An environmentally friendly waterproof coating and its preparation method

Abstract

The present invention relates to the technical field of coatings, and discloses an environmentally friendly waterproof coating layer and a preparation method thereof. The environmentally friendly waterproof coating layer of the present invention comprises 100 parts by weight of epoxy resin, 10 - 25 parts by weight of a modified polyurethane toughening agent, 6.8 - 11.5 parts by weight of a curing agent, etc.; the side chain of the modified polyurethane toughening agent contains multiple alkyl long chains, which form physical chain entanglement with the epoxy resin molecular chain to form an interpenetrating network structure, significantly improving the interfacial bonding performance between polyurethane and epoxy resin. At the same time, the toughening agent contains a rigid benzene ring structure, greatly enhancing the impact resistance, impact strength and flexural strength of the epoxy resin. And it reduces the water absorption rate and improves the waterproof performance, having better practical applications in outdoor building fields such as road bridges, roof exterior walls, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and specifically to an environmentally friendly waterproof coating layer and a preparation method thereof. Background Art

[0002] Epoxy resins coatings are widely used in fields such as mechanical instruments, electronic and electrical, automotive and marine, and construction. Traditional epoxy resins have problems such as poor toughness and easy cracking, which will affect their anti-corrosion performance. The toughening modification of epoxy resins is a research hotspot. Polyurethane is a high-molecular compound with high toughness and excellent elasticity, and can be used as a toughening agent, which has important applications in high-molecular materials such as epoxy resins. Usually, functional groups such as amino groups and carboxyl groups need to be introduced into the polyurethane molecular chain to make terminal amino polyurethane, terminal carboxyl polyurethane, etc., and react with epoxy resins to cure, improving the interfacial bonding performance between the two, so as to achieve good toughening effects. Chinese Patent CN109651922B discloses a waterborne polyurethane toughened waterborne epoxy resin anti-corrosion coating and a preparation method thereof. Using polyisocyanate, oligomeric polyol, hydrophilic monomer, small molecule chain extender, amine chain extender, etc. as raw materials, the prepared waterborne polyurethane containing active hydrogen can improve the impact resistance, flexibility, corrosion resistance and other properties of epoxy resins. However, the preparation raw materials of this waterborne polyurethane are relatively complicated, and the waterborne polyurethane contains hydrophilic polyethers, carboxyl groups, etc. When added to the epoxy resin coating, it will increase the water absorption rate of the coating layer and affect the water resistance and waterproof performance of the coating. It is not conducive to the practical application of the coating layer in outdoor buildings such as road bridges, roof exterior walls, etc. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention solves the problem of poor toughness of the epoxy resin coating layer, and at the same time improves the water resistance and waterproof performance of the coating.

[0004] The present invention provides an environmentally friendly waterproof coating layer and a preparation method thereof. The coating layer includes 100 parts by weight of epoxy resin, 10 - 25 parts by weight of modified polyurethane toughening agent, 6.8 - 11.5 parts by weight of curing agent, 0.6 - 1 part by weight of defoaming agent, 0.3 - 0.6 part by weight of leveling agent, and 0.2 - 0.35 part by weight of wetting agent.

[0005] Preferably, the preparation method is: adding epoxy resin, modified polyurethane toughening agent, curing agent, defoaming agent, leveling agent, and wetting agent to a n-butanol solvent, stirring and mixing evenly to obtain an environmentally friendly waterproof coating; pouring the coating on the surface of the substrate, first baking and curing at 80 - 85 °C for 2 - 3 h, then curing at 120 - 130 °C for 3 - 3.5 h, and finally curing at 145 - 150 °C for 1 - 1.5 h to obtain an environmentally friendly waterproof coating layer.

[0006] Preferably, the curing agent is ethylenediamine, diethylenetriamine or triethylenetetramine.

[0007] Preferably, the preparation method of the modified polyurethane toughening agent is as follows:

[0008] (1) Add an amino monomer and p-hydroxybenzaldehyde with a molar ratio of 1:(2 - 2.1) to ethanol, carry out a condensation reflux reaction at 75 - 80 °C for 12 - 18 h, add sodium borohydride after cooling, react at room temperature for 2 - 3 h, carry out vacuum distillation, wash with water and ethanol, add the product to ethanol, heat and stir to dissolve, and cool for recrystallization to obtain an intermediate. The structural formula is or , where n is any integer from 10 to 16.

[0009] (2) Add the intermediate, 1-bromoalkane, and potassium carbonate with a molar ratio of 1:(3.2 - 5.4):(4 - 6) to acetonitrile, react at 40 - 50 °C for 18 - 24 h, carry out vacuum concentration, wash with water and ethanol, and recrystallize the product in chloroform to obtain an alkyl diol monomer. The structural formula is or , where n is any integer from 10 to 16.

[0010] (3) Add dry polyethylene glycol, a diisocyanate monomer, an alkyl diol monomer, and dibutyltin dilaurate to N,N-dimethylformamide, stir and react at 60 - 75 °C for 3 - 5 h, carry out vacuum distillation to remove N,N-dimethylformamide, wash with dichloromethane, and dry to obtain the modified polyurethane toughening agent.

[0011] Preferably, in (1), the amino monomer is ethylenediamine or diethylenetriamine.

[0012] Preferably, in (2), the molecular formula of the 1-bromoalkane is Br-C n H 2n+1 , where n is any integer from 10 to 16.

[0013] Preferably, in (1), the molar ratio of polyethylene glycol, the diisocyanate monomer, the alkyl diol monomer, and dibutyltin dilaurate is 1:(2.2 - 2.4):(1.1 - 1.2):(0.004 - 0.006).

[0014] Preferably, the diisocyanate monomer is hexamethylene diisocyanate, isophorone diisocyanate, or toluene-2,4-diisocyanate.

[0015] Advantageous technical effects of the present invention: By carrying out a polymerization reaction using polyethylene glycol, diisocyanate monomers, and diol monomers containing multiple alkyl long chains, a modified polyurethane toughening agent is obtained, which is used to toughen and modify epoxy resin coatings. The side chains of the modified polyurethane toughening agent contain multiple alkyl long chains, which form physical chain entanglement with the epoxy resin molecular chains, forming an interpenetrating network structure, significantly improving the interfacial bonding performance between polyurethane and epoxy resin, thereby enabling the polyurethane toughening agent to exhibit better toughening effects. At the same time, the toughening agent contains a rigid benzene ring structure, greatly enhancing the impact resistance, impact strength, and flexural strength of the epoxy resin.

[0016] The multiple alkyl long chains contained in the side chains of the modified polyurethane toughening agent of the present invention have stronger hydrophobicity, forming a hydrophobic network in the epoxy resin matrix, which is beneficial to reducing the water absorption rate and improving its waterproof performance. This enables the epoxy resin coating to have better practical applications in outdoor building fields such as road bridges, roof exteriors, etc. Specific embodiments

[0017] In order to more clearly illustrate the present invention and have a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0018] Example 1

[0019] (1) Add 10 mmol of diethylenetriamine and 20 mmol of p-hydroxybenzaldehyde to 60 mL of ethanol, stir and reflux at 80 °C for 12 h. After cooling, add 50 mmol of sodium borohydride, react at room temperature for 3 h, carry out vacuum distillation, wash with water and ethanol, add the product to ethanol, heat and stir to dissolve, and cool for recrystallization to obtain an intermediate. The reaction formula is:

[0020] .

[0021] (2) Add 10 mmol of the intermediate, 54 mmol of 1-bromododecane, and 54 mmol of potassium carbonate to 150 mL of acetonitrile, stir and react at 40 °C for 24 h, carry out vacuum concentration, wash with water and ethanol, and recrystallize the product in chloroform to obtain an alkyl diol monomer. The reaction formula is:

[0022] .

[0023] (3) Add 20 mmol of polyethylene glycol 800, 46 mmol of toluene-2,4-diisocyanate, 23 mmol of the alkyl diol monomer, and 0.1 mmol of dibutyltin dilaurate to 60 mL of N,N-dimethylformamide, stir and react at 75 °C for 3 h, carry out vacuum distillation to remove N,N-dimethylformamide, wash with dichloromethane, and dry to obtain the modified polyurethane toughening agent.

[0024] (4) Add 100 g of epoxy resin E44, 10 g of modified polyurethane toughening agent, 6.8 g of ethylenediamine, 0.6 g of defoaming agent BYK-A530, 0.5 g of leveling agent TEGO-2300, and 0.3 g of wetting agent TEGO Wet270 to 140 mL of n-butanol solvent, stir and mix evenly to obtain an environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 80 °C for 3 h first, then cure at 130 °C for 3 h, and finally cure at 145 °C for 1.5 h to obtain an environmentally friendly waterproof coating layer.

[0025] Example 2

[0026] (1) Add 10 mmol of ethylenediamine and 21 mmol of p-hydroxybenzaldehyde to 50 mL of ethanol, stir and reflux at 75 °C for 18 h. After cooling, add 54 mmol of sodium borohydride, react at room temperature for 3 h, distill under reduced pressure, wash with water and ethanol, add the product to ethanol, heat and stir to dissolve, and cool for recrystallization to obtain an intermediate. The reaction formula is:

[0027]

[0028] (2) Add 10 mmol of intermediate, 36 mmol of 1-bromohexadecane, and 48 mmol of potassium carbonate to 130 mL of acetonitrile, stir and react at 40 °C for 24 h, concentrate under reduced pressure, wash with water and ethanol, and recrystallize the product in chloroform to obtain an alkyl diol monomer. The reaction formula is:

[0029]

[0030] (3) Add 20 mmol of dry polyethylene glycol 800, 48 mmol of hexamethylene diisocyanate, 24 mmol of alkyl diol monomer, and 0.12 mmol of dibutyltin dilaurate to 70 mL of N,N-dimethylformamide, stir and react at 60 °C for 5 h, distill off N,N-dimethylformamide under reduced pressure, wash with dichloromethane, and dry to obtain a modified polyurethane toughening agent.

[0031] (4) Add 100 g of epoxy resin E44, 15 g of modified polyurethane toughening agent, 9.8 g of diethylenetriamine, 0.7 g of defoaming agent BYK-A530, 0.6 g of leveling agent TEGO-2300, and 0.35 g of wetting agent TEGO Wet270 to 160 mL of n-butanol solvent, stir and mix evenly to obtain an environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 85 °C for 2 h first, then cure at 120 °C for 3.5 h, and finally cure at 145 °C for 1.5 h to obtain an environmentally friendly waterproof coating layer.

[0032] Example 3

[0033] (1) Add 10 mmol of the intermediate (prepared in the same way as in Example 1), 48 mmol of 1-bromodecane, and 60 mmol of potassium carbonate to 150 mL of acetonitrile. Stir and react at 50 °C for 18 h, concentrate under reduced pressure, wash with water and ethanol, and recrystallize the product from chloroform to obtain the alkyl diol monomer. The structural formula is: .

[0034] (2) Add 20 mmol of dry polyethylene glycol 800, 44 mmol of isophorone diisocyanate, 22 mmol of the alkyl diol monomer, and 0.08 mmol of dibutyltin dilaurate to 60 mL of N,N-dimethylformamide. Stir and react at 70 °C for 4 h, distill off N,N-dimethylformamide under reduced pressure, wash with dichloromethane, and dry to obtain the modified polyurethane toughening agent.

[0035] (3) Add 100 g of epoxy resin E44, 20 g of the modified polyurethane toughening agent, 11.5 g of triethylenetetramine, 1 g of defoamer BYK-A530, 0.3 g of leveling agent TEGO-2300, and 0.3 g of wetting agent TEGO Wet270 to 160 mL of n-butanol solvent, stir and mix evenly to obtain the environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 85 °C for 2 h first, then cure at 120 °C for 3.5 h, and finally cure at 150 °C for 1 h to obtain the environmentally friendly waterproof coating layer.

[0036] Example 4

[0037] (1) Add 10 mmol of the intermediate (prepared in the same way as in Example 2), 32 mmol of 1-bromotetradecane, and 40 mmol of potassium carbonate to 120 mL of acetonitrile. Stir and react at 45 °C for 24 h, concentrate under reduced pressure, wash with water and ethanol, and recrystallize the product from chloroform to obtain the alkyl diol monomer. The structural formula is .

[0038] (2) Add 20 mmol of dry polyethylene glycol 800, 46 mmol of isophorone diisocyanate, 23 mmol of the alkyl diol monomer, and 0.12 mmol of dibutyltin dilaurate to 80 mL of N,N-dimethylformamide. Stir and react at 65 °C for 5 h, distill off N,N-dimethylformamide under reduced pressure, wash with dichloromethane, and dry to obtain the modified polyurethane toughening agent.

[0039] (3) Add 100 g of epoxy resin E44, 25 g of modified polyurethane toughening agent, 9.8 g of diethylenetriamine, 0.6 g of defoamer BYK-A530, 0.5 g of leveling agent TEGO-2300, and 0.2 g of wetting agent TEGO Wet270 to 180 mL of n-butanol solvent, stir and mix evenly to obtain an environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 80 °C for 3 h first, then cure at 120 °C for 3.5 h, and finally cure at 150 °C for 1 h to obtain an environmentally friendly waterproof coating layer.

[0040] Comparative Example 1

[0041] (1) Add 100 g of epoxy resin E44, 6.8 g of ethylenediamine, 0.6 g of defoamer BYK-A530, 0.5 g of leveling agent TEGO-2300, and 0.3 g of wetting agent TEGO Wet270 to 140 mL of n-butanol solvent, stir and mix evenly to obtain an environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 80 °C for 3 h first, then cure at 130 °C for 3 h, and finally cure at 145 °C for 1.5 h to obtain an environmentally friendly waterproof coating layer.

[0042] Comparative Example 2

[0043] (1) Add 20 mmol of polyethylene glycol 800, 46 mmol of toluene-2,4-diisocyanate, 23 mmol of 4,4'-biphenyldiol (structural formula is ) and 0.1 mmol of dibutyltin dilaurate to 60 mL of N,N-dimethylformamide, stir and react at 75 °C for 3 h, remove N,N-dimethylformamide by vacuum distillation, wash with dichloromethane, and dry to obtain a polyurethane toughening agent.

[0044] (2) Add 100 g of epoxy resin E44, 10 g of polyurethane toughening agent, 6.8 g of ethylenediamine, 0.6 g of defoamer BYK-A530, 0.5 g of leveling agent TEGO-2300, and 0.3 g of wetting agent TEGO Wet270 to 140 mL of n-butanol solvent, stir and mix evenly to obtain an environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 80 °C for 3 h first, then cure at 130 °C for 3 h, and finally cure at 145 °C for 1.5 h to obtain an environmentally friendly waterproof coating layer.

[0045] Comparative Example 3

[0046] (1) Add 10 mmol of diethylenetriamine and 20 mmol of p-hydroxybenzaldehyde to 60 mL of ethanol, stir and reflux at 80 °C for 12 h, distill under reduced pressure, add the product to ethanol, heat and stir to dissolve, and cool for recrystallization to obtain Intermediate 1. The structural formula is as follows:

[0047] 。

[0048] (2) Add 10 mmol of Intermediate 1, 18 mmol of 1-bromododecane, and 18 mmol of potassium carbonate to 90 mL of acetonitrile, stir and react at 40 °C for 24 h, concentrate under reduced pressure, wash with water and ethanol, and recrystallize the product from chloroform to obtain the alkyl diol monomer. The structural formula is as follows:

[0049] 。

[0050] (3) Add 20 mmol of dry polyethylene glycol 800, 46 mmol of toluene-2,4-diisocyanate, 23 mmol of alkyl diol monomer, and 0.1 mmol of dibutyltin dilaurate to 60 mL of N,N-dimethylformamide, stir and react at 75 °C for 3 h, distill off N,N-dimethylformamide under reduced pressure, wash with dichloromethane, and dry to obtain the modified polyurethane toughening agent.

[0051] (4) Add 100 g of epoxy resin E44, 10 g of modified polyurethane toughening agent, 6.8 g of ethylenediamine, 0.6 g of defoamer BYK-A530, 0.5 g of leveling agent TEGO-2300, and 0.3 g of wetting agent TEGO Wet270 to 140 mL of n-butanol solvent, stir and mix evenly to obtain the environmentally friendly waterproof coating; pour the coating on the surface of the substrate, bake and cure at 80 °C for 3 h first, then cure at 130 °C for 3 h, and finally cure at 145 °C for 1.5 h to obtain the environmentally friendly waterproof coating layer.

[0052] Test the impact resistance of the coating according to the method of GB / T 1732-2020. Pour the coating into a mold, and make a cast specimen by thermal curing. Test the impact strength and flexural strength of the cast specimen according to the method of GB / T 2567-2008.

[0053] Weigh the cast specimen, soak it in water, soak it at 80 °C for 72 h, take out the specimen, wipe the surface moisture, weigh it, and calculate the water absorption rate W. W = (m - m0) / m0 × 100%. m0 is the mass before water absorption, and m is the mass after water absorption.

[0054] Table 1 Coating Performance Test

[0055]

[0056] After testing, the epoxy resin coatings of Comparative Example 1 have low impact resistance, impact strength and flexural strength, poor toughness, unsatisfactory mechanical properties, and a large water absorption rate. The side chains of the modified polyurethane toughening agent added to the epoxy resin coatings of Examples 1-4 contain multiple long alkyl chains, which form physical chain entanglement with the epoxy resin molecular chains, forming an interpenetrating network structure, significantly improving the interfacial bonding performance between polyurethane and epoxy resin, so that the modified polyurethane toughening agent shows a better toughening effect. At the same time, the toughening agent contains a rigid benzene ring structure, greatly enhancing the toughness and mechanical properties of the epoxy resin, and having higher impact resistance, impact strength and flexural strength. And the multiple long alkyl chains contained in the side chain of the polyurethane toughening agent have stronger hydrophobicity, avoiding the problem of the increased hydrophilicity and water absorption rate of the epoxy resin caused by the addition of hydrophilic polyurethane. A large number of long alkyl chains form a hydrophobic network in the epoxy resin matrix, which is beneficial to reducing the water absorption rate of the coating and improving the water resistance and waterproof performance.

[0057] Compared with Example 1, in Comparative Example 2, conventional 4,4'-biphenol was used as a raw material, and the prepared polyurethane toughening agent did not contain multiple long alkyl chains, making it difficult to form physical chain entanglement with the epoxy resin molecular chains, and not improving the interfacial bonding performance between polyurethane and epoxy resin, resulting in a poor toughening effect of the polyurethane toughening agent, low impact resistance, impact strength and flexural strength of the epoxy resin, and the addition of hydrophilic polyether molecular chains in the polyurethane toughening agent leading to an increase in the water absorption rate of the epoxy resin and a deterioration in the water resistance and waterproof performance. In Comparative Example 3, the alkyl diol monomer contained only one long alkyl chain, and the physical chain entanglement between the prepared polyurethane toughening agent and the epoxy resin molecular chains was low, and the interfacial bonding performance was lower than that of Example 1, resulting in a poor toughening effect of the polyurethane toughening agent, and the impact resistance, impact strength and flexural strength being lower than those of Example 1. Moreover, with fewer long alkyl chains, the hydrophobicity of the polyurethane toughening agent was lower, resulting in a higher water absorption rate of the epoxy resin than that of Example 1 and unsatisfactory water resistance and waterproof performance.

[0058] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. An environmentally friendly waterproof coating layer, characterized in that, The environmentally friendly waterproof coating layer comprises 100 parts by weight of epoxy resin, 10 - 25 parts by weight of modified polyurethane toughening agent, 6.8 - 11.5 parts by weight of curing agent, 0.6 - 1 part by weight of defoaming agent, 0.3 - 0.6 part by weight of leveling agent and 0.2 - 0.35 part by weight of wetting agent; The preparation method of the modified polyurethane toughening agent is as follows: adding dry polyethylene glycol, diisocyanate monomer, alkyl diol monomer and dibutyltin dilaurate into N,N - dimethylformamide, reacting and then performing vacuum distillation, washing and drying to obtain the modified polyurethane toughening agent; The structural formula of the alkyl diol monomer is or , where n is any integer from 10 to 16.

2. The environmentally friendly waterproof coating layer according to claim 1, characterized in that, The curing agent is ethylenediamine, diethylenetriamine or triethylenetetramine.

3. The environmentally friendly waterproof coating layer according to claim 1, wherein, The temperature of the reaction is 60 - 75 °C and the reaction time is 3 - 5 h.

4. The environmentally friendly waterproof coating layer according to claim 1, wherein The molar ratio of the polyethylene glycol, diisocyanate monomer, alkyl diol monomer and dibutyltin dilaurate is 1:(2.2 - 2.4):(1.1 - 1.2):(0.004 - 0.006).

5. The environmentally friendly waterproof coating layer according to claim 4, wherein The diisocyanate monomer is hexamethylene diisocyanate, isophorone diisocyanate or toluene - 2,4 - diisocyanate.

6. The environmentally friendly waterproof coating layer according to claim 3, wherein The preparation method of the alkyl diol monomer is as follows: (1) Adding an amino monomer and p - hydroxybenzaldehyde with a molar ratio of 1:(2 - 2.1) into ethanol, carrying out a condensation reflux reaction at 75 - 80 °C for 12 - 18 h, cooling and then adding sodium borohydride, reacting at room temperature for 2 - 3 h, performing vacuum distillation, washing and recrystallizing to obtain an intermediate; (2) Adding the intermediate, 1 - bromoalkane and potassium carbonate into acetonitrile, reacting at 40 - 50 °C for 18 - 24 h, performing vacuum concentration, washing and recrystallizing to obtain the alkyl diol monomer.

7. The environmentally friendly waterproof coating layer according to claim 6, wherein, The amino monomer in (1) is ethylenediamine or diethylenetriamine.

8. The environmentally friendly waterproof coating layer according to claim 6, characterized in that, In (2), the molar ratio of the intermediate, 1 - bromoalkane and potassium carbonate is 1:(3.2 - 5.4):(4 - 6).

9. The environmentally friendly waterproof coating layer according to claim 8, wherein The molecular formula of the 1-bromoalkane in (2) is Br-C n H 2n+1 , where n is any integer from 10 to 16.

10. A method for preparing an environmentally friendly waterproof coating layer according to any one of claims 1-9, characterized in that, The preparation method is as follows: adding epoxy resin, modified polyurethane toughening agent, curing agent, defoaming agent, leveling agent and wetting agent into a n - butanol solvent, stirring and mixing evenly to obtain the environmentally friendly waterproof coating; pouring the coating on the surface of the substrate, baking and curing at 80 - 85 °C for 2 - 3 h first, then curing at 120 - 130 °C for 3 - 3.5 h, and finally curing at 145 - 150 °C for 1 - 1.5 h to obtain the environmentally friendly waterproof coating layer.

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