Method for catalytically synthesizing methyl-terminated polyoxyethylene / polyoxypropylene ether by double catalysts

Abstract

The invention relates to the technical field of fine chemical engineering. The method comprises the following steps: adding polyol polyoxyethylene / polyoxypropylene ether serving as an initiator and the double catalysts into a reaction kettle, fully stirring, adding an end-capping reagent into the reaction kettle, and reacting for 2-4 hours to obtain a methyl-terminated polyoxyethylene / polyoxypropylene ether solution; and the methyl-terminated polyoxyethylene / polyoxypropylene ether is prepared under mild conditions. The method is simple in process and safe to operate; according to the method, the traditional incomplete end capping is improved, the reaction temperature is reduced, and an end-capped product which is relatively high in end capping rate, light in product color, simple and easy to process by-products and stable in product quality is obtained on the basis of not changing the original equipment.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, particularly the field of fine chemicals. A method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ethers is disclosed. Background Technology

[0002] Ordinary polyol polyethers (hydroxyl-terminated) are prone to hydrolysis and chain scission under acidic, alkaline, or high-temperature and high-humidity environments, leading to a decrease in molecular weight, viscosity, and performance degradation. After end-capping, the terminal active hydroxyl groups are replaced by stable methoxy ether bonds. These ether bonds are more resistant to hydrolysis than uncapped hydroxyl groups, and end-capped polyethers can maintain stability and performance for a longer period of time in harsh environments. They also avoid the influence of the presence of hydroxyl groups, showing good prospects in defoamers, coating leveling agents, personal care products, and pesticide synergists. However, the methyl-terminated polyethers prepared by current processes have a wide molecular weight distribution and low end-capping rate.

[0003] Currently, the catalysts used for methyl-terminated polyol polyethers are all strongly basic catalysts, such as sodium metal, NaH, potassium methoxide, sodium methoxide, sodium hydroxide, and potassium hydroxide, or a combination of two. The reaction temperatures are all between 100 and 120°C. At higher temperatures, the resulting product has a darker color. Because this reaction is a solid-liquid reaction, and gas is involved in subsequent reactions, the compatibility between the three phases is poor, resulting in high mass transfer resistance and low reaction efficiency. This invention incorporates a phase transfer catalyst to enhance its solubility in the non-polar phase. The combination of the phase transfer catalyst and the basic catalyst improves the product conversion rate.

[0004] CN101497560A discloses a method for synthesizing polyethers by methyl-termined synthesis, which uses sodium methoxide as a catalyst. However, a vacuum methanol removal step is required in the alkoxide reaction, otherwise it will affect the subsequent reaction and increase the cost of methanol treatment, making the process complex.

[0005] CN101445434A discloses a method for synthesizing polyethers by methyl end-capping, which uses alkali metal sodium hydroxide or potassium hydroxide alone or in combination as catalysis. Due to insufficient solid-liquid mixing, the end-capping is incomplete, and a stronger alkaline catalyst, NaH, is used for secondary catalysis. CN111732723A discloses a dynamic stirred reactor with a multi-stage stirred tank using high shear and multi-layer stirring to solve the problem of insufficient solid-liquid or solid-liquid-gas phase mixing, which leads to poor end-capping efficiency. Although this equipment solves the problem, it is difficult to introduce and modify the equipment in a short period of time.

[0006] CN201710413295.9 discloses an allyl alcohol polyoxypropylene ether and its preparation method. The catalyst in this patent, dimethyl sulfate, is a highly toxic substance that causes serious environmental pollution. CN201510473015.4 discloses a method for producing allyl polyethers with high double bond content. This method uses metallic sodium as a catalyst. Metallic sodium is flammable and explosive, and it reacts with allyl alcohol to produce hydrogen gas, making industrial-scale production difficult. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing methyl-terminated polyethers using chloromethane as a capping agent in the presence of potassium hydroxide or sodium hydroxide. During the reaction, the byproduct water is removed to promote the complete reaction of the polyether with the alkali to form an alkoxide. The alkoxideized polyether is fully reacted with chloromethane in a high-pressure reactor to obtain the corresponding capped polyether, exhibiting high capping efficiency. The post-processing is simple, pollution-free, has high yield, and provides stable product quality.

[0008] To address the aforementioned technical problems, this invention provides a method for the dual-catalyst-catalyzed synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, comprising the following steps:

[0009] Step 1: Add polyol polyoxyethylene / polyoxypropylene ether and dual catalysts in a certain proportion, mix evenly, and carry out alkoxide reaction to obtain alkoxide polyether;

[0010] Step 2: Add a capping agent to the alkoxide-treated polyol polyoxyethylene / polyoxypropylene ether and react under mild conditions of low temperature and low pressure to obtain capped polyoxyethylene / polyoxypropylene ether.

[0011] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, in step 1, the dual catalyst is a solid base catalyst and a phase transfer catalyst.

[0012] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, in step 1, the phase transfer catalyst is tetrabutylammonium bromide or triethylbenzylammonium chloride.

[0013] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, in step 1, the alkaline catalyst is one or more of KOH, NaOH, sodium methoxide, and potassium methoxide.

[0014] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, the amount of the alkaline catalyst added is 1.0 to 1.8 times the molar ratio of polyol polyoxyethylene / polyoxypropylene ether.

[0015] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, the amount of phase transfer catalyst added is 0.05% to 0.5% of the total mass of the materials.

[0016] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, in step 1, the polyol polyoxyethylene / polyoxypropylene ether is a polyoxyethylene / polyoxypropylene ether containing hydroxyl groups of fatty alcohol, allyl alcohol, lauryl alcohol or ethylene glycol.

[0017] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, in step 1, the alkoxide reaction is carried out at a temperature of 40–95°C and a pressure of -0.09–-0.1 MPa.

[0018] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, in step 2, the capping agent is one or more of dimethyl carbonate, dimethyl sulfate, iodomethane, and chloromethane.

[0019] In the above-mentioned method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, step 2 involves a reaction temperature of 40–95°C and a reaction pressure of 0.03–0.35 MPa.

[0020] Compared with the existing technology, the present invention has the following advantages:

[0021] The method for methyl-terminated polyoxyethylene / polyoxypropylene ether of the present invention uses a dual catalyst for catalysis. The reaction can be completed at low temperature (45-95°C) and low pressure (0.03-0.35MPa). It has high reactivity, safe and easy-to-control process operation, simple post-processing, and easy separation of by-products. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below with reference to embodiments. Obviously, the embodiments described below are only some embodiments of this invention, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this invention and are not intended to limit this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0023] Example 1

[0024] First, add 500g of allyl alcohol polyoxyethylene ether (Mn=365) to a 3L reactor, then add 112g of potassium hydroxide and 0.5g of tetrabutylammonium bromide. Turn on the stirrer, purge with nitrogen five times, then raise the temperature and draw the negative pressure to -0.09MPa. Raise the temperature to 50℃~90℃ and start the heat and pressure holding reaction for 1~3h. Continuously introduce 80g of end-capping agent chloromethane, and maintain the pressure between 0.25~0.35MPa. After completion, continue stirring and aging for 3h. After degassing, discharge the material, neutralize, filter, and dehydrate under vacuum to obtain methoxy allyl polyoxyethylene ether.

[0025] Example 2

[0026] First, add 500g of allyl alcohol polyoxyethylene ether (Mn=1200) to a 3L reactor, then add 38g of sodium methoxide and 0.5g of tetrabutylammonium bromide. Turn on the stirrer, purge with nitrogen five times, then raise the temperature and draw the negative pressure to -0.09MPa. Raise the temperature to 50℃~90℃ and start the heat and pressure holding reaction for 1~3h. Continuously introduce 42g of end-capping agent chloromethane, and maintain the pressure between 0.25~0.35MPa. After completion, continue stirring and aging for 3h. After degassing, discharge the material, neutralize, filter, and dehydrate under vacuum to obtain end-capped allyl polyoxyethylene ether.

[0027] Example 3

[0028] First, add 500g of lauryl alcohol polyoxyethylene ether (Mn=750) to a 3L reactor, then add 60g of potassium hydroxide and 0.5g of tetrabutylammonium bromide. Turn on the stirrer, purge with nitrogen five times, then raise the temperature and draw the negative pressure to -0.09MPa. Raise the temperature to 50℃~90℃ and start the heat and pressure holding reaction for 1~3h. Continuously introduce 68g of end-capping agent chloromethane, and maintain the pressure between 0.25~0.35MPa. After completion, continue stirring and aging for 3h. After degassing, discharge the material, neutralize, filter, and dehydrate under vacuum to obtain end-capped lauryl alcohol polyoxyethylene ether.

[0029] Example 4

[0030] First, add 500g of allyl alcohol polyoxyethylene polyoxypropylene ether (Mn=1500) to a 3L reactor, then add 30g of sodium hydroxide and 0.5g of tetrabutylammonium bromide. Turn on the stirrer, purge with nitrogen five times, then raise the temperature and draw the negative pressure to -0.09MPa. Raise the temperature to 50℃~90℃ and start the heat and pressure holding reaction for 1~3h. Continuously introduce 35g of end-capping agent chloromethane, and maintain the pressure between 0.25~0.35MPa. After completion, continue stirring and aging for 3h. After degassing, discharge the material, neutralize, filter, and vacuum dehydrate to obtain end-capped allyl alcohol mixed polyether.

[0031] Comparative Example 1

[0032] (Excerpted from Example 1 of application number 200810163987.3) 1000 g of allyl alcohol random polyether (molecular weight 550) and 153 g of solid potassium hydroxide were added to a 2 L reactor and stirred vigorously. The reaction was carried out at 100-110°C under vacuum conditions (pressure -0.09 to -0.1 MPa) for 3 hours, simultaneously with dehydration. The temperature was then lowered to 80-90°C, and 147 g of chloromethane was slowly introduced while maintaining a pressure of 0.3 MPa. The reaction continued for 4 hours. 20 g of distilled water was added, and the mixture was stirred at 80°C for half an hour. After filtering to remove solid impurities, the end-capped polyether product was obtained.

[0033] The capping rate, color number, moisture content, and double bond retention rate of the above embodiments and comparative examples are shown in Table 1 below:

[0034] Table 1

[0035]

[0036] As shown in the table above, the dual catalyst not only solves the problem of uneven mixing during alkoxide formation, but also reduces reaction temperature and pressure, shortens reaction time, and improves reaction conversion rate. It is also convenient, safe, and controllable to operate. Furthermore, it exhibits a high end-capping rate and a high retention rate of double bonds.

Claims

1. A method for the dual-catalyst-catalyzed synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether, characterized in that, Includes the following steps: Step 1: Add polyol polyoxyethylene / polyoxypropylene ether and dual catalysts in a certain proportion, mix evenly, and carry out alkoxide reaction to obtain alkoxide polyether; Step 2: Add a capping agent to the alkoxide-treated polyol polyoxyethylene / polyoxypropylene ether and react under mild conditions of low temperature and low pressure to obtain capped polyoxyethylene / polyoxypropylene ether.

2. The method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 1, characterized in that: In step 1, the dual catalyst is a solid base catalyst and a phase transfer catalyst.

3. The method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 2, characterized in that: In step 1, the phase transfer catalyst is tetrabutylammonium bromide or triethylbenzylammonium chloride.

4. The method for the dual-catalyst catalytic synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 2, characterized in that: In step 1, the alkaline catalyst is one or more of KOH, NaOH, sodium methoxide, and potassium methoxide.

5. The method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 2, characterized in that: The amount of the alkaline catalyst added is 1.0 to 1.8 times the molar ratio of polyol polyoxyethylene / polyoxypropylene ether.

6. The method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 2, characterized in that: The amount of phase transfer catalyst added is 0.05% to 0.5% of the total mass of the material.

7. The method for the dual-catalyst catalytic synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 1, characterized in that: In step 1, the polyol polyoxyethylene / polyoxypropylene ether is a polyoxyethylene / polyoxypropylene ether containing fatty alcohol, allyl alcohol, lauryl alcohol or ethylene glycol terminal hydroxyl groups.

8. The method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 1, characterized in that: In step 1, the alkoxide reaction is carried out at a temperature of 40–95°C and a pressure of -0.09–-0.1 MPa.

9. The method for the dual-catalyst synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 1, characterized in that: In step 2, the capping agent is one or more of dimethyl carbonate, dimethyl sulfate, iodomethane, and chloromethane.

10. The method for the dual-catalyst catalytic synthesis of methyl-terminated polyoxyethylene / polyoxypropylene ether according to claim 1, characterized in that: In step 2, the reaction temperature is 40–95℃ and the reaction pressure is 0.03–0.35 MPa.

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