URETDIONE-CONTAINING POLYURETHANE-DISPERSIONS COMPRISING HYDROPHILIC GROUPS

Abstract

The present invention relates to a specific uretdione prepolymer, and an aqueous curable composition based on the specific uretdione prepolymer. Furthermore, it pertains to a process for curing said aqueous curable composition, the cured article obtained by this process and additionally to the use of said aqueous composition for coatings, adhesives and/or sealants.

Claims

1. A uretdione prepolymer, which comprises at least one uretdione group, and which is obtained by reacting A1) at least one uretdione polyisocyanate having an isocyanate functionality of at least 2.0, wherein said uretdione polyisocyanate is obtained from at least one aliphatic polyisocyanate, with A2) at least one polyalkoxy ether derivative comprising at least two OH groups, which are present on two different non neighboring atoms of the molecule and wherein at least one of the OH groups is not a terminal OH group, and A3) at least one reactant, which comprises at least one Zerewitinoff-active group and being different from A2 or which is H.sub.2O, in the presence of at least one catalyst, to obtain the uretdione prepolymer, wherein the prepolymer has an acid number of at most 4 mg KOH/g.

2. The uretdione prepolymer according to claim 1, wherein in a first step, the at least one uretdione polyisocyanate A1 is reacted, with the at least one polyalkoxy ether derivative A2 and in a second step the polymer obtained in the first step is reacted with the at least one reactant A3.

3. The uretdione prepolymer according to claim 1, wherein components A1 to A3 are reacted in a one-step process.

4. The uretdione prepolymer according to claim 1, wherein in a first step, the at least one uretdione polyisocyanate A1 is reacted with the at least one reactant A3 and in a second step the polymer obtained in the first step is reacted in a second step with the at least one polyalkoxy ether derivative A2.

5. The uretdione prepolymer according to claim 1, where-in said uretdione prepolymer is a nonionic prepolymer.

6. The uretdione prepolymer according to claim 1, wherein said uretdione prepolymer exhibits a zeta potential of at least 20 mV.

7. The uretdione prepolymer according to claim 1, wherein said uretdione polyisocyanate A1 is obtained from at least one cycloaliphatic polyisocyanate.

8. The uretdione prepolymer according to claim 1, wherein said uretdione polyisocyanate A1 is prepared from isophorone diisocyanate as the only polyisocyanate.

9. The uretdione prepolymer according to claim 1, wherein compound A2 is selected from compounds of formula (I): ##STR00006## wherein, X is H or alkyl; R is a C.sub.1-4 alkylene group; p is an integer of 2 to 50; in each unit p n is independently 0 or 1 and m is independently 0 or 1, with the proviso that at least one of n or m in each unit p is 1.

10. The uretdione prepolymer according to claim 1, wherein compound A3 is selected from the group consisting of at least one polyol, which is different from A2, from polyester polyols, polyether polyols, polyurethane polyols, polyacrylate polyols, polymethacrylate polyols, polycarbonate polyols, and mixtures thereof.

11. An aqueous, curable composition, comprising: the uretdione prepolymer according to claim 1, and optionally, at least one compound, which comprises at least one Zerewitinoff-active group and/or optionally, at least one azolate-compound.

12. The aqueous, curable composition according to claim 11, wherein said uretdione prepolymer is contained in a total amount of 3 to 40 wt. %, based on the total weight of the composition.

13. The aqueous, curable composition according to claim 11, wherein said azolate-compound is selected from the group consisting of at least one triazolate-compound of formula (III) or salts thereof and formula (IV) or salts thereof ##STR00007## wherein, R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently selected from a hydrogen atom, a halogen atom, a nitro group, a saturated or unsaturated, aliphatic or cycloaliphatic radical, an optionally substituted aromatic group comprising up to 20 carbon atoms and optionally, up to 3 heteroatoms selected from oxygen, sulfur, and nitrogen, an optionally substituted araliphatic group comprising up to 20 carbon atoms and optionally, up to 3 heteroatoms selected from oxygen, sulfur, and nitrogen, and wherein R.sup.3 and R.sup.4 of formula (IV) together with the carbon atoms of the 1,2,3-triazolate five-membered ring form fused rings with 3 to 6 carbon atoms.

14. The aqueous, curable composition according to claim 13, wherein said azolate-compound is selected from the group consisting of alkaline metal-1,2,4-triazolate, alkaline metal-1,2,3-triazolate, alkaline metal-benzotriazolate, alkaline earth metal-1,2,4-triazolate, alkaline earth metal-1,2,3-triazolate, and alkaline earth metal-benzotriazolate.

15. The aqueous, curable composition according to claim 11, wherein said at least one compound, which comprises at least one Zerewitinoff-active group is selected from the group consisting of polyester polyols, polyether polyols, polyurethane polyols, polyacrylate polyols, polymethacrylate polyols, polycarbonate polyols, and mixtures thereof.

16. The aqueous, curable composition according to claim 11, wherein said uretdione prepolymer is contained in an amount of 1 to 50 wt. % or said at least one compound, which comprises at least one Zerewitinoff-active group is contained in an amount of 0 to 80 wt.-% or said triazolate-compound is contained in an amount of 0.1 to 10 wt. %, based on the total weight of the composition, respectively.

17. A process for curing a liquid composition on a substrate, comprising a) applying on a substrate an aqueous, curable composition according to claim 11; and a) exposing the aqueous, curable composition to a temperature of 60 C. to 160 C. to cure said composition.

18. The cured article obtained by the process according to claim 17.

19. In a process for the production of one of a coating, an adhesive and a sealant, the improvement comprising including the composition according to claim 11.

Description

EXAMPLES

[0164] Compounds:

[0165] Ymer N120 (CAS number: 131483-27-7), a linear, trimethylolpropane started polyethylene glycol monomethyl ether, OH number 100-120 mg KOH/g) was acquired from Perstorp Holding AB, Malm, Sweden.

[0166] Polyester 1 OH-functional polyester prepared from 3039 g adipic acid, 4041 g isopthalic acid, 267 g 1,2-propylene glycol, 4773 g neopentyl glycol and 1419 g trimethylol propane (OH number: 181 mg KOH/g, acid number<3 mg KOH/g)

[0167] Other chemicals wereunless otherwise statedpurchased at Sigma-Aldrich Chemie GmbH, Munich, Germany [0168] IPDI uretdione (IPDI-dimer): To 1000 g (4.50 mol) of isophorone diisocyanate (IPDI) were added at room temperature under dry nitrogen and stirring 10 g (1%) of triisodecyl phosphite and 20 g (2%) of 4-dimethylaminopyridine (DMAP) as catalyst. After 20 h, the reaction mixture, which had an NCO content of 28.7%, corresponding to a degree of oligomerization of 21.8%, was freed from volatile components without prior addition of a catalyst poison with the aid of a thin-film evaporator at a temperature of 160 C. and a pressure of 0.3 mbar. [0169] This gave a pale yellow uretdione with a content of free NCO groups of 17.0%, a content of monomeric IPDI of 0.4% and a viscosity (according to DIN EN ISO 3219: 1994-10) of more than 200,000 mPas (23 C.).

[0170] Measurement Methods:

[0171] Unless noted otherwise, all of the analytical measurements refer to measurements at temperatures of 23 C.

[0172] All percentages refer, unless otherwise stated, to the weight.

[0173] The solids contents (non-volatile contents) were determined by heating a weighed sample (approx. 1 g) at 105 C. to constant weight. At constant weight, the solid-body content is calculated by reweighing the sample.

[0174] The pendulum hardness by the Knig method was measured on a glass plate according to DIN EN ISO 1522:2007-04.

[0175] NCO contents were determined volumetrically in accordance with DIN-EN ISO 11909:2007-05. The control on free NCO groups was carried out by means of IR spectroscopy (band at 2260 cm.sup.1).

[0176] The stated viscosities were determined by means of rotary viscometry in accordance with DIN 53019:2008-09 at 23 C. using a rotary viscometer with a shear rate of 186 l/s, from Anton Paar Germany GmbH, Ostfildern, Germany.

[0177] The average particle sizes (the number-average is given) of the polyurethane dispersions were determined following dilution with deionized water by means of laser correlation spectroscopy (instrument: Malvern Zetasizer 1000, Malver Inst. Limited, London, UK).

[0178] Zeta potential was measured by diluting one drop of the sample with 20 ml demineralized water and homogenized by stirring. Subsequently the zeta potential is determined at 23 C. in the Malvern Nanosizer ZS90 (Malvern Instruments, Herrenberg, Germany).

[0179] Acid number of the respective dispersion was determined according to DIN ISO 2114 1:2006-11. Instead of a mixture of toluene and ethanolas described in DIN ISO 2114 1:2006-11a mixture of acetone and ethanol (2:1 by weight) was used as solvent. The unit of the acid number is mg KOH per g of the analyzed sample.

[0180] Solvent Resistance and Water Resistance:

[0181] The cured coating films were tested for their resistance to xylene and water. A piece of cotton wool soaked with the test substance was placed on the coating surface and covered with a watch glass. After the specified exposure time, the cotton wool was removed; the exposed site was dried and immediately inspected. The evaluation of the softening or discoloring of the coating surface was carried out following the DIN EN ISO 4628-1:2016-07:

[0182] 0: unchanged, i.e. no perceptible change

[0183] 1: very slight, i.e. barely perceptible change

[0184] 2: slight, i.e. clearly perceptible change

[0185] 3: moderate, i.e. very clearly perceptible change

[0186] 4: considerable, i.e. pronounced change

[0187] 5: very marked change

[0188] Infrared Measurements:

[0189] The uretdione ring opening was characterized by an FT-IR spectrometer (tensor II with Platinum ATR unit (diamond crystal) from Bruker). The spectra were recorded in a wave number range of (4000-400) cm.sup.1. The maximum of the uretdione peak (about 1760 cm .sup.1) was evaluated. Peak heights to comparative systems were compared with an initial value set to 100% (uretdione film without catalyst, dried at room temperature) and variations relative to this (ratio formation). Uretdione peak height of films cured for 30 min at 180 C. were set to 0%. When measuring on an ATR crystal, the intensity of the spectrum depends on the occupation of the crystal surface. Since a comparable coverage of the crystal surface cannot be ensured in the case of different measurements by the sample preparation, a correction of this effect must be made for the ratio formation by normalizing all spectra on the peak of the CH stretching vibration (wave number range (3000-2800 cm.sup.1). In the case of the evaluation of peak heights as described above, a baseline correction of the spectra is additionally carried out.

[0190] Preparation of Uretdione Prepolymer Dispersion A (According to the Invention)

[0191] 149.0 g of IPDI uretdione were dissolved in 580 g acetone at 50 C. in a standard stirring apparatus. 64.6 g of Ymer N120 and 0.53 g of tin neodecanoate were added and the mixture was stirred at reflux under atmospheric pressure until the NCO content of 2.5% was reached. Then 213.2 g of polyester 1 were added and the mixture was stirred under reflux at atmospheric pressure until the NCO content dropped below 0.5%. The mixture was then dispersed by adding 213.2 g of water. The solvent was removed by distillation in vacuum; solid content was adjusted by addition of water.

[0192] The resulting white dispersion had the following properties:

[0193] Solids content: 37%

[0194] Average particle size (LCS): 107 nm

[0195] Viscosity (viscometer, 23 C.): 118 mPas

[0196] pH (23 C.): 5.3

[0197] Acid number: 0.9 mg KOH/g

[0198] Zeta potential: 16.4 mV

[0199] Comparative Dispersion 1

[0200] 149.1 g of IPDI-dimer were dissolved in 580 g acetone at 50 C. in a standard stirring apparatus. 63.4 g of Poly(ethylene glycol) methyl ether with an average Mn of 500 g/mol, 214.24 g of a OH-functional polyester 1 and 0.53 g of tin neodecanoate were added and the mixture was stirred at reflux under atmospheric pressure until the NCO content dropped below 0.5%. Then 794 g of water were added. The acetone was removed by distillation in vacuum; solid content was adjusted by addition of water.

[0201] The resulting white dispersion had the following properties:

[0202] Solids content: 35.7%

[0203] Average particle size (LCS): 166 nm

[0204] Viscosity (viscometer, 23 C.): 20 mPas

[0205] pH (23 C.): 5.4

[0206] Preparation of Anionic Uretdione Prepolymer Dispersion (Comparative Example) Comparative Dispersion 2

[0207] 150.3 g of IPDI-dimer were dissolved in 594 g acetone at 50 C. in a standard stirring apparatus. 12.8 g of dimethylol propionic acid, 201.3 g of a OH-functional polyester 1 and 0.55 g of tin neodecanoate were added and the mixture was stirred at reflux under atmospheric pressure until the NCO content dropped below 0.5%. Then 8.5 g N,N-dimethylamino-ethanol and 670 g of water were added. The acetone was removed by distillation in vacuum; solid content was adjusted by addition of water.

[0208] The resulting white dispersion had the following properties:

[0209] Solids content: 35.6%

[0210] Average particle size (LCS):108 nm

[0211] Viscosity (viscometer, 23 C.): 5 mPas

[0212] pH (23 C.): 8.5

[0213] Acid number: 7.3 mg KOH/g

[0214] Zeta potential: 45.7 mV

[0215] Tests of the Coatings

[0216] Clear coatings were prepared from the following composition:

[0217] 100 weight percent (20 g) of urethane prepolymer dispersion A (or comparative) was mixed with 6 weight percent (1.2 g) of a solution consisting of 0.12 g 1,2,4-Triazolate-Na and 1.08 g water.

[0218] The mixture was applied to glass or coil (CS-300570 coil coating test panel, purchased from Zanders PBL) using a coating squeegee with a layer thickness of 150-180 m (wet). The plates were dried at room temperature for 5 minutes and then baked at various temperatures for 30 minutes. The obtained films were evaluated at 23 C. at 50% relative humidity by pendulum hardness, water resistance and solvent resistance and an IR spectrum was recorded.

[0219] The following table shows the coating properties of the corresponding films.

[0220] Requirements for Coatings:

[0221] Pendulum hardness>100 s

[0222] Xylene test:<4

[0223] 10 weeks stable at room temperature and 40 C.

Inventive Examples Ex1 (with Catalyst) and Ex 2 (without Catalyst)

[0224] Clear Coat of the Following Compositions:

TABLE-US-00001 Ex 1 Ex 2 Dispersion A 20 g 20 g Catalyst 1,2,4-Triazolate-Na 1.2 g (10% in water)

[0225] Coating Properties (Before Storage):

TABLE-US-00002 Ex 1 Ex 2 Curing Time, 1 day; 1 day; Temperature room temp. room temp. Remaining intensity of IR- Percent >97% >97% peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 5 5 Ex 1 Ex 2 Curing Time, 30 min; 30 min; Temperature 100 C. 100 C. Remaining intensity of IR- Percent <3% >97% peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 2 5 Ex 1 Ex 2 Curing Time, 30 min; 30 min; Temperature 140 C. 140 C. Remaining intensity of IR- Percent <3% 92% peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 2 5

[0226] Coating Properties of Inventive Dispersion (Ex 1) which were Stored Beforehand at Room Temperature and at 40 C.:

TABLE-US-00003 20 g stored at 20 g stored at room temperature 40 C. Ex 1 for 10 weeks for 10 weeks Curing Time, 30 min; 30 min; Temperature 100 C. 100 C. Remaining intensity of IR- Percent <3 <3 peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 2-3 2-3

Comparative Examples 1 and 2: Comparative Dispersion 1

[0227] Clearcoat of the Following Compositions:

TABLE-US-00004 Comp. Ex 1 Comp. Ex 2 Comp. Dispersion 1 20 g 20 g Catalyst 1,2,4-Triazolate-Na 1.2 g (10% in water)

[0228] Coating Properties (Before Storage):

TABLE-US-00005 Comp. Ex 1 Comp. Ex 2 Curing Time, 30 min; 30 min; Temperature 100 C. 100 C. Remaining intensity of IR- Percent <3% >97% peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 4 5 Comp. Ex 1 Comp. Ex 2 Curing Time, 30 min; 30 min; Temperature 140 C. 140 C. Remaining intensity of IR- Percent <3% >97% peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 4 5

Comparative Examples 3 and 4: Comparative Dispersion 2

[0229] Clearcoat of the Following Compositions:

TABLE-US-00006 Comp. Ex 3 Comp. Ex 4 Comparative Dispersion 2 20 g 20 g Catalyst 1,2,4-Triazolate-Na 1.1 g (10 wt.-% in water)

[0230] Coating Properties (Before Storage):

TABLE-US-00007 Comp. Ex 3 Comp. Ex 4 Curing Time, 30 min; 30 min; Temperature 100 C. 100 C. Remaining intensity of IR- Percent >97 >97 peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 5 5 Comp. Ex 3 Comp. Ex 4 Curing Time, 30 min; 30 min; Temperature 140 C. 140 C. Remaining intensity of IR- Percent >97 >97 peak with peak maximum between 1750 and 1800 cm.sup.1 Resistance against xylene 5 min 4 4

[0231] Coating properties of non-inventive dispersions after storage at 40 C. or with catalyst could not be performed due to instability of these dispersions.

[0232] Stability Measurements of Examples and Comparative Example 1:

[0233] Dispersions were stored at room temperature or in a 40 C. oven with or without catalyst for 10 weeks. Stability of dispersion was evaluated by IR measurement before/after storage.

TABLE-US-00008 Inventive Comparative Dispersion Example A dispersion 1 Remaining intensity of IR-peak >97% Thickened after after storage at room temperature storage at RT without catalyst for 10 weeks for 8 weeks (peak maximum between 1750 and 1800 cm.sup.1) Remaining intensity of IR-peak >86% Thickened after storage at 40 C. without catalyst for 10 weeks (peak maximum between 1750 and 1800 cm.sup.1) Remaining intensity of IR-peak 87 Thickened after storage at room temperature with catalyst for 10 weeks (peak maximum between 1750 and 1800 cm.sup.1) Remaining intensity of IR-peak 44% Thickened after storage at 40 C. with catalyst for 10 weeks (peak maximum between 1750 and 1800 cm.sup.1)