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BACKGROUND OF THE INVENTION
Water soluble polymers can be prepared in several forms. For instance, it
is known in the art that water-soluble polymers can be dispersed into the
oil phase of water-in-oil emulsions. Conventional emulsion polymerization
techniques generally involve either:
(1) forming a water-in-oil emulsion of an aqueous solution of at least one
water-soluble ethylenically unsaturated monomer in an inert hydrophobic
liquid organic dispersion medium and polymerizing said monomer or monomers
in said dispersion medium to form a polymer emulsion; or
(2) forming a water soluble polymer and then emulsifying the polymer solids
into an emulsion having a hydrophobic liquid as the continuous phase.
In such polymerization methods, virtually any water soluble monomer
containing a CH.sub.2 =C functional group can be polymerized and dispersed
into a water-in-oil system. Thus, anionic, cationic, nonionic and
amphoteric emulsion polymers can be prepared by conventional emulsion
polymerization techniques.
Water-in-oil emulsions are generally comprised of three primary components
including: (1) a hydrophobic phase; (2) an aqueous phase; and (3) a
surfactant system. The hydrophobic phase generally comprises from about 5
to about 75%, by weight, of the emulsion. Any inert hydrophobic liquid can
be used as the hydrophobic phase. Preferred hydrophobic liquids, for
example, are selected from the group consisting of benzene, xylene,
toluene, mineral oils, kerosene, napthas, petroleums, and blends of
aromatic and aliphatic hydrocarbons containing 4 or greater carbon atoms.
Particularly preferred hydrophobic liquids are those selected from the
group consisting of a narrow fraction of a branch-chain hydrocarbon sold
by Witco Chemical Company under the tradename Kensol 61.RTM. and
branch-chain isoparafinic hydrocarbons sold by Exxon under the tradename
Isopar.RTM..
The aqueous phase generally comprises from about 25 to about 95%, by
weight, of the emulsion. This phase comprises the desired ethylenically
unsaturated monomer or monomers and water. Additionally, this phase may
contain an effective amount of a chelating agent, such as a sodium salt of
ethylene diamine tetracetic acid (EDTA) or nitrilotriacetate (NTA),
buffers, chain transfer agents or other additives. The monomer(s) to be
polymerized generally comprise about 10 to about 60%, by weight, of the
aqueous phase, with the balance being primarily water.
The surfactant system generally comprises about 0.5 to about 20%, by
weight, of the emulsion. Any surfactant system which effectively disperses
an aqueous phase into a hydrophobic phase can be used. See, for example,
U.S. Pat. No. 3,826,771, which discloses the use of sorbitan monooleate as
water-in-oil emulsifying agent; U.S. Pat. No. 3,278,506, which discloses
the use of ethylene oxide condensates of fatty acid amides as emulsifiers;
U.S. Pat. No. 3,284,393, which discloses the use of hexadecyl sodium
pthalate, sorbitan monooleate, sorbitan monostearate, cetyl or stearyl
sodium pthalate and metal soaps as water-in-oil emulsifiers; and U.S. Pat.
No. 4,024,097, which discloses the use of surfactant systems comprising an
oil-soluble alkanolamide, such as Witcamide.RTM. 511, which is
commercially available from Witco Chemical Company, and one or more
co-emulsifiers selected from the group consisting of unesterified
dialkanol fatty amides, quaternized ammonium salts of fatty tertiary
amines, salts of fatty tertiary amines, alkaline metal salts of fatty
acids and alkyl or alkylaryl sulfates or sulfonates.
U.S. Pat. Nos. 4,672,090 and 4,772,659 disclose a surfactant system which
comprises 25 to 85%, by weight, an oil-soluble alkanolamide; 5 to 35%, by
weight, a polyoxyethylene derivative of a sorbitan ester; and 0 to 50%, by
weight, sorbitan monooleate. Additionally, other surfactants, such as
sorbitan monostearate, may be used in combination with these primary
surfactants.
Emulsion polymers are generally produced by first mixing the surfactant
system with the hydrophobic phase. The aqueous phase is then typically
prepared by adding the monomer(s) to water in the desired concentration.
Additionally, a chelant, such as a sodium salt of EDTA, may be added to
the aqueous solution and the pH of the aqueous phase may be adjusted to
between about 3.0 and 10.0, depending on the monomer(s) used. The aqueous
monomer phase is then added to the mix containing the hydrophobic liquid
and the surfactant system. The surfactant system enables the aqueous
phase, which contains the monomer or monomers to be polymerized, to be
emulsified into the hydrophobic phase. Polymerization is then carried out
in the presence of a free radical generating catalyst, and the temperature
of the reaction mixture is generally maintained between about 5.degree.
and about 100.degree. C., preferably between about 20.degree. and about
50.degree. C., resulting in water-in-oil emulsion polymer. Any type of
free radical initiator can be used, including, for example persulfate and
azo initiators. High energy irradiation can also be used to initiate
polymerization.
The following patents provide further background relative to the
manufacture of emulsion polymers.
U.S. Pat. No. 3,041,318 discloses emulsifying an aqueous dispersion of a
polymer prepared from a compound containing a CH.sub.2 =C group into a
water-in-oil emulsion, and then precipitating the polymer therefrom as
discrete particles.
U.S. Pat. No. 3,284,393 discloses a water-in-oil emulsion polymerization
process wherein a water-soluble monomer is emulsified in an oil phase and
polymerized therein, resulting in a polymeric latex which is then
separated from the reaction medium.
U.S. Pat. Nos. 3,624,019 (reissued and reexamined as B1 Re 28,474) and
3,734,873 (reissued and reexamined as B1 Re 28,576) disclose the
preparation of water-in-oil emulsions of vinyl addition polymers using
various surfactants, particularly low HLB surfactants, as emulsifiers. The
polymers are dispersed into emulsions by means of agitation. Thus,
polymers which are powders or "lumplike agglomerates" are comminuted and
dispersed into the oil phase using mechanical energy. The specification at
column 3 states that "The invention contemplates using emulsions
containing between 5-75 percent by weight with preferred emulsions having
a polymer concentration within the range of 10-45% by weight. In some
cases the starting emulsions are converted to suspensions due to the
nature and the amount of the polymer present therein." Though purely
theoretical polymer concentrations of up to 75% are recited, the activity
range found in the examples is 23-37%.
U.S. Pat. No. 3,826,771 discloses "high solids" water-in-oil emulsions
which have a polymer concentration between about 20 and 50%, by weight,
based on emulsion weight. This reference discloses that the method of the
U.S. Pat. No. 3,041,318 cannot be used to prepare emulsions containing 20
to 50%, by weight, of a vinyl addition polymer having a molecular weight
in excess of 1,000,000 because aqueous solutions cannot be prepared
containing high enough concentrations of the polymer.
U.S. Pat. No. 3,888,945 discloses the use of azeotropic distillation to
remove water from a suspension of an aqueous solution of a polymer in a
non-polar suspending medium.
U.S. Pat. No. 3,997,492 discloses stable water-in-oil emulsion polymers
which have polymer concentrations between 10 and 50%, by weight, of the
emulsion.
U.S. Pat. No. 4,021,399 discloses a method for concentrating a water-in-oil
emulsion polymer by distilling under vacuum while maintaining the
water-to-oil phase ratio substantially equal to that of the, starting
latex. Though this method is stated to be useful in preparing emulsions
containing up to 70%, by weight, polymer, the examples are limited to
.gtoreq.48% active polymer.
U.S. Pat. No. 4,035,317 discloses a method for preparing free-flowing solid
polymer particles from water-in-oil emulsions. A hot gas stream is used
for drying.
U.S. Pat. No. 4,052,353 discloses the treatment of water-in-oil emulsions
via evaporation to reduce the water content thereof and to produce a
polymer stable to coagulation or agglomeration. The use of falling-film
evaporation is not disclosed or suggested.
U.S. Pat. No. 4,035,347 discloses a method for preparing substantially dry
polymers from water-in-oil emulsions using a thin film drying technique.
U.S. Pat. No. 4,528,321 discloses the distillation of dispersions to remove
water and other volatile components. Theoretical polymer concentrations as
high as 85%, by weight, are disclosed. .However, no examples are given
showing greater than 57% polymer.
UK Pat. No. 1,482,515 discloses water-in-oil emulsions which theoretically
contain up to 63% active polymer.
U.S. Pat. No. 4,506,062 discloses a reverse phase suspension polymerization
process and the use of azeotropic distillation to prepare polymer
dispersions in oil which theoretically contain up to 70% polymer solids.
In various examples the polymer dispersions of the earlier examples are
centrifuged to assess particle size range and shape. A centrifuge is used
in a standard compaction test; this reference does not, however, disclose
the use of a centrifuge to concentrate an emulsion. The process is
believed to degrade molecular weight and solubility properties.
U.S. Pat. No. 5,155,156 discloses a process wherein the water in a polymer
latex containing water and an emulsifier is evaporated, followed by
separation of the dried polymer from the emulsifier via filtration or
centrifugation, multiple washing steps and redispersion of the polymer
into a second oil. The water content of the polymer after drying is "most
preferably about 3% to 8%", and this reference does not disclose the use
of falling-film evaporation to dehydrate polymer emulsions. Though 85%
active polymer compositions are claimed, the maximum solids concentration
obtained in the examples is 68%.
In summary, the inventor, believe that the references discussed above
provide a comprehensive overview of the emulsion polymerization art, but
that they, alone or in combination, do not disclose or remotely suggest
the instant invention. While certain of these references suggest, in
purely theoretical terms, emulsions containing in excess of 70% active
polymer, stable emulsions at such concentrations are simply not
commercially available. This is verified by the examples of the above
references, which only show the preparation of emulsion polymers
containing less than about 70% active polymer.
Commercial emulsion polymer compositions contain substantial portions of
water and are much less active. For example, U.S. Pat. No. 4,035,317
states that: "Two problems still existed, however, in the first place, the
cost of transporting the emulsion is materially higher than if the polymer
per se were being transported. Since the emulsions contain, on the
average, only about 25-30% polymer, 70-75% of the material shipped is
useless oil and water. Secondly, the emulsions can present a stability
problem when exposed to temperatures below their freezing point."
Water soluble polymers containing in excess of about 60% solids are
currently only commercially available in dry or gel form. Dry polymers are
generally prepared by drying conventional solution polymers, and gels are
simply high viscosity polymer solutions which can not be transported as
liquids. They are generally adherent, tough, rubbery substances which
retain their shape when placed on flat surfaces. Gels are not generally
used is gel form but instead as dilute solutions of the polymer. Dilution
methods oftentimes involve mechanical steps which result in the
degradation of certain properties of the polymers, such as molecular
weight.
To obtain polymers having high molecular weights and good water solubility
properties, it is necessary to prevent crosslinking reactions during
polymerization to the extent possible. In this respect, it is desirable to
prepare polymers under relatively mild conditions, e.g., conducting
polymerization reactions using relatively low monomer concentrations.
Unfortunately, aqueous solution polymerization techniques which use low
monomer concentrations require that the resulting solution polymers be
dried to prepare powdered polymers, thus resulting in increased
manufacturing costs and degradation of polymer properties such as
molecular weight and solubility.
Though there is a long felt need in industry for stable, high molecular
weight, soluble, easily handled polymer delivery systems containing in
excess of 70% active polymer, this need has not been met because of the
art's inability to efficiently concentrate liquid polymer compositions to
a stable form having a high polymer content without substantially
degrading the resulting high solids polymers.
Also, while dry polymers provide high activity, handling and make-down
problems remain. A major benefit of the instant polymer compositions is
that the economic advantages of dry polymers compared to emulsion and
solution polymers can be realized along with the additional advantages
associated with emulsion polymerization techniques, such as that water
soluble polymers of high molecular weight are prepared in a pourable,
stable liquid form. This invention advances the art of polymer preparation
and delivery in that stable, pourable, high molecular weight, water
soluble polymer compositions containing in excess of about 60%, preferably
in excess of 70%, active polymer are now available.
It is also noteworthy that no prior art reference known to the inventors
discloses or suggests: 1) the use of falling-film evaporation to dehydrate
emulsion polymers, particularly to water contents of less than 3%, based
on total composition weight, and 2) the use of a separation means such as
a centrifuge to further concentrate a dehydrated polymer/emulsifying
surfactant/hydrophobic liquid composition produced via a falling-film
evaporator into a high solids end use product. This further supports the
novelty of the instant invention, which relates to the use of a
falling-film evaporation and additional steps to dehydrate and concentrate
starting water-in-oil emulsions, dispersions or suspensions, thereby
producing non-aqueous polymer/emulsifying surfactant/hydrophobic liquid
compositions containing less than about 5% water, preferably less than
about 3% water, and greater than 60%, preferably greater than 70%, polymer
solids.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a flow diagram illustrating the instant process for preparing
non-aqueous, high solids, stable, pourable polymer emulsions/suspensions.
SUMMARY OF THE INVENTION
The instant invention relates, in general terms, to non-aqueous
polymer/emulsifying surfactant/hydrophobic liquid compositions and to the
preparation of such compositions via the use of falling-film evaporation
and an additional separation step such as centrifugation, filtration or
evaporation to dehydrate and concentrate water-in-oil polymer
compositions. The resulting polymer compositions, which contain less than
5%, preferably less than 3%, more preferably less than 2%, water, and
greater than 60%, preferably greater than 70% polymer solids, based on
total composition weight, are pourable, stable, high solids cationic,
anionic, nonionic or amphoteric polymer emulsions or suspensions which are
substantially non-aqueous.
Conventional commercially available emulsions or suspensions of a water
soluble polymer in a continuous oil phase generally only contain up to
about 30-50 weight % polymer solids. This means that 50-70 weight % or
more of such emulsions is inactive. Nonetheless, the convenience of such
compositions mandates their wide use in industry.
The instant inventors have discovered that falling-film evaporators,
preferably when used in conjunction with one or more separation steps for
the removal of hydrophobic liquid, such as filtration,. evaporation or
centrifuge steps, are particularly well suited to remove water from
water-in-oil polymer compositions. Because falling-film evaporators
efficiently remove water from such compositions without thermally
punishing the polymer contained therein, falling-film evaporation enables
the preparation of stable, high solids polymer compositions which are
substantially non-aqueous and which generally retain the molecular weight
and solubility advantages of the starting emulsion.
Ideally, in the instant dehydration/concentration process, one starts with
a water-in-oil polymer suspension, dispersion or emulsion having a polymer
concentration of less than about 25%, preferably about 1 to about 15%,
based on total suspension or emulsion weight. If the polymer concentration
of the composition to be dehydrated and concentrated exceeds about 25%,
evaporator fouling tends to become troublesome. In such cases, dilution,
preferably using a suitable hydrophobic liquid, to a polymer concentration
of less than about 25% is recommended. The water-in-oil polymer
composition containing less than about 25% polymer solids is then
dehydrated in a falling-film evaporator, wherein the water content of the
composition is lowered to about 5% or less, preferably 3% or less, more
preferably to between about 0.1 and about 2.5%, most preferably to between
about 0.1 and about 1.5%, based on total composition weight, followed by
concentration via one or more separation steps to remove hydrophobic
liquid, such as centrifuge, evaporation and/or filtration steps.
Centrifugal separation is preferred. Also, a steric stabilizer is
preferably added to reduce the potential for compaction and/or separation
of the concentrated composition.
Falling-film evaporators are used for the dehydration step of the instant
process because they are believed to minimize heat punishment of the
polymer composition being dehydrated. Since polymers are heat sensitive,
this preserves the molecular weight and solubility properties of the
starting emulsion. In a falling-film evaporator, the starting emulsion is
exposed to high temperatures, preferably but not necessarily under vacuum,
for relatively short periods of time. This enables falling-film
evaporators to quickly flash water off of starting polymer compositions
without thermally degrading the polymer or substantially effecting the
stability of the starting emulsion.
After dehydration, the evaporator concentrate is treated via a second
separation process, such as a filtration, evaporation or centrifugation
process, to remove additional hydrophobic liquid. Preferably, the
evaportor concentrate is centrifuged to produce what is substantially a
polymer and emulsifier-in-oil composition containing in excess of about
60% polymer solids, preferably in excess of about 70% polymer solids, and
less than about 5%, preferably less than about 3%, and more preferably
less than about 2%, water. The raffinate from the centrifuge can be
optionally fed to a second separation device such as a centrifuge to
capture additional polymer solids, with the oil-rich raffinate stream of
the second centrifuge being recycled. Finally, the polymer and emulsifying
surfactant-in-oil composition produced by the centrifuge step(s) can be
stabilized against compaction or separation using a stabilizer such as a
steric stabilizer.
The instant process is designed to substantially increase the polymer
concentration of standard commercially available emulsions, suspensions or
dispersions without negatively impacting the performance of the polymer.
This means that, on an active basis, the volume of material which must be
handled is significantly reduced, which in turn makes the instant polymer
compositions valuable in applications where standard emulsions are not
suitable because of excessive storage requirements, such as offshore oil
drilling platform applications. In addition, the instant compositions
compete effectively with dry polymers due to their higher molecular
weights, improved performance, and comparable storage space requirements.
The instant products are also believed to offer advantages over standard
emulsions relative to convenience, stability, compaction, oil separation
and reduced susceptibility to gel formation during storage because of the
low moisture content of the material.
DETAILED DESCRIPTION OF THE INVENTION
In its broadest sense, the instant invention relates to non-aqueous, high
solids polymer compositions containing less than about 5%, preferably less
than about 3%, by weight water and greater than 60%, preferably greater
than about 70%, polymer solids, and to the preparation of the same through
the use of falling-film evaporation and one or more separation steps,
preferably centrifuge steps, to dehydrate and concentrate a starting
water-in-oil polymer emulsion or suspension.
The resulting compositions, which may be emulsions, suspensions or
dispersions, are stable, pourable compositions which are essentially
non-aqueous and which contain in excess of 60% polymer solids and less
than about 5% water, preferably in excess of 70% polymer and less than
about 3% water. More preferably, these compositions contain less than 2%
water.
Further, the instant invention relates to a process for removing water and
increasing the polymer concentration of a water-in-oil polymer composition
comprising a water soluble polymer, one or more emulsifying surfactants,
water and a hydrophobic liquid, which method comprises: a) dehydrating
said composition via an evaporation step to form a polymer/emulsifying
surfactant/hydrophobic liquid composition, and b) centrifuging,
evaporating or filtering said polymer/emulsifying surfactant/hydrophobic
liquid composition to remove some portion of said hydrophobic liquid
therefrom, thereby producing a concentrated polymer/emulsifying
surfactant/hydrophobic liquid composition containing less than about 5%,
preferably less than about 3% and more preferably less than about 2%,
based on total composition weight, of water. These concentrated
polymer/emulsifying surfactant hydrophobic liquid compositions generally
contain in excess of about 60% polymer solids, preferably in excess of
about 70% polymer solids. Preferably, as step c), an effective amount of a
steric stabilizer is added to the concentrated polymer composition to
improve its stability characteristics.
The instant invention is also directed to a water soluble
polymer/hydrophobic liquid/emulsifying surfactant composition or
suspension which contains less than about 5%, preferably less than about
3%, water and greater than about 60% polymer solids, based on total
composition weight. More preferably, these compositions contain less than
about 2% water and greater than about 70% polymer, based on total
composition weight.
Additionally, the instant invention is directed to a process for
concentrating a starting water-in-oil polymer composition comprising: 1)
about 25 to about 95%, based on total composition weight, of an aqueous
phase comprising about 10 to about 60%, based on the weight of 1), of a
water soluble polymer, and the balance water; 2) about 0.5 to about 20%,
based on total composition weight, of at least one emulsifying surfactant;
and 3) about 25 to about 95%, based on total composition weight, of a
hydrophobic liquid, which method comprises: a) dehydrating said
composition using an evaporator, preferably a falling-film evaporator, to
produce a polymer/emulsifying surfactant/hydrophobic liquid composition
which is substantially water free, i.e., which contains less than about
5%, preferably less than 3%, more preferably from about 0.1 to about 2.5%
water, and most preferably from about 0.1 to about 1.5%, water; b)
centrifuging said polymer/emulsifying surfactant/hydrophobic liquid
composition so as to remove some portion of said hydrophobic liquid
therefrom, thereby producing a concentrated polymer/emulsifying
surfactant/hydrophobic liquid composition and a centrifuge raffinate,
wherein said concentrated polymer/emulsifying surfactant/hydrophobic
liquid composition contains less than about 5%, preferably less than about
3%, more preferably less than about 2%, water, greater than about 60%,
more preferably greater than about 70%, polymer and about 0.1 to about 10%
emulsifying surfactant; c) optionally treating said centrifuge raffinate
in a second separation device, such as a centrifuge, filter or evaporator,
preferably a centrifuge, thereby producing a second concentrated polymer
composition and a second raffinate stream; d) optionally blending said
second concentrated polymer composition from said second separation device
with said concentrated polymer/emulsifying surfactant/hydrophobic liquid
composition and recycling or disposing of said second raffinate stream;
and e) optionally adding an effective amount of a steric stabilizer to the
resulting concentrated composition.
In this process, the evaporator is preferably a falling-film evaporator,
more preferably a thin film evaporator, the centrifuge of b) is preferably
a decanter centrifuge and the centrifuge of c) is preferably a partially
ejecting disk centrifuge. Also, if the polymer concentration of the
starting water-in-oil polymer compositions exceeds about 25%, based on
total composition weight, the starting composition is preferably diluted
with a suitable hydrophobic liquid oil so as to reduce the polymer
concentration to less than about 25%, preferably to between about 1 to
about 15% by weight, based on total composition weight. Compositions
produced by this process are also claimed.
The instant invention is further directed to a method for removing water
from a water-in-oil polymer composition which comprises passing said
composition through a falling-film evaporator. Thus, this invention
involves the use of a falling-film evaporator to dehydrate a starting
water-in-oil polymer emulsion, dispersion or suspension and to the
dehydrated product produced thereby. Preferably the starting water-in-oil
polymer emulsion, dispersion or suspension contains less than 25%, based
on the total weight of the starting emulsion, dispersion or suspension,
polymer. In cases where the starting polymer concentration is higher, a
hydrophobic oil dilution step is preferred. Thin film evaporators are the
most preferred type of falling-film evaporator. The products produced by
falling-film evaporators preferably contain less than about 3% water, more
preferably between about 0.1 and about 2.5% water, and most preferably
between about 0.1 and about 1.5% water.
The instant invention also relates to a method for concentrating a
dehydrated polymer composition by removing hydrophobic liquid therefrom,
which comprises treating a dehydrated polymer composition (e.g., an
emulsion, dispersion or suspension), particularly the dehydrated
composition produced by a falling-film evaporator, in at least one
concentration device such as a centrifuge, evaporator or filter,
preferably a centrifuge and more preferably a decanter centrifuge, to
produce a concentrated polymer/emulsifying surfactant/hydrophobic liquid
composition. The resulting compositions also comprise an integral part of
this invention. Preferably, the resulting composition contains in excess
of about 60%, more preferably in excess of about 70%, polymer solids and
less than about 5%, more preferably less than about 3%, and most
preferably less than about 2%, water. Decanter centrifuges have been found
by the inventors to be especially well suited to concentrate dehydrated
emulsions.
Still further, the instant invention relates to the use of a second
separation device such as a filter, evaporator or centrifuge, preferably a
centrifuge, to concentrate the raffinate of a first centrifuge used to
concentrate a polymer emulsion or suspension, which allows for additional
polymer capture and oil recycle. A partially ejecting disk centrifuge is
preferred for this application.
The inventors believe that any type of water-in-oil polymer composition can
be concentrated by the instant process. Thus, as used herein, the term
"water-in-oil polymer composition" includes virtually any water-in-oil
emulsion, dispersion or suspension containing a water soluble polymer
prepared from an ethylenically unsaturated monomer or monomers, wherein
said polymer is a portion of an aqueous phase which is dispersed,
emulsified or suspended by one or more surfactants in a system having a
hydrophobic liquid as the continuous phase, and wherein the polymer
comprises less than about 60%, by weight, of the composition.
The water-in-oil polymer compositions discussed herein can contain any type
of water soluble polymer prepared from one or more ethylenically
unsaturated monomers. Thus, the polymers may be nonionic, cationic,
anionic or amphoteric. The instant invention is generally applicable, for
example, to nonionic and anionic water soluble emulsions or suspensions of
ethylenically unsaturated polymers prepared from, inter alia, N-vinyl
pyrrolidone, N-vinyl formamide, ethoxylated acrylate and methacrylate
esters such as hydroxyethyl methacrylate (HEM) and the 5, 10 and 20 mole
ethoxylates of HEM, acrylamide, methacrylamide, N,N-dimethylacrylamide,
N-i-propylacrylamide, N-tertbutylacrylamide, acrylic acid, .alpha.-halo
acrylic acid, maleic acid or anhydride, itaconic acid, vinyl acetic acid,
allyl acetic acid, methacrylic acid, acrylonitrile, vinyl sulfonic acid,
allyl sulfonic acid, vinyl phosphonic acid, vinyl acetate,
2-acrylamido-2-methylpropane sulfonic acid (AMPSA),
2-methacrylamido-2-methylpropane sulfonic acid (methAMPSA), styrene
sulfonic acid, hydroxyalkyl acrylates, .beta.-carboxyethylacrylic acid,
.beta.-sulfoalkyl (meth)acrylates, sulfoalkyl methacrylates,
allyloxy-2-hydroxypropane sulfonic acid, and methacrylamido hydroxypropyl
sulfonic acid, alone or in combination, and salts of such polymers.
The polymers of this invention may also be cationic, such as polymers made
from dimethyldiallyl ammonium chloride (DMDAAC), diethyldiallyl ammonium
chloride (DEDAC), dimethyldiallyl ammonium bromide (DMDAAB),
diethyldiallyl ammonium bromide (DEDAAB), methyacryloyl-oxyethyltrimethyl
ammonium chloride (METAC), acryloyl-oxyethltrimethyl ammonium chloride
(AETAC), methacryloyl-oxyethyltrimethyl ammonium methosulfate (METAMS),
acryloyl-oxyethyltrimethyl ammonium methosulfate (AETAMS),
methacrylamido-propyltrimethyl ammonium chloride (MAPTAC),
dimethylaminoethylacrylate, dimethyl aminoethyl methacrylate,
dimethylamino propylmethacrylamide, alone or in combination, and polymers
made by polymerizing the above listed cationic monomers with nonionic
monomers such as any of the above listed nonionic monomers, particularly
acrylamide, methacrylamide or N, N-dimethylacrylamide.
Any amphoteric polymer can be used in the instant compositions, including,
but are not limited to, polymers made by polymerizing one or more of the
above listed anionic monomers with one or more of the above listed
cationic monomers, and especially polymers made from acrylic acid,
methacrylic acid and/or AMPSA or methAMPSA and DMDAAC, AETAC, METAC,
METAMS, and/or MAPTAC. Optionally, nonionic monomers may be included.
Also, betaine polymers can be made from
N(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethyl ammonium betaine,
alone or in combination with various nonionic monomers.
Generally, the anionic, nonionic, cationic or amphoteric polymers present
in the instant water-in-oil polymer compositions have molecular weights
greater than about 100,000, as determined by viscometry. Preferably,
molecular weights range from about 500,000 to about 50,000,000.
The instant process involves the concentration of a starting polymer
emulsion or suspension to greater than about 60% polymer solids,
preferably to greater than about 70% polymer solids. The resulting polymer
compositions are in a stable, pourable form, and the instant process
generally does not substantially alter the properties of the polymers in
the starting emulsion, particularly the molecular weight or solubility
characteristics of these polymers.
The compositions produced by the instant process are novel
polymer/emulsifying surfactant/hydrophobic liquid compositions which
contain less than about 5%, preferably less than about 3%, and more
preferably less than about 2%, based on total composition weight, water.
These compositions also comprise: a) at least about 60%, by weight, a
water soluble polymer, preferably at least about 70%, by weight, polymer;
b) about 10 to about 35%, by weight, hydrophobic liquid; c) at least about
0.1%, by weight, of at least one emulsifying surfactant; and optionally,
d) an effective amount of a steric stabilizer, all percentages being based
on total composition weight.
More preferably, the instant non aqueous compositions also comprise: a)
about 70-85% water soluble polymer; b) about 10 to about 25% hydrophobic
liquid; c) about 0.1 to about 10% of at least one emulsifying surfactant
stabilizing polymer; and d) optionally, an effective amount of a steric
stabilizer. Generally, inert materials are also present.
To prepare the instant compositions, a "starting composition" which may be
a polymer emulsion, dispersion or suspension, comprising an initial weight
concentration of water, an initial weight concentration of a hydrophobic
liquid, an initial weight concentration of at least one emulsifying
surfactant, and an initial weight concentration of a water soluble polymer
is dehydrated and concentrated by a process which comprises: a) diluting
the starting emulsion, if the initial polymer weight concentration exceeds
about 25% of said water-in-oil polymer composition, with a suitable
hydrophobic liquid so as to produce a water-in-oil composition having a
polymer weight concentration of from about 0.1 to about 25%, preferably
from about 1 to about 15%, based on composition weight; b) dehydrating the
composition of step a) by evaporating water from the water-in-oil polymer
composition of step a), preferably via falling-film evaporation, thereby
lowering said initial weight concentration of water to less than about 5%,
preferably less than about 3%, more preferably to between about 0.1 and
about 2.5% and most preferably to between about 0.1 to about 1.5%, and
producing an evaporator concentrate; and c) treating the evaporator
concentrate of step b) to remove some portion of the hydrophobic liquid
from said evaporator concentrate, for example by filtration, evaporation
or centrifugation, preferably by centrifugation, thereby producing a
concentrated composition which is substantially a water soluble polymer
and emulsifying surfactant suspension, dispersion or emulsion in a
hydrophobic liquid, and a raffinate, preferably a centrifuge raffinate.
The raffinate can optionally be treated in a second separation device such
as a filter, centrifuge or evaporator, preferably a centrifuge, to capture
additional polymers solids and to reclaim additional hydrophobic liquid.
The water | | |
