Coating Composition Comprising an Autoxidizable Alkyd-Based Resin and a Drier Composition

Abstract

The invention relates to a coating composition comprising an autoxidizable alkyd-based resin and a drier composition, the drier composition comprising: a) an iron-ligand complex comprising iron and at least one bispidine ligand; and b) a vanadium compound; wherein the amount of the vanadium compound is such that the coating composition comprises vanadium in a concentration in the range of from 0.01 wt % to 1.0 wt %, based on the solid weight of alkyd-based resin and wherein the amount of iron-ligand complex is such that the coating composition comprises iron in a concentration in the range of from 0.5.Math.10.sup.?4 wt % to 5.Math.10.sup.?3 wt %, based on the solid weight of alkyd-based resin.

Claims

1. A coating composition comprising an autoxidizable alkyd-based resin and a drier composition, the drier composition comprising: a) an iron-ligand complex comprising iron and at least one bispidine ligand; and b) a vanadium compound, wherein the amount of the vanadium compound is such that the coating composition comprises vanadium in a concentration in the range of from 0.01 wt % to 1.0 wt %, based on the solid weight of alkyd-based resin and wherein the amount of iron-ligand complex is such that the coating composition comprises iron in a concentration in the range of from 0.5.Math.10.sup.?4 wt % to 5.Math.10.sup.?3 wt %, based on the solid weight of alkyd-based resin.

2. The coating composition according to claim 1, wherein the coating composition is an aqueous coating composition.

3. The coating composition according to claim 1, wherein the bispidine ligand is a di-substituted 3-methyl-9-oxo-2,4-di(pyridine-2-yl)-7-(pyridine-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate according to the following general formula: ##STR00002## wherein R.sub.1 and R.sub.2 are, independently, selected from the group consisting of H, a C.sub.1-C.sub.20 alkyl, a C.sub.6-C.sub.20 aryl, and a polymeric residue.

4. The coating composition according to claim 3, wherein the ligand is dimethyl 3-methyl-9-oxo-2,4-di(pyridine-2-yl)-7-(pyridine-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate.

5. The coating composition according to claim 4, wherein the iron-ligand complex in a) is a Fe(II) complex of dimethyl 3-methyl-9-oxo-2,4-di(pyridine-2-yl)-7-(pyridine-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate.

6. The coating composition according to claim 5, wherein the iron-ligand complex is iron(1+), chloro[dimethyl-9,9-dihydroxy-3-methyl-2,4-di(2-pyridyl-?N)-7-[(2-pyridinyl-?N)methyl]-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate-?N3, ?N7]-, chloride(1?).

7. The coating composition according to claim 2, wherein the vanadium compound is a water-soluble vanadium compound.

8. The coating composition according to claim 7, wherein the water-soluble vanadium compound is a vanadium oxide and/or a vanadyl salt.

9. The coating composition according to claim 8, wherein the vanadyl salt is a vanadyl mono-carboxylate and/or a vanadyl di-carboxylate.

10. The coating composition according to claim 9, wherein the vanadyl salt is vanadyl oxalate.

11. The coating composition according to claim 1, wherein the amount of the vanadium compound is such that the coating composition comprises vanadium in a concentration in the range of from 0.03 wt % to 0.06 wt %, based on the solid weight of alkyd-based resin.

12. The coating composition according to claim 1, where the amount of iron-ligand complex is such that the coating composition comprises iron in a concentration in the range of from 1.Math.10.sup.?4 wt % to 1.Math.10.sup.?3 wt %, based on the solid weight of alkyd-based resin.

13. The coating composition according to claim 3 wherein R.sub.1 and R.sub.2 are, independently, a C.sub.1-C.sub.20 alkyl.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0015] The coating composition according to the invention is an autoxidizable alkyd-based coating composition, preferably an aqueous autoxidizable alkyd-based coating composition. The coating composition comprises an autoxidizable alkyd-based resin and a drier composition. The drier composition comprises:

[0016] a) an iron-ligand complex comprising iron and at least one bispidine ligand; and

[0017] b) a vanadium compound.

[0018] The bispidine ligand may be any bispidine ligand known to be suitable in metal-ligand driers for autoxidizable alkyd-based coating compositions. Suitable bispidine ligands are disclosed in H. B?rzel et al., Iron coordination chemistry with tetra-, penta- and hexadendate bispidine-type ligands, Inorganica Chimica Acta 337 (2002) 407-419, which bispidine ligands are herein disclosed by reference. A particular preferred bispidine ligand is a bispidon, also known as di-substituted 3-methyl-9-oxo-2,4-di(pyridine-2-yl)-7-(pyridine-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate of the following general formula:

##STR00001##

[0019] wherein R.sub.1 and R.sub.2 are, independently, selected from the group consisting of H, an alkyl group with 1 to 20 carbon atoms, an aryl group with 6 to 20 carbon atoms, and a polymeric residue. Preferably R.sub.1 and R.sub.2 are, independently, a straight or branched alkyl group with 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, or an aryl group with 6 to 20 carbon atoms. Preferred bispidon ligands include di-alkyl, di-aryl or di-polymeric 3-methyl-9-oxo-2,4-di(pyridine-2-yl)-7-(pyridine-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate. A particularly preferred ligand is dimethyl 3-methyl-9-oxo-2,4-di(pyridine-2-yl)-7-(pyridine-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate.

[0020] The iron in the iron-ligand complex may have any suitable oxidation state. Preferably, the iron is in its 2+ oxidation state, i.e. Fe(II).

[0021] Preferably the iron-ligand complex is [(bispidon)Fe(II)Cl]Cl or [(bispidon)Fe(II)SO.sub.4], more preferably [(bispidon)Fe(II)Cl]Cl, which is also known as iron(1+), chloro[dimethyl-9,9-dihydroxy-3-methyl-2,4-di(2-pyridyl-?N)-7-[(2-pyridinyl-?N)methyl]-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate-?N3, ?N7]-, chloride(1?). This complex is registered under CAS nr. 478945-46-9 and commercially available in solution as Borchi? Oxy-Coat from OMG Borchers.

[0022] The vanadium compound may be any vanadium compound known to be suitable as drier for autoxidizable alkyd-based coating compositions, such as a vanadium oxide, vanadium linoleate, vanadyl salts such as vanadyl carboxylates, vanadyl dicarboxylates, vanadyl phosphates, vanadyl acetonates such as for example vanadyl-bis-acetylacetonate ethylenediamine or vanadyl-bis-benzoylacetonate ethylenediamine and combinations of two or more thereof. Preferably, the vanadium compound is a vanadium oxide, a vanadyl salt, or a combination of a vanadium oxide and a vanadyl salt. Preferred vanadyl salts are vanadyl mono-carboxylates and vanadyl di-carboxylates, more preferably vanadyl acetate, vanadyl-2-ethylhexanoate, vanadyl oxalate, vanadyl malonate, or combinations of one or more thereof. Vanadyl oxalate or a combination of vanadium pentoxide and vanadyl oxalate are particularly preferred vanadium compounds. Preferably the vanadium compound is not a complex of vanadium and a nitrogen donor ligand. More preferably, the coating composition is free of any nitrogen donor ligand other than the bispidine ligand comprised in the iron-ligand complex.

[0023] If used in an aqueous coating composition, the vanadium compound preferably is a water-soluble vanadium compound. Reference herein to a water-soluble vanadium compound is to a vanadium compound that has a solubility in water of at least 0.5 grams per liter (at 20? C.), preferably at least 1.0 grams per liter (at 20? C.).

[0024] The drier composition and therewith the coating composition is preferably free of driers that are known as any primary driers other than the iron-ligand complex and the vanadium compound. Well-known primary driers include autoxidation catalysts comprising cobalt, manganese, cerium, iron or vanadium. Preferably, the drier composition is free of any cobalt-based, manganese-based, or cerium-based primary drier. The drier composition may further comprise compounds known as secondary driers, auxiliary driers or through driers, such as driers based on zirconium, bismuth, barium, aluminium, strontium, calcium, zinc, lithium, or potassium.

[0025] The autoxidizable alkyd-based resin may be any suitable autoxidizable alkyd-based resin. Such alkyd resins are known in the art. The alkyd resin may have any suitable molecular weight, oil length, or unsaturation of its fatty acid chains. The coating composition may be a coating composition based on an organic solvent or an aqueous coating composition, preferably an aqueous coating composition, i.e. a coating composition comprising an alkyd-resin emulsified in an aqueous medium. It has been found that in particular in an aqueous coating composition, the drier composition according to the invention has important advantages. A dried coating of such coating composition shows very good drying properties (good initial and final film hardness) whilst it does not show unacceptable yellowing.

[0026] It is an important advantage of the coating composition according to the invention that the amount of vanadium compound can be kept sufficiently low to avoid an unacceptable yellowing tendency, whilst initial and final hardness of the dried coating obtained are sufficiently high.

[0027] Preferably, the amount of the vanadium compound in the coating composition is such that the weight % of vanadium (calculated as metal) based on the solid weight of alkyd-based resin is less than 0.1 (V/solid alkyd % w/w), more preferably less than 0.08, even more preferably less than 0.06. In order to provide sufficient final hardness of the dried coating, the coating composition comprises at least 0.01 wt % vanadium, based on the solid weight of the alkyd-based resin, preferably at least 0.02 wt %, more preferably at least 0.03 wt %. A particularly suitable amount of vanadium is in the range of from 0.03 wt % to 0.06 wt %, based on the solid weight of alkyd-based resin.

[0028] The amount of the iron-ligand complex in the coating composition may be any suitable amount, including amounts of iron-ligand complex commonly used in alkyd-based coating compositions. The amount of iron (calculated as metal) in the coating composition does not exceed 5.Math.10.sup.?3 wt %, based on the weight of solid alkyd-based resin, preferably does not exceed 2.Math.10.sup.?3 wt %. A particularly suitable amount of iron is in the range of from 1.Math.10.sup.?4 to 1.Math.10.sup.?3 wt % based on the weight of solid alkyd-based resin.

Examples

[0029] White paints was prepared by adding to 50 weight parts of alkyd emulsion (Synaqua 4804, a commercially available aqueous emulsion of a short oil alkyd with 50 wt % solid alkyd; ex. Arkema): 25 weight parts Tiona 595 (95% titanium dioxide), 2 weight parts coalescence solvent, 15 weight parts water, 1 weight parts dispersant, 0.6 weight parts defoamer, and 6.4 weight parts rheology modifiers. Different white paints (paints no. 1 to 12) were prepared by adding different driers to a thus-prepared white paint.

[0030] Paint No. 1 (Comparative)

[0031] A commercially available cobalt-containing drier (ASK-Drier 2005, ex. ASK Chemicals) with 6 wt % cobalt was added in an amount of 1.6 wt %, based on the weight of solid alkyd resin.

[0032] Paint No. 2 (Comparative)

[0033] A solution of a Fe-bispidon complex (Borchi? Oxy-Coat, ex. Borchers OM Group; 1 wt % Fe-bispidon complex) was added in an amount of 0.3 wt %, based on the weight of solid alkyd resin.

[0034] Paints No. 3 to 6 (Comparative)

[0035] A solution of vanadyl oxalate (VP9950, ex. OMG Borchers; 6.5 wt % vanadium) was added in amounts of 0.3 wt % (paint no. 3), 0.6 wt % (paint no. 4), 1.0 wt % (paint no. 5) and 3.0 wt % (paint no. 6), based on the weight of solid alkyd resin.

[0036] Paints No. 7 to 11 (Invention)

[0037] A combination of Borchi? Oxy-Coat and VP9950 was added in the amounts given in Table 1, based on the weight of solid alkyd resin.

[0038] Paint No. 12 (Comparative)

[0039] Borchi? Oxy-Coat, manganese 2-ethyl hexanoate, and 1,4,7-trimethyl-1,4,7-triazacyclononane (ligand) were added to the white paint in the amounts given in Table 1, based on the weight of solid alkyd resin. The molar Mn to 1,4,7-trimethyl-1,4,7-triazacyclononane ratio was 2:1.

[0040] Films were prepared from the white paints and the K?nig hardness was measured after 1 day, 7 days and 28 days at 23? C. and 50% relative humidity. After these 28 days, the films were exposed for a further 100 hours to a temperature of 50? C. in an oven and the K?nig hardness was determined after an acclimatization of 4 hours at 23? C. at 50% relative humidity. The yellowing (b* values) of films made with the white paints was measured by the method described below.

[0041] K?nig Hardness

[0042] The K?nig hardness of films prepared from white paints no. 1 to 12 was assessed using the pendulum damping test according to DIN53157. A glass panel was coated with a 90 ?m wet film, held at 23? C. and 50% relative humidity and the hardness development in time was monitored with a K?nig pendulum. The number of oscillations needed to reduce from an initial deflection of 6? to a deflection of 3? was measured.

[0043] Yellowing

[0044] Color characteristics of paints no. 1 to 12 were measured on a Leneta opacity chart. Paint was applied on the chart using a rake with a radius of 0.7 mm and dried for 1 day at 23? C. Then, the color (CIE-Lab color space values) of the coatings was measured using a portable X-Rite Ci51 spectrophotometer. Then, the coatings were stored in the dark at 50? C. for 14 days and the color of the coatings (aged coatings) was measured again. The b* values are a measure for the yellowness of the paint and are given in Table 1.

[0045] The results of the hardness and yellowness measurements as shown in Table 1, show that coating compositions with a drier that combines an iron-ligand complex and a vanadium compound, yield a coating with an initial hardness and a final hardness comparable to a coating from a coating composition with a cobalt drier (compare paints no. 7 to 9 with paint no. 1). Moreover, such good initial and final hardness can be obtained at a vanadium concentration that is sufficiently low to obtain a yellowing tendency that is similar to or lower than the yellowing tendency of a coating composition with a cobalt-containing drier.

TABLE-US-00001 TABLE 1 Hardness and yellowing tendencies of white alkyd emulsion paints with different driers Co drier.sup.a BOC.sup.b VP9950.sup.c Mn/ligand Drier on Co on Drier on Fe on Drier on V on Mn on K?nig hardness solid solid solid solid solid solid solid +100 h, yellowing resin resin resin resin resin resin resin 1 d 7 d 28 d 50? C. 1 d 14 d Paint no. % w/w % w/w % w/w % w/w % w/w % w/w % w/w no. oscillations b* value 1 1.6 0.024 16 27 39 53 2.63 5.5 2 0.3 2.7 .Math. 10.sup.?4 15 18 20 24 1.71 4.23 3 0.3 0.02 10 17 20 29 1.12 4.05 4 0.6 0.04 12 17 20 50 1.41 4.76 5 1.0 0.07 16 22 35 83 3.7 6.7 6 3.0 0.20 17 24 35 78 6.81 8.05 7 0.1 0.9 .Math. 10.sup.?4 0.6 0.04 15 21 25 46 8 0.3 2.7 .Math. 10.sup.?4 0.6 0.04 15 19 22 58 2.42 5.09 9 1.0 9.0 .Math. 10.sup.?4 0.6 0.04 16 23 28 57 10 0.3 2.7 .Math. 10.sup.?4 0.3 0.02 15 18 20 36 2.23 4.81 11 0.3 2.7 .Math. 10.sup.?4 1.0 0.07 16 20 34 79 3.12 6.1 12 0.3 2.7 .Math. 10.sup.?4 0.07 15 18 19 25 3.21 7.86 .sup.aASK-Drier 2005, 6 wt % Co; .sup.bBorchi? Oxy-Coat, 0.09 wt % Fe; .sup.cVP9950, 6.5 wt % V