A method for preparing anionic aqueous polyaspartic acid ester resin and its application.

Abstract

This invention discloses a method for preparing and applying anionic waterborne polyaspartic acid ester resin. The preparation method is as follows: (1) reacting an aliphatic polyamine with dialkyl maleate to obtain polyaspartic acid ester; (2) performing an ester exchange reaction between the obtained polyaspartic acid ester and hydroxyalkyl sulfonate to obtain the anionic waterborne polyaspartic acid ester resin. This invention uses hydroxysulfonate to modify polyaspartic acid ester to obtain anionic waterborne polyaspartic acid ester resin with a dendritic macromolecular structure in which anionic sulfonic acid groups extend outward. It can achieve self-emulsification by using water as a solvent, and has better emulsification properties when combined with sulfonate-modified isocyanate curing agents. When applied to coatings, it can produce waterborne PAE polyurea coatings with high strength, high adhesion, and good wear resistance and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer coatings technology, and in particular to a method for preparing and applying anionic waterborne polyaspartic acid ester resin. Background Technology

[0002] Polyaspartic acid ester resin is a special type of sterically hindered secondary amine compound. Its steric hindrance and inductive effect reduce the reactivity of the secondary amine in the reaction with -NCO, resulting in a longer application time and higher film adhesion compared to traditional polyurea materials. Polyaspartic acid ester resin combined with aliphatic isocyanate curing agents produces polyaspartic acid ester polyurea (PAE polyurea) coatings with excellent elasticity, waterproofing, anti-slip properties, and wear resistance. These are excellent coatings and adhesives, widely used in floor coatings.

[0003] However, traditional polyaspartic acid ester resins are lipophilic and have poor water solubility, limiting their application to organic solvent-based or high-solids-content products. Existing technologies also include research on hydrophilic modification of polyaspartic acid ester resins. For example, Chinese patent CN111303368A discloses a waterborne polyaspartic acid ester resin and its preparation method, which involves a transesterification reaction between a hydrophilic alkyl-etherified monohydroxy polyether and a lipophilic polyaspartic acid intermediate to generate a hydrophilic polyaspartic acid ester resin product. However, this technology has the following drawbacks: 1. Insufficient monohydroxy polyether results in insufficient hydrophilicity, affecting usability; excessive monohydroxy polyether leads to difficulties in transesterification, and excessive polyether chains affect product performance, causing the resin to lose gloss and chalk later; 2. During the emulsification of the final product molecules, the polyether encapsulates the polyaspartic acid ester molecules, resulting in poor coating antibacterial properties, reduced wear resistance, reduced acid and alkali resistance, and reduced strength.

[0004] Furthermore, existing waterborne polyaspartic acid ester resins are mostly waterborne through polyether modification. When applied to coatings, the curing agent is often a sulfonate-modified anionic waterborne isocyanate curing agent (water-dispersible isocyanate curing agents modified with sulfonate are used in waterborne coatings and can rival solvent-based coatings in terms of curing, drying, water and chemical resistance). However, the two are not well compatible, and the emulsion is prone to instability during the addition of curing agent, resulting in insufficient coating strength and poor appearance. Summary of the Invention

[0005] This invention aims to overcome the problem of poor compatibility between polyether-modified waterborne polyaspartic ester resin and sulfonate-modified waterborne isocyanate curing agent in the prior art. It provides a method for preparing and applying anionic waterborne polyaspartic ester resin, resulting in an anionic waterborne polyaspartic ester resin with an extended dendritic macromolecular structure containing anionic sulfonic acid groups. This resin can achieve self-emulsification using water as a solvent and exhibits better emulsification properties when combined with sulfonate-modified isocyanate curing agents. When applied to coatings, it yields waterborne PAE polyurea coatings with high strength, high adhesion, good wear resistance, and corrosion resistance, comparable to solvent-based coatings in terms of curing, drying, water resistance, and chemical resistance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing anionic aqueous polyaspartic acid ester resin includes the following steps:

[0008] (1) Polyaspartic acid ester was prepared by reacting aliphatic polyprimary amines with dialkyl maleate.

[0009] (2) The obtained polyaspartic ester is subjected to transesterification reaction with hydroxyalkyl sulfonate to obtain the anionic aqueous polyaspartic ester resin.

[0010] This invention first prepares polyaspartic acid ester by reacting dialkyl maleate with an aliphatic polyamine, and then obtains anionic aqueous polyaspartic acid ester resin with an extended anionic sulfonic acid group through transesterification with hydroxyalkyl sulfonate. This invention first synthesizes polyaspartic acid ester and then performs transesterification with hydroxyalkyl sulfonate, avoiding the self-polymerization of dialkyl maleate at high temperatures that could affect product performance. The highly branched nature of the product gives the resulting aqueous polyaspartic acid ester resin good self-emulsifying properties, allowing for self-emulsification using water as a solvent. Simultaneously, the highly branched nature further increases the steric hindrance effect on the secondary amine groups, reducing the viscosity of the emulsion formed through water emulsification, thus providing sufficient working time when used in PAE polyurea coatings. Furthermore, the anionic waterborne polyaspartic ester resin prepared by this invention exhibits better emulsification properties when combined with a sulfonate-modified waterborne isocyanate curing agent, forming uniform emulsion particles. This avoids emulsion instability during the addition of the curing agent, thus preventing adverse effects on coating strength and appearance. Moreover, the sulfonate-modified polyaspartic ester resin demonstrates better strength and water resistance than the polyether-modified polyaspartic ester resin, and its curing, drying, and chemical resistance properties are comparable to solvent-based coatings.

[0011] Preferably, the hydroxyalkyl sulfonate in step (2) is selected from one or more of sodium hydroxymethyl sulfonate, sodium hydroxyethyl sulfonate, sodium 3-hydroxypropyl sulfonate, and sodium 4-hydroxybutyl sulfonate; the molar ratio of the hydroxyalkyl sulfonate added in step (2) to the dialkyl maleate added in step (1) is 1 to 2.5:1. If the amount of hydroxyalkyl sulfonate added is too small, the alkane group of the dialkyl maleate will be insufficiently substituted, resulting in decreased hydrophilicity; if the amount added is too large, it will cause a decrease in the proportion of secondary amines and hydroxyl groups in the dendritic resin, affecting the product performance.

[0012] Preferably, the reaction conditions in step (2) are as follows: a solution of polyaspartic acid ester and hydroxyalkyl sulfonate is mixed, a catalyst is added, and the transesterification reaction is carried out at 120-140°C for 4-8 hours. The solvent is then separated to obtain the aqueous polyaspartic acid ester resin.

[0013] Preferably, the catalyst is selected from one or more of sodium methoxide, triethylamine, and p-toluenesulfonic acid; the amount of catalyst added is 0.01 to 0.1% of the total mass of the reactants.

[0014] Preferably, in step (1), the molar ratio of dialkyl maleate to the amino group in the aliphatic polyamine is 1:0.95-1.

[0015] Preferably, the alkyl group in the dialkyl maleate ester in step (1) is selected from C1 to C8 straight-chain or branched alkyl groups; the aliphatic polyamine contains one of C5 to C8 straight-chain or branched alkyl groups, cycloalkyl groups or polyether groups.

[0016] Preferably, the dialkyl maleate mentioned in step (1) is selected from one or more of diethyl maleate, dimethyl maleate, di-n-propyl maleate, diisopropyl maleate, diisobutyl maleate, di-n-butyl maleate, di-sec-butyl maleate, di-tert-butyl maleate, di-n-pentyl maleate, diisopentyl maleate, and diisooctyl maleate; the aliphatic polyamine is selected from 4,4-diaminodicyclohexylmethane, 3, One or more of the following: 3-dimethyl-4,4-diaminodicyclohexylmethane, isophorone diamine, 1,6-hexanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 1-methyl-2,4-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,3-cyclopentanediamine, o-diaminomethylcyclopentane, and polyetheramine.

[0017] Preferably, the dialkyl maleate mentioned in step (1) is a mixture of dimethyl maleate and diethyl maleate, with a mass ratio of dimethyl maleate to diethyl maleate of 1:2 to 5. Dimethyl maleate and diethyl maleate facilitate transesterification, and the released methanol or ethanol is easy to handle. However, using dimethyl maleate alone will result in some dimethyl maleate crystallization, which is not conducive to the reaction. Therefore, the present invention uses an appropriate ratio of dimethyl maleate and diethyl maleate to react together, which can improve the performance of the obtained anionic waterborne polyaspartic acid ester resin.

[0018] Preferably, the reaction conditions in step (1) are as follows: the aliphatic polyamine and the antioxidant are mixed, and then the dialkyl maleate is added dropwise under nitrogen gas, and the reaction is carried out at 60-80°C for 8-30 hours to obtain polyaspartic acid ester; the amount of antioxidant added is 0.01-0.1% of the total mass of the reactants.

[0019] The present invention also provides an application of the anionic waterborne polyaspartic ester resin prepared by the above preparation method in a coating, wherein the coating comprises component A and component B, component A comprising the anionic waterborne polyaspartic ester resin and water; component B comprises a sulfonate-modified waterborne isocyanate curing agent.

[0020] Preferably, the sulfonate-modified waterborne isocyanate curing agent is selected from one or more of the following aminosulfonate-modified HDI trimers: Bayhydur Ultra 2487 / 1, Ultra 2547, Ultra 2655, Ultra 307, and Shiquanxing 202.

[0021] Preferably, by weight, component A comprises 40-80 parts of anionic waterborne polyaspartic ester resin, 0.1-1 parts of leveling agent, 0.1-1 parts of defoamer, and 20-60 parts of water.

[0022] Preferably, the mass ratio of component A to component B is 1 to 2.5:1.

[0023] Therefore, the present invention has the following beneficial effects:

[0024] (1) The prepared anionic waterborne polyaspartic acid ester resin has dendritic macromolecules with anionic sulfonic acid groups extending outwards and hydrophilic groups at the branch ends, which can achieve self-emulsification by using water as a solvent.

[0025] (2) The highly branched nature can also reduce the viscosity of the emulsion formed by water emulsification, allowing sufficient working time when used in PAE polyurea coatings;

[0026] (3) When used with sulfonate-modified waterborne isocyanate curing agents, it has better emulsification properties and can form uniform emulsion particles. It will not cause emulsion instability during the addition of curing agents, thus avoiding adverse effects on coating strength and appearance.

[0027] (4) Sulfonate-modified waterborne polyaspartic acid ester resin has better strength and water resistance than polyether-modified waterborne polyaspartic acid ester resin, and its curing, drying and water and chemical resistance properties are comparable to solvent-based coatings. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] In this invention, unless otherwise specified, all raw materials are available from the market or commonly used in the industry. The methods in the following embodiments are conventional methods in the field unless otherwise specified.

[0030] Example 1:

[0031] A method for preparing anionic aqueous polyaspartic acid ester resin, comprising the following steps:

[0032] (1) Add 4,4-diaminodicyclohexylmethane and antioxidant BHT to a reaction vessel, and add a mixture of dimethyl maleate and diethyl maleate dropwise under nitrogen gas. The molar ratio of the mixture of dimethyl maleate and diethyl maleate to the amino group in 4,4-diaminodicyclohexylmethane is 1:1, the molar ratio of dimethyl maleate to diethyl maleate is 1:4, and the amount of antioxidant added is 0.03 wt% of the total mass of the reactants. The Michael addition reaction is carried out at 70 °C for 20 hours to obtain polyaspartic acid ester.

[0033] (2) Add a toluene solution of sodium hydroxymethyl sulfonate to the obtained polyaspartic acid ester. The ratio of the number of moles of sodium hydroxymethyl sulfonate added to the total number of moles of the mixture of dimethyl maleate and diethyl maleate added in step (1) is 2:1. Then add 0.05% of p-toluenesulfonic acid as a catalyst and carry out the transesterification reaction at 130°C for 6 hours. Separate the solvent to obtain the anionic aqueous polyaspartic acid ester resin.

[0034] Example 2:

[0035] A method for preparing anionic aqueous polyaspartic acid ester resin, comprising the following steps:

[0036] (1) Add 4,4-diaminodicyclohexylmethane and antioxidant BHT to a reaction vessel, and add a mixture of dimethyl maleate and diethyl maleate dropwise under nitrogen gas. The molar ratio of the mixture of dimethyl maleate and diethyl maleate to the amino group in 4,4-diaminodicyclohexylmethane is 1:1, the molar ratio of dimethyl maleate to diethyl maleate is 1:4, and the amount of antioxidant added is 0.03 wt% of the total mass of the reactants. The Michael addition reaction is carried out at 70 °C for 20 hours to obtain polyaspartic acid ester.

[0037] (2) Add a toluene solution of sodium hydroxymethyl sulfonate to the obtained polyaspartic acid ester. The ratio of the number of moles of sodium hydroxymethyl sulfonate added to the total number of moles of the mixture of dimethyl maleate and diethyl maleate added in step (1) is 1:1. Then add 0.05% of p-toluenesulfonic acid as a catalyst and carry out the transesterification reaction at 130°C for 6 hours. Separate the solvent to obtain the anionic aqueous polyaspartic acid ester resin.

[0038] Example 3:

[0039] A method for preparing anionic aqueous polyaspartic acid ester resin, comprising the following steps:

[0040] (1) Add 4,4-diaminodicyclohexylmethane and antioxidant BHT to a reaction vessel, and add a mixture of dimethyl maleate and diethyl maleate dropwise under nitrogen gas. The molar ratio of the mixture of dimethyl maleate and diethyl maleate to the amino group in 4,4-diaminodicyclohexylmethane is 1:1, the molar ratio of dimethyl maleate to diethyl maleate is 1:2, and the amount of antioxidant added is 0.03 wt% of the total mass of the reactants. The Michael addition reaction is carried out at 70 °C for 20 hours to obtain polyaspartic acid ester.

[0041] (2) Add a toluene solution of sodium 3-hydroxypropyl sulfonate to the obtained polyaspartic acid ester. The ratio of the number of moles of sodium 3-hydroxypropyl sulfonate added to the total number of moles of the mixture of dimethyl maleate and diethyl maleate added in step (1) is 2.1:1. Then add 0.05% of p-toluenesulfonic acid as a catalyst and carry out transesterification reaction at 130°C for 6 hours. Separate the toluene to obtain the anionic aqueous polyaspartic acid ester resin.

[0042] Comparative Example 1 (without hydroxysulfonate modification):

[0043] A method for preparing polyaspartic acid ester resin includes the following steps: adding 4,4-diaminodicyclohexylmethane and antioxidant BHT to a reaction vessel; adding a mixture of dimethyl maleate and diethyl maleate dropwise under nitrogen purging, wherein the molar ratio of the mixture of dimethyl maleate and diethyl maleate to the amino group in 4,4-diaminodicyclohexylmethane is 1:1, the molar ratio of dimethyl maleate to diethyl maleate is 1:4, and the amount of antioxidant added is 0.03 wt% of the total mass of the reactants; and carrying out a Michael addition reaction at 70°C for 20 hours to obtain polyaspartic acid ester.

[0044] Comparative Example 2 (modified with polyether):

[0045] A method for preparing a polyether-modified waterborne polyaspartic acid ester resin, comprising the following steps:

[0046] (1) Add 4,4-diaminodicyclohexylmethane and antioxidant BHT to a reaction vessel, and add a mixture of dimethyl maleate and diethyl maleate dropwise under nitrogen gas. The molar ratio of the mixture of dimethyl maleate and diethyl maleate to the amino group in 4,4-diaminodicyclohexylmethane is 1:1, the molar ratio of dimethyl maleate to diethyl maleate is 1:2, and the amount of antioxidant added is 0.03 wt% of the total mass of the reactants. The Michael addition reaction is carried out at 70 °C for 20 hours to obtain polyaspartic acid ester.

[0047] (2) Add a toluene solution of MPEG100 to the obtained polyaspartic ester. The ratio of the number of moles of MPEG100 added to the total number of moles of the mixture of dimethyl maleate and diethyl maleate added in step (1) is 2.1:1. Then add 0.05% of p-toluenesulfonic acid as a catalyst and carry out transesterification reaction at 130°C for 6 hours. Separate the toluene to obtain the polyether modified waterborne polyaspartic ester resin.

[0048] Application Example 1:

[0049] A waterborne PAE polyurea coating comprises component A and component B. By weight, component A comprises 50 parts of the anionic waterborne polyaspartic ester resin prepared in Example 1, 0.2 parts of the leveling agent BYK-411, 0.3 parts of the defoamer TEGO-900, and 49.5 parts of water; component B is a sulfonate-modified waterborne isocyanate curing agent (Bayhydur 2547).

[0050] The preparation method of component A is as follows: anionic aqueous polyaspartic acid ester resin, leveling agent, and defoamer are added to a high-shear emulsifier, and an appropriate amount of water is added in batches for shear emulsification. This continues until all the water is added, resulting in a milky white emulsion with a bluish sheen.

[0051] The components of the waterborne PAE polyurea coatings in Application Examples 1-3 and Comparative Application Examples 1-4 are shown in the table below:

[0052]

[0053] Among them, Bayhydur 2547 is a sulfonate-modified waterborne isocyanate curing agent from Bayer, and Bayhydur 3100 is a polyether-modified waterborne isocyanate curing agent from Bayer.

[0054] The appearance, viscosity, emulsion appearance, and emulsion stability of component A in the above application examples and comparative application examples were tested (in accordance with GB / T11175-2002), and the results are shown in Table 1.

[0055] Table 1: Results of emulsification performance test of anionic waterborne polyaspartic acid ester resin.

[0056]

[0057]

[0058] In the above application examples and comparative application examples, components A and B were mixed evenly at a mass ratio of 1:1, and then a 100μm thick paint film was applied by roller coating. The performance was tested according to the requirements of GB / T 22374 for water-based coatings for floor coating materials. The results are shown in Table 2.

[0059] Table 2: Results of paint film performance tests.

[0060]

[0061] As can be seen from Tables 1 and 2, the coatings in Application Examples 1-3, which use the anionic waterborne polyaspartic ester prepared in this invention, exhibit good emulsifying properties and emulsion stability, and the paint film possesses good strength, hardness, water resistance, and weather resistance. The different proportions of hydrophilic functional groups in Application Examples 1 and 2 result in different emulsion particle sizes. Increasing the proportion of hydrophilic functional groups leads to smaller emulsion particle sizes, improved emulsifying properties, and increased coating hardness and adhesion strength; however, exceeding the substitution amount will negatively impact the coating performance.

[0062] In Comparative Example 1, no hydrophilic modification was performed on the polyaspartic ester, resulting in the inability to emulsify in water-based solvents as seen in Comparative Application Example 1. In Comparative Application Example 2, a mixture of polyether-modified waterborne polyaspartic ester resin and sulfonate-modified waterborne isocyanate curing agent was used. Due to poor compatibility between the two, the cured coating surface showed increased noise and slight color difference during roller coating. Simultaneously, the curing time was prolonged, and weather resistance decreased. In Comparative Application Example 3, a mixture of sulfonate-modified anionic waterborne polyaspartic ester resin prepared according to this invention and polyether-modified waterborne isocyanate curing agent resulted in prolonged curing time, reduced performance, and poor emulsification compatibility, leading to slight defects in the coating. In Comparative Application Example 4, a mixture of polyether-modified waterborne polyaspartic ester resin and polyether-modified waterborne isocyanate curing agent was used. Compared to the mixture of sulfonate-modified waterborne polyaspartic ester resin and sulfonate-modified waterborne isocyanate curing agent in the application examples, the coating appearance was flawless, but the coating hardness decreased sharply, and the coating exhibited loss of gloss and chalking.

Claims

1. Use of an anionic aqueous polyaspartate resin in a coating, characterized in that, The coating comprises component A and component B. Component A comprises anionic waterborne polyaspartic acid ester resin and water; component B comprises sulfonate-modified waterborne isocyanate curing agent. The preparation method of the anionic aqueous polyaspartic acid ester resin includes the following steps: (1) Polyaspartic acid ester was prepared by reacting aliphatic polyprimary amines with dialkyl maleate; (2) The obtained polyaspartic ester is subjected to transesterification reaction with hydroxyalkyl sulfonate to obtain the anionic aqueous polyaspartic ester resin.

2. Use of the anionic aqueous polyaspartate resin according to claim 1 in a coating, characterized in that, The hydroxyalkyl sulfonate mentioned in step (2) is selected from one or more of sodium hydroxymethyl sulfonate, sodium hydroxyethyl sulfonate, sodium 3-hydroxypropyl sulfonate, and sodium 4-hydroxybutyl sulfonate; the molar ratio of the hydroxyalkyl sulfonate added in step (2) to the dialkyl maleate added in step (1) is 2~2.5:

1.

3. Use of the anionic aqueous polyaspartate resin according to claim 1 or 2 in a coating, characterized in that, The reaction conditions in step (2) are as follows: a solution of polyaspartic acid ester and hydroxyalkyl sulfonate is mixed, a catalyst is added, and the transesterification reaction is carried out at 120~140℃ for 4~8 hours. The solvent is then separated to obtain the anionic aqueous polyaspartic acid ester resin.

4. Use of the anionic aqueous polyaspartate resin according to claim 1 in paints, characterized in that, In step (1), the molar ratio of dialkyl maleate to amino group in aliphatic polyamine is 1:0.95~1.

5. Use of the anionic aqueous polyaspartate resin according to claim 1 in paints, characterized in that, Its characteristics are, The alkyl group in the dialkyl maleate ester mentioned in step (1) is selected from C1 to C8 straight-chain or branched alkyl groups; the aliphatic polyprimary amine contains one of C5 to C8 straight-chain or branched alkyl groups, cycloalkyl groups or polyether groups.

6. Use of the anionic aqueous polyaspartate resin according to claim 1 in paints, characterized in that, The dialkyl maleate mentioned in step (1) is a mixture of dimethyl maleate and diethyl maleate, with a mass ratio of dimethyl maleate to diethyl maleate of 1:2~5.

7. Use of the anionic aqueous polyaspartate resin according to claim 1 in paints, characterized in that, The reaction conditions in step (1) are as follows: aliphatic polyamine and antioxidant are mixed, and then dialkyl maleate is added dropwise under nitrogen gas. The mixture is kept at 60-80°C for 8-30 hours to obtain polyaspartic acid ester. The amount of antioxidant added is 0.01-0.1% of the total mass of the reactants.

8. Use of the anionic aqueous polyaspartate resin according to claim 1 in a coating, characterized in that, The sulfonate-modified waterborne isocyanate curing agent is selected from one or more of the aminosulfonate-modified HDI trimers Bayhydur Ultra 2487 / 1, Ultra 2547, Ultra 2655, Ultra 307, and Shiquanxing 202.

9. Use of the anionic aqueous polyaspartate resin according to claim 1 in paints, characterized in that, By weight, component A comprises 40-80 parts of anionic waterborne polyaspartic ester resin, 0.1-1 parts of leveling agent, 0.1-1 parts of defoamer, and 20-60 parts of water.

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