A kind of polyaspartic acid ester resin and preparation method thereof

Abstract

The invention discloses a polyaspartic acid ester resin and a preparation method thereof, which belongs to the technical field of polyurea synthesis. The technical scheme thereof mainly includes the following steps: (1) stirring and heating 1 mol of maleic anhydride to 60-70°C, dripping 1.0-1.05 mol of alcohol thereto, reacting for 0.5-3h after the dripping is completed, and obtaining a maleic acid monoester; (2) adding a catalytic amount of a catalyst to the maleic acid monoester obtained in step (1) and mixing them uniformly, adding 350-400 g of glycidyl ester and mixing, and then reacting for 8-48h at a temperature of 80-150°C to obtain a modified maleate; (3) dripping 1-1.3 mol of alicyclic monoamine to the modified maleate obtained in step (2), reacting for 12-72h at a temperature of 60-80°C, and vacuuming to obtain a polyaspartic acid ester resin, thereby achieving the technical effect of no by-product generation during the reaction process and a simple preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurea synthesis, in particular to a polyaspartic acid ester resin and a preparation method thereof. Background Art

[0002] Polyaspartic acid ester resin reacts with isocyanate to form polyaspartic acid ester polyurea, referred to as aspartic acid polyurea. It is a new type of aliphatic, slow-reacting, high-performance coating material emerging in the polyurea industry and is known as the third-generation polyurea. It is solvent-free, low-viscosity, has a wide range of performance parameters, and a wide range of application scenarios. It is highly inclusive and can meet the needs of various coating processes. It is one of the best raw materials for making environmentally friendly coatings.

[0003] Polyaspartic acid resins are a class of secondary amine resins with an aspartic acid ester structure, prepared by the Michael addition reaction of maleic acid esters with primary amines. A defining characteristic of aspartic acid esters is that the secondary amine group in the aspartic acid ester structure is linked to the double-bonded carbon of the maleic acid ester, significantly reducing its activity due to the electron-withdrawing effect of the maleic acid ester carbonyl group at the β-position. Traditional polyaspartic acid ester resins are produced by the addition reaction of diethyl maleate with polyamines to form difunctional or polyfunctional aspartic acid ester structures. Industry research on polyaspartic acid ester resins primarily focuses on adjusting the polyamine structure, achieving polyaspartic acid ester resins with varying properties through the addition reaction of diethyl maleate with diamines, triamines, and other structures. The high cost of the polyamine materials used and the long preparation cycle of the addition reaction contribute to the high production cost of polyaspartic acid ester resins. Monoamines are inexpensive, but the monofunctional secondary amine obtained by adding monoamine to diethyl maleate cannot form a chain during the resin curing process. Therefore, the monoamine needs to be combined with a polyfunctional maleate to produce a polyfunctional secondary aspartamine. For example, the existing patent publication number CN110396053A discloses an aspart polyurea prepolymer and a preparation method thereof. The method comprises the following steps: first, preparing a dibasic maleate by reacting a diol with maleic anhydride; second, esterifying the dibasic maleate with an excess of an alkyl alcohol to produce the maleate; and third, reacting the maleate with an excess of a hindered amine to produce the prepolymer. However, this solution requires strong acid catalysis and separation of ethanol and water during the second step of alkyl alcohol esterification, which is still relatively difficult in actual production technology. The reasons are: since strong acids can corrode equipment, solid catalysts are often used, but the catalytic effect of solid catalysts is not as good as that of liquid acids. In addition, ethanol cannot be separated from water after it is mixed with water. Its dehydration and purification step requires special equipment, which increases costs. In addition, when the mixed ethanol cannot be dehydrated and recovered, new anhydrous ethanol needs to be continuously replenished, making the production cost relatively high. In addition, the second step of esterification easily causes the ester generated in the first step to undergo ester exchange, resulting in the disconnection of the dimaleate to a monomaleate. The monomaleate reacts with a monoamine to obtain a monoaspartic acid secondary amine. During the curing process of the polyaspartic acid ester resin, the monoaspartic acid secondary amine cannot form a chain, resulting in a dead end, which affects the coating performance of the polyurea resin coating. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a polyaspartic acid ester resin and a preparation method thereof, which can achieve the technical effects of no by-products generated during the reaction process and a simple preparation process.

[0005] The first aspect of the present invention provides a method for preparing a polyaspartic acid ester resin, which adopts the following technical solution:

[0006] A method for preparing a polyaspartic acid ester resin comprises the following steps:

[0007] (1) After stirring and heating 1 mol of maleic anhydride to 60-70°C, 1.0-1.05 mol of alcohol is added dropwise thereto. After the addition is complete, the reaction is continued for 0.5-3 hours to obtain a maleic acid monoester;

[0008] (2) adding a catalytic amount of a catalyst to the maleic acid monoester obtained in step (1) and mixing uniformly, then adding 350-400 g of glycidyl ester and mixing, and then reacting at a temperature of 80-150° C. for 8-48 hours to obtain a modified maleate;

[0009] (3) Add 1-1.3 mol of alicyclic monoamine dropwise to the modified maleate obtained in step (2), react at a temperature of 60-80° C. for 12-72 hours, and then evacuate to obtain a polyaspartic acid ester resin.

[0010] Preferably, the alcohol in step (1) is one of C1-C4 alkyl alcohols, such as anhydrous methanol, anhydrous ethanol, isopropanol, n-butanol, sec-butanol, and isobutanol. More preferably, the alcohol is anhydrous methanol or anhydrous ethanol.

[0011] Preferably, after the alcohol is added dropwise in step (1), the reaction is carried out at a temperature of 60-80°C.

[0012] Preferably, the added amount of the catalyst is 0.1-1% by weight of maleic anhydride.

[0013] Preferably, the catalyst is selected from one of Lewis acid and quaternary ammonium salt.

[0014] Preferably, the Lewis acid is boron trifluoride etherate.

[0015] Preferably, the glycidyl ester in step (2) is one of epoxidized soybean oil and epoxidized castor oil, and the epoxidized soybean oil has an epoxide value of ≥6.0%.

[0016] Preferably, the alicyclic monoamine is one of cyclohexylamine and 2-methylcyclohexylamine.

[0017] The second aspect of the present invention provides a polyaspartic acid ester resin obtained by the above-mentioned preparation method of the polyaspartic acid ester resin. The polyaspartic acid ester resin obtained in this application has the following typical structure:

[0018]

[0019] Wherein: R1 is one of C1-C4 alkyl groups, which can be one of methyl, ethyl, isopropyl, n-butyl, sec-butyl, and isobutyl;

[0020] R2 is cyclohexyl or 2-methylcyclohexyl.

[0021] In summary, the present invention has the following beneficial effects:

[0022] 1. The preparation method of the present application can obtain a polyaspartic acid ester resin with a functionality of 3-4, and the polyurea resin has good flexibility and elongation, and is suitable for preparing elastic polyurea coatings in combination with isocyanate prepolymers. It can also be used to improve the adhesion of conventional polyaspartic acid ester resin (F420, F520, etc.) coatings. When the polyaspartic acid ester resin obtained in the present application is used in combination with conventional polyaspartic acid ester resins (F420, F520), the flexibility of the coating can still reach 1 mm. The flexibility test is carried out in accordance with the relevant provisions of GB / T1731-1993 "Determination of Paint Film Flexibility". During the test, the painted tinplate is bent on mandrels of different diameters, and the minimum mandrel diameter (mm) that does not cause damage to the paint film after bending is used as the indicator.

[0023] 2. The preparation method of the polyaspartic acid ester resin provided in the present application directly undergoes Michael addition esterification of the epoxy group in the glycidyl ester with the carboxyl group and the carboxyl group in the maleic acid monoester to form a modified maleic acid ester. No by-products are produced in this process, and in the subsequent reaction process, the alicyclic monoamine preferentially reacts with the modified maleic acid ester in the same addition reaction to obtain the polyaspartic acid ester resin. Therefore, the overall yield of the reaction is high. Moreover, when the glycidyl ester is selected as epoxidized soybean oil or epoxidized castor oil, the cost is low, and the entire process can be completed in one reactor, which greatly simplifies the preparation process, reduces losses, and thus significantly reduces the production cost of the polyaspartic acid ester resin.

[0024] 3. When boron trifluoride ethyl ether is selected as the Lewis acid in this application, not only can the reaction efficiency of glycidyl ester and maleic acid monoester be guaranteed, but boron trifluoride ethyl ether also has no obvious corrosion to the equipment. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the examples.

[0026] The raw materials used in the examples and comparative examples of this application are all commercially available.

[0027] The embodiment of the present invention provides a method for preparing a polyaspartic acid ester resin, comprising the following steps:

[0028] (1) After stirring and heating 1 mol of maleic anhydride to 60-70°C, 1.0-1.05 mol of alcohol is added dropwise thereto. After the addition is complete, the reaction is continued for 0.5-1 hour to obtain a maleic acid monoester;

[0029] (2) adding a catalytic amount of a catalyst to the maleic acid monoester obtained in step (1) and mixing uniformly, then adding 350-400 g of glycidyl ester and mixing, and then reacting at a temperature of 80-150° C. for 8-48 hours to obtain a modified maleate;

[0030] (3) Add 1-1.3 mol of alicyclic monoamine dropwise to the modified maleate obtained in step (2), react at a temperature of 60-80° C. for 12-72 hours, and then evacuate to obtain a polyaspartic acid ester resin.

[0031] The reaction equations of the above steps (2) and (3) are as follows:

[0032]

[0033] Wherein: R1 is one of C1-C4 alkyl groups, such as one of methyl, ethyl, isopropyl, n-butyl, sec-butyl, and isobutyl;

[0034] R2 is cyclohexyl or 2-methylcyclohexyl.

[0035] Furthermore, after the alcohol is added dropwise in step (1), the reaction is carried out at a temperature of 60-80°C.

[0036] Furthermore, the added amount of the catalyst is 0.1-1% by weight of maleic anhydride.

[0037] Furthermore, the catalyst is selected from one of Lewis acid and quaternary ammonium salt.

[0038] Furthermore, the Lewis acid is selected as boron trifluoride etherate.

[0039] Furthermore, the glycidyl ester in step (2) is one of epoxidized soybean oil and epoxidized castor oil. Furthermore, the epoxidized soybean oil has an epoxidation value of ≥6.0%.

[0040] Furthermore, the alicyclic monoamine is one of cyclohexylamine and 2-methylcyclohexylamine.

[0041] Example 1

[0042] A method for preparing a polyaspartic acid ester resin comprises the following steps:

[0043] (1) After 1 mol (98 g) of maleic anhydride was heated to 60° C. with stirring, 1.0 mol (46 g) of anhydrous ethanol was added dropwise thereto while maintaining the stirring condition. After the addition was completed, the mixture was reacted at 60° C. for 1.5 hours to obtain a maleic acid monoester solution;

[0044] (2) adding boron trifluoride etherate in an amount equal to 0.1% by weight of maleic anhydride (i.e., 0.098 g) to the maleic acid monoester solution obtained in step (1) and mixing the mixture uniformly, then adding 350 g of epoxidized soybean oil having an epoxy value of 6.0% and mixing the mixture, and then reacting the mixture at 80° C. for 48 hours to obtain a modified maleate;

[0045] (3) After cooling the modified maleate obtained in step (2) to 60° C., 1.0 mol (99.2 g) of cyclohexylamine was added dropwise thereto in batches. The mixture was then reacted at 60° C. for 72 h. Low-boiling substances were removed by vacuum to obtain approximately 585.5 g of polyaspartic acid ester resin with a yield of 98.7%.

[0046] Example 2

[0047] A method for preparing a polyaspartic acid ester resin comprises the following steps:

[0048] (1) After 1 mol (98 g) of maleic anhydride was heated to 65° C. with stirring, 1.0 mol (74 g) of sec-butyl alcohol was added dropwise thereto. After the addition was completed, the mixture was reacted at 70° C. for 3 h to obtain a maleic acid monoester solution;

[0049] (2) adding boron trifluoride etherate in an amount equal to 0.1% by weight of maleic anhydride (i.e., 0.098 g) to the maleic acid monoester solution obtained in step (1) and mixing the mixture uniformly, then adding 350 g of epoxidized soybean oil having an epoxy value of 6.0% and mixing the mixture, and then reacting the mixture at 120° C. for 12 hours to obtain a modified maleate;

[0050] (3) After cooling the modified maleate obtained in step (2) to 60° C., 1.0 mol (99.2 g) of cyclohexylamine was added dropwise thereto. The mixture was then reacted at 80° C. for 24 h. Low-boiling substances were removed by vacuum to obtain approximately 612 g of polyaspartic acid ester resin with a yield of 98.5%.

[0051] Example 3

[0052] A method for preparing a polyaspartic acid ester resin comprises the following steps:

[0053] (1) After 1 mol (98 g) of maleic anhydride was heated to 70° C. with stirring, 1.0 mol (46 g) of anhydrous ethanol was added dropwise thereto. After the addition was complete, the mixture was reacted at 80° C. for 1 h to obtain a maleic acid monoester solution;

[0054] (2) adding boron trifluoride etherate in an amount equivalent to 0.1% by weight of maleic anhydride (i.e., 0.098 g) to the maleic acid monoester solution obtained in step (1) and mixing the mixture uniformly, then adding 350 g of epoxy castor oil and mixing the mixture, and then reacting the mixture at 150° C. for 8 h to obtain a modified maleate;

[0055] (3) After cooling the modified maleate obtained in step (2) to 60° C., 1.0 mol (99.2 g) of cyclohexylamine was added dropwise thereto. After reacting at 80° C. for 12 h, low-boiling substances were removed by vacuum to obtain about 577 g of polyaspartic acid ester resin with a yield of 97.3%.

[0056] Example 4

[0057] A method for preparing a polyaspartic acid ester resin comprises the following steps:

[0058] (1) After 1 mol (98 g) of maleic anhydride was heated to 65°C with stirring, 1.05 mol (48.3 g) of anhydrous ethanol was added dropwise thereto. After the addition was completed, the mixture was reacted at 70°C for 1 hour to obtain a maleic acid monoester solution;

[0059] (2) adding boron trifluoride etherate in an amount equal to 0.3% by weight of maleic anhydride (i.e., 0.29 g) to the maleic acid monoester solution obtained in step (1) and mixing the mixture uniformly, then adding 380 g of epoxidized soybean oil having an epoxy value of 6.0% and mixing the mixture, and then reacting the mixture at 120° C. for 12 h to obtain a modified maleate;

[0060] (3) After cooling the modified maleate obtained in step (2) to 60° C., 1.15 mol (114 g) of cyclohexylamine was added dropwise thereto, and then reacted at 80° C. for 24 h. Low-boiling substances were removed by vacuum to obtain about 620 g of polyaspartic acid ester resin with a yield of 96.8%.

[0061] Example 5

[0062] A method for preparing a polyaspartic acid ester resin comprises the following steps:

[0063] (1) After 1 mol (98 g) of maleic anhydride was heated to 65° C. with stirring, 1.05 mol (33.64 g) of anhydrous methanol was added dropwise thereto. After the addition was completed, the mixture was reacted at 70° C. for 0.5 h to obtain a maleic acid monoester solution;

[0064] (2) adding 1% (i.e., 0.98 g) of boron trifluoride etherate to the maleic anhydride solution obtained in step (1) and mixing the mixture uniformly, then adding 400 g of epoxidized soybean oil having an epoxy value of 6.0% and mixing the mixture, and then reacting the mixture at 120° C. for 12 h to obtain a modified maleate;

[0065] (3) After cooling the modified maleate obtained in step (2) to 60° C., 1.3 mol (147.2 g) of 2-methylcyclohexylamine was added dropwise thereto, and then reacted at 80° C. for 24 h. Low-boiling substances were removed by vacuum to obtain 645 g of polyaspartic acid ester resin with a yield of 94.9%.

[0066] Comparative Example 1

[0067] The polyaspartic acid ester resin is obtained by using the aspartic polyurea prepolymer and preparation method disclosed in Chinese patent CN110396053A and the technical solution of Example 1 in a coating.

[0068] Comparative Example 2

[0069] Conventional polyaspartic acid ester resin F420.

[0070] Comparative Example 3

[0071] Conventional polyaspartic acid ester resin F520.

[0072] Comparative Example 1

[0073] A method for preparing a polyaspartic acid ester resin is disclosed. The method differs from Example 1 in that the amount of epoxy soybean oil added in step (2) is 300 g. The remaining preparation steps and raw material amounts are the same as those in Example 1. The final polyaspartic acid ester resin obtained is about 534.5 g, with a yield of 98.4%.

[0074] Comparative Example 2

[0075] A method for preparing a polyaspartic acid ester resin is disclosed. The method differs from Example 1 in that the amount of epoxy soybean oil added in step (2) is 450 g. The remaining preparation steps and raw material amounts are the same as those in Example 1. The final polyaspartic acid ester resin obtained is about 685.4 g, with a yield of 98.8%.

[0076] Comparative Example 3

[0077] A method for preparing a polyaspartic acid ester resin is different from that of Example 1 in that, in step (2), boron trifluoride etherate in an amount corresponding to 0.1% by weight of maleic anhydride (i.e., 0.098 g) is added to the maleic acid monoester solution obtained in step (1), followed by uniform mixing. 350 g of epoxidized soybean oil having an epoxy value of 6.0% is then added and mixed, followed by reaction at 70° C. for 52 h to obtain a modified maleate. The remaining steps are the same as those of Example 1. Finally, about 583.2 g of the polyaspartic acid ester resin is obtained, with a yield of 98.3%.

[0078] Comparative Example 4

[0079] A method for preparing a polyaspartic acid ester resin is different from that of Example 1 in that, in step (2), boron trifluoride etherate in an amount corresponding to 0.1% by weight of maleic anhydride (i.e., 0.098 g) is added to the maleic acid monoester solution obtained in step (1), followed by uniform mixing. 350 g of epoxidized soybean oil having an epoxy value of 6.0% is then added and mixed, followed by reaction at 160° C. for 8 h to obtain a modified maleate. The remaining steps are the same as those of Example 1. Finally, about 580.4 g of the polyaspartic acid ester resin is obtained, with a yield of 97.9%.

[0080] Application Examples 1-5

[0081] The present application also provides a coating, which is prepared by mixing the polyaspartic acid ester resin obtained in Examples 1-5 with conventional polyaspartic acid ester resin F420 or conventional polyaspartic acid ester resin F520 to prepare Application Examples 1-5.

[0082] Comparative Application Examples 1-4

[0083] The polyaspartic acid ester resin obtained in Comparative Examples 1-4 was mixed with conventional polyaspartic acid ester resin F420 or conventional polyaspartic acid ester resin F520 to prepare Comparative Application Examples 1-4.

[0084] The components and contents of each coating are shown in Table 1.

[0085] Table 1 Components and contents of each coating (unit: g)

[0086]

[0087]

[0088] Note:

[0089] Since the polyaspartic acid ester resin prepared in this application has too high viscosity at room temperature, it is generally not used directly. Therefore, it needs to be used in combination with conventional polyaspartic acid ester resin F420 or conventional polyaspartic acid ester resin F520 for performance testing.

[0090] GB805A in Table 1 is a difunctional isocyanate prepolymer produced by Shenzhen Feiyang Junyan New Materials Co., Ltd., in which the NCO content is about 5%;

[0091] HT-600 is Wanhua's HDI trimer curing agent with an NCO content of approximately 23%.

[0092] Performance Testing

[0093] The paint films obtained from the above application examples, application control examples and application comparative examples were tested for hardness, flexibility, elongation, tensile strength and adhesion, wherein the elongation and tensile strength were tested in accordance with the provisions of GB / T16777-2008, and the adhesion was tested in accordance with the provisions of GB / T5210-2006 for the adhesion between the paint and the tile. The test results are shown in Table 2.

[0094] Table 2 Test results of various coating properties

[0095]

[0096]

[0097]

[0098] From Table 2 we can see that:

[0099] The polyaspartic acid resin obtained in Examples 1-4 was used in conjunction with conventional polyaspartic acid resin F420 to obtain coatings having good elongation and adhesion. This is because when the alicyclic monoamine was cyclohexylamine, the polyaspartic acid resin obtained had a high reactivity and could be directly cured with the difunctional prepolymer GB805A. Since GB805A is a linear long chain with a large molecular weight, the hardness of the cured coating was relatively low, the elongation was good, the tensile strength was slightly low, and the coating had good flexibility. However, when the alicyclic monoamine was 2-methylcyclohexylamine, the reactivity of the polyaspartic acid resin obtained was significantly reduced, making it difficult to directly cure with GB805A. Therefore, a curing agent with high reactivity was required. Therefore, after the polyaspartic acid resin obtained in Example 5 was cured by reaction with HT-600, it was found that the hardness and tensile strength of the coating obtained by the coating of Application Example 5 were better, but the elongation was lower. However, it can be seen from Table 2 that the elongation of the coatings obtained in Application Examples 1-5 of the present application is better than that in Application Control Examples 1-3.

[0100] Compared with Application Example 1, when the addition amount of epoxy soybean oil is less than 350 grams or greater than 400 grams, the elongation, tensile strength and adhesion of the coating obtained by Application Comparative Examples 1-2 are reduced. The reason is that when the amount of epoxy soybean oil is too low, the reaction of maleic acid monoester will be incomplete, and the subsequent presence of excess carboxylic acid will cause the Michael addition reaction to be hindered. In addition, the excess alicyclic monoamine is affected by the acid neutralization effect, resulting in subsequent difficulty in removal and a large amount of residue, which ultimately leads to a too short gel time of the product, which in turn affects the various properties of the coating; when the amount of epoxy soybean oil is too high, more common secondary amines will be generated, which will also significantly reduce the gel time of the product, and ultimately affect the various properties of the coating.

[0101] Compared with Application Example 1, when the reaction temperature of maleic acid monoester and epoxy soybean oil in step (2) is not within the range of this application, the elongation, tensile strength and adhesion of the coating obtained in Application Example 3-4 are lower than those in Application Example 1. The reason is that when the reaction temperature of maleic acid monoester and epoxy soybean oil is too low, the reaction time will be extended, and the esterification will be incomplete. A large part of the subsequent alicyclic monoamine will react with the epoxy group, and some will remain in the reaction system due to the neutralization effect of the carboxylic acid. The impurity content of the final polyaspartic acid ester resin is high. When the reaction temperature is higher than 150°C, the oil chain in the epoxy soybean oil will be oxidized and decomposed, which will also affect the performance of the final polyaspartic acid ester resin.

[0102] The embodiments of this specific implementation method are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a polyaspartic acid ester resin, characterized in that: The following steps are involved: (1) After stirring and heating 1 mol of maleic anhydride to 60-70° C., 1.0-1.05 mol of alcohol is added dropwise thereto, and after the addition is completed, the reaction is carried out at a temperature of 60-80° C. for 0.5-3 hours to obtain a maleic acid monoester; the alcohol is one of C1-C4 alkyl alcohols; (2) adding a catalytic amount of a catalyst to the maleic acid monoester obtained in step (1) and mixing uniformly, then adding 350-400 g of glycidyl ester and mixing, and then reacting at a temperature of 80-150° C. for 8-48 hours to obtain a modified maleate; the glycidyl ester is epoxidized soybean oil, and the catalyst is selected from one of a Lewis acid and a quaternary ammonium salt; (3) Add 1-1.3 mol of alicyclic monoamine dropwise to the modified maleate obtained in step (2), react at a temperature of 60-80° C. for 12-72 hours, and then evacuate to obtain a polyaspartic acid ester resin.

2. The method for preparing a polyaspartic acid ester resin according to claim 1, wherein: The added amount of the catalyst is 0.1-1% of the weight of maleic anhydride.

3. The method for preparing a polyaspartic acid ester resin according to claim 1, wherein: The Lewis acid is selected as boron trifluoride etherate.

4. The method for preparing a polyaspartic acid ester resin according to claim 1, wherein: The epoxy value of the epoxidized soybean oil is ≥6.0%.

5. The method for preparing a polyaspartic acid ester resin according to claim 1, wherein: The alicyclic monoamine is one of cyclohexylamine and 2-methylcyclohexylamine.

6. A polyaspartic acid ester resin obtained by the preparation method of the polyaspartic acid ester resin according to any one of claims 1 to 5, characterized in that: Including the following structural formula: Wherein: R1 is one of C1-C4 alkyl groups; R2 is cyclohexyl or 2-methylcyclohexyl.

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