Continuous crystallization method of 4, 4 '-diaminodiphenylmethane

Abstract

The invention provides a method for continuously crystallizing 4, 4 '-diaminodiphenylmethane. The method comprises the following steps: mixing a 4, 4 '-diaminodiphenylmethane crude product with a solvent, enabling the mixture to sequentially pass through a 1 # crystallization kettle, a 2 # crystallization kettle, a 3 # crystallization kettle, a 4 # crystallization kettle and a 5 # crystallization kettle at a set flow rate, and finally enabling the mixture to enter a centrifugal machine for solid-liquid separation to obtain the high-purity 4, 4'-diaminodiphenylmethane. The kettle-type continuous crystallization is realized, the crystallization efficiency is improved, the crystallization temperature change can be effectively controlled, the product crystal form is good, and the product purity is high.

Description

Technical Field

[0001] This invention belongs to the field of compound purification, and specifically relates to a method for continuous crystallization of 4,4'-diaminodiphenylmethane. Background Technology

[0002] 4,4'-Diaminodiphenylmethane (MDA), chemical formula C 13 H 14 N2, with a molecular weight of 198.26, is a symmetrical aromatic diamine compound. It exhibits a white to yellowish-brown flaky crystalline form at room temperature and pressure. When precipitated from water, it forms needle-like crystals, while when precipitated from benzene solvent, it forms flaky crystals. This substance is highly photosensitive, gradually deepening in color to black upon exposure to light. This is due to the oxidation of the amino group on the benzene ring under light to form a quinone structure. Its crystalline melting point is 89-91°C, its boiling point is 232°C (corresponding to a pressure of 2 mmHg), its density is approximately 1.15 g / cm³, and its flash point is as high as 221°C. These properties ensure its stability even under high-temperature processing conditions.

[0003] 4,4'-Diaminodiphenylmethane is one of the excellent curing agents for epoxy resins. It reacts with epoxy groups to form a three-dimensional cross-linked network structure, thereby endowing epoxy resin products with excellent heat resistance, mechanical strength, and chemical stability. During use, heating to 120-150°C is typically required to promote the curing reaction. As a curing agent, 4,4'-diaminodiphenylmethane is widely used in the production of composite materials, coatings, and adhesives. In the field of composite materials, it enhances the mechanical and heat resistance properties of materials, making them suitable for high-end applications such as aerospace and automotive manufacturing; in the field of coatings and adhesives, it improves the adhesion, abrasion resistance, and corrosion resistance of products.

[0004] As a key monomer or intermediate in the synthesis of polyurethane and polyimide, 4,4'-diaminodiphenylmethane plays a crucial role in the production of high-performance polymers. Polyurethane materials possess excellent elasticity, abrasion resistance, and chemical resistance, and are widely used in foam plastics, elastomers, adhesives, sealants, and coatings. Polyimide, with its superior high-temperature resistance, chemical corrosion resistance, and excellent electrical insulation properties, is widely used in high-end fields such as electronics, aerospace, and machinery. The use of 4,4'-diaminodiphenylmethane helps improve the performance of these polymers, meeting the high material requirements of various application areas.

[0005] 4,4'-Diaminodiphenylmethane is one of the important raw materials for dye manufacturing. In the dye industry, it can be used to produce various types of dyes, such as azo dyes. By reacting with different chemical substances, it can synthesize dye products with rich colors and diverse properties to meet the coloring needs of industries such as textiles, papermaking, and plastics. In addition, it can also be used to synthesize certain pesticide intermediates, thereby producing pesticide products with specific effects and supporting agricultural production.

[0006] In addition to the main applications mentioned above, 4,4'-diaminodiphenylmethane also has applications in other fields. For example, it can be used to produce insulating materials and Class H adhesives to meet the insulation and bonding performance requirements of the electronics and electrical industries; it can also be used to manufacture various polymer materials such as diisocyanates, polycarbonates, polysulfone resins, phenolic unsaturated resins, and polyetherimides, as well as products such as polyvinyl chloride heat stabilizers, plasticizers, agricultural fungicides, paints, and ultraviolet absorbers, providing basic raw materials and intermediates for different industries.

[0007] In summary, 4,4'-diaminodiphenylmethane, as an important chemical raw material, has wide and significant applications in multiple fields. Its use in polymer materials, rubber, dyes, pesticides, and analytical chemistry has not only driven the development of these industries but also provided strong support for modern industrial production and technological progress. With the continuous development of the chemical industry, the application scope of 4,4'-diaminodiphenylmethane is expected to further expand, and its application prospects in new material research and development, high-end manufacturing, and other fields will be even broader.

[0008] Currently, the industrial method for purifying 4,4'-diaminodiphenylmethane is distillation. The main isomer impurity is 2,4'-diaminodiphenylmethane. Since 2,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylmethane are isomers with very similar boiling points, they require distillation columns of 25 meters or more for partial separation and purification. The impurity content in the product is difficult to control below 0.3%, affecting product quality and resulting in high energy consumption and production costs. Although 2,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylmethane have small boiling points, their physicochemical properties differ. Recrystallization can be used for purification. Therefore, continuous recrystallization can achieve efficient purification of 4,4'-diaminodiphenylmethane. Summary of the Invention

[0009] This invention addresses the shortcomings of existing technologies for crystallizing 4,4'-diaminodiphenylmethane, such as low production efficiency, unstable yield, and unstable purity, by providing a continuous crystallization method for 4,4'-diaminodiphenylmethane. The method employs a continuous batch process for rapid cooling and crystallization of the 4,4'-diaminodiphenylmethane reflux solution.

[0010] The technical steps of this invention are as follows: crude 4,4'-diaminodiphenylmethane is mixed with a solvent and passed sequentially through crystallization kettles 1, 2, 3, 4, and 5 at a set flow rate. Finally, it enters a centrifuge for solid-liquid separation to obtain high-purity 4,4'-diaminodiphenylmethane.

[0011] The continuous reactor system consists of five crystallizing reactors (No. 1, No. 2, No. 3, No. 4, and No. 5) connected in series via overflow pipes. The slope of the overflow pipes is between 30° and 45°. The crystallizing reactors are made of enamel and have a volume of 5-10 m³. 3 .

[0012] The recrystallization solvent is one of tert-butanol, ethanol, 1,4-dioxane, 2-methyltetrahydrofuran, isopropanol, and n-butanol, preferably isopropanol.

[0013] The amount of recrystallization solvent added is 4-6 times that of 4,4'-diaminodiphenylmethane, and the flow rate is 350-500 kg / h, preferably 450 kg / h.

[0014] The stirring method of the crystallization vessel is one of paddle, screw, anchor, and propeller type, preferably propeller type; the stirring speed of crystallization vessel #1 is 200-300 r / min; the stirring speed of crystallization vessel #2 is 150-250 r / min; the stirring speed of crystallization vessel #3 is 100-150 r / min; the stirring speed of crystallization vessel #4 is 100-150 r / min; and the stirring speed of crystallization vessel #5 is 80-120 r / min.

[0015] The set temperature for crystallization reactor #1 is 75-80℃, for crystallization reactor #2 it is 60-65℃, for crystallization reactor #3 it is 50-55℃, for crystallization reactor #4 it is 30-35℃, and for crystallization reactor #5 it is 15-20℃.

[0016] The beneficial effects of this invention are:

[0017] (1) The device of the present invention is a continuous device, which improves the utilization rate of the crystallization vessel, ensures the stability of various process parameters during the production process, improves the crystallization efficiency of the product, ensures stable product quality, and the continuous operation greatly improves work efficiency and economic benefits.

[0018] (2) The obtained product crystal particles are uniform, which reduces the embedding of impurities and improves the purity and stability of the product.

[0019] (3) Continuous recrystallization consumes less energy, has lower investment costs, and higher production efficiency than distillation. Attached Figure Description

[0020] Figure 1 This is a flowchart of the continuous crystallization process;

[0021] Figure 2 Crystal diagram of continuous crystallization product;

[0022] Figure 3 This is a crystal diagram of an intermittent crystallization product. Detailed Implementation

[0023] Example 1:

[0024] Aniline (3000 kg) was transported to a 10 m... 3 In an enamel-lined reactor, with stirring started, hydrochloric acid (37%, 2000 kg) was added dropwise at room temperature over 5 hours. Then, formaldehyde aqueous solution (37%, 660 kg) was added dropwise over 6 hours, with the temperature not exceeding 25°C. After the addition was complete, the temperature was raised to 80°C and the reaction was maintained at this temperature for 10 hours. The reaction solution was then cooled to room temperature, and sodium hydroxide aqueous solution was added dropwise until the pH of the reaction solution reached 9. The mixture was allowed to stand and separate into layers. The organic phase was concentrated under vacuum to remove aniline, yielding crude 4,4'-diaminodiphenylmethane with a purity of 88.7%, 2.3% isomer impurities, and 9% polyamines.

[0025] Example 2:

[0026] Five 10 m units were used 3 Enameled crystallizers are connected in series, with material conveyed between them via overflow. The feed flow rate is controlled at 450 kg / h, flowing in from the inlet of crystallizer #1 and overflowing sequentially through crystallizers #2, #3, #4, and #5. The temperatures of crystallizers #1, #2, #3, #4, and #5 are controlled at 75-80℃, #2 at 60-65℃, #3 at 50-55℃, #4 at 30-35℃, and #5 at 15-20℃. After exiting crystallizer #5, the material is centrifuged and dried to obtain 4,4'-diaminodiphenylmethane with a purity of 99.3% and a yield of 87.5% (calculated based on the theoretical product amount fed into the crude product per unit time and the amount of pure product obtained).

[0027] Comparative Example 1

[0028] In a 250 mL flask, 50 g of crude 4,4'-diaminodiphenylmethane and 100 g of ethanol were added. The mixture was heated to 80 °C and kept at that temperature for 1 h. The temperature was then lowered to 15 °C, filtered, and dried to obtain a white solid. The yield was 82.5%, and the purity was 98.7%.

[0029] Comparative Example 2

[0030] In a 250 mL flask, 50 g of crude 4,4'-diaminodiphenylmethane, 150 g of ethylene glycol, and 150 g of N,N-dimethylformamide were added. The mixture was heated to 80 °C and held at that temperature for 1 h. The temperature was then lowered to 15 °C, filtered, and dried to obtain a white solid. The yield was 78.6%, and the purity was 99.0%.

[0031] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for continuous crystallization of 4,4'-diaminodiphenylmethane, characterized in that, The crude 4,4'-diaminodiphenyl methane is mixed with a solvent, and sequentially passes through a 1st crystallization kettle, a 2nd crystallization kettle, a 3rd crystallization kettle, a 4th crystallization kettle, and a 5th crystallization kettle at a set flow rate, and finally enters a centrifuge for solid-liquid separation to obtain high-purity 4,4'-diaminodiphenyl methane.

2. A method for continuous crystallization of 4,4'-diaminodiphenylmethane, characterized in that, The kettle continuous device is 1# crystallization kettle, 2# crystallization kettle, 3# crystallization kettle, 4# crystallization kettle, 5# crystallization kettle through overflow pipeline 5-stage series connection, the slope of the overflow pipeline is between 30°~45°;The material of the crystallization kettle is enamel;The volume of the crystallization kettle is 5-10 m 3 .

3. A method for continuous crystallization of 4,4'-diaminodiphenylmethane, characterized in that, The recrystallization solvent in the method is one of tert-butyl alcohol, ethanol, 1,4-dioxane, 2-methyltetrahydrofuran, isopropyl alcohol, and n-butanol.

4. A method for continuous crystallization of 4,4'-diaminodiphenylmethane, characterized in that, The recrystallization solvent is added in an amount of 4-6 times that of the 4,4'-diaminodiphenyl methane, and the flow rate is 350-500 kg / h.

5. A method for continuous crystallization of 4,4'-diaminodiphenylmethane, characterized in that, The stirring mode of the crystallization kettle is one of paddle type, screw type, anchor type, and propelling type; the stirring speed of the 1st crystallization kettle is 200-300 r / min; the stirring speed of the 2nd crystallization kettle is 150-250 r / min; the stirring speed of the 3rd crystallization kettle is 100-150 r / min; the stirring speed of the 4th crystallization kettle is 100-150 r / min; and the stirring speed of the 5th crystallization kettle is 80-120 r / min.

6. A method for continuous crystallization of 4,4'-diaminodiphenylmethane, characterized in that, The set temperature of the 1st crystallization kettle is 75-80℃, the set temperature of the 2nd crystallization kettle is 60-65℃, the set temperature of the 3rd crystallization kettle is 50-55℃, the set temperature of the 4th crystallization kettle is 30-35℃, and the set temperature of the 5th crystallization kettle is 15-20℃.

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