Low reflectance powder coating composition

Abstract

A powder coating composition comprising: (a) a first acrylic powder resin having a hydroxyl value of at least about 180; (b) a second acrylic powder resin having a hydroxyl value between about 45 and about 80; (c) a crosslinker reactive with the hydroxyl functional acrylic resins; and (d) an acicular filler.

Claims

1. A powder coating composition comprising: (a) a first hydroxyl functional acrylic powder resin having a hydroxyl value of at least about 180 and having a Tg of at least 35 C.; (b) a second hydroxyl functional acrylic powder resin having a hydroxyl value between about 45 and about 80 and having a Tg of at least 35 C.; (c) a blocked isocyanate crosslinker reactive with the first hydroxyl functional acrylic powder resin and the second hydroxyl functional acrylic resin; and (d) wollastonite; and wherein the weight ratio of the first acrylic powder resin to the second acrylic powder resin is at least about 0.5, the first acrylic powder resin is present at a level to provide between about 33.3 weight percent and 85.1 weight percent of the total combined weight of the first acrylic powder resin and the second acrylic powder resin, the blocked isocyanate crosslinker is present at a level about 1.0 to about 1.5 equivalents of isocyanate functionality for each equivalent of active hydrogen of the first and second hydroxyl functional acrylic resins, the wollastonite is present at a level of at least 10% to about 25% by weight of the coating composition, and the coating composition when applied to a substrate and cured will have a 60 gloss less than 1 and an 85 gloss 3.5 or less.

2. The powder coating composition of claim 1, wherein the second hydroxyl functional acrylic powder resin has a hydroxyl value of about 60.

3. The powder coating composition of claim 1, wherein the weight ratio of the first acrylic powder resin to the second acrylic powder resin is about 1.0.

4. A powder coating composition comprising: (a) a first hydroxyl functional acrylic powder resin having a hydroxyl value of at least about 250 and having a Tg of at least 35 C.; (b) a second hydroxyl functional acrylic powder resin having a hydroxyl value between about 45 and about 80 and having a Tg of at least 35 C.; (c) a blocked isocyanate crosslinker reactive with the first hydroxyl functional acrylic powder resin and the second hydroxyl functional acrylic powder resin; and (d) wollastonite; and wherein the weight ratio of the first acrylic powder resin to the second acrylic powder resin is at least about 0.5, the first acrylic powder resin is present at a level to provide between about 33.3 weight percent and 85.1 weight percent of the total combined weight of the first acrylic powder resin and the second acrylic powder resin, the blocked isocyanate crosslinker is present at a level about 1.0 to about 1.5 equivalents of isocyanate functionality for each equivalent of active hydrogen of the first and second hydroxyl functional acrylic resins, the wollastonite is present at a level of at least 10% to about 25% by weight of the coating composition, and the coating composition when applied to a substrate and cured will have a 60 gloss less than 1 and an 85 gloss 3.5 or less.

Description

(1) The following examples illustrate embodiments and practices of advantage to a more complete understanding of the invention. Low reflectance powder coating compositions may be prepared as shown in Table 1. Unless otherwise stated, parts means parts-by-weight and percent is percent-by-weight, and equivalent weight is on a weight solids basis.

(2) Coating compositions as set forth in Table 1 may be prepared by blending and extruding the listed raw materials. The extrudate may then be cooled and fractured to produce a powder coating which may be applied to a suitable substrate and baked before testing for gloss and other properties.

(3) TABLE-US-00001 RAW MATERIAL EX. #1 EX. #2 Hydroxy 150 184 functional acrylic.sup.1 Hydroxy 150 184 functional acrylic.sup.2 Blocked 349 281 isocyanate.sup.3 Flow agent.sup.4 10 10 Benzoin 5 5 Wollastonite 210 210 Surfactant.sup.5 4 4 Hindered 20 Amine Light Stabilizer.sup.6 UV Absorber.sup.7 40 Iron oxide 47.5 47.5 black pigment Carbon black 2.5 2.5 powder Gloss 60/85 0.4/2.4 0.5/3.2 .sup.1Acrylic powder resin having a hydroxyl number of 60. .sup.2Acrylic powder resin having a hydroxyl number of 250. .sup.3VestagonB 1530 e-caprolactam blocked IPDI commercially available from Degussa. .sup.4Resiflow P-67 flow agent commercially available from Estron Chemical. .sup.5SURFYNOL 104S surfactant commercially available from Air Products. .sup.6TINUVIN 144 HALS commercially available from BASF .sup.7TINUVIN 928 commercially available from BASF

(4) While this invention has been described by a specific number of embodiments, other variations and modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.