JP5704881B2 - Hopper dryer for drying equipment for granular plastic materials - Google Patents

Description

The present invention is a plastic material, to a hopper dryer are used in particular Drying apparatus pelletized or granular plastic material.

  Certain plastic materials are hygroscopic, so when left in the atmosphere, they contain several percent or less of moisture due to the temperature and humidity of the atmosphere. The plastic raw material supplied to the plastic molding machine is usually supplied in the form of pellets, that is, as a granular plastic material (hereinafter simply referred to as pellets). However, if the pellet contains more water than specified, hydrolysis occurs. The resin deteriorates and the strength and toughness of the molded product deteriorates. Further, the fluidity of the molten resin becomes excessive, so that overfilling occurs in the mold, and problems such as generation of burrs and shape defects occur. Alternatively, this may cause a so-called “silver stripe” in which a molded product has a poor gloss or a silver-white stripe on the surface.

  Therefore, it is necessary to dry the pellets supplied to the plastic molding machine to a predetermined content by using a pellet drying device called a hopper dryer. For example, in the case of nylon 66 in a packaged state, it is about 0.1 (%) at the time of opening, but when it is opened and left in the atmosphere for 3 to 4 hours, it normally absorbs moisture in the atmosphere and the amount of water is 0.3 to It becomes 0.5 (%). Therefore, in order to supply to a plastic molding machine, the moisture content must be dried to 0.1 (%) or less.

  The basic structure of a conventionally used pellet drying apparatus is that dry hot air is blown to a metal hopper dryer filled with pellets, and the pellets fed from the raw material inlet installed at the upper end of the hopper dryer are The inside of the hopper dryer is slowly lowered and dried to a predetermined moisture content while being discharged from the raw material discharge port at the lower end of the hopper dryer.

  The inventor previously heated and circulated the gas in a path passing through the inside of the hopper dryer in the above-described drying process, and injected nitrogen gas generated by a nitrogen gas generator into the circulation path. A drying method and a drying apparatus that can perform high-level drying with inexpensive equipment by discharging surplus gas from the middle of the circulation path have been proposed (see, for example, Patent Document 1). According to this technique, nitrogen gas has a very low moisture content compared to the atmosphere and is very dry, so that the pellets can be highly dried. In addition, since the oxygen concentration is gradually diluted by injecting nitrogen gas in the drying apparatus, there is an advantage that the oxidation of the pellet is suppressed. Further, since moisture is discharged together with the surplus gas from the middle of the circulation path, drying is further promoted. The hopper dryer retains the pellets therein until the pellets are sufficiently dried.

  Further, in the above hopper dryer, the inventor is configured such that the drying container is composed of a cylindrical accommodating portion that is vertically divided into two and a conical discharge portion that is provided downward from the accommodating portion. A heated air blower pipe for blowing heated air for heating the pellets and a heated air exhaust pipe for exhausting the pellets are fixed to the apparatus by penetrating through one divided body of the cylindrical housing part, and the cylindrical housing part Proposed that the other divided body is connected to the one divided body through a hinge so as to be freely opened and closed (see, for example, Patent Document 2). According to this technique, since the inside of the drying container can be opened without disconnecting any pipes or the like, there is an advantage that the inside of the drying container can be easily cleaned or inspected when switching the pellets.

Japanese Patent No. 3052082 JP 2001-009834 A

  However, in the drying apparatus described in Patent Document 1, nitrogen gas injected into the heating gas circulation path is generated by supplying compressed air to a nitrogen generator. For this reason, the moisture contained in the compressed air hinders the generation of high-purity nitrogen gas by the nitrogen generator, which in turn reduces the dehumidifying effect.

  In addition, when high-level drying is performed by injecting nitrogen gas into the circulation path as described above, the airtightness of the drying container is required. However, the cylindrical shape of the drying container as described in Patent Document 2 is required. In the structure in which the housing portion is divided into two vertically, it becomes a problem how to secure the sealing property of the divided surface. That is, in order to ensure airtightness, it is preferable to have a structure in which a resin sealing material that is easily elastically deformed is interposed between the divided surfaces. There is a problem that wear powder or the like may be mixed. In order to avoid mixing of wear powder and the like, for example, it is necessary to abut the divided surfaces and fix them with a clamp or the like. However, with this structure, it becomes difficult to obtain airtightness, and the thermal efficiency is lowered.

The present invention was made in view of the background art described above, that the aim is to provide a hopper dryer for Drying apparatus particulate plastic material which can be compared with the conventional obtain a higher thermal efficiency It is in.

In order to achieve such an object, the gist of the present invention is that the drying container for accommodating the granular plastic material supplied from the outlet pipe of the supply hopper provided on the upper cover is divided into two vertically. A cylindrical storage portion, and a conical discharge portion whose upper end is in close contact with the lower inner surface of the storage portion and whose diameter is reduced downward and a discharge port is provided at the lower end, are formed in the internal space of the drying container. A heating air blower pipe that blows heated air that heats the granular plastic material and a heated air exhaust pipe that exhausts the heated air penetrate through one divided body of the cylindrical housing and are fixed to the device, A hopper dryer for a granular plastic material drying device in which the other divided body of the cylindrical housing portion is connected to the one divided body through a hinge so as to be opened and closed, and (a) the conical discharge portion The upper end is an annular resin seal Together are brought into close contact with the lower inner surface of the tubular housing portion through, its upper edge is to cover the resin sealing material by being bent on the outer peripheral side.

According to the present invention, the upper end of the conical discharge portion is brought into close contact with the lower inner surface of the cylindrical housing portion via the annular resin seal material, and the upper end edge of the discharge portion is on the outer peripheral side. Since the resin sealing material is covered by being bent, the drying container is secured with air tightness by the resin sealing material without exposing the resin sealing material to the inside of the drying container. Therefore, it is possible to ensure the airtightness of the container while preventing the granular plastic material put into the dry container from touching the resin sealing material and mixing the wear powder, etc., so that the thermal efficiency is improved and the granular plastic material Can be efficiently dried.

Here, preferably, the hopper dryer can be applied to a method for drying a granular plastic material as follows. That is, by circulating a heated gas heated to a predetermined temperature through a path passing through the inside of the drying container, the granular plastic material charged from the inlet into the drying container is dried to a predetermined moisture amount and supplied to the plastic molding machine. A method for drying granular plastic material discharged from a discharge port, wherein (a) compressed air is dehumidified with a polymer membrane dryer and supplied to a nitrogen generator to generate nitrogen gas, A part of the heating gas containing the nitrogen gas is exhausted from an exhaust passage provided on the path by an amount corresponding to the injection amount while being injected into the path.
Preferably, the hopper dryer is applied to a drying apparatus for a granular plastic material as described below. That is, a granular plastic material drying apparatus for drying a granular plastic material to a predetermined moisture amount and supplying it to a plastic molding machine, (a) having an inlet for the granular plastic material in the upper portion and the lower portion thereof A drying container having a discharge port; (b) a gas circulation path formed by a path passing through the drying container; (c) a heating device and a blower for circulating heating gas through the gas circulation path; ) A nitrogen generator for injecting nitrogen gas into the gas circulation path; (e) a polymer membrane dryer for dehumidifying compressed air and supplying it to the nitrogen generator; and (f) the gas circulation. And an exhaust port for discharging excess heating gas from the passage.
According to such a drying method and drying apparatus, compressed air is dehumidified with a polymer membrane dryer and is supplied to the nitrogen generator. Therefore, the nitrogen generator generates high-purity nitrogen gas with extremely low moisture. Generated. Therefore, high purity and low moisture content nitrogen gas is injected into the heating gas circulation path, so the effect of nitrogen gas injection is further enhanced, that is, the drying efficiency is increased and the granular plastic material is dried more efficiently. .
In the drying method and the drying apparatus , the input port is provided in the upper part of the drying container, and the discharge port is provided in the lower part thereof.

Also, preferably, the compressed air supplied prior SL polymer film dryer are those having a pressure of 0.45 (MPa) or less. In this way, there is an advantage that compressed air having a pressure that can be stably supplied in the factory can be used.

Also, preferably, in the hopper dryer, the bisected cylindrical housing portion, division surface located on an opposite side is brought into close contact through the resin packing the connected division surface at the hinge In addition, a metal cover that covers the resin packing is provided on the inner peripheral side. In this way, the split surface of the cylindrical housing portion is hermetically closed via the resin packing, and the inner peripheral surface of the resin packing is covered with the metal cover and is not exposed in the housing portion. Airtightness can be secured while suppressing the mixing of wear powder and the like in the resin packing.

Also, preferably, in the hopper dryer, bisected the tubular housing part of the split body intended to cover through the heat-insulating layer on the outer circumferential side is attached respectively, it said hinge is attached to them cover ing. In this way, the housing portion does not directly touch the outside air, heat loss is reduced, and accidents such as an operator accidentally touching the heated housing portion to get burned are prevented.

  Preferably, the heating device is a heater provided between the blower and the drying container.

It is a figure explaining the structure of the drying apparatus of the granular plastic material of this invention. It is the perspective view which cut | disconnected a part of the state which opened the hopper dryer with which the drying apparatus of FIG. 1 was equipped. It is sectional drawing explaining the seal structure of the pellet storage cylinder and pellet discharge part in the hopper dryer of FIG. It is sectional drawing explaining the structure of the door packing part in the hopper dryer of FIG. It is a figure which shows the relationship between the drying time at the time of drying a granular plastic material using the drying apparatus of FIG. 1, and a moisture content with a comparative example.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a diagram for explaining the configuration of a drying apparatus 10 according to an embodiment of the present invention. An upper part of a hopper dryer 14 that accommodates undried pellets 12 is cylindrical and a lower part is constricted in a conical shape. Although not shown, there is an inlet for pellets 12 and an outlet 16 for pellets 12 is provided at the lower end. Further, a heated air blower pipe 18 that enters from the upper surface, hangs downward at the center, expands in a conical shape, and has a jet outlet on the entire surface is disposed inside the hopper dryer 14. In this embodiment, the pellet 12 corresponds to a granular plastic material, and the hopper dryer 14 corresponds to a drying container.

  The air blowing side of the blower 20 is connected to one end of a blower pipe 24 via a circulating air heating heater 22, and the tip of the blower pipe 24 is connected to the upper end of the heated air blower pipe 18. The circulating air heating heater 22 is controlled in air temperature by a temperature controller (not shown). One end of the circulation circuit 26 a is connected to the upper surface of the hopper dryer 14, and the other end of the circulation circuit 26 a is connected to the circulation filter 28, and the circulation gas discharged from the hopper dryer 14 flows into the circulation filter 28. . In the present embodiment, the circulating air heater 22 corresponds to a heating device.

  Most of the circulating gas purified by the circulation filter 28 circulates from the outlet 30a to the intake side of the blower 20 through the circulation circuit 26b. In this embodiment, a gas circulation path is formed by the blower pipe 24, the circulation circuit 26a, and the circulation circuit 26b. The polymer membrane dryer 32 takes in air pressurized to, for example, about 0.45 (MPa) from the compressed air inlet 34 and dehumidifies it, for example, at atmospheric pressure with a generation efficiency of dehumidified air of about 50 to 60 (%). Produces dry air with a dew point of about -40 (° C). The “dehumidification air generation efficiency” is the percentage of the outlet air flow rate relative to the inlet air flow rate of the polymer membrane dryer 32. For example, the inlet air flow rate is 176 (NL / min) and the outlet air flow rate is 90. In the case of (NL / min), the dehumidified air generation efficiency is 51 (%). The outlet air flow rate is determined according to the capacity of the hopper dryer 14, and the above value is, for example, the outlet air flow rate when the material charge is 100 (kg).

  The dry air generated by the polymer membrane dryer 32 is supplied to the nitrogen generator 36. Since the nitrogen generator 36 generates nitrogen and is connected to the air supply side of the blower 20 via the nitrogen supply circuit 38, the nitrogen generator 36 becomes excessive due to the injection of nitrogen gas from the other outlet 30b of the circulation filter 28. Gas is discharged. In this embodiment, the outlet 30b corresponds to the exhaust port. The excess gas discharged from the outlet 30b is sent to the discharge port 16 of the hopper dryer 14 by the excess gas circuit 40, and is used as a carrier gas when the pellets 12 are sent to the molding machine as necessary.

  According to the present embodiment, in the drying apparatus 10, the dry air dehumidified by the polymer membrane dryer 32 is supplied to the nitrogen generator 36 as described above, so that the processing efficiency by the nitrogen generator 36 is increased. That is, since the nitrogen purity is increased and the water content is further reduced, the nitrogen is supplied to the hopper dryer 14 via the nitrogen supply circuit 38 and the circulating air heater 22, so that the drying efficiency of the pellets 12 is improved. There is an advantage that can be increased. The outlet air flow rate of the polymer membrane dryer 32 is designed so that the amount of nitrogen gas generated by the nitrogen generator 36 is an appropriate amount corresponding to the capacity of the hopper dryer 14.

  FIG. 2 is a diagram for explaining the structure of the hopper dryer 14, and is a perspective view showing a cut-off portion at an intermediate portion in the vertical direction with the divided body on the open / close side of the divided pellet housing cylinder 42 opened. is there.

  In FIG. 2, the pellet receiving cylinder 42 is entirely cylindrical and is made of a metal material such as stainless steel, and is vertically divided into two on a plane passing through the cylindrical axis line. It is housed in box bodies 46a and 46b that form an octagon in plan view. A heated air blower pipe 18 and a heated air exhaust pipe 48 are provided through the upper surface of the box 46a on the side fixed to the machine base. The heated air exhaust pipe 48 is connected to the circulation circuit 26a. On the other hand, a pellet supply pipe 52 of a pellet supply hopper 50 is provided through the upper surface of the open / close side divided body 44b of the pellet storage cylinder. The pellet supply hopper 50 is provided with an air supply pipe 54a and an exhaust pipe 54b. The pellet 12 is carried into the pellet supply hopper 50 together with the air flowing through the air supply pipe 54a, and the pellet 12 separated from the air is the pellet supply hopper. The air blown in and remaining in the air 50 passes through a filter (not shown) and is exhausted from the exhaust pipe 54b. An opening / closing plate is provided at the lower end of the pellet supply pipe 52, and the opening / closing plate is opened / closed by a lever (not shown) so that the pellet 12 is supplied to the hopper dryer 14. In the present embodiment, the pellet accommodating cylinder 42 corresponds to a cylindrical accommodating portion, and the pellet supply pipe 52 corresponds to an inlet or outlet pipe.

  Furthermore, the heated air blower pipe 18 penetrating the upper surface of the box 46a has a central axis at the center of the heated air blower pipe 18 when the two divided bodies 44a and 44b are combined to form the pellet housing cylinder 42. Is provided with a bent portion 56. The tip of the heated air blower pipe 18 facing the conical pellet discharge portion 58 has a cone 18a whose diameter increases downward, and a cone whose diameter overlaps with the cone 18a and decreases in diameter downward. 18b, and a plurality of punch holes 18c pass through the lower cone 18b so that hot air from the heated air blower pipe 18 is blown out. Further, the discharge port 18d at the lower end of the conical body 18b under the heated air blower pipe 18 opens toward the discharge port 16 at the lower end of the inverted conical pellet discharge unit 58.

  The pellet discharge part 58 is made of a metal material like the pellet container 42, and the upper end of the pellet discharge part 58 is the side of the divided body 44a fixed to the machine base via an annular packing 60 (see FIG. 3 described later). The pellet discharge port 16 is open at the lower end, and the pellet discharge portion 58 is fixed to the machine base by a fixing plate 62 attached to the outer periphery thereof. The hot air blown by the heated air blower pipe 18 is blown out from a large number of punch holes 18c provided in the lower cone 18b, and is also blown out from the discharge port 18d at the front end that opens to face the pellet discharge port 16. The hot air discharged from the punch hole 18c and the discharge port 18d rises in the pellet housing cylinder 42 and is discharged from the heated air exhaust pipe 48.

  As shown in FIG. 3, the annular packing 60 has a triangular shape whose cross-sectional shape is an upward slope, and is fixed by welding or the like slightly below the upper end of the pellet discharge portion 58. It is supported from below by an annular packing receiver 64. Further, the upper end edge 66 of the pellet discharge portion 58 is slightly bent on the outer peripheral side, and substantially covers the packing 60 so that it is not exposed to the internal space of the hopper dryer 14. Therefore, the pellet 12 does not contact the packing 60.

  The packing 60 is made of, for example, silicone rubber. Silicone has a characteristic of maintaining high airtightness in the hopper dryer 14 at a high temperature. However, it is known that when silicone is mixed in a resin, the coating of a product that requires a coating process becomes poor. Therefore, it is desirable that the drying apparatus 10 for drying plastic pellets has a structure in which the pellets 12 do not touch the silicone. According to the present embodiment, since the packing 60 is covered with the upper edge 66 of the pellet discharge portion 58 as described above, the contact of the pellets 12 with the airtightness is ensured and the silicone is preferably mixed into the resin. It is suppressed. In this embodiment, the packing 60 corresponds to a resin sealing material.

  Returning to FIG. 2, the fixed box body 46a and the open / close box body 46b are connected to each other by a plurality of hinges 68 provided at appropriate positions. In addition, band-like packings 70 (see FIG. 4 described later) extending along the vertical direction are attached to the split surfaces 44c and 44d of the split body 44 on both the connection side and the open / close side to open and close. By closing the box 46b on the side, the two divided bodies 44a and 44b are combined to form the pellet housing cylinder 42. At this time, the fixed box body 46a and the opened / closed box body 46b are fastened to each other by a plurality of latches 72 provided at appropriate positions. At this time, the upper end portion of the pellet discharge portion 58 is pressure-bonded to the open / close-side divided body 44b through the packing 60.

  The packing 70 is made of silicone resin, and as shown in FIG. 4, an enlarged horizontal section of the vicinity of the dividing surfaces 44 c and 44 d shows a metal packing fixed to the dividing surface 44 c of the divided body 44 a extending along the vertical direction. It is fixed by a bolt 76 via a plate 74. The packing fixing plate 74 has a substantially L-shaped cross section, and includes a fixing portion 74a positioned on the dividing surface 44c and a packing cover portion 74b extending substantially along the inner peripheral surfaces of the dividing bodies 44a and 44b. Become. The packing cover portion 74b has a stepped portion 74c that is slightly bent at an intermediate portion, and the stepped portion 74c is brought into contact with the divided surface 44d of the divided body 44b. In this embodiment, the packing 70 corresponds to a resin packing, and the packing cover portion 74b corresponds to a metal cover.

  The packing 70 is called a saddle type, and includes a semicircular elastic portion 70 a and a fixing portion 70 b fixed to the packing fixing plate 74. The figure shows a state in which the elastic portion 70a is slightly crushed by being pressed against the dividing surface 44d. The fixing portion 70b is fixed by being clamped between the fixing portion 74a of the packing fixing plate 74 and the flat packing fixing plate 78.

  With this configuration, according to this embodiment, the packing 70 is elastically crushed to ensure airtightness, and the packing 70 is covered by the packing cover portion 74b of the packing fixing plate 74. Therefore, since it is not exposed to the inner surface of the pellet housing cylinder 42, there is no problem that the wear powder is mixed with the packing 70 when the pellet 12 is dried.

  Note that the stepped portion 74c is for preventing excessive closing when the divided body 44 is closed, and thereby, airtight failure due to one piece of the packing 70 is suppressed.

  Test results obtained by subjecting the pellets 12 to a drying process using the drying apparatus 10 configured as described above will be described. In the drying test, pellets 12 made of polybutylene terephthalate (PBT) were used. The drying temperature was set to 120 (° C.), 12.5 (kg) pellets 12 were subjected to a drying treatment, and then the moisture content of the pellets 12 was measured. The measurement results are shown in Table 1 and FIG. 5 together with the results of the comparative example. In the comparative example, the pellet 12 is similarly dried using a drying device configured in the same manner as the drying device 10 except that the polymer membrane dryer 32 is not provided. The moisture content was measured using a Karl Fischer moisture meter (MKC-210) with a moisture vaporizer (ADP-351) manufactured by Kyoto Electronics Industry Co., Ltd., at a vaporization temperature of 180 (° C) for 30 minutes. went. The air temperature during the drying treatment is 25 (° C.) in the example and 23 (° C.) in the comparative example, and the air temperature during the moisture content measurement is 25 (° C.) in the example and 24 (° C.) in the comparative example. is there.

  As shown in Table 1 and FIG. 5, according to the drying apparatus 10 of the present example, the moisture content decreases to 0.0092 (%) in one hour of drying time. That is, the time required for drying to a moisture content of 0.01 (%) or less is only 1 hour. On the other hand, in the drying apparatus of the comparative example that does not include the polymer membrane dryer 32, the moisture content remains at 0.0398 (%) in the drying time of 1 hour.

  In any of the examples and comparative examples, the moisture content tends to be further reduced when the drying time is increased. In the examples, drying can be performed to an extremely low moisture content of 0.0077 (%) in 3 hours and 0.0050 (%) in 4 hours. On the other hand, in the comparative example, it is 0.0213 (%) in 2 hours, 0.0075 (%) in 3 hours, and 0.0051 (%) in 4 hours. That is, in order to obtain a moisture content of 0.01 (%) or less in the comparative example, a drying time of 3 hours or more is required. In the embodiment, as described above, since the drying time is 1 hour, it is apparent that the drying efficiency is remarkably improved by the drying apparatus 10 provided with the polymer membrane dryer 32.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

10: Drying device, 12: Pellet, 14: Hopper dryer, 16: Discharge port, 18: Heated air blow pipe, 18a: Cone, 18b: Cone, 18c: Punch hole, 18d: Discharge port, 20: Blower, 22: Heater for circulating air heating, 24: Blow pipe, 26a: Circulating circuit, 26b: Circulating circuit, 28: Circulating filter, 30a: Outlet, 30b: Outlet, 32: Polymer membrane dryer, 34: Compressed air inlet 36: Nitrogen generator, 38: Nitrogen supply circuit, 40: Excess gas circuit, 42: Pellet container, 44a and 44b: Divided bodies, 44c, 44d: Divided surfaces, 46a and 46b: Box bodies, 48: Heated air Exhaust pipe, 50: pellet supply hopper, 52: pellet supply pipe, 54a: air supply pipe, 54b: exhaust pipe, 56: bent part, 58: pellet discharge part, 60: packing, 62: fixing plate, 6 : Packing receiver, 66: upper edge, 68: hinge, 70: packing, 70a: elastic part, 70b: fixing part, 72: latch, 74: packing fixing plate, 74a: fixing part, 74b: packing cover part, 74c: Stepped part, 76: bolt, 78: packing fixing plate

Claims (2)

A cylindrical container divided vertically into a drying container for accommodating the granular plastic material supplied from the outlet pipe of the supply hopper provided on the upper surface lid, and the upper end is in close contact with the lower inner surface of the container A heated air blower pipe that blows heated air that heats the granular plastic material into the internal space of the drying container, and is configured from a conical discharge part that is reduced in diameter toward the lower side and provided with a discharge port at the lower end. A heated air exhaust pipe for exhausting the heated air is fixed to the apparatus by penetrating the one divided body of the cylindrical housing portion, and the other divided body of the cylindrical housing portion is fixed to the one divided body. A hopper dryer for a granular plastic material drying device connected to a hinge via a hinge,
The upper end of the conical discharge part is brought into close contact with the lower inner surface of the cylindrical housing part via an annular resin sealing material, and the upper edge of the upper part is bent to the outer peripheral side to make the resin A hopper dryer for a granular plastic material drying apparatus, characterized by covering a sealing material. The two-divided cylindrical housing has a metal cover that covers the resin packing while a divided surface located on the opposite side of the divided surface connected by the hinge is brought into close contact with the resin packing. The hopper dryer for a granular plastic material drying apparatus according to claim 1 , wherein the hopper dryer is provided on the inner peripheral side.

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