PROCESS FOR THE SPRAY APPLICATION OF AQUEOUS PAINTS BY UTILIZING AN AIR SHROUD

• US 3,857,511 A
• Filed: 07/31/1973
• Issued: 12/31/1974
• Est. Priority Date: 07/31/1973
• Status: Expired due to Term

• Current Assignee: Tirunillayi S. Govindan
• Original Assignee: Tirunillayi S. Govindan
• Inventors: Govindan, Tirunillayi S.
• Primary Examiner(s): Wood, Jr., M. Henson
• Assistant Examiner(s): Mar, Michael Y.
• Application Number:
  US05/384,354
• Time in Patent Office: 518 Days
• Field of Search: 239/8,11,290,291,296,297 117/14R
• US Class Current: 239/11
• CPC Class Codes: B05B 12/18 using fluids, e.g. gas streams
• CPC Class Codes: B05B 7/066 with an inner liquid outlet surrounded by at least one annular gas outlet
• CPC Class Codes: B05B 7/0815 with at least one gas jet intersecting a jet constituted by a liquid or a mixture containing a liquid for controlling the shape of the latter
• CPC Class Codes: B05B 7/1209 the controlling means for each liquid or other fluent material being manual and interdependent

Abstract

The improved process applies an aqueous paint to a substrate by air spraying a paint with a spray gun utilizing atomizing air at a flow rate of about 5-40 cubic feet per minute and at an air pressure of 30-95 pounds per square inch at the spray gun and a paint flow rate of about 5-30 ounces per minute, wherein the gun forms a cone or a fan of air atomized paint which is applied to the substrate and the paint is baked to form a uniform finish on the substrate; the improvement that is used with this process comprises utilizing an air shroud that substantially encircles the atomized paint spray with a cone or a fan of air that is at about 15*-95*C. and the flow rate of air for the shroud is about 10-250 cubic feet per minute; this shroud provides a uniform atmosphere for drying the paint during spraying on the substrate; THE IMPROVED PROCESS IS PARTICULARLY USEFUL FOR APPLYING EXTERIOR AQUEOUS BASE PAINTS ON AUTOMOBILE AND TRUCK BODIES TO FORM A HIGH QUALITY FINISH OF UNIFORM COLOR, HUE AND APPEARANCE.

Claims

1. In the process for applying an aqueous paint of a thermosetting acrylic enamel to a substrate by air-spraying the paint with a spray gun utilizing atomized air at a flow rate of 5-40 cubic feet per minute and at an air pressure of 30-95 pounds per square inch at the spray gun and a paint flow rate of 5-30 ounces per minute which forms a cone of air atomized paint which is appliedd to the substrate and baked to form a uniform finish on the substrate, the improvement in the use therewith comprising an air shroud that substantially encircles the cone of air atomized paint, wherein the air of the shroud is at 15*-95*C. and the air flow rate is 10-250 cubic feet per minute, and wherein the air shroud provides a uniform atmosphere for drying the aqueous paint during spraying of the substrate.

2. 10-40 percent by weight, based on the weight of the film-forming constituents, of a water-dispersible alkylated melamine formaldehyde resin having 1-4 carbon atoms in the alkyl groups, and the composition is at least partially neutralized with a water-solublel amine and has a pH of about 6-9.

3. The process of claim 2 in which the aqueous thermosetting acrylic paint contains the film-forming constituents:

4. The process of claim 2 in which the acrylic enamel comprises 10 to 60 percent by weight of film-forming constituents and correspondingly 9 to 40 percent by weight of water and up to 20 percent by weight of a solvent for the film-forming constituents;

wherein the film-forming constituents consist essentially of

5. The process of claim 4 in which the acrylic polymer enamel consists essentially of 50-60 l percent by weight of methyl methacrylate, 30-40 percent by weight of butyl acrylate, 5-10 percent by weight of hydroxyethyl acrylate, and 4-12 percent by weight of acrylic acid and the polymer has an acid number of about 35-100 and a carboxyl to hydroxyl ratio of about 1:

0.3 to 1;

1.5, then the acrylic polymer has a weight average molecular weight of about 10,000-50,000.

6. The process of claim 4 in which the acrylic polymer of the enamel consists essentially of 28-32 percent by weight of styrene, 22-26 percent by weight of methyl methacrylate, 30-35 percent by weight of butyl acrylate, 7-9 percent by weight of hydroxyethyl acrylate, 4-6 percent by weight of acrylic acid and has an acid number of about 30-50 and a carboxyl to hydroxyl ratio of 1:

0.4 to 1;

1.5 and the polymer has a weight average molecular weight of about 10,000-50,000.

7. The process of claim 1 in which he atomizing air is heated to 40*C. to 150*C.

8. The process of claim 1 in which the air utilized for the air shroud is bone dry air.

9. The proess of claim 1 in which the spray gun is a hand spray gun.

10. The process of claim 1 in which the spray gun is an automatic spray gun.

11. The process of claim 1 in which the substrate that is painted is steel.