Process for the preparation of powder coatings

A technology of powder coating and coating, which is applied in the direction of powder coating, coating, and thin material treatment, and can solve problems such as low efficiency, loss of technical performance of coating, and difficulty in control

Inactive Publication Date: 2007-12-05
EI DU PONT DE NEMOURS & CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Adjust gloss to the desired level by using matting agents such as waxes, silica, glass beads and crystallized resins, and by using dry blends of chemically incompatible powders, or by using different process operating conditions , such as different curing conditions, are often difficult to control or inefficient, or often cause the coating to lose some technical properties

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0052] Unirradiated UV powder coating composition

[0053] 1.1 A preparation method of a transparent coating composition: 97 wt % of Uvecoat ® 1000 (UCB Surface Specialties), a kind of unsaturated polyester with methacrylate groups, 2 wt % of Irgacure ® 2959 as a photoinitiator (Ciba) and 1 wt % Powdermate(R) EX-486 (Troy Chemical Company) as a flow additive was dry blended.

[0054] After each component is mixed in the mixer, the coating composition is further extruded in a twin-screw extruder, and the extruder is set at a temperature of 110-120°C. After extrusion, the molten composition is cooled on a cooling belt and the resulting product is correspondingly pressed into small tablets. The flakes are then milled and sieved to achieve a typical particle size distribution suitable for electrostatic spraying: 5-120 μm.

[0055] 1.2 A preparation method of a transparent coating composition: dry mix 88.5 wt % of Uvecoat ® 1000 (UCB Surface Specialties), a kind of unsaturated ...

Embodiment 2

[0059] Irradiated IV Powder Coating Compositions

[0060] The irradiated powder coating was prepared using the same powder formulation as previously described in Example 1.1. A powder coating sample (100 g) was carefully charged into a powder sieve (150 μm mesh opening) equipped with a mechanical stirrer. After the agitator is activated, the powder begins to flow intermittently through the screen into the plastic tank receiver located on the ground. The distance between the screen and the receiver was set at 100 cm. To irradiate the powder, a UV lamp was installed between the powder screen and the receiver, at half the distance (50 cm) between the screen and the receiver. The distance between the UV lamp and the center of the passing powder (calculated from the center of the sieve) was fixed at 12 cm. To provide safety, the powder area is isolated from the UV source with an additionally installed quartz plate. The time required to fully complete the powder coating charge...

Embodiment 3

[0063] UV powder coating composition according to the invention

[0064] Powder coating samples formulated and processed as previously described in Example 1.1 and Example 2 were mixed in a ratio of 25:75, respectively. The resulting powders were thoroughly mixed and applied using a laboratory mixer. With an electrostatic spray gun, the powder was sprayed on a metal plate coated with a black cationic electrodeposition primer to a film thickness of 80 μm. The sprayed powder pattern was heated at 120°C for 10 minutes using a combination of IR and convective heating. The hot metal plate with the fused powder coating was then UV cured by means of a medium pressure Hg lamp (melting 240 W / cm radiation source, the strongest operating wavelength region is 200-390 nm). The UV dose for the curing step should be adjusted so that the coating is fully cured; typically, the UV dose is about 3000mJ / cm 2 .

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Abstract

The invention relates to a process of preparation of powder coating compositions providing a desired gloss level of the resulted coatings comprising the following steps of a) providing particles of at least one powder coating composition having a number average particle size in the range of 1 to 300 mum, and b) mixing these particles with particles of at least one powder coating composition having a number average particle size in the range of 1 to 300 mum, the particles of which are irradiated with high energy radiation under near-ambient temperature, in a mixing ratio of 1:99 to 99:1; the process according to the invention provides powder coating compositions producing a desired gloss level of the coatings by varying the time period and / or the intensity of the high energy irradiation of the powder coating particles or by varying the mixing ratio between the non-irradiated powder particles and the irradiated powder particles.

Description

technical field [0001] The invention relates to a method for preparing a powder coating composition, wherein the coating has different gloss effects on different substrates. Background technique [0002] Powder coatings that can be cured by ultraviolet (UV) light have been in development for many years. Typically, these compositions contain a binder resin having ethylenically unsaturated groups and a photoinitiator specifically for initiating photopolymerization. This makes it possible for the above compositions to cure in a very short time, improving quality and productivity at low operating and equipment costs. [0003] Adjust gloss to the desired level by using matting agents such as waxes, silica, glass beads and crystallized resins, and by using dry blends of chemically incompatible powders, or by using different process operating conditions , such as different curing conditions, are often difficult to control or inefficient, or often cause the coating to lose some te...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C09D5/03
CPCC09D5/032Y10T428/31504C09D5/031
Inventor O·H·德克M·乌尔夫U·维尔肯赫纳
Owner EI DU PONT DE NEMOURS & CO
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