Carboxy-functional dimer fatty acid-based reaction products and aqueous basecoat materials comprising said products

Abstract

The present invention relates to a pigmented aqueous basecoat material comprising a carboxy-functional dimer fatty acid-based reaction product which is preparable by reaction of (a) dimer fatty acids with (b) at least one compound of the general structural formula (I) ##STR00001##
where R is a C.sub.3 to C.sub.6 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of 120 to 6000 g/mol, components (a) and (b) are used in a molar ratio of at least 1/1 and the resulting reaction product possesses a number-average molecular weight of 1000 to 20 000 g/mol and an acid number of 10 to 120 mg KOH/g.

Claims

1. A pigmented aqueous basecoat material, comprising: a carboxy-functional dimer fatty acid-based reaction product which is produced by reaction of (a) at least on dimer fatty acid with (b) at least one compound of the general structural formula (I): ##STR00004## wherein: R is a C.sub.3 to C.sub.6 alkylene radical; n is selected such that the compound (b) possesses a number-average molecular weight of 120 to 6000 g/mol; components (a) and (b) are used in a molar ratio of at least 1/1; and the reaction product possesses a number-average molecular weight of 1000 to 20 000 g/mol and an acid number of 10 to 120 mg KOH/g.

2. The basecoat material as claimed in claim 1, wherein the dimer fatty acid comprises at least 90 wt % of dimeric molecules, less than 5 wt % of trimeric molecules, and less than 5 wt % of monomeric molecules.

3. The basecoat material as claimed in claim 1, wherein the compound (b) possesses a number-average molecular weight of 180 to 2500 g/mol.

4. The basecoat material as claimed in claim 1, wherein the group R in the general structural formula (I) comprises tetramethylene radicals.

5. The basecoat material as claimed in claim 1, wherein components (a) and (b) are used in a molar ratio of 1.1/1 to 3/1.

6. The basecoat material as claimed in claim 1, wherein the reaction product possesses a number-average molecular weight of 2500 to 10 000 g/mol.

7. The basecoat material as claimed in claim 1, wherein the reaction product possesses an acid number of 12 to 80 mg KOH/g.

8. The basecoat material as claimed in claim 1, wherein the components (a) and (b) are used in a molar ratio of 1.2/1 to 2/1.

9. The pigmented aqueous basecoat material as claimed in claim 1, wherein the sum total of the weight-percentage fractions, based on the total weight of the pigmented aqueous basecoat material, of all the dimer fatty acid-based reaction products is 0.1 to 30 wt %.

10. The pigmented aqueous basecoat material as claimed in claim 1, further comprising a polyurethane resin that is grafted by olefinically unsaturated monomers and comprises hydroxyl groups, and a melamine resin.

11. A carboxy-functional dimer fatty acid-based reaction product which is produced by reaction of (a) at least one dimer fatty acids with (b) at least one compound of the general structural formula (I): ##STR00005## wherein: R is a C.sub.3 to C.sub.6 alkylene radical; n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of 120 to 6000 g/mol; components (a) and (b) are used in a molar ratio of at least 1/1; and the resulting reaction product possesses a number-average molecular weight of 1000 to 20 000 g/mol and an acid number of 10 to 120 mg KOH/g.

12. A pigmented aqueous basecoat material, comprising: the reaction product of claim 11, wherein the pigmented aqueous basecoat material is adapted to function as a basecoat material for improving the stability with respect to optical defects in paint systems.

13. A method for producing a multicoat paint system, the method comprising: (1) applying the pigmented aqueous basecoat material of claim 1 to a substrate, (2) forming a polymer film from the basecoat material applied in stage (1), (3) applying a clearcoat material to the polymer film, and then (4) curing the polymer film together with the clearcoat film.

14. The method as claimed in claim 13, wherein the substrate is a metallic substrate coated with a cured electrocoat film, and all of the films applied to the electrocoat film are cured jointly.

15. A multicoat paint system produced by the method of claim 13.

16. A method for improving stability with respect to optical defects in a paint system, the method comprising: applying a pigmented aqueous basecoat material comprising the reaction product of claim 11 to a surface to form a basecoat; and painting a surface of the basecoat.

Description

EXAMPLES

(1) Specification of Particular Components and Measurement Methods

(2) Polyester 1 (P1):

(3) Prepared in accordance with example D, column 16, lines 37 to 59 of DE 4009858 A, using butyl glycol instead of butanol as organic solvent, the solvents present thus being butyl glycol and water. The corresponding dispersion of the polyester has a solids content of 60 wt %.

(4) Dimer Fatty Acid (a):

(5) The dimer fatty acid used contains less than 1.5 wt % of trimeric molecules, 98 wt % of dimeric molecules, and less than 0.3 wt % of fatty acid (monomer). It is prepared on the basis of linolenic, linoleic, and oleic acid (Pripol 1012-LQ-(GD) (from Croda)).

(6) Determination of the Number-average Molecular Weight:

(7) The number-average molecular weight was determined by means of vapor pressure osmosis. Measurement was effected using a vapor pressure osmometer (model 10.00 from Knauer) on concentration series of the component under investigation in toluene at 50 C., with benzophenone as calibration substance for determination of the experimental calibration constant of the instrument employed (in accordance with E. Schrder, G. Mller, K.-F. Arndt, Leitfaden der Polymercharakterisierung [Introduction to polymer characterization], Akademie-Verlag, Berlin, pp. 47-54, 1982, in which, though, benzil was used as calibration substance).

(8) Production of Inventive Reaction Products (IR):

(9) IR1:

(10) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer, condenser, thermometer for overhead temperature measurement, and water separator, 604.6 g of linear PolyTHF250 (from BASF SE) with an OH number of 448.9 mg KOH/g (2.418 mol), 1818.5 g of dimer fatty acid (3.139 mol), and 75.0 g of xylene were heated to 100 C. in the presence of 1.9 g of di-n-butyltin oxide (Axion CS 2455, from Chemtura) (OH number determined according to DIN 53240). Heating was continued slowly until the onset of condensation. Then, at a maximum overhead temperature of 85 C., heating was continued in steps up to 186 C. The progress of the reaction was monitored by determination of the acid number. When an acid number of 38.1 mg KOH/g had been reached, remaining xylene was removed by distillation under reduced pressure. This gave a resin which was liquid at room temperature.

(11) Gas chromatography found a xylene content of less than 0.1%.

(12) The number-average molecular weight and the acid number of the polymer were determined.

(13) After cooling, the polyester was dissolved in butyl glycol (from BASF SE), as an 80% polymer solution.

(14) Amount of condensate (water): 81.2 g

(15) Acid number (polymer): 38.0 mg KOH/g

(16) Number-average molecular weight (polymer): 2800 g/mol

(17) Solids content (after dissolution) (60 min at 130 C.): 80.2%

(18) Viscosity (80% strength in butyl glycol): 2110 mPas, (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 1000 s.sup.1)

(19) IR2:

(20) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer, condenser, and water separator, 1107.3 g of linear PolyTHF650 (from BASF SE) with an OH number of 172.6 mg KOH/g (1.704 mol), 1315.8 g of dimer fatty acid (2.271 mol), and 75.0 g of xylene were heated to 100 C. in the presence of 1.9 g of di-n-butyltin oxide (Axion CS 2455, from Chemtura) (OH number determined according to DIN 53240). Heating was continued slowly until the onset of condensation. Then, at a maximum overhead temperature of 85 C., heating was continued in steps up to 200 C. The progress of the reaction was monitored by determination of the acid number. When an acid number of 28.8 mg KOH/g had been reached, remaining xylene was removed by distillation under reduced pressure. This gave a resin which was liquid at room temperature.

(21) Gas chromatography found a xylene content of less than 0.1%.

(22) The number-average molecular weight and the acid number of the polymer were determined.

(23) After cooling, the polyester was dissolved in butyl glycol (from BASF SE), as an 80% polymer solution.

(24) Amount of condensate (water): 60.7 g

(25) Acid number (polymer): 28.5 mg KOH/g

(26) Number-average molecular weight (polymer): 4000 g/mol

(27) Solids content (after dissolution) (60 min at 130 C.): 80.4%

(28) Viscosity (80% strength in butyl glycol): 2950 mPas, (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 1000 s.sup.1)

(29) IR3:

(30) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer, condenser, and water separator, 1373.6 g of linear PolyTHF1000 (from BASF SE) with an OH number of 111.0 mg KOH/g (1.359 mol), 1049.4 g of dimer fatty acid (1.811 mol), and 75.0 g of xylene were heated to 100 C. in the presence of 1.9 g of di-n-butyltin oxide (Axion CS 2455, from Chemtura) (OH number determined according to DIN 53240). Heating was continued slowly until the onset of condensation. Then, at a maximum overhead temperature of 85 C., heating was continued in steps up to 190 C. The progress of the reaction was monitored by determination of the acid number. When an acid number of 22.2 mg KOH/g had been reached, remaining xylene was removed by distillation under reduced pressure. This gave a resin which was liquid at room temperature.

(31) Gas chromatography found a xylene content of less than 0.1%.

(32) The number-average molecular weight and the acid number of the polymer were determined.

(33) After cooling, the polyester was dissolved in butyl glycol (from BASF SE), as an 80% polymer solution.

(34) Amount of condensate (water): 47.0 g

(35) Acid number (polymer): 22.2 mg KOH/g

(36) Number-average molecular weight (polymer): 5200 g/mol

(37) Solids content (after dissolution) (60 min at 130 C.): 80.3%

(38) Viscosity (80% strength in butyl glycol): 4200 mPas, (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 1000 s.sup.1)

(39) Production of Aqueous Basecoat Materials

(40) Production of a Silver Comparative Waterborne Basecoat 1 (C1)

(41) The components listed under aqueous phase in table A were stirred together in the order stated to form an aqueous mixture. In the next step an organic mixture was prepared from the components listed under organic phase. The organic mixture was added to the aqueous mixture. The combined mixture was then stirred for 10 minutes and adjusted, using deionized water and dimethylethanolamine, to a pH of 8 and to a spray viscosity of 58 mPas under a shearing load of 1000 s.sup.1 as measured with a rotary viscometer (Rheomat RM 180 instrument from Mettler-Toledo) at 23 C.

(42) TABLE-US-00001 TABLE A Parts by Component weight Aqueous phase 3% NaMg phyllosilicate solution 26 Deionized water 13.6 Butyl glycol 2.8 Polyurethane-modified polyacrylate; 4.5 prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A 50% strength by weight solution of 0.6 Rheovis PU 1250 (BASF), rheological agent P1 3.2 TMDD (BASF) 0.3 melamine-formaldehyde resin (Cymel 203 4.1 from Cytec) 10% dimethylethanolamine in water 0.3 polyurethane-based graft copolymer; 20.4 prepared as per page 19, line 44 to page 20, line 21 of DE 19948004 A, solids content adjusted to 32.5 wt % with deionized water TMDD (BASF) 1.6 3% strength by weight aqueous Rheovis AS 3.9 S130 solution; rheological agent, available from BASF Organic phase Mixture of two commercial aluminum 6.2 pigments, available from Altana-Eckart Butyl glycol 7.5 P1 5

(43) Production of an Inventive Waterborne Basecoat Material 1 (I1)

(44) To produce the inventive waterborne basecoat material I1, a paint was produced as for the production of the comparative waterborne basecoat material 1 (C1), using IR1, instead of the polyester P1, both in the aqueous phase and in the organic phase. IR1 here was used in dissolved form (80% strength based on solids content). Based on the solids fraction (nonvolatile fraction), the amount of IR1 used in I1 was the same as that of the polyester P1 used in C1. The different amounts of butyl glycol arising from the different solid contents of IR1 and of dispersion P1 were compensated in the formulation I1 by corresponding addition of butyl glycol.

(45) Preparation of Inventive Basecoat Materials 2 and 3 (I2 and I3)

(46) In the same way as for the preparation of I1, inventive basecoat materials I2 and I3 were prepared using the dissolved reaction products IR2 and IR3. Compensation for the different solids contents in relation to the polyester dispersion P1 took place again by corresponding addition of butyl glycol.

(47) Table 1 shows again the polyesters and reaction products, and their proportions (based on the total amount of the waterborne basecoat materials), used in waterborne basecoat materials (WBM) C1 and I1 to I3, as an overview.

(48) TABLE-US-00002 TABLE 1 Compositions of WBM C1 and I1 to I3 WBM [% by wt.] Reaction product C1 4.92 P1 I1 4.92 IR1 I2 4.92 IR2 I3 4.92 IR3

(49) Comparison Between Waterborne Basecoat Materials C1 and I1 to I3

(50) To determine the pinholing limit and pinhole count, multicoat paint systems were produced by the following general method:

(51) A cathodically electrocoated steel sheet of dimensions 3050 cm was provided with an adhesive strip on one longitudinal edge, in order to be able to determine the film thickness differences after the coating. The particular waterborne basecoat material was applied electrostatically in wedge format. The resulting waterborne basecoat film was flashed off at room temperature for four minutes and subsequently intermediately dried in a forced air oven at 70 C. for 10 minutes. A customary two-component clearcoat material was applied electrostatically in a film thickness of 35 micrometers to the dried waterborne basecoat film. The resulting clearcoat film was flashed off at room temperature for 20 minutes. The waterborne basecoat film and the clearcoat film were then cured in a forced air oven at 140 C. for 20 minutes. Following visual evaluation of the pinholes in the resulting wedge-shaped multicoat paint system, the film thickness of the pinholing limit and the number of pinholes above this film thickness (in other words, the total number of pinholes on the painted sheet) were ascertained. The results can be found in table 2.

(52) TABLE-US-00003 TABLE 2 Pinholing limit and pinhole count of multicoat paint systems produced using waterborne basecoat materials C1 and I1 to I3 WBM Pinholing limit (micrometers) Pinhole count C1 22 25 I1 24 18 I2 26 15 I3 29 9

(53) The results emphasize the fact that the use of the reaction products of the invention or of the waterborne basecoat materials of the invention significantly increases the pinholing limit by comparison with the comparative waterborne basecoat material C1, and at the same time reduces the pinhole count.

(54) Production of a Silver Comparative Waterborne Basecoat Material 2 (C2)

(55) The components listed under aqueous phase in table B were stirred together in the order stated to form an aqueous mixture. In the next step an organic mixture was prepared from the components listed under organic phase. The organic mixture was added to the aqueous mixture. The combined mixture was then stirred for 10 minutes and adjusted, using deionized water and dimethylethanolamine, to a pH of 8 and to a spray viscosity of 58 mPas under a shearing load of 1000 s.sup.1 as measured with a rotary viscometer (Rheomat RM 180 instrument from Mettler-Toledo) at 23 C.

(56) TABLE-US-00004 TABLE B Parts by Component weight Aqueous phase 3% NaMg phyllosilicate solution 26 Deionized water 21.7 Butyl glycol 2.8 Polyurethane-modified polyacrylate; 4.5 prepared as per page 7, line 55 to page 8, line 23 of DE 4437535 A 50% strength by weight solution of 0.6 Rheovis PU 1250 (BASF), rheological agent P1 13.3 TMDD (BASF) 0.3 Melamine-formaldehyde resin (Cymel 203 4.1 from Cytec) 10% dimethylethanolamine in water 0.3 polyurethane-based graft copolymer; 1.8 prepared as per page 19, line 44 to page 20, line 21 of DE 19948004 A, solids content adjusted to 32.5 wt % with deionized water TMDD (BASF) 1.6 3% strength by weight aqueous Rheovis 3.9 AS S130 solution; rheological agent, available from BASF Organic phase Mixture of two commercial aluminum 6.2 pigments, available from Altana-Eckart Butyl glycol 7.5 P1 5

(57) Preparation of Inventive Waterborne Basecoat Materials 4 to 6 (I4 to I16)

(58) In the same way as for the preparation of I1 to I3, inventive basecoat materials I4 to I6 were produced using the reaction products IR1 and IR3 on the basis of the comparative basecoat material C2 (table B) and with replacement of the polyester dispersion P1. Compensation for the different solids contents in relation to the polyester dispersion P1 took place again by corresponding addition of butyl glycol.

(59) TABLE-US-00005 TABLE 3 Compositions of WBM C2 and I4 to I6 WBM [% by wt.] Reaction product C2 10.98 P1 I4 10.98 IR1 I5 10.98 IR2 I6 10.98 IR3

(60) Comparison Between Waterborne Basecoat Materials C2 and I4 to I6

(61) As above for the multicoat paint systems produced using waterborne basecoat materials C1 and I1 to I3, multicoat paint systems were produced using aqueous basecoat materials C2 and I4 to I6. The evaluation in terms of pinholing limit and pinhole count also took place in the same way. The results can be found in table 4.

(62) TABLE-US-00006 TABLE 4 Pinholing limit and pinhole count of multicoat paint systems produced using waterborne basecoat materials C2 and I4 to I6 WBM Pinholing limit (micrometers) Pinhole count C2 14 63 I4 21 23 I5 23 18 I6 27 8

(63) The results again emphasize the fact that the use of the reaction products of the invention or of the waterborne basecoat materials of the invention significantly increases the pinholing limit by comparison with the comparative waterborne basecoat material C2, and at the same time reduces the pinhole count.