WO2015092028A1 - Method for preparing dispersions of polyurethane by polymerisation in a miniemulsion - Google Patents

Abstract

The present invention relates to a method for preparing a dispersion of polyurethane particles, which comprises the following steps: a) placing at least one (poly)isocyanate monomer and at least one polyol monomer of formula (I): (I) in the presence of an aqueous phase comprising at least one surfactant and an organic phase comprising at least one polymerisation catalyst, thus obtaining a two-phase mixture; b) emulsifying the two-phase mixture obtained in step a), thus obtaining a miniemulsion of oil-in-water, formed by droplets of said organic phase, with a mean size of 50 nm to 500 nm, dispersed in said aqueous phase; and c) polymerising the (poly)isocyanate and polyol monomers of formula (I), thus obtaining solid particles of polyurethane, with a mean size of 50 nm to 500 nm, dispersed in said aqueous phase. Figure: none.

Description

 Process for the preparation of polyurethane dispersions by mini emulsion polymerization

The present invention relates to a process for the preparation of polyurethane particle dispersions by mini-emulsion polymerization.

 The present invention also relates to novel dispersions of polyurethane particles and their uses.

The mini-emulsion polymerization technique makes it possible to obtain dispersions of monodisperse particles (latex) of polyurethane, having a particle size of between 50 nm and 500 nm (nanoparticles). Nevertheless, the polyol monomers used for the preparation of polyurethane particles are generally derived from the petroleum industry (such as butanediol, hexanediol, octanediol, polyether polyols).

(PEG, PPG), polyesterpolyols (PCL), etc.).

 There is therefore a need for new dispersions of stable polyurethane particles, not derived from petrochemistry, and in particular biosourced and biodegradable dispersions.

 In a mini-emulsion polymerization process, it is preferable to limit the influence of particle growth by Ostwald ripening and coalescence growth which has the effect of destabilizing the emulsion. For this purpose, a surfactant is generally used to control coalescence and a hydrophobic agent to inhibit Ostwald ripening.

 However, such a hydrophobic agent is trapped in the formed polyurethane particles, which can lead to changes in the properties of the final material (film, coating), after spreading and drying the latex on a given surface. Furthermore, it is preferable to avoid the presence of toxic hydrophobic agent in the dispersions obtained, in particular with a view to the use of the latter in the field of paints or adhesives.

 Thus, there is also a need for novel processes for preparing polyurethane particle dispersions, advantageously providing particle dispersions free of a hydrophobic agent.

The present invention relates to a process for the preparation of polyurethane particle dispersions by miniemulsion polymerization from biosourced monomers. More specifically, the subject of the present invention is a process for preparing a dispersion of polyurethane particles, comprising the following steps:

a) bringing into contact with an aqueous phase comprising at least one surfactant and with an organic phase comprising at least one polymerization catalyst, at least one (poly) isocyanate monomer and at least one polyol monomer of formula (I):

 in which :

 R represents a linear or branched alkyl group comprising from 2 to 30 carbon atoms, said alkyl group being substituted by at least one hydroxyl group, and possibly containing one or more unsaturations; and

 R 'represents a linear or branched alkyl group comprising from 2 to 30 carbon atoms, said alkyl group being substituted by at least one hydroxyl group,

 by which we obtain a bi-phasic mixture,

 b) the emulsification of the bi-phasic mixture obtained in step a), in which an oil-in-water miniemulsion formed of droplets of the said organic phase, with an average size ranging from 50 nm to 500 nm, is obtained; dispersed in said aqueous phase, and

 c) the polymerization of the (poly) isocyanate and polyol monomers of formula (I), in which solid particles of polyurethane, of average size ranging from 50 nm to 500 nm, are obtained, dispersed in said aqueous phase.

Process description

 During step a), the various reagents (monomers polyol, (poly) isocyanate and optional alkanepolyol comonomer, and polymerization catalyst) and the other ingredients, non-reactive, but necessary for the formation and stabilization, are brought into contact with each other. the mini-emulsion (water, surfactant and any hydrophobic agent).

 During step b), the bi-phasic mixture obtained in step a) is emulsified so as to form an emulsion, and more particularly a mini-emulsion.

In general, the term "emulsion" means a heterogeneous mixture composed of two immiscible liquids, one forming the continuous phase and the other forming the dispersed phase. By "mini-emulsion" is meant a particular case of emulsion, in which wherein the dispersed droplets have an average size of 50 nm to 500 nm, preferably 100 nm to 400 nm, and more preferably 200 nm to 400 nm, in a continuous aqueous phase.

 In the context of the present invention, during step b), a so-called "oil-in-water" mini-emulsion is formed, the continuous phase being the aqueous phase and the dispersed phase being the organic phase.

 The average size of the organic phase droplets can be measured by dynamic light scattering, for example using a Zetasiser Nano ZS90 from Malvern, at a 90 ° angle, at room temperature (the refractive index used is that of polystyrene latex).

 During step b), shearing is applied to the bi-phasic mixture capable of forming a mini-emulsion as defined above. Such methods are known per se. Such shear can be applied using a mechanical stirrer or using ultrasonication.

Preferably, the emulsification step b) is carried out by ultrasonication, preferably by maintaining the bi-phasic mixture obtained in step a) at a temperature ranging from 0 ° C. to 10 ° C.

 The emulsification by ultrasonication is known per se and makes it possible to obtain efficiently a mini-emulsion whose dispersed droplets have a mean size of from 50 nm to 500 nm, preferably from 100 nm to 400 nm, and more preferably from 200 nm to 400 nm.

 Preferably, the emulsification is carried out for a period of from 30 seconds to 300 seconds, preferably from 50 seconds to 150 seconds, and preferably for about 120 seconds.

 According to one embodiment, step a) and step b) take place simultaneously, that is to say that the two-phase mixture is formed by bringing into contact the organic phase and the aqueous phase while simultaneously applying a shear able to emulsify said mixture.

 In step c), the polymerization is initiated by placing in conditions capable of reacting the polymerization catalyst, typically by raising the temperature.

To do this, the polymerization step c) is typically carried out by heating the miniemulsion obtained in step b) at a temperature of from 40 ° C. to 80 ° C., preferably from 40 ° C. to 70 ° C. C, and preferably at 60 ° C. These temperature ranges can be adapted according to the temperature at which the polymerization catalyst becomes reactive (this being described below).

 The polymerization step c) generally lasts from 1 h to 24 h, preferably from 2 h to 10 h, and preferably approximately 4 h.

 Step c) is generally carried out with stirring using a mechanical stirrer.

 At the end of step c), the droplets of the miniemulsion of step b) were converted into solid particles of polyurethane dispersed in the aqueous phase.

 This gives a dispersion of polyurethane particles in the aqueous phase.

 In the context of the present invention, "dispersion" means a stable suspension of solid objects, preferably individualized and non-agglomerated, in a continuous liquid phase.

 The mini-emulsion polymerization makes it possible, in a manner known per se, to obtain dispersed particles (latex) of average size equivalent to the average size of the droplets of the mini-emulsion from which they are derived.

 Thus, the polyurethane particles of the dispersion obtained at the end of step c) have a mean size of from 50 nm to 500 nm, preferably from 100 nm to 400 nm, and more preferably from 200 nm to 400 nm.

 The average size of the dispersed particles can be measured by dynamic light scattering, using a Zetasiser Nano ZS90 from Malvern, at a 90 ° angle, at room temperature.

 Within the dispersion of polyurethane particles obtained according to the process of the invention, the particles are preferably individualized and non-agglomerated objects.

 The process of the invention makes it possible to obtain polyurethane particles having a polydispersity of from 0.05 to 0.5, preferably from 0.1 to 0.3, and more preferably from 0.1 to 0.2.

 In the context of the invention, the term "polydispersity index" means the size distribution of the particles formed. The polydispersity index can be measured by dynamic light scattering, using a Zetasiser Nano ZS90 from Malvern, at a 90 ° angle, at room temperature.

The process of the invention makes it possible to obtain dispersions having a solid content of from 10% to 50% by weight relative to the total mass of the aqueous phase of the dispersion. Preferably, the level of solid is greater than 20%, preferably greater than 30%. In the context of the invention, the term "solid content" means the ratio of the total mass of the solid polyurethane particles to the total mass of the aqueous phase of the dispersion. In practice, the level of solid corresponds to the ratio of the mass of the organic phase to the mass of the aqueous phase, it is therefore a theoretical value, which can be determined before the implementation of the method.

The different reagents and non-reactive ingredients of the organic phase and the aqueous phase will now be described. Polyol monomer of formula (I)

 By "polyol" is meant an organic chemical compound having at least two hydroxyl groups. The polyols used in the process of the present invention typically comprise from 2 to 6, preferably from 2 to 4, preferably from 2 to 3, hydroxyl groups.

 The polyol monomer of formula (I) can be a diol or a triol.

The polyol monomer of formula (I) can be obtained by reaction between a fatty acid and a polyol P ₀ , in particular an aliphatic polyol such as for example an aliphatic diol or triol, or by transesterification reaction between an ester of a fatty acid and a polyol, especially an aliphatic diol or triol.

 According to one embodiment, the fatty acid mentioned above is selected from the group consisting of ricinoleic acid.

According to one embodiment, the polyol P ₀ mentioned above is a diol, preferably selected from the group consisting of propanediol, butanediol, pentanediol, hexanediol and decanediol. Advantageously, the polyol P ₀ is butanediol.

 The polyol monomers of formula (I) have the advantage of being biosourced, that is to say that they can be obtained from fatty acids or esters of fatty acids of vegetable origin (as ricinoleic acid obtained from castor oil).

 The process of the invention therefore represents an ecological alternative to the processes for preparing polyurethane particles using, as monomer polyols, monomers from the petroleum industry.

According to one embodiment, in formula (I), R represents a linear or branched alkyl group comprising from 5 to 25 carbon atoms, preferably from 10 to 20 carbon atoms, said alkyl group being substituted by at least one hydroxyl group, and possibly containing one or more unsaturations.

According to one embodiment, R comprises a single unsaturation. According to one embodiment, R is an alkyl comprising from 10 to 20 carbon atoms, comprises a single unsaturation and is substituted by a single hydroxyl group.

 According to one embodiment, R represents a linear alkyl group comprising 17 carbon atoms, said alkyl group comprising unsaturation and being substituted by a hydroxyl function.

In particular, R can represent the radical of the following formula:

In the formula above, the bond on which the symbol is located means that said bond is connected to the carbonyl function of the compound of formula (I).

According to one embodiment, R 'represents a linear or branched alkyl group comprising from 2 to 20 carbon atoms, preferably from 2 to 10 carbon atoms, and preferably from 4 carbon atoms.

 According to one embodiment, R 'represents a linear alkyl group.

 According to one embodiment, R 'represents a branched alkyl group.

According to one embodiment, R 'represents the radical of the following formula:

In the above formula, the bond on which the symbol is located means that said bond is connected to the oxygen atom of the ester function of the compound of formula (I).

 According to one embodiment, the polyol monomer of the organic phase is a diol.

According to one embodiment, the polyol monomer of the organic phase is a diol corresponding to the formula (1-1):

 in which :

the groups to A ₅ independently represent a methylene chain optionally substituted by a C ₁ -C ₆ alkyl group,

- n _1; n ₃ and n ₄ are from 1 to 15, and

n ₂ and n ₅ are from 0 to 15. Preferably, in the formula (1-1), r 1 is from 1 to 5.

Preferably, in the formula (1-1), n ₂ = 0.

Preferably, in the formula (1-1), n ₃ is from 2 to 8.

Preferably, in the formula (1-1), n ₄ is from 1 to 4.

Preferably, in formula (1-1), n ₅ is comprised of 4 to 8.

dans laquelle : According to one embodiment, the polyol monomer of the organic phase is a diol corresponding to formula (I-2):

in which :

 n-i is from 1 to 5,

- n ₃ is from 2 to 8,

- n ₄ is from 1 to 4, and

- n ₅ is from 4 to 8.

According to one embodiment, the polyol monomer of the organic phase is a diol corresponding to formula (I-3):

According to one embodiment, the polyol monomer of the organic phase is a diol corresponding to formula (I-4):

According to one embodiment, the polyol monomer of the organic phase is a triol.

According to one embodiment, the polyol monomer of the organic phase is a triol corresponding to the formula (1-1 '):

 in which :

the groups to A ₅ independently represent a methylene chain optionally substituted by a C ₁ -C ₆ alkyl group,

- laughed _! , n ₂ , n ₃ and n ₄ are from 1 to 15, and

- n ₅ is from 0 to 15.

Preferably, in the formula (-1 '), ni is from 1 to 5.

Preferably, in the formula (-1 '), n ₂ is from 1 to 5.

Preferably, in the formula (-1 '), n ₃ is from 2 to 8.

Preferably, in the formula (-1 '), n ₄ is from 1 to 4.

Preferably, in formula (-1), n ₅ is comprised of 4 to 8.

Alkanepolyol comonomer

 According to one embodiment, the organic phase of step a) further comprises an alkanepolyol comonomer comprising from 2 to 12 carbon atoms and at least two hydroxyl groups.

 By "comonomer" is meant an additional monomer different from the polyol monomers described above and polyisocyanate monomers described hereinafter.

By "alkanepolyol" is meant a C ₂ -C ₁₂ alkane of which at least two hydrogen atoms are replaced by a hydroxyl group. These hydroxyl groups may be terminal or well arranged on the alkyl chain of the alkane polyol.

Preferably, the alkanepolyol comonomer is an alkanediol (also called diol), that is to say a C ₂ -C ₁₂ alkane of which exactly two hydrogen atoms are replaced by a hydroxyl group.

 Preferably, the alkane polyol comonomer is a non-geminal diol.

 Preferably, the alkane polyol comonomer is a diol corresponding to the formula

(II):

HO- (CH ₂ ) _k -OH (II)

 in which k is an integer from 2 to 12.

 Preferably, in formula (II), k is from 3 to 6.

As the alkanepolyol comonomer, mention may be made of propane-1,3-diol, butane-1,4-diol, hexanediol or octanediol. When present, the alkane polyol comonomer is present in a mass content of from 20% to 95%, preferably from 40% to 90% relative to the total weight of monomers polyols included in the organic phase.

 In other words, the monomer polyol (1): alkane polyol monomer weight ratio is preferably from 5:95 to 80:20, advantageously from 10:90 to 60:40.

 By varying the amount and the nature of the alkanepolyol comonomer, the physico-chemical and thermomechanical properties of the polyurethane obtained can be modulated. For example, using 1,3-propanediol as an alkane polyol comonomer increases the glass transition temperature of the polymer formed.

 Fashion with hydrophobic agent

 The method of the invention can be implemented in the presence of a hydrophobic agent in the organic phase to stabilize the droplets of the miniemulsion of step b).

 Because of its hydrophobicity, such a hydrophobic agent is contained in the droplets of organic phase and can fight against Ostwald ripening which tends to destabilize the mini-emulsion. The hydrophobic agent is not reactive and is intended to remain trapped in the polyurethane particles formed by polymerization.

 In the context of the invention, and unless otherwise stated, the hydrophobic agent is an organic compound for which logP> 3 or logS <- 3. The term "hydrophobic agent" is also understood to mean a "non-reactive fatty substance".

 In the context of the invention, "logP" makes it possible to measure the differential solubility of a given substance in two solvents (octanol / water partition coefficient), "LogP" being defined as follows: logarithm of the ratio of the concentrations of the substance given in octanol and in water:

LogP = log (C _October / C water

 The value, "LogP", is typically used to determine the hydrophilic or hydrophobic character of a given substance. When the logP value is zero, this means that the given substance is as soluble in octanol as in water.

 "LogP" can be determined according to known methods, and in particular using prediction software, such as ALOGPS2.1.

 In the context of the invention, "LogS" is the logarithm of the solubility S of a given substance in water at room temperature (20-25 ° C), the solubility S being in mol / L.

"LogS" can be determined according to known methods, and in particular using prediction software, such as ALOGPS2.1 In the context of the invention, and unless otherwise stated, the term "non-reactive fatty substance" means a compound which does not react chemically with the substrates used in the process of the invention or with the constituents of the dispersion. final.

As hydrophobic agent may be mentioned a compound selected from the group consisting of hydrocarbon compounds such as linear or branched alkanes, optionally substituted by at least one halogen cyclic alkanes, aryl optionally substituted with at least one halogen; perfluoroalkyls; perfluoroaryls; fatty alcohols; oligostyrenes; silanes; siloxanes, linear or cyclic; vegetable, animal, semi-synthetic and / or synthetic oils; ; and polyesters.

As a hydrophobic agent, mention may also be made of one of those described in documents US 2005/0124757 and US 2006/0058454. It is in particular a compound chosen from the group consisting of crosslinking agents, such as amino resins; protected polyisocyanates; tris (alkoxycarbonylamino) triazines; esters of α, β-olefinically unsaturated carboxylic acids and of alcohols comprising from 12 to 30 carbon atoms in the main chain; esters of vinyl alcohol and / or allyl alcohol and aliphatic monocarboxylic, monosulphonic and / or monophosphonic acid comprising from 12 to 30 atoms in the molecule; amides of α, β-olefinically unsaturated carboxylic acids comprising from 3 to 6 carbon atoms and alkylamines comprising from 12 to 30 carbon atoms in the alkyl chain; macromonomers based on unsaturated compounds containing about one olefinically unsaturated group on average per molecule; macromonomers of polysiloxanes containing at least one olefinically unsaturated group on average per molecule; polymeric and / or oligomeric addition polymerization, polycondensation and / or polyaddition products; water insoluble molecular weight regulators such as mercaptans; alkanols and / or alkylamines comprising at least 12 carbon atoms in the alkyl chains; organosilanes and / or organosiloxanes; and hydrophobic dyes.

As part of ^the invention, polyisocyanate means "protected" polyisocyanate whose isocyanate functions have been protected by an agent called "blocker" in order to make them inert with respect to active hydrogen. This blockage or this protection is reversible. This is called "deblocking" or "deprotection" of the isocyanate functions.

More specifically, as hydrophobic agent, there may be mentioned a compound selected from the group consisting of linear or branched C ₆ -C ₂ 4 alkanes; C ₅ -C ₁₂ cyclic alkanes; fatty alcohols having at least 6 carbon atoms; oligostyrenes; silanes of the formula SiR _a R _b R _c R _d wherein R _a to R _d independently represent an alkyl group -C _6; linear or cyclic siloxanes of the formula (SiOR ₂ ) _n wherein n is an integer of 2 to 10 and R is a C ₁ -C ₆ alkyl or phenyl; vegetable oils; perfluoroalkyls; perfluoroaryls; and polyesters.

As hydrophobic agent of linear alkane type, mention may be made of hexane (C ₆ ) and hexadecane (C ₁₆ ).

As a hydrophobic agent of fatty alcohol type, mention may be made of cetyl alcohol (Ci ₆ ) or dodecanol (C 12).

 Oligostyrene-type hydrophobic agents include oligostyrenes having a molar mass of the order of 1000 g / mol.

As hydrophobic agent of silane type, there may be mentioned the compound of formula Si (CH ₂ CH ₃ ) ₄ .

As hydrophobic agent of the siloxane type, mention may be made of the cyclic compound of formula [Si (CH ₃ ) ₂ 0] ₄ .

 As a hydrophobic agent of vegetable oil type, mention may be made of olive oil, castor oil, sunflower oil and linseed standole.

 As a perfluoroaryl-type hydrophobic agent, mention may be made of perfluorobenzene.

 The hydrophobic agent is generally comprised in a mass proportion of from 0% to 10% relative to the total mass of the organic phase, preferably from 2% to 8%, and preferably from 3% to 4%. Hydrophobic-free mode

 Surprisingly, it has been observed that, in the preparation of polyurethane particles from a polyol monomer of formula (I), it is not necessary to use a non-reactive hydrophobic agent to stabilize the miniaturize. emulsion formed in step b).

According to one embodiment, the method of the invention is implemented in the absence of any hydrophobic agent, especially as defined above. The process according to this embodiment is such that it does not implement hydrophobic agent, which means that none of the steps of the method implements or requires a hydrophobic agent. Thus, according to an advantageous embodiment, the two-phase mixture obtained in step a) is free of any hydrophobic agent usually used in the field of mini-emulsion polymerization, that is to say of any body non-reactive fat may remain trapped within the polyurethane particles obtained in step c).

 According to this advantageous embodiment, the miniemulsion obtained in step b) is stable, contrary to what would have been expected from the state of the art according to which the use of a hydrophobic agent is recommended ( mandatory).

More particularly, according to one embodiment, the bi-phasic mixture obtained in step a) is free of any hydrophobic agent as defined above. In particular, the bi-phasic mixture obtained in step a) is free of any hydrophobic agent selected from the group consisting of linear or branched C ₆ -C ₂ 4 alkanes; C ₅ -C ₁₂ cyclic alkanes; fatty alcohols having at least 6 carbon atoms; oligostyrenes; silanes of formula SiR _a RbR _c Rd where R _a to R _d independently represent a C1-C6 alkyl group; linear or cyclic siloxanes of formula (SiOR ₂ ) _n wherein n is an integer of 2 to 10 and R is a C ₆ -C ₆ alkyl or phenyl; vegetable oils; perfluoroalkyls; perfluoroaryls; and polyesters.

According to a variant of this embodiment, the organic phase of step a) consists of at least one polymerization catalyst, at least one (poly) isocyanate monomer and at least one polyol monomer of formula (I), and optionally at least one alkanepolyol comonomer having from 2 to 12 carbon atoms.

According to this variant, the organic phase of step a) is therefore free of any hydrophobic agent and / or any non-reactive fatty substance. This advantageous embodiment (as well as its variant) makes it possible to obtain particles free from any hydrophobic agent, that is to say from any non-reactive fatty substance. With the dispersions of particles obtained according to this mode, there is no risk of release of said hydrophobic agent, nor risk of toxicity of said hydrophobic agent, nor risk of modifying the properties of the final coating after spreading and drying of the dispersion on a given surface. Monomer (polv) isocvanate

 By "(poly) isocyanate" is meant a monomer comprising at least two isocyanate functional groups (-N = C = O).

 According to one embodiment, from 1 to 10 molar equivalents of (poly) isocyanate are used relative to the number of moles of polyol monomers (polyol monomer of formula (I) + optional alkanepolyol comonomer). In particular, from 1 to 5 equivalents, preferably from 1 to 2 equivalents, preferably from 1 to 1, 2 equivalents of (poly) isocyanate are used in the process of the invention.

 Preferably, the molar ratio [monomer polyol (I) + comonomer alkane polyol]: monomer (poly) isocyanate is from 1: 1 to 1: 1, 2.

 According to one embodiment, the (poly) isocyanate monomer is a diisocyanate.

By "diisocyanate" is meant a monomer comprising exactly two isocyanate functions (-N = C = O).

 The diisocyanate may especially be chosen from the group consisting of diphenylmethylene 2,2'-diisocyanate, diphenylmethylene 4,4'-diisocyanate, 4'-dibenzyl diisocyanate, toluene 2,6-diisocyanate, 2,4-diisocyanate, 2,4-diisocyanate and 2,4-diisocyanate. Diphenylmethylene diisocyanate, 2,4'-dibenzyldiisocyanate, 2,4-toluene diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate.

 Preferably, the diisocyanate is isophorone diisocyanate.

Polymerization catalyst

 The polymerization catalyst makes it possible to trigger the polymerization reaction between the polyol monomers and the monomers (poly) isocyanate which, during step c), converts the organic phase droplets of the miniemulsion obtained in step b ) in polyurethane particles.

 As the polymerization catalyst, mention may be made of tin compounds, such as dibutyltin dilaurate.

 According to one embodiment, the amount of polymerization catalyst is from 0.01% to 0.9% by weight relative to the total mass of the organic phase, preferably from 0.1% to 0.5% and preferably about 0.4%.

surfactant

The aqueous phase brought together in step a) comprises water and at least one surfactant. According to one embodiment, the surfactant is chosen from the group consisting of anionic surfactants, cationic surfactants and nonionic, so-called steric surfactants.

 A single surfactant or a mixture of surfactants can be used.

 As the anionic surfactant, a surfactant selected from the group consisting of fatty acid salts, sulfonates, and sulfuric derivatives can be used. Sodium dodecyl sulfate (SDS), sodium lauryl ether sulphate and the sodium salt of vinylbenzylsulphosuccinic acid may be mentioned. Preferably, the surfactant is sodium dodecyl sulfate (SDS).

 As a cationic surfactant, a quaternary ammonium salt such as cetyltrimethylammonium bromide or trimethyldecylammonium chloride can be used.

 As a nonionic surfactant, it is possible to use a surfactant chosen from polyalcohol or fatty acid esters, sucrose esters, sorbitan or sorbitol esters, ethoxylated copolymers or polyoxyethylene alkyl ether. Preferably, the nonionic surfactants are selected from the group consisting of polyoxyethylene (20) sorbitan monostearate (tween® 60), polyoxyethylene (20) sorbitan monooleate (tween® 80), Pluronic® F68, steareth-10 (Brij®76), steareth-20 (Brij®78), oleth-10 (Brij®96 or Brij®97), oleth-20 (Brij®98 or Brij®99), Brij®700 and sorbitan monostearate (span® 60). Preferably, the surfactant is Brij®700.

 The surfactant of the process according to the invention has a hydrophobic part, which is in contact with the surface of the droplets constituting the dispersed organic phase, and a hydrophilic part, which is in contact with the continuous aqueous phase. The surfactant is therefore placed at the interface between the dispersed organic phase and the continuous aqueous phase and, within the miniemulsion formed in step b), it thus makes it possible to stabilize the droplets of said miniemulsion, and to avoid the phenomenon of coalescence between said droplets.

 According to one embodiment, the amount of surfactant is from 0.1% to 30% by weight relative to the weight of the aqueous phase, preferably from 0.2% to 10% by weight, and preferably from 0, 2% to 5%.

 Alternatively, the proportion of surfactant can be expressed in terms of its CMC (critical micelle concentration). The critical micellar concentration is the concentration of surfactant in a medium (usually pure water) above which micelles of said surfactant form spontaneously.

According to one embodiment, the surfactant is present in a concentration corresponding to 1 to 10 times its CMC. The present invention also relates to a dispersion of particles (latex) of polyurethane from biosourced monomers.

The present invention also relates to a dispersion of polyurethane particles that can be obtained by the process as defined above.

 Unlike dispersions of the state of the art, generally derived from monomers of fossil origin, the dispersions according to the invention have the advantage of being derived from biosourced monomers, the polyol monomers of formula (I) being able to be obtained from fatty acids or fatty acid esters of vegetable origin (such as ricinoleic acid obtained from castor oil).

 Furthermore, in the embodiment according to which the polyol monomers of formula (I) are diols, the use of said monomers in the process of the invention advantageously leads to dispersions of biosourced, recyclable and / or biodegradable polyurethane particles. .

The subject of the present invention is also a dispersion of polyurethane particles that can be obtained by the process as defined above, in which the two-phase mixture of step a) is free of any hydrophobic agent as described. above.

 According to one embodiment, the subject of the present invention is a dispersion of polyurethane particles that can be obtained by the process as defined above, in which the process is carried out in the absence of any hydrophobic agent, that is to say that none of the steps of the process requires the implementation of hydrophobic agent as defined above.

The dispersion of the invention obtained according to this process has the additional advantage of being free of any hydrophobic agent which may be toxic, of being salted out by the particles, and / or of modifying the properties of the final coating after spreading and drying the dispersion on a given surface.

The dispersions according to the invention are useful, for example as an additive, in an adhesive, surfactant, paint, varnish, coating composition or in a cosmetic composition. The dispersions obtained by the embodiment of the process according to the invention in which no hydrophobic agent is used have the advantage of being free from any hydrophobic agent capable of modifying the surface properties of said dispersions once they have been applied to a surface.

EXAMPLES

suppliers

 Sodium Dodecyl Sulfate (SDS): Sigma-Aldrich

Dibutyltin Dilaurate: Sigma-Aldrich

 Isophorone diisocyanate (IPDI): Sigma-Aldrich

Hexadecane: Sigma-Aldrich

Linen standolie: Iterg

Castor oil: Iterg

Propanediol: Sigma-Aldrich

Hexanediol: Sigma-Aldrich

Comparative Example 1: Use of hexanediol as polyol

 In this comparative example, hexanediol and isophorone diisocyanate (IPDI) were used as monomers in equimolar amounts. Sodium dodecyl sulfate was used as a surfactant and dibutyltin dilaurate as a polymerization catalyst (0.4% by weight relative to the weight of the organic phase).

 Several hydrophobic agents have been tested, namely: hexadecane, castor oil and linseed standole.

Example 1 A: In the absence of hydrophobic agent

 In this example, no hydrophobic agent was used. A solid content of 20% by weight was tested. The aqueous phase consists of 20 g of deionized water containing 2 to 10 CMC of SDS. The organic phase contains 1.73 g of hexanediol, 3.25 g of isophorone diisocyanate and 20 mg of dibutyltin dilaurate.

 After emulsification by ultrasonication, it was observed that the average size of the droplets of the mini-emulsion increases to a total phase shift. This phenomenon is attributed to the ripening of Ostwald.

 Thus, in the absence of hydrophobic agent, the mini-emulsion formed is not stable.

When hexanediol is used as the polyol monomer, the use of a hydrophobic agent is therefore necessary for the stabilization of the miniemulsion.

Example 1 B: Use of Linen Standolie as Hydrophobic Agent

An aqueous phase was prepared by dissolving 140 mg of SDS in 20 ml of distilled water. An organic phase was prepared by mixing 1.73 g of hexanediol, 3.25 g of isophorone diisocyanate, 20 mg of dibutyltin dilaurate and 160 mg of flaxseed.

 The ultrasonic probe (Sonic ultrasonic amplifier with a maximum power of 750 W) was immersed in the aqueous phase cooled by an ice bath. As soon as the ultrasound was switched on, the organic phase was quickly incorporated. The ultrasonic emulsification lasted 120 seconds in pulsed mode (in cycles of 5 seconds of ultrasound followed by 2 seconds of rest).

 The milky emulsion obtained was introduced into a reactor at 60 ° C. with an anchor-type mechanical stirrer at 800 rpm. The polymerization lasted 4 hours, then the resulting latex was recovered and analyzed.

 The characteristics of the latex were measured by dynamic light scattering at an angle of 90 °. The polyurethane particles have an average size of 320 nm, with a polydispersity index (PDI) of 0.12.

 The characteristics of Example 1 B are summarized in the following Table:

Example 1 C: Use of hexadecane as hydrophobic agent

 The procedure of Example 1B was reproduced by replacing the linoleum standole with hexadecane as a hydrophobic agent.

 The characteristics of Example 1C are summarized in the following Table:

Example 2 Use of a Polyol Mixture Comprising a Bio-based Diol in the Absence of a Hydrophobic Agent

Exemple 2A : Utilisation du monoester (1 ) et du 1 ,3-propanediol en l'absence d'agent hydrophobe In this example, an alkanediol comonomer in combination with the following monoester (1), derived from castor oil (butanol ester of ricinoleic acid), was used as monomer polyols:

Example 2A: Use of Monoester (1) and 1,3-Propanediol in the Absence of Hydrophobic Agent

 An aqueous phase was prepared by dissolving 3.37 g of Brij® 700 in 19.13 ml of distilled water. An organic phase was prepared by mixing 568 mg of 1,3-propanediol, 63 mg of monoester (1), 1.696 g of isophorone diisocyanate and 0.25 mg of dibutyltin dilaurate. No hydrophobic agents were used.

The ultrasound probe was immersed in the aqueous phase cooled by an ice bath. As soon as the ultrasound was switched on, the organic phase was quickly incorporated. Ultrasonic emulsification lasted 120 seconds (24 pulses of 5 seconds, spaced 2 seconds apart).

 The milky emulsion obtained was introduced into a reactor at 60 ° C. with an anchor-type mechanical stirrer at 800 rpm. The polymerization lasted 4 hours, then the resulting latex was recovered and analyzed.

 The characteristics of the latex were measured by dynamic light scattering at an angle of 90 °.

 The characteristics of Example 2A are summarized in the following Table:

Example 2B: Use of Monoester (1) and Hexanediol in the Absence of Hydrophobic Agent

 The procedure of Example 2A was repeated substituting 1, 3-propanediol with hexanediol, and Brij® 700 with SDS. Higher solids levels were obtained.

 The characteristics of Example 2B are summarized in the following Table:

Example 3 Use of a Bio-based Polyol

 Example 3A: Use of a Biobased Polyol in the Presence of a Hydrophobic Agent In this example, the monoester (1) was used as the sole polyol monomer.

An aqueous phase was prepared by dissolving 150 mg of SDS in 12.5 ml of distilled water. An organic phase was prepared by mixing 7.23 g of monoester (1), 5.22 g of isophorone diisocyanate (IPDI), 50 mg of dibutyltin dilaurate and linseed standole (3.2% by weight) as hydrophobic agent.

 The ultrasound probe was immersed in the aqueous phase cooled by an ice bath. As soon as the ultrasound was switched on, the organic phase was quickly incorporated. Ultrasonic emulsification lasted 120 seconds.

 The milky emulsion obtained was introduced into a reactor at 60 ° C. with an anchor-type mechanical stirrer at 800 rpm. The polymerization lasted 4 hours, then the resulting latex was recovered and analyzed.

 The characteristics of the latex are measured by dynamic light scattering at an angle of 90 °.

 The characteristics of Example 3A are summarized in the following Table:

Example 3B: Use of a Biosourced Polyol in the Absence of a Hydrophobic Agent In this example, the monoester (1) was used as the sole polyol monomer.

An aqueous phase was prepared by dissolving 150 mg of SDS in 12.5 ml of distilled water. An organic phase was prepared by mixing 7.23 g of monoester (1), 5.22 g of isophorone diisocyanate (IPDI) and 50 mg of dibutyltin dilaurate. No hydrophobic agents were used.

 The ultrasound probe was immersed in the aqueous phase cooled by an ice bath. As soon as the ultrasound was switched on, the organic phase was quickly incorporated. Ultrasonic emulsification lasted 120 seconds.

 The milky emulsion obtained was introduced into a reactor at 60 ° C. with an anchor-type mechanical stirrer at 800 rpm. The polymerization lasted 4 hours, then the resulting latex was recovered and analyzed.

The characteristics of the latex are measured by dynamic light scattering at an angle of 90 °. The weight average molecular weight (M _w ), the number average molecular weight (M _n ) and the dispersity (D) were measured by steric exclusion chromatography in THF, calibrated with polystyrene. The characteristics of Example 3B are summarized in the following Table:

Example 4: Use of another biosourced polyol

Example 4A: Use of a biobased polyol in the presence of hydrophobic agent

 In this example, the monoester (2) was used as the sole polyol monomer.

 The monomer (2) is derived from castor oil (ricinoleic acid propanediol ester) and has the following formula:

A procedure similar to that of Example 3A was used, with two types of hydrophobic agent: hexadecane and sunflower oil.

The characteristics of Example 4A are summarized in the following Table

Example 4B: Use of a Bio-based Polyol in the Absence of Hydrophobic Agent

In this example, the monoester (2) as defined above was used as the sole polyol monomer.

A procedure similar to that of Example 4A was used.

The characteristics of Example 4B are summarized in the following Table Solids rate (1): IPDI Catalyst Size of the latex

 SDS

 (% by mass) (molar ratio) (mass%)

 20% 1: 1 0.4% 3.5 CMC 238 nm

Claims

1. Process for preparing a dispersion of polyurethane particles, comprising the following steps: a) bringing together an aqueous phase comprising at least one surfactant and an organic phase comprising at least one polymerization catalyst, at least one (poly)isocyanate monomer and at least one polyol monomer of formula (I):

in which : - R represents an alkyl group, linear or branched, comprising from 2 to 30 carbon atoms, said alkyl group being substituted by at least one hydroxyl group, and possibly containing one or more unsaturations; And - R' represents an alkyl group, linear or branched, comprising from 2 to 30 carbon atoms, said alkyl group being substituted by at least one hydroxyl group, by which we obtain a bi-phasic mixture, b) emulsification of the two-phase mixture obtained in step a), by which a mini-oil-in-water emulsion is obtained, formed of droplets of said organic phase, of average size ranging from 50 nm to 500 nm , dispersed in said aqueous phase, and c) the polymerization of the (poly)isocyanate and polyol monomers of formula (I), by which solid polyurethane particles are obtained, with an average size of 50 nm to 500 nm, dispersed in said aqueous phase. 2. Method according to claim 1, in which the two-phase mixture obtained in step a) is free of any hydrophobic agent chosen from the group consisting of linear or branched C ₆ -C ₂ 4 alkanes; cyclic C ₅ -C ₁₂ alkanes; fatty alcohols containing at least 6 carbon atoms; oligostyrenes; silanes of formula SiR _a R _b R _c R _d where R _a to R _d independently represent a CC ₆ alkyl group; siloxanes, linear or cyclic, of formula (SiOR ₂ ) _n where n is an integer from 2 to 10 and R is C 1 -C alkyl or phenyl; vegetable oils; perfluoroalkyls; perfluoroaryls; and polyesters. Method according to claim 1, characterized in that it does not use a hydrophobic agent. Process according to any one of claims 1 to 3, wherein the organic phase of step a) further comprises an alkanepolyol comonomer comprising from 2 to 12 carbon atoms and at least two hydroxyl groups. Process according to any one of claims 1 to 4, in which the organic phase of step a) consists of at least one polymerization catalyst, at least one (poly)isocyanate monomer and at least one polyol monomer of formula (I) as defined in claim 1, and optionally at least one alkanepolyol comonomer as defined in claim 3. Process according to any one of claims 1 to 5, in which the polyol monomer is a diol corresponding to formula (1-1):

in which : - the groups Ai to A ₅ independently represent a methylene link optionally substituted by a C 1 -C alkyl group, - ni, n ₃ and n ₄ are included from 1 to 15, and - n ₂ and n ₅ are included from 0 to 15. Process according to any one of claims 1 to 6, in which the polyol monomer is a diol corresponding to formula (I-2):

in which : - ni is included from 1 to 5, - n ₃ is included from 2 to 8, - n ₄ is included from 1 to 4, and - n ₅ is included from 4 to 8. 8. Method according to any one of claims 1 to 7, in which the polyol monomer is a diol corresponding to formula (I-3) or (I-4):

9. Method according to any one of claims 1 to 8, in which the (poly)isocyanate monomer is a diisocyanate. 10. Dispersion of polyurethane particles capable of being obtained by the process as defined in one of claims 1 to 9. 1 1 . Use of a dispersion according to claim 10 in an adhesive, surfactant, paint, varnish, coating composition or in a cosmetic composition.