Preparation method of allyl alcohol random polyether

Abstract

The invention relates to the technical field of preparation of allyl alcohol polyether, in particular to a preparation method of allyl alcohol random polyether. According to the method, allyl alcohol is used as an initiator and is subjected to a polymerization reaction with ethylene oxide and epoxypropane in the presence of a non-metal organic catalyst. The method comprises the following steps: firstly, activating a mixed solution of part of ethylene oxide and propylene oxide, an initiator and a catalyst, then continuously dropwise adding the residual mixed solution into a sealed reaction system for growth polymerization, and finally recovering the catalyst through reduced pressure distillation to directly obtain a high-purity product. The method is simple in process route, avoids complex post-treatment steps such as neutralization and adsorption required by using a noble metal or sodium alcoholate catalyst, is high in catalyst recovery rate, extremely low in potassium and sodium ion content (less than or equal to 3ppm) in the product, and capable of accurately regulating and controlling the molecular weight in a range of 1400-3100, remarkably reduces the production cost, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of allyl alcohol polyether preparation technology, and specifically to a method for preparing allyl alcohol random polyether. Background Technology

[0002] Allyl alcohol polyethers are a class of polyether polyols with allyl double bonds at the molecular ends. These active double bonds endow them with excellent subsequent reaction properties, allowing them to be introduced into various polymer structures through addition, grafting, and other chemical reactions. Therefore, allyl alcohol polyethers, as a key functional intermediate, are widely used in fine chemical fields such as polyurethane foam stabilizers, pesticide emulsifiers, high-performance defoamers, textile auxiliaries, and specialty surfactants. Their molecular weight, molecular weight distribution, double bond retention rate (characterized by iodine value), and metal ion impurity content are the core indicators determining their final application performance.

[0003] In existing technologies, the industrial production of allyl alcohol polyethers largely relies on anionic polymerization catalytic systems. For example, Chinese patent CN110305309A discloses a method for preparing allyl alcohol polyethers using a phosphazene catalyst, followed by methyl end-capping with sodium alkoxide. While this method yields products with a narrow molecular weight distribution, the phosphazene catalyst used is extremely expensive and difficult to recycle, resulting in high production costs. Chinese patent CN114656628A reports a method for preparing high molecular weight allyl alcohol polyethers using a supported rubidium-based nanocatalyst. This catalyst exhibits high activity and produces products with a narrow molecular weight distribution; however, the catalyst preparation process is complex, involving the precious metal rubidium and nanocarriers, leading to high raw material and preparation costs. A more common catalytic system uses alkali metal catalysts such as sodium alkoxide and potassium alkoxide, as disclosed in Chinese patent CN107266673B. This method requires a large amount of sodium alkoxide, and after the reaction, it must undergo multiple processes such as acid neutralization and adsorbent purification to remove residual metal ions. The process is long, generates a large amount of wastewater and waste residue, and it is difficult to stably control the residual metal ions in the product at an extremely low level, which affects its application in high-end fields.

[0004] In summary, existing allyl alcohol polyether preparation technologies generally suffer from the following common problems: either they rely on expensive and non-recyclable catalysts, resulting in poor economic efficiency; or they use metal catalysts, leading to cumbersome post-processing and potential product contamination. Therefore, developing a simple, catalyst-recyclable, high-purity, and low-cost green preparation method for allyl alcohol polyethers is of great significance for promoting the technological upgrading of related downstream industries. This invention is an innovative study addressing the aforementioned technical deficiencies. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing allyl alcohol random polyether. This method utilizes a distillable and recyclable non-metallic organic catalyst and optimizes the "activation-stepwise feeding" polymerization and one-step distillation purification process. It aims to solve the problems of complex processes, cumbersome post-processing, high residual metal ions in the product, and high production costs caused by the use of expensive or metallic catalysts in existing technologies. This achieves the goals of efficient catalyst recycling, high product purity, and suitability for industrial-scale green production.

[0006] A method for preparing an allyl alcohol random polyether includes the following steps: (1) Raw material preparation: Prepare a mixture of ethylene oxide (EO) and propylene oxide (PO); (2) Polymerization reaction: Under inert gas protection and vacuum conditions, allyl alcohol initiator, catalyst and appropriate amount of mixture prepared in step (1) are mixed and heated for activation; then under sealed reaction conditions, appropriate amount of mixture prepared in step (1) is continuously added dropwise to carry out polymerization reaction; after the reaction is completed, it is kept warm and matured to obtain crude polyether solution; (3) Post-processing: The crude polyether solution obtained in step (2) is subjected to vacuum distillation to distill off other boiling point components. The remaining components are allyl alcohol random polyether. The distilled components mainly include the catalyst in step (2) and are used for the next batch of reaction.

[0007] Preferably, in step (1), the mass ratio of ethylene oxide to propylene oxide is (2.5-3.5):2.

[0008] Preferably, in step (2), the catalyst is at least one of N-methylmorpholine, bis(dimethylaminoethyl) ether, and bis(dimorpholinoethyl) ether; the mass of the catalyst added is 30%-75% of the mass of allyl alcohol.

[0009] Preferably, in step (2), the activation temperature is 45-55℃ and the vacuum degree is not lower than -0.095MPa; the activation step lasts for 0.5-1.5h.

[0010] Preferably, in step (2), the mass ratio of the allyl alcohol initiator to the mixture prepared in step (1) for the first addition and the mixture prepared in step (1) for the second addition is 1:(0.8-1.2):(15-25); the first addition of the mixture prepared in step (1) refers to the addition before the heating and activation.

[0011] Preferably, the second addition step (1) of the mixture preparation is added by continuous dripping, with a dripping time of 3-6 hours and a dripping rate of 8-10 g / min.

[0012] Preferably, in step (2), the reaction temperature of the polymerization reaction is 65-95℃; the ripening step is carried out at the reaction temperature and the ripening time is 1.5-2.5h.

[0013] Preferably, in step (3), the vacuum degree of the reduced pressure distillation is not lower than -0.098 MPa, and the heating rate is 5-8 °C / min.

[0014] Preferably, the other boiling points mentioned in step (3) are 0-100℃.

[0015] The allyl alcohol random polyether prepared by this invention has an average molecular weight of 1400-3100, an iodine value of 8.4-17.8 mgI / g, and a total content of potassium and sodium ions ≤3ppm.

[0016] The ethylene oxide and propylene oxide mentioned in step (1) have a purity of ≥99.0% and a moisture content of ≤0.05%.

[0017] Beneficial technical effects of the present invention: 1. Simplified Process and Significantly Reduced Costs: The use of a distillable, recoverable non-metallic catalyst replaces expensive or non-recoverable catalyst systems. Only one distillation step is required after the reaction to simultaneously recover the catalyst and purify the product, eliminating the multiple complex post-processing steps necessary for traditional metal catalyst processes, such as neutralization, washing, adsorption, and filtration. The process flow is greatly shortened, equipment investment and operating costs are significantly reduced, and emissions of waste gas, wastewater, and solid waste are drastically decreased. The overall production cost has a clear advantage, making it highly suitable for large-scale industrial production.

[0018] 2. Improved Product Purity and Performance: Because no metal catalyst is used throughout the process, and the catalyst is physically separated, the allyl alcohol random polyether product prepared by this invention has extremely low levels of metal ion impurities such as potassium and sodium, which can be stably controlled below 3 ppm, and in some examples, they are even undetectable. Simultaneously, through an optimized stepwise feeding polymerization process, the molecular weight of the product can be precisely designed within the range of 1400-3100, and the iodine value is stable between 8.4-17.8 mgI / g, indicating that the active double bonds are effectively preserved.

[0019] 3. Strong Green Environmental Protection and Sustainability: The closed-loop recycling of the catalyst is a prominent environmental benefit of this invention. The catalyst recovery rate is over 95%, achieving highly efficient resource utilization and reducing chemical consumption at the source. The entire production process does not involve the neutralization of strong acids or alkalis or the generation of saline wastewater, significantly improving environmental friendliness and aligning with current trends in green chemistry and clean production. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the method for preparing allyl alcohol random polyether of the present invention. Detailed Implementation

[0021] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0022] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by those skilled in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of those skilled in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or identical to those described in the embodiments of this invention may be used to implement this invention.

[0023] Unless otherwise stated, the test methods, detection methods and preparation methods disclosed in this invention all adopt conventional techniques in this technical field.

[0024] N-Methylmorpholine (abbreviated as NMM), bis(dimethylaminoethyl) ether (abbreviated as BDMAEE), bis(dimorpholinoethyl) ether (DMDEE); Example 1 A method for preparing 1500 molecular weight allyl alcohol random polyether, using N-methylmorpholine as catalyst, allyl alcohol as initiator, and the mixture of ethylene oxide and propylene oxide from step (1) as raw material, to prepare allyl alcohol polyether, and the following steps are performed sequentially: Add 80g of allyl alcohol and 60g of N-methylmorpholine (i.e., catalyst) to a 3000ml stainless steel autoclave. Replace the air in the autoclave with nitrogen three times, and evacuate to a vacuum of -0.095MPa. Add 100g of the mixture of ethylene oxide and propylene oxide from step (1), heat to 50℃ for 1h, and heat to 70℃ under sealed conditions for reaction. Then continuously add 2072g of the mixture of ethylene oxide and propylene oxide from step (1). After the addition is completed, keep warm at 75℃ for 2h, cool down to 60℃, and vent. Transfer the autoclave liquid to a 3000ml three-necked flask, distill under reduced pressure at a vacuum of -0.098MPa, and distill off the 0-100℃ component. The distillate is the catalyst and can be reused in the next batch. The liquid remaining in the three-necked flask is allyl alcohol random polyether with a molecular weight of 1508, an iodine value of 17.2mgI / g, and a total potassium and sodium ion content of 1ppm.

[0025] Examples 2-6 were obtained by changing the catalyst, catalyst dosage, and reaction temperature in Example 1, while keeping the rest the same as in Example 1. The obtained allyl alcohol random polyether and related information about the catalyst are shown in Table 1.

[0026] Table 1 Example 7 A method for preparing 3000 molecular weight allyl alcohol random polyether, using N-methylmorpholine as catalyst, allyl alcohol as initiator, and the mixture of ethylene oxide and propylene oxide from step (1) as raw material, to prepare allyl alcohol polyether, and the following steps are performed sequentially: Add 40g allyl alcohol and 60g N-methylmorpholine (i.e., catalyst) to a 3000ml stainless steel autoclave. Replace the air in the autoclave with nitrogen three times, and evacuate to a vacuum of -0.095MPa. Add 100g of the mixture of ethylene oxide and propylene oxide from step (1), heat to 70℃ for 1h, and heat to 90℃ under sealed conditions for reaction. Then continuously add 2175g of the mixture of ethylene oxide and propylene oxide from step (1). After the addition is completed, keep warm at 95℃ for 2h, cool down to 60℃, and vent. Transfer the autoclave liquid to a 3000ml three-necked flask, distill under reduced pressure at a vacuum of -0.098MPa, and distill off the 0-100℃ component. The distillate is the catalyst and can be reused in the next batch. The liquid remaining in the three-necked flask is allyl alcohol random polyether. Molecular weight: 2958, iodine value: 8.4mgI / g, total potassium and sodium ion content: 1ppm. Examples 8-12 were obtained by changing the catalyst, catalyst dosage, and reaction temperature in Example 7, making them identical to those in Example 1. Detailed data on allyl alcohol random polyether and catalyst are shown in Table 2.

[0027] Table 2 Comparative Example 1 (using the metal catalyst KOH) Referring to the material ratio and target molecular weight of Example 1, the catalyst was replaced with KOH at 1% by mass of allyl alcohol, and the remaining steps were the same. After the reaction was completed, phosphoric acid was added to the crude product to neutralize it, followed by magnesium silicate adsorption and filtration to remove potassium ions. Finally, low-boiling substances were removed under reduced pressure to obtain the product. The metal ion content and molecular weight distribution were tested.

[0028] Comparative Example 2 (catalyst not recovered, one-step feeding) The material ratios were the same as in Example 1, but the catalyst distillation and recovery were not performed. The feeding method was also changed: the entire EO / PO mixture was added to the autoclave at the beginning of the reaction, followed by activation and polymerization. The remaining steps were the same. The iodine value and molecular weight distribution of the product were tested and compared with those of Example 1.

[0029] Comparative Example 3 (using CN114656628A supported rubidium catalyst) Following the method described in Example 1 of prior art document CN114656628A, an Rb-NHPA supported catalyst was prepared and used to catalyze the polymerization of allyl alcohol with EO / PO (as in this invention), with a target molecular weight of 1500. The catalyst cost, complexity of the preparation steps, and performance of the final product were recorded.

[0030] Comparative Example 4 (using the two-step sodium alkoxide method described in CN107266673B) Following the typical method described in prior art document CN107266673B, oligomers were first prepared using boron trifluoride diethyl ether as a catalyst, followed by chain growth using sodium methoxide as a catalyst, with a target molecular weight of 3000. The consumption of sodium methoxide, the number of post-treatment steps, the amount of wastewater generated, and the potassium and sodium ion content of the final product were recorded. Comparative Examples 1 and 4, due to the use of strong alkaline metal catalysts such as KOH or sodium alkoxide, have their cations (K... + Na + After polymerization, these substances exist firmly in the product as alkoxides or hydroxides, making them difficult to remove by simple physical methods. Removal requires chemical neutralization and adsorption, leading to complex processes, high levels of residual ions in the product, and the potential introduction of other impurities. In contrast, the organic amine / ether catalyst used in this invention has moderate alkalinity, primarily acting as a nucleophile to initiate polymerization without introducing metal ions. Furthermore, its molecular characteristics allow for complete removal from the polymer matrix via distillation, which is the fundamental reason for achieving ultra-high purity and extremely simplified post-processing.

[0031] Comparative Example 2 used a one-step feeding method, resulting in excessively high monomer concentration in the initial stage of the reaction. This led to intense and uneven exothermic reactions, easily causing localized overheating. High temperatures exacerbate the isomerization side reaction of propylene oxide under alkaline conditions, generating impurities such as acrolein, which lack polymerization activity. This process consumes monomers and may cause cross-linking, manifested as a decrease in iodine value (double bond loss). The "activation-continuous dripping" mode of this invention effectively controls the reaction rate and thermal balance, maximally suppressing side reactions and ensuring the regularity of chain growth and the integrity of double bonds.

[0032] While the supported catalyst in Comparative Example 3 yielded a narrow product distribution, its core innovation lay in the catalyst's nanostructure and high activity, failing to address issues such as high catalyst cost, cumbersome preparation, and potential metal leaching. This invention takes a different approach, selecting inexpensive, readily available, and completely separable heterogeneous / quasi-homogeneous small-molecule organic catalysts. Through process design, it leverages the strengths and mitigates the weaknesses, achieving substantial improvements in economy, ease of operation, and environmental friendliness while ensuring high product performance (narrow distribution, high purity). In particular, the DMDEE catalyst, with its unique bismorpholine ring structure, likely provides a superior active site environment and stability, resulting in the highest recovery rate and lowest metal ion residue.

[0033] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing allyl alcohol random polyether, characterized in that, Includes the following steps: (1) Raw material preparation: Prepare a mixture of ethylene oxide and propylene oxide; (2) Polymerization reaction: Under inert gas protection and vacuum conditions, allyl alcohol initiator, catalyst and appropriate amount of mixture prepared in step (1) are mixed and heated for activation; then under sealed reaction conditions, appropriate amount of mixture prepared in step (1) is continuously added dropwise to carry out polymerization reaction; after the reaction is completed, it is kept warm and matured to obtain crude polyether solution; (3) Post-processing: The crude polyether solution obtained in step (2) is subjected to vacuum distillation to distill off other boiling point components. The remaining components are allyl alcohol random polyether. The distilled components mainly include the catalyst in step (2) and are used for the next batch of reaction.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of ethylene oxide to propylene oxide is (2.5-3.5):

2.

3. The preparation method according to claim 1, characterized in that: In step (2), the catalyst is at least one of N-methylmorpholine, bis(dimethylaminoethyl) ether, and bis(dimorpholinoethyl) ether; the mass of the catalyst added is 30%-75% of the mass of allyl alcohol.

4. The preparation method according to claim 1, characterized in that: In step (2), the activation temperature is 45-55℃ and the vacuum degree is not lower than -0.095MPa; the activation step lasts for 0.5-1.5h.

5. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of allyl alcohol initiator to the mixture prepared in step (1) for the first addition and the mixture prepared in step (1) for the second addition is 1:(0.8-1.2):(15-25).

6. The preparation method according to claim 5, characterized in that: The second addition step (1) prepares the mixture by continuous dripping, with a dripping time of 3-6 hours and a dripping rate of 8-10 g / min.

7. The preparation method according to claim 1, characterized in that: In step (2), the reaction temperature of the polymerization reaction is 65-95℃; the ripening step is carried out at the reaction temperature and the ripening time is 1.5-2.5h.

8. The preparation method according to claim 1, characterized in that: In step (3), the vacuum degree of the reduced pressure distillation is not lower than -0.098 MPa, and the heating rate is 5-8℃ / min.

9. The preparation method according to claim 1, characterized in that: The other boiling points mentioned in step (3) are 0-100℃.

10. The preparation method according to any one of claims 1-9, characterized in that: The prepared allyl alcohol random polyether has an average molecular weight of 1400-3100, an iodine value of 8.4-17.8 mgI / g, and a total potassium and sodium ion content of ≤3ppm.

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