JP3010375B2 - Method and apparatus for producing thermoplastic resin foam - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for producing a thermoplastic resin foam.

[Prior Art] Conventionally, thermoplastic resin foams have been formed into sheets and used as food packaging materials and containers.
In recent years, with the spread of microwave ovens, a foam container that can withstand heating in a microwave oven has been desired. However, it has been impossible to produce a thermoplastic resin foam excellent in heat resistance and heat insulation that can meet this demand by the following conventional production methods.

Conventionally, thermoplastic resin foams have generally been manufactured by an extrusion molding method. As an example of this method, for example,
The case where the tandem type foam extruder shown in the figure is used will be described. First, a foaming agent or a gas for foaming is added to the thermoplastic resin heated and plasticized by the extruder, and the mixture is kneaded. It is manufactured by molding into a sheet. In this method, the surface of the foam 3 extruded from the die 15 is brought into contact with the atmosphere, immediately quenched, and the resin of the surface layer is solidified without foaming, thereby forming a thin unfoamed layer (skin layer) on the surface. Was formed. By forming the skin layer on the surface in this manner, the bending rigidity of the foam 3 is increased and sheeting is facilitated, and the skin layer is formed smoothly, so that a foam having a beautiful appearance has been manufactured. . The foam surface is cooled by air cooling by air jet from the air blowing slit 4 and the air blowing ring 2 toward the surface, and by circulating water inside the mandrel 1 to lower the temperature of the mandrel surface. It was done.

Under such a state of the art, it is intended to produce a foam having excellent heat resistance.
It has been considered to use a heat-resistant polystyrene resin having a T) of 100 ° C. or higher, crystallized polyethylene terephthalate (c-PET), polymethylpentene (trade name: TPX), heat-resistant composite paper, and polypropylene with an inorganic filler. However, the above-mentioned conventional method is effective when a thermoplastic resin having a relatively low heat distortion temperature is used as a raw material, but when a resin having a high heat deformation temperature and a high heat resistance is used as a raw material, the heat deformation temperature is low. It is not possible to obtain a suitable foam such as when a relatively low resin is used as a raw material, and in particular, when a resin having a heat distortion temperature of 20 ° C. or higher than a normal resin is used, it is almost impossible to commercialize the resin. there were. In other words, the higher the heat distortion temperature of the resin, the higher the plasticity temperature of the resin, and the sudden drop in temperature when extruded from the die into the atmosphere reduces the resin elongation. Becomes extremely difficult. In addition, since the expansion ratio of the foam (the specific gravity of the unfoamed material / the specific gravity of the foamed material) is reduced, the density of the foam is increased and the heat insulating property is deteriorated. It is not practical to increase the thickness of the foam in order to improve the heat insulating property because the cost of the product increases. For this reason, it has been substantially impossible to produce a thermoplastic resin foam having good foaming properties, which is excellent in heat resistance and heat insulation, by a conventional method.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the prior art, and has a suitable expansion ratio (specific gravity of unfoamed material / It is an object of the present invention to provide a method and an apparatus for producing a thermoplastic resin foam which can be mass-produced at a low cost, with excellent heat insulation and heat resistance foamed at a specific gravity of the foam.

[Means for Solving the Problems] The present inventors have conducted intensive studies to solve the problems, and as a result, by extruding a resin extruded from a die into a gas heated to an appropriate temperature, each resin is extruded. By providing a cooling rate in accordance with the thermal characteristics of the foam, even if the resin used as the raw material has a high heat distortion temperature, the foam elongation at the time of taking the foam sheet is appropriately maintained, and a suitable expansion ratio is obtained. It has been found that a foam sheet foamed with (unfoamed specific gravity / foamed specific gravity) can be easily produced, and the production method and production apparatus of the present invention have been developed.

That is, the present invention relates to a method of adding a foaming agent or a gas for foaming to a thermoplastic resin heated and plasticized in an extruder, kneading the thermoplastic resin, lowering the thermoplastic resin at a temperature lower than the resin extrusion temperature, and breaking the resin during foam molding. A method for producing a thermoplastic resin foam, which comprises extruding into a gas heated to a temperature range that guarantees that elongation is maintained at 50% or more, and performing molding under a controlled cooling rate. In a resin foam manufacturing apparatus comprising an extruder section, a foam molding section, and a foam take-up section, there is a foam expansion section connected to the extruder section, and the foaming section is formed through an outlet of the extruder section. In addition to providing a resin foam heat retaining means comprising a jacket mechanism which can be extended and contracted in the resin extrusion direction over the body expansion section, the cooling rate of the resin foam extruded from the extruder into the foam expansion section is controlled by the resin foam. Adjust from inside And a heat transfer or heat transfer means provided with a temperature control mechanism for preparing a thermoplastic resin foam, further comprising an extruder section, a foam molding section, and a foam take-off section. In a resin foam manufacturing apparatus comprising: a heating gas spraying means having a temperature control mechanism for adjusting a cooling rate of the resin foam extruded from the extruder section from the inside of the resin foam; Heating means provided with a temperature control mechanism for heating the surface of the molding core-shaped body in contact with the resin foam, and an extruder section and a foam expansion section connected to the extruder section, which can be expanded and contracted in the resin extrusion direction. A heating gas supply means for heating the outer surface of the extruded resin foam in a range from the outlet of the extruder section to the foam molding section, while providing a heat retaining means for the resin foam comprising an outer shell mechanism; An apparatus for producing a thermoplastic resin foam, comprising: a cooling delay unit for delaying a cooling rate of the resin foam.

An example of the method for producing a thermoplastic resin foam of the present invention will be described based on an example of the apparatus for producing a thermoplastic resin foam of the present invention. The method for producing a thermoplastic resin foam of the present invention comprises the steps of kneading a foaming agent or a foaming gas into a plasticized resin using a production apparatus including an extruder unit, a foam molding unit, and a take-up unit. Is extruded from a die, and is an effective method particularly when a thermoplastic resin having a high heat distortion temperature is used as a raw material. In the present invention, first, a foaming agent or a gas for foaming is press-fitted and kneaded into a thermoplastic resin having high heat resistance, which is plasticized by heating in an extruder, and is extruded from a die of an extruding portion. The resin molded body extruded from the die is exposed to a temperature-regulated gas on its inner surface and / or outer surface, or by means of heat conduction or heat transfer.
The molding is performed while adjusting the cooling rate. That is, in the method of the present invention, a high-temperature foam extruded from a die is not quenched, but the foam is once maintained at an appropriate temperature to provide a cooling rate in accordance with the thermal characteristics of the raw material resin. It is.

In the present invention, the temperature employed for cooling the foam extruded from the die is preferably a temperature at which the elongation at break of the resin is 50% or more. If the elongation at break of the resin is less than 50%, the elongation of the resin at the time of take-up is small, and the resin is cut by the tensile stress at the time of take-up, and cannot be formed into a sheet.

[Operation] By adjusting the cooling rate so that the cooling rate of the foam extruded from the die is lower than in the case of the conventional extrusion molding, the elongation of the resin can be appropriately maintained, and the sheet can be easily formed. In addition, since a suitable elastic modulus can be secured, it is possible to obtain a foam having a low density and excellent heat insulating properties, in which bubbles are hardly broken. In addition, since this foam is usually made of a resin having high heat resistance, it goes without saying that it is excellent in heat resistance.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by the following examples.

Embodiment 1 FIGS. 1, 2 and 3 show one embodiment of the present invention.
A method for producing a thermoplastic resin foam using the production apparatus shown in the figure will be described with reference to Tables 1 and 2. FIG. 1 shows an extruder part and a foam molding part of a tandem type foam extruder (two extruders having a diameter of 60 mm and 100 mm connected) used in the present embodiment. FIG. 1 is an enlarged view of the foam molded part of FIG. The first
FIG. 2 and FIG. 2 show a state in which the foam of FIG. 3 is extruded from the die of FIG. FIG. 3 shows the same part as FIG. 2, but shows a state in which nothing is extruded from the die 15 in the figure.

In this example, five types of foams were produced using the resins of Samples 1 to 5 shown in Table 1 as raw materials in the same manner as described below. First, fine talc powder is added to the sample resin as a bubble regulator.
1.5 parts by weight were blended and charged into the hopper 16 of the first stage extruder at a rate of 30 kg per hour. At that time, Freon 22 as a foaming agent was press-fitted from the press-in port 17 at a ratio of about 5% by weight to the raw material resin. Next, the temperature of the cylinder of the first extruder was set at 250 ° C., and the rear end of the cylinder of the second extruder was set at 175 ° C.
The temperature was adjusted to 140 ° C. and the tip side was adjusted to 140 ° C., and the resin was extruded from the die 15. Air heated to 120 ° C. by the hot air generator 10 was sprayed onto the inner surface of the extruded foam at a pressure of 1 atm or more from the air blowing slit 4 to maintain the foam at a constant temperature. The foam 3 whose air has been sprayed on the inner surface rides on the mandrel 1 while expanding its inner diameter, and is taken off at an appropriate speed. This mandrel 1 has a maximum diameter of 225m
It has a cylindrical structure with a length of 330 m and a length of 330 mm, so that silicone oil can be circulated from the circulating thermostat 8 into the mandrel cylinder via the heat-resistant hose 7. That is, silicone oil was circulated inside the cylinder, the surface of the mandrel was kept at 120 ° C., and the foam moving there was kept warm. On the other hand, the air blowing ring 2 provided at the center of the mandrel is equipped with a heat retaining device 6 made of a transparent polycarbonate and having an extendable / retractable covering mechanism, which has a shape enclosing the mandrel toward the die. Air at 80 ° C. was always flowed from the air blowing ring 2 between the apparatus and the foam to keep the outer surface of the foam passing therethrough. That is, the hot air of 80 ° C. from the hot air generator 13 is blown out from the air blowing ring 2 via the heat-resistant flexible hose 5. Further, the air from the compressor 18 is blown through the hot air generator 10 and the copper pipe 9 for transporting compressed air, and the hot air of 120 ° C. is blown out from the air blowing slit 4 through the center of the mandrel 1.
Then, the temperature of the heat conductor 11 near the slit 4 for blowing air is measured by the temperature control unit 12 along the copper pipe 9 for compressed air transportation, and the temperature of the hot air in the hot air generator 10 is controlled. It is. The foam extruded from the die in this way is kept warm from the inner and outer surfaces while moving to the center of the mandrel, and is taken at a constant speed to control the cooling rate of the foam, and the elongation at break of the resin is 50% or more. Temperature. The foam that passed over the mandrel was cut into a sheet by the cutter 14, 2.3 mm thick, 690 mm wide
Was produced. Table 2 shows the results of examining various properties such as density, appearance, and physical properties of the foam produced from the resins of Samples 1 to 5 by the above method.

As can be seen from Table 2, the plate-like foams produced from the resins of Samples 1 to 5 by the above method all have a low-density and good-looking surface, and are also excellent in heat resistance. Met.

Embodiment 2 Another embodiment of the present invention will be described with reference to Table 2.

This example was performed in the same manner as in Example 1 except that the diameter of the mandrel was 180 mm and the blending amount of the fine powder talc was 1.0 part by weight. In this example, the resin of Sample 1 used in Example 1 was used as a raw material. In addition, the results of examining various properties such as the density, appearance, and physical properties of the foam produced in this example are shown in the respective columns of Table 2.

In this example, a plate-like foam having a thickness of about 2.5 mm and a width of 570 mm was manufactured. As can be seen from Table 2, this foam has a low-density and good-looking surface, and further has a heat resistance. Was also excellent.

Comparative Example 1 As a comparative example to the present invention, a thermoplastic resin foam was manufactured by a conventional method using the conventional manufacturing apparatus shown in FIGS. 4 and 5. FIG. 4 shows an extruder section composed of a tandem type foam extruder (two extruders having a diameter of 60 mm and 100 mm connected together) and a foam molding section used in the comparative example. Is an enlarged view of the foam molded part shown in FIG. 4 and 5 show a state in which the foam shown in FIG. 3 is extruded from the die 15 in FIG.

In this comparative example, the same procedure was performed except that all the steps of keeping the foam extruded from the die in Example 1 were removed. In this comparative example, the resin of sample 1 used in Example 1 was used as a raw material.

However, in the method of the present comparative example, since the cooling rate of the foam extruded from the die is too fast, the elongation of the resin becomes too small at the time of taking out the foam, and the foam is cut by the tensile stress at the time of taking out, It could not be made into a sheet.

[Comparative Example 2] As another comparative example with respect to the present invention, the holding temperature of the foam extruded from the die was set to 50 ° C or less by using the apparatus shown in FIGS. 1, 2 and 3. The temperature of the foam was adjusted to 125 ° C. or less for resin A and 105 ° C. or less for resin D in the molded portion.

In this comparative example, the temperature of the foam extruded from the die is
The procedure was performed in the same manner as in Example 1 except that the breaking elongation of the resin was set to 50% or less. The resin A and the resin D of the sample 1 used in Example 1 were used as the raw material resin.

However, in the method of this comparative example, since the cooling rate of the foam extruded from the die is too fast, the elongation of the resin becomes too small at 50% or less at the time of taking out, and the foam is cut by the tensile stress at the time of taking out. , Could not be made into a sheet.

[Effects of the Invention] With the advent of the present invention, a thermoplastic resin foam having excellent heat resistance can be produced from a resin having a heat distortion temperature higher than that of a normal foam molding resin and having high heat resistance as a raw material. became. In addition, since the expansion ratio (specific gravity of unfoamed material / specific gravity of foamed material) and the elongation of the foam when the foamed sheet is taken off can be suitably maintained, the heat insulating property is improved, and the sheeting can be facilitated. Was. Therefore, it is not necessary to increase the thickness of the foam, and the foam can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional side view showing an extruder section and a foam molding section of an example of the production apparatus of the present invention. FIG. 2 is an enlarged schematic side sectional view of a foam molding part of the manufacturing apparatus of FIG. FIG. 3 is a perspective view showing an example of a foam molding section of the production apparatus of the present invention. FIG. 4 is a schematic side sectional view showing an example of an extruder section and a foam molding section of a conventional manufacturing apparatus. FIG. 5 is a schematic side sectional view in which a foam molding part of the manufacturing apparatus of FIG. 4 is enlarged. DESCRIPTION OF SYMBOLS 1 ... Mandrel 2 ... Ring for air blowing 3 ... Foam 4 ... Slit for air blowing 5 ... Heat resistant flexible hose 6 ... Heat insulation device 7 ... Heat resistant hose 8 ... Circulating constant temperature oil layer 9 Copper pipe for compressed air transport 10 Hot air generator 11 Heat conductor 12 Temperature control unit 13 Hot air generator 14 Cutter 15 Dies 16 Hopper 17 Pressure inlet 18 ……Air Compressor

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Kuno 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (56) References JP-A-59-152827 (JP, A) JP-A-4 -27519 (JP, A) JP 42-26954 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (3)

(57) [Claims] 1. A foaming agent or a gas for foaming is added and kneaded to a thermoplastic resin heated and plasticized in an extruder, and the thermoplastic resin is cooled to a temperature lower than the resin extrusion temperature and the breaking elongation of the resin during foam molding. Extruding into a gas heated to a temperature range that guarantees that the temperature of the thermoplastic resin is maintained at 50% or more, and molding under a controlled cooling rate. 2. A resin foam manufacturing apparatus comprising an extruder section, a foam molding section, and a foam take-up section, wherein there is a foam expansion section connected to said extruder section, and said foam expansion section is connected to an outlet of said extruder section. In addition to providing a resin foam heat-insulating means comprising a jacket mechanism which can expand and contract in the resin extrusion direction over the foam expansion section, the cooling rate of the resin foam extruded from the extruder section to the foam expansion section is controlled by the resin. An apparatus for producing a thermoplastic resin foam, comprising a heat conducting or heat transfer means provided with a temperature control mechanism for adjusting the temperature from the inside of the foam. 3. A resin foam manufacturing apparatus comprising an extruder section, a foam molding section and a foam take-up section, wherein the cooling rate of the resin foam extruded from the extruder section is controlled from the inside of the resin foam. A heating gas spraying means having a temperature control mechanism for adjusting; a heating means having a temperature control mechanism for heating the surface of the molding core-shaped object in contact with the extruded resin foam; an extruder section; In addition to providing a resin foam heat retaining means comprising a covering mechanism which is capable of expanding and contracting in the resin extrusion direction over a foam expanding section connected to the extruder section, a resin foam is provided in a range from an outlet of the extruder section to the foam molding section. An apparatus for producing a thermoplastic resin foam, comprising: a cooling delay means for delaying a cooling rate of the resin foam, the heating gas supply means for heating an outer surface of the extruded resin foam.