A kind of highly weather-resistant water-based acrylic polyurethane topcoat and preparation method thereof

Abstract

The present application relates to the technical field of waterborne coatings, and specifically discloses a highly weather-resistant waterborne acrylic polyurethane topcoat and a preparation method thereof. The highly weather-resistant waterborne acrylic polyurethane topcoat is prepared by mixing component A and component B, and component B is made of the following raw materials in parts by mass: 50-65 parts of isocyanate, 10-15 parts of cosolvent, and 3-5 parts of composite lauryl amine. The preparation of composite lauryl amine includes the following steps: (1) acylation reaction of lauryl amine to obtain acylated lauryl amine; (2) reaction of acylated lauryl amine with bromine to obtain brominated lauryl amine; (3) grafting brominated lauryl amine with graphene oxide to obtain product M; (4) dissolving M, deprotecting, and grinding to obtain composite lauryl amine. Component A and component B are mixed to obtain a highly weather-resistant waterborne acrylic polyurethane topcoat. Using composite lauryl amine as an additive to component B can reduce the loss of isocyanate in the raw materials and reduce the amount of CO2 gas generated during the mixing process of the topcoat.

Description

Technical Field

[0001] The present application relates to the technical field of waterborne coatings, and more specifically, to a highly weather-resistant waterborne acrylic polyurethane topcoat and a preparation method thereof. Background Art

[0002] Water-based acrylic polyurethane topcoat is an environmentally friendly coating, mainly prepared by mixing acrylic polyurethane resin, curing agent, pigment, additives and water. Compared with other topcoats, water-based acrylic polyurethane topcoat uses water as a diluent and does not contain formaldehyde. It can significantly reduce the emission of volatile organic solvents and has less pollution to the environment. At the same time, water-based acrylic polyurethane topcoat can be firmly attached to a variety of substrates after painting, and has strong adhesion and durability. As a protective topcoat, it is used in steel structures, buildings, bridges and light industrial products.

[0003] Among the topcoat components, acrylic polyurethane resin is usually mixed with high-grade acrylic resin, pigment, additives, etc. as the hydroxyl component, and aliphatic isocyanate is the isocyanate component, which is obtained by blending and crosslinking. However, since isocyanate can react with water at room temperature and generate small molecules and carbon dioxide. This causes 5%-10% consumption of isocyanate in the preparation process of the topcoat. The consumed isocyanate does not participate in the synthesis of polyurethane, reducing the yield of polyurethane in the topcoat crosslinking system. In addition, the generated CO2 gas will affect the surface state of the topcoat, causing defects and bubbles on the surface of the topcoat. In industry, the ratio of isocyanate to hydroxyl raw materials is usually adjusted to make the reacted isocyanate slightly excessive, so that even if a small amount of isocyanate is lost, it will not affect the final crosslinked polyurethane yield; at the same time, a defoamer is added during the topcoat mixing process to reduce the residual bubbles in the topcoat.

[0004] The Chinese patent application document with application publication number CN113583505A discloses a low-foam coating dispersing wetting agent and a preparation method thereof. The polyurethane prepolymer with a cross-linked structure is obtained by reacting modified isophorone diisocyanate with epichlorohydrin. The polyurethane prepolymer is then sheared with water to finally obtain a low-foam coating dispersing wetting agent. The wetting agent can significantly reduce the foaming of the coating and play a role in assisting the dispersion of the coating.

[0005] In the above documents, although the addition of low-foam coating dispersing wetting agent enhances the stability of raw materials in the topcoat preparation process, it does not improve the isocyanate consumption problem. The isocyanate groups exposed to the water environment will still react with water to generate CO2 gas. Therefore, there is still a need to find a method that can reduce isocyanate loss and CO2 gas generation. Summary of the invention

[0006] In order to further reduce isocyanate loss and CO2 gas generation, the present application provides a highly weather-resistant water-based acrylic polyurethane topcoat and a preparation method thereof.

[0007] In a first aspect, the present application provides a highly weather-resistant water-based acrylic polyurethane topcoat, which is prepared by mixing component A and component B, wherein component A is prepared from the following raw materials in parts by weight: 35-45 parts of water-based hydroxy acrylic emulsion, 20-25 parts of water, and 10-15 parts of titanium dioxide; component B is prepared from the following raw materials in parts by weight: 50-65 parts of isocyanate, 10-15 parts of cosolvent, and 3-5 parts of composite lauryl amine;

[0008] The preparation of the composite lauryl amine comprises the following steps:

[0009] (1) dissolving lauryl amine, adding a catalyst and an acylation reagent, controlling the temperature, reacting, adding water to extract and separate the liquid, and drying to obtain acylated lauryl amine;

[0010] (2) adding acylated lauryl amine to a bromine-carbon tetrachloride solution, adding a catalyst, controlling the reaction temperature and time, and distilling to obtain bromolaurylamine;

[0011] (3) dissolving and dispersing graphene oxide, adding sodium hydroxide solution dropwise for reaction, then adding lauryl bromide, a mixed solvent and a catalyst for reaction, filtering and washing the precipitate, and drying the precipitate to obtain a product denoted as M;

[0012] (4) M is dissolved, a mixed acid is added dropwise, the pH is adjusted for the first time, the amino protecting group is removed by reaction, and then a sodium hydroxide solution is added dropwise under ice bath conditions to adjust the pH to neutral, the precipitate is filtered, the precipitate is dried and then ground to obtain a composite lauryl amine.

[0013] By adopting the above technical solution, lauryl amine is a structure of amino grafted alkyl chain, in which the amino part can form a polyurea structure with the isocyanate group on the isocyanate, and a polyurea protective layer can be covered on the surface of the isocyanate through the reaction, which is used to isolate the water molecules in the water solvent from the contact with the isocyanate, reduce the consumption of the reaction between the isocyanate and the water and the generation of CO2 gas. Through subsequent bromination and esterification grafting, the lauryl amine molecules can be fixed to the GO sheet layer, thereby reducing the disadvantage that the lauryl amine small molecules themselves are easily dissolved from the topcoat coating, and better protect the isocyanate dispersion liquid, reducing the consumption of isocyanate.

[0014] Preferably, in step (1), the catalyst is 4-dimethylaminopyridine and the acylation reagent is di-tert-butyl dicarbonate.

[0015] By adopting the above technical solution, 4-dimethylaminopyridine is a strongly nucleophilic acylation catalyst, which can ensure that the terminal amino group of lauryl amine reacts effectively with the acylating agent, thereby realizing the acylation protection of lauryl amine. Di-tert-butyl dicarbonate, as an acylation reaction agent, introduces a tert-butyloxycarbonyl protecting group to the terminal amino group of lauryl amine in the acylation reaction, which can shield the active N atom through a large steric hindrance, thereby reducing the probability of the N atom being preferentially replaced in the subsequent reaction.

[0016] Preferably, in step (1), the reaction temperature is 30-40°C.

[0017] By adopting the above technical solution, within this temperature range, the acylation protection effect of di-tert-butyl dicarbonate on lauryl amine is the best.

[0018] Preferably, in step (2), the reaction temperature is 5-10°C and the reaction time is 0.5-1h.

[0019] By adopting the above technical scheme, a bromine substituent can be introduced into the alkyl chain of laurylamine, and regulating the low temperature environment and reaction time is conducive to the bromination reaction of the alkyl group to produce a monobrominated product as the main product, thereby avoiding the impact of polybromination reactions on subsequent products and the waste of bromine raw materials.

[0020] Preferably, in step (3), the mixed solvent is prepared from anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:(1-1.5).

[0021] By adopting the above technical scheme, a good solvent for esterification grafting reaction can be obtained, and the treatment effect is best when using this solvent. Esterification grafting is a reaction between the carboxyl group on the surface of graphene oxide and the bromine position of the alkyl chain of lauryl amine. Under the action of the esterification reaction catalyst, the bromine position of lauryl amine continuously reacts with the carboxyl site of graphene oxide, thereby grafting multiple short chains of lauryl amine on the graphene oxide sheet, enhancing the protective effect of lauryl amine on isocyanate in the raw material component of the topcoat, and at the same time achieving the fixation of lauryl amine small molecules.

[0022] Preferably, in step (4), the mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of (1-1.5):1.

[0023] By adopting the above technical solution, trifluoroacetic acid is a weak oxidizing organic strong acid, which can protonate the amino N atom protected by the tert-butyloxycarbonyl group, and can remove the tert-butyloxycarbonyl structure grafted on the amino group by cooperating with hydrochloric acid.

[0024] Preferably, in step (4), the pH is first adjusted to 2-3.

[0025] By adopting the above technical scheme, the amino deprotection reaction of bromolaurylamine is relatively complete under acidic conditions. At the same time, in a hydrogen ion-rich environment, the N atom of the deacylated laurylamine can combine with the hydrogen ions in the solvent to restore the complete amino structure.

[0026] In a second aspect, the present application provides a method for preparing a highly weather-resistant water-based acrylic polyurethane topcoat, comprising the following steps:

[0027] (S01) mixing a water-based hydroxy acrylic emulsion, titanium dioxide and water, stirring and dispersing, and then adding an auxiliary agent and stirring to obtain component A;

[0028] (S02) mixing isocyanate, a co-solvent and composite lauryl amine, and stirring to obtain component B;

[0029] (S03) Component A is mixed with component B, and stirred to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

[0030] Preferably, in the step (S02), the co-solvent is prepared from propylene glycol diacetate and methylal in a mass ratio of 1:1.

[0031] By adopting the above technical scheme, the obtained high weather resistance water-based acrylic polyurethane topcoat has the best mixing and coating effects.

[0032] Preferably, in the step (S03), component A and component B are mixed in a mass ratio of (1.5-2):1.

[0033] By adopting the above technical scheme, the highly weather-resistant water-based acrylic polyurethane topcoat prepared has the best use effect.

[0034] In summary, this application has the following beneficial effects:

[0035] 1. The present application uses composite lauryl amine as an additive of topcoat component B, which has two effects. On the one hand, the amino group in the composite lauryl amine can react with the isocyanate group on the isocyanate to form a polyurea structure, thereby uniformly coating the surface of the isocyanate dispersion droplets with a barrier layer that can serve as a temporary water barrier to prevent the isocyanate from directly contacting the aqueous solvent. On the other hand, the presence of the barrier layer inhibits the reaction of the isocyanate dispersion liquid wrapped inside with water, reducing the generation of the reaction product CO2 and the consumption of isocyanate.

[0036] 2. In this application, graphene oxide is preferably used as a template for isocyanate grafting. Through esterification reaction, lauryl amine small molecules can be fixed on the graphene oxide plate layer, reducing the risk of lauryl amine small molecules being unstable in the topcoat and easily seeping out of the topcoat with increasing temperature; at the same time, the addition of graphene oxide also enhances the strength of the topcoat and its ability to resist acid, alkali and salt corrosion.

[0037] 3. The highly weather-resistant waterborne acrylic polyurethane topcoat prepared by adding the composite lauryl amine of the present application has excellent weather resistance and can effectively reduce the isocyanate loss during the topcoat preparation process and the amount of CO2 gas generated by the reaction with the water solvent. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 : Bar chart of the amount of CO2 gas generated during the mixing of component A and component B in Examples 1-5 of the present application and Comparative Examples 1-2. DETAILED DESCRIPTION

[0039] Example 1

[0040] In this embodiment, the highly weather-resistant water-based acrylic polyurethane topcoat is prepared by mixing component A and component B. Component A is made of the following raw materials by weight: 35 g of water-based hydroxy acrylic emulsion, 20 g of deionized water, 10 g of rutile titanium dioxide, 3 g of talc, 7 g of wollastonite, 1 g of dispersant KMT-3604, 0.5 g of defoamer ZB-2408, and 0.2 g of water-based coating leveling agent 1045. Component B is made of the following raw materials by weight: 50 g of isocyanate, 10 g of cosolvent, and 3 g of composite lauryl amine.

[0041] The preparation steps of composite lauryl amine in this embodiment are as follows:

[0042] (1) Take 4.3 g of lauryl amine and dissolve it in 150 mL of DMF solvent. Add 0.3 g of catalyst 4-dimethylaminopyridine and 4 g of di-tert-butyl dicarbonate. Adjust the temperature to 30 °C and control the magnetic stirring speed to 50 rpm. React for 10 h. Then add 450 mL of deionized water to extract the DMF solvent. Finally, separate the upper light yellow liquid and dry it to obtain acylated lauryl amine.

[0043] (2) Add 3 g of bromine to 50 mL of carbon tetrachloride solution, then add acylated lauryl amine, add 0.02 g of CeO2 catalyst, stir at 100 rpm, temperature 5 °C, react for 0.5 h, and distill the solvent to obtain bromolaurylamine.

[0044] (3) Take 0.5 g of graphene oxide (50 μm) and add it to 50 mL of deionized water, then add dispersant 0.2 g of sodium dodecylbenzene sulfonate, 1 g of polyethylene glycol, and 0.5 g of gum arabic. Adjust the magnetic stirring speed to 100 rpm and stir for 10 min. Then, add 5 mL of sodium hydroxide solution with a molar concentration of 0.5 mol / L to the system, adjust the temperature to 50 °C and react for 1 h. Then, add bromolaurylamine, and add 50 mL of mixed solvent and 0.5 g of catalyst cuprous oxide. Raise the temperature to 65 °C and continue the reaction for 3 h. Finally, filter the precipitate, wash and dry it. The product is recorded as M.

[0045] (4) M was dissolved in 30 mL of carbon dichloride, and 5 mL of mixed acid was added dropwise, the pH was adjusted to 2, the magnetic stirring speed was controlled to 100 rpm, and the reaction was stopped after 20 min. Then, a sodium hydroxide solution with a mass concentration of 3% was added to the system at a rate of 10 mL / min under ice bath conditions, and the pH was adjusted to 7. The precipitate was filtered and dried, and then transferred to a ball mill for full grinding. After filtering, a composite lauryl amine with an average particle size of 20 μm was obtained.

[0046] The method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat in this embodiment comprises the following steps:

[0047] (S01) Mixing water-based hydroxy acrylic emulsion, rutile titanium dioxide, talc, wollastonite, dispersant KMT-3604 and deionized water, dispersing at 1500 rpm for 20 min, then adding defoamer ZB-2408 and water-based coating leveling agent 1045, stirring at 1000 rpm for 10 min, to obtain component A;

[0048] (S02) In a light-proof and moisture-proof environment, isocyanate, a co-solvent and composite lauryl amine are mixed, the stirring speed is controlled to be 1200 rpm, and the stirring is performed for 5 minutes to obtain component B;

[0049] (S03) 30 g of component A was mixed with 20 g of component B, the stirring speed was controlled to 100 rpm, and the mixture was stirred for 0.5 h to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

[0050] The mixed solvent is prepared by anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:1. The mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of 1:1. The cosolvent is prepared by mixing propylene glycol diacetate and methylal in a mass ratio of 1:1. The water-based hydroxy acrylic emulsion (model: HD-8426) is provided by Shanghai Xunda New Materials Technology Co., Ltd. Isocyanate (brand: Huntsman, MDI type) is provided by Foshan Jinjia New Materials Technology Co., Ltd.

[0051] Example 2

[0052] In this embodiment, the highly weather-resistant water-based acrylic polyurethane topcoat is prepared by mixing component A and component B. Component A is made of the following raw materials by weight: 40 g of water-based hydroxy acrylic emulsion, 20 g of deionized water, 10 g of rutile titanium dioxide, 3 g of talcum powder, 7 g of wollastonite, 1 g of dispersant KMT-3604, 0.5 g of defoamer ZB-2408, and 0.5 g of water-based coating leveling agent 1045. Component B is made of the following raw materials by weight: 55 g of isocyanate, 10 g of cosolvent, and 4 g of modified lauryl amine.

[0053] The preparation steps of composite lauryl amine in this embodiment are as follows:

[0054] (1) Take 4.6 g of lauryl amine and dissolve it in 150 mL of DMF solvent. Add 0.3 g of catalyst 4-dimethylaminopyridine and 4 g of di-tert-butyl dicarbonate. Adjust the temperature to 35 °C and control the magnetic stirring speed to 55 rpm. React for 12 h. Then add 450 mL of deionized water to extract the DMF solvent. Finally, separate the upper light yellow liquid and dry it to obtain acylated lauryl amine.

[0055] (2) Add 3.2 g of bromine to 50 mL of carbon tetrachloride solution, then add acylated lauryl amine, add 0.04 g of CeO2 catalyst, stir at 100 rpm, temperature 5 °C, react for 1 h, and distill the solvent to obtain bromolaurylamine.

[0056] (3) Take 0.7 g of graphene oxide (50 μm) and add it to 50 mL of deionized water, then add dispersant 0.2 g of sodium dodecylbenzene sulfonate, 1 g of polyethylene glycol, and 0.5 g of gum arabic, adjust the magnetic stirring speed to 100 rpm, stir for 10 min, then add 5 mL of 0.5 mol / L sodium hydroxide solution to the system, adjust the temperature to 65 °C and react for 1 h, then add bromolaurylamine, and add 75 mL of mixed solvent and 0.5 g of catalyst cuprous oxide, raise the temperature to 70 °C and continue the reaction for 3 h, finally filter the precipitate, wash and dry it, and the obtained product is recorded as M.

[0057] (4) M was dissolved in 30 mL of carbon dichloride, and 7 mL of mixed acid was added dropwise, the pH was adjusted to 2.5, the magnetic stirring speed was controlled to 100 rpm, and the reaction was stopped after 25 min. Then, a sodium hydroxide solution with a mass concentration of 3% was added to the system at a rate of 10 mL / min under ice bath conditions, and the pH was adjusted to 7. The precipitate was filtered and dried, and then transferred to a ball mill for full grinding. After filtering, a composite lauryl amine with an average particle size of 20 μm was obtained.

[0058] The method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat in this embodiment comprises the following steps:

[0059] (S01) Mixing water-based hydroxy acrylic emulsion, rutile titanium dioxide, talc, wollastonite, dispersant KMT-3604 and deionized water, dispersing at 1500 rpm for 30 min, then adding defoamer ZB-2408 and water-based coating leveling agent 1045, stirring at 1000 rpm for 10 min, to obtain component A;

[0060] (S02) In a light-proof and moisture-proof environment, isocyanate, a co-solvent and composite lauryl amine are mixed, the stirring speed is controlled to be 1200 rpm, and the stirring is performed for 10 minutes to obtain component B;

[0061] (S03) 30 g of component A was mixed with 20 g of component B, the stirring speed was controlled to 100 rpm, and the mixture was stirred for 0.5 h to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

[0062] The mixed solvent is prepared by anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:1. The mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of 1:1. The cosolvent is prepared by mixing propylene glycol diacetate and methylal in a mass ratio of 1:1. The water-based hydroxy acrylic emulsion (model: HD-8426) is provided by Shanghai Xunda New Materials Technology Co., Ltd. Isocyanate (brand: Huntsman, MDI type) is provided by Foshan Jinjia New Materials Technology Co., Ltd.

[0063] Example 3

[0064] In this embodiment, the highly weather-resistant water-based acrylic polyurethane topcoat is prepared by mixing component A and component B. Component A is made of the following raw materials by weight: 45 g of water-based hydroxy acrylic emulsion, 25 g of deionized water, 10 g of rutile titanium dioxide, 5 g of talc, 7 g of wollastonite, 2 g of dispersant KMT-3604, 1 g of defoamer ZB-2408, and 0.2 g of water-based coating leveling agent 1045. Component B is made of the following raw materials by weight: 60 g of isocyanate, 15 g of cosolvent, and 5 g of modified lauryl amine.

[0065] The preparation steps of composite lauryl amine in this embodiment are as follows:

[0066] (1) Take 5 g of lauryl amine and dissolve it in 150 mL of DMF solvent. Add 0.4 g of catalyst 4-dimethylaminopyridine and 5 g of di-tert-butyl dicarbonate. Adjust the temperature to 40 °C and control the magnetic stirring speed to 75 rpm. React for 13 h. Then add 450 mL of deionized water to extract the DMF solvent. Finally, separate the upper light yellow liquid and dry it to obtain acylated lauryl amine.

[0067] (2) Add 3.5 g of bromine to 50 mL of carbon tetrachloride solution, then add acylated lauryl amine, add 0.04 g of CeO2 catalyst, stir at 100 rpm, temperature 10 °C, react for 0.5 h, and distill the solvent to obtain bromolaurylamine.

[0068] (3) Take 0.5 g of graphene oxide (75 μm) and add it to 50 mL of deionized water, then add dispersant 0.2 g of sodium dodecylbenzene sulfonate, 1 g of polyethylene glycol, and 0.5 g of gum arabic, adjust the magnetic stirring speed to 100 rpm, stir for 15 min, then add 5 mL of 0.5 mol / L sodium hydroxide solution to the system, adjust the temperature to 50 °C and react for 2 h, then add bromolaurylamine, and add 75 mL of mixed solvent and 0.5 g of catalyst cuprous oxide, raise the temperature to 70 °C and continue the reaction for 3 h, finally filter the precipitate, wash and dry it, and the obtained product is recorded as M.

[0069] (4) M was dissolved in 30 mL of carbon dichloride, 10 mL of mixed acid was added dropwise, the pH was adjusted to 3, the magnetic stirring speed was controlled to 100 rpm, and the reaction was stopped after 25 min. Then, a sodium hydroxide solution with a mass concentration of 3% was added to the system at a rate of 10 mL / min under ice bath conditions, the pH was adjusted to 7, and then the precipitate was filtered out, the precipitate was dried and then transferred to a ball mill for full grinding, and after filtering, a composite lauryl amine with an average particle size of 25 μm was obtained.

[0070] The method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat in this embodiment comprises the following steps:

[0071] (S01) Mixing water-based hydroxy acrylic emulsion, rutile titanium dioxide, talc, wollastonite, dispersant KMT-3604 and deionized water, dispersing at 1500 rpm for 20 min, then adding defoamer ZB-2408 and water-based coating leveling agent 1045, stirring at 1000 rpm for 10 min, to obtain component A;

[0072] (S02) In a light-proof and moisture-proof environment, isocyanate, a co-solvent and composite lauryl amine are mixed, the stirring speed is controlled to be 1200 rpm, and the stirring is performed for 10 minutes to obtain component B;

[0073] (S03) 35 g of component A was mixed with 20 g of component B, the stirring speed was controlled to 100 rpm, and the mixture was stirred for 0.5 h to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

[0074] The mixed solvent is prepared by anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:1. The mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of 1:1. The cosolvent is prepared by mixing propylene glycol diacetate and methylal in a mass ratio of 1:1. The water-based hydroxy acrylic emulsion (model: HD-8426) is provided by Shanghai Xunda New Materials Technology Co., Ltd. Isocyanate (brand: Huntsman, MDI type) is provided by Foshan Jinjia New Materials Technology Co., Ltd.

[0075] Example 4

[0076] In this embodiment, the highly weather-resistant water-based acrylic polyurethane topcoat is prepared by mixing component A and component B. Component A is made of the following raw materials by weight: 45 g of water-based hydroxy acrylic emulsion, 20 g of deionized water, 15 g of rutile titanium dioxide, 3 g of talcum powder, 10 g of wollastonite, 1 g of dispersant KMT-3604, 1 g of defoamer ZB-2408, and 0.2 g of water-based coating leveling agent 1045. Component B is made of the following raw materials by weight: 60 g of isocyanate, 20 g of cosolvent, and 5 g of modified lauryl amine.

[0077] The preparation steps of composite lauryl amine in this embodiment are as follows:

[0078] (1) Take 5.1 g of lauryl amine and dissolve it in 150 mL of DMF solvent. Add 0.5 g of catalyst 4-dimethylaminopyridine and 5 g of di-tert-butyl dicarbonate. Adjust the temperature to 35 °C and control the magnetic stirring speed to 75 rpm. React for 13 h. Then add 450 mL of deionized water to extract the DMF solvent. Finally, separate the upper light yellow liquid and dry it to obtain acylated lauryl amine.

[0079] (2) Add 3.5 g of bromine to 50 mL of carbon tetrachloride solution, then add acylated lauryl amine, add 0.03 g of CeO2 catalyst, stir at 100 rpm, temperature 5 °C, react for 1 h, and distill the solvent to obtain bromolaurylamine.

[0080] (3) Take 0.7 g of graphene oxide (75 μm) and add it to 50 mL of deionized water, then add dispersant 0.2 g of sodium dodecylbenzene sulfonate, 1 g of polyethylene glycol, and 0.5 g of gum arabic, adjust the magnetic stirring speed to 100 rpm, stir for 20 min, then add 5 mL of 0.5 mol / L sodium hydroxide solution to the system, adjust the temperature to 55 °C and react for 3 h, then add bromolaurylamine, and add 55 mL of mixed solvent and 1 g of catalyst cuprous oxide, raise the temperature to 65 °C and continue the reaction for 3 h, finally filter the precipitate, wash and dry it, and the obtained product is recorded as M.

[0081] (4) M was dissolved in 30 mL of carbon dichloride, 10 mL of mixed acid was added dropwise, the pH was adjusted to 3, the magnetic stirring speed was controlled to 100 rpm, and the reaction was stopped after 20 min. Then, a sodium hydroxide solution with a mass concentration of 3% was added to the system at a rate of 10 mL / min under ice bath conditions, the pH was adjusted to 7, and then the precipitate was filtered out, the precipitate was dried and then transferred to a ball mill for full grinding, and after filtering, a composite lauryl amine with an average particle size of 25 μm was obtained.

[0082] The method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat in this embodiment comprises the following steps:

[0083] (S01) Mixing water-based hydroxy acrylic emulsion, rutile titanium dioxide, talc, wollastonite, dispersant KMT-3604 and deionized water, dispersing at 1500 rpm for 30 min, then adding defoamer ZB-2408 and water-based coating leveling agent 1045, stirring at 1000 rpm for 10 min, to obtain component A;

[0084] (S02) In a light-proof and moisture-proof environment, isocyanate, a co-solvent and composite lauryl amine are mixed, the stirring speed is controlled to be 1200 rpm, and the stirring is performed for 10 minutes to obtain component B;

[0085] (S03) 35 g of component A was mixed with 20 g of component B, the stirring speed was controlled to 100 rpm, and the mixture was stirred for 0.5 h to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

[0086] The mixed solvent is prepared by mixing anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:1.5. The mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of 1.5:1. The cosolvent is prepared by mixing propylene glycol diacetate and methylal in a mass ratio of 1:1. The water-based hydroxylated acrylic emulsion (model: HD-8426) is provided by Shanghai Xunda New Materials Technology Co., Ltd. Isocyanate (brand: Huntsman, MDI type) is provided by Foshan Jinjia New Materials Technology Co., Ltd.

[0087] Example 5

[0088] In this embodiment, the highly weather-resistant water-based acrylic polyurethane topcoat is prepared by mixing component A and component B, wherein component A is made of the following raw materials by weight: 35 g of water-based hydroxy acrylic emulsion, 20 g of deionized water, 10 g of rutile titanium dioxide, 3 g of talcum powder, 7 g of wollastonite, 1 g of dispersant KMT-3604, 1 g of defoamer ZB-2408, and 0.5 g of water-based coating leveling agent 1045; and component B is made of the following raw materials by weight: 65 g of isocyanate, 20 g of cosolvent, and 5 g of modified lauryl amine.

[0089] The preparation steps of composite lauryl amine in this embodiment are as follows:

[0090] (1) Take 5.7 g of lauryl amine and dissolve it in 150 mL of DMF solvent. Add 0.5 g of catalyst 4-dimethylaminopyridine and 5 g of di-tert-butyl dicarbonate. Adjust the temperature to 40 °C and control the magnetic stirring speed to 75 rpm. React for 15 h. Then add 450 mL of deionized water to extract the DMF solvent. Finally, separate the upper light yellow liquid and dry it to obtain acylated lauryl amine.

[0091] (2) Add 4 g of bromine to 50 mL of carbon tetrachloride solution, then add acylated lauryl amine, add 0.04 g of CeO2 catalyst, stir at 100 rpm, temperature 10 °C, react for 1 h, and distill the solvent to obtain bromolaurylamine.

[0092] (3) Take 1g of graphene oxide (100μm) and add it to 50mL of deionized water, then add dispersant 0.2g of sodium dodecylbenzene sulfonate, 1g of polyethylene glycol, and 0.5g of gum arabic, adjust the magnetic stirring speed to 100rpm, stir for 20min, then add 5mL of sodium hydroxide solution with a molar concentration of 0.5mol / L to the system, adjust the temperature to 65℃ and react for 3h, then add bromolaurylamine, and add 75mL of mixed solvent and 1g of catalyst cuprous oxide, raise the temperature to 70℃ and continue the reaction for 4h, finally filter the precipitate, wash and dry it, and the obtained product is recorded as M.

[0093] (4) M was dissolved in 30 mL of carbon dichloride, 10 mL of mixed acid was added dropwise, the pH was adjusted to 2-3, the magnetic stirring speed was controlled to 100 rpm, and the reaction was stopped after 20 min. Then, a sodium hydroxide solution with a mass concentration of 3% was added to the system at a rate of 10 mL / min under ice bath conditions, the pH was adjusted to 7, and then the precipitate was filtered out, the precipitate was dried and then transferred to a ball mill for full grinding, and after filtering, a composite lauryl amine with an average particle size of 30 μm was obtained.

[0094] The method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat in this embodiment comprises the following steps:

[0095] (S01) Mixing water-based hydroxy acrylic emulsion, rutile titanium dioxide, talc, wollastonite, dispersant KMT-3604 and deionized water, dispersing at 1500 rpm for 25 min, then adding defoamer ZB-2408 and water-based coating leveling agent 1045, stirring at 1000 rpm for 10 min, to obtain component A;

[0096] (S02) In a light-proof and moisture-proof environment, isocyanate, a co-solvent and composite lauryl amine are mixed, the stirring speed is controlled to be 1200 rpm, and the stirring is performed for 10 minutes to obtain component B;

[0097] (S03) 40 g of component A was mixed with 20 g of component B, the stirring speed was controlled to 100 rpm, and the mixture was stirred for 0.5 h to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

[0098] The mixed solvent is prepared by mixing anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:1.5. The mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of 1.5:1. The cosolvent is prepared by mixing propylene glycol diacetate and methylal in a mass ratio of 1:1. The water-based hydroxylated acrylic emulsion (model: HD-8426) is provided by Shanghai Xunda New Materials Technology Co., Ltd. Isocyanate (brand: Huntsman, MDI type) is provided by Foshan Jinjia New Materials Technology Co., Ltd.

[0099] Comparative Example 1

[0100] The difference between this comparative example and Example 1 is that an equal amount of untreated lauryl amine is used instead of composite lauryl amine, and the other conditions are the same as those in Example 1.

[0101] Comparative Example 2

[0102] The difference between this comparative example and Example 1 is that lauryl amine is directly mixed with graphene oxide instead of composite lauryl amine, and the other conditions are the same as those in Example 1.

[0103] Performance testing

[0104] Table 1 Performance test method table of Examples 1-5 and Comparative Examples 1-2

[0105]

[0106] Carbon dioxide gas volume test

[0107] Take a 50mL three-necked bottle, connect a nitrogen conduit at the vent, and pre-exclude the air in the three-necked bottle. The outlet is connected to a barium hydroxide precipitation tank with a molar concentration of 0.5mol / L by a conduit, and then 7.5g of component A and 5g of component B prepared in Example 1-5 and Comparative Example 1-2 are added to the three-necked bottle, and then the feed port is closed, and N2 is continuously introduced into the three-necked bottle at a speed of 20mL / min, the temperature is 45°C, the magnetic stirring speed is 150rpm, and continuous stirring is performed. When it is observed that no more precipitation is generated in the barium hydroxide precipitation tank, the ventilation device is turned off. Filter the precipitate in the barium hydroxide precipitation tank, and weigh it after drying. Finally, according to the mass of barium carbonate collected, the amount of CO2 gas generated during the mixing process of component A and component B is calculated.

[0108] Table 2 Performance test results of Examples 1-5 and Comparative Examples 1-2

[0109]

[0110] By analyzing Examples 1-5 and Comparative Examples 1-2 and combining with Table 2, it can be seen that the topcoat prepared by Examples 1-5 is superior to Comparative Examples 1-2 in pencil hardness (scratch) and impact resistance, and is more effective in improving the salt spray resistance and acid-base performance of the topcoat.

[0111] Analyze Examples 1-5 and Comparative Examples 1-2 and combine Table 2 and Figure 1 It can be seen that the composite lauryl amine prepared by using Examples 1-5 can effectively reduce the amount of carbon dioxide gas generated during the preparation of the topcoat, and exhibits a better effect on the appearance of the coating film than that of Comparative Examples 1-2.

[0112] By analyzing Examples 1-5 and Comparative Examples 1-2 and combining Tables 1 and 2, it can be seen that the highly weather-resistant waterborne acrylic polyurethane topcoat prepared in the examples can meet the actual application requirements and meet the requirements for the topcoat coating performance in the national standards.

[0113] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A highly weather-resistant water-based acrylic polyurethane topcoat, characterized in that: The composition is prepared by mixing component A and component B, wherein component A is prepared by the following raw materials in parts by weight: 35-45 parts of water-based hydroxy acrylic emulsion, 20-25 parts of water, and 10-15 parts of titanium dioxide; component B is prepared by the following raw materials in parts by weight: 50-65 parts of isocyanate, 10-15 parts of cosolvent, and 3-5 parts of composite lauryl amine; The preparation of the composite lauryl amine comprises the following steps: (1) dissolving lauryl amine, adding a catalyst and an acylation reagent, controlling the temperature, reacting, adding water to extract and separate the liquid, and drying to obtain acylated lauryl amine; (2) adding acylated lauryl amine to a bromine-carbon tetrachloride solution, adding a catalyst, controlling the reaction temperature and time, and distilling to obtain bromolaurylamine; (3) dissolving and dispersing graphene oxide, adding sodium hydroxide solution dropwise for reaction, then adding lauryl bromide, a mixed solvent and a catalyst for reaction, filtering and washing the precipitate, and drying the precipitate to obtain a product denoted as M; (4) M is dissolved, a mixed acid is added dropwise, the pH is adjusted for the first time, the amino protecting group is removed by reaction, and then a sodium hydroxide solution is added dropwise under ice bath conditions to adjust the pH to neutral, the precipitate is filtered, the precipitate is dried and then ground to obtain a composite lauryl amine.

2. A highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 1, characterized in that: In the step (1), the catalyst is 4-dimethylaminopyridine, and the acylation reagent is di-tert-butyl dicarbonate.

3. A highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 1, characterized in that: In the step (1), the reaction temperature is 30-40°C.

4. A highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 1, characterized in that: In the step (2), the reaction temperature is 5-10°C and the reaction time is 0.5-1h.

5. A highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 1, characterized in that: In the step (3), the mixed solvent is prepared from anhydrous ethanol, dimethyl sulfoxide and hexamethylphosphoric acid triamide in a mass ratio of 6:2:(1-1.5).

6. A highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 1, characterized in that: In the step (4), the mixed acid is prepared by mixing trifluoroacetic acid and 1 mol / L HCl in a mass ratio of (1-1.5):

1.

7. A highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 1, characterized in that: In the step (4), the pH is first adjusted to 2-3.

8. A method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat as claimed in claim 1, characterized in that: The steps include: (S01) mixing a water-based hydroxy acrylic emulsion, titanium dioxide and water, stirring and dispersing, and then adding an auxiliary agent and stirring to obtain component A; (S02) mixing isocyanate, a co-solvent and composite lauryl amine, and stirring to obtain component B; (S03) Component A is mixed with component B, and stirred to obtain a highly weather-resistant water-based acrylic polyurethane topcoat.

9. The method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat according to claim 8, characterized in that: In the step (S02), the co-solvent is prepared from propylene glycol diacetate and methylal in a mass ratio of 1:

1.

10. A method for preparing a highly weather-resistant waterborne acrylic polyurethane topcoat as claimed in claim 8, characterized in that: In the step (S03), component A and component B are mixed in a mass ratio of (1.5-2):1.

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