Water-dispersible polyisocyanates

Abstract

The present invention relates to improved water-dispersible polyisocyanates with enhanced gloss, more particularly for two-component polyurethane coating materials.

Claims

1. A water-dispersible polyisocyanate (A), comprising as synthesis components in the following wt % based on isocyanate groups in synthesis component (a): (a) at least one diisocyanate or polyisocyanate; and (b) 0.5 to 30 wt % of a mixture of compounds of formulae (I) and (II): ##STR00004## wherein: R.sup.1 and R.sup.2 independently of one another represent alkyl, cycloalkyl or aryl, optionally substituted by aryl, alkyl, aryloxy, alkyloxy, heteroatoms and/or heterocycles; a molar ratio of the compound (II) to the compound (I) ranges from 5:95 to 95:5; (c) 0.3 to 25 wt %, based on isocyanate-reactive groups in (c), of at least one monofunctional polyalkylene glycol of formula
R.sup.4O[X.sub.i].sub.kH, wherein: R.sup.4 represents C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkyl uninterrupted or interrupted by one or more of an oxygen atom and a sulfur atom, or is C.sub.6-C.sub.12 aryl, C.sub.5-C.sub.12 cycloalkyl or a five- or six-membered heterocycle comprising at least one of an oxygen, nitrogen and sulfur atom, it being possible for each of stated radicals to be substituted by functional groups, aryl, alkyl, aryloxy, alkyloxy, halogen, heteroatoms and/or heterocycles; k represents an integer from 5 to 40; and each X.sub.i for i=1 to k is independently selected from the group consisting of CH.sub.2CH.sub.2O, CH.sub.2CH(CH.sub.3)O, CH(CH.sub.3)CH.sub.2O, CH.sub.2C(CH.sub.3).sub.2O, C(CH.sub.3).sub.2CH.sub.2O, CH.sub.2CHVin-O, CHVin-CH.sub.2O, CH.sub.2CHPh-O, and CHPh-CH.sub.2O, in which Ph is phenyl and Vin is vinyl; (d) 0 to 15 wt %, based on isocyanate-reactive groups in (d), of at least one high molecular mass diol or polyol; and (e) 0 to 15 wt %, based on isocyanate-reactive groups in (e), of at least one low molecular mass diol or polyol.

2. The water-dispersible polyisocyanate (A) according to claim 1, wherein component (a) is a polyisocyanate synthesized from at least one (cyclo)aliphatic isocyanate.

3. The water-dispersible polyisocyanate (A) according to claim 1, wherein component (a) is a polyisocyanate comprising at least one of an allophanate group and an isocyanurate group and is based on isophorone diisocyanate, 1,6-hexamethylene diisocyanate or both.

4. The water-dispersible polyisocyanate (A) according to claim 1, wherein the compound (b) is selected from the group consisting of mono methyl phosphate, di methyl phosphate, mono ethyl phosphate, di ethyl phosphate, mono n-butyl phosphate, di n-butyl phosphate, mono 2-ethylhexyl phosphate, di 2-ethylhexyl phosphate, and mixtures thereof.

5. The water-dispersible polyisocyanate (A) according to claim 1, having the following construction, based on isocyanate groups in synthesis component (a): (b) 0.8 to 25 wt % of compounds of formula (I) and/or (II), (c) 0.5 to 20 wt %, based on isocyanate-reactive groups in (c), (d) 0 to 10 wt %, based on isocyanate-reactive groups in (d), and (e) 0 to 10 wt %, based on isocyanate-reactive groups in (e).

6. The water-dispersible polyisocyanate (A) according to claim 1, wherein phosphate groups in compound (b) have been at least partly neutralized.

7. The water-dispersible polyisocyanate (A) according to claim 1, wherein phosphate groups in compound (b) have been at least partly neutralized with tertiary amines.

8. The water-dispersible polyisocyanate (A) according to claim 1, wherein, in component (b), R.sup.1 and R.sup.2 independently of one another represent unsubstituted alkyl or unsubstituted aryl.

9. The water-dispersible polyisocyanate (A) according to claim 8, wherein R.sup.1 and R.sup.2 independently of one another are selected from the group consisting of phenyl, methyl, ethyl, n-butyl, and 2-ethylhexyl.

10. An aqueous coating composition, comprising at least one water-dispersible polyisocyanate (A) according to claim 1 and optionally at least one binder selected from the group consisting of polyacrylate-polyol dispersions, polyester-polyol dispersions, polyether-polyol dispersions, polyurethane-polyol dispersions, polycarbonate-polyol dispersions, and their hybrids.

11. A process, comprising coating an article with a coating composition comprising at least one water-dispersible polyisocyanate (A) according to claim 1, wherein the article is selected from the group consisting of a wood, a wood veneer, a paper, a paperboard, a cardboard, a textile, a film, a leather, a nonwoven, a plastic surface, a glass, a ceramic, a mineral building material, a cement molding, a fiber-cement slab, and a fiber-cement metal, each of which may optionally have been precoated or pretreated.

12. A process, comprising coating an article with a coating composition comprising at least one water-dispersible polyisocyanate (A) according to claim 1, wherein the article is selected from the group consisting of buildings, (large) vehicles, aircraft, industrial applications, decorative coatings, bridges, buildings, power masts, tanks, containers, pipelines, power stations, chemical plants, ships, cranes, posts, sheet piling, valves, pipes, fittings, flanges, couplings, halls, roofs, structural steel, furniture, windows, doors, woodblock flooring, can coating and coil coating, for floor coverings, parking levels, in hospitals, and in automobile finishes as OEM and refinish application.

13. A coating material, adhesive or sealant comprising at least one polyisocyanate according to claim 1.

14. A substrate coated, bonded or sealed with a coating material, adhesive or sealant according to claim 13.

Description

EXAMPLES

(1) Polyisocyanate A

(2) Polyisocyanate prepared by trimerizing some of the isocyanate groups of 1,6-diisocyanatohexane (HDI) and containing isocyanurate groups, said polyisocyanate being composed substantially of tris(6-isocyanatohexyl) isocyanurate and its higher homologs, with an NCO content of 22.2% and a viscosity at 23? C. of 2800 mPa*s (commercially available as BASONAT? HI100 at BASF SE, Ludwigshafen, Germany)

(3) Hydrophilic Compound B1

(4) Monofunctional polyethylene oxide prepared starting from methanol and with potassium hydroxide catalysis, with an average OH number of 112 mg KOH/g, measured to DIN 53 240, corresponding to a molecular weight of 500 g/mol. The residues of catalyst still present were subsequently neutralized with acetic acid and the product was desalinated. In the course of this procedure, potassium acetate formed was also removed.

(5) Hydrophilic Compound B2

(6) Mixture of 250 g 2-ethylhexyl phosphate (45 mol % mono ester and 55 mol % di ester) and 177 g dimethyl cyclohexyl amine.

Example 1

(7) 250 g Polyisocyanate A, 5 g hydrophilic compound B1 and 20 g hydrophilic compound B2 were reacted at 90? C. for 3 hours. The product obtained had an NCO content of 18.9% and a viscosity of 3650 mPas at 23? C.

Comparative Example 1

(8) 180 g Polyisocyanate A and 20 g hydrophilic compound B1 were reacted at 90? C. for 3 hours. The product obtained had an NCO content of 18.8% and a viscosity of 2500 mPas at 23? C.

Comparative Example 2

(9) 250 g Polyisocyanate A and 32.7 g hydrophilic compound B2 were reacted at 90? C. for 3 hours. The product obtained had an NCO content of 18.7% and a viscosity of 4280 mPas at 23? C.

Comparative Example 3

(10) 250 g Polyisocyanate A and 20 g hydrophilic compound B2 were reacted at 90? C. for 3 hours. The product obtained had an NCO content of 19.4% and a viscosity of 3600 mPas at 23? C.

Comparative Example 4

(11) 250 g Polyisocyanate A and 5 g hydrophilic compound B2 were reacted at 90? C. for 3 hours. The product obtained had an NCO content of 20.9% and a viscosity of 2550 mPas at 23? C.

(12) Coating Formulation and Properties

(13) Formulation

(14) 100 g Luhydran? S938T (acrylate-based waterborne polyol commercially available from BASF SE, OH-number 100 mg KOH/g, 45% in water) were admixed with 2.5 g butyldiglycolacetate and 6.7 g butylgylcolacetate as film forming agent. The pH of the mixture was adjusted to 8.5 by using 0.9 g of a 50 wt % solution of dimethyl ethanolamine in water. The application viscosity was adjusted using 7.8 g water and 0.52 g BYK? 340 (Fa. BYK) defoamer were added.

(15) The polyisocyanates from the above examples were diluted to a solids content of 80% with dipropylene glycol dimethyl ether.

(16) 5 g of the thus obtained solution were added to 45 g of the above-mentioned polyol, the mixture was stirred by hand, using a wooden spatula for 20 seconds at 140 to 180 rpm. Thereafter the films were applied to card board with a film-drawing frame (box-type coating bar) in a wet film thickness of 150 ?m.

(17) The gloss was measured at the stated angle (20?, 60? and 90?) after drying at 30 minutes at 60? C. using a micro-TRI-gloss ? apparatus of BYK.

(18) The average diameter (z-average) of the particles was measured at 25? C. by means of dynamic light scattering using the Malvern? Zetasizer 1000.

(19) TABLE-US-00001 Emulsifier Emulsifier NCO Particle B1 B2 Viscosity Content Size Gloss Example (wt %) (wt %) (mPa .Math. s) (wt %) (nm) 20? 60? 90? Example 1 2 8 3650 18.9 138 23 62 93 CompEx 1 10 0 2500 18.8 580 6 29 43 CompEx 2 0 13 4280 18.7 260 7 36 78 CompEx 3 0 8 3600 19.4 3800 1 11 43 CompEx 4 * 2 0 2550 20.9 * not dispersible in water

(20) Comparative Examples 1 and 2 were adjusted to comparable NCO contents as Example 1. The emulsifiability and gloss retention were lower than in the example according to the invention.

(21) Comparative Examples 3 and 4 used the same amounts of the single emulsifiers as in Example 1. Emulsifiability, viscosity, and gloss were worse than in the example according to the invention.