Retention capacity of cigarette filters
United States Patent Albein et all.  
 [451 Apr; 22, 1975 RETENTION CAPACITY OF CIGARETTE FILTERS Inventors: Klaus Albein, Denzlingen; Dieter Imbery, Mundingen; I-Ianspeter Oesterle, Waldkirch. all of Germany Deutsche Rhodiaceta AG, Freiburg im Breisgau, Germany Filed: May 31, 1973 Appl. No: 365,587  
 Assignee:  
 Foreign Application Priority Data June 5, I972 Germany 222729l US. Cl. 131/266 Int. Cl. A24f 7/04 Field of Search 131/266, 267, 109  
 References Cited UNITED STATES PATENTS 4/1967 Berger ct al. l3l/266 FOREIGN PATENTS OR APPLICATIONS 758,429 10/1956 United Kingdom l3l/l0.9 952.978 1956 Gennany 423/625 897,843 1953 Germany 423/625 Primary E.tanzinrRobert W. Michell Assistant Examiner-V. A. Millin Attorney, Agent, or Firm-Bucknam and Archer 4 Claims, N0 Drawings RETENTION CAPACITY OF CIGARETTE FILTERS This invention relates to filters for cigarettes and more specifically to filters of superior retention capacity for nicotine, tars and other chemicals present in tobacco smoke.  
  It has long been known that tars, nicotine and other specific chemical substances present in cigarette smoke can be retained in cigarette filters consisting of crimped fibers of cellulose 2 /2 acetate.  
  It has also been alleged that the retention capacity of such filters can be improved by incorporation into the filters adsorbent substances such as mainly activated carbon, but also silicon dioxide of high specific surface, also aluminum oxide and aluminum hydroxide, that is substances likewise of high specific surface. The aluminum hydroxides used have been mainly amorphous material or mixtures of amorphous material and alpha hydroxide (bayerite), but mixtures of amorphous material and diaspore or boehmite or the gamma modification (hydrargillite), have also been used. These mixtures have been classified generally as aluminum hydroxide, although their chemical composition varies between Al(OH or, expressed in another form, the composition may vary from AI O X 3H O, to A1 X H O. It has been solely the result of the respective manufacturing process, for instance stirring out in the Bayer process, whether one or another mixture is present. Moreover, no information has ever been given about the crystallinity of these substances, nor has any special significance even been attributed to the crystallinity of cific surface comparable to the other kndwn retention improvers, surprisingly, it exhibits, clue to its high proportion of monoclinic pseudohexagonal crystalline platelets, such a high retention -improving capacity that it would never have been expected on the basis of its specific surface. Surprisingly it has also been found that this material exhibits particularly good retention capacity for acidic as well as basic substances due to its amphoteric character. This was by no means to be expected, because with aluminum oxide adjusted to have neutral properties, the adsorption of acid substances, for example phenol, is considerably inferior, despite the high specific surface. Thus, for example, the neutral N 0 Woelm used for chromatography, exhibits at a specific surface of 78 m g a phenol retention of 71%, while the material used in the present invention, with a specific surface of 6 8 m g, exhibits a phenol retention of 79%.  
  As is evident from Table l, the retention of the aluminum oxide trihydrate hydrargillite used in the present invention for tars, nicotine and phenols, is a function of the specific surface only to a minor extent, but is dependent, to a much greater extent, on the degree of crystallinity.  
  The data in Table 2 show that the substances with high specific surface are not particularly good adsorbers for tars, nicotine and phenol present in cigarette smoke. This is contrary to the common belief. As is clearly evident from the water adsorption, however, these substances are in themselves, in accordance with their specific surface, good adsorbers in the percolation process of chemical substances, as is generally known from the results of column chromatography with such substances. It is therefore evident, from Table l and 2 without doubt, that the crystallinity, namely the monoclinic-pseudohexagonal platelet form, is responsible in major degree for the adsorption capacity of the aluminum oxide trihydrate used in the present invention. T,50  
 TABLE 2 Titer of a single fiber: Retention 2.l denier y=cross section of the single fiber Specific surface H O Total titer of the filter tow of powder in adsorption of crimped fibers of cellulose mlg (BET Wt. of 2,5 acetate 42,000 denier Support Nicotine Tar Phenol meth.) powder Comparison 0 36 37 60 Hydrargillite 3.8 55 57 79 7 0.6 more than 90% crystalline Al O 3.8 46 7] 78 4.6 neutral Al 0 3.8 48 49 72 98 3.2 acid Al O 3.8 45 47 71 l02 4.0 alkaline A1 0 X 3.8 47 74 260 12.4 A H O I What is claimed is:  
  1. A filter for cigarettes which comprises cellulose acetate fibers powdered with aluminum oxide trihydrate hydrargillite of specific surface 4 15 m g, comprising more than crystalline monoclinicpseudohexagonal platelets.  
 2. A filter for cigarettes according to claim 1 which comprises a plug of cellulose 2% acetate as the support material.  
  3. The method of adsorbing nicotine, tars and phenol line monoclinic-pseudohexagonal platelets. present in the smokefrom cigarettes, which comprises 4. The method according to claim 3 wherein said filproviding the cigarettes with filters comprising alumiter comprises cellulose 2 /2 acetate as the support.  
 num oxide trihydrate which is more than 80% crystal- UNITED STATES PATENT OFFICE I CERTIFICATE OF CQRRECTION Patent 2:0. ,878,854 Da d April 22, l75  
 Inventor) Klaus Alfoien, Denzlinger Qt 511 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 ,1. The name of the first inventor is;  
 Klaus Albien. This name has been incorrectly spelled in two instances, at page 1, left column, line 2 and line 5.  
  3. Table l, which is page 5 of the application, has been omitted. A copy of Table l is attached hereto.  
 Signed and Scaled this twenty-third D ay Of September 1975 [SEAL] v Arrest:  
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