EP2049573A2

EP2049573A2 - Process of free-radical polymerization in aqueous dispersion for the preparation of polymers

Info

Publication number: EP2049573A2
Application number: EP07787075A
Authority: EP
Inventors: Patrick Lacroix-Desmazes; Jeff Tonnar
Original assignee: Centro de Investigacion y Desarollo Technologico SA de CV CENIDET
Current assignee: Macro M SA de CV
Priority date: 2006-07-04
Filing date: 2007-07-04
Publication date: 2009-04-22
Also published as: JP2009541567A; WO2008003729A2; US20090306302A1; WO2008003729A3; JP5201419B2; FR2903409A1; US20090292071A1; MX2008016485A; US8541524B2; EP2041185A1; EP2041185B1; WO2008003728A1

Abstract

Process of free-radical polymerization in aqueous dispersion for the preparation of polymers, employing (A) at least one ethylenically unsaturated monomer, one of which is employed as the principal monomer and is selected from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, vinylic pyridine derivatives, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives, and N-vinyl monomers, (B) at least one free-radical initiator selected from diazo compounds, peroxides and dialkyldiphenylalkanes, (C) molecular iodine, and (D) at least one oxidizing agent whose solubility in water is at least 10 g/l, of which at least one may be the one (B); said process comprising the steps whereby (1) at least one fraction of each of compounds (A), (B), (C) and (D) is introduced into a reactor, and (2) the contents of the reactor are reacted while introducing into the reactor the remainder, where appropriate, of each of compounds (A), (B), (C) and (D). Process of free-radical polymerization in aqueous dispersion for the preparation of block copolymers starting from polymers prepared by the abovementioned process.

Description

Radical polymerization process in aqueous dispersion for the preparation of polymers

The present application claims the benefit of U.S. Provisional Application 60/818276 filed July 5, 2006.

The present invention relates to a radical polymerization process in aqueous dispersion for the preparation of polymers and a radical polymerization process in aqueous dispersion for the preparation of block copolymers.

While radical polymerization is the chain polymerization mechanism that accommodates the least demanding experimental conditions and the widest range of monomers, giving it the characteristics of a living polymerization has remained a major challenge for a very long time. The main limitation of conventional free-radical polymerization stems from the crucial importance of irreversible termination reactions, by combination and / or disproportionation of the radicals responsible for chain growth. The growing chains are primed, grow and then end randomly and irreversibly, along with the priming of new chains. The polymerization ends when all the polymer chains are inactive, which are of variable length and unpredictable. This technique therefore offers little opportunity to act on the molar mass, the distribution of molar masses, the nature of the chain ends and, more generally, the molecular structure of the polymer.

In recent years, significant efforts have been made successfully to develop new radical polymerization techniques to minimize the relative importance of irreversible termination reactions, vis-à-vis the priming and propagation reactions. These techniques are called controlled radical polymerization. The common characteristic of the techniques developed is the use of a control agent (X) which transiently converts the radical of the growing chain into a dormant species (PX) that is to say in equilibrium with the active species (P).

Among the best known methods, mention may be made of nitroxide-controlled radical polymerization (Nitroxide-Mediated Polymerization or NMP), Atom Transfer Radical Polymerization (ATRP), addition-fragmentation chain transfer (Reversible Addition- Fragmentation Chain Transfer Polymerization or RAFT / MADIX) and the transfer of iodine (Iodine Transfer Polymerization or ITP) which use respectively nitroxide radicals, activated halides in the presence of metal complexes, dithiocarbonyl compounds and iodinated organic molecules as control agents.

Although these methods have been successfully studied in the case of solution and bulk polymerization, few studies have concerned aqueous dispersion polymerization, widely used at the industrial level. More recently, the technique of iodine transfer in reverse mode (Reverse

Iodine Transfer Polymerization or RITP) using iodine as a control agent has also been developed. Thus, the application WO 03/097704 discloses such a controlled radical polymerization process according to which at least one ethylenically unsaturated monomer is polymerized in the presence of at least one radical-generating agent and molecular iodine.

In the particular case of the RITP polymerization, a molecular iodine molecule controlling two polymerization chains, the target average molar mass (M _n ) of the polymer, for a conversion of 100%, is controlled by the ratio between the mass of monomer and twice the number of initial moles of iodine (n _{12; mit1} ai) according to equation 1 below, in which MA-I is the molar mass of the chain ends:

M _n = (mass of monomer) / (2x ni2, mitiai) + MA-I (equation 1) If the text of the application WO 03/097704 describes the polymerization of vinyl chloride in aqueous suspension, the process in question does not allow, however, not to obtain a polymer whose experimental average molar mass (20 000) is very close to the theoretical average molar mass (target molecular weight taking into account the conversion rate) (8700).

There remains therefore a need to develop a controlled radical polymerization process in aqueous dispersion, the control of which would be such that the theoretical average molecular weight for the polymer to be obtained is very close to that actually measured after polymerization.

The present invention therefore relates to a radical polymerization process in aqueous dispersion for the preparation of polymers which allows a better control of the polymerization and therefore the average molar mass of the polymers obtained compared to the processes of the prior art while preserving their benefits. For this purpose, the invention relates to a radical polymerization process in aqueous dispersion for the preparation of polymers using

(A) at least one ethylenically unsaturated monomer, one of which is used as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers,

(B) at least one radical generating agent selected from diazocompounds, peroxides and dialkyldiphenylalkanes,

(C) molecular iodine, and

(D) at least one oxidant whose solubility in water is at least 10 g / l, at least one of which may be one of (B); which comprises the steps according to which (1) at least one fraction of each of the compounds is introduced into a reactor

(A), (B), (C) and (D); and

(2) reacting the contents of the reactor, while introducing therein the possible balance of each of the compounds (A), (B), (C) and (D).

By polymerization in aqueous dispersion is meant the polymerization processes taking place in water in the presence of at least one surfactant.

By at least one surfactant it is meant that the polymerization process can take place in the presence of one or more surfactants.

By surfactant is meant any compound having in its structure one or more hydrophilic parts and one or more hydrophobic parts. This hydrophilic / hydrophobic balance allows the surfactant to have an interfacial activity which makes it possible to ensure dispersion and stabilization of the aqueous and organic phases in the presence.

Some polymerizations in aqueous dispersion can be carried out in the absence of surfactant but with the consequence of the formation of aqueous dispersions unstable and characterized by a very low solids content. The present invention does not relate to such polymerizations but to polymerizations in aqueous dispersion carried out in the presence of at least one surfactant.

Among the surfactants, there may be mentioned dispersing agents, also called protective colloids or suspending agents (hereinafter referred to as dispersing agents), but also emulsifiers. The term "aqueous dispersion polymerization" is intended to denote radical polymerization in aqueous suspension, radical polymerization in aqueous microsuspension, radical polymerization in aqueous emulsion and radical polymerization in aqueous miniemulsion. By radical polymerization in aqueous suspension is meant any radical polymerization process being carried out in an aqueous medium in the presence of dispersing agents as surfactants and oil-soluble radical generating agents.

By polymerization in aqueous microsuspension, also called homogenized aqueous dispersion, is meant any radical polymerization process in which is implemented oil-soluble radical generating agents and is carried out an emulsion of monomer droplets through a powerful mechanical agitation and which is characterized by the presence of emulsifying agents as surfactants. By radical polymerization in aqueous emulsion is meant any radical polymerization process being carried out in an aqueous medium in the presence of emulsifiers as surfactants and agents for generating water-soluble radicals. The aqueous emulsion polymerization is sometimes also called ab initio emulsion polymerization. The expression "aqueous mini-emulsion polymerization" is intended to denote any radical polymerization process in which oil-soluble radical generating agents and / or water-soluble radical-generating agents and a hydrophobic agent are used and an emulsion of droplets is produced. of monomers thanks to a powerful mechanical agitation and which is characterized by the presence of emulsifiers and optionally dispersing agents as surfactants.

By way of examples of dispersing agents, mention may be made of partially hydrolysed polyvinylacetates, gelatin, starch, polyvinylpyrrolidinone, copolymers of vinyl acetate and of maleic anhydride, cellulose-soluble ethers derivatives which are soluble in water. water such as methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose.

Preferably, the dispersing agents are water-soluble cellulosic ether derivatives. Of these, hydroxypropyl methylcellulose is particularly preferred. The emulsifiers may be anionic emulsifiers, nonionic emulsifiers or cationic emulsifiers.

Among the anionic emulsifiers, non-limiting mention may be made of alkyl sulphates such as sodium lauryl sulphate, alkyl sulphonates such as sodium dodecylbenzene sulphonate and pure sodium 1-hexadecanesulphonate or in the form of a mixture of C 12 -C 20 alkyl sulphonates sometimes called paraffins sulfonates, alkylaryl mono or disulfonates and dialkyl sulfosuccinates such as sodium diethylhexylsulfosuccinate and sodium dihexylsulfosuccinate.

Among the nonionic emulsifiers, mention may be made in a nonlimiting manner, alkyl- or alkylarylethoxylated derivatives, alkyl- or alkylarylpropoxylated derivatives and sugar esters or ethers.

Among the cationic emulsifiers, mention may be made of ethoxylated alkylamines and propoxylated alkylamines.

The emulsifiers are preferably anionic emulsifiers, optionally in admixture with one or more nonionic emulsifiers. Anionic emulsifiers are particularly preferred. The hydrophobic agents may be alkanes such as hexadecane, silanes, siloxanes, perfluorinated alkanes or compounds usually used as pigments, comonomers, transfer agents, initiators or plasticizers as long as they are hydrophobic.

The process for the preparation of polymers according to the invention uses at least one ethylenically unsaturated monomer, one of which is used as the main monomer and is chosen from styrene and its derivatives, the acid acrylic acid and its derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N monomers -vinyliques.

By at least one ethylenically unsaturated monomer, one of them being used as the main monomer, it is meant that the polymerization process may employ one or more ethylenically unsaturated monomers and that in the case where several monomers are, one of them is the main monomer. The term "main monomer" is intended to denote the monomer present in a proportion of at least 100% by weight of the monomer mixture and which will generate at least 100% by weight of the monomeric units of the polymer obtained, where n is the number of monomers in the monomer unit. the monomeric mixture. The ethylenically unsaturated monomer used as the main monomer is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, derivatives vinyls of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers.

Among the styrene derivatives, mention may be made of para-tert-butylstyrene, para-methylstyrene, meta-methylstyrene, alpha-methylstyrene, para-bromostyrene, para-chlorostyrene and meta- (1-chloroethyl) styrene, para-fluorostyrene, para-trifluoromethylstyrene, meta-trifluoromethylstyrene, pentafluorostyrene, para-acetoxystyrene, para-methoxystyrene, para-tertbutoxystyrene, para-epoxystyrene, para-aminostyrene, alkali metal salts styrene para-sulfonic acid, vinylbenzoic acid, alkali metal salts of vinylbenzoic acid, para-chloromethylstyrene, perfluorooctylethylenoxymethylstyrene, N, N-dimethylvinylbenzylamine, vinylbenzyltrimethylammonium chloride, 3-isopropenyl- alpha, alpha-dimethylbenzyl isocyanate. Styrene is particularly preferred.

By derivatives of acrylic acid is meant salts of acrylic acid such as alkali metal salts, acrylic acid protected with a trimethylsilyl group, tert-butyl, tetrahydropyranyl, 1-ethoxyethyl or benzyl, the acrylates alkyl, acrylonitrile, acrylamide and its derivatives.

Among the alkyl acrylates, mention may be made of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, acrylate and the like. s-butyl, isobutyl acrylate, tert-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, stearyl acrylate, acrylate glycidyl, benzyl acrylate, isobornyl acrylate, lauryl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, 2-dimethylaminoethyl acrylate, acrylate chloride 2-trimethylaminoethyl, the potassium salt of 3-sulfopropyl acrylate, fluoroalkyl acrylates such as 1,1,2,2-tetrahydroperfluorodecyl acrylate, allyl acrylate, vinyl acrylate, sugars and nucleosides protected or not such as 2-beta-D-glucopyranosyloxyethyl acrylate, n-butyl alpha-fluoro acrylate, 2- (2-bromopropionyloxy) ethyl acrylate, 2- (2-bromoisobutyryloxy) ethyl acrylate, carboxyethyl acrylate, tetrahydropyranyl acrylate, 1-ethoxyethyl acrylate and acrylate macromonomers such as poly (ethylene oxide) acrylate and poly (dimethylsiloxane) acrylate. Particularly preferred are butyl acrylate and 2-ethylhexyl acrylate.

Among the derivatives of acrylamide, there may be mentioned N, N-dimethylacrylamide, tert-butylacrylamide, N-hydroxymethylacrylamide, N-acetamidoacrylamide,

N-methylolacrylamide, N-methylolacrylamide methyl ether, 2-acrylamido-2-methylpropane sulfonic acid (AMPS) or a sodium salt thereof, for example sodium salt of 3-acrylamido-3- methylbutanoate and N-isopropylacrylamide. By derivatives of methacrylic acid is meant salts of methacrylic acid such as alkali metal salts, methacrylic acid protected with a trimethylsilyl group, tert-butyl, tetrahydropyranyl, 1-ethoxyethyl or benzyl, methacrylates of alkyl, methacrylonitrile, methacrylamide and its derivatives. Among the alkyl methacrylates, mention may be made of methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, s-butyl methacrylate and methacrylate. isobutyl, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, glycidyl methacrylate, benzyl methacrylate, isobornyl methacrylate , bornyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, fluoroalkyl methacrylates such as 1,1,2,2-tetrahydroperfluorodecyl methacrylate, allyl methacrylate, vinyl methacrylate, tetrahydropyranyl methacrylate 2- (N-morpholino) ethyl methacrylate, 2- (dimethylamino) ethyl methacrylate, 2-trimethylaminoethyl methacrylate chloride, 2-aminoethyl methacrylate, methacrylate 2-sulfoethyl methacrylate, the potassium salt of 3-sulfopropyl methacrylate, protected or unprotected sugars and nucleosides such as 5'-methacrylouridine, 2- (2-bromopropionyloxy) ethyl methacrylate, methacrylate 2- (2-bromoisobutyryloxy) ethyl, the

N, N-dimethyl-N-methacryloxyethyl-N- (3-sulfopropylammonium betaine), acetoacetoxyethyl methacrylate, carboxyethyl methacrylate, 1-ethoxyethyl methacrylate and methacrylate macromonomers such as poly (ethylene oxide) methacrylate and poly (dimethylsiloxane) methacrylate. Particularly preferred are methyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate.

Among the methacrylamide derivatives, there may be mentioned N, N- (2-hydroxypropyl) methacrylamide, [3- (methacryloylamino) propyl] trimethyl ammonium chloride, methacryloylaminopropyldimethylammonium sulfobetaine.

Among the diene monomers, mention may be made of butadiene, isoprene, chloroprene and isobutene. Particularly preferred are butadiene and chloroprene. Among the vinyl esters, mention may be made of vinyl acetate, vinyl trifluoroacetate, vinyl versatate, the ethylenic ester of tert-decanoic acid (VeoValO), the ethylenic ester of neononanoic acid (VeoVa9 ) and vinyl pivalate. Vinyl acetate is particularly preferred. Among the vinyl ethers, there may be mentioned methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isobutyl vinyl ether, n-butyl vinyl ether, cyclohexyl vinyl ether, 2-methoxyethyl vinyl ether, 2-chloroethyl vinyl ether, 2-chloroethyl propenyl ether, 3-bromo-n-propyl vinyl ether, 4-chloro-n-butyl vinyl ether, 2-hydroxy ethyl vinyl ether A-hydroxy butyl vinyl ether, 6-hydroxyhexyl vinyl ether, 4-hydroxymethyl cyclohexyl methyl vinyl ether, triethylene glycol monovinyl ether, diethylene glycol monovinyl ether, n-butyldiethoxy vinyl ether, n-hexyl ethoxy vinyl ether, methyl dipropylene glycol vinyl ether, cyclohexanediethanol monovinyl ether and 2-ethylhexylethoxy vinyl ether. Among the vinyl derivatives of pyridine, there may be mentioned 4-vinyl pyridine, 3-vinyl pyridine, 2-vinyl pyridine and 1 - (3-sulfopropyl) -2-vinylpyridinium betaine.

Among the derivatives of vinylsulphonic acid and of vinylphosphonic acid, mention may be made of their salts and their esters.

N-vinyl monomers include N-vinylcarbazole, N-vinylcarbamate, N-vinylcaprolactam, N-vinylpyrrolidinone and N-vinylimidazole. The process according to the invention is therefore advantageously a radical polymerization process in aqueous dispersion for the preparation of polymers of styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives, N-vinyl monomers.

By polymers is meant homopolymers and copolymers of these monomers as the main monomer. By copolymers is meant the copolymers of one of the aforementioned monomers, which is the main monomer, with one or more monomers copolymerizable therewith. Among the copolymerizable monomers, mention may be made, in a non-limiting manner, of the monomers listed above as main monomer but also the monomers of the maleimide, maleate, fumarate and allylic type as well as itaconic acid, cro tonic acid and maleic anhydride.

The process according to the invention is preferably a radical polymerization process in aqueous dispersion for the preparation of polymers of styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters and vinyl ethers.

The process according to the invention is particularly preferably a radical polymerization process in aqueous dispersion for the preparation of polymers of styrene and its derivatives, acrylic acid and its derivatives and methacrylic acid and its derivatives .

The mode of introduction of the ethylenically unsaturated monomer (s) (A) in the process according to the invention may be variable.

Thus, in the case where (A) consists of a single ethylenically unsaturated monomer, all the monomer can be introduced in step (1) or a fraction thereof can be introduced in step (1). and the balance in step (2). The introduction to step (2) preferably takes place continuously.

In the case where (A) consists of at least two ethylenically unsaturated monomers, one part of the monomers can be introduced in step (1) and the other part in step (2), preferably in a continuous manner. . In the particular case where (A) consists of a mixture of at least two ethylenically unsaturated monomers, the entire mixture can be introduced in step (1) or a fraction of the mixture can be introduced in step ( 1) and the balance of the same mixture introduced in step (2), preferably in a continuous manner.

The process for the preparation of polymers according to the invention uses at least one agent generating radicals chosen from diazocompounds, peroxides and dialkyldiphenylalkanes.

By at least one radical-generating agent chosen from diazocompounds, peroxides and dialkyldiphenylalkanes, it is meant that the polymerization process may use one or more radical-generating agents chosen from diazocompounds, peroxides and dialkyldiphenylalkanes.

In the remainder of the text, the expression "radical generating agent" used in the singular or the plural must be understood as designating one or more radical-generating agents unless it is designated otherwise.

The process according to the invention preferably employs at least one agent generating radicals chosen from diazocompounds and peroxides.

In a particularly preferred manner, the process according to the invention uses a single radical-generating agent.

The radical-generating agents may be oil-soluble or water-soluble.

By oil-soluble radical generating agents is meant the soluble radical generating agents in the monomer or monomers, as used for the polymerization in aqueous suspension, microsuspension or aqueous mini-emulsion.

The term "water-soluble radical-generating agents" is intended to mean the water-soluble radical generating agents as used for the aqueous emulsion or mini-emulsion polymerization. The agent that generates water-soluble radicals may be an oxidizer as defined below.

As examples of oil-soluble diazocompounds, mention may be made

2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile),

2,2'-azobis (2,4-dimethylvaleronitrile), (1-phenylethyl) azodiphenylmethane,

2,2'-azobisisobutyronitrile, • 1,1'-azobis (1-cyclohexanecarbonitrile),

2,2'-azobis (2-methylbutyronitrile),

2,2'-azobis (2,4,4-trimethylpentane),

2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, and 2,2'-azobis (2-methylpropane).

As examples of water-soluble diazocompounds, mention may be made

2- (carbamoylazo) -isobutyronitrile,

• 4,4'-azobis (4-cyanovaleric acid),

Ammonium 4,4'-azobis (4-cyanovalerate), 4,4'-azobis (4-cyanovalerate) sodium,

Potassium 4,4'-azobis (4-cyanovalerate),

2,2'-azobis (N, N'-dimethyleneisobutyramidine),

• 2,2'-azobis dihydrochloride (N, N'-dimethyleneisobutyramidine),

2,2'-azobis (2-amidinopropane) dihydrochloride; 2,2'-azobis [2-methyl-N- (1,1-bis (hydroxymethyl) -2-hydroxyethyl) propionamide],

2,2'-azobis [2-methyl-N- (1,1-bis (hydroxymethyl) ethyl) propionamide],

2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], and

• 2,2'-azobis dihydrate (isobutyramide). 4,4'-Azobis (4-cyanovaleric), ammonium 4,4'-azobis (4-cyanovalerate), 4,4'-azobis (4-cyanovalerate) sodium and 4,4 potassium azobis (4-cyanovalerate) are preferred.

As examples of oil-soluble peroxides, mention may be made of

Diacyl peroxides such as dilauroyl peroxide, dibenzoyl peroxide and didecanoyl peroxide,

• succinoyl peroxide,

Organic hydroperoxides such as cumyl hydroperoxide and tert-amyl hydroperoxide,

Dialkyl peroxydicarbonates such as diisopropyl peroxydicarbonate, dimyristyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, di [2-ethylhexyl] peroxydicarbonate, di [4-tert-butyl] cyclohexyl peroxydicarbonate and dicetyl peroxydicarbonate,

• Peresters such as t-amylperpivalate, t-butylperpivalate, t-amylperoxneodecanoate, t-butylperoxneodecanoate and cumylperoxineodecanoate. As examples of water-soluble peroxides, mention may be made of

Inorganic peroxides, such as sodium, potassium and ammonium persulfates,

• tert-butyl hydroperoxide, • hydrogen peroxide and

• perborates.

Persulfates of sodium, potassium and ammonium as well as hydrogen peroxide are preferred.

The mode of introduction of the radical generating agent (s) (B) in the process according to the invention may be variable.

Thus, in the case where (B) consists of a single radical-generating agent, all of the radical generating agent can be introduced in step (1) or a fraction thereof can be introduced to step (1) and the balance in step (2). The introduction to step (2) preferably takes place continuously.

In the case where (B) consists of at least two radical generators, a part of the radical-generating agents can be introduced in step (1) and the other part in step (2), preferably continuously.

In the particular case where (B) consists of a mixture of at least two radical generators, the entire mixture can be introduced in step (1) or a fraction of the mixture can be introduced in step ( 1) and the balance of the same mixture in step (2), preferably continuously.

The process according to the invention uses (C) molecular iodine. Molecular iodine can be used as such or in the form of a precursor thereof.

By precursor is meant a compound capable of forming molecular iodine in the polymerization medium. Examples of such precursors include iodides of alkali metals, such as sodium iodide or potassium iodide. The conversion of the precursor to molecular iodine can be obtained by adding an oxidant (D ') in the polymerization medium. The oxidant (D ') that can be used for this purpose meets the definition of oxidant (D) as detailed below.

The number of moles of molecular iodine (C) relative to the number of moles of (A) is advantageously at least 2.5 × 10 ^-5 , preferably at least ⁵ × 10 ^-5 and particularly preferably at least 10 ^-4 . In addition, the number of moles of molecular iodine (C) relative to the number of moles of (A) is advantageously at most 10 ^-1 and preferably at most 10 ^-2 .

Advantageously, at least 50 mol% of the molecular iodine (C) or its precursor and the oxidant (D ') are introduced into the reactor in step (1). Preferably, the 100% of the molecular iodine (C) or its precursor and the oxidant (D ') are introduced into the reactor in step (1). They may be introduced in step (1) at one time or in a continuous injection before step (2) begins. The oxidant (D ') may be introduced into the reactor from the beginning of step (1) or delayed, all at once or in a continuous injection.

The method according to the invention implements (D) at least one oxidant whose solubility in water is at least 10 g / 1, at least one of which may be one of (B).

By at least one oxidant (D) is meant that the polymerization process can implement one or more oxidants (D).

In the remainder of the text, the expression "oxidant" used in the singular or in the plural must be understood as designating one or more oxidants, unless it is designated otherwise.

By oxidant (D) is meant any compound which is able to oxidize iodide ions to molecular iodine; in other words, which is capable of generating an oxidation-reduction reaction with the iodide ions so that the iodide ions are oxidized to molecular iodine and the oxidant is reduced in its reduced form and therefore has a potential redox higher than that of the pair I ₂ ZI ^" (0.53). The oxidant (D) according to the invention has a solubility in water of at least

10 g / l, preferably at least 20 g / l and particularly preferably at least 30 g / l.

Among the oxidants (D) having a solubility in water of at least 10 g / l, there may be mentioned in particular sodium persulfate, potassium persulfate, ammonium persulfate, hydrogen peroxide, the compounds generating MnO ₄ ^" , ClO ^" , ClO ₂ ^" , ClO ₃ ^" ions, manganese (III) salts and iron (III) salts such as ferric citrate, ammonic / ferric citrate, ammonic / ferric sulfate, ferric acetylacetonate, ferric bromide, ferric phosphate and ferric pyrophosphate. Preferred are sodium persulfate, potassium persulfate, ammonium persulfate and hydrogen peroxide. By at least one oxidant, at least one of which may be one of (B), it is meant that at least one of the oxidants (D) is one of the radical-generating agents (B), in particular the one of the water-soluble radical generating agents (B), or that none of the oxidants is one of the radical-generating agents (B), in particular one of the water-soluble radical generating agents (B).

According to the process according to the invention, it is advantageous to reduce the acidic pH of the aqueous phase in order to improve the yield of the reaction.

The mode of introduction of the oxidant (s) (D) in the process according to the invention may be variable. The whole of (D) can be introduced in step (1) or a fraction of it can be introduced in step (1) and the balance in step (2). The introduction is preferably continuous. The introduction to step (2) preferably takes place continuously.

Preferably, all of (D) is introduced into the reactor between the beginning of step (1) and the moment of step (2) where the conversion rate reaches 70%.

According to a first preferred embodiment, the process according to the invention is either an aqueous suspension polymerization process or an aqueous suspension microsuspension polymerization process, preferably in aqueous suspension, for the preparation of polymers employing

(B) at least one oil-soluble radical generating agent selected from oil-soluble diazocompounds and oil-soluble peroxides,

(C) molecular iodine, and (D) at least one oxidant whose solubility in water is at least 10 g / l, none of which is one of (B); which comprises the steps according to which (1) at least one fraction of each of the compounds (A), (B), (C) and (D) is introduced into a reactor; and (2) reacting the reactor contents while introducing the balance of each of the compounds (A), (B), (C) and (D). The features defined previously in general in the context of the method according to the invention apply to the first preferred embodiment of the method according to the invention.

In the particular case of the first preferred embodiment of the process according to the invention, the radical-generating agent being oil-soluble, the process implements (D) at least one oxidant whose solubility in water is from minus 10 g / 1.

In the particular case of the first preferred embodiment of the process according to the invention, advantageously, none of the oxidants is one of the radical-generating agents (B).

In the particular case of the first preferred embodiment of the process according to the invention, a single oil-soluble radical generating agent (B) is preferably used.

According to this first preferred embodiment, a single oxidant is preferably used as oxidant (D). The preferred oxidant (D) is hydrogen peroxide.

According to this first embodiment, in the case where the molecular iodine (C) is used in the form of a precursor and it is then necessary to add an oxidant (D ') in the medium. method for generating iodine, the added oxidant (D ') is preferably hydrogen peroxide.

The total number of moles of oxidant (oxidizing agent (D) and optionally oxidizing agent (D ') relative to the number of moles of molecular iodine is preferably at least 0.5, particularly preferably at least 1.5, of very particularly preferably at least 2 and most preferably at least 3. A ratio of at least 4 is particularly advantageous.

The total number of moles of oxidant (oxidant (D) and optionally oxidizing agent (D ') relative to the number of moles of molecular iodine is preferably at most 10, particularly preferably at most 9.

According to a second preferred embodiment, the process according to the invention is an aqueous emulsion polymerization process for the preparation of polymers which implements

(A) at least one ethylenically unsaturated monomer, one of which is used as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, derivatives vinyls of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers, (B) at least one water-soluble radical generating agent selected from water-soluble diazocompounds and water-soluble peroxides, (C ) of molecular iodine, and

(D) at least one oxidant whose solubility in water is at least 10 g / l, at least one of which may be one of (B); which includes the steps that

(1) introducing into a reactor at least a fraction of each of the compounds (A), (B), (C) and (D); and

The features defined previously generally in the context of the method according to the invention apply to the second preferred embodiment of the method according to the invention.

According to the second preferred embodiment of the process according to the invention, at least one of the oxidants (D) may be one of the water-soluble radical generating agents (B), preferably at least one of the oxidizing agents (D). ) is one of the water-soluble radical generating agents (B). The total number of moles of oxidants (oxidizing agent (D) and optionally oxidizing agent (D ')) and radical-generating agents (B) relative to the number of moles of molecular iodine is preferably at least 1.5, from particularly preferably at least 2, most preferably at least 2.5 and most preferably at least 3. A ratio of at least 4 is particularly preferred.

The total number of moles of oxidants (oxidizing agent (D) and optionally oxidizing agent (D ')) and radical generating agents (B) relative to the number of moles of molecular iodine is preferably at most 11, from In a particularly preferred embodiment of the second preferred embodiment of the process according to the invention, the process according to the invention is an aqueous emulsion polymerization process for the preparation of polymers employing (A) at least one ethylenically unsaturated monomer, one of which is used as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers,

(B) at least one water-soluble radical generating agent selected from water-soluble diazocompounds and water-soluble peroxides,

(C) molecular iodine, and

(D) an oxidant whose solubility in water is at least 10 g / l which is one of (B), and comprising the steps (1) to (2) above.

According to a first subvariant of the first particularly preferred variant, the process according to the invention is an aqueous emulsion polymerization process for the preparation of polymers employing

(B) a water-soluble radical generating agent selected from water-soluble diazocompounds and water-soluble peroxides, (C) molecular iodine, and

(D) an oxidant whose solubility in water is at least 10 g / l which is (B), and comprising the steps (1) to (2) above,

Preferably, the radical-generating and oxidizing agent is chosen from sodium persulfate, ammonium persulfate and potassium persulfate.

According to this first sub-variant, in the case where the molecular iodine (C) is used in the form of a precursor and it is then necessary to add an oxidizing agent (D ') in the medium method for generating the iodine, the oxidant (D ') may be the radical generating agent (B) and oxidizing agent (D) or an oxidizing agent (D') different from (B), such as, for example, the peroxide of 'hydrogen. Preferably, the oxidant (D ') is the radical generating agent (B) and oxidizing agent (D).

According to a second sub-variant of the first particularly preferred variant, the process according to the invention is an aqueous emulsion polymerization process for the preparation of polymers using

(A) at least one ethylenically unsaturated monomer, one of which is implemented as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, vinyl derivatives of the pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers,

(B) two water-soluble radical generating agents selected from water-soluble diazocompounds and water-soluble peroxides,

(C) molecular iodine, and

(D) an oxidant whose solubility in water is at least 10 g / l which is one of (B), and comprising the steps (1) to (2) above,

Preferably, one of the radical-generating agents is chosen from ammonium 4,4'-azobis (4-cyanovalerate), sodium 4,4'-azobis (4-cyanovalerate) and 4,4-azobis (4-cyanovalerate). potassium azobis (4-cyanovalerate) and the other which is also the oxidant (D) is hydrogen peroxide.

According to this second sub-variant, in the case where the molecular iodine (C) is used in the form of a precursor and it is then necessary to add an oxidant (D ') in the medium for polymerization to generate iodine, the oxidant (D ') is preferably the oxidant (D), thus particularly preferably hydrogen peroxide.

The first subvariant is preferred to the second subvariant. According to a second preferred variant of the second preferred embodiment of the process according to the invention, the process according to the invention is an aqueous emulsion polymerization process for the preparation of polymers implementing

(C) molecular iodine, and (D) two oxidants whose solubility in water is at least 10 g / l, each one being one of (B), comprising steps (1) to (i) 2) above, According to this second variant of the second preferred embodiment of the process according to the invention, the process uses a persulfate chosen from sodium persulfate, ammonium persulfate and potassium persulfate, and hydrogen peroxide. According to this second variant, in the case where the molecular iodine (C) is used in the form of a precursor and it is then necessary to add an oxidant (D ') in the polymerization medium to generate the iodine, the oxidant (D ') may be one of the two oxidants (D) or an oxidant different from the two oxidants (D). Preferably, the oxidant (D ') is one of the two oxidants (D), thus particularly preferably one of the above-mentioned persulfates or hydrogen peroxide.

According to a third variant of the second preferred embodiment of the process according to the invention, the process according to the invention is an aqueous emulsion polymerization process for the preparation of polymers employing

(C) molecular iodine, and (D) an oxidant whose solubility in water is at least 10 g / l which is not one of (B), and comprising the steps of (1) ) to (2) above.

According to a third preferred embodiment, the process according to the invention is an aqueous miniemulsion polymerization process for the preparation of polymers using (A) at least one ethylenically unsaturated monomer, one of which is implemented as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, vinyl derivatives of the pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers, (B) at least one oil-soluble radical generating agent selected from oil-soluble diazocompounds and oil-soluble peroxides and / or at least one water-soluble radical generating agent selected from water-soluble diazocomposites and water-soluble peroxides, (C) molecular iodine, and

The features defined previously generally in the context of the method according to the invention apply to the third preferred embodiment of the method according to the invention.

According to a first preferred variant of the third preferred embodiment, the process according to the invention is an aqueous miniemulsion polymerization process for the preparation of polymers using (A) at least one ethylenically unsaturated monomer, one of which between them is implemented as the main monomer and is selected from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers, (B) at least one oil-soluble radical generating agent chosen from oil-soluble diazocompounds and oil-soluble peroxides,

(C) molecular iodine, and

(D) at least one oxidant whose solubility in water is at least 10 g / l, none of which is one of (B), and comprising the steps (1) to (2) above. According to this first preferred variant, the radical-generating agent being oil-soluble, the process uses (D) at least one oxidant whose solubility in water is at least 10 g / l.

According to this same variant, advantageously, none of the oxidants is one of the radical-generating agents (B). According to this same variant, a single oil-soluble radical generating agent (B) is preferably used. A single oxidant is also preferably used as oxidant (D). The preferred oxidant (D) is hydrogen peroxide.

According to this first preferred variant of the third embodiment, in the case where the molecular iodine (C) is used in the form of a precursor and it is then necessary to add an oxidizing agent (D ' ) in the polymerization medium to generate iodine, the added oxidant (D ') is preferably hydrogen peroxide.

The total number of moles of oxidants (oxidizing agent (D) and optionally oxidizing agent (D ')) relative to the number of moles of molecular iodine is preferably at least 0.5, particularly preferably at least 1.5, of very particularly preferably at least 2 and most preferably at least 3. A ratio of at least 4 is particularly advantageous.

The total number of moles of oxidants (oxidizing agent (D) and optionally oxidizing agent (D ')) relative to the number of moles of molecular iodine is preferably at most 10, particularly preferably at most 9.

According to a second variant of the third preferred embodiment, the process according to the invention is an aqueous miniemulsion polymerization process for the preparation of polymers using (A) at least one ethylenically unsaturated monomer, one of which between them is implemented as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, derivatives vinyl pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers,

(C) molecular iodine, and

(D) at least one oxidant whose solubility in water is at least 10 g / l, at least one of which is one of (B), and comprising the steps (1) to (2) above.

According to this second variant, the radical-generating agent being water-soluble, the process uses (D) at least one oxidant whose solubility in water is at least 10 g / l, of which at least one is one of (B).

According to this same variant, a single water-soluble radical generating agent (B) is preferably used. A single oxidant is also preferably used as oxidant (D). The generating agent of water-soluble radicals and the oxidant (D) are particularly preferably the same compound. The particularly preferred oxidant (D) and radical generating agent (B) is selected from sodium persulfate, potassium persulfate and ammonium persulfate. According to this second variant of the third embodiment, in the case where the molecular iodine (C) is used in the form of a precursor and it is then necessary to add an oxidant (D ') in the polymerization medium for generating iodine, the added oxidant (D ') is preferably the radical generating agent (B) and oxidizing agent (D). The total number of moles of oxidants (oxidizing agent (D) and optionally oxidizing agent (D ')) and radical-generating agents (B) relative to the number of moles of molecular iodine is preferably at least 1.5, from particularly preferably at least 2, most preferably at least 2.5 and most preferably at least 3. A ratio of at least 4 is particularly preferred.

The total number of moles of oxidants (oxidizing agent (D) and optionally oxidizing agent (D ')) and radical generating agents (B) relative to the number of moles of molecular iodine is preferably at most 11, from in a particularly preferred manner of at most 10. In order to react the reactor contents according to step (2), means are used by which radicals are generated within it. For this purpose, it can especially heat it or expose it to intense light radiation.

The temperature at which the reactor contents is reacted is advantageously at least 30 ^° C. and preferably at least 40 ^° C. In addition, it is advantageously at most 200 ^° C. and preferably at most 120 ^° C.

Advantageously, step (2) is carried out until the ethylenically unsaturated monomer or monomers have reacted within certain limits. The step (2) is carried out until the conversion rate of the ethylenically unsaturated monomer (s) is preferably at least 82%. Step (2) will be carried out until the conversion rate of the ethylenically unsaturated monomer (s) is preferably at most 100%.

The radical polymerization process for the preparation of polymers according to the invention may optionally also comprise a step (3) during which the reaction is terminated by introducing a chemical agent capable of decomposing the excess radical generating agent. and / or extracting the fraction of (A) which has not reacted, these operations being performed simultaneously or successively, in the reactor or outside thereof.

When the fraction of (A) which has not reacted has a sufficient volatility, it will be advantageously extracted from the contents of the reactor by drawing it under vacuum and / or by steam distillation.

The radical polymerization process for the preparation of polymers according to the invention may optionally further comprise a step, subsequent to the preceding steps, in which the polymer is isolated from the reactor contents (step (4)). To isolate the polymer from the contents of the reactor, all the separation techniques known to those skilled in the art, in particular dewatering and drying in a fluidized bed, may be carried out in addition to the demonomerization treatment already discussed above ( especially when the polymer has been produced by a slurry process) and spray drying or coagulation drying (particularly when the polymer has been produced by an emulsion or mini-emulsion process). These operations are advantageously carried out outside the reactor.

In the case where the synthesis of block copolymers is envisaged, no action is preferably taken on the aqueous dispersion containing the polymer prepared by the process according to the invention; this being then used as it is for the synthesis process of block copolymers according to the invention.

Next, the present invention relates to a radical polymerization process in aqueous dispersion for the preparation of block copolymers. For this purpose, the invention relates to a radical polymerization process in aqueous dispersion for the preparation of block copolymers using (A ') at least one ethylenically unsaturated monomer chosen from styrene and its derivatives, acrylic acid and its derivatives. derivatives, methacrylic acid and its derivatives, dienics, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers, and (E ') at least one polymer chosen from the polymers prepared by the process according to the invention as described above and from the precursor block copolymers prepared by reacting at least one ethylenically unsaturated monomer as defined in (A') and at least one polymer selected from the polymers prepared by the process according to the invention as described above, which comprises the steps according to which

(1 ') is introduced into a reactor at least a fraction of (A') and at least a fraction of (E '), then

(2 ') the reactor contents are reacted, while introducing the possible balance of (A') and the possible balance of (E '), and (3') the reaction is terminated.

Inasmuch as the polymerization is advantageously alive, the process for the preparation of block copolymers according to the invention advantageously makes it possible to prepare copolymers comprising two blocks by polymerizing (A ') in the presence of a polymer prepared by the process according to the invention. invention as described above but also copolymers of more than two blocks for example three blocks by polymerizing (A ') in the presence of a precursor block copolymer already comprising two blocks and so on.

The radical polymerization process for the preparation of block copolymers according to the invention has the same characteristics and preferences as those described above concerning the radical polymerization process for the preparation of polymers according to the invention, unless contraindicated or unless it is stated otherwise.

The number of ethylenically unsaturated monomers constituting (A ') can be any.

(E ') can be introduced into the reactor in any form whatsoever, especially in the form of an aqueous powder or dispersion, and after being isolated or not from the reactor contents in which it was previously prepared . (E ') is introduced into the reactor preferably in the form of an aqueous dispersion containing the polymer prepared by the process according to the invention; this being then used as it is for the process of synthesis of block copolymers according to the invention without having undergone prior treatment. The number of polymers constituting (E ') may be any but preferably 1.

Preferably, all of (E ') is introduced into the reactor in step (1'). The weight of (E ') with respect to the weight of (A') is advantageously at least 0.05, preferably at least 0.1 and particularly preferably at least 0.5. In addition, it is advantageously at most 19, preferably at most 10 and particularly preferably at most 4. In the radical polymerization process for the preparation of block copolymers according to the invention, optionally further introduced in the reactor, in step (1 ') and / or in step (2'), (B ' ) at least one radical generating agent selected from peroxides, diazocompounds and dialkyldiphenylalkanes. (B ') has the same characteristics and preferences as (B), and to whatever degree of preference it is. Preferably, introducing (B '). (B ') may be introduced entirely in step (1'), partly in step (1 ') and partly in step (2') or completely in step (2 '). To terminate the reaction (step (3 ')), it is possible, for example, to cool the contents of the reactor and / or introduce therein a chemical agent capable of decomposing the excess radical generating agent and / or extracting the fraction thereof. (A ') which has not reacted (demonomerization), these operations can be performed simultaneously or successively, in the reactor or outside thereof. The demonomerization operation can be carried out as described above for step (3). Finally, the radical polymerization process for the preparation of block copolymers according to the invention may optionally further comprise a step (4 '), subsequent to the preceding steps, wherein the copolymer is isolated from the reactor contents. Step (4 ') can be performed as previously described for step (4).

The radical polymerization method in aqueous dispersion for the preparation of polymers according to the invention has multiple advantages.

It is characterized by a controlled character well asserted, although using monomers deemed inherently prone to transfer the radical activity of the growing polymer chains on themselves (transfer reactions on monomer) and / or dead polymer chains ( transfer reactions on polymer).

Compared to the basic method using iodine as a control agent described in the prior art, the process according to the invention makes it possible to improve the control of the number-average molecular weight (or weight) of the polymers prepared in dispersion. aqueous as well as their polydispersity. Thus, it can be seen that the difference between the theoretical molecular mass and the experimental molecular mass is significantly smaller than in the case of the previous process. Another very important advantage of the radical polymerization process for the preparation of polymers and the radical polymerization process For the preparation of block copolymers according to the invention is that the growth of the polymer chains prepared in aqueous dispersion can be restarted by reacting the polymers with ethylenically unsaturated monomers, identical or different from those which had been polymerized beforehand. In this way, block copolymers can be prepared. On the contrary, according to the "conventional" radical polymerization process, it is not usually possible to synthesize such copolymers.

Another advantage of the radical polymerization processes according to the invention is that they do not require the use of usually expensive raw materials such as iodinated organic transfer agents.

A last specific advantage to the first sub-variant of the first particularly preferred variant of the second embodiment is that it is entirely appropriate for industrial operation in terms of saving industrial hygiene costs.

The following examples are intended to illustrate the invention without limiting its scope. Determination of conversion to monomer

The degree of conversion to monomers was determined by gravimetric analysis in an aluminum cup. For this, a known amount of aqueous dispersion was weighed. A grain of inhibitor was then added to stop the polymerization and the water and residual monomer were evaporated. The dry polymer extract was recovered after drying under vacuum at 40 ^° C. and the degree of conversion calculated according to the equation: (Esf-Eso) / (Esth-Eso) in which Esf is the final dry extract, Eso is the initial extract and Esth is the theoretical final dry extract at 100% conversion. Determination of molecular weights

The target molecular weight (M _njVls e _e ), for a 100% conversion, was determined by applying the formula according to equation (1) namely M _njVls ee = (monomer mass) / (2x ni2, mitiai) + MA-I (equation 1) according to which nomai is the number of initial moles of molecular iodine and M _A - _I is the molar mass of the chain ends (A being the end of chain from the radical generating agent and I being the iodine atom).

The theoretical molecular weight (M _{n> t} h) was determined by considering the conversion according to M _{n> t} h = (mass of monomer) x (conversion to monomer) / (2x n _{12; mitl} ai) + MA-I. The experimental molecular weight (M _njexp ) was determined by steric exclusion chromatography on dry samples dissolved in tetrahydrofuran using a Spectra Physics Instruments SP8810 pump equipped with a Shodex RIse-61 refractometric detector, a spectrometric detector Milton Roy Ultra-Violet and two columns thermostated at 30 ^° C. of 300 mm (mixed-C PL-gel 5 μm columns from Polymer Laboratories - molecular weight ranges: 2x10 ² - 2x10 ⁶ g.mol ^"1 ) Tetrahydrofuran was used as eluent at a flow rate of 1 ml.min ^-1 . Calibration was performed using polystyrene standards from Polymer Laboratories. The Mark-Houwmk coefficients of polystyrene (K = 11.4 × 10 ^-5 dl.g ^-1 , α = 0.716) and poly (n-butyl acrylate) (K = 12.2 × 10 ^-5 dl g ^-1 , α = 0.700) were used for the calculations in the case of polyBuA samples.

The polydispersity index PDI = M _w / M _n is the ratio of the weight-average molecular weight to the number-average molecular mass determined by steric exclusion chromatography. Determination of the average diameter

The average particle diameter of the aqueous dispersion (d _p ) was determined using a Nanotrac Particle Size Analyzer 250 particle analyzer (Microtrac Inc.) based on the retro-scattering of light and the Doppler effect.

Used materials

Styrene (Acros, 99%), n-butyl acrylate (BuA, Aldrich, 99%) and methyl methacrylate (MMA, Aldrich) were purified by vacuum distillation before use. Iodine (I ₂ , Aldrich, 99.8%), sodium iodide (NaI, Acros 99%),

1-hexadecanesulphonate sodium (Lancaster, 99%), sodium dodecyl sulphate (SDS, Aldrich, 98%), potassium persulfate (KPS, Aldrich, 99%), di (4-tert-butylcyclohexyl) peroxydicarbonate ( Perkadox 16S, Akzo Nobel, 95%), hydrogen peroxide (Acros, 30% solution by weight in water), n-hexadecane (Acros, 99%), 4,4'-azobis acid (4-cyanovaleric) (ACPA, Fluka, 98%), sodium hydroxide (Carlos Erba), hydroethylcellulose (Aldrich, Mv = 9000 gmol ^-1 , DS 1.50, MS 2.5) were used as received. 2, 2'-azobisisobutyronitrile (AIBN, Fluka, 98%) was purified by recrystallization from methanol The water was deionized by passage through ion exchange columns. Example 1 (according to the invention)

120 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was then thermostated at 85 ° C. with stirring at 250 rpm. A solution of sodium 1-hexadecanesulphonate (0.031 g, M = 328.49 gmol ^-1 , 0.094 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a brine solution. 'I ₂ (0.3815 g, M = 253.81 g.mole ^"1, 1.5 mmol) in BuA (15 g, M = 128 ^{g.mole" 1,} 117 mmol). Finally, a solution of KPS (1.8 g, M = 270.31 gmol ^"1 , 6.65 mmol) in 20 g of water was added and the polymerization continued under argon, in the absence of light and for 17 hours.

The molar ratio [KPS] / [I2], the intended molecular weight (M _njVls é _e), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> th),} the experimental molecular weight (M _njexp ), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (dp) are shown in Table 1. Example 2 (according to the invention)

120 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was then thermostated at 85 ° C. with stirring at 250 rpm. A solution of sodium 1-hexadecanesulphonate (30 mg, M = 328.49 gmol ^-1 , 0.0913 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of 'I ₂ (190 mg, M = 253.81 g.mole ^"1, 0.748 mmol) in BuA (15 g, M = 128 ^{g.mole" 1,} 117 mmol). Finally, a solution of KPS (907 mg, M = 270.31 gmol ^"1 , 3.35 mmol) in 20 g of water was added and the polymerization continued under argon atmosphere, in the absence of light and for 8 hours.

The molar ratio [KPS] / [I2], the intended molecular weight (M _njVls é _e), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> th),} the experimental molecular weight (M _njexp ), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (dp) are shown in Table 1. Example 3 (according to the invention)

120 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was then thermostated at 85 ° C. with stirring at 250 rpm. A solution of sodium 1-hexadecanesulphonate (30 mg, M = 328.49 gmol ^-1 , 0.0913 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of 'I ₂ (96.1 mg, M = 253.81 g.mole ^"1, 0.378 mmol) in BuA (15 g, M = 128 ^{g.mole" 1,} 117 mmol). Finally, a solution of KPS (452 mg, M = 270.31 gmol ^"1 , 1.67 mmol) in 20 g of water was added and the polymerization continued under argon in the absence of light and for 22 hours.

The molar ratio [KPS] / [I2], the intended molecular weight (M _njVls é _e), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> th),} the experimental molecular weight (M _njexp ), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (dp) are shown in Table 1. Example 4 (according to the invention)

110 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was then thermostated at 85 ° C. with stirring at 250 rpm. A solution of sodium 1-hexadecanesulphonate (30 mg, M = 328.49 gmol ^-1 , 0.0913 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of NaI (227 mg, m = 149.89 gmol ^-1 , 1.514 mmol) in water (10 g). Butyl acrylate (15 g, M = 128 gmol ^-1 , 117 mmol) was then added Finally, a solution of KPS (1.164 g, M = 270.31 gmol ^-1 , 4.31 mmol) was added g of water was added and the polymerization continued under argon atmosphere, in the absence of light and for 8 hours.

The molar ratio [KPS] / [I2], the intended molecular weight (M _njVls é _e), the polymerization time, the conversion rate, the theoretical molecular weight (M _n, th), the experimental molecular weight (M _njexp ), the polydispersity index (PDI) and the average particle diameter of the aqueous dispersion (d _p ) are given in Table 1. Table 1

It appears from Table 1 that the experimental molecular mass is either lower than the theoretical molecular weight, or slightly higher than the theoretical molecular weight; which attests to a very good control of the polymerization.

Example 5 (comparative)

120 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was then thermostated at 85 ° C. with stirring at 250 rpm. A solution of SDS (59 mg, M = 228.28 gmol ^-1 , 0.205 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of I ₂ ( 191 mg, M = 253.81 gmol ^-1 , 0.753 mmol) in BuA (15.22 g, M = 128 gmol ^-1 , 119 mmol) Finally, a solution of ACPA (358.8 mg, M = 280.28 g mole ^"1 , 1.28 mmol) neutralized with sodium hydroxide (0.104 g, M = 40 g, mole ^{" 1} , 2.6 mmol) in water (20 g) was added and the polymerization continued under argon atmosphere at room temperature. absence of light and for 7 hours The pH measured at the end of the experiment after recovery of the aqueous dispersion was 5.2.

The target molecular weight (M _njVls _e ) of 10400 g. mole ^-1 , the polymerization time was 7 hours, the conversion rate 99%, the theoretical molecular weight (M _{n> t} h) of 10300 _g.mol ^-1 , the experimental molecular mass (M _{n / y} p) of 31000 g. mole ^"1 , the polydispersity index (PDI) of 1.97 and the average particle diameter of the aqueous dispersion (d _p ) of 106.

The experimental molecular mass obtained much higher than the theoretical molecular weight attests to poor control of the polymerization in this example where no oxidant is added. Example 6 (according to the invention)

A polyBuA-b- [poly (BuA-co-styrene)] block copolymer was prepared by seeded polymerization of styrene. Thus, 40.45 g (0.64 mmol) of the aqueous dispersion obtained in Example 1 (80% conversion) was introduced into a 100 ml glass reactor and purged by bubbling argon for 20 minutes. A solution of AIBN (0.0182 g, M = 164 gmol ^-1 , 0.11 mmol) in styrene (5.02 g, M = 104 gmol ^-1 , 48.3 mmol) was added to the aqueous latex dispersion. seed. The reaction medium was stirred for 1 hour and the polymerization continued under argon in the absence of light and for 14 hours at 75 ° C.

The intended molecular weight (M _njVls é _e), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> th),} the experimental molecular weight (M _njeX p), the polydispersity index (PDI ) measured on the obtained block copolymer are shown in Table 2 as well as the average particle diameter of the aqueous dispersion (d _p ).

The theoretical molecular weight (M _{n> t} h) was calculated using the equation

M _{n> t} h = + [(mass of styrene and residual BuA) x conversion rate (styrene + BuA) / (number of moles of polyBuA-I)]

A good correlation was found between the theoretical molecular weight (taking into account the conversion to monomers in the second block) and the experimental molecular weight, a sign of the living character of the polyBuA obtained in Example 1.

Table 2

Example 7 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of Perkadox 16S (1.495). mg, M = 398.5 gmol ^"1 , 3.75 mmol), I ₂ (0.3833 g, M = 253.81 gmol ^-1 , 1.51 mmol) and n-hexadecane (0.45 g, M = 226.45 gol). ^"1 , 1.99 mmol) in styrene (15 g, M = 104 gmol ^-1 , 144 mmol), then the solution was miniemulsified by ultrasonification (Bioclock Scientific Vibra CEL 75043, 5 min, 8 KHz) under a argon stream and the mini-emulsion was purged for another 15 minutes with argon. The reactor was thermostated at 60 ^° C. and the polymerization continued under an argon atmosphere, with magnetic stirring and in the absence of light for 20 hours. An aqueous solution of hydrogen peroxide (0.7 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 gmol ^-1 , 6.17 mmol) in 15 g of water was injected for 3 hours from the beginning of the reaction using a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (M _njVls ee), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _njexp ), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 3. Example 8 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. The reaction medium was purged for 15 minutes with argon. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon followed by a solution of Perkadox 16S (746). mg, M = 398.5 gmol ^-1 , 1.87 mmol), I ₂ (0.1903 g, M = 253.81 gmol ^-1 , 0.748 mmol) and n-hexadecane (0.45 g, M = 226.45 gol). ^"1 , 1.99 mmol) in styrene (15 g, m = 104 gmol ^-1 , 144 mmol), then the solution was miniemulsified by ultrasonication (Bioclock Scientific Vibra CeIl 75043, 5 min, 8 KHz) under a Argon flow and the mini-emulsion was purged for another 15 minutes with argon The reactor was thermostated at 60 ^° C. and the polymerization was continued under argon atmosphere, with magnetic stirring and in the absence of light for 16 hours An aqueous solution of hydrogen peroxide (0.3 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 gmol ^-1 , 2.65 mmol) in 15 g of water was injected during 3 hours from the beginning of the reaction by means of a perfusor

Compact Braun equipped with a 20 ml Terumo syringe. The pH measured at the end of the experiment after recovery of the aqueous dispersion was 3.36. The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (M _njVls ee), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _njeX p), the polydispersity index (PDI) and the average particle diameter of the aqueous dispersion (d _p ) are shown in Table 3. Example 9 (comparative)

Example 8 was reproduced in the absence of iodine, hydrochloric acid and hydrogen peroxide, all other conditions being equal. The pH measured at the end of the experiment after recovery of the aqueous dispersion was 4.74. The polymerization time, the conversion rate, the experimental molecular mass (M _{n> exp} ), the polydispersity index (PDI) and the average particle diameter of the aqueous dispersion (d _p ) are shown in Table 3. Example 10 (comparative)

Example 8 was repeated in the absence of hydrochloric acid and hydrogen peroxide and with a Perkadox / iodine ratio of 2 instead of 2.5, all other conditions being equal. The pH of the aqueous phase measured at the end of the experiment after recovery of the aqueous dispersion was 2.36. The polymerization time, the conversion rate, the experimental molecular weight (M _{n> exp} ), the polydispersity index (PDI) and the average particle diameter of the aqueous dispersion (d _p ) are given in Table 3.

The target molecular weight (M _njVls e _e ), the polymerization time, the conversion rate, the experimental molecular weight (M _njexp ), the polydispersity index (PDI) and the average particle diameter of the aqueous dispersion (d _p ) are shown in Table 3. Example 11 (according to the invention)

Example 8 was reproduced in the absence of hydrochloric acid, all other conditions being equal. The pH of the aqueous phase measured at the end of the experiment after recovery of the aqueous dispersion was 6.75 and the polymerization time was 18 hours.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (M _njVls ee), the polymerization time, the conversion rate, the experimental molecular mass (M _njexp ), the polydispersity index (PDI) ) and the mean diameter of the particles of the aqueous dispersion (d _p ) are shown in Table 3. Example 12 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. The reaction medium was purged for 15 minutes with argon. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of Perkadox 16S (375 mg, M = 398.5 gmol ^"1 , 0.94 mmol), I ₂ (0.0952 g, M = 253.81 g / mole ^-1 , 0.375 mmol) and n-hexadecane (0.45 g, M = 226.45 gmol ^-1 , 1.99 mmol) in styrene (15 g, m = 104 gmol ^-1 , 144 mmol), then the solution was miniemulsified by ultrasonification (Bioclock Scientific Vibra CEL 75043, 5 min, 8 KHz) under a flow of argon and the mini-emulsion was purged for another 14 minutes with argon The reactor was thermostated at 60 ^° C. and the polymerization was continued under argon, with magnetic stirring and in the absence of light for 14 hours. Aqueous solution of hydrogen peroxide (0.277 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 gmol ^-1 , 2.44 mmol) in 15 g of water. was injected for 3 hours from the beginning of the reaction using a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _nyX p), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 3.

Table 3

na: not applicable

From the results presented in Table 3, it appears that the experimental molecular weight of the polymers obtained in the examples according to the invention 7, 8 and 12 is either similar to the theoretical molecular weight, or slightly higher than this one; which attests to a very good control of the polymerization.

On the other hand, comparison of experimental molecular weight and theoretical molecular weight values for Example 10 (comparative) not involving the addition of an oxidant, it appears that the control is bad.

Comparison of the results of Examples 8 and 11 illustrates that the acidification of the aqueous dispersion makes it possible to improve the yield of the polymerization reaction while maintaining good control of the polymerization.

In the absence of iodine (Example 9), the PDI is much higher and the polymer obtained does not allow to restart the chains to make a block copolymer. Example 13 (according to the invention)

42.5 g (M = 4900 gmol ^"1 , 0.55 mmol) of the aqueous dispersion obtained in Example 7 (76% monomer conversion) were introduced into a 100 ml glass reactor and purged by argon bubbling. for 20 minutes A solution of AIBN (0.0233 g, M = 164 gmol ^-1 , 0.142 mmol) in styrene (3.01 g, M = 104 gmol ^-1 , 28.9 mmol) was added to the dispersion The reaction medium was stirred for 1 hour and the polymerization continued under argon, in the absence of light and for 22 hours at 75 ° C.

The target molecular weight (M _njVls e _e ), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular weight (M _njexp ) and the polydispersity index (PDI) measured on the block copolymer obtained are shown in Table 4 as well as the average particle diameter of the aqueous dispersion (d _p ).

M _{n> t} h = M p _nj _r ernierbioc + [(styrene mass) x (conversion rate) / (number of moles of the first block)]

A good correlation was found between the theoretical molecular mass and the experimental molecular mass, a sign of the living character of the aqueous dispersion obtained according to Example 7.

Table 4

Example 14 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of AIBN (427 mg, m.p. = 164 gmol ^"1 , 2.6 mmol), I ₂ (0.1922 g, M = 253.81 gmol ^-1 , 0.76 mmol) and n-hexadecane (0.45 g, M = 226.45 gmol ^-1) . 1.99 mmol) in butyl acrylate (15 g, M = 128 gmol ^-1 , 117 mmol), then the reaction medium was purged for 15 minutes with argon, the solution was miniemulsified by ultrasonication (Bioclock Scientific Vibra CeIl 75043, 1.5 min, 8 KHz) under a stream of argon and the mini-emulsion was purged for another 15 minutes with argon The reactor was thermostated at 85 ° C. and the polymerization continued under an argon atmosphere, with magnetic stirring and in the absence of light for 16 hours An aqueous solution of hydrogen peroxide (0.53 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 g.mole ^{" 1} , 4.71 mmol) in 10 g of water was injected for 2 hours starting the injection just before total discoloration of the reaction medium by means of a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _nyX p), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 5.

Table 5

Example 15 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon followed by a solution of AIBN (931). mg, M = 164 gmol ^"1 , 5.67 mmol), I ₂ (0.3865 g, M = 253.81 gmol ^-1 , 1.52 mmol) and n-hexadecane (0.45 g, M = 226.45 gol). ¹ , 1.99 mmol) in butyl acrylate (15 g, m = 128 g mol ^-1 , 117 mmol), then the reaction medium was purged for 15 minutes with argon, the solution was miniemulsified by ultrasonification (Bioclock Scientific Vibra CeIl 75043, 1.5 min, 8 KHz) under an argon flow and the miniemulsion was purged for another 15 minutes with argon. The reactor was thermostated at 85 ° C. and the polymerization continued under an argon atmosphere, with magnetic stirring and in the absence of light for 6 hours. An aqueous solution of hydrogen peroxide (0.97 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 g mol ^-1 , 8.56 mmol) in 10 g of water was injected for 2 hours starting the injection just before total discoloration of the reaction medium using a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _n , _X p), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 6. Example 16 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of AIBN (0.224). mg, M = 164 gmol ^-1 , 1.36 mmol), I ₂ (0.0952 g, M = 253.81 gmol ^-1 , 0.375 mmol) and n-hexadecane (0.45 g, M = 226.45 gol). ¹ , 1.99 mmol) in butyl acrylate (15 g, M = 128 gmol ^-1 , 117 mmol), then the reaction medium was purged for 15 minutes with argon, the solution was Ultrasound miniemulsified (Bioclock Scientific Vibra CeIl 75043, 1.5 min, 8 KHz) under a stream of argon and the miniemulsion was purged for another 15 minutes with argon The reactor was thermostated at 85 ° C. and the polymerization was completed. continued under an argon atmosphere, with magnetic stirring and in the absence of light for 16 hours An aqueous solution of hydrogen peroxide (0.265 g of a solution of hydrogen peroxide in water at 30% by weight) ds, M = 34 gmol ^"1 , 2.33 mmol) in 10 g of water was injected for 2 hours starting the injection just before total discoloration of the reaction medium by means of a Compact Braun infuser equipped with a syringe Terumo of 20 ml. The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _nyX p), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 6.

Table 6

Example 17 (according to the invention)

A polyBuA-b- [poly (BuA-co-styrene)] block copolymer was prepared by seeded polymerization of styrene. 40.75 g (M = 9200 gmol ^-1 , 0.32 mmol) of the aqueous dispersion obtained in Example 14 (85% monomer conversion) as seed latex and AIBN solution (0.02 g, M = 164 g .mole ^"1 , 0.122 mmol) in styrene

(5.14 g, M = 104 gmol ^"1 , 49.4 mmol) were introduced into a 100 ml glass reactor and purged by bubbling argon for 15 minutes.The polymerization was continued for 20 hours, with magnetic stirring , under an argon atmosphere, in the absence of light and at 80 ^° C.

The intended molecular weight (M _njVls é _e), the polymerization time, conversion rate, the theoretical molecular weight (M _{n> th),} the experimental molecular weight (M _njeX p) and the polydispersity index (PDI ) measured on the block copolymer obtained are shown in Table 7 as well as the average particle diameter of the aqueous dispersion (d _p ).

The theoretical molecular weight (M _{n> t} h) was calculated using the equation M _{n> t} h = + [(mass of styrene and residual BuA) x (conversion rate (styrene + BuA)) / (number of moles of polyBuA-I)] A good correlation was found between the theoretical molecular mass and the experimental molecular mass, sign of the living character of the aqueous dispersion obtained according to Example 14. Table 7

Example 18 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of Perkadox 16S (1.06). g, M = 398.5 gmol ^"1 , 2.66 mmol), I ₂ (0.1903 g, M = 253.81 gmol ^-1 , 0.75 mmol) and n-hexadecane (0.45 g, M = 226.45 gol). ¹ , 1.99 mmol) in methyl methacrylate (15 g, M = 100 gmol ^-1 , 150 mmol), then the reaction medium was purged for 15 minutes with argon and the solution was miniemulsified by ultrasonification (Bioclock Scientific Vibra CeIl 75043, 1.5 min, 8 KHz) under a stream of argon The reactor was thermostated at 64 ° C. and the polymerization continued under an argon atmosphere, with magnetic stirring and in the absence of light for 16 hours An aqueous solution of hydrogen peroxide (0.59 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 gmol ^-1 , 5.20 mmol) in 15 g of water was injected d at the start of the reaction for 3 hours using a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _nyX p), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 8.

Table 8

Example 19 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon followed by a solution of Perkadox 16S (2.115 g, m.p. = 398.5 gmol ^"1 , 5.3 mmol), I ₂ (0.3828 g, M = 253.81 gmol ^-1 , 1.51 mmol) and n-hexadecane (0.45 g, M = 226.45 gmol- ¹ , 1.99 mmol) in methyl methacrylate (15 g, M = 100 gmol ^-1 , 150 mmol), then the reaction medium was purged for 15 minutes with argon and the solution was miniemulsified by ultrasonication ( Bioclock Scientific Vibra CeIl 75043, 1.5 min, 8 KHz) under a stream of argon The reactor was thermostated at 64 ° C. and the polymerization continued under an argon atmosphere, with magnetic stirring and in the absence of light for 16 hours. Aqueous solution of hydrogen peroxide (0.57 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 gmol ^-1 , 5.03 mmol) in 16 g of water. was injected from the beginning of the reaction for 3 hours using a Compact Braun infuser equipped with a 20 ml Terumo syringe. The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _n , _X p), the polydispersity index (PDI) and the mean particle diameter of the aqueous dispersion (d _p ) are given in Table 9. Example 20 (according to the invention)

140 g of water were placed in a 250 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 1 ml of 0.1N hydrochloric acid. A solution of SDS (400 mg, M = 288.28 gmol ^-1 , 1.39 mmol) in water (10 g) was added to the reactor under a stream of argon, followed by a solution of Perkadox 16S (0.5233 g, M = 398.5 gmol ^"1 , 1.31 mmol), I ₂ (0.0975 g, M = 253.81 gmol ^-1 , 0.384 mmol) and n-hexadecane (0.45 g, M = 226.45 gol). ¹ , 1.99 mmol) in methyl methacrylate (15 g, M = 100 gmol ^-1 , 150 mmol), then the reaction medium was purged for 15 minutes with argon and the solution was miniemulsified ultrasonication (Bioclock Scientific Vibra CeIl 75043, 1.5 min, 8 KHz) under a stream of argon The reactor was thermostated at 64 ° C. and the polymerization was continued under an argon atmosphere, with magnetic stirring and in the absence of light for 16 hours An aqueous solution of hydrogen peroxide (0.39 g of a solution of hydrogen peroxide in water at 30% by weight, M = 34 gmol ^-1 , 3.44 mmol) in 16 g d water was injected e from the beginning of the reaction for 3 hours using a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (Mn, target), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _nyX p), the polydispersity index (PDI) and the average particle diameter of the aqueous dispersion (d _p ) are given in Table 9.

Table 9

Example 21 (according to the invention) A solution of hydroxyethylcellulose (0.055 g) in 50 g of water was placed in a 100 ml glass reactor and thoroughly purged with argon for 30 minutes. The reaction medium was acidified by addition of 0.5 ml of 0.1N hydrochloric acid. The reactor was thermostated at 60 ⁰ C. A solution of Perkadox 16S (591 mg, M = 398.5 g.mole ^"1, 1.48 mmol) and I ₂ (0.1263 g, M = 253.81 ^{g.mole" 1,} 0.50 mmol) in styrene (10 g, m = 104 g mol ^-1) ,

96 mmol) was added dropwise under argon in the reaction medium with vigorous stirring and the polymerization continued under argon, with magnetic stirring and in the absence of light for 16 hours. An aqueous solution of hydrogen peroxide (0.34 g of a hydrogen peroxide solution in water at 30 wt%, M = 34 g.mole ^"1, 3 mmol) in 12 g of water was injected during the first 2 hours using a Compact Braun infuser equipped with a 20 ml Terumo syringe.

The molar ratio [hydrogen peroxide] / [I2], the target molecular weight (M _njVls ee), the polymerization time, the conversion rate, the theoretical molecular weight (M _{n> t} h), the experimental molecular mass (M _njeX p), the polydispersity index (PDI) are shown in Table 10.

Table 10

Claims

CLAIMS 1 - Radical polymerization process in aqueous dispersion for the preparation of polymers using (A) at least one ethylenically unsaturated monomer, one of which is used as the main monomer and is chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, vinyl pyridine derivatives, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers, (B) at least one radical-generating agent chosen from diazocompounds, peroxides and dialkyldiphenylalkanes, (C) molecular iodine, and (D) at least one oxidant whose solubility in water is at least 10 g/1 of which at least one may be one of (B); which includes the steps by which

(1) at least a fraction of each of the compounds (A), (B), (C) and (D) is introduced into a reactor; And

(2) the contents of the reactor are reacted, while introducing the possible balance of each of the compounds (A), (B), (C) and (D).

2 - Process according to claim 1, characterized in that it is an aqueous suspension polymerization process using, in addition to (A) and (C),

(B) at least one agent generating oil-soluble radicals chosen from oil-soluble diazocompounds and oil-soluble peroxides, and

(D) at least one oxidant whose solubility in water is at least 10 g/1, none of which is one of (B).

3 - Process according to claim 1, characterized in that it is an aqueous emulsion polymerization process using, in addition to (A) and (C), (B) at least one agent generating water-soluble radicals chosen from water-soluble diazocompounds and water-soluble peroxides, and

(D) at least one oxidant whose solubility in water is at least 10 g/1 of which at least one may be one of (B).

4 - Method according to claim 3, characterized in that it implements

(B) at least one agent generating water-soluble radicals chosen from water-soluble diazocompounds and water-soluble peroxides, and

(D) an oxidant having a water solubility of at least 10 g/1 which is one of (B).

5 - Method according to claim 4, characterized in that it implements

(B) a water-soluble radical generating agent chosen from water-soluble diazocompounds and water-soluble peroxides, and

(D) an oxidant whose solubility in water is at least 10 g/1 which is (B).

6 - Method according to claim 4, characterized in that it implements

(B) two water-soluble radical generating agents chosen from water-soluble diazocompounds and water-soluble peroxides, and

7 - Method according to claim 3, characterized in that it implements

(D) two oxidants having a water solubility of at least 10 g/1, each being one of (B).

8 - Method according to claim 3, characterized in that it implements

(B) at least one agent generating water-soluble radicals chosen from water-soluble diazocompounds and water-soluble peroxides, and (D) an oxidant having a water solubility of at least 10 g/1 that is not one of (B).

9 - Process according to claim 1, characterized in that it is an aqueous mini-emulsion polymerization process using, in addition to (A) and (C),

(B) at least one agent generating oil-soluble radicals chosen from oil-soluble diazocompounds and oil-soluble peroxides and/or at least one agent generating water-soluble radicals chosen from water-soluble diazocompounds and water-soluble peroxides, and

(D) at least one oxidant whose solubility in water is at least 10 g/1, at least one of which may be one of (B).

10 - Radical polymerization process in aqueous dispersion for the preparation of block copolymers using

(A') at least one ethylenically unsaturated monomer chosen from styrene and its derivatives, acrylic acid and its derivatives, methacrylic acid and its derivatives, dienes, vinyl esters, vinyl ethers, vinyl derivatives of pyridine, vinylsulphonic acid and its derivatives, vinylphosphonic acid and its derivatives and N-vinyl monomers, and

(E') at least one polymer chosen from the polymers prepared by the process according to claim 1 and from the precursor block copolymers prepared by reacting at least one ethylenically unsaturated monomer as defined in (A') and at least one polymer chosen from the polymers prepared by the process according to claim 1,

which includes the steps by which

(1 ') at least one fraction of (A') and at least one fraction of (E') are introduced into a reactor, then

(2') the contents of the reactor are reacted, while introducing the possible balance of (A') and the possible balance of (E'), and

(3') we end the reaction.