JP5751718B2 - Screen changer and pre-filling method of screen changer - Google Patents

Description

  The present invention relates to a screen changer that can suitably perform pre-filling performed when a screen changer provided in an extruder or the like is replaced, and a pre-filling method thereof.

  An extruder or the like is provided with a screen changer for removing dust, foreign substances, deteriorated products, impurities, and the like contained in the molten resin when the molten resin generated by melting and kneading the resin raw material is extruded. . This screen changer may cause clogging or breakage of a screen used for filtering dust and the like, and various proposals have been made regarding replacement of the screen and removal of dust attached to the screen.

  Regarding the replacement of the screen, a DB (DUAL BAR SCREEN CHANGER) type screen changer, a slider type screen changer or the like is preferable because the screen can be replaced without stopping the supply of the molten resin. The DB type screen changer is a system in which a pair of branch paths are provided in a main channel to which molten resin generated by an extruder or the like is supplied, and the screen can be changed for each one of the branch paths. The slider-type screen changer is a system in which a slider provided with a plurality of screens is provided across the main flow path, and the screen can be replaced and used by moving the slider.

  In replacing the screen of such a screen changer, since there is a large amount of air in the resin flow path or space in which the replaced screen is provided, the resin flow path is first filled with molten resin in advance. The screen changer is operated in a normal state after the preliminary filling operation for releasing the air.

  For example, in Patent Document 1, in a DB-type screen changer, a conventional material injection channel and a first one are provided at an intermediate position where a filtration portion provided penetrating in a direction perpendicular to the axis of a slide bar is hermetically blocked by a housing through hole. In addition to the air vent channel, there has been proposed a screen changer provided with a second air vent channel communicating from the uppermost part of the downstream chamber to the outside. According to this screen changer, the air in the flow path of the slide bar and the filtration part can be completely discharged.

  In Patent Document 2, in a slider-type screen changer, a shallow concave portion of 0.01 to 0.1 mm that communicates with the filtration portion at the corner of the slider screen holding frame and acts as an air collecting gap is further provided. There has been proposed a screen changer provided with a fine air vent passage. According to this screen changer, the air can be surely removed, and the clogging of the molten resin generated in the recess when the air is released can be easily removed and cleaned.

JP-A-8-90635 JP 2006-116908 JP

  In such a conventional screen changer, various proposals have been made regarding what type of screen changer is preferable as the air vent structure in the preliminary filling. However, there is no suggestion or description on how or pre-filling is performed. In addition, there is no description or proposal regarding a solution regarding problems such as foaming of the molten resin in the pre-filling, excessive blowing, or breakage of the screen due to an inappropriate pre-filling speed. In recent years, demand for resins with high fluidity has increased due to demands for weight reduction of resin molded bodies, and development of resins with higher fluidity has been underway. As the fluidity of the resin is higher, the above-mentioned problem is more likely to occur, and thus appropriate prefilling is required.

  In view of such conventional problems and requirements, the present invention can prevent the occurrence of problems associated with foaming or blowing up of molten resin in pre-filling, or inappropriate pre-filling speed, and high quality and production efficiency. It is an object of the present invention to provide a high screen changer and a prefilling method for the screen changer.

  The screen changer according to the present invention is provided in a branch path in which a melted and kneaded molten resin from a main channel flows into a housing in which a pair of slide bars are fitted, and is branched into two resin channels. A screen changer provided with a resin flow path that passes through a screen and a breaker plate provided in the pair of slide bars, and then merges again into one resin flow path and feeds it to the main flow path. Is carried out by advancing and retracting the slide bar fitted in the housing, and pre-filling the molten resin by flowing molten resin from the main flow path into the empty branch path on the side where the replaced new screen is mounted. In the screen changer which puts the branch path and the new screen into an operating state after performing air venting existing in the road, the slide bar is advanced and retracted. A position sensor to detect, a drive means for moving the slide bar back and forth, and a pre-fill control device for controlling the filling speed or time in the pre-fill by controlling the drive means based on the output of the position sensor. Do it.

  In the above invention, the pre-filling of the molten resin is performed through a resin supply path having a fine cross section with respect to the main flow path, and the length of the resin supply path can be adjusted by moving the slide bar back and forth. It is good. The resin supply path is preferably controlled to be short when the viscosity of the molten resin is high and long when the viscosity of the molten resin is low.

  In addition, in order to confirm the timing of changing the length of the resin supply path by the advance and retreat of the slide bar, it is preferable to provide a temperature sensor for detecting the temperature of the outlet portion opening outside the air vent groove for venting air in the branch path. It is preferable to provide a temperature sensor that detects the temperature of the inlet portion that opens to the branch path of the air vent groove.

  The screen changer pre-filling method according to the present invention is a screen changer capable of replacing the screen while continuing to supply the molten resin supplied from the main flow path. A prefilling method of a screen changer for pre-filling the molten resin by flowing the molten resin into the empty resin flow channel on the side, wherein the air is present in the resin flow channel, and based on the viscosity of the molten resin, This is done by controlling the filling rate or time in the pre-filling.

  In the pre-filling method of the screen changer, it is preferable to control the filling speed in the pre-filling stepwise and gradually. And it is good to control so that a filling speed may be once decelerated before preliminary filling is completed about control of the filling speed in preliminary filling.

  According to the present invention, efficient preliminary filling can be performed, and a high-quality molten resin can be supplied with high productivity.

It is a schematic diagram which shows the structure of the screen changer which concerns on this invention. It is a fragmentary sectional view which cuts through the branch path of the housing of the part in which the slide bar of FIG. 1 was fitted. It is explanatory drawing in the case of performing preliminary filling and air bleeding after mounting of a new screen. It is a graph which shows the relationship between the length of a resin supply path, and preliminary filling time. It is explanatory drawing explaining the preliminary filling method which concerns on this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of a screen changer according to the present invention. As shown in FIG. 1, the screen changer 10 is a DB type screen changer in which a pair of slide bars 15 (15A, 15B) are fitted in a housing 11, and the slide bar 15 includes a hydraulic unit 26 and a cylinder 27. The drive means 25 comprising (27A, 27B) can be moved back and forth inside the housing 11. The screen changer 10 includes a position sensor 35 (35A, 35B) that detects the advance / retreat position of the slide bar 15, and a pre-fill control device that controls the filling speed or time in the pre-fill based on the output of the position sensor 35. And 30. Preliminary filling means that when the screen used for filtering the melted and kneaded molten resin supplied from the main channel is replaced, there is no molten resin on the side on which the replaced new screen is mounted. It means that molten resin is caused to flow into an empty resin flow path filled with air, and the air existing in the resin flow path is vented.

In the screen changer 10, the molten resin flows in the housing 11 as shown in FIG. That is, as shown in FIG. 2 (a), the molten and kneaded molten resin supplied from the main flow path 12 passes through the branch path 13 (13A, 13B), the screen 22, and the breaker plate 23 , It merges again and flows through the main channel 12. As a result, dust, foreign matter, deteriorated products, impurities, and the like contained in the molten resin can be removed, and the screen on which the dust is accumulated is replaced with a new screen before clogging occurs.

The screen 22 is exchanged as shown in FIGS. That is, the screen is exchanged in a state where the slide bar 15 (15A) fitted to one side of the branch path 13 is pulled out and the molten resin does not flow toward the branch path 13A as shown in FIG. 2 (b). . Then, in the state shown in FIG. 2C in which the slide bar 15A is pulled back, the molten resin is supplied from the resin supply path 16 to the empty branch path 13A, and preliminary filling is performed.

  The preliminary filling according to the present invention will be described with reference to FIG. FIG. 3 is a partial cross-sectional view that cuts the branch path portion, and shows a cross section orthogonal to the cross section shown in FIG. The resin supply path 16 is formed by a groove provided on the surface portion of the slide bar 15, the slide bar 15 and the housing 11. The cross section of the resin supply path 16 is finer than that of the main flow path 12. When the molten resin is supplied through the resin supply path 16, the air in the branch path 13A is discharged through the air vent groove 17. In the case of this example, the air vent groove 18 is also provided in the branch path 13A on the downstream side of the screen 22.

  Since the resin supply path 16 is formed by a groove or the like provided on the surface portion of the slide bar 15 as described above, as shown in FIG. 4, a portion (length l) that opens to the branch path 13A of the groove Is present, the length (Ll) of the resin supply path 16 is shortened. That is, in the present invention, the length of the resin supply path can be adjusted by moving the slide bar back and forth.

  FIG. 4 shows the preliminary filling time when the preliminary filling is performed by changing the l / L ratio related to the length of the resin supply path. That is, the relationship between the filling time (preliminary filling time) until lending of the molten resin in the branch path 13 and the completion of air venting in the branch path is shown. In FIG. 4, the horizontal axis is l / L, and the vertical axis is the normalized time. The normalization time is the ratio of the prefill time at each l / L value with the prefill time at l / L = 10% as a reference (1.00).

  In FIG. 4, curve a is for a low viscosity resin and curve b is for a high viscosity resin. A resin having a low viscosity indicates a resin having an MFR (melt mass flow rate) exceeding 100 g / 10 min. A high viscosity resin is one having an MFR of 50 g / 10 or less. As shown in Fig. 4, in the case of a resin with low viscosity, when l (open length) increases slightly, the pre-filling time decreases rapidly, and when l / L = 30% is exceeded, the filling time opens. It is almost constant regardless of length. On the other hand, in the case of resin with high viscosity, even if the open length increases, the pre-filling time hardly changes, but when the open length is long (resin supply path is short) and exceeds l / L = 75% The prefill time is rapidly shortened.

  In the case of a resin with low viscosity, if rapid filling is performed with a long open length and a fast filling speed, the molten resin that has passed through the resin supply path and opened to the atmosphere will foam, making it difficult to vent the air. The resin flow is easy to damage the screen by hitting the screen directly. On the other hand, in the case of a resin having a high viscosity, there is a problem that if the open length is not kept sufficiently (the resin supply path is short), the filling speed becomes slow and the time required for air venting becomes long. Furthermore, in order to reliably remove the air in the branch path, it is necessary to fill the molten resin until the molten resin blows out from the air vent groove, and the preliminary filling is completed by blowing the molten resin. However, regardless of the viscosity of the molten resin, the blowout of the molten resin from the air vent groove is dangerous if it is abrupt or large, and may cause damage to the equipment.

  The above problems can be prevented by performing preliminary filling as shown in FIG. For example, in the case of a molten resin having a low viscosity, the prefilling speed or time is controlled as shown by curve a. That is, the resin supply path is in a state of l / L = a1% shown in FIG. Next, the molten resin is filled for t2 hours with the resin supply path in a state of l / L = a3%. The time t1 for switching the resin supply path from l / L = a1% to l / L = a3% is preferably when the molten resin is filled to the extent that the height of the outlet of the resin supply path 16 is reached. Thereby, since foaming of molten resin is suppressed, the filling rate of molten resin can be increased. The timing for performing the switching can be easily determined by detecting the temperature at the height of the outlet of the resin supply path 16 with a temperature sensor provided in the branch path or in the vicinity of the inner wall of the branch path. The required time calculated from the integration of the resin filling speed without providing a temperature sensor may be set in advance as a timer.

  If preliminary filling is completed while the resin supply path is switched to l / L = a3% and the filling speed is increased, the blowout at the completion of preliminary filling tends to be excessive. For this reason, it is preferable to complete the preliminary filling by finally setting the resin supply path to 1 / L = a2% in order to temporarily reduce the filling speed. The timing for switching the resin supply path from l / L = a3% to l / L = a2% is easily determined by detecting the temperature at the inlet or outlet of the branch path 13A of the air vent groove 17 with a temperature sensor. be able to. The required time calculated from the integration of the resin filling speed without providing a temperature sensor may be set in advance as a timer.

  In order to confirm that the air has been completely removed from the branch path 13A including the air vent groove 17 and the like (preliminary filling has been completed), a temperature sensor is provided at the outlet that opens to the outside of the air vent groove 17. Can do. An example in which this temperature sensor is provided in the screen changer 10 is shown in FIG. The temperature sensor 37 (37A, 37B) is preferably a non-contact type temperature sensor. The completion of the preliminary filling can also be confirmed visually by blowing up the molten resin at the outlet of the air vent groove 17.

  After the blowout of the molten resin is confirmed by the temperature sensor 37 or visual observation, the slide bar 15A is immediately pulled back to the normal operating state shown in FIG. The filling time t3 performed with the resin supply path in the state of l / L = a2% is an appropriate time until the molten resin blowout confirmation.

  On the other hand, in the case of a molten resin having a high viscosity, the pre-filling speed or time is controlled as shown by curve b. That is, the resin supply path is in a state of l / L = b1% shown in FIG. Then, the filling speed is slightly reduced to 1 / L = b2% to complete the preliminary filling.

  The screen changer 10 according to the present invention can perform pre-filling controlled as described above. That is, the position sensor 35 detects the advance / retreat position of the slide bar 15, and the preliminary filling control device 30 controls the driving means 20 to control the l / L value of the resin supply path and the holding interval. In addition, optimum prefilling according to the viscosity of the molten resin (type of resin, melting temperature) can be performed.

  As the driving means 25, a combination of an electric motor and a screw, a step motor or the like can be used. The position sensor 35 is preferably a linear sensor that can detect any forward / backward position of the slide bar 15 so as to cope with a change in the type and grade of the target resin. However, if the type, grade, etc. of the target resin are constant, the number of limit switches corresponding to the step to be controlled can be used. The pre-filling control device 30 is preferably a computer-controlled one capable of program control. However, it is possible to use a control means by sequence control or a combination of a timer and an on-off switch.

  The screen changer 10 according to the present invention and the preliminary filling method performed in the screen changer 10 have been described above. The preliminary filling method according to the present invention can be implemented not only in a DB type screen changer such as the screen changer 10 but also in a slider type screen changer, for example.

10 screen changer
11 Housing
12 Main flow path
13, 13A, 13B branch
15, 15A, 15B Slide bar
16 Resin supply path
17, 18 Air vent groove
22 screen
23 Breaker plate
25 Drive means
26 Hydraulic unit
27, 27A, 27B cylinder
30 Pre-fill controller
35 Position sensor
37, 37A, 37B Temperature sensor

Claims (8)

The pair of slide bars provided in the branch path into which the melted and kneaded molten resin from the main flow path flows into the housing in which the pair of slide bars are fitted and branched into two resin flow paths is provided. A screen changer provided with a resin flow path that passes through the screen and the breaker plate and then merges again into one resin flow path and sends it to the main flow path,
The replacement of the screen is performed by advancing and retracting the slide bar fitted to the housing, and the molten resin is allowed to flow from the main flow path into the empty branch path on the side where the replaced new screen is mounted, and is pre-filled. In the screen changer that puts the branch path and the new screen into an operating state after venting the air existing in the branch path.
A position sensor for detecting the advancing / retreating position of the slide bar, and a driving means for advancing / retreating the slide bar;
A screen changer having a pre-filling control device that controls the filling speed or time in the pre-filling by controlling the driving means based on the output of the position sensor.   The pre-filling of the molten resin is performed through a resin supply path having a fine cross section with respect to the main flow path, and the length of the resin supply path can be adjusted by moving the slide bar back and forth. The screen changer according to claim 1.   The screen changer according to claim 2, wherein the resin supply path is controlled to be short when the viscosity of the molten resin is high and long when the viscosity of the molten resin is low.   The screen changer according to any one of claims 1 to 3, further comprising a temperature sensor that detects a temperature of an outlet portion that opens to the outside of an air vent groove that vents air in the branch path.   The screen changer according to claim 4, further comprising a temperature sensor that detects a temperature of an inlet portion that opens to the branch path of the air vent groove. In a screen changer that can replace the screen while continuing to supply the molten resin supplied from the main flow path, the molten resin flows into the empty resin flow path on the side where the new screen replaced when the screen is replaced is installed. A prefilling method for a screen changer in which a resin is introduced and prefilled, and the air present in the resin flow path is vented.
A pre-filling method of a screen changer for controlling a filling speed or time in pre-filling based on the viscosity of the molten resin. Prefill method of screen changer according to claim 6 for controlling the filling rate in the preliminary filling step by step, and gradually speed Kunar so.   The prefilling method for a screen changer according to claim 6 or 7, wherein in the control of the filling speed in the prefilling, the filling speed is controlled to be once reduced before the prefilling is completed.

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