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US-12616996-B2 - Methods for coating substrates

US12616996B2US 12616996 B2US12616996 B2US 12616996B2US-12616996-B2

Abstract

Coated substrates, methods of coating substrates, and coatings for substrates are provided. In an exemplary embodiment, a method for coating a substrate includes coating the substrate with a primer to form a primer layer, where the primer comprises a primer conductivity additive, a primer adhesion promotor additive, a primer binder, and primer volatiles. The primer layer is flash dried to reduce the primer volatiles to about 20 weight percent or less. The primer layer is coated with a total color coat layer prior to curing the primer layer, and then the total color coat layer and the primer layer are cured to form a cured substrate coating. The cured substrate coating has a substrate coating percent transmissivity of specified amounts or less at four different wavelength ranges, and the cured primer layer has a primer layer transmissivity less than that of the substrate coating percent transmissivity.

Inventors

  • Michael R. Koerner
  • Hao Huang

Assignees

  • AXALTA COATING SYSTEMS IP CO., LLC

Dates

Publication Date
20260505
Application Date
20210914

Claims (11)

  1. 1 . A method of coating a substrate, the method comprising the steps of; coating the substrate with a primer to form a primer layer, wherein the primer comprises a primer conductivity additive, a primer adhesion promotor additive, a primer binder, and primer volatiles; flash drying the primer layer such that the primer volatiles are present in the primer layer at a concentration of about 20 weight percent or less, based on a total weight of the primer layer, wherein the primer binder is uncured; coating the primer layer with a total color coat layer prior to curing the primer layer; and curing the total color coat layer and the primer layer to form a cured substrate coating having a substrate coating percent transmissivity of: (1) about 0.02 or less at wavelengths of from 280 nm to 400 nm; (2) about 0.10 or less at wavelengths of from 400 nm to 430 nm; (3) about 0.25 or less at wavelengths of 430 nm to 470 nm; and (4) about 0.5 or less at wavelengths of 470 nm to 500 nm, and wherein the primer layer, when cured, has a primer layer percent transmissivity of: (1) about 0.025 to about 0.05 at wavelengths of from 280 nm to 400 nm; (2) about 0.15 to about 0.5 at wavelengths of from 400 nm to 430 nm; (3) about 0.30 to about 1.0 at wavelengths of 430 nm to 470 nm; and (4) about 0.6 to about 2.0 at wavelengths of 470 nm to 500 nm; wherein coating the substrate with the total color coat layer comprises: coating the primer layer with a first color coat comprising a first activation additive to form a first color coat layer prior to curing the primer layer; and coating the first color coat layer with a second color coat that is free of isocyanate to form a second color coat layer prior to curing the first color coat layer, wherein the total color coat layer comprises the first color coat layer and the second color coat layer.
  2. 2 . The method of claim 1 , wherein the first activation additive comprises an isocyanate.
  3. 3 . The method of claim 1 , wherein: the first color coat layer comprises a first binder, the second color coat layer comprises a second binder, and the first binder is the same as the second binder.
  4. 4 . The method of claim 1 , wherein: coating the primer layer with the first color coat comprises coating the primer layer wherein the first color coat comprises a first solvent that is primarily water; and coating the first color coat layer with the second color coat comprises coating the first color coat layer wherein the second color coat comprises a second solvent that is primarily water.
  5. 5 . The method of claim 1 , wherein: curing the total color coat layer and the primer layer comprises crosslinking the primer binder, a first binder, and a second binder.
  6. 6 . The method of claim 1 , wherein: coating the substrate with the primer comprises coating the substrate wherein the substrate comprises a first portion that is primarily plastic, and where the substrate comprises a second portion that is primarily metallic.
  7. 7 . The method of claim 6 , wherein: the second portion of the substrate comprises an e-coating.
  8. 8 . The method of claim 6 , further comprising: flame treating the first portion of the substrate prior to coating the substrate with the primer.
  9. 9 . The method of claim 1 , wherein: curing the total color coat layer and the primer layer comprises curing the primer layer such that the primer layer has a primer layer thickness of from about 3 to about 8 microns when cured.
  10. 10 . The method of claim 1 , wherein: coating the substrate with the primer comprises coating the substrate with wherein the primer comprises a primer pigment, and wherein the primer has a primer pigment to primer binder ratio of 8 or greater, based on a total weight of the primer binder in the primer, and the total weight of the primer pigment in the primer.
  11. 11 . The method of claim 1 , wherein: applying the primer comprises forming the primer layer having a surface conductivity of about 10 5 ohms or greater at a distance of 4.45 millimeters from a central electrode to a plurality of perimeter probes around the central probe.

Description

PRIORITY CLAIM This application is a U.S. National-Stage entry under 35 U.S.C. § 371 based on International Application No. PCT/US21/50230, filed Sep. 14, 2021, which was published under PCT Article 21(2), and which claims priority to U.S. Provisional Patent Application Ser. No. 63/078,704 filed on Sep. 15, 2020, which is incorporated herein by reference. TECHNICAL FIELD The present disclosure generally relates to methods and coatings for substrates, and more particularly relates to methods and coatings for providing a single system including a primer and color coats that may be utilized over both plastic and metallic substrates. BACKGROUND Automobiles and other articles frequently include a variety of different surfaces that require coating. For example, many modern automobile bumpers are primarily plastic, where the body is primarily metallic. However, the same color is desired on both the plastic bumper and the metallic body. Primers for use on plastic materials often include an adhesion promotor additive, because primers without the adhesion promotor additive tend to adhere poorly to the plastic substrate and peel. Metallic substrates often include an electro-deposition coating or “e-coat,” which is an electronically applied coating used for corrosion protection and other purposes. Chemical bonds in the e-coat are susceptible to degraded by ultraviolet and visible light radiation, so overlying coatings should block incoming radiation with wavelengths of about 300 to 500 nanometers. The substrate may be grounded and the applied coatings charged to improve transfer efficiency and produce a more even coating, but plastic components are generally poor electrical conductors. A conductive primer can provide the grounding benefit to plastic components for subsequent layer applications, but this adds another requirement for the primer. The different requirements for different portions of automobiles or other mixed substrates often result in different coating systems for the various coating layers. Production lines for automobiles or other substrates are often designed for specific coating operations. Manufacturers also desire coating operation that utilize short cycle times to control costs. A single coating system that can be used for different portions of a substrate would eliminate the need for separate coating lines for different materials. Therefore, for cost savings, efficiency, and productivity, a single coating line that can be used for different types of substrates is desired. A single coating line that utilizes short cycle times would further speed productivity and efficiency. A single coating process that can be used for substrates with different types of components would also reduce manufacturing space, manpower, inventory, and other resources, because fewer coating process lines would need to be supported. Thinner coats also reduce the cost for the coating material, because less material is used. Historically, a primer layer has included components that provide the e-coat with all the desired protection from electromagnetic radiation, as well as high levels of opacity so the underlying components would be hidden. Darker colors in the overlying color coats tend to provide higher levels of protection from electromagnetic radiation, as well as providing higher levels of opacity for hiding the underlying components. However, a coating system should be able to support the use lighter colors as well as darker colors. Some coating systems do not include a primer, but this requires higher levels of pigmentation in the color coats to provide the desired hiding, and the use of a single coat to provide the desired opacity tends to result in poor flake orientation that is less aesthetically pleasing. Thinner primer coats facilitate wet on wet coating, because thinner primer layers dry faster and run less than thicker primer layers. Water or other solvents in the color coat tend to penetrate into the underlying primer layer, which exacerbates the problem of running when wet on wet coating practices are used. Accordingly, it is desirable to develop coatings for a substrate and methods for coating a substrate that include a plastic portion and a metallic portion, where the different portions may be simultaneously coated. In addition, it is desirable to provide a coating system that balances the desires of (1) a rapid application system using thin primer layers for wet on wet application, (2) good adhesion to a variety of different substrates, (3) conductivity of the coating system, and (4) protection from electromagnetic radiation. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawing and this background. BRIEF SUMMARY Coated substrates, methods of coating substrates, and coatings for substrates are provided. In an exemplary embodiment, a method fo