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THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. CONVERSION OF NORMAL CIGARETTE PAPER INTO
LOW IGNITION PROPENSITY CIGARETTE PAPER AND A PROCESS FOR THE SAME


2. Applicant(s)
(a) NAME :
(b) NATIONALITY
(c) ADDRESS :

Golden Tobacco Limited
An Indian Company.
Tobacco House, S.V.Road, Vile Parle (West) Mumbai - 400 056. India.

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:


FIELD OF THE INVENTION
The present invention relates to a low ignition propensity cigarette paper and processes for manufacturing the same. More particularly, the present invention provides a low ignition propensity cigarette paper having one or more thermoplastic polymer suspension coated areas suitable for commercial use and methods of making such polymer suspensions printed cigarette.
BACKGROUND AND PRIOR ART
Low ignition propensity cigarette paper is desired for safety as well as regulatory reasons or making cigarettes having specific coated areas such that, if lit, and upon contacting a combustible substrate, for example, have a tendency to self extinguish themselves when burning front reaches a coated area in the cigarette unless actuated by other means, when, for example, air is drawn on by the smoker; or held in a free burn state in which the burning cigarette is sufficiently exposed to the air on all of its sides.
Conventional cigarette papers (also referred to as base papers) that are currently being used as cigarette wrappers have high ignition propensity. This is so because the natural porosities of these conventional cigarette papers are high. There have been various attempts, reported in the prior art, to modify the ignition propensity of the conventional cigarette papers. Some of these include polymer coatings particularly thermoplastic polymer coatings in the form of bands on the outer surface of the cigarette wrapper. However, these modified cigarette wrappers have various drawbacks.
US6645605 provides products including cigarette papers containing a thermoplastic polymer aqueous suspension coated region(s) having reduced (Coresta) porosities suitable for making products with reduced burn rates. The invention uses high concentrations of thermoplastic polymer, enough to achieve sufficient paper porosity closure and hence cigarette burn rate retardation. The invention also provides ways to get sufficiently high enough concentrations of thermoplastic polymers into an aqueous

vehicle at an low enough viscosity capable of being printed onto paper and/or wrappers
via existing commercial printing techniques thus avoiding the cost of separate off-line
converting processes and the problems of solvent fumes and fire hazards around paper
machines.
However, it is found that use of water as solvent affects the strength of the paper and
causes breakage of paper during cigarette manufacture.
US5878754 provides a smoking article, particularly a cigarette, having improved ignition proclivity characteristics. Particularly, the invention provides a smoking article wrapper for use with smoking articles, particularly cigarettes, which promotes self-extinguishing of the smoking article if the article is dropped or left unattended on a flammable substrate. Herein ethyl cellulose is used as active material dissolved in isopropyl alcohol. Dissolution of ethyl cellulose is very much dependent on the content of ethoxy group. Hence its use is restricted to the purity of the material.
US6129087 provides a smoking article with reduced ignition propensity, which reduces the temperature in the combustion zone of a smoking article. In carrying out the objects of the invention it has been found that with the inclusion of metallic strips having high heat conductivity, such as aluminum, copper, silver, gold, platinum, and the like, at the interface between the tobacco blend in the smoking article and the cigarette paper there is a decrease in the number of ignitions on one or more of the various weight cotton duct fabrics. The invention provides use of heat conducting metallic strip longitudinally along the cigarette length. Use of metals like silver, platinum and their alloys has been mentioned. Such use may not be practically possible due to cost factor. It also suggests that such use is mainly to reduce the burning temperature of the lighted portion.
Thus there is a need to modify the ignition propensity of the conventional cigarette papers.
The present inventors have now found that a cigarette paper which is reduced in the air permeability of base cigarette paper by applying thermoplastic polymer film coating
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solution to at least a part of the base cigarette paper and at the same time eliminating the reported problems of crinkling and puckering in the coated areas of the cigarette paper.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a low ignition propensity cigarette paper of plurality of burn limiting areas in the form of strips formed of thermoplastic polymer suspension comprising
(i) 3.2 to 32.5% by wt. of a thermostatic polymer base;
(ii) 25 to 92% by wt. of a solvent;
(iii) 0.1 to 7.8% by wt. of plasticizers; and
(iv) 2.0 to 20% by wt. of fillers.
According to another aspect of the present invention there is provided a method for manufacturing a low ignition propensity cigarette paper comprising steps of converting a cigarette paper into a low ignition propensity cigarette paper wherein burn limiting areas are in a form of plurality of strips.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a low ignition propensity cigarette paper having a basic weight exceeding 20 g/m2 and a plurality of burn limiting areas are formed by applying a burn limiting agent constituted of one or more organic solvents based thermoplastic polymer solution of shellac with other fillers and plasticizers so as to obtain coresta porosities of less than 16 is provided. The present invention further provides a method for manufacturing a cigarette paper for low ignition propensity cigarettes comprising a

plurality of regions of a thermoplastic polymer film forming suspension printed on to a surface of a base paper.
According to the present invention the low propensity cigarette paper comprising plurality of burn limiting areas wherein the said burn limiting areas formed by applying a burn limiting agent constituted of one or more organic solvents polymer solution of shellac with other fillers and plasticizers, whose viscosity is between 8 and 35 seconds at 25°C by Ford cup viscometer, so as to obtain coresta porosities of less than 16. Further the cigarette paper of the present invention has a thermoplastic polymer suspension printed on to a base paper. Thermoplastic polymers are those polymers that are capable of softening when heated and hardening when cooled.
The present invention provides ways to get sufficiently high enough concentrations of polymers with fillers and plasticizers into one or more organic vehicle at a low enough viscosity, which is more than 8 sees, by ford cup method, capable of being printed onto paper via existing commercial printing techniques thus reduces the cost of off-line converting process and avoiding the problems of solvent fumes and fire hazards around paper machines. The present invention also provides ways to eliminate the consequences due to the application of aqueous polymer solutions such as reducing the strength of the paper and also the paper crinkling or puckering in the coated areas.
According to the present invention there is provided a method for converting a cigarette paper into a low ignition propensity cigarette paper wherein the burn limiting areas are in a form of plurality of strips formed by thermoplastic polymer suspension printed on to a surface paper along a mechanic path so as to pass through a thermoplastic polymer suspension-printing station and applying at said station, a thermoplastic polymer suspension to a surface of the base paper so as to form a plurality of areas containing said suspension. The plurality of areas on the base paper has a coresta porosities ranging from 0 to 16 or 0 to 10. The burn limiting areas are in a form of plurality of circular bands, which extend in the circumferential direction of the tobacco rod and are apart from one another in the longitudinal direction of the tobacco rod, when the cigarette paper wraps a

tobacco rod, which provides a cigarette exhibiting PFLB value of 0 to 11%. Thermoplastic polymer suspension printing station is a press rotogravure station. The base cigarette paper usually has a basic weight exceeding 20 g/m2. The basic weight is usually 70 g/m2 or less and preferably more than 19g/m2, but 36g/m2 or less. The inherent air permeability of the base cigarette paper is usually 30 to 120 coresta units and preferably 80 or less coresta units.
According to the present invention, shellac is used as a prime burn limiting agent. Shellac is derived from hardened secretions of an insect, Laccifera lace, more commonly known as the lac insect. Although shellac coatings are enteric and non-toxic, shellac exhibits physical properties, which make formation of such coatings problematic.
According to a preferred aspect the said thermostatic polymer solution comprises from 3.2% to 32.5%o by weight of shellac and 25 to 92% by weight of organic solvents and further comprises from 2.0 to 22% by weight of fillers and plasticizers wherein the shellac is selected from the grades seed lac, kusmi seed lac, kusmi buttons, button lac, dewaxed lac, dewaxed orange lac, bleaced lac, blonde dewaxed and the like.
The said polymer solution preferably comprises (i) 3.2-32.5% by weight of a thermostatic polymer base, (ii) 25-92% by weight of solvent, (iii) 0.1-7.8%) by weight of plasticizers, (iv) 2.0-20%) by weight of fillers. The above mixture is prepared so as to achieve the required viscosity of more than 8 sees or less than 35 sees when measured at 25°c by ford cup method.
The preferred aspect of the said process of converting normal cigarette paper into low ignition propensity cigarette paper comprises
a) Providing a mixture comprising 3.2-32.5% by weight of shellac, 25-92% by weight of solution forming medium, 0.1-7.8% by weight of plasticizer, 2-20%o by weight of fillers.


b) Providing a cigarette paper has a basis weight exceeding 20g/m2. The basis weight is usually 70g/m2 or less and preferably more than 19g/m2, but 36g/m2 or less. The inherent air permeability of the base cigarette paper is usually 30 to 120 coresta units and preferably 80 or less coresta units
c) A plurality of burn limiting areas, which are respectively formed by application of the polymer solution by means of various printing methods preferably by press rotogravure, are arranged apart from one another on one surface of the base cigarette paper. When the cigarette paper wraps a tobacco rod, these burn limiting areas may extend in the longitudinal direction of the tobacco rod, so that they are arranged in the form of equidistant plural strips apart from one another in the direction of the circumference of the tobacco rod. Alternatively, the burn limiting areas may extend in the circumferential direction of the tobacco rod, so that they are arranged in the form of plural circular bands apart from one another in the longitudinal direction of the tobacco rod.
d) In the present invention, the total coating amount (dry basis) of the shellac burn limiting agent is less than 3.5g/m2 of the coating area. A coating amount of as low as 0.15 to 2.5g/m2 can achieve sufficiently reduced ignition propensities. The cigarette paper according to the invention can provide a cigarette (cigarette in which tobacco filler is wrapped by the cigarette paper) exhibiting a percent full-length burn (PFLB) of 0 to 11% when measured according to ASTM E-2187-04.
e) In one embodiment of the invention, the thermoplastic polymer suspension treated areas of the base paper are such that the treated areas form series of bands separated by untreated areas. The width of the bands on the cigarette paper can be from 5 mm to 10 mm separated by 18 mm to 23 mm untreated areas. While the untreated areas can have coresta porosities ranging from 30 to 120, the treated areas should have coresta porosities less than 16. Preferred coresta porosities from about 0 to 15.7. More preferred coresta porosities are


from about 0.2 to 13. Still more preferred coresta porosities are from about 0 to 10.
f) Shown in FIGURE 1 is a perspective view of a cigarette with a wrapping paper (low propensity cigarette paper) containing thermoplastic polymer printed areas to achieve reduced porosity of the paper in those areas. The printed areas 2a,2b,2c are the regions that have reduced porosity. The areas without printed suspension l,la,lb,lc have original porosity. 3 is tipping area of the cigarette.
g) FIGURE 2 provides the detailed process flow chart of the conversion.
EXAMPLES
The following examples further illustrate the present invention, however, should not be constructed as in any way limiting its scope. The examples below are carried out using standard techniques, that are well known and routine to those of skill in the art, except where otherwise described in detail.
EXAMPLE 1
Polymer Mixture Composition
The composition of polymer mixture is as follows :
Shellac 5.5% by weight
Plasticizer ( propylene glycol or glycerin ) 4.7% by weight
Filler (calcium carbonate or calcium oxide or both ) 15.2% by weight
Solvent (isopropyl alcohol or ethanol or both ) 74.6% by weight.


Process For Low Propensity Cigarette Paper
i. Providing a cigarette paper has a basis weight exceeding 20g/m2. The basis weight is usually 70g/m2 or less and preferably more than 19g/m2, but 36g/m2 or less. The inherent air permeability of the base cigarette paper is usually 30 to 120 coresta units and preferably 80 or less coresta units
ii. A plurality of burn limiting areas, which are respectively formed by application of the above polymer solution, whose viscosity is between 12 and 24 sees by ford cup at 25°c, by means of various printing methods preferably by press rotogravure, are arranged apart from one another on one surface of the base cigarette paper. When the cigarette paper wraps a tobacco rod, these burn limiting areas may extend in the longitudinal direction of the tobacco rod, so that they are arranged in the form of equidistant plural strips apart from one another in the direction of the circumference of the tobacco rod. Alternatively, the burn limiting areas may extend in the circumferential direction of the tobacco rod, so that they are arranged in the form of plural circular bands apart from one another in the longitudinal direction of the tobacco rod.
iii. In the present example 1, the total coating amount (dry basis) of the shellac burn limiting agent is less than 2.5g/m2 of the coating area. A coating amount of as low as 0.15 to 2.5g/m2 can achieve sufficiently reduced ignition propensities. The cigarette paper according to the invention can provide a cigarette (cigarette in which tobacco filler is wrapped by the cigarette paper) exhibiting a percent full-length burn (PFLB) of 5 to 15% when measured according to ASTM E-2187-04.
EXAMPLE 2
Polymer Mixture Composition
The composition of polymer mixture is as follows :

Shellac 12.2% by weight
Plasticizer ( polyethylene glycol or glycerin ) 1.7% by weight Filler ( zinc oxide or titanium dioxide or both ) 9.8% by weight Solvent (isopropyl alcohol or ethyl acetate or both ) 76.3% by weight.
Process For Low Propensity Cigarette Paper
i. Providing a cigarette paper has a basis weight exceeding 20g/m2. The basis weight is usually 70g/m2 or less and preferably more than 19g/m2, but 36g/m2 or less. The inherent air permeability of the base cigarette paper is usually 30 to 120 coresta units and preferably 80 or less coresta units
ii. A plurality of burn limiting areas, which are respectively formed by application of the above polymer solution, whose viscosity is between 14 and 28 sees by ford cup at 25°c, by means of various printing methods preferably by press rotogravure, are arranged apart from one another on one surface of the base cigarette paper. When the cigarette paper wraps a tobacco rod, these burn limiting areas may extend in the longitudinal direction of the tobacco rod, so that they are arranged in the form of equidistant plural strips apart from one another in the direction of the circumference of the tobacco rod. Alternatively, the burn limiting areas may extend in the circumferential direction of the tobacco rod, so that they are arranged in the form of plural circular bands apart from one another in the longitudinal direction of the tobacco rod.
iii. In the present example 1, the total coating amount (dry basis) of the shellac burn limiting agent is less than 2.8g/m2 of the coating area. A coating amount of as low as 0.15 to 2.5g/m2 can achieve sufficiently reduced ignition propensities. The cigarette paper according to the invention can provide a cigarette (cigarette in which tobacco filler is


wrapped by the cigarette paper) exhibiting a percent full-length burn (PFLB) of 1 to 11% when measured according to ASTM E-2187-04.
EXAMPLE 3
Polymer Mixture Composition
The composition of polymer mixture is as follows :
Shellac 31.4% by weight
Plasticizer ( polyethylene glycol or glycerin) 0.8% by weight
Filler (titanium dioxide ) 9.8% by weight
Solvent (isopropyl alcohol or ethanol or both ) 58.0% by weight.
Process For Low Propensity Cigarette Paper
i. Providing a cigarette paper has a basis weight exceeding 20g/m2. The basis weight is usually 70g/m2 or less and preferably more than 19g/m2, but 36g/m2 or less. The inherent air permeability of the base cigarette paper is usually 30 to 120 coresta units and preferably 80 or less coresta units
ii. A plurality of burn limiting areas, which are respectively formed by application of the above polymer solution, whose viscosity is between 18 and 32 sees by ford cup at 25°c, by means of various printing methods preferably by press rotogravure, are arranged apart from one another on one surface of the base cigarette paper. When the cigarette paper wraps a tobacco rod, these burn limiting areas may extend in the longitudinal direction of the tobacco rod, so that they are arranged in the form of equidistant plural strips apart from one another in the direction of the circumference of the tobacco rod. Alternatively, the burn limiting areas


may extend in the circumferential direction of the tobacco rod, so that they are arranged in the form of plural circular bands apart from one another in the longitudinal direction of the tobacco rod.
iii. In the present example 1, the total coating amount (dry basis) of the shellac burn limiting agent is less than 3.5g/m2 of the coating area. A coating amount of as low as 0.15 to 2.5g/m2 can achieve sufficiently reduced ignition propensities. The cigarette paper according to the invention can provide a cigarette (cigarette in which tobacco filler is wrapped by the cigarette paper) exhibiting a percent full-length burn (PFLB) of 0 to 5% when measured according to ASTM E-2187-04.


WE CLAIM
1. A low ignition propensity cigarette paper of plurality of burn limiting areas in the
form of strips formed of thermoplastic polymer suspension comprising
(v) 3.2 to 32.5% by wt. of a thermostatic polymer base;
(vi) 25 to 92% by wt. of a solvent;
(vii) 0.1 to 7.8%o by wt. of plasticizers; and
(viii) 2.0 to 20%> by wt. of fillers.
2. The low ignition propensity cigarette paper as claimed in claim 1 wherein said
thermostatic polymer suspension has a viscosity ranges from 8 to 35 seconds at
25° C
3. The low ignition propensity cigarette paper as claimed in claim 1 wherein said thermostatic polymer base is shellac.
4. The low ignition propensity cigarette paper as claimed in claim 1 wherein said solvent is an organic solvent.
5. The low ignition propensity cigarette paper as claimed in claim 4 wherein said organic solvent is selected from a group consisting of isopropyl alcohol, ethanol and ethyl acetate.
6. The low ignition propensity cigarette paper as claimed in claim 1 wherein said fillers and plasticizers are selected from a group consisting of calcium carbonate, calcium oxide, propylene glycol, titanium dioxide, zinc oxide, glycerin, polyethylene glycol, calcium alginate, hydroxybutyl methylcellulose.

7. The low ignition propensity cigarette paper as claimed in any of the preceding claims comprising base cigarette paper having a basic weight ranging from 20 g/m2- 70g/m2.
8. The low ignition propensity cigarette paper as claimed in any of the preceding claims further comprising burn limiting areas in a form of plurality of strips extending in a longitudinal direction of the tobacco rod and are apart from one another in a circumferential direction of the tobacco rod, when the cigarette paper wraps a tobacco rod.
9. A method for manufacturing a low ignition propensity cigarette paper comprising steps of converting a cigarette paper into a low ignition propensity cigarette paper wherein burn limiting areas are in a form of plurality of strips.
10. A method as claimed in claim 9 wherein said strips being formed by thermoplastic polymer suspension printed on to a surface paper along a mechanic path so as to pass through a thermoplastic polymer suspension-printing station.
11. A method as claimed in claim 10 wherein said station is being treated by thermoplastic polymer suspension to a surface of the base paper so as to form a plurality of areas containing said suspension.
12. A method as claimed in claim 11 wherein said plurality of areas on the base paper has a coresta porosities ranging from 0 to 16 or 0 to 10.