GB1602063A

GB1602063A - Polymer beads

Info

Publication number: GB1602063A
Application number: GB19793/78A
Authority: GB
Original assignee: Rohm and Haas Co
Current assignee: Rohm and Haas Co
Priority date: 1977-05-17
Filing date: 1978-05-16
Publication date: 1981-11-04
Also published as: ZA782707B; AR221700A1; FR2391233B1; JPS625923B2; DE2820947C2; ES469929A1; JPS53141389A; BE867104A; IN148471B; BR7803065A; MX148905A; DE2820947A1; IT1198295B; AU3611578A; FR2391233A1; AU516299B2; IT7868122A0

Description

(54) POLYMER BEADS (71) We, ROHM AND HAAS COMPANY, a corporation organized under the State of Delaware, United States of America, of Independence Mall West, Philadelphia, Pennsylvania 19015, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention is concerned with the preparation of crosslinked vinyl copolymers as discrete copolymer beads in aqueous dispersions, with the beads themselves and with ion exchange resins for which the beads constitute the base polymer matrix.

The techniques of preparing crosslinked vinyl copolymers in bead form (as precursors for conversion into ion exchange resins) by free-radical catalyzed polymerization of the monomer mixture in aqueous dispersion are well known. The term "crosslinked vinyl copolymer" in this specification means crosslinked, insoluble, infusible copolymers of 50 to 99.5 mole percent preferably 80 to 99% units of vinyl non-allylic aromatic monomer containing a single vinyl group e.g., styrene, vinyl toluene, vinyl naphthalene, ethyl vinyl benzene, vinyl chlorobenzene and chloromethyl styrene units, with 0.5 to 50 mole percent, preferably I to 20%, of units of crosslinker monomer compound having at least two active non-allylic vinyl groups, for example, divinyl benzene, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, divinyl toluene, trivinyl benzene, divinyl chlorobenzene, divinylpyridine, divinylnaphthalene, ethylene glycol diacrylate, neopentyl glycol dimethacrylate, diethylene glycol divinylether, bisphenol - A - dimethacrylate, pentaerythritol tetra- and trimethacrylates, divinylxylene, divinylethylbenzene, divinyl sulfone, divinyl ketone, divinyl sulfide, N,N' - methylene - diacrylamide, N,N' - methylene - dimethacrylamide, N,N' - ethylene - diacrylamide, trivinyl naphthalene, polyvinyl anthracenes and the polyvinyl ethers of glycol, glycerol, pentaerythritol, resorcinol and the monothio and dithio derivatives of glycols. The copolymer may include units of up to 5 mole percent of other vinyl monomers which do not fundamentally affect the nature of the resin matrix, for example, acrylonitrile and butadiene units and others as known in the art.

In this specification "vinyl" includes "vinylidene", when used generically.

The conventional conditions of polymerization used heretofore lead to crosslinked vinyl copolymers, which, when converted to ion exchange resins by attachment of functional groups thereto, have certain operational deficiencies resulting from physical weaknesses.

The present invention may be used to yield ion exchange resins in which the polymer beads have greater mechanical strength and increased resistance to those swelling pressures which are produced within a bead during acid/base cycling (i.e., osmotic shock). Greater mechanical strength manifests itself in improved resistance to physical breakdown from external forces such as weight of the resin column bed, high fluid flows and backwashing. Thus, the physically strong ion exchange resins of this invention are especially useful in treating fluid streams at high flow rates, for example in condensate polishing applications in which resins of lesser quality are prone to mechanical breakdown and short life spans.

In the past, it has generally been the practice to exclude reaction modifiers in the preparation of crosslinked vinyl polymers used as the base matrix copolymer for ion exchange resins because they have been regarded as detrimental to the properties of these copolymers. U.S. 2,241,770 teaches that styrene is stabilized for storage by treatment with a representative modifier, phenylacetylene, with the admonition to remove the phenylacetylene from the monomer prior to its polymerization. While polymerization of styrene in conjunction with phenylacetylene at temperatures between 100 C and 225"C to produce a linear, uncrosslinked polymer is described in U.S. 2,290,547, there is no suggestion in the art that crosslinked copolymers useful for conversion into greatly improved ion exchange resins could be derived from polymerization systems incorporating modifiers such as phenyl-acetylene. British patent 1,261,427 teaches that the gel effect in the polymerization of acrylonitrile, acrylates and methacrylates or copolymerization thereof with styrene or vinyl acetate can be reduced or eliminated by the use of cyclic compounds such as 1,4-cyclohexadiene and terpinolene. Again, there is no suggestion in this art that such modifiers are useful in preparing improved crosslinked copolymers. U.S. Patent No. 3,976,629 discloses the use of various aliphatic compounds containing at least two polymerizable bonds, such as isoprene and cyclopentadiene, as crosslinkers in aliphatic monomer mixtures. Combinations of aromatic and polyunsaturated aliphatic crosslinker including compounds used herein as rate modifiers, are also known in the prior ion exchange art (see, e.g., U.S. Patent 3,674,728). These polyunsaturated aliphatic materials have been employed previously at much higher levels than herein for different purposes and under different polymerization conditions.

In accordance with this invention, vinyl monomer, crosslinking monomer, and other optional monomer are polymerized in aqueous dispersion in the presence of free-radical initiator and from 0.01 to 10 millimoles, per mole of monomer, of organic acetylenically or allylically unsaturated compound, said compound being capable of moderating rate of polymerization by "allylically unsaturated" we mean that the compound has a -CH < group attached to an aliphatic > CH=CH < group. Representative modifiers are phenyl-acetylene, terpinolene, bicycloheptadiene, dimethyloctatriene, dimer of cyclopentadiene, dimer of methylcyclopentadiene, terpenes, a-methyl styrene, methyl styrene dimer, limonene, cyclohexadiene, methyl cyclohexadiene, camphene, geraniol, farnesol, 2-norbornene, cyclododecatriene, cyclooctadiene, cyclododecene, allyl benzene and 4 - vinyl - 1 - cyclohexene Other allylically unsaturated monomers useful as modifiers include allyl acrylate, diallyl mareate, diallyl fumarate, diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate, diallyl tartrate.

diallyl silicate, triallyl tricarballylate, triallyl aconitrate, triallyl citrate, triallyl phosphate and the polyallyl ethers of glycol, glycerol, pentaerythritol and resorcinol.

A preferred amount of modifier is 0.1 to 10 millimoles per mole of monomer, more preferably 0.2 to 5 millimoles per mole of monomer.

The polymerization is normally carried out at a temperature from 30 to 950C, preferably 45 to 850 C, and more preferably from 50 to 75"C. It is desirable to employ lower temperatures of reaction in the earlier stages of the polymerization, for example until at least about 50% of the monomers in the dispersion are reacted, preferably 75% or more. The free radical initiator used in the process of the invention is one capable of catalyzing polymerization at the aforesaid temperatures, which are in general somewhat lower, e.g., from 15 to 350C lower, than those normally used in suspension polymerization for similar products.

Suitable initiators include di(4- t- butycyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, di - (sec - butyl) - peroxydicarbonate, di - (2 ethylhexyl) peroxy dicarbonate, dibenzyl peroxydicarbonate, diisopropyl peroxydicarbonate, azobis (isobutyronitrile), azobis (2,4 - dimethylvaleronitrile), tbutyl peroxypivalate, lauroyl peroxide, benzoyl peroxide, t-butyl peroctoate and tbutyl peroxyisobutyrate. The amount of initiator is normally from about 0.1 to 2 percent, based on monomer weight, preferably 0.3 to 1%. It also may be advantageous when using catalysts which are active at relatively low temperatures, such as 30dO"C, to employ a second so-called "chaser catalyst" which is active at higher temperature, e.g., 75--1000C., in order to achieve higher yields of crosslinked vinyl polymer, for example, from about 0.05 to 0.1 ó based on monomer weight of such initiators as benzoyl peroxide, t-butyl peroctoate and tbutyl peroxyisobutyrate.

The aqueous medium in which the polymerization is conducted in dispersion form will usually contain minor amounts of the conventional suspension additives, that is, dispersants such as xanthan gum (biosynthetic polysaccharide), poly(diallyl dimethyl ammonium chloride), polyacrylic acid (and salts), polyacrylamide, magnesium silicate, and hydrolyzed poly(styrene-maleic anhydride); protective colloids such as carboxymethyl cellulose, hydroxyalkyl cellulose, methyl cellulose, polyvinyl alcohol, gelatin, and alginates; buffering aids such as phosphate and borate salts; and pH control chemicals such as sodium hydroxide and sodium carbonate.

The crosslinked, high-molecular weight copolymers may be recovered from the reactor as hard, discrete beads of particle size within the range of 0.02 to 2 mm, average particle size being 0.2 to 1 mm. These copolymers may be converted to ion exchange resins by attachment of functional groups thereto by conventional means, suitable functional groups including sulfonamide, trialkylamino, tetraalkyl ammonium, carboxyl, carboxylate, sulfonic, sulfonate, hydroxyalkyl ammonium, iminodiacetate, amine oxide, phosphonate, and others known in the art.

Functionalizing reactions which may be performed on vinyl aromatic copolymers to produce ion exchange resins are exemplified by sulfonation with concentrated sulfuric acid, chlorosulfonation with chlorosulfonic acid followed by amination, reaction with sulfuryl chloride or thionyl chloride followed by amination, and chloromethylation followed by amination. Typical functionalizing reactions on (vinyl) acrylic copolymers include hydrolysis to acrylic acid resins, amidolysis, transesterification, and the like. Ion exchange resins may be further delineated by the types: strong acid cation, i.e., containing the groupings sulfonic (-SO3H) or sulfonate (-SO3M), where M is usually an alkali metal ion); weak acid cation, i.e., containing the groupings carboxyl (-CO2ll) or carboxylate (CO2M, where M is usually an alkali metal ion); strong base anion, i.e., containing the tetraalkyl ammonium groupings: -NR3X, where R is an alkyl or hydroxy alkyl group and X is usually chloride or hydroxide; and weak base anion, i.e., containing a trialkylamino group, -NR2, where R is an alkyl or hydroxyalkyl group.

The improvements in the properties of polymers when they are produced according to this invention are evident when the crosslinked copolymers are converted to ion exchange resins by the attachment of the aforesaid functional groups. The enhanced physical strength of these latter resins is apparent from their resistance to crushing which is conveniently measured on the Chatillon instrument, as well as by visual inspection before and after use in ion exchange applications.

For example, strongly acidic styrene-type resins frequently exhibit Chatillon values in the range of about 1000 to about 5000 gm, force per bead, in contrast to resins derived from copolymers prepared by prior art polymerization methods which have Chatillon values of 50 to 500 gm/bead. Similarly, strong base sytrene-type resins of the invention frequently exhibit Chatillon values of about 500 to 1500 in contrast with resins derived from copolymers prepared by prior art methods which have Chatillon values of 25 to 400.

Some preferred embodiments of this invention will now be described, for illustration only, in the following Examples, which also include information on prior art techniques for comparative purposes only.

Examples 1-3 A. Polymer beads are made in a polymerization reactor which is a two-liter, three neck, round bottom flask equipped with a two-blade paddle stirrer, thermometer, condenser, heating mantle with temperature controller, and provision for sweeping in a blanket of inert gas. Into this reactor is charged a monomer mixture consisting of 491.7 g. styrene, 85.5 g. divinylbenzene, 8.8 g.

methyl acrylate, 0.293 g. methylcyclopentadiene dimer, 2.64 g. di - (4 - t butylcyclohexyl)peroxydicarbonate, and 0.293 g. t-butyl peroctoate. The head space is swept with 8% O2 in nitrogen for 30 minutes at 50 cc./min. Then an aqueous phase is added consisting of 510 g. water, 20.1 g. poly-(diallyl dimethyl ammonium chloride) dispersant ("Padmac A"), 1.6 g. gelatin protective colloid ("Pharmagel"), 0.88 g. boric acid, 0.59 g. sodium nitrite, and sufficient 50% sodium hydroxide solution to maintain pH between 10 and 10.5. The stirrer is started and the gas sweep is changed to all nitrogen. The reaction mixture is heated from room temperature to 55+20C over 45 minutes and held at this temperature for 7 hours.

The polymerization is finished off by holding at 750C for one hour and 95"C for another hour. The copolymer beads are washed and excess water is removed by vacuum filtration on a Buchner funnel.

B. In another polymer bead production carried out in like manner, except for the omission of the oxygen-nitrogen sweep, 500.5 g. styrene, 85.5 g. divinylbenzene, 0.586 g. methylcyclopentadiene dimer, and 2.2 g. benzoyl peroxide are mixed with an aqueous phase composed of 510 g. water, 20.1 g. "Padmac A" dispersant, 1.6 g.

"Pharmagel" colloid, 0.88 g. boric acid, 0.59 g. sodium nitrite, and sufficient 50"" sodium hydroxide solution to maintain pH between 10 and 10.5. The reaction mixture is heated from room temperature to 75"C over a 45 min. period and held at 73--77"C for four hours. The polymerization is finished off at a temperature of 95"C. maintained for one hour. The copolymer beads are washed and prepared for functionalization.

Ion exchange resins are then made from the above polymer beads using the technique which follows.

A portion of wet polymer beads as prepared above (110 gms.) is added to 600 grams of 95% H2SO4 in a one liter flask equipped with stirrer, condenser, dropping funnel, thermometer, caustic scrubber and heating means. Thirty nine grams of ethylene dichloride (bead swelling agent) are added, and the suspension is heated from 30"C to 120"C over a 3 hour period. This is followed by a hydration procedure in which water is added to quench the product. The polymer beads are transferred to a backwash tower and backwashed to remove residual acid.

Ion exchange resin products prepared by functionalizing (by sulfonation as above) the copolymer from polymerization method B are characterized in Table 1.

Other exemplary modifiers, instead of methylcyclopentadiene dimer (MCPD) were utilized to yield improvements in bead appearance. Also the polymerization processes were repeated omitting the polymerization modifier to give comparative resins.

TABLE 1 Appearance (Perfect/ Modifier Chatillon Cracked Example (mmole/mole monomer) (g/bead) Fragmented) 1 MCPD (0.6) 520 89/10/1 2 Terpinolene (0.7) 780 82/15/3 3 Phenylacetylene (1.0) 670 89/4/7 Comparative None 400 53/45/2 Comparative None 440 55/41/4 An even greater improvement in bead quality is observed with ion exchange resin on the basis of copolymer from polymerization method A. The sulfonated resin derived therefrom is characterized by the following properties.

Whole beads 100% Cracked beads 3% Fractured beads 0% Perfect beads 97% Friability: Chatillon value, g/bead 1880 Solids, H+ form 47.0 ,Ó Salt Splitting Cation capacity, meq./g dry 5.06 Examples 4--6 Further crosslinked styrene copolymers are prepared as above in polymerization A with variations in the concentration of the modifier, MCPD, then sulfonated as described above to yield ion exchange resins. The properties of these resins are compared to commercial sulfonated resins made from copolymers prepared without modifier addition and with the properties of a sulfonated resin made on the basis of copolymer prepared by polymerization A with modifier omitted. The results are given in Table 2.

TABLE 2 Modifier Conc., mmole per Chatillon, Microcycling Stability* Example Mole Monomer g/bead Before** After 4 0.15 1870 98/2/0 96/4/0 5 0.3 1700 98/2/0 - 6 0.3 1880 97/3/0 93/7/0 Comparative Commercial Resin 300 72/26/2 49/46/5 Commercial Resin 510 98.5/1.5/0 55/42/3 Comparative None 1170 82/16/2 Notes: *100 cycles with IN Hcl and 0.5N NaOH solutions.

**Perfect/Cracked/Fragmented.

Examples 7 and 8 Other crosslinked styrene copolymers are prepared in accordance with this invention using a representative reaction modifier, then chloromethylated and aminated in conventional manner to form strong base, anion exchange resins, the properties of which are compared to commercial resins having the same functional groups and made from copolymers prepared without modifier addition. The results are given in Table 3.

TABLE 3 MCPD Modifier Anion Exchange Microcycling Conc., (mmole/mole Chatillon Capacity, Stability* Example monomer) (g/bead) meq/gm % Solids Before** After 7 0.3 372 4.22 45.5 99/1/0 95/5/0 8 0.6 278 4.30 45.2 98/2/0 90/9/1 Commercial Resin X - 140 4.20 46.0 94/6/0 72/28/0 Commercial Resin Y - 400 4.40 42.5 97/3/0 90/9/0 *100 cycles with hot (50"C) lNNaOH and 0.25 NHCl-0.25 NH2SO4 solutions.

**Perfect/Cracked/Fragmented In like manner, ion exchange resins derived from crosslinked styrene copolymers prepared employing other polymerization modifiers mentioned earlier herein exhibit comparable properties of high mechanical strength and resistance to osmotic shock.

WHAT WE CLAIM IS: 1. A process for preparing beads of crosslinked copolymer containing (a) 50 to 99.5 mole % units of non-allylic, aromatic monomer containing a single vinyl group and (b) 0.5 to 50 mole % units of crosslinker monomer having at least two active non-allylic vinyl groups, by free radical polymerization in aqueous dispersion wherein the polymerization reaction is carried out in the presence of from 0.01 to 10 millimoles per mole of monomer of reaction moderating modifier which comprises one or more acetylenically or allylically unsaturated organic compounds admixed with the monomer.

2. A process as claimed in Claim 1 wherein the monomer (a) comprises styrene and the monomer (b) comprises divinylbenzene.

3. A process as claimed in any preceding claim wherein the modifier comprises one or more of: phenylacetylene, terpinolene and the dimer of methylcyclopentadiene.

4. A process as claimed in any preceding claim which is carried out at a temperature of 30 to 950 C.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

TABLE 2 Modifier Conc., mmole per Chatillon, Microcycling Stability* Example Mole Monomer g/bead Before** After

4 0.15 1870 98/2/0 96/4/0

5 0.3 1700 98/2/0 -

6 0.3 1880 97/3/0 93/7/0 Comparative Commercial Resin 300 72/26/2 49/46/5 Commercial Resin 510 98.5/1.5/0 55/42/3 Comparative None 1170 82/16/2 Notes: *100 cycles with IN Hcl and 0.5N NaOH solutions.

**Perfect/Cracked/Fragmented.

Examples 7 and 8 Other crosslinked styrene copolymers are prepared in accordance with this invention using a representative reaction modifier, then chloromethylated and aminated in conventional manner to form strong base, anion exchange resins, the properties of which are compared to commercial resins having the same functional groups and made from copolymers prepared without modifier addition. The results are given in Table 3.

TABLE 3 MCPD Modifier Anion Exchange Microcycling Conc., (mmole/mole Chatillon Capacity, Stability* Example monomer) (g/bead) meq/gm % Solids Before** After

7 0.3 372 4.22 45.5 99/1/0 95/5/0

8 0.6 278 4.30 45.2 98/2/0 90/9/1 Commercial Resin X - 140 4.20 46.0 94/6/0 72/28/0 Commercial Resin Y - 400 4.40 42.5 97/3/0 90/9/0 *100 cycles with hot (50"C) lNNaOH and 0.25 NHCl-0.25 NH2SO4 solutions.

**Perfect/Cracked/Fragmented In like manner, ion exchange resins derived from crosslinked styrene copolymers prepared employing other polymerization modifiers mentioned earlier herein exhibit comparable properties of high mechanical strength and resistance to osmotic shock.

WHAT WE CLAIM IS: 1. A process for preparing beads of crosslinked copolymer containing (a) 50 to 99.5 mole % units of non-allylic, aromatic monomer containing a single vinyl group and (b) 0.5 to 50 mole % units of crosslinker monomer having at least two active non-allylic vinyl groups, by free radical polymerization in aqueous dispersion wherein the polymerization reaction is carried out in the presence of from 0.01 to 10 millimoles per mole of monomer of reaction moderating modifier which comprises one or more acetylenically or allylically unsaturated organic compounds admixed with the monomer.
2. A process as claimed in Claim 1 wherein the monomer (a) comprises styrene and the monomer (b) comprises divinylbenzene.
3. A process as claimed in any preceding claim wherein the modifier comprises one or more of: phenylacetylene, terpinolene and the dimer of methylcyclopentadiene.
4. A process as claimed in any preceding claim which is carried out at a temperature of 30 to 950 C.
5. A process as claimed in any preceding claim wherein the concentration of

modifier is 0.1 to 10 millimoles per mole of monomer.
6. A process as claimed in any preceding claim wherein the concentration of modifier is from 0.2 to 5 millimoles per mole of monomer.
7. A process as claimed in any preceding claim which is carried out at a temperature of 45 to 85"C.
8. A process as claimed in Claim 1 substantially as described in any one of the foregoing Examples.
9. Beads of crosslinked copolymer containing (a) 50 to 99.5 mole 'í) units of non-allylic aromatic monomer containing a single vinyl group and (b) 0.5 to 50 mole % units of crosslinker monomer containing at least two active non-allylic vinyl groups, whenever prepared by a process as claimed in any one of Claims I to 5.
10. Beads of crosslinked copolymer containing (a) 50 to 99.5 mole , units of non-allylic aromatic monomer containing a single vinyl group and (b) 0.5 to 50 mole % units of crosslinker monomer containing at least two active non-allylic vinyl groups, whenever prepared by a process as claimed in any one of Claims 6 to 8.
11. A process for producing ion exchange resin which comprises adding ion exchange functional groups to copolymer product as claimed in Claim 9.
12. A process for producing ion exchange resin which comprises adding ion exchange functional groups to copolymer product as claimed in Claim 10.
13. An ion exchange resin obtained by attaching sulfonamide, sulfonic, sulfonate, carboxyl, carboxylate, trialkylamino, tetraalkyl ammonium, hydroxyalkyl ammonium, iminodiacetate, amine oxide, and/or phosphonate functional groups to copolymer product as claimed in Claim 11.
14. An ion exchange resin obtained by attaching sulfonamide, sulfonic, sulfonate, carboxyl, carboxylate, trialkylamino, tetraalkyl ammonium, hydroxyalkyl ammonium, iminodiacetate, amine oxide, and/or phosphonate functional groups to copolymer product as claimed in Claim 12.