Polymer in multicoat color and/or effect paint systems

Abstract

The present invention relates to a polymer, preparable by reacting at least one polymer, preparable by reacting (a) dimer fatty acids with at least (b) one polyether having a C3 to C6 alkylene radical and a number-average molecular weight of 450 to 2200 g/mol, components (a) and (b) are used in a molar ratio of 0.7/2.3 to 1.3/1.7, and the resulting polymer has a number-average molecular weight of 1500 to 5000 g/mol and an acid number <10 mg KOH/a, at least one polyether with a C3 to C6 alkylene radical and with a number-average molecular weight of 250 to 3000 g/mol, at least one compound having at least one anionic group and/or at least one functional group capable of forming anions, and at least one, more particularly at least two, isocyanate-reactive functional groups, at least one polyisocyanate, and optionally at least one monool or diol, at least one compound having more than two isocyanate-reactive functional groups, and optionally neutralizing the groups of component (C) that are capable of forming anions.

Claims

1. A polymer obtained by reacting: (A) at least one polymer, prepared by reacting: (a) at least one dimer fatty acid, with (b) at least one polyether of formula (I): ##STR00005## wherein: R is a C.sub.3 to C.sub.6 alkylene radical, n is selected so that said polyether has a number-average molecular weight of 450 to 2,200 g/mol, a molar ratio of the components (a) and (b) is 0.7/2.3 to 1.3/1.7, and n the polymer (A) has a number-average molecular weight of 1,500 to 5,000 g/mol and an acid number less than 10 mg KOH/g; (B) at least one polyether of formula (II): ##STR00006## wherein R is a C.sub.3 to C.sub.6 alkylene radical, and n is selected so that said polyether (B) has a number-average molecular weight of 250 to 3,000 g/mol; (C) at least one compound having at least one anionic group, at least one functional group capable of forming anions, or both and having at least one isocyanate-reactive functional group, wherein the compound (C) is different from the polyether (A) and the polyether (B); (D) at least one polyisocyanate; (E) optionally at least one monool or diol which is different from the polyether (A), the polyether (B) and the compound (C); and (F) at least one compound having more than two isocyanate-reactive functional groups, wherein the compound (F) is different from the polyether (A), the polyether (B) and the compound (C), and optionally neutralizes the at least one anionic group of the compound (C) that is capable of forming anions.

2. The polymer according to claim 1, wherein the at least one dimer fatty acid (a) comprises at least 90% by weight of dimeric molecules, less than 5% by weight of trimeric molecules, and less than 5% by weight of monomeric molecules and other by-products.

3. The polymer according to claim 1, wherein said polyether of formula (I) is a polypropylene glycol or a polytetrahydrofuran and has a number-average molecular weight of 800 to 1,200 g/mol.

4. The polymer according to claim 1, wherein said polyether of formula (II) is a polypropylene glycol or a polytetrahydrofuran and has a number-average molecular weight of 1,800 to 2,200 g/mol.

5. The polymer according to claim 1, wherein a molar ratio of the dimer fatty acid (a) and the polyether (b) is 0.9/2.1 to 1.1/1.9.

6. The polymer according to claim 1, which has a number-average molecular weight of 5,000 to 50,000 g/mol.

7. The polymer according to claim 1, which has an acid number of less than 50 mg KOH/g.

8. A pigmented aqueous basecoat material, comprising at least one polymer according to claim 1.

9. The pigmented aqueous basecoat material according to claim 8, wherein the sum total of the weight-percentage fractions, based on the total weight of the pigmented aqueous basecoat material, of all polymers is 0.1% to 30% by weight.

10. The pigmented aqueous basecoat material according to claim 8, further comprising, as a further binder, at least one further polyurethane resin which is different from said at least one polymer.

11. A method for promoting adhesion, the method comprising: incorporating the polymer according to claim 1 into a pigmented aqueous basecoat material; and forming a polymer film of the pigmented aqueous basecoast material adhered to a surface of a substrate.

12. A method for producing a multicoat paint system, the method comprising: (1) applying the pigmented aqueous basecoat material according to claim 8 to a substrate; (2) forming a basecoat polymer film from the pigmented aqueous basecoat material applied in step (1); (3) applying a clearcoat film to the basecoat polymer film; and subsequently (4) curing the basecoat polymer film together with the clearcoat film.

13. The method according to claim 12, wherein said substrate is a multicoat paint system which has defect areas.

14. A multicoat paint system obtained by the method according to claim 12.

15. A multicoat paint system obtained by the method according to claim 13.

Description

EXAMPLES

(1) Specification of Certain Components and Measurement Methods Employed

(2) Dimer Fatty Acid:

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

(4) Determination of the Number-Average Molecular Weight:

(5) The number-average molecular weight was determined by means of vapor pressure osmosis. Measurement took place 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 the determination of the experimental calibration constant of the instrument employed (in accordance with E. Schrder, G. Mller, K.-F. Arndt, Leitfaden der Polymercharakterisierung, Akademie-Verlag, Berlin, pp. 47-54, 1982, in which benzil was used as calibration substance).

(6) Preparation of the Polyester Prepolymer PP1

(7) In a 4 l stainless steel reactor, equipped with anchor stirrer, thermometer, condenser, thermometer for overhead temperature measurement, and water separator, 2 mol of polyTHF1000, 579.3 g of dimerized fatty acid (Pripol 1012, Uniqema), (1 mol) and 51 g of cyclohexane are heated to 100 C. Heating is continued slowly until the onset of condensation. At a maximum overhead temperature of 85 C., heating is then continued gradually up to 220 C. The progress of the reaction is monitored via determination of the acid number. When an acid number of 3 mg KOH/g has been reached, remaining cyclohexane is removed by distillation under vacuum. This gives a viscous resin, having a viscosity of 4500-5800 mPas (measured at 23 C. using a rotary viscometer from Brookfield, model CAP 2000+, spindle 3, shear rate: 1333 s.sup.1).

(8) The calculated molecular weight of the polyester prepolymer is 2399 g/mol, and it has an OH functionality of 2.

(9) Experimental Data:

(10) Mn: 2200 g/mol

(11) Viscosity: 5549 mPas (measured at 23 C. with Brookfield CAP 2000+ rotary viscometer, spindle 3, shear rate: 1333s.sup.1)

(12) Preparation of the Polyester Prepolymer PP2

(13) The linear polyester polyol PP2 was prepared in the same way as for PP1 from dimerized fatty acid (Pripol 1012, Uniqema), isophthalic acid (BP Chemicals) and hexane-1,6-diol (BASF SE) (weight ratio of the starting materials: dimeric fatty acid to isophthalic acid to hexane-1,6-diol=54.00:30.02:15.98) and had a hydroxyl number of 73 mg KOH/g solids and a (calculated) number-average molecular weight of 1379 g/mol with an OH functionality of 2.0.

(14) Experimental Data:

(15) Mn: 1250 g/mol

(16) Viscosity: 632 mPas (measured at 23 C. with a Brookfield CAP 2000+ rotary viscometer, spindle 3, shear rate: 10 000 s.sup.1)

(17) Preparation of the Polyester Prepolymer PP3

(18) In the same way as for PP1, a linear polyester prepolymer is prepared. Hexanediol is now replaced on a molar basis for an equimolar mixture of neopentyl glycol and hexanediol. This gives a linear polyester resin having a number-average molecular weight of 1349 g/mol with an OH functionality of 2.0.

(19) Experimental Data:

(20) Mn: 1320 g/mol

(21) Viscosity: 430 mPas (measured at 23 C. with a Brookfield CAP 2000+ rotary viscometer, spindle 3, shear rate: 10 000 s.sup.1)

(22) Preparation of the Polyurethanes PU1 to PU4

(23) In a 4 l stainless steel reactor, equipped with stirrer, reflux condenser and thermometer, the polyurethane dispersion is synthesized in accordance with a modified acetone process.

(24) For this purpose, components A1-A7, in the quantities indicated in table 1, are combined together with methyl ethyl ketone, and are reacted with stirring at 80-82 C. The reaction is monitored by titrating the isocyanate content with dibutylamine in accordance with DIN EN ISO 3251. When the isocyanate content is constant and has reached 0.8%-1.2%, based on the solution present, a molar excess of 115%, based on the amount of free NCO measured, of trimethylolpropane is added (n[NCO prepolymer]/n[trimethylolpropane]=1.15). The synthesis is continued until the NCO content has reached a value of less than 0.3%, based on the solution. The viscosity is then 1200-1400 mPas (in 1:1 mixture with N-ethyl-2-pyrrolidone, plate/cone, CAP 03, 5000/s, 23 C.)

(25) The isocyanate which remains is then left to be consumed by reaction with an excess of butanol at 80-82 C. for 3 hours.

(26) For the neutralization, a mixture of diethanolamine and water is then added, and in this way the carboxyl functions are neutralized to an extent of about 65%-70%.

(27) After a further 30 minutes, fully demineralized water is added to give a solids content (without methyl ethyl ketone) of about 28%-30%. The methyl ethyl ketone is then removed by vacuum distillation, and the resin is subsequently adjusted to a solids content as per table 2. PU1 is subsequently admixed with 18% by weight of Pluriol P900 as cosolvent.

(28) TABLE-US-00001 TABLE 1 Components for the preparation of the polyurethanes Parts by weight Component PU1 PU2 PU3 PU4 (A1) Dimethylpropionic 108.9 109.5 113.1 109.0 acid (A2) Dicyclohexylmethane 587.7 747.4 607.0 4,4-diisocyanate (A3) Isophorone 534.8 diisocyanate (A4) Neopentyl glycol 22.6 79.5 36.7 35.3 (A5) PolyTHF 2000 1423.9 873.3 841.2 (A6) PP1 822.3 841.2 (A7) PP2 1218.7 (B1) Trimethylolpropane 56.6 86.0 66.6 64.2 (B2) Diethanolamine 54.8 53.66 53.3 51.37

(29) Examples PU3 and PU4 are dispersions of inventive polymers, and examples PU1 and PU2 are comparative examples.

(30) Table 2 reports parameters of the individual dispersions.

(31) TABLE-US-00002 TABLE 2 Parameters of the polyurethanes Parts by weight PU3 PU4 Component PU1 PU2 (inventive) (inventive) Mn/g/mol 35 703 29 791 38 131 37 437 Acid number 24.6 18.8 19.4 18.6 Solids 30.0 30.5 34.4 34.7 content/%

(32) Preparation of the Polyurethane PU5

(33) In the same way as for the preparation of the polyurethanes PU1 to PU4, the polyurethane PU5 is prepared by reacting 1227 g of the polyester PP3, 106.80 g of dimethylolpropionic acid, 17.51 g of neopenthyl glycol, 539 g of tetramethylxylylene diisocyanate at a solids content of 60% in methyl ethyl ketone. When an NCO content of 1.0-1.25% has been reached, 90 g of trimethylolpropane are added. As soon as the viscosity as measured with a Brookfield CAP 03 plate/cone viscometer at 10 000/s has reached 300-380 mPas (in dilution with N-ethylpyrrolidone in a ratio of 10:6), any isocyanate present is consumed by reaction with an excess of butylglycol.

(34) Thereafter the methyl ethyl ketone is removed fully by distillation. Dimethylethanolamine is added to make the degree of neutralization 85%. A solids content of 60% is then set using further butylglycol.

(35) Preparation of the Mixing Varnish

(36) To prepare the mixing varnish, first of all components A1 and A2 are combined as per table 3 and mixed. When a homogeneous mixture is obtained, components B1 to B4 in the order stated are added with stirring.

(37) TABLE-US-00003 TABLE 3 Components for preparing the mixing varnish Component Parts by weight (A1) Water 300 (A2) Phyllosilicate 10 (Laponite RD) (B1) Polyurethane binder 228 composition (25% solids, 5% Pluriol P900, 70% water) (B2) Acrylate thickener 1 (B3) Dimethylethanolamine 2 (B4) Water 450

(38) Preparation of Waterborne Basecoat Materials

(39) The waterborne basecoat materials were prepared by combining the constituents listed in table 4 and milling them in a laboratory bead mill to a Hegmann particle size of 5 micrometers.

(40) Each of the waterborne basecoat materials is subsequently admixed with 140 parts by weight of the mixing varnish.

(41) TABLE-US-00004 TABLE 4 Components for preparing the waterborne basecoat materials Parts by weight E3 E4 Component E1 E2 (inventive) (inventive) PU5 10 10 10 10 PU1 47 PU2 46.2 PU3 41.0 PU4 40.6 Fully demineralized 13.9 14.6 19.8 20.3 water Polyurethane 0.14 0.14 0.14 0.14 thickener Heliogen Green 25 25 25 25 L9361 Wetting agent 4 4 4 4 based on an unsaturated diol

(42) Production of Multicoat Paint Systems, and Performance Analysis of the Multicoat Paint Systems

(43) The resulting basecoat materials E1 to E4 are each applied with 2.5 spray passes in a film thickness of 10-12 m to a panel coated with cathodic electrocoat (Cathoguard 500 black, BASF Coatings GmbH), with a waiting period after each spray pass for the basecoat material to dry to a matt appearance. This is followed by application of a commercial clearcoat material of the Glasurit brand, after which evaporation is allowed to take place at room temperature for 15 minutes, followed by drying in a forced-air oven at 60 C. for 30 minutes.

(44) The panels are then stored at room temperature for 7 days, after which they are stored in an oven at 80 C. for 5 days.

(45) The painted metal panels are then scored using a scoring stylus (e.g., Erichsen model 463) fitted with a 0.5 mm blade, the scoring marks being made twice over a length of 50-60 mm in crosswise fashion at an angle of 90 to one another, and down to the metal. The metal panels are then clamped in so that the scored cross is positioned centrally beneath a circular cutout with a diameter of 40 mm.

(46) At a water temperature of 505 and a pressure of 120 bar, and also at a distance of 1003 mm, the water jet is swung over the cutout 30 times within 30 seconds. The relative fraction of the flaking is then assessed. The results are reported in table 4.

(47) TABLE-US-00005 E3 E4 E1 E2 (inventive) (inventive) Delamination in % >95 80 20 <5