Patent GB-1161462-A (GB)
Title: Process for Treating Polyester Fibre
IPC: B29D30/40
Filed: 1967-12-14
Abstract: 1,161,462. Polyester filament treatment. E.I. DU PONT DE NEMOURS & CO. 14 Dec., 1967 [14 Dec., 1966], No. 56800/67. Heading B5B. A process for treating polyester fibre to improve the bonding ability of its surface to rubber, comprises coating the polyester fibre, when incompletely oriented and capable of being stretched to at least twice its length, by applying to its surface a solution of an organic isocyanate of low volatility in an inert volatile liquid and then drawing the isocyanate-coated fibre at a temperature of at least 120 C. in the presence of steam to at least twice its length. The terms "polyester fibre", "organic isocyanate of low volatility" and "inert volatile liquid" are defined in the Specification. The organic isocyanate may have a boiling point greater than 250 C., and contain at least one isocyanate group attached to a primary or secondary carbon atom in the molecule, the total number of isocyanate, urea, urethane and amide groups in the molecule being at least 2 and its molecular weight divided by this number being less than 250. Specificed isocyanates include polymethylene polyphenyl isocyanate, methylenebis-(4-phenylisocyanate), N-α-trimethoxysilanopropyl-N-3-isocyanato-4-methyl-phenyl urea, toluene diisocyanate - trimer, ethylene - bis - (N - 3 - isocyanato - 4 - methyl - phenyl urethane), and ethylene-bis-(N-6-isocyanato-nhexylurethane). The inert volatile liquid may be an inert organic liquid having a boiling point below 250 C. which is a hydrocarbon, ether, ketone or ester or a mixture thereof, specified liquids including xylene, ethyl acetate, bis- (2-methoxy-ethyl)-ether or 3-pentanone or a mixture thereof. The preferred polyester is polyethylene terephthalate, and the isocyanate solution may be applied to give a coating weighing 0À05 to 1À5% by weight of the structure. Drawing may be effected for 9À1 millisecond to 0À5 second, suitably at a temperature of 250 to 400 C., and the process is preferably carried out in a coupled melt spinning of polyester fibre/coating of fibre/steam drawing of coated fibre operation. Alternatively, the filaments may be spun to form yarn and drawn in separate operations, the isocyanate solution being applied to the undrawn yarn at the drawing machine. If desired, the drawing operation may be carried out in two or more steps, provided that the step in which the filaments are heated in steam follows application of the isocyanate solution and involves a draw ratio of at least two times. If desired, the drawn fibre may be first treated with a solution of an amine, suitably hydroxy ethylamine or triethylamine, to react with any remaining isocyanate groups, and a post-draw finish containing a lubricating agent may be applied to the drawn fibre, a specified lubricating agent being poly- (# . hydroxy - ethylammonium) acrylate. The isocyanate solution may be applied in admixture with a lubricating agent consisting of a polysiloxane having isocyanate side chains, a specified polysiloxane having the formula where R is an aliphatic or aromatic hydrocarbon diradical, m is 0, 1, 2 or 3 and n is an integer from 2 to 50. In a preferred embodiment polyethylene teryphthalate is melt spun into fibre, the spun fibre is coated with a solution of polymethylene polyphenyl isocyanate in a volatile hydrocarbon to form a coating weighing 0À05 to 1À5% by weight of the fibre, and the coated fibre drawn at a temperature of 250 to 400 C. in the presence of steam to at least twice its length. Oriented polyester fibre so made has a thin surface layer of a molecularly entangled mixture of the polyester and a cross-linked polyurea, the polyurea being the reaction product of steam and a polyisocyanate having a boiling point above 250 C. and being present in a proportion of 0À05 to 1À5% by weight of the fibre. Fibre so treated is especially suitable for bonding to rubber by means of an adhesive. In apparatus as shown, filaments 1 from spinneret 2 pass over applicator roll 3 which applies isocyanate solution contained in pan 4. The treated filaments then pass around feed roll 5 and separator roll 6, thence through steam jet device 7 to draw rolls 8, 9 and proceed to conventional wind-up means.