CA1042127A - Continuous method of agglomerating aqueous latices and apparatus therefor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
There is disclosed a continuous method for agglomerating latices of a polymer to provide ??rge particles. An acid anhydride solution is continuously admixed with an aqueous latex of a polymer followed by passing the admixture through a conduit with laminar-flow wherein the passage-time through said conduit is sufficient to hydrolyze the acid anhydride and produce agglomeration of said particles providing an agglomer-ated admixture followed by continuously stabilizing said agglomerated admixture with an emulsifying material providing a stabilized agglomerated latex.

Description

~0~'~127 CONTINUOUS MFTilOD OF AGGLOMERATINC AQUEOUS LATICES
AND APPARATUS THEREFOR

Latices of various polymers are useful for a wide range of applications. In recent years, rubber latices have been widely employed for the manufarture of rubber-reinforced plas-tics such as impact styrene and ABS materials. Although rubbers may be mechanically admixed with such polymers, greatly improved results are obtained by providing chemical adhesion between the rubber phase and the matrix by grafting at least a portion of the matrix polymer onto the rubber particles. It has also been noted that the impact strength of the rubber-modified composi-. .
tions at times is dependent upon the size of the rubber parti-cles dispersed therein within certain limits so that there has been interest in increasing the size of the rubber particles obtained in conventional latex polymerization processes.
In U.S.P. 3,558,541 to William 0. Dalton, issuing on January 26, 1971, there is disclosed an improved batch process for agglomerating latices based upon the use of acid anhydrides and latices containing organic acid salts as the emulsifying agents. The acid anhydride destroys the emulsifying agent be-cause of its higher ionization constant and the unstabilized latex permits the particles to collide and agglomerate into lsrge particles which are subsequently stabilized.
This technique has proven highly effective in obtaining latices with particle sizes varying with the polymer and rang-ing up to about 1 micron. However, there has remained a desire to obtain even larger particles with some latices and a desire to reduce the amount of the relatively expensive acid anhydride and time required to obtain particles of a given size.

- 2 - ~

iO4Z127 C-08-12-02g5 In ~.S.P. 3,551,370 to William 0. Dalton issuing o.
December 2, 1970, there is disclosed an improved batch process for agglomerating aqueous latices of a suitable polymer wherein an inorganic electrolyte is added to the latex prior to admix-ture with a water-soluble acid anhydride. Such batch process handling large volumes of latex and anhydride solution, require mixing in large stirred tank, hence has considerable difficulty in uniformly mixing said materials, time-wise, before the pH
drops too far in localized areas and the mixing can then cause serious coagulation and nonuniformities batch to batch as well as loss of coagulated latex.

0~-12-Q295A

The process of the present inven-tion comprises:
A continuous process for agglomerating polymer particles in an aqueous latex, the steps comprising:
A. feeding continuously into a mixing zone an aqueous solution of a water soluble organic acid anhydride, while simulta-neously feeding continuously into said mixing zone an aqueous latex of a low heat distortion polymer, said polymer being formed from at least one ethylenically un-saturated monomer, the particles of said polymer being small and adherent upon col-lision and said latex containing an emulsi-fying agent, which is a salt of an organic acid with an ionization constant lower than that of the acid of the anhydridej B. mixing continuously said solution of said water soiuble organic acid anhydride with said latex in said mixing zone forming an admixture;
C. passing continuously said admixture from said mixing zone through a perforated mem-ber forming a wall section of said mixing C-08-12-0295 l~ZlZ7 zone through a perforated member forming a wall section of said mixing zone into an interconnected conduit;
D. flowing continuously, said admixture under laminar flow, induced by said perforated member, through said conduit wherein said admixture has a passage-time through said conduit sufficient to hydrolyze the acid anhydride, agglomerating the particles Or the polymer to a predetermined size, forming an agglomerated admixture;
E. -moving continuously said agglomerated admix-ture from said conduit through a low-shear zone being interconnected at one end portion to said conduit and having a withdrawal port at an opposite end portion;
F. stabilizing continuously said agglomerated admixture moving through said low-shear zone by adding an emulsifying material selected from the group consisting of an acid-stable emulsirying compound or a basic compound and combinations thereof, said stabilizing being prior to sub~ecting said agglomerated admix-ture to substantial shear which would cause coagulation of said agglomeratd admixture;
and G. withdrswing continuously said stabilizing agglomerated admixture from said low-shear zone st said opposite end by a withdrawal ~-08-12-0295 l~ZlZ7 means providing flow-mixing in said stabil-ized agglomerated admixture.
The process of this invention can be csrried out in various spparatus, preferably in an apparatus comprising:

A. a mixing zone having a first feed port for an agglomerating solution stream, a second feed port for a latex stream, a mixing means located in said zone to mix said feed streams forming an admixture, a perforated member, forming at least a portion of a wall section of said mixing zone, said member providing a flow-through port for said admixture induc-ing laminar-flow in said admixture, B. an annular conduit to carry said laminar-flow-. 15 ing admixture having a first orifice coincid-ing and interconnected with said perforated member and a second orifice in an oppos-ite end Or said conduit, C. a low-sbear zone having a first inlet port in one end Or said low-shear zone interconnected with said second orifice of said conduit to carry an agglomerated admixture at least one additional inlet port located in an opposite end o~ said low-shear zone for feeding an emulsifying material to stabilize said agglom-erated mixture and an outlet port in said C-08-12-0295 1~4~Z7 opposite end, D. a withdrawal means, interconnec-ted with said outlet port Or said low-shear zon~, for said stabilized aeglomerated admixture.
DRAWINGS
~he present invention is better understood by reference to the attached drawings wherein:
Figure 1 is a diagrammatic side elevation view of an apparatus assemgly suitable for the practice of the present invention with the conduit operating in a preferred substantially verticle position.
Figure ? is a diagrammatic side elevation view of the low shear-zone and withdrawal means showing addi-tional feed ports for the emulsifying materials.
Figure 3 is a diagrammatic end view of said low shear zone and said withdrawal means showing locations of feed ports.
Figure 4 is a diagrammatic view of a mixing zone com-prising a cylindrical stirred tank having a multi-paddle agitator with wall baffles positioned be-tween paddles and a perforated member as a upper wall section interconnected with a conduit.
Figure 5 is a diagrammatic view of a mixing zone com-prising a cylindrical stirred tank having a marine-propeller agitator position generally in the center Or the tank.
Figure 6 is a disgrammatic view of an apparatus assem-bly for the process oriented such that the admixture floYs generally down~ardly through the conduit, C-08-12-0295 l~Z~
dnring the operation of the process, showing essentially all of the elements of the apparatus necessary for operation of the process.
Figure 7 is a diagrammatic view of an apparatus assem-bly oriented such that the admixture flows gener-ally horizontally through the conduit, during the operation of the process, showing essentially all elements of the apparatus necessary for operation of the process.
Figure 8 is a diagrammatic view of an apparatus assem-bly (not to scale) showing essentially all the elements of the apparatus necessary for operation ~ of the process including a feed system for the latex and mixing-feed system for the anhydride solution.

As will be readily appreciated, various factors affect optimum operation of the process and the several variables must be considered in determining the process conditions required ~or a given latex and/or a given particle size increase. The efrect Or suCh variables also determlne the comblnatlon Of elements to be used ln the apparatu5 and nill be dlscussed at lêngth hereln-arter and lllustrated ln the examples.
The Polymeric Latex The aqueous latices which may be used in the present invention are those Or polymers having low heat distortion properties with particles having surfaces sufficiently soft or tacky under the conaitions of operation 80 that the particles ` will adhere to each other upon collision once the protection of the emulsifying agent is removed or impaired. Such polymers may C-08-12-0295 l~Zl~
be inherently soft and/or tacky such as rubbers or they may be rendered so by swelling with a solvent prior to the process of the present invention.
Thus, the low heat distortion polymers with which the 5 present invent~on may be employed are the rubber polymers such as the diene rubbers, polyisoprene rubbers, acrylate rubbers, ethylene-propylene rubbers snd mixtures thereof.
The preferred latices are those of diene rubbers or mixtures of diene rubbers, i.e., any rubbery polymers (a poly-mer having a second order transition temperature not higherthan 0 centigrade, preferably not higher than -20 centigrade, as determined by ASTM Test D-746-52T) of one or more con~u-gated, l,3-dienes, e.g., butadiene, isoprene, piperylene, chloroprene, etc. Such rubbers include homopolymers of con~u-gated 1,3-dienes and copolymers or block copolymers 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-dimetkylRtyrene, the ar-ethylstyrenes, p-tert-butylstyrene, etc.; an alpha-alkylsty-rene, such as alpha-methylstyrene, alpha-ethylstyrene, alpha-mcthyl-p-methylstyrene, etc.; vlnyl naphthalene, etc.); arhalo mono~inylidene aromatic hydrocarbons (e.g., the o-, m- and p-chlorostyrene, 2,4-dibromostyrene, 2-methyl-4-chlorostyrene, etc.) acrylonitrile; methacrylonitrile; alkyl acryla'es (e.g., methyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc.), the corresponding alkyl methacrylates; acrylamides (e.g., acrylamide, methacrylamide, ~-butylacrylamide, etc.); unsatur-ated ketones (e.g., vlnyl methyl ketone, methyl isopropenyl _ g _ 1~4~127 ketone, etc.) alphe-olefins (e.g., ethylene, propylene, etc.);
pyridines; vinyl esters (e.g., vinyl acetate, vinyl stearate, etc.); vinyl and vinylidene halides (e.g., the ViDyl and vinyli-dene chlorides and vinylidene chlorides and bromides, etc.);
and the like.
A preferred group Or rubbers are those consisting es-sentially of 75.0 to 100.0 percent by weight Or butadiene and/or isoprene and up to 25.0 percent by weight Or a monomer selected from the group consisting Or monovinylidene aromatic hydrocarbons (e.g., styrene), and unsaturated nitriles (e.g., acrylonitrile) or mixtures thereof. Particularly advantageous substrates are butadiene homopolymer or interpolymers Or 90.0 to 95.0 percent by weight butadiene and 5.0 to 10.0 percent by weight of acrylonitrile or styrene.
As the content Or a non-rubbery monomer in a rubber copolymer approaches 50 percent by weight Or the interpolymer, there is a tendency to form coagulum so that the preferred rub-bery interpolymers will normally contain less than about 35.0 percent Or a non-rubbery monomer, particularly when such a monomer is polar.
Although the rubber polymer may contain minor amounts Or a crosslinklng agent, generally less than about 2.0 percent by weight, excessi~e crosslinking of the polymer should be avoided since it renders the surface Or the particles relatively hard and the particles do not adhere to each other upon colli-sion. Subsequent to agglomeration in accordance with the pres-ent invention, the particles may be highly crosslinked ir 80 desired with possible benerits in agglomerated particle stabil-ity, although high crosslinking may be undesirable for some C-08-12-0295 l~ZlZ7 processes to uhich the rubber may later be subJected and wherein solution or optimum dispersion of the rubber is desired.
The polymeric solids content of the latices may vary from as little as about 5.0 percent by weight to as much as about 60.0 percent by weight; the preferred latices contain about 20.0 to 40.0 percent solids. The more dilute latices are not so conducive to formation of optimum particle size within reasonable time periods and the more concentrated latices some-times tend to introduce a need for more critical process con-trol. Generally, however, the particle size of the agglomerateincreases with increasing solids content in the latex.
The-latex must contain an emulsifying agent which is the salt of an organic acid with an ionization constant which is lower than that of the anhydride to be used in the process, such as, for example, the conventionally employed fatty acid soaps such as sodium oleate, sodium stearate, sodium palmitate, the equivalent potassium salts, and mixtures thereof such as rubber reserve soap. Generally, such fatty acid soaps may be characterized as the alkali metal salts of the C12-C22 aliphatic acids although ammonium salts may be useful in some limited ap-plications. In addition, the latex may contain other emulsify-ing agents such as the Rnionics or non-ionics so long as these other emulsirying agents are not present in such a concentration as to render the latex stable to the acid anhydride. As will be appreciated, the amount of the emulsifying agent will nor-mally vary with the concentration of the latex and the particu-lar polymer involved; latices containing substantial excesses Or emulsifylng agent over that required for stability are not desirably employed.

C-08-12-0295 1~21~
The Acid Anhydride Various organic anhydrides may be used in the present invention if they possess the requisite degree of water solu-bility, and a relatively high ionization constant for the acid components. To be effective, the acid anhydride must be suffi-ciently water soluble to hydrolyze and provide acid radicals for reaction with enough emulsifying agent to reduce the sta-bility of the latex for collision of the particles and the re-sultant agglomeration. The ionization constant will be depen-dent upon that of the particular acid of the emulsifying agent,but generally, the water-soluble acid anhydrides have signifi-cantly higher ionization constants than the conventionally em-ployed alkali metal soaps.
IllustratiYe of the acid anhydrides are acetic acid anhydride, maleic acid anhydride, and propionic acid anhydride.
Whether the acid is saturated or dicarboxylic appears to be of no significance. In order to achieve the desired homogeneous admixture within the latex rapidly and prior to appreciable hydrolysis, it may b~ desirable to admix the anhydride initially with an organic solvent therefor which is readily miscible with - water. For exsmple, methanol, ethanol and acetone m~y be used advantageously to dissolve maleic acid anhydride and propionic acid anhydride and e~en the more highly soluble acetic acid anhydride, ratios Or 1-3 parts solvent per part of anhydride being satisfactory. The resultant organic solution may then be admixed with a small volume of water which is then added to the latex. Alternatively, the more soluble anhydrides are de-sirably dissolved in a ~mall volume of water which is then added to and admixed with the latex so as to obtain a homoge-104;~127 neous admixture rapidly. Heat may also be used to facilitate instant solution of the anhydride in a carrier for addition to the latex, but premature hydrolysis of the anhydride should be avoided.
The amount of anhydride required will vary with the amount of the emulsifying agent present in the latex which is to be reacted therewith, and with the desired size of the ag-glomerated particles to be obtained. In addition, it has been noted that the acid anhydride tends to be more effective in latices o~ rubber interpolymers containing polar monomers Rince - increasing the amount of polar monomer tends to decrease the amount of anhydride required for equivalent particle size in-crease.
Although amounts of anhydride equal to one-tenth the stoichiometric equivalent of the emulsifying agent (a molar ratio Or 1: 20 since there are two acid radicals) will produce some agglomeration in most instances, the amount employed is preferably at least one-fourth the stoichiometric equivalent.
For optimum operation, the acid anhydride is added in excess of the stoichiometric equivalent Or the emulsifying agent, and oftentimes, several times in excess thereof. Amounts in excess of five times the stoichiometric amount pro~ide no significant additional benefit in terms Or speed and may interfere with the ~tability of the agglomerated latex or with the properties of the polymer by introducing excessive acidity or corrosive action.
The Ag~lomerating Reaction As previously indicated, the acid anhydride must be homogeneously distributed throughout the latex to achieve proper results. ~owever, the admixture of the anhydride and the latex , . .

C-08-12-0295 1~1~7 must be effected prior to appreciable hydrolysis of the anhy-dride or under conditions of minimal agitation~ If the anhy-dride has hydrolyzed and the latex-anhydride mixture is sub-~ected to appreciable agitation, the polymer particles tend to coagulate rather than agglomerate under controllable conditions and the coagulum cannot be utilized.
Accordingly, the anhydride or any carrier solution thereof should be dispersed throughout the latex rapidly prior to appreciable dissociation of the anhydride. Thus, carrier solutions of the anhydride with water should not be allowed to stand for long periods or should be maintained under conditions which inhibit hydrolysis of the anhydride such as by storage under refrigeration. It may be desirable in some in~tances to admix the anhydride and the latex at chilled temperatures to minimize hydrolysis, but, generally, the relatively low rate Or hydrolysis Or the anhydrides will permit admixture by conven-tional agitation techniques.
The temperature at which the agglomerating reaction is conducted has not been found to exert any apprecisble effect upon the size of the agglomerated particles althoug~ lt does influence the time required for the reaction to take place and to produce the desîred particle size as indicated above. Since the rate Or hydrolysis of the anhydride tends to be reduced by a decrease in temperature and the Brownian movement of the par-ticles also tends to be reduced, the time required for equiva-lent results is extended by decrease in temperature but the re-action can be performed satisractorily at any temperature above the rreezing point Or the latex 80 long as the anhydride is surriciently soluble at that temperature. Conveniently, the 1(~4'~1;~7 agglomeration reaction carried out in the conduit is conducted at ambient temperatures or above preferably in the range of 30 to 50C. for flow-through or passage-times of 0.5 to 60 minutes, preferably 0.5 to 10 minutes. Longer periods and higher tem-peratures may be employed with no significant benefit.
The particle size of the agglomerate can be varied by selecting the conditions of the agglomerating reaction such as time, temperature, anhydride and ratio of anhydride to emulsify-ing agent. In addition, the particle size will tend to increase with increase in the solids content of the latex. With the present invention, it is possible to readily obtain an increase in particle size diameters from original latex particles, in the range of 0.01-0.2 micron (weight average), to agglomerated latex particles of 0.1-0.8 microns. Particles as large as o.8-1.0 microns and e~en larger ha~e been obtained with some latices depending on their emulsirying system. The weight a~erage particle size diameter can be determined by a published procedure of Gra~es, M. J. et.al., "Size Analysis of Subsie~e Powders Using a Centrirugal Photosedimentometer", Lritish Chem-ical Engineering, 9:742-744 (1964). A Model 3000 Particle Size Analyzer from the Martin Sweets Company, 3131 West Market Street, Louisville, Kentucky was used.
Stabilization of the Agglomerated Latex After the agglomerating reaction has proceded to the desired extent, the agglomerated latex must be stabilized before it is subJected to any great measure of agitation to a~oid ror-mation Or coagulum. This may be effected by adding a separate, acid-stable emulsi~ying agent or by adding a basic alkali metal compound to react ~ith the acid Or the emulsifying agent orig-C-08-12-0295 104Z~Z7 inally present and thereby regenerate the slkali metal soap in sufficient amount to provide stability. In either instance, the agitation re~uired to disperse the added material through-out the latex should be minimized, and the emulsifying agent or alkali metal compound i9 desirably added in aqueous solution to facilitate dispersion and minimize undesirable agitation. After dispersion of the stabilizer has been effected, the latex may be agitated as required for subsequent processing and other re-actions such as grafting and the like.
The amount Or the stabilizing emulsifying agent may vary from as little as about 0.03 to 15.0 parts per 100 parts of polymer, and even higher since there is no tendency for the agglomerated particles to redisperse. Generally, amounts Or about 0.07-3.00 parts per 100 parts polymer, and preferably 0.1-1.0 part, are utilized.
Among the added emulsifying agents which may be employed are anionic emulsifying agents such as alkali metal salts of long chain sulfonic acids and sodium dodecyl diphenyl bisulfon-ate, and nonionic emulsifying agents such as ethoxylated octyl phenol. ~ormally the non-ionic agents are required to be added in larger amounts than the anionics.
If the emulsirying agent is to be regenerated, an alkali metal hydroxide or other basic compound such as a carbonate is coDveniently employed. The amount added is preferably at least the stoichiometric equivalent required to react with the anhy-dride added although somewhat smaller amounts may be used with some lessening in stability Or the latex. Amounts Or more than two times the stoichiometric equivalent may have an adverse effect upon some latices ~o that the preferred amounts are C-08-12-0295 104~ 7 0.9-1.5 times the stoichiometric equivalent of the anhydride (1.8-3.0 times the molar amount of anhydride).
The Inorganic Electrolyte Various water-soluble monovalent and polyvalent metal and ammonium salts may be used as the inorganic electrolyte in-cluding halides5 sulfates, nitrates and phosphates depending upon the latex and the presence of radicals therein which might be adversely effected thereby. Exemplary of the materials which have been advantageously employed are magnesium sulfate, aluminum sulfate, sodium chloride, potassium chloride, sodium sulfate, ammonium chloride, ammonium sulfate and similar phos-phate salts, etc. From the standpoint of minimizing contamina-tion the prererred electrolyte are the salts of the alksli metals and ammonia. The alkali metal and ammonium halides and sulrates have proven highly advantageous from the standpoint of control, cost, minimal adverse effect upon the latices and op-timum cooperation with the acid anhydride.
The amount of the inorganic electrolyte will vary with the particular latex, the particular acid anhydride and the amount thereor, and the particle size that is desired. Gener-ally, beneficial errects are obtained with as little as 0.05 parts Or the electrolyte per 100 parts Or the polymer Or the latex but preferably the amount Or the electrolyte is at least 0.2 part per 100 parts Or the latex polymer. The maximum amount Or the electrolyte will vary with the psrticular acid anhydride and the particular electrolyte selected. With sodium chloride and one part Or an acetic anhydride in a 38 percent solids polybutadiene latex, the maximum amount o~ electrolyte that can be added without causing coagulation is about 3.0 C-08-12-0295 ~2~7 parts per 100 parts of the latex polymer. However, magnesium sulfate and aluminum sulfate may be used in larger amounts with some latices without producing coagulation of the latex.
The inorganic electrolyte may be added to the emulsion of the monomers before polymerization thereof to produce the latex polymer or it may be added to the polymerized latex. In the latter instance, care should be taken to introduce the electrolyte fairly slowly or in a dilute solution so as to avoid excessive concentration at any point uithin the latex and thus prevent coagulation. Efforts to add the electrolyte together with the acid anhydride have proven such a technique to be quite unreliable since coagulation occurs quite orten.
In practice, the continuous agglomeration process has been round to be more easily controlled than the batch process of the prior art, producing a more uniform particle size, with-out batch to batch variations or serious coagulation.
Reading on the previously given summarY:
Step (A) is carried out by feeding simultaneously and continuously an aqueous solution Or a water soluble inorganic anhydride and an aqueous latex Or a lou heat distortion poly-mer. The ~eeding is carried out by proportional-reeding o~
stoichiometric amounts, already described, Or said solution and said latex under pressure to said mixing zone while maintaining a reed-pressure in said mixing zone surricient to overcome a pressure-head o~ said flowing admixture in said conduit and a pressure-drop of said admixture rlouing through said perrorated member, providing a rlou-rste and passsge-time for sald admix-ture through s61d conduit surricient to agglomerate said poly-C-08-12-0295 1~21~7 ~er particles to a predetermined size. Those skilled in the art will recognize that the feed-pressure will ~ary with the pres-sure-hesd or volume-head of the conduit primarily, as the pres-sure drop through the perforated member is relatively small.
T he conduit ls inclined generally upward, preferably being oriented in a substantially vertical position.
In such positions the pressure-head will be larger and the feed pressures are increased accordingly. The feeds may be pressur-ized by any convenient means such as pumps, gravity feed or gas pressure. The feed streams are carried by pressure to the mix-ing zone as separate feeds entering the mixing ~one, pre~er-ably, at ports in opposite sections Or the mixing zone to in-sure that the feed streams mix quickly at a mixing interrsce insuring uniform admixture before excessi~e hydrolysis and ag-glomeration can occur.
The anhydride is a liquid and is soluble in water but is not readily dissolved, hence must be dispersed rapidly by high shear agitation so that it dissolves quickly. The anhy-dride is readily soluble in a temperature range of from about 5 to 50C., preferably 20 to 40C. Dissolving times Or less than 10 seconds csn be used, prererably less than 5 seconds.
High-shear mixing mesns, colloiders or blenders sre prererred ~or the continuous ln-line dispersion and dissolving o~ the s anhydride. Electronic or hydrodynamic ultrasonic sonifiers have been round to be practical, e.g., The "Sonifier-Disruptor"
sold under that trade name by Heat Sy~tems-Ultrasonic, Inc., Or Plainvie~, L.I., New York or the "Sonalator" sold under that trade name by Sonic Engineering Corp., Connecticut Avenue, ~orwalk, Connecticut.

-- 19 -- . .

104'~1'~7 The anhydride is mixed with latex as guickly as possible in step (B) to insure a uniform admixture before additional hy-drolysis of the anhydride occurs during mixing. When mixing at temperatures of 30C. less than about 30 seconds is preferred, at 40C. less than about 20 seconds and at 50C. less than about 10 seconds. In operation, the dissolving time of the anhydride to form the solution and the mixing time to form the admixture is carried out under a time-temperature schedule to insure that the total time used is less than the time required to hydrolyze that amount of the anhydride equal to about 30% of the molar equivalent amount of the emulsifying agent contained in the latex before it passes on to the agglomeration step in the con-duit. Preferably, the amount of hydrolysis is less than about 30% of the molar equivalent amount of the emulsifying agent ranging from about 10 to 20%, most preferably from about 5 to 10%.
If the latex contains a bufrering agent, then the time for hydrolysis of the anhydride should be less than that time required to hydrolyze that amount Or anhydride equal to 30S Or the molar equivalent Or the emulsi~ying agent plus the buffer-ing agent contained in the latex. The sverage residence time Or the admixture in the mixing zone is critical to the opera-tion Or the process. The pR Or the sverage rubber latex to be agglomerated is commonly in the range Or 9 to 10. As soon as the anhydride solution mixes with the latex the pH will decrease quickly in a residence ti~e Or seco~ds at temperatures oi' 30 to 50~C. preferred ror efricient operations. The latex beco~es shear sensitive ss the pH drops below the pK value Or the emul-sifying agent, e.g., Rubber ~eserve soap at sbout pR7. Hence, 104ZlZ7 C-0~-12-0295 the admixture is passed out of the mixing zone before the pH
decreases below the pX value of this emulsirying agent lnto the laminar-flow conduit where agglomeration does occur without agitation and coagulation. If the pH of the admixture drops below the pK of the emulsifying agent in the mixing zone the latex becomes too unstable to mix under high-flow agitation and serious coagulation can occur. The pH then is best controlled in the time-temperature cycles already described for dissolving and mixing the anhydride.
Step (B) is carried out by coDtinuously mixiDg said solution and said latex under high-flow mixing agitation in said mixing zone to form sn admixture. The flow rate in said admixture should be sufficiently high so as to admix as quickly as possible without coagulating the latex. Generally, the agi-tation is provided by high-flow agitators used to circulate the admixture such as propellers. n at blade turbines or multi-paddle agitators having wall bafrles positioned between paddles.
The mixing qtep is carried out in a minimum aversee residence-time for the admixture in the mixing zone consistent wi;th uni-form mixing.
The high-flow agitation described takes place in a mix-ing zone designed to provide an average turnover value for said admixture in sald mixing zone before leaving said zone such that the turnover value has a range of from about 3 to 10 per residence time Or said admixture. Mixing perrormance ln ssid mixing zone can be determined by the rollowing equations for a turbine agitated continuous stirred tank (CST):

C-08-12~0295 1~1~7 Qp = 0.5 ND3 T = Q t N

where ~ = rpm of agitator (rpm) D = agitator diameter (cm) Qp = aeitat~r volumetric pumping rate (llter /mln.) t = CST residence time (min.) V = CS~ volume (llter 3) TN = average number of CST turnover per average residence time The concepts Or such design are well understood by those skilled in the art and can be round in rererence: Gray, J. B., Uhl. V. W., Mixing Theory and Practice, Vol. 1, 205, 1966.
Prefersbly the mixing zone is a cylindrical tank having an agitator located generally in the center Or the tank. The tank generally has a length to diameter ratio from about 0.3 to 2, preferably 0.5 to 1. The tsnk has an integral perforated member as a wall section Or the tank ~herein the diameter of the perforated member and the tank are about the same diameter, preferably the same diameter, as that Or the conduit.
The prererred design provides uniform mixing throughout the tank and allovs the admixture to rlow uniformly through the perforated di~k inducing laminar rlow in the conduit, hence, providing high turbulent ~low in the tank for mixing and sub-stantially only laminar flow in the conduit as the admixture is passed under pressure through the mixing tank.
The agitators used in the mixing tank can be any conven-C-08-12-0295 1~ZlZ7 tional high-flow mixing sgitator such as a turbine paddle or propeller type with a turbine type being preferred. The rota-tional speed of the agitator blades can vary with the size o~
the mixing zone which determines the diameter Or the blades.
Agitator tip speed is commonly used as Q measure Or the degree of agitation in a liquid mixing system. The tip speed (TS) of an agitator in m./mln is glven by the formula:

TS = r Da x rpm where Da is the diameter Or the agitator blades in m. and rpm. is the rotational speed Or the agitator in revolutions per minute. Hi~h flow agitation is obtained with top speeds in the range from 9 to 457 m./min., preferably 12 to 31 m./mln.
The agitator can have a wiping blade attached to the shart Or the agitator displaced vertically from the turbine blades and operating to wipe the perrorated member free Or aDy coagulum that may rorm and have a tendency to build snd rill the perrora-tions. The wiping blade csn be incllDed against the face Or the perrorated member providing a wiping action with l~w drag rorces and minimized mixing shear. As an alternative, the wiping blade can be positioDed less than 1.27 cm prererably less than 0.6 cm from the perrorated member, hence, cleanlng the perrorated member by the shear-~low Or the admixture past the member.
The present procegs and apparatus then has the great utlllty Or provldlng a method Or agglomeratlng large volumes of latex whereln~
the latex and anhydrlde are mlxed contlnuously and qulckly wlth- ;
out coagulatlon ln a relatlve gmall mlxlng zone wlth a mlnlmum resldence-tlme.

C-08-12-0295 l~lZ7 Step (C) is carried out by pressurized-rlow through the mixing zone wherein the highly agitated admixture is continu-ously passed through a perforated member forming an integral wall section of the mixing zone into an interconnected conduit.
The perforated member is preferably a perforated cyll~drical plate which induces laminar-flow in the admixture as it rlows through the member so that turbulence is minimized and coagula-tion will not occur as the admixture agglomerates in the lsminar-rlow conduit. The perforated member then acts as a breaker-plate that separates the high-flow turbulent flow in the mixing zone from the laminar-flow in the conduit such that the laminar flow is essentially rree of any turbulence and the shear rate 18 less than about 1 sec.l in the laminar-flow conduit.
The perforated member has a plurality Or perrorations and during operation Or the process acts as a breaker plate, providing a back-pressure on the mixing zone side Or the member surricient to overcome the pressure di~ferentlal, created by agitation in the mixing zone, egualizing said pressure differ-eDtial across the perrorated member in the mixing zone i~suring and inducing laminar ~low through the perforated msmber into the conduit. The perrorated member, during operation, also provides a pressure drop, on the conduit side Or the me~ber, Dot less tbaD about the highest pressure gradient in the mi~ing lD~uring laminar rlow through the perforated member. The per-rorations preferably have a length to diameter ratio range ~romabout 0.1 to 4 and the total free-area of the perroratlons 18 rrom about 1 to 10% Or the total area Or the per~orated member.
The perrorated members have a diameter about the same diameter as the mixlng zone and the coDdult. In practice, the apparatus C-08-12-029s ~04Z~27 ~izing i8 ba~ed on the ~ize Or the conduit needed to insure passage-time for the admixture that will agglomerate a prede-termined particle size con~istent wlth a flow rate that has a shear-rate less than 1 sec.~l. The conduits can vary from 10 to 61 cm or larger in diameter and their length sized to give the volume through-put consistent with passage-time and a shear rate of less than 1 sec.~l, e.g., 12 to 152 cm or longer. The perforated plate can have a thickness of 0.16 to 1.27 cm with the perforation diameter sized as described. The apparatus is conveniently fabricated of stainless steel, preferably glass lined steel or glasæ.
Step (D) is carried out by continuously flowing the ad-mixture undér laminar flow through said conduit. The passage time being sufficient to hydrolyze the anhydride sufficiently to agglomerate the particle size of the polymer to a predeter-mined size forming an agglomerated miYture. The particle size Or the latex commonly renges from about 0.01 to 0.2 microns in diameter snd is agglomerated to particles ranging in a~erage size from about 0.1 to 1.0 microns in diameter preferably averaging from about 0.3 to O.ô microns. The parti.cles ~ormed are monodisperse having a narrow size distribution with a par-ticle size dispersity range o~ 1.1 to 1.4 (weight average/number a~erage particle diameter). The metbod for determining welght average particle aizo diamoter has been described. The number average particle size diameter is determined by preparing a photomicrograph of a dispersion of the particles and measuring ; the particles determining the a~erage diameter as a number average.
The anhydride hydrolyzes during the passage-time through said conduit dropping the pH from about 7 to any desired level between ~ and 7, the particle size determined by the ultimate pH reached, with the lower the pH the larger the particle. The pH can be controlled by stoichimetric control wherein the anhy-dride is added in the molar amounts needed to reach a predeter-mined pH value knowing the stoichimetric equivalents supplied by the emulsifying agent combined in the latex. The passage-time of the admixture through the conduit allows the agglomera-tion reaction to occur and the passage-time is controlled to a passage-time sufficient to produce a given particle size, said passage-time ranging rrom about 0.5 to 60 minutes pre~erably from about l to 10 minutes. Within this passage-time range, particles can be prepared ranging from about 0.2 to 1.0 microns in diameter prererably from about 0.3 to O.ô microns (weight average).
To provide a predetermined dwell time, the conduit is sized to provide the passage-time needed. Generally, a length to diameter ratio of from about 10 to 36 is used, preferably 15 to 25 uith the volume scaled to give a predetermined passage-time for the given flow rate through the column.
The d~ameter Or the conduit is such that the shear atthe ~all o~ the corduit is less than about 1 sec.~l ~or latices that have pH lowered to less than 7 and become unstable. The shear rate at the wall can be approximated by the formula:

Shear Rate at Wall = 4Q
of Conduit ~

Q = total volumetric flow rate (llter/sec.) r = radiu~ of conduit (cm) 104~1Z7 It ls evident that the shear rate 18 sensltlve to the radius (dlameter) of the condult. Hence, a mlnlmum dlameter con-sistent wlth a shear-rate Or less than about l sec. l is preferred.
Condults Or 5 to61om1n dlameter have been found practlcal wlth a 30.5cm dlameter condult passing up to about 2650 llter/hour Or latex havlng about 30-40 percent by weight sol~ds w~th a shear rate of less than about l sec.~l. Those skllled ln the art wlll appreclate that higher shear rates can be used dependlng on the stablllty Or the latex to shear wlthout coagulatlon.
The maxlmum dlameter Or the condult ls determlned by the dlameter of the mlxlng zone and perrorated member. In one embodl-ment the condult can be orlented generally upward, preferable ln a substantlally vertlcal posltlon wlth the admlxture rlowlng up-wardly through the condult.
The process accordlng to the apparatus as derlned above can be operatlve wlth the condult orlented ln a generally downward posltlon wlth the admlxture rlowlng downwardly through the conduit ~rom a mlxlng zone feedlng downwardly through a perrorated member.
The low shear zone becomes an extenglon Or the condult havlng at least one inlet port ror addlng the emulsl~ylng materlal, stablllz-lng the agglomerated admlxture. The wlthdrawal means lnterconnects wlth sald low shear zone ln llne, havirgan admixture liquld-level controlllng means, such as a manometer-like piplng arrangement, havlng a generally vertlcal plpe arm extendlng to an elevatlon surrlclent to control the rlow durlng operatlon Or tho process.
The apparatus rOr thls process can be operated ln a generally horlzontal posltlon wlth the condult belng orlented generally horl-zontally. The mlxlng zono reeds horlzontally wlth axls Or the zone orlent-104'~ 7 al~y horizontally ~nd the perforated member being oriented gen-erally vertically in the downstream wall of the mixlng zone in-terconnected with the hor$zontally oriented conduit. The low shear zone operates in a eenerallY horizontal orientation being an extension of the conduit having a outlet port iD a bottom section interconnected with a withdrawal means and a qdmixture liquid level control means, ror contracting the flow during operation of the process.
The conduit can be temperatured controlled by a tempera-ture control me~ns, e.g., a heat exchange ~acket 80 that the temperature gradient between the conduit and the laminar-flow-ing admixture is minimized and laminar-rlow is maintsined with-out shearing or mixing min$mizing coagulation during the ag-glomeration reaction.
Step (E) is carried out by continuously moving the ag-glomerated admixture from said conduit through a low-shear zone being interconnected at one end portion with the conduit and having a outlet port at an oppositc end portion. Said low-shear zone ha~ing a shear rate of less than about 1 6ec.~l. ;In a pre-rerred embodiment, the low-shear zone is oriented g~nerally horizontally as a rlow-through chamber wherein a botto~ wall section is integral with a rirst inlet port lnterconnected with ~ald conduit and said outlet port. The chambei ha~ing upwardly extending side-wall sections such that the depth o~ the chamber ln at least about twice the diameter o~ said conduit. The di-mensions are such that the agglomerated admixture rlows throu8h with prererably a rree upper sur~ace ~or reduclng shear and pro-viding a surface ~or re~oval Or possible floating coagulum ~or3ed upstream.

~04212~

In a pref~rred embodiment Or the present inventlon, the la~inar-flowing admixture ~10WB generally upward through said conduit in step (D) such that any low density coagulu~ formed during agglomeration is carried to the low-shear zone ~or flota-tion and removed in the low-shear zone with the condult remain-ing essentially free of coagulum insurlng laminar-flow.
Step (F) is carried out by continuously stabilizing said agglomerated admixture moving through said low-shear zone with an emulsirying material, said mateiial being provided by means selected ~rom the group consisting Or adding an acid- -; stable emulsifying compound or regeneration of said salt by addition of a basic compound and combinations thereor, said stabiliziDg being prior to subJecting said agglomerated admix- ;-ture to substantial shear which would cause coagulation Or sald agglomerated admixture. The stabilization Or the agglomerated admixture has been described. The present process adds the emulsi~ying material to the agglomerated admixture in step (F) by ports located iD the sidewalls o* the low-shear zone. In one preferred embodiment, at least one part can be locate-d in 20 the sidewall section~ in the general proximlty o* a~ outlet port ror said low-shear zone 80 that the emulsirying material can be added be~ore *loY-~ixing oocurs in the withdraYal ~eans .na the agglomerated aa~lxture can be stabllized during ~low-mixing without coagulation o~ the latex. The e~ulslrying ~a-terial is pressure rea on a stoichiometrlc-basis in the range o* *rom about 0.03 to 15 parts per 100 parts o~ latex r-moved at the outlet port. Th- emul~ ying material can be red through additional parts located in the Yithdrawal means, a~ one pre-Serred embodlment, to insure additional ~tabilization o~ the .

- 29 _ C-08-12-0295 1~7 a~glom~rated admixture. Such ports can be interconnected with pressurized nozzle or noz~le means to ~id in the distribution of the emulsifying materi~l in the ~ithdrawal means which pro-vides flow mixing. Another me~ns ~or distributing the emulsi-fying means in the ~gglomerated admixture can be a bleed-device such as a porous sintered rlng or a fibrous wick placed around the outlet port of the low shear zone to bleed the msterial into the flowing admixture. The low shear zone preferably has, as one embodiment, a liquid level control means interconnected with said withdràwal means to control the liquid level in the low-shear zone.
S~ep (G) is carried out by continuously withdrawing the stabilized agglomerated admixture ~rom the low-shear zone by a ~ithdrawal means providing ~low-mlxing in said stabilized ag-glomerated admixture. The ~low-mixing in withdrawal step (G) is produced by a pressure-drop in the stabilized agglomerated admixture as it flous through the withdrawal means. In a pre-~erred embodiment, the member can be an annular pipe intercon-nected with the outlet port and having at least one diameter reduction to speed flow and induce mixing. In line' pipe-line mixers, commonly used in the industry, can be used.
In one preferred embodiment the level control means can be lnterconnectod with Jaid withdra~al means to control the liquid level in said loY-shesr zone.
In an embodiment Or the present lnventlon, the process can utlllze the apparatus to run ln parallel wlth two agglomeratlng processes preparlng stablllzed agglomerated admlxtures Or two dl~-ferent dlameters, e.g., one process preparlng partlcles o~ 0.3 mlc-rons and one process preparlng partlcles of 0.6 mlcrons and combin-10421'~7 iDe the two streams to prepsre Q feed stream ha~ing a bimodal particle size distribution which then can be.grafted as a rubber phase for high impact strength polymers. The psrticle size can range from 0.1 to 1.0 microns (weight average) with the small particles preferably ranging from about 0.1 to 0.4 microns and the large particles preferably ranging from about 0.5 to 1.0 microns.
DETAILED DESCRIPTION OF THE DRAWI~GS
In Figure 1, there is seen a mixing zone 9 comprising a cylindrical stirred tank 10, a first feed port 11 and a second feed port 12, a mixing means comprising a turbine agitator 13, a perforated member comprising a perforated cylindricsl plate ; 1~ having perforations 15. The stirred tank ~eeds through the plate into an annular conduit 16, ha~lng a rirst orifice 17 and - 15 a second orifice 18 and a temperature control means comprising a heat-exchange ~acket 19. The conduit ~eeds into a low-shesr zone 20 comprising a first inlet port 21, at least one addi-- tional inlet port 22 and an outlet port 23. The outlet port reeds into a ~ithdrawal means comprising an annular pipe.24 20 ha~ing at least one diameter reductlon, said pipe 24 having at least one inlet port 25. Said withdrawal means roeding into a manometer-like l~guid-le~el control means 26 co~prisi~g a ~irst pipe means 27 and a second pipe ~eans 28. A ~irst feed ~eans comprising a pump 29 is interconnected with said flrst feed . 25 port 11 and a second feed means comprislng a pump 29~ iæ inter-connected uith said second reed port 1-2.
In Figure 2, i8 seen a diagrsmmatic ~iew of low shear zone 30 ha~ing additional inlet ports 31, an annular bottom wall section 32, upuardly extending side-wsll sections 33, out-.

~. . - .

104Zl'~7 let port 34 and withdrawal means 35 have inlet ports 36 and diameter reductions 37.
In Figure 3, is seen an end view Or low-shear zone 30 and withdrawai means 35 through section 3-3. 8sid lo~ shear 5 zone having inlet port 31 and outlet port 34. Said withdrawal means having inlet port 36 and diameter reductions 37.
In Figure 4, is seen 8 mixing zone 50 comprising a multipaddle agitator 51 having wall baffles 52 positioned be-tween pa~dles, a stirred tank 53. a rirst feed port 54 and a second feed port 55. A perforated member 56 having perfora-tio~s 57. Wiping blades 50 are shown attached to agitator 51 i~ contact.with perforated member 56.
In Figure 5 is seen a mixing zone 60 having a mixing means comprising a marine-propeller agitator 61.
In Figure 6, is seen an apparatus assembly ~or the pro-cess operating such that the admixture rlo~s generally down-wardly through the annulsr conduit during agglomeration having mixing zone 70, conduit 72, perrorated member 71, shear zone 73 having inlet port 7~ and withdrawal means 75 havlng inlet port 76 and a liguid level control ~eans 77, said conduit having a rirst oririce 78 and a secoDd oririce 79, said low-shear zone having inlet port ôO and outlet port 81 said withdrawal zone ha~ing inlet port 82 and outlet port ô3. Said miYlng zone havinB agitator 84.
In Pigure 7, is seen an apparatus asse2bly ror the pro-ces9 operating such that the admixture rlows generally hori-zontally through said annular conduit during agglo~eration having a mixing zone 90, a perrorated member 91, an annular conduit 92 having a rirst oririce 93 and a secona ori~ice 94, a : - 32 -low shear zone 95 having a first inlet port 96, outlet port 97, additional input ports 9ô, B withdrawal means 99 havlng an in-let port 100, an outlet port 101 and B liquid-level control means 102, said mixing zone having an agitator 103.
In Figure a, i5 seen a diagrammatic flow drawing illus-trating (not in scale) B process as carried out in a continuou~
manner using the apparatus of the present invention comprising an agitated hold tank 110 for the latex fed from in B continu-ous reactor, not shown, said hold tank jacketed rOr temperature control, a pump 111 for pressure feeding the latex to a mixing zone 112 having an aeitator 113, a perforated ~e~ber 114, ~eed-ing an annular conduit 115 having a first rlanged oririce 116 and a second flanged ori~ice 117 feeding a low-shear zone 118, having a ~irst inlet port 119, an outlet port 120, additional inlet port 121, a withdra~al ~ean~ 122, ha~ing an lnlet port 123, an outlet port 124, and a liquid level control ~eans 125, a high shear mixer 126 and a pu~p 127.
EMBODIME~I~
The follo~ing examples are set ~orth to illustrate more clearly disclose the prlnciples and practico Or tho in~ention to one skilled in the art aDd are not intended to be r-stri¢tive but merely to be illu6trati~e Or the in~ention herein contained.

LATEX A
A latex i8 prepared by polymer1zing butadiene and acry-j lonitrile to obtain a rubber polymer containlng 97 parts buta-diene and 3 parts acrylonitrile. The latex containo 40.0 per-- cent solids and 1.2 parts Or sodium oleate per 100 parts o~
latex (pphpl) as an e~ulsi~ying a8ent and 0.24 parts pphl o~

` ~04ZlZ7 sodium sull~te during poly~eriz~tion. The particle size of the polymer i9 observed to be O.Oô microns (weight average).
LATEX B
Part A is repeated with a latex containing 0.25 pphpl of sodium sulfate during polymerization. At the conclusion of the polymerization, 0.2 pphpl of additional ~odium sulrate is added to the latex a 10 percent solution as an agglomeration additi~e. The particle size of the polymer i8 observed to be about 0.08 microns (weight sverage~.

An apparatus of Figure 8 is used having a mixing zone Or Figure 4 uith a diameter of 5.lcm and a length of 4.4 cm . .
Solutions Or acetic anhydride are prepared by continu-ously mixing 15 pphpl (parts per hundred parts latex) o~ water and 0.2 to o.8 pphpl Or acetic anhydride with an Ultrasonic Soni~ier Model W-185 having an a~erage residence tlme Or less than 10 sec. The perforated member o~ the mixing zone is a glass plate being 5.1 cm ln dlameter, ô.3cm thlc~ havlng 13 evenly spaced perrorations ô.3cm dlameter provldlng a per-roration area 5 percent o~ the area Or the plate. The conduiti~ a glass column having a diameter o~ 5.1cm and a length o~
114 cm. The low shear zone ha~ slde-wall~ Or 12.7cm and a length Or 25 cm running a 75 percent fillage wlth a ~ree admixture sur~ace. The low-shear zone has four iDlet ports for 25 addition o~ an emulsi~ylng materlal (10 perceDt solution o~ do-decyl diphenylether di~ulronate) added at tho rato o~ 8 pphpl to stabillze the agglomerated admiYture. Thc withdrawal meaDs is a pipe having a 2 to 1 diameter reduction providiDg ~low-mixiDg o~ the stabilized agglomerated admixture. The latox at C-08-l2 0295 104Z127 42C, is fed to the mixi~g zone at 0.34 Kg/hr slmultaneously with a stream of the anhydride solution at about 25C., forming the admixture by high shear mlxing u~ing an agitator tip speed of 13.7m/mln; passing the admlxture through the per~orated member inducing laminar flow in the conduit; flowing the admix-ture through the conduit at a calculated shear rate of . 51 sec. 1 for 8.9 minutes agglomerating the polymer particles followed by stabilizing the agglomerated admixtures and with-drawing said admixture through the withdrawal means with flow-mixing. Tsble 1 summarizes the experimental runs made, usinganhydride solution feeds supplying anhydride ranging from 0.2 to O.ô pphpl.

Agglomersted Anhydride Particle Size Ex~. Latex ~h~l (microns)~
2 A 0.8 o.48

3 A 0.4 0.36

4 A 0.2 0.12 B o.6 0.74 6 B 0.4 0.29 weight a~erage LATEX C
A lates is prepared by polymorizing butsdlene snd scry-lonitrile to obtain a rubber polymer containing 95 parts buta-diene and 5 parts acrylonitrile. The latex contained 40% solids and 1.2 parts Or soaium ole-te emulsi~ier. The polymerization ~as initiated by a redox syste~ o~ iron ana soaium ~ormaldehyde - 35 ~

sulfonxylate. The emulsion was further stabilized with acid stable emulsifying compound 9.02 pphpl of sodium dodecyl di-phenyl ether disulfonate. The particle size of the polymer is obser~ed to be about 0.10 micron~ (weight average).

The procedures of Experiment 2 were carried out using Latex C of Example 7. Table 2 summarizes the experimental runs made.

Agglomerated Anhydride Particle Size Exv. Latex P~h~l (microns) 8 C 0.7 o.69 9 C 0.4 0.30 - 36 _

Claims (60)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A continuous process for agglomerating polymer particles in an aqueous latex, the steps comprising:
A. feeding continuously into a mixing zone an aqueous solution of a water soluble organic acid anhydride, while simultaneously feeding continuously into said mixing zone an aqueous latex of a low heat distortion polymer, said polymer being formed from at least one ethylenically unsaturated monomer, the particles of said polymer being small and adherent upon collision and said latex containing an emulsifying agent, which is a salt of an organic acid with an ionization constant lower than that of the acid of the anhydride;
B. mixing continuously said solution of said water soluble organic acid anhydride with said latex in said mixing zone forming an admixture;
C. passing continuously said admixture from said mixing zone through a perforated member forming a wall section of said mixing zone into an interconnected conduit;
D. flowing continuously, said admixture under laminar flow, induced by said perforated member, through said conduit wherein said admixture has a passage-time through said conduit sufficient to hydrolyze the acid anhydride, agglomerating the parti-cles of the polymer to a predetermined size, forming an agglomerated admixture;
E. moving continuously said agglomerated admixture from said conduit through a low-shear zone being interconnected at one end portion to said conduit and having a withdrawal port at an opposite end por-tion;
F. stabilizing continuously said agglomerated admixture moving through said low-shear zone by adding an emulsifying material selected from the group consisting of an acid-stable emulsifying compound or a basic compound and combinations thereof, said stabilizing being prior to subjecting said agglomerated admixture to substantial shear which would cause coagulation of said agglomerated admixture; and G. withdrawing continuously said stabilizing agglomerated admixture from said low-shear zone at said opposite end by a withdrawal means providing flow-mixing in said stabile-ised agglomerated admixture.

2. The process of Claim 1, wherein said polymer is a diene rubber polymer.

3. The process of Claim 1, wherein said organic acid anhydride is selected from the group consisting of acetic acid anhydride and maleic acid anhydride, and mixtures thereof.

4. The process of Claim 1, wherein said emulsifying agent is a fatty acid soap.

5. The process of Claim 1, wherein said emulsifying material is regenerated from the acidified emulsifying agent by adding to said latex a basic alkali metal compound.

6. A process of Claim 1, wherein said acid-stable emulsifying compound is selected from the group consisting of nonionic organic compounds and anionic organic compounds and mixtures thereof.

7. The process of Claim 1, wherein said acid anhydride is initially dissolved in water of a volume less than that of said latex and said solution is fed in step (A) with said latex.

8. The process of Claim 7, wherein a water-miscible organic solvent for said acid anhydride is admixed therewith in a ratio of about 1-3 parts solvent per part anhydride to facili-tate solution in the water.

9. The process of Claim 1, wherein said acid anhydride is fed in said solution in step (A) in a molar amount at least equal to one-half the molar amount of said emulsifying agent contained in said latex.

10. A process of Claim 1, wherein said aqueous latex has present before feeding, said acid-stable emulsifying compound, selected from the group consisting of anionic and nonionic emul-sifying compounds or mixtures thereof, in an amount less than that sufficient to render said latex stable to acid anhydride agglomeration.

11. A process of Claim 10, wherein said acid-stable emulsifying compound is present in from about 0.01 to 1.0 parts per 100 parts of latex polymer.

12. A process of Claim 10, wherein said acid-stable emulsifying compound is sodium dodecyl diphenylether disulfon-ate.

13. A process of Claim 1, wherein said acid-stable emulsifying compound for stabilizing said agglomerated mixture in step (F) is added in from about 0.03 to 15 parts per 100 parts of latex polymer.

14. A process of Claim 1, wherein said acid-stable emulsifying compound is sodium dodecyl diphenylether disulfon-ate.

15. A process of Claim 1, wherein said aqueous latex has present before feeding a water soluble inorganic electro-lyte being a salt of a cation selected from the group consist-ing of alkali metals, alkaline earth metals, ammonia and mix-tures thereof.

16. A process of Claim 15, wherein said inorganic electrolyte is an alkali metal halide.

17. A process of Claim 15, wherein said inorganic electrolyte is present in from about 0.05 to 3.0 parts per 100 parts of latex polymer.

18. A process of Claim 1, wherein said feeding of step (A) is carried out by proportional-feeding said solution and said latex to said mixing zone while maintaining a feed-pressure to said mixing zone sufficient to overcome the pressure-head of said flowing admixture in said conduit and the pressure-drop of said admixture through said perforated member, providing a flow-rate and passage-time for said admixture through said con-duit sufficient to agglomerate said polymer particles to a pre-determined size.

19. A process of Claim 18, wherein said passage-time is from about 0.5 to 60 minutes.

20. A process of Claim 1, wherein said mixing of step (B) is carried out with an agitator having blades turning at a tip speed ranging from about 30 to 1500 ft./min.

21. A process of Claim 1, wherein said mixing of step (B) provides an average turnover value having a range of from about 3 to 10 per average residence time of said admixture, said average residence ranging from 10 to 30 seconds.

22. A process of Claim 1, wherein the temperature of said flowing admixture of step (D) is controlled such that the temperature gradient between said conduit and said flowing ad-mixture is controlled and minimized sufficiently to maintain laminar flow in said admixture.

23. A process of Claim 1, the liquid-level in said low shear zone being controlled by a liquid-level control means.

24. A process of Claim 23, said liquid-level control means being interconnected with said withdrawal means, con-trolling the liquid level in said low shear zone during the operation of said process.

25. A process of Claim 1, wherein said flow-mixing in withdrawing step (G) is produced by lowering the pressure of said stabilized agglomerated admixture as it flows through said withdrawal means, said means being an annular pipe having at least one diameter reduction.

26. A process of Claim 1, said laminar-flowing admix-ture, flowing generally upward through said conduit in step (D) such that low density coagulum formed during agglomeration is carried to said low-shear zone for flotation and removal, said conduit remaining essentially free of said coagulum insuring laminar flow.

27. A process of Claim 1, wherein said aqueous solution of a water soluble organic acid anhydride is continuously pre-pared by simultaneously feeding said anhydride and said water into a high-shear mixing means such that said anhydride is dis-persed and dissolved in said water having a temperature ranging from about 5 to 40°C. and passed through said high-shear mixing means in less than 10 seconds forming said solution being con-tinuously fed to said agglomerating process.

28. A process of Claim 1, wherein said mixing of step (B) provides an average residence time in said mixing such that the residence time is less than that time required to hydrolyze an amount of said anhydride equal to 30% of the molar equiva-lent amount of the emulsifying agent contained in said latex, said mixing step being carried out at a temperature ranging from about 20 to 50°C.

29. A process of Claim 1, wherein said stabilized ag-glomerated admixture withdrawn in step (G) has present agglom-erated polymer particles ranging from about 0.1 to 1.0 microns in diameter.

30. A process of Claim 29, wherein said agglomerated polymer particles range from 0.1 to 0.4 microns.

31. A process of Claim 29, wherein said agglomerated polymer particles range from about 0.5 to 1.0 microns.

32. A continuous process for agglomerating polymer particles in aqueous latices wherein the agglomerated polymer particles have a bimodal particle size distribution comprising, operating a first process of Claim 1, wherein a first stabil-ized agglomerated admixture withdrawn in step (G) has present agglomerated polymer particles having polymer particles ranging from about 0.1 to 0.4 microns and simultaneously operating a second process of Claim 1 wherein a second stabilized agglom-erated admixture withdrawn in step (G) has present agglomerated polymer particles ranging from about 0.5 to 1.0 microns, ad-mixing said first and second admixture and forming a third stabilized agglomerated admixture having a bimodal particle size distribution.

33. An apparatus for continuously agglomerating particles in an aqueous latex comprising:
(A) a mixing zone having a first feed port for an agglomerating solution stream, a second feed port for a latex stream, a mixing means located in said zone to mix said feed streams forming an admixture, a perforated member, forming at least a portion of a wall section of said mixing zone, said member providing a flow-through port for said admixture inducing laminar-flow in said admixture, (B) an annular conduit to carry said laminar-flowing admixture having a first orifice coinciding and interconnected with said perforated member and a second orifice in an opposite end of said conduit, (C) a low-shear zone having a first inlet port in one end of said low-shear zone inter-connected with said second orifice of said conduit to carry an agglomerated admixture, at least one additional inlet port located in an opposite end of said low-shear zone for feeding an emulsifying material to stabilize said agglomerated mixture and an outlet port in said opposite end, (D) a withdrawal means, interconnected with said outlet port of said low-shear zone, for said stabilized agglomerated admixture.

34. An apparatus of Claim 33, wherein said low-shear zone is a flow-through chamber for said agglomerated admixture, oriented generally horizontally, said chamber having a bottom-wall section integral with said first inlet port and said outlet port, upwardly extending side-wall sections such that the depth of said chamber is at least about twice the diameter of said conduit.

35. An apparatus of Claim 33, wherein said withdrawal means, is an annular pipe having at least one diameter reduction providing a flow-mixing zone for said stabilized agglomerated admixture.

36. An apparatus of Claim 35, wherein said pipe has at least one inlet port for said emulsifying material.

37. An apparatus of Claim 33, wherein said first mixing zone is a cylindrical stirred tank having said first and second feed ports located in the opposite wall section of said tank, said mixing means being a high-flow agitator located generally in the center of said tank.

38. An apparatus of Claim 37 wherein said agitator is a turbine agitator.

39. An apparatus of Claim 37 wherein said agitator is a propeller agitator.

40. An apparatus of Claim 33 wherein said agitator is a multi-paddle agitator having wall baffles positioned between paddles.

41. An apparatus of Claim 33 wherein said stirred tank has a diameter about equal to the diameter of said conduit.

42. An apparatus of Claim 33 wherein said stirred tank has a turnover value having a range of from about 3 to 10 per residence time of said admixture.

43. An apparatus of Claim 33 wherein said tank has a length to diameter ratio of about 0.3 to 2.

44. An apparatus of Claim 33 wherein said perforated member is a perforated cylindrical plate having a diameter about equal to the diameter of the conduit.

45. An apparatus of Claim 33 wherein said conduit has a length to diameter ratio of from about 10 to 36.

46. An apparatus of Claim 45 wherein said conduit has a temperature control means.

47. An apparatus of Claim 46 wherein said temperature control means is a heat-exchange jacket.

48. An apparatus of Claim 33 having a liquid level con-trol means interconnected with said withdrawal means to control the liquid level in said low-shear zone.

49. An apparatus of Claim 47 wherein said control means is a manometer-like piping arrangement comprising a first pipe means interconnected with said withdrawal means, adapted during operation of said apparatus, to accommodate the flow rate of said stabilized agglomerated admixture from said withdrawal means and a second pipe means interconnected with said first pipe means extending in a generally vertical direction, adapted during operation of said apparatus, to develop and maintain a head of fluid pressure sufficient to create a controlled fluid level in said low shear zone.

50. An apparatus of Claim 33 wherein said conduit has a volume that provides a passage-time in said conduit, during the operation of said apparatus, sufficient to agglomerate said particles in said latex to a controlled and predetermined par-ticle size, said conduit being upwardly inclined to carry said laminar flowing admixture.

51. An apparatus of Claim 33 wherein a first feed means is interconnected to said first feed port to feed said agglomer-ating solution and a second feed means is interconnected with said second feed port to feed said latex, said first and second feed means, during operation of said apparatus, providing pro-portional-feeds of said solution and latex at rates sufficient to agglomerate said admixture in said column while maintaining a feed-pressure in said first mixing zone sufficient to overcome the pressure-head of the agglomerated mixture in said conduit and the pressure drop across said perforated member.

52. An apparatus of Claim 51 wherein said first and second feed means are pumps.

53. An apparatus of Claim 51 wherein said first and second feed means are gravity feed systems.

54. An apparatus of Claim 51 wherein said first and second feed means are gas-pressure feed systems.

55. An apparatus of Claim 33 wherein said perforated member is a perforated cylindrical plate having at least about 6 perforations, provides a pressure drop not less than about the highest pressure-gradient in said mixing zone, said per-forations having a length to diameter ratio ranging from about 0.1 to 4 and wherein the total free-area of said perforations is from about 1 to 10% of the total area of said perforated member.

56. An apparatus of Claim 51 wherein said agitator has at least one wiping blade in contact with said perforated mem-ber for cleaning said perforated member during operation of said process.

57. An apparatus of Claim 51 wherein said agitator has at least one wiping blade positioned with a clearance of less than about 0.25 inch from said perforated member for cleaning said perforated member during operation of said process.

58. An apparatus of Claim 33 wherein said conduit is oriented in substantially a vertical position such that said laminar-flowing admixture flows vertically in said conduit during operation of said apparatus.

59. An apparatus of Claim 33 wherein said conduit is oriented in substantially a horizontally position such that said laminar-flowing admixture flows horizontally in said con-duit during operation of said apparatus.

60. An apparatus of Claim 33 wherein said conduit is oriented downwardly such that said laminar-flowing admixture flows downwardly in said conduit during the operation of said apparatus.