| 摘要 |
In cold-hardening plastic compositions suitable for use as adhesives, coating compositions, impregnants, &c. and comprising urea, melamine or phenol-aldehyde condensates, or proteins, e.g. casein, gluten and a hardening agent, premature hardening is prevented by providing the hardening agents with a coating which is dissolved off when a solvent, e.g. water, is added to make up the adhesive &c. The coating is applied by the usual pill-coating procedure and materials such as starch, china clay, gypsum, talc, graphite may be used as coating materials, also sugar, size, dextrin solutions may be used or a suspension of a synthetic resin, e.g. a vinyl resin. Adhesion of the coating agents may be obtained by a preliminary coating with an adhesive substance. Hardening agents specified are ammonium salts, e.g. phosphates, chloride, potassium persulphate, oxalic acid, tartaric acid, betanaphthalene sulphonic acid, alkali hydroxides and carbonates, hexamine, formaldehyde. A stable dry glue is prepared by adding to a comminuted urea-aldehyde resin a hardener made by melting together 50 parts ammonium chloride and 50 parts urea in a little water, allowing to solidify, comminuting and coating the particles with 10 parts finely-ground, dead burned gypsum. There are also described hardening pills made of (2) ammonium chloride spray coated with alcohol and starch and used in conjunction with melamine resin and rye flour; (3) tablets of rye flour and potassium persulphate coated with sugar solution and china clay; (4) paraformaldehyde and potato starch grains spray coated with alcohol-sugar solution and used in conjunction with gluten glue; (5) beta-naphthalene sulphonic acid grains spray coated with vinyl resin and used to harden an acid hardenable phenol-aldehyde resin. The melamine resin used in (2) and (3) is obtained by condensing 1 mol. melamine with 2 or 3 mols. aqueous neutral formaldehyde until a cooled test portion gives turbidity with 3 parts water, evaporating and drying under vacuo.ALSO:In cold-hardening plastic compositions suitable for use as adhesives, coating compositions, impregnants &c. and comprising urea, melamine or phenol-aldehyde condensates, or proteins, e.g., casein gluten and a hardening agent, premature hardening is prevented by providing the hardening agents with a coating which is dissolved off when a solvent, e.g., water, is added to make up the adhesive &c. The coating is applied by the usual pill-coating procedure and materials such as starch, china clay, gypsum, talc, graphite may be used as coating materials also sugar, size, dextrin solutions may be used or a suspension of a synthetic resin, e.g., a vinyl resin. Adhesion of the coating agents may be obtained by a preliminary coating with an adhesive substance. Hardening agents specified are ammonium salts, e.g., phosphates, chloride, potassium persulphate, oxalic acid, tartaric acid, beta-naphthalene sulphonic acid, alkali hydroxides and carbonates, hexamine, formaldehyde. A stable dry glue is prepared by adding to a comminuted ureaaldehyde resin a hardener made by melting together 50 pts. ammonium chloride and 50 pts. urea in a little water allowing to solidify, comminuting and coating the particles with 10 pts. finely ground dead burned gypsum. There are also described hardening pills made of (2) ammonium chloride spray-coated with alcohol and starch and used in conjunction with melamine resin and rye flour (3) tablets of rye flour and potassium persulphate coated with sugar solution and china clay (4) paraformaldehyde and potato starch grains spray coated with alcohol-sugar solution and used in conjunction with gluten glue. (5) beta-naphthalene sulphonic acid grains spray coated with vinyl resin and used to harden an acid hardenable phenol-aldehyde resin.
|
