A low-sensitization aspartic resin and a preparation method thereof

Abstract

The application provides a low-sensitization aspartic resin and a preparation method thereof, and relates to the technical field of aspartic resin. The low-sensitization aspartic resin comprises a secondary amino resin with a structure shown in the figure, and diethyl fumarate and / or diethyl maleate, and the content of the diethyl fumarate and / or diethyl maleate is not more than 0.5% of the weight of the aspartic resin. X is selected from divalent organic structures with an average molecular weight of 50-5000 that are inert to isocyanate groups at 100 DEG C after removing two primary amino groups from a diamine compound, Et represents an ethyl group, R1 is selected from C2-C8 alkyl groups, and the mole percentage of C4-C8 alkyl groups in R1 is not less than 10%. The aspartic resin provided by the application has no great change in curing performance, and is basically non-sensitizing.

Description

Technical Field

[0001] This invention belongs to the field of aspartic resin technology, and relates to a low-allergenic aspartic resin and its preparation method. Background Technology

[0002] Aspartic resin is typically prepared by a Michael addition reaction between dialkyl maleate and organic polyamines, with diethyl maleate being the most commonly used dialkyl maleate. To promote a more complete reaction of the organic polyamines and avoid the influence of residual primary amine groups on the curing time of the aspartic resin, an excess of diethyl maleate is usually added. However, under the reaction conditions used in the synthesis of aspartic resin, diethyl maleate gradually converts to diethyl fumarate, which has lower reactivity, leading to a slower reaction rate and an increase in residual diethyl maleate and diethyl fumarate. Diethyl maleate and diethyl fumarate are highly irritating to human skin, bronchial mucosa, and throat mucosa. Using the above method for preparing aspartic resin, the content of free diethyl maleate and / or diethyl fumarate in the aspartic resin can reach 2 wt% or even higher, which can cause strong sensitization to human skin, bronchial mucosa, and throat mucosa. Diethyl maleate has a boiling point of approximately 220°C at 1 atmosphere. Conventional vacuum distillation methods are insufficient to reduce the diethyl maleate content in aspartic resin to 2 wt% or less. To reduce free diethyl maleate and / or diethyl fumarate in aspartic resin, the industry generally employs short-path molecular distillation, which can reduce the content of free diethyl maleate and / or diethyl fumarate to 0.5 wt%. When the content of diethyl maleate and / or diethyl fumarate in aspartic resin does not exceed 0.5 wt%, its irritant and sensitizing effects on humans are very low. However, short-path molecular distillation suffers from problems such as expensive equipment, increased production cycles, and higher costs, which significantly restricts the application of aspartic resin and the development of the industry.

[0003] Therefore, the industry urgently needs to improve the current process methods to reduce equipment investment, improve production efficiency, and thus reduce the cost of aspartic resin. At the same time, the content of diethyl maleate and / or diethyl fumarate in aspartic resin should be controlled to no more than 0.5 wt% to avoid causing sensitization to the human body. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a low-allergenic aspartic resin and its preparation method.

[0005] The technical solution of the present invention is as follows:

[0006] A hypoallergenic aspartic resin comprises a secondary amino resin with the structure shown in formula (1) and diethyl fumarate and / or diethyl maleate comprising no more than 0.5% by weight of the aspartic resin.

[0007]

[0008] Wherein, X is selected from the divalent organic structure with an average molecular weight of 50-5000 that is reactive with isocyanate groups at 100℃ after the removal of two primary amino groups from a diamine compound; Et represents ethyl; R1 is selected from C2-C8 alkyl groups, wherein the molar percentage of C4-C8 alkyl groups in R1 is not less than 10%.

[0009] Preferably, the molar percentage of C4-C8 alkyl groups in R1 is not less than 20%.

[0010] Preferably, the sum of the weight percentages of the diethyl fumarate and the diethyl maleate in the aspartic resin does not exceed 0.5%.

[0011] Preferably, the diamine compound is selected from one or a combination of two or more of the following: 4,4'-diaminodicyclohexylmethane, 3,3'-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 polyetheramines.

[0012] A method for preparing a low-sensitivity aspartic resin according to any of the above embodiments: the diamine compound and diethyl maleate are added dropwise to the diamine compound under stirring, with a molar ratio of 1:0.5-0.95. After the addition is completed, the temperature is raised to 40-70°C for reaction. The reaction continues until the sum of the weight percentages of diethyl maleate and diethyl fumarate does not exceed 0.5%. Maleate ester with the structure shown in formula (2) is added, and the temperature is adjusted to 60-100°C for reaction for 24-96 hours. Then, the low-boiling substances are removed by vacuuming at 80-100°C to obtain the low-sensitivity aspartic resin.

[0013] R2OCOCH=CHCOOR2 (2)

[0014] R2 is selected from C4-C8 alkyl groups.

[0015] Preferably, R2 is selected from C4 alkyl groups.

[0016] Preferably, the diamine compound is selected from one or a combination of two or more of the following: 4,4'-diaminodicyclohexylmethane, 3,3'-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 polyetheramines.

[0017] Preferably, the molar ratio of the primary amino group to the diethyl maleate in the diamine compound is 1:0.5-0.9.

[0018] Preferably, the molar ratio of the primary amino group to the maleic ester in the diamine compound is 1:0.1-0.6.

[0019] Preferably, the ratio of the molar number of the primary amino group in the diamine compound to the sum of the molar numbers of the diethyl maleate and the maleate ester is 1:1-1.1.

[0020] The beneficial effects of this invention are:

[0021] (1) In the aspartic resin of the present invention, the ester structure of the secondary amino resin contains alkyl groups of C4 and above. By controlling the content of alkyl groups of C4 and above, the weight percentage of diethyl fumarate and / or diethyl maleate can be controlled to no more than 0.5% without affecting the performance of the aspartic resin, thus avoiding sensitization to the human body.

[0022] (2) In the preparation of the secondary amino resin of the present invention, by using an excess of diamine compound, the reaction between the diamine compound and diethyl maleate can be carried out at a relatively low temperature, thereby minimizing the conversion of diethyl maleate to diethyl fumarate, effectively increasing the reaction rate and promoting the complete reaction of diethyl maleate / diethyl fumarate. Moreover, the excess diamine compound can be reacted by adding maleate ester with the structure shown in formula (2) above. Even if a small amount of unreacted maleate ester remains in the aspartic resin, it will not cause sensitization to the human body. Detailed Implementation

[0023] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0024] To address the problems of sensitization caused by excessive diethyl maleate and / or diethyl fumarate content in aspartic resin prepared using diethyl maleate in existing technologies, and the high equipment investment, long production cycle, and low production efficiency resulting from using short-path molecular distillation to reduce the diethyl maleate and / or diethyl fumarate content in aspartic resin, the inventors unexpectedly discovered that maleate diol esters and fumarate diol esters prepared using C4 or higher alkyl alcohols as reaction raw materials have almost no irritation to human skin. Based on this, the present invention proposes a low-sensitivity aspartic resin, comprising a secondary amino resin with the structure shown in formula (1) and diethyl fumarate and / or diethyl maleate accounting for no more than 0.5% of the weight of the aspartic resin.

[0025]

[0026] Wherein, X is selected from the divalent organic structure of a diamine compound after the removal of two primary amino groups, which is reactive with isocyanate groups at 100℃ and has an average molecular weight of 50-5000; Et represents ethyl; R1 is selected from C2-C8 alkyl groups, and the molar percentage of C4-C8 alkyl groups in R1 is not less than 10%.

[0027] In this invention, the ester structure of the secondary amino resin shown in formula (1) contains a certain proportion of C4-C8 alkyl groups. Without affecting the curing performance of the aspartic resin, the content of diethyl fumarate and / or diethyl maleate in the aspartic resin does not exceed 0.5%, thereby avoiding sensitization to the human body.

[0028] In a preferred embodiment of the present invention, the molar percentage of C4-C8 alkyl groups in R1 is not less than 20%. For example, the molar percentage of C4-C8 alkyl groups in R1 can be any value from 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc., without particular limitation. For example, R1 can be a combination of ethyl and C4 alkyl groups in molar ratios of 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, etc. More preferably, the molar percentage of C4-C8 alkyl groups in R1 is not higher than 80%. Since C4-C8 alkyl groups have a longer chain length than ethyl groups and a stronger internal plasticizing effect, if the molar percentage of C4-C8 alkyl groups in R1 is too high, the tensile strength of the aspartic resin will decrease significantly, but the elongation at break will increase significantly.

[0029] In a preferred embodiment of the present invention, the sum of the weight percentages of diethyl fumarate and diethyl maleate in the aspartic resin does not exceed 0.5%. Both diethyl fumarate and diethyl maleate are sensitizing, and the lower the sum of the weight percentages of these two substances, the better. It is generally considered that a sum of weight percentages not exceeding 0.5% indicates very low sensitization to humans or essentially no sensitization to humans.

[0030] In a preferred embodiment of the present invention, the diamine compound is selected from one or a combination of two or more of the following: 4,4'-diaminodicyclohexylmethane, 3,3'-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 polyetheramines. The diamine compounds used in this invention are commonly used in the art and generally contain cycloalkylamines and polyetheramines. For example, polyetheramines can be polyetheramine D-230, polyetheramine D-400, polyetheramine D-2000, polyetheramine ED-600, polyetheramine ED-900, polyetheramine T-403, polyetheramine T-5000, etc., and can be purchased directly from the market.

[0031] In another aspect, the present invention proposes a method for preparing the low-sensitivity aspartic resin described in any of the above embodiments. The method involves slowly adding diethyl maleate dropwise to the diamine compound under stirring, according to a molar ratio of diamine compound to diethyl maleate of 1:0.5-0.95. After the addition is completed, the temperature is raised to 40-70°C for reaction. The reaction continues until the sum of the weight percentages of diethyl maleate and diethyl fumarate does not exceed 0.5%. Maleate ester with the structure shown in formula (2) is added, and the temperature is adjusted to 60-100°C for reaction for 24-96 hours. Then, the low-boiling-point substances are removed by vacuuming at 80-100°C to obtain the low-sensitivity aspartic resin.

[0032] R2OCOCH=CHCOOR2 (2)

[0033] R2 is selected from C4-C8 alkyl groups.

[0034] In the preparation of the present invention, an excess of diamine compound relative to diethyl maleate is first used, which has the following effects: (A) promoting the complete reaction of diethyl maleate; (B) lowering the reaction temperature and minimizing the conversion of diethyl maleate to diethyl fumarate, which has low reactivity; (C) increasing the reaction rate; then, the maleate ester shown in formula (2) is added to completely react the excess diamine compound and avoid the residual diamine compound affecting the operating time of the aspartic resin. In the present invention, the maleate ester shown in formula (2) is used, and the ester group is connected to a C4-C8 alkyl group. The maleate ester shown in formula (2) has a higher molecular weight and boiling point than diethyl maleate / diethyl fumarate and has very low sensitization to humans.

[0035] In the above preparation method of the present invention, the reaction process can be monitored by high performance liquid chromatography or gas chromatography. For specific operation methods of high performance liquid chromatography, please refer to the prior art "Determination of diethyl maleate by high performance liquid chromatography" (Zhejiang Chemical Industry, Vol. 37, No. 7, 2006, pp. 21-22).

[0036] In a preferred embodiment of the present invention, R2 is selected from C4 alkyl groups. The inventors unexpectedly discovered that using alkyl alcohols with higher carbon numbers during the synthesis of maleic acid diol esters and fumarate diol esters resulted in lower sensitization. For example, dibutyl maleate has a much lower sensitization rate than diethyl maleate, but its reactivity is also reduced; dibutyl maleate has lower reactivity than diethyl maleate. Considering both reactivity and sensitization to humans, selecting C4 alkyl groups for R2 is more suitable. Specifically, the C4 alkyl group can be n-butyl or isobutyl, and the maleate ester represented by formula (2) can be dibutyl maleate or diisobutyl maleate.

[0037] In a preferred embodiment of the present invention, the diamine compound is selected from one or a combination of two or more of the following: 4,4'-diaminodicyclohexylmethane, 3,3'-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 polyetheramines.

[0038] In a preferred embodiment of the present invention, the molar ratio of the primary amino group to diethyl maleate in the diamine compound is 1:0.5-0.9. For example, the molar ratio of the primary amino group to diethyl maleate in the diamine compound can be any value from 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, etc., without any particular limitation.

[0039] In a preferred embodiment of the present invention, the molar ratio of the primary amino group to the maleic ester in the diamine compound is 1:0.1-0.6. For example, the molar ratio of the primary amino group to the maleic ester in the diamine compound can be any value from 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, etc., without any particular limitation.

[0040] In a preferred embodiment of the present invention, the ratio of the molar number of the primary amino group in the diamine compound to the sum of the molar numbers of diethyl maleate and maleate ester is 1:1-1.1. The sum of the molar numbers of diethyl maleate and maleate ester is sufficient or excessive compared to the molar number of the primary amino group in the diamine compound, which can promote the complete reaction of the diamine compound and minimize the residue of the primary amino group. For example, the ratio of the molar number of the primary amino group in the diamine compound to the sum of the molar numbers of diethyl maleate and maleate ester can be any value from 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.05, 1:1.07, 1:1.08, 1:1, etc., without particular limitation.

[0041] The technical solutions of the present invention will be further described and explained below with reference to various embodiments.

[0042] Example 1

[0043] 210.4 g (1 mol) of 4,4'-diaminodicyclohexylmethane was added to a four-necked flask, followed by the slow dropwise addition of 275.5 g (1.6 mol) of diethyl maleate. After the addition was complete, the reaction was maintained at 45°C for 72 h. A sample was taken, and high-performance liquid chromatography (HPLC) was used to determine that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the reactants was 0.03%. Then, 136.8 g (0.6 mol) of diisobutyl maleate was added, and the reaction was continued at 75°C for another 96 h. The mixture was then vacuumed for 1 h at 80°C-85°C and -0.099 MPa to obtain a low-sensitivity aspartic resin. HPLC analysis showed that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the product was 0.14%.

[0044] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is about 40%.

[0045] Example 2

[0046] The difference between this embodiment and Example 1 is that in Example 1, the weight of diisobutyl maleate was adjusted from 136.8g to 114.2g (0.5mol). The remaining steps remained unchanged, and the combined weight percentage of diethyl maleate and diethyl fumarate in the obtained low-sensitivity aspartic resin, as determined by high-performance liquid chromatography, was 0.15%.

[0047] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is about 40%.

[0048] Example 3

[0049] 210.4 g (1 mol) of 4,4'-diaminodicyclohexylmethane was added to a four-necked flask, followed by the slow dropwise addition of 172.2 g (1 mol) of diethyl maleate. After the addition was complete, the reaction was maintained at 60 °C for 50 h. A sample was taken and analyzed by high-performance liquid chromatography (HPLC), revealing that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the reactants was 0.15%. Then, 251.3 g (1.1 mol) of diisobutyl maleate was added, and the reaction was continued at 80 °C for another 84 h. The mixture was then vacuumed for 1 h at 85 °C-90 °C and -0.099 MPa to obtain a low-sensitivity aspartic resin. HPLC analysis showed that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the product was 0.24%.

[0050] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is approximately 100%.

[0051] Example 4

[0052] 210.4 g (1 mol) of 4,4'-diaminodicyclohexylmethane was added to a four-necked flask, followed by the slow dropwise addition of 206.6 g (1.2 mol) of diethyl maleate. After the addition was complete, the reaction was maintained at 60 °C for 58 h. A sample was taken and analyzed by high-performance liquid chromatography (HPLC), revealing that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the reactants was 0.07%. Then, 228.3 g (1 mol) of diisobutyl maleate was added, and the reaction was continued at 90 °C for another 60 h. The mixture was then vacuumed for 1 h at 85 °C-90 °C and -0.099 MPa to obtain a low-sensitivity aspartic resin. HPLC analysis showed that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the product was 0.13%.

[0053] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is about 80%.

[0054] Example 5

[0055] 210.4 g (1 mol) of 4,4'-diaminodicyclohexylmethane was added to a four-necked flask, followed by the slow dropwise addition of 310 g (1.8 mol) of diethyl maleate. After the addition was complete, the reaction was maintained at 70 °C for 60 h. A sample was taken, and high-performance liquid chromatography (HPLC) was used to determine that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the reactants was 0.35%. Then, 57.1 g (0.25 mol) of diisobutyl maleate was added, and the reaction was continued at 90 °C for another 50 h. The mixture was then vacuumed for 1 h at 85 °C-90 °C and -0.099 MPa to obtain a low-sensitivity aspartic resin. HPLC analysis showed that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the product was 0.44%.

[0056] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is about 20%.

[0057] Comparative Example 1

[0058] 210.4 g (1 mol) of 4,4'-diaminodicyclohexylmethane was added to a four-necked flask, and 361.6 g (2.1 mol) of diethyl maleate was slowly added dropwise. After the addition was completed, the reaction was controlled at 60 °C for 96 h, and then vacuumed for 1 h at 130 °C-135 °C and -0.099 MPa to obtain aspartic resin. The weight percentage of diethyl maleate and diethyl fumarate in the aspartic resin product was determined by high performance liquid chromatography (HPLC) to be 2.4%, and the weight percentage of diethyl fumarate in the aspartic resin product was determined by HPLC to be 2.2%.

[0059] Example 6

[0060] 238.2 g (1 mol) of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane was added to a four-necked flask, followed by the slow dropwise addition of 275.5 g (1.6 mol) of diethyl maleate. After the addition was complete, the reaction was maintained at 70 °C for 72 h. A sample was taken, and high-performance liquid chromatography (HPLC) was used to determine that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the reactants was 0.04%. Then, 114.2 g (0.5 mol) of di-n-butyl maleate was added, and the reaction was continued at 90 °C for 55 h. The mixture was then vacuumed for 1 h at 85 °C-90 °C and -0.099 MPa to obtain a low-sensitivity aspartic resin. HPLC analysis showed that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the product was 0.15%.

[0061] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is about 40%.

[0062] Comparative Example 2

[0063] 238.2 g (1 mol) of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane was added to a four-necked flask, and 361.6 g (2.1 mol) of diethyl maleate was slowly added dropwise. After the addition was completed, the reaction was controlled at 70 °C for 96 h, and then vacuumed for 1 h at 130 °C-135 °C and -0.099 MPa to obtain aspartic resin. The weight percentage of diethyl maleate and diethyl fumarate in the aspartic resin product was determined by high performance liquid chromatography (HPLC) to be 2.5%, and the weight percentage of diethyl fumarate in the aspartic resin product was determined by HPLC to be 2.4%.

[0064] Example 7

[0065] 230 g (1 mol) of polyetheramine D-230 was added to a four-necked flask, followed by the slow dropwise addition of 240.1 g (1.4 mol) of diethyl maleate. After the addition was complete, the reaction was maintained at 65°C for 72 h. A sample was taken, and high-performance liquid chromatography (HPLC) was used to determine that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the reactants was 0.05%. Then, 136.8 g (0.6 mol) of diisobutyl maleate was added, and the reaction was continued at 80°C for another 72 h. The mixture was then vacuumed for 1 h at 90°C-95°C and -0.098 MPa to obtain a low-sensitivity aspartic resin. HPLC analysis showed that the sum of the weight percentages of diethyl maleate and diethyl fumarate in the product was 0.17%.

[0066] Based on the reaction results, the molar percentage of isobutyl in R1 of the secondary amino resin with the structure shown in formula (1) above is about 60%.

[0067] Performance test comparison

[0068] Prepare polyaspartic acid ester coatings according to the following formula.

[0069] Component A consists of 64% aspartic resin, 5% hydroxyl acrylic resin, 5% titanium dioxide, 25% barium sulfate, 0.2% dispersant, 0.4% defoamer, 0.2% leveling agent and 0.2% anti-settling agent.

[0070] Component B: Composed of an adduct curing agent prepared from 3% HDI trimer, 10% HMDI and 87% IPDI with polyether polyol.

[0071] Component A and component B were mixed uniformly in a ratio of 1:1.05, where the total molar content of secondary amine and hydroxyl groups in component A was equal to the molar content of isocyanate NCO groups in component B, to obtain a polyaspartic ester coating. The prepared polyaspartic ester coating was made into a film with a thickness of 0.5 mm and cured at 35±2℃ for 15 days. The testing methods and indicators were performed according to T / CWA204-2021 "Aspartic Polyurea Waterproof Coating Standard". The test performance data are shown in Table 1.

[0072] Table 1 Performance Data

[0073]

[0074] As can be seen from the data results in Table 1 above, the low-sensitivity aspartic resin of the present invention is similar in performance to the aspartic resin obtained by conventional preparation methods.

[0075] The low-sensitivity aspartic resin of this invention has a very low combined content of diethyl maleate and diethyl fumarate. Therefore, it can also be physically blended with existing aspartic resins (such as F420 resin and F520 resin from Feiyang Junyan) to reduce the content of diethyl maleate and diethyl fumarate in existing aspartic resins. While maintaining essentially the same curing performance, the sensitivity of the aspartic resin is significantly reduced.

[0076] The blending ratio of the low-allergenic aspartic resin of the present invention to existing aspartic resins can be 1:1, 2:1, etc. by weight. For example, in Example 1 of the present invention, the low-allergenic aspartic resin and F420 resin are blended at a weight ratio of 1:1. In the resulting aspartic resin composition, the sum of the weight percentages of diethyl maleate and diethyl fumarate can be reduced to 1.5% or less, such as 1.3% or 1.2%. Lower weight percentages of diethyl maleate and diethyl fumarate mean lower allergenicity. The curing properties of the aspartic resin composition are basically close to those of F420 resin, and the various performance indicators of the aspartic resin composition are basically within 95-105% of the performance indicators of F420 resin.

[0077] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-allergenic aspartic resin, characterized in that, The diamine compound and diethyl maleate were mixed in a molar ratio of 1:0.5-0.

95. The diethyl maleate was slowly added dropwise to the diamine compound under stirring. After the addition was completed, the temperature was raised to 40-70°C to react. The reaction continued until the weight percentage of diethyl maleate and diethyl fumarate did not exceed 0.5%. The maleate ester shown in the structure of formula (2) was added. The temperature was adjusted to 60-100°C and the reaction was carried out for 24-96 hours. Then, the low-boiling-point substances were removed by vacuuming at 80-100°C to obtain the low-sensitivity aspartic resin. R2OCOCH=CHCOOR2(2) R2 is selected from C4-C8 alkyl groups; The aspartic resin comprises a secondary amino resin with the structure shown in formula (1) and diethyl fumarate and / or diethyl maleate accounting for no more than 0.5% of the weight of the aspartic resin. （1） Wherein, X is selected from the divalent organic structure with an average molecular weight of 50-5000 that is reactive with isocyanate groups at 100℃ after the removal of two primary amino groups from a diamine compound; Et represents ethyl; R1 is selected from C2-C8 alkyl groups, wherein the molar percentage of C4-C8 alkyl groups in R1 is not less than 10%.

2. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, The molar percentage of C4-C8 alkyl groups in R1 is not less than 20%.

3. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, R2 is selected from C4 alkyl groups.

4. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, The sum of the weight percentages of the diethyl fumarate and the diethyl maleate in the aspartic resin does not exceed 0.5%.

5. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, The diamine compound is selected from one or more of 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, isophorone diamine, 1-methyl-2,4-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,3-cyclopentanediamine, and o-diaminemethylcyclopentane.

6. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, The molar ratio of the primary amino group to the diethyl maleate in the diamine compound is 1:0.5-0.

9.

7. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, The molar ratio of the primary amino group to the maleic ester in the diamine compound is 1:0.1-0.

6.

8. The method for preparing the low-sensitivity aspartic resin according to claim 1, characterized in that, The ratio of the molar number of the primary amino group in the diamine compound to the sum of the molar numbers of the diethyl maleate and the maleate ester is 1:1-1.1.

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