| 摘要 |
Methane dithiol and mercapto-terminated polythiomethylenes are made by (a) the reaction of 1.75-10 moles of hydrogen sulphide as a liquid with 1 mole of formaldehyde at super-atmospheric pressure and at temperatures of 40-150 DEG C. to give a normally liquid intermediate whose IR spectrum indicates the presence of mercapto and hydroxyl groups, (b) treating this intermediate with an aqueous non-oxidizing mineral acid at a temperature of 25-175 DEG C. at least until the IR absorption characteristics of the hydroxyl group disappear and (c) recovering the bis mercaptan formed of the structure <FORM:0976820/C1/1> where n is 1 or more, corresponding to an average molecular weight of up to about 160. The formaldehyde employed may be in the form of an aqueous solution or paraformaldehyde. The molecular weight of the product tends to increase as the proportion of hydrogen sulphide to formaldehyde increases and as the reaction time lengthens. The intermediate, of which part at least is believed to be of the structure <FORM:0976820/C1/2> is preferably contacted with 4-6N sulphuric or hydrochloric acid. The molecular weight of the resulting dimercaptan can be increased by heating the product in water at neutral pH. The three stages can be combined into a continuous process. In examples stage (a) is carried out in a nitrogen-purged stainless steel bomb at 60 degrees so that an autogenous pressure of at least 25 atmospheres is maintained and stage (b) is effected by stirring for 6 hours under a nitrogen atmosphere at 100 DEG C. In Example 3 methane dithiol is obtained using a H2S:HCHO ratio of 10:1 and in Examples 1-4 a variety of polythiomethylenes are prepared using varying proportions of reactants in stage (a) and aqueous phases of differing pH in stage (b). In Example 5 the product from Example 1 is heated with distilled water, increasing the average molecular weight from 155 to 258. |
