Wrapper constructions for self-extinguishing smoking articles

Abstract

The invention is an improved specially designed wrapper construction for smoking articles producing controlled burn properties of smoking articles such as cigarettes so that the cigarette will self-extinguish after free burning in air for a designed time period. In addition, the wrapper construction results in cigarettes with reduced tendency to ignite combustible substrates, such as upholstered furniture, when in contact with them. Therefore, smoking articles with this wrapper construction reduce the likelihood of accidental fires, yet they free-burn rapidly for a designed period of time without puffing. However, during a normal puffing sequence the behavior of cigarettes with these wrappers is indistinguishable from commercial cigarettes. On the other hand, other self-extinguishing cigarettes go out without puffing and therefore have to be relighted frequently. The wrapper constructions of the present invention include single or double wraps of cigarette paper which are inherently incapable without elevated levels of burn promoting chemical or supporting cigarette free burn. The construction is modified by application of a plurality of zones of elevated levels of burn promoter to the extent that the cigarette burns normally in the treated zones. Thus, when the burning coal advances to an area of untreated wrap, it reliably self-extinguishes unless puffed. The extent of the treated zones controls the time required for the cigarette to self-extinguish. Required wrappers are preferably those having a Burn Mode Index ('BMI') as defined in the range of from about 1.5 cm.sup.-1 to about 6.0 cm.sup.-1 for the single wrap embodiment and, for the double wrap embodiment, about 0.1 cm.sup.-1 to about 4.0 cm.sup.-1 for the inner wrap and about 2 cm.sup.-1 to about 40 cm.sup.-1 for the outer wrap depending on the BMI of the inner wrap. The wrappers and smoking articles of the invention may be produced using conventional methods and equipment.