CN115957644A - Preparation method for improving strong alkali resistance of polyvinylidene fluoride membrane - Google Patents
Preparation method for improving strong alkali resistance of polyvinylidene fluoride membrane Download PDFInfo
- Publication number
- CN115957644A CN115957644A CN202111189561.7A CN202111189561A CN115957644A CN 115957644 A CN115957644 A CN 115957644A CN 202111189561 A CN202111189561 A CN 202111189561A CN 115957644 A CN115957644 A CN 115957644A
- Authority
- CN
- China
- Prior art keywords
- polyvinylidene fluoride
- membrane
- alkali resistance
- preparation
- strong alkali
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Treatments Of Macromolecular Shaped Articles (AREA)
Abstract
The invention discloses a preparation method for improving strong alkali resistance of a polyvinylidene fluoride membrane, which comprises the following steps: and (3) irradiating the polyvinylidene fluoride membrane I by adopting a high-energy electron beam or Co-60 gamma rays to obtain a strong-alkali-resistant polyvinylidene fluoride membrane II. The preparation method disclosed by the invention is simple to operate and easy to realize, and can be used for remarkably improving the strong alkali resistance of the PVDF membrane.
Description
Technical Field
The invention belongs to the field of high polymer materials, and particularly relates to a preparation method for improving strong alkali resistance of a polyvinylidene fluoride membrane.
Background
Polyvinylidene fluoride resin is the second largest fluorine material next to Polytetrafluoroethylene (PTFE). The preparation method is mainly applied to the fields of coatings, products, water treatment membranes, lithium battery binders and the like. Polyvinylidene fluoride resin has good mechanical properties and acid resistance, but is poor in strong alkali resistance. Generally, when the pH of the solution is equal to or greater than 11, the polyvinylidene fluoride membrane becomes yellow or even black after being soaked therein for a certain period of time.
When the polyvinylidene fluoride membrane is used in the field of water treatment, the polyvinylidene fluoride membrane is mainly used for separating and filtering organic matters. After a period of use, the outer surface of the polyvinylidene fluoride membrane wire is polluted and blocked, and needs to be treated by a strong alkaline cleaning agent regularly to recover the basic performance of the membrane wire. This can cause varying degrees of deterioration in the mechanical properties and appearance of the polyvinylidene fluoride film. Therefore, the problem of strong alkali resistance of the polyvinylidene fluoride membrane needs to be solved urgently.
In the structure of polyvinylidene fluoride resin, -CH 2 -and-CF 2 -with "-CH 2 -CF 2 - "connected in a" head-to-tail "manner, with-CF 2 -CF 2 - "means connected is called" head-to-head "connected, in" -CH 2 -CH 2 - "mode connection is referred to as" tail-to-tail "connection. When the polyvinylidene fluoride resin is actually applied, the alkaline groups can attack adjacent C-F and C-H bonds, so that the molecules of the polyvinylidene fluoride resin continuously undergo elimination reaction to remove HF, a head-tail structure is formed, the performance is changed, and the use is limited due to the loss of the characteristics.
The head-tail structure is the main reason of no alkali resistance, and the effective solutions are few at present. Most of the VDF monomers are copolymerized by introducing a second component, so that the regularity of the polyvinylidene fluoride main chain structure is reduced. However, this method seriously impairs many excellent properties of the polyvinylidene fluoride resin itself. Chinese patent CN112337323B discloses a polyvinylidene fluoride polymer separation membrane and a preparation method thereof, wherein a layer of alkyl anion compound capable of resisting alkali attack is formed on the surface of the polyvinylidene fluoride membrane material, thereby achieving the purpose of improving the alkali corrosion resistance of the polyvinylidene fluoride membrane material. The method can improve the alkali resistance of the polyvinylidene fluoride membrane material, but the steps are more and complicated, and finally, an ultraviolet lamp is needed for irradiation and solidification to realize the alkali resistance of the polyvinylidene fluoride membrane material.
Disclosure of Invention
In order to solve the problems, the invention provides a preparation method for improving the strong alkali resistance of the polyvinylidene fluoride membrane, and the prepared polyvinylidene fluoride membrane has the advantages of good strong alkali resistance, simple operation, easy realization and no three wastes.
The invention is realized by the following technical scheme:
a preparation method for improving the strong alkali resistance of a polyvinylidene fluoride membrane adopts high-energy electron beams or Co-60 gamma rays to irradiate the polyvinylidene fluoride membrane I to obtain a strong alkali resistance polyvinylidene fluoride membrane II.
Specifically, the irradiation dose is 25 to 250kGy; preferably, the irradiation dose is 75 to 200kGy; more preferably, the irradiation dose is 100 to 150kGy.
The polyvinylidene fluoride membrane II disclosed by the invention can tolerate an alkaline solution with the pH value of more than or equal to 11.
Irradiation has two effects on most polymer molecular chains, namely irradiation crosslinking on the one hand and irradiation degradation on the other hand. For polyvinylidene fluoride polymers, the polymer undergoes radiation degradation to the predominant radiation reaction after being irradiated by high energy electron beam or Co-60 gamma rays. After the polyvinylidene fluoride membrane I is irradiated, the main chain structure rearrangement of the main chain is completed mainly in a degradation reduction mode, so that the strong-alkali-resistant polyvinylidene fluoride membrane II is obtained.
Specifically, after the polyvinylidene fluoride membrane I is irradiated by a high-energy electron beam or Co-60 gamma rays, a large number of free radicals are generated on the surface of the polyvinylidene fluoride membrane I, the free radicals can generate main chain structure rearrangement to generate a new head-to-head or tail-to-tail structure, so that the original head-to-tail structure is damaged, the alkali resistance of the polyvinylidene fluoride membrane I can be effectively improved, and the obtained polyvinylidene fluoride membrane II can permanently resist strong alkali.
However, when hydrophilic monomers and peroxides exist in the polyvinylidene fluoride membrane I, after high-energy electron beams or Co-60 gamma rays are adopted for irradiation, the peroxides are activated to generate free radicals, and the free radicals can be preferentially subjected to graft polymerization with the hydrophilic monomers, so that the phenomenon of structural rearrangement can not occur.
The polyvinylidene fluoride film has no specific requirement, and common polyvinylidene fluoride films in the market can be rearranged under the irradiation of high-energy electron beams or Co-60 gamma rays. The polyvinylidene fluoride membrane I is selected from a polyvinylidene fluoride film or a polyvinylidene fluoride filter membrane. The polyvinylidene fluoride film with proper thickness or the polyvinylidene fluoride filter membrane with proper wall thickness can generate free radicals on the surface of the membrane under irradiation to generate a rearrangement structure.
Specifically, the polyvinylidene fluoride film is not too thick, and the thickness of the polyvinylidene fluoride film is 5 μm to 2mm, preferably 20 μm to 1mm.
The wall thickness of the polyvinylidene fluoride filter membrane is 20-2 mm, and the membrane pores are 5-1 μm; preferably, the polyvinylidene fluoride filter membrane has a wall thickness of 50 μm to 1mm and membrane pores of 50nm to 500nm.
The polyvinylidene fluoride film is a nonporous film prepared by adopting methods such as an extrusion casting method, a blow molding method or a hot pressing method; the polyvinylidene fluoride filter membrane is selected from a hollow fiber membrane or a flat filter membrane prepared by a non-solvent induced phase separation method (NIPS method) and woven pipes or reinforcing ribs derived from the NIPS method, and a hollow fiber membrane or a flat filter membrane prepared by a thermal induced phase separation method (TIPS method).
Compared with the prior art, the invention has the beneficial effects that:
the preparation method provided by the invention is simple to operate and easy to realize, and can be used for remarkably improving the strong alkali resistance of the polyvinylidene fluoride membrane.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
Example 1
Irradiating the homogeneous polyvinylidene fluoride hollow fiber filter membrane prepared by the NIPS method by adopting Co-60 gamma rays, measuring the irradiation to be 25kGy, putting the membrane wire into a NaOH (pH = 14) solution, and putting the membrane wire into an oven at 40 ℃ for heating. After heating for 4h, membrane yarn sample 1 was obtained.
Example 2
Irradiating a homogeneous polyvinylidene fluoride hollow fiber filter membrane prepared by an NIPS method by adopting Co-60 gamma rays, measuring the irradiation to be 100kGy, putting membrane filaments into a NaOH (pH = 14) solution, and putting the membrane filaments into an oven at 40 ℃ for heating. After heating for 4h, membrane yarn sample 2 was obtained.
Example 3
Irradiating a homogeneous polyvinylidene fluoride hollow fiber filter membrane prepared by an NIPS method by adopting Co-60 gamma rays, measuring the irradiation to be 250kGy, putting membrane filaments into a NaOH (pH = 14) solution, and putting the membrane filaments into an oven at 40 ℃ for heating. After heating for 4h, membrane filament sample 3 was obtained.
Comparative example 1
Directly putting homogeneous polyvinylidene fluoride hollow fiber filter membrane filaments prepared by an NIPS method into a NaOH (pH = 14) solution, and putting the filter membrane filaments into an oven at 40 ℃ for heating. After heating for 4h, membrane thread control 1 was obtained.
The samples prepared in examples 1 to 3 and comparative example 1 were subjected to performance tests, and the obtained performance index data are recorded in table 1, and the main test analysis methods included:
(1) The reduction of the elongation at break of the film filaments is tested: according to the national standard GB/T3916-1997, a universal electronic tensile machine is adopted to carry out mechanical property test, and the test conditions are as follows: the temperature is 25 ℃, the stretching speed is 50mm/min, the length of the hollow fiber membrane sample is 200mm, and the gauge length is 150mm. And (3) calculating the elongation at break of the membrane yarn by adopting an elongation at break formula, wherein the calculation formula is as follows:
elongation at break:
ρ＝L/L 0
in the formula: l is the elongation of the sample, L 0 Is a test sampleThe original length.
Reduction of elongation at break% = (ρ =) 0 -ρ)/ρ 0*100％
In the formula: ρ is a unit of a gradient 0 The elongation at break before irradiation, ρ is the elongation at break after irradiation.
(2) Yellowness Index (YI) of test membrane filaments: the yellowness index test was carried out according to ASTM E313-2015, using a bench-top spectrocolorimeter (model: hunterlab ColorQuest XE), under the following test conditions: temperature (23 + -3) ° C, relative humidity (50 + -20)%, plastic to standard international commission on illumination (CIE) standard C illuminant, the tests are disclosed as follows:
Y＝100(1.28X-1.06Z)/Y
in the formula: x, Y and Z are respectively the measured stimulus values
(3) And (3) testing the proportion of head and tail structures: the samples were characterized by NMR methods.
Test results of samples prepared in Table 1, examples 1 to 3 and comparative example 1
| Index (I) | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Radiation dose, kGy | 25 | 100 | 250 | 0 |
| Decrease in breaking elongation by% | 15.3 | 3.6 | 8.8 | 49.6 |
| Yellowness Index (YI) | 6.61 | 4.89 | 5.35 | 10.47 |
| Head-to-tail structural proportion before irradiation% | 92.86％ | 92.86％ | 92.86％ | 92.86％ |
| The ratio of head to tail structure after irradiation% | 72.04％ | 70.22％ | 66.06％ | 92.83％ |
As can be seen from Table 1, the decrease of the breaking elongation and the yellowness index of the irradiated sample are greatly improved, which indicates that the irradiation can effectively improve the strong alkali resistance of the polyvinylidene fluoride. With the reduction of the proportion of the head-tail structure, the strong alkali resistance of the polyvinylidene fluoride after irradiation is further improved.
Claims (6)
1. A preparation method for improving strong alkali resistance of a polyvinylidene fluoride membrane is characterized by comprising the following steps: the preparation method comprises the following steps: and (3) irradiating the polyvinylidene fluoride membrane I by adopting a high-energy electron beam or Co-60 gamma rays to obtain a strong-alkali-resistant polyvinylidene fluoride membrane II.
2. The preparation method for improving the strong alkali resistance of the polyvinylidene fluoride membrane according to claim 1, characterized in that: the irradiation dose is 25-250 kGy.
3. The preparation method for improving the strong alkali resistance of the polyvinylidene fluoride membrane according to claim 1, characterized in that: the polyvinylidene fluoride membrane II can tolerate alkaline solution with the pH value being more than or equal to 11.
4. The preparation method for improving the strong alkali resistance of the polyvinylidene fluoride membrane according to claim 1, characterized in that: the polyvinylidene fluoride membrane I is selected from a polyvinylidene fluoride film or a polyvinylidene fluoride filter membrane.
5. The preparation method for improving the strong alkali resistance of the polyvinylidene fluoride membrane according to claim 4, characterized in that: the thickness of the polyvinylidene fluoride film is 5 mu m-2 mm.
6. The method for preparing polyvinylidene fluoride membrane with improved strong alkali resistance according to claim 4, wherein: the wall thickness of the polyvinylidene fluoride filter membrane is 20-2 mm, and the membrane pores are 5-1 μm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111189561.7A CN115957644A (en) | 2021-10-13 | 2021-10-13 | Preparation method for improving strong alkali resistance of polyvinylidene fluoride membrane |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111189561.7A CN115957644A (en) | 2021-10-13 | 2021-10-13 | Preparation method for improving strong alkali resistance of polyvinylidene fluoride membrane |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115957644A true CN115957644A (en) | 2023-04-14 |
Family
ID=87356545
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111189561.7A Pending CN115957644A (en) | 2021-10-13 | 2021-10-13 | Preparation method for improving strong alkali resistance of polyvinylidene fluoride membrane |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115957644A (en) |
-
2021
- 2021-10-13 CN CN202111189561.7A patent/CN115957644A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR870000360B1 (en) | High strength polyacrylonitril fiber and it's producing method | |
| CN104194001B (en) | A kind of preparation method of the macromolecules cross-linking agent for ultraviolet light cross-linking polyolefin | |
| CN109161046B (en) | Polytetrafluoroethylene grafted membrane and preparation method thereof | |
| US4132682A (en) | Process for preparing cation-exchange membrane | |
| US20180201708A1 (en) | Fluororesin and method for its production | |
| CN115957644A (en) | Preparation method for improving strong alkali resistance of polyvinylidene fluoride membrane | |
| US4148979A (en) | Method of improving characteristics of cation-exchange membrane by swelling in water miscible organic solvent | |
| EP3833697B1 (en) | Self crosslinking pvdf | |
| KR100992557B1 (en) | Preparation Method of Ion Selective Fibrous Nano-form using Hyperbranched Polystyrene with Reactive Acrylic Resin | |
| KR870001386B1 (en) | High strength high elastic rate polyacryliro nitrilic fiber | |
| JP2012201727A (en) | Method for producing polyacrylonitrile copolymer, method for producing carbon fiber precursor fiber and method for producing carbon fiber | |
| Hegazy et al. | Radiation initiated grafting onto fluoro polymers for membrane preparation II | |
| CN114230737B (en) | Perfluoro ether fluororubber and preparation method and application thereof | |
| CN109467785B (en) | Heat-resistant cold-resistant non-cracking PE alloy material for road cone | |
| CN104893189A (en) | Preparation method of enhanced polyvinylidene fluoride resin | |
| CN115651111B (en) | Environment-friendly polyvinylidene fluoride resin and preparation method thereof | |
| US3475357A (en) | Method of preparing regenerated cellulose-styrene graft copolymer | |
| KR20110078249A (en) | Preparation method of polyacrylonitrile precursor based carbon fiber | |
| US3276990A (en) | Process for the production of cation permselective membranes | |
| EP0098572B1 (en) | Acrylonitrile polymer film and process for preparing same | |
| JP7460599B2 (en) | Crosslinkable blends of VDF copolymers | |
| CN114437490B (en) | Preparation method for modifying polyvinyl chloride by utilizing gamma ray radiation | |
| CN114566755B (en) | Preparation method of fluorine-containing polymer diaphragm for lithium battery | |
| CN111072839B (en) | Large-crosslinking-density rapidly-vulcanized fluorine-containing elastomer and preparation method thereof | |
| KR101536780B1 (en) | Method of preparing for polyacrylonitrile based carbon fiber |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |