Patent GB-588503-A (GB)
Title: Improvements in or relating to dispersions of synthetic elastomers
IPC: C08K5/17
Filed: 1945-02-23
Abstract: The pH of alkaline latices of synthetic elastomers is reduced by adding an aliphatic amino acid in which the amino hydrogens may be replaced by alkyl groups and which contain an equal number of amine and acid groups.  The aliphatic amino acids, which may be glycine, alanine, b -alanine, a -amino n- or iso-butyric acid, taurine, sarcosine or epsilon amino caproic acid, may be added in strong aqueous solution, or in the form of a slurry together with bentonite. The synthetic elastomers may be polymerized butadiene, isoprene, chloroprene or other haloprenes, or interpolymers of these compounds with styrene, vinylidene chloride, vinylethynyl carbinols, acrylic and methacrylic esters and nitriles.  A suitable polychloroprene is obtained by emulsifying chloroprene in the presence of rosin, sulphur, sodium hydroxide and potassium persulphate and polymerizing in nitrogen, diethanolamine being added subsequently.  Similarly, polybutadiene and interpolymers of butadiene and isoprene with styrene and acrylonitrile are obtained by polymerizing the appropriate monomers in a mixture chosen from oleic acid, wood rosin, mercaptans, sodium hydroxide, potassium persulphate and ferricyanide and the sodium salt of formaldehyde-naphthalene sulphonic acid, the polymerized material being stabilized with phenyl a -naphthylamine and diphenylamine. In an example, a latex concentrated by means of sodium alginate is mixed with sodium silico-fluoride and the pH reduced to 9.3 by means of 20 per cent glycine solution.  The amino acid may be combined with dispersions of vulcanizing agents, colours, fillers, accelerators or activators which may be added at any stage of the process.ALSO:The pH of alkaline latices of synthetic elastomers is reduced by adding an aliphatic amino acid in which the amino hydrogens may be replaced by alkyl groups and which contain an equal number of amine and acid groups.  The aliphatic amino acids which may be glycine, alanine, b -alanine, a -amino n-, or a -amino isobutyric acid, taurine, sarcosine or epsilon amino caproic acid, may be added in strong aqueous solution, or in the form of a slurry together with bentonite.  The synthetic elastomers may be polymerized butadiene, isoprene, chloroprene or other haloprenes, or interpolymers of these compounds with styrene, vinylidene chloride, vinylethynyl carbinols, acrylic and methacrylic esters and nitriles. The elastomers may be polymerized in the presence of various dispersing agents (see Group IV), and after cooling, an emulsion of phenyl a  naphthylamine and diphenylamine may be added.  In an example, a neoprene latex containing 64 per cent. solids has its pH reduced from 12.3 to 9.7 by the addition of 20 per cent. glycine solution after which the latex is compounded with zinc oxide, phenyl b  naphthylamine and sodium silico-fluoride.  In a further example, a latex concentrated by means of sodium alginate is mixed with sodium silico-fluoride and the pH reduced to 9.3 by means of 20 per cent. glycine solution. The amino acid may be combined with dispersions of vulcanizing agents, colours, fillers, accelerators or activators which may be added at any stage of the process.  The resultant latices are suitable for use in processes involving acid coagulation such as moulding with fluosilicates, nitroparaffin, or ammonium nitrate as gelling agents, spinning thread into acid baths, or making foam sponge products by the fluosilicate gelation process.