Preparation method of chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane

Abstract

The invention discloses a preparation method of a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane, which comprises the following steps: (1) blending a chloromethylated polymer, a pore-forming agent and N, N-dimethylformamide, slowly dropwise adding a small amount of amino silane coupling agent, and carrying out cross-linking reaction on the chloromethylated polymer and the amino silane coupling agent to obtain a cross-linked polymer; a polymer containing a siloxane side chain is obtained through a reaction between amino and chloromethyl, and a three-dimensional network structure is formed; and (2) carrying out hydrolysis reaction on the amino silane coupling agent in a coagulating bath in a phase conversion process, and then carrying out dehydration condensation to form the chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane. The preparation method comprises the following steps: introducing a siloxane group with a self-crosslinking function into a side chain of a film-forming polymer by utilizing a reaction of an amino silane coupling agent and a chloromethylated polymer, and carrying out self-crosslinking of the film-forming polymer by virtue of a synchronous hydrolytic polycondensation reaction of the siloxane side chain group in a phase inversion process, so as to prepare the crosslinked ultrafiltration membrane.

Description

Technical Field

[0001] The invention belongs to the field of membrane technology, and in particular relates to a method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane. Background Art

[0002] Silane coupling agents are a class of organosilicon compounds containing silane groups (-SiR3), where R represents an alkyl, aryl or other organic group. They can connect two or more materials of different properties by chemical bonding to improve the biocompatibility and bonding strength of the materials. Silane coupling agents are mainly used to enhance the bonding properties between organic materials (such as plastics and rubbers) and inorganic fillers (such as wollastonite and silica). In recent years, silane coupling agents have shown great application potential in many scientific fields such as medical materials, rubber industry, and bonding glass fibers.

[0003] At the same time, the combination of silane coupling agent and ultrafiltration membrane material can greatly increase the viscosity of the casting solution and improve the structure and performance of the membrane. However, since general silane coupling agents cannot stably exist in ultrafiltration membranes, it is difficult to guarantee the structural properties of ultrafiltration membranes. Therefore, it is very important to use silane coupling agents with special structures to enable them to be stably integrated into ultrafiltration membranes.

[0004] The modification of ultrafiltration membranes often uses interfacial polymerization or cross-linking reaction. Cross-linking reaction refers to the reaction of two or more molecules (generally linear molecules) bonding and cross-linking to form relatively stable molecules (bulk molecules) with a network structure. This reaction transforms linear or slightly branched macromolecules into a three-dimensional network structure, thereby improving the strength, heat resistance, wear resistance, solvent resistance and other properties. Amino-containing silane coupling agents are prone to cross-linking reactions with chloromethyl-containing polymers. Therefore, a cross-linking reaction is used to ensure the complete integration of the silane coupling agent, so that an ultrafiltration membrane with excellent structural performance can be obtained. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane. The preparation method uses a chloromethylated polymer as a membrane-forming polymer, utilizes the reaction of an amino silane coupling agent with the chloromethylated polymer to introduce a siloxane group with a self-crosslinking function into the side chain of the membrane-forming polymer, and performs self-crosslinking of the membrane-forming polymer through a synchronous hydrolysis and polycondensation reaction of the siloxane side chain group during a phase conversion process, thereby preparing a cross-linked ultrafiltration membrane with a smaller pore size and higher retention performance.

[0006] In order to achieve the above object, the technical solution created by the present invention is implemented in the following manner:

[0007] A method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane comprises the following steps:

[0008] (1) Blending a chloromethylated polymer, a pore-forming agent, and N,N-dimethylformamide, slowly dropping a small amount of an amino-type silane coupling agent, the chloromethylated polymer and the amino-type silane coupling agent undergo a cross-linking reaction, and a polymer containing a siloxane side chain is obtained through a reaction between the amino group and the chloromethyl group, thereby forming a three-dimensional network structure;

[0009] (2) The amino silane coupling agent undergoes a hydrolysis reaction during the phase transition in the coagulation bath, and then undergoes a dehydration condensation reaction to form a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane.

[0010] Furthermore, a chloromethylated polymer is used as a film-forming polymer, and a siloxane group with a self-crosslinking function is introduced into the side chain of the film-forming polymer by utilizing the reaction between an amino silane coupling agent and the chloromethylated polymer. The self-crosslinking of the film-forming polymer is carried out through the synchronous hydrolysis and polycondensation reaction of the siloxane side chain groups during the phase inversion process, thereby preparing the cross-linked ultrafiltration membrane.

[0011] Furthermore, the chloromethylated polymer in step (1) comprises one or more of chloromethylated polysulfone, chloromethylated polyethersulfone, chloromethylated polyetherketone, chloromethylated polyetheretherketone, and chloromethylated polyetherketoneketone, wherein the degree of chloromethylation of the polymer is between 55% and 95%.

[0012] Furthermore, the mass fraction of the chloromethylated polymer in step (1) is 17% to 21%.

[0013] Furthermore, the pore-forming agent in step (1) is polyvinyl pyrrolidone, with a molecular weight of 10,000 to 58,000 and a mass fraction of 1% to 3%.

[0014] Furthermore, the amino-based silane coupling agent in step (1) includes one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, anilinomethyltriethoxysilane, and polyaminoalkyltrialkoxysilane.

[0015] Furthermore, the concentration of the amino silane coupling agent solution in step (1) is 0.1% to 5% of the chloromethylated polymer.

[0016] The invention adopts the cross-linking reaction between amino group and chloromethyl group to obtain the polymer containing siloxane side chain, and then utilizes the phase inversion method in the film-forming process to complete the exchange of the accompanying solvent-non-solvent (water), and the siloxane side chain rapidly undergoes hydrolysis and condensation reaction to form a cross-linked ultrafiltration membrane. The ultrafiltration membrane prepared by the method has strong mechanical properties and high density, and can achieve a high retention effect on BSA.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The materials used are easy to obtain, including chloromethylated polymers and silane coupling agents, with a wide variety of options;

[0019] 2. The silane coupling agent and chloromethylation have a good degree of cross-linking, and the prepared membrane has good mechanical properties and is not easy to deform.

[0020] 3. The addition of silane coupling agent can greatly increase the viscosity of the casting solution, thereby improving the density of the film;

[0021] 4. The membrane preparation process is simple and easy, and the manufacturing cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow diagram of the method for preparing the chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane of the present invention;

[0023] Figure 2-Figure 6 It is a scanning electron microscope comparison diagram of the cross-section of the ultrafiltration membrane of Comparative Example 1 and the cross-linked ultrafiltration membranes of silane coupling agents with different mass fractions in Example 1, Example 4, Example 5 and Example 6. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] In order to enable relevant persons in the art to understand the present invention more clearly, the present invention will be further described in detail below with reference to examples. The following selected embodiments are preferred implementation modes of the present invention, and the scope of protection claimed in the present invention is not limited thereto.

[0026] The present invention provides a method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane, comprising the following steps: (1) blending a chloromethylated polymer, a pore-forming agent, and N,N-dimethylformamide, slowly dripping a small amount of an amino-type silane coupling agent, causing the chloromethylated polymer and the amino-type silane coupling agent to undergo a cross-linking reaction, and obtaining a polymer containing a siloxane side chain through the reaction between the amino group and the chloromethyl group, thereby forming a three-dimensional network structure; (2) the amino-type silane coupling agent undergoes a hydrolysis reaction during the phase transition process in a coagulation bath, and then undergoes dehydration condensation to form a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane. The reaction process is selected from chloromethylated polysulfone and 3-aminopropyltriethoxysilane as an example, and the specific reaction process is shown in the following formula:

[0027]

[0028] Example 1

[0029] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed in a round-bottom flask in a mass ratio of 0.17:0.03:0.80. After being evenly mixed, a small amount of silane coupling agent is slowly added dropwise, and the mass of the silane coupling agent is 0.5% of the mass of the chloromethylated polymer. After the cross-linking reaction is completed, it is quickly placed in a coagulation bath to form a film by a phase inversion method.

[0030] Example 2

[0031] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed in a round-bottom flask in a mass ratio of 0.18:0.03:0.79. After being evenly mixed, a small amount of silane coupling agent is slowly added dropwise, and the mass of the silane coupling agent is 0.5% of the mass of the chloromethylated polymer. After the cross-linking reaction is completed, it is quickly placed in a coagulation bath to form a film by a phase inversion method.

[0032] Example 3

[0033] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed in a round-bottom flask, the mass ratio of chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide is (0.19:0.03:0.78). After being evenly mixed, a small amount of silane coupling agent is slowly added dropwise, the mass of the silane coupling agent is 0.5% of the mass of the chloromethylated polymer. After the cross-linking reaction is completed, it is quickly placed in a coagulation bath to form a film by a phase inversion method.

[0034] Example 4

[0035] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed in a round-bottom flask, the mass ratio of chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide is 0.17:0.03:0.78. After being evenly mixed, a small amount of silane coupling agent is slowly added dropwise, the mass of the silane coupling agent is 1% of the mass of the chloromethylated polymer. After the cross-linking reaction is completed, it is quickly placed in a coagulation bath to form a film by a phase inversion method.

[0036] Example 5

[0037] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed in a round-bottom flask, the mass ratio of chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide is 0.17:0.03:0.78. After being evenly mixed, a small amount of silane coupling agent is slowly added dropwise, the mass of the silane coupling agent is 2% of the mass of the chloromethylated polymer. After the cross-linking reaction is completed, it is quickly placed in a coagulation bath to form a film by a phase inversion method.

[0038] Example 6

[0039] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide are mixed in a round-bottom flask, the mass ratio of chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide is 0.17:0.03:0.78. After being evenly mixed, a small amount of silane coupling agent is slowly added dropwise, the mass of the silane coupling agent is 3% of the mass of the chloromethylated polymer. After the cross-linking reaction is completed, it is quickly placed in a coagulation bath to form a film by a phase inversion method.

[0040] Comparative Example 1

[0041] Chloromethylated polymer, polyvinyl pyrrolidone and N,N-dimethylformamide were mixed in a round-bottom flask in a mass ratio of 0.17:0.03:0.78. After being mixed evenly, they were quickly placed in a coagulation bath to form a film by a phase inversion method.

[0042] The properties of the prepared chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane are shown in Table 1:

[0043] Retention rate of BSA (%) <![CDATA[The water flux of BSA (Lm -2 h -1 bar -1 )]]> Example 1 90.83 68.78 Example 2 92.47 59.67 Example 3 95.10 45.34 Example 4 90.83 68.78 Example 5 93.95 57.43 Example 6 95.26 50.26 Comparative Example 1 78.37 78.25

[0044] Table 1 Performance table of ultrafiltration membranes prepared in Examples 1-6 and Comparative Examples.

[0045] In Examples 1-6, it can be seen that with the increase in the mass fraction of the chloromethylated polymer, the overall viscosity of the casting solution increases, the compactness of the membrane is enhanced, and the BSA retention effect and water flux change significantly. With the addition of the silane coupling agent, the degree of crosslinking is significantly improved, and the condensation thickness gradually increases, which will lead to an increase in the thickness of the dense layer formed and a decrease in the thickness of the sponge layer, resulting in an increase in the retention rate of bovine serum and a decrease in the water flux.

[0046] It can be seen from Comparative Example 1 that the addition of silane coupling agent from scratch causes a significant change in the structure of the ultrafiltration membrane, resulting in the disappearance of the finger-like pores and the thickening of the dense layer, resulting in high retention performance of the ultrafiltration membrane.

[0047] The above description is a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane, characterized in that The steps include: (1) Blending a chloromethylated polymer, a pore-forming agent, and N,N-dimethylformamide, slowly adding a small amount of an amino-type silane coupling agent, the chloromethylated polymer and the amino-type silane coupling agent undergo a cross-linking reaction, and a polymer containing a siloxane side chain is obtained through the reaction between the amino group and the chloromethyl group, thereby forming a three-dimensional network structure; (2) The amino silane coupling agent undergoes a hydrolysis reaction during the phase transition in the coagulation bath, and then undergoes dehydration condensation to form a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane.

2. The method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane according to claim 1, characterized in that: A chloromethylated polymer is used as a membrane-forming polymer, and a siloxane group with a self-crosslinking function is introduced into the side chain of the membrane-forming polymer by utilizing the reaction of an amino silane coupling agent and the chloromethylated polymer. The self-crosslinking of the membrane-forming polymer is carried out through the synchronous hydrolysis and polycondensation reaction of the siloxane side chain group during the phase inversion process, so as to prepare the cross-linked ultrafiltration membrane.

3. The method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane according to claim 1, characterized in that: The chloromethylated polymer in step (1) comprises one or more of chloromethylated polysulfone, chloromethylated polyethersulfone, chloromethylated polyetherketone, chloromethylated polyetheretherketone, and chloromethylated polyetherketoneketone, wherein the degree of chloromethylation of the polymer is between 55% and 95%.

4. The method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane according to claim 1, characterized in that: The mass fraction of the chloromethylated polymer in step (1) is 17% to 21%.

5. The method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane according to claim 1, characterized in that: The pore-forming agent in step (1) is polyvinyl pyrrolidone, with a molecular weight of 10,000 to 58,000 and a mass fraction of 1% to 3%.

6. The method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane according to claim 1, characterized in that: The amino-based silane coupling agent in step (1) includes one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, anilinomethyltriethoxysilane, and polyaminoalkyltrialkoxysilane.

7. The method for preparing a chloromethylated polymer-silane coupling agent cross-linked ultrafiltration membrane according to claim 1, characterized in that: The concentration of the amino silane coupling agent solution in step (1) is 0.1% to 5% of the chloromethylated polymer.

Images