JPS5851364B2 - Waterproof cable for submerged electrical equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waterproof cable for submerged electrical equipment used in various submerged electrical equipment such as submersible pumps.

When it comes to electrical equipment used in various types of liquids, the most important functional points to keep in mind are maintaining electrical insulation and waterproof properties.

Cables used for submerged electrical equipment have traditionally been fitted with a rubber bushing integrally molded to the rubber sheathed cable, or molded separately to prevent water from seeping into the equipment from the exposed part of the cable and equipment. A rubber bushing was fitted around the outer circumference of the cable and glued to provide liquid tightness.

In recent years, this type of waterproof cable has come to be used in a variety of water conditions, and due to requirements such as chemical resistance and flexibility, and from the economic point of view, vinyl cables with a polyvinyl chloride sheath have been used. -Full became widely used.

However, vinyl has the drawback of significantly inferior backing properties compared to rubber (mainly chloroprene).

For this reason, vinyl is not suitable for bushings for submerged equipment that requires waterproofness, and even though vinyl sheaths have come to be used for cables, rubber bushings are still used for bushings. is the current situation.

Traditionally, rubber adhesives were used to bond vinyl and rubber.

However, in the case of vinyl-sheathed cables that require flexibility, vinyl with plasticizer is used as the sheath material to make it soft, and due to the influence of the plasticizer, rubber-based adhesives alone cannot connect the vinyl sheath and rubber. has poor adhesion,
Sufficient adhesive strength cannot be obtained.

In addition, the conventional type had the disadvantage that the plasticizer in the vinyl diffused into the rubber bushing over time, and the adhesive strength between the rubber bushing and the vinyl tended to decrease over time.

Conventionally, therefore, a plasticizer-containing vinyl sheath and a rubber bushing were bonded by applying a primer made of methyl methacrylate graft rubber as an undercoat and applying a rubber adhesive thereon.

In this way, sufficient adhesion strength is exhibited and is very good.

Adding incyanate to the primer, applying the primer, drying the primer, applying rubber adhesive, etc. are complicated and time-consuming processes, and the work time is also long, making it difficult to save labor and improve work efficiency during mass production. desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a waterproof cable for submerged electrical equipment that can be easily and efficiently bonded while achieving an adhesive strength comparable to or higher than that of conventional cables.

Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 to 3, the waterproof cable for submerged electrical equipment of this embodiment has a plurality of stranded conductors 1, and the outer periphery of each stranded conductor 1 is covered with a plasticizer-containing vinyl insulation layer 2. The wires are each coated with a vinyl-free R electric wire 3.

These vinyl-cut R electric wires 3 are twisted together, and a plasticizer-containing vinyl sheath 4 is commonly coated thereon.

At one end in the length direction of the plasticizer-containing vinyl sheath 4, the vinyl sheath 4 is removed to expose each vinyl insulated wire 3, and at this portion, each vinyl insulating layer 2 is removed over a required length, and the vinyl insulating layer 2 is removed at that portion. Each stranded conductor 1 is filled with a waterproofing material 5 such as solder to form a stranded conductor waterproof portion 6, respectively.

A primer (for example, Chemlock 205, sold by Konishi Kako Co., Ltd.) is applied to the waterproof part 6 of each stranded conductor, and a rubber and metal adhesive (
For example, the intermediate adhesive layer 7 is formed by applying Chemlock 220) and wrapping raw rubber tape thereon.

On the plasticizer-containing vinyl sheath 4 near the end, add a triphenylmethane-triisocyanate solution (for example, Tesmodor R manufactured by Bayer AG of West Germany in a 1:1 solution of toluene).
An incyanate adhesive layer 8 is formed by applying a solution diluted to

That is, this incyanate adhesive layer 8 is an adhesive layer containing incyanate as the sole adhesive component, which has conventionally been unthinkable to be used alone.

A rubber bushing 9 is integrally formed around the vinyl insulated wire 3 and the isocyanate adhesive layer 8 on both sides of the stranded conductor waterproof portion 6, and is vulcanized.

9A is a tapered portion of the rubber bushing 9.

The rubber bushing 9 is formed by wrapping unvulcanized rubber around the outer periphery of the processed portion of the cable, fitting it into the outer periphery with a mold, heating and pressurizing it to shape it, and vulcanizing it.

When the rubber bushing 9 is formed in this manner, the plasticizer-containing vinyl sheath 4 and the rubber bushing 9 are firmly adhered to each other via the incyanate adhesive layer 8.

The adhesive strength is comparable to that of a rubber bushing obtained by a conventional adhesive method using a primer and a rubber adhesive.

However, according to the present invention, the primer is not required, and therefore the application process and the drying process are omitted.
The process is simplified, labor is saved, and working time is shortened, so that waterproof cables for submerged electrical equipment can be manufactured efficiently.

The bonding mechanism between plasticizer-containing vinyl and rubber using triphenylmethane-triisocyanate as the sole adhesive is thought to be that they are bonded by vulcanization (crosslinking) during heating and pressurization.

Further, when the incyanate adhesive layer 8 is present, the migration of the plasticizer from the plasticizer-containing vinyl sheath 4 to the rubber bushing 9 can be prevented by the incyanate adhesive layer 8,
Stable adhesive strength can be obtained.

When bonding the plasticizer-containing vinyl sheath 4 and the rubber bushing 9, an isocyanate adhesive prepared by diluting incyanate with toluene at a ratio of 1:1 showed no difference in adhesive strength compared to applying the undiluted solution, and diluted The drying speed of the coated surface is faster with the solution, and the work can be done more quickly and at a lower cost.

According to experiments, it was confirmed that the adhesive strength of incyanate did not decrease even if it was diluted several times with a diluent.

When diluted and used in this way, a diluent such as toluene is much cheaper than an isocyanate solution, and is suitable as an extremely low-cost adhesive.

Also, if the components of the rubber bushing 9 are as follows,
It has been found that the adhesive strength between the plasticizer-containing vinyl sheath 4 and the rubber bushing 9 can be further improved.

That is, as the rubber for forming the rubber bushing 9, a rubber whose main filler is about 30 to 80 parts by weight of calcium carbonate made of ultrafine particles is used.

The method of forming the rubber bushing 9 in this case is the same as described above.

That is, unvulcanized rubber containing 30 to 80 parts by weight of calcium carbonate made up of ultrafine particles as the main filler is wrapped around the outer circumference of the processed portion of the cable described above, fitted into the outer circumference with a mold, and molded by heating and pressurizing. Rubber bushing 9 is obtained by vulcanizing at the same time.

When the rubber bushing 9 is formed from a special component in this manner, the plasticizer-containing vinyl sheath 4 and the rubber bushing 9 are more firmly bonded to each other via the incyanate adhesive layer 8.

The adhesive strength between plasticized vinyl and rubber is greatly influenced by the type and amount of filler added to the rubber (Possible fillers include clay, talc, calcium carbonate, etc., but experiments have shown that fatty acids It has been found that when calcium carbonate made of ultrafine particles (for example, average particle diameter of 0.04 μm or less) treated with is used as a filler, stronger adhesive strength can be obtained and the electrical insulation is also excellent.

If the blending ratio of calcium carbonate is selected to be about 30 to 80 parts by weight, a sufficiently strong adhesive strength can be obtained within this range, but if it is outside this range, i.e. less than about 30 parts by weight, the reinforcing properties for rubber will decrease. If the reinforcing property exceeds about 80 parts by weight, the adhesive strength decreases to be equal to or lower than the conventional adhesive strength.

In addition, when the particle size of calcium carbonate is selected to be extremely fine, the surface area of calcium carbonate becomes large, and therefore, the surface activity becomes large, the compatibility with rubber increases, and the reinforcing property increases.

In particular, the meaning of particle size in the present invention is with respect to the adhesion of rubber.

The effect of increasing the cohesive force of rubber molecules on the adhesive surface is that clay and light calcium carbonate (average particle diameter of 0.1μ or more)
It is smaller and less effective than calcium carbonate, which consists of extremely fine particles (for example, average particle size 0.04 μ).

Incidentally, silica-based fillers also have a sufficient adhesive effect, but are unsuitable because their electrical properties are extremely poor and their water absorption is extremely large.

Examples of compounding rubbers for rubber bushings and examples of adhesion using these rubbers are shown in Tables 1 and 2.

In Table 2, adhesive method 1 refers to the conventional adhesive method in which a primer containing isocyanate is applied and then a rubber adhesive is applied, and adhesive method 2 refers to the method in which triphenylmethane-triisocyanate is applied. Refers to the adhesive method used in the present invention that is applied as an adhesive and does not use a primer.

In addition, in adhesion method 1, Nisdyne #277B (trade name, manufactured by Sekisui Chemical Co., Ltd.) was used as a primer, to which triphenylmethane triisocyanate was added as an isocyanate.

The same Nisdyne #277NPU was used as the rubber adhesive.

As is clear from Table 2, the rubber for bushings containing ultrafine particles of calcium carbonate is more effective than the rubber for bushings containing calcined clay (formulation example 1) and the rubber for bushings containing ultrafine particle calcium carbonate (formulation example 2). Rubber (formulation example 3) has greater adhesive strength.

Further, Adhesion Method 1 and Adhesion Method 2 show the same tendency of adhesive strength, and there is almost no difference between them, and it is clear that sufficient adhesive strength can be obtained even when Adhesion Method 2 is used.

As described above, according to the present invention, although adhesive strength comparable to that of the conventional method can be obtained, the number of man-hours required for the adhesive is small;
It has the advantage of being able to perform bonding work efficiently in a short time.

Table 3 shows blending examples of the plasticizer-containing vinyl used in Table 2.

In addition, submerged electrical equipment generally has an integrally molded rubber bushing that is constantly immersed in the liquid, and we conducted an experiment on the change in adhesive strength over time assuming that it was immersed in water for a long time. The results shown in Table 4 were obtained.

Table 4 shows the results of a peel test on samples left under various environmental conditions. Even under each condition, there was almost no change in adhesive strength even after 30 days, adhesive method 1 and adhesive method 2.
Even in the case of , there is almost no difference, which is good.

When the adhesive strength, insulation resistance, and bending peeling of the rubber bushing portion of the waterproof cable for submerged electrical equipment according to the present invention were tested, the results shown in Table 5 were obtained.

As is clear from Table 5, there is almost no difference in each property between Adhesion Example 5 and Adhesion Example 6.

The average particle diameter of the calcium carbonate made of ultrafine particles blended into the rubber for rubber bushings in Compounding Example 3 is approximately 0.0.
Although it is desirable that the particle size is 4μ or less, the present invention is not limited thereto, and the average particle size may be larger than about 0.04μ (for example, about 0.08μ or less) as long as it does not fall into the category of minor particles. Of course.

Moreover, as the isocyanate, in addition to those mentioned above, paraphenylene diisocyanate, toluene diisocyanate, etc. can be similarly used as the adhesive.

As explained above, the waterproof cable for submerged electrical equipment of the present invention is made by bonding a rubber bushing and a plastic perforated vinyl sheath with an adhesive containing incyanate as a sole adhesive component, which was previously unthinkable to be used alone. However, by using such an adhesive, even without using a primer, it is possible to obtain an adhesive strength comparable to that obtained by bonding a single layer of primer and a rubber adhesive layer.

Furthermore, according to the present invention, the cost of adhesion is lower than that when adhering with adhesives having multiple adhesive components, and troublesome work such as selecting the mixing ratio of adhesive components and mixing work can be omitted. .

Moreover, the isocyanate adhesive can be used even if the isocyanate is diluted, and the adhesive cost can be further reduced.

Furthermore, according to the present invention, a primer is not required, and therefore the steps of coating and drying are omitted, making it possible to manufacture economically and efficiently in a short time.

Furthermore, the presence of the incyanate adhesive layer can effectively prevent the plasticizer in the vinyl from migrating into the rubber bushing and reducing the adhesive strength over time.

Furthermore, in the second invention, since about 30 to 80 parts by weight of calcium carbonate made of ultrafine particles is blended as a filler in the rubber bushing, the adhesive strength between the rubber bushing and the plastic pierced vinyl sheath is further improved. Electrical insulation can also be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a bushing portion showing an embodiment of the waterproof cable according to the present invention, FIG. FIG. 3 is a vertical cross-sectional view of the stranded conductor waterproof section. 4...Plastic pierced vinyl sheath, 8...
・Incyanate adhesive layer, 9...Rubber bushing.

Claims (1)

[Scope of Claims] 1. A waterproof cable for submerged electrical equipment in which a rubber bushing is integrally provided on a plasticizer-containing vinyl sheath near the end of the cable, and the rubber bushing is vulcanized. Bushing is a waterproof cable for submerged electrical equipment that is bonded with an incyanate adhesive layer that contains incyanate as the sole adhesive component. 2. The waterproof cable for submerged electrical equipment according to claim 1, wherein the isocyanate is triisocyanate. 3. In a waterproof cable for submerged electrical equipment in which a rubber bushing is integrally provided on a plasticizer-containing vinyl sheath near the end of the cable, and the rubber bushing is vulcanized, the vinyl sheath and rubber bushing are made of incyanate. A submerged electrical device that is bonded with an incyanate adhesive layer as a sole adhesive component, and the rubber bushing contains about 30 to 80 parts by weight of calcium carbonate made of ultrafine particles as a filler. waterproof cable. 4. The waterproof cable for submerged electrical equipment according to claim 3, wherein the isocyanate is triisocyanate.