BIOBASED URETHANE (METH)ACRYLATE FOR USE IN CLADDING

Abstract

A radiation curable and at least partially biobased urethane (meth)acrylate for use in a one-component coating composition for cladding an outdoor surface of a building, obtained from the reaction of at least the following compounds: a. A polyisocyanate compound having a biobased carbon content of at least 20%, preferably at least 50%, as determined by method A of the standard ASTM D6866-12: 2008, and b. A (meth)acrylate compound, different from compound a, and containing a reactive group capable to react with isocyanate groups.

Claims

1. A radiation curable and at least partially biobased urethane (meth)acrylate for use in a coating composition for cladding an outdoor surface of a building, obtained from the reaction of at least the following compounds: a. A polyisocyanate compound having a biobased carbon content of at least 20%, preferably at least 50%, as determined by method A of the standard ASTM D6866-12: 2008, and b. A (meth)acrylate compound, different from compound a, and containing a reactive group capable to react with isocyanate groups.

2. The urethane (meth) acrylate according to claim 1, wherein the coating composition is a one-component coating composition.

3. The urethane (meth)acrylate according to claim 1, wherein compound a comprises at least 2, preferably from 2 to 5, more preferably from 3 to 5, yet more preferably from 3.5 to 4.5 isocyanate groups.

4. The urethane (meth)acrylate according to claim 1, wherein the polyisocyanate compound comprises an oligomer of a diisocyanate.

5. The urethane (meth)acrylate according to claim 4, wherein the oligomer is a trimer.

6. The urethane (meth)acrylate according to claim 1, wherein the polyisocyanate compound is aliphatic.

7. The urethane (meth)acrylate according to claim 6, wherein the polyisocyanate compound is a monomer or an oligomer of a C.sub.2-C.sub.8, preferably C.sub.5-C.sub.6 aliphatic diisocyanate.

8. The urethane (meth)acrylate according to claim 1, wherein the polyisocyanate compound has an isocyanate content of at least 15 wt %.

9. The urethane (meth)acrylate according to claim 1, wherein said following compounds further comprise: c. a polyol, different from compounds a and b.

10. A coating composition for cladding an outdoor surface of a building comprising the urethane (meth)acrylate according to claim 1.

11. A coating composition according to claim 10, which is a one-component coating composition.

12. The composition according to claim 10, further comprising a reactive diluent.

13. The composition according to claim 10, further comprising a UV absorber and/or a hindered amine light stabilizer.

14. The composition according to claim 10, further comprising a one or more additives selected from the group consisting of rheology modifiers, photoinitiators, inhibitors, light absorbers, wetting agents, plasticizers, non-reactive diluents, and flexibilizers.

15. A process for preparing a radiation curable and at least partially biobased urethane (meth)acrylate for use in a coating for cladding an outdoor surface of a building, comprising the step of reacting together at least the following compounds: a. A polyisocyanate having a biobased carbon content of at least 20%, preferably at least 50%, as determined by method A of the standard ASTM D6866-12: 2008, and b. A (meth)acrylate compound, different from compound a, and containing a reactive group capable to react with isocyanate groups.

16. A process for curing a urethane (meth)acrylate according to claim 1 comprising exposing the urethane (meth)acrylate to one or more of an electron beam or an UV radiation.

17. Use of an urethane (meth)acrylate according to claim 1, for covering an outdoor surface.

18. Use according to claim 17 for forming a top coat on the outdoor surface.

19. Substrate coated with a urethane (meth)acrylate according to claim 1.

Description

EXAMPLE 1: PREPARATION OF A BIO URETHANE METHACRYLATE

[0106] A partially biobased-urethane methacrylate resin according to an embodiment of the first aspect of this invention was prepared using the following materials:

TABLE-US-00001 Raw material Quantity (in grams) Desmodur ® eco N 7300 1000 hydroxyethyl acrylate 333.7 Hydroxypropyl acrylate 166.1 Dibutyltin laurate 0.8 2-ethyl-1,3-hexanediol 69.7 Hexanediol diacrylate 386

[0107] Desmodur® eco N 7300 from Covestro Deutschland, Leverkusen, Germany

[0108] Hexanediol diacrylate from allnex, Frankfurt, Germany

[0109] The isocyanate (Desmodur® eco N 7300) together with the catalyst and extra stabilizer butylated hydroxy toluene was charged in a 3-liter glass reactor with reflux condenser with stirrer and thermometer and heated to 60° C. by means of an oil bath. The hydroxypropyl acrylate was then added slowly with a dosing pump while stirring.

[0110] During the addition of the hydroxypropyl acrylate, the temperature was kept at no more than 65° C. Once all of the hydroxypropyl acrylate was added, the temperature was raised to 65° C. and hydroxyethyl acrylate was added slowly again under stirring and the temperature was kept at 70° C. max. When all of the hydroxyethyl acrylate was added and the NCO content was stable (tested by reverse titration, using dibutylamine) the 2-ethyl-1,3-hexanediol was added and the temperature was kept at 80° C. until the end of the reaction.

EXAMPLE 2: PREPARATION OF A COATING COMPOSITION FROM THE URETHANE METHACRYLATE OF EXAMPLE 1

[0111] The product obtained in example 1 was diluted with HDDA (hexanediol diacrylate) and drummed off. The viscosity of the product was 160000 mPas at 23° C. It was further diluted with 12.5 gram of HDDA to bring the viscosity to 28600 mPas at 23° C.

[0112] The resulting resin was a clear liquid with a color of 41 APHA and containing less than 100 ppm of residual HEA and HPA.

[0113] This intermediate composition contained 80% urethane acrylate resin, which has a bio-carbon content of about 44%.

[0114] It was then formulated as a cladding as indicated in the table below:

TABLE-US-00002 Cladding pbw Example 1 70 HDDA 30 Irgacure 1173/TPO 8/2 4 Tinuvin 292 2 Tinuvin 400 1 Additol XL 6526 1

EXAMPLE 3: COATING OF A FIBRE CEMENT PANEL WITH THE COMPOSITION OF EXAMPLE 2

[0115] A fibre cement panel was coated by wet spray with 120 g/m.sup.2 of a UV-PUD primer. The composition of the primer is shown in the table below:

TABLE-US-00003 UV-PUD primer pbw UCECOAT 7630 100 pigment 3 BYK 346 0.5 BYK 1770 0.3 Irgacure 1173/TPO 8/2 1.5 Additol VXW 6360 x Tafigel PU 64 1/1 water x

[0116] UCECOAT 7630 was obtained from allnex.

[0117] This primer was then dried at 60° C. and UV-cured at 6 m/min with a 80 W Ga+Hg UV source.

[0118] Once cured, the primer was sanded before applying the coating of example 2.

[0119] 30 g/m.sup.2 of the coating of example 2 was applied on the primer with a roller coater. It was then cured at 6 m/min with first a 80 W Ga+Hg light source followed by a 120 W Hg light source. This resulted in an about 30 μm thick clear finish.

EXAMPLE 4: EXPOSING OF THE COATING OF EXAMPLE 3 TO A XENON LIGHT

[0120] The coating of Example 3 has been subjected to xenon weathering testing (including water spray) according to EN ISO 16474-2, method A, cycle 1, for a total testing time of 4000 hours. After 500, 1000, 1500, 1887, 2504, 3505, and 4000 hours of xenon-testing had been completed, the coating has been optically analysed. Up to 3505 hours of testing, no visible defects could be observed. The coating was still intact. Only at 4000 hours of testing could some defects be observed, although not at the level of the coating but at the level of the interface between the primer and the substrate. In particular, delamination points between the fiber cement and the primer could be seen. This testifies of the excellent weathering resistance of the coating according this embodiment of the present invention.

EXAMPLE 5: EXPOSING THE COATING OF EXAMPLE 3 TO A QUV-B 313 TESTING WITH CONDENSATION AT 55° C.

[0121] The coating of Example 3 has been subjected for three months to exposure to a QUV-B 313 testing with condensation at 55° C. and no visible defects could be observed.

EXAMPLE 6: MEASUREMENT OF OPTICAL PROPERTIES AND STAIN RESISTANCE OF THE COATING COMPOSITION OF EXAMPLE 2 UPON UV CURE

[0122] A 24 μm wet film and a 60 μm wet film of the coating composition of Example 2 were formed on separate white Leneta papers, then UV cured at 6 m/min with a 80 W Ga UV source and a Hg UV source. No significant yellowing was observed by the end of the curing. For the coating resulting from the 24 μm wet film, the gloss at 60° and 85° were measured and stain tests were performed by exposing the coating 24 h to a staining to substance. The results are summarized in the table below:

TABLE-US-00004 Gloss 60°  94.1 85° 100.4  24 hours stain test Mustard 3 Coffee 5 2% Eosine/water .sup. 2.sup.− Methylene blue 2 1% Iodine/water 2

[0123] The gloss values are good values for cladding.

[0124] The staining score range from 1 (worse) to 5 (best).