RU2235488C1 - Filter for cigarettes - Google Patents

Abstract

FIELD: filtering of tobacco smoke from hazardous components.

SUBSTANCE: filter is made from fibrous-porous material fabricated by pneumatic extrusion method from polypropylene with melt flow index ≥ 20 g/10 min, is formed from fibers of 3-5 micron thickness, which are cohesively engaged with one another at contact points. Said material carries electret charge with surface density of 5-12 nK/cm², said charge being imparted to material in the process of pneumatic extrusion molding by processing of melt at the stage of exit from spinneret into negative corona discharge field.

EFFECT: provision for producing of absorption active filter from inert non-toxic materials.

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Description

The invention relates to filters intended for use in cigarettes with the aim of filtering tobacco smoke from harmful components.

Despite the ever-increasing attention to people's health and the tightening of environmental requirements, the consumption of tobacco products in the world does not decrease. Actions to limit smoking in public places, at work, etc., undertaken at the state level, as well as preventive measures remain ineffective. In this regard, the problem of maintaining health lies mainly with the consumers of tobacco products themselves and with developers of the technology for manufacturing cigarettes and their elements (tobacco, paper, filter). Society has long come to the conclusion that tobacco and its components are harmful to the human body. Since the 1950s, when the first data appeared that tobacco smoke could cause cancer, attempts are being made to reduce the content of substances harmful to health in the smoke.

It is generally accepted that nicotine and tar are the main substances that cause harm to tobacco smoke. Most of the rules for regulating their content in tobacco products in all countries are based on the approach developed by the US Federal Trade Commission (FTK) in the mid-1960s. It consists in the fact that a special smoking machine does a puff every minute until a certain length of cigarette is smoked, after which the sediment accumulated on the filter of the smoking machine is analyzed. The method is approved by the International Organization for Standardization (ISO) and is commonly referred to as the ISO-FTK method.

Nicotine is volatile only in free form, and in tobacco is present mainly in salt (bound). During combustion, it goes into free form and is absorbed in the body. The greater the ratio of free and bound nicotine, the more bioavailable nicotine is for absorption. To reduce this ratio, it is advisable to increase the pH of tobacco smoke by adding ammonium and / or urea salts to the tobacco.

The resin, according to the ISO-FTK method, is all that remains on the filter of a smoking machine minus nicotine and water. When smoking, smoke enters the body in the form of a concentrated aerosol, which, when cooled, condenses and forms a resin that settles in the airways. Resin is a mixture of many substances with different levels of toxicity and carcinogenicity. The resin composition of different tobacco products can vary greatly and, therefore, their harm to the human body can vary. The substances contained in the resin cause cancer and other lung diseases, and also reduce the effectiveness of the immune system. However, tar as an indicator does not reflect the entire composition of tobacco smoke. Among the carcinogens present in tobacco smoke, two classes of malignant pathogens are distinguished: polycyclic aromatic hydrocarbons (for example, benzopyrene) and tobacco-specific (that is, not contained in other natural substances) nitrosamines. Unfortunately, there are no rules governing the content of these carcinogens in tobacco smoke. There is almost no data on the actual toxicity of various tobacco additives, although new dangerous components can also form during their combustion.

Despite the insufficient scientific study of the problem of determining the remaining harmful substances in tobacco smoke, caused by commercial considerations and market reasons, the maximum content of tar and nicotine in cigarettes is established and monitored worldwide at the state level. There is an opinion that one of the effective ways to reduce their concentration is the manufacture of so-called "light" cigarettes. Differentiation of "standard", "lungs", etc. Cigarettes are currently based on the amount of tar and nicotine released by smoking cigarettes, measured by the ISO-FTK method.

In the early 1970s. A new method of processing tobacco has been developed - freeze-drying. This process uses substances such as alcohol, freons, carbon dioxide, ammonia, ammonium carbonate, nitrogen and water. According to advertisements, the use of freeze-dried and / or so-called “resuspended” tobacco helps to reduce the amount of tobacco leaf required per cigarette on average by almost half. Today's “regular” American cigarettes consist of 15% frozen tobacco, “light” cigarettes 25%, and “ultra-light” cigarettes comprise up to 50% of such tobacco. However, according to experts, all attempts to adjust the composition of tobacco (the addition of sugar, sweeteners, flavorings, cocoa, menthol, etc.) can reduce the tar content in cigarettes by no more than 40%. In addition, menthol, for example, has an anesthetic effect (due to which menthol cigarettes can be pulled deeper, but the lower parts of the lungs are affected) and can contribute to the metabolic activation of tobacco carcinogens.

The reduction of tar emissions measured by the smoking machine is achieved by two main methods: filters and ventilation.

A traditional cigarette filter is a device made of a porous material (e.g. paper, cotton, cork) attached to the end of a cigar or cigarette to absorb moisture, tar, nicotine and various impurities. The filter may also be a special holder in which a cigar or cigarette (mouthpiece) is inserted.

In 1954, the first cigarette filter was made from cellulose acetate, which soon became the most popular in the tobacco industry around the world. The most commonly used type of cellulose acetate is secondary cellulose acetate containing 5-10% glycerol triacetate as a plasticizer. Filters based on it slightly reduce the intake of suspended smoke particles into the smoker's body. Acrolein, phenols and highly carcinogenic nitrosamines are selectively removed by such filters. Their effectiveness can be increased by reducing the diameter of the filaments (fibers), increasing the length of the filter, or adding certain substances to the fibers. So, activated carbon is widely known for its ability to remove certain components of the gas phase from smoke. Cigarette filters made from cellulose acetate mixed with activated carbon can selectively remove up to 40% carbon and nitrogen oxides, 80% hydrogen cyanide and 70% acrolein and benzene from cigarette smoke. It is characteristic that mixed filters reduce the content of suspended particles less efficiently than pure acetate filters. Such selectivity leads to the fact that in most cases almost as many tar and nicotine enter the body of a smoked filter cigarette as he would get from cigarettes without a filter.

The development of new cigarette filters continues around the world. The problems facing cigarette manufacturers are trying to solve by using polymer fibers and various additives.

A known filter for cigarettes [RF patent 2010546, IPC ⁶ A 24 D 3/14, 1994 (publ.)], Which consists of several separate parts made of fibers of an organic polymer, and between these parts there is an adsorbent agent representing lignin, impregnated with organosilicon monomer.

A patented filter for cigarettes with an absorbent agent [RF patent 2045921, IPC ⁶ A 24 D 3/16, 1995 (publ.).], Made from fibers of an organic polymer (for example, from cellulose, acetate or cellulose acetate fiber), impregnated with 3- 5% alcohol solution of salicylic acid (from 0.09 to 0.14 wt.% From the weight of the fibers), and it is indicated that such a filter reduces the nicotine content in the main stream of tobacco smoke by 47%, tar by 37% and carbon monoxide by 16%, and also quite effectively captures benzopyrene, volatile and tobacco-specific N-n trozaminy and metals.

A tobacco filter has been developed [RF patent 94024343, IPC A 24 D 3/14, 1996 (publ.)]. which consists of at least two sections sequentially located along the course of the tobacco smoke: the outer one, located on the side of the smoker and made of cellulose-containing or acetate fiber, and the middle one, located on the side of the tobacco, filled with an adsorbent (14-28 mg) of porous carbon fibers (may have a fabric structure) with a carbon amount of at least 95% and a specific surface area of 700 to 1,500 m ² / g, which increases the filter's absorption capacity with respect to nicotine, resins, carbon monoxide.

A filter for cigarettes is also known [RF patent 2113810, IPC ⁶ A 24 D 3/14, 1998 (publ.)], In which, to increase the efficiency of sorption of toxic and carcinogenic products of tobacco pyrolysis to a fiber-based filter made of acetate or cellulose-containing fibers, add 20-30 mg of granular sorbent, which is a granule of artificial or natural zeolites impregnated with an organosilicon monomer - N, N'-bis (3-triethoxysilylpropyl) thiocarbamide.

The disadvantages of the above technical solutions are the specifics of the synthetic materials used for the manufacture of the filter. According to many doctors, it is the "light" cigarettes with an acetate filter that are the most harmful type of tobacco products. The filter in them is usually longer and denser than the standard, and therefore has a relatively high aerodynamic drag (drag resistance). The rate of smoke entering the lungs plays a major role in the smoking process. The traditional acetate filter extinguishes this speed by more than 60% and makes the smoker exert more effort by drawing the smoke deeper into the lungs, which, of course, is much more harmful. Particles of thin acetate fibers with each deep puff easily enter the lungs and (unlike nicotine) are not excreted from the body. Their chemical properties are close to those of other polyesters, which creates an increased health hazard. It is established that, according to their carcinogenicity, cigarettes of the "Lights" class with an acetate filter share the first place with ordinary (strong) filters. Thus, the use of synthetic filters not only does not reduce, but also increases the risk to health. In addition, the use of additives increases the risk of the formation of harmful substances in tobacco smoke; for example, incomplete combustion of coal leads to the formation of carbon monoxide. Finally, the traditional method involves the manufacture of acetate fibers according to the so-called "mortar" technology (from polymer solutions), which is low-tech and environmentally unsafe, since it involves the use of bulky technological schemes and toxic solvents.

Along with attempts to modify acetate filters, searches are underway for other materials with a structural organization that is optimal for use in tobacco products.

A cigarette filter has been developed [RF patent 2130279, IPC ⁶ A 24 D 3/10, 1999 (publ.)] Containing hydro-entangled lyocell fibers; High efficiency of such filters, good taste, stain resistance, physical elasticity and optimal characteristics of air passage are indicated.

Also patented is a method for producing biodegradable filter elements or filter tows for tobacco smoke filters from vegetable raw materials [RF patent 2153828, IPC ⁷ 24 D 3/08, 2000 (publ.)], Where filter material (fibers, films and foams) are made by extrusion from biopolymers based on thermoplastic starch and its polymer compositions with fast and complete degradability.

Despite a number of advantages, the listed filters based on natural raw materials have an important drawback - the relatively high chemical activity of biopolymers combined with the relative complexity of the chemical composition, which creates the conditions for the formation of a wide range of chemical compounds during filtering of hot tobacco dye, including toxic ones such as carbon monoxide, formaldehyde, etc. In addition, the capture of contaminants remains completely mechanical.

One of the closest analogues of the claimed invention is a filtering agent for cigarettes, which offers bicomponent fibers with a sheath and a core containing a core of a thermoplastic material, preferably polypropylene, completely coated, preferably made of plasticized cellulose acetate, a copolymer of ethylene and vinyl acetate, polyvinyl alcohol or a copolymer of ethylene and vinyl alcohol [Filtering agent for tobacco smoke, filter rod, cigar This and the method of manufacturing a filter product for tobacco smoke. [RF patent No. 21297986, A 24 D 3/10, 1999].

A filter is made by melt blowing to an average fiber diameter of 10 microns or less. It is indicated that the filters retain the desired taste and technological properties of conventional cellulose acetate filter elements, but are significantly less expensive. Very thin fibers can be formed with different cross-sections, providing a larger surface area and requiring less air in the processes of melt blowing and processing. In the manufacture of shells of polyvinyl alcohol or a copolymer of ethylene and vinyl alcohol, the filter elements are easily destroyed under the influence of environmental conditions, leaving behind only a lot of very thin, essentially invisible fibers. The manufacturing method involves continuous pneumatic extrusion of molten core-forming and shell-forming materials through many holes in the extrusion head in order to obtain a strongly interwoven strand of bicomponent fibers (each fiber contains a continuous core of core-forming material, completely surrounded by a shell of shell-forming material), collecting this strand in the form of a rod, heating it for bonding fibers at points of contact, cooling and cutting to form stitching rod into separate segments.

Essentially, in the proposed easily exfoliating filter, the polyolefin core is considered non-absorbent and serves solely to increase the strength of the fibers and reduce the plasticizers or additives spent on the production. As the absorbent material, the sheath of fibers from cellulose acetate or vinyl polymers and copolymers acts. Embodiments of the invention propose to increase the absorption properties of the product by the use of additives (activated carbon, etc.). This technical solution has a number of disadvantages:

1) the high chemical activity of vinyl polymers and copolymers, which can lead to adverse chemical reactions during the filtration of coke with the formation of toxic vinyl monomers, carbon monoxide, formaldehyde, etc .;

2) insufficient absorption capacity of the filter material as a whole, which forces the use of various additives.

The prototype of the claimed invention is a filter for cigarettes in a ventilated cigarette [Ventilated cigarette, patent EP 0254004, IPC 7 F 24 D 3/08, 1988], which consists of polymer fibers that make up a fibrous-porous material made of polypropylene with a flow index of 13 g / 10 min pneumatic extrusion formation and formed by fibers from 0.1 to 20 μm thick, bonded to each other at points of contact. The prototype has the following disadvantages:

1) lack of manufacturability of pneumatic extrusion processing of polypropylene with the specified yield index and the need to use powerful air flows and the equipment providing it;

2) the impossibility of realizing high absorption activity.

The tasks to which the claimed invention is directed are to produce an absorption-active filter from inert non-toxic materials without using any additives, while simultaneously increasing the manufacturability of the process of its formation.

This result is achieved by the fact that it is proposed to use a filter for cigarettes, consisting of a fibrous-porous material made of polypropylene by pneumatic extrusion formation and formed by fibers with a thickness of 3-5 μm, with polypropylene with a melt flow index ≥20 g / 10 min, the fibers are cohesive bonded at contact points, and the material carries an electret charge to a surface density of 5 to 12 nC / cm ^2, imparted thereto during formation by melt processing at the stage of the spinneret by e negative corona discharge.

The invention consists in the following. The fibrous material of the inventive filter is manufactured by pneumatic extrusion technology, which is more economical and environmentally friendly than mortar technology for the formation of polyester fiber cigarette filters of most analogues. The inventive filter has a developed system of pores, which allows to realize a sieve effect when filtering smoke. The filter material has a low tendency to delamination due to the sufficiently strong cohesive bonding of the fibers at the contact points achieved by pneumatic extrusion formation. Polypropylene used in the manufacture of the filter is non-toxic and chemically inert, which, even with the unlikely occurrence of fiber fragments in the oral cavity, does not cause harm to health, and also eliminates the likelihood of chemical reactions with components of tobacco smoke. Finally, the inventive filter does not contain any additional ingredients that could undergo chemical transformations with the formation of toxic compounds during the performance of their working functions or, when the filter is delaminated, enter the respiratory system, being carried away by the stream of filtered smoke. The inventive filter exhibits increased absorption activity in relation to the harmful components of tobacco smoke due to the action of electrostatic forces due to the presence of an electret charge. The proposed technical solution is based on the special role of electret charge in trapping solid and liquid particles of airborne pollutants long ago noted by experts, which is used to develop modern respiratory protection for respirators [Kravtsov AG, Goldade VA, Zotov SV Polymer electret filter materials for respiratory protection. Gomel: IMMS NASB, 2003, 204 s].

Thus, the inventive filter has the following essential features of novelty in comparison with the prototype:

- the fibers are cohesively bonded at the contact points;

- the material carries an electret charge with a surface density of 5 to 12 nC / cm ² , imparted to it during formation by processing the melt at the stage of exit from the die in the field of negative corona discharge.

Here is an example implementation of the invention.

The initial material for pneumatic extrusion is granular Kaplen brand polypropylene (Kapotnya, Moscow Region, Russia) with a melt flow index ≥20 g / 10 min. The main technological unit is a single-screw extruder with three heating zones, equipped with a heated die head and a drum-type forming device that rotates and reciprocates. The extruder is brought to the operating mode by setting the temperature in the heating zones: 1 - 190 ° C, 2 - 290 ° C, 3 - 370 ° C and on a die head 350 ° C. At a distance of 150 mm from the die, a forming device is located, at a distance of 50 mm from the die, an electrification zone consisting of corona and ground electrodes and connected to a high-voltage generator. Using a compression unit, compressed air is supplied to the extruder under a pressure of 1.5-2 atm. The granulate is poured into the hopper of the extruder and, creating a negative corona discharge in the electrification zone (by setting the strength of the electrifying field within 10-20 kV / cm), the material is sprayed onto a moving forming device, forming a fibrous-porous layer. The parameters of pneumatic spray control, visually controlling the appearance of the material, the absence of the effect of droplet formation or fusion of fibers. Upon reaching the thickness of the fibrous-porous layer of 30 mm, the field is turned off, the supply of compressed air to the extruder is stopped, and the web is removed from the forming device. Further, cylinders with a length of L = 30 ± 0.5 mm and a diameter of D = 7.9 ± 0.1 mm are made from the web by an auxiliary stamping operation. These cylinders with a material density of ρ = 0.19 g / cm ³ and fibers with a thickness of H = 3-5 μm, carrying an electret charge with an effective surface density of 5-12 nC / cm [GOST 25209-82. Plastics and polymeric films. Methods for determining the surface charges of electrets] are the inventive cigarette filter. The applied technological scheme is practically waste-free: the unspent fibrous-porous material that accumulates after punching after grinding into pieces of 1-2 cm in size can be subjected to repeated pneumatic extrusion processing [Kravtsov A.G. A method for analyzing the structure and properties of regenerated polymer fibrous filter materials for fine air purification // Materials Science, 2001, No. 4, p. 47-52].

For testing, “model” cigarettes were made, for which the inventive electret filters formed under different electrification conditions were placed in “L @ M” cigarettes instead of acetate filters removed from them so that the length of the “model” cigarette did not differ from the length of the original and was within the limits established by regulatory documentation [GOST 3935-2000 (interstate standard). Cigarettes General specifications].

An experimental batch of cigarettes with new filters was subjected to comparative tests, during which the content of nicotine, tar, and puff resistance were evaluated.

The essence of the tests was as follows. Cigarettes were smoked on a Hewlett-Packard smoking machine. The design and technical capabilities of the machine, as well as the test conditions, met the regulated standard [GOST ISO 3308-97 (interstate standard). Ordinary laboratory machine for smoking cigarettes (smoking machine). Definitions and standard conditions]. The wet condensate of tobacco smoke released during smoking was collected in a trap equipped with a fiberglass filter. The mass of wet condensate was estimated by the gravimetric method by comparison with the mass of a clean trap. Next, the wet condensate was extracted from a fiberglass filter, after which the nicotine content was determined by gas chromatography [GOST 30570-98 (interstate standard). Cigarettes Determination of nicotine content in smoke condensate. The method of gas chromatography.] And water [GOST 30622.1-98. Cigarettes Determination of water content in smoke condensate. Gas chromatography method]. The obtained value was used to determine the mass of nicotine-free dry condensate of gas smoke, i.e. resins [GOST 30571-98 (interstate standard). Cigarettes Determination of wet and nicotine-free dry condensate (resin) in cigarette smoke using a laboratory smoking machine]. Additionally, with the help of the sensors of the smoking machine, the cigarette puff resistance was measured [GOST ISO 6565-97 (interstate standard). Tobacco and tobacco products. Puff resistance of cigarettes and filters. Terms, standard conditions and basic definitions]. We compared the performance of model cigarettes with those of the L @ M, L @ M Lights, and L @ M Super Lights cigarettes, which we tested on a smoking machine under the same conditions. Preliminary studies found that the filter in L @ M cigarettes has a length L = 30 mm and a density ρ = 0.17 g / cm ³ , in L @ M Lights cigarettes with the same length L = 30 mm it has a higher density ρ = 0.19 g / cm ³ , and in cigarettes "L @ M Super Lights" has a greater length L = 35 mm and an even higher density ρ = 0.21 g / cm ³ . Increasing the length and increasing the density, apparently, is for the manufacturer of these cigarettes the main way to reduce the level of nicotine and resins. The table shows the results of comparative tests.

From the above data it is seen that according to the main indicators used in assessing the quality of cigarettes, the claimed electret filter is not inferior and sometimes surpasses the traditional acetate filter. Moreover, it is the electret charge that turns out to be the key factor determining the absorption activity of the filter material. In the applied technological scheme, the charge value can be easily adjusted by changing the field strength of the corona discharge. Depending on the magnitude of the electret charge of the filter, “model” cigarettes with the claimed filter of the same size and density can meet the criteria for nicotine and tar content, for cigarettes of the “L @ M Lights”, “L @ M Super Lights” classes, having the same or better consumer properties (lack of delamination effect, low drag resistance, etc.).

The invention may find application in the tobacco industry in the manufacture of cigarette filters.

Claims (1)

Filter for cigarettes, consisting of a fibrous-porous material made of polypropylene by a pneumatic extrusion formation and formed by fibers with a thickness of 3-5 μm, characterized in that polypropylene with a melt flow index ≥ 20 g / 10 min is used, while the material is formed by fibers cohesively bonded in the contact areas, and carries electric charge with a surface density of 5 to 12 nC / cm ^2, imparted thereto during formation by melt processing step it exits the spinneret in the negative coronas th stage.