Polyether-based reaction products and aqueous basecoat materials comprising said products

Abstract

The present invention relates to a pigmented aqueous basecoat material comprising a polyether-based reaction product which is preparable by reaction of (a) at least one dicarboxylic acid of the formula (I)
HOOCYCOOH(I)
in which Y is a divalent aliphatic, aromatic or araliphatic hydrocarbon radical having from 4 to 11 carbon atoms, with (b) at least one polyether of the general structural formula (II) ##STR00001##
in which R is a C.sub.4 to C.sub.6 alkylene radical and n is selected accordingly such that the polyether (b) possesses a number-average molecular weight of 200 to 4000 g/mol, where components (a) and (b) are used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and the resulting reaction product possesses a number-average molecular weight of 500 to 15 000 g/mol and an acid number of less than 10 mg KOH/g.

Claims

1. A pigmented aqueous basecoat material, comprising a polyether-based reaction product which is preparable by reaction of: (a) at least one dicarboxylic of formula (I)
HOOCYCOOH(I) wherein Y is a divalent aliphatic, aromatic or araliphatic hydrocarbon radical having from 4 to 11 carbon atoms, with (b) at least one polyether of structural formula (II) ##STR00004## wherein R is a C.sub.4 to C.sub.6 alkylene radical and n is selected accordingly such that the polyether (b) has a number-average molecular weight of 200 to 4000 g/mol, wherein components (a) and (b) are used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and a resulting reaction product has a number-average molecular weight of 500 to 15,000 g/mol and an acid number of less than 10 mg KOH/g.

2. The basecoat material as claimed in claim 1, wherein the polyether (b) has a number-average molecular weight of 800 to 3200 g/mol.

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

4. The basecoat material as claimed in claim 1, wherein components (a) and (b) are used in a molar ratio of 0.9/2.1 to 1.5/1.8.

5. The basecoat material as claimed in claim 1, wherein the polyether-based reaction product has a number-average molecular weight of 1240 to 5000 g/mol.

6. The basecoat material as claimed in claim 1, wherein the divalent radical Y is an aromatic radical.

7. The basecoat material as claimed in claim 1, wherein the divalent radical Y is a saturated aliphatic radical.

8. The basecoat material as claimed in claim 6, wherein the divalent radical Y has 4 to 6 carbon atoms.

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

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

11. A multicoat paint system, comprising a pigmented aqueous basecoat material comprising a reaction product preparable by reaction of: (a) at least one dicarboxylic acid of formula (I)
HOOCYCOOH(I) wherein Y is a divalent aliphatic, aromatic or araliphatic hydrocarbon radical having from 4 to 11 carbon atoms, with (b) at least one polyether of structural formula (II) ##STR00005## wherein R is a C.sub.4 to C.sub.6 alkylene radical and n is selected accordingly such that the polyether (b) has a number-average molecular weight of 200 to 4000 g/mol, wherein components (a) and (b) are used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and a resulting reaction product has a number-average molecular weight of 500 to 15,000 g/mol and an acid number of less than 10 mg KOH/g.

12. A method for producing a multicoat paint system, the method comprising: (1) applying a pigmented aqueous basecoat material to a substrate; (2) forming a basecoat polymer film from the basecoat material applied in the applying (1); (3) applying a clearcoat material to the resulting basecoat film; and then (4) curing the basecoat film together with the clearcoat film, wherein the pigmented aqueous basecoat material in the applying (1) is the basecoat material as claimed in claim 1.

13. The method as claimed in claim 12, 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.

14. A multicoat paint system producible by the method as claimed in claim 12.

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) Determination of the Number-Average Molecular Weight:

(5) 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).

(6) Production of Reaction Products (IR) to be Used in Accordance with the Invention:

(7) IR1:

(8) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer, condenser, thermometer for overhead temperature measurement, and water separator, 1845.7 g of linear PolyTHF1000 (from BASF SE) with an OH number of 111.0 mg KOH/g (1.826 mol), 135.2 g of phthalic anhydride (from BASF SE), (0.913 mol) and 64.0 g of cyclohexane were heated to 100 C. in the presence of 1.6 g of di-n-butyltin oxide (Axion CS 2455, from Chemtura). Heating was continued slowly until the onset of condensation. At a maximum overhead temperature of 85 C., heating was then continued in steps to 218 C. The progress of the reaction was monitored via determination of the acid number. When an acid number of 0.4 mg KOH/g had been reached, remaining cyclohexane was removed by distillation under reduced pressure. This gave, after 24 hours, a polymer which was solid at room temperature.

(9) Gas chromatography found a cyclohexane content of less than 0.1%. The number-average molecular weight of the polymer was determined.

(10) Amount of condensation (water): 15.5 g

(11) Acid number: 0.4 mg KOH/g

(12) Number-average molecular weight: 2000 g/mol

(13) Solids content (GC): 100.0%

(14) Viscosity (resin:xylene=2:1): 185 mPas,

(15) (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 10 000 s.sup.1).

(16) IR2:

(17) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer, condenser, thermometer for overhead temperature measurement, and water separator, 1847.4 g of linear PolyTHF1000 (from BASF SE) with an OH number of 111.0 mg KOH/g (1.827 mol), 133.5 g of adipic acid (from BASF SE), (0.914 mol) and 64.0 g of cyclohexane were heated to 100 C. in the presence of 1.6 g of di-n-butyltin oxide (Axion CS 2455, from Chemtura). Heating was continued slowly until the onset of condensation. At a maximum overhead temperature of 85 C., heating was then continued in steps to 200 C. The progress of the reaction was monitored via determination of the acid number. When an acid number of 0.4 mg KOH/g had been reached, remaining cyclohexane was removed by distillation under reduced pressure. This gave, after 24 hours, a polymer which was solid at room temperature.

(18) Gas chromatography found a cyclohexane content of less than 0.1%. The number-average molecular weight of the polymer was determined.

(19) Amount of condensation (water): 32.9 g

(20) Acid number: 0.4 mg KOH/g

(21) Number-average molecular weight: 2100 g/mol

(22) Solids content (GC): 100.0%

(23) Viscosity (resin:xylene=2:1): 197 mPas,

(24) (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 10 000 s.sup.1).

(25) Production of Aqueous Basecoat Materials

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

(27) 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.

(28) 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 4.1 203 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 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
Production of Inventive Waterborne Basecoat Materials 1 and 2 (I1 and I2)

(29) 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 100% form (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. For the production of the waterborne basecoat material I2, the procedure was the same as for I1, with the reaction product IR2 being used instead of IR1.

(30) 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 and I2, as an overview.

(31) TABLE-US-00002 TABLE 1 Compositions of WBM C1 and I2 to I2 WBM [% by wt.] Reaction product C1 4.92 P1 I1 4.92 IR1 I2 4.92 IR2
Comparison Between Waterborne Basecoat Materials C1 and I1 and I2

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

(33) 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.

(34) TABLE-US-00003 TABLE 2 Pinholing limit and pinhole count of multicoat paint systems produced using waterborne basecoat materials C1 and I1 and I2 WBM Pinholing limit (micrometers) Pinhole count C1 22 25 I1 29 7 I2 32 1

(35) The results emphasize the fact that the use 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.

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

(37) 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.

(38) 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 4.1 203 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
Preparation of Inventive Waterborne Basecoat Materials 3 and 4 (I3 and I4)

(39) In the same way as for the preparation of I1 and I2, inventive basecoat materials I3 (containing IR1) and I4 (containing IR2) were produced using the reaction products IR1 and IR2 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.

(40) TABLE-US-00005 TABLE 3 Compositions of WBM C2 and I3 and I4 WBM [% by wt.] Reaction product C2 10.98 P1 I3 10.98 IR1 I4 10.98 IR2
Comparison Between Waterborne Basecoat Materials C2 and I3 and I4

(41) As above for the multicoat paint systems produced using waterborne basecoat materials C1 and I1 to I2, multicoat paint systems were produced using aqueous basecoat materials C2 and I3 and I4. 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.

(42) TABLE-US-00006 TABLE 4 Pinholing limit and pinhole count of multicoat paint systems produced using waterborne basecoat materials C2 and I3 and I4 WBM Pinholing limit (micrometers) Pinhole count C2 14 63 I3 27 15 I4 24 9

(43) The results again emphasize the fact that the use 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.