NOVEL TWO-COMPONENT CLEAR COAT SYSTEMS COMPRISING POLYASPARTIC ACID ESTER

Abstract

The present invention relates to two-component clear-coat systems comprising polyaspartic esters having primary amino groups and small amounts of dialkyl fumarates, to a process for the production thereof, and to the use thereof in the production of coatings for vehicle repair applications and to substrates coated therewith.

Claims

1. A two-component coating composition comprising a) at least one polyaspartic ester-containing component A; b) at least one polyisocyanate component B; c) optionally one or more components C that are different from A and are reactive towards isocyanate groups; d) at least one water scavenger and/or hydrolysis stabilizer (component D1); and optionally other auxiliaries and additives (component D2), wherein component A comprises one or more polyaspartic esters of the general formula (I) ##STR00004## in which X is an m-valent organic radical, optionally containing one or more heteroatoms, as can be obtained by removing the primary amino groups from a corresponding polyamine that has (cyclo)aliphatically or araliphatically attached primary amino groups and is in the molecular weight range from 60 to 6000 g/mol, and which may contain further functional groups that are reactive towards isocyanate groups and/or that are inert at temperatures of up to 100° C., R1 and R2 are identical or different organic radicals each having 1 to 18 carbon atoms, m is an integer >1, and one or more polyaspartic esters having a primary amino group that are of the general formula (II) ##STR00005## in which n is m-1, X and radicals R1 and R2 have the meanings defined above, wherein a proportion of compounds of the general formula (II) corresponds to ≥4% to ≤20% of a total area (measured as area % in a gas chromatogram (GC), wherein the total area corresponds to a sum of the areas is the GC of compounds of the two general formulas (I) and (II) and is equal to 100% and wherein dialkyl fumarates are present in component A in amounts from ≥0.01% to ≤1.2% by weight based on a total weight of component A.

2. The two-component coating compositions according to claim 1, wherein the proportion of compounds of the general formula (II) is >4% of the total area in the GC (measured as area % in the gas chromatogram).

3. The two-component coating composition according to claim 1, wherein the proportion of compounds of the general formula (II) is ≤15% of the total area in the GC (measured as area % in the gas chromatogram).

4. Th two-component coating composition according to claim 1, wherein dialkyl fumarates are present in component A in an amount from ≥0.01% to ≤1% by weight based on the total weight of component A.

5. The two-component coating composition according to claim 1, wherein dialkyl fumarates are present in component A in an amount from ≥0.01% to ≤0.1% by weight based on the total weight of component A.

6. A process for producing a coating on a substrate comprising: i) applying the two-component coating composition according to claim 1 to at least part of a substrate to be coated; and ii) curing the coating composition from step i).

7. A substrate coated with a coating obtained in accordance with the process according to claim 6.

8. The process for producing a coating on a substrate according to claim 6, wherein the coating is a clear coat.

9. The process according to claim 8, wherein the clear coat is a refinishing clear coat.

10. A method of producing water-stable coatings, comprising preparing a coating comprising the two-component coating composition of claim 1.

11. The substrate coated with a coating according to claim 7, wherein the coating is a clear coat.

12. The substrate coated with a coating according to claim 8, wherein the clear coat is a refinishing clear coat.

Description

EXPERIMENTAL SECTION

[0119] Raw Materials and Substrates:

[0120] PACM 20: A mixture of 2,4- and 4,4′-diaminodicyclohexylmethane, manufacturer: Evonik

[0121] Desmodur N 3900: A low-viscosity HDI trimer containing approx. 23.5% NCO, manufacturer: Covestro

[0122] Byk 331: Polyether-modified polydimethylsiloxane surface additive, manufacturer: Byk

[0123] Tinuvin 384-2: Benzenepropanoic acid, 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy, C.sub.7-C.sub.9 branched and linear alkyl esters, a light stabilizer from BASF

[0124] Additive OF: Triethyl orthoformate, an additive from Borchers

[0125] Substrate: Coil-coating coated test plates, grey, supplier: Heinz Zanders Prüf-Blech-Logistik in Solingen

[0126] Methods:

[0127] Diethyl fumarate contents were quantitatively determined using a GC method with an internal standard. An Agilent 6890 gas chromatograph with a standard GC capillary (100% polysiloxane phase) and FID detector were used. The injector temperature (split outlet) was 180° C.; helium was used as the carrier gas. The quantitation limit of this method was 300 ppm.

[0128] GC-MS analyses were carried out using an Agilent 6890 gas chromatograph and Agilent 5973 mass spectrum detector with standard ionization (electron impact) at 70 eV, a standard GC capillary (100% polysiloxane phase) and split injection at an injector temperature of 250° C.

[0129] Evaluation of the gas chromatogram was in area %.

[0130] All viscosity measurements were carried out using a Physica MCR 51 rheometer from Anton Paar Germany GmbH (DE) in accordance with DIN EN ISO 3219:1994-10.

[0131] Hazen colour index values were determined on a Lico 400 colourimeter from Hach Lange GmbH, Dusseldorf in accordance with DIN EN ISO 6271:2016-05

[0132] Amine values were determined titrimetrically in accordance with EN ISO 9702:1998 (perchloric acid method) with the exception that the results were expressed as the amine value. The amine value in mg KOH/g was calculated according to the following equation:

[00001]$\mathrm{Amine}\mathrm{value}=\frac{\left(a-b\right)\times 5,61}{W}$

[0133] a=Volume of perchloric acid consumed in the main test, in millilitres, c=0.1 mol/l;

[0134] b=Volume of perchloric acid consumed in the blank test, in millilitres, c=0.1 mol/l;

[0135] W=Weight of sample, in grams

[0136] The condensation water test was carried out in accordance with DIN EN ISO 6270-2:2017. Blistering was assessed in accordance with DIN EN ISO 4628-2:2016 (n.c.=no change/bl.=number of blisters/bs.=blister size).

EXAMPLE 1 (COMPARATIVE)

[0137] Polyaspartic ester commercially available from Covestro under the name Desmophen NH 1420. Material data:

TABLE-US-00001 Monoamines of the formula (II) (GC-MS): 4.0% Diethyl fumarate (GC) 2.9% by weight Viscosity 1220 mPas Colour index 27 APHA Amine value 201 mg KOH/g

EXAMPLE 2

[0138] 341.8 g of PACM 20 was initially charged at 23° C. under dry nitrogen, with stirring. To this was added dropwise 567.6 g of diethyl maleate, ensuring that the temperature did not rise above 60° C. At the end of the addition, the temperature was adjusted to 45° C. and the mixture was stirred at 45° C. for 2 hours. The mixture was then stored at 23° C. for 7 weeks. The content of diethyl fumarate after storage was 2.7% by weight. Diethyl fumarate was then distilled off at 120° C. and 0.2 mbar. A light-coloured product was obtained that had the following material data:

TABLE-US-00002 Monoamines of the formula (II) (GC-MS): 5.3% Diethyl fumarate (GC) 0.08% by weight Viscosity 1810 mPas Colour index 19 APHA Amine value 203 mg KOH/g

[0139] Testing in Coatings

[0140] Preparation of a Coating Base

[0141] To the amount of component A shown in table 1 were added the additives and the amount of butyl acetate shown in the table, and the mixture was stirred homogeneously.

[0142] Preparation of the Hardener Solution

[0143] To the amount of component B shown in table 1 was added the amount of butyl acetate shown, and the mixture was stirred homogeneously.

[0144] Coating structure: The substrate was coated with a deep black Permahyd Series 280 basecoat (supplier: Spies Hecker GmbH in Cologne) by means of an air-pressure spraying process using a Sata Jet RP, nozzle 1.3 mm/2.1 bar) and dried for 20 minutes at room temperature (layer thickness of the dry film: 15 μm). 2C clear coats were produced by mixing components A and B immediately before application by stirring for 15 s with a wooden spatula and then applying to the precoated substrate in an air-pressure spraying process using a Sata Jet RP, nozzle 1.3 mm/2.1 bar. Drying was at room temperature (24° C./30% rel. humidity) for 7 days. Brilliant, high-gloss coatings with a layer thickness of 50-60 μm were obtained.

TABLE-US-00003 TABLE 1 Composition of the clear coats Example 4 Example 3 (according to (comparative) the invention) Component A Desmophen NH 1420 from example 1 42.94 Polyaspartic ester from example 2 42.94 Byk 331 (10% in BA) 0.07 0.07 Tinuvin 384-2 (50% in BA) 3.53 3.53 Additives OF (98%) 3.00 3.00 Butyl acetate 12.58 12.58 Component B Desmodur N 3900 (100%) 27.89 28.44 Butyl acetate 9.99 9.44 Sum 100.00 100.00

TABLE-US-00004 TABLE 2 Results of the condensation water test Example 4 Example 3 (according to (comparative) the invention) Layer thickness in μm 51 63 Gloss 20°/Haze 0 value 87/16 87/12 Condensation water test after 24 h n.c. n.c. Condensation water test after 48 h n.c. n.c. Condensation water test after 72 h n.c. n.c. Condensation water test after 96 h 2 bl. bs. 2 n.c. Condensation water test after 168 h 1 bl. bs. 2, 1 bl. n.c. bs. 5 Condensation water test after 192 h 1 bl. bs. 2, 1 bl. n.c. bs. 5 Condensation water test after 216 h 1 bl. bs. 2, 1 bl. n.c. bs. 5 Condensation water test after 240 h 1 bl. bs. 2, 1 bl. 2 bl. bs. 2 bs. 5, 2 cracks

[0145] The comparison coating from example 3 was already showing blistering after 96 h in the condensation water test, whereas the coating according to the invention from example 4 did not show blistering until after 240 h. These results provide evidence that the polyaspartic ester compositions according to the invention are able to achieve significant industrial advantages over conventional coatings.

[0146] Coatings are considered to be water-resistant/water-stable (evaluation in accordance with DIN EN ISO 4628-2:2016) if the condensation test (in accordance with DIN EN ISO 6270-2:2017) results in no change in the coating even after 100 hours, preferably even after 150 hours, most preferably even after 200 hours.

TABLE-US-00005 TABLE 3 Coating properties of coatings Example 4 (according to Example 3 Temperature: 24° C. the invention) (comparative) Air humidity: 48% Solids content in % at spray   74.9   81.1 viscosity (calc.) Flow time DIN 4 mm (sec) 0 h 16 17  5′ 17 18 10′ 18 20 15′ 19 24 20′ 20 27 25′ 22 31 30′ 25 40 Drying (min) T 1 12 15 RT T 3 25 30 T 4 40 45 Layer thickness (μm) approx. 50 approx. 50 Drying (min) T 1 immediately immediately 30′-60° C. T 3 15 20 T 4 25 30 Layer thickness (μm) approx. 50 approx. 50

[0147] Comparison of the coating properties shown in table 3 for the comparison coating (example 4) with the coatings according to the invention (examples 3) demonstrates that the coatings according to the invention dry more rapidly while having an unchanged pot life.