A filter material for a cigarette filter and a method of making the same

Abstract

The application provides a filter material for cigarette filters and a preparation method thereof, and belongs to the technical field of filter materials. Modified sepiolite fibers are obtained by activating and mixing acid treatment on sepiolite fibers; modified activated carbon fibers are obtained by the following steps: pretreating activated carbon fibers with an alkali solution, adding the activated carbon fibers into a Cu-doped titanium solution, reacting in a high-temperature reaction kettle, and modifying through polydopamine coating; the modified activated carbon fibers are mixed with modified sepiolite fibers and polylactic acid by heating and melting; melt spinning, traction, and water bath drawing are performed; and then, curling and drying are performed to shape, so that the obtained yarn is the filter material for cigarette filters. The filter material has the advantages of good adsorption, degradation and reduction of harmful substances, good mechanical properties, high strength, good elasticity, good degradable performance, and obvious reduction of environmental pollution, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filter material, in particular to a filter material for cigarette filter and a preparation method thereof. BACKGROUND

[0002] Cigarette filter has the function of filtering, blocking and adsorbing harmful components such as nicotine and tar in smoke. In addition to the above functions, a good filter material should also be able to improve the taste of smoke, reduce the irritation of smoke to the oral cavity and harm to human health. As a relatively mature technology, the material currently used to manufacture cigarette filters is generally made of cellulose acetate fibers and polypropylene fibers. Considering the processing performance and the overall performance of the final produced filter, cellulose acetate fibers are the first choice, and cellulose acetate fiber filters are mostly used in high-end cigarettes.

[0003] The filter part left after smoking a cigarette is discarded, and cellulose acetate fibers and polypropylene fibers are difficult to be biodegraded in the natural environment. In addition to the harm to human health, cigarettes also cause environmental pollution. Humans cannot completely leave cigarettes, and in addition to reducing the harm of cigarettes to the human body, solving the environmental pollution problem caused by the disposal of filters has become a problem that the cigarette industry must face.

[0004] On the other hand, cellulose acetate fibers are chemical products made from high-quality wood. From wood to cellulose to esterified cellulose acetate, a large amount of wood raw materials is consumed, and many pollution problems are also accompanied in the production process.

[0005] Therefore, from the perspective of lack of wood resources or from the perspective of improving environmental pollution, it is necessary to find a biodegradable material to replace the existing cellulose acetate and polypropylene fiber raw materials, to manufacture degradable cigarette filters, and to at least reduce the harm caused by cigarette production in the aspect of environmental protection. It is an urgent problem that the cigarette production industry needs to solve.

[0006] The production process of cigarette filter mainly includes the processes of melt spinning of raw materials to form cigarette tows, and plasticizing and setting to form rods, and finally processing into filter rods. The spinnability of the raw material, i.e. whether it is easy to be spun into fine fibers, and the drawing performance and adhesion effect of the fiber tow will ultimately affect the comprehensive performance of the filter rod and the filter, including the filtration performance, and mechanical properties such as appearance, hardness and air resistance. Cellulose acetate fibers are selected as the main processing raw material for cigarette filters due to their excellent properties. When looking for a substitute material, it is necessary to meet two conditions, i.e. biodegradability and the requirement of filter rod processing.

[0007] A technology for manufacturing cigarette filter tow fibers and filter rods for cigarettes using lactic acid polymer resin is disclosed in Chinese patent CN100569127C and Chinese patent application CN101023811A. Although the prior published patent application teaches that lactic acid polymer can be used for processing of cigarette filters, and compared with the already commercialized cellulose acetate filter rods and polypropylene filter rods, the polylactic acid cigarette filter rods not only have the advantages of complete biodegradability and low production cost, but also show good results in terms of filtration performance and physical and mechanical properties of the manufactured filter rods, it can be seen from the content recorded in the specification that the main resin used in the technical solution is a mixture of one specification or multiple specifications of polylactic acid, or a copolymer of lactide and caprolactone, lactide, or lactide and caprolactone and ethylene glycol. These resins are all polymerized from lactones, and the prepared polymer is a random polymer. Such material has high brittleness, is prone to hydrolysis, requires low moisture content of the material (less than 0.5 parts per million) during processing, and has poor heat resistance and low heat distortion temperature (only 58℃). Since the cigarette tow requires certain flexibility and good deformation, and requires high heat resistance, there are still many unsatisfactory and to-be-improved places for the cigarette enterprises to promote the production of the above-mentioned prior published lactic acid polymer cigarette filter rods.

[0008] Chinese patent CN102423132B discloses a plant polysaccharide cigarette filter and a preparation method thereof. The method mixes plant polysaccharides, starch, adsorbents, plasticizers, emulsifiers, waterproof agents and plant proteins, and then prepares the filter rod by freeze-drying method. The filter rod can reduce the content of nicotine, tar and nicotine, but the preparation of the filter rod requires a large number of raw materials, resulting in a complex preparation process and the need to remove bubbles in the preparation process. SUMMARY

[0009] The purpose of the present application is to provide a filter material for cigarette filters and a preparation method thereof. The modified polylactic acid is melt-spun to prepare a tow with strong adsorption capacity for smoke, high efficiency of tar and nicotine interception. At the same time, the introduction of modified sepiolite fiber and modified activated carbon fiber greatly improves the adsorption and degradation of harmful substances, reduces the inhalation of harmful substances, and has good mechanical properties, high strength, good elasticity, good biodegradability, and significantly reduced environmental pollution, which has a broad application prospect.

[0010] The technical solution of the present application is realized as follows:

[0011] The application provides a preparation method of a filter material for a cigarette filter, comprising the following steps: modifying sepiolite fibers by activating and mixing acid treatment; pretreating activated carbon fibers by alkali solution, adding Cu-doped titanium solution, and reacting in a high-temperature reaction kettle; modifying the activated carbon fibers by polydopamine coating; mixing the modified sepiolite fibers and the modified activated carbon fibers with polylactic acid by heating and melting; performing melt spinning, traction, water bath drawing, and then winding and drying to obtain a yarn bundle, which is the filter material for the cigarette filter.

[0012] As a further improvement of the application, the following steps are included:

[0013] S1. Modification of sepiolite fibers: after high-temperature activation of sepiolite fibers, the fibers are added into mixed acid, stirred and reacted, filtered, washed, and dried to obtain modified sepiolite fibers.

[0014] S2. Preparation of Cu-doped titanium solution: soluble copper salt is dissolved in water, hydrochloric acid is added, and the mixture is stirred and mixed uniformly, a mixed solution of methanol and ethanol is added, and titanium chloride is added under stirring to obtain Cu-doped titanium solution.

[0015] S3. Pretreatment of activated carbon fibers: activated carbon fibers are added into alkali solution, stirred and reacted, filtered, washed, and dried to obtain pretreated activated carbon fibers.

[0016] S4. Preparation of Cu / C-doped TiO2 supported activated carbon fibers: the pretreated activated carbon fibers are added into Cu-doped titanium solution, stirred and mixed uniformly, high-temperature reacted, washed, and dried to obtain Cu / C-doped TiO2 supported activated carbon fibers.

[0017] S5. Preparation of modified activated carbon fibers: the Cu / C-doped TiO2 supported activated carbon fibers are added into water, dopamine hydrochloride and a catalyst are added, heated and stirred to react, filtered, washed, and dried to obtain modified activated carbon fibers.

[0018] S6. Coating modification of polylactic acid: polylactic acid is heated and melted, modified sepiolite fibers and modified activated carbon fibers are added, and homogenously stirred to obtain modified polylactic acid.

[0019] S7. Preparation of the filter material for the cigarette filter: the modified polylactic acid is melt-spun, the cooled yarn bundle is wound by a traction machine and a belt conveyor, the drawn yarn bundle is water-bath drawn in a water tank, and then wound and dried to obtain the yarn bundle, which is the filter material for the cigarette filter.

[0020] As a further improvement of the present application, the temperature of the high-temperature activation in step S1 is 280-320℃, the activation is 1-2h, the mixed acid is a mixture of inorganic acid and organic acid, the inorganic acid is HCl or sulfuric acid, the organic acid is at least one selected from stearic acid, octanoic acid, heptanoic acid, cinnamic acid, preferably, the mixed acid is a mixture of 2-4mol / L HCl solution and 20-25wt% stearic acid in a volume ratio of 1-2:1, the mass ratio of the sepiolite fiber and the mixed acid is 10-12:20-30, the temperature of the stirring reaction is 40-45℃, and the time is 1-2h.

[0021] As a further improvement of the present application, the soluble copper salt in step S2 is at least one selected from copper chloride, copper sulfate, copper nitrate, the mass ratio of the soluble copper salt, hydrochloric acid, methanol, ethanol and titanium chloride is 2-3:3-5:20-30:15-20:12-15, the concentration of the hydrochloric acid is 0.5-1mol / L; the alkali solution in step S3 is 10-15wt% NaOH or KOH solution, the mass ratio of the activated carbon fiber and the alkali solution is 10-15:30-40, the temperature of the stirring reaction is 45-50℃, and the time is 0.5-1h.

[0022] As a further improvement of the present application, the mass ratio of the pretreated activated carbon fiber and the Cu-doped titanium solution in step S4 is 12-15:20-25, the temperature of the high-temperature reaction is 300-400℃, and the time is 2-4h.

[0023] As a further improvement of the present application, the mass ratio of the Cu / C-doped TiO2 solid-supported activated carbon fiber, dopamine hydrochloride and catalyst in step S5 is 12-15:17-20:2-3, the catalyst is Tirs-HCl solution with pH=8.5-9, the temperature of the heating stirring reaction is 45-55℃, and the time is 2-3h.

[0024] As a further improvement of the present application, the heating temperature in step S6 is 180-200℃, the mass ratio of the polylactic acid, modified sepiolite fiber and modified activated carbon fiber is 15-20:3-5:4-7, the rotation speed of the homogenizing stirring is 3000-5000r / min, and the time is 15-20min.

[0025] As a further improvement of the present application, the screw temperature in the melt spinning process in step S7 is 180-220℃, the filter temperature is 170℃-230℃, the tank temperature is 170℃-230℃, the straight pipe temperature is 170℃-230℃, the spun yarn is cooled with dry air, the cooling temperature is 0℃-40℃, the roller rotation speed of the traction machine is 500-2200r / min, the frequency is 25-50Hz, the belt conveyor feeding wheel speed is 400-1200r / min, and the water temperature in the water tank is 30-50℃.

[0026] As a further improvement of the present application, the following steps are specifically included:

[0027] S1. Modification of sepiolite fibers: 10-12 parts by weight of sepiolite fibers are activated at 280-320℃ for 1-2h, then added to 20-30 parts by weight of mixed acid, stirred at 40-45℃ for 1-2h, filtered, washed, and dried to obtain modified sepiolite fibers;

[0028] The mixed acid is a mixture of 2-4mol / L HCl solution and 20-25wt% stearic acid in a volume ratio of 1-2:1;

[0029] S2. Preparation of Cu-doped titanium solution: 2-3 parts by weight of soluble copper salt is dissolved in water, 3-5 parts by weight of 0.5-1mol / L hydrochloric acid is added, stirred and mixed uniformly, a mixed solution of 20-30 parts by weight of methanol and 15-20 parts by weight of ethanol is added, and 12-15 parts by weight of titanium chloride is added under stirring to obtain a Cu-doped titanium solution;

[0030] S3. Pretreatment of activated carbon fibers: 10-15 parts by weight of activated carbon fibers are added to 30-40 parts by weight of 10-15wt% NaOH or KOH solution, stirred and reacted at 45-50℃ for 0.5-1h, filtered, washed, and dried to obtain pretreated activated carbon fibers;

[0031] S4. Preparation of Cu / C-doped TiO2 supported activated carbon fibers: 12-15 parts by weight of pretreated activated carbon fibers are added to 20-25 parts by weight of Cu-doped titanium solution, stirred and mixed uniformly, and stirred and reacted at 300-400℃ for 2-4h, washed, and dried to obtain Cu / C-doped TiO2 supported activated carbon fibers;

[0032] S5. Preparation of modified activated carbon fibers: 12-15 parts by weight of Cu / C-doped TiO2 supported activated carbon fibers are added to water, 17-20 parts by weight of dopamine hydrochloride and 2-3 parts by weight of catalyst are added, heated to 45-55℃, stirred and reacted for 2-3h, filtered, washed, and dried to obtain modified activated carbon fibers;

[0033] The catalyst is Tirs-HCl solution with pH=8.5-9;

[0034] S6. Coated modification of polylactic acid: 15-20 parts by weight of polylactic acid is heated to 180-200 DEG C, 3-5 parts by weight of modified sepiolite fiber and 4-7 parts by weight of modified activated carbon fiber are added under melting condition, and homogenously stirred at 3000-5000 r / min for 15-20 min to obtain modified polylactic acid;

[0035] S7. Preparation of filter material for cigarette filter: the modified polylactic acid is melt-spun, the cooled filament is coated with oil, wound by slow traction machine, drawn by steam box, wound by fast traction machine and belt conveyor, the drawn filament is water-bath drawn in a water tank, and then crimped and dried to obtain the filter material for cigarette filter;

[0036] The screw temperature in the melt spinning process is 180-220 DEG C, the filter temperature is 170 DEG C-230 DEG C, the box temperature is 170 DEG C-230 DEG C, the straight pipe temperature is 170 DEG C-230 DEG C, the ejected filament is cooled by dry air, the cooling temperature is 0 DEG C-40 DEG C, the roller rotation speed of the traction machine is 500-2200 r / min, the frequency is 25-50 Hz, the feeding wheel speed of the belt conveyor is 400-1200 r / min, and the water temperature in the water tank is 30-50 DEG C.

[0037] The application further protects the filter material for cigarette filter prepared by the above preparation method.

[0038] The application has the following beneficial effects:

[0039] The filter is a bridge between the smoker and the mainstream smoke, which can effectively intercept the total particulate matter in the mainstream smoke of cigarette and reduce the tar content in the cigarette. The acetate fiber filter can effectively reduce tar and other harmful substances, and is clean, non-toxic, colorless, odorless and relatively easy to make into a filter, but cannot adsorb and remove aldehyde compounds (such as acetaldehyde and propylene aldehyde) and benzene and toluene in the smoke, and does not have a degradable effect, which can easily damage the environment in long-term use.

[0040] Sepiolite has a large specific surface area and excellent selective adsorption, and is a fibrous clay mineral rich in magnesium and silicon, and the standard crystal chemical formula is Mg8Si 12O30(OH)4(OH2)4·8H2O, which is composed of silicon-oxygen tetrahedron and magnesium-oxygen octahedron and has a chain, layer and fiber transition structure. It has a large specific surface area and three types of adsorption centers on its surface: (1) oxygen atoms in the silicon-oxygen tetrahedron layer; (2) water molecules paired with magnesium ions at the edge, which can form hydrogen bonds with adsorbates; and (3) Si-OH groups formed by the rupture of Si-O-Si bonds on the outer surface of the tetrahedron layer, which can interact with molecules adsorbed on the outer surface of the meerschaum and form covalent bonds with some organic reagents. Therefore, it has strong adsorption performance.

[0041] The present application first performs high-temperature activation to remove zeolite water in the meerschaum, increase the pore size of the meerschaum, and increase the strength and number of surface activation centers.

[0042] Then, mixed acid modification is performed, in which inorganic acid activation can remove calcium carbonate impurities in the meerschaum, purify the sample, and at the same time, ion exchange with Ca 2+ , K + , Na + , Fe 3+ , and increase its pore volume, thereby increasing the adsorption performance. Organic acid esterification is performed with the Si-OH on the surface of the meerschaum, different carbon chain lengths of hydroxyl groups are introduced to improve the hydrophobicity of the surface, the hydrophobic groups are arranged on the surface, the surface tension of the meerschaum is reduced, the dispersion degree of the meerschaum is effectively improved, and aggregation and caking are prevented.

[0043] The activated carbon fiber can adsorb most of the harmful gases in the smoke. The cigarette filter with activated carbon fiber as the purification material can effectively reduce the harmful substances such as nicotine and tar in the smoke through adsorption, remove the miscellaneous odor in the cigarette, and maintain the traditional roasted tobacco flavor.

[0044] Further, the activated carbon fiber is treated with alkali, and a large number of active groups such as hydroxyl groups are formed on the surface, which is convenient for the subsequent deposition of titanium dioxide.

[0045] The application prepares a Cu-doped titanium solution, since TiO2 belongs to a wide band gap semiconductor, so that it can excite valence band electrons to form electron-hole pairs only in the ultraviolet range, and in the visible light range, due to the limitation of energy, it is difficult to excite the valence electrons of TiO2, so that TiO2 cannot produce ideal photocatalysis in the visible light range. The application synthesizes Cu-doped nano-TiO2 with a carbon layer on the surface by introducing methanol and ethanol, high-temperature reaction kettle reaction, not only reduces the number of hydroxyl groups on the surface of nano-TiO2 to prevent its agglomeration, and the carbon layer on the surface of nano-TiO2 can play the role of photosensitizer, and the light energy of visible light is transferred to TiO2, and the visible light photocatalytic efficiency of TiO2 is enhanced. The doping of Cu makes the band gap of TiO2 significantly narrow, the absorption threshold wavelength red shifts, and longer wavelength photons can be absorbed, thereby increasing the photocatalytic ability of nano-TiO2 photocatalytic material in the visible light region.

[0046] The application introduces Cu / C-doped TiO2 photocatalytic material on the surface of activated carbon fiber, so that it has good photocatalysis in the visible light region, thereby effectively adsorbing formaldehyde and other organic carcinogenic volatile substances and simultaneously having photocatalytic degradation effect, reducing the amount of organic volatile substances absorbed by the human body, and simultaneously having good antibacterial effect, through purification of the filter tip, greatly reducing the harm of smoking to the human body, improving the cleanliness of the filter tip, and being beneficial to human health.

[0047] The modified activated carbon fiber modified by polydopamine can be better and more fully dispersed in the polylactic acid matrix through the active groups such as hydroxyl groups, amino groups and carboxyl groups on the surface, and simultaneously, the mechanical properties, adsorption properties and degradation antibacterial properties of the modified polylactic acid can be stably improved.

[0048] The modified polylactic acid prepared in the application is melt-spun, the obtained filament has strong adsorption capacity for flue gas and high interception efficiency for tar and nicotine, simultaneously, the introduction of modified sepiolite fiber and modified activated carbon fiber greatly improves the adsorption and degradation of harmful substances, reduces the inhalation of harmful substances, simultaneously, has good mechanical properties, high strength, good elasticity, good degradable performance, and significantly reduced environmental pollution, and has wide application prospect. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the application will be clearly and completely described below, obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0050] The sepiolite fiber has a purity of >99%, a particle size of 300 meshes, and is purchased from Lingshou County Hongrun Mineral Product Processing Factory.

[0051] Activated carbon fiber, purity > 95%, particle size 500 mesh, purchased from Henan Zhongji Purification Material Co., Ltd.

[0052] Polylactic acid, model HP411, density 1.25 g.cm 3 , purchased from Ningbo Jiayuan Technology Co., Ltd.

[0053] Example 1

[0054] The embodiment provides a preparation method of filter material for a cigarette filter, and specifically comprises the following steps:

[0055] S1. Modification of sepiolite fiber: 10 parts by weight of sepiolite fiber is activated at 280 DEG C for 1 h, then added into 20 parts by weight of mixed acid, stirred at 40 DEG C for 1 h, filtered, ball milled for 2 h, washed, and dried to obtain modified sepiolite fiber;

[0056] The mixed acid is a mixture of 2 mol / L HCl solution and 20 wt% stearic acid in a volume ratio of 1:1;

[0057] S2. Preparation of Cu-doped titanium solution: 2 parts by weight of copper nitrate is dissolved in 70 parts by weight of water, 3 parts by weight of 1 mol / L hydrochloric acid is added, stirred and mixed for 10 min, a mixed solution of 20 parts by weight of methanol and 15 parts by weight of ethanol is added, 12 parts by weight of titanium chloride is added under stirring, stirred and mixed for 10 min to obtain the Cu-doped titanium solution;

[0058] S3. Pretreatment of activated carbon fiber: 10 parts by weight of activated carbon fiber is added into 30 parts by weight of 10 wt% NaOH solution, stirred and reacted at 45 DEG C for 0.5 h, filtered, ball milled for 2 h, washed, and dried to obtain pretreated activated carbon fiber;

[0059] S4. Preparation of Cu / C-doped TiO2 supported activated carbon fiber: 12 parts by weight of pretreated activated carbon fiber is added into 20 parts by weight of Cu-doped titanium solution, stirred and mixed for 20 min, stirred and reacted at 300 DEG C for 2 h, washed, and dried to obtain Cu / C-doped TiO2 supported activated carbon fiber;

[0060] S5. Preparation of modified activated carbon fiber: 12 parts by weight of Cu / C-doped TiO2 supported activated carbon fiber is added into 100 parts by weight of water, 17 parts by weight of dopamine hydrochloride and 2 parts by weight of catalyst are added, heated to 45 DEG C, stirred and reacted for 2 h, filtered, washed, and dried to obtain modified activated carbon fiber;

[0061] The catalyst is Tirs-HCl solution with pH = 8.5;

[0062] S6. Coating modification of polylactic acid: 15 parts by weight of polylactic acid is heated to 180℃, and 3 parts by weight of modified sepiolite fiber and 4 parts by weight of modified activated carbon fiber are added under molten conditions. Homogeneous stirring is carried out at 3000r / min for 15min to obtain modified polylactic acid;

[0063] S7. Preparation of filter material for cigarette filter: the modified polylactic acid is melt-spun, and the cooled filament is coated with oil, wound by a slow traction machine, stretched in a steam box, wound by a fast traction machine, and wound by a belt conveyor. The stretched filament is water-bathed in a water tank, and then crimped and dried to obtain a filament which is the filter material for cigarette filter;

[0064] The screw temperature in the melt spinning process is 180℃, the filter temperature is 170℃, the box temperature is 170℃, the straight pipe temperature is 170℃, the ejected filament is cooled by dry air, the cooling temperature is 0℃, the roller rotation speed of the traction machine is 500r / min, the frequency is 25Hz, the feeding wheel speed of the belt conveyor is 400r / min, and the water temperature in the water tank is 30℃.

[0065] Example 2

[0066] The embodiment provides a preparation method of filter material for cigarette filter, which specifically comprises the following steps:

[0067] S1. Modification of sepiolite fiber: 12 parts by weight of sepiolite fiber is activated at 320℃ for 2h, and then added into 30 parts by weight of mixed acid, and stirred at 45℃ for 2h. After filtration, ball milling is carried out for 2h, and then washing and drying are carried out to obtain modified sepiolite fiber.

[0068] The mixed acid is a mixture of 4mol / L HCl solution and 25wt% stearic acid in a volume ratio of 2:1;

[0069] S2. Preparation of Cu-doped titanium solution: 3 parts by weight of copper chloride is dissolved in 70 parts by weight of water, 5 parts by weight of 0.5mol / L hydrochloric acid is added, and stirring is carried out for 10min. A mixed solution of 30 parts by weight of methanol and 20 parts by weight of ethanol is added under stirring, and 15 parts by weight of titanium chloride is added and stirred for 10min to obtain Cu-doped titanium solution.

[0070] S3. Pretreatment of activated carbon fiber: 15 parts by weight of activated carbon fiber is added into 40 parts by weight of 15wt% KOH solution, and stirring is carried out at 50℃ for 1h. After filtration, ball milling is carried out for 2h, and then washing and drying are carried out to obtain pretreated activated carbon fiber.

[0071] S4. Preparation of Cu / C-doped TiO2 immobilized activated carbon fiber: 15 parts by weight of pretreated activated carbon fiber was added into 25 parts by weight of Cu-doped titanium solution, stirred and mixed for 20 min, stirred and reacted at 400℃ for 4 h, washed, dried, and Cu / C-doped TiO2 immobilized activated carbon fiber was prepared;

[0072] S5. Preparation of modified activated carbon fiber: 15 parts by weight of Cu / C-doped TiO2 immobilized activated carbon fiber was added into 100 parts by weight of water, 20 parts by weight of dopamine hydrochloride and 3 parts by weight of catalyst were added, heated to 55℃, stirred and reacted for 3 h, filtered, washed, dried, and modified activated carbon fiber was prepared;

[0073] The catalyst is Tirs-HCl solution with pH = 9;

[0074] S6. Coating modification of polylactic acid: 20 parts by weight of polylactic acid was heated to 200℃, 5 parts by weight of modified sepiolite fiber and 7 parts by weight of modified activated carbon fiber were added under molten conditions, and homogenously stirred at 5000 r / min for 20 min to obtain modified polylactic acid;

[0075] S7. Preparation of filter material for cigarette filter: the modified polylactic acid was melt-spun, the cooled filament was coated with oil, wound by slow traction machine, tractioned in steam box, wound by fast traction machine and belt conveyor, the drawn filament was water-bathed in water tank, and then crimped and dried to be shaped to obtain the filter material for cigarette filter;

[0076] The screw temperature in the melt spinning process was 220℃, the filter temperature was 230℃, the box temperature was 230℃, the straight pipe temperature was 230℃, the emitted filament was cooled by dry air, the cooling temperature was 40℃, the roller rotation speed of the traction machine was 2200 r / min, the frequency was 50 Hz, the feeding wheel speed of the belt conveyor was 1200 r / min, and the water temperature in the water tank was 50℃.

[0077] Example 3

[0078] The embodiment provides a preparation method of filter material for cigarette filter, which specifically comprises the following steps:

[0079] S1. Modification of sepiolite fiber: 11 parts by weight of sepiolite fiber was activated at 300℃ for 1.5 h, then 25 parts by weight of mixed acid was added, stirred and reacted at 43℃ for 1.5 h, filtered, ball-milled for 2 h, washed, dried, and modified sepiolite fiber was obtained;

[0080] The mixed acid is a mixture of 3 mol / L HCl solution and 22 wt% stearic acid with a volume ratio of 1.5:1;

[0081] S2. Preparation of Cu-doped titanium solution: 2.5 parts by weight of copper sulfate was dissolved in 70 parts by weight of water, 4 parts by weight of 0.7 mol / L hydrochloric acid was added, stirred and mixed for 10 min, a mixed solution of 25 parts by weight of methanol and 17 parts by weight of ethanol was added, 13.5 parts by weight of titanium chloride was added under stirring, stirred and mixed for 10 min, to obtain a Cu-doped titanium solution;

[0082] S3. Pretreatment of activated carbon fiber: 12 parts by weight of activated carbon fiber was added to 35 parts by weight of 12wt% NaOH solution, stirred and reacted at 47℃ for 1h, filtered, ball milled for 2h, washed, dried, to obtain pretreated activated carbon fiber;

[0083] S4. Preparation of Cu / C-doped TiO2 supported activated carbon fiber: 13.5 parts by weight of pretreated activated carbon fiber was added to 22 parts by weight of Cu-doped titanium solution, stirred and mixed for 20 min, stirred and reacted at 350℃ for 3h, washed, dried, to obtain Cu / C-doped TiO2 supported activated carbon fiber;

[0084] S5. Preparation of modified activated carbon fiber: 13.5 parts by weight of Cu / C-doped TiO2 supported activated carbon fiber was added to 100 parts by weight of water, 18.5 parts by weight of dopamine hydrochloride and 2.5 parts by weight of catalyst were added, heated to 50℃, stirred and reacted for 2.5h, filtered, washed, dried, to obtain modified activated carbon fiber;

[0085] The catalyst is Tirs-HCl solution with pH=8.7;

[0086] S6. Coating modification of polylactic acid: 17 parts by weight of polylactic acid was heated to 190℃, under melting condition, 4 parts by weight of modified sepiolite fiber and 5 parts by weight of modified activated carbon fiber were added, homogenously stirred at 4000r / min for 17 min, to obtain modified polylactic acid;

[0087] S7. Preparation of filter material for cigarette filter: the modified polylactic acid was melt-spun, the cooled filament was coated with oil agent, wound by slow traction machine, traction in steam box, wound by fast traction machine and belt conveyor, the drawn filament in water tank was crimped and dried, to obtain the filter material for cigarette filter;

[0088] The screw temperature in melt spinning process was 200℃, the filter temperature was 210℃, the box temperature was 210℃, the straight pipe temperature was 210℃, the jetted filament was cooled by dry air, the cooling temperature was 20℃, the roller rotation speed of the traction machine was 1200r / min, the frequency was 35Hz, the feeding wheel speed of the belt conveyor was 800r / min, the water temperature in the water tank was 40℃.

[0089] Example 4

[0090] The difference compared with Example 3 is that the mixed acid is a single 3 mol / L HC1 solution.

[0091] Example 5

[0092] The difference compared with Example 3 is that the mixed acid is a single 22 wt% stearic acid.

[0093] Comparative Example 1

[0094] The difference compared with Example 3 is that high-temperature activation is not performed in step S1.

[0095] The details are as follows:

[0096] S1. Modification of the sepiolite fiber: 11 parts by weight of sepiolite fiber was added to 25 parts by weight of mixed acid, stirred at 43°C for 1.5 h, filtered, ball milled for 2 h, washed, dried, and modified sepiolite fiber was obtained.

[0097] The mixed acid is a mixture of 3 mol / L HC1 solution and 22 wt% stearic acid in a volume ratio of 1.5:1.

[0098] Comparative Example 2

[0099] The difference compared with Example 3 is that the mixed acid modification is not performed in step S1.

[0100] The details are as follows:

[0101] S1. Modification of the sepiolite fiber: 11 parts by weight of sepiolite fiber was added to 25 parts by weight of mixed acid, stirred at 43°C for 1.5 h, filtered, ball milled for 2 h, washed, dried, and modified sepiolite fiber was obtained.

[0102] Comparative Example 3

[0103] The difference compared with Example 3 is that copper sulfate is not added in step S2.

[0104] The details are as follows:

[0105] S2. Preparation of the titanium solution: 4 parts by weight of 0.7 mol / L HC1 was added to 70 parts by weight of water, stirred and mixed for 10 min, a mixed solution of 25 parts by weight of methanol and 17 parts by weight of ethanol was added, 13.5 parts by weight of titanium chloride was added under stirring, stirred and mixed for 10 min, and a titanium solution was obtained.

[0106] Comparative Example 4

[0107] The difference compared with Example 3 is that the mixed solution of methanol and ethanol is not added in step S2.

[0108] The details are as follows:

[0109] S2. Preparation of Cu-doped titanium solution: 2.5 parts by weight of copper sulfate was dissolved in 70 parts by weight of water, 4 parts by weight of 0.7 mol / L hydrochloric acid was added, stirred and mixed for 10 min, 13.5 parts by weight of titanium chloride was added under stirring, stirred and mixed for 10 min, to obtain a Cu-doped titanium solution.

[0110] Comparative Example 5

[0111] Compared with Example 3, the difference lies in that no copper sulfate and mixed solution of methanol and ethanol is added in step S2.

[0112] The details are as follows:

[0113] S2. Preparation of titanium solution: 4 parts by weight of 0.7 mol / L hydrochloric acid was added to 70 parts by weight of water, stirred and mixed for 10 min, 13.5 parts by weight of titanium chloride was added under stirring, stirred and mixed for 10 min, to obtain a titanium solution.

[0114] Comparative Example 6

[0115] Compared with Example 3, the difference lies in that steps S2 and S4 are not performed.

[0116] The details are as follows:

[0117] S1. Modification of sepiolite fiber: 11 parts by weight of sepiolite fiber was activated at 300℃ for 1.5h, then added into 25 parts by weight of mixed acid, stirred and reacted at 43℃ for 1.5h, filtered, ball milled for 2h, washed, and dried to obtain modified sepiolite fiber;

[0118] The mixed acid is a mixture of 3 mol / L HCl solution and 22 wt% stearic acid at a volume ratio of 1.5:1;

[0119] S2. Pretreatment of activated carbon fiber: 12 parts by weight of activated carbon fiber was added into 35 parts by weight of 12 wt% NaOH solution, stirred and reacted at 47℃ for 1h, filtered, ball milled for 2h, washed, and dried to obtain pretreated activated carbon fiber;

[0120] S3. Preparation of modified activated carbon fiber: 13.5 parts by weight of pretreated activated carbon fiber was added into 100 parts by weight of water, 18.5 parts by weight of dopamine hydrochloride and 2.5 parts by weight of catalyst were added, heated to 50℃, stirred and reacted for 2.5h, filtered, washed, and dried to obtain modified activated carbon fiber;

[0121] The catalyst is Tirs-HCl solution with pH=8.7;

[0122] S4. Coating modification of polylactic acid: 17 parts by weight of polylactic acid was heated to 190°C, 4 parts by weight of modified sepiolite fiber and 5 parts by weight of modified activated carbon fiber were added under the condition of melting, and homogenously stirred at 4000 r / min for 17 min to obtain modified polylactic acid;

[0123] S5. Preparation of filter material for cigarette filter: the modified polylactic acid was melt-spun, the obtained filament was coated with oil agent, wound by slow traction machine, stretched by steam box, wound by fast traction machine and belt conveyor, and then stretched by water bath in water tank, and then crimped and dried to obtain the filter material for cigarette filter;

[0124] The screw temperature was 200°C, the filter temperature was 210°C, the box temperature was 210°C, the straight pipe temperature was 210°C, the ejected filament was cooled by dry air, the cooling temperature was 20°C, the roller rotation speed of the traction machine was 1200 r / min, the frequency was 35 Hz, and the feeding wheel speed of the belt conveyor was 800 r / min. The water temperature in the water tank was 40°C.

[0125] Comparative Example 7

[0126] Compared with Example 3, the difference is that step S5 is not performed.

[0127] The details are as follows:

[0128] S1. Modification of sepiolite fiber: 11 parts by weight of sepiolite fiber was activated at 300°C for 1.5 h, then added into 25 parts by weight of mixed acid, stirred at 43°C for 1.5 h, filtered, ball-milled for 2 h, washed, and dried to obtain modified sepiolite fiber;

[0129] The mixed acid is a mixture of 3 mol / L HCl solution and 22 wt% stearic acid at a volume ratio of 1.5:1;

[0130] S2. Preparation of Cu-doped titanium solution: 2.5 parts by weight of copper sulfate was dissolved in 70 parts by weight of water, 4 parts by weight of 0.7 mol / L hydrochloric acid was added, stirred and mixed for 10 min, 25 parts by weight of a mixed solution of methanol and ethanol was added, and 13.5 parts by weight of titanium chloride was added under stirring and mixed for 10 min to obtain Cu-doped titanium solution;

[0131] S3. Pretreatment of activated carbon fiber: 12 parts by weight of activated carbon fiber was added into 35 parts by weight of 12 wt% NaOH solution, stirred and reacted at 47°C for 1 h, filtered, ball-milled for 2 h, washed, and dried to obtain pretreated activated carbon fiber;

[0132] S4. Preparation of Cu / C-doped TiO2 immobilized activated carbon fiber: 13.5 parts by weight of pretreated activated carbon fiber was added into 22 parts by weight of Cu-doped titanium solution, stirred and mixed for 20 min, stirred and reacted at 350℃ for 3 h, washed, dried, and Cu / C-doped TiO2 immobilized activated carbon fiber was prepared;

[0133] S5. Coating modification of polylactic acid: 17 parts by weight of polylactic acid was heated to 190℃, 4 parts by weight of modified sepiolite fiber and 5 parts by weight of Cu / C-doped TiO2 immobilized activated carbon fiber were added under molten conditions, and homogenously stirred at 4000 r / min for 17 min to obtain modified polylactic acid;

[0134] S6. Preparation of filter material for cigarette filter: the modified polylactic acid was melt-spun, the cooled filament was coated with oil, wound by slow traction machine, steamed in steam box, wound by fast traction machine and belt conveyor, the drawn filament was water-bathed in water tank, and then crimped and dried to obtain the filter material for cigarette filter;

[0135] The screw temperature was 200℃, the filter temperature was 210℃, the box temperature was 210℃, the straight pipe temperature was 210℃, the ejected filament was cooled by dry air, the cooling temperature was 20℃, the roller rotation speed of the traction machine was 1200 r / min, the frequency was 35 Hz, the feeding wheel speed of the belt conveyor was 800 r / min, and the water temperature in the water tank was 40℃.

[0136] Comparative Example 8

[0137] Compared with Example 3, the difference was that the same amount of sepiolite fiber was used instead of modified sepiolite fiber in step S6.

[0138] Specifically as follows:

[0139] S6. Coating modification of polylactic acid: 17 parts by weight of polylactic acid was heated to 190℃, 4 parts by weight of modified sepiolite fiber and 5 parts by weight of Cu / C-doped TiO2 immobilized activated carbon fiber were added under molten conditions, and homogenously stirred at 4000 r / min for 17 min to obtain modified polylactic acid.

[0140] Comparative Example 9

[0141] Compared with Example 3, the difference was that the same amount of activated carbon fiber was used instead of modified activated carbon fiber in step S6.

[0142] Specifically as follows:

[0143] S6. Coating modification of polylactic acid: 17 parts by weight of polylactic acid was heated to 190℃, 4 parts by weight of modified sepiolite fiber and 5 parts by weight of Cu / C-doped TiO2 immobilized activated carbon fiber were added under molten conditions, and homogenously stirred at 4000 r / min for 17 min to obtain modified polylactic acid.

[0144] Comparative Example 10

[0145] Compared with Example 3, the difference is that no modified sepiolite fiber and modified activated carbon fiber are added in step S6.

[0146] The details are as follows:

[0147] S6. Melting of polylactic acid: 17 parts by weight of polylactic acid is heated to 190℃ to be melted to obtain polylactic acid.

[0148] Test Example 1

[0149] The cigarette filter made of the filter material prepared from the cigarette filter for filter material of Examples 1-5 and Comparative Examples 1-10 of the present application is tested for performance.

[0150] The release amounts (the contents of each substance collected after passing through the filter) of total particulate matter, nicotine and moisture in the mainstream smoke of the cigarette are determined according to the methods of GB / T 19609-2004 "Determination of total particulate matter and tar in cigarettes by smoking machine for routine analysis", GB / T 23355-2009 "Determination of nicotine in total particulate matter of cigarettes - Gas chromatographic method" and GB / T 23203.1-2013 "Determination of moisture in total particulate matter of cigarettes - Part 1: Gas chromatographic method". The tar content is calculated by nicotine, moisture and tar as total particulate matter. The carbon monoxide content can be directly read.

[0151] The results are shown in Table 1.

[0152] Table 1

[0153] Group Total particulate (mg / cig) Nicotine (mg / cig) Tar (mg / cig) Carbon monoxide (mg / cig) Example 1 1.20 0.10 2.01 8.75 Example 2 1.17 0.09 1.97 8.71 Example 3 1.15 0.07 1.92 8.68 Example 4 1.56 0.19 2.43 10.12 Example 5 1.62 0.21 2.49 10.09 Comparative Example 1 1.59 0.20 2.48 10.17 Comparative Example 2 1.77 0.24 2.54 10.21 Comparative Example 3 1.69 0.22 2.51 10.19 Comparative Example 4 1.71 0.25 2.56 10.24 Comparative Example 5 1.80 0.27 2.67 10.35 Comparative Example 6 1.97 0.30 2.69 10.52 Comparative Example 7 1.64 0.22 2.51 10.10 Comparative Example 8 2.02 0.32 2.72 10.78 Comparative Example 9 2.15 0.36 2.77 10.84 Comparative Example 10 2.84 0.41 2.86 11.02

[0154] As shown in the above table, the cigarette filter made of the filter material prepared from the cigarette filter for filter material of Examples 1-3 of the present application can adsorb the harmful substances in the cigarette, and the effect is remarkable.

[0155] Test Example 2

[0156] The degradation rates of the cigarette filter for filter material prepared from the cigarette filter for filter material of Examples 1-5 and Comparative Examples 1-10 of the present application are detected according to the requirement of ISO 14855, and the degradation rate results of 60 days are shown in Table 2.

[0157] Table 2

[0158] Group Degradation rate in 60 days (%) Example 1 95.7 Example 2 96.2 Example 3 96.5 Example 4 94.9 Example 5 95.1 Comparative Example 1 94.8 Comparative Example 2 94.5 Comparative Example 3 90.1 Comparative Example 4 89.4 Comparative Example 5 86.7 Comparative Example 6 82.4 Comparative Example 7 91.3 Comparative Example 8 93.2 Comparative Example 9 81.3 Comparative Example 10 78.9

[0159] As shown in the above table, the cigarette filter for filter material prepared from the cigarette filter for filter material of Examples 1-3 of the present application has a good degradation effect within 60 days.

[0160] Test Example 3

[0161] The cigarette filter produced by the cigarette filter material of the present application is subjected to performance test.

[0162] The tensile strength and elongation at break of the monofilament sample are measured using a low speed elongation tensile testing machine at a tensile speed of 60 mm / min.

[0163] The cigarette filter produced by the cigarette filter material of the present application is subjected to performance test.

[0164] The results are shown in Table 3.

[0165] Table 3

[0166] Group Inhale resistance (PD) Monofilament tensile strength (g / d) Monofilament elongation at break (%) Example 1 335 3.7 12.2 Example 2 330 3.6 12.1 Example 3 340 3.8 12.5 Example 4 345 3.5 11.8 Example 5 350 3.4 11.6 Comparative Example 1 350 3.4 11.4 Comparative Example 2 355 3.3 11.0 Comparative Example 3 350 3.2 11.3 Comparative Example 4 345 3.3 11.1 Comparative Example 5 355 3.1 10.9 Comparative Example 6 360 3.0 10.2 Comparative Example 7 350 2.9 10.0 Comparative Example 8 360 3.2 10.8 Comparative Example 9 365 2.8 9.8 Comparative Example 10 370 2.7 9.4

[0167] As shown in the above table, the monofilament produced by the cigarette filter material of the present application has good mechanical properties, and the inhalation resistance of the filter produced therefrom is uniform and ranges between 330 and 340.

[0168] In Example 4 and 5, the mixed acid is a single 3 mol / L HCl solution or 22 wt% stearic acid. In Comparative Example 2, the mixed acid modification is not performed in step S1. The adsorption performance of harmful substances in cigarettes is reduced. In the present application, the inorganic acid activation can remove the calcium carbonate impurities in the sepiolite, purify the sample, and increase the Ca 2+ , K + , Na + , Fe 3+ exchange occurs, and the pore volume is increased, thereby increasing the adsorption performance. The organic acid esterifies with the Si-OH on the surface of the sepiolite, improves the hydrophobicity of the surface by introducing hydroxyl groups with different carbon chain lengths, arranges the hydrophobic groups on the surface, reduces the surface tension of the sepiolite, effectively improves the dispersion degree of the sepiolite, and prevents the sepiolite from aggregating and caking.

[0169] In Comparative Example 1, the high-temperature activation is not performed in step S1. The adsorption performance of harmful substances in cigarettes is reduced. In the present application, the high-temperature activation is performed first to remove the zeolite water in the sepiolite, increase the pore size of the sepiolite, and increase the strength and number of the surface activation centers.

[0170] In Comparative Example 8, the modified sepiolite fibers are replaced by an equal amount of sepiolite fibers in step S6. The adsorption performance of harmful substances in cigarettes is reduced, and the mechanical properties of the monofilament are reduced.

[0171] Compared to Example 3, Comparative Examples 3 and 4 did not include copper sulfate or a mixed solution of methanol and ethanol in step S2. Comparative Example 5, compared to Example 3, did not include a mixed solution of copper sulfate, methanol, and ethanol in step S2. The adsorption performance and degradation performance of harmful substances in cigarettes decreased. This invention prepares a Cu-doped titanium solution. Since TiO2 is a wide-bandgap semiconductor, it can only excite valence electrons to form electron-hole pairs in the ultraviolet range. In the visible light range, due to energy limitations, it is difficult to excite valence electrons in TiO2, making it unable to produce ideal photocatalytic activity. This invention synthesizes Cu-doped nano-TiO2 with a carbon layer on its surface by introducing methanol and ethanol and reacting in a high-temperature reactor. This not only reduces the number of hydroxyl groups on the surface of nano-TiO2 to prevent aggregation, but also allows the carbon layer on the surface of nano-TiO2 to act as a photosensitizer, transferring visible light energy to TiO2 and enhancing the visible light photocatalytic efficiency of TiO2. Cu doping significantly narrows the band gap of TiO2, redshifts the absorption threshold wavelength, and allows it to absorb longer wavelength photons, thus increasing the photocatalytic activity of nano-TiO2 photocatalysts in the visible light region. Simultaneously, the presence of nano-TiO2 can also catalyze the degradation of filter materials.

[0172] Compared to Example 3, Comparative Example 6 omitted steps S2 and S4. The adsorption performance and degradation performance of harmful substances in cigarettes decreased. This invention introduces Cu / C-doped TiO2 photocatalyst material onto the surface of activated carbon fiber, enabling it to exhibit good photocatalysis in the visible light region. This allows for the effective adsorption of formaldehyde and other carcinogenic volatile organic compounds while simultaneously undergoing photocatalytic degradation, reducing the amount of volatile organic compounds absorbed by the human body. Furthermore, it possesses excellent antibacterial and bacteriostatic effects. Through the purification of the filter, the harm caused by smoking to the human body is significantly reduced, the cleanliness of the cigarette holder is improved, and it is beneficial to human health.

[0173] Compared to Example 3, Comparative Example 7 did not perform step S5. The adsorption performance for harmful substances in cigarettes decreased, the mechanical properties of the monofilament decreased, and the resistance increased. The modified activated carbon fiber of this invention, after being modified with polydopamine, can be better and more fully dispersed in the polylactic acid matrix through its surface active groups such as hydroxyl, amino, and carboxyl groups. Simultaneously, it can stably improve the mechanical properties, adsorption properties, and degradation and antibacterial properties of the modified polylactic acid.

[0174] Compared to Example 3, Comparative Example 9 involved replacing the modified activated carbon fiber with an equal amount of activated carbon stone fiber in step S6. This resulted in decreased adsorption performance for harmful substances in cigarette smoke, reduced mechanical properties of the monofilament, increased resistance, and decreased biodegradability.

[0175] Comparative Example 10 does not add modified sepiolite fiber and modified activated carbon fiber in step S6 compared with Example 3. The adsorption performance of harmful substances in cigarettes is reduced, the single fiber mechanical property is reduced, the resistance is increased, and the degradability is reduced. Sepiolite has a large specific surface area and excellent selective adsorption, and is a fibrous clay mineral rich in magnesium and silicon. Its standard crystal chemical formula is Mg8Si 12 O30(OH)4(OH2)4·8H2O, composed of silicon-oxygen tetrahedron and magnesium-oxygen octahedron, has a chain-like and layered fibrous transition structure. It has a large specific surface area, and there are three types of adsorption centers on its surface: (1) oxygen atoms in the silicon-oxygen tetrahedron layer; (2) water molecules paired with magnesium ions at the edge, which can form hydrogen bonds with adsorbates; (3) Si-OH groups formed by the rupture of Si-O-Si bonds on the outer surface of the tetrahedral layer, which can interact with molecules adsorbed on the outer surface of sepiolite and form covalent bonds with some organic reagents. Therefore, it has strong adsorption performance. Activated carbon fiber can adsorb most of the harmful gases in smoke. The filter tip using activated carbon fiber as the purification material can effectively reduce the harmful substances such as nicotine and tar in smoke through adsorption, remove the miscellaneous odor in cigarettes, and maintain the traditional roasted tobacco flavor.

[0176] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a filter material for cigarette filters, characterized in that, Includes the following steps: S1. Modification of sepiolite fiber: After high-temperature activation of sepiolite fiber, it is added to a mixed acid, stirred and reacted, filtered, washed and dried to obtain modified sepiolite fiber. S2. Preparation of Cu-doped titanium solution: Dissolve soluble copper salt in water, add hydrochloric acid, stir and mix evenly, add a mixed solution of methanol and ethanol, and add titanium chloride under stirring to obtain Cu-doped titanium solution; S3. Pretreatment of activated carbon fiber: Add activated carbon fiber to alkaline solution, stir to react, filter, wash, and dry to obtain pretreated activated carbon fiber; S4. Preparation of Cu / C doped TiO2 supported activated carbon fiber: Pretreated activated carbon fiber was added to Cu doped titanium solution, stirred and mixed evenly, reacted at high temperature, washed and dried to obtain Cu / C doped TiO2 supported activated carbon fiber. S5. Preparation of modified activated carbon fiber: Cu / C doped TiO2 supported activated carbon fiber was added to water, dopamine hydrochloride and catalyst were added, the mixture was heated and stirred to react, filtered, washed and dried to obtain modified activated carbon fiber; S6. Coating modification of polylactic acid: Polylactic acid is heated and melted, modified sepiolite fiber and modified activated carbon fiber are added, and the mixture is stirred homogenously to obtain modified polylactic acid; S7. Preparation of filter material for cigarette filters: Modified polylactic acid is melt-spun, and the cooled filaments are wound by a traction machine and a belt conveyor. The drawn filaments are stretched in a water bath in a water tank, and then curled and dried to form the filaments. The resulting filaments are the filter material for cigarette filters.

2. The preparation method according to claim 1, characterized in that, The high-temperature activation in step S1 is performed at a temperature of 280-320℃ for 1-2 hours. The mixed acid is a mixture of inorganic and organic acids. The inorganic acid is HCl or sulfuric acid, and the organic acid is selected from at least one of stearic acid, octanoic acid, heptanoic acid, and cinnamic acid. The mass ratio of sepiolite fiber to mixed acid is 10-12:20-30. The stirring reaction is performed at a temperature of 40-45℃ for 1-2 hours.

3. The preparation method according to claim 1, characterized in that, The mixed acid is a mixture of 2-4 mol / L HCl solution and 20-25 wt% stearic acid in a volume ratio of 1-2:

1.

4. The preparation method according to claim 1, characterized in that, In step S2, the soluble copper salt is selected from at least one of copper chloride, copper sulfate, and copper nitrate. The mass ratio of the soluble copper salt, hydrochloric acid, methanol, ethanol, and titanium chloride is 2-3:3-5:20-30:15-20:12-15, and the concentration of the hydrochloric acid is 0.5-1 mol / L. In step S3, the alkaline solution is a 10-15 wt% NaOH or KOH solution. The mass ratio of the activated carbon fiber to the alkaline solution is 10-15:30-40. The stirring reaction temperature is 45-50℃, and the time is 0.5-1 h.

5. The preparation method according to claim 1, characterized in that, In step S4, the mass ratio of the pretreated activated carbon fiber to the Cu-doped titanium solution is 12-15:20-25, and the high-temperature reaction is carried out at 300-400℃ for 2-4 hours.

6. The preparation method according to claim 1, characterized in that, In step S5, the mass ratio of Cu / C-doped TiO2-supported activated carbon fiber, dopamine hydrochloride, and catalyst is 12-15:17-20:2-3. The catalyst is a Tirs-HCl solution with pH=8.5-9. The heating and stirring reaction is carried out at a temperature of 45-55℃ for 2-3 hours.

7. The preparation method according to claim 1, characterized in that, The heating temperature in step S6 is 180-200℃, the mass ratio of polylactic acid, modified sepiolite fiber and modified activated carbon fiber is 15-20:3-5:4-7, the stirring speed is 3000-5000 r / min and the time is 15-20 min.

8. The preparation method according to claim 1, characterized in that, In step S7, the screw temperature during melt spinning is 180-220℃, the filter temperature is 170℃-230℃, the box temperature is 170℃-230℃, the straight tube temperature is 170℃-230℃, the ejected filaments are cooled with dry air at a temperature of 0℃-40℃, the roller speed of the traction machine is 500-2200 r / min, the frequency is 25-50 Hz, the feed wheel speed of the belt conveyor is 400-1200 r / min, and the water temperature in the water tank is 30-50℃.

9. The preparation method according to claim 1, characterized in that, Specifically, the following steps are included: S1. Modification of sepiolite fiber: 10-12 parts by weight of sepiolite fiber were activated at 280-320℃ for 1-2 hours, then added to 20-30 parts by weight of mixed acid, stirred at 40-45℃ for 1-2 hours, filtered, washed, and dried to obtain modified sepiolite fiber. The mixed acid is a mixture of 2-4 mol / L HCl solution and 20-25 wt% stearic acid in a volume ratio of 1-2:1; S2. Preparation of Cu-doped titanium solution: Dissolve 2-3 parts by weight of soluble copper salt in water, add 3-5 parts by weight of 0.5-1 mol / L hydrochloric acid, stir and mix evenly, add 20-30 parts by weight of methanol and 15-20 parts by weight of ethanol mixed solution, and add 12-15 parts by weight of titanium chloride under stirring to obtain Cu-doped titanium solution. S3. Pretreatment of activated carbon fiber: Add 10-15 parts by weight of activated carbon fiber to 30-40 parts by weight of 10-15 wt% NaOH or KOH solution, stir and react at 45-50℃ for 0.5-1 h, filter, wash, and dry to obtain pretreated activated carbon fiber. S4. Preparation of Cu / C doped TiO2 supported activated carbon fiber: 12-15 parts by weight of pretreated activated carbon fiber were added to 20-25 parts by weight of Cu doped titanium solution, stirred and mixed evenly, stirred and reacted at 300-400℃ for 2-4 hours, washed and dried to obtain Cu / C doped TiO2 supported activated carbon fiber. S5. Preparation of modified activated carbon fiber: 12-15 parts by weight of Cu / C doped TiO2 supported activated carbon fiber were added to water, along with 17-20 parts by weight of dopamine hydrochloride and 2-3 parts by weight of catalyst. The mixture was heated to 45-55℃ and stirred for 2-3 hours. The mixture was then filtered, washed, and dried to obtain modified activated carbon fiber. The catalyst is a Tirs-HCl solution with a pH of 8.5-9; S6. Coating modification of polylactic acid: Heat 15-20 parts by weight of polylactic acid to 180-200℃, and under molten conditions, add 3-5 parts by weight of modified sepiolite fiber and 4-7 parts by weight of modified activated carbon fiber, and stir homogenously at 3000-5000r / min for 15-20min to obtain modified polylactic acid. S7. Preparation of filter material for cigarette filters: Modified polylactic acid is melt-spun, and the cooled filaments are coated with oil, wound by a slow traction machine, drawn by a steam box, wound by a fast traction machine, and wound by a belt conveyor. The drawn filaments are stretched in a water bath in a water tank, and then curled and dried to form the filaments. The resulting filaments are the filter material for cigarette filters. During the melt spinning process, the screw temperature is 180-220℃, the filter temperature is 170℃-230℃, the box temperature is 170℃-230℃, and the straight tube temperature is 170℃-230℃. The extruded filaments are cooled with dry air at a temperature of 0℃-40℃. The roller speed of the traction machine is 500-2200 r / min, the frequency is 25-50 Hz, the feed wheel speed of the belt conveyor is 400-1200 r / min, and the water temperature in the water tank is 30-50℃.

10. A filter material for cigarette filters prepared by the method according to any one of claims 1-9.