Filter element suitable for use in smoking articles and method for producing the same

Abstract

A filter element suitable for use in a smoking article and a method for producing the same. The filter element comprises cellulose acetate fibers, which are bonded together by a polyhydroxyalkyl ester (PHA) surrounding the cellulose acetate fibers. The PHA is used as a binder for the cellulose acetate fibers instead of triacetin or other binders. The PHA is a highly biodegradable polymer that can bond the cellulose acetate fibers when applied to the fiber surface, so that random connection points are formed, thereby maintaining a space between the fibers suitable for the appropriate pressure drop during smoking and giving the filter element a suitable hardness. In addition, since the PHA has a relatively high melting point and is substantially insoluble in water, it will not soften or melt when it is subjected to the warm and humid smoke generated during smoking a cigarette, thereby preventing the filter element from softening or collapsing during smoking. In addition, the presence of PHA on the surface of the cellulose acetate fibers forming the filter element causes a significant reduction in toxic substances in cigarette smoke, especially toxic substances with respect to reactive oxygen species.

Description

Background Art

[0001] The present invention relates to a filter element suitable for use in a smoking article, and to a method for producing the same. More particularly, the present invention relates to a filter element suitable for use in a smoking article, and to a method for producing the same, wherein the filter element comprises a bundle of fibers bonded by a biodegradable material, particularly a polyhydroxyalkanoate (PHA).

[0002] Smoking articles, such as cigarettes, generally have a substantially cylindrical rod-like structure and include a roll of smokeable material, such as tobacco shreds surrounded by a paper wrapper, thereby forming a so-called "smokable rod". Typically, a cigarette has a cylindrical filter element aligned with the smokeable rod in an end-to-end relationship. Typically, the filter element comprises a cellulose acetate fiber bundle surrounded by a paper material, and the filter element is attached to one end of the smokeable rod using a surrounding wrapping material called a "tipped material". Conventional cellulose acetate fibers (which are produced in the form of bundles, also referred to as "tows") are bonded with a suitable plasticizer (generally triacetin (glycerol triacetate)), which is capable of bonding the short fibers to each other to produce a relatively firm and rigid structure that does not soften or collapse during smoking.

[0003] With regard to environmental sustainability, currently available filter technologies for forming filter elements have several disadvantages. For example, conventional filter elements comprising cellulose acetate fibers bonded by triacetin require an undesirably long time to actually biodegrade (generally about two to ten years). Certain filter elements for cigarettes comprising materials that can promote biodegradation of the filter element after use have been developed. For example, it has been noted that certain additives can be added to the filter material to improve 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 by two or more fiber inputs with different physical properties. A first plurality of cellulose acetate staple fibers and a second plurality of degradable polymer staple fibers are blended to obtain a fiber mixture, wherein the staple fibers of the fiber mixture are 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 the filter element. Exemplary biodegradable materials for degradable staple fibers include aliphatic polyesters, cellulose acetate embedded with 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 the structure -[C(O)-RO]n-, wherein n is an integer representing the number of monomer units in the polymer chain, and R is an aliphatic hydrocarbon with a straight or branched chain, preferably C 1 -C 10 Alkylene, more preferably C 1 -C 6 Exemplary aliphatic polyesters include polyglycolic acid (PGA), polylactic acid (PLA) (e.g., poly (L-lactic acid) or poly (DL-lactic acid)), polyhydroxyalkylates (PHA) (e.g., polyhydroxypropionate, polyhydroxyvalerate, polyhydroxybutyrate, polyhydroxyhexanoate, and polyhydroxyoctanoate), polycaprolactone (PCL), polybutylene succinate, polybutylene succinate adipate, and copolymers thereof (e.g., polyhydroxybutyrate-co-hydroxyvalerate (PHBV)).

[0005] Another long-standing problem faced by cigarette manufacturers is to provide filter elements that are more effective in absorbing toxic components of cigarette smoke in order to reduce the well-known risks to human health caused by several by-products generated by the combustion of tobacco and paper, such as polycyclic aromatic hydrocarbons (PAHs), heavy metals, reactive oxygen species (ROS), etc.

[0006] For example, US2012 / 0160255 discloses an electrospun fiber felt cigarette filter for removing toxic compounds from cigarette smoke, which comprises biomacromolecules, multiple additives, solvents and acceptable polymer carriers. The biomacromolecules include polynuclear complexes with multiple metal ions and combinations thereof. The polynuclear complexes are polyporphyrin rings, and the polymetallic ions include ferrous ions, cuprous ions, manganese ions and zinc ions. The biomacromolecules are selected from engineered polymerized hemoglobin and / or chlorophyll.

[0007] US 9,032,970 discloses a method for reducing the amount of Po in cigarette smoke. 210, polycyclic aromatic hydrocarbons (PAH), heavy metal elements and free radicals, wherein in addition to the common components of known cigarette filters, the filter also contains AlOOH·H 2 O and / or Al 2 O 3 and / or aluminosilicates, and grape seeds and cereal husks as antioxidants, and optionally astaxanthin and / or cranberry as additional antioxidants. Summary of the invention

[0008] The problem faced by the Applicant is that of improving the biodegradability of filter elements for use in smoking articles, in particular cigarettes, by using a biodegradable material that does not require modifications to the manufacturing process in a way that is unacceptable for industrial production and that guarantees adequate properties in terms of mechanical resistance during the manufacture of the filter elements with equipment operating at high speeds, thermal resistance during smoking, while still providing the desired taste and filtration properties associated with conventional cigarette filters.

[0009] The applicant has found that the above technical problems and other technical problems better described below can be solved by using polyhydroxyalkylate (PHA) as a binder for cellulose acetate fibers instead of triacetin or other binders, which is a highly biodegradable polymer that can bind cellulose acetate fibers when applied to the fiber surface so that random connection points are formed, thereby maintaining spaces between the fibers suitable for the appropriate pressure drop during smoking and giving the filter element appropriate hardness. In addition, since PHA has a relatively high melting point and is substantially insoluble in water, it does not soften or melt when it is subjected to warm and humid smoke generated during smoking a cigarette, thereby preventing the filter element from softening or collapsing during smoking.

[0010] Furthermore, the applicant has found that the presence of PHA on the surface of the cellulose acetate fibers forming the filter element leads to a significant reduction in toxic substances in cigarette smoke, especially with regard to reactive oxygen species (ROS). Thus, in addition to being more biodegradable relative to conventional filter elements, the filter element according to the invention is also particularly effective in reducing the risks to the health of smokers by quenching the ROS present in cigarette smoke.

[0011] It is well known that ROS are toxic to cells and are the cause of oxidative stress. More than a hundred diseases are associated with ROS, such as diabetes, inflammatory immune damage, autoimmune diseases, tissue damage caused by blood loss, and cancer.

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

[0013] According to a second aspect, the present invention relates to a method for producing a filter element suitable for use in a smoking article, the method comprising:

[0014] embedding the cellulose acetate fiber bundle in the aqueous suspension of PHA to obtain a wet cellulose acetate fiber bundle covered with the PHA suspension;

[0015] forming the wet bundle into the form of a continuous elongated element;

[0016] 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;

[0017] cooling the heated continuous elongated element to effect crystallization of the PHA;

[0018] The continuous elongated element thus obtained is cut into segments of predetermined length.

[0019] According to another aspect, the invention relates to a method for quenching reactive oxygen species (ROS) in smoke generated by a smoking article, wherein the method comprises providing a smoking article with a filter element as defined above.

[0020] According to another aspect, the invention relates to the use of a filter element as defined above, inserted into a smoking article, for quenching reactive oxygen species (ROS) in smoke generated by the smoking article.

[0021] For the purposes of this specification and the claims that follow, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like are to be understood as being modified in all instances by the term "about." Furthermore, all ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0022] With regard to smoking articles, the term includes, according to the present invention, not only conventional cigarettes that are smoked by burning at high temperatures, but also smoking systems recently launched on the market, generally referred to as "heat-not-burn tobacco" systems, in which tobacco rods are not burned but only heated to produce an aerosol containing nicotine and other chemicals (e.g. Philip Morris's IQOS TMKit). In such a system, a small-sized cigarette is used that includes a tobacco rod with different filtering means and a filter element that is usually made of a cellulose acetate filter bonded by triacetin. When in a conventional cigarette, the length of the filter element is usually about 2.3 cm, and in a "cigarette" for a "heat-not-burn tobacco" system, the length of the filter element is usually about 0.5 cm.

[0023] As for the cellulose acetate fibers that can be used in the filter element according to the present invention, they are well known in the field of cigarette manufacturing. They are typically in the form of continuous filaments, with a diameter expressed in denier per filament (dpf) of generally 1 to 15, more preferably 5 to 10. Denier per filament (dpf) is a measure of the weight of a single fiber filament per unit length, specifically grams per 9000 meters. The shape of the cross section of the single filament can vary and can be, for example, rectangular, circular, oval or multi-lobed.

[0024] The total denier of the cellulose acetate fiber bundle is typically in the range of 20,000 denier to 80,000 denier, preferably 30,000 denier to 60,000 denier.

[0025] Preferably, the PHA according to the present invention is a polymer comprising repeating units of formula (I):

[0026] -O-CHR 1 -(CH 2 ) n -CO- (Ⅰ)

[0027] in:

[0028] R 1 Selected from: C 1 -C 12 Alkyl, C 4 -C 16 Cycloalkyl, C 2 -C 12 Alkenyl, the C 1 -C 12 Alkyl, the C 4 -C 16 Cycloalkyl, the C 2 -C 12 The alkenyl group is optionally selected from halogen (F, Cl, Br), -CN, -OH, -OOH, -OR, -COOR (R = C 1 -C 4 alkyl, benzyl) is substituted with at least one group;

[0029] n is 0 or an integer of 1 to 6, and preferably 1 or 2.

[0030] Preferably, R1 is methyl or ethyl, and n is 1 or 2.

[0031] The PHA may be a homopolymer, a copolymer or a terpolymer. In the case of a copolymer or a terpolymer, the PHA may consist of different repeating units of formula (I) or of a combination of at least one repeating unit of formula (I) and at least one repeating unit derived from a comonomer copolymerizable with a hydroxyalkyl ester (e.g., a lactone or a lactam). In the latter case, the repeating unit of formula (I) is present in an amount equal to at least 10 mol % relative to the total number of moles of the repeating units.

[0032] Particularly preferred repeating units of the formula (I) are repeating units derived from 3-hydroxybutyrate, 3-hydroxyvalerate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxyundec-10-enoate, 4-hydroxyvalerate.

[0033] 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-hydroxyundec-10-enoate) (PHOU), poly(3-hydroxybutyrate-co-3-hydroxyvalerate-4-hydroxyvalerate) (PHBVV), polyhydroxybutyrate-hydroxyvalerate copolymers, or mixtures thereof.

[0034] Particularly preferred PHAs for the purposes of the present invention are polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

[0035] Preferably, the weight average molecular weight (M w ) is from 10,000 Da to 1,000,000 Da.

[0036] About the production of PHA, this is preferably achieved by microbial fermentation of organic substrates (e.g. carbohydrates or other fermentable substrates, such as glycerol) via microbial strains capable of producing PHA, and then recovering PHA from cell mass. For further details, see, for example, patent applications WO 99 / 23146, WO 2011 / 045625 and WO 2015 / 015315. Substrates suitable for producing PHA by fermentation can be obtained particularly from the processing of vegetables, such as juice, molasses, and slurries derived from the processing of beets and sugar cane. In addition to sucrose and other carbohydrates, these substrates also typically include organic growth factors, nitrogen, phosphorus, and / or other minerals that can be used as nutrients for cell growth. Alternatives are glycerol, which is a low-cost organic carbon source and a byproduct of biodiesel production, which can optionally be mixed with levulinic acid (see, for example, US 8 956 835 B2).

[0037] As for the method for producing a filter element according to the present invention, it can be carried out by a machine commonly used in cigarette manufacturing when cellulose acetate fibers are bound by triacetin. First, a bundle of cellulose acetate fibers is embedded in an aqueous suspension of PHA. The use of an aqueous suspension of PHA is advantageous because the use of organic solvents for PHA is avoided, such as chlorinated organic solvents (usually chloroform), which are harmful to the environment and may be too aggressive to cellulose acetate fibers.

[0038] 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 a PHA suspension. In order to achieve regular bonding of cellulose acetate fibers with PHA, it is important that the bundles are fully and uniformly embedded in the PHA suspension. The concentration of PHA in the suspension is preferably 1% w / v to 20% w / v, more preferably 5% w / v to 15% w / v.

[0039] The wet bundle is then formed into a continuous elongated element, usually in the form of a substantially cylindrical shape. The forming may be carried out by conventional machines as are well known to cigarette manufacturers.

[0040] Subsequently, the continuous elongated element is heated to a temperature of 140 to 180°C for a time sufficient to melt the PHA and evaporate the water originating from the PHA suspension. This step allows the cellulose acetate fibers to be coated with PHA so as to achieve a strong bond between the fibers when the PHA returns to a crystalline state.

[0041] Thus, the heated continuous elongated element is cooled to achieve crystallization of the PHA. The elongated element thus obtained is formed of cellulose acetate fibers bonded by the PHA and has a relatively strong and rigid structure suitable for producing filter elements for use in the cigarette manufacturing industrial process. The cutting of the final elongated element can be carried out according to techniques well known in the field of cigarette manufacturing.

[0042] The amount of PHA present in the final elongated element is selected to give the filter element the desired stiffness and to maintain spaces between the fibers suitable for the correct pressure drop during smoking. Preferably, the amount of PHA in the filter element is from 5% to 30% by weight, preferably from 10% to 20% by weight, relative to the total weight of the filter element. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the experimental system for measuring reactive oxygen species (ROS) in cigarette smoke.

[0044] The following examples are provided to further illustrate the present invention. Example

[0045] Production of filter elements.

[0046] An aqueous suspension of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (Mw: 700 KDa) having a concentration of 10% w / v was sprayed on a bundle of cellulose acetate fibers by using a spray gun.

[0047] To produce samples of filter elements for subsequent testing, wet cellulose acetate fiber bundles embedded in PHBV suspension were inserted into PTFE (polytetrafluoroethylene) tubes with a length of 20 cm and a diameter of 0.8 cm. The tube wall had through holes of 0.26 mm diameter to facilitate evaporation of water during subsequent heating.

[0048] The tube containing the wet cellulose acetate fiber bundle was heated in an oven at 170°C for 15 minutes, a time sufficient to melt the PHBV but not to degrade the cellulose acetate.

[0049] Thereafter, the tube was taken out of the oven and cooled at room temperature to achieve recrystallization of the PHBV and to allow the cellulose acetate fibers to bond to each other.

[0050] The filter rods were then cut at different lengths (2.3 cm and 0.5 cm) and the amount of PHBV measured in the final filter was 10 wt % relative to the total weight of the filter.

[0051] The filter characterized by a length of 2.3 cm and a diameter of 0.8 cm exhibited an average weight of 0.160 g, while the filter characterized by a length of 0.5 cm and a diameter of 0.8 cm exhibited an average weight of 0.045 g.

[0052] Determination of ROS.

[0053] (a) Sampling system.

[0054] Mainstream smoke was generated using a computer-controlled Single Cigarette Smoking Machine (SCSM, CH Technologies) under standard smoking conditions (cigarette burning for 8 to 9 minutes at 2 seconds, 35 mL puffs per minute) according to Federal Trade Commission (FTC) protocols. 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 was Figure 1 ROS from mainstream smoke were collected using Marlboro (red) cigarettes (no filter).

[0055] exist Figure 1 In the embodiment, the SCSM (1) is connected to three impactors (2) containing DCFH-HRP solution, which receive smoke generated by a cigarette (3) connected to the first impactor through a filter holder (4). The exhaust smoke leaves the SCSM through a tube (5). The SCSM is connected to a laptop computer (6) for data recording and processing.

[0056] (b) Sample preparation and analysis.

[0057] -Preparation of fluorescent probes and standards for ROS in cigarette smoke.

[0058] 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 ethanol (ACS grade, Pharmo, USA). 10 mL of the solution was mixed with 40 mL of 0.01 M sodium hydroxide (NaOH) and allowed to stand at room temperature in the dark for 30 minutes for hydrolysis. Then 200 mL of phosphate buffer was added to the solution, which was prepared by disodium hydrogen phosphate (Na 2 HPO 4 , SigmaAldrich, MO, USA) and anhydrous sodium dihydrogen phosphate (NaH2 PO 4 , Fluka, Germany) was mixed to obtain a pH of 7.2. Horseradish peroxidase (HRP, Sigma Aldrich, USA) was used as a catalyst at a concentration of 0.5 units / mL. The final DCFH concentration of the working solution was 5 μM.

[0059] By using the standard H 2 O 2 The calibration curve converts fluorescence intensity using equivalent H 2 O 2 The concentration of ROS was expressed as 1.0×10 -7 nmol, 2.0×10 -7 nmol, 3.0×10 -7 nmol and 4.0×10 -7 nmol of four H 2 O 2 Standards. A standard blank was obtained by mixing 0.1 mL of deionized Milli-Q water (resistivity>18.2 M□) with the probe. The standards were placed in a cuvette 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-5301Pc, Japan).

[0060] (c) Analysis of reactive oxygen species (ROS).

[0061] Then take a sample, take out 3mL of reagent solution from each impactor (each containing 20mL), put it into a cuvette, and incubate it in a water bath at 37°C for 15 minutes. Usually, the fluorescence intensity of the solution in the impactor is within the range of the standard. After the amount of ROS in each impactor is obtained using the volume of the solution, the contents of all three impactors are combined. Take a portion of the solution and measure the fluorescence intensity.

[0062] Obtain a sampling blank by running the puff system without any cigarette burning and analyze in the same manner. Subtract the sampling blank value from the sample results.

[0063] As reported in Table 1, the amount of ROS was also measured for smoke generated by commercial cigarettes.

[0064] More details on ROS analysis can be found in: 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.

[0065] Determination of pressure drop and hardness.

[0066] Samples of filter elements according to the invention (Bio-on filters) 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).

[0067] The hardness was measured using a durometer (ASTM D2240 Type A, ISO 868).

[0068] The results are reported in Table 1.

[0069] Table 1.

[0070]

[0071]

[0072] *Detection limit: 1.5nmol

[0073] Without being bound by any theory, it is believed that the positive effect of the presence of PHA in the filter element on ROS quenching is mainly due to the monomer unit -O-CHR 1 -(CH 2 )n-CO- structure. With the three-membered carbon atom -CHR 1 -Attached hydrogen is particularly reactive in forming hydrogen radicals that quench ROS by inactivating them via free radical reactions.

Claims

1. A method for producing a filter element suitable for use in a smoking article, the filter element comprising cellulose acetate fibers bonded together by a polyhydroxyalkanoate (PHA) surrounding the cellulose acetate fibers, the method include: embedding a cellulose acetate fiber bundle in an aqueous suspension of polyhydroxyalkylate (PHA) to obtain a wet cellulose acetate fiber bundle covered with the polyhydroxyalkylate (PHA) suspension; forming the wet bundle into the form of 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 polyhydroxyalkanoate (PHA) and evaporate water; cooling the heated continuous elongated element to effect crystallization of the polyhydroxyalkanoate (PHA); The continuous elongated element thus obtained is cut into segments of predetermined length.

2. The method of claim 1, wherein the total denier of the cellulose acetate fiber bundle is in the range of 20,000 denier to 80,000 denier.

3. The method of claim 2, wherein the total denier of the cellulose acetate fiber bundle is in the range of 30,000 denier to 60,000 denier.

4. The method of claim 1, wherein the polyhydroxyalkanoate (PHA) is a polymer comprising repeating units of formula (I): -O-CHR 1 -(CH 2 ) n -CO- (I) in ： R 1 Selected from: C 1 -C 12 Alkyl, C 4 -C 16 Cycloalkyl, C 2 -C 12 Alkenyl, the C 1 -C 12 Alkyl, the C 4 -C 16 Cycloalkyl, the C 2 -C 12 The alkenyl group is optionally substituted with at least one group selected from halogen, -CN, -OH, -OOH, -OR, -COOR, wherein R=C 1 -C 4 Alkyl, benzyl; n is 0 or an integer of 1 to 6.

5. The method according to claim 4, wherein n is 1 or 2 in formula (I).

6. The method according to claim 4 or 5, wherein the polyhydroxyalkanoate (PHA) is selected from polyhydroxybutyrate (PHB) and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

7. The method according to claim 1, wherein the weight average molecular weight (M w ) is from 10,000 Da to 1,000,000 Da.

8. The method of claim 1, wherein the polyhydroxyalkanoate (PHA) is present in the filter element at 5 wt% to 30 wt% relative to the total weight of the filter element.

9. The method of claim 8, wherein the polyhydroxyalkanoate (PHA) is present in the filter element at 10 wt% to 20 wt% relative to the total weight of the filter element.

10. The method of claim 1, wherein the cellulose acetate fibers have a diameter in the range of 1 to 15 in denier per filament (dpf).

11. The method of claim 10, wherein the cellulose acetate fibers have a diameter in the range of 5 to 10 in denier per filament (dpf).

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