U.S. patent application number 11/000858 was filed with the patent office on 2005-07-14 for preparation of particles by hydrolysis of a metal cation in the presence of a polymer.
Invention is credited to Anthony, Olivier, Cadena, Nathalie, Gerardin, Corine, Labeau, Marie-Pierre.
Application Number | 20050153858 11/000858 |
Document ID | / |
Family ID | 25122872 |
Filed Date | 2005-07-14 |
United States Patent
Application |
20050153858 |
Kind Code |
A1 |
Anthony, Olivier ; et
al. |
July 14, 2005 |
Preparation of particles by hydrolysis of a metal cation in the
presence of a polymer
Abstract
A subject matter of the invention is a process for the
preparation of particles comprising at least one copper ion, which
comprises the stage of bringing into contact a precursor a copper
cation, optionally partially hydrolyzed, with at least one
water-soluble comb copolymer. Likewise, a subject matter of the
invention is particles capable of being prepared according to the
process of the invention, said particles exhibiting a mean size of
between 2 and 500 nm and preferably between 2 and 300 nm. Finally,
it relates to the use of such particles in the mechanical polishing
of hard objects, in the preparation of pigments or mixed ceramics
for the electronic industry, in the reinforcing of polymeric
matrices, in fungicidal or biocidal dispersions, in the scavenging
of sulfur derivatives or the scavenging of unpleasant smells.
Inventors: |
Anthony, Olivier; (Enghien
Les Bains, FR) ; Gerardin, Corine; (Saint Georges
D'Orques, FR) ; Cadena, Nathalie; (Union City,
NJ) ; Labeau, Marie-Pierre; (Levallois-Perret,
FR) |
Correspondence
Address: |
JEAN-LOUIS SEUGNET
PHODIA INC.
Bldg. N-2
259 Prospect Plains Road
CRANBURY
NJ
08512-7500
US
|
Family ID: |
25122872 |
Appl. No.: |
11/000858 |
Filed: |
December 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11000858 |
Dec 1, 2004 |
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09781475 |
Feb 12, 2001 |
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6844026 |
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Current U.S.
Class: |
510/301 |
Current CPC
Class: |
C01P 2004/50 20130101;
C01P 2006/22 20130101; C09K 3/1436 20130101; C01P 2004/64 20130101;
C01P 2006/80 20130101; C01P 2006/60 20130101; C01G 3/02 20130101;
C09C 3/10 20130101; B82Y 30/00 20130101; C09K 3/1409 20130101; C01G
1/02 20130101; C01P 2004/62 20130101; C01G 1/00 20130101; C01P
2004/84 20130101 |
Class at
Publication: |
510/301 |
International
Class: |
C11D 003/00 |
Claims
1-28. (canceled)
29. A process for the preparation of particles comprising at least
one copper ion which comprises the following stages: a) at least
one precursor comprising a copper cation is dissolved or dispersed
in an aqueous medium; b) a partial hydrolysis of said precursor is
optionally carried out, c) the precursor resulting from stage a) or
the partially hydrolyzed precursor resulting from stage b) is
brought into contact with at least one water-soluble comb copolymer
comprising either a complexing anionic backbone and stabilizing
hydrophilic side chains or a stabilizing hydrophilic neutral
backbone and complexing anionic side chains or at least one of the
two abovementioned copolymers in combination with at least one
complexing anionic hydrophilic polymer; and d) a partial or
complete hydrolysis of the product obtained during stage c) is
carried out.
30. A process according to claim 29, wherein the precursor is in
the form of an aqueous solution of a water-soluble salt of copper,
said salt being selected from the group consisting of nitrates,
sulfates, chlorides, and phosphates.
31. A process according to one of claim 30, wherein the precursor
is in the form of an aqueous dispersion of particles or of
aggregates of particles comprising a hydroxide, a hydroxide oxide
or a partially hydrolyzed water-soluble salt of a copper cation,
optionally combined with an oxide of a metal copper.
32. A process according to the claim 31, wherein the particles or
the aggregates have a mean size of less than or equal to 100
nm.
33. A process according to the claim 32, wherein the particles or
the aggregates have a mean size of between 2 and 100 nm.
34. A process according to claim 29, wherein the hydrolyses of
stage b) and that of stage d) are carried out in the presence of a
base which is an alkali metal hydroxide, an alkaline earth metal
hydroxide, or aqueous ammonia.
35. A process according to claim 34, wherein the base is chosen
from sodium hydroxide, potassium hydroxide, calcium hydroxide or
aqueous ammonia, alone or as mixtures.
36. A process according to claim 29, wherein the base employed
during optional stage b), and during stage d) corresponds to 50 to
130% of a stoichiometric amount needed to completely hydrolyze the
precursor.
37. A process according to claim 36, wherein, if n1 is non zero and
represents the number of moles of base employed during stage b), n2
represents the number of moles of base employed during stage d) and
n represents the sum of n1 and n2, then n1 and n2 conform to the
following inequalities 0<n1.ltoreq.0.8n and
0.2n.ltoreq.n2<n.
38. A process according to claim 29, wherein the water-soluble comb
copolymer, optionally combined with the water-soluble polymer, is
chosen so that the comb copolymer, optionally combined with the
hydrophilic polymer, forms a transparent solution at 10% by weight
in water at a temperature which is the lowest temperature to which
said comb copolymer, optionally combined with the hydrophilic
polymer, is subjected in the process.
39. A process according to claim 38, wherein the weight-average
molecular mass (Mw) is between 2 000 and 5.times.10.sup.5
g/mol.
40. A process according to claim 39, wherein the water-soluble comb
copolymer comprises a complexing anionic hydrophilic backbone and
nonionic stabilizing hydrophilic side chains, said backbone being
obtained from monomers chosen from unsaturated monocarboxylic
acids, unsaturated polycarboxylic acids or their anhydride form, or
unsaturated sulfonic acids, optionally in combination with one or
more water-insoluble monomers.
41. A process according to claim 40, wherein the monomers forming
the nonionic side chains are macromonomer entities selected from
the group consisting of macromonomers of poly(ethylene glycol)
(meth)acrylate, poly(vinyl alcohol) (meth)acrylate,
poly(hydroxy(C.sub.1-C.sub.4)alkyl (meth)acrylate) (meth)acrylate,
poly(N-methylolacrylamide) (meth)acrylate and
poly((meth)acrylamide) (meth)acrylate).
42. A process according to claim 41, wherein the nonionic side
chains exhibit a poly(ethylene glycol) number-average molar mass of
between 200 and 10 000 g/mol.
43. A process according to claim 41, wherein the copolymer
comprises a stabilizing hydrophilic neutral backbone and complexing
anionic hydrophilic side chains, said neutral backbone being
obtained from ethylene oxide in the form of an oligomer or of a
polymer.
44. A process according to claim 43, wherein the side chains are
obtained from monomers selected from the group consisting of
unsaturated carboxylic acids, polycarboxylic acids, anhydride form
of polycarboxylic acids, unsaturated amino acids and unsaturated
sulfonic acids.
45. A process according to claim 40, wherein the monomers forming
the complexing anionic backbone or the complexing anionic side
chains is combined with, or partially substituted by, esters of
unsaturated carboxylic acids, optionally carrying a sulfonated
group or a hydroxyl group; esters of unsaturated carboxylic acid;
linear or branched hydrocarbonaceous monomers comprising at least
one carbon-carbon double bond which comprise 2 to 10 carbon atoms
in the longest chain; vinylaromatic monomers;
.alpha.,.beta.-ethylenically unsaturated nitrites;
.alpha.,.beta.-ethylenically unsaturated amides; vinyl ether; or
N-vinylpyrrolidone.
46. A process according to one of claim 45, wherein the copolymer
is combined with at least one polymer obtained by polymerization of
at least one anionic monomer which are unsaturated carboxylic
acids, polycarboxylic acids or their anhydride form, or unsaturated
sulfonic acids.
47. A process according to claim 46, wherein the polymer has a
weight-average molar mass of between 2 000 and 5.times.10.sup.5
g/mol.
48. A process according to claim 29, wherein the level of copolymer
employed during stage c), which is the molar ratio of the
complexing group of the copolymer of the anionic hydrophilic part
or parts to the number of mole of the copper cation present in the
precursor, is between 0.05 and 2.
49. A process according to claim 29, wherein of at least 80% of the
particles obtained at the end of stage d) have a mean size between
2 and 500 nm.
50. A process according to claim 29, wherein, after stage d), a
stage e) of maturing is further carried out at a temperature of
between 10.degree. C. and a temperature of less than or equal to
the boiling point of said dispersion.
51. A process according to claim 50, wherein, after stage d) or
after stage e), a stage f) a concentration of the dispersion is
carried out.
52. A process according to claim 50, wherein the concentration is
carried out by partially or completely separating the particles
from the medium of the dispersion and then optionally by
redispersing the particles thus obtained in an appropriate amount
of aqueous medium.
53. A process according to claim 52, wherein the separation stage
is carried out is by ultrafiltration, dialysis, precipitation,
centrifugation, ultracentrifugation, complete or partial
evaporation, with or without heating, of the aqueous medium of the
dispersion.
54. A process for the preparation of a fungicidal or biocidal
composition comprising the step of preparing particles by the
process defined in claim 29.
Description
[0001] A subject-matter of the present invention is a process for
the preparation of inorganic particles by hydrolysis of a compound
comprising one or more metal cations and the particles thus
obtained.
[0002] Compounds in the form of divided solids, whether the latter
are divided in the dry form or alternatively in the form of
dispersions, are used in numerous fields. This is, for example, the
case in the field of plant-protection formulations, where some
pesticides are found to be inorganic particles, such as fungicidal
copper hydroxide, which forms part of the composition of Bordeaux
mixture. Still in this field, plant-protection formulations can
comprise nutrient elements in the form of metals. The case may also
be found in the field of pigments, where rare earth metal oxides or
hydroxides are employed.
[0003] One of the problems encountered is to be able to have
available particles comprising one metal or several which are
chemically stable when they are in the form of a powder but which
remain stable when they are in the form of a dispersion. It is
therefore advantageous again to cite the case of copper. Thus, the
difficulty with this compound is that the hydroxide is first of all
relatively difficult to disperse. However, in addition, it exhibits
the disadvantage of not being chemically stable over time. This is
because copper hydroxide dehydrates more or less rapidly to copper
oxide. Furthermore, the control exerted over the growth of copper
hydroxide particles during its synthesis is far from being
efficient. Consequently, the distribution of the particle sizes is
very broad, which can represent a disadvantage during the use of
said particles. This is one of the reasons why Bordeaux mixture is
very often sold commercially in the form of a powder and not of a
suspension; it being possible for the powders to be stored.
[0004] Likewise, the particles must be in a position to be able to
be easily dispersed, to form dispersions which are sufficiently
stable, in particular which do not separate by settling on storage
or when they are used.
[0005] An object of the present invention is to provide particles
in the dry or dispersed form which are chemically stable in both
these presentations, which are easily dispersible in an aqueous
medium and which give access to dispersions which do not separate
by settling on storage.
[0006] These aims and others are achieved by the present invention,
a first subject matter of which is a process for the preparation of
particles comprising at least one metal ion in which the following
stages are employed:
[0007] a) at least one precursor comprising at least one metal
cation is dissolved or dispersed in an aqueous medium;
[0008] b) a partial hydrolysis of said precursor is optionally
carried out,
[0009] c) the precursor resulting from stage a) or the optionally
hydrolyzed precursor resulting from stage b) is brought into
contact with at least one water-soluble comb copolymer comprising
either a complexing anionic backbone and stabilizing hydrophilic
side chains or a stabilizing neutral hydrophilic backbone and
complexing anionic side chains or at least one of the two
abovementioned copolymers in combination with at least one
complexing anionic hydrophilic polymer;
[0010] d) a partial or complete hydrolysis of the product obtained
during stage c) is carried out.
[0011] A subject matter of the present invention is likewise the
particles capable of being obtained by employing the process
according to the invention, the mean size of which is between 2 and
500 nm.
[0012] One of the advantages of the present invention is that the
process makes it possible to efficiently control the growth of the
particles.
[0013] Furthermore, because of their preparation process, the
particles obtained are easily redispersible. This is because the
polymeric coating which they exhibit has the consequence of
facilitating the resuspension of said particles.
[0014] However, other advantages and characteristics of the present
invention will become more clearly apparent on reading the
description and examples which will follow.
[0015] As has been indicated above, a subject matter of the present
invention is first of all a process for the preparation of
particles comprising at least one metal ion which comprises the
following stages:
[0016] a) at least one precursor comprising a metal cation is
dissolved or dispersed in aqueous medium;
[0017] b) a partial hydrolysis of said precursor is optionally
carried out,
[0018] c) the precursor resulting from stage a) or the optionally
hydrolyzed precursor resulting from stage b) is brought into
contact with at least one water-soluble comb copolymer comprising
either a complexing anionic backbone and stabilizing hydrophilic
side chains or a stabilizing neutral hydrophilic backbone and
complexing anionic side chains or at least one of the two
abovementioned copolymers in combination with at least one
complexing anionic hydrophilic polymer;
[0019] d) a partial or complete hydrolysis of the product obtained
during stage c) is carried out.
[0020] First of all, the precursor comprises at least one metal
cation which is chosen more particularly from the metals from
columns IIIA, IVA, VIII, IB, IIB, IIIB and VB of the Periodic
Table, the lanthanides and the actinides. It is specified that the
Periodic Table is that which appeared in the bulletin de socits
chimiques de France of January 1966.
[0021] According to a specific embodiment of the invention, the
metal cation is chosen from titanium, iron, cobalt, nickel, copper,
aluminum, zinc, gold, silver, platinum, cerium, lanthanum, yttrium,
iridium, ruthenium, rhodium, osmium or palladium. These cations
being present alone or as mixtures. It should be noted that it is
not impossible to employ a mixed precursor and/or a mixture of
several precursors comprising only one cation.
[0022] A first alternative form of the invention consists in
employing the precursor in the form of an aqueous solution. In such
a case, the precursor is used in the form of a water-soluble salt.
Said salt is preferably chosen from nitrates, sulfates, chlorides,
phosphates or their mixtures. The salt or salts can also be chosen
from non-polymeric complexing agents, such as citrates, lactates or
their mixtures.
[0023] A second alternative form of the invention consists in
employing said precursor in the form of an aqueous suspension. Said
particles are preferably suspended solids. According to this
alternative form, the precursor can be composed of particles, of
aggregates of particles or of their combination.
[0024] According to an advantageous embodiment of the present
invention, the particles or the aggregates of particles have a mean
size of less than or equal to 100 nm, more particularly of between
2 and 100 nm and preferably of between 2 and 90 nm. The mean size
of the particles/aggregates is measured by dynamic light
scattering.
[0025] In addition, these particles and/or aggregates of particles
more particularly comprise a hydroxide, a hydroxide oxide or a
partially hydrolyzed water-soluble salt of a metal cation, alone or
as mixtures, optionally combined with an oxide of a metal cation.
Here again, various possibilities can be envisaged, from the
presence of one metal cation present in one form to the presence of
several cations in various forms.
[0026] Such particles can be obtained by employing processes known
to a person skilled in the art.
[0027] The aqueous medium in which the salts, or particles,
aggregates of particles or water-soluble salts, or their
combinations is preferably water. It should be noted that the use
of an aqueous medium comprising at least one water-miscible solvent
can be envisaged. Mention may in particular be made, by way of
illustration, of short alcohols, such as ethanol or isopropyl
alcohol.
[0028] Once the suspending/dissolving has been carried out, a
particularly advantageous embodiment of the present invention
consists in employing a partial hydrolysis of the precursor.
[0029] Generally, this hydrolysis, if it is carried out, is carried
out in the presence of a base chosen from alkali metal or alkaline
earth metal hydroxides and aqueous ammonia.
[0030] Advantageously, the base is more particularly chosen from
sodium hydroxide, potassium hydroxide, calcium hydroxide or aqueous
ammonia, alone or as mixtures.
[0031] This partial hydrolysis is generally carried out by adding
the neutralizing base to the solution/dispersion.
[0032] This operation, when it takes place, is conventionally
carried out with stirring.
[0033] According to an important characteristic of the process of
the invention, the precursor obtained after the
dissolving/dispersing described during stage a) or the partially
hydrolyzed precursor resulting from stage b) is subsequently
brought into contact with at least one water-soluble comb copolymer
comprising a complexing anionic backbone and stabilizing
hydrophilic side chains or a stabilizing neutral hydrophilic
backbone and complexing anionic side chains or at least one of the
two above-mentioned copolymers in combination with at least one
complexing anionic hydrophilic polymer.
[0034] It is pointed out that the term "complexing" covers not only
complexing in the strict sense (shearing of orbitals) but it
intends also to cover bonds of ionic type.
[0035] In a particularly advantageous way, the polymer employed
during stage c) exhibits a weight-average molecular mass (Mw) of
between 2 000 and 5.times.10.sup.5 g/mol, preferably of between 3
000 and 10.sup.5 g/mol. The weight-average molar mass is usually
measured by GPC (polyethylene glycol standard).
[0036] According to an advantageous embodiment of the present
invention, the polymers, whether they are comb copolymers or
hydrophilic polymers, employed in the process according to the
invention are chosen from polymers which give a transparent
solution in water at the lowest temperature to which said polymer
(or said comb and hydrophilic polymers) is subjected during the
implementation of the process; the content by weight of polymer(s)
in the solution being 50% by weight.
[0037] A first embodiment of the invention consists in using at
least one water-soluble comb copolymer comprising a complexing
anionic backbone and stabilizing hydrophilic side chains which are
preferably nonionic hydrophilic chains. According to a preferred
embodiment of the invention, the water-soluble comb copolymer
comprises a complexing anionic hydrophilic backbone.
[0038] Use is preferably made of a copolymer comprising a fraction
by weight of nonionic hydrophilic side chains which is greater than
the fraction by weight of complexing ionic monomer.
[0039] The anionic backbone is more particularly obtained from
monomers chosen from unsaturated monocarboxylic acids,
polycarboxylic acids or their anhydride form, unsaturated amino
acids or unsaturated sulfonic acids.
[0040] Mention may be made, as examples of suitable monomers,
without intending to be restricted thereto, of:
[0041] acrylic acid or methacrylic acid,
[0042] vinylsulfonic acid, 2-propene-1-sulfonic acid,
methallylsulfonic acid, sulfopropyl (meth)acrylate, styrenesulfonic
acid or acrylamidomethylpropanesulfonic acid,
[0043] vinylbenzoic acid,
[0044] fumaric acid, itaconic acid, citraconic acid, maleic acid,
their salts or their anhydrides,
[0045] vinylphosphonic acid.
[0046] It is possible to use, in addition to the abovementioned
anionic monomers, water-soluble nonionic monomers:
[0047] hydroxyalkyl esters of .alpha.,.beta.-ethylenically
unsaturated acids, such as hydroxyethyl or hydroxypropyl acrylates
or methacrylates, acrylamide, and the like.
[0048] It is likewise possible to combine the abovementioned
monomers with precursors chosen from monomers, the units of which,
once incorporated in the polymer chain, can be converted, in
particular by a chemical treatment such as hydrolysis, to
water-soluble units. They are, for example, tert-butyl
(meth)acrylate, inter alia.
[0049] The use of hydrophobic monomers is not excluded either.
However, if monomers of this type are present, their proportions
are such that the comb copolymer, optionally combined with the
hydrophilic polymer, forms a transparent solution at 50% by weight
in water at the lowest temperature to which said comb copolymer,
optionally combined with the hydrophilic polymer, is subjected in
the process.
[0050] Mention may be made, among hydrophobic monomers which can be
used, of, for example, linear or branched hydrocarbonaceous
monomers comprising at least one carbon-carbon double bond which
comprise 2 to 10 carbon atoms in the longest chain. Mention may be
made, by way of examples, of vinylaromatic monomers, such as
styrene or vinyltoluene, alkyl acrylates, alkyl methacrylates,
acrylamide derivatives, such as N-alkyl- or N,N-dialkylacrylamides
or N-alkyl- or N,N-dialkyl-methacrylamides,
.alpha.,.beta.-ethylenically unsaturated nitriles, such as
acrylonitrile, .alpha.,.beta.-ethylenically unsaturated amides,
such as acrylamide, or vinyl ether, such as methyl or ethyl vinyl
ether.
[0051] The monomers forming the nonionic side chains are chosen
more particularly from macromonomer entities. It should be recalled
that, within the meaning of the present invention, a macromonomer
denotes a macromolecule carrying one or more ethylenically
functional groups which can be polymerized by the radical
route.
[0052] Mention may be made, by way of examples, of macromonomers of
poly(ethylene glycol) (meth)acrylate, poly(vinyl alcohol)
(meth)acrylate, poly(hydroxy(C.sub.1-C.sub.4)-alkyl (meth)acrylate)
(meth)acrylate, poly(N-methylol-acrylamide) (meth)acrylate or
poly((meth)acrylamide) (meth)acrylate type.
[0053] These macromonomers can in particular be obtained, inter
alia, by transesterification of methyl acrylate (or methacrylate)
or of (meth)acrylic anhydride or of acryloyl or methacryloyl
chloride. They can also be obtained by direct esterification of
acrylic or methacrylic acid.
[0054] Some macromonomers can also be obtained by telomerization,
such as those of the poly((meth)acryl-amide) (meth)acrylate
type.
[0055] The monomers forming the nonionic side chains which are
preferred in the context of the present invention are poly(ethylene
glycol) methacrylates. According to a preferred embodiment, the
nonionic side chains exhibit a poly(ethylene glycol) number-average
molar mass of between 200 and 10 000 g/mol, preferably between 300
and 2 000 g/mol.
[0056] A second embodiment of the invention consists in using a
copolymer comprising a stabilizing neutral hydrophilic backbone and
complexing anionic side chains. According to a preferred
embodiment, the water-soluble comb copolymer comprises complexing
anionic hydrophilic side chains.
[0057] The neutral hydrophilic backbone is advantageously obtained
from ethylene oxide and can be provided in the form of an oligomer
or of a polymer.
[0058] With regard to the side chains, they can be obtained from
monomers chosen from unsaturated carboxylic acids, polycarboxylic
acids or their anhydride form, or unsaturated sulfonic acids
(nonlimiting examples). Reference may be made to the lists of
monomers of this type given in the context of the first embodiment.
The monomers employed are preferably chosen from unsaturated
carboxylic acids or unsaturated sulfonic acids.
[0059] It would not be departing from the scope of this second
embodiment to incorporate, among the monomers, water-insoluble
monomers or water-soluble nonionic monomers, such as, in
particular, those indicated above in the context of the preceding
alternative form. Thus, monomers of the type of esters of
unsaturated carboxylic acids, which is optionally substituted, such
as alkyl or hydroxyalkyl (meth)acrylates, glycidyl (meth)acrylates,
sulfopropyl (meth)acrylates or vinyl acetate, can be incorporated.
Likewise, linear or branched C.sub.2-C.sub.10 hydrocarbonaceous
monomers comprising at least one carbon-carbon double bond,
vinylaromatic monomers, .alpha.,.beta.-ethylenically unsaturated
nitriles, .alpha.,.beta.-ethylenically unsaturated amides, vinyl
ethers, N-vinylpyrrolidone, and the like, can be incorporated.
[0060] It should be noted that, if monomers of this type are
present, their proportions are such that the comb copolymer,
optionally combined with the hydrophilic polymer, forms a
transparent solution at 50% by weight in water at the lowest
temperature to which said comb copolymer, optionally combined with
the hydrophilic polymer, is subjected in the process.
[0061] According to a third embodiment of the invention, at least
one of the two above-mentioned copolymers is employed in
combination with at least one complexing anionic hydrophilic
polymer.
[0062] This polymer can more particularly be obtained by
polymerization of at least one anionic monomer chosen from
unsaturated carboxylic acids, polycarboxylic acids or their
anhydride form, unsaturated amino acids or unsaturated sulfonic
acids. Reference may be made to the list of the monomers of this
type given above.
[0063] Said polymer can be a homopolymer or a copolymer in which
the distribution of the monomers is random.
[0064] The preparation of polymers of this type is fully known to a
person skilled in the art. It takes place under radical conditions,
in the aqueous phase, with the use of initiators which are
conventional in the field (for example, azobis(cyanovaleric acid)
or azobis(methylpropionamid- e hydrochloride)). (AIBN is not
water-soluble.) More particularly, the weight-average molar mass of
the polymer (Mw) [lacuna] between 2 000 and 5.times.10.sup.5 g/mol,
preferably between 3 000 and 10.sup.5 g/mol. The weight-average
molar mass is usually measured by GPC (polyethylene glycol
standard). According to an advantageous alternative form of the
invention, the weight-average molar mass of the polymer is less
than or equal to that of the comb copolymer with which it is
combined.
[0065] Furthermore, according to a preferred embodiment of the
invention, said polymer is water-soluble. More specifically, it
forms a transparent solution at 10% by weight in water at the
lowest temperature to which said water-soluble polymer is subjected
in the process. Finally, it also forms a transparent solution in
water under the same temperature conditions when it is combined
with the comb copolymer.
[0066] In the context of this specific alternative form of the
invention, the content of polymer with respect to that of the comb
copolymer with which it is combined is between 1% and 1 000%.
[0067] The comb polymers of the first and second embodiment of the
invention which have just been described are well known to a person
skilled in the art. They can be obtained by various methods, such
as, for example, copolymerization of a monomer of anionic type with
a nonionic monomer or macromonomer or alternatively by
polymerization or a monomer of anionic type, followed by grafting
of nonionic chains.
[0068] The grafting of the side polymeric segments onto a backbone
polymeric segment can be carried out according to conventional
techniques familiar to a person skilled in the art (European
Polymer Journal, 4, 343 (1968), for example).
[0069] Mention may in particular be made, among these conventional
techniques, of those referred to as direct grafting and
polymerization.
[0070] Direct grafting consists in polymerizing the chosen
monomer(s) by the radical route in the presence of the polymer
selected to form the backbone of the final product. If the
monomer/backbone pair and the operating conditions are carefully
chosen, then there may be a transfer reaction between the growing
macroradical and the backbone. This reaction creates a radical on
the backbone and it is from this radical that the graft grows. The
primary radical resulting from the initiator can also contribute to
the transfer reactions.
[0071] For its part, the copolymerization employs, in a first step,
the grafting to the end of the nonionic segment of a functional
group which can be polymerized by the radical route. This grafting
can be carried out by conventional organic chemistry methods. Then,
in a second step, the macromonomer thus obtained is polymerized
with the monomer chosen to form the backbone and a polymer referred
to as a "comb" polymer is obtained.
[0072] It is obvious to a person skilled in the art that, when a
macromonomer and a monomer, chosen so that these two entities are
strongly combined by hydrogen bonds, are polymerized, then there is
simultaneously direct grafting to the polymeric segment of the
macromonomer and incorporation of this macromonomer in the polymer
chain by simple polymerization of its polymerizable end. In this
case, the structure obtained is substantially more branched or even
crosslinked than in the two preceding cases.
[0073] Whatever the method chosen, the polymerization and the
grafting preferably take place in the aqueous phase.
[0074] In addition, it is advantageously carried out in the
presence of a polymerization initiator, preferably a water-soluble
polymerization initiator. The latter can be chosen in particular
from peroxides, such as alkali metal or ammonium persulfates,
azobis(cyanovaleric acid), azobis(methylpropionamide
hydrochloride), and the like.
[0075] In the case of polymers which exhibit a nonionic backbone
and anionic side chains, it is possible to proceed, for example, by
radical polymerization, again preferably in the aqueous phase, of
monomers of anionic type, from which the grafts derive, with an
oligomer or polymer deriving from ethylene oxide.
[0076] The polymerization operation is carried out in the presence
of a polymerization initiator which is preferably water-soluble.
Mention may be made, among initiators which can be envisaged, by
way of examples, of peroxides, such as alkali metal or ammonium
persulfates, initiators of azo type, such as
2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] or
4,4'-azobis(4-cyanovaleric acid), or redox systems based on an
oxidizing agent, such as aqueous hydrogen peroxide solution or
alkali metal persulfates, and on reducing agents, such as alkali
metal bisulfites.
[0077] The temperature at which the polymerization is carried out
can vary within wide limits. By way of illustration, the reaction
is carried out between 60 and 100.degree. C.
[0078] Stage c), corresponding to bringing the solution/dispersion
obtained after stage a) or b) into contact with the copolymer, is
preferably carried out with stirring.
[0079] The amount of copolymer, optionally in combination with the
homopolymer, is such that the molar ratio of the complexing group
of the complexing anionic hydrophilic part(s) to the number of mole
of the metal cation present in the precursor is advantageously
between 0.05 and 10, more particularly between 0.1 and 1. It should
be pointed out that, generally, the higher this molar ratio, the
smaller the size of the particles obtained on conclusion of the
process according to the invention.
[0080] Once homogenization has been carried out, a hydrolysis stage
(stage d)) is carried out.
[0081] This stage consists in bringing a base into contact with the
mixture obtained in the preceding stage. More particularly, the
base is added to the mixture of stage d), preferably with
stirring.
[0082] Generally, the hydrolysis of stage d) is itself also carried
out in the presence of a base chosen from alkali metal or alkaline
earth metal hydroxides and aqueous ammonia. The base is preferably
chosen from sodium hydroxide, potassium hydroxide, calcium
hydroxide or aqueous ammonia, alone or as a mixture.
[0083] It should be noted, and this constitutes an additional
advantage of the process according to the invention, that the
hydrolysis carried out during this stage d) can result in a
completely or incompletely hydrolyzed compound being obtained. This
is because it may be advantageous in some fields of application to
have available particles which are not completely hydrolyzed.
[0084] In the case where hydrolysis is complete, in other words
when the total amount of base introduced during stages b) (if it
takes place) and d) corresponds at least to the charge of the metal
cation or cations, the resulting particles comprise an oxide,
hydroxide and/or hydroxide oxide.
[0085] The amount of base employed during stage b), if it takes
place, and during stage d) usually corresponds to 50 to 130% of the
stoichiometric amount needed to completely hydrolyze the precursor,
preferably from 70 to 100% of the stoichiometric amount.
Preferably, in many scenarios, it is preferable to employ a total
amount of base corresponding substantially to the
stoichiometry.
[0086] According to a more specific embodiment of the invention, if
n1 is non zero and represents the number of moles of base employed
during stage b), n2 represents the number of moles of base employed
during stage d) and n represents the sum of n1 and n2, then n1 and
n2 conform to the following inequalities 0<n1.ltoreq.0.8n,
preferably 0.3.ltoreq.n1.ltoreq.0.6, and 0.2n.ltoreq.n2<n,
preferably 0.4.ltoreq.n2.ltoreq.0.7.
[0087] It should be remembered that n corresponds to the number of
moles of base required to result either in partial hydrolysis or in
complete hydrolysis (with or without excess base) of the
precursor.
[0088] In addition, it should be noted that the size of the
particles obtained after stage d) can be modified-according to the
degree of hydrolysis during stage b), if it takes place. Thus, the
higher n1, the greater the size of the particles resulting from
stage d).
[0089] According to an embodiment of the present invention, stages
a) to d) are carried out in an aqueous medium with a pH which is
preferably adjusted to between 5 and 12, preferably at a pH at
least equal to the pKa of the anionic component or components of
the comb copolymer.
[0090] The temperatures employed during stages a) to d) can be
determined without difficulty by a person skilled in the art. They
are conventionally between 0.degree. C. and the boiling temperature
of the aqueous medium (usually in the vicinity of 100.degree. C.).
More particularly, the temperature is between 10 and 50.degree. C.,
preferably between 20 and 50.degree. C. Advantageously, the
temperature is close to ambient temperature. The temperature may or
may not be kept constant during stages a) to d).
[0091] On conclusion of this hydrolysis stage d), particles are
obtained which are found more particularly in the form of
colloids.
[0092] Advantageously, the size, moreover, of at least 80% by
weight of said particles is between 2 and 500 nm, preferably
between 2 and 200 nm.
[0093] According to a specific embodiment of the invention, an
additional stage of maturing of the colloidal dispersion can be
carried out after the hydrolysis stage d).
[0094] The temperature at which this additional stage e) is carried
out is generally between 20.degree. C. and a temperature less than
or equal to the boiling point of said dispersion.
[0095] Optionally, after stage d) or after stage e), if it takes
place, the process according to the invention can comprise an
additional stage f) of concentration of the dispersion. This
additional concentration stage can be carried out in particular by
partially or completely separating the particles from the medium of
the dispersion and then optionally by redispersing the particles
thus obtained in an appropriate amount of aqueous medium.
[0096] More particularly, the separation stage can be carried out
by ultrafiltration, dialysis, precipitation (generally by means of
a poor solvent or non-solvent for the polymer(s)), centrifugation
or ultracentrifugation, by complete or partial evaporation, with or
without heating, of the aqueous medium of the dispersion, or by
lyophilization, it being possible for these stages to be carried
out alone or in combination.
[0097] A subject matter of the present invention is likewise the
particles capable of being obtained by the process according to the
invention, said particles exhibiting a mean size of between 2 and
500 nm and preferably between 2 and 300 nm. The size is measured by
dynamic light scattering.
[0098] These particles exhibit the advantage, once dried, of being
able to be easily redispersed in an aqueous medium. Without wishing
to be restricted by a specific theory, the particles, because of
their process of preparation, are coated with the polymer. This
coating is an aid to the redispersion.
[0099] Mention may be made, among possible applications for the
colloidal systems prepared by the process according to the
invention, of the mechanical polishing of hard objects, such as
metal components, the preparation of pigments or mixed ceramics for
the electronics industry, the reinforcing of polymeric matrices,
fungicidal or biocidal dispersions, and the scavenging of sulfur
derivatives and more generally the scavenging of unpleasant
smells.
[0100] The following examples illustrate the invention without
limiting the scope thereof.
EXAMPLE 1
[0101] The object of this example is the synthesis of a comb
copolymer with the acrylic acid/poly(ethylene glycol) methacrylate
(molar ratio: 88/12) theoretical composition.
[0102] The copolymerization of acrylic acid and of PEG methacrylate
is carried out by the radical route in ethanol, with
azobis(isobutyronitrile- ) (AIBN) (1.6 molar % with respect to the
monomers) as initiator, as follows:
[0103] The following:
[0104] 115.14 g of ethanol
[0105] 0.2444 g of AIBN
[0106] 5.87 g of acrylic acid
[0107] 23.45 g of PEG-2000 methacrylate (Laporte), dissolved in
37.05 g of water,
[0108] are introduced, at 25.degree. C. under nitrogen, into a 500
ml three-necked round-bottomed flask equipped with a magnetic rod,
with a nitrogen inlet and with an oil bath.
[0109] The temperature is subsequently brought to 75.degree. C. It
is maintained at 75.degree. C. for 6 and a half hours.
[0110] The ethanol is subsequently removed under vacuum at
45.degree. C. (rotary evaporator) and then the product is dissolved
in water (concentration by mass: 32.67%).
[0111] The weight-average molar mass is 36 000 g/mol. It is
determined by aqueous GPC at ambient temperature (Shodex columns,
water/acetonitrile 80/20 w/w, PEG standardization, marker: ethylene
glycol). The polydispersity index (PI) is approximately 2.3 (it
represents the ratio of the mass-average molar mass to the mass
molar mass at the tip).
[0112] The polymer is subsequently purified by dialysis against
pure water for 7 days in a dialysis bag with a cutoff threshold of
3 500 daltons.
[0113] Finally, the polymer is lyophilized.
[0114] The final composition of the polymer is subsequently
determined by acid/base titration of a 1% by weight solution of
copolymer with 0.05M NaOH.
[0115] The result is as follows: 13% by weight of acrylic acid and
87% by weight of PEG methacrylate.
EXAMPLE 2
[0116] The object of this example is the preparation of a colloidal
suspension, stabilized by a comb copolymer, of partially hydrolyzed
copper chloride. 3 ml of an 8.times.10.sup.-3M aqueous CuCl.sub.2
solution are poured into a beaker.
[0117] 0.150 ml of a 0.2M aqueous sodium hydroxide solution is
subsequently added with magnetic stirring.
[0118] Stirring of the solution is continued for 10 minutes.
[0119] The degree of prehydrolysis of the copper is then
OH/Cu=1.25.
[0120] 0.110 ml of a 4.97% by weight solution of comb copolymer
obtained in Example 1, after having adjusted the pH of the
copolymer solution to 5.3, is added with stirring.
[0121] The acrylic acid/Cu molar ratio is 0.4.
[0122] 1.24 ml of Millipore water are subsequently added with
magnetic stirring.
[0123] The molar concentration of copper is
5.33.times.10.sup.-3M.
[0124] The suspension obtained is blue and slightly cloudy, and its
pH is 5.4.
[0125] The hydrodynamic radius of the particles, measured by
dynamic light scattering, is 108 nm.
EXAMPLE 3
[0126] This example relates to the preparation of a colloidal
suspension, stabilized by a comb copolymer, of copper
hydroxide.
[0127] 3 ml of an 8.times.10.sup.-3M aqueous CuCl.sub.2 solution
are poured into a beaker.
[0128] 0.150 ml of a 0.2M aqueous sodium hydroxide solution is
subsequently added with magnetic stirring.
[0129] Stirring of the solution is continued for 10 minutes.
[0130] The degree of prehydrolysis of the copper is then
OH/Cu=1.25.
[0131] 0.110 ml of a 4.97% by weight solution of comb copolymer
obtained in Example 1, after having adjusted the pH of the
copolymer solution to 5.3, is added with stirring.
[0132] The acrylic acid/Cu molar ratio is 0.4.
[0133] 0.090 ml of a 0.2M aqueous [lacuna] solution is subsequently
added with magnetic stirring.
[0134] Stirring of the solution is continued for 5 minutes.
[0135] The final degree of hydrolysis of the copper is then
OH/Cu=2.0.
[0136] 1.25 ml of Millipore water are subsequently added with
magnetic stirring.
[0137] The dispersion thus obtained is blue and slightly cloudy.
The molar concentration of copper is 5.33.times.10.sup.-3M and the
pH is 7.8 after 9 days.
[0138] The hydrodynamic radius of the particles, measured by
dynamic light scattering, is 108 nm.
EXAMPLE 4
[0139] The object of this example is the preparation of a colloidal
suspension, stabilized by a comb copolymer, of copper hydroxide at
a higher concentration.
[0140] 3 ml of a 4.times.10.sup.-2M aqueous CuCl.sub.2 solution are
poured into a beaker.
[0141] 0.155 ml of a 0.96M aqueous sodium hydroxide solution is
subsequently added with magnetic stirring.
[0142] Stirring of the solution is continued for 10 minutes.
[0143] The degree of prehydrolysis of the copper is then
OH/Cu=1.25.
[0144] 0.67 ml of a 4.97% by weight solution of comb copolymer
obtained in Example 1, after having adjusted the pH of the
copolymer solution to 5.3, is added with stirring.
[0145] The acrylic acid/Cu molar ratio is 0.5.
[0146] 0.094 ml of a 0.96M aqueous [lacuna] solution is
subsequently added with magnetic stirring.
[0147] Stirring of the solution is continued for 5 minutes.
[0148] The final degree of hydrolysis of the copper is then
OH/Cu=2.0.
[0149] 0.58 ml of Millipore water is subsequently added with
magnetic stirring.
[0150] The dispersion thus obtained is blue and cloudy.
[0151] The molar concentration of copper is 2.67.times.10.sup.-2M
and the pH is 9.4 after 6 days.
[0152] The hydrodynamic radius of the particles, measured by
dynamic light scattering, is 95 nm.
EXAMPLE 5
[0153] This example illustrates the drying and the redispersion of
a colloidal suspension, stabilized by a comb copolymer, of copper
hydroxide.
[0154] 4.5 ml of a copper hydroxide suspension synthesized
according to the procedure described in Example 3 are dried in a
beaker for at least 12 hours in a laminar-flow hood without
heating.
[0155] 4 ml of Millipore water are subsequently added to the dried
particles with magnetic stirring.
[0156] The hydrodynamic radius of the particles, measured by
dynamic light scattering after stirring for 10 minutes, is 135 nm
instead of 115 nm before drying. The difference between the two
values is within the range of error of the technique and shows that
there is no aggregation.
EXAMPLE 6
[0157] This example illustrates the drying and the redispersion of
a more concentrated colloidal suspension, stabilized by a comb
copolymer, of copper hydroxide.
[0158] 21 ml of a copper hydroxide suspension synthesized according
to the procedure described in Example 3 are dried in a beaker for
at least 12 hours in a laminar-flow hood without heating.
[0159] 1 ml of Millipore water is subsequently added to the dried
particles with magnetic stirring.
[0160] The final concentration of copper is thus 21 times higher
than before the drying stage.
[0161] The hydrodynamic radius of the particles, measured by
dynamic light scattering after stirring for 10 minutes, is 124 nm
instead of 115 nm before drying.
* * * * *