Abstract:
This invention relates to a material for tobacco smoke filters. This material comprises cellulose fibers containing amino groups and is obtainable by reacting certain amino compounds with certain reactive cellulose derivatives. Preferably, the filter material of the present invention contains from 70 μmoles to 2 mmoles of amino groups per gram of filter material.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a material for tobacco smoke filters. This material comprises cellulose fibers containing amino groups and is obtainable by the process steps of the present invention as specified in the following description and patent claims. 
     It is an important advantage of the filter materials of the present invention that they exhibit improved selective retention capacity for gas phase constituents, better than that of the cellulose 2,5-acetates hitherto employed. 
     Furthermore, no transfer of the active groups into the main smoke occurs, since these active groups are chemically fixed to the cellulose fiber. Finally, the filter material of the invention can also be converted to filter sticks on commercial machinery. 
     SUMMARY OF THE INVENTION 
     The filter materials prepared according to the present invention are distinguished by improved selective retention capacity for gas phase constituents of tobacco smoke, for example hydrogen cyanide, nitric oxide and volatile aldehydes. 
     The reactive cellulose derivatives of the general formulae ##STR1## where R 1  is chlorine or amino and  C --O-- is a cellulose radical, ##STR2## where R 2  is hydrogen or chlorine, ##STR3## are obtained by reacting cellulose with reactants which are for the most part known from the chemistry of reactive dyes. For example, derivative I is obtained by reacting cellulose with dichloroaminotriazines or with trichlorotriazines and derivative II by a similar reaction with trichlorodiazines or tetrachlorodiazines. Derivative III is obtained by reacting cellulose with 2,3-dichloroquinoxalines, derivative IV by reaction with divinyl sulfone or with compounds which on alkaline fixing to the cellulose molecule are converted to such groups, and derivative VI by reaction with epichlorohydrin. Derivative V is formed on reacting cellulose with cyanogen bromide. 
     The reactive cellulose derivatives thus obtained are subsequently reacted with amino compounds such as ammonia, guanidine, amino acids having a ratio of amino groups to carboxyl groups of not less than 2:1, diamines of the general formula ##STR4## where n is 2-6 and R 3  and R 4  are each, independently of one another, hydrogen or alkyl groups having 1-4 carbon atoms or together form a cyclopentyl, cyclohexyl, pyrrol, imidazole, pyrrolidine, piperidine or morpholine ring, or polyamines of the general formula ##STR5## where p is 2-6 or polyethyleneimines of the formula 
     
         H.sub.2 N-(CH.sub.2 -CH.sub.2 -NH).sub.q -CH.sub.2 -CH.sub.2 -NH.sub.2 (IX) 
    
     where q is 1-6. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The filter materials of the present invention are prepared by converting the optionally partially acetylated cellulose material, by means of the above-mentioned activating reactants, to a reactive cellulose derivative intermediate of the above general formulae I-VI which serves as the starting compound for all the filter materials described below. Preferred activating reactants are cyanogen bromide, 2,4,6-trichlorotriazine (cyanuric chloride) and epichlorohydrin. 
     The reactive cellulose derivative intermediate thus obtained is reacted with ammonia or with various amines, aminoacids or guanidino derivatives, as illustrated above, to give the desired end products. Specific examples of aminoacids which are especially suitable for the preparation of the filter materials of the invention are arginine, histidine, tryptophane, α,γ-diaminobutyric acid, ornithine, citrulline and canavanine. 
     The polyamines of the general formula VIII, in particular, include histamine. 
     The filter materials thus obtained preferably contain the following basic groups: amino, ethylenediamino, hexamethylenediamino, polyethyleneimino, histidino, histamino, arginino and guanidino. 
     According to an advantageous embodiment of the invention, the starting material is a partially acetylated cellulose which contains an average of 0.5-1.5 acetyl groups per glucose unit. Preferably, the modified filter materials of the present invention contain from 70 μmoles to 2 mmoles of amino groups per gram of filter substance. 
     The invention is explained in more detail below in relation to preparation examples. The following examples of certain embodiments of the present invention are illustrative only and are not to be construed as limiting in any way. 
    
    
     EXAMPLE 1 
     10 grams of fibrous cellulose acetate (DS≈0.5) are shaken for 30 minutes with a 15% strength aqueous-alcoholic sodium hydroxide solution. The product is thoroughly squeezed out and is then shaken for a further hour with 18.5 grams of 2,4,6-trichlorotriazine in 200 ml of toluene. The reactive intermediate thus obtained is filtered off, washed with a small amount of ice-cold water and then shaken for 16 hours with 400 ml of 10% strength aqueous ammonia solution. The end product is thoroughly washed with 0.1 M NaHCO 3  solution and with water. The washed end product is then dried in vacuo over silica gel. 
     The active group equivalents are determined titrimetrically. 950 μ-equivalents of amino groups have been bonded per gram of filter material. 
     EXAMPLE 2 
     10 grams of fibrous cellulose acetate (DS≈1) are stirred for 15 minutes with 1,000 ml of a freshly prepared aqueous cyanogen bromide solution (25 mg of BrCN/ml) at room temperature, under constant pH conditions (pH 11). The intermediate is filtered off and washed thoroughly with 0.1 M aqueous NaHCO 3  solution, and the excess wash solution is pressed out. The intermediate is then stirred for 16 hours with a solution of 14 grams of diaminohexane in 400 ml of 0.1 M aqueous NaHCO 3  (T=4° C.). The end product is filtered off, washed with NaHCO 3  solution, then water and dried in vacuo over silica gel. 
     The filter material contains 580 μ-equivalents of amino groups per gram. 
     EXAMPLE 3 
     10 grams of fibrous cellulose acetate (DS≈0.5) are treated as described in Example 1, up to the step where the intermediate is isolated. Thereafter, the product obtained is shaken for 16 hours at room temperature with a solution of 10.5 grams of arginine in 400 ml of 0.1 M aqueous NaHCO 3 . The end product is filtered off, washed thoroughly with NaHCO 3  solution and water and dried in vacuo over silica gel. Titrimetric determination shows 1.3 μ-equivalents of active groups per gram of filter material. 
     SMOKING TEST 
     The filter materials of the present invention were tested in a smoking test. For this purpose, the filter materials were introduced into a 23 mm long chamber filter whose ends were closed with 7 mm thick cellulose acetate plugs. Similar tests with untreated starting material and with commercial cellulose acetate (DS 2.5) were used for comparison. The sample filters and the comparison filters were attached to 63 mm long commercial cigarette bodies. 
     All the samples were selected according to weight and draw resistance (115±5 mm water-column for the total cigarette, the draw resistance attributable to the filter being 55±3 mm water-column). 
     After conditioning, the cigarettes were smoked on an RM 20 CS smoking machine under the conditions of one draw per minute, 35 ml draw volume and 2 seconds draw duration. The following results were obtained: 
     
         ______________________________________       Hydrogen  Volatile Aldehydes                                Nitric       Cyanide   (determined as OxideSample      (μg)   acetaldehyde)(μg)                                (μg)______________________________________Cellulose acetate       251       716            302(comparison)Untreated starting       263       767            288materialSample 1    158       643            164Sample 2    183       640            186Sample 3    208       578            183Sample 4    169       553            167Sample 5    174       550            212______________________________________ Sample 1: diaminohexylcellulose acetate according to Example No. 2 Sample 2: diaminohexylcellulose acetate, prepared analogously to Examples No. 1 and 3 Sample 3: condensation product of cellulose acetate, cyanuric chloride an NH.sub.3, according to Example No. 1 Sample 4: argininocellulose acetate, according to Example No. 3 Sample 5: diaminoethylcellulose acetate, prepared analogously to Example No. 2 
    
     It follows from the table that in every case significant reductions in the gas phase constituents were obtained relative to commercial cellulose acetate and untreated comparison materials. 
     While the above is illustrated of what is now contemplated to be the best mode of carrying out the invention, the present invention is subject to modification without departing from the spirit and scope of the invention. Therefore, the invention is not restricted to the particular method and materials illustrated and described, but covers all modifications which may fall within the scope of the following claims. It is applicants&#39; intention in the following claims to cover such modifications and variations as fall within the true spirit and scope of the invention.