IONICALLY HYDROPHILIZED POLYISOCYANATES WITH IMPROVED DRYING

Abstract

The invention relates to a polyisocyanate mixture comprising a polyisocyanate component A) having aliphatically and/or cycloaliphatically bonded isocyanate groups and a polyisocyanate component B) having araliphatically and/or aromatically bonded isocyanate groups, characterized in that the polyisocyanate component A) comprises at least 0.85% by weight of sulfonate groups (calculated as SO.sub.3; molar weight=80 g/mol) in chemically bonded form and the proportion of the polyisocyanate component B) is 7 to 43% by weight of the total amount of the components A) and B). The invention further relates to the use thereof and also coating compositions comprising the polyisocyanate mixture and also the substrates coated with these coating compositions.

Claims

1. Polyisocyanate mixture comprising a polyisocyanate component A) having aliphatically and/or cycloaliphatically bonded isocyanate groups and a polyisocyanate component B) having araliphatically and/or aromatically bonded isocyanate groups, characterized in that the polyisocyanate component A) comprises at least 0.85% by weight of sulfonate groups (calculated as SO.sub.3; molar weight=80 g/mol) in chemically bonded form and the proportion of the polyisocyanate component B) is 7 to 43% by weight of the total amount of the components A) and B).

2. Polyisocyanate mixture according to claim 1, characterized in that the polyisocyanate component A) is a reaction product of at least one aliphatic and/or cycloaliphatic polyisocyanate C) with at least one organic compound D) bearing at least one group that is reactive to isocyanate groups and which comprises one or more sulfonic acid and/or sulfonate groups, and optionally at least one non-ionic hydrophilic or hydrophobic compound E) comprising at least one group that is reactive to isocyanate groups, which has been prepared optionally in the presence of further auxiliaries and additives F).

3. Polyisocyanate mixture according to claim 2, characterized in that the polyisocyanate C) is any diisocyanates and/or polyisocyanates having aliphatically and/or cycloaliphatically bonded isocyanate groups.

4. Polyisocyanate mixture according to claim 2, characterized in that the polyisocyanate C) is those based on PDI, HDI, IPDI and/or 4,4′-diisocyanatodicyclohexylmethane.

5. Polyisocyanate mixture according to claim 2, characterized in that the organic compound D) is a hydroxy-, mercapto- and/or amino-functional sulfonic acid and/or salt thereof.

6. Polyisocyanate mixture according to claim 2, characterized in that the organic compound D) is an amino-functional sulfonic acid of the general formula (III) and/or salt thereof, ##STR00004## wherein in formula (III) R.sup.5 and R.sup.6 are each independently identical or different radicals and are hydrogen or saturated or unsaturated, linear or branched, aliphatic or cycloaliphatic or aromatic organic radicals having 1 to 18 carbon atoms, which are substituted or unsubstituted and/or comprise heteroatoms in the chain, wherein R.sup.5 and R.sup.6, in combination with each other and optionally one further nitrogen atom or one oxygen atom, may form cycloaliphatic or heterocyclic rings having 3 to 8 carbon atoms, which may optionally be further substituted, and R.sup.7 is a linear or branched aliphatic radical having 2 to 6 carbon atoms.

7. Polyisocyanate mixture according to claim 2, characterized in that the organic compound D) is 2-isopropylaminoethane-1-sulfonic acid, 3-i sopropylaminopropane-1-sulfonic acid, 4-isopropylaminobutane-1-sulfonic acid, 2-cyclohexylaminoethane-1-sulfonic acid, 3-cyclohexylaminopropane-1-sulfonic acid and/or 4-cyclohexylaminobutane-1-sulfonic acid and/or salts thereof.

8. Polyisocyanate mixture according to claim 2, characterized in that the organic compound D) is present to an extent of at least 20 mol % in the form of sulfonate groups neutralized with N,N-dimethylbutylamine, N,N-diethylmethylamine, N,N-diisopropylethylamine, N,N-dimethylcyclohexylamine, N-methylpiperidine, N-ethylmorpholine.

9. Polyisocyanate mixture according to claim 2, characterized in that the non-ionic hydrophilic or hydrophobic organic compound E) is pure polyethylene oxide polyether alcohols and/or mixed polyalkylene oxide polyether alcohols, the alkylene oxide units of which consist of ethylene oxide units to an extent of at least 70 mol %, and/or aliphatic alcohols or fatty acid ester alcohols which comprise in each case at least 8 carbon atoms.

10. Polyisocyanate mixture according to claim 1, characterized in that the polyisocyanate component A) comprises at least 0.90% by weight, of sulfonate groups (calculated as SO.sub.3; molar weight=80 g/mol) in chemically bonded form.

11. Polyisocyanate mixture according to claim 1, characterized in that the polyisocyanate component B) is polyisocyanates having urethane and/or isocyanate structure obtainable from monomeric 2,4- and/or 2,6-TDI by reaction with polyols and/or oligomerization.

12. Polyisocyanate mixture according to claim 1, characterized in that the proportion of the polyisocyanate component B) is 10 to 40% by weight, of the total amount of the components A) and B).

13. Use of at least one polyisocyanate mixture according to claim 1 as starting components in the production of polyurethane plastics.

14. Coating composition comprising at least one polyisocyanate mixture according to claim 1.

15. Substrate, coated with a coating composition according to claim 14 optionally cured by the action of heat.

Description

EXAMPLES

[0109] All percentages are based on weight unless otherwise noted.

[0110] The NCO contents were determined by titrimetry in accordance with DIN EN ISO 11909:2007-05.

[0111] All viscosity measurements were taken with a Physica MCR 51 rheometer from Anton Paar Germany GmbH (DE) according to DIN EN ISO 3219:1994-10 at a shear rate of 250 s.sup.−1.

[0112] The residual monomer contents were measured according to DIN EN ISO 10283:2007-11 by gas chromatography with an internal standard.

[0113] Water contents were determined by volumetric titration by Karl Fischer in accordance with DIN 53715 (created based on DIN 51777 Part 1 (1973 edition)) using a Titrando 841 automatic titration unit from Methrom. The measurement range of this method is from 0.01 to 99% by weight.

[0114] The gloss of the coatings obtained was measured by reflectometry in accordance with DIN EN ISO 2813:2015-02 at the 60° and 20° angle. The higher the measurement value, the higher the gloss.

[0115] The haze was measured in accordance with DIN EN ISO 13803:2015-02 at the 20° angle. The lower the haze value, the more free of cloudiness is the coating.

[0116] The pendulum damping according to Konig was determined in accordance with DIN EN ISO 1522; 2007-04 on glass plates.

[0117] The drying properties of the coating systems were determined in accordance with DIN 53 150:2002-09.

[0118] The maximum blister-free layer thickness (degree of blistering) was determined in accordance with DIN EN ISO 4628-2:2016-07.

[0119] The resistance to chemicals was determined by the method described in DIN EN 12720:2014-02 using coffee, red wine, water, mustard and ethanol as test liquids.

STARTING COMPOUNDS

Polyisocyanates C)

Polyisocyanate C1

[0120] HDI polyisocyanate comprising isocyanurate groups, produced by catalytic trimerization of HDI based on Example 11 of EP-A 330 966, with the modification that the reaction was stopped by addition of dibutyl phosphate at an NCO content of the crude mixture of 40%. Subsequently, unconverted HDI was removed by thin-film distillation at a temperature of 130° C. and a pressure of 0.2 mbar. [0121] NCO content: 21.7% [0122] NCO functionality: 3.4 [0123] Monomeric HDI: 0.1% [0124] Viscosity (23° C.): 3080 mPas [0125] Colour number (Hazen): 18

Polyisocyanate C2

[0126] PDI polyisocyanate comprising isocyanurate groups, produced by catalytic trimerization of PDI by the method described in WO 2016/146579 for the polyisocyanate component A2). The reaction was deactivated at an NCO content of the crude mixture of 36.7% by addition of an equimolar amount of dibutyl phosphate, based on the amount of catalyst used, and further stirring for 30 minutes at 80° C. Subsequently, unconverted PDI was removed by thin-film distillation at a temperature of 140° C. and a pressure of 0.5 mbar. [0127] NCO content: 21.8% [0128] NCO functionality: 3.5 [0129] Monomeric PDI: 0.09% [0130] Viscosity (23° C.): 9850 mPas [0131] Colour number (Hazen): 34

[0132] Aminosulfonic Acids D)

[0133] 3-(Cyclohexylamino)propanesulfonic acid (Sigma-Aldrich Chemie Gmbh, Munich, Del.) was used as aminosulfonic acid, which had a water content of 0.4% after 3 hours' drying under vacuum (100° C./ca. 0.5 mbar).

Polyisocyanate Component A1)

[0134] 943.9 g (4.88 val) of the isocyanurate group-containing starting polyisocyanate C1) were stirred together with 36.0 g (0.16 val) of 3-(cyclohexylamino)propanesulfonic acid (CAPS), 20.1 g (0.16 mol) of dimethylcyclohexylamine and 0.05 g (50 ppm) of 2,6-di-tert-butyl-4-methylphenol under dry nitrogen at 100° C. for 4:00 hours until a substantially clear polyisocyanate mixture comprising sulfonate groups prevailed. After cooling to room temperature and filtration over a T 5500 filter layer (Seitz), the following characteristic data were determined: [0135] NCO content: 19.8% [0136] NCO functionality: 3.3 [0137] Viscosity (23° C.): 8210 mPas [0138] Colour number (Hazen): 18 [0139] Sulfonate group content: 1.30% (calculated as SO.sub.3; molar weight %=80 g/mol)

Polyisocyanate Component A2)

[0140] 960.7 g (4.92 val) of the isocyanurate group-containing starting polyisocyanate C1) were stirred together with 25.0 g (0.11 val) of 3-(cyclohexylamino)propanesulfonic acid (CAPS), 14.3 g (0.11 mol) of dimethylcyclohexylamine and 0.05 g (50 ppm) of 2,6-di-tert-butyl-4-methylphenol under dry nitrogen at 100° C. for 3:30 hours until a substantially clear polyisocyanate mixture comprising sulfonate groups prevailed. After cooling to room temperature and filtration over a T 5500 filter layer (Seitz), the following characteristic data were determined: [0141] NCO content: 20.2% [0142] NCO functionality: 3.3 [0143] Viscosity (23° C.): 4050 mPas [0144] Colour number (Hazen): 18 [0145] Sulfonate group content: 0.90% (calculated as SO.sub.3; molar weight %=80 g/mol)

Polyisocyanate Component A3)

[0146] 965.3 g (4.99 val) of the isocyanurate group-containing starting polyisocyanate C1) were stirred together with 22.1 g (0.10 val) of 3-(cyclohexylamino)propanesulfonic acid (CAPS), 12.6 g (0.10 mol) of dimethylcyclohexylamine and 0.05 g (50 ppm) of 2,6-di-tert-butyl-4-methylphenol under dry nitrogen at 100° C. for 3:30 hours until a substantially clear polyisocyanate mixture comprising sulfonate groups prevailed. After cooling to room temperature and filtration over a T 5500 filter layer (Seitz), the following characteristic data were determined: [0147] NCO content: 20.5% [0148] NCO functionality: 3.3 [0149] Viscosity (23° C.): 3740 mPas [0150] Colour number (Hazen): 20 [0151] Sulfonate group content: 0.80% (calculated as SO.sub.3; molar weight %=80 g/mol)

Polyisocyanate Component A4)

[0152] 937.2 g (4.86 val) of the isocyanurate group-containing starting polyisocyanate C2) were stirred together with 40.0 g (0.18 val) of 3-(cyclohexylamino)propanesulfonic acid (CAPS), 22.8 g (0.18 mol) of dimethylcyclohexylamine, 0.05 g (50 ppm) of 2,6-di-tert-butyl-4-methylphenol and 250 g of MPA under dry nitrogen at 100° C. for 3:15 hours until a substantially clear polyisocyanate mixture comprising sulfonate groups prevailed. After cooling to room temperature and filtration over a T 5500 filter layer (Seitz), the following characteristic data were determined: [0153] NCO content: 15.7% [0154] NCO functionality: 3.4 [0155] Solids content: 80% [0156] Viscosity (23° C.): 3420 mPas [0157] Colour number (Hazen): 17 [0158] Sulfonate group content: 1.45% (calculated as SO.sub.3; molar weight %=80 g/mol, on solids)

Polyisocyanate Component B1)

[0159] Urethane group-containing TDI polyisocyanate, produced based on Example 4 of EP-A 0 546 399, with the modification that a mixture of 80% 2,4-TDI and 20% 2,6-TDI is used and the resulting pale yellow resin is dissolved at 60% strength in 1-methoxy-2-propyl acetate (MPA). [0160] NCO content: 10.6% [0161] NCO functionality: 3.3 [0162] Monomeric 2,4-TDI: 0.13% [0163] Monomeric 2,6-TDI: 0.14% [0164] Viscosity (23° C.): 370 mPas [0165] Colour number (Hazen): 34

Examples 1 to 10 (Inventive and Comparative)

[0166] The polyisocyanate components A1), A2) and A3) were mixed with polyisocyanate component B1) at 30° C. in varying ratios and homogenized by stirring for 30 minutes. The solids content of the polyisocyanate mixtures was subsequently adjusted with MPA to 70% in each case.

[0167] Table 1 below shows the respective compositions and characteristic data of the polyisocyanate mixtures obtained.

Examples 11 to 20 (Inventive and Comparative)

[0168] 100 parts by weight of a commercial aqueous hydroxy-functional polyacrylate dispersion having a solids content of 40% and an OH content of 3.0%, based on resin solids, obtainable under the name Bayhydrol A 2651 (Covestro AG, Leverkusen), were mixed with 2.6 parts by weight of a commercial non-ionic wetting agent (Surfynol AD01, Evonik Materials Netherlands BV, Utrecht), 0.16 parts by weight of a commercial flow control additive (TEGO Flow 425, Evonik Resource Efficiency GmbH, Essen) and 0.16 parts by weight of a commercial thickener (OPTIFLO-TVS VF, BYK-Chemie GmbH, Wesel). To this clearcoat material were added the polyisocyanate mixtures of Examples 1 to 10, in each case in the amounts specified in Table 2 (in each case corresponding to an equivalent ratio of isocyanate groups to alcoholic hydroxyl groups of 1.5:1) and the mixture was homogenized by stirring at 1000 rpm for 5 minutes. The solids contents of the clearcoats were then adjusted to 45% by addition of water.

[0169] For comparison, using the identical method, a clearcoat was likewise produced from 100 parts by weight of Bayhydrol A 2651 and 32.12 parts by weight of the polyisocyanate component A1) in MPA or 32.4 parts by weight of a 70% solution of the polyisocyanate component A4) (in each case corresponding to an equivalent ratio of isocyanate groups to alcoholic hydroxyl groups of 1.5:1).

[0170] The coatings were applied with the aid of a film drawing frame in a wet film layer thickness of 200 μm (ca. 90 μm dry) on glass plates and black plexiglass sheets and were dried in each case at room temperature (ca. 25° C.) and 50% relative air humidity. Table 2 shows paint-related properties of the coatings obtained.

[0171] The processing time of the application-ready mixtures was >6 hours in all cases.

TABLE-US-00001 TABLE 1 Example 1 6 8 Comparative 2 3 4 5 Comparative 7 Comparative 9 10 Polyisocyanate component A1) 664.7 630.1 559.8 489.9 420.0 385.0 — — 525.0 — Polyisocyanate component A2) — — — — — — 630.1 — — — Polyisocyanate component A3) — — — — — — — 630.1 — — Polyisocyanate component A4) — — — — — — — — — 743.9 Polyisocyanate component B1) 58.9 116.4 233.6 350.2 466.7 525.0 116.4 116.4 291.7 174.9 MPA 276.4 253.4 206.6 159.9 113.3 90.0 253.4 253.4 183.3 81.2 NCO content [%] 13.8 13.7 13.6 13.4 13.3 13.2 14.0 14.1 13.5 13.5 Viscosity (23° C.): [mPas] 115 125 222 261 326 342 193 188 256 305 Solids content [%] 70 70 70 70 70 70 70 70 70 70 SO.sub.3; content in A1) .sup.a) [%] 1.30 1.30 1.30 1.30 1.30 1.30 0.90 0.80 1.30 1.45 Proportion of B1) .sup.b) [%] 5.0 10.0 20.0 30.0 40.0 45.0 10.0 10.0 25.0 15.0 .sup.a) calculated as SO.sub.3; molar weight = 80 g/mol (on solids) .sup.b) based on the total amount of the components A1) and B1), (in each case solid/solid)

TABLE-US-00002 TABLE 2 Example 11 12 17 Comparative Comparative 13 14 15 16 Comparative Polyisocyanate component A1) [parts by weight] .sup.a), b) 32.12 — — — — — — Polyisocyanate mixture from example 1 [parts by weight] .sup.a) — 32.30 — — — — — Polyisocyanate mixture from example 2 [parts by weight] .sup.a) — — 32.47 — — — — Polyisocyanate mixture from example 3 [parts by weight] .sup.a) — — — 32.83 — — — Polyisocyanate mixture from example 4 [parts by weight] .sup.a) — — — — 33.19 — — Polyisocyanate mixture from example 5 [parts by weight] .sup.a) — — — — — 33.50 — Polyisocyanate mixture from example 6 [parts by weight] .sup.a) — — — — — — 33.75 Gloss at 20°/60° C. 86/92 85/90 85/90 85/91 83/90 84/91 19/54 Haze 8 7 7 11 12 33 303 Drying .sup.c) T1 [min at 23° C.] 53 53 52 52 50 48 48 T4 [min at 23° C.] 360 344 276 260 249 216 224 Pendulum hardness .sup.d) [s] after 3 h/23° C. 10 21 35 34 40 48 16 after 6 h/23° C. 51 44 51 65 61 61 21 after 1 d/23° C. 76 58 63 85 79 71 34 after 7 d/23° C. 91 81 80 95 91 88 61 Example 19 22 18 Comparative 20 21 Comparative Polyisocyanate mixture from example 7 [parts by weight] .sup.a) 31.8 — — — — Polyisocyanate mixture from example 8 [parts by weight] .sup.a) — 31.6 — — — Polyisocyanate mixture from example 9 [parts by weight] .sup.a) — — 33.0 — — Polyisocyanate mixture from example 10 [parts by weight] .sup.a) — — — 33.0 — Polyisocyanate component A4) [parts by weight] .sup.a), b) — — — — 32.4 Gloss at 20°/60° C. 79/88 59/81 84/90 83/90 85/90 Haze 23 167 10 13 9 Drying .sup.c) T1 [min at 23° C.] 54 51 53 56 55 T4 [min at 23° C.] 265 272 230 255 383 Pendulum hardness .sup.d) [s] after 3 h/23° C. 27 25 37 32 18 after 6 h/23° C. 50 48 64 64 54 after 1 d/23° C. 65 62 79 80 76 after 7 d/23° C. 84 81 92 91 95 .sup.a) based on 100 parts by weight of Bayhydrol A 2651 .sup.b) as 70% solution in MPA .sup.c) determination of drying in accordance with DIN EN ISO 9117-5: 2012-11 .sup.d) König pendulum hardness (DIN 53157), measured on RT-dried coating films

[0172] The examples 13 to 16 and 20 show that the use of the polyisocyanate mixtures according to the invention from Examples 2 to 5 and 9 in combination with the aqueous binder give shiny, clear practically turbidity-free coating films which, compared to the crosslinked coatings with the pure aliphatic polyisocyanate A1) (Example 11) and with the polyisocyanate mixture of Example 1, which comprises only 5% by weight of aromatic polyisocyanate (Example 12), have the advantage of a distinctly more rapid drying (T4) at unchanged long pot life of >6 hours. Comparative Example 17 shows that the polyisocyanate mixture having a proportion of 45% by weight of aromatic polyisocyanate B1) is incompatible with the aqueous binder dispersion and gives a highly cloudy coating film recognizable by the low gloss.

[0173] The comparison of examples 18 and 19 demonstrates that in order to achieve clear, turbidity-free coating films, a certain minimum amount of sulfonate groups in polyisocyanate component A) is required.

[0174] Example 21 and comparative Example 22 show the advantage of the more rapid drying of the polyisocyanate mixtures according to the invention by the example of an isocyanurate-containing PDI polyisocyanate.

Examples 23 and 24 (Comparative)

[0175] To determine the maximum blister-free layer thickness, the clearcoat from Example 20 and comparative Example 11 was applied to black plexiglass sheets with the aid of a step gap film applicator and in each case dried at room temperature (ca. 25° C.) and 55% relative air humidity. The following table shows the degrees of blistering evaluated visually in accordance with DIN EN ISO 4628-2:2016-07 (0=best grade; 5=worst grade) for various layer thicknesses applied.

TABLE-US-00003 TABLE 3 Example 24 23 Comparative Clearcoat from Example 20 11 Layer thickness applied 200 250 300 400 500 200 250 300 400 500 [μm] Amount of blistering 0 0 0 2 2.5 0 0 1 4 4.5 Blister size 0 0 0 2 2 0 0 1 2 2

[0176] The comparison shows that the coating film (Example 20) crosslinked with the polyisocyanate mixture according to the invention from Example 9, despite its proportion of aromatic isocyanate groups that are highly reactive to water, at an application layer thickness of 300 μm, still dries completely blister-free, and even at higher application thicknesses shows a distinctly lower blister formation than the coating from Example 11 crosslinked with the pure aliphatic polyisocyanate component A1).

Example 25 and 26 (Inventive and Comparative)

[0177] 100 parts by weight of a commercial aqueous hydroxy-functional polyacrylate dispersion having a solids content of 40% and an OH content of 3.0%, based on resin solids, obtainable under the name Bayhydrol A 2651 (Covestro AG, Leverkusen), were mixed with 2.8 parts by weight of a commercial non-ionic wetting agent (Surfynol AD01, Evonik Materials Netherlands BV, Utrecht), 38.2 parts by weight of a commercial aqueous white pigment dispersion (White Aquamac 6, Proquimac PFC, S.A., Barcelona, Spain), 2.0 parts by weight of a commercial thickener (OPTIFLO-TVS VF, BYK-Chemie GmbH, Wesel) and 29.8 parts by weight deionized water, to give a white coating. To this stock mixture were added 37.4 parts by weight of the polyisocyanate mixture from Example 9 (corresponding to an equivalent ratio of isocyanate groups to alcoholic hydroxyl groups of 1.7:1) and the mixture was homogenized by stirring at 1000 rpm for 5 minutes.

[0178] For comparison, using the identical method, a white coating was produced from 100 parts by weight of Bayhydrol A 2651 and 36.3 parts by weight of a 70% solution of the polyisocyanate component A1) in MPA (corresponding to an equivalent ratio of isocyanate groups to alcoholic hydroxyl groups of 1.7:1).

[0179] The coatings were applied with the aid of a film drawing frame in a wet film layer thickness of 200 μm (ca. 90 μm dry) on glass plates and were dried in each case at 50° C. for 16 hours. After a further 24 hours at 23° C., the white coatings thus obtained were tested for chemical resistance in accordance with DIN EN 12720:2014-02. Table 4 below shows the test results after various testing periods.

TABLE-US-00004 TABLE 4 Example Test time 25 26 Comparative Resistance .sup.a) to Coffee 6 h 5 5 16 h 5 5 Red wine 6 h 5 5 16 h 5 5 Water 6 h 5 5 16 h 5 5 Mustard 6 h 5 5 16 h 5 5 Ethanol .sup.b) 1 h 4.5 4.5 .sup.a) method in accordance with DIN EN 12720: 2014-02, evaluation 0 to 5 (0 = worst, 5 = best grade) .sup.b) as 48% aqueous solution

[0180] The examples show that the coating film (Example 25) crosslinked with the inventive polyisocyanate mixture from Example 9 has as good resistance to household chemicals as the coating crosslinked with the pure aliphatic polyisocyanate component A1).