GB1085816A - Process for the manufacture of linear polyamides - Google Patents

Abstract

Polyamides are produced continuously by pumping a mixture of water, an aminocarboxylic acid or a salt of a diamine and a dicarboxylic acid through a heated tube the dimensions of which are defined by the following conditions: I.-The diameter of the tube increases from inlet to outlet; II.-The total volume in c.c. (V) is from 1600 to 3600 times the rate of output of polyamide in kgm./hr. (Q); III.-The diameter of the tube in mm. at any point is between dmax and dmin as defined by the following equations: <FORM:1085816/C3/1> where n is the volume of the tube in c.c. between its inlet and the point in question. Suitable diamines, dicarboxylic acids and aminoacids are of formula NH2XNH2, HOCOYCOOH and NH2ZCOOH respectively where X is a chain of p methylene radicals and (not linked to nitrogen) q meta- or para-phenylene radicals, Y is a chain of r methylene radicals and s meta- or para-phenylene radicals, Z is a chain of t methylene radicals and (not linked to nitrogen) u meta- or para-phenylene radicals, p and s are positive integers, r is zero or a positive integer, q, s and u are 0-2, p is at least 6 if q is zero and s is not zero but at least 2 if q is not zero, r is at least 4 if q is not zero and s is zero, p + r is at least 6 and t is at least 5 if u is zero but at least 3 if u is not zero. X, Y and Z may be alkyl substituted and may contain -O- links in the chain provided the groups -OO-, -OCH2N= and -OCH2CH2CO- are absent. Many monomers are specified including hexamethylene diammonium adipate. The reaction mixture may contain 40% of more monomer but the ratio should be such that the monomer is dissolved in the water at the polymerization temperature. The reaction mixture may also contain monoamines and monobasic acids, e.g. CH3COOH, as viscosity stabilizers, dyes, pigments, dyestuff formers, thermo- and photo-stabilizers, plasticizers, e.g. phenols, glycols and sulphonamides, delustrants, other polyamides and other resins. The cross-section of the reaction tube may be circular or non-circular provided in the latter case the maximum diameter does not exceed 4 times the minimum diameter. Tubes specified are of 14-118 mm. diameter. They may be in a horizontal or vertical helix, in the latter case the inlet being at the top or bottom. The tube may be heated by a diphenyl/diphenyl ether jacket to a temperature at least 10 DEG C. above the m.p. of the polymer, e.g. 275-300 DEG C. The process may be used to produce homo- and copolyamides which may be spun into fibres, films and ribbons at 240-300 DEG C. In examples hexamethylene diamine is added to the reaction mixture.