JPH01171682A - Method for improving appearance of multilayer finish coating - Google Patents

Abstract

PURPOSE: To form multilayer surface finishes on automobiles or the like by laminating a layer of a guide coating compsn. consisting of an aq. carrier and water contg. a polymeric binder as a medium on a basic primer layer. CONSTITUTION: The aq. medium guide coating compsn. contg. the aq. carrier and the polymeric binder is laminated on the basic primer layer and is then dried without crosslinking and curing. Next, the surface of the guide coating layer is coated with a base coating compsn. consisting of the water as the medium and further, the surface thereof is coated with a clear top coating compsn., following which the coating is completely cured by heating. As a result, the multilayer finish coating films consisting of the guide coating, the base coating and the clear top coating are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved method of forming a layered surface finish on automobiles and trucks.

In particular, the method of the present invention produces a surface finish with improved appearance.

[Conventional technology]

Multi-layer surface finishes, especially clearcoat/basecoat finishes, are suitable for example Benefiel
No. 3,6i, 147 (issued February 1, 1972). in general,
Solvent-based coating compositions have been used to form these multilayer surface finishes.

[Problem that the invention seeks to solve]

Water-based (Water)-based finish coats in combination with either solvent-based or water-based clear coat finishes have been commercially tested to meet recent air quality standards. However, it would be desirable to be able to improve the appearance of waterborne valve-based paint finishes containing metal flake pigments.

In particular, head-on-brightness
It would be desirable if s) could be improved. The present invention provides a method for forming clearcoat/basecoat finishes with a high quality appearance that is acceptable to the automotive industry with a waterborne basecoat composition containing metal flake pigments. An improved method and compositions that can be applied by the method are provided.

[Summary of the invention]

The present invention provides a method for applying a multilayer finish on a substrate having a primer layer adhered thereto, a layer of a waterborne base coating composition containing metal flake pigments, and a layer of a clear top coating composition. Concerning an improved method.

This improved method is as follows.

A layer of an aqueous guide coating composition containing an aqueous carrier and a polymeric binder is applied to the primer layer prior to application of the aqueous base coating composition.

The guide coating is then dried at room temperature or at an elevated temperature without crosslinking or curing of the guide coating. Next, applying a water-based base coating composition to the guide coating, applying a clear top coating composition to the base coating,
The resulting multi-coat is then baked at elevated temperatures to complete the coating. This: Two.

The resulting multi/a finish consisting of a guide coating, base coating and clear top coating on the substrate has an improved appearance.

[Means for solving problems]

The improved method of the present invention is used for improving the appearance of waterborne base coating compositions/clear coating compositions applied to autobases and trucks. In this method, a guide coating is applied over the base primer coating and then dried but not cured. This guide coating can be dried at room temperature, e.g. 20-25°C, taking care not to crosslink the guide coating, or baked for a short time at elevated temperatures below 180°C, or for rapid drying. It can also be exposed to infrared radiation. A water-borne base coating is then applied over the guide coating, followed by applying a NiClear coating composition over the base coating and baking the resulting coated substrate at elevated temperatures to complete the process. The resulting basecoat/clearcoat finish is improved in particular with respect to frontal gloss compared to a clearcoat/colorcoat finish without the guide coating composition. It has a unique appearance.

The guide coating composition is an aqueous based composition containing about 10-75 wt. of a film-forming binder and preferably a crosslinking agent and a pigment.

Typically, an aqueous latex is used as the film-forming binder, preferably an acrylic latex.

An alkylated melamine formaldehyde crosslinking agent can be incorporated into the composition. Any of the conventional pigments used in coating compositions or primers can be used in the core composition.

Typically, the binder of the guide coating composition is an acrylic latex, but other water-dispersible or water-soluble polymers can be used. Latex is prepared using conventional emulsion polymerization methods. This method involves a polymerization catalyst such as ammonium persulfate, water, a surfactant, and usually ammonia or an amine (such as aminoethylpromonol).
Neutralizing agents such as are used. Polymerization is carried out at conventional temperatures of about 50 DEG to 90 DEG C. for about 1 to 5 hours to form a latex.

The polymers used in latexes are alkyl methacrylates, alkyl acrylates, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, and ethylenically unsaturated polymerizable mono- or dicarboxylic acids.

Difunctional acrylates or methacrylates can also be used.

Typical alkyl methacrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, ucryl methacrylate, and the like.

Typical alkyl acrylates are methyl acrylate, ethyl acrylate, polyacrylate, butyl acrylate, hexyl acrylate.

These include octyl acrylate, nonyl acrylate, and acrylic acrylate.

Typical hydroxyalkyl acrylates and methacrylates that can be used include hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and the like.

Typical polymerizable mono- or dicarboxylic acids that can be used are methacrylic acid, acrylic acid, itaconic acid, maleic acid, and the like.

Difunctional monomers that can be used include allyl methacrylate,
Allyl acrylate, and other diacrylates.

One of the preferred latex polymers is 10 to 20 wt%
of methyl methacrylate, 70-80 wt'1 butyl acrylate, 2-9 wt% hydroxyethyl acrylate, and 1-5 wt% methacrylic acid.

The latex itself without a crosslinking agent can be used as a guide coating composition. This has the advantage that the latex is not crosslinked by drying or baking at elevated temperatures.

Generally, the guide coating contains about 5-40 wt% crosslinker based on the weight of the binder. One preferred composition is about 5-30 wt% crosslinker and 70-95 wt%
wt% latex polymer.

Typical monomeric and polymeric alkylated melamine formaldehyde crosslinkers that can be used include partially or highly; dimethylated melamine formaldehyde resins such as '07mel''600 resin, hybrid ethers, and butylated melamine formaldehyde resins or alkyl groups. Other partially or fully (nialkylated) melamine formaldehyde resins having from 1 to 6 carbon atoms in 1 to 6 carbon atoms. One preferred resin is a methylated melamine formaldehyde resin with methoxymethyl-imino functionality. Another preferred resin is "Cymel" 605, a highly semethylated melamine formaldehyde resin containing reactive alkoxy groups.

The guide coating composition can be used as an unpigmented clear, but preferably contains pigment in a pigment to binder weight ratio of about 0.5/100 to 300/100. Generally, the pigment provides additional hiding and is usually the same as the pigment in the base coating composition. Typical pigments used include titanium dioxide, other metal oxides (e.g. zinc oxide and iron oxide), carbon black, organic pigments and dyes, metal flake pigments (
For example, aluminum flakes) filler pigments, silica, etc. Preferably, the composition comprises metal flake pigments,
For example, it contains aluminum flakes. The pigment is formulated into a millbase using conventional processing procedures, and the millbase is then blended with a latex and a crosslinking agent to form the guide coating composition.

The substrates on which the guide coating is applied are those commonly used on car and truck bodies.

Examples include cold rolled steel, phosphate treated steel, polyester reinforced fiberglass, reaction injection molded urethane, and amorphous polyamide.

Typically, these substrates are coated with alkyd resins, epochene resins, or polyester primers.

After the primer is applied to the substrate and cured, the guide coating composition is applied. Any of the conventional application methods can be used, such as spraying or electrostatic spraying. The coating is approximately 2
．． Apply to provide a dry film thickness of 0.1-1.0 mils.

The coating is then dried but not completely cured or crosslinked. The base coating composition is applied by spray or electrostatic spray g.
yields a dry film thickness of ~1.5 mil).

The clear coating composition is applied by spray or electrostatic spray to a dry film thickness of about 0.5 to 6.0 mils. The resulting multi-coat finish is then baked at about 120-175c for about 15 minutes to 1 hour to form a glossy finish with excellent front gloss and good appearance.

The base coating composition can be any of the commonly used compositions such as acrylic or polyester containing crosslinking agents. These compositions may be solvent-based or aqueous solutions or dispersions. The method of the present invention is.

It is particularly useful for waterborne base coatings containing metal flake pigments, resulting in a finish with improved surface gloss. However, improvements are also observed with the use of solvent-based basecoat finishes.

Clear coating compositions are solvent-based or water-based compositions of acrylic or polyester polymers containing crosslinking agents or other types of compositions commonly used as clear coating compositions. A composition may be used.

Guide coating compositions can also be used with two-component basecoat/clearcoat compositions that do not require baking for curing, such as two-component acrylic urethanes, acrylic esters, acrylic alkyds, epoxy esters, and the like. These two-component compositions are used for refinishing automobiles and trucks. Application of the guide coating composition is as described above, followed by application of the two-component base coating composition and clear coating composition and curing at room temperature or forced drying at elevated temperatures.

The following examples specifically illustrate the invention.

All parts and parts are by weight unless otherwise specified.

[Implementation row] A latex M was prepared by filling each of the following raw material components into a polymerization container equipped with a stirrer and a heat source.

Part 1 part by weight deionized water
2535.0 Alkyl Phenol Ethylene 16.4 Years Oxide Anionic Surfactant Portion 2 Anionic Surfactant (as above) 23.
4 Methyl methacrylate monomer 369
0 Butyl methacrylate monomer 1622.
4 Deionized water 2335.0 parts 6 Deionized water 225.0 Ammonium persulfate 7.0 parts 4 Deionized water 1097.07 Ionic surfactant (as described above) 11.7 Methacrylic acid 81.7 Hydroxyethyl acrylate monomer 116.8 Acrylic acid butyl monomer 385.5 parts 5 Yue ionized water 85.0 Ammonium persulfate 2.3 parts 6 Deionized water 451.0 Aminoethylpropanol 60.7 Total 9434.
6. Fill part 1 into a polymerization vessel and heat to about 86°C. Pre-mix part 2. Approximately 10 portions of Portion 2 are added and the resulting reaction mixture is maintained at approximately 80°C. part 6
about 10% of the reaction mixture was added and the reaction mixture was maintained at the above temperature. The remainder of Portion 2 is added along with about 72% of Portion 6 over two 60 minutes while adjusting the reaction mixture to about 85°C. The remainder of Portion 3 is added along with Portion 4 over a period of 30 minutes while adjusting the reaction mixture to 85°C. Add portion 5 and heat the reaction mixture to about 5°C; 60°C.
Hold for a minute. Add portion 6 over 30 minutes and hold at temperature for approximately 1 hour. Chamber the obtained latex! Cool and filter.

pass

The latex has a polymer solids content of 2 suf L4 and...7.
Has 2. The polymer consists of 14.1% methyl methacrylate, 78.0% butyl acrylate, 6.2% methacrylic acid, and 4.5% hydroxyethyl acrylate.

The millbase was prepared as follows.

Part by weight Ethylene glycol heptanobutyl ether 55.1
3. Mixed fatty acid and resin polyoxy 4.
87 Ethylene Ester Total 100.00 Fill two mixing containers with the above ingredients and mix thoroughly.

The following guide coating compositions A-C were formulated.

Deionized water 488.01029.010
29.0 Deionized water 541.0 - -
Dimethylethanolamine 23.4 2
3.4 23.4 sweet ffT 6Ll/2.427
1.42657.4 Guide coating composition A as described above
- each of C was sprayed on a separate phosphated steel panel coated with an epoxy/polyester electrodeposited primer; one of the panels where each composition was sprayed on four separate 77 panels; was dried at room temperature of about 25° C. for about 50 minutes. The second pile was baked at about 40° C. for about 2 minutes (this was enough time to dry the coating but not cure it). The third panel was baked at about 121° C. for about 10 minutes (this was enough time to cure the coating). The fourth panel was baked at 121° C. for approximately '50 minutes (this was sufficient to cure the coating). In each case, the dried guide coating was approximately 0.5 mils thick when dry.

It was.

A base coating is then applied by spraying a layer of Composition A, described above, onto each of the coated panels described above, and the base coating is allowed to dry at room temperature for approximately 10 minutes.
A dry coating of 7μ (0.5 mil) thickness was formed. A clear topcoat was then spray applied and the coated panels were baked at about 120° C. for about 30 minutes to form a clearcoat/basecoat finish.

The clear coating composition described above is comprised of approximately 68%
% solids content. Among the aromatic hydrocarbons, the polymer is styrene/butyl methacrylate/butyl acrylate/acrylic hydroxyethyl/acrylic acid is about 14
．． It has a ratio of 9/28/I C+/25/2.5.

Two control examples of each guide coat PiXA-C on phosphated and primed steel panels were prepared as described above. That is, /Minel was coated with a base coat and a clear coat as described above. However, the guide coating was peeled off. Each nomonel was incubated under the same conditions.

These panels are used as a control example to demonstrate prior art preparation of clearcoat/basecoat finishes.

Front gloss was measured on each of the panels prepared above using the spectrophotometer described in Lee et al., US Pat. No. 4,412,744, issued Nov. 1, 1983. The results are as follows.

Control example (without guide coating) 113
-Guide coating film A 2'X10
4℃ 120 Guide Coating Film A 10'
X121℃ 112 Same guide coating film A as control example 30'X121℃ 11
2 guide coating film B 2'X104℃
124 Guide coating film B 10'X121℃ 11
6 Same guide coating film B as control example 30'X12
1℃ 115 guide coating film C2'X104℃ 1
22 guide coating dc 10'X121℃
120 Guide Coating C30' x 121 DEG C. 120 The above data show that when no guide coating is used (control) the front gloss is significantly lower than with the guide coating. In addition, guide coatings A and B are formed by baking at 121°C for 10' and 121°C for 50'.
When the guide coating is fully cured, the front gloss is substantially lower compared to mere drying or partial curing of the guide coating.

In the case of Guide Coating C, which is an acrylic latex without crosslinking agent, no curing occurs and the desired improvement with the use of this guide coating is that all bakes are observed at temperature.

Patent applicant: 2 people other than E.I. du Pont de Nemoers & Compagnie

Claims (1)

[Claims] 1) Applying a layer of a water-borne guide coating composition containing an aqueous carrier and a polymeric binder to a primer layer of a substrate, without crosslinking or curing the guide coating composition. drying, applying a waterborne base coating composition to the guide coating, applying a clear top coating composition to the base coating, and at an elevated temperature to fully cure the resulting multilayer finish. baking, whereby the resulting multilayer finish consisting of a guide coating, a base coating and a clear top coating on the substrate is characterized by an improved appearance, a primer layer containing metal flake pigments; An improved method for applying a multilayer finish onto a substrate having a layer of a waterborne base coating composition and a layer of a clear coating composition adhered to the base coating. 2) The method of claim 1, wherein the guide coating composition comprises a polymeric latex binder crosslinker and an aqueous carrier. 3) The method of claim 2, wherein the guide coating composition comprises an acrylic polymer latex binder, an alkylated melamine formaldehyde crosslinker, a metal flake pigment, and an aqueous carrier. 4) The method according to claim 3, wherein the acrylic polymer of the latex contains hydroxy groups and carboxy groups. 5) The method of claim 4, wherein the acrylic polymer consists essentially of an alkyl methacrylate, an alkyl acrylate, a hydroxyalkyl methacrylate or a hydroxyalkyl acrylate, and an ethylenically unsaturated carboxylic acid. 6) The method according to claim 5, wherein the acrylic polymer contains a difunctional acrylate or methacrylate. 7) The method of claim 5, wherein the acrylic polymer consists essentially of methyl methacrylate, butyl acrylate, hydroxyethyl acrylate, and methacrylic acid. 8) The method according to claim 7, wherein the acrylic polymer contains allyl methacrylate. 9) The method of claim 1, wherein the guide coating composition is dried at about 20-185°C. 10) The guide coating composition consists of an acrylic polymer latex consisting essentially of an alkyl methacrylate, an alkyl acrylate, a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, and an ethylenically unsaturated carboxylic acid, and an alkylated melamine formaldehyde resin. The method according to claim 2, which comprises a crosslinking agent. 11) The method of claim 1, wherein the guide coating composition comprises a polymer latex and an aqueous carrier. 12) The method of claim 11, wherein the polymer latex comprises an acrylic polymer consisting essentially of an alkyl methacrylate, an alkyl acrylate, a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, and an ethylenically unsaturated carboxylic acid. . 13) applying a layer of an aqueous guide coating composition comprising an aqueous carrier and a polymeric binder to a primer layer of a substrate, drying the composition without crosslinking or curing the guide coating composition; The coating is coated with a room temperature curable waterborne base coating composition, the base coat is coated with a room temperature curable clear top coating composition, and the resulting multilayer finish is fully cured at room temperature. Guide coating on the substrate, base coating,
and a clear top coating, characterized in that the resulting multilayer finish has an improved appearance;
An improved method for applying a multilayer finish onto a substrate having a primer layer, a layer of an aqueous base coating composition containing a metal flake pigment, and a layer of a clear coating composition adhered to the base coating. method. 14) about 10-75 wt% binder and 25-9
0 wt% aqueous carrier, the binder being about 10-20 wt% methyl methacrylate, based on the weight of the polymer, 70-80 wt% based on the weight of the polymer.
t% butyl acrylate, based on the weight of the polymer.
60-95w dispersed acrylic polymer consisting essentially of ~9wt% hydroxyethyl acrylate and 1-5wt% methacrylic acid based on the weight of the polymer.
t%; A guide coating composition consisting essentially of 5 to 40 wt% of an alkylated melamine formaldehyde resin and containing pigment in a pigment to binder ratio of about 0.5/100 to 300/100. 15) from a layer of the guide coating composition of claim 14 deposited on a primer-coated substrate, a pigmented base coating deposited on the guide coating composition, and a clear top layer deposited on the base coating. A primer coated substrate with a cured multi-layer finish. 16) Guide coating is approximately 2.54~25.4μ (
0.1 to 1.0 mils) thick; the base coating is about 5.08 to 38.1 microns (0.2 to 1.5 mils) thick;
and clear top coating approximately 12.7~152
．． 16. The coated substrate of claim 15 having a thickness of 4 microns (0.5 to 6 mils).