ACID INDICATOR SYSTEM

Abstract

The invention relates to an indicator system, a method for optically displaying the progress of curing a composition, the use of colourants with a xanthene skeleton to optically display the progress of curing compositions, a kit-of-parts, and a method for increasing the clock rate between a coating step and an additional, downstream processing step for objects.

Claims

1.-15. (canceled)

16. An indicator system comprising a composition which comprises at least one NCO-reactive compound and at least one polyisocyanate, and comprising at least one proton source and at least one indicator dye, the at least one indicator dye having at least one xanthene skeleton, for indicating the curing of the composition by change in color of the at least one indicator dye, wherein the at least one indicator dye, has a first color after contacting with the uncured composition and in the cured composition is colorless.

17. The indicator system as claimed in claim 16, wherein the at least one indicator dye and the at least one proton source are applied on a surface of an inert carrier, the inert carrier optionally being applied with a second surface, which faces away from the first surface, on a second inert carrier, the second carrier preferably being selected from the group consisting of polymer foils, metal foils, paper and/or card, and the inert carrier being colorless and transparent, and the second carrier preferably being white.

18. The indicator system as claimed in claim 16, wherein the at least one indicator dye has at least one fluoran skeleton.

19. The indicator system as claimed in claim 16, wherein the at least one proton source is a Brnsted acid.

20. The indicator system as claimed in claim 19, wherein the Brnsted acid is selected from the group consisting of nonpolymeric carboxylic acids, hydroxycarboxylic acids, phosphoric and sulfonic acids with organic substitution, and mixtures thereof.

21. The indicator system as claimed in claim 16, wherein the at least one polyisocyanate in the composition is an aliphatic and/or cycloaliphatic polyisocyanate.

22. The indicator system as claimed in claim 16, wherein the at least one NCO-reactive compound is selected from the group consisting of polyaspartic esters, polyacrylate polyols, polyester polyols, and mixtures thereof.

23. The indicator system as claimed in claim 16, wherein the composition is a polyurethane and/or polyurea coating material.

24. A method for optically indicating the curing progress of a composition which comprises at least one NCO-reactive compound and at least one polyisocyanate, wherein the method comprises the following steps: (a) providing at least one indicator dye and at least one proton source, the at least one indicator dye having at least one xanthene skeleton, and the at least one indicator dye and the at least one proton source being applied on a surface of an inert carrier, (b) contacting the at least one indicator dye and the at least one proton source from step (a) with the uncured composition, the at least one indicator dye having a first color, and (c) curing the composition, the at least one indicator dye indicating the curing of the composition through color switch from the first color to colorless.

25. The method as claimed in claim 24, the inert carrier being a polymer foil or a glass fiber web.

26. The method as claimed in claim 24, wherein the inert carrier, by a second surface, which faces away from the first surface, is applied on a second inert carrier.

27. A method for optically ascertaining the curing progress of a composition comprising at least one NCO-reactive compound and at least one polyisocyanate, with at least one indicator dye and at least one proton source, the at least one indicator dye having at least one xanthene skeleton, wherein, after contacting of the at least one indicator dye and of the at least one proton source with the composition, the color of the at least one indicator dye is compared with a color scale in order to ascertain the curing progress.

28. A method comprising utilizing an indicator dye with xanthene skeleton, in the presence of at least one proton source, for optically indicating the curing progress of compositions comprising at least one NCO-reactive compound and at least one polyisocyanate, wherein the at least one indicator dye has a first color after contacting with the uncured composition and in the sufficiently cured composition is colorless.

29. A kit of parts comprising at least one indicator dye, the at least one indicator dye having at least one xanthene skeleton, at least one proton source, a composition comprising at least one NCO-reactive compound and at least one polyisocyanate.

30. A method for increasing the cycle frequency between a coating step and a further downstream step in the processing of objects which are coated with a composition which comprises at least one NCO-reactive compound and at least one polyisocyanate, wherein at least one indicator dye is contacted with the composition in the presence of at least one proton source in order to indicate the curing progress of the coating, the at least one indicator dye having at least one xanthene skeleton.

Description

EXAMPLES

1) General Remarks

1.1) Determination of Drying Level in Accordance with DIN EN ISO 9117-5:2012

[0121] Using a four-way paint applicator, the coating material under test was drawn down on a glass plate. The measurement of time began with the act of drawdown.

[0122] Drying level 1 (T1) was awarded when, using a fine-hairbrush, it was possible to remove around 0.5 g of fine glass beads (diameter 2 mm) scattered over the surface.

[0123] For drying levels 2 to 4 (T2 to T4), the coating on a filter paper was loaded with different weights (T2 20 g, T3 200 g, T4 2 kg) for a duration of 60 seconds, after which the sample plate was dropped onto the bench top vertically from a height of about 30 mm. If the paper fell off, the drying level was reached.

[0124] Drying level 5 (T5) was tested as for drying level 4. For this level, however, there had to be no perceptible change in the surface of the loaded coating.

1.2) Color Values According to Color Scale

[0125] A color scale was drawn up, and then compared with the appearance of the coatings. The color scale was drawn up using the RGB color space provisions of the Microsoft Excel 2010 software (Format Cells/Fill/More Colors/Custom), with each hue being assigned a number in sequence of falling color intensity (from 1really intensive magenta red to 14colorless) and being printed out using a commercial printer (RICOH MP C 3003) on white paper (name IQ appeal 80 g/m.sup.2 from Mondi Paper Sales Deutschland GmbH, Unterfhring, DE).

[0126] For the visual assessment, clearcoats were drawn down onto a colorless glass plate in a wet film thickness of 200 m using a film-drawing frame (Byk-Gardner GmbH, Geretsried, DE). The coated glass plate was then placed onto a white paper sheet (manufacturer as above) and the hue was compared visually with the color scale during and/or after drying/curing.

TABLE-US-00001 TABLE 1 Color scale based on RGB color model Defined color value Red Green Blue 1 (strong red to 230 0 126 magenta) 2 255 21 149 3 255 41 158 4 255 63 168 5 255 83 177 6 255 101 185 7 255 121 194 8 255 143 204 9 255 163 213 10 255 183 222 11 255 201 231 12 255 221 240 13 255 243 250 14 (colorless) 255 255 255

1.3) Chemicals Used

[0127] The following dyes were obtained from Sigma-Aldrich Chemie GmbH, Munich, DE, and used without further pretreatment:

[0128] Dye #1 (I=inventive): 2,4,5,7-Tetrabromo-3,4,5,6-tetrachlorofluorescein

[0129] Dye #2 (I): 2,4,5,7-Tetrabromofluorescein disodium salt (eosin Y)

[0130] Dye #3 (I): 2,4,5,7-Tetraiodofluorescein (erythrosine B)

[0131] Dye #4 (I): 3,4,5,6-Tetrachloro-2,4,5,7-tetraiodofluorescein (rose bengal)

[0132] Dye #5 (I): 2,4,5,7-Tetrabromo-3,4,5,6-tetrachlorofluorescein disodium salt (phloxine B)

[0133] Dye #6 (C=comparative example): 2,6-Diphenyl-4-(2,4,6-triphenyl-1-pyridinio)phenolate (Reichardt dye)

[0134] Dye #7 (C): 5-Amino-9-(diethylamino)benzo[a]phenoxazin-7-ium (Nile blue)

[0135] Dye #8 (C): 3,3-Bis(4-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone)

[0136] Dye #9 (C): 3,7-Diamino-5-phenylphenazinium chloride (phenosafranine)

[0137] DBTL: Dibutyltin dilaurate, catalyst, CAS 77-58-7 (Aldrich, DE),

[0138] Setalux D A HS 1272 (72% in butyl acetate): OH-containing polyacrylate polyol (Nuplex, NL),

[0139] MPA: 1-Methoxy-2-propyl acetate, CAS 108-65-6, solvent (BASF SE, DE),

[0140] Butyl acetate: Acetic acid n-butyl ester, CAS 123-86-4, solvent (BASF SE, DE),

[0141] Xylene: Solvent (Azelis, BE)

[0142] Diacetone alcohol: Solvent (Sigma-Aldrich, DE)

[0143] Desmodur N 3600: Polyisocyanate based on trimers of hexamethylene diisocyanate, NCO content 23.0%, viscosity 1200 mPa s at 23 C. (Covestro Deutschland AG, DE),

[0144] Desmodur N 3900: Polyisocyanate based on trimers of hexamethylene diisocyanate, NCO content 23.5%, viscosity 730 mPa s at 23 C. (Covestro Deutschland AG, DE),

[0145] Bentone 38: organic derivative of a hectorite mineral for rheology control (Elementis Service Centre NV, NL),

[0146] Desmophen NH 1420: Amino-functional reaction partner for polyisocyanates, amine number 200, viscosity 1500 mPa s at 23 C. (Covestro Deutschland AG, DE),

[0147] Desmophen NH 1520: Amino-functional reaction partner for polyisocyanates, amine number 190, viscosity 1400 mPa s at 23 C. (Covestro Deutschland AG, DE),

[0148] Tinuvin 292: HALS light stabilizer, sterically hindered amine, basic, Tinuvin 384: Light stabilizer, UV absorber (both BASF SE, DE),

[0149] Aerosil 300: hydrophilic fumed silica (Evonik Resource Efficiency GmbH, DE),

[0150] Makrofol DE 1-1 000000, polycarbonate foil (Covestro Deutschland AG, DE)

[0151] Adhesive laminating foil GH-X173 natural (from Bischof u. Klein, Germany),

[0152] Dibutyl phosphate, racemic DL lactic acid, dodecylbenzenesulfonic acid: (all Sigma-Aldrich, DE)

[0153] Deltron Progress VHS Rapid D8135; curing agent 8214, activated diluent 8217: commercial automotive refinish clearcoat system, all PPG Sales and Services GmbH, DE

2) Examples

2.1) Example 1

[0154] Preparation of a clearcoat formulation with dye indicators, and application and drying thereof.

TABLE-US-00002 TABLE 2 Preparation of indicator dye solutions Diacetone Indicator Indicator Amount of indicator alcohol/dibutyl Color of solution dye dye [mg] phosphate 1:1 [g] solution 1 (I) # 1 46 10 Red 2 (I) # 2 54 10 Orange 3 (I) # 3 83 10 Red 4 (I) # 4 42 10 Red 5 (I) # 5 53 10 Red 6 (C) # 6 47 10 Blue 7 (C) # 7 42 10 Blue 8 (C) # 8 68 10 Blue 9 (C) # 9 54 10 Red Key: I = Inventive, C = Comparative example

[0155] The indicator dyes prepared were first mixed with an isocyanate-reactive coating component by stirring. The perceived color of the solution was recorded after the end of the stirring procedure (table 4). Then an isocyanate-containing component was added and stirred in homogeneously, and the perceived color was recorded (table 4), and the coating material (see table 3) together with indicator dye was drawn down onto a colorless glass plate at 200 m (wet) using a film-drawing bar, and the perceived color of the wet drawdown was recorded (table 4). The coating was dried at room temperature for 16 hours and changes in the color were monitored optically, until the coating was dry and hard. For comparison, in each case only the isocyanate-reactive component with indicator, but without isocyanate-containing component, was drawn down and dried. These drawdowns were still tacky after 16 hours. Furthermore, both the clearcoat with indicator and just the isocyanate-reactive component with indicator were each kept in a closed glass bottle, and the change in color was assessed visually after 16 hours. The isocyanate-reactive component kept in the bottle was still liquid. The clearcoat in the bottle reacted to form a viscous mass. The observed colors of the liquid and drawn-down coatings are set out in table 4.

TABLE-US-00003 TABLE 3 Composition of coating 1 - solventborne 2K PU clearcoat Coating 1 Initial mass Isocyanate-reactive component Setalux D A HS 1272 50.0 g Tinuvin 292 0.6 g Tinuvin 384 0.8 g Dibutyltin dilaurate 1.6 g (1% solution in n-butyl acetate) Mixture of Butyl acetate/1- 12.6 g methoxyprop-2-yl acetate/xylene (1/1/1) Indicator dye 2.0 g Isocyanate-containing component Desmodur N 3600 18.4 g Mixture of Butyl acetate/1- 14.0 g methoxyprop-2-yl acetate/xylene (1/1/1) Total (coating) 100.0 g

TABLE-US-00004 TABLE 4 Observed colors of indicator dye solutions, of mixtures of the indicator dye solutions with the NCO-reactive component and also with the composition in glass bottles and the coating drawdowns-both immediately after mixing and after 16 h storage temperature. 1-1 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 Example (I) (I) (I) (I) (I) (C), (V) (C) (C) Indicator dye #1 #2 #3 #4 #5 #6 #7 #8 #9 Color of indicator dye Red Red Red Red Red Blue Blue Blue Red isolution Color of isocyanate- Red Red Red Red Red Brown Violet Blue Red reactive component with indicator dye solution immediately in the bottle Color of isocyanate- Red Red Red Red Red Brown Violet Blue Red reactive component with indicator dye solution in the bottle after 16 h Color of coating 1 Red Red Red Red Red Brown Violet Blue Red with indicator dye solution immediately in the bottle Color of coating 1 in Red Red Red Red Red Brown Violet Blue Red the bottle with indicator dye solution in the bottle after 16 h Glass drawdown, Red Red Red Red Red Green Violet Blue Red coating 1 immediately Glass drawdown, Colorless Colorless Colorless Colorless Colorless Green Violet Blue Red coating 1 after 16 hr

[0156] Examples 1-1 to 1-9 above show that all of the coatings when kept in the bottle react to form a viscous mass, owing to the inability of the solvents used to escape. In these cases there is no change in color.

[0157] Examples 1-1 to 1-5 according to the invention show that the coatings change color on drying and curing on a glass plate. The color intensities decrease over 16 hours. Coatings comprising the indicator dye #1, #2, #3, #4 and #5 are colorless after 16 h. The clearcoats containing the comparative dyes (solvatochrom #6; redox or pH indicators #7, #8, #9), on the other hand, do not change color during drying and curing of the coating.

2.2) Example 2

[0158] The coatings from example 1, with indicators #1, #3 and #4 added, were again drawn down to glass plates and dried at room temperature. On full decoloring of the coating (color value 14 according to color scale), the drying level of the coating was immediately determined (table 5).

TABLE-US-00005 TABLE 5 Determination of the drying level of coatings with three different indicators Example 2-1 Example 2-2 Example 2-3 with coating 1 with coating 1 with coating 1 and indicator Drying and indicator Drying and indicator Drying dye level dye level dye level #1 T3 #2 T1 #3 T1

[0159] Example 2 shows that different drying levels of the coatings can be indicated depending on the indicator dye of the invention that is selected.

2.3) Example 3

[0160] Where two indicator dye mixtures were prepared: As comparative [indicator #10(C)], 40 g of Aerosil 300 were stirred using a dissolver into 380 g of diacetone alcohol, initially at a slow dissolver speed, followed by homogenization at 1000 rpm for 30 minutes. 0.05 g of indicator dye #1 was dissolved in 10.8 g of this mixture. In accordance with the invention [indicator #11(I)], 0.17 g of indicator dye #1 was dissolved in 40.0 g of the above mixture of diacetone alcohol and Aerosil, and 1.46 g of dibutyl phosphate were added. The coatings described in table 6 were subsequently prepared by mixing of the components. The last component to be added was the isocyanate-containing component, and immediately thereafter the coatings were drawn down onto a colorless glass plate at 200 m (wet) using a film-drawing bar. The coating was dried at room temperature for 16 hours and changes in the color were monitored optically, until the coating was dry and hard.

TABLE-US-00006 TABLE 6 Effect of acid on the indicators in different coatings Example Example Example Coating 3-1 (C) 3-2 (C) 3-3(I) Isocyanate-reactive component Setalux D A HS 1272 7.5 g 7.5 g 7.5 g Tinuvin 292 0.1 g 0.1 g Dibutyltin dilaurate 0.3 g 0.3 g 0.3 g (1% solution in n-butyl acetate) Mixture of Butyl acetate/1-meth- 3.3 g 3.3 g 3.3 g oxyprop-2-yl acetate/xylene (1/1/1) Indicator #10(C) 3.0 g 3.0 g Indicator #11(I) 3.0 g Isocyanate-containing component Desmodur N 3600 2.8 g 2.8 g 2.8 g Total (coating) 16.9 g 17.0 g 17.0 g Film drawdown, glass plate Perceived colors according (200 m wet), drying at RT to color scale as per table 1 Starting value 3 2 4 after 1 h 8 4 7 after 1.5 h 9 4 12 after 3 h 12 4 14 after 5 h 14 4 14 after 16 h 14 4 14

[0161] From comparative examples 3-1 and 3-2 it can be seen that adding a basic light stabilizer (Tinuvin 292) disrupts the indicator system, and so the coating 3-2 no longer fades out. Only the indicator system of the invention fades out as drying progresses even with the light stabilizer present.

2.4) Example 4

[0162] An indicator dye solution was prepared by dissolving 55 mg of indicator dye #5 in 3.63 g of diacetone alcohol and 3.63 g of 1-methoxypropy-2-yl acetate. This solution was admixed with 2.00 g of Bentone 38 and 0.7 g of dibutyl phosphate, which were stirred in. This suspension was drawn down uniformly using a 0.5 wire-wound coating bar onto a smooth polycarbonate foil of MAKROFOL DE 1-1 000000 (1 mm thick). The foil was then dried in a forced air oven at 95 C. for 5 minutes. The resulting coated foil was uncolored, with a matt surface. On the side coated with dye, the foil was subsequently lined with an adhesive laminating foil GH-X173 natural (from Bischof u. Klein, Lengerich, Germany). The foil assembly was cut using scissors into strips with a length of 15 cm and a width of 15 cm.

[0163] Following removal of the laminating foils, the coating 1 from example 1, albeit without addition of an indicator, was drawn down on a foil strip. Over the course of 10 to 30 seconds, the coating turned red. This was followed by drying at room temperature. In the course of drying, the color of the coating was checked at defined times against the color scale as per table 1 (table 7). After 240 minutes, the coating was assessed as having a drying level of T4.

TABLE-US-00007 TABLE 7 Change in color values according to the color scale as per table 1, over time, of coating 1 without indicator dye, drawn down onto polycarbonate foil precoated with indicator dye, during drying and curing Defined color values Time according to color scale 0.0 min [start] 14 (colorless) 0.5 min 5 (red) 30 min 6 60 min 10 90 min 12 180 min 13 210 min 13 240 min 14 (colorless)

[0164] The example above shows that it is also possible to apply the indicator dye to a carrier; where the carrier is subsequently coated with a clearcoat, the latter first takes on color and then decolors again during drying and curing.

2.5) Example 5

[0165] Coating of a glass plate, precoated with indicator, with a coating material based on a polyaspartic ester and a polyisocyanate.

[0166] Where two indicator dye mixtures were prepared: 60 g of Bentone 38 were stirred into 240 g of diacetone alcohol using a dissolver, initially at a slow dissolver speed, followed by homogenization at 200 rpm for 30 minutes. First, 0.05 g of indicator dye #1 was dissolved in 10.0 g of this mixture [comparative indicator #12(C)], and secondly 0.05 g of indicator dye #1 and 4-dodecylbenzenesulfonic acid were dissolved in 9.4 g of this mixture [indicator #13(I)]. The indicator dye mixtures were each applied to a colorless glass plate in a wet film thickness of 50 m using a wire-wound coating bar. The coated glass plates were dried in a forced air oven at 95 C. for 5 minutes. The coating described in table 8 was subsequently produced by mixing of the components. The last component to be added was the isocyanate-containing component, and immediately thereafter the coating was drawn down using a film-drawing bar at 200 m (wet) onto the indicator dye layer of the two previously coated glass plates. The coating was dried at room temperature for 4 hours and changes in the color were monitored optically. The coating was dry after about 1 hour and hard (fingerprint no longer visible) after 2.5 hours.

TABLE-US-00008 TABLE 8 Effect of acid on the indicators in different coatings Example Example Coating 5-1 (C) 5-2 (I) Isocyanate-reactive component Desmophen NH 1420 7.1 g 7.5 g Desmophen NH 1520 2.4 g 2.4 g Tinuvin 292 0.1 g 0.1 g Butyl acetate 4.6 g 4.6 g Isocyanate-containing component Desmodur N 3900 5.9 g 5.9 g Total (coating) 20.1 g 20.1 g Film drawdown, glass plate (200 m Indicator Indicator wet), precoated with: Drying at RT #12(C) #13(I) Starting value (after 5 min) 4 4 after 0.5 h 5 9 after 1 h 6 11 after 2 h 6 12 after 3 h 6 13 after 4 h 6 13

[0167] Only in the case of inventive example 5-2, with acid in the indicator dye mixture, is there fade-out of the coating on the glass plate. In the comparative example, the same coating without acid in the indicator dye mixture, in spite of the dye being the same, does not change.

2.6) Example 6

[0168] An indicator dye mixture was prepared by dissolving 100 mg of indicator dye #5 in 7.26 g of diacetone alcohol and 7.26 g of 1-methoxypropy-2-yl acetate. This solution was admixed with 4.00 g of Bentone 38 and 1.24 g of racemic lactic acid, and the mixture was homogenized. This mixture was drawn down onto a foil and dried as in example 4. A section of this foil measuring 15 cm times 15 cm was mounted on a substrate carrier in a coating booth, using double-sided adhesive tape, such that the section of foil was also coated during the clearcoat finishing of a metal panel precoated with primer and basecoat. A commercial 2K PU clearcoat from PPG Sales and Services GmbH, DE (Deltron Progress UHS Rapid D8135; curing agent 8214, activated diluent 8217, mixing ratio 3:1:0.6) was applied as detailed in the technical sheet RLD212V of December 2008, in a dry film thickness of 50 m, using a compressed-air spray gun. The coated panel and the coated foil were dried at room temperature for 3.5 hours.

[0169] The foil thus coated was assessed for its color development according to the color scale, and in parallel the curing of the clearcoat on the panel was assessed (table 9).

TABLE-US-00009 TABLE 9 Color development of a foil coated with a commercial automotive refinish clearcoat, and coated beforehand with indicator dye, and evolution of curing of the simultaneously coated metal panel Color evolution of Color according coating on foil to scale Curing on panel Starting value (after 5 min) 7 tacky after 0.5 h 10 slightly tacky after 1 h 12 dry to touch after 2.5 h 13 dry after 3.5 h 13 hard

[0170] The example shows that the curing of the coating on the panel can also be indicated by the evolution in color of the co-coated foil which had been precoated with indicator.