DE2910289C2 - - Google Patents

Description

The invention relates to a sheet-shaped filter material with increased capture potential for electronegative submicron impurities according to the preamble of claim 1 and a method for producing such a filter material according to the preamble of claim 6 and also a method for removing electronegative submicron impurities from aqueous liquids using of the sheet-like filter material according to the invention according to claim 10.

Small particle size contaminants are filtered from liquids using various porous filter media through which the contaminated liquid is passed. In order to act as a filter, the medium must allow the liquid, usually water, to pass through while retaining the particulate contaminants. The retention of contaminants is accomplished by one of the following two distinct filtration mechanisms, namely ( 1 ) mechanical retention and ( 2 ) particle capture by electrokinetic effects. With mechanical retention, the particle is removed by physical trapping when attempting to pass through a hole that is smaller than itself. In the case of electrokinetic trapping, the particle collides with a surface in the porous filter medium and is attracted by short-range attractive forces retained on the surface.

With the exception of microporous polymer membranes known porous filter media for the filtration of fine particles Are suitable from fiber or fiber impurities Fiber-particle mixtures created by vacuum matting from a aqueous slurry have been dynamically formed, whereupon the finished sheet has been dried. In such fibrous Filter media in which the retention of particulate  Contamination depends on the mechanical attraction, it is required that the pore size of the filter medium be smaller than the particle size of the contaminants coming from the liquid should be removed. For the removal of fine submicron impurities due to a mechanical attraction, the filter medium  therefore have correspondingly fine pores. Because the pore size of such leaves mainly of size and morphology the materials used to form the sheet is determined, it is necessary that one or more of the component materials have a very small size, for example fibers are of small diameter (see, for example, US Pat 31 58 532, 32 38 056, 32 46 767, 33 53 682 and 35 73 158).

If the size of the impurities to be removed by filtration decreases and in particular reaches the submicron range, then The difficulties and costs increase to suitably sized Fiber structures for optimal filtration through mechanical To get attraction. There is therefore considerable interest on the use of fine, particulate substances, for example of diatomaceous earth.

With such materials, however, it is necessary to provide a matrix in order to ensure a coherent, to have manageable structure. Therefore, at least one of the component materials is the leaf has a long, self-binding structural fiber, in order for the sheet to have sufficient structural integrity both in the wet state, as formed, as well as in the final dried state to lend to handling during treatment and suitability allow for the intended application. Non-refined Cellulose fibers, such as. B. from wood pulp, cotton, cellulose acetate or rayon are commonly used. These fibers are typically relatively large, with commercial diameters are in the range of 6 to 60 µm. Wood pulp that very often because of its low cost, fiber diameter, which go from 15 to 25 µm, and fiber lengths from about 0.85 to about 6.5 mm.

Sheet-shaped filter media or leaflets from a filter medium usually by vacuum felting of the component material formed from an aqueous slurry. Vacuum felting on a holey surface, usually a wire mesh, which in practice vary from 50 mesh to 200 mesh  can, the mesh openings can go from 280 µm to 70 µm, carried out. Finer meshes are due to constipation problems and / or Structural defects unsuitable.

The size of the holes in the holed vacuum matting surface and the pore size of the cellulose fiber matrix of the sheet formed are compared to some or all dimensions of the fine fibers or particulate components needed to make the desired Submicron filter media sheets are required, fairly large. The retention of such fine components during vacuum formation The filter media sheets are difficult and impose the selection of such materials, the special details of the educational process the filter media sheets and, most importantly, the achievable extent of filtration behavior severe restrictions on. Fine fibers, their length compared to their diameter can be big, cause fewer problems and they will reasonably well restrained. On the other hand, fine, particulate ones tend Materials during leaf formation, a very to show bad reluctance.

Flocculation with polymeric retention agents or coagulation is a measure to improve the retention of fine, Particulate materials have been applied to the agglomeration of particles, creating an effective, large dimension is obtained. A filter sheet made from a well flocculated Slurry has been made, however, has one Wide particle size distribution, with small pores in the flakes occur and there are large pores between the flakes. The existence these larger pores limits the ability of the filter sheets to to remove fine impurities. The use of a Flocculation to ensure high retention in the filter medium is therefore somewhat unproductive.

It is naturally possible to apply hydrodynamic shear forces breaking up the flakes and continuing to make charge modifications, until the system takes on a stable, disperse form Has. This will make a relatively uniform sheet with a narrow one Get pore size distribution. The retention of the particulate  Materials in such a system is very low, resulting in an accompanying decrease in filtration performance leads.

In addition to controlling the dispersion properties (and therefore the porosity of the sheet) and obtaining a wet strength charge modifiers are used to reduce the zeta potential to control the leaf components and the behavior the electrokinetic trapping of lightly charged contaminants to bring it to a maximum value. Be in practice cationic charge modifiers used as most naturally occurring contaminant surfaces at a liquid pH of practical interest are anionic. A preferred one Charge modifier is a melamine formaldehyde colloid, that for filter sheets in US-PSen 40 07 113, accordingly DE 24 22 426 and 40 07 114 is described.

In general, filter media are modified in the charge Items can be used without further treatment after the Media education used. However, if a treatment of biological fluids is provided, then the filter media usually sanitization or sterilization measures under harsh conditions, e.g. B. relatively high temperatures and pressing, subjected. These conditions can be certain Decreased behavior of various charge-modified Media cause or over the content of extractable substances increase permissible limits. Although this phenomenon still has not been fully elucidated, it can be assumed that there is a loss or degradation of the resin itself or the charge functionality of the system by physical or chemical effects. In any case appears they are specific to the choice of resin. In particular the system modified with melamine-formaldehyde colloid is not capable of satisfactory autoclave or hot water rinse conditions to withstand causing significant amounts of charge are lost and thus the effective lifespan is limited. This charge modifier, the low molecular weight is also in terms of the extent of charge modification available  limited. Substitutes to meet these limitations encounter are of particular interest.

The object of the invention is therefore charge-modified, sheet-shaped Filter media with increased filtration performance in particular for the highly effective removal of submicron contaminants to provide aqueous systems.

The invention is also intended to provide a sheet-shaped filter medium be made available that have a high content of fine, has particulate materials.

The invention further aims to provide a filter medium that is aseptic can be made or sterilized, provided that is resistant to degradation with such treatment and that maintains sufficient charge potential, for increased electronic capture of lightly charged Impurities.

The task is solved by the leaf-shaped filter material according to claim 1. The sub-claims 2 to 5 designate advantageous Embodiments of the filter materials. The manufacture of the filter materials according to the invention is carried out according to claim 6. Advantageous embodiments of the method are in claims 7 to 9 specified. The removal method according to the invention of electronegative submicron contaminants from aqueous Liquids are made according to claim 10. A preferred embodiment includes claim 11.

According to the invention, charge-modified, sheet-shaped filter media are used manufactured by a fiber system for the sheet formation the self-binding media matrix is used, the struck Cellulose fibers, usually a moderate to high pulp, that a fiber system with a Canadian standard freedom (Canadian Standard Freeness) from 100 to 600 ml, preferably 200 to 300 ml or less obtained. The provision  of shorter or more fibrillated fibers allows the Retention of fine, particulate materials in preferred Embodiments ranging from 50% up to 70% or more on the weight of the sheet.

The charge modifier that is selective for manufacturing the filter media that are sanitized or sterilized is a cationic polyamido polyaminepichlorohydrin resin, which resists degradation from such treatment, and a sufficient positive charge potential maintains that an increased  electrokinetic capture of small, negatively charged Impurities is caused. This enables sterilizable filter media that are non-toxic, less than 1.5% extractable Contain substances that are effective when used, nevertheless they have autoclave conditions of e.g. B. 130 ° C, under one pressure of 6.8 kg for 1 hour or a hot water rinse flow of 82 ° C for 1 hour exposed at a flow rate of 225 cc / min are. Surprisingly, such filter media also show up significantly improved behavior in the filtration of liquids compared with an intermediate pH (5-8) to high pH to charge modified with a cationic melamine formaldehyde colloid System.

The sheet-shaped filter medium, which is preferably felted by vacuum a cationically disperse, aqueous slurry made from beaten or ground cellulose fibers and fine, particulate Materials has been formed shows a uniform, high Porosity and a fine pore size structure with excellent Filtration and flow properties.

It is noted that the high retention of particulate Substances that can be obtained according to the invention as are significant if the total amount of cellulose fibers is considered which acts as a matrix. Thus, in preferred Embodiments the cellulose pulp as little as 10 account for up to 20% of the total leaf weight.

Relatively high retention of particulate matter (up to about 45% by weight) have already been obtained in filtration technology, but only at the expense of an unacceptably high pressure drop the tight construction used was due. In contrast can the sheet-shaped filter media according to the invention in a be constructed in such a way that they can withstand even a load of 70% show only low differential pressure drops, e.g. B. less than 0.28 kg / cm² (4.0 psid).  

Combinations of fibers with different dimensions for filters are already known and z. B. in U.S. Patents 21 44 781, 23 72 437, 27 08 982 and 30 34 981. The retention of Ion exchange resins is related to the freedom from pulp described in US Pat. No. 2,955,067.

The invention is explained in more detail in the drawings. It shows:

Fig. 1 is a diagram of the normalized flow potential versus time, are compared in the equilibrium Ausspülkurven for a prior art filter sheet and an inventive filter sheet with each other;

Comparing Figures 2 and 3 are graphs of the normalized flow potential and the turbidity of the effluent as a function of time, in the challenge tests of monodisperse latex impurity at a known filter sheet and a filter sheet according to the invention with one another.

Fig. 4 is a graph of normalized flow potential versus time in which equilibrium rinse curves of a known filter sheet are compared with a filter sheet according to the invention in untreated form, in an autoclave-treated form and in a form rinsed with hot water.

The sheet-shaped filter media according to the invention are made of cationic modified filter elements usually manufactured in In the form of cationically disperse, aqueous slurries, the cellulose fibers and optimized contents of fine, particulate Contain materials such as diatomaceous earth or pearlite. The filter elements can be in the slurry and in the dynamic sheet made by vacuum felting and drying cationically be modified or the filter elements can be pretreated and closed Filter sheets are deformed. A special feature of the invention is the provision of filter media sheets in which the Retained particulate content compared to a conventional sheet is raised.  

The state of refinement of a wood pulp fiber is determined by means of a "Freedom Tests" determined at which the flow rate through a shaping cushion of the fibers is determined on a standard sieve. The "Canadian Standard Freedom Tester" (Canadian Standard Freeness Tester) applied. With this method the volume of water (expressed in ml) measured from a receptacle that has an opening outlet on the bottom overflows. The Canadian standard freedom measurements are described herein used. Coarse unbeaten wood pulp fibers result in high drain speeds into the receptacle from the strainer what to leads to large overflow volumes and therefore results in a high degree of freedom. Typical wood pulps show values for the Canadian standard freedom from +400 ml to +800 ml. In the manufacture of paper or filter media such pulps can use mechanical refining processes, for example, subjected to beating or grinding be, whereby the cellulose fibers cut and / or be fibrillated. Such beaten fibers have lower Process speeds and therefore lower freedom values.

According to the invention, such a beaten pulp is in the self-binding Matrix of filter media used. Canadian standard freedom of the pulp system varies according to the selection the pulp and it can split the different states or display refinement, for example if different Pulps or differently beaten pulps for leaf formation be used. The beaten pulp is used, however, that a composite or average value from usually 100 to 600 ml is obtained, with lower ones Values, e.g. B. 200-300 ml or less, for a higher solids retention to be favoured.

The wood pulp can only comprise as little as 10% by weight, whereby up to 20 to 30% by weight of the total amount are preferred to a filter media sheet to get that has structural properties that are necessary for technical filtration purposes are suitable.  

Behavior is improved by changing the amount of fine, particulate Material in the sheet-shaped filter medium maximized. While only as little as 10% fine, particulate material a noticeable improvement in the filtration behavior of everyone Media types, optimal behavior is obtained when one the maximum amount of fine particulate material used. The structural properties are ideal for technical filtration practicable maximum amount of about 70 wt .-% near. For less demanding Slightly higher levels are possible for application purposes. Contents of 50-70% by weight are generally used.

There are different types of fine, anionic, particulate Materials that are suitable for the intended purpose, e.g. B. Diatomaceous earth, pearlite, talc, silica gel, polymeric particulate Materials, for example produced by emulsion or suspension polymerization, such as polystyrene, polyacrylates, polyvinyl acetate, Polyethylene (or other such materials as in emulsions and Emulsion Technology, Lissant, Kenneth J., Marcel Dekker, 1974 described), activated carbon, molecular sieves, clay etc. should be functional the fine, particulate materials have a specific surface of more than 1 m² / g and / or particle diameter of less than 10 µm. In a broad sense, any fine, particulate can Suitable material (such as J. M. Filter Cel, Standard Super Cel, Celite 512, Hydro Super Cel, Speed Plus and Speedflow; Dicalite 215 and Dicalite 416 and Dicalite 436). The review can be done by known techniques. From the standpoint of Size, morphology, cost, compatibility with the Fluid and general behavior become finer grades of Diatomaceous earth and pearlite filter aids with an average Particle size less than 5 microns preferred. In many cases result in mixtures of several types of fine, particulate Materials such as diatomaceous earth and pearlite in the weight ratio of about 80/20 to 20/80 a better filtration behavior or a better cost / behavior comparison than how using a single type is achievable. Similarly, mixtures in all proportions of relatively coarse and fine, particulate  Materials, e.g. B. 50/50 parts by weight of particulate materials with a diameter of 10 and 5 microns can be used.

Suitable cationic polyamido polyaminepichlorohydrin resins are for example in US Pat. Nos. 29 26 116, 29 26 154, 32 24 986, 33 32 901 and 33 82 096. You can make it be that a dicarboxylic acid with a polyamine dimer reacted to produce a water-soluble polymer with Epichlorohydrin is implemented further. The dimer units can general formula

H₂N [(CH₂) ₂-NH] _x - (CH₂) ₂-NH₂

where x is an integer from 1 to 7. The dicarboxylic acid can be aromatic or aliphatic. examples for this are Adipic acid, azelaic acid, diglycolic acid, oxalic acid and malonic acid. The cationic charge is converted into tertiary or by the amine function quaternized configuration induced. Other suitable charge modifiers Resins in which a heterocyclic dicarboxylic acid has been used as the starting substance, z. B. in the US-PS 37 61 350. The cationic polyamido-polyaminepichlorohydrin resins are commercially available, for example, as Polycup 1884, 2002 or S2064 (Hercules); Cascamide Resin pR-420 (Borden) or Nopcobond 35 (Nopco) available.

In papermaking, where sometimes cationic charge modifier the aim is to keep the charge at approx to decrease the isoelectric point to increase effectiveness to maximize the matting of the fibers. When it comes to filtration a maximum charge is desired to the distance of charged To increase particles by electrokinetic mechanisms. In the present Case, the surface charge of at least one of the negative loaded filter elements, d. H. cellulose, or particulate Material diminishes, making the surface less is made electronegative. If necessary (and preferably) reversed the charge by adding enough cationic charge modifier  is deposited to make the surfaces electropositive to make at least certain electropositive areas or places in the filter sheet can be obtained. A charge reversal to effect, one naturally goes through the isoelectric Point through. Then a positive charge up to the maximum practical value trained.

The amount of the charge modifier used in the present invention is therefore preferably the one that is sufficient that at least one cationically disperse system is obtained, d. H. a system where there is no visible flocculation under ambient conditions in the absence of applied hydrodynamic Shear forces occur. The system therefore essentially contains discrete fiber / particle material elements that have a positive Have charge or zeta potential and which are relatively uniform or homogeneous in and through the aqueous medium are distributed. The specific value naturally varies depending on the system and the chosen modifier. In individual cases, however, the amount can be determined by some Preliminary tests can be determined. So z. B. the turning point of one Curve of the retention of the particulates depending on from the amount of the charge modifier to the minimum Value for better behavior. A content of 2% is therefore suitable for a polyamido-polyaminepichlorohydrin resin. Although further modifier advantageously used If desired, this value represents that fixed balance on cost performance basis. Pre-modified Filter elements, e.g. B. particulate material with the Charge modifier has been precoated, of course in any way in the filter sheets in similar Results are incorporated. If one is cationic disperse slurry is not used, then a charge modification by controlling the levels of the modifier reduced.

The charge modification caused can be determined by measuring the zeta Surface potential and through an improved filtration performance  demonstrated for negatively charged particles in liquid systems will.

The pulp and particulate material slurry is formed in any way. The order of addition these components to water to make the initial slurry education seems relatively unimportant. The consistency of the Slurry is the one for practical suspension of the components is the highest possible and is about 4%. The System is subjected to hydrodynamic shear forces, for example a paddle mixer, whereupon the charge modifier is added to the slurry.

The extent of the shear is not critical; d. H. everyone else appropriate shear rate or shear stress with regard to the available facility, the preferred treatment time etc., can be applied. The degree of shear, however, will simply selected and applied so that the flakes are broken open and the system is dispersed during treatment Condition is maintained. Natural is after education in a cationically disperse slurry Absence of applied shear from flaking free.

After the charge modification, the slurry is treated with further Water to the right consistency for vacuum matting sheet formation is usually 0.5 to 2.5%, depending on the type of device used to form the sheet is used, diluted in a known manner. The slurry is formed into a sheet and in the usual way in the oven dried. The behavior of the sheet is related to the drying parameters in relationships. Optimal conditions can be energy considerations or reflect the course of the thermal treatment, being unnecessarily exposed to elevated temperatures is minimized, especially if you think of the Decomposition or scorching point of the system is approaching.  

According to a preferred embodiment of the invention, they are leaf-shaped Filter media from filter elements, d. H. a particulate Material and a self-binding matrix of cellulose pulp, of which at least one material has been charge modified, produced and wherein the pulp contains beaten pulp that a Canadian standard clearance of up to 600 ml, preferably less than 300 ml, e.g. B. 100-200 ml. The charge modifier consists of a cationic polyamido-polyaminepichlorohydrin resin and it is applied in an amount that the Electronegativity of the surface is reduced, preferably in an amount that a charge reversal over the isoelectric point is obtained, for example, an addition amount of about 2 wt .-%. Sheet-shaped filter media treated in this way can be autoclaved treated, rinsed with hot water or on otherwise treated at elevated temperatures to avoid the Sterilize or sterilize the structure. Additionally, that they have a special suitability for the filtration of biological Have liquids, these sheets can also be used for Filtration can be used without a rinsing delay because in ions present in the structure during sterilization or Sterilization has been removed.

The advantages of the cationic polyamido-polyaminepichlorohydrin resin can be seen dramatically from the drawings. These represent the results of the tests according to Examples 6 and 7. The resin used in the present invention maintains a high charge and a removal capacity and it has a longer effective Lifespan than the cationic melamine formaldehyde colloid of the US PS 40 07 113.

The sheet-shaped filter media can be subjected to standardized tests such as the following:

Filtration performance test

This test detects a contaminated liquid with a specific Turbidity through the test filter with a constant vacuum  drawn under standard conditions. The turbidity of the outflow will (using a Hach model 2100A turbidimeter) and as a percentage filtration performance compared to the inlet turbidity, calculated as

expressed. The test impurity is Hyplar (manufactured by Grumbacher), namely, a polydisperse acrylic latex made by Emulsion polymerization containing colloidal polymer particles 0.05 to 1.0 µm. The contamination level is 25-200 NTU (Nephelometric turbidity units) in distilled water a pH of 6.5-7.0. The filter sheet becomes disks with cut to a diameter of 57 mm and then into a vacuum filter holder, Millipore 47. 100 ml of the so produced Contamination dispersion are then under through the disc Filtered using a vacuum of 58.4 cm Hg.

Membrane protection test

In this test, the contaminated liquid is under standard conditions through the test filter medium and a membrane in series pumped at a constant flow rate and the differential pressure is recorded over time. The time or the total volume the liquid that occurs at a defined pressure increase flows through is a measure of the life of the pre-filter and it stands satisfactorily with the usage behavior in relationship. Typically a 47 mm 0.22 µm membrane used at a flow rate of 225 ml / min. The Test compound is the same polydisperse acrylic latex as described above (Hyplar). The content of the pollution is 5-50 NTU (Hach Turbidimeter Model 2100A). The test continues, until the differential pressure across either the membrane or the test filter exceeds 0.35-0.70 kg / cm². Membrane protection times less than a few minutes show no practical use Effect.  

Oil flow test

100 SSU oil is used as a measure of the porosity of the filter media sheets pumped through the leaf sample until a differential pressure drop of 0.35 kg / cm² is obtained. At this point the flow rate (ml / min) recorded.

Normalized flow potential

Measuring the flow potential is a common method to determine the zeta potential, d. H. of the electrical potential in excess over the surface and the surrounding liquid to the hydrodynamic shear plane via the mass potential of the Liquid. In this test the flow potential values determined and for differing pressure drops in the tested media normally, the results being in units of mV / 0.3 m of water can be specified. The filter medium is evaluated by the Filter medium is rinsed out with water until the measured flow potential assumes a relatively stable, maximum value. To the filter medium has stopped at this point, a significant one To release ions into the water, d. H. the inlet resistance is equal to the outlet resistance.

The test cell for the filter medium is based on the type of Oulman et al. a. JAWWA 56: 915 (1964). It consists of Lucite with a effective area of 20.3 cm³ (diameter 5.1 cm) and them is provided with soot black electrodes. Water and mercury pressure gauges are used to measure the pressure drop across the test medium to eat. The values of the flow potential (which by agreement have opposite signs like the zeta Potential and the surface charge) with a high impedance voltmeter measured. The influence and outflow resistance become with conductivity flow cells (cell constant = 0.02 / cm) below Monitored using a resistance bridge.

Upon obtaining equilibrium flow potential (i.e. after flushing out) can cause contamination provocation tests  be carried out in the same system, with an aqueous Single size dispersion of a monodisperse latex used the 90 ° light scattering intensity (selected for high sensitivity to particle diameters in the range of 0.1 to 1.0 µm) of the inflow and outflow can be measured, whereby a quantitative determination of the filtration performance of the Filter medium is obtained. The turbidity of the outflow is below Measured using a Moniteck opacimeter. The entrance exam is selected to range from 15 to 20 NTU is, with a Dow diagnostic emulsion with 0.109 microns, consisting from a polymerized polystyrene latex dispersion and the flow rate is kept relatively constant becomes. The above tests are exactly in a lecture at 71st Annual AICHE Meeting (1978): "Measuring the Electrokinetic Properties of Charged Filter Media "Knight et al.

In the following examples, all proportions are based on the total weight of pulp and particulate material with the exclusion of the Charge modifier related.

Example 1

A number of filter sheets were produced, with Weyerhauser Coho-Kraft pulp was used that was specified Values had been struck. Grefco Dicalite 416 Perlite with an average particle size of 3.9 microns was used.

A charge modifier was used in these experiments cationic polyamine polyamide epichlorohydrin resin (Hercules Polycup 1884; about 100,000 mole weight, particle size about 150 Å).

The total addition amount (on a dry basis) of the component materials was 80 g with the exception of the charge modifier. A constant ratio of pulp (30 wt .-% or 24 g) and particulate material (70 wt% or 56 g) was maintained.  The components became water in a 1 liter polyethylene jar added with vigorous stirring, creating an aqueous slurry was obtained with a constancy of 2%. Then it became Charge modifier added (the system became a hydrodynamic Shear action using a Hei-Dolph stirrer (Polyscience Inc.) with four propeller blades when adjusting 2 rotated at about 700 rpm, subjected). The slurry was then diluted to a consistency of 0.5% and into a leaf with a thickness of about 0.41 to 0.51 cm (depending on the retention) vacuum matted. This was done in a handheld device with the Dimensions 23 cm x 30 cm using a 100 mesh screen. The Sheet was then removed in a static oven at 177 ° C dried to constant weight. Then the final weight recorded. The comparison of the final weight of the sheet with the entire material added the determination allowed of the total solids retained in the sheet. The filter sheets filtration (membrane protection) and oil flow tests, as described above. The results are in Table I. compiled.  

Table I

From the above test values it can be seen that samples which are not charge modified, essentially no membrane protection showed. The solids retention improved with a reduced average CSF value of the pulp system used. The lowest freedom systems failed due to Pillow blockage with little increase in membrane pressure drop.

Example 2

A series of tests were carried out according to Example 1, wherein as a particulate Grefco Perlite 426 with a average particle size of 4.2 microns and a constant Content 2% of charge modifier (Hercules 1884) used has been. The results are summarized in Table II.  

Table 2

Example 3

A. Particulate filter aid was in an aqueous slurry with a constancy of 2.5% with the above Held by Hercules 1884 charge modifier Contact time of about 15 min. long pre-coated, insulated, drain left and dried at 121 ° C for 30 min.

The treated particulate filter material was in 100 ml of water slurried and through a porous fritted glass holder base in a vacuum filter holder, Millipore 47 mm, filtered until a Cake with a thickness of 0.64 cm had been formed. Then Filtration performance tests performed. The results are in Table III compiled.  

Table III

The improvement of the filtration behavior with the charge modification is particularly dramatic with larger, particulate materials.

Example 3

B. An aqueous slurry of the precoated particulate material prepared as above was formed into a filter sheet containing 30% by weight of beaten pulp as a matrix. It was dried. The pulp system used had a freedom value of 130 CSF. Membrane protection tests were carried out, the results of which are summarized in Table IV.

Example 3

C. A preformed sheet containing a 130 CSF pulp system (30% by weight) and Perlite 416 as a particulate treated with Hercules 1884 resin (2% solids), dried and hardened. The membrane protection time was during the filtration tests 6.5 min. Failure occurred due to bed clogging 0.35 kg / cm².

Example 4

A. As in Example 3A, mechanically defibered cellulose was used (Solka Floc) precoated with cationic resin (Hercules 1884), dried and hardened. It became a filter cake deformed and examined for filtration performance. The received Results are summarized in Table V.  

Table V

Example 4

B. A filter sheet was made from a 30% untreated slurry Cellulose pulp and 70% pre-treated, defibered cellulose formed according to Example 4 A and tested as in Example III B The results obtained are summarized in Table VI.  

Table VI

Example 5

Filter media were produced as in Example 1, 70% particulate and 30% pulp were used. As particulate material became diatomaceous earth (Grefco Dicalite 215) used. The system was made with 2% cationic resin (Hercules Polycup 1884) surface modified. The pulp system was varied to the presence of a more battered To reflect pulp. Accordingly, increased the solids retention from 49.3% by weight to 80.0% by weight.

Example 6

In this example, the behavior of a known, with a cationic melamine formaldehyde colloid (Parez 607) charge modified Filter sheet (see. US-PS 40 07 113) with a according to the invention with a cationic polyamido-polyaminepichlorohydrin resin (Hercules Polycup 1884) modified sheet compared.

A. Filter sheets were made from 70% by weight cellulose pulp system (CSF 130) and 30% by weight of a 50/50 mixture of diatomaceous earth and Pearlite made. They were formed in an identical way by producing a cationically disperse, aqueous slurry was, this was vacuum matted and the product in Oven was dried, except that optimized charge modifier levels (7% for Parez 607 and 2% for Hercules 1884) and drying conditions were applied.

Normalized flow potential values were determined over time using the test conditions described above. Equilibrium rinse curves that had been plotted for the respective filter media are compared in FIG. 1. It can be seen that the known (melamine formaldehyde) media have an abnormal rinse curve which rises very quickly to a peak and then slowly decreases with time. Accordingly, the blades produced according to the invention show an increasing negative, normalized flow potential, which is stabilized at a high equilibrium value, which indicates a high positive surface tension.

B. The same filter media were then challenged with contaminated liquid (0.109 µm Dow Diagnostics latex dispersion; 5.5 pH). The filtration performance and the normalized flow potential were plotted against one another in FIGS. 2 and 3. The known system (cationic melamine-formaldehyde colloid) ( FIG. 2) is compared with the medium according to the invention modified with polyamido-polyamine-pichlorohydrin ( FIG. 3). The negatively charged latex particles were essentially quantitatively removed by electrokinetic capture and absorption. The normalized flow potential drops linearly from a negative value through zero and then asymptotically approaches a positive value. When the flow potential approaches zero and passes through, the outflow turbidity decreases (breakthrough). This increase continues until the haze of the effluent approaches the inlet haze asymptotically, indicating that all of the latex is flowing through the filter medium.

The filter sheets according to the invention ( FIG. 3) maintained their filtration behavior significantly longer than the known filters ( FIG. 2).

Example 7

In this example another comparison was made between the invention Filter sheets and known filter sheets (melamine formaldehyde) in the untreated state as well as in the state of a Autoclave treatment and carried out in the state of hot water rinsing. The latter treatments are used to sterilize the Filter media made with biological fluids should be used.  

A. Filter sheets were made and tested in the same manner as in Example 6B, except that in addition to the untreated materials, additional filter sheets were made which were run under autoclave conditions (113 ° C under a pressure of 6.8 kg for a period of 1 hour) or hot water rinsing conditions (1 hour with water at 82 ° C and a flow rate of 225 ccm / min). The results of the comparison of the flow potentials are shown graphically in FIG. 4.

It can be seen that the known (with melamine formaldehyde) modified filter media their positive charge under the conditions vorloren used for sterilization. In contrast, those with cationic polyamido-polyaminepichlorohydrin held modified filter sheets not only their effectiveness at, but they also showed the sharp applied Conditions improved behavior.

B. The untreated and autoclave-treated filter media, manufactured in part A, were still comparative membrane protection tests subjected (inlet turbidity 50 NTU, 0.2 µm membrane, Flow rate 225 ml / min). The results obtained are summarized in Table VII.  

Table VII

From the above values it can be seen that the respective charge modified Systems competing in the untreated state responded to these tests, with failure due to membrane blockage in the case of the known system and by pillow blockage in the case of the system according to the invention. To the autoclave treatment was the membrane protection time known system significantly deteriorated.

"Biological liquids" are intended to refer to liquid systems be understood, which depend on living organisms conduct or should be supplied to this and in the usual Were handled and treated under sterilized conditions so that sterilized media is required for filtration are. Examples of this are isotonic solutions for I.M. or I.V. administration, solutions for administration per os and solutions for topical application, biological Waste or other body fluids that are filterable Bodies can contain as impurities, e.g. B. bacteria, Viruses or pyrogens, conveniently for examination or removal by immobilization or fixation the filter medium or trapped therein isolated or separated will.

Filter media according to the invention can be used alone or in combination used with other such media to Pharmaceutica, such as antibiotics, saline solutions, dextrose solutions, Vaccines, blood plasmas, serums, sterile water or eye wash fluids, Drinks such as liqueurs, gin, vodka, beer, scotch, Whiskey, sweet and dry wines, champagne or brandy, cosmetics, such as mouthwashes, perfumeries, shampoos, hair tonics, Face creams or shaving lotions, food products, such as wine vinegar, vegetable oils, extracts, syrups, fruit juices, Makeup water or cooking oils, chemicals such as antiseptics, Insecticides, photographic solutions, galvanic solutions, Cleaning compounds, solvents and lubricating oils and Treat to remove submicron particles, bacterial Remove impurities and colloidal veils dissolve.

Claims (11)

1. Sheet-shaped filter materials with increased trapping potential for electronegative submicron contaminants from aqueous liquids contaminated therewith, comprising a fine, particulate material and a self-binding matrix made of cellulose fibers, the surface of the particulate material and / or the cellulose fibers with a cationic resin in a sufficient amount is modified to give the surface of the filter material a positive zeta potential, characterized in that the beaten cellulose fibers have a Canadian standard freedom of less than 600 ml, the surface is modified with a cationic polyamido-polyamine-epichlorohydrin resin and the filter material consists of at least 50% by weight of the particulate material. 2. Filter material according to claim 1, characterized, that the resin is present in an amount of about 1 to 3% by weight is. 3. Filter material according to one of claims 1 to 2, characterized, that the fine, particulate material is at least 50% by weight Diatomaceous earth includes. 4. Filter material according to one of claims 1 to 3, characterized, that the fine, particulate material is a mixture of Diatomaceous earth and pearlite.   5. Filter material according to one of claims 1 to 4, characterized, that the fine, particulate material is average Particle dimension less than about 1 micron. 6. Process for the production of a sheet material one of claims 1 to 5, wherein one of a filter sheet a fine, particulate material and a cellulose pulp system forms as a self-binding matrix, the Surfaces of at least the particulate material or / and the cellulose pulp with a cationic resin in a sufficient amount is modified to the surface to give the filter medium a positive zeta potential, characterized, that one uses a beaten pulp as the pulp system, giving the system a Canadian standard freedom of less than 600 ml is awarded as a cationic resin Polyamido-polyamine-epichlorohydrin used and that one for Formation of the filter sheet at least 50% of the fine, particulate Material used. 7. The method according to claim 6, characterized, that the leaf is sanitized or sterilized. 8. The method according to claim 7, characterized, that the sheet is treated in an autoclave. 9. The method according to claim 7, characterized, that you rinse the sheet with hot water. 10. Method of removing electronegative submicron contaminants from aqueous liquids contaminated with it,  characterized, that one after the liquid through a filter material sheet passes claims 1 to 5. 11. The method according to claim 10, characterized, that one for removing submicron contaminants biological fluids the fluid through an aseptic made or sterilized filter sheet according to one of the Claims 1 to 5 passes through.