FR3072961B1 - NON-TOXIC BIOSOURCE SOLVENT FOR REALIZING POLYURETHANE COATINGS - Google Patents

Abstract

The present invention relates to a crosslinkable polyurethane coating composition comprising a polyol moiety, a polyisocyanate moiety, isosorbide and a solvent comprising dimethylisosorbide, and a process for producing a polyurethane coating on a substrate from this composition. and the coating thus obtained. The invention also relates to the use of dimethylisosorbide as compatibilization promoter of a mixture comprising isosorbide and an aliphatic polyisocyanate.

Description

Field of the invention

The present invention relates to the field of polyurethanes and more particularly to polyurethane coatings.

The present invention relates in particular to a polyurethane composition comprising isosorbide as the chain extender diol and the polyurethane coating obtained from this composition. The invention also relates to the use of dimethylisosorbide (DMI) as a solvent and compatibilizer in a crosslinkable liquid polyurethane coating composition which comprises a polyol moiety, a polyisocyanate moiety and isosorbide as monomers.

Technological background

In the coatings market, there is a growing demand for renewable products. However, in order to apply the coating in good conditions, it is necessary to use a suitable solvent.

Indeed, in a coating composition, the solvent must generally meet several criteria: it must reduce the viscosity of the composition, play the role of accounting between the components of the formulation, allow a uniform and homogeneous deposition of the composition on the substrate and evaporate only at the end of the reaction.

One of the current technical challenges is to achieve the implementation of thin coatings, necessarily requiring a solvent, minimizing the irritating or toxic volatile organic compounds (VOCs) to ensure the safety of the manipulators and end users. Current solutions of non-reactive diluent use a large majority of VOCs whose impact on health is not neutral. Reactive diluent solutions, supposedly less problematic, also show their limits since these products have a greater impact on the health of the people who handle them and it has been shown that traces of unreacted diluent are still present in the finished product.

The toxicological safety of solvent-synthesized coatings is a major concern because most organic solvents are toxic by contact or inhalation. It is therefore essential to protect, on the one hand, the handlers who use large quantities of such solvents during the manufacture of the coatings and, on the other hand, the end users who may be exposed to the presence of residual solvent in the coating.

The great versatility of polyurethanes make them the material of choice for coatings. With a very wide range of hardness, very good resistance to shocks and cracking and very good chemical resistance, they are suitable for coating all types of surfaces.

A crosslinked polyurethane coating is conventionally obtained by reacting a long chain polyol, a short chain diol and a polyisocyanate. Various compounds are described in the literature for each of these reagents. In general, at least one of the two mixtures, either the polyol mixture or the polyisocyanate mixture, has a functionality greater than two in order to obtain a network. The level of compounds of functionality greater than 2 makes it possible to adapt the crosslinking density and is thus one of the solutions for adapting the properties of the network.

The polyisocyanate is generally an aliphatic polyisocyanate or a mixture of polyisocyanates having -NCO functionality strictly greater than 2 when used with polyols of average functionality equal to two. In fact, with respect to the aromatic polyisocyanates, the aliphatic polyisocyanates make it possible to obtain coatings which are advantageously resistant to yellowing when exposed to light. The -NCO functionality strictly greater than 2 provides a crosslinked polyurethane.

The long chain polyol is generally a polyether polyol type diol or a polyester polyol which may in particular have a molecular weight of 400 to 4000 g / mol.

The short chain diol, also called chain extender diol, is generally 1,4-butanediol.

The long chain polyol imparts flexibility to the polyurethane coating. The short chain diol contributes to the hardness of the coating with the polyisocyanate.

A polyurethane coating traditionally has a single glass transition temperature (Tg). Indeed, a coating obtained with a material having a macroscopic phase segregation would have a white color related to the heterogeneity of the material, these different phases resulting in optical phenomena that make the material opaque. The Tg of a polyurethane coating is greater than or equal to 30 ° C so as not to give it tack in the usual conditions of use.

There is a need for novel crosslinked polyurethane coatings which exhibit good mechanical properties, good adhesion to the substrate and high stability over time.

The Applicant has discovered that the replacement of 1,4-butanediol (BDO) as a chain extender with isosorbide makes it possible to improve the properties of the polyurethane coating obtained, in particular the adhesion to the substrate, the impact resistance. and the folding resistance. In addition, the use of isosorbide makes it possible to increase the Tg and the rigidity of the coating and to improve the UV stability with respect to the same coating obtained with BDO.

However, in order to apply a coating in good conditions, it is necessary to use a suitable solvent.

In a coating formulation, the main function of the solvent is to reduce the viscosity of the formulation to facilitate its application to a substrate. As such, the amount of solvent can be adjusted to control the viscosity of the solutions to be applied.

The solvent may also act as compatibilization promoter between the components of the formulation in the case where they are not miscible with each other and thus allow their reaction. On the other hand, the solvent must evaporate only at the end of the crosslinking reaction. Indeed, the more the chemical reaction proceeds, the more the phase separation between immiscible components becomes limited. For reactions that occur at temperatures above the boiling point of the solvent, the solvent must slowly evaporate to minimize phase separation of the reagents when they are immiscible at the beginning of the crosslinking reaction. . For example, the reaction involving isosorbide and isophorone diisocyanate (or its derivatives) achieves a high rate of progress at reaction temperatures above 110 ° C. The use of a solvent having a boiling point above this temperature is therefore essential.

Isosorbide dimethyl ether (also called dimethyl isosorbide) is a recognized bio-sourced non-toxic organic solvent.

Surprisingly, isosorbide dimethyl ether has appeared to be an excellent compatibilizing promoter for isosorbide and polyisocyanates, thus making it possible to ensure good homogeneity of the material in the context of the preparation of polyurethane coatings.

Its use for the synthesis and application of solvent-based polyurethane coatings thus makes it possible to respond to the problem of toxicity inherent to the organic solvents used in this type of composition. Summary of the invention

According to a first object, the invention relates to a crosslinkable polyurethane coating composition comprising: a polyol fraction comprising a polyol chosen from a polyester polyol, a polyether polyol, a polycarbonate polyol or a mixture thereof; a polyisocyanate moiety comprising an aliphatic polyisocyanate; isosorbide and a solvent comprising dimethylisosorbide, the polyol fraction comprising at least one polyol having a mean functionality -OH strictly greater than 2 and / or the polyisocyanate fraction comprising at least one polyisocyanate having a mean functionality -NCO strictly greater than 2 .

According to a second subject, the invention relates to the use of dimethylisosorbide as compatibilization promoter of a mixture comprising isosorbide and an aliphatic polyisocyanate.

According to a third subject, the invention relates to a process for manufacturing a polyurethane coating on a substrate comprising the following steps: (1) the isosorbide mixture, of a polyol fraction comprising a polyol chosen from a polyester polyol, a polyether polyol a polycarbonate polyol or a mixture thereof and a polyisocyanate fraction comprising an aliphatic polyisocyanate in the presence of a solvent, the polyol fraction comprising at least one polyol having a functionality -OH strictly greater than 2 and / or the polyisocyanate fraction comprising at least one polyisocyanate having a -NCO functionality strictly greater than 2; then (2) depositing on the substrate a layer of the mixture obtained in step (1), and (3) crosslinking the layer applied in step (2); characterized in that the solvent comprises dimethylisosorbide.

detailed description

Polyurethane coating composition

The present invention relates to a crosslinkable polyurethane coating composition.

For the purposes of the present invention, the term "crosslinkable composition for a polyurethane coating" is intended to mean a composition capable of providing a polyurethane coating after crosslinking the composition.

For the purposes of the present invention, the term "polyurethane coating" is intended to mean a crosslinked polyurethane deposited on a solid substrate in the form of a thin layer, for example a layer having a thickness of 20 μm to 500 μm, in particular 20 μm, 50 μm. pm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm or 450 μm. It may be for example protective coatings, decorative, or surface treatment. Protective films, varnishes and paints are coatings within the meaning of the present invention.

For the purposes of the present invention, "crosslinking" is understood to mean the formation of one or more three-dimensional networks by creating chemical bonds between the polymer chains. A polymer may be crosslinked when it comprises a monomer unit having more than 2 reactive functions in polymerization. Thus, the crosslinked polyurethane of the invention is obtained by introducing into the polyurethane coating composition a polyol having a functionality -OH strictly greater than 2 and / or a polyisocyanate having a -NCO functionality strictly greater than 2. The crosslinking may especially be performed under the action of heat or irradiation with a UV beam, optionally in the presence of a catalyst.

The composition according to the invention is liquid at a temperature of 25 ° C, and can thus be applied to a substrate by conventional means such as spraying, with a brush, or even with a roller.

The crosslinkable polyurethane coating composition according to the invention is distinguished from a thermoplastic polyurethane (TPU) composition and a polyurethane adhesive composition.

Thus, the polyurethane coating obtained by crosslinking the composition according to the invention has a single glass transition temperature (Tg), said Tg being greater than or equal to 20 ° C, preferably greater than or equal to 25 ° C, more preferably greater than or equal to 30 ° C. The Tg of the polyurethane coating obtained by crosslinking the composition according to the invention may in particular be measured by dynamic mechanical analysis or differential scanning calorimetry.

isosorbide

The composition according to the invention comprises isosorbide. Isosorbide is used as the chain extender diol. Isosorbide is a cycloaliphatic diol corresponding to the formula:

The term "isosorbide" as used in the present application encompasses all stereoisomers (i.e. enantiomers or diastereoisomers) of isosorbide, i.e. isoidide and isomannide, among others.

The crosslinkable composition according to the invention comprises a polyisocyanate and isosorbide as monomers and a solvent.

The polyisocyanate is typically selected from a diisocyanate, a triisocyanate or a mixture thereof.

The term "diisocyanate" and "triisocyanate" means a compound which comprises respectively two isocyanate functional groups and three isocyanate functional groups.

Polyol fraction

The composition according to the invention comprises a polyol fraction.

The polyol moiety comprises or consists of a polyol or a mixture of polyols.

For the purposes of the present invention, the term "polyol" means a compound having an OH functionality greater than or equal to 2. The term polyol therefore includes diols and triols. Isosorbide is not considered as a polyol within the meaning of the present invention.

By "-OH functionality" is meant in the sense of the present invention, the total number of reactive hydroxyl functions per molecule of compound. The functionality -OH (f0H) can be calculated from the hydroxyl number (Ioh) z and the number-average molar mass of the polyol (Mnpolyol) according to the following formula: foH = (Ioh χ Mnpoiyoi) / 56 100 The hydroxyl number can be measured by acetylation followed by a back titration with potash according to ISO 14900: 2001, Plastics - Polyols for the production of polyurethane - Determination of the hydroxyl number. The hydroxyl number is expressed in mg KOH / g which corresponds to the amount of KOH in mg which is necessary to neutralize 1 g of polyol.

According to a particular embodiment, the polyol fraction comprises or consists of a diol or a mixture of diols.

According to another particular embodiment, the polyol fraction comprises or consists of a mixture of diol and triol.

The polyol of the polyol fraction may in particular have a molecular weight of between 400 and 4000 g / mol, preferably between 500 and 2000 g / mol and more preferably between 600 and 1500 g / mol.

The polyol of the polyol moiety is a polyester polyol or a polyether polyol or a polycarbonate polyol. The polyester polyol, polyether polyol and polycarbonate polyol are preferably linear polyols which may contain aliphatic, alicyclic or heterocyclic monomer units.

For the purposes of the present invention, the term "linear polyol" means a polyol which does not comprise a side chain having a reactive function for the polymerization.

The polyether polyol, also called polyalkylene ether polyol, is preferably a linear polyether having two terminal hydroxyl functions. The alkylene portion can comprise 2 to 10 carbon atoms, preferably 2 to 4 carbon atoms. It may especially be obtained by opening a cyclic ether, such as an epoxide, with a glycol. The polyether polyols according to the present invention comprise block or random glycol copolyethers, in particular block or random copolymers of ethylene oxide and of propylene oxide. Examples of polyether polyols according to the present invention are polyethylene glycol (PEG), polypropylene glycol (PPG), poly (oxyethyleneoxypropylene) glycol, polytetramethylene ether glycol (PTMEG) or a mixture thereof.

The polyester polyol is preferably a linear polyester having two terminal hydroxyl functions. It can be obtained by linear condensation of at least one glycol with at least one dicarboxylic acid or by reaction of a cyclic ester with a glycol. Polyester polyols according to the present invention comprise block or random glycol copolyesters, such copolyesters polyols may in particular be obtained by using a mixture of at least two glycols and / or at least two dicarboxylic acids. The glycols used may comprise 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, 1,3-propanediol, butylene glycol, 1,4-butanediol and 1,6-hexanediol. The dicarboxylic acids used generally have 4 to 10 carbon atoms, such as succinic acid, glutamic acid, glutaric acid, octanedioic acid, sebacic acid, maleic acid, fumaric acid, adipic acid, azelaic acid, phthalic acid, isophthalic acid and terephthalic acid. The dicarboxylic acid used may be a dicarboxylic fatty acid, that is to say a saturated or unsaturated aliphatic dicarboxylic acid comprising from 8 to 44 atoms between the acid functional groups which may for example be synthesized by dimerization of unsaturated aliphatic monocarboxylic acids or unsaturated aliphatic esters having 8 to 22 carbon atoms such as linoleic acid and linolenic acid. The cyclic ester used is usually epsilon-caprolactone. Examples of polyester polyols according to the present invention are polytetechelic polyesters of the poly (ethylene adipate) type, poly (propylene adipate), poly (propylene-co-ethylene adipate), poly (butylene adipate), poly (ethylene-cobutylene adipate) poly (caprolactone) diol, a copolymer of caprolactone and lactide or a mixture thereof.

The polycarbonate polyol is preferably a linear polycarbonate having two terminal hydroxyl functions. It can be obtained by linear condensation of at least one glycol with at least one alkyl carbonate derivative or phosgene. The polycarbonates polyols according to the present invention comprise the block or random glycol copolycarbonates, such copolycarbonates polyols may in particular be obtained by using a mixture of at least two glycols and alkyl carbonate. The diols can be linear aliphatic diols, cyclic diols or heterocyclic diols. Polycarbonate can also be obtained by reaction between propylene oxide and CO 2.

According to a preferred embodiment, the polyol fraction comprises a polyol chosen from a polyethylene glycol (PEG), a polypropylene glycol (PPG), a polytetramethylene ether glycol (PTMEG), a poly (caprolactone) diol or a mixture thereof; preferably a PTMEG; more preferably a PTMEG having a molecular weight of 250 g / mol to 3000 g / mol, more particularly 400 g / mol to 2000 g / mol.

The amount of polyol relative to the amount of isosorbide is adjusted in order to obtain a molar ratio of all the functions -OH of the polyol fraction over all of the -OH functions of the isosorbide of between 0.2 and 2; preferably between 0.3 and 1, more preferably between 0.4 and 0.6.

Polyisocyanate fraction

The composition according to the invention comprises a polyisocyanate fraction.

The polyisocyanate moiety comprises or consists of a polyisocyanate or a mixture of polyisocyanates.

For the purposes of the present invention, the term "polyisocyanate" is intended to mean a compound having a -NCO functionality of greater than or equal to 2. The term "polyisocyanate" therefore notably includes diisocyanates having a functionality -NCO equal to 2, triisocyanates having a functionality of NCO equal to 3, as well as polyisocyanates having a -NCO functionality strictly greater than 2 and strictly less than 3.

By "-NCO functionality" is meant, in the sense of the present invention, the total number of reactive isocyanate functions per molecule of compound. The -NCO functionality can be estimated by calculation after NCO titration by back-dosing the excess dibutylamine with hydrochloric acid (according to EN ISO 14896-2006).

The polyisocyanate moiety comprises an aliphatic polyisocyanate.

For the purposes of the present invention, the term "aliphatic polyisocyanate" is intended to mean a polyisocyanate which does not contain an aromatic ring. The term aliphatic polyisocyanate therefore includes non-cyclic aliphatic polyisocyanates and cycloaliphatic polyisocyanates.

According to one particular embodiment, the aliphatic polyisocyanate has a functionality - NCO strictly greater than 2, preferably the aliphatic polyisocyanate is chosen from a trimer of diisocyanate, more particularly a diisocyanate isocyanurate or a diisocyanate biuret or a diisocyanate iminooxadiazine dione to the following formulas:

in which R is a C4-C30 alkylene group, preferably a C4-C20 alkylene group. For the purposes of the present invention, the term "C4-C30 alkylene group" means a divalent alkyl chain comprising 4 to 30 carbon atoms. carbon, saturated or partially saturated, linear, linear or branched, and may include an aliphatic ring.

According to a particular embodiment, the aliphatic polyisocyanate is chosen from a trimer of pentamethylene diisocyanate (t-PMDI), a trimer of hexamethylene diisocyanate (t-HDI), a trimer of isophorone diisocyanate (t-IPDI) or a their mixtures; preferably an IPDI trimer or a PMDI trimer.

The polyisocyanate fraction of the composition according to the invention may further comprise an aliphatic diisocyanate. Preferably, the aliphatic diisocyanate is selected from pentamethylene diisocyanate (PMDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene dicyclohexyl diisocyanate (HMDI or hydrogenated MDI) or a mixture thereof; more preferably IPDI.

The polyisocyanate fraction may in particular comprise at least 5 mol% relative to the -NCO functions, in particular at least 10 mol% relative to the -NCO functions, more particularly at least 15 mol% relative to the -NCO functions, of aliphatic polyisocyanate. particular embodiment, the polyisocyanate fraction of the composition according to the invention comprises: 0 to 40 mol% relative to the -NCO functions of aliphatic polyisocyanate; and 60 to 100 mol% relative to the -NCO functions of aliphatic diisocyanate.

The total amount of polyisocyanate relative to the amount of isosorbide and polyol is adjusted in order to obtain a molar ratio of all the functions -OH of the polyol fraction and of isosorbide on all the functions -NCO the polyisocyanate fraction of between 0.8 and 1.2, preferably between 0.95 and 1.05.

Solvent

The composition according to the invention comprises a solvent which contains in particular dimethylisosorbide (DMI).

Dimethylisosorbide is a cycloaliphatic ether having the formula:

The term "dimethylisosorbide" as used in this application encompasses all stereoisomers (i.e., enantiomers or diastereoisomers) of dimethylisosorbide.

The amount of solvent in the composition may be between 10 and 60%, preferably between 20 and 50% by weight relative to the total weight of the formulation.

The proportion of dimethylisosorbide in the solvent may be at least 15% by weight, in particular at least 25% by weight, relative to the total weight of the solvent.

The solvent may further contain a solvent other than dimethylisosorbide, such as, for example, a ketone, a hydrocarbon solvent, an ether, an ester, a nitrile, a sulfone, dimethylsulfoxide, an aromatic compound or a mixture thereof.

The ketone may be chosen from butan-2-one, cyclopentanone, acetone, methyl isobutyl ketone, cyclohexanone or benzophenone. The hydrocarbon may be selected from pentane or hexane, or a chlorinated hydrocarbon.

The ether may be chosen from ethyl ether, n-butyl ether, diphenyl ether, 1,4-dioxane, tetrahydrofuran or 2-methoxyethyl ether. The ester may be selected from ethyl acetate, ethylene carbonate, or propylene carbonate, or a ketoester.

The nitrile may be selected from acetonitrile or benzonitrile.

The sulfone may be chosen from dimethylsulfone or diphenylsulfone glycol-ether-ester.

The aromatic compound may be selected from benzotrifluoride, terphenyl or naphthalene.

Preferably, the solvent is selected from 2-butanone, cyclopentanone, dimethylisosorbide or a mixture thereof, more preferably a mixture of 2-butanone and DMI.

Catalyst

The composition according to the invention may further comprise a catalyst. The catalyst makes it possible to accelerate the polymerization reaction and / or to increase the degree of polymerization of the polyurethane.

Examples of catalyst that can be introduced into the composition are organic or inorganic acid salts; organometallic derivatives of bismuth, lead, tin, antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, manganese or zirconium; phosphines; organic tertiary amines; or a mixture thereof. Preferably, the catalyst is dibutyltin dilaurate.

According to a particular embodiment, the amount of catalyst is between 0.001 and 5%, preferably between 0.005 and 1.0% by weight relative to the total weight of the polyol fraction, the polyisocyanate fraction and isosorbide.

additives

The composition according to the invention may also comprise a spreading agent. The spreading agent makes it possible to obtain, before crosslinking, a good spread of the composition when it is applied to the substrate. The spreading agent may be particularly useful in preventing crater formation in the coating by lowering the surface tension of the composition.

An example of a spreading agent that can be introduced into the composition according to the invention is a polyether modified polydimethylsiloxane such as BYK 307 sold by BYK.

The amount of leveling agent in the composition is from 0.01 to 0.2%, preferably 0.05 to 0.15%, by weight relative to the total weight of the polyol fraction, of the polyisocyanate fraction and isosorbide.

The composition according to the invention may also comprise other additives, for example polymerization inhibitors, surfactants, antioxidants, dyes, pigments, light absorbers, stabilizers, coalescing agents, control additives rheology, opacifiers, thermal or ultraviolet protection additives, anti-static agents, antibacterial, anti-fouling or anti-fungal agents.

Preferably, the composition according to the invention comprises less than 10%, more preferably less than 2% by weight of these additives, relative to the weight of the composition.

Process for producing the crosslinkable polyurethane coating composition

The composition according to the invention may be prepared by mixing the ingredients which constitute it, in particular with stirring. The amount of solvent makes it possible to adjust the viscosity of the composition.

Process for manufacturing the polyurethane coating

The method of manufacturing the polyurethane coating according to the invention comprises the following steps: (1) The isosorbide mixture, of a polyol fraction comprising a polyol chosen from a polyester polyol, a polyether polyol a polycarbonate polyol or a mixture thereof and a polyisocyanate moiety comprising an aliphatic polyisocyanate having -NCO functionality strictly greater than 2 in the presence of a solvent, the polyol moiety comprising at least one polyol having OH functionality strictly greater than 2 and / or the polyisocyanate moiety comprising at least one polyisocyanate having a -NCO functionality strictly greater than 2; then (2) depositing on the substrate a layer of the mixture obtained in step (1), and (3) crosslinking the layer applied in step (2); and is characterized in that the solvent comprises dimethylisosorbide.

The deposition of the composition may be carried out according to any means known to those skilled in the art, for example by dipping, by spin coating, by "barcoater", by "tape casting", by spraying or with the aid of a brush or a roll. The thickness of the deposited layer is adjusted according to the thickness of the coating that is desired. The thickness of the deposited layer may, for example, be between 100 nm and 2 mm, preferably from 100 to 500 micrometers. Preferably, the layer has a uniform thickness, so as to obtain a uniform final coating.

The substrate on which the coating is applied can be of any kind. It may be a particular substrate of wood, metal, plastic, glass or paper.

The process according to the invention also comprises a step of crosslinking the composition.

The crosslinking of the composition can in particular be done by heating. According to a particular embodiment, the heating is carried out at a temperature ranging from 100 ° C. to 250 ° C., preferably from 150 ° C. to 200 ° C. In particular, the temperature can be increased in temperature increments or by using a temperature ramp.

The duration of the heating may especially be between 1h and 5h, preferably between 1h30 and 3h.

Heating can also be carried out under vacuum.

The coatings obtained which are also objects of the present invention possess interesting properties. In particular, the coatings obtained may have at least one of the following properties: a good transparency; a low refractive index; - high gloss; good adhesion to the substrate; - a high hardness; good resistance to abrasion or wear; good chemical resistance, to solvents for example with water or good resistance to water, but also to bases and acids; - good resistance to impact / impact; and a good resistance to deformation.

The invention also relates to the use of dimethylisosorbide as compatibilization promoter of a mixture comprising isosorbide and an aliphatic polyisocyanate.

According to one embodiment, the aliphatic polyisocyanate has a -NCO functionality strictly greater than 2.

The term "compatibilization promoter" is understood to mean an agent that promotes miscibility between two compounds. The immiscibility of two compounds gives rise to a phase separation. A compatibilization promoter thus helps to avoid a phase separation when the two compounds are mixed.

According to the invention, dimethylisosorbide helps to avoid phase separation when isosorbide and an aliphatic polyisocyanate are mixed, and thus promotes the production of a homogeneous mixture.

The present invention will be described in more detail with the aid of the examples which follow and which are in no way limiting.

Examples

In the examples, the following products were used: polyol: poly (tetramethylene glycol) of molecular weight 650 g / mol (PTMEG 650) (Sigma-Aldrich) - polyisocyanate: trimer of pentamethylene diisocyanate (t-PMDI) (Covestro) - diisocyanate: isophorone diisocyanate (IPDI) (Aldrich) - diol Chain extender: isosorbide (rocket) - solvent: 2-butanone (Sigma Aldrich), cyclopentanone (Sigma Aldrich) and dimethylisosorbide (rocket) - additive: polyether modified polydimethylsiloxane ( BYK 307) (BYK) catalyst: dibutyltin dilaurate (DBTDL) (Sigma-Aldrich)

The following tests were performed on a PTMEG 650g / mol / 80% IPDI-20% t-PMDI / Isosorbide formulation in stoichiometry -OH macrodiol / -NCO / -OH diol of 1: 3.05: 2. The crosslinking is then carried out in a vacuum oven with the following temperature cycle: 1 h at 100 ° C., followed by a ramp at 3 ° C./min up to 140 ° C., then a plateau at 140 ° C. for 1 hour. then a ramp at 3 ° C / min up to 160 ° C and a tray at 160 ° C for 30 min. The first tray allows the start of the reaction while maintaining the solvent to maximize compatibility between the various components. The second plate makes it possible to begin to evaporate the heavy solvent while continuing the reaction. The last tray allows to completely evaporate the solvent.

Counterexample 1: Butan-2-one test

The low boiling point (80 ° C.) and the volatility of the butan-2-one solvent do not make it possible to obtain a fairly long compatibilization of the composition during the crosslinking step: the solvent evaporates too quickly, which leads to a demixing of the components and therefore the impossibility of obtaining a reaction. The resulting coating is very thin, sticky, inhomogeneous and burnished in places.

Polyurethane composition example in solvent 40% 2-

Butanone: - PTMEG 650: 1.42 g - t-PMDI: 2.94g - Isosorbide: 0.64g - Butanone: 3.30g - DBTDL: 0.05g

Counterexample 2: Cyclopentanone test

The coating obtained with this solvent is crosslinked, the compatibilization of the components operates and the solvent evaporates slowly enough to allow the reaction between the OH and the NCO functions. However, there is a difficult wetting and craters in the absence of additive. In addition, cyclopentanone is not included in substances considered non-hazardous by Regulation (EC) No. 1272/2008.

Example of a 20% cyclopentanone solvent polyurethane composition: PTMEG 650: 1.18 g - IPDI: 1.10 g - t-PMDI: 0.20 g - Isosorbide: 0.53 g - Cyclopentanone: 0.75 g - DBTDL: 0.03 g

Examples 1 and 2: Test with isosorbide dimethyl ether

The coating obtained with this solvent is crosslinked, the compatibilization of the components operates and the solvent evaporates slowly enough to allow the reaction between the OH and the NCO functions.

Example of a 25% DMI + 5% butanone solvent polyurethane composition: PTMEG 650: 1.18 g-IPDI: 1.10 g-t-PMDI: 0.20 g-Isosorbide: 0.53 g-DMI: 1.07 g-BYK 307: 0.003 g-2 -butanone: 0.218g - DBTDL: 0.0008g

Claims (17)

A crosslinkable polyurethane coating composition comprising: a polyol moiety comprising a polyol selected from a polyester polyol, a polyether polyol, a polycarbonate polyol, or a mixture thereof; a polyisocyanate moiety comprising an aliphatic polyisocyanate; isosorbide and a solvent comprising dimethylisosorbide, the polyol moiety comprising at least one polyol having a functionality-OH strictly greater than 2 and / or the polyisocyanate moiety comprising at least one polyisocyanate having a functionality -NCO strictly greater than 2. 2. Composition according to claim 1, characterized in that the proportion of dimethylisosorbide in the solvent is at least 15% by weight, in particular at least 25% by weight, relative to the total weight of the solvent. 3. Composition according to claim 1 or 2, characterized in that the solvent further comprises a ketone, a hydrocarbon solvent, an ether, an ester, a nitrile, a sulfone, dimethylsulfoxide, an aromatic compound or a mixture of these. this. 4. Composition according to any one of claims 1 to 3, characterized in that the polyurethane coating obtained by crosslinking the composition has a single glass transition temperature Tg, said Tg being greater than or equal to 20 ° C, preferably higher or equal to 25 ° C, more preferably greater than or equal to 30 ° C. 5. Composition according to any one of claims 1 to 4, characterized in that the molar ratio of all functions -OH of the polyol fraction and of isosorbide on all of the -NCO functions of the polyisocyanate fraction. is between 0.8 and 1.2, preferably between 0.95 and 1.05. 6. Composition according to any one of Claims 1 to 5, characterized in that the molar ratio of all the functions -OH of the polyol fraction to all the functions -OH of the isosorbide is between 0, 2 and 2; preferably between 0.3 and 1, more preferably between 0.4 and 0.6. 7. Composition according to any one of claims 1 to 6, characterized in that the polyol has a molecular weight between 400 and 4000 g / mol, preferably between 500 and 2000 g / mol and more preferably between 600 and 1500 g / mol. 8. Composition according to any one of claims 1 to 7, characterized in that the polyol is a diol or a mixture of diols. 9. Composition according to any one of claims 1 to 8, characterized in that the polyol is chosen from a polyethylene glycol (PEG), a polypropylene glycol (PPG), a polytetramethylene ether glycol (PTMEG), a poly (caprolactone) diol, or a mixture thereof; preferably a PTMEG; more preferably, a PTMEG having a molecular weight of 250 g / mol to 3000 g / mol, more particularly 400 g / mol to 2000 g / mol. 10. Composition according to any one of claims 1 to 9, characterized in that the aliphatic polyisocyanate has -NCO functionality strictly greater than 2, preferably is selected from a trimer of pentamethylene diisocyanate (t-PMDI), a trimer d hexamethylene diisocyanate (t-HDI), a trimer of isophorone diisocyanate (t-IPDI) or a mixture thereof; preferably an IPDI trimer or a PMDI trimer. 11. Composition according to any one of claims 1 to 10, characterized in that the polyisocyanate fraction further comprises an aliphatic diisocyanate; preferably selected from pentamethylene diisocyanate (PDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene dicyclohexyl diisocyanate (HMDI or hydrogenated MDI), or a mixture thereof; more preferably IPDI. 12. Composition according to any one of Claims 1 to 11, characterized in that the polyisocyanate fraction comprises at least 5 mol% relative to the -NCO functions, in particular at least 10 mol% relative to the -NCO functions, more particularly at least 15 mol% relative to the functions -NCO, of aliphatic polyisocyanate. 13. Composition according to any one of claims 1 to 12, characterized in that the polyisocyanate fraction comprises: 0 to 40 mol% relative to -NCO functions of aliphatic polyisocyanate; and 60 to 100 mol% relative to the -NCO functions of aliphatic diisocyanate. 14. Composition according to any one of claims 1 to 4, characterized in that it further comprises a catalyst, a spreading agent, a polymerization inhibitor, a surfactant, an antioxidant, a pigment or dye, an absorber of light, a stabilizer, a coalescing agent, a rheology control additive, an opacifier, a thermal or ultraviolet protection additive, an antistatic agent, an antibacterial agent, antifouling agent or antifungal agent. 15. Use of dimethylisosorbide as compatibilization promoter of a mixture comprising isosorbide and an aliphatic polyisocyanate. A process for producing a polyurethane coating on a substrate comprising the following steps: (1) The isosorbide mixture of a polyol moiety comprising a polyol selected from a polyester polyol, a polyether polyol, a polycarbonate polyol or a polyol their mixtures and a polyisocyanate fraction comprising an aliphatic polyisocyanate in the presence of a solvent, the polyol fraction comprising at least one polyol having a functionality-OH strictly greater than 2 and / or the polyisocyanate moiety comprising at least one polyisocyanate having a functionality -NCO strictly greater than 2; then (2) depositing on the substrate a layer of the mixture obtained in step (1), and (3) crosslinking the layer applied in step (2); characterized in that the solvent comprises dimethylisosorbide. 17. A polyurethane coating obtainable by the process as defined in claim 16.