METALLIC PAINTS WITH HIGH HIDING POWER AND ORGANIC BINDER RESIN FOR THESE PAINTS

Abstract

The invention relates to organic binder resins for aqueous coatings, comprising: a) a polymer P1, bearing reactive groups X1: hydroxyl and Y1: carboxyl with an OH number as a weight percentage of OH ranging from 2% to 5% and an acid number IA mg KOH/g of at least 10, said polymer P1 having a mass Mn1 of less than 25 000, and b) a polymer P2 bearing reactive groups X2: hydroxyl with an OH number as a weight percentage of OH ranging from 0.5% to 2.5%, groups Y2: carboxyl with an acid number IA in mg KOH/g<25, and groups Z2 chosen from acetoxy and/or diacetone and said polymer P2 having a mass Mn2 of greater than 500,000.

The invention also relates to a process for preparing said resin, to a metallic coating composition comprising said resin and metallic pigment, and to the use thereof.

Claims

1. An organic binder resin for aqueous coatings comprising: a) a polymer P1, bearing reactive groups X1: hydroxyl and Y1: carboxyl with, respectively, an OH number expressed as weight percentage of OH ranging from 2% to 5%, and an acid number IA expressed in mg KOH/g of at least 10, and said polymer P1 having a number-average molecular mass Mn1 (by GPC in THF with polystyrene calibration) of less than 25 000, b) a polymer P2 bearing reactive groups X2: hydroxyl with an OH number expressed as weight percentage of OH ranging from 0.5% to 2.5%, groups Y2: carboxyl corresponding to an acid number IA expressed in mg KOH/g<25, and groups Z2 chosen from acetoxy and/or diacetone and said polymer P2 having a number-average molecular mass Mn2 of greater than 500,000.

2. The resin as claimed in claim 1, wherein the weight ratio between the polymer P1 and the polymer P2, P1/P2, ranges from 50/50 to 95/5.

3. The resin as claimed in claim 1, wherein said resin is in dispersion in water with a content of solids P1+P2 ranging from 30% to 60%.

4. The resin as claimed in claim 1 wherein said polymer P2 comprises a crosslinking agent bearing at least two hydrazide groups.

5. The resin as claimed in claim 1 wherein said resin is in the form of a mixture of respective aqueous dispersions of the polymers P1 and P2.

6. The resin as claimed in claim 1 wherein said polymer P1 is in the form of an aqueous dispersion without any surfactant or dispersant, having a mean particle size ranging from 50 to 250 nm according to the method ISO 13320.

7. The resin as claimed in claim 1 wherein said polymer P2 is in the form of an aqueous dispersion comprising a surfactant selected from surfactants simultaneously comprising a nonionic structure and an anionic group.

8. The resin as claimed in claim 1 wherein said polymer P1 and said polymer P2 have respective glass transition temperatures Tg1 and Tg2, measured by DSC (10° C./min, two passes), as follows: Tg1 less than or equal to 30° C., Tg2 greater than 30° C.

9. The resin as claimed in claim 1 wherein said polymer P1 and/or said polymer P2 are respective binary mixtures of two copolymers, one of which is more hydrophilic.

10. The resin as claimed in claim 1 wherein said polymer P1 is in the form of a post-dispersion of said polymer after its preparation by solution radical polymerization in organic solvent medium, said polymer being dispersible in aqueous post-dispersion and not comprising any dispersant or surfactant.

11. The resin as claimed in claim 1 wherein said polymer P1 comprises an acrylic copolymer or a styrene-acrylic polymer.

12. The resin as claimed in claim 1 wherein said polymer P1 is a copolymer containing, as monomer units starting with a following overall monomer mixture: a1) at least one C.sub.2-C.sub.4 hydroxyalkyl (meth)acrylate, a2) at least one C.sub.1-C.sub.2 alkyl methacrylate, a3) at least one C.sub.4-C.sub.8 alkyl acrylate, a4) at least one C.sub.10-C.sub.14 alkyl (meth)acrylate monomer, a5) (meth)acrylic acid, and a6) optionally, at least one vinylaromatic monomer.

13. The resin as claimed in claim 1 wherein said polymer P2 is a copolymer in aqueous dispersion obtained by emulsion polymerization.

14. The resin as claimed in claim 1 wherein said polymer P2 is a copolymer containing, as monomer units starting with a following monomer mixture: b1) at least one C.sub.2-C.sub.4 hydroxyalkyl (meth)acrylate, b2) at least one C.sub.1-C.sub.2 alkyl methacrylate, b3) at least one C.sub.4-C.sub.8 alkyl methacrylate, b4) (meth)acrylic acid, b5) at least one from among the following monomers: diacetone acrylamide and/or one from among (meth)acrylate bearing at least one acetoacetate group, and b6) at least one di(meth)acrylate of a C.sub.4-C.sub.8 diol.

15. A process for preparing a resin as claimed in claim 1, said process comprising the following steps: i) preparing polymer P1 as defined in claim 1, comprising solution radical polymerization followed by post-emulsification in aqueous medium to give rise to an aqueous dispersion of said polymer P1, ii) preparing by emulsion polymerization of an aqueous dispersion of polymer P2, as defined in claim 1, and iii) mixing of said aqueous dispersion of said polymer P1 with that of said polymer P2.

16. A coating composition comprising at least one organic binder resin as defined in claim 1.

17. The coating composition as claimed in claim 16, which is a metallic coating composition comprising, in addition to said organic binder resin (P1+P2), at least one metallic pigment with a content of said pigment relative to said dry organic binder (solids) ranging from 15% to 40% by weight.

18. The coating composition as claimed in claim 16, which is an aqueous metallic coating composition with a content of solids P1+P2 ranging from 5% to 30% relative to the weight of said composition.

19. The composition as claimed in claim 16 wherein said metallic pigment is selected from the group consisting of aluminum and copper pigments in the form of flakes.

20. The composition as claimed in claim 16 which is a metallic paint.

21. The composition as claimed in claim 16 which is an aqueous metallic paint with an aluminum pigment as metallic pigment.

22. The composition as claimed in claim 16 further comprising at least one crosslinking agent that is reactive with the hydroxyl groups of said polymer P1 and P2 and selected from the group consisting of melamines, polyisocyanates and carboxylic anhydrides.

23. The coating composition as claimed in claim 16 which is a composition having the reaction behavior of a one-component composition (1k), with, in this case, the crosslinking agent being a melamine or a blocked polyisocyanate, the reaction taking place solely after heating or, according to a second possibility, said coating composition is a composition having the reaction behavior of a two-component composition (2k), with, in this case, the crosslinking agent being a non-blocked polyisocyanate or a carboxylic anhydride, in which case the reaction takes place after mixing with said crosslinking agent.

24. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

Description

EXPERIMENTAL SECTION

1) Starting Materials Used for Synthesis and Application Formulations

[0059] See Table 1 below.

Starting Materials Used

[0060]

TABLE-US-00001 TABLE 1 Commercial Technical ref. Chemical name Supplier function SYNAQUA ® Hydroxylated and ARKEMA Polymer P1 E21011 carboxylated acrylic polymer dispersion ENCOR ® Self-crosslinkable ARKEMA Polymer P2 2171 hydroxylated acrylic emulsion CYMEL ® Methylated melamine ALLNEX Crosslinking 303 LF with a low form- agent aldehyde content TOLONATE ® Blocked aliphatic VENCOREX Crosslinking D2 polyisocyanate agent STAPA IL Aluminum pigment ECKART Pigment HYDROLAN ® paste (weight aluminium 8154 percentage of Al: 60) HYCRYL ® Associative thickener ARKEMA Thickener 0210 DISPERBYK ® Block polymer BYK Wetting 190 dispersant dispersant

[0061] The characteristics of the polymers P1 and P2 used as components of the resin according to the invention are featured in table 2 below.

[0062] Summary of the characteristics of P1 (SYNAQUA E21011) and P2 (ENCOR 2171)

TABLE-US-00002 TABLE 2 Solids OH/resin Carboxyl Acetoxy/ content Tg Ref. Mn (weight %) (mg KOH/g) diacetone (%) (° C.) SYNAQUA ® >2000 3 18 no 45 20 E21011 (P1) and <10000 ENCOR ® 2171 >500000 1.3 12 yes 43 35 (P2)

3) Preparation of the Metallic Paint Formulations

[0063] The overall characteristics of the four formulations tested are given in table 3 below.

Overall Characteristics

[0064]

TABLE-US-00003 TABLE 3 Ref. Characteristic 1 2 3 4 Invention/ inven- compar- inven- compar- comparative tion ative tion ative P1/P2 ratio (by 80/20 100/0 80/20 100/0 dry weight) Crosslinking Melamine Melamine Polyisocyanate Polyisocyanate agent (Cymel ® (Cymel ® (Tolonate ® (Tolonate ® 303 LF) 303 LF) D2) D2) Ratio P1 + 80/20 80/20 — — P2/melamine (by dry weight) NCO/OH mole — — 1.32 1.32 ratio Pigment/binder 0.20 0.20 0.20 0.20 ratio Calculated dry 20.6 20.6 20.6 20.6 extract % Calculated 15.6 15.6 15.6 15.6 GC % pH (ISO 976) 7.8 7.7 7.6 7.7

[0065] Procedure for preparing the metallic paint formulations: in the order indicated according to the following steps A) to E), add compositions 1 to 4 of table 4 below: [0066] A) Add composition 1 and homogenize for 30 min [0067] B) Add composition 2 to composition 1 and homogenize for 15 min [0068] C) Premix composition 3 and then add it to 1+2 and homogenize for 10 min [0069] D) Premix composition 4 and add it to 1+2+3 and then homogenize for 10 min [0070] E) Add composition 5 to 1+2+3+4 and stir for 5 min [0071] F) Add by dispersing components 6, 7, 8 and 9 in the order indicated

Detailed Formulations of Metallic Paints (Weight %)

[0072]

TABLE-US-00004 TABLE 4 References Composition Component 1 2 3 4 1 STAPA IL HYDROLAN ® 5.4 5.4 5.5 5.5 8154 DISPERBYK ® 190 0.6 0.6 0.6 0.6 Butyl glycol 5.0 5.0 5.0 5.0 Dimethyl sulfoxide 1.7 1.7 1.7 1.7 2 Dimethylethanolamine/20% 1.1 1.1 1.1 1.1 HYCRYL ® 0210/10% 4.4 4.4 4.4 4.4 Demineralized water 5.1 5.1 5.1 5.1 3 ENCOR ® 2171 5.3 4.7 Demineralized water 17.2 17.2 17.3 4 SYNAQUA ® E21011 23.7 28.3 18.0 21.5 CYMEL ® 303 LF 3.3 3.3 TOLONATE ® D2 7.9 8.5 Demineralized water 17.2 5 HYCRYL ® 0210/10% 5.0 5.0 5.0 5.0 6 Dimethylethanolamine/20% 0.3 0.3 0.3 0.3 7 Demineralized water 8.0 8.1 8.1 8.1 8 n-Butanol 0.8 0.8 0.8 0.8 9 Demineralized water 13.1 13.3 14.5 15.2 TOTAL 100.0 100.0 100.0 100.0

4) Application Tests and Conditions

[0073] Description of the tests and methods used:

Conditions for Applying the Metallic Paint Formulation

[0074] Bar coater 100 μm [0075] Wet film thickness 100 μm [0076] Test specimens of tinplate type 250*125*0.3 mm (L*I*thickness), type TC100 (Espan Color)

Drying

[0077] 10 min flash at room temperature (23° C.±2° C., RH 50±5%) [0078] Baking for 20 min at 140° C.

Measurements

[0079] Masking power according to the standard ISO 6504 (Minolta CM2600D spectrophotometer) [0080] Gloss at angles of 20°, 60° and 85° (Micro tri gloss glossmeter—Byk/Gardner) in gloss units (gu) according to the standard ISO 2813.

5) Application Results

[0081] Results presented in table 5 below concerning the masking power of the paint.

[0082] Results of measurement of the masking power (ISO 6504) on test formulations 1 to 4

TABLE-US-00005 TABLE 5 Formulation ref. 1 2 3 4 Dry thickness in μm 17 ± 2 17 ± 2 18 ± 2 15 ± 2 (ISO 2808) Masking power (ISO 99.7 95.9 99.6 95.4 6504)

[0083] The gloss results are presented in table 6 below.

Gloss Results (ISO 2813)

[0084]

TABLE-US-00006 TABLE 6 Formulation ref. Background Angle 1 2 3 4 White 20° 27 13 28 5 60° 77 50 78 18 85° 84 69 85 21 Black 20° 24 13 25 4 60° 74 49 75 17 85° 82 66 83 20