Environment-friendly coating for green building exterior wall and preparation method of environment-friendly coating

Abstract

The invention relates to the technical field of coatings, and discloses an environment-friendly coating for a green building exterior wall and a preparation method thereof.The preparation method comprises the steps that toluene-2, 4-diisocyanate and hydroxypropionyl phthalimide alkyl amide are reacted, then reacted with epoxy resin and neutralized; and finally, adding water, an emulsifier, a defoaming agent, a dispersing agent and pigments and fillers to obtain the environment-friendly coating for the green building external wall. The water-based paint is clear, transparent, free of layering, good in dispersity and excellent in storage stability. And the flexible alkyl long chain is grafted into the epoxy resin, so that a good toughening effect can be achieved, and the bending strength and impact strength of an epoxy resin casting body can be improved. The high-temperature-resistant phenyl imide ring group is grafted into an epoxy resin molecular chain, the initial thermal decomposition temperature of the epoxy resin can be increased, and the high-temperature-resistant phenyl imide ring group has wide application prospects in the fields of high-performance heat-resistant anti-ultraviolet weather-resistant coatings, building outer walls and the like.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to an environmentally friendly coating for exterior walls of green buildings and a preparation method thereof. Background Art

[0002] Water-based paint uses water as a solvent, is green and pollution-free, and is widely used in building exterior walls, furniture and wood products, electronic appliances, vehicles and ships, etc. Among them, water-based epoxy resin has the advantages of good storage stability, high mechanical strength, and excellent corrosion resistance, and is widely used. However, epoxy resin has poor film toughness, is easy to crack, and has poor heat resistance, UV resistance and other properties, and poor weather resistance, which is not conducive to the practical application of epoxy resin in outdoor products such as building exterior walls.

[0003] At present, the methods for modifying epoxy resin mainly include blending modification, grafting modification and other methods; for example, by reacting maleic anhydride with the hydroxyl group of epoxy resin, hydrophilic carboxyl groups can be introduced to obtain water-based epoxy resin with excellent performance. Introducing flexible long-chain alkyl groups into epoxy resin can also improve its toughness. Patent CN112645905B discloses an epoxy resin with long alkyl side chains and its preparation and curing methods, introducing functional double bond functional groups into biphenyl structure, and then using mercapto-ene click reaction to graft n-dodecyl mercaptan onto the side chain of biphenyl structure to obtain epoxy resin monomer containing long alkyl side chains, which can improve the toughness and hydrophobicity of epoxy resin. However, this patent does not improve the heat resistance and other properties of epoxy resin. Summary of the invention

[0004] (I) Technical problems to be solved: In view of the deficiencies in the prior art, the present invention provides an environmentally friendly coating for exterior walls of green buildings and a preparation method thereof, which solves the problems of poor toughness, easy cracking, poor heat resistance and poor weather resistance of water-based epoxy resin coatings.

[0005] (ii) Technical solution: A method for preparing an environmentally friendly coating for the exterior walls of green buildings: add acetone, toluene-2,4-diisocyanate, and hydroxypropionic acid phthalimide alkylamide into a reaction container, heat to 50-60°C, use the di-n-butylamine method to monitor the amount of -NCO groups in the reaction system during the reaction, then add a catalyst dibutyltin dilaurate and an epoxy resin, heat to 65-75°C, stir the reaction for 3-5 hours, cool after the reaction, add triethylamine for neutralization, add water, remove acetone by rotary evaporation, add an emulsifier, a defoamer, a dispersant, and a pigment, and disperse in a high-speed disperser to obtain an environmentally friendly coating for the exterior walls of green buildings.

[0006] The hydroxypropionylphthalimide alkylamide has the structural formula (I) as follows:

[0007] n is any integer between 12 and 18.

[0008] Preferably, the usage ratio of toluene-2,4-diisocyanate, hydroxypropionic acid 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 hydroxypropionic acid phthalimide alkylamide is:

[0010] (1) Adding dichloromethane, trimellitic anhydride chloride, and an alkylamine compound into a reaction vessel, distilling under reduced pressure after the reaction, washing, and drying to obtain phthalic anhydride alkylamide;

[0011] (2) Add a solvent, toluene as a cosolvent, phthalic anhydride alkylamide, and DL-serine to a reaction vessel, cool the reaction vessel after reaction, add methanol to precipitate the precipitate, filter, wash, and recrystallize to obtain hydroxypropionic acid phthalimide alkylamide.

[0012] Preferably, the ratio of trimellitic anhydride chloride to the alkylamine compound in (1) is (1-1.3) mol:1 mol; the structural formula of the alkylamine compound is H2N-C n H 2n+1 , n is any integer between 12 and 18.

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

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

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

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

[0017] (III) Technical effect: The present invention uses trimellitic anhydride chloride, alkylamine compounds such as octadecylamine, DL-serine, etc. as reactants, and obtains hydroxypropionic acid phthalimide alkylamide through amidation and imide cyclization reaction. The hydroxyl contained in it reacts with toluene-2,4-diisocyanate to generate TDI semi-addition product containing isocyanate group, and then the isocyanate group reacts with the hydroxyl group in bisphenol A epoxy resin, thereby introducing hydrophilic carboxyl group and amide bond, flexible alkyl long chain and phenylimide structure into the epoxy resin molecular chain.

[0018] The epoxy resin of the present invention contains hydrophilic carboxyl groups, amide bonds and other groups, which can give it good water solubility, and the obtained water-based coating is clear and transparent, non-stratified, good in dispersibility and excellent in storage stability. In addition, the flexible alkyl long chain is grafted into the epoxy resin, which can play a good toughening role and is conducive to improving the bending strength and impact strength of the epoxy resin casting.

[0019] The invention grafts a high temperature resistant phenylimide ring group into the epoxy resin molecular chain, which can increase the initial thermal decomposition temperature thereof and show better heat resistance. In addition, the phenylimide ring group has strong structural stability and good anti-ultraviolet performance. After the epoxy resin casting body is subjected to an ultraviolet lamp aging test, the decrease in bending strength and impact strength is small, and the weather resistance is excellent. The invention has broad application prospects in the fields of high-performance heat-resistant, anti-ultraviolet and weather-resistant coatings, building exterior walls, and the like. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only 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 chloride, and 0.05 mol of octadecylamine to a reaction vessel, and react at 15°C for 9 hours. After the reaction, distill under reduced pressure, 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 cosolvent, 0.05 mmol of phthalic anhydride alkylamide, and 0.05 mmol of DL-serine to the reaction vessel, heat to 140°C, react for 10 hours, cool, add methanol to precipitate, filter, wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionic acid 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 hydroxypropionic acid phthalimide alkylamide to a reaction container, heat to 50° C., and use the di-n-butylamine method to monitor the amount of -NCO groups in the reaction system until it reaches 0.02 mol during the reaction. Then, add 0.1 mmol of catalyst dibutyltin dilaurate and 100 g of bisphenol A epoxy resin, heat to 70° C., and stir to react for 3 hours. The reaction formula is as follows:

[0027]

[0028] After the above reaction, the mixture was cooled, triethylamine was added for neutralization, 120 mL of water was added, acetone was removed by rotary evaporation, 1.3 g of emulsifier nonionic polyether NP8836, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE 408, and 22 g of pigment filler titanium dioxide were added, and dispersed in a high-speed disperser to obtain an environmentally friendly coating for exterior walls of green buildings.

[0029] Example 2

[0030] (1) Add 150 mL of dichloromethane, 0.065 mol of trimellitic anhydride chloride, and 0.05 mol of hexadecylamine into a reaction vessel, and react at 25° C. for 8 h. After the reaction, distill under reduced pressure, 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 cosolvent, 0.05 mmol of phthalic anhydride alkylamide, and 0.06 mmol of DL-serine to a reaction container, heat to 140°C, react for 8 hours, cool, add methanol to precipitate, filter, wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionic acid phthalimide alkylamide.

[0032] (3) Add 15 mL of acetone, 0.04 mol of toluene-2,4-diisocyanate, and 0.04 mol of hydroxypropionic acid phthalimide alkylamide to a reaction container, heat to 50° C., use the di-n-butylamine method to monitor the amount of -NCO groups in the reaction system until it reaches 0.04 mol during the reaction, then add 0.05 mmol of catalyst dibutyltin dilaurate and 100 g of bisphenol A type epoxy resin, heat to 65° C., stir and react for 5 h, cool after the reaction, add triethylamine to neutralize, add 100 mL of water, remove acetone by rotary evaporation, add 1.3 g of emulsifier nonionic polyether NP8836, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE 408, and 22 g of pigment filler titanium dioxide, and disperse in a high-speed disperser to obtain an environmentally friendly coating for the exterior walls of green buildings.

[0033] Example 3

[0034] (1) Add 100 mL of dichloromethane, 0.05 mol of trimellitic anhydride chloride, and 0.05 mol of dodecylamine into a reaction vessel, and react at 20° C. for 6 h. After the reaction, distill under reduced pressure, 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 to a reaction vessel, heat to 130°C, react for 12 hours, cool, add methanol to precipitate, filter, wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionic acid phthalimide alkylamide.

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

[0037] Comparative Example 1

[0038] (1) Add 100 g of bisphenol A epoxy resin, 120 mL of water, 1.3 g of emulsifier nonionic polyether NP8836, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE 408, and 22 g of pigment titanium dioxide into a reaction container, 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 chloride, and 0.05 mol of n-propylamine into a reaction vessel, and react at 15° C. for 9 h. After the reaction, distill under reduced pressure, 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 cosolvent, 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 hours, cool, add methanol to precipitate, filter, wash with methanol, and then recrystallize in chloroform to obtain hydroxypropionic acid phthalimide alkylamide.

[0042] (3) Add 15 mL of acetone, 0.02 mol of toluene-2,4-diisocyanate, and 0.02 mol of hydroxypropionic acid phthalimide alkylamide to a reaction container, heat to 50° C., use the di-n-butylamine method to monitor the amount of -NCO groups in the reaction system until it reaches 0.02 mol during the reaction, then add 0.05 mmol of catalyst dibutyltin dilaurate and 100 g of bisphenol A type epoxy resin, heat to 70° C., stir and react for 3 h, cool after the reaction, add triethylamine to neutralize, add 120 mL of water, remove acetone by rotary evaporation, add 1.3 g of emulsifier nonionic polyether NP8836, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE 408, and 22 g of pigment filler titanium dioxide, and disperse in a high-speed disperser to obtain an environmentally friendly coating for the exterior walls of green buildings.

[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: ), heated to 50°C, during the reaction, the amount of -NCO groups in the reaction system was monitored by the di-n-butylamine method until it reached 0.02 mol, then 0.05 mmol of catalyst dibutyltin dilaurate and 100 g of bisphenol A epoxy resin were added, heated to 70°C, stirred for reaction for 3 h, cooled after the reaction, triethylamine was added for neutralization, 120 mL of water was added, acetone was removed by rotary evaporation, 1.3 g of emulsifier non-ionic polyether NP8836, 0.8 g of defoamer TEGO8030, 0.9 g of dispersant ALCOSPERSE408, and 22 g of pigment filler titanium dioxide were added, and dispersed in a high-speed disperser to obtain an environmentally friendly coating for exterior walls of green buildings.

[0045] The coating was left standing at room temperature for 3 months, and the state and storage stability of the coating were observed.

[0046] 11g of curing agent diethylenetriamine was added to the coating, cast into a mold, vacuum degassed, cured at 100°C for 4h, then cured at 140°C for 5h, and demolded to form a casting. The flexural strength and impact strength of the casting were tested according to GB / T 2567-2008.

[0047] The casting was subjected to an ultraviolet lamp aging test in an ultraviolet aging test box, with the wavelength of the ultraviolet lamp being 360nm, the power being 60W, and the irradiation time being 120h, and then the bending strength and impact strength of the casting were tested.

[0048] 5 mg of epoxy resin casting was weighed and placed in a thermogravimetric analyzer to perform a thermogravimetric performance test in a nitrogen atmosphere with a heating rate of 5°C / min and a temperature range of 30-700°C. The test results are shown in the table below.

[0049]

[0050] As can be seen from the above table, in Example 1-3, toluene-2,4-diisocyanate (TDI) is reacted with hydroxypropionic acid phthalimide alkylamide to generate a TDI semi-addition product containing an isocyanate group, and then the isocyanate group reacts with the hydroxyl group in the bisphenol A epoxy resin, thereby combining the hydrophilic carboxyl group and the amide bond, the flexible alkyl long chain and the phenylimide ring. The structure is introduced into the epoxy resin molecular chain. The hydrophilic carboxyl group and the amide bond can give the epoxy resin good water solubility, and the obtained water-based coating is clear and transparent, non-stratified, well dispersible, and has excellent storage stability. In addition, the flexible alkyl long chain is grafted into the epoxy resin, which can play a good toughening role, which is beneficial to improve the bending strength and impact strength of the epoxy resin casting. In addition, the high-temperature resistant phenylimide ring group is grafted into the epoxy resin molecular chain, which can increase its initial (mass loss 5%) thermal decomposition temperature and show better heat resistance. In addition, the phenylimide ring group has strong structural stability and good UV resistance. After the epoxy resin casting has been subjected to the UV lamp aging test, the decrease in bending strength and impact strength is small, and the weather resistance is excellent.

[0051] Comparative Example 1 uses water as solvent and bisphenol A epoxy resin as the main component of the coating. However, bisphenol A epoxy resin has poor water solubility and cannot obtain a water-based coating with good dispersibility. The coating is obviously stratified and has poor storage stability. In addition, the initial thermal decomposition temperature is low. After the ultraviolet lamp aging test, the flexural strength and impact strength decrease significantly, and the weather resistance is poor.

[0052] Compared with Example 1, Comparative Example 2 uses n-propylamine as a reactant, and the obtained hydroxypropionic acid phthalimide alkylamide does not contain a flexible alkyl long chain, and is grafted into the epoxy resin molecular chain, and cannot play a toughening role, and the bending strength and impact strength are significantly lower than those of Example 1. However, Comparative Example 2 grafts hydrophilic carboxyl groups and phenylimide ring groups into the epoxy resin molecular chain, and the water-based 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 of Comparative Example 1, and after the ultraviolet lamp aging test, the decrease in bending strength and impact strength is small, and the weather resistance is excellent.

[0053] Compared with Example 1, Comparative Example 3 uses 3-hydroxypropionic acid and toluene-2,4-diisocyanate to react to obtain a TDI semi-addition product, which is then reacted with a bisphenol A epoxy resin to graft the hydrophilic carboxyl group into the epoxy resin molecular chain, which can improve the water solubility of the epoxy resin. The obtained water-based coating is clear and transparent, does not delaminate, and has good storage stability. However, the flexible alkyl long chain and the phenylimide ring group 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 ultraviolet lamp aging test, the bending strength and impact strength decrease significantly, and the weather resistance is poor.

[0054] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways. As long as they do not deviate from the scope defined by the present invention, they shall 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, It is 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 exterior walls of green buildings; The hydroxypropionylphthalimide alkylamide has the structural formula (I) as follows: n is any integer between 12 and 18.

2. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, It is characterized in that 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.

3. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 1, It is characterized in that The preparation method of the hydroxypropionic acid phthalimide alkylamide is: (1) adding dichloromethane, trimellitic anhydride chloride, and an alkylamine compound into a reaction vessel, distilling under reduced pressure after the reaction, washing, and drying to obtain phthalic anhydride alkylamide; (2) Add a solvent, toluene as a cosolvent, phthalic anhydride alkylamide, and DL-serine to a reaction vessel, cool the reaction vessel after reaction, add methanol to precipitate the precipitate, filter, wash, and recrystallize to obtain hydroxypropionic acid phthalimide alkylamide.

4. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 3, It is characterized in that The ratio of trimellitic anhydride chloride to the alkylamine compound in (1) is (1-1.3) mol:1 mol; the structural formula of the alkylamine compound is H 2 NC n H 2n+1 , n is any integer between 12 and 18.

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

6. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 3, It is 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.

7. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 3, It is characterized in that The ratio of phthalic anhydride alkylamide to DL-serine in (2) is 1 mol:(1-1.2) mol.

8. The method for preparing the environmentally friendly coating for green building exterior walls according to claim 3, It is characterized in that The reaction temperature in (2) is 130-140° C., and the reaction time is 8-12 h.

9. An environmentally friendly coating for exterior walls of green buildings obtained by the preparation method according to any one of claims 1 to 8.

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