JPS6161485B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a watertight mixture that is press-fitted between the strands of strands of a watertight insulated electric wire. Conventionally, watertight mixtures for insulated wires include high-viscosity compounds that are filled when stranding wires, polyethylene wax dissolved in polybutene oil, and liquid epoxy resin with a hardening agent added inside the stranded wires. A type that is press-filled between the wires has been proposed, and more recently, a mixture of ethylene vinyl acetate copolymer or ethylene ethyl acrylate copolymer and low molecular weight polyethylene with a melt index of 300 or more ( Japanese Unexamined Patent Publication 1973-
163708) is proposed. However, all of the above materials belong to the hot melt type with high heat softening properties, so they have low tensile strength at room temperature, a marked decrease in tensile strength at high temperatures, and are easily deformed. The disadvantage was that the performance of the watertight insulated wire deteriorated due to the large amount of water. The present invention has been made with attention to this point,
It is a watertight mixture that improves the watertightness and adhesion as well as its physical properties at high temperatures through crosslinking.The gist is that ester gum, terpene resin, terpene phenol resin, and ionomer are added to the ethylene terpolymer. resin, petroleum rosin,
It is a watertight mixture for insulated wires with crosslinking properties, which is made by blending at least one tackifier and crosslinking agent selected from aliphatic petroleum resins, etc. More precisely, it is an ethylene/α mixture with a melt index of 30 or less. An insulating watertight mixture for injection into stranded wires, containing 5 to 30 parts by weight of the above-mentioned tackifier and an effective amount of a crosslinking agent to 100 parts by weight of an olefinic terpolymer, and containing no plasticizer. It is a thing. The present invention uses ethylene terpolymer as a main component and crosslinks it to strengthen the bond between the watertight mixture and the conductor as well as the external insulator (polyethylene or crosslinked polyethylene) and improve watertightness. This ethylene terpolymer is composed of ethylene, α-
It is composed of three components of olefin and diene such as butadiene, and those having a melt index of 30 or less, such as commercially available products such as Mitsui Elastomer X75 (manufactured by Mitsui Petrochemicals), can be suitably used. In this ethylene terpolymer, ester gum,
using at least one tackifier selected from terpene resins, terpene phenol resins, ionomer resins, petroleum rosins, aliphatic petroleum resins, etc.;
Further, sulfur, hydroperoxide, ketone peroxide, hydrogen peroxide, etc. are blended as a crosslinking agent. The proportion of the tackifier in these formulations is 1 to 70 parts by weight, preferably 5 to 30 parts by weight, per 100 parts by weight of the ethylene terpolymer. If this amount is too small, the tackiness will be low, and if it is too large, the physical properties and thermal stability of the watertight mixture obtained by crosslinking will deteriorate. Further, the peroxide is suitably used in an amount of 0.3 to 5 parts by weight, and other antioxidants and colorants may be added as long as they do not impair the properties of the mixture. The watertight mixture of the present invention obtained by the above formulation is press-filled into a stranded wire made by twisting strands of wire using an extruder, and then crosslinked together with the external insulator under conditions such as high temperature and pressurized steam. This makes it a watertight insulated wire. Hereinafter, the present invention will be specifically explained with reference to Examples. First, watertight mixtures shown in Examples 1 to 3 and Comparative Examples 1 to 2 below were prepared. Example 1 Ethylene Terpolymer (Mitsui Elastomer
100 parts by weight Ionomer resin 10 Crosslinking agent 0.6 Antiaging agent 0.8 Example 3 Ethylene terpolymer (Mitsui Elastomer X75)
100 parts by weight Terpene resin 30 Crosslinking agent 3 Anti-aging agent 0.4 Comparative example 1 Ethylene terpolymer (Mitsui Elastomer X75)
100 parts by weight Terpene resin 10 Anti-aging agent 0.4 Comparative example 2 Ethylene terpolymer (Mitsui Elastomer X75)
100 parts by weight Terpene resin 70 Anti-aging agent 0.6 Each of the watertight mixtures obtained in Examples 1 to 3 and Comparative Examples 1 and 2 above was evaluated by the method shown below. The results are shown in Table 1. (1) Room temperature tensile strength and elongation: room temperature tensile fracture strength,
Tensile elongation at break was measured. (2) Tensile strength and elongation at 90°C: Tensile strength and elongation at break were measured in a 90°C oven. (3) Adhesive strength to copper plate and cross-linked polyethylene: A 1 mm-thick watertight mixture sheet was sandwiched between a 1-mm-thick copper plate and a cross-linked polyethylene sheet at 150°C.
After press bonding for 10 minutes at 50 kg/cm ² , the adhesive strength was measured using a tensile tester. (4) Vikatto softening point: The Vikatto softening point was measured by raising the temperature to 50°C for 1 hour. (5) Heating deformation rate: 90℃ preheating for 30 minutes, heating load 1 for 30 minutes
The amount of deformation was measured in kg. (6) Loss of volatilization: The loss of volatilization after 96 hours in a 150°C oven was measured gravimetrically.

【table】

[Table] As is clear from Table 1, by crosslinking the watertight mixture according to the present invention, the physical properties at room temperature and high temperature are improved, and the adhesion to copper and crosslinked polyethylene is on the same level as conventional products. It is. Next, the watertightness of insulated wires using the watertight mixtures of Examples 1 to 3 above was tested as follows. In other words, when a water pressure of 10.0 kg/cm ² was applied to one end of a 2 m long watertight outdoor cross-linked polyethylene insulated wire and maintained for 24 hours, and the amount of water leaked from the other end was measured, there was no leakage at all, indicating complete watertightness. showed that. Since the present invention is as described above, by press-fitting the stranded wire between the strands of wire and crosslinking it, the tensile strength at room temperature and high temperature is high, and the heat deformation rate and volatile content are low. A watertight insulated wire with excellent properties can be obtained.

Claims (1)

[Claims] 1. At least one adhesive selected from ester gum, terpene resin, terpene phenol resin, ionomer resin, petroleum rosin, aliphatic petroleum resin, etc. per 100 parts by weight of ethylene/α-olefin terpolymer having a melt index of 30 or less. An insulating watertight mixture for injection into stranded wires, characterized in that it contains 5 to 30 parts by weight of a imparting agent and an effective amount of a crosslinking agent, and does not contain a plasticizer.