Separation membrane for post-processing and refining of epoxy resin production

Abstract

The invention discloses a separation membrane for post-treatment and refining of epoxy resin production, and relates to the technical field of membrane separation, the key points of the technical scheme are as follows: the separation membrane is an ultra-high molecular weight polyethylene porous membrane, the separation membrane is biaxially oriented or uniaxially oriented, the aperture of the separation membrane is 5-100 nm, and the thickness of the separation membrane is 0.05-20 [mu] m. According to the method, the pore diameter of the UHMWPE separation membrane is precisely designed according to the dissolution diameter of a solute contained in an epoxy resin reaction product in an organic solvent, and meanwhile, the pore diameter is precisely regulated and controlled by combining biaxial stretching with uniaxial stretching, so that impurities such as inorganic chlorine and organic byproducts in epoxy resin can be efficiently separated out, and the separation efficiency is improved. The high-efficiency separation process does not need repeated washing and multiple times of extraction, so that the generation of wastewater is reduced from the source, the wastewater treatment cost is reduced, the purification time is greatly shortened, the production efficiency is improved, and the production of the epoxy resin is more continuous and large-scale.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and more specifically, it relates to a separation membrane for the post-treatment and refining of epoxy resin production. Background Art

[0002] As a thermosetting resin material with excellent properties, epoxy resin has a wide range of applications in many fields. Its production process mainly includes steps such as raw material preparation, synthesis, and post-treatment and refining. In the raw material preparation stage, bisphenol A (BPA) and epichlorohydrin (ECH) are the main raw materials, and an alkaline catalyst such as sodium hydroxide (NaOH) is also required; in the synthesis stage, there are two methods, namely the one-step method and the two-step method. In the one-step synthesis, bisphenol A, epichlorohydrin, and an appropriate amount of sodium hydroxide are mixed and directly reacted at a certain temperature to form a preliminary epoxy resin; in the two-step method, an etherification reaction is first carried out to generate a chlorohydrin ether intermediate, and then an alkaline substance is added to promote the closure of the epoxy group to form an epoxy resin; the post-treatment and refining stage is crucial. After the reaction is completed, the product needs to be neutralized, desalted, the organic chlorine content is reduced, the solvent is removed by evaporation, and further purification and stabilization treatments are carried out. During this process, raw materials, unreacted monomers, catalysts, by-products, etc. may come into contact with water to form saline wastewater. To recover the resin and improve the purity, washing with water or extraction with other solvents is often required to separate the resin from sodium chloride, resulting in a large amount of high-concentration saline wastewater, which is complex to treat and has a high cost.

[0003] Currently, the purification of epoxy resin is mainly carried out by multiple extractions with toluene and water. However, this method still has the following deficiencies: on the one hand, the competitive dissolution relationship of inorganic chlorine in toluene and water causes a part of the inorganic chlorine to always dissolve in toluene, resulting in poor removal effect and the material properties not meeting the index requirements; on the other hand, repeated dissolution and multiple extractions not only generate a large amount of harmful wastewater, causing waste of resources and an increase in production costs, but also limit the purity of epoxy resin and reduce the yield.

[0004] Therefore, the present invention aims at a separation membrane for the post-treatment and refining of epoxy resin production to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide a separation membrane for the post-treatment and purification of epoxy resin production. According to the dissolved diameters of the solutes contained in the epoxy resin reaction products in organic solvents, the present invention accurately designs the pore diameters of the UHMWPE separation membrane, and at the same time uses biaxial stretching combined with uniaxial stretching to accurately regulate the pore diameters, so as to be able to efficiently separate impurities such as inorganic chlorine and organic by-products in the epoxy resin, significantly improve the purity of the epoxy resin. This efficient separation process does not require repeated water washing and multiple extractions, reduces the generation of wastewater from the source, reduces the wastewater treatment cost, greatly shortens the purification time, improves the production efficiency, and makes the production of epoxy resin more continuous and large-scale.

[0006] The above technical object of the present invention is achieved through the following technical solutions: A separation membrane for the post-treatment and purification of epoxy resin production, the separation membrane is a ultra-high molecular weight polyethylene porous membrane, the separation membrane is biaxially oriented or uniaxially oriented, the pore diameter of the separation membrane is 5 nm to 100 nm, and the thickness is 0.05 μm to 20 μm.

[0007] The present invention is further provided as: The porosity of the separation membrane is 60% to 95%.

[0008] The present invention is further provided as: The tensile strength of the separation membrane is at least 200 MPa.

[0009] The present invention also provides a device for purifying epoxy resin reaction products, including a separation membrane for the post-treatment and purification of epoxy resin production.

[0010] The present invention is further provided as: The separation membrane is at least one layer.

[0011] The present invention is further provided as: The device includes a vacuum pump.

[0012] In summary, the present invention has the following beneficial effects:

[0013] 1. By accurately regulating the pore diameter of the UHMWPE separation membrane, the present invention can efficiently separate impurities such as inorganic chlorine and organic by-products in the epoxy resin, significantly improve the purity of the epoxy resin. This efficient separation process does not require repeated water washing and multiple extractions, greatly shortens the purification time, improves the production efficiency, and makes the production of epoxy resin more continuous and large-scale;

[0014] 2. The present invention adopts the UHMWPE membrane separation technology, avoiding steps such as multiple water washing and solvent extraction, reducing the generation of wastewater from the source, reducing the wastewater treatment cost, reducing the environmental pollution, meeting the environmental protection requirements, and solving the problem that the traditional epoxy resin purification method will generate a large amount of saline wastewater, causing great pressure on the environment;

[0015] 3. The epoxy resin purified by using the UHMWPE separation membrane in the present invention has significantly reduced hydrolyzable chlorine content and total chlorine content, the product performance is more stable, the quality reaches a higher standard, which helps to improve the competitiveness of epoxy resin in high-end application fields and meet the market demand for high-quality epoxy resin;

[0016] 4. The present invention not only reduces the wastewater treatment link and saves the corresponding treatment cost, but also the efficient purification process improves the yield of epoxy resin, reduces the loss of raw materials, simplifies the production process flow, reduces equipment investment and operation cost, thus reducing the production cost of epoxy resin as a whole and improving the economic benefits of production enterprises;

[0017] 5. The UHMWPE separation membrane in the present invention has good mechanical properties and solvent resistance characteristics, can operate stably under relatively wide temperature, pressure and other conditions, is not easy to be damaged and has a long service life. Its operation process is relatively simple, easy to control and maintain, and has relatively low technical requirements for operators, which is conducive to large-scale popularization and application in industrial production;

[0018] 6. The present invention reduces the risk of environmental pollution by reducing wastewater discharge, and at the same time avoids the problem of volatile organic compound (VOCs) emissions that may be brought about by the use of a large amount of organic solvents in the traditional purification process, helps to create a cleaner and safer production environment, and conforms to the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the synthesis steps of epoxy resin in the embodiment of the present invention;

[0020] Figure 2 is a schematic diagram of the purification process of epoxy resin in the embodiment of the present invention;

[0021] Figure 3 is a schematic diagram for observing the surface pore structure of the separation membrane uniaxially stretched 144 times and the separation membrane biaxially stretched 144 times in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following will further describe the present invention in detail Figures 1 - 3 with reference to the attached

[0023] Example: A purification verification experiment of a separation membrane for post-treatment and refining in the production of epoxy resin

[0024] Experimental group 1:

[0025] Preparation of biaxially oriented UHMWPE separation membrane: UHMWPE powder (Celanese GUR4152) and mineral oil (Total A360B) were used, with a mass ratio of 1:9. After stirring and mixing at room temperature, they were extruded into a gel casting sheet at 180 °C using a twin-screw extruder;

[0026] The gel cast sheet was preheated at 120 °C for 120 seconds using a biaxial stretching device, biaxially stretched synchronously at a speed of 2% / s by 144 times, then the separation membrane was fixed with a carbon fiber mold frame, the mineral oil was removed with n-hexane, and the n-hexane was removed by freeze-drying to obtain the UHMWPE separation membrane.

[0027] Synthesis and purification of epoxy resin: Dicyclopentadienyl phenol and epichlorohydrin were added to a three-necked flask with a mass ratio of 1:6, nitrogen was continuously introduced, and the flow rate was maintained at 0.02 until the reaction material tumbled; it was stirred at 50 °C for 20 min to mix evenly, and 49% NaOH aqueous solution with a total amount of 0.5 wt% was added dropwise, and the etherification reaction was carried out for 2 h; the temperature was raised to 70 °C, and then 49% NaOH aqueous solution with 1.8 times the amount of phenolic hydroxyl groups was added dropwise using a dropping funnel, and the dropping was completed in 30 min. The ring-closure reaction was calculated for 4 h from the start of adding the alkali solution;

[0028] After washing with water to remove salts, liquid separation was carried out, and the lower-layer epichlorohydrin phase was collected, and vacuum distillation was carried out, controlling the temperature at 120 °C and the pressure at 10 - 30 mbar. When no liquid dripped out, it was pumped for another 30 min;

[0029] The organic phase was dissolved with methyl isobutyl ketone 4 times the amount of phenol, and separated using the UHMWPE separation membrane under a pressure of 1 Mpa to obtain dicyclopentadiene epoxy resin.

[0030] Experimental group 2:

[0031] Preparation of biaxially oriented UHMWPE separation membrane: UHMWPE powder (Celanese GUR4152) and mineral oil (Total A360B) with a mass ratio of 1:9 were used. After stirring and mixing at room temperature, it was extruded into a gel cast sheet at 180 °C using a twin-screw extruder;

[0032] The gel cast sheet was first preheated at 120 °C for 120 seconds using a biaxial stretching device, biaxially stretched synchronously at a speed of 2% / s by 16 times, then uniaxially stretched restrictedly at 125 °C at a speed of 0.7% / s by 9 times, totaling 144 times. Then the separation membrane was fixed with a carbon fiber mold frame, the mineral oil was removed with n-hexane, and the n-hexane was removed by freeze-drying to obtain the UHMWPE separation membrane.

[0033] Synthesis and purification of epoxy resin: Dicyclopentadienyl phenol and epichlorohydrin were added to a three-necked flask with a mass ratio of 1:6, nitrogen was continuously introduced, and the flow rate was maintained at 0.02 until the reaction material tumbled; it was stirred at 50 °C for 20 min to mix evenly, and 49% NaOH aqueous solution with a total amount of 0.5 wt% was added dropwise, and the etherification reaction was carried out for 2 h; the temperature was raised to 70 °C, and then 49% NaOH aqueous solution with 1.8 times the amount of phenolic hydroxyl groups was added dropwise using a dropping funnel, and the dropping was completed in 30 min. The ring-closure reaction was calculated for 4 h from the start of adding the alkali solution;

[0034] After desalting by washing with water, liquid separation is carried out, the lower layer of epichlorohydrin phase is collected, and vacuum distillation is carried out. Control the temperature at 120 °C and the pressure at 10 - 30 mbar. When no liquid drips out, pump for another 30 min.

[0035] Dissolve the organic phase with methyl isobutyl ketone which is 4 times the amount of phenol, and separate it with a UHMWPE separation membrane under a pressure of 1 Mpa to obtain dicyclopentadiene epoxy resin.

[0036] Experimental group 3:

[0037] Synthesis and purification of epoxy resin: Add dicyclopentadiene phenol and epichlorohydrin to a three-necked flask with a mass ratio of 1:6. Continuously introduce nitrogen with a flow rate maintained at 0.02 until the reaction material tumbles; stir at 50 °C for 20 min to mix evenly, add 49% NaOH aqueous solution with a total amount of 0.5 wt%, and carry out etherification reaction for 2 h; raise the temperature to 70 °C, then use a dropping funnel to add 49% NaOH aqueous solution which is 1.8 times the amount of phenolic hydroxyl groups, finish dropping in 30 min, and calculate the ring-closure reaction for 4 h starting from the start of adding the alkali solution.

[0038] After desalting by washing with water, liquid separation is carried out, the lower layer of epichlorohydrin phase is collected, and vacuum distillation is carried out. Control the temperature at 120 °C and the pressure at 10 - 30 mbar. When no liquid drips out, pump for another 30 min.

[0039] Dissolve the organic phase with methyl isobutyl ketone which is 4 times the amount of phenol, and filter with medium-speed filter paper under a pressure of 1 Mpa to obtain dicyclopentadiene epoxy resin.

[0040] Control group 1:

[0041] Synthesis and purification of epoxy resin: Add dicyclopentadiene phenol and epichlorohydrin to a three-necked flask with a mass ratio of 1:6. Continuously introduce nitrogen with a flow rate maintained at 0.02 until the reaction material tumbles; stir at 50 °C for 20 min to mix evenly, add 49% NaOH aqueous solution with a total amount of 0.5 wt%, and carry out etherification reaction for 2 h; raise the temperature to 70 °C, then use a dropping funnel to add 49% NaOH aqueous solution which is 1.8 times the amount of phenolic hydroxyl groups, finish dropping in 30 min, and calculate the ring-closure reaction for 4 h starting from the start of adding the alkali solution.

[0042] After desalting by washing with water, liquid separation is carried out, the lower layer of epichlorohydrin phase is collected, and vacuum distillation is carried out. Control the temperature at 120 °C and the pressure at 10 - 30 mbar. When no liquid drips out, pump for another 30 min.

[0043] Dissolve it by adding methyl isobutyl ketone which is 4 times the amount of phenol, add pure water which is 1 time the amount of phenol, wash with water to remove salts, and obtain the upper organic phase. Add NaOH (49%) which is 30% of the amount of phenol to the upper organic phase, and carry out a refining reaction at 90 °C for 2 h; the added pure water is 1 time the amount of phenol, keep it warm at 90 °C for 10 min, wash away the generated salts, then carry out a liquid separation operation, repeat the operation 5 times, and add sodium dihydrogen phosphate which is 0.5 wt% of the amount of phenol to neutralize the resin to be neutral during the third liquid separation; distill off methyl isobutyl ketone under reduced pressure, at a temperature of 130 °C and a pressure of 10 - 30 mbar. When no liquid drips out, take samples every 10 min. When the resin can harden at room temperature, test its softening point, and stop the reduced pressure distillation operation when it meets the specified value to obtain dicyclopentadiene epoxy resin.

[0044] Experimental data:

[0045] Test the final dicyclopentadiene epoxy resin products obtained in the above Experimental Group 1, Experimental Group 2, Experimental Group 3 and Control Group 1, and the results are shown in Table 1:

[0046] Table 1 Test Table of Dicyclopentadiene Epoxy Resin Products

[0047]

[0048] As can be seen from Table 1, the epoxy resin products obtained in Experimental Group 1 and Experimental Group 2 purified by using the UHMWPE separation membrane of the present invention show good performance in terms of epoxy equivalent, softening point, melt viscosity, etc., and the hydrolyzable chlorine content and total chlorine content are significantly lower than those in Control Group 1, indicating that the separation membrane of the present invention can effectively improve the purity of epoxy resin and reduce the content of harmful impurities. While in Experimental Group 3, the traditional filter paper filtration method is adopted, and the product purity and performance are not as good as those of the examples using the separation membrane, further verifying the superiority of the present invention.

[0049] In addition, as Figure 3 shown, observe the surface pore structure of the separation membrane biaxially stretched 144 times and the separation membrane uniaxially stretched 144 times, and it is found that there is a certain relationship between the stretching ratio and the rejection molecular weight, as shown in Table 2 specifically:

[0050] Table 2 Relationship Table between Stretching Ratio and Rejection Molecular Weight

[0051] Stretching ratio Thickness (μm) Molecular weight cut-off Unstretched 95 300 Biaxially stretched 16 times 22.5 400 Biaxially stretched 16 times and then uniaxially stretched 9 times 1.2 150 Biaxially stretched 144 times 1.2 200

[0052] As can be seen from Table 2, through the combined method of biaxial stretching and uniaxial stretching, the pore size and rejection molecular weight of the UHMWPE separation membrane can be effectively regulated, so as to meet the requirements of different epoxy resin purifications, and further improve the practicability and flexibility of the present invention.

[0053] In summary, the UHMWPE membrane separation technology removes chloride ions and organic by-products in epoxy resin products to purify epoxy resin, significantly reducing wastewater generation. The hydrolyzable chlorine content and total chlorine content in the purified epoxy resin are significantly decreased. The separation efficiency is increased and the epoxy resin yield is improved.

[0054] This specific embodiment is only an explanation of the present invention and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A separation membrane for the post-treatment and refining of epoxy resin production, characterized in that: The separation membrane is a porous ultra-high molecular weight polyethylene membrane, the separation membrane is biaxially oriented or uniaxially oriented, the pore size of the separation membrane is 5 nm to 100 nm, and the thickness is 0.05 μm to 20 μm.

2. The separation membrane for post-treatment and refining in epoxy resin production according to claim 1, characterized in that: The porosity of the separation membrane is 60% to 95%.

3. The separation membrane for post-treatment and refining in epoxy resin production according to claim 1, characterized in that: The tensile strength of the separation membrane is at least 200 MPa.

4. An apparatus for purifying epoxy resin reaction products, characterized in that: It includes a separation membrane for post-treatment and refining in epoxy resin production as described in claim 1.

5. The device for purifying epoxy resin reaction products according to claim 4, characterized in that: The separation membrane is at least one layer.

6. The device for purifying epoxy resin reaction products according to claim 4, wherein: The device includes a vacuum pump.

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