Patent GB-923524-A (GB)
Title: A process and apparatus for mixing measured proportions of ingredients
IPC: B29B7/80
Filed: 1960-07-01
Abstract: In an apparatus for reacting polymer components of differing viscosities supplied under different pressures, the fall in pressure of a less viscous liquid component is retarded at shut-off in order that the more viscous liquid component <PICT:0923524/III/1> shall not continue to flow from the delivery pipe into the mixing chamber after the flow of the less viscous liquid has ceased.  As shown, components of higher and lower viscosity are pumped from containers 12, 19 respectively by coupled high pressure pumps 18, 22 driven by a motor 23, through delivery hoses 28, 29 to a mixing head 30 into which they are injected by nozzles 37, 38 set to open and close at a pressure of 80 atmospheres.  The pumps each have a by-pass 45, 46 with adjustable pressure relief valves 24, 25 (see Fig. 2, not shown) which open in response to the cessation of flow of the components as by stopping of the motor 23, the passages in the valves 24, 25 being adjusted so that the pressures fall in the delivery hoses 28, 29 at rates which ensure that the shut-off pressure is reached simultaneously at the nozzles 37 and 38.  Alternatively the valves 24, 25 may be actuated by contact manometers 26a, 27a, so that the opening of valve 25 is delayed until the pressure of the high viscosity component has fallen to a pre-determined level.  More than two components may be mixed, all three being injected into the mixing chamber or two being first pre-mixed.  The containers, pumps and hoses may be heated to maintain suitable viscosities.  The apparatus may be controlled manually or by automatic programming device.  The apparatus is described with particular reference to the mixing of toluylene di-isocyanate and a polyether activator to form a polyurethane foam, (see Group IV(a)). Specifications 769,680, 769,682, 826,622 and 826,623 are referred to.ALSO:In a process for intermittently mixing and measuring the reaction components for the production of plastics, in which the components are injected into a mixing chamber at the same nozzle opening and closing pressures, the fall in pressure of the less viscous component is delayed at shut-off in order that the more viscous component shall not continue to flow into the mixing chamber after the flow of the less viscous component has ceased. In a polyurethane composition the more viscous component comprises 100 parts w/w of a polyether activator mixture of viscosity about 500cP/25 DEG C., and consisting of 95,2 parts of a polyether prepared by addition of propylene oxide to trimethylol propane (OH number 56); 0,4 part of N,N1-trimethylol-b -aminoethyl-piperazine; 1,5 parts of a siloxane-ethylene oxide copolymer and 2,9 parts water.  The less viscous component comprises 45,3 parts w/w of toluylene diisocyanate containing the 2,4- and 2,6-isomer in the ratio 80:20, of viscosity 3cP/25 DEG C.  The delivery output of the pump for the first component is 9,000 cc./min. and its working pressure reaches 222 atm., that for the second component being 100 atm. and the injection nozzles being set to open and close at 80 atm. Specifications 769,680, 769,682, 826,622 and 826,623 are referred to.