LOW GLOSS POWDER COATING

Abstract

This disclosure relates to a curable, matte, preferably dull-matte, powder coating composition, accommodating superior chemical resistance through a complex of cross linkable fluoro containing organic compounds (A), preferably fluoro containing oligomers and/or polymers, and one or more cross linker(s) (B) able to react with (A), wherein the powder coating formulation additionally comprises one or more compound(s) (C) able to react with (A) and/or (B).

Claims

1. A curable powder coating composition comprising one or more cross-linkable fluoro containing organic oligomer(s) and/or polymer(s) (A) and one or more crosslinker(s) (B) able to react with (A), wherein the powder coating formulation additionally comprises one or more compound(s) (C) able to react with (A) and/or (B), the powder coating composition further comprising melamine and/or a melamine derivative.

2. (canceled)

3. The powder coating composition of claim 1, wherein a weight-ratio of (C)/(B) is between 0.01 and 1.0.

4. The powder coating composition of claim 3, wherein the weight-ratio of (C)/(B) is between 0.05 and 0.4.

5. The powder coating composition of claim 1, wherein (C) comprises free carboxylic acid groups.

6. The powder coating composition of claim 5, wherein (C) comprises more than one free carboxylic group.

7. The powder coating composition of claim 1, wherein (C) comprises dodecanedioic acid and/or a pyromellitic group.

8. The powder coating composition of claim 1, wherein (B) comprises an isocyanate based crosslinkers and/or a uretdione group.

9. The powder coating composition of claim 8, wherein (B) comprises blocked isocyanate based crosslinker.

10. (canceled)

11. The powder coating composition of claim 1, further comprising one or more phyllosilicate in a total phyllosilicate weight-concentration of between 3 and 30 weight percent based on overall powder coating formulation.

12. The powder coating composition of claim 11, wherein the phyllosilicate comprises at least one china clay, smectite clay, and/or derivative of either.

13. The powder coating composition of claim 12, wherein phyllosilicate comprises an organic derivatives of a china clay or a smectite clay.

14. A coating made with a powder coating composition of claim 1 and having a gloss below 30, measured at 60.

15. The coating of claim 14, further defined as having a gloss below 15, measured at 60.

16. The coating of claim 15, further defined as having a gloss below 5, measured at 60.

17. A method of producing a powder coated item comprising: obtaining a powder coating composition of claim 1; and using the powder coating composition to powder coat an item.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0021] Slight variations above and below the given ranges can be used to achieve substantially the same results. The subject matter of the present invention is characterized by the accompanying claims, in which every combination of one or more subclaims to a specific independent claim is also meant to be explicitly disclosed, even if such a subclaim is, for formal reasons, only referring to one specific other claim.

Fluor Compound

[0022] The fluoro containing organic compounds (A) mentioned hereinafter are preferably fluoro-resins with functional groups suitable to react with the crosslinkers (B) and (C) according to the present invention. Such kind of materials are for example FEVE and they are known under the trade name Lumiflon.

Crosslinkers

[0023] The powder coating composition according to the present invention further comprises one or more crosslinker(s) able to react with the functional groups of the polyester and/or acrylic resins used, such as blocked isocyanates, uretdiones, cyclic-amide and/or multi-acid compounds to name a few. For a better chemical stability blocked isocyanates are preferred compared to blocked uretdiones. Also glycolurile are suitable option in such cases. Such a combination according to the present invention taken alone can produce a chemical resistant powder coating with gloss values <25, in particular <10 measured at a 60 angle. Critically defined by the combination of (A) and (B), the invention at hand has the ability to provide a powder coating, that is able to create a dull-matte finish with a gloss value under 10, measured at 60. With the addition of other raw materials, the measured gloss value may vary accordingly, in either direction. Suitable crosslinkers are well known in the field and are for example listed in U.S. Pat. No. 9,012,556 and or in U.S. Pat. No. 9,206,320.

[0024] In some embodiments of the invention, a blocked cycloaliphatic polyisocyanate is used as crosslinker. In one embodiment, -caprolactam blocked trimethylolpropane 4,4-methylene dicyclohexyl diisocyanate (H12MDI) adduct, with a Tg of 55 C., is used. In particular a blocked cycloaliphatic polyisocyanate should have an NCO % of about 14.0, contain a functionality of 2.2, and have a Tg value near or about 60 C. In another embodiment of the present invention a -caprolactam blocked trimethylolpropane isophorone diisocyanate adduct, which should contain a cyclic amide or caporic acid, having a Tg value of or near 52 C., is used to crosslink hydroxyl functional groups of the used fluor polymer.

[0025] In a further embodiment of the present invention the hardener (C) in the system comprises one or more carboxylic acid(s) and/or salt(s) of carboxylic acid(s) containing hardeners present in a weight-concentration of below or equal to 50%, preferably below or equal to 20% and most preferably below or equal to 15% of (C). Surprisingly it was found that adding that kind of material into the hardener system (C) allows further gloss reductions even at an already low level of gloss.

[0026] Especially the combination of dicarboxylic acids such as nonanedioic acid, decanedioic acid, undecanedioic acid preferably dodecanedioic acid with a combination of 1,2,4,5 benzenetetracarboxylic acid with 2-phenyl-2-imidazoline pyromellitate (1:1) (CAS 54553-90-1) was preferred as use of such a combination showed an additional gloss reduction even at a gloss level in the range below 3 (measured at 60 angle).

[0027] In a special embodiment of the present invention the combination from dicarboxylic acids such as nonanedioic acid, decanedioic acid, undecanedioic acid preferably dodecanedioic acid with melamine was also surprisingly found to have an addition gloss reduction effect at very low gloss levels in the range below 3 (measured at 60 angle).

[0028] Surprisingly, in case of using melamine as component (C) and isocyanates as component (B) it was also found by IR investigations that the aromatic NH.sub.2-group of melamine seemed to be able to react with the isocyanate after treatment at 200 C.

Pigments and Fillers

[0029] Depending on the color and the associated pigment volume concentration, different filler types, for further gloss reduction, can be used, which fillers are commonly known in the field of powder coatings. However, coarse barium sulfate, preferably Kaolinite in combination with rheological modifiers, such as derivatives of smectite clay were found to have a very effective gloss reduction effect.

[0030] The utilization or non-utilization of pigments, whether organic- or inorganic-based, can be implemented into the president invention, also regarding the requirements of the MIL-PRF-32348 specification. Such suitable/non-suitable pigments include, but are not limited to titanium dioxides, antimony oxides, chromium oxides, zinc oxides, calcium carbonates, fumed cilicas and zinc phosphates, to name a few. In addition, different forms of fillers, including, but not limited to barium sulfates, calcium carbonate, and/or baryates, can be used as well.

Additives:

[0031] In the present invention, flow control agents may be added to the formulation in an amount of preferably from 0-15 percent by weight of the total powder composition. In one embodiment, a carboxyl functional acrylic polymer productwhich has been converted into free-flowing powder by adsorption onto silica-type carrierprovides excellent recoatability, clarity and appearance.

Degassing Agents:

[0032] As degassing agents benzoin is preferred. an alternatives can be Powdermate 542 DG from Estron Chemical.

Production of the Powder Coating:

[0033] The powder coatings according to the present invention can be produced by standard production procedures well known in the art, such as extruding the components of the coating composition, grinding of the cooled extrudate to a suitable particle size and applying the coating powder to suitable substrates. The application can be performed using any method available, e.g., using electrostatic spraying guns, or by using a fluidized bed.

[0034] For some embodiments it might be useful to produce two separate powder coatings, however based on the experiments with the powder coating according to the present invention low gloss levels up to below 1 can even be achieved via a so called one component system.

[0035] The substrate to be coated can be provided at ambient or at an elevated temperature.

[0036] The powder coating according to the present invention can principally be cured at a broad temperature range of about 130 C.-250 C. for 5 to 50 min. However, a preferred curing cycle is 15 min at 200 C. If necessary, the substrate can be pretreated by common means known in the art like sand-blasting, conversion coating etc., and/or one or more primer coatings can be applied before the substrate is coated with the coating composition according to the present invention described herein.

Examples

[0037] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those who are experienced in the field of interest will readily appreciate that an exceptional amount of modifications are possible in the exemplary embodiments; not straying from the core techniques and advantages of this invention. In addition, the current invention is not limited to all such modifications and embodiments disclosed.

[0038] If not otherwise stated, the powder coatings shown in the examples were produced via the following route.

[0039] Blending: Pilot 3 by Thermo PrismAfter weighing together the compounds of the formulation it was blended with 1000 RPM for 1 min.

[0040] Extruder: Twin screw Extruder ZSK 18 by Coperion.

[0041] Temperature Zones: 60, 80, 100, 120, 120 [ C.].

[0042] Screw configuration: Standard configuration for powder coatings as known by persons skilled in the art.

[0043] Feeder: Torque 30-40% at 600 RPM

[0044] Milling: ICM 2.4The chips for the milling should be approximately 1 cm.sup.3 or smaller to guarantee a good transportation inside the mill. The temperature of the air inside the mill should not exceed 15 C. because the particles may be stuck on the lower half of the cyclone wall. The speed of the mill must be set high enough for the almost thermoplastic chips to break, the particles thus obtained need to be small enough to produce a closed surface.

[0045] Particle size distribution: PSD Measuring instrument: Mastersizer 2000

[0046] Dry-Dispers unit: Scirocco 2000

[0047] After milling, an uppercut at 100 m should be made to prevent defects on the surface. The PSD was measured with 3.5 bar to rip apart particles that may have built agglomerates.

TABLE-US-00001 10 m 13-20% 20 m 34-42% 32 m 50-60% 65 m 80-90% 100 m 99% d(0, 1) 5-8 m d(0, 5) 26-32 m d(0, 9) 54-68 m

[0048] Spaying behavior: After sieving the powder, an anticaking agent (aluminumoxid 0.2%) should be mixed into the formulation. The particles will build less agglomerates and a better electrostatic charge could also be observed.

[0049] Spraying: OptitronicPistol control unit by GemaAfter a lot of sprayed probes, the following custom setting has been found that proved to provide excellent results for CARC formulations.

TABLE-US-00002 High voltage [kV] 45 Current [A] 20 Powder output [Nm.sup.3/h] 90 Airflow [Nm.sup.3/h] 2.5 Curing condition 200 C./10 min

[0050] DS2 Test Method (Chemical resistance test): The chemical resistance test with the DS2 contaminating agent simulates the Army Research Laboratory (ARL) methodology for contamination, against chemical warfare agents (CWA).

[0051] DS2 will neutralize all known toxic chemical agents.

[0052] The DS2 contamination agent contains 70% diethylenetriamine, 28% ethylene glycol monomethyl ether and 2% sodium hydroxide (3N).

[0053] One drop (1 to 2 mL) of the DS2 reagent was added to the surface of the final powder coating, the surface was covered with a watch glass and the DS2 reagent attacked the surface for 30 minutes at room temperature. The DS2 reagent was washed off with water. The evaluation criteria for testing results are no brightening and swelling. Numerical valuations ranging from 1 to 3 were assigned. 1 is the best performance and 3 the poorest. To get rate 1, no surface changes were visible, for rate 2 only slight surface changes were visible (such as subtle brightening), for rate 3 strong brightening occurred.

[0054] Flexibility: Determination of flexibility was made in accordance with ASTM 0522, method B, using a 1.4 inch mandrel. The coating was sprayed, according to manufacturers' recommendations, on a steel panel, tinplated 0.010 inches (0.0254 cm) thick. The coating was examined for cracks over the area of the bend.

Examples

[0055]

TABLE-US-00003 5 6 7 Raw material 1 2 3 4 (comp.) (comp.) (comp.) Lumiflon LF-710F 54.00 54.00 54.00 54.00 54.00 75.92 54 Crelan NW 5 15.00 15.00 15.00 15.00 15.00 20.72 15 Melamin 1.00 1.00 3.00 Dodecandioic acid 1.00 1.00 3.00 DDDA RB 68 1.00 1.00 Lanco Wax TF 1890 1 Benzoin 0.70 0.70 0.70 0.70 0.70 0.7 Raven 2000 Black 0.99 0.99 0.99 0.99 0.99 0.99 0.99 Pigment 2.37 2.37 2.37 2.37 2.37 2.37 2.37 Bayferrox 316 Lanxess Inorganic Pigments, Germany Portafill A40 26.94 China Clay 24.94 24.94 24.94 20.94 25.94 Sum 100 100 100 100 100 100 100 Gloss at 20/60/85 0.9/10/18 0.8/8/14 0.7/7/12 0.8/8/15 4/27/66 35/67/88 1.3/15/25
For more details on the suppliers of the raw materials see sample 8, 9, and 10.

[0056] Sample 1 shows a formulation which shows the principle combination of a fluor-containing resin and an additional hardener DDDA and RB68 according to the present invention. As can be seen, this kind of formulation already has led to a gloss of 10 at 60 even without any structuring agent. In comparison thereto, the samples 5, 6 and 7 marked comp. (which are for comparative reasons and not according to the present invention) show a higher gloss level of 27, 67 and 15 measured at 60. The comparison of samples 5 and 6 shows the effect of the filler on the gloss in powder coating formulations, leaving out the filler led to a strong increase in the gloss level. Additionally, it was surprisingly found that also the type of the filler has an enormous effect on the gloss level (comparison of samples 5 and 7). However, to come to very low gloss levelsespecially below 10the addition of additional hardeners in curable fluoropolymer containing powder coatings according to the present invention was surprisingly suitable. Samples 2 and 3 show that surprisingly the use of melamine additionally led to a reduction of the gloss. Increase of the concentration of the additional hardeners did not led to a further reduction in the gloss in sample 4. It was found that high concentration of additional hardeners, like DDDA, could lead to a reduction in storage stability.

[0057] Very good results of gloss and mechanical features as well as of the chemical stability were found with the following three formulations 8, 9 and 10. Therefore, these formulations are even suitable for military applications. To get to a desired gloss levels below 2 or even below 1 in formulations like 9 and 10, which showed a high level of pigment concentration, it was surprisingly found that the use of a special filler based on smectite, like Bentone SD-3, provided such desired levels. Based on that kind of formulations it was surprisingly found that the combination of more hardeners led to a further decrease of gloss as can be seen in the following table:

TABLE-US-00004 Additional Hardener Wt %/Ratio Gloss@60 Gloss@85 DDDA 0.9 1.7-1.2 2.5-1.9 Melamine/PIP 1.0/2.7 0.8 1.1 Melamine/DDDA 1.0/0.9 0.7 0.1 DDDA Dodecanedioic Acid CAS No. [693-23-2] PIP 2-Phenyl-2-Imidazoline-pyromellitate CAS No. [54553-90-1] Melamine Melamine CAS No. [108-78-1]

[0058] Sample 8

TABLE-US-00005 No. Constituent/Source Description Wt % 1 Fluorocopolymer FEVE (Fluoroethylene- 54.00 Lumiflon LF-710F Alky Vinyl Ether) AGC Chemicals Americas, copolymer with a Inc. hydroxyl value of 46 mg KOH/g 2 Crelan NW 5 Blocked cycloaliphatic 15.00 Covestro AG polyisocyanate with a Leverkusen, Germany total NCO content of 12.7% 3 Melamine in combination Melamine 1.00 with DDDA CAS No. [108-78-1] Borealis Agrolinz with an EW of 42 g/Eq Melamine GmbH, Austria 4 DDDA in combination Dodecanedioic acid 0.90 with Melamine CAS No. [693-23-2] Invista, Germany with an EW of 115 g/Eq 5 Lanco 1890 N Fluoroethylene based 1.00 Lubrizol Ltd, UK agent CAS No. [9002-84-0] 6 Resiflow P-64F Carboxyl functional 1.00 Worlee Chemie acrylic Estron Chemicals, Germany flow control agent 7 Benzoin Benzoin 0.70 CAS No. [119-53-9] 8 Raven 2000 Black Furnace carbon black 0.99 Columbian Chemicals (C.I. Pigment Black 6) Company, Georgia CAS No. [1333-86-4] 9 Bayferrox 316 Iron oxide 2.37 Lanxess Inorganic Pigments, (C.I. Pigment Black 11) Germany CAS No. [1317-61-9] 10 China Clay Extra ST Kaolinite 23.04 Kamig AG, Austria CAS No.[00-1332-58-7] Total 100.00

[0059] Sample 9

TABLE-US-00006 No. Constituent/Source Description Wt % 1 Fluorocopolymer FEVE (Fluoroethylene- 54.00 Lumiflon LF-710F Alky Vinyl Ether) AGC Chemicals Americas, copolymer with a Inc. hydroxyl value of 46 mg KOH/g 2 Crelan NW 5 Blocked cycloaliphatic 15.00 Covestro AG polyisocyanate Leverkusen, Germany with a total NCO content of 12.7% 3 Melamine in combination Melamine 1.00 with DDDA CAS No. [108-78-1] Borealis Agrolinz with an EW of 42 g/Eq Melamine GmbH, Austria 4 DDDA in combination Dodecanedioic acid 0.90 with Melamine CAS No. [693-23-2] Invista, Germany with an EW of 115 g/Eq 5 Lanco 1890 N Fluoroethylene based 1.00 Lubrizol Ltd, UK agent CAS No. [9002-84-0] 6 Resiflow P-64F Carboxyl functional 1.00 Worlee Chemie acrylic Estron Chemicals, Germany flow control agent 7 Benzoin Benzoin 0.70 CAS No. [119-53-9] 8 Duropal Yellow 6218 Bismuth vanadate 0.65 Habich, Austria (C.I. Pigment Yellow 184) CAS No. [14059-33-7] 9 Bayferrox 943 Iron Oxide 2.35 Lanxess Inorganic Pigments, (C.I. Pigment Yellow 42) Germany CAS No. [20344-49-4] 10 Colortherm Green GN Chromium oxide 5.95 Lanxess Inorganic Pigments, (C.I. Pigment Green 17) Germany CAS No. [1308-38-9] 11 Bayferrox 316 Iron oxide 3.00 Lanxess Inorganic Pigments, (C.I. Pigment Black 11) Germany CAS No. [1317-61-9] 12 Kronos 2310 Rutile Titanium Dioxide 0.22 Kronos International Inc. (C.I. Pigment White 6) CAS No. [13463-67-7] 13 Bentone SD-3 Organic derivative of a 2.00 Elementis Specialties smectite clay CAS No. [121888-67-3] 14 China Clay Extra ST Kaolinite 12.23 Kamig AG, Austria CAS No. [00-1332-58-7] Total 100.00

[0060] Sample 10

TABLE-US-00007 No. Constituent/Source Description Wt % 1 Fluorocopolymer FEVE (Fluoroethylene- 54.00 Lumiflon LF-710F Alky Vinyl Ether) AGC Chemicals Americas, copolymer with a Inc. hydroxyl value of 46 mg KOH/g 2 Crelan NW 5 Blocked cycloaliphatic 15.00 Covestro AG polyisocyanate with a Leverkusen, Germany total NCO content of 12.7% 3 Melamine in combination Melamine 1.00 with DDDA CAS No. [108-78-1] Borealis Agrolinz with an EW of 42 g/Eq Melamine GmbH, Austria 4 DDDA in combination Dodecanedioic acid 0.90 with Melamine CAS No. [693-23-2] Invista, Germany with an EW of 115 g/Eq 5 Lanco 1890 N Fluoroethylene based 1.00 Lubrizol Ltd, UK agent CAS No. [9002-84-0] 6 Resiflow P-64F Carboxyl functional 1.00 Worlee Chemie acrylic Estron Chemicals, Germany flow control agent 7 Benzoin Benzoin 0.70 CAS No. [119-53-9] 8 Colortherm Yellow 10 Iron Oxide 0.83 Lanxess (C.I. Pigment Yellow 42) CAS No. [51274-00-1] 9 Bayferrox 3920 Iron Oxide 1.13 Lanxess (C.I. Pigment Yellow 42) CAS No. [51274-00-1] 10 Bayferrox 130 B Iron Oxide 0.41 Lanxess (C.I. Pigment Red 101) CAS No. [1309-37-1] 11 Colortherm Green GN Chromium Oxide 1.00 Lanxess (C.I. Pigment Green 17) CAS No. [1308-38-9] 12 Kronos 2310 Rutile Titanium Dioxide 12.83 Kronos International Inc. (C.I. Pigment White 6) CAS No. [13463-67-7] 13 Bentone SD-3 Organic derivative of a 2.00 Elementis Specialties smectite clay CAS No. [121888-67-3] 14 China Clay Extra ST Kaolinite 8.20 Kamig AG, Austria CAS No.[00-1332-58-7] Total 100.00

[0061] Gloss Results of Samples 8-10

TABLE-US-00008 Gloss 8 9 10 20 0.1 0.2 0.8 60 0.9 0.6 1.1 85 1.3 0.7 0.7

[0062] Chemical Resistance Results of Samples 10-15 According to the DS2 Test

TABLE-US-00009 8 9 10 Value 1 Value 1 Value 1

[0063] Mechanical Results According to ASTM 0522, Method B, Using a 1.4 Inch Mandrel

TABLE-US-00010 8 9 10 passed passed passed