Carboxy-functional 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 compound of the formula (I)
X.sub.1YX.sub.2(I)
in which
X.sub.1 and X.sub.2, independently of one another, are each a functional group which is reactive toward hydroxyl groups, and Y is a divalent aliphatic or araliphatic, carboxy-functional organic radical having a number-average molecular weight of 100 to 1000 g/mol,
with
(b) at least one polyether of the general structural formula (II) ##STR00001##
in which
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 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 10 to 120 mg KOH/g.

Claims

1. A pigmented aqueous basecoat material, comprising a polyether-based reaction product obtained by reacting (a) at least one compound of formula (I):
X.sub.1YX.sub.2(I), with (b) at least one polyether of formula (II): ##STR00004## wherein: X.sub.1 and X.sub.2, independently of one another, are each a functional group which is reactive toward hydroxyl groups; Y is a divalent aliphatic or araliphatic, carboxy-functional organic radical having a number-average molecular weight of 100 to 1000 g/mol; 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 200 to 4000 g/mol; wherein the compound (a) of the formula (I) is obtained by reacting at least one dihydroxycarboxylic acid with at least one organic diisocyanate, the hydroxyl groups of the dihydroxycarboxylic acid reacting with isocyanate groups of the at least one organic diisocyanate to form urethane bonds, and the diisocyanate being reacted in a molar excess; wherein a molar ratio of the component (a) to the component (b) is in the reaction ranges from 0.7/2.3 to 1.6/1.7; and wherein the polyether-based reaction product possesses a number-average molecular weight of 500 to 15 000 g/mol and an acid number of 10 to 120 mg KOH/g.

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

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

4. The pigmented aqueous basecoat material as claimed in claim 1, wherein the molar ratio of the component (a) to the component (b) is in the reaction ranges from 0.9/2.1 to 1.5/1.8.

5. The pigmented aqueous basecoat material as claimed in claim 1, wherein the polyether-based reaction product possesses a number-average molecular weight of 1500 to 7500 g/mol.

6. The pigmented aqueous basecoat material as claimed in claim 1, wherein the dihydroxycarboxylic acid is a saturated aliphatic dihydroxycarboxylic acid having 4 to 12 carbon atoms, and a molar ratio of dihydroxycarboxylic acid to the organic diisocyanate is from 0.9/2.1 to 1.5/1,8.

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

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

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

10. The method as claimed in claim 9, 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.

11. A multicoat paint system obtained by the method as claimed in claim 9.

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 Inventive Reaction Products (IR):

(7) IR2:

(8) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer and condenser, 134.10 g of dimethylolpropionic acid (DMPA) (1.0 mol), 488.58 g of tetramethylenexylylene diisocyanate (TMXDI from Cytec, 2.0 mol) and 415 g of methyl ethyl ketone were weighed out. The mixture is heated to 80 C. with stirring and is maintained until a sample no longer showed any crystalline fractions of the DMPA. Added at this point to this reaction mixture were 2000 g of linear, diolic PolyTHF1000 (BASF SE) with an OH number of 112 mg KOH/g (2.0 mol) (OH number determined according to DIN 53240). The reaction mixture is held further at 80 C. The progress of the reaction was monitored by titration to determine the level of NCO groups (DIN EN ISO 11909). Where an NCO content of less than/equal to 0.1% had been reached, 10 g of n-butanol were added to the reaction mixture. The mixture was then stirred at the stated temperature for a further hour. The methyl ethyl ketone needed for the reaction was subsequently stripped off under reduced pressure. This gives a resin which is crystalline at room temperature and has an acid number of 21.2 mg KOH/g.

(9) The solids content of the resin is 100% (measured at 130 C. for 1 hour in a forced air oven on a 1 g sample with addition of 1 ml of methyl ethyl ketone).

(10) Number-average molecular weight: 2470 g/mol

(11) Viscosity 70% strength in butyl glycol: 1280 mPas, (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 5000 s.sup.1)

(12) IR3:

(13) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer and condenser, 134.10 g of dimethylolpropionic acid (DMPA), 524.0 g of bis(4-isocyanatocyclohexyl)methane (Desmodur W from Bayer Material Science, 2.0 mol) and 439 g of methyl ethyl ketone were weighed out. The mixture is heated to 80 C. with stirring and is maintained until a sample no longer showed any crystalline fractions of the DMPA. Added at this point to this reaction mixture were 2000 g of linear, diolic PolyTHF1000 (BASF SE) with an OH number of 112 mg KOH/g (2.0 mol) (OH number determined according to DIN 53240). The reaction mixture is held further at 80 C. The progress of the reaction was monitored by titration to determine the level of NCO groups (DIN EN ISO 11909). Where an NCO content of less than/equal to 0.1% had been reached, 132.9 g of butyl glycol were added to the reaction mixture. The mixture was then stirred at the stated temperature for a further hour. The methyl ethyl ketone needed for the reaction was subsequently stripped off under reduced pressure. This gives a resin which is crystalline at room temperature and has an acid number of 19.7 mg KOH/g.

(14) The solids content of the resin is 92.4% (measured at 130 C. for 1 hour in a forced air oven on a 1 g sample with addition of 1 ml of methyl ethyl ketone).

(15) Number-average molecular weight: 2500 g/mol

(16) Viscosity 70% strength in butyl glycol: 5410 mPas, (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 1250 s.sup.1)

(17) IR4:

(18) In a 4 l stainless steel reactor equipped with anchor stirrer, thermometer and condenser, 134.10 g of dimethylolpropionic acid (DMPA), 444.0 g of isophorone diisocyanate and 385 g of methyl ethyl ketone were weighed out. The mixture is heated to 80 C. with stirring and is maintained until a sample no longer showed any crystalline fractions of the DMPA. Added at this point to this reaction mixture were 2000 g of linear, diolic PolyTHF1000 (BASF SE) with an OH number of 112 mg KOH/g (2.0 mol) (OH number determined according to DIN 53240). The reaction mixture is held further at 80 C. The progress of the reaction was monitored by titration to determine the level of NCO groups (DIN EN ISO 11909). Where an NCO content of less than/equal to 0.2% had been reached, 130 g of butyl glycol were added to the reaction mixture. The mixture was then stirred at the stated temperature for a further hour. The methyl ethyl ketone needed for the reaction was subsequently stripped off under reduced pressure. This gives a resin which is crystalline at room temperature and has an acid number of 19.1 mg KOH/g.

(19) The solids content of the resin is 94.0% (measured at 130 C. for 1 hour in a forced air oven on a 1 g sample with addition of 1 ml of methyl ethyl ketone).

(20) Number-average molecular weight: 2320 g/mol

(21) Viscosity 65% strength in butyl glycol: 3072 mPas, (measured at 23 C. using a rotational viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 2500 s.sup.1)

(22) Production of Aqueous Basecoat Materials

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

(24) 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.

(25) 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
Production of an Inventive Waterborne Basecoat Material 2 (I2)

(26) To produce the inventive waterborne basecoat material I2, a paint was produced as for the production of the comparative waterborne basecoat material 1 (C1), using IR2, instead of the polyester P1, both in the aqueous phase and in the organic phase. IR2 here was used in 100% form (based on solids content). Based on the solids fraction (nonvolatile fraction), the amount of IR2 used in I2 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 IR2 and of dispersion P1 were compensated in the formulation I2 by corresponding addition of butyl glycol.

(27) Preparation of Inventive Basecoat Materials 3 and 4 (I3, I4)

(28) In the same way as for the preparation of I2, inventive basecoat materials I3 and I4 were prepared using the reaction products IR3 and IR4. Compensation for the different solids contents in relation to the polyester dispersion P1 took place again by corresponding addition of butyl glycol.

(29) 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 I2 to I4, as an overview.

(30) TABLE-US-00002 TABLE 1 Compositions of WBM C1 and I2 to I4 WBM [% by wt.] Reaction product C1 4.92 P1 I2 4.92 IR2 I3 4.92 IR3 I4 4.92 IR4
Comparison Between Waterborne Basecoat Materials C1 and I2 to I4

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

(32) 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.

(33) TABLE-US-00003 TABLE 2 Pinholing limit and pinhole count of multicoat paint systems produced using waterborne basecoat materials C1 and I2 to I4 WBM Pinholing limit (micrometers) Pinhole count C1 22 25 I2 27 1 I3 29 2 I4 24 10

(34) 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.

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

(36) 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.

(37) 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 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
Preparation of an Inventive Waterborne Basecoat Material 6 (I6)

(38) In the same way as for the preparation of I2 to I4, the inventive basecoat material I6 (containing IR4) was produced using the reaction product IR4 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.

(39) TABLE-US-00005 TABLE 3 Compositions of WBM C2 and I6 WBM [% by wt.] Reaction product C2 10.98 P1 I6 10.98 IR4
Comparison Between Waterborne Basecoat Materials C2 and I6

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

(41) TABLE-US-00006 TABLE 4 Pinholing limit and pinhole count of multicoat paint systems produced using waterborne basecoat materials C2 and I6 WBM Pinholing limit (micrometers) Pinhole count C2 14 63 I6 26 8

(42) 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.