COATING COMPOSITION WITH ANTICORROSION EFFECT

Abstract

The present invention relates to a coating composition comprising at least one binder (A) comprising at least one polymeric resin (A1) and at least one crosslinking agent (A2), at least one anticorrosion pigment (B), and at least one organic solvent (C), where (B) is an alloy of Zn and Mg and optionally at least one further metal and/or semimetal, the coating composition having a pigment volume concentration (PVC) in a range from 5.0% to 25.0%, and comprising the anticorrosion pigment (B) in an amount in a range from 5.0 to 25.0 wt %, based on the total weight of the coating composition, to the use thereof for the at least partial coating of a metallic substrate with a primer coat, to a method for the at least partial coating of such a substrate with such a primer coat, to a substrate at least partially coated therewith, and to a component or article produced from such a substrate.

Claims

1: A coating composition, comprising: at least one binder (A) comprising at least one polymeric resin (A1) and at least one crosslinking agent (A2), at least one anticorrosion pigment (B), and at least one organic solvent (C), and optionally at least one further component (D), wherein the anticorrosion pigment (B) is an alloy of zinc and magnesium and optionally at least one further metal and/or semimetal, and comprises zinc in an amount of at least 70 wt %, magnesium in an amount of at least 20 wt %, and the optionally present at least one further metal and/or semimetal in an amount of at most 10 wt %, based in each case on the total weight of the anticorrosion pigment (B), where the amounts in % by weight of zinc, of magnesium, and of the optionally present at least one further metal and/or semimetal that are present in the anticorrosion pigment (B) add up in total to 100 wt %, wherein the coating composition has a pigment volume concentration (PVC) in a range from 5.0% to 25.0%, and wherein the coating composition comprises the anticorrosion pigment (B) in an amount in a range from 5.0 to 25.0 wt %, based on the total weight of the coating composition.

2: The coating composition as claimed in claim 1, wherein the coating composition has a pigment volume concentration (PVC) in a range from 5.0% to 20.0%.

3: The coating composition as claimed in claim 1, wherein the coating composition comprises the anticorrosion pigment (B) in an amount in a range from 5.0 to <20.0 wt %, based on the total weight of the coating composition.

4: The coating composition as claimed in claim 1, wherein the relative weight ratio of the anticorrosion pigment (B) to further, different pigments and fillers optionally present in the coating composition is in a range from 25:1 to 1:5.

5: The coating composition as claimed in claim 1, wherein the relative weight ratio of the at least one binder (A), based on the solids fraction of the binder (A) in the coating composition, and of the at least one anticorrosion pigment (B) in the coating composition to one another is in a range from 5:1 to 1.5:1.

6: The coating composition as claimed in claim 1, wherein the anticorrosion pigment (B) is an alloy of zinc and magnesium and optionally at least one further metal and/or semimetal, and comprises zinc in an amount in a range from 70 wt % to 80 wt %, magnesium in an amount in a range from 20 wt % to 30 wt %, and the optionally present at least one further metal and/or semimetal in an amount in a range from 0.1 to 8 wt %, based in each case on the total weight of the anticorrosion pigment (B), and the amounts in weight % of zinc, of magnesium, and of the optionally present at least one further metal and/or semimetal that are present in the anticorrosion pigment (B) adding up in total to 100 wt %.

7: The coating composition as claimed in claim 1, wherein at least 70 to 100 mol % of the further metal and/or semimetal present in the anticorrosion pigment (B) are selected from the group consisting of Li, Ce, Be, Y, Ti, Zr, Cr, Mn, Fe, Cu, B, Al, Si, and Sn, and also mixtures thereof.

8: The coating composition as claimed in claim 1, wherein the anticorrosion pigment (B) is platelet-shaped and has an average particle size D.sub.50 in the 1 to 50 m range and an average platelet thickness in the range from 50 to 750 nm.

9: The coating composition as claimed in claim 1, wherein the binder (A) comprises at least one polymeric epoxy resin (A1) and at least one crosslinking agent (A2) having at least functional amino groups.

10: The coating composition as claimed in claim 1, wherein the binder (A) comprises at least two different polymeric epoxy resins (A1) and/or at least two different crosslinking agents (A2) having at least functional amino groups.

11: The coating composition as claimed in claim 1, wherein the at least one crosslinking agent (A2) has functional silane groups.

12. (canceled)

13: A method for the at least partial coating of a metallic substrate with a primer coat, the method comprising: (1) at least partly contacting the metallic substrate with the coating composition as claimed in claim 1.

14: A method for the at least partial coating of a substrate with a multicoat paint system, the method comprising: (1) at least partly contacting the metallic substrate with the coating composition as claimed in claim 1 for the at least partial application of a primer coat to the substrate, and (2) applying a topcoat to the primer coat applied during (1).

15: A metallic substrate at least partially coated with the coating composition as claimed in claim 1.

Description

INVENTIVE AND COMPARATIVE EXAMPLES

[0123] Unless otherwise noted, the amounts in parts are parts by weight, and the amounts in percent are in each case percentages by weight.

1. Preparation of Inventive Coating Compositions

1.1 Preparation of a Crosslinker Composition H

[0124] The components listed in table 1 below are combined in the stated order at a temperature in the range of 18-23 C. with stirring to prepare the crosslinker composition H.

TABLE-US-00001 TABLE 1 Crosslinker composition H Components for Amount of Solids fraction preparing crosslinker component of component in composition H in H [wt %] H [wt %] 1 Aradur 3204 XW29 51.55 12.89 2 Aradur 115 BD 4.6 4.6 3 Cardolite NC 562 24.8 16.12 4 Ancamine K54 0.2 0.2 5 3-Methoxypropanol 6 6 Isobutanol 3.75 7 Xylene 7.5 8 Diethylenetriamine 0.6 0.6 9 Solvent naphtha 1 160/180 Aradur 3204 XW29 is a commercially available solution of a polyamine adduct from Huntsman. It has a solids fraction of 25 wt %, based on its total weight. Aradur 115 BD is a commercially available polyamidoimidazoline from Vantico, with a solids fraction of 100 wt %. Cardolite NC 562 is a commercially available phenalkamine adduct from Cardolite. It has a solids fraction of 65 wt %, based on its total weight. Ancamine K54 is a commercially available accelerator from Air Products, containing 2,4,6-tri(dimethyl-aminomethyl)phenol. Diethylenetriamine acts as a crosslinking agent.

[0125] The crosslinker composition H has a nonvolatile fraction of 34.41 wt %.

1.2 Preparation of Paint Base Compositions S1, S2, S3, S4, and S5

[0126] The components listed in table 2 below are combined in the stated order at a temperature in the range of 18-23 C. with stirring to give the respective paint base composition.

TABLE-US-00002 TABLE 2 Paint base compositions Components for producing the respective paint base composition S1 S2 S3 S4 S5 1 Araldite EPN X 80/wt % 40 40 40 40 40 2 Araldite DY 3601/wt % 10 10 10 10 10 3 Disperbyk 161/wt % 0.5 0.5 0.5 0.5 0.5 4 Aerosil 972 V/wt % 1 1 1 1 1 5 Sipernate P 820 A/wt % 1 1 1 1 1 6 Sikron SF600 15 7 KP1/wt % 34.5 19.5 8 KP2/wt % 16.4 31.0 9 TiO.sub.2/wt % 10 10 1.0 10 Talc/wt % 9.6 5.6 11 Calcium carbonate/wt % 6.0 12 Black iron oxide 0.4 pigment/wt % 13 Barium sulfate/wt % 6.0 14 Methyl isobutyl 3.4 3.4 ketone/wt % 15 Methoxypropanol/wt % 3.4 3.4 3.4 16 Cyclohexanone/wt % 2.5 2.5 2.5 17 Isobutanol/wt % 3.5 3.5 3.5 3.5 3.5 18 Xylene/wt % 3.7 3.7 3.7 3.7 3.7 19 Butyl glycol acetate/wt % 0.9 0.9 0.9 0.9 0.9 20 Plastopal EBS 400/wt % 0.6 0.6 0.6 0.6 0.6 21 Byk 325/wt % 0.4 0.4 0.4 0.4 0.4 22 Dow Corning Z 6040/wt % 0.5 0.5 0.5 0.5 0.5 Araldite EPN X 80 (DEN 438-X80) is a polymeric epoxy resin from Dow Chemicals. It has a solids fraction of 80 wt %, based on its total weight. The remaining 20 wt % is xylene. Araldite DY 3601 is a polypropylene glycol-based epoxy resin from Dow Chemicals and has a solids content of 100 wt %. Disperbyk 161 is a commercially available dispersant from Byk with a solids content of 30 wt %. Aerosil 972 V is a commercially available hydrophobized fumed silica from Evonik, with a density of 2.7 g/cm.sup.3. Sipernate P 820 A is a commercially available filler from Evonik, with a density of 2.7 g/cm.sup.3. Sikron SF600 is an SiO.sub.2-based, ultrafinely ground product from Quarzwerke Group, with a density of 2.7 g/cm.sup.3. Plastopal EBS 400 is a commercially available urea-formaldehyde resin from BASF, with a solids content of 60 wt %. Byk 325 is a commercially available flow control assistant from Byk, with a solids content of 52 wt %. Dow Corning Z 6040 is based on glycidyloxypropyltrimethoxysilane.

[0127] The pigments and fillers usedTiO.sub.2, talc, calcium carbonate, black iron oxide pigment, and barium sulfateeach have a density of 4.5 g/cm.sup.3.

[0128] KP1 is a composition which comprises an inventively employed anticorrosion pigment (B). KP1 contains 90.5 wt %, based on the total weight of KP1, of the anticorrosion pigment (B), 4.5 wt % of xylene, and 5.5 wt % of Terlitol. Terlitol (white spirit) is a commercially available solvent mixture. The anticorrosion pigment (B) contains about >20 wt % magnesium and >70 wt % zinc. The anticorrosion pigment (B) further contains at least Si as further metal and/or semimetal, in an amount <1 wt %. The density of the anticorrosion pigment (B) is 4.4 g/cm.sup.3.

[0129] KP2 is a composition which comprises an inventively employed anticorrosion pigment (B). KP2 contains 87 wt %, based on the total weight of KP2, of the anticorrosion pigment (B), and 13 wt % of Terlitol. Terlitol (white spirit) is a commercially available solvent mixture. The anticorrosion pigment (B) contains >20 wt % magnesium and >70 wt % zinc. The anticorrosion pigment (B) further contains at least Si as further metal and/or semimetal, in an amount <1 wt %. The density of the anticorrosion pigment (B) is 4.4 g/cm.sup.3.

1.3 Preparation of Paint Base Compositions S6, S7, S8, S9, and S10

[0130] The components listed in table 3 below are combined in the stated order at a temperature in the range of 18-23 C. with stirring to give the respective paint base composition.

TABLE-US-00003 TABLE 3 Paint base compositions Components for producing the respective paint base composition S6 S7 S8 S9 S10 1 Araldite EPN X 80/wt % 40 40 40 40 24.70 2 Araldite DY 3601/wt % 10 10 10 10 6.20 3 Disperbyk 161/wt % 0.5 0.5 0.5 0.5 0.30 4 Aerosil 972 V/wt % 1 1 1 1 0.61 5 Sipernate P 820 A/wt % 1 1 1 1 0.61 6 KP1/wt % 6.0 14.0 28.0 58.0 7 TiO.sub.2/wt % 10 10 8 Talc/wt % 9.6 9.6 9.6 4.0 9 Calcium carbonate/wt % 6.0 6.0 6.0 10 Black iron oxide 0.4 0.4 pigment/wt % 11 Barium sulfate/wt % 6.0 2.40 12 Methoxypropanol/wt % 3.4 3.4 3.4 3.4 2.10 13 Cyclohexanone/wt % 2.5 2.5 2.5 2.5 1.5 14 Isobutanol/wt % 3.5 3.5 3.5 3.5 2.2 15 Xylene/wt % 3.7 3.7 3.7 3.7 2.3 16 Butyl glycol acetate/wt % 0.9 0.9 0.9 0.9 0.56 17 Plastopal EBS 400/wt % 0.6 0.6 0.6 0.6 0.37 18 Byk 325/wt % 0.4 0.4 0.4 0.4 0.25 19 Dow Corning Z 6040/wt % 0.5 0.5 0.5 0.5 0.30

1.4 Preparation of Inventive Coating Compositions Z1, Z2, Z3, Z4, Z5, and Z6, and of Comparative Coating Compositions V1, V2, V3, and V4

[0131] 73 parts by weight in each case of the crosslinker composition H are added to 100 parts by weight of each of the paint base compositions S1, S2, S3, S4, and S5, prior to the respective application to a substrate, with stirring and at a temperature in the range of 18-23 C., to give the coating compositions Z1, Z2, Z3, Z4, and V1.

[0132] 70 parts by weight in each case of the crosslinker composition H are added to 100 parts by weight of each of the paint base compositions S6, S7, S8, and S9, prior to the respective application to a substrate, with stirring and at a temperature in the range of 18-23 C., to give the coating compositions Z5 and Z6 and also V2 and V3.

[0133] 50 parts by weight of the crosslinker composition H are added to 100 parts by weight of the paint base composition S10, prior to the respective application to a substrate, with stirring and at a temperature in the range of 18-23 C., to give the coating composition V4.

TABLE-US-00004 TABLE 4 gives a corresponding overview: Amount of anticorrosion Coating Paint base Crosslinker PVC pigment (B) composition component composition [%] .sup.# [wt %] * Z1 S1 (100 H (73 parts 10.43 18.06 (inventive) parts by by weight) weight) Z2 S2 (100 H (73 parts 13.10 10.20 (inventive) parts by by weight) weight) V1 (not S3 (100 H (73 parts 10.29 inventive) parts by by weight) weight) Z3 S4 (100 H (73 parts 9.78 8.25 (inventive) parts by by weight) weight) Z4 S5 (100 H (73 parts 9.31 15.59 (inventive) parts by by weight) weight) V2 (not S6 (100 H (70 parts 10.44 inventive) parts by by weight) weight) V3 (not S7 (100 H (70 parts 10.32 3.19 inventive) part by by weight) weight) Z5 S8 (100 H (70 parts 10.17 7.45 (inventive) parts by by weight) weight) Z6 S9 (100 H (70 parts 9.92 14.91 (inventive) parts by by weight) weight) V4 (not S10 (100 H (50 parts 21.31 35.0 inventive) parts by by weight) weight) * The amount of anticorrosion pigment (B) reported in weight % is based in each case on the total weight of the respective coating composition. .sup.# Where no specific densities have been reported for the individual components relevant to the calculation of the PVC, the calculation is based on a density of 1.0 g/cm.sup.3 for each of these components.

[0134] Comparative coating composition V4 is a comparative example as per WO 2014/029779 A2 and WO 2014/029781 A2 (cf. basecoat as per table on page 45 of WO 2014/029781 A2 or as per the table on pages 40 and 41 of WO 2014/029779 A2): the coating compositions described therein in each case contain >25 wt % of the anticorrosion pigment described therein (and also have a PVC>25%), based on the respective coating composition.

2. Production of Coated Substrates Using One of the Inventive or Comparative Coating Compositions

[0135] One of the coating compositions Z1 to Z6 or one of the comparative coating compositions V1 to V4 is applied in each case as a primer coating on a metal panel substrate made from a commercially available aluminum alloy (EN AW 2024, substrate T1). Each of the compositions Z1 to Z6 or V1 to V4 is applied directly after its above-described preparation as a primer coat on each substrate.

[0136] The metal panels employed have a total area of approximately 70 cm.sup.2. Each panel was pretreated by means of tartaric-sulfuric acid anodizing (TSA) as per DIN EN 4704 (date: May 2012).

[0137] One of the inventive coating compositions Z1 to Z6 is applied to one side of each substrate (T1) by spraying using a spray gun. The dry film thickness is 20-25 m in each case. This is followed by drying through storage over 24 hours at 15-25 C.

[0138] Subsequently, a topcoat is applied to each of the resulting coated substrates, in a dry film thickness of to 80 m, to give the coated panels T1Z1, T1Z2, T1Z3, T1Z4, T1Z5, and T1Z6, and also T1V1, T1V2, T1V3, and T1V4. The topcoat is applied using in each case the commercial product Glasurit from the 68 line (RAL 9010), a two-component polyurethane-based topcoat material. Subsequent drying or curing took place by means of storage of the coated panels for a time of 7 days at 15-25 C.

3. Investigation of the Adhesion Properties and Corrosion Prevention Effect on the Coated Substrates

[0139] Investigations are carried out on the substrates T1Z1, T1Z2, T1Z3, T1Z4, T1Z5, and T1Z6, and also T1V1, T1V2, T1V3, and T1V4, coated with one of the coating compositions Z1 to Z6 and V1 to V4, respectively.

[0140] All of the tests below were carried out in accordance with the methods of determination specified above. Each value in table 5a and 5b, in which the respective results are summarized, is the average from a double or triple determination.

TABLE-US-00005 TABLE 5a Adhesive Adhesive Coated strength strength substrate Adhesion.sup.1 Adhesion.sup.2 [N/mm.sup.2].sup.3 [N/mm.sup.2].sup.4 T1Z1 0 1 2.80 3.10 T1Z2 0 0 3.40 3.60 T1V1 0 0 3.50 5.03 T1Z3 0 0 2.86 4.11 T1Z4 0 0 3.09 3.66 .sup.1Evaluation of adhesion between coating and topcoat by cross-cut test prior to constant humidity testing .sup.2Evaluation of adhesion between coating and topcoat by cross-cut test after constant humidity testing .sup.3Adhesive strength in [N/mm.sup.2] prior to constant humidity testing .sup.4Adhesive strength in [N/mm.sup.2] after constant humidity testing

TABLE-US-00006 TABLE 5b Coated substrate Adhesion.sup.1 Adhesion.sup.2 Adhesion.sup.3 T1V2 0 0 4.04 T1V3 0 0 5.48 T1Z5 0 0 5.54 T1Z6 0 0 4.46 T1V4 1 5 * .sup.1Evaluation of adhesion between coating and topcoat by cross-cut test prior to constant humidity testing .sup.2Evaluation of adhesion between coating and topcoat by cross-cut test after constant humidity testing .sup.3Adhesive strength in [N/mm.sup.2] after constant humidity testing * Delamination of the topcoat from the coated substrate is observed.

[0141] As can be seen from table 5b, with a comparative coating composition V4 (as per WO 2014/029779 A2 and WO 2014/029781 A2), with a comparatively high pigment content in terms of anticorrosion pigment described therein, of >25 wt %, and with a PVC>25%, after the constant humidity testing has been carried out, it is no longer possible to observe sufficient adhesion of the topcoat on the substrate T1 coated with the inventive coating composition, since there is delamination or inadequate adhesion after the cross-cut test conducted. In contrast, the coating compositions of the invention, with an anticorrosion pigment (B) content in a range from 5.0 to 25.0 wt % and with a PVC in the range from 5.0 to 25.0%, are notable for effective adhesion properties even under these conditions.

[0142] While corresponding adhesion properties can be obtained using V2 (no anticorrosion pigment (B)) and V3 (anticorrosion pigment (B) content <5 wt %), sufficient corrosion prevention is no longer achieved with these comparative coating compositions, when set against the inventive coating compositions, as table 5c makes clear:

TABLE-US-00007 TABLE 5c Maximum thread length [mm] after Coated 1000 h of filiform substrate corrosion T1V2 11.2 T1V3 10.2 T1Z5 7.39 T1Z6 6.45