Abstract:
A wrapper for a smoking article which, when wrapped about a tobacco column, provides improved sidestream smoke reduction, improved ash formation, and acceptable mainstream smoke taste and sidestream smoke odor subjectives. These objectives are attained by forming a single cellulosic sheet containing a filler comprising basic magnesium carbonate and, where desired, a co-filler of calcium carbonate. In addition, the sheet may be treated with a burning chemical such as alkali metal salts of organic carboxylic acids, and compatible acids.

Description:
SUMMARY OF THE INVENTION 
     This invention relates to smoking articles such as cigarettes, cigars, and the like, and the wrapper for the tobacco column thereof that is fabricated into a cigarette or cigar with a suitable tobacco column, which provide an acceptable burn rate, produce light-colored, well-formed ash which clings tightly without premature flaking, have significantly reduced sidestream smoke generation compared to a conventional cigarette and deliver both mainstream and sidestream smoke with acceptable taste and aroma. These desirable properties are achieved when certain defined levels of basic magnesium carbonate, by itself, or in combination with calcium carbonate co-filler, are employed to produce a base cigarette paper or cigar wrapper and this paper is subjected to treatment with burning chemicals such as alkali metal carboxylic acid salts. 
     BACKGROUND OF THE INVENTION 
     The reduced-sidestream-smoke cigarette paper patents which describe magnesium oxide/magnesium hydroxide as paper fillers, which are assigned to Olin Corporation, Ecusta Corporation, or P. H. Glatfelter Company, and which define burning chemical types and levels are U.S. Pat. Nos. 4,231,377; 4,450,847; 4,881,557; and 4,915,118. These patents disclose alkali metal acetates, citrates, nitrates, carbonates, and tartarates as burning chemical types at levels in the sheet ranging from 0.5% to 8.0%. 
     The Kimberly-Clark patents dealing with reduced-sidestream-smoke cigarette paper are U.S. Pat. Nos. 4,461,311 and 4,805,644. These patents disclose the sodium and potassium salts of carbonic, formic, acetic, propionic, malic, lactic, glycolic, citric, tartaric, fumaric, oxalic, malonic, nitric and phosphoric acids at levels in the sheet up to 25% by weight. U.S. Pat. No. 4,805,644 dealing with reduced-sidestream-smoke cigarette paper discloses various paper fillers with at least about 20 M 2/  g superficial surface area, when incorporated in paper at 5% to 50% by weight, and results in a wrapper that provides reduced sidestream smoke. 
     U.S. Pat. No. 3,744,496, assigned to Olin Corporation, discloses a carbon-filled paper to wrap cigarettes and/or cigars preferably used as an inner liner with regular cigarette paper or cigar wrapper as an outer wrap. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It has been experimentally determined that by using basic magnesium carbonate as a filler in the furnish of the cellulosic-based paper by itself and in combination with calcium carbonate as a co-filler, provides an enhancement in sidestream smoke reduction compared to that of a conventional calcium carbonate filled cigarette paper or cigar wrapper, while maintaining acceptable ash quality, static burn rate, mainstream and sidestream taste and aroma. The truly novel finding of this invention is the reduced sidestream smoke obtained with a novel filler(s). 
     PARAMETERS OF THE INVENTION 
     Basis Weight: 25 to 100 g/M 2  (preferred--35 to 65 g/M 2 ) 
     Basic Magnesium Carbonate Content: 5% to 50% based on base weight of the paper (preferred 10% to 40%). 
     Calcium Carbonate Content: 0% to 40% (preferred 10% to 40%), based on the base weight of the paper. 
     Porosity: 3 to 25 Coresta (preferred--5 to 15 Coresta) 
     Basic Magnesium Carbonate Type: xMgCO 3 .yMg(OH) 2 .zH 2  O where x, y, and z are integers or fractions. 
     Burning Chemical: Alkali metal salts of organic carboxylic acids selected from a group consisting of citric, malic, lactic, glycolic, tartaric, fumaric, maleic, malonic, glutaric, adipic, acetic and succinic. 
     Addition Rate of Burning Chemical: 0.5% to 6% of the base weight of the paper. 
     Smoking Articles: Cigarettes, cigars and the like. 
     
                                           TABLE I__________________________________________________________________________Sidestream Reduction               Basic      Basis          CaCO.sub.3               Magnesium                  Static      Weight          Percent               Carbonate                     Porosity             Burn Rate                                                SSDR.sup.1Cigarette Paper      (g/M.sup.2)          (%)  (%)   Coresta                          Filler          (mg/min)                                                (mg/min)__________________________________________________________________________Control-Ecusta 12556      25.0          30.0  0.0  25   CaCO.sub.3      56.7  2.13Heavyweight +      45.0          20.0  0.0  9    CaCO.sub.3      50.7  1.461% K3 CitrateLSS-Basic MgCO.sub.3.sup.2      45.0          25.0 15.0  12.0 Martin Marietta BMC2                                          57.5  1.02LSS-Basic MgCO.sub.3.sup.2      45.0          25.0 15.0  17.4 Morton Thiokol Elastocarb                                          66.6  1.02                          HeavyLSS-Basic MgCO.sub.3.sup.2      45.0          25.0 15.0  16.9 Morton Thiokol Elastocarb                                          59.1  0.96                          LightLSS-Basic MgCO.sub.3.sup.2      45.0           0.0 30.0  11.2 Alfa Magnesium Carbonate                                          55.1c 1.06LSS-Basic MgCO.sub.3.sup.2      55.0           0.0 30.0  11.0 Alfa Magnesium Carbonate                                          61.6c 0.97LSS-Basic MgCO.sub.3.sup.2      65.0           0.0 30.0  11.2 Alfa Magnesium Carbonate                                          62.7c 0.85LSS-Basic MgCO.sub.3.sup.2      45.0           0.0 30.0  12.8 Aldrich Magnesium Carbonate                                          53.9  1.06                          BasicLSS-Basic MgCO.sub.3.sup.2      55.0           0.0 30.0  12.4 Aldrich Magnesium Carbonate                                          54.6  0.95                          BasicLSS-Basic MgCO.sub.3.sup.2      65.0           0.0 30.0  12.0 Aldrich Magnesium Carbonate                                          56.3  0.87                          BasicLSS-Basic MgCO.sub.3.sup.3      45.0          15.0 25.0   5.0 Martin Marietta BMC2                                          55.7  0.92LSS-Basic MgCO.sub.3.sup.2      45.0          15.0 25.0   7.0 Morton Thiokol Elastocarb                                          55.5  0.94                          LightLSS-Basic MgCO.sub.3.sup.2      45.0          15.0 25.0   9.4 Morton Thiokol Elastocarb                                          58.9  0.89                          HeavyLSS-Basic MgCO.sub.3.sup.4      45.0          15.0 25.0   5.0 Martin Marietta BMC2                                          58.0  0.87LSS-Basic MgCO.sub.3.sup.4      45.0           0.0 40.0   7.5 Martin Marietta BMC2                                          44.2  0.72LSS-Basic MgCO.sub.3.sup.2      45.0          15.0 25.0  12.4 Marine Magnesium Magcarb                                          64.1  0.89__________________________________________________________________________ .sup.1 SSDR = Sidestream Delivery Rate (mg/min) .sup.2 Burning Chemical Content  5.1% Potassium Acetate .sup.3 Burning Chemical Content  5.1% Potassium Acetate + 6% Sucrose .sup.4 Burning Chemical Content  5.6% Potassium Citrate + 2% Citric Acid 6% Sucrose 
    
     Comments on Table I 
     It can be concluded from Table I above that all of the basic magnesium carbonates of various compositions evaluated are effective in significantly reducing the sidestream delivery rate in combination with calcium carbonate as a co-filler, or as a filler by itself, in paper. Burn rate control depends upon buring chemical type and level, basis weight, sheet porosity, filler type and level, sheet density and basic magnesium carbonate type and level in paper. 
     
                       TABLE II______________________________________Ash PropertiesTest cigarettes - Commercial 100 mm &#34;LIGHTS&#34; brand withstandard paper removed and replaced with the experimentalreduced sidestream smoke cigarette paper.Cigarette Paper      Static Ash    Puffed Ash______________________________________Control.sup.1      Tight Shrinkage                    Tight Shrinkage      Light Grey    Light Grey      No Flake Fall Off                    No Flake Fall Off      Solid Sheath  Small Adhering Flakes45 g/M.sup.2,.sup.2      Some Shrinkage                    Tight ShrinkageBasic Magnesium      Light Grey    Light GreyCarbonate = 30%      Loose Flakes  Few Loose Flakes      Small Flakes  Small Flakes45 g/M.sup.2,.sup.3      Tight Shrinkage                    Tight ShrinkageBasic Magnesium      Light Grey    Light GreyCarbonate - 25%      Few Loose Flakes                    No Flake Fall OffCalcium    Small Flakes  Solid SheathCarbonate - 10%______________________________________ .sup.1 Ecusta 12556 cigarette paper: 30% Calcium Carbonate; 25 Coresta Porosity; 25 g/M.sup.2 ; 0.55 Citrate Burning Chemicals .sup.2 30% Alfa Basic Magnesium Carbonate; 11.2 Coresta Porosity; 45 g/M.sup.2 ; 5.1% Potassium Acetate Burning Chemical .sup.3 25% Morton Thiokol Elastocarb Light Basic Magnesium Carbonate; 15% Calcium Carbonate Filler; 7 Coresta Porosity; 45 g/M.sup.2 ; 5.1% Potassium Acetate Burning Chemical 
    
     Comments on Table II 
     The ash properties results stated in Table II indicate that combination of basic magnesium carbonate/calcium carbonate-filled cellulosic fiber paper is giving ash properties very similar to that obtained with regular cigarette paper (control) with no significant differences observed between these two papers. 
     
                                           TABLE III__________________________________________________________________________Particle Size and Surface Area Characteristics of Basic MagnesiumCarbonate Fillers                                  Particle.sup.1                                  Size (um) Surface.sup.2                 Chemical                        Number                             Number                                  Volume                                       Volume                                            AreaFiller      Vendor    Composition                        Median                             Mode Median                                       Mode (M.sup.2 /g)__________________________________________________________________________BMC-2       Martin Marietta                 Basic MgCO.sub.3                        1.47 1.24 4.83 1.79 11.04Elastocarb Tech heavy       Morton Thiokol                 Basic MgCO.sub.3                        2.51 1.41 10.01                                       9.26 16.90Elastocarb Tech Light       Morton Thiokol                 Basic MgCO.sub.3                        2.04 1.28 6.37 7.17 19.01Magcarb L   Marine Magnesium                 Basic MgCO.sub.3                        1.74 1.54 6.19 9.88 31.98__________________________________________________________________________ .sup.1 Particle size measured by Coulter Multisizer instrument .sup.2 Surface area by B.E.T. method Comments on Table III The basic magnesium carbonate filler characteristics are presented in terms of particle size and surface area. Based on results presented in Table I on sidestream delivery rate, it is conclusive that filler surface area does not directly correlate with sidestream reduction efficiency. As presented in Table I and III, above, surface area of basic magnesium carbonate fillers ranging from 11 M.sup.2 /g to 32 M.sup.2 /g was evaluated and all fillers were determined to be equivalent in their sidestream reduction activity. This observation is markedly contrary to the claim of Hampl, et al, (U.S. Pat. No. 4,805,644) that as filler surface area increases, the sidestream smoke reduction (%) increases.