Note: Descriptions are shown in the official language in which they were submitted.
1~14~ ~
This invention is directed to ion exchange resins
of exceptional physical strength and form and method of
preparing the same. More specifically, superior ion
exchange resins are prepared by utilizing as polymerization
catalysts a specific group of peroxyester and peroxydicar-
bonate catalysts in the polymerization of monomers to form
ion exchange beads.
The techniques of preparing crosslinked vinyl
copolymers in bead form (as precursors for conversion
into ion exchange resins) by free-radical catalyzed polymer-
ization of the monomer mixture in aqueous dispersion are
well known. The term "crosslinked vinyl copolymer" and the
like is used for the sake of brevity herein to signify coply-
mers of a major proportion, e.g., from 50 upwards to about
99.5 mole percent, preferably 80 to 99%, of a monovinyl
monomer, for example, monovinyl aromatic monomers, e.g.,
styrene, vinyl, toluene, vinyl naphthalene, ethyl vinyl benzene,
vinyl chlorobenzene, chloromethyl styrene, and the like,
and esters of acrylic and methacrylic acid, e.g., methyl
acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate,
butyl acrylate, tert-butyl acrylate, ethyl hexyl acrylate,
cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate,
phenyl acrylate, alkyl phenyl acrylate, ethoxymethyl acrylate,
ethoxypropyl acrylate, propoxypropyl acrylate, ethoxyphenyl
acrylate, ethoxybenzyl acrylate, ethoxycyclohexylacrylate,
and the corresponding esters of methacrylic acid, with a
minor proportion, e.g., of from about 0.5 up to 50 mole
percent, preferably 1 to 20% of polyvinyl compounds having
at least two active vinyl groups polymerizable with the afore-
said monovinyl monomer to form a crosslinked, insoluble,
--2--
1~14~
infusible copolymer, said polyvinyl compounds being, for
example, divinyl benzene, trimethylolpropane trimethacrylate,
ethylene glycol dimethacrylate, divinyl toluene, trivinyl
benzene, divinyl chlorobenzene, diallyl phthalate,
divinylpyridine, divinylnaphthalene, ethylene glycol di-
acrylate, neopentyl glycol dimethacrylate, diethylene
glycol divinylether, bisphenol-A-dimethacrylate, pentaerythri-
tol tetra- and trimethacrylates, divinylxylene, divinyl-
ethylbenzene, divinyl sulfone, divinyl ketone, divinyl sul-
fide, allyl acrylate, diallyl maleate, diallyl fumarate,
diallyl succinate, diallyl carbonate, diallyl malonate,
diallyl oxalate, diallyl adipate, diallyl sebacate, divinyl
sebacate, diallyl tartrate, diallyl silicate, triallyl tri-
carballylate, triallyl aconitate, triallyl citrate, triallyl
phosphate, N,N'-methylenediacrylamide, N,NI-methylene dimeth-
acrylamide, N,N'-ethylene-diacrylamide, trivinyl naphthalene,
polyvinyl anthracenes and the polyallyl and polyvinyl ethers
of glycol, glycerol, pentaerythritol, resorcinol and the mono-
thio and dithio derivatives of glycols. The copolymer may -: -
2Q also have incorporated therein polymerized units of up to
- about 5 mole ~ of other vinyl monomers which do not affect
the basic nature of the resin matrix, for example methyl acry- ~:;
late, acrylonitrile, butadiene and others known in the art.
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 deficien-
- cies resulting from physical weaknesses.
: The practice of the present invention yields ion
exchange resins in which the polymer beads have greater
mechanical strength, improved perfect bead count, and
increased resistance to swelling pressures which are pro-
duced within a bead during acid/base cycling (i.e., osmotic
shock). The greater mechanical strength of the beads mani-
fests 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
stronger ion exchange resins embodied herein are especially
useful in treating fluid streams of high flow rates, for
example, condensate polishing applications in which resins
of lesser quality are prone to mechanical breakdown and short
` life spans.
In copending Canadian Patent Applications, Serial Nos.
296,359 (Dales) and 303,589 (Howell et al) filed February 6,
1978 and May 17, 1978, respectively, it has been
proposed to improve ion exchange resin quality by means of
controlling the oxygen content of the monomer mixture during
polymerization and/or the addition of a "reaction modifier"
to the monomer mixture. The teachings of these copending
Canadian applications may be utilized in combination with
the present invention.
The present invention resides in the finding that
a particular group of peroxy catalysts, not heretofore known
to have advantages in the manufacture of ion exchange polymers,
produce a polymer which, when functionalized, is substan-
~ tially and unexpectedly superior to corresponding materials
- available heretofore. The catalysts which yield these advan-
tages may be characterized generally as peroxyesters and
peroxydicarbonates. The peroxyesters include the alkyl esters
--4--
X
Or peroxycarboxylic acids and the alkylene bis(es~ers)
.Or peroxycarboxylic aclds, which peroxyesters fall within
the general rormula:
o
( Rl-C-O-O ) XR2
wherein Rl is a branched alkyl o~ 3 to 12 carbon atoms and
having a secondary or tertiary carbon linked to the carbonyl.
group;
x is a positive integer having a value of 1 or 2, and
when x is 1, R2 is a branched alkyl radical containing a .
tertiary carbon attached to the oxygen, that is:
C--R ,' '
1 ~ :
wherein R',.R" and R"' are independently selected from linear
or branched lower alkyl, and when x is 2, R2 is an alkylene .
. or aralkylene group, in either case terminating in tertiary
1 carbons attached to the oxygen, that is~
R' R'
---C R"' - C -
- R" R"
wherein R' and R" are as defined above and R"' is a phenylene
or lower alkylene group.
The peroxyester catalysts are presently available
20 commercially under the trademark "Lucidol" (Lucidol Division,)
- Pennwalt Corporation) and are recommended ror vinyl polymer-
izations.
The peroxydicarbonate catalysts useful by the pre-
sent invention fall within the general formula
.. ,`~~` ~
,, ,~
~4~
o o
11 11
Y--OC--O--O--C O- Z
wherein Y and Z are independently selected from lower alkyl,
cycloalkyl, alkyl-substituted cycloalkyl, and aralkyl. These
materials are available commercially from Lucidol Division,
Pennwalt Corporation under the tradenark "Iupersol", and N~y
Chemical Corporation under the trademark "Percadox".
A preferred group of peroxyester catalysts include
t-butyl peroctoate, t-butyl peroxy-2-ethyl-hexanoate,
t-butyl peroxyisobutyrate, t-butyl peroxyneodecanoate, t-amyl
peroctoate, and 2,5-dimethyl-2,5-bis(2-ethyl-hexanoylperoxy)-
hexane.
; A preferred group of peroxydicarbonate catalysts
include, Di(4-t-butylcyclohexyl)peroxydicarbonate, D (sec-
butyl)peroxydicarbonate, Di(2-ethylhexyl)peroxydicarbonate,
Dicetyl peroxydicarbonate, and Dicyclohexyl peroxydlcarbonate.
In accordance with this invention, the vinyl
- monomer, crosslinking monomer and any other optional monomer
or monomers, are polymerized in an aqueous dispersion con-
taining the peroxy catalyst (alternatively "free radical
initiator") and additionally, if desired, oxygen and~or a
"reaction n~difier" as disclosed in the copending Canadian appli-
cations mentioned supra. Generally, from about 0.1% to
~ about 2.0% Or catalyst by weight Or the monomer mixture is
-- required to obtain the benefits of the invention, with
the preferred amount being from 0.3% t~ 1.0~1 by weignt
~he monomer mixture. The methods Or polymerization
utilized by the invention does not generally depart from the
well known methods available heretofore for m~nufacture of
--6--
~4 ~_ ~
ion exchange polymers and resins.
The polymerization is normally carried out at
temperatures ranging from about 30C to about 90C, prefer-
- ably 45C to 80C and even more preferably 50C to 75C.
In a preferred embodiment, it is desirable to employ lower
temperatures of reaction in the initial stages of polymeriza-
tion, that is until at least about 50%, preferably 75% or
more, of the monomers in the dispersion are reacted. The
above-stated temperatures are for the initial stages of
polymerization; during final stages of polymerization the
temperature is desirably raised 20C-30C above the temper-
ature used for the initial stages. As~taught in the copending
Canadian pabent applications mentioned supra, it is possible bo
operate at temperatures 15-35C below temperatures normally ~
15 used in prior art methods. When ~perating at lower temper- ~ ~-
atures, e.g., 30C-60C using catalysts of the invention
("Percadox" type) it may be desirable to emp~y a second so-called
- "chaser catalyst" whlch is active at higher temperatures,
e.g.~ 75-100C, in order to achieve higher yields of
crosslinked vinyl polymer, for example, from about 0.05 to
- 0.1% based on monomer weight of such initiators as benzoyl
peroxide, t-butyl peroctoate, t-butyl peroxyisobutyrate, and
the like.
The aqueous media in which the polymerization is
conducted in dispersion form will contain minor amounts of
the conventional suspension additives, that is, dispersants
such as xanthan gum (biosynthetic polysaccaride), poly-
(diallyl dimethyl ammonium chloride), polyacrylic acid (and
salts), polyacrylamide, magnesium silicate, and hydrolyzed
poly(styrene-maleic anhydride); protective colloids such as
*Trademark 7
.. ~
~4~-7
carboxymethyl cellulose, hydroxyalkyl cellulose, rncthyl
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
are recovered from the reactor as hard, discrete beads of
particle size within the range of about 0.02 to 2 mm,
average particle size being on the order of 0.2 to 1 mm.
These copolymers are converted to ion exchange resins by
attachment Or functional groups thereto by conventional
means, such as 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 (-SO3~1) or
sulfonate (-SO3M, where M is usually an alkali metal ion);
weak acid cation, i.e., containing the groupings carboxyl
(CO2H) or carboxylate (-CO~M, where M is usually an al'~ali
metal ion); strong base anion, i.e., containing the te ra-
1~, ;4r )~
alkyl ammonium groupings: -NR3X, where R is an alkyl or
~hydroxy alkyl group and X ls 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 the resins
produced according to this invention are not evident until
.
the crosslinked copolymers are converted to ion exchange
resins by the attachment Or the aforesaid functional groups.
The enhanced physical strength of these latter resins is --
apparent from their resistance to crushing which is conven-
iently measured on the Chatillon instrument, as well as by
visual inspection before and after use in ion exchange
.
applications. For example, strong acid, styrene-type resins
produced in accordance with the preferred method of this
invention frequently exhibit Chat-illon values in the range
Or 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 in the
range Or about 50 to 500 gm/bead. Similarly, strong base
styrene-type resins of the invention frequently exhibit
Chatillon values o~ about 500 to 1500 in contrast to resins
derived from copolymers prepared by prior art methods which
` - have Chatillon values of 25 to 400.
The process of the invention is clarified by the
following illustrative examples which are not to be construed
as limitative thereo~
Example 1
. . ~
-` The polymerization reactor is a two liter, three neck,
round bottom flask equipped with a two blade paddle stirrer,
3 thermometer, condenser, heating mantle with temperature
., ~ . .
controller al~d provision for sweeplng with an incrt gas.
Into this reactor is charged a monomer mixture consisting
Or 500.4 g styrene and 85.6 g divinylbenzene, and 1.9 g
t-butyl peroctoate. The head space is swept with nitrogen
and the aqueous phase is then added: 510 g water, 20.1 g
poly(diallyldimethyl ammonium chloride) dispersant, 1.6 g
Or gelatin protective colloid, o.88 g boric acid, and
sufficient 50% sodium hydroxide solution to maintain pH
between 10.0 and 10.5. The stirrer is started and the
reaction mixture is heated from room temperature to 75C
over 45 minutes and held at this temperature for 4.0 hours.
Thereafter, the polymerization is "finished off" by holding
the reaction mixture at 95 C for 1 hour. The copolymer
beads are separated, washed and prepared for functionalization.
A strong acid resin may-be prepared from the
copolymer of Example 1 by means of the following alternative
; procedures.
Sulfonation A
A portion of the copolymer beads as prepared above
(110 g) is added to 600 g of 95% H2S04 is 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 30C to 130C over a three
hour period. This is followed by a hydration procedure in
which water is added to quench the product. The sulfonated
- product is then washed to remove residual acid. The physical
properties of the strong acid resin product are set forth
in Table I, hereinafter.
--10--
~-
Sulfonation E3
A portlon Or the copolymer beads as prepared in
Example I above ( 50g) is added to 315 g Or 94% H2S04 in a
one liter flask equipped with stirrer, condenser, dropping
funnel, thermometer, caustic scrubber, and heating Means.
Thirty grams of ethylene dichloride (bead swelling agent)
are added, and the suspension is heated to 60-65C where it is
held for one hour. The mixture is then heated to 115C and
held there for 4 hours. This is followed by a hydration
- 10 step in which water is added to quench the product. The
sulfonated product is then washed to remove residual acid.
0f the first eighteen specific examples herein,
Examples 1, 2, 4-7, and 11-18 the copolymer products were
` functionalized by Sulfonation method "A", and the remaining
Examples employed Sulfonation method "B".
Example 2
Using the same procedure set forth in Example 1, a
copolymer ion exchange resin precursor was prepared from iden-
~- tical starting materials in identical amounts. The properties
of the product, after sulfonation are as given below in
Table I.
Example 3
Following the procedure of Example 1, 254.5 g of
styrene, 42.4 grams of divinylbenzene, 3.0 g methyl acrylate~
25 and 1. 5 g t-butyl perOctoate were charged to the reactor.
"I'
The aqueous phase consisted of 270 g H20, 10.0 g poly(diallyl
dimethyl ammonium chloride), o.8 g of gelatin protective
colloid, 0.45 g boric acid and 50% NaOE~ solution to maintain
the p~l between 10.0 and 10. 5. The reaction mixture was heated
30 to 75C for 2.7 hours, then 95c for an additional hour. The
I
,,
product was was~led and sulronated. The properties Or the
resin are given below in Table I.
ExamPle 4
~ollowing the procedure of Example l, 491.7g
of styrene, 85.5 g of divinylbenzene, 8.8 g methyl acrylate,
0.51 g methylcyclopentadiene dimer, and 1.90 g t-butyl-
peroctoate were charged to the reactor. The aqueous phase
consi-sted of ~10.0 g H2O, 20.1 g of poly(diall~l dimethyl
ammonium chloride), 1.6 g of gelatin protective colloid,
0.83 g boric acid and 50% NaOH solution to maintain the pH
between 10.0 and 10.5. The reaction mixture was heated to
75C for 4 hours and then 95C for an additional hour. The
product was washed and sulfonated. The properties of the
resin are given below in Table I.
Example 5
Following the procedure of Example l, 491.7 grams
~- of styrene, 85.5 grams of divinylbenzene, 8.8 g of methyl
acrylate, 0.59 g methylcyclopentadiene dimer, and 1.90 g
. of t-butylperoctoate were charged to the reactor. The aqueous
phase consisted Or 510.0 g of H2O, 20.1 g poly(dially-l
d~methyl ammonium chloride), 1.6 g gelatin protective colloid,
o.88 g boric acid and sufficient 50% NaOH solution to main-
tain the pH between 10.0 and 10.5. The reaction mixture was
heated to 75C for 4 hours and 95C for an additional hour.
The product was washed and sulfonated. The properties of
the resin are given below in Table I.
ExamPle 6
Following the procedure of Example 5, using the
same organic and aqueous phases, a resin was prepared having
the properties set forth in Table I.
-12-
i
`7
Examp]c 7
.
~ `ollowing the procedure Or Example 1, but
including the reaction modifier ~-methylstyrene dimer
(0.59 g) and the initiator t-butyl peroctoate (1.9 g) a
resin was prepared having the properties set forth in Table I.
Example 8
Following the procedure of Example 1, but including
3.0 g methyl acrylate, 1.5 g t-butyl peroctoate, and 0.3 g
cycloheptatriene (reaction modifier), a resin was prepared
having the properties set forth in Table I.
Example 9
Following the general procedure of Example 1, but
including 3.0 g methyl acrylate, 1.5 g t-butyl peroctoate
and 0.3 g norbornene (reaction modifier) a resin was pre-
pared having the properties set forth in Table I.
Exampie 10
Following the general procedure of Example 1, butincluding 3.0 g methyl acrylate, 1.5 g t-butyl peroctoate
and 0.3 g dicyclopentadiene (reaction modifier) a resin was
prepared having the properties set forth in Table I.
- Example 11
Following the general procedure of Example 1, but
including 8.8 g methyl acrylate, 0.29 g methylcyclopentadiene
dimer (reaction modifier) and 2.64 g di-(4-t-butylcyclohexyl)-
peroxydicarbonate (Percodox 16 - T.M.) a resin was prepared
having the properties set forth in Table I. A blanket of
8% 2 in N2 was swept over the reaction mixture for 30
minutes. Also 0.59 sodium nitrite was used in the aqueous
phase to prevent polymerization therein (also in Examples 12
and 13 which follow).
.,~ .
-13-
. ., .. .. ~ . .. ... . . ..
1~4C~ 7
Example 12
Following the general procedure Or Example 1,
but including 8.8 g methyl acrylate, 0.29 g methylcyclo-
pentadlene dimer, and 2.64 g di-(4-t-butylcyclohexyl)-
peroxydicarbonate (initiator) in the organic phase a resinwas prepared. The initial polymerization was conducted at
57% for seven hours after which the temperature was raised
to 95% for 1 hour. The properties Or the resin were as
shown in Table I.
Example 13
Following the general procedure of Example 1, but
-using 8.8 methyl acrylate and 2.64 g di-(4-t-butylcyclohexyl)-
peroxydicarbonate (but no reaction modifier) and a reaction
temperature of 56C for seven hours and 75C for two hours,
a resin was prepared having the properties set forth in
TabIe I.
- Example 14
Following the general procedure of Example 1, but
using 1.9 g of 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)-
hexane (initiator) and a reaction temperature of 70C for4 hours followed by 90C for 1 hour, a resin was prepared
having the properties set forth in Table I.
- Example 15
, ; .
Following the general procedure of Example 1, but
using 1.12 g t-butyl peroxyneodecanoate (initiator) an
initial reaction temperature of 53-54C for 4.5 hours and
70C for 1 hour thereafter, a resin was prepared having the
properties set forth in Table I.
The following examples illustrate the prior art
method of preparation and products resultin& therefrom.
~-
-14-
~ ~ ~ 4~ ~ 7
Example 16
Following the general procedure Or Example 1, using
2.20 gra~s of benzoyl perox..de (initiator) an ini'~ial reaction
temperature of 75C for 4 hours and a final temperature Or
95C for 1 hour, a resin was prepared having the properties
set forth in Table I.
Examples 17 and 18
Example 16 was repeated twice and the products
: resulting had properties set forth in Table I.
. 10 The resins produced according to the foregoing
examples were tested to determine the percentage whole bead
count (%WB) percentage perfect bead count (%PB) the crushing
strength of the beads (Chatillon test method) and the %
reduction of the perfect bead count arter repeated cycling
in acid and base solutions (on accelerated usage test). All
tests were conducted on thé resin after sulfonation.
:
~ ` ' ` ':
.
.
~-' . .
,
~4 ~ J
TABLE I
PHYSICAL P~OPERTIES OF RESI~S
% Reduction
Example Chatillon in PB After
No. %WB %PB _g./bead Cycling
1 98 98 1110 6
2 98 92 lloo
3 99 95 1520 5*
4 loO 98 1610 6
99 97 1065 3
6 100 97 915
7 99 97 914 2
- 8 99 98 1810 3*
9 99 95 1450 .2*
~0 99 98 l9oO 8~ -
:~ 11 97 98 1770 - :
12 98 98 1400 . o
13 98 84 1170 - - -
14 100 96 695
98 87 goo - - :
16 99 go 325 49
` 17 99 91 335 52
18 97 78 515 39
*50 cycles with lN HCl and lN NaOH, all others have
100 cycles with lN HCl and O. 5N NaOH
Weak and strong base resins having improved ~rop- .. ;
25 erties may also be prepared in accordance with the present
invention, substituting the well known methods for post-
~- -functionalizing the copolymer resin to produce weak or strong
anion exchange groups for the sulfonation method shown above.
A preferred method known in the art for functionalizing with
30 anion exchange groups involves chloromethylation followed
-16-
by aminat~on.
Examples 19-20
; Two styrene/divinylbenzene strong base resins
were prepared followlng the general procedure Or Example 1
for the copolymer, and using conventional chloromethylation/
amination procedures to functionalize the copolymer. The
copolymer of Example 19 utilized terpinolene as a reaction
modifier and 2,6-dimethyl-2,4,6-octatriene was utilized
for Example 20. Both copolymers utilized t-butyl peroctoate
as the initiator. A control sample of a commercial strong
base resin produced without reaction modifier and using a
~` conventional prior art initiator was produced for comparative
purposes. The properties of the resins produced are set
forth in Table II.
~` 15 TABLE II
` PROPERTIES OF STRONG BASE RESINS
F` "
Example Chatillion
No. %WB %PB g./bead
19 100 98 610
` 20 20 100 99 750
-~ Control
-~ (commercial
strong base resin) 100 94 140
As used herein and in the appended claims the
acid/base cycling test is conducted with 1 normal HCl and
0.5 normal NaOH at room temperature for 100 cycles, at
approximately two cycles per hour.
.
- -17-
','
'
