JPS606363B2 - Crosslinking method for posoolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for crosslinking polyolefins.

This type of crosslinking method that has been proposed in the past involves measuring and mixing a polymer such as a polyolefin, a silane compound, and a radical generator, extruding it while carrying out a heating graft reaction, and granulating the resulting silyl-modified polyolefin pellets. This was a method in which siloxane condensation catalyst masterbatch pellets, which had been mixed and granulated in advance, were fed into a hopper at a constant rate and exposed to moisture after extrusion to obtain the final crosslinked chemical product.

This method involves a process of extrusion granulation while carrying out a graft reaction, which complicates the work, which increases manufacturing costs, and there is also a risk that the silyl-modified polyolefin pellets will absorb moisture and cause a crosslinking reaction, resulting in poor quality. Therefore, there were troublesome problems such as the need for adequate storage management. In addition, a manufacturing method recently developed as a one-step method (Japanese Patent Publication No. 52-29338) removes the influence of moisture by performing silyl modification and extrusion at the same time.
Moreover, although this method was designed to simplify the process, it had drawbacks such as requiring a special extrusion machine with an injection port and a large L/D ratio.

The biggest feature of the water cross-linking method is that the general-purpose L/D is relatively 4.
・It is possible to make crosslinked products even by using an extruder (L/D: about 24/1), and for that purpose, it is desirable that the one-step method can also be applied to a general-purpose extruder. Otherwise, the purpose of simplifying the process will be halved.

Therefore, such technological improvements are desired.
Furthermore, in the one-step method, silyl modification and molding extrusion are performed simultaneously, so there is a restriction that no components that inhibit the grafting reaction are used. Therefore, the antioxidants used for this are extremely limited, and it is difficult to achieve a high degree of stabilization, so technological improvements in this respect are also required. The present invention provides a method for improving these drawbacks, by using a general-purpose extruder, omitting the grafting reaction and granulation process of polyolefin, and adding a silyl modifier and a small amount of antioxidant in advance. The pellets containing the agent and the pellets containing the siloxane condensation catalyst and isophthalic acid dihydrazide compound are fed into the hopper of an extruder and extruded to perform silyl modification and molding at the same time, removing the influence of moisture and stabilizing the quality. In addition to simplifying the manufacturing process and process, it also has a high degree of oxidation and copper damage prevention effect. Bis-isophthalate (alpha-phenoxypropionyl hydrazide) is effective as a copper damage inhibitor.This substance has no graft-inhibiting properties, and when used in combination with an antioxidant, it suppresses severe oxidation and copper damage deterioration. It was discovered that this effect was effective, and it became possible to manufacture highly stabilized products with a high degree of crosslinking.

ZThe gist of the present invention is as follows. (1) Put the polyolefin pellet, silane compound, radical generator, and antioxidant (in an amount within a range that does not inhibit the graft reaction) into a Henschel mixer and heat it to impregnate it, or use a two-ribbon blender, etc. The materials are mixed using a mixing device, transferred to a closed container, and heated to 70-8000°C for impregnation.

{2} Similarly, a polyolefin pellet is impregnated with a siloxane condensation catalyst and isophthalic acid dihydrazide compound 2.

Glue Thereafter, the materials obtained in {1} and (2) are continuously metered and mixed into the hopper of a general-purpose extruder, and heated and reacted through the extruder to form the desired molded product.

3{4' Thereafter, it is exposed to moisture to obtain a crosslinked molded article. Examples of antioxidants include polymeric amine compounds such as poly-2,2,4-trimethyl-1,2-dihydroquinoline, thiodiethylene bis(3,5-di-tert-butyl-4-hydroxy)hydrocin 3 O
A compound or isof that has both an H group and an -S- group. OH or -
It is desirable to use a compound containing S- alone. Furthermore, the isophthalic acid dihydrazide compounds include bis isophthalic acid (alphaphenoxypropionyl hydrazide) and bis isophthalic acid (penzoyl hydrazide).

An embodiment of the present invention will be described below. Examples Low-density polyethylene (manufactured by Ube Industries, Ltd., UBEC-4) having a density of 0.922 ta' and a melting index of 1.0 h/1 h
00N) and a liquid obtained by dissolving 2.0 parts of vinylsilane, 0.15 parts of dicumyl peroxide (DCP), and a predetermined amount of antioxidant, were preheated with steam to a temperature of 8,000. The pellets were placed in a Henschel mixer (capacity: 9) and stirred for 15 minutes to produce impregnated pellets (A).

By the same method (the same polyethylene beret 1 as in A)
0 Ikari Mariko dibutyltin diurarate 1. A pellet (B) impregnated with anchor and isophthalic acid dihydrazide was prepared. Next, the ratio of (A)/(B) is 19/1, and the mixture is fed to a hopper using an automatic quantitative mixing device (two hoppers, one type), and 65/kite (L/D=22/1) Using a single-screw extruder, an electric wire was made by extrusion coating the conductor circumference under the following conditions.

Temperature of barrel belt 1 in extruder 16000〃
〃 2 〃 2000
0 〃 3 〃 22
0ko○〃 Temperature of cross head part 22000
Wire size---Conductor diameter 1.6 Side single wire extruded insulation thickness 0. At 80:00, the electric wire was cut off.
After soaking in hot water for 1 hour, the insulator was extracted in 11,000 xylene for 24 hours, thoroughly dried, and the insoluble gel content was measured.

In addition, the electric wire after crosslinking is in [1] state of contact with steel conductor and {
2) A heating aging test was conducted using only the insulator in an air oven at 150 qo to determine the time required for the sample to deteriorate and spots to appear. Table 1 shows the results for each of Blend Examples 1 to 6.

Table 1* Each compounding ratio is in parts by weight The present invention has significant improvements in terms of economy, workability, and performance compared to conventionally known methods, particularly in the following points.

(1) Omitting the granulation process greatly simplifies the manufacturing process, improving work efficiency and reducing manufacturing costs.

(2) Since there is no liquid echo, the quality is extremely stable, and a crosslinked product with a smooth appearance can be obtained even during long hours of continuous work. (3) The crosslinking density is higher than that of conventional methods.

4■ Heat resistance, aging resistance, and steel deterioration resistance have been significantly improved,
The wire coating can omit the separator on the conductor and can be used in direct contact with the copper conductor. This invention can be applied not only to the method for manufacturing electric wires as described in the above embodiment, but also to the manufacture of crosslinked products such as tubes, pipes, and sheets, and even to injection molded products using the same extrusion method, all of which have great effects. can be expected.

Claims (1)

[Claims] 1. A polyolefin containing a silane compound, an antioxidant, and a radical generator is mixed with a polyolefin containing a siloxane condensation catalyst and an isophthalic acid hydrazide compound, and extrusion molded while reacting with heat, and then an extrusion molded product obtained. A method for crosslinking polyolefin, which comprises crosslinking by bringing water into contact with the polyolefin.