[001] The present invention relates to a composition of alkoxyamines having better storage stability, in particular in the presence of monomers and/or solvent.

[002] The present invention also relates to the use of these compositions of alkoxyamines for the synthesis of polymers and copolymers, as well as the polymers obtained with these new compositions of alkoxyamines.

[Technical problem]

[003] Alkoxyamines are molecules which allow the controlled radical polymerization of monomers having double bonds (vinyl, styrenic, (meth) acrylic, etc.). It is thus possible to access the synthesis of block copolymers.

[004] This technology, which is widely described in the literature, however, remains discreet on the industrial level because obstacles remain. Non-compatibility with certain monomers, incomplete conversion, insufficient stability under certain conditions, in particular in the presence of monomers or solvents.

[005] During the industrial implementation of the synthesis of copolymers by controlled radical polymerization in the presence of alkoxyamines, it is however necessary to leave the alkoxyamines for several hours, or even several days, in the presence of monomers or solvents in pre-mix reactors or intermediate storage at unregulated temperatures.

[006] Thus, faced with the lack of reproducibility of the syntheses conducted by the applicant, numerous studies have been carried out and have demonstrated the lack of stability of an alkoxyamine-solvent system over time, the solvent possibly being a monomer or several monomers, sometimes well below the temperature conditions used for the polymerization.

[007] These studies have shown in particular a change in the NMR spectra of the alkoxyamine over time, without a mechanism or an explanation being able to be given.

[008] Thus the applicant has conducted new work with the aim of eliminating or reducing this problem.

[009] The applicant has discovered that the alkoxyamines must contain a minimum of solvent in order to preserve the character of acceptable reactivity and to be considered stable. The reactivity of a given alkoxyamine in the presence of monomer under polymerization conditions is assessed by measuring the polymerization kinetics, for example measuring the degree of conversion over time. A polymerization carried out with an alkoxyamine fresh from the refrigerator is thus compared to a polymerization carried out with the same alkoxyamine but having remained several days in a solvent.

[0010] The applicant has thus discovered that an alkoxyamine-solvent composition, the solvent possibly being a monomer or several monomers, is all the more stable the lower the quantity of solvent, that is to say that it retains its responsive character. However, it is impossible to obtain a strictly pure alkoxyamine. The various processes and industrial manufacturing steps of alkoxyamines always lead to the presence of solvent together with the alkoxyamine at the end of the polymerization process. The applicant has thus found that beyond a certain amount of solvent, the alkoxyamine could no longer be considered as a useful chemical reagent industrially for carrying out a controlled or uncontrolled radical polymerization.

[Summary of Invention]

The invention relates to a composition of at least one alkoxyamine and at least one solvent in a closed and transportable or non-transportable storage container, the solvent possibly being polar or apolar, or even consisting of one or more monomers, the said solvent being present in quantities of between 0 and 65% by mass with respect to the alkoxyamine or alkoxyamines, 0 excluded.

[Detailed description]

[0012] Any type of alkoxyamine can be used in the context of the invention. The Applicant has thus demonstrated that with two different alkoxyamines, the character of stability deteriorates in the presence of solvent over time. The alkoxyamines can be polyalkoxyamines (that is to say multifunctional alkoxyamines) but also monofunctional or multifunctional macro-alkoxyamines, that is to say alkoxyamines resulting from an addition reaction of alkoxyamine on one or more monomers.

Preferably, the preferred alkoxyamines are those whose nitroxide (also called controller fragment) is chosen from the following:

- the nitroxides of formula

(with R=Me,Et)

[0014]

-(2,2,6,6-tetramethylpiperidin-l-yl)oxy or (2,2,6,6-tetramethylpiperidin-l-yl)oxyl

-N-tert-butyl-l-phenyl-2-methylpropyl nitroxide,

-N-(2-hydroxymethylpropyl)-l-phenyl-2-methylpropyl nitroxide,

-N-tert-butyl-l-dibenzylphosphono-2, 2-dimethyl-propyl nitroxide

-N-tertiobutyl-l-di (2, 2, 2-trifluoroethyl) phosphono-2, 2-dimethylpropyl-nitroxide,

-N-tert-butyl[(1-diethylphosphono)-2-methylpropyl] nitroxide,

-N-(1-methylethyl)-1-cyclohexyl-l-(diethyl-phosphono)nitroxide,

-N-(1-phenylbenzyl)-[(1-diethylphosphono)-1-methylethyl]nitroxide,

-N-phenyl-l-diethylphosphono-2, 2-dimethylpropylnitroxide,

-N-phenyl-l-diethylphosphono-1-methylethylnitroxide,

-N-(l-phenyl2-methylpropyl)-1-diethylphosphonomethylethylnitroxide,

N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide.

The latter nitroxide is the preferred nitroxide. As regards alkoxyamines, all the alkoxyamines associated with the preceding nitroxides may be concerned by the invention and in particular N- (2-methylpropyl) -N- (l-diethylphosphono-2, 2-dimethylpropyl) -O- (2 -carboxyprop-2-yl)hydroxylamine.

The invention also relates to a composition of at least one alkoxyamine and at least one solvent, the solvent possibly being polar or apolar, or even consisting of one or more

monomers, said solvent being present in amounts of between 0 and 65% by weight relative to the alkoxyamine or alkoxyamines, 0 excluded.

The composition of at least one alkoxyamine and at least one solvent, optionally in a closed and transportable or non-transportable storage container, contains between 0 and 65% by weight of solvent, 0 excluded, and preferably less than 10%, so preferably less than 1% and even more preferably less than 0.5%.

The present invention also relates to the use of these compositions of alkoxyamines for the synthesis of polymers and copolymers, as well as the polymers obtained with the compositions of alkoxyamines object of the invention, whether they are homopolymers, copolymers statistics, block copolymers (di-blocks, tri-blocks, multi-blocks) .

The solvent can be of any type, polar or apolar, alone or in mixtures. The term “solvent” is understood to mean a solvent whose solubility of the alkoxyamine(s) can range up to 70% by mass in the said solvent. Among the solvents which may form part of the composition of the invention, mention may be made of alkanes, linear or not, aromatic solvents such as toluene or xylenes, alcohols, ketones or even esters.

[0018] In the context of the invention, any type of monomer capable of radically polymerizing is also considered among the solvents. The Applicant has thus shown that the phenomenon of degradation of stability was also observed when the alkoxyamine is dissolved in monomers.

[0019] The character of reactivity is considered acceptable when the alkoxyamine stored in the presence of solvent for more than 4 days, the polymerization kinetics of a given monomer at a given polymerization temperature with this composition is not further slowed down 5% in conversion value.

As regards the monomers which may form part of the composition of the invention, it may be any type of monomer carrying a double bond, provided that it is a solvent for the alkoxyamine.

The following monomers will be noted in particular: vinyl, vinylidene, diene, olefinic, allylic or (meth)acrylic monomers. This monomer is chosen more particularly from vinylaromatic monomers such as styrene or substituted styrenes, in particular alpha-methylstyrene, silylated styrenes, acrylic monomers such as acrylic acid or its salts, alkyl acrylates, cycloalkyl or aryl such as methyl, ethyl, butyl, ethylhexyl or phenyl acrylate, hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate, etheralkyl acrylates such as 2-methoxyethyl acrylate, alkoxy- or aryloxy-polyalkylene glycol acrylates such as methoxypolyethylene glycol acrylates, hexene and 1-octene, 1,1-diphenyl ethylene, diene monomers including butadiene, isoprene as well as fluorinated olefin monomers, and vinylidene monomers, among which vinylidene fluoride may be mentioned, alone or in mixed. Preferably, they are alkyl (meth)acrylates, and in particular butyl acrylate, as well as styrene.

With regard to the closed and transportable storage container or not, this can be a container of any shape, any capacity and any nature, but preferably it is a cylindrical was or a bottle of a capacity of less than 200 liters in plastic material. The storage container, closed and transportable or not, can also be a bag made of plastic material. The closed and transportable or non-transportable storage container can also be a metal storage capacity, for example in a manufacturing workshop.

[0023] Example 1

The alkoxyamine used is N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyprop-2-yl)hydroxylamine, the structural formula of which is as follows:

It is available from Arkema under the name Blocbuilder ® .

A kinetic follow-up of a polymerization of butyl acrylate is carried out in mass and in solvent phase (30% by mass in toluene at 122° C.) with Blocbuilder ® fresh out of the refrigerator.

The amount of Blocbuilder ® is fixed at 1.57% by mass relative to the butyl acrylate. The conversions are monitored by measuring the dry extract of polymer converted by evaporation of the unreacted butyl acrylate in a vacuum oven at 130°C. The conversion results are given in table 1 below and correspond to test 1.

Example 2

The Blocbuilder ® is left in toluene at different concentrations as well as in ethanol for 4 days in a closed container at 20°C. A monofunctional macromolecular alkoxyamine, product of the addition of 15 butyl acrylate entities to the Blocbuilder® was also tested. It is called Blocbuilder ® Abul5 and its synthesis can be undertaken simply according to the protocol described in EP1526138.

The conditions of these stays are given below in the table

1:

Example 3

Each solution from the tests of Example 2 is used to carry out a polymerization of butyl acrylate according to the protocol of Example 1 with kinetic monitoring by measuring the level of solid over time. The molar proportion of alkoxyamine is identical in all the tests.

The conversion rates (%) as a function of time are measured and given in Table 2:

The associated graph is given in Figure 1.

The following observations are noted:

-The fastest conversion is obtained with the alkoxyamine not having stayed 4 days in toluene (test 1).

- The solvent does not matter. Tests 3 in toluene and 5 in ethanol lead to the same result.

The greater the quantity of solvent, the more the alkoxyamine is degraded after 4 days (tests 3 and 4).

-A macroalkoxyamine also exhibits degradation after a stay of 4 days in toluene (test 2).

Example 4:

A C H NMR analysis confirms a significant level of degradation when the Blocbuilder® alkoxyamine has remained 10 days in chloroform. Without it being possible to interpret the reactions involved through the signals which appear after 10 days, the NMR analysis shows the lack of stability of the alkoxyamine in the presence of solvent. (Figure 2)

Claims

1 Composition of at least one alkoxyamine and at least one solvent in a closed and transportable or non-transportable storage container, the solvent possibly being polar or apolar, or even consisting of one or more monomers, the said solvent being present in amounts comprised between 0 and 65% by weight with respect to the alkoxyamine or the alkoxyamines, 0 excluded.

2 Composition according to claim 1 wherein the solvent is present in an amount between 0 and 10%, 0 excluded.

3 Composition according to claim 1 in which

the alkoxyamine is N-(2-methylpropyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxyprop-2-yl)hydroxylamine.

4 Composition according to claim 1 in which

1 alkoxyamine is a polyalkoxyamine.

5 Composition according to claim 1 in which

1 alkoxyamine is a macro-alkoxyamine.

6 Use of a composition according to claims 1 to

5 for the synthesis of polymers.

7 Polymer obtained according to the use of claim

6.