WO2015067833A1 - Self-healing polyurethanes - Google Patents

Abstract

The invention relates to coumarins of formula (I), to polyols and polyurethanes comprising said coumarin, and to the method for producing said polyurethanes, the use thereof in the preparation of coating films, and the method thereof for healing a damaged surface of said polyurethane.

Description

 Self-healing polyurethanes

Field of the Invention The present invention relates to coumarins of formula (I), polyols and polyurethanes obtained from said coumarin, as well as the process for obtaining said polyurethanes, their use in the preparation of coating films and their process of repair of a damaged surface of said polyurethane.

Background of the invention

Self-repair systems of polymeric materials based on the microencapsulation of a repairing agent, application of an external stimulus, such as heat or light, and supramolecular chemistry, such as the formation of H bonds, are known in the prior art. .

Microencapsulation is a system that has a high percentage of recovery of the damaged polymer. However, it only allows recovery once, that is, if the same area is damaged again, there is no recovery. Other disadvantages of this system is the difficulty in ensuring that the contents of the microcapsules are capable of going completely outside, having to have a catalyst in the polymer matrix, high cost, environmental toxicity, stability and processing of This type of materials.

Self-repair through the use of supramolecular chemistry has the disadvantage that it does not allow transparent polymers to be obtained, transparency being an essential aspect in many applications of polymers. Self-repair by applying an external stimulus, such as light (photochemical self-repair) does not use catalysts. Therefore, it is an economically favorable system and does not harm the environment. In addition, it allows to obtain transparent polymers. Various photochemical self-repair systems of polymers based on reversible photo-cross-linking reactions of chromophores groups have been described [Liu Y.-L. and Chuo T.-W., Polym Chem (2013), 4, 2194-2205; Froimowicz H. et al., Macromol Rapid Commun (201 1), 32, 468-473; and Ghosh B. and Urban MW, Science (2009), 323, 1458-1460]. Among the chromophores groups, the use of coumarins has been described due to their ability to undergo reversible dimerization [Ling J. et al., J Mater Chem (2011), 21, 18373-18380; Ling J. et al., Polymer (2012), 53, 2691-2698; and CN 1021535856]. Said reversible dimerization occurs at wavelengths over 350 nm or solar radiation, producing a photodimerization [2 + 2] between two coumarins present in the polymer structure resulting in the formation of a cyclobutane ring, and wavelengths less than 260 nm, the inverse reaction occurs, that is, the photocision and therefore, the two double bonds are regenerated again, giving rise to the starting coumarin, as shown in Scheme 1, where R represents the chain polymeric This photodimerization-photo-excision allows the self-repair of the polymer in the damaged area, since when the polymer surface is damaged by mechanical stress, the weakest chemical bonds are those of the dimer, and therefore, these are the bonds that are cleaved. Upon irradiation with light of wavelength less than 260 nm, the previously cleaved bonds of coumarins dimerize and result in polymer repair.

 Scheme 1

The reversibility of the photodimerization-photoscision reactions of the coumarins allows to obtain polymeric systems of multiple recovery, that is, the self-repair can take place as many times as necessary.

In particular, Ling et al. [J Mater Chem (2011), 21, 18373-18380] describes the self-repair of polyurethanes by introducing a phenolic derivative of coumarin as a side chain of the structure of a polyurethane obtained from a trimer of hexamethylene diisocyanate, polyethylene glycol 400 and 7-hydroxyethoxy-4- methyl coumarin, whose structure is shown below. However, the polyurethane obtained presents problems of gelation, therefore presenting difficulties for its application as a film-like coating.

To solve the problems of gelation, Ling et al. [Polym (2012), 53, 2691-2698] describe the use of dihydroxylated coumarins in the synthesis of self-repairable polyurethanes, so that coumarin is integrated into the main polyurethane chain. Specifically, a polyurethane obtained from isophorone isocyanate, polyethylene glycol 400 or 800 and 5,7-bis (2-hydroxyethoxy) -4-methyl coumarin is described, the structure of which is shown below.

No obstante, hay una necesidad de disponer de poliuretanos autorreparables mejorados, en particular respecto a los tiempos de irradiación necesarios para la autorreparación, así como la eficiencia de dicha autorreparación. Sorprendentemente, los inventores han descubierto que recubrimientos de poliuretano que comprenden derivados dihidroxilados de cumarina de fórmula (I) presentan mayor reactividad al ser irradiados y por lo tanto un mayor porcentaje de autorreparación, además de presentar propiedades de múltiples ciclos de autorreparación, transparencia y elevadas prestaciones mecánicas.

However, there is a need to have improved self-repairable polyurethanes, in particular with respect to the irradiation times necessary for self-repair, as well as the efficiency of said self-repair. Surprisingly, the inventors have discovered that polyurethane coatings comprising dihydroxylated coumarin derivatives of formula (I) have greater reactivity when irradiated and therefore a higher percentage of self-repair, in addition to presenting properties of multiple cycles of self-repair, transparency and high mechanical performance

Summary of the invention In a first aspect, the invention relates to the compound of formula (I):

 (I)

 where

Ri _2, R ₃ and R ₄ are independently selected from the group consisting of H, alkyl and alkoxy CC ₆ CC _6;

Z is CR ₅ or N;

R ₅ is selected from the group consisting of H and CC ₆ alkyl; Y

 n is a number selected from the group consisting of 1, 2, 3 and 4;

or a stereoisomer thereof.

In a second aspect, the invention relates to a polyol (A) obtainable by reaction of one or more compounds of formula (I) as defined in the first aspect, with one or more compounds (B) in the presence of a catalyst, wherein the compound (B) comprises a functional group selected from -C (= 0) -0- and -O- and optionally a hydroxyl group, with the proviso that when the groups -C (= 0) - O -and -O- are not part of a cycle the hydroxyl group must be present.

In a third aspect, the invention relates to a process for obtaining a polyurethane comprising reacting a mixture comprising:

- one to more polyisocyanates (C) comprising at least two isocyanate groups, - one or more polyols selected from the group consisting of a polyol (A) as defined in the second aspect and a compound of formula (I) or mixtures thereof, and

 - optionally one or more polyols (D) selected from the group consisting of polyester polyols and polyether polyols,

in an aprotic organic solvent,

in the presence of a catalyst,

wherein the ratio of polyisocyanate equivalents (C) to the sum of equivalents of polyol (A) and polyol (D) in the reaction mixture is between 2: 1 and 1: 1, 2, and where the ratio between the sum of the equivalents of polyol (A) and the equivalents of the compound of formula (I) with respect to the equivalents of polyisocyanate (C) is between 1% and 95%.

In a fourth aspect, the invention relates to a polyurethane obtainable by the procedure defined in the third aspect.

In a fifth aspect, the invention relates to the use of a polyurethane as defined in the fourth aspect in the preparation of a coating. In a sixth aspect, the invention relates to a method of repairing a coating as defined in the fifth aspect that exposing said coating to light comprising a radiation with a wavelength between 310 nm and 370 nm. Detailed description of the invention

In the context of the present invention, the term "alkyl" refers to a linear or branched hydrocarbon chain radical consisting of carbon and hydrogen atoms, which does not contain unsaturations, having 1 to 6, preferably 1 to 3 atoms carbon, and which is attached to the rest of the molecule by a single bond, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, n-pentyl, etc.

The term "alkoxy", herein, refers to an alkyl radical, as defined above, attached to the rest of the molecule by a group -O-, for example, methoxy, ethoxy, n-propioxyl, isopropoxy , n-butoxy, t-butoxy. The term "alkylene", herein, refers to a linear hydrocarbon chain radical consisting of carbon atoms and hydrogen, which has the number of carbon atoms indicated in each case and that is attached to the rest of the molecule from both ends by simple bonds, for example, ethylene (- CH2-CH2-), n-propylene (-CH2-CH2-CH2-), n-butylene (-CH2-CH2-CH2-CH2-), n- pentilen (- CH2-CH2-CH2-CH2-CH2-), etc.

The term "cycloalkyl", herein, refers to a saturated carbocyclic ring having from 3 to 8 carbon atoms, preferably from 4 to 6 carbon atoms, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl

The term "cycloalkylene", herein, refers to a saturated carbocyclic ring radical having from 3 to 8 carbon atoms, preferably from 4 to 6 carbon atoms, and which is attached to the rest of the molecule from two different carbon atoms by simple bonds, for example, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene and cyclooctylene. The term "aryl", herein, refers to an aromatic hydrocarbon radical such as phenyl, naphthyl or anthracil. The aryl radical may be optionally substituted by one or more substituents such as hydroxyl, halogen, alkyl, and alkoxy, as defined herein. The term "halogen" or "halo", herein, refers to -F, -Cl, -Br and -I.

The term "hydroxyl" or "hydroxy" refers to a group -OH.

The term "aliphatic", herein, refers to cyclic or acyclic, linear or branched, saturated or unsaturated hydrocarbon compounds, excluding aromatic compounds.

The term "aromatic", herein, refers to a mono or polycyclic hydrocarbon comprising at least one unsaturated ring that satisfies the rule of Hückel of aromaticity. Examples of aromatic rings are phenyl, indanyl, indenyl, naphthyl, phenentrile and anthracil.

The term "stereoisomer", herein, refers to compounds formed by the same atoms joined by the same sequence of bonds but having different three-dimensional structures that are not interchangeable, for example isomers due to the presence of chiral centers (enantiomers , diastereomers and mixtures thereof including the racemic mixture), isomers due to the presence of multiple bonds (c / ^' s, trans and mixtures thereof).

The term "equivalent", herein, refers to the moles of compound per reactive units present in said compound, for example, one mole of diisocyanate are two equivalents of diisocyanate, while one mole of monoisocyanate is an equivalent of monoisocyanate .

Compound of formula (I)

In the first aspect, the invention relates to a coumarin derivative which is a compound of formula (I), as defined above.

In a particular embodiment, the invention is directed to a compound of formula (I), as defined above wherein R ₂ , R 3 and R ₄ are independently selected from the group consisting of H, C 1 -C 3 alkyl and CrC alkoxy ₃ ; Z is CR ₅ or N; R ₅ is selected from the group consisting of H and CrC ₃ alkyl; and n is a number selected from the group consisting of 1, 2, 3 and 4.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R ^ is selected from the group consisting of H, C1-C3 alkyl and CrC ₃ alkoxy; preferably from the group consisting of H, CrC ₃ alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferably R ^ is methyl.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R ₂ is selected from the group consisting of H, C1-C3 alkyl and CrC ₃ alkoxy; preferably from the group consisting in H, CrC ₃ alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferred R ₂ is H.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R ₃ is selected from the group consisting of H, CC ₃ alkyl and CrC ₃ alkoxy; preferably from the group consisting of H, CC ₃ alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferably R ₃ is H. In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R ₄ is selected from the group consisting of H, CC ₃ alkyl and CC ₃ alkoxy; preferably from the group consisting of H, CC ₃ alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferred R ₄ is H.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein Z is CR ₅ and R ₅ is selected from the group consisting of H and CC ₃ alkyl; preferably from the group consisting of H, methyl and ethyl; most preferred R ₅ is methyl.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein n is a number selected from the group consisting of 1, 2 and 3; preferably from the group consisting of 1 and 2; most preferred n is 1.

In a preferred embodiment, the present invention is directed to a compound of formula (I) wherein Z is CR ₅ and n is selected from the group consisting of 1 and 2.

In another preferred embodiment, the present invention is directed to a compound of formula (I) as defined above in which R ^ is selected from the group consisting of H, methyl and ethyl, and R ₂ , R ₃ and R ₄ they are H.

In another preferred embodiment, the present invention is directed to a compound of formula (I) as defined above, wherein R ^ is methyl, R ₂ , R ₃ and R ₄ are H, Z is CR ₅ , R ₅ is methyl and n is 1. The compound of formula (I) can be obtained by esterification reaction between the acid (IV) or a precursor thereof such as an anhydride or an acid halide and the corresponding 7- hydroxycoumarin (III), as shown in the Scheme 2, by procedures known to the person skilled in the art and described in Smith MB and March J. in March's Advanced Organic Chemistry Reactions, Mechanisms, and Structure, 6 ^to Ed. John Wiley & Sons.

 (IV)

 Scheme 2

The acid (IV) alcohol groups can be protected by alcohol protecting groups (GP) known to those skilled in the art and described, for example in Wuts, PGM and Greene TW in Protecting groups in Organic Synthesis, 4 ^to Ed. Wiley - Interscience, and in Kocienski PJ in Protecting Groups, 3 ^to Ed. Georg Thieme Verlag, as shown in Scheme 3. For example, ethers (including acetal formation) and silylated derivatives.

The esterification reaction can be carried out from the acid (IV), preferably with the protected hydroxyl groups, with acid catalysis, by methods known to those skilled in the art or can also be carried out by activating the acid (IV), preferably with protected hydroxyl groups, by formation of the anhydride, for example in the presence of dimethylaminopyridine and subsequent reaction with coumarin (III).

Scheme 3 Preferably, the process for obtaining the compound of formula (I) comprises the steps defined in Scheme 3, that is, protection of the hydroxyl groups of the acid (IV) to yield the acid (V), by conventional procedures, followed of activation of the acid (V) by formation of the anhydride (VI) by conventional methods such as in the presence of dicyclohexylcarbodiimide (DDC), and reaction of the anhydride (VI) with 7-hydroxycoumarin (III) to yield the ester (VII) , which, after deprotection of the hydroxyl groups by conventional methods yields the compound of formula (I).

Polyol (A)

In the second aspect, the invention relates to a polyol (A) obtainable by condensation reaction of one or more compounds of formula (I) as defined above, with one or more compounds (B) in the presence of a catalyst, wherein the compound (B) comprises a functional group selected from -C (= 0) -0- and -O- (which will participate in the condensation reaction to join one of the hydroxyl groups of the compound (I)) and optionally a hydroxyl group with the proviso that when the -C (= 0) -0- and -O- groups are not part of a cycle the hydroxyl group must be present.

In one embodiment of the present invention the compound (B) is a lactone or a cyclic ether, that is to say it comprises a group -C (= 0) -0- or a group -O- forming part of a cycla. Examples of this type of compounds are lactones such as ε-caprolactone and cyclic ethers such as ethylene oxide and propylene oxide.

In another embodiment of the present invention the compound (B) comprises a group -C (= 0) -0- or a group -O- that will participate in the reaction of joining one of the hydroxyl groups of the compound (I), and a hydroxyl group. Examples of such compounds are hydroxy acids, which comprise a carboxylic acid at one end and a hydroxyl group at the other end, hydroxy esters, which comprise an ester at one end and a hydroxyl group at the other end.

In a preferred embodiment of the invention, the compound (B) is a lactone; preferably selected from the group consisting of ε-caprolactone, δ-valerolactone, γ-butyrolactone, and β-propiolactone; more preferably selected from the group consisting of ε-caprolactone, δ-valerolactone; most preferred lactone is ε-caprolactone. The catalyst used can be a tertiary amine, such as, for example, triethylamine, triethylene diamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1, 4- diazabicyclo [2.2.2] octane, dimethylcyclohexylamine, dimethylpiperazine; organic derivatives of tin, mercury, lead, bismuth, zinc and potassium, such as tin octanoate, dibutyltin dilaurate tin isooctanoate, potassium octanoate and potassium acetate. Preferably the catalyst is selected from the group consisting of tin octanoate, tin isooctanoate, dibutyltin dilaurate, triethylamine, triethylenediamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1,4-diazabicyclo [2.2.2] octane, dimethylcyclohexylamine; more preferably it is independently selected from the group consisting of tin octanoate, tin isooctanoate and dibutyltin dilaurate; Most preferably, the catalyst is tin octanoate.

In a particular embodiment, the reaction is carried out in the absence of solvent.

In another embodiment the reaction is carried out in the presence of an aprotic organic solvent independently selected from the group consisting of dimethylformamide, butyl acetate, dimethyl sulfoxide, dimethylacetamide, tetrahydrofuran, dioxane, ethyl acetate, acetone, cyclohexanone, ethyl methyl ketone, acetonitrile, hexane , toluene, dichloromethane and mixture of pampering; more preferably it is independently selected from the group consisting of dimethylformamide, butyl acetate, dimethylacetamide, dimethylsulfoxide and mixture thereof; most preferably, the aprotic organic solvent is dimethylformamide, butyl acetate or mixture thereof.

Preferably, the reaction is carried out at a temperature between 50 ° C and 150 ° C, more preferably between 70 ° C and 130 ° C, most preferably between 90 ° C and 10 ° C. In a particular embodiment, the invention is directed to a polyol (A) obtainable by reaction of one or more compounds (B) and one or more compounds of formula (I) where the molar ratio compounds (B) to compounds of formula ( I) is between 80: 1 and 1: 1, more preferably between 40: 1 and 1: 5: 1. In a particular embodiment, the invention is directed to a polyol (A) whose average molecular weight is 200 Dalton a 10000 Dalton, preferably from 200 Dalton to 2000 Dalton.

In another preferred embodiment, the polyol (A) is a compound of formula (II):

 (II)

wherein R ₂ , R 3, R ₄ , Z and n are as defined for the compound of formula (I), m is a number between 2 and 6, yo and p are independently selected from a number between 0 and 40 with the condition that at least one of oyp is nonzero.

Polyurethane In general, polyurethanes are obtained from three monomers: a relatively long and flexible chain polyol, which constitutes the soft segments of the polyurethane, a polyisocyanate, and a short chain polyol, also called a chain extender if it is difunctional or crosslinking if it has a functionality greater than 2. The reaction of the polyisocyanate with the chain extender forms the hard segments of the polyurethane.

In the third aspect, the present invention relates to a process for obtaining a polyurethane comprising the coumarin derivative of formula (I) defined above, said method comprising reacting a mixture comprising:

 - one to more polyisocyanates (C) comprising at least two isocyanate groups,

- one or more polyols selected from the group consisting of a polyol (A) as defined above and a compound of formula (I) or mixtures thereof, and

- optionally one or more polyols (D) selected from the group consisting of aliphatic polyols, polyester polyols and polyether polyols, in an aprotic organic solvent,

in the presence of a catalyst,

wherein the ratio of polyisocyanate equivalents (C) to the sum of equivalents of polyol (A) and polyol (D) in the reaction mixture is between 2: 1 and 1: 1, 2, and where the ratio between the sum of the equivalents of polyol (A) and the equivalents of the compound of formula (I) with respect to the equivalents of polyisocyanate (C) is between 1% and 95%, preferably between 2% and 60%.

The term "polyisocyanate", in the context of the present invention, should be understood as a compound comprising two or more, preferably two, aliphatic and / or aromatic, preferably aliphatic, isocyanate groups. Examples of aliphatic polyisocyanates are hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), tetramethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecyanate diisocyanate diisocyanate diisocyanate ), 1,1,6,6-tetrahydroperfluorohexamethylene (TFDI) diisocyanate, isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate (CDI), 1,3-dicyclohexane diisocyanate, 1,2-dicyclohexane diisocyanate , 1,3-bis (isocyanatomethyl) cyclohexane (H ₆ XDI), 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI) and mixtures thereof. Examples of aromatic polyisocyanates are 2,4- and 2,6-toluene diisocyanate (TDI), para-phenylene diisocyanate (PPDI), 4,4'-diphenylmethane diisocyanate and their 2,4 'and 2,2' isomers (MDI), tetramethylxylene diisocyanate (TMXDI), 1,5-naphthalene diisocyanate (NDI), 1,3-bis (1- isocyanate-1-mylethylethyl) benzene, mefa-xylylene diisocyanate and mixtures thereof. In a preferred embodiment, the isocyanate (C) is selected from the group consisting of C ₂ -C ₂ alkylene diisocyanate or linear or branched optionally substituted with 1 to 10 substituents independently selected from halogen, C ₃ -C ₈ cycloalkylene diisocyanate optionally substituted with 1 to 4 substituents independently selected from the group consisting of CC ₃ alkyl and halogen, CrC ₆ alkylene diisocyanate C ₃ -C ₈ cycloalkylene optionally substituted with 1 to 4 substituents independently selected from the group consisting of CC alkyl ₃ and halogen, and cycloalkylene diisocyanate C ₃ -C ₈ -alkylene CrC ₆ -cycloalkylene , C ₃ -C ₈ optionally substituted with 1 to 4 substituents independently selected from the group consisting of CC ₃ alkyl and halogen; preferably the group consisting of diisocyanate of hexamethylene (HDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), tetramethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, dimeryl diisocyanate (DDI) 1 , 6,6-tetrahydroperfluorohexamethylene (TFDI), isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate (CDI), 1, 3- dicyclohexane diisocyanate, 1, 2-dicyclohexane diisocyanate, 1,3-bis ( isocyanatomethyl) cyclohexane (H ₆ XDI), 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI) and mixtures thereof; more preferably it is selected from the group consisting of hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), tetramethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate; Most preferably, the polyisocyanate is hexamethylene diisocyanate (HDI).

Polyol (D) refers to a compound that has at least two terminal hydroxyl groups and is selected from the group consisting of aliphatic polyols, polyester polyols and polyether polyols. Preferably, it is selected from the group consisting of polyester polyols and polyether polyols and has an average molecular weight between 200 Dalton and 10000 Dalton, preferably between 200 Dalton and 4000 Dalton, and is selected from the group consisting of polyester polyols and polyether polyols.

Preferred aliphatic polyols are diols, such as 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,3-propanediol, 1,2-propanediol and mixtures thereof.

Polyether polyols comprise, in addition to the terminal hydroxyl groups, non-terminal ether groups. Polyether polyols include polyethylene glycols, polypropylene glycols, mixed polyglycols based on ethylene oxide and propylene oxide, polytetramethylene glycols and polytetrahydrofurans.

Polyester polyols comprise, in addition to the terminal hydroxyl groups, non-terminal ester groups. Polyester polyols are obtained by condensation of diols and dicarboxylic acids, their anhydrides and esters. Examples of polyester polyols are condensation products based on ethylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol or neopentyl glycol, with adipic acid or isophthalic acid. Too polycaprolactones, poly (meth) acrylic polyols and polycarbonates belong to the group of polyol polyesters. Polycaprolactones are obtained from the reaction between phosgene, aliphatic carbonates or aromatic carbonates, such as diphenylcarbonate or diethyl carbonate, with dihydric or polyhydric alcohols. The polycaprolactones are obtained by polyaddition of lactones, such as, for example, ε-caprolactone, with an initiator compound having reactive hydrogen atoms, such as water, alcohols, amines or bisphenol A. The (meth) acrylic polyols are obtained by radical copolymerization. of (a) monomers of (meth) acrylic acids or esters, such as acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and hexyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate and hexyl methacrylate and (b) hydroxyalkyl (meth) acrylate monomers, such as hydroxyethyl acrylates, hydroxypropyl methacrylates, hydroxypropyl methacrylates, glycyl acrylate and glycyl acrylate. Combinations of polyesters, polycaprolactones, acrylic polyols and polycarbonates can also be used.

In a preferred embodiment, the polyol (D) is selected from the group consisting of polycaprolactones, polyethylene glycols, polypropylene glycols, mixed polyglycols of ethylene oxide and propylene oxide, polytetramethylene glycols, polytetrahydrofurans and mixture thereof, wherein the polyol (D) it has an average molecular weight between 200 Dalton and 10000 Dalton, preferably between 200 Dalton and 4000 Dalton; preferably it is selected from the group consisting of polycaprolactones, polyethylene glycols, polypropylene glycols, mixed polyglycols of ethylene oxide and propylene oxide and mixture thereof, wherein the polyol (D) has an average molecular weight between 200 Dalton and 10,000 Dalton; most preferred, the polyol (D) is selected from the group consisting of polycaprolactones, polyethylene glycols and mixtures thereof, wherein the polyol (D) has an average molecular weight between 200 Dalton and 4000 Dalton. Aprotic organic solvent is preferably an organic solvent selected from the group consisting of dimethylformamide, butyl acetate, dimethylsulfoxide, dimethylacetamide, tetrahydrofuran, dioxane, ethyl acetate, acetone, cyclohexanone, ethyl methyl ketone, acetonitrile. hexane, toluene, dichloromethane and mixture of pampering; preferably it is selected from the group consisting of dimethylformamide, butyl acetate, dimethylacetamide, dimethylsulfoxide and mixture thereof; most preferred, the Aprotic organic solvent is dimethylformamide, butyl acetate or mixture thereof.

The catalyst is a suitable catalyst for carrying out the polyurethane formation reaction, such as tertiary amines, such as, for example, triethylamine, triethylenediamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1, 4- diazabicyclo [2.2.2] octane, dimethylcyclohexylamine , dimethylpiperazine; organic derivatives of tin, mercury, lead, bismuth, zinc or potassium, such as tin octanoate, dibutyltin dilaurate tin isooctanoate, potassium octanoate and potassium acetate.

In a preferred embodiment, the catalyst is selected from the group consisting of tin octanoate, tin isooctanoate, dibutyltin dilaurate, triethylamine, triethylenediamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1, 4- diazabicyl [2.2.2] octane, dimethylcyclohexylamine; more preferably it is selected from the group consisting of tin octanoate, tin isooctanoate, dibutyltin dilaurate and potassium octanoate; Most preferably, the catalyst is tin octanoate. Typically, the catalyst is added in an amount comprised between 0.01% and 5% by moles relative to the moles of isocyanate (C), preferably between 0.01% and 0.05% by moles relative to the moles of isocyanate (C).

The polyurethane formation process is preferably carried out at a temperature between 50 ° C and 150 ° C, more preferably between 50 ° C and 100 ° C, most preferably between 65 ° C and 85 ° C.

Typically, the formation of polyurethanes is carried out by stirring for a time not exceeding 24 hours, preferably less than 12 hours, followed by heating above room temperature, and not exceeding 150 ° C, preferably below 100 ° C most preferred between room temperature and 85 ° C.

In a particular embodiment, the process according to the invention comprises reacting a mixture comprising one or more polyisocyanates (C) and one or more polyols (A). In another particular embodiment, the process according to the invention comprises reacting a mixture comprising one or more polyisocyanates (C), one or more polyols (A) and one or more polyols (D).

In another particular embodiment, the process according to the invention comprises reacting a mixture comprising one or more polyisocyanates (C), one or more compounds of formula (I) and one or more polyols (D). In another particular embodiment, the process according to the invention comprises reacting a mixture comprising one or more polyisocyanates (C), one or more compounds of formula (I) and one or more polyols (A).

In a preferred embodiment, the process according to the invention comprises reacting a mixture comprising one or more polyisocyanates (C), one or more compounds of formula (I), one or more polyols (A) and one or more polyols (D) .

In one embodiment of the process of the invention, the ratio of equivalents of polyisocyanate (C) to the sum of equivalents of polyol (A) and polyol (D) in the reaction mixture is between 2: 1 and 1: 1, 2 , preferably between 1: 5: 1 and 1: 1, 1, more preferably between 1, 2: 1 and 1: 1, 1, even more preferably between 1, 1: 1 and 1: 1, 05, most preferred 1 , 05: 1.

In an embodiment of the process of the invention, the ratio between the sum of the equivalents of polyol (A) and the equivalents of compound of formula (I) with respect to the equivalents of polyisocyanate (C) is comprised between 1% and 95 %, preferably between 2% and 60%.

In a particular embodiment, the invention is directed to a process for obtaining polyurethanes as defined above comprising:

 - reacting a mixture comprising a polyisocyanate (C) comprising at least two isocyanate groups,

 - a compound of formula (I) as defined above, and

- a compound of formula (II) (polyol (A)) as defined above, in the presence of a catalyst, wherein the ratio of equivalents of polyisocyanate (C) to equivalents of polyol (A) in the reaction mixture is between 2: 1 and 1: 1.2, preferably between 1.5: 1 and 1: 1.1, more preferably between 1.2: 1 and 1: 1.1, even more preferably between 1.1: 1 and 1: 1.05, most preferably 1.05: 1, and

wherein the ratio between the sum of the equivalents of polyol (A) and the equivalents of compound of formula (I) with respect to the equivalents of polyisocyanate (C) is between 1% and 95%, preferably between 2% and 60%.

In a preferred embodiment, the invention is directed to a process for obtaining polyurethanes as defined above comprising:

 - reacting a mixture comprising a polyisocyanate (C) selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, preferably tetradecamethane diisocyanate, preferably tetradecamethane diisocyanate group consisting of hexamethylene diisocyanate and isophorone diisocyanate,

 - a compound of formula (I) as defined above, and

 - a compound of formula (II) (polyol (A)) as defined above, in the presence of a catalyst,

wherein the ratio of equivalents of polyisocyanate (C) to equivalents of polyol (A) in the reaction mixture is between 2: 1 and 1: 1.2, preferably between 1.5: 1 and 1: 1.1, more preferably between 1.2: 1 and 1: 1.1, even more preferably between 1.1: 1 and 1: 1.05, most preferably 1.05: 1, and

wherein the ratio between the sum of the equivalents of polyol (A) and the equivalents of compound of formula (I) with respect to the equivalents of polyisocyanate (C) is between 1% and 95%, preferably between 2% and 60%.

In another aspect, the present invention relates to a polyurethane obtainable by the procedures defined above.

Uses of polyurethane

Another aspect relates to the use of said polyurethane in the preparation of a coating, preferably incorporated as an additive for varnishes and paints, preferably in varnishes and paints for plastic and metal substrates, more preferably in varnishes and paints for the automotive sector.

Preferably the coating has a thickness of less than 150 μηι, more preferably less than 140 μηι, more preferably less than 130 μηι, more preferably less than 120 μηι, more preferably less than 1 10 μηι, 100 μηι, more preferably less than 90 μηι, even more preferably less than 80 μηι, even more preferably less than 70 μηι, even more preferably less than 60 μηι, even more preferably less than 50 μηι, even more preferably less than 40 μηι, even more preferably less than 30 μηι, most preferred less than 20 μηι.

The polyurethane coatings have a solid matter content of the water-dilutable polyurethanes amounts to 75 to 90% by weight, preferably 70 to 90% by weight and especially preferably 75 to 90% by weight. The rest that is missing up to 100% by weight is constituted by and additives customary in the change of coatings comprising polyurethanes.

The coating agents comprising the polyurethanes according to the invention are suitable for all fields of use in which painting and coating systems are used, in particular in those with high demands on the surface quality and strength of the films, eg surface coating of mineral construction material, varnishing and sealing of wood and wood-derived materials, coating of metal surfaces (metal coating), coating and lacquering of asphalt or bituminous coatings, lacquering and sealing of various surfaces of plastic (plastic coating) as well as high gloss lacquers, in particular for the automotive sector.

The coating agents containing the polyurethanes according to the invention are usually used in monolayer lacquers or in the transparent or covering layer (upper layer) of multilayer structures.

The application of the coating can be carried out by the different spraying procedures such as, for example, spraying with compressed, direct or electrostatic air using two-component spray installations or, if necessary, two components. Lacquers and coating agents containing dispersions described above can however also be applied by other methods, for example by extension, rollers or scrapers.

Polyurethane repair

Said (coating of) polyurethane defined above, incorporates coumarin fragments of formula (I) in its structure that confer the self-repair properties by photodimerization-photoscision of the coumarin derivatives, and allows obtaining multiple recovery polymeric systems.

Therefore, in another aspect, the present invention relates to a method of repairing a coating comprising a polyurethane as defined above comprising exposing said coating to light comprising a radiation with a wavelength between 310 nm and 370 nm, preferably between 340 nm, preferably for 120 minutes to 180 minutes.

Said exposure to radiation comprising the defined wavelengths achieves the formation of the dimers of the coumarin derivative and therefore the repair of the polyurethane.

Preferably, the exposure is made of light comprising radiation of wavelengths comprised between 330 nm and 370 nm; more preferably between 340 nm and 360 nm; most preferred at 350 nm. "Repair of a coating" should be understood as the decrease in the number or magnitude of the defects present in said coating, "defects" being understood as the discontinuities observed when examining the coating at an increase of x20. Examples of such defects are scratches and cracks. In a more preferred embodiment, the repair process comprises a previous stage of exposure a coating comprising the light polyurethane comprising a radiation with a wavelength between 240 and 260 nm, preferably for 1 min to 20min. Preferably, the irradiation is performed at wavelengths between 200 nm and 260 nm; more preferably between 240 nm and 260 nm; most preferred at 254 nm.

Said irradiation cleaves dimers that had not been cleaved when the polyurethane was damaged, and subsequently dimers are re-formed by the irradiation step defined above.

Preferably the defects have a depth of less than 70 μηι, more preferably less than 65 μηι, even more preferably less than 60 μηι, even more preferably less than 55 μηι, even more preferably less than 50 μηι, even more preferably less than 45 μηι, even more preferably less than 40 μηι, even more preferably less than 35 μηι, even more preferably less than 30 μηι, even more preferably less than 25 μηι, most preferably less than 20 μηι. The following examples are merely illustrative and should not be considered as limiting the invention.

Examples Materials and methods

IR spectra were recorded using a Perkin-Elmer Spectrum One FT-IR spectrometer with ATR accessory (attenuated total reflectance spectrometer). To carry out the measurement, 4 scans were performed at a resolution of 4 cm ^"1. The 1 H and 13 C NMR spectra were recorded at room temperature on a Varian Inova 400 spectrometer (400 MHz 1 H and 100 MHz 13 C). As solvent, DMSO-d6 was used.The spectra were referenced with the residual solvent signal [δ (ppm) 2.50 (1 H) and 39.51 (13C)]. The characterization of the thermal properties of the synthesized polyurethanes was performed in a Mettler Toledo DSC822e calorimeter, recording the spectra at a heating rate of 10 ° C / min. To carry out the observation of the photoreversibility of the cleavage-dimerization of the coumarin derivative comprised in the polyurethane coatings, the spectrometry was used UV / Visible For this, the Perkin Elmer Lambda 35 spectrometer was used. The film (coating) was made by evaporation of a DMF solution on a face of a quartz cuvette. It was recorded between 240 nm and 400 nm. In order to quantify this photoreversibility, the Raman Renishaw in Vía microscope spectrophotometer was used. Aggression of the coating is carried out by means of the Erichsen 239-11 scratcher, which allows the realization of stripes with different forces from 1 to 20N. This device has a tip of 1 mm in diameter, which slides over the coating 2.2 cm at a speed of 0.02 m / s. In this work, UV radiation has been used to carry out the photodimerization and photoscision reaction of the synthesized polyurethanes. It should be noted that two types of UV furnaces have been used:

• UVP 1000: irradiation at 254 nm

 · DYMAX 2000-PC UV equipment: 320-400 nm irradiation

To carry out the quantification of the self-repair, the equipment used is a 3D optical profilometer from the SENSOFAR house (model ΡΙ_μ NEOX), which allows measuring the surface roughness of the sample on the micrometric and nanometric scale without the need for contact.

Example 1: Synthesis of 4-hydroxymarine-7-yl ester of 4-hydroxy-3- hydroxymethyl-3-methylbutyric acid Synthesis of 2,2,5-trimethyl- [1,3] dioxane-5-carboxylic acid (DMPA)

In a 500 ml round bottom flask 50 g of 2,2-bis (methoxy) propionic acid (0.373 mol) (DMPA), 69 ml_ of 2,2-dimethoxypropane (0.569 mol) (DMP) and 3 are added, 55 g (0.0187 mol) of p-toluenesulfonic acid monohydrate. Subsequently, 250 ml_ of acetone (58.08 g / mol) is added and stirred at room temperature for 4h. After this period of time, 18 mL of 2M NH ₃ in EtOH (0.036 mol) is added. A fine white precipitate appears. The reaction is placed on the rotary evaporator and removes the solvent at room temperature (after the end of week) approximately 600 mL of dichloromethane (CH ₂ CI ₂ ) is added. It is extracted with water (3x120 mL). The decanted dichloromethane is dried with anhydrous magnesium sulfate overnight. The next day, MgS0 ₄ is filtered with a conical funnel and a pleat filter and dichloromethane is removed in the rotary evaporator at atmospheric pressure. When everything has been distilled, it is dried under vacuum in the desiccator and a beige-orange solid is obtained.

Synthesis of 2,2,5-trimethyl- [1,3] dioxane-5-carboxylic acid anhydride (DMPAA)

2.5 grams of DMPA (14.36 mmol) is dissolved in 10 mL of dichloromethane together with 1.48 g (7.17 mmol) of Ν, Ν-dicyclohexylcarbodiimide (DCC) and allowed to stir for 48 h at room temperature. Finally, the DCC-urea complex is filtered under vacuum and the solvent is evaporated. The oily anhydrous obtained is dried under vacuum. Synthesis of 2,2,5-trimethyl- [1,3] dioxan-5-yl) acetic acid 4-methylcoumarin-7-yl ester

Se disuelven 2 g (6,021 mmol) del éster 4-metilcumarina-7-ilo del ácido 2,2,5-trimetil- [1 ,3]dioxan-5-il)acético sintetizado en el apartado anterior en 25 ml_ de metanol. Posteriormente, se adicionan 3,8 g de la resina Dowex H⁺ se filtra y se lava con cuidado con metanol. El metanol se evapora en el rotavapor para dar lugar al compuesto del título en forma de cristales de color blanco. 0.71 g 7-hydroxy-4-methylcomarin (4.04 mmol) (HMC) is added together with 0.09885 g of 4-dimethylaminopyridine (0.81 mmol) (DMAP), which is dissolved in 11.01 mL of anhydrous pyridine and subsequently diluted with 24.84 mL of dichloromethane. The DMPAA anhydride obtained in the previous step is subsequently added 2 g (6.05 mmol) and allowed to react for 5 hours at room temperature. The excess anhydride is extinguished by stirring the reaction overnight with 4 mL of a pyridine: water solution in a 1: 1 ratio. Subsequently, the organic phase is diluted with 100 mL of dichloromethane (84.93 g / mol; 1.326 g / cm ³ ) and extracted with NaHS0 ₄ (1 M) (2x40 mL) and two other extractions with Na ₂ C0 ₃ to 10% and 40 mL of NaCI. Finally, the organic phase is dried with anhydrous magnesium sulfate and subsequently filtered and the solvent is evaporated in the rotary evaporator. The solid white product obtained from vacuum drying. synthesis of the 4-hydroxy-3-hydroxymethyl-3-methylbutyric acid 4-methylcoumarin-7-yl ester

2 g (6,021 mmol) of the 2,2,5-trimethyl- [1,3] dioxan-5-yl) acetic acid synthesized in the above section are dissolved in 25 ml_ of methanol. Subsequently, 3.8 g of the Dowex H ⁺ resin is added, filtered and washed carefully with methanol. The methanol is evaporated in the rotary evaporator to give the title compound as white crystals.

1 H NMR (400MHz, DMSO- _d6 ) 5: 7.81 (s, 1 H, H-Ar), 7.13 (s, 1 H, H-Ar), 7, 10 (d, J = 8, 7Hz, 1 H, H-Ar) 6.38 (s, 1 H, C = CH), 4.98 (dd, J = 8.6, 2.4, 2H, OH), 3.68 (m, 2H, CH), 3.51 (m, 2H, CH) 2.43 (s, 3H, CH ₃ ) 1.17 (s, 3H, CH ₃ )

Example 2: Polyol Synthesis

6 g (0.052mol) of ε-caprolactone and coumarin obtained in example 1 (4 g, 0.0136 mol) is introduced into the reaction balloon. The tin octanoate catalyst (SnOct ₂ ) is then added with a concentration of 0.1% based on the weight of ε-caprolactone. Once all reagents are added, the reaction is heated at 100 ° C for 24 hours under continuous stirring. After this period of time, the formulated polyol is dried under vacuum. The molecular weight characterization was carried out by ¹ H NMR, quantifying a molecular weight of 725 g / mol. Example 3: Synthesis of polyurethane coating Hexamethylene diisocyanate (HDI, 1.31g = 15.6 meq) is introduced into a completely dry reaction balloon of 25 mL volume. Next, the PCL 530 polyol (polycaprolactone diol of average molecular weight 530 Dalton) (3.52 g = 13.4 meq) is introduced and 15 mL of anhydrous DMF is added. Subsequently, the coumarin ester derivative obtained in example 1 (0.26g = 1.8 meq) is poured and 2 mL of anhydrous DMF is added. Then the catalyst, tin octanoate (SnOct ₂ , 63 mg = 0.15 meq) is added. It is allowed to react under stirring at 80 ° C and for three hours. When this period of time has elapsed, it is left reacting at room temperature overnight and the next day, the corresponding coating is performed. To do this, the polymer is poured into a mold, which is on a plate and allowed to dry until evaporation of the DMF solvent. A coating with a thickness of 100 μηι is obtained.

Claims

1. Form compound

(YO) where Ri, 2, R ₃ and R ₄ are independently selected from the group consisting of H, CC ₆ alkyl and CC ₆ alkoxy; Z is CR ₅ or N; R ₅ is selected from the group consisting of H and CC ₆ alkyl; and n is a number selected from the group consisting of 1, 2, 3 and 4; or a stereoisomer thereof. 2. Compound of formula (I) according to claim 1 wherein Z is _CR5 , and n is selected from the group consisting of 1 and 2. 3. Compound of formula (I) according to any of the preceding claims wherein R^ is selected from the group consisting of H, methyl and ethyl, and R ₂ , R3 and R ₄ are H. 4. Compound of formula (I) according to any of the preceding claims, wherein R^ is methyl, _R2 , R3 and _R4 are H, Z is _CR5 , _R5 is methyl and n is 1. 5. Polyol (A) obtainable by reaction of a compound of formula (I) as defined in any of claims 1 to 4, with a compound (B) in the presence of a catalyst, where the compound (B) comprises a functional group selected from -C(=0)-0- and -O- and optionally a hydroxyl group, with the proviso that when the groups -C(=0)-0- and -O- are not part of a cycle the hydroxyl group must be present. 6. Polyol (A) according to claim 5, wherein the compound (B) is a lactone. 7. Polyol (A) according to any of claims 5 or 6 which is a compound of formula (II):

(ll) where R ₂ , R3, R ₄ , Z and n are as defined in any of claims 1 to 4, m is a number between 2 and 6, i and p are independently selected from a number between 0 and 40 with the condition that at least one of o and p is non-zero. 8. Procedure for obtaining a polyurethane that comprises reacting a mixture that comprises: - one or more polyisocyanates (C) comprising at least two isocyanate groups, - one or more polyols selected from the group consisting of a polyol (A) as defined in any of claims 5 to 7 and a compound of formula (I) as defined in any of claims 1 to 4 or mixtures of the same, and - optionally one or more polyols (D) selected from the group consisting of polyester polyols and polyether polyols, in an aprotic organic solvent, in the presence of a catalyst, where the ratio of equivalents of polyisocyanate (C) to the sum of equivalents of polyol (A) and polyol (D) in the reaction mixture is between 2: 1 and 1: 1.2, and where the ratio between the sum of the equivalents of polyol (A) and the equivalents of the compound of formula (I) with respect to the equivalents of polyisocyanate (C) is between 1% and 95%. 9. Process according to claim 8, wherein the polyisocyanate (C) is selected from the group consisting of linear or branched C ₂ -C ₂ alkylene diisocyanate optionally substituted with 1 to 10 substituents independently selected from halogens, cycloalkylene diisocyanate C ₃ -C ₈ optionally substituted with 1 to 4 substituents independently selected from the group consisting of CC ₃ alkyl and halogen, CrC ₆ -C ₃ -C ₈ alkylene diisocyanate optionally substituted with 1 to 4 substituents independently selected from the group consisting of CC ₃ alkyl and halogen, and C ₃ -C ₈ cycloalkylene diisocyanate - CC ₆ alkylene - C ₃ -C ₈ cycloalkylene diisocyanate optionally substituted with 1 to 4 substituents independently selected from the group consisting of CC ₃ alkyl and halogen. 10. Method according to any of claims 8 or 9, wherein the polyol (D) is selected from the group consisting of polycaprolactones, polyethylene glycols, prolipropylene glycols, mixed polyglycols of ethylene oxide and propylene oxide, polytetramethyl glycols, polytetrahydrofurans and a mixture of the themselves, where the polyol (D) has an average molecular weight between 200 Dalton and 10,000 Dalton. Process according to any of claims 8 to 10, wherein the catalyst is selected from the group consisting of tin octanoate, tin isooctanoate, dibutyltin dilaurate, triethylamine, triethylenediamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1,4-diazabicyl [2.2.2]octane, dimethylcyclohexylamine, potassium octanoate. 12. Method according to any of claims 8 to 11, wherein the aprotic organic solvent is selected from the group consisting of dimethylformamide, butyl acetate and a mixture thereof. 13. Method according to any of claims 8 to 12 comprising: - reacting a mixture comprising a polyisocyanate (C) selected from the group consisting of hexamethylene diisocyanate, isophorone diisocyanate, tetramethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, and tetradecamethylene diisocyanate, - a compound of formula (I) as defined in any of claims 1 to 4, and - a polyol (A) as defined in claim 7, in the presence of a catalyst, where the ratio of polyisocyanate equivalents (C) to polyol equivalents (A) in the reaction mixture is between 2:1 and 1:1,2, and where the ratio between the sum of the equivalents of polyol (A) and the equivalents of the compound of formula (I) with respect to the equivalents of polyisocyanate (C) is between 1% and 95%. Polyurethane obtainable by the procedure defined in any of claims 8 to 13. Use of a polyurethane according to claim 14 in the preparation of a coating. Repair procedure for a coating comprising a polyurethane as defined in claim 15, the procedure comprising exposing said coating to light comprising radiation with a wavelength between 310 nm and 370 nm. Repair method according to claim 16 comprising exposing the damaged surface of the polyurethane to light comprising radiation with a wavelength between 240 nm and 260 nm prior to the exposure defined in claim 16.