A method for purifying N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide

Abstract

The invention discloses a method for purifying N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide. Firstly, a solvent is added into a crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide to dissolve the crude product and reduce the viscosity of the solution; then an anti-solvent is added, and the difference in solubility of the anti-solvent to free amine and N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is utilized so that most of the free amine can smoothly enter the anti-solvent added subsequently, so that the free amine and N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide are separated and the free amine content is significantly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for purifying N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide. Background Art

[0002] N,N,N',N'-Tetrakis(β-hydroxypropyl)adipamide, chemical formula is C18H36N2O6, relative molecular weight is 376.49, trade name is curing agent 1260, white powder solid, its chemical structure is as follows:

[0003]

[0004] At present, the preparation method of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is generally synthesized under alkaline conditions using diisopropanolamine and dimethyl adipate as raw materials. However, since the raw material diisopropanolamine has a low aminolysis reaction activity, the synthetic product contains a large amount of diisopropanolamine raw materials, resulting in a high content of free amine in the product. Therefore, it is difficult to achieve a high yield and selectivity with conventional synthesis processes, and the by-products also increase the difficulty of the subsequent crystallization separation process, which is not conducive to product application.

[0005] At present, the commonly used separation and purification methods for such products are separation by solvent, such as separation by methanol / acetone mixed solvent system, or separation by non-solvent melt crystallization, etc. However, since N,N,N',N'-tetra(β-hydroxypropyl) adipamide and diisopropanolamine have a mutual solubilization effect, and since the crystallization performance of N,N,N',N'-tetra(β-hydroxypropyl) adipamide is poor, it takes several weeks to complete its crystallization in the mixture. Therefore, the above separation solvent system and melt crystallization method are not suitable for the separation and purification of N,N,N',N'-tetra(β-hydroxypropyl) adipamide products. Therefore, it is difficult to obtain products with lower free amine content by conventional solvent crystallization methods. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to provide a method for purifying N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide in view of the deficiencies of the prior art. The purification method of the present invention can separate free amine from N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide, and significantly reduce the free amine content in the N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product.

[0007] Technical solution: The purpose of the present invention is achieved through the following technical solution:

[0008] The present invention provides a method for purifying N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide, comprising the following steps:

[0009] (1) adding a solvent to a crude product of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide containing free amine, stirring and dissolving; the mass ratio of the solvent to the crude product of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is 1:(1-10);

[0010] (2) continuing to stir at a set temperature of 0-30° C., and when crystallization occurs, adding an anti-solvent dropwise while maintaining stirring until crystallization is complete; the mass ratio of the anti-solvent to the crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is (1-10):1;

[0011] (3) filtering to obtain crystals, which are dried to obtain N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product.

[0012] The crude N,N,N',N'-tetra(β-hydroxypropyl) adipamide in the present invention is a crude N,N,N',N'-tetra(β-hydroxypropyl) adipamide product synthesized by the prior art with a high free amine content, or a crude product still having a high free amine content after crystallization separation, wherein the free amine content in the crude product is 10 mgKOH / g to 90 mgKOH / g. Too high a free amine content means that more diisopropanolamine raw material remains, making the mutual solubilization effect between the diisopropanolamine and N,N,N',N'-tetra(β-hydroxypropyl) adipamide more obvious, thereby being unfavorable for crystallization separation.

[0013] The invention firstly adds a solvent into a crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide to dissolve the crude product and reduce the viscosity of the solution, then adds an anti-solvent, and utilizes the difference in solubility of the anti-solvent to free amine and N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide so that most of the free amine can smoothly enter the subsequently added anti-solvent, thereby completing the separation of the free amine and N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide.

[0014] A smaller amount of solvent added cannot reduce the viscosity of the crystallized material, while a larger amount of solvent added will significantly increase the amount of anti-solvent added, which is not conducive to the optimization of the process flow. The present invention finds that: under the above-mentioned amount of solvent, while ensuring the reduction of material viscosity, a better product purity can be achieved under the condition of a lower amount of anti-solvent added.

[0015] In order to ensure complete crystallization, in step (2), the temperature is set at 0-30°C.

[0016] In a preferred embodiment, during the crystallization process, the temperature is gradually reduced from 30°C to 0°C.

[0017] Since the crystallization rate of N,N,N',N'-tetra(β-hydroxypropyl) adipamide is slow, if the initial temperature is too low, after the anti-solvent is dripped, N,N,N',N'-tetra(β-hydroxypropyl) adipamide is not fully crystallized, and it is separated from the crystallization system, and it is easy to form a colloidal material, which is not conducive to the crystallization process. At the same time, more diisopropanolamine raw materials are entrained, and it is difficult to obtain a high-purity crystal product. Therefore, within the above temperature range, the crystals can be fully grown to form a powdery crystal product by gradually cooling the temperature, which is conducive to subsequent filtration and drying, and can maximize the crystallization of N,N,N',N'-tetra(β-hydroxypropyl) adipamide. At the beginning of crystallization, at a relatively high temperature, a certain amount of fine crystal nuclei can be formed. Since a certain amount of crystal nuclei already exist in the solution, as the temperature decreases, N,N,N',N'-tetra(β-hydroxypropyl) adipamide is gradually crystallized and wrapped around the existing crystal nuclei to form crystal grains, which gradually grow to form large grains. Compared with a single crystallization temperature, the gradual cooling method for crystallization can reduce the crystallization time and improve the product purity. Compared with a single crystallization temperature, the free amine value in the N,N,N',N'-tetra(β-hydroxypropyl) adipamide product crystallized by the gradual cooling method can be reduced by 5%-10%.

[0018] In order to fully dissolve the diisopropanolamine in the crude N,N,N',N'-tetra(β-hydroxypropyl) adipamide product, the mass ratio of the anti-solvent to the crude N,N,N',N'-tetra(β-hydroxypropyl) adipamide is (1-10): 1. If the amount of anti-solvent added is too low, a relatively viscous crystal slurry will be formed, which is not conducive to subsequent filtration and separation; although the anti-solvent has a low solubility in the N,N,N',N'-tetra(β-hydroxypropyl) adipamide product, too much anti-solvent will also increase the amount of N,N,N',N'-tetra(β-hydroxypropyl) adipamide dissolved in the crystallization system, which is not conducive to improving the crystallization yield.

[0019] Preferably, in step (1), the solvent is an alcohol solvent, an ether solvent, or a mixture of multiple alcohol solvents, or a mixture of an alcohol solvent and an ether solvent. That is, a single alcohol solvent or an ether solvent can be used as the solvent, or a mixture of multiple alcohol solvents can be used as the solvent, or a mixture of an alcohol solvent and an ether solvent can be used as the solvent.

[0020] Furthermore, the alcohol solvent is methanol, ethanol, n-propanol, isopropanol or n-butanol.

[0021] Furthermore, the ether solvent is 1,4-dioxane.

[0022] The addition of alcohol or ether solvents can reduce the viscosity of the crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product, facilitate the mixing of the anti-solvent and the crystallization material in the initial stage, and promote the crystallization process.

[0023] Preferably, in step (2), the anti-solvent is added dropwise for 5-24 hours.

[0024] As mentioned above, since the crystallization rate of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is slow, the anti-solvent dropping rate is too fast, which will also cause N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide to quickly separate from the crystallization system, thereby forming a colloidal substance, which is not conducive to the crystallization process; the anti-solvent dropping time is 5-24 hours. Under the said dropping time conditions, a high degree of crystallinity can be guaranteed, thereby reducing the entrainment of diisopropanolamine raw material and improving the purity of the crystallized product.

[0025] Preferably, in step (2), the anti-solvent is an alkylamine or a mixture of multiple alkylamines, that is, a single alkylamine or a mixture of multiple alkylamines can be used as the anti-solvent.

[0026] More preferably, the alkylamine is triethylamine, tripropylamine, triisopropylamine, N,N-dimethylethylamine, N-methyldiethylamine, N,N-dimethylisopropylamine, N-methyldiisopropylamine, N,N-diethylisopropylamine or N-methyldiethylamine.

[0027] Alkylamine solvents have a large solubility for diisopropanolamine, but a small solubility for N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide. By adding a certain amount of alkylamine solvents to the crystallization system, N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide can be gradually crystallized and precipitated, thereby achieving the purpose of separating free amine.

[0028] Beneficial effects:

[0029] The invention firstly adds a solvent into a crude N,N,N',N'-tetra(β-hydroxypropyl)adipamide to dissolve the crude product and reduce the viscosity of the solution, then adds an anti-solvent, utilizes the difference in solubility of the anti-solvent to free amine and N,N,N',N'-tetra(β-hydroxypropyl)adipamide, enables most of the free amine to smoothly enter the anti-solvent added subsequently, completes the separation of the free amine and N,N,N',N'-tetra(β-hydroxypropyl)adipamide, significantly reduces the free amine content in the N,N,N',N'-tetra(β-hydroxypropyl)adipamide product, and makes the free amine content of the product significantly lower than 8 mgKOH / g. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0031] Example 1

[0032] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 10.0 mgKOH / g, add 10.0 g of 1,4-dioxane, stir to dissolve, stir at 30°C, add 100.0 g of anti-solvent N-methyldiisopropylamine dropwise, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 74.0 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 4.2 mgKOH / g.

[0033] Example 2

[0034] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 10.0 mgKOH / g, add 10.0 g of 1,4-dioxane, stir to dissolve, stir at 30°C, gradually add 500.0 g of anti-solvent triethylamine, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 93.2 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 4.8 mgKOH / g.

[0035] Example 3

[0036] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 10.0 mgKOH / g, add 50.0 g of methanol, stir to dissolve, stir at 30°C, add 100.0 g of anti-solvent triethylamine dropwise, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 57.5 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 4.2 mgKOH / g.

[0037] Example 4

[0038] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 10.0 mgKOH / g, add 50.0 g of methanol, stir to dissolve, stir at 30°C, add 1000.0 g of anti-solvent N-methyldiethylamine dropwise, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 89.7 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 2.2 mgKOH / g.

[0039] Example 5

[0040] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 10.0 g of 1,4-dioxane, stir to dissolve, stir at 30°C, add 100.0 g of anti-solvent triethylamine dropwise, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 67.4 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 6.9 mgKOH / g.

[0041] Example 6

[0042] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 10.0 g of 1,4-dioxane, stir to dissolve, stir at 30°C, add dropwise a mixed solution of 200.0 g of triethylamine and 300.0 g of N,N-dimethylisopropylamine as an anti-solvent, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 72.3 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 5.0 mgKOH / g.

[0043] Example 7

[0044] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mg KOH / g, add 50.0 g of methanol, stir to dissolve, stir at 30°C, add 100.0 g of anti-solvent triethylamine dropwise, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 50.4 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 5.2 mg KOH / g.

[0045] Example 8

[0046] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide having a free amine content of 90.0 mgKOH / g, add 50.0 g of methanol, stir to dissolve, stir at 30°C, add dropwise a mixed solution of 100.0 g of triethylamine, 100.0 g of tripropylamine, 400.0 g of N-methyldiethylamine, 300.0 g of N-methyldiisopropylamine and 100.0 g of triisopropylamine as an anti-solvent, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 68.3 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product having a free amine content of 5.5 mgKOH / g.

[0047] Example 9

[0048] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 100.0 g of ethanol, stir to dissolve, stir at 30°C, add 1000.0 g of anti-solvent triethylamine dropwise, stir and crystallize for 24 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 66.2 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 5.7 mgKOH / g.

[0049] Example 10

[0050] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 25.0 g of methanol and 25.0 g of ethanol, stir to dissolve, stir at 30°C, add 1000.0 g of anti-solvent triethylamine dropwise, stir and crystallize for 24 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 71.5 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 4.9 mgKOH / g.

[0051] Embodiment 11

[0052] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 50.0 g of methanol, stir to dissolve, stir at 30°C, add dropwise a mixture of 500.0 g of anti-solvent triethylamine and 500.0 g of N-methyldiisopropylamine, stir and crystallize for 24 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 74.3 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 4.9 mgKOH / g.

[0053] Example 12

[0054] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 50.0 g of ethanol and 50.0 g of 1,4-dioxane, stir to dissolve, stir at 30°C, add 1000 g of anti-solvent triethylamine dropwise, stir and crystallize for 16 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 63.2 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 5.1 mgKOH / g.

[0055] Embodiment 13

[0056] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 100.0 g of ethanol, stir to dissolve, stir at 30°C, add 700 g of anti-solvent triethylamine dropwise, stir and crystallize for 16 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 62.1 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 6.2 mgKOH / g.

[0057] Embodiment 14

[0058] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 50.0 g of methanol, stir to dissolve, stir at 30°C, add 300 g of anti-solvent triethylamine dropwise, stir and crystallize for 5 hours, and gradually cool to 0°C. The slurry obtained after crystallization is centrifuged and dried to obtain 66.4 g of N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product with a free amine content of 3.5 mgKOH / g.

[0059] Comparative Example 1

[0060] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 90.0 mgKOH / g, add 50.0 g of methanol, stir to dissolve, stir at 0°C, add 300 g of anti-solvent triethylamine at one time, and stir to form a gelatinous substance that is difficult to separate.

[0061] Comparative Example 2

[0062] Take 100.0 g of crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide with a free amine content of 10.0 mgKOH / g, add 10.0 g of 1,4-dioxane, stir to dissolve, stir at 10°C, add 500.0 g of anti-solvent triethylamine at one time, and a colloid is formed after stirring, which is difficult to separate. After continuing to stir, a clump of material gradually forms on and around the stirring paddle, wrapping the stirring paddle and making it difficult to separate.

[0063] At present, there are no relevant national standards or industry standards for N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide products. According to the requirements of the relevant standard "Hydroxyalkylamide Curing Agent" for similar products, the free amine content (i.e., alkalinity) of qualified products should be lower than 8 mgKOH / g. The free amine content of the N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product obtained according to the technical solution of the present invention is significantly lower than 8 mgKOH / g.

[0064] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for purifying N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide, characterized in that: The steps include: (1) adding a solvent to a crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide containing free amine, stirring and dissolving; the mass ratio of the solvent to the crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is 1:(1-10); (2) continuing to stir at a set temperature of 0-30° C., and when crystallization occurs, adding an anti-solvent dropwise while maintaining stirring until crystallization is complete; the mass ratio of the anti-solvent to the crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is (1-10):1; (3) filtering to obtain crystals, which are dried to obtain N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product; In step (1), the solvent is an alcohol solvent, an ether solvent, or a mixture of multiple alcohol solvents, or a mixture of an alcohol solvent and an ether solvent; The alcohol solvent is methanol, ethanol, n-propanol, isopropanol or n-butanol; the ether solvent is 1,4-dioxane; In step (2), the anti-solvent is an alkylamine or a mixture of multiple alkylamines; The alkylamine is triethylamine, tripropylamine, triisopropylamine, N,N-dimethylethylamine, N,N-dimethylisopropylamine, N-methyldiisopropylamine, N,N-diethylisopropylamine or N-methyldiethylamine; In step (2), during the crystallization process, the temperature is gradually reduced from 30°C to 0°C; The crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide is a crude N,N,N',N'-tetrakis(β-hydroxypropyl)adipamide product synthesized by prior art with a high free amine content, or a crude product still having a high free amine content after crystallization separation, wherein the free amine content in the crude product is 10 mgKOH / g to 90 mgKOH / g.

2. The purification method according to claim 1, characterized in that In step (2), the anti-solvent is added dropwise for 5-24 hours.

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