THEREOF

Statement of U.S Government Support

[001] This invention was supported by the National Science Foundation EPSCoR Track II program DakotaBioCon Grant No. IIA-1330840. The U.S. government has certain rights in the invention.

Cross-Reference to Related Applications

[002] This application claims priority to U.S. Provisional Application No. 62/315,418, filed March 30, 2016. The disclosure of this provisional application is incorporated herein by reference.

Background of the Invention

[003] In attempts to reduce the use of petrochemical-based materials, many biobased alternatives are currently under investigation. While many biobased alternatives are aliphatic such as cellulose and tryglycerides (see Belgacem, M. N.; Gandini, A.; Editors, Monomers, Polymers and Composites from Renewable Resources, Elsevier Ltd.: 2008; p 552 pp), there remains a need for biobased aromatic compounds to replace the aromatic petrochemical based materials. Lignin is of recent interest as the most abundant aromatic biopolymer, comprising between 25-35% of woody biomass and providing structural integrity to plants. See Carrier et al., Biomass Bioenergy 2011, 35(1), 298-307. Lignin's aromatic nature offers excellent thermal and mechanical properties. As a byproduct of the Kraft Pulp Process, lignin is considered a waste stream, making it readily available at a cost-effective price. Degradation of lignin results in a variety of low molecular weight compounds, such as syringaldehyde, vanillic acid, and vanillin. Of the degradation products, vanillin is the most abundant byproduct resulting from the alkaline oxidative depolymerization of lignin (see Pinto et al., In Lignin as Source of Fine Chemicals: Vanillin and Syringaldehyde, Springer: 2012; pp 381-420), and is the only compound that is currently produced from lignin on a commercial scale. See Bomgardner et al., Chem. & Eng. News 2014, 92(6), 14. Therefore, vanillin is currently under investigation as a possible monomer for thermoset systems (see Fache et al., Green Chemistry 2014, 16(4), 1987-1998), offering unique functionality for crosslinking. See Fache et al., European Polymer Journal 2015, 67, 527-538.

[004] Melamine-formaldehyde (MF) resins are widely used in laminate flooring, countertops, cabinetry, surface coatings, textile finishes, and paper processing. See Binder and Dunky, 2004, Melamine- Formaldehyde Resins, Encyclopedia of Polymer Science and Technology In the field of coatings, melamine-formaldehyde resins are most commonly crosslinked using polyols (including phenols), undergoing transetherification with the activated alkoxymethyl group or etherification of methylol groups. See Wicks et al., Organic Coatings, 3rd ed. Wiley: Hoboken, NJ, 2007.

Summary of the Invention

[005] This invention relates to novel compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to a method of making the novel compositions of the invention comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to novel curable coating compositions comprising at least one melamine-formaldehyde resin and the compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to a method of making the novel curable coating compositions of the invention comprising at least one melamine-formaldehyde resin and the compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to methods of applying curable coating compositions of the invention to substrates. The invention also relates to an article of manufacture comprising a curable coating composition of the invention and a method of making such article.

[006] Other features, objects, and advantages of the invention are apparent in the detailed description that follows. It should be understood, however, that the detailed description, while indicating preferred embodiments of the invention, are given by way of illustration only, not limitation. Various changes and modifications within the scope of the invention will become apparent to those skilled in the art.

Brief Description of the Figures

[007] Figure 1 shows the ¹ H NMR spectrum of acetoacetylated 1,4-butanediol.

[008] Figure 2(a) shows the melamine-formaldehyde coatings without vanillin.

[009] Figure 2(b) shows the melamine-formaldehyde coatings with vanillin.

[0010] Figure 3 shows the salt spray exposure of Joncryl 504, 1,3-propanediol + vanillin (1,3-PD

+ Van), and glycerol + vanillin (Glycerol + Van). [0011] Figure 4 shows the acid etch resistance on Joncryl 504, 1,3-propanediol + vanillin (1,3-PD + Van), and glycerol + vanillin (Glycerol + Van).

Description of the Invention

[0012] This invention relates to novel compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to a method of making the novel compositions of the invention comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to novel curable coating compositions comprising at least one melamine-formaldehyde resin and the compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to a method of making the novel curable coating compositions of the invention comprising at least one melamine-formaldehyde resin and the compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin. The invention also relates to methods of applying curable coating compositions of the invention to substrates. The invention also relates to an article of manufacture comprising a curable coating composition of the invention and a method of making such article.

[0013] Acetoacetylated Polyol

[0014] The at least one acetoacetylated polyol that may be used in the invention comprises the reaction product of at least one acetoacetate and at least one polyol.

[0015] The at least one acetoacetate that may be used in the invention includes, but is not limited to, any suitable acetoacetate having the following general structure:

wherein R is a C1-C6 straight chain or branched alkyl, preferably a C2-C4 straight chain or branched alkyl, such as methyl, ethyl, propyl, butyl, and tert-butyl. Methyl acetoacetate, ethyl acetoacetate, and tert-butyl acetoacetate (TBAA) are preferred acetoacetates that may be used in the invention, with TBAA being particularly preferred.

[0016] The at least one polyol that may be used in the invention includes, but is not limited to, any suitable polyol known in the art, such as a diol, a triol, a tetraol, or mixtures thereof. Diols that may be used in the invention include, but are not limited to, those having the following general structure:

where R is a C2-C10 alkylene group and a C2-C10 alkylene ether group. Exemplary diols that may be used in the invention include, but are not limited to, diethyleneglycol (DEG), 2-butyl-2-ethyl- 1,3-propane diol (BEPD), ethylene glycol, 1,2-propane diol, 1,3-propane diol, 2-methyl-l,3- propane diol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4- cyclohexanedimethanol, neopentyl glycol (NPG), and mixtures thereof. Triols that may be used in the invention include, but are not limited to, C3-C10 alkyl triols. Exemplary triols that may be used in the invention include, but are not limited to, trimethylolpropane (TMP), trimethylol ethane (TME), glycerol, and mixtures thereof. Polyols having 4 or more hydroxyl groups that may be used in the invention include, but are not limited to, pentaerithritol, di-trimethylolpropane, di-pentaerithritol, tri-pentaerithritol, sucrose, glucose, mannose, fructose, galactose, raffinose, copolymers of styrene and allyl alcohol, polyglycidol, poly(dimethylpropionic acid), and mixtures thereof. Higher molecular weight polymer polyols may also be used in the invention including polyether, polyester, and acrylic polyols. Polyether polyols include, but are not limited to, poly(ethylene oxide), poly(propylene oxide), poly(tetramethylene oxide), and the like. Polyester polyols are the reaction products of monomeric polyols with monomeric polyacids made using an excess of the polyol. Acrylic polyols are copolymers of methacrylic acid, acrylic acid, or esters of methacrylic acid or acrylic acid wherein at least one of the monomers contains a hydroxyl group. Examples of hydroxyl group containing acrylic monomers include, but are not limited to, hydroxy ethyl acrylate, hydroxy propyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate, and the like.

[0017] The acetoacetylation of a polyol to form the acetoacetylated polyols that can be used in the invention is known in the art and has been described in U.S. Pat. No. 4,551,523, which is incorporated herein by reference. A convenient way to introduce acetoacetate groups to a polyol is by transesterification with tert-butyl acetoacetate (TBAA) as described in U. S. Pat. No. 5,051,529, which is incorporated herein by reference. The number of acetoacetoxy groups introduced into the polyol may be varied. The polyol may be fully acetoacetylated, where substantially all of the hydroxyl groups have been replaced with acetoacetoxy groups, or it may be partially acetoacetylated, where only a fraction of the available hydroxyl groups have been replaced with acetoacetoxy groups. It is understood in the art that some residual hydroxyl groups may remain even when full acetoacetylation is desired. In some applications, as discussed below, residual hydroxyl groups may provide benefits to the resin. When substantially all the hydroxyl groups are converted to acetoacetoxy groups corresponds to a 1:1 ratio of hydroxyl groups to acetoacetoxy groups and where a portion of the acetoacetoxy groups is converted the ratio is less than 1:1.

[0018] I n one embodiment, the at least one acetoacetylated polyol that may be used in the invention has the following general structure:

wherein R is a C ₂ -C ₁₀ alkylene group and a C ₂ -C ₁₀ alkylene ether group. I n another embodiment, the at least one acetoacetylated polyol that may be used in the invention has the general structure:

wherein R' is derived from any polyol having two or more hydroxyl groups.

[0019] Vanillin

[0020] Vanillin, shown below, is a phenolic aldehyde resulting from the depolymerization of lignin:

Vanillin [0021] Lignin, an abundant aromatic bio-polymer, is a key component of woody plants and is found in the cell walls of plants that grow on dry land. Commercially, lignin is sourced from wood products and produced as a by-product from pulping processes which convert wood into wood pulp and extract cellulose. Currently lignin is treated as a waste product in the pulp and paper industries.

[0022] In one embodiment, the reaction product of the at least one acetoacetylated polyol and the vanillin, which is present in the novel composition of the invention, has the following general structure:

wherein R is a C2-C10 alkylene group and a C2-C10 alkylene ether group. In another embodiment, the reaction product of the at least one acetoacetylated polyol and the vanillin, which is present in the novel composition of the invention, has the following general structure:

wherein R' is derived from any polyol having two or more hydroxyl groups.

[0023] I n a one embodiment, the amount of vanillin reacted with the acetoacetylated polyol is in a ratio of one mole of vanillin to one acetoacetate group. However, in the case of the use of a highly acetoacetylated polyol, it is also possible to use less than one mole of vanillin per acetoacetate group, provided that there are on average at least two vanillin-derived phenolic groups per molecule.

[0024] Melamine-Formaldehyde Resins

[0025] The at least one melamine-formaldehyde resin that may be used in the invention includes any suitable melamine-formaldehyde resin. Exemplary melamine-formaldehyde resins that may be used in the invention include, but are not limited to, highly methylated melamine resins, methylated high imino melamine resins, partially methylated melamine resins, highly alkylated melamine resins, high imino melamine resins, n-butylated melamine resins, highly n-butylated melamine resins, n-butylated high imino melamine resins, and iso-butylated melamine resins, such as those commercially sold under the tradename CYMEL by Allnex, the tradename RESIMEN E by I NEOS, and the tradenames ASTRO and ARICEL by Hexion. The at least one melamine-formaldehyde resin in the curable coating composition of the invention is present in an amount ranging from about 2 to about 90 weight %, preferably about 10 to about 60 weight %, and most preferably about 10 to about 50 weight %. I n other embodiments, urea resins and benzoguanamine and glycoluril resins may be used in the invention, and may be present in an amount ranging from about 2 to about 90 weight %, preferably about 10 to about 60 weight %, and most preferably about 10 to about 50 weight %.

[0026] As discussed above, the invention also relates to a novel synthetic approach for making the novel compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin and for making the novel curable coating compositions incorporating the novel compositions comprising the reaction product of at least one acetoacetylated polyol and vanillin into melamine-formaldehyde resin compositions. In one embodiment, the novel compositions comprising at least one melamine-formaldehyde resin and the reaction product of at least one acetoacetylated polyol and vanillin can be prepared by first acetoacetylating at least one polyol, such as 1,3-propanediol (1,3-PD), 1,4-butanediol (1,4-BD), 1,5-pentanediol (1,5-PD), 1,6-hexane- diol (1,6-HD), glycerol, or mixtures thereof, with, for example, tert-butyl acetoacetate (TBAA). See, e.g., Scheme 1 (reaction 1). Next, vanillin, in an optional solvent, such as, for example, methanol, can be added to the acetoacetylated polyol in the presence of a base, such as piperidine, forming an enone (reaction 2). This reaction is known as the Knoevenagel Condensation. Simultaneously, a melamine-formaldehyde resin (such as, for example, Cymel 301 ^® ) ca n be also incorporated into the mixture, using an optional solvent, such as, for example, methanol, forming a curable coating composition of the invention (reaction 3). Alternatively, the process ca n be carried out in steps wherein the synthesis of the Knoevenagel reaction is carried out first forming a composition of the invention comprising the reaction product of at least one acetoacetylated polyol and vanillin (reaction 2), followed by the addition of the melamine- formaldehyde resin to form a curable coating composition of the invention (reaction 3). Curing occurs as the melamine-formaldehyde reacts with the free phenolic groups on the vanillin enone. The curable coating compositions of the invention can be coated on substrates, such as, for example, steel panels, and cured at suitable temperatures and times (e.g., 160°C for 20 minutes) to form durable coatings with excellent solvent resistance, hardness, adhesion, and toughness.

Scheme 1: 1. Acetoacetylation of polyols with TBAA; 2. Knoevenagel Condensation with vanillin addition and 3. Crosslinking with MF resin.

[0027] A catalyst may be used to accelerate the rate of the Knoevenagel Condensation to make a composition of the invention comprising the reaction product of at least one acetoacetylated polyol and vanillin. Examples include, but are not limited to, sodium hydroxide, potassium hydroxide, pyridine, piperidine, l,8-diazabicyclo[5.4.0]undec-7-ene, l,5-diazabicyclo[4.3.0]non- 5-ene, l,5,7-Triazabicyclo[4.4.0]dec-5-ene, and the like. Organic bases are preferred due to their better solubility in organic solvents. A mixture of base catalysts may be used as well. This catalyst can be used in an amount ranging from about 0.001 to about 5 weight %, preferably about 0.01 to about 1.0 weight %.

[0028] A catalyst may also be used to accelerate the curing reaction of the Knoevenagel Condensation product with the melamine-formaldehyde resin to make a coating composition of the invention. Organic acids are preferred. Examples include, but are not limited to, methane sulfonic acid, p-toluene sulfonic acid (PTSA), dodecylbenzene sulfonic acid, and the like. Blocked acid catalysts can be used to improve storage stability. See Wicks et al., Organic Coatings, 3rd ed. Wiley: Hoboken, NJ, 2007. A mixture of acid actalysts may be used as well. This catalyst can be used in an amount ranging from about 0.01 to about 10 weight %, preferably about 0.1 to about 5 weight %, and most preferebly about 0.1 to about 1.0 weight %.

[0029] A curable coating composition of the invention contains optionally one or more solvents. A curable coating composition of the invention may be solvent-free or may optionally contain a solvent such as hydrocarbon, ester, ketone, ether, ether-ester, alcohol, or ether-alcohol type solvents. Examples of solvents that can be added to the curable coating compositions of the invention include, but are not limited to, benzene, toluene, aromatic 100, aromatic 150, methyl amyl ketone, butyl acetate, tert-butyl acetate, diethyl ether, ethylethoxy propionate, isopropanol, butanol, butoxyethanol, acetone, THF, methyl ethyl ketone (MEK), xylene, etc. The curable coating composition may be a solution in such a solvent or mixture of solvents. Alternatively, the solvent system may include water or be water-based (>50% water in the solvent system).

[0030] Pigments and other additives known in the art to control coating rheology and surface properties can also be incorporated in a coating composition of the invention. For example, a coating composition of the invention may further contain coating additives. Such coating additives include, but are not limited to, one or more leveling, rheology, and flow control agents such as silicones, fluorocarbons, or cellulosics; extenders; reactive coalescing aids such as those described in U.S. Pat. No. 5,349,026, incorporated herein by reference; plasticizers; flatting agents; pigment wetting and dispersing agents and surfactants; ultraviolet (UV) absorbers; UV light stabilizers; tinting pigments; colorants; defoaming and antifoaming agents; anti-settling, anti-sag and bodying agents; anti-skinning agents; anti-flooding and anti-floating agents; biocides, fungicides and mildewcides; corrosion inhibitors; thickening agents; or coalescing agents. Specific examples of such additives can be found in Raw Materials Index, published by the National Paint & Coatings Association, 1500 Rhode Island Avenue, N.W., Washington, D.C. 20005. Further examples of such additives may be found in U.S. Pat. No. 5,371,148, incorporated herein by reference.

[0031] Examples of flatting agents that may be used in the coatings of the invention include, but are not limited to, synthetic silica, available from the Davison Chemical Division of W. R. Grace & Company as SYLOID ^® ; polypropylene, available from Hercules Inc., as HERCOFLAT ^® ; synthetic silicate, available from J. M. Huber Corporation, as ZEOLEX ^® .

[0032] Examples of viscosity, suspension, and flow control agents that may be used in the coatings of the invention include, but are not limited to, polyaminoamide phosphate, high molecular weight carboxylic acid salts of polyamine amides, and alkylene amine salts of an unsaturated fatty acid, all available from BYK Chemie U.S.A. as ANTI TERRA ^® . Further examples include, but are not limited to, polysiloxane copolymers, polyacrylate solution, cellulose esters, hydroxyethyl cellulose, hydroxypropyl cellulose, polyamide wax, polyolefin wax, hydroxypropyl methyl cellulose, polyethylene oxide, and the like.

[0033] Fillers may also be added to the coating compositions of the invention, including, but not limited to, calcium carbonate such as calcite, dolomite, talc, mica, feldspar, barium sulfate, kaolin, nephelin, silica, perlite, magnesium oxide, and quartz flour, etc. Fillers (and pigments) may also be added in the form of nanotubes or fibers, thus, apart from the before-mentioned examples of fillers, the coating composition may also comprise fibers, e.g., those generally and specifically described in WO 00/77102, incorporated herein by reference.

[0034] As discussed above, the invention also relates to the use of a curable coating composition of the invention which may be coated onto a substrate and cured using techniques known in the art. The substrate can be any common substrate such as paper, polyester films such as polyethylene and polypropylene, metals such as aluminum and steel, glass, urethane elastomers, primed (painted) substrates, and the like. The curable coating composition of the invention may be cured at room temperature (ambient cure) or at elevated temperatures (thermal cure).

[0035] As also discussed above, in another embodiment of the invention, the invention relates to an article of manufacture comprising a curable coating composition of the invention and a method of making such article.

Examples

[0036] Materials

[0037] All polyols (1,3-propanediol (1,3-PD); 1,4-butanediol (1,4-BD); 1,5-pentanediol (1,5-PD); 1,6-hexanediol (1,6-HD); and glycerol) were purchased from Sigma Aldrich. Eastman Chemical Company provided tert-butyl acetoacetate (TBAA). Alfa Aesar supplied vanillin (99%) and piperidine. Cymel 301 was obtained from Cytec (Allnex). Methanol was purchased from BDH. BYK-370, a silicone surface additive, was obtained from BYK.

[0038] Acetoacetylation of Polyols

[0039] 0.1 mol of polyol was mixed with 0.3 mol of TBAA in a round bottom flask with a dean stark trap connected. The reaction was run at 150°C for 4 hours, and tert-butanol was collected as the reaction proceeded. Reaction completion was determined by ¹ H NMR. Any excess TBAA and tert-butanol was removed under vacuum. Each polyol was separately acetoacetylated using the same procedure.

[0040] Knoevenagel Condensation/Melamine-Formaldehyde Crosslinking

[0041] 0.048 mol of vanillin was solubilized in 2.34 mL of methanol in a 40 mL glass vial at 60°C while stirring. 0.024 mol of acetoacetylated polyol and Cymel 301 (~10% and 37% used for each acetoacetylated diol) were added to the vanillin-methanol solution and mixed on a vortexer for 30 seconds. 82 μί of BYK-370 and 0.9 mmol of piperidine were added to the vial and mixed for 10 minutes. A 40% solution of pTSA in methanol was added as the catalyst (0.710 mL) and mixed on a vortexer for 30 seconds.

[0042] Coatings were made using an 8-mil drawdown bar. Two coatings were made for each sample, and the substrates used were iron phosphated steel panels (Bonderite 1000). The coatings were cured in an oven at 160°C for 20 minutes and kept at room temperature for one week before any testing was performed.

[0043] Coating Characterization

[0044] Coatings were characterized using the following methods: [0045] Dry film thickness: The dry film thickness (DFT) of each coating was measured using Byko-test 8500 from BYK Additives. The average of ten film thickness measurements was reported for each coating.

[0046] MEK Double Rubs: Methyl ethyl ketone (MEK) double rub test (ASTM D 5402) determined the chemical resistance and extent of crosslinking of the coating network.

Cheesecloth was saturated with methyl ethyl ketone. The cloth was rubbed up and down the coating surface in the same location, with one forward and backward motion equaling one double rub. Every 25 double rubs, the cloth was re-soaked with MEK. The reported number relates to the number of MEK double rubs on the coating before any sign of failure was observed (cracks, coating removal, etc.).

[0047] Reverse Impact Strength: A Gardener impact tester (ASTM D 2794) determined the reverse impact strength of the coatings.

[0048] Pencil Hardness: ASTM D 3363 determined the pencil hardness of the coatings. Pencils of various hardness (6B - 6H) were pushed across the coatings at a 45° angle in ¼ inch stroke. The value measured is hardest pencil that will not rupture or scratch the coating.

[0049] Konig Hardness: Konig pendulum hardness (ASTM D 4366) measured the surface hardness of the coatings and the results were reported in seconds. Using a Konig Pendulum, the coating hardness was determined by the oscillation damping of the pendulum.

[0050] Salt Spray: Salt spray (ASTM B117) measured the corrosion resistance of the coatings. Coatings were scribed and exposed to a chamber with continuous 5% NaCI spray, and corrosion was observed. [0051] Acid Etch Resistance: The acid etch resistance (ASTM D7356/7356-M13) of the coatings was measured. The following was added to a 500 mL flask: 7.5 g of 0.02 N H ₂ S0 ₄ , 1.1 g 0.3% HN0 ₃ , 2.25 g 0.02 N NaOH, 0.6 g of 0.01 M CaCI ₂ , 0.5 g 0.01 M KCI, and diluted with deionized water to 500 mL. 0.5 mL of acid rain solution was pipetted onto the coatings and covered with a watch glass for 24 hours. The watch glass was removed after 24 hours and the solution was wiped away using a Kimwipe. Coatings were observed under an optical microscope.

Results

[0052] Acetoacetylation of Polyols

[0053] ¹ H NMR confirmed the acetoacetylated products. Figure 1 shows the ¹ H NMR spectrum of acetoacetylated 1,4-butanediol with each peak labeled. Slight amounts of starting materials are present. The keto-enol tautomerization was identified with the acetoacetate group. All the polyols that were acetoacetylated showed the enol form as well.

[0054] Cured Coatings

[0055] The coatings with vanillin had a yellowish glossy appearance, whereas the coatings without vanillin were clear and glossy as can be seen in Figures 2(a) and 2(b), respectively. All coatings were tack free after curing.

[0056] Coating Characterization

[0057] Coatings were characterized one-week post cure. Table 1 shows the coatings properties from the characterization. Certain trends were identified based on the diol chain length and the addition of vanillin. As the diol/triol chain length decreases, the MEK double rubs (DRs) and hardness increases. Coatings made from 1,6-hexanediol exhibited poor solvent resistance and hardness. However, coatings made from 1,3-propanediol and glycerol exhibited good solvent resistance and hardness.

[0058] Beyond the polyol chain length, the incorporation of vanillin also significantly affected the properties, specifically impact and hardness. Vanillin improved the impact properties, indicating more flexibility within the system. There are, however, some discrepancies between the pencil hardness and Konig hardness. Vanillin improved the pencil hardness, yet lowered the Konig hardness.

[0059] I n summary, the optimal coatings in this system are those with glycerol or 1,3- propanediol, as well as vanillin.

Table 1: Coating Characterization

[0060] Solt Sproy

[0061] For understanding corrosion resistance, only the coatings with optimal performance were chosen. This included the 1,3-PD with vanillin and the glycerol with vanillin coatings. Each coating was run in duplicates in the salt spray chamber and compared to Joncryl 504 (20%) MF standard. [0062] From the salt spray results (Figure 3), it is evident that both the 1,3-PD and Glycerol coatings outperformed the Joncryl 504 standard. At 40 hours, the glycerol coating had minimal corrosion and best appearance.

[0063] Acid Resistance

[0064] Similar to Salt Spray testing, only the best coatings (determined from the coating characterization results, Table 1) were chosen. After 24 hours of an acid rain solution left on the coating, visible yellow spots remained on each coating surface (Figure 4). The coatings were observed under an optical microscope, and yellow stains were confirmed. The surface of the coatings was left undamaged, however.

[0065] Experimental Conclusions

[0066] Coatings of the invention were synthesized using melamine-formaldehyde resins and acetoacetylated diols and vanillin. The addition of vanillin showed significant increase in impact and hardness properties. It was also observed that the lower molecular weight chain polyols, glycerol and 1,3-PD, exhibited superior solvent resistance and hardness. Therefore, the optimal coating formulations were those with lower molecular polyol chain lengths as well as the incorporation of vanillin.

[0067] The crosslinked melamine-formaldehyde coatings offer great potential for incorporation of more biobased materials, furthering the reduction of petrochemical dependence. Vanillin, specifically, has proven to be of particular interest as a biobased monomer for thermoset systems.