| 摘要 |
The molecular weight of polyamides as defined below is increased by a continuous process in which the polymer is heated and agitated for 10-60 minutes at a temperature above its m.p. and 260 DEG C. during which time it is maintained in the form of an unsupported filament under an atmosphere having a water vapour pressure not exceeding 10 mm. Hg for a number of seconds not less than the quotient obtained by dividing the surface area of the filament in square decimeters by its volume in c.c. The starting polyamides are defined as those derived by elimination of 96% of the theoretical water of condensation from a mixture of a diamine of formula NH2-X-NH2 and a dicarboxylic acid of formula HOCO-Y-COOH or an amino-acid of formula NH2-Z-COOH, wherein X is a chain of p+4q methylene groups or p-methylene groups and q phenylene groups, Y is a chain of r+4s methylene groups or r-methylene groups and s-phenylene groups, Z is a chain of t+4u methylene groups or t-methylene groups and u phenylene groups, q and s=0-2 at least one of them being 1 or 2, u=1 or 2, p=at least 2 but at least 6 if q is 0, r=at least 4 if s=0, p+r=at least 6 and t at least 3. Numerous monomers are specified including hexamethylene diamine, adipic acid, m-xylene diamine, p - (b - carboxyethoxy) - g - phenylpropionic acid and copolyamide forming mixtures thereof. The atmosphere having a water vapour pressure not exceeding 10 mm. Hg may be an inert gas stream, e.g. N2. In one embodiment of the invention the untreated polyamide falls from a spinneret in the form of molten filaments into a pool of the molten polymer from which the finished product is withdrawn. In another embodiment a stream of the initial polyamide is allowed to collect into a pool which is stirred. Polyamide from this pool is pumped up a pipe and through a spinneret above the liquid surface and the filaments issuing from the spinneret are allowed to fall back into the same pool from which the final product is withdrawn. The product may have an intrinsic viscosity of at least 0.7 and a fatigue resistance of at least 60% strength retention. |
