FR2815635A1 - Polymerization of monomers in an aqueous solution comprises adding a salt in several portions to maintain fluidity - Google Patents

Abstract

Polymerization of monomers in an aqueous solution in the presence of a water-soluble polymer dispersant or coagulant and a salt comprises adding the salt in several portions, one portion being added before that start of polymerization and one or more other portions being adding during the early stages of polymerization. An Independent claim is also included for polymers and copolymers produced by the process.

Description

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Aqueous dispersions of a water-soluble polymer, process for their preparation, and their applications

The invention relates to the technical sector of water-in-water dispersions and in particular to aqueous dispersions of water-soluble polymers.

The dispersions are obtained by polymerization in an aqueous solution of a mixture of monomers in the presence of a water-soluble polymer (called dispersant or coagulant) and optionally a salt.

A first type of dispersion has been described by US Pat. No. 4,380,600. The dispersions are obtained by polymerization of a mixture of water-soluble monomers in the presence of a water-soluble polymer of the poly (ethylene glycol), poly (ethylene imine) type, sodium polyacrylate, soluble starches etc ...

Following this invention, two main lines of research have been explored: One of the methods is described in CA 2,096,471 (Rohm). In this process, an aqueous dispersion is obtained by polymerization of a mixture comprising a water-soluble monomer, a hydrophobic monomer and an amphiphilic monomer in the presence of a polymeric coagulant present in a significant proportion (> 10% by weight and in general of the order of 15%).

In parallel with the Röhm process, characterized by the absence of salt in the reaction mixture, US Pat. No. 4,929,655 (Hymo) constitutes one of the first patents that gave rise to industrial development. In this process, an aqueous dispersion is obtained by precipitation polymerization of a mixture of water-soluble monomers containing at least one hydrophobic monomer of the acryloyloxyethylidimethylbenzyl ammonium chloride type in an aqueous salt solution in the presence of a dispersant (<5% by weight and usually <2%).

The main technical problems encountered by industry for this type of polymerization and inherent to the processes described above are: viscosity problems: the water-soluble polymer formed during an aqueous dispersion polymerization will tend to be in solution , which will cause an increase in the viscosity of the reaction mixture (risk of runaway reaction) and a decrease in the fluidity of the final product.

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- les problèmes de stabilité : les particules de polymères formées ont tendance à se coller entre-elles et à prendre en masse aussi bien en cours de polymérisation que pendant le stockage.

stability problems: the formed polymer particles have a tendency to stick to each other and to build up both during polymerization and during storage.

The Prior Art It is well known to those skilled in the art that the process described in US Pat. No. 4,929,655 (HYMO) leads to high viscosities during the polymerization, requiring either the use of reactors specific to the implementation. such mixtures and / or is the limitation of the level of active material of the dispersion (<15% by weight). In addition this document covers an extremely precise and limited combination.

In the prior art, the changes made to try to overcome this problem are numerous. The patent EP 0 657 478 (NALCO) aims to overcome this disadvantage by adding salt at an initial and constant concentration of between 17 to 19%. This level is described as being optimum for polymerizing monomer systems similar to those described in US Pat. No. 4,929,655; however, the salt content remains high and the viscosities encountered during polymerization remain nonetheless high.

In a perspective very close to the Hymo patent, the patent WO 98/14405 (CYTEC) describes in particular the use of a mixture consisting of a chaotropic salt and optionally a kosmotropic salt (according to the Hofmeister series) or a salt. organic and a water-soluble polymer as precipitating medium of the dispersion.

In a comparable manner, patent EP 0 637 598 (NALCO) relates to the use of a dispersant obtained by copolymerization of DADMAC with a hydrophobic quaternary ammonium compound prepared from dialkylaminoacrylates or dialkylaminomethacrylates or alkyl esters of acrylic acid.

An alternative for reducing the viscosity of the reaction mixture during the polymerization is reported in EP 0 630 909 (NALCO). It consists in adding a fraction of the monomer mixture during the polymerization.

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Enfin le brevet WO 98/31749 (Allied Colloids) s'apparente également au brevet CA 2, 096, 471 (Röhm) par le fait qu'il réunit un floculant et un coagulant. L'utilisation d'un monomère hydrophobe n'est pas nécessaire et ce procédé diffère du brevet de Rôhm par le fait qu'il nécessite la présence d'un sel. Tout comme pour le brevet CA 2, 096, 471 (Röhm), le taux en floculant reste faible et de l'ordre de 10% tandis que le taux de coagulant demeure élevé et de l'ordre de 20%.

Finally, patent WO 98/31749 (Allied Colloids) is also similar to patent CA 2, 096, 471 (Röhm) in that it combines a flocculant and a coagulant. The use of a hydrophobic monomer is not necessary and this method differs from the Rohm patent in that it requires the presence of a salt. As for the CA 2, 096, 471 (Röhm) patent, the flocculant content remains low and of the order of 10% while the level of coagulant remains high and of the order of 20%.

 DESCRIPTION OF THE INVENTION For dispersions prepared in the presence of salt, it is well known that the addition of an additional fraction of salt to the final dispersion (after polymerization) makes it possible on the one hand to fluidify it and to on the other hand to improve its stability by adjusting the density of the continuous phase to that of the polymer particles.

Surprisingly and contrary to the observations developed in the patent EP 0 630 909 (p 5, 129-32), it has been discovered that, for identical conditions and formulations, the addition of salt in a fractionated manner-at least one part before polymerization and the rest in one or more additional successive fractions at the beginning of polymerization-more precisely, preferably but not limited to, during the first third or preferably the first quarter of the total polymerization time, makes it possible to improve optimal fluidity of the reaction mixture during polymerization by limiting and optimizing the viscosity variations.

Thanks to these additions sequenced in the first part of the polymerization (after addition of the catalyst), carried out in the form of one or more salt fractions in addition to the amount introduced into the initial formulation (before polymerization), it is possible surprisingly to obtain aqueous dispersions of polymers having a good fluidity throughout the polymerization process, a high level of active material (> 15% and up to 30%) and having a good stability, in a very wide range. wide molecular weight, and thus allowing the use of standard industrial facilities identical to those used for inverse emulsions.

By 1 st part of the polymerization is meant the period following initiation covering the first 1/3 of the total polymerization time, preferably the first 1/4, relative to the total polymerization time after initiation.

By active ingredient is meant throughout the present application the true fraction of flocculant, with the exception of the coagulant and / or dispersant fractions.

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Selon un mode préféré de l'invention, la ou les fractions successives supplémentaires de sel sont ajoutées en effet pendant le premier 1/4 du temps total de polymérisation après initiation.

According to a preferred embodiment of the invention, the additional successive salt fraction or fractions are added during the first 1/4 of the total polymerization time after initiation.

 The successive salt fraction or fractions added during polymerization represent a level of about 1 to 50% by weight relative to the total amount present in the mixture during the polymerization. In a preferred embodiment of the invention, the salt fraction (s) added during polymerization represent a total of about 5 to 50% by weight relative to the total amount of salt present in the mixture, and preferably about 10 at 40%.

This process is also characterized in that the level of water-soluble polymer (dispersant) present with the salt remains low and is less than 5% by total weight of the dispersion and preferably less than 3%.

The present invention more specifically relates to the methods which have just been described and their embodiments and variants.

The present invention also covers: the polymers and copolymers obtained by the processes described; the application in industry of the polymers and copolymers described; the paper industry (retention, draining, etc.), water treatment (drinking or wastewater), generally all coagulation / flocculation techniques, the mining industry, industry petroleum and refining, the cosmetics industry, the textile industry, and all similar applications that will be obvious to those skilled in the art.

The present invention also applies to and covers any type of nonionic, anionic, cationic or amphoteric polymers and copolymers obtained by the processes described, as well as linear or slightly or strongly branched, or crosslinked (by a proportion of crosslinking agent), and their applications as already mentioned.

It will be noted that, from their origin, the water-in-water dispersions have been developed to complete the range of standard water-in-oil emulsions and that the applications in industry of these two types of emulsions, comprising polymers of a similar nature, are, obviously, the same.

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Les dispersions de l'invention sont obtenues par polymérisation dans une solution aqueuse d'un mélange de monomères en présence d'un ou plusieurs polymère (s) hydrosoluble (s) (appelé (s) dispersant (s) ou coagulant (s)) et éventuellement d'un sel.

The dispersions of the invention are obtained by polymerization in an aqueous solution of a monomer mixture in the presence of one or more water-soluble polymer (s) (called dispersant (s) or coagulant (s)) and possibly a salt.

MONOMERS In a non-limiting manner, the following monomers and their combinations may be used.

méthacrylamide, les dérivés de l'acrylamide comme les N-alkylacrylamide par exemple le N-isopropylacrylamide, le N-tert-butylacrylamide, l'octylacrylamide ainsi que les N, Ndialkylacrylamides comme le N-N-diméthylacrylamide et le N-méthylolacrylamide. Nonionic monomers: The nonionic monomers useful according to the invention may be chosen from water-soluble vinyl monomers. Preferred monomers belonging to this class include acrylamide and

methacrylamide, acrylamide derivatives such as N-alkylacrylamide, for example N-isopropylacrylamide, N-tert-butylacrylamide, octylacrylamide and N, N-dialkylacrylamides such as N, N-dimethylacrylamide and N-methylolacrylamide.

Vinylformamid, N-vinylpyridine, Nvinylpyrrolidone, hydroxyalkyl acrylates and methacrylates can also be used. A preferred nonionic vinyl monomer will be acrylamide. Other nonionic monomers can be used without departing from the scope of the invention, especially hydrophobic monomers: styrene, alkyl (meth) acrylate and aryl (meth) acrylate.

comprennent l'acide acrylique, l'acide méthacrylique, l'acide acrylamidométhylpropanesulfonique, l'acide acrylamidométhylbutanoïque, l'acide maléique, l'acide fumarique, l'acide itaconique, l'acide vinylsulfonique, l'acide styrène sulfonique, l'acide vinylphosphonique, l'acide allylsulfonique, l'acide allylphosphonique et leurs sels solubles dans l'eau d'un métal alcalin, d'un métal alcalins terreux, et d'ammonium. Anionic Monomers: The anionically charged monomers useful in the present invention can be selected from a broad group. The monomers may have acrylic, vinyl, maleic, fumaric or allylic functional groups and may contain a carboxy, phosphonate, sulphonate or other anionic group or the corresponding ammonium or alkaline earth metal or alkali metal salt. of 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 sulfonic acid, acid vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid and their water-soluble salts of an alkali metal, an alkaline earth metal, and ammonium.

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Cationic monomers As cationic monomers can be used those corresponding to the following formula:

dans laquelle RI représente H ou CH ; R2 et Ra représentent des groupes alkyle en Ci-C3 ; R4 représente H ou un groupe alkyle en CI-C22 ou un groupement (alkyl) aryle ou un goupement aryle substitué ; A1 représente un atome d'oxygène ou NH ; B, représente un groupe alkylène en C2-C1Q ou un groupe hydroxypropylène, et X- est un contre ion anionique. Les monomères cationiques tels que les dérivés d'halogénures de diallyldialkylammonium peuvent également être utilisés.

wherein R1 is H or CH; R2 and Ra are C1-C3 alkyl; R4 is H or C1-C22 alkyl or an (alkyl) aryl group or substituted aryl group; A1 represents an oxygen atom or NH; B represents a C2-C10 alkylene group or a hydroxypropylene group, and X- is an anionic counterion. Cationic monomers such as diallyldialkylammonium halide derivatives may also be used.

peuvent être le sodium, le potassium, l'ammonium, le magnésium, l'aluminium. SEL Any organic or inorganic salt allowing the insolubilization of the polymer prepared can be used according to the invention. Preferred salts are those comprising the sulfate, dihydrogenphosphate, phosphate and halide anions. The corresponding cations

can be sodium, potassium, ammonium, magnesium, aluminum.

The simultaneous use of two or more of these salts is also possible.

DISPERSANTS As dispersants are effective a polymeric electrolyte and / or a polyol and / or carbohydrate derivatives soluble in an aqueous salt solution.

The use of a single dispersant or a mixture of dispersants is also possible.

In a nonlimiting manner, the preferred dispersing polymers are: For dispersions of anionically charged polymers: the particularly preferred dispersing polymers are homopolymers and copolymers obtained from 2-acrylamido-2-methyl-1-propane sulfonic acid or of its salts or of the acid

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(méth) acrylique ou de ses sels et les copolymères obtenus à partir de ces monomères et des monomères non ioniques précédemment cités. Pour les dispersions de polymères à charge cationique : les polymères dispersants particulièrement préférés sont des polyamines, comme par exemple les polymères issus de la condensation de l'épichlorhydrine et de la diméthylamine, des homopolymères et copolymères obtenus à partir d'un ou plusieurs monomère (s) cationique (s) ; comme monomères cationiques, on citera par exemple des dérivés quaternisés de N, N-diméthylamino éthyl (méth) acrylate, N, N-diméthylamino propyl (méth) acrylate, N, N-diméthylamino propyl (méth) acrylamide ou N, Ndiméthylamino hydroxypropyl (méth) acrylate ou des halogénures de diallyidialkylammonium, et les copolymères obtenus à partir de ces monomères et des monomères non ioniques précédemment cités.

(meth) acrylic or its salts and the copolymers obtained from these monomers and nonionic monomers mentioned above. For dispersions of cationically charged polymers: the particularly preferred dispersing polymers are polyamines, for example polymers derived from the condensation of epichlorohydrin and dimethylamine, homopolymers and copolymers obtained from one or more monomers ( s) cationic (s); cationic monomers which may be mentioned for example are quaternized derivatives of N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylamino propyl (meth) acrylate, N, N-dimethylamino propyl (meth) acrylamide or N, N-dimethylamino hydroxypropyl ( meth) acrylate or diallyldialkylammonium halides, and the copolymers obtained from these monomers and the aforementioned nonionic monomers.

Particularly preferred dispersing polymers are also polyalkylene ethers, for example polyethylene glycol, polypropylene glycol or 2-acrylamido-2-methyl-1-propane sulfonic acid homopolymer, polydiallyldimethylammonium chloride (poly-DADMAC) and / or polyacryloyloxyethyltrimethylammonium chloride and their derivatives.

EXEMPLES Les viscosités sont des viscosités Brookfield mesurées avec les modules LV 2,3 ou 4 et à la vitesse de 60,30 ou 12 tours par minute selon les polymères. Certain additives known to those skilled in the art can also be used. Non-limiting way include glycerol, ethylene glycol, propylene glycol ...

EXAMPLES The viscosities are Brookfield viscosities measured with the LV 2.3 or 4 modules and at the speed of 60.30 or 12 revolutions per minute depending on the polymers.

d'acryloyloxyéthylltriméthylmammonium (ADC) à 80%, 135. 52g de chlorure d'acryloyloxyéthyldiméthylbenzylammonium (ADBZ) à 80% EXAMPLE 1 Copolymer AM / ADC / ADBZ 65/8/27: Active Ingredient: 20% In a 1 liter reactor equipped with agitation, a thermometer, a condenser and a nitrogen inlet, Monomers: 137.17 g of acrylamide (AM) at 50%, 28.75 g of chloride

80% acryloyloxyethylltrimethylammonium (ADC) 135. 52g of 80% acryloyloxyethyldimethylbenzylammonium chloride (ADBZ)

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Le dispersant : 74, 3g d'une solution aqueuse à 20% d'homopolymère de chlorure de diallyldiméthyl ammonium (polyDADMAC).

The dispersant: 74.3 g of a 20% aqueous solution of diallyldimethylammonium chloride homopolymer (polyDADMAC).

Salt: 127.15g of ammonium sulphate with 6.14g of glycerol and 469.55g of water.

The mixture is heated at 38 ° C. and degassed with nitrogen for 1 / 2h.

An azo initiator such as VA044 (start of polymerization) is then added. The temperature is maintained at 38OC. Ammonium sulfate fractions of 7.14 g are added 40 min, 1 h 20 and 2 h after the addition of the initiator.

A new fraction of azo initiator (identical or different from that used during the priming) is introduced after 5:30 of polymerization.

The polymerization is complete after 8:30 of reaction.

VA 044 TM is a 2, 2'-Azobis [2- (2-imidazolin-2-yl) propane dihydrochloride compound marketed by the company WAKO.

Example 2: Same as Example 1 except that the entire fraction of the ammonium salt is introduced into the initial formulation.

Example 3: Same as Example 1 except that 21.42 g of salt are introduced after 1h15 of polymerization.

Example 4: Same as Example 1 except that 21.42 g of salt are introduced after 3 hours of polymerization.

Example 5: Same as Example 1 except that 21.42 g of salt are introduced at the end of polymerization.

The peak viscosities obtained during the polymerization of the mixtures for Examples 1 to 5 were recorded in Table 1.

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Tableau 1

Table 1

<Tb>
<tb> Fraction <SEP> of <SEP> NF <SEP> Time <SEP> Fraction <SEP> of <SEP> salt <SEP> Viscosity
<tb> salt <SEP> initial <SEP> (%) <SEP> supp. <SEP> adding <SEP> in <SEP> adding <SEP> (%) <SEP> bulk <SEP> max
<tb> Example <SEP> 1 <SEP> 85.6 <SEP> 40min <SEP> 4.8
<tb> invention <SEP> 3 <SEP> 1h20 <SEP> 4.8 <SEP> 820 <SEP> cp
<tb> 2h <SEP> 4.8
<tb> Example <SEP> 2 <SEP> 100 <SEP> - <SEP> - <SEP> - <SEP> 10000 <SEP> cp
<tb> Example <SEP> 3 <SEP> 85.6 <SEP> 1 <SEP> 1h15 <SEP> 14.4 <SEP> 3300 <SEP> cp
<tb> invention
<tb> Example <SEP> 4 <SEP> 85.6 <SEP> 1 <SEP> 3H <SEP> 14.4 <SEP> 7000 <SEP> cp
<tb> Example <SEP> 5 <SEP> 85.6 <SEP> 1 <SEP> 8:30 <SEP> 14.4 <SEP> 9400 <SEP> cp
<Tb>
NF: number of additional fractions added fractionally after initiating the polymerization. Conclusion: Very high maximum viscosities are observed when all the ammonium sulphate is introduced into the initial formulation (eg 2) or a further fraction of ammonium sulphate is introduced at the end (eg 5) or after 3H polymerization (eg 4).

A total amount of identical salts, the addition of a single fraction of ammonium sulfate at the beginning of polymerization (eg 3) improves the fluidity of the mixture, the latter can be further improved by the subsequent addition of several salt fractions in the first part of the polymerization (eg 1) defined previously.

The single figure shows the variation of the viscosity of the reaction mixture during the polymerization as a function of time for Examples 1, 2 and 4.

It can be seen that the advantage of the invention lies in the fact that it makes it possible to maintain a very low level of viscosity throughout the polymerization, avoiding the variations and increases in viscosity of the reaction mixture, which makes it possible to eliminate the problems and the risks of runaway reaction related to

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problèmes d'échange en milieu fortement visqueux qui sont inhérents aux autres procédés de polymérisation tels que décrits dans l'art antérieur.

exchange problems in highly viscous medium which are inherent in other polymerization processes as described in the prior art.

Example 6: Same as Example 1 except for the dispersant: 81 g of a 20% aqueous solution of poly (ADC) (replacing the poly (DADMAC)) and 462.58 g of water.

Maximum Viscosity of Dispersion: 1100 cp Example 6 shows that all the advantage of the invention is retained whatever the type of dispersant used.

EXAMPLE 7 Copolymer AM / ADBZ 90/10: Active Ingredient: 20% Identical to Example 1 with the exception of the monomers: 281.13 g of 50% acrylamide, 74.30 g of acryloyloxyethyldimethylbenzylammonium chloride at 80% and 415. 56g of water.

Maximum viscosity of dispersion: 1500 cp

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Exemple 8 : Copolymère AM/ADC/ADBZ 25/27/48 : matière active : 20% Identique à l'exemple 1 à l'exception des monomères : 35.56g d'acrylamide à 50%, 65.40g de chlorure d'acryloyloxyéthyl triméthymammonium à 80%, 162.38g de chlorure d'acryloyloxyéthyldiméthyl benzyl ammonium à 80% et 507.65g d'eau.

EXAMPLE 8 Copolymer AM / ADC / ADBZ 25/27/48 Active Ingredient: 20% Identical to Example 1 with the exception of monomers: 35.56 g of 50% acrylamide and 65.40 g of acryloyloxyethyl trimethylammonium chloride at 80%, 162.38 g of acryloyloxyethyldimethyl benzyl ammonium chloride at 80% and 507.65 g of water.

Maximum Dispersion Viscosity: 760 cp Examples 1.7 and 8 show that polymer dispersions can be prepared in a wide range of tonicity according to the process of the invention while maintaining good fluidity.

EXAMPLE 9 Copolymer AM / ADC / ADBZ 50/15/35 Active Ingredient: 25% Identical to Example 1 with the exception of the monomers: 111.57 g of 50% acrylamide, 57.00 g of sodium chloride. 80% acryloyloxyethyltrimethymammonium, 185.76 g of 80% acryloyloxyethyldimethylbenzylammonium chloride and 416.65 g of water.

Maximum dispersion viscosity: 1800 cp Example 10: AM / ADC / ADBZ 50/15/35 copolymer: active ingredient: 30% Same as Example 1 except for the monomers: 133.89 g of 50% acrylamide 68.40 g of 80% acryloyloxyethylltrimethymammonium chloride, 222.92 g of 80% acryloyloxyethyldimethylbenzylammonium chloride and 345.78 g of water.

Maximum viscosity of the dispersion: 2900 cp Examples 1.9 and 10 show that the dispersions of the invention can be carried out with high levels of active material (> 25%).

EXAMPLE 11 AM / Acrylic Acid 70/30 Copolymer: Active Ingredient: 18% In a reactor equipped with stirring, a thermometer, a condenser and a nitrogen inlet, the following are introduced: monomers: 250.94g of 50% acrylamide, 54.50g of acrylic acid

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Le dispersant : 7. 1 g d'un homopolymère de l'acide acrylamidométhylpropane sulfonique Les sels 60g de sulfate de sodium et 72g de sulfate d'ammonium avec 4.83g de soude à 50%, 18g de glycérol et 507,13 d'eau.

The dispersant: 7. 1 g of a homopolymer of acrylamidomethylpropanesulphonic acid The salts 60 g of sodium sulphate and 72 g of ammonium sulphate with 4.83 g of 50% sodium hydroxide, 18 g of glycerol and 507.13 of water .

The mixture is heated at 38 ° C. and degassed with nitrogen for 1 / 2h. An azo initiator such as VA044 (start of polymerization) is then added. The temperature is maintained at 38OC. Ammonium sulfate fractions of 8.5 g are added after 25 min, 40 min and 1 h 15 min.

A new fraction of azo initiator (identical or different from that used during the priming) is introduced after 3 hours of polymerization.

The polymerization is complete after 4:30 of reaction.

Maximum dispersion viscosity: 480 cp Example 12: Same as Example 11 except that all of the ammonium sulfate fraction is introduced into the initial formulation.

Maximum viscosity of the dispersion: 3900 cp It can be seen (eg 11 & 12) that the process of the invention also makes it possible to improve the fluidity of polymer dispersions comprising an anionic filler.

In conclusion, the various examples made according to the process of the invention, which illustrate it without however limiting it, show the improvements obtained relating to the fluidity of the reaction mixture during the polymerization process leading to stable final dispersions (with low salt content).

Claims (12)

 A process for polymerizing a monomer or a mixture of monomers in an aqueous solution in the presence of one or more water-soluble polymer (s) (called dispersant (s) or coagulant (s)) and of a salt or a mixture of salts, characterized in that the salt addition is carried out fractionally-a part before polymerization and a part in at least one or more additional successive fractions during the first part of the polymerization . More specifically, in a preferred but nonlimiting manner, the first part of the polymerization is understood to mean the period following initiation covering the first 1/3 of the total polymerization time, preferably the first 1/4, relative to the total time polymerization after initiation. 2 Process according to claim 1, characterized in that the additions sequenced in the first part of the polymerization (after addition of the catalyst), carried out in the form of one or more salt fractions in addition to the quantity introduced in the initial formulation. (before polymerization), lead to aqueous dispersions of polymers having a good fluidity throughout the polymerization process, a high active matter content (> 15% and up to 30%) and having a good stability, in a range very broad molecular weight. The term "polymerization part" refers to the period following initiation covering the first 1/3 of the total polymerization time, preferably the first 1/4, relative to the total polymerization time after initiation. Process according to claim 1 or 2, characterized in that the additional successive fraction (s) of salt are added during the first 1/4 of the total polymerization time after initiation. Process according to any one of Claims 1 to 3, characterized in that the successive salt fraction or fractions added during polymerization represent a level of approximately 1 to 50% by weight relative to the total amount present in the mixture at room temperature. during the polymerization, preferably about 5 to 50% by weight and more preferably about 10 to 40%. <Desc / Clms Page number 14>

 Process according to any one of Claims 1 to 4, characterized in that the level of water-soluble polymer (dispersant) present with the salt remains low and is less than 5% by total weight of the dispersion and preferably less than 3%. Process according to any one of Claims 1 to 5, characterized in that the following monomers and their combinations can be used.  butylacrylamide, octylacrylamide and N, N-dialkylacrylamides such as N-N-dimethylacrylamide and N-methylolacrylamide. Vinylformamid, N-vinylpyridine, N-vinylpyrrolidone, hydroxyalkyl acrylates and methacrylates can also be used. A preferred nonionic vinyl monomer will be acrylamide. Other nonionic monomers can be used without departing from the scope of the invention, especially hydrophobic monomers: styrene, alkyl (meth) acrylate and aryl (meth) acrylate.

Nonionic Monomers The nonionic monomers useful according to the invention may be chosen from water-soluble vinyl monomers. Preferred monomers belonging to this class include acrylamide and methacrylamide, acrylamide derivatives such as N-alkylacrylamide for example N-isopropylacrylamide, N-tert- Anionic Monomers The anionically charged monomers useful in the present invention may be selected from a broad group. The monomers may have acrylic, vinyl, maleic, fumaric or allylic functional groups and may contain a carboxy, phosphonate, sulphonate or other anionic group or the corresponding ammonium or alkaline earth metal or alkali metal salt. of such a monomer.  vinylsulfonic acid, styrene sulfonic acid, vinylphosphonic acid, allylsulfonic acid, allylphosphonic acid and their water-soluble salts of an alkali metal, an alkaline earth metal, and ammonium .

Examples of suitable monomers include acrylic acid, methacrylic acid, acrylamidomethylpropanesulfonic acid, acrylamidomethylbutanoic acid, maleic acid, fumaric acid, itaconic acid, <Desc / Clms Page number 15>  wherein R1 is H or CH 3; R2 and Ra are C1-C8 alkyl; R4 is H or C1-C22 alkyl or an (alkyl) aryl group or substituted aryl group; A 1 represents an oxygen atom or NH; B represents a C2-C10 allenene group or a hydroxypropylene group, and X- is an anionic counterion.

 Cationic monomers As cationic monomers, those having the following formula may be used:

Cationic monomers such as diallyldialkylammonium halide derivatives may also be used. 7 Process according to any one of claims 1 to 6 characterized in that one can use any organic or inorganic salt for insolubilization of the prepared polymer is used according to the invention. Preferred salts are those comprising the sulfate, dihydrogenphosphate, phosphate and halide anions. The corresponding cations can be sodium, potassium, ammonium, magnesium, aluminum. The simultaneous use of two or more of these salts is also possible. The process of any one of claims 1 to 7, wherein the dispersant is a polymeric electrolyte and / or a polyol and / or a carbohydrate derivative soluble in aqueous salt solution; the preferred dispersing polymers being: For dispersions of anionically charged polymers: the particularly preferred dispersing polymers are homopolymers and copolymers obtained from 2-acrylamido-2-methyl-1-propanesulfonic acid or its salts or from (meth) acrylic acid or its salts and the copolymers obtained from these monomers and nonionic monomers mentioned above. <Desc / Clms Page number 16>

For dispersions of cationically charged polymers: the particularly preferred dispersing polymers are polyamines, for example polymers derived from the condensation of epichlorohydrin and dimethylamine, homopolymers and copolymers obtained from one or more monomers ( s) cationic (s); cationic monomers that may be mentioned for example are quaternized derivatives of N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylamino propyl (meth) acrylate, N, N-dimethylamino propyl (meth) acrylamide or N, N-dimethylamino hydroxypropyl ( meth) acrylate or diallyldialkylammonium halides, and the copolymers obtained from these monomers and nonionic monomers mentioned above. Particularly preferred dispersing polymers are polyalkylene ethers, for example polyethylene glycol, polypropylene glycol or 2-acrylamido-2-methyl-1-propane sulfonic acid homopolymer, polydiallyldimethylammonium chloride (poly-DADMAC) and / or polyacryloyloxyethyltrimethyl ammonium chloride and their derivatives. The process of any one of claims 1 to 8, wherein the dispersant is a single dispersant or a dispersant mixture. Polymers and copolymers characterized in that they are obtained by a process according to any one of claims 1 to 9. 11 Nonionic, anionic, cationic or amphoteric polymers and copolymers according to claim 10, both linear and slightly or strongly branched, or crosslinked (by an effective proportion of crosslinking agent). 12 Application in the industry of polymers and copolymers according to claim 10 or 11 and processes according to any one of claims 1 to 9, including the paper industry, the treatment of water (drinkable or used), generally all the techniques of coagulation 1 flocculation, the mining industry, the petroleum and refining industry, the cosmetics industry, the textile industry, and all similar applications that will be obvious to those skilled in the art.