阅读说明：本技术 持久亲水均孔超滤膜的制备方法 (Preparation method of durable hydrophilic uniform-pore ultrafiltration membrane ) 是由 武春瑞 厍景国 高海富 陈小乐 宋姿萍 吕晓龙 于 2021-07-26 设计创作，主要内容包括：本发明提出一种持久亲水均孔超滤膜的制备方法,首先,在聚合物膜材料的常规溶解条件下,引发、完成亲水链在聚合物链上的接枝反应,即溶解同步亲水化；进而,在该聚合物溶液(初生态膜)进入凝固浴后,利用凝固浴引发该亲水链间的交联反应,同步调控相分离成膜进程,即亲水链交联协同相分离。通过交联结构干涉聚合物分子链运动、相分离固化成膜进程,形成较均匀、规整的聚合物网络结构,实现超滤膜孔结构均一化。该方法反应条件温和,制备方法简单,在制膜过程中实现超滤膜亲水化及孔径均一化,促进超滤膜渗透通量、分离性能与抗污染能力同步提升。(The invention provides a preparation method of a lasting hydrophilic homogeneous pore ultrafiltration membrane, which comprises the following steps of firstly, initiating and finishing a grafting reaction of a hydrophilic chain on a polymer chain under the conventional dissolving condition of a polymer membrane material, namely dissolving and synchronously hydrophilizing; furthermore, after the polymer solution (nascent state membrane) enters the coagulation bath, the coagulation bath is used for initiating the crosslinking reaction among the hydrophilic chains, and the phase separation and film formation process is synchronously regulated and controlled, namely the hydrophilic chain crosslinking is cooperated with the phase separation. The uniform and regular polymer network structure is formed by interfering the movement of polymer molecular chains and the film forming process of phase separation and solidification through the cross-linked structure, and the homogenization of the pore structure of the ultrafiltration membrane is realized. The method has mild reaction conditions and simple preparation method, realizes hydrophilization and aperture homogenization of the ultrafiltration membrane in the membrane preparation process, and promotes the synchronous improvement of the permeation flux, the separation performance and the anti-pollution capability of the ultrafiltration membrane.)

1. A preparation method of a durable hydrophilic uniform-pore ultrafiltration membrane is characterized by comprising the following steps: the method comprises the following steps:

1) dissolution synchronous hydrophilization: stirring a polymer membrane material with reaction sites, reactive active hydrophilic molecules, a membrane forming pore-forming agent and a solvent at constant temperature, and finishing hydrophilic chain grafting under the conventional dissolving condition of the polymer membrane material, namely dissolving and synchronously hydrophilizing;

2) crosslinking synergistic phase separation: the method comprises the steps of completing dissolving of a synchronously hydrophilized polymer solution, preparing an ultrafiltration membrane by using a dry-wet phase separation method, initiating a cross-linking reaction between hydrophilic chains by using a coagulating bath, regulating and controlling a phase separation process by the aid of a formed cross-linking network in a coordinated mode, limiting movement of the polymer chains and formation and growth of micelles, forming a uniform polymer network structure, and obtaining the ultrafiltration membrane with a uniform membrane pore structure, namely the long-acting hydrophilic uniform-pore ultrafiltration membrane.

2. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the polymer film material with the reaction sites accounts for 13-20 wt% of the casting solution, the solvent accounts for 86-75 wt% of the casting solution, the reactive hydrophilic molecules account for 0.1-20 wt% of the casting solution, the film forming pore-forming agent accounts for 0.1-20 wt% of the casting solution, and the total amount is 100%.

3. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the polymer membrane material is a polymer material containing C-X, wherein X is Cl or F functional groups.

4. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 3, wherein: the polymer film material is one or a mixture of more than two of polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene fluoride and polyvinylidene fluoride-chlorotrifluoroethylene copolymer.

5. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the reactive active hydrophilic molecules are hydrophilic molecules which can be grafted on a polymer molecular chain and contain secondary crosslinkable groups.

6. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 5, wherein: the reactive active hydrophilic molecule is one or a mixture of more than two of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropylmethyldimethoxysilane, aminopropylmethyldiethoxysilane, diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyldimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropyltrimethoxysilane and 3-piperazinylpropyldimethoxysilane.

7. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the pore-forming agent is one or a mixture of more than two of polyethylene glycol or polyvinylpyrrolidone with the molecular weight of 200-20000.

8. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the solvent is one or a mixture of more than two of dimethylformamide, dimethyl sulfoxide and dimethylacetamide.

9. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the constant-temperature stirring temperature is 40-80 ℃, and the stirring time is 2-48 h.

10. The method of preparing a durable hydrophilic homopore ultrafiltration membrane according to claim 1, wherein: the coagulating bath is an aqueous solution of sodium hydroxide or hydrochloric acid, the concentration is 1-30 wt%, and the temperature of the coagulating bath is controlled at 25-80 ℃.

Technical Field

The invention belongs to the field of filtration membranes, relates to an ultrafiltration membrane, and particularly relates to a preparation method of a durable hydrophilic uniform pore ultrafiltration membrane.

Background

Polyvinyl chloride, polyvinylidene fluoride-chlorotrifluoroethylene and the like are widely used membrane materials in the ultrafiltration process, and have the characteristics of excellent acid and alkali resistance, chemical stability, mechanical stability, weather resistance and the like. However, due to the hydrophobic nature, the problems of pollution and low flux are easy to occur during the use process, and the application of the hydrophobic material is limited, therefore, the hydrophilic material is usually introduced by a blending method to increase the hydrophilicity of the ultrafiltration membrane. However, the introduction of the hydrophilic material increases the hydrophilicity of the polymer, so that the affinity between the molecular chain and the coagulant is enhanced, the hydrophilic molecular chain forms epitaxial growth towards the coagulation bath, and open pores are formed on the surface of the membrane; meanwhile, because there is no stable chemical bond between the hydrophilic molecule and the membrane material, the hydrophilic molecule is easy to lose in the using process, resulting in the reduction of the membrane performance.

Disclosure of Invention

The invention aims to provide a preparation method of a lasting hydrophilic pore-equalizing ultrafiltration membrane, which synchronously realizes hydrophilization and pore size equalization of a membrane material in a membrane preparation process by a method of dissolution grafting hydrophilization-crosslinking synergistic phase separation, and promotes the synchronous improvement of the permeation flux, the separation performance and the anti-pollution capability of the ultrafiltration membrane.

In order to realize the purpose, the specific technical scheme of the preparation method of the durable hydrophilic uniform pore ultrafiltration membrane is as follows:

the preparation method of the durable hydrophilic uniform pore ultrafiltration membrane comprises the following steps:

stirring a polymer membrane material with reaction sites, reactive active hydrophilic molecules, a membrane forming pore-forming agent and a solvent at constant temperature, and finishing hydrophilic chain grafting under the conventional dissolving condition of the polymer membrane material to form a membrane casting solution; and then, preparing the ultrafiltration membrane by using a dry-wet phase separation method, and initiating a hydrophilic interchain crosslinking reaction and curing to form a membrane by using a coagulating bath, thus obtaining the finished ultrafiltration membrane.

The preparation method of the lasting hydrophilic uniform-pore ultrafiltration membrane comprises the following steps: the polymer membrane material accounts for 13-20 wt% of the membrane casting solution, the solvent accounts for 86-75 wt% of the membrane casting solution, the pore-forming agent accounts for 0.1-20 wt% of the membrane casting solution, the reactive molecules account for 0.1-20 wt% of the membrane casting solution, and the total amount is 100%.

The polymer film material is one or a mixture of polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene fluoride and polyvinylidene fluoride-chlorotrifluoroethylene copolymer; the pore-foaming agent is one or a mixture of polyethylene glycol with the molecular weight of 200-20000 and polyvinylpyrrolidone; the solvent is one or a mixture of more of dimethylformamide, dimethyl sulfoxide and dimethylacetamide; the constant-temperature mixing and stirring temperature of the polymer film forming material, the pore-forming agent, the solvent and the reactive active hydrophilic molecules is 40-80 ℃, and the constant-temperature mixing and stirring time is 2-48 h; the reactive active hydrophilic molecules refer to hydrophilic molecules which can be grafted on polymer molecular chains and can be secondarily crosslinked, such as: aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropylmethyldimethoxysilane, aminopropylmethyldiethoxysilane, diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyldimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropyltrimethoxysilane, 3-piperazinylpropyldimethoxysilane, and the like; the coagulating bath is aqueous solution of sodium hydroxide or hydrochloric acid, the concentration is kept between 1 and 30 weight percent, and the temperature of the coagulating bath is controlled between 25 and 80 ℃. The ultrafiltration membrane is one of a flat membrane or a hollow fiber membrane.

The ultrafiltration membrane is mainly used for removing impurities in water through pore size screening, and due to randomness of a phase separation process, most of the ultrafiltration membranes are relatively wide in pore size distribution, so that the separation efficiency of the separation membrane is limited. From the analysis of the phase separation principle of ultrafiltration membrane formation, the separation pore size and distribution of the ultrafiltration membrane are mainly influenced by the migration and solidification process of polymer molecular chains in the membrane casting solution in the phase separation process, namely the formation, growth, solidification and the like of polymer micelles. If the anchor points which can be excited by a coagulant system can be arranged in the polymer molecular chain/hydrophilic graft chain of the membrane material, stable interaction among the polymer molecular chains is formed by exciting the anchor points in the phase separation process, so that the nucleation and growth processes of relatively random polymer micelles are converted into controllable polymer networks for forming and curing, the more accurate regulation of the migration, reaction-crosslinking network formation and curing of the polymer chains is realized, and the uniform regulation and control of the pore diameter of the ultrafiltration membrane becomes possible.

The invention is based on that molecules such as polyvinyl chloride, polyvinylidene fluoride-chlorotrifluoroethylene contain C-X (X refers to F or Cl and the like) bonds, can be used as reaction sites for in-situ grafting, and utilizes the chemical reaction of functional groups and active bonds of molecular chains of membrane materials to initiate and finish grafting of hydrophilic chains on the polymer chains under the conventional dissolving conditions of the polymer membrane materials, namely, dissolving and synchronously hydrophilizing to realize the lasting hydrophilization of the membrane materials; furthermore, after the polymer solution (nascent state membrane) enters the coagulation bath, the coagulation bath is used for initiating the crosslinking reaction among the hydrophilic chains, and the phase separation and film formation process is synchronously regulated and controlled, namely the hydrophilic chain crosslinking is cooperated with the phase separation. The uniform pore structure is obtained by interfering the movement of polymer molecular chains and the film forming process of phase separation and solidification through a crosslinking structure to form a uniform and regular polymer network structure. The method synchronously realizes hydrophilization and aperture homogenization of the membrane material in the membrane preparation process, and promotes the synchronous improvement of the permeation flux, the separation performance and the anti-pollution capability of the ultrafiltration membrane.

The invention has the advantages and beneficial effects that:

1. the invention realizes the lasting hydrophilization of the polymer film material under the condition of dissolving the polymer film material;

2. in the phase separation process, a coagulation bath is used for initiating a crosslinking reaction among the hydrophilic chains, and a more uniform and regular polymer network structure is formed in the ultrafiltration membrane through the interference of a crosslinking structure with the movement of molecular chains of a polymer membrane material and the phase separation curing film-forming process, so that the uniform regulation and control of the pore structure of the ultrafiltration membrane are realized;

3. the method realizes synchronous improvement of the permeation flux, the separation performance and the anti-pollution capability of the ultrafiltration membrane by using a dissolving grafting hydrophilization-crosslinking synergistic phase separation method.

Drawings

FIG. 1 is a schematic diagram of a method of the present invention;

FIG. 2 is a graph showing the comparison of the dissolution of ultrafiltration membranes with different amounts of active hydrophilic molecules in a solvent;

FIG. 3 is a comparison graph of the pore size and pore size distribution of ultrafiltration membranes with different amounts of active hydrophilic molecules added;

FIG. 4 is a graph showing the comparison of anti-pollution performance of ultrafiltration membranes with different amounts of active molecules added.

Detailed Description

In order to better understand the purpose, structure and function of the present invention, the following is a more detailed description of the preparation method of a high performance ultrafiltration membrane of the present invention.

Examples 1 to 11:

weighing 13 wt% of polyvinyl chloride resin (polymer membrane material), 5 wt% of polyethylene glycol 200 (pore-forming agent) and 75 wt% of dimethylformamide (solvent), adding 7 wt% of reactive active hydrophilic molecules, stirring at a constant temperature of 40 ℃ for 48 hours until the reactive active hydrophilic molecules are completely dissolved to form a uniform solution, scraping the membrane, and then putting the membrane into a coagulation bath with a crosslinking factor to prepare the flat ultrafiltration membrane by using a phase inversion method. The reactive hydrophilic molecular species and coagulation bath composition are shown in table 1, with the coagulation bath temperature being 25 ℃.

TABLE 1 Effect of adding different reactive molecules on the Performance of polyvinyl chloride Flat Membrane

Table 1 shows the influence of adding different reactive molecules into the membrane casting solution on the hydrophilicity and hydrophobicity and the anti-pollution performance of the PVC ultrafiltration membrane. Wherein example 1 is a control, examples 2 to 11 are polyvinyl chloride ultrafiltration membranes prepared by phase inversion of aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropylmethyldimethoxysilane, aminopropylmethyldiethoxysilane, diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropyldimethoxysilane, mercaptopropyltriethoxysilane, mercaptopropyltrimethoxysilane, 3-piperazinylpropyldimethoxysilane in deionized water at different pH's in the casting solution. Compared with the control group of example 1, the ultrafiltration membrane has lower water contact angle, the water contact angle is kept stable after pure water runs for 300 hours, and the flux recovery rate of the ultrafiltration membrane is obviously improved compared with that of the control group, so that the hydrophilicity of the ultrafiltration membrane is improved after reactive ammonia molecules are introduced into the membrane casting solution, the lasting hydrophilicity is obtained, and the pollution resistance of the ultrafiltration membrane is improved.

Examples 12 to 16

Weighing 20 wt% of polyvinylidene fluoride resin (polymer membrane material), 3 wt% of polyvinylpyrrolidone (pore-forming agent) and a certain amount of dimethylformamide (solvent), finally adding a certain amount of aminopropyl trimethoxysilane (reactive active hydrophilic molecules), keeping the total amount of the membrane casting solution at 100%, stirring at a constant temperature of 80 ℃ for 24 hours until the membrane casting solution is completely dissolved to form a uniform solution, scraping the membrane, and then putting the membrane into a coagulation bath with a crosslinking factor to prepare the flat ultrafiltration membrane by using a phase inversion method.

The amount of aminopropyl trimethoxysilane added was as shown in table 2, the coagulation bath was deionized water having a PH of 8.5, and the coagulation bath temperature was 80 ℃.

TABLE 2 influence of reactive active molecule addition on the polyvinylidene fluoride hollow fiber membrane Performance

Table 2 shows the effect of reactive molecule addition on the performance of polyvinylidene fluoride hollow fiber ultrafiltration membranes. Examples 12 to 16 were ultrafiltration membranes prepared by adding different amounts of reactive active molecules to the membrane casting solution, and compared with control example 1, the flux of the ultrafiltration membrane showed an increasing trend as the amount of the added reactive molecules increased, and the retention of stable BSA molecules was maintained, the water contact angle was significantly decreased, the flux recovery rate was increased, and the normalized flux results are shown in fig. 4, where M0 is the control, i.e., the ultrafiltration membrane to which no reactive molecules were added, and M1 and M2 are examples 12 and 13, and compared with M0, the ultrafiltration membrane exhibited improved anti-contamination performance after the addition of the reactive molecules and increased as the amount of the added reactive molecules increased, thereby demonstrating that increasing the amount of the added reactive molecules contributes to the improvement of hydrophilicity, anti-contamination performance, and filtration performance; the dissolution of the ultrafiltration membranes obtained in examples 12 to 16 in the solvent dimethylacetamide is shown in fig. 2, wherein M0 is a control group, i.e., an ultrafiltration membrane without the addition of reactive molecules, M1, M2, M3 and M4 respectively correspond to examples 12, 13, 14 and 15, and compared with a control group M0, the ultrafiltration membrane gradually becomes insoluble and the crosslinking degree increases with the increase of the addition amount of the reactive molecules, thereby proving that the molecular chains of the ultrafiltration membrane are successfully crosslinked after the addition of the reactive molecules; the pore size and pore size distribution of the ultrafiltration membranes obtained in examples 12 to 15 are shown in fig. 3, wherein M0 is a control group example 1, M1, M2, M3 and M4 correspond to examples 12, 13, 14 and 15, respectively, compared with a control group M0, the pore size of the ultrafiltration membrane becomes more uniform from the wider distribution of M0 after the reactive molecules are added, and the average pore size of the ultrafiltration membrane becomes larger under the condition that the maximum pore size of the ultrafiltration membrane is consistent with the increase of the addition amount of the reactive molecules, thereby helping to improve the separation efficiency of the ultrafiltration membrane, and thus, the pore size of the ultrafiltration membrane is uniform after the reactive molecules are added.

It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.