WO2006018236A1 - Thermally curable coating material, use thereof and method for the production of powder paints - Google Patents

Abstract

The invention relates to thermally curable coating materials, containing a carboxyl-functional polyester, which is produced by a condensation reaction of aliphatic and/or cycloaliphatic and/or aromatic polycarboxylic acids and anhydrides, a ß-hydroxyalkylamide by adding certain additives and/or stoke modifiers.

Description

Thermosetting coating composition, its use and process for producing powder coatings

The invention relates to thermosetting coating compositions comprising a carboxyl-functional polyester which is prepared by a condensation reaction of aliphatic and / or cycloaliphatic and / or aromatic polycarboxylic acids and anhydrides, a β-hydroxyalkylamide with the addition of certain additives or impact modifiers.

Powder coatings which contain carboxyl-functional polyesters and β-hydroxyalkylamides as binders have been known for some time.

No. 4,801,680 describes powder coatings based on carboxyl-functional polyesters and .beta.-hydroxyalkylamides, where the polyester has a Tg in the range from 30.degree. C. to 85.degree. C. and the equivalent ratio of .beta.-hydroxyalkylamide equivalents to carboxylic acid equivalents Range from 0.6: 1 to 1.6: 1. lies.

Toxicologically harmless powder coatings based on carboxyl-functional polyesters and .beta.-hydroxyalkylamides, in addition to excellent mechanical properties, also have very good weathering stability and are therefore suitable for use in outdoor areas.

However, such powder coatings show a reduction of the results of the impact test according to ASTM D 2794 and / or even poorer results of the impact test (Reverse Impact Test) after prolonged weathering in the field (Florida test) and / or storage under changing climatic conditions AS D 2794.

Proceeding from this, it was an object of the present invention to provide a coating composition and a method for the production thereof by which the disadvantage of the deterioration of the mechanical properties of powder coatings can be eliminated or at least minimized.

This object is achieved by the heat-curable coating composition according to claim 1 and the process for the preparation of powder coatings according to claim 13. The further dependent claims show advantageous developments. Claim 14 describes the use of the coating compositions according to the invention.

The coating composition according to the invention consists of: A) a carboxyl-functional polyester prepared by a condensation reaction of aliphatic and / or cycloaliphatic and / or aromatic polycarboxylic acids and anhydrides, the Polyes¬ ter a Tg in the range of 30 ° C to 80 ° C and an acid number of about 20 to 100 mg KOH / g, and

B) a β-hydroxyalkylamide, wherein the equivalent ratio of β-hydroxyalkylamide equivalents to carboxylic acid equivalents in the range 0.6: 1 to 1.6: 1, and

C) a fatty acid ester of sugars whose fatty acid radicals contain from 20 to 24 carbon atoms.

Surprisingly, it has been found that the addition of specially selected additives has the disadvantage of impairing the mechanical properties

(Impact test according to ASTM D 2794) of powder coatings based on carboxyl-functional polyesters and ß-hydroxyalkylamides can be improved. According to the invention, fatty acid esters of sugars are used whose fatty acid radicals contain 2 to 24 carbon atoms.

The fatty acid radicals preferably have 12 to 24 carbon atoms, more preferably 16 to 24 carbon atoms.

The proportion of fatty acid esters of sugars based on the total mass is preferably between 0.001 and 5 wt .-%, more preferably between. 0.01 and 5 wt .-%. The degree of esterification of the sugars used is between. 7 and 8.

For the sugars used. The short-chain fatty acid residues preferably contain 6 to 10 carbon atoms. Particular preference is given to the short-chain fatty acid radical selected from the group consisting of acetic acid, butyric acid, caproic acid, caprylic acid and capric acid.

The long-chain fatty acid radical used is preferably one from the group of behenic acid and stearic acid.

Suitable carboxyl-functional polyesters can be prepared by the condensation processes known to the polyesters (esterification and / or transesterification) according to the prior art. Also suitable catalysts, such as e.g. Dibutyltin oxide or Titantetrabuty- lat, may optionally be used.

Carboxyl-functional copolyesters contain as acid components mainly aromatic polybasic carboxylic acids, for example terephthalic acid, isophthalic acid, phthalic acid, pyromellitic acid, trimellitic acid, 3,6-dichlorophthalic acid, tetrachlorophthalic acid and, where available, their anhydride, chloride or ester. In most cases, they contain at least 50 mol% terephthalic acid and / or isophthalic acid, preferably 80 mol%. The rest of the acids (difference to 100 mol%) consists of aliphatic and / or cycloaliphatic polybasic acids, such as, for example, 1,4-cyclohexadicarboxylic acid, Tetrahydrophthalic acid, hexachlorophthalic acid, aze¬ lainsäure, sebacic acid, decanedicarboxylic acid, adipic acid, dodecanedicarboxylic acid, succinic acid, maleic acid or diniere fatty acids, hydroxycarboxylic acids and / or lactones, such as 12-hydroxystearic acid, ε-caprolactam or Hydroxpivalinsäure of Neopen- tylglycols can be used.

In small amounts, monocarboxylic acids, e.g. Benzoic acid, tert-butylbenzoic acid, hexahydrobenzoic acid, and saturated aliphatic monocarboxylic acids are used.

Suitable alcohol components include aliphatic diols, e.g. Ethylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethylpropanediol-1,3 (neopentyl glycol), 2,5-hexanediol, 1.6 Hexanediol, 2, 2- [bis (4-hydroxycyclohexyl)] propane, 1, 4-dimethylolcyclohexane, diethylene glycol, dipropylene glycol and 2,2-bis [4- (2-hydroxy)] phenylpropane. In small amounts, polyols are also used, e.g. Glycerol, hexanetriol, pentaerytlitol, sorbitol, trimethylolethane, trimethylolpropane, and tris (2-hydroxy) isocyanurate.

The β-hydroxyalkylamides of the coating composition according to the invention must contain at least two β-hydroxyalkylamide groups per molecule and are preferably characterized by the following formula:

Formula I:

in which R _{1 is} hydrogen or C ₁ -C ₅ -alkyl, R 2 is hydrogen, C ₁ -C ₅ -alkyl or

(HO-HC (R1) -CH ₂₎ -

in which R1 has the meaning given above and. A is a chemical bond or a monovalent or polyvalent organic group derived from gesät¬ saturated, unsaturated or aromatic hydrocarbon groups, including substituted Kohlen¬ hydrogen groups having 2 to 20 carbon atoms, m is 1 to 2, n is 0 to 2 and n + m is at least 2.

For the coating composition according to the invention, particular preference is given to β-hydroxyalkylamides

● bis [N, N'-di (.beta.-hydroxyethyl) adipamide] bis [N, N'-di (.beta.-hydroxypropyl) adipamide The preparation of the .beta.-hydroxyalkylamides takes place in a known manner by reacting the esters of the corresponding Dicarboxylic acid with alkanolamines in the heat,

The equivalent ratio of β-hydroxyalkylamide equivalents to carboxylic acid equivalents is preferably in the range from 0.6 to 1.6: 1. The customary pigments and / or fillers and / or additives can be used for the production of powder coatings. These are additives from the group of accelerators, leveling and thinning agents, heat, UV and / or HALS stabilizers and / or tribo-additives and, as required, matting material, such as waxes. The preparation of the powder coatings is preferably carried out in the melt by co-extrusion of all formulation ingredients at temperatures between 60 to 140 ° C. The extrudate is then cooled, ground and sieved to a particle size <90 microns. In principle, other methods for the production of the. Powder coatings suitable, such as mixing of the formulation ingredients in solution and subsequent precipitation or removal by distillation of the Lösemit¬ means. The application of the powder coating according to the invention is carried out by the methods customary for powder coatings, for example by means of an electrostatic spraying device

(Corona or Tribo) or by the Wirbelbettverfah ren.

Reference to the following examples, the inventive subject matter is to be described in detail, without limiting this to the embodiments shown here.

In the examples given below, the investigations of the mechanical properties were carried out in each case according to the methods described below: The test of mechanical properties (Schlagprü¬ test, Reverse Impact Test) is carried out according to ASTM D 2794. Here, the back of a powder coated sheet coated sheet (about 80 micron layer thickness) by means of a falling weight of increasing load ausge¬ sets and the drop weight (measured in inch * pound) at which the coating bursts.

In order to simulate the reduction of the impact test results in long-term outdoor weathering, coated aluminum sheets (layer thickness 70 to 90 μm also O-panels AL-36 5005H 14/08 [0.8 mm]) were used under extremely fluctuating climatic conditions (8h at 40 ° C / 10% relative humidity, 16 h at 40 ° C / 100% relative humidity). The impact tests were carried out in each case at the end of the dry period according to the method described above on the basis of ASTM D 2794.

Comparative Example 1 (RAL 3016)

694.16 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of approx. 60 ° C., 36.53 g of Primid XL-552 (Bis [N, N'-butyl) di (β-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 15.71 g Kronos Titan 2160 (TiO ₂ from Kronos (D)), 149.18 g Bianco Fisso ABR (BaSO ₄ of Company Iciesse SPH (I)), 1.27 g Red Colortherm 130M (pigment from Bayer (D)), 13.27 g Red Irgazine DPP BO (pigment from Ciba (CH)), 75.44 g Yellow Bayferrox 943 (pigment of Bayer (D)), 1.04 g of Yellow Paliotol L 2140HD (pigment from BASF (D)), 10.96 g of Resiflow PV88 (polyacrylate-based leveling agent, commercial product of Worley-Chemie GmbH), and 2.44 g Benzoin are dry-mixed in a Henschel mixer at 700 rpm for 30 s and then mixed on a Thysson co-kneader

(TSK 20) extruded at a jacket temperature of 110 ° C and a screw revolution of 500 rpm. The extrudate is cooled, ground and sieved to <90 μm.

The powder coatings are electrostatically (corona or tribo) on aluminum sheets (O-panel ÄL-36 5005 H 14/08 (0.8 mm)), as well as on steel sheets (Q-panel R-36 (0.8 mm.)) applied and cured at a Einbrenntempe¬ temperature of 180 ° C and a baking time of 15 min in the electric furnace UT6060 from Heraeus (D). The layer thickness is about 80 microns.

Table 1 shows the results of the impact test.

FIG. 1 shows the change of the reverse impact under the test conditions defined above. Example 1 (RAL 3016)

687.21 g of Crylcoat 7630 (carbo-κ-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of about 60 ° C., - 36.17 g of Primid XL-552 (bis [N, N ' -di (.beta.-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 15.55 g Kronos Titan 2160 (TiO ₂ from Kronos (D)), 147.69 g Bianco Fisso ABR (BaSO ₄ from Iciesse SPH (I)), 1.25 g Red Colortherm 130M (pigment from Bayer (D)), 13. 14 g Red Irgazine DPP BO (pigment from Ciba (CH)), 74.69 g Yellow Bayferrox 943 (pigment from Bayer (D)), 1.02 g Yellow Paliotol L 2140HD (pigment from BASF (D)), 10.85 g Resiflow PV88 (leveling agent based on polyacrylate, commercial product from Worlee-Chemie GmbH), and 2.41 g of benzoin, 10.00 g of V6842 (additive from EMS Chemie AG (CH)) are processed and tested analogously to Comparative Example 1 to form powder coating.

Table 1 shows the results of the impact test.

Fig. 1 shows the change of the reverse impact

(Impact test) under the test conditions defined above.

Comparative Example 2 (RAL 5010)

694.32 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg 60 g, 36.54 g of Primid XL-552 (bis [N, N'-di (β-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 28, 88 g Kronos Titan 2160 (TiO ₂ from Kronos (D)), 208.91 g Bianco Fisso ÄBR (BaSO ₄ from Iciesse SPH (I)), 3.15 g Rosa Rubin Hostaperm E (pigment from Clariant (D)), 11.15 g Blue Heliogene K6911D (pigment from BASF (D)), 3, -65 g Yellow Bayferrox 3420 (pigment from Bayer (D)), 10.96 g Resiflow PV88 (leveling agent on polyethylene acrylate base, commercial product of Worlée-Chemie GmbH), and 2.44 g of benzoin are processed and tested analogously to Comparative Example 1 to form powder coating.

Table 1 shows the results of the impact test.

2 shows the change of the reverse impact under the test conditions defined above.

Example 2 (RAL 5010)

687.82 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of approx. 60 ° C., 36.18 g of Primid XL-552 (bis [N, N '] di (β-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 28.59 g Kronos Titan 2160 (TiO ₂ from Kronos (D)), 206.82 g Bianco Fisso ABR (BaSO ₄ of Company Iciesse SPH (I)), 3.12 g Rosa Rubin Hostaperm E (pigment from Clariant (D)), 11.03 g Blue Heliogene K6911D (pigment from BASF (D)), 3.62 g of Yellow Bayferrox 3420 (pigment from Bayer (D)), 10.85 g of Resiflow PV88 (polyacrylate-based leveling agent, commercial product of Worlée-Chemie GmbH), and 2.41 g of benzoin, 10.00 g V6842 (additive from EMS Chemie AG (CH)) are processed into powder coating analogously to comparative example 1 and tested.

Table 1 shows the results of the impact test.

FIG. 2 shows the change in the reverse impact under the test conditions defined above.

Comparative Example 3 (RAL 6005)

694.28 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of approx. 60 ° C., 36.54 g of Primid XL-552 (bis [N, N '] di (β-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 6.14 g Kronos Titan 2160 (TiO ₂ from Kronos (D)), 187.58 g Bianco Fisso ABR (BaSO ₄ of Company Iciesse SPH. (I)), 34.01 g Green. Heliogenic K8730 (pigment from BASF (D)), 3.12 g Black Bayferrox 316 (pigment from Bayer (D)), 24.95 g Yellow Bayferrox 3910 (pigment from Bayer (D)) , 10.96 g of Resiflow PV88 (polyacrylate-based leveling agent, commercial product of Worlée-Chemie GmbH), and 2.44 g of benzoin are processed into powder coating analogously to Comparative Example 1 and tested. Table 1 shows the results of the impact test.

Fig. 3 shows the change of the reverse impact

(Impact test) under the test conditions defined above.

Example 3 (RAL 6005)

687.33 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of approx. 60 ° C., 36.18 g of Primid XL-552 (bis [N, N '] di (β-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 6.08 g Kronos Titan 2160 (TiO ₂ from Kronos (D)), 185.70 g Biancσ Fisso ABR (BaSO ₄ of Company Iciesse SPH (I)), 33.67 g of Green Heliogene K8730 (pigment from BASF (D)), 3.09 g of Black Bayferrox 316 (pigment from Bayer (D)), 24.70 g of Yellow Bayferrox 3910 (pigment from Bayer (D)), 10.85 g Resiflow PV88 (polyacrylate leveling agent, commercial product of Worlée-Chemie GmbH), and 2.41 g of benzoin, 10.00 g of V6842 (Ad additive from EMS Chemie AG (CH)) are processed and tested analogously to Comparative Example 1 to powder coating.

Table 1 shows the results of the impact test.

3 shows the change of the reverse impact under the test conditions defined above. conditions.

Comparative Example 4 (EAL 8014)

694.41 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of approx. 60 ° C., 36.55 g of Primid XL-552 (bis [N, N '] di (β-hydroxyethyl) adipamide from EMS-Chemie AG (CH)), 209.54 g Bianco Fisso ABR (BaSO ₄ from Iciesse SPH (I), 34.11 g Yellow Bayferox 920 (pigment of the company Bayer (D)), 9.29 g Red Colortherm 130M (pigment from Bayer (D)), 2.42 g Special Black 4 (pigment from Degussa (D)), 0.28 g Yellow Colortherm 10 (cf. Pigment from Bayer (D)), 10.96 g of Resiflow PV88 (leveling agent based on polyacrylate, commercial product of Worlée-Chemie GmbH), and 2.44 g of benzoin are processed into powder coating analogously to Comparative Example 1 and blended reviewed.

Table 1 shows the results of the impact test.

4 shows the change in the reverse impact under the test conditions defined above.

Example 4 (RAL 8014)

687.33 g of Crylcoat 7630 (carboxyl-functional copolyester from UCB) having an acid number of 33 mg KOH / g and a Tg of about 60 ° C., 36.18 g of Primid XL 552 (bis [N, N'-di (β-hydroxyethyl) adipamide from EMS-Cherαie AG (CH)), 207.45 g Bianco Fisso ABR (BaSO ₄ from Iciesse SPH (I), 33.77 g Yellow Bayferox 920 (pigment from Bayer (D)), 9.19 g Red Colortherm 130M (pigment from Bayer (D)), 2.39 g Special Black 4 (pigment from Degussa (D)) , 0/28 g Yellow Colortherm 10 (pigment from Bayer (D)), 10.85 g Resiflow PV88 (polyacrylate-based leveling agent, hands-on product of Worlée-Chemie GmbH), and 2.41 g of benzoin, 10.00 g V6842 (additive from EMS Chemie AG (CH)) are processed and tested analogously to Comparative Example 1 to form powder coating.

Table 1 shows the results of the impact test.

4 shows the change in the reverse impact under the test conditions defined above.

Table 1:

Claims

claims 1 . Thermosetting coating composition comprising (A) a carboxyl-functional polyester produced by a condensation reaction of aliphatic and / or cycloaliphatic polyols with aliphatic and / or cycloaliphatic and / or aromatic polycarboxylic acids and anhydrides, the polyester having a Tg in the range from 30 ° C to 80 ° C and an acid number of about 20 to 100 mg KOH / g, and (B) a β-hydroxyalkylamide wherein the equivalent ratio of β-hydroxyalkylamide equivalents to carboxylic acid equivalents is in the range of 0.6: 1 to 1.6: 1, and (C) at least one fatty acid ester of sugars whose fatty acid residues contain 2 to 24 carbon atoms. 2. thermosetting coating composition according to claim 1, characterized in that the fatty acid residues Contain from 12 to 24 carbon atoms. 3. thermosetting coating composition according to any one of the preceding claims, characterized in that the fatty acid residues contain 16 to 24 carbon atoms. 4. thermosetting coating composition according to any one of the preceding claims, characterized in that the proportion of Fatty acid esters of sugars based on the total Ge mass between 0.001 and 5 wt .-%, in particular between 0.01 and 5 wt .-% is. 5. thermosetting coating composition according to any one of the preceding claims, characterized in that the long-chain fatty acid radical is selected from the group of behenic acid and stearic acid. 6. thermosetting coating composition according to any one of the preceding claims, characterized in that the degree of esterification of the sugars is in the range of 7 to 8. 7. thermosetting coating compositions according to any one of the preceding claims, characterized in that the β-hydroxy-allyklamid has the formula I. Formula I

f in which R Wasserstof or C ₁ - C ₅ -alkyl, f R2 Wasserstof, C ₁ -C ₅ alkyl, or (HO-CH (R ₄ ) -CH ₂ ) - R ⁴ is hydrogen or C ¹ -C ⁵ -alkyl and A is a chemical bond or a monovalent or polyvalent organic group, derived from saturated, unsaturated or aromatic hydrocarbon groups, including substituted hydrocarbon groups with 2 to 20 carbon atoms, where m = 1 to 2, n = 0 to 2 and n + m ≥ 2. 8. thermosetting coating compositions according to any one of the preceding claims, characterized in that the β-hydroxyalkyl amide is selected from the group consisting of bis [N, N'-di (β-hydroxyethyl) adipamide and bis [N, N'-di (β-hydroxypropyl) adipamide. 9. thermosetting coating composition according to any one of the preceding claims, characterized in that in addition Pigmen¬ te, fillers, heat stabilizers, yellowing stabilizers, Triboadditive and / or further Tere additives are included. 10. thermosetting coating composition according to claim 9, characterized in that a phosphate is contained as Hitzestabilisa¬ gate. 11. thermosetting coating composition according to any one of claims 9 or 10, characterized in that as further Additi ve leveling agents, degassing agents are included. 12. A process for the preparation of powder coatings, wherein in the melt by coextrusion of all formulation constituents of the coating compositions according to any one of claims 1 to 11 and additionally customary pigments and / or fillers and / or additives at Tempe¬ temperatures between 60 ° C. and 140 ° C produces an extrudate, this is then cooled, ground and sieved to a particle size of <90 microns. 13. Use of the coating composition according to any one of claims 1 to 11 as a protective layer.