Patent GB-461681-A (GB)
Title: Improvements in and relating to dielectrics for electrical apparatus
IPC: H01B3/24
Filed: 1935-08-21
Abstract: Aryl-alkyl ethers halogenated in the aryl nucleus, alone or with appropriate additions, are used as dielectric materials in electric condensers, cables, bushings and like apparatus. Suitable ethers are obtainable by heating a polyhalogenated aromatic hydrocarbon with an aliphatic alcohol and an alkali, preferably in the presence of a catalyst such as cuprous chloride. Examples are given in which (1) an isomeric tetrachlorobenzene mixture is heated with ethyl alcohol and an equimolecular proportion of caustic soda to yield a trichlorophenetole; various physical properties of the product are specified, and the properties of a condenser containing the product as dielectric are compared with those of a condenser containing mineral oil; (2) as in example 1 but with a higher proportion of alkali, the product being a mixture of di- and tri-chlorophenetoles; various physical properties of the product are specified; (3) p-dichlorobenzene is heated with ethyl alcohol and caustic soda; (4) an isomeric trichlorobenzene mixture is treated as in example 3; various physical properties of the product, and of a mixture of the product with the product of example 1, are specified; (5) chlorinated diphenyl containing about 60 per cent of chlorine is heated with methyl alcohol and caustic soda; (6) an isomeric trichlorobenzene mixture is treated as in example 5; in each example the mixture is heated to about 240--260 DEG  C. in the presence of a little cuprous chloride.  The chlorine compounds used in the examples may be replaced by the corresponding fluorine, bromine or iodine compounds, and the caustic soda may be replaced by caustic potash or calcium hydroxide.  Suitable ethers are obtainable similarly from polyhalogen derivatives of naphthalene, anthracene, and diphenylbenzenes, and also from hexachlorobenzene.  Suitable materials which may be used with the halogenated ethers are mineral, vegetable and animal oils, such as transformer oil, trichlorobenzene, halogenated diphenyl compounds, and chlorinated derivatves of diphenylmethane, naphthalene, diphenylethane, and benzophenone.  The Specification as open to inspection under Sect. 91 states that the halogenated ethers, or mixtures containing them, may be used as lubricants, and refers also to the use of the ethers in switchgear apparatus and electric transformers.  This subject-matter does not appear in the Specification as accepted.ALSO:Aryl-alkyl ethers halogenated in the aryl nucleus are obtained by heating a polyhalogenated aromatic hydrocarbon with an aliphatic alcohol and an alkali.  Examples are given in which (1) an isomeric tetrachlorobenzene mixture is heated with ethyl alcohol and caustic soda to yield a trichlorophenetole; various physical properties of the product are specified; (2) as in example 1 but with a higher proportion of alkali, the product being a mixture of di- and tri-chlorophenetoles; various physical properties of the product are specified; (3) p-dichlorobenzene is heated with ethyl alcohol and caustic soda; (4) an isomeric trichlorobenzene mixture is treated as in example 3; various physical properties of the product, and of a mixture of the product with the product of example 1, are specified; (5) chlorinated diphenyl containing about 60 per cent of chlorine is heated with methyl alcohol and caustic soda; (6) an isomeric trichlorobenzene mixture is treated as in example 5.  The chlorine compounds used in the examples may be replaced by the corresponding fluorine, bromine or iodine compounds, and the caustic soda may be replaced by caustic potash or calcium hydroxide.  Suitable ethers are obtainable similarly from polyhalogen derivatives of naphthalene, anthracene and diphenylbenzenes, and also from hexachlorobenzene.  Specified materials which may be mixed with the halogenated ethers are mineral, vegetable and animal oils, such as transformer oil, trichlorobenzene, halogenated diphenyl compounds and chlorinated derivatives of diphenylmethane, naphthalene, diphenylethane, and benzophenone.  The Specification as open to inspection under Sect. 91 states that the halogenated ethers, or mixtures containing them, may be used as lubricants.  This subject-matter does not appear in the Specification as accepted.