JPH0137812B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to waterproofing admixtures for use in waterproofing cables. A waterproof cable is a cable in which the space between wire cores in the cable is completely filled with a waterproofing compound to highly protect the insulation properties of the cable. A petrolatum-based mixture is used, and a polybutene-based mixture is used in Japan. Petrolatum-based mixtures are made by adding low-molecular-weight polyethylene or petroleum wax, antioxidants, etc. to petrolatum after petroleum refinement, and polybutene-based mixtures are made by adding petroleum wax, antioxidants, etc. to polybutene. , any mixture of
When heated to a fluid state and injected into a cable sheath, the volume shrinks as the temperature returns to room temperature, resulting in cracks in the mixture between the core and sheath and between the cores. This creates a gap and forms a passage for water, which poses a problem in terms of waterproof performance, and both mixtures are sticky and require a lot of effort to wipe off when connecting cables. There were drawbacks such as: The present invention solves the above-mentioned drawbacks, and the waterproof mixture consisting of petrolatum or polybutene, a water-absorbing resin, low molecular weight polyethylene or petroleum wax, and additives is solid at room temperature and becomes fluid when heated. It can be easily filled into the cable sheath, and even if water tries to enter the cable due to volumetric shrinkage, the water-absorbing resin in the mixture will actively absorb this water. As a result, water that would otherwise not enter the cable is trapped near the inlet, making it difficult for it to penetrate and diffuse in the longitudinal direction of the cable. Waterproof properties can be significantly improved. On the other hand, when processing the terminals of waterproof cables during connection work, if the cable sheath is removed and a small amount of water is applied, the water-absorbing resin contained in the waterproof cable mixture will swell, resulting in petrolatum, polybutene, low It swells into a cotton-like consistency while incorporating the substances constituting the mixture of molecular weight polyethylene or petroleum wax and additives, and is easy to handle as it does not become sticky and can be easily removed. To explain in more detail about each substance that composes the mixture of the present invention, petrolatum or polybutene, which is the main component of the mixture, has essentially excellent electrical insulation, becomes viscous with slight heating, and is water resistant. , which has a function as a binder in the mixture, and petroleum refined petrolatum is usually used as the petrolatum. Next, as water-absorbing resins, starch-based resins include acrylonitrile grafted hydrolysates and acrylic acid grafted products, cellulose-based resins include graft polymers and carboxymethylated products, and synthetic resins include: There are polyacrylic acid type, polyvinyl alcohol type, polyethylene oxide type, sodium acrylate acrylamide copolymer type, and isobutylene maleic acid copolymer type, and their water absorption properties are as described above. Low molecular weight polyethylene or petroleum wax are both linear hydrocarbons that serve to make the mixture solid at room temperature and fluid at elevated temperatures. Examples of low molecular weight polyethylene include A/C polyethylene, and examples of petroleum waxes include paraffin wax and microcrystalline wax. Antioxidants act to prevent acidification of mixtures, for example, as phenolic stabilizers,
Tetrakis[methylene-3(3.5-di-t-butyl-4-hydroxy-phenyl)propionate]methane...trade name Irganox 1010, 4,
4'-thio-bis(3-methyl-6-t-butylphenol)...Product name Santonox R, 2,6
-Di-t-butyl-P-cresol...Product name
Examples include BHT, etc., but are not limited to this. Other additives include inorganic fillers such as clay, calcium carbonate, silica, magnesium carbonate, and talc to adjust viscosity, increase weight to reduce costs, and improve electrical properties. It is also possible to do so. The mixture of the present invention is formed from the above materials, and typical compositions are as follows. Petrolatum or polybutene 100 parts by weight Water-absorbing resin 1-50 Low molecular weight polyethylene or petroleum wax
1 to 50 〃 Antioxidant 0.1 to 2 〃 Other additives 10 to 50 〃 In the above composition, if the amount of water absorbent resin is less than 1 part by weight, it is considered that the water capture is insufficient for practical purposes. On the other hand, if the amount is more than 50 parts by weight, the mixture tends to become hard and contains more resin components than necessary, making it difficult to fill the cable. If the amount of low molecular weight polyethylene or petroleum wax is less than 1 part by weight, fluidity upon heating will be improved, but the softening temperature will drop too much, and if it is more than 50 parts by weight, the mixture will be difficult to soften and fluidize when heated. If the amount of the antioxidant is less than 0.1 part by weight, the mixture will not have sufficient oxidation prevention, and if it is more than 2 parts by weight, the amount will be too much for the antioxidant effect, resulting in waste. In addition, as other additives, inorganic fillers may be added; if it is less than 10 parts by weight, there is no effect, and if it is more than 50 parts by weight, the viscosity of the mixture tends to become harder than necessary. Incidentally, the characteristics of the mixture according to the present invention and the mixture of the comparative example are as follows.

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Claims (1)

[Claims] 1 100 parts by weight of petrolatum or polybutene,
1 to 50 parts by weight of water absorbent resin, 1 to 50 parts by weight of low molecular weight polyethylene or petroleum wax, and antioxidant
1. A mixture for waterproof cables, comprising 0.1 to 2 parts by weight and 10 to 50 parts by weight of other additives.