JPS6013247B2 - Method for manufacturing cross-linked polyethylene insulated power cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to an improved method of making crosslinked polyethylene power cables.

Accordingly, the semiconducting layer in cross-linked polyethylene power cables is made of polyethylene and/or ethylene copolymer (hereinafter referred to as polyolefin) to improve heat resistance.
A crosslinked semiconductive layer was created by adding conductive carbon black and an organic peroxide to the polyolefin and coating the polyolefin with the organic peroxide.

In addition, in this case, if a gap exists between the crosslinked polyolefin insulating layer and the crosslinked semiconducting layer, electric discharge occurs in the gap and leads to cable breakage, so the generation of such a gap is prevented and the adhesion between the insulator and the semiconducting layer is improved. In order to do this, it is common to form a cable by coextruding two layers, an inner semiconducting layer and an insulating layer, or three layers, an inner semiconducting layer, an insulating layer, and an outer semiconducting layer. Usually, it is used for relatively low-voltage cables when two layers, an inner semiconducting turtle layer and an insulating layer, are formed by co-extrusion. It is common to form On the other hand, in the case of high-voltage cables, since the electrical stress is high, it is common to mold three layers, an inner semiconducting layer, an insulating layer, and an outer semiconducting layer, by coextrusion. However, in these cases, it is necessary that crosslinking does not occur during extrusion molding of each composition, and it is necessary that crosslinking progress rapidly in the step of heating and crosslinking after molding. Although it has been strongly desired to satisfy these contradictory properties, it has been almost impossible to actually satisfy these contradictory properties. For this reason, if a semiconducting layer and an insulating layer are continuously formed by extrusion molding over a long period of time, the compounded peroxide decomposes and crosslinks the resin to some extent, causing scorching of the composition. In order to prevent this, it is necessary to stop the extruder after continuous use for several hours and clean the inside of the extruder cylinder. This was a cause of deterioration in characteristics. The present invention solves the above-mentioned problems by applying silane crosslinking technology.
Even in continuous extrusion molding processing for a long time exceeding the melting time, stable production could be carried out without causing scorch of the composition.

In the method of the present invention, first, 0.05 to 2.0 parts by weight of polyolefin 10 is used. parts by weight of an organic peroxide and 0.5 to 1 parts by weight of the general formula RRSiY2 (in which R
is an olefinically unsaturated monovalent hydrocarbon group or a hydrocarbonoxy group, each Y is a hydrolyzable organic group, and R' is an R group or a Y group). Composition (1) obtained by blending necessary additives such as antioxidants is reacted at a temperature of 185° C. or higher to form a silane-grafted polyolefin.

This silane-grafted polyolefin' semiconductive mixture {C}, which is a mixture of 8 to 7 parts by weight of conductive carbon black and a silanol condensation catalyst, is extruded onto a conductor to form an internal semiconductive layer, and then the A composition consisting of a silane-grafted polyolefin and a silanol condensation catalyst is extruded to form an insulating layer, or the semiconductor conductive mixture [q] is further extruded on the outer periphery to form an outer semiconductive layer to form a coated conductor, and then The bound coated conductor is treated with water to create a crosslinking bond between both the semiconducting layer material and the insulating layer material, resulting in a crosslinked polyethylene power cable. In the above method, the semiconducting layer and the insulating layer may be formed by extruding two or three layers separately, but it is preferable to form them by simultaneous extrusion of two or three layers.

Examples of the organic peroxide used in the preparation of the silane-grafted polyolefin in the present invention include penzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, and lauroyl peroxide.

The organic peroxide is added in an amount of 0.05 to 2.0 parts by weight per 100 parts by weight of polyolefin. The reason for this is that in order to react a silane compound and a polyolefin to obtain a silane-grafted polyolefin, the organic peroxide must be added in an amount of 0.05 parts by weight.
Parts by weight or more are required; 2. This is because parts by weight are sufficient. The silane compound used in the preparation of the graft polyolefin is represented by the general formula RR'SiY, where R is an olefinically unsaturated monovalent hydrocarbon group or a hydrocarbonoxy group, such as pinyl, allyl, butenyl, Cyclohexenyl, cyclobentadienyl, CH2C(CH3)COO(C&)3-, CH2=
C (CQ) COOCH2C Buddha 0 (C Fan) 31, and C
H2=C(CH3)C CH2Hisushi8CH20(CH2
) 3 - can be traversed, and Y is an alkoxy group such as methoxy, ethoxy, butoxy, an acyloxy group such as formyloxy, acetoxy, propionoxy, an oxime group, e.g. 1ON=C (CH3)
2, -ON=OCH3C2 day 5 and -ON=C(C6
5) 2 or substituted amino groups, such as alkylamino and arylamino groups, such as NHC, are any hydrolyzable organic groups such as -NHC and -NH (C6). .

The reason why the silane compound is added in an amount of 0.5 to 1 part by weight per part by weight of Polyolefino 10 is that the silane compound is added in an amount of 0.5 to 1 part by weight per part by weight of Polyolefino 10.
This is because if the amount is less than 5 parts by weight, no crosslinking effect will be obtained, while if the amount exceeds 10 parts by weight, the gel fraction of the crosslinked product obtained will not increase. Next, a small amount of the silanol condensation catalyst, such as dibutyltin dilaurate, used in the present invention may be used, and even if the amount is increased, the crosslinking time will only be shortened, and the final gel fraction will not change.

As mentioned above, in the present invention, first, the composition is mixed with 185 qo
The reaction is carried out at the above temperature to complete the reaction of the organic peroxide to form a silane-grafted polyolefin 'B}, which is obtained by mixing this silane-grafted polyolefin 'B) with a predetermined amount of conductive carbon black and a silanol condensation catalyst. The semiconductive mixture is used as the material for forming the inner semiconductive layer and the outer semiconductive layer of the target power cable, while the mixture of the silano-grafted polyolefin {B} and the silanol condensation catalyst is extruded onto the conductor as the material for forming the insulating layer. This extrusion process does not cause so-called burns and allows high-temperature extrusion (e.g. 20000) to obtain coated cables of excellent quality, and subsequent treatment of the resulting coated cable with water (e.g. Cross-linking can be introduced into the coating material by contacting it with water vapor or water in liquid state).
As a result, a crosslinked polyethylene power cable with excellent heat resistance can be obtained.

In addition, when manufacturing cables, the crosslinking reaction in the sheathing material does not occur during extrusion coating, but occurs during water treatment after the sheathing process. This greatly contributes to improving quality and production.

The invention will be illustrated with reference to the following examples.

EXAMPLE In this example, the characteristics of a silane crosslinked polyethylene power cable manufactured by the method of the present invention described below and a cable manufactured by conventional organic peroxide crosslinking were compared.

Cable (i) 2 parts by weight of vinyltrimethoxysilane and 0.0 parts by weight of dicumyl peroxide based on 100 parts by weight of low density polyethylene.
2 parts by weight and 4,4-thiobis(6) as an antioxidant.
3,000.5 parts by weight of tertiary butyl 3-methylphenol (trade name: NOCRAC) were mixed in a Henschel mixer and extruded at 200°C in an extruder to obtain a silane-grafted polyethylene beret 'a'.

Next, the above-mentioned beret [M00 parts by weight, 6 parts by weight of acetylene black and 0.0 parts by weight of dibutyltin dilaurate.
05 parts by weight were added and kneaded using a Banbury mixer to obtain Berets [b].

The pellet 'b- prepared as above has a cross-sectional area of 200
After forming an internal semiconductive layer by extrusion on the conductor of the fence (material temperature 140q0), an insulating composition prepared by mixing a silanol catalyst with a silane-grafted polyethylene pellet [a] was extruded around the outer periphery. The thickness of the semiconductive layer is 1. The thickness of the insulator layer is 3. It was a success. Also,
The extrusion molding of each of the above-mentioned coating materials was carried out by two-layer simultaneous extrusion. So I got 6. The Iso V polyethylene insulated cable was soaked in 80q0 warm water for 5 hours and crosslinked. After continuous production for 120 hours according to the above method, a low cable sample was taken at the point after continuous extrusion. The insulating shielding layer was constructed by wrapping conductive tape and copper tape. Cable (il) The above-mentioned pellet [a'1] used in cable (i)
60 parts by weight of acetylene black and 0.05 parts by weight of dibutyl tin dilaurate were added to 0 ton part by weight, and this mixture was mixed with a 25-inch roll to obtain Beret'c}.

After continuously extruding this pellet for 120 hours, 6. A prototype V-crosslinked polyethylene insulated cable was produced. A sample cable low was taken from the cable produced in this manner at the point after extrusion. Using 0.5 parts by weight of vinyltrimethoxysilane, 0.05 parts by weight of dicumyl peroxide, and 0.5 parts by weight of Nocrac 300 as an antioxidant for 100 parts by weight of low-density polyethylene on the cable side, A silane-grafted polyethylene pellet was prepared in the same manner as in the case of cable ti), and with respect to the weight part of the pellet 10, acetylene black 6 was added to the weight part and dibutyltin dilaurate was added to the silane-grafted polyethylene pellet.
05 parts by weight was added and this mixture was continuously extruded for 12 hours.
．． We prototyped a micro-V cross-linked polyethylene insulated cable.

A sample cable of 10 m was sampled from the cable thus produced after continuous extrusion. 100 parts by weight of low-density polyethylene on the cable side, 1.5 parts by weight of dicumyl peroxide, 6 parts by weight of acetylene black, and 3000.5 parts by weight of Nocrac as an antioxidant were kneaded in a Banbury mixer and extruded. Teberet'd}.

Beret'd) was extruded onto a conductor with a cross-sectional area of 200 quarts (material temperature 140 quarts) to form a semiconductive layer, and then 2. A pellet containing 3,000.5 parts by weight of Nokrac as an antioxidant was extruded to form an insulating layer.

The extrusion coating process was carried out by two-layer simultaneous extrusion. After extrusion, the coated cable was crosslinked by treatment with 19 picoC water vapor for 20 minutes. 6. By the above method. We made a prototype of Iso V cross-linked polyethylene insulated cable. In addition, using this method, Renzuki extrusion processing is performed once.
Ten cable samples were collected over two feeding periods. The results of investigating the characteristics of cable samples manufactured by the above cables (ii), (iii) and other methods are shown below.

The gel fraction in the table is based on the 5-hour toluene immersion method.

As described above, in the method of the present invention, a cable having stable electrical properties even after continuous extrusion processing for 120 hours can be obtained, whereas in the cable produced by the conventional method for continuous 12 hours, the electrical properties are significantly deteriorated.

This is because the semiconductive material, which has poor extrusion processability, was scorched in the extruder during continuous extrusion, and this scorched material formed protrusions within the semiconductive layer. Furthermore, as shown by the gel fraction of the semiconductive layer, the method of the present invention provides the same degree of crosslinking as the conventional method. Next, in order to examine the interface between the insulator and the internal semiconducting layer, the cable was cut in the longitudinal direction and the number of protrusions per 2 lengths was determined. The results are shown below. (Note) Protrusions with a height of 250 mm or more from the interface were counted.

From the above, in particular, the semiconductive composition appears as protrusions in the semiconductive layer formed by scorching in the extruder in conventional methods, but in the method of the present invention, semiconductive compositions appear as protrusions even in long-time continuous extrusion. Scorch does not occur in the conductive composition, and therefore a power cable with stable electrical properties can be obtained.

Claims (1)

[Claims] 1 On the conductor, 0.05 to 2.0 parts by weight of organic peroxide and 0.5 to 10 parts by weight of general formula RR'S per 100 parts by weight of polyethylene and/or ethylene copolymer.
iY_2 (in the formula, R is an olefinically unsaturated monovalent hydrocarbon group or a hydrocarbonoxy group, each Y represents a hydrolyzable organic group, and R' is an R group or a Y group); The silane grafted polyolefin (B) obtained by blending each of the silane compounds and reacting them,
After forming a semiconductive layer by extruding a semiconductive mixture (C) in which 8 to 70 parts by weight of conductive carbon black and a silanol condensation catalyst are mixed, a semiconductive layer is formed on the outer periphery of the silane grafted polyolefin (B) and a silanol condensation catalyst. After extruding the composition to form an insulating layer, or further extruding the semiconducting mixture (C) on the outer periphery to form a semiconducting layer to form a coated conductor, the coated conductor is treated with water. A method for producing a cross-linked polyethylene insulated power cable, characterized by causing a cross-linking reaction in a coating layer.