Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
  • B01D61/362—Pervaporation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
  • B01D71/06—Organic material
  • B01D71/74—Natural macromolecular material or derivatives thereof

Definitions

• the invention relates to the use of collagen films as a membrane for pervaporation separation processes.
• Pervaporation is the selective transport of substances from the liquid phase to the vapor phase.
• the separation takes place by means of a non-porous solution diffusion membrane.
• a liquid mixture to be separated is passed onto such a membrane, the space on the other side of the membrane being evacuated and kept under reduced pressure.
• the membrane has a significantly increased permeability for one or more components of the mixture. This selectivity can be described by the solubility and / or diffusivity of the individual components in the membrane.
• the driving force is the concentration gradient of the permeant components penetrating the membrane over the membrane thickness.
• a component with higher solubility and more favorable diffusion properties in the membrane matrix can be withdrawn as permeate in vapor phase on the back after penetrating the membrane, while a component with lower solubility or less favorable diffusion properties is retained (retentate).
• the vaporous permeate is directions liquefied and discharged again. The described principle of such a pervaporation device is shown in FIG. 1.
• the literature describes a large number of different membrane types which can be used in pervaporation processes. These are primarily membranes made from a wide variety of plastics, such as Polyamides, N-vinylpyrrolidone graft polymers, polyvinyl pyridine, fluorine-containing cation exchange membranes, polyethylene, polypropylene, graft copolymers with a main chain made of polystyrene and a side chain made of perfluoroalkylacrylate and poly (disubstituted acetylene) / polyorganosiloxane / polyorganosiloxane.
• plastics such as Polyamides, N-vinylpyrrolidone graft polymers, polyvinyl pyridine, fluorine-containing cation exchange membranes, polyethylene, polypropylene, graft copolymers with a main chain made of polystyrene and a side chain made of perfluoroalkylacrylate and poly (d
• solution diffusion membranes made from various natural substances are also known.
• chitosan was modified in a wide variety of ways.
• JP-OS 60031803 describes a membrane made of deaerated and saponified chitosan.
• JP-OS 62004407 describes the polymerization of chitosan with polar vinyl monomers.
• the vinyl monomers contain acidic, basic or other functional groups or partly contain nitrogen, oxygen, sulfur, Phosphorus or halogen atoms with which the amino groups of the glucosamines can interact.
• Another type of membrane is formed by the inclusion of metal ions.
• JP-OS 61287407 describes the storage of heavy metal ions in membranes made of chitosan. These are preferably metals of group IV or a higher group of the periodic table in the form of their oxides, cyanides or thiocyanates.
• Cellulose membranes are also described in the literature. In addition to the long-known membranes made from cellulose triacetate (CTA), membranes made from regenerated cellulose are also described in JP-OS 61200927 and from cellulose carbamate in DE-OS 37 14 784.
• CTA cellulose triacetate
• a membrane made of regenerated cellulose modified with divalent cations and anions is known from JP-OS 61000404.
• a composite membrane is described in JP-OS 62171705.
• the outer layer is a cross-linking product of a multifunctional melamine component and a water-soluble polysaccharide, which contains a sulfonic acid or a sulfonate group, e.g. Sulfoethyl cellulose or its alkali salts.
• the thickness of the layer described is less than 3 ⁇ m.
• JP-OS 58008505 an aqueous, alkaline solution of dextran is applied to a porous support made of polysulfone resin, and the dextran is crosslinked by adding epihalohydrin and then heating.
• JP-OS 63016007 describes a solution diffusion membrane made of alginic acid, which is crosslinked by means of polyvalent metal ions, alkali and transition metals and metals from groups Illb and IVb of the periodic table being used.
• Collagen films are used as packaging material, in particular for meat products, and in the cosmetic and medical field, e.g. known as wound covers, implants or as a starting material for surgical sewing thread. They are also used in cell culture, where permeable films are used to adhere certain cell types, especially epithelial cells.
• DE-PS 19 45 527 describes such a collagen film which is preferably highly porous because of the exchange of culture medium. Such cell cultures are also used as the basis for the formation of artificial skin.
• a porous separation membrane based on collagen is described in D ⁇ -PS 20 04 987 for the area of dialysis.
• a film of microcrystalline collagen can be used as an osmosis membrane for the desalination of water.
• the object of the present invention was to provide a highly effective, non-porous membrane for use in pervaporation separation processes.
• All conventional collagen films which can be produced by methods known per se are suitable for the use according to the invention of collagen films as solution diffusion membranes for pervaporation processes.
• Representative of the known films the films known from CA-PS 885 901 and DE-PS 19 45 527 are mentioned.
• an acidic collagen mass is advantageously produced from the bovine skin gap using an alkaline digestion process, subsequent acidification and comminution of the material obtained, which further additives, in particular plasticizers, crosslinking agents and other high-molecular substances such as gelatin, gluten, alginates, soy protein, casein or Zein can be added.
• Such a mass can be poured into a pouring frame on a support and coagulated and dried there.
• an extrusion or continuous casting process is preferred, in which the film mass is pressed or cast through a slot nozzle onto an endless conveyor belt, then dried and. finally wound up under constant tension, as described for example in DE-PS 19 45 527.
• the film mass is applied directly to the later carrier, for example a web of a polypropylene spunbonded fabric, which moves at the same speed as the film.
• the carrier fleece and the film can only be loosely joined together in the separation cell.
• the preferred thickness in the dry state of foils produced in this way is 2-150 ⁇ m, a thickness of 10-30 ⁇ m is particularly preferred.
• the collagen foil can be modified in various ways.
• the degree of crosslinking can be varied by reaction with substances which form hydrogen bonds (for example vegetable tanning agents, phenols), ionic bridges (polyvalent cations), coordinative bonds (for example in chrome tanning) or covalent linkages (for example aldehydes) , Dialdehydes, diisocyanates or other at least bifunctional reactive compounds) are capable.
• Cross-links can also be generated by the action of high-energy radiation (UV or X-rays) or by heat curing. Combinations of different networking techniques are possible.
• Hydrophilization, hydrophobization and / or variation of the charge pattern by implementations known from peptide and protein chemistry can be mentioned as further modification options.
• the collagen membranes described are used in pervaporation devices, which can have the basic structure shown schematically in FIG. 1.
• the membrane (4) is applied to a support disc (5) located in a separation space (1).
• the separation space (1) which is equipped on the inlet side (8) with a heating (2) and stirring device (3), allows the vapors passing through the membrane to be drawn off as liquefied permeate (9) after passing through a condenser (7).
• the separation chamber is connected to a vacuum pump (6) to generate the vacuum on the permeate side necessary for the passage of steam.
• the solution components that do not diffuse through the membrane are drawn off on the feed side as so-called retentate (10).
• the use according to the invention is not restricted to the use of collagen flat films. It is also conceivable to use collagen tubular films. For this purpose, a collagen tubular film is applied to the inside and outside of a perforated support tube. Several such pipes can be combined in modules, such as those e.g. are known in plants for ultrafiltration or reverse osmosis.
• a collagen film made from alkaline pretreated cowhide which was processed into a mass after acidification was used, the thickness of which in the dry state is 10 ⁇ m.
• Fig. 2 indicates the concentration of water in the permeate as a function of the concentration of water in the feed.
• values that lie on the diagonal drawn in FIG. 2 would mean the lack of any selectivity, whereas if water passed exclusively through the membrane, ie a concentration of water in the permeate of 100%, one would complete selectivity would be present.
• a collagen film with a thickness of 25 ⁇ m was used, which was produced as described in Example 1. in the Following their preparation, a reaction with EDC (N- (3-dimethylaminopropyl) -N'-ethylcarbodiimide hydrochloride) was carried out to increase the degree of crosslinking.
• EDC N- (3-dimethylaminopropyl) -N'-ethylcarbodiimide hydrochloride
• Ethanol / water mixtures with compositions covering all concentration ranges were subjected to pervaporation separation at a temperature on the inlet side of the separation space of 30 ° C. and a permeate-side pressure of ⁇ 4 mbar.
• the results obtained are summarized in FIGS. 4 and 5.
• 4 shows the concentration of water in the permeate as a function of the concentration of water in the feed.
• the depiction of the dependence of the total flux density J kg / m 2 xh on the ethanol content contained in the feed (FIG. 5) shows an approximately exponential decrease in the total flux density with increasing ethanol concentration.
• a collagen membrane, produced as in Example 1, with a thickness of 25 ⁇ m was used to concentrate acetic acid from acetic acid / water mixtures.
• the temperature on the feed side was 30 ° C. and the pressure on the permeate side was 4 mbar.
• the total flux density J decreases with increasing content of acetic acid in the feed in the manner shown in FIG. 7.
• a collagen membrane as described in Example 3 was subjected to chrome tanning after its production.
• the membrane modified in this way was used to concentrate monoethylene glycol from a monoethylene glycol / water mixture.
• the temperature on the inlet side was 40 ° C, the pressure on the permeate side ⁇ 4 mbar.
• FIG. 9 shows the dependence of the total flux density J on the content of monoethylene glycol contained in the feed.
• a collagen membrane as described in Example 3 is used to concentrate the apple juice aroma.
• concentration level is used as a measure of the concentration, which indicates how many parts by volume of the dearomatized juice have to be mixed with a part by volume of the concentrate in order to obtain a finished juice.
• an apple juice aroma of concentration level 1: 150 was concentrated at a temperature on the inlet side of 30 ° C. and a pressure on the permeate side of 4 mbar up to concentration levels 1: 500 and 1: 2000.
• the flow rate is shown in FIG. 10 as a function of time. One hour after the start, it sets itself to the very high, constant value of approx. 8 kg / m 2 xh. The flavor concentrates thus obtained became one in the ⁇ l
• a collagen film, produced as in Example 1, with a thickness of 25 ⁇ m was used to concentrate the ingredients of white wine by dehydration. Separation was carried out at an operating temperature on the feed side of 20 C C, the pressure on the permeate side was ⁇ 10 mbar. In the course of the experiment, flow rates of initially 2.7 kg / m 2 h and finally 1.4 kg / m 2 h were measured.
• the selectivity (and the flow rates for water (J H2O) were determined for the use according to the invention of a collagen membrane at 30 ° C. for a 5% and a 95% ethanol solution in water.
• the separation factor £ of the collagen membrane examined is calculated from W p / (1-Wp) / Wf * _ (1-Wf), where W p is the permeate mass fraction and where Wf is the mass fraction of the feed mixture.
• the literature data for the CTA (cellulose triacetate) and CMV membranes (commercial ion exchange membrane “Selemion”) were taken from W. Böddeker, "Pervaporation through membranes and their application for the separation of liquid mixtures", Düsseldorf 1986.
• the literature data used for comparison refer to an operating temperature of 60 ° C. Since the flow rate increases with increasing temperature, the comparison of the literature number values valid for 60 ° C with the experimentally determined values for 30 ° C for the collagen membrane examined reveals that the flow rates when using the collagen membrane according to the invention are about have values many times higher.
• the collagen membrane shows a selectivity increased by a factor of 3.5-7 compared to the commercially available pervaporation membranes, for the higher ethanol concentration the selectivity of the collagen membrane compared to the CTA membrane is approx. 30% increased and almost double the selectivity value when compared with the CMV membrane.

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• Engineering & Computer Science (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

Priority Applications (2)

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Publications (1)

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ID=6368930

Family Applications (1)

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Citations (7)

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• 1988
  • 1988-12-10 DE DE3841716A patent/DE3841716A1/de active Granted
• 1989
  • 1989-12-06 AU AU48317/90A patent/AU632527B2/en not_active Ceased
  • 1989-12-06 ES ES90900799T patent/ES2058884T3/es not_active Expired - Lifetime
  • 1989-12-06 EP EP90900799A patent/EP0447467B1/de not_active Expired - Lifetime
  • 1989-12-06 DE DE9090900799T patent/DE58905190D1/de not_active Expired - Fee Related
  • 1989-12-06 WO PCT/EP1989/001494 patent/WO1990006166A1/de not_active Ceased
  • 1989-12-08 CA CA002004996A patent/CA2004996A1/en not_active Abandoned

Patent Citations (7)

Non-Patent Citations (1)

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