Alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membrane and application thereof

Abstract

The invention relates to the technical field of hollow fiber membranes, and discloses an alkali-resistant hydrophobic and oleophobic finishing agent for a hollow fiber membrane and application of the alkali-resistant hydrophobic and oleophobic finishing agent for the hollow fiber membrane. Perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds are adopted as comonomers and subjected to a copolymerization reaction in a solvent under the action of a thermal radical initiator, and the alkali-resistant hydrophobic and oleophobic finishing agent is obtained. Perfluoroalkyl is introduced into a main chain of a polymer in the alkali-resistant hydrophobic and oleophobic finishing agent for the hollow fiber membrane, a polymerization unit is an acrylate group and perfluoroalkyl alternating chain segment, and after the perfluoroalkyl is introduced into the main chain, the perfluoroalkyl has a strong electron withdrawing effect, so that an electron shielding protection effect can be achieved on the acrylate group of a side chain; compared with the prior art, the water-proof and oil-proof agent has the advantages that the water-proof and oil-proof agent can be degraded after a long time by using alkali with higher temperature and higher concentration, so that the water-proof and oil-proof effects can be effectively ensured, and even if the perfluoroalkyl on a side chain is lost, the perfluoroalkyl on a main chain can still provide a certain oleophobic effect to prevent oleophobic failure.

Description

Technical Field

[0001] This invention relates to the field of hollow fiber membrane technology, specifically to an alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes and its application. Background Technology

[0002] Currently, industrially produced hollow fiber membranes are generally prepared using melt stretching or phase separation methods. Some of these materials are hydrophobic, preventing water from crossing the membrane and causing penetration and wetting. They are used for gas filtration, permeation, or liquid degassing and aeration, and have reached a certain scale. Common examples include PS, PE, PP, PMP, and PTFE membranes.

[0003] However, in some special applications, the gas being breathed or filtered may be unclean, containing oil droplets; the liquid being degassed or aerated may not be pure water, but may contain impurities such as alcohols, esters, hydrocarbons, or other organic matter, or bacteria and microorganisms; or the liquid to be degassed or aerated may be a liquid with low surface tension, such as ink. In these cases, the originally hydrophobic membrane pores may become wetted, losing their ability to breathe, filter, degause, or aerated.

[0004] To enable hollow fiber membranes to withstand wetting by low-surface-tension liquids such as inks, alcohols, and esters, the natural approach is to treat the membrane with perfluoroacrylate-based conformal coatings, achieving an oil-repellent rating of 6 or higher, thus fulfilling the objective to some extent. However, the presence of acrylate groups in the polymer units of perfluoroacrylate-based conformal coatings, which are susceptible to strong alkalis, limits the application of some degassing membranes. For instance, in the field of ammonia removal using hollow fiber membranes, ammonia nitrogen wastewater treated with a pH=12 sodium hydroxide solution is required before entering the hollow fiber membrane module. Sodium hydroxide damages the ester groups in the polyperfluoroacrylate, causing the oleophobic layer to fail. The market urgently needs an alkali-resistant, hydrophobic, and oleophobic coating that can produce hollow fiber membranes with both oil-repellent and alkali-resistant properties to address these issues. Summary of the Invention

[0005] This invention provides an alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes and its application, solving the problems mentioned in the background art.

[0006] This invention provides the following technical solution: an alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes, which uses perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds as comonomers, and is obtained by copolymerization reaction in a solvent under the action of a thermal free radical initiator. The polymer in the hollow fiber membrane alkali-resistant, hydrophobic, and oleophobic finishing agent introduces perfluoroalkyl groups into the main chain, and the polymerization unit is an alternating segment of acrylate groups and perfluoroalkyl groups. The perfluoroalkyl groups on the main chain protect the ester groups on the side chains. When the perfluoroalkyl groups on the side chains are attacked by alkali, they fall off and become ineffective, and the perfluoroalkyl groups on the main chain achieve the oleophobic effect.

[0007] The alkali-resistant hydrophobic and oleophobic finishing agent for this hollow fiber membrane introduces perfluoroalkyl groups into the main chain of perfluoroalkyl acrylate compounds. Due to the strong electron-withdrawing effect of perfluoroalkyl groups, they can provide electron shielding protection for the acrylate groups on the side chains. Degradation requires higher temperatures and higher concentrations of alkali over a long period of time, which effectively ensures the waterproof and oil-repellent effect. Even if the perfluoroalkyl groups on the side chains are lost, the perfluoroalkyl groups on the main chain can still provide a certain degree of oleophobic effect, preventing oleophobic failure.

[0008] As an optional solution for the alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes described in this invention, the perfluoroalkyl acrylate compound is a compound obtained by esterifying a fatty alcohol having 2-10 carbon atoms and whose alkyl hydrogens are all or partially replaced by fluorine atoms with acrylic acid or methacrylate, such as tetrafluoropropyl methacrylate, perfluorobutyl acrylate, perfluorohexyl acrylate, perfluorohexyl ethyl acrylate, perfluorooctyl ethyl acrylate, perfluorooctyl acrylate, or perfluorodecyl acrylate.

[0009] As an alternative to the alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes described in this invention, the divinyl perfluoroalkane compound is a compound whose molecular formula contains two vinyl groups at the head and tail, such as 1,6-divinylperfluorohexane or 1,4-divinylperfluorobutane.

[0010] As an optional solution for the alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes described in this invention, the thermal free radical initiator is a compound that provides free radicals and initiates the polymerization reaction when heated, such as azobisisobutyronitrile, azobisisoheptanenitrile, or peroxide.

[0011] As an optional solution for the alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes described in this invention, the solvent includes solvents capable of dissolving perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds, and simultaneously capable of dissolving polymers obtained by copolymerizing perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds, such as perfluoroethers, hexafluoroisopropanol, hexafluoropropylene trimer, or perfluorooctane. Perfluoroethers include methyl perfluoroisobutyl ether, ethyl perfluoroisobutyl ether under the 3M brand trade name HFE-7200, etc.

[0012] A hollow fiber membrane processed using any of the above-mentioned alkali-resistant, hydrophobic, and oleophobic finishing agents, comprising: diluting any of the above-mentioned hollow fiber membranes with an alkali-resistant, hydrophobic, and oleophobic finishing agent; immersing the hollow fiber membrane in the agent for a certain period of time; and then removing and drying it to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane.

[0013] The present invention has the following beneficial effects: After the perfluoroalkyl group is introduced into the main chain of the perfluoroalkyl acrylate compound in the hollow fiber membrane, the perfluoroalkyl group has a strong electron-withdrawing effect, which can play an electron shielding protection role for the acrylate groups on the side chain. It requires higher temperature and higher concentration of alkali to degrade over a long period of time, which can effectively ensure the waterproof and oil-repellent effect. Even if the perfluoroalkyl group on the side chain is lost, the perfluoroalkyl group on the main chain can still provide a certain oil-repellent effect to prevent oil-repellent failure. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the reaction process in Example 3. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] In the field of hollow fiber membrane ammonia removal, ammonia nitrogen wastewater needs to be treated with a sodium hydroxide solution at pH=12 before entering the hollow fiber membrane module. Sodium hydroxide damages the ester groups in perfluoroacrylate, causing the oleophobic layer to fail. Therefore, while ensuring the oleophobic performance of the hollow fiber membrane, it is necessary to improve the alkali resistance of the hollow fiber oleophobic coating. Compared to polymers obtained entirely from perfluoroalkyl acrylate compounds, the copolymerization of perfluoroalkyl acrylate with divinyl perfluoroalkane compounds results in polymer units where the polymeric units change from simple acrylate groups to segments with alternating acrylate and perfluoroalkyl groups. It is well known that acrylate groups are not resistant to strong alkalis and will undergo saponification in strong alkalis, which can occur at room temperature. The polymer segments are decomposed to form perfluoroalkyl alcohols and acrylates, while the main chain lacks oleophobic groups, resulting in the loss of hydrophobic and oleophobic effects. After introducing perfluoroalkyl groups into the main chain, the strong electron-withdrawing effect of perfluoroalkyl groups can provide electron shielding protection for the acrylate groups on the side chain. Higher temperatures and higher concentrations of alkali are required for degradation over a long period of time, which can effectively ensure the waterproof and oil-repellent effect. Even if the perfluoroalkyl groups on the side chain are lost, the perfluoroalkyl groups on the main chain can still provide a certain degree of oleophobic effect to prevent oleophobic failure.

[0017] Common three-proof finishing agents have the following structural formulas:

[0018] Its ester group is not resistant to strong bases.

[0019] The structural formula of the polymer synthesized in this application is as follows:

[0020] The main chain can also provide oleophobic effect by protecting the perfluoroalkyl groups on the side chain through electronic shielding. This is achieved by introducing perfluoroalkyl groups into the polymer main chain to protect the ester groups on the side chain and prevent the perfluoroalkyl groups on the side chain from falling off when attacked by alkali. Even if the perfluoroalkyl groups on the side chain fail, the perfluoroalkyl groups on the main chain can still provide oleophobic effect.

[0021] Example 1

[0022] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of tetrafluoropropyl methacrylate; 0.1g of 1,6-divinylperfluorohexane; 0.1g of azobisisobutyronitrile; and 100g of perfluorooctane. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of perfluorooctane is added. Stirring is continued for 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0023] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 1 hour, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobic grade, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0024] Example 2

[0025] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorobutyl acrylate; 0.2g of 1,6-divinylperfluorohexane; 0.1g of azobisisobutyronitrile; and 100g of perfluorooctane. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of perfluorooctane is added. Stirring continues for 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0026] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 10 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0027] Example 3

[0028] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorohexyl ethyl acrylate; 0.5g of 1,4-divinylperfluorobutane; 0.1g of azobisisoheptanenitrile; and 100g of HFE-7200 ethyl perfluoroisobutyl ether. The mixture is heated to 60°C, stirred for 8 hours, cooled to room temperature, and then 900g of HFE-7200 ethyl perfluoroisobutyl ether is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0029] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 20 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0030] In this embodiment, the reaction process is as follows: Figure 1 As shown, ideally, unit a (unit c) and unit b appear alternately, and the crosslinking effect provided by divinyl perfluoroalkane compounds is the most sufficient. However, since the initial molar ratio of the two monomers is not equal to 1, the molar amount of perfluoroalkyl acrylate compounds is much greater than that of divinyl perfluoroalkane compounds. Generally, unit a is repeated many times while unit b is repeated less often. This is beneficial to make full use of the strong oleophobic properties of perfluoroalkyl acrylate compounds and to prevent the excessive generation of branches caused by repeated entry of unit b into the polymer backbone.

[0031] Example 4

[0032] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorooctyl acrylate; 2g of 1,6-divinylperfluorohexane; 0.1g of azobisisoheptanenitrile; and 100g of HFE-7200 ethyl perfluoroisobutyl ether. The mixture is heated to 60°C, stirred for 8 hours, cooled to room temperature, and then 900g of HFE-7200 ethyl perfluoroisobutyl ether is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0033] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 20 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0034] Example 5

[0035] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorooctyl acrylate; 2g of 1,4-divinylperfluorobutane; 0.1g of azobisisobutyronitrile; and 100g of perfluorooctane. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of perfluorooctane is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0036] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0037] Example 6

[0038] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorobutyl acrylate; 2g of 1,4-divinylperfluorobutane; 0.1g of azobisisobutyronitrile; and 100g of hexafluoroisopropanol. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of hexafluoroisopropanol is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0039] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0040] Example 7

[0041] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorobutyl acrylate; 2g of 1,6-divinylperfluorohexane; 0.1g of azobisisobutyronitrile; and 100g of hexafluoroisopropanol. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of hexafluoroisopropanol is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0042] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0043] Example 8

[0044] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorooctyl acrylate; 4g of 1,6-divinylperfluorohexane; 0.1g of azobisisobutyronitrile; and 100g of hexafluoroisopropanol. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of hexafluoroisopropanol is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0045] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0046] Example 9

[0047] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 10g of perfluorooctyl acrylate; 4g of 1,6-divinylperfluorohexane; 0.1g of azobisisobutyronitrile; and 100g of hexafluoropropylene trimer; heating to 80°C; stirring for 8 hours; cooling to room temperature; adding 900g of hexafluoropropylene trimer; and continuing to stir for 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0048] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0049] Example 10

[0050] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 15g of perfluorooctyl acrylate; 4g of 1,6-divinylperfluorohexane; 0.1g of azobisisobutyronitrile; and 100g of hexafluoropropylene trimer. The mixture is heated to 80°C, stirred for 8 hours, cooled to room temperature, and then 900g of hexafluoropropylene trimer is added. The mixture is stirred for another 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0051] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this embodiment, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0052] Comparative Example

[0053] An alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes and an alkali-resistant hydrophobic and oleophobic hollow fiber membrane are disclosed. The preparation of the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes includes: adding the following reagents to a three-necked flask: 110g of perfluorooctyl acrylate; 0.1g of azobisisobutyronitrile; and 100g of perfluorooctane; heating to 80°C; stirring for 8 hours; cooling to room temperature; adding 900g of perfluorooctane; and continuing to stir for 10 minutes to obtain the alkali-resistant hydrophobic and oleophobic finishing agent for hollow fiber membranes.

[0054] The preparation of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane includes: immersing the hollow fiber membrane in the alkali-resistant, hydrophobic, and oleophobic finishing agent prepared in this comparative example, leaving it for 30 minutes, then placing the hollow fiber in an oven and drying it completely to obtain the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane. Finally, the air flux, oleophobicity rating, and alkali resistance of the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane are tested, as shown in Table 1.

[0055] Table 1:

[0056] .

[0057] As can be seen from the test results in Table 1, the alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane prepared in this application has good air flux and a high oleophobic grade. When testing its alkali resistance, it was found that the alkali resistance is excellent, and the oleophobic grade remains high even after immersion in an alkaline solution.

[0058] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes, characterized in that, The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes is obtained by copolymerizing perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds in a solvent under the action of a thermal free radical initiator. The polymer in the hollow fiber membrane alkali-resistant, hydrophobic, and oleophobic finishing agent introduces perfluoroalkyl groups into the main chain. The polymerization unit consists of alternating segments of acrylate groups and perfluoroalkyl groups. The perfluoroalkyl groups on the main chain protect the ester groups on the side chains. When the perfluoroalkyl groups on the side chains are attacked by alkali, they fall off and become ineffective, and the perfluoroalkyl groups on the main chain achieve the oleophobic effect.

2. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1, characterized in that: Perfluoroalkyl acrylates are compounds obtained by esterifying fatty alcohols with 2-10 carbon atoms and alkyl hydrogens wholly or partially replaced by fluorine atoms with acrylic acid or methacrylate.

3. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1 or 2, characterized in that: Perfluoroalkyl acrylates include: tetrafluoropropyl methacrylate, perfluorobutyl acrylate, perfluorohexyl acrylate, perfluorohexyl ethyl acrylate, perfluorooctyl ethyl acrylate, perfluorooctyl acrylate, or perfluorodecyl acrylate.

4. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1, characterized in that: Divinyl perfluoroalkane compounds are compounds whose molecular formula contains two vinyl groups at the head and tail.

5. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1 or 4, characterized in that: Divinyl perfluoroalkane compounds include 1,6-divinylperfluorohexane or 1,4-divinylperfluorobutane.

6. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1, characterized in that: Thermal free radical initiators are compounds that provide free radicals when heated in a polymerization reaction, thereby initiating the polymerization reaction.

7. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1 or 6, characterized in that: Thermal free radical initiators include azobisisobutyronitrile, azobisisoheptanenitrile, or peroxides.

8. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1, characterized in that: Solvents include those capable of dissolving perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds, as well as solvents capable of dissolving polymers obtained by copolymerizing perfluoroalkyl acrylate compounds and divinyl perfluoroalkane compounds.

9. The alkali-resistant, hydrophobic, and oleophobic finishing agent for hollow fiber membranes according to claim 1 or 8, characterized in that: Solvents include perfluoroethers, hexafluoroisopropanol, perfluorohexyl ethyl acrylate, perfluorooctyl ethyl acrylate, or perfluorooctane.

10. An alkali-resistant, hydrophobic, and oleophobic hollow fiber membrane, characterized in that: The hollow fiber membrane is immersed in the hollow fiber membrane of any one of claims 1-9 and left for a certain period of time with an alkali-resistant hydrophobic and oleophobic finishing agent, and then taken out and dried to obtain an alkali-resistant hydrophobic and oleophobic hollow fiber membrane.

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