JPH0367101B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a cable insulated with cross-linked polyethylene by silane cross-linking, and particularly to a method of manufacturing a cable that improves the thermal deformation rate of an insulator. The conventional method for manufacturing cross-linked polyethylene cables using silane cross-linking is to add a silanol condensation catalyst to silane-grafted polyethylene, which is obtained by reacting polyethylene with an organic silane and a free radical-forming compound, to coat the conductor by extrusion, and then to coat the conductor in water or in a hot water bath. After crosslinking with silane, a polyvinyl chloride sheath was extruded and coated in a separate step. The term "organosilane" herein refers to the general formula RR'SiY ₂ (R is a monovalent olefinic unsaturated hydrocarbon group or hydrocarboxyl group, Y is a hydrolyzable organic group,
R' is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon group or the same group as the group Y), and R is vinyl, allyl, butenyl, cyclohexenyl, cyclopentadienyl, cyclohexadiene. enyl, _CH2 =C( _CH3 )COO( _CH2 ) _3- ,
_CH2 =C( _CH3 ) _{COOCH2CH2O ( CH2} ) _3- , _CH2
=C( _CH3 ) _{COOCH2CH2OCH2CH ( OH} ) _CH2O
(CH ₂ ) ₃ -, etc., and Y is any hydrolyzable organic group, such as an alkoxy group such as a methoxy group, an ethoxy group, a butoxy group, a formyloxy group,
Acyloxy group such as acetoxy group or propionoxy group, -ON=C( _CH3 ) ₂ , -ON=C
(CH ₃ )C ₂ H ₅ , -ON=C(C ₆ H ₅ ) ₂ oximo group, -NHC ₂ H ₅ such as aramino group, etc. Among these, the same group or different groups 2
I use it. R' is a monovalent hydrocarbon group other than an aliphatic hydrocarbon group, such as methyl, ethyl, propyl, tetrazyl, octadecyl, phenyl, benzyl, tolyl, or the same group as the group Y. Among these silanes, RSiY ₃ type silanes are most preferred, and vinyltriethoxysilane and vinyltrimethoxysilane are particularly preferred. A free radical-generating compound is a compound that can generate free radicals in a polyolefin under the conditions of a grafting reaction and has a half-life at the reaction temperature of 6 minutes or less, preferably 1 minute or less. Organic peroxides or peresters such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, 2.5
-di(peroxybenzoate)hexyne-3,
1,3-bis(t-butylperoxyisopropyl)benzene, lauroyl peroxide, t-
Butyl peracetate, 2,5-dimethyl-2.
5-di(t-butylperoxy)hexyne-3,
Examples include 2,5-dimel-2,5-di(t-butylperoxy)hexane and t-butylperbenzoate. Also, azo compounds such as azobisisobutyronitrile and dimethylazodiisobutyrate can be used similarly. Silanol condensation catalysts are organometallic compounds such as dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin octoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, tetranonyl titanate. , lead stearate, zinc stearate, cadmium stearate, barium stearate, calcium stearate, etc. are used. As mentioned above, in the conventional method, a silanol condensation catalyst is added to silane-grafted polyethylene, the conductor is coated by extrusion, and the silane is cross-linked by passing it in water or hot water. Moreover, the thermal deformation rate of the insulator is high, so the vinyl chloride sheath must be coated by extrusion in a separate process. The present inventors discovered that in order to improve cable manufacturing efficiency, it is desirable to carry out extrusion coating on the conductor, cross-linking of the coating, and extrusion coating of the sheath in tandem in one step, but this is not possible with conventional technology. is as described above. In view of this situation, the inventor of the present invention has improved the silane crosslinking method as a result of various studies, and by using water or hot water shower, the heat deformation rate of the insulator has been improved, and the tandem extrusion of PVC sheath has been realized and the quality has been improved. It was possible to efficiently manufacture a crosslinked polyethylene cable with excellent properties. Hereinafter, the present invention will be explained with reference to the drawings. A conductor W is sent out from a delivery reel 1, passed through a caterpillar traction device 2, and an insulator is extruded and coated with a first extruder 3 that extrudes silane crosslinking and polyethylene. The compound used here is made by adding a silanol condensation catalyst to silane-grafted polyethylene.
Extrusion coating at ~250°C. The extrusion-coated cable core C is vigorously showered with water or a hot water shower 4 to effect water crosslinking, and then a vinyl chloride compound is extrusion-coated by a second extruder 5 and passed through a cooling water tank 6 before being applied to the cable core C. The crosslinked polyethylene cable is wound up by a winding machine 8 via a traction device (pulling machine) 7. At this time, it is preferable to remove water droplets on the surface of the internal cable core by wiping with a sponge or the like immediately before extruding the vinyl chloride sheath, since foaming will not occur in the vinyl chloride sheath. Next, embodiments of the present invention will be described. Polyethylene (density 0.920 melt flow rate
2.0g/10min) 100 parts by weight, 2 parts by weight of vinylmethoxysilane, 0.05 parts by weight of dicumyl peroxide
Parts by weight and 0.08 parts by weight of dibutyltin dilaurate were mixed and kneaded, and extruded and coated on a conductor with a nominal cross-sectional area of 200 ml to a thickness of 2.5 mm using a first extruder (bore diameter 115 mmφ, L/D = 25). After showering with warm water at ℃, the second extruder (diameter 150mmφ,
L/D=25) with a polyvinyl chloride sheath of 1.7
A cross-linked polyethylene cable was manufactured by extrusion coating to a thickness of mm. Comparative Example 1 A cross-linked polyethylene cable was produced in the same manner as in Example except that the cable was passed through a cooling water tank instead of a hot water shower. Comparative Example 2 A cross-linked polyethylene cable was produced in the same manner as in Comparative Example 1, except that the extrusion coating of cross-linked polyethylene and the extrusion coating of polyvinyl chloride were performed in separate steps. The results of a comparative test of the physical properties of the crosslinked polyethylene insulators of the crosslinked polyethylene cables obtained by the methods of the above Examples and Comparative Examples are as follows.

[Table] As is clear from the results of this comparative test, the heating deformation rate of the method of the present invention is much better than that of the comparative example. In particular, hot water showering is more likely to absorb water into polyethylene than cold water showering, and the crosslinking reaction is sufficiently likely to occur, making tandem extrusion possible.

[Brief explanation of drawings]

The figure is a schematic explanatory diagram of an embodiment of the present invention. 3...First extruder, 4...Water or hot water shower, 5...Second extruder, C...Cable core.

Claims (1)

[Claims] 1 Add a silanol condensation catalyst to silane-grafted polyethylene, which is made by reacting organic silane and a free radical-generating compound with polyethylene, extrude it onto a conductor, apply water or hot water shower to promote the silane crosslinking reaction, and extrude a polyvinyl chloride sheath. 1. A method for manufacturing a crosslinked polyethylene cable, characterized in that extrusion coating on the conductor, crosslinking of the coating, and extrusion coating of the sheath are carried out in tandem in one step.