WO2000001757A1 - Acrylic polymers in substantially aqueous suspensions - Google Patents

Abstract

The invention concerns novel high molecular weight polymers, prepared in a dispersion containing practically no oil phase. The monomers are first polymerised in a water-in-oil emulsion, including, in a non-exclusive example, a specific hydrophobic monomer. The resulting emulsion is dried for example by azeotropic evaporation or by spray drying; a coarse powder is obtained which can be re-dispersed in an aqueous medium wherein the water soluble polymer is not soluble, by applying a shearing sufficient to obtain a fine dispersion. The resulting dispersion may be cationic, anionic or non-ionic, or amphoteric and is useful for treating water, in the paper-making industry, the oil and parapetrolic industry, for ore and mineral processing, conditioning soils and foodstuff processing and packaging.

Description

 ACRYLIC POLYMERS IN ESSENTIALLY AQUEOUS DISPERSIONS.

The present invention relates to the technical sector of water-soluble or swellable acrylic polymers.

More particularly, the invention relates to obtaining essentially aqueous dispersions of polymers of this type.

By “essentially aqueous” is meant here dispersions or emulsions containing practically only the polymer and an aqueous phase, with inseparable oily residues originating from a water-in-oil emulsion polymerization process in which the oil phase may have been eliminated according to the invention, with the exception of said residues. The oily residues may also contain traces of surfactants used either during the water-in-oil emulsion polymerization process, or in subsequent steps.

Without wishing to be bound by a precise proportion, the applicant is able to indicate for general information that the term "essentially aqueous" or the equivalent terminologies used in the present application represents a total of oily residues less than 5% by weight of a dispersion according to the invention at 10% - 30% by weight of polymer, which is a representative commercial concentration range.

Technological background:

Numerous water-soluble or water-swellable polymers have been developed and supplied over the past thirty years or so, in very numerous industrial sectors such as water treatment and in particular waste water, the manufacture of sheets of paper and cardboard, l petroleum and petroleum services industry, the processing of ores and various minerals such as fillers and pigments, including recovery of alumina by the so-called "Bayer" process, soil conditioning, treatment and conditioning of foodstuffs, cosmetics and the like.

These polymers fulfill numerous functions, the most important of which are those of flocculant, coagulant, flotation agent, thickener, dispersants, and the like.

The invention relates to all of these functions and applications, which are well known to those skilled in the art and will not be repeated here.

The monomers and, consequently, the polymers manufactured and used in these applications are also well known to those skilled in the art. Most of the polymers used are copolymers of acrylamide and acrylic acid, and quaternary salts of dimethylaminoethyl acrylate. In most cases, modern polymers are supplied in the form of powders, or water-in-oil emulsions, or solutions. Only a very small number of water-soluble or swellable polymers are supplied in the form of aqueous dispersions.

Advantages and disadvantages of powders:

It is a concentrated form which reduces the storage and transport costs.

This concentrated form reduces storage and transport costs, does not involve the use of other chemicals which would increase the cost of the raw material, does not involve too many complications aimed at satisfying national and international regulations, such as especially those relating to the environment and the like. However, this form requires additional treatment, loads in terms of work and energy, both at the manufacturing level and at the level of the final application. Dry polymer powders must be recovered by some type of drying operation or removal of liquids under solvent, and then require solubilization and dispersion before use. Not only is a lot of energy used for drying the product at high temperatures, but the heating operation can also generate a certain crosslinking which creates insoluble parts in the polymer. It is also necessary to use extremely bulky and expensive mechanical equipment for handling the polymer during its preparation and processing, which involves investment and maintenance costs. Finally, at the level of the final application of the powder, a charge of polymer often requires a slow addition of said polymer to water or another medium to be treated, this addition to be followed by long and vigorous stirring and possibly , in addition, the so-called aging waiting period.

Advantages and disadvantages of solutions:

These polymers are easy to prepare and use, their production does not require significant investment, and the product which is used in the final application contains only polymer and water. However, this technique has an important drawback: in order to maintain the viscosity of the solution at a value lower than that where the product would no longer be pumpable, it is necessary to reduce either the molecular weight of the polymer or the concentration of the polymer in the solution. As it is impossible to obtain simultaneously the high molecular weight which is now required for most modern applications, and the high content of active material (polymer) which is necessary to keep the cost of transport and the cost of storage, this form of polymer in solution in water has never been widely used in industry.

Advantages and disadvantages of reverse water-in-oil emulsions:

This technique was originally described in USP Patent No. 3,284,393, of November 8, 1966, Vanderhoff et al., And in USP No. Re 28,474 reissued on July 8, 1974, DR Anderson AJ Frisque. This technique requires conventional equipment and low costs for the production and processing of the polymer. It also almost completely reduces the formation of insoluble parts in the polymer. The water-in-oil type emulsion can contain a reasonably high concentration of polymer while remaining fluid, and the high specific surface of the dispersed phase of the polymer makes the polymer solubilization or swelling very fast. Consequently, the use of a water-in-oil type emulsion means that the end user must not only buy the polymer but also oily type surfactants and in some cases a rather large amount of water must be transported, while all of these products will be introduced into the load used. This also results in a significant additional cost of the raw material, transport and storage, and there are difficulties, moreover, in satisfying national or international regulations or regulations.

Advantages and disadvantages of aqueous dispersions

An aqueous dispersion technique has been developed in order to avoid the disadvantages of the above three techniques and to try to combine their advantages.

In this technique, the polymerization is carried out in water containing a salt and / or other chemical agents in solution or in dispersion. The monomer or mixture of monomers is soluble in this aqueous mixture. The polymer formed during the polymerization precipitates when it reaches a sufficiently high molecular weight. At the end of the polymerization, a liquid dispersion of polymer particles in suspension in the aqueous mixture is recovered. This dispersion can be diluted in pure water, then the dilution of the salt and / or other chemical agents in solution or dispersed stops their action. preventing the polymer from dissolving in water. The polymer can therefore go into solution.

The advantages of this technique are obvious. As for these dispersions, the cost of the raw material is low, i.e. similar to that of powdered polymers, since the product is composed almost essentially of polymer and salt and small amounts of other chemicals, and water, while there is no oil, surfactant, or large amounts of other expensive chemicals in the product. The product has the same determining advantage as the water-in-oil type emulsion, which has very rapid solubilization or swelling of the polymer in water, due to the large specific surface of the dispersed phase of the polymer. The polymer content in the dispersion can be quite high, up to 30%, which avoids the major drawback of the solution form of the polymer.

Prior art

The first descriptions of techniques for preparing aqueous dispersions of water-soluble or water-swellable polymers can be found in USP No. 4,380,600 by Hosoda et al., And in USP No. 4,929,655 by Takeda and Kawano, as well as in USP N ° 5,600,590 by Takeda and Kawano also. During the past 15 years, several other publications have been made on this subject, following these first patents.

In US patent 4,380,600, April 19, 1983, Hosoda et al (Showa Denko), aqueous dispersions of water-soluble polymer obtained by precipitation polymerization in the presence of polyethylene glycol or other polar polymers are described. The molecular weight of the polymer obtained is low and does not correspond to what those skilled in the art call a flocculant. In this context, mention will be made of patent EP 0 170 394 according to which a powder is dispersed in a solution of a balancing agent which forms an aqueous continuous phase and which is chosen according to the case, and from the very specific combinations described, among anionic polymers, polyDADMAC, polyethylene imine, a reaction product of epichlorohydrin and the like. The particle sizes of the polymer thus dispersed are greater than 20 or 50 or 100 microns, and up to mm, which reveals one of the limits of the use of powders, ie the impossibility of obtaining particle sizes very weak. The stability of such products is very low. It is in fact a dispersion of fines, therefore unstable.

This Allied Colloids patent (European patent 0 170 394 inventors Farrar and Flesher) therefore describes in fact aqueous dispersions of finely ground powder. These dispersions which have not known any commercial development have the disadvantage of having to use large amounts of balancing agent and that of having coarse polymer particle sizes which prevent rapid dissolution of the polymer when the add the dispersion to the water.

The examples describe balancing systems, but not the process for obtaining the polymers used. This 1985 patent did not give rise to commercial products, and it predates recent advances in oil-free products, which themselves have limits that are irreconcilable with industrial use.

In the patent US Pat. by precipitation polymerization of a mixture of monomers comprising at least one hydrophobic monomer of the dimethylaminoethyl acrylate type quaternized with benzyl chloride, in the presence of a dispersing polymer based on dimethylaminoethyl acrylate quaternized with benzyl chloride and / or a salt inorganic of the ammonium sulafte type. The molecular weight of the polymer obtained is low and does not correspond to what those skilled in the art call a flocculant.

In the European patent 0 630 909 filed on May 31, 1994, inventors Ramesh et al (Nalco) there is described a method of continuous addition of monomer in a precipitation polymerization process under conditions close to the patents of Kyoritsu Yuki cited above. . The aim is to reduce the viscosity peak of the dispersion during the polymerization phase and to allow the polymer concentration in the final dispersion to be increased. The molecular weight of the polymer obtained is low and does not correspond to what those skilled in the art call a flocculant.

In the European patent 0 657 478 filed on December 9, 1994, inventors Werges et al (Nalco) there is described an optimization of the amount of salt in a precipitation polymerization process under conditions close to the patents of Kyoritsu Yuki cited above. The aim is also to reduce the viscosity peak of the dispersion during the polymerization phase and to allow the polymer concentration in the final dispersion to be increased. The molecular weight of the polymer obtained is low and does not correspond to what those skilled in the art call a flocculant.

In European patent 0 637 598 filed on June 10, 1994, inventors Ramesh and Cramm (Nalco), a use of a dispersing polymer consisting of Dadmac units copolymerized with a hydrophobic monomer is described in a precipitation polymerization process under close conditions. of the Kyoritsu Yuki patents cited above. The aim is also to reduce the viscosity peak of the dispersion during the polymerization phase and to allow the polymer concentration in the final dispersion to be increased. The molecular weight of the polymer obtained is low and does not correspond to what those skilled in the art call a flocculant.

In the European patent 0 573 793 filed on May 8, 1992, inventors Messner et al. (Rohm GmbH) there is described a polymer dispersion soluble in water obtained by copolymerization of a monomer soluble in water with a hydrophobic monomer and an amphiphilic monomer in the presence of a large (about 10%) amount of Dadmac homopolymer. In this process there is no use of salt. The molecular weight of the polymer obtained is low and does not correspond to what those skilled in the art call a flocculant.

Also known is US patent 5,614,602 filed July 9, 1996, inventors Connors et al (BetzDearborn) or are described dispersions comparable to those described in previous patents. Their main teaching is the use of N-Alkylacrylamide or NN-dialkylacrylamide as a hydrophobic monomer. The resulting products seem to have the same disadvantages as the previous patents. There is no known industrial development corresponding to this patent.

We also know US patent 5,696,228 filed October 3, 1996, inventor Coville (Cytec) or are described dispersions comparable to those described in previous patents. The resulting products have the same disadvantage of low molecular weight. There is no known industrial development corresponding to this patent.

Many problems have been solved in this technique from the start, that is to say the appearance of technology, as can be seen from the above list of the prior art. However, there remains a totally decisive problem, which explains why this technique has not been used, until now, by the producers of polymers, as much as the powder or water-in-oil emulsion forms. This decisive and even prohibitive drawback lies in the fact that none of the techniques described above in the prior art can lead to a molecular weight of the polymer as high as that obtained in the techniques of powder or emulsion water-in -oil. This is a very important problem since most modern applications of water-soluble or water-swellable polymers, and in particular in the field of waste water treatment, papermaking, petroleum industries or para-petroleum, mineral or mineral processing, and the like, in which the main use is as a flocculant, require a very high molecular weight.

The present invention provides a method which can solve this problem, and can make it possible to obtain aqueous dispersions of polymers soluble in water or swellable with water, having a very high molecular weight, and which can therefore be then use in a large number of applications, with the requirements of modern industry, and in particular as flocculating agents in water treatment, papermaking, the petroleum and para-petroleum industries, the treatment of minerals and ores , with results at least equal to those of the best products that we know how to prepare today using powder or water-in-oil emulsion techniques.

As can be seen from reading the above patents, this technique has solved many problems. However, one problem remains to be solved, that of obtaining very high molecular weights. None of the systems developed for aqueous dispersions has managed to reach, by far, the high molecular weights that we now know how to obtain corally in emulsion or powder systems, of the order of tens of millions. of Dalton and above, on the order of several tens of millions of Dalton. This problem is essential, because the industry - in particular in all the aforementioned technical sectors, and in particular for applications as flocculants - is accustomed to using polymers of very low molecular weight and it would be impossible for it to return to average molecular weights or weak, of the order of a million, or a few million, of Dalton. This impossibility is due to the decisive advantages of very high molecular weights in terms of efficiency and cost and to the investments made for at least two decades to the use of very high molecular weights. The current impossibility of achieving very high molecular weights is undoubtedly the reason why no commercial aqueous dispersion type system, which can be used in major applications, has been developed.

Without wishing to be bound by any theory, the Applicant considers that the precipitation operation would be the main cause of the impossibility of reaching high molecular weights. The Applicant considers that this operation could be such as to prematurely stop the propagation of the polymer chains.

The major current techniques are therefore blocked in their advancement towards a flocculant as "perfect" as possible, ie bringing together a maximum of the advantages of the previous techniques, and a minimum of their disadvantages:

powders by their very long dissolution time, which cannot currently be reduced considerably;

reverse emulsions by their high content in the oily phase;

the few attempts at aqueous emulsions by a rhedibitory limitation in molecular weight.

Summary of the invention

An object of the invention is to provide a system of hydro-soluble (co) polymer (s) or swellable with water, in aqueous or essentially aqueous dispersion, having a very high molecular weight and capable of consequence of being used in the aforementioned applications, and in particular as flocculants in the various industries indicated and others known to those skilled in the art.

Another object of the invention is to propose a process for the preparation of such systems or dispersions. Another object of the invention relates to the application of these systems and dispersions in the abovementioned industries, in particular as flocculants.

According to the general method of the invention, a conventional (co) polymerization in reverse emulsion (water-in-oil) is carried out in a first step leading to the very high molecular weight desired, then the emulsion is dried in a second step to obtaining the (co) polymer in powder form, then dispersing the powder (co) polymer thus obtained in an aqueous medium in which it is not soluble or only slightly soluble.

According to a first preferred embodiment of the invention, the drying of the emulsion in the second step is carried out by azeotropic evaporation followed by sedimentation and filtration.

According to a second preferred embodiment of the invention, the drying of the emulsion in the second step is carried out by a spray-drying technique or "spray-drying".

One such spray drying technique has previously been developed by The Dow Chemical Company for drying polyacrylamide emulsions.

This process, which has been used in Central America, consists of loading the emulsion in a spray dryer; at the outlet of the dryer, the fines are sent under nitrogen to a cyclone; at the high outlet of the cyclone, the flow is directed to a scrubber which allows the fines contained in an oil phase to be separated into the bottom product. The top product is directed to a condenser then a decanter, which allows the oil phase to be recycled and the water to be separated. The product at the bottom of the cyclone is combined with the product leaving the dryer. The whole is directed to a mixer then to a compactor, a crusher, a sieve or selector and the desired product is obtained at the desired particle size. The compaction can be helped by a binder, preferably water so as not to introduce an oil phase. We can according to a mode of realization combine compaction cylinders with a pre-granulator then a granulator then a sieve, all possibly in vertical arrangement.

According to a preferred variant, the spray dryer is a device with high energy spraying, and particles of dimensions <20 or <10 microns are obtained; the compactor is replaced by resuspension in water, to a particle size <10 microns, then we pass to the colloid mill which allows to reach a dimension of the order of a micron.

This variant will be the technology preferably used according to the invention.

According to a third preferred embodiment of the invention, the oil used for the oil-in-water (co) polymerization in emulsion of the first stage has a flash point less than about 65 ° vs.

According to an entirely preferred embodiment of the general method according to the invention, in the first step, the copolymerization of a mixture of monomers soluble in water or dispersed if they are insoluble in water is carried out. at least one has a hydrophobic character. Preferably, the initial mixture of monomers will comprise a hydrophobic fraction representing between approximately 1 and 40 mol%, preferably 15 and 25 mol% of the mixture of monomers.

According to another embodiment of the general method of the invention, the aqueous medium used in the third step for the dispersion of the powder consists of an aqueous mixture comprising at least one salt and / or other chemical additives in solution whose function is to prevent the dissolution of the (co) polymer powder in the aqueous medium. According to a preferred embodiment, said aqueous medium will comprise chemical agents in solution or dispersed if they are insoluble in water, the function of which is to promote the dispersion of the (co) polymer powder and / or d 'exert a stabilizing effect on the dispersion thus obtained, or an encapsulating effect.

By "encapsulating effect" is meant here the coating of the polymer particles, by means of a chemical or physicochemical surface reaction, with a layer of one or more polymeric or other additives, for example with a polymerization reaction or surface precipitation, by covalent bonds or not.

According to yet a preferred embodiment of the invention, a shear is applied to the aqueous dispersion of the coarse polymer powder to reduce the size of the particles of polymer in dispersion to a size as close as possible to the size obtained. during the first emulsion polymerization step, ie <20 or 10 microns, preferably <5 or of the order of 1 micron or <1 micron.

According to the invention, an aqueous or substantially aqueous dispersion of a water-soluble or swellable (co) polymer is recovered at the end of the third step.

The crucial advantage of the invention is that this polymer has the same chemical characteristics as the polymer obtained during the first step in water-in-oil emulsion, and in particular the very high molecular weight desired. By an appropriate choice of monomers, the polymer obtained can be anionic, cationic, nonionic or amphoteric, and very preferably contains the abovementioned proportion of hydrophobic groups.

The invention applies in particular to the preparation of branched or crosslinked copolymers. We know that these (co) polymers are particularly useful as flocculants for the treatment of waste water and in particular municipal effluents.

The invention also applies to linear or slightly or strongly branched (co) polymers, in particular those branched or crosslinked with a proportion of crosslinking agent, in particular, by way of an often preferred but nonlimiting example, of MBA (methylenebisacrylamide ) between about 5 and about 30 ppm or 60 ppm to obtain a flocculant, or from 5 to 1000 ppm, preferably> 30 and up to 100 or more (1000) to obtain a thickener or a superabsorbent.

The following crosslinking or branching agents may be used, including the MBA.

Cross-linking or branching monomers:

The compounds used as crosslinking or branching monomers contain at least two polymerizable groups. Examples of compounds comprising two ethylenically unsaturated groups which can be polymerized by the radical route are the following:

(1) Alkenyldi (meth) acrylates, such as 1, 6-hexanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, 1, 12-dodecanediol di (meth) acrylate, 1, 18-octadecanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, methylene di (meth) acrylate, 2,2'-bis (hydroxymethyl) -1, 3-propanediol di (meth) acrylate, and preferably ethylene glycol di ( meth) acrylate, 1,3-propanediol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, and 1,4-butanediol di (meth) acrylate;

(2) Alkylene di (meth) acrylamides, for example N-methylene di (meth) acrylamide, N, N'-3-methylbutylidene bis (meth) acrylamide, N, N'- (1, 2-dihydroxyethyl) bis (meth ) acrylamide, and preferably N, N'-hexamethylene bis (meth) acrylamide, and in particular preferably N, N'-methylene bis (meth) acrylamide;

(3) Polyalkoxydi (meth) acrylates of the following formula: ROOR

H2C = C— C— O— ((CH ^) - O—) p _ C— C - CH ^

in which R represents a methyl radical or a hydrogen group; m represents an integer in the range 2-6; and p represents an integer in the range 2-50.

Examples of such products include polypropylene glycol di (meth) acrylates (m = 3), with p in the range 4-25; polybutylene glycol di (meth) acrylates (m = 4), with p in the range 5-40; and preferably polyethylene glycol di (meth) acrylates (m = 2), with p in the range 2-45, for example diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate; and, more preferably, polyethylene glycol di (meth) acrylates with p in the range 5-20;

(4) examples of additional di (meth) acrylates which can be used include the following: benzylidene di (meth) acrylate, bisphenol-A di (meth) acrylate, 1,3-di (meth) acryloyloxy-2-propanol, hydroquinone di (meth) acrylate, ethanedithiol di (meth) acrylate, propanedithiol di (meth) acrylate, polyethylenedithiol di (meth) acrylate and polypropylenedithiol di (meth) acrylate;

(5) the divinyl compounds are, for example, the following: 1,4-butanediol divinyl ether, divinylbenzene, butadiene, 1,6-hexadiene; di (meth) allyl compounds, such as, for example, di (meth) allyl phthalate or di (meth) allyl succinate; vinyl (meth) acrylic compounds, such as, for example, vinyl (meth) acrylate; or preferably (meth) allyl (meth) acrylic compounds, such as for example allyl (meth) acrylate.

Examples of compounds having three or more ethylenically unsaturated polymerizable groups which can be used according to the invention include the following: glycerin tri (meth) acrylate, 2,2-dihydroxymethyl-1-butanol tri ( meth) acrylate, trimethylolpropane triethoxy tri (meth) acrylate, trimethacrylamide, (meth) allylidene di (meth) acrylate, 3-allyloxy-1, 2-propanediol di (meth) acrylate, triallyl cyanurate or triallyl isocyanurate; and also (as representative compounds comprising more than three ethylenically unsaturated polymerizable groups) pentaerythritol tetra (meth) acrylate and N, N, N'N'-tetra (meth) acryloyl-1, 5-pentanediamine.

The invention also relates to a process for preparing a system of hydro-soluble (water) or swellable (co) polymer (s) with water, in aqueous or essentially aqueous dispersion, having a very high molecular weight, of order of several millions to several tens of millions of Dalton, characterized in that a conventional (co) polymerization in reverse emulsion (water-in-oil) is carried out in a first step, leading to the desired very high molecular weight, then dry the emulsion in a second step to obtain the (co) polymer in powder form, then disperse the (co) polymer powder thus obtained in an aqueous medium in which it is not soluble or only slightly soluble.

The invention also relates to a process characterized in that in the first step of water-in-oil reverse emulsion polymerization, no branching or crosslinking agent is used, or else as agent branching or crosslinking an agent chosen from the agents listed below. above.

According to a particular embodiment of the invention, starting from an inverse emulsion of the appropriate monomers, such as those mentioned or used in the two patents EP '780 and EP'237, a suitable proportion of crosslinking or branching agent is added, usually between 5 and 60, preferably 10 and 40 ppm, it is polymerized in reverse emulsion and the product obtained is transformed into a powder by

Either a spray drying step of the type described above,

• either an agglomeration stage preceding a filtration stage. Polymers such as those described in EP'780 or EP'237, which can be used directly as flocculants, are then obtained directly in the form of a powder.

Detailed description of the invention:

The present invention relates to a process for preparing an aqueous dispersion of a water-soluble or water-swellable polymer, which is characterized by the following steps:

1st stage: A monomer or a mixture of monomers is polymerized in the form of a water-in-oil emulsion, in a manner widely known to those skilled in the art. The polymer thus recovered must have the inherent property of being soluble in water but of not being soluble, or then very sparingly soluble, in the aqueous mixture which will be described in the 3rd step. The oil used in the composition of the above-mentioned water-in-oil emulsion should preferably have a flash point of less than 65 ° C., so that it can be easily evaporated.

2nd stage: The water-in-oil emulsion of the 1st stage is dried by an azeotropic evaporation technique, followed by a sedimentation and filtration stage, or else is dried by a spray drying technique (“spray -drying ”). A polymer is recovered at this stage in the form of a coarse powder.

3rd stage: The coarse polymer powder recovered in the 2nd stage is dispersed in an aqueous mixture comprising a salt and / or other chemical agents in solution or in dispersion, the aim of which is to avoid the solubilization of the polymer in the medium under consideration, and to simultaneously promote its good dispersion, while preferably having a stabilizing effect. Then, a shear is applied in order to reduce the particle size of the polymer thus dispersed up to a particle size as close as possible to the initial dimension of the polymer particle obtained in the water-in-oil emulsion at the end of the first step.

An aqueous dispersion of the water-soluble or water-swellable polymer is thus recovered. This aqueous dispersion has the same chemical characteristics as the polymer which was prepared initially by a water-in-oil emulsion polymerization in the first step. This dispersion can be based on an anionic, cationic, nonionic, amphoteric polymer, and the polymer generally contains hydrophobic groups, so that the polymer is soluble in water but insoluble in the aqueous mixture comprising a salt and / or other chemical agents in solution or dispersed, in the middle of the third stage, where the solubilization of the polymer is avoided and where, on the contrary, good dispersion is favored with a stabilizing effect.

FIRST E T A P E: POLYMERIZATION IN REVERSE WATER EMULSION N S -H U I LE:

The following monomers can be used. Vinyl addition monomers

Nonionic monomers

The nonionic monomers which are useful according to the invention can be chosen from all the water-soluble allylic or vinyl monomers which do not have a sensitive anionic or cationic charge. Preferred monomers belonging to this class include acrylamide and methacrylamide, N-isopropylacrylamide, Nt-butylacrylamide, and N-methylolacrylamide. Also vinylformamide, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkyl acrylates and methacrylates can be used. A non-vinyl monomer preferred ionic will be acrylamide. Other nonionic monomers can be used, without departing from the scope of the invention.

The anionic monomers

The anionically charged monomers useful in the present invention can be selected from a large group. The monomers can have acrylic, vinyl, maleic, allylic functionalities and contain a carboxy, phosphonate, sulfonate group or another group with an anionic charge, or else the ammonium or alkaline earth metal or alkali metal salt thereof. such a monomer.

Examples of suitable monomers include acrylic acid, methacrylic acid, acrylamidomethylpropanesulfonic acid, acrylamidomethylbutanoic acid, maleic acid, fumaric acid, itaconic acid, vinylsulfonic acid, styrene acid sulfonic, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid, a sulfomethylated acrylamide, a phosphonomethylated acrylamide and their water-soluble salts of an alkali metal, an alkaline earth metal, and ammonium.

Cationic monomers

As cationic monomers, those corresponding to the following formula may be used:

CH2 = C - R1 R2

0 = C - A1 - B1 - N + - R4 X-

R3 wherein R represents H or CH ₃ ; R ₂ and R ₃ represent CC ₃ alkyl groups; R ₄ represents H or a CC ₃ alkyl group; A ^ represents an oxygen or NH atom; B represents a C ₂ -C ₄ alkylene group or a hydroxypropylene group, and X ^" is an anionic counterion.

The cationic monomers can also be chosen from the monomers corresponding to the following general formula:

wherein R represents H or CH ₃ ; R ₂ and R ₃ each represents a CC ₃ alkyl group; A ^ represents an oxygen or NH atom; B represents a C ₂ -C ₄ alkylene group or a hydroxypropylene group; and X ^ represents an anionic counter ion.

Also usable are halides of diallyldialkylammonium.

Hydrophobic monomers:

The hydrophobic monomers can be chosen from acrylamide derivatives such as N-alkylacrylamide for example N-isopropylacrylamide, N-tert-butylacrylamide, octylacrylamide as well as N, N-dialkylacrylamides such as N-N-dimethyiacrylamide.

The hydrophobic monomers can also be chosen from the following cationic monomers:

wherein R ₁ represents H or CH ₃ ; R ₂ and R ₃ each represents a C ₁ -C ₃ alkyl group; A ₁ represents an oxygen atom or NH; B ₁ represents a C ₂ -C ₄ alkylene group or a hydroxypropylene group; and X ^ represents an anionic counter ion.

The hydrophobic monomers can also be chosen from the following cationic monomers:

CH2 = C - R1 R2

0 = C - A1 - B1 - N + - R4 X-

I R3

wherein R _t represents H or CH ₃ ; R ₂ and R ₃ represent CC ₃ alkyl groups; R ₄ represents H or a C 1 -C ₄ alkyl group; A represents an oxygen or NH atom; B ₁ represents a C ₂ -C ₁₀ alkylene group or a hydroxypropylene group, and X ^" is an anionic counter ion.

The monomers corresponding to the following general formula can also be used in the present invention:

R1

CH2 = C - R2 W, O _{n Λ} 0 _Λ 0 / _IΛ 0 _Λ 1-7, _B 57

22 in which R ₁ represents a hydrogen atom or a CC ₅ alkyl group;

R ₂ represents a C ₁ -C ₂₀ alkyl, cycloalkyl, aryl, or aralkyl group, or else R ₂ represents the group -C (O) -ZR ₃ , in which Z represents O, NH, or NR ₃ , and

R ₃ represents a C 1 -C 4 alkyl, cycloalkyl, aryl or aralkyl group and the aryl group preferably contains from 6 to 12 carbon atoms.

Examples of such hydrophobic monomers include the following: styrene, α-methylstyrene, p-methylstyrene, p-vinyltoluene, vinylcyclopentane, vinylcyclohexane, vinylcyclooctane, propene, 1-butene, isobutene, 2-methyl-1 -butene, 2- methyl-1-hexane, 2 propyl-1- hexane, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, eicosyl (meth) acrylate, cyclopentyl (meth ) acrylate, cyclohexyl (meth) acrylate, cyclooctyl (meth) acrylate, phenyl (meth) acrylate, 4-methylphenyl (meth) acrylate, and 4-methoxyphenyl (meth) acrylate. In addition, the following hydrophobic monomers are also included: ethylene, vinylidene chloride, vinylidene fluoride, vinyl chloride, and other mainly araliphatic compounds having polymerizable double bonds.

All mixtures of these hydrophobic monomers are also possible.

Surfactant monomers

The surfactant monomers which can be used according to the invention can, for example, be the monomer compounds of the following formula:

wherein A1 is O, NH, or NR ₄ ;

R ₄ represents a CC ₄ alkyl group;

R ₅ represents a hydrogen atom or a methyl group;

R ₆ represents a CC ₁₈ alkylene group;

R ₇ and R ₈ , independently of one another, represent a CC ₆ alkyl group;

R ₉ represents a CC ₆ alkylene group;

R ₁₀ represents a C ₈ -C ₃₂ alkyl, aryl, or aralkyl group; and

X represents a halogen atom, OCN, SCN, SO ^ H ^ or acetate.

In addition, the surface-active monomers can be compounds of the following formula:

wherein A ,, R ₅ , R ₆ , R ₇ , R8 and X are as defined above; and

R ' _g represents a C ^ C ^ alkyl group.

Examples of this type of monomer are: CH ₃ CH ₃

CH2 = C - C - O- CH2 - CH2 - ® _N - CH2 - C - O - C12H25 Cl ^ϋ

He | he

O CH3 O

CH3 CH3

CH2 = C - C - NH— (CH2 - CH2) 6— ^Θ 'jNsj —— u CiH-133 Cl ^θ or

I

O CH3

CH ₃ CH3

CH2 = C - C- O CH2— CH2 © θ

N CH12H25 CI

O CH3

The following monomers can also be preferably used:

R

CH ^ ≈≈C— C— A _χ - (Y— 0) n - R _{{χ /}

O

O dans laquelle A₂ représente O, NH, ou NR₁₃ ;

O wherein A ₂ represents O, NH, or NR ₁₃ ;

NR ₁₃ represents an alkyl group in O, -0,; R represents a hydrogen atom or a methyl group; R ₁₂ represents a C ₈ -C ₃₂ alkyl, aryl, or aralkyl group; R _'12 represents a hydrogen atom or an alkyl C, - C _4;

R ₁₄ represents a 0, -0 ^ alkylene group; Y represents a C ₂ -C ₆ alkylene group; and n represents an integer in the range 1-50.

Among these monomers, the following can preferably be used:

CH ₃

CH2 ≈ C - C - O - (CH2— CH2 - 0) 20 - Ci 3H27

O

CH3

CH2 = C - C - NH— (CH2— CH2 - 0) 40 - C18H37

O

CH

CH₃ I CH2 = C— C — O — (CH2— CH2)6 — (° — ^CH2 — CH₂)20 — OH

CH ₃ I CH2 = C— C - O - (CH2— CH2) 6 - (° - ^CH 2 - CH ₂ ) 20 - OH

II

O

Amphoteric monomers

Mention may be made of N, N-dimethyl-N-methacryloxyethyl-N- (3-sulfopropyl) ammonium betaine, and I methacrylic acid amidopropyl-dimethylammoniumpropyl sulfobetaine

The patents cited above as well as PCT / US 97/04275, USP 5,696,194, EP 0 637 598, EP 0 630 909, and USP 2143564 are incorporated here for reference and those skilled in the art may usefully refer to them.

The water-in-oil reverse emulsion polymerization techniques are those which are also well established to date, as well as the surfactants and oil phases used, as notably described in patents such as 3, 284,393 which are incorporated here for reference and to which the skilled person can usefully refer.

The branching and crosslinking agents, as well as their proportions, are as described in particular in the abovementioned patents EP'780 and EP'237.

The reverse emulsion (co) polymerization reactions of the first step optionally include a functionalization of the (co) polymer by a Mannich base reaction, a hydroxamate function, hydrophobic side chains, or glyoxal. S SECOND STEP: DRYING THE MU LS ION:

Azeotropic evaporation / agglomeration / filtration:

In this area, reference will be made to patents such as USP 5,696,228, WO 97 / 48,755 (USSN 08 / 668,288), WO 97 / 48,750, WO 97 / 48,732, WO 97 / 34,945, WO 96/10589, USP 5,346,986 , 5,684,107, EP 0 412 388, EP 0 238 050, USP 4,873,299, EP 0 742 231, WO 90/08789 or EP 0 224 923

Drying by evaporation ("sprav-drying"):

Reference will be made to the preferred method described above.

THIRD STEP: POWDER DISPERSION:

It is possible to use a salt known in the techniques of precipitation of polymers, such as the following.

Salt:

Any organic or inorganic salt allowing the insolubilization of the prerarated polymer can be used according to the invention. Preferred salts are those comprising the sulfate, hydrogenphosphate, phosphate anions. The corresponding cations can be sodium, ammonium, magnesium, aluminum. The simultaneous use of two or more of these salts is also possible.

Dispersants, stabilizers, and other additives for the preparation of the dispersion:

The following stabilizers or dispersants may be used according to the invention. Stabilizers or dispersants:

The polymer dispersant is a polymer different from the polymer which it is desired to prepare with regard to its chemical composition and its number average molecular weight Mw, and it is incompatible with the polymer which it is desired to prepare. The molecular weight of the polymeric dispersant is in the range of 1,000 to 500,000 Dalton, preferably in the range of 10,000-400,000 Dalton. The term "incompatible" used herein indicates that the dispersant is immiscible in the polymer. This creates an additional interface and the free energy of the polymer increases. The polymer system is thermodynamically unstable.

According to the invention, polymer dispersants of the quaternary ammonium salt type may be used.

All of the monomers mentioned above as a component of the polymer that we want to prepare, but preferably:

The quaternized salts of reaction products of a polyamine and an acrylate-type compound, prepared for example from methyl acrylate and ethylenediamine, methacryloyloxyethyl) trimethyl ammonium chloride, lediallylmethyl (beta-propionamido) ammonium chloride , (beta-methacryloyloxyethyl) trimethylammonium methyl sulfate and the like, quaternized levinyllactam, the quaternized salt of vinylbenzyitrialkylamines such as for example vinylbenzyltrimethylammonium chloride, the quaternized salt of vinyl heterocyclic monomers comprising a nitrogenous ring, such as (1, 2- dimethyl-5-vinylpyridinium, methyl sulfate), (2-vinyl-2-imidazolinium, chloride) and the like, the dialkyldiallylammonium salt comprising diallyldimethylammonium chloride, and methacrylamidopropyltrimethylammonium chloride.

The polymer dispersant can contain functional groups chosen from the following: ether, hydroxyl, carboxyl, sulfone, sulfate ester, amino, amido, imino, tert-amino, and / or quaternary ammonium. Examples of the dispersant which may usefully be mentioned as being advantageous according to the invention are the following: derivatives of the cellulose, polyethylene glycols, polypropylene glycols, copolymers of ethylene glycol and propylene glycol, polyvinyl acetates, polyvinyl alcohols, starches and starch derivatives, dextrans, polyvinylpyrrolidones, polyvinylpyridines, polyethyleneimines, polyvinylimidazoles, polyvinylsuccinimides, polyvinyl-polyvinyl -1, 3-oxazolid-2-ones, polyvinyl-2- methylimidazolines, and copolymers which may contain units of monomer components, polymers mentioned above, and may also contain, for example, units of maleic acid , maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, (meth) acrylic acid, acrylamido methyl propane sulfonic acid and (meth) acrylic acid salts or monomer units of (meth) acrylamide.

Preferred polymeric dispersants are polyalkylene ethers, for example polyethylene glycol, polypropylene glycol or poly-1,4-butylene glycol.

Particularly preferred polymeric dispersants are polyelectrolytes, for example polymers which contain (meth) acrylic acid salts as components of anionic monomer; or which contain, as cationic components, methyl chloride-quaternized derivatives of N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate or N, N-dimethylaminohydroxypropyl ( meth) acrylate.

As particularly preferred dispersing polymers, mention will be made of polydiallyldimethylammonium chloride (poly-DADMAC), comprising an average molecular weight Mw of between 50,000 and 400,000 Dalton and polyacryloyloxyethyl) trimethyl ammonium chloride of average molecular weight Mw of between 50,000 and 400,000 Dalton.

The invention also relates to a process for preparing powders, effective as such as flocculants, of linear, branched or crosslinked copolymers obtained by reverse emulsion polymerization, characterized in that steps 1 and 2 of the process are carried out general described above, with the particular means described. Other characteristics and advantages of the invention will appear better on reading the description and the nonlimiting examples which follow.

In the following examples, the UL standard Brookfield viscosity is determined on a solution of 1 g / l of dry polymer and 1 M in NaCl, using a Brookfield viscometer equipped with the UL adapter set at the speed of 60 revolutions / minute. at 25 ° C.

Versenex 80 is a complexing or chelating agent (pentasodium salt of ethylene diamine pentaacetic acid)

Sodium bromate and sodium metabisulfite constitute a redox couple generating free radicals which initiate polymerization.

AIBN (Azobis-iso-butyro-nitrile) and V50 (2,2'-azobis (2-amidinopropane) di-hydrochloride) are azo initiators.

Bulk viscosity is measured with a Brookfield viscometer set to 30 rpm at 25 ° C

Example 1

Step 1: Water-in-oil emulsion polymerization:

The polymerization is carried out in a 1.5-liter reactor equipped with a stirrer with helical blades, a nitrogen inlet and a vent, a reflux condenser, a thermometer. The aqueous phase and the organic phase are mixed in this reactor and the particle size is reduced to approximately 1 micron by shearing this suspension using a kitchen mixer. A bubbling of nitrogen is applied to the contents of the reactor in order to remove the oxygen. Then a solution of sodium metabisulfite (5g / l in water) is continuously added to the reactor by means of a syringe pump. The temperature increases to 45 ° C then a cooling is applied to maintain the temperature between 45 ° C and 55 ° C. The polymerization time is approximately 3 hours. The average diameter of the particles in suspension in the oil is 1 micron.

Aqueous phase:

Acrylamide 50% 498.2 g

Dimethylaminoethyl acrylate

/ quaternized with 80% methyl chloride 49.9 g

Dimethylaminoethyl acrylate

/ quaternized with 80% benzyl chloride 139.4 g

Water 25.3 g

Sodium bromate (50g / l solution in water) 1.6g

Versenex 80 0.61 g

pH adjusted to 5.0 with sulfuric acid

Organic phase:

Isopar J (Exxon) 260 g

Sorbitan monooleate 20 g Hypemer 2296 (HERE) 5 g

The final product contains 40% dry polymer.

The standard UL viscosity of this polymer is 3.7 cps.

Step 2: Drying the water-in-oil emulsion:

All of the above water-in-oil emulsion is then dried in a NIRO SN 1601 "spray drier" equipped with a centrifugal atomizer. The water and isopar J are condensed and then separated by decantation. Isopar J is recovered and purified for reuse.

At the exit of the "Spray drier" a coarse powder of 20 to 500 microns is recovered. This powder is ground and sieved to a particle size of less than 10 microns.

Step 3: Dispersion in the aqueous mixture:

200 g of the powder less than 10 microns recovered from step 2 is dispersed in the following mixture:

Water 330 g

Ammonium sulfate 150 g

Copolymer of quaternized dimethylaminoethyl acrylate

with 80% methyl chloride and dimethylaminoethyl acrylate quaternized with 80% benzyl chloride (molecular weight 800,000)

60g

Glycerol 10 g

This dispersing operation is carried out in a container equipped with a laboratory mixer of the UltraTurrax type. The powder is poured slowly into the vortex formed by agitation.

The final product is a white dispersion with a Bulk viscosity of 7000 cps. The final amount of dry polymer in this dispersion is 33.1%, and the standard UL viscosity of this polymer is 3.5 cps.

Example 2

Step 1: Water-in-oil emulsion polymerization:

The procedure is as in Example 1 with the following initial composition:

Aqueous phase:

Acrylamide 50% 507.4 g

Dimethylaminoethyl acrylate quaternized with 80% methyl chloride 101.5 g

Stearyl methacrylate 71, 1 g

Water 32.8 g

Sodium bromate (50g / l solution in water) 1.6g

Versenex 80 0.62 g

pH adjusted to 5.0 with sulfuric acid

Oily phase:

Isopar J (Exxon) 260 g

Sorbitan monooleate 20 g

Hypemer 2296 (HERE) 5 g

The final product contains 40.6% dry polymer.

The standard UL viscosity of this polymer is 3.8 cps.

Step 2: Drying the water-in-oil emulsion:

All of the above water-in-oil emulsion is then dried in a NIRO SN 1601 "spray drier" equipped with a centrifugal atomizer. The water and isopar J are condensed and then separated by decantation. Isopar J is recovered and purified for reuse. At the exit of the "Spray drier" a coarse powder of 20 to 500 microns is recovered. This powder is ground and sieved to a particle size of less than 10 microns.

Step 3: Dispersion in the aqueous mixture:

200 g of the powder less than 10 microns recovered from step 2 is dispersed in the following mixture:

Water 330 g

Ammonium sulfate 150 g

Homopolymer (molecular weight 500,000) of acrylate

of quaternized dimethylaminoethyl with methyl chloride 80% 60 g

Glycerol 10 g

This dispersing operation is carried out in a container equipped with a laboratory mixer of the UltraTurrax type. The powder is poured slowly into the vortex formed by agitation.

The final product is a dispersion with a Bulk viscosity of 10,000 cps. The final amount of dry polymer in this dispersion is 33.1%, and the standard UL viscosity of this polymer is 3.5 cps. Example 3

The three-step procedure of Example 1 is repeated, but with the following initial composition of the water-in-oil emulsion:

Aqueous phase:

Acrylamide 50% 464.3 g

Dimethylaminoethyl acrylate

-quaterized with 80% methyl chloride 52.7 g

Vinyl acetate 140.4 g

Ter-butyl acrylamide 42.1 g

Water 13.1 g

Sodium bromate (50g / l solution in water) 1.8g

Versenex 80 0.57 g

pH adjusted to 5.0 with sulfuric acid

Organic phase:

Isopar J (Exxon) 260 g

Sorbitan monooleate 20 g

Hypemer 2296 (HERE) 5 g The final product is a fluid dispersion which has a Bulk viscosity of 7500 cps. The particles remain in suspension for more than 8 days without the appearance of a phase shift.

Example 4

The three-step procedure of Example 1 is repeated, but with the following initial composition of the water-in-oil emulsion:

Acrylamide 50% 399.9 g

Acrylic acid 43.4 g

Stearyl methacrylate 136 g

Ethyl hexyl acrylate 36.8 g

Soda 50% 87 g

Water 9.7 g

Sodium bromate (50g / l solution in water) 1.7g

Versenex 80 0.49 g

pH adjusted to 7.0

Organic phase:

Isopar J (Exxon) 260 g

Sorbitan monooleate 20 g

Ethoxylated sorbitan monooleate 8 moles 5 g The final product is a dispersion of particles of less than 10 microns which has a Bulk viscosity of 10,000 cps. The particles remain in suspension for more than 8 days without the appearance of a phase shift.

Example 5

In this example, the procedure is the same as in Example 1, with the same initial water-in-oil emulsion, but the emulsion in step 2 is dried as follows:

500 g of the water-in-oil emulsion are placed after polymerization in a 2-liter glass reactor fitted with a thermometer and a water separator, together with 300 ml of Isopar J. the mixture is stirred at 300 rpm. the contents of the reactor are then heated to a temperature between 70 ° C and 80 ° C, and the water is removed by azeotropic entrainment. The training is done in 4 hours. The resulting polymer suspension settles at the bottom of the reactor quickly. The contents of the reactor are transferred by filtering and the polymer is thus isolated from isopar J. The polymer recovered on the filter is then dried under vacuum at 50 ° C., then ground and sieved in order to obtain a powder of size less than less than 10 microns. Then this powder is treated according to the same process of step 3 of Example 1.

The final product is a dispersion of particles of less than 10 microns which has a Bulk viscosity of 11000 cps. The particles remain more than 8 days in suspension without the appearance of a phase shift. Example 6

In this example, the procedure is the same as in Example 1, with the same initial water-in-oil emulsion, but the following aqueous mixture is used in step 3 to disperse the prepared powder:

Water 330 g

Ammonium sulfate 150 g

Homopolymer (molecular weight 300,000) of dadmac 60 g

Glycerol 10 g

The final product is a dispersion of particles of less than 10 microns which has a Bulk viscosity of 8000 cps. The particles remain more than 8 days in suspension without the appearance of a phase shift. The final amount of dry polymer in this dispersion is 33.1%, and the standard UL viscosity of this polymer is 3.6 cps.

Example 7

In this example, the procedure is the same as in Example 1, with the same initial water-in-oil emulsion, but the following aqueous mixture is used in step 3 to disperse the prepared powder: Water 330 g

Ammonium sulfate 150 g

Sodium citrate 25 g

Piuriol P4000 (Polypropylene glycol, BASF company) 60 g

Glycerol 10 g

The final product is a dispersion of particles of less than 10 microns which has a Bulk viscosity of 12,000 cps. The particles remain more than 8 days in suspension without the appearance of a phase shift. The final amount of dry polymer in this dispersion is 32%, and the standard UL viscosity of this polymer is 3.3 cps.

Example 8

The three-step procedure of Example 1 is repeated, but with the following initial composition of the water-in-oil emulsion:

Aqueous phase:

Acrylamide 50% 491, 3 g

Dimethylaminoethyl acrylate

/ quaternized with methyl chloride 80% 53.6 g Hexyl ethyl acrylate 137.8 g

Methylene bis acrylamide 0.043 g

Water 30 g

Sodium bromate (50g / l solution in water) 1.7g

Versenex 80 0.6 g

pH adjusted to 5.0 with sulfuric acid

Organic phase:

Isopar J (Exxon) 245 g

Sorbitan sesquioleate 20 g

Ethoxylated sorbitan trioleate 20 moles 15 g

Hypemer 1083 (HERE) 5 g

Steps 2 and 3 are identical to Example 1.

The final product is a dispersion of particles smaller than 10 microns which has a Bulk viscosity of 16,000 cps. The particles remain in suspension for more than 15 days without the appearance of a phase shift, the final product is a polymer comprising ramifications (bridging between the macromolecules) and which has a dry polymer content equal to 32.4%, and the UL viscosity standard of this polymer is 1.8 cps.

Example 9 The three-step procedure of Example 1 is repeated, but with the following initial composition of the water-in-oil emulsion:

Aqueous phase:

Acrylamide 50% 161, 8 g

Ter-butyl acrylamide 24.5 g

Vinyl acetate 27.2 g

Dimethylaminoethyl acrylate

/ quaternized with 80% benzyl chloride 85.5 g

Dimethylaminoethyl acrylate

/ quaternized with 80% methyl chloride 152.9 g

Sodium hypophosphite (5g / l in water) 0.5 g

Water 262.5 g

Sodium bromate (50g / l solution in water) 1 g

Versenex 80 0.2 g

V 50 (azobis amidinopropane hydrochloride) 0.4 g

pH adjusted to 5.0 with sulfuric acid

Organic phase:

Isopar J (Exxon) 262 g Hypemer 1083 (HERE) 12 g

SCS 4913 (ICI, surfactant monomer based on maleic acid) 10 g

Phases 2 and 3 are identical to Example 1.

The final product is a dispersion of particles smaller than 10 microns which has a Bulk viscosity of 13000 cps. The particles remain in suspension for more than 15 days without the appearance of a phase shift. The final product has a dry polymer content of 33%, and the standard UL viscosity of this polymer is 4.3 cps.

The product dissolves quickly (10 s) in water by simple pouring and light stirring. A solution having a viscosity of 250 cps is obtained by pouring 1 g of this dispersion into 200 cc of distilled water.

Example 1 0

Aqueous phase: 224.8 g

Acrylic acid 58.9 g

Stearyl methacrylate 110.8 g

Sodium hydroxide 50% 65.4 g

Water 260.4 g

Sodium bromate (50g / l solution in water) 1.6g

Versenex 80 0.61 g

AIBN 0.5 g The pH is adjusted to 7.0

Organic phase:

Isopar J (Exxon) 250 g

Sorbitan monooleate 22 g

Hypemer 2296 (HERE) 5 g

The final product contains 30% dry polymer.

The standard UL viscosity of this polymer is 6.7 cps. Phase 2 is then carried out in the same manner as in Example 1.

Step 3: Dispersion in the aqueous mixture:

200 g of the powder less than 10 microns recovered from step 2 is dispersed in the following mixture:

Water 330 g

Sodium sulfate 125 g

Acrylamide / Acrylic acid / AMPS terpolymer neutralized by

sodium hydroxide for a pH of 7.00 (molecular weight 250,000) 75 g

Polyvinyl alcohol 10 g

The final product is a dispersion with a Bulk viscosity of 15,000 cps. The final amount of dry polymer in this dispersion is 34.9%, and the standard UL viscosity of this polymer is 5.9 cps.

Claims

1. - Method for preparing a system of (co) polymer (s) hydro soluble (s) or swellable (s) with water, in aqueous or essentially aqueous dispersion, having a very high molecular weight, of the order of several million to several tens of millions of Dalton, characterized in that a conventional (co) polymerization in reverse emulsion (water-in-oil) is carried out in a first step, leading to the desired very high molecular weight, and then dried. emulsion in a second step to obtain the (co) polymer in powder form, then the powder (co) polymer thus obtained is dispersed in an aqueous medium in which it is not soluble or only slightly soluble. 2. - Method according to claim 1, characterized in that the drying of the emulsion in the second step is carried out by azeotropic evaporation followed by sedimentation and filtration. 3. - Method according to claim 1, characterized in that the drying of the emulsion in the second step is carried out by a spray drying technique or "spray-drying". 4. - Method according to claim 3, characterized in that this drying process of the second step consists in sending the emulsion in a dryer by high energy spraying, then the product obtained is redissolved in water to a dimension of <20 or <10 microns, then to a colloid mill which gives a particle size <20 or 10 microns, preferably <5 microns or of the order of 1 micron or less. 5. - Method according to any one of claims 1 to 4, characterized in that the oil used for the (co) polymerization in first stage oil-in-water emulsion has a flash point below about 65 ° C. 6. - Method according to any one of claims 1 to 5, characterized in that one carries out in the first step the copolymerization of a mixture of monomers soluble in water, or in dispersion in water s' they are insoluble, at least one of which has a hydrophobic character. 7. - Method according to claim 6, characterized in that the initial mixture of monomers will comprise a hydrophobic fraction representing between about 1 and 40, preferably 15 and 25% by weight of the mixture of monomers. 8. - Method according to any one of claims 1 to 7, characterized in that the aqueous medium used in the third step for the dispersion of the powder consists of an aqueous mixture comprising at least one salt and / or other additives chemical solutions whose function is to prevent the dissolution of the (co) polymer powder in the aqueous medium. 9. - Method according to claim 8, characterized in that said aqueous medium will comprise chemical agents in solution or in dispersion in water if they are insoluble, the function of which is to promote the dispersion of the powder of (co) polymer and / or to exert a stabilizing effect on the dispersion thus obtained, or an encapsulating effect. 10. - Method according to any one of claims 1 to 9, characterized in that one applies to the aqueous dispersion of the coarse polymer powder a shear adapted to reduce the size of the particles of polymer in dispersion to a dimension also as close as possible to the dimension obtained during the first emulsion polymerization step, of the order of 1 micron or less. 11. - Process for preparing powders, effective as such as flocculants, of linear, branched or crosslinked copolymers obtained by reverse emulsion polymerization, characterized in that steps 1 and 2 of the process according to any one of claims 1 to 5. 12. - Method according to claim 1 1 for preparing powders, effective as such as flocculants, of linear, branched or crosslinked copolymers obtained by reverse emulsion polymerization characterized in that the (co) polymers obtained are either linear or slightly or strongly branched or crosslinked with a proportion of crosslinking agent, in particular MBA (methylenebisacrylamide) of between approximately 5 and approximately 60 ppm, and starting from an inverse emulsion of the appropriate monomers, optionally a suitable proportion of crosslinking or branching agent, polymerization in reverse emulsion and the product obtained is transformed into a powder by either a spray drying step of the type described above, or an agglomeration step preceding a filtration step. 13. - Method according to claim 1 1 or 12 for preparing powders, effective as such as thickeners, superabsorbents, of linear, branched or crosslinked copolymers obtained by reverse emulsion polymerization characterized in that one starts from a reverse emulsion of the appropriate monomers, optionally adding a suitable proportion of crosslinking or branching agent, usually between 5 and 1000, preferably 5 to 30 or> 30 or> 100 ppm, polymerize in reverse emulsion and transform the product obtained into a powder by either a spray drying step of the type described above, or an agglomeration step preceding a filtration step. 14. - Method according to any one of claims 1 to 13, characterized in that in the first step of polymerization in reverse water-in-oil emulsion the hydrophilic monomers which can be used are chosen from: Nonionic monomers which can be chosen from all the water-soluble allylic or vinyl monomers which do not have a sensitive anionic or cationic charge, such as acrylamide and methacrylamide, N-isopropylacrylamide, Nt-butylacrylamide, and N-methylolacrylamide , vinylformamide, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkyl acrylates and methacrylates, preferably acrylamide. The anionic monomers which can be chosen from monomers having acrylic, vinyl, maleic, allylic functionalities and / or containing a carboxy, phosphonate, sulfonate group or another group with an anionic charge, or alternatively the ammonium or alkaline earth metal salt or of corresponding alkali metal of such a monomer, such as acrylic acid, methacrylic acid, acrylamidomethypropane sulfonic acid, acrylamidomethylbutanoic acid, maleic acid, fumaric acid, itaconic acid, vinylsulfonic acid , styrene sulfonic acid, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid, a sulfomethylated acrylamide, a phosphonomethylated acrylamide and their water-soluble salts of an alkali metal, of an alkaline earth metal, and ammonium. Cationic monomers are chosen from those corresponding to the following general formulas: CH2 = C - R1 R2 0 = C - A1 - B1 - N + - R4 X- I R3 in which R _ι represents H or CH ₃ ; R ₂ and R ₃ represent C -C ₃ alkyl groups; R ₄ is H or alkyl C ^ C _g; A represents an oxygen or NH atom; B represents a C ₂ -C ₄ alkylene group or a hydroxypropylene group, and X ^" is an anionic counterion. Or

in which R represents H or CH ₃ ; R ₂ and R ₃ each represents a CC ₃ alkyl group; A represents an oxygen or NH atom; B represents a C ₂ -C ₄ alkylene group or a hydroxypropylene group; and X, ^" represents an anionic counterion or the diallyldialkylammonium halides. Surfactant monomers can be chosen from those corresponding to the following formula:

wherein A, is O, NH, or NR ₄ ; R ₄ represents a CC ₄ alkyl group; R ₅ represents a hydrogen atom or a methyl group; R ₆ represents an alkylene group in O, -0 ^; R ₇ and R _g , independently of one another, represent a CC ₆ alkyl group; R _g represents an O, -C ₈ alkylene group; R ₁₀ represents a C ₈ -C ₃₂ alkyl, aryl, or aralkyl group; and X represents a halogen atom, OCN, SCN, SO ^ H ,, or acetate. or

wherein A ,, R ₅ , R ₆ , R ₇ , R ₈ , and X are as defined above for Formula II; and R ' ₉ represents a CC ₁₈ alkyl group. or CH ₃ CH ₃ CH2 = C - C - O— CH2 - CH - © _N - CH - C— O— C ₁₂ H ₂ 5 Cl ^θ Il | he O CH3 O CH3 CH3 CH2≈C - C - NH— (CH2 - CH2) 6— ®N - CH ₃ Cl ^θ _or He I O CH ₃ CH ₃ CH ₃ CH2 = C - C - O - CH2 - CH2 © θ N - CH12H25 CI O CH3 or Ru CH ^ == C - C— A, - (Y— O) n - R ^ O CH, "R _| - O - (Y ~ 0) n - R ' _{l2 /}

O wherein A ₂ represents O, NH, or NR ₁₃ ; NR ₁₃ represents a CC ₄ alkyl group; R represents a hydrogen atom or a methyl group; R ₁₂ represents a C ₈ -C ₃₂ alkyl, aryl, or aralkyl group; R _'12 represents a hydrogen atom or an alkyl C, - C 4 ' R ₁₄ represents a CC ₁₈ alkylene group; Y represents a C ₂ -C ₆ alkylene group; and n represents an integer in the range 1 -50. OR CH ₃ CH2 = C - C - O - (CH2— CH2 - 0) 20 - ^C 13H27 O CH3 CH2 = C - C "NH— (CH2— CH2 - O) 40 - ^C 18H37 O

CH ₃ CH ₃ I CH ₂ = C - C - O - (CH ₂ - CH ₂ ) 6 - (° - ^{Ch |} 2 - CH ₂ ) 20 - OH O Cross-linking or branching monomers: have at least two polymerizable groups, such as: (1) Alkenyldi (meth) acrylates, such as 1, 6-hexanediol di (meth) acrylate, 1, 10-decanediol di (meth) acrylate, 1, 12-dodecanediol di (meth) acrylate, 1, 18-octadecanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, methylene di (meth) acrylate, 2,2'-bis (hydroxymethyl) -1, 3-propanediol di (meth) acrylate, and preferably ethylene glycol di ( meth) acrylate, 1,3-propanediol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, and 1,4-butanediol di (meth) acrylate; (2) Alkylene di (meth) acrylamides, for example N-methylene di (meth) acrylamide, N, N'-3-methylbutylidene bis (meth) acrylamide, N, N'- (1, 2-dihydroxyethylene) bis (meth ) acrylamide, and preferably N, N'-hexamethylene bis (meth) acrylamide, and in particular preferably N, N'-methylene bis (meth) acrylamide; (3) Polyalkoxydi (meth) acrylates of the following formula: R O O R

in which R ₁₃ represents a methyl radical or a hydrogen group; m represents an integer in the range 2-6; and p represents an integer in the range 2-50. or like the polypropylene glycol di (meth) acrylates (m = 3), with p in the range 4-25; polybutylene glycol di (meth) acrylates (m = 4), with p in the range 5-40; and preferably polyethylene glycol di (meth) acrylates (m = 2), with p in the range 2-45, for example diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate; and, more preferably, polyethylene glycol di (meth) acrylates with p in the range 5-20; (4) examples of additional di (meth) acrylates which can be used include the following: benzylidene di (meth) acrylate, bisphenol-A di (meth) acrylate, 1,3-di (meth) acryloyloxy-2-propanol, hydroquinone di (meth) acrylate, ethanedithiol di (meth) acrylate, propanedithiol di (meth) acrylate, polyethylenedithiol di (meth) acrylate and polypropylenedithiol di (meth) acrylate; (5) the divinyl compounds are, for example, the following: 1,4-butanediol divinyl ether, divinylbenzene, butadiene, 1,6-hexadiene; di (meth) allyl compounds, such as, for example, di (meth) allyl phthalate or di (meth) allyl succinate; vinyl (meth) acrylic compounds, such as, for example, vinyl (meth) acrylate; or preferably (meth) allyl (meth) acrylic compounds, such as for example allyl (meth) acrylate. or as the following: glycerin tri (meth) acrylate, 2,2- dihydroxymethyl-1 -butanol tri (meth) acrylate, trimethylolpropane triethoxy tri (meth) acrylate, trimethacrylamide, (meth) allylidene di (meth) acrylate, 3-allyloxy -1, 2-propanediol di (meth) acrylate, triallyl cyanurate or triallyl isocyanurate; and also (as representative compounds comprising more than three polymerizable ethylenically unsaturated groups) pentaerythritol tetra (meth) acrylate and N, N, N'N'-tetra (meth) acryloyl-1,5-pentanediamine. 15. - Method according to any one of claims 1 to 13, characterized in that in the first step of polymerization in reverse water-in-oil emulsion the hydrophobic monomers which it can be used are chosen from the following: Hydrophobic monomers: acrylamide derivatives such as N-alkylacrylamide for example N-isopropylacrylamide, N-tert-butylacrylamide, octylacrylamide as well as N, N-dialkylacrylamides such as NN-dimethylacrylamide OR

in which R represents H or CH ₃ ; R ₂ and R ₃ each represents a C 1 -C 6 alkyl group; A ₁ represents an oxygen atom or NH; B ₁ represents a C ₂ -C ₄ alkylene group or a hydroxypropylene group; and X ^ represents an anionic counter ion. or CH2 = C - R1 R2 0 = C - A1 - B1 - N + - R4 X- I R3 wherein R _t represents H or CH ₃ ; R ₂ and R ₃ represent CC ₃ alkyl groups; R ₄ represents H or a C ₅ -C ₂₂ alkyl group; A ₁ represents an oxygen atom or NH; B represents a C ₂ -C ₁₀ alkylene group or a hydroxypropylene group, and X ^" is an anionic counterion. or R1 CH2 = C - R2 in which R represents a hydrogen atom or a CC ₅ alkyl group; R ₂ represents alkyl, cycloalkyl, aryl, aralkyl or C ^ C _gg, or R ₂ represents the group -C (0) -ZR ₃ wherein Z is O, NH, or NR _3, and R ₃ represents a C ₁ -C ₂₀ alkyl, cycloalkyl, aryl or aralkyl group, and the aryl group preferably contains from 6 to 12 carbon atoms. or the following: styrene, α-methylstyrene, p-methylstyrene, p- vinyltoluene, vinylcyclopentane, vinylcyclohexane, vinylcyclooctane, propene, 1 -butene, isobutene, 2-methyl-1 -butene, 2-methyl-1 -hexane, 2 propyl -1-hexane, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth ) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, eicosyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate , cyclooctyl (meth) acrylate, phenyl (meth) acrylate, 4-methylphenyl (meth) acrylate, and 4-methoxyphenyl (meth) acrylate. In addition, the following hydrophobic monomers are also included: ethylene, vinylidene chloride, vinylidene fluoride, vinyl chloride, and other mainly araliphatic compounds having polymerizable double bonds. 16. - Method according to any one of claims 1 to 13, characterized in that in the first step of polymerization in reverse emulsion (water-in-oil) the polymerization optionally comprises a functionalization of the (co) polymer by a reaction Mannich base, a hydroxamate function, hydrophobic side chains, or glyoxal. 17. - Method according to any one of claims 1 to 13, characterized in that in the first step of polymerization in reverse water-in-oil emulsion, no branching or crosslinking agent or methylenebisacrylamide (MBA) is used, or one of the branching or crosslinking monomers of claim 14. 18. - Method according to claim 17, characterized in that the proportion of branching or crosslinking agent is between 5 and 60 ppm, preferably between 10 and 40 ppm or> 30 or> 100 ppm. 19. - Method according to any one of claims 1 to 10 and 14 to 18, characterized in that one carries out the third stage of dispersion of the coarse powder using an aqueous medium in which one incorporates a salt known in the polymer precipitation techniques, such as: Any organic or inorganic salt allowing the insolubilization of the prerarated polymer can be used according to the invention, preferably those comprising the sulfate, hydrogenphosphate, phosphate anions, the corresponding cations possibly being sodium, ammonium, magnesium, aluminum, or their mixtures. 20. - Method according to any one of claims 1 to 10 and 14 to 19, characterized in that the third stage of dispersion of the coarse powder is carried out using an aqueous medium in which dispersants, stabilizers are incorporated, and other additives for the preparation of the dispersion and chosen from: Dispersants, stabilizers, and other additives for the preparation of the dispersion: Stabilizers or dispersants: polymer different from the polymer which one wants to prepare with regard to its chemical composition and its average molecular weight in number Mw, and incompatible with the polymer which one wants to prepare, and whose molecular weight is in the range from 1,000 to 500,000 Dalton, preferably in the range 10,000-400,000 Dalton. or of the quaternary ammonium salt type all the monomers mentioned above as a component of the polymer the quaternized salts of reaction products of a polyamine and of an acrylate type compound, prepared for example from methyl acrylate and ethylenediamine, methacryloyloxyethyl) trimethyl ammonium chloride, lediallylmethyl (beta-propionamido) ammonium chloride , (beta-methacryloyloxyethyl) thmethylammonium methyl sulfate and the like, quaternized levinyllactam, the quaternized salt of vinylbenzyltrialkylamines such as for example vinylbenzyltrimethylammonium chloride, the quaternized salt of vinyl-heterocyclic monomers comprising a nitrogenous ring, such as (1, 2- dimethyl-5-vinylpyridinium, methyl sulfate), (2-vinyl-2-imidazolinium, chloride) and the like, the dialkyldiallylammonium salt comprising diallyldimethylammonium chloride, and methacrylamidopropyltrimethylammonium chloride. or which may contain functional groups chosen from the following: ether, hydroxyl, carboxyl, sulfone, sulfate ester, amino, amido, imino, tert-amino, and / or quaternary ammonium, such as: cellulose derivatives, polyethylene glycols, polypropylene glycols , copolymers of ethylene glycol and propylene glycol, polyvinyl acetates, polyvinyl alcohols, starches and starch derivatives, dextrans, polyvinylpyrrolidones, polyvinylpyridines, polyethyleneimines, polyvinylimidazo.es, polyvinylsuccinimides, polyvinyl-2-methylsuccinimides, oxazolid-2-ones, polyvinyl-2-methylimidazolines, and the copolymers which may contain units of monomer components, polymers mentioned above, and may also contain, for example, units of maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, (meth) acrylic acid, acrylamido methyl propane sulfonic acid and (meth) acrylic acid salts or (meth) acrylamide monomer units. and preferably polyalkylene ethers, for example polyethylene glycol, polypropylene glycol or poly-1,4-butylene glycol. and particularly preferably polyelectrolytes, for example polymers which contain (meth) acrylic acid salts as components of anionic monomer; or which contain, as cationic components, methyl chloride-quaternized derivatives of N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate or N, N-dimethylaminohydroxypropyl ( meth) acrylate. or alternatively, polydiallyldimethylammonium chloride (poly-DADMAC), comprising an average molecular weight Mw between 50,000 and 400,000 Dalton and polyacryloyloxyethyl) trimethyl ammonium chloride with an average molecular weight Mw between 50,000 and 400,000 Dalton. 21. - System of (co) polymer (s) hydro soluble (s) or swellable (s) with water, in aqueous or essentially aqueous dispersion, having a very high molecular weight, of the order of several millions to several tens of millions of Dalton, characterized in that it is prepared by a process according to any one of Claims 1 to 10 and 14 to 20. 22. - Powders, effective as such as flocculants, of branched or crosslinked copolymers obtained by reverse emulsion polymerization, characterized in that they have been prepared by a process according to any one of claims 11 to 13. 23. - Use of the systems or powders according to claim 21 or 22 as flocculant. 24. - Use of the systems or powders according to claim 21 or 22 as flocculant in industrial sectors such as water treatment and in particular waste water, the manufacture of sheets of paper and cardboard, the petroleum industry and petroleum services, the treatment of ores and various minerals such as fillers and pigments, the recovery of alumina by the so-called "Bayer" process, soil conditioning, treatment and packaging of foodstuffs, cosmetics and the like. 25. - Use of the systems or powders according to claim 21 or 22 in industrial sectors such as water treatment and in particular waste water, the manufacture of sheets of paper and cardboard, the petroleum industry and petroleum services, the treatment ores and various minerals such as fillers and pigments, recovery of alumina by the so-called "Bayer" process, soil conditioning, treatment and conditioning of foodstuffs, cosmetics and the like, as thickening agents, dispersants , superabsorbents.