Acetoacetyl Thermosetting Resin for Gel Coat

Abstract

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 method of making a styrene free gel coat composition, comprising:
 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; and   combining the acetoacetylated polyhydroxy polyol with one or more multifunctional acrylate monomers or oligomers, a thixotropic agent, and a base catalyst, to form a crosslinkable, styrene free, thermosetting gel coat composition having a viscosity at ambient temperature of about 50 to 1200 cps under high shear and of about 8,000 to about 25,000 cps at low shear.   
     
     
         2 . The method of  claim 1 , wherein the polyhydroxy polyol has at least three hydroxyl groups per molecule. 
     
     
         3 . The method of  claim 1 , wherein the acetoacetylated polyhydroxy polyol has at least three acetoacetyl functional groups per oligomer. 
     
     
         4 . The method 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 method of  claim 1 , wherein the molar ratio of the acetoacetate functional group of acetoacetylated polyhydroxy polyol to the acrylate functional group of one or more acrylate monomers or oligomers is 0.2 to 5.0. 
     
     
         6 . The method of  claim 5 , wherein the molar ratio is 0.3 to 3.0. 
     
     
         7 . The method of  claim 1 , 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 one or more additives including the thixotropic agent,   based on the total weight of the composition.   
     
     
         8 . The method of  claim 1 , further comprising allowing the gel coat composition to cure at ambient temperature to form a crosslinked, thermoset gel coat comprising crosslinked acetoacetylate-functionalized acrylate oligomers. 
     
     
         9 . The method of  claim 8 , wherein the gel coat is at least 50% crosslinked. 
     
     
         10 . The method of  claim 8 , wherein the gel coat is 70 to 100% crosslinked. 
     
     
         11 . The method of  claim 1 , wherein the polyhydroxy polyol is selected from the group consisting of methyl propanediol (MPD), trimethylolpropane (TMP), trimethylpentanediol, di-trimethylolpropane (di-TMP), butyl ethyl propanediol (BEPD), neopentyl glycol (NEO), pentaerythritol (Penta), di-pentaerythritol (di-Penta), tris-2-hydroxyethyl isocyanurate (THEW), 4,4′-isopropylidenedicyclohexanol (hydrogenated bisphenol-A (HBP A), and hydroxyl-functionalized acrylic polymers, and mixtures thereof. 
     
     
         12 . The method of  claim 1 , wherein the C 1 -C 5  alkyl acetoacetate is selected from the group consisting of methyl acetoacetate (MAA), ethyl acetoacetate (EAA), n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate, tert-butyl acetoacetate (TBAA), pentyl (amyl) acetoacetate, n-pentyl acetoacetate, isopentyl acetoacetate, tert-pentyl acetoacetate, and acetoacetate-functionalized acrylic polymer based on acetoacetoxyethyl methacrylate, and mixtures thereof. 
     
     
         13 . The method of  claim 1 , 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. 
     
     
         14 . The method of  claim 13 , 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. 
     
     
         15 . The method of  claim 13 , wherein the additive component comprises titanium dioxide. 
     
     
         16 . The method of  claim 1 , wherein the thixotropic agent is selected from the group consisting of fumed silica, precipitated silica, and bentonite clay, and mixtures thereof. 
     
     
         17 . The method of  claim 1 , wherein the base catalyst is selected from the group consisting of 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4,3,0]non-5-ene (DBN), 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4,4,0]dec-5-ene (MTBD), tetramethylguanidine (TMG) and 1,4-diazabicyclo[2.2.2]octane (DABCO), and N′-butyl-N″,N″-dicyclohexylguanidine, and mixtures thereof. 
     
     
         18 . A method of making a gel coated article, comprising:
 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;   combining the acetoacetylated polyhydroxy polyol with one or more multifunctional acrylate monomers or oligomers, at least one additive component, and a base catalyst, to form a crosslinkable thermosetting gel coat composition having a viscosity at ambient temperature of about 50 to 1200 cps under high shear and of about 8,000 to about 25,000 cps at low shear; 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.   
     
     
         19 . The method of  claim 18 , wherein the polyhydroxy polyol has at least three hydroxyl groups per molecule. 
     
     
         20 - 30 . (canceled) 
     
     
         31 . The method of  claim 1 , wherein the polyhydroxy polyol is selected from the group consisting of di-pentaerythritol (di-Penta), tris-2-hydroxyethyl isocyanurate (THEIC), 4,4′-isopropylidenedicyclohexanol (hydrogenated bisphenol-A (HBP A), and hydroxyl-functionalized acrylic polymers, and mixtures thereof.