U.S. patent application number 11/449427 was filed with the patent office on 2007-12-13 for process for macroporous acrylic resins.
Invention is credited to James Charles Bohling, Roy Jeffrey Furbank, Bruce Maurice Rosenbaum.
Application Number | 20070287760 11/449427 |
Document ID | / |
Family ID | 38822734 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070287760 |
Kind Code |
A1 |
Bohling; James Charles ; et
al. |
December 13, 2007 |
PROCESS FOR MACROPOROUS ACRYLIC RESINS
Abstract
A method for producing a macroporous acrylic resin in an aqueous
suspension from a C.sub.1-C.sub.4 alkyl acrylate, an organic
solvent and a crosslinker.
Inventors: |
Bohling; James Charles;
(Lansdale, PA) ; Furbank; Roy Jeffrey; (Lansdale,
PA) ; Rosenbaum; Bruce Maurice; (Fort Washington,
PA) |
Correspondence
Address: |
ROHM AND HAAS COMPANY;PATENT DEPARTMENT
100 INDEPENDENCE MALL WEST
PHILADELPHIA
PA
19106-2399
US
|
Family ID: |
38822734 |
Appl. No.: |
11/449427 |
Filed: |
June 8, 2006 |
Current U.S.
Class: |
521/64 ; 521/142;
526/318; 526/319; 526/328; 526/329.7; 526/336 |
Current CPC
Class: |
C08J 2333/08 20130101;
C08J 2203/14 20130101; Y10T 428/2982 20150115; C08J 9/286
20130101 |
Class at
Publication: |
521/64 ; 526/319;
526/318; 526/328; 526/329.7; 526/336; 521/142 |
International
Class: |
C08J 9/28 20060101
C08J009/28 |
Claims
1. A method for producing a macroporous acrylic resin; said method
comprising steps of: (a) combining: (i) water; (ii) a
C.sub.1-C.sub.4 alkyl acrylate; (iii) a crosslinker; (iv) an
organic solvent; and (v) a polymerization initiator; to form a
reaction mixture; (b) forming a stable dispersion of organic
droplets, and allowing said droplets to react to form a resin; (c)
adding an acid or a base without removing more than 50% of said
organic solvent; and (d) heating to hydrolyze ester groups on the
resin.
2. The method of claim 1 in which said acid or base is an inorganic
hydroxide, and the organic solvent is selected from among
C.sub.7-C.sub.10 hydrocarbons, C.sub.3-C.sub.10 halogenated
hydrocarbons, C.sub.4-C.sub.10 ketones, C.sub.4-C.sub.10 alcohols,
C.sub.4-C.sub.10 alkyl esters, C.sub.4-C.sub.10 aryl esters,
C.sub.4-C.sub.10 mixed alkyl/aryl esters, and combinations
thereof.
3. A method for producing a macroporous acrylic resin; said method
comprising steps of: (a) combining: (i) water; (ii) at least one
monoethylenically unsaturated monomer selected from C.sub.1-C.sub.4
alkyl acrylates, acrylonitrile and methacrylic acid; (iii) a
crosslinker; and (iv) a polymerization initiator; to form a
reaction mixture; (b) forming a stable dispersion of organic
droplets, and allowing said droplets to react to form a resin; (c)
adding an acid or a base without removing more than 50% of said
aqueous solution; and (d) heating to hydrolyze ester or nitrile
groups on the resin.
4. The method of claim 3 in which said at least one
monoethylenically unsaturated monomer is at least one
C.sub.1-C.sub.4 alkyl acrylate, and further comprising an organic
solvent in the reaction mixture.
5. The method of claim 4 further comprising distilling at least 50%
of the organic solvent during hydrolysis of ester groups on the
resin, without removing more than 50% of said aqueous solution; and
in which said acid or base is an inorganic hydroxide, and the
organic solvent is selected from among C.sub.7-C.sub.10
hydrocarbons, C.sub.3-C.sub.10 halogenated hydrocarbons,
C.sub.4-C.sub.10 ketones, C.sub.4-C.sub.10 alcohols,
C.sub.4-C.sub.10 alkyl esters, C.sub.4-C.sub.10 aryl esters,
C.sub.4-C.sub.10 mixed alkyl/aryl esters, and combinations
thereof.
6. A method for producing a macroporous core-shell acrylic resin
bead; said method comprising steps of: (a) combining: (i) water;
(ii) a C.sub.1-C.sub.4 alkyl acrylate; (iii) a crosslinker; (iv) a
hydrophobic organic solvent; and (v) a polymerization initiator;
(b) forming a stable dispersion of organic droplets, and allowing
said droplets to react to form a resin; (c) adding an acid or a
base without removing more than 50% of said aqueous solution; and
(d) heating to hydrolyze ester groups on the resin.
7. The method of claim 6 further comprising distilling at least 50%
of the organic solvent without removing more than 50% of said
aqueous solution.
8. The method of claim 7 in which solvent is distilled during
hydrolysis of ester groups on the resin, and the hydrophobic
solvent is selected from among C.sub.7-C.sub.10 hydrocarbons,
C.sub.3-C.sub.10 halogenated hydrocarbons, C.sub.4-C.sub.10
ketones, and combinations thereof.
9-10. (canceled)
11. The method of claim 2 in which said crosslinker is present in
an amount of at least 5%, based on total amount of C.sub.1-C.sub.4
alkyl acrylate and crosslinker.
12. The method of claim 11 in which said C.sub.1-C.sub.4 alkyl
acrylate is methyl acrylate.
13. The method of claim 12 in which eaid organic solvent is present
in an amount from 30% to 80%, based on total amount of methyl
acrylate, crosslinker and organic solvent,
14. The method of claim 5 in which said crosslinker is present in
an amount of at least 5%, based on total amount of said at least
one monoethylenically unsaturated monomer and crosslinker.
15. The method of claim 14 in which said at least one
monoethylenically unsaturated monomer is methyl acrylate.
16. The method of claim 8 in which said crosslinker is present in
an amount of at least 5%, based on total amount of C.sub.1-C.sub.4
alkyl acrylate and crosslinker.
17. The method of claim 16 in which said C1-C4 alkyl acrylate is
methyl acrylate.
18. The method of claim 17 in which said hydrophobic organic
solvent is present in an amount from 30% to 80%, based on total
amount of methyl acrylate, crosslinker and organic solvent.
Description
[0001] The present invention relates to an improved method for
producing macroporous acrylic resins.
[0002] Typically, macroporous acrylic resins are produced in an
aqueous suspension with aid of a porogen (an organic solvent) which
must be removed at the end of the polymerization. For example, U.S.
Pat. No. 4,486,313 discloses a process for making macroporous
resins. Production of resins having carboxylic acid substituents
requires an additional step because (meth)acrylic acid is
substantially water soluble. It is preferable to polymerize a
water-insoluble precursor to (meth)acrylic acid, e.g., alkyl
(meth)acrylates, then to hydrolyze the alkyl esters on the resin to
carboxylic acid groups. In a typical process the resin copolymer is
produced by polymerizing a monoethylenically unsaturated monomer, a
multiethylenically unsaturated monomer (crosslinker) and porogen.
The porogen is then removed by distillation or optionally by
solvent washing. The product is then often washed and transferred
to another vessel for hydrolysis.
[0003] The problem addressed by this invention is the inefficiency
of the typical process used to make macroporous acrylic resins.
STATEMENT OF THE INVENTION
[0004] The present invention is directed to a method for producing
a macroporous acrylic resin. The method comprises steps of: (a)
combining: (i) water; (ii) a C.sub.1-C.sub.4 alkyl acrylate; (iii)
a crosslinker; (iv) an organic solvent; and (v) a polymerization
initiator; to form a reaction mixture; (b) forming a stable
dispersion of organic droplets, and allowing said droplets to react
to form a resin; (c)adding an acid or a base without removing more
than 50% of said organic solvent; and (d) heating to hydrolyze
ester groups on the resin.
[0005] The present invention is further directed to a method for
producing a macroporous acrylic resin. The method comprises steps
of: (a) combining: (i) water; (ii) at least one monoethylenically
unsaturated monomer selected from among C.sub.1-C.sub.4 alkyl
acrylates, acrylonitrile and methacrylic acid; (iii) a crosslinker;
and (iv) a polymerization initiator; to form a reaction mixture;
(b) forming a stable dispersion of organic droplets, and allowing
said droplets to react to form a resin; (c) adding an acid or a
base without removing more than 50% of said aqueous solution; and
(d) heating to hydrolyze ester or nitrile groups on the resin.
[0006] The present invention is further directed to a method for
producing a macroporous core-shell acrylic resin bead. The method
comprises steps of: (a) combining in an aqueous solution a
C.sub.1-C.sub.4 alkyl acrylate, a crosslinker, a hydrophobic
solvent and a polymerization initiator; (b) agitating to form a
stable dispersion of organic droplets, and allowing said droplets
to react to form a resin; (c) adding an acid or a base without
removing more than 50% of said aqueous solution; and (d) heating to
hydrolyze ester groups on the resin.
[0007] The present invention is further directed to a macroporous
core-shell resin bead having carboxylic acid groups. The bead
comprises a core region surrounded by a shell region. The bead has
from 3% to 100% of monomer residues derived from crosslinker, an
average pore diameter of at least 1.5 nm, and an average particle
size from 10 .mu.m to 900 .mu.m; wherein at least 90% of the
carboxylic acid groups in the bead are in the shell region, and the
shell region comprises from 5% to 75% of the bead by volume.
DETAILED DESCRIPTION OF THE INVENTION
[0008] All percentages and ppm values are by weight, and are on the
basis of total weight of the composition, and all temperatures are
in .degree. C., unless otherwise indicated. The terms
"(meth)acrylic" and "(meth)acrylate" refer to acrylic or
methacrylic, and acrylate or methacrylate, respectively. The term
"acrylic polymers" refers to polymers comprising at least 50%
monomer units derived from among acrylonitrile (AN); acrylamide
(AM) and its N-substituted derivatives; acrylic acid (AA),
methacrylic acid (MAA), and their esters; and itaconic acid (IA).
Esters of AA and MAA include, but are not limited to, methyl
methacrylate (MMA), ethyl methacrylate (EMA), butyl methacrylate
(BMA), ethylhexyl methacrylate (EHMA), lauryl methacrylate (LMA),
hydroxyethyl methacrylate (HEMA), methyl acrylate (MA), ethyl
acrylate (EA), butyl acrylate (BA), ethylhexyl acrylate (EHA) and
hydroxyethyl acrylate (HEA), as well as other esters of AA or MAA,
e.g., alkyl, hydroxyalkyl and aminoalkyl esters. Derivatives of
acrylamide include, e.g., methylol acrylamide (MLAM). Acrylic
polymers also may contain monomer units derived from other
monoethylenically unsaturated monomers, e.g., styrene or
substituted styrenes; other .alpha.,.beta.-unsaturated carboxylic
acids, esters and amides; vinyl esters or halides; etc. Preferably,
an acrylic polymer contains less than 30% of these other monomer
units, more preferably less than 10%, and most preferably the
acrylic polymers are substantially free of monomer units other than
those of AA, MAA, their esters and a crosslinker, preferably
DVB.
[0009] The acrylic resin of this invention comprises residues
derived from at least one monoethylenically unsaturated monomer
selected from among C.sub.1-C.sub.4 alkyl acrylates, acrylonitrile
and methacrylic acid. Preferably, C.sub.1-C.sub.4 alkyl acrylates
are C.sub.1-C.sub.2 alkyl acrylates. The resin further comprises
residues derived from a crosslinker. Preferably, the resin is
produced from a mixture of monoethylenically unsaturated monomers
and crosslinkers that is at least 70% monoethylenically unsaturated
monomer, more preferably at least 80% and most preferably at least
85%, based on the total weight of monoethylenically unsaturated
monomers and crosslinkers. Preferably, the mixture of
monoethylenically unsaturated monomers and crosslinkers has no more
than 97% monoethylenically unsaturated monomer, more preferably no
more than 95%, more preferably no more than 94% and most preferably
no more than 92%, based on the total weight of monoethylenically
unsaturated monomers and crosslinkers. Preferred crosslinkers
include, e.g., divinylbenzene (DVB), trivinylcyclohexane (TVCH),
divinyltoluene, di- and tri-allyl maleate, triallyl phosphate,
allyl methacrylate, diallyl itaconate, ethylene glycol divinyl
ether (EGDMA), triethylene glycol dimethacrylate, tetraethylene
glycol dimethacrylate, ditrimethylolpropane dimethacrylate;
1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate,
1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate,
pentaerythritol and dipentaerythritol dimethacrylate, bisphenol A
dimethacrylate, dimethacrylates of propylene, dipropylene and
higher propylene glycols; trimethylolpropane ethoxylated
tri(meth)acrylate, trimethylolpropane tri(meth)acrylate (TMPT(M)A)
and diethylene glycol divinyl ether (DEGDVE). The most preferred
crosslinkers are DVB, DEGDVE and TMPTMA. Preferably, the resin is
produced from a mixture of monoethylenically unsaturated monomers
and crosslinkers that is from 3% to 100% crosslinker(s), based on
the total weight of monomers and crosslinkers. More preferably the
amount of crosslinker(s) is at least 5%, more preferably at least
6%, and most preferably at least 8%. In one preferred embodiment,
the amount of crosslinker(s) is no more than 30%, more preferably
no more than 20%, and most preferably no more than 15%. The resin
of this invention may include residues of more than one
monoethylenically unsaturated monomer and/or more than one
crosslinker.
[0010] In one embodiment of the invention, the resin is a highly
crosslinked material made from a mixture of monoethylenically
unsaturated monomers and crosslinkers that is at least 80%
crosslinker(s), based on the total weight of monomers and
crosslinkers. A highly crosslinked resin, even one that is made
from 100% crosslinker, and no monoethylenically unsaturated
monomer, can be hydrolyzed in the presence of a porogen to produce
a resin having carboxylic acid functionality, provided that the
crosslinker is one having ester functionality, e.g., a di- or
tri-(meth)acrylate. In such a case, the polymer will be degraded
slightly where the ester groups have been hydrolyzed to produce
carboxylic acid functionality.
[0011] Macroporous resins are those having a surface area from 5
m.sup.2/g to 2000 m.sup.2/g, and an average pore diameter of at
least 1.5 nm. Preferably, macroporous resin beads have an average
particle size from 10 .mu.m to 900 .mu.m, more preferably from 100
.mu.m to 500 .mu.m. Macroporous resin beads are not comprised of
aggregates of clusters of smaller particles, but are substantially
spherical in shape. Preferably, particle size is measured in the
unswollen condition, i.e., before any neutralization to raise the
pH to 6 or higher. The macroporous acrylic resin beads in the
present invention preferably are produced by a suspension
polymerization. A typical bead preparation, for example, may
include preparation of a continuous aqueous phase solution
containing typical suspension aids, for example, dispersants,
protective colloids and buffers. Preferably, to aid in production
of relatively small beads, a surfactant is included in the aqueous
solution, preferably a sodium alkyl sulfate surfactant. A stable
dispersion of the organic phase, i.e., the monomer(s), crosslinker,
organic solvent if present, can be produced by several known
methods, including jetting (see U.S. Pat. No. 4,444,961), seed
expansion technology (see U.S. Pub. No. 2003/0109657), and vigorous
agitation of the two-phase mixture. After the dispersion is formed,
agitation is maintained during the polymerization process. The
aqueous solution is combined with a mixture containing at least one
monoethylenically unsaturated monomer and/or at least one
crosslinker, and at least one free-radical initiator. Preferably,
the total initiator level is from 0.25 mole percent to 2 mole %,
based on the total monomer charge, preferably from 0.4 mole percent
to 1.5 mole percent, more preferably from 0.4 mole percent to 1
mole percent, and most preferably from 0.5 mole percent to 0.8 mole
percent. The mixture of monomers is then polymerized at elevated
temperature. Preferably, the polymerization is continued for a time
sufficient to reduce the unreacted vinyl monomer content to less
than 1% of the starting amount.
[0012] Polymerization initiators useful in the present invention
include monomer-soluble initiators such as peroxides,
hydroperoxides, peroxyesters and related initiators; for example
benzoyl peroxide (BPO), tert-butyl hydroperoxide, cumene peroxide,
tetralin peroxide, acetyl peroxide, caproyl peroxide, tert-butyl
peroctoate (also known as tert-butylperoxy-2-ethylhexanoate), tert
amyl peroctoate, tert-butyl perbenzoate, tert-butyl diperphthalate,
dicyclohexyl peroxydicarbonate,
di(4-tert-butylcyclohexyl)peroxydicarbonate, methyl ethyl ketone
peroxide and methylated polyethyleneimine. Also useful are azo
initiators such as azodiisobutyronitrile, azodiisobutyramide, 2,2'
azo-bis(2,4-dimethylvaleronitrile),
azo-bis(.alpha.-methyl-butyronitrile) and dimethyl-, diethyl- or
dibutyl azo-bis(methylvalerate). Preferred peroxide initiators are
diacyl peroxides, such as benzoyl peroxide, and peroxyesters, such
as tert-butyl peroctoate and tert-butyl perbenzoate.
[0013] Dispersants and suspending agents useful in the present
invention include nonionic surfactants having a
hydroxyalkylcellulose backbone, a hydrophobic alkyl side chain
containing from 1 to 24 carbon atoms, and an average of from 1 to
8, preferably from 1 to 5, ethylene oxide groups substituting each
repeating unit of the hydroxyalkyl-cellulose backbone, the alkyl
side chains being present at a level of 0.1 to 10 alkyl groups per
100 repeating units in the hydroxyalkylcellulose backbone. The
alkyl group in the hydroxyalkylcellulose may contain from 1 to 24
carbons, and may be linear, branched or cyclic. More preferred is a
hydroxyethylcellulose containing from 0.1 to 10 (C.sub.16)alkyl
side chains per 100 anhydroglucose units and from about 2.5 to 4
ethylene oxide groups substituting each anhydroglucose unit. Other
examples of dispersants include polyvinyl alcohol, methyl
cellulose, starch, modified starch, hydrolyzed ethylene-maleic
anhydride polymers, hydrolyzed styrene-maleic anhydride polymers,
acrylamide-sodium acrylate polymers, and polyvinylimidazoline
polymers. Typical use levels of dispersants are from about 0.01 to
about 4%, based upon the total aqueous-phase weight.
[0014] The organic solvent which is present in one embodiment of
the method of this invention has a boiling point of at least
70.degree. C.; in one embodiment of the invention, the boiling
point is no higher than 180.degree. C. Preferably, the organic
solvent is a good solvent for the monomers, but not for the
polymer. Preferably, it is not an ethylenically unsaturated
monomer, e.g., a (meth)acrylate, a (meth)acrylic acid, a
(meth)acrylamide, a styrene monomer, or a vinyl alkanoate.
Preferably, the organic solvent is not a carboxylic acid, a
water-soluble solvent (i.e., one having water solubility >10% by
weight), or one which could interfere with polymerization, e.g., an
alkyl thiol. Preferably the organic solvent is selected from among
C.sub.7-C.sub.10 hydrocarbons, C.sub.3-C.sub.10 halogenated
hydrocarbons, C.sub.4-C.sub.10 ketones, C.sub.4-C.sub.10 alcohols,
C.sub.4-C.sub.10 alkyl esters, C.sub.4-C.sub.10 aryl esters,
C.sub.4-C.sub.10 mixed alkyl/aryl esters, and combinations thereof.
Especially preferred solvents include methyl isobutyl ketone
(MIBK), diisobutyl ketone (DIBK), methyl isobutyl carbinol (MIBC),
1,2-dichloropropane, toluene (tol), xylenes, isooctane,
chlorobenzene and n-butyl acetate. Methods for producing resin
beads in the presence of solvents are disclosed, e.g., in U.S. Pat.
No. 4,486,313. An organic solvent present during the polymerization
process is also referred to as a porogen. The amount of solvent
added, as a percentage of the monoethylenically unsaturated
monomers, crosslinkers and solvent, preferably is from 30% to 80%,
more preferably from 35% to 60%.
[0015] In one embodiment of the invention in which at least one
monomer is selected from among acrylonitrile and methacrylic acid,
a macroporous resin can be produced without addition of an organic
solvent to serve as a porogen. In this embodiment, acrylonitrile or
methacrylic acid acts as a porogen. In another embodiment in which
at least one monomer is selected from among C.sub.1-C.sub.4 alkyl
acrylates, preferably an organic solvent is present in the reaction
mixture.
[0016] An acid or base used in the method of this invention is any
acid or base that is water-soluble (at least 20% by weight) and
capable of hydrolyzing carboxylic esters under the conditions
stated herein. Preferably, bases have a pK.sub.a of at least 12,
and acids have a pK.sub.a no greater than 2. Preferred bases are
inorganic hydroxides. An inorganic hydroxide base can be any
readily water-soluble hydroxide-containing compound, preferably an
alkali metal hydroxide or a quaternary ammonium hydroxide, and most
preferably sodium or potassium hydroxide. Preferred acids are
sulfuric acid and hydrochloric acid.
[0017] It has been found that, unexpectedly, one can perform the
hydrolysis after the polymerization is complete in the
polymerization liquor (aqueous solution) itself, without separating
the resin beads from the aqueous liquor or from the organic
solvent, if one was used. Preferably, most of the liquor still is
present during the hydrolysis. In some instances it may be
desirable to drain some of the liquor. In one embodiment of the
invention, at least 50% of the aqueous solution is present during
hydrolysis, more preferably at least 75%, more preferably at least
90%, and most preferably substantially all of the aqueous solution
remains. In one embodiment of the invention, some of the porogen
and some of the water of the dispersing phase are removed by
distillation, followed by addition of caustic and heating for some
period of time at elevated temperatures. This improved process
saves cycle time and resources as there is no washing or draining
between polymerization and hydrolysis. The water from the
polymerization aqueous phase is conserved and combined with acid or
base to form the hydrolysis liquor in the polymerization vessel in
the presence of the resin beads. Another advantage is that by
diluting the acid or base in the vessel, heat is generated which
reduces energy usage required to reach the hydrolysis reaction
temperature and for the distillation of porogen if required. There
is also less attrition on the beads and less chance for cross
contamination with the reduced handling.
[0018] In one embodiment of the invention, the hydrolysis is
performed concurrently with distillation of the porogen as one
step. In this process, at the end of the polymerization base (or
acid) is added to the reaction mixture containing the porogen-laden
polymer beads and heated to distillation temperature. The porogen
is distilled without removing the bulk of the aqueous solution.
Preferably, at least 50% of the aqueous solution remains in the
reactor during distillation, more preferably at least 75%, more
preferably at least 90%, and most preferably substantially all of
the aqueous solution remains. In some instances, a multi-phase
system is visible as the process progresses and the resin becomes
converted because the porogen is expelled during the hydrolysis.
Optionally at this point, when the separate porogen phase is noted
(typically at the top of the reaction medium) and the resin has
become more dense than the hydrolysis media, the resin may be
washed in upflow mode to remove the porogen and avoid the bulk of
the distillation.
[0019] In one embodiment of the invention, at least 50% of the
porogen remains at the beginning of the hydrolysis. Preferably, at
least 75% of the porogen remains, more preferably at least 90%. In
this embodiment, the aqueous phase optionally remains during
distillation, as described above, or the aqueous phase is removed,
but without removing porogen, which appears as a separate
phase.
[0020] Preferred conditions for hydrolysis are a temperature in the
range from 80.degree. C. to 110.degree. C., more preferably from
85.degree. C. to 105.degree. C. Hydrolysis time should be
sufficient for conversion of at least 99% of the ester groups to
carboxylic acid groups. Typical times are from 3 hours to 15 hours,
preferably from 5 hours to 10 hours. When porogen is being
distilled concurrently with hydrolysis, times may be longer to
allow more complete removal of porogen.
[0021] In one embodiment of the invention, distillation of porogen
is continued until at least 80% of the porogen has been removed
from the reaction mixture, most preferably until at least 95% of
the porogen has been removed. Times and temperatures vary
considerably depending on the pressure at which distillation
occurs. Typically, the temperature is increases steadily during
distillation as lower-boiling azeotropes distill from the mixture.
Preferred conditions for distillation of porogen prior to
hydrolysis are a temperature in the range from 50.degree. C. to
130.degree. C., more preferably from 60.degree. C. to 110.degree.
C. Typical times are from 3 hours to 15 hours, preferably from 5
hours to 10 hours. Of course, if porogen separates from the aqueous
phase and is removed mechanically, as described above, the
distillation times would be shorter.
[0022] In one embodiment of the invention, a hydrophobic organic
solvent is used as a porogen, and said hydrophobic solvent slows
hydrolysis of ester or nitrile groups in the resin bead. In this
embodiment, only the ester or nitrile groups near the outside of
the resin bead are hydrolyzed. Hydrophobic solvents are those
organic solvents defined herein as suitable porogens, with the
exception of alcohols, amines and esters. Examples of hydrophobic
solvents include, e.g., C.sub.7-C.sub.10 hydrocarbons,
C.sub.3-C.sub.10 halogenated hydrocarbons, C.sub.4-C.sub.10
ketones, and combinations thereof Preferred hydrophobic solvents
include, e.g., toluene, 1,2-dichloropropane, xylene and isooctane.
This produces a macroporous resin bead having a "core-shell"
structure, i.e., one in which the polymer at the center of the bead
differs significantly in composition from the polymer at the
surface of the bead. In core-shell beads, the core is a roughly
spherical region surrounded by a shell. In this particular case,
the polymer at or near the surface of the bead has carboxylic acid
groups, while the polymer at or near the center is substantially
free of carboxylic acid groups, i.e., it has less than 1%
carboxylic acid groups by weight. The polymer at or near the center
of the bead has nitrile or ester groups. Preferably, at least 90%
of the carboxylic acid groups in the bead are in the shell region,
more preferably at least 95%, and most preferably at least 99%.
Preferably, the shell region comprises no more than 50% of the bead
by volume, more preferably no more than 30%. Preferably, the shell
region comprises at least 5% of the bead by volume, more preferably
at least 10%. The size of the shell region can be controlled
through selection of the porogen and by varying the hydrolysis
conditions. The size of the shell can be increased by use of more
rigorous hydrolysis conditions, and also by use of a less
hydrophobic solvent as a porogen.
EXAMPLES
[0023] Polymerizations were conducted using the following
systems:
TABLE-US-00001 Temp Monomer DVB % Porogen (%) Dispersant Initiator
(.degree. C.) 1 MA 12 TOL (45) MHEC.sup.1 1% BPO 70 2 MA 12 MIBK
(45) MHEC 1% BPO 70 3 MA 10 MIBK (45) PADMAC/ 1% BPO 70
Pharmagel.sup.2 4 MA 12 MIBC (45) MHEC 1% BPO 70 5 MA 12 DIBK (45)
MHEC 1% BPO 70 .sup.1Methyl hydroxyethyl cellulose .sup.2PADMAC is
a polyquaternary ammonium salt; Pharmagel is a gelatin
material.
[0024] Four schemes for performing the hydrolysis and strip of the
resulting copolymer were used, as follows:
TABLE-US-00002 A Standard/traditional
Polymerize.fwdarw.strip.fwdarw.wash.fwdarw.hydrolyze.fwdarw.
procedure wash B No washing after
Polymerize.fwdarw.strip.fwdarw.hydrolyze.fwdarw.wash polymerization
C Low temperature Polymerize.fwdarw.strip/hydrolyze.fwdarw.wash
hydro-strip D High temperature hydro-
Polymerize.fwdarw.strip/hydrolyze.fwdarw.wash strip
Example 1
Standard Procedure with Washing
[0025] A mixture of 178.1 g methyl acrylate, 41.9 g divinylbenzene
(63% active ingredient), 180.0 g toluene, and 2.82 g benzoyl
peroxide (78% active ingredient) was charged to a 2 L round bottom
flask containing an aqueous solution of 0.60 g methyl hydroxyethyl
cellulose, 3.60 g boric acid, 1.8 g of 50% sodium hydroxide, and
594.0 g deionized water. The aqueous solution was adjusted to a pH
of 9 with small amounts of additional boric acid and sodium
hydroxide. The mixture was agitated until a stable dispersion of
organic droplets had formed in the aqueous phase and then the
mixture was heated to 70.degree. C. for 8 hours.
[0026] The resulting copolymer beads and reaction mixture was then
split in half and each half was distilled at temperatures ranging
from 90-100.degree. C. to remove the toluene porogen from the
beads. The distillation was performed until no further toluene was
evident in the distillate receiver. The resulting toluene
recoveries were 91% and 92% for the two halves of the batch.
[0027] The first half of the batch was then removed from the
reactor and transferred to a Buchner funnel where the remaining
liquid reaction mixture was drained and the beads subsequently
washed with four bed volumes of water. The beads were then returned
to the reactor with 491 g of water. The mixture was agitated and
327.4 g of 50% sodium hydroxide was added. The resulting mixture
was then heated to 93.degree. C. for seven hours during which time
the resin beads were hydrolyzed to the sodium salt form of the
carboxylic acid. The resin was then washed with water and converted
to the hydrogen form using 10% sulfuric acid. The percent volume
change (decrease) of the resin from the sodium form to the hydrogen
form was 54%. The resulting moisture holding capacity (MHC) of this
resin was 57.9% and the weight and volume capacities were 9.78 eq/L
and 2.94 eq/L, respectively.
Example 2
Standard Procedure without Washing
[0028] The second half of the batch from Example 1 was returned to
the reactor without the water washing step and the caustic
hydrolysis performed as in that example. Subsequent to the
hydrolysis the resin was washed and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 55%. The
resulting moisture holding capacity (MHC) of this resin was 59.9%
and the weight and volume capacities were 10.08 eq/L and 2.90 eq/L,
respectively.
Example 3
Low Temperature Hydrostrip
[0029] A mixture of 178.1 g methyl acrylate, 41.9 g divinylbenzene
(63% active ingredient), 180.0 g toluene, and 2.82 g benzoyl
peroxide (78% active ingredient) was charged to a 2 L round bottom
flask containing an aqueous solution of 0.60 g methyl hydroxyethyl
cellulose, 3.60 g boric acid, 1.8 g of 50% sodium hydroxide, and
594.0 g deionized water. The aqueous solution was adjusted to a pH
of 9 with small amounts of additional boric acid and sodium
hydroxide. The mixture was agitated until a stable dispersion of
organic droplets had formed in the aqueous phase and then the
mixture was heated to 70.degree. C. for 8 hours. The resulting
copolymer beads and reaction mixture was then split in half.
[0030] The first half of the batch was then immediately hydrolyzed
with 327.4 g of 50% sodium hydroxide without first removing the
porogen from the resin in a distillation step. The reaction mixture
was heated to 93 .degree. C. and held for seven hours. During the
hydrolysis a small amount of a two-phase liquid mixture collected
in the distillate trap. The liquid phases were separated using a
separatory funnel and consisted of 6.7 g toluene (corresponds to 7%
recovery) and 1.7 g of an aqueous layer. The resulting beads were
observed using an optical microscope and it was found that the
beads had a core-shell appearance. The shell was approximately 10
.mu.m thick and was due to only the outer region of the beads being
hydrolyzed. The core of the beads were not hydrolyzed and still
contained toluene.
[0031] This mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid consisted of a single
aqueous phase and no toluene was recovered from the reaction
mixture. The resin was then washed with water and returned to the
reactor and distilled. During this distillation an additional 61.4
g of toluene was recovered (corresponding to a total toluene
recovery of 76%).
[0032] The resin was then washed with water and converted to the
hydrogen form using 10% sulfuric acid. The percent volume change
(decrease) of the resin from the sodium form to the hydrogen form
was 20%. The resulting moisture holding capacity (MHC) of this
resin was 60.1% and the weight and volume capacities were 5.14 eq/L
and 1.51 eq/L, respectively.
Example 4
High Temperature Hydrostrip
[0033] The second half of the batch from Example 3 was returned to
the reactor and the caustic hydrolysis performed as in that example
although at more elevated temperature. After initially reaching
93.degree. C. the temperature was increased to drive the
distillation of porogen concurrently with the hydrolysis. Over the
seven hours of the experiment the maximum temperature achieved was
105.degree. C. The distillate composition after the combined
hydrolysis-distillation was 20.0 g toluene (22% recovery) and 28.2
g aqueous. These beads also had the core-shell appearance described
in Example 3 although in this case the shell was larger
(approximately 25 .mu.m). This mixture was then transferred to a
Buchner funnel and the liquid drained. The drained liquid consisted
of a single aqueous phase and no toluene was recovered from the
reaction mixture. The resin was then washed with water and returned
to the reactor and distilled. During this distillation an
additional 52.0 g of toluene was recovered (total toluene recovery
of 80%).
[0034] The resin was washed and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 32%. The
resulting moisture holding capacity (MHC) of this resin was 61.9%
and the weight and volume capacities were 6.62 eq/L and 1.85 eq/L,
respectively.
Example 5
Standard Procedure with Washing
[0035] A mixture of 178.1 g methyl acrylate, 41.9 g divinylbenzene
(63% active ingredient), 180.0 g methyl isobutyl ketone (MIBK), and
2.82 g benzoyl peroxide (78% active ingredient) was charged to a 2
L round bottom flask containing an aqueous solution of 0.60 g
methyl hydroxyethyl cellulose, 3.60 g boric acid, 1.8 g of 50%
sodium hydroxide, and 594.0 g deionized water. The aqueous solution
was adjusted to a pH of 9 with small amounts of additional boric
acid and sodium hydroxide. The mixture was agitated until a stable
dispersion of organic droplets had formed in the aqueous phase and
then the mixture was heated to 70.degree. C. for 8 hours.
[0036] The resulting copolymer beads and reaction mixture was then
split in half and each half was distilled at temperatures ranging
from 90-100.degree. C. to remove the MIBK porogen from the beads.
The distillation was performed until no further MIBK was evident in
the distillate receiver. The resulting MIBK recoveries were 93% and
90% for the two halves of the batch.
[0037] The first half of the batch was then removed from the
reactor and transferred to a Buchner funnel where the remaining
liquid reaction mixture was drained and the beads subsequently
washed with four bed volumes of water. The beads were then returned
to the reactor with 491 g of water. The mixture was agitated and
327.4 g of 50% sodium hydroxide was added. The resulting mixture
was then heated to 93.degree. C. for seven hours during which time
the resin beads were hydrolyzed to the sodium salt form of the
carboxylic acid. The resin was then washed with water and converted
to the hydrogen form using 10% sulfuric acid. The percent volume
change (decrease) of the resin from the sodium form to the hydrogen
form was 57%. The resulting moisture holding capacity (MHC) of this
resin was 64.3% and the weight and volume capacities were 9.36 eq/L
and 2.46 eq/L, respectively.
Example 6
Standard Procedure without Washing
[0038] The second half of the batch from Example 5 was returned to
the reactor without the water washing step and the caustic
hydrolysis performed as in that example. Subsequent to the
hydrolysis the resin was washed and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 54%. The
resulting moisture holding capacity (MHC) of this resin was 63.5%
and the weight and volume capacities were 9.62 eq/L and 2.58 eq/L,
respectively.
Example 7
Low Temperature Hydrostrip
[0039] A mixture of 178.1 g methyl acrylate, 41.9 g divinylbenzene
(63% active ingredient), 180.0 g MIBK, and 2.82 g benzoyl peroxide
(78% active ingredient) was charged to a 2 L round bottom flask
containing an aqueous solution of 0.60 g methyl hydroxyethyl
cellulose, 3.60 g boric acid, 1.8 g of 50% sodium hydroxide, and
594.0 g deionized water. The aqueous solution was adjusted to a pH
of 9 with small amounts of additional boric acid and sodium
hydroxide. The mixture was agitated until a stable dispersion of
organic droplets had formed in the aqueous phase and then the
mixture was heated to 70.degree. C. for 8 hours. The resulting
copolymer beads and reaction mixture was then split in half.
[0040] The first half of the batch was then immediately hydrolyzed
with 327.4 g of 50% sodium hydroxide without first removing the
porogen from the resin in a distillation step. The reaction mixture
was heated to 93.degree. C. and held for seven hours. During the
hydrolysis a two-phase liquid mixture collected in the distillate
trap. The liquid phases were separated using a separatory funnel
and consisted of 74.0 g MIBK (corresponds to 82% recovery) and 14.7
g of an aqueous layer. The resulting beads were observed using an
optical microscope and the beads were opaque and had a uniform
appearance (no core-shell structure evident).
[0041] This mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid consisted of a single
aqueous phase and no MIBK was recovered from the reaction mixture.
The resin was then washed with water and returned to the reactor
and distilled. During this distillation an additional 4.6 g of MIBK
was recovered (corresponding to a total MIBK recovery of 87%).
[0042] The resin was then washed with water and converted to the
hydrogen form using 10% sulfuric acid. The percent volume change
(decrease) of the resin from the sodium form to the hydrogen form
was 54%. The resulting moisture holding capacity (MHC) of this
resin was 64.6% and the weight and volume capacities were 9.63 eq/L
and 2.50 eq/L, respectively.
Example 8
High Temperature Hydrostrip
[0043] The second half of the batch from Example 7 was returned to
the reactor and the caustic hydrolysis performed as in that example
although at more elevated temperature. After initially reaching
93.degree. C. the temperature was increased to drive the
distillation of porogen concurrently with the hydrolysis. Over the
seven hours of the experiment the maximum temperature achieved was
105.degree. C. The distillate composition after the combined
hydrolysis-distillation was 94.0 g MIBK (100% recovery) and 38.9 g
aqueous. The beads were opaque and of uniform appearance as in
Example 7. The mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid consisted of a single
aqueous phase and no MIBK was recovered from the reaction mixture.
The resin was then washed with water and returned to the reactor
and distilled. During this distillation no additional MIBK was
recovered.
[0044] The resin was washed and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 54%. The
resulting moisture holding capacity (MHC) of this resin was 64.7%
and the weight and volume capacities were 9.88 eq/L and 2.56 eq/L,
respectively.
Example 9
Low Temperature Hydrostrip
[0045] A mixture of 185.1 g methyl acrylate, 34.9 g divinylbenzene
(63% active ingredient), 180.0 g MIBK, and 2.82 g benzoyl peroxide
(78% active ingredient) was charged to a 2 L round bottom flask
containing an aqueous solution of 1.1 g Pharmagel, 8.5 g Padmac A,
and 594.0 g deionized water. The aqueous solution was adjusted to a
pH of 9 with small amounts of boric acid and 50% sodium hydroxide.
The mixture was agitated until a stable dispersion of organic
droplets had formed in the aqueous phase and then the mixture was
heated to 70.degree. C. for 8 hours. The resulting copolymer beads
and reaction mixture was then split in half.
[0046] The first half of the batch was then immediately hydrolyzed
with 327.4 g of 50% sodium hydroxide without first removing the
porogen from the resin in a distillation step. The reaction mixture
was heated to 93.degree. C. and held for seven hours. During the
hydrolysis a two-phase liquid mixture collected in the distillate
trap. The liquid phases were separated using a separatory funnel
and consisted of 86.9 g MIBK (corresponds to 97% recovery) and 18.3
g of an aqueous layer. The resulting beads were observed using an
optical microscope and the beads were opaque and had a uniform
appearance.
[0047] This mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid consisted of a single
aqueous phase and no MIBK was recovered from the reaction mixture.
The resin was then washed with water and returned to the reactor
and distilled. During this distillation an additional 4.1 g of MIBK
was recovered (corresponding to a total MIBK recovery of 100%).
[0048] The resin was then washed with water and converted to the
hydrogen form using 10% sulfuric acid. The percent volume change
(decrease) of the resin from the sodium form to the hydrogen form
was 61%. The resulting moisture holding capacity (MHC) of this
resin was 68.6% and the weight and volume capacities were 10.78
eq/L and 1.95 eq/L, respectively.
Example 10
High Temperature Hydrostrip
[0049] The second half of the batch from Example 9 was returned to
the reactor and the caustic hydrolysis performed as in that example
although at more elevated temperature. After initially reaching
93.degree. C. the temperature was increased to drive the
distillation of porogen concurrently with the hydrolysis. Over the
seven hours of the experiment the maximum temperature achieved was
105.degree. C. The distillate composition after the combined
hydrolysis-distillation was 80.5 g MIBK (89% recovery) and 126.0 g
aqueous. The beads were opaque and of uniform appearance as in
Example 9. The mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid consisted of a single
aqueous phase and no MIBK was recovered from the reaction mixture.
The resin was then washed with water and returned to the reactor
and distilled. During this distillation no additional MIBK was
recovered.
[0050] The resin was washed and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 61%. The
resulting moisture holding capacity (MHC) of this resin was 69.2%
and the weight and volume capacities were 10.98 eq/L and 1.82 eq/L,
respectively.
Example 11
Standard Procedure without Washing
[0051] A mixture of 178.1 g methyl acrylate, 41.9g divinylbenzene
(63% active ingredient), 180.0 g methyl isobutyl carbinol (MIBC),
and 2.82 g benzoyl peroxide (78% active ingredient) was charged to
a 2 L round bottom flask containing an aqueous solution of 0.60 g
methyl hydroxyethyl cellulose, 3.60 g boric acid, 1.8 g of 50%
sodium hydroxide, and 594.0 g deionized water. The aqueous solution
was adjusted to a pH of 9 with small amounts of additional boric
acid and sodium hydroxide. The mixture was agitated until a stable
dispersion of organic droplets had formed in the aqueous phase and
then the mixture was heated to 70.degree. C. for 8 hours.
[0052] The resulting copolymer beads and reaction mixture was then
split in half. The first half was distilled at temperatures ranging
from 90-100.degree. C. to remove the MIBC porogen from the beads.
The distillation was performed until no further MIBC was recovered
in the distillate receiver. The resulting MIBC recovery was
95%.
[0053] The caustic hydrolysis was then performed by adjusting the
water content in the reactor to 491 g and adding 327.4 g of 50%
sodium hydroxide. The resulting mixture was then mixed and heated
to 93.degree. C. for seven hours during which time the resin beads
were hydrolyzed to the sodium salt form of the carboxylic acid. The
resin was then washed with water and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 43%. The
resulting moisture holding capacity (MHC) of this resin was 71.4%
and the weight and volume capacities were 8.74 eq/L and 1.70 eq/L,
respectively.
Example 12
Low Temperature Hydrostrip
[0054] The second half of the batch from Example 11 was hydrolyzed
with 327.4 g of 50% sodium hydroxide without first removing the
porogen from the resin in a distillation step. The reaction mixture
was heated to 93.degree. C. and held for seven hours. During the
hydrolysis no liquid was recovered in the distillate receiver. The
resulting beads were observed using an optical microscope and no
core-shell appearance was evident.
[0055] This mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid contained small droplets of
MIBC dispersed throughout the aqueous phase and could not be
separated and quantified. The resin was then washed with water and
returned to the reactor and distilled until no additional MIBC was
observed to collect in the distillate receiver. During this
distillation 25.6 g of MIBC was recovered (corresponding to a total
MIBC recovery of 29%). By difference, the remaining 71% of the MIBC
was driven from the beads during the hydrolysis.
[0056] The resin was then washed with water and converted to the
hydrogen form using 10% sulfuric acid. The percent volume change
(decrease) of the resin from the sodium form to the hydrogen form
was 42%. The resulting moisture holding capacity (MHC) of this
resin was 71.5% and the weight and volume capacities were 8.68 eq/L
and 1.73 eq/L, respectively.
Example 13
Standard Procedure without Washing
[0057] A mixture of 178.1 g methyl acrylate, 41.9 g divinylbenzene
(63% active ingredient), 180.0 g diisobutyl ketone (DIBK), and 2.82
g benzoyl peroxide (78% active ingredient) was charged to a 2 L
round bottom flask containing an aqueous solution of 0.60 g methyl
hydroxyethyl cellulose, 3.60 g boric acid, 1.8 g of 50% sodium
hydroxide, and 594.0 g deionized water. The aqueous solution was
adjusted to a pH of 9 with small amounts of additional boric acid
and sodium hydroxide. The mixture was agitated until a stable
dispersion of organic droplets had formed in the aqueous phase and
then the mixture was heated to 70.degree. C. for 8 hours.
[0058] The resulting copolymer beads and reaction mixture was then
split in half. The first half was distilled at temperatures ranging
from 90-100.degree. C. to remove the DIBK porogen from the beads.
The distillation was performed until no further DIBK was recovered
in the distillate receiver. The resulting DIBK recovery was
92%.
[0059] The caustic hydrolysis was then performed by adjusting the
water content in the reactor to 491 g and adding 327.4 g of 50%
sodium hydroxide. The resulting mixture was then mixed and heated
to 93.degree. C. for seven hours during which time the resin beads
were hydrolyzed to the sodium salt form of the carboxylic acid. The
resin was then washed with water and converted to the hydrogen form
using 10% sulfuric acid. The percent volume change (decrease) of
the resin from the sodium form to the hydrogen form was 47%. The
resulting moisture holding capacity (MHC) of this resin was 69.7%
and the weight and volume capacities were 9.76 eq/L and 2.17 eq/L,
respectively.
Example 14
Low Temperature Hydrostrip
[0060] The second half of the batch from Example 13 was hydrolyzed
with 327.4 g of 50% sodium hydroxide without first removing the
porogen from the resin in a distillation step. The reaction mixture
was heated to 93.degree. C. and held for seven hours. During the
hydrolysis no liquid was recovered in the distillate receiver. The
resulting beads were observed using an optical microscope and a
core-shell appearance was evident. This core was observed to
decrease in diameter with time during the hydrolysis but a
significant core remained unhydrolyzed at the end of the seven hour
hold.
[0061] This mixture was then transferred to a Buchner funnel and
the liquid drained. The drained liquid contained 41.3 g DIBK. The
resin was then washed with water and returned to the reactor and
distilled until no additional DIBK was observed to collect in the
distillate receiver. During this distillation 21.8 g of DIBK was
recovered (corresponding to a total DIBK recovery of 24%). By
difference, the remaining 76% of the DIBK was driven from the beads
during the hydrolysis.
[0062] The resin was then washed with water and converted to the
hydrogen form using 10% sulfuric acid. The percent volume change
(decrease) of the resin from the sodium form to the hydrogen form
was 47%. The resulting moisture holding capacity (MHC) of this
resin was 69.4% and the weight and volume capacities were 9.29 eq/L
and 2.04 eq/L, respectively.
MHC and Capacity Results
TABLE-US-00003 [0063] vol. por. wt. cap. cap. Ex. mon. (45%) DVB
disp scheme MHC eq./kg eq./L 1 MA tol 12% MHEC A 57.9 9.78 2.94 2
MA tol 12% MHEC B 59.9 10.08 2.90 3 MA tol 12% MHEC C 60.1 5.14
1.51 4 MA tol 12% MHEC D 61.9 6.62 1.85 5 MA MIBK 12% MHEC A 64.3
9.36 2.46 6 MA MIBK 12% MHEC B 63.5 9.62 2.58 7 MA MIBK 12% MHEC C
64.6 9.63 2.50 8 MA MIBK 12% MHEC D 64.7 9.88 2.56 9 MA MIBK 10%
note 1 C 68.6 10.78 1.95 10 MA MIBK 10% note 1 D 69.2 10.98 1.82 11
MA MIBC 12 MHEC B 71.4 8.74 1.70 12 MA MIBC 12 MHEC C 71.5 8.68
1.73 13 MA DIBK 12 MHEC B 69.7 9.76 2.17 14 MA DIBK 12 MHEC C 69.4
9.29 2.04 1. PADMAC/Pharmagel
Volume Change Upon Acid Conversion Results
TABLE-US-00004 [0064] por. V.sub.i V.sub.f .DELTA.V/V.sub.i Ex.
mon. (45%) DVB disp scheme (mL) (mL) (%) 1 MA tol 12% MHEC A 100 46
54 2 MA tol 12% MHEC B 100 45 55 3 MA tol 12% MHEC C 100 80 20 4 MA
tol 12% MHEC D 100 68 32 5 MA MIBK 12% MHEC A 100 43 57 6 MA MIBK
12% MHEC B 100 46 54 7 MA MIBK 12% MHEC C 100 46 54 8 MA MIBK 12%
MHEC D 100 46 54 9 MA MIBK 10% note 1 C 79 31 61 10 MA MIBK 10%
note 1 D 79 31 61 11 MA MIBC 12 MHEC B 100 57 43 12 MA MIBC 12 MHEC
C 100 58 42 13 MA DIBK 12 MHEC B 100 53 47 14 MA DIBK 12 MHEC C 100
54 46 1. PADMAC/Pharmagel
Structure of Core-Shell Resin Beads
[0065] Analysis by SEM--Core-shell beads made according to the
method of this invention were analyzed with a scanning electron
microscope to determine shell thickness and location of carboxylic
acid functionality. Samples were cut in half with a razor and
mounted on an aluminum stub with carbon tape, and given a light
carbon coating. X-ray maps of the cross-sections were collected on
a JEOL JSM-840 Scanning Electron Microscope equipped with a
Princeton Gamma Tech Imix Energy Dispersive Spectrometer. The
operating conditions of the microscope were as follows:
accelerating voltage, 20 KeV; probe current, 6.times.10.sup.-9 amp.
The maps were collected for 1800 seconds at the 256 pixel setting
in the PGT software.
[0066] Beads made according to Examples 3 and 4, with toluene as
the porogen, were analyzed. Beads from Example 3 had a shell
thickness of approximately 10 .mu.m (0.0016 mm.sup.3, 9.2% of total
bead volume of 0.0173 mm.sup.3). Of two sizes of beads analyzed
from Example 4, a larger bead had a shell thickness of
approximately 15-20 .mu.m (0.0053 mm.sup.3, 18.6% of total bead
volume of 0.0283 mm.sup.3); and two smaller beads with the same
shell thickness had an average shell volume of 0.00117 mm.sup.3,
24% of total average bead volume of 0.00485 mm.sup.3. In each case,
the sodium ions associated with the carboxylic acid groups appeared
only in the shell volume.
[0067] Analysis by visual microscopy--Samples from hydrolysis were
placed onto covered microscope plates with deionized water. The
resin was observed with a Zeiss Stemi 2000 C microscope. The
magnification was varied until the growing shell could be seen
clearly. Photos were obtained using a camera integrated into the
microscope and printed with 200 .mu.m calipers in the image to
assist in determining shell and core thickness. Samples of beads
made with MIBK as the porogen were hydrolyzed with MIBK still
present in the beads, and examined visually at different hydrolysis
times. The shell thickness as a function of time is shown in the
following table. The average particle size of the beads increased
from 181 .mu.m to 306 .mu.m during hydrolysis.
TABLE-US-00005 shell hydrolysis time, thickness, .mu.m minutes Ex.
9 Ex. 10 0 0 0 30 21 31 45 42 63 60 50 63 90 63 92 120 93 118 180
143
[0068] These results indicate that the shell thickness can be
controlled according to the choice of porogen and the hydrolysis
conditions.
* * * * *