JPS5926107B2 - Simple method for covering wire joints - Google Patents

Description

[Detailed description of the invention] The present invention relates to a new and simple method for covering wire joints.

Conventional methods for insulating and covering the soldered joints of electric wires include wrapping them with adhesive tape or covering them with heat-shrinkable tubes.

These methods are effective and simple coating methods when applied to low voltage and low current equipment. However, when applied to high-voltage, high-current equipment, sufficient insulation properties cannot be obtained at the joints of electric wires, and the adhesion between the metal joints and the coating layer is insufficient, which prevents moisture from penetrating. This caused corona discharge and insulation defects.

In response, attempts have been made to increase the adhesion between the coating layers by using heat-shrinkable tubes containing adhesive or adhesive, but in this case, it is not possible to coat the joints uniformly.
If there is a void inside, a gap will also be created in the part that comes into contact with the outside air.

Therefore, when used in an environment with a lot of moisture or dust, dielectric breakdown may occur in a short period of time (1) This is not an appropriate coating method. The inventors of the present invention have conducted extensive research to overcome the above-mentioned problems, and as a result, we have found a bonding wire that can be used in environments such as underwater and dusty environments, and that can be easily coated with insulation. They found a method for covering the parts and completed the present invention.

That is, in the present invention, the joint portion of the electric wire is placed in the hollow part of a pipe-like covering made of a heat-shrinkable tube whose inner wall is provided with a thermosetting resin layer that is solid at room temperature, and then the covering is heated. The present invention relates to a method of covering electric wire joint portions.

The pipe-shaped covering according to the present invention has a thermosetting resin layer formed inside a heat-shrinkable tube as described above.

The thickness or volume of the thermosetting resin layer depends on the shrinkage rate of the heat-shrinkable tube, but at least it must be such that the resin can completely fill the inside of the tube when the tube is completely shrunk. Therefore, the shape of the hollow portion in which the joint portion of the electric wire is placed and the shape of the heat-shrinkable tube may be made in any shape as long as it does not interfere with the coating operation. Furthermore, the injected resin must form a dense layer on the inner wall of the heat-shrinkable tube without creating bubbles. In the method of the present invention, the thermosetting resin is first brought into a molten state, and then the heat-shrinkable tube is heat-shrinked, so the melting point of the thermosetting resin must be lower than the contraction temperature of the heat-shrinkable tube. For example, 60-9"C is preferable.

The thermosetting resin that is solid at room temperature used in the present invention is a hydrogenated product of polyhydroxybutadiene polymer having the general formula (1): (wherein, Rl, R2 and R3 are the same or different carbon atoms, respectively). 1 to 3 lower alkyl groups, n is an integer of 1 to 4) and general formula (): (wherein R4 is an aliphatic hydrocarbon having 8 to 20 carbon atoms) A mixture containing an isocyanate masked by a phenol compound (representing a residue) as a curing agent, or a mixture with a melting point of 60 to 60
Examples include a mixture of an epoxy resin having two or more epoxy groups in the molecule and containing a complex salt of boron trifluoride blocked with an amine as a curing agent.

Examples of the isocyanate compound represented by the general formula (1) used as a curing agent in the present invention include 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate, 3-isocyanateethyl-3,
5,5-trimethylcyclohexyl isocyanate, 3
-isocyanate methyl 3,5,5-triethylcyclohexyl isocyanate, etc., and examples of the phenol compounds represented by the general formula () include octylphenol, nonylphenol, decylphenol, undecylphenol, dodecylphenol, tridecylphenol, etc. can give.

Examples of the isocyanate masked by a phenol compound include 2,4-toluene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate. Examples of epoxy resins having two or more epoxy groups in the molecule include Epicoat 1001.
(manufactured by Ciel Chemical Co., Ltd.), GY6O7l (manufactured by Ciba. Kirkey Co., Ltd.), etc., as well as Epicote 828, Epicote 1004, Epicote 1007 (all manufactured by Ciel Chemical Co., Ltd.), DER43l, and DER438 (all manufactured by Tau Chemical Co., Ltd.). Examples include those in which the melting point of a locust epoxy resin is adjusted to 60 to 90°C by blending with the like. If the melting point of an epoxy resin having two or more epoxy groups in the molecule is lower than 60°C, it will easily flow at room temperature, and if it is higher than 90°C, there is a risk that the heat-shrinkable tube will shrink when melted. Both are undesirable because they are difficult to operate. Furthermore, the heat-shrinkable tube according to the present invention may be made of, for example, ethylene propylene rubber, silicone rubber, crosslinked polyethylene, or the like.

The heat shrinkage temperature of the heat shrinkable tube is 100 to 1
40°C is preferred. Next, the coating method of the present invention will be explained in detail based on the drawings, but the present invention is not limited thereto.

Fig. 1 is an explanatory diagram of the electric wire coated according to the present invention;
3 is a cross-sectional view of the pipe-shaped covering shown in FIG. 2, and FIG. 4 is a process explanatory diagram of the coating method of the invention.

To cover the joint 2 between the cable wire 1 and the electric wire 3 shown in FIG. 1, the covering shown in FIGS. 2 and 3 is attached to the joint 2 shown in FIG.

Here, the heat-shrinkable tube 4 shown in FIGS. 2 and 3 is made of ethylene propylene rubber, and shrinks at around 130°C (shrinkage ratio 2: 2). In the example, as the thermosetting resin 5, 3-isocyanate methyl-3,5 , 7.8 parts by weight of 5-trimethylsilclohexyl isocyanate and 4.8 parts by weight of 2,4-toluene diisocyanate masked with nonylphenol are used.

This thermosetting resin has fluidity at 70 to 80°C and has a temperature of 12
By heating to 0-150℃! ) Cures in 1 to 3 hours to give a rubbery cured product. Furthermore, the curing speed at room temperature is sufficiently slow. Moreover, the covering body shown in FIGS. 2 and 3 is produced by the following procedure.

That is, the above-mentioned thermosetting resin is heated to 80° C., defoamed, and then injected into the void of the heat-shrinkable tube. The air gap is located at the center of the heat-shrinkable tube, and the inner diameter of the heat-shrinkable tube is 0.
．． It is formed by setting metal rods or glass rods that are 86 to 065 times larger. After injecting the thermosetting resin, the resin is rapidly cooled and the metal rod or glass rod is removed to obtain a pipe-shaped covering as shown in FIGS. 2 and 3. The diameter of the hollow part 6 of the covering is preferably 0.86 to 0.5 times, particularly 0.7 to 0.6 times, the inner diameter of the heat-shrinkable tube.

This value takes into account that when the heat-shrinkable tube shrinks at a shrinkage ratio of 2:1, the internal volume of the heat-shrinkable tube decreases. In the case of double, the value is when the heat-shrinkable tube is completely shrunk. To insulate the joints of electric wires using the sheathing fabricated in this way, first place the joints of the wires in the hollow part of the pipe-shaped sheath, and then heat-shrink the cable wire side of the heat-shrinkable tube. let

Thereafter, the thermosetting resin is melted in an oven at 80°C. This process leaves the joints completely filled with resin. The other side of the heat-shrinkable tube is then heated to shrink, sealing the resin within the heat-shrinkable tube.

As a final step, the joints treated as described above are heated to 140° C. in an oven to cure the resin.

At this time, the unshrinked portion of the heat-shrinkable tube contracts and applies appropriate pressure to the encapsulating resin, so that the joint portion of the electric wire can be completely sealed and covered. Electric wires coated by the method of the present invention were tested at 100 V under water. When a 5A current test was conducted, no dielectric breakdown occurred for 7 days, giving good results.

For comparison, we conducted a test under the same conditions as above for one using an adhesive tape wrapping method (5 wraps at the joint) and one using a heat-shrinkable tube lined with adhesive. , within several hours} and within two days, respectively.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the electric wire coated according to the present invention, Figure 2
3 is a cross-sectional view of the pipe-shaped covering shown in FIG. 2, and FIG. 4 is a process explanatory diagram of the coating method of the invention. (Symbols in the drawing), 1... Cable wire, 2... Joint part, 3... Electric wire, 4... Heat-shrinkable tube, 5...
・Thermosetting resin, 6...Hollow part.

Claims (1)

[Claims] 1. A joint portion of an electric wire is placed in the hollow part of a pipe-shaped covering made of a heat-shrinkable tube whose inner wall is provided with a thermosetting resin layer that is solid at room temperature, and then the covering is A simple method for covering wire joints that involves heating. 2 Thermosetting resin that is solid at room temperature is a hydrogenated product of polyhydroxybutadiene polymer, and there are general formulas ▲ mathematical formulas, chemical formulas, tables, etc. ▼ (I) (in the formula, R^1, R^2
and R^3 are the same or different and each represents a lower alkyl group having 1 to 3 carbon atoms, and n is an integer of 1 to 4)
Isocyanate compound represented by and general formula (II):
▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R^
4 represents an aliphatic hydrocarbon residue having 8 to 20 carbon atoms)
The coating method according to claim 1, wherein the coating method is a mixture of isocyanates masked by a phenolic compound represented by: 3 Thermosetting resin that is solid at room temperature has a melting point of 60 to 90
The coating method according to claim 1, which is a mixture of an epoxy resin having two or more epoxy groups in the molecule and a complex salt of boron trifluoride blocked with an amine.