Low-basis-weight para-aramid nanopaper for honeycomb preparation and manufacturing method of low-basis-weight para-aramid nanopaper
Through the mixed coating and hot pressing process of para-aramid nanofibers and chopped fibers and resin auxiliary materials, the problems of low paper formation rate and poor density in honeycomb preparation of low quantitative aramid paper are solved, and high-strength and dense surface aramid paper is achieved, which is suitable for aerospace and other fields.
Patent Information
- Application Number
- CN202510777750.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-11
- Publication Date
- 2025-08-15
AI Technical Summary
In the existing process of preparing para-aramid paper, there are problems such as low paper-forming rate, poor paper-forming density, uneven drying and easy cracks, and high energy consumption. It is especially difficult to achieve high strength and density in the honeycomb preparation of low-quantitative aramid paper.
The para-aramid nanofibers and chopped fibers are mixed with resin auxiliary materials, and the amount of macromolecular chain resin auxiliary materials and the film forming characteristics of the drying cylinder are controlled through coating, drying and hot pressing processes to prepare low-quantitative para-aramid nanopaper.
The high strength and surface density of low-quantitative paraposition aramid nanopaper are achieved, avoiding the problems of thin wet paper sheets, large differences between the two sides, and high energy consumption, and improving the performance of honeycomb materials.
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Figure BDA0005444833660000111
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of papermaking, and in particular relates to a low-weight para-aramid nanopaper for honeycomb preparation and a manufacturing method thereof. Background Art
[0002] The advantages of aramid paper honeycomb core materials are light weight, high strength, high modulus, strong structural stability, and sound insulation, heat insulation, and flame retardancy. They can be used as lightweight and high-strength structural materials in key areas such as aerospace, rail transportation, and national defense. Among them, honeycomb structural materials made from aviation-grade aramid paper-based materials can be used in antenna covers, radomes, wall panels, doors, floors, and other parts of civil aircraft, helicopters, transport aircraft, fighter jets, and other spacecraft, as high-rigidity, secondary load-bearing components of the aircraft. Aramid honeycomb, as the preferred core material for aircraft composite honeycomb sandwich structures, can reduce the structural mass of the aircraft while achieving functional components such as wave transmission, noise reduction, and heat insulation. Because the performance of para-aramid paper honeycombs is far superior to that of meta-aramid paper honeycombs, in recent years, the performance requirements for para-aramid honeycombs have also developed in the direction of lightweight and high strength, and low quantitative and high strength requirements have also been put forward for para-aramid paper-based materials.
[0003] There are two existing technologies for preparing para-aramid paper: papermaking using a mixture of para-chopped fibers and meta-precipitated fibers, and papermaking using a mixture of para-chopped fibers and para-aramid nanofibers. The existing technology for preparing aramid paper mainly adopts a wet papermaking mode, in which different pulps are mixed and then sizing and dewatering are performed to form wet paper sheets, which are then pressed, dried, rewound, and hot-pressed into shape. The forming methods in the existing technologies all have the disadvantages of large differences between the two sides of the paper sheet due to the loss of para-aramid nanofibers or meta-precipitated fibers during filtration, low paper yields, high energy consumption for recycling, and easy paper breakage during transfer of low-weight aramid paper sheets due to excessive thinness. The loss of nanofibers or precipitated fibers results in poor paper density. In the actual preparation process, cracks may occur due to the low weight and thickness of the paper sheets and uneven drying of the paper sheets.
[0004] Therefore, providing a low-weight para-aramid nanopaper with good overall performance becomes a problem to be solved. Summary of the Invention
[0005] In view of this, the technical problem to be solved by the present invention is to provide a low-weight para-aramid nanopaper for honeycomb preparation and a manufacturing method thereof. The para-aramid nanopaper provided by the present invention has a small weight, a dense surface, and the prepared honeycomb is impermeable to glue.
[0006] The present invention provides a method for manufacturing low-weight para-aramid nanopaper for honeycomb preparation, comprising the following steps:
[0007] preparing a mixed slurry of para-aramid nanofibers, para-aramid chopped fibers and resin auxiliary materials, wherein the resin auxiliary materials include a resin material and auxiliary materials, and the auxiliary materials are selected from one or more of carboxymethyl cellulose, polyacrylamide and cationic starch;
[0008] coating and drying the mixed slurry to obtain a paper sheet;
[0009] The paper sheets are rewound and hot-pressed to obtain low-weight para-aramid nanopaper.
[0010] Preferably, the added proportion of the resin auxiliary material is 0.05-1.00% of the absolute dry fiber mass percentage.
[0011] Preferably, the fiber diameter of the para-aramid nanofiber is 10 to 200 nm.
[0012] Preferably, the length of the para-aramid chopped fibers is 1 to 10 mm.
[0013] Preferably, the mass ratio of the para-aramid nanofibers to the para-aramid chopped fibers is 60-100:0-40.
[0014] Preferably, the resin material is selected from one or more of polyamide epichlorohydrin and polyethyleneimine.
[0015] Preferably, in the mixed slurry, the total mass concentration of the para-aramid nanofibers and the para-aramid chopped fibers is 0.05% to 0.5%.
[0016] Preferably, the coating and drying include:
[0017] Apply the mixed slurry onto the drying cylinder, and apply the second layer after the bottom layer is dried and dehydrated to have strength, and apply the slurry cumulatively in sequence;
[0018] After the coating reaches the required state, the paper sheet is peeled off at one time to obtain the paper sheet.
[0019] Preferably, the hot pressing pressure is 20-50 MPa, the hot pressing temperature is 260-400° C., and the number of hot pressing times is 1-2 times.
[0020] The present invention also provides a low-weight para-aramid nanopaper for honeycomb preparation obtained by the above-mentioned manufacturing method, wherein the weight range of the para-aramid nanopaper is 15 to 25 g / m 2 , thickness 0.005~0.025mm.
[0021] Compared to the prior art, the present invention provides a method for manufacturing low-weight para-aramid nanopaper for honeycomb production, comprising the following steps: preparing a mixed slurry of para-aramid nanofibers, para-aramid chopped fibers, and a resin auxiliary material, the resin auxiliary material comprising a resin material and an auxiliary material selected from one or more of carboxymethyl cellulose, polyacrylamide, and cationic starch; coating and drying the mixed slurry to obtain a paper sheet; and rewinding and hot-pressing the paper sheet to obtain the low-weight para-aramid nanopaper. The present invention fully utilizes the characteristics of para-aramid nanofibers: large specific surface area, strong bonding strength, homogeneous and uniform properties in an aqueous phase, and rapid drying and dehydration to form a film. Furthermore, the present invention utilizes a macromolecular chain resin auxiliary material to control the thinning process, resulting in a method for producing low-weight, high-performance para-aramid paper. This method avoids the problems encountered in conventional papermaking processes, such as excessively thin wet paper sheets, easy breakage, large differences between the two sides of the wet paper sheet, poor paper sheet density, high energy consumption for recycling, and cracking caused by excessive drying. The para-aramid paper prepared by this process has the characteristics of small basis weight, dense surface, and honeycomb-proof glue-proof. DETAILED DESCRIPTION
[0022] The present invention provides a method for manufacturing low-weight para-aramid nanopaper for honeycomb preparation, comprising the following steps:
[0023] preparing a mixed slurry of para-aramid nanofibers, para-aramid chopped fibers and a resin auxiliary material, wherein the auxiliary material is selected from one or more of carboxymethyl cellulose, polyacrylamide and cationic starch;
[0024] coating and drying the mixed slurry to obtain a paper sheet;
[0025] The paper sheets are rewound and hot-pressed to obtain low-weight para-aramid nanopaper.
[0026] In the present invention, the para-aramid short fibers are first treated, wherein the surface oil treatment scheme of the para-aramid short fibers is as follows: the para-aramid short fibers are pre-treated by washing with an aqueous solution of sodium dodecylbenzenesulfonate, the temperature of the washing pre-treatment of the para-aramid short fibers is 50°C to 60°C, the treatment time is 30min-40min, and then the fibers are washed with clean water, the pH is controlled to 7-8, and the fibers are dried for use.
[0027] During use, the para-aramid short-cut fibers that have been washed and pretreated are deflaked using a high-speed deflaker, so that the fiber bundles are fully dispersed into single fibers to form para-aramid short-cut fiber slurry. In the present invention, the deflaking is performed using water.
[0028] In the present invention, the length of the para-aramid short fibers is 1 to 10 mm, preferably 2 to 6 mm. If the length of the short fibers is less than 1 mm, the production becomes more difficult; if the length of the short fibers is greater than 10 mm, the fibers are prone to knotting, resulting in uneven pulp clumps during coating.
[0029] In the present invention, the para-aramid nanofiber can be a commercially available product or can be prepared by itself. Preferably, the preparation method of the para-aramid nanofiber includes the following steps:
[0030] (1) Modified polymerization:
[0031] Under nitrogen protection, the dehydrated solvent is added to a reaction vessel, a solubilizing salt and a surfactant are added under stirring, and the mixture is heated to 80-100° C. to dissolve the solubilizing salt and the surfactant to obtain a solution of the solubilizing salt and the surfactant. The heating time is 45-60 minutes, and the mixture is cooled in a cold water bath to 0-15° C. for 10 minutes. Paraphenylenediamine is added to the reaction vessel. After the paraphenylenediamine is dissolved, the reaction vessel is cooled to -15-0° C., and terephthaloyl chloride is added. The stirring speed is increased to 1000-2500 r / min, and the reaction is continued. The reaction time is 5-10 minutes, and the reaction temperature is -15-0° C. After the reaction system shows gelation, the stirring is stopped to obtain a jelly colloid. The molar concentration of p-phenylenediamine is 0.3-0.5 mol / L, the molar ratio of terephthaloyl chloride and p-phenylenediamine is (1.007-1.012):1; the mass ratio of the solubilizing salt and p-phenylenediamine is (0.25-2):1; the mass ratio of the surfactant and p-phenylenediamine is (0.25-2):1, the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide or hexamethylphosphoramide mixed in any proportion; the solubilizing salt is one or more of calcium chloride, lithium chloride or magnesium chloride mixed in any proportion. The surfactant is a polyoxyethylene ether nonionic surfactant having a molecular weight of 500 to 6000, and one or both end groups of the polymer are hydroxyl, amino, carboxyl, siloxy or methoxy, or a quaternary ammonium salt cationic surfactant, specifically hexadecyltrimethylammonium bromide or dodecyldimethylbenzylammonium chloride, or a heterocyclic cationic surfactant, specifically dodecylpyridinium chloride or octadecyl cationic alkyl imidazoline, or a polymeric cationic surfactant, specifically polyvinylpyridinium quaternary ammonium salt or cationic polyacrylamide;
[0032] (2) Dispersion into fibers:
[0033] A dispersant is added to the jelly of step (1) above, the amount of the dispersant added being 5 to 50 times the amount of the solvent used in step (1) above, so that the jelly is swollen, and the swollen jelly is stirred at high speed to form a homogeneous system at a stirring speed of 3000 to 5000 r / min for 5 minutes, and a coagulant is added to the homogeneous system under strong stirring to obtain a uniform and stable suspension containing para-aramid nanofibers, or the homogeneous system is injected into a high-speed stirring coagulation bath at a stirring speed of 4000 to 6000 r / min for 10 minutes to obtain a suspension containing para-aramid nanofibers. A uniform and stable suspension of 1000 t / m fibers, wherein the content of para-aramid nanofibers is 0.01 wt% to 1 wt%, and the uniform and stable suspension containing the para-aramid nanofibers is heated and concentrated at a temperature of 50 to 120° C. for 1 to 6 hours to obtain a high-concentration para-aramid nanofiber suspension; the dispersant is a mixture of one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide or hexamethylphosphoramide in any proportion; and the coagulant is a mixture of one or more of water, acetone, methanol, ethanol, propanol or butanol liquid alcohols in any proportion;
[0034] (3) Drying:
[0035] The high-concentration para-aramid nanofiber suspension in step (2) is dried to obtain para-aramid nanofibers. The drying method is any one of spray drying, vacuum dehydration drying or freeze drying.
[0036] In the present invention, the diameter of the para-aramid nanofiber is 10 to 200 nanometers.
[0037] In the present invention, the viscosity of the para-aramid nanofiber is 1.0-4.0 dL / g, and the preferred viscosity index is 2.0-3.0 dL / g.
[0038] In the present invention, the mass ratio of the para-aramid nanofibers to the para-aramid chopped fibers is 60-100%:0-40%, and can be 60%:40%, 65%:35%, 70%:30%, 75%:25%, 80%:20%, 85%:15%, 90%:10%, 95%:5%, 100%:0%, or any value between 60-100%:0-40%, preferably 75-95%:5-25%.
[0039] The pulp concentration of the para-aramid nanofibers and para-aramid chopped fibers in the mixed slurry is 0.05% to 0.5%, and can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between 0.05% and 0.5%, preferably 0.1% to 0.3%.
[0040] In the present invention, the slurry also includes a resin auxiliary material, and the resin auxiliary material includes a resin material and an auxiliary material, wherein the auxiliary material is selected from one or more of carboxymethyl cellulose, polyacrylamide, and cationic starch. The addition ratio of the resin auxiliary material accounts for 0.05 to 1.00% of the absolute dry fiber dosage, and can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any value between 0.05-1.00%, preferably 0.1% to 0.6%. In the present invention, it is preferred to pre-dilute the resin auxiliary material to a mass concentration of 0.05% to 0.5%, which can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between 0.05% and 0.5%.
[0041] The resin material is selected from one or more of polyamide epichlorohydrin and polyethyleneimine. The strength of the wet paper sheet is enhanced by adding the resin material. The added amount of the resin material accounts for 0.02% to 0.50% of the absolute dry fiber mass percentage, and can be 0.02%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any value between 0.02% and 0.50%.
[0042] In the present invention, the preparation method of the mixed slurry comprises the following steps:
[0043] The deoiled para-aramid short fibers are decomposed in an aqueous phase, and the decomposition concentration is controlled at 0.01% to 0.1%, which can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, or any value between 0.01% and 0.1%, and is set aside.
[0044] The para-aramid nanofibers are dispersed in an aqueous phase at a concentration of 0.1 to 1.0%, which may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or any value between 0.1 and 1.0%. After the dispersed slurry is evenly dispersed, it is passed through a desander and a pressure screen to remove impurities before use.
[0045] After the para-aramid nanofibers and the short-cut fibers are uniformly mixed in a slurry mixing kettle, the slurry concentration is adjusted to 0.05% to 0.5%.
[0046] Then, resin auxiliary materials are added to the slurry and mixed to obtain a mixed slurry.
[0047] Next, the mixed slurry is coated and dried to obtain a paper sheet. Specifically, the mixed slurry is evenly coated on the drying cylinder, and the second layer is applied after the bottom layer is dried and dehydrated to have strength, and the coating is cumulatively applied in sequence. After the coating is applied to the paper sheet to meet the requirements, it is peeled off at one time by a scraper. If the thickness of the first drying coating does not meet the requirements, the paper sheet can be used as the base layer and the coating can be continued on every two drying cans until it meets the product requirements. The drying cylinder is controlled to have a temperature of 105-300°C, which can be 105, 120, 150, 170, 200, 220, 250, 270, 300, or any value between 105-300°C, preferably 150-220°C. In the present invention, the heating method can be steam heating or electric heating. The rotational linear speed of the drying cylinder is 1-10m / min, which can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value between 1-10m / min.
[0048] After rewinding and hot pressing the paper sheets that meet the requirements, a low-quantity, high-strength para-aramid nanopaper is obtained. The present invention does not specifically limit the specific methods of rewinding and hot pressing, and the rewinding and hot pressing in the paper machine process known to those skilled in the art can be used. Among them, an electrostatic eliminator is set before curling to eliminate the influence of static electricity on the curling of the paper sheets. The pressure of the hot pressing is 20-50MPa, which can be 20, 25, 30, 35, 40, 45, 50, or any value between 20-50MPa. The temperature of the hot pressing is 260-400℃, which can be 260, 300, 320, 350, 370, 400, or any value between 260-400℃. The number of hot pressing times is 1-2 times. In some specific embodiments of the present invention, a roller hot press is used for hot pressing.
[0049] The present invention makes full use of the film-forming property of para-aramid nanofibers and can realize the industrial production of different low-weight aramid papers by controlling the dosage of macromolecular chain resin auxiliary materials, the film-forming temperature of the drying cylinder, and the gap and number of sizing and coating.
[0050] The present invention provides a solution for the low-quantity industrial operation of 1414 para-aramid paper. The process method of the present invention produces 1414 aramid paper with a dense surface that is impermeable to water, oil, and heat. It solves the problems of nodes and penetration in the preparation of aramid paper honeycombs, and can also improve the overall insulation performance and dimensional stability of the paper sheets. It has good application prospects in honeycomb and insulation component applications.
[0051] The present invention also provides a low-weight para-aramid nanopaper prepared by the above method, wherein the paper is 1414 para-aramid material and does not contain other fiber components; the weight range of the para-aramid nanopaper is 15-25g / m 2 , thickness 0.005-0.025mm.
[0052] The present invention fully utilizes the characteristics of para-aramid nanofibers, such as large specific surface area, strong bonding force, homogeneity in aqueous phase, and rapid drying and dehydration to form a film. It also develops a method for controlling the thinning process of the material by adding macromolecular chain auxiliary materials, and improves its overall performance by relying on chemical crosslinking or physical bonding, thereby obtaining a method for preparing low-quantity, high-performance para-aramid paper. This method avoids the problems encountered in conventional papermaking processes, such as excessively thin wet paper sheets, easy breakage, large differences between the two sides of the wet paper sheets, poor paper sheet density, high energy consumption for recycling and reuse, and easy cracking due to excessive drying. The para-aramid paper prepared by this process has the characteristics of low quantitative, dense surface, and honeycomb-proof glue production.
[0053] The present invention adopts the high-performance, low-weight 1414 para-aramid paper provided, which has broad application prospects and is of great significance for promoting the development of high-tech industries, improving the specifications and grades of products such as high-strength specialty paper, and promoting the development and application of related industries.
[0054] In order to further understand the present invention, the low-weight para-aramid nanopaper for honeycomb preparation and the manufacturing method thereof provided by the present invention are described below in conjunction with examples. The protection scope of the present invention is not limited by the following examples.
[0055] In the following examples and comparative examples, the preparation method of the para-aramid nanofibers used is as follows:
[0056] (1) Under nitrogen protection, 100 mL of dehydrated N-methylpyrrolidone (NMP) was added to a reaction vessel. 4.844 g of CaCl2, 1.157 g of LiCl, and 3 g of PEG-2000 (polyethylene glycol with a molecular weight of 2000) were added under stirring. The mixture was heated to 100°C to dissolve the solubilizing salt and surfactant to obtain a solution of the solubilizing salt and surfactant. The heating time was 45 minutes. The mixture was then cooled in a cold water bath to 15°C for about 10 minutes. 4.326 g of p-phenylenediamine (PPD) was added to the reaction vessel. After the p-phenylenediamine was dissolved, the reaction vessel was cooled to 0°C. Terephthaloyl chloride (TPC) was then added, and the stirring speed was increased to 2000 r / min. The reaction was continued for 5 minutes at 0°C. After the reaction system showed gelation, the stirring was stopped to obtain a jelly colloid.
[0057] (2) 1 L of dispersant N-methylpyrrolidone (NMP) was added to the above-mentioned jelly to swell the jelly, and the swollen jelly was stirred into a uniform system at a high speed of 3000 r / min for 5 min. The above-mentioned uniform system was injected into high-speed stirred water at a stirring speed of 4000 r / min for 10 min to obtain a uniform and stable suspension containing para-aramid nanofibers. The uniform and stable suspension containing para-aramid nanofibers was heated and concentrated at a heating temperature of 100° C. for 2 h to obtain a high-concentration (fiber content 10 wt%) para-aramid nanofiber suspension;
[0058] (3) The high-concentration (fiber content 10 wt%) para-aramid nanofiber suspension prepared in step (2) is spray-dried to obtain para-aramid nanofibers having a diameter of about 10 to 200 nanometers (average diameter 80 nm) and a length of 1 to 100 μm, with a high aspect ratio.
[0059] The para-aramid chopped fibers used in the following embodiments of the present invention are purchased from the market and have a specification of 1.5D.
[0060] In the present invention, unless otherwise specified, all percentages are by mass.
[0061] Example 1
[0062] A low-weight para-aramid nanopaper for honeycomb preparation, comprising para-aramid chopped fibers, para-aramid nanofibers, and other raw materials, wherein the chopped fibers are all 6 mm in length.
[0063] (1) Treatment of chopped fibers: The chopped fibers were treated with a volume-molar concentration of 1.2×10 -3 mol / L, a sodium dodecylbenzenesulfonate aqueous solution at a temperature of 60°C for washing pretreatment, the treatment time is 30 min, and then washed with clean water, and then the para-aramid short fibers are deflaked by a high-speed deflaker, and the deflaking concentration is 0.02% to prepare a para-aramid short fiber slurry.
[0064] (2) Nanofiber treatment: para-aramid nanofibers (average diameter 80 nm, viscosity 2.2 dL / g) were added to deionized water and stirred and dispersed, with the total concentration being 0.5%.
[0065] (3) The pulps of (1) and (2) are mixed and the chopped fibers and the nanofibers are mixed in a fiber mass ratio of 95%:5%, and the pulp concentration of the para-aramid nanofibers and chopped fibers is adjusted to 0.06%.
[0066] (4) Polyamide epichlorohydrin (0.1%) and carboxymethyl cellulose (0.1%) were added to the mixed slurry successively, with each pre-diluted to a concentration of 0.1%. The addition ratio of the two was 0.2% of the absolute dry fiber dosage.
[0067] (5) The drying cylinder is set at a temperature of 200°C and a rotation speed of 2 m / min. The initial coating thickness is 0.01 mm and the number of coatings is 4. After the paper sheet is dried, it can be transferred and wound to obtain the finished dry aramid paper.
[0068] (6) The paper sample prepared in (5) was preheated at high temperature and then calendered, and hot pressed on a hot press with a pressure of 40 MPa, a hot pressing temperature of 300 ° C, and two hot pressing times to obtain a composite aramid paper (quantity 24 g / m 2 ).
[0069] Example 2
[0070] A low-weight para-aramid nanopaper for honeycomb preparation, comprising para-aramid chopped fibers, para-aramid nanofibers, and other raw materials, wherein the chopped fibers are all 4 mm in length.
[0071] (1) Treatment of chopped fibers: The chopped fibers were treated with a volume-molar concentration of 1.2×10 -3 mol / L, a sodium dodecylbenzenesulfonate aqueous solution at a temperature of 60°C for washing pretreatment, the treatment time is 30 min, and then washed with clean water, and then the para-aramid short fibers are deflaked by a high-speed deflaker, and the deflaking concentration is 0.04% to prepare a para-aramid short fiber slurry.
[0072] (2) Nanofiber treatment: para-aramid nanofibers (average diameter 80 nm, viscosity 2.2 dL / g) were added to deionized water and stirred and dispersed, with the total concentration being 0.5%.
[0073] (3) The pulps of (1) and (2) are mixed and the chopped fibers and the nanofibers are mixed in a fiber mass ratio of 90%:10%, and the pulp concentration of the para-aramid nanofibers and chopped fibers is adjusted to 0.10%.
[0074] (4) Polyamide epichlorohydrin (0.15%) and polyacrylamide (0.15%) were added to the mixed slurry successively, with each pre-diluted to a concentration of 0.1%. The addition ratio of the two was 0.3% of the absolute dry fiber dosage.
[0075] (5) The drying cylinder temperature is set at 180°C and the rotation speed is 3 m / min. The initial coating thickness is 0.01 mm and the number of coatings is 3. After the paper sheet is dried, it can be transferred and wound to obtain the finished dry aramid paper.
[0076] (6) The paper sample prepared in (5) was preheated at high temperature and then calendered, and hot pressed on a hot press with the pressure controlled at 35 MPa, the hot pressing temperature at 320°C, and the hot pressing times once to obtain a composite aramid paper (quantity 22 g / m 2 ).
[0077] Example 3
[0078] A low-weight para-aramid nanopaper for honeycomb preparation, comprising para-aramid chopped fibers, para-aramid nanofibers, and other raw materials, wherein the chopped fibers are all 2 mm in length.
[0079] (1) Treatment of chopped fibers: The chopped fibers were treated with a volume-molar concentration of 1.2×10 -3 mol / L, a sodium dodecylbenzenesulfonate aqueous solution at a temperature of 60°C for washing pretreatment, the treatment time is 30 min, and then washed with clean water, and then the para-aramid short fibers are deflaked by a high-speed deflaker, and the deflaking concentration is 0.08% to prepare a para-aramid short fiber slurry.
[0080] (2) Nanofiber treatment: para-aramid nanofibers (average diameter 80 nm, viscosity 2.2 dL / g) were added to deionized water and stirred and dispersed, with the total concentration being 0.5%.
[0081] (3) The pulps of (1) and (2) are mixed and the chopped fibers and the nanofibers are mixed in a fiber mass ratio of 80%:20%, and the pulp concentration of the para-aramid nanofibers and chopped fibers is adjusted to 0.12%.
[0082] (4) Polyethyleneimine (0.2%) and cationic starch (0.3%) were added to the mixed slurry successively, with each pre-diluted to a concentration of 0.1%, and the addition ratio was 0.5% of the absolute dry fiber dosage.
[0083] (5) The drying cylinder temperature is set at 160°C and the rotation speed is 4 m / min. The initial coating thickness is 0.01 mm and the number of coatings is 2. After the paper sheet is dried, it can be transferred and wound to obtain the finished dry aramid paper.
[0084] (6) The paper sample prepared in (5) was preheated at high temperature and then calendered, and hot pressed on a hot press with the pressure controlled at 28 MPa, the hot pressing temperature at 280°C, and the hot pressing times once to obtain a composite aramid paper (quantity 18 g / m 2 ).
[0085] Example 4
[0086] A low-weight para-aramid nanopaper for honeycomb preparation, comprising para-aramid chopped fibers, para-aramid nanofibers, and other raw materials, wherein the chopped fibers are all 1 mm in length.
[0087] (1) Treatment of chopped fibers: The chopped fibers were treated with a volume-molar concentration of 1.2×10 -3 mol / L, a sodium dodecylbenzenesulfonate aqueous solution at a temperature of 60°C for washing pretreatment, the treatment time is 30 min, and then washed with clean water, and then the para-aramid short fibers are deflaked by a high-speed deflaker, and the deflaking concentration is 0.1% to prepare a para-aramid short fiber slurry.
[0088] (2) Nanofiber treatment: para-aramid nanofibers (average diameter 80 nm, viscosity 2.2 dL / g) were added to deionized water and stirred and dispersed, with the total concentration being 0.5%.
[0089] (3) The pulps of (1) and (2) are mixed and the chopped fibers and the nanofibers are mixed in a mass ratio of 70%:30%, and the pulp concentration of the para-aramid nanofibers and chopped fibers is adjusted to 0.30%.
[0090] (4) Polyethyleneimine (0.15%) and polyacrylamide (0.25%) were added to the mixed slurry in sequence, with a dilution concentration of 0.1% and an addition ratio of 0.4% of the absolute dry fiber dosage.
[0091] (5) The drying cylinder temperature is set at 230°C and the rotation speed is 6 m / min. The initial coating thickness is 0.01 mm and the number of coatings is 3. After the paper sheet is dried, it can be transferred and wound to obtain the finished dry aramid paper.
[0092] (6) The paper sample prepared in (5) was preheated at high temperature and then calendered, and hot pressed on a hot press with the pressure controlled at 25 MPa, the hot pressing temperature at 350°C, and the hot pressing times once to obtain a composite aramid paper (quantity 16 g / m 2 ).
[0093] Comparative Example 1
[0094] A low-weight para-aramid nanopaper for honeycomb preparation, comprising para-aramid chopped fibers, para-aramid nanofibers, and other raw materials, wherein the chopped fibers are all 2 mm in length.
[0095] (1) Treatment of chopped fibers: The chopped fibers were treated with a volume-molar concentration of 1.2×10 -3 mol / L, a sodium dodecylbenzenesulfonate aqueous solution at a temperature of 60°C for washing pretreatment, the treatment time is 30 min, and then washed with clean water, and then the para-aramid short fibers are deflaked by a high-speed deflaker, and the deflaking concentration is 0.08% to prepare a para-aramid short fiber slurry.
[0096] (2) Nanofiber treatment: para-aramid nanofibers (average diameter 80 nm, viscosity 2.2 dL / g) were added to deionized water and stirred and dispersed, with the total concentration being 0.5%.
[0097] (3) The pulps of (1) and (2) are mixed and the chopped fibers and the nanofibers are mixed in a fiber mass ratio of 80%:20%, and the pulp concentration of the para-aramid nanofibers and chopped fibers is adjusted to 0.12%.
[0098] (4) No resin auxiliary materials as described are added to the mixed slurry.
[0099] (5) The drying cylinder temperature is set at 160°C and the rotation speed is 4 m / min. The initial coating thickness is 0.01 mm and the number of coatings is 2. After the paper sheet is dried, it can be transferred and wound to obtain the finished dry aramid paper.
[0100] (6) The paper sample prepared in (5) was preheated at high temperature and then calendered, and hot pressed on a hot press with the pressure controlled at 28 MPa, the hot pressing temperature at 280°C, and the hot pressing times once to obtain a composite aramid paper (quantity 17 g / m 2 ).
[0101] The performance, air permeability, and permeability of the aramid paper samples of Examples 1-4 and Comparative Example 1 of the present invention were analyzed and tested using the following testing standards:
[0102] The paper sample basis weight shall be in accordance with GB T 451.2-2002 “Paper and board - Determination of basis weight”;
[0103] The thickness of paper samples shall comply with GB T 451.3-2002 “Paper and board - Determination of thickness”;
[0104] The tensile strength and elongation of paper samples are in accordance with GBT12914-2008 "Paper and board - Determination of tensile strength";
[0105] The tearing strength of paper samples adopts GB / T455-2002 "Determination of tearing strength of paper and board";
[0106] The air permeability is determined according to GBT 458-2008 “Paper and board - Determination of air permeability”;
[0107] The density of the paper sheet is verified by using clean water for permeability testing for 60 seconds. If there is no permeation, it is qualified.
[0108] Test results:
[0109] Table 1
[0110]
[0111] To verify the data after phenolic resin impregnation, paper strips were cut and compared. The specific process parameters were: using a phenolic resin solution with a solid content of 48%, scraping off excess adhesive on the surface with a rubber sheet, then hanging it to dry, repeating this process twice, and finally curing it in a 130-degree oven. After curing, the paper sample tensile strength, elongation, and tear strength test standards were used. The data was averaged and compared as follows:
[0112] Table 2
[0113] Base paper properties <![CDATA[Quantitative g / m 2 > Tear strength mN Tensile strength N / m Elongation% Example 3 18 435 620 0.5 Comparative Example 1 17 208 568 0.2 Post-immersion performance <![CDATA[Quantitative g / m 2 > Tear strength mN Tensile strength N / m Elongation% Example 3 25 1105 5358 0.4 Comparative Example 1 27 510 4356 0.1
[0114] By comparison, it can be seen that the paper sample prepared by the method of the present invention has better strength, tear resistance and elongation after being impregnated with phenolic resin, which can significantly improve the performance of the product.
[0115] From the comparison of the above test data, it can be seen that the various performance indicators of the low-quantity para-aramid nanopaper for honeycomb preparation prepared by the method of the present invention are excellent. In the comparative example, when the tensile strength index of the paper sheet was slightly reduced, the tear index and elongation dropped significantly, and the toughness of the paper sheet was reduced. In the present invention, full use is made of the characteristics of para-aramid nanofibers that can be quickly dried and dehydrated to form a film, and the problem of low tear strength and easy cracking after nano-molding is effectively solved, thereby successfully developing low-quantity, high-performance para-aramid paper. This method avoids the problems of easy paper breakage caused by thin wet paper sheets, large difference between the two sides of the page, poor density, high energy consumption of nano-recycling, etc. in the conventional papermaking process. The para-aramid paper prepared by this process has the characteristics of small quantity, dense surface, and non-sticky honeycomb, which meets the requirements for the development of para-aramid honeycomb performance towards light weight and high strength.
[0116] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.
Claims
1. A method for manufacturing low-weight para-aramid nanopaper for honeycomb preparation, characterized in that: The following steps are involved: preparing a mixed slurry of para-aramid nanofibers, para-aramid chopped fibers and resin auxiliary materials, wherein the resin auxiliary materials include a resin material and auxiliary materials, and the auxiliary materials are selected from one or more of carboxymethyl cellulose, polyacrylamide and cationic starch; coating and drying the mixed slurry to obtain a paper sheet; The paper sheets are rewound and hot-pressed to obtain low-weight para-aramid nanopaper.
2. The manufacturing method according to claim 1, characterized in that The added proportion of the resin auxiliary material accounts for 0.05-1.00% of the mass percentage of the absolute dry fiber.
3. The manufacturing method according to claim 1, characterized in that The fiber diameter of the para-aramid nanofiber is 10 to 200 nm.
4. The manufacturing method according to claim 1, characterized in that The length of the para-aramid chopped fibers is 1 to 10 mm.
5. The manufacturing method according to claim 1, characterized in that The mass ratio of the para-aramid nanofiber to the para-aramid chopped fibers is 60-100:0-40.
6. The manufacturing method according to claim 1, characterized in that The resin material is selected from one or more of polyamide epichlorohydrin and polyethyleneimine.
7. The manufacturing method according to claim 1, characterized in that In the mixed slurry, the total mass concentration of the para-aramid nanofibers and the para-aramid chopped fibers is 0.05% to 0.5%.
8. The manufacturing method according to claim 1, characterized in that The coating and drying include: Apply the mixed slurry onto the drying cylinder, and apply the second layer after the bottom layer is dried and dehydrated to have strength, and apply the slurry cumulatively in sequence; After the coating reaches the required state, the paper sheet is peeled off at one time to obtain the paper sheet.
9. The manufacturing method according to claim 1, characterized in that The hot pressing pressure is 20-50 MPa, the hot pressing temperature is 260-400° C., and the number of hot pressing times is 1-2 times.
10. A low-weight para-aramid nanopaper for honeycomb preparation prepared by the manufacturing method according to any one of claims 1 to 9, characterized in that: The quantitative range of the para-aramid nanopaper is 15 to 25 g / m 2 , thickness 0.005~0.025mm.