A method for the synthesis of a bio-based polyester polyol for spandex using an immobilized bed catalyst

Abstract

This invention discloses a method for synthesizing polyester polyols for bio-based spandex using a fixed-bed catalytic method, belonging to the fields of polymer synthesis and enzyme catalysis. The method includes (1) preparing SiO2 nanoparticles using a reverse microemulsion method, dispersing the SiO2 nanoparticles in an organic solvent, adding hydrophobic silane and triethylamine, stirring and refluxing, washing and drying to obtain interfacially active SiO2; (2) adding an enzyme solution to deionized water and mixing to obtain an aqueous phase system, then dispersing the interfacially active SiO2 in an organic solvent by ultrasonication to obtain an oil phase system, and finally forming a Pickering emulsion with an immobilized enzyme catalyst by high-speed stirring; (3) loading the prepared Pickering emulsion with an immobilized enzyme catalyst into a fixed-bed reactor for continuous catalytic reaction, using an injection pump to precisely control the reaction flow rate, delivering the reactant solution from the top of the reactor, and periodically detecting the conversion rate of the outlet product. This invention is the first to apply enzyme-catalyzed fixed-bed mode to the ring-opening polymerization of bio-based cyclic lactones, realizing the continuous synthesis of polyester polyols. The enzyme catalysis conditions are mild, highly selective, and have few side reactions. The enzyme is not easily lost after immobilization and can be used continuously for a long time. The water in the enzyme solution is used as an initiator, saving costs. The raw materials are widely available, the device is simple and easy to scale up, and the obtained polyester polyol has a narrow molecular weight distribution and low acid value, which is suitable for dry spinning to prepare spandex fibers with high bio-based content.

Description

Technical Field

[0001] This invention relates to the field of polymer synthesis and enzyme catalysis technology, specifically to a method for synthesizing polyester polyols for bio-based spandex using fixed-bed catalysis. Technical Background

[0002] With increasingly scarce petroleum resources and stricter environmental requirements, utilizing renewable biomass to replace fossil fuels has become an important trend in the field of polymer materials. In spandex production, introducing bio-based monomers or intermediates at the raw material stage can significantly reduce the product's carbon footprint. Structurally, the soft segment of spandex mainly originates from polyols, which are key components determining the level of bio-based content. Therefore, developing bio-based polyols is a core issue in achieving high-performance bio-based spandex.

[0003] Currently, bio-based polyols include both plant-based and non-plant-based polyols, which are widely used in the chemical and pharmaceutical fields. Their preparation routes mainly include chemical modification of plant oil-based polyols, polycondensation reactions based on bio-fermentation monomers, and conversion of waste biomass-derived platform compounds. In existing technologies, most polyester polyols used for melt-spun spandex are prepared via polycondensation reactions. However, polyester polyols cannot be used for dry-spun spandex and suffer from problems such as difficulty in precisely controlling molecular structure, wide molecular weight distribution, complex end-group structures, numerous side reactions, high product color, and insufficient batch stability. Controlled ring-opening polymerization can prepare polyester polyols with preset molecular weights, narrow molecular weight distributions, and well-defined end-group structures, which can then be used for dry-spun bio-based spandex. While traditional batch ring-opening polymerization can produce polyester polyols, it is limited by problems such as low mass and heat transfer efficiency and uneven mixing in the reactor. It often requires long-term high-temperature reactions, which can easily trigger side reactions such as transesterification, degradation and coloring. This results in a wide molecular weight distribution, complex end-group structure and poor batch stability of the product, and it is difficult to achieve continuous production, which restricts its application in high-end fields such as spandex.

[0004] Existing bio-based polyols are mainly divided into two categories: plant-based and non-plant-based. Preparation routes include chemical modification of vegetable oils, monomer condensation polymerization through bio-fermentation, and conversion of biomass platform compounds. Polyester polyols used in spandex have traditionally employed condensation polymerization, but this route suffers from problems such as a wide molecular weight distribution, complex end-group structures, numerous side reactions, and poor batch-to-batch stability. Furthermore, the resulting products are difficult to use directly in dry spinning. Controlled ring-opening polymerization can effectively solve these problems, producing polyester polyols with pre-defined molecular weights, narrow distributions, and well-defined end groups, making it more suitable for dry spinning processes. However, conventional batch-type ring-opening polymerization is limited by the reactor's mass and heat transfer efficiency, often requiring prolonged high-temperature reactions. This easily induces side reactions such as transesterification, degradation, and coloring, leading to a wide molecular weight distribution, disordered end groups, large batch-to-batch variations, and difficulty in achieving continuous production. This limits its application in fields like spandex where high raw material quality is crucial.

[0005] In recent years, Pickering emulsions have attracted attention due to their good stability and large oil-water interface area, and have been the subject of numerous studies in enzyme catalysis and biphasic reactions. Combining continuous flow reaction modes with Pickering emulsions can construct fixed-bed catalytic systems, allowing reactants to continuously flow through an emulsion or granular bed of supported catalyst while simultaneously achieving online product separation. Currently, this type of fixed-bed catalysis technology is mostly used for the enzymatic synthesis of small-molecule chiral compounds and has not yet been widely applied to the continuous preparation of bio-based polyester polyols, nor has there been any report of further using its products in spandex spinning. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for synthesizing polyester polyols for bio-based spandex using a fixed-bed catalytic method.

[0007] To achieve the above objectives, the present invention employs the following technical solution.

[0008] (1) Preparation of interfacially active SiO2: 80-100nm SiO2 nanoparticles were prepared by reverse microemulsion method. The SiO2 nanoparticles were dispersed in an organic solvent and hydrophobic silane and triethylamine (catalyst) were added. The mixture was stirred and refluxed for 2-4 hours under nitrogen protection at 60-120℃. The mixture was then centrifuged and the obtained solid was washed 3-4 times with toluene and ethanol respectively. After vacuum drying, interfacially active SiO2 was obtained.

[0009] (2) Preparation of Pickering emulsion for immobilized catalyst: The enzyme solution was added to deionized water and mixed to obtain an aqueous phase system. Then, the interfacial active SiO2 was dispersed in an organic solvent by ultrasonication to obtain an oil phase system. Finally, the Pickering emulsion for immobilized enzyme catalyst was formed by high-speed stirring.

[0010] (3) The Pickering emulsion of the supported catalyst prepared above is loaded into a fixed bed reactor for continuous catalytic reaction. The reaction flow rate is precisely controlled by an injection pump, and the reactant solution is delivered from the top of the reactor with an inner diameter of 4 mm. The conversion rate of the outlet product is detected at regular intervals. The reactor temperature is 25-50℃. The reactor flow rate range is 0.2-10 ml / h.

[0011] (4) The organic solvent mentioned in step (1) is any one of toluene, heptane, hexane, ethyl acetate, methyl tert-butyl ether or octane.

[0012] (5) The hydrophobic silane mentioned in step (1) is any one of methyltrimethoxysilane, dichlorodimethoxysilane, or octyltrimethoxysilane.

[0013] (6) The enzyme mentioned in step (2) is any one of Candida antarcticis lipase A (CALA), Candida antarcticis lipase B (CALB), Candida corporis lipase (CRL) or Burkholderia cepacia lipase (BCL).

[0014] (7) The high-speed stirring speed in step (2) is 10000-12000 rpm.

[0015] (8) The reactant solution in step (3) is a lactone monomer solution, and the monomer structure I has the following structural formula:

[0016]

[0017] R is selected from ethyl, propyl, isopropyl, butyl, pentyl, hexyl, and decyl.

[0018] Beneficial effects:

[0019] (1) This invention is the first to apply enzyme-catalyzed fixed-bed mode to the ring-opening polymerization of bio-based cyclic lactones, realizing the continuous synthesis of polyester polyols, changing the limitations of traditional batch reactor operation, and the device is simple, easy to control, and suitable for large-scale production.

[0020] (2) Enzyme-catalyzed reactions have advantages such as mild conditions, high catalytic efficiency, and strong specificity. Their high efficiency in chemical, stereo, and regioselectivity helps to reduce costs, improve reaction efficiency, avoid unnecessary side reactions, and reduce environmental pollution.

[0021] (3) The enzyme is immobilized on the support and is not easily lost in the fixed bed. It can be used continuously for a long time without the need for separation and recovery each time as in homogeneous catalysis, which significantly reduces the cost of catalyst and the hassle of operation.

[0022] (4) The trace amount of water contained in the enzyme solution can act as an initiator for ring-opening polymerization, eliminating the need for additional alcohol initiators, thus saving on raw material costs and subsequent separation and purification steps. At the same time, it avoids impurities and side reactions that may be introduced by adding external initiators. Attached Figure Description

[0023] The embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein...

[0024] Figure 1 This is a scanning electron microscope image of the SiO2 nanoparticles prepared in Example 1 of this invention.

[0025] Figure 2 This is a diagram showing the water contact angle of the SiO2 nanoparticles prepared in Example 1 of this invention before modification.

[0026] Figure 3 : This is a water contact angle diagram of the SiO2 nanoparticles prepared in Example 1 of this invention after hydrophobic modification.

[0027] Figure 4 : This is a Pickering morphology image obtained in Example 1 of the present invention.

[0028] Figure 5 : The hydrogen spectrum of the polyester polyol product prepared in Example 1 of this invention. Detailed Implementation

[0029] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0030] Example 1

[0031] 1) Disperse 1.5g of dried SiO2 nanoparticles into 8mL of toluene, add 3mmol of methyltrimethoxysilane and 3mmol of triethylamine, and reflux at 110℃ under nitrogen protection for 4 hours with stirring. Then centrifuge, wash and dry to obtain interfacially active nano-SiO2.

[0032] 2) Add 0.2 mL of CALB enzyme solution with a concentration of 2 mg / mL to 6.5 mL of deionized water and mix evenly by magnetic stirring; then, ultrasonically disperse 0.18 g of interfacial active SiO2 in 8 mL of toluene and add it to the above mixture of deionized water and enzyme; finally, stir at high speed of 10000 rpm to form a Pickering emulsion with immobilized enzyme catalyst.

[0033] 3) The Pickering emulsion of the prepared supported catalyst was transferred to a fixed-bed reactor with an inner diameter of 4 mm, and the reactor temperature was set to 30 °C. A 0.1 mol / L solution of 1,4-dioxane-5,8-dione toluene was introduced by a syringe pump at a flow rate of 3 mL / h to carry out the ring-opening polymerization reaction. The reaction was carried out continuously for 100 hours, and the conversion rate reached 80%.

[0034] Example 2

[0035] The preparation method is the same as in Example 1, except that the hydrophobic silane in step (1) is dichlorodimethoxysilane, and the reaction is carried out continuously for 100 hours, with a conversion rate of 73%.

[0036] Example 3

[0037] The preparation method is the same as in Example 1, except that the organic solvent in step (1) is ethyl acetate, and the reaction is carried out continuously for 100 hours, with a conversion rate of 75%.

[0038] Example 4

[0039] The preparation method is the same as in Example 1, except that the enzyme solution in step (2) is BCL enzyme, and the reaction is carried out continuously for 100 hours, with a conversion rate of 65%.

[0040] Example 5

[0041] The preparation method is the same as in Example 1, except that the high-speed stirring speed in step (2) is 11,000 rpm, the reaction is carried out continuously for 100 hours, and the conversion rate reaches 88%.

[0042] Example 6

[0043] The preparation method is the same as in Example 1, except that the high-speed stirring speed in step (2) is 11,000 rpm, the reaction is carried out continuously for 100 hours, and the conversion rate reaches 85%.

[0044] Example 7

[0045] The preparation method is the same as in Example 1, except that the reactor temperature in step (3) is 45°C, the reaction is carried out continuously for 100 hours, and the conversion rate reaches 91%.

[0046] Example 8

[0047] The preparation method is the same as in Example 1, except that the reactor temperature in step (3) is 45°C, the reaction is carried out continuously for 100 hours, and the conversion rate reaches 91%.

[0048] Example 9

[0049] The preparation method is the same as in Example 1, except that the flow rate in step (3) is 5 ml / h, the reaction is carried out continuously for 100 hours, and the conversion rate reaches 71%.

[0050] Example 10

[0051] The preparation method is the same as in Example 1, except that the cyclic ester monomer in step (3) is [missing information], and the reaction is carried out continuously for 100 hours, with a conversion rate of 71%.

Claims

1. A method for synthesizing polyester polyols for bio-based spandex using immobilized bed catalysis, characterized in that, Includes the following steps: (1) Preparation of interfacially active SiO2: 80-100nm SiO2 nanoparticles were prepared by reverse microemulsion method. The SiO2 nanoparticles were dispersed in an organic solvent, and hydrophobic silane and triethylamine (catalyst) were added. The mixture was stirred and refluxed at 60-120℃ under nitrogen protection for 2-4 hours. The mixture was then centrifuged and the obtained solid was washed with toluene and ethanol 3-4 times respectively. After vacuum drying, interfacially active SiO2 was obtained. (2) Preparation of Pickering emulsion for immobilized enzyme catalyst: The enzyme solution was added to deionized water and mixed to obtain an aqueous phase system. Then, the interfacial active SiO2 was dispersed in an organic solvent by ultrasonication to obtain an oil phase system. Finally, the Pickering emulsion for immobilized enzyme catalyst was formed by high-speed stirring. (3) The Pickering emulsion of the immobilized enzyme catalyst prepared above is loaded into a fixed bed reactor for continuous catalytic reaction. The reaction flow rate is precisely controlled by an injection pump, and the reactant solution is delivered from the top of the reactor with an inner diameter of 4 mm. The conversion rate of the outlet product is detected at regular intervals. The reactor temperature is 25-50℃. The reactor flow rate range is 0.2-10 ml / h.

2. The organic solvent of claim 1 is any one of toluene, heptane, hexane, ethyl acetate, methyl tert-butyl ether, or octane.

3. The hydrophobic silane of claim 1 is any one of methyltrimethoxysilane, dichlorodimethoxysilane, and octyltrimethoxysilane.

4. The enzyme described in claim 1 is any one of Candida antarcticis lipase A (CALA), Candida antarcticis lipase B (CALB), Candida corporis lipase (CRL), or Burkholderia cepacia lipase (BCL).

5. The high-speed stirring speed of claim 1 is 10000-12000 rpm.

6. The reactant solution of claim 1 is a lactone monomer solution, wherein the monomer structure I has the following structural formula: R is selected from ethyl, propyl, isopropyl, butyl, pentyl, hexyl, and decyl.

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