JPH04201538A - Manufacture and apparatus for thermoplastic resin foam body - Google Patents

Abstract

PURPOSE:To mass-produce at low cost a foamed body having good heat insulation and heat resistance, foamed at a suitable foaming magnification by providing a heat insulation device on the expansion part of a foam body through an extruder discharging port. CONSTITUTION:A heat insulation device 6 is provided on a foam body expansion part through an extruder discharging port, and a foaming agent or foaming gas is application-kneaded onto the thermoplastic resin plasticized through heating in an extruding machine, and then molded by extruding it into heated air. In this manner, cooling velocity according to the thermal characteristics of respective resin is given thereto, whereby even resin to be employed as a material has a thermal deformable temperature, a foamed body sheet that is foamed at suitable foaming magnification can be manufactured readily by appropriately keeping the expansion of a foaming body 3 during the period of pulling the foamed body sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Industrial Application Field The present invention relates to a method and apparatus for producing a thermoplastic resin foam.

[Prior art] Thermoplastic resin foams have traditionally been formed into sheets and used as food packaging materials and containers, but with the spread of microwave ovens in recent years, thermoplastic resin foams have been made into sheets that can withstand heating in microwave ovens. Foam containers have become desirable. However, it has been impossible to manufacture thermoplastic resin foams with excellent heat resistance and heat insulation properties that can meet these demands using the conventional manufacturing methods described below.

Conventionally, thermoplastic resin foams have generally been manufactured by extrusion molding. As an example of this method, a case will be described in which a tandem foaming extruder shown in FIG. 4 is used.

First, a blowing agent or foaming gas is added and kneaded to thermoplastic resin that has been heated and plasticized in the extruder section, and this is forcibly extruded from the die 15 of the foam molding section. It is manufactured by molding it into a sheet. In this method, the surface of the foam 3 extruded from the die 15 is brought into contact with the atmosphere and immediately quenched to solidify the resin in the surface layer while remaining unfoamed, thereby forming a thin unfoamed layer (skin layer) on the surface. was being formed. By forming the skin layer on the surface in this way, the bending rigidity of the foam 3 is increased, making it easier to form a sheet, and since the skin layer is formed smoothly, a foam with a beautiful appearance can be manufactured. . Note that the surface of the foam is cooled by air cooling by jetting air toward the surface from the air blowing slit 4 and the air blowing ring 2, and by circulating water inside the mandrel 1 to lower the mandrel surface temperature. It was done.

It was planned to produce a foam with excellent heat resistance under such state of technology, and the raw material had a heat distortion temperature (HDT).
) of 100° C. or higher, crystallized polyethylene terephthalate (c-PET), polymethylpentene (trade name: TPX), heat-resistant composite paper, polypropylene containing inorganic fillers, etc. have been considered. However, the above conventional method is effective when the raw material is a thermoplastic resin with a relatively low heat distortion temperature, but when the raw material is a resin with a high heat distortion temperature and high heat resistance, the heat distortion temperature is low. It is not possible to obtain a suitable foam as when using a relatively low-quality resin as a raw material,
In particular, when using a resin whose heat distortion temperature is 20° C. or more higher than that of ordinary resins, it has been almost impossible to commercialize the product. In other words, since the plasticization temperature of the resin is high, when it is extruded from the die into the atmosphere, the temperature suddenly drops and the elongation of the resin becomes smaller, making it easier for the foam to break when taken off. It becomes extremely difficult to make sheets. Moreover, the expansion ratio of the foam (unfoamed specific gravity/foamed specific gravity)
This decreases the density of the foam, which increases the density of the foam and deteriorates its insulation properties. Note that increasing the thickness of the foam to improve heat insulation is not practical because it increases product cost. Therefore, it has been virtually impossible to produce thermoplastic resin foams with excellent heat resistance and heat insulation properties and good foaming properties using conventional methods.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art described above, and achieves a suitable expansion ratio (unfoamed product specific gravity/ The purpose of the present invention is to provide a method and apparatus for producing a thermoplastic resin foam that can be mass-produced at low cost and has excellent heat insulation and heat resistance.

[Means for Solving the Problem] As a result of intensive research to solve the problem, the present inventors have found that each resin can be By providing a cooling rate that matches the thermal properties of the foam, even if the resin used as a raw material has a high heat deformation temperature, the elongation of the foam at the time of taking the foam sheet is maintained at an appropriate level, and the appropriate expansion ratio can be achieved. The inventors discovered that a foamed sheet can be easily produced with the ratio (specific gravity of unfoamed product/specific gravity of foamed product), and were able to develop the production method and production apparatus of the present invention.

An example of the method for manufacturing a thermoplastic resin foam of the present invention will be described based on an example of an apparatus for manufacturing a thermoplastic resin foam of the present invention. The method for producing a thermoplastic resin foam of the present invention involves kneading a blowing agent or a foaming gas into a plasticized resin using a production device consisting of an extruder section, a foam molding section, and a take-off section. This method is particularly effective when the raw material is a thermoplastic resin with a high heat deformation temperature. In the present invention, first, a foaming agent or a foaming gas is pressurized and mixed into a highly heat-resistant thermoplastic resin that has been plasticized by heating in an extruder, and then extruded from a die in an extrusion section. The resin molded body extruded from the die is molded while controlling its cooling rate by applying temperature-controlled gas to its inner and/or outer surfaces, or by heat conduction or heat transfer. That is, the method of the present invention does not rapidly cool the high-temperature foam extruded from a die, but instead maintains the foam at an appropriate temperature to provide a cooling rate that matches the thermal characteristics of the raw material resin. There is.

In the present invention, the temperature employed to cool 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 temperature is such that the elongation at break of the resin is less than 50%, the elongation of the resin at the time of collection is small;
It is cut due to the tensile stress at the time of taking over and cannot be made into a sheet.

[Function] By adjusting the cooling rate of the foam extruded from the die to be slower than in conventional extrusion molding, the elongation of the resin can be maintained at an appropriate level, making it easier to form sheets. . In addition, since a suitable elastic modulus can be ensured,
It becomes possible to obtain a low-density foam with excellent heat insulating properties, in which cell collapse is less likely to occur. Note that since the second foam is usually made from a resin with high heat resistance, it goes without saying that it has excellent heat resistance.

The present invention will be explained in more detail with reference to Examples below. However, the scope of the present invention is not limited by the following examples.

[Example 1] As an example of the present invention, Tables 1 and 2 are used to describe a method for manufacturing a thermoplastic resin foam using the manufacturing apparatus shown in FIGS. 1, 2, and 3. I will explain. Note that Figure 1 shows the tandem foaming extruder (6) used in this example.
The extruder section and the foam molding section of the extruder (which is a combination of two extruders of diameters 0 and 100 mm) are shown, and FIG. 2 is an enlarged view of the foam molding section of FIG. 1. In addition, the first
The figure and FIG. 2 show the state in which the foam 3 in the figure is extruded from the die 15 in the figure. Figure 3 shows the second
Although the same part as the figure is shown, nothing is extruded from the die 15 in the figure.

In this example, five types of foams were manufactured using the resins of Samples 1 to 5 shown in Table 1 as raw materials by the same method shown below. First, add 1 portion of finely powdered talc to the sample resin as a bubble control agent.
．． 5 parts by weight, and the first one at a rate of 30 kg per hour.
The mixture was charged into the hopper 16 of a stage extruder. At this time, Freon 22 was press-injected as a foaming agent through the injection 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 adjusted to 250°C, the rear end side of the cylinder of the second stage extruder was adjusted to 175°C, and the front end side was adjusted to 1'40°C, and the resin was extruded from the die 15. .

The inner surface of the extruded foam is heated by a hot air generator 10.
Air heated to 20° C. was injected from the air blowing slit 4 at a pressure of 1 atmosphere or more to maintain the foam at a constant temperature. The foam 3, whose inner surface is injected with air, rests on the mandrel 1 while expanding its inner diameter, and is taken up at an appropriate speed. This mandrel 1 had a cylindrical structure with a maximum diameter of 220 nm and a length of 330 nm, and silicone oil was circulated inside the cylinder to maintain the mandrel surface at 120° C. and keep the foam moving there warm. On the other hand, the air blowing ring 2 installed in the center of the mandrel is equipped with a transparent polycarbonate expandable thermal insulation bag W6 that encloses the mandrel toward the die. Air at 80° C. was constantly flowed between the air blowing ring 2 and the body, and the outer surface of the foam passing through this was kept warm. While the foam extruded from the die moves to the center of the mandrel in this way, it is kept warm from the inside and outside surfaces, and by taking it off at a constant speed, the cooling rate of the foam is controlled and the elongation at break of the resin is 50% or more. It was maintained at a temperature of The foam passed over the mandrel is cut into sheets with a cutter 14 to a thickness of 2. 3m+*
, a plate-shaped foam having a width of 690 mm was manufactured. Note that sample 1~
Table 2 shows the results of examining various properties such as density, appearance, and physical properties of the foam produced from the resin No. 5 by the above method.

As can be seen from Table 2, the plate-shaped foams manufactured from the resins of Samples 1 to 5 by the above method all have low density and surfaces with good appearance, and also have excellent heat resistance. Met.

Table 1 (Margin below) [Example 2] Another example of the present invention will be described using Table 2.

This example is Example 1 except that the diameter of the mandrel was 180 mm and the amount of finely powdered talc was 1.0 parts by weight.
I did the same thing. Further, in this example, the resin of Sample 1 used in Example 1 was used as a raw material. The results of examining various properties such as 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-shaped foam with a thickness of about 2.5cm and a width of 57C1 nm was produced.As can be seen from Table 2, this foam has a low density and a surface with good appearance, and is also heat resistant. It also had excellent properties.

[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. Note that FIG. 4 shows the extruder section and foam molding section consisting of a tandem foam extrusion machine (two extruders of 60 mm and 100 mm diameter connected) used in this comparative example. The figure is an enlarged view of the foam molding section in FIG. 4. In addition, Figures 4 and 5
The figure shows the state in which the foam 3 in the figure is extruded from the die 15 in the figure.

This comparative example was carried out in the same manner as in Example 1 except that the step of keeping the foam extruded from the die warm was completely removed. Further, in this comparative example, the resin of Sample 1 used in Example 1 was used as a raw material.

However, in the method of this comparative example, the cooling rate of the foam extruded from the die is too fast, so the elongation of the resin becomes too small when the foam is taken off, and it is broken by the tensile stress at the time of taking it off. It was not possible to make it into a sheet.

[Comparative Example 2] As another comparative example to the present invention, the holding temperature of the foam extruded from the die was set to 50° C. or lower using the apparatus shown in FIGS. 1, 2, and 3. The temperature of the foam was adjusted to drop to 125°C or less in the case of resin A and 105°C or less in the case of resin A at the molding part.

This comparative example was carried out in the same manner as in Example 1, except that the temperature of the foam extruded from the die was set so that the elongation at break of the resin was 50% or less. Further, as the raw resin, resin A and resin resin of sample 1 used in Example 1 were used as raw materials.

However, in the method of this comparative example, the cooling rate of the foam extruded from the die is too fast, so the elongation of the resin is too small at less than 50% at the time of taking it off, and it is broken by the tensile stress at the time of taking it off. , it could not be made into a sheet.

[Effects of the Invention] With the advent of the present invention, it has become possible to manufacture thermoplastic resin foams with excellent heat resistance using resins with higher heat distortion temperatures and higher heat resistance than ordinary foam molding resins as raw materials. became. Also, foaming ratio (specific gravity of unfoamed product/specific gravity of foamed product)
In addition, since the elongation of the foam sheet can be maintained at a suitable level when the foam sheet is taken up, the insulation properties are improved and it is now possible to easily form the foam into a sheet. Therefore, there is no need to make the foam thicker, and it can be manufactured at a lower cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic side sectional view showing an extruder section and a foam molding section of an example of the manufacturing apparatus of the present invention. FIG. 2 is an enlarged schematic side sectional view of the foam molding section of the manufacturing apparatus shown in FIG. 1. FIG. FIG. 3 is a perspective view showing an example of the foam molding section of the manufacturing 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 an enlarged schematic side sectional view of the foam molding section of the manufacturing apparatus shown in FIG. 4. Explanation of symbols 1... Mandrel 2... Air blowing ring 3... Foam 4... Air blowing slit 5... Heat resistant flexible hose 6... Heat retention device 7 ... Heat resistant hose 8 ... Circulating constant temperature oil layer 9 ... Copper for compressed air transportation / (Eve 10 ... Hot air generator 11 ... Heat conductor 12 ..., temperature Control unit, unit 13...Hot air generator 14...Cutter 15...Dice 16...Hopper 17...Press inlet 18...Air compressor Patent applicant Dowa Mining Co., Ltd. company

Claims (5)

[Claims] (1) A thermoplastic resin that is produced by adding and kneading a foaming agent or foaming gas to a thermoplastic resin that has been plasticized by heating in an extruder, and then extruding this into a heated gas to perform molding. Method of manufacturing foam. (2) The method according to claim 1, wherein the temperature of the heated gas is within a temperature range that ensures that the elongation at break of the resin during foam molding is maintained at 50% or more. (3) There is an extruder and a foam expansion section connected to the extruder,
A thermoplastic resin foam manufacturing device that is equipped with a heat retaining device extending from the extruder outlet to the expansion section of the foam. (4) A claim characterized in that the foam expansion section is provided with heat conduction or heat transfer means for adjusting the cooling rate of the resin molded body extruded from the extruder from inside the molded body. 3. The manufacturing apparatus according to 3. (5) Heated gas blowing means for adjusting the cooling rate of the resin molded body extruded from the extruder from the inside of the molded body, for heating the surface of the molding core-shaped object with which the extruded resin molded body comes into contact. heating means, and a cooling delay for delaying the cooling rate during foam molding by supplying heated gas to the outer surface of the extruded resin molding in the range from the extruder outlet to the molding part of the foam. 4. A device according to claim 3, comprising means.