Powder Coating Compositions and Coatings Formed Therefrom

Abstract

A powder coating composition can include: a polyester polymer comprising carboxylic acid functional groups; a crosslinker reactive with the carboxylic acid functional groups of the polyester polymer; and a thermoplastic fluoropolymer unreactive with the polyester polymer and crosslinker. The powder coating composition is substantially free of an isocyanate functional crosslinker.

Claims

1. A powder coating composition comprising: a polyester polymer comprising carboxylic acid functional groups and having an acid value of at least 15 mg KOH/g; a crosslinker reactive with the carboxylic acid functional groups of the polyester polymer; and a thermoplastic fluoropolymer unreactive with the polyester polymer and crosslinker, wherein the powder coating composition is substantially free of an isocyanate functional crosslinker.

2. The powder coating composition of claim 1, wherein the polyester polymer comprises at least 20 weight % based on the total solids weight of the powder coating composition.

3. The powder coating composition of claim 1, wherein the fluoropolymer comprises 40 weight % or less based on the total solids weight of the powder coating composition.

4. The powder coating composition of claim 1, wherein the polyester polymer has an acid value within a range of at least 20 and up to 70 mg KOH/g.

5. The powder coating composition of claim 1, wherein the polyester polymer has a glass transition temperature within a range of from 10 to 100 C.

6. The powder coating composition of claim 1, wherein the polyester polymer has a melt viscosity at 165 C. within a range of from 5 to 100 Pa.Math.s as measured by a Cone and Plate Viscometer according to ASTM D 4287.

7. The powder coating composition of claim 1, wherein the thermoplastic fluoropolymer comprises a fluoropolyether polymer, a polyvinylidene fluoride polymer, or a combination thereof.

8. The powder coating composition of claim 7, wherein the thermoplastic fluoropolymer comprises a fluoropolyether polymer.

9. The powder coating composition of claim 8, wherein the fluoropolyether polymer is a fluoroethylene vinyl ether copolymer.

10. The powder coating composition of claim 7, wherein the thermoplastic fluoropolymer comprises a polyvinylidene fluoride polymer.

11. The powder coating composition of claim 1, wherein the thermoplastic fluoropolymer has a glass transition temperature within a range of from 10 to 100 C.

12. The powder coating composition of claim 1, wherein a weight ratio of the polyester polymer to the thermoplastic fluoropolymer is from 80:20 to 60:40.

13. The powder coating composition of claim 1, wherein the crosslinker comprises a hydroxylalkyl amide compound, an epoxy-functional compound, or a combination thereof.

14. The powder coating composition of claim 13, wherein the crosslinker comprises both a hydroxylalkyl amide compound and an epoxy functional (meth)acrylic compound.

15. The powder coating composition of claim 14, wherein an amount of the epoxy functional (meth)acrylic compound in the powder coating composition is greater than an amount of the hydroxylalkyl amide compound, the amounts based on the total solids weight of the powder coating composition.

16. The powder coating composition of claim 1, wherein the powder coating composition further comprises a pigment.

17. The powder coating composition of claim 1, wherein the powder coating composition is substantially free of epsilon-caprolactam and/or triglycidyl isocyanurate.

18. The powder coating composition of claim 1, wherein the powder coating composition is substantially free of an organic ultraviolet absorber.

19. The powder coating composition of claim 1, wherein when cured, the powder coating composition forms a single coating layer comprising the polyester polymer and the fluoropolymer.

20. A substrate at least partially coated with a coating formed from the powder coating composition of claim 1.

21. The substrate of claim 20, wherein the coating formed from the powder coating composition of claim 1 comprises a single coating layer formed directly over a surface of the substrate.

Description

EXAMPLES 1-5 AND COMPARATIVE EXAMPLE 1

Preparation of Curable Coating Compositions

[0065] Six (6) curable coating compositions were prepared from the components listed in Table 1.

TABLE-US-00001 TABLE 1 Ex. C1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Component (grams) (grams) (grams) (grams) (grams) (grams) Reafree 5700 .sup.1 343 382 553 617 427 481.1 Lunamer 552 .sup.2 7 8 22 33 23 18.4 Isocryl EP-575 .sup.3 50 60 35 34 Lumiflon 710F .sup.4 204 200 200 200 200 194 Vestagon B-1530 .sup.5 46 Resiflow PL-200A .sup.6 9 9 9 9 9 8.7 Powdermate 542DG .sup.7 5 5 5 5 4.9 Benzoin .sup.8 5 Black 430 .sup.9 96 100 106.7 1200 EZ .sup.10 10 0.7 Yellow 193 .sup.11 14.5 19.4 Tronox CR-880 .sup.12 336 336 12 336 19.4 Exbar W4 .sup.13 43.5 36 82.7 Mearlin Bright White 10 139X .sup.14 Mearlin Sparkle 139P .sup.15 20 .sup.1 A polyester resin based on isophthalic acid having an acid value of about 32 to 38, commercially available from Arkema. .sup.2 Hydroxyalkylamide crosslinker, commercially available from DKSH. .sup.3 Matting epoxy-functional acrylic crosslinker, commercially available from Estron Chemical. .sup.4 Fluoroethylene vinyl ether resin, commercially available from AGC Chemicals. .sup.5 Isocyanate Crosslinker blocked with -Caprolactam, commercially available from Evonik. .sup.6 Acrylic/silica flow and leveling control agent, commercially available from Estron Chemical. .sup.7 Degassing/debubbling agent, commercially available from Troy Corporation. .sup.8 Degassing/debubbling agent, commercially available from Mitsubishi Chemical Corp. .sup.9 C.I. Pigment Black 28, commercially available from The Shepherd Color Company. .sup.10 C.I. Pigment Red 101, commercially available from Dequing Tongcheng Co., Ltd. .sup.11 C.I. Pigment Brown 24, commercially available from The Shepherd Color Company. .sup.12 Titanium dioxide pigment, commercially available from Tronox. .sup.13 White barium sulfate with a median particle size of 4 microns, commercially available from Excalibar Minerals. .sup.14 Mica coated with titanium dioxide, stannic oxide, and chromium hydroxide having a mass median diameter particle size in the 18.2 to 21.1 micron range, commercially available from BASF Corporation. .sup.15 Mica coated with titanium dioxide, stannic oxide, and chromium hydroxide having a mass median diameter particle size in the 32 to 46 micron range, commercially available from BASF Corporation.

[0066] For Examples 1-4 and Comparative Example 1 (C1), each of the components listed in Table 1 were weighed in a plastic bag and mixed by shaking vigorously in the bag for 30 seconds to form a dry homogeneous mixture. For Example 5, the first eleven ingredients listed in Table 1 were used to form an intermediate solid particulate powder coating composition. This intermediate solid particulate powder coating composition was weighed in a plastic bag along with the final two ingredients in Table 1 and mixed by shaking vigorously in the bag for 30 seconds to yield a final solid particulate powder coating composition that is free flowing.

[0067] Each mixture was melt mixed in a Theysohn 30mm twin screw extruder with a moderately aggressive screw configuration and a speed of 500 RPM. The first extruder zone was set at 50 C., and the second zone was set to 100 C. The feed rate was such that a torque of 30-35% was observed on the equipment. The mixtures were dropped onto a set of chill rolls to cool and re-solidify the mixtures into solid chips. The chips were milled using a coffee grinder and sieved through a 104 micron screen to obtain a mass median diameter particle size of 35-40 microns. The resulting coating compositions for each of Examples 1-5 and Comparative Example 1 (C1) were solid particulate powder coating compositions that were free flowing.

[0068] All powder coating compositions from Examples 1-5 and Comparative Example 1 were applied over several chromate pretreated 0.025 inch by 3 inch by 6 inch aluminum panels at film thicknesses shown in Table 1 and heated for 15 minutes at 400 F. Various properties of the cured coatings, determined by tests performed on these coated panels, are shown in Table 2.

TABLE-US-00002 TABLE 2 Example Example Example Example Example Example Property/test C1 1 2 3 4 5 Coating Thickness 2.5 2.5 2.5 2.5 2.5 2.5 (mils) .sup.16 60 Degree Gloss .sup.17 6.4 9.9 36 82 85 26 Dry Adhesion (% of 0% .sup.0% 0% 0% 0% 0% area removed) .sup.18 Boiling Water Adhesion >65% 5-15% 0% 0% 0% 0% (% of area removed) .sup.19 Forward Impact Pass Pass Pass Pass Resistance (Adhesion Loss from Tape Pull - Pass/Fail) .sup.20 Reverse Impact (% of >50% .sup.<5% area removed) .sup.21 Cyclic Corrosion 0-0.5 mm 0-0.5 mm Resistance - Average Scribe Creepage (mm) .sup.22 Humidity Resistance .sup.23 No No Blisters Blisters .sup.16 Per ASTM D7091-13 test method using Elcometer 415 Model B Dual FNF gauge. .sup.17 Per ASTM D523-14 test method using BYK Gardner micro-TRI-gloss. .sup.18 Per ASTM D3359-09 test method B. .sup.19 Per AAMA 2605-17A Section 8.4.1.2 and ASTM D3359-09 test method B. .sup.20 Per AAMA 2605-17A Section 8.5. .sup.21 Per AAMA 2605-17A Section 8.5 with the following exceptions: The impact was applied to the opposite side of the coating. The percentage of the coating removed after the tape pull in the impacted area was estimated. 0.025 inch by 3 inch by 6 inch aluminum panels with no pretreatment were used to complete this test instead of the chromate pretreated panels. .sup.22 Per AAMA 2605-17A Section 8.8.2 and ASTM G85, Annex A5 for conducting the cyclic corrosion test and ASTM D 1654 for measuring the average scribe creepage. .sup.23 Per AAMA 2605-17A Section 8.8.1 and ASTM D4585-13.

[0069] As shown in Table 2, the coatings prepared from the coating compositions of Examples 1-5 of the present invention exhibit a broad gloss range, good adhesion, impact resistance, corrosion resistance, and humidity resistance. In contrast to Examples 1-5 of the present invention, Comparative Example 1, which utilizes an isocyanate crosslinker reactive with both the acid-functional polyester polymer and the fluoropolymer, exhibits a poor boiling water adhesion as measured by percentage area of the coating removed. Comparative Example 1 also shows poor reverse impact resistance in contrast with Example 1 of the present invention.

EXAMPLES 6-9

Preparation of Curable Coating Compositions

[0070] Four (4) curable coating compositions were prepared from the components listed in Table 3.

TABLE-US-00003 TABLE 3 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Component (grams) (grams) (grams) (grams) Kynar PG-11 PVDF .sup.24 100.0 200.0 150.0 150.0 Lunamer 552 .sup.2 11.6 8.2 26.0 16.2 Uralac P883 .sup.25 363.5 266.8 35 Uralac P5525 .sup.26 299 Uralac P886 .sup.27 308.8 Powdermate 575 .sup.28 15.0 15.0 15.0 15.0 Benzoin .sup.8 2.4 2.4 2.5 2.5 Monarch 1300 Black .sup.29 7.5 7.5 7.5 7.5 .sup.24 A Polyvinylidene fluoride (PVDF)/Kynar 500 grade fluoropolymer commercially available from Arkema. .sup.25 A polyester resin based on isophthalic acid having an acid value of about 18 to 22, commercially available from DSM Resins. .sup.26 A polyester resin based on isophthalic acid having an acid value of about 49 to 54, commercially available from DSM Resins. .sup.27 A polyester resin based on isophthalic acid having an acid value of about 33 to 37, commercially available from DSM Resins. .sup.28 Acrylic flow and leveling control agent, commercially available from Troy Corporation. .sup.29 Monarch 1300 Carbon Black, commercially available from Cabot Corporation.

[0071] Each of the components listed in Table 3 for Examples 6-9 were weighed in a plastic bag and mixed by shaking vigorously in the bag for 30 seconds to form a dry homogeneous mixture. The mixture was melt mixed in a Werner & Pfleiderer 30mm twin screw extruder with a moderately aggressive screw configuration and a speed of 450 RPM. The first extruder zone was set at 75 C., and the second zone was set to 75 C. The feed rate was such that a torque of 30-35% was observed on the equipment. The mixtures were dropped onto a set of chill rolls to cool and re-solidify the mixtures into solid chips. The chips were milled using a coffee grinder and sieved through a 104 micron screen to obtain a mass median diameter particle size of 35-40 microns. The resulting coating compositions for each of Examples 6-9 were solid particulate powder coating compositions that were free flowing.

[0072] Each powder coating composition from Examples 6-9 were applied over several chromate pretreated 0.025 inch by 3 inch by 6 inch aluminum panels at film thicknesses shown in Table 1 and heated for 15 minutes at 425 F. Various properties of the cured coatings, determined by tests performed on these coated panels, are shown in Table 4.

TABLE-US-00004 TABLE 4 Property/test Example 6 Example 7 Example 8 Example 9 Coating Thickness (mils) .sup.16 2.5 2.5 2.5 2.5 60 Degree Gloss .sup.17 38.5 22.5 30.2 31.4 Dry Adhesion 0% 0% 0% 0% (% of area removed) .sup.18 Boiling Water Adhesion 0% 0% 0% 0% (% of area removed) .sup.19 Forward Impact Resistance Pass Pass Pass Pass (Adhesion Loss from Tape PullPass/Fail) .sup.20 Reverse Impact <5% <5% <5% <5% (% of area removed) .sup.21 250 Hr. CASS Corrosion 0-0.5 mm 0-0.5 mm 0-0.5 mm 0-0.5 mm ResistanceAverage Scribe Creepage (mm) .sup.30 Humidity Resistance .sup.23 No Blisters No Blisters No Blisters No Blisters .sup.30 Per ASTM B368 for conducting Copper Accelerated-Acetic Acid Salt Spray corrosion test and ASTM D 1654 for measuring the average scribe creepage.

[0073] As shown in Table 4, the coatings formed from the compositions of Examples 6-9 all exhibited good adhesion, impact resistance, corrosion resistance, and humidity resistance.

[0074] In view of the foregoing the present invention is directed inter alia, without being limited thereto, to the following clauses.

[0075] Clause 1: A powder coating composition comprising a polyester polymer comprising carboxylic acid functional groups and having an acid value of at least 15 mg/KOH; a crosslinker reactive with the carboxylic acid functional groups of the polyester polymer; and a thermoplastic fluoropolymer unreactive with the polyester polymer and crosslinker, wherein the powder coating composition is substantially free of an isocyanate functional crosslinker.

[0076] Clause 2: The powder coating composition of clause 1, wherein the polyester polymer comprises at least 20 weight%, at least 30 weight %, at least 35 weight %, at least 40 weight %, at least 50 weight %, or at least 60 weight %, based on the total solids weight of the powder coating composition.

[0077] Clause 3: The powder coating composition of clauses 1 or 2, wherein the fluoropolymer comprises 40 weight % or less, 30 weight % or less, or 25 weight % or less, based on the total solids weight of the powder coating composition

[0078] Clause 4: The powder coating composition of any of clauses 1 to 3, comprising the crosslinker in an amount of from 1 to 30 weight %, from 1 to 20 weight %, or from 2 to 15 weight %, based on the total solids weight of the powder coating composition.

[0079] Clause 5: The powder coating composition of any of clauses 1 to 4, wherein the polyester polymer has an acid value within a range of at least 20 and up to 70 mg KOH/g, such as of at least 20 and up to 50 mg KOH/g.

[0080] Clause 6: The powder coating composition of any of clauses 1 to 5, wherein the polyester polymer has a glass transition temperature within a range of from 10 to 100 C., from 25 to 85 C., or from 45 to 70 C.

[0081] Clause 7: The powder coating composition of any of clauses 1 to 6, wherein the polyester polymer has an a melt viscosity at 165 C. within a range of from 5 to 100 Pa.Math.s, from 7 to 85 Pa.Math.s, or from 9 to 70 Pa.Math.s.

[0082] Clause 8: The powder coating composition of any of clauses 1 to 7, wherein the thermoplastic fluoropolymer comprises a fluoropolyether polymer, a polyvinylidene fluoride polymer, or a combination thereof.

[0083] Clause 9: The powder coating composition of clause 8, wherein the thermoplastic fluoropolymer comprises a fluoropolyether polymer such as a fluoroethylene vinyl ether copolymer.

[0084] Clause 10: The powder coating composition of clause 8, wherein the thermoplastic fluoropolymer comprises a polyvinylidene fluoride polymer.

[0085] Clause 11: The powder coating composition of any of clauses 1 to 10, wherein the thermoplastic fluoropolymer has a glass transition temperature within a range of from 10 to 100 C., from 25 to 85 C., or from 34 to 70 C.

[0086] Clause 12: The powder coating composition of any of clauses 1 to 11, wherein an amount of the polyester polymer in the powder coating composition is greater than an amount of the thermoplastic fluoropolymer, the amounts based on the total solids weight of the powder coating composition.

[0087] Clause 13: The powder coating composition of clause 12, wherein a weight ratio of the polyester polymer to the thermoplastic fluoropolymer is from 80:20 to 60:40, from 80:20 to 55:45, or from 76:24 to 65:35.

[0088] Clause 14: The powder coating composition of any of clauses 1 to 13, wherein the crosslinker comprises a hydroxylalkyl amide compound, an epoxy functional compound or a combination thereof.

[0089] Clause 15: The powder coating composition of clause 14, wherein the crosslinker comprises a hydroxylalkyl amide compound and an epoxy functional acrylic compound.

[0090] Clause 16: The powder coating composition of clause 15, wherein an amount of the epoxy functional acrylic compound in the powder coating composition is greater than an amount of the hydroxylalkyl amide compound, the amounts based on the total solids weight of the powder coating composition.

[0091] Clause 17: The powder coating composition of clause 15, wherein a weight ratio of the hydroxylalkyl amide compound to the epoxy functional acrylic compound is from 1:14 to 6:1, from 1:10 to 5:1, from 1:7 to 4:1, from 1:14 to 1:1, from 1:10 to 1:1, from 1:7 to 1:1, or from 5:1 to 3:1.

[0092] Clause 18: The powder coating composition of any of clauses 1 to 17, wherein the powder coating composition further comprises a pigment.

[0093] Clause 19: The powder coating composition of any of clauses 1 to 18, wherein the powder coating composition is substantially free, essentially free, or completely free of epsilon-caprolactam and/or tricglycidyl isocyanurate.

[0094] Clause 20: The powder coating composition of any of clauses 1 to 19, wherein the powder coating composition is substantially free, essentially free, or completely free of an organic ultraviolet absorber.

[0095] Clause 21: The powder coating composition of any of clauses 1 to 20, wherein the polyester polymer is derived from a reaction of an aliphatic polyol with a polycarboxylic acid or anhydride.

[0096] Clause 22: The powder coating composition of clause 21, wherein the polycarboxylic acid is a cyclic polycarboxylic acid.

[0097] Clause 23: The powder coating composition of any of clauses 21 or 22, wherein the polycarboyxlic acid is an aromatic polycarboxylic acid.

[0098] Clause 24: The powder coating composition of any of clauses 21 to 23, wherein the polycarboxylic acid is a diacid.

[0099] Clause 25: The powder coating composition of any of clauses 21 to 24, wherein the polycarboxylic acid is isophthalic acid.

[0100] Clause 26: The powder coating composition of any of clauses 21 to 25, wherein the aliphatic polyol comprises from 2 to 12 carbon atoms, for example being selected from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexane dimethanol, trimethylol propane or a combination of any of the foregoing.

[0101] Clause 27: The powder coating composition of any one of clauses 1 to 26, wherein the powder coating composition comprises a matting agent.

[0102] Clause 28: The powder coating composition of any one of clauses 1 to 27, wherein when cured, the powder coating composition forms a single coating layer comprising the polyester polymer and the fluoropolymer.

[0103] Clause 29: A substrate at least partially coated with a coating formed from the powder coating composition of any of clauses 1 to 28.

[0104] Clause 30: The substrate of clause 29, wherein the coating formed from the powder coating composition according to any one of clauses 1 to 28 comprises a single coating layer, which may for example be formed directly over the surface of the substrate.

[0105] Clause 31: A method for coating a substrate comprising applying the coating composition of any of clauses 1 to 28 to a substrate and curing the coating composition.

[0106] Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.