FILTER ELEMENT SUITABLE FOR USE IN SMOKING ARTICLES AND PROCESS FOR MANUFACTURING SAME - Patent application

Abstract

This article relates to a filter element suitable for use in smoking articles and a manufacturing process for the same. The filter element comprises cellulose acetate fibers bound together by a polyhydroxyalkanoate (PHA) that surrounds the cellulose acetate fibers. PHA is used as a binder for the cellulose acetate fibers, instead of triacetin or other binders. It is a highly biodegradable polymer that, when applied to the fiber surface, can bind the cellulose acetate fibers together, causing the formation of random connection points, maintaining a consistent spacing between fibers suitable for the correct pressure drop during smoking, and imparting appropriate hardness to the filter element. Furthermore, PHA has a relatively high melting point and is virtually insoluble in water, so it does not soften or dissolve even when exposed to the warm, moist smoke generated during cigarette smoking, thereby preventing the filter element from softening and disintegrating during smoking. Furthermore, the presence of PHA on the surface of the cellulose acetate fibers that form the filter element significantly reduces toxic substances in cigarette smoke, particularly reactive oxygen species (ROS).

Description

[Technical field]

[0001] The present invention relates to a filter element suitable for use in a smoking article and a process for its manufacture. More specifically, the present invention relates to a filter element suitable for use in a smoking article, comprising bundles of fibers bound by a biodegradable material, in particular polyhydroxyalkanoate (PHA), and a process for its manufacture. [Background technology]

[0002] Smoking articles, such as cigarettes, usually have a substantially cylindrical rod-like structure and include a roll of smokable material, such as tobacco, wrapped in a paper wrapper, thereby forming a so-called "smokable rod". Typically, cigarettes have a cylindrical filter element aligned in an end-to-end relationship with the smokable rod. Typically, the filter element includes a bundle of cellulose acetate fibers circumscribed by a paper material, and the filter element is attached to one end of the smokable rod using a circumscribing wrapping material known as a "tipping material". Conventional cellulose acetate fibers (manufactured in bundles, also known as "tows") are bonded with a suitable plasticizer, usually glyceryl triacetate (triacetin), which can bind the staple fibers together to create a relatively firm, rigid structure that does not soften or disintegrate during smoking.

[0003] In terms of environmental sustainability, currently available filter technologies for forming filter elements have some drawbacks. For example, conventional filter elements containing cellulose acetate fibers bound by triacetin require an undesirably long time (usually on the order of 2 to 10 years) to actually biodegrade. Certain filter elements for cigarettes have been developed that contain materials that can promote the biodegradation of the filter element after use. For example, attention has been paid to certain additives that can be added to filter materials to enhance degradability (see, for example, US 5,913,311, US 5,947,126, US 5,970,988 and US 6,571,802).

[0004] US2017 / 0354179 discloses a smoking article including a filter element formed from two or more fibrous inputs having different physical properties. A first plurality of staple cellulose acetate fibers and a second plurality of degradable polymer staple fibers are blended to obtain a fiber mixture, the staple fibers of the fiber mixture being randomly oriented. The degradable polymer staple fibers can be treated to increase hydrophobicity. The staple fibers of the fiber mixture can then be bonded to form a fiber bundle that can be incorporated into a filter element. Exemplary biodegradable materials for the degradable staple fibers include aliphatic polyesters, cellulose acetate with embedded starch particles, cellulose coated with acetyl groups, polyvinyl alcohol, starch, polybutylene succinate, proteins, polysaccharides (e.g., cellulose and / or calcium alginate), and copolymers and blends thereof. Exemplary aliphatic polyesters have a -[C(O)-RO]- structure, where n is an integer representing the number of monomer units in the polymer chain, and R is an aliphatic hydrocarbon, preferably a C1-C10 alkylene, more preferably a C1-C6 alkylene, with a straight or branched chain. Exemplary aliphatic polyesters include polyglycolic acid (PGA), polylactic acid (PLA) (e.g., poly(L-lactic acid) or poly(DL-lactic acid)), polyhydroxyalkanoates (PHAs) such as polyhydroxypropionate, polyhydroxyvalerate, polyhydroxybutyrate, polyhydroxyhexanoate, and polyhydroxyoctanoate, polycaprolactone (PCL), polybutylene succinate, polybutylene succinate adipate, and copolymers thereof (e.g., polyhydroxybutyrate-co-hydroxyvalerate (PHBV)).

[0005] Another challenge that cigarette manufacturers have long faced is to provide filter elements that more effectively absorb the toxic components of cigarette smoke, thereby reducing the well-known risks to human health posed by some of the by-products produced by the combustion of tobacco and paper, such as polycyclic aromatic hydrocarbons (PAHs), heavy metals and reactive oxygen species (ROS).

[0006] For example, US2012 / 0160255 discloses a cigarette filter of electrospun fiber mat for removing toxic compounds from cigarette smoke, comprising a biopolymer, multiple additives, a solvent and an acceptable polymer carrier. The biopolymer comprises a polynuclear complex with multiple metal ions and combinations thereof. The polynuclear complex is a polyporphyrin ring, and the multiple metal ions include ferrous ions, cuprous ions, manganese ions and zinc ions. The biopolymer is selected from the group consisting of modified polyhemoglobin and / or chlorophyll.

[0007] US9,032,970 is a toxic substance found in cigarette smoke. 210 The present invention discloses a cigarette filter for reducing the amount of polycyclic aromatic hydrocarbons (PAHs), heavy metal elements, and free radicals, which in addition to the common components of known cigarette filters contains AlOOH·H2O, and / or Al2O3, and / or silicoaluminate, as well as grape seed and skin meal as antioxidants, and optionally contains astaxanthin and / or cranberry as further antioxidants. Summary of the Invention [Problem to be solved by the invention]

[0008] The Applicant has been faced with the problem of improving the biodegradability of filter elements used in smoking articles, and in particular cigarettes, by using biodegradable materials that do not require the modification of the manufacturing process in a way that is unacceptable for industrial production and that, while offering the desired taste and filtration properties associated with conventional cigarette filters, ensure adequate properties in terms of mechanical resistance during the manufacture of the filter elements in plants operating at high speeds, and resistance to heating during smoking.

[0009] The applicant has found that the above technical problems and other problems detailed herein can be solved by using polyhydroxyalkanoate (PHA) as a binder for cellulose acetate fibers instead of triacetin or other binders. Polyhydroxyalkanoate (PHA) is a biodegradable polymer that, when applied to the fiber surface, can bond cellulose acetate fibers, thereby causing the formation of random connection points to maintain a constant space between the fibers suitable for the correct pressure drop during smoking and to provide the filter element with the appropriate hardness. Furthermore, PHA has a relatively high melting point and is substantially insoluble in water, so it does not soften or melt when exposed to the warm, moist smoke generated when smoking a cigarette, preventing the filter element from softening and disintegrating during smoking.

[0010] Moreover, applicants have found that the presence of PHA on the surface of the cellulose acetate fibers forming the filter element significantly reduces toxic substances in cigarette smoke, particularly with respect to reactive oxygen species (ROS). Thus, in addition to being more biodegradable than conventional filter elements, the filter element of the present invention is particularly effective in reducing risks to a smoker's health by suppressing ROS present in cigarette smoke.

[0011] It is well known that ROS are toxic to cells and cause oxidative stress, and over 100 diseases are associated with ROS, including diabetes, inflammatory immune damage, autoimmune systemic diseases, tissue damage caused by blood loss and cancer. [Means for solving the problem]

[0012] Thus, according to a first aspect, the present invention relates to a filter element suitable for use in a smoking article, comprising cellulose acetate fibres bonded by a polyhydroxyalkanoate (PHA) surrounding the cellulose acetate fibres.

[0013] According to a second aspect, the present invention provides a process for producing a filter element suitable for use in a smoking article, comprising: embedding a bundle of cellulose acetate fibers in an aqueous suspension of PHA to obtain a wet bundle of cellulose acetate fibers covered with a PHA suspension; forming the wetted bundle into a continuous elongated element; heating the continuous elongated element to a temperature of 140° C. to 180° C. for a time sufficient to melt the PHA and evaporate the water; cooling the heated continuous elongated element to crystallize the PHA; and c) cutting the resulting continuous elongated element into segments of predetermined length.

[0014] According to another aspect, the present invention relates to a method for inhibiting reactive oxygen species (ROS) in smoke produced by a smoking article, comprising providing a smoking article with a filter element as defined above.

[0015] According to another aspect, the present invention relates to the use of a filter element inserted in a smoking article as defined above for suppressing reactive oxygen species (ROS) in the smoke produced by the smoking article.

[0016] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like, are to be understood in all instances to be modified by the term "about." Moreover, all ranges include any combination of the maximum and minimum points disclosed, as well as any intermediate ranges therein, which may or may not be specifically recited herein.

[0017] With regard to smoking articles, according to the present invention, the term includes not only conventional cigarettes that are smoked by burning at high temperatures, but also smoking systems that have been marketed in recent years, traditionally known as "heat-not-burn tobacco" (such as Philip Morris' IQOS™ kit), in which a tobacco rod is not burned but is only heated to generate an aerosol containing nicotine and other chemicals. In such systems, a type of cigarette with small dimensions is used that includes a tobacco rod with different filtering means, including a filter element that is usually made of a cellulose acetate filter bound by triacetin. In conventional cigarettes, the length of the filter element is generally about 2.3 cm, while in "cigarettes" used in "heat-not-burn" systems, the length of the filter element is generally about 0.5 cm.

[0018] The cellulose acetate fibers that can be used in the filter element according to the invention are well known in the art of cigarette manufacturing. They are usually in the form of continuous filaments, generally with a diameter, expressed as denier per filament (dpf), between 1 and 15, more preferably between 5 and 10. Denier per filament (dpf) is a measure of the weight per unit length of an individual filament of the fiber, specifically grams per 9000 meters. The shape of the cross section of the individual filaments may vary, for example, be rectangular, circular, oblong or multilobal in shape.

[0019] The bundle of cellulose acetate fibers usually has a total denier in the range of 20,000 denier to 80,000 denier, preferably in the range of 30,000 denier to 60,000 denier.

[0020] Preferably, the PHA according to the present invention has the following formula (I): -O-CHR1-(CH2) n -CO-... Formula (I) [wherein R1 is selected from C1-C12 alkyl, C4-C16 cycloalkyl, C2-C12 alkenyl, and is optionally substituted with at least one group selected from halogen (F, Cl, Br), -CN, -OH, -OOH, -OR, -COOR (R = C1-C4 alkyl, benzyl); n is zero or an integer of 1 to 6, preferably 1 or 2]. Preferably, R1 is methyl or ethyl and n is 1 or 2.

[0021] PHAs can be either homopolymers, copolymers or terpolymers. In the case of copolymers or terpolymers, they can consist of different repeat units of formula (I) or at least one repeat unit of formula (I) in combination with at least one repeat unit derived from a comonomer capable of copolymerizing with hydroxyalkanoates, such as a lactone or lactam. In the latter case, the repeat unit of formula (I) is present in an amount equal to at least 10 mol %, relative to the total number of moles of repeat units.

[0022] Particularly preferred repeat units of formula (I) are those derived from 3-hydroxybutyrate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxyundec-10-enoate, 4-hydroxyvalerate.

[0023] Particularly preferred PHAs are polyhydroxybutyrate (PHB), poly-3-hydroxyvalerate (PHV), poly-3-hydroxyhexanoate (PHH), poly-3-hydroxyoctanoate (PHO), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxyoctanoate-co-3-hydroxyundecen-10-enoate) (PHOU), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-4-hydroxyvalerate) (PHBVV), polyhydroxybutyrate-hydroxyvalerate copolymer, or mixtures thereof.

[0024] For purposes of the present invention, particularly preferred PHAs are polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

[0025] Preferably, the PHA has a weight average molecular weight (Mw) in the range of 10,000 to 1,000,000 Da.

[0026] The production of PHA is preferably achieved by microbial fermentation of an organic substrate (e.g. carbohydrates or other fermentable substrates such as glycerol) via a microbial strain capable of producing PHA, and the subsequent recovery of the PHA from the cell mass. For details, see, for example, patent applications WO99 / 23146, WO2011 / 045625 and WO2015 / 015315. Substrates suitable for the production of PHA by fermentation can be obtained in particular from vegetable processing, for example the juice, molasses and pulp obtained from sugar beet and sugar cane processing. These substrates generally contain, in addition to sucrose and other carbohydrates, organic growth factors, nitrogen, phosphorus and / or other minerals useful as nutrients for cell growth. An alternative is glycerol, a low-cost organic carbon source that is a by-product of biodiesel production, which can be optionally used in a mixture with levulinic acid (see, for example, US8 956 835 B2).

[0027] As regards the manufacturing process of the filter element according to the invention, it can be carried out by machines commonly used for the manufacture of cigarettes, where cellulose acetate fibers are bound with triacetin. First, a bundle of cellulose acetate fibers is embedded in an aqueous suspension of PHA. Using an aqueous suspension of PHA is advantageous, since it avoids the use of organic solvents for PHA, such as chlorinated organic solvents (usually chloroform), which are harmful to the environment and may be too aggressive for cellulose acetate fibers.

[0028] The embedding of the bundles can be carried out according to known techniques, for example by spraying the bundles with a PHA suspension or by immersing the bundles in the PHA suspension. In order to regularly bond the cellulose acetate fibers with PHA, it is important to completely and uniformly embed the bundles in the PHA suspension. The concentration of PHA in the suspension is preferably 1% to 20% w / v, more preferably 5% to 15% w / v.

[0029] The wet bundle is then formed into a continuous elongated element, usually of substantially cylindrical shape, which may be carried out by conventional machinery well known to cigarette manufacturers.

[0030] The continuous elongated element is then heated to a temperature of 140°C to 180°C for a time sufficient to melt the PHA and evaporate the water from the PHA suspension. The above steps coat the cellulose acetate fibers with the PHA, providing a strong bond between the fibers when the PHA reverts to a crystalline state.

[0031] The heated continuous elongated element is then cooled to crystallize the PHA. The elongated elements thus obtained, formed by cellulose acetate fibers bound by the PHA, have a relatively solid and rigid structure suitable for producing filter elements for use in the industrial process of cigarette manufacturing. The final cutting of the elongated elements can be carried out according to techniques well known in the art of cigarette manufacturing.

[0032] The amount of PHA present in the final elongated element is selected to provide the desired stiffness to the filter element while maintaining a consistent spacing between the fibers for the correct pressure drop during smoking. Preferably, the amount of PHA in the filter element is 5-30% by weight, preferably 10-20% by weight, based on the total weight of the filter element. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 shows a schematic diagram of a mainstream smoke sampling system using a computer-controlled single cigarette smoking machine.

[0034] The following examples are provided to further illustrate the present invention. EXAMPLES

[0035] [Manufacture of filter elements] An aqueous suspension of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (Mw: 700 KDa) at a concentration of 10% w / v was sprayed onto the bundles of cellulose acetate fibers using an airbrush.

[0036] To prepare the filter element specimens for subsequent testing, a wet bundle of cellulose acetate fibers embedded with the PHBV suspension was inserted into a PTFE (polytetrafluoroethylene) tube 20 cm long and 0.8 cm in diameter, with a through hole of 0.26 mm diameter in the tube wall to facilitate the evaporation of water during subsequent heating.

[0037] The tube containing the wet bundle of cellulose acetate fibers was heated in an oven at 170° C. for 15 minutes, a time sufficient to melt the PHBV without decomposing the cellulose acetate.

[0038] The tube was then removed from the oven and cooled at room temperature, allowing the PHBV to recrystallize and bond the cellulose acetate fibers to each other.

[0039] The filter rods were then cut into different lengths (2.3 cm and 0.5 cm). The amount of PHBV measured in the final filter was 10% by weight relative to the total weight of the filter.

[0040] Filters characterized by a length of 2.3 cm and a diameter of 0.8 cm exhibited an average weight of 0.160 g, while filters characterized by a length of 0.5 cm and a diameter of 0.8 cm exhibited an average weight of 0.045 g.

[0041] [ROS Decision] (a) Sampling system Mainstream smoke was generated using a computer-controlled single cigarette smoking machine (SCSM, CH Technologies) under standard smoking conditions following Federal Trade Commission (FTC) protocols (cigarettes burned for 8–9 min with 35 mL puffs at 2 s per minute). Three impingers were filled with 20 mL of 2´,7´-dichlorofluorescein-horseradish peroxidase (DCFH-HRP) solution and used to collect gas-phase ROS from mainstream smoke. The experimental system is shown diagrammatically in Figure 1. Marlboro (red) cigarettes (without filters) were used to collect ROS from mainstream smoke.

[0042] In Figure 1, the SCSM (1) is connected to three impingers (2) containing DCFH-HRP solution that receives smoke produced by a cigarette (3) connected to the first impinger by a filter holder (4). Exhaust smoke leaves the SCSM through a pipe (5). The SCSM is connected to a laptop (6) for data recording and elaboration.

[0043] (b) Sample preparation and analysis - Preparation of fluorescent probes and standards for ROS in cigarette smoke

[0044] The fluorescent probe used to determine ROS in this study was DCFH. A 1 mM stock solution was prepared by dissolving 2´,7´-dichlorofluorescein diacetate (DCFH-DA; Calbiochem, USA) in ethyl alcohol (ACS grade, Pharmo, USA). 10 mL of the solution was mixed with 40 mL of 0.01 M sodium hydroxide (NaOH) and left in the dark for 30 min to allow hydrolysis. Then, 200 mL of phosphate buffer, obtained by mixing disodium hydrogen phosphate (Na2HPO4, Sigma Aldrich, MO, USA) with sodium dihydrogen phosphate anhydrous (NaH2PO4, Fluka, Germany) to pH 7.2, was added to the above solution. Horseradish peroxidase (HRP, Sigma Aldrich, USA) was used as a catalyst at a concentration of 0.5 units / mL. The final DCFH concentration in this working solution was 5 μM.

[0045] Equivalent H2O2 concentrations were used to express ROS concentrations by converting the fluorescence intensity utilizing a standard H2O2 calibration curve. ROS concentrations of 1.0, 2.0, 3.0, and 4.0 × 10 were obtained by mixing 0.1 mL of hydrogen peroxide (ACS grade, Sigma Aldrich, USA) with 3 mL of DCFH-HRP working solution. -7 Four concentrations of H2O2 standards in nmol were prepared. Standard blanks were obtained by mixing 0.1 mL of deionized Milli-Q water (resistivity >18.2 MΩ) with the probe. The standards were placed in cuvettes and incubated in a water bath at 37°C. The formation of 2,7-dichlorofluorescein was monitored by measuring fluorescence (excitation wavelength: 504 nm, emission wavelength: 524 nm) using a Shimadzu spectrophotometer (model: RF-5301 PC, Japan).

[0046] (c) Analysis of reactive oxygen species (ROS) Following sampling, 3 mL of reagent solution was removed from each impinger (each containing 20 mL), placed in a cuvette, and incubated in a 37°C water bath for 15 min. Generally, the fluorescence intensity of the impinger solutions was within the standard range. The volume of the solution was used to obtain the amount of ROS in each impinger, and the contents of all three impingers were then combined into one. An aliquot of the solution was taken and the fluorescence intensity was measured. A sampling blank was obtained by operating the smoking system without burning cigarettes and analyzed in the same way. The sampling blank values ​​were subtracted from the sample results.

[0047] The amount of ROS was also measured in the smoke from commercial cigarettes, as reported in Table 1.

[0048] For further details on ROS analysis, see: Jiayuan Zhao & Philip K. Hopke, “Concentration of Reactive Oxygen Species (ROS) in Mainstream and Sidestream Cigarette Smoke,” Aerosol Science and Technology, 46:191-197, 2012; Mohammad Arifur Rahman & Philip K. Hopke, “Assessment of Methods for the Measurement of Wood Fuel Compositions,” Energy Fuels 2017, 31, 5, 5215-5221.

[0049] Pressure drop and hardness determination Samples of the filter element according to the invention (Bio-on filter) were tested to measure the pressure drop caused by the filter and the hardness of the filter. The same measurements were made on commercial cigarettes. The pressure drop was measured using a Laminar Flow Element (Dwyer Instrument Inc., USA). The hardness was measured using a durometer, ASTM D2240 Type A, ISO868.

[0050] The results are shown in Table 1. [Table 1]

[0051] Without being bound by any theory, the positive effect of the presence of PHA in the filter element on ROS suppression is believed to be mainly due to the monomer unit -O-CHR1-(CH2) n This is thought to be due to the -CO- structure. The hydrogen attached to the carbon atom at the third position, -CHR1-, is particularly reactive and forms hydrogen radicals that suppress ROS by inactivating them through radical reactions.

Claims

1. A process for producing a filter element suitable for use in a smoking article, the filter element comprising cellulose acetate fibers bound by a polyhydroxyalkanoate (PHA) surrounding the cellulose acetate fibers; The manufacturing process comprises: embedding a bundle of cellulose acetate fibers with an aqueous suspension of PHA to obtain a wet bundle of cellulose acetate fibers covered with said PHA suspension; shaping the wetted bundle into a continuous elongated element; heating the continuous elongated element to a temperature of 140° C. to 180° C. for a time sufficient to melt the PHA and evaporate water; cooling the heated continuous elongated element to crystallize the PHA; and cutting the resulting continuous elongated element into segments of predetermined length.

2. 2. The process of claim 1, wherein the bundles of cellulose acetate fibers have a total denier in the range of 20,000 denier to 80,000 denier, preferably in the range of 30,000 denier to 60,000 denier.

3. The PHA is represented by the following formula (I): -O-CHR 1 -(CH 2 ) n -CO-...Formula (I) [wherein R 1 is selected from C1-C12 alkyl, C4-C16 cycloalkyl, C2-C12 alkenyl, and is optionally substituted with at least one group selected from halogen (F, Cl, Br), -CN, -OH, -OOH, -OR, -COOR (R = C1-C4 alkyl, benzyl); 2. The process of claim 1, wherein n is zero or an integer from 1 to 6, preferably 1 or 2.

4. The process of claim 3, wherein the PHA is selected from polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

5. The process of claim 1, wherein the PHA has a weight average molecular weight (Mw) in the range of 10,000 to 1,000,000 Da.

6. The process of claim 1, wherein the PHA is present in an amount of 5 to 30% by weight, preferably 10 to 20% by weight, based on the total weight of the filter element.

7. The process of claim 1, wherein the cellulose acetate fibers have a diameter, expressed as denier per filament (dpf), of 1 to 15, more preferably 5 to 10.

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