Patent GB-1467693-A (GB)
Title: Polymerization process
IPC: C08F2/02
Filed: 1974-09-18
Abstract: 1467693 Graft polymerization process MONSANTO CO 18 Sept 1974 [19 Sept 1973] 40631/74 Heading C3G A bulk graft polymerization process comprises the steps: (A) charging continuously to an initial stirred isothermal reaction zone a monoalkenyl aromatic monomer having 2 to 15% by weight of a rubber dissolved therein, (B) maintaining reaction conditions in said zone having a constant fillage of from 10 to 100% of its volume with said monomer/rubber composition such as to produce a steady state polymerization of said monomer at a temperature of 110 to 140 C. under a pressure of 1À03 to 11À5 kg./cm.<SP>2</SP> wherein 10 to 50% by weight of the monomer is polymerized to a first polymer, at least a portion of said first polymer being grafted to said rubber and the remainder being dissolved in said monomer as a monomer-polymer phase, said rubber and grafted rubber being uniformly dispersed under shearing agitation in said phase as rubber-monomer particles having a weight average diameter of 0À5 to 10 microns and having occluded therein a portion of said monomer-polymer phase, (C) withdrawing continuously from said initial reaction zone said monomer-polymer phase having rubber-monomer particles dispersed therein as a first mixture, (D) charging continuously said first mixture to the first stage of a continuous staged isobaric reaction zone having a plurality of stages so as to produce linear flow through said stages downstream to a final stage, each of said stages operating at constant gravimetric fillage of 10 to 90% of its volume of polymerizing first mixture, (E) maintaining conditions in said isobaric zone so as to polymerize said first mixture by progressive multistage linear flow polymerization, all said stages operating with shearing agitation and common evaporative vapour phase cooling under isobaric conditions in said isobaric zone, providing each said stage with steady state polymerization at controlled temperature and interfacial liquid contact, stage to stage establishing a pressure gradient from the first stage downstream to the final stage causing substantially linear flow through said isobaric zone, all said stages operating at predetermined conversion levels producing a composite polymer as a second polymer in said isobaric zone having a predetermined molecular weight distribution and average molecular weight, thereby maintaining the structural integrity of said rubbermonomer particles, said second zone producing a second mixture having a second polymer solids content determined by said multistage steady state polymerization and evaporation of said monomer, (F) withdrawing continuously said second mixture from said final stage, said second mixture comprising first and second polymer as a combined polymer, at least a portion of said first and second polymer being grafted to said diene rubber and the remainder being dissolved in said monomer-polymer phase, having 2 to 15% by weight based on the second mixture of said rubber moiety dispersed therein as grafted rubber-monomer particles having a weight average diameter of 0À5 to 10 microns and having occluded therein a portion of said monomer-polymer phase, (G) removing continuously a vapour phase evolved from said polymerizing first mixture in said isobaric zone at a rate sufficient to maintain the temperature of said first mixture at a predetermined temperature of from 130 to 180 C. and under a predetermined isobaric pressure of 0À42 to 2À04 kg./cm.<SP>2</SP>, (H) withdrawing said second mixture from said final stage at a rate approximating the total rate at which all additions are made to all stages of said continuous staged isobaric stirred reaction zone, (I) heating the said second mixture at sufficiently elevated temperatures of from 200 to 250 C. until the said grafted rubber-monomer particles are crosslinked to a predetermined swelling index of from 7 to 20 and (J) separating said polymeric solids from said second mixture volatile phase, wherein said polymeric solids comprise a polyblend of said combined polymers having dispersed therein crosslinked rubber particles having occluded and grafted first and second polymers and a weight average diameter of 0À5 to 10 microns. Examples are given in which the alkenyl aromatic monomer is styrene and the rubber is polybutadiene.