Ambient cure compositions for making coatings having humidity and corrosion resistance and methods of use

Abstract

The present invention provides substantially isocyanate-free multicomponent compositions useful in making rapid dry primer compositions and coatings, the compositions comprising one or more carboxylic acid compounds that contain one of a benzothiazole, benzoxazole, or benzimidazole group, preferably, that contain a benzothiazole group, one or more hydrophobic sulfonic acid catalyst, one or more pigment, extender or filler, one or more a) polycarbamates from alkyd polyol or acrylic polyol and one or more b) a polyaldehydes or the acetal or hemiacetal thereof as a second component. The multicomponent compositions cure quickly at a temperature of from 0 C. to less than 80 C. to form a crosslinked polyurethane coating having improved humidity and corrosion resistance.

Claims

1. A substantially isocyanate free multicomponent primer composition curable at 0 to 80 C., and useful for direct to metal coatings comprising: one or more pigments, extenders and/or fillers, providing a pigment volume concentration of from 15 to 60%; from 2.5 to 14.4 wt. % of one or more ion-exchanged amorphous silicas containing a metal cation, based on the total weight of the composition, from 0.5 to 5 wt. % of one or more carboxylic acid compounds that contain one of a benzothiazole, benzoxazole, or benzimidazole group, based on the total weight of the composition; from 0.01 to 10 wt. % of one or more hydrophobic sulfonic acid catalysts, based on the total weight of the composition, one or more a) polycarbamates of an alkyd polyol, an acrylic polyol, or their mixtures, and one or more b) polyaldehydes or acetals or hemiacetals thereof in a component separate from the one or more polycarbamates.

2. The multicomponent composition as claimed in claim 1, wherein the one or more ion-exchanged amorphous silicas contains a divalent or trivalent metal cation.

3. The multicomponent composition as claimed in claim 2, wherein the one or more ion-exchanged amorphous silicas contains calcium or zinc as the divalent or trivalent metal cation.

4. The multicomponent composition as claimed in claim 1, wherein the total amount of the one or more ion-exchanged amorphous silicas ranges from 2.5 to 12.5 wt. %, based on the total weight of the composition.

5. The multicomponent composition as claimed in claim 1, wherein the one or more carboxylic acid compounds contains a benzothiazole group.

6. The multicomponent composition as claimed in claim 1, wherein the one or more carboxylic acid compounds contains a benzothiazole group and is a dicarboxylic acid compound.

7. The multicomponent composition as claimed in claim 1, wherein the total amount of the one or more carboxylic acid compounds ranges from 0.5 to 5 wt. %, based on the total weight of the composition.

8. The multicomponent composition as claimed in claim 1, wherein the one or more hydrophobic sulfonic acid catalysts have a solubility in water at 25 C. of less than 40 wt. %.

9. The multicomponent composition as claimed in claim 1, wherein the total amount of the one or more hydrophobic sulfonic acid catalysts ranges from 0.01 to 10 wt. %, based on the total weight of the composition.

10. The multicomponent composition as claimed in claim 1, further comprising one or more epoxy silane.

11. The multicomponent composition as claimed in claim 1, having a pigment volume concentration (PVC) of from 15 to 60%.

12. The multicomponent composition as claimed in claim 1, wherein the one or more a) polycarbamates is a polycarbamate prepared from an alkyd polyol having a hydroxyl number from 50 to 250.

13. The multicomponent composition as claimed in claim 1, wherein the one or more b) polyaldehydes, or acetals or hemiacetals thereof, is a 1,3 cyclohexanedicarboxaldehyde (CHDA), a 1,4-cyclohexanedicarboxaldehyde (CHDA), their admixture, or acetals or hemiacetals thereof.

14. The multicomponent composition as claimed in claim 1, wherein the composition further comprises one or more curing inhibitors comprising water or a C.sub.1 to C.sub.5 alkyl alcohol.

15. A method for making the multicomponent composition as claimed in claim 1, comprising grinding together the one or more ion-exchanged amorphous silicas, the one or more carboxylic acid compounds, and the one or more hydrophobic sulfonic acid catalysts with the one or more pigments, extenders, and/or fillers, with one or more dispersants to form a pigment mixture.

16. A method for using the multicomponent composition as claimed in claim 1, comprising applying the composition to a metal substrate to form a coating layer, and curing the coating layer at a temperature of from 0 to 80 C. to form a crosslinked polyurethane.

17. The method as claimed in claim 16, further comprising applying a pigmented basecoat or colorcoat composition to the coating layer to form a pigmented basecoat or colorcoat layer and curing the pigmented basecoat or colorcoat layer to form a cured pigmented basecoat or colorcoat.

18. The method as claimed in claim 17, further comprising applying a clearcoat composition to the cured pigmented basecoat or colorcoat layer, and curing the clearcoat composition to form an automotive coating finish.

19. An automotive coating finish comprising: a metal substrate, one or more crosslinked polyurethane coating layers, formed from the composition as claimed in claim 1, on the metal substrate, a cured pigmented basecoat or colorcoat layer on the one or more crosslinked polyurethane coating layers, and a cured clearcoat layer on the cured pigmented basecoat or colorcoat layer.

Description

EXAMPLES

(1) Unless otherwise specified, all temperatures are room temperature and all pressures are 1 atmosphere or ambient pressure.

Example A: Two Stage Alkyd Polyol Synthesis

(2) First Stage: Alcoholysis. To a 5 L three-neck round bottom flask was added sunflower oil (1388.9 g). A glass stir rod and paddle were placed in the middle joint of the flask. The flask was attached to a lattice with overhead stirring, and an oil bath at room temperature was raised to submerge the flask. The setpoint on the bath was 220 C. and heating and stirring were started. To the stirred oil, pentaerythritol (713.6 g) and dibutyltin catalyst (1200 ppm on total reactor charge were added. Once all reactants were added, a packed condenser with a set point of 95 C. was attached to one of the side joints and topped with a hose adaptor that was connected to a bubbler. To the other side neck, a second hose-adaptor was attached and connected to a nitrogen inlet. A slow nitrogen sweep was placed on the system and observed in the bubbler. The reaction mixture was allowed to heat and mix overnight to ensure high conversion. This stage was completed when a monoglyceride of the sunflower oil was achieved, meaning that the reactor contents homogeneously dispersed in methanol at one part resin to three parts methanol.

(3) Second Stage. The 5 L three-neck flask containing the alcoholysis mixture from the first stage was equipped with a glass stir shaft and paddle. The flask was attached to a lattice with overhead stirring. An oil bath at room temperature was raised to submerge the flask. The set point on the bath was 220 C. and heating and stirring were started. To the flask, isophthalic acid (359.0 g), phthalic anhydride (538.5 g), and xylenes (2% on total charge) were added. Then, a Dean-Stark trap was connected to one of the side joints and topped with a Friedrichs condenser connected to an outlet bubbler. A nitrogen sweep was placed on the system. The system was allowed to heat (220 C.) and the water formed was distilled out as an azeotrope with xylenes. This second stage of the reaction was monitored by removing samples from the reactor and titrating the acid value (AV). The reaction was allowed to progress until the desired AV (8.0 mg KOH/g) was reached. The alkyd polyol had a measured OH number of 180 mg KOH/g (on solids). Then the reaction contents were poured into a glass jar and allowed to cool to room temperature under a pad of nitrogen.

Example B: Alkyd Polycarbamate Synthesis

(4) A reaction was carried out in a 2000 ml round bottom reactor system equipped with a mechanical stirrer, reflux condenser, nitrogen gas purge system and temperature control. A heating mantle was used for temperature control. The reactor was charged with the alkyd polyol (2000 g) from Example A, above, diluted to a final solids level of 60-70% in xylene, to achieve a process viscosity which allowed efficient stirring at 140 C. The catalyst, Fascat 4201 dibutyl tin oxide (DBTO, Arkema, Inc., Philadelphia, Pa.), was added to the alkyd polyol in the reactor at 0.6 wt. % on solids. The amount urea (99.5 wt. % pure, Sigma-Aldrich, St. Louis, Mo.) used was calculated based on the hydroxyl value for the alkyd polyol to target 62% conversion of the hydroxyl groups. For the 2000 g batch of alkyd polyol, 238.7 g total of urea was first dissolved in distilled water to make a 50 wt % aqueous solution. The alkyd-solvent-catalyst mixture in the reactor was slowly heated to 140 C. and nitrogen purged for at least 30 min. Urea solution was loaded into 60 ml glass syringes and was carefully fed into the reactor at a constant controlled rate through a syringe pump. The urea solution was steadily fed into the reactor over 6-10 hrs. Azeotropic vapor was formed and cooled in the condenser, which was then collected in the Dean-Stark trap. The reaction was carefully maintained at 140 C., mixing at 500-600 rpm and continued for 10-12 hr until completion. Samples were taken periodically for NMR and GPC analysis. The Carbamate Conversion (from hydroxyl to carbamate) was calculated at 59%.

(5) The polycarbamate from Example B was formulated as shown in Example 1, below.

Examples 1 and 1A: Multicomponent Composition Formulation of Polycarbamate from Alkyd Polyol

(6) TABLE-US-00001 TABLE 1 Formulation of a multicomponent composition of Example 1 Weight Material (g) Component A Alkyd polycarbamate (53.5 wt % in xylene, EW on solids = 36.17 318.8 as determined by hydroxyl value titration) Toluene (solvent) 15.23 Methyl ethyl ketone (solvent) 7.41 DISPERBYK-110 (carboxylic acid functional solution 0.94 polymer dispersant 52% solids in methoxypropylacetate/alkylbenzenes (Byk USA, Wallingford, CT) TIONA 595 TiO.sub.2 (Cristal, Hunt Valley, MD) 4.16 NICRON Talc 665 (Imerys, Paris, France 4.16 SHIELDEX CS311 calcium containing ion-exchanged 6.76 amorphous silica (W. R. Grace, Chicago, IL) HALOX 650 Organic Diacid (benzthiazol-2-ylthio 1.47 succinic acid) (CAS 95154-01-1, ICL\Advanced Additives, Hammond, IN) MILWHITE B1 barytes (Milwhite, Brownsville, TX) 4.76 Grind Sub-Total 81.07 Let Down Ethanol 9.88 Diacetone alcohol 1.98 Total Part A 92.93 SILQUEST A-187 Epoxy Silane (Momentive) 0.65 Cyclohexanedicarboxaldehyde (CHDA, EW as received = 4.76 78.35, EW on active solids = 70) Dinonylnaphthalene Disulfonic Acid (DNNDSA) (55 wt % 1.67 in isopropanol) Total 100.00

(7) TABLE-US-00002 TABLE 1A Comparative formulation of Example 1A* Material Grams Alkyd polycarbamate (53.5 wt % in xylene, EW on solids = 34.11 318.8 as determined by hydroxyl value titration Xylene (solvent) 0.31 Toluene (solvent) 14.49 MEK (solvent) 7.05 DISPERBYK-110 (carboxylic acid functional solution 1.09 polymer dispersant 52% solids in methoxypropylacetate/alkylbenzenes, Byk USA, Wallingford, CT) TIONA 595 TiO.sub.2 (Cristal, Hunt Valley, MD) 6.88 NICRON Talc 665 (Imerys, Paris, France) 6.88 Burgess OPTIWHITE, Calcined aluminum silicate 4.39 pigment (Burgess Pigment, Sanderson, GA) MILWHITE B1 barytes (Milwhite, Brownsville, TX) 7.83 Grind Sub-total 83.04 LetDown Ethanol 9.40 Diacetone alcohol 1.88 Total Part A 94.32 CHDA (EW as received = 78.35; EW on active solids = 70) 4.53 Dinonylnaphthalene Disulfonic Acid (DNNDSA) (55 wt. % 1.15 in isopropanol) Total 100.00 *Denotes Comparative Example.

(8) For Example 1, Part A was prepared using overhead mixing with a DYSPERMAT mixer (VMA-Getzman, Reichshof, Del.). A Hegman gauge was used to determine how finely ground the pigments are dispersed in the paint. The mixed paint had a value of 5.5 Hegman units or greater. To the Part A, CHDA was added with overhead stirring followed by the addition of the hydrophobic sulfonic acid ester catalyst, DNNDSA, prior to spraying.

(9) For Example 2, Part A used the same process as Example 1 and 1A. Part B was prepared the day before use where to the ethanol was added CHDA followed by the XC-315 catalyst. Part B was added to Part A prior to spraying.

(10) TABLE-US-00003 TABLE 2 Example 2- Formulation of a multicomponent composition Weight Material (g) Component A Alkyd polycarbamate (56.7 wt % in xylene, EW on solids = 34.40 339.2 as determined by hydroxyl value titration) Xylene (solvent) 2.02 Toluene (solvent) 15.34 Methyl ethyl ketone (solvent) 7.46 DISPERBYK-110 (carboxylic acid functional solution 0.95 polymer dispersant 52% solids in methoxypropylacetate/alkylbenzenes (Byk USA, Wallingford, CT) TIONA 595 TiO.sub.2 (Cristal, Hunt Valley, MD) 4.19 NICRON Talc 665 (Imerys, Paris, FR) 4.19 SHIELDEX CS311 calcium containing ion-exchanged 6.81 amorphous silica (W. R. Grace) HALOX 650 Organic Diacid (benzthiazol-2-ylthio 1.48 succinic acid) (CAS 95154-01-1 (ICL\Advanced Additives, Hammond, IN) MILWHITE B1 barium sulfate (Milwhite, Brownsville, TX) 4.79 Diacetone alcohol (solvent) 1.99 Total Part A 82.63 Part B Ethanol 9.97 Cyclohexanedicarboxaldehyde (CHDA, EW as received = 4.32 74, EW on active solids = 70) Hydrophobic sulfonic acid XC-315 (King Industries, 2.08 Norwalk, CT) Total 100.00

(11) Each formulation was sprayed in two coats, with a 10 minute flash time in between each coat. The time to sand was measured after the second 10 minute flash of the second applied coating. The coating was applied to cold roll steel panels sanded with 80 grit sand paper. For panels with base and clear coats, the base and clear coat were applied after the primed panels were sanded. A commercial black base coat was then applied after the panels were sanded according to manufacturer's recommendations. A commercial clear coat (2 coats sprayed) was applied over the base coat according to the manufacturer's recommendations. The panels were cured overnight at room temperature prior to evaluations.

(12) Substrate Preparation:

(13) For Example 1 and 1A, cold roll steel test panels were prepared for refinish with a Hutchens 4500 (Hutchens, Pasadena, Calif.) 15 cm finish DA sander with 80 grit sandpaper. After the panel was sanded smooth, the pane panel off with compressed air to remove dust from the prepared surface. Using a red SCOTCH-BRITE pad scuff (3M, Minneapolis, Minn.) the surface in a uniform direction until all scuff marks are the same depth and direction.

(14) The applied formulations in the indicated Examples 1 and 1A to 2 were tested, as follows.

(15) Test Methods:

(16) Time to Sand:

(17) The sandability was determined by the time reached where using hand sanding, 320 grit sandpaper did not cake with primer and material was easily shaken or knocked off the sand paper. An acceptable result would be ability to sand in less than 1 h. Sanding results for Examples 1 and Comparative Example 1 are presented in Table 1.

(18) Thickness of the Coating:

(19) Measured by ASTM D7091-05 (Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals (2005)).

(20) MEK Double Rub Resistance:

(21) In Examples 1 to 1A and 2, a MEK Rub test Machine (DJH Designs, Oakville, ON, CA) was used to evaluate coating resistance to methyl ethyl ketone (MEK) similar to ASTM D 4752-98 (1998). Coatings were cured at room temperature (24 C.) and 50% relative humidity for the indicated time. The tester moved a cotton pad, attached to a weighted block that applies a force of 0.155 kg/cm.sup.2 (2.2 lb/in.sup.2), in a back and forth motion across the coated panel. Each back and forth is referred to as one double rub. Rubbing was continued until the indicated failure occurred, and that number of double rubs was recorded. Unless otherwise indicated, rubbing was continued until the coating was cut through and the substrate became visible in any area, and that number of double rubs was recorded. An acceptable result is at least 100-200 double rubs.

(22) Tape Crosscut Adhesion:

(23) Crosscut adhesion was measured and rated according to a modified version of ASTM D-3359-09 (2009) where a 10 cm piece of PERMACEL 99 pressure adhesive (3M, Minneapolis, Minn.) tape was laid over the indicated 20 coating and a 3 mm blade was used to make a crosscut in testing how well the coating adheres to the substrate when the tape is pulled off. ASTM ratings range from 0A to 5A where a rating of 5A is desired. According to the method, the scale reads as: 5A (no peeling or removal); (4A) Trace peeling or removal along incisions or at their intersection; (3A) Jagged removal along incisions up to 1.6 mm ( 1/16 in.) 25 on either side; (2A) Jagged removal along most of incisions up to 3.2 mm ( in.) on either side; (1A) Removal from most of the area of the X under the tape; and (0A) Removal beyond the area under the tape. An acceptable result is 4A or higher.

(24) Humidity Resistance Testing:

(25) Coated panels were cured for 7 days at ambient temperature prior to being placed on a Cleveland humidity chamber with 100% condensing humidity at 38 C. for 96 h before observation for blistering and defects.

(26) TABLE-US-00004 TABLE 3 Time to Sand the Primer Comparative Example 1 Example 1A Example 2 Time to sand 40 40 40 primer (min)

(27) TABLE-US-00005 TABLE 3A Coating performance Example 1 Comparative Example 1A* With Corrosion Inhibitor Without Corrosion Inhibitor Primer/ Primer/ Primer/ Primer/ Base/ Base/ Base/ Base/ Coated Panel Primer Primer Clear Clear Primer Primer Clear Clear Film Thickness 83.8 88.9 86.4 86.4 (microns) MEK double rubs 24 h Initial <5 <5 <5 <5 Damage/Mar 24 h 25% Film Loss or 133 >200 197 >200 200 rubs 7 d Initial Damage/Mar <5 <5 <5 <5 7 d 25% Film Loss or >200 >200 >200 >200 200 rubs Cross Hatch Adhesion 24 hour 4B 4B 5B 5B 5B 5B 5B 5B 7 Day 3B 3B 5B 5B 5B 5B 5B 5B *Denotes Comparative Example.

(28) TABLE-US-00006 TABLE 3B Coating performance Example 2 With Corrosion Inhibitor Primer/ Primer/ Base/ Base/ Coated Panel Primer Primer Clear Clear Film Thickness (microns) 71.9 85.6 133.9 116.4 MEK double rubs 24 h Initial Damage/Mar <5 <5 24 h 25% Film Loss or 200 rubs >200 >200 7 d Initial Damage/Mar <5 <5 7 d 25% Film Loss or 200 rubs >200 >200 Cross Hatch Adhesion 24 hour 5B 5B 5B 5B 7 Day 5B 5B 4B 5B

(29) TABLE-US-00007 TABLE 4 Coating humidity performance.sup.1 Example 1 Example 1A* Example 2 With Corrosion Without Corrosion With Corrosion Inhibitor Inhibitor Inhibitor Primer/ Primer/ Primer/ Base/ Base/ Base/ Coated panels Primer Clear Primer Clear Primer Clear Film 76.2 147.3 53.3 121.9 81.28 128.79 Thickness (microns) Observations No No 1-4 mm 1-3 mm No blisters No blisters post humidity blisters blisters blisters, blisters, all observed observed exposure* observed observed 60% of panel panel *Denotes Comparative Example; 1. Panels cured for 7 day at ambient temperature prior to humidity exposure (Cleveland humidity chamber) for 96 h at 38 C. (100% condensing humidity).

(30) As shown in Tables 3A, 3B and 4, above, the Example 1 and 2 inventive primer exhibits improved humidity resistance (Table 4) as observed by no blistering of the coated panels. The inventive Examples do not compromise the ability to sand the primer in less than 1 h, sanding in the same time as the comparative example (40 min). In addition, there was no rusting observed in any panels containing the inventive primer.