CA1087792A - Continuous mass polymerization process for polybends - Google Patents
Continuous mass polymerization process for polybendsInfo
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- CA1087792A CA1087792A CA279,319A CA279319A CA1087792A CA 1087792 A CA1087792 A CA 1087792A CA 279319 A CA279319 A CA 279319A CA 1087792 A CA1087792 A CA 1087792A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F12/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F279/00—Macromolecular compounds obtained by polymerising monomers on to polymers of monomers having two or more carbon-to-carbon double bonds as defined in group C08F36/00
- C08F279/02—Macromolecular compounds obtained by polymerising monomers on to polymers of monomers having two or more carbon-to-carbon double bonds as defined in group C08F36/00 on to polymers of conjugated dienes
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- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Graft Or Block Polymers (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
APPLICATION FOR
LETTERS PATENT
FOR
CONTINUOUS MASS POLYMERIZATION PROCESS
FOR POLYBLENDS
ABSTRACT OF THE DISCLOSURE
The invention relates to an improved process for the continuous mass polymerization of solutions comprising monoalkenyl aromatic monomers having a diene rubber dis-solved therein, wherein the process continuously and progressively polymerizes said solution in a single re-action zone under staged, evaporatively cooled, linear flow, stirred polymerization producing a polyblend com-prising a matrix polymer phase of predetermined molecular weight and molecular weight distribution and a dispersed rubber phase having present grafted and occluded polymer providing high rubber efficiency for toughening said polyblend.
Inventors: Robert H. M. Simon Thomas M. McAuley
LETTERS PATENT
FOR
CONTINUOUS MASS POLYMERIZATION PROCESS
FOR POLYBLENDS
ABSTRACT OF THE DISCLOSURE
The invention relates to an improved process for the continuous mass polymerization of solutions comprising monoalkenyl aromatic monomers having a diene rubber dis-solved therein, wherein the process continuously and progressively polymerizes said solution in a single re-action zone under staged, evaporatively cooled, linear flow, stirred polymerization producing a polyblend com-prising a matrix polymer phase of predetermined molecular weight and molecular weight distribution and a dispersed rubber phase having present grafted and occluded polymer providing high rubber efficiency for toughening said polyblend.
Inventors: Robert H. M. Simon Thomas M. McAuley
Description
10~7792 CONTINUOUS MASS POLYMERIZATION PROCESS FOR POLYBLENDS
As is well known, polyblends of rubber with monoalkenyl aromatic polymers have significant advantages in providing com-positions of desirable resistance to impact for many applica-tions. Various processes have been suggested or utilized forthe manufacture of such polyblends including emulsion, suspen-sion and mass polymerization techniques, and combinations thereof. Although graft blends of a monoal~enyl aromatic mono-mer and rubber prepared in mass exhibit desirable properties, this technique has a practical limitation upon the maximum de-gree of conversion of monomers to polymer which can be effected because of the high viscosities and accompanying power and equipment requirements, which are encountered when the reactions are carried beyond a fairly low degree of conversion after phase inversion takes place. As a result, techni~ues have been adopted wherein the initial polymerization is carried out in mass to a point of conversion beyond phase inversion at which the vis~osity levels are still of practical magnitudes, after which the resulting prepolymerization syrup is suspended in water or other inert liquid and polymerization of the monomers carried to substantial completion.
Stein, et.al. in U. S. Patent No. 2,862,906 discloses a mass/suspension method of polymerization styrene having diene rubbers dissolved therein with the rubber being grafted, in-verted and dispersed as rubber particles under agitation. After ; phase inversion, the viscous mixture is suspended in water and polymerization is completed producing a polyblend in the form of beads.
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Such mass/suspension processes are used commercially, however, present the economic problems of batch operations re-quiring long cycles at relatively low temperatures to control the heat of polymerization. Continuous mass polymerization pro-cesses have great economic advantages if they can be run at higher temperatures and higher rates with the necessary control of the great heats of polymerization. In the case of polyblends, the dispersed rubber phase must be formed and stabilized as to its morphology,bringing it through the continuous polymerization of the rigid matrix polymer phase so that the physical proper-ties of the polyblend meet exacting property specifications.
Various methods have been developed for the continuous mass polymerization of polyblends. Ruffing, et.al. in U. S.
Patent No. 3,243,481 disclose a process wherein diene rubbers are dissolved in predominantly monovinylidene aromatic monomers and polymerized in four reaction zones. Such processes require physically separated reactors providing different reacting con-ditions for each step of polymerization involving costly multi-ple reactors and specialized equipment.
Bronstert, et.al. in U. S. Patent No. 3,~58,946 a simi-lar process wherein the prepolymerization step is run to a solids content of no more than 16 percent to provide a rubber particle having a particular structure. Bronstert discloses a need for separated nonstirred downstream reactors for final polymeriza-tion,each providing a particular set of reacting conditions to insure final properties for the polyblend.
U. S. Patent No. 3,903,202 discloses a process for the continuous mass polymerization of polyblends using two reactors as a more simple process for polymerizing such polyblends.
'8-12-0343A
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The present process relates to an improved continuous process for ~he mass polymerization of a solution comprising a monoalkenyl aromatic monomer having a diene rubber dissolved therein wherein the improvement comprises:
A. charging continuously said solution to a first stage of a staged isobaric stirred reaction zone, B. maintaining conditions in said reaction zone so as to polymeri2e said solution by sequential multistage substantially linear flow polymerization, each said sequential stage having continuous flow-through liquid contact stage-to-stage within said zone, establishing a pressure gradient from said f~rst stage downstream to a final stage causing substantially linear flow, all stages operating wich shearing agitation and common evaporative vapor phase cooling under isobaric conditions, providing each stage with steady state polymeri~ation at a controlled temperature of from 100-180C. under a pressure of from 4,000 to 60,000 kgsJm2, each said stage operating , at a predetermined higher conversion level ; 2; of from 10 to 90 percent, C. producing continuously a matrix polymer phase comprising a polymonoalkenyl aromatic polymer having a predetermined,average molecular : - 4 -08-12-034~
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weight of from 35,000 to 100,000 MWSt having dispersed therein said diene rubber phase as particles having an average diameter of from 0.5 to 10 microns for~ing a polymerization mixture comprising polymer, rubber particles and monomer, D. withdrawing continuously said polymerization mixture from said final stage, E. continuously heating said polymerization mixture to temperatures of from 180-250C. until said rubber particles are cross-linked to a predetermined swelling index, and F. continuously separating said monomer from said polymerization mixture providing a poly-l'j blend comprising said polymonoalkenyl aromatic polymer and said diene rubber particles.
Monomers The monomer used in the present invention comprises at least one monoalkenyl aromatic monomer of the formula ~ f = ~X2 Ar :,.
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_ 5 _ ~08779Z
where Ar is selected from the group consisting of phenyl, halo-phenyl, alkylphenyl , alkylhalophenyl and mixtures thereof and X is selected from the group consisting of hydrogen and ~n alkyl radical of less than three carbon atoms.
Exemplary of the monomers that can be employed in the present process are styrene; alpha-alkyl monovinylidene mono-aromatic compounds, e.g. alpha-methylstyrene, alpha-ethylstyrene, alpha-methylvinyltoluene, etc.; ring-substitu~ed alkyl styrenes, e.g. vinyl toluene, o-ethylstyrene, p-ethylstyrene, 2,'1 dimethyl-styrene, etc.; ring-substituted halostyrenes, e.g. o-chlorosty-rene, p-chlorostyrene, o-bromostyrene, 2,4-dichlorostyrene, etc.;
ring-alkyl, ring-halo-substituted styrenes, e.g. 2-chloro-4-methylstyrene, 2,6-dichloro-4-methylstyrene, etc. If so de-sired, mixtures of such monovinylidene aromatic monomers may be employed.
The process can also be used to polymerize monomer solu-tion of a diene rubber wherein comonomers are used with the monoalkenyl aromatic monomers, in particular the alkenyl nitrile monomers such as acrylonitrile and methacrylonitrile and mix-tures thereof. Here such monomer solutions comprise 50 to 99 pe~cent by weight of the monoalkenyl aromatic monomer, 1 to39 percent by weight of an alkenyl nitrile monomer and to 20 percent by weight of said diene rubber, forming monoalkenyl aromatic copolymer polyblends of said solution composition.
In addition to the monomers to be polymerized, the formu-lation can contain catalyst where required and other desirable components such as stabilizers, molecular weight regulators, etc.
,:
08-12-0343 1 ~ ~ 9 2 The polymerization may be initiated by thermal monomeric free radicals, however, any free radical generating catalyst may be used in the practice of this invention including actinic ir-radiation. Conventional monomer-soluble peroxy and perazo cata-lysts may be used. Exemplary catalysts are di-tert-butyl per-oxide, benzoyl peroxide, lauroyl peroxide, oleyl peroxide, toluyl peroxide, di-tert-butyl diperphthalate, tert-butyl peracetate, tert-butyl perbenzoate, dicumyl peroxide, tert-butyl peroxide isopropyl carbonate, 2,5-di~.ethyl-2,5-di(tert-butyl-10peroxy) hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy) hexene-3 or hexyne-3, tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, cyclopentane hydroperoxide, pinane hydro-peroxide, 2,5-dimethylhexane-2,5-di~ydroperoxide, etc., and mix-tures thereof.
15The catalyst is generally included within the range of 0.001 to 3.0 percent by weight, and preferably on the order of 0.005 to 1.0 percent by weight of the polymerizable material, depending primarily upon po}ymerization~temperatures.
As is well known, it is often desirable to incorporate ` ?~ molecular weight regulators such as mercaptans, halides and ter-penes in relatively small percentages by weight, on the order of 0.001 to 1.0 percent by weight of the polymerizable material.
~ ~rom 2 to 20 percent diluents such as ethylbenzane, ethyltoluene, - ethylxylene, diethylbenzene or benzene may be added to the mono-~, mer composition to control viscosities at high conversions and also provide some molecular weight regulation. In addition, it ~087792 may be desirable to include relatively small amounts of antioxi-dants or stabilizers such as the conventional alkylated phenols.
Alternatively, these may be added during or after polymerization.
The formulation may also contain other additives such as plasti-cizers, lubricants, colorants and non-reactive preformed poly-meric materials which are suitable or dispersible therein.
Rubbers The diene rubbers used are those soluble in the monomers described. The preferred diene rubbers are those having a second order transition temperature not higher than 0 centigrade, preferably not higher th~n -20 centigrade, as determined by ASTM Test D-746-52T) of one or more of the conjugated, 1,3 dienes, e.g. butadiene, isoprene, 2-chloro-1,3-butadiene, 1 ; chloro-1,3-butadiene, piperylene, etc. Such rubbers include co-polymers and block copolymers of conjugated 1,3-dienes with up to an equal amount by weight of one or more copolymerizable mono-ethylenically unsaturated monomers, such as monovinylidene aro-matic hydrocarbons (e.g. styrene; an aralkylstyrene, such as the o-, m- and p-methylstyrenes, 2,4-dimethylstyrene, the arethyl-20 styrenes, p-tert-butylstyrene, etc.; an alphamethylstyrene, alphaethylstyrene, alpha-methyl-p-methyl styrene, etc.; vinyl naphthalene, etc.); arhalo monovinylidene aromatic hydrocarbons (e.g. the o-, m- and p-chlorostyrene, 2,4-dibromostyrene, 2-methyl-4-chlorostyrene, etc.); acrylonitrile; methacrylonitrile;
alkyl acrylates (e.g. methyl acrylate, butyl acrylate, 2-ethyl-~8779Z
hexyl acrylate, etc.), the corresponding alkyl methacrylates;
arcylamides te.g. acrylamide, methacrylamide, N-butylacrylamide, etc.); unsaturated ketones (e.g. vinyl methyl ketone, methyl isopropenyl ketone, etc.); alpha-olefins ~e.g. ethylene, pro-pylene, etc.); pyridines; vinyl esters (e.g. vinyl acetate, vinylstearate, etc.); vinyl and vinylidene halides (e.g. the vinyl and vinylidene chlorides and bromides, etc.); and the like.
- Although the rubber may contain up to 2.0 percent of a crosslinking agent, based on the weight of the rubber-form-ing monomer or monomers, crosslinking may present problems in dissolving the rubber in the monomers for the graft polymeriza-tion reaction. In addition, excessive crosslinking can result in loss of the rubbery characteristics.
A preferred group of rubbers are the stereospecific polybutadiene rubbers formed by ~he polymerization of 1,3-buta-diene. These rubbers have a cis-isomer content of 30-98 percent and a trans-isomer content of 70-2 percent and generally contain at least 85 percent of polybutadiene formed by 1,4 addition with no more than about 15 percent by 1,2 addition. Mooney viscosities of the rubber (ML-4, 100C.) can range from 20 to 70 with a second order transition temperature of from -50 to -105C. as determined by ~STM
Test D-746-52T.
~ Process A monomer solution comprising at least one monoalkenyl aromatic monomer having from 1-20 percent by weight of a diene rubber dissolved therein is charged continuously as a monomer-rubber solution to the first stages of a staged isobaric stirred reaction zone. A suitable staged reactor is disclosed in U. S.
. i Patent No. 3,903,202. The monomer is polymerized at temperatures of 110 - 145C. in the first stage converting 10-50 percent by weight of the monomer to an alkenyl aromatic polymer having a molecular weight of 40,000 to 100,000 MWSt. At least a portion of the polymer polymerized is grafted as polymer mole-cules to the diene rubber as a superstrate.
Although the amount of polymeric superstrate grafted onto the rubber substrate may vary from as little as 10.0 parts by weight to 100.0 parts of substrate to as much as 250.0 per 100.0 parts and even higher, the preferred graft copolymers will generally have a superstrate to substrate ratio of 20 to 200:100 and most desirably 30 to 150:100. With graft ratios 30 to 150:100, a highly desirable degree of improvement in various properties generally is obtained.
The remainder of the poiymer formed is dissolved in said monomer composition as polymerized forming a monomer-polymer solution. The monomer-polymer solution or phase is incompatible with the monomer-rubber solution or phase and phase separation is observed by the well known Dobry effect. As the polymer con-centration of the monomer-polymer phase increases and has a volume slightly larger than the monomer-rubber phase, the mono- `
mer-rubber phase disperses as rubber-monomer particles aided by the shearing agitation of the stirred first reaction zone.
The agitation must be significant and of high enough shear to disperse and size the rubber particles uniformly throughout the monomer-polymer phase. The intensity of the stirring will vary with the size and geometry of the reactor, however, simple experimentation with a given stirred reactor will establish the sufficient amount of stirring needed to '` ~ 08779Z
insure the homogeneous dispersion of the rubber particles throughout the monomer-polymer phase. The particle size of the rubber can be varied from a weight average particle dia-meter of from 0.5 to 10 microns preferably from 0.5 to 5 microns to provide a balance between the impact strength and the gloss of the rubber reinforced polyblend. Higher stirring rates and shearing agitation can lower the size of the dispersed rubber particle, hence, must be controlled to provide sufficient stirring to size the particles to the predetermined size needed and insure homogeneous dispersion.
At steady state polymerization, in the first stage, the continuously charged monomer composition containing 1 to 20 per-cent by weight diene rubber disperses almost instantaneously, under stirring, forming the rubber-monomer particles which on complete polymerization form discrete rubber particles. The conversion of monomers to polymers in the first stage is con-trolled between 10-50 percent and must have a weight percent level that provides a polymer content in excess of the rubber content of the monomer composition to insure the dispersion of the monomer-rubber phase to a rubber-monomer particle phase having a predetermined size and being dispersed uniformly throughout the monomer-polymer phase.
The rubber particle becomes grafted with a polymer in the first stages which aids its dispersion and stabilizes the morphology of the particle. During the dispersion of the rubber-monomer particles, some monomer-polymer phase is oc-cluded within the particle. The total amount of occluded mono-mer-polymer phase and grafted polymer present in the particles can be from 1 to 5 grams for each gram said diene rubber.
~8-12-0343 The dispersed rubber phase increases the toughness of the polymeric polyblend as measured by its Izod impact strength by Test ASTM D-256-56. It has been found that the impact strength of polyblends increase with the weight percent rubber dispersed in the polyblend in the range of 1 to 20 percent as used in the present invention. The impact strength is also de-termined by the size of the dispersed rubber particles, with the larger particles providing higher impact strength in the range of 0.5 to 10 microns measured as a weight average particle size diameter with a photosedimentometer by the published procedure of Graves, M. J. et.al., "Size Analysis of Subsieve Powders Using a Centrifugal Photosedimentometer," British Chemical En-gineering 9:742-744 (1964). A Model 30~0 Particle Size Analyzer from Martin Sweets Company, 3131 West Market Street, Louisville, Kentucky was used.
The weight average diameter of the rubber particles also affects gloss with smaller particles giving high gloss and the larger particles giving low gloss to the fabricated polyblend article such as a molding or sheet product. One must balance impact strength and gloss requirements in seiecting an optimum rubber particle size. The range of 0.5 to 10 microns can be used with the range of 0.5 to 5 microns being preferred and 0.8 to ~ microns being most preferred for optimum impact strength and gloss.
Processwise, in the first stage, one must ~1) form and disperse the rubber particle, and ~2) graft and stabilize the rubber particle maintaining its size and morphology or structure.
The amount of occluded monomer-polymer phase described above is held at a pretetermined level described above by steady state polymerization wherein the monomer is converted to polymer, at least a portion of which, grafts to the rubber, stabilizing the rubber particle. It has been found that the higher the amount of occlusion stabilized within the rubber particle the more efficiently the rubber phase is used in toughening the polyblend.
The rubber particle acts much as a pure rubber particle if the occlusions are controlled at the amount described above during their stabilization in the initial stages and throughout the total polymerization process. The rubber particle is also grafted externally, stabilizing its structure as to size and its dispersibility in the monomer-polymer phase.
The first stage forms a polymerization mixture of a monomer-polymer phase having the rubber phase described dis-persed therein. The mixture is polymerized by progressive multistage substantial linear flow polymerizations with the conversion of polymer advancing from 10-50 percent conversion in the first stage to 50 to 90 percent conversion in the final stage of the staged isobaric stirred reaction zone. This provides a gradual progressive increase of polymer in the monomer-polymer phase. This has been found to be important in maintaining the morphology or structure of the dispersed rubber-monomer particles.
It has been found unexpectedly that in the first stage as the rubber particle is formed, that the rubber-monomer par-ticle has a monomer contenL that corresponds to the monomer con-tent of the monomer-polymer phase. The rubber-monomer particle will stabilize at this level as the monomer polymerizes inside the rubber particle and grafted polymer is formed on the out-side. Hence, it has been found that the lower the level of con-version or polymer in the monomer-polymer phase of the first stage the higher the amount of monomer found in the rubber-monomer particles formed as the rubber solution is charged and dispersed in the monomer-polymer phase. Conversely, if the con-version is high in the initial stage, less monomer is occludedin the rubber phase particle on dispersion. As described earlier, the mixture is polymerized in the staged linear flow zone, and the percent by weight of polymer being formed is pro-gressively higher with each stage having a slightly higher polymer content. The staged linear progressive polymerization was found not only to control the polymerization of the monomer giving desirable polymers but was found unexpectedly to preserve the integrity of the rubber particles. Although not completely understood, as the rubber particle becomes grafted and the monomer-polymer phase forms in the occluded monomer of the rubber particle, the monomer is not readily extracted from the rubber particle by the monomer-polymer phase as the polymer con- ;~
tent increases gradually in the monomer-polymer phase during polymerizing in the staged reactor. It is thought that since the polymerization in the multistaged linear reaction zone is - so gradual that polymer is being formed in both the rubber particle and the monomer-polymer phase at about the same rate, hence, the total polymer content of the occluded monomer-polymer phase of the rubber particle is about the same as polymer con-tent of the monomer-polymer phase and monomer is not extracted, hence, the weight percent of occlusion is stabilized and remains substantially constant after formation in the initial reactor.
It has been found possible to analyze the amount of total occluded polymer phase and grafted polymers. The final 10~7792 polymerized polyblend product (1 gram) are dispersed in a 50/50 acetone/methyl ethyl ketone solvent tlO ml) which dissolves the polymer phase matrix leaving the rubber phase dispersed. The rubber phase is separated from the dispersion by centrifuge as a gel and dried in a vacuum oven at 50C. for 12 hours and weighed as a dry gel.
~ Dry gel Weight of dry gel x 100 - in Polyblend Weight of polyblend Occlusions ~ ~ Percgent rubber~ x 100 Parts** by weight.
of graft polymer ) ~ dry ge~-~ rubber and occluded poly- ) - Percent rubber mer per unit weight of rubber *Percent rubber determined by infra-red spectrochemical analysis of the dry gel.
*~The present invention preferably has 20 ' present about 0.5 to 5 grams of occluded and grafted polymer per gram of diene rubber.
The swelling index of the rubber graft particles is de-termined by taking the dry gel above and dispersing it in tolu-ene for 12 hours. The gel is separated ~y centrifuge and the supernatant toluene drained free. The wet gel is weighed and then dried in a vacuum oven for 12 hours at 50C. and weighed.
Swelling Index - weight of dry gel As described earlier the amount of occlusions and graft polymer present in the rubber particle is present in the amount 1U~792 of 0.5 to 5 part for each part of diene rubber. The percent dry gel measured above then is the percent gel in the polymerized polyblend and represents the dispersed rubber phase having polymeric occlusions and polymeric graft. The percent gel varies with the percent rubber charged in the monomer composi-tion and the total amount of graft and occluded polymer present in the rubber phase.
The swelling index of the rubber as determined above is - important to the final properties of the polyblend. A low swelling index indicates that the rubber has been crosslinked by the monomer as it polymerizes to a polymer phase in the rubber-monomer particle during step (E). Generally, the con-version of monomer to polymer in the occlusion follows the rate of conversion of monomer to polymer in the monomer-polymer phase being carried out in steps (B) and (E). In step (E) the temperature of the second mixture is raised to 185 to 250C.
- and the monomer vapors are separated in step (F) to give a finished polyblend. The rubber particles become crosslinked by heating the mixture to from 185 to 250C. for sufficient time to crosslink the rubber particles such that they have a swelling index of from 7 to 20 preferably from 8 to 16.
Preferably, the polymer of the matrix phase of the poly-blends produced by this invention have a dispersion index (MW/Mn), wherein Mw is a weight average molecular weight and Mn is a number average molecular weight, ranging from 2.0 to 4.0 preferably 2.2 to 3.5. The dispersion index is well known to those skilled in the art and represents the molecular weight distribution with the lower values having narrow molecular weight distribution and higher values having broader molecular weight 108~79Z
~ 08-12-0343 distribution. The average molecular weight of the polymer of the matrix phase preferable range from-~5,000 to 100,000 Staud-inger, preferably 35,000 to 70,000.
STAGED POLYMERIZATION
The polymerization is carried out in a generally hori-zontal, cylinderical, flow-through, staged, isobaric stirred re-action zone maintaining conditions so as to polymerize said first mixture by progressive multistage substantially linear flow-through polymerization; all said stages operating with shearing agitation and common evaporation vapor phase cooling under iso-baric conditions in said reaction zone, providing each said stage with steady state polymerization at controlled temperature, and interfacial liquid contact stage-to-stage establishing a hydrau-lic pressure gradient from the first stage downstream to the final stage, causing substantially linear flow-through said re-action zone; all said stages operating at predetermined conver-sion levels producing a polymer in said reaction zone having a predetermined molecular weight distribution and average molecu-lar weight maintaining the structural integrity of said dis-persed rubber particle, said reaction zone producing a polymer-ization mixture having a total polymer content being determined by said multistage steady state polymerization and evaporation of said monomers.
The reactor operates under controlled iso~aric conditions~
~or the range of temperatures normally of interest for alkenyl aromatic monomers, e.g. styrene polymerization, the operating pressure will range from 4,000-20,000 Kg/m2. The styrene reaction is exothermic, and cooling is provided primarily by vaporization o~
a part of the monomer from the reacting mass. F~rther cooling can be provided by jacket. Cooling by the con-1(~87792 densed recycle monomer feeding into reaction zone is also pro-vided. The mass is in a boiling condition, and temperature is determined by the natural relationship between vapor pressure and boiling point. This relationship is also a function of the S relative amounts of polymer, monomer, and other substances (e.g.
dissolved rubber, solvents, and additives.) Since, as material progresses through this reactor, the amount of polymer continu-ously increases and the amount of monomer corresponding decreases via polymerization, and monomer content further decreases due to vaporization loss, the temperature progressively increases from inlet to outlet stages.
To accommodate the natural swell of the boiling mass, and to provide space for vapor disengagement, the reactor is usually run at a fillage of 10 to 90 percent preferably 40 to 80 percent of its volume.
Vapor passes out of the reactor to an external condenser where it is condensed and may also be subcooled. This conden-sate may then be returned to the inlet compartment of the re-actor wherein it is reheated by condensation of a fraction of the previously evolved vapors and mixed with other incoming free materials.
In a multi-compartment staged reactor, each stage is well mixed, and the reaction mass is substantially homogeneous within itself. The discs which separate the stages discourage backflow of material between compartments. The clearance be-tween disc and shell does permit some backflow, and also permits the necessary forwarding of material through the compartments from reactor inlet to outlet giving substantially linear flow.
In a compartmented staged reactor, the first stage has a - 18 _ ~08779Z
`08-12-0343 relatively low conversion level, since it is being continuously fed by monomer solution. However, the rate of conversion in this stage is relatively high because of the high concentration of monomer.
In each succeeding stage, the conversion level is higher than in the preceding one, which tends to lower the rate of con-version. Offsetting this effect, however, are the facts that the temperature is higher, and that monomer is being vaporized out of the mass. Thus, the total conversion to polymer obtained per unit fillage volume of the staged reactor is higher than that which could be obtained in a single stage reactor producing an equal final conversion level at equal temperature.
Clearance between rotating disc compartment baffles and cylindrical wall may be from 1 to 10 percent of shell radius, the larger values being appropriate to the high conversion end of the reactor where viseosity is at maximum. Stage-to-stage forward flow of the polymerizing mixture is through this clear-ance, and vapor from the polymerizing mixture also counterflow through the clearance, above the surface level of the mass.
The monomer-polymer solution flows through the reaction zone under substantially linear flow, with minimized back mixing, from the first stage to the final stage under a liquid pressure gradient from the first stage to the last stage. Temperature in the reaction zone is contr~lled by pressure wherein the pressure is regulated to cause the polymerizing solution to boil under its heat of polymerization removing a monomer-vapor phase at a rate sufficient to maintain the temperature of the polymerizing solution at a temperature of from 100 to 180C. and under iso-_ 19 _ ~ 08779Z ;' ' 08-12-0~43 baric conditions of 6 to 29 psia (4,000-20,000 kg/m2).
The monomer, e.g. styrene, polymerizes giving off about 300 BTU per pound polymerized. The heat of vaporization of sty-rene is about 150 BTU per pound vaporized, hence, the reactor generally removes about 2 pounds of monomer from the polymeriz-ing syrup per pound of polystyrene converted which is recycled bac~ to the polymerizing first stage at that rate to maintain steady state polymerization under controlled temperature and isobaric conditions.
In operation, the reaction zone can be filled from about 15 to 90 percent of its volume with the polymerizing solution, the remaining volume thereof being occupied by vaporized mono-mers. A mixture is withdrawn from the last stage of the reac-tion zone wherein the degree of conversion can range from about 50 percent to as high as 90 percent. The last stage of the re-action zone is generally maintained at higher temperatures ~130-lôOC. ) than the first stage of the reaction zone produc-ing polymers having average molecular weights in the lower range of 30,000 to 70,000 Staudinger. The combined polymer can have lecular weight range of 30,000 to 100,000 Staudinger prefer-ably ~5,000 to 70,000 Staudinger. This flexibility affords the ability to produce a wide range of polymers of varying molecular weight distribution and at varying levels of fillage of the re-action zone.
In the operation of the reaction zone it is preferred to employ a continuous staged isobaric stirred reactor which is controlled by withdrawal of vaporized monomer above the liquid level maintained therein in order to control the tempera-ture in such second reaction zone. This withdrawn stream of _ 20 -~08779Z
~8-12-0343 vaporized monomer is condensed in a condenser and collected in a receiver. It can be returned to the first stage of the reaction zone.
A preferred method of control of the reaction zone is the temperature within the final stage of reactor. The control system involves sensing the temperature in the liquid phase in the final stage of reactor and employing a signal so generated to control a temperature controller modified by a signal from a set point generator at a preselected temperature value. The re-sulting signal modified by a signal generated by sensing the pressure in the vapor phase of said reactor is employed to con-trol a pressure controller which in turn controls a pressure valve in the vent line from the recycled condensed monomer re-ceiver. By so adjusting the pressure above the condensed mono-mer in the receiver the temperature of the final stage in the reactor is very closely and rapidly controlled to a preselected desired value. The temperature in each stage rapidly achieves an equilibrium value-based on the reactor pressure and the poly-meric solids content of the polymerizing solution in each stage.
The utilization of the present process gives an overall production process for high impact strength polyalXenyl aromatic polyblends. The polymer, dispersed rubber and monomer mixture called the polymerization mixture comprises the liquid phase effluent from the reactor. Said mixture having a polymeric solids content of from about 50 to about 90 percent by weight is withdrawn therefrom by suitable means such as a gear pump and passed to a heating and devolatilization zone or zones.
One zone of devolatilization which can be operated at pressures below atmospheric, or degrees of vacuum. However, the ~08779Z
process of the present invention can be operated by the use of two or multiple zones of devolatilization as desired. In the process outlined the vaporized alkenyl aromatic monomers as well as low oligomers thereof are removed from the first devolatiliza-S tion zone, condensed and passed to a receiver. From the receiver a stream of the condensed monomers and oligomers can be recycled to the first stage of the reactor. Likewise, the monomers and oligomers vaporized in a second devolatilization zone generally operated at somewhat lower pressure than the first are with-drawn, condensed and passed to a receiver. From this receiver a stream of condensed monomers and oligomers can also be recycled to the reactor. Preferably, the oligomers vaporized in either devolatilization zone can be separated from the vaporized mono-mer by distillation and separately recycled to the reaction zone or purged from the process.
In the production of certain of the desired polymers it has generally been found advantageous to add certain high boil-ing organic compounds to the polymers produced and the addition is preferably made during polymerization. These additives in-clude internal lubricants such as mineral oil or other heavy oil and mold release agents such as fatty acids, fatty acid esters or salts and waxes. These additions can be conveniently made to the reaction zone and are preferably made to the last stage by means of the multiple metering pumps.
~hen operating in the manner described above, the proper control of reactors of the variable fillage type affords one the extremely useful advantage of ability to produce polymers of specific physical properties and molecular weight distribut~on over a range of capacities of from as low as 3~ to as high as 10~779z 100 percent of design capacity for the single production facil-ity described. This flexibility in useful capacity is highly desirable to afford ready response to changes in market demand for total polymers or in the market percentage for various poly-mers produced in such a production facility.
The following examples are set forth to illustrate more clearly the principles and practice of this invention to one skilled in the art. They are not intended to be restrictive but merely illustrative of the invention herein described. All parts are by weight unless otherwise indicated. All molecular weights are in Staudinger values unless otherwise noted.
A monomer composition consisting of 5.6 parts by weight of stereospecific polybutadiene rubber in 94.4 parts by weight of styrene monomer is prepared by agitating the mixture at 40C.
for 8 hours (Diene 55 Rubber is available from Firestone Rubber Company, Akron, Ohio). To the above monomer composition is added .1 part of octadecyl 3-~3',5'-di-tert-butyl-4-hydroxy-phenyl) propionate and 24 parts of recycled styrene monomer.
This mixture is fed at 38 kg./hr. continuously to a re-actor that has approximately .89 1. capacity and operates at about 45 percent fillage.
The reactor is 135 c~. long. The agitator con-sists of a horizontal shaft on which are fixed a series of paddles 5.08 cm. wide alternating at right angles to one another. Along the shaft and rotating with it are two circular - baffles with an average radial clearance of 0.95 cm., ro-tating at 10 rpm. These baffles are positioned to divide the reactor into 3 stages of approximately equal volume. Into the '''' ~087792 downstream compartment of this reactor is fed a stream ; consisting of 1 part of white mineral oil. The pressure in the reactor is maintained at 0.91 kg/cm2 with the first stage at 125C. and the final stage at 153C. The polymerizing syrup exiting the reactor contains 70 per-cent solids. Styrene vapor evaporated in this reactor is condensed and returned to the first stage compartment.
The syrup in the downstream compartment is pumped contin-uously from the reactor at a rate to maintain essentially constant reactor fillage and is pumped to the inlet of a ; tube and shell heating means. This stage is maintained at 4.55 kg/cm2 via a throttling valve on the exit side of the heater. The syrup exiting this preheater stage is at 170C. After passing through the throttling valve, the syrup flows into a two stage devolatilizing means as dis-closed in U.S. Patent No. 3,928,300 and found to be one suitable means of devolatilization. The first stage de-volatilizer was operated at 220C. and about 60 torr.
After passing through the devolatilizer interstage valve, regulated to maintain approximately constant fillage in the first devolatilizer stage, the melt flows into the second stage devolatilizer chamber maintained at 15 torr.
A suitable method of devolatilization is disclosed in U.S. Patent No. 3,928,300.
Vapors exiting the devolatilizer chambers are condensed and recycled to the first compartment of the reactor. 0.9 kgs/hr. of these condensed vapors are withdrawn as purge. The devolatilized melt is pumped ,":
from the second devolatilizer compartment through a die to form a plurality of strands which are then cooled and cut into pellets. The resulting polymer 1()87792 has a Staudinger molecular weight of ~9,000 and a dispersion ~x~x of 2.2.
TyPical Properties Izod Impact Strength 1.27 x 1.27 om. bar ~Kg/cm/cm2) 5.45 Tensile Strength @ yield (Kg/ ~ ) 275 Tensile ~trength ~ faii (Kg/om2) 294 Tensile èlongation at fail t%) 39 Swelling Index 9 Parts graft and occlusions 1~ parts/part rubber 1~60 ~ubber particle size t~;crons) 3.8 ~XAMPLE 2 tUse of Initiator) ~he process was operated using the apparatus and proce-dure of ~xample 1 except as noted below:
a~ the reactor agitator was operated at about ~0 rpm.
~) the feed monomer composition also contained
As is well known, polyblends of rubber with monoalkenyl aromatic polymers have significant advantages in providing com-positions of desirable resistance to impact for many applica-tions. Various processes have been suggested or utilized forthe manufacture of such polyblends including emulsion, suspen-sion and mass polymerization techniques, and combinations thereof. Although graft blends of a monoal~enyl aromatic mono-mer and rubber prepared in mass exhibit desirable properties, this technique has a practical limitation upon the maximum de-gree of conversion of monomers to polymer which can be effected because of the high viscosities and accompanying power and equipment requirements, which are encountered when the reactions are carried beyond a fairly low degree of conversion after phase inversion takes place. As a result, techni~ues have been adopted wherein the initial polymerization is carried out in mass to a point of conversion beyond phase inversion at which the vis~osity levels are still of practical magnitudes, after which the resulting prepolymerization syrup is suspended in water or other inert liquid and polymerization of the monomers carried to substantial completion.
Stein, et.al. in U. S. Patent No. 2,862,906 discloses a mass/suspension method of polymerization styrene having diene rubbers dissolved therein with the rubber being grafted, in-verted and dispersed as rubber particles under agitation. After ; phase inversion, the viscous mixture is suspended in water and polymerization is completed producing a polyblend in the form of beads.
'~ ~
1~:)8779Z
Such mass/suspension processes are used commercially, however, present the economic problems of batch operations re-quiring long cycles at relatively low temperatures to control the heat of polymerization. Continuous mass polymerization pro-cesses have great economic advantages if they can be run at higher temperatures and higher rates with the necessary control of the great heats of polymerization. In the case of polyblends, the dispersed rubber phase must be formed and stabilized as to its morphology,bringing it through the continuous polymerization of the rigid matrix polymer phase so that the physical proper-ties of the polyblend meet exacting property specifications.
Various methods have been developed for the continuous mass polymerization of polyblends. Ruffing, et.al. in U. S.
Patent No. 3,243,481 disclose a process wherein diene rubbers are dissolved in predominantly monovinylidene aromatic monomers and polymerized in four reaction zones. Such processes require physically separated reactors providing different reacting con-ditions for each step of polymerization involving costly multi-ple reactors and specialized equipment.
Bronstert, et.al. in U. S. Patent No. 3,~58,946 a simi-lar process wherein the prepolymerization step is run to a solids content of no more than 16 percent to provide a rubber particle having a particular structure. Bronstert discloses a need for separated nonstirred downstream reactors for final polymeriza-tion,each providing a particular set of reacting conditions to insure final properties for the polyblend.
U. S. Patent No. 3,903,202 discloses a process for the continuous mass polymerization of polyblends using two reactors as a more simple process for polymerizing such polyblends.
'8-12-0343A
108'779Z
The present process relates to an improved continuous process for ~he mass polymerization of a solution comprising a monoalkenyl aromatic monomer having a diene rubber dissolved therein wherein the improvement comprises:
A. charging continuously said solution to a first stage of a staged isobaric stirred reaction zone, B. maintaining conditions in said reaction zone so as to polymeri2e said solution by sequential multistage substantially linear flow polymerization, each said sequential stage having continuous flow-through liquid contact stage-to-stage within said zone, establishing a pressure gradient from said f~rst stage downstream to a final stage causing substantially linear flow, all stages operating wich shearing agitation and common evaporative vapor phase cooling under isobaric conditions, providing each stage with steady state polymeri~ation at a controlled temperature of from 100-180C. under a pressure of from 4,000 to 60,000 kgsJm2, each said stage operating , at a predetermined higher conversion level ; 2; of from 10 to 90 percent, C. producing continuously a matrix polymer phase comprising a polymonoalkenyl aromatic polymer having a predetermined,average molecular : - 4 -08-12-034~
~.08779Z
weight of from 35,000 to 100,000 MWSt having dispersed therein said diene rubber phase as particles having an average diameter of from 0.5 to 10 microns for~ing a polymerization mixture comprising polymer, rubber particles and monomer, D. withdrawing continuously said polymerization mixture from said final stage, E. continuously heating said polymerization mixture to temperatures of from 180-250C. until said rubber particles are cross-linked to a predetermined swelling index, and F. continuously separating said monomer from said polymerization mixture providing a poly-l'j blend comprising said polymonoalkenyl aromatic polymer and said diene rubber particles.
Monomers The monomer used in the present invention comprises at least one monoalkenyl aromatic monomer of the formula ~ f = ~X2 Ar :,.
".~
_ 5 _ ~08779Z
where Ar is selected from the group consisting of phenyl, halo-phenyl, alkylphenyl , alkylhalophenyl and mixtures thereof and X is selected from the group consisting of hydrogen and ~n alkyl radical of less than three carbon atoms.
Exemplary of the monomers that can be employed in the present process are styrene; alpha-alkyl monovinylidene mono-aromatic compounds, e.g. alpha-methylstyrene, alpha-ethylstyrene, alpha-methylvinyltoluene, etc.; ring-substitu~ed alkyl styrenes, e.g. vinyl toluene, o-ethylstyrene, p-ethylstyrene, 2,'1 dimethyl-styrene, etc.; ring-substituted halostyrenes, e.g. o-chlorosty-rene, p-chlorostyrene, o-bromostyrene, 2,4-dichlorostyrene, etc.;
ring-alkyl, ring-halo-substituted styrenes, e.g. 2-chloro-4-methylstyrene, 2,6-dichloro-4-methylstyrene, etc. If so de-sired, mixtures of such monovinylidene aromatic monomers may be employed.
The process can also be used to polymerize monomer solu-tion of a diene rubber wherein comonomers are used with the monoalkenyl aromatic monomers, in particular the alkenyl nitrile monomers such as acrylonitrile and methacrylonitrile and mix-tures thereof. Here such monomer solutions comprise 50 to 99 pe~cent by weight of the monoalkenyl aromatic monomer, 1 to39 percent by weight of an alkenyl nitrile monomer and to 20 percent by weight of said diene rubber, forming monoalkenyl aromatic copolymer polyblends of said solution composition.
In addition to the monomers to be polymerized, the formu-lation can contain catalyst where required and other desirable components such as stabilizers, molecular weight regulators, etc.
,:
08-12-0343 1 ~ ~ 9 2 The polymerization may be initiated by thermal monomeric free radicals, however, any free radical generating catalyst may be used in the practice of this invention including actinic ir-radiation. Conventional monomer-soluble peroxy and perazo cata-lysts may be used. Exemplary catalysts are di-tert-butyl per-oxide, benzoyl peroxide, lauroyl peroxide, oleyl peroxide, toluyl peroxide, di-tert-butyl diperphthalate, tert-butyl peracetate, tert-butyl perbenzoate, dicumyl peroxide, tert-butyl peroxide isopropyl carbonate, 2,5-di~.ethyl-2,5-di(tert-butyl-10peroxy) hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy) hexene-3 or hexyne-3, tert-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, cyclopentane hydroperoxide, pinane hydro-peroxide, 2,5-dimethylhexane-2,5-di~ydroperoxide, etc., and mix-tures thereof.
15The catalyst is generally included within the range of 0.001 to 3.0 percent by weight, and preferably on the order of 0.005 to 1.0 percent by weight of the polymerizable material, depending primarily upon po}ymerization~temperatures.
As is well known, it is often desirable to incorporate ` ?~ molecular weight regulators such as mercaptans, halides and ter-penes in relatively small percentages by weight, on the order of 0.001 to 1.0 percent by weight of the polymerizable material.
~ ~rom 2 to 20 percent diluents such as ethylbenzane, ethyltoluene, - ethylxylene, diethylbenzene or benzene may be added to the mono-~, mer composition to control viscosities at high conversions and also provide some molecular weight regulation. In addition, it ~087792 may be desirable to include relatively small amounts of antioxi-dants or stabilizers such as the conventional alkylated phenols.
Alternatively, these may be added during or after polymerization.
The formulation may also contain other additives such as plasti-cizers, lubricants, colorants and non-reactive preformed poly-meric materials which are suitable or dispersible therein.
Rubbers The diene rubbers used are those soluble in the monomers described. The preferred diene rubbers are those having a second order transition temperature not higher than 0 centigrade, preferably not higher th~n -20 centigrade, as determined by ASTM Test D-746-52T) of one or more of the conjugated, 1,3 dienes, e.g. butadiene, isoprene, 2-chloro-1,3-butadiene, 1 ; chloro-1,3-butadiene, piperylene, etc. Such rubbers include co-polymers and block copolymers of conjugated 1,3-dienes with up to an equal amount by weight of one or more copolymerizable mono-ethylenically unsaturated monomers, such as monovinylidene aro-matic hydrocarbons (e.g. styrene; an aralkylstyrene, such as the o-, m- and p-methylstyrenes, 2,4-dimethylstyrene, the arethyl-20 styrenes, p-tert-butylstyrene, etc.; an alphamethylstyrene, alphaethylstyrene, alpha-methyl-p-methyl styrene, etc.; vinyl naphthalene, etc.); arhalo monovinylidene aromatic hydrocarbons (e.g. the o-, m- and p-chlorostyrene, 2,4-dibromostyrene, 2-methyl-4-chlorostyrene, etc.); acrylonitrile; methacrylonitrile;
alkyl acrylates (e.g. methyl acrylate, butyl acrylate, 2-ethyl-~8779Z
hexyl acrylate, etc.), the corresponding alkyl methacrylates;
arcylamides te.g. acrylamide, methacrylamide, N-butylacrylamide, etc.); unsaturated ketones (e.g. vinyl methyl ketone, methyl isopropenyl ketone, etc.); alpha-olefins ~e.g. ethylene, pro-pylene, etc.); pyridines; vinyl esters (e.g. vinyl acetate, vinylstearate, etc.); vinyl and vinylidene halides (e.g. the vinyl and vinylidene chlorides and bromides, etc.); and the like.
- Although the rubber may contain up to 2.0 percent of a crosslinking agent, based on the weight of the rubber-form-ing monomer or monomers, crosslinking may present problems in dissolving the rubber in the monomers for the graft polymeriza-tion reaction. In addition, excessive crosslinking can result in loss of the rubbery characteristics.
A preferred group of rubbers are the stereospecific polybutadiene rubbers formed by ~he polymerization of 1,3-buta-diene. These rubbers have a cis-isomer content of 30-98 percent and a trans-isomer content of 70-2 percent and generally contain at least 85 percent of polybutadiene formed by 1,4 addition with no more than about 15 percent by 1,2 addition. Mooney viscosities of the rubber (ML-4, 100C.) can range from 20 to 70 with a second order transition temperature of from -50 to -105C. as determined by ~STM
Test D-746-52T.
~ Process A monomer solution comprising at least one monoalkenyl aromatic monomer having from 1-20 percent by weight of a diene rubber dissolved therein is charged continuously as a monomer-rubber solution to the first stages of a staged isobaric stirred reaction zone. A suitable staged reactor is disclosed in U. S.
. i Patent No. 3,903,202. The monomer is polymerized at temperatures of 110 - 145C. in the first stage converting 10-50 percent by weight of the monomer to an alkenyl aromatic polymer having a molecular weight of 40,000 to 100,000 MWSt. At least a portion of the polymer polymerized is grafted as polymer mole-cules to the diene rubber as a superstrate.
Although the amount of polymeric superstrate grafted onto the rubber substrate may vary from as little as 10.0 parts by weight to 100.0 parts of substrate to as much as 250.0 per 100.0 parts and even higher, the preferred graft copolymers will generally have a superstrate to substrate ratio of 20 to 200:100 and most desirably 30 to 150:100. With graft ratios 30 to 150:100, a highly desirable degree of improvement in various properties generally is obtained.
The remainder of the poiymer formed is dissolved in said monomer composition as polymerized forming a monomer-polymer solution. The monomer-polymer solution or phase is incompatible with the monomer-rubber solution or phase and phase separation is observed by the well known Dobry effect. As the polymer con-centration of the monomer-polymer phase increases and has a volume slightly larger than the monomer-rubber phase, the mono- `
mer-rubber phase disperses as rubber-monomer particles aided by the shearing agitation of the stirred first reaction zone.
The agitation must be significant and of high enough shear to disperse and size the rubber particles uniformly throughout the monomer-polymer phase. The intensity of the stirring will vary with the size and geometry of the reactor, however, simple experimentation with a given stirred reactor will establish the sufficient amount of stirring needed to '` ~ 08779Z
insure the homogeneous dispersion of the rubber particles throughout the monomer-polymer phase. The particle size of the rubber can be varied from a weight average particle dia-meter of from 0.5 to 10 microns preferably from 0.5 to 5 microns to provide a balance between the impact strength and the gloss of the rubber reinforced polyblend. Higher stirring rates and shearing agitation can lower the size of the dispersed rubber particle, hence, must be controlled to provide sufficient stirring to size the particles to the predetermined size needed and insure homogeneous dispersion.
At steady state polymerization, in the first stage, the continuously charged monomer composition containing 1 to 20 per-cent by weight diene rubber disperses almost instantaneously, under stirring, forming the rubber-monomer particles which on complete polymerization form discrete rubber particles. The conversion of monomers to polymers in the first stage is con-trolled between 10-50 percent and must have a weight percent level that provides a polymer content in excess of the rubber content of the monomer composition to insure the dispersion of the monomer-rubber phase to a rubber-monomer particle phase having a predetermined size and being dispersed uniformly throughout the monomer-polymer phase.
The rubber particle becomes grafted with a polymer in the first stages which aids its dispersion and stabilizes the morphology of the particle. During the dispersion of the rubber-monomer particles, some monomer-polymer phase is oc-cluded within the particle. The total amount of occluded mono-mer-polymer phase and grafted polymer present in the particles can be from 1 to 5 grams for each gram said diene rubber.
~8-12-0343 The dispersed rubber phase increases the toughness of the polymeric polyblend as measured by its Izod impact strength by Test ASTM D-256-56. It has been found that the impact strength of polyblends increase with the weight percent rubber dispersed in the polyblend in the range of 1 to 20 percent as used in the present invention. The impact strength is also de-termined by the size of the dispersed rubber particles, with the larger particles providing higher impact strength in the range of 0.5 to 10 microns measured as a weight average particle size diameter with a photosedimentometer by the published procedure of Graves, M. J. et.al., "Size Analysis of Subsieve Powders Using a Centrifugal Photosedimentometer," British Chemical En-gineering 9:742-744 (1964). A Model 30~0 Particle Size Analyzer from Martin Sweets Company, 3131 West Market Street, Louisville, Kentucky was used.
The weight average diameter of the rubber particles also affects gloss with smaller particles giving high gloss and the larger particles giving low gloss to the fabricated polyblend article such as a molding or sheet product. One must balance impact strength and gloss requirements in seiecting an optimum rubber particle size. The range of 0.5 to 10 microns can be used with the range of 0.5 to 5 microns being preferred and 0.8 to ~ microns being most preferred for optimum impact strength and gloss.
Processwise, in the first stage, one must ~1) form and disperse the rubber particle, and ~2) graft and stabilize the rubber particle maintaining its size and morphology or structure.
The amount of occluded monomer-polymer phase described above is held at a pretetermined level described above by steady state polymerization wherein the monomer is converted to polymer, at least a portion of which, grafts to the rubber, stabilizing the rubber particle. It has been found that the higher the amount of occlusion stabilized within the rubber particle the more efficiently the rubber phase is used in toughening the polyblend.
The rubber particle acts much as a pure rubber particle if the occlusions are controlled at the amount described above during their stabilization in the initial stages and throughout the total polymerization process. The rubber particle is also grafted externally, stabilizing its structure as to size and its dispersibility in the monomer-polymer phase.
The first stage forms a polymerization mixture of a monomer-polymer phase having the rubber phase described dis-persed therein. The mixture is polymerized by progressive multistage substantial linear flow polymerizations with the conversion of polymer advancing from 10-50 percent conversion in the first stage to 50 to 90 percent conversion in the final stage of the staged isobaric stirred reaction zone. This provides a gradual progressive increase of polymer in the monomer-polymer phase. This has been found to be important in maintaining the morphology or structure of the dispersed rubber-monomer particles.
It has been found unexpectedly that in the first stage as the rubber particle is formed, that the rubber-monomer par-ticle has a monomer contenL that corresponds to the monomer con-tent of the monomer-polymer phase. The rubber-monomer particle will stabilize at this level as the monomer polymerizes inside the rubber particle and grafted polymer is formed on the out-side. Hence, it has been found that the lower the level of con-version or polymer in the monomer-polymer phase of the first stage the higher the amount of monomer found in the rubber-monomer particles formed as the rubber solution is charged and dispersed in the monomer-polymer phase. Conversely, if the con-version is high in the initial stage, less monomer is occludedin the rubber phase particle on dispersion. As described earlier, the mixture is polymerized in the staged linear flow zone, and the percent by weight of polymer being formed is pro-gressively higher with each stage having a slightly higher polymer content. The staged linear progressive polymerization was found not only to control the polymerization of the monomer giving desirable polymers but was found unexpectedly to preserve the integrity of the rubber particles. Although not completely understood, as the rubber particle becomes grafted and the monomer-polymer phase forms in the occluded monomer of the rubber particle, the monomer is not readily extracted from the rubber particle by the monomer-polymer phase as the polymer con- ;~
tent increases gradually in the monomer-polymer phase during polymerizing in the staged reactor. It is thought that since the polymerization in the multistaged linear reaction zone is - so gradual that polymer is being formed in both the rubber particle and the monomer-polymer phase at about the same rate, hence, the total polymer content of the occluded monomer-polymer phase of the rubber particle is about the same as polymer con-tent of the monomer-polymer phase and monomer is not extracted, hence, the weight percent of occlusion is stabilized and remains substantially constant after formation in the initial reactor.
It has been found possible to analyze the amount of total occluded polymer phase and grafted polymers. The final 10~7792 polymerized polyblend product (1 gram) are dispersed in a 50/50 acetone/methyl ethyl ketone solvent tlO ml) which dissolves the polymer phase matrix leaving the rubber phase dispersed. The rubber phase is separated from the dispersion by centrifuge as a gel and dried in a vacuum oven at 50C. for 12 hours and weighed as a dry gel.
~ Dry gel Weight of dry gel x 100 - in Polyblend Weight of polyblend Occlusions ~ ~ Percgent rubber~ x 100 Parts** by weight.
of graft polymer ) ~ dry ge~-~ rubber and occluded poly- ) - Percent rubber mer per unit weight of rubber *Percent rubber determined by infra-red spectrochemical analysis of the dry gel.
*~The present invention preferably has 20 ' present about 0.5 to 5 grams of occluded and grafted polymer per gram of diene rubber.
The swelling index of the rubber graft particles is de-termined by taking the dry gel above and dispersing it in tolu-ene for 12 hours. The gel is separated ~y centrifuge and the supernatant toluene drained free. The wet gel is weighed and then dried in a vacuum oven for 12 hours at 50C. and weighed.
Swelling Index - weight of dry gel As described earlier the amount of occlusions and graft polymer present in the rubber particle is present in the amount 1U~792 of 0.5 to 5 part for each part of diene rubber. The percent dry gel measured above then is the percent gel in the polymerized polyblend and represents the dispersed rubber phase having polymeric occlusions and polymeric graft. The percent gel varies with the percent rubber charged in the monomer composi-tion and the total amount of graft and occluded polymer present in the rubber phase.
The swelling index of the rubber as determined above is - important to the final properties of the polyblend. A low swelling index indicates that the rubber has been crosslinked by the monomer as it polymerizes to a polymer phase in the rubber-monomer particle during step (E). Generally, the con-version of monomer to polymer in the occlusion follows the rate of conversion of monomer to polymer in the monomer-polymer phase being carried out in steps (B) and (E). In step (E) the temperature of the second mixture is raised to 185 to 250C.
- and the monomer vapors are separated in step (F) to give a finished polyblend. The rubber particles become crosslinked by heating the mixture to from 185 to 250C. for sufficient time to crosslink the rubber particles such that they have a swelling index of from 7 to 20 preferably from 8 to 16.
Preferably, the polymer of the matrix phase of the poly-blends produced by this invention have a dispersion index (MW/Mn), wherein Mw is a weight average molecular weight and Mn is a number average molecular weight, ranging from 2.0 to 4.0 preferably 2.2 to 3.5. The dispersion index is well known to those skilled in the art and represents the molecular weight distribution with the lower values having narrow molecular weight distribution and higher values having broader molecular weight 108~79Z
~ 08-12-0343 distribution. The average molecular weight of the polymer of the matrix phase preferable range from-~5,000 to 100,000 Staud-inger, preferably 35,000 to 70,000.
STAGED POLYMERIZATION
The polymerization is carried out in a generally hori-zontal, cylinderical, flow-through, staged, isobaric stirred re-action zone maintaining conditions so as to polymerize said first mixture by progressive multistage substantially linear flow-through polymerization; all said stages operating with shearing agitation and common evaporation vapor phase cooling under iso-baric conditions in said reaction zone, providing each said stage with steady state polymerization at controlled temperature, and interfacial liquid contact stage-to-stage establishing a hydrau-lic pressure gradient from the first stage downstream to the final stage, causing substantially linear flow-through said re-action zone; all said stages operating at predetermined conver-sion levels producing a polymer in said reaction zone having a predetermined molecular weight distribution and average molecu-lar weight maintaining the structural integrity of said dis-persed rubber particle, said reaction zone producing a polymer-ization mixture having a total polymer content being determined by said multistage steady state polymerization and evaporation of said monomers.
The reactor operates under controlled iso~aric conditions~
~or the range of temperatures normally of interest for alkenyl aromatic monomers, e.g. styrene polymerization, the operating pressure will range from 4,000-20,000 Kg/m2. The styrene reaction is exothermic, and cooling is provided primarily by vaporization o~
a part of the monomer from the reacting mass. F~rther cooling can be provided by jacket. Cooling by the con-1(~87792 densed recycle monomer feeding into reaction zone is also pro-vided. The mass is in a boiling condition, and temperature is determined by the natural relationship between vapor pressure and boiling point. This relationship is also a function of the S relative amounts of polymer, monomer, and other substances (e.g.
dissolved rubber, solvents, and additives.) Since, as material progresses through this reactor, the amount of polymer continu-ously increases and the amount of monomer corresponding decreases via polymerization, and monomer content further decreases due to vaporization loss, the temperature progressively increases from inlet to outlet stages.
To accommodate the natural swell of the boiling mass, and to provide space for vapor disengagement, the reactor is usually run at a fillage of 10 to 90 percent preferably 40 to 80 percent of its volume.
Vapor passes out of the reactor to an external condenser where it is condensed and may also be subcooled. This conden-sate may then be returned to the inlet compartment of the re-actor wherein it is reheated by condensation of a fraction of the previously evolved vapors and mixed with other incoming free materials.
In a multi-compartment staged reactor, each stage is well mixed, and the reaction mass is substantially homogeneous within itself. The discs which separate the stages discourage backflow of material between compartments. The clearance be-tween disc and shell does permit some backflow, and also permits the necessary forwarding of material through the compartments from reactor inlet to outlet giving substantially linear flow.
In a compartmented staged reactor, the first stage has a - 18 _ ~08779Z
`08-12-0343 relatively low conversion level, since it is being continuously fed by monomer solution. However, the rate of conversion in this stage is relatively high because of the high concentration of monomer.
In each succeeding stage, the conversion level is higher than in the preceding one, which tends to lower the rate of con-version. Offsetting this effect, however, are the facts that the temperature is higher, and that monomer is being vaporized out of the mass. Thus, the total conversion to polymer obtained per unit fillage volume of the staged reactor is higher than that which could be obtained in a single stage reactor producing an equal final conversion level at equal temperature.
Clearance between rotating disc compartment baffles and cylindrical wall may be from 1 to 10 percent of shell radius, the larger values being appropriate to the high conversion end of the reactor where viseosity is at maximum. Stage-to-stage forward flow of the polymerizing mixture is through this clear-ance, and vapor from the polymerizing mixture also counterflow through the clearance, above the surface level of the mass.
The monomer-polymer solution flows through the reaction zone under substantially linear flow, with minimized back mixing, from the first stage to the final stage under a liquid pressure gradient from the first stage to the last stage. Temperature in the reaction zone is contr~lled by pressure wherein the pressure is regulated to cause the polymerizing solution to boil under its heat of polymerization removing a monomer-vapor phase at a rate sufficient to maintain the temperature of the polymerizing solution at a temperature of from 100 to 180C. and under iso-_ 19 _ ~ 08779Z ;' ' 08-12-0~43 baric conditions of 6 to 29 psia (4,000-20,000 kg/m2).
The monomer, e.g. styrene, polymerizes giving off about 300 BTU per pound polymerized. The heat of vaporization of sty-rene is about 150 BTU per pound vaporized, hence, the reactor generally removes about 2 pounds of monomer from the polymeriz-ing syrup per pound of polystyrene converted which is recycled bac~ to the polymerizing first stage at that rate to maintain steady state polymerization under controlled temperature and isobaric conditions.
In operation, the reaction zone can be filled from about 15 to 90 percent of its volume with the polymerizing solution, the remaining volume thereof being occupied by vaporized mono-mers. A mixture is withdrawn from the last stage of the reac-tion zone wherein the degree of conversion can range from about 50 percent to as high as 90 percent. The last stage of the re-action zone is generally maintained at higher temperatures ~130-lôOC. ) than the first stage of the reaction zone produc-ing polymers having average molecular weights in the lower range of 30,000 to 70,000 Staudinger. The combined polymer can have lecular weight range of 30,000 to 100,000 Staudinger prefer-ably ~5,000 to 70,000 Staudinger. This flexibility affords the ability to produce a wide range of polymers of varying molecular weight distribution and at varying levels of fillage of the re-action zone.
In the operation of the reaction zone it is preferred to employ a continuous staged isobaric stirred reactor which is controlled by withdrawal of vaporized monomer above the liquid level maintained therein in order to control the tempera-ture in such second reaction zone. This withdrawn stream of _ 20 -~08779Z
~8-12-0343 vaporized monomer is condensed in a condenser and collected in a receiver. It can be returned to the first stage of the reaction zone.
A preferred method of control of the reaction zone is the temperature within the final stage of reactor. The control system involves sensing the temperature in the liquid phase in the final stage of reactor and employing a signal so generated to control a temperature controller modified by a signal from a set point generator at a preselected temperature value. The re-sulting signal modified by a signal generated by sensing the pressure in the vapor phase of said reactor is employed to con-trol a pressure controller which in turn controls a pressure valve in the vent line from the recycled condensed monomer re-ceiver. By so adjusting the pressure above the condensed mono-mer in the receiver the temperature of the final stage in the reactor is very closely and rapidly controlled to a preselected desired value. The temperature in each stage rapidly achieves an equilibrium value-based on the reactor pressure and the poly-meric solids content of the polymerizing solution in each stage.
The utilization of the present process gives an overall production process for high impact strength polyalXenyl aromatic polyblends. The polymer, dispersed rubber and monomer mixture called the polymerization mixture comprises the liquid phase effluent from the reactor. Said mixture having a polymeric solids content of from about 50 to about 90 percent by weight is withdrawn therefrom by suitable means such as a gear pump and passed to a heating and devolatilization zone or zones.
One zone of devolatilization which can be operated at pressures below atmospheric, or degrees of vacuum. However, the ~08779Z
process of the present invention can be operated by the use of two or multiple zones of devolatilization as desired. In the process outlined the vaporized alkenyl aromatic monomers as well as low oligomers thereof are removed from the first devolatiliza-S tion zone, condensed and passed to a receiver. From the receiver a stream of the condensed monomers and oligomers can be recycled to the first stage of the reactor. Likewise, the monomers and oligomers vaporized in a second devolatilization zone generally operated at somewhat lower pressure than the first are with-drawn, condensed and passed to a receiver. From this receiver a stream of condensed monomers and oligomers can also be recycled to the reactor. Preferably, the oligomers vaporized in either devolatilization zone can be separated from the vaporized mono-mer by distillation and separately recycled to the reaction zone or purged from the process.
In the production of certain of the desired polymers it has generally been found advantageous to add certain high boil-ing organic compounds to the polymers produced and the addition is preferably made during polymerization. These additives in-clude internal lubricants such as mineral oil or other heavy oil and mold release agents such as fatty acids, fatty acid esters or salts and waxes. These additions can be conveniently made to the reaction zone and are preferably made to the last stage by means of the multiple metering pumps.
~hen operating in the manner described above, the proper control of reactors of the variable fillage type affords one the extremely useful advantage of ability to produce polymers of specific physical properties and molecular weight distribut~on over a range of capacities of from as low as 3~ to as high as 10~779z 100 percent of design capacity for the single production facil-ity described. This flexibility in useful capacity is highly desirable to afford ready response to changes in market demand for total polymers or in the market percentage for various poly-mers produced in such a production facility.
The following examples are set forth to illustrate more clearly the principles and practice of this invention to one skilled in the art. They are not intended to be restrictive but merely illustrative of the invention herein described. All parts are by weight unless otherwise indicated. All molecular weights are in Staudinger values unless otherwise noted.
A monomer composition consisting of 5.6 parts by weight of stereospecific polybutadiene rubber in 94.4 parts by weight of styrene monomer is prepared by agitating the mixture at 40C.
for 8 hours (Diene 55 Rubber is available from Firestone Rubber Company, Akron, Ohio). To the above monomer composition is added .1 part of octadecyl 3-~3',5'-di-tert-butyl-4-hydroxy-phenyl) propionate and 24 parts of recycled styrene monomer.
This mixture is fed at 38 kg./hr. continuously to a re-actor that has approximately .89 1. capacity and operates at about 45 percent fillage.
The reactor is 135 c~. long. The agitator con-sists of a horizontal shaft on which are fixed a series of paddles 5.08 cm. wide alternating at right angles to one another. Along the shaft and rotating with it are two circular - baffles with an average radial clearance of 0.95 cm., ro-tating at 10 rpm. These baffles are positioned to divide the reactor into 3 stages of approximately equal volume. Into the '''' ~087792 downstream compartment of this reactor is fed a stream ; consisting of 1 part of white mineral oil. The pressure in the reactor is maintained at 0.91 kg/cm2 with the first stage at 125C. and the final stage at 153C. The polymerizing syrup exiting the reactor contains 70 per-cent solids. Styrene vapor evaporated in this reactor is condensed and returned to the first stage compartment.
The syrup in the downstream compartment is pumped contin-uously from the reactor at a rate to maintain essentially constant reactor fillage and is pumped to the inlet of a ; tube and shell heating means. This stage is maintained at 4.55 kg/cm2 via a throttling valve on the exit side of the heater. The syrup exiting this preheater stage is at 170C. After passing through the throttling valve, the syrup flows into a two stage devolatilizing means as dis-closed in U.S. Patent No. 3,928,300 and found to be one suitable means of devolatilization. The first stage de-volatilizer was operated at 220C. and about 60 torr.
After passing through the devolatilizer interstage valve, regulated to maintain approximately constant fillage in the first devolatilizer stage, the melt flows into the second stage devolatilizer chamber maintained at 15 torr.
A suitable method of devolatilization is disclosed in U.S. Patent No. 3,928,300.
Vapors exiting the devolatilizer chambers are condensed and recycled to the first compartment of the reactor. 0.9 kgs/hr. of these condensed vapors are withdrawn as purge. The devolatilized melt is pumped ,":
from the second devolatilizer compartment through a die to form a plurality of strands which are then cooled and cut into pellets. The resulting polymer 1()87792 has a Staudinger molecular weight of ~9,000 and a dispersion ~x~x of 2.2.
TyPical Properties Izod Impact Strength 1.27 x 1.27 om. bar ~Kg/cm/cm2) 5.45 Tensile Strength @ yield (Kg/ ~ ) 275 Tensile ~trength ~ faii (Kg/om2) 294 Tensile èlongation at fail t%) 39 Swelling Index 9 Parts graft and occlusions 1~ parts/part rubber 1~60 ~ubber particle size t~;crons) 3.8 ~XAMPLE 2 tUse of Initiator) ~he process was operated using the apparatus and proce-dure of ~xample 1 except as noted below:
a~ the reactor agitator was operated at about ~0 rpm.
~) the feed monomer composition also contained
2~ .~06 parts dicumyl peroxide.
c) reactor fillage ~i?as approximately 40~.
; d) the reactor was maintained at a pressure of 0.80 Kg/cm2.
~e) t~e ~elt in the final stage reactor compart-
c) reactor fillage ~i?as approximately 40~.
; d) the reactor was maintained at a pressure of 0.80 Kg/cm2.
~e) t~e ~elt in the final stage reactor compart-
3~ Eent was maintained at approx~mately 146C.
f~ the.melt exiting the reactor contained a~out - 2~ -65% solids.
lYpical Properties Izod Kg. cm./om. . 6.0 Tensile @ yield Kg./cm2301 S Tensile @ fail Kg/om2 322 Elongation at fail 35 : S.I.(Swelling Index) 8 6raft and Occlusions : parts/parts rubber 1.80 Rubber particle size (micx~s) 3.3 Staudinger MW 58,000 Dispersion Index 2.4 Monomer C position Having Lower Rubber Content The process was operated using the apparatus and proi cedure of Example 1 except as noted below:
a) the reactor agitator was operated at 40 rpm.
20b) the feed monomer composition contained 3.3 parts rubber and 96.7 parts styrene c) reactor fillage was approximately 50%.
.~ d) melt exiting the first preheater stage . . was at 195&.
. .
_ 26 -~087792 d3-12-0343 Dical ProPerties Izod Kg. cm/cm. 4.36 Tensile @ yield Kg/cm2 365 Tensile @ Fail Xg/cm2 359 Elongation @ fail 20 Swelling Index 9 Parts graft and occlusions/
part rubber -1,40 Rubber particle size ~microns) 3.1`
Staudinger MW SS,000 Dispersion Index 3.1 ~XAMPLE 4 (Higher rubber level, more reactor compartments) Monomer feed composition s~milar to Example 1 but con-taining 8 parts rubber, 92 parts styrene and 29 parts recycled styrene monomer. The mixture is fed at 59.1 Kg./hr. to a reactor similar to that of Example 1 except that it has 8 circular baffles dividing it into 9 stages of approximately equal volume. The reactor agitator rotates at 15 rpm and oper-ates at 59 percent fillage. ~he reactor pressure is maintained at 1.16 Kg./cm2 and the syrup temperature in the final compartment at 157C. The exiting syrup from the reactor contains 68 percent solids and is then devolatil-ized, extruded ~hrough a die, into a plurality of strands, which are cooled and pe}letized. Vapors from the devolatilizer are , ` condensed and recycled to the first compartment of the reactor.
1.36 Kg/hr. of tnis condensate was withdrawn as purge.
' ~ ..
"'`
- 27 ~
~08~792 Typical ProPerties Izod (Rg.cm/cm) 12.C
Tensile @ yield (Xg/cm2) 34;
Tensile @ fail (Kg/cm2) 302 Elongation @ fail 24 Swelling Index 13.6 Parts graft and occlusions~
part rubber 0.67 Rubber particle size (microns)1.5 EXAMPLE S
Exàmple 1 was repeated using a solution of 7.2 parts of rubber dissolved in 92.8 parts of a monomer composition compris-ing 7,5 weight percent of styrene and 25 weight percent of acrylonitrile. m e solution was processed as in Example 1 and lS the polyblend separated had the following properties.
Izod Impact Strength 16.4 Kg.cm/cm.
Tensile Strength at yield 457 Kg/c~2 Tensile Strength at fail 359 Kg/cm2 - Tensile elongation at fail25 percent Swelling index 12 - Parts graft and occlusions/ 1.5 part rubber Rubber particle size 1.2 microns ~ ' A
.
- 2~ - ~
f~ the.melt exiting the reactor contained a~out - 2~ -65% solids.
lYpical Properties Izod Kg. cm./om. . 6.0 Tensile @ yield Kg./cm2301 S Tensile @ fail Kg/om2 322 Elongation at fail 35 : S.I.(Swelling Index) 8 6raft and Occlusions : parts/parts rubber 1.80 Rubber particle size (micx~s) 3.3 Staudinger MW 58,000 Dispersion Index 2.4 Monomer C position Having Lower Rubber Content The process was operated using the apparatus and proi cedure of Example 1 except as noted below:
a) the reactor agitator was operated at 40 rpm.
20b) the feed monomer composition contained 3.3 parts rubber and 96.7 parts styrene c) reactor fillage was approximately 50%.
.~ d) melt exiting the first preheater stage . . was at 195&.
. .
_ 26 -~087792 d3-12-0343 Dical ProPerties Izod Kg. cm/cm. 4.36 Tensile @ yield Kg/cm2 365 Tensile @ Fail Xg/cm2 359 Elongation @ fail 20 Swelling Index 9 Parts graft and occlusions/
part rubber -1,40 Rubber particle size ~microns) 3.1`
Staudinger MW SS,000 Dispersion Index 3.1 ~XAMPLE 4 (Higher rubber level, more reactor compartments) Monomer feed composition s~milar to Example 1 but con-taining 8 parts rubber, 92 parts styrene and 29 parts recycled styrene monomer. The mixture is fed at 59.1 Kg./hr. to a reactor similar to that of Example 1 except that it has 8 circular baffles dividing it into 9 stages of approximately equal volume. The reactor agitator rotates at 15 rpm and oper-ates at 59 percent fillage. ~he reactor pressure is maintained at 1.16 Kg./cm2 and the syrup temperature in the final compartment at 157C. The exiting syrup from the reactor contains 68 percent solids and is then devolatil-ized, extruded ~hrough a die, into a plurality of strands, which are cooled and pe}letized. Vapors from the devolatilizer are , ` condensed and recycled to the first compartment of the reactor.
1.36 Kg/hr. of tnis condensate was withdrawn as purge.
' ~ ..
"'`
- 27 ~
~08~792 Typical ProPerties Izod (Rg.cm/cm) 12.C
Tensile @ yield (Xg/cm2) 34;
Tensile @ fail (Kg/cm2) 302 Elongation @ fail 24 Swelling Index 13.6 Parts graft and occlusions~
part rubber 0.67 Rubber particle size (microns)1.5 EXAMPLE S
Exàmple 1 was repeated using a solution of 7.2 parts of rubber dissolved in 92.8 parts of a monomer composition compris-ing 7,5 weight percent of styrene and 25 weight percent of acrylonitrile. m e solution was processed as in Example 1 and lS the polyblend separated had the following properties.
Izod Impact Strength 16.4 Kg.cm/cm.
Tensile Strength at yield 457 Kg/c~2 Tensile Strength at fail 359 Kg/cm2 - Tensile elongation at fail25 percent Swelling index 12 - Parts graft and occlusions/ 1.5 part rubber Rubber particle size 1.2 microns ~ ' A
.
- 2~ - ~
Claims (22)
1. An improved continuous process for the mass poly-merization of a solution comprising a monoalkenyl aromatic monomer having a diene rubber dissolved therein wherein the improvement comprises:
A. charging continuously said solution to a first stage of a staged isobaric stirred reaction zone, B. maintaining conditions in said reaction zone so as to polymerize said solution by sequential multistage substantially linear flow polymerization, each said sequential stage having continuous flow-through liquid contact stage to stage within said zone establishing a pressure gradient from said first stage downstream to a final stage causing substantially linear flow, all stages operating with shearing agitation and common evaporative vapor phase cooling under isobaric con-ditions, providing each stage with steady state polymerization at a controlled temperature of from about 100-180°C. under a pressure of from about 4,000 to 60,000 kgs/m2, each said stage operating at a predetermined higher conversion level of from about 10 to 90 percent, C. producing continuously a matrix polymer phase comprising a polymonoalkenyl aro-matic polymer having a predetermined average molecular weight of from about 35,000 to 100,000 MWSt having dispersed therein said diene rubber phase as par-ticles having an average diameter of from about 0.5 to 10 microns forming a polymerization mixture comprising polymer, rubber particles and monomer, D. withdrawing continuously said polymeriza-tion mixture from said final stage, E. continuously heating said polymerization mixture to temperatures of from about 180-250°C. until said rubber particles are crosslinked to a predetermined swell-ing index, and F. continuously separating said monomer from said polymerization mixture providing a polyblend comprising said polymonoalkenyl aromatic polymer and said diene rubber particles.
A. charging continuously said solution to a first stage of a staged isobaric stirred reaction zone, B. maintaining conditions in said reaction zone so as to polymerize said solution by sequential multistage substantially linear flow polymerization, each said sequential stage having continuous flow-through liquid contact stage to stage within said zone establishing a pressure gradient from said first stage downstream to a final stage causing substantially linear flow, all stages operating with shearing agitation and common evaporative vapor phase cooling under isobaric con-ditions, providing each stage with steady state polymerization at a controlled temperature of from about 100-180°C. under a pressure of from about 4,000 to 60,000 kgs/m2, each said stage operating at a predetermined higher conversion level of from about 10 to 90 percent, C. producing continuously a matrix polymer phase comprising a polymonoalkenyl aro-matic polymer having a predetermined average molecular weight of from about 35,000 to 100,000 MWSt having dispersed therein said diene rubber phase as par-ticles having an average diameter of from about 0.5 to 10 microns forming a polymerization mixture comprising polymer, rubber particles and monomer, D. withdrawing continuously said polymeriza-tion mixture from said final stage, E. continuously heating said polymerization mixture to temperatures of from about 180-250°C. until said rubber particles are crosslinked to a predetermined swell-ing index, and F. continuously separating said monomer from said polymerization mixture providing a polyblend comprising said polymonoalkenyl aromatic polymer and said diene rubber particles.
2. A process of Claim 1, wherein said monoalkenyl aromatic compound is selected from the group consisting of styrene, a-methyl styrene, chlorostyrene, dichlorostyrene, bromostyrene or dibromostyrene and mixtures thereof.
3. A process of Claim 1, wherein said diene rubber is selected from the group consisting of polybutadiene, polyiso-prene, poly-2-chlorobutadiene, poly-1-chlorobutadiene, copoly-mers and block copolymers of butadiene-styrene, butadiene-chloroprene, chloroprene-styrene, chloroprene-isoprene, 2-chlorobutadiene-1-chlorobutadiene and mixtures thereof.
4. A process of Claim 1, wherein said diene rubber is polybutadiene.
5. A process of Claim 4, wherein said polybutadiene rubber has a cis isomer content of about 30 to 98 percent and a Tg range of from about -50°C. to -105°C.
6. A process of Claim 1, wherein said monoalkenyl aromatic monomer is styrene.
7. A process of Claim 1, wherein said common evapora-tive vapor phase cooling is carried out by continuously simul-taneously removing a vapor phase comprising said monomer from the stages of said reaction zone at rates sufficient to main-tain said solution in each stage at a predetermined temperature of from about 100-180°C. and under a predetermined pressure of from about 5,000 to 60,000 kgs/m3.
8. A process of Claim 7, wherein the vapor phase con-tinuously removed is liquified and continuously returned to said reaction zone at a rate such that said steady state polymerization is maintained.
9. A process of Claim 8, wherein said liquified vapor phase is returned to the first stage of said reaction zone.
10. A process of Claim 1, wherein said solution is charged in step (A) at a rate approximately equal to the rate at which said polymerization mixture is withdrawn in step (D).
11. A process of Claim 1, wherein said reaction zone has 2 to 15 stages.
12. A process of Claim 1, wherein said reaction zone is a substantially horizontal, continuous, staged, isobaric, stirred reactor.
13. A process of Claim 1, wherein said solution has present about 0.001 to 3.0 percent by weight of a free radical generating catalyst.
14. A process of Claim 1, wherein said free radical generating catalyst is selected from the group consisting of di-tert-butyl peroxide, tert-butyl peracetate, benzoyl perox-ide, lauroyl peroxide, tert-butyl perbenzoate, dicumyl perox-ide, tert-butyl peroxide and isopropyl carbonate or mixtures thereof.
15. A process of Claim 1, wherein said monoalkenyl aromatic monomer is styrene and said diene rubber is poly-butadiene.
16. A process of Claim 1, wherein said solution con-tains said diene rubber dissolved in amounts of from about 1 to 20 percent by weight.
17. A process of Claim 1, wherein each of said stages operates at a substantially constant gravimetric fillage of from about 15 to 90 percent of its volume during the steady state polymerization of said solution.
18. A process of Claim 1, wherein said first stage is operated at temperatures of from about 100 to 145°C. and a con-version level of 10 to 50 percent with said final stage operating at a temperature of from about 130 to 180°C. and a conversion of from about 50 to 90 percent.
19. A process of Claim 1, wherein said solution com-prises about 60 to 98 percent by weight of said monoalkenyl aromatic monomer, about 1 to 39 percent by weight of an alkenyl nitrile monomer and about 1 to 20 percent by weight of said diene rubber.
20. A process of Claim 19, wherein said alkenyl nitrile monomer is acrylonitrile, methacrylonitrile or mixtures thereof.
21. A process of Claim 19, wherein said monoalkenyl aromatic monomer is styrene, said alkenyl nitrile monomer is acrylonitrile and said diene rubber is polybutadiene.
22. A process of Claim 1, wherein said polyblend separated in step (F) has rubber particles having present grafted and occluded polymer in an amount of about 0.5 to 5 parts per part rubber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US69118476A | 1976-05-28 | 1976-05-28 | |
| US691,184 | 1976-05-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1087792A true CA1087792A (en) | 1980-10-14 |
Family
ID=24775489
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA279,319A Expired CA1087792A (en) | 1976-05-28 | 1977-05-27 | Continuous mass polymerization process for polybends |
Country Status (13)
| Country | Link |
|---|---|
| JP (1) | JPS52146491A (en) |
| AR (1) | AR216913A1 (en) |
| AU (1) | AU507807B2 (en) |
| BE (1) | BE855128A (en) |
| BR (1) | BR7703471A (en) |
| CA (1) | CA1087792A (en) |
| DE (1) | DE2724163A1 (en) |
| ES (1) | ES459128A1 (en) |
| FR (1) | FR2352838A1 (en) |
| GB (1) | GB1555725A (en) |
| IL (1) | IL52174A (en) |
| IT (1) | IT1076797B (en) |
| SE (1) | SE435293B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1230085B (en) * | 1989-05-24 | 1991-10-05 | Montedipe Spa | PROCESS FOR THE MASS AND CONTINUOUS PRODUCTION OF (CO) AROMATIC SHOCKPROOF VINYL POLYMERS. |
| GB9420644D0 (en) * | 1994-10-13 | 1994-11-30 | Dow Chemical Co | Non-linear styrenic polymer-based foams |
| US5830924A (en) * | 1994-10-13 | 1998-11-03 | The Dow Chemical Company | Non-linear styrenic polymer-based foams |
| GB9420645D0 (en) * | 1994-10-13 | 1994-11-30 | Dow Chemical Co | Non-linear stytrenic polymer compositions and articles prepared therefrom |
| EP1988119A1 (en) * | 2007-05-01 | 2008-11-05 | Nova Innovene International S.A. | Expandable polystyrene composition |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1175262A (en) * | 1967-07-26 | 1969-12-23 | Shell Int Research | The Manufacture of Polyvinyl-Aromatic Compounds, and the Resulting Polymers. |
| AU3226971A (en) * | 1970-08-13 | 1973-02-15 | The Dom Chemical Company | Process forthe production of polymers containing a reinforcing polymer therein |
| US3903202A (en) * | 1973-09-19 | 1975-09-02 | Monsanto Co | Continuous mass polymerization process for polyblends |
| US3927983A (en) * | 1973-09-19 | 1975-12-23 | Monsanto Co | Continuous staged isobaric stirred polymerization apparatus |
| US3903200A (en) * | 1974-03-07 | 1975-09-02 | Monsanto Co | Continuous mass polymerization process for ABS polymeric polyblends |
| BE830308A (en) * | 1974-06-25 | 1975-12-17 | PROCESS FOR PREPARING AN IMPACT-RESISTANT POLYMER OF A VINYLAROMATIC COMPOUND |
-
1977
- 1977-05-25 ES ES459128A patent/ES459128A1/en not_active Expired
- 1977-05-27 JP JP6127677A patent/JPS52146491A/en active Granted
- 1977-05-27 CA CA279,319A patent/CA1087792A/en not_active Expired
- 1977-05-27 DE DE19772724163 patent/DE2724163A1/en not_active Ceased
- 1977-05-27 IL IL52174A patent/IL52174A/en unknown
- 1977-05-27 IT IT24108/77A patent/IT1076797B/en active
- 1977-05-27 BR BR7703471A patent/BR7703471A/en unknown
- 1977-05-27 FR FR7716312A patent/FR2352838A1/en active Granted
- 1977-05-27 AU AU25560/77A patent/AU507807B2/en not_active Expired
- 1977-05-27 BE BE177981A patent/BE855128A/en not_active IP Right Cessation
- 1977-05-27 GB GB22525/77A patent/GB1555725A/en not_active Expired
- 1977-05-27 AR AR267792A patent/AR216913A1/en active
- 1977-05-27 SE SE7706244A patent/SE435293B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| GB1555725A (en) | 1979-11-14 |
| DE2724163A1 (en) | 1977-12-08 |
| IL52174A (en) | 1980-07-31 |
| AR216913A1 (en) | 1980-02-15 |
| FR2352838B1 (en) | 1981-07-10 |
| FR2352838A1 (en) | 1977-12-23 |
| SE435293B (en) | 1984-09-17 |
| BE855128A (en) | 1977-11-28 |
| JPS559408B2 (en) | 1980-03-10 |
| ES459128A1 (en) | 1978-04-01 |
| AU507807B2 (en) | 1980-02-28 |
| JPS52146491A (en) | 1977-12-06 |
| IL52174A0 (en) | 1977-07-31 |
| AU2556077A (en) | 1978-11-30 |
| IT1076797B (en) | 1985-04-27 |
| SE7706244L (en) | 1977-11-29 |
| BR7703471A (en) | 1978-01-10 |
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