CN1300227C - Microporous membrane and its preparing process and use thereof - Google Patents

Abstract

The present invention discloses a microporous membrane, a preparing process thereof and a use thereof. The microporous membrane is prepared from cellulose and is in a microporous eyed structure, the average pore size is smaller than 60 nm, and the porosity is from 81 to 87%. The preparing process for the microporous membrane comprises the following steps: at a room temperature, cellulose is dissolved in 7 to 8 wt% of sodium hydroxide precooled at 8 DEG C below zero to 15 DEG C and 11 to 12 wt% of urea water solution, and a strong cellulose solution is prepared; a film is scraped on a glass plate by a flow casting method, and the microporous film is obtained after congealing in coagulating bath and regeneration. The microporous film of the present invention has the advantages of a thin, homogeneous and multiporous eyed structure, narrow pore size distribution, high penetrability, favorable mechanical property, high luminous transmittance, simple preparing process, low preparation cost, etc.; the microporous film can be used for seedling raise, coverage, permeability packaging and material separation in the fields of agriculture, chemical industry, food and environment.

Description

A kind of microporous membrane and its production and use

Technical field

The present invention relates to a kind of microporous membrane and its production and use, belong to the natural polymer field, also belong to chemical, agricultural, environmental engineering, separation engineering field.

Background technology

Plant cellulose is the abundantest renewable resources of the earth, is expected one of main industrial chemicals that becomes 21 century.Yet, the Mierocrystalline cellulose processing system film way by chemical modification always traditionally, be about to the derivatived cellulose that Mierocrystalline cellulose is transformed into solubility, obtain regenerated cellulose film such as common cellophane of producing by viscose process (Cellphane) or the regeneration cuprammonium cellulose membrane of producing by cuprammonium process (Cuprophane) (ZL 02132866.8) with solvent reclamation again.Industrialized so far viscose process prepares existing more than the 100 year history of glassine paper, owing to have serious environmental pollution in producing, comprises CS in the viscose glue preparation process ₂Introducing, solidify cellulose xanthate ester in the regenerative process and meet acid and decompose the H that discharges ₂S and SO ₂And Zn in the waste liquid ²⁺Problems such as discharging (J.Macromol.Sci.-Rev.Macromol.Chem., 1980, C18 (1), 1), cause many developed countries to close the factory that viscose process is produced glassine paper.Novel solvent has appearred in recent years, be N-methyl morpholine oxide (NMMO) (J.Polym.Sci.:Polym.Lett.Ed.1979,17,219), and the international artificial silk in Brussels in 1989 and the synthon Bureau of Standards (BISFA) be the category name of the cellulosic fibre of making by these class methods " Lyocell ".But owing to it costs an arm and a leg, the spinning temperature height, the suitability for industrialized production slower development.In addition, reported that Mierocrystalline cellulose and urea at high temperature react the generation cellulose carbamate, directly be dissolved in then and obtain spinning solution (Finnish Patent 61003 in the diluted alkaline; Finnish Patent 62318; U.S.Patent 4404369), but the amount of urea height, and also have by product, be difficult to extensive industrialization.Recently, we adopt 7～8wt%NaOH/10～12wt% aqueous solution of urea to be pre-chilled to-8 ℃～-12 ℃, add cotton linters cellulose immediately, rapidly dissolvable Mierocrystalline cellulose under stirring at room (ZL 03128386.1).This kind method is because fast simple cellulose dissolution step and inexpensive, free of contamination solvent system, makes it have an application prospect industrial.

Summary of the invention

The purpose of this invention is to provide a kind of microporous membrane and its production and use, resulting microporous membrane can be used as ventilation property and perviousness covering, packing and parting material.

For achieving the above object, technical scheme provided by the invention is: a kind of microporous membrane, and this microporous membrane is made of Mierocrystalline cellulose, is the porous eyed structure, and mean pore size is less than 60nm, and porosity is 81～87%.

Above-mentioned microporous membrane has clear opening, and the microporous membrane water flux density is 25-250mLh ^-1m ^-2MmHg ^-1

The present invention also provides the preparation method of above-mentioned microporous membrane, at room temperature, with sodium hydroxide and 11～12wt% aqueous solution of urea dissolving cellulos through 7～8wt% of-8 ℃～-15 ℃ of precoolings, make the Mierocrystalline cellulose strong solution, with casting method knifing on sheet glass, obtain microporous membrane after in precipitation bath, solidifying regeneration; Described precipitation bath is 5～20wt%Na ₂SO ₄The aqueous solution, 3～20wt% (NH ₄) ₂SO ₄The aqueous solution, H ₂O, C ₂H ₅OH or (CH ₃) ₂CO, setting time is 10～25min, temperature of solidification is 0～55 ℃.

The microporous membrane that makes can be kept in 2% formaldehyde/20% Virahol be used as the fibrination pore membrane, also can be fixed in air, to dry on the poly (methyl methacrylate) plate and make ventilation property transparency cellulose film.

Above-mentioned Mierocrystalline cellulose strong solution is the cellulose solution of 3-6wt%.

The microporous membrane that the present invention makes in agricultural, chemical industry, food or environmental area as grow seedlings, the application of covering or air permeable wrapping or parting material.

Compared with the prior art, the present invention has remarkable technical progress.At first present method is at the directly quick dissolving cellulos of the sodium hydroxide/aqueous solution of urea of precooling, prepares microporous membrane then.It is compared with the method for cuprammonium process and No. 03128386.1 patent application with traditional viscose process, by selection to peptizer and curing condition, the microporous membrane that makes the present invention make has thin thickness, uniform narrow, penetrating quality, clear opening and higher mechanical property and transmittance uniformly preferably of porous eyed structure, bigger mean pore size, pore size distribution, and manufacture method is simple, low production cost.Can be widely used in growing seedlings in agricultural, chemical industry, food, the environmental area, covering, air permeable wrapping and parting material.

Description of drawings

The sem photograph of the microporous membrane that accompanying drawing makes for the present invention; Wherein figure (a) is the sem photograph of the one side that contacts with peptizer of microporous membrane; Figure (b) is the sem photograph in microporous membrane cross section; Figure (c) is the sem photograph of the one side that contacts with sheet glass of microporous membrane.

Embodiment

Below in conjunction with specific embodiment technical scheme of the present invention is described further:

Embodiment 1

Get cotton linters cellulose slurry (polymerization degree 500) 8.4g, add 200g and be chilled in advance in-10 ℃ the 7wt%NaOH/12wt% urea mixed aqueous solution, at room temperature stirred 5 minutes, Mierocrystalline cellulose dissolves fully.At 10,000 rev/mins, 15 ℃ made it the degassing down in centrifugal 30 minutes, obtain transparent cellulose solution with ultracentrifuge.System has the glass-tube of copper wire (diameter 0.5mm) to put into 15 ℃, 15wt%Na immediately behind knifing on the sheet glass with two ends ₂SO ₄Took out after solidifying in the aqueous solution, regenerate 15 minutes, water is rinsed well.Wet film is kept in 2wt% formaldehyde/20wt% isopropanol water solution and is used for separation and infiltration etc. as porous-film.This wet film directly carries out the mensuration of aperture and water flux density.Wet film is attached to dry naturally in air on the poly (methyl methacrylate) plate obtains regenerated cellulose film for measuring its mechanical property, packing and mulch film material that it can be used as ventilation property and has penetrating power.Record its mean pore size (2r by flow velocity method and small-sized ultra-filtration equipment _f), porosity (P _r) and water flux density (J).Its tensile strength (σ _b) and elongation at break (ε _b) on tension testing machine according to international standard ISO 527-2,1993 (E) measure.Transmittance (Tr) records (400～800nm) with ultraviolet-visible spectrometer.

Embodiment 2

Get cotton linters cellulose slurry (polymerization degree 500) 8.4g, add 200g and be chilled in advance in-12 ℃ the 7wt%NaOH/11wt% urea mixed aqueous solution, at room temperature stirred 5 minutes, Mierocrystalline cellulose dissolves fully.At 10,000 rev/mins, 15 ℃ made it the degassing down in centrifugal 30 minutes, obtain transparent cellulose solution with ultracentrifuge.System has the glass-tube of copper wire (diameter 0.5mm) to put into 25 ℃, 5wt% (NH immediately behind knifing on the sheet glass with two ends ₄) ₂SO ₄Took out after solidifying in the aqueous solution, regenerate 10 minutes, water is rinsed well.Wet film is kept in 2wt% formaldehyde/20wt% isopropanol water solution and is used for separation and infiltration etc. as porous-film.This wet film directly carries out the mensuration of aperture and water flux density.Wet film is attached to dry naturally in air on the poly (methyl methacrylate) plate obtains regenerated cellulose film for measuring its mechanical property, packing and mulch film material that it can be used as ventilation property and has penetrating power.Record its mean pore size (2r by flow velocity method and small-sized ultra-filtration equipment _f), porosity (P _r) and water flux density (J).Its tensile strength (σ _b) and elongation at break (ε _b) on tension testing machine according to international standard ISO 527-2,1993 (E) measure.Transmittance (T _r) record (400～800nm) with ultraviolet-visible spectrometer.

Embodiment 3

Get cotton linters cellulose slurry (polymerization degree 500) 8.4g, add 200g and be chilled in advance in-10 ℃ the 7wt%NaOH/12wt% urea mixed aqueous solution, at room temperature stirred 5 minutes, Mierocrystalline cellulose dissolves fully.At 10,000 rev/mins, 15 ℃ made it the degassing down in centrifugal 30 minutes, obtain transparent cellulose solution with ultracentrifuge.The glass-tube that copper wire (diameter 0.5mm) arranged with two ends systems taking-up after putting into 25 ℃, pure water behind the knifing on the sheet glass immediately and solidifying, regenerate 15 minutes, water is rinsed well.Wet film is kept in 2wt% formaldehyde/20wt% isopropanol water solution and is used for separation and infiltration etc. as porous-film.This wet film directly carries out the mensuration of aperture and water flux density.Wet film is attached to dry naturally in air on the poly (methyl methacrylate) plate obtains regenerated cellulose film for measuring its mechanical property, packing and mulch film material that it can be used as ventilation property and has penetrating power.Record its mean pore size (2r by flow velocity method and small-sized ultra-filtration equipment _f), porosity (P _r) and water flux density (J).Its tensile strength (σ _b) and elongation at break (ε _b) on tension testing machine according to international standard ISO 527-2,1993 (E) measure.Transmittance (T _r) record (400～800nm) with ultraviolet-visible spectrometer.

Embodiment 4

Get cotton linters cellulose slurry (polymerization degree 500) 8.4g, add 200g and be chilled in advance in-13 ℃ the 8wt%NaOH/12wt% urea mixed aqueous solution, at room temperature stirred 5 minutes, Mierocrystalline cellulose dissolves fully.At 10,000 rev/mins, 15 ℃ made it the degassing down in centrifugal 30 minutes, obtain transparent cellulose solution with ultracentrifuge.The glass-tube that copper wire (diameter 0.5mm) arranged with two ends systems taking-up after putting into 55 ℃, dehydrated alcohol behind the knifing on the sheet glass immediately and solidifying, regenerate 20 minutes, water is rinsed well.Wet film is kept in 2wt% formaldehyde/20wt% isopropanol water solution and is used for separation and infiltration etc. as porous-film.This wet film directly carries out the mensuration of aperture and water flux density.Wet film is attached to dry naturally in air on the poly (methyl methacrylate) plate obtains regenerated cellulose film for measuring its mechanical property, packing and mulch film material that it can be used as ventilation property and has penetrating power.Record its mean pore size (2r by flow velocity method and small-sized ultra-filtration equipment _f), porosity (P _r) and water flux density (J).Its tensile strength (σ _b) and elongation at break (ε _b) on tension testing machine according to international standard ISO 527-2,1993 (E) measure.Transmittance (T _r) record (400～800nm) with ultraviolet-visible spectrometer.

Embodiment 5

Get cotton linters cellulose slurry (polymerization degree 500) 8.4g, add 200g and be chilled in advance in-10 ℃ the 7wt%NaOH/12wt% urea mixed aqueous solution, at room temperature stirred 5 minutes, Mierocrystalline cellulose dissolves fully.At 10,000 rev/mins, 15 ℃ made it the degassing down in centrifugal 30 minutes, obtain transparent cellulose solution with ultracentrifuge.The glass-tube that copper wire (diameter 0.5mm) arranged with two ends systems taking-up after putting into 15 ℃, acetone behind the knifing on the sheet glass immediately and solidifying, regenerate 25 minutes, water is rinsed well.Wet film is kept in 2wt% formaldehyde/20wt% isopropanol water solution and is used for separation and infiltration etc. as porous-film.This wet film directly carries out the mensuration of aperture and water flux density.Wet film is attached to dry naturally in air on the poly (methyl methacrylate) plate obtains regenerated cellulose film for measuring its mechanical property, packing and mulch film material that it can be used as ventilation property and has penetrating power.Record its mean pore size (2r by flow velocity method and small-sized ultra-filtration equipment _f), porosity (P _r) and water flux density (J).Its tensile strength (σ _b) and elongation at break (ε _b) on tension testing machine according to international standard ISO 527-2,1993 (E) measure.Transmittance (T _r) record (400～800nm) with ultraviolet-visible spectrometer.

The performance measurement result of each microporous membrane comes together in subordinate list 1 among the above embodiment.Accompanying drawing show by scanning electron microscope observation to the pattern of surface (a) (one side that contacts with peptizer), cross section (b) and the back side (c) (one side that contacts with sheet glass) of microporous membrane.Microporous membrane shows uniform porous eyed structure as seen from the figure.

The performance measurement result of subordinate list 1 microporous membrane

The film numbering	P r (％)	2r f (nm)	J(mLh -1m -2 mmHg -1)	σ b(MPa)	ε b(％)	T r(％)
							Embodiment 1 embodiment 2 embodiment 3 embodiment 4 embodiment 5	84 85 85 86 81	38.1 32.3 34.4 56.8 25.7	46.42 42.86 42.87 198.5 32.76	98.1 93.0 70.6 76.9 79.2	10.8 10.1 13.5 8.56 9.45	87.2 81.4 75.8 85.2 73.8

Above-mentionedly record its mean pore size (2r by flow velocity method and small-sized ultra-filtration equipment _f), porosity (P _r) and water flux density (J) method and install as follows:

Measure the thickness d (cm) of circular hygrometric state RC film and the weight W (g) of dry back sample, be calculated as follows the porosity (P of hygrometric state RC film _r).【Hongo T.，Yamane C.，Saito M.，Okajima K.，Super-molecular structure controllingthe swelling beahavior of regenerated cellulose memrbnaes，Polym.J.，1996，28(9)，769-779】【Yang G，Zhang L.，Regenerated cellulose microporous membranes by mixing cellulose cuoxamwith a water soluble polymer，J.Membrane Sci，1996，114(2)，149-155】

$P_r=1-\frac{{\mathrm{\ρ}}_m}{{\mathrm{\ρ}}_c}=1-\frac{W}{{\mathrm{\ρ}}_c\mathrm{\π}{R}^{2}d}$

R is the radius of hygrometric state film in the formula, ρ _cBe the cellulosic density (1.5gcm of body ^-3), ρ _mBe the apparent density of hygrometric state film, i.e. the density of the water filled RC film of micropore.

According to flow velocity method [Yang G, Zhang L., Regenerated cellulose microporous membranes by mixingcellulose cuoxam with a water soluble polymer, J.Membrane Sci., 1996,114 (2), 149-155], with the average pore diameter (2rs of modified form Bruss film penetration instrument [" modified form Bruss membrane permeation is taken into account dynamic osmometry ", Hubei Province's scientific and technological achievement second prize, 1985] at 30 ℃ of measurement wet films _f).r _fAccording to Kuhn Equation for Calculating [Kuhn W, Grenze Z., Derdurchl  ssigkeit von Filtriet-und L  slichkeits membrane, Z. Electrochem.Ber.Vunsenges.Phys.Chem., 1951,55,207-215]:

$r_f={\left[\frac{\mathrm{k\ηd}{(\mathrm{d\υ}/\mathrm{dt})}_i}{P_r\mathrm{\Δ}{P}_{i}S}\right]}^{1/2}$ $k=3.1\×{(1-P_r^2)}^{1/2}$

In the formula, η is the absolute viscosity (gscm of fluid (ethanol) ^-2); D, the thickness of wet film (cm); (dv/dt) _i, kapillary fluid column discrepancy in elevation Δ H _iThe time, fluid is by the flow velocity (cm of film ³s ^-1); Δ P _i, fluid column pressure reduction (gcm ^-2), Δ P _i=Δ H _iρ, ρ is the density of fluid solution, is worth to be 0.7801gcm ^-3S, the useful area (cm of wet film ²); P _r, the porosity of wet film; K, the apparent dimension of pore distribution.

Water flux density (J) is measured [" Dong Ruan; Lina Zhang; Yuan Mao; Ming Zeng; Xiaobin Li; Microporous membranes prepared from cellulose inNaOH/thiourea aqueous solution, Journal of Membrane Science 241 (2004) 265-274 ", the UFR in this article is water flux density of the present invention (J)] with small-sized ultra-filtration equipment under 1 atm difference in room temperature.The diameter in ultrafiltration pond is 65mm, height 150mm.To try film as filtering layer, being full of water and control pressure in the pond is 0.1MPa, measures and sees through the effusive volume of water of film in the certain hour.Water flux density (J) is calculated as follows:

$J=\frac{V}{S\×t\×P}$

J represents water flux density in the formula, and unit is mLh ^-1m ^-2MmHg; T, the test duration; V, efflux volume; P, pressure (0.1MPa); S is the useful area (7.07cm of film ²).

Claims (6)

1. microporous membrane, it is characterized in that: this microporous membrane is made of Mierocrystalline cellulose, is the porous eyed structure, and mean pore size is less than 60nm, and porosity is 80～90%.

2. microporous membrane according to claim 1 is characterized in that: have clear opening, the microporous membrane water flux density is 25-250mLh ^-1m ^-2MmHg ^-1

3. the preparation method of claim 1 or 2 described microporous membranes, it is characterized in that: at room temperature, with sodium hydroxide and 11～12wt% aqueous solution of urea dissolving cellulos through 7～8wt% of-8 ℃～-15 ℃ of precoolings, make the Mierocrystalline cellulose strong solution, with casting method knifing on sheet glass, obtain microporous membrane after in precipitation bath, solidifying regeneration; Described precipitation bath is 5～20wt%Na ₂SO ₄The aqueous solution, 3～20wt% (NH ₄) ₂SO ₄The aqueous solution, H ₂O, C ₂H ₅OH or (CH ₃) ₂CO, setting time is 10～25min, temperature of solidification is 0～55 ℃.

4. preparation method according to claim 3 is characterized in that: the microporous membrane that makes is fixed on to dry in air on the poly (methyl methacrylate) plate makes ventilation property transparency cellulose film.

5. according to claim 3 or 4 described preparation methods, it is characterized in that: above-mentioned Mierocrystalline cellulose strong solution is the cellulose solution of 3-6wt%.

Claim 1 or 2 described microporous membranes in agricultural, chemical industry, food or environmental area as grow seedlings, the application of covering or air permeable wrapping or parting material.

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