TWO-COMPONENT SYSTEM FOR ELASTIC COATINGS

Abstract

The present invention relates to a two-component system comprising a component A) comprising at least one polymeric polyol which has an OH content of 4.5 wt %, based on the total solids content of the polymeric polyol, and a component B) comprising at least one polyisocyanate which has a number average isocyanate group functionality of 4.0 to 10.0, based on the total solids content of the polyisocyanate, a fraction of 25 wt %, based on the total solids content of the polyisocyanate, of oligomers containing isocyanate groups and having a number-average molecular weight of 780 g/mol, and an isocyanurate group fraction of 5 mol % to 70 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate. The invention further relates to a method for producing a coating on a substrate, to the coating obtainable by this method, and to the coated substrate.

Claims

1. A two-component system comprising component A) comprising at least one polymeric polyol which has an OH content of 4.5 wt %, based on the total solids content of the polymeric polyol, and component B) comprising at least one polyisocyanate which has a number average isocyanate group functionality of 4.0 to 10.0, based on the total solids content of the polyisocyanate, a fraction of 25 wt %, based on the total solids content of the polyisocyanate, of oligomers containing isocyanate groups and having a number-average molecular weight of 780 g/mol, and an isocyanurate group fraction of 5 mol % to 70 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate.

2. The two-component system according to claim 1, wherein that polyisocyanate comprises at least one oligomer which contains one or more isocyanurate groups and one or more allophanate groups, which in each case are joined chemically to one another via an aliphatic, cycloaliphatic or araliphatic group having a molecular weight of 56 to 316 g/mol.

3. The two-component system according to claim 1, wherein the number average isocyanate group functionality is 4.5 to 9.0, based on the total solids content of the polyisocyanate.

4. The two-component system according claim 1, wherein the fraction of the oligomers containing isocyanate groups and having a number-average molecular weight of 780 g/mol is 22 wt %, based on the total solids content of the polyisocyanate.

5. The two-component system according to claim 1, wherein the fraction of isocyanurate groups is 10 mol % to 60 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate.

6. The two-component system according claim 1, wherein the polyisocyanate has a fraction of allophanate groups of 30 mol % to 95 mol %, based on the total amount of isocyanurate groups and allophanate groups in the polyisocyanate.

7. The two-component system according to claim 2, wherein the one or more isocyanurate groups and one or more allophanate groups of the oligomer are each joined chemically to one another via a linear or branched aliphatic group in the molecular weight range from 56 to 316 g/mol, via a 1,5-pentyl or 1,6-hexyl group.

8. The two-component system according to claim 1, wherein the polyisocyanate is obtained by oligomerization of at least one aliphatic, cycloaliphatic or araliphatic monomeric diisocyanate having a molecular weight of 140 to 400 g/mol and at least one hydroxy-functional compound having an OH functionality of 2 and 6 in the presence of a catalyst.

9. The two-component system according to claim 8, wherein the hydroxy-functional compound has an OH functionality of 3 and 5 and a molecular weight of 85 to 2000 g/mol.

10. The two-component system according to claim 1, wherein the polymeric polyol present at least in component A) is a polycarbonate polyol.

11. The two-component system according to claim 1, wherein component A) consists to an extent of 30 wt %, preferably 30 and 50 wt %, of the polymeric polyol, based on the total weight of component A), and the balance to 100 wt % is composed of one or more polymeric polyester, polyether and/or polycarbonate polyols which are different from the polymeric polyol, and also, optionally, of one or more additives.

12. The two-component system according to claim 1, wherein a further constituent of component A) of the two-component system is water.

13. In a method for producing a coating, the improvement comprising including the two component system according to claim 1.

14. A method for producing a coating on a substrate, comprising the following steps: 1) providing a substrate; 2) applying at least one two-component system according to claim 1; 3) curing the two-component system applied in step 2), optionally with supply of heat, wherein the two-component system optionally comprises one or more additives.

15. The coating produced or producible by the method according to claim 14.

16. A substrate at least partially coated with the coating according to claim 15.

Description

EXAMPLES

[0103] All percentages are by weight, unless indicated otherwise.

[0104] The determination of the NCO contents was carried out titrimetrically in accordance with DIN EN ISO 11909:2007-05.

[0105] The residual monomer contents were determined gas-chromatographically using an internal standard in accordance with DIN EN ISO 10283:2007-11.

[0106] All viscosity measurements were carried out in accordance with DIN EN ISO 3219:1994-10 using a cone/plate measuring instrument. Unless indicated otherwise, measurements were carried out at a temperature of 23 C.

[0107] The content of oligomers having a number average molecular weight 780 g/mol was determined by gel permeation chromatography in accordance with DIN 55672-1:2016-03 using polystyrene as standard and tetrahydrofuran as eluent.

[0108] The Konig hardness was determined in accordance with DIN EN ISO 1522:2007-04 on glass plates.

[0109] Raw Materials

[0110] Desmophen 670 BA (Covestro Deutschland AG), hydroxy-functional polyester, 80% in butyl acetate, hydroxyl content 3.5%.

[0111] Desmophen C 1200 (Covestro Deutschland AG), linear aliphatic polycarbonate polyester, 100%, hydroxyl content 1.7%.

[0112] Bayhydrol U 355 (Covestro Deutschland AG), approx. 55% in water/NMP/DMEA, approx. 42:2:1, aliphatic, hydroxyfunctional polyester polyurethane dispersion, OH content approx. 0.8%

[0113] Bayhydrol UH 340/1 (Covestro Deutschland AG), approx. 40% in water, aliphatic anionic polyurethane dispersion.

[0114] Impranil DLC-F (Covestro Deutschland AG), approx. 40% in water, ionic/anionic polycarbonate ester polyurethane dispersion.

[0115] Desmodur N 3300 (Covestro Deutschland AG), 100% content, aliphatic polyisocyanate, NCO content 21.8%.

[0116] Bayhydur 304 (Covestro Deutschland AG), 100% content, hydrophilically modified, aliphatic polyisocyanate based on hexamethylene diisocyanate (HDI), NCO content 18.2%

[0117] DBTL, dibutyltin dilaurate (CAS 77-58-7, Aldrich), 10% solution in butyl acetate BYK 333 (Byk Chemie GmbH) wetting agent

[0118] Glide 410 (Evonik), leveling agent

[0119] BYK 093 (Byk Chemie GmbH), defoamer

[0120] DC-51 (Dow Corning), slip-additive

[0121] Acematt 3300, TS100, OK 607 (Evonik), matting agents

[0122] Solvents:

[0123] BA: butyl acetate

[0124] MPA: methoxypropylacetate

[0125] X: Xylene

[0126] Inventive Polyisocyanate Crosslinkers:

[0127] Polyisocyanate 1

[0128] A 1 L four-necked flask with stirrer, N.sub.2 inlet, condenser, thermometer and drying tube is charged with 840 g (5.0 mol) of hexamethylene diisocyanate (HDI) at 110 C. At the same temperature, 33.5 g (0.25 mol) of trimethylolpropane were added over about 1 h. Stirring was continued for about 2 h until urethanization was complete. When the urethane stage was reached (NCO value of 44.5%), the temperature was lowered to 95 C. For the allophanatization and simultaneous trimerization, a 0.5% trimethylbenzylammonium hydroxide solution in 2-ethylhexanol/2-ethylhexane-1,3-diol, 1:1, was metered in. At an NCO value of 36%, the reaction was ended by addition of 10% dibutyl phosphate solution in HDI in a weight ratio of 100 parts of catalyst to 3 parts of stopping agent. For complete neutralization, stirring was continued at 95 C. for 30 minutes more. The crude solution was subsequently freed from monomeric HDI in a short-path evaporator at 140 C. and <0.1 mbar. Viscosity of the resin after removal of monomeric HDI was 35.000 mPas. The colourless, clear resin, 80% in butyl acetate, had an NCO content of 15.4%, a viscosity of 500 mPas and a monomeric HDI content of <0.3%.

[0129] Polyisocyanate 2

[0130] A 1 L four-necked flask with stirrer, N.sub.2 inlet, condenser, thermometer and drying tube was charged with 630 g (3.75 mol) of hexamethylene diisocyanate (HDI) at 110 C. At the same temperature, 20.1 g (0.15 mol) of trimethylolpropane were added over about 1 h. Stirring was continued for about 2 h until urethanization was complete. When the urethane stage was reached (NCO value of 45.55%), the temperature was lowered to 95 C. For the allophanatization, a 5% Zn octoate solution in 2-ethylhexanol was metered in. Following complete allophanatization (NCO value of 42.65%), the catalyst was stopped with a 5% strength solution of isophthaloyl dichloride in HDI in a weight ratio of 1:1. For complete neutralization, stirring was continued at 100 C. for 30 minutes more. The crude solution was subsequently freed from monomeric HDI in a short-path evaporator at 140 C. and <0.1 mbar. Viscosity of the resin after removal of monomeric HDI was 35.000 mPas. The colourless, clear resin, 80% in butyl acetate, had an NCO content of 15.3%, a viscosity of 540 mPas and a monomeric HDI content of <0.3%.

[0131] Polyisocyanate 3

[0132] A 1 L four-necked flask with stirrer, N.sub.2 inlet, condenser, thermometer and drying tube was charged with 882 g (5.25 mol) of hexamethylene diisocyanate (HDI) at 110 C. At the same temperature, 27.0 g (0.30 mol) of 1,3-butanediol were added over about 1 h. Stirring was continued for about 2 h until urethanization was complete. When the urethane stage was reached (NCO value of 45.75%), the temperature was lowered to 95 C. For the allophanatization, a 5% Zn octoate solution in 2-ethylhexanol was metered in. Following complete allophanatization (NCO value of 43.0%), the catalyst was stopped with a 5% strength solution of isophthaloyl dichloride in HDI in a weight ratio of 1:1. For complete neutralization, stirring was continued at 100 C. for 30 minutes more. The crude solution was subsequently freed from monomeric HDI in a short-path evaporator at 140 C. and <0.1 mbar. The colourless, clear resin, had an NCO content of 19.9%, a viscosity of 3250 mPas/23 C. and a monomeric HDI content of <0.3%.

[0133] Polyisocyanate 4

[0134] A 1 L four-necked flask with stirrer, N.sub.2 inlet, condenser, thermometer and drying tube was charged with 770 g (5.0 mol) of pentamethylene diisocyanate (PDI) at 110 C. At the same temperature, 33.5 g (0.25 mol) of trimethylolpropane were added over about 1 h. Stirring was continued for about 2 h until urethanization was complete. When the urethane stage was reached (NCO value of 48.35%), the temperature was lowered to 95 C. For the allophanatization and simultaneous trimerization, a 1.5% trimethylbenzylammonium hydroxide solution in 2-ethylhexanol/2-ethylhexane-1,3-diol, 1:1, was metered in. At an NCO value of 39.5%, the reaction was ended by addition of a 10% dibutyl phosphate solution in PDI in a weight ratio of 100 parts of catalyst to 7.5 parts of stopping agent. For complete neutralization, stirring was continued at 95 C. for 30 minutes more. The crude solution was subsequently freed from monomeric PDI in a short-path evaporator at 140 C. and <0.1 mbar. Viscosity of the resin after removal of monomeric HDI was 60.000 mPas. The colourless, clear resin, 80% in butyl acetate, had an NCO content of 16.2%, a viscosity of 1150 mPas and a monomeric PDI content of <0.3%.

[0135] Non-Inventive Polyisocyanates

[0136] Polyisocyanate 5 was prepared according to EP 1445271, example 2.

[0137] Polyisocyanate 6 was prepared according to EP 1445271, example 3. Instead of Excenol 1030, a poly(propyleneoxide) polyether with following data was used: Mw (weight average) 1020 g/mol; OH-number 150 mg KOH/g; viscosity 300 mPas, functionality 3.

[0138] Examples for Solvent Borne Two-Component Systems:

[0139] Preparation of Component A:

[0140] Composition of polyol blends were prepared by introducing the ingredients set forth in table 1 below. Desmophen 670 BA and Desmophen C 1200 were placed into a vessel, DBTL, BYK333, Glide 410 were added into the vessel and dispersed at 1 000 rpm (2.1 m/s) for about 10 min. Eventually, Acematt 3300 was added in 4 steps and dispersed at 2000 rpm (4.2 m/s) for about 30 min.

TABLE-US-00001 TABLE 1 Composition of the polyols 1 to 4 polyol 1 polyol 2 polyol 3 polyol 4 Desmophen 670 BA 19.2 19.2 19.2 19.2 Desmophen C 1200 15.3 15.3 15.3 15.3 DBTL, 10% in BA 0.6 0.4 0.2 0.0 BYK 333 0.4 0.4 0.4 0.4 Glide 410 0.4 0.4 0.4 0.4 Acematt 3300 4.0 4.0 4.0 4.0 MPA/BA/Xy (1:1:1) 28.4 28.4 28.4 28.4 Total polyol 68.3 68.1 67.9 67.7

[0141] Preparation of Component B:

[0142] Crosslinkers 1-9 were prepared by introducing the ingredients according to table 2 below.

TABLE-US-00002 TABLE 2 Crosslinkers 1-9 Crosslinker 1 2 3 4 5 6 7 (comp.) (inv.) (inv.) (inv.) (inv.) (inv.) (inv.) Desmodur N 3300 100 30 24.15 polyisocyanate 1 100 polyisocyanate 2 100 75.85 polyisocyanate 3 100 70 polyisocyanate 4 100 NCO wt.- % 21.8 18.02 15.3 19.9 16.2 20.47 16.87 mol 0 0.41 0.51 0.47 0.41 0.41 0.41 allophanate/mol free isocyanate* mol 0.37 0.15 0.03 0.03 0.15 0.15 0.15 isocyanurate/mol free isocyanate* Crosslinker 8 9 (comp.) (comp.) polyisocyanate 5 100 polyisocyanate 6 100 NCO wt.- % 20.6 15.2 * From .sup.13C NMR spectra, calculated as molar ratio of allophanate and isocyanurate groups over free isocyanate groups

[0143] Preparation of the Two-Component-Systems:

[0144] Component A and component B (NCO:OH equivalent ratio 1.1:1) were mixed under stirring by hand for 2 minutes prior to application. The coating compositions were then applied to PC/ABS (white and black), glass and aluminium substrates via conventional spray equipment to a dry film thickness of 40 to 50 m. The samples were flashed off under ambient condition (23 C.) for 5 min, force dried at 60 C. for 30 min and then stored at 23 C. and 50% relative humidity for 1 week prior to testing.

TABLE-US-00003 TABLE 3 Solvent borne two-component-systems polyol 1 polyol 2 polyol 3 polyol 4 (68.3 g) (68.1 g) (67.9 g) (67.7 g) Crosslinker 1 (comparison) 11.6 g 11.6 g 11.6 g 11.6 g Crosslinker 2 (inventive) 16.4 g 16.4 g 16.4 g 16.4 g Crosslinker 3 (inventive) 16.5 g Crosslinker 4 (inventive) 12.7 g Crosslinker 5 (inventive) 15.6 g Crosslinker 6 (inventive) 12.3 g Crosslinker 7 (inventive) 15.0 g Crosslinker 8 (inventive) 12.3 g Crosslinker 9 (inventive) 16.6 g

[0145] Evaluation of the Coating Films Based on the Solvent Borne Two-Component-Systems:

[0146] Impression Mark Test: Test of Initial Curing Speed

[0147] Immediately after baking at 60 C. for 30 min and cooling to 23 C. for 45 min, a weight of 500 g over a plastic film was placed on top of the films for 30 min. After removal of both weight and plastic film, appearance was checked immediately. The results can be seen in table 4 (rating: 0=poor, excessive marks; 5=best, no signs of marks). Those coatings cured with the inventive crosslinker 2 showed significantly less thermoplasticity, as a result of faster initial curing.

TABLE-US-00004 TABLE 4 Impression mark test of crosslinkers 1-2 and polyols 1-4 polyol 1 polyol 2 polyol 3 polyol 4 Crosslinker 1 5 5 3 1 (comparison) Crosslinker 2 5 5 5 3 (inventive) Crosslinker 8 5 (comparison) Crosslinker 9 5 (comparison)

[0148] Drying Speed:

[0149] After application, coatings were allowed to flash off and cured at 60 C. as described above, then cooled down to 23 C. for 10 min. Then, a 200 g load with paper was placed on top for 30 seconds, and then the load was carefully removed. The panel was turned upside down to see if the paper automatically falls down or not. If the paper falls automatically down the drying test is successfully passed. Otherwise, the paper still sticks to the coating (not passed). The results are shown in table 5.

TABLE-US-00005 TABLE 5 Drying properties of crosslinkers 1-7 and polyol 2 Crosslinker 1 (comparison) 2 3 4 5 6 7 polyol 2 Tacky Pass Pass Tacky Pass Tacky Pass

[0150] Abrasion Resistance:

[0151] Abrasion resistance of the coating was tested by a Tabor abrasion tester, using a load of 1 000 g, CS-10 wheels for 500 cycles and 1 000 cycles, and finally checking the weight loss (less weight loss means better abrasion resistance). The results can be seen in table 6.

TABLE-US-00006 TABLE 6 Abrasion resistance of crosslinkers 1-9 and polyol 2 Crosslinker 1 (comparison) 2 3 4 5 6 7 8 9 500 cycles/mg 48 4 17 16 5 30 9 53 64 1 000 cycles/mg 81 22 45 42 32 49 41 97 126

[0152] MEK Resistance:

[0153] The MEK solvent resistance of the coating was tested by placing a drop of MEK (0.1 ml) on the coating film and checking how many minutes passed until the coating film was dissolved by MEK (longer period means better solvent resistance). The results are shown in table 7.

TABLE-US-00007 TABLE 7 MEK solvent resistance crosslinkers 1-9 and polyol 2 Crosslinker 1 (comp.) 2 3 4 5 6 7 8 9 Film 16 min 26 min 26 min 20 min 22 min 18 min 20 min 17 min 12 min destroyed after

[0154] Suntan Lotion and DEET Resistance:

[0155] The suntan lotion and insect repellent (DEET, 8.0%) resistance of the coating was tested by placing 0.2 ml of NIVEA SPF 30+PA++ suntan lotion on a 2 inch square, and then placing the coated panel into a climate chamber (60 C., 95% humidity) for 48 hours. After the test, the panels were cooled to 23 C. Next, the residual suntan lotion/DEET was removed with a tissue paper and the appearance was visually checked: 5 is the best (unchanged), 1 is the worst (totally destroyed). Finally, cross cut adhesion was measured (3M tape #600). The results can be seen in table 8 and table 9.

TABLE-US-00008 TABLE 8 Suntan lotion resistance of crosslinkers 1-9 and polyol 2 Crosslinker 1 8 9 (comp.) 2 3 4 5 6 7 (comp.) (comp.) Appearance 3 4 4 4 3 3 3 3 3 Adhesion 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100

TABLE-US-00009 TABLE 9 DEET resistance of crosslinkers 1-9 and polyol 2 Crosslinker 1 8 9 (comp.) 2 3 4 5 6 7 (comp.) (comp.) Appearance 2 4 1 1 1 1 1 1 1 Adhesion 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100 100/100

[0156] Examples for Water Borne Two-Component-Systems:

[0157] Preparation of Component A:

[0158] Composition of polyol 5 was prepared by introducing the ingredients shown in table 10. The polyurethane dispersions Bayhydrol U 355, Bayhydrol UH 340/1 and Impranil DLC-F were placed in a vessel, BYK348, BYK 093, DC-51 were added into the vessel sequentially, and dispersed at 1 000 rpm for about 10 min. OK607 and TS100 were added into the vessel stepwise and then dispersed at 2000 rpm during 30 min.

TABLE-US-00010 TABLE 10 Composition of polyol 5 Polyol 5 Bayhydrol U 355 32.6 Bayhydrol UH 340/1 29.8 Impranil DLC-F 15 Deionized water 15.2 BYK 093 0.5 BYK 348 0.4 DC-51 1 OK 607 1.5 TS 100 4 Total 100.00

[0159] Preparation of Component B:

TABLE-US-00011 TABLE 11 Compositions of crosslinkers 10 and 11 (parts by weight) Crosslinker 10 Crosslinker 11 (comparative) (inventive) Bayhydur 304 100 50 (comparative) polyisocyanate1 59.1 (inventive)

[0160] Evaluation of the Coating Films Based on the Water Borne Two-Component-Systems:

TABLE-US-00012 TABLE 12 Water borne two-component-systems (parts by weight) polyol 5 (100 g) polyol 5 (100 g) Crosslinker 10 5.6 Crosslinker 11 6.1

[0161] The coating compositions according to table 12 were applied to polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) white & black, glass and Aluminium substrates via conventional spray equipment to a dry film thickness of 40 to 50 m. The samples were allowed to flash off under ambient conditions for 5 min, baked at 60 C. for 30 min and then returned to ambient condition for 1 week prior to testing.

[0162] Impression Mark Test:

[0163] After the coating film was baked at 60 C. for 30 min, cooling to ambient temperature during 45 min, a weight of 500 g on plastic package film was applied at R.T. for 30 min, then appearance was checked immediately after testing (see table 13). The panel was evaluated in a range between 0=poor, excessive marks and 5=best, no signs of marks.

TABLE-US-00013 TABLE 13 Impression mark test of coating compositions of polyol 5 and crosslinker 10 and 11 Crosslinker 10 Crosslinker 11 Crosslinker (comparative) (inventive) Impression mark test 2 3

[0164] RCA Resistance Test:

[0165] An R.C.A abrasion wear tester with 175 g load was used. After 200 cycles, appearance of the test areas was checked visually: 5 is best, 1 is worst (see table 14).

TABLE-US-00014 TABLE 14 RCA test of coating compositions of polyol 5 with crosslinkers 10 and 11 Crosslinker 10 Crosslinker 11 Crosslinker (comparative) (inventive) RCA result 1 3

[0166] Abrasion Resistance:

[0167] Abrasion resistance of the coating was tested by a Taber abrasion tester, using a load of 1 000 g, CS-10 wheels for 500 cycles and 1 000 cycles, and finally checking the weight loss (less weight loss means better abrasion resistance). The results are shown in table 15.

TABLE-US-00015 TABLE 15 Abrasion resistance of coating compositions of polyol 5 and crosslinkers 10 and 11 Crosslinker 10 Crosslinker 11 Crosslinker (comparative) (inventive) 500 cycles/mg 89 70 1000 cycles/mg 221 200

[0168] Ethanol Resistance:

[0169] The ethanol resistance of the coating was tested by placing a drop of ethanol (0.1 ml) on the coating film, then checking appearance after 5 min & 10 min. The results are shown in table 16.

TABLE-US-00016 TABLE 16 ethanol resistance of coating compositions of polyol 5 and crosslinkers 10 and 11 Crosslinker 10 Crosslinker 11 Crosslinker (comparative) (inventive) ethanol-5 min slight trace pass ethanol-10 min slight trace very slight trace

[0170] DEET Resistance:

[0171] The insect repellent (DEET, 8.0%) resistance of the coating was tested by placing 0.2 ml of DEET on a 2 inch square, and then placing the coated panel into a climate chamber (60 C., 95% humidity) for 24 hours. After the test, the panels were cooled to 23 C. Next, the residual suntan lotion/DEET was removed with a tissue paper and the appearance was visually checked: 5=best (unchanged), 1=worst (totally destroyed). The results are shown in table 17.

TABLE-US-00017 TABLE 17 DEET resistance of polyol 5 and crosslinkers 10 and 11 Crosslinker 10 Crosslinker 11 Crosslinker (comparative) (inventive) Appearance 2/blisters 4/very slight blisters

[0172] As a summary, it could be proven that using the inventive polyisocyanate crosslinkers and especially the inventive two-component-systems, in solventas well as water borne formulations results in faster drying and better chemical resistance, while elasticity/abrasion resistance is kept on the same or even higher level. Non inventive, allophanate poylisocyanates without isocyanurate groups (polyisocyanates 5 and 6) show a high level of elasticity/abrasion resistance, however fail to meet the required chemical resistance.