Further, the average bubble size was as fine as 6.5 μm, and the surface was beautiful, had no irregularities, and had a glossy smooth surface.

[0035]

Example 2 This example was carried out in exactly the same manner as in Example 1 except that carbon dioxide was used instead of the nitrogen gas used as the foaming agent in Example 1. Carbon dioxide was injected to account for about 0.18%. The resulting foamable sheet has an unfoamed glossy surface,
It had a thickness of 0.21 mm.

The amount of carbon dioxide was 0.32 cc. With respect to the amorphous polyamide resin used as the resin. mm / c
m ² . sec. It had a gas permeability of cmHg × 10 ¹⁰ .

After leaving the obtained foamed sheet in air at about 25 ° C. for 4 hours, the periphery thereof is fixed to a frame, and the central portion is irradiated with far-infrared rays for 10 seconds to reduce the surface temperature of the sheet to about 15 ° C.
It was foamed by heating to 0 ° C. and molded into a shallow container of 120 mm in width, 80 mm in width and 25 mm in depth, sandwiched between molds. Then, the obtained container was foamed uniformly and finely, and the surface was a glossy smooth surface. The container is foamed about 2.5 times, and the thickness of the container bottom is 0.43m
m and the average bubble was 18.2μ.

[0038]

Example 3 This example was carried out in substantially the same manner as in Example 1, except that an amorphous thermoplastic polyethylene terephthalate resin (Kodak Pet 6763, manufactured by Eastman Chemical Co.) was used instead of the polyamide resin. Therefore, the extrusion conditions were slightly changed. The details are as follows.

The same tandem extruder as in Example 1 was used, and the above resin was charged at a rate of 12 kg per hour. The barrel temperature of the extruder was adjusted to 150 to 250 ° C., the pressure in the extruder was initially set to 150 kg / cm ² , and nitrogen gas was injected into the resin so that the nitrogen gas occupied 0.21%. The pressure inside the extruder after that was 230 kg / c.
m ² , the resin temperature was 165 ° C., and the outlet temperature of the die was 150 ° C., which was 15 ° C. lower than the resin temperature, and was extruded in a sheet shape. The extruded sheet was quenched with water in the same manner as in Example 1 to obtain a foamable sheet having a thickness of 0.20 mm.

The nitrogen gas was added at 0.40 cc. To the amorphous thermoplastic polyethylene terephthalate resin. m
m / cm ² . sec. It had a gas permeability of cmHg × 10 ¹⁰ .

The above foamable sheet was placed in air at about 17 ° C. for 4 hours.
After leaving for a period of time, this was fixed to a frame, and the center portion was irradiated with far-infrared rays for 5 seconds to heat the surface of the sheet to 120 ° C., foamed, and pressed and molded to a thickness of 100 mm, width 8 mm.
A shallow container of 0 mm and a depth of 30 mm was made. The resulting container is uniformly and finely foamed and has a bottom thickness of 0.33.
mm, the expansion ratio was 1.8 times, the average cell diameter was 8μ, and the surface was a glossy glossy surface.

[0042]

EXAMPLE 4 This example was carried out in substantially the same manner as in Example 1, except that the resin was changed and a polycarbonate resin (manufactured by Teijin Chemicals Ltd., Panlite L-
1250), the extrusion conditions were slightly changed accordingly. Specifically, it was implemented as follows.

The same tandem extruder as in Example 1 was used, except that only the thickness of the mouthpiece opening was changed to 0.2 mm, and the above polycarbonate resin was added at 15 K / hour.
g. Extruder barrel temperature 230-2
The temperature in the extruder was adjusted to 90 ° C.
Nitrogen gas was injected into the resin as cm ² , and the nitrogen gas occupied 0.13%. Thereafter, the pressure in the extruder was set to 220 kg / cm ² , the resin temperature was set to 250 ° C., and the temperature at the outlet of the die was extruded into a sheet at 242 ° C. lower than the resin temperature by 8 ° C. The extruded sheet was rapidly cooled with water in the same manner as in Example 1 to obtain a foamable sheet having a thickness of 0.28 mm.

The nitrogen gas was supplied to the polycarbonate resin at 3.1 cc. mm / cm ² . sec. cm
It had a gas permeability of Hg × 10 ¹⁰ .

The obtained foamable sheet was wound in a roll and left to stand in air at about 22 ° C. for 5 hours, and then fixed around the sheet with a frame. The container was heated by contact, foamed, and vacuum-formed to form a shallow container having a depth of 130 mm, a width of 100 mm, and a depth of 30 mm. The obtained container was foamed uniformly and finely, and the surface was a glossy smooth surface. The bottom thickness of the container was 0.48 mm, the expansion ratio was 1.9 times, and the average cell diameter was 15.8 μm.

[0046]

Example 5 The foamed sheet wound up in the form of a roll in Example 1 was allowed to stand in air at 30 ° C. for 4 days, and its periphery was fixed with a frame, and the central portion was irradiated with far infrared rays for 10 seconds. The surface of the sheet was heated to 150 ° C., foamed and vacuum-formed to form a shallow container 130 mm long, 100 mm wide and 30 mm deep. The obtained container was foamed uniformly and finely, and the expansion ratio was 2.5 times. The thickness of the container bottom was 0.40 mm. The average bubble size was 8.7μ. The surface of the container was a glossy smooth surface.

[0047]

Comparative Example 1 This comparative example was carried out in substantially the same manner as in Example 4, except that carbon dioxide was used instead of nitrogen gas as a blowing agent, and the operating conditions were slightly changed accordingly. The details are as follows.

The same tandem extruder and die as in Example 4 were used, and the polycarbonate resin was added thereto for one hour.
Charged at a rate of 3 kg. Extruder barrel temperature 230
-290 ° C and the initial pressure in the extruder was 105K
Carbon dioxide was injected into the resin at g / cm ² so that carbon dioxide occupied 0.25%. Thereafter, the pressure in the extruder was set to 255 kg / cm ² , the resin temperature was set to 245 ° C., and the temperature at the outlet of the die was lower by 10 ° C. than the resin temperature.
Extruded in a sheet at 35 ° C. The extruded sheet was quenched with water in the same manner as in Example 1, and had a thickness of 0.26 m.
m foamable sheet was obtained.

It should be noted that carbon dioxide was 85.2 cc. mm / cm ² . se
c. It had a gas permeability of cmHg × 10 ¹⁰ , which was larger than the gas permeability specified in the present invention.

The obtained foamable sheet was wound into a roll and stored in air at 25 ° C. for 5 hours, and the periphery was fixed with a frame, and the central portion was brought into contact with a heating plate at 160 ° C. for 7 seconds. Heated, foamed and vacuum formed, 13
A container having a length of 0 mm, a width of 100 mm, and a depth of 30 mm was prepared. Although the obtained container was well foamed, the bubbles were large, the surface was uneven, and the surface was not smooth. The expansion ratio of the container was 2.7 times, the average cell diameter was 45 μm, and the bottom thickness was 0.62 mm.

Therefore, it was confirmed that when the gas permeability exceeded the ratio specified in the present invention, uniform and fine foaming was not possible.

[0052]

Comparative Example 2 This comparative example was carried out in the same manner as in Example 1, except that a polystyrene resin (Stylon 666, manufactured by Asahi Kasei Kogyo Co., Ltd.) was used instead of the polyamide resin. changed. The details are as follows.

The same apparatus as in Example 1 was used, and the polystyrene resin was introduced into the apparatus at a rate of 12 kg per hour. The barrel temperature of the extruder was adjusted to 150-230 ° C., the initial pressure in the extruder was set to 120 kg / cm ² , nitrogen gas was injected into the resin, and the nitrogen gas was 0.21%
To occupy. The pressure inside the extruder is 240 kg
/ Cm ² , the resin temperature was 178 ° C., and the temperature at the outlet of the die was 173 ° C., which was 5 ° C. lower than the resin temperature, and was extruded into a sheet. The extruded sheet was rapidly cooled in the same manner as in Example 1 to obtain a foamable sheet having a thickness of 0.25 mm.

The nitrogen gas was supplied to the polystyrene resin at 35.3 cc. mm / cm ² . sec. cmH
It had a gas permeability of g × 10 ¹⁰ , which was higher than the gas permeability specified in the present invention.

The obtained foamable sheet is wound into a roll and left in the air at 20 ° C. for 3 hours. Then, the periphery is fixed to a frame, and the central portion is brought into contact with a heating plate at 120 ° C. for 10 seconds. Then, it was heated and tried to foam, but did not foam. Therefore, it was confirmed that even after nitrogen gas was injected into the polystyrene resin, the nitrogen gas escaped after 3 hours, and the foaming ability was lost.

As a precautionary measure, 30 minutes after the foamable sheet was obtained, the periphery of the foamable sheet was fixed to a frame, and the central portion was heated by contacting it with a heating plate at 120 ° C. for 7 seconds. The foamable sheet foamed. The expansion ratio is 2.5
Twice and the thickness was 0.59 mm. The average cell diameter was 11 μm, which was fine because it was once taken out as a foamable sheet, and was 200 μm of the average cell diameter of a polystyrene resin foam foamed by one-stage foaming.
It was much finer than.

[0057]

Comparative Example 3 This comparative example was carried out in the same manner as in Example 1, except that the resin was changed to use a high-impact polystyrene resin (manufactured by Mitsubishi Monsanto, Dialex HT-516) instead of the polyamide resin. Accordingly, the operating conditions were slightly changed. The details are as follows.

The same apparatus as in Example 1 was used, and the high-impact polystyrene resin was added thereto at an rate of 1 hour / hour.
Charged at a rate of 2 kg. Extruder barrel temperature 150
Adjust to −220 ° C. and set the initial pressure in the extruder to 90 kg
/ Cm ² , and nitrogen gas was injected into the resin so that the nitrogen gas occupied 0.15%. Thereafter, the pressure in the extruder was set to 230 kg / cm ² , the resin temperature was set to 175 ° C., and the temperature at the outlet of the die was set to 165 ° C., which was lower by 10 ° C. than the resin temperature, and extruded into a sheet. The extruded sheet was rapidly cooled in the same manner as in Example 1 to obtain a foamable sheet having a thickness of 0.24 mm.

The nitrogen gas was supplied to the high impact polystyrene resin at 48.6 cc. mm / cm ² .
sec. It has a gas permeability of cmHg × 10 ¹⁰ ,
It was larger than the gas permeability defined in the present invention.

The obtained foamable sheet was wound into a roll and left in air at 17 ° C. for 3 hours, and then the periphery was fixed to a frame, and the central portion was irradiated with far infrared rays for 10 seconds to form a sheet. The surface was heated to 120 ° C., but did not foam. Therefore, it was confirmed that even after the nitrogen gas was injected into the high-impact polystyrene resin, the nitrogen gas escaped after 3 hours and the foaming ability was lost.

As a precautionary measure, when the foamable sheet was heated to 120 ° C. 30 minutes after the foamable sheet was obtained, the foamable sheet foamed. Its expansion ratio is 2.1
The thickness was 0.48 mm. Further, the average cell diameter was 7.4 μm, and was once taken out as a foamable sheet, so that it was smaller than the average cell diameter of ordinary polystyrene resin foam.

[0062]

Example 6 This example was carried out in substantially the same manner as in Example 1, except that the blowing agent was changed to use butane gas instead of nitrogen gas, so that the extrusion conditions were slightly changed accordingly. Specifically, it was implemented as follows.

The same tandem extruder as in Example 1 was used, except that only the thickness of the opening of the mouthpiece was changed to 0.4 mm, and an amorphous polyamide resin (Novamid X21 manufactured by Mitsubishi Kasei KK) was used in one hour. Charged at a rate of 13 kg. The barrel temperature of this extruder was adjusted within the range of 200 to 260 ° C., the initial pressure in the extruder was set to 150 kg / cm ² , and butane gas was injected into the resin.
To occupy. The pressure inside the extruder after that was 230 kg
/ Cm ² , the resin temperature was 226 ° C., and the outlet temperature of the die was 219 ° C. lower than the resin temperature by 7 ° C., and the sheet was extruded. The extruded sheet was rapidly cooled with water in the same manner as in Example 1 to obtain a foamable sheet having a thickness of 0.28 mm.

The amount of butane gas was 0.73 cc. With respect to the amorphous polyamide resin. mm / cm ² . sec.
It had a gas permeability of cmHg × 10 ¹⁰ .

The above foamable sheet was placed in air at about 15 ° C.
After standing for a few days, the periphery of the sheet is fixed with a frame, and the center of the sheet is brought into contact with a heating plate at 148 ° C. for 7 seconds to foam and vacuum form the sheet to a length of 100 mm.
A shallow container having a depth of 30 mm and a depth of 30 mm was prepared. The obtained container was foamed uniformly and finely, and the surface was a glossy smooth surface. The thickness of the bottom of the container was 0.75 mm, the expansion ratio was 3.2 times, and the average cell diameter was 25.7 μm.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI B29K 105: 04 (56) References JP-A-59-232831 (JP, A) JP-A-4-356540 (JP, A) US Pat. No. 4,473,665 (US, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 44/00- 44/60 B29C 47/00-47/96 B29C 67/20 C08J 9/00-9/14

Claims (1)

(57) [Claims] 1. An extruder is supplied with a polyamide, thermoplastic polyester or polycarbonate resin, and each resin has a gas permeability of 10 cc. At 25 ° C. and a relative humidity of 50%. mm / cm ² . sec. cmHg × 10 ¹⁰
The following gas was injected into the resin in the extruder and the resin 10
A resin composition containing gas in a proportion of 0.01 to 3.0 parts by weight with respect to 0 parts by weight is extruded from an extruder as an unfoamed sheet, and the extruded sheet is immediately introduced into a liquid at 50 ° C. or lower. Quenched and kept in an unfoamed state, take out the unfoamed foamable resin sheet, store it for a while, then heat it and bring it into close contact with an appropriate mold to perform foaming and molding simultaneously. And a method for producing a synthetic resin foam molded article.