Preparation method of anti-ultraviolet aging marking paint

Abstract

This invention relates to the field of coating technology and discloses a method for preparing an anti-UV aging marking coating. The invention uses 3,4-dihydroxybenzaldehyde, 2-hydroxy-4-methoxy-3'-aminobenzophenone, sodium borohydride, etc., as reactants to prepare a benzophenone anti-UV absorber containing catechol groups. This absorber is then compounded with nano-zirconia, waterborne hydroxyl acrylic resin, etc., to obtain component A. An isocyanate curing agent is used as component B, resulting in a two-component polyurethane anti-UV aging marking coating. The catechol groups of the benzophenone anti-UV absorber coordinate with the surface of the nano-zirconia, thereby modifying the surface of the nano-zirconia with the anti-UV absorber. After organic modification, the dispersibility of the nano-zirconia improves, which is beneficial for improving the wear resistance and mechanical properties of the coating film, while also providing excellent anti-UV aging performance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a method for preparing an anti-UV aging marking coating. Background Technology

[0002] Two-component polyurethane coatings typically consist of polyols, isocyanate curing agents, fillers, and additives. They have important applications in building materials, instrumentation, and automotive manufacturing. Traditional waterborne polyurethane coatings suffer from poor abrasion resistance and UV aging resistance, hindering their practical application in outdoor transportation and road marking.

[0003] Nano-zirconia is a common nanofiller with good thermochemical stability, high resistance to acid and alkali corrosion, high strength, and good toughness. It is widely used in polymer materials such as coatings, plastics, and rubber to improve the corrosion resistance, mechanical strength, and abrasion resistance of materials. Typically, nano-zirconia is surface-modified using silane coupling agents, oleic acid, dopamine, and other catechol derivatives to improve its dispersibility and compatibility with polymer resins. Chinese patent CN106519955B discloses a superhydrophobic anti-corrosion coating for power transmission and transformation equipment and its preparation method. It modifies nano-zirconia with a silane coupling agent and blends it with modified nano-silica, polyurethane resin, and ultraviolet absorber UV-P. The resulting coating has advantages such as superhydrophobicity and corrosion resistance. However, this patented coating does not exhibit good abrasion resistance, which is detrimental to the practical application of polyurethane in abrasion-resistant coatings such as markings and signage. Summary of the Invention

[0004] (I) The technical problem solved by the present invention is that the present invention solves the problem of poor UV aging resistance and wear resistance of two-component polyurethane coatings.

[0005] (II) The technical solution of the present invention is: an anti-ultraviolet aging marking paint, comprising component A and component B; component A consists of 2-10 parts by weight of nano-zirconia, 0.5-2 parts by weight of benzophenone anti-ultraviolet absorber, 100 parts by weight of water-based hydroxyl acrylic resin, 0.4-1 parts by weight of defoamer, 0.3-0.6 parts by weight of leveling agent, 16-22 parts by weight of pigment, and 0.6-0.9 parts by weight of dispersant. Component B is 16-20 parts by weight of isocyanate curing agent.

[0006] The preferred method for preparing UV-resistant marking paint is as follows:

[0007] (1) Add water and nano zirconium dioxide to the container, disperse by ultrasonication, add ethanol and benzophenone anti-UV absorber, stir and modify at 20-30℃ for 18-24h, remove ethanol by rotary evaporation, add water-based hydroxy acrylic resin, defoamer, leveling agent, pigment and dispersant, and shear disperse to obtain component A; add component B 16-20 isocyanate curing agent to component A to obtain anti-UV aging marking paint.

[0008] Preferably, the preparation method of benzophenone as an anti-ultraviolet absorber is as follows:

[0009] (1) Add 3,4-dihydroxybenzaldehyde and 2-hydroxy-4-methoxy-3'-aminobenzophenone to ethanol, stir and react at 20-40℃ for 2-6h, heat to volatilize, rotary evaporate until a large amount of precipitate is precipitated, filter, wash with water, dry, and obtain benzophenone intermediate.

[0010] (2) Add the intermediate sodium borohydride to ethanol, stir the reaction at 30-40℃ for 4-5 h, remove the ethanol by rotary evaporation, add water, neutralize the pH to 7 by adding acetic acid solution dropwise, extract with dichloromethane, dry the organic layer with anhydrous sodium sulfate, filter to remove sodium sulfate, evaporate the filtrate by rotary evaporation, and recrystallize the product in ethanol to obtain benzophenone as an anti-UV absorber. The reaction formula is as follows:

[0011] .

[0012] Preferably, the molar ratio of 3,4-dihydroxybenzaldehyde and 2-hydroxy-4-methoxy-3'-aminobenzophenone in (1) is (1-1.1):1.

[0013] Preferably, in (2), the molar ratio of intermediate sodium borohydride is 1:(1.3-1.5).

[0014] (III) Beneficial Technical Effects of the Invention: The present invention uses 3,4-dihydroxybenzaldehyde, 2-hydroxy-4-methoxy-3'-aminobenzophenone, sodium borohydride, etc. as reactants to prepare a benzophenone UV absorber containing catechol groups. Using this as the UV absorber, nano-zirconia as the nanofiller, and waterborne hydroxy acrylic resin as the waterborne polyol, component A is obtained by compounding, and isocyanate curing agent is used as component B to obtain a two-component polyurethane UV-resistant marking coating.

[0015] In this invention, during the stirring modification process, the catechol groups of the benzophenone UV absorber coordinate with the surface of nano-zirconia, thereby modifying the surface of the nano-zirconia with the UV absorber. After organic modification, the dispersibility of the nano-zirconia improves, which is beneficial for improving the wear resistance and mechanical properties of the polyurethane coating film. Furthermore, the UV absorber contains active imino groups, which act as reaction sites. During the curing process, they can react with the isocyanate curing agent, thereby chemically bridging and bonding the nano-zirconia with the polyurethane molecular chains through the benzophenone UV absorber. This improves the interfacial bonding strength between the zirconium dioxide and polyurethane, significantly reduces frictional mass loss, improves wear resistance, and simultaneously enhances the impact resistance and flexibility of the coating film.

[0016] The benzophenone UV absorber of this invention contains a 2-hydroxybenzophenone structure, which can absorb ultraviolet light, convert light energy into chemical energy, reduce the damage of ultraviolet light to the paint film, and decrease the gloss loss rate of the paint film, thereby enhancing the anti-ultraviolet aging performance of the paint film. The resulting coating has excellent practical applications in outdoor traffic, road markings, and other fields. Detailed Implementation

[0017] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0018] The following water-based hydroxyl acrylic resin, model BH811, with a hydroxyl value of 2.5%, was purchased from Dongguan Guangtong Chemical Products Co., Ltd. Nano-zirconia, with a particle size between 20-30 nm, was purchased from Hebei Yuehan Metal Materials Sales Co., Ltd.

[0019] 2-Hydroxy-4-methoxy-3'-aminobenzophenone was prepared according to the method described in the paper "Synthesis Study of 2-Hydroxy-4-methoxy-3'-aminobenzophenone and its Alkylates" published in the November 2006 issue of the journal *Journal of Dalian University of Technology*, Vol. 46, No. 6. The structural formula is as follows: .

[0020] Example 1:

[0021] (1) Add 30 mmol of 3,4-dihydroxybenzaldehyde and 30 mmol of 2-hydroxy-4-methoxy-3'-aminobenzophenone to 50 mL of ethanol, stir at 25 °C for 6 h, heat to volatilize, rotary evaporate until a large amount of precipitate is precipitated, filter, wash with water, dry, and obtain benzophenone intermediate.

[0022] (2) Add 20 mmol of intermediate and 28 mmol of sodium borohydride to 40 mL of ethanol, stir at 40 °C for 4 h, remove ethanol by rotary evaporation, add 40 mL of water, add acetic acid solution to neutralize pH to 7, add dichloromethane for extraction, dry the organic layer with anhydrous sodium sulfate, filter to remove sodium sulfate, evaporate the filtrate by rotary evaporation, recrystallize the product in ethanol to obtain benzophenone anti-ultraviolet absorber.

[0023] (3) Add 200mL of water and 20g of nano-zirconia to the container, disperse by ultrasonication, add 100mL of ethanol and 5g of benzophenone anti-UV absorber, stir and modify at 25℃ for 24h, remove ethanol by rotary evaporation, add 1000g of water-based hydroxyl acrylic resin, 8g of defoamer, 4g of leveling agent (model TEGO4100), 220g of pigment iron oxide yellow, and 9g of ammonium phosphate salt anionic polymeric dispersant (model RX-181), shear and disperse to obtain component A, and then add 175g of component B isocyanate curing agent (model Covestro xp2655) to obtain anti-UV aging marking paint.

[0024] Example 2:

[0025] (1) Add 30 mmol of 3,4-dihydroxybenzaldehyde and 32 mmol of 2-hydroxy-4-methoxy-3'-aminobenzophenone to 60 mL of ethanol, stir at 20 °C for 6 h, heat to volatilize, rotary evaporate until a large amount of precipitate is precipitated, filter, wash with water, dry to obtain benzophenone intermediate.

[0026] (2) Add 20 mmol of intermediate and 30 mmol of sodium borohydride to 50 mL of ethanol, stir at 30 °C for 5 h, remove ethanol by rotary evaporation, add 40 mL of water, add acetic acid solution to neutralize pH to 7, add dichloromethane for extraction, dry the organic layer with anhydrous sodium sulfate, filter to remove sodium sulfate, evaporate the filtrate by rotary evaporation, recrystallize the product in ethanol to obtain benzophenone anti-ultraviolet absorber.

[0027] (3) Add 300mL of water and 60g of nano-zirconia to the container, disperse by ultrasonication, add 150mL of ethanol and 12g of benzophenone anti-UV absorber, stir and modify at 30℃ for 18h, remove ethanol by rotary evaporation, add 1000g of water-based hydroxyl acrylic resin, 10g of defoamer, 3g of leveling agent (model TEGO4100), 160g of pigment iron oxide yellow, and 6g of ammonium phosphate salt anionic polymeric dispersant (model RX-181), shear and disperse to obtain component A, and then add component B 160g of isocyanate curing agent (model Covestro xp2655) to obtain anti-UV aging marking paint.

[0028] Example 3:

[0029] (1) Add 30 mmol of 3,4-dihydroxybenzaldehyde and 30 mmol of 2-hydroxy-4-methoxy-3'-aminobenzophenone to 60 mL of ethanol, stir at 40 °C for 2 h, heat to volatilize, rotary evaporate until a large amount of precipitate is precipitated, filter, wash with water, dry to obtain benzophenone intermediate.

[0030] (2) Add 20 mmol of intermediate and 26 mmol of sodium borohydride to 40 mL of ethanol, stir at 35 °C for 5 h, remove ethanol by rotary evaporation, add 30 mL of water, add acetic acid solution to neutralize pH to 7, add dichloromethane for extraction, dry the organic layer with anhydrous sodium sulfate, filter to remove sodium sulfate, evaporate the filtrate by rotary evaporation, recrystallize the product in ethanol to obtain benzophenone anti-ultraviolet absorber.

[0031] (3) Add 300mL of water and 100g of nano-zirconia to the container, disperse by ultrasonication, add 200mL of ethanol and 20g of benzophenone anti-UV absorber, stir and modify at 20℃ for 24h, remove ethanol by rotary evaporation, add 1000g of water-based hydroxyl acrylic resin, 4g of defoamer, 6g of leveling agent (model TEGO4100), 180g of pigment iron oxide yellow, and 8g of ammonium phosphate salt anionic polymeric dispersant (model RX-181), shear and disperse to obtain component A, and then add component B 200g of isocyanate curing agent (model Covestro xp2655) to obtain anti-UV aging marking paint.

[0032] Comparative Example 1:

[0033] (1) Add 300mL of water, 1000g of waterborne hydroxy acrylic resin, 8g of defoamer, 4g of leveling agent (model TEGO4100), 220g of pigment iron oxide yellow, and 9g of ammonium phosphate salt anionic polymeric dispersant (model RX-181) to the container, shear and disperse to obtain component A, and then add 175g of component B isocyanate curing agent (model Covestro xp2655) to obtain the marking paint.

[0034] Comparative Example 2:

[0035] (1) Add 200mL of water and 20g of nano zirconium dioxide to the container, disperse by ultrasonication, add 1000g of waterborne hydroxyl acrylic resin, 8g of defoamer, 4g of leveling agent (model TEGO4100), 220g of pigment iron oxide yellow, and 9g of ammonium phosphate salt anionic polymeric dispersant (model RX-181), disperse by shearing to obtain component A, and then add 175g of component B isocyanate curing agent (model Covestro xp2655) to obtain the marking paint.

[0036] Comparative Example 3

[0037] (1) Add 200mL of water, 5g of benzophenone UV absorber (prepared from Example 1), 1000g of waterborne hydroxyl acrylic resin, 8g of defoamer, 4g of leveling agent (model TEGO4100), 220g of pigment iron oxide yellow, and 9g of ammonium phosphate anionic polymeric dispersant (model RX-181) to the container, and shear and disperse to obtain component A. Then add 175g of isocyanate curing agent (model Covestro xp2655) to component B to obtain the marking paint.

[0038] Comparative Example 4:

[0039] (1) Add 200mL of water and 20g of nano-zirconia to the container, disperse by ultrasonication, add 100mL of ethanol and 5g of 2-hydroxybenzophenone (CAS Registry No. 117-99-7), stir and modify at 25℃ for 24h, remove ethanol by rotary evaporation, add 1000g of waterborne hydroxy acrylic resin, 8g of defoamer, 4g of leveling agent (model TEGO4100), 220g of pigment iron oxide yellow, and 9g of ammonium phosphate salt anionic polymeric dispersant (model RX-181), shear and disperse to obtain component A, and then add 175g of isocyanate curing agent (model Covestro xp2655) to obtain the marking paint.

[0040] Comparative Example 5:

[0041] (1) Add 200mL of water and 20g of nano-zirconia to the container, disperse by ultrasonication, add 100mL of ethanol and 5g of benzophenone intermediate (prepared by Example 1), stir and modify at 25℃ for 24h, remove ethanol by rotary evaporation, add 1000g of waterborne hydroxyl acrylic resin, 8g of defoamer, 4g of leveling agent (model TEGO4100), 220g of pigment iron oxide yellow, and 9g of ammonium phosphate salt anionic polymeric dispersant (model RX-181), shear and disperse to obtain component A, and then add 175g of isocyanate curing agent (model Covestro xp2655) to obtain the marking paint.

[0042] The coating is applied to the surface of a tinplate substrate and dried and cured at 70°C for 24 hours. Abrasion resistance and frictional mass loss are tested according to GB / T 1768-2006. The impact resistance of the coating film is tested according to GB / T 1732-2020. Flexibility is tested according to GB / T 1731-2020.

[0043] The paint film was placed in a fluorescent ultraviolet aging test chamber (wavelength 280-340nm, power 9.5KW) and subjected to an aging test for 7 days according to GB / T 14522-2008. The gloss and gloss loss rate of the paint film before and after aging were tested according to GB / T 1766-2008. Each group of samples was tested 5 times, and the average value was taken. The lower the gloss loss rate, the better the UV aging resistance.

[0044] Table 1 Coating Performance Tests

[0045] Frictional mass loss (mg) Impact resistance (kg·cm) Flexibility (mm) Light loss rate (%) Example 1 33.8 50 1 13.62 Example 2 28.0 55 1 6.81 Example 3 21.6 45 2 2.65 Comparative Example 1 39.2 30 2 66.54 Comparative Example 2 37.7 35 2 66.23 Comparative Example 3 39.4 30 2 13.70 Comparative Example 4 37.8 35 2 13.09 Comparative Example 5 34.6 45 1 13.43

[0046] The two-component polyurethane marking paint of Comparative Example 1 did not contain nano-zirconia and benzophenone UV absorbers, resulting in significant frictional mass loss of the paint film, poor impact resistance and flexibility, high gloss loss rate, and poor UV resistance.

[0047] Comparative Example 2 incorporated nano-zirconia, which has poor compatibility with polyurethane and does not significantly improve the wear resistance and mechanical properties of the coating film. This results in significant frictional mass loss, poor impact resistance and flexibility, high gloss loss, and poor UV resistance.

[0048] Comparative Example 3, with the addition of only benzophenone as an anti-UV absorber, showed a significant reduction in gloss loss and improved UV resistance, but poor abrasion resistance, impact resistance, and flexibility.

[0049] In Examples 1-3, nano-zirconia and benzophenone UV absorbers were added to the two-component polyurethane marking coatings. The UV absorber contains catechol groups, which coordinate with the surface of the nano-zirconia during the stirring modification process, thereby modifying the surface of the nano-zirconia with the UV absorber. Organic modification of the zirconia improves its dispersibility, enhancing the wear resistance and mechanical properties of the polyurethane coating film. Furthermore, the UV absorber contains active imino groups, which act as reaction sites. During curing, these groups react with the isocyanate curing agent, chemically bridging and bonding the nano-zirconia with the polyurethane molecular chains through the benzophenone UV absorber. This improves the interfacial bonding strength between the zirconia and polyurethane, further enhancing the film's performance. The resulting coating exhibits low frictional mass loss, improved wear resistance, excellent impact resistance, and superior flexibility. Additionally, the benzophenone UV absorber absorbs ultraviolet light, converting light energy into chemical energy, improving the film's resistance to UV aging and significantly reducing gloss loss.

[0050] Compared with Example 1, Comparative Example 4 added conventional 2-hydroxybenzophenone, which does not contain catechol structure and cannot coordinate with the surface of nano-zirconia. Therefore, it cannot achieve organic modification of the surface of zirconia, does not improve its dispersibility, and does not improve the interfacial bonding strength between it and polyurethane, resulting in poor wear resistance, impact resistance and flexibility of the coating film.

[0051] Compared with Example 1, the benzophenone intermediate added in Comparative Example 5 contains a catechol structure, which can coordinate with the zirconium dioxide surface. After organic modification, the dispersibility of zirconium dioxide is improved, which is beneficial to improving the wear resistance and other properties of the paint film. However, the benzophenone intermediate does not contain imino groups, and has fewer reaction sites with the isocyanate curing agent. As a result, the interfacial bonding strength between zirconium dioxide and polyurethane is lower than that in Example 1, the frictional mass loss of the paint film is higher than that in Example 1, the impact resistance is lower than that in Example 1, and the wear resistance and mechanical properties are poor.

Claims

1. A method for preparing an anti-UV aging marking paint, characterized in that, The preparation method includes the following steps: adding water and 2-10 parts by weight of nano-zirconia to a container, ultrasonically dispersing, and adding ethanol and 0.5-2 parts by weight of the following structural formula: The benzophenone UV absorber was modified by stirring, and the ethanol was removed by rotary evaporation. Then, 100 parts by weight of waterborne hydroxyl acrylic resin, 0.4-1 parts by weight of defoamer, 0.3-0.6 parts by weight of leveling agent, 16-22 parts by weight of pigment, and 0.6-0.9 parts by weight of dispersant were added and sheared to obtain component A. 16-20 parts by weight of isocyanate curing agent (component B) were added to component A to obtain UV-resistant marking paint.

2. The preparation method of the anti-UV aging marking paint according to claim 1, characterized in that, The temperature during the stirring modification is 20-30℃, and the time is 18-24h.

3. The method for preparing the anti-UV aging marking paint according to claim 1, characterized in that, The preparation method of the benzophenone UV absorber is as follows: (1) Add 3,4-dihydroxybenzaldehyde and 2-hydroxy-4-methoxy-3'-aminobenzophenone to ethanol, stir and react, then heat to volatilize, and rotary evaporate until a precipitate is formed. Filter, wash and dry to obtain benzophenone intermediate. (2) Add the intermediate sodium borohydride to ethanol, stir and react, then evaporate by rotary evaporation, add water, add acetic acid solution dropwise for neutralization, extract and recrystallize the product to obtain benzophenone anti-ultraviolet absorber.

4. The method for preparing the anti-UV aging marking paint according to claim 1, characterized in that, The molar ratio of 3,4-dihydroxybenzaldehyde and 2-hydroxy-4-methoxy-3'-aminobenzophenone in (1) is (1-1.1):

1.

5. The method for preparing the anti-UV aging marking paint according to claim 1, characterized in that, The reaction temperature in (1) is 20-40℃ and the reaction time is 2-6h.

6. The method for preparing the anti-UV aging marking paint according to claim 1, characterized in that, In (2), the molar ratio of the intermediate to sodium borohydride is 1:(1.3-1.5).

7. The method for preparing the anti-UV aging marking paint according to claim 1, characterized in that, In step (2), the reaction temperature is 30-40℃ and the reaction time is 4-5h.

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