| abstract |
The invention is an improved wrapper construction for smoking articles such as cigarettes resulting in a reduced tendency to ignite combustible materials accidentally or carelessly coming into contact with the lit cigarette. The wrapper constructions and smoking articles of the invention have a specially designed structure which causes a cigarette to go out quickly when in contact with a substrate, including many commonly-encountered substrates made of combustible materials. This structure is characterized by a Burn Mode Index ("BMI") as defined for the wrapper of between about 1.5 cm-1 and 5.0 cm-1 for a single wrap embodiment. For an alternative double wrapped embodiment, the outer wrap will have a BMI in the range of from about 2.0 cm-1 to about 40 cm-1 depending on the BMI of the inner wrap which may vary between about 0.1 cm-1 to 4.0 cm-1. The preferred amount of burn promoter is at least 15 mg anhydrous potassium citrate per gram of bone dry paper or stoichiometrically equivalent amounts of other burn promoting salts. Preferred substrate embodiments include paper made from flax or other cellulosic fibers, treated with elevated amounts of an alkali metal burn promoter such as alkali metal salts of carboxylic acids, especially potassium salts. In contrast to other attempts, these results are obtained without a significant sacrifice of desired taste and smoke deliveries, for example, without unacceptable increases in puff count or significant increases in delivered tar and carbon monoxide. Wrapper constructions and smoking articles of this invention may be manufactured using conventional cigarette paper processes and equipment. |