JP2009241339A - Control method of plasticizing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of a plasticizing device capable of discharging a gas or water content in a heating cylinder without a vent hole. <P>SOLUTION: In the control method of the plasticizing device 15 using a screw 3 where a first field zone FZ1, a first compression zone CZ1 and a first metering zone MZ1 are formed in order from the inlet side of a material M to the forward direction so that the screw flight height may be successively reduced, also, a decompression zone DZ is formed in front of the first metering zone MZ1 so that the screw flight height thereof may become higher than that of the first metering zone MZ1, and also, a second field zone FZ2, a second compression zone CZ2 and a second metering zone MZ2 are formed in order from the decompression zone DZ to the forward direction so that the screw flight height may be successively reduced; a material supply device 13 is controlled to limit the supply amount of the material M so that the first field zone FZ1, the first compression zone CZ1 and the first metering zone MZ1 may not be filled with the material M or the melt material Mm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control method in a plasticizing apparatus that exhausts gas and moisture in a heating cylinder.

  The gas and moisture generated during the process of plasticizing and melting the raw material in the heating cylinder of the molding machine to form a molten raw material cause defective phenomena such as silver streaks and haze in the molded product formed from the molten raw material. Therefore, conventionally, various measures have been taken to remove gas and moisture from the inside of the heating cylinder. For example, as shown in Patent Document 1, gas or moisture generated from a decompression unit provided between two stages of compression units of a screw is degassed from a vent hole provided by drilling in an intermediate part of a heating cylinder There is. However, this vent type injection device has a problem that the molten material swells from the vent hole or that the deteriorated molten material near the vent hole is mixed into the heating cylinder. Therefore, as disclosed in Patent Document 1, an additional device such as a core or a cylinder for pushing the molten resin that has been vented up into the heating cylinder is required.

JP 59-29137 A

  The present invention has been made to solve the above-described problems, and provides a method for controlling a plasticizing apparatus that can effectively exhaust gas and moisture in a heating cylinder without providing a vent hole. With the goal.

  In the present invention, the first feed zone, the first compression zone, and the first metering zone are formed so that the flight height is sequentially reduced from the rear, which is the raw material inlet side, to the front. A compression zone adjacent to the front is formed so that a flight height is higher than a flight height of the first metering zone, and further, a second feed zone, a second compression zone, The second metering zone is formed so that the flight height is sequentially reduced, and a screw having a flight whose outer diameter is slightly smaller than the inner diameter of the inner hole of the heating cylinder is rotatably fitted to the heating cylinder having no vent hole. A method for controlling a plasticizing apparatus for plasticizing the raw material, the raw material being supplied to the heating cylinder The material supply apparatus relates to a control method for a plasticizing apparatus that limits and controls the supply amount of the raw material so that the first feed zone, the first compression zone, and the first metering zone are not filled with the raw material or the molten raw material. .

  According to the control method of the plasticizing apparatus of the present invention, the gas and moisture in the heating cylinder can be effectively exhausted without providing the vent hole.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view of a plasticizing apparatus for carrying out the present invention.

  The screw 3 is rotatably fitted in an inner hole 10 of a heating cylinder 4 provided in a plasticizing device 15 of a molding machine such as an injection molding machine or an extruder. The heating cylinder 4 is a thick cylinder, one end on the rear side is fixed to a housing (not shown) of the plasticizing device 15, and the cylinder head 1 is fixed to the other end surface on the front side. . A nozzle or the like (not shown) is fixed to the cylinder head 1. A raw material inlet 7 opening upward is perforated on the side surface of the rear end of the heating cylinder 4. A raw material supply device 13 is airtightly connected to the raw material inlet 7. The raw material supply device 13 is configured to feed a predetermined amount of the raw material M supplied in a two-stage manner while maintaining hermeticity by shutters 11, 11 that are alternately opened and closed, a rotary valve having a recess (not shown), or the like. 12, the conveyance amount is limited and controlled and supplied to the raw material inlet 7. A portion of the screw 3 that is inserted into the inner hole 10 of the heating cylinder 4 and that corresponds to the end of the raw material inlet 7 is a screw base 8. The screw base 8 has a cylindrical shape having a diameter slightly smaller than the inner diameter of the inner hole 10, and is in sliding contact with a packing (not shown) provided on the rear end face of the heating cylinder 4 so that the rear end of the heating cylinder 4 is airtight. . Further, since the groove between the flight pitches is filled with the molten raw material Mm in which the raw material M is melted in front of the screw 3, the inside of the rear portion of the heating cylinder 4 is airtight. Therefore, the vacuum pump 14 provided in the raw material supply device 13 above the raw material inlet 7 can effectively suck the gas and moisture generated from the molten raw material Mm by reducing the pressure inside the heating cylinder 4. In the extruder, the backflow prevention valve 2 is not provided.

  From the screw base 8 at the rear part to the front end face to which the backflow prevention valve 2 is fixed, the screw 3 protrudes in a spiral manner at the same pitch on the outer periphery of a round bar whose diameter changes according to the position in the axial direction. The outer periphery diameter of all the flights is the same, and is formed in a form that is slightly smaller than the inner diameter of the inner hole 10. And based on the change according to the axial direction position of the diameter of the said round bar, the flight 6 is the 1st feed zone FZ1, 1st compression zone CZ1, 1st meter in order from the back which is the inlet_port | entrance side of a raw material to the front. The ring zones MZ1 are formed so that their flight heights are successively reduced, and the decompression zone DZ is adjacent to the front of the first metering zone MZ1 and the flight height is higher than the flight height of the first metering zone MZ1. Further, the second feed zone FZ2, the second compression zone CZ2, and the second metering zone MZ2 are formed in order from the decompression zone DZ forward so that their flight heights are sequentially lowered. .

  Next, plasticization by the screw 3 will be described. The raw material M supplied from the raw material supply device 13 through the raw material inlet 7 under the control of the inner hole 10 of the heating cylinder 4 has a relatively high flight height and a relatively large and constant pitch groove volume. In zone FZ1, it is conveyed forward while receiving heat from heating cylinder 4 and screw 3. The raw material M starts to melt from the middle part of the first feed zone FZ1. The raw material supply device 13 feeds so that the molten raw material Mm in which the raw material M is melted is unevenly distributed along the unmelted raw material M on the front side surface of the flight 6 (the rear side surface when viewed from the pitch groove of the flight 6). The supply speed of the raw material M is controlled by adjusting the rotational speed of the screw 12. That is, on the side surface on the rear side of the flight 6, there is almost no raw material M and molten raw material Mm at the time of plasticization in normal molding, and gas and moisture can be easily circulated. However, when the screw 3 is washed to change the type and color of the raw material M, the supply of the raw material M is controlled by the raw material supply device 13 so that the raw material inlet 7 is filled without limiting the supply amount, and the flight 6 It is necessary that the pitch grooves of the material are substantially filled with the raw material M and the molten raw material Mm.

  The first compression zone CZ1 adjacent to the front side of the first feed zone FZ1 is formed so that the flight height is tapered forward from that of the first feed zone FZ1. In the first compression zone CZ1, the raw material M and the molten raw material Mm are compressed and the melting is promoted because the pitch groove volume decreases. The raw material M and the molten raw material Mm increase in the ratio of the molten raw material Mm, and are conveyed while adhering to the entire side surface on the front side of the flight 6 and being kneaded. Further, the gas and moisture released in this process flow through the gap communicating with the flight grooves of the first compression zone CZ1 and the first feed zone FZ1, and are discharged backward. The first metering zone MZ1 adjacent to the front side of the first compression zone CZ1 is formed so that the flight height is constant from the front end of the first compression zone CZ1 to the front. In the first metering zone MZ1, the raw material M is all melted to become only the molten raw material Mm.

  The decompression zone DZ adjacent to the front side of the first metering zone MZ1 is formed such that the flight height increases in a tapered manner at a short distance of about one pitch from the first metering zone MZ1 to the front. Yes. In the decompression zone DZ, the volume of the pitch groove is rapidly expanded, so that the compressed molten raw material Mm is decompressed, and the gas and moisture contained in the molten raw material Mm are effectively released. The gas and moisture released in the decompression zone DZ circulate through the gaps in the first metering zone MZ1, the first compression zone CZ1, and the first feed zone FZ1, and then circulate to the rear part of the screw 3. The gas and moisture that have reached the vicinity of the raw material inlet 7 at the rear part of the screw 3 are discharged into the atmosphere through a gap provided as appropriate, or are forced into the air from the space near the raw material inlet 7 that is formed airtight by the vacuum pump 14. Exhausted.

  The second feed zone FZ2 adjacent to the front of the decompression zone DZ has a constant flight height from the foremost end of the decompression zone DZ to the front. The second compression zone CZ2 adjacent to the front side of the second feed zone FZ2 is formed so that the flight height is tapered forward from that of the second feed zone FZ2. In the second compression zone CZ2, the molten raw material Mm is compressed because the pitch groove volume decreases, and the melting is promoted / executed again. The second metering zone MZ2 adjacent to the front side of the second compression zone CZ2 has a flight height that is constant from the front end of the second compression zone CZ2 to the front. The second metering zone MZ <b> 2 extrudes a high-quality molten raw material Mm that does not include gas and moisture to the front of the screw 3. In the injection molding machine, a predetermined amount of molten raw material Mm is stored in the front part of the heating cylinder 4, and the screw 3 retracted against the screw back pressure is injected and advanced to inject and fill a mold (not shown).

  Table 1 shows the moisture content of the molded product thus injection-molded together with the moisture content of the molded product molded by an injection molding machine equipped with a conventional screw for comparison. The molding raw material in this molding is an ABS resin material (Clarastic GA-501), and the initial moisture content is about 3000 ppm. The molded product was 200 × 250 mmMax, and the sprue portion was subjected to moisture content measurement. L / D in a table | surface remove | divides the length of a screw by the diameter, and is an parameter | index which shows the effective length of a screw. The L / D20 screw is a general-purpose general-purpose screw. The conventional screw of L / D28 is a screw having only a feed zone, a compression zone, and a metering zone. The screw according to the present invention has a feed zone, a compression zone, and a metering zone in two stages and has a decompression zone.

  As is clear from Table 1, the higher the raw material supply limit and the lower the screw back pressure, the lower the density of the raw material and molten raw material in the pitch groove of the screw and the larger the voids, so moisture discharge Is promoted. Further, when the inside of the heating cylinder is depressurized by vacuum suction, an extremely remarkable decrease in moisture content is observed. In particular, vacuum suction is effective when L / D is increased. This is considered to be due to an increase in the residence time of the molten raw material in the heating cylinder. Thus, the control method of the present invention using the screw 3 satisfies all the requirements that are considered to be effective for the discharge of moisture and gas. That is, after the raw material M is completely melted, the pressure is reduced, the material M is retained for a relatively long time, and the released gas and moisture are forcibly sucked and discharged from the secured flow path. Thus, in the plasticizing apparatus of the present invention, since the heating cylinder does not have a vent hole, the gas and moisture in the heating cylinder are very effectively produced without causing serious problems such as vent-up of the molten raw material. Can be discharged.

  The present invention is not limited to the embodiments described above, and various modifications can be added and implemented without departing from the spirit of the invention.

It is a longitudinal cross-sectional view which shows the state by which the screw which implements this invention was inserted by the heating cylinder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Backflow prevention valve 3 Screw 4 Heating cylinder 6 Flight 7 Raw material inlet 8 Screw base 10 Inner hole 11 Shutter 12 Feed screw 13 Raw material supply apparatus 14 Vacuum pump 15 Plasticizing apparatus M Raw material Mm Molten raw material FZ1 1st feed zone FZ2 2nd feed zone CZ1 1st compression zone CZ2 2nd compression zone MZ1 1st metering zone MZ2 2nd metering zone DZ Decompression zone

Claims (3)

The first feed zone, the first compression zone, and the first metering zone are formed in order from the rear, which is the raw material inlet side, in order from the rear to the front, and adjacent to the front of the first metering zone. The decompression zone is formed so that the flight height is higher than the flight height of the first metering zone, and further, the second feed zone, the second compression zone, and the second metering are sequentially forward from the decompression zone. A zone is formed so that the flight height is sequentially reduced, and a screw having a flight whose outer diameter is slightly smaller than the inner diameter of the inner hole of the heating cylinder is rotatably inserted into the heating cylinder having no vent hole, A method for controlling a plasticizing apparatus for plasticizing a raw material,
The raw material supply device for supplying the raw material to the heating cylinder limits the supply amount of the raw material so that the first feed zone, the first compression zone, and the first metering zone are not filled with the raw material or the molten raw material. A method for controlling a plasticizing apparatus, comprising controlling the plasticizing apparatus.   The control method of the plasticizing apparatus which implements the control of Claim 1 in the atmosphere where the inside of the said heating cylinder was pressure-reduced.   A method for controlling a plasticizing apparatus, wherein the raw material supply apparatus is controlled so that a supply amount of the raw material is not limited when the screw according to claim 1 or 2 is washed.

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