ES2537618B1 - Self-healing polyurethanes - Google Patents

Abstract

Self-repairable polyurethanes. # The present invention relates to coumarins of formula (I), polyols and polyurethanes comprising said coumarin, as well as the method of obtaining said polyurethanes, their use in the preparation of coating films and their repair procedure. a damaged surface of said polyurethane.

Description

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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 method of obtaining said polyurethanes, their use in the preparation of coating films and their surface repair procedure damaged from said polyurethane.

Background of the invention

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

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 chromophore groups have been described [Liu Y.-L. and Chuo T.- W., Polym Chem (2013), 4, 2194-2205; Froimowicz H. et al., Macromol Rapid Commun (2011), 32, 468-473; and Ghosh B. and Urban M.W., Science (2009), 323, 1458-1460]. Among the chromophore 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 CN1021535856]. Said reversible dimerization occurs at wavelengths over 350 nm or solar radiation, producing a photodimerization [2 + 2] between two coumarins present in the polymeric structure giving rise to 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-photoescision allows the self-repair of the polymer in the damaged area, since when the polymeric surface is damaged by mechanical stress, the weakest chemical bonds are those of the dimer, and therefore, these are the bonds that are cleaved. When irradiated with light of wavelength less than 260 nm, the previously cleaved bonds of coumarins dimerize and result in polymer repair.

 XX

     rrR

 XJ 350 nm XXX rV

 Y

 n ^ o ----- T 254 nm O ^ S T Y0

 OR

 OR

 OR

 OR

Scheme 1

5 The reversibility of the photodimerization-photoscision reactions of coumarins makes it possible to obtain multiple recovery polymer systems, 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-methylcoumarin, whose structure is shown below. However, the polyurethane obtained presents problems of gelation, therefore presenting difficulties for its application as a film-shaped coating.

O o o

'n H 6 I I 6H

o ^ Ao

hJ \

o ^ O

image 1

OR

OR

m

To solve the problems of gelation, Ling et al. [Polym (2012), 53, 2691-2698] 20 describe the use of dihydroxylated coumarins in the synthesis of self-repairable polyurethanes, so that the 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-methylcoumarin is described, the structure of which is shown below.

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image2

Or

n

Y

m

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 compound of formula (I):

image3

R4 ^ OH

OR

Or f

V-

OH

(I)

where

R1, R2, R3 and R4 are independently selected from the group consisting of H, Ci-Ca alkyl and Ci-Ca alkoxy;

Z is CR5 or N;

R5 is selected from the group consisting of H and C1-Ca alkyl; and 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 reacting 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 (= O) -O- and -O- and optionally a hydroxyl group, with the proviso that when the -C (= O) -O groups -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 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 the second aspect and a compound of formula (I) or mixtures thereof, and

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

wherein 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 comprised between 1% and 95%.

In a fourth aspect, the invention relates to a polyurethane obtainable by the method 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 that 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-proprioxyl, isopropoxy , n-butoxy, t-butoxy.

The term "alkylene", herein, refers to a linear hydrocarbon chain radical consisting of carbon and hydrogen atoms, which has the number of carbon atoms indicated in each case and which 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 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 optionally be

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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 Huckel's aromaticity rule. Examples of aromatic rings are phenyl, indanyl, indenyl, naphthyl, phenentrile and anthracil.

The term "stereoisomer", herein, refers to compounds formed by the same atoms linked 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 racemic mixture), isomers due to the presence of multiple bonds (cis, 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 R1, R2, R3 and R4 are independently selected from the group consisting of H, C1-C3 alkyl and C1 alkoxy -C3; Z is CR5 or N; R5 is selected from the group consisting of H and C1-C3 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 R1 is selected from the group consisting of H, C1-C3 alkyl and C1-C3 alkoxy; preferably from the group consisting of H, C1-C3 alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferred R1 is methyl.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R2 is selected from the group consisting of H, C1-C3 alkyl and C1-C3 alkoxy; preferably from the group consisting of H, C1-C3 alkyl; even more preferably from the group consisting of H, methyl and ethyl; R2 is most preferred.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R3 is selected from the group consisting of H,

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C1-C3 alkyl and C1-C3 alkoxy; preferably from the group consisting of H, C1-C3 alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferred R3 is H.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein R4 is selected from the group consisting of H, C1-C3 alkyl and C1-C3 alkoxy; preferably from the group consisting of H, C1-C3 alkyl; even more preferably from the group consisting of H, methyl and ethyl; most preferred R4 is

H.

In another particular embodiment, the invention is directed to a compound of formula (I), as defined above, wherein Z is CR5 and R5 is selected from the group consisting of H and C1-C3 alkyl; preferably from the group consisting of H, methyl and ethyl; most preferred R5 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

I.

In a preferred embodiment, the present invention is directed to a compound of formula (I) wherein Z is CR5 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 R1 is selected from the group consisting of H, methyl and ethyl, and R2, R3 and R4 are H.

In another preferred embodiment, the present invention is directed to a compound of formula (I) as defined above, wherein R1 is methyl, R2, R3 and R4 are H, Z is CR5, R5 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, 6th Ed. John Wiley & Sons.

image4

Oh

HO

O T -

X ^ -z ^ oh '

image5

or r

OH

z ^ ^ oh

(IV)

(I)

Scheme 2

R

4

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

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The esterification reaction can be carried out from the acid (IV), preferably with the protected hydroxyl groups, with acid catalysis, by methods known to the person 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).

Oh

HO

Or {

Jl ^ Z ^ OH

, OGP

HO

Or {

A ^^ / ogp

image6

(IV)

(V)

GPO .OGP

O O {

gpo ^ z ^ AoX ^ .z ^ ogp

(VI) n

D d

D d

image7

A ^ .zO ° h

image8

OGP

4th r

X ^ Z ^ / OPG

(I)

(VII)

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 by 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, the compound of formula (I) yields.

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 (= O) -O- 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 (= O) -O- and -O- groups are not part of a cycle the hydroxyl group must be present.

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In one embodiment of the present invention the compound (B) is a lactone or a tic ether, that is to say it comprises a group -C (= O) -O- or a group -O- forming part of a cycle. Examples of this type of compounds are lactones such as--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 (= O) -O- or a group -O- that participates in the reaction of to bind to one of the hydroxyl groups of the compound (I), and a hydroxyl group. Examples of such compounds are hydroxyacids, which comprise a carboxylic acid at one end and a hydroxyl group at the other end, hydroxyl esters, which comprise an ester at one end and a hydroxyl group at the other end.

In a preferred embodiment of the invention, compound (B) is a lactone; preferably selected from the group consisting of £ -caprolactone, 5-valerolactone, and -butyrolactone, and p-propiolactone; more preferably selected from the group consisting of £ -caprolactone, 5-valerolactone; most preferred lactone is £ -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 stannous octanoate, dibutyl ethane stano isooctanoate, potassium octanoate and potassium acetate. Preferably the catalyst is selected from the group consisting of stano octanoate, stan isooctanoate, dibutyl methane dilaurate, triethylamine, triethylene diamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1,4-diazabicyclo [2.2.2] octane, dimethylcyclohexylamine; more preferably it is independently selected from the group consisting of stano octanoate, stan isooctanoate and dibutyl methane dilaurate; Most preferably, the catalyst is stannous 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, ethylmethyl 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 110 ° 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 to 10,000 Dalton, preferably 200 Dalton to 2000 Dalton.

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

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H '

O o

^ -o o- ^ ~ r °

'' m I I [m ■ J0 ^ Z ^ '

H

image9

OR

OR

R2

(II)

wherein R1, R2, R3, R4, 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

p

R

one

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 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 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 organic aprotic solvent, in the presence of a catalyst,

wherein 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 comprised 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

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(DDI), 1,1,6,6-tetrahydroperfluorohexamethylene diisocyanate (TFDI), isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate (CDI), 1,3-dicyclohexane diisocyanate, 1,2-diisocyanate -dicyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI) 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 its 2,4 'and 2,2' isomers (MDI), tetramethylxylene diisocyanate (TMXDI), 1,5-naphthalene diisocyanate (NDI), 1,3-bis (1-isocyanate-1-mylethyl) benzene, mete-xylylene diisocyanate and mixtures thereof.

In a preferred embodiment, the isocyanate (C) is selected from the group consisting of linear or branched C2-C20 alkylene diisocyanate optionally substituted with 1 to 10 substituents independently selected from halogen, C3-C8 cycloalkylene diisocyanate optionally substituted with 1 to 4 substituents independently selected from the group consisting of C1-C3 alkyl and halogen, C1-C6 alkylene diisocyanate C3-C8 cycloalkylene optionally substituted with 1 to 4 substituents independently selected from the group consisting of C1-C3 alkyl and halogen, and C3-C8-cycloalkylene diisocyanate-C1-C6-C3-C8-cycloalkylene optionally substituted with 1 to 4 substituents independently selected from the group consisting of C1-C3 alkyl and halogen; preferably, the group consisting of hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate (TMDI), tetramethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, tetradecamethylene diisocyanate dimeryl (DDI), 1,1,6,6-tetrahydroperfluorohexamethylene diisocyanate (TFDI), isophorone diisocyanate (IPDI), 1,4-cyclohexane diisocyanate (CDI), 1,3-dicyclohexane diisocyanate, diisocyanate 1, 2-dicyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI) 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 10,000 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 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. Polycaprolactones, (meth) acrylic polyols and polycarbonates also belong to the polyol polyester group. Polycaprolactones are obtained from the reaction between phosgene, aliphatic carbonates or

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aromatic carbonates, such as diphenylcarbonate or diethyl carbonate, with dihydric or polyhydric alcohols. The polycaprolactones are obtained by polyadicion of lactones, such as for example £ -caprolactone, with an initiator compounds that have 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) monomers of (meth) hydroxyalkyl acrylates, such as hydroxyethyl acrylates, hydroxyethyl methacrylates, hydroxypropyl methacrylates, hydroxypropyl methacrylate and glycidyl acrylate. You can also use combinations of polyesters, polycaprolactones, acrylic polyols and polycarbonates.

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 mixture 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, dimethyl sulfoxide, 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 preferably, 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 stannous, mercury, lead, bismuth, zinc or potassium, such as stannous octanoate, dibutyl methane dilaurate isooctanoate, potassium octanoate and potassium acetate.

In a preferred embodiment, the catalyst is selected from the group consisting of stano octanoate, stano isooctanoate, dibutyl methane 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 stano octanoate, stan isooctanoate, dibutyl methane dilaurate and potassium octanoate; Most preferably, the catalyst is stannous octanoate.

Typically, the catalyst is added in an amount comprised between 0.01% and 5% in moles relative to the isocyanate moles (C), preferably between 0.01% and 0.05% in moles relative to the isocyanate moles (C).

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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

(TO).

In another particular embodiment, the method 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 method 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 method 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 an 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 comprised 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 comprised 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

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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 comprised 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 is related to the use of said polyurethane in the preparation of a coating, preferably incorporated as a varnish and paint additive, 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 pm, more preferably less than 140 pm, more preferably less than 130 pm, more preferably less than 120 pm, more preferably less than 110 pm, 100 pm, more preferably less than 90 pm, even more preferably less than 80 pm, even more preferably less than 70 pm, even more preferably less than 60 pm, even more preferably less than 50 pm, even more preferably less than 40 pm, even more preferably less than 30 pm, most preferred less than 20 pm.

The polyurethane coatings have a solid matter content of the water-dilutable polyurethanes amounts to 75 to 90% by weight, preferably to 70 to 90% by weight and especially preferably to 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 paint and coating systems are used, in particular in those with high demands on surface quality and resistance 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

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asphalt or bituminous coatings, lacquered and sealed of various plastic surfaces (plastics 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, for example, spraying with compressed, direct or electrostatic air using two-component spray installations or, if necessary, two components. The lacquers and coating agents containing the dispersions described above may, however, also be applied by other methods, for example by extension, rollers or scrapers.

Polyurethane Reparation

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 dimer 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 the 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 at 20min.

Preferably, 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 the dimers that had not been cleaved when the polyurethane was damaged, and then the dimers are re-formed by the irradiation stage defined above.

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Preferably the defects have a depth of less than 70 pm, more preferably less than 65 pm, even more preferably less than 60 pm, even more

preferably less than 55 pm, even more preferably less than 50 pm, even more

preferably less than 45 pm, even more preferably less than 40 pm, even more

preferably less than 35 pm, even more preferably less than 30 pm, even more

preferably less than 25 pm, most preferred less than 20 pm.

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 1H and 13C NMR spectra were recorded at room temperature on a Varian Inova 400 spectrometer (400MHz 1H and 100 MHz 13C). DMSO-d6 was used as solvent. The spectra were referenced with the residual solvent signal [5 (ppm) 2.50 (1H) and 39.51 (13C)].

The characterization of the thermal properties of the synthesized polyurethanes was carried out 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 UV / Visible spectrometry was used. 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 Via microscope spectrophotometer was used.

The aggression of the coating is carried out by means of the Erichsen 239-II scratcher, which allows the realization of stripes with different forces from 1 to 20N. This device has a 1mm diameter tip, 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 photosecision 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 (PLp NEOX model), which allows to measure the surface roughness of the sample on the micrometric and nanometric scale without the need for contact.

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Example 1: Synthesis of the 4-methylcoumarin-7-yl ester of 4-hydroxy-3-hydroxymethyl-3- methylbutyric acid

Synthesis of 2,2,5-trimethyl-H, 31-dioxane-5-carboxylic acid (DMPA)

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COOH

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 NH3 in EtOH (0.036 mol) is added. A fine white precipitate appears. The reaction is placed on the rotary evaporator and the solvent is removed at room temperature (after the weekend) approximately 600 mL of dichloromethane (CH2Cl2) is added. It is extracted with water (3x120 mL). The decanted dichloromethane is dried with anhydrous magnesium sulfate overnight. The next day, the MgSO4 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-H, 31-dioxane-5-carboxylic acid anhydride (DMPAA)

O o

2.5 grams of DMPA (14.36 mmol) is dissolved in 10 mL of dichloromethane together with 1.48 g (7.17 mmol) of N, N-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 the ester 4-methylcoumarin-7-yl of the acid 2,2,5-trimethyl-H, 31-dioxan-5-yl) acetic acid

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 of the anhydride is extinguished by stirring the reaction overnight with 4 mL of a solution of pyridine: water in a 1: 1 ratio. Subsequently, the organic phase is diluted with 100 mL of dichloromethane (84.93 g / mol; 1,326 g / cm3) and extracted with NaHSO4 (1M) (2x40 mL) and two other extractions with 10% Na2CO3 and 40 mL of NaCl Finally, the organic phase is dried with anhydrous magnesium sulfate and subsequently filtered and the solvent evaporated in the rotary evaporator. The solid white product obtained from dry to vacuum.

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Synthesis of the 4-methylcoumarin-7-yl ester of 4-hydroxy-3-hydroxymethyl-3-methylbutyl acid

OH

2 g (6,021 mmol) of the 4-methylcoumarin-7-yl ester 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.

1H NMR (400MHz, DMSO-d6) 5: 7.81 (s, 1H, H-Ar), 7.13 (s, 1H, H-Ar), 7.10 (d, J = 8.7Hz, 1H , H-Ar) 6.38 (s, 1H, C = CH), 4.98 (dd, J = 8.6, 2.4, 2H, OH), 3.68 (m, 2H, CH), 3.51 (m, 2H, C-H) 2.43 (s, 3H, CH3) 1.17 (s, 3H, CH3)

Example 2: Polyol Synthesis

6 g (0.052mol) of £ -caprolactone and coumarin obtained in example 1 (4 g, 0.0136 mol) is introduced into the reaction balloon. Next, the tin octanoate catalyst (SnOct2) with a concentration of 0.1% with respect to the weight of £ -caprolactone is added. Once all reagents are added, the reaction is heated to 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 (SnOct2, 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 on the following day, the corresponding coating is performed. For 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 of a thickness of 100 pm is obtained.

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Claims (17)

5 10 fifteen twenty 25 30 one. Compound of formula (I): image 1 R4 or ^ OH Z. OH (I) where R1, R2, R3 and R4 are independently selected from the group consisting of H, C1-C6 alkyl and C1-C6 alkoxy; Z is CR5 or N; R5 is selected from the group consisting of H and C1-C6 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 R1 is selected from the group consisting of H, methyl and ethyl, and R2, R3 and R4 are H. 4. Compound of formula (I) according to any of the preceding claims, wherein R1 is methyl, R2, R3 and R4 are H, Z is CR5, R5 is methyl and n is 1. 5. Polyol (A) obtainable by reacting a compound of formula (I) as defined in any one of claims 1 to 4, with a compound (B) in the presence of a catalyst, wherein the compound (B) comprises a functional group selected from - C (= O) -O- and -O- and optionally a hydroxyl group, with the proviso that when the groups -C (= O) -O- and -O- are not part of a 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): 5 10 fifteen twenty 25 30 35 O o -o ^ N, j ^ image2 OR p R one 2 H (II) wherein R1, R2, R3, R4, Z and n are as defined in any of claims 1 to 4, 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. 8. Method for obtaining a polyurethane comprising reacting a mixture comprising: - 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 one of claims 5 to 7 and a compound of formula (I) as defined in any one of claims 1 to 4 or mixtures of them, and - optionally one or more polyols (D) selected from the group consisting of polyester polyols and polyether polyols, in an organic aprotic solvent, in the presence of a catalyst, wherein 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 comprised between 1% and 95%. 9. Method according to claim 8, wherein the polyisocyanate (C) is selected from the group consisting of linear or branched C2-C20 alkylene diisocyanate optionally substituted with 1 to 10 substituents independently selected from halogens, C3-C8 cycloalkylene diisocyanate optionally substituted with 1 to 4 substituents independently selected from the group consisting of C1-C3 alkyl and halogen, C1-C6 alkylene diisocyanate C3-C8 cycloalkylene optionally substituted with 1 to 4 substituents independently selected from the group consisting of C1 alkyl -C3 and halogen, and C3-C8-cycloalkylene diisocyanate C1-C6-C3-C8-cycloalkylene optionally substituted with 1 to 4 substituents independently selected from the group consisting of C1-C3 alkyl and halogen. 10. The 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, 5 10 fifteen twenty 25 30 35 40 polytetramethylene glycols, polytetrahydrofurans and mixture thereof, wherein the polyol (D) has an average molecular weight between 200 Dalton and 10000 Dalton. 11. The method according to any one of claims 8 to 10, wherein the catalyst is selected from the group consisting of stano octanoate, stano isooctanoate, dibutylmethane dilaurate, triethylamine, triethylenediamine, methylethanolamine, triethanolamine, dimethylethanolamine, pyridine, 1.4 -diazabicyl [2.2.2] octane, dimethylcyclohexylamine, potassium octanoate. 12. The 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 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, tetradecamethylene diisocyanate - a compound of formula (I) as defined in any one of claims 1 to 4, and - a polyol (A) as defined in claim 7, in the presence of a catalyst, wherein the ratio of equivalents of polyisocyanate (C) to equivalents of polyol (A) in the reaction mixture is comprised 2: 1 and 1: 1,2, 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 comprised between 1% and 95%. 14. Polyurethane obtainable by the method defined in any of claims 8 to 13. 15. Use of a polyurethane according to claim 14 in the preparation of a coating. 16. Procedure for repairing a coating comprising a polyurethane as defined in claim 15, the method comprising exposing said coating to light comprising a radiation with a wavelength between 310 nm and 370 nm. 17. Repair method according to claim 16 comprising exposing the damaged surface of the polyurethane to light comprising a radiation with a wavelength between 240 nm and 260 nm prior to the exposure defined in claim 16.