FILTER COMPRISING A PAPER SUBSTRATE COMPRISING A MONOLAYER BASE WEB WITH DIFFERENT FIBROUS PORTIONS

Abstract

Filters and filter media are provided that comprise a paper substrate. Methods of making the filters and filter media, and products containing the filter, such as smoking articles and vaping articles, are also provided. The paper substrate comprises a monolayer base web having a first portion and a second portion. the first portion and the second portion are disposed adjacent each other along a thickness direction of the monolayer base web. The fibers of the first portion are intermeshed with the fibers of the second portion in a transition zone. The second portion may comprise more fibers, in terms of mass per unit area, than the first portion. the density of the paper substrate may be from about 200 mg/cm.sup.3 to about 300 mg/cm.sup.3.

Claims

1. A filter media comprising: a paper substrate, the paper substrate comprising a monolayer base web having a first portion and a second portion, the first portion and the second portion being disposed adjacent each other along a thickness direction of the monolayer base web; wherein the fibers of the first portion are intermeshed with the fibers of the second portion in a transition zone; wherein the second portion comprises more fibers, in terms of mass per unit area, than the first portion; and wherein the density of the paper substrate is from 200 mg/cm.sup.3 to 300 mg/cm.sup.3.

2. The filter media of claim 1, wherein the air permeability of the paper substrate is greater than 4000 Coresta Unit (CU).

3. The filter media of claim 1, wherein the thickness of the paper substrate is about 100 m to about 200 m.

4. The filter media of claim 1, wherein the basis weight of the paper substrate is about 25 to about 55 g/m.sup.2.

5. The filter media of claim 1, wherein the tensile strength ratio MD/CD of the paper substrate is about 2 to about 3.2.

6. The filter media of claim 1, wherein the fibers of the first portion are curled fibers and the fibers of the second portion are uncurled fibers.

7. The filter media of claim 6, wherein the curled fibers have a spiral or helical shape.

8. The filter media of claim 1, wherein the fibers of the first portion and the fibers of the second portion are selected from the group consisting of wood fibers, natural fibers and combinations thereof.

9. The filter media of claim 1, wherein the paper substrate has a specific volume of about 4.5 cm.sup.3/g to about 9 cm.sup.3/g.

10. The filter media of claim 1, wherein a weight ratio between fibers of the first portion to fibers of the second portion is about 20:80.

11. The filter of claim 10, wherein the weight ratio is about 40:60.

12. A filter comprising the filter media of claim 1.

13. The filter of claim 12 for use with a smoking article or a vaping article.

14. A smoking or vaping article comprising: a filter media comprising a paper substrate, the paper substrate comprising a monolayer base web having a first portion and a second portion, the first portion and the second portion being disposed adjacent each other along a thickness direction of the monolayer base web; wherein the fibers of the first portion are intermeshed with the fibers of the second portion in a transition zone; wherein the second portion comprises more fibers, in terms of mass per unit area, than the first portion; and wherein the density of the paper substrate is from 200 mg/cm.sup.3 to 300 mg/cm.sup.3.

15. A method for producing a paper substrate comprising: forming a monolayer base web on a substrate; and removing the monolayer base web from the substrate to produce the paper substrate.

16. The method of claim 15, further comprising: wet laying a first portion on the substrate by disposing a first slurry containing fibers on the substrate; and while the first portion is still wet, wet laying a second portion on to the first portion to allow intermeshing of the fibers in the first portion with the second portion.

17. The method of claim 16, further comprising removing liquid from the first and second portions to form the monolayer base web.

18. The method of claim 15, further comprising: wet laying the second portion on the substrate by disposing a second slurry containing fibers on the substrate; and while the second portion is still wet, wet laying the first portion on the second portion, to allow intermeshing of the fibers in the first portion with the second portion.

19. The method of claim 18, further comprising: removing liquid from the first and second portions to form the monolayer base web.

20. The method of claim 15, further comprising: forming a rod from the paper substrate produced by the process for producing a paper substrate: wrapping the rod with a sheet of plug wrap paper; depositing an adhesive line at the junction of the sheet of plug wrap paper to obtain a rod of filtering material; and cutting the rod of filtering material to produce the filter.

Description

DETAILED DESCRIPTION

[0030] This description and the accompanying drawings illustrate exemplary embodiments and should not be taken as limiting, with the claims defining the scope of the present description, including equivalents. Various mechanical, compositional, structural, and operational changes may be made without departing from the scope of this description and the claims, including equivalents. In some instances, well-known structures and techniques have not been shown or described in detail so as not to obscure the description. Like numbers in two or more figures represent the same or similar elements. Furthermore, elements and their associated aspects that are described in detail with reference to one embodiment may, whenever practical, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment and is not described with reference to a second embodiment, the element may nevertheless be claimed as included in the second embodiment. Moreover, the depictions herein are for illustrative purposes only and do not necessarily reflect the actual shape, size, or dimensions of the system or illustrated components.

[0031] It is noted that, as used in this specification and the appended claims, the singular forms a, an, and the, and any singular use of any word, include plural referents unless expressly and unequivocally limited to one referent. As used herein, the term include and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

[0032] Except as otherwise noted, any quantitative values are approximate whether the word about or approximately or the like are stated or not. The materials, methods, and examples described herein are illustrative only and not intended to be limiting.

[0033] All references cited herein are hereby incorporated by reference in their entireties. In the event of a conflict in a definition with a cited reference, the present teachings control.

[0034] As used herein, the terms about or approximately means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, about can mean within three or more than three standard deviations, per=the practice in the art. Alternatively, about can mean a range of up to 20%, preferably up to 10%, more preferably up to 5%, and more preferably still up to 1% of a given value. Also, particularly with respect to systems or processes, the term can mean within an order of magnitude, preferably within five-fold, and more preferably within 5 thin two-fold, of a value. Wt % herein, unless otherwise specified is w/w %.

[0035] Filters and filter media are provided herein. In one aspect, the filter media comprise a paper substrate as a filter media. The paper substrate comprises a monolayer base web having a first portion and a second portion.

[0036] In embodiments, the first portion and the second portion are disposed next to each other along a thickness direction of the monolayer base web. The fibers of the first portion may be intermeshed with the fibers of the second portion in a transition zone.

[0037] In embodiments, the second portion comprises more fibers, in terms of mass per unit area, than the first portion. The density of the paper substrate may be from about 200 mg/cm.sup.3 to about 300 mg/cm.sup.3, or about 220 mg/cm.sup.3 to 270 mg/cm.sup.3, or about 230 mg/cm.sup.3 to 260 mg/cm.sup.3.

[0038] The term monolayer base web is used herein to mean a fibrous sheet made of a single layer.

[0039] The monolayer base web has a first portion and a second portion, and the first portion and second portions are disposed next to each other along a thickness direction of the monolayer base web. The first portion and second portion may be lamellar, i.e. having first and second dimensions that are both larger than a third dimension (i.e. a thickness direction), and typically overlie one another and occupy the same area of the monolayer base web. The thickness direction is from one face of the monolayer base web to the other face of the monolayer base web, and is typically the shortest distance from opposing faces of the monolayer base web. The fibers from the first portion are intermeshed with the fibers from the second portionthis may be from forming first and second portion together, e.g. by wet laying both first and second portion together, as described herein, to allow intermeshing of the fibers. Accordingly, at the point where the first and second portions meet in the layer, fibers from the first portion intermesh with the second portion, binding first and second portions together. This allows a continuum of the intermeshed fibrous structure through the thickness of the monolayer base web and therefore a continuum of voids through the thickness of the monolayer base web, and avoids an abrupt interface as would be seen when two separately-formed fibrous layers are contacted together.

[0040] The first and second portion formed may be as described herein, e.g. wherein the weight ratio of the fibers in the first portion to the fibers in the second portion is n:1, wherein n is >1, and wherein the monolayer base web comprises two different types of cellulosic fiber and the second portion comprises more synthetic fibers, in terms of mass per unit area, than the first portion.

[0041] The weight ratio of fibers of the first portion to the fibers of the second portion may be from 20:80 to 40:60, or about 25:75 to 35:65.

[0042] The fibers of the first portion may be curled fibers, and the fibers of the second portion may be uncurled fibers.

[0043] In contrast to the uncurled fibers, the curled fibers are fibers having a shape of spiral or helix. Moreover, the curled fibers differ from the uncurled by the air permeability. Indeed, the air permeability of the curled fibers is at least 20% higher than uncurled fibers.

[0044] The density of the monolayer base web of the filter is attributed at least in part to the curled fibers and the uncurled fibers.

[0045] Independently from each other, the fibers of the first portion and the fibers of the second portion may be wood fibers, natural fibers or combinations thereof.

[0046] The wood fibers may be hardwood pulp, bleached hardwood pulp, softwood pulp, bleached softwood pulp, softwood fluff pulp, lyocell fibers (cellulose fibers which are ground and dissolved in N-methylmorpholine N-oxide monohydrate for the purpose of obtaining fibers with a cross section of variable shape (round, oval, cross-shaped, circular, lamellar cross section) with calibrated length and mass per unit length, which the person skilled in the art can choose depending on their needs), viscose fibers (fibers obtained by dissolving cellulose by means of modification of its hydroxyl groups by carbon disulfide (CS.sub.2) and then precipitating it in the presence of sulfuric acid (H.sub.2SO.sub.4) for the purpose of obtaining fibers with a cross section of variable shape (round, oval, cross-shaped, circular, lamellar cross section) with calibrated length and mass per unit length, which the person skilled in the art can choose depending on their needs) or mixtures thereof, in particular bleached softwood pulp, softwood pulp, softwood fluff pulp, lyocell fibers, viscose fibers or mixtures thereof, more particularly bleached softwood pulp, softwood pulp, softwood fluff pulp or mixtures thereof.

[0047] Natural fibers such as leaf fibers, fruit fibers, seed fibers, bast fibers, stalk fibers, reed fibers or mixtures thereof, in particular leaf fibers, seed fibers, bast fibers or mixtures thereof, more particularly bast fibers.

[0048] For the purposes of the present application, bast fiber denotes a plant fiber contained in the bast of the plants. The bast fibers may be abaca fibers, hemp fiber, Indian hemp fiber, jute fiber, kenaf fiber, kudzu fiber, coin vine fiber, flax fiber, okra fiber, nettle fiber, papyrus fiber, ramie fiber, sisal fiber, esparto fiber or mixtures thereof, in particular hemp fiber, flax fiber, sisal fiber or mixtures thereof, more particularly flax fiber, sisal fiber, or mixtures thereof.

[0049] For the purposes of the present application, seed fiber denotes a fiber obtained from seeds of a plant. The seed fibers may be cotton fiber, kapok fiber, luffa fiber, milkweed fiber or mixtures thereof.

[0050] The air permeability of the paper substrate may be higher than 4000 CORESTA Unit (CU), or about 6000 CU to about 12000 CU, or about 9000 CU to about 1100 CU. An air permeability in these ranges is advantageously higher than the air permeability of a paper substrate used in the standard paper filters, i.e. about 3300 CU. This higher air permeability can explain the better nicotine retention capacity of the filter of the present invention than the nicotine retention capacity of the standard paper filters.

[0051] The air permeability of the paper substrate can be determined by ISO 2965:2009. The paper substrate can be conditioned for at least 30 min at 23 C. and 50% humidity before the measurement.

[0052] The thickness of the paper substrate may be from about 100 m to about 200 m, or about 120 m to about 180 m, or about 130 m to about 170 m.

[0053] The basis weight of the paper substrate may be about 25 g/m.sup.2 to about 55 g/m.sup.2, or about 30 g/m.sup.2 to about 50 g/m.sup.2, or about 35 g/m.sup.2 to about 45 g/m.sup.2 measured as per ISO 536:2012.

[0054] The skilled person knows how to adapt the basis weight and the thickness of the paper substrate to reach the required density since the density of the paper substrate is calculated by dividing its basis weight by its thickness.

[0055] The standard ISO 534:2011 can be used to determine the thickness of paper substrate. The paper substrate can be conditioned for at least 30 min at 23 C. and 50% humidity before the measurement.

[0056] The standard ISO 536:2012 can be used to determine the basis weight of the paper substrate. The paper substrate can be conditioned for at least 30 min at 23 C. and 50% humidity before the measurement.

[0057] The tensile strength ratio MD/CD of the paper substrate may be about 2.0 to about 3.2, or about 2.1 to 2.8, or about 2.2 to 2.7. These ranges of tensile strength ratio ensures that the mechanical properties of the paper substrate are sufficient to produce the filter of the present invention.

[0058] The tensile strength ratio is obtained by dividing tensile strength values measured in machine direction (MD) by tensile strength values measured in cross direction (CD). The tensile strength values in machine direction (MD) and the tensile strength values in cross direction (CD) may be measured at 15 mm band size as per ISO 1924-2 2009-05.

[0059] The elongation at break in machine direction (MD) of the paper substrate may be from about 1.4% to about 2.5%, or about 1.5% to about 2.4%, or about 1.6% to about 2.2%.

[0060] The elongation at break in cross direction (CD) of the paper substrate may be about 3.0% to about 5.5%, or about 3.2% to 5.2%, or about 3.5% to 5.0%.

[0061] The elongation at break in machine direction (MD) and the elongation at break in cross direction (CD) may be measured at 15 mm band size as per ISO 1924-2 2009-05.

[0062] The specific volume of the paper substrate may be from 4.5 cm.sup.3/g to 9 cm.sup.3/g, from 5 cm.sup.3/g to 7 cm.sup.3/g, more particularly from 5.5 cm.sup.3/g to 6.5 cm.sup.3/g.

[0063] The specific volume, Vsp, is obtained by the following formula:

[00001]$\mathrm{Vsp}=(\mathrm{thickness}\mathrm{1000})/\mathrm{grammage}.$

[0064] In one embodiment, the weight ratio of the fibers of the first portion to the fibers of the second portion may be from 20:80 to 40:60, the thickness of the of the paper substrate may be from 100 m to 200 m, the tensile strength ratio MD/CD of the paper substrate may be from 2 to 3.2, the fibers of the first portion and of the second portion may be wood fibers, the fibers of the first portion may be curled fibers and the fibers of the second portion may be uncurled fibers, and the specific volume of the paper substrate may be from 4.5 cm.sup.3/g to 9 cm.sup.3/g.

[0065] In one embodiment, the weight ratio of the fibers of the first portion to the fibers of the second portion may be from 20:80 to 40:60, the thickness of the of the paper substrate may be from 100 m to 200 m, the tensile strength ratio MD/CD of the paper substrate may be from 2.2 to 2.7, the fibers of the first portion and of the second portion may be wood fibers, the fibers of the first portion may be curled fibers and the fibers of the second portion may be uncurled fibers, and the specific volume of the paper substrate may be from 5.5 cm.sup.3/g to 6.5 cm.sup.3/g.

[0066] The filter may be a filter for a smoking article or a vaping article. For the purposes of the present application, smoking article denotes an article comprising tobacco and/or any other plant intended to be smoked. For example, the smoking article may be a machine-manufactured cigarette, a roll-your-own cigarette or a make-your-own cigarette.

[0067] Typically, the filter for a smoking article has a right circular cylindrical shape and comprises an outer envelope of plug wrap paper for a smoking article, in particular for a cigarette, and the paper substrate as defined above located within the outer envelope.

[0068] For the purposes of the present application, vaping article denotes an article comprising tobacco and/or any other plant intended to be vaped, which is intended to be inserted into a device which heats the tobacco and/or the plant without burning said tobacco/plant and which enables delivery of an aerosol to a user. For example, the vaping article can be a tobacco stick.

[0069] Typically, the filter for a vaping article has a right circular cylindrical shape and comprises an outer envelope of plug wrap paper for a vaping article, in particular for a tobacco stick, and the paper substrate as defined above located within the outer envelope.

[0070] The filter can comprise: an outer envelope of plug wrap paper for a filter for a smoking or vaping article, and the paper substrate within the outer envelope.

[0071] The filter may have a right circular cylindrical shape.

[0072] According to another aspect, a smoking article is provided comprising a filter as defined above.

[0073] According to another aspect, a vaping article is provided comprising a filter as defined above.

[0074] According to another aspect, a process for producing a paper substrate as defined above, comprising the following steps: a1) forming a monolayer base web on a substrate, and a2) removing the monolayer base web from the substrate to produce the paper substrate.

[0075] The monolayer base web may be made using any suitable technique that allows intermeshing of fibers, including, but not limited to, wet laying, air laying and foam forming or laying of fibers. Wet laying is preferred, since it typically results in a thinner fibrous layer than, for example, air laying.

[0076] For example, step a1) may comprise the following sub-steps: a111) wet laying the first portion on the substrate by disposing a first slurry containing fibers on the substrate and, while the first portion is still wet, wet laying the second portion on the first portion, to allow intermeshing of the fibers in the first portion with the second portion, and then a112) removing liquid from the first and second portions to form the monolayer base web.

[0077] Alternatively, step a1) may comprise the following sub-steps: a121) wet laying the second portion on the substrate by disposing a second slurry containing fibers on the substrate and, while the second portion is still wet, wet laying the first portion on the second portion, to allow intermeshing of the fibers in the first portion with the second portion, and then a122) removing liquid from the first and second portions to form the monolayer base web.

[0078] The first and second slurries may be wet laid using a paper making machine, such as a fourdrinier or a rotoformer. The paper making machine preferably has a dual channel headbox, i.e. allowing two different slurries to be laid on top of one another.

[0079] The substrate may be a porous substrate, such as a wire mesh or porous screen, that allows liquid from the slurries to flow through, but not the fibers from the slurries to flow through. The liquid may be removed by vacuum, e.g. by reducing the pressure below the porous substrate, to effect a flow of liquid through the substrate.

[0080] The first slurry and second slurry as applied to the substrate may, respectively, contain the same or different types and proportions of fibers to form the monolayer base web. The concentrations of the different types of fibers within the first and second slurries and the relative volumes of first and second slurries applied to the substrate can be adjusted by the skilled person to reflect the desired relative amounts of fibers within the first and second portions. For example, the weight ratio of the fibers in the first portion to the fibers in the second portion is n:1, wherein n is >1. Accordingly, to achieve this with first and second slurries with the same total concentration of fibers as one another, a greater volume of the first slurry is laid down on a substrate (to form the first portion) in a wet laying technique, than the volume of the second slurry laid down on the first portion; similarly, where the first and second slurries have same total concentration of fibers then the relative volumes of first and second slurries laid down on the substrate (or, in the case of the second slurry, on the first portion formed by the first slurry), i.e. volume of first slurry:volume of second slurry, may be n:1, e.g. wherein n is 2 to 10, optionally 3 to 5, optionally 3.5 to 4.5 optionally about 4. If the total concentration of fibers in first and second slurries is different, then the volume of the slurry laid down on the substrate can be adjusted accordingly by the skilled person, to ensure that the weight ratio of the fibers in the first portion to the fibers in the second portion is n:1, wherein n is >1.

[0081] According to another aspect, a process for producing a filter as defined above for a smoking article or vaping article comprises: a2) forming a rod from the paper substrate produced by the process for producing a paper substrate as defined above, b2) wrapping the rod with a sheet of plug wrap paper, and c2) depositing an adhesive line at the junction of the sheet of plug wrap paper to obtain a rod of filtering material, and d2) cutting the rod of filtering material to produce the filter.

[0082] The paper substrate involved in step a2) can be shaped.

[0083] The process may comprise, before step a2), a step of shaping the paper substrate by crimping, embossing, folding, compression or combinations thereof.

EXAMPLES

Example 1: Paper Substrate Manufacturing

[0084] The paper substrate was produced as follows: A slurry comprising softwood fibers and hardwood fibers with a weight ratio of 90:10 is introduced into first head-box of a wet laid process. A slurry comprising only softwood fibers as fibers is introduced into a second headbox of a wetland process. A first portion is wetlaid on a porous substrate from the first-head box, then while the first portion is still wet, the second portion is wet laid on the first portion from the second-head box. The liquid is removed from the first and second portions are dried to remove to form a monolayer base web. The monolayer base web is then removed from the porous substrate to obtain the paper substrate.

[0085] The ratio of the fibers of the first portion to the fibers of the second portion is 70:30 respectively.

[0086] The paper substrate obtained paper has a density of 245 mg/cm.sup.3, a basis weight of 40 g/m.sup.2, a thickness of 161 m and a permeability of 10930 CU.

[0087] The properties of the manufactured paper substrate (referred as paper substrate of Example 1 below) and of a conventional paper substrate (referred as conventional paper substrate below) used in standard paper filters are presented in Table 1.

TABLE-US-00001 TABLE 1 conventional paper Paper substrate substrate of Example 1 Density (mg/cm.sup.3) 429 245 Basis weight 36 40 (g .Math. m.sup.2) Thickness (m) 84 161 Permeability (CU) 3300 10931

Example 2: Filter Manufacturing

[0088] A filter rod for a smoking article was manufactured with a nonporous plug wrap paper having a basis weight of 23.5 g/m.sup.2 as an outer envelope and the paper substrate of Example 1.

[0089] A filter rod for a smoking article was manufactured with a nonporous plug wrap paper having a basis weight of 23.5 g/m.sup.2 as an outer envelope and the conventional paper substrate.

[0090] The properties of these two filter rods were compared with the properties of a commercial cellulose acetate filter rod from Marlboro Red France.

[0091] The filter rod hardness was measured by a standard method by use a Filtrona DHT200 equipment. Results are expressed at % of crushing versus initial diameter of filter.

[0092] The characteristics of the filters are given in Table 2 below.

[0093] Table 2 demonstrates that the filters according to the invention have: [0094] higher hardness than hardness of the conventional paper filter, and [0095] hardness of the same magnitude of order or higher than the hardness of the commercial cellulose acetate filter.

TABLE-US-00002 TABLE 2 Commercial Comparative Filter with cellulose paper Paper substrate acetate filter filter of Example 1 Filter rod weight n.d. 232 229 (mg) Hardness of filter 95% 92% 96% rod (%)

Example 3: Manufacture and Characterization of Cigarettes

[0096] Cigarettes were prepared using the filters rods described in Example 2. The filters were cut to 21 mm length. To form the cigarettes, the rods of tobacco were assembled with the cut filters using nonporous 35 g/m.sup.2 tipping paper. A commercial American blend tobacco was used to form the rods of tobacco. The cigarettes were prepared with a pressure difference similar to that of the commercial cigarette. The ventilation of the cigarettes was blocked.

[0097] The cigarettes prepared were smoked on a Borgwaldt RM20 smoking machine in accordance with the standard ISO 3308:2000. The pressure drop was measured in accordance with the standard ISO 6565:2002. The nicotine content in the smoke was measured in accordance with the standard ISO 10315:2000. The smoking results are given in Table 3 below.

[0098] Table 3 demonstrates that, with an equivalent pressure drop, the difference between the nicotine retention of the cigarettes with the filter according to the invention and the nicotine retention of the cigarettes with the commercial cellulose acetate filter is lower than the difference between the nicotine retention of the cigarette with the conventional paper filter and the nicotine retention of the cigarettes with the commercial cellulose acetate filter.

TABLE-US-00003 TABLE 3 Commercial Comparative Filter with cellulose paper Paper substrate acetate filter filter of Example 1 Cigarette pressure 104 116 116 drop (mmWg) Nicotine retention 0% 41% 31% in smoke vs cellulose acetate

[0099] While the devices, systems, and methods have been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be affected by those skilled in the art. Accordingly, the foregoing description should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.