JP2003340822A - Kneading screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To well knead a molten raw material and a liquid-like additive material. <P>SOLUTION: A kneading screw comprises: a supply unit 1 for conveying the raw material from an upstream side to a downstream side with respect to the conveying direction of the raw material; a compressing unit 2 for melting the material conveyed by the unit 1; and a metering unit 3 for homogenizing the material molten by the unit 2, sequentially provided. The screw further comprises: at least one agitating kneading means 4, 5; 6, 7; 8, 9 including cross saws 4, 6, 8 for agitating the liquid-like additive material to be injected in the raw material in the raw material at the downstream side of the unit 3 with respect to the conveying direction of the material, and madoc units 5, 7, 9 provided at the downstream of the saws 4, 6, 8 for kneading the material agitated with the additive material by the saws 4, 6, 8. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a kneading screw for kneading a molten raw material.

[0002]

2. Description of the Related Art FIG. 3 is a plan view showing a conventional kneading screw.

The conventional kneading screw shown in FIG. 3 is rotatably disposed in a cylinder (not shown) in which a through hole for conveying the raw material is formed. From the upstream side with respect to the conveying direction of the raw material. A supply unit 101 that conveys the raw material that has been supplied into the through-hole, a compression unit 102 that melts the raw material that has been conveyed by the supply unit 101, and a raw material that has been melted by the compression unit 102 are homogeneously distributed toward the downstream side. Measuring unit 103
Further, a mud dock section 104 for kneading the raw material homogenized by the measuring section 103 and a discharging section 105 for discharging the molten resin kneaded by the mud dock section 104 are sequentially configured. A flight 106 for transporting the raw material is provided from the supply unit 101 to the measuring unit 103.

FIG. 4 is an enlarged view of the maddock portion of the kneading screw shown in FIG.

A suction side groove 104a connected to the metering section 103 of the kneading screw, a discharge side groove 104b connected to the discharge section 105, and a suction side groove 104a are formed on the surface of the mud dock section 104.
104 provided between the discharge groove 104b and the discharge side groove 104b
A plurality of kneading grooves configured as a set with c are provided in the circumferential direction.

The gap 104c has a clearance of 1 mm or less between it and the inner wall surface (not shown) of the cylinder.
The gap between 4a and the discharge side groove 104b and the inner wall surface of the cylinder is larger than this. Therefore, when the molten resin passes through the gap 104c, a high shearing force is applied to the molten raw material, whereby the molten raw material is kneaded so that the unmelted material in the molten raw material, the mass of the additive material, and the like become fine.

Next, the kneading operation by the conventional kneading screw described above will be described.

From the supply port (not shown) of the cylinder to the supply unit 1
The raw material such as pellets supplied to
By rotating in the direction of the arrow in the flight 106
Is carried in the right direction in the figure. The cylinder is provided with a heater, and the raw material is gradually heated in the process of being conveyed.

The raw material conveyed by the supply unit 101 next reaches the compression unit 102. In the compression part 102, the groove depth of the flight becomes gradually shallower toward the downstream side in the flow direction of the raw material, and therefore the gap between the outer peripheral surface of the screw shaft part and the cylinder inner wall surface is gradually narrowed. for that reason,
While the raw material is conveyed in the compression unit 102, shearing force is gradually and strongly applied to the raw material. Further, the raw material is the compression unit 102.
It is heated by the heater of the cylinder even while being transported in. Therefore, the raw material is melted by the shearing force and the heat of the heater while being conveyed in the compression unit 102.

The raw material melted in the compression section 102 is kneaded and homogenized in the measuring section 103. In addition, the weighing unit 103
Then, a liquid additive such as liquid oil is injected and kneaded with the raw material.

Thereafter, the raw material enters the suction side groove 104a of the mud dock portion 104, passes through the gap 104c, and is discharged from the discharge side groove 104b to the discharge portion 105. Since the gap with the inner wall surface (not shown) of the cylinder in the gap 104c is as narrow as 1 mm or less as described above, the raw material is unmelted in the molten raw material due to the high shearing force applied when passing through the gap 104c. Further kneading is carried out so that the lumps of things and additive materials become finer.

The raw material kneaded in the mud dock section 104 is pushed out by the discharge section 105 and discharged to the outside from the discharge port (not shown) of the cylinder.

[0013]

However, in the conventional kneading screw constructed as described above, when the liquid additive is injected into the molten raw material of the measuring section, the pressure of the molten raw material is fluctuated, or the molten raw material is melted. Liquid bubbles and liquid lumps of the liquid additive may occur in the liquid additive. When such a state occurs, the raw materials may be discharged without being sufficiently kneaded in the metering section or the mud dock section. Then, when the final product molded from such a raw material is a film or the like, defective products occur at a particularly high rate.

Therefore, an object of the present invention is to provide a kneading screw capable of kneading a molten raw material and a liquid additive in a good condition.

[0015]

In order to achieve the above object, the kneading screw of the present invention is fed from the upstream side to the downstream side with respect to the feed direction of the raw material, and is fed by the feed section for feeding the raw material. In a kneading screw in which a compression section for melting the above-mentioned raw material and a measuring section for homogenizing the above-mentioned raw material melted in the compression section are sequentially provided, a liquid additive injected into the above-mentioned raw material At least one agitating and kneading means that is provided on the downstream side of the cross saw section with respect to the transport direction, and a mud dock section for kneading the raw material in which the liquid additive is agitated by the cross saw section. It is characterized in that it is provided on the downstream side of the measuring section with respect to the conveying direction of the raw material.

According to the kneading screw of the present invention, when the liquid additive is injected into the raw material that has been melted from the supply section through the metering section and carried to the cross saw section, the liquid additive is injected into the cross saw section. It is stirred into the raw material. The raw material in which the liquid additive is agitated is a maddock provided on the downstream side of the cross saw section so as to make the unmelted material in the raw material fine and to eliminate liquid bubbles and liquid lumps of the liquid additive generated in the raw material. Kneaded in the department. As described above, the kneading screw of the present invention is configured such that after the liquid additive is stirred in the raw material in the cross saw portion, the raw material is kneaded in the maddock portion. It is possible to suppress the pressure fluctuations that occur and prevent liquid bubbles and liquid lumps of the liquid additive from occurring in the molten raw material.

Further, when the kneading screw has a plurality of stirring and kneading means, after stirring the liquid additive injected into the raw material and kneading the raw material by the stirring and kneading means on the upstream side, By another stirring and kneading means provided on the downstream side of the stirring and kneading means, further stirring of the liquid additive injected into the raw material and kneading of the raw material are performed, thereby adding the liquid additive in the raw material. Can be increased in stages. Therefore, according to the kneading screw of the present invention, it is possible to increase the addition rate of the liquid additive in the resulting raw material.

Further, the cross saw portion may be constituted by providing a plurality of notches on a flight provided on the outer peripheral surface of the shaft portion of the kneading screw.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view showing an embodiment of the kneading screw of the present invention. FIG. 1 (a) shows the rear end side half thereof, and FIG. 1 (b) shows the front end side half thereof.

The kneading screw of this embodiment is also provided with a supply unit 1, a compression unit 2, and a measuring unit 3 in this order from the upstream side to the downstream side in the material conveying direction. These configurations are the same as the configurations of the supply unit 101, the compression unit 102, and the measuring unit 103 in the conventional kneading screw shown in FIG. 3, and thus detailed description thereof will be omitted.

In the kneading screw of this embodiment, the measuring section 3 is followed by a first cross saw section 4, a first mud dock section 5,
A second cross saw section 6, a second maddock section 7, a third cross saw section 8 and a third mud dock section 9 are further provided. The cross saw parts 4, 6, 8 are for stirring the liquid additive injected into the raw material, and the mudock parts 5, 7, 9 are for kneading the raw material in which the liquid additive is stirred. The first cross saw section 4 and the first mud dock section 5 constitute a first stirring and kneading means, and
2nd by the cross-saw part 6 of 2nd and the 2nd Maddock part 7
The stirring and kneading means of No. 3 is constituted, and the third cross saw section 8 and the third mudock section 9 constitute the third stirring and kneading means.

Here, since the structure of each of the madocks 5, 7, and 9 is the same as that of the conventional madocks described with reference to FIG. 4, a detailed description of the madocks will be omitted.

FIG. 2 is a view showing an example of the cross saw section of the kneading screw shown in FIG.

Each cross saw section of the kneading screw of this embodiment has a flight 20 formed in the same direction as the flight 10 provided from the supply section 1 to the measuring section 3 on the outer peripheral surface of the shaft section of the kneading screw. The flight 20 is provided with a plurality of notches 20a at intervals. Therefore, the flow of the molten raw material conveyed by the flight 20 is as shown by the arrow in FIG.
It is divided into one that passes through the cutout portion 20a and one that does not pass through. Since the flow of the molten raw material is divided at each of the plurality of cutout portions 20a, the molten raw material and the liquid additive are agitated and homogenized when passing through the cross saw portion.

Next, the kneading operation by the kneading screw of this embodiment will be described.

From the supply port (not shown) of the cylinder to the supply unit 1.
The raw materials such as pellets supplied to the are conveyed by the flight 10 as in the case of the conventional kneading screw, melted in the compression section 2 and then kneaded in the measuring section 3 to be homogenized. The raw material is then conveyed to the first cross saw section 4.

The cylinder is provided with an injection hole (not shown) communicating with the first cross saw section 4. When the liquid additive is injected into the first cross saw section 4 through the injection hole, the liquid The additive material is agitated in the raw material by the first cross saw section 4. The raw material in which the liquid additive is agitated makes the unmelted material in the raw material fine, and eliminates liquid bubbles and liquid lumps of the liquid additive generated in the raw material.
Kneaded in. The raw material is subsequently conveyed to the second cross saw section 6.

The cylinder is also provided with an injection hole (not shown) communicating with the second cross saw section 6, and when the liquid additive is injected into the second cross saw section 6 through this injection hole,
The liquid additive is agitated with the raw material by the second cross saw section 6. The raw material in which the liquid additive is agitated is kneaded in the second mud dock section 7 so as to make the unmelted material in the raw material fine and to eliminate liquid bubbles and liquid lumps of the liquid additive generated in the raw material.

Since there is a certain limit to the ability to stir and knead the raw material and the liquid additive with only one stirring and kneading means, there is also a certain limit to the amount of the liquid additive that can be added to the raw material. However, the liquid additive can be added stepwise to the raw material by continuously providing a plurality of stirring and kneading means as in the present embodiment, and as a result, the addition amount of the liquid additive in the raw material is increased. It is possible to let

The raw material conveyed from the second mud dock section 7 is further kneaded by the third cross saw section 8 and the third mud dock section 9 so that there is no difference in temperature or viscosity between the raw material and the liquid additive. It is pushed out from the third madock portion 9 in the closed state.

As described above, the kneading screw of this embodiment has at least one stirring and kneading means 4, 5; 6, 7; 8, 9
The molten raw material and the liquid additive are stirred in the cross saw parts 4, 6 and 8 and kneaded in the mudock parts 5, 7 and 9 so that the molten raw material and the liquid additive can be well mixed. It is possible to knead.

[0033]

EXAMPLE Next, an example of the kneading screw described above will be described.

In this embodiment, the inner diameter of the cylinder is 90 mm.
The outer diameter of the screw was 87 mm, and the length L of the screw was 34 D (here, “D” means the outer diameter of the screw. The same applies hereinafter). The injection position of the additive material is 18D from the rear end of the screw (first cross saw part 4) and 2
The position is 4D (the second cross saw portion 6).

The raw material resin has a viscosity of 900 at 260 ° C.
Kneading of resin raw material to which liquid additive is added, using LDPE (low density polyethylene) of Pa · s, liquid oil and fat having a viscosity of 0.04 Pa · s at 90 ° C. as the liquid additive,
Extrusion was performed.

As a comparative example, the conventional screw shown in FIG. 3 was used to knead and extrude the resin raw material and the liquid additive. Also in the conventional screw, the inner diameter of the cylinder was 90 mm and the outer diameter of the screw was 87 mm.

Table 1 shows the kneading results with the screw of this example and the screw of the comparative example.

[0038]

[Table 1]

As can be seen from Table 1, according to the screw of the present embodiment, the addition rate of the liquid additive can be increased by about 1% as compared with the conventional screw, which occurs when the liquid additive is added. The pressure fluctuation of the raw material could be suppressed to about 1/7. Further, there were no liquid bubbles or liquid lumps in the raw material obtained by kneading, and the raw material into which the liquid additive was injected could be satisfactorily kneaded.

[0040]

As described above, the kneading screw of the present invention is provided with a cross saw portion for stirring the liquid additive injected into the raw material into the raw material and a cross saw portion provided downstream of the cross saw portion in the conveying direction. Since at least one agitating and kneading means consisting of a mudock portion for kneading the raw material in which the liquid additive is agitated is provided on the downstream side of the measuring section in the raw material conveying direction, the following effects can be obtained. . (1) After the liquid additive is stirred in the raw material in the cross saw section, the raw material is kneaded in the mudock section, so that the pressure fluctuation generated in the molten raw material at the time of injecting the liquid additive is suppressed,
It is possible to prevent liquid bubbles and liquid lumps of the liquid additive from being generated in the molten raw material. (2) By providing a plurality of stirring and kneading means, the addition rate of the liquid additive in the raw material can be increased stepwise, and the addition rate of the liquid additive in the resulting raw material can be increased.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a kneading screw of the present invention.

FIG. 2 is a diagram showing an example of a cross saw section included in the kneading screw shown in FIG.

FIG. 3 is a plan view showing a conventional kneading screw.

FIG. 4 is an enlarged view of a maddock portion in the kneading screw shown in FIG.

[Explanation of symbols]

1 supply section 2 Compressor 3 Weighing department 4 First cross saw section 5 First Maddock 6 Second cross saw section 7 Second Maddock 8 Third cross saw section 9 Third Maddock 10, 20 flights 20a Notch

Claims (2)

[Claims] 1. A supply unit (1) for conveying the raw material from the upstream side to the downstream side in the conveying direction of the raw material, and a compression unit (2) for melting the raw material conveyed by the supply unit (1). And a metering unit (3) for homogenizing the raw material melted in the compression unit (2) in this order, a liquid additive injected into the raw material is stirred in the raw material. The cross saw section (4, 6, 8) is provided on the downstream side of the cross saw section (4, 6, 8) in the transport direction, and the liquid additive is agitated by the cross saw section (4, 6, 8). And at least one stirring and kneading means (4,5,6,7,8,9) consisting of a mudock section (5,7,9) for kneading the raw material, and the measuring section (3 ) Is provided on the downstream side of Kneading screw you. 2. The cross saw portion (4, 6, 8) is configured by providing a plurality of cutout portions (20a) on a flight (20) provided on an outer peripheral surface of a shaft portion of the kneading screw. The kneading screw according to claim 1, which is present.