JPH0337575B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to an improvement in a method for manufacturing a crosslinked polyolefin cable having an insulating layer made of a so-called polyolefin such as polyethylene or an ethylene-propylene copolymer. (Technical Background and Problems of the Invention) Conventionally, in the manufacturing method of cross-linked polyolefin cables, the main polyolefin, cross-linking agent, anti-aging agent, and other compounding agents blended as necessary are first kneaded using a Banbury mixer or the like. After obtaining the uncrosslinked polyolefin mixture, the uncrosslinked polyolefin mixture is granulated and fed to an extruder, extruded and coated onto a conductor or cable core, and then heated to crosslink the coating layer. is being carried out. Furthermore, from the viewpoint of simplifying the process, a method was proposed in which a crosslinking agent was directly press-fitted into a cable extruder to produce a crosslinked polyolefin cable in one process.
This method has been proposed in JP-A No. 31181, Japanese Patent Laid-Open No. 145873-1973, and the like. When implementing these crosslinking agent injection extrusion methods, if the crosslinking agent is a solid such as dicumyl peroxide (DCP), it must be kept at a temperature above its melting point during supply, and keeping it warm will prevent the decomposition of the crosslinking agent. This results in a disadvantage of poor storage stability. Therefore, the liquid cross-linking agent 2,5-dimethyl-
It was also considered to use 2,5-di-tert-butylperoxyhexane or 2,5-dimethyl-2,5-di-tert-butylperoxyhexine-3, but these have low activation energy for decomposition. but
Because it is smaller than DCP, the degree of crosslinking is not sufficient,
Furthermore, when used with DCP, it is difficult to react under the same temperature conditions because there is a considerable difference in decomposition temperature with DCP, and these crosslinking agents also have the disadvantage of reducing heat aging characteristics. (Purpose of the Invention) The present invention has been made with attention to these points, and provides a method for manufacturing a crosslinked polyolefin power cable with excellent electrical properties and aging characteristics by using a liquid crosslinking agent that can be stored for a long time. This is what we are trying to provide. (Summary of the invention) The present invention comprises (A) 100 parts by weight of a polyolefin composition;
(B) 0.5 to 7 parts by weight of a crosslinking agent consisting of 10 to 90% by weight of t-butylcumyl peroxide and 90 to 10% by weight of dicumyl peroxide; and (C) 5 to 7 parts by weight of the above crosslinking agent.
The method is characterized in that 40% by weight of a liquid anti-aging agent is supplied to an extruder, extruded and coated onto a conductor, and then heated and crosslinked. The polyolefin composition used in the present invention may be ordinary polyethylene, an ethylene-vinyl acetate copolymer, a composition consisting of polyethylene and ethylene-vinyl acetate, or a composition obtained by mixing these with other additives as necessary. It will be done. Furthermore, the use of a certain range of DCP and t-butylcumyl peroxide as the crosslinking agent used in the present invention allows for a range that maintains a liquid state and a sufficient degree of crosslinking (78% or more) as shown in Table 1. This is so that you can be saved.

[Table] Also, the amount of crosslinking agent was limited to 0.5 to 7 parts by weight per 100 parts by weight of polyolefin, because if it is less than 0.5 parts by weight, the desired degree of crosslinking cannot be obtained, and if it is more than 7 parts by weight, scorch will occur. It's for a reason. A particularly preferred range is 1 to 3 parts by weight. Next, as a liquid anti-aging agent, thioether-based bis-{2-methyl-4[3-N-alkylthiopropionyloxy]-5-tbutylphenyl}
In addition to sulfide, phenol-based, phosphite-based, or phenol-based antiaging agents can be used singly or in combination, but in particular, the amount of antiaging agent here is defined as 5 to 40% by weight of the amount of crosslinking agent. This is because, as shown in Table 2, a sufficient degree of crosslinking and a value satisfying heat aging characteristics can be obtained.

[Table] The method for producing the crosslinked polyolefin cable in the present invention is a conventional method, but the crosslinking agent and anti-aging agent can be added at any point from the feed section to the head of the extruder. (Example of the present invention) Next, an example will be described. Supplying a mixture having the composition shown in Table 3 to an extruder,
Extrusion coating was performed on a conductor using a conventional method. In addition, as conventional examples, examples are given in which a solid crosslinking agent is used, a liquid which has a high decomposition temperature and low activation energy, or a solid anti-aging agent. Table 3 also shows the degree of crosslinking and heat aging characteristics of the extruded insulating layer, and whether or not it is necessary to keep the crosslinking agent warm.

【table】

[Table] (Effects of the Invention) As described above, according to the production method of the present invention, the crosslinking agent or antiaging agent can be added to the hopper of the extruder without the need for heat insulation equipment for the crosslinking agent and antiaging agent. Therefore, the equipment can be simplified and a crosslinked polyolefin cable with better heat aging characteristics can be obtained.

Claims (1)

[Scope of Claims] 1 (A) 100 parts by weight of a polyolefin composition; (B) 10 parts by weight of a polyolefin composition;
~90% by weight of t-butylcumyl peroxide and
0.5 to 7 parts by weight of a crosslinking agent consisting of 90 to 10% by weight of dicumyl peroxide and (C) a liquid anti-aging agent of 5 to 40% by weight of the crosslinking agent are fed to an extruder and extruded onto a conductor. A method for producing a crosslinked polyolefin power cable, which comprises coating and then crosslinking by heating. 2 Anti-aging agent is a general formula Claim 1, which is a thioether compound represented by (R: C ₁₂ to C ₁₄ alkyl group)
A method for producing a cross-linked polyolefin power cable as described in Section 1.