Preparation method of waterproof and weather-resistant water-based paint for road

Abstract

The present application relates to the technical field of paint, and disclose a kind of preparation method of waterproof weatherable water-based paint for road, 100 parts by weight water-based epoxy resin, 2-5 parts by weight 2,4-diamino alkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 1-5 parts by weight modified silicon dioxide etc. are mixed, to obtain waterproof weatherable water-based paint for road.Epoxy resin coating in thermal curing process, the carboxyl group of 2,4-diamino alkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine can participate in the curing reaction of epoxy resin, play good toughening effect, reduce water absorption, improve the ultraviolet resistance and weatherability.Nano-silica is modified, and the dispersibility and compatibility in coating are better, can play better reinforcing and toughening effect, and be conducive to improving the impact strength and bending strength of coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a method for preparing a waterproof and weather-resistant water-based coating for roads. Background Technology

[0002] Epoxy resin coatings are widely used in road and bridge construction, building decoration, electronics, and shipping due to their excellent anti-corrosion, insulation, and mechanical strength. However, epoxy resin coatings have poor toughness, and prolonged exposure to sunlight and rain outdoors can easily lead to aging, cracking, and decreased protective performance. Therefore, it is necessary to improve the toughness, water resistance, and UV resistance of epoxy resin coatings. Adding UV absorbers to the coating can improve its UV resistance and weather resistance. Common UV absorbers include benzophenones, triazoles, and triazines.

[0003] Nano-silica has a large specific surface area, high mechanical strength, and good heat resistance, making it important for toughening and modifying polymer materials such as epoxy resins, acrylic resins, and polyvinyl chloride. Chinese patent CN110819216B discloses a low-temperature curing powder coating and its preparation method, using modified nano-silica, a diamino UV absorber, carboxyl-terminated polyester resin, and epoxy resin as raw materials. The resulting powder coating exhibits good UV aging resistance. However, this patent does not improve the water resistance, impact strength, or flexural strength of epoxy resin coatings. Summary of the Invention

[0004] (I) Technical problem to be solved: The present invention provides a water-based epoxy coating for roads that is waterproof, wear-resistant, weather-resistant and UV-resistant.

[0005] (II) Technical Solution: A method for preparing a waterproof and weather-resistant water-based coating for roads:

[0006] (1) Add isopropanol, 2-5 parts by weight of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, and sodium hydroxide aqueous solution to the reaction vessel. After stirring, add 100 parts by weight of nano-silica, heat to 70-90℃, stir and modify for 3-6 hours. During stirring, reflux the mixture, filter, wash with isopropanol and water in sequence, and dry to obtain modified silica.

[0007] (2) Add 100 parts by weight of waterborne epoxy resin, 2-5 parts by weight of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 1-5 parts by weight of modified silica, 0.5-0.8 parts by weight of defoamer, and 0.2-0.4 parts by weight of leveling agent to a container, stir and mix well, and then add 2.7-3.4 parts by weight of curing agent to obtain a waterproof and weather-resistant waterborne coating for roads.

[0008] Preferably, the mass fraction of the sodium hydroxide aqueous solution is 0.5-3%.

[0009] Preferably, the curing agent is 2-ethyl-4-methylimidazole or 2-methylimidazole.

[0010] A preferred method for preparing 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine is as follows: 1,4-dioxane, 160-184 parts by weight of aminoalkyl acid, and 180-230 parts by weight of N,N-diisopropylethylamine are added to a reaction vessel. A solution of 1,4-dioxane containing 100 parts by weight of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine is added dropwise in an ice-water bath. The mixture is first stirred at room temperature for 2-3 hours, then heated to 70-90°C and reacted for 8-12 hours. The reaction is carried out under reflux, and the solvent is removed by vacuum distillation. The product is washed with ice water, and recrystallized from isopropanol to obtain 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. The reaction formula is:

[0011]

[0012] Preferably, the structural formula of the condensed reflux aminoalkyl acid is as follows: a is 9, 10, or 11.

[0013] (III) Technical effects: The 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine prepared by this invention contains carboxyl groups. During the heating modification process, the carboxyl groups interact with the surface of silica, thereby achieving surface modification of nano-silica, reducing the agglomeration of silica, and improving its dispersibility in waterborne epoxy resin coatings.

[0014] This invention uses waterborne epoxy resin as the film-forming substance of the coating, adds 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine as an anti-ultraviolet absorber, and modified silica as a toughening and reinforcing agent. After modification, the nano-silica reduces agglomeration and has better dispersibility and compatibility in waterborne epoxy resin coatings, which can play a better role in reinforcing and toughening, and is beneficial to improving the mechanical properties of the coating such as impact strength and flexural strength.

[0015] In the thermosetting process of the epoxy resin coating of the present invention, the carboxyl group of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine can participate in the curing reaction of epoxy resin, which improves the crosslinking degree and compactness of the epoxy resin molecular chain, inhibits water molecules from entering the epoxy resin matrix, and introduces hydrophobic and flexible long-chain alkyl groups into the epoxy resin molecular chain, which plays a good toughening role, improves the impact strength and flexural strength of epoxy resin, and reduces water absorption.

[0016] The 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine of this invention contains an o-phenolic triazine ring structure, which can absorb ultraviolet light and convert light energy into chemical energy. This results in coatings with higher ultraviolet absorption and lower ultraviolet light transmittance, exhibiting excellent UV resistance. Consequently, epoxy resin waterborne coatings exhibit better water resistance, UV resistance, weather resistance, and mechanical properties. Attached Figure Description

[0017] Figure 1 The infrared spectrum of 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine from Example 1 is shown. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] The preparation method of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine is as follows: 120 mL of chlorobenzene and 30 mmol of cyanuric chloride were added to a reaction vessel. 33 mmol of aluminum trichloride and 36 mmol of resorcinol were added in an ice-water bath. The reaction was allowed to proceed for 8 hours. The solution was then poured into 120 mL of water, the pH was adjusted to 2, and the mixture was allowed to stand for 18 hours. After filtration, the solution was washed with ether, dried, and then added to acetone. The mixture was heated and filtered to obtain 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. The structural formula is as follows:

[0020] Waterborne epoxy resin, Henan Shuizhihuan Industrial Co., Ltd. Nano-silica, average particle size 15µm, Shanghai Yingcheng New Materials Co., Ltd.

[0021] Example 1:

[0022] (1) Add 40 mL of 1,4-dioxane, 17.3 g (86.07 mmol) of 11-aminoundecanoic acid and 18 g of N,N-diisopropylethylamine to the reaction vessel. Add 20 mL of a 1,4-dioxane solution containing 10 g of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine dropwise in an ice-water bath. Stir the reaction at room temperature for 3 h, then heat to 75 °C and react for 12 h. Remove the solvent by vacuum distillation, wash with ice water, and recrystallize the product in isopropanol to obtain 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. Figure 13417 cm⁻¹ in the infrared spectrum -1 The absorption peak is the phenolic hydroxyl group -OH, at 2942 cm⁻¹. -1 The absorption peak is for the alkyl chain -CH2, at 1722 cm⁻¹. -1 It is the absorption peak of the carboxyl carbonyl group -C=O-.

[0023] (2) Add 30 mL of isopropanol, 40 mg of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine and 6 mL of 0.5% sodium hydroxide aqueous solution to the reaction vessel. After stirring, add 2 g of nano silica, heat to 80 °C, stir and modify for 3 h. During stirring, reflux the solution, filter, wash with isopropanol and water in sequence, and dry to obtain modified silica.

[0024] (3) Add 100g of waterborne epoxy resin, 2g of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 1g of modified silica, 0.5g of defoamer TEGO FOAMEX 825, and 0.4g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3.4g of curing agent 2-ethyl-4-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0025] Example 2:

[0026] (1) Add 40 mL of 1,4-dioxane, 16 g of 10-aminodecanoic acid, and 23 g of N,N-diisopropylethylamine to a reaction vessel. Add 20 mL of a 1,4-dioxane solution containing 10 g of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine dropwise in an ice-water bath. Stir the reaction at room temperature for 2 h, then heat to 90 °C and react for 8 h. During the reaction, reflux the solution and remove the solvent by vacuum distillation. Wash with ice water and recrystallize the product in isopropanol to obtain 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine.

[0027] (2) Add 40 mL of isopropanol, 70 mg of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine and 5 mL of 3% sodium hydroxide aqueous solution to the reaction vessel. After stirring, add 2 g of nano silica, heat to 70 °C, stir and modify for 6 h. During stirring, reflux the solution, filter, wash with isopropanol and water in sequence, and dry to obtain modified silica.

[0028] (3) Add 100g of waterborne epoxy resin, 3.5g of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 3g of modified silica, 0.8g of defoamer TEGO FOAMEX 825, and 0.2g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3g of curing agent 2-ethyl-4-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0029] Example 3:

[0030] (1) Add 50 mL of 1,4-dioxane, 18.4 g of 12-aminododecanoic acid, and 21.3 g of N,N-diisopropylethylamine to a reaction vessel. Add 25 mL of a 1,4-dioxane solution containing 10 g of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine dropwise in an ice-water bath. Stir the reaction at room temperature for 3 h, then heat to 70 °C and react for 12 h. During the reaction, reflux the solution and remove the solvent by vacuum distillation. Wash with ice water and recrystallize the product in isopropanol to obtain 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine.

[0031] (2) Add 40 mL of isopropanol, 100 mg of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine and 5 mL of 2% sodium hydroxide aqueous solution to the reaction vessel. After stirring, add 2 g of nano silica, heat to 90 °C, stir and modify for 4 h. During stirring, reflux the solution, filter, wash with isopropanol and water in sequence, and dry to obtain modified silica.

[0032] (3) Add 100g of waterborne epoxy resin, 5g of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 5g of modified silica, 0.8g of defoamer TEGO FOAMEX 825, and 0.2g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 2.7g of curing agent 2-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0033] Comparative Example 1:

[0034] (1) Add 100g of waterborne epoxy resin, 0.5g of defoamer TEGO FOAMEX 825 and 0.4g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3.4g of curing agent 2-ethyl-4-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0035] Comparative Example 2:

[0036] (1) Add 100g of waterborne epoxy resin, 2g of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine (prepared according to the method of Example 1), 0.5g of defoamer TEGO FOAMEX 825, and 0.4g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3.4g of curing agent 2-ethyl-4-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0037] Comparative Example 3:

[0038] (1) Add 100g of waterborne epoxy resin, 1g of modified silica (prepared according to the method of Example 1), 0.5g of defoamer TEGO FOAMEX 825, and 0.4g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3.4g of curing agent 2-ethyl-4-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0039] Comparative Example 4:

[0040] (1) Add 100g of waterborne epoxy resin, 2g of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine (prepared according to the method of Example 1), 1g of nano silica, 0.5g of defoamer TEGO FOAMEX 825, and 0.4g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3.4g of curing agent 2-ethyl-4-methylimidazolium to obtain a waterproof and weather-resistant waterborne coating for roads.

[0041] Comparative Example 5:

[0042] (1) Add 40 mL of 1,4-dioxane, 7.66 g (86.07 mmol) of β-alanine, and 18 g of N,N-diisopropylethylamine to a reaction vessel. Add 20 mL of a solution containing 10 g of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine dropwise in an ice-water bath. Stir the reaction at room temperature for 3 h, then heat to 75 °C and react for 12 h. Remove the solvent by vacuum distillation, wash with ice water, and recrystallize the product from isopropanol to obtain 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. The structural formula is:

[0043]

[0044] (2) Add 30 mL of isopropanol, 40 mg of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine and 6 mL of 0.5% sodium hydroxide aqueous solution to the reaction vessel. After stirring, add 2 g of nano silica, heat to 80 °C, stir and modify for 3 h. During stirring, reflux the solution, filter, wash with isopropanol and water in sequence, and dry to obtain modified silica.

[0045] (3) Add 100g of waterborne epoxy resin, 2g of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 1g of modified silica, 0.5g of defoamer TEGO FOAMEX 825, and 0.4g of leveling agent EfkaSL3034 to a container, stir and mix well, and then add 3.4g of curing agent 2-ethyl-4-methylimidazole to obtain a waterproof and weather-resistant waterborne coating for roads.

[0046] The water-based coating (without adding a hardener) was left at room temperature for 30 days, and the emulsion dispersion was observed.

[0047] Table 1

[0048] Dispersion Example 1 No layering, no sedimentation Example 2 No layering, no sedimentation Example 3 No layering, no sedimentation Comparative Example 1 No layering, no sedimentation Comparative Example 2 No layering, no sedimentation Comparative Example 3 No layering, no sedimentation Comparative Example 4 No stratification, with obvious sediment. Comparative Example 5 No layering, no sedimentation

[0049] As shown in the table above, the water-based coatings prepared in Examples 1-3 and Comparative Examples 3-4 showed no precipitation and good dispersibility. This is mainly because the nano-silica was modified on the surface by 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, which reduced agglomeration and improved the dispersibility of the water-based epoxy resin coating, making it difficult to form precipitates.

[0050] The silica added in Comparative Example 4 was not surface modified, resulting in poor dispersibility in waterborne epoxy resin coatings, and it was prone to agglomeration and precipitation.

[0051] Water-based coatings were sprayed onto the tinplate surface and cured at 85°C for 5 hours to form a paint film. The transmittance of the paint film to ultraviolet light at 365nm was tested using a UV-Vis spectrophotometer and a transmittance meter. The lower the transmittance, the greater the ultraviolet light absorption rate, and the better the UV resistance.

[0052] The water-based coating was poured into a mold, cured at 85°C for 8 hours, and then cooled to room temperature to form a cast specimen. Impact strength and flexural strength were tested according to the national standard GB / T 2567-2021.

[0053] Weigh the cast sample and record it as m0. Immerse it completely in water at 25℃ for 72 hours. Remove the cast sample, blot the surface moisture with filter paper, weigh it again and record it as m1. Calculate the water absorption rate Q. The calculation formula is Q=(m1-m0) / m0×100%.

[0054] Table 2

[0055]

[0056] As shown in the table above, the waterborne epoxy resin coating of Comparative Example 1 has high UV transmittance and water absorption, and poor UV resistance, waterproofing and weather resistance. At the same time, it has low impact strength and flexural strength, and poor toughness.

[0057] The waterborne epoxy resin coatings in Examples 1-3 incorporated 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, which contains long-chain alkyl and carboxyl groups. The carboxyl groups participate in the curing reaction of the epoxy resin, increasing the cross-linking degree and compactness of the epoxy resin molecular chain, inhibiting water molecules from entering the epoxy resin matrix. Simultaneously, the introduction of hydrophobic and flexible long-chain alkyl groups into the epoxy resin molecular chain provides excellent toughening, improving the impact strength and flexural strength of the epoxy resin while reducing water absorption. 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine contains an o-phenolic triazine ring structure. It can absorb ultraviolet rays and convert light energy into chemical energy, giving the coating film a higher ultraviolet absorption rate and lower ultraviolet light transmittance, thus exhibiting excellent UV resistance. Furthermore, the nano-silica, after surface modification with 2,4-diaminoalkyl acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, reduces agglomeration, improves its dispersibility and compatibility in waterborne epoxy resin coatings, and provides better reinforcement and toughening effects, thereby improving the coating's impact strength, flexural strength, and other mechanical properties.

[0058] Comparative Example 2 added 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, which reduced the UV transmittance and water absorption of the coating film, and improved its UV resistance and water resistance compared to Comparative Example 1. It also increased toughness, impact strength and flexural strength. However, no modified nano-silica was added, which resulted in lower impact strength and flexural strength than in Example 1.

[0059] Comparative Example 3, with the addition of modified silica, exhibited increased impact and flexural strength. However, lacking the addition of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, the epoxy resin coating showed poor toughness, lower than that of Example 1, and higher UV transmittance and water absorption, resulting in poor UV resistance and water resistance. However, the UV transmittance of Comparative Example 3 was slightly lower than that of Comparative Example 1, possibly because the modified silica surface contained a small amount of 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, which could slightly absorb ultraviolet light and reduce the UV transmittance of the coating film.

[0060] The nano-silica added in Comparative Example 4 was not surface modified, so it was prone to agglomeration and had poor dispersibility. It also had poor compatibility with epoxy resin, resulting in poor reinforcement and toughening effects. Its impact strength and flexural strength were lower than those in Example 1.

[0061] Comparative Example 5, which uses β-alanine as a raw material to prepare 2,4-diaminoalkyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, does not contain hydrophobic and flexible alkyl long chains, resulting in poor toughness and high water absorption of the epoxy resin.

Claims

1. A method for producing a waterproof weather-resistant water-based paint for roads, characterized by, The preparation method is as follows: (1) adding isopropyl alcohol, 2,4-diaminoalkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, and an aqueous sodium hydroxide solution into a reaction container, stirring, adding nano-silica, heating to a modification temperature, stirring to modify, filtering, washing, and drying to obtain modified silica; (2) adding 100 parts by weight of an aqueous epoxy resin, 2-5 parts by weight of 2,4-diaminoalkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 1-5 parts by weight of modified silica, 0.5-0.8 parts by weight of a defoaming agent, and 0.2-0.4 parts by weight of a leveling agent into a container, stirring to mix, and then adding 2.7-3.4 parts by weight of a curing agent to obtain a waterproof and weather-resistant water-based paint for roads; The 2,4-diaminoalkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine has the structural formula: a is 9, 10 or 11.

2. The method for preparing a road waterproofing weatherable water-based paint according to claim 1, characterized by, The modification temperature in the (1) is 70-90℃, and the modification time is 3-6h.

3. The method for preparing a road waterproofing weatherable water-based paint according to claim 1, characterized in that, The amount of nano-silica used in the (1) is 100 parts by weight, and the amount of 2,4-diaminoalkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine used is 2-5 parts by weight.

4. The method for preparing a road waterproofing weatherable water-based paint according to claim 1, characterized in that, The mass fraction of the aqueous sodium hydroxide solution is 0.5-3%.

5. The method for preparing a waterproof and weather-resistant water-based coating for roads according to claim 1, characterized in that, The preparation method of the 2,4-diaminoalkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine is as follows: adding 1,4-dioxane, aminoalkanoic acid, and N,N-diisopropylethylamine into a reaction container, adding a 1,4-dioxane solution of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine dropwise in an ice water bath, stirring to react, distilling under reduced pressure, washing, recrystallizing, and obtaining 2,4-diaminoalkanoic acid-6-(2,4-dihydroxyphenyl)-1,3,5-triazine.

6. The method for preparing a road waterproofing weatherable water-based paint according to claim 5, characterized by, The reaction is first performed at room temperature for 2-3h, and then performed at 70-90℃ for 8-12h.

7. The method for preparing a road waterproofing weatherable water-based paint according to claim 5, characterized by, The amount of 2,4-dichloro-6-(2,4-dihydroxyphenyl)-1,3,5-triazine used is 100 parts by weight, the amount of aminoalkanoic acid used is 160-184 parts by weight, and the amount of N,N-diisopropylethylamine used is 180-230 parts by weight.

8. The method for preparing a road waterproofing weatherable water-based paint according to claim 7, characterized by, The aminoalkanoic acid has the structural formula a is 9, 10 or 11.

9. The method for preparing a waterproof and weather-resistant water-based coating for roads according to claim 1, characterized in that, The curing agent in the (2) is 2-ethyl-4-methylimidazole or 2-methylimidazole.

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