High-strength PBO composite insulation paper and preparation method thereof

Abstract

The invention belongs to the field of new materials and specialty paper, and discloses high-strength PBO composite insulation paper and a preparation method thereof.The preparation method mainly comprises the following steps that the surface of PBO base paper is coated with a blending modified PHA precursor solution, and modified PHA-PBO composite paper is formed; and drying the composite paper, and carrying out hot pressing to obtain the high-strength PBO composite insulation paper. Compared with untreated PBO paper or common PHA-PBO composite paper, the composite paper prepared by the method has the advantages that the porosity of the PBO paper can be greatly reduced, the uniformity of the PBO paper is further remarkably improved, the modified PBO paper with excellent mechanical properties is obtained, the breakdown strength of the PBO paper is further improved, and the insulating property of the PBO paper is improved.

Description

Technical Field

[0001] The invention belongs to the field of new materials and special papers, and discloses a high-strength PBO composite insulating paper and a preparation method thereof. Background Art

[0002] PBO fiber (poly(p-phenylene benzobisoxazole) fiber, ZylonAS) is a linear polyaromatic heterocyclic liquid crystal polymer molecule. PBO fiber has higher specific strength, specific modulus and high temperature resistance than para-aramid, so it is regarded as a new generation of super fiber for advanced structural composite materials in aerospace.

[0003] PBO paper is made from PBO chopped fibers and pulp. Its special chemical structure determines that it still has excellent electrical properties in high temperature and humid environments. It does not melt or burn at a high temperature of 300°C, has stable chemical properties, and can still maintain good mechanical properties. It is a high-grade H-level or above insulating paper and can be used in generators, motors, dry-type transformers, etc. above H-level. PBO honeycomb materials prepared by gluing, laminating, pressing, and shaping PBO paper are used for aircraft radar antenna covers and secondary load-bearing structural parts on aircraft, such as wings, fairings, floors, engine hoods, and cabin doors.

[0004] However, with the continuous development and upgrading of electrical engineering, in order to ensure the safe operation of high-power traction transformers, generators and other related equipment, higher requirements are put forward for the mechanical strength and insulation performance of high-performance paper-based materials in complex working environments. Generally, in the process of producing PBO paper, since PBO chopped fibers and pulp need to be papered and hot pressed, PBO chopped fibers are rod-shaped and have a relatively smooth surface, providing a skeleton structure for the paper. Pulp fibers are relatively flexible and have a large specific surface area, which wraps the chopped fibers and forms PBO paper with certain strength properties. The interwoven mesh structure of fibers is conducive to dispersing the structural stress of paper-based materials and can better maintain the strength of paper. However, due to the smooth surface of PBO chopped fibers, fewer chemically active groups, poor adhesion and wettability, weak interfacial bonding, and many pore structures between loosely bonded fibers, the prepared PBO paper has a high internal porosity (40%-60%), and PBO pulp cannot be melted. In addition, the surface of PBO fibers is smooth, inert, and there is a lack of bonding between fibers. There is no bonding between fibers during papermaking, and the mechanical properties of paper are very poor.

[0005] Therefore, improving the strength and insulation properties of PBO paper has become one of the urgent problems to be solved in the field of electrical engineering. Summary of the invention

[0006] In view of the many deficiencies in the prior art, the present invention provides a high-strength PBO composite insulating paper and a preparation method thereof, the main steps of which are as follows: coating the surface of PBO base paper with a blended modified PHA precursor solution to form a modified PHA-PBO composite paper; drying the composite paper and hot pressing it to obtain a high-strength PBO composite insulating paper. Compared with untreated PBO paper or ordinary PHA-PBO composite paper, the composite paper prepared by the above method can greatly reduce the porosity of PBO paper, thereby significantly improving the uniformity of PBO paper, obtaining a modified PBO paper with excellent mechanical properties, further improving the breakdown strength of PBO paper, and improving the insulation performance of PBO paper.

[0007] The specific technical solutions of the present invention are as follows: The inventor first provides a method for preparing high-strength PBO composite insulating paper, the specific steps are as follows: (1) Preparation of PBO base paper PBO chopped fibers, PBO pulp fibers and PBO precipitated fibers are placed in a water-containing deflaker for high-speed dispersion, and a dispersant is added to finally obtain uniformly dispersed PBO pulp, which is then put on a screen for pressure forming and vacuum dried to obtain PBO base paper.

[0008] Wherein, by weight, 30-50 parts of PBO chopped fibers, 5-15 parts of PBO pulp fibers, and 30-80 parts of PBO precipitated fibers are used; The length of the PBO short-cut fibers used is 2-8 mm, the fineness is 2-5 dtex; the specific surface area of ​​the PBO pulp fibers is 12-21 m 2 / g, average fiber length 0.5-1.4mm; PBO precipitated fiber specific surface area 20-32 m 2 / g, and the average fiber length is 0.3-1.2mm.

[0009] The dispersant used is one of hydroxyethyl cellulose, sodium lignin sulfonate, maleic acid acrylic acid copolymer, polyoxyethylene ether and non-ionic polyacrylamide, or a mixture of any two or more thereof; the amount of the dispersant is 0.2-2wt% of the total mass of the three fibers; the dispersion time is 15-60min, and the concentration of the obtained PBO pulp is 0.2-5wt%.

[0010] (2) Preparation of precursor PHA polymer solution In a reactor, add an appropriate amount of aprotic polar solvent under a nitrogen atmosphere, then add monomer 4,6-diaminoresorcinol hydrochloride (DAR hydrochloride), terephthaloyl chloride (TPC) and antioxidant stannous chloride in sequence, and stir for 10-40 minutes; add catalyst picoline, stir and react at -10-40°C for 10-25 hours to obtain a PHA polymer solution.

[0011] The non-protonic polar solvent is selected from one or a combination of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone; the molar ratio of 4,6-diaminoresorcinol hydrochloride (DAR hydrochloride) to terephthaloyl chloride (TPC) is 1:1, the amount of 4,6-diaminoresorcinol hydrochloride is 9-17wt% of the total mass of the final PHA polymer solution; the amount of stannous chloride is 0.3-1.2wt% of the mass of DAR hydrochloride; and the amount of picoline is 0.5-2.5wt% of the mass of DAR hydrochloride.

[0012] (3) Preparation of Mica Nanosheets and Precursor PHA Polymer Blend Solution The PHA polymer solution is diluted with the same non-protonic polar solvent as in step (2) to obtain a polymer solution with a solid content of 3-12 wt %; mica nanosheets are ultrasonically dispersed in an appropriate amount of the same non-protonic polar solvent as in step (2), wherein the concentration of the mica nanosheet dispersion is 1-8 wt %, and then the ultrasonically dispersed mica nanosheet dispersion is added to the continuously stirred PHA polymer solution, and the stirring is continued for 6-10 hours.

[0013] The amount of mica nanosheets used is 0.2-3wt% of the total mass of the three types of fibers, and the ultrasonic dispersion time is 3-20h.

[0014] Different from the prior art, the present invention does not add mica nanosheets to the PBO papermaking process for mixing and dispersion, but the mica nanosheets are ultrasonically dispersed and then slowly added to the PHA polymer solution to obtain a mixed solution after a long period of stirring and dispersion. The apparent viscosity of the PHA polymer solution is low after dilution, which ensures that the mica nanosheets are well dispersed in the PHA solution.

[0015] (4) Preparation of modified PBO composite paper The PBO base paper is spread flat on the funnel, and the blended solution is filled into the gaps in the paper and covers the surface by vacuum filtration process, and then further dried. The other side of the composite paper is treated in the same way, and then washed with water to remove the residual solvent and dried. Finally, the modified PHA-PBO composite paper is subjected to hot pressing and high-temperature thermal cyclization to obtain high-strength PBO composite insulation paper.

[0016] The paper is dried in a step-by-step drying method, maintaining 80°C for 1 hour, 100°C for 3 hours, and 120°C for 5 hours; the conditions for hot pressing and high-temperature thermal cyclization are: temperature of 150-270°C, pressure of 4-20MPa, time of 10-60s, hot pressing times of 1-6 times; thermal cyclization temperature of 300-450°C, time of 10-30min, and vacuum degree of -0.05MPa to -0.095Mpa.

[0017] The purpose of heat pressing is to reduce the pores and defects in the paper, increase the physical and mechanical locking effect between fibers, help form a dense paper structure, and improve the overall performance of the paper.

[0018] The high-strength PBO composite insulation paper prepared by the above method has a basis weight of 40-100 g / m 2 , thickness 40-110μm, tensile strength 90-160MPa, breakdown strength 30-100KV / mm. Compared with existing PBO base paper, aramid composite insulation paper or PBO insulation paper, it has significant improvements in mechanical properties and insulation properties.

[0019] The inventor further claims to protect the high-strength PBO composite insulation paper obtained by the above preparation method.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) Compared with the conventional PBO paper preparation process, the PHA prepared by the PBO composite paper preparation process of the present invention is easily soluble in aprotic organic solvents, has a low apparent viscosity, and can be fully filled into the gaps inside the PBO paper. The PHA precursor can be closed at high temperature to form PBO molecules, which can avoid interface compatibility problems. In addition, the PHA precursor preparation process is simple and safe to operate. The solvent used can be reused and recycled, and has no harm to the environment.

[0021] (2) The present invention uses a double-sided vacuum filtration method to allow the mica nanosheet / PHA polymer blend solution to fully penetrate into the voids of the PBO base paper, and the mica nanosheets with excellent insulation performance and high volume resistivity are infiltrated into the paper voids, which will further improve the insulation performance of the PBO paper. At the same time, the dense film formed on the surface of the paper forms a complete wrapping of the chopped fibers, and the solvent will partially swell the PBO chopped fibers. The addition of mica nanosheets and the swelling effect of the solvent will increase the interfacial bonding area between the fibers, thereby improving the stress transfer between the interfaces and shortening the distance between the fibers. Therefore, the strength of the PBO composite paper will be greatly improved. The use of PHA / mica nanosheet blend solution to coat and fill the surface of the paper containing voids can effectively improve the uniformity of the paper, which further reduces the possibility of charge injection, resulting in smaller breakdown holes and no obvious fibers at the edges.

[0022] (3) PBO pulp fiber and fibrils can improve the interaction between PBO composite paper fibers and play a role of "bridging and bonding" between fibers. The present invention uses both PBO pulp fiber and fibrils. The selected pulp fiber has many branches, high crystallinity, certain strength, and presents a three-dimensional network structure in the PBO base paper. After being softened by heat, it can better bond the chopped fibers and fibrils together. The fibrils are in the form of a film, with low crystallinity, good fragmentation, length uniformity and surface activity, fine filament crystal structure, large specific surface area, better dispersion performance and mechanical bonding force, and can effectively wrap the chopped fibers and pulp fibers. In addition, adding a certain proportion of fibrils in the PBO papermaking process can better promote the interaction between the chopped fibers, improve the uniformity of the paper, and ultimately increase the interlayer bonding strength and mechanical properties of the paper.

[0023] In summary, the high-strength PBO composite insulating paper and the preparation method thereof provided by the present invention have the advantages of simple preparation operation, green environmental protection, and controllable process. The content of mica nanosheet material and the solid content of PHA solution can also be adjusted according to needs to obtain PBO paper with different strengths and insulating properties, which can meet the application needs in the fields of aerospace, national defense and military, electrical and transportation. DETAILED DESCRIPTION

[0024] The above contents of the present invention will be further described in detail below. The following are only preferred embodiments of the present invention, but this should not be understood as the scope of the above subject of the present invention being limited to the following examples. All technologies implemented based on the above contents of the present invention belong to the scope of the present invention. Unless otherwise specified, the following embodiments are all completed using conventional existing technologies.

[0025] Embodiment 1 A method for preparing high-strength PBO composite insulating paper comprises the following steps: (1) Preparation of PBO base paper PBO chopped fibers: PBO pulp fibers: PBO precipitated fibers are gradually added into a deflaker containing water at a weight ratio of 50:15:35 for high-speed dispersion, and 0.5% of the total weight of the three fibers of hydroxyethyl cellulose are added as a dispersant and stirred at high speed for 20 minutes to finally obtain a uniformly dispersed PBO pulp with a concentration of 0.5wt%, which is then put on a screen for pressure molding and vacuum dried to obtain a PBO base paper; The length of the short-cut fiber is 6 mm, the fineness is 5 dtex, the average length of the pulp fiber is 1.3 mm, and the specific surface area is 13 m 2 / g, the average length of the precipitated fibers is 1.1 mm, and the specific surface area is 24 m 2 / g.

[0026] (2) Preparation of precursor PHA polymer solution In a reactor, under a nitrogen atmosphere, add 190 g of N,N-dimethylacetamide, then add 0.25 g of antioxidant stannous chloride, 27.1 g of monomer 4,6-diaminoresorcinol hydrochloride, and 25.8 g of terephthaloyl chloride in sequence, and stir for 18 min; add 0.47 g of picoline, stir and react at 6°C for 25 h to obtain a PHA polymer solution.

[0027] (3) Preparation of Mica Nanosheets and Precursor PHA Polymer Blend Solution The PHA polymer solution was diluted with N,N-dimethylacetamide to obtain a PHA solution with a mass fraction of 5wt%. The mica nanosheets were ultrasonically dispersed in an appropriate amount of N,N-dimethylacetamide solvent for 5 hours to prepare a mica nanosheet dispersion with a concentration of 5.5wt%, in which the mass of the mica nanosheets accounted for 0.5wt% of the total mass of the three fibers. The mica nanosheet dispersion was then gradually added to the continuously stirred 5wt% PHA solution and stirred for 7 hours to obtain a mica nanosheet / PHA blend solution.

[0028] (4) Preparation of modified PBO composite paper The PBO base paper was laid flat on the funnel, and the blended solution was filled into the gaps of the paper and covered the surface using a vacuum filtration process with a vacuum degree of -0.06 MPa, and then further dried. The other side of the composite paper was treated in the same way, and then washed with water to remove the residual solvent and dried.

[0029] The drying method is to maintain at 80°C for 1 hour, 100°C for 3 hours, and 120°C for 5 hours. Finally, the modified PHA-PBO composite paper is hot pressed at a temperature of 180°C, a time of 20 seconds, a pressure of 8MPa, and hot pressing for 4 times. The hot-pressed composite paper is subjected to high-temperature thermal cyclization at a vacuum degree of -0.06MPa, a temperature of 350°C, and a time of 20min to obtain a modified PBO composite paper.

[0030] After testing, the tensile strength of the PBO base paper in this embodiment is 43.2MPa, and the breakdown strength is 36.5KV / mm. The basis weight of the modified PBO composite paper is 45g / m 2 , thickness 58.4μm, tensile strength 109.2MPa, breakdown strength 54.8KV / mm.

[0031] Embodiment 2 A method for preparing high-strength PBO composite insulating paper comprises the following steps: Steps (1) and (2) are the same as in Example 1; (3) Preparation of Mica Nanosheets and Precursor PHA Polymer Blend Solution The PHA polymer solution was diluted with N,N-dimethylacetamide to obtain a PHA solution with a mass fraction of 8wt%. The mica nanosheets were ultrasonically dispersed in an appropriate amount of N,N-dimethylacetamide solvent for 9 hours to prepare a mica nanosheet dispersion with a concentration of 4wt%, in which the mass of the mica nanosheets accounted for 1wt% of the total mass of the three fibers. The mica nanosheet dispersion was then gradually added to the continuously stirred 8wt% PHA solution and stirred for 7 hours to obtain a mica nanosheet / PHA blend solution.

[0032] (4) Preparation of modified PBO composite paper The PBO base paper was laid flat on the funnel, and the blended solution was filled into the gaps of the paper and covered the surface by a vacuum filtration process with a vacuum degree of -0.08MPa, and further dried. The other side of the composite paper was treated in the same way, and then washed with water to remove the residual solvent and dried. The drying method was 80℃ for 1 hour, 100℃ for 3 hours, and 120℃ for 5 hours. Finally, the modified PHA-PBO composite paper was hot-pressed at a temperature of 220℃, a time of 30s, a pressure of 13MPa, and hot-pressed 3 times. The hot-pressed composite paper was subjected to high-temperature thermal cyclization, with a vacuum degree of -0.07MPa, a temperature of 400℃, and a time of 20min to obtain a modified PBO composite paper.

[0033] After testing, the tensile strength of the PBO base paper in this embodiment is 43.2MPa, and the breakdown strength is 36.5KV / mm. The basis weight of the modified PBO composite paper is 53g / m 2 , thickness 62.3μm, tensile strength 116.8MPa, breakdown strength 61.7KV / mm.

[0034] Embodiment 3 A method for preparing high-strength PBO composite insulating paper comprises the following steps: Steps (1) and (2) are the same as in Example 1; (3) Preparation of Mica Nanosheets and Precursor PHA Polymer Blend Solution The PHA polymer solution was diluted with N,N-dimethylacetamide to obtain a PHA solution with a mass fraction of 11wt%. The mica nanosheets were ultrasonically dispersed in an appropriate amount of N,N-dimethylacetamide solvent for 9h to prepare a mica nanosheet dispersion with a concentration of 3wt%, in which the mass of the mica nanosheets accounted for 1.5wt% of the total mass of the three fibers. The mica nanosheet dispersion was then gradually added to the continuously stirred 11wt% PHA solution and stirred for 9h to obtain a mica nanosheet / PHA blend solution.

[0035] (4) Preparation of modified PBO composite paper The PBO base paper was laid flat on the funnel, and the blended solution was filled into the gaps of the paper and covered the surface by a vacuum filtration process with a vacuum degree of -0.09MPa, and further dried. The other side of the composite paper was treated in the same way, and then washed with water to remove the residual solvent and dried. The drying method was 80℃ for 1 hour, 100℃ for 3 hours, and 120℃ for 5 hours. Finally, the modified PHA-PBO composite paper was hot-pressed at a temperature of 250℃, a time of 18s, a pressure of 17MPa, and hot-pressed twice. The hot-pressed composite paper was subjected to high-temperature thermal cyclization, with a vacuum degree of -0.08MPa, a temperature of 450℃, and a time of 30min to obtain a modified PBO composite paper.

[0036] After testing, the tensile strength of the PBO base paper in this embodiment is 43.2MPa, and the breakdown strength is 36.5KV / mm. The basis weight of the modified PBO composite paper is 60g / m 2 , thickness 70.3μm, tensile strength 130.4MPa, breakdown strength 74.1KV / mm.

[0037] Example 4 A method for preparing high-strength PBO composite insulating paper comprises the following steps: (1) Preparation of PBO base paper PBO chopped fiber: PBO pulp fiber: PBO precipitated fiber are gradually added into a deflaker containing water in a weight ratio of 35:20:45 and dispersed at high speed. 0.8% of the total weight of the three types of fibers of polyoxyethylene ether are added as a dispersant and stirred at high speed for 30 minutes to finally obtain a uniformly dispersed PBO pulp with a concentration of 1.2wt%. The pulp is then put on a screen for pressure forming and vacuum dried to obtain PBO base paper.

[0038] The length of the short-cut fiber is 5 mm, the fineness is 4 dtex, the average length of the pulp fiber is 0.8 mm, and the specific surface area is 16 m 2 / g, the average length of the precipitated fibers is 0.7 mm, and the specific surface area is 27 m 2 / g.

[0039] (2) Preparation of precursor PHA polymer solution In a reactor, under a nitrogen atmosphere, add 175 g of N,N-dimethylacetamide, then add 0.08 g of antioxidant stannous chloride, 21.48 g of monomer 4,6-diaminoresorcinol hydrochloride, and 20.47 g of terephthaloyl chloride in sequence, and stir for 20 min; add 0.31 g of picoline, stir and react at 0°C for 18 h to obtain a PHA polymer solution.

[0040] Steps (3) and (4) are the same as in Example 3; After testing, the tensile strength of the PBO base paper in this embodiment is 48.5MPa, and the breakdown strength is 40.1KV / mm. The basis weight of the modified PBO composite paper is 67g / m 2 , thickness 63.6μm, tensile strength 140.4MPa, breakdown strength 79.4KV / mm.

[0041] Example 5 A method for preparing high-strength PBO composite insulating paper comprises the following steps: (1) Preparation of PBO base paper PBO chopped fiber: PBO pulp fiber: PBO precipitated fiber are gradually added into a deflaker containing water in a weight ratio of 25:10:65 and dispersed at high speed. Polyoxyethylene ether accounting for 1.2% of the total weight of the three types of fibers is added as a dispersant and stirred at high speed for 50 minutes to finally obtain a uniformly dispersed PBO pulp with a concentration of 1.0wt%. The pulp is then put on a screen for pressure forming and vacuum dried to obtain PBO base paper.

[0042] The length of the short-cut fiber is 3 mm, the fineness is 2.5 dtex, the average length of the pulp fiber is 0.6 mm, and the specific surface area is 20 m 2 / g, the average length of the precipitated fibers is 0.4 mm, and the specific surface area is 30 m 2 / g.

[0043] (2) Preparation of precursor PHA polymer solution In a reactor, under a nitrogen atmosphere, add 150 g of N,N-dimethylacetamide, then add 0.15 g of antioxidant stannous chloride, 19.57 g of monomer 4,6-diaminoresorcinol hydrochloride, and 18.65 g of terephthaloyl chloride in sequence, and stir for 30 min; add 0.39 g of picoline, stir and react at 6°C for 20 h to obtain a PHA polymer solution.

[0044] Steps (3) and (4) are the same as in Example 3; After testing, the tensile strength of the PBO base paper in this embodiment is 51.7MPa, and the breakdown strength is 43.1KV / mm. The basis weight of the modified PBO composite paper is 63g / m 2 , thickness 55.8μm, tensile strength 148.2MPa, breakdown strength 88.4KV / mm.

[0045] Comparative Example A method for preparing a PBO composite paper, the steps are as follows: (1) Preparation of PBO base paper PBO chopped fibers and PBO pulp fibers were gradually added into a water-containing deflaker at a weight ratio of 40:60 and dispersed at high speed. Hydroxyethyl cellulose (0.5% of the total weight of the two fibers) was added as a dispersant and stirred at high speed for 50 minutes to finally obtain a uniformly dispersed PBO pulp with a concentration of 1wt%. The pulp was then put on a screen for pressure forming and vacuum dried to obtain PBO base paper.

[0046] The length of the short-cut fiber is 5 mm, the fineness is 4 dtex, the average length of the pulp fiber is 0.6 mm, and the specific surface area is 24 m 2 / g, (2) Preparation of precursor PHA polymer solution In a reactor, under a nitrogen atmosphere, add 150 g of N,N-dimethylacetamide, then add 0.15 g of antioxidant stannous chloride, 19.57 g of monomer 4,6-diaminoresorcinol hydrochloride, and 18.65 g of terephthaloyl chloride in sequence, and stir for 30 min; add 0.39 g of picoline, stir and react at 6°C for 20 h to obtain a PHA polymer solution.

[0047] (3) Preparation of PBO composite paper The PHA polymer solution was diluted with N-methylpyrrolidone to obtain a PHA solution with a mass fraction of 11wt%. The PBO base paper was placed flat on the platform, and the 11wt% PHA solution was evenly applied to the surface of the paper with a scraper. The paper was soaked in the aqueous solution and washed for 1h, and then dried. The other side of the paper was treated in the same way. The drying method was 80℃ for 1 hour, 100℃ for 3 hours, and 120℃ for 5 hours. Finally, the obtained PHA-PBO composite paper was hot pressed at a hot pressing temperature of 220℃, a time of 6min, and a pressure of 15MPa. The hot-pressed composite paper was subjected to high-temperature thermal cyclization, with a vacuum degree of -0.06MPa, a temperature of 400℃, and a time of 23min to obtain PBO composite paper.

[0048] After testing, the tensile strength of the PBO base paper in this comparative example is 34.2 MPa, and the breakdown strength is 28.7 KV / mm. The tensile strength of the modified PBO composite paper is 61.3 MPa, and the breakdown strength is 47.2 KV / mm.

[0049] By comparing the above comparative examples and embodiments, it can be seen that the technical solution of the present invention uses mica nanosheets mixed with polyhydroxyamide (PHA) precursor solution, and the process has always used non-protonic polar solvents, which has the advantages of energy saving, environmental protection, and resource recycling; PBO precipitated fibers are used as the paper matrix, which effectively improves the structure of PBO paper and improves the comprehensive performance of paper. The high-temperature cyclization of PHA precursors to PBO avoids the problem of poor interface compatibility and improves the uniformity of paper. The introduction of mica nanosheets can greatly improve the mechanical properties of PBO paper and improve the breakdown strength of PBO paper. At the same time, the content of mica nanosheet material and the solid content of PHA solution can be adjusted according to demand to obtain PBO paper with different strengths and insulation properties, which can meet the application needs in aerospace, national defense, military, electrical, and transportation.

[0050] The above embodiments show and describe the basic principles, product features and advantages of the method of the present invention. The present invention is not limited by the above embodiments. Without departing from the scope of the present invention, the present invention may have various changes and improvements, all of which are required to be included in the scope of protection.

Claims

1. A method for preparing high-strength PBO composite insulating paper, characterized in that: The specific steps are as follows: (1) Preparation of PBO base paper PBO chopped fibers, PBO pulp fibers, and PBO precipitated fibers are placed in a deflaker containing water for high-speed dispersion, and a dispersant is added to finally obtain PBO pulp with a concentration of 0.2-5wt%, and then put on a screen for pressure forming, and vacuum drying to obtain PBO base paper; Wherein, by weight, 30-50 parts of PBO chopped fibers, 5-15 parts of PBO pulp fibers, and 30-80 parts of PBO precipitated fibers are used; (2) Preparation of precursor PHA polymer solution In a reactor, add an appropriate amount of aprotic polar solvent under a nitrogen atmosphere, then add monomer 4,6-diaminoresorcinol hydrochloride, terephthaloyl chloride and antioxidant stannous chloride in sequence, and stir for 10-40 minutes; add catalyst picoline, stir and react at -10-40°C for 10-25 hours to obtain a PHA polymer solution; (3) Preparation of Mica Nanosheets and Precursor PHA Polymer Blend Solution The PHA polymer solution is diluted with the same non-protonic polar solvent as in step (2) to obtain a polymer solution with a solid content of 3-12wt%; mica nanosheets are ultrasonically dispersed in an appropriate amount of the same non-protonic polar solvent as in step (2), wherein the concentration of the mica nanosheet dispersion is 1-8wt%, and then the ultrasonically dispersed mica nanosheet dispersion is added to the continuously stirred PHA polymer solution, and the stirring is continued for 6-10h; wherein the amount of mica nanosheets is 0.2-3wt% of the total mass of the three fibers, and the ultrasonic dispersion time is 3-20h; (4) Preparation of modified PBO composite paper The PBO base paper is spread flat on a funnel, and the blended solution is filled into the gaps in the paper and covers the surface by a vacuum filtration process, and then further dried; the other side of the composite paper is treated in the same way, and then washed with water to remove the residual solvent and dried; finally, the modified PHA-PBO composite paper is subjected to hot pressing and high-temperature thermal cyclization to obtain high-strength PBO composite insulation paper.

2. The method for preparing the high-strength PBO composite insulating paper according to claim 1, characterized in that: The PBO short-cut fibers used in step (1) have a length of 2-8 mm and a fineness of 2-5 dtex; the specific surface area of ​​the PBO pulp fibers is 12-21 m 2 / g, average fiber length 0.5-1.4mm; PBO precipitated fiber specific surface area 20-32m 2 / g, and the average fiber length is 0.3-1.2mm.

3. The method for preparing the high-strength PBO composite insulating paper according to claim 1 or 2, characterized in that: The dispersant used in step (1) is one of hydroxyethyl cellulose, sodium lignin sulfonate, maleic acid acrylic acid copolymer, polyoxyethylene ether and non-ionic polyacrylamide, or a mixture of any two or more thereof; the amount of the dispersant is 0.2-2wt% of the total mass of the three fibers; and the dispersion time is 15-60min.

4. The method for preparing the high-strength PBO composite insulating paper according to claim 1, characterized in that: In step (2), the aprotic polar solvent is selected from one or a combination of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

5. The method for preparing the high-strength PBO composite insulating paper according to claim 1 or 4, characterized in that: In step (2), the molar ratio of 4,6-diaminoresorcinol hydrochloride to terephthaloyl chloride is 1:1, the amount of 4,6-diaminoresorcinol hydrochloride is 9-17wt% of the total mass of the final PHA polymer solution; the amount of stannous chloride is 0.3-1.2wt% of the mass of 4,6-diaminoresorcinol hydrochloride; and the amount of picoline is 0.5-2.5wt% of the mass of 4,6-diaminoresorcinol hydrochloride.

6. The method for preparing the high-strength PBO composite insulating paper according to claim 1, characterized in that: In step (4), the paper is dried in a stepwise manner at 80°C for 1 hour, 100°C for 3 hours, and 120°C for 5 hours.

7. The method for preparing high-strength PBO composite insulating paper according to claim 1, characterized in that: The hot pressing conditions in step (4) are: temperature of 150-270°C, pressure of 4-20MPa, time of 10-60s, and number of hot pressing times of 1-6 times.

8. The method for preparing the high-strength PBO composite insulating paper according to claim 1 or 7, characterized in that: The conditions for high temperature thermal cyclization in step (4) are: thermal cyclization temperature 300-450°C, time 10-30 min, and vacuum degree of -0.05 MPa to -0.095 MPa.

9. High-strength PBO composite insulating paper prepared by the method according to any one of claims 1 to 8.

10. The high-strength PBO composite insulating paper according to claim 9, characterized in that: Basis weight: 40-100g / m 2 , thickness 40-110μm, tensile strength 90-160MPa, breakdown strength 30-100KV / mm.