JPS5933621Y2 - Rubber/plastic extruder for crosslinking - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a crosslinking rubber/plastic extruder used for manufacturing crosslinked rubber/plastic insulated wires, etc.

Conventionally, in the production of cross-linked rubber/plastic insulated wires, the cross-linking agent is mixed with the raw material rubber/plastic of the insulation material using an open roll, a Banbury mixer, etc. to produce a mixture containing the cross-linking agent, and this mixture is then passed through an extruder. The rubber and plastic insulated wires obtained by extrusion coating on the conductor are
Crosslinked rubber/plastic insulated wires were obtained by crosslinking the plastic insulation layer.

However, in this manufacturing method, it is first necessary to knead a crosslinking agent into the rubber or plastic, which increases manufacturing costs and also allows foreign matter to get mixed into the wires, which can damage the insulation layer of the wire. There was a risk of adverse effects.

Further, when a volatile crosslinking agent is mixed, there is a drawback that it volatilizes during crosslinking and does not reach a predetermined amount.

To solve these problems, an extruder has been proposed in which the crosslinking agent is directly injected into the extruder from multiple locations in the longitudinal direction of the compression zone of the extruder, and the crosslinking agent and rubber/plastic are mixed in the extruder. There is.

According to such an extruder, the various drawbacks mentioned above can be solved.

Although it is preferable to inject the crosslinking agent into the rubber/plastic from multiple locations in the longitudinal direction in the compression zone of the extruder in order to make the dispersion of the crosslinking agent uniform in the rubber/plastic, On the other hand, if the injection points of the crosslinking agent are located at different positions in the longitudinal direction of the extruder, the internal pressure of the extruder cylinder at each injection point will be different, and this will cause the pump stroke and motor for injecting the crosslinking agent to be different. A drawback arises in that the rotation speed, etc., must be set separately for each injection location.

Another disadvantage is that a pump must be provided for each injection point.

The object of the present invention is to provide a rubber/plastic extruder for crosslinking which allows crosslinking agents to be injected into a cylinder from multiple locations without the above-mentioned drawbacks.

Hereinafter, specific examples of the present invention will be explained in detail with reference to the drawings.

As shown in FIGS. 1 and 2, the extruder of this embodiment is equipped with a cylinder 2 containing a screw 1, and a hopper 3 is provided at the base of the cylinder 2 to supply rubber and plastic. It has become.

A fly IB is spirally protruded from the shaft 1A of the screw 1, and the structure is such that the flight 1B kneads rubber and plastic while pushing it out to the exit side.

A compression zone 4 is formed over a required section in the extruder by narrowing the pitch of the flight 1B of the screw 1 midway or gradually increasing the diameter of the shaft 1A of the screw 1 midway, and this compression zone 4 is A plurality of crosslinking agent injection holes 5A, 5B are formed on the same circumference in the longitudinal direction, and these injection holes 5A, 5B are connected to a common pump (not shown) via injection pipes 6A, 6B. , cylinder 2
A crosslinking agent is injected into the inside.

In the screw 1 at the positions corresponding to the injection holes 5A and 5B, the flight 1B is omitted, and instead, a large number of protrusions 1C are provided to protrude radially.

According to such an extruder, the positions of the injection holes 5A and 5B in the longitudinal direction of the cylinder 2 are the same, so the pressure inside the cylinder 2 at the position of each injection hole 5A and 5B is the same. Therefore, one pump can be used to inject the crosslinking agent.

Since the screw 1 at the injection position is provided with a large number of protrusions 1C, the flow of the rubber/plastic can be disturbed and the crosslinking agent and the rubber/plastic can be kneaded well.

In this case, it is preferable to mix an antioxidant into the crosslinking agent to prevent crosslinking reactions, ie, scorch, in the extruder.

The antioxidant and the crosslinking agent can also be injected through separate injection holes 5A and 5B.

The reason why the crosslinking agent was injected into the compression zone 4 of the extruder in this example is that in the supply zone 7 of the extruder corresponding to the hopper 3, the rubber/plastic is not melted and slips. This is because the amount is small, it is not stable, and the dispersibility of the crosslinking agent is poor, while the dispersibility of the crosslinking agent is poor in the metering zone 9 of the extruder near the crosshead 8, both of which are undesirable.

Table 1 shows the results of a comparative experiment of the crosslinking agent injection points and dispersibility when the crosslinking agent was injected from 1, 2, and 3 points in the circumferential direction while maintaining the same longitudinal position in the compression zone 4.

However, the conditions in this case are as follows.

Extruder 5Q mmφ, L/D=20, compression ratio 3
Rotation speed 3Q rpm Resin used Polyethylene, density 0.92 g/c
rn3, Mll, 0 Additives and amounts Dicumyl peroxide, resin 100
PHR: 2.0 PHR Pump Plunger pump crosslinking extrusion was carried out at 160° C. for 30 minutes.

Note that it is preferable to inject the alignment inhibitor simultaneously with the injection of the crosslinking agent.

In this way, it is possible to prevent scorch from occurring in areas where the concentration of the crosslinking agent is high.

Rubbers and plastics that can be used in this invention include polyolefins such as polyethylene and polypropylene, ethylene-vinyl acetate copolymers, styrene-butadiene copolymers, ethylene-propylene copolymers, and mixtures of polyethylene and other polymers. can be given.

In addition, as a crosslinking agent, dicumyl peroxide, ditertiary butyl peroxydiisopropylbenzene,
, 5-dimethyl 2.5-di(t-butylperoxy)hexane, and 2,5-dimethyl 2.5(t-butylperoxy)hexane.

Amine-based antioxidants are generally used for rubber and plastics.

Examples include phenol type, imidazole type, and combinations of these.

Among these, phenolic compounds that are compatible with the above-mentioned crosslinking agents are preferred.

Example 1 L/D=22. Compression ratio=3. Measuring zone groove depth 2mm
In a 150 mmφ extruder equipped with a single screw, 2.0 parts of a crosslinking agent made of molten dicumyl peroxide and an antioxidant made of 4,4' thiobis-(6-tert-butyl-3-methylphenol) were added. 0.2 part of the dissolved material was press-fitted from two places in the circumferential direction of the compression zone, and 6
A 6KV class cross-linked polyethylene cable was manufactured.

The characteristics of this cable are shown in Table 2.

Example 2 Under the same conditions as in Example 1, a crosslinking agent and an antioxidant were press-fitted from three locations in the circumferential direction of the compression zone to produce a 66 KV class crosslinked polyethylene cable.

The characteristics of this cable are shown in Table 2. Comparative Example A 66 KV class cross-linked polyethylene cable was manufactured by press-fitting a cross-linking agent and an antioxidant from one location in the compression zone under the same conditions as in Example 1.

The characteristics of this cable are shown in Table 2.

As explained above, in the crosslinking rubber/plastic extruder according to the present invention, the plurality of crosslinking agent injection holes are at the same longitudinal position in the compression zone, so the internal pressure of the cylinder in each injection hole is almost the same. Therefore, the injection pressure in each injection hole may be the same, and the crosslinking agent can be injected from one supply means.

Further, since a large number of protrusions are protruded from the screw corresponding to these injection holes to disturb the flow of the rubber/plastic, the crosslinking agent and the rubber/plastic can be mixed well.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway side view showing an embodiment of an extruder according to the present invention, and FIG. 2 is a longitudinal cross-sectional view of a main part of the extruder. 1...screw, 1A...shaft, 1B...flight, 1C...protrusion,
2...Cylinder, 4...Compression zone, 5A, 5B...Crosslinking agent injection hole.

Claims (1)

[Scope of utility model registration request] The cylinder is equipped with a screw, and a plurality of crosslinking agent injection holes are provided in the middle of the cylinder, and the crosslinking rubber/plastic and crosslinking agent supplied into the cylinder are kneaded by the screw and extruded. In the plastic extruder, the plurality of crosslinking agent injection holes are provided at the same position in the longitudinal direction and at different positions in the circumferential direction at positions of the cylinder corresponding to the compression zone of the extruder, and A rubber/plastic extruder for crosslinking, characterized in that a plurality of protrusions are protruded at locations corresponding to the crosslinking agent injection holes in order to disrupt the flow of resin.