A low-chlorine bisphenol A epoxy resin and its preparation method and application

Abstract

The present invention relates to a low-chlorine bisphenol A epoxy resin and a preparation method and application thereof, and relates to the technical field of epoxy resin refining. The preparation method comprises the following steps: preparing an aqueous phase: mixing an alkali, an emulsifier, and an emulsion stabilizer to prepare an aqueous phase; preparing an oil phase: mixing an epoxy resin and a solvent, stirring, and preparing an oil phase; preparing a low-chlorine bisphenol A epoxy resin: mixing the oil phase and the aqueous phase, homogenizing, forming an O / W type Pickering emulsion, adding a catalyst, heating in a water bath, stirring, extracting and separating with an extraction solvent, obtaining an organic phase, removing the organic solvent, and obtaining a low-chlorine bisphenol A epoxy resin. The preparation method has a simple and convenient process, good controllability, green environmental protection, low production cost, and the prepared low-chlorine bisphenol A epoxy resin has a lower total chlorine content.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy resin refining, in particular to a low-chlorine bisphenol A epoxy resin and a preparation method and application thereof. Background Art

[0002] Bisphenol A epoxy resin is a polymer compound formed by the polycondensation of bisphenol A and epichlorohydrin under alkaline conditions. The cured epoxy resin has excellent properties, such as chemical corrosion resistance, high mechanical strength and good electrical insulation, and is therefore widely used in coatings, adhesives, potting and electronic casting. However, during the curing process, when the cross-linking density of the epoxy resin is high, it will also lead to large internal stress, causing defects in toughness, heat resistance and impact resistance, which to a certain extent restricts the application scope of bisphenol A epoxy resin.

[0003] During the synthesis of bisphenol A epoxy resin, side reactions will occur in both the epichlorohydrin etherification stage and the dehydrochlorination cyclization stage, making it difficult for the reaction to be complete, and ultimately leading to the formation of organic chlorine, that is, the presence of hydrolyzed chlorine and non-hydrolyzed chlorine in the finished resin. These residual chlorine contents will reduce the crosslinking density of the epoxy resin cured product, which is manifested as a decrease in the heat deformation temperature. It is worth mentioning that when the heating temperature is higher than the heat deformation temperature, the adverse effects caused include increased high-temperature dielectric loss and reduced high-temperature volume resistance. Therefore, in order to ensure that the insulation level and electrical performance meet the standard requirements, improving the purity of epoxy resin and reducing the content of organic chlorine have also attracted widespread attention and research from scientific researchers.

[0004] At present, the quality of epoxy resin is improved mainly by optimizing the synthesis process, reducing the "hydrolyzed chlorine" compounds generated by incomplete main reaction and the "non-hydrolyzed chlorine" compounds generated by side reactions. For example, a two-step heat preservation method is used to first perform a pre-ring-opening reaction, and then liquid alkali is added twice under different reaction conditions to perform a growth reaction and a ring-closing reaction. The chlorine content of the synthesized epoxy resin is below 450ppm, and the epoxy value is below 0.51moL / 100g. Compared with the various data of the epoxy resin in the comparative example, this technology effectively improves the quality of the epoxy resin obtained; some researchers also use non-protonic polar solvents as co-solvents, use 1.0-2.5mm solid alkali metal hydroxides as catalysts, and react phenol or alcohol raw materials with epichlorohydrin in one step. This preparation process not only reduces the water content in the reaction system, but also avoids the increase of by-products and other problems, and finally synthesizes an epoxy resin with a total chlorine content of less than 200ppm. Secondly, there are many studies that use post-treatment refining and washing technology to achieve the purpose of reducing the chlorine content of epoxy resin. In the refining stage, the epoxy resin is placed in a refined alkaline environment in the presence of a co-catalyst for reaction. In the water washing stage, the pH value of the solution is adjusted to neutral with analytical water and pure water, and the organic solvent is removed to obtain a bisphenol A type liquid epoxy resin with a hydrolyzable chlorine content of less than 0.030% and an inorganic chlorine content of less than 0.001%. Other researchers have polarized the organic chlorine and reduced metal in the epoxy resin in an electromagnetic field by combining crude epoxy resin with a carbonized MOFs material with reduced metals to increase the reaction activity of the two. The epoxy resin is used as the mobile phase to flow through the MOFs material as the stationary phase reactant. The two come into contact and react, and the chlorine content of the epoxy resin can be effectively reduced. However, most of the above-mentioned process methods have the problems of complex processes, difficulty in industrial promotion, or poor controllability. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a low-chlorine bisphenol A epoxy resin. The preparation method has a simple and convenient process, good controllability, is green and environmentally friendly, and has low production cost. The prepared bisphenol A epoxy resin has a lower total chlorine content.

[0006] In order to achieve the above object, the present invention provides a method for preparing a low-chlorine bisphenol A epoxy resin, comprising the following steps:

[0007] Preparing an aqueous phase: mixing alkali, water, an emulsifier, and an emulsion stabilizer to prepare an aqueous phase;

[0008] Preparing the oil phase: mixing the epoxy resin and the solvent, stirring, and preparing the oil phase;

[0009] Preparation of low-chlorine bisphenol A epoxy resin: mixing an oil phase and an aqueous phase, homogenizing to form an O / W type Pickering emulsion, adding a catalyst, heating in a water bath, stirring, extracting and separating with an extraction solvent to obtain an organic phase, removing the organic solvent, and obtaining a low-chlorine bisphenol A epoxy resin.

[0010] The preparation method emulsifies the epoxy resin in an alkaline aqueous solution through an emulsifier and an emulsion stabilizer to form micron-sized micelles, and increases the contact area between the microemulsion colloid and the alkali and introduces a catalyst to increase the reaction progress of the hydrolyzable chlorine in the total chlorine and the alkali, thereby purifying the epoxy resin and reducing the total chlorine content in the epoxy resin.

[0011] In one embodiment, the emulsifier includes nano zinc oxide, and the emulsion stabilizer includes microcrystalline cellulose.

[0012] The O / W Pickering emulsion formed by the emulsifier and emulsion stabilizer with the epoxy resin has good stability.

[0013] In one embodiment, the epoxy resin includes bisphenol A epoxy resin.

[0014] In one embodiment, the volume ratio of water to solvent is (6-9):3.

[0015] In one embodiment, the mass percentage of the base in the aqueous phase is 10-50%, the mass percentage of the emulsifier is 5-20%, and the mass percentage of the emulsion stabilizer is 0.5-0.7%;

[0016] The mass percentage of the catalyst to the epoxy resin is 1-2%.

[0017] If the amount of the above emulsifier and emulsion stabilizer is too little, the molecules are insufficient to cover the oil-water interface, and the formed emulsion is unstable; if it is too much, the emulsion will be too viscous, affecting the quality of the emulsion. Before the above epoxy resin is refined, its chlorine content is relatively high.

[0018] In one embodiment, in the step of preparing the aqueous phase, ultrasound is used for mixing, the ultrasound time is 25-30 min, and the ultrasound power is 360-380 W;

[0019] In the step of preparing low-chlorine bisphenol A epoxy resin, the homogenization speed is 20000-22000 r / min, and the homogenization time is 4-5 min; the water bath heating temperature is 55-60° C., and the water bath heating time is 4-5 h.

[0020] In one embodiment, the solvent comprises butanone, the catalyst comprises glycerol, and the extraction solvent comprises butanone.

[0021] In one embodiment, the O / W Pickering emulsion includes a microemulsion colloid, and the microemulsion colloid is spherical and / or quasi-spherical; the microemulsion colloid includes a core and a shell, the core includes epoxy resin, and the shell includes nano zinc oxide particles and microcrystalline cellulose.

[0022] In the microemulsion colloid, nano zinc oxide particles constitute the shell layer, microcrystalline cellulose is mixed therein as a shell layer reinforcement material, and epoxy resin is embedded in the inner core as a core material. The microemulsion colloids have good dispersion, less overlapping parts, and no large aggregation.

[0023] The invention also provides a low-chlorine bisphenol A epoxy resin obtained by the preparation method.

[0024] In one embodiment, the low-chlorine type is a bisphenol A epoxy resin with a total chlorine content of ≤1200 ppm.

[0025] The above-mentioned low-chlorine bisphenol A epoxy resin has a lower total chlorine content and a lower viscosity. The low chloride ion content can improve the electrical insulation properties of the epoxy resin, slow down the performance degradation of the epoxy resin in a humid environment, and reduce the corrosion to electronic components, etc., and has good application potential.

[0026] In one embodiment, the total chlorine content is the sum of the contents of inorganic chlorine and organic chlorine.

[0027] The present invention also provides the use of the low-chlorine bisphenol A epoxy resin or the preparation method in the preparation of coatings, adhesives, potting glue or electronic casting resins.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] A low-chlorine bisphenol A epoxy resin and a preparation method and application thereof of the present invention. In the present invention, the chlorine reduction process of the preparation method is as follows: Figure 1 As shown, reducing the total chlorine content of epoxy resin is specifically divided into two stages. In the first stage, the epoxy resin is heated in a water bath under the alkaline environment of sodium hydroxide aqueous solution to react the sodium hydroxide with the chlorine impurities in the crude epoxy resin. In the second stage, the dechlorinated epoxy resin is extracted from the entire system with an extraction solvent, and finally the purpose of reducing the total chlorine content of the epoxy resin is achieved. The preparation method emulsifies the epoxy resin in an alkaline aqueous solution to form micrometer-sized micelles. In this process, the colloidal particles are orderly arranged at the oil-water interface, thereby forming a dense interface film, so that the microemulsion colloid in the O / W type Pickering emulsion is a spherical particle with a core-shell structure (such as Figure 2 As shown in the figure, the structure increases the contact area between the colloidal particles and the alkali solution, thereby allowing the alkali to fully react with the hydrolyzable chlorine in the epoxy resin. In addition, the addition of a catalyst increases the reaction progress of the hydrolyzable chlorine in the epoxy resin and sodium hydroxide, and the total chlorine content and viscosity of the obtained epoxy resin product are both low, which has good application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The present invention is a chlorine reduction process flow chart of bisphenol A epoxy resin;

[0031] Figure 2 Schematic diagram of the formation of the Pickering emulsion of the present invention;

[0032] Figure 3 These are photos of the Pickering emulsions prepared in Examples 1 to 3 taken under an industrial microscope;

[0033] Figure 4 The particle size distribution diagram of the Pickering emulsion prepared in Examples 1 to 3;

[0034] Figure 5 The viscosity diagram of bisphenol A epoxy resin after chlorine reduction in Examples 1 to 3 and Comparative Examples 1 to 2, wherein the "crude product" refers to the raw epoxy resin, that is, the epoxy resin that has not been refined. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0037] source:

[0038] Unless otherwise specified, the reagents, materials, and equipment used in this example are all commercially available; the experimental methods are all conventional experimental methods in the art unless otherwise specified.

[0039] Example 1

[0040] Prepare the aqueous phase: weigh 35 g of solid NaOH and dissolve it in 35 ml of water. Then put 3.5 g of ZnO powder and 0.3693 g of microcrystalline cellulose into a 200 ml beaker A filled with 50% NaOH, mix well and disperse by ultrasonic for 20-30 min.

[0041] Prepare the oil phase: Take another beaker B, weigh 15g of 128E epoxy resin, add 15ml of butanone and stir to completely dissolve it.

[0042] Preparation of low-chlorine bisphenol A epoxy resin: Pour the oil phase in B into A and homogenize it for about 5 minutes at a speed of 22000r / min using a homogenizer. In a water-oil mixture system with a volume ratio of 7:3, an ideal Pickering emulsion is formed.

[0043] After homogenization, 0.15 g of propylene glycol was added dropwise, and the mixture was placed in a constant temperature stirring water bath and stirred continuously at 55°C for 5 hours to allow the alkali solution to fully rinse the epoxy resin. After heating in the water bath, an appropriate amount of butanone solvent was used for extraction. After separation, the organic solvent in the resin was removed by rotary evaporation to obtain the epoxy resin product after chlorination reduction. The Pickering emulsion prepared in this example under an industrial microscope is shown in the figure. Figure 3 (a) shows that the particle size distribution is Figure 4 As shown in the "10% emulsification" curve, the viscosity is Figure 5 This is shown as the "10% emulsification" point in the curve.

[0044] Example 2

[0045] Prepare the aqueous phase: weigh 35 g of solid NaOH and dissolve it in 35 ml of water. Then put 5.25 g of ZnO powder and 0.3693 g of microcrystalline cellulose into a 200 ml beaker A filled with 50% NaOH, mix well and disperse by ultrasonic for 20-30 min.

[0046] Prepare the oil phase: Take another beaker B, weigh 15g of 128E epoxy resin, add 15ml of butanone and stir to completely dissolve it.

[0047] Preparation of low-chlorine bisphenol A epoxy resin: Pour the oil phase in B into A and homogenize it for about 5 minutes at a speed of 22000r / min using a homogenizer. In a water-oil mixture system with a volume ratio of 7:3, an ideal Pickering emulsion is formed.

[0048] After homogenization, 0.15 g of propylene glycol was added dropwise, and the mixture was placed in a constant temperature stirring water bath and stirred continuously at 55°C for 5 hours to allow the alkali solution to fully rinse the epoxy resin. After heating in the water bath, an appropriate amount of butanone solvent was used for extraction. After separation, the organic solvent in the resin was removed by rotary evaporation to obtain the epoxy resin product after chlorination reduction. The Pickering emulsion prepared in this example under an industrial microscope is shown in the figure. Figure 3 (b) shows that the particle size distribution is Figure 4 As shown in the "15% emulsification" curve, the viscosity is Figure 5 This is shown as the “15% emulsification” point in the curve.

[0049] Example 3

[0050] Prepare the aqueous phase: weigh 35 g of solid NaOH and dissolve it in 35 ml of water. Then put 7.0 g of ZnO powder and 0.3693 g of microcrystalline cellulose into a 200 ml beaker A filled with 50% NaOH, mix well and disperse by ultrasonic for 20-30 min.

[0051] Prepare the oil phase: Take another beaker B, weigh 15g of 128E epoxy resin, add 15ml of butanone and stir to completely dissolve it.

[0052] Preparation of low-chlorine bisphenol A epoxy resin: Pour the oil phase in B into A and homogenize it for about 5 minutes at a speed of 22000r / min using a homogenizer. In a water-oil mixture system with a volume ratio of 7:3, an ideal Pickering emulsion is formed.

[0053] After homogenization, 0.15 g of propylene glycol was added dropwise, and the mixture was placed in a constant temperature stirring water bath and stirred continuously at 55°C for 5 hours to allow the alkali solution to fully rinse the epoxy resin. After heating in the water bath, an appropriate amount of butanone solvent was used for extraction. After separation, the organic solvent in the resin was removed by rotary evaporation to obtain the epoxy resin product after chlorination reduction. The Pickering emulsion prepared in this example under an industrial microscope is shown in the figure. Figure 3 (c) shows that the particle size distribution is Figure 4 As shown in the "20% emulsification" curve, the viscosity is Figure 5 This is shown as the “20% emulsification” point in the curve.

[0054] Comparative Example 1

[0055] Prepare the aqueous phase: weigh 11.6667 g of solid NaOH and dissolve it in 35 ml of water. Then put 2.10 g of ZnO powder and 0.2345 g of microcrystalline cellulose into a 200 ml beaker A filled with 15% NaOH, mix well and disperse by ultrasonic for 20-30 min.

[0056] Prepare the oil phase: Take another beaker B, weigh 15g of 128E epoxy resin, add 15ml of butanone and stir to completely dissolve it.

[0057] Preparation of low-chlorine bisphenol A epoxy resin: Pour the oil phase in B into A and homogenize it with a homogenizer at a speed of 21000r / min for about 5 minutes. In a water-oil mixture system with a volume ratio of 7:3, an ideal Pickering emulsion is formed.

[0058] After homogenization, add 0.15g of propylene glycol and place in a constant temperature stirring water bath pot at 55°C for continuous stirring for 5 hours to allow the alkali solution to fully wash the epoxy resin. After the water bath heating is completed, use an appropriate amount of butanone solvent for extraction, separate the liquids and remove the organic solvent in the resin by rotary evaporation to obtain the finished epoxy resin after chlorination reduction. Viscosity Figure 5 This is shown as the “6% emulsification” point in the curve.

[0059] Comparative Example 2

[0060] Prepare the aqueous phase: weigh 11.6667 g of solid NaOH and dissolve it in 35 ml of water. Then put 2.45 g of ZnO powder and 0.2345 g of microcrystalline cellulose into a 200 ml beaker A filled with 15% NaOH, mix well and disperse by ultrasonic for 20-30 min.

[0061] Prepare the oil phase: Take another beaker B, weigh 15g of 128E epoxy resin, add 15ml of butanone and stir to completely dissolve it.

[0062] Preparation of low-chlorine bisphenol A epoxy resin: Pour the oil phase in B into A and homogenize it with a homogenizer at a speed of 23000r / min for about 5 minutes. In a water-oil mixture system with a volume ratio of 7:3, an ideal Pickering emulsion is formed.

[0063] After homogenization, add 0.15g of propylene glycol and place in a constant temperature stirring water bath pot at 55°C for continuous stirring for 5 hours to allow the alkali solution to fully wash the epoxy resin. After the water bath heating is completed, use an appropriate amount of butanone solvent for extraction, separate the liquids and remove the organic solvent in the resin by rotary evaporation to obtain the finished epoxy resin after chlorination reduction. Viscosity Figure 5 This is shown as the “7% emulsification” point in the curve.

[0064] Comparative Example 3

[0065] Prepare the aqueous phase: weigh 0.706 g of solid NaOH and dissolve it in 4 ml of deionized water to prepare a 15% NaOH solution.

[0066] Preparation of oil phase: 12.09 g of 128E epoxy resin and 30 ml of butanone were added to a three-necked flask.

[0067] Preparation of bisphenol A epoxy resin: 3.627g of 15% NaOH solution and 0.1209g of propylene glycol were added dropwise to the three-necked flask and reacted at 55°C for 5h. Then, the mixture was washed with deionized water for 2-3 times, and the organic solvent in the resin was removed by rotary evaporation after separation to obtain the epoxy resin product after chlorination reduction.

[0068] Experimental example

[0069] The finished epoxy resin products prepared in each embodiment and comparative example were tested.

[0070] Test Method: Tests were performed on finished epoxy resin products according to ISO 21627-3:2009.

[0071] The test results are shown in the following table.

[0072] Table 1 Properties of epoxy resins prepared in various embodiments and comparative examples

[0073] Total chlorine content (initial) / ppm Total chlorine content (final) / ppm Removal rate / % Example 1 1800 977 45.72 Example 2 1800 1161 35.50 Example 3 1800 1157 35.72 Comparative Example 1 1800 1505 16.39 Comparative Example 2 1800 1487 17.39 Comparative Example 3 1800 1652 8.22％

[0074] As can be seen from Table 1, the total chlorine content of the liquid epoxy resin obtained in Examples 1-3 is ≤1200ppm, and the maximum removal rate reaches 45.72%, while the total chlorine content of Comparative Examples 1-2 is about 1500ppm, and the removal rate is maintained at about 17%. This may be because the amount of emulsifier used is low, resulting in poor stability of the emulsion formed, and the size of the emulsion droplets formed is also uneven, which increases the adverse effects such as agglomeration and flocculation of the emulsion, and ultimately affects the removal rate of the emulsion, thereby showing this degradation effect.

[0075] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a low-chlorine bisphenol A epoxy resin, characterized in that: The following steps are involved: Preparing an aqueous phase: mixing an alkali, water, an emulsifier, and an emulsion stabilizer to prepare an aqueous phase; the alkali comprises sodium hydroxide, the emulsifier comprises nano zinc oxide, and the emulsion stabilizer comprises microcrystalline cellulose; the mass percentage of the alkali in the aqueous phase is 10-50%, the mass percentage of the emulsifier is 5-20%, and the mass percentage of the emulsion stabilizer is 0.5-0.7%; the mixing is performed by ultrasound, the ultrasound time is 25-30 minutes, and the ultrasound power is 360-380W; Prepare the oil phase: mix the epoxy resin and the solvent, stir, and prepare the oil phase; the solvent is butanone; the volume ratio of water to the solvent is (6-9):3; Preparation of low-chlorine bisphenol A epoxy resin: mixing an oil phase and an aqueous phase, homogenizing to form an O / W type Pickering emulsion, adding a catalyst, heating in a water bath, stirring, extracting and separating with an extraction solvent to obtain an organic phase, removing the organic solvent to obtain a low-chlorine bisphenol A epoxy resin; the mass percentage of the catalyst to the epoxy resin is 1-2%; the catalyst is glycerol; the extraction solvent includes butanone; the homogenizing speed is 20000-22000 r / min, and the homogenizing time is 4-5 minutes; the water bath heating temperature is 55-60°C, and the water bath heating time is 4-5 hours.

2. The preparation method according to claim 1, characterized in that: The O / W type Pickering emulsion comprises a microemulsion colloid, which is spherical and / or quasi-spherical; the microemulsion colloid comprises an inner core and a shell layer, wherein the inner core comprises epoxy resin, and the shell layer comprises nano zinc oxide particles and microcrystalline cellulose.

3. The low-chlorine bisphenol A epoxy resin prepared by the preparation method according to any one of claims 1 to 2.

4. The low-chlorine bisphenol A epoxy resin according to claim 3, characterized in that: The low-chlorine type is a bisphenol A type epoxy resin with a total chlorine content of ≤1200ppm.

5. Use of the low-chlorine bisphenol A epoxy resin according to claim 3 or the preparation method according to any one of claims 1 to 2 in the preparation of coatings, adhesives, potting compounds or electronic casting resins.

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