CIGARETTE PAPER HAVING LOW SUSCEPTIBILITY TO IGNITION AND PREPARATION METHOD THEREFOR FIELD OF THE INVENTION The present invention relates to the field of cigarette processing, in particular to a method for preparing a cigarette paper having low susceptibility to ignition BACKGROUND OF THE INVENTION Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. According to statistics compiled by Consumer Product Safety Commission (CPSC) in USA, the major cause of devastating fires is due to the burning cigarette placed on bed or upholstered furniture like sofa, directly resulting in 20% of fire deaths. Almost 900 persons are dead and more than 250 persons are injured each year, causing up to 400 million dollars of economic losses. The proposal of a cigarette having low susceptibility to ignition throughout the world is nainiv aimed at reducing fire losses, and thus the large-scale international cigarette paper manufacturers such as Moody international Group as well as VVattens Paper Co., Ltd., etc. launch cigarette papers with a reduced risk of fire. The current cigarettes having low susceptibility to ignition are designed in such a way that a flame-retardant belt is installed in the cigarette paper so as to be self-extinguishable under a non-suctioning condition, when the cigarette is placed on the inflammables. However, after the cigarette paper is coated with the flame-retardant belt, when the cigarette burns to the flame-retardant belt, it will lead to two phenomena: ) the cigarette in hand is easy to extinguish under the non-suetioring condition and needs to be relit; 2) the irritation of fumes and the amount of offensive odor are increased in association with the generation of smells, affecting the quality in smoking of cigarettes. Currently, the two negative effects mentioned above have become serious impediments to the enhancement of overall quality in smoking of cigarette having low susceptibility to ignition. At present, there is no domestic product of cigarette having low susceptibility to ignition which is not only capable of maintaining the flammability in its natural state in order to meet the design requirements of cigarette with low ignition, but also preventing the influence on the overall quality in smoking thereof at the same time. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. SUMMARY OF THE INVENTION According to a first aspect, the present invention provides a cigarette paper having low susceptibility to ignition, comprising: a common cigarette paper, and a coating, consisting of a film former, a viscosity modifier and a filler, brushed or printed on an intemal surface of the common cigarette paper to constitute a coating belt, wherein said film former is selected from one or more of the following substances starch, cyclo dextrin, maltodextrin pectin, and gelatin; said viscosity modifier is selected from one or more of the following substances: alkali metal alginates, polyvinyl alcohol, and sodium carboxymethyl cellulose; said filler is selected from one or more of the following substances: calcium carbonate, magnesium hydroxide, and aluminum hydroxide; wherein the mass percentage of said filn former with respect to cigarette paper is 3%-6%, the mass percentage of said viscosity modifier with respect to cigarette paper is 0,1%-1%, the mass percentage of said filler with respect to cigarette paper is 5%-10%. According to a second aspect, the present invention provides a method for preparing the cigarette paper having low susceptibility to ignition according to any one of claims I to 6, wherein the method comprises the flowing steps: (1) preparing a common cigarette paper with a certain specification; (2) formulating said filler into a suspension with a mass percentage of 40%-60% filer, and then homogeneously stirring the suspension; (3) at room temperature, adding said viscosity modifier into the suspension of step (2) to provide an aqueous solution with a mass percentage of 2%-4% viscosity modifier, and then stirring for 10 minutes; (4) at room temperature, adding said film former into the aqueous solution of step (3) to provide an aqueous solution with a mass percentage of 25%-35% film former, and then stirring for 20 minutes; (5) adding the formulation of step (4) by means of printing and coating to the surface of the cigarette paper at a certain interval via a screen, Unless the context clearly requires otherwise throughout the description and the claims, the words "comprise" "coinprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense: that is to say, in the sense of "including, but not limited to". Embodiments of the present invention are intended to provide a cigarette paper having low susceptibility to ignition and method for preparing the samet. When the cigarette naturally burns to the coating belt in the atmosphere, it would have a low probability of extinguishment or even be inextinguishable; whereas under the standard condition of test, contact substrate filter paper has a high probability of extinguishment, and does not have significantly negative effect on the fumes and the overall quality in smoking of cigarette. Said cigarette paper having low susceptibility to ignition comprises a common cigarette paper made by paper-making process and a coating consisting of a film former, a viscosity modifier and a filler, brushed or printed on an internal surface of the common cigarette paper to constitute a coating belt. Said film former is selected from one or more of the following substances: starch, cyclodextrin, maltodextrin, pectin, and gelatin; said viscosity modifier is selected from one or more of the following substances: alkali metal alginates, polyvinyl alcohol, and sodium carboxymethyl cellulose; said filler is selected from one or more of the following substances: calcium carbonate, magnesium hydroxide, and aluminum hydroxide; the mass percentage of said film former with respect to cigarette paper is 3%-6%, the mass percentage of said viscosity modifier with respect to cigarette paper is 0.1%-i%, the mass percentage of said filler with respect to cigarette paper is 5%~10% Said filn former comprised in coating belt includes the following components with their mass percentages with respect to cigarette paper: % .5% of starch, 1%--2.0% of cyclodextrin, i%-2.5% of maitodextrin; or ll .5% of starch, i%92 0% of pectin, 1%-2,5% of gelatin; said viscosity modifier comprised in coating belt includes the following components with their mass percentages with respect to cigarette paper: 005%40.8% of alkali metal alginates, 0.05%,-0.2% of polyvinyl alcohol or sodium carboxymethyl cellulose; said filler comprised in coating belt includes the following components with their mass percentages with respect to cigarette paper 5%~8% of calcium carbonate, 0%~2% of magnesium hydroxide or aluminum hydroxide.
- 3a A method for preparing the cigarette paper having low susceptibility to ignition as described above comprises the following steps: (1) Preparing a common cigarette paper with a certain specification; (2) Said filler is fomulated into a suspension with a mass percentage of 40%-60%, and then homogeneously stirred; (3) At room temperature, said viscosity modifier component is added into the suspension obtained in step (2) to provide an aqueous solution with a mass percentage of 2%-4%, and then stirred for 10 minutes; (4) At room temperature, said film former component is then added into the aqueous solution obtained in step (3) to provide an aqueous solution with a mass percentage of 25%~35%, and then stirred for 20 minutes: (5) By means of printing and coating, the size formulated in step (4) is added onto the surface of the cigarette paper at a certain interval via a screen. The present invention employs a screen with a certain interval; the width of coating belt is 6mm or 8mm, Compared with the prior art, embodiments of the present invention have achieved the following technical effects: 1. By means of printing via a screen, the present invention obtains5 a coating belt with a certain interval, capable of ensuring the uniformity of coating and simplifying the operation; 2. By optimizing the combination of various materials, the present invention picks out more suitable film forers, viscosity modifiers and fillers. By controlling the coating amount, these additives can effectively adjust the air permeability of cigarette paper, maintain the adjustability of cigarette having low ignition, and meet different design requirements for cigarette having low ignition; meanwhile, these additives can decrease the transparency of coating belt, and guarantee a consistent appearance for cigarette; 3. All the film fonners anad viscosity modifiers provided in the present invention are safe additives for food products and the fillers are common fillers for paper-making process, which ensures the irmocuousness, safety and environmental friendliness of cigarette products; 4. The coating belt in the present invention is prepared by printing via a screen. After being rolled into a cigarette, the cigarette has a low probability of extinguishment or even can be - Th ~nextinguishabIe, when naturally burning to the coating belt in the atmosphere; whereas under the standard condition of test, contact substrate filter paper has a high probability of extinguishment, and does not have significantly negative effect on the released amounts of nannful components in cigarette f~me.s and the overall quality in smoking of cigarette; -- / / / / / / / / 7/ / / / / / / / / / / / / / / / / / / / / / / / / / 7 / / / / / / / / / / 7 / / / / / / /
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-4 5. The present invention will greatly improve the quality of cigarette having low-ignition and the good functioning of production process, bring good social and economic benefits, and possibly become a new economic growth point for cigarette products. DETAILED DESCRIPTION OF THE EMBODIMENTS By virtue of the specific embodiments below, the present invention will be further illustrated. The preparation of cigarette paper having low susceptibility to ignition basically employs the existing paper-making process such as defiberation of fiber starting materials, beating, adjustment of ratio between long-fiber and short-fiber, addition of filler(s) and functional auxiliary agent(s), followed by formation of dehydrated paper, and subsequential pressing, drying, rolling and rerolling to carry out the production of cigarette paper. The cigarette paper having low susceptibility to ignition of the present invention comprises a common cigarette paper made by paper-making process, characterized in that a coating consisting of a film former, a viscosity modifier and a filler is brushed or printed on an internal surface of the common cigarette paper to constitute a coating belt. Said film former is selected from one or more of the following substances: starch, cyclodextrin, maltodextrin, pectin, and gelatin; said viscosity modifier is selected from one or more of the following substances: alkali metal alginates, polyvinyl alcohol, and sodium carboxymethyl cellulose; said filler is selected from one or more of the following substances: calcium carbonate, magnesium hydroxide, and aluminum hydroxide; the mass percentage of said film former with respect to cigarette paper is 3%-6%, the mass percentage of said viscosity modifier with respect to cigarette paper is 0.1 %-1%, the mass percentage of said filler with respect to cigarette paper is 5%- 0%. Said film former comprised in coating belt includes the following components with their mass percentages with respect to cigarette paper: 1%-1.5% of starch, 1%-2.0% of cyclodextrin, 1%~2.5% of maltodextrin; or 1%-1.5% of starch, 1%-2.0% of pectin, 1%-2.5% of gelatin; said viscosity modifier comprised in coating belt includes the following components with their mass percentages with respect to cigarette paper: 0.05%-0.8% of alkali metal alginates, 0.05%-0.2% of polyvinyl alcohol or sodium carboxymethyl cellulose; said filler comprised in coating belt includes the following components with their mass percentages with respect to cigarette paper: 5%-8% of calcium carbonate, 0%-2% of magnesium hydroxide or aluminum hydroxide.
-5 A method for preparing the cigarette paper having low susceptibility to ignition as described above comprises the following steps: (1) Preparing a common cigarette paper with a certain specification; (2) Said filler is formulated into a suspension with a mass percentage of 40%-60%, and then homogeneously stirred; (3) At room temperature, said viscosity modifier component is added into the suspension obtained in step (2) to provide an aqueous solution with a mass percentage of 2%-4%, and then stirred for 10 minutes; (4) At room temperature, said film former component is then added into the aqueous solution obtained in step (3) to provide an aqueous solution with a mass percentage of 25%~35%, and then stirred for 20 minutes; (5) By means of printing and coating, the size formulated in step (4) is added onto the surface of the cigarette paper at a certain interval via a screen The present invention employs a screen with a certain interval; the width of coating belt is 6mm or 8mm. Examples: The preparation of cigarette paper in cigarette having low susceptibility to ignition according to the present invention and the coating process by printing via a screen would be described hereinafter. . Cigarette Paper 1. The Characters of Cigarette Paper The specified weight range of cigarette paper is 20-1 OOg/m 2 , the air permeability of cigarette paper is 20-90 Coresta; 2. The Application of Various Inorganic Fillers (1) Calcium carbonate, light calcium carbonate powder or a newly prepared suspension of calcium carbonate. The mass percentage thereof ranges from 15% to 50%, with respect to final paper product; -6 (2) Magnesium-containing material with a large specific surface area, it may be magnesium oxide powder, magnesium hydroxide powder or newly prepared magnesium hydroxide. The mass percentage of magnesium ion represented by magnesium hydroxide ranges from 5% to 40%, with respect to final paper product; (3) Trihydroxyaluminum and aluminum salt compound, it refers to the filler for making paper such as aluminum sulfate, sodium metaaluminate, polymeric aluminum chloride, aluminum hydroxide and the like. The mass percentage of aluminum ion represented by aluminum oxide ranges from 5% to 30%, with respect to final cigarette paper product; (4) Silicon oxide or silicate or a mixture thereof, including silicon oxides with different forms, alkali metal salts or alkaline earth metal salts or aluminum salts of silicic acid with different forms. The mass percentage of silicon represented by silicon oxide ranges from 1% to 10%, with respect to final paper product; 3. The Application of Organic Oxidizer The organic oxidizer used in the present invention refers to alkali metal salts of carboxylic acids: potassium or sodium salts of acetic acid, succinic acid, tartraric acid, citric acid, fumaric acid and the like. Potassium and sodium ions could be derived from one or more carboxylates, the content of potassium ion comprised in cigarette paper may range from 0% to 100% by weight with respect to the total content of potassium and sodium ions. Similarly, the content of sodium ion may range from 0% to 100% by weight with respect to the total content of potassium and sodium ions. The total content of potassium and sodium ions comprised in cigarette paper ranges from 0.5% to 10% by weight. The present invention has no special requirements on paper fibers. Natural fibers for general production can be used. I. Coating process by printing via a screen 1. Preparation of Coating Solution The coating belt in cigarette paper having low susceptibility to ignition according to the present application comprises a film former, a viscosity modifier, and a filler. At room temperature, the filler is formulated into a suspension of 40%-60%, and then homogeneously stirred; the viscosity modifier component is then added to provide an aqueous solution of 2%-4%, and stirred for 10 minutes; the film former component is finally added to provide an aqueous solution of 25%-35%, and stirred for 20 minutes; the coating solution is thus obtained.
2. The coating process via a screen Using the coating process by printing via a screen, the aforesaid coating solution is transferred to the inner surface of cigarette paper vja a screen with a certain interval The selected width of c ating belt may be 6mm or 8mm. The coating machine is set to coat the cigarette paper on one side, the speed of coating is 100mhni the temperature of drying is 100'C. After rerolling and slitting, the final cigarette paper having low susceptibility to ignition can be obtained. By applying the aforesaid technology to the production of cigarette, the cigarette paper thus produced could improve the quality of cigarette having low susceptibility to ignition. This could be illustrated by specific examples: Example I To 700kg of wood pulp, 500kg of calcium carbonate was added. Potassium citrate with a mass percentage of 40% and sodium citrate with a mass percentage of 6% were formulated and added as oxidizers. The cigarette paper was produced according to common method for making paper. The characters of cigarette paper were controlled by device as 28gmn of specified weight and S0 Coresta of air permeability At room temperature, to a bulk for formulating coating solution, a certain amount of calcium carbonate as filler was added and formulated into a suspension with a mass percentage of 50%, and then honogeneously stirred; alkali netal alginate and polyvinyl alcohol as viscosity modifiers with respective mass percentages of 2% and 1% were added thereinto, and then honogeneously stirred; starch, maltodextrin and cyclodextrin as film rmners with respective mass percentages of 5%, 8% and 12% were added thereinto, and then homogeneously stirred The width of coating belt printed via a screen may be 6mm. Example 2 The production process of cigarette paper prepaed according to Example 1. At room temperature, to a bulk for formulating coating solution, a certain arnount of calcium carbonate as filler was added and formulated into a suspension with a mass percentage of 50%, and then homogeneously stirred; alkali metal alginate and sodium carboxylimethyl cellulose as viscosity modifiers with resp ective mass percentages of 2% and 1% were added thereinto, and then homogeneously stirred; starch, ialtodextrin and cyclodextrin as film former with respective mass percentages of 5% 8% and 12% were added thereinto, and then homogeneously stirred. The width of coating belt printed via a screen may be 6mm. Example 3 The production process of cigarette paper prepared according to Example 1. At room temperature, to a bulk for formulating coating solution, a certain amount of calcium carbonate as filler was added and formulated into a suspension with a mass percentage of 50%, and then homogeneously stirred; alkali metal alginate and polyvinyl alcohol as viscosity modifiers with respective mass percentages of 3% and 1% were added thereinto, and then homogeneously stirred; starch, pectin and gelatin as film formers with respective mass percentages of 5%, 8% and 12% were added thereinto, and then homogeneously stirred. The width of coating belt printed via a screen may be 6mm. Example 4 The production process of cigarette paper prepared according to Example 1. At room temperature, to a bulk for formulating coating solution, a certain amount of calcium carbonate as filler was added and formulated into a suspension with a mass percentage of 50%, and then homogeneously stirred; alkali metal alginate and polyvinyl alcohol as viscosity modifiers with respective mass percentages of 3% and 1% were added thereinto, and then homogeneously stirred; starch, maltodextrin and cyclodextrin as film formers with respective mass percentages of 5%, 10% and 15% were added thereinto, and then homogeneously stirred. The width of coating belt printed via a screen may be 6mm. Example 5 The production process of cigarette paper prepared according to Example 1. At room temperature, to a bulk for formulating coating solution, a certain amount of calcium carbonate as filler was added and formulated into a suspension with a mass percentage of 50%, and then homogeneously stirred; alkali metal alginate and polyvinyl alcohol as viscosity modifiers with respective mass percentages of 3% and 1% were added thereinto, and then homogeneously stirred; starch, maltodextrin and cyclodextrin as film formers with respective mass percentages of 5%, 12% and 18% were added thereinto, and then homogeneously stirred. The width of coating belt printed via a screen may be 6mm. The effects of different embodiments on major physical indicators of cigarette paper were investigated. The cigarette paper without printing coating belt was used as original cigarette paper. The results were shown in Table 1. It could be seen from the results in Table that, compared with the original cigarette paper, all those coated by printing via a screen according to different Examples exhibited an increase of 4g/m 2 in specific weight, whereas the air permeabilities of cigarette papers decreased from 80 -9 Coresta (Unit: CU) for control sample to 5-20 Coresta respectively for different Examples; various Examples had little effect on other physical indicators of cigarette paper. Table 1. The comparison of major physical indicators between various Examples and original cigarette paper control Example Example Example Example Example Test items sample 1 2 3 4 5 Specific weight g/m 28.1 31.8 31.6 32.1 32.0 32.4 Air permeability of coatingbeltCU 15.8 12.4 14.3 10.3 7.5 Air permeability o f uncoaerea CU 80.4 78.9 80.2 79.6 80.6 79.8 uncoated area CU Whiteness % 91.0 90.0 90.0 90.0 90.0 90.0 Opacity % 74.2 74.5 74.7 75.1 74.8 75.0 Ash content % 17.8 18.0 18.2 18.1 18.1 18.3 Tensile energy asoi oene y 10.2 9.94 9.83 9.78 9.82 9.75 absorption Under the same condition, the tobacco of a domestic cigarette marketed under a certain brand for export was adopted to prepare samples. The sample made of common cigarette paper was taken as control sample. According to FASE test method (for horizontally placed cigarettes which naturally burns in the atmospheric) and ASTM E2187- 04 test method (performed on specific filler paper substrate in test box) for cigarette having low susceptibility to ignition, the ignitions of control sample and samples provided in various Examples were measured. The results were shown in Table 2. Table 2. The probabilities of extinguishment of cigarette samples under different test methods Test Control Example Example Example Example Example Sadr mtos sample 1 2 3 4 5 Sadr FASE 0% 0% 0% 2.5% 0% 4.2% 92.5 97.5 ASTM 0.8% 92.5% 100% 100 % >75% The number of cigarette tested: 120 -10 It could be seen from the test results that, according to FASE test method, the samples having coating belt provided in various Examples were of very low probabilities of extinguishment or even inextinguishable; according to ASTM E2187-04 test method, they were of probabilities of extinguishment of more than 90%, meeting the standard requirement of probability of extinguishment of more than 75%, with a low susceptibility to ignition, By means of smoking machine, the assay of fumes was performed on cigarette samples having low susceptibility to ignition provided in various Examples and control cigarette sample. The test results were shown in Table 3. Table 3. The results of assay of fumes on samples of various Examples and control Labeled Labeled Total amount Amount Amount of amount of Amount Times of Sample amount of particulate of nicotine carbon carbon of tar smoking number of tar matter in fumes monooxide . monoxide mg/pic mg/pic time/pic mg/ppic mg/pic mg/pcpm/pi mg/pic Control 10 12 11.95 9.3 0.90 11.2 6.8 Examplel 10 12 11.74 8.8 0.89 10.9 6.8 Example2 10 12 12.82 9.6 0.96 11.6 7.0 Example3 10 12 12.54 9.5 0.93 11.9 6.9 Example4 10 12 12.12 9.5 0.91 11.4 7.0 Example 10 12 12.28 10.0 0.94 12.1 7.1 From the test results of fume indicators in Table, it could also be seen that, by adjusting the air permeability of original cigarette paper, the fume indicators of the samples having low susceptibility to ignition provided in various Examples and control sample marginally changed, meeting the design requirements of labeling on cigarette box. The sensory quality of cigarette having low susceptibility to ignition was evaluated. The results showed that, compared with control sample, all the samples provided in various Examples were slightly irritating. However, it had no significant negative effect on the overall quality in smoking of cigarette, due to the particularity of cigarette having low susceptibility to ignition. Therefore, we only need to maintain the original quality in smoking of cigarette, under a premise of meeting the design requirement of low ignition. In summary, by printing via a screen, the present invention is intended to add a coating belt comprising a film former, a viscosity modifier and a filler onto a cigarette paper. The naturally burning cigarette sample is inextinguishable in the atmosphere. Whereas, under the condition that meets the requirement of extinguishment on the combustible substrate, the - 11 fumes indicators of cigarette were less affected, without affecting the overall quality in smoking of cigarette.