Patent GB-780244-A (GB)
Title: Improvements in or relating to the production of films upon textile fabrics or the like
Inventor: BAXTER DAVID GEORGE HARRY
IPC: D06N3/00
Filed: 1952-09-03
Abstract: <PICT:0780244/IV (a)/1> Films of synthetic resins are formed on textile fabrics or like porous materials by forming a plastisol dispersion of the resin in a plasticizer (which does not dissolve the resin at atmospheric temperature but does so at elevated temperatures) without the addition of a volatile solvent, successively casting and curing two or more films of the dispersion one upon another, each film being at least partially cured before a subsequent film is cast theron, applying the textile fabric or like material to the last applied film before curing it, and subjecting the plastisol film and fabric to an elevated temperature to cause the resin to dissolve in the plasticizer and to cure the film so formed, whereby the cured film is bonded to the textile or like material without appreciable penetration thereinto.  Suitable plastisols may be made by dispersing two grades of finely divided polyvinyl chloride into a mixture of plasticizers, e.g. dioctyl phthalate and tritolyl phosphate, or dicapryl phthalate and tritolyl phosphate.  The process may be carried out in an apparatus including an endless band adapted to provide a continuously moving casting surface, two or more containers for a plastisol of the resin or resins positioned above the casting surface, means for discharging a regulated supply of the plastisol on to the casting surface, or on to an at least partially cured previously cast film, means for spreading the plastisol as a film on the surface or previously cast film, means for applying a textile or other porous material to the plastisol film, a heating means positioned adjacent to the band and adapted to heat the plastisol film sufficiently to cure the film, and stripping means for removing the cured film from the band.  The invention is particularly applicable to the formation of films of polyvinyl chloride, but may also be used to form films of polyvinyl acetate and its copolymers. In the example 30 parts by weight each of two grades of polyvinyl chloride differing in the amount of heat required for their complete gelation are mixed and dispersed in a mixture of 30 parts by weight of di-octyl phthalate and 10 parts by weight of tri-tolyl phosphate, and the mix is heated to 38-42 DEG  C. with addition of pigments. The mix is then further worked for 45 minutes, strained through 60-mesh wire gauze and allowed to stand for 24 hours in order to deaerate it.  As shown, the plastisol thus produced is fed at atmospheric temperature from a container 6 provided with a discharge orifice 7 controlled by an adjustable gate 8 on to the upper run 1a of an endless belt 1 driven at a speed of about 30 feet per minute by means of a driving pulley 2 to form a layer on the upper run 1a which is reduced to a thickness of 15 mils. by means of a doctor blade 9 co-operating with a fixed support 10.  The layer is heated to 90-95 DEG  C. by means of the electrically heated plate 11 and then passes through a cooling chamber 12 in which its temperature is reduced to atmospheric by the passage of cool air through the chamber.  A second layer of the same plastisol of about the same thickness is then fed on to the belt from a second feed hopper 13 and the combined film is carried by the belt through the nip of a pair of rollers 14, into which nip is also fed a linen tape 15 continuously supplied from the roll 16 and passing over rollers 17 and a guide surface 18.  The laminated product is then carried over a further heater 19 where it is heated to 150-180 DEG  C. and finally carried by the band 1 through a second cooling chamber 20 to a stripping roller 21; the band 1 may be of 5 per cent carbon steel, to facilitate stripping of the film, and may have an engraved or profiled surface. Specification 611,385 is referred to.