Abstract:
The invention relates to cigarette paper ( 1 ) providing self-extinguishing properties to a cigarette made therefrom, wherein the cigarette paper comprises at least one discrete region ( 2 ) that is perforated and comprises a permeability to air that is greater than the permeability to air outside of the perforated region. The perforated region is preferably present in a finished filter cigarette in the vicinity of the filter ( 5 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a cigarette paper that provides a cigarette manufactured therefrom with self-extinguishing properties and has at least one discrete perforated area. 
       BACKGROUND ART 
       [0002]    Due to legal regulations regarding the self-extinguishment of cigarettes, there is a need within the cigarette industry to provide cigarettes which ensure this self-extinguishment. Smoldering cigarettes left unattended are thus to be prevented from igniting furniture, beds or other home textiles. It is thus sought to produce cigarettes which have a reduced tendency to ignite other materials if the smoldering cigarette comes into contact with these materials. 
         [0003]    A test to determine the ignition tendency of cigarettes is described in ASTM E2187-04b. The test consists of placing a smoldering cigarette on a substrate consisting of 10 layers of a filter paper. The test is performed on 40 cigarettes and the percentage of the cigarettes which self-extinguish on the substrate before the glowing cone reaches the cigarette filter is determined. 
         [0004]    Within the scope of the invention, the self-extinguishing property can be understood for example to mean that at least the majority of the cigarettes tested according to ASTM E2187-04bfulfill the aforesaid criterion, that is to say the percentage is above 50%. 
         [0005]    A typical cigarette consists of tobacco, which is enwrapped by a cigarette paper and together therewith forms a typically cylindrical tobacco rod. The tobacco rod is usually adjoined by the filter, which consists typically of cellulose acetate fibers. The filter and the tobacco rod are enwrapped by the tipping paper. The tipping paper connects the filter to the tobacco rod. 
         [0006]    The self-extinguishment of a cigarette is in most cases achieved by corresponding design of the cigarette paper, that is to say of the paper enwrapping the tobacco. The cigarette paper is designed such that the diffusion constant is so low, at least in some areas of the cigarette paper, that insufficient oxygen to maintain the smoldering process reaches the glowing cone. As a consequence, the smoldering cigarette self-extinguishes. 
         [0007]    Typical cigarette papers consist of cellulose fibers, obtained from wood, flax or other materials. Mixtures of cellulose fibers of different origin can also be utilized. Cigarette papers have a typical basis weight of 10 g/m 2  to 60 g/m 2 , wherein the range of 20 g/m 2  to 35 g/m 2  is generally preferred. 
         [0008]    Cigarette papers often also comprise inorganic, mineral fillers, which are added to the paper in a mass fraction of 10% to 40%. A frequently used filler material is chalk (calcium carbonate), but other oxides and carbonates, such as magnesium oxide and aluminum hydroxide, can also be utilized. 
         [0009]    Cigarette paper can also be equipped with burning salts, which increase or reduce the burn rate of the paper. Sodium citrate and tripotassium citrate as well as mixtures thereof are used very frequently and are added to the paper in an amount of 0% to 5% of the paper mass. The group of burning salts of technical relevance additionally comprises citrates, malates, tartrates, acetates, nitrates, succinates, fumarates, gluconates, glycolates, lactates, oxalates, salicylates, α-hydroxycaprylates and phosphates, however. 
         [0010]    Cigarette papers are typically produced in rolls having a width between 0.3 m to 5 m and for example a recut into bobbins having a width, derived from the cigarette circumference, typically of 9 mm to 35 mm. 
         [0011]    One possible method to obtain self-extinguishment is to choose a cigarette paper of which the diffusion constant is already so low as a result of the paper production process that the cigarette extinguishes by itself. As a consequence however, the flow of air into the cigarette, that is to say the air permeability, is highly reduced due to a pressure difference. This has proven to be disadvantageous, since the smoke in the tobacco rod of the cigarette can only be diluted to a very small extent by the inflowing air during the smoking process and the cigarette smoke values for tar, nicotine and especially carbon monoxide are increased considerably. For example, the air permeability of such papers is less than 10 CORESTA Units (1 CORESTA Unit=1 CU=1 cm 3 /(cm 3  min kPa)), whereas typical cigarette papers, which are not self-extinguishing, have an air permeability between 20 CU and 300 CU. 
         [0012]    This disadvantage is eliminated by perforating the cigarette paper over its entire surface. Large holes compared to the natural pore structure are thus created in the paper and increase the air permeability, but cause little change to the diffusion constant of the paper. A diluting airflow into the cigarette during the smoking process is thus enabled and the cigarette smoke values are lowered without impairing the self-extinguishment of cigarettes manufactured from this paper in the above-mentioned test. 
         [0013]    This perforation can be carried out by different methods. For example, electrostatic perforation is used, in which the paper is transported through one or more spark discharge gaps, which burn holes into the paper. These holes typically have a diameter between 5 μm and 100 μm. Furthermore, laser perforation can be used, which generates slightly larger holes having a typical diameter between 50 μm and 500 p.m. A further example is mechanical perforation, in which needles or similar tools produce holes in the paper. These holes have a typical diameter between 100 μm and 2000 μm. 
         [0014]    The air permeability achieved with the perforation methods can be very high, for example up to more than 6000 CU, although the cigarette papers are generally perforated such that the air permeability after the perforation is between 50 CU and 500 CU. 
         [0015]    The perforation process can be performed after paper production on separate, dedicated perforation machines in roll or bobbin width. Of course, perforation on the cigarette machine is also possible, that is to say before, during or after the production of cigarettes or similar tobacco products from the cigarette paper on the cigarette machine, by any desired perforation method. 
         [0016]    Perforation of a cigarette paper over the entire surface thereof, said cigarette paper having low initial air permeability, has a significant disadvantage however in the smoker&#39;s acceptance of a cigarette manufactured from this paper. Because of the high air permeability, a lot of diluting air flows into the cigarette during the smoking process. The tobacco rod and therefore also the perforated cigarette paper are then consumed during the smoking process. The area through which the diluting air can flow into the cigarette is thus reduced with every puff taken by the smoker on the smoldering cigarette as well as during the smoldering process. This causes the smoker to receive an amount of tar, nicotine and carbon monoxide that increases with each puff as the tobacco rod becomes accordingly shorter. He thus feels that the cigarette is getting “stronger” with each puff. This sensation is undesirable. 
         [0017]    One possibility to compensate for this effect is not to choose constant air permeability over the length of the tobacco rod, but instead to provide a continuous air permeability profile along the cigarette shaft by perforation of the cigarette profile so that during the smoking process the increase in the cigarette smoke values with each puff is reduced to the greatest possible extent. A repeated continuous air permeability profile is therefore to be produced over the cigarette paper web by perforation. 
         [0018]    Although this method is theoretically possible, substantial technical problems arise. On the one hand the regulation of the perforation device for producing such a continuous profile is very demanding and the continuous measurement of the air permeability for the regulation can only be carried out imprecisely and is not feasible at high speed. The speed at which such profiles can be produced, if at all possible, is also accordingly low. 
         [0019]    On the other hand, the endless tobacco rod formed from the cigarette paper on the cigarette machine has to be cut precisely at the beginning and at the end of such a continuous air permeability profile, so that the air permeability profile is in the correct position on the finished cigarette. The beginning of the profile can only be detected very imprecisely however, if at all, due to the continuous progression of the air permeability. 
         [0020]    The object of the present invention is therefore to overcome the disadvantages of the prior art. 
       SUMMARY 
       [0021]    The object of the invention is achieved by a cigarette paper that provides a cigarette manufactured therefrom with self-extinguishing properties, wherein the cigarette paper comprises at least a first discrete area, which is perforated and has an air permeability greater than the air permeability beyond the first perforated area. 
         [0022]    In one embodiment of the cigarette paper, the air permeability within the first perforated area is constant over the entire perforated area. 
         [0023]    In one embodiment of the cigarette paper, the air permeability within the first perforated area is from 50 CU to 2000 CU, preferably from 100 CU to 1000 CU. 
         [0024]    In one embodiment of the cigarette paper, the width of the first perforated area is between 2 mm and 25 mm, preferably between 4 mm and 12 mm, more preferably between 5 mm and 9 mm. 
         [0025]    In one embodiment, the cigarette paper further comprises a short side A, which is intended to face a filter in the finished cigarette, wherein the first perforated area is located within the third of the cigarette paper length adjacent to the short side A, preferably within the quarter of the cigarette paper length adjacent to the short side A, and more preferably within the fifth of the cigarette paper length adjacent to the short side A. 
         [0026]    In one embodiment, the cigarette paper further comprises a short side A, which is intended to face a filter ( 6 ) in the finished cigarette, wherein the mean air permeability within the half or third of the cigarette paper length adjacent to the short side A is greater than the mean air permeability of the remaining part of the cigarette paper. 
         [0027]    In one embodiment, the cigarette paper comprises at least a second discrete area, which is perforated and separated from the first perforated area by a non-perforated area. In one embodiment of the cigarette paper, the second perforated area is further away from the first short side than the first perforated area. 
         [0028]    In one embodiment of the cigarette paper, the air permeability within the second perforated area is lower than the air permeability within the first perforated area. 
         [0029]    In one embodiment, the cigarette paper comprises at least one further discrete area, which is perforated and is separated from the first perforated area and the second perforated area by at least one non-perforated area. 
         [0030]    In one embodiment of the cigarette paper, the further perforated area is located further away from the short side A than the first perforated area and the second perforated area. 
         [0031]    In one embodiment of the cigarette paper, the air permeability within the further perforated area is lower than the air permeability within the first perforated area and the second perforated area. 
         [0032]    In one embodiment of the cigarette paper, the air permeability within the second perforated area and/or the further perforated area is constant over the respective entire perforated area. 
         [0033]    In one embodiment of the cigarette paper, the air permeability within the second perforated area and/or the further perforated area is from 50 CU to 2000 CU, preferably from 100 CU to 1000 CU. 
         [0034]    In one embodiment of the cigarette paper, the width of the second perforated area and/or of the further perforated area is between 2 mm to 25 mm, preferably between 4 mm and 12 mm, and more preferably between 5 mm and 9 mm. 
         [0035]    In one embodiment of the cigarette paper, the air permeability beyond a perforated area is less than 15 CU, preferably less than 10 CU. 
         [0036]    In one embodiment, the diffusivity of the cigarette paper (beyond and within a perforated area) or the mean diffusivity of the cigarette paper is less than 0.35 cm/s, preferably less than 0.25 cm/s, and more preferably less than 0.20 cm/s. 
         [0037]    In one embodiment, the cigarette paper comprises one or more mineral fillers, selected from the group consisting of carbonates and oxides, preferably from the group consisting of calcium carbonate, aluminum hydroxide and magnesium oxide, and the weight fraction of the one or more mineral fillers is particularly preferably from 10% to 40%. 
         [0038]    In one embodiment, the cigarette paper comprises one or more burning salts, selected from the group consisting of citrates, malates, tartrates, acetates, nitrates, succinates, fumarates, gluconates, glycolates, lactates, oxalates, salicylates, μ-hydroxycaprylates and phosphates, preferably selected from the group consisting of sodium-citrate and tripotassiumcitrate, and the content of the one or more burning salts is particularly preferably up to 5% by weight. 
         [0039]    In one embodiment, the cigarette paper has a basis weight of 10 g/m 2  to 60 g/m 2 , preferably of 20 g/m 2  to 35 g/m 2 . 
         [0040]    The object of the present invention is furthermore achieved by a filter cigarette, comprising a cigarette paper according to the present invention and furthermore comprising a filter and a tipping paper, wherein the distance between the tipping paper and the first perforated area is less than 10 mm, preferably less than 5 mm. 
         [0041]    The object of the present invention is furthermore achieved by a method for producing a cigarette paper according to the present invention, said method comprising a perforation step to create at least one perforated area by electrostatic perforation, laser perforation and/or mechanical perforation. 
         [0042]    In one embodiment of the method, the perforation step is carried out on a cigarette machine or alternatively on a device separate from the cigarette machine. 
         [0043]    The object of the present invention is furthermore achieved by the use of a paper (base paper) to produce a cigarette paper according to the present invention, preferably by a method according to the present invention, wherein the paper is provided in the form of a paper web having a width of 0.3 m to 5 m or alternatively of 9 mm to 35 mm. 
         [0044]    In one embodiment of the use, the air permeability of the base paper is less than 15 CU, preferably less than 10 CU. 
         [0045]    In one embodiment of the use, the base paper has a diffusivity of less than 0.35 cm/s, preferably of less than 0.25 cm/s, most preferably of less than 0.20 cm/s. 
         [0046]    In one embodiment of the use, the base paper comprises a mineral filler selected from the group consisting of carbonates and oxides, preferably selected from the group consisting of calcium carbonate, aluminum hydroxide and magnesium oxide, and the weight fraction of the one or more mineral fillers is particularly preferably from 10% to 40%. 
         [0047]    In one embodiment of the use, the base paper comprises one or more burning salts selected from the group consisting of citrates, malates, tartrates, acetates, nitrates, succinates, fumarates, gluconates, glycolates, lactates, oxalates, salicylates, α-hydroxycaprylates and phosphates, preferably selected from the group consisting of sodium citrate and tripotassium citrate, and the content of the one or more burning salts is particularly preferably up to 5% by weight. 
         [0048]    In one embodiment of the use, the base paper has a basis weight of 10 g/m 2  to 60 g/m 2 , preferably of 20 g/m 2  to 35 g/m 2 . 
         [0049]    The object of the present invention is furthermore achieved by use of a cigarette paper according to the present invention to produce a cigarette according the present invention. 
         [0050]    The present invention is based on the fact that it has surprisingly been found that it is not necessary to produce a continuous air permeability profile but that it is instead sufficient to perforate, over the cigarette paper, a discrete area with constant air permeability arranged close to the cigarette filter to achieve a comparably good effect. 
         [0051]    If one discrete perforated area close to the filter is insufficient, because the cigarette smoke values are still too high, further discrete areas with different air permeability can of course be produced by perforation and are then located accordingly closer to the end of the cigarette to be lit. Two such discrete perforated areas are often sufficient. 
         [0052]    If two or more discrete perforated areas—viewed in longitudinal direction of a cigarette to be produced from this paper—are arranged in succession, there is still preferably a tendency to increase the air permeability in the direction towards the mouthpiece, that is to say the end opposite the end to be lit. For example, the mean air permeability in the half or third of the cigarette paper closer to the mouthpiece is preferably higher than in the remaining part of the cigarette paper. 
         [0053]    Although the cause of this effect is not fully known, the following explanation may give an indication as to how it is achieved. During the smoking process, a negative pressure with respect to the ambient air is produced at the mouth end of the cigarette to cause an airflow through the cigarette and to transport the smoke through the filter to the smoker. This negative pressure decreases along the cigarette, so that approximately no pressure difference exists between the point directly in front of the glowing cone and the ambient air. 
         [0054]    A discrete perforated area located close to the cigarette filter is then situated in an area of the tobacco rod in which the pressure difference between the ambient air and the inside of the tobacco rod is high during the smoking process, that is to say a comparably large amount of air can flow into the tobacco rod. In areas closer to the glowing cone and further away from the mouth end, this pressure difference is smaller. These areas therefore contribute less to the air volume flowing into the cigarette and there is little influence on the cigarette smoke values during a puff if these areas are not perforated, that is to say have low air permeability. 
         [0055]    Since the perforated areas are discrete in nature and are clearly separated from the non-perforated areas, they can be clearly detected with optical sensors and it is not difficult to synchronize the paper feed and the cutting process on the cigarette machine such that the discrete areas on each cigarette are situated in the desired position close to the filter. 
         [0056]    Additionally, the air permeability in each of the perforated areas is constant. Therefore the perforation device just needs to be switched on and off at a frequency corresponding to the speed of the paper web. This is much easier than following a continuous air permeability profile. Also, perforation of discrete areas with different air permeability, which is constant within the region however, causes no difficulties since the perforation power of the perforation device can be adjusted easily each time said device is switched on or off. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0057]      FIG. 1  is a schematic illustration of a cigarette with an exemplary embodiment of the cigarette paper  1  according to the invention, comprising a first perforated area  2 , a second perforated area  3  and further perforated areas  4 . In this illustration, the cigarette paper  1  is partly unrolled from the tobacco column  7  of the cigarette. A filter  6  and tipping paper  5  partially enwrapping it as well as a short side A are also illustrated. 
           [0058]      FIG. 2  shows the specific perforation pattern of the cigarette paper to achieve the desired effect. This pattern results from the typical production process of machine-made cigarettes. The perforated areas of the wrapper, denoted by numbers, in  FIG. 2  correspond to those of  FIG. 1 . When producing cigarettes, an endless tobacco rod is first formed and is then cut along lines B into pieces measuring double the length of the tobacco rod of a cigarette. In a subsequent step of the cigarette production process, this double-length part of the tobacco rod is cut into two pieces along line C and separated in the axial direction so that a double-length filter tip can be placed in between. The entire double-length filter and sub-area of the tobacco rods adjacent to the filter are adhered and wrapped with a double-width tipping paper. After this, the double cigarette, connected by the double length filter, is cut into two cigarettes by a final cut through the middle of the filter. The pattern to be produced by perforation on the cigarette paper can also be adapted to other methods of cigarette production. 
       
    
    
     DETAILED DESCRIPTION 
     Example 1 
       [0059]    Starting point of the examples is a cigarette paper having the following specification: 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Basis weight 
                 28 g/m 2   
               
               
                   
                 Filler fraction 
                 21% of the paper mass 
               
               
                   
                 Filler 
                 chalk 
               
               
                   
                 Burning salt fraction 
                 1% 
               
               
                   
                 Burning salt 
                 potassium citrate 
               
               
                   
                 Air permeability 
                 6 CU 
               
               
                   
                 Diffusivity 
                 0.2 cm/s (for CO 2 ) 
               
               
                   
                   
               
             
          
         
       
     
         [0060]    The diffusivity is the diffusion constant of the paper [cm 2 /s] divided by the thickness of the paper [cm]. It is a transfer coefficient and describes the gas flow through the paper at a given concentration difference independently of the thickness of the paper. The diffusivity can be measured for example with a CO 2  diffusivity meter by Sodim. 
         [0061]    Of course, equally good results can also be achieved with other cigarette papers, for example with a different basis weight, different fillers and filler fraction, different burning salts and different burning salt fraction, as long as the air permeability thereof before perforation correspondingly low, that is to say typically less than approximately 15 CU, or the diffusion constant thereof is less than approximately 0.35 cm/s, to ensure the self-extinguishment of the cigarettes manufactured therefrom. 
         [0062]    This cigarette paper was then perforated electrostatically over its entire surface, so that an air permeability of 50 CU, 100 CU, 150 CU and 200 CU was achieved. 
         [0063]    Further paper samples were prepared from the same cigarette paper, in which discrete areas were perforated instead of the entire surface. These areas were designed as bands, so that the perforated area had a defined width but enclosed the cigarette entirely in the circumferential direction. The papers were equipped with one or two bands, although there is no reason why more bands cannot also be provided, however. The specifications of these papers are listed in Table 1: 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Specifications of the paper samples 
               
             
          
           
               
                   
                 Area 1 
                 Area 2 
                 Comparable air 
               
             
          
           
               
                   
                 Distance* 
                 Width 
                 Air Permeability 
                 Distance* 
                 Width 
                 Air Permeability 
                 permeability ** 
               
               
                 Sample 
                 [mm] 
                 [mm] 
                 [CU] 
                 [mm] 
                 [mm] 
                 [CU] 
                 [CU] 
               
               
                   
               
             
          
           
               
                 A 
                 1 
                 6 
                 160 
                   
                   
                   
                 50 
               
               
                 B 
                 1 
                 6 
                 650 
                   
                   
                   
                 200 
               
               
                 C 
                 1 
                 6 
                 120 
                 30 
                 6 
                 120 
                 50 
               
               
                 D 
                 1 
                 6 
                 240 
                 30 
                 6 
                 240 
                 100 
               
               
                 E 
                 1 
                 6 
                 370 
                 30 
                 6 
                 370 
                 150 
               
               
                 F 
                 1 
                 6 
                 500 
                 30 
                 6 
                 500 
                 200 
               
               
                 G 
                 3 
                 6 
                 160 
                   
                   
                   
                 50 
               
               
                 H 
                 5 
                 6 
                 160 
                   
                   
                   
                 50 
               
               
                 J 
                 1 
                 7 
                 140 
                   
                   
                   
                 50 
               
               
                 K 
                 1 
                 9 
                 110 
                   
                   
                   
                 50 
               
               
                 L 
                 1 
                 6 
                 130 
                 30 
                 6 
                 90 
                 50 
               
               
                 M 
                 1 
                 6 
                 410 
                 30 
                 6 
                 270 
                 150 
               
               
                 N 
                 1 
                 20 
                 90 
                   
                   
                   
                 50 
               
               
                   
               
               
                 *The distance is the gap from the front edge of the tipping paper to the beginning of the discrete perforated area. 
               
               
                 ** The comparable air permeability is the air permeability of the cigarette paper perforated over its entire surface that provides the same cigarette smoke values on the test cigarette as the cigarette paper perforated in discrete areas. 
               
             
          
         
       
     
         [0064]    Cigarettes with the following specifications were manufactured from all papers: 
         [0000]                                                                  Cigarette length   84   mm           Filter length   20   mm           Length of the tipping paper   24   mm           Length of the tobacco rod   64   mm           Length of visible tobacco rod   60   mm           Diameter   7.8   mm           Tobacco weight   650   mg                Tobacco Blend   American Blend           Degree of filter ventilation   15%                        
These specifications are understood to be merely exemplary, and the invention can of course be applied to any other cigarette design with comparable success.
 
         [0065]    The ignition propensity of all cigarette samples was first tested according to ASTM E2187-04b. In accordance with ASTM E2187-04b, 40 cigarettes were tested per cigarette paper and 90% or more of the tested cigarettes of all samples self-extinguished, wherein no statistically significant differences between the samples could be found. 
         [0066]    The cigarettes were further smoked by the method presented in DIN ISO 4387. With this method, a volume of 35 cm 3  in 2 seconds is drawn at the mouth end of the smoldering cigarette every minute. This drawing of 35 cm 3  is called a puff. The procedure is repeated until the cigarette is smoked below a minimum length defined by the standard. The smoke is drawn through a glass fiber filter, which is chemically analyzed later on. From this, the nicotine-free dry condensate (“tar”) and the nicotine are determined and are usually given in units of mg per cigarette. 
         [0067]    The machine smoking was carried out on a smoking machine of the Borgwaldt RM20 type, which was modified however such that every puff of the cigarette was passed through a different glass fiber filter, so that the cigarette smoke values of each puff could be determined after analysis. 20 cigarettes from each paper sample were machine-smoked in this way. 
         [0068]    Since the cigarette is lit at the first puff, the first puff is an exception with respect to its cigarette smoke values and will be excluded from the considerations. It is also possible during the standardized, machine smoking that the last puff cannot be fully carried out, because the cigarette falls below the prescribed minimum length during the puff. Such a puff (“fractional puff”) is recorded as a fraction of a whole puff. To simplify the presentation, the last puff is therefore also excluded from the considerations. 
         [0069]    Generally, there is a monotone increase of the cigarette smoke values from puff to puff. To describe the non-uniformity of the cigarette smoke values from puff to puff the ratio of the nicotine-free condensate (“tar”) between the penultimate puff and the second puff of the cigarette is calculated. This ratio is listed in Table 2. The higher this ratio, the stronger the cigarette smoke values increase from puff to puff and the more non-uniform is the puff profile. 
         [0000]                                                        TABLE 2                   Non-uniformity of the cigarette smoke values                Penultimate Ratio of Tar:       Reduction       Sample   second puff   Comparative Value***   |%|                    A   1.23   1.42   −13.4       B   1.65   2.08   −20.7       C   1.25   1.42   −12.0       D   1.36   1.55   −12.2       E   1.53   1.73   −11.6       F   1.72   2.08   −17.3       G   1.30   1.42   −8.4       H   1.35   1.42   −4.9       J   1.22   1.42   −14.1       K   1.25   1.42   −12.0       L   1.23   1.42   −13.4       M   1.47   1.73   −15.0       N   1.31   1.42   −7.7               ***The comparative value is the ratio of tar between the penultimate and the second puff for a cigarette with a cigarette paper perforated over the entire surface and with the air permeability given in Table 1.            
All samples show an improvement in the uniformity of the puff profile, wherein typically a reduction of the observed tar ratios of approximately 5% to 20% is achieved.
 
       Example 2 
     Samples A and B 
       [0070]    At first it can be seen that the concentration of the perforation in discrete areas close to the filter allows a reduction in the air permeability, since the perforated areas are now located in a region in which the difference between the ambient air pressure and the pressure within the tobacco rod during the smoking process is higher than in regions located closer to the glowing cone. The paper, which is perforated over the entire surface, has an air permeability of 50 CU over a length of 60 mm, whilst sample A is perforated only over a tenth of this length, namely 6 mm. It would be expected that, to get the same airflow into the cigarette, the air permeability needs to be 10 times as high, that is to say 500 CU. Surprisingly, it can be seen that just 160 CU are sufficient to achieve the same cigarette smoke values. Regarding the uniformity of the puff profile, an improvement in the tar ratio of approximately 13% from 1.42 to 1.23 is achieved. 
         [0071]    At higher air permeabilities (sample B), this effect becomes even more pronounced. In this case too, an air permeability of 650 CU instead of a nominal value of 200×60/6=2000 CU is sufficient. 
       Example 3 
     Samples C-F 
       [0072]    If the cigarette paper is perforated in two discrete areas instead of one discrete area, then cigarette smoke values comparable to a cigarette with a cigarette paper perforated over the entire surface can be achieved with even lower air permeability. This is obvious, since the perforated surface area is now twice as large compared to just one perforated area. Theoretically, the air permeability of sample C could be chosen to be half as much, that is to say 80 CU. However, the second perforated area is located further away from the mouth end and therefore in a region in which the pressure difference is no longer as high. Moreover, it is consumed during the smoking process. Its contribution is therefore smaller and hence both areas of sample C needed to be perforated with 120 CU to obtain cigarette smoke values comparable to those of a cigarette with a 50 CU paper perforated over the entire surface. These considerations apply accordingly at the higher air permeabilities of samples D, E and F. 
         [0073]    With regard to the ratio of the tar values, a distinct improvement of approximately 10% to 20% compared to perforation over the entire surface can be seen, though this improvement is not as distinct as with just one perforated area. 
         [0074]    Due to the lower air permeability, it is possible to carry out perforation at lower power and higher speed, and therefore this advantage has to be weighed against the reduced improvement in the uniformity of the puff profile. 
       Example 4 
     Samples A, G and H 
       [0075]    The samples A, G and H differ solely in the distance of the perforated area from the front edge of the tipping paper. For sample A it is 1 mm, for sample G it is 3 mm, and finally for sample H it is 5 mm. It was found that an improvement in the uniformity of the puff profile was achieved compared to the paper perforated over the entire surface, but the extent of this improvement decreases quickly if the first perforated area is too far away from the front edge of the tipping paper. More specifically, the improvement decreases from 13% to approximately 8% at 3 mm to just 5% at 5 mm distance. It is therefore preferred to keep this distance at least smaller than 10 mm and preferably smaller than 5 mm. 
       Example 5 
     Samples A, J, K and N and B 
       [0076]    The samples A, J, K and N differ firstly in the width of the perforated area. The air permeability was also adjusted accordingly to obtain comparable cigarette smoke values. Sample A, with a width of 6 mm, has 160 CU, sample J, with a width of 7 mm, has approximately 140 CU, and sample K, with a width of 9 mm, has just 110 CU, and sample N, with a width of 20 mm, lastly has just 80 CU. 
         [0077]    An improvement in the uniformity of the puff profile from 7% to 14% could be achieved. This shows that the influence of the width is rather small. It may be assumed that the perforated area may also have a width of more than 20 mm if an improvement is to be achieved. Based on this data, the maximum width of the perforated area will be chosen to be approximately 25 mm. 
         [0078]    The minimum width is limited by the maximum air permeability that can be achieved by perforation devices in such a narrow region without impairing the tensile strength of the paper too much. Considering sample B, with 650 CU over a width of 6 mm as starting point, then a 2 mm wide area must be perforated nominally to 1950 CU to get the same result. This is already a very high air permeability that is difficult to achieve in such a small area, which is why the width of the perforated area is to be between 2 mm and 25 mm, preferably between 4 mm and 12 mm, and more preferably between 5 mm and 9 mm. 
       Example 6 
     Sample A, E, L and M 
       [0079]    Finally, samples L and M show that the air permeability of the two perforated areas need not be the same. Based on the previous results, it seems to be advantageous to perforate more intensely the area located closer to the mouth end. For samples L and M, the air permeability of the first area is approximately 150% of the air permeability of the second area. 
         [0080]    At approximately 13% (sample L), the achieved improvement in the ratio of the tar values is comparable to a paper with a perforated area from sample A. 
         [0081]    At higher air permeability however, as in samples E and M, it can be seen that, at −11.6%, the use of the same perforation level in both areas (sample E, 370 CU) provides a result worse than with the unequally perforated paper from sample M (410 CU/270 CU) with a −15% change in the tar ratio. 
         [0082]    In any case, it can be assumed from these results that it is not advantageous to perforate the second area more intensely than the first area. As far as it is technically expedient and reconcilable with the cigarette smoke values, it is sought to perforate the second area less intensely. 
         [0083]    Similarly, for a plurality of perforated areas, it is true that, viewed from the mouth end to the glowing cone, each area should be perforated less intensely than its predecessor. 
         [0084]    There is also no reason to provide the areas with different widths. Likewise, the position of the perforated areas can also be varied. 
         [0085]    On the whole, many further variations of this invention are conceivable and the examples here merely illustrate the principle of the invention and are not intended to be limiting.