Patent GB-535138-A (GB)
Title: Process for coating surfaces
IPC: B05D1/00
Filed: 1939-09-28
Abstract: 535,138. Polyamides ; coatings. DU PONT DE NEMOURS & CO.. E. I. Sept. 28. 1939, No. 26811. Convention date, Sept. 29, 1938. [Class 2 (iii)] [Also in Group III] Surfaces, such as those of metal or ceramic ware, are coated by applying to them a deposit of finely divided polyamide and fusing the deposit preferably in a non-oxidizing atmosphere. The fused coating is preferably quenched. Suitable polyamides, which are those known to be fibre-forming, include polyhexamethylene adipamide, sebacamide and pimelamide, polytetramethylene adipamide, polydecamethylene adipamide or p-phenylene acetamide, polypentamethylene terephthalamide, polymerized e-aminocaproic acid and polymers derived from polyamide forming reactants and other bifunctional compounds such as glycols and hydroxy acids. The finely divided polyamide may be obtained by grinding a polyamide of lower molecular weight followed by heating the powder below its fusion point so as to raise the molecular weight, by spraying molten polyamide into a cooling medium such as a non-oxidizing gas or liquid or by dilution of a solution of a polyamide with a non-solvent. The deposit of the powder may be applied from an agitated sieve or from an aqueous slurry followed by drying. Plasticizers, softeners, pigments, dyes, fillers, resins or cellulose derivatives may be added to the powder. The fusing is preferably effected in a non-oxidizing atmosphere under conditions which give a maximum rate of heat transfer such as placing the object bearing the deposit on a pre-heated metal plate in a muffle furnace. The coatings, which may be transparent, translucent or opaque or which may incorporate various finishes such as pearl or tortoiseshell may be variegated by placing different powders on different parts of the same plate or by superposing different powders on the same plate and then fusing ; may be patterned or may contain designs such as direction signs. Coated metals may be die-drawn or die-stamped without damaging the coating. The product may be used in the manufacture of coated cans, trays, food containers, push buttons, motor-car accessories, cartridge cases, furniture parts such as wireless cabinets, table tops, counters, benches, seats, switchplates and doors. In examples : (1) hexamethylene diammonium adipate, adipic acid and water are heated in an autoclave in the presence of carbon dioxide to yield a product which is forced out in the form of a tape and then ground, the powder so obtained being sifted on to a steel plate, fused and quenched in cold water : (2) hexamethylene diammonium adipate. acetic acid and water are heated in an autoclave in the absence of oxygen and the product dried, ground and blended with water to yield a slurry ; the slurry is sprayed on to a brass plate and the coating fused, by floating on a metal bath or by placing in a muffle furnace, and then quenched ; (3) ground polyhexamethylene adipamide is heated with 2:2-bis-p-hydroxyphenylpropane in the presence of water and methanol and the dried powder, which has absorbed some of the hydroxyphenylpropane is sieved on to a sanded steel plate, fusing by floating on to molten metal and quenched ; (4) polyhexamethylene adipamide is ground with titanium dioxide, the powder heated below its fusing point, the cooled powder sieved on to a steel plate, fused by floating on to a molten metal bath and quenched; (5) a ground interpolyamide prepared by heating a mixture of hexamethylene diammonium adipate and decamethylene diammonium sebacate is sieved on to a sanded steel plate, fused by floating on to molten metal, and quenched ; (6) adipic acid, ethylene glycol, hexamethylene diammonium adipate and water are heated in the presence of carbon dioxide and the product, cut into small pieces, is spread on a sanded steel plate, fused by floating on to molten metal and quenched ; (7) ground polyhexamethyleneadipamide is spread on to a porous plate, fused by floating onto a metal bath and then quenched.