JP2871807B2 - Molten resin extrusion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The molten resin extruder of the present invention is used, for example, for producing a crosslinked polyethylene insulated cable.

(Prior Art) Conventionally, when manufacturing a crosslinked polyethylene insulated cable, for example, the following is performed.

First, as shown in FIG. 4, the pellet-shaped resin material a supplied to the extruder B is kneaded by the screw D in the extruder B, and at the same time, is heated by the heater in the cylinder E of the extruder B to be appropriately heated. Melts at an appropriate temperature. At this time, an anti-aging agent having a melting point of 155 ° C. is usually kneaded in the molten resin A. The kneaded molten resin A is supplied to an extruder B
Through a fine screen F of about 1000 mesh set on the breaker plate J on the extrusion port C side of
The screen F removes foreign matter mixed in the resin A. At this time, if the temperature of the molten resin A is low,
When the antioxidant does not melt, the antioxidant cannot be uniformly kneaded into the molten resin A, and the resistance of the resin A when passing through the fine screen F increases, resulting in extremely low temperature. The screen F may be broken by the resistance. Therefore, the temperature of the molten resin A is usually set to a high temperature of about 160 ° C.

And the molten resin A extruded from the extrusion port C of the extruder B
Is supplied to a crosshead H through a resin passage K in a connecting nozzle G shown in FIG. 4, and a cross-linking agent is injected and kneaded into the resin A in the crosshead H, and the cross-linking agent is formed on the outer periphery of the core wire To form a crosslinked polyethylene insulated cable. At this time, if the temperature of the molten resin A remains at about 160 ° C., burning tends to occur. Therefore, it is necessary to lower the temperature of the resin A to about 120 ° C.

Therefore, conventionally, the entirety of the connection nozzle G through which the molten resin A passes is air-cooled from the outside, or the refrigerant is extruded by flowing a refrigerant into a refrigerant passage I provided on the outer periphery of the connection nozzle G as shown in FIG. The entire molten resin A was forcibly cooled from the outside.

Incidentally, in the case of a resin containing no cross-linking agent, there is no fear of burning even at 160 ° C., but the molten resin becomes too soft and is difficult to be uniformly coated on the core wire by extrusion, and uneven thickness is apt to occur.

(Problems to be Solved by the Invention) In the conventional extrusion coating method, in the method of cooling the molten resin A by cooling the entire connection nozzle G from the outside, the resin A in the outer portion in the nozzle G is cooled. However, there is a problem that the resin A in the inner portion is not sufficiently cooled, and the temperature of the resin A tends to vary.

In the conventional extrusion coating method, in the method of cooling the molten resin A by flowing the refrigerant in the refrigerant passage I, if the temperature of the refrigerant is excessively lowered, the resin A in the outer portion in the connection nozzle G solidifies. I had a question.

(Object of the Invention) It is an object of the present invention to provide a molten resin extruder which can cool a molten resin to a uniform temperature without variation in the temperature of the molten resin and which does not have a fear of solidifying the molten resin.

(Means for Solving the Problems) As shown in FIGS. 1 to 3, the molten resin extruder of the present invention connects an extruder B and a crosshead H to each other and forms a resin passage K therein. In a molten resin extruding apparatus comprising the connected nozzle G, a resin cooling unit 1 having refrigerant passages 2 and 14 for cooling the molten resin A is provided in a resin passage K formed in the connection nozzle G, It is characterized in that the molten resin A is cooled from the inside.

(Operation) In the molten resin extruder of the present invention, the molten resin A extruded from the extrusion port C of the extruder B as shown in FIGS.
While the resin is passed through the resin passage K of the connecting nozzle G and supplied to the crosshead H, the resin cooling unit 1 provided in the passage K and having the refrigerant passage 2 for cooling the molten resin A cools the passage K. Since the passing molten resin A is cooled from the inside, the molten resin A passing through the resin passage 2 is cooled substantially uniformly.

(Embodiment) FIGS. 1 and 2 show different embodiments of the molten resin extruder of the present invention.

Reference numeral 1 shown in these figures denotes a resin cooling unit. The resin cooling unit 1 is provided in a resin passage K in a connection nozzle G that supplies a molten resin A extruded from an extruder B to a crosshead H. .

The resin cooling section 1 has an extrusion port C of an extruder B formed.
A plurality of resin passage holes 2 for branching and passing the molten resin A extruded from the resin are formed. In the embodiment of FIGS. 1 and 2, as shown in FIG. 1B, one resin cooling portion 1 has a central portion, and four resin passage holes 2 penetrate the upper, lower, left and right sides of the resin cooling portion 1. Is formed.

In the resin cooling section 1 shown in FIGS. 1 and 2, a refrigerant passage 3 is formed around each of the resin passage holes 2. First
In the embodiment shown in the figure, the refrigerant passage 3 is formed around the central resin passage hole 2 and around the four resin passage holes 2 around the center, as shown in FIG. Accordingly, two reciprocating refrigerant passages 3 are formed around each resin passage hole 2 as shown in FIG. In the embodiment of FIG. 2, the refrigerant passage 3 is formed three times around the central resin passage hole 2 and three times outside the four resin passage holes 2 around the center as shown in FIG. As a result, FIG.
As shown in FIG. 6, six reciprocating refrigerant passages 3 are formed around each resin passage hole 2.

These resin cooling section 1, resin passage hole 2, refrigerant passage 3
For example, a metal pipe such as a copper pipe or a SUS pipe is formed into a desired shape of the refrigerant passage 3, and is set in a mold of the resin cooling unit 1, and then the molten metal is poured into the mold. A resin cooling section 1 is formed, and after cooling, a resin passage hole 2 is formed to complete the resin cooling section.

Then, the molten resin A was cooled by the molten resin extruder of the present invention as follows.

As the material of the resin A to be supplied, a low-density polyethylene pellet material a having a density of 0.92 and an MI of 3.0 was used.

The extruder B used had an inner diameter of 150φ and an L / D of 22. The screw D in the extruder B used had a conventional conventional-field-compression-metering ratio of L / D length = 10-7-5 and groove depth = 20/10.

The temperature setting of the cylinder E of the extruder B is 180-170-160-1
The temperature was 60 ° C., and the rotation speed of the screw D was 40 RPM.

As the resin cooling unit 1, 275 resin passage holes 2 having an inner diameter of 4 mm are formed in a resin cooling unit 1 having an outer diameter of 100 mm (not shown), and a refrigerant passage 3 having an inner diameter of 1/4 " The one formed in a spiral shape on the outer periphery of the hole 2 was used.

In addition, oil is used as a refrigerant, and oil temperature of 100-120 ° C is 5 l / m
In, the refrigerant circulated in the refrigerant passage 3.

With the molten resin extruder of the present invention, the molten resin A is approximately 120.
Cooled down to a uniform low temperature of ° C. On the other hand, the molten resin A cooled by the conventional molten resin extruder has a variation in the radial direction such that the temperature of the outer peripheral portion of the connecting nozzle G is 170 ° C. and the temperature of the central portion thereof is 190 ° C. Was not done.

FIG. 3 shows another embodiment of the molten resin extruder of the present invention.

The resin cooling unit 1 of this embodiment includes an inlet cooling unit 10 closely fitted in the resin passage K of the connecting nozzle G, an outlet cooling unit 11 closely fitted in the passage K, and a refrigerant connecting them. And a tube 12. The inlet cooling unit 10 and the outlet cooling unit 11
3a, three resin passage holes 13 through which the molten resin A passes are respectively formed as shown in FIG. 3a, and the inside of the other parts except the resin passage hole 13 is formed. A series of refrigerant passages 14 are formed, and the refrigerant pipes 12 communicate with the refrigerant passages 14 in both the cooling units 10 and 11, and the refrigerant passage 14 in the inlet cooling unit 10 is provided outside the connection nozzle G. The refrigerant flow passage 14 in the outlet cooling unit 11 is connected to a refrigerant outlet 16 provided outside the connection nozzle G. As a result, the refrigerant supplied from the refrigerant inlet 15 is filled in the refrigerant passage 14 of the inlet cooling unit 10, and the refrigerant pipe
The refrigerant is filled in the refrigerant passage 14 of the outlet cooling unit 11 through the refrigerant outlet 12, and is further discharged from the refrigerant outlet 16.

(Effect of the Invention) In the molten resin extruder of the present invention, the refrigerant passages 2 and 14 formed in the resin passage K in the connecting nozzle G for connecting the extruder B and the crosshead H and cooling the molten resin are formed. Since the resin cooling section 1 is provided, the molten resin A passing through the passage K is uniformly cooled from the inside thereof to a temperature suitable for extrusion molding, and the temperature of the molten resin A varies as in the related art. And the problem that the molten resin A is partially solidified is solved.

[Brief description of the drawings]

FIG. 1a is an overall structural view showing one embodiment of a molten resin extruder of the present invention, FIG. 1b is a sectional view taken along line ZZ of FIG. 1a, FIG. 1c is a sectional view taken along line YY of FIG. FIG. 2A is a structural view showing another embodiment of the molten resin extruder of the present invention, and FIG.
FIG. 3C is a sectional view taken along line WW of FIG.
Is a structural view showing still another embodiment of the molten resin extruder of the present invention, FIG. B is a sectional view taken along line V-V of FIG. A, and FIG. 4 is an overall structural diagram showing an example of a conventional molten resin extruder. It is. 1 is a resin cooling section, 2 is a refrigerant passage A is a resin B is an extruder G is a connecting nozzle H is a crosshead K is a resin passage

Claims (1)

(57) [Claims] An extruder (B), a crosshead (H),
In a molten resin extruder comprising: a connecting nozzle (G) connecting the two and having a resin passage (K) formed therein,
In the resin passage K formed in the connection nozzle (G),
A resin cooling section (1) having a refrigerant passage (2, 14) for cooling the molten resin (A), wherein the molten resin (A) is cooled from the inside thereof; apparatus.