Aqueous polyurethane dispersions

Abstract

The present invention relates to radiation-curable, aqueous dispersions based on polyurethane acrylates (i), which are characterized in that the polyurethane acrylate (i) comprises as builder components A) one or more aromatic polyepoxy(meth)acrylates with an OH number of from 20 to 300 mg of KOH/g of substance, C) one or more oligo- or polyesters containing unsaturated fatty acids with an OH number of from 15 to 300 mg of KOH/g of substance and an iodine number of greater than 50 g of I.sub.2/100 g of substance, E) one or more compounds with at least one group which is reactive towards isocyanate and additionally at least one group having a hydrophilizing action and F) one or more organic polyisocyanates, a process for the preparation thereof, the use of the coating compositions as lacquers and/or adhesives, and objects and substrates provided with these lacquers and/or adhesives.

Claims

1. A radiation-curable aqueous dispersion comprising a polyurethane acrylate (i), wherein the polyurethane acrylate (i) comprises: A) 15 to 35 wt. % of one or more reaction product of (meth)acrylic acid with aromatic glycidyl ethers which are chosen from the group consisting of monomeric, oligomeric or polymeric bisphenol A, bisphenol F, alkoxylated derivatives thereof, and combinations thereof, C) 25 to 50 wt. % of the transesterification product of castor oil and an unsaturated fatty acid, E) is hydroxypivalic acid and/or dimethylolpropionic acid and F) one or more organic polyisocyanates selected from the group consisting of 1,6-Hexamethylene-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane and 4,4-diisocyanato-dicyclohexylmethane, homologues or oligomers of 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 4,4-diisocyanato-dicyclohexylmethane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and/or uretdione groups, and mixtures thereof, wherein the molar ratios of isocyanate groups in F) to groups in A) to E) which are reactive towards isocyanate are from 0.8:1 to 2.5:1, and, optionally, as component (ii) a reactive diluent with at least one group which can undergo free radical polymerization, wherein (i) and (ii) add up to 100 wt. %.

2. The radiation-curable aqueous dispersion according to claim 1, further comprising a component B) which differs from A) and has at least one group which is reactive towards isocyanate and at least one radiation-curable double bond.

3. The radiation-curable aqueous dispersion according to claim 1, further comprising a component D) which has one or more compounds with at least one group which is reactive towards isocyanate, but neither radiation-curable nor oxidatively curable double bonds.

4. The radiation-curable aqueous dispersion according to claim 1, further comprising a component G) which differs from A) to F) and has at least one amine function.

5. The radiation-curable aqueous dispersion according to claim 1, wherein the aqueous dispersion comprises as component (ii) a reactive diluent with at least one group which can undergo free radical polymerization.

6. The radiation-curable aqueous dispersion according to claim 1, wherein component C) is the transesterification product of castor oil and soy bean oil.

7. The radiation-curable aqueous dispersion according to claim 1, wherein the dispersion is free from unsaturated dicyclopentadiene-modified polyester resin.

8. A process for the preparation of the radiation-curable aqueous dispersion according to claim 4, comprising: obtaining a polyurethane acrylate (i) by reaction of components A) to E) with component F) in one or more reaction steps, optionally adding a neutralizing agent before, during or after the preparation of the addition product of A) to F) to produce the ionic groups necessary for the dispersing operation; and dispersing by adding water to the addition product of A) to F) or transferring of the addition product of A) to F) into an aqueous reservoir, and optionally chain lengthening by means of component G) before, during or after the dispersing.

9. A method for producing of a coating comprising applying the radiation-curable aqueous dispersion according to claim 1 to a substrate.

10. A coating composition comprising the radiation-curable aqueous dispersion according to claim 1.

11. A method for coating comprising applying the coating composition according to claim 10 in pigmented formulations to wood or plastic.

12. A substrate coated with the coating composition according to claim 10.

13. The radiation-curable aqueous dispersion according to claim 1, further comprising a siccative selected from the group consisting of salts of lead, cobalt, iron, manganese, and copper.

14. The radiation-curable aqueous dispersion according to claim 13, wherein component C) is the transesterification product of castor oil and soy bean oil.

15. The radiation-curable aqueous dispersion according to claim 6, wherein component A) is bisphenol A diglycidyl diacrylate and component F) is 4,4-diisocyanato-dicyclohexylmethane.

Description

EXAMPLES

(1) The NCO content was in each case monitored titrimetrically in accordance with DIN 53185.

(2) The solids content of the polyurethane dispersion was determined gravimetrically after all the non-volatile constituents had been evaporated off, in accordance with DIN 53216.

(3) The average particle size was determined by laser correlation spectroscopy.

(4) The flow time was determined in accordance with DIN 53211 with the aid of the 4 mm DIN cup.

(5) The OH number was determined in accordance with DIN 53240 using acetic anhydride, and the iodine number in accordance with DIN 53241-1.

(6) Room temperature means 23 C.

(7) 1) Polyester Based on Unsaturated Oils.

(8) 3,200 g of castor oil and 1,600 g of soya oil as well as 2.4 g of lithium hydroxide were weighed into a 5 l reactor with a distillation attachment. A stream of nitrogen (5 l/h) was passed through the reactant. The mixture was heated up to 240 C. in the course of 140 min. After 7 h at 240 C., the mixture was cooled. OH number: 109 mg of KOH/g of substance, acid number: 3.2 mg of KOH/g of substance, iodine number: 97 mg of I.sub.2/100 g of substance.

(9) 2) Preparation of a Radiation-Curable Aqueous Polyurethane Dispersion (According to the Invention)

(10) 168.9 parts of the bisphenol A diglycidyl diacrylate AgiSyn1010 (AGI Corp., Taipeh, Taiwan), component A), 247.1 parts of polyester 1), component C), 32.0 parts of dimethylolpropionic acid, component E), 323.1 parts of 4,4-diisocyanatodicyclohexylmethane, component F), and 0.7 part of dibutyltin dilaurate were dissolved in 220 parts of acetone and the solution was reacted at 60 C., while stirring, to an NCO content of 4.0 wt. %. Neutralization was then carried out by addition and stirring in of 21.0 parts of triethylamine, and 78.6 parts of the ditrimethylolpropane tetraacrylate Ebecryl 140 (Cytec Surface Specialties SA/NV, Drogenbos, Belgium), component (ii), were added. The clear solution was introduced into 1,230 parts of water, while stirring. Thereafter, a mixture of 22.3 parts of ethylenediamine, component G), and 84.0 parts of water was added to the dispersion, while stirring. The acetone was then distilled off from the dispersion under a slight vacuum. A radiation-curable aqueous polyurethane dispersion 2) having a solids content of 37 wt. %, a flow time of 18 sec, an average particle size of 95 nm and a pH of 8.4 was obtained.

(11) 3) Preparation of a Radiation-Curable Aqueous Polyurethane Dispersion (According to the Invention)

(12) 37.3 parts of the bisphenol A diglycidyl diacrylate AgiSyn 1010 (AGI Corp., Taipeh, Taiwan), component A), 120.7 parts of the polyester acrylate AgiSyn 720 (AGI Corp., Taipeh, Taiwan), component B), 109.8 parts of polyester 1), component C), 8.2 parts of trimethylolpropane, component D), 4.5 parts of 1,4-butanediol, component D), 22.1 parts of dimethylolpropionic acid, component E), 199.9 parts of 4,4-diisocyanatodicyclohexylmethane, component F), and 0.6 part of dibutyltin dilaurate were dissolved in 175 parts of acetone and the solution was reacted at 60 C., while stirring, to an NCO content of 1.9 wt. %. Neutralization was then carried out by addition and stirring in of 15.2 parts of triethylamine. The clear solution was introduced into 900 parts of water, while stirring. Thereafter, a mixture of 8.1 parts of ethylenediamine, component G), and 24.0 parts of water was added to the dispersion, while stirring. The acetone was then distilled off from the dispersion under a slight vacuum. A radiation-curable aqueous polyurethane dispersion 3) having a solids content of 40 wt. %, a flow time of 24 sec, an average particle size of 146 nm and a pH of 8.8 was obtained.

(13) 4) Preparation of a Radiation-Curable Aqueous Polyurethane Dispersion (not According to the Invention)

(14) 241.5 parts of the bisphenol A diglycidyl diacrylate AgiSyn 1010 (AGI Corp., Taipeh, Taiwan), component A), 127.27 parts of the polyester Desmophen PE 170 HN (Bayer MaterialScience AG, Leverkusen, Del.), component D), 5.25 parts of neopentyl glycol, component D), 31.98 parts of dimethylolpropionic acid, component E), 323.10 parts of 4,4-diisocyanatodicyclohexylmethane, component F), and 0.7 part of dibutyltin dilaurate were dissolved in 200 parts of acetone and the solution was reacted at 50 C., while stirring, to an NCO content of 3.7 wt. %. A mixture of 80.50 parts of the propoxylated glycerol triacrylate OTA 480 (Cytec Surface Specialties SA/NV, Drogenbos, Belgium), component (ii), and 78.32 parts of the ditrimethylolpropane tetraacrylate Ebecryl 140 (Cytec Surface Specialties SA/NV, Drogenbos, Belgium), component (ii), was added to the solution obtained in this way and was stirred in. Neutralization was then carried out by addition and stirring in of 22.93 parts of triethylamine. The clear solution was introduced into 1,150 parts of water, while stirring. Thereafter, a mixture of 22.36 parts of ethylenediamine, component G), and 134.2 parts of water was added to the dispersion, while stirring. The acetone was then distilled off from the dispersion under a slight vacuum. A radiation-curable aqueous polyurethane dispersion 4) having a solids content of 40 wt. %, a flow time of 34 sec, an average particle size of 125 nm and a pH of 8.5 was obtained.

(15) 5) Preparation of the Unsaturated Dicyclopentadiene-Modified Polyester Resin a1) from EP-A 1 914 253

(16) 42.47 parts of maleic anhydride and 22.95 parts of diethylene glycol were weighed into a high-grade steel apparatus with electrical heating, internal cooling coil, anchor stirrer, reflux condenser, column, glass bridge and nitrogen inlet or pass-over line, the mixture was rendered inert with nitrogen and heated to 150 C. in the course of one hour, while passing nitrogen over and by utilizing the exothermic reaction, and was stirred at this temperature for one hour in order to conclude the formation of the half-ester. After cooling to 140 C., 16.45 parts of dicyclopentadiene were added and the mixture was kept at 140 C. for four hours. At the end of this, the acid number (205+/5) and OH number (<15) were determined. 5.95 parts of ethylene glycol, 17.73 parts of diethylene glycol and 0.2 part of toluhydroquinone were then added. The mixture was heated up to 190 C. such that the overhead temperature did not rise above 105 C., and was kept at this temperature until an acid number of approx. 12 and a hydroxyl number of from 105 to 125 mg of KOH/g of substance was reached by esterification. After cooling to 150 C., 0.1 part of toluhydroquinone and 0.03 part of trimethylhydroquinone were added. The mixture was then cooled further to 55 C. and dissolved in acetone. A 71% strength solution of a dicyclopentadiene-modified unsaturated polyester resin 5) resulted.

(17) 6) Preparation of a Radiation-Curable Aqueous Polyurethane Dispersion Based on an Unsaturated Dicyclopentadiene-Modified Polyester Resin, Example 2) from EP-A 1 914 253 (Not According to the Invention)

(18) 158.4 parts of the acetone solution prepared in Example 5), 425.6 parts of the polyester acrylate Laromer PE 44 F (BASF AG, Ludwigshafen, Del.), component B), 26.8 parts of dimethylolpropionic acid, component E), 50.4 parts of hexamethylene-diisocyanate and 102.2 parts of isophorone-diisocyanate, component F), and 0.6 part of dibutyltin dilaurate were dissolved in 180 parts of acetone and the solution was reacted at 50 C., while stirring, to an NCO content of 1.6 wt. %. 20.2 parts of triethylamine were added to the polymer solution obtained in this way and were stirred in. The clear solution formed was then introduced into 1,100 parts of distilled water, while stirring, and a mixture of 10.2 parts of ethylenediamine, component G), and 31.0 parts of water was added to the dispersion, while stirring. The acetone was distilled off from the dispersion under a slight vacuum. Polyurethane dispersion 6) containing an unsaturated dicyclopentadiene-modified polyester and having a solids content of 40 wt. %, a flow time of 27 sec, an average particle size of 112 nm and a pH of 8.1 was obtained.

(19) TABLE-US-00001 TABLE 1 Formulations for colour-pigmented systems Yellow-pigmented Yellow-pigmented lacquer [A-1] and red- lacquer [A-3] and red- pigmented lacquer pigmented lacquer [A-2] without siccative [A-4] with siccative (parts by weight) (parts by weight) UV dispersion.sup.1 100.0 100.0 BYK 093.sup.2 0.4 0.4 BYK 346.sup.3 0.3 0.3 Borchi Oxy Coat.sup.4 0.1 Acematt TS 100.sup.5 0.5 0.5 Aquamatt 208.sup.6 2.0 2.0 Irgacure 5007 0.5 0.5 Irgacure 819 DW.sup.8 1.0 1.0 Tafigel PU 50.sup.9 1.6 1.6 Pigment Xfast 5.9 5.9 (yellow or red).sup.10 Water 11.2 11.2 Total 123.4 123.5 .sup.1Adapted to 35% solids with water/butyl glycol = 1/1 .sup.2Defoamer based on polysiloxane from BYK, Wesel, DE .sup.3Flow agent based on a polyether-modified hydroxy-functional polydimethylsiloxane from BYK, Wesel, DE .sup.4Siccative for oxidative drying based on iron from OMG Borchers GmbH, Langenfeld, DE .sup.5Matting agent based on silica from Evonik Industries AG, Essen, DE .sup.6Aqueous dispersion of a polyethylene wax from BYK, Wesel, DE .sup.7A mixture of benzophenone and (1-hydroxycyclohexyl) phenyl ketone from Ciba, Lampertheim, DE .sup.8Phenyl-bis-(2,4,6-trimethylbenzoyl)-phosphine oxide from. Ciba, Lampertheim, DE .sup.9Thickener based on polyurethane from Mnzing Chemie GmbH, Heilbronn, DE .sup.10Yellow pigment: Xfast yellow 1256 (arylide yellow), red pigment: Xfast red 3860 (diketo-pyrrolo-pyrrole) from BASF SE, Ludwigshafen, DE

(20) TABLE-US-00002 TABLE 2 Application and curing conditions for colour-pigmented systems Pigmented lacquers [A-1], [A-2], [A-3], [A-4] Substrate wood Application by knife-coating box knife, 2 150 m, wet film Thermal drying 10 min, 50 C. Radiation curing 3 m/min (Ga + Hg), 80 W

(21) After the thermal drying for evaporation of the water, the coatings of Examples 2, 3 and 4 were very resistant to blocking, i.e. a finger could be pressed on the coating without an impression being left behind. The coating from Example 6 was still slightly tacky and correspondingly sensitive to dust or mechanical destruction. After the radiation curing, the coated substrates were stored for three days at room temperature and then subjected to the tests. During the three days at room temperature, oxidative curing by atmospheric oxygen took place.

(22) TABLE-US-00003 TABLE 3 Data on the use testing of the yellow-pigmented lacquer without siccative [A-1], 1 h after the radiation curing, before the oxidative curing Use testing.sup.11 UV dispersion Example 4 Example 6 Exam- Exam- (compar- (EP-A ple 2 ple 3 ison) 1 914 253) Resistance to water, 16 h 4 4 4 3 Resistance to coffee, 16 h 3 3 4 3 Resistance to red wine, 16 h 3 3 4 3 Resistance to ethanol/water 3 3 3 1 (50%), 6 h Resistance to ethanol/water 3 3 3 1 (50%), 16 h .sup.11The resistance properties are evaluated by visual inspection after the exposure (duration in hours).

(23) Rating 5: No visible changes (no damage)

(24) Rating 4: Slight change in shine or colour shade, only visible if the light source reflects in the test surface on or close to the marking and is reflected directly to the eye of the viewer, or some demarcated markings just detectable (swelling ring detectable, or no softening detectable with the fingernail).

(25) Rating 3: Slight marking to be seen from several viewing angles, for example an almost complete circle or circular area just detectable (swelling ring detectable, scratch tracks of the fingernail detectable)

(26) Rating 2: Severe marking, but the surface structure is largely unchanged. (closed swelling ring, scratch tracks detectable).

(27) Rating 1: Severe marking, but the surface structure is largely unchanged, marking can be scratched through to the substrate.

(28) For the oxidative curing, the coatings were stored at room temperature for three days.

(29) TABLE-US-00004 TABLE 4 Data on the use testing of the yellow-pigmented lacquer without siccative [A-1], after radiation curing and oxidative curing Use testing.sup.12 UV dispersion Example 4 Example 6 Exam- Exam- (compar- (EP-A ple 2 ple 3 ison) 1 914 253) Resistance to water, 16 h 4 4 4 3 Resistance to coffee, 16 h 5 5 5 3 Resistance to red wine, 16 h 5 4 4 3 Resistance to ethanol/water 4 3 3 1 (50%), 6 h Resistance to ethanol/water 4 3 3 1 (50%), 16 h .sup.12see footnote 11, Table 3

(30) TABLE-US-00005 TABLE 5 Data on the use testing of the yellow-pigmented lacquer with siccative [A-3], after radiation curing and oxidative curing Use testing.sup.13 UV dispersion Example 4 Example 6 Exam- Exam- (compar- (EP-A ple 2 ple 3 ison) 1 914 253) Resistance to water, 16 h 5 5 4 3 Resistance to coffee, 16 h 5 5 5 3 Resistance to red wine, 16 h 5 5 4 3 Resistance to ethanol/water 5 4 3 1 (50%), 6 h Resistance to ethanol/water 4 3 3 1 (50%), 16 h .sup.13see footnote 11, Table 3

(31) TABLE-US-00006 TABLE 6 Data on the use testing of the red-pigmented lacquer without siccative [A-2], after radiation curing and oxidative curing Use testing.sup.14 UV dispersion Example 4 Example 6 Exam- Exam- (compar- (EP-A ple 2 ple 3 ison) 1 914 253) Resistance to water, 16 h 4 4 4 3 Resistance to coffee, 16 h 5 5 5 3 Resistance to red wine, 16 h 5 4 4 3 Resistance to ethanol/water 4 3 3 1 (50%), 6 h Resistance to ethanol/water 3 3 3 1 (50%), 16 h .sup.14see footnote 11, Table 3

(32) TABLE-US-00007 TABLE 7 Data on the use testing of the red-pigmented lacquer with siccative [A-4], after radiation curing and oxidative curing Use testing.sup.15 UV dispersion Example 4 Example 6 Exam- Exam- (compar- (EP-A ple 2 ple 3 ison) 1 914 253) Resistance to water, 16 h 5 5 4 3 Resistance to coffee, 16 h 5 5 5 3 Resistance to red wine, 16 h 5 5 4 3 Resistance to ethanol/water 5 4 3 1 (50%), 6 h Resistance to ethanol/water 5 3 3 1 (50%), 16 h .sup.15see footnote 11, Table 3

(33) Table 3 shows the chemical resistance directly after the radiation curing. An oxidative curing has scarcely taken place at this point in time. The coatings of Examples 1 and 2 according to the invention already have quite good resistances and lie at the level of Comparison Example 4. From experience, the coatings from purely oxidatively drying systems, such as e.g. those from alkyd resins or aqueous polyurethane dispersions based on alkyd resins, are still very soft at this point in time, and testing of the mechanical and chemical resistances was therefore not carried out with these systems.

(34) Substrates which are coated with the binders according to the invention can already be assembled and subsequently cure further oxidatively during storage or during transportation.

(35) The effect of oxidative curing, which takes place at room temperature three days after the radiation curing, is shown in Tables 4 to 7. Examples 2 and 3 according to the invention show better resistances than Comparison Examples 4 and 6 both in the yellow and in the red lacquer without siccative (Tables 4 and 6). This becomes clear in particular in the case of water/ethanol (50%). It is to be emphasized again that Example 4 is indeed based on polyepoxyacrylate, but no polyesters containing unsaturated fatty acids are present. The advantage of the combination of polyepoxyacrylate and polyester containing unsaturated fatty acids as in Examples 2 and 3 thereby becomes clear.

(36) By the addition of siccative (Tables 5 and 7), the resistances of Examples 2 and 3 become still better, whereas in Examples 4 and 6 no improvement is to be seen, since they contain no oxidatively curable groups. The addition of siccative accelerates the oxidative curing. The coatings without siccative will arrive at similarly good results after a longer time.

(37) It likewise becomes clear that the higher contents of aromatic polyepoxyacrylate and polyester containing unsaturated fatty acids in Example 2 lead to better resistances compared with Example 3.