Flame-retardant air filter paper containing aramid nanofiber coating and preparation method thereof

Abstract

The present invention relates to the technical field of paper-based functional materials, and in particular to a flame-retardant air filter paper containing aramid nanofiber coating and a preparation method thereof. The flame-retardant air filter paper comprises, by weight, 25 to 50 parts of softwood pulp, 22 to 40 parts of mercerized pulp, 14 to 24 parts of aramid short-cut fibers, 5 to 10 parts of polyester fibers, 1 to 3 parts of wet strength agent, 8 to 16 parts of aramid nanofibers, 1 to 2 parts of dispersant, 4 to 7 parts of melamine formaldehyde resin, and 3 to 5 parts of acrylic emulsion. The flame-retardant air filter paper prepared by the present invention does not require the addition of flame retardants, and overcomes the defects of traditional air filter paper that the amount of flame retardant added is large and the flame retardant components are easy to lose. The flame-retardant air filter paper of the present invention has high mechanical strength and filtering accuracy, and can also maintain a stable and lasting flame retardant effect and good flexibility, and can be applied to the fields of high-end flame-retardant automobile air filter paper.

Description

Technical Field

[0001] The invention relates to flame-retardant air filter paper containing aramid nanofiber coating and a preparation method thereof, belonging to the technical field of paper-based functional materials. Background Art

[0002] Air filter paper, fuel filter paper and oil filter paper are collectively known as the three filter papers in the automotive industry, and are important filter materials in the automotive industry. Among them, air filter paper is the core material of the air filter in the automobile engine, with the advantages of light weight, good filtering effect and stable performance. As an important component of the automobile engine, the main function of the air filter is to filter impurities in the air, reduce the wear of the engine cylinder and piston ring, and thus extend the service life of the engine. Since the engine of a car generates a lot of heat when it is working, especially high-performance cars such as sports cars or racing cars, once the engine backfires or inhales high-temperature particles, it may cause the filter paper to burn, bringing a very large safety hazard. In order to avoid the above situation, flame-retardant air filter paper has been widely used. At present, domestic manufacturers usually use additive flame retardants to flame retardant the filter paper. Although the air filter paper obtained by this method has certain flame retardant properties, the flame retardant durability is poor, and it will have a great impact on the physical properties of the filter paper itself. Therefore, the flame-retardant air filter paper produced generally has problems such as non-persistent flame retardant effect, low filtering accuracy and poor mechanical strength, which cannot meet the application needs of the high-end automobile market.

[0003] Chinese patent application CN112252085A discloses a high temperature resistant flame retardant automobile air filter paper and its preparation method and application. Although the air filter paper is endowed with strong high temperature resistance and flame retardancy as well as high strength and filtering accuracy by adjusting the raw material ratio and coating, the raw materials used are too many, the operation is relatively cumbersome, and the addition of solid fillers will reduce the flexibility of the air filter paper, which will have an adverse effect on the processing process from filter paper to filter element.

[0004] Chinese patent application CN113445364A discloses a flame retardant air filter paper and a preparation method thereof. A flame retardant air filter paper with high flame retardancy, high strength and good toughness is prepared by mixing and papermaking multiple high-performance fibers, but the average pore size is large and the filtering accuracy is average. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a flame-retardant air filter paper containing an aramid nanofiber coating and a preparation method thereof. No flame retardant needs to be added to the filter paper, thereby overcoming the defects of traditional air filter paper, such as a large amount of flame retardant added and easy loss of flame retardant components, achieving a long-lasting and stable flame retardant effect. In addition, the air filter paper has better strength performance, filtration efficiency and filtration accuracy.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: a flame-retardant air filter paper containing aramid nanofiber coating, which comprises, by weight: 25-50 parts of coniferous wood pulp, 22-40 parts of mercerized pulp, 14-24 parts of aramid short fibers, 5-10 parts of polyester fibers, 1-3 parts of wet strength agent, 8-16 parts of aramid nanofibers, 1-2 parts of dispersant, 4-7 parts of melamine formaldehyde resin, and 3-5 parts of acrylic emulsion.

[0007] Furthermore, the wet strength agent is polyamide epichlorohydrin.

[0008] Furthermore, the dispersant is polyethylene oxide or polyacrylamide.

[0009] Furthermore, the average diameter of the aramid nanofibers is 40-100 nm.

[0010] Preferably, the average diameter of the aramid nanofibers is 40-70 nm.

[0011] The present invention also discloses a method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating, the preparation method comprising:

[0012] S1. Preparation of filter paper base paper:

[0013] The component softwood pulp and mercerized pulp are mixed and beaten to 25-55°SR, and then the component aramid short-cut fiber, polyester fiber and wet strength agent are added to mix and disperse to make filter paper base paper;

[0014] S2. Coating of aramid nanofibers:

[0015] The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating liquid; the aramid nanofiber coating liquid is evenly coated on both sides of the filter paper base paper;

[0016] S3, calendering treatment:

[0017] The filter paper base coated with the aramid nanofiber coating liquid in step S2 is subjected to low-temperature calendering treatment to obtain a filter paper base with an aramid nanofiber coating;

[0018] S4, resin impregnation treatment:

[0019] The component amounts of melamine formaldehyde resin and acrylic emulsion are mixed and compounded to prepare an impregnation liquid, the filter paper base paper with aramid nanofiber coating prepared in step S3 is placed in the impregnation liquid for impregnation treatment, and then dried to obtain the flame-retardant air filter paper.

[0020] Furthermore, in step S2, the mass fraction of aramid nanofibers in the aramid nanofiber coating liquid is 0.5-2.0%.

[0021] Preferably, in step S2, the mass fraction of aramid nanofibers in the aramid nanofiber coating liquid is 1.5-2.0%.

[0022] Furthermore, in step S3, the calendering temperature of the low-temperature calendering treatment is 80-180° C., the pressure is 1 MPa-6 MPa, and the vehicle speed is 5-20 m / min.

[0023] Preferably, in step S3, the calendering temperature of the low-temperature calendering treatment is 130-160° C., the pressure is 3 MPa-5 MPa, and the vehicle speed is 10-16 m / min.

[0024] Furthermore, in step S4, the immersion time is 10 to 20 seconds.

[0025] Preferably, in step S4, the immersion time is 15 to 20 seconds.

[0026] Furthermore, in step S4, the drying temperature is 100-120° C., and the drying time is 8-18 min.

[0027] Preferably, in step S4, the drying temperature is 110-120° C., and the drying time is 10-15 min.

[0028] The beneficial effects of the present invention are:

[0029] The flame-retardant air filter paper prepared by the present invention does not require the addition of flame retardants, has high mechanical strength and filtration accuracy, can maintain a stable and lasting flame retardant effect and good flexibility, and can be applied to fields such as high-end flame-retardant automobile air filter paper.

[0030] The aramid nanofiber used in the present invention has good flame retardant properties and thermal stability, acts on the surface of base paper in the form of a coating, is protected by resin after impregnation, and does not need to be additionally added with a flame retardant in the filter paper, thereby overcoming the defects of a large amount of flame retardant added to the traditional air filter paper and the easy loss of the flame retardant component, and achieving a lasting and stable flame retardant effect. At the same time, the mechanical strength of the filter paper will not be adversely affected by the addition of the flame retardant, and the calendering treatment can promote the combination between the fibers, thereby ensuring that the overall mechanical strength of the flame retardant air filter paper is at a high level and has good flexibility. In addition, the high specific surface area of ​​the aramid nanofiber makes it have excellent performance in the air filter, can effectively filter fine particles, and effectively improves the filtration efficiency and filtration precision of the filter paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic cross-sectional view of the flame-retardant air filter paper containing aramid nanofiber coating according to the present invention;

[0032] In the figure, 1. filter paper base paper; 2. aramid nanofiber coating; 3. resin layer. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0035] The invention discloses a flame retardant air filter paper containing aramid nanofiber coating. The flame retardant air filter paper comprises, by weight, 25-50 parts of softwood pulp, 22-40 parts of mercerized pulp, 14-24 parts of aramid short-cut fibers (length of 5-8 mm), 5-10 parts of polyester fibers (length of 5-7 mm), 1-3 parts of wet strength agent, 8-16 parts of aramid nanofibers, 1-2 parts of dispersant, 4-7 parts of melamine formaldehyde resin and 3-5 parts of acrylic emulsion.

[0036] Specifically, the wet strength agent is polyamide epichlorohydrin.

[0037] Specifically, the dispersant is polyethylene oxide or polyacrylamide.

[0038] Specifically, the average diameter of the aramid nanofibers is 40-100 nm.

[0039] Preferably, the average diameter of the aramid nanofibers is 40-70 nm.

[0040] Sources of raw materials used in the embodiments of the present invention:

[0041] The softwood pulp was provided by Shandong Daoxin New Materials Co., Ltd., the mercerized pulp was provided by Qingdao Ruilibo International Trade Co., Ltd., the aramid short-cut fiber was provided by Taihe New Materials Group Co., Ltd., the polyester fiber was provided by Huvis Chemical Fiber Co., Ltd., the melamine formaldehyde resin was provided by Shandong Linxiang Chemical Co., Ltd., the acrylic emulsion was provided by Puyang Bluestar New Materials Co., Ltd., the polyamide epichlorohydrin was provided by Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., the polyethylene oxide was provided by Suzhou Qihang Biotechnology Co., Ltd., and the polyacrylamide was provided by Shenzhen Changlong Technology Co., Ltd. However, it does not constitute a limitation on the technical solution of the present invention.

[0042] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating 2, the preparation method comprising:

[0043] S1. Preparation of filter paper base 1:

[0044] The component softwood pulp and mercerized pulp are mixed and beaten to 25-55°SR, and then the component aramid short-cut fiber, polyester fiber and wet strength agent are added to mix and disperse to produce filter paper base paper 1;

[0045] S2. Coating of aramid nanofibers:

[0046] The aramid nanofibers, dispersant and deionized water are compounded to prepare an aramid nanofiber coating liquid; the aramid nanofiber coating liquid is evenly coated on both sides of the filter paper base paper 1;

[0047] S3, calendering treatment:

[0048] The filter paper base 1 coated with the aramid nanofiber coating liquid in step S2 is subjected to low-temperature calendering treatment to obtain the filter paper base 1 with the aramid nanofiber coating 2;

[0049] S4, resin impregnation treatment:

[0050] The melamine formaldehyde resin and acrylic emulsion are mixed and compounded to form an impregnation liquid, and the filter paper base paper 1 with the aramid nanofiber coating 2 prepared in step S3 is placed in the impregnation liquid to obtain a resin layer 3, and then dried to obtain the flame retardant air filter paper. The cross-sectional view of the flame retardant air filter paper is as follows Figure 1 shown.

[0051] Specifically, in step S2, the mass fraction of aramid nanofibers in the aramid nanofiber coating liquid is 0.5-2.0%.

[0052] Preferably, in step S2, the mass fraction of aramid nanofibers in the aramid nanofiber coating liquid is 1.5-2.0%.

[0053] Specifically, in step S3, the calendering temperature of the low-temperature calendering treatment is 80-180° C., the pressure is 1 MPa-6 MPa, and the vehicle speed is 5-20 m / min.

[0054] Preferably, in step S3, the calendering temperature of the low-temperature calendering treatment is 130-160° C., the pressure is 3 MPa-5 MPa, and the vehicle speed is 10-16 m / min.

[0055] Specifically, in step S4, the immersion time is 10 to 20 seconds.

[0056] Preferably, in step S4, the immersion time is 15 to 20 seconds.

[0057] Specifically, in step S4, the drying temperature is 100-120° C., and the drying time is 8-18 min.

[0058] Preferably, in step S4, the drying temperature is 110-120° C., and the drying time is 10-15 min.

[0059] Example 1

[0060] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 35 parts of coniferous wood pulp, 25 parts of mercerized pulp, 15 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 10 parts of aramid nanofibers, 2 parts of dispersant, 6 parts of melamine formaldehyde resin, and 3 parts of acrylic emulsion.

[0061] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyethylene oxide.

[0062] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0063] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0064] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 1.0% and the average diameter of the aramid nanofibers is 50 nm.

[0065] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 150° C., the pressure is 4 MPa, and the speed is 10 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0066] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0067] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 110° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0068] Example 2

[0069] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 35 parts of coniferous wood pulp, 25 parts of mercerized pulp, 20 parts of aramid short fibers, 6 parts of polyester fibers, 2 parts of wet strength agent, 12 parts of aramid nanofibers, 2 parts of dispersant, 6 parts of melamine formaldehyde resin, and 3 parts of acrylic emulsion.

[0070] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyacrylamide.

[0071] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0072] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 40°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0073] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 1.0% and the average diameter of the aramid nanofibers is 50 nm.

[0074] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 160° C., the pressure is 4 MPa, and the speed is 10 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0075] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0076] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 110° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0077] Example 3

[0078] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 25 parts of mercerized pulp, 15 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 8 parts of aramid nanofibers, 2 parts of dispersant, 6 parts of melamine formaldehyde resin, and 5 parts of acrylic emulsion.

[0079] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyethylene oxide.

[0080] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0081] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0082] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 1.0% and the average diameter of the aramid nanofibers is 50 nm.

[0083] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 140° C., the pressure is 4 MPa, and the speed is 12 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0084] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0085] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 120° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0086] Example 4

[0087] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 30 parts of mercerized pulp, 18 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 8 parts of aramid nanofibers, 2 parts of dispersant, 4 parts of melamine formaldehyde resin, and 5 parts of acrylic emulsion.

[0088] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyacrylamide.

[0089] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0090] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0091] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 1.5% and the average diameter of the aramid nanofibers is 50 nm.

[0092] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 120° C., the pressure is 4 MPa, and the speed is 12 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0093] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0094] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 120° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0095] Example 5

[0096] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 25 parts of coniferous wood pulp, 40 parts of mercerized pulp, 24 parts of aramid short fibers, 5 parts of polyester fibers, 1 part of wet strength agent, 16 parts of aramid nanofibers, 1 part of dispersant, 7 parts of melamine formaldehyde resin, and 4 parts of acrylic emulsion.

[0097] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyethylene oxide.

[0098] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0099] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 25°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0100] (2) The aramid nanofibers, dispersant and deionized water were mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution was 1.5% and the average diameter of the aramid nanofibers was 70 nm.

[0101] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 80° C., the pressure is 6 MPa, and the speed is 5 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0102] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0103] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 20 seconds, and then taken out for drying at a temperature of 100° C. for 18 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0104] Example 6

[0105] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 50 parts of coniferous wood pulp, 22 parts of mercerized pulp, 14 parts of aramid short fibers, 10 parts of polyester fibers, 3 parts of wet strength agent, 11 parts of aramid nanofibers, 1 part of dispersant, 6 parts of melamine formaldehyde resin, and 4 parts of acrylic emulsion.

[0106] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyethylene oxide.

[0107] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0108] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 55°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to produce filter paper base paper.

[0109] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 0.5% and the average diameter of the aramid nanofibers is 40 nm.

[0110] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 130° C., the pressure is 3 MPa, and the speed is 16 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0111] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0112] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 10 seconds, and then taken out for drying at a temperature of 120° C. for 8 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0113] Example 7

[0114] This embodiment illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 30 parts of mercerized pulp, 16 parts of aramid short fibers, 6 parts of polyester fibers, 3 parts of wet strength agent, 10 parts of aramid nanofibers, 1 part of dispersant, 6 parts of melamine formaldehyde resin, and 4 parts of acrylic emulsion.

[0115] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyacrylamide.

[0116] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0117] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 40°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0118] (2) The aramid nanofibers, dispersant and deionized water are compounded to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 2.0% and the average diameter of the aramid nanofibers is 100 nm.

[0119] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 180° C., the pressure is 1 MPa, and the speed is 20 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0120] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0121] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 110° C. for 15 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0122] Comparative Example 1

[0123] The flame retardant air filter paper was prepared by the same method as in Example 4, except that: no low temperature calendering operation was performed in this comparative example 1. The specific experiment is as follows:

[0124] This comparative example illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 30 parts of mercerized pulp, 18 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 8 parts of aramid nanofibers, 2 parts of dispersant, 4 parts of melamine formaldehyde resin, and 5 parts of acrylic emulsion.

[0125] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyacrylamide.

[0126] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0127] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0128] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 1.5% and the average diameter of the aramid nanofibers is 50 nm.

[0129] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base to obtain the filter paper base with the aramid nanofiber coating.

[0130] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0131] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 120° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0132] Comparative Example 2

[0133] The air filter paper was prepared by the same method as in Example 4, except that the aramid nanofibers were not coated in this comparative example 2. The specific experimental process is as follows:

[0134] This comparative example illustrates an air filter paper, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 30 parts of mercerized pulp, 18 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 4 parts of melamine formaldehyde resin, and 5 parts of acrylic emulsion.

[0135] The wet strength agent is polyamide epichlorohydrin.

[0136] A method for preparing a flame retardant air filter paper comprises the following steps:

[0137] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0138] (2) The filter paper base paper in step (1) is subjected to low-temperature calendering treatment by using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 120° C., the pressure is 4 MPa, and the speed is 12 m / min. Thus, the filter paper base paper after calendering treatment is obtained.

[0139] (3) Mix the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0140] (4) The calendered filter paper obtained in step (2) is placed in the impregnation solution obtained in step (3) for 15 seconds, and then taken out for drying at a temperature of 120° C. for 10 minutes. After drying, the air filter paper is obtained.

[0141] Comparative Example 3

[0142] The flame retardant air filter paper was prepared by the same method as in Example 4, except that the concentration of aramid nanofibers in the aramid nanofiber coating solution in this comparative example 3 was increased, and the mass fraction of aramid nanofibers in the aramid nanofiber coating solution in this comparative example 3 was 3.0%. The specific experimental process is as follows:

[0143] This comparative example illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 30 parts of mercerized pulp, 18 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 8 parts of aramid nanofibers, 2 parts of dispersant, 4 parts of melamine formaldehyde resin, and 5 parts of acrylic emulsion.

[0144] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyacrylamide.

[0145] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0146] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0147] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 3.0% and the average diameter of the aramid nanofibers is 50 nm.

[0148] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then low-temperature calendering treatment is performed using a roller hot press, wherein the calendering temperature of the low-temperature calendering treatment is 120° C., the pressure is 4 MPa, and the speed is 12 m / min. A filter paper base paper with an aramid nanofiber coating is obtained.

[0149] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0150] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 120° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0151] Comparative Example 4

[0152] The flame retardant air filter paper was prepared by the same method as in Example 4, except that the calendering pressure in this comparative example 4 was increased, and the calendering pressure in this comparative example 6 was 8 MPa. The specific experimental process is as follows:

[0153] This comparative example illustrates a flame retardant air filter paper containing aramid nanofiber coating, which is composed of the following raw materials in parts by weight: 40 parts of coniferous wood pulp, 30 parts of mercerized pulp, 18 parts of aramid short fibers, 8 parts of polyester fibers, 2 parts of wet strength agent, 8 parts of aramid nanofibers, 2 parts of dispersant, 4 parts of melamine formaldehyde resin, and 5 parts of acrylic emulsion.

[0154] The wet strength agent is polyamide epichlorohydrin; and the dispersant is polyacrylamide.

[0155] A method for preparing a flame-retardant air filter paper containing an aramid nanofiber coating comprises the following steps:

[0156] (1) Put the component softwood pulp and mercerized pulp into a Wall-E pulper for mixing and beating to 35°SR, then add the component aramid short-cut fiber, polyester fiber and wet strength agent for mixing and disintegrating to make filter paper base paper.

[0157] (2) The aramid nanofibers, dispersant and deionized water are mixed to prepare an aramid nanofiber coating solution, wherein the mass fraction of the aramid nanofibers in the coating solution is 1.5% and the average diameter of the aramid nanofibers is 50 nm.

[0158] (3) The aramid nanofiber coating liquid prepared in step (2) is evenly coated on the surface of the filter paper base paper, and then calendered using a roller hot press at a temperature of 120° C., a pressure of 8 MPa, and a speed of 12 m / min to obtain a filter paper base paper with an aramid nanofiber coating.

[0159] (4) Mixing the component amounts of melamine formaldehyde resin and acrylic emulsion to prepare an impregnation solution.

[0160] (5) The filter paper base paper with aramid nanofiber coating obtained in step (3) is immersed in the impregnation solution obtained in step (4) for 15 seconds, and then taken out for drying at a temperature of 120° C. for 10 minutes. After drying, the flame-retardant air filter paper with aramid nanofiber coating is obtained.

[0161] The air filter papers prepared in the above examples and comparative examples were subjected to performance tests, and the specific results are shown in Table 1. The specific test methods involved are:

[0162] The tensile index of air filter paper samples was tested according to GB / T 12914-2008 standard;

[0163] Test the bursting index of air filter paper samples according to GB / T454-2002 standard;

[0164] According to the test method for burning performance of flame-retardant paper and paperboard GB / T 14656-2009, the flame-retardant air filter paper samples were subjected to vertical burning test;

[0165] The average pore size of the filter paper samples was tested according to GB / T 2679.14-1996 standard;

[0166] Filtration efficiency tests were performed according to ISO 5011-2014.

[0167] Table 1 Air filter paper performance test data

[0168]

[0169] It can be seen from the data in Table 1 above that the air filter paper prepared by the preparation method of the present invention in Examples 1 to 7 exhibits higher mechanical strength and filtration efficiency as well as good flame retardant properties.

[0170] From the data comparison between Comparative Example 1 and Example 4, it can be seen that: if low-temperature calendering treatment is not performed, the performance of the air filter paper will be significantly reduced; in the preparation process of flame-retardant air filter paper containing aramid nanofiber coating, low-temperature calendering treatment can not only improve the mechanical strength of the filter paper, but also is beneficial to the improvement of the filtration efficiency and flame retardant properties of the air filter paper.

[0171] From the comparison of the data of Comparative Example 2 and Example 4, it can be seen that when the air filter paper does not contain the aramid nanofiber coating, the mechanical strength, filtration performance and flame retardant performance of the air filter paper are significantly reduced.

[0172] From the comparison of the data of Comparative Example 3 and Example 4, it can be seen that if the concentration of aramid nanofibers in the aramid nanofiber coating liquid is too high, the coating liquid will be relatively viscous, resulting in uneven coating on the paper surface, and various indicators of the filter paper will decrease to varying degrees. Therefore, the concentration conditions defined in the present invention are more conducive to obtaining flame-retardant air filter paper with excellent performance.

[0173] From the comparison of the data of Comparative Example 4 and Example 4, it can be seen that if the calendering pressure is too high, the structure and strength of the internal fibers of the filter paper will be damaged, cracks and wrinkles will easily appear on the surface of the filter paper, and the mechanical properties and filtering performance of the filter paper will be seriously affected. Therefore, the calendering conditions defined in the present invention are more conducive to obtaining flame-retardant air filter paper with excellent performance.

[0174] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0175] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for preparing a flame-retardant air filter paper containing aramid nanofiber coating, characterized in that: The flame retardant air filter paper is composed of the following components in parts by weight: 25-50 parts of softwood pulp, 22-40 parts of mercerized pulp, 14-24 parts of aramid short fibers, 5-10 parts of polyester fibers, 1-3 parts of wet strength agent, 8-16 parts of aramid nanofibers, 1-2 parts of dispersant, 4-7 parts of melamine formaldehyde resin, and 3-5 parts of acrylic emulsion; The preparation method is: S1. Preparation of filter paper base paper: The component softwood pulp and mercerized pulp are mixed and beaten to 25-55°SR, and then the component aramid short-cut fiber, polyester fiber and wet strength agent are added to mix and disperse to make filter paper base paper; S2. Coating of aramid nanofibers: The aramid nanofibers, dispersant and deionized water are compounded to prepare an aramid nanofiber coating liquid; the aramid nanofiber coating liquid is evenly coated on both sides of the filter paper base paper; the mass fraction of the aramid nanofibers in the aramid nanofiber coating liquid is 0.5-2.0%; S3, calendering treatment: The filter paper base coated with the aramid nanofiber coating liquid in step S2 is subjected to low-temperature calendering treatment to obtain a filter paper base with an aramid nanofiber coating; the calendering temperature of the low-temperature calendering treatment is 80-180° C. and the pressure is 1 MPa-6 MPa; S4, resin impregnation treatment: The component amounts of melamine formaldehyde resin and acrylic emulsion are mixed and compounded to prepare an impregnation liquid, the filter paper base paper with aramid nanofiber coating prepared in step S3 is placed in the impregnation liquid for impregnation treatment, and then dried to obtain the flame-retardant air filter paper, and the impregnation time is 10 to 20 seconds.

2. The method for preparing a flame-retardant air filter paper containing aramid nanofiber coating according to claim 1, characterized in that: The wet strength agent is polyamide epichlorohydrin.

3. The method for preparing a flame-retardant air filter paper containing aramid nanofiber coating according to claim 1, characterized in that: The dispersant is polyethylene oxide or polyacrylamide.

4. The method for preparing a flame-retardant air filter paper containing aramid nanofiber coating according to claim 1, characterized in that: The average diameter of the aramid nanofibers is 40-100 nm.

5. The method for preparing a flame-retardant air filter paper containing aramid nanofiber coating according to claim 1, characterized in that: In step S3, the vehicle speed is 5-20 m / min.

6. The method for preparing a flame-retardant air filter paper containing aramid nanofiber coating according to claim 5, characterized in that: In step S3, the calendering temperature of the low-temperature calendering treatment is 130-160° C., the pressure is 3 MPa-5 MPa, and the vehicle speed is 10-16 m / min.

7. The method for preparing a flame-retardant air filter paper containing aramid nanofiber coating according to claim 1, characterized in that: In step S4, the drying temperature is 100-120° C., and the drying time is 8-18 min.

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