WO2002096954A1

WO2002096954A1 - Preparation of hydrophilic polymer powders with low grain size distribution

Info

Publication number: WO2002096954A1
Application number: PCT/FR2001/001635
Authority: WO
Inventors: Jean-Marc Corpart; Manuel Hidalgo; Fabienne Vauloup; Myriam Gourmand; André Kowalik
Original assignee: Atofina
Priority date: 2001-05-28
Filing date: 2001-05-28
Publication date: 2002-12-05

Abstract

The invention concerns a method for obtaining hydrophilic polymers in powder form of low grain size distribution, based on invert emulsion polymerisation followed by azeotropic distillation of water then a distillation of the organic phase. The inventive hydrophilic polymers are useful in various applications such as water treatment and sludge dehydration. They can also be used as retention agent in the paper making industry and as thickening agents. They can likewise be used to control water uptake and hence moisture content in materials when dispersed therein.

Description

PREPARATION OF LOW HYDROPHILIC POLYMER POWDERS

GRANULOMETRY

The present invention relates to the field of hydrophilic polymers of associative nature or not presented in the form of powders of small particle size with elementary particle sizes of the order of 0.1 to 10 μm, and more particularly to their process. obtaining.

It describes the powders obtained as well as their different applications in the form of dispersions or aqueous solutions. These powders can also be used, in certain applications, in the form of dispersions concentrated in organic solvents in which they are not soluble such as, for example, hydrocarbon oils.

The hydrophilic polymers of the invention can thus be used inter alia as flocculants for water treatment, as sludge dewatering agents, as retention agents in the paper industry and as thickeners in fields such as paints, cosmetics, glues and adhesives, construction, textiles (pigment printing) and paper. They can also be used to control the water uptake and therefore the moisture content of materials when they are dispersed within them.

The hydrophilic polymers to which the present invention relates are products consisting of linear or branched macromolecules, partially crosslinked or not, comprising hydrophobic or non-hydrophobic chemical groups, of generally high molecular mass, of the order of one to several million. daltons. They are generally obtained by a process of polymerization in a dispersed medium in the first stage of which the continuous phase is an organic phase and the dispersed phase an aqueous solution of the constituent monomers. Thus, the so-called reverse suspension polymerization technique has been known for a long time and has been described in numerous patents (see for example, US patents 3,957,739, US 4,093,776 and EP 441, 507). At the end of this reverse suspension polymerization process, the recovery of the polymers is relatively easy and a powder of generally spherical morphology is finally obtained with a particle size distribution classically between 50 and 400 μm. By optimizing the formulation of the reverse suspension and in particular the choice of the surfactant (s) used as well as their quantity, by varying the stirring conditions, it is possible to obtain particles of smaller size up to a lower average value of the order of 20 // m. This reverse suspension polymerization technique therefore appears not suited to the aim pursued here of synthesizing much finer particles.

Another polymerization technique in a dispersed medium of the water in oil type can also be envisaged. This is the reverse emulsion polymerization technique, also well known for a long time and described in numerous patents or in articles in the literature (see, for example, the review article by F. Candau "Inverse Emulsion and micro emulsion polymerization "in Emulsion Polymerization and Emulsion Polymers, Edited by PA Lowell and MS El Aasser, 1997, chap 21, 723, John Wiley & Sons Ltd).

It consists in dispersing by vigorous stirring, in the presence of surfactants, an aqueous phase containing hydrophilic monomers in a continuous organic phase. The polymerization of this system in the presence of a radical initiator leads to the production of reverse latexes containing the hydrophilic polymers targeted. The average particle sizes obtained with such a reverse emulsion polymerization technique are small on the order of 0.1 to 5 μm and therefore perfectly within the range of sizes sought here.

However, unlike the case of the reverse suspension described above, it is difficult in the case of the reverse emulsion polymerization technique to isolate the polymer synthesized in the form of a powder using a simple recovery process well suited to production on an industrial scale. Consequently, the reverse emulsions containing hydrophilic polymers are mainly used directly in the form of liquids, by reversing the reverse emulsions in an aqueous phase, generally in the presence of a wetting agent (surfactant of strong hydrophilic-hydrophobic balance (HLB) ), which allows rapid dissolution of the polymers in water (see for example US Pat. No. 3,642,019). This inversion system is particularly disadvantageous because the continuous phase of the reverse emulsion, ie an organic solvent, also remains present in water. On the one hand, it is thus lost, which economically is not interesting and on the other hand, its presence can be criticized in terms of environmental protection.

Various methods have been proposed in the literature for obtaining hydrophilic polymers in the form of a powder from the reverse emulsion. Thus, US Pat. No. 3,284,393 describes a reverse emulsion polymerization process which leads to very fine average particle sizes, for example 0.1 μm. The polymers cannot be easily isolated from the emulsion and it is necessary to precipitate them using a large amount of non-solvent and then to recover them, in solid form, by filtration. This process is only difficult to industrialize because it requires reprocessing large quantities of organic effluents. US Pat. No. 4,059,552 also describes the production of particles of hydrophilic polymers of small size, the average diameter of which is less than 4 μm. These polymers are prepared by reverse emulsion polymerization of water-soluble monomers in the presence of crosslinking agents. The water is removed by azeotropic distillation then a flocculant is added to the medium so as to destabilize the polymer particles which are recovered in solid form, by filtration. Using a flocculant is complicated and can cause reproducibility problems. In addition, the aggregation of particles caused by the flocculant can become irreversible, which removes the interest of the process if obtaining particles individual items of small size and likely to be redispersed later is targeted. Patent CA 2,021,759 claims the synthesis of hydrophilic polymers in reverse emulsion followed by azeotropic distillation to remove the water. The polymer powder is then isolated by filtration. This process requires a specific composition of the reverse emulsion and in particular the joint use of at least one surfactant, at least one protective colloid and optionally a polar organic solvent used as agglomerating agent for the powder. This formulation is complicated and the filtration process can be particularly long because the size of the elementary particles is very small (diameters ranging from 0.1 to 20 μm). Finally, such a method has the drawback of requiring expensive equipment which is difficult to operate both for the solid-liquid separation operation by filtration and for the treatment of effluents (recovery of fines in the organic effluent). In conclusion, the approach advocated in patent CA 2,021, 759 seems complicated and economically unprofitable.

It appears from the above that there is no fully satisfactory method in technical and economic terms for obtaining hydrophilic polymers in the form of a powder, the size of the elementary particles of which is fine and typically between 0.1 and 10 μm.

The Applicant has now found and perfected a process which makes it possible to obtain a powder having these characteristics under industrially satisfactory operating conditions and without the need for a particularly complicated formulation. According to a first form, the invention relates to powders of hydrophilic polymers and their uses. According to another form, the invention relates to the process for the preparation of these powders.

The method according to the invention consists in preparing, in a first step, hydrophilic polymers by reverse emulsion polymerization of essentially water-soluble monomers, in the presence of a polymerization initiator and at least one surfactant, then, in a second step, to remove the water by azeotropic distillation. Finally, the powder is obtained by distillation of the organic phase, for example, in a paddle dryer.

The hydrophilic polymers according to the invention are preferably those which result from the polymerization of one or more ethylenic unsaturated monomers with high solubility in water. Optionally, the use, in small proportions of unsaturated ethylenic monomers with low or medium solubility, in water is possible. These polymers can be linear, branched or partially crosslinked. Another aspect of the invention relates to their associative nature or not. In all cases, these polymers are generally hydrophilic and soluble, or dispersible in the form of microgels, in water, which makes them capable of being used as flocculants, as additives in papermaking or as thickeners, among others applications. The hydrophilic polymers of the invention contain:

90 to 100% by mole of units derived from at least one monomer A chosen from the group consisting of unsaturated ethylene monomers with high solubility in water,

0 to 10 mol% of units derived from at least one monomer B chosen from the group consisting of unsaturated ethylenic monomers with low or medium solubility in water,

0 to 1% by mole of units derived from at least one crosslinking agent C,

- 0 to 5 mol% of units derived from at least one monomer D containing a hydrophobic group, or from the chemical modification of the polymer with chemical reagents, intended to create hydrophobic groups.

The unsaturated ethylenic monomers A with high water solubility which can be used in this invention are, for example, ethylenic monomers comprising carboxylic groups and their sodium, potassium, ammoniacal or amine salts such as triethylamine, butylamine, morpholine and ethanolamine. Such monomers are for example acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid. May also be used the amides of these carboxylic acids and in particular, acrylamide and methacrylamide and their N-substituted derivatives with high water solubility, their esters with high water solubility such as dimethyl or diethyl amino (ethyl or propyl) (meth) acrylate and their salts, the quaternized derivatives of these cationic esters such as, for example, acryloxy ethyl trimethylammonium chloride. Examples of other usable monomers are provided by 2-acrylamido-2-methylpropane sulfonic acid (AMPS), vinylsulfonic acid, vinylphosphoric acid, vinyllactic acid and their salts, acrylonitrile, N- vinylpyrrolidone, N-methylformamide, vinyl acetate, N-vinylimidazoline and its derivatives, N-vinylimidazole and diallylammonium derivatives such as, for example, dimethyldiallylammonium chloride, dimethyldiallylammonium bromide, diethyldiallylammonium chloride .

The use of small amounts of comonomers with low or medium solubility in water makes it possible, in certain cases, to modify the application properties of the polymers by making them more or less compatible with various materials used in the context of the targeted applications. The unsaturated ethylenic B monomers with low or medium solubility in water which can possibly be used are, for example, styrene, vinyl acetate, methyl acrylate, ethyl acrylate, acrylate butyl, methyl methacrylate, hydroxyethyl acrylate or hydroxyethyl methacrylate.

Since self-crosslinking due to transfer reactions during polymerization is often not sufficient to crosslink the polymers to the level required by applications using partially crosslinked polymers, the use of crosslinking agents C is necessary. These agents can be polyunsaturated monomers, ie, comprising, at least, two nonconjugated ethylenic double bonds. Such monomers contain at least two identical or different groups, of acrylic, methacrylic, vinyl or allylic type and, by way of illustration, may be chosen from di (meth) acrylamide derivatives such as N-methylene-bis-acrylamide, or poly (meth) acrylates such as polyethylene glycol di (meth) acrylates, ethylene glycol diacrylate, trimethylolpropane tri (meth) acrylate, propylene glycol diacrylate, butanediol diacrylate hexanediol di (meth) acrylate or alternatively diallylic compounds such as diallylacetic acid, diallylphthalate or pentaerythritol diallyl ether. An example of a polyunsaturated crosslinking monomer having two different groups is allyl methacrylate.

Other crosslinking agents other than the polyunsaturated monomers may also be useful for partially crosslinking the hydrophilic polymers which are the subject of this invention. These are, on the one hand, functional ethylenic monomers comprising an unsaturation and a functional group of alcohol, acid, amino, epoxide, metal salt or other chemically reactive group type, and, on the other hand, saturated polyfunctional compounds comprising at least two functional groups of alcohol, acid, amino, epoxide, metal salt or other chemically reactive type. Examples of the former are N-methyloI acrylamide, N-methyloI methacrylamide, glycidyl acrylate and glycidyl methacrylate. Examples of the second are glyoxal, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, epichlorohydrin, ethylene di-amine and zinc acetate.

The invention includes the possibility of giving the polymers obtained an associative character in solution. To do this, copolymerization with a monomer D carrying a hydrophobic group is a very useful route. Alternatively, the chemical modification of the polymer by treatment with chemical reagents after the polymerization can also be carried out. The monomers carrying a hydrophobic group, useful in the context of this invention, are preferably ethylenic monomers containing a group of formula: (1) (CH2-CH2O) _n -R in which R is a hydrophobic group containing at least 8 carbon atoms, n is an integer between 0 and 50 and preferably between 8 and 25. In the case of a hydrophobic modification after polymerization, it is possible to use molecules comprising groups which are potentially reactive with the polymer previously synthesized. In particular, the molecules intended to modify the backbone of the polymer are chosen so as to be adapted to the reactive groups present on this polymer. The reactive groups present on the polymer can be of different chemical nature and generally, depending on the case, groups of carboxylic type (use of (meth) acrylic acid) or amino type (use of dimethyl or diethyl amino (ethyl or propyl) ( meth) acrylate). The molecules intended to modify the polymer then have the following chemical structure:

(2) R1 -X- (CH2-CH2O) - _n R in which R is a hydrophobic group containing at least 8 carbon atoms, n is an integer between 0 and 50, R1 is a functional group of epoxide type, alcohol, amino, isocyanate, halogen atom, carboxylic acid, X is a junction group between R1 and the ethylene oxide groups and can comprise carbon, nitrogen, oxygen and sulfur atoms; X may be absent.

When the polymer comprises amide groups (for example in the case of the use of acrylamide), transamidation reactions can also be used to provide hydrophobic groups as taught in US Pat. No. 4,921,903.

The process for the preparation of the aqueous dispersions of hydrophilic polymers of the invention itself constituting another object of the invention is that of reverse emulsion polymerization, followed by a phase of dehydration by distillation, which, in turn, is followed by a phase of elimination of the continuous organic phase by distillation to obtain the fine powders of the invention, the elementary particles of which have an average size of between 0.1 and 10 μm and preferably between 0.2 and 5 μm.

The method of the invention consists of:

- Reverse emulsion by mixing and stirring an organic phase containing at least one surfactant and an aqueous phase containing 20 to 80% by weight and. preferably 30 to 60% of at least one monomer; the mass ratio between aqueous phase and organic phase is between 0.5 and 4.0 and preferably between 2.5 and 3.5 and the surfactant content of the emulsion is from 0.1 to 10% by weight and preferably from 0.5 to 6%, polymerization using a radical initiator at a temperature between 5 and 120 ° C, removal of water from the reverse emulsion by azeotropic distillation, and - the final elimination of the organic phase by distillation and obtaining the powder.

The various operations required are now described more fully below.

The organic phase is prepared by dissolving a surfactant or a mixture of surfactants capable of stabilizing water-in-oil emulsions in oil. The amounts of surfactant or of the mixture of surfactants to be dissolved therein can vary between 0.1 and 10% of the final total weight of the emulsion and preferably between 0.5 and 6% of the weight of the emulsion. The surfactants used are generally nonionic surfactants and have a hydrophilic-lipophilic balance (HLB) of between 3 and 10 on the Griffin scale (in the case of a mixture of surfactants, this is the resulting HLB ). As surfactant, there may be mentioned, for example, sorbitan monooleate, sorbitan sesquioleate or a mixture thereof, as well as surfactant copolymers, for example, of the triblock copolymer type ABA (Hypermer B246, Hypermer B261 from ICI) where A is a polyester derived from 12-hydroxy stearic acid and B is a polyethylene oxide or branched copolymers such as those described for example in patents CA 2,021, 759 and DE 3,220.1 14.

The aqueous phase is prepared separately by adding, in demineralized water, the monomer or mixture of monomers, and optionally of the crosslinking agent and / or of a monomer carrying hydrophobic groups. A metal cation complexing agent can also be added. Similarly, the aqueous phase may contain one or more non-polymerizable salt (s) such as sodium acetate, sodium formate or sodium chloride at a concentration of up to 10% by mass in the 'water. The aqueous phase thus prepared then contains between 20 and 90% by weight of material other than water, and preferably, between 30 and 60% by weight of material other than water.

The aqueous phase to organic phase mass ratio is between 0.5 and 4.0 and preferably between 2.5 and 3.5. The initial emulsion is then prepared according to the following two steps

: the aqueous phase is first slowly introduced into the organic phase with gentle stirring and then the emulsion is stirred by an intensive mixer (for example, a rotor-stator type mixer of Ultra-turrax brand) for a short time period ranging from a few seconds to 10 minutes while ensuring external cooling so as to prevent the temperature of the emulsion from exceeding 30 to 40 ° C.

The emulsion thus prepared is transferred to a polymerization reactor equipped with a double jacket allowing the circulation of a heat transfer fluid to heat / cool the system, a tapping allowing the introduction of a probe to measure the temperature of the system, a nozzle allowing the introduction of nitrogen gas to expel the oxygen which inhibits the polymerization reaction, a stirrer for example, in the form of an anchor linked to a motor making it possible to rotate at variable speed, d '' an inlet allowing the addition of additives and a vapor outlet linked to a condensation / reflux system. The emulsion is kept in the reactor at room temperature, with stirring and bubbling nitrogen for a period of 20 to 120 minutes, and preferably 30 to 90 minutes.

During degassing of the emulsion, the polymerization initiator is prepared. Two types of initiators can be envisaged in the context of the invention, namely, an initiator whose decomposition kinetics allows polymerization temperatures between 40 and 90 ° C or a reducing-oxidizing (redox) initiator system , allowing polymerization temperatures between 5 and 120 ° C. The second possibility is preferred in the context of this invention. The amounts of initiator to be used vary between 0.005 and 0.5% relative to the total weight of monomer (s), and preferably between 0.01 and 0.1% relative to the weight of (s) ) monomer (s). In the case of redox systems, the sum of the weights of oxidant and reducing agent is considered to define the ratio to the weight of the monomer (s), and the oxidizing / reducing ratio can range from 20/1 to 1/1 , and preferably from 10/1 to 3/1. Generally, diluted initiator solutions are prepared, depending on the type of initiator chosen. The initiators used can be water-soluble or liposoluble.

After degassing with nitrogen, the temperature at the start of polymerization is fixed, and the diluted solution of the thermal initiator or the oxidant of the redox initiation system is added to the reactor. Depending on the solubility of the initiator, an aqueous or organic solution is used. In the case of priming by a redox system, a waiting time necessary for the correct mixing of the oxidant within the emulsion is necessary before starting the addition of the diluted reducing solution; the latter is aqueous or organic, depending on the nature of the reducing agent chosen. The addition takes place slowly, the speed of addition being a parameter for controlling the exotherm developed by rapid polymerization. By varying the speed of addition of the reducing solution, the temperature rise of the reactor is controlled. Priming by a redox system allows reverse emulsion polymerization according to a so-called "ballistic" process, during which the temperature at the start of polymerization can be ambient or sub-ambient temperature, and the final polymerization temperature is often between 40 and 95 ° C, the rise occurring fairly quickly and being controlled by the rate of addition of the reducing solution. Priming with a thermal initiator allows, through a judicious choice of the temperature at the start of polymerization, polymerizations closer to isothermal polymerizations, with temperature increases more moderate compared to the initial temperature of polymerization. In this case, the initial polymerization temperature is often between 40 and 65 ° C. The so-called "ballistic" method is preferred in the context of this invention.

After the first polymerization phase, the end of which is marked by a cessation of the exotherm generated in the emulsion, the polymerization reaction is terminated during a new phase known as "cooking" where the reactor temperature is set between 75 and 120 ° C., and preferably between 80 and 100 C. This cooking phase can be used to chemically modify the polymer by adding to the medium a reactive compound carrying the hydrophobic group such as those described above or to complete the crosslinking by adding into the reverse emulsion a reactive polyfunctional compound such as those described above.

Thermal initiators which can be used include, for example, azo-bis-isobutyronitrile and benzoyl peroxide. Redox couples are preferred in the context of this invention and include, for example, the following couples: tert-butyl hydroperoxide / sodium, potassium or ammonium methabisulfite, cumene hydroperoxide / thionyl chloride, cumene hydroperoxide / methabisulfite sodium, potassium or ammonium, sodium, potassium or ammonium persulfate / sodium, potassium or ammonium metabisulfite, sodium, potassium or ammonium persulfate / ascorbic acid, hydrogen peroxide / ascorbic acid.

At the end of the cooking period, the duration of which is often between 30 and 90 minutes, the resulting latex is subjected to azeotropic distillation so as to remove the water, then the organic solvent is itself distilled to obtain the fine powder. . During these drying phases, it is possible, as during the baking phase, to modify the structure of the polymer by providing it with hydrophobic modifications or by crosslinking it. The organic phase is most often constituted by a non-reactive hydrocarbon liquid, which only plays the role of a dispersive medium. The hydrocarbon liquids which can be used for the present invention are compounds which are chemically inert with respect to the monomers and polymers formed. They must form an azeotrope with water so that it can be removed by azeotropic distillation; when this condition is not met, instead of obtaining, in the end, a fluid powder, large agglomerates are obtained. It is also necessary that their boiling point is sufficiently low so that they can be evaporated from the powder without the latter undergoing thermal degradation; in practice, their boiling point must at most be equal to 100 ° C. Meet these characteristics, for example, n-heptane, cyclohexane, iso-octane, toluene or their mixtures.

It may be advantageous to introduce into the medium, before or after the polymerization, a surfactant or a mixture of surfactants usually used to stabilize an emulsion of oil-in-water type. If the surfactant or mixture of surfactants is added after the polymerization, it can be added before the distillation phases or after the azeotropic distillation of water. The surfactant or mixture of surfactants is used in a proportion of the order of 0.5 to 10% by weight and preferably from 2 to 5% relative to the monomers. One of the obvious advantages of adding at least one surfactant of this type is that its presence makes it possible to obtain a translucent to transparent solution (or gel) when the powder obtained is redissolved in water, which can be very appreciable in certain applications. In the absence of this additive, the solution (or gel) is turbid. The surfactants capable of stabilizing an oil-in-water emulsion used are generally nonionic surfactants and have a hydrophilic-lipophilic balance (HLB) of between 10 and 18 (in the case of a mixture of surfactants, this is the Resulting HLB). By way of examples, mention may be made of ethoxylated nonylphenols (the average number of moles of ethylene oxide determines the HLB), ethoxylated fatty alcohols, sorbitan or ethoxylated sorbitol esters.

The powder finally obtained after drying consists of agglomerates of low cohesion, themselves made up of elementary particles whose size varies from 0.1 to 10 μm. The average size of the agglomerates obtained is of the order of a few hundred micrometers and typically between 100 and 800 μm. The powder can be easily deagglomerated, in the form of elementary particles, when it is dispersed in an organic non-solvent and subjected to agitation and / or to ultrasound. Similarly, introduced into water in moderate concentration (at most a few percent), the agglomerates rapidly disintegrate into elementary particles and lead to the formation of a viscous solution up to the consistency of a gel.

The following examples illustrate the invention without limiting it. In these examples, the data concerning the sizes of the elementary particles and of the agglomerates are obtained either with a scanning electron microscope or using a laser granulometer, by dispersing the powder in an anhydrous ethanol medium. The powders are typically disagglomerated by subjecting these dispersions to ultrasound for 60 minutes. The water content of the powders is, in all cases, less than 10%.

Example 1 Summary:

In a stirred reactor comprising a double jacket, a tapping allowing the introduction of a temperature probe and reagent inlets, 176.4 grams of glacial acrylic acid (Elf-Atochem) are mixed with gentle stirring with 44.1 grams of water demineralized.

In parallel, an aqueous sodium hydroxide solution is prepared by very slow addition of 78.4 grams of sodium hydroxide pellets, analytical reagent, to 202.4 grams of demineralized water. After total dissolution of the sodium hydroxide and cooling of the solution (the dissolution is exothermic), this solution is added dropwise to the reactor containing acrylic acid. The operation is carried out with stirring, taking care not to allow an increase in temperature in the medium beyond 30 ° C.

In a stirred container, 161 grams of heptane is mixed with

17.5 grams of sorbitan monooleate until completely dissolved. This solution constitutes the organic phase.

In a stirred container, the acrylic acid solution partially neutralized by soda, the preparation of which has just been described, is introduced. 0.17 grams of N-methylene-bis-acrylamide are added thereto and

0.64 grams of the complexing agent Versenex 80 (Dow Chemical). This solution constitutes the aqueous phase.

The organic and aqueous phases are mixed by slow introduction and with stirring of the aqueous phase in a container containing the organic phase. The mixture is stirred normally for 15 minutes before being passed through the intensive mixer (Ultra-turrax T50) for 5 minutes at a speed of 10,000 rpm. Precautions to cool the container containing the mixture are taken to prevent the temperature from exceeding 30 ° C during the passage through the intensive mixer.

The emulsion thus prepared is introduced into a 1.5-liter polymerization reactor, equipped with a double jacket with circulation of a heat-transfer fluid allowing the contents of the reactor to be heated or cooled, a tapping allowing the introduction of '' a gas stream at inside the reactor, a nozzle allowing the introduction of a temperature probe, a “leaf” agitator linked to a variable speed motor, a reagent inlet and a linked vapor outlet to a condensation / reflux system with the possibility of removing condensates. The stirring speed is fixed at 260 rpm and the oxygen is removed by bubbling nitrogen through at room temperature for one hour. This time is used to prepare a solution of cumene hydroperoxide by adding 0.036 grams of a commercial solution at 80% by weight in cumene, of cumene hydroperoxide, in 4.96 grams of heptane. A solution of sodium metabisulfite is also prepared, by adding 0.1 grams of sodium metabisulfite in 99.9 grams of demineralized water.

The 5 grams of cumene hydroperoxide solution are introduced into the reactor after one hour of degassing; nitrogen bubbling and stirring are maintained. 10 minutes after this addition (during this period of time, by isolating the jacket, the heat transfer fluid is heated to 50 ° C), 2 grams of Na ₂ S ₂ O ₅ solution are introduced into the reactor and then the rest of the sodium metabisulfite solution is added at a rate of 30 to 50 milliliters per hour. The circulation of the heat transfer fluid is restored inside the jacket. The start of polymerization causes a rapid increase in the reactor temperature. The addition of the sodium metabisulfite solution is stopped as soon as the temperature stops rising. The unused sodium metabisulfite solution is discarded. The circulation of the heat transfer fluid in the double jacket is maintained and its temperature is fixed at 80 ° C., the bubbling of nitrogen is reduced. The product is kept stirring for one hour for "cooking". Then introduced 100 grams of heptane; the temperature of the jacket is increased to 11.5 ° C for the concentration step. After elimination of 70% to 75% of the amount of water, the reaction medium is cooled. At room temperature, the reaction medium is transferred to a horizontally positioned paddle dryer, provided with a double jacket, 2 nozzles, one for nitrogen, the other for the temperature probe and an agitator linked to a variable speed motor. The temperature of the jacket fluid is raised to 11 ° C. The remaining water is eliminated and then the organic phase until the powder (P1) is obtained. We finish with a light nitrogen sweep at the end of drying.

Characteristics of the powder: The powder (P1) obtained has the following characteristics:

- average size of the agglomerates: 380 μm,

- average size of the elementary particles after deagglomeration with ultrasound: <10 μm.

The viscosity of a gel containing 1% powder (P1) in water is 11000 cP (measured with a Broo field viscometer, module 6 and speed 50 rpm).

Use of the powder in pigment printing:

In 430 grams of water, 2 grams of antifoam are successively added (Erol AT3 from the company PPG Chemicals) and 6.5 grams of the powder (P1). A high viscosity gel is obtained. The initial pH of the order of

6.0 is adjusted to 9.0 with a 28% aqueous ammonia solution.

50 grams of acrylic binder (REPOLEM 1,121 TK dry extract 45%, from the company Elf Atochem) are added, with stirring and maintaining the pH at 9.0. The viscosity is 7400cP, the viscosity being measured with a Brookfield device with the mobile No. 6 at 50 rpm.

100 grams of the white paste thus obtained are taken, to which 3 grams of lmperon KB blue pigment from the company Dystar are added.

The pigmented paste thus prepared is applied to a cotton fabric using a printing table according to the conventional method well known to those skilled in the art. The printed fabric is heat set in the oven at 160 ° C for five minutes.

Using the powder (P1) as a thickener in the paste, a very good printing quality is obtained, without defects and with very good color rendering.

Example 2

Synthesis: In a stirred reactor comprising a double jacket, a tapping allowing the introduction of a temperature probe and reagent inlets, 1,85.2 grams of glacial acrylic acid (Elf-Atochem) are mixed with gentle stirring with 46.3 grams demineralized water. At the same time, an aqueous sodium hydroxide solution is prepared by very slow addition of 72 grams of sodium hydroxide tablet, analytical reagent, to 1,992 grams of demineralized water. After total dissolution of the sodium hydroxide and cooling of the solution (the dissolution is exothermic), this solution is added dropwise to the reactor containing acrylic acid. The operation is carried out with stirring, taking care not to allow an increase in temperature in the medium beyond 30 ° C.

In a stirred container, 148.5 grams of heptane are mixed with 11.8 grams of Hypermer 2296 (surfactant copolymer from the company

HERE) until their complete dissolution. This solution constitutes the organic phase. In a stirred container, the acrylic acid solution partially neutralized by sodium hydroxide, the preparation of which has just been described, is introduced and 0.08 grams of N-methylene-bis-acrylamide as well as 0.67 grams of Versenex 80 complexing agent (Dow Chemical) are added. This solution constitutes the aqueous phase. The organic and aqueous phases are mixed by slow introduction and with stirring of the aqueous phase in a container containing the phase organic. The mixture is stirred normally for 15 minutes and then subjected to intensive mixing (Ultra-turrax T50) for 5 minutes at a speed of 10,000 rpm. Precautions to cool the container containing the mixture are taken to prevent the temperature from exceeding 30 ° C during the passage through the intensive mixer.

The emulsion thus prepared is introduced into a 1.5-liter polymerization reactor, equipped with a double jacket with circulation of a heat-transfer fluid allowing the contents of the reactor to be heated or cooled, a tapping allowing the introduction of '' a gas stream inside the reactor, a tapping allowing the introduction of a temperature probe, an agitator with 2 inclined quadrupal blades linked to a variable speed motor, a reagent inlet and d '' a vapor outlet linked to a condensation / reflux system with the possibility of removing condensates.

The stirring speed is fixed at 700 rpm and the oxygen is removed by bubbling nitrogen through at room temperature for one hour. This time is used to prepare a 2% potassium persulfate (PPS) solution in demineralized water. A solution of sodium metabisulfite is also prepared, by adding 0.1 gram of sodium metabisulfite in 99.9 grams of demineralized water. 0.93 gram of PPS solution is introduced into the reactor after one hour of degassing, the nitrogen bubbling and stirring are maintained. 10 minutes after this addition, (during this time, by isolating the jacket, the heat transfer fluid is heated to 50 ° C), 2 grams of Na ₂ S ₂ O ₅ solution are introduced into the reactor and then the rest of the sodium metabisulfite solution is added at a speed of 30 to 50 milliliters per hour. The circulation of the heat transfer fluid is restored inside the double jacket. The start of polymerization causes a rapid increase in the reactor temperature. The addition of the sodium metabisulfite solution is stopped as soon as the temperature stops rising. The unused sodium metabisulfite solution is discarded. The circulation of the heat transfer fluid in the jacket is maintained and its temperature is fixed at 80 ° C; nitrogen sparging is reduced. The product is kept stirring for one hour for "cooking". After one hour, 100 grams of heptane are introduced, the temperature of the jacket is increased to 11.5 ° C for the concentration step. After elimination of 70% to 75% of water, the reaction medium is cooled.

At room temperature, the reaction medium is transferred to a paddle dryer, positioned horizontally, provided with 2 nozzles, one for nitrogen, the other for the temperature probe and an agitator linked to a variable speed motor. The temperature of the jacket fluid is raised to 11.5 ° C. The remaining water is eliminated, then the organic phase until the powder is obtained (P2) and a light nitrogen sweep is completed at the end of drying.

Characteristics of the powder:

The powder (P2) obtained has the following characteristics:

- average size of agglomerates: 385 μm,

- average size of the elementary particles after deagglomeration with ultrasound: <5 μm.

The viscosity of a gel containing 1% powder (P2) in water is 23,000 cP (measured with a Brookfield viscometer, module 6, speed 50 rpm).

Use of the powder in pigment printing:

In 430 grams of water, 2 grams of antifoam (Erol AT3 from PPG Chemicals) and 5 grams of powder (P2) are successively added. A high viscosity gel is obtained. The initial pH of the order of 6.0 is adjusted to 9.0 with a 28% aqueous ammonia solution. 50 grams of acrylic binder (REPOLEM 1,121 TK dry extract 45%, from Elf Atochem) are added with stirring and maintaining the pH at 9.0.

The viscosity, measured with a Brookfield device with the mobile No. 6 at 50 rpm, is 7400cP.

100 grams of the white paste thus obtained are taken, to which are added 3 grams of blue pigment Imperon KB from the company Dystar. The pigmented paste thus prepared is applied to a cotton fabric using a printing table according to the conventional method well known to those skilled in the art.

The printed fabric is heat set in the oven at 160 ° C for five minutes.

Using the powder (P2) as a thickener in the paste, a very good printing quality is obtained, without defects and with very good color rendering. Example 3

Summary:

In a stirred reactor comprising a double cooling jacket, a tapping allowing the introduction of a temperature probe and reagent inlets, 185.2 grams of glacial acrylic acid (Elf-Atochem) are mixed with gentle stirring with 46 , 3 grams of demineralized water. In parallel, an aqueous sodium hydroxide solution is prepared by very slow addition of 72 grams of sodium hydroxide tablets, analytical reagent, to 209 grams of demineralized water. After total dissolution of the sodium hydroxide and cooling of the solution (the dissolution is exothermic), this solution is added dropwise to the reactor containing acrylic acid. The operation is carried out with stirring, taking care not to allow an increase in temperature in the medium beyond 30 ° C. In a stirred container, 148.5 grams of heptane are mixed with 11.8 grams of Hyper 2296 until the latter are completely dissolved. This solution constitutes the organic phase.

In a stirred container, the acrylic acid solution partially neutralized by soda, the preparation of which has just been described, is introduced as well as 4 grams of a 2% solution in water of ethylene glycol diglycidyl ether and 0 67 grams of Versenex 80 complexing agent (Dow

Chemical). This solution constitutes the aqueous phase.

The organic and aqueous phases are mixed by slow introduction and with stirring of the aqueous phase in a container containing the organic phase. The mixture is stirred normally for 15 minutes and then passed through the intensive mixer (Ultra-turrax T50) for 5 minutes at a speed of 10,000 rpm. Precautions to cool the container containing the mixture are taken to prevent the temperature from exceeding 30 ° C during the passage through the intensive mixer.

The stirring speed is fixed at 700 rpm and the oxygen is removed by bubbling nitrogen through at room temperature for one hour. This time is taken advantage of for the preparation of an aqueous 2% potassium persulfate solution and a sodium metabisulfite solution is also prepared, by adding 0.1 gram of sodium metabisulfite to 99.9 grams of demineralized water. . 0.93 grams of potassium persulfate solution are introduced into the reactor after one hour of degassing; nitrogen sparging and agitation are maintained. 10 minutes after this addition, (during this time, by isolating the jacket, the heat transfer fluid is heated to 50 ° C), 2.0 grams of Na ₂ S ₂ O ₅ solution are introduced into the reactor and then the rest of the sodium metabisulfite solution is added at a speed of 30 to 50 milliliters per hour. The circulation of the heat transfer fluid is restored inside the double jacket. The start of polymerization causes a rapid increase in the reactor temperature. The addition of the sodium metabisulfite solution is stopped as soon as the temperature stops rising. The unused sodium metabisulfite solution is discarded.

The circulation of the heat transfer fluid in the double jacket is maintained and its temperature is fixed at 80 ° C., the bubbling of nitrogen is reduced. The product is kept stirring for one hour for "cooking". Then introduced 100 grams of heptane, then the temperature of the jacket is increased to 1 15 ° C for the concentration step. After elimination of 70% to 75% of water, the reaction medium is cooled and then, at ambient temperature, it is transferred to a dryer (double jacket reactor) positioned horizontally, provided with 2 nozzles, one for nitrogen, the other for a temperature probe and an agitator linked to a variable speed motor. The temperature of the jacket fluid is raised to 11 ° C. The remaining water is eliminated, then the organic phase until the powder (P3) is obtained and a light sweep of nitrogen is terminated at the end of drying.

Characteristics of the powder:

The powder (P3) obtained has the following characteristics:

- average size of agglomerates: 270 μm,

- average size of the elementary particles after deagglomeration with ultrasound: <5 μm. The viscosity of a gel containing 1% powder (P3) in water is 15,400 cP (measured with a Brookfield viscometer, module 6, speed 50 rpm).

Use of the powder in pigment printing:

In 430 grams of water, 2 grams of antifoam (Erol AT3 from PPG Chemicals) and 5.5 grams of powder (P3) are successively added. A high viscosity gel is obtained. The initial pH of the order of 6.0 is adjusted to 9.0 with a 28% aqueous ammonia solution. 100 grams of the white paste thus obtained are taken, to which are added 3 grams of blue pigment Imperon KB from the company Dystar.

The pigmented paste thus prepared is applied to a cotton fabric using a printing table according to the conventional method well known to those skilled in the art. The printed fabric is heat set in the oven at 160 ° C for 5 minutes.

Using the synthesized product as a thickener in the paste, a very good printing quality is obtained, without defects and with very good color rendering.

Example 4

A reverse emulsion synthesis is carried out, under operating conditions comparable to those of Example 3, with the same compounds used in identical proportions. After the cooking phase, 4.5 grams of polyoxyethylenated nonylphenolpolyoxyethylenated comprising 10 ethylene oxide units (HLB = 13.3) are introduced into the medium, followed by distillation of the solvents (water then heptane). under the same conditions as in Example 3.

The powder (P4) is obtained, the characteristics of which are as follows - average size of the agglomerates: 280 μm,

The viscosity of a gel containing 1% powder (P4) in water is 15,000 cP (measured with a Brookfield viscometer, module 6, speed 50 rpm).

On the other hand, while the gel containing 1% of powder (P3) in water is turbid, that which is prepared with the powder (P4) is clear and transparent.

Used in pigment printing under the same conditions as in Example 3, the powder (P4) leads to similar application results.

Example 5

Summary:

In a stirred reactor comprising a double cooling jacket, a tapping allowing the introduction of a temperature probe and reagent inlets, 1 13.4 grams of glacial acrylic acid (Elf-Atochem) are mixed with gentle stirring with 28.3 grams of demineralized water. In parallel, an aqueous sodium hydroxide solution is prepared by very slow addition of 53 grams of sodium hydroxide tablets, analytical reagent, to 232 grams of demineralized water. After total dissolution of the sodium hydroxide and cooling of the solution (the dissolution is exothermic), this solution is added dropwise to the reactor containing acrylic acid. The operation is carried out with stirring, taking care not to allow an increase in temperature in the medium beyond 30 ° C.

In a stirred container, 225 grams of heptane are mixed with 21 grams of Hypermer 2296 until the latter are completely dissolved. This solution constitutes the organic phase. The solution of acrylic acid partially neutralized by soda, the preparation of which has just been described, is introduced into a stirred container and then 277.2 grams of an aqueous solution at 50% by weight of acrylamide are added, as well as 0 , 1 gram of N-methylene-bis-acrylamide and 0.9 grams of Versenex 80 complexing agent (Dow Chemical). This solution constitutes the aqueous phase.

The stirring speed is fixed at 700 rpm and the oxygen is removed by bubbling nitrogen through at room temperature for one hour. This time is taken advantage of for the preparation of a solution of cumene hydroperoxide by adding 0.053 grams of a commercial solution at 80% by weight in cumene, of cumene hydroperoxide, in 5 grams of heptane. A solution of sodium metabisulfite is also prepared, by adding 0.133 grams of sodium metabisulfite in 100 grams of demineralized water. The 5 grams of cumene hydroperoxide solution are introduced into the reactor after one hour of degassing; nitrogen sparging and agitation are maintained. 15 minutes after this addition, (during this time, by isolating the jacket, the heat transfer fluid is heated to 50 ° C), 2.0 grams of Na ₂ S ₂ O ₅ solution are introduced into the reactor and then the rest of the sodium metabisulfite solution is added at a speed of 30 to 50 milliliters per hour. The circulation of the heat transfer fluid is restored inside the double jacket. The start of polymerization causes a rapid increase in the reactor temperature. The addition of the sodium metabisulfite solution is stopped as soon as the temperature stops rising. The unused sodium metabisulfite solution is discarded.

The circulation of the heat transfer fluid in the double jacket is maintained and its temperature is fixed at 80 ° C., the bubbling of nitrogen is reduced. The product is kept stirring for one hour for "cooking". Then introduced 100 grams of heptane, then the temperature of the jacket is increased to 1 15 ° C for the concentration step. After elimination of 70% to 75% of water, the reaction medium is cooled and then, at ambient temperature, it is transferred to a dryer (double jacket reactor) positioned horizontally, provided with 2 nozzles, one for nitrogen, the other for a temperature probe and an agitator linked to a variable speed motor. The temperature of the jacket fluid is raised to 11 ° C. The remaining water is eliminated, then the organic phase until the powder is obtained (P5) and the process ends with a light sweep of nitrogen at the end of drying.

Characteristics of the powder:

The powder (P5) obtained has the following characteristics:

- average size of the agglomerates: 250 μm,

Claims

1. Aggregates of hydrophilic polymers of low cohesion having an average size of between 50 and 1000 μm, made up of elementary particles of hydrophilic polymers of individual size between 0.1 and 10 μm and preferably between 0.2 and 5 μm.

2. Agglomerates according to claim 1, characterized in that said polymers consist of: - 90 to 100% by mole of units derived from at least one monomer A chosen from the group consisting of unsaturated ethylenic monomers with high solubility in water ,

0 to 10 mol% of units derived from at least one monomer B chosen from the group consisting of unsaturated ethylene monomers with low or medium solubility in water,

0 to 1% by mole of units derived from at least one crosslinking agent C,

- 0 to 5 mol% of units derived from at least one monomer D containing a hydrophobic group, or from the chemical modification of the polymer with chemical reagents E, intended to create hydrophobic groups.

3. Agglomerates according to one of the preceding claims, characterized in that A is chosen from the group consisting of the following monomers: ethylenic monomers comprising carboxylic groups such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and their sodium, potassium, ammoniacal or amine salts such as triethylamine, butylamine, morpholine and ethanolamine, the amides of these carboxylic acids and in particular, acrylamide and methacrylamide as well that their N-substituted derivatives at high water solubility, their esters with high water solubility such as dimethyl or diethyl amino (ethyl or propyl) (meth) acrylate and their salts, the quaternized derivatives of these cationic esters such as, for example, chloride acryloxyethyl trimethylammonium, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), vinylsulfonic acid, vinylphosphoric acid, vinyllactic acid and their salts, acrylonitrile, N-vinylpyrrolidone, N- methylformamide, vinyl acetate, N-vinylimidazoline and its derivatives, N-vinylimidazole and derivatives of the diallylammonium type such as dimethyldiallylammonium chloride, dimethyldiallylammonium bromide, diethyldiallylammonium chloride.

4. Agglomerates according to one of the preceding claims, characterized in that B is chosen from the group consisting of: vinyl acetate, styrene, methyl acrylate, ethyl acrylate, butyl acrylate , methyl methacrylate, hydroxyethyl acrylate or hydroxyethyl methacrylate.

5. Agglomerates according to one of the preceding claims, characterized in that C is chosen from the group containing: - polyunsaturated monomers comprising, at least, two identical or different nonconjugated ethylenic double bonds, of acrylic, methacrylic, vinyl type or allyl derivatives such as di (meth) acrylamides such as N-methylene-bis-acrylamide, or poly (meth) acrylates such as di (meth) acrylates of polyethylene glycol, the ^"diacrylate of ethylene glycol, tri (meth) trimethylolpropane acrylate, propylene glycol diacrylate, butanediol diacrylate, hexanediol di (meth) acrylate, diallylic compounds - functional ethylenic monomers comprising an unsaturation and a functional group of alcohol, acid, amino, epoxide, metal salt or other chemically reactive group type, such as N-methylol acrylamide, N-methyloI methacrylamide, glycidyl acrylate and glycidyl methacrylate

saturated polyfunctional compounds comprising at least two functional groups of alcohol, acid, amino, epoxide, metal salt or other chemically reactive group such as glyoxal, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, epichlorohydrin, ethylene di-amine and zinc acetate.

6. Agglomerates according to one of the preceding claims, characterized in that D is chosen from the group consisting of ethylenic monomers containing a group of formula:

(1) (CH2-CH2O) _n -R in which R is a hydrophobic group containing at least 8 carbon atoms, n is an integer between 0 and 50 and preferably between 8 and 25.

7. Agglomerates according to one of claims 1 to 5 characterized in that the reagent E is chosen from the group consisting of molecules having the following chemical structure:

8 Process for obtaining agglomerates of hydrophilic polymers such as those of the preceding claims consisting of:

the reverse emulsion by mixing and stirring an organic phase containing at least one surfactant and an aqueous phase containing from 20 to 80% by weight and preferably from 30 to 60% of at least one monomer; the mass ratio between aqueous phase and organic phase being between 0.5 and 4.0 and preferably between 2.5 and 3.5 and the surfactant content of the emulsion being from 0.1 to 10% by weight and preferably from 0.5 to 6%,

- polymerization using a radical initiator at a temperature between 5 and 120 ° C., the quantity of initiator to be used varying between 0.005 and 0.5% relative to the total weight of monomer (s) ( s), and preferably between 0.01 and 0.1% relative to the weight of monomer (s),

- removal of the water from the reverse emulsion by azeotropic distillation, and

- the final elimination of the organic phase by distillation and obtaining the powder.

9. Method according to claim 8 characterized in that the organic phase is a hydrocarbon liquid forming an azeotrope with water such as n-heptane, cyclohexane, iso-octane, toluene and their mixtures.

10. The method of claim 8 or 9 characterized in that the surfactant is chosen from the group of generally nonionic surfactants having a hydrophilic-lipophilic balance (HLB) between 3 and 10 on the Griffin scale.

1 1. Process according to Claim 10, characterized in that the surfactant is chosen from sorbitan monooleate, sorbitan sesquioleate, their mixture or the surfactant copolymers, for example, of the ABA triblock copolymer type where A is a polyester derived from 1 2-hydroxy stearic acid and B is a polyethylene oxide.

1 2. Method according to one of claims 8 to 1 1 characterized in that the polymerization is initiated by a liposoluble or water-soluble radical initiator selected from initiators whose kinetics of decomposition allows polymerization temperatures between 40 and 1 20 ° C or the reducer / oxidant (redox) initiator pairs allowing polymerization temperatures between 5 and 120 ° C.

13. The method of claim 1 2 characterized in that the initiation is ensured by a redox system which allows reverse emulsion polymerization according to a process called "ballistic", during which the temperature of polymerization start is room temperature or under ambient, and the final polymerization temperature is between 40 and 95 ° C., the temperature rise being controlled by the rate of addition of the reducing solution, the oxidant being initially present within the emulsion.

14. Method according to one of claims 8 to 13 characterized in that one operates a baking phase after the polymerization phase by bringing the reactor temperature between 75 and 120 ° C, and preferably between 80 and 100 C, for a period of between 30 and 90 minutes.

1 5. Process according to one of the preceding claims, characterized in that the chemical modification of the polymer is carried out by adding the reactive compound E of claim 7 to the medium, either during the cooking phase or during the distillation phases.

1 6. Method according to one of the preceding claims characterized in that the crosslinking is completed by the addition in the medium of the polyfunctional compound of claim 5 either during the cooking phase or during the distillation phases.

17. Method according to one of the preceding claims, characterized in that a high HLB surfactant of between 10 and 18 at a content of between 0.5 and 10% is added to the reverse emulsion, before or after the polymerization. by weight and preferably from 2 to 5% relative to the monomers. 18 Organic dispersion containing from 1.0 to 60.0% by weight of hydrophilic polymers obtained by the dispersion of the agglomerates according to claims 1 to 7 in an organic non-solvent.

1 9 Aqueous solution containing from 0.1 to 30% by weight of hydrophilic polymers obtained by the dissolution of the agglomerates according to one of claims 1 to 7.

Use of the agglomerates of claims 1 to 7 as thickeners in a composition for pigment printing. 21. Use of the agglomerates of claims 1 to 7 as flocculants for water treatment, as sludge dewatering agents, as retention agents in the paper industry, as thickeners in fields such as paints, cosmetics, adhesives and adhesives, ^" building, textiles and paper and as materials control agents.