Note: Descriptions are shown in the official language in which they were submitted.
CA 02036422 2000-09-11
1
TITLE
PROCESS FOR PREPARING
STABILIZED POLYMER DISPERSION
Technical Field
This invention relates to a process for
preparing a stabilized polymer dispersion. It is more
particularly directed to a process for preparing a
dispersion of a polymer having an acrylic polymer core
component and a polymeric stabilizer component, in
which the stabilizer component is prepared using a
cobalt catalytic chain transfer agent.
Backaround and Summary of the Invention
The stabilized polymeric dispersions
prepared according to this invention are described in
a general way in U.S. Patent 4,746,714 to Spinelli,
Scopazzi and Antonelli.
While those dispersions function very well
for their intended purpose, the method described for
their preparation provides no convenient way for
incorporating living functional groups, especially
hydroxyl groups, on the chains of the stabilizer
polymer molecules. These functional groups confer
certain advantages when the polymer system is to be
cross-linked with melamines or isocyanates.
It has now been found that such groups can
be easily incorporated on the stabilizer polymer
molecules, in any number, if one uses a cobalt
catalytic chain transfer agent in the polymer's
preparation.
Detailed Description
The principal polymers of the dispersions
prepared according to the invention are described in
A-0333 35 U.S. Patent 4,746,714, previously mentioned.
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CA 02036422 2000-09-11
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The polymers described there have core
components of acrylic polymers and substantially
linear acrylic polymeric stabilizer components, each
having a terminal polymerizable functional group,
which are grafted to the core component at one end of
the chain.
Illustrative of monomers which can be used
to prepare the core components are those shown in the
'714 patent, column 3, line 55, to column 4, line 25.
to Isocyanate, silane and amine functional monomers can
also be used. Preferred for use in the process of the
invention are methyl methacrylate, hydroxyethyl
methacrylate, methacrylic acid, methyl acrylate,
' styrene and glycidyl methacrylate.
The monomers used to.prepare the stabilizer
component according to the invention can be any of the
conventional polymerizable ethylenically unsaturated
monomers. Preferred for use are butyl methacrylate,
isobutyl methacrylate, 2-ethylhexyl methacrylate,
hydroxyethyl methacrylate, methyl methacrylate,
glycidyl methacrylate, itaconic acid or anhydride,
malefic acid or anhydride, styrene, isocyanatoethyl
methacrylate, benzene 1-(1-isocyanato-1-methyl
ethyl)-3,4(1-methyl ethenyl), methacrylic acid,
acrylic acid, silanes and amines.
The ratio of monomer units in the final
polymer is a matter of choice, as will be understood
by those skilled in this art.
The catalytic chain transfer agent used in
the process of the invention can be any compound which
contains Co+2. Cobalt chelates are preferred,
especially those described in U.S. Patent 4,680,352 to
Janowicz and Melby, and U.S. Patent 4,722,984 to
2
3 r:~ ~~ s~s
Janowicz. Most preferred are pentacyanocobaltate
(II), diaquabis(borondifluorodimethyl-
glyoximato)cobaltate (II) and diaquabis(borondifluoro-
diphenylglyoximato)cobaltate (II).
The chain transfer agents are ordinarily
used at concentrations of 5-150 ppm based on monomers.
The process is run in two steps, the second
of which can be run immediately after the first but
which is ordinarily run after a pause for analysis and
to permit more efficient use of the reactor.
In step one, a mixture of stabilizer
monomers and organic liquid is heated, preferably to
reflux temperature for ease of control, and to it is
added the catalytic chain transfer agent of choice,
additional monomers) and solvent, and the usual
amount of a conventional polymerization initiator such
as azo- or peroxide initiators. The reaction is run,
with additions of monomers and initiator as needed,
until the desired stabilizer component is obtained
(ordinarily having a Mw of 5000-12000).
In step two, an organic liquid which is a
solvent for the stabilizer component but a non-solvent
for the core component is added to the product of step
one. "Solvent" and "non-solvent" are being used in the
conventional sense, as will be understood by those
skilled in the polymer art. Illustrative of organic
liquids which can be used are aromatic- and aliphatic
hydrocarbons such as heptane and VM&P naphtha.
Mixtures of liquids can also be used. The
stabilizer/liquid ratio is of secondary importance,
but is usually in the range 1/2 to 1/4 (weight).
35
3
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The resulting mixture is again heated,
preferably to reflux temperature far better control
and to it are added the core monomers and a
conventional initiator such as one of those previously
mentioned, in the usual amount. Polymerization is
continued, with additions of liquid and initiator as
needed, until it is complete, as determined by
periodic sampling and analysis.
The dispersions prepared according to the
process of the invention can be used to modify the
rheology and/or the physical properties of
conventional coating compositions at concentrations of
1-80%, preferably l0-40%, by weight of the total
composition.
Examples
Those skilled in the art will be able to
practice this invention more easily after referring to
the following illustrative examples.
Those artisans will no doubt be able to
compose numerous variations on the themes disclosed,
such as changing the amounts of ingredients slightly
but insignificantly from those shown, adding innocuous
substances, or substituting equivalent or nearly
equivalent components for those shown. All such
variations are considered to be within the inventive
concept.
In the examples, all par-is are by weight
unless indicated otherwise.
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4
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Example 1
Part A
To a reaction vessel were charged
Toluene 827.2 parts
5 n-butyl methacrylate 447.9
2-Ethylhexyl methacrylate 588.9
3-methacryloxypropyl-
trimethoxysilane (A-174) 108.1
This mixture was brought to reflux temperature, held
there under nitrogen with stirring, and to it was then
added, over a ten-minute period, a solution of
1,1°-azobis(cyclohexane-
carbonitrile) (initiator) 1.14 parts
Diaquabis(borondifluoro-
dimethylglyoximato)-
cobaltate(II) 0.023
n-butyl methacrylate 80.7
Toluene 42.1
The reaction mixture was then held at reflux
temperature, with stirring, and to it was added, over
a 60-minute period, a mixture of
n-butyl methacrylate 209.0
2-ethylhexyl methacrylate 271.6
A-174 (described above) 63.6
Initiator 1.95
This was followed immediately by the addition of a
solution of
5
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n-butyl methacrylate 209.0 parts
2-ethylhexyl methacrylate 304.9
A-174 (described above) 63.0
Initiator 2.12
Toluene 84.4
over a 180-minute period while maintaining reflux
temperature. The reaction mixture was then held at
reflux temperature, with stirring, for 30 minutes
after which time was added, over a 60-minute period, a
mixture of
Toluene 105.9 parts
Initiator 0.5
This reaction mixture was held at reflux temperature
for 60 minutes, and toluene (246.3 parts) was then
added to it and the mixture cooled. The resulting
solution, 64.2% solids, contained the stabilizer
component 2-EHMA/IBMA/A-174 50/40/10.
Part B
To a reaction vessel were charged
Product of (A) 265.0 parts
Heptane 396.0
This mixture was brought to reflux temperature and to
it were then added 0.6 parts of t-butyl peroctoate.
The mixture was then held at reflux temperature and to
it were immediately and simultaneously added, over a
210-minute period,
(1) A solution of
Methyl methacrylate 207.9 parts
Methyl acrylate 103.9
6
7
Styrene 62.4
A-174 41.6
Heptane 19.3
Product of A 128.8
and
(2j A solution of
Heptane 67.7
t-butyl peroctoate 6.2
The resulting mixture was held at reflux~temperature
for 45 minutes, and to it was then added, over a
30-minute period, at reflux, a solution of
Heptane 24.7 parts
t-butyl peroctoate 4.1
This was again held at reflux temperature for 60
minutes, and 119.7 parts of solvent were boiled off to
give a dispersion containing 55% solids.
The composition of the principal polymer in
the resulting product was
srlA/ 2-EHrIA/A-17 4/rrniA/riA/sTx
14.4/18.8/9.9/31.6/15.8/9.5
Example 2
Part A
To a reaction vessel were charged
Toluene 853.5 parts
Isobutyl methacrylate 495.2
2-ethylhexyl methacrylate 434.2
Hydroxyethyl methacrylate 151.5
7
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The mixture was brought to reflux temperature (129°C),
held there under nitrogen with stirring, and to it was
then added, over a 10-minute period, a solution of
Diaquabis(borondifluoro-
dimethylglyoximato)-
cobaltate II 0.033 parts
1,1'-azobis(cyclohexane-
carbonitrile) (initiator) 1.0
Hydroxyethyl methacrylate 36.6
Toluene 38.0
The reaction mixture was held at reflux temperature
with stirring and to it was added, over a 240-minute
period, a mixture of
Isobutyl methacrylate 353.1 parts
2-ethylhexyl methacrylate 414.0
Hydroxyethyl methacrylate 213.8
Toluene 76.3
The reaction mixture was then held at reflux
temperature with stirring for 30 minutes, after which
time was added, over a 60-minute period, a mixture of
Toluene 227.9 parts
Initiator 0.9
The reaction mixture was further held at reflux
temperature for 60 minutes and then cooled. The
resulting solution, 63.6% solids, contained the
stabilizer component 2-EHMA/IBMA/HEMA 40/40/20.
Part B
To a reaction vessel were charged
8
9
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,
~
. 1..1
Product of A 639.2 parts
Isopropanol 44.0
Petroleum naphtha 62.8
Heptane 790.6
Xylol g9,1
The mixture was brought to reflux temperature (a2°C)
and to it were added 1.6 parts of t-butyl peroctoate.
The reaction mixture was held at reflux temperature
and to it were immediately and simultaneously added,
over a 210-minute period,
(1) a solution of
Methacrylic acid 42.2 parts
Hydroxyethyl-
acrylate 264.7
Methyl methacrylate 370.3
Methyl acrylate 190.6
Styrene 158.9
Glycidyl methacrylate 32.2
Xylol 49.1
Product of A 320.9
and
(2) a solution of
Petroleum naphtha 157.0 parts
Butanol 27.9
t-butyl peroctoate 15.9
3o The reaction mixture was then held at reflux
temperature for 45 minutes and to it was then added,
over a 30-minute period, at reflux, a solution of
Butanol 62.8 parts
t-butyl peroctoate 10.4
9
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. "a '.,.y3 f~
. . , .
The reaction mixture was held at reflux temperature
for a further 60 minutes, at which time 304.8 parts of
solvent were boiled off, to give a dispersion
containing 55~ solids.
The composition of 'the principal polymer in
the resulting product was
5
IBMA/2EHMA/HEMA/MMA/MA/S/MAA/GMA
2~.7/20.7/12.8/13/6.7f 5.5/1.5/1.1
The pentacyanocobaltates (II) and diaqua-
l0 bis(borondifluorodiphenylglyoximato)cobaltate (II) can
replace the
diaquabis(borondifluorodimethylglyoximato)cobaltate
(II) catalytic chain transfer agent in the foregoing
procedures, in equivalent amounts, with substantially
the same result.
25
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