Composite microfiber filtering material as well as preparation method and application thereof

Abstract

The invention belongs to the field of filter materials, and relates to a composite microfiber filter material as well as a preparation method and application thereof. The material comprises a polylactic acid electrostatic spinning fiber layer and a polylactic acid melt-blown fiber layer which are compounded together, the polylactic acid electrostatic spinning fiber layer is prepared from an electret polylactic acid composition through electrostatic spinning, and the polylactic acid melt-blown fiber layer is prepared from the electret polylactic acid composition through melt-blown molding; the electret polylactic acid composition is prepared from the following components in parts by weight: 100 parts of polylactic acid, 0.2 to 4 parts of a composite electret, 0.2 to 2.5 parts of a plasticizer, 0.05 to 0.5 part of a dispersing agent and 0.01 to 0.5 part of an antioxidant. The composite microfiber filtering material comprises the melt-blown layer and the electrostatic spinning superfine fiber layer, the melt-blown layer is used for coarse filtration, the electrostatic spinning superfine fiber layer is used for fine filtration, the problems that the filtering performance of a single melt-blown layer is insufficient and the filtering resistance of a single electrostatic spinning layer is too large can be solved, and the effects of high efficiency and low resistance are achieved.

Description

Technical Field

[0001] This invention belongs to the field of filter materials, specifically relating to a composite microfiber filter material, as well as the preparation method and application of the composite microfiber filter material. Background Technology

[0002] Air filter membranes are materials used to filter and purify air. They capture airborne particles, bacteria, viruses, and other pollutants, and are widely used in various fields of daily life and production. Currently, most air filter membranes are nonwoven fiber membranes. Compared to traditional knitted and woven fiber membranes, nonwoven fiber membranes are three-dimensional mesh materials composed of randomly arranged fiber aggregates. Due to the intricate and disordered structure of the fibers, numerous complex and interwoven three-dimensional spatial channels are formed between the fibers. When dust-laden airflow passes through the membrane, the probability of collision between dust particles and fibers increases, enhancing the retention capacity of dust particles and thus improving the membrane's filtration efficiency. Simultaneously, the disordered fiber stacking creates numerous three-dimensional pore structures, providing pathways for airflow, thus achieving both efficient dust filtration and reduced filtration resistance. Currently, nonwoven fiber air filter membranes mainly include meltblown (electret) fiber membranes, ultrafine glass fiber membranes, spunbond fiber membranes, and electrospun fiber membranes. Air filter membranes exhibit significant differences in filtration performance and membrane functionality due to variations in their manufacturing processes. Polylactic acid (PLA) nanofibers prepared by electrospinning possess high specific surface area and unique interfacial properties, showing great potential for applications in wound dressings, tissue engineering, and food packaging. However, improving the toughness of PLA nanofiber products and achieving efficient, green, and environmentally friendly preparation processes remain challenges. Based on the principle of raw material solidification into fibers, electrospinning can be divided into solution electrospinning and melt electrospinning. Compared to solution electrospinning, melt electrospinning offers advantages such as a safe and environmentally friendly preparation process and the absence of yield loss due to solvent evaporation, making it an important and efficient method for the safe preparation of nanofibers. However, due to the poor dielectric properties and high viscosity of the melt, fiber refinement is extremely difficult, and the rapid cooling of the melt jet leads to poor mechanical properties and low toughness in the finished products. Currently, a common method is to use plasticizers to reduce melt viscosity, thereby reducing fiber diameter and improving the elongation at break of the fiber membrane. Meltblown nonwoven fibers have a large specific surface area, high porosity, short process flow, and high production efficiency, making them widely used in medical and health applications, filtration materials, and battery separators. Electrospun fiber membranes exhibit a nanoscale effect, with the surface of the fiber membrane enriched with electrostatic charges, resulting in high filtration efficiency and wide applications in fine filtration. However, in practical applications, the filtration performance of a single meltblown nonwoven fabric is insufficient, and the strength of a single electrospun fiber membrane is inadequate. Summary of the Invention

[0003] The purpose of this invention is to provide a composite microfiber filter material and its preparation method. The composite microfiber filter material of this invention comprises a meltblown layer and an electrospun ultrafine fiber layer. The meltblown layer is used for coarse filtration, and the electrospun ultrafine fiber layer is used for fine filtration. This overcomes the problems of insufficient filtration performance of a single meltblown layer and excessive resistance in a single electrospun layer, achieving a high-efficiency, low-resistance effect.

[0004] A first aspect of the present invention provides a composite microfiber filter material, the material comprising a polylactic acid electrospun fiber layer and a polylactic acid meltblown fiber layer compositely together, the polylactic acid electrospun fiber layer being obtained by electrospinning an electret polylactic acid composition, and the polylactic acid meltblown fiber layer being obtained by meltblowing an electret polylactic acid composition; the electret polylactic acid composition comprising the following components in parts by weight: 100 parts polylactic acid, 0.2-4 parts composite electret, 0.2-2.5 parts plasticizer, 0.05-0.5 parts dispersant, and 0.01-0.5 parts antioxidant; the composite electret comprising tourmaline powder, hindered amine light stabilizer, hydroxystearate, and dendritic polymer.

[0005] The second aspect of the present invention provides a method for preparing the above-mentioned composite microfiber filter material, comprising the following steps: obtaining a polylactic acid meltblown fiber layer by meltblowing a raw material of electret polylactic acid composition, and obtaining the composite microfiber filter material by electrospinning polylactic acid on the surface of the polylactic acid meltblown fiber layer as a base fabric.

[0006] A third aspect of the present invention provides the application of the above-mentioned composite microfiber filter material, wherein the polylactic acid meltblown fiber layer is used as the surface layer.

[0007] The advantages and technical effects of the composite microfiber filter material of the present invention include:

[0008] (1) This invention employs a novel organic-inorganic composite electret. In preparing the organic-inorganic composite electret, hydroxystearate and dendritic polymer are introduced. Through intensive melting and processing, tourmaline and hindered amine can be fully mixed, achieving a synergistic effect. Simultaneously, the hindered amine, hydroxystearate, and dendritic polymer effectively isolate the tourmaline powder, solving its agglomeration problem and ensuring uniform dispersion of tourmaline in polylactic acid. This reduces the fiber breakage caused by tourmaline agglomeration, improves the uniformity of tourmaline, and also enhances the dispersibility of the hindered amine, thus synergistically improving the electret effect. Hydroxystearate acts as a lubricant and dispersant, and the hydroxyl functional groups further improve the compatibility with tourmaline.

[0009] (2) The composite electret of the present invention can solve the problems of large electret addition, excessively thick polylactic acid fibers, high fiber breakage rate and low filtration efficiency in the preparation of electrospun polylactic acid materials using ordinary inorganic electrets.

[0010] (3) Since the electret already contains dendritic polymers, it is preferable to add resinous polymers separately as plasticizers in the overall formulation system to further improve the dispersibility of the composite electret in polylactic acid and improve the electret effect when preparing high-flow polylactic acid.

[0011] (4) The raw materials used in this invention are environmentally friendly and meet the requirements of biodegradability. The use of plasticizers and composite electret masterbatches can achieve good fluidity at lower processing temperatures. The excellent dispersibility and synergistic effect of the electret, as well as the special design of the resin formulation, further improve the dispersibility of the electret and can spin finer PLA fibers.

[0012] (5) In the composite fiber filter material of the present invention, the electret meltblown layer is used for coarse filtration and the electrostatic ultrafine fiber layer is used for fine filtration. This can make up for the insufficient filtration performance of a single meltblown layer and the excessive resistance of a single electrostatic spinning filter, and achieve the effect of high efficiency and low resistance. Under preferred conditions, the filtration efficiency can be greater than 99% and the resistance can be less than 150Pa.

[0013] (6) The preparation process of this invention is simple, and the resulting filter material has a wide range of applications in masks, protective clothing, surgical gowns, air purification, and especially in the field of high-efficiency air filtration under certain external forces.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0015] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0016] This invention provides a composite microfiber filter material, comprising a polylactic acid electrospun fiber layer and a polylactic acid meltblown fiber layer bonded together. The polylactic acid electrospun fiber layer is obtained by electrospinning an electret polylactic acid composition, and the polylactic acid meltblown fiber layer is obtained by meltblowing an electret polylactic acid composition. The electret polylactic acid composition comprises the following components in parts by weight: 100 parts polylactic acid, 0.2-4 parts composite electret, 0.2-2.5 parts plasticizer, 0.05-0.5 parts dispersant, and 0.01-0.5 parts antioxidant. The composite electret comprises tourmaline powder, hindered amine light stabilizer, hydroxystearate, and dendritic polymer.

[0017] The content of the composite electret can be, for example, any one of the following values: 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts, or a value within the range of any two of the above values.

[0018] The content of the plasticizer can be, for example, any one of 0.2 parts, 0.4 parts, 0.6 parts, 0.8 parts, 1 part, 1.5 parts, 2 parts, or 2.5 parts, or a value within a range of any two of the above values.

[0019] The content of the dispersant can be, for example, any one of 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, or 0.5 parts, or a value within a range of any two of the above values.

[0020] The content of the antioxidant can be, for example, any one of the following values, or a value within the range of any two of the above: 0.01 parts, 0.03 parts, 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, and 0.5 parts.

[0021] According to a preferred embodiment of the present invention, the polylactic acid blend comprises the following components in parts by weight: 100 parts polylactic acid, 0.5 to 3 parts composite electret, 0.5 to 2 parts plasticizer, 0.1 to 0.3 parts dispersant, and 0.05 to 0.2 parts antioxidant.

[0022] According to the present invention, by controlling the content of each component of the composite electret, a better material is obtained. Preferably, by weight, the composite electret comprises: 20-70 parts of tourmaline powder, 15-60 parts of hindered amine light stabilizer, 5-20 parts of hydroxystearate, and 5-30 parts of dendritic polymer.

[0023] The content of the tourmaline powder can be any one of 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, or 70 parts, or a value within the range of any two of the above.

[0024] The content of the hindered amine light stabilizer can be any one of 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, or 60 parts, or a value within the range of any two of the above values.

[0025] According to a preferred embodiment of the present invention, the composite electret comprises, by weight, 40-50 parts of tourmaline powder; 25-35 parts of hindered amine light stabilizer; 10-20 parts of hydroxystearate; and 10-20 parts of dendritic polymer.

[0026] According to a preferred embodiment of the present invention, the hindered amine light stabilizer includes at least one of light stabilizer 944, light stabilizer 770, light stabilizer 622 and light stabilizer 2020, preferably light stabilizer 944.

[0027] According to a preferred embodiment of the present invention, the hydroxystearate is at least one of magnesium hydroxystearate, zinc hydroxystearate and calcium hydroxystearate, preferably magnesium hydroxystearate.

[0028] According to a preferred embodiment of the present invention, the dendritic polymer is a dendritic polyester.

[0029] The aforementioned dendritic polyester is commercially available. In one specific embodiment of the present invention, the dendritic polyester is purchased from Weihai Chenyuan Molecular New Materials Co., Ltd., and its grades are CYD-817, CYD-2106, CYD-6404, and CYD-1050, with CYD-817 being preferred.

[0030] According to the present invention, the added composite electret is preferably a particulate powder, and more preferably, the particle size of the composite electret is D90≦3μm.

[0031] The composite electret of this invention incorporates hydroxystearate and dendritic polymer. Through intensive melting and processing, tourmaline and hindered amine light stabilizer can be fully mixed, resulting in a synergistic effect. At the same time, the hindered amine light stabilizer, hydroxystearate, and dendritic polymer can effectively isolate tourmaline powder, solving its agglomeration problem, allowing tourmaline to be uniformly dispersed in polylactic acid, reducing the fiber breakage caused by tourmaline agglomeration, and improving the uniformity of tourmaline. It also improves the dispersibility of the hindered amine light stabilizer, thus synergistically enhancing the electret effect.

[0032] According to the present invention, the composite electret is preferably prepared by a method comprising the following steps: mixing the components uniformly, then kneading, optionally cooling and optionally pulverizing, to obtain the composite electret.

[0033] According to a preferred embodiment of the present invention, the mixing is carried out in a continuous internal mixer, and the mixing temperature can be set to 90-200°C, preferably 140-180°C; the mixing time is 2-20 minutes, preferably 5-10 minutes. If the temperature is too high or the time is too long, it can easily cause the light stabilizer, hydroxystearate, and dendritic polymer to decompose; if the temperature is too low or the time is too short, the organic components will not be plasticized, and it will be difficult to form a uniform dispersion system.

[0034] The present invention does not particularly limit the polylactic acid in the composition. Preferably, the polylactic acid has a melt index of 20 to 60 g / 10 min at 210°C and 2.16 kg load.

[0035] According to a preferred embodiment of the present invention, the plasticizer is a dendritic polymer, preferably a dendritic polyester.

[0036] The aforementioned dendritic polyester is commercially available. In one specific embodiment of the present invention, the dendritic polyester is purchased from Weihai Chenyuan Molecular New Materials Co., Ltd., with grades CYD-817, CYD-2106, CYD-6404, and CYD-1050, preferably CYD-817. Since the electret already contains dendritic polymer, it is also preferable to add a resinous polymer separately as a plasticizer in the overall formulation system. This further improves the dispersibility of the composite electret in polylactic acid during the melt preparation of high-flow polylactic acid in a twin-screw extruder, thereby enhancing the electret effect.

[0037] The dispersant and antioxidant used in this invention can be conventional components in the art, and the dosage can also be conventional. Preferably, the dispersant is ethylene bis-stearamide (EBS). The antioxidant is a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and tris(2,4-di-tert-butylphenyl) phosphite (168), with a weight ratio of 1:1 to 3.

[0038] The basis weight of the two layers in the composite material can be set as needed, and the basis weight of the polylactic acid electrospun fiber layer can be 0.01 to 100 g / m². 2 The basis weight of the polylactic acid meltblown fiber layer can be 0.01–100 g / m². 2 .

[0039] The weight can be listed as 0.1 g / m³. 2 0.5g / m 2 1g / m 2 5g / m 2 10g / m 2 15g / m 2 20g / m 2 25g / m 2 30g / m 2 35g / m 2 40g / m 2 45g / m 2 50g / m 2 55g / m 2 60g / m 2 65g / m 2 70g / m 2 75g / m 2 80g / m 2 85g / m 2 90g / m 2 95g / m 2 100g / m 2 110g / m 2 120g / m 2130g / m 2 140g / m 2 150g / m 2 160g / m 2 170g / m 2 180g / m 2 190g / m 2 200g / m 2 The values ​​can be any one of the above values ​​or any combination of the above values. The weight of each layer can be independently selected from the above range.

[0040] For filtration applications, the sum of the basis weights of the two fiber layers needs to meet a certain requirement to ensure that the composite material has good filtration performance. Preferably, the sum of the basis weights of the two fiber layers is greater than or equal to 40 g / m³. 2 According to the present invention, the basis weights of the two fiber layers can be equal, as in many conventional composite layers. However, the inventors of the present invention have discovered that controlling the basis weight of the polylactic acid electrospun fiber layer to be greater than that of the polylactic acid meltblown fiber layer can achieve better filtration and drag reduction effects. Preferably, the difference in basis weight between the two fiber layers is less than or equal to 25 g / m². 2 .

[0041] According to a more preferred embodiment of the present invention, the sum of the basis weights of the polylactic acid electrospun fiber layer and the polylactic acid meltblown fiber layer is controlled to be greater than or equal to 50 g / m². 2 And less than or equal to 90g / m 2 The difference in weight is less than or equal to 20 g / m 2 And greater than or equal to 10g / m 2 This allows for a higher balance between efficiency and low resistance.

[0042] The sum of the weights of the polylactic acid electrospun fiber layer and the polylactic acid meltblown fiber layer can be listed as 50 g / m². 2 60g / m 2 65g / m 2 70g / m 2 75g / m 2 80g / m 2 85g / m 2 90g / m 2 The value is any one of the values ​​or any two of the values ​​listed above within a range.

[0043] The weight difference between the polylactic acid electrospun fiber layer and the polylactic acid meltblown fiber layer can be 20 g / m². 2 19g / m 2 18g / m 2 17g / m 2 16g / m2 15g / m 2 14g / m 2 13g / m 2 12g / m 2 11g / m 2 10g / m 2 The value is any one of the values ​​or any two of the values ​​listed above within a range.

[0044] This invention can further control the difference in fiber diameter between the two layers. Specifically, the diameter of the electrospun fibers in the polylactic acid electrospun fiber layer is smaller than the diameter of the meltblown fibers in the polylactic acid meltblown fiber layer. Using the larger-diameter meltblown layer for coarse filtration and the smaller-diameter electrospun fiber layer for fine filtration achieves better filtration results. Preferably, the diameter of the electrospun fibers is 0.5–3 μm, and the diameter of the meltblown fibers is 3–5 μm.

[0045] The present invention also provides a method for preparing the composite microfiber filter material, comprising the following steps: obtaining a polylactic acid meltblown fiber layer by meltblowing a raw material of electret polylactic acid composition, and obtaining the composite microfiber filter material by electrospinning polylactic acid on the surface of the polylactic acid meltblown fiber layer as a base fabric.

[0046] Specifically, it includes the following steps:

[0047] 1) The electret polylactic acid composition raw materials are melt-blended and then extruded and granulated to obtain polylactic acid granules;

[0048] 2) The polylactic acid granules obtained in step 1) are used to prepare polylactic acid meltblown fiber layers using meltblown nonwoven fabric equipment;

[0049] 3) Electrospin the polylactic acid granules obtained in step 1), and use the polylactic acid meltblown fiber layer in step 2) as the base fabric, and spray polylactic acid electrospun onto its surface to obtain the composite microfiber filter material.

[0050] According to the present invention, the granulation temperature can be 160–230°C, preferably 180–200°C. Excessive temperature can easily cause excessive degradation of polylactic acid, leading to decreased performance and excessive odor; insufficient temperature makes it difficult to significantly increase the melt flow index, thus failing to meet the requirements for preparing ultrafine fibers in the polylactic acid electrospun fiber layer.

[0051] The present invention can adopt a relatively conventional meltblown process. Preferably, the meltblown process conditions in step (2) include: melt temperature of 220-260℃, hot air temperature of 260-270℃, metering pump speed of 5-8g / min, mesh belt speed of 5-8m / min, and receiving distance of 30-50cm.

[0052] According to the present invention, in step (3), the electrospinning is preferably carried out by melt differential electrospinning, and the preferred process conditions include: spinning temperature of 190-260℃, spinning voltage of 45-55kV, micro extruder extrusion flow rate of 6-20g / h, distance between spinning nozzle and electrode plate of 100-200mm, distance between electrode plate and upper surface of receiving roller of 100-300mm, wind speed of 10-30m / s, roller speed of 300-2000r / min, and a secondary electric field applied during the spinning process.

[0053] The composite microfiber filter material of the present invention can be used to prepare filter products (such as masks). When applied, the polylactic acid meltblown fiber layer serves as the surface layer, i.e., the side facing the filter material.

[0054] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0055] The embodiments and comparative examples of the present invention use the following raw materials, but the present invention is not limited to these raw materials:

[0056] Polylactic acid (PLA), brand name REVODE210, Zhejiang Hisun Biomaterials Co., Ltd.; the melt flow rate was determined according to GB / T 3682-2018 "Determination of melt mass flow rate and melt volume flow rate of thermoplastic plastics", and the melt flow index was 50 g / 10 min at 210℃ and 2.16 kg load.

[0057] Tourmaline powder: commercially available, particle size D90≦1μm.

[0058] Plasticizer, dendritic polymer: dendritic polyester, grade CYD-817, Weihai Chenyuan Molecular New Materials Co., Ltd.

[0059] Magnesium hydroxystearate: Commercially available.

[0060] Dispersant: Ethylene bis-stearamide (EBS), Kao EBS EB-FF.

[0061] Antioxidants: Antioxidant 1010, Antioxidant 168, BASF.

[0062] Performance testing

[0063] The average fiber diameter was tested according to GB / T 36422-2018 standard.

[0064] The weight was tested in accordance with GB / T 24218.1-2009.

[0065] The filtration performance test was conducted in accordance with GB 2626-2019, using sodium chloride (NaCl) particulate matter for testing, with a test flow rate of 85 L / min.

[0066] The melt flow index was determined according to the melt mass flow rate in GB / T 3682-2018 "Determination of melt mass flow rate and melt volume flow rate of thermoplastics" under the following test conditions: 210℃, 2.16kg load.

[0067] All dosages in the tables are by weight, and the unit weight for each dosage is the same.

[0068] Example 1 and Comparative Example 1

[0069] This embodiment illustrates the preparation of the composite electret of the present invention.

[0070] Tourmaline powder, hindered amine light stabilizer 944, dendritic polymer CYD-817, and magnesium hydroxystearate were mixed evenly in a high-speed mixer according to the formula ratio in Table 1, and then kneaded in a continuous internal mixer at 160℃ for 5 minutes to prepare composite electret powder. The powder was then pulverized into composite electret powder with D90≦3μm by an air jet mill.

[0071] Table 1. Proportions of each component in the electret

[0072] serial number Tourmaline powder Light stabilizer 944 CYD-817 Magnesium hydroxystearate Example 1-1 70 15 5 10 Examples 1-2 20 60 10 10 Examples 1-3 50 30 10 10 Examples 1-4 30 50 10 10 Examples 1-5 40 30 20 10 Examples 1-6 30 40 10 20 Comparative Example 1-1 100 / / / Comparative Examples 1-2 / 100 / / Comparative Examples 1-3 50 50 / / Comparative Examples 1-4 40 50 10 / Comparative Examples 1-5 40 50 / 10

[0073] Test Example 1

[0074] This test example uses PLA electrospun fiber membrane to study the influence of the composite electret composition of the present invention on membrane performance.

[0075] High-flow electret polylactic acid (PLA) was prepared by twin-screw granulation using 100 parts of polylactic acid, 1.5 parts of plasticizer CYD-817, 1 part of composite electret, 0.05 parts of antioxidant 1010, 0.05 parts of antioxidant 168, and 0.2 parts of dispersant EBS. After drying at 70°C for 4 hours, a melt differential electrospinning machine was used to prepare a product with a basis weight of 50 g / m². 2 PLA electrospun fiber membrane.

[0076] The electrospinning process conditions are as follows: spinning temperature 190–260℃, spinning voltage 45–55kV, micro extruder flow rate 12g / h, distance between spinning nozzle and electrode plate 175mm, distance between electrode plate and upper surface of receiving roller 240mm, air velocity 20m / s, and roller speed 1500r / min. A secondary electric field needs to be applied during the spinning process.

[0077] The polylactic acid formulation and the properties of PLA electrospun fiber membrane are shown in Table 2.

[0078] Table 2 Polylactic acid formulation and performance of PLA electrospun fiber membrane

[0079]

[0080] It can be seen that the filtration efficiency of the electrospun fiber membrane in the examples with added composite electret is better than that of the comparative examples. The PLA membranes obtained by adding composite electret in Examples 1-3 and 1-5 have the highest filtration efficiency and also better breathing resistance, indicating that the performance of the composite electret components is better when the dosage of each component is within a more preferred range. In contrast, the electrospun fiber membranes prepared by adding tourmaline alone or using hindered amine light stabilizer 944 alone in Comparative Examples 1-1 and 1-2 have very low filtration efficiency.

[0081] The composite electrets prepared in Optimized Examples 1-5 were selected, and their proportions were adjusted. At the same time, the proportions of plasticizers were also adjusted to prepare high-flow polylactic acid blends and electrospun polylactic acid fiber membranes. The specific formulations and properties are shown in Table 3.

[0082] Table 3 Polylactic acid formulation and performance of PLA electrospun fiber membrane

[0083]

[0084] It can be seen that adding 0.5 to 3 parts of composite electret can achieve a filtration efficiency of over 95%. When the content reaches 5 parts, the filtration efficiency decreases. This may be due to the excessive tourmaline content, which causes uneven fiber distribution. As can be seen from the last two rows of the table, the excessive plasticizer content further increases the melt index, but the filtration efficiency decreases. This may be because the melt index is too high, the molecular weight of polylactic acid is too low, and it is unstable during spinning, resulting in the prepared fibers not achieving optimal distribution.

[0085] Example 2 and Comparative Example 2

[0086] This embodiment illustrates the preparation of the polylactic acid composition, polylactic acid meltblown fabric, electrospun polylactic acid fiber membrane, and composite filter membrane of the present invention.

[0087] Preparation of polylactic acid composition: By weight, 100 parts of polylactic acid, 1.5 parts of plasticizer, 1 part of composite electret prepared in Examples 1-5, 0.05 parts of antioxidant 1010, 0.05 parts of antioxidant 168 and 0.2 parts of dispersant EBS are mixed evenly in a high-speed mixer to obtain a polylactic acid composition; then the polylactic acid composition is extruded and granulated by a twin-screw extruder to obtain polylactic acid composition granules, wherein the extrusion temperature is 180-200℃.

[0088] Preparation of polylactic acid meltblown fabric: After drying polylactic acid granules at 70℃ for 4 hours, the granules were meltblown using a meltblown testing machine to obtain polylactic acid meltblown fabrics of different basis weights with an average fiber diameter of 3.7μm. The meltblown process included: melt temperature of 240℃, hot air temperature of 265℃, metering pump speed of 6g / min, conveyor belt speed of 6m / min, and receiving distance of 40cm.

[0089] Preparation of electrospun polylactic acid fiber membranes and composite filter membranes:

[0090] Using polylactic acid meltblown fabric as the base material, polylactic acid composite granules were electrospun using melt differential electrospinning and then sprayed onto the surface of the polylactic acid meltblown fabric to obtain electrospun polylactic acid fiber membranes and composite filter membranes of different basis weights. The average fiber diameter of the electrospun polylactic acid fiber membrane was 1.1 μm. The electrospinning process conditions were: spinning temperature 190–260℃, spinning voltage 45–55 kV, micro-extruder extrusion flow rate 12 g / h, distance between the spinning nozzle and electrode plate 175 mm, distance between the electrode plate and the upper surface of the receiving roller 240 mm, air velocity 20 m / s, and roller speed 1500 r / min. A secondary electric field was applied during the spinning process.

[0091] The filtration effect and air resistance of composite filter membranes formed by meltblown fabrics of different basis weights and electrospun fabrics of different basis weights are shown in Tables 4 and 5.

[0092] Table 4

[0093]

[0094]

[0095] Note: "-" indicates a filtration efficiency of less than 95%. The left side of " / " represents the filtration efficiency in % and the right side represents the air resistance in Pa.

[0096] Table 5

[0097] serial number <![CDATA[Meltblown fabric g / m 2 > <![CDATA[Electrospun fiber membrane g / m 2 > Filtration efficiency (%) Breathing resistance (Pa) Comparative Example 1 100 0 99.436 192.2 Comparative Example 2 0 100 99.916 218.6

[0098] As can be seen from the data in Table 4, composite filter media need to have a strength of at least 40 g / m³. 2 To achieve high filtration efficiency with significant application value, the basis weight of the electrospun layer should be slightly higher than that of the meltblown layer. Under optimal conditions, composite filter media can achieve filtration efficiencies exceeding 99% and breathing resistance below 150 Pa.

[0099] As can be seen from the data in Table 5, to achieve a filtration efficiency of over 99% when using meltblown fabric or electrospun fiber membrane alone, the basis weight needs to be 100 g / m³. 2At such a weight, the breathing resistance is as high as 190Pa or more, which is difficult to meet the usage requirements.

[0100] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0101] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A composite micro-fiber filter material, characterized by, The material comprises a polylactic acid electrospun fiber layer and a polylactic acid melt-blown fiber layer compounded together, the polylactic acid electrospun fiber layer is prepared by electrospinning of a polylactic acid electret composition, and the polylactic acid melt-blown fiber layer is prepared by melt-blown forming of the polylactic acid electret composition; the polylactic acid electret composition comprises the following components in parts by weight: 100 parts of polylactic acid, 0.2-4 parts of a composite electret, 0.2-2.5 parts of a plasticizer, 0.05-0.5 parts of a dispersing agent, and 0.01-0.5 parts of an antioxidant; the composite electret comprises tourmaline powder, a hindered amine light stabilizer, a hydroxyl stearate, and a dendritic polymer.

2. The composite micro-fiber filtration material of claim 1, wherein, The polylactic acid electret composition comprises the following components in parts by weight: 100 parts of polylactic acid, 0.5-3 parts of a composite electret, 0.5-2 parts of a plasticizer, 0.1-0.3 parts of a dispersing agent, and 0.05-0.2 parts of an antioxidant.

3. The composite micro-fiber filtration material of claim 1, wherein, The composite electret comprises, in parts by weight: 20-70 parts of tourmaline powder, 15-60 parts of a hindered amine light stabilizer, 5-20 parts of a hydroxyl stearate, and 5-30 parts of a dendritic polymer; preferably, the composite electret comprises, in parts by weight: 40-50 parts of tourmaline powder, 25-35 parts of a hindered amine light stabilizer, 10-20 parts of a hydroxyl stearate, and 10-20 parts of a dendritic polymer.

4. The composite micro-fiber filtration material of claim 1, wherein, The hindered amine light stabilizer comprises at least one of light stabilizer 944, light stabilizer 770, light stabilizer 622, and light stabilizer 2020, and is preferably light stabilizer 944.

5. The composite micro-fiber filtration material of claim 1, wherein, The hydroxyl stearate is at least one of magnesium hydroxyl stearate, zinc hydroxyl stearate, and calcium hydroxyl stearate, and is preferably magnesium hydroxyl stearate.

6. The composite micro-fiber filtration material of claim 1, wherein, The dendritic polymer is a dendritic polyester.

7. The composite micro-fiber filtration material of claim 1, wherein, The composite electret has a particle size of D90≤3 μm.

8. The composite micro-fiber filtration material of claim 1, wherein, The composite electret is prepared by a method comprising the following steps: uniformly mixing the components, and then mixing, optionally cooling, and optionally crushing to obtain the composite electret.

9. The composite micro-fiber filtration material of claim 8, wherein, The mixing is performed in a continuous internal mixer at a mixing temperature of 90-200°C, preferably 140-180°C, and a mixing time of 2-20 minutes, preferably 5-10 minutes.

10. The composite micro-fibrous filter material according to any one of claims 1-9, wherein, The polylactic acid has a melt index of 20-60 g / 10 min at 210°C under a load of 2.16 kg. The plasticizer is a dendritic polymer, and is preferably a dendritic polyester. The dispersing agent is ethylene bis-stearamide. The antioxidant is a mixture of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]pentaerythritol (1010) and tris(2,4-di-tert-butylphenyl)phosphite (168) at a weight ratio of 1:1-3.

11. The composite micro-fibrous filter material of claim 1, wherein, The poly-lactic-acid electrospun fiber layer has a gram weight of 0.01-100 g / m 2 The poly-lactic-acid melt-blown fiber layer has a gram weight of 0.01-100 g / m 2 The gram weight of the poly-lactic-acid electrospun fiber layer is greater than that of the poly-lactic-acid melt-blown fiber layer, and the sum of the gram weights of the two is greater than or equal to 40 g / m 2 The difference between the gram weights is less than or equal to 25 g / m 2 .

12. The composite micro-fiber filtration material of claim 11, wherein, the sum of the grammage of the polylactic acid electrospun fiber layer and the polylactic acid melt blown fiber layer is greater than or equal to 50 g / m 2 and less than or equal to 90 g / m 2 , the difference of the grammage is less than or equal to 20 g / m 2 and greater than or equal to 10 g / m 2 .

13. The composite micro-fibrous filter material of claim 1, wherein, The diameter of the electrospun fibers in the polylactic acid electrospun fiber layer is smaller than the diameter of the melt-blown fibers in the polylactic acid melt-blown fiber layer; preferably, the diameter of the electrospun fibers is 0.5-3 μm, and the diameter of the melt-blown fibers is 3-5 μm.

14. A method of making the composite micro-fibrous filter material of any one of claims 1-13, comprising the steps of: The polylactic acid melt-blown fiber layer is prepared by melt-blown forming of the polylactic acid electret composition raw material, and the polylactic acid electrospun fiber layer is obtained by spraying polylactic acid electrospun fibers on the surface of the polylactic acid melt-blown fiber layer as a base cloth.

15. The method of manufacturing according to claim 14, wherein, The method comprises the following steps: 1) melt blending and extruding the raw material of the electret polylactic acid composition to obtain polylactic acid granules; 2) using the polylactic acid granules obtained in step 1) to prepare a polylactic acid melt-blown fiber layer by using a melt-blown non-woven fabric device; 3) electrospinning the polylactic acid granules obtained in step 1) to obtain the composite micro-fiber filter material by spraying polylactic acid electrospun fibers on the surface of the polylactic acid melt-blown fiber layer obtained in step 2).

16. The method of manufacturing according to claim 15, wherein, The temperature for the granulation is 160-230°C, preferably 180-200°C.

17. The production method according to claim 14 or 15, wherein The process conditions for the melt-blown include: melt temperature 220-260°C, hot air temperature 260-270°C, metering pump speed 5-8 g / min, web speed 5-8 m / min, and receiving distance 30-50 cm.

18. The production method according to claim 14 or 15, wherein, The electrospinning uses a melt differential electrospinning method, and the process conditions include: spinning temperature 190-260°C, spinning voltage 45-55 kV, micro-extruder extrusion flow rate 6-20 g / h, distance between the spinning nozzle and the electrode plate 100-200 mm, distance between the electrode plate and the upper surface of the receiving roller 100-300 mm, air speed 10-30 m / s, roller speed 300-2000 r / min, and secondary electric field applied during the spinning process.

19. Use of the composite micro-fiber filter material according to any one of claims 1-13 in the preparation of a filter product, wherein the polylactic acid melt-blown fiber layer is used as the surface layer.

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