JP2003311738A - Continuous drying method for pellets - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a continuous drying method for pellets making the shape stability of pellets comprising a synthetic resin compound excellent, high in drying efficiency and reduced in the irregularity of a drying degree at every drying lot. <P>SOLUTION: In the continuous drying method for pellets, a strand comprising the synthetic resin compound continuously extruded from a continuous extrusion molding machine while kneaded is fed to a watering hot-cutting unit to be cooled, cut and granulated to form pellets. Next, these pellets are dehydrated in a centrifugal dehydrator and dried in a dryer into which drying air is sent. Cooling water used in the watering hot-cutting unit is warm water regulated to a definite temperature. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a continuous drying method for pellets. More specifically, the present invention relates to a method for continuously drying synthetic resin compound pellets, which is an insulating coating material for insulated wires.

[0002]

2. Description of the Related Art Generally, an insulated wire is manufactured by extrusion-coating a conductor with an insulating material, for example, a rubber insulating material, a synthetic resin insulating material or the like, using an extruder.

Among these, the synthetic resin insulating material includes a synthetic resin pellet purchased from a synthetic resin maker and extruded as it is by an extruder, and a synthetic resin pellet purchased from a synthetic resin maker. In some cases, synthetic resin compound pellets obtained by kneading and pelletizing an antioxidant and the like are extrusion-coated with an extruder.

FIG. 3 is a partially omitted front view showing a conventional continuous drying method of pellets.

In FIG. 3, reference numeral 10 denotes a continuous extrusion molding machine, and 11
Is a drive motor, 12 is a drive shaft, 13 is a speed change mechanism, 14 is a synthetic resin compound supply hopper, 15 is a screw, 16 is an extrusion head, 20 is a watering hot cut unit, 30 is a cooling water supply mechanism, and 32 is water supply. Tank, 33 is water supply pump, 35 is water supply pipe, 40 is granulated pellet supply pipe, 50 is centrifugal dehydrator, 51 is dehydrated pellet supply pipe, 52 is dehydrated pellet delivery hopper, 53
Is a constant flow rate vibration device, 54 is a constant flow rate pellet supply pipe,
60 is a circulation type dryer, 61 is a constant flow rate pellet supply hopper, 62 is a dry hopper, 63 is a constant flow rate pellet suction rotary valve, 64 is a dry pellet delivery rotary valve, 70 is a dry air supply unit, 71 is dry air It is a supply pipe.

That is, in the conventional pellet continuous drying method, first, the drive motor 11 of the continuous extrusion molding machine 10 is turned on, and thereby the screw 15 is rotated via the drive shaft 12 and the speed change mechanism 13.

Next, while the screw 15 of the continuous extrusion molding machine 10 is thus rotated, a synthetic resin compound, for example, a halogen-free flame-retardant polyolefin compound is charged into the synthetic resin compound supply hopper 14. The halogen-free flame-retardant polyolefin compound charged here is kneaded by a screw 15, and then extruded as a flame-retardant polyolefin compound strand from an extrusion head 16.

Next, the flame-retardant polyolefin compound strands extruded in this way are sent to the watering hot-cut unit 20, where they are cooled by the cooling water sent from the cooling water supply mechanism 30, and then pelletized by a cutter. It is cut and granulated into flame-retardant polyolefin compound pellets.

Here, the cooling water supply mechanism 30 comprises a water supply tank 32, a water supply pump 33, and a water supply pipe 35.

A large amount of cooling water adheres to the flame-retardant polyolefin compound pellets sent from the watering hot cut unit 20 to the granulated pellet supply pipe 40.

Then, the flame-retardant polyolefin compound pellets sent out to the granulated pellet supply pipe 40 are sent to the centrifugal dehydrator 50, and the centrifugal dehydrator 50.
Is dehydrated while being spirally blown up from the bottom to the top. The water dehydrated here can be drained through a drain pipe on the bottom surface of the centrifugal dehydrator 50 (not shown).

Next, the flame-retardant polyolefin compound pellets centrifugally dehydrated in this way are sent to a constant flow rate vibrating device 53 through a dehydrated pellet supply pipe 51 and a dehydrated pellet delivery hopper 52, where they are made to have a constant flow rate. It

Next, when the constant flow rate pellet suction rotary valve 63 of the circulation type dryer 60 is opened, the constant flow rate flame-retardant polyolefin compound pellets are made into the constant flow rate pellet supply pipe 54 and the constant flow rate pellet supply hopper. And 61 into the drying hopper 62 of the circulation type dryer 60.

Next, the constant flow rate flame-retardant polyolefin compound pellets sent into the dry hopper 62 are mixed with the dry air sent from the dry air supply unit 70 into the dry hopper 62 through the dry air supply pipe 71. The admixtures allow the flame-retardant polyolefin compound pellets to dry.

FIG. 4 is an explanatory view of the enlarged function of the main part of FIG.

In FIG. 4, 60 is a circulation type dryer, 61 is a constant flow rate pellet feeding hopper, 62 is a drying hopper,
63 is a constant flow rate pellet suction rotary valve, 64 is a dry pellet delivery rotary valve, 70 is a dry air supply unit, 71 is a dry air supply pipe, 74 is an air cooler, 75 is an adsorption rotor, 76 is a first moisture removal pipe,
Reference numeral 77 is a second water removal pipe.

That is, the flame-retardant polyolefin compound pellets of which the constant flow rate is made constant by the constant flow rate vibrating device 53 of FIG. 3 are the constant flow rate pellets when the constant flow rate pellet suction rotary valve 63 of the circulation dryer 60 is opened. It is sent into the drying hopper 62 of the circulation type dryer 60 via the supply hopper 61. Here, the flame-retardant polyolefin compound pellets fed from the upper part inside the dry hopper 62 contain water, and the water is supplied from the dry air supply unit 70 through the dry air supply pipe 71 to the inner bottom part of the dry hopper 62. It is extruded by the dry air fed into it, whereby the flame-retardant polyolefin compound pellets are dried. The moisture generated in this drying process is sent to the air cooler 74 and the adsorption rotor 75 through the first moisture removal pipe 76 and the second moisture removal pipe 77, and the moisture is adsorbed by the adsorption rotor 75 there. There is.

Here, the drying time of the flame-retardant polyolefin compound pellets in the drying hopper 62 depends on the rotary speed of the constant flow rate pellet suction rotary valve 63 and the dry pellet delivery rotary valve 64.
It can be controlled as appropriate by the difference in rotation from the number of rotations of.

Next, the flame-retardant polyolefin compound pellets dried here are sent out from a dry pellet sending rotary valve 64 into a storage container (not shown),
It is then sealed and stored.

[0020]

As described above, in the conventional continuous drying method of pellets, the water generated during the drying process of the flame-retardant polyolefin compound pellets is
It is sent out to the air cooler 74 through the water removal pipe 76 and the second water removal pipe 77, and then the adsorption rotor 7
5 is used for adsorption.

However, when a large amount of water is generated during the drying process of the flame-retardant polyolefin compound pellets, it may exceed the limit of adsorption by the adsorption rotor 75. When water exceeds the limit that can be adsorbed by the adsorption rotor 75, the water overflowing from the adsorption rotor 75 is absorbed by the air cooler 74 and the first water removal pipe 7.
6 and the second moisture removal pipe 77, the drying hopper 62.
It will flow back inward. As a result, the drying operation is likely to be unstable, and the dryness of the obtained flame-retardant polyolefin compound pellets greatly varies. In addition, this conventional continuous drying method of pellets has the drawback that the service life of the adsorption rotor 75 is short and the cooling cost thereof is high.

Further, the conventional continuous pellet drying method has the following problems.

(1) The shape of the synthetic resin compound strand, which is an intermediate product of the flame-retardant polyolefin compound pellet, is the watering hot cut unit 2
Since the temperature of the cooling water sent to 0 fluctuates, there was a problem that it greatly fluctuated.

(2) Since the shape of the synthetic resin compound strand of the intermediate product varies in this way, there is a problem that the shape of the flame-retardant polyolefin compound pellet obtained by cutting it also varies greatly depending on the production lot.

(3) Since the water temperature of the cooling water changes,
There was a problem that the drainage of the synthetic resin compound strand of the intermediate product also varied.

That is, in the conventional continuous drying method of pellets, as shown in FIG. 4, the drying rises quickly, but the half-way drying operation is unstable, and the dryness of the flame-retardant polyolefin compound pellets is large between lots. There are problems such as variations, short life of the adsorption rotor, and increased cooling cost.

The present invention has been made in view of the above points, and the purpose thereof is to solve the above-mentioned drawbacks of the prior art, the shape stability of synthetic resin compound pellets is excellent, and the drying efficiency thereof is also excellent. It is an object of the present invention to provide a continuous drying method of pellets, which has a high price and can reduce the variation in the dryness between the drying lots.

[0028]

Means for Solving the Problems The gist of the present invention is that a synthetic resin mixture is continuously supplied from a synthetic resin compound supply hopper of a continuous extrusion molding machine and kneaded and extruded by the continuous extrusion molding machine. Synthetic resin compound strands, then send the synthetic resin compound strands into a watering hot cut unit and spray cooling water to cool and then cut the cooled synthetic resin compound strands to form pellets,
Next, the pellets are sent to a centrifugal dehydrator for dehydration, and then a constant flow rate vibrating device is used to obtain a constant flow rate, and then the constant flow rate pellets are sent into a drying hopper of a dryer to which dry air is being sent. In the continuous drying method of pellets to be dried, the cooling water used in the watering hot cut unit is hot water whose temperature is adjusted to a constant temperature.

Here, the water temperature of the hot water is a temperature at which the synthetic resin compound strand can be cut into pellets and the pellets obtained by the cutting can maintain an appropriate preheating temperature in the centrifugal dehydrator in the next step. preferable.

In the present invention, the dry air sent into the drying hopper of the dryer is preferably heated dry air heated to a constant temperature.

As the dryer used in the present invention, a one-pass type circulation dryer is preferable.

That is, the conventional continuous drying method for pellets has a drawback that the drying start-up speed is slow, but the continuous drying method for pellets of the present invention controls the water film temperature during watering hot cut to a constant temperature. However, the warm water film is sprayed with the constant temperature water, and the synthetic resin compound pellets can be preheated by the warm water film, so that the dehydration can be effectively performed, and as a result, the drying start-up speed can be increased.

The synthetic resin compound to be used in the continuous drying method of the pellets of the present invention may be one that is industrially used, such as a non-halogen flame-retardant polyolefin compound or a soft vinyl chloride resin compound as shown below. is there. [Example of non-halogen flame-retardant polyolefin compound] Polyolefin 100 parts by weight Metal hydroxide 70 parts by weight Colorant 3 parts by weight Anti-aging agent 1 part by weight [Example of soft vinyl chloride resin compound] Vinyl chloride resin 100 parts by weight Plasticizer 80 Parts by weight filler 30 parts by weight stabilizer 3 parts by weight

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the continuous pellet drying method of the present invention will be described below.

FIG. 1 is a partially omitted front view showing an embodiment of a continuous pellet drying method of the present invention.

In FIG. 1, 10 is a continuous extrusion molding machine, and 11
Is a drive motor, 12 is a drive shaft, 13 is a speed change mechanism, 14 is a synthetic resin compound supply hopper, 15 is a screw, 16 is an extrusion head, 20 is a watering hot cut unit, 30 'is a temperature control cooling water supply mechanism, 31
Is a heat source, 32 is a water supply tank, 33 is a water supply pump, 3
4 is a water temperature adjusting device, 35 is a water supply pipe, 40 is a granulated pellet supply pipe, 50 is a centrifugal dehydrator, 51 is a dehydrated pellet supply pipe, 52 is a dehydrated pellet delivery hopper, 53 is a constant flow rate vibration device, and 54 is Constant flow pellet supply pipe, 60 'one-pass circulation dryer, 61 constant flow pellet supply hopper, 62 dry hopper, 63 constant flow pellet suction rotary valve, 64 dry pellet delivery rotary valve, 70 ′ Is a one-pass type dry air supply unit, 71 is a dry air supply pipe, 72 is an air heating device, and 73 is an adjusted dry air supply pipe.

That is, in one embodiment of the continuous pellet drying method of the present invention, first, the drive motor 11 of the continuous extruder 10 is turned on, whereby the drive shaft 12 and the speed change mechanism 1 are turned on.
The screw 15 is rotated via 3.

Next, while the screw 15 of the continuous extruder 10 is being rotated, a synthetic resin compound, for example, a non-halogen flame-retardant polyolefin compound is charged into the synthetic resin compound supply hopper 14. The halogen-free flame-retardant polyolefin compound charged here is kneaded by a screw 15, and then extruded as a flame-retardant polyolefin compound strand from an extrusion head 16.

Next, the flame-retardant polyolefin compound strand extruded in this way is sent to the watering hot-cut unit 20, where it is cooled by the cooling water supplied from the cooling water supply mechanism 30 and adjusted to the optimum water temperature. Then, it is cut into pellets with a cutter and granulated to obtain flame-retardant polyolefin compound pellets.

Here, the temperature control cooling water supply mechanism 30
′ Is a water supply tank 32, a heat source 31 capable of heating water in the water supply tank 32, and a water supply pump 33.
And a water temperature adjusting device 34 and a water supply pipe 35. Water is previously put in the water supply tank 32,
Before starting the operation, high-temperature steam or the like is sent from the heat source 31 into the water supply tank 32 to make hot water having a predetermined water temperature. After the operation is stabilized, the temperature of the hot water and the granulated flame-retardant polyolefin compound pellets themselves are monitored and maintained at an optimum temperature by the water temperature adjusting device 34. Therefore, in one embodiment of the continuous pellet drying method of the present invention, the flame-retardant polyolefin compound strand extruded from the extrusion head 16 of the continuous extruder 10 is most suitable for cutting,
And the optimum water temperature for dehydration and drying in the next step, for example, water temperature 30 ° C
It can be cooled with warm water.

As described above, the flame-retardant polyolefin compound strand is optimal for cutting and can be cooled with hot water having the optimum water temperature for dehydration and drying. Therefore, the cooled flame-retardant polyolefin compound strand has a uniform shape. Can be cut and granulated into flame-retardant polyolefin compound pellets. Moreover, since the flame-retardant polyolefin compound pellets cut and granulated here have an appropriate temperature, they are excellent in dehydration / dryability in the next step.

Next, a large amount of cooling water is attached to the flame-retardant polyolefin compound pellets sent from the watering hot cut unit 20 to the granulated pellet supply pipe 40. Therefore, this granulated pellet supply pipe 40
The flame-retardant polyolefin compound pellets sent out to are sent to the centrifugal dehydrator 50. The flame-retardant polyolefin compound pellets thus sent to the centrifugal dehydrator 50 are the centrifugal dehydrator 50.
Is dehydrated while being spirally blown up from the bottom to the top. The water dehydrated here can be drained through a drain pipe on the bottom surface of the centrifugal dehydrator 50 (not shown).

Next, the flame-retardant polyolefin compound pellets thus centrifugally dehydrated are sent to the constant flow rate vibration device 53 through the dehydrated pellet supply pipe 51 and the dehydrated pellet delivery hopper 52, and the constant flow rate is made there. It

Next, the flame-retardant polyolefin compound pellets having the constant flow rate are opened by opening the constant-flow rate pellet suction rotary valve 63 of the one-pass type circulation dryer 60 'to establish the constant-flow rate pellet supply pipe 54. It is sent into the drying hopper 62 of the one-pass type circulation dryer 60 ′ through the flow rate pellet supply hopper 61. At the inner bottom of the drying hopper 62, the one-pass type dry air supply unit 70 ′ is sent to the air heating device 72 through the dry air supply pipe 71, and the heated dry air heated there is passed through the adjusted dry air supply pipe 73. Have been sent. The heated drying air sent from the bottom of the drying hopper 62 through the adjusted drying air supply pipe 73 collides with the flame-retardant polyolefin compound pellets sent from the upper part of the drying hopper 62 rapidly and uniformly. Therefore, the flame-retardant polyolefin compound pellets can be dried quickly and uniformly.

The uniformly dried flame-retardant polyolefin compound pellets are delivered from the dry pellet delivery rotary valve 64 into a storage container (not shown) installed outside the one-pass type circulation dryer 60 ', and then sealed. It is designed to be stored as

Here, the drying time of the flame-retardant polyolefin compound pellets in the drying hopper 62 depends on the rotary speed of the constant flow rate pellet suction rotary valve 63 and the dry pellet delivery rotary valve 64.
It can be arbitrarily controlled by the difference in rotation from the number of rotations of.

FIG. 2 is an explanatory view of an enlarged function of a main part of FIG.

In FIG. 2, 60 is a circulation type dryer, 61 is a constant flow rate pellet feeding hopper, 62 is a drying hopper,
Reference numeral 63 is a constant flow rate pellet suction rotary valve, 64 is a dry pellet delivery rotary valve, 65 is a one-pass moisture delivery pipe, 70 'is a one-pass type dry air supply unit, 73 is an adjusted dry air supply pipe, 74 is an air cooler, and 75 is The adsorption rotor, 76 is a first water removal pipe removal pipe.

That is, the flame-retardant polyolefin compound pellets of which the constant flow rate is oscillated by the constant flow rate oscillating device 53 of FIG. 1 are the constant flow rate pellets when the constant flow rate pellet suction rotary valve 63 of the circulation dryer 60 is opened. It is sent into the drying hopper 62 of the circulation type dryer 60 via the supply hopper 61. Moisture is contained in the flame-retardant polyolefin compound pellets fed from the upper portion inside the dry hopper 62, and the moisture is contained in the dry hopper 62 from the one-pass type dry air supply unit 70 ′ via the adjusted dry air supply pipe 73. The flame-retardant polyolefin compound pellets are quickly and uniformly dried by being efficiently extruded by the heated drying air sent to the inner bottom. Moisture generated during this drying process passes through the first moisture removal pipe 76 and the air cooler 7
4 and is adsorbed there by the adsorption rotor 75 quickly and efficiently. Further, when water overflows into the drying hopper 62, the water can be quickly and efficiently discharged to the outside through the one-pass water delivery pipe 65. Therefore, the obtained flame-retardant polyolefin compound pellets can be completely dried, and the variation in the drying operation among lots can be eliminated. (Continuous Example 1 Method of Continuous Drying of Pellet) The flame-retardant polyolefin compositions a to g shown in Table 1 were continuously kneaded, extruded with a flame-retardant polyolefin compound strand, and granulated with a flame-retardant polyolefin compound pellet. Then, continuous drying of the pellets was performed on the flame-retardant polyolefin compound pellets. (Continuous Drying Method for Pellets of Example 1) The flame-retardant polyolefin compositions a to g shown in Table 1 were continuously kneaded, extruded with a flame-retardant polyolefin compound strand, and granulated with a flame-retardant polyolefin compound pellet. Then, continuous drying of the pellets was performed on the flame-retardant polyolefin compound pellets.
(Flame-retardant polyolefin composition used) Table 1 shows a composition table of the flame-retardant polyolefin compositions a to g used therein. (Test Results) Table 2 shows the results of these experiments.

[0050]

[Table 1]

[0051]

[Table 2]

As can be seen from Table 2, in the conventional continuous drying method of pellets, the water content of the dehydrated resin to be supplied is high and the supply temperature of the dehydrated resin is as low as 30 ° C. As a result, the resin after the final drying is dried. Had a water content of 0.10 to 0.20%.

On the other hand, in the continuous drying method of pellets according to the embodiment of the present invention, the water content of the dehydrated resin to be supplied is low and the supply temperature of the dehydrated resin can be as high as 70 ° C. It is possible to dry the resin after the final drying with almost no water content.

In the pellet continuous drying method according to the embodiment of the present invention, the constant flow rate oscillating device 53 is used, but a fixed amount supply feeder or the like can also be used.

In addition, the continuous drying method for pellets according to one embodiment of the present invention is applied to the continuous drying of the synthetic resin compound pellet immediately after being molded by the continuous granulation molding apparatus, but of course the synthetic resin stored It can also be used for continuous drying of compound pellets.

[0056]

According to the continuous drying method of pellets of the present invention, the synthetic resin compound pellets immediately after being molded by the continuous granulating and molding apparatus can be continuously and almost completely dried. It is useful.

[Brief description of drawings]

FIG. 1 is a partially omitted front explanatory view showing an embodiment of a continuous drying method of pellets of the present invention.

FIG. 2 is an explanatory view of an enlarged function of a main part of FIG.

FIG. 3 is a partially omitted front view showing a conventional continuous drying method of pellets.

FIG. 4 is an explanatory view of an enlarged function of a main part of FIG.

[Explanation of symbols]

10 Continuous extruder 11 Drive motor 12 drive shaft 13 speed change mechanism 14 Synthetic resin compound supply hopper 15 screws 16 extrusion head 20 Watering Hot Cut Unit 30 Cooling water supply mechanism 30 'Temperature control cooling water supply mechanism 31 heat source 32 Water supply tank 33 Water supply pump 34 Water temperature controller 35 water supply pipe 40 Granulation pellet supply pipe 50 Centrifugal dehydrator 51 Dehydration pellet supply pipe 52 Dewatering pellet delivery hopper 53 Constant flow rate vibration device 54 Constant flow rate pellet supply pipe 60 circulating dryer 60 'One-pass circulation dryer 61 Constant flow rate pellet feeding hopper 62 Drying hopper 63 Constant flow rate pellet suction rotary valve 64 Dry pellet delivery rotary valve 65 One-pass moisture delivery tube 70 Dry air supply unit 70 'One-pass type dry air supply unit 71 Dry air supply pipe 72 Air heating device 73 Adjusting Dry Air Supply Pipe 74 Air cooler 75 Adsorption rotor 76 First water removal pipe 77 Second moisture removal pipe

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Claims (2)

[Claims] 1. A synthetic resin compound supply hopper of a continuous extrusion molding machine, while continuously feeding a synthetic resin mixture from the continuous extrusion molding machine, kneading and extruding the synthetic resin compound strand to obtain a synthetic resin compound strand, and then the synthetic resin compound strand. Is sent into the watering hot cut unit and cooled by spraying cooling water, and then the cooled synthetic resin compound strand is cut and granulated into pellets, and then the pellets are sent to a centrifugal dehydrator for dehydration. In the continuous drying method of pellets, in which a constant flow rate is adjusted to a constant flow rate by a vibrating device, and then the constant flow rate pellets are fed into a drying hopper of a dryer in which dry air is being fed to be dried, The cooling water used in the cutting unit is hot water whose temperature is adjusted to a constant temperature. Continuous method of drying the pellet that. 2. The continuous drying method for pellets according to claim 1, wherein the drying air fed into the drying hopper is heated drying air heated to a constant temperature.