Note: Descriptions are shown in the official language in which they were submitted.
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Preparation of pulverulent polymers based on N-vinylcaprolactam
The present invention relates to an improved process for the
5 preparation of pulverulent polymers based on N-vinylcaprolactam
by polymerizing
A) from 50 to 100% by weight of N-vinylcaprolactam with
10 B) from 0 to 50% by weight of further N-vinyllactams,
heteroaromatic vinyl compounds, vinyl esters, C1-C10-alkyl
acrylates or methacrylates, or a mixture thereof, and
C) from 0 to 5% by weight of monoethylenically unsaturated
monomers containing acid groups.
In the field of hair cosmetology there is particularly strong
interest in solid, ie. pulverulent, polymers which are free from
organic solvents, such as alcohols, since as a result of the ever
20 tightening worldwide statutory regulations regarding organic
solvents and propellants in hairsprays and similar products the
demand is almost exclusively now for only those polymers which
have been prepared on a purely aqueous basis. Furthermore, solid
polymers generally have handling advantages over solutions or
25 dispersions; problems which may be mentioned in this context are,
in particular, the problem of contamination, especially of
aqueous polymer solutions, with microorganisms during storage,
and the problem of transportation, owing to the greater weight.
30 In the field of hair cosmetology, polyvinylcaprolactam and
copolymers thereof with usually relatively small quantities of
comonomers are known to be film formers having outstanding
properties. However, such polymers are also used in other
technical fields.
The Journal of Applied Polymer Science, Vol. 12 (1968), pp.
1835-1842 (1) discloses that above about 30 to 35 C
polyvinylcaprolactam which has been prepared by bulk
polymerization or solution polymerization in toluene is
40 precipitated from its aqueous solutions. US-A 4 521 404 (2)
reveals that copolymers of N-vinylcaprolactam, for example with
N-vinylpyrrolidone, prepared by solution polymerization in
anhydrous ethanol followed by distillation to remove the solvent,
behave similarly and give rise at least to instances of
45 cloudiness when the corresponding aqueous solutions are heated
gently, for example to about 55 C in the case of a 1:1 by weight
N-vinylcaprolactam-N-vinylpyrrolidone copolymer. In general, such
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precipitates are obtained as rubberlike solids which can no
longer be handled. This prejudice concerning the impossibility of
preparing a pulverulent, easily handled N-vinylcaprolactam
polymer by this method has so far prevented the drying of such
5 polymers from aqueous solution by means of industrial drying
techniques which are customary for such polymers, since these
techniques generally entail the heating - at least for a short
time - of these aqueous solutions.
10 W0 92/17509 (3) shows us the possibility of preparing solid
pulverulent N-vinylcaprolactam polymers, for example
N-vinylcaprolactam homopolymer or N-vinylcaprolactam-acrylic acid
copolymer by precipitation polymerization from organic solvents
such as alkanes and cycloalkanes, examples being heptane or
15 cyclohexane.
It is an object of the present invention to provide a process for
preparing pulverulent N-vinylcaprolactams from a solution which
is aqueous or can be converted to an aqueous solution, for which
20 it is possible to employ customary industrial drying techniques.
We have found that this object is achieved by the process defined
at the outset, which comprises subjecting the monomers A, B and C
25 (i) to polymerization in homogeneous, water-containing solution,
which contains from 10 to 95% by weight of a water-miscible
organic solvent, based on the water, or in a homogeneous
mixture comprising from 0 to 90% by weight of water and from
100 to 10% by weight of methanol, in the presence of a
free-radical initiator, and then replacing the organic
solvent by water, or
(ii)to polymerization in aqueous emulsion in the presence of a
free-radical initiator and in the presence or absence of an
emulsifier
and subjecting the resulting aqueous polymer solutions or
dispersions to a drying technique which is customary for such
formulations, in order to produce pulverulent polymers.
In a preferred embodiment, polymerization in (ii) is carried out
in the absence of a monomer C but in the presence of an
emulsifier. However, if at least 30% by weight, based on the
overall quantity of the monomers, of a further N-vinyllactam is
45 present as monomer B, the use of an emulsifier in the
polymerization is preferably omitted.
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Suitable monomers B are further N-vinyllactams, especially
N-vinylpyrrolidone and N-vinylpiperidones, heteroaromatic vinyl
compounds, especially N-vinylimidazole and vinylpyridines or
vinylpyridine N-oxides, vinyl esters, especially vinyl acetate
5 and vinyl propionate, and also C1-C1O-alkyl (meth)acrylates,
especially methyl, ethyl or butyl acrylate or the corresponding
methacrylate.
Suitable monomers C are monoethylenically unsaturated compounds
10 cont~;n;ng at least one acid group, for example a carboxyl group,
a sulfonic acid group or a phosphonic acid group. Examples of
such compounds are acrylic acid, methacrylic acid, dimethacrylic
acid, ethylacrylic acid, crotonic acid, allylacetic acid or
vinylacetic acid. Other suitable compounds are monoethylenically
15 unsaturated dicarboxylic acids, for example maleic acid, fumaric
acid, itaconic acid, mesaconic acid, methylenemalonic acid,
citraconic acid, maleic anhydride, itaconic anhydride and
methylenemalonic anhydride, the anhydrides normally hydrolyzing
to form the corresponding dicarboxylic acids on introduction into
20 water. Also suitable as monomers C are monomers cont~;n;ng
sulfonic acid groups, examples being
2-acrylamido-2-methylpropanesulfonic acid, 3-sulfopropyl
(meth)acrylate, vinylsulfonic acid, methallylsulfonic acid or
allylsulfonic acid, and monomers cont~;n;ng phosphonic acid
25 groups, such as vinylphosphonic acid. The monomers C can be
employed either alone or in a mixture with one another.
Preferred monomers C are acrylic acid, methacrylic acid, maleic
acid, maleic anhydride, fumaric acid, itaconic acid,
30 2-acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid,
3-sulfopropyl acrylate or methacrylate, and vinylphosphonic acid.
In the polymerization the monomers C can be employed either in
the form of the free acids or, preferably, in the form of their
35 alkali metal, alkaline earth metal or ammonium salts. It is
advantageous to employ these salts of the monomers C as aqueous
solutions. In this context, particularly important cations are
sodium, potassium, magnesium and calcium, but also lithium,
strontium and barium. The salts of the monomers C are normally
40 prepared by customary neutralization of the acids in an aqueous
medium.
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In a preferred embodiment, the polymers employed comprise
A) from 90 to 100% by weight, in particular from 95 to 100% by
weight, of N-vinylcaprolactam with
B) from 0 to 10% by weight, in particular from 0.1 to 5% by
weight, of the monomers B and
C) from 0 to 5% by weight, in particular from 0.1 to 3% by
weight, of the monomers C.
Particular preference is given to copolymers comprising
A) from 95 to 99.9% by weight, in particular from 97 to 99.5% by
weight, of N-vinylcaprolactam with
C) frQm 0.1 to 5% by weight, in particular from 0.5 to 3% by
weight, of the monomers C,
20 it being possible to prepare these copolymers in accordance with
embodiment (i) or in accordance with embodiment (ii), preferably
without emulsifier.
Particular preference is also given to homopolymers comprising
25 100% by weight of N-vinylcaprolactam A, it being possible to
prepare these polymers preferably in accordance with embodiment
(i) in pure methanol, or preferably in accordance with embodiment
(ii) with emulsifier.
30 Where polymerization is carried out in accordance with embodiment
(i) in a homogeneous mixture of water and a water-miscible
organic solvent, use is preferably made of a C2-C4-alkanol,
especially ethanol or isopropanol. In this case the proportion of
organic solvent, based on the water, is from 10 to 95% by weight,
35 preferably from 25 to 85% by weight and, in particular, from 50
to 75% by weight.
The use of water/methanol mixtures, and especially of pure
methanol, in embodiment (i) is particularly advantageous for the
40 preparation of N-vinylcaprolactam homopolymers or of copolymers
of N-vinylcaprolactam with further N-vinyllactams B, especially
with N-vinylpyrrolidone.
In both embodiments (i) and (ii) the concentration of the
45 polymers in the aqueous reaction mixture is usually from 10 to
70% by weight, preferably from 15 to 50% by weight. The pH of the
aqueous solution is at least 6 and is preferably in the range
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from 7 to 9, the pH of the aqueous reaction solution generally
being established by the addition of an alkali metal base or
~1 kAl; ne earth metal base. In this context the simplest procedure
is to employ the monomers C as aqueous solutions of their alkali
5 metal, alkaline earth metal or ammonium salts with a pH of at
least 6. However, it is also possible to add the monomers C in
unneutralized form to the reaction mixture and to add at the same
time an at least equivalent quantity of a corresponding base in
order to bring the pH of the reaction mixture into the desired
10 range of 6 or more.
Polymerization is generally carried out at from 40 to 150 C,
preferably at from 60 to 100 C, under atmospheric pressure or
superatmospheric pressure, in the presence of free-radical
15 initiators. These polymerization initiators are normally added in
quantities of from 0.01 to 20% by weight, preferably from 0.05 to
10% by weight, based on the monomers.
Suitable free-radical initiators are commonly all those compounds
20 which have a half life of less than 3 hours at the particular
polymerization temperature which is chosen. Preference is given
to water-soluble and ionic initiators, examples being hydrogen
peroxide, sodium persulfate, potassium persulfate, ammonium
persulfate, 2,2'-azobis(N,N'-dimethyleneisobutyramidine)
25 dihydrochloride, 2,2'-azobis(2-amidinopropane) dihydrochloride,
2,2'-azobis(dimethyl isobutyrate), 4,4'-azobis(4-cyanopentanoic
acid) and tert-butyl perpivalate.
Compounds which are less preferred, but which can also be
30 employed in certain circumstances, are those polymerization
initiators which are insoluble or of only limited solubility in
water, such as tert-amyl perpivalate, dioctanoyl peroxide,
dilauroyl peroxide, 2,2'-azobis(2,4-dimethylvaleronitrile),
dibenzoyl peroxide, tert-butyl per-2-ethylhexanoate, tert-amyl
35 per-2-ethylhexanoate, tert-butyl permaleate or
2~2~-azobis(isobutyronitrile)~ and also redox initiators, such as
heavy metal salt-hydrogen peroxide systems.
In general, a suitable base is used to neutralize the aqueous
40 solution of the polymerization initiators before it is added to
the polymerization medium.
The molecular weight of the polymers can be controlled by adding
regulators to the reaction mixture, control in most cases
45 implying reduction. Therefore, in a preferred embodiment of the
invention in (ii), a regulator is additionally employed in order
to control the molecular weight. Examples of suitable regulators
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are lower alcohols such as methanol, ethanol, propanol,
n-butanol, isopropanol, isobutanol and pentanol. However, other
suitable molecular weight regulators are those compounds which
are customarily employed for this purpose, such as organic sulfur
5 compounds, for example 2-mercaptoethanol, butyl mercaptan,
dodecyl mercaptan, thioacetic acid or thiolactic acid, halogen
compounds, for example carbon tetrachloride or
l,l,l-tribromopropane, or formic acid and derivatives thereof.
10 An appropriate choice of regulator, initiator, polymerization
temperature and monomer concentration establishes the K value of
the polymer obtained, which is a measure of the molecular weight.
The Fikentscher K values of the resulting polymers are usually
from 10 to 300, preferably from 15 to 200, and are measured on a
15 1% strength by weight aqueous solution at 25 C ~in accordance with
H. Fikentscher, Cellulose-Chemie, Volume 13 (1932), pp. 58-64 and
71-74).
Suitable emulsifiers which may be required for embodiment (ii)
20 are all systems which are customary for this type of
polymerization with virtually no restriction. Suitable
emulsifiers in this context include neutral, anionic and cationic
types. A wide variety of such emulsifiers is described in the
literature, for example in the article by R. Hensch in Ul l~-nn 'S
25 Encyclopedia of Industrial Chemistry, 5th edition (1987),
Volume A9, pp. 297-339.
Examples of emulsifiers which can be employed successfully are
anionic compounds, especially alkali metal, ammonium and amine
30 salts of relatively long-chain fatty acids, alkali metal salts of
sulfuric esters of fatty alcohols and fatty alcohol ethers, for
example sodium lauryl ether sulfate, with from 1 to 15 mol of
ethylene oxide, and of alkylphenols, alkali metal salts of
dialkyl sulfosuccinates, and also alkali metal salts of the
35 sulfonic acids of alkylbenzenes, for example sodium dodecyl
sulfate, alkylnaphthalenes and of naphthalene. However, it is
also possible to use cationic compounds, examples being fatty
amines, quaternary ammonium compounds or quaternized pyridines,
morpholines or imidazolines. Other highly suitable compounds are
40 polyol fatty acid esters reacted with from 2 to 30 mol of
ethylene oxide, for example sorbitan monooleate with 20 mol of
ethylene oxide. It is common to employ mixtures of different
types of emulsifier.
45 In the presence of monomers C it is not necesssary in principle
to add an emulsifier, since the ionic groups in the monomers C
themselves have emulsifier properties in respect of the monomers
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and/or of the polymers formed therefrom. However, in such a case
the addition of a customary emulsifier may not be
disadvantageous, and in some cases even facilitates the
polymerization process.
The polymerization reaction is generally carried out in stirred
reactors fitted with anchor, paddle, impeller or multistep pulsed
countercurrent stirrers. Where high concentrations are employed,
it is advantageous to use compounders or similar apparatus. For
10 polymerization it is possible to charge the entire batch to the
reactor and, after heating it to the desired temperature, to
start the reaction by adding the initiator. With this procedure,
however, the dissipation of the heat of polymerization presents
problems. It is more advantageous, therefore, to charge the
15 solvent to the reactor and to meter in the monomers, in undiluted
form or as an aqueous monomer solution, and the initiator, as a
solution in water or alcohol, in portions or continuously, at the
chosen polymerization temperature. It is often also of advantage
for the progress of the reaction to charge the solvent to the
20 reactor and to meter in the monomers, the initiator and the
neutralizing agent required to maintain the necessary pH under
the polymerization conditions.
The replacement of organic solvent by water in embodiment (i) is
25 normally carried out by adding the appropriate quantity of water
to the reaction batch after polymerization has been carried out
and after simultaneous or subsequent removal of the solvent by
distillation under atmospheric or subatmospheric pressure. It is
particularly advantageous to separate off the organic solvent by
30 steam distillation.
Suitable drying techniques for the production of pulverulent
polymers are all those techniques which are suitable for drying
aqueous solutions. Preferred techniques are spray drying,
35 fluidized-bed spray drying, roller drying and belt drying, while
less preferred but equally possible techniques are freeze drying
and freeze concentrating.
The polymer powders obtainable in accordance with the invention
40 by drying from aqueous solution are soluble in alcohols, water
and mixtures thereof and possess the known superb properties as
auxiliaries in cosmetic hair preparations, for example as
additives for hair lacquers or hairspray.
45 The polymer powders prepared in accordance with the invention can
also be used as binders for transfer printing, as lubricant
additives, as soil conditioners and as agrochemical seed-dressing
0050/44512 2 1 7 8 3 2 8
auxiliaries, in slow-release fertilizer formulations and in
agricultural formulations with adhesion properties, as rust
inhibitors or agents for removing rust from metallic surfaces, as
scale inhibitors or scale removers, as auxiliaries in the
5 recovery of petroleum from oil-containing water and in the
extraction and transportation of oil and natural gas, as agents
releasing the active compound in pharmaceutical preparations, as
cleaners for wastewaters, as raw materials for adhesives, as
detergent additives and as auxiliaries in the photographic
10 industry, in immunochemicals and in cosmetic skin preparations.
The homopolymers and copolymers of vinylcaprolactam described in
the context of the present invention no longer exhibit the
phenomenon of precipitation at elevated temperature, but instead
15 form a stable latex above 35 C, which on cooling to below this
temperature undergoes completely reversible transition to form a
clear solution. As a consequence, these polymers are very easy to
dry by means of conventional drying techniques.
20 Examples
The examples-which follow serve to illustrate the invention. The
K value in each example was determined on a 1% strength by weight
solution in water at 25 C by the method of Fikentscher.
Example 1
A solution of 5 g of 2-acrylamido-2-methylpropanesulfonic acid in
50 g of water was adjusted to a pH of 7 using dilute sodium
30 hydroxide solution. 150 g of ethanol and 395 g of
N-vinylcaprolactam were added to form a homogeneous solution
(feed 1). Feed 2 was prepared from 2 g of tert-butyl perpivalate
and 85 g of ethanol.
35 A homogeneous mixture of 100 g of N-vinylcaprolactam, 100 g of
ethanol, 10 g of water and 0.5 g of tert-butyl perpivalate was
introduced into a 2 l stirred vessel fitted with stirrer, heating
device, reflux condenser, metering device, gas inlet and gas
outlet, and the mixture was heated to 75 C while stirring and
40 passing in nitrogen. After the polymerization had commenced,
which is evident from a rise in the viscosity of the initial
charge, feeds 1 and 2 were run in simultaneously over the course
of 3 hours. In order to remove residual monomer,
post-polymerization was carried out by running in a solution of
45 4 g of tert-butyl perpivalate in 100 g of ethanol over a period
of 8 h at 75 C and then maint~;n;ng the mixture at this
temperature for a further 3 hours. In order to produce the purely
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g
aqueous solution, 500 g of water were run in, and steam was
passed in in order to distill off the ethanol at an internal
temperature of 100 C at the end. A white polymer latex of low
viscosity was obtained which on cooling became a clear, viscous
5 polymer solution.
The solution had a solids content of 35% by weight and a residual
N-vinylcaprolactam content of < 50 ppm. The K value of the
polymer was 34. Spray drying gave a white, odorless powder.
Examples 2 and 3
The procedure of Example 1 was followed using in each case 2% by
weight of acrylic acid or methacrylic acid together with 98% by
15 weight of N-vinylcaprolactam as neutralized comonomers. Spray
drying gave white powders having a K value in the range from 30
to 40.
Example 4
A solution of 4 g of 2-acrylamido-2-methylpropanesulfonic acid,
0.5 g of 4~4C-azobis(4-cyanopentanoic acid) and 2 g of
thioglycolic acid in 100 g of water was adjusted to a pH of 7
using dilute sodium hydroxide solution (feed 1).
Polymerization was carried out using a 2 1 stirred vessel fitted
with stirrer, heating device, reflux condenser, metering device,
gas inlet and gas outlet. The initial charge was a solution of
2 g of 2-acrylamido-2-methylpropanesulfonic acid, 0.5 g of
30 4,4'-azobis(4-cyanopentanoic acid) and 1 g of thioglycolic acid
in 600 g of water, which charge was adjusted to a pH of 7 using
dilute sodium hydroxide solution. Addition of 100 g of melted
N-vinylcaprolactam followed by intense stirring gave an emulsion.
This emulsion was heated to 90 C while passing in nitrogen. After
35 the polymerization had commenced, which is evident from the
exothermic reaction, feed 1 and 200 g of melted
N-vinylcaprolactam were run in simultaneously over the course of
3 hours.
40 In order to remove residual monomer, post-polymerization was
carried out by running in a solution of the sodium salt of 0.5 g
of 4,4'-azobis(4-cyanopentanoic acid) in 100 g of water over a
period of 8 hours at 90 C and then main~;n;ng the mixture at this
temperature for a further 3 hours. In order to reduce the
45 residual monomer content further, a steam distillation was
~ ~ 0050/44512 21 7~328
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carried out. A white polymer latex of low viscosity was obtained
which on cooling became a clear, viscous polymer solution.
The solution had a solids content of 25% and a residual
5 N-vinylcaprolactam content of < 50 ppm. The K value of the
polymer was 33. Spray drying gave a white, odorless powder.
Examples 5 and 6
10 The procedure of Example 1 was followed using in each case 2% by
weight of acrylic acid or methacrylic acid together with 98% by
weight of N-vinylcaprolactam as neutralized comonomers. Spray
drying gave white powders having a K value in the range from 25
to 40. By varying the amount of regulator used it was possible to
15 obtain polymers with K values in the range from 15 to 200.
Example 7
A solution of 1 g of 4,4~-azobis(4-cyanopentanoic acid) in 50 g
20 of water was adjusted to a pH of 7 using dilute sodium hydroxide
solution (feed 1).
Polymerization was carried out using a 2 l stirred vessel fitted
with stirrer, heating device, reflux condenser, metering device,
25 gas inlet and gas outlet. The initial charge was a solution of
0.5 g of 4,4'-azobis(4-cyanopentanoic acid) and 3.5 g of sodium
dodecyl sulfate in 600 g of water, which charge was adjusted to a
pH of 7 using dilute sodium hydroxide solution. Addition of 100 g
of melted N-vinylcaprolactam followed by intense stirring gave an
30 emulsion. This emulsion was heated to 90 C while passing in
nitrogen. After the polymerization had commenced, which is
evident from the exothermic reaction, feed 1 and a mixture of
200 g of melted N-vinylcaprolactam and 6.5 g of Tween~80
(sorbitan monooleate reacted with 20 mol of ethylene oxide, from
35 Atlas-Chemie) were run in simultaneously over the course of 3
hours.
In order to remove residual monomer, post-polymerization was
carried out by running in a solution of the sodium salt of 0.5 g
40 of 4,4'-azobis(4-cyanopentanoic acid) in 100 g of water over a
period of 8 hours at 90 C and then maint~;n;ng the mixture at this
temperature for a further 3 hours. In order to reduce the
residual monomer content further, a steam distillation was
carried out. A white polymer latex of low viscosity was obtained
45 which on cooling became a clear, viscous polymer solution.
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The solution had a solids content of 35% and a residual
N-vinylcaprolactam content of 100 ppm. The K value of the polymer
was 45. Spray drying gave a white, odorless powder.
5 Example 8
A solution of 5 g of 4,4'-azobis(4-cyanopentanoic acid) in 500 g
of water was adjusted to a pH of 7 using dilute sodium hydroxide
solution (feed 1).
Polymerization was carried out using a 3 l stirred vessel fitted
with stirrer, heating device, reflux condenser, metering device,
gas inlet and gas outlet. The polymerization was carried out
batchwise, for which purpose a mixture of 1500 g of water, 70 g
15 of feed 1, 400 g of N-vinylpyrrolidone and 400 g of melted
N-vinylcaprolactam was prepared. A suspension was obtained by
intense stirring, which was heated to an internal temperature of
gO C while passing in nitrogen. After the polymerization had
commenced, which is evident from the exothermic reaction and the
20 viscosity rise of the polymerization medium, feed 1 was run in
over the course of 5 hours. During the polymerization the batch
was diluted with about 1500 g of water. Subsequently, in order to
reduce the residual monomer content, the batch was held at 90 C
for a further 3 hours. In order to reduce the residual monomer
25 content further, a steam distillation was carried out. A white
polymer latex was obtained which on cooling became a clear
polymer solution of high viscosity.
The solution had a solids content of about 19% by weight and a
30 residual N-vinylcaprolactam content of 400 ppm. The K value of
the polymer was 83. Spray drying from a highly dilute solution or
roller drying gave a white, odorless powder.
Example 9
Following the procedure of Example 8, a 1:1 by weight mixture of
N-vinylpyrrolidone and N-vinylcaprolactam in homogeneous solution
in methanol was polymerized using t-butyl perpivalate as
polymerization initiator. After replacing the solvent by water a
40 white latex was obtained which on cooling became a viscous, clear
solution.
The solution had a solids content of about 37% by weight and a
residual N-vinylcaprolactam content of 500 ppm. The K value of
45 the polymer was in the range from 60 to 70. Spray drying from a
0050/44512
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12
highly dilute solution or roller drying gave a white, odorless
powder.
