| 摘要 |
The vulcanization of rubber is controlled to avoid scorching &c., by incorporating, in addition to an accelerator, an acidic retarding agent, and at any time before or during vulcanization nullifying the retarding effect by treatment with ammonia. As examples of acidic retarders, are organic and inorganic acids, acid salts, heavy metal salts of strong acids, acid anhydrides, acid chlorides and the like, the following being specifically mentioned:-sulphuric, phosphoric, hydrochloric, o-chlorobenzoic, o-nitrobenzoic, salicylic, acetic, mono-chloracetic, dichloracetic, trichloracetic, sulphanilic, b -naphthalene sulphonic and picric acids, dinitro-phenol, b -naphthalene sulphonic chloride, p-toluene sulphonic chloride, phthalic anhydride, sodium acid sulphate, monosodium phosphate, zinc chloride, zinc nitrate, mercuric chloride, stannous chloride, calcium chloride, magnesium chloride, aluminium chloride, ammonium chloride, ammonium nitrate and the like. The accelerator used may be of the "ultra" or "semi-ultra" types such as thiuram disulphides, thiuram monosulphides, and mercapto thiazoles or such as dithiocarbamic esters and aldehyde-amines, but should be of such a character that ammonia will co-operate with or allow activation during vulcanization. Accelerators excluded are those which are inactivated by ammonia such as oxy - n - butyl thiocarbonic acid disulphide. Twelve examples are given showing the results obtained with various mixes, including cr</>zepe and sprayed rubber. In one example latex containing ammonium phosphate is spray dried whereupon some ammonia is liberated leaving spray dried rubber containing a mixture of the two acid phosphates and some free phosphoric acid. This is then incorporated in an accelerator containing mix and vulcanized in a mixture of air and ammonia. Specifications 218,247, [Class 70, Indiarubber &c.], and 340,573 are referred to. |
