Nano composite material filter paper and preparation method thereof

Abstract

The invention provides nano composite material filter paper and a preparation method thereof, and relates to the technical field of filter paper. The nano composite material filter paper is prepared from the following raw material components: double-component polyurethane glue, paper pulp and nano aluminum oxide. The paper pulp and the nano aluminum oxide can be subjected to surface treatment by adopting a silane coupling agent containing an aspartate structure in advance, so that the compatibility with the two-component polyurethane glue is improved, and the filtering performance and the mechanical performance of the filter paper are improved.

Description

Technical Field

[0001] This invention belongs to the field of filter paper technology, and relates to a nanocomposite filter paper and its preparation method. Background Technology

[0002] Filter paper is a filter material that uses paper fibers as the main filter media. It can effectively intercept particulate pollutants and has a wide range of applications in air filtration. The performance requirements for filter paper generally focus on its filtration performance, but from a practical application perspective, filter paper also needs to have good mechanical properties to prevent damage during installation and / or use. Chinese patent CN107587378A discloses air filter paper containing carbon nanomaterials, using a water-based adhesive (polyurethane adhesive, acrylic resin adhesive, or phenolic resin adhesive) as the bonding matrix material between the fiber material and the carbon nanomaterials. However, for paper fiber filter paper, due to the high water absorption rate of paper fibers, using a water-based adhesive can cause the paper fibers to absorb too much water, thus affecting the performance of the filter paper.

[0003] The existing technology generally uses glycidyl methacrylate (GMA) for graft modification of paper fibers. There are two main methods: (1) the ring-opening reaction of the epoxy group on GMA with the hydroxyl group on paper fiber to graft a single GMA structure onto the surface of paper fiber; (2) the free radical polymerization reaction of the carbon-carbon double bond on GMA with the hydroxyl group on paper fiber to polymerize multiple GMA molecules into polymer segments.

[0004] Polyurethane possesses excellent mechanical strength and elasticity, making it a suitable polymer substrate for filter paper. Polyurethane adhesives are typically used in its preparation. However, grafting GMA onto paper fibers presents the following drawbacks when combined with polyurethane adhesives: the open-ring structure or free radical polymer products of GMA exhibit significant polarity differences compared to polyurethane, leading to insufficient compatibility.

[0005] Therefore, filter paper using paper fibers needs further improvement and optimization. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a nanocomposite filter paper and its preparation method.

[0007] The technical solution of the present invention is as follows:

[0008] A nanocomposite filter paper, by 100% weight, comprises: 10-25% two-component polyurethane adhesive, 70-85% pulp and 5-20% nano alumina;

[0009] The pulp and the nano-alumina are pre-treated individually with a silane coupling agent as shown in formula (1);

[0010]

[0011] Among them, R 1 R 2 R 4 and R 5 Individually selected from C1-C4 alkyl groups, R 3 It is an absent, C1-C6 alkylene or substituted C1-C30 alkylene, x≥2, y≥0, x+y=3.

[0012] Preferably, when the pulp undergoes surface treatment, the structure of the silane coupling agent is as shown in formula (2).

[0013]

[0014] Among them, R 6 Selected from C2-C6 alkylene groups, R 7 Selected from C1-C4 alkyl groups, a≥1, b≥0, a+b≤3.

[0015] More preferably, the R 6 Selected from B and / or C.

[0016] More preferably, the values ​​of a and b satisfy: a = 1, b = 0.

[0017] More preferably, the silane coupling agent of the structure shown in formula (2) is obtained by Michael addition reaction of the aminosilane coupling agent of formula (3) and the dialkyl maleate of formula (4) and then Michael addition reaction of the alkenylsilane coupling agent of formula (5).

[0018] (OR 1 ) x R 2 y Si(CH2CH2CH2NH) a+b CH2CH2NH2(3)

[0019] R 4 OCOCH=CHCOOR 5 (4)

[0020] CH2=CHR 8 Si(OR 7 )3 (5)

[0021] Among them, R 8 It is either absent or a C1-C4 alkylene group.

[0022] Preferably, when the nano-alumina undergoes surface treatment, the structure of the silane coupling agent is as shown in formula (6).

[0023]

[0024] Preferably, the average length of the pulp is 2-6 mm, and the moisture content of the pulp is not higher than 1 wt%.

[0025] The average particle size of the nano-alumina is 1-200 nm.

[0026] Preferably, the grafting rate of the pulp after surface treatment is 60-90%;

[0027] The grafting rate is calculated as follows: η = a1 / a0, where η is the grafting rate, a1 is the actual grafting amount, and a0 is the complete grafting amount.

[0028] Preferably, the grafting rate of the nano-alumina after surface treatment is 40-70%.

[0029] A method for preparing nanocomposite filter paper according to any of the above embodiments, wherein the hydroxyl-containing component of the two-component polyurethane adhesive, the pulp and the nano alumina are mixed evenly and then mixed evenly with the curing agent component of the two-component polyurethane adhesive, crosslinked and cured to obtain the nanocomposite filter paper.

[0030] Alternatively, the hydroxyl-containing component of the two-component polyurethane adhesive, the pulp, the nano-alumina, and the organic solvent are mixed evenly, the organic solvent is removed, and then the mixture is mixed evenly with the curing agent component of the two-component polyurethane adhesive, and cross-linked and cured to obtain the nanocomposite filter paper.

[0031] The beneficial effects of this invention are:

[0032] (1) In this invention, aspartic acid ester silane coupling agents are used to treat the surface of pulp and nano alumina respectively, which improves the dispersibility of pulp and nano alumina in polyurethane adhesive and improves the filtration performance and mechanical properties of filter paper.

[0033] (2) The present invention performs incomplete surface treatment on pulp and nano alumina respectively, which not only improves dispersibility, but also brings out the surface characteristics of pulp and nano alumina, further improving the filtration performance and mechanical properties of filter paper. Detailed Implementation

[0034] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0035] On the one hand, the present invention proposes a nanocomposite filter paper, which, by 100% weight, comprises: 10-25% two-component polyurethane adhesive, 70-85% pulp and 5-20% nano alumina;

[0036] The pulp and nano-alumina were pre-treated individually with the silane coupling agent shown in formula (1);

[0037]

[0038] Among them, R 1 R 2 R 4 and R 5 Individually selected from C1-C4 alkyl groups, R 3 It is an absent, C1-C6 alkylene or substituted C1-C30 alkylene, x≥2, y≥0, x+y=3.

[0039] Pulp has a natural "fiber interwoven network" that can form interconnected and interwoven micron-level pores, serving as the "main channel" for filter paper filtration and ensuring low resistance when gases, liquids, and other fluids pass through the filter paper. Nano-alumina has a high specific surface area and abundant surface hydroxyl groups, which can capture tiny particles through "physical adsorption" and adsorb pollutants such as heavy metal ions, acidic gases, and some small organic molecules through "chemical adsorption". Therefore, using pulp and nano-alumina as filter paper materials can achieve the filtration characteristics of "nanoscale interception + micron-level flow", resulting in high filtration efficiency, good filtration effect, and low energy consumption. However, pulp and nano-alumina have abundant hydroxyl groups (or carboxyl groups) on their surfaces, which may cause the following problems when mixed with polyurethane adhesive: (1) poor compatibility with polyurethane adhesive, resulting in poor dispersion of pulp and nano-alumina, which will affect the filtration performance and mechanical strength of the filter paper; (2) a large number of hydroxyl groups will consume a large amount of isocyanate curing agent in polyurethane adhesive, which may affect the curing of polyurethane adhesive. The present invention uses the silane coupling agent shown in formula (1) to treat the surface of pulp and nano alumina respectively. It can chemically graft organic structures containing aspartic acid esters onto the surface of pulp and nano alumina, thereby improving the compatibility with polyurethane adhesive. The surface-treated pulp and nano alumina can be better dispersed in polyurethane adhesive. Moreover, the aspartic acid ester structure can participate in the curing reaction of polyurethane adhesive, further improving the dispersion stability. Nano alumina can even play a certain reinforcing role for filter paper.

[0040] For the silane coupling agent shown in formula (1) above, there are no particular restrictions on the preparation method; it can be prepared from a silane coupling agent (OR) 1 ) x R 2 y SiR 3 CH2CH2NH2 and dialkyl maleate R 4 OCOCH=CHCOOR 5 Michael's additive reaction was obtained.

[0041] The surface treatment method in this invention is not particularly limited and can refer to the methods of the prior art. Taking pulp as an example, a surface treatment method can be as follows: add untreated pulp to a mixed solvent composed of anhydrous ethanol and deionized water in a volume ratio of 8:2, with a concentration of 1-5wt%, add a certain amount of silane coupling agent as shown in formula (1), stir at room temperature for 1-3h, then heat to 60℃ and continue the reaction for 1-3h, filter, wash with anhydrous ethanol, and dry to obtain the final product.

[0042] In some embodiments, when the pulp undergoes surface treatment, the structure of the silane coupling agent shown in formula (1) is further shown in formula (2).

[0043]

[0044] Among them, R 6 Selected from C2-C6 alkylene groups, R 7 Selected from C1-C4 alkyl groups, a≥1, b≥0, a+b≤3.

[0045] The silane coupling agent shown in formula (2) contains multiple alkoxysilane groups. One silane coupling agent molecule can react with multiple hydroxyl groups on the pulp surface. It can both react to remove the hydroxyl groups on the pulp surface and introduce organic structures on the pulp surface through chemical bonds, while avoiding the influence of introducing too many organic structures on the pulp performance, such as filtration performance.

[0046] Furthermore, R 6 Selected from B and / or C.

[0047] Furthermore, the values ​​of a and b satisfy: a = 1, b = 0.

[0048] Furthermore, the silane coupling agent shown in formula (2) is obtained by Michael addition reaction of the aminosilane coupling agent shown in formula (3) and the dialkyl maleate shown in formula (4) and then Michael addition reaction of the alkenylsilane coupling agent shown in formula (5).

[0049] (OR 1 ) x R 2 y Si(CH2CH2CH2NH) a+b CH2CH2NH2(3)

[0050] R 4 OCOCH=CHCOOR 5 (4)

[0051] CH2=CHR 8 Si(OR 7 )3 (5)

[0052] Among them, R8 It is either absent or a C1-C4 alkylene group.

[0053] The dialkyl maleate shown in formula (4) first undergoes a Michael addition reaction with the -NH2 group in the aminosilane coupling agent shown in formula (3). The intermediate product contains an unreacted -NH- group (-CH2CH2CH2NH-). Then, it undergoes another Michael addition reaction with the alkenylsilane coupling agent to obtain the silane coupling agent shown in formula (2).

[0054] The aforementioned aminosilane coupling agents can be β-aminoethyl-γ-aminopropyltrimethoxysilane, β-aminoethyl-γ-aminopropyltriethoxysilane, β-aminoethyl-γ-aminopropylmethyldimethoxysilane, etc., and can be obtained directly from the market.

[0055] The aforementioned dialkyl maleate esters can be dimethyl maleate, diethyl maleate, diisopropyl maleate, dibutyl maleate, etc., and can be obtained directly from the market.

[0056] The aforementioned alkenylsilane coupling agents can be vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, etc., and can be obtained directly from the market.

[0057] In some embodiments, when nano-alumina is surface-treated, the structure of the silane coupling agent shown in formula (1) is as shown in formula (6).

[0058]

[0059] The silane coupling agent shown in formula (6) above can be obtained by Michael addition reaction of silane coupling agents such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-aminopropylmethyldimethoxysilane with dimethyl maleate, diethyl maleate, etc.

[0060] In some embodiments, the average length of the pulp is 2-6 mm, and the moisture content of the pulp is not higher than 1 wt%.

[0061] The average particle size of nano-alumina is 1-200 nm.

[0062] While increasing the average length of the pulp makes dispersion more difficult, it can improve the mechanical strength and filtration performance of the filter cloth. For example, the average length of the pulp can be any value or any value between 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, and 6mm, without any particular restrictions. The moisture content of the pulp needs to be controlled at a low level to avoid affecting the mixing with the two-component polyurethane adhesive. The moisture content can be 0.5wt%, 0.8wt%, or 1wt%. The average particle size of the nano-alumina can be 1nm, 5nm, 10nm, 30nm, 50nm, 60nm, 80nm, 100nm, 120nm, 150nm, 180nm, or 200nm, or further, the average particle size of the nano-alumina can be 1-100nm.

[0063] In some embodiments, the grafting rate of the pulp after surface treatment is 60-90%;

[0064] The grafting rate is calculated as follows: η = a1 / a0, where η is the grafting rate, a1 is the actual grafting amount, and a0 is the complete grafting amount.

[0065] Specifically, the grafting amount α can be calculated as the weight difference of the pulp before and after surface treatment: α = M1 - M0, where M1 is the weight of the pulp after surface treatment and M0 is the weight of the pulp before surface treatment. When calculating α0, M1 is the weight of the pulp after complete surface treatment; when calculating α1, M1 is the weight of the pulp after partial surface treatment. For complete surface treatment of the pulp, it can be achieved by adding an excess of silane coupling agent.

[0066] The grafting rate of pulp after surface treatment is 60-90%. This process removes some (or most) of the hydroxyl groups on the pulp surface and chemically grafts organic structures onto it, improving compatibility with two-component polyurethane adhesives. Furthermore, the remaining hydroxyl groups on the pulp surface can form hydrogen bonds with polyurethane, which further enhances the mechanical properties of the filter paper. If the grafting rate after surface treatment is insufficient, a large number of hydroxyl groups will remain on the surface, leading to poor compatibility between the pulp and polyurethane adhesives. For example, the grafting rate after surface treatment can be any value from 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc., or any value in between, without particular limitations.

[0067] In some embodiments, the grafting rate of nano-alumina after surface treatment is 40-70%.

[0068] The grafting rate is calculated according to the above-mentioned calculation method. The grafting rate of nano-alumina after surface treatment is 40-70%. This process removes some hydroxyl groups from the surface of nano-alumina and grafts organic structures onto it, improving its compatibility with two-component polyurethane adhesives. Furthermore, some hydroxyl groups remain on the surface of nano-alumina, which can form hydrogen bonds with polyurethane, improving the mechanical properties of the filter paper, and can also continue to exert the adsorption capacity of the remaining hydroxyl groups on the nano-alumina surface, improving the filtration performance of the filter paper. If the surface treatment of nano-alumina is complete, with few or virtually no hydroxyl groups, although this is beneficial for its reinforcing effect, it cannot fully exert its adsorption capacity. For example, the grafting rate of nano-alumina after surface treatment can be any value or any value between 40%, 45%, 50%, 55%, 60%, 65%, and 70%, without any particular limitation.

[0069] The grafting rates of the pulp and nano-alumina can be adjusted by the weight of the added silane coupling agent. Adding an excess of silane coupling agent for surface treatment yields fully treated pulp, while reducing the weight of the silane coupling agent to a certain range yields partially treated pulp.

[0070] On the other hand, the present invention also proposes a method for preparing nanocomposite filter paper according to any of the above embodiments, wherein the hydroxyl-containing component (component A) of the two-component polyurethane adhesive, pulp and nano alumina are mixed evenly and then mixed evenly with the curing agent component (component B) of the two-component polyurethane adhesive, crosslinked and cured to obtain nanocomposite filter paper.

[0071] Alternatively, an organic solvent can be added first to improve dispersion efficiency and effect, and then the organic solvent can be removed. Specifically, the hydroxyl-containing component (component A) of the two-component polyurethane adhesive, pulp, nano-alumina and organic solvent (such as acetone, butyl acetate, ethyl acetate, etc.) can be mixed evenly, and after removing the organic solvent, it can be mixed evenly with the curing agent component (component B) of the two-component polyurethane adhesive, crosslinked and cured to obtain nanocomposite filter paper.

[0072] In this invention, since the organic structures grafted onto the surfaces of pulp and nano-alumina contain NH groups, which can react with the isocyanate curing agent in the two-component polyurethane, it is necessary to increase the amount of isocyanate curing agent in the two-component polyurethane and set the molar ratio of active hydrogen (OH and NH) to NCO groups to 1:1.02-1.1.

[0073] The thickness of the filter paper in this invention is not particularly limited and can be 0.05-2 mm.

[0074] The technical solution of the present invention will be further described and explained below based on various preparation examples and embodiments.

[0075] Preparation Examples 1-3: Preparation of Silane Coupling Agents

[0076] Preparation Example 1

[0077] 1 mol of 3-aminopropyltrimethoxysilane was added to the reaction vessel, and 1.1 mol of diethyl maleate was added dropwise. After the addition was completed, the temperature was raised to 60℃ and reacted for 72 h. The temperature was raised to 120℃ and the pressure was reduced to 5 Pa to remove excess diethyl maleate by molecular short-path distillation to obtain the silane coupling agent, denoted as S-1.

[0078] Preparation Example 2

[0079] 1 mol of β-aminoethyl-γ-aminopropyltrimethoxysilane was added to the reaction vessel, and 1.1 mol of diethyl maleate was added dropwise. After the addition was completed, the temperature was raised to 60℃ and reacted for 72 h. The temperature was then raised to 120℃ and the pressure was reduced to 5 Pa to remove excess diethyl maleate by molecular short-path distillation to obtain the silane coupling agent, denoted as S-2.

[0080] Preparation Example 3

[0081] 1 mol of silane coupling agent S-2 from Preparation Example 2 was added to the reaction vessel, the temperature was raised to 40°C, and 1.5 mol of vinyltrimethoxysilane was added dropwise. After the addition was complete, the temperature was raised to 80°C and the reaction was carried out for 96 h. The excess vinyltrimethoxysilane was removed by reducing the pressure to no more than 50 Pa to obtain the silane coupling agent, which was denoted as S-3.

[0082] Preparation Examples 4-8: Preparation of Surface-Treated Pulp

[0083] Preparation Example 4

[0084] 10g of pulp with an average size of 4mm was added to a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 8:2, with a concentration of 2wt%. 4g of silane coupling agent S-2 from Preparation Example 2 was added, and the mixture was stirred at room temperature for 2h. The temperature was then raised to 60℃ and the reaction continued for 2h. The mixture was filtered, and the filtrate was washed three times with anhydrous ethanol. It was dried at 60℃ for 2h and then dried overnight at 110℃ to obtain the treated pulp, denoted as P-1, which is a fully surface-treated pulp.

[0085] Preparation Example 5

[0086] The difference between this preparation example and Preparation Example 4 is that in Preparation Example 4, the silane coupling agent S-2 was replaced with the same weight of the silane coupling agent S-3 from Preparation Example 3. The remaining steps remained unchanged. The treated pulp, denoted as P-2, was obtained, representing complete surface treatment.

[0087] Preparation Example 6

[0088] The difference between this preparation example and Preparation Example 5 is that in Preparation Example 5, the silane coupling agent S-3 was adjusted from 4g to 2.7g. The remaining steps remained unchanged. The treated pulp was obtained and designated P-3. The grafting rate of pulp P-3 was measured to be 86%.

[0089] Preparation Example 7

[0090] The difference between this preparation example and Preparation Example 5 is that in Preparation Example 5, the silane coupling agent S-3 was changed from 4g to 2g. The remaining steps remained unchanged. The treated pulp was obtained and designated P-4. The grafting rate of pulp P-4 was measured to be 62%.

[0091] Preparation Example 8

[0092] The difference between this preparation example and Preparation Example 5 is that in Preparation Example 5, the silane coupling agent S-3 was adjusted from 4g to 1.7g. The remaining steps remained unchanged. The treated pulp was obtained and designated P-5. The grafting rate of pulp P-5 was measured to be 55%.

[0093] Preparation Examples 9-13: Preparation of Surface-Treated Nano-Alumina

[0094] Preparation Example 9

[0095] 10g of nano-alumina with an average particle size of 30nm was added to a mixed solvent of anhydrous ethanol and deionized water in a volume ratio of 8:2, with a concentration of 1.5wt%. 3.5g of silane coupling agent S-1 from Preparation Example 1 was added, and the mixture was stirred at room temperature for 2h. The temperature was then raised to 60℃ and the reaction was continued for 2h. The mixture was filtered, and the filtrate was washed three times with anhydrous ethanol. The mixture was then dried at 60℃ overnight to obtain the treated nano-alumina, denoted as A-1, which represents complete surface treatment.

[0096] Preparation Example 10

[0097] The difference between this preparation example and Preparation Example 9 is that in Preparation Example 9, the amount of silane coupling agent S-1 was adjusted from 3.5 g to 2.5 g. The remaining steps remained unchanged. The treated nano-alumina was obtained, denoted as A-2. The grafting rate of nano-alumina A-2 was measured to be 81%.

[0098] Preparation Example 11

[0099] The difference between this preparation example and Preparation Example 9 is that in Preparation Example 9, the amount of silane coupling agent S-1 was adjusted from 3.5 g to 2.1 g. The remaining steps remained unchanged. The treated nano-alumina was obtained, denoted as A-3. The grafting rate of nano-alumina A-3 was measured to be 67%.

[0100] Preparation Example 12

[0101] The difference between this preparation example and Preparation Example 9 is that in Preparation Example 9, the amount of silane coupling agent S-1 was adjusted from 3.5 g to 1.5 g. The remaining steps remained unchanged. The treated nano-alumina was obtained and designated A-4. The grafting rate of nano-alumina A-3 was measured to be 45%.

[0102] Preparation Example 13

[0103] The difference between this preparation example and Preparation Example 9 is that in Preparation Example 9, the amount of silane coupling agent S-1 was adjusted from 3.5 g to 1 g. The remaining steps remained unchanged. The treated nano-alumina was obtained and designated A-5. The grafting rate of nano-alumina A-4 was measured to be 32%.

[0104] In the following examples and comparative examples, the ratio of the sum of the molar numbers of OH and NH in the raw material components to the molar number of NCO is 1:1.05.

[0105] Example 1

[0106] The raw material components of the nanocomposite filter paper include: 20g of two-component polyurethane adhesive, 65g of pulp P-1 from Preparation Example 4, and 15g of nano-alumina A-1 from Preparation Example 9.

[0107] Component A of the two-component polyurethane adhesive, pulp P-1, nano-alumina A-1, and butyl acetate (10% by weight) were mixed and stirred at a high speed of 1500 rpm for 30 min. The mixture was then heated to 60℃ to remove butyl acetate under reduced pressure. After cooling to room temperature, component B of the two-component polyurethane adhesive was added, and the mixture was stirred at a speed of 600 rpm for 10 min. The mixture was then transferred to a mold for cross-linking and curing to obtain a nanocomposite filter paper with a thickness of 0.2 mm.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that in Example 1, pulp P-1 was replaced with an equal weight of GMA-treated pulp. The remaining steps remained unchanged.

[0110] The method for treating pulp with GMA is as follows: Pulp with an average size of 4 mm is pre-dried at 110℃ for 2 hours to remove water. 10 g of dried pulp is added to a mixed solvent of anhydrous ethanol and DMF in a volume ratio of 7:3 (2 wt%), 4 g of GMA and 0.15 g of pyridine are added, the temperature is raised to 50℃ and the reaction continues for 3 hours. After filtration, the filtrate is washed three times with anhydrous ethanol and dried overnight at 60℃ to obtain GMA-treated pulp, denoted as P-GMA, which represents complete surface treatment.

[0111] Example 2

[0112] The difference between this embodiment and Embodiment 1 is that in Embodiment 1, the pulp P-1 of Preparation Example 4 is replaced with an equal weight of the pulp P-2 of Preparation Example 5. The remaining steps remain unchanged.

[0113] Example 3

[0114] The difference between this embodiment and Embodiment 2 is that in Embodiment 2, the pulp P-2 in Preparation Example 5 is replaced with an equal weight of the pulp P-3 in Preparation Example 6, and the nano-alumina A-1 in Preparation Example 9 is replaced with an equal weight of the nano-alumina A-2 in Preparation Example 10. The remaining steps remain unchanged.

[0115] Example 4

[0116] The difference between this embodiment and Example 3 is that in Example 3, the nano-alumina A-2 from Preparation Example 10 was replaced with an equal weight of nano-alumina A-3 from Preparation Example 11. The remaining steps remain unchanged.

[0117] Example 5

[0118] The difference between this embodiment and Embodiment 3 is that in Embodiment 3, the nano-alumina A-2 of Preparation Example 10 was replaced with an equal weight of nano-alumina A-4 of Preparation Example 12. The remaining steps remained unchanged.

[0119] Example 6

[0120] The difference between this embodiment and Example 3 is that in Example 3, the nano-alumina A-2 from Preparation Example 10 was replaced with an equal weight of nano-alumina A-5 from Preparation Example 13. The remaining steps remained unchanged.

[0121] Example 7

[0122] The raw material composition of the nanocomposite filter paper, by 100% weight, includes: 18% two-component polyurethane adhesive, 65% pulp P-2 of Preparation Example 5, and 17% nano alumina A-3 of Preparation Example 11.

[0123] Nanocomposite filter paper with a thickness of 0.3 mm was prepared according to the method in Example 1.

[0124] Example 8

[0125] The difference between this embodiment and Embodiment 7 is that in Embodiment 7, the pulp P-2 of Preparation Example 5 is replaced with an equal weight of the pulp P-3 of Preparation Example 6. The remaining steps remain unchanged.

[0126] Example 9

[0127] The difference between this embodiment and Embodiment 7 is that in Embodiment 7, the pulp P-2 of Preparation Example 5 is replaced with an equal weight of the pulp P-4 of Preparation Example 7. The remaining steps remain unchanged.

[0128] Example 10

[0129] The difference between this embodiment and Embodiment 7 is that in Embodiment 7, the pulp P-2 of Preparation Example 5 is replaced with an equal weight of the pulp P-5 of Preparation Example 8. The remaining steps remain unchanged.

[0130] Example 11

[0131] The difference between this embodiment and Embodiment 7 is that in Embodiment 7, the pulp P-2 of Preparation Example 5 is replaced with an equal weight of the pulp P-5 of Preparation Example 8, and the nano-alumina A-3 of Preparation Example 11 is replaced with an equal weight of the nano-alumina A-5 of Preparation Example 13. The remaining steps remain unchanged.

[0132] Performance testing

[0133] The airflow rate was tested according to the method in GB / T 32085.1-2015 and was 300 m³ / s. 3 The initial pressure drop at / h. The lower the initial pressure drop, the lower the filtration resistance of the filter paper and the better the filtration effect.

[0134] The airflow rate was tested according to the method in GB / T 32085.1-2015 and was 300 m³ / s. 3 The filtration efficiency for particles with a diameter of 0.1 μm is measured at a rate of / h. A higher filtration efficiency indicates better filtration capability of the filter paper.

[0135] The rated flow rate was tested according to the method in GB / T 32085.2-2015, and the flow rate was 150 m³ / s. 3 / h, adsorption efficiency of toluene 1 minute from zero. The initial concentration of toluene is 80 ppm.

[0136] Mechanical strength: Tensile strength was tested using an electronic tensile testing machine.

[0137] The results for the filter paper in each embodiment are shown in Table 1 below.

[0138] Table 1

[0139]

[0140] As shown in Table 1 above, compared with Comparative Example 1, the pulp surface treated with the silane coupling agent of the present invention exhibits lower gas resistance, higher filtration and adsorption effects, and higher mechanical strength compared with surface treatment using GMA. This indicates that the pulp surface treated with the silane coupling agent of the present invention has better compatibility with polyurethane adhesives. Comparative Example 2 and Example 1, the silane coupling agent molecule contains two trimethoxysilane groups, compared to containing only one trimethoxysilane group, introducing fewer organic structures, resulting in lower gas resistance and better filtration and adsorption effects on the filter paper. Comparative Examples 2-6 and Examples 7-11, the grafting rate of the organic structures grafted onto the surface of the pulp and nano-alumina is within a suitable range, exhibiting good filtration and adsorption performance and mechanical strength.

[0141] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A nanocomposite filter paper, characterized in that, By 100% weight, the raw material composition includes: 10-25% two-component polyurethane adhesive, 70-85% pulp and 5-20% nano-alumina; The pulp and the nano-alumina are pre-treated individually with a silane coupling agent as shown in formula (1); Among them, R 1 R 2 R 4 and R 5 Individually selected from C1-C4 alkyl groups, R 3 It is an absent, C1-C6 alkylene or substituted C1-C30 alkylene, x≥2, y≥0, x+y=3.

2. The nanocomposite filter paper according to claim 1, characterized in that, When the pulp undergoes surface treatment, the structure of the silane coupling agent is shown in formula (2). Among them, R 6 Selected from C2-C6 alkylene groups, R 7 Selected from C1-C4 alkyl groups, a≥1, b≥0, a+b≤3.

3. The nanocomposite filter paper according to claim 2, characterized in that, The R 6 Selected from B and / or C.

4. The nanocomposite filter paper according to claim 2, characterized in that, The values ​​of a and b satisfy: a = 1, b = 0.

5. The nanocomposite filter paper according to claim 2, characterized in that, The silane coupling agent with the structure shown in formula (2) is obtained by Michael addition reaction of the aminosilane coupling agent shown in formula (3) and the dialkyl maleate shown in formula (4) and then Michael addition reaction of the alkenylsilane coupling agent shown in formula (5). (OR 1 ) x R 2 y Si(CH2CH2CH2NH) a+b CH2CH2NH2(3) R 4 OCOCH=CHCOOR 5 (4) CH2=CHR 8 Si(OR 7 )3 (5) Among them, R 8 It is either absent or a C1-C4 alkylene group.

6. The nanocomposite filter paper according to claim 1, characterized in that, When the nano-alumina undergoes surface treatment, the structure of the silane coupling agent is shown in formula (6).

7. The nanocomposite filter paper according to claim 1, characterized in that, The average length of the pulp is 2-6 mm, and the moisture content of the pulp is not higher than 1 wt%. The average particle size of the nano-alumina is 1-200 nm.

8. The nanocomposite filter paper according to claim 1, characterized in that, The grafting rate of the pulp after surface treatment is 60-90%; The grafting rate is calculated as follows: η = a1 / a0, where η is the grafting rate, a1 is the actual grafting amount of the silane coupling agent, and a0 is the complete grafting amount of the silane coupling agent.

9. The nanocomposite filter paper according to claim 1, characterized in that, The grafting rate of the nano-alumina surface after surface treatment is 30-60%.

10. A method for preparing nanocomposite filter paper according to any one of claims 1-9, characterized in that, The hydroxyl-containing component of the two-component polyurethane adhesive, the pulp, and the nano-alumina are mixed evenly and then mixed evenly with the curing agent component of the two-component polyurethane adhesive, and cross-linked and cured to obtain the nano-composite filter paper. Alternatively, the hydroxyl-containing component of the two-component polyurethane adhesive, the pulp, the nano-alumina, and the organic solvent are mixed evenly, the organic solvent is removed, and then the mixture is mixed evenly with the curing agent component of the two-component polyurethane adhesive, and cross-linked and cured to obtain the nanocomposite filter paper.

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