CN108824067B - Para-aramid paper and preparation method thereof - Google Patents
Para-aramid paper and preparation method thereof Download PDFInfo
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- CN108824067B CN108824067B CN201810562334.6A CN201810562334A CN108824067B CN 108824067 B CN108824067 B CN 108824067B CN 201810562334 A CN201810562334 A CN 201810562334A CN 108824067 B CN108824067 B CN 108824067B
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
- D21H13/10—Organic non-cellulose fibres
- D21H13/20—Organic non-cellulose fibres from macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- D21H13/26—Polyamides; Polyimides
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Abstract
The invention provides a preparation method of para-aramid paper, which comprises the following steps: carrying out net surfing molding on the para-aramid nano-fiber feed liquid to obtain wet paper; carrying out multi-stage buffer squeezing dehydration on the wet paper to obtain dehydrated wet paper; sequentially carrying out multistage low-temperature drying and tension-assisted drying on the dehydrated wet paper for drying and forming to obtain para-aramid paper; the method for forming the upper net comprises the following steps: sizing para-aramid nano-fiber feed liquid, filtering water, and forming a wet paper blank on the surface of a forming net; and (3) performing vacuum suction on the lower surface of the wet paper blank, and performing bidirectional dehydration by using an upper top net former to perform dehydration combination on the upper surface of the wet paper blank to obtain wet paper. The aramid paper with good uniformity and excellent mechanical property and insulating property can be prepared by adopting a special net-feeding forming process, a multi-stage buffer squeezing process, a multi-stage low-temperature drying process and a tension auxiliary drying process. The invention also provides para-aramid paper.
Description
Technical Field
The invention relates to the technical field of film materials, in particular to para-aramid paper and a preparation method thereof.
Background
Para-aramid paper (PAP) is a high-performance special film material, has the advantages of high strength and modulus, excellent dimensional stability, excellent electrical insulating property, chemical corrosion resistance, light weight and the like, and can be used as a structural material, an insulating material, a wave-transmitting and filtering material and the like to be widely applied to industries such as aerospace, military equipment, electronic and electrical appliances and the like.
The raw materials currently used for preparing PAP are mainly para-aramid staple fiber, pulp or fibrids, and sometimes meta-aramid or other thermoplastic resins are added as reinforcing agents. The papermaking process is also complex, the fibers are generally required to be beaten into slurry through a special process, and the dispersing agent is required to be added to improve the dispersibility and stability of the slurry. Even so, it is difficult to prepare PAP with stable properties. Because the PAP thickness is generally tens of microns (partial PAP thickness for special use is more than 100 microns), and the diameter of the para-aramid short fiber is about 10 microns, the main structure size of the pulp and the fibrid is also from hundreds of nanometers to several microns, once the pulp is dispersed unevenly, the PAP is easily uneven, and further the PAP performance is unstable. In addition, the addition of meta-aramid fibers and dispersing aids also worsens the PAP performance. Meta-aramid has a large hygroscopicity, which causes a decrease in dimensional stability under PAP high humidity, and is difficult to meet the requirements of high-precision products. The addition of the dispersant is not favorable for the dielectric property of PAP on one hand, and can generate a large amount of wastewater on the other hand, thereby polluting the environment or increasing the production cost.
In addition, the problems of difficult dehydration, low wet strength of the prepared wet paper, large size shrinkage in the drying process and the like exist in the process of adopting the all-nanofiber paper making, and the performance of the prepared para-aramid paper is seriously influenced. Therefore, the development of a high-performance PAP preparation process is a problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, the present invention provides a para-aramid paper and a preparation method thereof, and the preparation method of the para-aramid paper provided by the present invention is simple in process, and the prepared para-aramid paper is excellent in mechanical and electrical properties.
The invention provides a preparation method of para-aramid paper, which comprises the following steps:
carrying out net surfing molding on the para-aramid nano-fiber feed liquid to obtain wet paper;
carrying out multi-stage buffer squeezing dehydration treatment on the wet paper to obtain dehydrated wet paper;
and drying and press polishing the dehydrated wet paper to obtain the para-aramid paper.
In the invention, the diameter of the para-aramid nano-fiber in the para-aramid nano-fiber material liquid is preferably 10-100 nm, more preferably 20-80 nm, more preferably 30-70 nm, and most preferably 40-60 nm; the length of the para-aramid nano-fiber in the para-aramid nano-fiber feed liquid is preferably 100nm to 1000 μm, more preferably 500nm to 800 μm, more preferably 800nm to 600 μm, and most preferably 1 μm to 500 μm.
In the invention, the solvent in the para-aramid nanofiber solution is preferably water, and more preferably deionized water. In the invention, the mass concentration of the aramid nanofiber feed liquid is preferably 0.5-2.5%, more preferably 1-2%, and most preferably 1.5%.
The preparation method of the para-aramid nano-fiber feed liquid is not particularly limited, and the para-aramid nano-fiber feed liquid is prepared by a method well known by the technical personnel in the field. In the invention, the preparation method of the para-aramid nanofiber solution is preferably as follows:
under the action of chloride and polyethylene glycol, performing polycondensation reaction on p-phenylenediamine and paraphthaloyl chloride in N-methylpyrrolidone to obtain a reaction product;
mixing the reaction product with a solvent and then crushing to obtain a mixed system;
and mixing the mixed system with water and stirring to obtain the para-aramid nano-fiber feed liquid.
In the present invention, the polycondensation reaction is preferably carried out under the protection of a protective gas such as nitrogen.
In the invention, the chloride is preferably one or more of calcium chloride, lithium chloride and magnesium chloride; the number average molecular weight of the polyethylene glycol is preferably 2000-2500, and more preferably 2100-2200. In the invention, the mass ratio of the chloride to the polyethylene glycol is preferably (1-3): 1, more preferably (1.5 to 2.5): 1, most preferably 2: 1. In the invention, the chloride and the polyethylene glycol can reduce fiber flocculation and improve molecular activity.
In the present invention, it is preferable that the chloride and the polyethylene glycol are mixed and dissolved first, then the p-phenylenediamine is added to the obtained solution, and after the p-phenylenediamine is dissolved, the terephthaloyl chloride is added to carry out the polycondensation reaction. In the invention, the mixing and dissolving temperature is preferably 80-120 ℃, more preferably 90-110 ℃, and most preferably 100 ℃.
In the present invention, the polycondensation reaction is preferably carried out in an ice-water bath, maintaining the temperature of the reaction system at not more than 70 ℃. In the present invention, the polycondensation reaction is preferably carried out under stirring conditions, and the stirring speed is preferably 1500 to 2500r/min, more preferably 1800 to 2200r/min, and most preferably 2000 r/min.
In the invention, the polycondensation reaction is carried out until the reaction system forms a jelly and the Wessenberg effect appears, and the reaction product is obtained. In the present invention, the temperature of the polycondensation reaction is preferably-15 to 0 ℃, more preferably-10 to-5 ℃.
In the invention, the mass-to-volume ratio of the reaction product to the solvent is preferably 1g (35-45) mL, more preferably 1g (38-42) mL, and most preferably 1g: 40 mL. In the present invention, the solvent is preferably N-methylpyrrolidone or methanol.
In the invention, the crushing equipment is preferably a tissue crusher, and the crushing time is preferably 4-6 min, and more preferably 5 min.
In the invention, the equipment for mixing and stirring the mixing system and water is preferably a tissue pulverizer, and the stirring time is preferably 8-12 min, and more preferably 10 min. In the present invention, the water is preferably deionized water.
In the invention, after the para-aramid nano-fiber feed liquid is obtained, the para-aramid nano-fiber feed liquid is preferably repeatedly washed to remove impurities in the para-aramid nano-fiber feed liquid; the washing apparatus is preferably a high speed centrifuge or a continuous countercurrent belt washer.
The para-aramid paper is prepared by preferably adopting the para-aramid nano-fiber feed liquid prepared by the special process, the diameter of the para-aramid nano-fiber feed liquid is less than 100nm, beating is not needed in the process of preparing the para-aramid paper by adopting the nano-fiber feed liquid, a dispersing agent is not needed to be added, and the prepared para-aramid paper has good uniformity and excellent mechanical property and insulating property; the preparation method has simple process, and the obtained para-aramid paper has good performance.
In the invention, the upper wire forming is preferably formed by spraying or coating para-aramid nano-fiber feed liquid on the upper wire by adopting an inclined wire forming or long wire forming technology; the forming apparatus is preferably a wire former or fourdrinier former. In the invention, the aperture of the forming net adopted by the upper net forming is preferably 100-300 meshes, more preferably 150-250 meshes, and most preferably 200 meshes, so as to avoid the para-aramid nano-fiber feed liquid from leaking from the meshes. In the present invention, the method of forming the upper wire is preferably:
sizing the para-aramid nano-fiber feed liquid, filtering water, and forming a wet paper blank on the surface of a forming net;
and performing vacuum suction on the lower surface of the wet paper blank, and performing bidirectional dehydration by adopting a mode of combining dehydration of an upper top net former on the upper surface of the wet paper blank to obtain wet paper.
In the invention, the sizing is preferably performed by using warm water sizing; the temperature of the warm water sizing is preferably 40-60 ℃. In the present invention, the draining time is preferably 20 to 30 seconds, more preferably 22 to 28 seconds, and most preferably 24 to 26 seconds. According to the invention, warm water sizing is adopted during forming of the pulp, so that agglomeration among fibers can be reduced, the water filtering efficiency is improved, the water filtering time is reduced to 20-30 s from 3-5 min, the length of a net part is greatly shortened, and the problem of low speed of papermaking of the full-nano para-aramid fibers is solved.
In the present invention, the degree of vacuum of the vacuum suction is preferably-0.01 to-0.1 MPa, more preferably-0.02 to-0.09 MPa, and most preferably-0.03 to-0.06 MPa. In the invention, the lower surface of the wet paper blank is preferably dewatered by vacuum suction firstly and then dewatered by the upper top net former, and the dewatering method provided by the invention combines the vacuum suction and the dewatering of the upper top net former, thereby realizing the bidirectional dewatering of the wet paper blank. In the present invention, the degree of vacuum of the vacuum suction dewatering is preferably gradually increased as the dryness of the wet paper web increases; preferably, the vacuum applied during the vacuum application increases from-0.01 MPa to-0.1 MPa as the dryness of the wet embryonic web increases from 3% to 5%.
In the present invention, the dryness of the wet paper sheet obtained after the dewatering by the upper wire former is preferably 8 to 10%, more preferably 8.5 to 9.5%, and most preferably 9%.
The para-aramid paper is prepared by adopting the special wire-feeding forming process, the wire-feeding forming process adopts a dehydration mode combining bottom vacuum suction and top former dehydration, and preferably adopts a dehydration mode combining step-by-step vacuum suction (namely, a mode of gradually increasing the vacuum degree of the vacuum suction along with the increase of the dryness of the wet paper blank) and top wire former dehydration, so that the fiber lap joint of the formed paper can be tight, and the prepared para-aramid paper has better mechanical property and electrical insulating property.
In the present invention, the wet paper is preferably separated from the forming wire by vacuum suction transfer because of its low strength. The invention adopts multi-stage buffer squeezing dehydration to carry out dehydration treatment on the wet paper, and the method can effectively reduce the water content and improve the wet strength of the dehydrated wet paper. In the present invention, the multistage buffering press dewatering is to gradually increase the press dewatering pressure with the increase of the dryness of the dewatered wet paper, and the number of press stages of the multistage buffering press dewatering refers to the number of press pressure increases. In the invention, the pressing stage number of the multi-stage buffer pressing dehydration is preferably 2-5, more preferably 3-5, and most preferably 4-5. In the present invention, it is preferable that the press pressure of the multi-stage buffer press dewatering is increased from 0.05MPa to 0.35MPa in a gradient of 0.05MPa as the dryness of the dewatered wet paper sheet is increased from 10% to 15%.
In the invention, the multi-stage buffer press dehydration is preferably vacuum press dehydration, and the vacuum degree of the vacuum press dehydration is preferably-20 to-40 KPa, more preferably-25 to-35 KPa, and most preferably-30 KPa. In the invention, the high-pressure water pressure for cleaning the coarse cotton cloth in the multi-stage buffer pressing dehydration process is preferably 1.5-2.5 MPa, more preferably 1.8-2.2 MPa, and most preferably 2 MPa.
In the invention, the drying is multistage low-temperature drying and tension auxiliary drying, preferably, the multistage low-temperature drying process is adopted to dry the paper firstly, then the paper is shaped, and the tension auxiliary drying process is adopted to further dry the paper when the paper is shaped. The special drying process combining multistage low-temperature drying and tension-assisted drying can be used for drying paper better, large size shrinkage in the drying process is avoided, and the prepared para-aramid paper has good uniformity, mechanical properties and electrical properties.
In the invention, the multistage low-temperature drying refers to gradually increasing the drying temperature along with the increase of the dryness of the paper, and the stage number of the multistage low-temperature drying refers to the number of times of increasing the drying temperature. In the invention, the number of stages of the multistage low-temperature drying is preferably 6-10 stages, more preferably 7-10 stages, and most preferably 9-10 stages. In the invention, the multistage low-temperature drying method is preferably steam drying, heat transfer oil heating multi-group drying cylinder drying or electromagnetic heating roller drying. In the present invention, it is preferable to gradually increase the drying temperature from 60 ℃ to 120 ℃ as the paper dryness increases from 12% to 30%.
In the invention, preferably, the paper is shaped after the paper dryness reaches 30%, and tension-assisted drying is adopted during the paper shaping, wherein the tension-assisted drying is preferably to adopt a tensioning device to stretch and shape the paper and simultaneously heat and dry the paper, so that the problems of wrinkling and shrinkage of the paper are avoided. In the invention, the tension device is preferably a dry net with large tension, and the tension of the tension auxiliary drying is preferably 4-10 KN/m, more preferably 6-9 KN/m, and most preferably 6.5-8 KN/m. In the present invention, the method of heating and drying is preferably direct heating using a large-roll-diameter drying cylinder. In the invention, the temperature of the tension auxiliary drying is preferably 120-160 ℃, more preferably 130-150 ℃, and most preferably 135-145 ℃. In the invention, the time for the tension-assisted drying is preferably 0.5-15 min, more preferably 1-10 min, more preferably 2-8 min, and most preferably 3-6 min.
The calendering method is not particularly limited by the invention, and the conventional calendering technical scheme adopted when preparing the para-aramid paper, which is well known to those skilled in the art, can be adopted.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other examples, which may be modified or appreciated by those of ordinary skill in the art based on the examples given herein, are intended to be within the scope of the present invention.
Testing the tensile strength and the elongation of the para-aramid paper prepared by the invention by using GB/T12914-1991 Standard of determination of tensile strength of paper and paperboard (constant-speed stretching method); adopting IEC 60819-2: 2001 "non-cellulosic paper for electricians part 2: test method' tests the tearing strength of the para-aramid paper prepared by the invention.
GB/T1408.1-2006 insulating material electrical strength test method part 1 is adopted: and testing under power frequency according to the standard, and detecting the electrical insulation performance of the para-aramid paper prepared by the invention.
The para-aramid nanofiber suspension used in the following examples of the present invention was prepared as follows:
to a 300mL reactor, 100mL of N-methylpyrrolidone (NMP) was added, and 10g of CaCl was added with stirring under nitrogen2And 5g of polyethylene glycol (PEG) having a molecular weight of 2100, which are dissolved by heating to 100 ℃. To be treated with CaCl2After the PEG is completely dissolved, cooling the dissolved solution system to 15 ℃ by using an ice water bath, adding 4.326g of p-phenylenediamine (PPD) for dissolving, adding 8.178g of terephthaloyl chloride (TPC) after the PPD is completely dissolved, stirring at a high speed (2000r/min) for carrying out polycondensation reaction, keeping the ice water bath in the polymerization process, and keeping the temperature of the system not to exceed 70 ℃; stopping stirring when the polycondensation reaction is carried out until the system forms a colloid and the Wessenberg effect appears, and removingRemoving ice water bath, taking out 5g of jelly, adding 200mL of NMP, rapidly stirring with a tissue pulverizer for 5min to break the swelled jelly, and forming a uniform and stable mixed system in NMP. Adding 200mL of water into the mixed system, and quickly stirring for 10min by using a tissue crusher to obtain uniform and stable film-forming suspension; in order to remove NMP and CaCl from the suspension2And PEG and other impurities, repeatedly washing the suspension with water by using a continuous countercurrent belt washing machine, and finally dispersing the suspension into uniform slurry by using deionized water to obtain the para-aramid nano-fiber suspension with the mass concentration of 0.5%, wherein the diameter of the para-aramid nano-fiber is about 20nm, and the average length is about 100 mu m.
Example 1
Spraying the para-aramid nano-fiber suspension onto an inclined wire under high pressure by using an inclined wire former inclined wire forming technology for forming, wherein the mesh number of the forming wire is 100 meshes, and performing bidirectional dehydration on a coating sprayed onto the inclined wire by adopting a dehydration mode combining lower vacuum suction dehydration and upper net former dehydration in the forming process; in the vacuum suction dewatering process, as the dryness of the wet paper blank is increased from 3 percent to 5 percent, the vacuum degree of vacuum suction is increased from-0.06 MPa to-0.1 MPa, and the wet paper is obtained.
And stripping the formed wet paper from the forming net by using a vacuum adsorption transfer method, and then carrying out vacuum press dehydration, wherein in the vacuum press dehydration process, as the dryness of the wet paper is increased to 10%, the pressure of the vacuum press dehydration is sequentially increased from 0.15MPa, 0.20MPa, 0.25MPa and 0.30MPa (4-level buffer vacuum press dehydration), the vacuum degree of the vacuum press dehydration is-20 KPa, and the high-pressure water pressure for cleaning the coarse cotton cloth in the vacuum press dehydration process is 1.5 MPa.
Drying the dewatered paper by 8-level steam, increasing the drying temperature from 80 ℃ to 120 ℃ along with the increase of the dryness of the dewatered paper, then carrying out heat setting on the paper under the stretching action of a tension device with the tension of 7.5kN/m, wherein the heat setting temperature is 130 ℃ for 6min, and finally carrying out calendaring forming to obtain the para-aramid paper.
The thickness of the para-aramid paper prepared in the embodiment 1 of the invention is 50 μm. The performance of the alloy is tested according to the method, and the test result is that the tensile strength is 60MPa, and the elongation is 1.7%; the tearing strength is 800 mN; the electrical insulation performance was 95 kV/mm.
Example 2:
spraying the para-aramid nano-fiber suspension onto an inclined wire under high pressure by using an inclined wire former inclined wire forming technology for forming, wherein the mesh number of the forming wire is 100 meshes, and performing bidirectional dehydration on a coating sprayed onto the inclined wire by adopting a dehydration mode combining lower vacuum suction dehydration and upper net former dehydration in the forming process; in the vacuum suction dewatering process, the vacuum degree of the vacuum suction dewatering is increased from-0.01 MPa to-0.05 MPa along with the increase of the dryness of the wet paper blank from 3 percent to 5 percent, and the wet paper is obtained.
And stripping the formed wet paper from the forming net by using a vacuum adsorption transfer method, and then carrying out vacuum press dehydration, wherein in the vacuum press dehydration process, the vacuum press dehydration pressure is increased from 0.15MPa, 0.20MPa, 0.25MPa and 0.30MPa in sequence (4-level buffer vacuum press dehydration) along with the increase of the dryness of the wet paper to 15 percent, the vacuum degree of the vacuum press dehydration is-40 KPa, and the high-pressure water pressure for cleaning the coarse cotton cloth in the vacuum press dehydration process is 2.5 MPa.
And (3) drying the dewatered paper by 8-grade steam, increasing the drying temperature from 80 ℃ to 120 ℃ along with the increase of the dryness of the dewatered paper, then carrying out heat setting on the paper under the stretching action of a tension device with the tension of 7.5kN/m, wherein the heat setting temperature is 130 ℃ for 6min, and finally carrying out calendaring molding to obtain the para-aramid paper.
The thickness of the para-aramid paper prepared in the embodiment 2 of the invention is 80 μm. The performance of the alloy is tested according to the method, and the test result is that the tensile strength is 120MPa, and the elongation is 1.7%; the tearability is 1400 mN; the electrical insulation performance was 85 kV/mm.
Example 3:
spraying the para-aramid nano-fiber suspension onto an inclined wire under high pressure by using an inclined wire former inclined wire forming technology for forming, wherein the mesh number of the forming wire is 100 meshes, and performing bidirectional dehydration on a coating sprayed onto the inclined wire by adopting a dehydration mode combining lower vacuum suction dehydration and upper net jacking forming dehydration in the forming process; in the vacuum suction dewatering process, the vacuum degree of the vacuum suction dewatering is increased from-0.01 MPa to-0.05 MPa along with the increase of the dryness of the wet paper blank from 3 percent to 5 percent, and the wet paper is obtained.
And stripping the formed wet paper from the forming net by using a vacuum adsorption transfer method, and then carrying out vacuum press dehydration, wherein in the vacuum press dehydration process, as the dryness of the wet paper is increased to 12%, the pressure of the vacuum press dehydration is sequentially increased from 0.20MPa, 0.25MPa, 0.30MPa and 0.35MPa (4-level buffer vacuum press dehydration), the vacuum degree of the vacuum press dehydration is-30 KPa, and the high-pressure water pressure for cleaning the coarse cotton cloth in the vacuum press dehydration process is 2 MPa.
And (2) drying the dewatered paper by 8-grade steam, increasing the drying temperature from 100 ℃ to 120 ℃ along with the increase of the dryness of the dewatered paper, then carrying out heat setting on the paper under the stretching action of a tension device with the tension of 7kN/m, wherein the heat setting temperature is 140 ℃ for 9min, and finally carrying out calendaring molding to obtain the para-aramid paper.
The thickness of the para-aramid paper prepared in the embodiment 3 of the invention is 120 μm. The performance of the alloy is tested according to the method, and the test result is that the tensile strength is 110MPa, and the elongation is 1.5%; the tearability is 2000 mN; the electrical insulation performance was 70 kV/mm.
Example 4:
spraying the para-aramid nano-fiber suspension onto an inclined wire under high pressure by using an inclined wire former inclined wire forming technology for forming, wherein the mesh number of the forming wire is 100 meshes, and performing bidirectional dehydration on a coating sprayed onto the inclined wire by adopting a dehydration mode combining lower vacuum suction dehydration and upper net former dehydration in the forming process; in the vacuum suction dewatering process, the vacuum degree of vacuum suction is increased from-0.01 MPa to-0.05 MPa along with the increase of the dryness of the wet paper blank from 3 percent to 5 percent, and the wet paper is obtained.
And stripping the formed wet paper from the forming net by using a vacuum adsorption transfer method, and then carrying out vacuum press dehydration, wherein in the vacuum press dehydration process, as the dryness of the wet paper is increased to 13%, the pressure of the vacuum press dehydration is sequentially increased from 0.15MPa, 0.20MPa, 0.25MPa and 0.30MPa (4-level buffer vacuum press dehydration), the vacuum degree of the vacuum press dehydration is-35 KPa, and the high-pressure water pressure for cleaning the coarse cotton cloth in the vacuum press dehydration process is 2.2 MPa.
And (3) drying the dewatered paper by 8 steam, increasing the drying temperature from 100 ℃ to 120 ℃ along with the increase of the dryness of the dewatered paper, then carrying out heat setting on the paper under the stretching action of a tension device with the tension of 7kN/m, wherein the heat setting temperature is 140 ℃ for 12min, and finally carrying out calendaring molding to obtain the para-aramid paper.
The thickness of the para-aramid paper prepared in the embodiment 4 of the invention is 200 μm. The performance of the alloy is tested according to the method, and the test result is that the tensile strength is 150MPa, and the elongation is 1.5%; the electric insulation performance of the tear strength of 2000mN is 60 kV/mm.
Comparative example 1
Adopts the aramid paper sold in the market, Nicotiana Cishi Dada YT 836.
The para-aramid paper of comparative example 1 of the present invention was tested for properties according to the above method, and as a result, the tensile strength was 45 MPa; elongation of 2.0%; the tearability is 1200 mN; the electrical insulation performance was 16 kV/mm.
Comparative example 2
The para-aramid paper is prepared according to the method of the example 1, and the difference of the para-aramid paper from the example 1 is that the upper net forming method is to directly spray para-aramid nano-fiber feed liquid onto an inclined net for forming under high pressure, and only an upper net former is used for dewatering.
The thickness of the para-aramid paper prepared in comparative example 2 of the present invention was 50 μm; the performance of the para-aramid paper prepared in comparative example 2 of the present invention was tested according to the above method, and the test result was that the tensile strength was 45 MPa; elongation of 1.5%; the tearability is 750 mN; the electrical insulation performance was 60 kV/mm.
Comparative example 3
The para-aramid paper is prepared according to the method of the example 1, and the difference of the para-aramid paper from the example 1 is that the upper wire forming method is to directly spray para-aramid nano-fiber feed liquid onto an inclined wire under high pressure for forming, and only lower vacuum suction dehydration is carried out.
The thickness of the para-aramid paper prepared in comparative example 3 of the present invention was 50 μm; the para-aramid paper prepared in comparative example 3 of the present invention was tested for properties according to the above method, and the test result was that the tensile strength was 40 MPa; elongation of 1.4%; the tearability is 600 mN; the electrical insulation performance was 40 kV/mm.
From the above embodiments, the present invention provides a method for preparing para-aramid paper, including: carrying out net surfing molding on the para-aramid nano-fiber feed liquid to obtain wet paper; carrying out multi-stage buffer squeezing dehydration on the wet paper to obtain dehydrated wet paper; sequentially carrying out a multistage low-temperature drying process and a tension auxiliary drying process on the dehydrated wet paper for drying and forming to obtain para-aramid paper; the method for forming the upper net comprises the following steps: sizing the para-aramid nano-fiber feed liquid, filtering water, and forming a wet paper blank on the surface of a forming net; and carrying out vacuum suction dehydration on the lower surface of the wet paper blank, and then carrying out bidirectional dehydration on the upper surface of the wet paper blank by using an upper top net former in a dehydration-water combination mode to obtain wet paper. The aramid paper with good uniformity and excellent mechanical property and insulating property can be prepared by adopting a special net-feeding forming process, a multi-stage buffer squeezing process, a multi-stage low-temperature drying process and a tension auxiliary drying process.
While only the preferred embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (6)
1. A preparation method of para-aramid paper comprises the following steps:
carrying out net surfing molding on the para-aramid nano-fiber feed liquid to obtain wet paper;
carrying out multi-stage buffer squeezing dehydration treatment on the wet paper to obtain dehydrated wet paper;
drying and press polishing the dehydrated wet paper to obtain para-aramid paper;
the drying is multi-stage low-temperature drying and tension auxiliary drying;
the method for forming the upper net comprises the following steps:
sizing the para-aramid nano-fiber feed liquid, filtering water, and forming a wet paper blank on the surface of a forming net;
performing vacuum suction on the lower surface of the wet paper blank, and performing bidirectional dehydration by adopting a mode of combining dehydration of an upper top net former on the upper surface of the wet paper blank to obtain wet paper; the vacuum degree of the vacuum suction dehydration is gradually increased along with the increase of the dryness of the wet paper blank;
the vacuum degree of the vacuum suction is-0.01 to-0.1 MPa;
the dryness of the wet paper is 8-10%;
the pressing stage number of the multi-stage buffer pressing dehydration is 2-5; the pressure of the multistage buffer squeezing dehydration is gradually increased within the range of 0.05-0.35 MPa;
the drying stage number of the multistage low-temperature drying is 6-10, and the temperature of the multistage low-temperature drying is gradually increased within the range of 60-120 ℃.
2. The method according to claim 1, wherein the diameter of the para-aramid nanofibers in the para-aramid nanofiber solution is 10-100 nm.
3. The method according to claim 1, wherein the para-aramid nanofiber solution has a length of 100nm to 1000 μm.
4. The method according to claim 1, wherein the mass concentration of the para-aramid nanofiber solution is 0.5-2.5%.
5. The method according to claim 1, wherein the tension-assisted drying has a tension of 4 to 10kN/m and the temperature of the tension-assisted drying is 120 to 160 ℃.
6. A para-aramid paper prepared by the method of claim 1.
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| CN111218841A (en) * | 2019-11-28 | 2020-06-02 | 陕西科技大学 | Nano aramid paper-based material and preparation method and application thereof |
| CN114481677B (en) * | 2022-01-04 | 2023-03-10 | 煤炭科学研究总院有限公司 | Modified para-aramid paper and preparation method and application thereof |
| CN115125765A (en) * | 2022-06-14 | 2022-09-30 | 株洲时代华先材料科技有限公司 | Preparation method of low-air permeability and low-quantitative meta-aramid honeycomb paper |
| CN115418885B (en) * | 2022-09-15 | 2023-09-01 | 黄河三角洲京博化工研究院有限公司 | Low-dielectric-loss aramid paper and preparation method thereof |
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