Note: Descriptions are shown in the official language in which they were submitted.
13032~
BLOCK COPOLYMER DISPERSANTS
BACKGROUND OF ~HE INVENTION
Polymeric materials have previously been
known wh~ch are effective for dispersing pigments in
organic solvents. Such pol~meric dispersant6 are
typically of the AB or B~B types, in which a polar
group known as th~ A ~egment is present in the m~lecule
to f~cilitate attachment to a pigment surface, and at
least one non-polar portion known as the B segment is
present to enhance stearic stabilization of the pigment
particles in a dispersion.
Baker et al, in U~ S. Patent 3,912,677,
disclose th~ benefits of polymers containing ionic
groups, in specific cases where the ionic groups are in
the ~orm of a salt with a salt-~orming component or
counterion. ~he salt-forming component has an affinity
for the surface of organi~ pigment particles, and is
capable of reaction with the polar-bound ionic group so
as to form a salt. However, continued effort has been
directed to improve the perfo~nance of polymeric
d~sper~ants~ and to find effective dispersants that do
i not require khe use o~ special salt-forming components,
j the u~e of which complicates the manufacture of the
I dispereants, and can introduce undesirable color.
S~IMARY OF THE INVENTIOM
The pres~nt invention is based on the dis-
! covery that block copolymers composed of similar
monomers, but whiah exhibit substantially different
polarity, one of the blocks having cationic ammonium,phosphonium, or sulfonium moieties, provide excellent
performance as piyment di~p~rsants, without-the need
for ~pecial salt-forming components.
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Specifically, the instant inYention pr~ides
a block copolymer consi~ting e~sentially of
(a) about ~rom 0~1 to 50 ~, by weight of the
copolymer, of at least one block having a number
average molecular weight of about from 200 to 10, 000
and prepared ~rom at least one monomer ~elected from
compounds of the general formulas CH2=C~C02R and
CH2=CCH3C02R, wherein R is alkyl or alkyl ether of ~-20
carbon atoms, the block further containing at least 2
pendant ionic moieties of the general formula -A(Rl)mX,
wherein A is selerted from N , P , and S: Rl ars
independently selected ~rom alkyl or alkyl ether of
; 1-20 carbon atoms, phenyl or substituted phenyl, m is 3
when A is N or P, and m is 2 when A is S, and X is
selected from halides and conjugate bases of organic
acids, the backbone o~ the block being composed of
ethylenically unsaturated units, and
(b) about from 99.9 to 50 %, by weight of the
! copolymer, o~ at least one blook having a number
average molecular weight of about from 500 to 100,000
. and prepared ~rom monomers selected from compounds ofthe general formulas CH2-CHC02R and CH2=CCH3C02R,
whereln R is alkyl or alkyl ether of 1-20 carbon atoms.
These compounds can be, and preferably are,
prepared by group transfer polymerization techniques,
exhibit excellent performance as dispersants and do not
require salt-forming counterions for satis~actory
performance.
DETAILED DESCRIPTION OF THE INVENTION
Monomers which can be used in the preparation
of the dispersants o~ the present invention inolude
those a~xylate~ and methacrylates de~cr~bed in Webster,
: 35
~0:~67
~ 3 -
U.S. Patent 4,508,880 at column 8, lines 4 to 58, with
the exception of 3-methacryl-oxypropyl acrylate; and
2-methacryloxyethyl acrylate and linalate. Monomers
which are preferred ~or the first block of the
copolymer, containing the pendant ionic groups, include
dimethyl aminoethyl methacrylate and diethyl aminoethyl
metha~rylate. Monomers which are pre~erred for the
s~cond (b) block ~f the copolymers include methyl
meth~crylate, butyl methacrylate and 2-ethylhexyl
methacrylate.
The polymers of the present invention can be
prepared by conventional anionic polymerization
techniqueæ, in which a first block of the copolymer is
formed, and, upon complet~on of the ~irst block, ~
~econd monomer 6tream is started to form a ~bsequent
block of the pol~mer. However, the react~on
temperatur2~ using such technique~ ~hould be maintained
at a low level, for example, 0 to -40 degrees
Centigrade, ~o that side reactions are minimized and
the desired blocks, o~ the speaifled molecular weights,
are obtained.
~ o attain the desired mole~ular weight of
Qach block as well as uniformity in the blocks, Group
Tranefer Polymerizaticn techni~ues are advantageously,
and preferably, used, ~uch as those described in the
Aforementioned Webster, U.S. Patent 4,508,880.
In accordance with that process, an unsaturated
monomer is contacted with an initiator and
a catalyst system containing silicon, tin
or germanium, undex which the pol~merization proceeds
in a controlled manner, as oppos~d the random manner
typical o~ polymerization reactions, ~o that a
subetantially linear polymer can be prepar~d having
)32~7
polymer chains which are uniform and of the desired
molecular weight.
In the preparation of dispersants of the
present invention, the order in which the blocks are
prepared is not critical. Either the block containing
the pendant ionic moieties or the blocX not containing
the6e moieties can be prepared first.
Catalysts which can be used include those
dl~closed in U.S. Patent 4,508,880 at column 11, lines
42 to 68.
Initiators which can be used include those
indicated in the aforementioned Webster patent at
Column g, line 25 to CQ1Umn 10 line 13. Preferred
initiators include
1-(2-trimethyl-siloxyethoxy)-1-trimethyl-
siloxy-2-methylpropene; 1-(2-~1-ethoxyethoxy]-
ethoxy-l-trimethylsiloxy-2-methylpropene; and
l-methoxy-l-trimethylsiloxy-2-methylpropene.
If the dispersant is prepared by ~irst
forming the bloak without the pendant ionic groups,
then the~e blocks are reacted, u ing the same general
procedure~, to form the block~ containing the pendant
ionia groups. The same general reactants are used for
these ~ec.ond bloaks, except that the monomer~ and their
relative quantities are selected to have an average of
at least two cationic units, or their precursors, in
each block~ The cationic unit~ can be ~n the required
quaternary or te~tiary configuration as pol~merized,
or, more typi~ally and preferably, can be primary,
secondary or tertiary amine~ phosphine or thioether
13~ 7
compounds which are converted to the quaternary or
tertiary state after the formation of the basic
polymer structure. While a wide variety of monomers
can be so used, methacrylates have been found to be
particularly satisfactory, including, for example,
2-(dimethylamino) ethyl methacrylate,
2~(diethylamino)ethyl methacrylate, glycidyl
methacrylate, and t-butyl aminoethyl methacrylate.
Similar monomers can be used to introduce ionic groups
based on phosphorus and sulfur, as will be evident to
the skilled artisan.
The pendant ionic moieties have the general
formula -A(R1~mX, wherein A is selected from N, P, and
S, R1 are independently selected from alkyl or alkyl
ether of 1-20 carbon atoms, phenyl or alkyl
substituted phenyl, m is 3 when A is N or P, and m is
2 when A is S, and X is selected from halides and
conjugate bases of organic acids. Preferably, A is
nitrogen, and X is selected from the group consisting
o~ carboxylates, sulfonates and phosphates.
After ~ormation of the basic polymer
structure, the cationic precursor can be brought into
contact with conventional alkylation agents such as an
alkyl halide, alkyl sulfonate, alkyl toluene
sulfonate, trialkyl phosphate or aralkyl halide.
Alkylation agents which have been found to be
particularly satisfactory include methyl toluene
sulfonate, dimethyl sulfate, and benzyl chloride.
The physical characteristics of the block
copolymers of the present in~ention, including the
molecular weight of the blocks and the presence of the
ionic moieties on one of the blocks) can be confirmed
by conventional analytical techniques, including
- 5 -
B
~ ~3~32~7
differential ~canning calorimetry, nuclear magnetic
resonance, gas chromatrography and infrared analysis.
For example, the chemical composition o~ the blocks can
be determined by proton nuclear magnetic re~onance or
infraread analy~i6, or by pyrolysis and gas
chromatographic analysis. The block sizes ln the
copolymers can be determined by nuclear m~gnetic
resonanae, gla~s transition temperature, ~olubility or
micella ~ormation a~ measured by ~ua~i elastic light
10 ~cattering.
The resulting block copolymers exhibit
excellent parformance as dispersants. Accordingly,
they can be used ef~ectiv~ly a~ pigment dispersants in
paint formulations and a~ oil additives. Pigment
dispersions typically ~omprise pigment, s~lvent and
dispersant, and can be prepared, for exampl~, as
des~ribed in Baker et al, U.S. Patent 3,912,677.
While similar compounds have been 90 used in the
past, the present copolymers are effective without
the use of counter-ions such as ionized rosin acid
or sulEonated aromatic hydrocarbon that have been
previously found necessary for satisfactory
dispersant performance~ In addition, the
uniform block charaatex in th2 present compounds
provides improved and more reliable d~spersant
per~ormance.
; In th~ following Examples, dispersant quality
ie measured by ~and grinding a mixture o~ pigment,
solvent and d~persant and determining what proportion
of disper~ant (if any) will give a uniform di~persion,
appearing liXe ~tained glass at an optical magnifica-
tion Q~ ~50x. In contrast, floccula~ed ~igment has
i~land~ of color intersper~ed with areas of relatively
3267
- 7 -
clear ~olvent. The degree of dl~persion is evaluated
on an arbitrary ~cale of 1 to 4 as follows:
1 - deflocculated dispersion in which pigment
particles ~r~ uni~ormly separated and in which brownian
motion of parti~les i~ evident.
2 - slightly flocculated dispersion in which
pigment parkicles are separated but immobile (no
significant evidence of brownian motion).
3 - flocculated disper ions in which pigment
lD particles are loosely aggregated wlth 60me voids
between aggregates.
4 - severely flocculated dispereions ln which
i pigment particles are highly aggregated with larg~
voids between aggregatQs.
The di6per~ants prepared in th~ Examples were
evaluated with a variaty of standard pigments and in
~olvents. The solvents used were methylisobutyl ketone
(MIBK or M~, toluene tT), xylenes (X), and ~cetone (A).
The ~ollowing ~tandard pigments were used in the
evaluation:
W505 - phthalocy~nine blue, red toned
I (monastral* blue)
W552 - phthaocyanine blue, floaculation
re~istant green s~ade, toner
WS73 - tetrachloro CPC blue: phthalocyanine
~lue toner, green ~hade, improved rheology
W673 - tetraohloro isoindolinone - irgazin
yellow
W805 ~ monastral magenta - quinacridone type
magenta toner
W811 - monastral red - quinacridone type red
toner
* denotes trade mark
.
1303267
W853 - organic red tone - quinacridone type -
monastral transparent red B RT-233
In all Example~ o~ the invention, the blocks
: of the copolymers containing the pendant ionic groups
had a molecular weight o~ about from 200 to 10,000, and
the blocks without the pendant ionic groups had a
molecular weight of about ~rom 500 to 100,000. The
speci~ic molecular weight~ can be determined by the
skilled artisan from the data appearing in the
particular Examples. In all Examplas of the invention,
an average of at least 2 pendant ionic groups were
present in each block (a) o~ the copolymer prepared.
Example 1
A reaction vessel was charged with 316 g
tetrahydrofuran ~THF), 0.5 mL xylenes, 4.1 g
l~methoxy-l-trimethylsiloxy-~ m~thylpropene
("init.iatox"), and 0.100 mL 1 M tetrabutylammonium
3-chlorobenzoate in ac~tonitrile ("catalyst"). To
prepare an A block free from pendant ionic groupd, two
feeds were be~un simultaneously; ~1.2 g of methyl
methacrylate (MMA) was added in 20 minutes, and 0.350
mL catalysk in 3 ml THF was added over 2 hours. Twenty
minutes a~ker the addition o~ the MMA, 28.9 g of
2-N,N-dimethylamlnoethyl methacrylate ~DMEAMA) was
added over 10 minutes for the preparation of a block
containing pendant ionic groups. Twenty minutes after
; the addition of the ~MAEMA, 91.9 g of MMA was added
over 20 minutes. One hour after the second addition of
MMAI 5 mL o~ methanol was added. The resin (251 g) was
added to heptane (700 mL), the resulting solid was
separated from the liquid, and the solid was washPd
with 700 mL of heptane and dried.
13~326~
To quaternize the amine groups in the
resulting block copolymer, a portion (30.69 g) of the
copolymer was dissolved in THF (50.5 g) and benzyl
chloride (~.0 ~ wa~ added. The result~ng eolution was
refluxed for about 3 hours before the addition of 50.5
g isopropanol. Refluxing was continued for 5 more
hours. The resulting resin showed a solids content of
2~ % and an tertiary amine content o~ 0.31 mM~gram,
indicating substantially ~omplete quaternization of the
amine group~.
The copolymer was evaluated as a pi~ment
dispersant, ar.d exhibited a dispersion rating of 1 in
MIBK (~1) for standard pigments W505, W552, W573, W673,
W805, and W811. The copolymer was also evaluated with
6tandard pigment W8~3 in MIBK, acetone and toluene ~o
give ratings of M3, Al and T3, respectively.
Examplas 2-4 and Comparative Example A
In Comparative Example A, an ABA block
copolymer was prepared having terlary pendant ionic
groups attached to the B ~egment. The general composi-
tion o~ the block copolymer was
MMA/BMA//DMAEMA//MMA/~MA in expected degrees of
polymerization o~ 20/20//8//20/20. In Examples 2-4,
thi~ block copolymer wa~ ~uaterized with three
different quaternlzing agents to form a composition of
the pre~ent invention.
In Comparative Example A, a reaction ~essel
was charged with 1361 g THF, 21.5 g initiator, and 1.2
mL catalyst. A feed of 581.5 g of 41.3 wt % MMA in
butyl methacrylate was added o~er 20 minutes, while an
ice bath was u~ed to m~intain the reaction temperature
between 20 and 35 C. Simul~aneously, a 150 minute feed
:~l3032~i7
-- 10 --
of 2.4 ml catalyst in 2.6 ml THF was started.
Forty-five minutes after the end of the first monomer
feed, a twenty minute feed of 173.3 g of
2-N,N-dimethylaminoethyl methacrylat~ wa~ added. Forty
minut~s after tha end of the second mono~er feed, a
twenty minute feed of 505.1 g of 41.3 wt % MMA in BMA
was added. Ice cooling was again used. A~ter about 16
hours, 40 ml of methanol was added.
The resulting block copolymer with tertiary
pendant ionic groups was evaluated as a pigment
~ dispersant, and the results summarized in Table I.
I .In Example 2, a reaction mixture of 513.2 g
of the block copolymer of Comparative Example A, 126 g
ethanol, and 25.0 g iodomQthane was refluxed ~or three
hours. The resulting block copolymer, with quaternized
pendant ionic groups, was evaluated as a pigment
dispersant, and the results summarized in Table I.
! In Example 3, a reaction mixture of 500.2 g
of the block copolymer of Comparative Example A, 125 g
ethanol, and 30.3 g benzyl bromide was refluxed for
~ixtean hours. The resulting block copolymer, with
q~laternized pendant ionio groups, was evaluated as
before, and the results summarized in ~able T.
ln Exampla 4, a reaction mixture of 200.2 g
of the block copolymer o~ Comparative Example A, 50.0 g
' isopropanol, and 11.5 g methyl p-toluenesulfonate was
refluxed for sixteen hours. The resultlng block
copolymar, with quaternized pendant ionic groups, was
evaluated as before, and the results summariæed in
Table I.
~303~
-- 11 --
TABLE I - DISPERSION RATINGS
Example
Control A 2 3 4
Pigment
W552Al,X4,T4,M3Al,Xl,Tl,Ml Al,Ml,Tl,X1
W573A3 Ml,X3 Ml,X3 1,A3,Tl
N673~ ~ M1
W8 05 Al Ml, Xl Ml, Xl Ml
W811 . A4 Ml,X3 Ml,X3 Ml
W853 Al Ml, X4 M1, X4 Ml
~ .
Example 5
An AB block copolymer was prepared having the
general composition EHMA//DEAEMA 42//12. A reaction
ve3sel was charged with 205 g toluene, 1. 94 g lnitia-
tor, and 0.111 mL catalyst. Simultaneously, a l-hour
faed of 0.222 mL catalyst in 5 mL toluen~, and a 20
m~nute feed o~ 92.3 g 2-ethylhexyl methaarylate were
~tarted. After 40 minutes, 0.111 mL catalyst was
added. After 3 hours more, 0.111 mL catalyst was added,
and a ten-minute feed of Z0.92 g 2-N,N-dimethylamino-
2~ ethyl methacrylate was added. A~ter 16 hours fuxther,
5 mL of methanol was added. A portion (150 g) of ths
resulting resin was diluted with 37.~1 g ethanol, 9.16
g benzyl bromide was added, and the resulting mixture
was refluxed ~or 18 hour~.
The copolymer was evaluated as a dispersant
for standard piyments, and found to glve an X4 rating
for pigment W505, and Xl rating~ for pigments W573,
W805, W811, and W853.
,-
~303;~7
- 12 -
Examples 6-7 and Comparative Examples B-H
In Examples 6-7 ~nd Comparative Examples B-H,
comparison~ were made between blocked and random
copol~mers of similar composition, and with varying
degrees of ~uaternization of the pendant ionic moieties
on each~
In the preparation of the random copolymer, a
xeaction ves~el was charged with 127,2 g toluene, 2.26
g initiator, 74.5 g BMA, 52.6 g MMA, 29.7 g
2-N,N-diethylaminoethyl methacrylate, and 0. 030 mL
catalyst, Cooling wa~ used to maintain the reaction
temperatur~ below 40 C. Aft~r 4 hours reaction, 5 mL
methanol was added.
In the preparation of the blocked copolymer,
a reaction ves~el was charged with 130.3 g toluene, 0.5
ml xyl~nes, 2.~7 g initiator, 76.4 g BMA, and 54.0 g
MMA, and 0.030 mL catalyst. Cooling was used to keep
the reaction temperature below 40 C. After 70 minutes
reaction, ~imultaneous feeds o~ 29.4 g DEAEMA over 10
minutes and 0.20 mL catalyst in 5 mL toluene over 20
minutes wer~ started. After a further hour of reac-
tion, S mL methanol was added.
The re~ulting copolymers, having tertiary
pendant ionic groups and representing Comparative
Examples ~ and C, were evaluated as dispersants for
~tandard pigm~nt W552, and both exhibited ratings of
A3, M4, and T4.
In Comparative Examples D-H and Examples 6
and 7, the block copolymers of Comparative Examples B
and C were each diluted by comhining 65 g resin and
19.5 g ~sopropanol. A 20 g portion of the resulting
resin was guaternized using methyl p-toluenesulfonate,
u~ing 25 mole %, 50 mole %, 75 mole %, or ~5 mole % of
- ~3~3267
- 13 -
methyl p-toluenesulfonate, based on amine content. The
rasulting solutions were held at room temperature for
10 day~. The xe~ulting quaternized copolymer6 were
evaluatad a~ pigm~nt dispersants and the results
6ummarized below.
2S % QUATERNIZE~
Example D E
(RANDOM) (BLOCKED)
Pigment
; W573 A3, M3, X3 A3, Ml, X2
W805 A4, ~4, X4 A4, ~4, X2
~811 Al, Ml, X2 Al, Ml, Xl
W853 Al, Ml, X3 Al, Ml, X2
50 % QUATERNIZED
1 20 Exampla F 6
(~NDOM) (BLOCKED)
W573 X3 Xl
W805 X4 Xl
W811 X3 Xl
W853 X3 Xl
75 ~ QUATE~NIZED
Example G 7
(RANDOM3 (BLOCKED)
W573 X3 Xl
W305 X4 Xl
W811 X3 Xl
~3032~;~
-- 14 --
W~53 X3 Xl
9 5 % QUAI'ERNI ZED
Example H 8
(RANDOM) (A) (BLOCKED)
W573 Al, M2, X2 Al, Ml, Xl
W805 Al, M3, X4 A3, M4, X2
W8 11 Al, M1, X3 A1, M1, Xl
W8 5 3 Al, ~1, X3 Al, Ml, Xl
i
.
.. ~
