CA1222107A - Membrane comprising regenerated cellulose, having improved diffusion properties, and process for its manufacture - Google Patents
Membrane comprising regenerated cellulose, having improved diffusion properties, and process for its manufactureInfo
- Publication number
- CA1222107A CA1222107A CA000453887A CA453887A CA1222107A CA 1222107 A CA1222107 A CA 1222107A CA 000453887 A CA000453887 A CA 000453887A CA 453887 A CA453887 A CA 453887A CA 1222107 A CA1222107 A CA 1222107A
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- CA
- Canada
- Prior art keywords
- viscose
- water
- membrane
- admixed liquid
- soluble
- Prior art date
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Classifications
-
- 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
- B01D71/08—Polysaccharides
- B01D71/10—Cellulose; Modified cellulose
Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is a viscose membrane of regenerated cellulose, useful as a dialysis membrane, especially as a hemodialysis membrane, produced from a viscose solution which includes viscose and at least one low or high molecular weight compound which can be dissolved, emulsified or dispersed in water. Also disclosed are a process for producing the viscose membrane and a hemodialysis method and/or apparatus employing said membrane.
Disclosed is a viscose membrane of regenerated cellulose, useful as a dialysis membrane, especially as a hemodialysis membrane, produced from a viscose solution which includes viscose and at least one low or high molecular weight compound which can be dissolved, emulsified or dispersed in water. Also disclosed are a process for producing the viscose membrane and a hemodialysis method and/or apparatus employing said membrane.
Description
~2;~21~7 MEMBRANE COMPRISING R~GENERATED CELLULOSE, HAVING
_ IMPROVED DIFFUSION PROPERTIES, AND PROCESS FOR
.
ITS MANUFACTURE
BACXGROUND OF THE INVENTION
The present invention relates to a viscose membrane for dialysis, in particular hemodialysis, which is prepared from regenerated cellulose having improved diffusion properties, and to a process ror the manufacture of such a membrane.
The dialytic process and the apparatus known as "artificial kidneys" are primarily used for the treatment of chronic kidney diseases, wherein toxic metabolites and metabolites normally contained in urine are removed from the patient's blood by means of membranes which are preferably permselective, i.e, selectively permeable. Metabolites are compounds of living cells which control the normal course of metabolic reactions, as well as products of metabolism formed or catabolized in human or animal organisms.
Metabolites normally contained in urine are low molecular weight compounds, such as urea, creatinine or water, and higher molecular weight compounds, such as carbohydrates and peptides, which are removed from the blood and leave the ~22~7 body with the urine if the kidneys are properly working.
The purpose of the hemodialytic process is to transfer, to such an extent as possible quantitatively, the toxic metabolites and the metabolites normally contained in urine, out of the blood and into a rinsing fluid, especially with the aid of dissolution/diffusion processes, through the gel-like pores of a permselective membrane. The driving force for the diffusion of any diffusable substance through the membrane is the difference in concentration on each side of the membrane (diffusive permeability).
A low pressure gradient is sufficient for the permeation of water (ultrafiltration), produced by means of a higher hydrostatic pressure prevailing on the blood side of the dialyzer or a reduced pressure being applied to the dialysis side.
Besides good compatibility with blood and good wet strength, a good dialyzing capacity, i.e., permeability, is expected from a suitable dialysis membrane. For practical purposes, regenerated cellulose has proved to be a very suitable membrane material. In addition, membranes of fully synthe tic material s based, for exa mpl e , o n polyacrylonitrile, cellulose acetate or polycarbonate, can also be economically produced on a large industrial scale and have been successfully employed in the construction of dialyzers in recent times.
Commercially available dialysis membranes consisting of regenerated cellulose are preferably manufactured by two fundamentally different processes, viz. either by the viscose process or by the cuprammonium process. According to the first process, a viscose solution prepared by xanthogenation is "spun", i.e., coagulated, to form sheet-like bodies of viscose gel, which are then regenerated in an acid medium to form cellulose hydrate gel, washed, desulfurized, treated with plasticizers, and dried.
122Z10~7 According to the second process, cellulose is converted by means of an aqueous ammonical solution ("Schweizer's Reagent") into a clear solution of a complex compound which is then coaqulated to form sheet-like bodies. The cellulose is then regenerated in a suitable medium.
Due to their completely different methods of manufacture, the membranes produced by these processes differ greatly in their structure, and, consequently show substantial differences in their dialytic properties.
Thus, the membranes manufactured by the cuprammonium process have the disadvantage that their molecular weight exclusion limit is restricted to about 5,000 to lO,000 Dalton, so that metabolites of medium and high molecular weight collect in the blood of the patient during dialysis.
Furthermore, this process requires relatively expensive measures for recovery of the copper salts and for purification of the membrane from copper traces.
Although the known viscose membranes do not have these drawbacks, their dialyzing capacity has thus far not been satisfactory or the membranes exhibit only poor wet strength. Therefore, the membranes are hardly suitable for the purpose of hemodialysis, particularly since ultrafiltration and diffusive permeability of known dialyzing tubes made of cellulose hydrate manufactured by the viscose process are normally insufficient.
A membrane which is produced by the viscose process and which satisfies these high demands is described by European Patent No. 0,001,047, equivalent to U.S. Patent No.
4,354,938. According to that publication, the object of the invention is to improve the diffusive permeability, the ultrafiltration and, at the same time, the wet strength of the known membranes. This object is achieved by providing a membrane which, in the dry, stress-free state, is essentially equally oriented in the longitudinal and the -~Z22107 transverse directions.
Although the described viscose membrane is successfully employed due to its balanced properties as to mechanical strength and permeability, it has yet to be found effective enough in a number of cases, and it would be desirable to improve its diffusion properties and thus to increase its dialyzing capacity. By the production of very thin membranes, the ultrafiltration and the diffusive permeability can be increased; however, in doing so, serious problems arise as a result of the decreasing wet strength (expressed by the measured bursting pressure) which results from a reduction of the wall thickness. Because of this insufficient wet strength, conventional dialyzer constructions must, for example, be equipped with a very complicated profile to support the membranes, in order to keep the blood filling volume of the apparatus as small or constant as possible when a trans-membrane pressure is applied.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a membrane of regenerated cellulose prepared by the viscose process having improved dialyzing properties.
A particular object of the invention is to provide a viscose membrane having improved ultrafiltration and diffusive permeability properties.
Another object of the invention is to provide a viscose membrane having improved ultrafiltration and diffusive permeability properties while retaining a satisfactory wet strength.
1;~2;~
A further object of the invention is to produce a viscose membrane of regenerated cellulose in which the tendency of the cellulose surfaces to adhere to one another is substantially reduced.
Yet another object of the invention is to provide an improved viscose solution for producing the regenerated cellulose membrane.
Another object of the invention is the provision of a dialysis process and/or apparatus employing the viscose membrane according to the invention.
A still further object of the invention is the provision of a viscose membrane useful in hemodialytic processes, as well as a hemodialysis process and/or apparatus employing this membrane.
In addition, it is an object of the present invention to provide a process for producing a viscose membrane of the type described above.
In accomplishing the foregoing objects, there has been provided in accordance with one aspect of the present invention, a viscose membrane of regenerated cellulose, having improved dialytic properties produced from a viscose solution comprising viscose and an admixed liquid comprising at least one low or high molecular weight compound which can be dissolved, emulsified or dispersed in water. In accordance with a preferred embodiment, the compound added to the admixed liquid comprises at least one hydroxyl and/or carboxyl group.
In accordance with another aspect of the present invention, there has been provided a viscose solution for producing a viscose membrane of regenerated cellulose, comprising: viscose;
~ 3 ~
~22;2~
and an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary, or tertiary monohydric or polyhydric alcohols, hydroxyl yroup-containing, carboxyl group-containing, or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water.
In accordance with another aspect of the present invention, there has been provided a process for the production of a viscose membrane of regenerated cellulose, comprising the steps of chemically converting cel.lulose into alkali cellulose, converting the alkali cellulose into viscose, adding to the viscose an admixed liquid comprising at least one low or high molecular weight compound which can - 5a -122Z10'7 be dissolved, emulsified or dispersed in water, and subsequently extruding the liquid-containing viscose into a precipitation ba~h.
Also in accordance with the invention, there has 5 been provided a hemodialysis process and/or apparatus which employs as the hemodialysis membrane the viscose membrane defined above.
Further objects, features and advantages of the present invention will become apparent from the detailed 10 description of preferred embodiments which follows.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
-The membrane of the present invention has a thickness of up to about 50 /um, an ultrafiltration rate ranging between about 15 x 10 5 and 30 x 10 5 (cm/sec.bar), 15 and exhibits a diffusive permeability of about 8 x 10 4 to 11 x 10 (cm/sec) measured by means of the permeation of urea, and of about 9 x 10 5 to 13.5 x 10 5 (cm/sec), measured by means of the permeation of vitamin B12.
The diffusion and permeability properties of 20 dialysis membranes are evaluated by means of ultrafiltration and diffusive permeabilities for urea and vitamin B12, in accordance with the standards of the U.S. Department of Health, Education and Welfare (see DHEW publication (NIH) 77-1294, Washington, D.C. (1977), pp. 7-28, entitled:
25 "Evaluation of Hemodialysis and Dialysis Membranes").
The ultrafiltration (mechanical permeability) is determined using distilled water in a stirred cylindrical cell (500 rpm; 350 ml), at pressures of 0.1 to 3 bar and a temperature of 20C (membrane surface area 43 cm2).
The diffusive permeability is measured at 37C, using support-free membranes, and aqueous solutions containing 1,500 ppm of urea or 1,000 ppm of vitamin B12.
~, , .
~222107 The concentration differences were continuously measured by means of a differential refractometer of the "Lamidur" type (made by Winopal).
The membranes according ~o this invention can be of a planar or tubular shape. Tubular membranes can be produced using one of the known techniques for the manufacture of seamless tubings or for the formation of a tube from a planar cellulose membrane by means of a glued overlapped seam.
In preferred embodiments, the membrane according to this invention has an ultrafiltration rate of about 19 x 10 5 to 25 x 10 5 (cm/sec.bar), and a diffusive permeability of about 8.5 x 10 4 to 10 x 10 4 (cm/sec) for urea and about 10 x 10 5 to 12.5 x 10 5 (cm/sec) for vitamin B12. At the same time, the wet strength of the membrane should not be less than about 0.33 bar, determined as the bursting pressure according to DIN 53 113. The dry thickness of the membrane preferably is about 20 to 40 /um.
The object of the present invention is also accomplished by providing a process for the manufacture of the membrane according to the present invention. This process is based on the conventional viscose process mentioned at the outset. In a process of this type, cellulose is chemically converted to alkali cellulose, the alkali cellulose is reacted with carbon disulfide, and the resulting xanthate is dissolved in an aqueous alkaline solution. This solution, which is referred to as viscose by those skilled in the art, in general contains from about 5 to 10% by weight of cellulose, for example, sulfite pulp prepared from soft wood, and from about 4 to 7% by weight, relative to the total weight of the solution,of sodium hydroxide. For example, the membrane can be prepared by a process similar to that described in European Patent No.
0,012,928 ~equivalent to U.S. Patent No. 4,287,334), ~h~
~22~0~
According to the process of the present invention, a liquid is added to the viscose produced in this way before it passes into the spinning nozzle, through which it is extruded into the precipitation liquid. This admixed liquid, in particular, is a diluted aqueous solution or an emulsion or dispersion of high or low molecular weight organic compounds which in water form solutions, emulsions or dispersions, and which preferahly have hydroxyl groups and/or carboxyl groups. If appropriate, this liquid can also contain inorganic compounds which are soluble in water or an aqueous alkali, and surfactants which act as emulsion or dispersion stabilizers.
The substances which are added to and mixed with the viscose include primary, secondary or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing and/or carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalies, the substances being used in the form of emulsions or dispersions in water. Alcohols, water-soluble polymers and surfactants or inor-ganic compounds dissolved in water or aqueous alkali, which are either present alone or as a mixture, can be mixed with water.
The liquid can contain the alcohols methanol, ethanol, propanol-(l), propanol-(2), 2-methylpropanol-(2), ethane diol, propane diol-(1,2,), glycerol, which are completely miscible with water, and the alcohols butanol-(l), butanol-(2), which are not completely miscible with water, saturated aliphatic carboxylic acids having more than 10 carbon atoms, such as lauric acid, myristic acid, palmitic acid, unsaturated fatty acids, such as oleic acid or linoleic acid, water-soluble cellulose derivatives, such as methyl cellulose, hydroxyethyl cellulose, carboxymethyl _ ~ _ 12ZZ~07 cellulose, polyvinyl alcohol, alyinic acid, non-ionogenic surfactants, such as glycerol fatty acid ester or sorbitan fatty acid ester or polyoxyethylene sorbitan fatty acid ester or glycerol sorbitan fatty acid ester, inorganic substances which are soluble in water or aqueous alkali metal hydroxide, such as sodium sulfate, lithium sulfate and sodium silicates (for example, water glass).
The liquid, which can be a solution, emulsion or dispersion is advantageously added to the viscose after ripening, and, if appropriate,immediately before the viscose is spun, i.e., enters the spinning nozzle, and is well mixed with the viscose in a customary homogenizer. The amount of added liquid varies between about 5 and 100~ by weight, preferably about 20 to 50~ by weight, relative to the weight of the viscose.
The liquid added to the viscose can be a mixture of water and the alcohols which are completely miscible with water, wherein the alcohol content is about 5 to 50~, preferably about 10 to 25%. In cases where the alcohols employed are not completely miscible with water, i.e., are partially miscible, such as, for example, the butanols mentioned above, it can be useful, if a certain concentration is exceeded, to add one or several alcohols which are completely miscible with water, for example, ethanol as solutes, in order to obtain a clear solution. A
mixture of this type can, for example, be comprised of about 5 to 50% by weight, preferably about 10 to 2S~ by weight, of alcohols which are completely miscible with water, to which about 5 to 25% by weight, preferably about 5 to 10% by weight, of the above-mentioned partially water-miscible alcohols are added.
Water-insoluble, aliphatic carboxylic acids having 10 or more carbon atoms which are to be added to the viscose, can be finely distributed in the water by g _ .
~Z2Z107 emulsification, with the aid of non-ionogenic surfactants, for example, derivatives of sorbitan fatty acid esters, using known methods which are, for example, described in the publication "Das Atlas HLB-System", published by Atlas-Chemie GmbH, Essen (July 1971). Such non-ionogenic surfactants are, for example, available from Atlas-Chemie GmbH under the tradenames of SPAN or TWEEN. A surfactant content of about 3 to 15% by weight is required for a stable emulsion. When completely water-miscible alcohols, such as ethanol, are used as solutes in the above-mentioned amounts, the admixture of non-ionogenic surfactants can in some cases be reduced or omitted.
It is preferable to add solutes when water-insoluble aliphatic compounds are employed, because due to a high content of surfactants, for example, of more than about 5%
by weight, the danger of foam formation is increased in the spinning liquids required for cellulose hydrate regeneration.
On the other hand, it has been found that non-ionogenic surfactants employed in aqueous liquids in accordance with this invention improve the permeability of viscose membranes, so that these surfactants are not only used because of their emulsifying effect, but because even small amounts, for example, about 0.5~ by weight, of non-ionogenic surfactants in the liquid, added in accordance with the process of the present invention, increase the permeability of the membranes.
In another embodiment of the instant invention, inorganic compounds which are soluble in water or aqueous alkali metal hydroxide solutions are added to the aqueous liquid. Suitable inorganic compounds include sodium sulfate, lithium sulfate and/or sodium silicate (water glass). The concentrations of these compounds in the liquid vary between about 0.2 and 10% by weight, preferably between ~rQd~ tn~ t~s ~ 1 ~2:2Z~07 about 2 and 5~ by weight, for sodium sulfate or lithium sulfate and/or between about 0.1 and 3% by weight, preferably between about 0.3 and 2% by weight, for sodium silicate.
All described liquids can additionally contain water-soluble polymers, for example, soluble cellulose compounds with methyl, hydroxyethyl and/or carboxymethyl side groups, in concentrations of between about 1 to 10, preferably about 2 to 5~ by weight. Polyvinyl alcohols and natural water-soluble polymers, such as the alginic acids or the sodium and potassium salts thereof, can likewise be used.
Of the described liquids, those which comprise water and completely water-miscible alcohols, such as methanol and ethanol, are particularly effective. Using these liquids, membranes possessing an extraordinarily high permeability can be produced with only a slight impairment of the wet strength.
The addition of water- insoluble long-chain aliphatic carboxylic acids not only improves the permeability of the membranes, but also affects the adhesion of adjacent viscose membrane surfaces. The mutual adhesion of the viscose membranes is reduced so that the opening of tubular membranes is facilitated, or viscose membranes can be unwound from a roll without being damaged.
Further features and advantages of the present invention are described in the Examples below. Unless otherwise specified, all percentages are to be understood as percent by weight.
~222~7 100 parts by weight each of a viscose having a cellulose content of between 6 and 8%, a sodium hydroxide content of between 5 and 6% and a salt point (for the definition and method of determination see: K. Goetze, Chemiefasern (Chemical Fibers), 3rd edition, 1967, volume II, p. 1181, Springer-Verlag Berlin/Heidelberg/New York) between 1 and 3, whereby 30 to 35% of carbon disulfide, relative to the weight of the dry cellulose, was employed to produce the viscose, are well mixed, by stirring with about 50, 100 c>r 150 parts by weight, respectively, of the liquids described in Table 1 and freed from stirred-in air bubbles by means of a centrifuge. The bubble-free viscose solution is spread on a glass plate having a size of 30 cm x 25 cm and uniformly distributed by means of a doctor knife (gap width 0.5 mm). Subsequently~ the glass plate carrying the viscose layer is immersed in an aqueous solution of 12%
sulfuric acid and 15% sodium sulfate (a so-called Mueller bath) for 10 minutes, whereby the viscose coagulates and is regenerated into a cellulose hydrate film. The film formed in this way is washed in water of 60C for 15 to 20 minutes, to remove acids and salts. The clear, transparent viscose gel membrane is stored in distilled water for measurement of the membrane properties.
c~, 1222107 .. Ul ~ C77 _ -, `~ o ~ ~ ~ ~ ~ .
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~ ~ Z . ~ o ~-~222107 For reasons of simplicity, the viscose gel membranes obtained were not dried, but used in the wet state for the measurements. Therefore, the indicated permeability values are not intended as an absolute evaluation, b~t rather as a comparative evaluation of the various membranes with respect to one another.
The tests show that the ultrafiltration could be considerably increased by the admixtures. Tests No. 3, 4 and 5 show high ultrafiltration rates. The mechanical strength of Test No. 3 ~addition of water and ethanol) exceeds that of comparative Test No. 2 (addition of water only).
A non-reinforced tubing of cellulose hydrate gel is produced in known manner by the viscose process. For producing the tubing, liquids as described in Table 2 are continually added to and mixed with the viscose, using a commercially available homogenizer, before the viscose enters the spinning nozzle. The spinning bath employed contains 10% sulfuric acid, 13~ sodium sulfate and 10~
ammonium sulfate. After treatment with an aqueous solution containing 40% glycerol, the tubing is inflated with compressed air and radially twisted as described in European Patent No. 0,001,047. The tubing is dried with hot air having a temperature of 150C in the inflated state, laid flat and wound up. The tubing produced according to this invention, i.e., from viscose and admixed liquids, is compared with a regenerated cellulose tubing which was prepared from viscose without the admixture of liquids (see Table 2).
. 122Z1~7 Table 2 Te9t set-up ! ' 2 3 Admixtures in ~0 by weight, relative to viscose*
Water 0 30.0 38.6 Ethanol 0 12.g 0 Glycerol 4.3 ~el fl,at width . rmm! 38 34 35 ~ry flat width (mm) 49 49 49 Weight per unit area (g/m2) 40 47 46 ~ry thic~ness (~m) 29 32 31 Wet thickness ~m) 54 63 63 Glycerol content ~~0) 58 56 60 Tearing streng~l, wet ~N/mm2) lengthwise 11.4 10.9 10.2 transverse ~.4 7.8 6.2 ~longation at break, wet ~~0) lengthwise 45 39 40 transverse 66 72 SS
~ursting pressure** (bar) 0.36 0.35 0.31 Ultrafiltration ~cm/s~bar) 8.3-10 ~ 22.8~10 ~ 20.0-10 Permeability (cm/s) Urea 7.4~10 4 9.8-10-4 8.3~104 Vitamin ~12 7.9~10-5 12.0~10-5 11.0-10 * Composition of viscoseas in Example 1 ** Measured acc. to DIN 53113 (measurement performed without rubber membrane) A non-reinforced tubing of cellulose hydrate gel is produced in known manner by the viscose process. For the production of the tubing, the viscose is continually mixed as indicated in Table 3 before entering the spinning nozzle and further processed as described in Example 2. The tubing according to the invention is compared with a tubing of regenerated cellulose which was produced from viscose which did not contain the liquid admixtures (see Table 3).
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.~ , ~.Z22~07 Apart from their considerably improved permeability properties, the regenerated cellulose tubings made of viscose containing a fatty acid admixture (lauric acid or palmitic acid, see Table 3, Tests No. 4 and S) still present another advantage. By the addition of fatty acid the tendency of the cellulose surfaces to adhere to one another is substantially reduced. Laid-flat tubings which contain these admixtures can be unwound from a reel without difficulty and can be opened without being damaged. These properties are of particular importance for the processing of the viscose membranes in the preparation of a dialyzer.
_ IMPROVED DIFFUSION PROPERTIES, AND PROCESS FOR
.
ITS MANUFACTURE
BACXGROUND OF THE INVENTION
The present invention relates to a viscose membrane for dialysis, in particular hemodialysis, which is prepared from regenerated cellulose having improved diffusion properties, and to a process ror the manufacture of such a membrane.
The dialytic process and the apparatus known as "artificial kidneys" are primarily used for the treatment of chronic kidney diseases, wherein toxic metabolites and metabolites normally contained in urine are removed from the patient's blood by means of membranes which are preferably permselective, i.e, selectively permeable. Metabolites are compounds of living cells which control the normal course of metabolic reactions, as well as products of metabolism formed or catabolized in human or animal organisms.
Metabolites normally contained in urine are low molecular weight compounds, such as urea, creatinine or water, and higher molecular weight compounds, such as carbohydrates and peptides, which are removed from the blood and leave the ~22~7 body with the urine if the kidneys are properly working.
The purpose of the hemodialytic process is to transfer, to such an extent as possible quantitatively, the toxic metabolites and the metabolites normally contained in urine, out of the blood and into a rinsing fluid, especially with the aid of dissolution/diffusion processes, through the gel-like pores of a permselective membrane. The driving force for the diffusion of any diffusable substance through the membrane is the difference in concentration on each side of the membrane (diffusive permeability).
A low pressure gradient is sufficient for the permeation of water (ultrafiltration), produced by means of a higher hydrostatic pressure prevailing on the blood side of the dialyzer or a reduced pressure being applied to the dialysis side.
Besides good compatibility with blood and good wet strength, a good dialyzing capacity, i.e., permeability, is expected from a suitable dialysis membrane. For practical purposes, regenerated cellulose has proved to be a very suitable membrane material. In addition, membranes of fully synthe tic material s based, for exa mpl e , o n polyacrylonitrile, cellulose acetate or polycarbonate, can also be economically produced on a large industrial scale and have been successfully employed in the construction of dialyzers in recent times.
Commercially available dialysis membranes consisting of regenerated cellulose are preferably manufactured by two fundamentally different processes, viz. either by the viscose process or by the cuprammonium process. According to the first process, a viscose solution prepared by xanthogenation is "spun", i.e., coagulated, to form sheet-like bodies of viscose gel, which are then regenerated in an acid medium to form cellulose hydrate gel, washed, desulfurized, treated with plasticizers, and dried.
122Z10~7 According to the second process, cellulose is converted by means of an aqueous ammonical solution ("Schweizer's Reagent") into a clear solution of a complex compound which is then coaqulated to form sheet-like bodies. The cellulose is then regenerated in a suitable medium.
Due to their completely different methods of manufacture, the membranes produced by these processes differ greatly in their structure, and, consequently show substantial differences in their dialytic properties.
Thus, the membranes manufactured by the cuprammonium process have the disadvantage that their molecular weight exclusion limit is restricted to about 5,000 to lO,000 Dalton, so that metabolites of medium and high molecular weight collect in the blood of the patient during dialysis.
Furthermore, this process requires relatively expensive measures for recovery of the copper salts and for purification of the membrane from copper traces.
Although the known viscose membranes do not have these drawbacks, their dialyzing capacity has thus far not been satisfactory or the membranes exhibit only poor wet strength. Therefore, the membranes are hardly suitable for the purpose of hemodialysis, particularly since ultrafiltration and diffusive permeability of known dialyzing tubes made of cellulose hydrate manufactured by the viscose process are normally insufficient.
A membrane which is produced by the viscose process and which satisfies these high demands is described by European Patent No. 0,001,047, equivalent to U.S. Patent No.
4,354,938. According to that publication, the object of the invention is to improve the diffusive permeability, the ultrafiltration and, at the same time, the wet strength of the known membranes. This object is achieved by providing a membrane which, in the dry, stress-free state, is essentially equally oriented in the longitudinal and the -~Z22107 transverse directions.
Although the described viscose membrane is successfully employed due to its balanced properties as to mechanical strength and permeability, it has yet to be found effective enough in a number of cases, and it would be desirable to improve its diffusion properties and thus to increase its dialyzing capacity. By the production of very thin membranes, the ultrafiltration and the diffusive permeability can be increased; however, in doing so, serious problems arise as a result of the decreasing wet strength (expressed by the measured bursting pressure) which results from a reduction of the wall thickness. Because of this insufficient wet strength, conventional dialyzer constructions must, for example, be equipped with a very complicated profile to support the membranes, in order to keep the blood filling volume of the apparatus as small or constant as possible when a trans-membrane pressure is applied.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a membrane of regenerated cellulose prepared by the viscose process having improved dialyzing properties.
A particular object of the invention is to provide a viscose membrane having improved ultrafiltration and diffusive permeability properties.
Another object of the invention is to provide a viscose membrane having improved ultrafiltration and diffusive permeability properties while retaining a satisfactory wet strength.
1;~2;~
A further object of the invention is to produce a viscose membrane of regenerated cellulose in which the tendency of the cellulose surfaces to adhere to one another is substantially reduced.
Yet another object of the invention is to provide an improved viscose solution for producing the regenerated cellulose membrane.
Another object of the invention is the provision of a dialysis process and/or apparatus employing the viscose membrane according to the invention.
A still further object of the invention is the provision of a viscose membrane useful in hemodialytic processes, as well as a hemodialysis process and/or apparatus employing this membrane.
In addition, it is an object of the present invention to provide a process for producing a viscose membrane of the type described above.
In accomplishing the foregoing objects, there has been provided in accordance with one aspect of the present invention, a viscose membrane of regenerated cellulose, having improved dialytic properties produced from a viscose solution comprising viscose and an admixed liquid comprising at least one low or high molecular weight compound which can be dissolved, emulsified or dispersed in water. In accordance with a preferred embodiment, the compound added to the admixed liquid comprises at least one hydroxyl and/or carboxyl group.
In accordance with another aspect of the present invention, there has been provided a viscose solution for producing a viscose membrane of regenerated cellulose, comprising: viscose;
~ 3 ~
~22;2~
and an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary, or tertiary monohydric or polyhydric alcohols, hydroxyl yroup-containing, carboxyl group-containing, or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water.
In accordance with another aspect of the present invention, there has been provided a process for the production of a viscose membrane of regenerated cellulose, comprising the steps of chemically converting cel.lulose into alkali cellulose, converting the alkali cellulose into viscose, adding to the viscose an admixed liquid comprising at least one low or high molecular weight compound which can - 5a -122Z10'7 be dissolved, emulsified or dispersed in water, and subsequently extruding the liquid-containing viscose into a precipitation ba~h.
Also in accordance with the invention, there has 5 been provided a hemodialysis process and/or apparatus which employs as the hemodialysis membrane the viscose membrane defined above.
Further objects, features and advantages of the present invention will become apparent from the detailed 10 description of preferred embodiments which follows.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
-The membrane of the present invention has a thickness of up to about 50 /um, an ultrafiltration rate ranging between about 15 x 10 5 and 30 x 10 5 (cm/sec.bar), 15 and exhibits a diffusive permeability of about 8 x 10 4 to 11 x 10 (cm/sec) measured by means of the permeation of urea, and of about 9 x 10 5 to 13.5 x 10 5 (cm/sec), measured by means of the permeation of vitamin B12.
The diffusion and permeability properties of 20 dialysis membranes are evaluated by means of ultrafiltration and diffusive permeabilities for urea and vitamin B12, in accordance with the standards of the U.S. Department of Health, Education and Welfare (see DHEW publication (NIH) 77-1294, Washington, D.C. (1977), pp. 7-28, entitled:
25 "Evaluation of Hemodialysis and Dialysis Membranes").
The ultrafiltration (mechanical permeability) is determined using distilled water in a stirred cylindrical cell (500 rpm; 350 ml), at pressures of 0.1 to 3 bar and a temperature of 20C (membrane surface area 43 cm2).
The diffusive permeability is measured at 37C, using support-free membranes, and aqueous solutions containing 1,500 ppm of urea or 1,000 ppm of vitamin B12.
~, , .
~222107 The concentration differences were continuously measured by means of a differential refractometer of the "Lamidur" type (made by Winopal).
The membranes according ~o this invention can be of a planar or tubular shape. Tubular membranes can be produced using one of the known techniques for the manufacture of seamless tubings or for the formation of a tube from a planar cellulose membrane by means of a glued overlapped seam.
In preferred embodiments, the membrane according to this invention has an ultrafiltration rate of about 19 x 10 5 to 25 x 10 5 (cm/sec.bar), and a diffusive permeability of about 8.5 x 10 4 to 10 x 10 4 (cm/sec) for urea and about 10 x 10 5 to 12.5 x 10 5 (cm/sec) for vitamin B12. At the same time, the wet strength of the membrane should not be less than about 0.33 bar, determined as the bursting pressure according to DIN 53 113. The dry thickness of the membrane preferably is about 20 to 40 /um.
The object of the present invention is also accomplished by providing a process for the manufacture of the membrane according to the present invention. This process is based on the conventional viscose process mentioned at the outset. In a process of this type, cellulose is chemically converted to alkali cellulose, the alkali cellulose is reacted with carbon disulfide, and the resulting xanthate is dissolved in an aqueous alkaline solution. This solution, which is referred to as viscose by those skilled in the art, in general contains from about 5 to 10% by weight of cellulose, for example, sulfite pulp prepared from soft wood, and from about 4 to 7% by weight, relative to the total weight of the solution,of sodium hydroxide. For example, the membrane can be prepared by a process similar to that described in European Patent No.
0,012,928 ~equivalent to U.S. Patent No. 4,287,334), ~h~
~22~0~
According to the process of the present invention, a liquid is added to the viscose produced in this way before it passes into the spinning nozzle, through which it is extruded into the precipitation liquid. This admixed liquid, in particular, is a diluted aqueous solution or an emulsion or dispersion of high or low molecular weight organic compounds which in water form solutions, emulsions or dispersions, and which preferahly have hydroxyl groups and/or carboxyl groups. If appropriate, this liquid can also contain inorganic compounds which are soluble in water or an aqueous alkali, and surfactants which act as emulsion or dispersion stabilizers.
The substances which are added to and mixed with the viscose include primary, secondary or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing and/or carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalies, the substances being used in the form of emulsions or dispersions in water. Alcohols, water-soluble polymers and surfactants or inor-ganic compounds dissolved in water or aqueous alkali, which are either present alone or as a mixture, can be mixed with water.
The liquid can contain the alcohols methanol, ethanol, propanol-(l), propanol-(2), 2-methylpropanol-(2), ethane diol, propane diol-(1,2,), glycerol, which are completely miscible with water, and the alcohols butanol-(l), butanol-(2), which are not completely miscible with water, saturated aliphatic carboxylic acids having more than 10 carbon atoms, such as lauric acid, myristic acid, palmitic acid, unsaturated fatty acids, such as oleic acid or linoleic acid, water-soluble cellulose derivatives, such as methyl cellulose, hydroxyethyl cellulose, carboxymethyl _ ~ _ 12ZZ~07 cellulose, polyvinyl alcohol, alyinic acid, non-ionogenic surfactants, such as glycerol fatty acid ester or sorbitan fatty acid ester or polyoxyethylene sorbitan fatty acid ester or glycerol sorbitan fatty acid ester, inorganic substances which are soluble in water or aqueous alkali metal hydroxide, such as sodium sulfate, lithium sulfate and sodium silicates (for example, water glass).
The liquid, which can be a solution, emulsion or dispersion is advantageously added to the viscose after ripening, and, if appropriate,immediately before the viscose is spun, i.e., enters the spinning nozzle, and is well mixed with the viscose in a customary homogenizer. The amount of added liquid varies between about 5 and 100~ by weight, preferably about 20 to 50~ by weight, relative to the weight of the viscose.
The liquid added to the viscose can be a mixture of water and the alcohols which are completely miscible with water, wherein the alcohol content is about 5 to 50~, preferably about 10 to 25%. In cases where the alcohols employed are not completely miscible with water, i.e., are partially miscible, such as, for example, the butanols mentioned above, it can be useful, if a certain concentration is exceeded, to add one or several alcohols which are completely miscible with water, for example, ethanol as solutes, in order to obtain a clear solution. A
mixture of this type can, for example, be comprised of about 5 to 50% by weight, preferably about 10 to 2S~ by weight, of alcohols which are completely miscible with water, to which about 5 to 25% by weight, preferably about 5 to 10% by weight, of the above-mentioned partially water-miscible alcohols are added.
Water-insoluble, aliphatic carboxylic acids having 10 or more carbon atoms which are to be added to the viscose, can be finely distributed in the water by g _ .
~Z2Z107 emulsification, with the aid of non-ionogenic surfactants, for example, derivatives of sorbitan fatty acid esters, using known methods which are, for example, described in the publication "Das Atlas HLB-System", published by Atlas-Chemie GmbH, Essen (July 1971). Such non-ionogenic surfactants are, for example, available from Atlas-Chemie GmbH under the tradenames of SPAN or TWEEN. A surfactant content of about 3 to 15% by weight is required for a stable emulsion. When completely water-miscible alcohols, such as ethanol, are used as solutes in the above-mentioned amounts, the admixture of non-ionogenic surfactants can in some cases be reduced or omitted.
It is preferable to add solutes when water-insoluble aliphatic compounds are employed, because due to a high content of surfactants, for example, of more than about 5%
by weight, the danger of foam formation is increased in the spinning liquids required for cellulose hydrate regeneration.
On the other hand, it has been found that non-ionogenic surfactants employed in aqueous liquids in accordance with this invention improve the permeability of viscose membranes, so that these surfactants are not only used because of their emulsifying effect, but because even small amounts, for example, about 0.5~ by weight, of non-ionogenic surfactants in the liquid, added in accordance with the process of the present invention, increase the permeability of the membranes.
In another embodiment of the instant invention, inorganic compounds which are soluble in water or aqueous alkali metal hydroxide solutions are added to the aqueous liquid. Suitable inorganic compounds include sodium sulfate, lithium sulfate and/or sodium silicate (water glass). The concentrations of these compounds in the liquid vary between about 0.2 and 10% by weight, preferably between ~rQd~ tn~ t~s ~ 1 ~2:2Z~07 about 2 and 5~ by weight, for sodium sulfate or lithium sulfate and/or between about 0.1 and 3% by weight, preferably between about 0.3 and 2% by weight, for sodium silicate.
All described liquids can additionally contain water-soluble polymers, for example, soluble cellulose compounds with methyl, hydroxyethyl and/or carboxymethyl side groups, in concentrations of between about 1 to 10, preferably about 2 to 5~ by weight. Polyvinyl alcohols and natural water-soluble polymers, such as the alginic acids or the sodium and potassium salts thereof, can likewise be used.
Of the described liquids, those which comprise water and completely water-miscible alcohols, such as methanol and ethanol, are particularly effective. Using these liquids, membranes possessing an extraordinarily high permeability can be produced with only a slight impairment of the wet strength.
The addition of water- insoluble long-chain aliphatic carboxylic acids not only improves the permeability of the membranes, but also affects the adhesion of adjacent viscose membrane surfaces. The mutual adhesion of the viscose membranes is reduced so that the opening of tubular membranes is facilitated, or viscose membranes can be unwound from a roll without being damaged.
Further features and advantages of the present invention are described in the Examples below. Unless otherwise specified, all percentages are to be understood as percent by weight.
~222~7 100 parts by weight each of a viscose having a cellulose content of between 6 and 8%, a sodium hydroxide content of between 5 and 6% and a salt point (for the definition and method of determination see: K. Goetze, Chemiefasern (Chemical Fibers), 3rd edition, 1967, volume II, p. 1181, Springer-Verlag Berlin/Heidelberg/New York) between 1 and 3, whereby 30 to 35% of carbon disulfide, relative to the weight of the dry cellulose, was employed to produce the viscose, are well mixed, by stirring with about 50, 100 c>r 150 parts by weight, respectively, of the liquids described in Table 1 and freed from stirred-in air bubbles by means of a centrifuge. The bubble-free viscose solution is spread on a glass plate having a size of 30 cm x 25 cm and uniformly distributed by means of a doctor knife (gap width 0.5 mm). Subsequently~ the glass plate carrying the viscose layer is immersed in an aqueous solution of 12%
sulfuric acid and 15% sodium sulfate (a so-called Mueller bath) for 10 minutes, whereby the viscose coagulates and is regenerated into a cellulose hydrate film. The film formed in this way is washed in water of 60C for 15 to 20 minutes, to remove acids and salts. The clear, transparent viscose gel membrane is stored in distilled water for measurement of the membrane properties.
c~, 1222107 .. Ul ~ C77 _ -, `~ o ~ ~ ~ ~ ~ .
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~ ~ Z . ~ o ~-~222107 For reasons of simplicity, the viscose gel membranes obtained were not dried, but used in the wet state for the measurements. Therefore, the indicated permeability values are not intended as an absolute evaluation, b~t rather as a comparative evaluation of the various membranes with respect to one another.
The tests show that the ultrafiltration could be considerably increased by the admixtures. Tests No. 3, 4 and 5 show high ultrafiltration rates. The mechanical strength of Test No. 3 ~addition of water and ethanol) exceeds that of comparative Test No. 2 (addition of water only).
A non-reinforced tubing of cellulose hydrate gel is produced in known manner by the viscose process. For producing the tubing, liquids as described in Table 2 are continually added to and mixed with the viscose, using a commercially available homogenizer, before the viscose enters the spinning nozzle. The spinning bath employed contains 10% sulfuric acid, 13~ sodium sulfate and 10~
ammonium sulfate. After treatment with an aqueous solution containing 40% glycerol, the tubing is inflated with compressed air and radially twisted as described in European Patent No. 0,001,047. The tubing is dried with hot air having a temperature of 150C in the inflated state, laid flat and wound up. The tubing produced according to this invention, i.e., from viscose and admixed liquids, is compared with a regenerated cellulose tubing which was prepared from viscose without the admixture of liquids (see Table 2).
. 122Z1~7 Table 2 Te9t set-up ! ' 2 3 Admixtures in ~0 by weight, relative to viscose*
Water 0 30.0 38.6 Ethanol 0 12.g 0 Glycerol 4.3 ~el fl,at width . rmm! 38 34 35 ~ry flat width (mm) 49 49 49 Weight per unit area (g/m2) 40 47 46 ~ry thic~ness (~m) 29 32 31 Wet thickness ~m) 54 63 63 Glycerol content ~~0) 58 56 60 Tearing streng~l, wet ~N/mm2) lengthwise 11.4 10.9 10.2 transverse ~.4 7.8 6.2 ~longation at break, wet ~~0) lengthwise 45 39 40 transverse 66 72 SS
~ursting pressure** (bar) 0.36 0.35 0.31 Ultrafiltration ~cm/s~bar) 8.3-10 ~ 22.8~10 ~ 20.0-10 Permeability (cm/s) Urea 7.4~10 4 9.8-10-4 8.3~104 Vitamin ~12 7.9~10-5 12.0~10-5 11.0-10 * Composition of viscoseas in Example 1 ** Measured acc. to DIN 53113 (measurement performed without rubber membrane) A non-reinforced tubing of cellulose hydrate gel is produced in known manner by the viscose process. For the production of the tubing, the viscose is continually mixed as indicated in Table 3 before entering the spinning nozzle and further processed as described in Example 2. The tubing according to the invention is compared with a tubing of regenerated cellulose which was produced from viscose which did not contain the liquid admixtures (see Table 3).
12;~2~07 _ .,, ~ ."
~ ~ ~ ~ 0 3 ^
~ _ ~ _ =~ -- 2 -- _ X ~ . .
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_ ~
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r~ O ~ O O O O O ~ a ~o ~ O cn C 1` 3 ~ ~ h r~ _ t~ ~ ~ er U~
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vl X ~ L. C ' ~ ~ ~ L_ L_ ~ ~ ~ C -- ~ r - ~ w = E ;J
~-- Q ~ J = w ~ cl~ ~, L co ~ ~ ~ ~ u, L~ E ~ Q C
D U. =-- ~ Z-- AW O -- ~ '~ Q ~ Q o r ~ L.
Q w a ;~ !J Q 3 Q ::~ L w ~ w ~ _ J l_ ~ _ ~
,_~_ ~S: L ~ ' 1 ~' ~ ~ -- Z ,J _ ~ ^ ~, ~ .~ ~ ~ ~ ~ ~ *
.~ , ~.Z22~07 Apart from their considerably improved permeability properties, the regenerated cellulose tubings made of viscose containing a fatty acid admixture (lauric acid or palmitic acid, see Table 3, Tests No. 4 and S) still present another advantage. By the addition of fatty acid the tendency of the cellulose surfaces to adhere to one another is substantially reduced. Laid-flat tubings which contain these admixtures can be unwound from a reel without difficulty and can be opened without being damaged. These properties are of particular importance for the processing of the viscose membranes in the preparation of a dialyzer.
Claims (28)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A viscose membrane suitable for dialysis, comprising a regenerated cellulose membrane having a dry thickness of up to about 50 µm, an ultrafiltration rate within the range of from about 15 x 10-5 to 30 x 10-5 (cm/sec.bar) and a diffusive perm-eability of between about 8 x 10-4 and 11 x 10-4(cm/sec), determined by means of the permeation of urea, and of between about 9 x 10-5 and 13.5 x 10-5 (cm/sec), determined by means of the permeation of vitamin B12.
2. A viscose membrane as defined in claim 1, comprising a tubular membrane which, at a wet strength of at least 0.33 bar, has an ultrafiltration rate within the range of from about 18 x 10-5 to 30 x 10-5 (cm/sec.bar), a diffusive permeability to urea of about 8 x 10-4 to 11 x 10-4 (cm/sec), a diffusive permea-bility to vitamin B12 of from about 9.5 x 10-5 to 13.5 x 10-5 (cm/sec).
3. A viscose membrane as defined in claim 2, wherein the ultrafiltration rate is within the range of from about 19 x 10-5 to 25 x 10-5 (cm/sec.bar), the diffusive permeability to urea is about 8.5 x 10-4 (cm/sec) and the diffusive permeability to vitamin B12 is between about 10 x 10-5 and 12.5 x 10-5 (cm/sec).
4. A viscose membrane as defined in claim 1, which has a dry thickness of between about 20 to 40 µm.
5. A viscose membrane as defined in claim 1, produced from a viscose solution comprising viscose and an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing, carboxyl group-containing, or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water.
6. A process for the production of a viscose membrane of regenerated cellulose, comprising the steps of:
chemically converting cellulose into alkali cellulose;
converting said alkali cellulose into viscose;
adding to said viscose an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing, carboxyl group-containing or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water; and subsequently extruding said liquid-containing viscose into a precipitation bath.
chemically converting cellulose into alkali cellulose;
converting said alkali cellulose into viscose;
adding to said viscose an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing, carboxyl group-containing or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water; and subsequently extruding said liquid-containing viscose into a precipitation bath.
7. A process as defined in claim 6, wherein said viscose solution comprises from about 5 to 100% of said admixed liquid, relative to the weight of said viscose.
8. A process as defined in claim 7, wherein said viscose solution comprises from about 20 to 50% of said admixed liquid, relative to the weight of the viscose.
9. A process as defined in claim 6, wherein said compound of said admixed liquid comprises at least one hydroxyl and/or carboxyl group.
10. A process as defined in claim 6, wherein said admixed liquid comprises water and from about 5 to 50% of a completely water-miscible alcohol, relative to the total weight of said admixed liquid.
11. A process as defined in Claim 10, wherein said admixed liquid comprises from about 10 to 25% of said alcohol, relative to the total weight of said admixed liquid.
12. A process as defined in Claim 6, wherein said admixed liquid comprises water and from about 5 to 25% by weight, relative to the weight of said admixed liquid, of a partially water-miscible alcohol.
13. A process as defined in Claim 12, wherein said admixed liquid comprises from about 5 to 10% of said alcohol.
14. A process as defined in Claim 12, wherein said admixed liquid further comprises up to about 50% by weight of a completely water-miscible alcohol.
15. A process as defined in Claim 6, wherein said admixed liquid comprises an inorganic compound soluble in water or an aqueous alkali.
16. A process as defined in Claim 15, wherein said admixed liquid comprises from about 0.2 to 10% by weight, relative to the total weight of said admixed liquid, of an alkali metal sulfate.
17. A process as defined in Claim 15, wherein said admixed liquid comprises from about 0.1 to 3% by weight, relative to the total weight of said admixed liquid, of an alkali metal silicate.
18. A process as defined in claim 6, wherein said admixed liquid comprises water, a water-soluble aliphatic carboxylic acid having 10 or more carbon atoms and a non-ionogenic surfactant, a completely water-soluble alcohol or a combination of said surfactant and said alcohol.
19. A process as defined in claim 6, wherein said admixed liquid further comprises a non-ionogenic surfactant.
20. A process as defined in claim 6, wherein said admixed liquid further comprises from about 1 to 10% of a water-soluble polymer.
21. A viscose solution for producing a viscose membrane of regenerated cellulose, comprising:
viscose; and an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary, or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing, carboxyl group-containing, or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water.
viscose; and an admixed liquid comprising at least one low or high molecular weight compound selected from the group consisting of primary, secondary, or tertiary monohydric or polyhydric alcohols, hydroxyl group-containing, carboxyl group-containing, or hydroxyl and carboxyl group-containing water-soluble polymers, water-soluble surfactants or salts which are soluble in water or aqueous alkalis, which can be dissolved, emulsified or dispersed in water.
22. A hemodialysis process, comprising the steps of contacting blood with a first side of a viscose membrane as defined in claim 1;
applying a pressure differential over said membrane;
and removing toxic metabolites and metabolites normally contained in urine from the second side of said membrane.
applying a pressure differential over said membrane;
and removing toxic metabolites and metabolites normally contained in urine from the second side of said membrane.
23. A viscose solution as claimed in claim 21, wherein said admixed liquid comprises ethanol.
24. A viscose solution as claimed in claim 21, wherein said admixed liquid comprises glycerol.
25. A viscose solution as claimed in claim 21, wherein said admixed liquid comprises an alkali metal sulfate.
26. A viscose solution as claimed in claim 25; wherein said admixed liquid comprises sodium sulfate.
27. A viscose solution as claimed in claim 21, wherein said admixed liquid comprises tertiary butanol and lauric acid.
28. A viscose solution as claimed in claim 21, wherein said admixed liquid comprises tertiary butanol and palmitic acid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19833317037 DE3317037A1 (en) | 1983-05-10 | 1983-05-10 | REGENERATED CELLULOSE MEMBRANE WITH IMPROVED DIFFUSION PROPERTIES AND METHOD FOR PRODUCING THE SAME |
| DEP3317037.1 | 1983-05-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1222107A true CA1222107A (en) | 1987-05-26 |
Family
ID=6198633
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000453887A Expired CA1222107A (en) | 1983-05-10 | 1984-05-09 | Membrane comprising regenerated cellulose, having improved diffusion properties, and process for its manufacture |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0128325A3 (en) |
| JP (1) | JPS59206007A (en) |
| CA (1) | CA1222107A (en) |
| DE (1) | DE3317037A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5360636A (en) * | 1992-01-07 | 1994-11-01 | Akzo Nv | Method for coating cellulosic membranes |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3633737A1 (en) * | 1986-10-03 | 1988-04-14 | Akzo Gmbh | METHOD FOR TREATING CELLULOSIC RAW MATERIALS |
| EP0580879B1 (en) * | 1992-06-25 | 1996-04-17 | Sächsische Kunstseiden GmbH | Process for increasing the dimensional and spinning stability of capillar hollow membranes |
| AT513536A1 (en) * | 2012-11-15 | 2014-05-15 | Glanzstoff Bohemia S R O | Process for the preparation of cellulosic moldings |
| CN106574056A (en) * | 2014-08-15 | 2017-04-19 | 陶氏环球技术有限责任公司 | Ethylcellulose dispersion and powder |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2736569B2 (en) * | 1977-08-13 | 1979-07-19 | Hoechst Ag, 6000 Frankfurt | Viscous membrane for hemodialysis and process for their manufacture |
| DE2823985C2 (en) * | 1978-06-01 | 1986-01-02 | Akzo Gmbh, 5600 Wuppertal | Dialysis membrane |
| DE2855061A1 (en) * | 1978-12-20 | 1980-06-26 | Hoechst Ag | METHOD FOR PRODUCING VISCOSE |
| IN153421B (en) * | 1978-12-28 | 1984-07-14 | Exxon Research Engineering Co | |
| CA1153171A (en) * | 1979-12-17 | 1983-09-06 | David T. Chen | Cellulose semipermeable hollow fibers and method for making same |
| DE3021943A1 (en) * | 1980-06-12 | 1982-01-21 | Akzo Gmbh, 5600 Wuppertal | CELLULOSE DIALYSIS MEMBRANE |
| DE3042110A1 (en) * | 1980-11-07 | 1982-06-16 | Akzo Gmbh, 5600 Wuppertal | MICROPOROUS CELLULOSE MEMBRANE |
-
1983
- 1983-05-10 DE DE19833317037 patent/DE3317037A1/en not_active Withdrawn
-
1984
- 1984-05-02 EP EP84104912A patent/EP0128325A3/en not_active Withdrawn
- 1984-05-09 CA CA000453887A patent/CA1222107A/en not_active Expired
- 1984-05-10 JP JP59091985A patent/JPS59206007A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5360636A (en) * | 1992-01-07 | 1994-11-01 | Akzo Nv | Method for coating cellulosic membranes |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59206007A (en) | 1984-11-21 |
| EP0128325A2 (en) | 1984-12-19 |
| DE3317037A1 (en) | 1984-11-15 |
| EP0128325A3 (en) | 1987-04-22 |
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