Method and device for filter material plasma treatment

FIELD: tobacco industry.

SUBSTANCE: invention relates to a smoking product filter that includes a carbon-containing filter material the surface whereof is subjected to alteration by way of plasma treatment for modification of the filter material selective filtration properties.

EFFECT: intensification of acidic and basic properties of the filtering material surface.

19 cl, 3 dwg

The technical field

In General, the invention relates to filters, including filters for Smoking articles such as cigarettes.

The level of invention

Most of the cigarette includes a filter for vapor absorption and collection of the solid particles to tobacco smoke. The main component of most filters is the insertion of a fiber mass of cellulose acetate, wrapped with filter paper. This material is usually made in the form of synthetic fibers of cotton or wood pulp. To bond the fibers may be used plasticizer, for example, triacetin (glycerol triacetate).

In the filter must be combined with effective removal of unwanted components of cigarette smoke and the usability of the product by the consumer. Accordingly, there is a need to improve the operating characteristics of cigarette filters.

There are several ways of introducing carbon or activated carbon in cigarette filters to improve their filtering properties. For example, the carbon may be introduced as a separate element inside the filter, either in the form of particles can be distributed through the fiber mass filter and / or paper wrapper of the filter. In the US 2006/0151382 disclosed the use of non-porous carbon nanostructure material, except for materials on the basis of nanotubes suitable for cigars the spas filter. Carbon may be precipitated metal from the gas phase, for example, using chemical or physical deposition from the gas (vapor) phase. One of the drawbacks of chemical deposition from the gas phase is the fact that commonly used solvents, which can lead to contamination and unwanted residues.

The invention

In the present invention proposes a method of manufacturing a material for a filter, comprising carbon, suitable for use in Smoking products. The method involves changing the properties of a selective filtering material of the filter by changing the surface of the filter material. The change of the surface is plasma-processed.

Processing through or nonequilibrium low-temperature plasma (see, for example, Ortmeyer (Wertheimer), and others; Treatment of materials by low-temperature plasma: past, present and future; a Plasma process and polymers (Low Temperature Plasma Processing of Materials: Past, Present and Future; Plasma Processes and Polymers), 2, 7-15, 2005) it is possible to modify the chemical composition and structure of the surfaces of the material, including the materials of the filter, while maintaining constant their bulk properties. The use of plasma allows to apply the filter material coated with the specified chemical composition and properties, or to impart to the material of the filter paraneoplasia chemical properties. If configured plasma parameters, obtaining such surfaces with a variety of chemical compounds, including some that cannot be obtained in solutions. In addition, plasma processes, there is no need to use solvents that eliminates the problem of contamination and residues, and weakens the impact of the modification process on the environment. Like, caused by exposure to the plasma, changes in the composition and structure of the surface usually affect the filtration properties. For example, increasing the surface area (for example, due to roughness) can lead to better absorption of volatile compounds, as well as to the new chemical composition of the surface that includes the desired chemical group.

Modified filter properties are usually not the same for all parts of the smoke, but they can become more selective. This allows for targeted modification of the filtering properties of the filter materials so that some parts of the smoke will be suppressed more than others. This will result in a Smoking product with improved characteristics, retaining its appeal to consumers.

Possible modifications of the filter is increased acidity of its surface directed to sweat nsaline improve absorption of key chemical components, present in the smoke, or, on the contrary, increased alkaline nature of the surface to improve the absorption of acidic compounds.

Thus, selective modification of the filtering properties of the filter material may include increased absorption of acidic elements.

Alternatively, selective modification of the filtering properties of the filter material may include increased absorption of alkaline elements (components).

Alternatively, selective modification of the filtering properties of the filter material may include increased hydrophilicity of the surface of the material.

The increased hydrophobic properties of the filter can provide better resistance to moisture.

It should be understood that the particular filter material may be successively subjected to one or more modifying treatments for receiving, as a result, filter one or more properties. Thus, the filter material may be, for example, subjected to two different types of plasma processing. It should be borne in mind that the particular filter may consist of separate pieces of material, each of which is subjected to its plasma processing to obtain a desired range of the filtering properties of the resulting filter. Thus, the filter material may include a first material, otvergnuty first plasma process, and the second material are subjected to a second plasma process.

Gases that may be used in plasma processing include NH₃(for major groups, including nitrogen), and N₂and H₂alternatively; and O₂(for more acid groups) with water vapor as an alternative. Plasma development properties, as well as plasma etching, to a large extent depends on the properties of the sublayer, namely, the final chemical composition of the grafted surface strongly depends on the nature of the material of the underlayer. The treatment of plasma-chemical deposition from the gas phase (POLL or PE-CVD). Plasma Enhanced Chemical Vapour Deposition), in contrast, much weaker depends on the properties of the sublayer. Thus, plasma processing may include, for example, plasma chemical deposition from the gas phase of acrylic acid. Plasma treatment can also, or alternatively, include etching with oxygen and (or) NH₃.

As an example, gas/steam connections that can be used to create a coating on the surface by means of POLL - processing, possibly in a mixture with argon or other inert buffer gases can lead acrylic acid (AA) or other organic acids (for coating with acid groups and properties on the surface), allylamine (AAM) or other organic amines (for coating with major groups and properties on the surface). Proper adjustment of the plasma parameters, for example, power, pressure, nature of the input compounds and their consumption, when appropriate to the diagnosis, usually allows you to configure the dissociation supplied connections on the input, and hence the density of active particles (radicals, atoms, ions, and other), which can interact with the sublayer and, thus, the composition and properties of the modified substrate, the Changing nature of the input gas/steam connection, usually called "monomer" in POLL-processing, allows to obtain a large number of coatings with different properties and nature (for example, the type of silica, Teflon and others), some of which are widely used in industry.

The filter material may include carbon in granular form. Before putting in the filter (for example, application in fiber weight of cellulose acetate), the carbon may be subjected to plasma processing in this granular form in an appropriately arranged plasma reactor. In another embodiment, the carbon is introduced into the medium before plasma treatment. For example, the carbon may be introduced into the fiber or sheet material, such as paper. In the process equipment can be used coiled fiber feeding or sheet material to ensure transmission of the filter material with vosi the plasma chamber. One of the possible options, the filter material is passed through several processing chambers, each of which is designed for plasma treatment of its type.

The invention also features a filter material suitable for use in Smoking products. The filter material may include carbon, the surface of which was modified by plasma treatment to modify the properties of selective filtration filter.

In accordance with the invention, also proposed a Smoking article (e.g., cigarette), including such a filter.

Thus, the described in the present disclosure principle mainly includes changing, by processing a non-equilibrium plasma, chemical composition and other properties of the surface of the filter material in order to ensure that this surface is more effective absorption of cigarette smoke, and other similar items. In one embodiment, as the material of the filter uses activated carbon in granular form (e.g., cigarettes), which is subjected to plasma treatment to modify the properties of the surface. Similar granules of carbon, subjected to plasma processing was performed experiments with simulation area, which demonstrated improved filtration properties in terms of removal of certain with the Charter of the parts of the smoke, compared with untreated granules of carbon.

Brief description of drawings

To better explain the present invention will be used with reference to the examples shown on the following drawings:

figure 1 schematically presents the chamber of the plasma reactor suitable for processing granular materials homogeneous plasma, in accordance with one embodiment of the invention;

figure 2 schematically presents the chamber of the plasma reactor with roll feed material suitable for material processing sublayer supplied in the form of a tape, in accordance with one embodiment of the invention;;

figure 3 presents data on the contact angle of water (WCA - from the English. water contact angle)obtained from aqueous solutions at different pH, graphite subjected to the same plasma processing used to report the surface of the granules of carbon predetermined acidic/basic properties, in accordance with one embodiment of the invention.

Detailed description of the invention

Plasma processing

Non-equilibrium cold plasma of low pressure (i.e., plasma at room temperature, instead of thermal plasma at a temperature of thousands of degrees) is a valuable tool that can be used for mo is eficacia composition and surface topography of the material, without changing its bulk properties. Plasma processing is used in many industries, including microelectronics, semiconductors, packaging, food and medicine, automotive, corrosion protection and biomaterials. We can distinguish three main classes of plasma processing, namely: Plasma Etching, i.e. removing material through the formation of volatile products resulting from the interaction of the material with the active particles generated in the plasma; plasma-chemical deposition from the gas phase (POLL), ie, thin (5-1000 nm) of organic or inorganic coatings; and the actual plasma processing, i.e, the inculcation of functional groups on the material using glow discharge. Grafted functional groups may be partially associated with the formation, to a certain extent, cross-links with the workpiece surface.

Plasma etching, coating and processing inculcation of groups can be conducted in the reactor low pressure appropriate configuration at a pressure of, for example, from 10^-2up to 10 mm Hg (~1,3-1300 PA). For excitation in the feed gas glow discharge, uses an electromagnetic field applied by electrodes or other means (for example, a coil placed around corporator). Typically used variables (e.g., radio frequency, with a frequency of 13.56 MHz), and not a static electric field. Materials subjected to glow discharge, are modified by the interaction of the generated gas in the plasma particles (atoms, radicals, ions) from the surface of the material. After plasma treatment with low weight molecules, formed in the plasma during recombination reactions, and unreacted monomer molecules is pumped from the reactor.

Plasma treatment modifies the surface of materials by synthesis of stable boundary surfaces. Between the active particles in the plasma phase and the material of the underlayer are formed covalent bonds. As should be clear to the specialist, the longer the duration of the plasma treatment, the greater the thickness of the coating, created POLL, the more the quantity (depth) of the etched material in the process of engraving and stronger manifestation of functional groups grafted plasma treatments. Typically, the resulting modification of the surface can be controlled by proper adjustment and control of technical parameters such as input power, frequency and modulation of the applied electric field; properties, flow rate and pressure of the supplied gas; temperature, bias voltage and C is ogene sublayer and other These externally managed options, in turn, affect various internal factors such as the degree of ionization of the injected gas; density active (atoms, ions, radicals and other) particles in the plasma phase; the uniformity of the process; the speed of coating, engraving and processing. Internal parameters can be controlled using various diagnostic tools, for example, optical emission spectroscopy, laser-induced fluorescence and absorption spectroscopy (as visible in the UV range and in the infrared range).

As shown in the present disclosure, the treatment with plasma of low pressure is used to change the chemical composition and surface properties of carbon, which, in turn, affect its filtering properties. Figure 1 shows the reactor, suitable for plasma processing of granular materials. The size of the granules of such materials may be in the range of 18-40 mesh, which corresponds to about 420-1000 μm. Shown in figure 1, the reactor is a rotating device that allows uniformly to handle up to 500 g of carbon granules RF glow discharge (13.56 MHz) when mixing. The reactor includes a rotating glass chamber 1 having a glass ledges 2, the fixed RF outer electrode 3, the ground electrode 4, the fixed flange 5 is rotating vacuum flange 6. Carbon sublayer may also, or alternatively, be used in another form, for example, graphite.

Figure 2 shows another chamber of a plasma reactor using a continuous roll feed of the tape. Luggage reactor includes a chamber 7 in which the first coil 8, the reaction chamber 9 with the RF electrode 10, and postquery 11, in which the second roll 12. Reaction chamber also includes a group of pumps 13. This configuration is suitable for materials in the form of a fiber or sheet, in contrast to the powder or granulated form, and ensures continuous processing. This setup can be used, for example, for processing pulp fiber weight (tow), which includes carbon particles. In this case, the tension and the curvature of the material can be carefully controlled depending on the properties of the fiber mass. In particular, the passage 14 to the fiber mass, shown in figure 2, has no sharp corners and sharp bends to avoid damage to the fiber mass. Device with roll feed, shown in figure 2, can also be used for processing of paper, impregnated, coated or covered with particles of carbon.

Figure 3 presents data related to the adjustment of the acidic/basic properties of the surface of carbon materials by means of plasma processing is I. In this case, is used glow discharge RF (13.56 MHz), fed About₂/NH₃(development properties) or a mixture of vapor AK/AAM (POLL), to modify the surface properties of flat graphite substrate using acidic (containing oxygen) and (or) core (containing nitrogen) surface groups.

Discharges, engrafting About₂/NH₃produced at a pressure of 0.25 mbar within two minutes, with power supplied from the RF oscillation equal to 100 Wary consumption was 10 cm³/s when the flow ratio AK/AAM 4/0, 2/2 0/4 cm³/s / cm³/s, and the flow of buffer gas AG 6 cm³/sizeranne the contact angle of water (WCA) of raw and grafted graphite/coated graphite was carried out drops of acid solution (model HC1) and the basic solution (NaOH) 2 μl.

Raw graphite surface showed values WCA approximately 90°, not changing with the change of the hydrogen ion exponent pH of the test solution, since the surface has no acidic/basic groups. All the studied discharges reduced the value of WCA graphite, as the added groups of both types, as O-and N - containing, either grafted or included in the coverage are polar and hydrophilic in relation to pure carbon.

Discharges with 100% O₂and 100% of AK) was added to the surface of the graphite KIS is now oxygen-containing groups (-COOH, HE, and others); data WCA were higher at low pH values, and then fell when used basic solutions (high pH), thanks to the interaction between the acid groups on the surface of the substrate and the solution. Exactly the opposite pattern was observed for discharges with a 100% NH₃and 100% AAM, when basic groups containing nitrogen (-NH₂and others), was added to the surface of the graphite; these dependencies WCA values were higher when using solutions with high pH, then decreased at acidic (low) pH due to the interaction, in this case, between the main groups on the surface of the substrate and the solution. Digit ratio between About 1/1₂and NH₃, AK AAM, groups of both types, both acid and basic, was added to the surface of the graphite at the same time, and was observed amphoteric reaction when the values of the WCA was decreasing (strong interaction of the surface with a solution) at low and high pH compared to neutral pH. These examples illustrate the extent to which you can control sublayer, using reagents with different properties during plasma processing.

Plasma treatment of carbon granules

The carbon granules were processed in a plasma reactor, for example, shown in figure 1, using various surface treatments aimed at making the stand is rnost acidic/basic properties, as shown in figure 3.

POLL in RF glow discharge with acrylic acid/argon

This POLL-treatment was carried out in the discharge fed by pairs of AK and AG. The ratio of flow Ah/AK, RF power fluctuations, pressure, rotation of the reactor and the length of the process is operated so that the formed coating with cross-links with the composition of CH_xAbout_ypermanently attached to the surface of the carbon granules, and the average thickness of which can be adjusted in the range of 5-50 nm.

Data characterizing manufactured in this way the samples obtained by the methods of diagnostic x-ray photoelectron spectroscopy (XPS). x-ray photoelectron spectroscopy, infrared spectroscopy with Fourier transform and WCA, showed, as expected, the presence of coatings with very high hydrophilicity (compared WCA figure 3 for 100% of AK), and WCA measurements were not possible (water absorbed) on the layer of granules due to its discontinuity. The acidic nature of this coating, as shown in figure 3, due to the presence of groups containing oxygen, including, among others, carboxylic, hydroxyl and carbonyl. The surface density of these groups in the coating depends on the degree of dissociation of the monomer AK in the plasma phase, which can be controlled by proper adjustment of the plasma parameters; for example, it is elsaelsa with decreasing input power and (or) with increasing pressure.

Caused by plasma layer has a composition and structure that is very different from conventional polyacrylic acid, where the oxygen only contain carboxyl groups. It is applied by plasma coating is characterized by a certain degree of cross-linkage (connection C-C and C-O), ensuring the stability of the coating in air and in water. Indeed, analysis of samples conducted some time after coating, after exposure to air and in water, showed no relevant changes in the composition.

Processing plasma in glow discharges in O₂

This processing is performed in the discharge, feeding oxygen O₂in some cases, in a mixture with argon. Process parameters can be controlled so that the surface carbon formed oxidized layer chemical groups containing oxygen (carboxyl, hydroxyl and carbonyl), enhancing its polar (hydrophilic, acid). The oxygen atoms formed in the plasma from disintegrated molecules O₂and their activity against carbon materials is very high. The carbon is consumed through reaction etching (complete combustion), in which the molecules of co and CO₂, and remains oxidized layer on the carbon. The average thickness of the modified layer is very small, the etching rate is reguliruetsja plasma parameters. In General, the higher the density of oxygen atoms in the plasma, the higher the etching rate, with a concomitant increase in roughness and surface area of the oxidized carbon.

For prepared by this method samples the data on the composition obtained by XPS and WCA show noticeable hydrophilic surface on the carbon, and the WCA measurements were not possible (water absorbed) on the layer of granules. Grafted surface shows some acidic character due to the presence of oxygenated functional groups, as shown in figure 3 a horizontal line for graphite. The stability of the treated surface to the air is very high, according to the composition during aging.

Processing plasma in glow discharges in NH₃

Such processing (development group) is held in the discharge fed NH₃in some cases, in a mixture with argon. Process parameters can be controlled so that the surface of the carbon layer was formed chemical groups containing nitrogen (for example, amino, imino, and others), as a result of interaction with nitrogen-containing radicals, formed by dissociation of NH₃. Compared to plasma treatment with oxygen, discharges with NH₃run less active processes of surface modification, and the etching rate is very low. The average thickness of the modi the data layer is very small; and the roughness and surface area of carbon after exposure to plasma NH3 varies slightly.

Data on the composition obtained by XPS and WCA show noticeable hydrophilic surface of the carbon, and the WCA measurements were not possible (water absorbed) on the layer of granules. Grafted nitrogen surface shows some basic character due to the presence of nitrogen-containing functional groups, as shown in figure 3. The stability of the treated surface to the air is very high, according to the composition during aging.

Discussion of results

Carbon: chemistry of smoke

Six standard samples of coconut charcoal (~10 g each) were treated with plasma in a rotating reactor is depicted in figure 1 type. The parameters supplied gas and the operating parameters of the reactor are shown in table 1:

After plasma treatment, 60 mg each OBR is botanas carbon additive was introduced into the volume filter (12 mm tip mouthpiece of cellulose acetate, which takes in the mouth of the smoker/5 mm filter additive/10mm tip of cellulose acetate), attached to the rod with tobacco-Virginia type, having a density of 229 mg/cm³length 56 mm, with a total length of the circumference of the cigarette 24,6 mm Additional supply of air in the filter tip was not used, in order not to introduce extraneous variables.

As a regulated used two parameters. In the first change in cigarette design, similar to that described above, was added 60 mg of raw carbon. Second, the filter has been used, the empty volume with a length of 5 mm Before the test cigarettes were subjected to aging at a temperature of 22°C and 60% relative humidity for three weeks. The test of the Smoking was carried out in accordance with the requirements of ISO, ie, one puff volume of 35 ml duration of 2 s were made every minute. The content of the products obtained were normalized to the tar, and carried out the calculation of the percentage change relative to the cigarette with raw carbon, the results of which are shown in Table 2 (a reduction of 21% and more darkened. Positive values correspond to stronger reduction compared to untreated carbon).

On the basic chemical composition of smoke between carbon treated, and carbon, not treated, there is a difference, for example, the tar was about 10 mg/cigarette, similar levels were CO₂etc. In samples 2 and 5 showed significant improvements for some compounds in the vapor phase, when compared to untreated carbon, while in samples 3 and 4 improvements are not noted. Samples 5 and 6, despite the same input gas vary considerably according to the percentage reduction. This is probably due to the fact that the surface density of carboxyl groups significantly depends on the degree of dissociation of the monomer molecules in the phase of the plasma, for example, decreases with increasing power.

Although the specialist will be apparent, various modifications of the described specific embodiments, the present invention is not limited to any particular described here options for implementation, and is defined by the attached claims and its equivalents.

1. The filter for Smoking articles of the Oia, includes filter material containing carbon, the surface of which is modified by plasma treatment to modify the properties of selective filtering material of the filter.

2. The filter according to claim 1, in which the carbon is in pellet form.

3. The filter according to claim 2, in which the granular carbon is embedded in the canvas.

4. The filter material Smoking articles containing granulated carbon, the surface of which is modified by plasma treatment to modify the properties of the selective filtering of filter material, and the granular carbon is embedded in the canvas.

5. The filter according to claim 3 or a filter material according to claim 4, in which in can be used as basis tow of cellulose acetate or paper.

6. The filter according to claim 1 or a filter material according to claim 4, in which the first part of the carbon has been modified surface in accordance with the first plasma curing process, and the second part of the carbon has been modified surface in accordance with the second plasma curing process.

7. A Smoking article comprising a filter according to claim 1 or a filter material according to claim 4.

8. A method of manufacturing the filter material Smoking articles according to claim 4, containing carbon, in the exercise of which modify selective filtering properties of the material, f is ltra by modifying its surface, performed by plasma processing.

9. A method of manufacturing a filter Smoking articles, comprising a filter material containing carbon, in the exercise of which modify selective filtering properties of the filter material by modifying its surface, which is performed through plasma processing.

10. The method according to claim 9, in which at selective modification of the filtering properties of the filter material increases the absorption of acidic elements.

11. The method according to claim 9, in which at selective modification of the filtering properties of the filter material increases the absorption of alkaline elements.

12. The method according to claim 9, in which at selective modification of the filtering properties of the filter material enhance the hydrophilic properties of its surface.

13. The method according to any of PP or 9, in which the plasma treatment includes a plasma chemical deposition from the gas phase with the use of acrylic acid.

14. The method according to claim 9, in which the plasma processing includes etching with the use of O₂and (or) NH₃.

15. The method according to any of PP or 9, which is subjected to the filter material two different plasma technological applications.

16. The method according to any of PP or 9, in which the filter material includes a first material subjected to the first plasma technology is practical processing, and the second material are subjected to a second plasma process.

17. The method according to any of PP or 9, in which the filter material includes carbon in granular form.

18. The method according to any of PP or 9, in which the filter material is a fiber or sheet material.

19. The method according to p, in which the plasma processing using a rolled supply of fiber or sheet material for transmission of filter material through the plasma chamber.