JPS5951686B2 - Cross-linked tube for long rubber and plastic bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for attaching a heated elongated body to the outer peripheral surface of a elongated body made of rubber or plastic without using heated and pressurized steam immediately after extrusion molding. This invention relates to a crosslinking cylinder for a long rubber or plastic body that performs crosslinking while bringing the inner surfaces of a passage hole into contact with each other.

For example, a long rubber or plastic body extruded at high pressure from an extruder will have a reduced pressure and an increased outer diameter immediately after passing through a molding die.

Furthermore, in extrusion of electric cables and the like, if the speed of the extruded rubber or plastic elongated body is increased by the speed of the core wire, the outer diameter immediately after molding will be larger than the outer diameter at the time of molding.

On the other hand, the rubber or plastic long body extruded from an extruder is usually heated to a temperature of 1200 to 140°C for polyethylene, but it is placed in a crosslinking tube and heated to a temperature of about 1500 to 350°C that suits the purpose. Ru.

The temperature of the rubber or plastic elongated body being crosslinked in the crosslinking cylinder increases and it thermally expands. For the above reasons, the rubber or plastic elongated body tends to expand in the radial direction over the entire length of the heating zone immediately after die molding.

However, if the elongated body passage hole of the heated bridging cylinder has a straight shape with a uniform inner diameter, thermal expansion in the radial direction cannot occur, and the contact pressure between the outer surface of the rubber or plastic elongated body and the inner surface of the bridging cylinder becomes large. As the contact resistance increases in the direction of travel, it may be difficult to manufacture products efficiently. An object of the present invention is to provide a crosslinking tube for a rubber or plastic elongated body that can efficiently crosslink without generating large contact pressure on the rubber or plastic elongated body being crosslinked within the crosslinking tube.

Embodiments of the present invention will be described in detail below with reference to the drawings.
FIG. 1 shows an example in which the present invention is applied to a crosslinked tube of a crosslinked polyethylene cable. Extruder crosshead 1
The uncrosslinked polyethylene elongate body 5 extruded from between the nipple 2 and the die 3 onto the outer periphery of the core wire 4 is passed through the elongate body passage hole 7 of the crosslinking tube 6 connected to the crosshead 1. Thermal crosslinking is carried out in the heating zone HZ. The heating zone HZ portion of the bridging cylinder 6 is heated to about 150° to 350° C. by a heater (not shown) or by directly applying electricity to the bridging cylinder 6. The heating zone HZ starts from part A and continues to part B, and its length is as short as 1 to 2 m, and as long as 20 m or 30 m. Polyethylene is heated to a predetermined temperature while passing through the heating zone HZ,
Thermal expansion. Assuming that the diameter of the polyethylene long body 5 at the starting end A of the heating zone HZ is d, and the diameter of the polyethylene long body 5 at the terminal end B is D, considering simple thermal expansion in the absence of external restraint, D>d. becomes. If calculated as an example, the value will be approximately 1.02 to 1.15 of D/d.

Therefore, in the case of a polyethylene elongated body 5 having a diameter of 50 mm immediately after extrusion, the direct diameter increases to about 57.5 mm at most.

On the other hand, the elongated rubber or plastic body 5 extruded under high pressure inside the crosshead 1 becomes swollen immediately after the die 3 if there is no external restraint such as the bridge tube 6.

Therefore, in the present invention, immediately after being molded by the die 3, the rubber is formed with an inner surface that is larger in a step shape than the inside of the land portion of the molding die, and expands without restraint in the heating zone HZ. A long body passage hole 7 whose inner diameter changes from d to D in approximation to the change in the outer diameter of the plastic long body 5.
The purpose is to carry out crosslinking using a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6 having a crosslinking tube 6.

In this embodiment, the elongated body passage hole 7 is made such that the inner diameter on the inlet side of the heating zone is larger than the inner diameter of the land portion of the forming die, and the inner diameter is increased in steps so that the inner diameter on the outlet side is larger than that on the inlet side. This figure shows an example using a bridge tube 6 having the following structure. The crosslinked rubber or plastic elongated body 5 is fed into a cooling cylinder 8 connected to the crosslinking cylinder 6 and cooled by a cooling medium 9.

FIG. 2 shows a straight hole unit cylinder 6S having a straight long body passage hole 7S whose inner diameter is sequentially increased for each unit cylinder.
This figure shows an example in which a bridge tube 6 is obtained by sequentially connecting the tubes.

Depending on how heating energy is applied, elongated body passage holes may have various inner shapes.

Alternatively, a lubricant may be suitably injected into the elongate body passage hole from the outside to reduce the frictional force between the inner surface of the elongate body passage hole and the rubber or plastic surface, thereby making the movement smoother.

As explained above, in the cross-linked cylinder of the present invention, the elongated body passage hole in the heating zone has a shape in which the inner diameter on the inlet side of the zone is larger than the inner diameter of the forming die, and the inner diameter on the outlet side is larger than that on the inlet side. Crosslinking can be carried out efficiently without generating large contact pressure between the outer surface of the long rubber or plastic body to be crosslinked and the inner surface of the crosslinked cylinder.

Furthermore, the bridge tube of the present invention can be manufactured at almost no cost compared to conventional tubes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a bridge tube according to the present invention;
FIG. 2 is a vertical sectional view of only the upper half of another embodiment of the bridge tube according to the present invention. 5...Rubber, plastic elongated body, 6...Bridging tube, 7,7S...Elongate body passage hole.

Claims (1)

[Claims] 1. In a crosslinking tube for rubber or plastic elongated bodies that is connected to a molding die and performs thermal crosslinking while bringing the inner surface of the heated elongate body passage hole into contact with the outer peripheral surface of the rubber or plastic elongated body. , the elongated body passing hole in the heating zone has a shape in which the inner diameter on the inlet side of this zone is larger than the inner diameter of the land portion of the molding die, and the inner diameter on the outlet side is larger than that on the inlet side. Bridge tube for long bodies.