GB928309A - Method of coagulating rubbery polymer latices - Google Patents

Abstract

In coagulating natural rubber latex, polychloroprene latex, a latex of a homopolymer of a conjugated diolefin, a latex of a copolymer of a conjugated diolefin and an ethylenically unsaturated monomer or a mixture of any of these, the rubbery polymer latex is partially coagulated with a coagulant, a tackifying agent is dispersed in the partially coagulated latex and the partially coagulated latex is further coagulated with a coagulant. In a preferred procedure the latex is mixed with a tackifying agent in an amount to provide from 1 to 50 parts by weight of the tackifying agent for each 100 parts by weight of rubbery polymer, the mixture is partially coagulated, for example to the extent of from 5 to 80% by weight of the rubbery polymer originally present in the latex, tackifying agent is added to the partially coagulated latex in an amount to provide from 1 to 50 parts by weight of the tackifying agent for each 100 parts by weight of the rubbery polymer and then the partially coagulated latex is further coagulated in the presence of the added tackifying agents. The coagulant, e.g. sulphuric, hydrochloric, phosphoric and acetic acids or carbon dioxide, is preferably fresh coagulant substantially free of serum as described and claimed in Specification 928,310 divided from the present Specification. Tackifying agents: rubber polymer processing oil, rosin oil, disproportionated rosin acids, rosin, liquid low molecular weight polybutadiene, antioxidants such as the high temperature reaction product of di-phenylamine and acetone, N,N1-dioctyl paraphenylene diamine, pine tar oil, naphthenic acid, and asphaltic materials such as "mineral rubber"; the tackifying substances may be added as aqueous emulsions. The processing oils may be of paraffinic, aromatic, highly aromatic, naphthenic and highly naphthenic types. Synthetic rubber latices include copolymers of 1,3-butadiene, methyl-2-butadiene-1,3, pipelrylene and 2,3-dimethyl-buta-diene-1,3 with styrene or vinyl naphthalene; acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile, methacrylonitrile or methacrylamide; isobutylene; methyl vinyl ether; or methyl vinyl ketone. Pigmenting and/or reinforcing agents, for example, an aqueous slurry of carbon black prepared according to the method described in Specification 903,245, lignin, finely divided calcium silicate, clay, silica, zinc oxide, calcium carbonate and magnesium carbonate may be mixed with the latex prior to coagulating, brine solution and similar creaming agents preferably being omitted. According to an example, a 20% total solids content butadiene-styrene latex containing 100 parts butadiene-styrene rubbery polymer solids, and also 50 parts carbon black, 30 parts processing oil and 1,25 parts of an antioxidant was partially coagulated at about 150 DEG F. with fresh sulphuric acid solution free of serum and having a pH of 1,7. An emulsion of highly aromatic rubber processing oil was added to the partially coagulated latex and coagulation was completed at about 140 DEG F. by the addition of sufficient sulphuric acid to maintain a pH of about 3,0.