SE439116B - A filter material for purification of at least one essentially gaseous medium from at least one pre determined substance, filter as well as usage of the filter material - Google Patents

Abstract

A filter material for purification of at least one essentially gaseous medium like tobacco smoke, from at least one pre-determined substance comprised of a pre-determined amount of expandable, cross combined polymer carrier material in the form of open-pored, three dimensional branches with at least one, in that respect, essentially evenly divided substance that is able to essentially selectively remove the named substance from that medium passing through the filter.<IMAGE>

Description

78 209 30 7812935-0 mainly consists of oxygen, nitrogen, carbon monoxide and carbon dioxide.

When passing through a cigarette filter, the speed of the smoke is as large as about 35 cm / sec and the residence time of the smoke during which it can be brought into contact with the filter material, in a cigarette filter of normal length is therefore only of the order of 0.04 sec. The temperature of the filter reaching the cigarette smoke increases during the approach of the glow to the filter from approximately room temperature to 75 - 90 ° C.

Modern tobacco filter materials generally consist, for example, of gas-permeable organic material, mainly cellulose acetate fibers, or of activated carbon. Combinations of the above-mentioned materials were also widely used. When using conventional organic filter material, essentially only a mechanical separation of particles from the tobacco smoke takes place, since this material lacks a significant ability to remove harmful substances present in the gas phase.

Thus, cellulose ester fiber filters generally operate by trapping the portion of the particulate material in the smoke that passes between the fibers. The purpose of crumpling or similar deformation of the fibers in the filter is to increase the surface of the fibers which form contact surfaces with the smoke. Filters, consisting solely of such fibers, thus do not remove any major amount of undesirable components in the gas phase from the tobacco smoke.

Various substances have also been applied to the synthetic fibers used in filters, so that the fibers thereby more efficiently capture the particulate material.

But even these attempts have been less successful.

The use of activated carbon filter materials has brought advantages due to the ability of the activated carbon to adsorb harmful substances present in the gas phase. A disadvantage with activated carbon filters, however, is that they have low selectivity, ie indiscriminately adsorb from the gas phase also flavors and nicotine compounds, which the smoker actually intends to assimilate, which can lead to increased tobacco or cigarette consumption. The amount of activated carbon in, for example, a cigarette filter must therefore be limited, whereby, however, the filter's capacity in terms of adsorption of other, undesirable constituents in the smoke is reduced.

With an increase in the amount of activated carbon, however, it has sometimes been possible to remove a sufficient amount of certain harmful substances, but at the same time the suction resistance in the filter has also been increased, much thanks to the activated carbon-like pores and also carbon taste to the smoke phase.

For filtering tobacco smoke and other, at least substantially gaseous media, it has also been proposed to use filter constructions and filter materials, which as active agents contain organic substances, metal groups and / or organic salts. In this case, these agents have either themselves functioned as filter materials or have been bound to carrier materials, using activated carbon, various types of fiber, cellulose, cellulose derivative, etc. as carrier material. However, these filter constructions and materials have not been found either. be satisfactory, as great efficiency has been required during a short contact time between filter material and gaseous medium and the space available for accommodating the filter material has been limited, as is the case for, for example, cigarette filters.

A significant disadvantage with these hitherto similar filter devices / filter substances has thus been that their active surface has not been large enough for efficient filtration and at the same time appropriate storage / infiltration of active substances. Attempts have therefore been made to increase filtration efficiency. This has been done, among other things, by means of the use of so-called plasticides for bonding cellulose acetate fibers together or in some other way an attempt has been made to bind different fiber structure units to a network. These experiments have not proved successful because, at best, a macro-scale network system with a small three-dimensional area has been developed, ie mainly bonds between different fibers.

By, for example, treating cellulose / cellulose foam constituting an aqueous slurry of cellulose fibers and then treating this pulp with a water-resistant polymer film, a type of three-dimensional space network can be obtained, but this down-like product does not obtain predetermined three-dimensional holes. but these instead consist of a spectrum of different large holes and gap pockets which cannot be compared to built-up evenly sized pores, evenly distributed extending from surface to surface.

What is in fact needed, and which characterizes the invention as the subject of the patent application, are cross-links between polymerized molecules / molecular structures in order in this way to obtain a large efficient capillary network matrix, prepared in such a way that can determine in advance the three-dimensional structure of the capillary network matrix (its capillary system, etc.) by means of the degree of crosslinking.

The object of the present invention is to provide a new and advantageous filter material, whereby the above-mentioned inconveniences are substantially eliminated.

To that end, it is proposed according to the invention that a filter material for purifying a gaseous or substantially gaseous medium, in particular tobacco smoke, from at least one predetermined substance, in particular from cadmium compounds and / or carbon monoxide, comprises a a predetermined degree of swellable, crosslinked polymeric carrier material in the form of an open-pore three-dimensional branch with at least one substantially evenly distributed substance capable of substantially selectively removing said substance from the medium passing through the filter. The invention avoids the above-mentioned and other disadvantages and obtains an efficient, industrially easily manufacturable and inexpensive filter material, consisting of a porous base substance or skeletal substance with open through pores, in which skeletal substance on surprisingly simple and accurately reproducible can be extremely evenly distributed reactive or catalytically active active substances, such as active metal groups or compounds and / or organic compounds, and also substances, for example menthol or therapeutically active agents, to be added to it. by means of the filter material the medium is filtered. Thus, with the aid of this invention, one can also simultaneously add any desired substance, for example a flavoring or a flavoring substance to the smoke and with the aid of the invention balance and regulate the composition of the smoke also for taste sensational purposes.

The active substance (s) may be bound to the skeletal substance in any desired manner either before, during or after the crosslinking reaction, for which one or more crosslinking agents are used, for example bifunctional compounds such as epichlorohydrin, dichlorohydrin, diepoxybutane etc. or ionized radiation. The active substance or substances are suitably supplied in an amount of 2 to 50%, preferably 5 to 35%, based on the weight of the filter material, whereby they can be bound to the skeletal substance by chemical means, for example to anionic groups of the skeletal substance or the starting material thereof. or can be incorporated into the skeletal substance by infiltration. Combinations of these binding methods are also possible.

Furthermore, by selecting the starting material and degree of crosslinking, the pore size and total specificity can be set to the desired or optimal value in relation to the amount of active substance to be incorporated in the filter material and in relation to the conditions under which the filter material is to be used.

The crosslinked polymeric material may be a crosslinked hydroxyl group-containing polymer, preferably a crosslinked carbohydrate polymer, with a crosslinked polyhexose or a crosslinked polyhexose derivative being presently preferred. Said polyhexose or polyhexose derivatives may then consist of, respectively, derived from naturally occurring or synthetic carbohydrate polymer, such as cellulose, starch or inulin or dextran or mixtures thereof. The metals most particularly relevant to the filter material according to the invention consist of Ca, Mg, Ba, Fe, Al, Cu and the transition metals, in particular the transition metals Ti, V, Cr, Mn, Fe, Co, Ni, Mo and Pd, wherein metals or metals included in the filter material are selected on the basis of the selective properties especially desired in the filtration process in question. In this case, such metals or metal compounds can be selected which exert such a catalytic effect on specific harmful compounds in the medium filtered by the filter material that they are degraded or combined into less harmful or harmless compounds. Among such harmful compounds, which occur in tobacco smoke, may be mentioned carbon monoxide and hydrogen cyanide, as well as carcinogenic substances, such as phenol, catechol, resorcinol and benzpyrene.

A filter material according to the invention, which is particularly suitable for purifying essentially gaseous media, in particular tobacco smoke, from cadmium-containing compounds, comprises as active substance at least one calcium compound, suitably in the form of free inorganic calcium salt, although calcium may also be chemically bound to anionic groups , in particular carboxyl, sulfonic acid or phosphoric acid groups, in the skeletal polymer consisting of crosslinked polymer. The amount of Ca in the filter material can then advantageously amount to 2.5 - 25 th. A filter material according to the invention, which is capable of removing carbon monoxide from substantially gaseous media, especially tobacco smoke, advantageously comprises iron and / or copper in oxidized form or chloride form, which causes an oxidation of the carbon monoxide in the filter material flowing through the medium to carbon dioxide.

Advantageously, a filter material intended for tobacco smoke according to the invention may contain both calcium and iron and / or copper compounds, wherein the content of iron and / or copper should exceed one tenth of the calcium content.

With particular advantage, the filter material may be in the form of particles, primarily round grains or granules, for example may be in the form of spheres or cylinders with a transverse dimension of 0.005 - 3 mm, whereby the production of a filter material consisting of or the filter material containing filters with the desired, predeterminable flow resistance can be facilitated by selecting granule shape and size.

The filter material according to the invention can be used in combination or mixing with others, such as filter materials commonly used or useful materials. For example, it may advantageously be present in combination or mixing with particles or granules of a solely of crosslinked polymeric, porous material and / or particles or granules of activated carbon, suitably activated carbon obtained by pyrolysis and activation of an active substance containing filter material described above. .

The above-mentioned additives can be used to supplement the properties of the filter material, for example for setting the total adsorption capacity of the filter material and hydrophilic resp. hydrophobic properties. The latter properties can be influenced or adjusted also by choosing, among other things, the composition of the skeletal substance.

The main purpose of this filter or filter system according to the invention, which is suitable for the treatment of gaseous media and especially for the treatment of aerosols, especially within the limited volume available, for example, in a cigarette filter, is the following: 1. To remove harmful substances from the smoke 2. To remove decisive amounts of tar-like constituents from the smoke. 3. To remove predetermined amounts of alkaloids from the smoke. 4. To remove irritating substances from the gas phase of the smoke. 5. To maintain a satisfactory amount of flavors and aromas in the smoke and even achieve an improvement in the taste quality of the smoke. 78 15935-0 The main objects of the invention are achieved as a consequence of the following: The tar-like and particulate components are removed from the smoke by providing a large and suitable surface against which these components can abut. Existing filter constructions hitherto have not really been adequate in this respect while maintaining adequate suction resistance. Although most of the activated carbon filter constructions have had a sufficiently large felting area per se, since a large number of the pore particles of the carbon particles do not lead from surface to surface as would be desirable, but form actual appendixes or blind bags, part of the filtration surface becomes relatively inactive. .

With the filter material according to the invention, some completely surprising positive effects are achieved thanks to the fact that the carrier material contains means for effecting adsorption and / or absorption as well as removal of some irritating gaseous substances. The filter may contain the surfactant which contributes to the removal of toxic substances from the smoke.

Alkaloids and other components can be removed by suitable chemical action due to the presence of filter substances which are chemically combined therewith, whereby compounds are formed which are retained in the filter structure. As has been particularly suitable, it has been found that surface particles are treated with a suitable surface membrane substance, for example with cellulose acetate or the like.

Special selective properties can also be achieved in that a certain proportion of the particles or granules of the filter material or of said filter material additives are coated with a semipermeable layer of organic material, for example a layer of cellulose acetate.

It is known that the irritating effect on mucous membranes in connection with cigarette smoking is due at least in part to the presence in the gas phase of such compounds as aldehydes, sulfides, hydrogen cyanide, etc. The filter according to the invention removes significant amounts of these compounds. Phenols and acidic materials, which are known to be present in tobacco smoke and are reasonably believed to be harmful, are also removed in significant amounts.

The filter according to the invention comprises an extensive means for physical and chemical treatment of the flux of smoke, including pH regulation by removal of acidic components and fixation or binding of hazardous substances.

Crucial in this context is thus that this invention allows large variations in the concentration and proportions of active substances among themselves in the filter matrix.

The filter material according to the invention is further described in the following in the form of examples of the preparation thereof.

EXAMPLE 1 A filter material having excellent ability to remove cadmium from tobacco smoke could be prepared as follows: 100 g of dried crosslinked chromatographic gel having a grain size in the dry state in the range 0.5 - 0.75 mm and having a maximum swelling degree of 5 ml / gram was slurried by gentle stirring in 700 ml of distilled water at a temperature of 30 ° C, after which the gel was left to stand for a period of 5 hours. Then excess water (approx. 200 ml) was decanted and a 10% calcium chloride solution corresponding to the decanted amount of water was added. The gel with added calcium chloride solution was gently stirred for 2 hours and then allowed to stand for 1 hour to settle. excess of the added solution was decanted, after which the sedimented gel particles were filtered and dried, first at a temperature of 50 ° C for 24 hours, then at a temperature of 75 ° C for 10 hours and finally at a temperature of 85 ° C for a further 10 hours. 10 hours. The gel granules were then fed to a Büchner funnel and finally dried under reduced pressure at a temperature of 4000 for 1 hour. It could be stated that the grain shape was substantially unchanged, while swelling tests showed that the swelling ability had dropped from the original 5 ml / gram to about 2 ml / gram. Further examples of embodiments of the invention are given below.

According to a special embodiment of the invention, the filtration / flow properties of the new filter substance can be further increased if necessary by, for example, adding or infiltrating the matrix preparation or the finished granules with, for example, (NH 4) 2 CO 3 in aqueous solution in a suitable concentration and further. during the manufacturing process (NH4) removes 2CO3, NH4HCO3 with eg regulated heat treatment. In this process, NH3, H2O and CO2 are removed as gas from the grains, forming very porous and prickly grains which have surprisingly good gas permeability while maintaining effective filtration ability. You can also use other salts and compounds such as ammonium carbamate, NH 2 COONH 4, ammonium phosphate, (NH 4) H 2 PO 4. experiments described as well as the selection of suitable easily gasifiable sub- With the help of the type of infiltration substituents, filter grains with a large and predetermined internal variable space structure can be obtained. The following examples illustrate one embodiment of the invention.

According to a special embodiment of the invention, the filter substance is also characterized in that it consists of a crosslinked polymer constituting carrier with low suction resistance and a large and effective filtration surface for catalytically active redox groups, i.e. reduction oxidation systems. For example, iron and copper compounds are used as catalytically reducing oxidation systems. This embodiment is described in more detail in the following examples.

According to a particular embodiment of the invention, it has furthermore proved expedient with such an embodiment of the new gas filter that a certain number of sulfhydryl groups are introduced into it in advance in the crosslinked polymeric porous material, a polymeric material which may, for example, be based on starch, cellulose, dextrans and / or their hydroxylalkylated, esterified or etherified derivatives. This embodiment is described in more detail in the following examples. According to a particularly suitable embodiment of the invention - which has shown surprisingly good filtration effect - this filter substance is substituted, for example, by 2 hydroxyalkyl groups, whereby a filter substance with good general filtration properties is obtained. low suction resistance and more lipophilic character. This embodiment is described in the following examples.

According to a suitable embodiment of the invention, infiltrated into its filter substance, which is formed into grains against an average grain size between 50 - 500/1, preferably about 100 - 300 ß the aqueous solution of the phosphate at a temperature of 20 ° C and thereafter, by slurrying up the grains in trisodium ortho- dry and apply the grains to smokers.

With the help of this embodiment, surprisingly good results have been obtained with regard to the removal of the acid and phenol components of the smoke. By being able to accurately guarantee and regulate the content of the active component in the crosslinked material in advance, in which the active component is evenly distributed, filtration effects have been obtained which have hitherto been impossible to achieve in practice. The following examples describe in more detail these forms of application, the active substances of which are alkali metal compounds and alkaline earth compounds.

According to a particularly suitable embodiment of the invention, the crosslinked filter substance is substituted with, for example, a flavoring substance or some other desirable additive, for example into an inclusion complex, which comprises a carrier group and / or carrier compound and / or flavoring substance and from which added flavoring substance is released during smoking. when the tobacco smoke passes through the filter during smoking. This embodiment is described in more detail in the following examples.

The particulate filter material according to the invention suitably has a particle size which is predominantly about 10 - 800 / J and preferably predominantly between about 50 - 400 fl from 50 and 300 fl gives the best results, but variations. It has been found that a particle size between 12 may be desirable depending on proportions between possible other components, such as, for example, cellulose acetate fiber type components, carbon filter material and so on. In some filter constructions, grain particles from 0.1 mm - 2 mm size have proved to be expedient, among other things. Then closer to the example below.

The modifiable support matrix of the invention consists of a crosslinked polymeric support material in the form of a pre-adjustable swellable matrix forming a pre-adjustable dimensioned evenly distributed open-pore, from surface to surface, continuous capillary pore system in a three-dimensional branching material, support matrix , the swellability of which varies, for example, between 2 - 50 ml per gram of dry filter mass, preferably less than 4 ml of maximum swollen filter volume per gram of dry filter mass, used with at least one substance evenly evenly distributed therein for filtering gaseous media.

The invention can be modified in many further ways in addition to the examples given within the scope of the appended claims.

For example, the filter material can be provided with additives for setting the desired pH value on the medium passing through it during the filtration.

Crucial in this context is thus that this invention allows great variation, especially with regard to the concentration and proportion of active substances among themselves in the filter material.

Claims (8)

A filter material for purifying an at least substantially gaseous medium from at least one predetermined substance, characterized in that it comprises a to a predetermined degree of swellable, crosslinked polymeric carrier. material 1 in the form of an open-pore three-dimensional branch with at least one substance evenly evenly distributed therein, capable of substantially selectively removing said substance from the medium passing through the filter. Filter material according to claim 1, characterized in that the crosslinked polymeric carrier material is a crosslinked carbohydrate polymer, preferably a crosslinked polyhexose or a crosslinked polyhexose derivative. Filter material according to claim 2, characterized in that said polyhexose or polyhexose derivative consists of respective derivatives of naturally occurring or synthetic carbohydrate polymer, such as cellulose, starch or inulin or dextran or mixtures thereof. Filter material according to one of Claims 1 to 3, characterized in that the carrier material is swellable in a liquid, which is also present in liquid or vapor form in the medium to be filtered by means of the filter material. l Filter material according to any one of claims 1 to 4, characterized in that said substance comprises at least one metal from the group Ca, Mg, Ba, Al, Cu, transition metals and alkali metals. IN Filter material according to any one of claims 1 to 5, in particular for purifying a substantially gaseous medium from cadmium-containing compounds, characterized in that said substance comprises at least one calcium compound, suitably in the form of free inorganic calcium salt. 10 Sat 20 25 30 7812935-o, “J. Filter material according to any one of claims 1 to 6, characterized in that said substance comprises iron and / or copper in catalytically active groups in a redox system. Filter material according to any one of claims 1 to 7, characterized in that it is in the form of discrete or interconnected particles or granules, the shape of which is predetermined and the pores of which are evenly distributed in and extend from the surface. to surface through the particle resp. granules. å Filter material according to one of Claims 1 to 10, characterized in that it is present in admixture with particles or granules of a crosslinked polymeric, porous material only. I lO. Filter material according to any one of claims 1 to 9, characterized in that it is present in admixture with particles or granules of activated carbon, suitably activated carbon obtained by pyrolysis and activation of material according to any one of claims 1 to 8. any of claims 1 - 10, know - that at least a certain proportion of the particles ll. t e c k n a t or the granules are coated with a semipermeable layer of organic material, for example a layer of cellulose acetate. Filter, -especially for filtering tobacco smoke, characterized in that it contains filter material according to any one of claims l - ll. IN Use of filter material according to any one of claims 1 to 11 for filtering at least substantially gaseous media, in particular tobacco smoke.