Nanofiber composite nonwoven fabric for preparing cigarette filters, preparation method and application thereof

Abstract

The present invention provides a nanofiber composite nonwoven fabric for making cigarette filters, comprising a first nanofiber layer, an adsorption layer, a second nanofiber layer, and a substrate layer laminated together; the first nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the second nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the adsorption layer is made of one or more of activated carbon, carbon nanotubes, silica gel, zeolite, or modified carbon nanotubes; and the substrate layer is made of one or more of polyester, polyamide, polyurethane, polyether, polyimide, or modified polyimide. The nanofiber composite nonwoven fabric provided by the present invention has a strong selective adsorption capacity, reducing tobacco consumption and the intake of harmful substances such as carcinogenic components.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a nanofiber composite non-woven fabric for preparing cigarette filters, and a preparation method and application thereof. Background Art

[0002] Smoking is harmful, not only to human health but also to society. Cigarettes contain 69 carcinogens. Many diseases are directly linked to smoking, yet for those who cannot quit, cigarettes are an essential necessity. Regular smokers inhale toxic gases contaminated by smoke. Tobacco leaves contain the toxic substance nicotine. Smoking is most harmful to the respiratory tract, easily causing laryngitis, tracheitis, emphysema, and other diseases. When smoking, smoke enters the mouth, passes through the throat, trachea, and bronchi, and enters the bloodstream.

[0003] As people become increasingly concerned about the health effects of smoking, toxic and carcinogenic compounds need to be separated and removed through adsorption. Research on tar reduction and harm reduction technologies for cigarette products has attracted great attention from the tobacco industry.

[0004] Therefore, it is an urgent problem to obtain a nanofiber composite non-woven fabric with selective adsorption ability for preparing cigarette filters, reduce the content of harmful substances in smoke as much as possible, and reduce the harm of cigarettes to the human body. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a nanofiber composite non-woven fabric for preparing cigarette filters. The composite non-woven fabric of the present invention has a strong selective adsorption capacity, which reduces tobacco consumption and the intake of harmful substances such as carcinogenic components.

[0006] The present invention provides a nanofiber composite nonwoven fabric for preparing a cigarette filter, comprising a first nanofiber layer, an adsorption layer, a second nanofiber layer and a substrate layer stacked in sequence;

[0007] The first nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the second nanofiber layer is obtained by electrospinning polyacrylonitrile fibers;

[0008] The material of the adsorption layer is selected from one or more of activated carbon, carbon nanotubes, silica gel, zeolite or modified carbon nanotubes;

[0009] The substrate layer is selected from one or more of polyester, polyamide, polyurethane, polyether, polyimide or modified polyimide.

[0010] Preferably, the particle size of the adsorption material is 1 to 50 μm;

[0011] The adsorption material is modified carbon nanotubes; the modified carbon nanotubes are polyphthalic anhydride-β-cyclodextrin modified carbon nanotubes;

[0012] The weight ratio of the polyphthalic anhydride-β-cyclodextrin to the carbon nanotubes is 1:(5-15).

[0013] Preferably, the method for preparing the modified carbon nanotubes comprises:

[0014] S1) mixing carbon nanotubes and nitric acid, ultrasonically dispersing, and reacting to obtain carboxylated carbon nanotubes;

[0015] S2) ultrasonically dispersing the carboxylated carbon nanotubes in a solvent, stirring for reaction, then adding polyphthalic anhydride-β-cyclodextrin and a solvent, stirring for reaction, filtering, and drying to obtain the product.

[0016] Preferably, the substrate layer is modified polyimide; the modified polyimide is aminopropyl isobutyl POSS modified polyimide;

[0017] The molar ratio of the polyimide to the aminopropyl isobutyl POSS in the modified polyimide is (100-1):1.

[0018] Preferably, the preparation method of the modified polyimide comprises:

[0019] a1) reacting 1,3-bis(4-aminophenylcyclo)adamantane, a monomer, and m-cresol, then dropwise adding isoquinoline, heating, and reacting to obtain a polyimide solution;

[0020] a2) introducing an inert gas, adding aminopropyl isobutyl POSS to the polyimide solution, and heating the solution to react to obtain a modified polyimide.

[0021] Preferably, the diameter of the polyacrylonitrile fiber is 150-200 nm; the thickness of the first nanofiber layer is 1-5 μm; the thickness of the second nanofiber layer is 1-5 μm; the porosity of the first nanofiber layer is 75%-85%; the porosity of the second nanofiber layer is 75%-85%.

[0022] Preferably, the porosity of the substrate layer is 15% to 50%; the weight of the substrate layer is 20 to 40 g / m 2 .

[0023] The present invention provides a method for preparing a nanofiber composite nonwoven fabric, comprising the following steps:

[0024] A) laying a substrate layer flat, and depositing polyacrylonitrile fibers on the substrate layer by electrospinning to obtain a second nanofiber layer;

[0025] B) coating the adsorption layer material on the surface of the second nanofiber layer to obtain an adsorption layer;

[0026] C) depositing polyacrylonitrile fibers on the adsorption layer by electrospinning to obtain a first nanofiber layer.

[0027] The present invention provides a cigarette filter comprising the nanofiber composite non-woven fabric described in any one of the above technical solutions.

[0028] The present invention provides a cigarette, comprising the cigarette filter described in the above technical solution.

[0029] Compared to existing technologies, the present invention provides a nanofiber composite nonwoven fabric for making cigarette filters, comprising a first nanofiber layer, an adsorption layer, a second nanofiber layer, and a substrate layer laminated together. The first nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the second nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the adsorption layer is made of one or more of activated carbon, carbon nanotubes, silica gel, zeolite, or modified carbon nanotubes; and the substrate layer is made of one or more of polyester, polyamide, polyurethane, polyether, polyimide, or modified polyimide. The nanofiber composite nonwoven fabric provided by the present invention has a strong selective adsorption capacity, reducing tobacco consumption and the intake of harmful substances such as carcinogenic components. DETAILED DESCRIPTION

[0030] The present invention provides a nanofiber composite nonwoven fabric for preparing cigarette filters, and its preparation method and application. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the desired results. It should be noted in particular that all similar replacements and modifications are obvious to those skilled in the art and they all fall within the scope of protection of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0031] In this application, the term "and / or" describes the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural.

[0032] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items.

[0033] The present invention provides a nanofiber composite nonwoven fabric for preparing a cigarette filter, comprising a first nanofiber layer, an adsorption layer, a second nanofiber layer and a substrate layer stacked in sequence;

[0034] The first nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the second nanofiber layer is obtained by electrospinning polyacrylonitrile fibers;

[0035] The material of the adsorption layer is selected from one or more of activated carbon, carbon nanotubes, silica gel, zeolite or modified carbon nanotubes;

[0036] The substrate layer is selected from one or more of polyester, polyamide, polyurethane, polyether, polyimide or modified polyimide.

[0037] The nanofiber composite nonwoven fabric for preparing a cigarette filter provided by the present invention comprises a substrate layer.

[0038] The thickness of the substrate layer described in the present invention is 0.5-0.7 mm, preferably 0.50 mm, 0.52 mm, 0.53 mm, 0.54 mm, 0.55 mm, 0.56 mm; most preferably 0.55 mm.

[0039] The substrate layer of the present invention is selected from one or more of polyester, polyamide, polyurethane, polyether, polyimide or modified polyimide. Preferably, the substrate layer is one or more of polyimide or modified polyimide; more preferably, the substrate layer is modified polyimide.

[0040] According to the present invention, the preparation method of the modified polyimide comprises:

[0041] a1) reacting 1,3-bis(4-aminophenylcyclo)adamantane, a monomer, and m-cresol, then dropwise adding isoquinoline, heating, and reacting to obtain a polyimide solution;

[0042] a2) introducing an inert gas, adding aminopropyl isobutyl POSS to the polyimide solution, and heating the solution to react to obtain a modified polyimide.

[0043] The modified polyimide preparation method of the present invention comprises reacting 1,3-bis(4-aminophenylcyclo)adamantane, monomer, and m-cresol under an inert gas atmosphere; cooling the mixture to 0-5°C and stirring for 4 hours. The inert gas of the present invention is preferably nitrogen.

[0044] In a preferred embodiment, the monomer is selected from one or more of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA), pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 4,4'-diphenyl ether dianhydride (ODPA), p-phenylene-trimellitic dianhydride (TAHQ), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and ethylene glycol trimellitic anhydride (TMEG); most preferably, the monomer is bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) and pyromellitic dianhydride (PMDA).

[0045] In one embodiment, the molar ratio of the bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) to the pyromellitic dianhydride (PMDA) is (1-5):1, specifically 1:1, 2:1, 3:1, 4:1, or 5:1, or any value therebetween. Most preferably, the molar ratio of the bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) to the pyromellitic dianhydride (PMDA) is 3:1.

[0046] The temperature was slowly raised to room temperature, isoquinoline (1 ml) was added dropwise to the reaction system, the temperature was raised to 80° C., the reaction was kept at this temperature for 4 to 6 hours, and the temperature was lowered to room temperature to obtain a polyimide solution.

[0047] Inert gas is introduced, aminopropyl isobutyl POSS is slowly added to the polyimide solution of step (1), the temperature is raised to 300° C., and stirred for 2 hours to obtain modified polyimide. The inert gas described in the present invention is preferably nitrogen.

[0048] In a preferred embodiment, the porosity of the substrate layer is 15-50%, and may be 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%.

[0049] In a preferred embodiment, the weight of the substrate layer is 20 to 40 g / m 2 , for example, 21%, 24%, 28%, 33%, 38%, 39%, etc.

[0050] In a preferred embodiment, the molar ratio of the polyimide to the aminopropyl isobutyl POSS in the modified polyimide is (100-1):1.

[0051] In a preferred embodiment, the molar ratio of the polyimide to the aminopropyl isobutyl POSS in the modified polyimide is (85-50):1.

[0052] In a preferred embodiment, the molar ratio of the polyimide to the aminopropyl isobutyl POSS in the modified polyimide is 80:1.

[0053] The nanofiber composite nonwoven fabric for preparing a cigarette filter provided by the present invention comprises a first nanofiber layer and a second nanofiber layer.

[0054] According to the present invention, the first nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the second nanofiber layer is obtained by electrospinning polyacrylonitrile fibers;

[0055] In the present invention, the diameter of the polyacrylonitrile fiber is 150-200 nm; it can be 120 nm, 140 nm, 180 nm, or 200 nm.

[0056] The thickness of the first nanofiber layer is 1 to 5 μm; it can be 0.11 μm, 0.5 μm, 0.8 μm, 1.5 μm, 2.5 μm, 3.5 μm, 4.5 μm, 4.9 μm, etc.

[0057] The thickness of the second nanofiber layer is 1 to 5 μm, and can be 0.11 μm, 0.5 μm, 0.8 μm, 1.5 μm, 2.5 μm, 3.5 μm, 4.5 μm, 4.9 μm, etc.

[0058] The porosity of the first nanofiber layer is 75% to 85%; it can be 76%, 78%, 80%, 82%, 84%, etc.

[0059] The porosity of the second nanofiber layer is 75% to 85%; it can be 76%, 78%, 80%, 82%, 84%, etc.

[0060] The first and second nanofiber layers of the present invention are porous structures with an average pore size of 0.2-0.5 μm, for example, 0.25 μm, 0.28 μm, 0.30 μm, 0.32 μm, 0.35 μm, 0.40 μm, 0.44 μm, 0.48 μm, etc.

[0061] The first and second nanofiber layers obtained by the electrospinning method of the present invention have strong adsorption selectivity. The nanofiber layer and the adsorption layer have a synergistic effect to block particles with larger particle sizes and improve the adsorption of toxic small molecule gases by the adsorption material in the adsorption layer.

[0062] The nanofiber composite nonwoven fabric for preparing a cigarette filter provided by the present invention comprises an adsorption layer.

[0063] The thickness of the adsorption layer of the present invention is 15-25 μm, preferably 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, or 25 μm.

[0064] Specifically, the material of the adsorption layer is selected from one or more of activated carbon, carbon nanotubes, silica gel, zeolite or modified carbon nanotubes; the adsorption material is modified carbon nanotubes; the modified carbon nanotubes are polyphthalic anhydride-β-cyclodextrin modified carbon nanotubes;

[0065] In a preferred embodiment, the weight ratio of the polyphthalic anhydride-β-cyclodextrin to the carbon nanotubes in the modified carbon nanotubes is 1:(5-15); it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15; preferably, the weight ratio of the polyphthalic anhydride-β-cyclodextrin to the carbon nanotubes in the modified carbon nanotubes is 1:(8-12); more preferably, the weight ratio of the polyphthalic anhydride-β-cyclodextrin to the carbon nanotubes in the modified carbon nanotubes is 1:11.

[0066] The particle size of the adsorption material of the present invention is 1 to 50 μm; preferably 2 μm, 4 μm, 8 μm, 15 μm, 20 μm, 30 μm, 35 μm, 40 μm, 45 μm, 48 μm; or any point value between any two of the above.

[0067] The thickness of the adsorption layer of the present invention is 15-25 μm, preferably 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, or 25 μm.

[0068] According to the present invention, the method for preparing the modified carbon nanotubes comprises:

[0069] S1) mixing carbon nanotubes and nitric acid, ultrasonically dispersing, and reacting to obtain carboxylated carbon nanotubes;

[0070] S2) ultrasonically dispersing the carboxylated carbon nanotubes in a solvent, stirring for reaction, then adding polyphthalic anhydride-β-cyclodextrin and a solvent, stirring for reaction, filtering, and drying to obtain the product.

[0071] The preparation method of the modified carbon nanotubes of the present invention firstly mixes carbon nanotubes and dilute nitric acid, ultrasonically disperses them, and reacts them to obtain carboxylated carbon nanotubes; preferably, the carbon nanotubes are added to dilute nitric acid, ultrasonically dispersed for 30 minutes, and stirred at 80-100° C. for 20-48 hours; after the reaction is completed, the mixture is cooled to room temperature, poured into deionized water, filtered, washed with deionized water until neutral, and vacuum dried to obtain carboxylated carbon nanotubes.

[0072] The carboxylated carbon nanotubes are ultrasonically dispersed in a solvent (DMF) and stirred for reaction. The ultrasonic dispersion time is 30 to 50 minutes, more preferably 30 to 45 minutes. The stirring reaction is preferably carried out at 50 to 80°C for 20 to 24 hours to remove unreacted thionyl chloride, and more preferably at 55 to 75°C for 20 to 23 hours.

[0073] Then, polyphthalic anhydride-β-cyclodextrin and a solvent are added and stirred for reaction. The solvent is DMF. The stirring reaction is preferably carried out at 40-90° C. for 10 hours.

[0074] After the reaction is completed, the mixture is allowed to stand; filtered, washed with deionized water, and vacuum dried at 70° C. to obtain polyphthalic anhydride-β-cyclodextrin modified carbon nanotubes.

[0075] In a preferred embodiment, the mass volume ratio of the carbon nanotubes to the dilute nitric acid is 1 g: (40-80) ml; preferably, the mass volume ratio of the carbon nanotubes to the dilute nitric acid is 1 g: 60 ml.

[0076] In a preferred embodiment, the mass volume ratio of the carboxylated carbon nanotubes to the dichloride is 1g:(40-100)ml; the mass volume ratio of the carboxylated carbon nanotubes to the DMF is 1g:(20-50)ml; the mass volume ratio of the carboxylated carbon nanotubes to triethylamine is 1g:(1-5)ml; preferably, the mass volume ratio of the carboxylated carbon nanotubes to the dichloride is 1g:(50-80)ml; the mass volume ratio of the carboxylated carbon nanotubes to the DMF is 1g:(30-50)ml; the mass volume ratio of the carboxylated carbon nanotubes to triethylamine is 1g:(1-3)ml; more preferably, the mass volume ratio of the carboxylated carbon nanotubes to the dichloride is 1g:60ml; the mass volume ratio of the carboxylated carbon nanotubes to the DMF is 1g:40ml; the mass volume ratio of the carboxylated carbon nanotubes to triethylamine is 1g:2.2ml.

[0077] According to the present invention, the preparation method of the polyphthalic anhydride-β-cyclodextrin is as follows:

[0078] Add polyphthalic anhydride and β-cyclodextrin to DMF, heat to 80°C, keep warm for 10 hours, cool to room temperature, add dichloromethane and stir for 4 hours, filter, rinse with acetone, and dry under reduced pressure at 60°C for 24 hours to obtain polyphthalic anhydride-β-cyclodextrin.

[0079] In one embodiment of the present invention, the molar volume ratio of polyphthalic anhydride, β-cyclodextrin, DMF and dichloromethane is: 0.05 mol: 0.5 mol: 300 mL, 300 mL.

[0080] In a preferred embodiment, the nanofiber composite nonwoven fabric for preparing cigarette filters is used to absorb and filter particles and toxic gases in smoke.

[0081] In a preferred embodiment, the particles are tar particles;

[0082] The toxic gas is one or more of carbon monoxide, sulfur dioxide, and nitrosamines.

[0083] The present invention provides a method for preparing a nanofiber composite nonwoven fabric, comprising the following steps:

[0084] A) laying a substrate layer flat, and depositing polyacrylonitrile fibers on the substrate layer by electrospinning to obtain a second nanofiber layer;

[0085] B) coating the adsorption layer material on the surface of the second nanofiber layer to obtain an adsorption layer;

[0086] C) depositing polyacrylonitrile fibers on the adsorption layer by electrospinning to obtain a first nanofiber layer.

[0087] The preparation method of the nanofiber composite nonwoven fabric provided by the present invention comprises the following steps: firstly laying the substrate layer flat.

[0088] The preferred specific ones are:

[0089] The modified polyimide non-woven fabric is used as a substrate layer, the substrate layer is laid flat, and polyacrylonitrile fibers are deposited on the substrate layer by electrospinning to obtain a second nanofiber layer.

[0090] An adsorption layer composed of modified carbon nanotubes is evenly coated on the surface of the second nanofiber layer.

[0091] An electrospinning device is used to deposit polyacrylonitrile fibers on the adsorption layer through electrospinning to obtain a first nanofiber layer. The layers are bonded together by polymer adhesion to obtain a nanofiber composite nonwoven fabric for making cigarette filters.

[0092] The preparation methods of the modified carbon nanotubes and modified polyimide have been clearly described above and will not be repeated here.

[0093] The present invention provides a cigarette filter comprising the nanofiber composite non-woven fabric described in any one of the above technical solutions.

[0094] The present invention provides a cigarette, comprising the cigarette filter described in the above technical solution.

[0095] The present invention has the following beneficial effects:

[0096] (1) Polyphthalic anhydride-β-cyclodextrin is rich in a large number of hydrophilic hydroxyl, amino, and carboxyl groups. After it is cross-linked with carboxyl carbon nanotubes through chemical bonds to obtain modified carbon nanotubes, it not only gives the modified carbon nanotubes a large number of hydrophilic hydroxyl, amino, and carboxyl groups, but also interacts with the nanofiber layer through hydrogen bonds, greatly improving the dispersibility and compatibility of the carbon nanotubes. It can also adsorb small molecular gases such as carbon monoxide, sulfur dioxide, nitrogen dioxide, etc. At the same time, the modified multi-walled carbon nanotubes have a rich porous structure and a large specific surface area, which further enhances the adsorption and separation performance of particles and toxic gases in smoke.

[0097] (2) Polyimide has abundant heteroatoms (such as N, O) and high porosity. This application adopts different monomers and synthesis strategies to construct a novel porous polyimide with high gas adsorption capacity; aminopropyl isobutyl POSS modified polyimide forms an interpenetrating network structure, reduces the interfacial energy, and promotes the system to form a stable microphase structure, so that the material has excellent adsorption performance, mechanical strength and heat resistance. The modified polyimide of the present invention is a porous polyimide with a high specific surface area, rich alicyclic structure or a large number of polar groups, and has a strong adsorption capacity for lipophilic molecular weight compound vapors, smoke such as benzopyrene, anthraquinone, nitrosamine, etc.

[0098] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0099] The numerical ranges and parameters used in this disclosure are presented as precisely as possible to represent the relevant numerical values ​​of the specific embodiments. However, any numerical value inherently and inevitably contains standard deviations resulting from individual testing methods. Therefore, unless otherwise expressly stated, it should be understood that all numerical ranges or specific data used in this disclosure are subject to reasonable deviation within a certain range, for example, within 1% or 0.5%.

[0100] Some cases are described in the embodiments and comparative examples of the present invention, wherein the embodiments illustrate certain implementations of the present invention. However, this does not mean that the effects of the present invention can only be achieved in these cases.

[0101] Unless otherwise indicated, the following terms and phrases used herein are intended to have the following meanings. A particular phrase or term should not be construed as ambiguous or unclear unless specifically defined, but rather should be understood in accordance with its ordinary meaning. When a trade name appears herein, it is intended to refer to the corresponding commercial product or its active ingredient.

[0102] The intermediate compounds of the present invention can be prepared by a variety of synthetic methods well known to those skilled in the art, including the specific embodiments listed below, embodiments formed by combining them with other chemical synthesis methods, and equivalent replacement methods well known to those skilled in the art. Preferred embodiments include but are not limited to the examples of the present invention.

[0103] The chemical reactions of the present invention are carried out in suitable solvents that are compatible with the chemical transformations of the present invention and the reagents and materials required. To obtain the compounds of the present invention, it may sometimes be necessary for those skilled in the art to modify or select synthetic steps or reaction schemes based on existing embodiments.

[0104] To further illustrate the present invention, a nanofiber composite nonwoven fabric for preparing a cigarette filter provided by the present invention, a preparation method thereof, and applications thereof are described in detail below with reference to examples.

[0105] All solvents used in the present invention are commercially available and can be used without further purification. The reaction is generally carried out in anhydrous solvent under inert nitrogen.

[0106] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention.

[0107] The reagents and raw materials used in the present invention are commercially available.

[0108] In each embodiment of the present invention, the nanofiber layer is deposited by electrospinning. The process parameters of the electrospinning for depositing the nanofiber layer are: voltage of 20kV, needle diameter of 0.5mm, and feed rate of 20μL / min. In the electrospinning process, the polymer solution is ejected through the needle, and nanofibers are formed under the action of electrostatic force and deposited on the surface of the substrate layer. Changing the process parameters of electrospinning can change the thickness, average pore size, porosity and diameter of the polymer nanofibers formed in the polymer nanofiber layer.

[0109] Example 1

[0110] The nanofiber composite nonwoven fabric for preparing cigarette filters is prepared by the following steps:

[0111] (1) Take the weight of 25g / m 2A modified polyimide nonwoven fabric with a porosity of 40% is used as a substrate layer (the substrate layer has a thickness of 0.55 mm), the substrate layer is laid flat, and polyacrylonitrile fibers are deposited on the substrate layer by electrospinning using an electrospinning device to obtain a second nanofiber layer with a thickness of 5 μm;

[0112] (2) uniformly coating the surface of the second nanofiber layer with an adsorption layer composed of modified carbon nanotubes with a thickness of 20 μm and a particle size of 40 μm;

[0113] (3) using an electrospinning device to deposit polyacrylonitrile fibers on the adsorption layer by electrospinning to obtain a first nanofiber layer with a thickness of 5 μm;

[0114] The layers obtained in steps (1) to (3) are bonded together by polymer adhesion to obtain a nanofiber composite non-woven fabric for preparing a cigarette filter.

[0115] The preparation method of the modified carbon nanotubes is as follows:

[0116] (1) Carboxylation of carbon nanotubes:

[0117] Carbon nanotubes (20 g) were added to dilute nitric acid (1200 ml), ultrasonically dispersed for 30 min, and stirred at 80°C for 36 h. After the reaction, the mixture was cooled to room temperature, poured into deionized water, filtered, washed with deionized water until neutral, and vacuum dried to obtain carboxylated carbon nanotubes.

[0118] (2) Cyclodextrin modified carbon nanotubes:

[0119] Carboxylated carbon nanotubes (20 g) were added to thionyl chloride (1200 ml) and DMF (800 ml), and ultrasonically dispersed for 30-50 min. The mixture was stirred and reacted at 50-80° C. for 20-24 h. Unreacted thionyl chloride was removed, and then polyphthalic anhydride-β-cyclodextrin (1.8 g), triethylamine (60 ml) and DMF (800 ml) were added. The mixture was stirred and reacted at 40-90° C. for 10 h. After the reaction was completed, the mixture was allowed to stand, filtered, washed with deionized water, and vacuum dried at 70° C. to obtain polyphthalic anhydride-β-cyclodextrin modified carbon nanotubes.

[0120] The preparation method of the modified polyimide is as follows:

[0121] (1) Under nitrogen, 1,3-bis(4-aminophenyl ring)adamantane (purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.) (0.1 mol), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA, 0.15 mol), pyromellitic dianhydride (PMDA, 0.05 mol), and m-cresol (200 ml) were added to a reaction flask, cooled to 0-5 °C, stirred for 4 h, and slowly heated to room temperature. Isoquinoline (1 ml) was added dropwise to the reaction system, heated to 80 °C, kept warm for 5 h, and cooled to room temperature to obtain a polyimide solution.

[0122] (2) Nitrogen was introduced and aminopropyl isobutyl POSS (1.25 mmol) was slowly added to the polyimide solution of step (1), the temperature was raised to 300° C., and the mixture was stirred for 2 h to obtain a modified polyimide.

[0123] In Example 1, a nanofiber composite nonwoven fabric 1 was obtained.

[0124] Example 2

[0125] The only difference from Example 1 is that the weight in step (1) is 40 g / m 2 , a modified polyimide non-woven fabric with a porosity of 15% is used as the backing layer.

[0126] Example 2 obtains nanofiber composite nonwoven fabric 2.

[0127] Example 3

[0128] The only difference from Example 1 is that the weight of the material in step (1) is 20 g / m 2 , a modified polyimide non-woven fabric with a porosity of 50% is used as the backing layer.

[0129] Example 3 obtained nanofiber composite nonwoven fabric 3.

[0130] Example 4

[0131] The only difference from Example 1 is that in step (1), the molar ratio of the monomers of the modified polyimide, the bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA) and the pyromellitic dianhydride (PMDA) is 1:1.

[0132] Example 4 obtained nanofiber composite non-woven fabric 4.

[0133] Comparative Example 1

[0134] The only difference from Example 1 is that in step (1), a polyimide solution is used to replace the modified polyimide.

[0135] Comparative Example 1 obtained nanofiber composite nonwoven fabric 5.

[0136] Comparative Example 2

[0137] The only difference from Example 1 is that the monomer for modifying the polyimide in step (1) is only bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA).

[0138] Comparative Example 2 obtained nanofiber composite non-woven fabric 6.

[0139] Comparative Example 3

[0140] The only difference from Example 1 is that the monomer used to modify the polyimide in step (1) is only pyromellitic dianhydride (PMDA).

[0141] Comparative Example 3 obtained nanofiber composite nonwoven fabric 7.

[0142] Comparative Example 4

[0143] The only difference from Example 1 is that in step (2), β-cyclodextrin-modified carbon nanotubes are used to replace the modified carbon nanotubes (polyphthalic anhydride-β-cyclodextrin-modified carbon nanotubes).

[0144] Comparative Example 4 obtained nanofiber composite nonwoven fabric 8.

[0145] Comparative Example 5

[0146] The only difference from Example 1 is that in step (2), carbon nanotubes are used to replace modified carbon nanotubes.

[0147] Comparative Example 5 obtained nanofiber composite nonwoven fabric 9.

[0148] Comparative Example 6

[0149] The only difference from Example 1 is that polyimide is used in place of modified polyimide in step (1), and carbon nanotubes are used in place of modified carbon nanotubes in step (2).

[0150] Comparative Example 6 obtained a nanofiber composite nonwoven fabric 10.

[0151] 200 layers of the nanofiber composite non-woven fabrics 1-10 obtained in the above embodiments were taken respectively, overlapped in the same direction, and punched into a composite filter segment with a length of 10 mm and a diameter of 7.7 mm as the filter tip 1-10. Another layer of the nanofiber composite non-woven fabric 1 obtained in the above embodiment was taken and rolled into a composite filter segment with a length of 10 mm and a diameter of 7.7 mm as the filter tip 11. The filter tip 1-11 was fixed to one end of the cigarette without the filter tip, wherein one end of the first nanofiber layer of the filter tip 1-10 contacted the tobacco part, and the other end was connected to the smoking machine. Either end of the filter tip 11 was connected to the cigarette, and the other end was connected to the smoking machine. A cigarette with a cellulose acetate fiber filter tip with a length of 10 mm and a diameter of 7.7 mm was used as the control group, and the cigarette without the filter tip was used as the blank group. The filtration ability of the cigarette smoke was tested by the following test method, and the results are listed in Table 1.

[0152] (1) The filtration capacity of filters 1-11 and the control group for particulate matter and tar in cigarettes was tested using the method described in the national standard GB / T 19609-2004 "Determination of total particulate matter and tar in cigarettes by conventional analytical smoking machines". The test results of the blank group were used as reference values ​​for the content of particulate matter and tar in cigarettes.

[0153] (2) The carbon monoxide filtering capacity of filters 1-11 and the control group was tested according to the method described in the national standard GB / T 23356-2009 “Determination of carbon monoxide in the gas phase of cigarette smoke - Non-scattering infrared method”. The test results of the blank group were used as the reference value of the carbon monoxide content in the cigarette.

[0154] (3) The nicotine filtering capacity of filters 1-11 and the control group was tested according to the method described in the national standard GB / T 23355-2009 "Gas chromatography method for the determination of nicotine in the total particulate matter of cigarettes". The test results of the blank group were used as the reference value for the nicotine content in the cigarettes.

[0155] Table 1 Comparison of the filtering ability of filters 1-11 for various components in cigarettes

[0156]

[0157] It can be seen from the data in Table 1 that compared with traditional cigarette filters with cellulose acetate fiber as the main component, the cigarette filter prepared with the nanofiber composite non-woven fabric provided by the present invention as the main component has a stronger selective adsorption capacity and filtration effect for particulate matter, tar and carbon monoxide components in tobacco.

[0158] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A nanofiber composite nonwoven fabric for preparing a cigarette filter, characterized in that: It comprises a first nanofiber layer, an adsorption layer, a second nanofiber layer and a substrate layer stacked in sequence; The first nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; the second nanofiber layer is obtained by electrospinning polyacrylonitrile fibers; The material of the adsorption layer is selected from modified carbon nanotubes; the modified carbon nanotubes are polyphthalic anhydride-β-cyclodextrin modified carbon nanotubes; the weight ratio of the polyphthalic anhydride-β-cyclodextrin to the carbon nanotubes is 1:(5-15); The substrate layer is modified polyimide; the modified polyimide is aminopropyl isobutyl POSS modified polyimide; The molar ratio of the polyimide to the aminopropyl isobutyl POSS in the modified polyimide is (100-1):1; The monomers used in preparing the modified polyimide are bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and pyromellitic dianhydride.

2. The composite nonwoven fabric according to claim 1, characterized in that The particle size of the material of the adsorption layer is 1-50 μm.

3. The composite nonwoven fabric according to claim 1, characterized in that The preparation method of the modified carbon nanotubes comprises: S1) mixing carbon nanotubes and dilute nitric acid, dispersing by ultrasonication, and reacting to obtain carboxylated carbon nanotubes; S2) ultrasonically dispersing the carboxylated carbon nanotubes in a solvent, stirring for reaction, and then adding polyphthalic anhydride-β-cyclodextrin and a solvent, stirring for reaction, filtering, and drying to obtain the product.

4. The composite nonwoven fabric according to claim 1, characterized in that The preparation method of the modified polyimide comprises: a1) reacting 1,3-bis(4-aminophenylcyclo)adamantane, a monomer, and m-cresol, then dropwise adding isoquinoline, heating, and reacting to obtain a polyimide solution; a2) introducing an inert gas, adding aminopropyl isobutyl POSS to the polyimide solution, and heating the solution to react to obtain a modified polyimide.

5. The composite nonwoven fabric according to claim 1, wherein The diameter of the polyacrylonitrile fiber is 150-200 nm; the thickness of the first nanofiber layer is 1-5 μm; the thickness of the second nanofiber layer is 1-5 μm; the porosity of the first nanofiber layer is 75%-85%; the porosity of the second nanofiber layer is 75%-85%.

6. The composite nonwoven fabric according to claim 1, characterized in that The porosity of the substrate layer is 15% to 50%; the weight of the substrate layer is 20 to 40 g / m 2 .

7. A method for preparing the nanofiber composite nonwoven fabric according to claim 1, characterized in that: The steps include: A) Laying a substrate layer flat, and depositing polyacrylonitrile fibers on the substrate layer by electrospinning to obtain a second nanofiber layer; B) coating the adsorption layer material on the surface of the second nanofiber layer to obtain an adsorption layer; C) Polyacrylonitrile fibers are deposited on the adsorption layer by electrospinning to obtain the first nanofiber layer.

8. A cigarette filter, characterized in that: The nanofiber composite nonwoven fabric comprises the nanofiber composite nonwoven fabric according to any one of claims 1 to 6.

9. A cigarette, characterized in that The cigarette filter according to claim 8.

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