JP3187920B2 - Co-rotating twin screw extruder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a co-rotating twin-screw extruder for mixing a powder material into a plastic material.

[0002]

2. Description of the Related Art In recent years, as an extruder having a high kneading function, a rotary meshing twin-screw extruder in which a screw rotates in the same direction has been widely put to practical use. The screw and barrel of this conventional twin-screw extruder generally have the structure shown in FIG. 6, and the barrel 3 and the screws 2, 4, 6, 7, and 8 are kneaded and mixed with each other depending on the resin or application. The segment system is adopted so that the function (such as deaeration) can be changed, and the barrel 3 and the screws 2, 4, 6, 7, and 8 have a structure that can be appropriately rearranged as needed. In this case, the bore section of the barrel 3 is shaped like an eyeglass, and the screw is a normal screw partially having an inverted spiral portion. As a technique for further improving the kneading function of such an extruder, there is a technique in which a part of a bore section of a barrel 3 perpendicular to an axial direction is made polygonal, and a normal screw 4 is inserted into the bore. -397
No. 63 is known. In addition, the bulk density is small,
In order to mix powder material with high fluidity into the molten plastic material being fed by a screw, the extruder is used to apply pressure to the material with a screw to reduce entrainment of air in the powder material. Is generally adopted. FIG. 6 shows the powder material supply side feeder 16.

Next, the operation of the co-rotating twin-screw extruder will be described with reference to FIG.
Is fed to the left, heated and pressurized, stirred in the first kneading unit 4 and melted, and then usually enters the screw 6.
The powder raw material supplied by the side feeder 16 is
The screw 6 enters the ordinary screw 6 through the hole 5 formed in the barrel 3, and is sent to the left while the molten plastic and the powder raw material are mixed by the screw 6, and a part of the air contained in the powder raw material is converted to air. It escapes from the hole 17 and is pressurized,
The mixture is sufficiently kneaded in the second kneading section 7, reaches the next ordinary screw 8, and the pressure drops, and the air contained in the powder is deaerated through the air vent 9 provided in the screw 8. The mixed material of the plastic raw material and the powder raw material is supplied to the outlet 13
And into a die (not shown).

[0004]

However, FIG.
In the conventional extruder, a fine powder raw material having a small bulk density is fed by a screw of a side feeder so as to mix with the molten plastic into a cylinder downstream of the first kneading section 4 of the extruder while increasing the density. And the mixed material contains a large amount of air. Since the resin pressure increases in the second kneading section 7, the air contained in the powder material flows backward through the screw groove and returns to the inlet of the side feeder 16, so that the supply of the powder raw material is not performed smoothly. In addition, when the backflow air is mixed into the powder raw material supplied by reducing the content of air in the angle extruder as described above, the bulk density is reduced, the powder content in the molten plastic is temporarily reduced, and the mixing is performed. There is a disadvantage that the uniformity of the material is impaired. The present invention seeks to solve the above-mentioned conventional problems.

[0005]

SUMMARY OF THE INVENTION For this reason, the present invention provides a plastic material that has been heated and melted while being fed by a screw.
In a co-rotating twin-screw extruder that supplies and mixes a powder raw material, a first kneading unit, a second kneading unit, and a third kneading unit include:
A normal screw is provided downstream of each, and the
And the normal downstream of the first kneading section.
Supply of powder material force feeder to screw barrel
A port and a first air vent hole are provided, and the
A second air vent is provided in the barrel of the normal screw,
The barrel of the normal screw downstream of the third kneading section has
3 air vent holes are provided, and the second kneading section is fed upstream
It has a kneading screw with a large pitch and sends it downstream.
Configuration with kneading screws with small pitch
In Ranaru things, it is an unit for which a problem solution.

[0006]

In the process up to the first kneading section, the first air vent hole is provided near the powder supply section when the powder raw material is fed into the plastic material melted by heating and stirring.
Air released immediately after the powder raw materials are mixed can be released from the hole. Next, the mixed material is usually fed by a screw to reach the second kneading section, where the kneading screw having a large feeding capacity is mixed without increasing the pressure, and then the pressure is slightly increased in a kneading screw having a small feeding capacity. Mix well. In the upstream kneading screw, the feed pitch is large, and the barrel is polygonal, so the volume of space is large and the pressure and temperature do not rise so much. Is kept. In the case of a kneading screw with a small feed pitch, the resin temperature also rises because the pressure increases and the degree of kneading increases, but the air contained in the mixed material comes to the downstream normal screw,
When released to the atmospheric pressure, it escapes from the mixed material and is discharged from the second air vent. Further, since a third kneading section is provided to knead the material well to remove air and volatile gas, and a third air vent hole is formed in the ordinary screw barrel downstream thereof, the uniformity of the mixed material is further improved. You.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of the present invention; FIG. First, a first embodiment of a co-rotating twin-screw extruder according to the present invention will be described with reference to FIG. Reference numeral 2 denotes a normal screw, and the screw and the valley of the screw 2 enter each other as a set of two screws. Therefore, the barrel 3 of the screw 2 has an eyeglass-like bore cross section. When the two screws 2 rotate in the same direction in the same direction, the plastic material is heated and pressed while being sent to the left. 4
Is a first kneading section, which is composed of a kneading screw and a short reverse spiral screw. Reference numeral 5 denotes a powder material inlet of the barrel 3, and a force feeder 16 for powder material is attached to the inlet 5. A first air vent hole 17 is formed at the same position in the longitudinal direction as the inlet 5. Reference numeral 6 denotes an ordinary screw which acts to mix the powdery raw material supplied by the force feeder 16 and the molten plastic material and send them to the left. The second kneading section is composed of two types of screws 18, 19
The screw 18 is a kneading screw having a large feed pitch in the first half of the second kneading section, and the screw 19 is a kneading screw having a small feed pitch in the second half. The barrel 15 of the second kneading section
As shown in FIG. 4, the lumen shape is polygonal in order to enhance the kneading effect. Further, a normal screw 8 continues downstream of the second kneading section, and a second air vent hole 9 is provided in a barrel of the screw 8.
Has been opened. In addition, the third downstream of the normal screw 8
A kneading section 10 follows, which is composed of a kneading screw and a short reverse spiral screw. A normal screw 12 follows the third kneading section, and a third air vent hole 11 is formed in a barrel of the screw 12. 13 is an outlet for the plastic material to be extruded.

Next, the operation of the first embodiment shown in FIG. 1 will be described. The plastic pellets entering the barrel 3 from the material input port 1 of the extruder are sent to the left by the screw 2. While heating and pressurizing the first
It enters the kneading section 4, is stirred, melts and is usually extruded into the screw 6. Normally, the screw 6 has a large screw pitch and a large feeding capacity, and the powder raw material 16 is filled in the gaps between the screws that are not filled with the molten plastic.
, So that the mixing ratio becomes constant. Also, when the fine powder raw material has a small bulk density, the air content is large, and when it is mixed with the high-temperature molten plastic, the air expands and a large amount of air escapes. Let go. In the ordinary screw 6, the air is sent to the second kneading section without applying too much pressure to reduce the backflow of air, and the kneading screw 18 having a large feeding pitch in the second kneading section is mixed without increasing the pressure. Is kneaded strongly with a kneading screw 19 having a smaller size, and is sent to the downstream ordinary screw 8 . The air that has passed through the second kneading section and has escaped from the mixed material whose pressure has dropped is discharged from the second air vent 9 formed in the barrel 3. In the ordinary screw 8, the mixed material is pressurized while being mixed, and kneaded again in the third kneading section 10 to make up for the insufficient kneading in the second kneading section. In addition, the air, the active solvent gas, and the like that have escaped from the mixed material that has passed through the third kneading unit 10 are sucked out from the third air vent 11 formed in the barrel 3. And normal screw 12
The mixed material is sent while being pressurized, extruded from the extruder outlet 13 and sent to a die (not shown).

FIG. 2 shows a second embodiment of a co-rotating twin-screw extruder according to the present invention. This second embodiment is mostly the first
The structure of the first embodiment is the same as that of the first embodiment, except that the barrel of the second kneading unit is not a barrel 15 having a polygonal cross-section, but a normal cylindrical barrel 3 having an eyeglass-like cross-section. This is different from the embodiment. In the second embodiment, when a large amount of powder material having a low bulk density is mixed, the mixing performance of the second kneading section is lower than that of the first embodiment, so that the uniformity of the mixed material product is slightly reduced. When the mixing ratio of the body material is slightly low, sufficiently good performance can be exhibited.

FIG. 3 shows a third embodiment of a co-rotating twin-screw extruder according to the present invention. The third embodiment is also substantially the same in structure as the first embodiment, but differs from the first embodiment in that the barrel of the second kneading unit is a cylindrical barrel 3 having an ordinary eyeglass-like cross section. That is, the supply of the powder raw material is made to flow into the powder raw material inlet 20 by its own weight from the hopper placed above. Also in this case, when handling a powder material having a large air content, the powder material once in the barrel is pushed back to a large amount of air heated and separated from the material, and the material is uniformly mixed with the molten plastic material. And may result in a partially uneven extruded product.
However, if it is intended to mix a coarse powdery material having a low air content, a sufficiently good product can be produced even with an extruder having this structure.

[0011]

As described above in detail, according to the present invention, when the powder raw material is fed into the plastic material melted by heating and stirring in the process up to the first kneading section, the first air is supplied near the powder supply section. Since the holes are provided, the air released immediately after the powder raw materials are mixed can be released from the holes. Next, the mixed material is usually fed by a screw to reach the second kneading section, where the kneading screw having a large feeding capacity is mixed without increasing the pressure, and then the pressure is slightly increased in a kneading screw having a small feeding capacity. Mix well. In the kneading screw on the upstream side, the feed pitch is large and the barrel is polygonal, so the space volume is large, the pressure and the temperature do not rise so much, so the contained air does not escape in large quantities,
Therefore, an unbiased mixing state is maintained. In the case of a kneading screw with a small feed pitch, the resin temperature also rises because the pressure increases and the degree of kneading increases, but the air contained in the mixed material came to the normal screw downstream and was released to atmospheric pressure. Sometimes it escapes from the mixed material and is discharged through the second air vent. In order to further knead the material well, a third kneading section is provided to remove air and volatile gas, and a third air vent is provided in the ordinary screw barrel downstream of the kneading section.
The uniformity of the mixed material is further improved. Therefore, according to the present invention, stable extrusion can be performed while mixing a large amount of fine powder raw material supplied in a state of having a large air content and a small bulk density into a plastic material.

[Brief description of the drawings]

FIG. 1 is a plan sectional view of a co-rotating twin-screw extruder according to a first embodiment of the present invention.

FIG. 2 is a plan sectional view of a co-rotating twin-screw extruder according to a second embodiment of the present invention.

FIG. 3 is a plan sectional view of a co-rotating twin-screw extruder according to a third embodiment of the present invention.

FIG. 4 is a sectional view taken along the line A-A in FIG. 1;

FIG. 5 is a sectional view taken along line BB of FIG. 1;

FIG. 6 is a plan sectional view showing a conventional co-rotating twin-screw extruder.

[Explanation of symbols]

 2, 6, 8, 12 Normal screw 3 Barrel 4 First kneading unit 5 Powder material inlet 9 Second air vent 10 Third kneading unit 11 Third air vent 13 Extruder outlet 15 Polygon barrel 16 Raw material force feeder 17 First 1 Air vent hole 18, 19 Kneading screw

────────────────────────────────────────────────── (5) References JP-A-61-277421 (JP, A) JP-A-62-129311 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 47/00-47/96 B29B 7/88

Claims (1)

(57) [Claims] A first kneading section, a second kneading section, and a third kneading section in a co-rotating twin-screw extruder for supplying and mixing a powdery raw material to a plastic material heated and melted while being fed by a screw. With the department
With a normal screw downstream of it and placed in order from the upstream side
And the powder is placed in the barrel of the normal screw downstream of the first kneading section.
The feed port for the raw material force feeder and the first air vent hole are provided.
And a second screw is placed in the barrel of the normal screw downstream of the second kneading section.
An air vent hole is provided, and the barrel of the normal screw downstream of the third kneading section is provided with a
3 The air vent hole is provided, and the second kneading section is provided with a needy with a large feed pitch upstream.
With a screw and a small feed pitch downstream
A co-rotating twin-screw extruder comprising a ring screw .