JPS5889341A - Extruder for thermoplastic resin molding - Google Patents

Abstract

PURPOSE:To eliminate unevenness in temperature, kneading, and mixture through quiet substitution of a specified quantity of resin, by a method wherein a multi-screw thread is formed in a screw of a kneading mixing part for resin, pins are radially projected from a barrel inner surface into a plurality of grooves being formed in its periphery in the manner that its bottom is positioned in the same level as that of the trough diameter of screw. CONSTITUTION:An extruder 11 consists of a feed part 13a for preheating a thermoplastic resin material, charged through a hopper 14, by a heater 15 for conveyance, a compressing part 13b for fusing and kneading the material, and a weighing part 13c for further kneading it to make uniform the mixture and adjusting a supply amount to an adapter 16. A kneading and mixing device 17 is mounted from the terminal of the compressing part 13b to the weighing part 13c, and grooves 19, whose bottom is positioned in the same level as that of a surface of a root diameter of screw, are formed in a 3 or more threaded screw 18 in a peripheral direction at given intervals. A plurality of pins 20 are projected into the grooves 19 through an inner wall surface of a barrel 12, and are positioned so that they keep a taper gap between a gate 21 and them during the passage of it through the gate. Thus, resin in grooves 22-25 is flowed such that divided flow 22a-25a are branched from the main streams 22A-25A, and only a given quantity is flowed through a given gap into grooves 22-25, whereby only a given quantity of resin is substituted.

Description

[Detailed description of the invention] The present invention relates to an extrusion device for molding thermoplastic resin.

In general, extrusion equipment for thermoplastic resin molding plays an important role in the molding process to increase the amount of extrusion per unit time, that is, the productivity, and one method for increasing the amount of extrusion is the measuring section of the screw. Increasing the depth of the groove is being practiced. However, this method has the disadvantage that there is a large temperature difference between the bottom of the screw groove and the surface near the inner wall of the barrel, resulting in uneven temperature, uneven kneading, and uneven mixing, resulting in poor quality of the molded product.

Various efforts have been made to eliminate the above-mentioned drawbacks, and many inventions and ideas have been made. For example, as shown in Figure 1, most of the material resin to be processed has already exceeded its melting point (softening point) and is in a fluid state, but there are still parts where there is a large temperature difference between the material layers, i.e. In the area from the latter half of the compression section to the metering section, a pin 2 provided on the barrel 1 protrudes into an annular groove 4 whose bottom is the root diameter surface provided in the outer circumferential direction of the screw 3, and passes through the screw groove 5. A crosstalk and mixing device designed to disrupt the laminar flow of resin and equalize the resin temperature! There is one installed on screw 3.

If we observe this crosstalk and the state of the resin passing through the mixing device, we will see that due to the action of the pin 2, a small amount of the resin a is separated from the screw flight 6a-
Partial substitution (mixing) takes place through the cutout gate 7. This phenomenon occurs when flight 6 is provided with gate 7 as shown in Fig. 3, where the flight width is f and the gate width is Ygs.
When the lead angle is φ, the wrap length t of the cut-up portion of the flight 6 at the gate 7 is expressed by the following equation (1).

Since this crosstalk and mixing device is provided in a limited range (location) of the screw 3, the flight width f becomes smaller as the number of threads increases.

(2) Due to mixing effects, pin strength, etc., the gate width g, that is, the pin thickness, cannot be made too thin (small).

+31 In order to ensure productivity, the lead angle φ cannot be made large because the flight part of the crosstalk and mixing device also has a material propulsion function.

Due to such conditions, the wrap length t is often set to 1=0 according to Yamashiki.

As shown in FIG. 4, the pin 2 cannot block the gate 7 while the pin 2 is passing through the gate 7, and a leak occurs as shown by the arrow, and the amount of conveyance and displacement by the pin 2 is reduced. decrease, and the mixing effect weakens.

Now, if we consider the mixing effect coefficient m and the crosstalk effect coefficient B, m = c * v * v - (2) s = c, k - (3) and v hold, and m and si are each thicker. (to do, i.e. mix,
In order to achieve good crosstalk, it is necessary to increase c, v, η, and k in the +2J and 13J equations, respectively.

That is, since e = (number of pins) x (number of pins) x (number of threads), the groove depth is increased, the volume V is increased,
By increasing the number of threads and the number of pins (increasing the number of pins, the number of times the pins and gates come into contact with each other increases, which naturally reduces the amount of material leaking between the pins and gates).

k also increases.

The object of the present invention is to eliminate the above-mentioned drawbacks and provide an extrusion device equipped with a screw heating device and a mixing device that does not cause temperature unevenness, kneading, or mixing unevenness even if the groove in the measuring section is deep.

Next, one embodiment of the present invention will be explained with reference to FIGS.
is inserted rotatably. A material such as a thermoplastic resin is introduced into the screw 13 from a hopper 14 into the barrel 1 and is preheated by a heater 15 provided on the outer surface of the barrel 1. a supply section 13a that transfers the material to the supply section 13a, and a compression section that applies back pressure to the material sent from the supply section 13a and melts the material with heat generated by the renewal action of the heater 15 and the material and cross-wires the material. 13b and the material from the compressed part is further mixed and made uniform, and the tip part K1g of the barrel 1] is formed. A measuring unit 13 that adjusts the amount of material fed to the adapter 16 such as a die attached.
c is a provision. Reference numeral 17 denotes a cross-wire and mixing device, which is provided from near the end of the compression portion 13b of the screw to the metering portion, and is provided with at least three or more multi-thread screws J8;
There are provided five annular grooves 19 with grooves extending in the circumferential direction at predetermined intervals. A plurality of bottles project radially into the 1f19 from the inner wall surface of the barrel l;
As shown in the figure, as the screw rotates, between the notch-shaped resin passage 21 (referred to as gate) formed in the screw 18a, the pin addition is shown as a solid line addition from the position of the chain @ 20a. While passing through the gate 21 to reach the position, a predetermined interval δ or a Taber gap is always maintained. Therefore.

As shown in FIG. 8, the resin in each screw groove or 5 separates from the main stream ηA or 25A into its branch stream ηa or 25a, and extends a predetermined amount from a predetermined gap into the adjacent screw groove or δ. Since the resin flows smoothly, a certain amount of resin is replaced, and the drawbacks of the conventional method as described above are eliminated.

A is a plunger, which is provided adjacent to the terminal end of the mixing device, and has a first stop that does not go back to its outer circumferential surface while maintaining a small gap between it and the inner wall surface of the barrel 1. The grooves II a Y are alternately arranged in opposite directions so as not to communicate with each other, and are used when the kneading and mixing device is still insufficiently mixed or mixed. Of course,
Depending on the material, the plunger may not be necessary, so it is not necessarily necessary.

In addition, the gate and bottle can be used in various applications as shown in Figure 9.The gap can be set not only at a constant value but also at a wedge angle θ to create a cylindrical gap with a new shearing effect due to the wedge effect. You can also do that.

[Brief explanation of drawings]

FIG. 1 is a diagram of a conventional device. FIG. 2 is a diagram illustrating the flow of material in the gate. FIG. 3 is an explanatory diagram showing the relationship between the screw flight and the gate. FIG. 4 is a diagram explaining the flow of materials in a conventional device. 5 to 8 are diagrams showing one embodiment of the present invention,
FIG. 5 is a sectional view of an extrusion device according to the present invention. 6 is a cross-sectional view taken along line II in FIG. 5, and FIG. 7 is a diagram showing the positional relationship between pins and gates. FIG. 8 shows the development of a mixing and crosstalk device, and is a diagram illustrating the flow of materials. FIG. 9 is a diagram showing another embodiment of the crosstalk and mixing device according to the present invention. 13...screw, 17...crosstalk, mixing device, 18
...Multi-thread screw, 19...Groove, machining...pin, 21
...gate, 26...plunger. Applicant: Toshiba Machine Co., Ltd. Naka 7 (C) (2) c book 1

Claims (1)

[Claims] A supply section that introduces material into the barrel, preheats it, and sends it forward; and a back pressure is applied to the material from the supply section, and a 710 degree heat is applied to the material from outside the barrel. A screw transfer system consisting of a compression section that melts the material, mixes it, and transfers it to a measurement section for the next process, and a measurement section that further kneads and homogenizes the material from the compression section and adjusts the feed rate of the material. It has at least three or more multi-thread threads extending from near the end of the compression section to the measuring section, and the bottom diameter surface of the multi-thread thread is located at a predetermined interval in the axial direction from the outer peripheral surface of the multi-thread thread. ! A notch-shaped gate is provided in the multi-thread screw, and a plurality of pins protrude into the groove radially from the inner wall surface of the barrel toward the axis, and the pins move relative to each other as the screw rotates. An extrusion device for molding a thermoplastic resin, characterized in that it is provided with a mixing device that maintains a small gap between the bottle and the gate while passing through the groove. 2. A plunger is provided adjacent to the terminal end of the mixing device to maintain a small gap between the plunger and the inner wall surface of the barrel, so that the first stop grooves that do not penetrate through the outer circumferential surface of the plunger do not communicate with each other. They are characterized by being arranged alternately in opposite directions. An extrusion device for molding thermoplastic resin according to claim 1.