Silylated polyurethanes

1. A silylated polyurethane obtained by a process comprising the step of contacting at least one isocyanate which comprises 2,4′-methylene diphenyl diisocyanate with at least one isocyanate-reactive compound and with at least one aminosilane; wherein said at least one isocyanate comprises at most 45% by weight of said 2,4′-methylene diphenyl diisocyanate based on the total weight of said at least one isocyanate and wherein the silylated polyurethane is moisture curable and has a viscosity of at most 100 Pa·s wherein the viscosity is measured at 25° C. using Brookfield Viscometer according to the ASTM D 4889 standard without any plasticizer added to the silylated polyurethane.

2. The silylated polyurethane according to claim 1 , wherein said at least one isocyanate-reactive compound comprises at least one isocyanate-reactive group and wherein the molar ratio of the isocyanate groups of said at least one isocyanate to the isocyanate-reactive groups of said at least one isocyanate-reactive compound is of at least 1.1.

3. The silylated polyurethane according to claim 1 , wherein said at least one isocyanate comprises at most 40% by weight of 2,4′-methylene diphenyl diisocyanate based on the total weight of said at least one isocyanate.

4. The silylated polyurethane according to claim 1 , wherein said at least one isocyanate is a mixture comprising 2,4′-methylene diphenyl diisocyanate and at least one polyisocyanate selected from the group comprising 2,2′-methylene diphenyl diisocyanate; 4,4′-methylene diphenyl diisocyanate; hexamethylene diisocyanate; m- and p-phenylene diisocyanate; tolylene-2,4-diisocyanate; tolylene-2,6-diisocyanate; chlorophenylene-2,4-diisocyanate, naphthyl ene-1,5-diisocyanate, diphenylene-4,4′-diisocyanate, 4,4′-diisocyanate-3,3′-dimethyl-diphenyl, 3-methyl-diphenylmethane-4,4′-diisocyanate; diphenyl ether diisocyanate; cyclohexane-2,4-diisocyanate; cyclohexane-2,3-diisocyanate; 1-methylcyclohexyl-2,4-diisocyanate; 1-methylcyclohexyl-2,6-diisocyanate; bis-(isocyanatocyclohexyl)methane; 2,4,6-triisocyanatotoluene; 2,4,4-triisocyanatodiphenylether, isophorone diisocyanate, butylene diisocyanate, trimethylhexamethylene diisocyanate, isocyanatomethyl-1,8-octane diisocyanate, tetramethylxylene diisocyanate, 1,4-cyclohexanediisocyanate, and tolidine diisocyanate (TODI); oligomers such as pMDI, polymers, and mixtures thereof.

5. The silylated polyurethane according to claim 1 , wherein said at least one isocyanate is a mixture comprising 2,4′-methylene diphenyl diisocyanate and a polyisocyanate selected from the group comprising 2,2′-methylene diphenyl diisocyanate, 4,4′-methylene diphenyl diisocyanate, oligomers thereof, prepolymers thereof; and mixtures thereof.

6. The silylated polyurethane according to claim 1 , wherein said silylated polyurethane is obtainable by (a) contacting at least one isocyanate with at least one isocyanate-reactive compound and (b) contacting the product of step (a) with at least one aminosilane; and wherein the molar ratio of said at least one aminosilane, to the NCO isocyanate groups of the product of step (a) is greater than 0.5.

7. The silylated polyurethane according to claim 1 , wherein said at least one aminosilane is a compound of formula (I),

R 1 —NH—R 2 —Si—(OR 3 ) 3-n (R 4 ) n   (I)

wherein,

R 1 is selected from H; C 1-24 alkyl; C 3-24 cycloalkyl; C 6-24 aryl; or heteroaryl; and wherein said C 1-24 alkyl; C 3-24 cycloalkyl; C 6-24 aryl; or heteroaryl can be unsubstituted or substituted with one or more alkyl groups, cycloalkyl groups, aryl groups, halogen atoms or COOH groups;

R 2 is selected from C 1-20 alkylene or C 6-20 arylene;

R 3 is selected from C 1-20 alkyl; and C 6-20 aryl;

R 4 is selected from C 1-20 alkyl; and C 6-20 aryl;

n is an integer selected from 0, 1 or 2.

8. The silylated polyurethane according to claim 1 , wherein said at least one aminosilane is selected from the group comprising gamma-N-phenylaminopropyltrimethoxysilane, alpha-N-phenylaminomethyltrimethoxysilane, gamma-N-phenylaminopropyldimethoxymethylsilane, alpha-N-phenylaminomethyldimethoxymethylsilane, gamma-N-phenyl aminopropyltriethoxysilane, alpha-N-phenylaminomethyltriethoxysilane, gamma-N-phenylaminopropyldiethoxyethylsilane, alpha-N-phenylaminomethyldiethoxyethylsilane, gamma-N-butylaminopropyltrimethoxysilane, alpha-N-butylaminomethyltrimethoxysilane, gamma-N-butylaminopropyldimethoxymethylsilane, alpha-N-butylaminomethyldimethoxymethylsilane, gamma-N-butylaminopropyltriethoxysilane, alpha-N-butylaminomethyltriethoxysilane, gamma-N-butylaminopropyldiethoxyethylsilane, alpha-N-butylaminomethyldiethoxyethylsilane, gamma-N-methylaminopropyltrimethoxysilane, alpha-N-methylaminomethyltrimethoxysilane, gamma-N-methylaminopropyldimethoxymethylsilane, alpha-N-methylaminomethyldimethoxymethylsilane, gamma-N-methyl aminopropyltriethoxysilane, alpha-N-methylaminomethyltriethoxysilane, gamma-N-methylaminopropyldiethoxyethylsilane, alpha-N-methylaminomethyldiethoxy ethylsilane, gamma-N-cyclohexylaminopropyltrimethoxysilane, alpha-N-cyclohexylaminomethyltrimethoxysilane, gamma-N-cyclohexylaminopropyldimethoxymethyl silane, alpha-N-cyclohexylaminomethyldimethoxymethylsilane, gamma-N-cyclohexylaminopropyltriethoxysilane, alpha-N-cyclohexylaminomethyltriethoxysilane, gamma-N-cyclohexylaminopropyldiethoxyethylsilane, alpha-N-cyclohexylaminomethyldiethoxyethylsilane, gamma-aminopropyltrimethoxysilane, alpha-aminomethyltrimethoxysilane, gamma-aminopropyldimethoxymethylsilane, alpha-aminomethyldimethoxymethylsilane, gamma-aminopropyltriethoxysilane, alpha-aminomethyltriethoxysilane, gamma-aminopropyldiethoxyethylsilane, alpha-aminomethyldiethoxyethylsilane and mixtures thereof.

9. The silylated polyurethane according to claim 1 , wherein said at least one aminosilane is selected from the group comprising gamma-N-phenylaminopropyltrimethoxysilane, gamma-N-butylaminopropyltrimethoxysilane, gamma-N-methylaminopropyltrimethoxysilane, gamma-N-cyclohexylaminopropyltrimethoxysilane, gamma-aminopropyltrimethoxysilane, and mixtures thereof.

10. A process for preparing a silylated polyurethane according to claim 1 , wherein the process comprises the steps of:

(a) contacting at least one isocyanate with at least one isocyanate-reactive compound to form a reaction product;

(b) contacting the reaction product of step (a) with at least one aminosilane thereby preparing a silylated polyurethane; wherein said at least one isocyanate comprises 2,4′-methylene diphenyl diisocyanate, and wherein said at least one isocyanate comprises less than 50.0% by weight of said 2,4′-methylene diphenyl diisocyanate based on the total weight of said at least one isocyanate.

11. A composition comprising a silylated polyurethane as defined in claim 1 and optionally one or more additives.