Preparation method and application of plant fiber filter material

Abstract

The application discloses a preparation method and application of a plant fiber filter material, and belongs to the medical protection field and also belongs to the chemical and papermaking fields.The preparation method comprises the following steps: preparation of microfibrillated cellulose fiber, preparation of microfibrillated cellulose fiber with in-situ growth of ZIF-67, and preparation of the plant fiber filter material.The natural and renewable cellulose fiber is used as a barrier filter mask intermediate layer, has biodegradability, and solves the solid waste and micro-plastic pollution hidden danger caused by the disposal and accumulation of disposable masks.

Description

Technical Field

[0001] This invention relates to the field of medical protection, as well as the fields of chemistry and papermaking, specifically to a method for preparing and applying a plant fiber filter material. Background Technology

[0002] In recent years, especially after the COVID-19 pandemic, face masks have become an indispensable part of daily life and public health infrastructure. As the first line of defense against airborne pathogens, fine particulate matter (such as PM2.5), and harmful aerosols, face masks play a crucial role in respiratory protection and epidemic prevention. Face masks are typically worn over the mouth and nose, filtering inhaled air to block viruses, bacteria, dust, and volatile substances. Air-filtering masks are usually made of materials such as non-woven fabrics and meltblown layers, and are widely used due to their good breathability, ease of use, and effective filtration performance. With increasing global awareness of airborne health hazards, the development of multifunctional, sustainable, and high-performance mask materials has attracted widespread attention from academia and industry.

[0003] The types of masks vary depending on their protection level and the composition of their core materials. Medical protective masks, such as N95 and KN95, are mainly composed of multiple layers of meltblown fabric, which can block and filter more than 95% of toxic and harmful substances. Cloth masks, on the other hand, are mainly composed of cotton or gauze, which have almost no filtering effect and only serve the functions of dust protection and warmth. Most ordinary masks are mainly composed of three layers: an outer waterproof non-woven fabric, a middle meltblown fabric that plays a core filtering role, and an inner non-woven fabric with hydrophilic and moisture-absorbing properties, which can be used for daily medical or public places.

[0004] The most commonly used material in masks that plays a core role in filtration is meltblown nonwoven fabric. It is a nonwoven fabric with an ultra-fine fiber structure made of polypropylene (PP) through processes such as melt extrusion. The fiber diameter is usually between 1 and 5 μm. It has the characteristics of high specific surface area, high porosity, good filtration performance and low resistance. However, PP material is generally non-degradable after one use and is not environmentally friendly.

[0005] Secondly, nanofiber polymer films prepared using electrospinning methods, primarily made of materials such as polyurethane, polyamide (nylon), polyacrylonitrile, and polylactic acid, can be fabricated into nanoscale pores through electrospinning to intercept ultrafine particles. These pores are adjustable and offer high filtration efficiency, but are costly, limiting large-scale application, and are non-biodegradable. Barrier filter materials made from polyester or polyester composite fibers are also used as the middle layer of masks. They possess high strength, adjustable dimensions, and good heat resistance, but are also petroleum-based products and environmentally unfriendly.

[0006] Of course, there are also studies and applications using biomass materials as barrier filters, such as using natural cotton or gauze as a barrier layer, but the barrier effect is poor, only serving the purpose of covering the face, decoration, or warmth. Chitosan and nanocellulose composite membranes have also been studied and used, and they are environmentally friendly. However, due to the high cost of the fiber nano-sizing process, the practical application and promotion are relatively slow.

[0007] Disadvantages: Although the middle layer of current masks mostly uses high-efficiency filter materials such as polypropylene (PP) meltblown nonwoven fabric, polypropylene is a petroleum-based polymer and is non-degradable. Furthermore, while traditional meltblown fabric ensures high filtration efficiency, it exhibits a certain degree of pressure drop (i.e., air resistance), which can easily lead to breathing discomfort during prolonged wear, limiting its comfort application in specific groups (such as children and the elderly). Summary of the Invention

[0008] To address the problems of existing technologies, this invention provides a method for preparing and applying plant fiber filter materials. Natural, renewable cellulose fibers are used as the middle layer of a barrier filter mask, exhibiting biodegradability. Furthermore, the cellulose fibers, after microfibrillation treatment, are formed using conventional papermaking processes. The interwoven fibers create excellent breathable porosity, facilitating breathing during wear. By loading ZIF-67 material, pollutants can be adsorbed and blocked, thus fulfilling protective requirements.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing a plant fiber filter material includes the following steps: (1) Preparation of microfibrillated cellulose fibers The pulp board is immersed in water to fully swell the fibers. Then, water is added to dilute the pulp, which is then dispersed using a fiber dissociator. The dispersed pulp is then filtered and concentrated using a Buchner funnel to a pulp concentration of 5%-15%. At a pulp temperature of 25±5 ℃, the pulp is placed inside the wall of the PFI pulping chamber for beating and uniform distribution to obtain microfibrillated cellulose fibers.

[0011] Furthermore, the pulp board is at least one of coniferous wood, broadleaf wood, and bamboo.

[0012] Furthermore, the pulp board is torn into pieces and then soaked in water for 8-12 hours, with the size of the pieces being less than 2×2 cm.

[0013] Furthermore, after diluting the slurry with water, the concentration of the slurry is 0.1%-0.5%.

[0014] Furthermore, the beating degree of the microfibrillated cellulose fiber is 20-80 °SR.

[0015] (2) Preparation of microfibrillated cellulose fibers of ZIF-67 grown in situ Microfibrillated cellulose fibers were added to Co(NO3)2. In a 6H2O methanol solution, stir continuously for 8-12 hours, then add a certain volume of 2-methylimidazolium methanol solution, stir for 10-30 minutes, and then sonicate for 0.5-4 hours using an ultrasonic instrument. Finally, separate the ZIF-67 microfibrillated cellulose fibers in situ through a filtration device.

[0016] Furthermore, the microfibrillated cellulose fibers and Co(NO3)2 The ratio of 6 H2O methanol solution is 2-10 g (on an oven-dry basis) to 100 ml.

[0017] Furthermore, the Co(NO3)2 The concentration of 6H2O methanol solution is 1.0-1.5 wt.%, the concentration of 2-methylimidazolium methanol solution is 2.0-2.5 wt.%, and the concentration of Co(NO3)2 is... The volume ratio of 6H2O methanol solution to 2-methylimidazolium methanol solution is 1:1 to 1:2.

[0018] (3) Plant fiber filter material The microfibrillated cellulose fibers in which ZIF-67 is grown in situ are formed by papermaking process to obtain composite paper with ZIF-67 grown in situ (ZIF-67 loaded cellulose composite paper).

[0019] Furthermore, the ZIF-67 composite paper is manufactured according to a ratio of 20-200 g / m². 2 Quantitative.

[0020] Furthermore, the microfibrillated cellulose fibers of ZIF-67 grown in situ were weighed, dispersed in water to form a fiber suspension, and then quickly passed through a vacuum filtration device to prepare the shape. Then, the suspension was placed on a pressurizing device for pressurization, and finally, the composite paper of ZIF-67 grown in situ (ZIF-67 loaded cellulose composite paper) was prepared.

[0021] Furthermore, the concentration of the fiber suspension is less than or equal to 1%.

[0022] Furthermore, the pressure of the filtration device is 0.1-0.5 MPa, and the conditions of the pressurizing equipment are: pressure 5-20 MPa, temperature 100±5℃, and time 10-20 minutes.

[0023] The plant fiber filter material prepared by the above method.

[0024] The above-mentioned plant fiber filter material is used as a protective mask. ZIF-67 composite paper is used as the middle functional layer, and non-woven fabric is set on both sides of the middle layer. The non-woven fabric is used as the inner and outer support layers. The non-woven fabric, ZIF-67 composite paper and non-woven fabric are prepared into a sandwich structure by hot pressing composite technology.

[0025] Furthermore, the hot pressing conditions are: temperature 150-170℃, pressure 0.2-0.5MPa.

[0026] The specific processing and assembly steps are as follows: First, the ZIF-67 composite paper is cut to a size similar to commercially available disposable masks (approximately 17.5 cm × 9.5 cm) to fit wearing requirements. Second, the cut ZIF-67 composite paper is placed between two layers of soft, breathable non-woven fabric, and the three layers are firmly bonded using hot-pressing composite technology (150-170℃, 0.2 - 0.5MPa), forming a sandwich-style protective structure with ZIF-67 cellulose-loaded composite paper as the middle functional layer and non-woven fabric as the inner and outer support layers. Finally, by combining auxiliary structures such as ear loops and nose bridge strips, a practical protective mask is produced.

[0027] First, the controllable preparation of microfibrillated cellulose fibers is one of the key points. By controlling the beating degree (20–80°SR) through the PFI beating process, a gradual microfibrillation of the fiber structure from coarse to fine is achieved, significantly increasing the exposure of hydroxyl groups and the specific surface area of ​​the fiber surface, which is beneficial for the subsequent in-situ growth of ZIF-67. The in-situ growth composite method of ZIF-67 is another key point. Microfibrillated cellulose fibers are dispersed in a methanol solution of the metal precursor Co(NO3)2 and the organic ligand 2-methylimidazole, and ZIF-67 is uniformly grown in situ on the fiber surface by stirring and ultrasound. The third key point is that the wet forming and hot pressing processes of ZIF-67 composite paper are conducive to constructing a dense and mechanically strong composite structure. The fourth key point is the integrated design of ZIF-67 composite paper in masks, where ZIF-67 composite paper is used as an intermediate layer and combined with a non-woven fabric support layer to prepare a practical protective mask.

[0028] Research on using natural commercial pulp board through microfibrillation as a barrier filter material for face masks is limited and its application is not yet widespread. Furthermore, natural fibers are green and renewable biomass raw materials, inexpensive, and can partially replace petroleum-based products. The method of in-situ growth of ZIF-67 on microfibrillated cellulose fibers allows for the preparation of ZIF-67 composite paper using traditional papermaking processes, enabling large-scale commercial use. Therefore, this application seeks method protection.

[0029] The beneficial effects of this invention are: Compared with existing technologies (i.e., using meltblown fabric as the middle layer of masks), ZIF-67 composite paper, prepared by microfibrillating natural commercial pulp boards and growing ZIF-67 in situ, has the following characteristics as a barrier filter material for masks: 1) As a natural plant material, fiber has the advantages of being renewable, abundant in raw materials, and green and biodegradable; 2) Meltblown fabric can only be used for filtering solid particulate matter in the air, while ZIF-67 composite paper can not only block solid particulate matter, but also adsorb toxic and harmful gaseous pollutants such as formaldehyde. 3) ZIF-67 composite paper can control the degree of fiber microfibrillation by adjusting the beating degree, thereby controlling the pore structure of the fiber network and possessing customization capabilities. Attached Figure Description

[0030] Figure 1 These are scanning electron microscope images of cellulose fibers at different beating degrees (20-80 °SR). As beating increases, the degree of fiber fibrillation increases, resulting in many fine fibers.

[0031] Figure 2 This is a scanning electron microscope (SEM) image of ZIF-67 composite paper prepared from microfibrillated cellulose fibers (freezing degree 80 °SR) grown in situ with ZIF-67. The fiber surface is loaded with many ZIF-67 particles.

[0032] Figure 3 This is a mechanical strength diagram of ZIF-67 composite paper prepared from microfibrillated cellulose fibers (freezing degree 80 °SR) grown in situ. The composite paper has a stress close to 35 MPa, indicating very high strength.

[0033] Figure 4 This is a comparison chart of the filtration efficiency of solid particles for gauze, ordinary nonwoven fabric (PP), meltblown fabric (PP), and ZIF-67 composite paper (using microfibrillated cellulose fibers with a beating degree of 80 °SR).

[0034] Figure 5 This is an actual picture of a face mask made from ZIF-67 composite paper (using microfibrillated cellulose fibers with a beating degree of 80 °SR). The composite paper is perfectly suited to the flexibility requirements of face masks and can be directly adapted to existing mask materials. Detailed Implementation

[0035] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0036] Example 1 A method for preparing a plant fiber filter material includes the following steps: (1) Preparation of microfibrillated cellulose fibers Weigh 30 g of hardwood commercial pulp board (occasionally dry weight), tear it into small pieces smaller than 2 × 2 cm, and soak it in water for 12 hours to allow the fibers to fully swell. Then, dilute the pulp with water to a concentration of 0.5%, disperse it using a fiber dissociator, and concentrate the dispersed pulp solution using a Buchner funnel to a pulp concentration of 10%. Weigh 30 g of the pulp (occasionally dry weight), and at room temperature, place the pulp into the wall of a PFI beating chamber for beating and uniform distribution to obtain microfibrillated cellulose fibers with different freeness (20-80 °SR). Microfibrillated cellulose fibers with a freeness of 20 °SR are designated A1, A2 with a freeness of 40 °SR, A3 with a freeness of 60 °SR, and A4 with a freeness of 80 °SR.

[0037] (2) Preparation of in-situ grown ZIF-67 composite paper: Weigh 2 g (by oven-dry weight) of microfibrillated cellulose fibers (A1, A2, A3, A4) obtained in step (1) with different beating degrees, and add them to 100 ml of Co(NO3)2 The mixture was stirred continuously for 12 hours in a 1.3 wt.% H2O methanol solution at 500 r / min for 12 hours. Then, the same volume of a 2-methylimidazole (2.2 wt.%) methanol solution was added and stirred (at 500 r / min for 10 minutes). The mixture was then sonicated for 1 hour and separated by filtration to obtain in-situ grown ZIF-67 microfibrillated cellulose fibers.

[0038] According to 100g / m 2 Quantitatively, the microfibrillated cellulose fibers of in-situ grown ZIF-67 were weighed, dispersed in water to form a 1% fiber suspension, and then rapidly passed through a vacuum filtration device (0.1 MPa) to prepare the molding. The suspension was then placed on a pressurizing device with a pressure of 5 MPa, a temperature of 100℃, and a time of 10 minutes to finally prepare in-situ grown ZIF-67 composite paper (basis weight 100 g / m²). 2 ).

[0039] The filtration efficiency of medical gauze, ordinary nonwoven fabric (PP), meltblown fabric (PP), and ZIF-67 composite paper for solid particulate matter was tested. The method involved using two gas filter bottles, with a barrier material inserted between the bottles. Particulate contaminants were introduced through one side, while a particle detector was used to monitor the passage of particles through the other side. The particle filtration efficiency of the barrier material was then calculated.

[0040] Example 2 The specific processing and assembly operations for a protective mask are as follows: First, the ZIF-67 composite paper prepared in Example 1 was cut to a size similar to commercially available disposable masks (approximately 17.5 cm × 9.5 cm) to fit wearing requirements. Second, the cut ZIF-67 composite paper was placed between two layers of soft, breathable non-woven fabric (each layer being 2 mm thick). A hot-pressing composite technique (160°C, 0.3 MPa) was used to firmly bond the three layers, forming a sandwich-style protective structure with ZIF-67-loaded cellulose composite paper as the middle functional layer and non-woven fabric (PP) as the inner and outer support layers. Finally, by incorporating auxiliary structures such as ear loops and nose bridge strips, a practical protective mask was produced.

[0041] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing a plant fiber filter material, characterized in that, Includes the following steps: (1) Preparation of microfibrillated cellulose fibers The pulp board is soaked in water to fully swell the fibers. Then, water is added to dilute the pulp, and the pulp is dispersed using a fiber dissociator. The dispersed pulp is filtered and concentrated to a pulp concentration of 5%-15%. The pulp is then beaten at a pulp temperature of 25±5 ℃ to obtain microfibrillated cellulose fibers. (2) Preparation of microfibrillated cellulose fibers of ZIF-67 grown in situ Microfibrillated cellulose fibers were added to Co(NO3)2. In a methanol solution of 6H2O, stir for 8-12 hours, then add a certain volume of 2-methylimidazolium methanol solution, stir for 10-30 minutes, and then sonicate for 0.5-4 hours using an ultrasonic instrument. After filtration and separation, microfibrillated cellulose fibers of ZIF-67 grown in situ are obtained. (3) Plant fiber filter material In situ grown ZIF-67 microfibrillated cellulose fibers are formed using a papermaking process to obtain composite paper with in situ grown ZIF-67.

2. The method according to claim 1, characterized in that, In step (1), the pulp board is at least one of coniferous wood, broadleaf wood, and bamboo; After tearing the plywood into pieces, soak them in water for 8-12 hours. The size of the pieces should be less than 2×2 cm. After diluting the slurry with water, the concentration of the slurry is 0.1%-0.5%; The beating degree of the microfibrillated cellulose fiber is 20-80 °SR.

3. The method according to claim 1, characterized in that, In step (2), the microfibrillated cellulose fibers and Co(NO3)2 The ratio of 6H2O methanol solution is 2-10 g (on an oven-dry basis) : 100 mL; the Co(NO3)2 The concentration of 6 H2O methanol solution is 1.0-1.5 wt.%, the concentration of 2-methylimidazolium methanol solution is 2.0-2.5 wt.%, and the concentration of Co(NO3)2 is... The volume ratio of 6 H2O methanol solution to 2-methylimidazole methanol solution is 1:1 to 1:

2.

4. The method according to claim 1, characterized in that, In step (3), the microfibrillated cellulose fibers of ZIF-67 grown in situ are weighed, dispersed in water to form a fiber suspension, and then quickly prepared by a vacuum filter device. Finally, the suspension is placed on a pressurizing device for pressurization, and the composite paper of ZIF-67 grown in situ is prepared.

5. The method according to claim 1 or 4, characterized in that, The ZIF-67 composite paper is prepared at a density of 20-200 g / m². 2 Quantitative; The concentration of the fiber suspension is less than or equal to 1%; The pressure of the filtration device is 0.1-0.5 MPa, and the conditions of the pressurizing equipment are: pressure 5-20 MPa, temperature 100±5℃, time 10-20 minutes.

6. The plant fiber filter material prepared by the method according to any one of claims 1-5.

7. The application of the plant fiber filter material according to claim 6, characterized in that, The plant fiber filter material is used as a face mask.

8. The application according to claim 7, characterized in that, The mask uses ZIF-67 composite paper as the middle layer, and non-woven fabric is placed on both sides of the middle functional layer.

9. The application according to claim 8, characterized in that, Non-woven fabric, ZIF-67 composite paper, and non-woven fabric are prepared into a sandwich structure through hot-pressing composite technology.

10. The application according to claim 9, characterized in that, The hot pressing conditions are: temperature 150-170℃, pressure 0.2-0.5MPa.

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