CN102000516A - Method for preparing polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite hollow fiber film - Google Patents

Abstract

The invention discloses a method for preparing a polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite hollow fiber film, which comprises the following steps: (1) dissolving polydimethylsiloxane in normal hexane, adding a crosslinking agent, mixing, stirring for 0.5 to 2 hours, adding a catalyst, supplementing normal hexane till the polydimethylsiloxane mass percentage concentration of the mixed solution is 5 to 30 percent, stirring at room temperature for 8 to 16 hours, centrifuging, defoaming and preparing film solution, wherein the crosslinking agent is tetraethoxysilane, the mass ratio of the crosslinking and the polydimethylsiloxane is 0.06-0.1:1, the catalyst is dibutyltin dilaurate, and the mass ratio of the catalyst to the polydimethylsiloxane is 0.01-0.05:1; and (2) immersing a dried neutral polyvinylidene fluoride hollow fiber base film in the film-making solution for 2 to 3 seconds, taking the base film out, drying the base film at room temperature, repeating the film immersing and drying operation for 2 to 3 times, and drying under vacuum at 30 to 110 DEG C till complete crosslinking. In the invention, the process is simple; and the obtained hollow fiber film has an excellent separation effect on low-concentration ketone/butanol/ethanol solution.

Description

A kind of preparation method of PDMS/PVDF composite hollow fiber membrane

Technical field

The present invention relates to a kind of preparation method who is used for the organic PDMS/PVDF of infiltration evaporation penetrated preferably (dimethyl silicone polymer/Kynoar) composite hollow fiber membrane, belong to the infiltrating and vaporizing membrane separation field.

Background technology

As far back as 1861, Pasteur just found that bacterium can produce butanols.By 1945, the U.S. had 2/3 butanols to produce by biological fermentation process.But to the sixties in 20th century, owing to fermentation raw material price height, low, the product recovery cost height of production concentration, and under the impact of petroleum chemical industry, the biological butanol industry is made slow progress.Oil crisis appearred up to 1973, oil shortage, and ballooning oil prices makes biological butanol be subject to people's attention again.

Utilize clostridium acetobutylicum to produce in the zymotic fluid of butanols except containing butanols, also contain acetone and a spot of ethanol (being commonly called as the ABE fermentation).Because butanols and acetone is to the toxic effect of microorganism, when product reached certain concentration, microorganism stopped growing, and tangible product occurs and suppresses phenomenon, and this is the immediate cause that causes tunning concentration low.Therefore, must adopt effective method that product A BE is separated from zymotic fluid, ABE in the zymotic fluid is controlled at very low concentration, reduce product and suppress, improve productive rate and yield, and reduce the later separation cost.The technology that being applied to of having studied separated ABE comprises absorption, gas is carried, liquid-liquid extraction, the infiltration extraction, (Maddox such as counter-infiltration and infiltration evaporation, I.S.The acetone-butanol-ethanol fermentation:Recent progress in technology[J] .Biotechnol.Genet.Eng.Rev.1989,7,189-220), wherein infiltration evaporation is because its high selectivity, economy, advantages such as simplicity obtain extensive studies (Tong Cancan, Yang Lirong, Wu Jian equality. the progress of acetone separation coupling technology [J]. the chemical industry progress.2008，27(11)：1783-1789)。

Infiltration evaporation (pervaporation PV) is up-and-coming youngster in the membrane separation technique, to azeotropic and difficulty such as closely boil divide system to have superior stalling characteristic, be considered to be hopeful most to replace a kind of separation method of rectifying.Infiltration evaporation have in separation is big, centrifugation is not subjected to the component vapour-liquid equilibrium restriction, the process do not introduce other reagent, process is simple and operate advantages such as more convenient.

The infiltrating and vaporizing membrane that is applied to acetone/ethanol separation at present mainly contains the high molecular polymerization film, inoranic membrane and liquid film.Polyethers copolyamide (PEBA) is a kind of important macromolecular material, and the polymeric membrane that makes thickness 100 μ m with it to the separating effect of binary system (acetone-water, butanols-water, alcohol-water) is: separation factor alpha _Acetone=4.2, α _Butanols=8.2 and α _Ethanol=2.4, corresponding total permeation flux is respectively 27.4gm ^-2h ^-1, 65.3gm ^-2h ^-1And 37.2gm ^-2h ^-1(Liu, FF; Liu, L; Feng, XS.Separation of acetone-butanol-ethanol (ABE) from dilute aqueous solution by pervaporation[J] .Sep.Purif.Technol.2005,42 (3): 273-282); Inoranic membrane since material price costliness, liquid film because inferior positions such as poor stability have limited them in industrial application.

Above-mentioned film is flat sheet membrane basically, and its mechanical strength is not high, and the membrane area of unit volume is less, and the membrane module floor space is big, is not easy to industrial applications.Hollow-fibre membrane is compact conformation then, and the membrane area of unit volume is big, and self-cradling type has remarkable advantages on commercial Application.

Summary of the invention

The preparation method who the purpose of this invention is to provide a kind of PDMS/PVDF composite hollow fiber membrane.

For achieving the above object, the technical solution used in the present invention is: the preparation method of this PDMS/PVDF composite hollow fiber membrane may further comprise the steps:

(1) dimethyl silicone polymer is dissolved in the n-hexane, the back adds crosslinking agent and mixes stirring 0.5～2 hour, add catalyst again, it is 5～30% that the back replenish to add n-hexane mass percent concentration of dimethyl silicone polymer to the mixed liquor, stirring at room 8～16 hours, preparation liquid is made in centrifugal, deaeration; Described crosslinking agent is an ethyl orthosilicate, and the mass ratio of described crosslinking agent and dimethyl silicone polymer is 0.06～0.1: 1; Described catalyst is a dibutyl tin laurate, and the mass ratio of described catalyst and dimethyl silicone polymer is 0.01～0.05: 1;

The neutral Kynoar doughnut basement membrane that (2) will dry immersed in the described preparation liquid 2～3 seconds, the back is taken out and is at room temperature dried, repeat above-mentionedly to soak film, dry operation 2～3 times, it is extremely crosslinked fully 30～110 ℃ of following vacuum drying to put into vacuum drying oven then, makes the PDMS/PVDF composite hollow fiber membrane.

Compared with prior art, the present invention prepares that the technology of PDMS/PVDF composite hollow fiber membrane is simple, easy to operate, production cost is lower.The PDMS separating layer of prepared PDMS/PVDF composite hollow fiber membrane outer surface densification is good to acetone/ethanol selectivity, the separation factor height, the effect of the crosslinking agent ethyl orthosilicate that hydrophobicity is moderate has guaranteed considerable flux, can be used for the separation of acetone/alcohol fermentation liquid; The hydrophobic PVDF supporting layer of this film inner surface has excellent mechanical intensity, can play the self-supporting effect.And the injury of PDMS, PVDF material pair cell avirulence is difficult for contaminatedly, so this film can be processed into hollow fiber film assembly, directly with the fermentation system coupling, realizes that acetone butanol fermentation separates the industrialization that is coupled.

The specific embodiment

Below in conjunction with instantiation technical scheme of the present invention is described further.

Embodiment 1:

Claim 10g dimethyl silicone polymer (PDMS) to be dissolved in the 100g n-hexane, add 0.6g crosslinking agent ethyl orthosilicate, mix under the room temperature to stir and add 0.1g catalyst dibutyl tin laurate after 0.5 hour, adding n-hexane concentration of dimethyl silicone polymer to the mixed liquor is 5wt%, sealing back stirring at room 8 hours, gained solution is made preparation liquid through centrifugal, deaeration.Kynoar (PVDF) hollow-fibre membrane is extremely neutral with distilled water flushing, and room temperature is dried, and is stand-by as basement membrane.This basement membrane of handling was immersed in preparation liquid 2～3 seconds, take out the back room temperature and dry.Repeat to film 3 times, put into then vacuum drying oven 110 ℃ of following vacuum drying 10 hours to crosslinked fully, make the PDMS/PVDF composite hollow fiber membrane.The skin of gained composite hollow fiber membrane is fine and close PDMS separating layer, and internal layer is hydrophobic PVDF supporting layer.The PDMS/PVDF composite hollow fiber membrane of present embodiment gained is carried out organic solvent infiltration evaporation separating experiment, and performance is as shown in table 1:

Table 1

Annotate: test condition: 40 ℃ of temperature, downstream vacuum 0.3KPa.

Embodiment 2:

Claim the 10g dimethyl silicone polymer to be dissolved in the 50g n-hexane, add 1.0g crosslinking agent ethyl orthosilicate, mix under the room temperature to stir and add 0.5g catalyst dibutyl tin laurate after 1 hour, adding n-hexane concentration of dimethyl silicone polymer to the mixed liquor is 15wt%, sealing back stirring at room 12 hours, gained solution is made preparation liquid through centrifugal, deaeration.The PVDF hollow-fibre membrane is extremely neutral with distilled water flushing, and room temperature is dried, and is stand-by as basement membrane.This basement membrane of handling was immersed in preparation liquid 2～3 seconds, take out the back room temperature and dry.Repeat to film 3 times, put into then vacuum drying oven 30 ℃ of following vacuum drying 10 hours to crosslinked fully, make the PDMS/PVDF composite hollow fiber membrane.The skin of gained composite hollow fiber membrane is fine and close PDMS separating layer, and internal layer is hydrophobic PVDF supporting layer.The PDMS/PVDF composite hollow fiber membrane of present embodiment gained is carried out organic solvent infiltration evaporation separating experiment, and performance is as shown in table 2:

Table 2

Annotate: test condition: 40 ℃ of temperature, downstream vacuum 0.3KPa.

Embodiment 3:

Claim the 20g dimethyl silicone polymer to be dissolved in the 50g n-hexane, add 1.6g crosslinking agent ethyl orthosilicate, mix under the room temperature to stir and add 0.6g catalyst dibutyl tin laurate after 2 hours, adding n-hexane concentration of dimethyl silicone polymer to the mixed liquor is 30wt%, sealing back stirring at room 16 hours, gained solution is made preparation liquid through centrifugal, deaeration.The PVDF hollow-fibre membrane is extremely neutral with distilled water flushing, and room temperature is dried, and is stand-by as basement membrane.This basement membrane of handling was immersed in preparation liquid 2～3 seconds, take out the back room temperature and dry.Repeat to film 2 times, put into then vacuum drying oven 80 ℃ of following vacuum drying 10 hours to crosslinked fully, make the PDMS/PVDF composite hollow fiber membrane.The skin of gained composite hollow fiber membrane is fine and close PDMS separating layer, and internal layer is hydrophobic PVDF supporting layer.The PDMS/PVDF composite hollow fiber membrane of present embodiment gained is carried out organic solvent infiltration evaporation separating experiment, and performance is as shown in table 3:

Table 3

Annotate: test condition: 40 ℃ of temperature, downstream vacuum 0.3KPa.

By table 1 to table 3 as can be known, in low solvent strength scope (ABE concentration range in the ABE zymotic fluid), the separation factor of butanols and acetone has reached 10～30, the separation factor of ethanol is about 4, corresponding total permeation flux is also higher, and visible PDMS/PVDF composite hollow fiber membrane of the present invention has separating effect preferably to the acetone/ethanolic solution of low concentration.

Claims (1)

1. the preparation method of a PDMS/PVDF composite hollow fiber membrane is characterized in that this method may further comprise the steps:

(1) dimethyl silicone polymer is dissolved in the n-hexane, the back adds crosslinking agent and mixes stirring 0.5～2 hour, add catalyst again, it is 5～30% that the back replenish to add n-hexane mass percent concentration of dimethyl silicone polymer to the mixed liquor, stirring at room 8～16 hours, preparation liquid is made in centrifugal, deaeration; Described crosslinking agent is an ethyl orthosilicate, and the mass ratio of described crosslinking agent and dimethyl silicone polymer is 0.06～0.1: 1; Described catalyst is a dibutyl tin laurate, and the mass ratio of described catalyst and dimethyl silicone polymer is 0.01～0.05: 1;

The neutral Kynoar doughnut basement membrane that (2) will dry immersed in the described preparation liquid 2～3 seconds, the back is taken out and is at room temperature dried, repeat above-mentionedly to soak film, dry operation 2～3 times, it is extremely crosslinked fully 30～110 ℃ of following vacuum drying to put into vacuum drying oven then, makes the PDMS/PVDF composite hollow fiber membrane.