FR2736922A1 - PROCESS FOR THE PREPARATION OF AQUEOUS DISPERSION OF COMPOSITE PARTICLES COMPRISING LATEX PARTICLES AND INORGANIC PARTICLES - Google Patents

Abstract

The invention relates to aqueous dispersions of composite particles, said particles comprising each a plurality of organic polymer particles of a size comprised between 20 and 40 nm and which are adsorbed on a inorganic particle. The invention also relates to a process for the preparation of said aqueous dispersion, said process comprising the mixing in water of inorganic particles and a latex in the absence of dispersant. Said dispersions may particularly be used for the preparation of coating compositions or in paper manufacturing.

Description

PROCESS FOR THE PREPARATION OF AQUEOUS DISPERSION
COMPOSITE PARTICLES COMPRISING LATEX PARTICLES
AND INORGANIC PARTICLES
The invention relates to a process for encapsulating inorganic particles with polymer particles to form an aqueous dispersion of composite particles for use in coating compositions.
Composite particle dispersions comprising a plurality of latex particles adsorbed on an inorganic particle are known from the prior art. They can be obtained by different processes for encapsulating inorganic particles with a polymer.

 A first type of inorganic particle encapsulation process consists in polymerizing monomers in the presence of inorganic particles. These processes therefore consist in mixing the inorganic particles and the momères and initiating the polymerization of the latter. These methods have drawbacks because it is difficult to avoid parasitic nucleation of the latex particles forming and to prevent agglomeration phenomena of the inorganic particles during the polymerization.

In addition, these processes require very specific reactors and have a low productivity.

 A second type of process consists in mixing previously prepared latex particles and an aqueous dispersion of inorganic particles obtained using a dispersant. In order for the latex particles to bind to the surface of the inorganic particles, it is necessary to functionalize the surface of the latex particles with a group having a high affinity for the dispersed inorganic particles. It is thus possible to adsorb to the surface of the latex particles a water-soluble polymeric compound. It is also described the use of latex having specific acidic functions, for example dihydrogenphosphate or dicarboxylic functions, or a specific acid function rate, for example greater than 10% by weight of the latex. This type of process, however, does not allow to obtain a complete coating of the inorganic particles.

 An object of the present invention is to provide a new process for preparing dispersions of composite particles each comprising a plurality of latex particles adsorbed on an inorganic particle.

 Another object of the invention is to propose an encapsulation process leading to a complete coating of the inorganic particles irreversibly.

 Another object is to provide a method for encapsulating inorganic particles by any type of latex particles.

 Another object is to provide a method for rapid encapsulation of inorganic particles.

 Another object is to provide a composition for gloss paint, high coverage and improved whiteness.

 For these purposes, the invention relates to a method for preparing an aqueous dispersion of composite particles, said composite particles each comprising several latex particles adsorbed on an inorganic particle characterized in that inorganic particles are mixed in water and a latex in the absence of dispersant.

 The invention also relates to a coating composition characterized in that it comprises an aqueous dispersion of composite particles obtained by the above method.

 The invention also relates to the use of an aqueous dispersion of titanium dioxide-based composite particles obtained by the above method for improving the opacifying power, brightness and whiteness of a dried film of a coating composition containing said dispersion.

 The invention further relates to the use of an aqueous dispersion of titanium dioxide composite particles obtained by the above process for the manufacture of paper.

 Finally, the invention relates to a dispersion of pigments comprising the dispersion obtained by the process according to the invention.

 Figure 1 shows particles of a dispersion obtained according to the process of the invention.

 Figure 2 shows particles of a dispersion obtained according to a method of the prior art.

 The invention relates first of all to a process for preparing an aqueous dispersion of composite particles, said composite particles each comprising a plurality of latex particles adsorbed on an inorganic particle, characterized in that inorganic particles are mixed in water and a latex in the absence of dispersant.

 The process according to the invention differs from encapsulation processes starting from latex particles previously formed from the prior art in that it does not use an aqueous dispersion of inorganic particles and does not go through the preparation of a such dispersion of inorganic particles using a dispersant type polyelectrolyte or surfactant as described in the prior art.

 The process according to the invention generally uses inorganic particles in powder form which are mixed directly with the other raw materials of the process: latex and water. It is also possible to previously contact the inorganic particles with water and then mix them with latex. However, during this introduction into the water beforehand, no dispersant is used.

 The order of introduction of the starting products can be varied.

 For example, the inorganic particles may first be introduced into the water and then the latex added to this water / particle mixture. It is also possible to mix the latex and the water and then introduce the inorganic particles into the water-latex mixture. One can also consider mixing on one side a portion of the water with the inorganic particles, then on the other hand to mix the latex and the rest of water, and finally to mix these two premixes.

 Preferably, the process according to the invention is carried out by further mixing a water-soluble base in an amount necessary to bring the pH of the latex to a value of at least 3 and at most 10, preferably between 4 and 10, even more preferably between 7 and 10.

 Thus, the encapsulation process is carried out by mixing in water the inorganic particles, the latex and a water-soluble base, in the absence of dispersant.

 According to the method of the invention, the base is introduced in a predefined quantity. This predefined quantity is that which is added to the quantity of latex used in the process, the latex being alone without any other starting material of the process, makes it possible to bring the pH of said latex alone to a value of between 3 and 10, preferably between 4 and 10, still more preferably between 7 and 10. This amount of base may depend on the nature of the base used and the nature of the latex.

 Preferably, a sufficient amount of base is added to bring the pH of the latex to a pH of between 7 and 10. It has indeed been observed that working at basic pH makes it possible to reduce the viscosity of the dispersions during the process and the reduce the stirring required for the mixtures.

 According to the invention, the inorganic particles may be chosen from all the particles that may be coated with a polymer. It may be, for example, particles selected from the following inorganic materials: titanium dioxide, calcium carbonate, cerium oxide, cerium sulfide, barium sulfate, silica, iron oxide , Alumina, calcium sulphate, barium sulphate. Titanium oxide is of particular interest since dispersions of titanium oxide / polymer composite particles can find many applications, in particular in the field of paints and coatings or in the manufacture of plastics or paper.

 According to the invention, the inorganic particles have a size of a few μm. The size preferably corresponds to a pigment size finding an application for the pigments in the paint and coating compositions, it can be between 0.1 and 10 clam. In the case where the inorganic particles consist of titanium dioxide, their size is preferably of the order of 0.3 μl.

 According to the process of the invention, the latex can be of any possible nature.

Unlike the encapsulation processes described in the prior art, it is not necessary according to the method of the invention to use a latex having specific characteristics as to its nature or as to its rate of acid functions, so that the particles Inorganic materials can be coated according to the process of the invention with all types of latex particles.

Thus, it is possible to use any latex resulting from the emulsion polymerization of momères in the presence of a polymerization initiator chosen from azo initiators, peroxides, persulfates and peresters, and which may be water-soluble or soluble in the monomer used. It can be more precisely ::
an azo (azobisnitrile) initiator (hydro or oil-soluble) such as 2,2-azobisisobutyronitrile, 2,2'-azobis- (2-methylpropanenitrile), 2,21-azobis- (2,4-dimethylpentanenitrile) ), 2,2'-azobis- (2-methylbutane nitrile), 1,1'-azobis- (cyclohexano-acrylonitrile), 2,2'-azobis- (2,4-dimethyl-4-methoxyvaleronitrile), 2,2-azobis-2,4-dimethylvaleronitrile) and 2,2-azobis (2-amidinopropane) hydrochloride,
a peroxide initiator such as benzoyl peroxide, cumene hydroperoxide, hydrogen peroxide, acetyl peroxide, lauroyl peroxide,
. ammonium, sodium or potassium persulfate,
. peresters such as t-butyl peroxypivalate, acumyl peroxypivalate and t-butyl peroctoate.

 The pH of the aqueous phase of the latices used in the process according to the invention is generally at least 2, or even at least 3.

 The polymer of the latex particles may be film-forming or non-film-forming at room temperature. Its glass transition temperature Tg can be between -50 C and 150 C, preferably between 0 and 1200C.

The latex may be derived, for example, from the emulsion polymerization of monomers chosen from: (meth) acrylic acids and esters (in particular methyl methacrylate, ethyl acrylate, butyl acrylate, methacrylic acid) ,
Acrylic acid and mixtures thereof), acrylonitrile, styrene, divinylbenzene, vinyl acetate, ethylenically unsaturated carboxylic acids, acrylamide, methacrylamide, vinylidene chloride, butadiene, vinyl chloride ethylene glycol dimethacrylate or mixtures thereof.

 The polymerization medium defined above may also comprise monomers chosen from. sulfonated monomers such as sodium aminomethylpropanesulfonate (AMPS), sodium styrenesulfonate, sodium vinylsulfonate or sulfoethyl methacrylate (SEM), hydroxylated monomers such as hydroxyethyl methacrylate (HEMA), epoxy monomers such as methacrylate, glycidyl (GMA), the complexing monomers such as acetoacetoxyethyl methacrylate (AAEMA). These monomers make it possible to functionalize the latex particles and consequently the inorganic particles which are coated with such latex particles. The inorganic particles then have new properties or improved properties related to the presence of these functions.

 According to the process of the invention, it is possible to use a latex comprising polymer particles having an acid functional level of less than 10% by weight.

It is even possible to use latexes whose monomer particles do not comprise acid functions.

 In general, the latex used in the process according to the invention has a solid content of between 25 and 50% by weight.

 In a preferred manner, the latex used in the process according to the invention comprises particles whose diameter is between 5 and 100 nm, preferably between 20 and 40 nm. This size of latex particles ensures optimum recovery of inorganic particles when the latter have a size close to the pigment size. The latex may be, for example, of the Nanolatex® type, marketed by Rhne-Poulenc.

The required amount of latex to be provided to optimally cover the inorganic particles can be approximated beforehand. Indeed, it is known that the maximum number of latex particles that can be adsorbed on the surface of a much larger inorganic particle than the latex particles is given by formula (I):
2 X [A1 + A2 l 2
i3 A22
wherein A1 represents the diameter of the inorganic particles and A2 the diameter of the latex particles.

 Knowing the size of the latex particles, that of the inorganic particles and the densities of the inorganic particles and the polymer of the latex particles, it is possible to predict the amount of latex to be provided to obtain an optimal recovery.

 For example, in the case where it is sought to encapsulate titanium dioxide particles of size of the order of 0.3 .mu.m having a density of 4.1 g / cm.sup.3 at the rate of 24 nm latex particles based on 95% by weight of methyl methacrylate and 5% of methacrylic acid having a density of 1.1 gfcm3, the amount of latex to be introduced by weight is 9.08% by weight of the titanium dioxide particles introduced.

Among the latices that may be used in the process according to the invention, it is possible to choose a latex resulting from a preparation process comprising the following steps:
incremental addition of one or more ethylenically unsaturated monomers, capable of copolymerizing in an aqueous medium, to a reactor containing water and up to 6.3 parts per 100 parts of said monomers of one or more surfactants,
incremental addition of one or more polymerization initiators to said reactor,
and polymerizing said one or more ethylenically unsaturated monomers so that the average particle size of said polymerized monomers is less than 100 nm.

This process for preparing the latex may be more particularly that described in patent application EP-A-0 644205.
According to the process of the invention, the water-soluble base may be chosen from: sodium hydroxide, potassium hydroxide, ammonia, aminoalcohols such as triethanolamine, aminomethylpropanol or dimethylaminopropanol, functional amines such as polyetheramines, zirconium derivatives The polyetheramines may be, for example, the D - Series, ED - Series, T - Series and Du - Series JEFFAMINEs marketed by the company HUNTSMAN. The zirconium derivatives may be, for example, ammonium zirconium carbonate (AZC) or its stabilized form such as the
Bacote 20 marketed by MAGNESIUM ELEICTRON.

 The amount of water used in the process depends on the solids content desired for the final composite particle dispersion. It also depends on the dry extract of the starting latex which may already contain a large amount of water or a small amount of water.

 The process according to the invention can be carried out by introducing the reagents in a varied order. There are thus several embodiments of the method when a base is used.

According to a first embodiment of the method according to the invention, the following steps are carried out:
the latex, the water and the water-soluble base are mixed,
then the inorganic particles in powder form are added to this mixture while stirring.

 In a first step, the latex is introduced into water and then the water-soluble base is added so that the pH of the latex is brought to a value of between 3 and 10, preferably of between 4 and 10, more preferably between 7 and 10.

 In a second step, the inorganic particles in the form of powders are introduced into the mixture of water, latex and base. Simultaneously or following this introduction, the resulting mixture is stirred.

According to a second embodiment of the method according to the invention, the following steps are carried out:
the inorganic particles and the water are mixed,
the latex and the water-soluble base are mixed,
and then the latex mixture is added to the inorganic particles.

 In a first step, the inorganic and water particles are mixed. This mixture is generally carried out while stirring.

 In a second step, the base is added to the latex so that the pH of the latex is between 3 and 10, preferably between 4 and 10, more preferably between 7 and 10, and then this latex mixture is added. and basic to the mixture of inorganic particles and water.

 All these steps are generally carried out with stirring. However, this agitation can be much less important than in the first embodiment of the invention.

According to a variant of this second embodiment, it is possible to implement the following operations:
the inorganic particles, water and all or part of the water-soluble base amount are mixed,
the latex is mixed with the possible complement of the water-soluble base,
and then the latex mixture is added to the inorganic particles.

 The base can in fact be introduced into the mixture of water and inorganic particles for all or part of the quantity necessary to bring the pH of the latex to a value of between 3 and 10, preferably of between 4 and 10, and even more preferably, between 7 and 10. If only a part of the necessary amount of base is introduced with the inorganic particles, the base complement is mixed with the latex.

According to a third embodiment of the method according to the invention, the following steps are carried out:
the inorganic particles and water are mixed,
the latex and the water-soluble base are mixed,
and then the inorganic particles are added to the latex mixture.

 At first, the inorganic particles and the water are mixed. This mixture is generally carried out while stirring.

 In a second step, the base is added to the latex so that the pH of the latex is between 3 and 10, preferably between 4 and 10, more preferably between 7 and 10, and then the mixture of particles is added. inorganic and water to the mixture of latex and base.

 All these steps can be carried out with stirring. However, here too, this agitation can be much less important than in the first embodiment of the invention.

According to a variant of this third embodiment, it is possible to implement the following operations:
the inorganic particles, the water and all or part of the amount of the water-soluble base are mixed,
the latex is mixed with the possible complement of the water-soluble base,
and then the inorganic particles are added to the latex mixture.

 The base can in fact be introduced with the inorganic particles in the presence of water for all or part of the quantity necessary to bring the pH to a value of between 3 and 10, preferably of between 4 and 10, and even more preferentially of between 7 and 10. and 10. If only a portion of the necessary amount of base is introduced with the inorganic particles, the base supplement is mixed with the latex.

 It is also possible for the second and third embodiments to sequence the additions of the latex mixture into the inorganic particle mixture and vice versa. It is thus possible to add a part of the latex in a part of the inorganic particles and then add to this first mixture the complement of the inorganic particles and finally the rest of latex.

 For all the modes and variants of the process according to the invention, it is possible to work by adding water to the raw materials as it has been described previously, and it is also possible to work without adding water, that this being brought by the raw materials themselves. In the case where water is supplied in addition to the water of the raw materials of departure, it may be incorporated into the dispersion during the various steps of the process in fractional quantities. For example, partly with inorganic particles and partly with latex.

 For all the modes and variants of the process it is also possible to add at the end of the process when the inorganic particles are coated again with a base so as to adjust the pH of the final dispersion.

 It is possible to add an antifoam agent to the latex or inorganic particle mixtures because of the agitation to which these mixtures may be subjected.

 The method according to the invention makes it possible to obtain a total encapsulation of the inorganic particles. The encapsulation of inorganic particles is good if the encapsulated inorganic particles are perfectly dispersed and individualized.

Encapsulation is not successful if the inorganic particles are not fully coated with latex particles; in this case the poorly coated particles do not disperse well in the aqueous medium and agglomerate forming packets of particles suspended in the aqueous medium. This agglomeration effect can be demonstrated by passing the dispersion to ultrasound. A decrease in the particle size of the dispersion after ultrasound indicates that said particles were agglomerated in the dispersion and that the ultrasounds allowed them to be momentarily separated.

 The particle size of a dispersion of poorly encapsulated particles is therefore higher than that of well-coated particles. Therefore, the control of the encapsulation and dispersion of the inorganic particles can be carried out by comparing the size of the composite particles in the prepared dispersion with that of the well-individualized inorganic starting particles.

 Thus, if a perfect dispersion of composite particles is prepared according to the invention from starting inorganic particles having a size of 0.3 μm, and if the measurement of the size of the composite particles obtained in suspension in the aqueous medium is 0.3 μm, then the encapsulation is good. On the other hand, if this last measurement is higher, it means that the encapsulation is not total and that the particles are agglomerated.

 The method according to the invention makes it possible to obtain a total encapsulation immediately after the completion of the operations of the process. The dispersions obtained by the process according to the invention are directly usable.

 The dispersions obtained are very stable. After a storage period of 6 months, it can be seen that the composite particles have very weakly sedimented: simple stirring using a spatula makes it possible to redisperse them, unlike in the case of dispersions of inorganic particles that are not encapsulated.

 The process according to the invention leads to irreversible encapsulation.

 The solids levels of the dispersions obtained can be between 10 and 80%, preferably between 60 and 75%. This rate is controlled by the amount of water used for the implementation of the process.

The method according to the invention makes it possible to prepare dispersions of composite particles which may have a pH in a wide range generally between 3 and 11, preferably between 4 and 10, even more preferably between 7 and 9; and this regardless of the isoelectric point value (EIP) of the encapsulated inorganic particle. It is thus possible to prepare a titanium dioxide dispersion having a pH of between 3 and 11, whereas the PIE of this type of titanium dioxide is of the order of 7.5.
The process according to the invention leads to composite particles having a so-called raspberry structure.

 FIG. 1 is a photograph taken with a scanning electron microscope, magnification 100,000, of a dispersion of titanium dioxide particles encapsulated by latex particles based on 95% by weight of methyl methacrylate and 5% of acid. methacrylic according to the process of the invention (method 1 of the examples). In order to be observable, the latex particles were previously labeled with uranyl acetate. It is found that the particles of titanium dioxide are completely covered by the latex particles and that the encapsulation is perfectly successful. It is also noted that few latex particles are free, that is to say, not adsorbed on the surface of the titanium dioxide, which is an indication of the success of the encapsulation.

 FIG. 2 is a scanning electron micrograph, magnification 100,000, of a dispersion of titanium dioxide particles encapsulated by latex particles based on 95% by weight of methyl methacrylate and 5% of acid. methacrylic acid according to a method of the prior art (method of Comparative Example 10). In order to be observable, the latex particles were previously labeled with uranyl acetate. It is found that the titanium dioxide particles are not coated with latex particles and that the latex particles remain free suspended in water and not adsorbed on the titanium dioxide particles.

 The invention also relates to a coating composition comprising an aqueous dispersion of composite particles obtained by the process according to the invention. These coating compositions may in particular be emulsion paints.

 The composition usually comprises film-forming polymer binder latexes, particularly if the latex used to coat the inorganic particles is not film-forming at room temperature.

 This composition may contain other elements such as thickeners, colorants, coalescing agents, defoamers, biocides, etc.

 This composition may be manufactured by mixing the aqueous dispersion of composite particles obtained by the process according to the invention, a binder latex and optionally other additives.

 Preferably, the composition comprises dispersions of composite particles whose inorganic particles are coated with latex particles having a level of acid functionalities greater than 10% by weight.

 It is observed that the dispersions obtained according to the process of the invention are not destabilized when they are mixed with the other components of a composition, in particular with the binder latices, and that the inorganic particles remain perfectly encapsulated during this mixing by means of a control. electronic microscope.

 The invention also relates to the use of an aqueous dispersion of titanium dioxide-based composite particles obtained by the process according to the invention for improving the opacifying power, brightness and whiteness of a dried film of a composition. for coating containing said dispersion.

 Preferably, dispersions are used in which the inorganic particles are coated with latex particles having an acid functional level of greater than 10% by weight.

 The invention also relates to the use of the dispersions obtained by the process according to the invention for the manufacture of paper. The dispersions may for example be introduced directly into the mass in combination with a cationic agent, or may be used as a formulation in the layer for the preparation of coated paper.

 Finally, the invention relates to a dispersion of pigments comprising the dispersion obtained by the process according to the invention.

 Examples will now be given.

EXAMPLES
Example 1: Implementation of the first embodiment - proceeds 1
Raw materials.

# latex A:
composition 95% by weight of methyl methacrylate
5% by weight of methacrylic acid
emulsion polymerization preparation in the presence of lauryl sulphate and
of ammonium persulfate according to the teaching of EP-A
0 644 205
pH 3.1
24 nm particle size measured by TEM (electron microscopy
transmission) and XDC (X-ray photography)
solid content 28.8% by weight
density about 1.1 g / cm3
e inorganic particles ::
titanium dioxide surface-treated with Al203
marketed under the name RL 60 by RHONE POULENC
size 0.3 ijm measured using a BROOKHAVEN DCP 1000
(2000 rpm) on a highly diluted dispersion of
titanium dioxide using HMP and spent 2 min.
sounds
PIE 7.5 measured by zeta potential
density around 4.1 g / cm3
water soluble AMP 90 base of ANGUS (aminomethylpropanol)
e DREWPLUS T3200 antifoam from DREWAMEROID
Implementation:
222.2 g of latex A and then 300 g of deionized water are introduced into a beaker of 1 l.

The pH is brought to 8.7 by addition of 1 g of AMP 90. 0.7 g of DREWPLUS are then added.
T3200.

 The mixture is stirred with a RUSHTON turbine (deflocculating blade) at about 500 trin (Rayneri engine) and 800 g of titanium dioxide are added thereto. The stirring speed is then increased to 2000 rpm for 5 minutes.

Results:
A titanium dioxide dispersion having the following characteristics is obtained.

 The solids content is 65.1% by weight.

 The pH is 8.3.

 The viscosity, measured using a BROOKFIELD viscometer type DVII at 50 rpm and 23 ° C, is 136 mPa.s.

The particle size is measured by particle size using a BROOKHAVEN
DCP 1000 at 2000 rpm. It is 0.3 clam. Starting particles of titanium dioxide having a size of 0.3 μm, this means that the encapsulation is successful.

On the other hand, after ultrasonic passage of the dispersion for 1 or 2 min, no variation in size is observed, which confirms that the encapsulation is successful and the particles well dispersed.

Example 2: Implementation of the first embodiment - Method 2
The same method as in Example 1 is used and at the end of the latter, the dispersion obtained is stirred using a fast homogenizer disperser.
ULTRA-TURRAX from lKA WERK for 2 min.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Example 3: Implementation of the Second Embodiment - Method 3
The same raw materials are used as in Example 1.

 300 g of deionized water are introduced into a 1-liter beaker and 2 drops of AMP 90 and 0.7 g of DREWPLUS T3200 are added thereto. The mixture is stirred with a 4000 rpm deflocculating pale turbine and 800 g of titanium dioxide are introduced. 222.2 g of neutralized latex A at pH = 8.7 are then added with 1 g of AMP 90. The stirring speed is then reduced to 2000 rpm for 5 minutes.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Example 4: Implementation of a Variant of the Second Mode of Realization Process 4
The same raw materials are used as in example 1.

 300 g of deionized water are introduced into a beaker of the vessel and 2 drops of AMP 90 and 0.7 g of DREWPLUS T3200 are added thereto. The mixture is agitated using a deflocculated pale turbine by gradually increasing the stirring speed to 2000 trini and 576 g of titanium dioxide are introduced. 111.1 g of neutralized latex A at pH = 8.7 are then added with 1 g of AMP 90. Then the remainder of the titanium dioxide (224 g) is added and finally the rest of the latex (111.1 g).

 The stirring speed is maintained at 2000 rpm for 5 minutes.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Example 5: Implementation of a Variant Second Embodiment Process5
The same raw materials are used as in Example 1.

300 g of deionized water, 1 g of AMP 90 and 0.7 g of water are introduced into a beaker of
DREWPLUS T3200. The mixture is stirred with a defocused pale turbine at 500 rpm and 800 g of titanium dioxide are introduced. 222.2 g of latex are then added and the mixture is stirred for 5 minutes.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Example 6: Implementation of a Variant of the Third Embodiment Proceeds 6
The same raw materials are used as in Example 1.

 222 g of deionized water, 1 g of AMP 90 and 0.25 g of DREWPLUS T3200 are introduced into a beaker. The mixture is stirred with a deflocculating light turbine at 500 rpm and 800 g of titanium dioxide are introduced.

 In a second beaker, 222.2 g of latex to which 0.45 g of DREWPLUS T3200 is added. This mixture is stirred with a deflocculating light turbine at 500 rpm and the titanium dioxide mixture is introduced. Stirring is then maintained for 5 minutes.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Example 7: Implementation of a Variant of the Second Embodiment 7
The same raw materials are used as in example 1.

 300 g of deionized water, 0.5 g of AMP 90 and 0.7 g of DREWPLUS T3200 are introduced into a beaker. The mixture is stirred with a defocused pale turbine at 500 rpm and 800 g of titanium dioxide are introduced. 222.2 g of latex supplemented with 0.5 g of AMP 90 are then added and the mixture is stirred for 5 minutes.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Example 8: Implementation of a Variant of the Third Embodiment 8
The same raw materials are used as in Example 1.

 222 g of deionized water, 0.5 g of AMP 90 and 0.25 g of DREWPLUS T3200 are introduced into a beaker. The mixture is stirred with a 500-decimal impeller blade turbine and 800 g of titanium dioxide are introduced.

 In a second beaker, 222.2 g of latex are added to which 0.5 g of AMP 90 and 0.45 g of DREWPLUS T3200 are added. This mixture is stirred with a deflocculating light turbine at 500 rpm and the titanium dioxide mixture is introduced.

Stirring is then maintained for 5 minutes.

 Result: a titanium dioxide dispersion is obtained whose characteristics are collated in Table 1 and are measured in the same manner as in Example 1.

Table 1

<tb><SEP><SEP> Characteristics of <SEP> DisPersions <SEP> Obtained
<tb> Example <SEP> Extract <SEP> sec <SEP> pH <SEP> Viscosity <SEP> Granulometry
<tb><SEP> (% <SEP> in <SEP> weight) <SEP> (mPa.s) <SEP> (m)
<tb><SEP> 1 <SEP> 65.1 <SEP> 8.3 <SEP> 136 <SEP> 0.3
<tb><SEP> 2 <SEP> 65.4 <SEP> 8.3 <SEP> 430 <SEP> 0.3 <SEP>
<tb><SEP> 3 <SEP> 65 <SEP> 8.3 <SEP> 126 <SEP> 0.3
<tb><SEP> 4 <SEP> 65.1 <SEP> 8.3 <SEP> 150 <SEP> 0.3
<tb><SEP> 5 <SEP> 65 <SEP> 83 <SEP> 140 <SEP> 0.3
<tb><SEP> 6 <SEP> 65.2 <SEP> 8.3 <SEP> 300 <SEP> 03 <SEP>
<tb><SEP> 7 <SEP> 65.1 <SEP> 8.3 <SEP> 180 <SEP> 0.3
<tb><SEP> 8 <SEP> 65.2 <SEP> 8.3 <SEP> 200 <SEP> 0.3
<Tb>
It can be seen that whatever the process and the variant of the process used,
The encapsulation of the titanium dioxide particles is complete. It is also noted that certain processes lead to more or less viscous dispersions depending on the value of the dry extract.

Comparative Example 9: Preparation of a Titanium Dioxide Dispersion Using a Dispersant - Comparative Process 9
The raw materials used are the same as in Example 1.

 In a beaker of 1 I introduced 424 g of deionized water, 25.6 g of OROTAN 731, or 0.8% by weight relative to TiO 2, which is a dispersant of OROTAN 25% active ingredients, 6 g of DREWPLUS T3200 and 2 drops of AMP 90. 800 g of titanium dioxide are then dispersed by stirring the mixture with a defocused pale turbine at 500 rpm. Then the stirring speed is increased to 2000 rpm for 5 minutes.

 Result: a dispersion of titanium dioxide having the following characteristics is obtained.

 The measurements are performed in the same manner as in Example 1.

solid content: 65.4% by weight
pH: 9
viscosity: 460 mPa.s
particle size: 0.34 pm
The particle size of 0.34 μm indicates that the titanium dioxide particles are strongly agglomerated despite the presence of the dispersant. On the other hand, after ultrasonic passage for 2 min, the particle size of this dispersion is 0.32 pm, which shows that the titanium dioxide particles disintegrate with difficulty and do not disperse.

Comparative Example 10: Encapsulation Process Using a Titanium Dioxide Dispersion - Comparative Process
The raw materials used are the same as in Example 1.

 The same steps as the method 1 are carried out except for a part of a dispersion of titanium dioxide particles and not of a titanium dioxide powder.

A dispersion of titanium dioxide is prepared using 256 g of deionized water, 25.6 g of TAMOL 731, ie 0.8% by weight relative to TiO 2, and 0.6 g of DREWPLUS.
T3200. The solids content of this dispersion is 75% by weight.

A mixture of 222.2 g of latex A is prepared, ie 8% by weight relative to
TiO2, and 41 g of deionized water. This mixture is then neutralized to pH = 8.7 using 1 g of AMP 90.

 The neutralized latex is then mixed with the titanium dioxide dispersion.

 Result: a dispersion of titanium dioxide having the following characteristics is obtained.

 The measurements are performed in the same manner as in Example 1.

solid content: 65.5% by weight
pH: 8.7
viscosity: 512 mPA.s
particle size: 0.34 pm
The particle size of 0.34 μm indicates that the titanium dioxide particles are strongly agglomerated and the titanium dioxide particles are not encapsulated.

Example 11: Influence of the nature of the base
Process 2 of Example 2 is carried out with the same amounts of latex, water, DREWPLUS T3200 and titanium dioxide but modifying the nature of the base.

 The raw materials used are the same as in Example 1, except for the latex which has the same characteristics as latex A apart from the particle size of 26 nm.

 The AMP 90 is replaced by various other bases in amounts always allowing to bring the pH of the latex to a value of 8.7. The amount of water used is determined so as to obtain a final dry extract of the order of 65% by weight.

 The results are shown in Table 2. The methods of measurement are the same as in Example 1.

Table 2

<tb><SEP><SEP> Characteristics of
<tb><SEP> dispersions <SEP> obtained
<tb><SEP> Nature <SEP> of <SEP> the <SEP> basis <SEP> Quantity <SEP> of <SEP> basis <SEP> Granulometry <SEP> Viscosity
<tb><SEP> used <SEP> (g) <SEP> (M) <SEP> (mPa.s)
<tb><SEP> NH4OH <SEP> to <SEP> 20% <SEP> 1.6 <SEP> 0.3 <SEP> 117
<tb> JEFFAMINE # <SEP> M600 <SEP> (1) <SEP><SEP> 5.8 <SEP> 0.31 <SEP> 145
<tb><SEP> JEFFAMINE # <SEP><SEP> M1000 <SEP> 5.8 <SEP> 0.31 <SEP> 155
<tb><SEP> (2)
<tb><SEP> BACOTE20 <SEP> (3) <SEP> 9 <SEP> 0.31 <SEP> 116
<tb><SEP> NaOH <SEP> 1N <SEP> 9.4 <SEP> 0.3 <SEP> 108
<Tb>
(1) JEFFAMINES M600: poly (oxyethylene-oxypropylene) monoamine of molar ratio oxypropylene / oxyethylene: 9/1 and approximate molecular weight 600 marketed by HUNTSMAN
(2) JEFFAMINES M1000: poly (oxyethylene-oxypropylene) monoamine of oxypropylene / oxyethylene molar ratio: 3/19 and of approximate molecular weight 1000 marketed by HUNTSMAN at 66.6% in water
(3) BACOTEX 20 ammonium zirconium carbonate marketed by
MAGNESIUM ELEKTRON
The particle size and the viscosity are measured in the same way as in
Example 1

 It can be seen that depending on the nature of the base, the process makes it possible to encapsulate the titanium dioxide particles more or less well. Some bases make it possible to obtain total encapsulation, for example: 90-PAMP, ammonia and sodium hydroxide. The others provide an important improvement in the dispersion of titanium dioxide particles over conventional titanium dioxide dispersions (Comparative Example 9).

Example 12 Influence of the quantity of water used during the preparation process
The raw materials used are the same as in Example 1.

 Methods 1 and 5 are implemented by varying the amount of water used.

This variation plays directly on the value of the dry extract of the dispersions obtained and on their viscosity.

 The results are collated in Table 3. The measurements are carried out in the same manner as in Example 1.

Table 3

<tb><SEP><SEP> Characteristics of <SEP> DisPersions <SEP> Obtained
<tb> Process <SEP> set <SEP> in <SEP> i <SEP> Extract <SEP> sec <SEP> pH <SEP> Viscosity <SEP> Granulometry
<tb><SEP> work <SEP> (% <SEP> in <SEP> weight) <SEP> (mPa.s) <SEP>(<SEP> m <SEP>
<tb><SEP> 1 <SEP> 67.8 <SEP> 8.3 <SEQ> 870 <SEP> 0.3
<tb><SEP> 5 <SEP> 678 <SEP> 84 <SEP> 750 <SEP> 03 <SEP>
<tb><SEP> 1 <SEP> 69.7 <SEP> 8.2 <SEP> 2960 <SEP> 0.3 <SEP>
<Tb>
Whatever the amount of water used, the coating of the particles is optimal. However, it is preferred to work in the presence of a quantity of water to obtain a final solids content of about 65% by weight in order to have low viscosities (as in Examples 1 to 8).

Example 13: Influence of the rate of useful latexes with respect to the weight of inorganic particles
The raw materials used are the same as in Example 1.

 The method 1 is implemented by adjusting the dry latex content introduced by weight relative to titanium dioxide. The amount of water is modified relative to Example 1 so as to maintain a final dispersion having a solids content of about 65% by weight.

 The results are collated in Table 4. The measurements are carried out in the same manner as in Example 1.

Table 4

<tb><SEP><SEP> Characteristics of <SEP> Drops <SEP> Obtained
<tb> Rate <SEP> of <SEP> latex <SEP> A <SEP> in <SEP> Extract <SEP> sec <SEP> Viscosity <SEP> (mPas) <SEP> Granulometry
<tb><SEP> sec <SEP> I <SEP> TiO2 <SEP> (%) <SEP> (% <SEP> in <SEP> weight) <SEP>(<SEP> m) <SEP>
<tb><SEP> 5 <SEP> 65.2 <SEP> 3000 <SEP> 0.32
<tb><SEP> 6 <SEP> 65.2 <SE> 546 <SEP> 0.3
<tb><SEP> 7 <SEP> 65.2 <SEP> 400 <SEP> 0.3
<tb><SEP> 8 <SEP> 652 <SEP> 200 <SEP> 0.3
<tb><SEP> 10 <SEP> 65.3 <SEP> ~~ <SEP> 350 <SEP> 0.3
<Tb>
It is found that at least 6% latex A, the particles of which measure 24 nm, is required to obtain an optimal encapsulation of titanium dioxide particles of 0.3 μm. This result confirms the theoretical prediction of the formula ( I).

Example 14: Influence of the size of the latex particles
Process 2 is carried out by introducing 8% by weight of dry latex relative to the weight of the titanium dioxide particles.

 Latex of the same nature as Latex A but having different particle sizes are used. These latices are obtained in the same manner as latex A by modifying the level of emulsifying agent (lauryl sulphate) during the emulsion polymerization.

 The results are collated in Table 5. The measurements are carried out in the same manner as in Example 1.

Table 5

<tb><SEP> Characteristics <SEP> ues <SEP> of <SEP><SEP> dispersions obtained
<tb> Size <SEP> particles <SEP> Extract <SEP> sec <SEP> Viscosity <SEP> (mPas) <SEP> Granulometry <SEP> (pm)
<tb><SEP> latex <SEP> (nm) <SEP> (% <SEP> in <SEP> weight)
<tb><SEP> 48 <SEP> 51.5 <SEP> freeze <SEP> 0.36
<tb><SEP> 42 <SEP> 652 <SEP> 20000 <SEP> 0.33
<tb><SEP> 37 <SEP> 653 <SEP> 5540 <SEP> 0.3
<tb><SEP> 34 <SEP> 65.5 <SEQ> 4640 <SEP> 0.3
<tb><SEP> 31 <SEP> 65.3 <SEP> 2860 <SEP> 0.3
<tb><SEP> 28 <SEP> 65.3 <SEP> 1540 <SEP> 0.3
<tb><SEP> 26 <SEP> 65.4 <SEP> 830 <SEP> 0.3
<tb><SEP> 24 <SEP> 65.3 <SE> 468 <SEP> 0.3
<Tb>
This example also makes it possible to compare the theoretical predictions of the formula (I) with the practical results. It is found that if the latex particles have a size greater than 37 nm, a rate of 8% by weight of latex is dry. relative to the weight of the titanium dioxide particles is not sufficient to properly coat the titanium dioxide particles.

Example 15: Influence of the amount of base introduced
Process 1 is carried out with the same raw materials as in
Example 1 except that the latex used has a particle size of 26 nm.

 On the other hand, the AMP 90 is introduced in different amounts so as to neutralize the latex at different pH's.

 The results are collated in Table 6. The measurements are carried out in the same manner as in Example 1.

Table 6

<tb><SEP> Characteristics <SEP> of the <SEP> dispersions <SEP> obtained
<tb> pH <SEP> to <SEP> which <SEP> the <SEP> latex <SEP> pH <SEP> Extract <SEP> sec <SEP> Viscosity <SEP> Granulometry <SEP>
<tb><SEP> is <SEP> neutralized <SEP> (% <SEP> in <SEP> weight) <SEP> (mPa.s) <SEP> (m) <SEP>
<tb><SEP> 435 <SEP> 745 <SEP> 656 <SE> 2160 <SEP> 03 <SEP>
<tb><SEP> 6 <SEP> 7.65 <SEP> 65.3 <SEP> 1750 <SEP> 0.3
<tb><SEP> 7.1 <SEP> 7.8 <SEP> 65.1 <SEP> 930 <SEP> 0.3
<tb><SEP> 8 <SEP> 815 <SEP> 65.2 <SEP> 852 <SEP> 03 <SEP>
<tb><SEP> 8.7 <SEP> 8.4 <SEP> 65.4 <SEP> 830 <SEP> 0.3
<tb><SEP> 9.2 <SEP> 8.6 <SEP> 65.3 <SEP> 704 <SEP> 0.3
<tb><SEP> 10 <SEP> 9.1 <SEP> 65.4 <SEP> 664 <SEP> 0.3
<tb><SEP> 10.85 <SEP> 10.2 <SEP> 65.4 <SEP> 594 <SEP><SEP> 0.4 <SEP>
<Tb>
It is found that the encapsulation is always good as long as the amount of base introduced induces a latex pH of less than or equal to 10. If the amount of base introduced makes it possible to obtain a pH of the latex greater than 10, the coating does not is not realized.

 It is also noted that the higher the amount of base, the lower the viscosity. It is therefore interesting to work with large quantities of base while not exceeding the upper limit bringing the pH beyond 10.

Example 16: Influence of the rate of acid functions of latex
Various latices are prepared either based on methacrylic acid (MEA) and methyl methacrylate or on the basis of AMPS and methyl methacrylate and having various acid function levels.

 These latices are used for the preparation of dispersions according to method 1, the amount of base introduced being always that which makes it possible to bring the pH of the starting latex to 8.7 and the quantity of water that to obtain a close final dry extract. 65%.

 The results are collated in Table 7. The measurements are carried out in the same manner as in Example 1.

Table 7

<tb><SEP><SEP> Characteristics of <SEP><SEP> Latex <SEP><SEP> Characteristics <SEP> Characteristics of <SEP> Dispersions
<tb><SEP> obtained
<tb><SEP> rate of AME <SEP> Rate <SEP> Size <SEP> of <SEP> Extract <SEP> sec <SEP> Viscosity <SEP> Granulometry
<tb><SEP> (%) <SEP> of AMPS <SEP> (%) <SEP> particles <SEP> (% <SEP> in <SEP> weight) <SEP> | <SEP> (mPa.s) <SEP> | <SEP> Wrn) <SEP>
<tb><SEP> (nm)
<tb><SEP> 0 <SEP> 0 <SEP> 27 <SEP> 653 <SEP> 235 <SEP> 0.3
<tb><SEP> 3 <SEP> 0 <SEP> 26 <SEP> 65.4 <SEP> 690 <SEP> 0.3
<tb><SEP> 5 <SEP> 0 <SEP> 26 <SEP> 654 <SEP> 850 <SEP> 03 <SEP>
<tb><SEP> 7.5 <SEP> 0 <SEP> 25 <SEP> 65.4 <SEP> 2660 <SEP> 0.3
<tb><SEP> 10 <SEP> 0 <SEP> 25 <SEP> 652 <SEP> 4160 <SEP> 0.3 <SEP>
<tb><SEP> 0 <SEP> 4 <SEP> 27 <SEP> 65.2 <SEP> 650 <SEP> 0.3
<Tb>
It is found that an optimal coating is obtained regardless of the rate of acid functions of the latex, even if this level is zero, and whatever the nature of the acid functions.

 The influence of the nature of the latex polymer on the viscosity of the dispersions obtained is also noted.

Example 17: Influence of the Glass Transition Temperature <Tg) of the Latex
Various latexes are prepared based on methyl methacrylate (MMA), ethyl acrylate (AE) and 5% by weight of methacrylic acid (AME) having different Tg by varying the acrylate content. ethyl (AE).

 From these latices, titanium dioxide dispersions are prepared according to process 1 or 5, the amount of base introduced being always that making it possible to bring the pH of the starting latex to 8.7 and the quantity of water to obtain a final dry extract close to 65 or 70%.

 The results are collated in Table 8. The measurements are carried out in the same manner as in Example 1.

Table 8

<tb><SEP><SEP> Characteristics <SEP> Latex <SEP> of <SEP><SEP> Characteristics of <SEP><SEP> Dispersions Obtained
<tb><SEP> departure <SEP>
<tb> Process <SEP> Rate <SEP> of AE <SEP> Tg <SEP> Size <SEP> Extract <SEP> sec <SEP> Viscosity <SEP> Granulometry
<tb><SEP> in <SEP> weight <SEP> (C) <SEP> (nm) <SEP> (% <SEP> in <SEP> ids <SEP> | <SEP> (mPa.s)
<tb><SEP> 1 <SEP> 0 <SEP> 118 <SEP> 24 <SEP> 65.1 <SEP> 136 <SEP> | <SEP> 0.3
<tb><SEP> 1 <SEP> 5 <SEP> 103 <SEP> 24 <SEP> 65 <SEP> 128 <SEP> 0.3 <SEP> L <SEP> 03 <SEP>
<tb><SEP> 1 <SEP> 5 <SEP> 103 <SEP> 24 <SEP> 70 <SEP> 2400 <SEP> 0.3 <SEP>
<tb><SEP> 1 <SEP> 20 <SEP> 77 <SEP> 25 <SEP> 65.7 <SEP> 268 <SEP> 0.3
<tb><SEP> 1 <SEP> 40 <SEP> 49 <SEP> 23 <SEP> 65 <SE> 266 <SE> - SEP> 0.31
<tb><SEP> 5 <SEP> 55 <SEP> 32 <SEP> 25 <SEP> 65.2 <SEP> 180 <SEP> 0.32
<Tb>
Tg is measured by differential enthalpy analysis (DSC: "Differential
Scanning Calorimetry ").

 It is found that very good coatings are obtained for transition temperatures varying between 118 and 49 C.

EXAMPLE 18 Influence of the Nature of the Latex
Dispersions according to the invention are prepared from latex of different types.

These latices are prepared from the following mores:
MAM: methyl methacrylate
HEMA: hydroxyethyl methacrylate
AME: methacrylic acid STYR: styrene
ACRYL: acrylamide
AAEMA: acetoacetoxyethyl methacrylate
Dispersions according to process 1 or 2 are prepared from these latices by using a base amount which makes it possible to bring the pH of the starting latex to a value of 8.7 and a quantity of water making it possible to obtain an extract final dry of 65% by weight.

 The results are collated in Table 9. The measurements are carried out in the same manner as in Example 1.

Table 9

Characteristics <SEP> of <SEP> latex <SEP> of <SEP> departure <SEP> Characteristics <SEP> of <SEP> dispersions <SEP> obtained
<tb> Process <SEP> mis <SEP> Composition <SEP> latex <SEP> Size <SEP> particles <SEP> ES <SEP> (%) <SEP> Viscosimetry <SEP> pH <SEP> Granulometry
<tb> in <SEP> work <SEP> (% <SEP> in <SEP> weight) <SEP> (nm) <SEP> (mPa.s) <SEP> (m)
<tb> 2 <SEP> MAM <SEP> 85 <SEP>%
<tb> HEMA <SEP> 10 <SEP>% <SEP> 25 <SEP> 65.2 <SEP> 260 <SEP> 8.3 <SEP> 0.3
<tb> AME <SEP> 5 <SEP>%
<tb> 1 <SEP> MAM <SEP> 50 <SEP>%
<tb> STYR <SEP> 45 <SEP>% <SEP> 26 <SEP> 65.5 <SEP> 700 <SEP> 8.4 <SEP> 0.3
<tb> AME <SEP> 5 <SEP>%
<tb> 1 <SEP> MAM <SEP> 95 <SEP>%
<tb> ACRYL <SEP> 1 <SEP>% <SEP> 25 <SEP> 65.2 <SEP> 258 <SEP> 8.3 <SEP> 0.3
<tb> AME <SEP> 4 <SEP>%
<tb> 2 <SEP> MAM <SEP> 90 <SEP>%
<tb> AAEMA <SEP> 5 <SEP>% <SEP> 27 <SEP> 65.3 <SEP> 436 <SEP> 8.4 <SEP> 0.3
<tb> AME <SEP> 5 <SEP>%
<Tb>
It is observed that for all the various latices used there is a perfect encapsulation of the titanium dioxide particles.

Example 19: Mixtures for coating formulations
Dispersions obtained by the process according to the invention are mixed with a binder latex comprising particles based on film-forming polymers. This binder latex is DS 1029 or DS 1003 marketed by RHONE-POULENC; they are based on styrene butadiene polymer and have a TMFF (minimum temperature of film formation) of 0 C.

 The characteristics of the dispersions tested resulting from the process according to the invention or comparative dispersions are collated in Table 10.

The characteristics of the products used are as follows:
latex B: composition: 95% by weight of methyl methacrylate
5% by weight of methacrylic acid Tg = 118 ° C
latex C composition: 90% by weight of methyl methacrylate
5% by weight of methacrylic acid
5% by weight of ethyl acrylate Tg = 103 ° C
- latex D: identical to latex B but from a different production batch (lot
2)
latex E composition: 90% by weight of methyl methacrylate
5% by weight of methacrylic acid
5% by weight of acetoacetoxymethacrylate
- latex F: identical to latex B and D but from a production batch
different (lot 3)
The measurements are carried out in the same manner as in Example 1.

Table 10

Characteristics <SEP> of <SEP> products <SEP> of <SEP> departure <SEP> Characteristics <SEP> of <SEP> dispersions
<tb> Process <SEP> Dispersant <SEP> Latex <SEP> Size <SEP> particles <SEP> Extract <SEP> sec <SEP> (% <SEP> pH <SEP> Viscosimetry <SEP> Granulometry
<tb> latex <SEP> (nm) <SEP> in <SEP> weight) <SEP> (mPa.s) <SEP> (m)
<tb> Dispersion <SEP> I1 <SEP> 2 <SEP> Latex <SEP> B <SEP> 26 <SEP> 65.2 <SEP> 8.4 <SEP> 388 <SEP> 0.3
<tb> Dispersion <SEP> I2 <SEP> 2 <SEP> Latex <SEP> C <SEP> 24 <SEP> 65.2 <SEP> 8.4 <SEP> 282 <SEP> 0.3
<tb> Dispersion <SEP> I3 <SEP> 2 <SEP> Latex <SEP> D <SEP> 26 <SEP> 65.4 <SEP> 8.4 <SEP> 830 <SEP> 0.3
<tb> Dispersion <SEP> I4 <SEP> 2 <SEP> Latex <SEP> E <SEP> 27 <SEP> 65.3 <SEP> 8.4 <SEP> 436 <SEP> 0.3
<tb> Dispersion <SEP> I5 <SEP> 2 <SEP> Latex <SEP> F <SEP> 37 <SEP> 65.3 <SEP> 8.4 <SEP> 5540 <SEP> 0.3
<tb> Dispersion <SEP> C5 <SEP> 9 <SEP> Bevaloid <SEP> 6770 <SEP> 65 <SEP> 9 <SEP> 75 <SEP> 0.33
<tb> Dispersion <SEP> C6 <SEP> 10 <SEP> Bevaloid <SEP> 6770 <SEP> Latex <SEP> B <SEP> 26 <SEP> 65 <SEP> 8.7 <SEP> 98 <SEP> 0 33
<tb> Dispersion <SEP> C7 <SEP> 9 <SEP> Tamol <SEP> 731 <SEP> 65.4 <SEP> 9 <SEP> 370 <SEP> 0.34
<tb> Dispersion <SEP> C8 <SEP> 10 <SEP> Tamol <SEP> 731 <SEP> Latex <SEP> D <SEP> 26 <SEP> 65.2 <SEP> 8.7 <SEQ> 690 <SEP > 0.34
<tb> Dispersion <SEP> C9 <SEP> 10 <SEP> Tamol <SEP> 731 <SEP> Latex <SEP> E <SEP> 27 <SEP> 65.2 <SEP> 8.7 <SEP> 600 <SEP > 0.34
<Tb>
The dispersions defined in Table 10 are mixed with DS 1029 or
DS 1003 at different CPV concentrations.

In all the cases studied:
- CPV is given by the rate of composite particles based on titanium dioxide and latex in the binder formulation although the composite particles comprise a portion of latex.

 - the hiding power is measured by the Kubelka and Munk method according to DIN 53 162.

the gloss at 60 is measured according to DIN 53 773 using a DATACOLOR glossimeter,
- the luminance L * is measured according to the CIELAB system and the DIN 6174 standard using a DATACOLOR spectrocolorimeter.

 Case 1: The luminescence and coverage values of films from dispersion mixtures and DS 1029 binder latex were measured for a PVC of 20% by weight. The measurements are collated in Table 11.

Table 11

<tb> Dispersion <SEP> used <SEP> Luminance <SEP> L * <SEP> Power <SEP> covering
<tb><SEP> (m2 / |) <SEP>
<tb><SEP> Dispersion <SEP> I1 <SEP> 97.4 <SEP> 27.3
<tb><SEP> Dispersion <SEP> I2 <SEP> 97.4 <SEP> 25.5
<tb><SEP> Dispersion <SEP> C5 <SEP> 97 <SEP> 24.9
<tb><SEP> Dispersion <SEP> C6 <SEP> 97 <SEP> 23.7
<tb> Case 2: Luminosity, hiding power and gloss values of films from dispersions and DS 1029 binder latex were measured for a CPV of 30% by weight. The measurements are collated in Table 12.

Table 12

<tb><SEP> Dispersion <SEP> Brightness <SEP> to <SEP> Luminance <SEP> L * <SEP> Can
<tb><SEP> used <SEP> 60 <SEP> covering <SEP> (m2 / l)
<tb><SEP> Dispersion <SEP> I1 <SEP> 57.4 <SEP> 97.6 <SEP> 28.3
<tb><SEP> Dispersion <SEP> I2 <SEP> 56.2 <SEP> 97.6 <SEP> 26.4
<tb> Dispersion <SEP> C5 <SEP> 53.8 <SEP> 97.3 <SEP> 25.6
<tb> Dispersion <SEP> C6 <SEP> 46 <SEP> 97 <SEP> 24.6
<tb> Case 3: The hiding values of films from dispersion mixtures and DS 1003 binder latex were measured for a CPV of 30% by weight. The measurements are collated in Table 13.

Table 13

<tb> Dispersion <SEP> used <SEP> Power <SEP> covering
<tb><SEP> (m2 / l)
<tb><SEP> Dispersion <SEP> I3 <SEP> 35.8
<tb><SEP> Dis <SEP> ersion <SEP> 14 <SEP> 31 <SEP> 5
<tb><SEP> Dispersion <SEP> 15 <SEP> 31.4
<tb><SEP> Dispersion <SEP> C7 <SEP> 28.9
<tb><SEP> Dispersion <SEP> C8 <SEP> 27.6
<tb><SEP> Dispersion <SEP> C9 <SEP> 29.5 <SEP>
<tb> Case 4: The hiding values of films from dispersion mixtures and DS 1029 binder latex were measured for a CPV of 30% by weight. The measurements are collated in Table 14.

Table 14

<tb><SEP> Dispersion <SEP> used <SEP> Power <SEP> covering
<tb> (m2 / l)
<tb><SEP> Dispersion <SEP> I3 <SEP> 26.5
<tb><SEP> Dispersion <SEP> I4 <SEP> 29.6
<tb><SEP> Dispersion <SEP> I5 <SEP> 28.0
<tb><SEP> Dispersion <SEP> C7 <SEP> 25.5
<tb><SEP> Dispersion <SEP> C8 <SEP> 26.5
<tb><SEP> Dispersion <SEP> C9 <SEP> 25.6
<Tb>
It is found that titanium dioxide dispersions obtained by the process according to the invention exhibit improved hiding power, gloss and luminescence compared to previously-encapsulated titanium dioxide dispersions irrespective of the nature of the binder latex used. and the value of CPV.

Example 20- Formulations for painting
Various paint compositions are prepared from dispersions of Example 19 and Example 1 based on two types of paint formulations. The compositions of the formulations are collated in Tables 15 and 16.

Table 15

<tb><SEP>%<SEP> in <SEP> weight
<tb><SEP> Components <SEP> Formula <SEP> 1 <SEP> Formula <SEP> 2 <SEP> Formula <SEP> 3
<tb><SEP> water <SEP> 93.4 <SEP> 928 <SEP> 928 <SEP>
<tb><SEP> Dispersion <SEP> 11 <SEP> 193.2 <SEP> 0 <SEP> 0
<tb><SEP> Dispersion <SEP> C5 <SEP> 0 <SEP> 193.8 <SEP> 0
<tb><SEP> dispersion <SEP> C6 <SEP> 0 <SEP> 0 <SEP> 193.8
<tb><SEP> DREWPLUS <SEP> 0.29 <SEP> 0.29 <SEP> 0.29
<tb> Ammonia <SEP> to <SEP> 20 <SEP>% <SEP> 2.38 <SEP> 2.38 <SEP> 2.38
<tb><SEP> DS1003 <SEP> to <SEP> 50 <SEP>% <SEP> 157.3 <SEQ> 1573 <SEP> 157.3
<tb><SEP> AMP <SEP> 90 <SEP> 0.39 <SEP> 0.39 <SEP> 0.39
<tb> COATEX <SEP> RHEO <SEP> 2000 <SEP> 11.5 <SEP> 115 <SEP> 11.5
<tb><SEP> TEXANOL <SEP> 6.2 <SEP> 6.2 <SEP> 6.2
<Tb>
COATEX RHEO 2000 is a thickener marketed by COATEX.

TEXANOL is a coalescing agent marketed by EASTMAN KODAK.
Table 16

<tb><SEP>% in <SEP> weight
<tb><SEP> Components <SEP> Formula <SEP> 4 <SEP> Formula <SEP> 5
<tb><SEP> water <SEP> 257.2 <SEP> 385.5
<tb><SEP> BEVALOID <SEP> 67770 <SEP> 2.9 <SEP> 0
<tb><SEP> POLYMEKON <SEP> 1488 <SEP> 1.6 <SEP> 1.6
<tb><SEP> RL <SEP> 180 <SEP> 0
<tb> Dispersion <SEP> obtained <SEP> according to <SEP>
<tb><SEP> method <SEP> 1 <SEP> to <SEP> 67.8 <SEP>% <SEP> 0 <SEP> 265.5
<tb><SEP> of extract <SEP> sec <SEP> (*)
<tb><SEP> DOWANOL <SEP> DPNB <SEP> 29 <SEP> 29 <SEP>
<tb><SEP> AMP <SEP> 90 <SEP> 1 <SEP> 1
<tb><SEP> Ammonia <SEP> 6 <SEP> 6
<tb><SEP> DS <SEQ> 1029 <SEP> A <SEP> 50 <SEP>% <SEQ> 536.8 <SEQ> 536.8
<tb><SEP> RM2020 <SEP> 29.6 <SEP> 29.6
<Tb>
(t) this dispersion is characterized in Table 3, first line.

 POLYMEKON 1488 is an antifoam marketed by GOLDSCHMIDT.

 DOWANOL DPNB is a coalescence agent marketed by DOW.

 RM2020 is a thickening agent marketed by RHOM & HAAS.

 The measurements made on the paint films prepared from these formulations are collated in Table 17.

 The viscosity is measured as in Example 1.

 The hiding power, gloss and luminescence are measured as in Example 19.

 The contrast ratio is measured using contrast cards with a DATACOLOR device.

 The lightening power is measured according to DIN 55943.

Table 17

<tb><SEP> Formula <SEP> 1 <SEP> Formula <SEP> 2 <SEP> Formula <SEP> 3 <SEP> Formula <SEP> 4 <SEP> Formula <SEP> 5
SEP (comparative) SEP (comparative) SEP (comparative)
<tb><SEP> Viscosity <SEP> to <SEP> 5760 <SEP> 6720 <SEP> 2480 <SEP> | <SEP> 3200 <SEP> 4280
<tb><SEP> 50 <SEP> rpm <SEP> in
<tb><SEP> mPa.s
<tb><SEP> Ability <SEP> 25.4 <SEP> 24 <SEP> 24.2 <SEP> 17.9 <SEP> 18.7
<tb><SEP> covering
<tb><SEP> (m2 / l)
<tb><SEP> Ratio <SEP> of <SEP> 96.5 <SEP> 96 <SEP> 96.2 <SEP> 95.5 <SEP> 95.8
<tb><SEP> contrast
<tb><SEP> (%)
<tb><SEP> Coefficient <SEP> 255 <SEP> 231 <SEP> 230
<tb><SEP> of <SEP> broadcast
<tb><SEP> (mm-1)
<tb><SEP> Brightness <SEP> 20 <SEP> 62 <SEP> 71 <SEP> 942897518
<tb><SEP> L * <SEP> 95.7 <SEP> 95 <SEP> 94.8 <SEP> 94.8 <SEP> 95.8
<tb>#<SEP><SEP> L * <SEP> + <SEP> 0.9 <SEP> / <SEP> ref <SEP> 1 <SEP> + <SEP> 0.2 <SEP> / <SEP > ref <SEP> 1 <SEP> reference <SEP> 1 <SEP> reference <SEP> 2 <SEP> + <SEP> 1 <SEP> / <SEP> ref <SEP> 2
<tb><SEP> Ability <SEP> + <SEP> 0.55 <SEP> / <SEP> ref <SEP> 1 <SEP> - <SEP> 0.21 <SEP> / <SEP> ref <SEP> 1 <SEP> reference <SEP> 1 <SEP> reference <SEP> 2 <SEP> + <SEP> 1,23 / <SEP> ref <SEP> 2
<tb><SEP> brightening
<Tb>
The properties of paints comprising dispersions according to the invention are improved over those of the prior art.

Example 21 - Measurement of sedimentation
The control of the sedimentation of the dispersions according to the invention is carried out using a TURBISCAN MA 1000 apparatus according to the method developed in the article from Spectra Analyze No. 179, August 15, 1994, p.53.

 The sedimentations of dispersions I1, C5 and C6 defined in Table 10, Example 19, diluted to 50% in water were compared. The results are shown in Table 18.

Table 18

<tb><SEP><SEP> Intensity of <SEP><SEP> Transmission (%)
<tb> time <SEP> (h) <SEP> Dispersion <SEP> I1 <SEP> Dispersion <SEP> C6 <SEP> Dispersion <SEP> C5
<tb><SEP> 1 <SEP> 0.2 <SEP> 1.1 <SEP> 0.56
<tb><SEP> 2 <SEP> 0.4 <SEP> 2 <SEP> 1.83
<tb><SEP> 3 <SEP> 0.69 <SEP> 2.75 <SEP> 3.49
<tb><SEP> 4 <SEP> 1.05 <SEP> 33 <SEP> 457
<tb><SEP> 5 <SEP> 1.39 <SEP> 4.28 <SEP> 5.47
<tb><SEP> 6 <SEP> 1.84 <SEP> 4.77 <SEP> 6.30
<tb><SEP> 8 <SEP> 2.42 <SEP> 5.75 <SEP> 7.57
<tb><SEP> 10 <SEP> 2.99 <SEP> 6.63 <SEP> 8.40
<tb><SEP> 14 <SEP> 3.91 <SEP> 7.81 <SEP> 10.00
<tb><SEP> 24 <SEP> 5.61
<Tb>
It is found that the dispersion I1 according to the invention sediments much less than the dispersions of the prior art.

Claims (19)

1. A process for preparing an aqueous dispersion of composite particles, said composite particles each comprising several latex particles adsorbed on an inorganic particle characterized in that inorganic particles are mixed in water and a latex in the absence of dispersant. 2. Method according to claim 1 characterized in that is additionally added to the mixture a water-soluble base in an amount necessary to bring the pH of the latex to a value of at least 3 and at most 10, preferably between 4 and 10, even more preferably between 7 and 10. 3. Process according to claim 1 or 2, characterized in that the inorganic particles are chosen from: titanium dioxide, calcium carbonate, cerium oxide, cerium sulphide, barium sulphate, silica, ferrous oxide, ralumine, calcium sulphate, barium sulphate. 4. Method according to one of the preceding claims characterized in that the inorganic particles have a size between 0.1 and 10 lim. 5. Method according to one of the preceding claims characterized in that the latex is derived from the emulsion polymerization of monomers selected from: (meth) acrylic acids and esters (in particular methyl methacrylate, ethyl acrylate) , Butyl acrylate, methacrylic acid, acrylic acid and mixtures thereof), acrylonitrile, styrene, divinylbenzene, vinyl acetate, ethylenically unsaturated carboxylic acids, acrylamide, methacrylamide, vinylidene chloride, butadiene, vinyl chloride, ethylene glycol dimethacrylate or mixtures thereof. 6. Method according to one of the preceding claims characterized in that the polymerization medium also comprises monomers chosen from: sulfonated monomers such as sodium aminomethylpropanesulphonate (AMPS), sodium styrenesulphonate, sodium vinylsulphonate or sulfoethyl methacrylate (SEM), hydroxylated monomers such as hydroxyethyl methacrylate (HEMA), epoxy monomers such as glycidyl methacrylate (G MA), complexing monomers such as acetoacetoxyethyl methacrylate (AAEMA) 7. Method according to one of the preceding claims characterized in that the latex has a solids content of between 25 and 50% by weight. 8. Method according to one of the preceding claims characterized in that the latex comprises particles whose diameter is between 5 and 100 nm, preferably between 20 and 40 nm. 9. Method according to claim 8 characterized in that the latex is derived from a preparation process comprising the following steps: - incremental addition of one or more ethylenically unsaturated monomers, capable of copolymerizing in an aqueous medium, to a reactor containing and up to 6.3 parts, per 100 parts of said monomers, one or more surfactants, incrementally adding one or more polymerization initiators to said reactor, and polymerizing said one or more ethylenically unsaturated monomers so that the average particle size of said polymerized monomers is less than 100 nm. 10. Method according to one of the preceding claims characterized in that the water-soluble base is selected from: sodium hydroxide, potassium hydroxide, ammonia, aminoalcohols, functional amines, zirconium derivatives. 11. Method according to one of claims 2 to 10 characterized in that it comprises the following steps: - the latex is mixed with water and the water-soluble base, and then added to this mixture inorganic particles in the form of powder while shaking. 12. Method according to one of claims 2 to 10 characterized in that it comprises the following steps: - the inorganic particles are mixed with water, - the latex is mixed with the water-soluble base, - then the mixture is added latex-based inorganic particles. 13. Method according to one of claims 2 to 10 characterized in that it comprises the following steps: - the inorganic particles, water and all or part of the water-soluble amount of base are mixed, - the latex is mixed and the eventual complement of the water-soluble base, then the latex-based mixture is added to the inorganic particles. 14. Process according to one of Claims 2 to 10, characterized in that it comprises the following stages: the inorganic particles and the water are mixed, the latex is mixed with the water-soluble base, and then the particles are added; inorganic to the latex-based mixture. 15. Method according to one of claims 2 to 10 characterized in that it comprises the following steps: - the inorganic particles, water and all or part of the amount of the water-soluble base are mixed, - the latex is mixed and optionally adding the water-soluble base, and then adding the inorganic particles to the latex-based mixture. 16. coating composition characterized in that it comprises an aqueous dispersion of composite particles obtained by the method according to one of claims 1 to 15. 17. Use of an aqueous dispersion of titanium dioxide composite particles obtained by the process according to one of claims 1 to 15 for improving the opacifying power and brightness of a dried film of a coating composition containing said dispersion. 18. Use of an aqueous dispersion of titanium dioxide composite particles obtained by the method according to one of claims 1 to 15 for the manufacture of paper. 19. Pigment dispersion comprising the dispersion obtained by the process according to one of claims 1 to 15.