Removable, biodegradable coating

Abstract

The present invention relates to a functional coating obtained from an aqueous coating composition, which composition comprises a pigment and a polymeric binder, wherein the binder has a weight average molecular weight of from 2000 to 50000 g/mole, and an acid value of 40 to 250, and wherein the binder is a polyester comprising a side group introduced by a Diels-Alder and/or pericyclic Ene-reaction, wherein the side group contains an ionic group and/or an ion-forming group.

Claims

1. An aqueous coating composition for providing a removable functional coating, which coating is removable with a removing agent comprising a strong base wherein the strong base is an alkali metal hydroxide, the coating composition comprises a pigment and a polymeric binder, wherein the binder has a weight average molecular weight of from 2000 to 50000 g/mole, and an acid value of 40 to 250 mg KOH/g polymeric binder, wherein the binder is a polyester comprising a side group introduced by a Diels-Alder and/or pericyclic Ene-reaction, wherein the side group contains an ionic group.

2. The coating composition according to claim 1, wherein the binder is obtained by at least the following steps: (a) preparing an unsaturated polyester, (b) effecting a Diels-Alder reaction and/or pericyclic Ene-reaction between the unsaturated polyester and an unsaturated compound containing an ionic group and/or ion-forming group to obtain a polymer with side groups containing ionic groups and/or ion-forming groups, and (c) optionally converting at least part of the ion-forming groups present in the polymer to ionic groups.

3. The coating composition according to claim 2, wherein the unsaturated compound is a) a conjugated diene with carboxylic acid ionic groups and/or carboxylic acid ion forming groups; or b) an unsaturated compound(s) with ion forming groups to obtain a polymer with side groups containing ion-forming groups; or c) a conjugated diene with carboxylate forming groups to obtain a polymer with side groups containing carboxylic acid ion-forming groups.

4. The coating composition according to claim 2, wherein the unsaturated polyester is a linear or substantially linear unsaturated polyester.

5. The coating composition according to claim 1, wherein the binder has a weight average molecular weight of at least 5000 g/mole, and/or wherein the binder has a weight average molecular weight of at most 40000 g/mole.

6. The coating composition according to claim 1, wherein the acid value of the binder is from 60 to 160 mg KOH/g polymeric binder.

7. The coating composition according to claim 1, wherein the glass transition temperature of the binder is from 10 to 80° C.

8. The coating composition according to claim 1, wherein the polymeric binder is water-dispersible or water-soluble.

9. The coating composition according to claim 1, wherein the side group of the polymeric binder is represented by any one of structures ##STR00003## or any isomer thereof, wherein: R.sub.1 is selected from the group of anionic groups, which group consists of carboxylate (—COO.sup.−), sulphate (—OSO.sub.3.sup.31 ), phosphate (—OPO.sub.3.sup.31 ), sulphonate (—SO.sub.2O.sup.31 ), phosphinate (—POO.sup.−), phosphonate (—PO.sub.2O.sup.−) and substituted alkyl, alkenyl, aryl and alkylaryl groups of the formula —R.sub.12-A.sup.−; wherein R.sub.12 is linear or branched alkyl, alkenyl, aryl or alkylaryl moiety, which moiety has 1-12 carbon atoms; wherein A.sup.− is an anionic group selected from carboxylate, sulphate, phosphate, sulphonate, phosphinate and phosphonate; wherein R.sub.2-R.sub.11 may each be individually chosen from either the group of anionic groups defined for R.sub.1 or from the group consisting of hydrogen, alkyl, alkenyl, aryl and alkylaryl; wherein * represents a carbon atom of the polyester to which the side group is attached, and; wherein for structure (2), at least one of R.sub.5, R.sub.6, R.sub.7 and R.sub.8 must be an anionic group; wherein for structure (3), at least one of R.sub.5, R.sub.6, R.sub.8 R.sub.9 and R.sub.10 must be an anionic group; wherein for structure (4), at least one of R.sub.9 R.sub.10 and R.sub.11 must be an anionic group.

10. The coating composition according to claim 9, wherein A.sup.− is a carboxylate and/or wherein R.sub.2-R.sub.11 are each be individually chosen from either the group of anionic groups defined for R.sub.1 or from the group consisting of H, alkyl and alkenyl.

11. The coating composition according to claim 1, wherein the polymeric binder comprises at least one of the following structural units (5) and (6): ##STR00004## wherein R.sub.1 is COO.sup.−, R.sub.2 and R.sub.3 are H; and R.sub.4 is methyl; and wherein R.sub.11 is ethyl; R.sub.9 is COO.sup.−; and R.sub.10 is H; and/or any isomer thereof.

12. The coating composition according to claim 1, wherein the amount of binder is from 5 to 45 wt. % and the amount of pigment is from 55 to 95 wt. %, based on the dry weight of the aqueous coating composition.

13. The coating composition according to claim 1, wherein the pigment is selected from the group consisting of calcium carbonate, titanium dioxide, a silicate, gypsum, baryte, and combinations thereof.

14. The coating composition according to claim 1, wherein the coating composition further comprises a) an adhesion promotor selected from the group consisting of silanes; and/or b) a pigment divider; and/or c) a thickener.

15. The coating composition according to claim 1 having a pH in the range of 8.0-12.0.

16. A method for forming a functional coating on an outside wall and/or roof of a greenhouse, wherein the method comprises (1) applying the coating composition according to claims 1 and (2) drying the coating composition.

17. The coating composition according to claim 1, wherein the coating composition comprises a crosslinker in an amount of less than 1 wt. % based on the total weight of the coating composition.

18. The coating composition according to claim 1, wherein the coating composition comprises no crosslinker.

19. The coating composition according to claim 1, wherein the ionic group is selected from the group consisting of carboxylate (—COO.sup.−), sulphate (—OSO.sub.3.sup.−), phosphate (—OPO.sub.3.sup.−), sulphonate (—SO.sub.2O.sup.−), phosphinate (—POO.sup.−) and phosphonate (—PO.sub.2O.sup.−).

20. A functional coating removable with a removing agent comprising a strong base wherein the strong base is an alkali metal hydroxide, wherein the functional coating comprises a pigment and a polymeric binder, wherein the binder has a weight average molecular weight of from 2000 to 50000 g/mole, and an acid value of 40 to 250 mg KOH/g polymeric binder, wherein the binder is a polyester comprising a side group introduced by a Diels-Alder and/or pericyclic Ene-reaction, wherein the side group contains an ionic group.

21. A surface provided with a functional coating according to claim 20.

22. The surface according to claim 21, wherein the surface is an outside wall and/or roof of a greenhouse.

23. A method for removing a functional coating on an outside wall and/or roof of a greenhouse which coating is a coating according to claim 20, wherein the method comprises treating the functional coating with a removing agent which comprises water, a strong base and optionally a complex former, the strong base being present in an amount of from 1 to 10 wt. %, and the complex former, if present, is present in an amount of from 2 to 10 wt. %, based on the weight of the removing agent, and wherein the strong base is an alkali metal hydroxide.

Description

EXAMPLES

(1) Test Methods

(2) Stability of Aqueous Solutions

(3) Samples were put in 30 ml jars and sealed air-tight. All samples were clear, indicating good solubility in water. They were placed in an oven at 40° C. Biweekly the samples were checked for clarity. When the samples became hazy this indicated that the solubility in water is limited. From that moment, the sample is called unstable.

(4) Biodegradability

(5) Biodegradability is measured analogue to OECD 301 F: Manometric Respirometry. Instrument used was Aqualytic BOD-System AL606. Reference material is sodium acetate. Activated sludge was supplied by Tauw B.V. in Deventer, the Netherlands. The use of this activated sludge resulted in a degradation of the reference material, sodium acetate, of 17% after 14 days and 24% after 28 days. Calculated values are relative to the sodium acetate.

(6) Weight Average Molecular Weight M.sub.w and Number Average Molecular Weight M.sub.n

(7) The weight average molecular weight can be measured using size exclusion chromatography (SEC). The SEC analyses in these experiments were performed on an Advance Polymer Chromatography system (Waters APC), including a pump, auto injector, degasser, and column oven. The eluent was tetrahydrofuran (THF) to which 0.8 vol % acetic acid was added, based on the total volume of THF. The injection volume was 10 μl. The flow was established at 1.0 ml/min. Three Acquity APC columns of 15 cm with different pore sizes: 450 Å, 125 Å and 45 Å were applied in series at a temperature of 40° C. The detection was performed with a differential refractive index detector (Waters Acquity Refractive Index detector). The sample solutions were prepared with a concentration of 50 mg solids in 5 ml eluent (THF+0.8 vol % acetic acid, based on the total volume of THF), and the samples were dissolved for a period of 24 hours. Calibration is performed with 21 polystyrene standards (Agilent EasiCal), ranging from 162 to 3,000,000 g/mole. The calculation was performed with Empower 3 software (Waters) with a fourth order calibration curve. The obtained molar masses are polystyrene equivalent molar masses (g/mole).

(8) Acid Value

(9) The acid value may be calculated using a method based on ISO 2114. Sample (approximately 1.5 g, weighed to nearest 0.01 g) is dissolved in tetrahydrofurane (50 ml) and water (2 ml). The solution is titrated with 0.1 N potassium hydroxide in ethanol using o-cresolphthalein as indicator. Pink colour should persist for 10 seconds. Acid value (AV) is calculated by: AV=(ml KOH solution*0.1*56.11)/sample weight in grams. The acid value is expressed by mg KOH/g polymeric binder.

(10) Glass Transition Temperature T.sub.g

(11) The Tg was measured by DSC using the Mettler Tolledo 821 using ME-26763 alumina cups of 40 μl. The flow rate was 50 ml/min of nitrogen and the sample was loaded at a temperature range of 20-25° C. The sample was first heated to 150° C. using a rate of 20° C./min. At 150° C. the sample was cooled to 0° C. at a rate of −10° C./min. At 0° C. the sample was heated to 80° C. at a rate of 5° C./min. The reported Tg is the measured inflection point.

(12) Solids Content

(13) Solids content is measured on a Mettler Toledo HR73 Halogen Moisture Analyser. Sample (0.9-1.1 grams) is spread out in a spiral shape on the fluffy side of a Φ90 mm Macherey-Nagel MN85/90 filter paper held in a Φ100 mm Schuett-biotec aluminium weighing/IR sample dish. Drying temperature is 160° C. and automatic switch-off criterion set to 4 (medium-slow drying). The instrument shows the solids content in weight %.

Example 1: Preparation of Polymeric Binders 1-7

(14) In this example, polymeric binders 1-7 were prepared as described below.

(15) Polymeric Binder 1—Polymerization (Step a)

(16) Neopentylglycol (39.7 g), adipic acid (13.8 g), isophthalic acid (3.2 g), fumaric acid (22.4 g), benzoic acid (13.3 g), butyl stannoic acid (400 ppm) and hydroquinone monomethylether (300 ppm) were heated in a reactor with a flow of nitrogen gas to a temperature of 210° C. Water was removed using a vigreux column maintaining a maximum top temperature of 100° C. Once the top temperature of the column dropped below 80° C. the column was removed and the product was kept at atmospheric pressure for 1 hour. Using vacuum distillation, the reaction was continued until an acid number of <5 mg KOH/g was obtained. Then the mixture was cooled to 150° C.

(17) Polymeric Binder 1—Introducing Side Group (Step b)

(18) At 150° C. sorbic acid (21.6 g) was added under stirring and reacted for 2 hours, keeping the temperature at 150° C.-160° C., to yield a solid polymer after cooling.

(19) Polymeric Binders 2-9—Polymerization and Introducing Side Group

(20) Polymeric binders 2-9 were prepared in the same manner as polymeric binder 1, but with different compositions which are shown in Table 1. For binders 8 and 9, the saturated diol 1,2 propane diol was replaced using neopentyl glycol instead. For these binders, also lithium hydroxide monohydate was present as a result of the 1,2 propane diol synthesis, wherein LiOH was used to decrease etherification of the secondary hydroxy group. The test results are also reported in Table 1.

(21) TABLE-US-00001 TABLE 1 1 2 3 4 5 6 7 8 9 Neopentyl- 39.7 40.8 41.2 41.5 43.3 43.9 42.5 — — glycol (g) 1,2-Propane- — — — — — — — 36.5 35.8 diol (g) Adipic acid (g) 13.8 13.8 13.8 13.8 13.8 21.9 20.3 15.0 Isophthalic 3.2 9.7 12.4 14.2 26.8 12.9 35.6 16.6 21.1 acid (g) Fumaric acid 22.3 22.3 22.3 22.3 14.5 18.5 18.5 22.3 22.2 (g) Benzoic acid (g) 13.3 6.1 3.0 1.0 2.8 — — — 1.5 Butyl stannoic 400 400 400 400 400 400 400 800 800 acid (ppm) Hydro-quinone 300 300 300 300 300 300 300 450 450 monomethyl ether (ppm) LiOH mono- — — — — — — — 130 130 hydrate (ppm) Sorbic acid (g) 21.6 21.6 21.6 21.6 14.0 17.7 17.9 21.5 21.5 Measured Mn 1383 2166 2711 3794 3109 3650 4151 2303 2817 Measured Mw 3372 7327 10480 36028 10905 28026 38655 9106 10739 Measured Acid 110 109 111 108 73 87 89 106 112 Value (mg KOH/g) Tg (° C.) 15 — 29 41 29 18 66 31 38

(22) Polymeric Binder 1—side group conversion (step c)

(23) Polymeric binder 1 (30 g) was discharged in a mixing vessel containing water (66.7 g), preheated to 80° C., containing a 25% ammonia solution (3.3 g) to be able to neutralise approximately 80% of the acid groups of the polymer, and mixed until completely dissolved. After cooling additional ammonia was dosed to the final product, till a pH of 9.0 was reached and additional water was added to obtain a viscosity below 500 mPa.Math.s. The final polymeric binder solution had a solid content of 30% and was stable for at least 6 weeks at 40° C.

(24) Polymeric Binders 2-9—Side Group Conversion (Step c)

(25) In the same manner as polymeric binder 1, polymeric binders 2-9 were discharged in water and an ammonia solution to yield polymeric binder solutions 2-9 with solid content and pH as indicated in Table 2. The stability at 40° C. (see above) of binder solutions 1-6 was monitored for over 10 weeks. No phase separation was observed during this time. Such stability data have not (yet) been conducted for binder solutions 7, 8, and 9.

(26) Biodegradability was determined using the test described above. The biodegradability percentages were determined after 28 days of biodegradation.

(27) TABLE-US-00002 TABLE 2 Binder Solution 1 2 3 4 5 6 7 8 9 Polymeric binder 1 2 3 4 5 6 7 8 9 Solid Content (%) 30 31 29 31 27 31 25  34.1 35.6 pH 9.0 9.0 9.1 9.1 9.1 9.0 9.0   9.1 9.1 Stability (wks at >10 >10 >10 >10 >10 >10 — — — 40° C.) Biodegradability 83 48 46 23 27 41 — 51* — after 28 days (%) *This value was measured in a separate biodegradability test using a different activated sludge than the sludge used for binders 1-8 - this test was conducted according to OECD 301 F: Manometric Respirometry.

Example 2: Preparation of Polymeric Binder 10 (Comparative Example)

(28) Neopentylglycol (43.1 g), adipic acid (25.0 g), isophthalic acid (33.3 g) and butyl stannoic acid (400 ppm) were heated in a stirred reactor with a flow of nitrogen gas to a temperature of 240° C. Water was removed using a vigreux column maintaining a maximum top temperature of 100° C. Once the top temperature of the column dropped below 80° C. the column was removed and, using vacuum distillation, the reaction was continued until an acid number of <5 mg KOH/g was obtained. Then the mixture was cooled to 180° C. At 180° C. trimellitic anhydride (12.8 g) was added and reacted for 1 hour, keeping the temperature at 180° C. The reaction product had an acid value of 74.9 mg KOH/g and was diluted with acetone to obtain a solids content of 64.9%.

(29) The obtained reaction product (65.3 g) and 25% ammonia solution (2.6 g, to neutralise 68% of the acid value) were heated to a temperature of 40° C. in a stirred reactor. Water (420 g) was added in 8 minutes. Acetone and part of water was removed from the resulting emulsion by vacuum distillation at a temperature of 30-40° C. to obtain a solids content of 45.2%.

(30) This emulsion was stable for less than 2 weeks at 40° C.

Example 3: Preparation of the Coating Composition

(31) Aqueous coating composition with the following composition were prepared: 23.4 wt. % of polymeric binder solution; 49 wt. % CaCO.sub.3 pigment less than 1 wt. % additives such as ammonia, an adhesion promoter, antifoam and dispersant.

(32) The coating compositions were prepared for each of polymeric binder solutions 1-9 described above by mixing each binder solution with a CaCO.sub.3 pigment slurry and the additives.

Example 4: Preparation and Removability of the Coating

(33) A coating was prepared from the coating composition. First, the coating composition was diluted using 5 weight parts of water on 1 weight part of the aqueous coating composition. The diluted coating composition was applied to the surface of a glass plate and was subsequently allowed to dry. The coated glass plates were subjected for 24 hours to UV radiation in a UV chamber. Subsequently, the coated glass plates were subjected for 7 days to UV radiation in a climate chamber. While in the climate chamber, the coated glass plates were further subjected every 8 hours to 15 minutes of artificial rain (simulated using a water sprinkler).

(34) The wear resistance of the coating was determined by measuring the transmission of the coating using a spectrograph, both before and after subjecting the coatings to UV and climate chambers. An increase in transmission is an indication of wear.

(35) The removability of the coating was determined by applying the removing agent ReduClean diluted with 7 volume parts water (1:7) (ReduClean comprises a strong base and a complex former) to a strip of 5 cm of coating of the coated glass. After drying, the plate was analyzed for any remaining coating residue.

(36) The results of the wear resistance and removability test are shown in Table 3. All coatings showed acceptable removability and wear resistance. Coating composition V and VII showed the best wear resistance, although composition V scored a little lower than the rest on removability.

(37) TABLE-US-00003 TABLE 3 Coating Composition I II III IV V VI VII VIII IX Polymeric Binder 1 2 3 4 5 6 7 8 9 Removability + + + + + + − + + + Wear Resistance + − + + + + + + + + + + − + −

Example 5: Application of Coating Composition on Greenhouse

(38) An experiment was conducted wherein a coating composition according to the present invention comprising a biodegradable binder (coating composition A) was compared to a coating composition comprising a non-biodegradable binder, as described in EP 0 999 736 and available from Mardenkro under the name ReduSol (coating composition B).

(39) Coating composition A comprised the following ingredients: about 50 wt. % pigment (CaCO.sub.3); about 7 wt. % of polymeric binder 3; and less than 1 wt. % other additives, such as ammonia, an adhesion promoter, antifoam and dispersant. The weight amounts are based on the total weight of coating composition A.

(40) As the binder in coating composition A, a polyester prepared according to the method given above for polymeric binder 3 was used. The polymeric binder had a Mw of 10480 and an acid value of 111.

(41) The coating composition B comprised about 50 wt. % of an acrylic binder, the same amount and type of pigment used in coating composition A and less than 1 wt. % of other additives, such as ammonia, an adhesion promoter, antifoam and dispersant.

(42) The coating compositions were diluted with water by a factor of about 10. The resulting composition were applied to the roof surface of a greenhouse.

(43) Both coating compositions had desirable properties, such that it could be applied evenly on the surface of the greenhouse. The coating composition dried quickly, thereby forming a functional coating.

(44) After six weeks, the coatings were analyzed for any wear. There were no big differences observed for the two coatings. Although some wear of the coatings had taken place, both coatings were still in good condition.

(45) To test the removability of the coating, a removing agent based on sodium hydroxide (ReduClean, available from Mardenkro) was used by spraying the outside surface of the greenhouse. After 15 minutes, the surface was sprayed with water, which removed the coatings.

(46) Based on this Examples, it can be concluded that a coating composition comprising a biodegradable polymeric binder according to the present invention works just as well as the commercially available coating composition comprising an acrylic binder. Both coating compositions could be easily and evenly applied, were resistant to wear and were removable by a strong base.

Comparative Example 6: Removability Binders WO2013/123314

(47) In order to compare the removability of the coating composition according to the present invention and the removability of the coating compositions described in WO 2013/123314, the polymer of Example 1 of WO2013/123314 (binder 11) and a similar polymer with higher acid value (binder 12) were reproduced and used to coat a glass surface.

(48) Reworking WO 2013/123314:

(49) Binder 11 was prepared according to the experimental method described in Example 1 of WO2013/123314. Only example 1 was reproduced.

(50) Preparation Binder 11 (Example 1, WO2013/123314):

(51) Binder 11 was prepared according to the experimental method described in Example 1 of WO2013/123314.

(52) Binder 11 was synthesised according the recipe and experimental method as described for example 1 in WO2013/123314 but at a scale of 3214 grams solid polymer yield in a 5 ltr. glass reactor. A vigreux-type glass column was used instead of the packed column. The stirrer speeds were adapted to suppress foaming. For safety reasons, the reactor was not sampled during the time the column was in place and the column was removed before the addition of Maleic anhydride instead of afterwards, both to prevent sudden pressure build-up caused by reaction water floating back into the reactor. The viscosity was determined to be similar as in Example 1 of WO2013/123314. As the right acid value—viscosity balance was reached in stage 3 (before the addition of sorbic acid), it can be concluded that the deviations from the procedures in WO2013/123314 did not result in deviations in polymer properties. As diethylene glycol mono methyl ether was not available, 2-butoxyethanol (butylglycol) was used instead.

(53) The amounts of reactant used to prepare binder 11 are listed in Table 4 below. The resulting polymer solution had a solids content of 65.5%. The acid value of the polymeric binder was measured to be 21.1.

(54) Preparation Binder 12 (WO2013/123314 with Higher Acid Value)

(55) Binder 12 was prepared using the same experimental method as for binder 11, except that a higher relative amount of sorbic acid was used in order to obtain a binder with a higher acid value. The amount used of the other monomers used was adjusted as well in order to obtain the appropriate molar equivalent ratios.

(56) The amounts of reactant used to prepare binder 12 are listed in Table 4 below. The resulting polymer solution had a solids content of 66.0%. The acid value of the polymeric binder was measured to be 37.0.

(57) TABLE-US-00004 TABLE 4 binder 11 binder 12 1,4 cyclohexane dimethanol (g) 218.8 226.8 2-methyl-1,3-propane diol (g) 916.5 950.0 trimethylol propane (g) 14.8 15.3 isophthalic acid (g) 408.7 423.7 terephthalic acid (g) 1218.0 897.7 butyl stannoic acid (g) 3.2 3.2 decane dioic acid (g) 268.3 278.1 ethane diol (g) 145.8 151.2 maleic anhydride (g) 256.6 481.5 xylene (g) 192.0 192.0 sorbic acid (g) 120.6 226.4 Solids content of solution (wt. %) 65.5 66.0 Measured Acid Value (mg KOH/g) 21.1 37.0

(58) Removability Test:

(59) The removability with a strong base was evaluated for a coating based on binders 11 and 12. The removability test was the same as described in Example 4 above.

(60) A coating was prepared from binder solutions 11 and 12 as follows. First, each binder solution was diluted using 4 weight parts of acetone on 1 weight part of the binder dispersion. Acetone was used instead of water (used in Example 4) in order to obtain a solution that could suitably be applied to a glass surface (which could not be achieved for binders 11 and 12 when diluting the binder with water). The resulting diluted coating composition was applied to the surface of a glass plate and was subsequently allowed to dry. Two coated glass plates were prepared for both binder solution 11 and 12.

(61) The coated glass plates were subjected for 24 hours to UV radiation in a UV chamber. Subsequently, the coated glass plates were subjected for 7 days to UV radiation in a climate chamber. While in the climate chamber, the coated glass plates were further subjected every 8 hours to 15 minutes of artificial rain (simulated using a water sprinkler).

(62) The removability of the coating was determined by applying the removing agent ReduClean diluted with 7 volume parts water (ReduClean comprises a strong base and a complex former and is available from Mardenkro B.V.) to ⅓ part of the glass plate. After about 1 hour, the removing agent was removed by spraying the glass plates with water and subsequently dried.

(63) It was clear from visual inspection that no coating was removed by the removing agent. Furthermore, the coated glass plates were weighed before and after the treatment with the removing agent. The results are shown in Table 4.

(64) TABLE-US-00005 TABLE 5 Weight before treatment Weight after treatment glass plate binder with removing agent with removing agent #1 11 292.25 292.28 #2 11 298.03 298.03 #3 12 297.70 297.72 #4 12 292.70 292.70

CONCLUSION

(65) It can be concluded that the coating compositions based on binders 11 and 12 are not removable using a strong base. It is expected that the removability of the coating will become even worse when the polymeric binder would have been crosslinked.

(66) Example 2 of WO 2013/123314 A1 describes the preparation of an aqueous dispersion of Example 1 in combination with an epoxy functional acrylic resin which is capable of crosslinking with the carboxylic acid groups of the polymer of Example 1. In Example 4, another crosslinker is added before application of the composition to the surface.

(67) In view of the addition of crosslinkers, it can be expected that coatings based on the crosslinked binders prepared in Examples 2 and 4 of WO 2013/123314 A1 will have an even worse removability than the coatings based on binders 11 and 12.