JP2008215673A - Screw conveyor type treatment device and heat treatment method for granular material using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw conveyor type treatment device free from problems such that a device is clogged or LCP (liquid crystal polyester) pellet can not be removed as it bunches up together during drying or consolidates when left as it is after drying, in drying a material by a screw conveyor, for example, in drying the LCP pellet. <P>SOLUTION: In this screw conveyor-type treatment device 1, a cooling zone is provided behind a heating zone in a hollow screw conveyor 3 having a spiral structure on its inner wall, and a length of the cooling zone is 0.5L-2L when a length of the heating zone is L. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a continuous heating apparatus and a heat treatment method for a granular material using the same. More specifically, the present invention relates to a continuous heating apparatus suitable for drying granular materials such as thermoplastic resin powders and pellets and a method for producing the granular materials.

  When kneading or molding a thermoplastic resin such as a polyester resin, it is usually heated and melted. At this time, if the heat treatment is carried out with moisture brought in, the physical properties may be deteriorated due to hydrolysis or the like, and therefore it is necessary to dry as a pretreatment.

  However, when drying by heating, there is a problem that the surface of the thermoplastic resin softens and becomes dango-like when it is dried at a high temperature. The technique of drying while fluidizing the material with a stirring blade has been taken.

  However, if the resin is dried at a temperature at which it does not soften, it takes a long processing time to dry to the desired moisture content, and further, there are problems such as generation of powder from the material when a stirring blade is used. In order to solve this problem, Patent Document 1 proposes an apparatus and a method for drying a material while stirring it with a hollow screw conveyor.

However, when the material is dried by the screw conveyor, for example, when the LCP pellets are dried, when the heating temperature is high, the pellets are solidified when in a dango state during drying, or when the pellets that have become hot are left after drying. There were problems such as clogging of the device and inability to extract.
Special table 2000-50785 gazette

  An object of the present invention is to provide a screw conveyor type processing apparatus having no problems in the prior art as described above and a method for heat-treating a granular material using the processing apparatus.

  The present inventors have intensively studied to solve these problems, and have arrived at the screw conveyor type processing apparatus of the present invention and a method for drying a granular material using the screw conveyor type processing apparatus.

That is, the screw conveyor type processing apparatus of the present invention has the following configuration (1).
(1) In a hollow screw conveyor having a spiral structure on the inner wall, a cooling zone is provided after the heating zone, and when the length of the heating zone is L, the length of the cooling zone is 0.5L to 2L. A screw conveyor type processing apparatus.

Moreover, in the screw conveyor type processing apparatus of the present invention, more specifically, preferably, the screw conveyor type processing apparatus has any one of the following configurations (2) to (7).
(2) The screw according to (1), wherein a heating unit is installed in the heating zone, and the heating unit is at least one selected from a near infrared heater, a microwave generator, and a heated gas generator. Conveyor type processing equipment.
(3) The screw conveyor type processing apparatus according to (1) or (2), wherein a heating means is installed in the heating zone, and the heating means is located in a central region of the rotational diameter of the screw conveyor.
(4) The screw conveyor type processing apparatus according to any one of (1) to (3), wherein the cooling zone includes a cooling gas supply unit.
(5) The screw conveyor type processing device according to any one of (1) to (4), further comprising a device for cooling an outer peripheral portion of the cooling zone.
(6) The screw conveyor type processing apparatus according to any one of (1) to (5), wherein a baffle plate lower than a height of a spiral wall is provided between the spiral structures.
(7) The screw conveyor type processing apparatus according to (6), wherein there are 3 to 20 baffles per spiral perimeter.

Moreover, the heat processing method of the granular material of this invention which achieves the objective mentioned above has the structure of following (8).
(8) A heat treatment method for a granular material, characterized in that the granular material is supplied to the screw conveyor type processing apparatus according to any one of (1) to (7) to perform heat treatment.

More specifically, the heat treatment method for a granular material of the present invention that achieves the above-described object has any one of the following configurations (9) to (12).
(9) The method for heat-treating a granular material according to (8), wherein the granular material is a thermoplastic resin powder or a pellet.
(10) The thermoplastic resin is nylon, polyphenylene sulfide (hereinafter referred to as PPS), polybutylene terephthalate (hereinafter referred to as PBT), polyethylene terephthalate (hereinafter referred to as PET), acrylonitrile-butadiene-styrene copolymer (hereinafter referred to as ABS). ), Polypropylene (hereinafter referred to as PP), polycarbonate (hereinafter referred to as PC), and liquid crystal polyester resin (hereinafter referred to as LCP). Heat treatment method.
(11) The heat treatment of the granular material according to any one of (8) to (10) above, wherein the cooling gas supplied in the cooling zone is a gas dried to a dew point lower than the surface temperature of the granular material. Method.
(12) The method for heat-treating a granular material according to any one of the above (9) to (11), wherein the outlet temperature of the granular material is Tg + 80 ° C. or lower of the thermoplastic resin.

  If the screw conveyor type processing apparatus of the present invention and the heat treatment method for granular materials of the present invention are used, it is possible to produce granular materials such as liquid crystal polyester resin powders and pellets in a short period of time without solidifying them. The heat treatment can be performed with good properties.

  Hereinafter, embodiments of the screw conveyor type processing apparatus of the present invention and the granular material heat treatment method of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic explanatory view showing the configuration of an embodiment of the screw conveyor type processing apparatus of the present invention, and is a cross-sectional view in the horizontal direction with respect to the conveying direction. FIG. 2 is a cross-sectional view of the screw conveyor type processing apparatus shown in FIG. 1 in a direction perpendicular to the conveying direction.

  1 and 2, the screw conveyor type processing apparatus 1 of the present invention includes, for example, a granular material supply device 2, a hollow screw conveyor 3, a baffle plate 4, a heating device 5, and a discharge hopper 6. "Baffle" is a film in the middle of the adjacent spiral wall, like a waterfowl's foot web, and imparts conveying force by pushing the granular material. . In addition, this invention is not limited only to these examples.

  In the screw type conveyor 3 of the present invention, the granular material before drying is put into the hollow screw conveyor 3 installed horizontally with respect to the ground from the granular material feeder 1, and the discharge hopper 6 is rotated by the rotation of the hollow screw conveyor. It is conveyed toward. The granular material being conveyed is heated by the heating device 5 in the heating zone shown on the left side of FIG. 1 and cooled in the cooling zone.

  The apparatus of the present invention has a cooling zone after the heating zone, and when the length of the heating zone is L, the length of the cooling zone is 0.5L to 2L. Here, when the length of the cooling zone is less than 0.5 L, the cooling of the pellets is not sufficient, and the pellets are fused, and when the length is longer than 2 L, the apparatus becomes large. It is not preferable.

  Here, the “heating zone” refers to a region in the screw conveyor 3 where the granular material is heated by the heating device, and the length of the heating zone refers to a region in the screw conveyor 3 where the heating device is installed. Is the length of When the heating device is installed intermittently, the length from the first heating device to the last heating device is the length of the heating zone.

  The “cooling zone” refers to an area in the screw conveyor 3 where the granular material is not heated by the heating device. The length of the cooling zone refers to the portion of the screw conveyor 3 where the heating device is installed. Is the length of the area where the rear heating device is not installed. Specifically, it is the length from the end of the rear part of the last heating device until the granular material is conveyed to the discharge hopper 6 by the screw conveyor 3.

Hereinafter, the embodiment of the present invention shown in FIG. 1 will be described.
The granular material feeder 2 may be any material as long as it can quantitatively supply the granular material, and examples thereof include a weight-type screw feeder, a positive displacement screw feeder, and a rotary valve.

  The hollow screw conveyor 3 in the present invention is composed of a hollow cylinder 7 and a spiral wall 8 attached to the inner wall of the cylinder, and if necessary, a baffle plate 4 attached perpendicularly to the spiral wall. Consists of. If the diameter D of the hollow cylinder 7, the height H of the spiral wall 8 and the pitch distance B of the spiral wall are determined by the type of the granular material, the processing amount and the processing time, that is, the rotational speed of the hollow screw conveyor 3. Good. If the filling amount of the granular material between the spirals is too small, the granular material slides in the cylinder, is not stirred, and uniform heat treatment cannot be performed. Therefore, a filling amount larger than 50% and smaller than 100% with respect to the maximum filling amount It is preferable to do so. The material is not particularly limited as long as the material can withstand the temperature during the heat treatment, but stainless steel is preferable in order to prevent rust and the like from being mixed into the granular material. Moreover, since friction always occurs between the granular material surface and the hollow screw conveyor 3, it is preferable that the inner wall of the hollow screw conveyor 3 is subjected to wear resistance treatment.

  The baffle plate 4 in the present invention is attached to the inner wall of the hollow cylinder between the spiral walls 8 of the hollow screw conveyor 3. The angle θ of the baffle plate with respect to the tangent to the hollow cylinder 7 shown in FIG. 2 should be larger than the angle of repose of the granular material when the diameter connecting the baffle plate installation position and the center of the cylinder is horizontal to the ground. If θ is too large, the granular material enters and stays between the cylinder and the baffle plate. Therefore, it is preferable that the angle of repose of the granular material is smaller than θ <90 °. The height h of the baffle plate should be lower than that of the spiral wall 8, but if it is too low, the granular material cannot be efficiently stirred, and if it is too high, the granular material will get over the spiral wall and cause a short pass. It is preferable to set it as 0.5-0.8H. The width b of the baffle plate should be smaller than the pitch distance B of the spiral wall, but if it is too small, the granular material cannot be efficiently stirred, and if it is too large, the granular material will stay between the spiral wall and the baffle. Therefore, about 0.5B ≦ b ≦ 0.8B is preferable. A preferable number of baffle plates is 3 to 20 per spiral. The baffle may be made of any material that can withstand the temperature during heat treatment and the weight of the granular material, but stainless steel is preferable in order to prevent rust and the like from entering the granular material. Moreover, since friction always occurs between the granular material surface and the hollow screw conveyor 3, it is preferable that the inner wall of the hollow screw conveyor 3 is subjected to wear resistance treatment.

  The heating device 5 in the heating zone of the present invention may be any device that can heat the granular material, and a hollow near-infrared heater, a microwave generator, a heated gas, etc. is fried, but thermoplasticity generally having poor heat conduction. When heat-treating the resin, it is preferable to use near infrared rays that can be heat-treated to a high temperature in a short time.

  In the present invention, preferably, a heating means is installed in the heating zone, and the heating means is in the center region of the rotational diameter of the screw conveyor, which is efficiently uniform with respect to the granular material in the apparatus. This is to give heat to the. Here, the “central area of the rotational diameter of the screw conveyor” may be an area along the central axis of the screw conveyor, and the distance of the granular material from the outside of the heating device 5 is not particularly specified.

  On the other hand, the cooling in the cooling zone of the present invention may be natural cooling in the atmosphere, or air that has been dehumidified or cooled is blown onto the granular material, or a device that cools the outer periphery of the hollow cylinder 7 is attached. In addition, cooling may be performed by individual methods, or several cooling methods may be combined. The cooling zone is preferably provided with a gas supply, and the gas is preferably dehumidified air. In that case, the gas supplied in the cooling zone is preferably a gas dried to a dew point lower than the surface temperature of the granular material. This is to prevent the granular material dried in the heating zone from absorbing water again.

  Moreover, in this invention, it is preferable that the temperature of the granular material in the exit of a screw conveyor is a temperature which the granular material after heat processing does not melt | fuse. Specifically, it is preferable that the granular material is a thermoplastic resin (Tg (glass transition temperature) + 80 ° C.) or less. By setting it in this range, it is preferable because the granular material can be prevented from sticking after being discharged.

  In the present invention, the thermoplastic resin to be treated is preferably nylon, polyphenylene sulfide (hereinafter referred to as PPS), polybutylene terephthalate (hereinafter referred to as PBT), polyethylene terephthalate (hereinafter referred to as PET), acrylonitrile-butadiene. -A styrene copolymer (hereinafter referred to as ABS), polypropylene (hereinafter referred to as PP), polycarbonate (hereinafter referred to as PC), and liquid crystal polyester resin (hereinafter referred to as LCP). Since these thermoplastic resins are prone to undesirable phenomena such as hydrolysis due to the presence of moisture in processes involving heating and melting such as molding and compounding, the moisture is dried before being subjected to these processes. It is preferable, and it becomes a dango state by drying by heating, or pellets are easily fixed. When such a thermoplastic resin is dried, the treatment can be effectively performed by employing the present invention.

Next, the effects of the present invention will be specifically described by way of examples.
In this example, LCP resin pellets were dried using a near infrared high-speed dryer IRD-B-140 / 170-108 (hereinafter referred to as IRD dryer) manufactured by KREYENBORG. In this example, the LCP resin chip was evaluated for moisture before drying, moisture after drying, chip temperature after heat treatment, chip temperature at the exit of the hollow screw conveyor, and pellet fusion. The shape, implementation conditions, and evaluation method of the IRD dryer will be described below.

(1) IRD dryer Hollow cylinder 7 diameter D = 1400 mm, hollow cylinder length = 2700 mm, spiral wall 8 height H = 150 mm, pitch distance B = 120 mm, number of baffle plates = 10 baffle plate angles An apparatus having a 45 ° baffle width b = 60 mm was used.

  As the heating device in this example, a near-infrared lamp (manufactured by 42INVENTIONS) was used, and cooling was performed in the atmosphere.

(2) Pellet characteristics The liquid crystal polyester resin pellets used are as follows.
Material: LCP pellet (Toray Industries, Inc., Siberus L301E)
Glass transition temperature: 80 ° C
Melting point: 327 ° C
Angle of repose: 42 °

(3) Implementation conditions Test conditions are as follows.
Moisture before drying: 1100ppm
Pellet flow rate: 191 kg / h
Heating zone distance: 1800 mm (condition 1), 2700 mm (condition 2)
Cooling zone distance: 900 mm (condition 1), 0 mm (condition 2)
Infrared lamp output: 57.6kW

(4) Evaluation method The evaluation method is as follows.
Moisture measurement: Karl Fischer method Pellet temperature measurement: Measured using a surface thermometer for semi-solids (manufactured by Anritsu Keiki).
Pellet fusion: Pellet after heat treatment was allowed to stand in hopper 9 (body size part φ900 mm, lower cone angle 60 °, lower outlet port diameter φ80 mm) installed at a distance of 20 m from the discharge hopper shown in FIG. Judgment was made based on whether or not the hopper could be removed.

(5) Implementation conditions and results Table 1 shows the implementation conditions and results. In condition 1, the heating zone length according to the present invention is 1800 mm and the cooling zone length is 900 mm (cooling zone length = 0.5 L), and in condition 2, the heating zone length is a comparative example. The length of the cooling zone was 2700 mm and the length was 0 mm (no cooling zone).

  In condition 1 (the present invention) and condition 2 (comparative example), each was heat-treated continuously for 1 hour, blown to the hopper 9, and it was confirmed whether it could be extracted from the hopper after 1 hour from the start of the treatment.

  As a result, it was confirmed that extraction from the hopper was possible under condition 1 of the present invention, whereas extraction from the hopper was impossible under condition 2 of the comparative example.

It is a horizontal direction cross-sectional view for demonstrating the structure of the screw conveyor type processing apparatus of this invention, and is sectional drawing of a horizontal direction with respect to a conveyance direction. It is a cross-sectional view of the direction perpendicular to the axial direction (conveyance direction) for explaining the structure of the screw conveyor type processing apparatus of the present invention. In the Example, it is the schematic which showed the discharge | emission hopper used for performing evaluation regarding pellet fusion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw conveyor type processing apparatus 2 Granule supply apparatus 3 Hollow screw conveyor 4 Baffle plate 5 Heating apparatus 6 Discharge hopper 7 Hollow cylinder 8 Spiral wall 9 Hopper

Claims (12)

  In a hollow screw conveyor having a spiral structure on the inner wall, a cooling zone is provided after the heating zone, and when the length of the heating zone is L, the length of the cooling zone is 0.5 L to 2 L. A screw conveyor type processing apparatus.   The screw conveyor type processing apparatus according to claim 1, wherein a heating means is installed in the heating zone, and the heating means is at least one selected from a near infrared heater, a microwave generator, and a heated gas generator.   The screw conveyor type processing apparatus according to claim 1 or 2, wherein a heating means is installed in the heating zone, and the heating means is in a central region of a rotation diameter of the screw conveyor.   The screw conveyor type processing apparatus according to any one of claims 1 to 3, wherein a cooling gas supply unit is provided in the cooling zone.   The screw conveyor type processing apparatus according to any one of claims 1 to 4, further comprising an apparatus for cooling an outer peripheral portion of the cooling zone.   The screw conveyor type processing apparatus according to any one of claims 1 to 5, wherein a baffle plate lower than a height of a spiral wall is provided between the spiral structures.   The screw conveyor type processing apparatus according to claim 6, wherein there are 3 to 20 baffles per spiral perimeter.   A heat treatment method for a granular material, characterized in that the granular material is supplied to the screw conveyor type processing apparatus according to any one of claims 1 to 7 for heat treatment.   The method for heat-treating a granular material according to claim 8, wherein the granular material is a powder or a pellet of a thermoplastic resin.   The thermoplastic resin is at least one selected from nylon, polyphenylene sulfide, polybutylene terephthalate, polyethylene terephthalate, acrylonitrile-butadiene-styrene copolymer, polypropylene, polycarbonate, and liquid crystal polyester resin. The method for heat-treating the granular material according to 9.   The method for heat-treating a granular material according to any one of claims 8 to 10, wherein the cooling gas supplied in the cooling zone is a gas dried to a dew point lower than the surface temperature of the granular material.   The method for heat-treating a granular material according to any one of claims 9 to 11, wherein the temperature of the granular material at the outlet position of the screw conveyor type processing apparatus is (Tg + 80 of the thermoplastic resin) ° C or less. .

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