Note: Descriptions are shown in the official language in which they were submitted.
ALLIED COLLOIDS LIMITE~ 60/2388/02
POLYMERISATION PROCESSES AND POLYMERIC COMPOSITIOMS
Polymers that are formea from water soluble monomers
are frequently maae by re~erse phase polymerisation to
yield a stable water in vil d;spersion of the polymer.
It is we~l known to dehydrate this dispersion. A
typica], disclosure of such processes is in EP 126528.
In U.S. 4,059,552 and 4,172,066 it is proposed to
thicken an a~ueous medium using microbeads of a cross
linked water insoluble, water swellable, po~ymer formed
by reverse phase polymerisaf,ion from water soluble
monomers including a cross linking agent. In GB
2,007,238 a thickening blend is formed rom a water
soluble polymer and a water swellable cross linked
polymer. In European application 85300292.1
(unpublished at the prioritv date of this application) a
printing paste ~hickener is made by reverse phase
polymerisation of an ethylenically unsaturated acid that
has been partially neutralised and in the presence of a
cross linking agent, the ratio of acid groups to salt
groups being 80:20 to 10:90 during polymerisation.
It is well known to form polymers from a mixture of
monomers one of which includes a pendant hydrophobic
group that contains at least one hydrocarbyl group of at
least eight carbon a~oms. Such groups, especially when
carried by an alkoxy chain, tend to create association
between adjacent molecules. Frequently other monomers
used for the production of such polymers include
materials such as ethyl acrylate which is water
insoluble. Examples of disclosures of such polymers are
GB 1,167,524, 1,273,552, U.S. 4,138,381, 4,268,641
4,384,096, 4,463,151 and EP 13836 and 109820. It has
been proposed to make them by precipitation
polymerisation (~ 1,167,524) or solution polymerisation
(Il.S. 4,138,381) but in most instances they are made by
L~. ~
conventional emulsion polymerisation, i.e., by
emulsifying water insoluble monomexs into water and
polymerising to form an emulsion of the desirefl polymer.
Even in those patents where it is proposed to
polymerise in solution either in water or water solvent
mixtures the detailed description is always of ~he use of
water solvent mixtures (see for instance EP 63018). The
reason for this preference to polymerise as oil in water
emulsions or as solutions in organic solvents is probably
twofold. Firstly, the monomers containing the
hydrophobic group would be e~pected to be much less
miscible with water than conventional monomers, because
of the hydrophobe and so conventional processes in which
an aqueous solution of monomer is polymerised would be
expected to be inoperable. Secondly, the monomer that
includes the hydrophobe is often made from a high HLB
surfactant and so its presence in a monomer mixture would
be expected to destabilise any emulsion tha~ would be
destabilised by high HLB surfactants.
In EP 109820 it is proposed to make polymers of at
least 10~ of an acidic monomer that can be, for instance,
acrylic acid but which is methacrylic acid in the
examples, 0.5 to 30% of a particular type of hydrophobic
monomer, optionally a termonomer that can be selected
from a wide variety of materials including acrylamide but
which is, in all the examples, ethyl acrylate, and
optionally a cross linking agent, although no cross
linking agent is used in the examples. It is stated
that the polymer may be an emulsion copolymer obtainable
by copolymerisation in an aqueous or inverse emulsion
system, a suspension copolymer, a precipitation
copolymer, a solution copolymer, a solid copolymer or a
non-aqueous dispersion copolymer, but in all the examples
polymerisation is by the oil ;n water emulsion technique
~.
that is customarily used for associative polymers of this
general type.
In U.S. 4,423,199 the same inventors have the same
description of possible polymerisation processes, applied
to the production of polymers including a different type
of hydrophobic monomer. Again all the examples are
restricted to oil in water emulsion polymerisation of
linear polymers.
In U.S. ~,524,175 (not published until after the
priority date of this invention) a water in oil emulsion
of an acrylamide/dodecyl methacrylate copolymer is made
by a special reverse phase polymerisation wherein the
dodecyl methacrylate is dissolved in the oil phase,
instead of the aqueous phase, and an oil soluble
initiator is used instead of the conventional water
soluble initiator.
The present state of the art therefore is that
although reverse phase polymerisation has been mentioned
in the literature for the production of associative
polymers containing hydrophobic groups in practice the
only operative method that has been descrihed (since the
priority date of this invention) is in U.S. 4,524,175
involving a process in which the hydrophobic monomer is
in the oil phase instead of, as in true reverse phase
polymerisation, in the aqueous phase.
Reverse phase polymerisation is recognised as a
polymerisation technique that gives polymers of
particularly valuable properties for many purposes, for
instance as thickeners. ~owever it has not previously
been considered possible to apply this to the
po]ymerisation of associative polymers containing
hydrophobic groups.
A polymer according to the invention is made by
copolymerisation of ~a) ethylenically unsaturated monomer
containing a pendant hydrophobic group of at least 8
.~
~2~
carbon atoms and (b~ water solub~e ethylenically
unsaturated comonomer, and is characterised in that all
the monomers are, as a blend, soluble in water and the
polymer has been made by reverse phase polymerisation and
S the particles have a d~y size of below 4 microns.
A process according to the invention for making a
polymer comprises copolymerising the monomers and is
characterised in that all the monomers are, as a blend,
soluble in water and a dispersion in a non-aqueous liquid
is formed of an aqueous solution of a blend of all the
monomers and the blend is copolymerised hy re~Terse phase
polymerisation in the presence of a water soluble
initiator to form a stable dispersion of the aqueous
polymer in non-aqueous liquid.
Thus the invention depends in part upon the
discovery that 7.t is possible to form an ~queous solution
of a blend of all the monomers that can be stably
dispersed 7 n a non-~aqueous liquid for re~erse phase
polymerisation, even though one of the monomers provides
hydrophobic groups. Often that monomer is the ester or
amide of an ethylenica]ly unsaturated acid, or a /meth)
allyl ether, with a hydroxy terminated surfactant of HLB
above 8 and it is very surprising that such monomers can
be incorporated in the disperse phase of a water in oil
emulsion without destahilising the dispersion before or
after polymerisation.
The amount of the defined hydrophobic monomer must
not be so high that it does destabilise the dispersion or
that i~ does not go into solution in the aqueous blend.
Generally the amount of the monomer (a) is below SO~ by
wei~ht and usually below 25~, for instance 2 to lO~.
5uitable xesults are often obtained with values of 3 to
7~ by weight.
s
The monomer is pre~erably free of hydrophilic groups
such as unblocked acid, salt, amine, amide or hydroxyl
groups.
The monomer ~a) is preferably an ethylenically
unsaturated monomer including a group -BnAmR where A is
propox~ or butoxy, B is ethoxy (CH2CH20~, n is zero or,
preferably a positive integer generally above 5, often
above 10 and preferably 20 to 100 and m is generally zero
but, if n is a positive number, m can be a smaller
positive number. Thus à polyoxyethylene chain may be
interrupted by oxypropylene groups. By appropriate
choice of the value of n, m, and the group R it is
possible to control the solubility of the monomer and the
properties of the final polymer.
P~ is a hydrophobic group containing at least 8
carbon atoms. It can be a polyoxyalkylene chain where
the alkylene groups wholly or mainly are pro~,lene or
higher but preferaoly is a hydrocarbyl group.
The hydrocarbyl group generally contains from 8 to
30, preferably 10 to 24 and most preferably 12 to 18
carbon àtoms. It may be selected from alkyl, for
instance octyl 9 lauryl or stearyl, alkaryl such as ethyl
benzene l-C2H4Ph), aryl such as naphthyl, aralkyl such as
alkyl phenyl wherein the alkyl group generally contains 6
~o 12 carbon atoms, cycloaLkyl tincluding polycyclic
alkyl groups), or mixtures of one or more such groups.
Preferred hydrocarbyl groups are alkyl and aralkyl
groups. Any of these groups may additiona11y be
substituted provided the substituents do not render the
pendant group hydrophilic to an extent that the desired
improvement in properties due to the hydrophobic group is
lost.
~.
The n,onomer may be a (meth) acrylic or (meth)
allylic monomer. The linkage between the ethylenically
unsaturated carbon atom of the monorner and the group
-snA~R is generally a chain of at least two, and often at
least four atoms and often includes one or more amide,
amine, ether or ester groups within the chain. The
monomer may be di or polyfunctional, e.g., a derivative
of itaconic acid, in which event both acid groups ~,ay be
substituted by -BnAmR or one may be unsubstituted or
substituted by a different esterifying group, for
instance methyl or higher alkyl, e.g., butyl.
Preferred monomers are (meth) allylic ethers and
amides or esters of ethylenically unsaturated carboxylic
acids preferably acrylamide, acrylic acid, methacrylic
acid, maleic acid or itaconic acid. In esters, the
group may be bonded direct to the carboxylic group cf the
ethylenically unsaturated acid or may be bonded to an
esterifying group that may include an amino group or one
or more ether or ester linkages. For instance the group
R may be a quaternising group in, for instance, the amino
group of an amino alkyl esterifying group. In amides
the group -BnAmR may be bonded to a nitrogen atom of the
amide or may be bonded to the nitrogen atom of an
aminoalkyl group bonded to amide nitrogen, for instance
as a quaternising group. Preferably the monomer (a) is
a compound formed by reacting allyl chloride or alcohol
or an appropriate ethylenically unsaturated acid,
nitrile, halide or ester with a surfactant, preferably a
hydroxyl terminated surfactant, preferably having HLB
above 8.
Preferred monomers ~a) are compounds of the formula
RlCH=C(R )QBnAmR
where
R = C8-C30 alkyl or aralkyl,
R = COOR or Q~nAmR when R = H and Q ~ CH2O
or Rl = H
R = H or CH3 or
R2 = CH CooR3 and Q ~ CH2
R2 = CH2QBnAmR and Q ~ CH2O
R = H or Cl-C~ alkyl
Q = O when R and R or Q = CH2O, COO or COMR~ where R4 =
H or CH3, or CooR5~(R3)2.R.X where R = Cl-C8 alkyl
optionally substituted by hydroxyl, e.g., CH2-CH-CH2
OH
and X = anion, e.g., Cl Br or CH3SO4
or, when n, m = O, Q = CoNR4(R5)~tR3)2 X where R3, R ,
R5, and X are as above; or Coo~R5)ooc or COO(R )COO
where R5 is as above; or Coo(R5)ooc(R5)~R3)~.x or
Coo(R5)Coo(R5)~(R3)2.x where R, R3, R5 and X are as
above. A suitahle example of RX that can be used for
~uaternising is stearyl chloride.
The (meth) allyl ethers are particularly preferred
and give polymers having a particularly good combination
of performance, rheology, linearity and stability
properties during use. It is very surprising that they
are so good since all the recent developments in
associative polymers including hydrophobic groups have
used acrylic monomers and the allyl polymers proposed in
GB 1,167,524 and 1,273,552 appear to have been
unsuccessful commercially, possibly because of the form
in ~hich they were produced.
The allyl ethers may be made by, ~or instance,
reacting an appropriate surfactant alcohol with sodium or
sodium alkoxide to form the sodium derivative and then
reacting this with allyl chloride, or by reacting allyl
alcohol with the surfactant alcohol with or without
catalyst.
Compounds in which Q includes CoOR5COO may be made
by reacting, e.g., acrylic acid with a hydroxycarboxylic
acid followed by esterification with surfactant alcohol,
or by reacting a hydroxyalkyl ester of acrylic acid with
the half ester of succinic anhydride with a surfactant
alcohol. Compounds in which Q includes CoOR500C may be
made by forming a half ester of a dicarboxylic acid and a
surfactant alcohol, and reacting this, an unsaturated
acid and a diol.
All the other described monomers are described in
the quoted patents or can be obtained by routine methods.
It is particularly preferred in the invention that n
should be an integer of at least 5 and preferably at
least lO, m generally being zero, since the provision of
a polyoxylethylene chain promotes solubility of the
monomer in water or an aqueous blend. The monomer is
preferably soluble in water, that is to say that when it
i5 mixed into a dispersion of water and non-aqueous
]iquid it goes preferentially into the water phase.
The comonomer or comonomers ~b~ must provide a water
soluble blend with the monomer (a) and so will generally
consist of water soluble monomers, preferably highly
water soluble monomers. However small amounts, for
instance up to S~ or at the most 10~, of other water
insoluble monomers, for instance ethyl acrylate, may be
incorporated in the blend provided they do not come out
of solution. The comonomers ~b) are ~enerally acrylic
and may be non-ionic, a~ionic or cationic.
Suitable anionic monomers include acidic groups such
as acrylic acid, methacrylic acid, 2-acrylamiao-2-methyl
pr~pane sulph~nic acid or other unsaturated sulphonic or
carboxylic acids. Acids having high water solubility,
such as acrylic acid, may be present :in free acid or salt
form, or a blend thereof, but acids of lower solubility,
such as methacrylic acid, are preferably present in salt
form, i.e., alkali metal, ammonium or amine salt.
Non-ionic monomers, often used in combination with
anionic or cationic monomers, include acrylami~e or
methacrylamide. Suitable cationic monomers include
dialkylaminoalkyl acrylates or methacrylates and
dialkylaminoalkyl acrylamides or methacrylamides wherein
the substituents are such that the monomer is water
soluble. For instance the dialkylaminoalkyl groups may
be present in the form of soluble quaternary or other
salts.
Water soluble cross-linking monomers may be included
in an amount, generally below l~, such that the polymer
has the desired degree of swellability in aqueous
systems, or the polymer may be uncross-linked and soluble
in aqueous svstems.
Particularly preferred polymers of the invention are
those in which the monomers are acrylic acid ~as ~ree
acid or water soluble salt) or acrylami~e or a blend
thereof, and, especially, those that have been cross
linked by an amount of cross linking agert such that the
resultant polymer particles will swell but not dissolve
in aqueous systems, e.g., aqueous dilute alkali. For
instance the particles will swell by at least twice their
volume and oten at least lO times their volume. These
small, swellahle, cross linked anionic particles are of
particular ~alue as thickeners for print pastes. It is
~.
~2~f~
very surprising that the associative effect that is
believed to occur in associative polymers having the
described pendant hydrophobic groups does exist
beneficially in cross linked particles of the size
conventionally made by re~erse phase polymerisation, for
instance 0.3 to 3, generally about 1, I!m.
The proportions of anionic, non-ionic and cationic
monomers can vary widely and, in particular, any type of
monomer that is present can be present in an amount of,
typically, 10 to 100% by welght of the total amount of
monomer tb).
The reverse phase polymerisation process is
generally conducted in the presence of a polymeric
polymerisation stabiliser.
Suitable suspension stabilisers include amphiphathic
copolymers of hydrophobic monomers with hydrophilic
monomers and which are soluble or dispersible in liquids
of low polarity. The preferred stabilisers are either
completely soluble or form fine dispersions in the
continuous phase but are substantially insoluble in the
monomer solution. These are typified by copolymers of
alkyl acrylates or methacrylates with acrylic or
methacrylic acid and copolymers of alkyl acrylates or
methacrylates with dialkyl amino alkyl-(generally
dimethyl aminoethyl)-acrylate methacrylate or quaternary
ammonium or acid salt derivatives o these amino
monomers. The most suitahle of these are copolymers o~
alkyl m~thacrylates, where the alkyl group is a linear
hydrocarbon of 1~-18 carbon atoms, with methacrylic acid
or trimethyl-beta-methacryloxyethyl-ammonium chloride and
terpolymers with methyl methacrylate and
hydroxyethylacrylate. Suitab]e materials are described
in ~P 1,482,515, US 4,339,371 and EP 126528.
The choice of stabiliser is influenced by the
particular copolymer being manufactured. The stabilisers
~,
for polymers containing acrylic acid or its sodium salt
are preferably cationic and those for polymers containing
dimethyl amino methyl acrylate or its salts or quaternary
ammonium derivatives, or other cationic polymers, are
preferably anionic.
The amount of suspension polymerisation stabiliser
used is dependent on the size range of polymer particles
required because at least a mono-layer absorbed at the
interface betwen the polymer particle and the continuous
phase is required to stabilise the dispersion both during
polymerisation and during subsequent handling or use o~
it. Generally the amount of stabiliser is from O.OS to
10%, preferably 0.5 to 5%, based on the weight of the
aqueous dispersion when, as is preferred, the particle
size is to be small, for instance below 5 microns and
generally in the range 0.2 to 2 or 3 microns. If larger
particles are satisfactory then lower amounts of
stabiliser, for instance 0.01 to 0.5~, may be
satisfactorv.
The reverse phase polymerisation process may be a
reverse phase emulsion polymerisation process, in which
event it is conducted in the presence of a substantial
amount of water-in-oil, low ~LB, emulsifier, but
preferably the process is a reverse phase suspension
polymerisation process. Accordingly the aqueous monomer
droplets may be produced solely by the applicati.on of
shear to a mixture of the aqueous monomer and the oil and
stabiliser, but it is often convenient to include a small
amount of a water-in-oil, low HLB, emulsifier so as to
reduce the amount of shear that has to be applied to
achieve a given particle size. The low HL~ emulsifier
will have HLB below 7, and generally 4 to 6 ànd typical
emulsifiers are sorbitan monostearate, sorbitan
monooleate, glyceryl monostearate and various ethoxylated
fatty alcohols. They are usually soluble in the
12
non-aqueous liquid. The amount of low HLB emulsifier is
preferably below 1.5% or 2~, typically 0.1 to O . 8~ by
weight based on the weight of the aqueous monomer
dispersion in oil.
The non-aqueous liquid may be selected from any of
the non-aqueous liquids conventionally used in reverse
phase polymerisation processes, such as aromatic and
aliphatic hydrocarbons and halogenated hydrocarbons, for
instance as discussed in EP 126528. If desired it may
10 also include polar liquid as discussed in EP 126528.
Polymerisation is induced by the use of a water
soluble initiator in known manner. The use of oil
soluble initiator is unsatisfactory.
The resultant aqueous dispersions of monomer or
polymer in oil generally contain 20 to 60~ by weight oil,
15 to 50% by weight polymer or monomer and 15 to 50~ by
weight water.
The aqueous polymer dispersion may be dehydrated in
known manner, generally hy azeotropic distillation,
preferably under reduced pressure, the dehydration being
conducted for a sufficient time that the final product is
suhstant-ally anhydrous. Thus the water content in the
polymer particles will be below 25% and generally below
the ambient moisture content of the particles if they
were exposed to the atmosphere, i.e. generally below 10~
~y weight. The non-a~ueous liquid in the initial
aaueous dispersion is usually a blend of volatile and
non-volatile oils, the volatile oil being removed during
the azeotropic distillation. It may be replaced by
further non-aqueous liquid.
A high HLB surfactant may be added to the final
dispersion in order to facilitate its distribution into
water. The surfactant may be water soluble or oil
soluble and generally has HLB between 8 and 11.5.
The following are examples of the invention.
13
Example 1
A diester was formed between itaconic acid and the
10 mole ethoxylate of stearyl alcohol by direct
esterification in the presence of sulphuric acid.
A copolymer was formed by reverse phase suspension
polymerisation of this ester with ammonium acrylate. In
particular, an aqueous phase was formed of 144 parts
acrylic acid, 7 parts of the diester, 213 parts water, 81
parts 31.6~ aqueous ammonia and traces of
methylsnebis-acrylami~e and AZDN. A non-aqueous liquid
phase was formed of 15 parts SPAN ~0 ~trade mark), 42
parts o~ a 30% solution in SBPll o~ polymeric stabiliser
(a copolymer of 2 moles cetostearyl methacrylate with 1
mole methacrylic acid), 117 parts Pale Oil 150 and 149
parts SBPll. Polymerisation was allowed to proceed in
the usual wav and the resulting inverse emulsion was
dehydrated by distilling off water and SBPll under
reduced pressure to a inal pressure of 10 mm/hg and at a
temperature of 95C.
The resultins anhydrous dispersion was an effective
thickener, for instance in printing pastes.
Example 2
115.2 parts o~ acrylic acid, 28.8 parts of
acrylamide, 2.3 parts of a 9 mole ethylene oxide
condensate of non~lphenol acrylate (a water soluble
derivative), 220 parts of water, 65 parts 32~ aqueous
ammonia, 0.4 parts of Tetralon B, 0.04 parts of AZDN and
0.0~ parts of methylene bls-acrylamide were mixed to form
an aqueous phase. A non-aqueous liquid phase was formed
o~ 15 parts Span 80, 42 parts of a 30% w/w solution of a
1:2 molar copolymer o~ cekostearyl
methacrylate:methacrylic acid in SBPll, 117 parts of Pale
Oil 150 and 14~ parts of SBPll. The aqueous phase was
homogenised into the oil phase, deoxygenated ana
polymerised using 0.043 parts of sodium metabisulphite
la ~L24~
and 0.043 parts of tertiary butyl hydroperoxide. ~he
res~llting in~erse dispersion of hydrated polymer gel was
dehydrated by distillation under reduced pressure to a
final pressure of 10 mm of mercury at a temperature of
95C.
The resulting anhydrous dispersion was an effective
thickener.
Example _
1~1.8 par~s of a 79.2% solution of acrylic acid in
water, 0.4 parts of Tetralon B, 5.8 parts of the allyl
ether of a 10 mole ethoxylate of stearyl alcohol, 118
parts of water, 0.0424 parts of A2DN and 116 parts of a
29.9% solution of ammonia in water were mixed to form an
aqueous solution. A non-aqueous liquid phase was formed
15 from 7.4 parts oi Span 80, 42.4 parts of a 30% solution
in SBPll of an inverse dispersion stabiliser (copolymer
of 2 moles cetostearyl methacrylate with 1 mo e of
methacrylic acid), 127.3 parts of Pale Oil 60 and 145.7
parts of S~Pll~
The aqueous phase was homogenised into the oil
phase, deoxygenated and polymerised using 0.042 parts of
sodium metabisulphite dissolved in 2.058 parts of water
and tertiary butyl hydroperoxide added continuously as a
0.5~ solution in water at a rate of 0.14 parts per
minute. ~he resulting inverse dispersion of hydrated
polymer was distilled as in example 2 to yield a
dehydrated concentrated polymer dispersion to which was
added 2 parts of a 5 mole ethoxylate of nonyl phenol and
1 part of a 4 mole ethoxylat~ o~ a broad cut lauryl
alcohol per 100 parts of concentrated dehydrated
dispersion. This formed a dispersion of 50~ active
copolymer which dispersed with agitation in water to
yield a highly viscous polymer solution with the
characteristic Isoap gel' rheology of associated water
~2~
solu~le polymers. The polymer was a useful flocculant
for clay particles in water or sodium hydroxide solution.
Example 4
The process of Exan~ple 3 was repeated where the
aqueous phase contained in addition 0.06~ parts of
methylene bis acrylamide as bi-functional crosslinking
comonomer. The resultant dehydrated polymer particles
swelled in water to form a highly viscous but
non-viscoelastic paste useful as a vehicle for printing
textiles and other articles particularly on cloth
containing residual electrolyte where pastes thickened
with conventinal polyammonium acrylate microgel latices
give holoing, bleading or flushing of print colour~
Example S
A copolymer of 85 parts o acrylamide and 15 parts
of the allyl ether of a 10 mole etho~ylate of stearyl
alcohol was prepared by inverse dispersion
polymerisation.
Thus an aqueous solution containing 120.7 parts of
acrylamide, 0.~3 parts of Tetralon s, 269.6 parts of
water, 21.3 parts of the above allyl ether and 0.043
parts of A2DN with the pH adjusted to 5 was homogenise~
into an oil phase containing 7.3 parts of Span 80, 41.4
parts of the stabiliser solution of Example 3, 108.9
parts of Pale Oil 60 and 157.2 parts of ABPll. The
monomer solution dispersion was deoxygenated and
polymerised using 4.1 parts of a 0.1% solution of
tertiary butyl hydroperoxide in water using 10 parts of a
mole ethoxylate of nonylphenol per 100 parts of
dehydrated polymer dispersion. The product dispersed in
water to form a solution of 'soap gel' rheology
characteristic of associated polymer solutions which was
unaffected by mono or multivalent electrolytes. These
polymer solutions were found to be effective flocculants
16
for clay suspensions in water and as rheology modifiers
for printing pastes.
