A self-extinguishing cigarette particularly when in contact with a flammable surface wherein the wrapper which encloses the body of tobacco is provided with a coating deposited from an aqueous solution of an alkali silicate. The silicate solution contains from about 17 to 27 percent by weight of SiO.sub.2. The coating area of the silicate solution on the wrapper is from about 40 to 84 percent of the entire outside wrapper area. The silicate solution may have added thereto various beneficial additives such as acids, carbohydrates, colloids, humectants, fire retardent compounds, alumina gel compounds, or compatible compounds of the aforesaid additives.
This invention concerns the use of a class of coatings that are applied to the paper wrapper that encloses the cigarette's smoking medium, for limiting in a predictable manner the free burning time of the treated cigarette, or controlling the lapsed time prior to self-extinguishment after being lit and left unattended. The coating materials are generally identified as polymeric chlorine-containing film-forming latexes that cure at ambient temperature, forming flexible, water-resistant, flame-retardant deposits. Comparable results are obtained, for equivalent weight percentages of the deposited latex solids, by either pre-coating the portion of paper wrapper that encloses the charge of tobacco or smoking medium or by post-treatment of the external surface of the assembled cigarette. For cigarettes having paper wrappers coated to contain 19.+-.6 weight percent latex solids of this invention, based on the weight of the treated paper that encloses the smoking medium, after being lit and left unattended a self-extinguishing time of from 1 to 3 minutes can be expected, meeting a practicable compromise for the smoker between safety and smoking convenience.
This invention concerns the use of specific coatings that are applied to the paper wrapper that encloses the cigarette's smoking medium for limiting in a predictable manner the free burning time of the treated cigarette, or controlling the lapsed time prior to self-extinguishment after being lit and left unattended. The coating materials are generally identified as hydrophylic colloids or aqueous-soluble polymers, that are deposited singly or as mixtures from aqueous media, and are represented by locust bean gum, pectin, sodium carboxymethylcellulose, and guar gum, forming adherent, non-tacky, flexible coatings on the paper housing substrates, and significantly altering the burning characteristic of the resultant cigarettes. Comparable behaviors are obtained, for equivalent weight percentages of the deposited solids, by either precoating the portion of paper wrapper that subsequently encloses the charge of tobacco or by post-treatment of the external surface of the assembled cigarette. For cigarettes having paper wrapper coated to contain 20.+-.10 weight percent solids of this invention, based on the weight of the treated paper that encloses the smoking medium, after being lit and left unattended a self-extinguishing time of approximately 11/2 to 3 minutes can be expected, meeting a practicable compromise for the smoker between safety and smoking convenience.
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.sup.-1 and 5.0 cm.sup.-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.sup.-1 to about 40 cm.sup.-1 depending on the BMI of the inner wrap which may vary between about 0.1 cm.sup.-1 to 4.0 cm.sup.-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.
Cigarette paper is treated by one or the other of two alternative processes. The first alternative process is characterized by the step of coating between 40 and 100% of the surface area of the paper with an aqueous alkali metal silicate solution, the SiO.sub.2 concentration of which ranges from between 12 and 16% for 40% coverage to between 7 and 15% for full coverage. The second alternative process is characterized by two sequential uniform coatings of an aqueous alkali metal silicate solution, the SiO.sub.2 concentrations in each solution ranging from 1.7% to 6%.
A smoking article is manufactured through supplying a tobacco filler material onto a tobacco wrapping paper sheet that is transferred, wrapping the tobacco filler material supplied onto the tobacco wrapping paper sheet with the tobacco wrapping paper sheet so as to prepare a rod body, and cutting the rod body into a plurality of tobacco rods each having a prescribed length. The tobacco filler material contains at least 20% by weight of expanded tobacco material. The tobacco wrapping paper sheet is coated with the burn adjusting agent during transfer of the tobacco wrapping paper sheet.
