JPS63143704A - Semiconductive blend and semiconducting shrinkage tube comprising the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a semiconductive mixture used for connecting electrical cables, and a semiconductive shrink tube made of the mixture.

``Prior Art'' Some electrical cables, particularly high-voltage electrical cables, are provided with a semiconductive mixture coated directly above the conductor wire and outside the insulating coating.

Traditionally, semiconducting mixtures used for this purpose include rubber or ethylene-vinyl acetate copolymer (E
Semiconductive mixtures in which conductive carbon black is blended with resins such as VA) are used. In addition, in order to form a semiconductive coating on the connection part when connecting the above cable, a semiconductive shrink tube that shrinks when heated is used to facilitate cable connection. It is widely used.

This conventional semi-conductive shrink tube is made by molding a semi-conductive mixture containing conductive carbon black into the above-mentioned EVA resin, etc., into a tube shape, and can be used directly above the conductor connection part of the cable or outside the insulation coating. This semi-conductive shrink tube is inserted into a predetermined area and heated with a burner to cause contraction, thereby forming a semi-conductive coating on the target area.

"Problems to be Solved by the Invention" By the way, electric cables, especially high-voltage cables, have excellent physical and mechanical performance, high reliability, and a large allowable M flow. C held
There is a trend that V cables (cross-linked polyethylene electric cables) are being used more frequently.

On the other hand, since conventional semiconductive compounds are based on EVA resin, etc., they have poor adhesion with the polyethylene used as the insulating material of the Cv cable, and the polyethylene insulators and semiconducting A major problem was that the adhesive coating could not be tightly bonded to the adhesive coating.

In addition, conventional semiconductive shrink tubes made from semiconductive mixtures that are formed into tubes do not have a good shrinkage rate, and it is difficult to cover the target area tightly when connecting cables. There was a problem.

This invention solves the above-mentioned problems, and provides a semiconductive mixture that has good adhesion with polyethylene used in insulating materials such as CV cables, and also provides good shrinkage when molded into a tube shape. It is an object of the present invention to provide a semiconductive shrink tube made of the same.

"Means for solving the problem" In this invention, the ethyl acrylate content is 10 to 20
% and an MFR of 2 or less, 60 to 80 parts by weight of an ethylene-edyl acrylate copolymer, and MFrt
40 to 70 parts by weight of conductive carbon black was blended to 100 parts by weight of a resin consisting of 40 to 20 parts by weight of linear low-density polyethylene having a polyethylene of 5 or less. The solution is to make the mixture into a semiconductive mixture, and to form the mixture into a belt shape, crosslink it, and then mold it into a tube shape to form a semiconductive shrink tube.

Hereinafter, the semiconductive mixture of the present invention (first invention) and the semiconductive shrink tube made of the mixture (second invention) will be explained in detail.

The ethylene-ethyl acrylate copolymer (hereinafter referred to as EEA) used in the semiconductive mixture of the first invention is E
The ethyl acrylate content in the EA is 10 to 20%, and the MFR is 2 or less. If the ethyl acrylate content is less than 10%, the elongation of the semiconductive mixture will be insufficient, and if the ethyl acrylate content is less than 2%, the elongation of the semiconductive mixture will be insufficient.
If it exceeds 0%, the drawability of the semiconductive mixture deteriorates. Furthermore, if the MFR of EEA exceeds 2, the elongation of the semiconductive mixture will be poor, resulting in poor drawability.

Linear low-density polyethylene (hereinafter referred to as L-LDPE) used in the semiconductive mixture has an MFR of 5.
These are as follows. If the MFR exceeds 5, the semiconductive mixture has insufficient elongation.

"Biped EEA and L-LDPE have an EEA of 60 to 80.
40 to 20 parts by weight of L-LDPE are used. If the amount of L-LDPE in this mixed resin exceeds 40 parts by weight, the elongation of the semiconductive mixture will be insufficient and the flexibility will deteriorate.

Furthermore, if L-LDPE is less than 20 parts by weight, the volume resistivity of the semiconductive mixture will be high.

Conductive carbon black (used in semiconductive mixtures)
(hereinafter abbreviated as carbon) is acetylene black,
Commercially available products such as furnace black may be used; examples include Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.) and Palcan X.
C-72 (manufactured by Cubot) and the like are preferably used. This carbon is blended in 40 to 70 parts by weight with 100 parts by weight of the mixed resin of EEΔ and L-LDPE. If the carbon content is less than 40 parts by weight, the conductivity of the semiconductive mixture will be insufficient. On the other hand, if the carbon content exceeds 70 parts by weight, the elongation of the semiconductive mixture will be insufficient and the flexibility will deteriorate.

The semiconductive mixture of the first invention may contain the above-mentioned components according to their respective compounding ratios, and in addition to the above-mentioned components, other components such as crosslinking agents, anti-aging agents, and processing aids may be added. Ingredients may be mixed.

The semiconductive mixture of the first invention is superior to conventional semiconductive mixtures in that it has good adhesion to polyethylene, good elongation, and good shrinkability when made into a shrinkable tube. In particular, it exhibits excellent performance as a semiconducting Ti layer coating for cables such as C■ cables that are insulated with polyethylene.

Furthermore, the purpose of use of this semiconductive mixture is not limited to coating the cable with a semiconductive layer; for example, this mixture can be formed into a sheet and used as an antistatic sheet.

Next, the second invention will be explained with reference to the drawings. A second invention is a semiconductive shrink tube obtained by forming the semiconductive mixture of the first invention into a sheet shape (or tape shape), crosslinking this, and then forming it into a tube shape, and this shape is The second invention will be specifically explained below by exemplifying the semiconductive shrinkable tube of the second invention, although any shape may be used as long as it is in the shape of a tube, and the method for forming the tube into a tube is not limited.

FIG. 1 shows an example of the semiconductive shrink tube of the second invention. In this figure, the symbol l is a semiconductive shrink tube (hereinafter abbreviated as tube). This tube l is made of the semiconductive mixture described in the first invention, and includes a cylindrical tube body 2 and a locking protrusion integrally provided on the outer circumference of the tube body 2. It consists of 3. The locking protrusion 3 extends along the longitudinal direction of the tube body 2, and has an 'r-shaped cross section. In addition, a tube body 2 is provided at the center of the locking protrusion 3.
An incision gap 4 extending to the inner circumferential surface of the tube is formed along its longitudinal direction. This tube l can be split open by opening its incision gap 4, and by pushing this apart, the cable can be
The tube body 2 is coated on an object such as a conduit or a rod, the fastener 5 is fastened to the locking protrusion 3, and the tube body 2 is heated with a burner. The material shrinks and tightly covers objects such as cables. Such a tube 1 is manufactured as shown in FIGS. 2 to 4.

First, a long sheet 6 having a cross-sectional shape as shown in FIG. 2 is extruded using an extruder. Both ends of the sheet 6 in the width direction are bent into a hook shape to form a locking portion 7.7 which becomes one of the locking protrusions 3. This sheet 6 is then crosslinked. Crosslinking is carried out by adding an organic peroxide crosslinking agent such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 or dicumyl peroxide and heating it using an electron beam. A method of irradiating with light can be adopted. After this crosslinking, the sheet 6 is gripped by the locking portions 7.7 at both ends thereof and pulled in the width direction of the sheet 6, so that the width dimension is approximately 1.2 to 2.
The stretched sheet is stretched by varying times and cooled while maintaining this stretched state to obtain a stretched sheet 8 as shown in FIG. Thereafter, this stretched sheet 8 is cut to an appropriate length, bent so that the locking portions 7.7 are on the outside, and the locking portions 7.7 are aligned to form the incision gap 4. The result is a tube l as shown in the figure.

FIG. 5 shows another example of the semiconductive shrink tube of the second invention. The tube 9 shown in this figure is formed into a cylindrical shape using the semiconductive mixture of the first invention described above. This tube 9 is inserted into an object such as a cable, conduit, or rod, and the tube 9 is heated with a burner or the like to shrink and cover the object such as the cable tightly.

This tube 9 is manufactured as follows.

First, the semiconductive mixture of the first invention described above is extruded into a film. This film is then crosslinked. The crosslinking method is carried out by adding the above-mentioned crosslinking agent and heating and irradiating it with an electron beam. This crosslinked film is then stretched in the longitudinal direction to form a stretched film. Then, cut this stretched film into a tape shape.
It is formed into a tube shape as shown in FIG. In other words, the circular core bar 1 is cut using the taping machine 11 with the bipedal tape IO.
2 and wrap it multiple times to obtain the desired thickness. Next, the semiconductive mixture is heated above the melting point to melt and integrate the tape 1O, and then cooled and the core bar 12 is removed to obtain the tube 9.

Since the tubes I and 9 of the second invention are formed into a tube shape using the semiconductive mixture of the first invention, CV cables, etc., which could not be covered tightly with conventional semiconductive shrink tubes, etc. A semiconductive coating that exhibits good adhesion can be formed on a cable insulated with polyethylene. Further, since the tube 1.9 has good shrinkability, it is possible to form a semiconductive coating tightly onto the target location.

Examples of this invention are shown below.

"Example" Semiconductive mixtures of Examples (3 examples) and Comparative Examples (2 examples) of the present invention were manufactured according to the blending amounts shown in Table 1.

Table 1 below (numbers are parts by weight) EEA■ is Shiraishi Rexron EEA.
A-1150 (ethyl acrylate content 15%, MF
Ro, 75), EEA■ is Shiraishi Rexron EEA 8-270 (ethyl acrylate content 15%, MPRl
, 5), EEA ■ is Shiraishi Rexron EEA A-420
0 (Ethyl acrylate content 20%, MFR5, each of the above E E A are manufactured by Nippon Ishiura Chemical Tsuji), EV
A is manufactured by Mitsui-DuPont Polychemical Co., L-L D
PE manufactured by Nippon Unicar Co., Ltd. (MFR 3, 8), carbon or Denka Carbon (manufactured by Denki Kagaku Kogyo Co., Ltd.), anti-aging agent Tsukurak 300 (manufactured by Iriuchi Shinko Co., Ltd.), and processing aid used zinc stearate.

Each semiconductive mixture was produced by kneading the above-mentioned components under heating in a Banbury mixer, and the following tests were conducted using each of the semiconductive mixtures obtained thereby.

Using these semiconducting mixtures, first calculate the elongation of each,
Measured according to JIS K 7113-1981.

Next, each semiconducting mixture is processed into a sheet with a width of 0.5 mm, and then a irradiation crosslinking device is used to achieve a crosslinking degree of approximately 50% in terms of gel fraction (calculated without carbon components). It was cross-linked like this. Each crosslinked sort was then stretched using a stretching device. During this stretching operation, the maximum stretching ratio at which continuous and stable stretching was possible was measured, and this was taken as the stretchability.

Next, shrink tubes were created using each sheet stretched at the maximum stretching ratio, and each shrink tube was heated at 200°C.
The tube was heated for 1 hour, and the ratio of the diameter of the tube after shrinkage (after heating) to the diameter of the tube on the heated surface was measured, and this was taken as shrinkability.

In addition, connect each of the above shrink tubes to a Cv cable (6,6KV
, 200mm”) at 150°C on polyethylene insulation.
The material was heated to a moderate temperature to cause shrinkage, and then heated at 200° C. for 1 hour to attach it to a polyethylene insulator. 10mm to this
The adhesion of the shrink tube was examined by making a width scratch and peeling off the shrink tube. Based on this criterion for adhesion, cases where the shrink tube did not peel off were considered good, and cases where the shrink tube peeled off were judged as poor.

The results of each of the above tests are shown in Table 2.

As is clear from Table 2, the semiconductive mixture of the present invention has better elongation than the comparative example prepared with the intention of making a conventional semiconductive mixture, and also It was confirmed that the material had excellent shrinkage properties and adhesion to polyethylene.

On the other hand, Comparative Example A, which was intended to be a conventional semiconductive mixture, had poor shrinkability when made into a shrinkable tube and did not have good adhesion to polyethylene.

In addition, Comparative Example B shows an example when a material with an EEA MFR of 2 or more is blended. You will not be able to obtain a suitable shrink tube.

"Effect of the Invention J As explained above, the semiconductive mixture of the present invention and the semiconductive shrink tube formed from the mixture into a tube shape have excellent bone attachment properties between the mixture and the polyethylene insulator. Since it can be obtained well, it is possible to form a semiconductive coating with good bone attachment properties on polyethylene insulators, which have been difficult to coat with conventional semiconductive mixtures.

Further, since the semiconductive shrink tube of the present invention has good shrinkability, it is possible to easily and tightly cover a target area when connecting a cable.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of the semiconductive shrink tube of the present invention, FIGS. 2 to 4 are sectional views showing the manufacturing process of the semiconductive shrink tube shown in FIG. 6 and 6 are views showing other examples of the semiconductive shrink tube of the present invention, FIG. 5 is a perspective view of the semiconductive shrink tube, and FIG. 6 is a side view showing the manufacturing process. . l, 9...Tube (semi-conductive shrink tube) 6...
・Sheet.

Claims (2)

[Claims] (1) 60 to 80 parts by weight of an ethylene-ethyl acrylate copolymer having an ethyl acrylate content of 10 to 20% and an MFR of 2 or less, and 40 to 20 parts by weight of a linear low-density polyethylene having an MFR of 5 or less. 40 to 7 parts by weight of conductive carbon black to 100 parts by weight of the resin.
A semiconductive mixture containing 0 parts by weight. (2) 60 to 80 parts by weight of an ethylene-ethyl acrylate copolymer having an ethyl acrylate content of 10 to 20% and an MFR of 2 or less, and 40 to 20 parts by weight of a linear low-density polyethylene having an MFR of 5 or less. 40 to 7 parts by weight of conductive carbon black to 100 parts by weight of the resin.
A semiconductive shrink tube formed by forming a crosslinked sheet-like material of a semiconductive mixture containing 0 parts by weight into a tube shape.