JPH11300739A - Granulating method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the incidence of stuck-together pellts or grape-like pellets by a method wherein a melted resin film formed on a die surface is solidified by being sprayed with cooling water. SOLUTION: An annular plate 13 is fixed to the shaft supporting part 12 of a holder shaft 11. At both the sides of the plate, atomizing nozzles 14 are attached. Cooling water pipings 18 including a pump 15 or the like are connected to both the atomizing nozzles 14. Cooling water is atomized in mist against a die surface and cutters 5 from both the atomizing nozzles 14 so as to cool and solidify and peel off a melted resin film formed on the die surface. The stomizing angle is adjusted by changing the rotational frequency of the pump 15 and the pressure of cooling water. Cut pellets fall in the cooling water 2, which spirally runs on the peripheral surface of a cutter hood 1, and are cooled down and, at the same time, carried to an outlet 7. After that, the pellets are fed to an centrifugal drier and an automatic sifter so as to select single pellets, which are products, from stuck-together pellets and grape-like pellets. Thus, the incidence of stuck-together pellets or grape-like pellets an be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus suitable for granulating thermoplastic resins, especially high-melting polyolefins such as polymethylpentene, and more particularly to a method for extruding a melt extruded from a die attached to the tip of an extruder. The present invention relates to a method and an apparatus for granulating a resin by cutting a resin by a hot cut method.

[0002]

2. Description of the Related Art A method of pelletizing a resin material includes an aerial hot-cut method in which a molten resin extruded from a die is cut in air and dropped in cooling water to be cooled, and a molten resin is extruded into water. Well, there is an underwater cutting method that cools and pelletizes at the same time as cutting in water.

FIG. 1 shows an example of an aerial hot-cut method, in which cooling water is jetted obliquely tangentially to the inner peripheral surface of a cutter hood 1 so that a water film 2 flows spirally in the direction of the arrow in FIG. Is formed, a cutter 5 radially attached to a holder 4 rotationally driven by a motor 3 via a speed reducer is pressed against a die 6 attached to the tip of the extruder.
The molten resin to be extruded is cut into pellets, dropped into a water film, cooled, transported to the outlet 7 by a spiral water flow, and discharged.

[0004]

In the case of the underwater cutting method, clogging of the die tends to occur due to cooling of the resin. In particular, when the resin is a high melting point resin, the temperature difference between the cooling water and the resin becomes large, and the resin tends to be clogged by cooling. On the other hand, the aerial hot cut method has an advantage that clogging of the die does not easily occur even with a high melting point resin, but in this conventional method, cohesive pellets in which pellets are fused to each other are easily generated. However, it was not easy to cut so that a single pellet could be formed. Therefore, in this method, the cut pellets are passed through an automatic sieve to select individual pellets for commercialization, but the yield is reduced due to the large number of cohesive pellets. In particular, for a resin having a low melt flow rate (hereinafter, referred to as MFR) having a value of 50 or more, the occurrence rate of grape-like pellets in which two or more cohesive pellets or pellets are adhered in a dumpling form is high, and the yield is low. Met. Here, MFR is 2
The amount (g) of resin extruded from an orifice 2.1 mm in diameter and 8 mm in length when subjected to a force of 5 kg at 60 ° C. in 10 minutes, and is a value measured by a test method shown in ASTM D1238. (However, the measurement temperature was changed from 230 ° C in the test method to 260 ° C).

The present invention aims to improve the yield of products (single pellets) by reducing the incidence of cohesive pellets and grape-like pellets, and to reduce labor for removing pellets on sieves with an automatic sieve. It was made for the purpose.

[0006]

The present inventors have thought of improving the sharpness of a cutter blade in order to achieve the above object.
As a result of considering the cause of impairing the sharpness, it was determined that one of them was the presence of the molten resin film formed on the die surface, which caused the adhesion between the cutter blade and the die surface to be impaired. And the inventors solidified the resin film by spraying or spraying cooling water to remove the resin film formed on the die surface,
Considering separation from the die surface, when cooling water was actually sprayed on the resin film, the occurrence rate of cohesive pellets and grape-like pellets could be reduced, and the MFR value was 5%.
It has been found that the effect is particularly large for a resin of 0 or more. That is, according to the present invention, the MFR value at 260 ° C. is 1 to 500 g / 10 min, preferably 5 to 300 g / min.
In the resin granulation method in the range of 10 minutes, pellets remaining on the sieve without passing through the sieve composed of the cohesive pellets and the grape-like pellets, that is, pellets in which a plurality of pellets are stuck together to form a dumpling (hereinafter referred to as a pellet) , For convenience, this is referred to as “sieve pellets”). For example, in the case of polymethylpentene having an MFR in the range of 5 to 300 g / 10 minutes, the rate of generation of on-sieve pellets has conventionally been 5 to 10% by weight, but 20 to 4% by weight.
By applying the spray cooling water at 0 ° C., it was possible to greatly reduce the amount to 0.1 to 0.2% by weight.

The present invention has been made based on this finding. The molten resin extruded from a die attached to the tip of an extruder is cut by a rotating cutter while sliding on the die surface, pelletized, and dropped into water. In the granulation method based on an aerial hot cut method in which cooling is performed, cooling water is sprayed or sprayed to solidify a molten resin film formed on a die surface.

Another aspect of the present invention relates to an apparatus for performing the above method, which is radially mounted on a die attached to a tip of an extruder and a holder which is driven to rotate by a motor as a driving source, and is mounted on a die surface of the die. It consists of a cutter that rotates in a pressed state, and the molten resin extruded from the die is cut by the cutter into pellets, dropped into water and cooled by an aerial hot cut granulator, which is formed on the die surface. And a device including a nozzle for spraying or spraying cooling water to solidify the molten resin film.

The above-mentioned inventions are generally applied to thermoplastic resins, and are particularly suitable for polyolefins having an MFR of 5 to 500, which are liable to form cohesive pellets, especially resins having an MFR value of 50 or more. On the other hand, it is effective for reducing the incidence of cohesive pellets and grape-like pellets. As the cutter used in each of the above-mentioned inventions, for example, a conventional thin blade knife-shaped cutter 1 as shown in FIG.
0, as shown in FIG. 3 and FIG.
Cutter 9 attached so that its position can be adjusted in the circumferential direction
Etc. can be used. In this, it is desirable to use a hatchet-shaped cutter as shown in FIGS. The reason is as follows.

In the case of a knife-shaped cutter as shown in FIG. 2, if the cutter 10 is strongly pressed against the die surface by the cutter holder 4 in order to increase the surface pressure with the die surface, the tip of the cutter warps and is more likely to float than the die surface. However, when the surface pressure with the die surface is increased, the blades are liable to be worn, the service life is short, and the bending of the blades is large, so that a few hours of initial running-in operation is required. In the case of a hatchet-shaped cutter as shown in FIGS. 3 and 4, even if the surface pressure with the die surface is increased, the deflection of the cutter is small, and the cutting state is kept good by bringing the entire blade into close contact with the die surface. Can do,
This is because the cutter has a longer service life than the cutter shown in FIG. 1, can be used repeatedly by regrinding, and can eliminate a running-in operation.

From the above points, it is desirable that the cutter is a hatchet-shaped cutter as shown in FIGS. 3 and 4. Even in the case of this cutter, it is preferable to use a cutter under the following conditions to obtain a good cutting state. More desirable above. That is, as shown in FIGS. 3 and 4, the angle θ formed by a line passing through the holder axis center O and the blade 9 a (in this specification, this is referred to as a cutter mounting angle) is 25 to 45 °, and FIG. The rake angle α is 40 to 50 ° and the clearance angle γ is 15 to 20
° and the cutting edge angle β are 25 to 30 °. Of these conditions, the larger the rake angle α, the larger the angle ψ between the direction in which the cut pellets fly and the die surface as shown in FIG. 6, and the easier it is to fly away from the die surface.

The cooling water only needs to solidify the molten resin film formed on the die surface, and it is necessary that the die is supercooled so as not to cause clogging with the resin. It is desirable to attach. The spray angle can be adjusted by changing the pressure or the flow rate.
About 0 ° is effective.

[0013]

FIG. 7 shows an aerial hot cut type granulating apparatus shown in FIG. 1 in which an annular plate 13 is fixed to a shaft support 12 of a holder shaft 11 and spray nozzles 14 are provided on both sides of the annular plate 13. The cooling water pipe 18 including the pump 15, the pressure gauge 16, the valve 17 and the like is connected to both nozzles 14, and the cooling water is sprayed from both the spray nozzles 14 to the die surface. The spray is sprayed on the cutter 5, and the spray angle can be adjusted by changing the rotation speed of the pump 15 and changing the pressure of the cooling water.

The cut pellets fall into the cooling water 2 flowing spirally on the peripheral surface of the cutter hood 1 and are conveyed to the outlet 7 while being cooled. And then sieved through an automatic sieving machine to separate into single pellets, cohesive and grape-like pellets. Experimental Example 1 Granulation of polymethylpentene was performed as follows using an apparatus shown in FIG. 7 in which the cutter was a hatchet blade-shaped cutter 9 shown in FIG.

MFR of 1 to 10 g / 10 min, 20 to 40
g / 10 minutes and 3 in the range of 50 to 500 g / 10 minutes
For each type of poly-4-methyl-1-pentene resin, under the following cutting conditions, H.IKEUCHI & CO.,
Cooling water was atomized from a spray nozzle 14 manufactured by LTD and sprayed at a predetermined spray angle onto the die surface and the cutter 9 to perform cutting and granulation to obtain pellets. Cutting conditions Passing speed (linear speed) of the molten resin passing through the die hole: 70 to
100cm / sec About cutter Cutter rotation speed: 1700-3000rpm, Cutter mounting angle: 25-45 ° Cutter rake angle: 40-50 ° Cutter relief angle: 15-20 ° Cutter tip angle: 25-30 ° Cooling water Temperature: 20-40 ° C. Cooling water pressure: 4 kg / cm ² Spray angle: 15-30 degrees

After the obtained pellets were dried, they were passed through an automatic sieve, and the amount of pellets generated on the sieve was examined for each of the three types of resins in the MFR range. The results are shown in Table 1 below. The table shows a method of cutting without injecting cooling water into the die surface, that is, using the conventional apparatus shown in FIG. 1 and granulating the same resin under the same conditions using the hatchet cutter 9 shown in FIG. The results in the case where they were performed are also shown. When cutting without water injection as seen in Table 1,
It can be seen that the amount of pellets generated on the sieve increases.

[0017]

[Table 1]

EXPERIMENTAL EXAMPLE 2 Except that the cutter was a knife-shaped cutter 10 shown in FIG. 2, under the same conditions as in Experimental Example 1 above, the same resin was cut while cooling water was injected, and no cooling water was injected. It examined about the case where it cut with. The results are shown in Table 2 below.

[0019]

[Table 2]

EXPERIMENTAL EXAMPLE 3 Except that the cutter was a hatchet blade-shaped cutter 9 shown in FIG. 3, under the same conditions as in Experimental Example 1 above, the same resin was cut while cooling water was injected, and no cooling water was injected. It examined about the case where it cut with. Table 3 shows the results.

[0021]

[Table 3]

As can be seen from the results of Experimental Examples 1 to 3, when the cooling water was sprayed or sprayed, the MFR was in the range of 1 to 500 g / 10 min in comparison with the case where the cooling water was not sprayed or sprayed. It has been found that the rate of generation of on-sieve pellets decreases, and in particular, the higher the MFR resin having an MFR of 50 or more, the more the amount of on-sieve pellets decreases, and the resin has a remarkable effect on spraying cooling water. In the case of a resin having an MFR of 50 or more,
The use of the cutter shown in FIG. 3 and the use of the cutter shown in FIG. 4 having a small mounting angle rather than the use of the cutter shown in FIG. .

[0023]

According to the method and the apparatus according to the first and fifth aspects, the molten resin film formed on the die surface is cooled and solidified by spraying or spraying cooling water, and peeled off.
As a result, the cutter blade adheres to the die surface, maintaining good sharpness, reducing the incidence of cohesive pellets and grape-like pellets, improving product yield, and reducing the work of removing pellets on the sieve. It is possible to save labor.

According to the method of the second aspect, the cutting state can be kept good. When a hatchet-shaped cutter is used as the cutter as in the device according to claim 6,
Since the bending is small, the entire blade can be brought into close contact with the die surface to maintain a good cutting state, the running-in operation can be eliminated, the life is long, and the blade can be used repeatedly by polishing it.

According to the seventh and eighth aspects of the present invention, it is possible to maintain a good cutting state.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a conventional granulation apparatus.

FIG. 2 is a side view of a holder to which a conventional cutter is attached.

FIG. 3 is a side view showing an example of using a cutter according to the present invention.

FIG. 4 is a side view showing an example of use of another embodiment of the cutter according to the present invention.

FIG. 5 is an explanatory view of a cutter.

FIG. 6 is a view showing a direction in which pellets fly during cutting.

FIG. 7 is a schematic cross-sectional view of a granulation apparatus according to the present invention.

[Explanation of symbols]

 1. Cutter hood 2. Water film 3. Motor 4. Holder 5. Cutter 6. Die 7. Outlet 8. Pattern 9. Hatchet blade cutter 10. Knife cutter 11. Holder shaft 13, annular plate 14, spray nozzle 15, pump 16, pressure gauge 17, pipe 18, pipe

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuo Matsubara 1-2-1, Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Chemicals, Inc.

Claims (8)

[Claims] 1. A granulating method by an in-air hot-cut method in which molten resin extruded from a die attached to the extruder tip is cut into pellets by a rotating cutter while slidingly contacting the die surface, dropped into water and cooled. The method according to claim 1, wherein cooling water is sprayed or sprayed to solidify the molten resin film formed on the die surface. 2. The granulation method according to claim 1, wherein the spray angle of the cooling water is 15 to 30 °. 3. The resin subjected to granulation has an MFR value of 5 to 50.
The granulation method according to claim 1 or 2, wherein the amount is 0 g / 10 minutes. 4. The resin used for granulation is poly-4-methyl-1.
The granulation method according to any one of claims 1 to 3, wherein the granulation method is pentene. 5. A die attached to the tip of an extruder, and a cutter radially mounted on a holder which is rotated and driven by a motor as a driving source, and rotated while being pressed against the die surface of the die. In a granulator using an aerial hot-cut method in which the molten resin to be cut is pelletized by cutting with a cutter, dropped into water and cooled, spraying or spraying cooling water to solidify the molten resin film formed on the die surface. A granulating device comprising a device including a nozzle. 6. The granulating apparatus according to claim 5, wherein a cutter having high rigidity is used as the cutter. 7. The granulating apparatus according to claim 5, wherein the cutter has an attachment angle of 25 to 45 °. 8. The granulating apparatus according to claim 5, wherein the rake angle of the cutter is 40 to 50 °, the clearance angle is 15 to 20 °, and the cutting edge angle is 25 to 30 °.