Acetoacetyl thermosetting resin for gel coat
Zero VOC thermosetting gel coat and laminating resin compositions, and composites and articles, are produced using a multifunctional Michael acceptor, a multifunctional Michael donor and a base catalyst. The obtained low viscosity resin is useful for producing zero VOC gel coats and laminates having excellent curability at ambient temperatures.
1. A gel coated article, comprising a cured thermoset gel coat on a surface of the article, wherein the article is a reinforced resin composite comprising a resin and a reinforcing material, and said resin and the thermoset gel coat being crosslinked, solid and styrene free with zero VOCs, wherein:
the resin comprises crosslinked acetoacetylated polyhydroxy polyol and multifunctional acrylate monomer or oligomer, and
the thermoset get coat comprises crosslinked acetoacetylated polyhydroxy polyol, multifunctional acrylate monomer or oligomer, and a copolymer made by free radical copolymerization of vinyl monomers, wherein at least one of the vinyl monomers contains an acetoacetate functional group.
2. The gel coated article of claim 1 , wherein the acetoacetylated polyhydroxy polyol is formed by reacting a polyhydroxy polyol having at least two hydroxyl groups per molecule with a C 1 -C 5 alkyl acetoacetate in a transesterification process to form a crosslinkable, multifunctional acetoacetylated polyhydroxy polyol having at least two acetoacetyl functional groups per oligomer.
3. The gel coated article of claim 1 , wherein the polyhydroxy polyol has at least three hydroxyl groups per molecule.
4. The gel coated article of claim 1 , wherein the acetoacetylated polyhydroxy polyol has:
an acetoacetyl content of 5 to 80 weight %,
a hydroxyl number of 0 to 60 mg KOH/g,
an acid value of 0 to 5 mg KOH/g, and
a number average molecular weight (Mn) of 250 to 6000 g mole −1 .
5. The gel coated article of claim 1 , wherein the thermoset gel coat is formed from a crosslinkable, styrene free, thermosetting gel coat composition comprising the acetoacetylated polyhydroxy polyol, the one or more multifunctional acrylate monomers or oligomers, an additive component, and a base catalyst.
6. The gel coated article of claim 5 , wherein the gel coat composition comprises:
15 to 70 wt % of the acetoacetylated polyhydroxy polyol,
15 to 70 wt % of the one or more multifunctional acrylate monomers or oligomers, and
2 to 40 wt % of the additive component,
based on the total weight of the gel coat composition.
7. The gel coated article of claim 5 , wherein the additive component is selected from the group consisting of fillers, pigments, thixotropic agents, promoters, inhibitors, stabilizers, extenders, air release agents, leveling agents, and combinations thereof.
8. The gel coated article of claim 5 , wherein the additive component is a thixotropic agent selected from the group consisting of silicas and clays.
9. The gel coated article of claim 5 , wherein the additive component comprises a filler selected from the group consisting of clay, magnesium oxide, magnesium hydroxide, aluminum trihydrate (ATH), calcium carbonate, calcium silicate, mica, aluminum hydroxide, barium sulfate and talc, and mixtures thereof.
10. The gel coated article of claim 1 , wherein the reinforced resin composite comprises a reinforcing material selected from the group consisting of glass fiber, polyethylene fiber, carbon fiber, metal fiber, and ceramic fiber.
11. The gel coated article of claim 1 , wherein the article is selected from boat hulls, bath tub enclosures, pools, spas and body panels on cars and trucks.
12. The gel coated article of claim 1 , wherein the gel coat has a heat deflection temperature (HDT) from 34 to 86, as tested by ASTM D648.
13. The gel coated article of claim 1 , wherein the gel coat has a tensile strength from 7500 psi to 107600, and a tensile elongation from 1.9% to 4.3%.
14. The gel coated article of claim 1 , wherein the gel coat has a flexural strength from 8600 psi to 18130 psi.
15. The method of claim 1 , wherein the copolymer is made by free radical copolymerization of isobornyl methacrylate and acetoacetoxyethyl methacrylate.
16. The method of claim 1 , wherein the crosslinked acetoacetylated polyhydroxy polyol and multifunctional acrylate monomer or oligomer of the article is different from that of the thermoset gel coat.
17. A method of making a gel coated article, comprising:
providing a crosslinkable thermosetting gel coat composition having a viscosity at ambient temperature of 50 to 1200 cps under high shear and of 8,000 to 25,000 cps at low shear, wherein the composition comprises an acetoacetylated polyhydroxy polyol having at least two acetoacetyl functional groups, one or more multifunctional acrylate monomers or oligomers, a copolymer made by free radical copolymerization of vinyl monomers, wherein at least one of the vinyl monomers contains an acetoacetate functional group, at least one additive component, and a base catalyst; and
applying the thermosetting gel coat composition as an in-mold coating to a surface of a mold;
allowing the gel coat composition to cure at ambient temperature to form a partially crosslinked, tacky to tacky-free gel coat;
applying a material to be molded onto the partially crosslinked gel coat;
applying a crosslinkable laminating resin onto said material, the laminating resin comprising an acetoacetylated polyhydroxy polyol having at least two acetoacetyl functional groups per molecule, one or more multifunctional acrylate monomers or oligomers and a base catalyst; and
allowing the laminating resin and the gel coat to cure at ambient temperature to a solid, crosslinked, thermoset resin being styrene free.
18. The method of claim 17 , wherein the acetoacetylated polyhydroxy polyol has:
an acetoacetyl content of 5 to 80 weight %,
a hydroxyl number of 0 to 60 mg KOH/g,
an acid value of 0 to 5 mg KOH/g, and
a number average molecular weight (Mn) of 250 to 6000 g mole −1 .
19. The method of claim 17 , wherein the gel coat is 70 to 100% crosslinked.