JPH0137811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to waterproofing admixtures for use in waterproof cables. A waterproof cable is a cable that maintains a high degree of insulating properties by completely filling the space between wire cores with a waterproofing compound.The compound used for this is not allowed in foreign countries. Petrolatum-based mixtures, and in Japan, polybutene-based mixtures are used. 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. When both mixtures are heated to a fluid state and injected into the cable sheath, the volume shrinks as the temperature returns to room temperature, so the mixture is placed between the core and sheath and between the cores. The mixture cracks, creating gaps,
These areas form water passages, which poses problems in terms of waterproof performance, and both mixtures are sticky, making it very time-consuming to wipe them off when connecting cables. The present invention is a mixture for waterproof cables consisting of a naphthenic or paraffinic oil, a water-absorbing resin, a low molecular weight polyethylene or petroleum wax, an antioxidant and other additives added as necessary. The purpose of the present invention is to provide a waterproofing compound with excellent performance that prevents corrosion and is easy to wipe off upon connection. That is, the mixture for waterproof cables according to the present invention is obtained by heating and mixing the above-mentioned components at about 80 to 100 degrees Celsius.It is a gel-like solid at room temperature, but becomes soft and fluid when heated. It is as easy to inject into the sheath as traditional waterproofing admixtures. Since such a waterproof mixture shrinks as it returns to room temperature, it is inevitable that gaps will be created between the sheath and the core and between the cores. However, when water tries to enter the inside of the cable, it tries to enter through the gap, but the water-absorbing resin in the waterproofing mixture absorbs the water and swells. This water-absorbing resin is difficult to release water once absorbed, and the swollen water-absorbing resin fills the gap created by the contraction of the mixture, so water can no longer diffuse and the water travels through the cable. There's no fear. On the other hand, when connecting waterproof cables, when wiping off the waterproofing compound adhering to the terminal, if a small amount of water is applied, the water-absorbing resin swells while containing other components such as oil and polyethylene. Since it has a gel-like appearance, the mixture can be removed very easily. In more detail, the waterproof mixture of the present invention is as follows:
Among the oils in the mixture, naphthenic or paraffinic mineral oils have good electrical properties and are less likely to cause stress cracks to the polycarbonate connector material used for cable connections.
Moreover, it is inexpensive in terms of cost. On the other hand, aromatic mineral oils are not preferred because they tend to cause stress cracks in the polycarbonate connector material and have poor electrical properties. Next, water-absorbent resins include starch-based acrylonitrile grafted hydrolysates, acrylic acid graft compounds, cellulose-based graft polymers, carboxymethylated products, synthetic resin-based polyacrylates, polyvinyl alcohols, and polyethylene oxides. , a sodium acrylate acrylamide copolymer system, an isobutylene maleic acid copolymer system, or the like. Examples of the low molecular weight polyethylene include A/C polyethylene, and examples of the petroleum wax include paraffin wax and microcrystalline wax, which act effectively to make the mixture solid at room temperature and liquefied by heating. Furthermore, the antioxidant acts to prevent the mixture from oxidizing, and for example, as a phenolic stabilizer, tetrakis[methylene-3(3.5-di-t-butyl-4-hydroxy-phenyl)propionate]methane... …Product name Irganotx 1010,
4,4'-thio-bis(3-methyl-6-t-butylphenol)...Product name Santonox R,
2,6-di-t-butyl-P-cresol (trade name: BHT), etc., but is not limited thereto. Other additives that may be added as necessary include clay,
It is also possible to add inorganic fillers such as calcium carbonate, silica, magnesium carbonate, talc and the like. The preferred composition of the waterproofing mixture of the present invention is as follows. Oil 100 parts by weight Water-absorbing resin 1-50 Low molecular weight polyethylene or petroleum wax
10 to 50 〃 Antioxidant 0.1 to 1 〃 Other additives 10 to 50 〃 The residue above except for the water absorbing resin has essentially a waterproof effect, but adding the water absorbing resin It completely captures water, enhances the waterproof effect, does not become sticky when connected, and is easy to remove as it becomes tattered. If the water-absorbing resin is less than 1 part by weight, water will seep into the cable, and if it is more than 50 parts by weight, the cable will contain more resin than necessary. Furthermore, if the amount of low molecular weight polyethylene or petroleum wax is less than 10 parts by weight, the softening temperature will be too low, and if it is more than 50 parts by weight, the mixture may be difficult to soften and flow when heated. If the antioxidant is less than 0.1 part by weight, its effect will be insufficient, and if it is more than 1 part by weight, the amount will be excessive. Further, 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. Next, a comparison between the waterproof mixture of the present invention and a conventional waterproof mixture is as follows. 【table】

Claims (1)

[Claims] 1 100 parts by weight of naphthenic or paraffinic oil, 1 to 50 parts by weight of water absorbent resin, 10 to 50 parts by weight of low molecular weight polyethylene or petroleum wax, 0.1 to 1 part by weight of antioxidant, and other additives. Ten~
A mixture for waterproof cables consisting of 50 parts by weight.