JPH0542941B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a thermoplastic resin foam by homogeneously mixing a thermoplastic resin with a blowing agent and other additives and continuously extruding and foaming the mixture. (Prior Art) There are various manufacturing methods for obtaining thermoplastic resin foams, and among them, a manufacturing method using an extruder is widely practiced. After the blowing agent and other additives are homogeneously mixed into the thermoplastic resin under pressure using an extruder,
This is a very advantageous manufacturing method in practice, since thermoplastic resin foams in desired shapes, such as sheets or plates, can be continuously produced by extrusion under low pressure. Thus, in this manufacturing method, the blowing agent and other additives are homogeneously mixed while the thermoplastic resin is well melted at a high temperature, and the high temperature melted resin composition containing the blowing agent is brought to a temperature suitable for foaming. ,
Uniform cooling prior to extrusion is known to be a particularly important manufacturing challenge. Therefore, various methods and devices have been proposed for homogeneously mixing the foaming agent and the like and for uniformly cooling the resin composition containing the foaming agent and the like. Japanese Patent Publication No. 57-21454 discloses a method and apparatus for mixing molten resin and a foaming agent and uniformly cooling them to a temperature suitable for foaming by installing a static mixer after an extruder having a screw. is suggesting.
Although this method was quite successful in producing thick, low-density foam, the flow resistance of the resin applied to the static mixer was large and the extrusion rate decreased, especially when externally cooled. There were drawbacks such as deformation and destruction of parts and insufficient mixing and dispersion of the blowing agent. In order to solve these drawbacks, some of the inventors proposed a rotary mixing cooler and a zigzag mixer, which is a type of static mixer, in addition to an extruder, as disclosed in Japanese Patent Publication No. 60-52926. A manufacturing method and device using a mixer were proposed. This method has largely improved the deformation of the mixer by not cooling the zigzag mixer, but further improvements are desired to produce foams with lower density and foams with good homogeneous dispersion of additives. was. On the other hand, it is directly connected to the tip of the extruder screw described in Japanese Patent Application Laid-Open No. 57-87344 for homogeneously mixing other additives with molten resin, rubber, etc. An extrusion mixer is known that is equipped with a so-called cavity transfer mixer in which a large number of isolated recesses are formed on each of the outer surfaces of the mixer. The inventors came up with the idea of using the cavity transfer mixer in the above-mentioned extrusion mixer in the production of thermoplastic resin foam. Then, I remembered that even more improved thermoplastic resin foams can be produced by incorporating a cavity transfer mixer into the conventional foam production process as appropriate during the extrusion foaming process. (Structure of the Invention) The present invention has been made based on the above-mentioned knowledge in order to earnestly solve the problems in the production of conventional thermoplastic resin foams. In a method of extrusion foaming using a cooler that cools molten resin containing an agent, a rotating shaft is supported in a fixed cylinder between the extruder and the cooler, and the fixed The gap between the cylinder and the rotating shaft is used as a passage for the molten resin containing the foaming agent, and a number of isolated recesses are formed on the inner surface of the fixed cylinder and the outer surface of the rotating shaft relative to this, and the recesses between the fixed cylinder and the rotating shaft are formed. A mixer is installed in which the molten resin is transferred between the recesses, and the blowing agent and other additives are placed in an extruder or other mixing means on the upstream side of the mixer. The present invention provides a method for producing a thermoplastic resin foam, characterized in that the foam is pre-kneaded with a thermoplastic resin, supplied to the mixer, brought to a temperature suitable for foaming, and then extruded and foamed. (Object and operation of the invention) Therefore, an object of the present invention is to provide a manufacturing method that can homogeneously mix a larger amount of blowing agent into a molten thermoplastic resin than in the past. It is. As a result, a thermoplastic resin foam with high foaming and low density can be obtained, and a foam with a large thickness can also be obtained. Another object of the present invention is to provide a manufacturing method that can greatly improve the homogeneous dispersion of a blowing agent and other additives into a molten resin. As a result, a thermoplastic resin foam having good cell uniformity, physical properties, and quality can be obtained. Further, the homogeneous dispersion of the cell regulator such as talc is improved, the cells become finer, and a foam with good secondary moldability is obtained. Another object of the present invention is to provide a manufacturing method capable of homogeneously mixing two or more types of thermoplastic resins having poor compatibility. This makes it possible to mix many resins and produce a foam with desired characteristics. Still another object of the present invention is to provide a manufacturing method capable of homogeneously mixing a blowing agent, which is said to be difficult to mix with a thermoplastic resin. This is advantageous in the production of foams, since the blowing agent can be selected from a wide range of types. (Detailed Description of Embodiments of the Invention) The thermoplastic resin to be extruded and foamed in the present invention is not particularly limited. Typical examples include polystyrene, styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadiene copolymer, styrene-maleic anhydride copolymer, styrene-ethylene copolymer, poly d-methylstyrene, polyethylene, polypropylene, Ethylene-
Examples include propylene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polymethyl methacrylate, and polyamide. These polymers may be used alone or in combination of two or more. This invention has the advantage that it is possible to uniformly mix even relatively incompatible polymers, allowing for a wide selection of resins. Therefore, it is advantageous for producing thermoplastic resin foams having predetermined physical properties. The blowing agent mixed in this invention is not particularly limited, and volatile blowing agents or decomposable blowing agents are usually used. Volatile blowing agents include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, neopentane, isopentane, and hexane, alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane, methyl chloride, methylene chloride, and dichlorofluoromethane. , chlorotrifluoromethane, dichlorodifluoromethane, chlorodifluoromethane, trichlorofluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, and the like. Decomposable blowing agents include dinitrosopentamethylenetetramine,
Trinitrosotrimethylenetriamine, P,P'-
Oxybis (benzenesulfonylhydrazide),
Examples include azudicarboxylic acid amide. These blowing agents may be used alone or in combination of two or more. In this invention, the blowing agent is mixed upstream of the mixer. The usual method of mixing is to heat and melt the thermoplastic resin in an extruder, and then continuously press-inject the foaming agent into the extruder. There is also a method of supplying a thermoplastic resin containing a blowing agent to an extruder in advance. When mixing a large amount of a volatile blowing agent (5 to 50 parts by weight) per 100 parts by weight of resin to obtain a low-density foam, mix it with the molten resin in an extruder or another mixing means. It is preferable to pre-knead the blowing agent before supplying it to the mixer. Additionally, the present invention uses additives that are commonly mixed in when producing foams. These additives include cell regulators, flame retardants, stabilizers, lubricants, plasticizers, colorants, fillers, and the like. The extruder for melt-extruding the thermoplastic resin used in the present invention includes a single-screw or twin-screw extruder, and it is preferable to have a pin or other mixing means installed on the screw after press-fitting the blowing agent. As the cooling device used in the present invention, there are various cooling devices capable of adjusting the temperature of various resins having a heat exchange function, which have been developed and used in thermoplastic resin foam manufacturing equipment. For example, Special Public Interest Publication No. 60-52926
Publication No., Special Publication No. 31-5393, Special Publication No. 48-544
As described in Japanese Patent Publication No. 54-42026, a cooler having blades on a rotating shaft inside a cooling outer cylinder is preferably used. It is also preferable to use a cooling extruder that uses an extruder with a larger diameter than the extruder that melts the resin and rotates it gently with a rotating shaft with a small propulsive force to uniformly cool the resin. The mixer used in the present invention has a rotating shaft supported within a fixed cylinder, and the gap between the fixed cylinder and the rotating shaft is used as a passage for the molten resin, and the inner surface of the fixed cylinder and the rotating shaft relative thereto. A large number of isolated cavities are formed on each of the outer surfaces of the molten resin cavity transfer mixer, and the cavities of the fixed cylinder and the rotary shaft are provided at positions where they overlap each other during rotation. The shape of the cavity includes a hemispherical shape, a cylindrical shape, a diamond shape, etc., but a hemispherical shape that does not allow molten resin to remain is preferable. Preferably, these cavities are provided on the inner surface of the fixed cylinder and the outer surface of the rotating shaft in a staggered manner in the axial direction and the circumferential direction. Preferably, the total area of the openings of these cavities is increased so that the transfer surface occupies 60% or more of the inner surface of the fixed cylinder or the outer surface of the rotating shaft. The mixer is preferably installed at the highest temperature and pressure during the extrusion and foaming process. Therefore, there are cases in which the screw is connected to the tip of the screw of the extruder so that it rotates in the same way as the screw rotates, and cases where it is installed so that it can rotate independently from the rotation of the screw. In the latter case, the number of rotations can be arbitrarily controlled depending on the type of thermoplastic resin, the type of blowing agent and other additives, or their weight, which is convenient for adjusting heat generation and mixing conditions. In other words, flame retardants that are easily decomposed by heat,
This is because it can be rotated at a low speed when the fiber material is to be cut by applying high shear, and it can be rotated at a high speed when it is a volatile foaming agent whose viscosity is significantly different from that of the resin. Further, as the die used in the present invention, there are conventional dies such as a T die, coat hanger die, rectangular die, circular slit die, etc., and a sizing die is appropriately attached. An embodiment of this invention will be described based on FIG. 1 is an extruder, and 2 is a cooling extruder, which are arranged parallel to the extruder 1 and offset from the extruder 1. 3 is a mixer disposed between both extruders 1 and 2. The extruder 1 is comprised of the following: 4 is a first barrel, 5 is a cantilever type first screw rotatably inserted into the first pallet 4, and 6 is a first kneading section provided at the tip of the first screw 5, which is connected to the screw shaft. A cylinder 7 provided at the tip of
It consists of a large number of pins 8 protruding from the outer peripheral surface of the cylinder 7. Reference numeral 9 denotes a blowing agent pressure inlet provided at a location opposite to the boundary between the first screw 5 and the first kneading section 6 of the first pallet 4; 11 denotes a discharge port formed at the free end of the screw of the first pallet 4; 12 is the first
A raw material input port is formed at the end of the screw supporting side of the pallet 4, a raw material hopper 13 is provided at the input port 12, and a heater 14 is provided on the outer surface of the first barrel 4. The cooling extruder 2 is composed of the following: Reference numeral 16 denotes a second pallet, which has a spiral refrigerant passage 17. 18 and 19 are the refrigerant passages 1
7 entrance and exit. 20 is a cantilever type second screw rotatably inserted into the second barrel 16;
Reference numeral 21 denotes a base fixed to the free end of the screw of the second parel 16, and has a resin discharge port 22. 23 is a bearing that rotatably supports the base end of the second screw 20, 24 is a packing, 25 is a packing holder, 26 is a refrigerant flow path for cooling the packing, 27
28 is a resin injection port formed at the end of the screw supporting side of the second parallel 16, and 28 is a refrigerant supply pipe for supplying refrigerant into the second screw 20. The mixer 3 is composed of the following: 30 is a fixed cylinder, and 31 is a cantilevered rotating shaft rotatably inserted into the fixed cylinder 30, the axis of which is perpendicular to the axes of the first and second screws 5 and 20. There is. An inlet 32 formed on one side of the rotating shaft supporting side of the fixed cylinder 30 communicates with the outlet 11 of the extruder 1, and an outlet formed on the other side of the rotating shaft free end of the fixed cylinder 30. 33 is communicated with the resin injection port 27 of the cooling extruder 2. 34 is a stator provided on the inner surface of the fixed cylinder 30, and 35 and 36 are a number of isolated hemispherical cavities formed on the inner surface of the stator 34 and the outer peripheral surface of the rotating shaft 31, and are on the inner surface of the stator 34. Cavity 35
are located between the cavities 36 on the outer circumferential surface of the rotating shaft 31 so as to partially overlap each other during rotation. 3
7 is a shaft support that rotatably supports the rotating shaft 31; 38;
39 is a packing, 40 is a refrigerant flow passage for cooling the packing, 41 is a heater disposed on the outer peripheral surface of the fixed cylinder 30, and 42 is a refrigerant supply pipe for supplying the refrigerant into the rotating shaft 31. be. Next, the operation of the above configuration will be explained. 1st, 2nd
The screws 5 and 20 are rotated in the directions of arrows A and B, respectively, and the rotating shaft 31 is rotated in the direction of arrow C separately from the first and second screws 5 and 20, so that the raw material is transferred from the raw material hopper 13 to the first Supplied into parallel 4. Then, the raw material, that is, the resin, is sent in the direction of arrow D by the first screw 5, during which time it is heated and melted by the heater 14. A blowing agent is press-injected into the molten resin from the blowing agent injection port 9, and the added blowing agent is preliminarily mixed with the molten resin by the pin 8 of the first kneading section 6. The foaming agent-containing resin is then fed into the fixed cylinder 30 of the mixer 3 through the outlet 11 and the inlet 32.
In this mixer 3, the foaming agent is mixed and stirred by the cavity 36 of the rotating shaft 31 and the cavity 35 of the stator 34, and the foaming agent is uniformly dispersed within the tree. The principle of mixing and stirring will be explained using lines using the schematic diagrams shown in FIGS. 2a to 2h. First, the filament coming out from the bottom of the cavity 35 on the left side of the figure a extends along the inner circumferential surface of the cavity 35,
As shown in Figure b, the tip of the filament is pulled by the edge A between the cavities 36 of the rotating shaft 31 rotating in the direction of arrow C, and changes its direction, becoming the state shown in Figure c, As shown in Fig. d, the tip of the filament is bent by the edge roller, and as shown in Fig. e, the tip of the filament is cut by the edge roller and the stator 34.
As shown in Figure G, the tip of the filament is bent by the edge C, and as shown in Figure G, the edge C and the stator 34
The tip of the filament is cut by the edge d, and the tip of the filament is bent by the edge d, as shown in h of the figure. Thereafter, the same operation is repeated, the tips of the filaments are cut one after another, and the cut filament portions accumulate in the cavity 35. Therefore, according to this principle, the resin is stretched thin like the above-mentioned filaments,
It is chopped into small pieces and blowing agents and other additives are homogeneously dispersed within the resin. Next, the resin with the blowing agent homogeneously dispersed passes through the outlet 33 and the resin inlet 27 to the second barrel 16 of the cooling extruder 2.
sent inside. The foaming agent-containing resin in the second barrel 16 is sent in the direction of arrow E by the rotation of the second screw 20, and while being sent, the resin containing the foaming agent is transported through the refrigerant passing through the refrigerant passage 17, which is suitable for foaming. The material is cooled to a certain temperature, extruded from the outlet 22, and foamed. Further, another embodiment of the present invention will be described based on FIG. 3. In FIG. 3, parts that are the same as those shown in FIG. 1 are given the same numbers and their explanations will be omitted. 4
4 is a cooling device, and the stator 34 of the mixer 3
A connecting body 45 connected to the outlet side of the connecting body 45, an intermediate body 46 connected to the connecting body 45, and the intermediate body 46
An inner core 47 provided at the center of the side surface of the
7 concentrically and one end is connected to the intermediate body 46.
The outer cylinder 48 has an outer cylinder 48 connected to the outer cylinder 48, and a cap 49 fixed to the other end of the outer cylinder 48. A resin passage 50 formed between the inner core 47 and the outer cylinder 48 is connected to a communication passage 51 formed in the connecting body 45 and the intermediate body 46.
It is communicated with the inside of the mixer 3 via. 52
are cooling spaces formed in the inner core 47, 53, 54
5 is an inlet and an outlet for the refrigerant that passes through the intermediate body 46 from the outer peripheral surface of the intermediate body 46 and reaches the cooling space 52;
5 is a spiral refrigerant passage formed in the outer cylinder 48;
6 is an extrusion port formed in the base 49. 58 is an L-shaped communication pipe connecting the outlet 11 of the extruder 1 and the inlet 32 of the mixer 3; 59 is a static mixer disposed in the end of the communication pipe 58 on the mixer side; 6;
0 is a throttle nozzle disposed inside the end of the communicating tube 58 on the side of the extruder 1, and 61 is a heater disposed on the outer peripheral surface of the communicating tube 58. Then, the operation of the above configuration will be explained. Extruder 1
The flow velocity of the molten resin extruded from the discharge port 11 is increased by the throttle nozzle 60. The foaming agent press-injected from the foaming agent injection port 9 is added to the resin whose flow rate has been increased. The resin to which the foaming agent has been added is fed into a static mixer 59, where the resin and the foaming agent are preliminarily mixed. Next, the foaming agent-containing resin that has come out of the static mixer 59 is sent into the mixer 3, where the same action as in the first embodiment is performed to thoroughly knead the resin and the foaming agent, so that the foaming agent becomes homogeneous. The dispersed resin is sent into the resin passage 50 of the cooling device 44. While being extruded in the direction of arrow E, the foaming agent-containing resin in the resin passage 50 is cooled appropriately by the refrigerant passing through the refrigerant passage 55, and is extruded to the outside from the extrusion port 56, resulting in foaming. . When carrying out this invention, the cooling machine 63 shown in FIG. 4 can be used instead of the cooling extruder 2 shown in FIG. 1 or the cooling device 44 shown in FIG. 3. The cooler 63 shown in FIG. 4 is provided downstream of the mixer 3 in the first and second embodiments. The details will be explained below. 64 is an outer cylinder and has a spiral refrigerant passage 65. 6
6 is a cantilevered main shaft rotatably inserted into the outer cylinder 64; 67 is a resin inlet formed by penetrating near the end of the main shaft support side of the outer cylinder 64; and 68 is a discharge port 6.
The base with 9 and 70 are a refrigerant supply pipe for supplying refrigerant into the cooling space formed in the main shaft 66. The main shaft 66 is composed of a base end large diameter part 66A rotatably supported by the outer cylinder 64 via a bearing 74, a central small diameter part 66B, and a distal large diameter part 66C, and the resin supply for the central small diameter part 66B. An annular protrusion 6 is located at a location slightly downstream from the location facing the opening 67.
6D is provided. Reference numeral 72 designates a number of hurdle-shaped kneading rods protruding downstream from the annular protrusion 66D of the central small diameter portion 66B. Since the cooler 63 in FIG.
The foaming agent-containing resin that has entered into the annular protrusion 66
After being force-fed in the direction of arrow E beyond D and being kneaded by the kneading rod 72 of the main shaft 66 rotating in the direction of arrow F, it passes through the gap between the large-diameter tip 66C and the outer cylinder 64 and exits from the discharge port 69. It is extruded and foams. Next, an example will be described. Examples 1, 2, 3 In the apparatus shown in FIG. The inner diameter of the stator 34 and the rotating shaft 3 are 50 mm.
1, and the stator 34 and rotating shaft 31 are provided with six cavities 35, 36 in the circumferential direction and seven rows in the axial direction, and the diameter of the sphere of each hemispherical cavity 35, 36 is set to 0.4 mm. 23 and 23 respectively
24.5mm, and the depth of each cavity 35, 36 is 8 and 9.5mm, respectively.
The spacing between the centers in the axial direction is 22 mm, and the deviation of the cavities in the circumferential direction of the stator and rotating shaft is 1/2 of the gap between the centers of the rows of cavities.
It is approximately 13 mm, and the stator and rotating shaft cavity row shift is 1/2 of the axial cavity spacing, 11 mm.
and the rotation speed of the rotating shaft of mixer 3 is 106 rpm,
The temperature of the melt passing through the cooling extruder 2 was adjusted to 123° C., and the width of the outlet 22 of the die 21 was 100 mm, and the height thereof was 1 mm. In this device, 100 parts by weight of polystyrene [Stylon 679 (MF1 = 17) manufactured by Asahi Kasei Corporation] was uniformly mixed with 0.3 parts by weight of talc as a bubble regulator and 2.0 parts by weight of hexabromocyclododecane as a flame retardant. The raw material was supplied to an extruder 1, and the extruder 1 was operated to extrude the raw material at a rate of 55 kg per hour. Also,
Add dichlorodifluoromethane as a blowing agent to 100 parts by weight of polystyrene from the blowing agent injection port 9.
12.5 parts by weight was press-fitted. As a result, through the sizer attached to the base 21, the width is about 250 mm, the thickness is about 25 mm,
A plate-shaped foam with a density of 40 m ³ Kg/mm ² was obtained (see Table 1). Further, when similar tests were conducted by varying the amount of foaming agent, the rotation speed of the rotating shaft 31, etc., results as shown in Specific Examples 2 and 3 in the attached table were obtained.
Note that Comparative Example 1 in Table 1 shows the case where the mixer 3 was removed from the state shown in FIG.

[Table] Example 4 In the apparatus shown in FIG. 1, the inner diameter of the first barrel 4 of the extruder 1 is 50 mm, the inner diameter of the second barrel 16 of the cooling extruder 2 is 65 mm, and the stator 3 of the mixer 3 is
4 has an inner diameter of 90 mm, and the stator 34 and rotating shaft 31
With a gap of 0.2 mm between the
A row of cavities 35 and 36 are provided, and the diameters of the spheres of each hemispherical cavity 35 and 36 are 27 and 28, respectively.
mm, the depth of each cavity 35, 36 is 8 and 9.5 mm, respectively, the center-to-center spacing between cavities 35, 36 is 25 mm, and the displacement of the cavities in the circumferential direction of the stator and rotating shaft is The gap between the centers of the cavities is approximately 14mm, and the stator and rotating shaft cavity rows are offset by 12.5mm, which is 1/2 the gap between the cavities in the axial direction.
The rotation speed of the rotating shaft of the mixer 3 was set to 100 rpm, and the temperature of the melt passing through the cooling extruder 2 was adjusted to 159°C.
The discharge port 22 of the cap 21 was a circular slit with a diameter of 60 mm and a gap of 0.6 mm. In such an apparatus, a mixture of 100 parts by weight of polystyrene [Stylon 691 (MF1=2.3) manufactured by Asahi Kasei Corporation] and 2.0 parts by weight of talc as a bubble regulator is used as a raw material and is fed into the extruder 1 per hour.
It was fed at a rate of 28 kg and operated so that the raw material was extruded. Further, 3.5 parts by weight of butane was injected as a foaming agent through the injection port 9 per 100 parts by weight of polystyrene. As a result, it was cut in the extrusion direction at one point through the sizer attached to the nozzle 21, and the width was approximately 633 mm.
It was possible to obtain a sheet-like foam having a thickness of about 2 mm and a basis weight of 179 g/m ² and having a beautiful appearance and having uniform fine cells. After aging this foam at room temperature for 7 days,
The cell diameter was measured according to ASTMD2842-69, and as an evaluation of moldability, the secondary heat generation thickness was measured by heating at 120° C. for 12 seconds and is shown in Table 2. Comparative Example 2 As a result of carrying out the same manufacturing process as in Example 4 except that the mixer 3 was removed, the temperature of the molten resin was lowered.
Adjusted to 158℃, thickness approximately 2mm, width 633mm, weight 176
Although a sheet-like foamed product with a yield of 1.5 g/m ² was obtained, many lumps of aggregated talc were generated inside the sheet, the air bubbles were coarse, and the secondary foamability was poor.

[Table] Example 5 The manufacturing apparatus of Example 4 was used except that the cap 21 and sizer of Example 1 were added. In this equipment, 30% by weight of ethylene polymerized with styrene monomer permeated into the polyethylene resin is added to 100 parts by weight of polyethylene [Yukalon HE-30 (MI=0.3) manufactured by Mitsubishi Yuka Co., Ltd.]. , a mixture of 10 parts by weight of a mutually impregnated polymer with a styrene content of 70% by weight and a gel concentration of 18.6% by weight [Piocelan (registered trademark) manufactured by Sekisui Plastics Co., Ltd.] and 0.5 parts by weight of talc as a bubble regulator, 1 per hour,
It was fed to the extruder at a rate of 30Kg. On the other hand, as a blowing agent, 14 parts by weight of a mixture of 70% by weight of dichlorodifluoromethane and 30% by weight of butane was injected. The rotation speed of mixer 3 is 100 rpm,
Extrusion foaming was performed by adjusting the temperature of the molten resin passing through the cooling extruder 2 to 110°C. The obtained foam has a thickness of approximately 20 mm, a width of approximately 230 mm,
It had a uniform cell plate shape with a beautiful appearance and a density of 33 kg/m ³ . Comparative Example 3 When the same procedure was carried out as in Example 5 except that the mixer 3 was removed, there were scattered spots of high-density foamed parts that seemed to be due to poor mixing and dispersion, and many foaming agent gas pockets were generated. Only a plate-shaped foam with an uneven surface could be obtained. Further, another embodiment of the present invention will be explained based on FIG. 6. In FIG. 6, parts that are the same as those shown in FIGS. 1 and 4 are given the same numbers and their explanations will be omitted. 1 is an extruder, 63 is a cooler, and the extruder 1
The extruder 1 is arranged in parallel with the extruder 1, and the center of the extruder 1 is offset from that of the extruder 1. 32a is a resin supply pipe connecting the outlet 33 of the extruder 1 and the inlet 67 of the cooler 63. Reference numeral 31 denotes a rotating shaft concentrically connected to the cylinder 7 provided at the tip of the screw 5, and 35 and 36 indicate multiple shafts formed on the outer circumferential surface of the rotating shaft 31 and the inner circumferential surface of the pallet 4 facing thereto. The cavity is in the shape of an isolated hemispherical depression, and is the cavity 3 of the parallel 4.
5 are positioned between the cavities 36 of the rotary shaft 31 so as to overlap each other to form a mixer 3 capable of transferring resin. The length of the rotating shaft 31 is usually 2 to 8 times (preferably 4 to 6 times) the diameter of the screw. If it is 2 times or less, kneading will be insufficient, and if it is 8 times or more, heat generation will increase. The length of the cylinder 7 is usually 1 to 7 times (preferably 2 to 5 times) the diameter of the screw. If it is less than 1 times, preliminary kneading will be insufficient, and if it is more than 7 times, the kneading effect will not be improved any further. The cross-sectional area of the resin passing through the cylinder 7 is determined by the screw 5.
(preferably 1.5 to 3 times) larger than the resin passage cross section at the tip of the resin. If it is the other way around, the amount of resin supplied onto the cylinder 7 will be excessive, making it impossible to perform sufficient preliminary kneading. Further, the projection 8 provided on the cylinder 7 includes a cylindrical pin, a screw flight notch shape, and a dalmage shape. The operation of the above configuration will be explained below. Skrillyu 5
The main shaft 66 is rotated in the directions of arrows A and F, respectively, and raw material, that is, resin, is supplied into the barrel 4 from the input port 12. Then, the resin is sent in the direction of arrow D by the screw 5, during which time it is heated and melted by the heater 14. A foaming agent is press-injected into the molten resin from a foaming agent injection port 9, and the foaming agent and resin are preliminarily mixed by a projection 8. Next, the foaming agent-containing resin is forced into the gap between the rotating shaft 31 and the pallet 4 and kneaded by the cavities 35 and 36, so that the foaming agent is uniformly dispersed in the resin. The principle of kneading is the same as that shown in FIG. Next, the resin with the foaming agent homogeneously dispersed passes through the supply pipe 32a and enters the outer cylinder 64 of the cooler 63, passes over the annular protrusion 66D, is pumped in the direction of arrow E, and is fed in the direction of arrow F. After being kneaded by the rotating hurdle-shaped kneading rod 72 and cooled appropriately at the same time, the large diameter tip portion 66C and the outer cylinder 6 are mixed.
4 and is extruded from the discharge port 69, resulting in foaming. Next, examples will be specifically described. Example 6 In Fig. 6, the inner diameter of the barrel 4 is 50 mm, the diameter of the screw 5 is 50 mm, and the length of the cylinder 7 is 250 mm.
mm, the length of the rotating shaft 31 is 250 mm, the gap between the rotating shaft 31 and the parel 4 is 0.4 mm, and each of the rotating shaft 31 and the parel 4 has six pieces in the circumferential direction.
Seven rows of cavities 35 and 36 are provided in the axial direction, the diameter of the cavity 36 is 24.5 mm, and the depth is
9.5mm, and the diameter of cavity 35 is 23mm.
The depth is 8 mm, the distance between cavities 36 and 35 is 22 mm, and the rotation speed of screw 5 is
106 rpm, the temperature of the melt passing through the cooler 63 was adjusted to 123°C, and the width of the outlet 69 of the mouthpiece 68 was adjusted to 106 rpm.
100mm, and its height was 1mm. In this device, polystyrene [Styron 679 (MFI=17) manufactured by Asahi Kasei Corporation] is used as a base resin, and 0.3 parts by weight of talc as a bubble regulator and hexabromocyclododecane as a flame retardant are added to 100 parts by weight of the base resin. A uniform mixture of 2.0 parts by weight was supplied as a raw material to an extruder 1, and the extruder 1 was operated to extrude the raw material at a rate of 55 kg per hour. In addition, dichlorodifluoromethane is added to the base resin as a foaming agent from the foaming agent injection port 9.
12.5 parts by weight was press-fitted to 100 parts by weight. As a result, a plate-shaped foam having a width of about 250 mm, a thickness of about 25 mm, and a density of 40 Kg/m ³ was obtained through the sizer attached to the nozzle 68 (see Table 3). In addition, in Comparative Example 4 in Table 3, the rotating shaft 31 was removed,
This shows the case where the cavity 35 of the parallel 4 is removed.

[Table] As is clear from Table 3, according to the specific examples of the present invention, uniformly foamed foams could be obtained. (Effects of the Invention) The present invention is configured as described above, and since it is possible to homogeneously mix a larger amount of blowing agent into a thermoplastic resin than before, the thermoplastic resin can be highly foamed. A foam is produced. In addition, in this invention, the blowing agent and other additives are very well dispersed in the molten resin, so a thermoplastic resin foam with uniform cell conditions and good physical properties is obtained. As a result, a foam with good secondary moldability can be obtained. Furthermore, in the present invention, two or more relatively compatible thermoplastic resins can be homogeneously mixed, making it possible to produce a foam having desired characteristics. Furthermore, this invention makes it possible to use a blowing agent, which was previously considered impossible to mix in due to its poor dispersibility. As in the example, it was possible to homogeneously mix a large amount of dichlorodifluoromethane with polystyrene resin.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, Fig. 2 a to h are schematic illustrations showing the principle of mixing and agitation of a mixer, and Fig. 3 shows another embodiment of the invention. The vertical cross-sectional view, FIG.
FIG. 5 is a longitudinal sectional view showing a modified example of the cooler used in FIG. 3, FIG. 5 is a view taken along the - arrow in FIG. 4, and FIG. . Explanation of symbols, 1: extruder, 2: cooling extruder,
3: Mixer, 5: Screw, 30: Fixed tube, 3
1: Rotating shaft, 35, 36: Cavity, 44: Cooling device, 63: Cooler, 9: Foaming agent injection port, 6:
First kneading section, 21: mouthpiece, 22: discharge port.

Claims (1)

[Claims] 1. In a method of extrusion foaming using an extruder that heats and melts a thermoplastic resin and a cooler that cools the molten resin containing a foaming agent, The rotating shaft is supported within a fixed cylinder, and the gap between the fixed cylinder and the rotating shaft is used as a passage for the molten resin containing the foaming agent, and the inner surface of the fixed cylinder and the outer surface of the rotating shaft are A large number of isolated recesses are formed, the recesses of the fixed cylinder and the rotary shaft are provided at positions where they overlap each other during rotation, and a mixer is installed in which the molten resin is transferred between the recesses, and a mixer is installed upstream of the mixer. The foaming agent and other additives are pre-kneaded with the thermoplastic resin in an extruder or other mixing means before being fed to the mixer, cooled to a temperature suitable for foaming, and then extruded and foamed. Characteristic manufacturing method of thermoplastic resin foam. 2. The manufacturing method according to claim 1, wherein the rotating shaft of the mixer is rotated separately from the rotation of the screw of the extruder. 3. The manufacturing method according to claim 1, wherein the rotating shaft of the mixer is integrally connected to the tip of the screw of the extruder.