Dehydrated fibrous membrane, method for preparing the same, and use thereof

Abstract

The present application relates to the technical field of purification, and discloses a dehydrated fiber membrane and a preparation method and application thereof.A dehydrated fiber membrane, wherein the dehydrated fiber membrane comprises a hollow fiber membrane base, a first silane membrane, a first hydrophilic membrane and a first modified membrane are coated on the inner surface of the hollow fiber membrane base from inside to outside, and a second silane membrane, a second hydrophilic membrane and a second modified membrane are coated on the outer surface of the hollow fiber membrane base from inside to outside; the first hydrophilic membrane and the second hydrophilic membrane each independently contain an amide group; the first modified membrane contains a sulfonamide group; and the second modified membrane contains a pyrrole group, a sulfhydryl group and / or a sulfide group.The dehydrated fiber membrane can effectively reduce the content of oligomers in the hydroxyacetic acid dehydration process.

Description

Technical Field

[0001] This invention relates to the field of purification technology, specifically to a dehydrated fiber membrane, its preparation method, and its application. Background Technology

[0002] Glycolic acid, also known as glycolic acid, is the simplest α-amino acid. It is an important organic synthesis intermediate that can replace hydrochloric acid, citric acid, and EDTA in chemical cleaning. It can also be used to prepare anti-skin aging and whitening cosmetics, as a dyeing auxiliary in wool dyeing, and as a crosslinking coupling agent or catalyst in cellulose fabrics. Furthermore, due to the biodegradability of glycolic acid polymers, they can be used to prepare polyglycolic acid (PGA) or polylactic-co-glycolic acid (PLGA). These materials possess unique properties such as non-toxicity, biocompatibility, and in vitro and in vivo degradation, making them widely applicable in medical polymer fields such as suture reinforcement materials, bioabsorbable sutures, fracture fixation materials, drug delivery carriers, and tissue engineering.

[0003] Methods for synthesizing glycolic acid include the chloroacetic acid hydrolysis method (i.e., chloroacetic acid is hydrolyzed in the presence of sodium hydroxide to produce glycolic acid), the cyanidation method (using formaldehyde and hydrogen cyanide or sodium cyanide as initial raw materials, hydroxyacetonitrile is synthesized by adding cyanide, and then hydrolyzed under acidic conditions at a temperature of about 100-150℃ to obtain glycolic acid), the formaldehyde carbonylation method (under high temperature and high pressure conditions, using specific catalysts and reaction media, formaldehyde, carbon monoxide and water can be converted into glycolic acid through a alkylation reaction), and the dimethyl oxalate hydrogenation method (dimethyl oxalate is prepared by syngas, dimethyl oxalate is catalytically hydrogenated to prepare methyl glycolate, and then glycolate is hydrolyzed to obtain glycolic acid), etc.

[0004] When glycolic acid is used in high-end fields such as electronic cleaning agents or polymer monomers, its quality requirements are high. However, glycolic acid has the characteristics of easy polymerization when heated, easy decomposition at boiling point, and extremely low volatility, which greatly limits the separation methods. Currently available separation methods include crystallization, solvent extraction, and esterification.

[0005] Patent application CN113845415A discloses a method, apparatus, and application for the separation and purification of glycolic acid using a distillation-crystallization coupling technology. This method utilizes bio-based platform compound molecules as raw materials to synthesize glycolic acid, and then uses a vacuum distillation-crystallization coupling technology to separate and purify the obtained crude glycolic acid, yielding high-purity glycolic acid. This process is essentially a conventional separation method, and the resulting product is generally used in conventional fields such as industrial cleaning. Patent application CN112645814A discloses a method for purifying glycolic acid and glycolic acid crystals and their applications, which significantly improves the quality of glycolic acid through a molecular distillation-crystallization coupling method. This process is generally used for small-batch refining of glycolic acid, but its capacity is limited when used for large-batch degradable polymerizable monomers.

[0006] The paper "Extraction of Glycoacetic Acid by Solvent Extraction" (Journal of East China University of Science and Technology: Natural Science Edition, 1994, Vol. 2, pp. 148-153) discloses a method using trialkylphosphine oxide as the extractant and sulfonated kerosene as the diluent. Extraction is carried out at room temperature and with an initial aqueous phase pH of 1-3, with an extractant composition of 50% trialkylphosphine oxide and 50% sulfonated kerosene. Then, the glycolic acid in the loaded organic phase is back-extracted with deionized water, achieving a single back-extraction rate of 73.4% at 90°C. Products prepared using this process are generally used in routine cleaning applications; introducing the extractant can lead to the introduction of new impurities into the product.

[0007] The "Chemical Products Handbook - Organic Chemical Raw Materials" (Volume 1) (Institute of Scientific and Technological Information, Ministry of Chemical Industry, Beijing: Chemical Industry Press, 1985) introduces the esterification and hydrolysis purification method for glycolic acid. However, the repeated process of dehydration-esterification-hydrolysis of the hydrolyzed glycolic acid product leads to a decrease in the yield of glycolic acid.

[0008] Existing glycolic acid purification technologies primarily yield products used in routine cleaning applications. However, when applied to electronic-grade chemicals, particularly biodegradable polymer monomers, impurities such as oligomers in the glycolic acid products have been found to significantly impact the microscopic cleaning effect on circuit boards or silicon wafers, as well as the molecular weight of polyglycolic acid and the physicochemical properties of the polymer. Glycolic acid dehydration technology is a promising area within glycolic acid purification technology, and efficient dehydration processes are a crucial direction for improving glycolic acid quality. Summary of the Invention

[0009] The purpose of this invention is to overcome the problem of high oligomer formation during the dehydration process of glycolic acid in the prior art, and to provide a dehydrated fiber membrane, its preparation method and application, which can reduce the content of oligomers during the dehydration process of glycolic acid.

[0010] To achieve the above objectives, a first aspect of the present invention provides a dehydrated fiber membrane, wherein the dehydrated fiber membrane comprises a hollow fiber membrane substrate, a first silane membrane, a first hydrophilic membrane, and a first modified membrane sequentially coated on the inner surface of the hollow fiber membrane substrate from the inside out, and a second silane membrane, a second hydrophilic membrane, and a second modified membrane sequentially coated on the outer surface of the hollow fiber membrane substrate from the inside out; the first hydrophilic membrane and the second hydrophilic membrane each independently contain amide groups; the first modified membrane contains sulfonamide groups; and the second modified membrane contains pyrrole groups, mercapto groups, and / or sulfides.

[0011] A second aspect of the present invention provides a method for preparing a dehydrated fiber membrane, wherein the method includes:

[0012] (1) The inner and outer surfaces of the hollow fiber membrane substrate are subjected to silanization treatment to obtain a silanized hollow fiber membrane;

[0013] (2) The inner and outer surfaces of the silanized hollow fiber membrane are hydrophilically treated with hydrophilic components to obtain a hydrophilically treated hollow fiber membrane.

[0014] (3) The inner and outer surfaces of the hydrophilic hollow fiber membrane are subjected to first modification treatment and second modification treatment respectively using the first modification component and the second modification component to obtain a dehydrated fiber membrane; the hydrophilic component contains amide group, the first modification component contains sulfonamide group, and the second modification component contains pyrrole group, mercapto group and / or thioether.

[0015] The third aspect of the present invention provides the application of the dehydrated fiber membrane described in the first aspect or the dehydrated fiber membrane prepared by the preparation method described in the second aspect in the dehydration of hydroxy fatty acids, preferably in the dehydration separation of aqueous glycolic acid, and more preferably in the dehydration separation by contacting the aqueous glycolic acid with the dehydrated fiber membrane to obtain a dehydrated aqueous glycolic acid solution.

[0016] During their model testing, the inventors of this invention discovered that the dehydration of glycolic acid solutions typically employs distillation. In distillation, the water and glycolic acid to be separated are in a homogeneous mixture in the liquid phase. Heating this homogeneous liquid phase causes the volatile lighter component, water, to escape. However, due to the high heat sensitivity of glycolic acid, it polymerizes during heating to form oligomers or colored impurities, leading to a decrease in product purity and quality. This invention enhances the microscopic water distribution process, improving dehydration efficiency and reducing oligomer formation.

[0017] The hollow ceramic fiber membrane used in this invention has significantly improved strength compared to organic membranes, making it more suitable for heat-sensitive polymer systems. Through an external pressure flow direction (glycolic acid solution flowing through the shell side and clean aqueous phase flowing through the tube side), solid impurities in the material can be trapped on the outside of the hollow fiber membrane. Regeneration of the hollow fiber membrane can be easily achieved through backwashing from the inside. Subsequent silanization treatment further refines the pore size distribution of the fiber membrane. This silane membrane exhibits good temperature resistance in hot glycolic acid solution, and its service life meets the requirements for major overhaul intervals of the equipment.

[0018] The first and second hydrophilic membranes of this invention exhibit excellent hydrophilicity in aqueous glycolic acid solutions. Upon contact with water, they form a water-rich molecular structure, thereby creating an aqueous film layer outside the silane membrane. This aqueous film layer has a similar temperature to the bulk liquid phase, but with an extremely low concentration of glycolic acid solute, achieving a near-pure water layer state. Its overall volatility is close to that of pure water, significantly higher than that of the bulk liquid phase. This aqueous film layer is connected to the inner cavity of the hollow fiber membrane through silanized layer-modified pores. When there is negative pressure or carrier gas flow within the fiber membrane cavity, water molecules in the aqueous film layer continuously diffuse into the fiber membrane cavity under the influence of mass transfer, and are subsequently carried out of the glycolic acid solution system. Simultaneously, water molecules from the bulk liquid phase continuously enter this aqueous film layer, thereby achieving concentration and dehydration of the bulk liquid phase.

[0019] The second modified membrane of this invention is a selectively permeable layer, exhibiting low selective permeability to glycolic acid molecules in the glycolic acid solution and no significant inhibition of water molecule permeability. This allows water molecules in the bulk liquid phase to continuously transfer mass to the water film layer formed by the first modification treatment, and subsequently, further mass transfer to the inner cavity of the fiber membrane after silanization treatment. Due to the highly efficient barrier effect of the second modified membrane against glycolic acid molecules, a solution phase containing or rich in glycolic acid is formed on the outer side of the second modified membrane, while a high-purity aqueous phase is formed on the inner side. This achieves differential phase separation of the bulk liquid phase, transforming the dehydration of the low-volatility mixed liquid phase into the separation of the high-volatility, water-rich aqueous phase. This results in lower dehydration temperature, higher dehydration efficiency, and reduced side reactions during the dehydration process. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] In this invention, it is understood that the groups and their contents in the membrane layers mentioned herein were all determined by infrared spectroscopy, specifically under KBr pellet compression at 400 cm⁻¹. -1 -4000cm -1 Scan within the range.

[0022] In this invention, it is understood that the thickness of the film layers mentioned herein was measured by an X-ray fluorescence thickness gauge.

[0023] The first aspect of the present invention provides a dehydrated fiber membrane, wherein the dehydrated fiber membrane comprises a hollow fiber membrane substrate, a first silane membrane, a first hydrophilic membrane, and a first modified membrane sequentially coated on the inner surface of the hollow fiber membrane substrate from the inside out, and a second silane membrane, a second hydrophilic membrane, and a second modified membrane sequentially coated on the outer surface of the hollow fiber membrane substrate from the inside out; the first hydrophilic membrane and the second hydrophilic membrane each independently contain amide groups; the first modified membrane contains sulfonamide groups; and the second modified membrane contains pyrrole groups, mercapto groups, and / or sulfides.

[0024] In this invention, it is understood that the hollow fiber membrane substrate is a hollow fiber membrane with an internal hollow cylinder as conventionally defined in the art. The inner surface mentioned in this invention refers to the inner surface of the hollow cylinder, and the outer surface mentioned in this invention refers to the outer surface of the hollow cylinder.

[0025] In this invention, there is no particular limitation on the type of hollow fiber membrane substrate. Preferably, the hollow fiber membrane substrate is hollow ceramic fiber.

[0026] In a preferred embodiment, the hollow ceramic fiber has an inner diameter of 0.2-1 mm, an outer diameter of 1.2-2 mm, a pore size of 15-52 nm in the fiber membrane wall, and a porosity of 30-53%.

[0027] In a preferred embodiment, the hollow ceramic fiber membrane is made of silicon dioxide and / or alumina.

[0028] In a preferred embodiment, the first silane membrane and the second silane membrane each independently include a molar ratio of (-Si-O-Si-) to (-Si-OR) groups of 4-16; wherein M is silicon and / or aluminum derived from the hollow fiber membrane substrate. In this invention, it is understood that the (-Si-OR) group is formed by the dehydration condensation of silane and hydroxyl groups on the surface of the hollow fiber membrane substrate.

[0029] In a preferred embodiment, the thickness of the first silane film and the second silane film are each independently 10-21 micrometers.

[0030] In this invention, it is understood that the first silane membrane and the second silane membrane are prepared by immersing the hollow fiber membrane in the silane component, so that both the inner and outer surfaces of the hollow fiber membrane are in contact with the silane component. Therefore, the thickness of the first silane membrane and the content of the groups (-Si-O-Si-) and (-Si-OR) are the same.

[0031] In a preferred embodiment, the first silane membrane and the second silane membrane are each independently provided by at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate, and 3-(isobutenoyloxy)propyltrimethoxysilane.

[0032] In a preferred embodiment, based on the total surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of amide groups independently contained in the first and second hydrophilic membranes is 8-29.3 mmol / m². 2 The preferred value is 18-29.3 mmol / m². 2 The advantage of this preferred embodiment is that, based on the modification of the membrane pores and membrane surface by the silane membrane, a layer of hydrophilic groups is formed on the inner and outer surfaces of the membrane, thereby forming a water film layer in the aqueous system by absorbing water, creating a water-rich environment for subsequent dehydration and reducing the difficulty of dehydration.

[0033] In a preferred embodiment, the thickness of the first hydrophilic membrane and the second hydrophilic membrane are each independently 12-21 micrometers.

[0034] In this invention, it is understood that in the preparation process of the first and second hydrophilic membranes, the silane-treated fiber membrane substrate is immersed in the hydrophilic component, so that both the inner and outer surfaces of the hollow fiber membrane are in contact with the hydrophilic component. Therefore, the thickness and amide group content of the first and second hydrophilic membranes are the same.

[0035] In a preferred embodiment, based on the inner surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of sulfonamide groups in the first modified membrane is 0.6-1.4 mmol / m². 2 The preferred value is 0.9-1.4 mmol / m 2 The advantage of this preferred embodiment is that by further modifying the inner surface of the fiber membrane, the hydrophilicity of the inner surface is improved, which promotes the mass transfer of water from the outer surface to the inner surface.

[0036] In a preferred embodiment, the thickness of the first modified film is 0.3-0.8 micrometers.

[0037] In a preferred embodiment, based on the outer surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of pyrrole groups in the second modified membrane is 48-70 mmol / m². 2 The content of thiol groups and / or thioethers is 6-45 mmol / m 2 Preferably, the pyrrole group content is 59-70 mmol / m 2 The content of thiol groups and / or thioethers is 13.5-45 mmol / m³. 2The advantage of this preferred embodiment is that a selectively permeable layer is formed outside the hydrophilic layer on the outer surface of the hollow fiber membrane by grafting groups that repel glycolic acid, allowing the water components in the solution to easily pass through this layer into the hydrophilic layer.

[0038] In a preferred embodiment, based on the outer surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of thiol groups in the second modified membrane is 6-22 mmol / m². 2 The sulfide content is 6-22 mmol / m³. 2 The preferred thiol content is 13.5-22 mmol / m³. 2 The sulfide content is 13.5-22 mmol / m³. 2 .

[0039] In this invention, the thickness of the second modified film is 4-9 micrometers.

[0040] A second aspect of the present invention provides a method for preparing a dehydrated fiber membrane, wherein the method includes:

[0041] (1) The inner and outer surfaces of the hollow fiber membrane substrate are subjected to silanization treatment to obtain a silanized hollow fiber membrane;

[0042] (2) The inner and outer surfaces of the silanized hollow fiber membrane were hydrophilically treated with hydrophilic components to obtain a hydrophilically treated hollow fiber membrane.

[0043] (3) The inner and outer surfaces of the hydrophilic hollow fiber membrane are subjected to first modification treatment and second modification treatment respectively using the first modification component and the second modification component to obtain a dehydrated fiber membrane.

[0044] The hydrophilic component contains an amide group, the first modified component contains a sulfonamide group, and the second modified component contains a pyrrole group, a mercapto group, and / or a thioether.

[0045] In this invention, the type, material and characteristic parameters of the hollow fiber membrane substrate in step (1) have been described in the first aspect and will not be repeated here.

[0046] In this invention, there is no particular limitation on the preparation method of the hollow fiber membrane matrix. For example, it can be prepared by the following method: First, a casting solution is prepared, and then a hollow fiber preform is prepared by spinning and phase inversion. Subsequently, hollow ceramic fibers are obtained by drying and calcination. The preparation conditions of the hollow ceramic fibers are as follows: polyethersulfone (average molecular weight of 1000-3000), N-methylpyrrolidone, ceramic precursor (silica or alumina), and polyvinylpyrrolidone K90 are mixed in a mass ratio of (7-15):(60-90):(180-350):(3-8) and stirred at 70-90°C for 30-50 hours. Then, the mixture is allowed to stand for 6-10 hours to remove bubbles, and the casting solution is obtained. The inner and outer gel baths of the spinneret are filled with deionized water at 0-3℃. The inner diameter of the spinneret is 0.3-1.0 mm and the outer diameter is 1.3-2.0 mm. The casting solution flow rate is 5-9 ml / min, the casting solution pressure inside the spinneret is 150-400 kPa (gauge pressure), the ambient temperature is 20-30℃, and the ambient humidity is 45-60%. The casting solution undergoes solvent exchange with the inner and outer gel baths and solidifies through phase separation to form a hollow fiber preform. After washing the hollow fiber membrane preform 4-8 times with deionized water, it is dried with air at 20-30℃, then heated to 1600-1800℃ using a programmed temperature increase of 0.5-1℃ / min, held at that temperature for 3-6 hours, and then allowed to cool naturally to 20-30℃ to obtain the hollow ceramic fiber membrane matrix.

[0047] In a preferred embodiment, in step (1), the silanization treatment forms a first silane membrane on the inner surface of the hollow fiber membrane and a second silane membrane on the outer surface. In this invention, it is understood that the first silane membrane is coated on the inner surface of the hollow fiber membrane substrate, and the second silane membrane is coated on the outer surface of the hollow fiber membrane substrate. The advantage of this preferred embodiment is that silanization treats the inner and outer surfaces of the membrane, regulates the membrane pores, and improves the selectivity of water permeation.

[0048] In this invention, the thicknesses of the first silane film and the second silane film have been described in the first aspect and will not be repeated here.

[0049] In a preferred embodiment, the silanization process includes: contacting a silane reagent solution with the inner and outer surfaces of the hollow fiber membrane substrate, followed by drying and curing.

[0050] In this invention, there are no particular limitations on the contact conditions. Preferably, the number of contacts is 3-6 times, and the contact time for each contact is 3-6 minutes.

[0051] In this invention, there are no particular limitations on the drying and curing conditions. Preferably, the temperature is 110-130℃, the time is 30-50 minutes, and the number of drying and curing cycles is 3-6.

[0052] In this invention, preferably, the drying of the solid is carried out under a protective atmosphere, preferably an inert atmosphere or nitrogen.

[0053] In a preferred embodiment, in step (1), the silane reagent solution is obtained by mixing a silane reagent, water, and anhydrous low alcohol, and then performing pre-hydrolysis.

[0054] In a preferred embodiment, the pre-hydrolysis time is 15-30 hours.

[0055] In a preferred embodiment, the volume ratio of silane reagent: water: anhydrous low alcohol is (3.2-6.2):(5-8.1):(90-96).

[0056] In a preferred embodiment, the pH value of the silane reagent solution is 7.5-8.5.

[0057] In a preferred embodiment, the silane reagent is selected from at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate, and 3-(isobutenoyloxy)propyltrimethoxysilane.

[0058] In a preferred embodiment, the anhydrous low-carbon alcohol is anhydrous methanol and / or anhydrous ethanol.

[0059] In a preferred embodiment, in step (1), the amount of silane reagent solution used is such that the molar ratio of the groups (-Si-O-Si-) to the groups (-Si-OM) that independently comprise the first silane membrane and the second silane membrane is 4-16, wherein M is silicon and / or aluminum derived from the hollow fiber membrane matrix.

[0060] In a preferred embodiment, in step (2), the hydrophilic treatment causes the inner and outer surfaces of the silanized hollow fiber membrane to be coated with a first hydrophilic membrane and a second hydrophilic membrane, respectively, wherein the first hydrophilic membrane and the second hydrophilic membrane each independently contain amide groups.

[0061] In a preferred embodiment, based on the total surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of amide groups independently contained in the first and second hydrophilic membranes is 8-29.3 mmol / m². 2 The preferred value is 18-29.3 mmol / m². 2 .

[0062] In a preferred embodiment, step (2) includes contacting a solution containing a hydrophilic component with a silanized hollow fiber membrane.

[0063] In a preferred embodiment, in step (2), the mass ratio of the hydrophilic component to the first initiator to the first solvent in the solution containing the hydrophilic component is (6-11):(0.6-1.8):(230-275).

[0064] In a preferred embodiment, the first solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene.

[0065] In a preferred embodiment, the first initiator is selected from at least one of azo initiators, organic peroxide initiators, inorganic peroxide initiators, and redox initiators, preferably at least one of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and hydrogen peroxide, and more preferably benzoyl peroxide.

[0066] In a preferred embodiment, the hydrophilic component is an amide derivative, wherein the amide group is provided by an amide derivative, preferably by at least one of N,N'-[ethylenedi(oxymethylene)] bis(acrylamide), N,N'-(1,2-dihydroxyethylene) bisacrylamide, and hexamethylenebisacrylamide.

[0067] In a preferred embodiment, in step (2), the hydrophilic treatment conditions include: the liquid-to-solid volume ratio of the solution containing the hydrophilic component to the silanized hollow fiber membrane described in step (1) is 2-5, the immersion temperature is 55-75°C, and the time is 1.8-3.5h.

[0068] In a preferred embodiment, step (2) further includes hydrophilic post-treatment of the hydrophilic treatment product in a hydrophilic post-treatment agent.

[0069] In a preferred embodiment, the hydrophilic posttreatment agent is selected from at least one of anhydrous methanol, anhydrous ethanol, and anhydrous acetone, preferably anhydrous ethanol.

[0070] In a preferred embodiment, the conditions for the first post-soaking treatment include: soaking time of 35-300 min, drying temperature of 120-150℃, and drying time of 10-30 min.

[0071] In a preferred embodiment, in step (3), the first modification treatment causes the inner surface of the hydrophilically treated hollow fiber membrane to be coated with a first modified membrane, the first modified membrane containing sulfonamide groups.

[0072] In a preferred embodiment, based on the inner surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of sulfonamide groups in the first modified membrane is 0.6-1.4 mmol / m². 2 The preferred value is 0.9-1.4 mmol / m 2 .

[0073] In a preferred embodiment, step (3) includes contacting a solution containing the first modified component with a hydrophilically treated hollow fiber membrane.

[0074] In a preferred embodiment, in step (3), the mass ratio of polyether: first modified component: second initiator: water in the solution containing the first modified component is 100:(0.6-1.8):(0.1-0.5):(1-2.3).

[0075] In a preferred embodiment, the polyether has an average molecular weight of 800-2000.

[0076] In a preferred embodiment, the second initiator is selected from at least one of azo initiators, organic peroxide initiators, inorganic peroxide initiators, and redox initiators, preferably at least one of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and hydrogen peroxide, and more preferably benzoyl peroxide.

[0077] In a preferred embodiment, the first modifying component is provided by a sulfonamide derivative, preferably by at least one of vinylsulfonamide, 2-propylene-1-sulfonamide, and pentenesulfonamide.

[0078] In a preferred embodiment, step (3) includes the following first modification treatment conditions: introducing a solution containing the first modified component into the inner cavity of the hollow fiber membrane after hydrophilic treatment in step (2), with the back pressure at the outlet of the inner cavity measured by a gauge pressure gauge being 5-10 kg. In a specific embodiment, the first modification treatment includes: pumping a solution containing the first modified component into the inner cavity of the hollow fiber membrane after hydrophilic treatment in step (2), stopping the pumping of the solution containing the first modified component when fluid is present at the openings of the outer surface of the hollow fiber membrane. In this invention, the first modification treatment further includes treatment at 60-80°C for 0.6-1.5 hours under a protective atmosphere (preferably nitrogen). The advantage of this preferred embodiment is that by reacting the polyether in the solution containing the first modified component with water to form a gel, the polyether gel is pumped into the inner cavity of the hollow fiber membrane under pressure, and the pumping is stopped when fluid begins to seep out from the openings on the outer surface of the hollow fiber membrane, further hydrophilic modification of the inner cavity of the membrane is achieved separately, thereby forming a hydrophilic gradient distribution on the inner and outer surfaces of the hollow fiber membrane.

[0079] In a preferred embodiment, in step (3), the second modification treatment causes the outer surface of the hollow fiber membrane after the first modification treatment to be coated with a second modified membrane, the second modified membrane containing pyrrole groups, mercapto groups and / or thioethers.

[0080] In a preferred embodiment, the pyrrole group content is 48-70 mmol / m² based on the outer surface area of ​​the dry-based hollow fiber membrane matrix. 2The content of thiol groups and / or thioethers is 6-45 mmol / m 2 Preferably, the pyrrole group content is 58-70 mmol / m 2 The content of thiol groups and / or thioethers is 13.5-45 mmol / m³. 2 .

[0081] In a preferred embodiment, based on the outer surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of thiol groups in the second modified membrane is 6-22 mmol / m². 2 The sulfide content is 6-22 mmol / m³. 2 The preferred thiol content is 13.5-22 mmol / m³. 2 The sulfide content is 13.5-22 mmol / m³. 2 .

[0082] In a preferred embodiment, step (3) includes contacting a solution containing the second modified component with the hollow fiber membrane after the first modified treatment.

[0083] In this invention, it is understood that polyether has been used to gel fill the cavity of the hollow fiber membrane during the first modification process, and the cavity has been completely filled. Therefore, the second modification component exists only on the outer surface of the hollow fiber membrane.

[0084] In a preferred embodiment, in step (3), the mass ratio of the second modified component to the third initiator to the second solvent in the solution containing the second modified component is (13.5-28):(1.2-3.5):(200-300).

[0085] In a preferred embodiment, the second modified component has a molar ratio of pyrrole:thiol and / or thioether = (2.5-12):1.

[0086] In a preferred embodiment, in step (3), the second solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene.

[0087] In a preferred embodiment, in step (3), the pyrrole group in the second modified component is provided by a pyrrole derivative, preferably by at least one of methyl 4-vinyl-1H-pyrrole-3-carboxylate, methyl 5-vinyl-1H-pyrrole-2-carboxylate, 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, 5-allyl-4-methoxy-1,5-dihydro-2H-pyrrole-2-one, 1-allyl-2-cyclopentyl-1H-pyrrole, 1-(1-phenylvinyl)pyrrole, 3-isopropenyl-1-methyl-pyrrole, and 1-allyl-2-isopropenyl-1H-pyrrole; the mercapto group and / or thioether are provided by their respective derivatives, preferably by bis(4-methacryloylthiophenyl) thioether and / or allyl 2-mercaptopropionate.

[0088] In a preferred embodiment, in step (3), the second modification treatment conditions include: the liquid-to-solid volume ratio of the solution containing the second modified component to the hollow fiber membrane after the first modification treatment described in step (3) is 2-5, the immersion temperature is 57-78°C, and the time is 1-3 hours.

[0089] In a preferred embodiment, step (3) further includes subjecting the second modified product to a second immersion post-treatment in a second post-treatment agent.

[0090] In a preferred embodiment, the second post-treatment agent is selected from at least one of anhydrous methanol, anhydrous ethanol, and anhydrous acetone, preferably anhydrous ethanol.

[0091] In a preferred embodiment, the conditions for the second post-soaking treatment include: soaking time of 35-300 min, drying temperature of 120-150°C, and drying time of 10-30 min.

[0092] In a preferred embodiment, step (3) further includes immersing the second modified post-treatment product in an organic solvent.

[0093] In a preferred embodiment, the organic solvent is acetonitrile and / or diethyl ether, preferably acetonitrile. The advantage of this preferred embodiment is that it effectively removes polyether gel from the hollow fiber membrane cavity, restoring the membrane cavity and pores.

[0094] In a preferred embodiment, the conditions for the organic solvent immersion treatment include an immersion time of 35-300 min.

[0095] The third aspect of the present invention provides the application of the dehydrated fiber membrane described in the first aspect or the dehydrated fiber membrane prepared by the preparation method described in the second aspect in the dehydration of hydroxy fatty acids, preferably the application in the dehydration of aqueous glycolic acid, and more preferably the dehydration of aqueous glycolic acid by contacting the dehydrated fiber membrane to obtain a dehydrated aqueous glycolic acid solution.

[0096] In this invention, the source of the aqueous solution of glycolic acid is not particularly limited and can be any method conventionally defined in the art. Preferably, the aqueous solution of glycolic acid can be derived from at least one of the following methods: hydrolysis of chloroacetic acid, cyanation, formaldehyde carbonylation, electrolytic reduction of oxalic acid, coupling of formaldehyde and methyl formate, hydrogenation of dimethyl oxalate, and microbial catalysis.

[0097] In this invention, preferably, the aqueous solution of glycolic acid contains the following components: water content of 30-90% by mass percentage, glycolic acid content of 7-67%, and oligomer content of 0-3%.

[0098] In this invention, preferably, the oligomer is selected from at least one of glycolic acid dimers, trimers, tetramers, pentamers and hexamers.

[0099] In this invention, there are no particular limitations on the equipment used for dehydration separation. Preferably, the dehydration separation is carried out in a dehydration and purification unit, preferably a shell-and-tube structure dehydration and purification unit, in which the dehydrating fiber membranes are arranged in parallel. In this invention, it is understood that, preferably, the aqueous solution of glycolic acid flows through the shell side of the dehydration and purification unit (i.e., in contact with the outer surface of the hollow fiber membrane), and the dehydrated water component flows through the tube side of the dehydration and purification unit (i.e., in contact with the inner surface of the hollow fiber membrane).

[0100] In a preferred embodiment, the dehydration separation conditions include: a temperature of 40-80°C and a pressure of 50-200 kPa measured by a gauge manometer.

[0101] In this invention, the dehydrated fiber membrane can undergo dehydration enhancement treatment during use, for example, by using vacuum extraction or carrier gas entrainment to remove water from the inner cavity of the dehydrated fiber membrane. Preferably, the vacuum extraction pressure (gauge pressure) is -80 to -40 kPa. Preferably, the carrier gas entrainment gas medium is nitrogen, with a pressure (gauge pressure) of 50-200 kPa, a pressure difference between the carrier gas and the liquid phase (liquid phase side - carrier gas side) of 10-50 kPa, and an entrainment gas velocity of 0.2-1 m / s.

[0102] In a preferred embodiment, the oligomer content in the dehydrated aqueous glycolic acid solution is not higher than 3%, preferably not higher than 1.5%.

[0103] The present invention will be described in detail below through embodiments.

[0104] In this invention, the content of each functional group in the dehydrated fiber membrane is determined by the test method described above.

[0105] In this invention, component analysis employed a 20A high-performance liquid chromatography (HPLC) system (Shimadzu Corporation, Japan, equipped with an autosampler, 10AT and 10AD pumps, and a 20A multi-wavelength UV detector); and an ACQUITY UPLC / Xevo G2 QTOF ultra-high performance liquid chromatography-high resolution tandem mass spectrometry (Waters Corporation, USA, equipped with an autosampler and a diode array UV detector). HPLC conditions were as follows: column: Zorbax Eclipse Plus C18 (4.6 mm × 150 mm, 5 μm); mobile phase: water (containing 0.06% v phosphoric acid): acetonitrile = 95:5; flow rate: 1.0 mL / min; detection wavelength: 210 nm; column temperature: 35 °C; injection volume: 1 μL. Ultra-high performance liquid chromatography (UHPLC) conditions: Column: HSS T3 (2.1 mm × 100 mm, 1.7 μm); Mobile phase: water, methanol; Gradient elution (positive ion mode): 0 min V(water):V(methanol) = 85:15, after 2.5 min V(water):V(methanol) = 55:35, after 4 min V(water):V(methanol) = 10:90, flow rate: 0.45 mL / min; Gradient elution (negative ion mode): 0 min V(water):V(methanol) = 70:30, after 2.5 min V(water):V(methanol) = 55:35, after 3.5 min V(water):V(methanol) = 10:90; flow rate: 0.45 mL / min; Column temperature: 30 ℃; Injection volume: 3 μL. Mass spectrometry conditions: electrospray ionization source (ESI), positive or negative ion scanning mode, capillary voltage 2kV, cone voltage 30eV, ion source temperature: 120℃, desolventizing temperature 450℃, cone gas flow rate 50L / h, desolventizing gas (N2) flow rate 900L / h.

[0106] Example 1

[0107] The glycolic acid solution in this embodiment is derived from the hydrogenation process of dimethyl oxalate. The solution composition, by mass percentage, includes: 37.42% glycolic acid, 0.08% oligomer, and 62.5% water.

[0108] The method for preparing the dehydrated fiber membrane in this embodiment includes: (1) silanizing the inner and outer surfaces of hollow ceramic fibers to obtain a silanized hollow ceramic fiber membrane; (2) hydrophilic treatment of the inner and outer surfaces of the silanized hollow ceramic fiber membrane obtained in step (1); and (3) sequentially performing a first modification treatment and a second modification treatment on the silanized hollow ceramic fiber membrane obtained in step (2) to obtain a dehydrated fiber membrane.

[0109] The hollow ceramic fiber membrane was prepared using conventional methods in the field. First, a casting solution was prepared, and then a hollow fiber preform was obtained through spinning and phase inversion. Subsequently, the preform was dried and calcined to obtain hollow ceramic fibers. The preparation conditions for the hollow ceramic fibers were as follows: polyethersulfone (average molecular weight 2000), N-methylpyrrolidone, ceramic precursor (silica), and polyvinylpyrrolidone K90 were mixed in a mass ratio of 11.3:75.2:265:5.6 and stirred at 80°C for 40 hours, followed by standing for degassing for 8 hours to obtain the casting solution. The inner and outer gel baths of the spinneret were filled with deionized water at 1.5°C. The inner diameter of the spinneret was 0.63 mm, and the outer diameter was 1.64 mm. The casting solution flow rate was 7 mL / min, the pressure of the casting solution inside the spinneret was 280 kPa (gauge pressure), the ambient temperature was 25°C, and the ambient humidity was 53%. The casting solution underwent solvent exchange with the inner and outer gel baths and solidified through phase separation to form the hollow fiber preform. The hollow fiber membrane preform was washed six times with desalinated water, dried with air at 25°C, and then heated to 1700°C using a programmed temperature increase of 0.7°C / min, held at that temperature for 4.5 hours, and then allowed to cool naturally to 25°C to obtain the hollow ceramic fiber membrane. The prepared hollow ceramic fiber membrane has an inner diameter of 0.6 mm, an outer diameter of 1.6 mm, a pore size of 32.4 nm, and a porosity of 40%.

[0110] Step (1) involves silanizing the hollow ceramic fiber membrane using a conventional dip-coating modification method. The process includes treating the inner and outer surfaces of the hollow ceramic fiber membrane with a silane reagent solution (selected from 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate), followed by drying and curing to obtain the silanized hollow ceramic fiber membrane. The silane treatment conditions are as follows: the composition of the silane reagent solution, by volume, is silane reagent:deionized water:anhydrous ethanol = 4.7:6.5:93, pH value is 8.1, and the pre-hydrolysis time is 23 hours. The single dip-coating time with the silanizing reagent is 4.5 minutes, followed by drying and curing. The drying and curing temperature is 120℃, the drying time is 40 minutes, and the drying atmosphere is nitrogen. The silanizing reagent solution is continuously dip-coated and dried and cured 5 times. A hollow ceramic fiber membrane was obtained, with a silane film covering the inner and outer surfaces with a thickness of 15.3 micrometers and a molar ratio of (-Si-O-Si-) to (-Si-OR) groups of 9.3.

[0111] The hollow ceramic fiber membrane after silanization in step (1) was subjected to hydrophilic treatment to obtain a hydrophilic hollow ceramic fiber membrane. The hydrophilic solution used for hydrophilic treatment was selected from N,N′-(1,2-dihydroxyethylene)acrylamide, benzoyl peroxide, and solvent; the solvent was selected from toluene. The hydrophilic component, benzoyl peroxide, and solvent were in the following mass ratios: hydrophilic component: benzoyl peroxide: solvent = 8.1:1.2:250. The hydrophilic treatment conditions were as follows: the volume ratio (liquid-solid volume ratio) of the hydrophilic solution to the hollow ceramic fiber membrane obtained in step (1) was 3.5, the immersion temperature was 65℃, and the immersion time was 2.7 hours. After hydrophilic treatment, the amide group content in both the first and second hydrophilic membranes was 18.6 mmol / m³. 2 It has a thickness of 16.2 micrometers.

[0112] The hollow ceramic fiber membrane obtained in step (2) was subjected to hydrophilic post-treatment to obtain a hydrophilic post-treatment product. The hydrophilic post-treatment agent used was anhydrous ethanol. The hydrophilic post-treatment was carried out by immersion for 60 minutes. After hydrophilic post-treatment, it was dried in nitrogen at 135°C for 20 minutes.

[0113] Step (3) The first modification treatment includes contacting a solution containing the first modified component with a hydrophilically treated hollow fiber membrane (i.e., the hydrophilically post-treatment product). The mass ratio of polyether:first modified component:benzoyl peroxide:water in the solution containing the first modified component is 100:1.17:0.23:1.6. The average molecular weight of the polyether is 1500. The first modified component is a sulfonamide derivative, provided by 2-propylene-1-sulfonamide. The first modification treatment conditions include pumping the solution containing the first modified component into the inner cavity of the hydrophilically treated hollow fiber membrane from step (2). The back pressure at the outlet of the inner cavity is 7 kg using a gauge, and the pumping is stopped when fluid begins to seep from the openings on the outer surface of the hollow fiber membrane. The membrane is then treated at 70°C for 1.1 hours under a nitrogen atmosphere. The resulting first modified membrane, based on the inner surface area of ​​the dry-basis hollow fiber membrane matrix, has a sulfonamide group content of 0.92 mmol / m². 2 The thickness is 0.52 micrometers.

[0114] The first modified product obtained in step (3) undergoes a second modification treatment to obtain a hollow ceramic fiber membrane after the second modification treatment. The solution containing the second modified component used in the second modification treatment consists of the second modified component (the second modified component includes a pyrrole derivative and a mercapto derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the mercapto derivative is selected from allyl 2-mercaptopropionate), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 20.8: 2.4: 260. The pyrrole derivative and mercapto derivative, by molar ratio, are: pyrrole group: mercapto group = 7.3: 1. The conditions for the second modification treatment are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the second modified component to the hollow fiber membrane obtained in step (3) after the first modification treatment is 3.5; the treatment temperature is 68℃; and the treatment time is 2 hours. After the second modification treatment, the content of pyrrole groups in the second modified membrane is 58.8 mmol / m³. 2 The thiol content is 13.9 mmol / m³. 2 The thickness of the second modified film is 6.5 micrometers.

[0115] Following the second modification treatment, a dehydrated fiber membrane was obtained through a second post-modification treatment. The post-treatment agent used in the second modification treatment was anhydrous ethanol, and the soaking time was 60 minutes. The second post-modification treatment method was immersion. After the second post-modification treatment, the membrane was dried in nitrogen at 130°C for 20 minutes. The second post-modification treatment also included immersing the product in acetonitrile for 60 minutes.

[0116] The application of dehydrating fiber membranes in the dehydration of glycolic acid includes: contacting an aqueous glycolic acid solution with a dehydrating fiber membrane to obtain a dehydrated aqueous glycolic acid solution. The application employs a shell-and-tube dehydrating and purifying device, in which parallel-arranged dehydrating fiber membranes are arranged internally. The aqueous glycolic acid solution flows through the shell side of the dehydrating and purifying device, while the removed water component flows through the tube side. The temperature of the aqueous glycolic acid solution in contact with the dehydrating fiber membrane is 60°C, and the contact pressure (gauge pressure) is 125 kPa. Vacuum extraction is selected within the dehydrating membrane cavity, and the extraction pressure (gauge pressure) is -60 kPa.

[0117] The oligomer content in the concentrated glycolic acid solution is 0.97%.

[0118] Example 2

[0119] The same glycolic acid solution as in Example 1 was used.

[0120] According to the method of Example 1.

[0121] The hollow ceramic fiber membrane was prepared using conventional methods in the field. First, a casting solution was prepared, and then a hollow fiber preform was obtained through spinning and phase inversion. Subsequently, the preform was dried and calcined to obtain hollow ceramic fibers. The preparation conditions for the hollow ceramic fibers were as follows: polyethersulfone (average molecular weight 1500), N-methylpyrrolidone, ceramic precursor (silica), and polyvinylpyrrolidone K90 were mixed in a mass ratio of 13.2:86.2:340:7.3, stirred at 85°C for 46 hours, and then allowed to stand for degassing for 9 hours to obtain the casting solution. The inner and outer gel baths of the spinneret were filled with deionized water at 1°C. The inner diameter of the spinneret was 0.42 mm, and the outer diameter was 1.43 mm. The casting solution flow rate was 6 mL / min, the pressure of the casting solution inside the spinneret was 350 kPa (gauge pressure), the ambient temperature was 23°C, and the ambient humidity was 57%. The casting solution underwent solvent exchange with the inner and outer gel baths and solidified through phase separation to form the hollow fiber preform. The hollow fiber membrane preform was washed seven times with desalinated water, dried with air at 22°C, and then heated to 1630°C using a programmed temperature increase of 0.6°C / min, held at that temperature for 4 hours, and then allowed to cool naturally to 23°C to obtain the hollow ceramic fiber membrane. The prepared hollow ceramic fiber membrane has an inner diameter of 0.4 mm, an outer diameter of 1.4 mm, a pore size of 20.2 nm, and a porosity of 46%.

[0122] Step (1) involves silanizing the hollow ceramic fiber membrane using a conventional dip-coating modification method. The process includes treating the inner and outer surfaces of the hollow ceramic fiber membrane with a silane reagent solution (selected from 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate), followed by drying and curing to obtain the silanized hollow ceramic fiber membrane. The silane treatment conditions are as follows: the composition of the silane reagent solution, by volume, is silane reagent:deionized water:anhydrous ethanol = 5.6:7.3:91, pH value is 7.7, and the pre-hydrolysis time is 28 hours. The single dip-coating time with the silanizing reagent is 5.3 minutes, followed by drying and curing. The drying and curing temperature is 112℃, the drying time is 35 minutes, and the drying atmosphere is nitrogen. The silanizing reagent solution is used for continuous dip-coating and drying / curing six times. A hollow ceramic fiber membrane was obtained, with a silane membrane covering the inner and outer surfaces with a thickness of 17.8 micrometers and a molar ratio of (-Si-O-Si-) to (-Si-OR) groups of 12.2.

[0123] The hollow ceramic fiber membrane after silanization in step (1) was subjected to hydrophilic treatment to obtain a hydrophilic hollow ceramic fiber membrane. The hydrophilic solution used for hydrophilic treatment was selected from N,N′-(1,2-dihydroxyethylene)acrylamide, benzoyl peroxide, and solvent; the solvent was selected from toluene. The hydrophilic component, benzoyl peroxide, and solvent were in the following mass ratios: hydrophilic component: benzoyl peroxide: solvent = 9.6: 1.5: 240. The hydrophilic treatment conditions were as follows: the volume ratio (liquid-solid volume ratio) of the hydrophilic solution to the hollow ceramic fiber membrane obtained in step (1) was 4.5, the immersion temperature was 73℃, and the immersion time was 3.4 hours. After hydrophilic treatment, the amide group content in the first and second hydrophilic membranes was 26.8 mmol / m³. 2 It has a thickness of 18.5 micrometers.

[0124] The hollow ceramic fiber membrane obtained in step (2) after hydrophilic treatment was subjected to hydrophilic post-treatment to obtain a hydrophilic post-treatment product. The hydrophilic post-treatment agent used was anhydrous ethanol. The hydrophilic post-treatment was performed by immersion. After hydrophilic post-treatment, the membrane was dried in nitrogen at 125°C for 15 minutes.

[0125] Step (3) First modification treatment includes: contacting a solution containing the first modified component with a hydrophilically treated hollow fiber membrane (i.e., the hydrophilically post-treatment product). The mass ratio of polyether:first modified component:benzoyl peroxide:water in the solution containing the first modified component is 100:1.51:0.32:1.8. The average molecular weight of the polyether is 1800. The first modified component is a sulfonamide derivative, with the sulfonamide group provided by a sulfonamide derivative, preferably 2-propylene-1-sulfonamide. The first modification treatment conditions include: pumping the solution containing the first modified component into the inner cavity of the hydrophilically treated hollow fiber membrane from step (2), controlling the back pressure at the inner cavity outlet to be 9 kg using a gauge, stopping the pumping when fluid begins to seep from the outer surface openings of the hollow fiber membrane, and then treating at 75°C for 1.4 hours under a nitrogen atmosphere. The resulting first modified membrane, based on the inner surface area of ​​the dry-basis hollow fiber membrane matrix per square meter, had a sulfonamide group content of 1.22 mmol / m². 2 The thickness is 0.67 micrometers.

[0126] The first modified product obtained in step (3) is subjected to a second modification treatment to obtain a hollow ceramic fiber membrane after the second modification treatment. The solution containing the second modified component used in the second modification treatment consists of the second modified component (the second modified component includes a pyrrole derivative and a mercapto derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the mercapto derivative is selected from allyl 2-mercaptopropionate), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 26.3: 3.2: 220. Among them, the pyrrole derivative and mercapto derivative, by molar ratio, are: pyrrole group: mercapto group = 10.7: 1. The conditions for the second modification treatment are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the second modified component to the hollow ceramic fiber membrane obtained in step (3) is 4.5, the treatment temperature is 75℃, and the treatment time is 2.6 hours. After the second modification treatment, the content of pyrrole groups in the second modified membrane is 64.3 mmol / m³. 2 The thiol content is 17.5 mmol / m³. 2 The thickness of the second modified film is 8.2 micrometers.

[0127] Following the second modification treatment, a second post-modification treatment is performed to obtain a dehydrated fiber membrane. The post-treatment agent used in the second modification treatment is anhydrous ethanol, and the soaking time is 100 min. The second post-modification treatment method is immersion. After the second post-modification treatment, the membrane is dried in nitrogen at 123°C for 12 min. The second post-modification treatment also includes immersing the product in acetonitrile for 100 min.

[0128] The application of dehydrating fiber membranes in the dehydration of glycolic acid includes: contacting an aqueous glycolic acid solution with a dehydrating fiber membrane to obtain a dehydrated aqueous glycolic acid solution. The application employs a shell-and-tube dehydrating and purifying device, in which parallel-arranged dehydrating fiber membranes are arranged internally. The aqueous glycolic acid solution flows through the shell side of the dehydrating and purifying device, while the removed water component flows through the tube side. The temperature of the aqueous glycolic acid solution in contact with the dehydrating fiber membrane is 45°C, and the contact pressure (gauge pressure) is 60 kPa. Vacuum extraction is selected within the dehydrating membrane cavity, and the extraction pressure (gauge pressure) is -70 kPa.

[0129] The oligomer content in the concentrated glycolic acid solution is 0.31% by mass.

[0130] Example 3

[0131] The same glycolic acid solution as in Example 1 was used.

[0132] The hollow ceramic fiber membrane was prepared according to the method of Example 1. The preparation of the membrane was carried out using conventional methods in the art. First, a casting solution was prepared, and then a hollow fiber preform was obtained through spinning and phase inversion. Subsequently, the preform was dried and calcined to obtain hollow ceramic fibers. The preparation conditions for the hollow ceramic fibers were as follows: polyethersulfone (average molecular weight 2600), N-methylpyrrolidone, ceramic precursor (silica), and polyvinylpyrrolidone K90 were mixed in a mass ratio of 8.4:66.2:194:4.1, stirred at 73°C for 34 hours, and then allowed to stand for degassing for 7.2 hours to obtain the casting solution. The inner and outer gel baths of the spinneret were filled with deionized water at 2.3°C. The inner diameter of the spinneret was 0.85 mm and the outer diameter was 1.86 mm. The casting solution flow rate was 8.2 mL / min, the casting solution pressure inside the spinneret was 173 kPa (gauge pressure), the ambient temperature was 27°C, and the ambient humidity was 49%. The casting solution underwent solvent exchange with the inner and outer gel baths and solidified through phase separation to form a hollow fiber preform. After washing the hollow fiber membrane preform five times with deionized water, it was dried with air at 28°C, then heated to 1760°C using a programmed temperature increase of 0.9°C / min and held at that temperature for 5.3 hours, followed by natural cooling to 28°C to obtain the hollow ceramic fiber membrane. The prepared hollow ceramic fiber membrane had an inner diameter of 0.83 mm, an outer diameter of 1.84 mm, a pore size of 43.5 nm, and a porosity of 38.3%.

[0133] Step (1) involves silanizing the hollow ceramic fiber membrane using a conventional dip-coating modification method. The process includes treating the inner and outer surfaces of the hollow ceramic fiber membrane with a silane reagent solution (selected from 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate), followed by drying and curing to obtain the silanized hollow ceramic fiber membrane. The silane treatment conditions are as follows: the composition of the silane reagent solution, by volume, is silane reagent:deionized water:anhydrous ethanol = 3.8:6.1:94, pH value is 8.3, and the pre-hydrolysis time is 17 hours. The single dip-coating time with the silanizing reagent is 4.2 minutes, followed by drying and curing. The drying and curing temperature is 125℃, the drying time is 46 minutes, and the drying atmosphere is nitrogen. The silanizing reagent solution is used for continuous dip-coating and drying / curing four times. A hollow ceramic fiber membrane was obtained, with a silane film covering the inner and outer surfaces with a thickness of 13.5 micrometers and a molar ratio of (-Si-O-Si-) to (-Si-OR) groups of 6.8.

[0134] The hollow ceramic fiber membrane after silanization in step (1) was subjected to hydrophilic treatment to obtain a hydrophilic hollow ceramic fiber membrane. The hydrophilic solution used for hydrophilic treatment was selected from N,N′-(1,2-dihydroxyethylene)acrylamide, benzoyl peroxide, and solvent; the solvent was selected from toluene. The hydrophilic component, benzoyl peroxide, and solvent were in the following mass ratios: hydrophilic component: benzoyl peroxide: solvent = 7.4:0.8:253. The hydrophilic treatment conditions were as follows: the volume ratio (liquid-solid volume ratio) of the hydrophilic solution to the hollow ceramic fiber membrane obtained in step (1) was 3.2, the immersion temperature was 60℃, and the immersion time was 2.1 hours. After hydrophilic treatment, the amide group content in the first and second hydrophilic membranes was 13.2 mmol / m³. 2 It has a thickness of 14.3 micrometers.

[0135] The hollow ceramic fiber membrane obtained in step (2) after hydrophilic treatment was subjected to hydrophilic post-treatment to obtain a hydrophilic post-treatment product. The hydrophilic post-treatment agent used was anhydrous ethanol. The hydrophilic post-treatment was performed by immersion. After hydrophilic post-treatment, it was dried in nitrogen at 143°C for 26 minutes.

[0136] Step (3) First modification treatment includes: contacting a solution containing the first modified component with a hydrophilically treated hollow fiber membrane (i.e., the hydrophilically post-treatment product). The mass ratio of polyether:first modified component:benzoyl peroxide:water in the solution containing the first modified component is 100:0.83:0.19:1.2. The average molecular weight of the polyether is 1000. The first modified component is a sulfonamide derivative, with the sulfonamide group provided by a sulfonamide derivative, preferably 2-propylene-1-sulfonamide. The first modification treatment conditions include: pumping the solution containing the first modified component into the inner cavity of the hydrophilically treated hollow fiber membrane from step (2), controlling the back pressure at the inner cavity outlet to be 6 kg using a gauge, stopping the pumping when fluid begins to seep from the outer surface openings of the hollow fiber membrane, and then treating at 65°C for 0.8 hours under a nitrogen atmosphere. The resulting first modified membrane, based on the inner surface area of ​​the dry-basis hollow fiber membrane matrix per square meter, had a sulfonamide group content of 0.73 mmol / m². 2 The thickness is 0.41 micrometers.

[0137] The first modified product obtained in step (3) is subjected to a second modification treatment to obtain a hollow ceramic fiber membrane after the second modification treatment. The solution containing the second modified component used in the second modification treatment is the second modified component (the second modified component includes a pyrrole derivative and a mercapto derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the mercapto derivative is selected from allyl 2-mercaptopropionate), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The second modified component, benzoyl peroxide, and solvent, by mass parts, are: second modified component: benzoyl peroxide: solvent = 17.3: 1.4: 276. Among them, the pyrrole derivative and mercapto derivative, by molar ratio, are: pyrrole group: mercapto group = 5.6: 1. The treatment conditions for the second modification treatment are as follows: the volume ratio (liquid-solid volume ratio) of the solution containing the second modified component to the hollow ceramic fiber membrane obtained in step (3) is 2.8, the treatment temperature is 64℃, and the treatment time is 1.7 hours. After the second modification treatment, the content of pyrrole groups in the second modified membrane was 53.4 mmol / m. 2 The thiol content is 12.8 mmol / m 2 The thickness of the second modified film is 5.1 micrometers.

[0138] Following the second modification treatment, a dehydrated fiber membrane was obtained through a second post-modification treatment. The post-treatment agent used in the second modification treatment was anhydrous ethanol, and the soaking time was 40 minutes. The second modification treatment method was immersion. After the second modification treatment, the membrane was dried in nitrogen at 135°C for 17 minutes. The second modification treatment also included immersing the product in acetonitrile for 40 minutes.

[0139] The application of dehydrating fiber membranes in the dehydration of glycolic acid includes: contacting an aqueous glycolic acid solution with a dehydrating fiber membrane to obtain a dehydrated aqueous glycolic acid solution. The application employs a shell-and-tube dehydrating and purifying device, in which parallel-arranged dehydrating fiber membranes are arranged internally. The aqueous glycolic acid solution flows through the shell side of the dehydrating and purifying device, while the removed water component flows through the tube side. The temperature of the aqueous glycolic acid solution in contact with the dehydrating fiber membrane is 73°C, and the contact pressure (gauge pressure) is 150 kPa. Vacuum extraction is selected within the dehydrating membrane cavity, and the extraction pressure (gauge pressure) is -50 kPa.

[0140] The oligomer content in the concentrated glycolic acid solution is 1.7%.

[0141] Example 4

[0142] The method is the same as in Example 2, except that the composition of the raw material glycolic acid solution, by mass percentage, includes: 23.15% glycolic acid, 0.03% oligomer, and 76.82% water.

[0143] The oligomer content in the concentrated glycolic acid solution is 0.24% by mass.

[0144] Example 5

[0145] The method is the same as in Example 2, except that the composition of the raw material glycolic acid solution, by mass percentage, includes: 46.53% glycolic acid, 0.12% oligomer, and 53.35% water.

[0146] The oligomer content in the concentrated glycolic acid solution is 0.48%.

[0147] Example 6

[0148] The same glycolic acid solution as in Example 1 was used.

[0149] The method of Example 3 is followed, except that the first modified product obtained in step (3) is subjected to a second modified treatment to obtain a hollow ceramic fiber membrane after the second modified treatment. The solution containing the second modified component used in the second modified treatment consists of the second modified component (which includes a pyrrole derivative and a thioether derivative, wherein the pyrrole derivative is selected from 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, and the thioether derivative is selected from bis(4-methacryloylthiophenyl) thioether), benzoyl peroxide, and a solvent; the solvent is selected from toluene. The ratio of the second modified component, benzoyl peroxide, and solvent, by mass parts, is: second modified component: benzoyl peroxide: solvent = 19.7:1.5:272. The ratio of the pyrrole derivative to the thioether derivative, by molar ratio, is: pyrrole group: thioether group = 5.7:1. The conditions for the second modification treatment are as follows: the volume ratio (liquid-to-solid volume ratio) of the solution containing the second modified component to the hollow ceramic fiber membrane obtained in step (3) is 2.8, the treatment temperature is 65℃, and the treatment time is 1.6 hours. After the second modification treatment, the content of pyrrole groups in the second modified membrane is 53.6 mmol / m³. 2 The sulfide content was 12.3 mmol / m³. 2 The thickness of the second modified film is 4.9 micrometers.

[0150] Following the second modification treatment, a dehydrated fiber membrane was obtained through a second post-modification treatment. The post-treatment agent used in the second modification treatment was anhydrous ethanol, and the soaking time was 40 minutes. The second post-modification treatment method was immersion. After the second post-modification treatment, the membrane was dried in nitrogen at 135°C for 17 minutes. The second post-modification treatment also included immersing the product in acetonitrile for 40 minutes.

[0151] According to the application method in Example 3, the oligomer content in the concentrated glycolic acid solution is 1.8%.

[0152] Example 7

[0153] The same glycolic acid solution as in Example 1 was used.

[0154] The method of Example 3 is the same, except that hydrophilic post-treatment is not performed in step (2) and the second modification post-treatment (anhydrous ethanol post-treatment) is not performed in step (3).

[0155] After the first modification treatment, the content of sulfonamide groups in the first modified membrane was 0.68 mmol / m. 2 The thickness is 0.39 micrometers. After the second modification treatment, the content of pyrrole groups in the second modified membrane is 49.8 mmol / m. 2 The thiol content is 12.6 mmol / m 2 The thickness of the second modified film is 5 micrometers.

[0156] According to the application method in Example 3, the oligomer content in the concentrated glycolic acid solution is 1.9%.

[0157] Comparative Example 1

[0158] The same glycolic acid solution as in Example 1 was used.

[0159] The method is the same as in Example 3, except that conventional distillation dehydration is used, and negative pressure vacuum dehydration is used directly. The reboiler is a commercially available kettle type, and the column body is made of 250Y structured packing.

[0160] The oligomer content in the concentrated glycolic acid solution is 18.7%.

[0161] Comparative Example 2

[0162] The same glycolic acid solution as in Example 4 was used.

[0163] The method is the same as in Example 3, except that negative pressure vacuum dehydration is used directly, a commercially available kettle reboiler is used in the column, and 250Y structured packing is used in the column body.

[0164] The oligomer content in the concentrated glycolic acid solution is 17.2%.

[0165] Comparative Example 3

[0166] The same glycolic acid solution as in Example 5 was used.

[0167] The method is the same as in Example 3, except that negative pressure vacuum dehydration is used directly, a commercially available kettle reboiler is used in the column, and 250Y structured packing is used in the column body.

[0168] The oligomer content in the concentrated glycolic acid solution is 21.5%.

[0169] Comparative Example 4

[0170] The same glycolic acid solution as in Example 1 was used.

[0171] The method is the same as in Example 3, except that step (3) does not involve the first modification treatment.

[0172] After the second modification treatment, the content of pyrrole groups in the second modified membrane (referring to hollow fiber membranes containing the second modification on both the inner and outer surfaces) is 50.4 mmol / m². 2 The thiol content is 11.5 mmol / m 2 The thickness of the second modified film is 4.7 micrometers.

[0173] According to the application method in Example 3, the oligomer content in the concentrated glycolic acid solution is 2.8%.

[0174] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A dehydrated fiber membrane, characterized in that, The dehydrated fiber membrane comprises a hollow fiber membrane substrate, a first silane membrane, a first hydrophilic membrane, and a first modified membrane sequentially coated on the inner surface of the hollow fiber membrane substrate from the inside out, and a second silane membrane, a second hydrophilic membrane, and a second modified membrane sequentially coated on the outer surface of the hollow fiber membrane substrate from the inside out; the first hydrophilic membrane and the second hydrophilic membrane each independently contain amide groups; the first modified membrane contains sulfonamide groups; the second modified membrane contains pyrrole groups, and one or two of mercapto groups and thioethers; The hollow fiber membrane substrate is a hollow ceramic fiber membrane; Based on the total surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of amide groups independently contained in the first and second hydrophilic membranes is 8-29.3 mmol / m². 2 ; Based on the inner surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of sulfonamide groups in the first modified membrane is 0.6-1.4 mmol / m². 2 ; Based on the surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of pyrrole groups in the second modified membrane is 48-70 mmol / m². 2 The content of thiol groups and / or thioethers is 6-45 mmol / m 2 .

2. The dehydrated fiber membrane according to claim 1, wherein, The hollow ceramic fiber has an inner diameter of 0.2-1 mm, an outer diameter of 1.2-2 mm, a pore size of 15-52 nm, and a porosity of 30-53%. And / or, the hollow ceramic fiber membrane is made of silicon dioxide and / or aluminum oxide.

3. The dehydrated fiber membrane according to claim 1 or 2, wherein, The molar ratio of independent groups (-Si-O-Si-) to groups (-Si-OR) in the first silane membrane and the second silane membrane is 4-16; wherein R is silicon and / or aluminum derived from the hollow fiber membrane matrix; And / or, the thickness of the first silane film and the second silane film are each independently 10-21 micrometers; And / or, the first silane membrane and the second silane membrane are each independently provided by at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate and 3-(isobutenoyloxy)propyltrimethoxysilane.

4. The dehydrated fiber membrane according to claim 1 or 2, wherein, Based on the total surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of amide groups independently contained in the first and second hydrophilic membranes is 18-29.3 mmol / m². 2 ; And / or, the thickness of the first hydrophilic membrane and the second hydrophilic membrane are each independently 12-21 micrometers.

5. The dehydrated fiber membrane according to claim 1 or 2, wherein, Based on the inner surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of sulfonamide groups in the first modified membrane is 0.9-1.4 mmol / m². 2 ; And / or, the thickness of the first modified film is 0.3-0.8 micrometers.

6. The dehydrated fiber membrane according to claim 1 or 2, wherein, Based on the surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of pyrrole groups in the second modified membrane is 58-70 mmol / m². 2 The content of thiol groups and / or thioethers is 13.5-45 mmol / m³. 2 .

7. The dehydrated fiber membrane according to claim 1 or 2, wherein, Based on the surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of thiol groups in the second modified membrane is 6-22 mmol / m². 2 The sulfide content is 6-22 mmol / m³. 2 .

8. The dehydrated fiber membrane according to claim 6, wherein, Based on the surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of thiol groups in the second modified membrane is 13.5-22 mmol / m². 2 The sulfide content is 13.5-22 mmol / m³. 2 .

9. The dehydrated fiber membrane according to claim 1 or 2, wherein, The thickness of the second modified film is 4-9 micrometers.

10. A method for preparing the dehydrated fiber membrane according to claim 1, wherein, The method includes: (1) The inner and outer surfaces of the hollow fiber membrane substrate are subjected to silanization treatment to obtain a silanized hollow fiber membrane; (2) The inner and outer surfaces of the silanized hollow fiber membrane are hydrophilically treated with hydrophilic components to obtain a hydrophilically treated hollow fiber membrane; (3) The inner and outer surfaces of the hydrophilic hollow fiber membrane were subjected to first modification treatment and second modification treatment respectively using the first modification component and the second modification component to obtain a dehydrated fiber membrane; The hydrophilic component contains an amide group, the first modified component contains a sulfonamide group, the second modified component contains a pyrrole group, and one or two of a mercapto group and a thioether. In step (2), the hydrophilic treatment causes the inner and outer surfaces of the silanized hollow fiber membrane to be coated with a first hydrophilic membrane and a second hydrophilic membrane, respectively. In step (3), the first modification treatment causes the inner surface of the hydrophilic hollow fiber membrane to be coated with the first modified membrane. In step (3), the second modification treatment causes the outer surface of the hollow fiber membrane to be coated with a second modified membrane.

11. The method according to claim 10, wherein, In step (1), The hollow ceramic fiber has an inner diameter of 0.2-1 mm, an outer diameter of 1.2-2 mm, a pore size of 15-52 nm, and a porosity of 30-53%. And / or, the hollow ceramic fiber membrane is made of silicon dioxide and / or aluminum oxide.

12. The method according to claim 10 or 11, wherein, In step (1), the silanization process forms a first silane film on the inner surface of the hollow fiber membrane and a second silane film on the outer surface. The thickness of the first silane film and the second silane film are each independently 10-21 micrometers.

13. The method according to claim 10 or 11, wherein, In step (1), the silanization process includes: contacting the silane reagent solution with the inner and outer surfaces of the hollow fiber membrane substrate, and then drying and curing it.

14. The method according to claim 13, wherein, In step (1), the silane reagent solution is obtained by mixing silane reagent, water and anhydrous low alcohol, and then pre-hydrolyzing.

15. The method according to claim 14, wherein, In step (1), the volume ratio of silane reagent: water: anhydrous low alcohol is (3.2-6.2): ​​(5-8.1): (90-96).

16. The method according to claim 15, wherein, In step (1), the silane reagent is selected from at least one of 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl methacrylate, 2-hydroxy-3-[3-(trimethoxysilyl)propoxy]propyl acrylate and 3-(isobutenoyloxy)propyltrimethoxysilane.

17. The method according to claim 13, wherein, In step (1), the amount of silane reagent solution used is such that the molar ratio of groups (-Si-O-Si-) to groups (-Si-OR) independently included in the first silane membrane and the second silane membrane is 4-16, wherein R is silicon and / or aluminum from the hollow fiber membrane matrix.

18. The method according to claim 10 or 11, wherein, In step (2), based on the total surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of amide groups independently contained in the first and second hydrophilic membranes is 18-29.3 mmol / m². 2 .

19. The method according to claim 10 or 11, wherein, In step (2), the hydrophilic treatment includes: contacting a solution containing hydrophilic components with a silanized hollow fiber membrane.

20. The method according to claim 19, wherein, In step (2), the mass ratio of the hydrophilic component to the first initiator to the first solvent in the solution containing the hydrophilic component is (6-11):(0.6-1.8):(230-275).

21. The method according to claim 20, wherein, In step (2), the first solvent is selected from at least one of toluene, p-xylene, m-xylene, and o-xylene; And / or, the first initiator is selected from at least one of azo compounds, organic peroxides, inorganic peroxides, and redox compounds; And / or, the hydrophilic component is provided by an amide derivative.

22. The method according to claim 21, wherein, In step (2), The first initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and hydrogen peroxide.

23. The method according to claim 21, wherein, In step (2), the hydrophilic component is provided by at least one of N,N'-[ethylenedi(oxymethylene)] bis(acrylamide), N,N′-(1,2-dihydroxyethylene) bisacrylamide and hexamethylenebisacrylamide.

24. The method according to claim 19, wherein, In step (2), the hydrophilic treatment conditions include: the liquid-to-solid volume ratio of the solution containing hydrophilic components to the silanized hollow fiber membrane described in step (1) is 2-5, the immersion temperature is 55-75℃, and the time is 1.8-3.5h.

25. The method according to claim 19, wherein, Step (2) also includes hydrophilic post-treatment of the hydrophilic treatment product in a hydrophilic post-treatment agent.

26. The method of claim 25, wherein, The hydrophilic post-treatment agent is selected from at least one of anhydrous methanol, anhydrous ethanol, and anhydrous acetone.

27. The method according to claim 26, wherein, The hydrophilic post-treatment agent is anhydrous ethanol.

28. The method according to claim 25, wherein, The conditions for the hydrophilic post-treatment include: soaking time of 35-300 min, drying temperature of 120-150℃, and drying time of 10-30 min.

29. The method according to claim 10 or 11, wherein, In step (3), based on the inner surface area of ​​the dry-based hollow fiber membrane matrix per square meter, the content of sulfonamide groups in the first modified membrane is 0.8-1.4 mmol / m². 2 .

30. The method according to claim 10 or 11, wherein, In step (3), the first modification treatment includes: contacting the solution containing the first modified component with the hydrophilically treated hollow fiber membrane.

31. The method according to claim 30, wherein, In step (3), the mass ratio of polyether: first modified component: second initiator: water in the solution containing the first modified component is 100: (0.6-1.8): (0.1-0.5): (1-2.3).

32. The method according to claim 31, wherein, In step (3), the average molecular weight of the polyether is 800-2000; And / or, the second initiator is selected from at least one of azo, organic peroxide, inorganic peroxide, and redox initiators; And / or, the first modified component is provided by a sulfonamide derivative.

33. The method according to claim 32, wherein, In step (3), The second initiator is selected from at least one of azobisisobutyronitrile, benzoyl peroxide, potassium persulfate, and hydrogen peroxide.

34. The method according to claim 32, wherein, In step (3), the first modifying component is provided by at least one of vinylsulfonamide, 2-propylene-1-sulfonamide and pentenylsulfonamide.

35. The method according to claim 30, wherein, In step (3), the first modification treatment conditions include: introducing a solution containing the first modified component into the inner cavity of the hollow fiber membrane after hydrophilic treatment in step (2), and the back pressure at the outlet of the inner cavity is 5-11 kg as measured by a gauge pressure gauge.

36. The method according to claim 10 or 11, wherein, In step (3), based on the outer surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of pyrrole groups in the second modified membrane is 58-70 mmol / m². 2 The content of thiol groups and / or thioethers is 13.5-45 mmol / m³. 2 .

37. The method according to claim 10 or 11, wherein, In step (3), based on the surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of thiol groups in the second modified membrane is 6-22 mmol / m². 2 The sulfide content is 6-22 mmol / m³. 2 .

38. The method according to claim 36, wherein, In step (3), based on the surface area of ​​the dry-based hollow fiber membrane substrate per square meter, the content of thiol groups in the second modified membrane is 13.5-22 mmol / m². 2 The sulfide content is 13.5-22 mmol / m³. 2 .

39. The method according to claim 10 or 11, wherein, In step (3), the second modification treatment includes: contacting the solution containing the second modified component with the hollow fiber membrane after the first modification treatment.

40. The method according to claim 39, wherein, In step (3), the mass ratio of the second modified component to the third initiator to the second solvent in the solution containing the second modified component is (13.5-28):(1.2-3.5):(200-300).

41. The method according to claim 40, wherein, In step (3), the second solvent is selected from at least one of toluene, p-xylene, m-xylene and o-xylene.

42. The method according to claim 40, wherein, In step (3), the second modified component is provided by a pyrrole derivative.

43. The method according to claim 42, wherein, In step (3), the second modifying component is provided by at least one of methyl 4-vinyl-1H-pyrrole-3-carboxylate, methyl 5-vinyl-1H-pyrrole-2-carboxylate, 1-(3-buten-1-yl)-2-vinyl-1H-pyrrole, 5-allyl-4-methoxy-1,5-dihydro-2H-pyrrole-2-one, 1-allyl-2-cyclopentyl-1H-pyrrole, 1-(1-phenylvinyl)pyrrole, 3-isopropenyl-1-methyl-pyrrole, and 1-allyl-2-isopropenyl-1H-pyrrole.

44. The method according to claim 10 or 11, wherein, The thiol group and / or thioether are provided by their respective derivative classes.

45. The method according to claim 44, wherein, The mercapto group and / or thioether are provided by bis(4-methacryloylthiophenyl) thioether and / or allyl 2-mercaptopropionate.

46. ​​The method according to claim 39, wherein, In step (3), the second modification treatment conditions include: the liquid-to-solid volume ratio of the solution containing the second modified component to the hollow fiber membrane after the first modification treatment described in step (3) is 2-5, the immersion temperature is 57-78℃, and the time is 1-3h.

47. The method according to claim 39, wherein, Step (3) also includes subjecting the second modified product to a second immersion post-treatment in a second post-treatment agent.

48. The method according to claim 47, wherein, The second post-treatment agent is selected from at least one of anhydrous methanol, anhydrous ethanol, and anhydrous acetone; And / or, the conditions for the second post-soaking treatment include: soaking time of 35-300 min, drying temperature of 120-150℃, and drying time of 10-30 min.

49. The method according to claim 48, wherein, The second post-treatment agent is anhydrous ethanol.

50. The use of the dehydrated fiber membrane according to any one of claims 1-9 in hydroxy fatty acids.

51. The application according to claim 50, wherein, The application of the dehydrated fiber membrane in the dehydration of aqueous glycolic acid.

52. The application according to claim 51, wherein, Hydroxyacetic acid aqueous solution is contacted with a dehydrated fiber membrane for dehydration separation to obtain a dehydrated hydroacetic acid aqueous solution.

53. The application according to claim 52, wherein, The dehydration separation is carried out in a dehydration and purification apparatus.

54. The application according to claim 53, wherein, The dewatering and refining device adopts a shell-and-tube structure, in which dewatering fiber membranes are arranged in parallel.

55. The application according to claim 52, wherein, The conditions for dehydration and separation include: a temperature of 40-80℃ and a pressure of 50-200 kPa measured by a gauge manometer.

56. The application according to claim 52, wherein, The oligomer content in the dehydrated aqueous solution of glycolic acid is no more than 3%.

57. The application according to claim 56, wherein, The oligomer content in the dehydrated aqueous solution of glycolic acid is not higher than 1.5%.