POROUS COPOLYMERS HAVING A CELLULAR POLYMERIC STRUCTURE SUITABLE FOR PREPARING ION-EXCHANGE RESINS AND ADSORBENTS

Abstract: Novel porous copolymers are disclosed which can be used to prepare ion-exchange resins and polymeric adsorbents. The copolymers comprise a copolymer of at least one monovinylidene monomer and a crosslinking monomer and have a unique cellular pore structure. The cellular structure comprises a macroporous void phase which is dispersed within a continuous copolymer phase. The porous void phase comprises a plurality of cellular void spaces which are at least partially enclosed by walls of the continuous copolymer phase. Also disclosed are processes which can be used to prepare the porous copolymers, as well as ion-exchange resins and polymeric adsorbents using the porous copolymers.

Description: POROUS COPOLYMERS HAVING A CELLU LAR POLYMERIC STRUCTURE SU ITABLE FOR PREPARING ION-EXCHANGE RESINS AND ADSORBENTS The present invention concerns polymers suitable for use in making polymeric adsorbents and ion-exchange resins More particularly, the invention concerns porous polymers having a unique cellular polymeric structure. Ion-exchange resins are used by industry to separate chemical species from solutions containing them Such resins are prepared by substituting various types of functional groups onto a cross nked polymer matrix. The functional groups are capable of associating with chemical species so as to remove them from solution. Ion-exchange resins may be cation-, anion-, or chelate-exchange resins, depending on the choice of functional group substituted onto the copolymer matrix The polymer matrix may also be used in preparing polymeric adsorbents, such as the post-crossl inked adsorbent resins disclosed in U S Patent 4,950,332. The polymer matrix is typically in spneroidal bead form and is generally prepared by suspension polymerization of a finely divided organic phase within a continuous suspending medium The organic phase comprises monovinylidene monomers like styrene, polyvinylidene monomers like divinylbenzene and a free-radical polymerization initiator The copolymer beads produced may be microporous, i e., gel in character, or macroporous, depending upon whether a phase-separating diluent is added to tne organic phase The term " macroporous" refers to the fact that the copolymer has both macropores and and micropores The terms "microporous," "gef," and "macroporous" are well known in the art and generally describe the nature of the copolymer bead porosity. Microporous copolymer beads have pore sizes on the order of 50 Angstroms (A) or less, while macroporous copolymer Deads have macropores of 100 A or greater. Gel and macroporous copolymer beads, as well as their preparation, are further discussed in U.S Patent 4,256,840 Adsorbent resins based on a post-crossl inked, gel copolymer matrix can be difficult to manufacture as the gel copolymer is, in many instances, susceptible to breakage during the post-crosslinking step employed. Conventional macroporous cooolymers generally have better strength relative to gel copolymers and, as a result, are less susceptible to such breakage. However, adsorbent resins derived from such conventional macroporous copolymers may have less adsorption capacity relative to the gel adsorbent resin due to a higher degree of porosity, or void space As can be seen, it is desirable to develop a polymerization process for producing copolymer beads which nave sufficient strength to resist breakage and are aiso capable of oeing converted into resins with sufficient capacity. Such copolymer beads would be advantageous for use in preparing polymeric adsorbents, as well as ion-exchange resins The above-described objects are ootained by the novel porous copolymer disclosed herein More particularly, tne present invention concerns a porous copolymer of at least one monovinylidene monomer and a cross nking monomer present in an amount of from 0.3 to 5 weight percent based on total monomer weignt, characterized in that the porous copolymer comprises a cellular pore structure wherein a macroporous voiα phase is dispersed within a continuous copolymer phase, the void Dhase comprising a plurality of cellular void spaces which are at least partially enclosed by walls of the continuous copolymer phase Preferably, the porous copolymer is additionally post-cross nked in a swollen state in the presence of a Fπedel-Crafts catalyst to provide a plurality of bridging moieties which lιnκ together adjacent copolymer chains and thereby form rigid micropores The above-described porous copolymer can be used in preparing ion-exchange resins and polymeric adsorbents Another aspect of the invention is a suspension polymerization process for preparing a porous copolymer having a cellular polymeric structure characterized by contacting in the polymeπzable monomer phase at least one monovinylidene monomer, a crosslinking monomer in an amount of from 0 3 to 5 weight percent based on total monomer weight, at least one free-radical polymerization initiator in an amount of from 0 025 to 2 weight percent based on the monomer weight, and a phase-separating diluent present in an amount of from 30 to 80 weight percent based on weight of monomer and diluent at a temperature from 95 to 140°C A further aspect of the invention is a process for making a polymeric adsorbent characterized by: (a) contacting in a suspended polymeπzable monomer phase at least one monovinylidene aromatic monomer, a crosslinking monomer in an amount of from 0 3 to 5 weight percent based on total monomer weight, at least one free-radical polymerization initiator m an amount of from 0 025 to 2 weight percent based on the monomer weight, and a phase-separating diluent present in an amount of from 30 to 80 weight percent based on weight of monomer and diluent at a temperature of from 95 to 140°C to produce a porous copolymer having a cellular polymeric structure; and (b) post-crossl inking the porous copolymer in a swollen state in the presence of a Friedel-Crafts catalyst Figure 1 is a scanning electron photomicrograph (SEM) of a cross section trom a copolymer having a cellular polymeric structure as disclosed herein Figure 2 is a SEM of a cross section taken from a conventional macroporous copolymer Figures 3-5 are SEMs of adsoroents prepared from a copolymer having a ceιlula r polymeπc structure that may e obtained by tne process of Examples 3, 4, and 5, respectively, as more fully described hereinafter The porous copolymer has a unique cellular pore structure This cellular structure is illustrated by Fig 1 which is a scanning electron photomicrograph of a cross section from such a porous copolymer In reference to Fig 1 , it is seen that the cellular structure comprises a macroporous void phase which is dispersed within a continuous copolymer phase The void phase is dispersed so as to form a plurality of cellular void spaces which are at least partially enclosed by walls of the continuous copolymer phase As used herein, the term "a plurality of cellular void spaces which are at least partially enclosed by walls of the continuous copolymer phase" is intended to encompass copolymers wherein individual cellular void spaces may, or may not be completely enclosed by the continuous copolymer phase In the event that the copolymer phase completely encloses the cellular void spaces, the spaces would define a discontinuous void phase and essentially be a "closed cell " as that term is used in describing foams Where the copolymer phase only partially encloses the cellular void spaces, the spaces would be similar in appearance to an "open cell " as that term is used in discussing foam technology The terms open cell and closed cell are discussed in Ullmann's Encyclopedia of Industrial Chemistry, 5th Ed , Vol A-1 1 (VCH Publishers New York, N Y 1988) at pages 436-439 Fig 1 is an example of a closed cell structure In Fig 1 , the photomicrograph was obtained by reswel ng the copolymer in toluene and, finally, in /so-octane After polymerization, the copolymer was steam distilled to remove /so-octane therein that was used as an inert diluent during polymerization After distillation, the copolymer was dried and swollen to maximum swellability in an excess amount of toluene Thereafter, /so-octane was gradually added to the swollen copolymer such that the toluene in the copolymer was exchanged with /so-octane The copolymer was then dried and the photomicrograph taken thereafter In Figs. 2-5, the photomicrographs were taken with the respective copolymer or resins being in a dry state The copolymer or resins were not reswollen, as described above The cellular void spaces within the copolymer are essentially polygonal in shape with a diameter that generally ranges from 100 to 2000 A When post-crossl inked or functionalized as described hereinafter, the cellular void spaces may appear less polygonal in shape, and in many instances will appear essentially spherical This cellular structure is substantially different when compared to the structure of a conventional macroporous or macroreticular copolymer Fig 2 is another scanning electron photomicrograph which illustrates a cross section from a typical macroporous or macroreticular copolymer Macropores are seen as channels, or veins, of continuous void pnase that are disposed between a continuous copolymer phase Fig 2 illustrates that such conventional macroporous or macroreticular copolymers have a copolymer pnase consisting of an agglomerated mass of minute spherical gel copolymer particles, as described in U S Patent 4,224,415 In general, the copolymers of the invention are preferably prepared by suspension polymerization methods wherein a monomer mixture is suspended within an agitated, continuous suspending medium, as generally discussed in U S Patents 4,256,840 and 4,382, 124 The monomer mixture comprises at least one monovinylidene monomer, a cross- linking monomer, an effective amount of a phase-separating diluent, and an effective amount of a free-radical polymerization initiator The suspending medium may contain one or more suspending agents commonly employed in the art Polymerization is conducted by maintaining the suspension at a polymerizing temperature until reaching a desired degree of conversion of monomer to copolymer Another suitable polymerization method is generally descπoed in U S Patent 4,444,961 Specific parameters required for obtaining the cellular pore structure are described below The cellular structure is obtained by using an effective amount of a phase- separating diluent with minor amounts of crosslinking monomer It is also believed that the morphology of the cellular structure is promoted by adjusting the amount of free-radical polymerization initiator and the polymerization temperature The monomers employed are addition polymeπzable ethylenically uπsaturated compounds Such monomers are well known and reference is made to Polymer Processes, edited by Calvin E Schildknecht, puD shed in 1956 by Interscience Publishers, Inc , New York, Chapter III, "Polymerization in Suspension" at pp 69-109 for purposes of illustration In Table II on pp 78-81 of Schildknecht are listed diverse kinds of monomers suitable for practicing this invention Of such ethylenically unsaturated monomers, of particular interest are water-insoluble monovinylidene monomers, particularly monovinylidene aromatic monomers such as styrene, vinyl naphthalene, alkylene-substituted styrenes (particularly monoalkyl-substituted styrenes such as vinyltoluene and ethylstyrene) and halo-substituted styrenes, such as bromo- or chlorostyrene and vinylbenzylchloπde, acrylic monomers, such as methyl acrylate, ethyl acrylate, methyl ethyl acrylate, or methyl methacrylate; and mixtures of one or more of said monomers Preferred monovinylidene aromatic monomers include styrene, monoalkyl-substituted styrenes, and halo-sjdstituted styrenes Also suitable are diverse polyvinylidene compounds which may be employed as cross- linking monomers, such as polyvinylidene aromatics like divmylbenzene, divmyltoluene, divinylxylene, divinylnaphthalene, tπvinyibenzene, divinyldiohenyl ether, divmyldiphenylsul- fone, as well as diverse alkylene diacrylates and alkylene dimethacrylates Preferred crosslinking monomers are divmylbenzene, tπvinylbenzene, and ethylene glycol dimethacrylate Relatively minor amounts of crosslinking monomer assist with formation of a cellular structure For a preferred styrene-oivinyibenzene monomer system employing a C r alkane diluent, the amount of cross nKing monomer is preferably from 0 3 to 5 weight percent and more preferably from 1 to 4 weight percent based on total weight of monomers employed Notwithstanding the above, it snould be understood that such amounts of crosslinking monomer may not be necessary for other monomer/dnuent systems Phase-separating diluents used in preparing the porous copolymers are those which are a solvent for the monomers employed, but are non-solvents for the resulting copolymer As such, phase separation between the resulting copolymer and the monomer phase occurs as the copolymer forms Suitable phase-separating diluents are organic solvents which are substantially inert with respect to the suspending medium, monomers, and resulting copolymer Generally, organic solvents naving boiling points of at least 60°C are suitable and include aromatic hydrocarbons, aliphatic hydrocarbons, halogenated hydrocarbons, and aliphatic alcohols Examples of suitable diluents are hexane, heptane, /so-octane (2,2,4- tπ methyl entane), benzene, toluene, xylene, tert-amyl alcohol, n-butanol, sec-butanol, 2- ethyihexanol, and decanol The amount of phase-separating diluent employed is an important parameter for obtaining a cellular structure In general, for a given proportion of monovinylidene monomer, crosslinking monomer and initiator, and holding polymerization conditions constant, when the amount of diluent is relatively low the resulting copolymer structure is microporous, i e , it has pores generally less than 50 A in size As the amount of diluent is increased, it is believed that a transition point is reached wherein phase separation of the copolymer from the monomer/diluent phase occurs and the copolymer structure gradually changes from being essentially all microporous to one having a conventional macroporous or macroreticular structure, as illustrated by Fig 2 As the amount of diluent is increased beyond this initial transition point, it is believed that a second transition point is reached wnerein phase separation is more pronounced, and thereby gradually results in a cellular polymeric structure, as illustrated by Fig 1 The cellular copolymers are obtained by using an amount of diluent which is sufficient to reach this second transition point As those skilled in the art can appreciate, the amount of phase-separating diluent necessary to obtain a cellular structure varies with the choice of monomers, the amount of crosslinking monomer, and diluent employed for a given polymerization As a result, a sufficient amount of diluent must be determined more or less empirically for a given monomer- diluent system In a preferred styrene-di vinyl benzene monomer system employing a C o alkane diluent, such as hexane, heptane, or /so-octane, the amount of pnase-separatmg diluent required is desirably from 30 to 80 weight percent based on he weight of the monomers and diluent In this system, the amount of diluent is preferably from 35 to 50 weight percent The free-radical initiator may oe any one or a comPination of conventional initiators for generating free-radicals in tne polymerization of ethvienically unsaturated monomers Representative initiators are UV radiation and chemical initiators sucn as azo- compounds like azobisisobutyronitrile, and peroxygen compounds such as oenzoyi peroxide, t- butylperoctoate, t-butylperbenzoate and /so-propylpercarponate The free-radical initiator employed can also be used to promote formation of a cellular structure Generally, τor a given proportion of reactants ano polymerization conditions, an increase in the amount of initiator can increase the size of tne cells wnich are formed This result is exemplified by comparison of Figs 4 and 5, wherein the respective examples differ essentially in the amount of initiator employed An effective amount of free- radical initiator to obtain a cellular structure is from 0 005 to 10, and preferably from 0 025 to 2 weight percent, based on total monomer weight The polymerization temperature is also a parameter which can be used to promote formation of a cellular structure The polymerization temperature is preferably higher than those typically used in suspension polymerization of ethylenically unsaturated monomers The temperature is preferably from 95 to 140 C C, and more preferably from 100 to 10 1 20 ° c In the preferred suspension polymerization methods, the monomer phase is suspended within an agitated suspending medium which comprises a liquid that is substantially immiscible with the monomer phase Due to the fact that most monomers employed are primarily non-polar organic compounds, a preferred suspending medium is water Generally, 15 the suspending medium is employed in an amount from 30 to 70, and preferably from 35 to 50 weight percent based on total weight of the monomer mixture and suspending medium Various suspending agents are conventionally employed to assist with maintaining a relatively uniform suspension of monomer droplets within the suspending medium Illustrative suspending agents are gelatin, polyvinyl alcohol, magnesium nydroxide, hydroxyethylcellulose, 20 methylcelluloses, and carboxymethylmethylcellulose The amount of suspending agent used can vary widely depending on the monomers and suspending agents employed The porous copolymer beads obtained by suspension polymerization methods are essentially spheroidal in shape and have diameters which can vary widely, as those skilled in the art can appreciate. For most uses, bead diameters may be from 50 to 5000 μm 25 An adsorbent resin can be prepared from the resulting copolymer by post- crosslmking individual polymer chains after polymerization. Post-crosslinking may be achieved by swelling the copolymer with a swelling agent and subsequently reacting the copolymer with a polyfunctional alkylatmg or acylating agent, as is described in U S Patents 4, 191 ,813 and 4,263,407 30 To obtain an adsorbent such as that described in U S Patent 4,950,332, tne porous copolymer beads may be post-crossl inked in a swollen state in the presence of a Fπedel-Crafts catalyst to introduce rigid microporosity (pores witn a diameter of 50 A or less) into the copolymer In this type of process, the copolymer should be prepared trom a monomer mιxtu r e comprising a monovinylidene aromatic monomer, as the oost-crossl inking step requires the 35 presence of aromatic rings on individual polymer cnains Small amounts of non-aromatic monovinylidene monomers, preferably less than 30 weight percent based on monomer weight, can oe employed in the monomer mixture being polymerized, but it is less oesiraole to oo so as the resulting adsorbents may have decreased amounts of surface area and microporosity Pos * - crosslinking ot the copolymer wnile it is in a swollen state displaces and rearranges adjacent polymer chains, thereby causing an increase in the num er of micropores This rearrangement serves to increase overall porosity and surface area of the copoiymer, while also decreasing the average pore size Post-crossl inking also serves to impart rigidity to the copolymer structure, which is important for providing enhanced physical and dimensional stability to the copolymer A preferred method for post-crossl inking the copolymer comprises haloalkylating the copolymer with a haloalkylating agent, swelling the resulting haloalkylated copolymer with an inert swelling agent, and thereafter maintaining the swollen, haloalkylated copolymer at a temperature and in the presence of a Fπedel-Crafts catalyst such that haloalkyl moieties on the copolymer react with an aromatic ring of an adjacent copolymer chain to form a bridging moiety It is also preferred to supstantially remove excess haloalkylating agent and/or solvents employed in haloalkylating the copoiymer prior to oost-cross nking to obtain good quality copolymer and high surface area This type of method is described in U S Patent 4,950,332 In general, haloalkylation is achieved by contacting the copolymer with a haloalkylating agent under conditions sufficient to substitute the copolymer with haioaikyl moieties A preferred haloalkylating agent is chloromethyl methyl ether Preferably, the copolymer is haloalkylated by first swelling it under non-reactive conditions with the haloalkylating agent and an effective amount of a Fπedel-Crafts catalyst The haloalkylating agent advantageously has the Fπedel-Crafts catalyst incorporated therein The swollen copolymer beads are then maintained at a temperature sufficient to react the haloalkylating agent with the copolymer beads until achieving a desired degree of reaction In preparing the adsorbent materials, the porous copolymer is preferably halomethylated and most preferably chloromethylated Methods for haloalkylating copolymer particles are known Illustrative of such are U S Patents 2,642,417, 2,960,480, and 2,992,544 Chloromethyl methyl ether is commonly employed as a haloalkylating agent After haloalkylation, it is preterred to remove excess haloalkylating agent and/or solvents used during haloalkylation This can be accomplished by any method, such as washing with an organic solvent like methanol, or drying After naloalkylation, the copolymer is contacted witn a swelling agent to expand the copolymer structure Suitable swelling agents are solvents which are substantially inert during post-crosslinking of the haloalkylated copolymer and include chlorinated hydrocarbons, such as oichloroethane, chlorobenzene, dichlorobenzene, ethylene dichloπde, methylene chloride, and propylene dichloπde, or nitrogen-substituted aromatics, like nitrobenzene A preferred swelling agent is dichioroethane Advantageously, the copolymer is allowed to swell in an excess amount of the swelling agent for at least 30 minutes Preferably, the coooiymer is contacted with the swelling agent for a time sufficient to substantially attain equilibrium with respect to swelling of tne particular swelling agent employed It is also generally convenient to dissolve the Fπedel-Crafts catalyst employed in the subsequent post-crossl inking reaction within the swelling agent Once swollen, the haloalkylated copolymer is maintained at a temperature and i n the presence of a Fπedel-Crafts catalyst sucn that the bridging moieties are formed by reaction of the haloalkyl moieties with an adjacent aromatic ring Suitable catalysts are those discussed in connection with haloalkylation Preferably, the reaction temperature can be from 20 to 180°C for a period of at least 0 5 nours More preferably, the temperature is from 60 to 85°C Where the copolymer is chloromethylated, reaction of a chloromethyl group with the aromatic ring of an adjacent copolymer chain results in formation of a methylene bridge, i e , a -CH2- moiety, between two copolymer chains After formation of the bridging moiety, the swelling agent is removed by conventional methods, such as solvent extraction, washing, drying, or a combination thereof If a drying step is used, it is preferred to avoid an oxygen-containing atmosphere at temperatures above normal room temperature After post-crossl inking, the resulting polymeric adsorbent desirably has a specific surface area of at least 600 square meters per gram ("m 2 /g") of dry adsorbent resin, preferably at least 1000, more preferably at least 1200 m 2 /g Specific surface area may be determined by well-known BET nitrogen adsorption techniques In terms of porosity, the adsorbent preferably has from 0 5 to 1 5 cubic centimeters of pore volume per gram of adsorbent material ("cc/g") Most preferably, the adsorbent has from 0 7 to 1 3 cc/g of porosity If desired, the porous copolymer beads may be converted to ion-exchange resins by functionalizing them with ion-exchange or chelate-exchange functional groups Techniques for converting copolymers to anion-, cation-, and chelate-exchange resins are known In preparing anion- and chelate-exchange resins from poly(vιnylaromatιc) coooiymer beads, such as cross-linked polystyrene beads, the beads are first haloalkylated, preferably chloromethylated, and the anion- or chelate-exchange groups are subsequently substituted onto the haloalkylated copolymer The porous copolymer beads may be haloalkylated by the methods previously described Anion- or chelate-excnange resins may be prepared from the haloalkylated beads by contact with an ami ne compound capable of replacing the halogen of the haloalkyl group with an amme-based functional group Suitable compounds and methods for Drepaπng sucn resins are also illustrated in tne patents previously discussed concerning haloalkylation Weak-base anion resins may be prepared by contacting the haloalkylated copolymer beads with ammonia, a primary amine, a secondary amine, or oolyamines like ethylene diamine or propylene diamine Commonly employed primary and secondary amines include methylamine, ethylamme, Dutylamine, cyclohexylamine, oimethylamine, and diethylamine Strong-base anion resins may oe prepared by contact with tertiary amines, such as tπmethylamine, tπethylamine, oimethynsopropanolamine, or etnylmethyloropylamine Chelate resins may be prepared, for example, by contacting the haloalkylated copolymer beads with an aminopyπdine compound, such as a 2-pιcolylamιne Chelate- exchange resins may also be prepared by contacting the haloalkylated copolymer beads with a primary amine to initially convert the copolymer beads to a weak-base anion-excnange resin, followed by contact with a carboxyl-contammg compound, like chloroacetic acid, as described in U S Patent 2,888,441 Animation typically comprises contacting the haloalkylated copolymer Deads with an amine compound at a temperature of from 25°C to 150°C -or at least 1 hour Cation-exchange resins may be prepared from the copolymer beads using methods illustrated by U S Patents 3,266,007, 2,500,149; 2,631 ,127, 2,664,801 , and 2,764,564 In general, strong acid resins are prepared by reacting the copolymer with a sulfonatmg agent such as sulfuπc acid, chlorosulfonic acid, or sulfur tπoxide Contact with the sulfonatmg agent can be conducted neat, or with a swelling agent Contact may be conducted at temperatures from 0°C to 150°C The resulting cation-exchange resin may be converted to a desired metal salt form by contact with an aqueous solution of a salt or base containing the desired metal couπteπon For example, the resin can be converted to its calcium form by contact with a CaCl n or Ca(OH) 2 solution The resin can be converted to other forms in like manner using suitable water-soluble salts of the desi red metal The following examples are intended to illustrate the invention All parts and percentages are by weight and all temperatures are in degrees Celsius (°C), unless otherwise indicated Examples 1-10 Examples 1-10 concern preparation of copolymers having a cellular polymeric structure and also preparation of adsorbents by post-crossl inking the copolymers A suitable polymerization kettle equipped with agitation is charged with a monomer phase composed of measured amounts of styrene, a divmylbenzene mixture obtained from The Dow Chemical Company containing 55 weight percent divmylbenzene and 45 weight percent ethylvmyl benzene based on weight of the mixture, commercial grade iso- octane, and t-butylperbenzoate (t-BPB) and f-butylperoctoate (t-BPO) as free-radical initiators The proportion of each component, in terms of a weight percentage, employed in a particular example is listed in Table I After charging the kettle with the monomer phase, an aqueous phase composed of water, sodium dicnromate, and carboxymethylmethylcellulose (CMMC) is added The proportion of monomer onase to aqueous phase employed is 1 1 The proportion of specific aqueous pnase components, also in terms of a weight percentage, are listed in Table ( l l o IV) l t tn o TABLE I - MATERIALS AND CONDITIONS EMPLOYED IN EXAMPLES 1-10 % DVB or styrene = weight styrene or divinylbenzene total monomer weight % Diluent = weight diluent total weight of monomers + diluent * t-BPB or t-BPO = weight of initiator total monomer weight * Sodium Dichromate or CMMC = weight of component total weight of aqueous phase After adding the monomer and aqueous phases, the kettle is sealed and purged with nitrogen Agitation is initiated to size the monomer phase into droplets The kettle contents are heated to an initial polymerization temperature (Initial Temperature) as indicated in Table I and, subsequently, maintained at this temperature for a time (Initial Time) also indicated in Table I to obtain porous copolymer beads In two of the examples, the respective polymerizations are concluded by increasing the temperature to a temperature (Finish Temperature) and for a time (Finish Time) as indicated in Table I to more fully complete polymerization The kettle contents are then allowed to cool to room temperature The porous copolymer beads are recovered from the kettle, washed with water, and /so-octane is 0 removed by steam distillation The beads are finally allowed to dry at room temperature The porous coooiymer beads are then post-crossl inked by substituting the copolymer with chloromethyl groups, washing the beads to remove excess haloalkylating agent, swelling the chloromethylated copolymer beads with an inert swelling agent, and then reacting the chloromethyl groups in the presence of a Fπedel-Crafts catalyst For each example, 5 a 30 gram (g) portion of the respective beads and 500 milliliters (ml) of chloromethyl methyl ether (CMME) are placed in a 1 liter (L) reactor The copolymer beads are allowed to swell with the CMME under moderate agitation for 30 minutes (mm) Thereafter, 9 g of ferric chloride is added to the reactor The reactor contents are then maintained at a temperature of 45°C for 2 5 hours (hr) The reactor contents are cooled and washed with an excess amount of methanol o to remove the CMME from the beads. Excess liquid is removed from the reactor and the chloromethylated beads are again washed with methanol and finally recovered from the reactor The resulting methanol-moist chloromethylated beads are swollen with an excess amount of 1 ,2-dιchloroethane (EDC) in a 1 L reactor Thereafter, the reactor contents are 5 heated to distill off any residual amount of methanol from the beads Upon reacning an overhead product temperature of 82°C, distillation is discontinued and the beads are allowed to cool to 20°C A 9 g amount of ferric chloride catalyst is added to the reactor and the cooled beads are allowed to contact the catalyst for 30 mm The beads are then heated and maintained at a temperature of 80°C for 3 hrs After cooling the resulting adsorbent beads to 0 room temperature, the EDC is extracted by rinsing the beads five times with methanol Tne adsorbent beads are dried overnight in an oven at 120°C After drying, the beads are analyzed to determine the various physical properties listed in Table II Tne presence of a cellular polymeric structure is also confirmed by scanning electron microscopy Figs 4, 5, and 6 illustrate the structures obtainable from the methods of 5 Examples 3, 4, and 5 respectively Tne figures illustrate a structure wnerein a discontinuous porous void phase is dispersed within a continuous copolymer phase o in o TABLE II - PHYSICAL PROPERTY DATA FOR EXAMPLES 1-10 Crush Strength is determined by taking a representative sample of at least aoout 20 beads from a given sample of adsorbent or copolymer oeads, and determining the force, in grams, needed to fracture each oead using a Chatillon Scale, Model DPP-1 KG, available from J Chatillon & Sons Company. Crush strength is reported as the average of the force measurements obtained for the 20 beads. Volume average particle diameters are determined by use of a particle size analyzer obtained from the HIAC-Royco Company. The number of whole beads, expressed as a percent, is determined by microscopic examination of a representative sample of at least 200 beads The number of substantially o spherical beads in the sample is determined and a percentage is calculated therefrom Porosity and specific surface area data are determined by well-known BET nitrogen adsorption techniques Examples 1 1-12 The procedure of Examples 1-10 is substantially repeated, except that methyl 5 methacrylate (MMA) is added to the monomer phase being polymerized. The proportions of materials added to the kettle and polymerization temperature is listed in Table III. The proportion of monomer phase to aqueous phase employed is also 1 : 1 The physical properties of the resulting adsorbents are listed in Table IV. 0 5 0 5 TABLE III - MATERIALS AND CONDITIONS EMPLOYED IN EXAMPLES 11 and 12 % monomer = weight of an individual monomer total monomer weight % Diluent = weight diluent total weight of monomers + diluent * t-BPB or t-BPO = weight of component total monomer weight * Sodium Dichromate or CMMC = weight of component total weight of aqueous phase ιo o o TABLE IV - PHYSICAL PROPERTY DATA FOR EXAMPLES 11-12 *not eterm ne Example 13 Example 13 concerns preparation of a post-cross nked, anion-exchange resin from a copolymer having a cellular polymeric structure A 3 L polymerization kettle equipped with agitation is charged with a monomer phase composed of 744 9 g of styrene, 10 1 g of a divmylbenzene mixture obtained from The Dow Chemical Company containing 55 weight percent divmylbenzene and 45 weight percent ethylvinyl benzene based on weight of the mixture (a divmylbenzene content of 0 75 weight percent based on total monomer weight), 546 g of /so-octane (42 percent by weight based on weight of monomer and diluent), and 7 6 g of t-butylperbenzoate (t-BPB) as a free-radical o initiator After charging the kettle with the monomer pnase, an aqueous phase composed of 1040 g of deionized water, 3 3 g of a 67 percent aqueous sodium dichromate solution, ano 260 g of a 1 percent aqueous CMMC solution is added After adding the monomer and aqueous phases, the kettle is sealed and purged with nitrogen Agitation is initiated to size the monomer phase into droplets The kettle 5 contents are heated to a temperature of 100°C and maintained at that temperature for 18 hrs The polymerization was completed by heating the kettle contents to a temperature ot 1 10°C and maintaining the temperature for 2 hrs The kettle contents are then allowed to cool to room temperature The beads are recovered from the kettle, washed with water, and /so- octane is removed therefrom by steam distillation The beads are allowed to dry at room 0 temperature The presence of a cellular structure is confirmed by scanning electron microscopy A 30 g portion of the copolymer beads is placed with 600 ml of CMME in a 1 L reactor The copolymer beads are allowed to swell with the CMME under moderate agitation for 30 mm Thereafter, 9 g of ferric chloride is added to the reactor The reactor contents are 5 then maintained at a temperature of 45°C for 3 hrs The reactor contents are cooled and washed with an excess amount of methanol to remove the CMME from the beads Excess liquid is removed from the reactor and the chloromethylated beads are again washed with methanol The resulting methanol-moist chloromethylated beads are swollen witn an excess amount of EDC in a 1 L reactor Thereafter, the reactor contents are neated to distill off any 0 residual amount of methanol from the beads Upon reacning an overnead product temperature of 82 υ C, distillation is discontinued and the beads are allowed to cool to 20°C A 9 g amount of ferric chloride catalyst is added to the reactor and the cooled beaos are allowed to contact the catalyst for 30 mm The oeads are then neated and maintained at a temperature oτ 80°C for 3 hrs After cooling the resulting adsorbent beads to room temperature, the EDC is 5 extracted by rinsing the oeads five times with methanol The aosoroent Deads are dried overnight in an oven at 120°C The copolymer beads are then aminated with oimethvlamine An excess amount of aqueous dimethylamine solution is added to the beads in a 1 L r eactor along with 500 g of water. The beads are then heated to a temperature of 70°C and maintained at that temperature for 1 hr. The Dhysical properties of the resulting resin are determined as in Examples 1 -10. The resin has the following properties: a volume average particle diameter of 799 μm, 99 percent whole beads, 240 g/bead crush strength, and a water retention capacity of 77 percent. Water retention capacity is determined by well-known methods.

Claims: CLAIMS: 1 A porous copolymer of at least one monovinylidene monomer and a crosslinking monomer present in an amount of from 0 3 to 5 weight percent based on total monomer weight, characterized in that the porous copolymer comprises a cellular pore structure wherein a macroporous void phase is dispersed within a continuous copolymer phase, the void phase comprising a plurality of cellular void spaces which are at least papally enclosed by walls of the conti nuous copolymer phase 2 The porous copolymer of Claim 1 in which at least one monovinylidene monomer is styrene, vinyl benzyl chloride, vmyltoluene or ethylstyrene and in which the crosslinking monomer is divmylbenzene, tπvinyl benzene or ethylene glycol dimethacrylate 3 The porous copolymer of Claims 1 or 2 in which the cellular void spaces have diameters from 100 to 200θA 4 The porous copolymer of Claim 2 in which the cellular void spaces are completely enclosed by walls of the continuous copolymer phase 5 A suspension polymerization process for preparing a porous copolymer of Claim 1 having a cellular polymeric structure characterized by contacting in the polymerizable monomer phase at least one monovinylidene monomer, a crosslinking monomer in an amount of from 0 3 to 5 weight percent based on total monomer weight, at least one free-radical polymerization initiator in an amount of from 0 025 to 2 weight percent based on the monomer weight, and a phase-separating diluent present in an amount of from 30 to 80 weight percent based on weight of monomer and diluent at a temperature from 95 to 140°C 6 The process of Claim 5 in which at least one monovinylidene monomer is styrene, vinyl benzyl chloride, vmyltoluene or ethylstyrene and in which the crosslinking monomer is divmylbenzene, tπvinylbenzene or ethylene glycol dimethacrylate 7 The process of Claim 5 in which at least one free-radical polymerization initiator is t-butylperoctoate, t-butylperbenzoate, benzoyl peroxide, or iso- propyl percarbonate 8 The process of Claim 5 in which the phase-seoarating diluent is a C 6 alkane 9 The porous copolymer produced by the process of any one of Claims 5-8 10 A polymeric adsorbent characterized in that it comprises a copolymer of at least one monovinylidene aromatic monomer and a crosslinking monomer present in an amount of from 0 3 to 5 weight percent based on total monomer weight and having a cellular pore structure wnerein a macroporous void phase is dispersed within a continuous copolymer phase, the void phase comprising a plurality of cellular void spaces wnicn are at least partially enclosed by walls of the continuous copolymer phase, tne porous copolymer oeing post- crosslmked in a swollen state in the presence of a Friedel-Crafts catalyst to provide a plurality of bridging moieties which link together adjacent copolymer chains and tnereby form rigid micropores 1 1 The adsorbent of Claim 10 in which the bridging moieties are -CH - moieties 12 The adsorbent of Claims 10 or 1 1 in which at least one monovinylidene monomer is styrene, vinyl benzyl chloride, vmyltoluene or ethylstyrene and in which the crosslinking monomer is divmylbenzene, tπvinyl benzene or ethylene glycol dimethacrylate 13 The adsorbent of Claim 12 in which the cellular void spaces have diameters from 100 to 2000 A 14 The adsorbent of Claim 12 in which the cellular void spaces are completely enclosed by walls of the continuous copolymer phase 15 A process for making a polymeric adsorbent having cellular pore structure characterized by (a) contacting in a suspended polymerizable monomer phase at least one monovinylidene aromatic monomer, a crosslinking monomer in an amount of from 0 3 to 5 weight percent based on total monomer weight, at least one free-radical polymerization initiator in an amount of from 0.025 to 2 weight percent based on the monomer weight, and a phase-separating diluent present in an amount of from 30 to 80 weight percent based on weight of monomer and diluent at a temperature of from 95 to 140°C to produce a porous copolymer having a cellular polymeric structure; and (b) post-crossl inking the porous copolymer in a swollen state in the presence of a Friedel-Crafts catalyst. 16 The process of Claim 15 in which post-crossl inking is characterized by: removing the phase-separating diluent from the porous copolymer; contacting the copolymer with a haloalkylating agent under conditions sufficient to substitute the copolymer with haloalkyl moieties, removing any excess haloalkylating agent from the copolymer; swelling the copolymer with an inert swelling agent; maintaining the swollen copolymer at a temperature and in the presence of a Friedel-Crafts catalyst such that individual haloalkyl moieties on a copolymer chain react with an aromatic ring of an adjacent copolymer chain to form a bridging moiety; and removing the swelling solvent from the copolymer 17 The process of Claim 16 in which the haloalkylating agent is chloromethyl methyl ether 18 The process of Claim 16 in which the bridging moiety is a -CH - moiety 19 The process of Claim 16 in which the swelling solvent is 1 ,2-dιchioroethane 20 The polymeric adsorbent produced by the process of any one of Claims 15-19 AMENDED CLAIMS [received by the International Bureau on 2 February 1994 (02.02.94); original claims 2 and 13 cancelled; claims 1-20 amended and renumbered as claims 1 -18 ( 2 pages ) ] 1. A porous copolymer of at least one monovinylidene monomer and a crosslinking monomer present in an amount of from 0.3 to 5 weight percent based on total monomer weight, characterized in that the porous copolymer comprises a cellular pore structure wherein a macroporous void phase is dispersed within a continuous copolymer phase, 5 the void phase comprising a plurality of cellular void spaces having diameters from 100 to 200θA which are at least partially enclosed by walls of the continuous copolymer phase. 2. The porous copolymer of Claim 1 in which at least one monovinylidene monomer is styrene, vinyl benzyl chloride, vmyltoluene or ethylstyrene and in which the crosslinking monomer is divinyl benzene, trivinyl benzene or ethylene glycol dimethacrylate. 1 o 3. The porous copolymer of Claim 2 in which the cellular void spaces are completely enclosed by walls of the continuous copolymer phase. 4. A suspension polymerization process for preparing a porous copolymer of Claim 1 having a cellular polymeric structure characterized by contacting in the polymerizable monomer phase at least one monovinylidene monomer, a crosslinking monomer in an amount 15 of from 0.3 to 5 weight percent based on total monomer weight, at least one free-radical polymerization initiator i n an amount of from 0.025 to 2 weight percent based on the monomer weight, and a phase-separating diluent present in an amount of from 30 to 80 weight percent based on weight of monomer and diluent at a temperature from 95 to 140°C. 5. The process of Claim 4 in which at least one monovinylidene monomer is 20 styrene, vinylbenzyl chloride, vinyltoluene or ethylstyrene and in which the crosslinking monomer is divinyl benzene, trivinylbenzene or ethylene glycol dimethacrylate. 6. The process of Claim 4 in which at least one free-radical polymerization initiator is t-butylperoctoate, t-butylperbenzoate, benzoyl peroxide, or/so- propyl percarbonate. 25 7. The process of Claim 4 in which the phase-separating diluent is a C alkane. 8. The porous copolymer produced by the process of any one of Claims 4-7. 9. A polymeric adsorbent characterized in that it comprises a copolymer of at least one monovinylidene aromatic monomer and a crosslinking monomer present in an amount of from 0.3 to 5 weight percent based on total monomer weight and having a cellular 30 pore structure wherein a macroporous void phase is dispersed within a continuous copolymer phase, the void phase comprising a plurality of cellular void spaces having diameters from 100 to 2000A which are at least partially enclosed by walls of the continuous copolymer phase, the porous copolymer being post-crosslinked in a swollen state in the presence of a Friedel-Crafts catalyst to provide a plurality of bridging moieties which link together adjacent copolymer 35 chains and thereby form rigid micropores. 10. The adsorbent of Claim 9 in which the bridging moieties are -CH - moieties. 11. The adsorbent of Claims 9 or 10 in which at least one monovinylidene monomer is styrene, vinylbenzyl chloride, vmyltoluene or ethylstyrene and in which the crosslinking monomer is divinyl benzene, trivinyl benzene or ethylene glycol dimethacrylate. 12. The adsorbent of Claim 11 in which the cellular void spaces are completely enclosed by walls of the continuous copolymer phase. 13. A process for making a polymeric adsorbent having cellular pore structure characterized by: (a) contacting in a suspended polymerizable monomer phase at least one monovinylidene aromatic monomer, a crosslinking monomer in an amount of from 0.3 to 5 1 g weight percent based on total monomer weight, at least one free-radical polymerization initiator in an amount of from 0.025 to 2 weight percent based on the monomer weight, and a phase-separating diluent present in an amount of from 30 to 80 weight percent based on weight of monomer and diluent at a temperature of from 95 to 140°C to produce a porous copolymer having a cellular polymeric structure; and T5 (b) post-crosslinking the porous copolymer in a swollen state in the presence of a Friedel-Crafts catalyst. 14. The process of Claim 13 in which post-crosslinking is characterized by: removing the phase-separating diluent from the porous copolymer; contacting the copolymer with a haloalkylating agent under conditions sufficient 20 to substitute the copolymer with haloalkyl moieties; removing any excess haloalkylating agent from the copolymer; swelling the copolymer with an inert swelling agent; maintaining the swollen copolymer at a temperature and in the presence of a Friedel-Crafts catalyst such that individual haloalkyl moieties on a copolymer chain react with 25 an aromatic ring of an adjacent copolymer chain to form a bridging moiety; and removing the swelling solvent from the copolymer. 15. The process of Claim 14 in which the haloalkylating agent is chloromethyl methyl ether. 16. The process of Claim 14 in which the bridging moiety is a -CH 2 - moiety. 30 17. The process of Claim 14 in which the swelling solvent is 1,2-dichloroethane. 18. The polymeric adsorbent produced by the process of any one of Claims 13-17.

Inventors: DEMOPOLIS TOM N, DEMOPOLIS, TOM, N.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1993
Main classification: C08J9
IPC codes: B01J20, B01J41, C08F8, C08F12, C08F212, C08J9