A process for the preparation of a medium molecular weight diphenolic propane glycidyl ether

Abstract

This invention discloses a method for preparing medium molecular weight bisphenol A propane glycidyl ether. The method involves etherifying bisphenol A propane with epichlorohydrin using a polyethylene glycol-modified ionic liquid as a phase transfer catalyst. The resulting etherification product then undergoes a ring-closure reaction under an alkaline catalyst to obtain the medium molecular weight bisphenol A propane glycidyl ether. Compared to the traditional one-step production process, this method offers advantages such as high yield, good selectivity, low wastewater generation, and concentrated molecular weight distribution, thus meeting the application needs of the coatings industry.

Description

Technical Field

[0001] This invention relates to a method for preparing epoxy resin, and more particularly to a method for preparing medium molecular weight bisphenol A propane glycidyl ether, belonging to the field of epoxy resin synthesis technology. Background Technology

[0002] Medium molecular weight bisphenol A glycidyl ether is a type of high molecular weight polymer with an average molecular weight ≥900. It is solid at 25°C. Due to the presence of epoxy groups at both ends of its molecular structure and the generation of more hydroxyl groups between its chain segments compared to low molecular weight bisphenol A glycidyl ether, medium molecular weight bisphenol A glycidyl ether, when mixed with a curing agent and cured, exhibits excellent adhesion to both metal and non-metal surfaces and is widely used in the coatings industry.

[0003] The existing medium molecular weight bisphenol A propane glycidyl ether is mainly synthesized using a one-step method. Its main raw materials are epichlorohydrin, bisphenol A propane, and caustic soda, and it is produced using a solvent. First, pure water and caustic soda are mixed and diluted in a reaction vessel to form a low-concentration alkaline solution. Then, a measured amount of bisphenol A propane is added and fully dissolved. This solution is then transferred to the reaction vessel, where a measured amount of ECH is rapidly added at a certain temperature, and the reaction is maintained at this temperature. After the reaction is complete, a solvent is added to dissolve the solution. The solution is then sent to a purification vessel to remove salts, waste polymers, alkali, and other impurities to obtain the product.

[0004] One-step method:

[0005] Chinese patent CN102199275 A describes a one-step method for producing solid epoxy resin, which generates 2 tons of high-concentration saline wastewater per ton of epoxy resin produced. While the wastewater discharge is reduced by reusing raw brine and washing water, the fundamental synthetic reaction process remains unchanged. Chinese patent CN103923299 B discloses adding a low-concentration alkali metal compound to excess epichlorohydrin and bisphenol A, followed by a reduced-pressure azeotropic dehydration reaction to recover the remaining epichlorohydrin. The reaction solution is then further reacted with alkali to obtain crude resin. However, this process consumes significant time for epichlorohydrin recovery, and the high-temperature recovery process generates a series of side reactions, leading to a substantial increase in energy consumption.

[0006] Therefore, the existing methods for preparing diphenol propane glycidyl ether still suffer from problems such as low yield, poor selectivity, complex processes, high production costs, and serious pollution. There is an urgent need to develop an efficient, green, and simple preparation method to meet the needs of modern industry. Summary of the Invention

[0007] To address the shortcomings of existing technologies, such as low yield, poor selectivity, complex processes, high production costs, and severe pollution, the present invention aims to provide a method for preparing medium molecular weight bisphenol propane glycidyl ether. This method offers advantages such as high yield, good selectivity, low energy consumption, low wastewater discharge, and low production costs.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for preparing bisphenol A propane glycidyl ether, which involves reacting bisphenol A with epichlorohydrin in the presence of a cosolvent and a phase transfer catalyst, and then subjecting the etherification product to a ring-closing reaction in the presence of an alkaline catalyst.

[0009] The phase transfer catalyst is At least one of them, wherein M - OH - PF6 - 1 / 2CO3 2- or 1 / 2SO4 2- R is a C2 to C4 alkyl group.

[0010] This invention utilizes a halogen-free phase transfer catalyst instead of a low-concentration alkaline solution, enabling highly selective reactions between phenolic hydroxyl groups and epoxy groups during the etherification process. This allows for efficient etherification and reduces side reactions, eliminating the need to add large amounts of low-concentration alkali and epichlorohydrin during the etherification stage, thus avoiding the subsequent high-temperature recovery of the remaining epichlorohydrin. Furthermore, the addition of an alkali metal compound in the later stage achieves a ring-closing reaction, resulting in a medium-molecular-weight diphenol propane glycidyl ether product.

[0011] As a preferred embodiment, the PEG molecular weight in the phase transfer catalyst is 200 to 1200.

[0012] Because PEG catalysts have different properties depending on their molecular weight, ranging from colorless, odorless, viscous liquids to waxy solids, those with a molecular weight of 200-600 are liquids at room temperature, while those with a molecular weight above 600 gradually become semi-solids. As the molecular weight increases, their water solubility, vapor pressure, water absorption, and solubility in organic solvents decrease accordingly, while their freezing point, relative density, flash point, and viscosity increase accordingly. They do not react with many chemicals and do not hydrolyze. In this invention, PEG catalysts with a molecular weight of 200-1200 are selected to better catalyze the etherification reaction of bisphenol A and epichlorohydrin, which is beneficial to improving the reaction efficiency.

[0013] As a preferred embodiment, the co-solvent is at least one of toluene, xylene, n-butanol, n-pentanol, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, propylene glycol methyl ether, and propylene glycol ethyl ether.

[0014] As a preferred embodiment, the molar ratio of bisphenol A to epichlorohydrin is 1:1 to 2, more preferably 1:1.1 to 1.9. Generally, when the molar ratio of bisphenol A to epichlorohydrin is ≤1 / 3, the reaction yields low molecular weight bisphenol A propane glycidyl ether, which is liquid at room temperature; when 1 / 2 < bisphenol A to epichlorohydrin molar ratio < 1, the reaction yields medium molecular weight bisphenol A propane glycidyl ether, which is semi-solid or solid at room temperature. The medium molecular weight bisphenol A propane glycidyl ether synthesized within the preferred ratio range of this invention is for use in the coatings industry.

[0015] As a preferred embodiment, the amount of phase transfer catalyst is 0.1 to 0.5 wt% of bisphenol A. Controlling the amount of phase transfer catalyst within a suitable range can achieve better catalytic efficiency. Too little catalyst will not have a catalytic effect, while too much catalyst will waste resources and increase production costs.

[0016] As a preferred embodiment, the amount of the co-solvent is 0.5 to 1.1 times the mass of bisphenol A.

[0017] Controlling the amount of cosolvent within a suitable range is beneficial to improving reaction efficiency. Excessive cosolvent will dilute the reaction solution, prolong the reaction time, and require subsequent recovery of the cosolvent, resulting in increased energy consumption. Conversely, insufficient cosolvent will prevent bisphenol A solid from completely dissolving and participating in subsequent reactions, thus affecting the reaction effect.

[0018] As a preferred embodiment, the etherification reaction is performed under the following conditions: temperature of 60–100°C and time of 60–120 min.

[0019] In this etherification reaction, excessively high temperatures or excessively long reaction times can lead to increased side reactions, higher energy consumption, and negatively impact product yield and purity. Conversely, excessively low temperatures or excessively short reaction times can prevent the reaction from proceeding or result in incomplete reaction, thus failing to obtain the target product. Therefore, it is necessary to control the appropriate etherification temperature and time.

[0020] As a preferred embodiment, the alkaline catalyst is at least one of sodium hydroxide solution, potassium hydroxide solution, and calcium hydroxide solution.

[0021] As a preferred embodiment, the amount of the alkaline catalyst is 0.9 to 1.3 times the molar amount of epichlorohydrin.

[0022] Controlling the amount of alkaline catalyst within a reasonable range is beneficial to improving product yield and purity. If too much alkaline catalyst is used, the alkalinity of the reactants will increase, leading to an increase in the amount of waste polymers generated; if too little alkaline catalyst is used, the reaction will be incomplete, resulting in low product yield.

[0023] As a preferred embodiment, the mass concentration of the alkaline catalyst is 20% to 50%.

[0024] The concentration of the alkaline catalyst has a significant impact on the reaction process. If the concentration is too high, the reactants will accumulate alkalinely during dropwise addition, increasing the number of side reactions. Conversely, if the concentration is too low, more water will be introduced into the reaction system, thus affecting the reaction rate and increasing wastewater discharge. Therefore, controlling the mass concentration of the alkaline catalyst within the above-mentioned range can ensure reaction efficiency.

[0025] As a preferred embodiment, the closed-loop reaction conditions are: temperature of 40–90°C, alkali catalyst addition time controlled within the range of 30–120 min, and reaction continued for 60–120 min after the alkali catalyst is completely added.

[0026] During this reaction, it is crucial to control the reaction temperature and the rate of alkali catalyst addition within appropriate ranges. Excessively high ring-closure reaction temperatures can lead to violent reactions, potentially causing feedstock overflow and reactant coking; conversely, excessively low temperatures result in incomplete ring-closure, leading to a lower yield of the target product. Furthermore, the rate of alkali catalyst addition significantly impacts reaction efficiency. Too short an addition time (too fast a rate) causes the reactants to become too alkaline, increasing side reactions; too long an addition time (too slow a rate) increases batch production time, affecting unit capacity and reducing production efficiency.

[0027] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0028] (1) By using a halogen-free phase transfer catalyst to replace the low-concentration alkaline solution, the side reaction of epichlorohydrin hydrolysis is reduced, and the water in the reaction system is reduced from the source, thereby reducing the generation and discharge of wastewater.

[0029] (2) By using a special phase transfer catalyst, the reaction between the phenolic hydroxyl group and the epoxy group in the etherification reaction can be highly selective, so that the etherification reaction can proceed efficiently and the side reaction can be reduced. Therefore, it is not necessary to add a large amount of low-concentration base and epichlorohydrin in the etherification reaction stage, which would require the recovery of the remaining epichlorohydrin under high temperature conditions. The ring-closing reaction is achieved by adding an alkali metal compound in the later stage, thereby obtaining the medium molecular weight diphenol propane glycidyl ether product. Detailed Implementation

[0030] The following examples are intended to further illustrate the present invention, rather than to limit the scope of the claims.

[0031] Example 1

[0032] 228 g of bisphenol A, 106.3 g of epichlorohydrin, 114 g of toluene, and 1.14 g of PEG-200 modified with methylimidazolium (an anion of hydroxyl) as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 100 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 92 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 90 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water until pH 7, and toluene was removed under reduced pressure to obtain medium molecular weight bisphenol A propane glycidyl ether.

[0033] Analysis showed that the epoxy equivalent was 975 g / eq and the organochlorine content was 265 ppm. The epoxy equivalent was tested according to GB / T4612-2018 standard, and the organochlorine content was tested according to GB / T 4618.2-2008 standard.

[0034] Example 2

[0035] 228 g of bisphenol A, 129.5 g of epichlorohydrin, 114 g of methyl isobutyl ketone, and 1.14 g of PEG-400 modified with methylimidazolium sulfate as the phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 60 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 120 min. After the reaction was completed, 124 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 120 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water to pH 7 and the methyl isobutyl ketone was removed under reduced pressure to obtain medium molecular weight bisphenol A propane glycidyl ether. The epoxy equivalent was 675 g / eq, and the organochlorine content was 125 ppm.

[0036] Example 3

[0037] 228 g of bisphenol A, 136 g of epichlorohydrin, 180 g of propylene glycol methyl ether, and 1.14 g of PEG-800 modified with methylimidazolium carbonate anion as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 80 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 118 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 60 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water until pH 7, and the propylene glycol methyl ether was removed under reduced pressure to obtain medium molecular weight bisphenol A glycidyl ether. The epoxy equivalent was 452 g / eq, and the organochlorine content was 225 ppm.

[0038] Example 4

[0039] 228 g of bisphenol A, 136 g of epichlorohydrin, 180 g of propylene glycol methyl ether, and 1.14 g of PEG-800 modified with methylimidazolium carbonate anion as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 80 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 118 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 30 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water to pH 7 and the propylene glycol methyl ether was removed under reduced pressure to obtain medium molecular weight bisphenol A glycidyl ether. The epoxy equivalent was 741 g / eq, and the organochlorine content was 187 ppm.

[0040] Comparative Example 1

[0041] 228g of bisphenol A, 118g of 50% sodium hydroxide solution, and 442g of pure water were placed in a four-necked reaction flask and heated to 50°C. The mixture was mechanically stirred until the solids were completely dissolved. After the temperature stabilized at ≤50°C, 136g of epichlorohydrin was added in one go, and the mixture was heated to 90°C and reacted for 60 minutes. After the reaction was complete, 400g of toluene was added. After separation, the upper organic phase was collected and washed with water until pH=7. The toluene was removed under reduced pressure to obtain the epoxy resin. Analysis showed that the epoxy equivalent was 459g / eq and the organochlorine content was 306ppm.

[0042] Comparative Example 2

[0043] 228 g of bisphenol A, 106.3 g of epichlorohydrin, 114 g of toluene, and 0.114 g of PEG-200 modified with methylimidazolium (an anion of hydroxyl) as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 100 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 92 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 90 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water to pH 7 and toluene was removed under reduced pressure to obtain medium molecular weight bisphenol A glycidyl ether. Analysis showed that the epoxy equivalent was 1375 g / eq and the organochlorine content was 1801 ppm.

[0044] Comparative Example 3

[0045] 228 g of bisphenol A, 185 g of epichlorohydrin, 114 g of methyl isobutyl ketone, and 1.14 g of PEG-400 modified with methylimidazolium sulfate as the phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 60 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 120 min. After the reaction was completed, 177 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 120 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water to pH 7 and the methyl isobutyl ketone was removed under reduced pressure to obtain medium molecular weight bisphenol A propane glycidyl ether. Analysis showed that the epoxy equivalent was 328 g / eq, the organochlorine content was 267 ppm, the product was semi-solid at room temperature, and its average molecular weight was <900, therefore it does not belong to the category of medium molecular weight bisphenol A propane glycidyl ether.

[0046] Comparative Example 4

[0047] 228 g of bisphenol A, 136 g of epichlorohydrin, 180 g of propylene glycol methyl ether, and 1.14 g of PEG-800 modified with methylimidazolium carbonate anion as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 80 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 59 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 60 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water until pH 7, and the propylene glycol methyl ether was removed under reduced pressure to obtain medium molecular weight bisphenol A glycidyl ether. The epoxy equivalent was 589 g / eq, and the organochlorine content was 3158 ppm.

[0048] Comparative Example 5

[0049] 228 g of bisphenol A, 136 g of epichlorohydrin, 360 g of propylene glycol methyl ether, and 1.14 g of PEG-800 modified with methylimidazolium carbonate anion as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 80 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 118 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 60 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water until pH 7, and the propylene glycol methyl ether was removed under reduced pressure to obtain medium molecular weight bisphenol A glycidyl ether. The epoxy equivalent was 557 g / eq, and the organochlorine content was 1019 ppm.

[0050] Comparative Example 6

[0051] 228 g of bisphenol A, 106.3 g of epichlorohydrin, 114 g of toluene, and 1.14 g of PEG-200 modified with methylimidazolium (an anion of hydroxyl) as a phase transfer catalyst were placed in a four-necked reaction flask. The mixture was heated to 110 °C and mechanically stirred until the solids were completely dissolved. The reaction was continued for 90 min, then the temperature was lowered to 60 °C. After the temperature stabilized, 92 g of 50% sodium hydroxide aqueous solution was added using a constant flow pump over 90 min. After the addition of alkali, the reaction was continued at the same temperature for another 60 min. After the reaction was completed, the upper organic phase was washed with water until pH 7, and toluene was removed under reduced pressure to obtain medium molecular weight bisphenol A glycidyl ether. Analysis showed that the epoxy equivalent was 1124 g / eq and the organochlorine content was 927 ppm.

[0052] The above specific embodiments are merely detailed explanations of the technical solutions of the present invention. The present invention is not limited to the above embodiments. Those skilled in the art should understand that any improvements or substitutions made based on the above principles and spirit on the basis of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a medium molecular weight bisphenol propane glycidyl ether, characterized in that: Bisphenol A is etherified with epichlorohydrin in the presence of a cosolvent and a phase transfer catalyst. The resulting etherification product is then subjected to a ring-closing reaction in the presence of an alkaline catalyst to obtain the final product. The phase transfer catalyst is , , At least one of them, wherein M - OH - PF6 - 1 / 2CO3 2- or 1 / 2SO4 2- R is a C2~C4 alkyl group; The molar ratio of bisphenol A to epichlorohydrin is 1:1.1~1.

9.

2. The method for preparing a medium molecular weight bisphenol A propane glycidyl ether according to claim 1, characterized in that: The PEG in the phase transfer catalyst has a molecular weight of 200-1200.

3. The method for preparing a medium molecular weight bisphenol A propane glycidyl ether according to claim 1 or 2, characterized in that: The amount of phase transfer catalyst used is 0.1~0.5 wt% of bisphenol A.

4. The method for preparing a medium molecular weight bisphenol A propane glycidyl ether according to claim 1 or 2, characterized in that: The co-solvent is at least one of toluene, xylene, n-butanol, n-pentanol, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, propylene glycol methyl ether, and propylene glycol ethyl ether.

5. The method for preparing a diphenol propane glycidyl ether according to claim 1, characterized in that: The amount of the co-solvent used is 0.5 to 1.1 times the mass of bisphenol A.

6. The method for preparing a medium molecular weight bisphenol A propane glycidyl ether according to claim 1, characterized in that: The conditions for the etherification reaction are: temperature 60~100℃, time 60~120min.

7. The method for preparing a medium molecular weight bisphenol A propane glycidyl ether according to claim 1, characterized in that: The alkaline catalyst is at least one of sodium hydroxide solution, potassium hydroxide solution, and calcium hydroxide solution.

8. The method for preparing a medium molecular weight bisphenol A propane glycidyl ether according to claim 1 or 7, characterized in that: The amount of the alkaline catalyst used is 0.9 to 1.3 times the molar amount of epichlorohydrin; The mass concentration of the alkaline catalyst is 20% to 50%.

9. The method for preparing a diphenol propane glycidyl ether according to claim 1, characterized in that: The closed-loop reaction conditions are as follows: temperature is 40~90℃, the addition time of the alkaline catalyst is controlled within the range of 30~120min, and the reaction continues for 60~120min after the alkaline catalyst is completely added.