IMPROVEMENTS IN OR RELATING TO PARAFORMALDEHYDE PRODUCTION

摘要

1,201,662. Paraformaldehyde production. TENNECO CHEMICALS Inc. 23 Jan.; 1968 [1 Feb., 1967], No. 3601/68. Heading C3P. Paraformaldehyde is obtained by a process in which (a) an aqueous solution of formaldehyde is concentrated by heating, (b) the concentrated solution is heated to polymerize the formaldehyde, (c) the above steps (a) and (b) are repeated, and (d) the mixture is cooled and solidified to obtain the paraformaldehyde. Step (a) is carried out using a solution of 30 to 50% formaldehyde having a pH of 2 to 5, at a temperature of 140‹ to 200‹ C., a pressure of 75 to 150 mm. for 2 to 120 seconds, forming a solution containing 60 to 75% formaldehyde. Step (b) is carried out at 60‹ to 90‹ C. for 30 to 120 minutes. Step (a) is repeated to form a solution containing 82 to 88% formaldehyde. The repetition of step (b) is carried out at 100‹ to 140‹ C. at a pressure of 1 to 5 atmospheres for 1À5 to 4 hours.