CN116949812A - Treatment method for hydrophilic modification of PTFE (polytetrafluoroethylene) - Google Patents

Abstract

The invention discloses a method for hydrophilic modification of PTFE, which adopts a PTFE film as a reaction carrier, uses a polymer containing a large amount of hydrophilic groups to be injected circularly at a certain temperature as a cross-linking framework, uses boric acid as a cross-linking agent to carry out cross-linking reaction with the PTFE film at a certain temperature, and obtains the modified PTFE film through post-treatment. The invention has the advantages of low treatment cost, strong adhesive force and durability and environment-friendly treatment process.

Description

A treatment method for hydrophilic modification of PTFE

Technical field

The invention relates to the field of PTFE membrane modification, in particular to a treatment method for hydrophilic modification of PTFE.

Background technique

PTFE is a material with excellent heat resistance and corrosion resistance, but its surface is extremely hydrophobic, making it difficult to contact and adhere to water or other polar liquids in many applications. Therefore, in order to make PTFE materials To better contact and adhere to water or other liquids, hydrophilic modification treatment is required. Hydrophilic modification treatment can change the chemical properties of the PTFE surface and make the surface hydrophilic, thus improving its wettability and adhesion. attachment, making it useful in a wider range of applications.

Currently common PTFE hydrophilic treatment processes include plasma surface modification, which forms an oxide layer on the surface of PTFE through plasma treatment to increase its hydrophilicity; chemical modification, which uses chemical reagents to chemically modify the PTFE surface, such as acidification , alkalinization and vulcanization, etc.; solution dipping method, immersing PTFE in a hydrophilic solution to adsorb hydrophilic molecules on its surface; nano-coating method, coating a layer of nanometer layer on the surface of PTFE to make its surface have Hydrophilic. However, these PTFE hydrophilic processes have more or less the following defects: weak adhesion. PTFE hydrophilic processes usually require the use of chemicals to enhance their adhesion, but they are easy to fall off during chemical cleaning processes; poor durability, PTFE is hydrophilic The process may wear or fall off after long-term use, thereby reducing its effectiveness; Expensive, PTFE hydrophilic processes often require high material and equipment costs, which may make it uneconomical in some applications; Impact on the environment , the PTFE hydrophilic process may have a negative impact on the environment, such as waste water and waste gas during the production process. Therefore, there is an urgent need for a

Contents of the invention

The object of the present invention is to provide a treatment method for hydrophilic modification of PTFE. It has the advantages of low treatment cost, strong adhesion and durability, and the treatment process is environmentally friendly.

The technical solution of the present invention: a treatment method for hydrophilic modification of PTFE, using a PTFE membrane as a reaction carrier, using a high polymer containing hydrophilic groups to be cyclically injected at a certain temperature as a cross-linking skeleton, and using boric acid as a cross-linking skeleton. The linking agent undergoes a cross-linking reaction with the PTFE membrane at a certain temperature, and then is post-processed to obtain a modified PTFE membrane.

The aforementioned treatment method for hydrophilic modification of PTFE includes the following steps:

S1: Soak the PTFE membrane in organic solvent, then soak or rinse in cold water;

S2: Prepare hydrophilic polymer solution and boric acid solution;

S3: Circularly inject the hydrophilic polymer solution configured in S2 into the PTFE membrane;

S4: Take out the PTFE membrane in S3 and soak it in boric acid solution;

S5: Dry the soaked PTFE membrane to obtain a modified PTFE membrane.

In the aforementioned treatment method for hydrophilic modification of PTFE, polyvinyl alcohol and boric acid undergo a body-type polycondensation reaction, and the reactants form a network structure and are intertwined with PTFE fibers.

In the aforementioned treatment method for hydrophilic modification of PTFE, the PTFE membrane requires specific pretreatment, using an organic solvent with critical low surface tension to replace the air in the PTFE membrane pores, and using an aqueous phase to replace the organic solvent in the membrane pores.

In the aforementioned treatment method for hydrophilic modification of PTFE, the organic solvent in S1 includes isopropyl alcohol, ethanol and n-ethane.

In the aforementioned treatment method for hydrophilic modification of PTFE, the PTFE membrane is prepared by a biaxial stretching process to obtain a PTFE membrane with a flat plate or a centrally controlled fiber membrane structure.

In the aforementioned treatment method for hydrophilic modification of PTFE, the concentration of boric acid in S2 is 2-4%, the soaking time is 2-60 minutes, and the temperature is 10-95°C.

In the aforementioned treatment method for hydrophilic modification of PTFE, after the hydrophilic polymer solution is configured in S2, an auxiliary solution is added.

In the aforementioned PTFE hydrophilic modification treatment method, the hydrophilic polymer in S3 includes polyvinyl alcohol, polyethylene glycol and polyether polyol, including linear and branched chain structures, and the auxiliary solution includes Dimethyl sulfoxide and dimethyl acetamide.

In the aforementioned treatment method for hydrophilic modification of PTFE, the hydrophilic polymer solution in S3 is injected into the pores of the PTFE membrane with positive pressure or negative pressure, and the cyclic injection method includes dead-end and cross-flow methods. The cycle temperature is 10-95°C and the cycle time is 0.2-4 hours.

Compared with the existing technology, the beneficial effects of the present invention are reflected in:

1. The hydrophilic process of the present invention has strong adhesion to PTFE, can withstand cleaning with sodium hypochlorite, sodium hydroxide, hydrochloric acid and citric acid in common sewage treatment processes, and is not easy to fall off during chemical cleaning processes.

2. The hydrophilic process of the present invention has good durability and will not wear or fall off after long-term use. It can still maintain good hydrophilic properties under long-term use and repeated drying;

3. The use cost of the hydrophilic process of the present invention is low, the entire process does not require high material and equipment costs, and the unit membrane area is only 0.5-1.5 yuan;

4. In the hydrophilic modification process used in the present invention, except for certain non-essential auxiliary solvents, all other agents are environmentally friendly and can be easily removed without causing negative impacts on the environment.

Description of the drawings

Figure 1 is a reaction mechanism diagram of the present invention;

Figure 2 is the residual PVA concentration and contact angle distribution under different times of use in Example 1 of the present invention;

Figure 3 is a structural diagram of the dead-end and cross-flow circulation of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but this does not serve as a basis for limiting the present invention.

Example 1: A treatment method for hydrophilic modification of PTFE, including the following steps:

(1) Soak the PTFE hollow fiber membrane module in isopropyl alcohol for 5 seconds, and then soak in cold water for 20 seconds;

(2) Prepare a 1wt% polyvinyl alcohol solution with a water temperature of 90°C;

(3) Prepare 2.5wt% boric acid solution at a temperature of 35 degrees Celsius;

(4) Inject the prepared polyvinyl alcohol solution into the PTFE hollow fiber membrane module and circulate it for 1 hour using a cross-flow method, as shown in Figure 3;

(5) Take out the recycled diaphragm and put it into the boric acid solution and soak it for 5 minutes;

(6) Place the soaked diaphragm into a 90°C decompression oven to dry.

Example 2: A treatment method for hydrophilic modification of PTFE, including the following steps:

(1) Soak the PTFE hollow fiber membrane module in ethanol for 30 seconds, and then rinse with cold water for 30 seconds;

(2) Prepare a 2.5wt% polyvinyl alcohol solution, add 1.5wt% dimethyl sulfoxide, and the water temperature is 40°C;

(3) Prepare 2wt% boric acid solution at a temperature of 15°C;

(4) Inject the prepared polyvinyl alcohol solution into the PTFE hollow fiber membrane module and circulate it for 1 hour using the dead-end method, as shown in Figure 3;

(5) Take out the recycled diaphragm and put it into the boric acid solution and soak it for 1 hour;

(6) Place the soaked diaphragm into a 90°C decompression oven to dry.

Example 3: A treatment method for hydrophilic modification of PTFE, including the following steps:

(1) Soak the PTFE hollow fiber membrane module in n-hexane for 5 seconds;

(2) Prepare 1wt% polyvinyl alcohol solution at 90°C water temperature and cool to 25°C;

(3) Prepare 4wt% boric acid solution at a temperature of 25°C;

(4) Inject the prepared polyvinyl alcohol solution into the PTFE hollow fiber membrane module and circulate it for 1 hour using a cross-flow method, as shown in Figure 3;

(5) Take out the recycled diaphragm and put it into the boric acid solution and soak it for 1 hour;

(6) Place the soaked diaphragm into a 90°C decompression oven to dry.

In the above embodiment, polyvinyl alcohol and boric acid undergo a bulk polycondensation reaction, and the reactants form a network structure and are entangled with PTFE fibers. The specific reaction formula is as follows:

It can be seen from Figure 2 that the PVA residual concentration of the hydrophilic PTFE membrane becomes less and less as the number of uses increases, and the contact angle becomes larger and larger as the number of uses increases, and then tends to be stable, with good Hydrophilic and durable.

Among the above treatment process parameters: boric acid concentration is 2-4%, soaking time is 2-60 minutes, and temperature is 10-95°C. The concentration of boric acid is not easy to be too high or too low. Too high a concentration will cause crystallization in the diaphragm, making it difficult to move the long hydrophilic chains. In long-term use of the diaphragm, the durability of the long hydrophilic chains will be reduced. If the concentration of boric acid is too low, crosstalk will occur. The connection is insufficient, and the long hydrophilic chain is gradually lost during daily use.

In Example 3, crystals appeared on the surface of the membrane fiber, and the contact angle returned to about 15° after 14 days of washing with clean water.

The above are only the preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above-mentioned embodiments. All technical solutions that fall under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications may be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (10)

1. A treatment method for hydrophilic modification of PTFE, which is characterized by: using a PTFE membrane as a reaction carrier, using a polymer containing hydrophilic groups to be cyclically injected at a certain temperature as a cross-linking skeleton, and using boric acid as a cross-linking skeleton. The linking agent undergoes a cross-linking reaction with the PTFE membrane at a certain temperature, and then is post-processed to obtain a modified PTFE membrane. 2. A treatment method for hydrophilic modification of PTFE according to claim 1, characterized in that: comprising the following steps: S1: Soak the PTFE membrane in organic solvent, then soak or rinse in cold water; S2: Prepare hydrophilic polymer solution and boric acid solution; S3: Circularly inject the hydrophilic polymer solution configured in S2 into the PTFE membrane; S4: Take out the PTFE membrane in S3 and soak it in boric acid solution; S5: Dry the soaked PTFE membrane to obtain a modified PTFE membrane. 3. A treatment method for hydrophilic modification of PTFE according to claim 1 or 2, characterized in that polyvinyl alcohol and boric acid undergo a body-type polycondensation reaction, and the reactants form a network structure and are entangled with PTFE fibers. 4. A treatment method for hydrophilic modification of PTFE according to claim 2, characterized in that: the PTFE membrane requires specific pre-treatment, using an organic solvent with critical low surface tension to replace the air in the PTFE membrane pores, using water Phase replaces the organic solvent in the membrane pores. 5. A treatment method for hydrophilic modification of PTFE according to claim 2, characterized in that the organic solvent includes isopropyl alcohol, ethanol and n-ethane. 6. A treatment method for hydrophilic modification of PTFE according to claim 2, characterized in that: the PTFE membrane is prepared by a biaxial stretching process to obtain a PTFE membrane with a flat plate or a central fiber membrane structure. 7. A treatment method for hydrophilic modification of PTFE according to claim 2, characterized in that: the boric acid concentration in the S2 is 2-4%, the soaking time is 2-60 minutes, and the temperature is 10-95 ℃. 8. A processing method for hydrophilic modification of PTFE according to claim 2, characterized in that: after the hydrophilic polymer solution is configured in S2, an auxiliary solution is added. 9. A treatment method for hydrophilic modification of PTFE according to claim 8, characterized in that: the hydrophilic polymer includes polyvinyl alcohol, polyethylene glycol and polyether polyol, including linear and branched polyols. Chain structure, the auxiliary solution includes dimethyl sulfoxide and dimethyl acetamide. 10. A treatment method for hydrophilic modification of PTFE according to claim 2, characterized in that: the hydrophilic polymer solution in S3 is injected into the PTFE membrane pores in a positive pressure or negative pressure manner, and circulated Injection methods include dead-end and cross-flow methods, cycle temperature is 10-95°C, and cycle time is 0.2-4 hours.