U.S. patent application number 09/811663 was filed with the patent office on 2001-12-13 for continuous process for preparing polymers.
Invention is credited to Fitzwater, Susan Jane, McFadden, Dawn Marie.
Application Number | 20010051696 09/811663 |
Document ID | / |
Family ID | 26886262 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051696 |
Kind Code |
A1 |
Fitzwater, Susan Jane ; et
al. |
December 13, 2001 |
Continuous process for preparing polymers
Abstract
A continuous process for preparing polymers, preferably emulsion
polymers, with minimal fouling of the reactor is provided. The
process is effected in a reactor which does not contain a gas
phase, optionally by reducing the gas content of the reaction
mixture.
Inventors: |
Fitzwater, Susan Jane;
(Ambler, PA) ; McFadden, Dawn Marie; (Newtown,
PA) |
Correspondence
Address: |
ROHM AND HAAS COMPANY
PATENT DEPARTMENT
100 INDEPENDENCE MALL WEST
PHILADELPHIA
PA
19106-2399
US
|
Family ID: |
26886262 |
Appl. No.: |
09/811663 |
Filed: |
March 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60190618 |
Mar 20, 2000 |
|
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|
Current U.S.
Class: |
526/88 |
Current CPC
Class: |
Y10S 526/918 20130101;
C08F 2/22 20130101 |
Class at
Publication: |
526/88 |
International
Class: |
C08F 002/00 |
Claims
What is claimed:
1. A continuous process for preparing a polymer comprising
continuously feeding at least one reaction mixture containing at
least one monomer to a reactor wherein said reactor does not
contain a gas phase; polymerizing said monomer in said reactor; and
continuously removing said polymer from said reactor.
2. The process of claim 1 wherein said reactor comprises a
non-cylindrical channel.
3. The process according to claim 1 or claim 2 wherein the amount
of gas in said at least one reaction mixture does not exceed the
solubility limit of said gas at any time in said reactor.
4. The process of claim 3 wherein said polymer is an emulsion
polymer.
5. A method for reducing polymer fouling during a continuous
process for preparing a polymer comprising continuously feeding at
least one reaction mixture containing at least one monomer to a
reactor wherein said reactor does not contain a gas phase;
polymerizing said monomer in said reactor; and continuously
removing said polymer from said reactor.
Description
[0001] This invention relates to a continuous process for preparing
polymers and a method for the reduction of polymer fouling on
reactor surfaces, especially in a continuous process for preparing
emulsion polymers.
[0002] Polymers are typically prepared in batch, semi-continuous,
or continuous processes. Such processes are susceptible to various
degrees to polymer build-up or fouling on the reactor surfaces.
Polymer fouling results in the need to shut the reactors down and
clean the reactor surfaces which reduces available production time
and may, for certain reactor geometries such as tubular reactors,
be highly inconvenient.
[0003] European Patent Application 926 161 A discloses a continuous
process for preparing polymers in a reactor having a
non-cylindrical channel which provides low levels of fouling. Even
lower levels of fouling are desired.
[0004] "Effects of Dissolved Gas on Emulsions, Emulsion
Polymerization, and Surfactant Aggregation" by M. E. Karaman, et
al. J. Phys. Chem, 100, 15503-15507(1996) discloses that the
presence of dissolved gas in a batch polymerization has a role in
emulsion stability and emulsion polymerization.
[0005] We have now discovered that minimizing, preferably
eliminating, a separate gas phase in a continuous polymerization
reactor reduces polymer fouling on the reactor surfaces.
STATEMENT OF THE INVENTION
[0006] According to a first aspect of the present invention there
is provided a continuous process for preparing a polymer including
continuously feeding at least one reaction mixture containing at
least one monomer to a reactor wherein the reactor does not contain
a gas phase; polymerizing the monomer in the reactor; and
continuously removing the polymer from the reactor.
[0007] According to a second aspect of the present invention there
is provided a method for reducing polymer fouling during a
continuous process for preparing a polymer including continuously
feeding at least one reaction mixture containing at least one
monomer to a reactor wherein the reactor does not contain a gas
phase; polymerizing the monomer in the reactor; and continuously
removing the polymer from said reactor.
DETAILED DESCRIPTION
[0008] The present invention is directed to a process for preparing
a polymer including feeding at least one reaction mixture
containing at least one monomer to a reactor wherein the reactor
does not contain a gas phase; and polymerizing the monomer in the
reactor. Preferably, the present invention is directed to a
continuous process for preparing a polymer including continuously
feeding at least one reaction mixture containing at least one
monomer to a reactor wherein the reactor does not contain a gas
phase; polymerizing the monomer in the reactor; and continuously
removing the polymer from the reactor. In the case of a continuous
process the reactor may be a tubular reactor or channel whether,
cyclindrical or non-cylindrical in cross-section. By
"non-cylindrical" it is meant any shape whereby the reactant is
exposed to a greater surface area for a given length than a
cylindrical shape. Suitable non-cylindrical shapes of the channel
are for example, oval, ellipse, square, triangular, and
rectangular.
[0009] In a one embodiment a continuous process for preparing
polymers includes continuously feeding at least one reaction
mixture containing at least one monomer to at least one channel;
optionally, continuously controlling the temperature of the channel
by exposing the surface of the channel not exposed to the reactant
to a temperature control medium; polymerizing the monomer in at
least one channel; and continuously removing the polymer from at
least channel; desirably the rate at which the at least one
reaction mixture containing at least one monomer is fed to at least
one channel containing polymer is controlled, such that the amount
of monomer in the at least one channel does not exceed the amount
that may be swollen into the polymer in the at least one
channel.
[0010] The surface of the one or more channels not exposed to the
reaction mixture containing at least one monomer may be exposed to
a temperature control medium for the purpose of heating or cooling
the reaction misture. The temperature control medium may be a
solid, gas or liquid. A typical gas medium may be applied by simply
exposing the channel to air. A liquid medium may be for example,
water, brine, or glycol solvents such as ethylene glycol,
diethylene glycol, propylene glycol, dipropylene glycol, and the
like. A solid medium may be for example a refrigerated or an
electrically heated metal plate. It is preferable that the
temperature control medium be a liquid.
[0011] The process may be operated at any temperature. The
temperature typically ranges from 0 to 350.degree. C., preferably 1
to 200.degree. C., more preferably 3 to 100.degree. C. The process
may be operated under vacuum as low as 25 mm Hg, or at pressures up
to 5,000 psi. The flow rate through the channel for the process may
range from 50 ml/min to 750 L/min.
[0012] Pockets of gas in the reactor have been observed as
increased fouling regions in the reactor. Therefore, a distinct gas
phase is prevented, in part, through reactor design so that pockets
of gas are not maintained during the polymerization process;
further, the amount of gas present in the reaction mixture
desirably ranges from 0 to 100% of saturation at reaction
conditions (i.e., no free gas phase), preferably 0 to 50% of
saturation. Preheating feed streams, substituting gases, and
reduced pressures (vacuum) may be used to remove gas from the
reaction mixture containing at least one monomer being fed to one
or more non-cylindrical channels. With pre-heating of the feed
streams in a vented environment, the solubility of gas in the feed
streams decreases, thereby lowering the amount of gas entering the
reaction mixture. Spargeing feeds with a gas such as Helium will
displace the the air normally present; Helium has an advantage in
that its solubility varies only slightly with temperature.
[0013] The use of reduced pressure on the reaction mixture may be
effected in various ways. In one embodiment vacuum may be
maintained on the head space of a feed tank containing the reaction
mixture. In a second embodiment gas permeable tubing may be used to
deliver the reaction mixture to the reactor. This tubing may be
placed in a reduced pressure enviroment such as a vacuum chamber,
which allows gas present in the reaction mixture to be removed from
the feed stream, through the tubing wall into the vacuum chamber.
In a third embodiment a commercially available device for degassing
may be used such as a Versator manufactured by The Cornell Machine
Company. The Versator contains a degassing chamber which uses
centrifugal force to increase the gas liquid interface which leads
to increased degassing efficiency.
[0014] One advantage to using the Versator to degas is that it may
also be used as a premixer to emulsify the feed streams when an
emulsion polymerization is being carried out. The monomer emulsion
formed by the degassed aqueous and monomer streams is very
stable.
[0015] The channels may be constructed of any material suitable for
forming into the desired shape and capable of providing sufficient
heat transfer when exposed to a temperature control medium. Such
materials are for example plastics such as polycarbonate and
polypropylene, stainless-steel types 304 and 316; titanium, Monel,
Incoloy 825, Hastelloy C, phosphor bronze, and cupronickel. In
addition, the portion of the channel exposed to the reaction
mixture containing at least one monomer may be coated with
materials such as graphite or polytetrafluoroethylene to aid in
flow.
[0016] When more than one channel is used, the channels may be the
same or different length and may be run in series or in parallel.
Each channel may also be run at different reaction conditions, such
as at different temperature and pressure conditions.
[0017] At least one reaction mixture containing at least one
monomer is fed to the channels and flows through the channels,
preferably alternating with the temperature control medium. When
the polymer is "grown out", the rate at which the reaction mixture
is fed is critical. By "grown out" is meant that a polymer chain is
formed in a first channel, followed by growing or extending the
polymer chain in at least one channel. Therefore, during growing
out of the polymer, there is polymer present in the at least one
channel.
[0018] The reaction mixture containing at least one monomer flows
through the channels at a rate sufficient to polymerize the
monomer. In instances where a polymer product with a low
polydispersity index is desired, the residence time of the reaction
mixture containing at least one monomer is sufficient to yield a
polydispersity index of less than 2.0. The residence time is
typically less than 30 minutes, preferably less than 20 minutes.
The flow rate may be adjusted based on the desired residence time
in the channels and the total surface area of the channels. In
general, the higher the total surface area of the channels, the
faster the flow rate may be. The polymer is continuously removed
through an outlet of the channels.
[0019] The channel may have one or more inlets. The reaction
mixture containing at least one monomer may be fed into an inlet to
the channel which has a different inlet within the channel,
allowing a different reaction mixture containing at least one
monomer to be fed at a different point in the process. Where more
than one channel is used, the reaction mixture containing at least
one monomer may be fed through a series of channels, for example
the reaction mixture containing at least one monomer may be fed
through one channel into a connected channel. There may be inlets
between the connected channels to allow a different reaction
mixture containing at least one monomer to be fed at a different
point in the process to a separate channel. The different channels
may be run at different temperature and pressure conditions. The
reaction mixture containing at least one monomer may also be fed
into inlets in parallel channels, whereby the reaction mixture
containing at least one monomer flows through multiple channels at
the same time. The parallel channels may have different inlets
within the channels, allowing a different reaction mixture
containing at least one monomer to be fed at a different point in
the process to channels. The channels may be run at different
temperature and pressure conditions. The channels may have one or
more outlets. The polymer may be removed from the outlet of the
channel, or the polymer may be fed from the outlet of the channel
into one or more inlets of separate channels.
[0020] The process may be used for any type of polymerization, for
example, emulsion polymerization, solution polymerization, or
suspension polymerization. Polymerization may occur through
addition or condensation reactions. Addition reactions include free
radical, anionic, and cationic polymerizations. Emulsion
polymerizations prepared by the process of this invention may be
single stage or multi-stage. For multi-stage emulsion polymers, a
first monomer emulsion may be polymerized in a channel and a second
monomer emulsion may be fed either into a port in the channel, or
into a port before or in a second connected channel. The first
stage may also be pre-polymerized so that both the first stage and
the second monomer emulsion are fed to a single channel. More
flexibility in the process may be achieved by connecting up to ten
channels either in a series or in parallel to the process.
[0021] In another embodiment the reactor consists of
non-cylindrical channels and alternating channels for the
temperature control medium which may be, for example, certain types
of heat exchangers such as plate-frame, plate-fin, and spiral-plate
heat exchangers. The plate-frame heat exchanger consists of
standard plates which may be flat or corrugated. Corrugated plates
are preferred due to improved mixing of the monomer with the other
reactants. The plates serve as heat exchange surfaces and may be
made of stainless-steel types 304 and 316; titanium, Monel, Incoloy
825, Hastelloy C, phosphor bronze, and cupronickel. The plates may
be coated with materials such as graphite or
polytetrafluoroethylene. The plates form alternating
non-cylindrical channels for the reaction mixture containing at
least one monomer and the temperature control medium to flow
through. The plates are supported by a frame. Gaskets prevent
leakage where the plate and frame meet. The frame may be made of
clad stainless steel and enamel-coated mild steel.
[0022] The plate-fin heat exchanger is similar to the plate-frame
heat exchanger, but has a stack of layers, each consisting of a
corrugated fin between flat metal sheets. The sheets are sealed off
on two sides by channels or bars to form passages for the flow of
the reaction mixture containing at least one monomer and the
temperature control medium. The temperature control medium may flow
counter-current to or cocurrent with the reaction mixture
containing at least one monomer.
[0023] The spiral-plate heat exchanger is made from a pair of
plates rolled to provide long rectangular passages for the
temperature control medium and the reaction mixture containing at
least one monomer in counter-current or cocurrent flow.
[0024] The reaction mixture containing at least one monomer may be
a mixture of at least one monomer and at least one initiator and
solvent. Suitable solvents include, but are not limited to acetone,
water, ethanol, methanol, butanol, isopropanol, propylene glycol
monobutyl ether, ethylene glycol monobutyl ether, methylethyl
ketone, dimethylformamide, and dimethylsulfoxide. Where emulsion
polymerization is desired, surfactant may be combined with the
monomer, the initiator, and water. By surfactant is meant a
compound which reduces surface tension when dissolved in water or
water solutions, or which reduces interfacial tension between two
liquids, or between a liquid and a solid. Included in surfactants
are wetting agents, and emulsifiers. Suitable surfactants include,
but are not limited to anionic and nonionic emulsifiers such as
alkali and ammonium alkyl sulfates, for example sodium lauryl
sulfate, alkyl sulfonic acids, fatty acids, and oxyethylated alkyl
phenols. The amount of surfactant used is typically 1 to 6% by
weight, based on the weight of total monomer. The amount of water
used is typically from 5 to 90% by weight, based on the weight of
total monomer. Surfactant and water may also may be used in
downstream dilutions of polymer emulsions made from the monomer
emulsions. Suitable monomers include ethylenically unsaturated
monomers such as, for example, acrylic esters such as methyl
(meth)acrylate, ethyl acrylate, butyl (meth)acrylate, 2-ethylhexyl
acrylate, decyl (meth)acrylate, hydroxyethyl (meth)acrylate, and
hydroxypropyl (meth)acrylate; acrylamide or substituted
acrylamides; styrene or substituted styrenes; ethylene, propylene,
butadiene; vinyl acetate or other vinyl esters; vinyl monomers such
as vinyl chloride, vinylidene chloride, N-vinyl pyrolidone; and
acrylonitrile or methacrylonitrile. Copolymerizable ethylenically
unsaturated acid monomers such as, for example, (meth)acrylic acid,
crotonic acid, phosphoethyl methacrylate,
2-acrylamido-2-methyl-1-propane- sulfonic acid, sodium vinyl
sulfonate, itaconic acid, fumaric acid, maleic acid, monomethyl
itaconate, monomethyl fumarate, monobutyl fumarate, maleic
anhydride and salts thereof may also be used. Preferred monomers
are butyl acrylate, ethyl acrylate, 2-ethyl hexylacrylate, methyl
methacrylate, styrene, and vinyl acetate. More preferred monomers
are butyl acrylate, methyl methacrylate, and vinyl acetate. By
(meth)acrylate is meant both acrylate and methacrylate
monomers.
[0025] Electrolytes such as sodium hydroxide, sodium phosphate,
disodium phosphate, sodium carbonate, and ammonia may be added to
the reaction mixture containing at least one monomer. The
electrolyte may be added at from 0.1 to 15 percent based on the
total weight of the monomers in the reaction mixture.
[0026] A chelating agent such as ethylenediamine tetraacetic acid
may also be added to the reaction mixture containing at least one
monomer. The chelating agent may be added at from 0.01 to 2 percent
based on the total weight of the monomers in the reaction
mixture.
[0027] The method of initiation is not critical to the process of
the invention. Preferably, initiation is effected through the use
of thermal or redox initiation. Conventional free radical
initiators such as, for example, peroxygen compounds including
inorganic persulfate compounds such as ammonium persulfate,
potassium persulfate, and sodium persulfate; peroxides such as
hydrogen peroxide; organic hydroperoxides such as cumene
hydroperoxide and t-butyl hydroperoxide; organic peroxides such as
benzoyl peroxide, acetyl peroxide, lauroyl peroxide, peracetic
acid, and perbenzoic acid (sometimes activated by a water-soluble
reducing agent such as a ferrous compound or sodium bisulfite); as
well as other free-radical producing materials such as
2,2'-azobisisobutyronitrile may be used, typically at a level of
0.05% to 3% by weight, based on the weight of total monomer. Redox
systems using the same initiators coupled with a suitable reductant
(activator) such as, for example, isoascorbic acid, sodium
sulfoxylate formaldehyde, and sodium bisulfite may be used at
similar levels. Ferrous sulfate and other metal ions may be used as
promoters at similar levels. Other suitable methods of initiation
such as the use of irradiation with Ultra Violet light, electron
beam irradiation, gamma irradiation, Ultrasonic, or mechanical
means to induce free-radical generation are deemed to be within the
scope of this invention.
[0028] For an emulsion polymerization, the monomer emulsion must
not phase separate or otherwise become unstable in a manner that
interferes with the efficiency of the polymerization reaction. In
cases where the monomer emulsion has the tendency to become
unstable before polymerization, it may be premixed and thus
stabilized before being fed to the channel. A mixer such as a
static mixer or pre-mixer may be used in the process for this
purpose.
EXAMPLES
[0029] Abbreviations used throughout are:
[0030] %=percent DI=deionized mm=millimeters ml=milliliters
mm=minutes ml/min=milliliters per minute L=liters
[0031] For all Examples, monomer emulsions were prepared by
admixing butyl acrylate, methyl methacrylate, methacrylic acid, an
anionic surfactant, an electrolyte, a chelating agent, and water in
a line. The premixer was set at a speed such that an emulsion was
formed. All percents are by weight.
Example 1
[0032] A monomer mixture (46% butyl acrylate, 53% methyl
methacrylate, 1% methacrylic acid) was fed at 58.5 g/min from a 3.6
L tank to an evacuated premixer (Cornell Model D-8 Versator with a
vacuum of 55.9 mm(22 in) water). An aqueous mixture (1.4% anionic
surfactant) was fed at 11.4 g/min from a 7.6 L tank to the
pre-mixer. The pre-mixer was set to a speed such that a stable
monomer emulsion was produced. A 20 L aqueous feed tank was used to
feed hot DI water to the front of the process. A 10% ammonium
persulfate catalyst solution was prepared. The solution was mixed
well and fed to the catalyst feed tank. A 1.2% aqueous
ammonia/13.8% sodium laurel sulfate buffer solution was prepared.
The solution was mixed well and fed to the buffer feed tank. The
aqueous feeds were fed through 18 feet of peroxide cured gas
permeable tubing coiled in an evacuated chamber at 61.0 mm(24 in)
water. The aqueous catalyst feed tanks were sparged with N2. The
buffer feed tank was swept with N2.
[0033] DI water was heated to 95.degree. C. A Tranter UFX-6
plate-frame heat exchanger system was utilized as the reactor. The
water was pumped through the process lines in order to heat the
system. The temperature for the "water-side" of the reactors was
then set to 70.degree. C. Tempered water flow through the
"water-side" was begun. The reactor temperature was allowed to
equilibrate.
[0034] The DI water flow was adjusted to 64.8 g/min. The catalyst
pump was turned on to 5.68 ml/min and steam was injected into the
catalyst line to preheat the mixture to 95.degree. C. The buffer
pump was turned on to 11.03 ml/min. The monomer emulsion feed was
introduced before the reactor at a rate of 18.5 g/min. The
temperature of the water in the heating bath that fed a pipe in
pipe heat exchanger on the aqueous feed line was adjusted to insure
that the temperature of the emulsion at the heat exchanger inlet
was approximately 73.degree. C. The monomer emulsion was fed
continuously to the heat exchangers. The monomer was polymerized in
the heat exchangers. Polymer was continuously removed from the heat
exchangers and collected and cooled in the final product holding
tank. When the volume was low in any of the feed tanks it was
replenished with a charge equivalent to the original. After 4 hours
of running, warm soapy water was pumped through the system in order
to flush out any remaining emulsion. This was continued until the
exiting liquid was clear.
[0035] A stable latex with a 17.9% solids content and a mean weight
average particle diameter of 55 nm was obtained as a product. The
polydispersity of the product was 1.06. Reaction totaled 100%
conversion. The system was dismantled and the plates were weighed.
The plates weighed 23 grams more than before the experiment.
[0036] Comparative Example A
[0037] A monomer mixture (46% butyl acrylate, 53% methyl
methacrylate, 1% methacrylic acid) was fed at 58.5 g/min from a 3.6
L tank to a vented premixer (Cornell Model D-8 Versator with no
vacuum applied). An aqueous mixture (1.4% anionic surfactant) was
fed at 11.4 g/min from a 7.6 L tank to the pre-mixer. The pre-mixer
was set to a speed such that a stable monomer emulsion was
produced. A 20 L aqueous feed tank was used to feed hot DI water to
the front of the process. A 10% ammonium persulfate catalyst
solution was prepared. The solution was mixed well and fed to the
catalyst feed tank. A 1.2% aqueous ammonia/13.8% sodium laurel
sulfate buffer solution was prepared. The solution was mixed well
and fed to the buffer feed tank. The aqueous feeds were fed through
18 feet of peroxide cured gas permeable tubing coiled in a vented
chamber with no vaccum applied. The aqueous, catalyst feed tanks
were sparged with N2. The buffer feed tank was swept with N2.
[0038] DI water was heated to 95.degree. C. A Tranter UFX-6
plate-frame heat exchanger system was utilized as the reactor. The
water was pumped through the process lines in order to heat the
system. The temperature for the "water-side" of the reactors was
then set to 70.degree. C. Tempered water flow through the
"water-side" was begun. The reactor temperature was allowed to
equilibrate.
[0039] The DI water flow was adjusted to 64.8 g/min. The catalyst
pump was turned on to 5.68 ml/min and steam was injected into the
catalyst line to preheat the mixture to 95.degree. C. The buffer
pump was turned on to 11.03 ml/min. The monomer emulsion feed was
introduced before the reactor at a rate of 18.5 g/min. The
temperature of the water in the heating bath that fed a pipe in
pipe heat exchanger on the aqueous feed line was adjusted to insure
that the temperature of the emulsion at the heat exchanger inlet
was approximately 73.degree. C. The monomer emulsion was fed
continuously to the heat exchangers. The monomer was polymerized in
the heat exchangers. Polymer was continuously removed from the heat
exchangers and collected and cooled in the final product holding
tank. When the volume was low in any of the feed tanks it was
replenished with a charge equivalent to the original. After 4 hours
of running, warm soapy water was pumped through the system in order
to flush out any remaining emulsion. This was continued until the
exiting liquid was clear.
[0040] A stable latex with a 18.2% solids content and a mean weight
average particle diameter of 56.5 nm was obtained as a product. The
polydispersity of the product was 1.06. Reaction totaled 100%
conversion. The system was dismantled and the plates were weighed.
The plates weighed 49 grams more than before the experiment, i.e.,
more fouling was observed on the first plate channels for
Comparative Example A than in Example 1 of this invention.
Example 2
[0041] A monomer mixture (46% butyl acrylate, 53% methyl
methacrylate, 1% methacrylic acid) was fed at 58.5 g/min from a 3.6
L tank to an evacuated premixer (Cornell Model D-8 Versator with a
vacuum of 55.9 mm (22 in) water). An aqueous mixture (1.4% anionic
surfactant) was fed at 11.4 g/min from a 7.6 L tank to the
pre-mixer. The pre-mixer was set to a speed such that a stable
monomer emulsion was produced. A 20 L aqueous feed tank was used to
feed hot DI water to the front of the process. A 10% ammonium
persulfate catalyst solution was prepared. The solution was mixed
well and fed to the catalyst feed tank. A 1.2% aqueous
ammonia/13.8% sodium laurel sulfate buffer solution was prepared.
The solution was mixed well and fed to the buffer feed tank. The
aqueous feeds were fed through 18 feet of peroxide cured gas
permeable tubing coiled in an evacuated chamber at 61.0 mm (24 in)
water. The aqueous tanks were sparged with Helium. The buffer feed
and catalyst tanks were swept with Helium.
[0042] DI water was heated to 95.degree. C. A Tranter UFX-6
plate-frame heat exchanger system was utilized as the reactor. The
water was pumped through the process lines in order to heat the
system. The temperature for the "water-side" of the reactors was
then set to 70.degree. C. Tempered water flow through the
"water-side" was begun. The reactor temperature was allowed to
equilibrate.
[0043] The DI water flow was adjusted to 64.8 g/min. The catalyst
pump was turned on to 5.68 ml/min. The buffer pump was turned on to
11.03 ml/min. The monomer emulsion feed was introduced before the
reactor at a rate of 18.5 g/min. The temperature of the water in
the heating bath that fed a pipe in pipe heat exchanger on the
aqueous feed line was adjusted to insure that the temperature of
the emulsion at the heat exchanger inlet was approximately
73.degree. C. The monomer emulsion was fed continuously to the heat
exchangers. The monomer was polymerized in the heat exchangers.
Polymer was continuously removed from the heat exchangers and
collected and cooled in the final product holding tank. When the
volume was low in any of the feed tanks it was replenished with a
charge equivalent to the original. After 4 hours of running, warm
soapy water was pumped through the system in order to flush out any
remaining emulsion. This was continued until the exiting liquid was
clear.
[0044] A stable latex with a 17.1% solids content and a mean weight
average particle diameter of 56 nm was obtained as a product. The
polydispersity of the product was 1.05. Reaction totaled 100%
conversion. The system was dismantled and the plates were weighed.
The plates weighed 20 grams more than before the experiment.
Example 3
[0045] A monomer mixture (46% butyl acrylate, 53% methyl
methacrylate, 1% methacrylic acid) was fed at 58.5 g/min from a 3.6
L tank to an evacuated premixer (Cornell Model D-8 Versator with a
vacuum of 55.9 mm (22 in) water). An aqueous mixture (1.4% anionic
surfactant) was fed at 11.4 g/min from a 7.6 L tank to the
pre-mixer. The pre-mixer was set to a speed such that a stable
monomer emulsion was produced. A 20 L aqueous feed tank was used to
feed hot DI water to the front of the process. A 10% ammonium
persulfate catalyst solution was prepared. The solution was mixed
well and fed to the catalyst feed tank. A 1.2% aqueous
ammonia/13.8% sodium laurel sulfate buffer solution was prepared.
The solution was mixed well and fed to the buffer feed tank. The
aqueous feeds were fed through 18 feet of peroxide cured gas
permeable tubing coiled in an evacuated chamber at 24" water. The
aqueous, catalyst feed tanks were sparged with N2. The buffer feed
tank was swept with N2.
[0046] DI water was heated to 95.degree. C. A Tranter UFX-6
plate-frame heat exchangers system was utilized as the reactor. The
water was pumped through the process lines in order to heat the
system. The temperature for the "water-side" of the reactors was
then set to 70.degree. C. Tempered water flow through the
"water-side" was begun. The reactor temperature was allowed to
equilibrate.
[0047] The DI water flow was adjusted to 64.8 g/min. The catalyst
pump was turned on to 5.68 ml/min. The buffer pump was turned on to
11.03 ml/min. The monomer emulsion feed was introduced before the
reactor at a rate of 18.5 g/min. The temperature of the water in
the heating bath that fed a pipe in pipe heat exchanger on the
aqueous feed line was adjusted to insure that the temperature of
the emulsion at the heat exchanger inlet was approximately
73.degree. C. The monomer emulsion was fed continuously to the heat
exchangers. The monomer was polymerized in the heat exchangers.
Polymer was continuously removed from the heat exchangers and
collected and cooled in the final product holding tank. When the
volume was low in any of the feed tanks it was replenished with a
charge equivalent to the original. After 4 hours of running, warm
soapy water was pumped through the system in order to flush out any
remaining emulsion. This was continued until the exiting liquid was
clear.
[0048] A stable latex with a 17.5% solids content and a mean weight
average particle diameter of 55 nm was obtained as a product. The
polydispersity of the product was 1.06. Reaction totaled 100%
conversion. The system was dismantled and the plates were weighed.
The plates weighed 16 grams more than before the experiment.
* * * * *