DE19543055B4 - Large pore synthetic polymer membranes - Google Patents

Abstract

polymer membrane with a first porous Surface, a second porous one surface and a support body with a thickness between them, the support body being a network of porous flow channels between the first surface and the second surface is defined and the flow channels of the first surface to a point from the first surface by 15-50% of the thickness of the supporting body is removed, a substantially constant mit miter diameter have and from the point to the second surface gradually increasing have medium diameter.

Description

1. Technical area the invention:

The The invention relates to the field of microfiltration membranes; she relates in particular to microfiltration membranes made of synthetic polymers.

2. Underlying status of the technique:

High asymmetric polymer membranes consisting of phase-separated (inversion) Gußmischungen are in patents to Wrasidlo U.S. Patent 4,629,563 and 4,774,039 and Zepf, U.S. Patent 5,188,734 and 5,171,445 The disclosure of which is hereby incorporated by reference. Wrasidlo discloses highly asymmetric, integrally skinned membranes, which high flow rates and have excellent retention properties and which metastable biphasic liquid dispersions of polymers in solvent / non-solvent systems getting produced. Zepf discloses improved polymer membranes Wrasidlo type, which essentially has a larger number of surface pores with a more even Size and essential increased flow rates with reduced pore diameters of the covariance of the Have flow. The improved Zepf membranes are going through Modifications of the Wrasidlo method were obtained, which decreased Casting and quenching temperatures and reduced environmental influences between casting and cooling include. Zepf further teaches that reduced casting and cooling temperatures the sensitivity of the membrane manufacturing process to minor changes minimize the composition and process parameters.

A Phase-inverted polymer membrane is conventionally obtained by casting a solution or a mixture consisting of suitable polymer (s) with high Molecular weight, solvent (s) and non-solvent (s) exists in a thin one Film, a tube or a hollow fiber and precipitation of the polymer by one or several of the following processes: (a) evaporation of solvent and non-solvents; (b) contacting a non-solvent vapor, such as water vapor, which is absorbed on the exposed surface; (c) quenching in a non-solvent liquid, in general, water; or (d) thermally quenching the hot film, So that the solubility of the polymer is suddenly reduced.

The Non-solvent in the casting mix is not necessarily completely inert with respect to the polymer and indeed it is this usually not and will often referred to as swelling agent. As will be explained later, in the formulations of the Wrasidlo type the choice of both, the type and concentration of the non-solvent critical, so this the main factor for The determination is whether a mixture is in phase-separated state can exist or not.

in the general is the non-solvent the primary one pore-forming agent and its concentration in the mixture influenced in a large way the pore size and the Pore size distribution in the finished membrane. The polymer concentration also influences the pore size, but not as significant as the non-solvent. However, it affects those Strength and porosity (pore volume). additionally minor components may be added to the main components in the casting solution (mixture) such as surfactants or release agents.

polysulfone is especially for the formation of highly asymmetric membranes suitable, in particular for the Two-phase formulations according to Wrasidlo. These are not homogeneous Solutions, but consist of two separate phases, a solvent-rich clear solution of lower molecular weight polymer at low concentrations (eg, 7%) and the other, a polymer-rich cloudy (colloidal) solution of polymers with higher Molecular weight at high concentrations (eg 17%). The two Phases contain the three same constituents, namely polymer, solvent and non-solvents, however in complete different concentrations and molecular weight distributions. It is especially important that these two phases insoluble in one another and, if left alone, separate. The mixture must go through permanent stir be kept in dispersion until the time when the Casting for Movie done.

It is the non-solvent and its concentration in the casting mixture which causes the phase separation and not every non-solvent is capable of doing so. Those who do this may play It may also have a similar role as surfactants, perhaps by creating a critical micelle concentration by joining some of the larger polymer molecules into aggregates or colloids, which are then dispersed in the remaining non-colloidal solution. The two phases separate when left to stand, but each phase is quite stable. If the temperature of the mixture is changed, phase transfer occurs. Heating produces more of the clear phase; Cooling causes the reverse. Concentration changes have the same effect, but there is a critical concentration range or window in which the phase-separated system can exist, as discussed by Wrasidlo. Wrasidlo defines this region of instability in a phase diagram of such dispersed polymer / solvent / non-solvent at constant temperature, which lies between spinodal and binodal curves, wherein the polymer is not completely miscible with the solvent.

Because of the big hydrophobicity of the polymer and thermodynamically unstable conditions the casting mix, in which two phases are preformed, one solvent-rich and the other polymer rich (a condition that other systems go through, if they are subject to phase inversion), the unstable Wrasidlo mixture falls if it is quenched, very fast, forms a solid shell at the phase boundary and finally develops a highly asymmetric Membrane. Asymmetric here means a progressive change of Pore size along the cross section between the outer skin (the fine-pored side the membrane showing the air / solution phase boundary or the cooling solution / solution phase boundary during the casting forms) and the substructure. This is in contrast to the reverse osmosis and most ultrafiltration membranes, which have abrupt discontinuities between the outer skin and the substructure, and those in the prior art as well be called asymmetric.

polymers Membranes can likewise from homogeneous solutions be poured from polymers. The compositions of these formulations lie outside the spinodal / binodal region of the phase diagram of Wrasidlo. membranes, which from homogeneous solutions can also be poured be asymmetric, although usually not in the same high degree of asymmetry as those which were poured from phase-separated formulations.

The increase the size of the surface pores of membranes has been described. See UK patent 2,199,786 for Fuji (hereinafter referred to as "Fuji"). The stand The art teaches the cast polymer solution to be more moist Expose air to a phase inversion at one point below the surface to cause the membrane. See Fuji. The membranes, which after Fuji process have a characteristic Structure with relatively wide pores at the surface (i.e., 0.05 - 1.2 microns) followed of progressively contracting pore sizes up to followed by a phase inversion point below the surface from an opening the pores until an isotropic structure is reached, which is up to consist of the casting surface remains (i.e., 1 - 10 microns). Accordingly you can imagine the Fuji membranes such that they have a reverse asymmetry from the outer skin surface to the Point of inversion and further asymmetry into isotropic Structure have. The patent expressly teaches that slight asymmetry is used should be to extend the life of the membrane. Please refer Page 4, lines 7 - 29. Further it seems that the Fuji membranes in the generally be prepared from formulations which are realtiv high viscosities have. For example, the polymer concentrations are common pretty high and in some cases become membranes using polymers as non-solvent produced. See Example 2, page 12; Example 3, page 15.

synthetic Polymer membranes are considered to be high-retention, highly permeable Filters in many test methods, in the food and beverage industry and in medical laboratories. Many of these applications would be essential cost-effective and more economically interesting if the filtration area of the Membranes over that of existing Wrasidlo and Zepf type membranes would.

Summary of the invention

Corresponding the first embodiment the present invention provides a polymer membrane, which a first surface, a second surface and an intermediate support body, wherein the first surface is a has relatively open Porienstruktur and the second surface a having further open pore structure and wherein the support body a high level Asymmetry by at least 50% of the support body through but not more as 80 of the support body having.

Corresponding the second embodiment the present invention provides a polymer membrane, which is a first porous one Surface, a second porous one surface and an intermediate porous support body having a thickness, comprises the support body from the first surface to a point which is about 1/4 of the thickness of the support body, a generally isotropic structure and from this point to the second surface one generally asymmetric.

Corresponding the third embodiment the present invention provides a polymer membrane, which is a first porous one Surface, a second porous one surface and an intermediate support body having a thickness, comprises the support body porous Flow channels between the first and the second surface forms, wherein the flow channels a essentially constant mean diameter of the first surface to a point which is about 1/4 of the thickness of the support body and from this point to the second surface an increasing mean diameter exhibit.

Corresponding a fourth embodiment the present invention provides a porous polymer membrane which for the separation of a liquid Fraction of a suspension is suitable, comprising an integral porous Skin, which lies on one side of the membrane, wherein substantially all pores of the outer skin Have diameters larger than 1.2 microns are and a supporting region of Membrane, which lies below the outer skin and an asymmetric Owns structure.

Corresponding a fifth embodiment The present invention provides an improved asymmetric polymer membrane to disposal put, which is a first porous Surface, a second porous surface and an intermediate porous one supporting body having a thickness, wherein the improvement is a Region of generally isotropic structure from the first surface to a Point which is about 1/4 of the thickness of the support body comprises.

Corresponding a sixth embodiment The present invention provides a process for producing a Polymer membrane, which has a relatively large outer pore size, a essentially asymmetrical structure and improved flow rate has, available comprising the preparation of a metastable casting dispersion, which comprises a polymer-rich phase and a polymer-poor phase the selected one casting temperature, the casting the dispersion at the casting temperature in a thin one Layer, bringing the casting layer into contact with a pore-forming the atmosphere for a period of time, which is sufficient to form surface pores, which greater than 1.2 μm, Quenching the casting layer with a non-solvent-containing Cooling solution, in which is the solvent is miscible and in which the polymer is substantially insoluble, to precipitate the polymer as an integral membrane and recovering the membrane from the coolant.

Corresponding the seventh embodiment The present invention provides a process for producing a Polymer membrane, which has a relatively large outer pore size, a essentially asymmetric structure and improved flow rate is available comprising preparing a homogeneous casting solution which a polymer, a solvent for the Polymer and a non-solvent for the Polymer comprises at the casting temperature, the casting the dispersion at the casting temperature in a thin one Layer, bringing the casting layer into contact with a pore-forming the atmosphere for a period of time, which is sufficient to form surface pores, which greater than 1.2 μm, and quenching the casting solution with a non-solvent-containing Coolant, in which the solvent is miscible and in which the polymer is substantially insoluble, to precipitate the polymer as an integral membrane, recovering the Membrane from the cooling solution, wherein the membrane is substantially asymmetrical by at least 50% of the Membrane has through.

Corresponding an eighth embodiment The present invention is an integrally skinned, asymmetric Polysulfone membrane available which has a mean surface pore diameter of at least about 1.2 microns wherein the preparation is carried out according to the previously described method.

Corresponding the ninth embodiment The present invention provides an improved method of preparation skinned by intergral, provided highly asymmetric polymer membranes, wherein the improvement is contacting the cast layer with a gas atmosphere with a pore-forming atmosphere for one Period which is sufficient to form surface pores, which greater than 1.2 μm, includes.

Corresponding a tenth embodiment The present invention provides an improved diagnostic device to disposal which comprises a filtering device, which is an analyte containing, substantially particle-free filtrate to a Analyte detecting area of the device provides, wherein the Improvement of a filtering device containing one of the above described polymer membranes which surface pores of a middle Diameter greater than 1.2 μm and has a flow rate greater than about 4.5 cm / min / psi.

Corresponding an eleventh embodiment The present invention provides an improved diagnostic device to disposal comprising a lateral wick device, which a an analyte-containing, substantially particle-free sample from a sample application area to an analyte Area of the device transferred, wherein the improvement of a lateral wick device, which is one of the The above polymeric membranes include which surface pores having a mean diameter of about 1.2 microns and a lateral Transfer rate of greater than about 2 cm / min.

Corresponding a twelfth embodiment The present invention provides a filter unit, which comprises one of the polymer membranes described above.

In preferred embodiments In the invention, the polymer is a polysulfone. Preferably, the Bubble points of the membranes of the invention or membranes made or used in accordance with the invention be, no bigger than 25 psid and preferably from about 0.5 psid to about 25 psid, and more particularly Bubble points from about 5 psid to about 15 psid are preferred. Likewise preference is given to membranes according to the invention or produced according to the invention or membranes used which have an average flow rate for water from about 4.5 to 25 cm / min psid.

Short description of drawings

1 FIG. 12 shows a series of scanning electron micrographs of an open cell membrane of the present invention of a polysulfone polymer dispersion (Wrasidlo type) having a bubble point of 8 psid. FIG. 1a is the view of the outer skin surface of the membrane. 1b is the view of the casting surface of the membrane. 1c is a cross section through the membrane.

2 FIG. 12 shows a series of scanning electron micrographs of an open-cell membrane of the present invention of a polysulfone polymer dispersion (Wrasidlo type) having a bubble point of 11 psid. FIG. 2a is the view of the outer skin surface of the membrane. 2 B is the view of the casting surface of the membrane. 2c is a cross section through the membrane.

3 FIG. 12 shows a series of scanning electron micrographs of an open cell membrane of the present invention made of a polysulfone polymer dispersion (Wrasidlo type) having a bubble point of 16 psid. FIG. 3a is the view of the outer skin surface of the membrane. 3b is the view of the casting surface of the membrane. 3c is a cross section through the membrane.

4 is a series of scanning electron micrographs of a membrane made according to the invention from a homogeneous polysulfone formulation. 4a is the view of the outer skin surface of the membrane. 4b is the view of the casting surface of the membrane. 4c is a view of the cross section through the membrane.

5 is a series of scanning electron micrographs of a fine-pored polysulfone membrane prepared by the method of Zepf having a bubble point of 65. 5a is the view of the outer skin surface of the membrane. 5b is the view of the casting surface of the membrane. 5c is a view of the cross section through the membrane.

6 Figure 4 shows a plot of the velocity of a laterally moving liquid front in a series of membranes having different BTS (bubble points).

7 Figure 3 shows the plot of the volume of red cell-free plasma filtrate delivered within 10 seconds of polysulfone membranes having different bubble points.

Detailed description of the invention

The The present invention provides improved asymmetric polysulfone membranes with big Pores available, which improved flow rates and have wicking properties while having good release properties remain. The pore size and indirect the flow rate becomes Conveniently determined by measuring the bubble point, wherein the bubble point is the minimum required pressure, which is an air bubble through a moist membrane. Zepf Tap polymer membranes typically have bubble points, which are larger than 25 psid. The membranes of the invention have bubble points less than 25 psid compared to in the range of 0.5 to 25 psid, preferably 2 to 20 psid and more preferably 5 to 10 psid.

Furthermore have the membranes of the invention relatively large Skin pores compared to Wrasidlo and Zepf membranes on. For example, the mean outer pore sizes of the membranes of the invention are conventional greater than 1.2 μm and usually bigger than 2 to 3 μm or larger. in the In contrast, Wrasidlo and Zepf membranes have a mean outer pore size of less than 1.2 μm and usually less than 0.35 μm on.

in the In contrast to the classical asymmetric structure of the Wrasidlo and Zepf membranes generally comprise the membranes of the invention Asymmetries of the membrane of not more than 80%. In preferred embodiments are the minimum remaining 20% of the membrane in general isotropic regions.

It was found that the improved membranes of the invention have important advantages in the filtration application. For example can the membranes of the invention in conventional filtration applications, for example, those in the beer and wine filtration and in the Water treatment, to be used. In addition, the membranes of the invention are for diagnostic or biological applications, for example in the manufacture of biosensors.

The membranes according to the invention can both from homogeneous casting solutions as also be prepared from phase-separated mixtures, like this in Wrasidlo Patents No. '563 and '039 and the Zepf Patents '734 and' 445 is described.

in the is general in the preparation of the membranes of the invention the cast film exposed to the air to great surface pores on the exposed side, followed by a standard quench with non-solvent (eg water). The diameter of the surface pores may vary by duration the exposure time as well as by the humidity varies become. When exposed to the air any water vapor causes the failure of the polymer at and in the area below the exposed liquid film surface. Surprisingly was observed that forming a region on and below the surface, which forms an im has general isotropic structure with relatively large pore sizes. Below this The classical asymmetry is observed in the area. It is generally true that ever greater the humidity is, the bigger the surface pores are and vice versa at lower humidity, the surface becomes denser.

Structure of the Open Cell Membranes of the Invention The polymer membranes of this invention retain a significant portion of asymmetry, although they have relatively large outer skin pores. One suitable method for determining asymmetry and pore size is Scanning Electron Microscopy (SEM). The 1 to 3 show the cross-sections, the outer skin surface and the lower surface of the membranes prepared according to the invention, and the features of these figures can be compared with those used for Wrasidlo type fine-pored membranes 5 are shown.

In addition to Asymmetry of the membranes and the open-pore structure, is at the membranes of the invention the presence of an isotropic region unique to the skin surface extends to a point within the substructure of the membrane. Typically, the isotropic region extends through the membrane thickness at least 20%.

In the absence of SEM data, the asymmetry can be roughly estimated, as described by Kesting, Synthetic Polymer Membranes: A Structural Perspective, p. 275 (John Wiley & Sons, 2nd Editions (1985)), in which a small drop Ink or dye is applied to the dense surface of the membrane and allowed to pass through the membrane as well as spreading on the surface. The ratio of dye-coated areas gives a rough hint know the asymmetry or its extent. The pore size can also be determined by porosity analysis and independent bubble point measurement, with a larger bubble point indicating denser pores. In a classical asymmetric membrane, the surface pores are the densest. In the membranes of the invention, the densest pores are somewhere between the skin and the asymmetric region. Porometry relies on the application of gradually increasing pressures to a wet membrane and comparing the flow rate of gases with those of a dry membrane which provides both pore size and bubble point data. For these studies, a Coulter Porometer Model 0204 was used.

As already mentioned, contain the membranes of the invention a region which is generally isotropic and a region which is substantially asymmetrical. Generally isotropic (or isotropic Region) as used here means a region of in general constant pore size, like this is observed by means of REM, from the outer skin down through one Part of the support structure. The isotropic region may alternatively be considered as a region which flow channels of the having substantially constant mean diameters. In general is the mean outer pore size or the diameter of the outer skin pores the membranes of the invention greater than 1.2 μm. In the isotropic region, the outer pore size determines the mean Pore size within the isotropic region. For example, REM shows preferred membranes, that one Membrane with a mean outer pore size of 2 μm an average pore size within the isotropic region of 2 μm or greater. Similar Structures are observed in membranes showing outer skin pore sizes of 3 μm, 4 μm, 5 μm and etc. exhibit. However, it is desirable to have the isotropic region a Having distribution of pore sizes, which appear optically as isotropic. It is expected that the actual Pore sizes in the isotropic region vary (as is the case in every membrane).

typically, the isotropic region extends from the outer skin of the membrane into the supporting bodies to more than 15 the thickness of the membrane inside. Preferably extends the istotropic region is more than 20%, 25% or even 30% or more in the thickness of the membrane. In particularly preferred embodiments The isotropic region extends more than 25% in thickness the membrane inside. For example, the isotropic region extends in a 125 μm Membrane more than 25 μm from the skin into the supporting body into it.

The Designation essentially asymmetric or anisotropic (here the asymmetric region), as used here, means the degree similar to the asymmetry that disclosed by Wrasidlo and Zepf and which membranes owned by Wrasidlo and Zepf. In this regard, have membranes according to the invention a mean outer pore size of more than about 1.2 μm while on the reverse side, the side, which the auxiliary paper or tape while of the casting The SEM examination shows that the mean pore size is at least 2 times bigger, than the mean outer pore size. Therefore is the relationship from outer skin pore size to casting surface pore size greater than about 2: 1 and in particularly preferred embodiments it is 3: 1, 4: 1, 5: 1 or even 6: 1 or larger. Furthermore the asymmetry is more continuous only within the asymmetric region Gradient.

It should be noted that the above-mentioned asymmetry ratio relates only to the asymmetry measured on the surfaces. In fact, the asymmetry of the membranes according to the invention is significantly greater when considering the mean pore size in the asymmetric region above the casting surface in cross section in the scanning electron microscope. Compare for example 1c . 2c and 3c , The asymmetry of the membranes of the invention appears to be greater than 10: 1 or 20: 1 or perhaps as high as 100: 1 or even 200: 1.

Looking through the outer skin pores, one notices that the pore size in the isotropic region is slightly larger than the pores in the outer skin. This fact, in combination with the observed asymmetry, which is based on the surface / surface analysis over the cross-sectional analysis, shows that skin formation occurs on both surfaces. Without intending to be bound by any particular theory or mode of preparation, three plausible explanations for skin formation in the membranes of the present invention can be seen. First, when the cast film is exposed to the air, the water vapor begins to gel the film and forms the initial membrane in the upper region. However, not all of the polymer can be gelled in such a short time. Therefore, when the film contacts the cooling liquid, the remaining un-precipitated polymer forms the outer skin. Second, or alternatively, perhaps a better explanation is that surface contraction shrinks the pores because of inherent differences in surface tensions (say, by analogy with a drop of water or a bubble of soap, which minimizes their surface / volume ratio). Or, thirdly, a slight migration of the polymer to the surface could occur due to the steep gradient of the chemical potentials.

Further is due to the fact that the Bubble point of the membranes of the invention is generally larger as it is due to the observed pore sizes in the isotopic region or in the cast skin would expect clearly that one some contraction of pore size between the isotropic region and the asymmetric region. Surprisingly, conventional considerations would suggest that the Pores below the outer skin should be smaller than those of the outer skin. In fact, should they become progressively smaller with the depth, i.e. "reverse asymmetry". Diffusion is a slow process. Therefore, the pores formed below the outer skin should be less Steam "see" and therefore smaller be.

The Fuji membranes seem the conventional considerations to confirm and have a reverse asymmetry from the outer skin to an inversion point, which lies at shallow depth within the membrane. In contrast In addition, the pores in the membranes according to the invention appear below the outer skin of equal size or to be taller as the pores in the outer skin and remain within the region with such an isotropic or homogeneous pore distribution.

Therefore it seems that the Isotropic region of the membranes of the invention by a "dry process" interaction between the water vapor created in the air and the polymer film or at least caused which causes a homogeneous or isotropic formation. This is analogous to cellulose mixed ester or cellulose nitrate membranes. however it seems that one negligible Evaporation of the solvent or non-solvent is present, so that when Quench the coolant into flows and the isotropic region forms and consolidates and the asymmetric one Region consolidates.

With Regard to the possible Contraction of pore size distribution between the isotropic region and the asymmetric region, such as shown above, should be tried in the porometric analysis to explain denser pores (i.e., 1.0 μm maximum and 0.8 μm average pore size), where a process of a internal skin formation during the formation of the outer skin takes place in Wrasidlo and Zepf membranes. This possibility is described by Michaels in U.S. Patent No. 3,615,024, column 5, lines 43-54, in which it is disclosed that a gradual pore structure occurs when water permeation into a cast film through a condensed outer skin obstructed, which is formed by water in the first moment. Or, as illustrated above, it is alternatively possible that, although visually, the membranes in the isotropic area appear to be isotropic, this indeed have a pore distribution, which Porometriedaten and larger bubble points cause one would expect to see the large pore sizes.

Accordingly The membranes of the present invention differ in their Structure of the classical asymmetry in that the membranes of the invention substantially non-asymmetric (i.e., isotropic) from the skin to a point below the surface, which here as isotropic region as described above. Accordingly the asymmetric region of the membranes appears in less than about 75% of the total thickness of the membrane. On the other hand appears in conventional or classical asymmetric ones, as in Wrasidlo- and Zepf membranes, the asymmetric region through the entire or nearly entire thickness to go through the membrane. In contrast, Fuji membranes have in the area below the outer skin inverse or reverse asymmetry and underneath a slightly conventional one Asymmetry. It is expected that the possibly higher viscosities of the Fuji Gußformulierungen contribute to this structure.

Therefore have the membranes of the invention, Figuratively speaking, a funnel structure with respect to the arrangement through the flow channels the thickness of the membrane. For example, the pores are very large, on which the liquid which flows from the side into the membrane, which remains continuous during casting was. This is the asymmetric region, which is the conical part corresponds to a funnel. While the liquid flowing through the membrane, tighten the pore sizes or Flow channels slowly together until finally the liquid reaches a generally isotropic region, which pore sizes or Flow channels of im have substantial constant diameter, and then through the skin flows, wherein the isotropic region corresponds to the outlet opening of the funnel.

The structure of a typical open cell membrane of the present invention made from a Wrasidlo-type dispersion is disclosed in U.S.P. 1 to 3 shown. The membrane has outer skin pores of on average 3 μm ( 1a ), Cast surface pores averaging 20 μm ( 1b ) and the Cross-section shows an isotropic region with pores of about 3 microns extending from the skin to about 25% of the thickness of the membrane, followed by an asymmetric region beginning at pore sizes of about 3 microns and ending at about 20 microns the isotropic region rises towards the casting surface ( 1c ). As desired, the magnitude of the asymmetry calculated from these observations is about 6: 1. This particular membrane of the figure has a bubble point of 8 psid. The in the 2 and 3 The membranes shown have very similar structures, but have bubble points of 11 and 16 psid.

Membranes according to the invention can also be prepared from homogeneous solutions. Such membranes can be made with bubble points in the same range as those of Wrasidlo blends, but they tend to require longer exposure times in the air, and they do not have nearly the same amount of asymmetry as those of Wrasidlo type formulations. 4 shows the structure, as it appears in the scanning electron microscope, a membrane, which was made of a homogeneous polysulfone solution, including the outer skin surface ( 4a ), Casting surface ( 4b ) and a cross section through the membrane ( 4c ). This special membrane has a bubble point of 12 psid.

at the implementation of the manufacturing process with Wrasidlo-type formulations the water vapor on the exposed surfaces of the cast film forming relative greater Pores on both the surface as well as in a region that extends below, while the subsequent water cooling the rest Moved film into a highly asymmetric substructure. Because the movie during the Synthesis for Fractions of seconds or longer which may be exposed to moist air, it is safer, however not necessary to choose those Wrasidlo mixtures which are sufficiently stable with regard to phase separation, for example formulations, which under conventional casting process form asymmetric membranes whose pore size is 0.45 μm or 0.2 μm or smaller.

exemplary Membranes become when using a Polysulfonpolymeren in selected solvent / non-solvent systems educated; however, you can erfinungsgemäße membranes from countless Polymers are poured and therefore represent the proposed Formulations are only examples.

formulations

The Gußformulierungen for this Membranes consist of a polymer, a solvent and a non-solvent. In the polymers which can be used are included all polymers which are able to form membranes. To the polymers, which especially for the methods of the invention are suitable belong Polysulfones, polyamides, polyvinylidene halides, including polyvinylidene fluoride, Polycarbonates, polyacrylonitriles, including polyalkylacrylonitriles and polystyrenes. Mixtures of polymers can be used. To the preferred polymers include Lexan polycarbonate, AMOCO P-3500 polyarylsulfone, nylon 6 / T polyhexamethylene terephthalamide and polyvinylidene fluoride. A particularly preferred polymer is AMOCO P-3500 polyarylsulfone.

To the solvents, which in the formulations according to the invention be used, count dipolar aprotic solvents such as dimethylformamide, dimethylacetamide, dioxane, N-methylpyrrolidone, Dimethylsulfoxide, chloroform, tetramethylurea or tetrachloroethane. Further polymer / solvent pairs are disclosed, for example, in U.S. Patent 3,615,024, (Michaels).

To the appropriate non-solvents belong Alcohols, for example methanol, ethanol, isopropanol, amyl alcohols, Hexanols, heptanols and octanols; Alkanes such as hexane, propane, nitropropane, Heptanes and octanes; and ketones, ethers and esters such as Acetone, butyl ether, ethyl acetate and amyl acetate.

formulations for membranes of the Wrasidlo type are used according to the procedures described by Zepf manufactured, which are incorporated herein by reference. In general, the polymer becomes solvent at the casting temperature solved and the amount of non-solvent is described by Zepf by measuring the optical density selected to the desired cloudiness to achieve the formulation.

Homogeneous molding formulations may have a composition that is outside the spinodal / binodal region of the phase diagram. Suitable homogeneous formulations are any mixtures which contain at least a sufficient concentration of polymer to give a membrane of sufficient integrity and mechanical strength and not have too high a concentration at which the mixture is too viscous to be poured. Common homogenous salutary formulations contain from about 7 to 28% polymers or polymer blends and from 0 to 30% non-solvent (w / v), the rest is solvent. Solvents and non-solvents can also be mixtures.

at liquid cooling systems should the liquid be chemically inert with respect to the polymer, and more preferably miscible with the solvent to be the casting solution. The preferred coolant is water.

The cast membrane is hydrophobic. However, if desired, a surfactant or wetting agent may be added to either the formulation, the cooling liquid or the rinsing liquid to increase the hydrophilicity of the membrane. Preferred agents are polyhydroxycellulose, sodium dodecylsulfate, ethoxylated alcohols, glycerol esters and nonionic fluorocarbon surface active agents, for example those of the Zonyl ^Tm type (DuPont). The concentration of the surfactant in the solution is not critical and can range from fractions of percent (w / v) to over 10%.

Membrangußverfahren

The membranes according to the invention can be poured using any conventional method, wherein the casting dispersion or solution is applied in a layer on a nonporous support, of which the membrane later can be separated after quenching. The membranes can either manually (eg pouring, to water or spreading by hand on a casting surface and applying the cooling solution the surface) or automatically (eg pouring out or otherwise pour on a moving support) become. A preferred carrier is polyethylene coated paper. When casting, in particular during automatic casting, can mechanical distributors are used. Mechanical distributors include Spreading knife, doctor blade or spray / pressure systems. A preferred Applicator is a Umspritzform or slot press, which has a chamber into which the casting formulation is introduced and pushed out of this under pressure through a narrow gap. In Examples 1 to 3, the membranes are used a Abstreifmessers poured whose knife width typically between 250 to 450 μm often at 300 μm lies. After the cooling step is the manufactured microporous Membrane typically between 105 and 145 μm thick.

To the casting becomes quenched the dispersion. In a preferred embodiment the quenching is achieved by the cast membrane on a moving carrier in a cooling liquid, for example into a bath, being transferred. The cooling solution exists generally water, the temperature of which is usually at or near the casting temperature lies. By quenching falls the polymer in bath and can produce an outer skin which the required pore size and a supporting body with the characteristic structure. The resulting membrane will be in ordinary Way of trapped solvents washed free and can be dried to remove more residual solvent, thinner and cooling liquid to remove and you get so the finished membrane.

in the general should be the cast film exposed to air in the preparation of the membranes of the invention for and for such time, which is sufficient for the formation of large surface pores to effect as previously described. The shorter the exposure, the more the humidity must be higher and vice versa. The total moisture is the determining factor. At higher Ambient temperatures can reach relative humidity be the same effect lower. The temperatures of the casting mixture and the cooling bath are also important parameters. In general, the warmer the Mix the denser the membrane, the warmer the cooling, the more open the membrane.

Large and open-pored membrane from Wrasidlo-type formulations

To Initially, an attempt was made to make a membrane which is more porous than the 0.45 μm polysulfone membrane described by Zepf (BTS-25), in which the phase inversion formulation is equivalent the membrane formation theory as described in the Wrasidlo and Zepf patents, is modified, that is, the increase the optical density of the casting formulation by lowering the polymer concentration and increasing the Non-solvent concentration and also the increase the quenching temperature. The cast film was also briefly exposed to damp air before quenching.

It was expected to be one Gußformulierung, which has an optical density in the range of 1,800, compared to 0.600, forms a more open membrane than the available ones asymmetric membranes. Indeed the membrane produced was very open. Permeability showed that the Membrane has a bubble point of 4 psid, a flow rate for water of 17.7 cm / min / psid and a mean flow pore size of 2.0 μm.

A particularly preferred membrane was prepared by using a Wrasidlo-type dispersed phase, the phase inversion formulation for a 0.2 μm standard polysulfone membrane (BTS 45), and casting at lower temperatures than suggested by Zepf, Example 2 low casting index of 0.176 indicates a relatively stable casting dispersion. The cast film was exposed to damp air for a short time before quenching. The cast membrane was comparable in quality to the standard product, had a highly asymmetric substructure, as well as a bubble point of 8 psid and a water flow rate of 19.9 cm / min / psid. The porometric analysis showed a mean flow pore size of 0.9 μm as opposed to the 0.2 μm pore diameter and 45 psid bubble point obtained from the standard BTS-45 formulation when poured in the usual manner. Scanning electron micrographs ( 1 ) showed a highly asymmetric structure, free from any large macrovoids.

Large and open-pored membrane from a homogeneous formulation

example Figure 8 shows the preparation of membranes with open surface pores and a high flow rate, by bringing a cast film of a homogeneous solution with moist air before quenching in water. The pouring of a homogeneous solution, comprising 9% polysulfone in 72% solvent and 19% non-solvent and minimal exposure to moist air, produces a highly asymmetric Membrane, 0.2 μm or denser, with bubble points greater than 45 psid. Among the in the example described conditions of contacting with humid air, the membranes have a medium bubble point of about 12 psid and a flow rate for water of about 8.4 cm / min / psid.

example 9 describes the preparation of membranes from different homogeneous Formulations and variation of the time of exposure to moist Air. Independently from the formulation generated the increasing time of influence the environment larger surface pores, up to 8 μm on the tight side and flow rates for water up to more than 19 cm / min / psid, with corresponding bubble points of 3 to 4 psid. These membranes were satisfactorily asymmetric and had pores on the open side of over 100 μm. See Appendix 1.

In the initial one Experiments used 2-methoxyethanol as a non-solvent; however could also polyethylene glycol (PEG 400) and polyvinylpyrrolidone (PVP 10,000) in concentrations up to 25% of the total non-solvent concentration be used. It is interesting to note that PVP is 10000 in this case also acted as a good co-solvent.

at The experiments were the air temperature and humidity about Measured 12 inches (30.48 cm) above the cast plate. Unless air speeds were recorded, these were using a Staudruckmesser before the casting measured about 1 inch (2.45 cm) above the cast plate.

One good example for the influences The moisture can be found by carrying out experiments 1 and 2 in the Annex I compares. In the first experiment, the air was unmoved, and in the second experiment, under otherwise comparable conditions, the air was moving. The bubble points in the membrane were halved and the flow rate for water rose by a factor of 1.7. As expected, low moisture levels resulted to membranes with consequently low permeabilities and high bubble points, while higher humidity (i.e. 60%) and moving air membranes with reduced bubble points (i.e., 4 psid) and correspondingly high flow rates for water (down to 20.6 cm / min / psid).

The Movement of moist air over the surface of the cast film elevated the pore size; however excessive air currents disturb the liquid film and the steps forming it and cause irregularities in the product. Therefore, we think that the air flow is big enough but to continually renew the moist air not so great, that the surface disturbed is, preferably at a speed which is slightly greater as the casting speed.

The Homogeneous formulations are more advantageous in that they have a higher stability have the Wrasidlo type phase separation formulations, the latter formulations yielding membranes which have greater asymmetry seem to have.

Applications for the open-pored invention membranes

• (a) der abgestuften (asymmetrischen) Porenstruktur mit großen Porengrößen an der offenen Seite;
• (b) geringfügig kleineren (aber noch immer sehr großen) inneren Poren;
• (c) der isotropen Region unterhalb der Außenhaut; und
• (d) großen offenen Poren an der "Außenhaut"-seite, groß zumindest im Vergleich mit anderen Membranen.

The open cell polymer membranes of the present invention can enhance the function of many types of analytical devices, particularly those devices intended to be different Detect and measure analytes directly from a heterogeneous liquid sample in a single application step. The particular suitability of highly asymmetric membranes for diagnosis results from:

• (a) the stepped (asymmetric) pore structure with large pore sizes at the open side;
• (b) slightly smaller (but still very large) internal pores;
• (c) the isotropic region below the outer skin; and
• (d) large open pores on the "skin" side, large at least compared to other membranes.

These Properties produce excellent wicking effects, both lateral as well as vertically, with running speeds of the solvent front through these membranes at 3 to 4 times the rate than in comparable dense-pored membranes. At the same time they provide filtration properties to disposal. For example, in the analysis of blood samples, the plasma migrates from a drop of blood quickly through the membrane to the outer skin, while the red cells are retained by the membrane network of the filter cells become. The plasma can be obtained on the outer skin side and analyzed in a separate layer below the membrane become. With suitable, enclosed in the membrane, chemical Reagents and enzymes, the plasma can rapidly change to different Be examined ingredients, for example by colorimetry or coulometry. Likewise different by fixing specific antibodies to the membrane Analytes bound and measured. Non-specific bindings to the membrane can by prior treatment of the membrane with a solution biologically inert material, for example human or bovine Serum albumin should be excluded as known to those skilled in the art is. Accurate analyzes require the absence of nonspecific bound to the membrane, soluble Ingredients of the liquid Sample. A hydrophilic membrane, which with surface-active Substances coated is low, has non-specific binding properties; however may be a hydrophobic membrane in testing equipment in the conventional Be used to produce low non-specific bonds. The handling and the lateral / verti cal wick properties are the same as in hydrophobic membranes. The efficient implementation of analytical process depends from the rapid filtration or transport of the separated liquid samples from.

membranes, made of cellulose nitrate, cellulose acetate and mixtures thereof and occasionally also from their polymer blends, are commonly used for porous membrane layers used in such analytical devices. These membrane materials are re mechanical strength unsatisfactory and often lead to breakage during use, Storage and in particular in automated manufacturing processes. Nylon materials show significant, non-specific bonds due to the numerous active sites on the polyamide surface of the Material.

Of the Replacement of cellulose nitrate, nylon or less open polymer membranes by the open-pored invention Polymer membranes in the devices described, both the efficiency as well as the accuracy of the particular analytical Improve procedure for which the device is used. Conventional devices can be used in easy way for the use of membranes according to the invention customized become. Some of the many application options are:

Vertical filter devices

A Class of analytical devices contains a porous membrane containing a filtrate either to the bottom of the membrane or to one below it Transport reaction site. Chromogenic reagents for detection the analyte can be entrapped in the membrane and the colored product is in the filtrate made visible from the bottom. See, for example U.S.. Patent 4,774,192 (Terminello), the disclosure of which is hereby by Reference inserted in which chemical test systems for glucose, urea, alpha-amylase, bilirubin, Triglycerides, total cholesterol and creatinine are described as well Immunoassays in the form of test strips labeled with enzymes Contain immunoconjugates.

Other examples for Devices of this type are described in U.S. Pat. Patent 4,789, 085 (Allen et al.) For a blood filtration and measuring device and U.S. Pat. U.S. Patent 4,935,346 (Phillips et al.) Which discloses a porous membrane comprises which is impregnated with an analyte-specific reagent, at the same time a soluble one Filtrate from a whole blood sample, which on the upper surface of the Membrane is applied and to produce a colored reaction product, which indicates the concentration of the analyte. The revelation of this Patents are hereby incorporated by reference.

The membranes according to the invention possess the required properties, such as physical properties, chemical inertness and optical properties, which are needed to achieve the functionality chemical systems.

Lateral wick devices

lateral Wick devices operate due to capillary action or wicking properties the substrates, for example the membrane. See for example U.S. Patent 4,168,146 (Grubb et al.), Which is a diagnostic Device for disclosed immunological determinations, the device a porous carrier material to which antibody covalently bonded; this disclosure is hereby incorporated by reference inserted.

The Efficiency of such devices is due to the capillary action caused speed, with which the solution along the with antibodies or reactants coated Membrane moves, with the appropriate migration speed, the superior Handling and the reduced areas of non-specific bonds the membranes of the invention allow a much more accurate measurement, as devices According to the state of the art.

Membrane absorption devices

absorbing devices are generally described in U.S. Pat. U.S. Patent 4,125,372 (Kawai et al.) and this disclosure is hereby incorporated by reference. Because of their highly asymmetric structure have the membranes of the invention a superior one porosity or a superior one Opposite pore volume many conventional Absorptive materials according to the prior art. Therefore, the membranes according to the invention well suited for replacement in such devices. Using the membranes according to the invention modified devices and suitable reagents such as this The person skilled in the art is aware of the presence of a number of substances with greater sensitivity be detected as this is possible according to the prior art.

Other devices

In similar Way you can Blood screening devices and a variety of other biosensors Use of membranes according to the invention be suitably modified as known to those skilled in the art is. It is to be expected that such changed Devices that function equally or better than devices, Sensors and the like of the prior art.

filtration systems

The inventive polymer Membranes can also advantageously replace microporous filters, which in continuous laminar flow systems for the separation of plasma used by whole blood. A system of this kind is disclosed in U.S. Pat. Patent 4,212,742 (Solomon et al.), Which is hereby by Reference inserted is. The membranes of the invention have the property of having red blood cells in their large pores withhold and thus to increase the release effect of such laminar flow systems.

In similar Way you can the membranes of the invention used in a variety of other applications. A Particularly preferred embodiment of the invention is, for example a membrane used to filter yeast from beer and wine becomes. Because of the unique structural properties of the membranes, The yeast cells tend to be collected in the pores, with the yeast is retained in an intact form without disintegrating becomes. This reduces the bitter taste of beer and wine.

In such fields of application, the membranes of the invention can be packed and used in a conventional manner. In this sense, membranes of the invention are useful in applications currently perceived by classical asymmetric membranes such as VARA-FINE ^™ filter cartridges, VARA-FINE ^™ filter capsules, and FILTRITE ^™ products manufactured and sold by MEMTEC AMERICA CORPORATION. In such products, the cartridges and / or capsules are made by pouring the selected membrane into a support housing. If necessary, the membrane is usually folded to increase the available surface area of the membrane. The housing is typically made of an inert material, for example, simple polymeric material (ie polypropylene), special polymer materials (ie PVDF) or metals (ie stainless steel), depending on the field of application of the filter, for example the number of foreseen uses tion cycles, the environmental conditions such as solvents, temperatures, filtrates and the like and printing produced. Pouring is usually achieved by heat sealing or suitable adhesives.

typical Areas of application of the filtration systems described above are chemical, photographic, food, beverage, cosmetic, Magnetic tape and electronics industry. In these industries The filtration systems are used in a variety of procedures and cohere used. For example, solvent filtration, Acid filtration, Production and filtration of deionized water, beer and wine clarification and many other applications. In general, the membranes of the invention be used in almost all fields of application, as they are very inert are. The membranes have a good service life under extremely acidic conditions and extremely basic conditions, tolerate cleaning and oxidizing agents good and are thermally and chemically stable. As proof of the extreme usefulness and stability Of the membranes, it is interesting to note that the membranes are very successful in the filtration of hydrofluoric acid and sulfuric acid-containing etching solutions wastewater the electronics industry were used. At another extreme End are the membranes of the invention able to perform high-filtration tasks in extremely organic systems to fulfill, such as in waste and supply streams in the magnetic tape industry.

Of the Purpose, the objects and the advantages of the membranes of the present invention with reference to the following examples, tables and figures clear. Although the following examples have certain preferred properties of the invention, it is not intended that the invention in any way restrict.

example 1

Production of large pores asymmetric polysulfone membranes using the standard formulation according to Wrasidlo BTS-45 (0 2 μm)

A membrane of the invention having large diameter outer skin surface pores was prepared as follows. Basically, the membrane was made from a standard Wrasidlo polysulfone formulation which is used to make highly asymmetric membranes having a bubble point of 45 psid. The casting technique for making the membranes of the invention was similar. However, the air gap was increased and the relative humidity of the casting was recorded. The formulation was as follows: Formulation: Dimethylformamide (DMF, solvent) 73.72% Tert-amyl alcohol 15.56% Polysulfone (AMOCO P3500) 10.75% Gußindex 0.173

The formulation was cast in an automatic casting machine (conventional diagnostic purity). The formulation was cast by means of a doctor blade on polyethylene-coated paper under the following conditions: Casting conditions: Gußlösungstemperatur 105 ° F (41 ° C) Abkühlwassertemperatur 118 ° F (47.7 ° C) air gap 6 inches casting speed 20 Ft./min room temperature 77 ° F (25 ° C) relative humidity 59

After drying the resulting membrane, the membrane was removed. The removed membrane had the following properties: properties bubble point 8 psid Flow rate for water 19.9 cm / min / psid mean flow pore size 0.9 μm thickness 121 μm breaking strength 454 g / cm elongation 27

As the index shows, the casting solution was stable. The resulting membrane had a uniform, error-free surface appearance. Thickness, breaking strength and elongation were typical of the standard BTS-45 membrane.

however unlike the typical BTS-45 product, the membrane had one significantly lower bubble point with significantly increased flow rates. This membrane is referred to below as sample A.

Example 2

Production of membranes according to the invention with different bubble points

Two other membranes were prepared according to Example 1. Of the Louver became minor scaled down to 5.5 inches and 5 inches, and there were two membranes obtained with different bubble points. The membrane, which was made with a louver of 5.5 inches, had one Bubble point of 11 psid (sample B), while the membrane with a 5 inches louver had a bubble point of 16 psid (Sample C).

With Except for the bubble points, the membranes of Sample B and C were similar Properties such as the membrane of Sample A, which in Example 1 was produced.

Example 3

scanning electron Microscopy the membranes prepared in Examples 1 and 2

Scanning electron micrographs of the membranes prepared in Examples 1 and 2 were prepared. In general, images were taken of the outer skin surface, the casting surface and the cross-section of the membranes. The samples were cut and sputtered with gold by conventional methods. The images were taken with a scanning electron microscope made by JEOL Model No. 5200, which was equipped with a Polaroid camera. The results of the recordings are in the 1 to 3 shown.

1a Figure 5 shows the skin surface of the sample A membrane which had a bubble point of 8 psid at 5,000X. 1b is a recording of the casting surface at 1500 X and 1c is a cross-sectional image of the same membrane at 500X.

2a Figure 4 shows an outer skin surface of the sample B membrane which had a bubble point of 8 psid at 5000 X. 2 B is a recording of the casting surface at 1500 X and 2c is a cross-sectional image of the same membrane at 500X.

3a Figure 4 shows an outer skin surface of the sample B membrane which had a bubble point of 8 psid at 5000 X. 3b is a recording of the casting surface at 1500 X and 3c is a cross-sectional image of the same membrane at 500X.

As can be seen in the cross-sectional photographs, show the membranes a generally isotropic region below and within the Outer skin surface on. The isotropic region extends to more than a quarter. by the membrane thickness and possibly more than a third of the membrane thickness. Below the isotropic region, the membranes have an asymmetric region.

The extent of asymmetry of the membranes is best seen by considering the surface images in which the pore sizes on the surfaces can be observed. In the Sample A, 1a and 1b On average, the pore sizes are about 3 μm on the outer skin surface and 20 μm on the casting surface. In the sample B, in the 2a and 2 B On average, the pore sizes are about 2.5 μm on the outer skin surface and 15 μm on the casting surface. And at sample C, 3a and 3b The pore sizes on the outer skin surface are approximately 2 μm and 12 μm at the casting surface. In all cases, the degree of asymmetry is about 1: 6. However, remembering that the extent of asymmetry extends only two-thirds or three-quarters within the thickness of the membrane, the pore ratio is not as great as it would be if it extended through the entire thickness of the membrane.

Example 4

Representation of membranes of the Zepf type with different bubble points

In addition to The above formulations were two membranes from the conventional Zepf type produced. The membranes were after the Zepf patent manufactured with an air gap of less than one inch, example 2. The membranes formed had bubble points of 25 and 65 psid and are hereinafter referred to as sample D and sample E.

Scanning electron micrographs of the membranes show the classical Zepf membrane structure. 5a to 5c are scanning electron micrographs showing the skin surface, casting surface and cross section of the sample E membrane having a bubble point of 65 psid. In 5a , which is the absorption of the outer skin surface of the membrane of the sample E, the pores are significantly smaller than 1 micron and on average they have a mean diameter of 0.3 microns. In the picture of the cross section, 5c , the complete asymmetry of the membrane can be seen. The pore size gradually increases from the skin surface to the casting surface. The porosity of the casting surface is in 5b shown. The pores on the casting surface have an average diameter of 20 μm on average.

Example 5

Pore sizes determined from scanning electron microscopic investigations

The Pore sizes of various membranes prepared as described above, were examined to allow the quantitative determination of pore size. The results of these investigations are in the following table shown.

Table I

Example 6

Coulter data

The Structures of the various membranes of the examples were analyzed by means of of a Coulter Porometer Model No. 0204. The results are shown in the following table.

Table II

• * based on mean values from 3 samples

A remarkable structural property or phenomenon of the membranes of the invention it that the Coulter data significantly different from the actual one physical structures of the membrane differ as they pass through empirical investigations were obtained by means of SEM. For example in the following table, the minimum, maximum and average Pore sizes, determined according to Coulter, compared with those made by measurements of these Membranes were obtained by means of SEM.

Table III

As According to the Coulter analysis, the membranes seem similar To have pore sizes. Empirically, however, the membranes have extremely different surface structures. Further, the maximum and minimum pore sizes are observed in the Coulter analysis, not nearly by the cross-sectional studies reproduced by means of SEM. Further is to be expected that the bubble points in view of the open pore structure should be smaller than the observed or actual Bubble points.

Example 8

Production of polysulfone membranes from homogeneous solutions

The to water a homogeneous solution from 9% polysulfone (AMOCO P-3500), 10% 2-methoxyethanol and 72% dimethylformamide in the lab revealed a membrane with a bubble point of 72 psid, though the casting before quenching in water (45 ° C) within 0.25 sec of humid air (temperature 22 ° C, relative humidity 44%) was suspended. The same formulation gave a membrane with a bubble point of 12 psid when wet for 4 seconds Air at 22 ° C and 60% relative humidity. The casting was by means of a conventional casting device for diagnostic Purpose, a plastic tent was placed around the unit to keep out the moisture to increase.

Example 9

scanning electron Microscopy the membrane of the invention according to example 7

Scanning micrographs of the membrane according to the invention, which was prepared according to Example 7, were prepared. As mentioned, the membrane had a bubble point of 12 psid. The scanning electron micrographs were carried out analogously to Example 3. The results of the REM are in 4 shown. As expected, the membrane had an open pore structure on the outer skin surface ( 4a ). Also, the pore structure of the casting surface is very open, indicating a substantial asymmetry ( 4b ). In cross-section, the membrane is very similar to membranes of disperse formulations because of the presence of the isotropic region and the asymmetric region ( 4c ).

Example 10

Presentation of more membranes according to the invention from homogeneous formulations

Several different homogeneous polymer solutions were prepared and as described in Example 2 poured into plate membrane. This in Exposure to moist air as described in Annex 1, varied.

Example 11

biological Use of the membrane according to the invention

I. Lateral Wicking from open-pore membranes made from a formulation with Phase inversion:

An amount of 60 μl whole sheep blood was blotted on the open, blunt side of 1 × 4 cm strips of asymmetric membranes with BTS values from about BTS-25 to BTS-65 and open-cell BTS-4 membranes prepared as in example 9 , and measured the time taken for the plasma to travel a predetermined distance from the point of application. Both transverse (A) and outgoing (D) samples were examined. The results are in 6 shown.

A. Lateral Wicking:

A Amount of 60 μl Sheep's whole blood was spotted on a 1 × 4 cm strip of BTS-8 Membrane prepared by the method of Example 1 has been. The plasma front placed a distance of 25 mm in 40 seconds back. For comparison is the lateral wicking effect on porous membranes for 25 mm 180 seconds.

B. Vertical separation:

An amount of 25 μl of whole sheep blood was applied to the blunt side of a membrane as described in (a), the membrane having a surface area of 1 cm ² . The mass of the plasma taken up from the dense side and absorbed by the filter paper was about 10 mg.

C. Protein Binding:

• 1. Säurephosphatase bei Konzentrationen von 100 – 500 μg/ml zeigte beim Filtrieren durch eine 47 mm Scheibe aus Filtermaterial, welche gemäß den Beispielen 1 bis 4 hergestellt wurde, bei 0 bis 10 psi und über einen pH-Wert Bereich von 4,5 bis 9,5 weniger oder gleich 10% Absorption an der Membran
• 2. Malatdehydrogenase bei Konzentrationen von 100 – 500 μg/ml zeigte beim Filtrieren durch eine 47 mm Scheibe aus Filtermaterial, welche gemäß den Beispielen 1 bis 4 hergestellt wurde, bei 0 bis 10 psi und über einen pH-Wert Bereich von 4,5 bis 9,5 weniger oder gleich 10 Absorption an der Membran.
• 3. Lactatdehydrogenase bei Konzentrationen von 100 – 500 μg/ml zeigte beim Filtrieren durch eine 47 mm Scheibe aus Filtermaterial, welche gemäß den Beispielen 1 bis 4 hergestellt wurde, bei 0 bis 10 psi und über einen pH-Wert Bereich von 4,5 bis 9,5 weniger oder gleich 10 Absorption an der Membran.

Protein determinations were made for the following enzymes according to the Pierce BCA protein assay method with an optical density measurement at λ = 562 nm. The sensitivity of the study was 1 μg / ml and protein could be measured on the membrane at <0.3 mg / cm ² .

• 1. Acid phosphatase at concentrations of 100-500 μg / ml when filtered through a 47 mm disc of filter material prepared according to Examples 1-4, at 0 to 10 psi and over a pH range of 4.5 to 9.5 less than or equal to 10% absorption at the membrane
• 2. Malate dehydrogenase at concentrations of 100-500 μg / ml when filtered through a 47 mm disc of filter material prepared according to Examples 1-4, at 0 to 10 psi and over a pH range of 4.5 to 9.5 less than or equal to 10 absorption on the membrane.
• 3. Lactate dehydrogenase at concentrations of 100-500 μg / ml when filtered through a 47 mm disc of filter material prepared according to Examples 1-4, at 0 to 10 psi and over a pH range of 4.5 to 9.5 less than or equal to 10 absorption on the membrane.

equivalent

Even though the invention using certain preferred embodiments and with reference to certain specific examples and illustrations has been described, the invention is not limited thereby. As in detail the above description may be the scope the invention only by the appended claims and their equivalents limited.

Claims (16)

Polymer membrane with a first porous surface, a second porous surface and a support body with a thickness between them, the support body being a network of porous flow channels between the first surface and the second surface is defined and the flow channels of the first surface to a point from the first surface by 15-50% of the thickness of the supporting body is removed, a substantially constant mit miter diameter have and from the point to the second surface gradually increasing have medium diameter. The polymer membrane of claim 1, wherein the support body of the first surface to a point which is about 1/4 of the thickness of the support body, an isotropic structure and from this point to the second surface one having asymmetric structure. A polymer membrane according to claim 1, wherein the flow channels have a essentially constant mean diameter of the first surface to a point which is about 1/4 of the thickness of the support body and from this point to the second surface an increasing middle one Have diameter. Polymer membrane according to claim 1, which is for separation a liquid Fraction of a suspension is suitable, comprising: a integral porous Skin, which lies on one side of the membrane, wherein substantially all pores of the outer skin Have diameters larger than about 1.2 microns are; and a support region the membrane under the skin and an asymmetric one Owns structure. A polymer membrane according to claims 1 to 4, wherein the polymer a polysulfone is. The polymeric membrane of claims 1-5, which has a bubble point of from about 0.5 psid (3447 kg / ms ² ) to about 25 psid (172369 kg / ms ² ). The polymeric membrane of claims 1-6, wherein the bubble point is about 5 psid (34474 kg / ms ² ) to about 15 psid (103421 kg / ms ² ). The polymer membrane of claims 1-7 which has a mean flow rate for water of about 4.5 to 25 cm / min psid (per 6895 kg / ms ² ). The polymer membrane of claims 1 to 8 which has a bubble point no greater than 25 psid (172369 kg / ms ² ). A polymer membrane according to claims 1 to 9, wherein the supporting body an asymmetry by at least 50% of the supporting body but not more than 80 % of the supporting body through. A polymer membrane according to claims 1 to 10, wherein the supporting body an asymmetry of 2: 1 to 200: 1 by at least 50% of the support body but not more than 80% of the supporting body through. Process for the preparation of a polymer membrane according to Claims 1 to 11, comprising: producing a metastable casting dispersion, which comprises a polymer-rich phase and a polymer-poor phase the selected one casting temperature; the to water the dispersion at the casting temperature in a thin one Layer; contacting the casting layer with a pore-forming one the atmosphere for one Period which is sufficient to form surface pores, which greater than 1.2 μm; the Quenching the casting layer with a non-solvent-containing Coolant, in which the solvent is miscible and in which the polymer is substantially insoluble, to precipitate the polymer as an integral membrane; and the recovering the membrane from the coolant. A process for producing a polymer membrane according to claims 1 to 11, comprising: preparing a homogeneous casting solution comprising a polymer, a solvent for the polymer and a non-solvent for the polymer at the casting temperature; casting the dispersion at the pouring temperature into a thin layer; contacting the cast layer with a pore-forming atmosphere for a period of time which is exhausted is to form surface pores which are larger than 1.2 microns; and quenching the casting layer with a non-solvent-containing cooling liquid in which the solvent is miscible and in which the polymer is substantially insoluble to precipitate the polymer as an integral membrane; recovering the membrane from the cooling liquid, the membrane having substantially asymmetry through at least 50% of the support body. Use of a polymer membrane according to any one of claims 1 to 11 for a filter unit. Use of a polymer membrane according to any one of claims 1 to 11 for an improved diagnostic device comprising a filtration device which provides an analyte-containing substantially particle-free filtrate to an analyte-detecting portion of the device, the polymer membrane having surface pores of a mean diameter greater than than 1.2 microns and has a flow rate greater than about 4.5 cm / min psi (cm / min per 6895 kg / ms ² ). Use of a polymer membrane according to any one of claims 1 to 11 for an improved diagnostic device comprising a lateral Wick device containing an analyte substantially particle-free sample, from a sample application area to a Analyte-detecting region of the device transferred, wherein the polymer membrane surface pores has a mean diameter of about 1.2 microns and a lateral Transfer rate of more than 2 cm / min has.