Patent GB-722723-A (GB)
Title: Solutions of elastomers derived from di-isocyanate modified polyesters
IPC: C08G18/10
Filed: 1952-02-22
Abstract: <PICT:0722723/IV (a)/1> An elastomer obtained by reacting a linear polyester with an excess of a diisocyanate and reacting the resulting diisocyanate modified polyester with water, a dihydroxy compound (see Specification 700,608) or a diamine (see Specification 700,611) is dissolved in a dimethyl carbamyl compound.  The elastomer may be made by reacting the polyester with the diisocyanate at 100-130 DEG  C. for 10 minutes and reacting the product with water, the dihydroxy compound or the diamine at 100-120 DEG  C. until it solidifies. Suitable solvents are dimethyl formamide, dimethyl acetamide, dimethyl propionamide, methoxy dimethyl acetamide and those dimethyl carbamyl compounds disclosed in U.S.A. Specifications 2,404,713 to 2,404,728.  The solutions may be prepared either from the previously condensed end products or by producing the elastomers in presence of the solvents. Dissolution is accelerated by adding to the solvent a basic compound, e.g. dibutylamine or hexahydrodimethylaniline.  The solutions may be employed for impregnating and coating paper, fabrics, pressboard goods or leathers; as a binder in the manufacture of fibrous fleeces prepared from cellulose, textile fibres or leather; for the coating and spraying of natural or synthetic fibres and bristles; for bonding plastics, textiles, leather or paper; or for casting filaments or films.  The solutions may be compounded with other plastics and employed in making lacquers, threads, films or coatings.  Pastes containing 50-80 per cent by weight of the elastomer may be used for moulding; for brushing on to a substrate to form artificial leather; for making dipped articles (in which case the solvent may be removed by dipping the article in water or glycerol); or for extruding to form filaments or other articles; and may be compounded with fillers.  Solvent may be removed from the pastes by evaporation or by treatment with water, glycerol or other liquids miscible with the solvent but incompatible with the elastomer.  In examples: (1) an elastomer prepared from poylethylene glycol adipate (OH No.=60), 1,5-naphthylene diisocyanate and water is dissolved in dimethyl formamide; (2) a mixture of polyethylene glycol adipate (OH No.=57) and poly-1,2-propylene glycol adipate (OH No.=57) is reacted with 1,5-naphthylamine diisocyanate and water and the resulting elastomer dissolved in dimethyl acetamide; (3) an elastomer prepared from polyethylene glycol or adipate (OH No.=50), 2,4-toluylene diisocyanate and o-dichlorobenzidene is dissolved in dimethyl formamide; (4) polyethylene glycol adipate (OH No.=53) is dissolved in dimethyl formamide and the solution heated to 130 DEG C.  Then 1,5-naphthylene diisocyanate and subsequently a mixture of water and dimethyl formamide is added.  When evolution of carbon dioxide has ceased, further dimethyl formamide is added.  Extruding filaments.-The solution of the elastomer is extruded from spinning nozzles 1 into a glycerol bath 2 heated to 80 DEG  C., wherein the solvent is largely dissolved.  The bundle of filaments is conveyed into a water bath 8 at 50 DEG  C. wherein the filaments are liberated from residues of glycerol and solvent and are then wound on the bobbin 10 and dried at 120 DEG  C.