ONE-COMPONENT COATING COMPOSITION AND SUBSTRATES COATED WITH THE SAME

Abstract

A one-component coating composition comprises a polyester resin, an acrylic resin, and a blocked isocyanate resin, wherein the coat formed from the one-component coating composition has a formaldehyde content of less than 10 ppm. A substrate is coated with the one-component coating composition.

Claims

1. A one-component coating composition comprising a polyester resin, an acrylic resin, and a blocked isocyanate resin, wherein the coat formed from the one-component coating composition has a formaldehyde content of less than 10 ppm.

2. The one-component coating composition of claim 1, wherein the blocked isocyanate resin, the polyester resin, and the acrylic resin are in a weight ratio of 15:85-40:60.

3. The one-component coating composition of claim 1, wherein the polyester resin comprises a mixture of a polyester resin (a) and a polyester resin (b).

4. The one-component coating composition of claim 3, wherein the polyester resin (a) has an acid value of 5 to 20 mgKOH/g and a weight average molecular weight of 10,000 to 50,000.

5. The one-component coating composition of claim 3, wherein the polyester resin (b) has an acid value of 30 to 60 mgKOH/g and a weight average molecular weight of 3,000 to 6,000.

6. The one-component coating composition of claim 1, wherein the acrylic resin comprises a mixture of an acrylic resin (a) and an acrylic resin (b).

7. The one-component coating composition of claim 6, wherein the acrylic resin (a) has a pH value of 8 to 9, and an acid value of 5.5 to 8.5 mgKOH/g and an amine value of 5.6 to 8.4 mgKOH/g.

8. The one-component coating composition of claim 6, wherein the acrylic resin (b) has a pH value of 6 to 7, and an acid value of 2.5 to 6.0 mgKOH/g and an amine value of 0.6 to 2.8 mgKOH/g.

9. The one-component coating composition of any of the preceding claims, wherein the coat formed from the one-component coating composition is substantially free of formaldehyde.

10. A coated substrate, comprising: (i) a substrate, and (ii) a one-component coating composition deposited on at least a portion of the substrate, the one-component coating composition comprising a polyester resin, an acrylic resin, and a blocked isocyanate resin, wherein the coat formed from the one-component coating composition has a formaldehyde content of less than 10 ppm.

11. The coated substrate of claim 10, wherein the substrate comprises an automotive body.

Description

EXAMPLE

[0034] The following examples are provided to further illustrate the invention, which should not be considered as limiting the invention to the details as described therein. All parts and percentages in the examples and throughout the description are by weight unless otherwise indicated.

[0035] Preparation of Coating Compositions

Example 1

[0036] Each component and its amount for preparing the one-component coating composition of Example 1 is shown in Table 1 below and the coating composition is prepared according to the following procedure:

[0037] Aluminum paste is premixed with a solvent and polyester resin.sup.2, and dispersed for 30 mins for ready-to-use;

[0038] Polyester resin.sup.1, two acrylic resins and a cross-linking agent are mixed and adjusted to a pH value above 8.0, to which a substrate wetting agent, a leveling agent, and a defoamer are added with stirring. The mixture is stirred for 30 mins, and a cosolvent is added with stirring and mixed for 1 hr;

[0039] The pigment paste is added with stirring and mixed for 30 mins; and

[0040] Previously premixed aluminum paste is added and stirred for 30 mins to produce the coating composition of the present Example.

Comparative Example 1

[0041] Each component and its amount for preparing the one-component coating composition of Comparative Example 1 is shown in Table 1 below and the coating composition is prepared according to the following procedure:

[0042] Aluminum paste is premixed with a solvent and an amino resin, and dispersed for 30 mins for ready-to-use;

[0043] Polyester resin and acrylic resin are mixed and adjusted to a pH value above 8.0, to which a substrate wetting agent, a leveling agent, and a defoamer are added with stirring. The mixture is stirred for 30 mins, and then a cosolvent is added with stirring and mixed for 1 hr;

[0044] The pigment paste is added with stirring and mixed for 30 mins; and

[0045] Previously premixed aluminum paste is added and stirred for 30 mins to produce the coating composition of the Comparative Example.

TABLE-US-00001 TABLE 1 Formulation of Example's and Comparative Example's coating compositions Example 1 Comparative (wt %*) Example 1 (wt %) Polyester Resin .sup.1 15 17 Polyester Resin .sup.2 2 0 Acrylic Resin .sup.3 15 15 Acrylic Resin .sup.4 15 15 Cross-linking agent.sup.5 7 Cross-linking agent .sup.6 7 Pigmented Filler.sup.7 15 15 Adjuvant.sup.8 2 2 Solvent.sup.9 10 10 Water 19 19 Total 100 100 *based on the total weight of the coating composition (g): .sup.1 Polyester Resin VSM6299W/42WA, supplied by allnex, .sup.2 Polyester Resin SETAL 6306 SS 60, supplied by Nuplex, .sup.3 Acrylic Resin Setaqua 6802, supplied by Nuplex, .sup.4 Acrylic Resin Setaqua 6803, supplied by Nuplex, .sup.5Amino Resin RESIMENE 741 (Pentamethoxymethyl melamine formaldehyde resin), supplied by INEOS, .sup.6 Blocked Isocyanate BL2794, supplied by Bayer, .sup.7Aluminum Paste STAPA IL HYDROLAN VP57510/G, supplied by Eckart; water-borne black paste and water-borne blue paste, supplied by PPG, .sup.8Substrate Wetting Agent BYK349, supplied by BYK; Defoamer Surfyl-tg, supplied by Gas Chemical, .sup.9Sovlent - ethylene glycol monobutyl ether, propylene glycol methyl ether, and butanol.

[0046] Process for Preparation of the Coat:

[0047] Firstly, a water-borne basecoat (1225A from PPG a water-borne light grey basecoat) is applied to an electrophoresis plate substrate, which is subjected to flash-drying, dehydration, and baking (150 C., 30 mins) to produce a basecoat plate. Then, the water-borne color paints of Example 1 and Comparative Example 1 are applied to the basecoat plate, flash-dried, dehydrated (80 C., 5 mins), and cooled to room temperature. Finally, a clear coat (CC2000 1K from PPG, solvent-based high-tech finish varnish) is spray-coated, flash-dried, and baked at 140 C. for 30 mins, to produce coated substrates. The coated substrates are tested for the following performance.

[0048] Performance Tests

[0049] 1. Result Comparison of Formaldehyde Content Test for Wet Paints

[0050] The formaldehyde content is measured according to GB/T23993-2009 (measurement of formaldehyde content in a water-borne coating) by using an acetylacetone spectrophotometric method. Formaldehyde in the sample is distilled out via a distillation process. Formaldehyde in the fraction will react with acetylacetone with heating in an acetic acid-ammonium acetate buffering solution of pH 6.0 to generate a stable yellow complex. After cooling, absorbance is measured at 412 nm. The formaldehyde content in the sample is calculated based on the standard working curve.

TABLE-US-00002 TABLE 2 Formaldehyde Content Comparision between the Invention Example and Comparative Example Sample Plate Formaldehyde Content Example 1 7 ppm Comparative Example 1 1200 ppm

[0051] From the result comparison of formaldehyde content test above, it is observed that the coat formed from the one-component coating composition of the Invention Example 1 has a formaldehyde content far less than that of the coat formed from the coating composition of Comparative Example 1 using melamine formaldehyde as the cross-linking agent.

[0052] 2. Appearance Comparison

[0053] For comparing the appearance, a robot spinning cup atomizer is used to stimulate on-site spray coating. The appearance data are obtained by measurements via a BYK wavescan.

TABLE-US-00003 TABLE 3 Appearance Data Comparison between Invention Example and Comparative Example Basecoat Formula DOI LW SW H Example 1 85 4 18 Comparative Example 1 85 4 19 V Example 1 84 6.6 22 Comparative Example 1 84 7 22 Remark: H: representing horizonal sample plate which maintains horizontal during spray coating and baking; V: representing vertical sample plate which maintains vertical during spray coating and baking; DOI: representing clarity and brightness of images reflected on the surface of the paint film; LW and SW: representing long wave and short wave, respectively, a technical indicator for showing the state of ripple on the paint film surface in an Orange Peel instrument.

[0054] It is observed from the appearance data above that the coat formed from the one-component coating composition of the Invention Example 1 has appearance data substantially consistent with those of the coat formed from the coating composition of Comparative Example 1.

[0055] 3. Other Properties' Comparisons between Invention Example 1 and Comparative Example 1

[0056] According to the Table below, the coating compositions of Example 1 and Comparative Example 1 are tested for the following properties and results are shown in Table 4 below.

TABLE-US-00004 TABLE 4 Comparisons of Various Properties Comparative Testing Items Testing Description Testing Method Example 1 Example 1 Hardness Pencil Hardness H GB/T 6739 H H Adhesion Rating 0-1, no considerable GB/T 9286 0 0 difference between wet grinding zone and non-grinding zone (cross hatch) Impact Resistance 20 kg .Math. cm GB/T1732 >30 >30 Cup Drawing 3 mm GB/T 9753 6 6 Stone-striking Superior over 5B ASTM3170 5A 5A Resistance Gasoline Inserting sample into 97# GB/T1734 Pass Pass Resistance gasoline for 4 hr at room temperature; no defects including softening, blistering, gloss loss, peeling, and color-changing on the coat surface at 1 hr after being taken out Fuel Resistance Inserting sample into 0# diesel GB/T 9265 Pass Pass for 4 hr at room temperature; no defects including softening, blistering, gloss loss, peeling, and color-changing on the coat surface at 1 hr after being taken out Gasoline-wiping Same above, no undue GB/T1734 Pass Pass Resistance blushing in zones wiped by 97# gasoline Humidity Exposing sample for 96 hr in a GB/T 1740 Pass Pass Resistance closed chamber at a temperature of 47 1 C. and relative humidity of 96 2%, no defects including softening, blushing, blistering, gloss loss, peeling, and color-changing on the coat surface at 1 hr after being taken out, Composite Rating: GB 1 adhesion: rating 1 Water Resistance Dipping sample for 96 h at GB/T 5209 Pass Pass 40 2 C., appearance showing no blistering, wrinkling, adhesion: rating 0-1 Alkaline Inserting sample into an GB/T 9265 Pass Pass Resistance alkaline liquor for 4 hr at room (0.1 mol/L temperature; no defects NaOH) including softening, blistering, gloss loss, peeling, and color-changing on the coat surface at 1 hr after being taken out Acid Resistance Inserting sample into an acid GB/T 9265 Pass Pass (0.05 mol/L liquor for 4 hr at room H.sub.2SO.sub.4) temperature; no defects including no paste, floating, no speckle, blistering, gloss loss, on the coat surface at 1 hr after being taken out Salt-fog 1000 h GB/T 1771 Pass Pass Resistance 1. Single-side expanded corrosion <2 mm, no defects including rusting, blistering, cracking, flaking, bronzing in other zones; adhesion and hardness remaining no reduction in 1 hr of the salt-fog test; 2. Pitting corrosion or structural damage caused by rusting should not occur in five years (200,000 Km) for use in the South area of the Yangtze River Resistance to Exposure time 1500 h; GB/T 1865 Pass Pass Accelerated Composite rating including Ageing cracking, blistering, wrinkling, bronzing: GB 1; Adhesion, rating 1gloss loss 20%; Hardness HB; Impact Resistance 20 kg .Math. cm

[0057] It is observed from the Table above that the one-component coating composition of the present invention is comparable to the coating composition of the Comparative Example in various properties, but the formaldehyde content thereof is far below that of the Comparative Example.

[0058] Although particular aspects of this invention have been explained and described above, it will be evident to those skilled in the art that numerous variations and modifications to the present invention may be made without departing from the scope and spirit of the present invention. Therefore, the appended claims are intended to encompass these variations and modifications falling within the present invention.