Polyester polymers comprising lignin

Abstract

Disclosed is a polyester polymer prepared from a reaction mixture comprising a polyacid component and a polyol component that comprises lignin. Residues of lignin are incorporated into the backbone of the polyester polymer. Coatings comprising the same and substrates coated at least in part with such coatings are also disclosed.

Claims

1. A method of protecting a metal substrate from corrosion comprising: (i) applying a coating composition over at least a portion of a substrate comprising metal, the coating composition comprising a mixture of reactants comprising: (a) a polycarboxylic acid component; and (b) a polyol component consisting essentially of: (1) a lignin component consisting essentially of wheat straw lignin, and (2) at least one other hydroxyl functional component not including lignin, such that residues of the wheat straw lignin are incorporated into the coating composition, wherein the polycarboxylic acid component and the hydroxyl functional component not including lignin react to form a polyester, wherein the wheat straw lignin is incorporated into the backbone of the polyester, wherein the polyester contains from 10 to 20 weight % wheat straw lignin incorporated in the backbone based on total solids and the coating composition optionally comprises 0 to 20 weight % of wheat straw lignin as filler based on total solids; and (ii) curing the coating composition to form a thermoset polyester coating.

2. The method of claim 1, wherein in the metal comprises aluminum and/or steel.

3. The method of claim 1, wherein the coating composition further comprises a crosslinker reactive with hydroxyl groups of the coating composition.

4. The method of claim 1, wherein the coating composition further comprises a colorant.

5. The method of claim 1, wherein the coating composition is applied directly to the substrate as a primer coating composition.

6. The method of claim 5, further comprising applying a topcoat over the primer coating composition.

7. The method of claim 1, further comprising, prior to application of the coating composition, applying an undercoat over the at least a portion of the substrate, such that the undercoat is disposed between the substrate and the coating composition.

8. The method of claim 7, wherein the coating composition comprises a clearcoat.

9. The method of claim 1, wherein the cured coating exhibits flexibility such that the cured coating passes a reverse impact test at 30 lbs.

10. The method of claim 2, wherein the metal comprises hot dipped galvanized steel.

Description

EXAMPLES

Example 1: Polyester Polymers for Clearcoats

(1) Polyester polymers for use in clearcoat compositions were prepared using the components listed in Table 1. In each of Examples 1A, 1B, 1C, and 1D, all components except solvent were combined and heated under a nitrogen atmosphere to 220 C. and held for the time indicated in Table 1. The reaction products had acid values (mg KOH/g) as indicated in Table 1. The samples were cooled to ambient temperature and dissolved in solvent as indicated in Table 1.

(2) TABLE-US-00001 TABLE 1 Components (weight in grams) Ex. 1A Ex. 1B Ex. 1C Ex. 1D Control 10% lignin 20% lignin 10% lignin 2-methyl-1,3-propenediol 246.6 215.51 197.64 972 trimethylolpropane 8.27 7.22 6.63 32.59 adipic acid 59.02 51.57 47.29 232.6 isophthalic acid 191.24 167.09 153.24 753.6 phthalic anhydride 170.50 148.96 136.62 671.9 butyl stannoic acid 0.68 0.65 0.65 2.93 triphenyl phosphate 0.34 0.32 0.32 1.46 PROTOBIND 1000.sup.1 58.68 107.61 264.7 Conditions/Results Reaction time 10 12 14 16 Acid value (mgKOH/g) 3.8 9.5 12.0 10.1 Solvent added.sup.2 328.1 312.4 141.6 392.0 .sup.1Wheat straw lignin supplied by ALM India .sup.2Solvent mixture 63 wt. % 1-methoxy-2-propanol, 18.5 wt % butanol, 18.5 wt % SOLVESSO 100 (naptha solvent supplied by Exxon Mobil Chemical.)

Example 2: Clearcoats

(3) Clearcoat compositions were prepared from the polyester polymers of Example 1 by combining all solvents in a suitable sized container, and adding the polyester polymers and other components in the order shown in Table 2. The clearcoat compositions were drawn down on aluminum substrates to approximately 0.70 mil and baked in a conveyor oven for 30 seconds to a peak metal temperature of 450 F. All panels passed 100 MEK rubs (cure) and exhibited 5B crosshatch adhesion (no removal). Pencil hardness and gloss retention showed increases with the increase in lignin content. Flexibility was tested using reverse impact at 30 lbs. All offsets passed reverse impact with no pick and no cracking.

(4) TABLE-US-00002 TABLE 2 Ex. 2B Ex. 2C Components Ex. 2A (polyester with (polyester with (weight in grams) (control) 10% lignin) 20% lignin) Polyester Ex. 1A 139.67 Polyester Ex. 1B 127.43 Polyester Ex. 1C 128.07 hexamethoxymethyl 7.96 16.61 23.27 melamine resin.sup.3 butanol 3.00 3.00 3.00 DIAX 2770.sup.4 0.40 0.40 0.40 COROC A-72-A260.sup.5 0.50 0.50 0.50 COROC A-620-A2.sup.6 0.83 0.83 0.83 para-toluene sulfonic acid 0.50 0.50 0.50 SOLVESSO 100 12.50 21.00 26.00 ethylene glycol monobutyl 12.50 210.00 26.00 ether .sup.3Supplied by Allnex Belgium SA/NV, Brussels, Belgium .sup.4Hyberbranched hydrocarbon polymer supplied by Baker Hughes, Houston, TX .sup.5Acrylic resin supplied by Arkema Coating Resins, Cary, NC .sup.6Acrylic resin supplied by Arkema Coating Resins, Cary, NC

Example 3: Primers with Lignin Polyester

(5) Primer compositions were prepared from polyester polymers of Example 1 by combining all solvents in a suitable sized container and adding the polyester polymer and the other components in the order shown in Table 3.

(6) TABLE-US-00003 TABLE 3 No lignin in Wheat straw lignin Components primer resin in primer resin (weight in grams) Ex. 4A Ex. 4B Ex. 4C Ex. 4D Polyester Ex. 1A 123.0 123.0 Polyester Ex. 1D 90.5 90.5 phosphatized epoxy resin.sup.7 8.1 8.1 8.1 8.1 hexamethoxymethyl 15.0 15.0 36.6 36.6 melamine resin wheat straw lignin powder 20.0 20.0 (PROTOBIND 1000) filler n-butyl alcohol 3.0 SOLVESSO 100 7.0 24.5 15.5 35.8 2-butoxyethanol 7.0 24.5 15.5 35.8 toluene sulfonic acid solution 0.5 0.5 0.5 0.5 Total 160.6 218.6 166.7 227.3 .sup.7Supplied by PPG Industries, Inc.

(7) The topcoated samples were subjected to 2000 hours of salt spray testing to ASTM B117 in which the samples were exposed to a 5% NaCl salt fog at pH 6.2-7.2 at 35 C. (95 F.). Salt spray test results are reported in Table 4.

(8) TABLE-US-00004 TABLE 4 Salt Spray after 2000 Hours Scribe Creep Example (mm) Primer Composition Aluminum 4A 0 Polyester control 4B 0 Polyester resin and 20 wt. % wheat straw lignin powder added as filler 4C 0 Polyester/10% lignin resin 4D 0 Polyester/10% lignin resin and 20 wt. % wheat straw lignin powder HDG 4A 15.9 Polyester control 4B 5.9 Polyester resin and 20 wt. % wheat straw lignin powder added as filler 4C 8.7 Polyester/10% lignin resin 4D 5.6 Polyester/10% lignin resin and 20 wt. % wheat straw lignin powder

(9) Examples 4C and 4D (10% lignin, without and with lignin filler, respectively) exhibited improved corrosion resistance over Examples 4A and 4B (no lignin, without and with lignin filler, respectively).

(10) Although the present invention has been described with reference to specific details of certain embodiments thereof, it is not intended that such details should be regarded as limitations upon the scope of the invention except insofar as they are included in the accompanying claims.