An environmentally friendly coating for the exterior wall of a green building and its preparation method

Abstract

The present invention relates to the technical field of coatings, and discloses an environmentally friendly coating for green building exterior walls and a preparation method thereof. In the present invention, toluene-2,4-diisocyanate and hydroxypropionate phthalimide alkylamide are reacted, then reacted with epoxy resin, and neutralized; finally, water, emulsifier, defoamer, dispersant, pigment and filler are added to obtain the environmentally friendly coating for green building exterior walls. The water-based coating is clear and transparent, does not delaminate, has good dispersibility and excellent storage stability. And grafting flexible alkyl long chains into the epoxy resin can play a good toughening role, which is beneficial to improving the bending strength and impact strength of the epoxy resin casting body. Grafting the high-temperature resistant phenylimide ring group into the epoxy resin molecular chain can increase its initial thermal decomposition temperature, and has broad application prospects in the fields of high-performance heat-resistant, anti-ultraviolet and weather-resistant coatings, building exterior walls, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to an environmentally friendly coating for green building exterior walls and a preparation method thereof. Background Technique

[0002] Waterborne coatings use water as a solvent, are green, environmentally friendly and pollution-free, and are widely used in aspects such as building exterior walls, furniture and woodware, electronic appliances, vehicles and ships. Among them, waterborne epoxy resins have advantages such as good storage stability, high mechanical strength, and excellent corrosion resistance, and are widely used. However, epoxy resins have poor film toughness, are prone to cracking, and have poor heat resistance, ultraviolet resistance and other properties, and poor weather resistance, which is not conducive to the practical application of epoxy resins in outdoor products such as building exterior walls.

[0003] Currently, the main methods for modifying epoxy resins include blending modification, grafting modification, etc.; for example, reacting maleic anhydride with the hydroxyl groups of epoxy resins can introduce hydrophilic carboxyl groups to obtain waterborne epoxy resins with excellent properties. Introducing flexible long-chain alkyl groups into epoxy resins can also improve their toughness. Patent CN112645905B discloses an epoxy resin with long alkyl side chains and its preparation and curing methods. A functional double bond functional group is introduced into the biphenyl structure, and then n-dodecyl mercaptan is grafted onto the side chain of the biphenyl structure by thiol-ene click reaction to obtain an epoxy resin monomer containing long alkyl side chains, which can improve the toughness and hydrophobicity of epoxy resins. However, this patent does not improve the heat resistance and other properties of epoxy resins. Summary of the Invention

[0004] (1) Technical problems to be solved: Aiming at the deficiencies of the prior art, the present invention provides an environmentally friendly coating for green building exterior walls and a preparation method thereof, which solves the problems of poor toughness, easy cracking, and poor heat resistance and weather resistance of waterborne epoxy resin coatings.

[0005] (2) Technical solution: A preparation method of an environmentally friendly coating for green building exterior walls: Add acetone, toluene-2,4-diisocyanate, hydroxypropionate phthalimide alkylamide to a reaction vessel, heat to 50 - 60 °C, monitor the amount of -NCO groups in the reaction system by the di-n-butylamine method during the reaction, then add the catalyst dibutyltin dilaurate and epoxy resin, heat to 65 - 75 °C, stir and react for 3 - 5 h, cool after the reaction, add triethylamine for neutralization, add water, rotate and evaporate to remove acetone, add emulsifier, defoamer, dispersant, pigment and filler, and disperse in a high-speed disperser to obtain an environmentally friendly coating for green building exterior walls.

[0006] The hydroxypropionate phthalimide alkylamide has the structural formula of the following formula (Ⅰ);

[0007] n is any integer from 12 to 18.

[0008] Preferably, the dosage ratio of toluene - 2,4 - diisocyanate, hydroxypropionate phthalimide alkylamide, dibutyltin dilaurate, and epoxy resin is (0.02 - 0.07) mol : (0.02 - 0.07) mol : (0.05 - 0.18) mmol : 100 g.

[0009] Preferably, the preparation method of the hydroxypropionate phthalimide alkylamide is as follows:

[0010] (1) Add dichloromethane, trimellitic anhydride acyl chloride, and alkylamine compound to the reaction vessel. After the reaction, carry out vacuum distillation, washing, and drying to obtain phthalic anhydride alkylamide.

[0011] (2) Add solvent, toluene co - solvent, phthalic anhydride alkylamide, and DL - serine to the reaction vessel. After the reaction, cool, add methanol to precipitate the solid, filter, wash, and recrystallize to obtain hydroxypropionate phthalimide alkylamide.

[0012] Preferably, in (1), the ratio of trimellitic anhydride acyl chloride to alkylamine compound is (1 - 1.3) mol : 1 mol; the structural formula of the alkylamine compound is H 2 N - C n H 2n+1 , where n is any integer from 12 to 18.

[0013] Preferably, in (1), the reaction temperature is 15 - 25 °C and the reaction time is 6 - 9 h.

[0014] Preferably, in (2), the ratio of the solvent to the toluene co - solvent is 1 L : (0.2 - 0.3) L, and the solvent is N,N - dimethylformamide or N,N - dimethylacetamide.

[0015] Preferably, in (2), the ratio of phthalic anhydride alkylamide to DL - serine is 1 mol : (1 - 1.2) mol.

[0016] Preferably, in (2), the reaction temperature is 130 - 140 °C and the reaction time is 8 - 12 h.

[0017] (3) Technical effects: In the present invention, trimellitic anhydride acyl chloride, alkylamine compounds such as octadecylamine, and DL-serine are used as reactants. Through amidation and imide cyclization reactions, hydroxypropionate phthalimide alkylamide is obtained. The hydroxyl group contained therein reacts with toluene-2,4-diisocyanate to generate a TDI semi-addition product containing isocyanate groups, and then the isocyanate groups react with the hydroxyl groups in bisphenol A epoxy resin, thereby introducing hydrophilic carboxyl groups, amide bonds, flexible alkyl long chains, and phenylimide structures into the epoxy resin molecular chain.

[0018] The epoxy resin of the present invention contains groups such as hydrophilic carboxyl groups and amide bonds, which can endow it with good water solubility. The obtained waterborne coating is clear and transparent, does not delaminate, has good dispersibility, and excellent storage stability. And grafting flexible alkyl long chains onto the epoxy resin can play a good toughening role, which is beneficial to improving the flexural strength and impact strength of the epoxy resin casting.

[0019] In the present invention, the high-temperature-resistant phenylimide ring group is grafted onto the epoxy resin molecular chain, which can increase its initial thermal decomposition temperature and exhibit better heat resistance. And the phenylimide ring group has strong structural stability and good ultraviolet resistance. After the epoxy resin casting undergoes an ultraviolet lamp aging experiment, the decline in flexural strength and impact strength is small, and the weather resistance is excellent. It has broad application prospects in the fields of high-performance heat-resistant, ultraviolet-resistant, and weather-resistant coatings, building exterior walls, etc. Detailed implementation methods

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0021] Example 1

[0022] (1) Add 100 mL of dichloromethane, 0.05 mol of trimellitic anhydride acyl chloride, and 0.05 mol of octadecylamine to a reaction vessel, react at 15 °C for 9 h, and after the reaction, perform reduced pressure distillation, wash with petroleum ether, and dry to obtain phthalic anhydride alkylamide. The reaction formula is:

[0023]

[0024] (2) Add 30 mL of N,N-dimethylacetamide solvent, 6 mL of toluene co-solvent, 0.05 mmol of phthalic anhydride alkylamide, and 0.05 mmol of DL-serine to a reaction vessel, heat to 140 °C, react for 10 h, cool, add methanol to precipitate a solid, filter, wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionate phthalimide alkylamide. The reaction formula is:

[0025]

[0026] (3) Add 15 mL of acetone, 0.02 mol of toluene-2,4-diisocyanate, and 0.02 mol of hydroxypropionate phthalimide alkylamide to the reaction vessel, heat to 50 °C, and monitor the amount of -NCO groups in the reaction system by the di-n-butylamine method until 0.02 mol. Then add 0.1 mmol of the catalyst dibutyltin dilaurate and 100 g of bisphenol A epoxy resin, heat to 70 °C, and stir and react for 3 h; the reaction formula is as follows:

[0027]

[0028] After the above reaction, cool, add triethylamine for neutralization, add 120 mL of water, rotary evaporate to remove acetone, add 1.3 g of the emulsifier nonionic polyether NP8836, 0.8 g of the defoamer TEGO8030, 0.9 g of the dispersant ALCOSPERSE 408, and 22 g of the pigment and filler titanium dioxide, and disperse in a high-speed disperser to obtain an environmentally friendly coating for the exterior wall of green buildings.

[0029] Example 2

[0030] (1) Add 150 mL of dichloromethane, 0.065 mol of trimellitic anhydride acyl chloride, and 0.05 mol of hexadecylamine to the reaction vessel, react at 25 °C for 8 h, perform vacuum distillation after the reaction, wash with petroleum ether, and dry to obtain phthalic anhydride alkylamide.

[0031] (2) Add 30 mL of N,N-dimethylformamide solvent, 9 mL of toluene co-solvent, 0.05 mmol of phthalic anhydride alkylamide, and 0.06 mmol of DL-serine to the reaction vessel, heat to 140 °C, react for 8 h, cool, add methanol to precipitate the precipitate, filter and wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionate phthalimide alkylamide.

[0032] (3) Add 15 mL of acetone, 0.04 mol of toluene - 2,4 - diisocyanate, and 0.04 mol of hydroxypropionate phthalimide alkylamide into the reaction vessel. Heat it to 50 °C. During the reaction, monitor the amount of -NCO groups in the reaction system by the dibutylamine method until it reaches 0.04 mol. Then add 0.05 mmol of the catalyst dibutyltin dilaurate, 100 g of bisphenol A epoxy resin, heat it to 65 °C, and stir the reaction for 5 h. After the reaction, cool it, add triethylamine for neutralization, add 100 mL of water, remove acetone by rotary evaporation, add 1.3 g of the emulsifier non - ionic polyether NP8836, 0.8 g of the defoamer TEGO8030, 0.9 g of the dispersant ALCOSPERSE 408, and 22 g of the pigment and filler titanium dioxide, and disperse them in a high - speed disperser to obtain an environmentally friendly coating for green building exterior walls.

[0033] Example 3

[0034] (1) Add 100 mL of dichloromethane, 0.05 mol of trimellitic anhydride acyl chloride, and 0.05 mol of dodecylamine into the reaction vessel. React at 20 °C for 6 h. After the reaction, perform vacuum distillation, wash with petroleum ether, and dry to obtain phthalic anhydride alkylamide.

[0035] (2) Add 30 mL of N,N - dimethylacetamide solvent, 6 mL of toluene cosolvent, 0.05 mmol of phthalic anhydride alkylamide, and 0.05 mmol of DL - serine into the reaction vessel. Heat it to 130 °C and react for 12 h. Cool it, add methanol to precipitate the product, filter and wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionate phthalimide alkylamide.

[0036] (3) Add 15 mL of acetone, 0.07 mol of toluene - 2,4 - diisocyanate, and 0.07 mol of hydroxypropionate phthalimide alkylamide into the reaction vessel. Heat it to 60 °C. During the reaction, monitor the amount of -NCO groups in the reaction system by the dibutylamine method until it reaches 0.07 mol. Then add 0.18 mmol of the catalyst dibutyltin dilaurate, 100 g of bisphenol A epoxy resin, heat it to 75 °C, and stir the reaction for 3 h. After the reaction, cool it, add triethylamine for neutralization, add 120 mL of water, remove acetone by rotary evaporation, add 1.3 g of the emulsifier non - ionic polyether NP8836, 0.8 g of the defoamer TEGO8030, 0.9 g of the dispersant ALCOSPERSE 408, and 22 g of the pigment and filler titanium dioxide, and disperse them in a high - speed disperser to obtain an environmentally friendly coating for green building exterior walls.

[0037] Comparative Example 1

[0038] (1) Add 100 g of bisphenol A epoxy resin, 120 mL of water, 1.3 g of non-ionic polyether NP8836 as emulsifier, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE 408, and 22 g of pigment and filler titanium dioxide into the reaction vessel, and disperse in a high-speed disperser to obtain an epoxy resin coating for building exterior walls.

[0039] Comparative Example 2

[0040] (1) Add 100 mL of dichloromethane, 0.05 mol of trimellitic anhydride acyl chloride, and 0.05 mol of n-propylamine into the reaction vessel, react at 15 °C for 9 h, perform vacuum distillation after the reaction, wash with petroleum ether, and dry to obtain phthalic anhydride alkylamide.

[0041] (2) Add 30 mL of N,N-dimethylacetamide solvent, 6 mL of toluene co-solvent, 0.05 mmol of phthalic anhydride alkylamide, and 0.05 mmol of DL-serine into the reaction vessel, heat to 140 °C, react for 10 h, cool, add methanol to precipitate the precipitate, filter and wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionate phthalimide alkylamide.

[0042] (3) Add 15 mL of acetone, 0.02 mol of toluene-2,4-diisocyanate, and 0.02 mol of hydroxypropionate phthalimide alkylamide into the reaction vessel, heat to 50 °C, monitor the amount of -NCO groups in the reaction system by the dibutylamine method until 0.02 mol, then add 0.05 mmol of catalyst dibutyltin dilaurate, 100 g of bisphenol A epoxy resin, heat to 70 °C, stir and react for 3 h, cool after the reaction, add triethylamine for neutralization, add 120 mL of water, rotary evaporate to remove acetone, add 1.3 g of non-ionic polyether NP8836 as emulsifier, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE 408, and 22 g of pigment and filler titanium dioxide, and disperse in a high-speed disperser to obtain an environmentally friendly coating for green building exterior walls.

[0043] Comparative Example 3

[0044] (1) Add 15 mL of acetone, 0.02 mol of toluene-2,4-diisocyanate, and 0.02 mol of 3-hydroxypropionic acid (structural formula is ) Heat to 50 °C, monitor the amount of -NCO groups in the reaction system by the dibutylamine method until it reaches 0.02 mol during the reaction, then add 0.05 mmol of the catalyst dibutyltin dilaurate, 100 g of bisphenol A epoxy resin, heat to 70 °C, stir and react for 3 h. After the reaction, cool, add triethylamine for neutralization, add 120 mL of water, rotary evaporate to remove acetone, add 1.3 g of the emulsifier nonionic polyether NP8836, 0.8 g of the defoamer TEGO8030, 0.9 g of the dispersant ALCOSPERSE408, and 22 g of the pigment and filler titanium dioxide, and disperse in a high-speed disperser to obtain an environmentally friendly coating for green building exterior walls.

[0045] Let the coating stand at room temperature for 3 months, and observe the state and storage stability of the coating.

[0046] Add 11 g of the curing agent diethylenetriamine to the coating, cast it into a mold, degas under vacuum, cure at 100 °C for 4 h, then cure at 140 °C for 5 h, and demold to make a casting. Test the flexural strength and impact strength of the casting according to the method of GB / T 2567-2008.

[0047] Conduct an ultraviolet lamp aging experiment on the casting in an ultraviolet aging test chamber. The wavelength of the ultraviolet lamp is 360 nm, the power is 60 W, and the irradiation time is 120 h. Then test the flexural strength and impact strength of the casting.

[0048] Weigh 5 mg of the epoxy resin casting and place it in a thermogravimetric analyzer to conduct thermogravimetric performance testing in the nitrogen range. The heating rate is 5 °C / min, and the temperature range is 30 - 700 °C. The test results are shown in the following table.

[0049]

[0050] As can be seen from the above table, in Examples 1 - 3, toluene - 2,4 - diisocyanate (TDI) reacts with hydroxypropionate phthalimide alkylamide to generate a TDI semi - addition product containing isocyanate groups, and then the isocyanate groups react with the hydroxyl groups in bisphenol A epoxy resin, thereby introducing hydrophilic carboxyl groups and amide bonds, flexible alkyl long chains and phenylimide rings The structure is introduced into the epoxy resin molecular chain. The hydrophilic carboxyl groups and amide bonds can endow the epoxy resin with good water solubility. The obtained waterborne coating is clear and transparent, without stratification, has good dispersibility and excellent storage stability. And grafting flexible alkyl long chains into the epoxy resin can play a good toughening role, which is beneficial to improving the bending strength and impact strength of the epoxy resin casting. And grafting the high-temperature resistant phenylimide ring group into the epoxy resin molecular chain can increase its initial (5% mass loss) thermal decomposition temperature, showing better heat resistance. And the phenylimide ring group has strong structural stability and good UV resistance. After the epoxy resin casting undergoes the UV lamp aging experiment, the decrease in bending strength and impact strength is small, and the weather resistance is excellent.

[0051] In Comparative Example 1, water is used as the solvent and bisphenol A epoxy resin is used as the main component of the coating. However, the water solubility of bisphenol A epoxy resin is very poor, and a waterborne coating with good dispersibility cannot be obtained. The coating is significantly stratified and has very poor storage stability. And the initial thermal decomposition temperature is relatively low. After the UV lamp aging experiment, the decrease in bending strength and impact strength is large, and the weather resistance is poor.

[0052] Compared with Example 1, in Comparative Example 2, n-propylamine is used as the reactant, and the obtained hydroxypropionate phthalimide alkylamide does not contain flexible alkyl long chains. When grafted into the epoxy resin molecular chain, it cannot play a toughening role, and the bending strength and impact strength are significantly lower than those in Example 1. However, in Comparative Example 2, the hydrophilic carboxyl groups and phenylimide ring groups are grafted into the epoxy resin molecular chain. The waterborne coating is clear and transparent, without stratification, and has better storage stability than Comparative Example 1. And the initial thermal decomposition temperature is significantly higher than that in Comparative Example 1. And after the UV lamp aging experiment, the decrease in bending strength and impact strength is small, and the weather resistance is excellent.

[0053] Compared with Example 1, in Comparative Example 3, 3-hydroxypropionic acid and toluene-2,4-diisocyanate are used for reaction to obtain a TDI semi-addition product, and then reacted with bisphenol A epoxy resin to graft the hydrophilic carboxyl groups into the epoxy resin molecular chain, which can improve the water solubility of the epoxy resin. The obtained waterborne coating is clear and transparent, without stratification, and has good storage stability. However, the flexible alkyl long chains and phenylimide ring groups are not grafted into the epoxy resin molecular chain. The epoxy resin casting has poor toughness, low initial thermal decomposition temperature and heat resistance. And after the UV lamp aging experiment, the decrease in bending strength and impact strength is large, and the weather resistance is poor.

[0054] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the scope defined by the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly coating for exterior walls of green buildings, characterized in that: The preparation method is as follows: acetone, toluene-2,4-diisocyanate, and hydroxypropionic acid phthalimide alkylamide are added to a reaction container, heated to 50-60° C., the amount of -NCO groups in the reaction system is monitored by a di-n-butylamine method during the reaction, and then a catalyst dibutyltin dilaurate and an epoxy resin are added, heated to 65-75° C., stirred for reaction for 3-5 hours, cooled after the reaction, triethylamine is added for neutralization, water is added, acetone is removed by rotary evaporation, an emulsifier, a defoamer, a dispersant, and a pigment are added, and the mixture is dispersed in a high-speed disperser to obtain an environmentally friendly coating for the exterior wall of a green building; the toluene-2,4-diisocyanate, hydroxypropionic acid phthalimide alkylamide, dibutyltin dilaurate, and epoxy resin are used in a ratio of (0.02-0.07) mol: (0.02-0.07) mol: (0.05-0.18) mmol: 100 g; Hydroxypropionic acid phthalimide alkylamide has the structural formula (I) as follows: n is any integer between 12 and 18; The preparation method of hydroxypropionic acid phthalimide alkylamide is as follows: (1) Adding dichloromethane, trimellitic anhydride chloride, and an alkylamine compound into a reaction vessel, performing vacuum distillation after the reaction, washing, and drying to obtain phthalic anhydride alkylamide; wherein the structural formula of the alkylamine compound is H2N-C n H 2n+1 , n is any integer between 12 and 18; (2) adding a solvent, toluene as a cosolvent, phthalic anhydride alkylamide, and DL-serine to a reaction vessel, cooling after the reaction, adding methanol to precipitate the precipitate, filtering, washing, and recrystallizing to obtain hydroxypropionic acid phthalimide alkylamide.

2. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, characterized in that: The ratio of trimellitic anhydride chloride to the alkylamine compound in (1) is (1-1.3) mol:1 mol.

3. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, characterized in that: The reaction temperature in (1) is 15-25°C and the reaction time is 6-9h.

4. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, characterized in that: In the above (2), the ratio of the solvent to toluene as a co-solvent is 1 L:(0.2-0.3) L, and the solvent is N,N-dimethylformamide or N,N-dimethylacetamide.

5. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, characterized in that: The ratio of phthalic anhydride alkylamide to DL-serine in (2) is 1 mol:(1-1.2) mol.

6. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, characterized in that: The reaction temperature in (2) is 130-140° C., and the reaction time is 8-12 h.

7. An environmentally friendly coating for exterior walls of green buildings obtained by the preparation method according to any one of claims 1 to 6.

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