PROCESSES FOR PRODUCING FILTER ELEMENTS SUITABLE FOR USE IN SMOKING ARTICLES

Abstract

A process for producing a filter element suitable for use in smoking articles may include: embedding a bundle of cellulose acetate fibers with an aqueous suspension of polyhydroxyalkanoate (PHA) to obtain a wet bundle of the cellulose acetate fibers covered by the aqueous suspension of the PHA; shaping the wet bundle in a form of a continuous elongated element; heating the continuous elongated element to temperature greater than or equal to 140° C. and less than or equal to 180° C. for time sufficient to melt the PHA and to evaporate water from the continuous elongated element; cooling the heated continuous elongated element to obtain crystallization of the PHA; and cutting the so-obtained continuous elongated element into segments of predetermined length.

Claims

1-9. (canceled)

10. A process for producing a filter element suitable for use in smoking articles, the process comprising: embedding a bundle of cellulose acetate fibers with an aqueous suspension of polyhydroxyalkanoate (PHA) to obtain a wet bundle of the cellulose acetate fibers covered by the aqueous suspension of the PHA; shaping the wet bundle in a form of a continuous elongated element; heating the continuous elongated element to temperature greater than or equal to 140° C. and less than or equal to 180° C. for time sufficient to melt the PHA and to evaporate water from the continuous elongated element; cooling the heated continuous elongated element to obtain crystallization of the PHA; and cutting the so-obtained continuous elongated element into segments of predetermined length.

11. The process of claim 10, wherein the embedding of the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA comprises thoroughly embedding the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA.

12. The process of claim 10, wherein the embedding of the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA comprises uniformly embedding the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA.

13. The process of claim 10, wherein the embedding of the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA comprises spraying the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA.

14. The process of claim 10, wherein the embedding of the bundle of the cellulose acetate fibers with the aqueous suspension of the PHA comprises immersing the bundle of the cellulose acetate fibers in the aqueous suspension of the PHA.

15. The process of claim 10, wherein a mass concentration of the PHA in the aqueous suspension is greater than or equal to 1% weight per volume (% w/v) and less than or equal to 20% w/v.

16. The process of claim 10, wherein a mass concentration of the PHA in the aqueous suspension is greater than or equal to 5% weight per volume (% w/v) and less than or equal to 15% w/v.

17. The process of claim 10, wherein prior to the embedding, the bundle of the cellulose acetate fibers has total denier greater than or equal to 20,000 denier and less than or equal to 80,000 denier.

18. The process of claim 10, wherein prior to the embedding, the bundle of the cellulose acetate fibers has total denier greater than or equal to 30,000 denier and less than or equal to 60,000 denier.

19. The process of claim 10, wherein the PHA has a weight-average molecular weight (M.sub.w) greater than or equal to 10,000 daltons (Da) and less than or equal to 1,000,000 Da.

20. The process of claim 10, wherein the PHA is present in an amount greater than or equal to 5% by weight and less than or equal to 30% by weight with respect to a total weight of the filter element.

21. The process of claim 10, wherein the PHA is present in an amount greater than or equal to 10% by weight and less than or equal to 20% by weight with respect to a total weight of the filter element.

22. The process of claim 10, wherein the cellulose acetate fibers have diameter, expressed as denier per filament (dpf), greater than or equal to 1 and less than or equal to 15.

23. The process of claim 10, wherein the cellulose acetate fibers have diameter, expressed as denier per filament (dpf), greater than or equal to 5 and less than or equal to 10.

24. The process of claim 10, wherein the PHA comprises at least one homopolymer.

25. The process of claim 10, wherein the PHA comprises at least one copolymer.

26. The process of claim 10, wherein the PHA comprises at least one terpolymer.

27. The process of claim 10, wherein the PHA comprises 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.

28. The process of claim 10, wherein the PHA is selected from polyhydroxybutyrate (PHB) or poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

29. The process of claim 10, wherein the PHA comprises polyhydroxybutyrate (PHB) or poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV).

Description

EXAMPLES

[0043] Production of the Filter Element.

[0044] An aqueous suspension of poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) (Mw: 700 KDa) at a concentration of 10% w/v, was sprayed on a bundle of cellulose acetate fibers by using an airbrush.

[0045] To produce specimens of the filter element to be used for the subsequent tests, the wet bundle of cellulose acetate fibers embedded by the PHBV suspension was inserted into a tube of PTFE (polytetrafluoroethylene) having a length of 20 cm and a diameter of 0.8 cm. The tube wall had passing holes of 0.26 mm diameter to promote evaporation of water during the subsequent heating.

[0046] The tube containing the wet bundle of cellulose acetate fibers was heated at 170° C. in an oven for 15 minutes, a time sufficient to melt the PHBV, but not to degrade the cellulose acetate.

[0047] Afterwards, the tube was removed from the oven and cooled at room temperature to obtain re-crystallization of the PHBV and to allow the binding of cellulose acetate fibers to one another.

[0048] Then, the filter rods were cut at different lengths (2.3 cm and 0.5 cm), and the amount of PHBV measured in the final filters was 10% by weight, with respect to the total weight of the filter.

[0049] The filters characterized by a length of 2.3 cm, a diameter of 0.8 cm, showed an average weight of 0.160 g, on the other hand the filters characterized by a length of 0.5 cm, a diameter of 0.8 cm, showed an average weight of 0.045 g.

[0050] Determination of ROS.

[0051] (a) Sampling System.

[0052] A computer-controlled Single Cigarette Smoking Machine (SCSM, CH Technologies) was used to generate mainstream smoke under standard smoking conditions (cigarettes burn for 8-9 min with a 2-s, 35-mL puff every minute) according to the Federal Trade Commission (FTC) protocol. Three impingers were filled with 20 mL of a 2′,7′-dichlorofluorescin-horseradish peroxidase (DCFH-HRP) solution and used to collect gas-phase ROS for mainstream smoke. The experimental system is shown schematically in FIG. 1. Marlboro (red) cigarettes (without filter) were used to collect ROS from mainstream smoke.

[0053] In FIG. 1, the SCSM (1) is connected to the three impingers (2) containing the DCFH-HRP solution which receives the smoke produced by the cigarette (3) connected to the first impinger by means of a filter holder (4). The exhaust smoke exits the SCSM through a pipe (5). The SCSM is connected to a laptop (6) for data recordal and elaboration.

[0054] (b) Sample Preparation and Analysis.

[0055] Preparation of Fluorescent Probes and Standards for ROS in Cigarette Smoke.

[0056] The fluorescent probe used to determine ROS in this study was DCFH. A 1 mM stock solution was prepared by dissolving 2′,7′-dichlorofluorescin diacetate (DCFH-DA; Calbiochem, USA) into ethyl alcohol (ACS grade, Pharmo, USA). A 10 mL solution was mixed with 40 mL 0.01 M sodium hydroxide (NaOH) and left in a dark room temperature for 30 min to hydrolyze. Then 200 mL of phosphate buffer, obtained by mixing sodium phosphate dibasic (Na.sub.2HPO.sub.4, Sigma Aldrich, MO, USA) with sodium phosphate dihydrogen phosphate anhydrous (NaH.sub.2PO.sub.4, Fluka, Germany) to achieve a pH of 7.2, was added to the solution. Horseradish peroxidase (HRP, Sigma Aldrich, USA) was used as the catalyst with a concentration of 0.5 units/mL. The final DCFH concentration of this working solution was 5 μM.

[0057] Equivalent H.sub.2O.sub.2 concentration was used to express the ROS concentrations by converting fluorescence intensity using a standard H.sub.2O.sub.2 calibration curve. Four H.sub.2O.sub.2 standards with the concentrations of 1.0, 2.0, 3.0, and 4.0×10.sup.−7 nmol were prepared by mixing 0.1 mL hydrogen peroxide (ACS grade, Sigma Aldrich, USA) with 3 mL DCFH-HRP working solution. Standard blanks were obtained by mixing 0.1 mL deionized Milli-Q water (resistivity>18.2 MΩ) with probe. The standards were placed in cuvettes and incubated at 37° C. in a water bath. Formation of 2,7-dichlorofluorescin was monitored by measuring fluorescence (excitation wavelength: 504 nm; emission wavelength: 524 nm) using a Shimadzu Spectrophotometer (model: RF-5301 PC, Japan).

[0058] (c) Analysis of Reactive Oxygen Substances (ROS).

[0059] Subsequent to sampling, 3 mL of the reagent solution was removed from each impinger (each contains 20 mL), placed into a cuvette, and incubated for 15 min at 37° C. in water bath. Generally, the fluorescence intensities of the solutions in impingers were within the range of the standards. After using the volume of the solution to get the amount of ROS in each impinger, the contents of all three impingers were combined. An aliquot of the solution was taken and the fluorescence intensity was measured. Sampling blanks were obtained by operating the smoking system without any cigarette burning and analyzed in the same way. Sampling blank values were subtracted from sample results. The amount of ROS was measured also on the smoke produced by commercial cigarettes as reported in Table 1.

[0060] Further details about ROS analysis can be found in: [0061] 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; [0062] Mohammad Arifur Rahman & Philip K. Hopke, “Assessment of Methods for the Measurement of Wood Fuel Compositions”, Energy Fuels 2017, 31, 5, 5215-5221.

[0063] Determination of Pressure Drop and Hardness.

[0064] The samples of filter elements according to the present invention (Bio-on filters) were tested to measure pressure drop caused by the filter and hardness of the filter. The same measurements were made for the commercial cigarettes. Pressure drop was measured using Laminar Flow Element (Dwyer Instrument Inc., USA). Hardness was measured using Durometer, ASTM D2240 type A, ISO 868.

[0065] The results are reported in Table 1.

TABLE-US-00001 TABLE 1 Pressure Average ROS * Standard Drop Hardness Samples (nmol/cigarette) Deviation (Pascal) (lb/inch.sup.2) No Filter 120.0 2.5 — — Commercial 40.0 3.0 200.0 451 Marlboro Filter Commercial 37.0 0.9 174.2 475 Camel Filter Commercial 36.0 0.7 211.5 396 Newport Filter Bio-on Filter - 19.9 1.9 81.1 252 2.7 cm Bio-on Filter - 21.2 2.1 85.1 251 2.3 cm Commercial HEET 36.7 5.0 42 499 Malboro 0.5 cm (electronic cigarette) Bio-on filter 11.7 3.9 20 240 0.5 cm * Detection limit: 1.5 nmol

[0066] Without being bound to any theory, the positive effect on ROS quenching by the presence of a PHA in the filter element is believed to be mainly due to the structure of the monomer unit —O—CHR.sub.1—(CH.sub.2).sub.n—CO—. The hydrogen linked to the ternary carbon atom —CHR.sub.1— is particularly reactive with formation of a hydrogen radical that quenches the ROS, by inactivating the same via radical reaction.