High-density micro-crepe insulation paper for electricians and manufacturing method thereof

Abstract

The invention discloses high-density micro-crepe insulation paper for electricians and a manufacturing method of the high-density micro-crepe insulation paper, and belongs to the technical field of insulation paper manufacturing. The method comprises the following steps: by taking 100% unbleached sulfate softwood pulp as a raw material, sequentially preparing pulp and purifying to obtain pulp; the preparation method comprises the following steps: carrying out wet papermaking and preliminary dehydration on the pulp to prepare a wet paper sheet, then carrying out pre-pressing and secondary pre-pressing, then carrying out micro-wrinkling treatment on the wet paper sheet, and then sequentially carrying out multi-stage squeezing, drying cylinder supporting pressing, first-stage drying, semi-wet calendaring, second-stage drying, four-roller calendaring and paper rolling to prepare the high-density micro-wrinkled insulation paper for the electrician. The method is used for manufacturing the insulation paper with higher density, more uniform and fine micro-wrinkle structure and excellent insulation performance.

Description

Technical Field

[0001] The invention belongs to the technical field of insulating paper manufacturing, and in particular relates to high-density micro-corrugated insulating paper for electrical use and a manufacturing method thereof. Background Art

[0002] In today's world of rapid technological advancement, the application scenarios of insulating paper are constantly expanding and deepening. From large-scale high-voltage power transmission equipment to sophisticated small electronic components, insulating paper occupies a pivotal position. As various industries have increasingly higher requirements for equipment performance, stability and safety, more stringent standards have been put forward for the performance of insulating paper. Especially in special environments such as high humidity and strong electromagnetic interference, as well as high-end equipment such as ultra-high voltage transformers and high-performance integrated circuits, insulating paper must not only have a higher density to enhance electrical strength, but also have better insulation performance and high-quality ductility. The high-density micro-wrinkled insulating paper form can optimize its physical and electrical properties.

[0003] However, the current traditional insulating paper manufacturing methods have many problems that need to be solved. In terms of density, the density of insulating paper produced by conventional processes is usually difficult to meet the needs of high-end application scenarios. The lower density causes the insulating paper to have insufficient electrical strength when subjected to high voltage, which is prone to safety hazards such as electrical breakdown, limiting its application in high-voltage electrical equipment. Conventional insulating paper for cables performs poorly in terms of flexibility and buffering performance, which in turn restricts the further expansion of insulating paper applications in fields such as high-performance electronic components. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a high-density micro-corrugated insulating paper for electrical use and a method for manufacturing the same, so as to produce insulating paper with higher density, more uniform and fine micro-corrugated structure and excellent insulating performance. This method can not only meet the strict requirements of current high-end equipment and special environments for insulating paper, but also open up new paths for the wide application of insulating paper in related fields and promote technological progress in the power and electronics industries.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for manufacturing high-density micro-corrugated insulating paper for electrical use, comprising the following steps: Using 100% unbleached softwood kraft pulp as raw material, pulp is prepared and purified in sequence to obtain the stock; the stock is wet papermaking and preliminarily dewatered to obtain a wet paper sheet, then pre-pressed and secondarily pre-pressed, and then the wet paper sheet is subjected to micro-creasing treatment to form wrinkles, and then multi-stage pressing, dryer support pressing, first-stage drying, semi-wet calendering, second-stage drying, four-roll calendering and winding are carried out in sequence to obtain a high-density micro-creased insulating paper for electrical engineering; wherein, the process of subjecting the wet paper sheet to micro-creasing treatment to form wrinkles is as follows: the wet paper is scraped off from the creasing cylinder by the doctor blade of the creasing roll, and the angle of the doctor blade of the creasing roll is 15° to 45°; and by controlling the speed difference between the receiving felt and the creasing cylinder, the creasing rate is controlled to be 5% to 15%.

[0006] In one embodiment, the pulp preparation includes pulping and refining in sequence; the beating degree after pulp preparation is 30°SR to 40°SR.

[0007] In one embodiment, the wet papermaking uses a three-cylinder headbox, and the basis weight of the stock on the forming wire is 50 to 150 g / m 2 .

[0008] In one embodiment, the line pressure of the pre-pressing and second pre-pressing is 10 to 20 kN / m.

[0009] In one embodiment, the multi-stage pressing includes first-stage pressing and second-stage pressing in sequence; the line pressure of the multi-stage pressing and the dryer support pressing is 10 to 20 kN / m; the set temperature of the dryer support pressing is 100°C to 120°C.

[0010] In one embodiment, the dryness of the wet paper after the multi-stage pressing is 40% to 50%; the dryness of the wet paper after the dryer support pressing is 50% to 60%; the dry paper density after the multi-stage pressing and the dryer support pressing is 1.0 to 1.2 g / cm 3 .

[0011] In one embodiment, the set temperature of the first-stage drying is 120°C to 140°C; the set temperature of the second-stage drying is 80°C to 100°C.

[0012] In one embodiment, the line pressure of the semi-wet calendering is 20 to 30 kN / m; the line pressure of the four-roll calendering is 30 to 40 kN / m.

[0013] In one embodiment, the moisture content of the paper after the four-roll calendering is below 10%.

[0014] The present invention also provides a high-density micro-creased insulating paper for electrical engineering prepared by using the manufacturing method of the above high-density micro-creased insulating paper for electrical engineering.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a manufacturing method for a high-density micro-wrinkled insulating paper for electrical engineering. To improve the density and performance of the insulating paper and optimize its physical properties, the wet paper sheet is subjected to micro-wrinkling treatment to form a micro-wrinkled structure, and the tightness is further enhanced through semi-dry calendering. First, the present invention selects 100% high-purity unbleached sulfate softwood pulp fibers as raw materials, and through pulp preparation, purification and slag removal treatment, the insulating performance of the raw materials is ensured. Through multi-stage pre-pressing, the paper structure becomes more compact. This compact structure not only enhances the electrical insulation performance of the insulating paper, enabling it to withstand higher voltages and reducing the risk of electrical breakdown, but also improves the mechanical strength, making the insulating paper more durable and less prone to breakage in practical applications. Secondly, the wet forming method with multiple cylinder molds is adopted to make the fiber arrangement of the paper more uniform, reduce the thickness deviation defect of the paper web, improve the bonding force between fibers, meet the production requirements of papers with different basis weights, and make it not easy to break during operations such as bending and curling, thus broadening the application range of the insulating paper, especially suitable for scenarios such as internal wiring of electronic devices with requirements for flexibility. Thirdly, the wrinkling method is adopted in the wet paper stage, and then through multi-stage pressing treatment, an insulating paper type with a flat surface but micro-wrinkles inside is achieved. The formed micro-wrinkled structure is uniform and fine, bringing multiple advantages to the insulating paper. On the one hand, the increased surface area enables charges to be more evenly dispersed, reducing the risk of insulation failure caused by local charge accumulation; on the other hand, the micro-wrinkled structure improves the flexibility and buffering performance of the insulating paper to a certain extent, enabling it to better adapt to complex application environments. For example, in electronic devices, it can effectively buffer the impact on the insulating paper caused by factors such as vibration and temperature changes, further enhancing the overall insulation performance. Then, after wrinkling, multi-stage pressing and carrier roll pressing are used to remove part of the moisture in the wet paper web, which can effectively improve the tightness of the insulating paper while ensuring the micro-wrinkled structure of the paper, and the surface of the insulating paper is modified by calendering the semi-dry paper web and the fully dry paper web, making the appearance and tightness of the insulating paper more excellent. Finally, the method of controlling the drying temperature in stages is an important guarantee for ensuring the quality of the insulating paper. The semi-dry calendering process ensures that the bonding of the cardboard and the wrinkle form are not damaged while improving the appearance quality and tightness of the insulator. By reasonably setting the temperature and time at different stages, problems such as deformation and cracking caused by excessive water loss of the paper due to too high temperature are avoided, and at the same time, the drying time is prevented from being too long due to too low temperature, which affects the production efficiency. This staged drying control method ensures the stability of the micro-wrinkled structure and has more stable and reliable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of the manufacturing method for the high-density micro-wrinkled insulating paper for electrical engineering of the present invention; Figure 2 is an SEM image of the high-density micro-wrinkled insulating paper for electrical engineering obtained by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art regarding the present invention. In case of conflicts, the definition in this specification shall prevail.

[0018] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being restricted by any specific theory or mechanism.

[0019] The present invention focuses on the specific technical field of insulating paper manufacturing. As a key material in the power and electronics industries, the innovation and development of insulating paper manufacturing technology play a decisive role in the technological upgrading of related industries and the improvement of product performance. The manufacturing method of high-density micro-wrinkled insulating paper involved in the present invention aims to bring new breakthroughs and development opportunities to the field of insulating paper manufacturing through unique processes and technologies.

[0020] See Figure 1 , Figure 1 , which is the process flow of high-density micro-wrinkled insulating paper, including pulp preparation, purification, wet forming, pre-pressing, secondary pre-pressing, wrinkling, first-stage pressing, second-stage pressing, dryer supporting pressing, first-stage drying, semi-wet calendering, second-stage drying, four-roll calendering, and paper winding.

[0021] The pulp preparation process includes pulping and refining, grinding the pulp board to the beating degree and wet weight required by the process; purification includes using a magnetic separator, high-concentration slag remover, low-concentration slag remover, metal particle remover, and pressure screen to remove slag and precisely screen it; wet forming uses a three-cylinder headbox, and controls the pulp on the forming wire to be between 50 and 150 g / m 2 ; the pre-pressing and secondary pre-pressing can control the line pressure between 10 and 20 kN / m; the scraper of the wrinkling roller scrapes the wet paper from the wrinkling cylinder, precisely controls the angle of the wrinkling scraper between 15° and 45°, and ensures the wrinkling rate is between 5% and 15% through the speed difference between the receiving felt and the wrinkling cylinder; the first-stage pressing, second-stage pressing, and dryer supporting pressing can control the line pressure between 10 and 20 kN / m. The dryness of the wet paper after the first-stage pressing and second-stage pressing can reach 40% - 50%, and the dryness of the wet paper after the dryer supporting pressing is 50% - 60%. The dry paper tightness after the first-stage pressing, second-stage pressing, and dryer supporting pressing is increased to 1.0 - 1.2 g / cm 3; The set temperature for the first-stage drying is 120°C to 140°C; the set temperature for the second-stage drying is 80°C to 100°C; the line pressure for semi-wet calendering is 20 to 30 kN / m; the line pressure for four-roll calendering is 30 to 40 kN / m; the first-stage drying, semi-wet calendering, second-stage drying, and four-roll calendering further reduce the moisture content of the paper to below 10% and modify the surface of the insulating paper, making the appearance and tightness of the insulating paper more excellent.

[0022] The present invention provides a manufacturing method for a high-density micro-wrinkled insulating paper for electrical engineering, specifically including the following steps: S1: Raw material preparation: 100% unbleached sulfate softwood pulp is selected as the basic raw material. To ensure product quality, it is deslagged and precisely screened through a magnetic separator, high-consistency cleaners, low-consistency cleaners, metal particle separators, and pressure screens. And it is subjected to beating treatment by a professional beating equipment, and the beating degree is precisely controlled between 30 and 40°SR. This beating degree range can effectively optimize the morphology and performance of wood pulp fibers and lay a foundation for subsequent paper forming.

[0023] S2: Paper making and forming: A mature wet paper making process is adopted to accurately transport the uniformly mixed pulp to the headbox of the paper machine. The headbox, as a key component for paper forming, is responsible for uniformly spraying the pulp onto the forming wire. Through the weir opening and lip opening, the pulp on the forming wire is strictly controlled between 50 and 150 g / m 2 between. By precisely controlling these two key parameters, it is ensured that the wet paper sheet initially dewatered on the forming wire has a uniform thickness and good structure, providing a high-quality blank for subsequent micro-wrinkling treatment and drying processes.

[0024] S3: Then, pre-pressing and secondary pre-pressing are carried out. The line pressure for pre-pressing and secondary pre-pressing is 10 to 20 kN / m. After pre-pressing and secondary pre-pressing, the dryness of the wet paper embryo (sheet) can reach 30% to 40%, ensuring that the wet paper embryo has a certain wet strength before wrinkling, which is convenient for the formation of micro-wrinkles.

[0025] S4: Micro-wrinkle formation: Micro-wrinkling treatment is carried out on the wet paper sheet, which is one of the key steps of the present invention. The wet paper sheet is scraped off from the wrinkling cylinder by the doctor blade of the wrinkling roller. The angle of the doctor blade for wrinkling is precisely controlled between 15° and 45°, and through the speed difference between the transfer felt and the wrinkling cylinder, the wrinkling rate is ensured to be between 5% and 15%. This micro-wrinkle structure can not only increase the surface area of the insulating paper, be beneficial to charge dispersion, and improve the insulation performance, but also endow the insulating paper with better flexibility and buffering performance to meet the requirements of different application scenarios to a certain extent.

[0026] S5: Multi-stage pressing: After the wet paper is wrinkled, it goes through the first and second stages of pressing. The line pressure of the first and second stages of pressing is 10-20 kN / m. After the first and second stages of pressing, the wet paper dryness can reach 40%-50%. The wet paper web passes through the support and drying of the drying cylinder with a line pressure of 10-20 kN / m and a set temperature of 100℃~120℃. The wet paper dryness after the support of the drying cylinder can reach 50%-60%. Multi-stage pressing can discharge the moisture of the wet paper web on the one hand, and improve the tightness and interlayer bonding of the insulating paper on the other hand. The tightness of the dry paper after the first, second and dryer presses is 1.0-1.2 g / cm 3 .

[0027] S6: Drying treatment: Superheated water heating is used to control the temperature of the drying cylinder by controlling the steam pressure. The wet paper first passes through the large drying cylinder in the drying cylinder support pressure, and the drying cylinder temperature is 100℃~120℃. The micro-wrinkled insulation paper is initially characterized, and then a drying stage is performed. The temperature of the first drying cylinder group in the first drying stage is 120℃~140℃. This stage mainly removes most of the free water on the surface of the wet paper sheet, and at the same time, the micro-wrinkle structure is initially fixed. After the wet paper passes through the first drying cylinder group, it is calendered by semi-wet rollers. After semi-wet calendering with a warp pressure of 20~30kN / m, it enters the second drying cylinder for second drying. The temperature of the second drying cylinder group is 80℃~100℃, which further removes the internal bound water of the paper and makes the paper reach the required dryness. After the second drying cylinder group, it passes through the four-roll calendering with a line pressure of 30~40kN / m to modify the surface of the insulation paper, making the appearance and tightness of the insulation paper more excellent. The whole drying process is kept well ventilated to ensure that the moisture in the wet paper is fully evaporated, and finally a high-density micro-wrinkle insulation paper with ideal density, uniform micro-wrinkle structure and excellent insulation performance is obtained. The microstructure of the high-density micro-wrinkle insulation paper for electrical use is as follows: Figure 2 shown.

[0028] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0029] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0030] Example 1 Raw material preparation stage: Select 100% unbleached sulfate softwood pulp. Put the pulp into a high-efficiency pulper, set the blade speed of the pulper at 1500 - 1800 revolutions per minute, and control the pulping time within 10 - 20 minutes to fully break the pulp. Use a refining equipment with a constant power, adjust the disc gap and power, and grind the pulp fibers until the beating degree reaches 35 - 38°SR. Use a high-precision sensor to monitor the operating parameters of the refining equipment in real time, and the disc gap is accurate to ±0.01mm; The pulp passes through a magnetic separator, a high-consistency cleaner, a low-consistency cleaner, a metal particle remover, and a pressure screen in sequence for deep slag removal and screening.

[0031] Paper forming stage: Adopt an advanced wet paper-making process based on automatic control technology. By precisely adjusting the weir opening and lip opening, use automatic control technology to control the pulp quantity on the forming wire at 70 - 80g / m 2 , with the error controlled within ±1g / m 2 . Use the three-cylinder headbox distribution method. By optimizing parameters such as the wire speed of the cylinder at 60 - 80m / min and the vacuum degree of the wire section controlled between -0.04 - 0.06MPa, make the paper fibers evenly distributed on the forming wire and initially dehydrate to form a wet paper sheet. After the wet paper sheet enters the wet paper machine, it passes through pre-pressing and secondary pre-pressing in sequence. The line pressure of pre-pressing and secondary pre-pressing is controlled at 10 - 16kN / m, so that the dryness of the wet paper reaches 30 - 35%, ensuring the wet strength of the wet paper sheet and preparing for the formation of micro-wrinkles.

[0032] Micro-wrinkle formation stage: Introduce the wet paper sheet into a carefully debugged wrinkling system, which is equipped with an advanced angle adjustment device and a high-precision angle sensor. By adjusting the rotatable shaft under the doctor blade holder, use the angle sensor to accurately set the angle of the wrinkling doctor blade at 30 - 35°, with the error controlled within ±1°. At the same time, through a high-precision speed control system, which uses an encoder to monitor the speed of the transfer felt at 50 - 70m / min in real time, make the wrinkling rate reach 10%. Under these conditions, the number of micro-wrinkles formed on the surface of the wet paper sheet reaches 8 - 10 per centimeter, and the wrinkle width is uniform, between 0.10 - 0.15mm, thus forming a uniform and fine micro-wrinkle structure. This micro-wrinkle structure not only increases the surface area of the insulating paper, is conducive to charge dispersion, and improves the insulation performance, but also endows the insulating paper with good flexibility and buffering performance.

[0033] Multi-stage pressing stage: After the wet paper is wrinkled, first perform one-stage pressing, control the line pressure at 12 - 18kN / m, so that the dryness of the wet paper reaches 35 - 40%, and at the same time increase the paper density to 1.05 - 1.10g / cm 3Next, secondary pressing is carried out, also using a hydraulic pressing device, controlling the line pressure to be 15 - 20 kN / m, further increasing the dryness of the wet paper to 40 - 45% and the tightness to 1.10 - 1.15 g / cm 3 The wet paper web is supported and dried by a heated dryer cylinder. During this process, a high-precision pressure control device is used, which is linked with the temperature control system of the dryer cylinder, controlling the line pressure to be 10 - 15 kN / m, making the dryness of the wet paper reach 50 - 55%, and at the same time further increasing the tightness of the insulating paper to 1.15 - 1.2 g / cm 3 , significantly enhancing the interlayer bonding property. During this process, by adjusting the temperature and pressure of the dryer cylinder and the pressure distribution of the support rollers, it is ensured that while the wet paper is dehydrated, the fibers are more closely bonded together.

[0034] Drying treatment stage: The superheated water heating method is adopted. Through the precise regulation of the steam pressure, the intelligent temperature control system is used to control the temperature of the dryer cylinder. The wet paper first passes through a large dryer cylinder with a temperature set at 110 - 120 °C to preliminarily characterize the micro-wrinkled insulating paper, ensuring that the micro-wrinkled structure remains stable during the preliminary drying process. The temperature control accuracy of the large dryer cylinder reaches ±1 °C, which is achieved by adjusting the steam flow rate and the condensate discharge rate. Subsequently, after passing through the first-stage dryer cylinder group, semi-wet calendering between rollers is carried out; after passing through the second-stage dryer cylinder group, four-roll calendering is carried out. Entering the first-stage dryer cylinder group, the temperature is set at 120 - 130 °C. By reasonably setting the ventilation volume of the dryer cylinder at 1000 - 1500 m 3 / h, most of the free moisture on the surface of the wet paper sheet is removed, and at the same time the micro-wrinkled structure is preliminarily fixed, ensuring that the shape and quantity of the micro-wrinkles remain basically unchanged. The ventilation system uses a variable-frequency fan to adjust the ventilation volume in real time according to the humidity inside the dryer cylinder.

[0035] By precisely adjusting the pressure of the calender rollers for semi-wet calendering to be 25 - 30 kN / m and matching and adjusting parameters such as the rotational speed according to the running speed of the paper, the surface of the insulating paper is modified to make the appearance of the insulating paper more flat and smooth, and the tightness is further increased.

[0036] After semi-wet calendering, it enters the second-stage dryer cylinder. The temperature of the second-stage dryer cylinder group is set at 80 - 90 °C to further remove the bound moisture inside the paper, making the paper reach the required dryness degree, with the water content controlled between 6% - 8%, and at the same time ensuring the stability of the micro-wrinkled structure, making the tightness of the formed paper finally stable at 1.20 g / cm 3 or so, with stable and reliable performance.

[0037] Post-treatment stage: The formed paper is calendered in the way of four-roll three-pressure zones, and the line pressure is controlled at 30 - 35 kN / m to modify the surface of the paper to form a smooth paper surface and ensure the surface characteristics of the paper sheet. After calendering, the paper sheet enters the rewinder for winding to form a formed paper roll.

[0038] Example 2 Raw material preparation stage: Select 100% unbleached sulfate softwood pulp. Put the pulp into a high-efficiency pulper, set the blade speed of the pulper at 1500 - 1800 revolutions per minute, and control the pulping time within 10 - 20 minutes to fully break the pulp. Use a refining equipment with a constant power, adjust the disc gap and power, and grind the pulp fibers until the beating degree reaches 32 - 35°SR. Use high-precision sensors to monitor the operating parameters of the refining equipment in real time, with the disc gap accurate to ±0.01mm; The pulp passes through a magnetic separator, a high-consistency rejecter, a low-consistency rejecter, a metal particle remover, and a pressure screen in sequence for deep slag removal and screening.

[0039] Paper making and forming stage: Adopt an advanced wet paper making process based on automation control technology. By precisely adjusting the weir opening and lip opening, using automation control technology, through debugging the weir opening and lip opening, and using an automatic adjustment device, control the pulp on the forming wire to a basis weight of 110 - 120 g / m 2 , with the deviation controlled within ±2 g / m 2 . This process is subject to real-time feedback and adjustment through an on-line basis weight monitoring system to ensure the accuracy of the basis weight. The thickness uniformity is controlled within ±0.08mm, providing a wet paper sheet with reliable quality for subsequent processes. After the wet paper sheet leaves the wet paper machine, it passes through pre-pressing and secondary pre-pressing in sequence. The line pressure of pre-pressing and secondary pre-pressing is controlled at 15 - 20 kN / m to make the dryness of the wet paper reach 35 - 40%, ensuring the wet strength of the wet paper sheet and preparing for the formation of micro-wrinkles.

[0040] Micro-wrinkle formation stage: Introduce the wet paper sheet into a carefully debugged wrinkling system, which is equipped with an advanced angle adjustment device and a high-precision angle sensor. By adjusting the rotatable shaft under the doctor blade holder, use the angle sensor to precisely set the angle of the wrinkling doctor blade at 20 - 25°, with the error controlled within ±1°. At the same time, through a high-precision speed control system, which uses an encoder to monitor the speed of the transfer felt in real time at 40 - 60 m / min, the wrinkling rate reaches 8%. Under these conditions, the number of micro-wrinkles formed on the surface of the wet paper sheet reaches 6 - 8 per centimeter, and the wrinkle width is uniform, between 0.15 - 0.35mm, thus forming a uniform and fine micro-wrinkle structure. This micro-wrinkle structure can effectively improve the performance of the insulating paper and meet the requirements of different application scenarios.

[0041] Multi-stage pressing stage: After the wet paper is wrinkled, perform one-stage pressing. Use a pneumatic pressing device, set the line pressure at 10 - 12 kN / m, make the dryness of the wet paper reach 40 - 45%, and increase the tightness to 1.00 - 1.05 g / cm 3Subsequently, the second-stage pressing is carried out. The pneumatic pressing equipment is also adopted, and the relevant parameters are precisely controlled again. The line pressure is set to 12 - 15 kN / m, so that the dryness of the wet paper is increased to 45 - 50%, and the tightness is increased to 1.05 - 1.10 g / cm 3 , and the wet paper web is supported and dried by the heated dryer cylinder. The line pressure in this process is controlled to be 18 - 20 kN / m, so that the dryness of the wet paper reaches 50 - 55%, and the tightness of the insulating paper is enhanced to 1.10 - 1.15 g / cm 3 , effectively improving the interlayer bonding property.

[0042] Drying treatment stage: The superheated water heating method is adopted. Through the precise regulation of the steam pressure and the use of an advanced temperature control system, the precise control of the dryer cylinder temperature is achieved. The wet paper first passes through a large dryer cylinder with a temperature of 120 - 130 °C to preliminarily shape the micro-wrinkled insulating paper and ensure that the micro-wrinkles are not damaged in the initial drying stage. The temperature control accuracy of the large dryer cylinder reaches ±1.5 °C, which is achieved by adjusting the steam pressure and flow rate. Subsequently, after the wet paper passes through the first-stage dryer cylinder group, semi-wet calendering between rollers is carried out; after passing through the second-stage dryer cylinder group, four-roller calendering is carried out. When entering the first-stage dryer cylinder group, the temperature is set at 130 - 140 °C to remove a large amount of free water on the surface of the wet paper sheet, initially fix the micro-wrinkle structure, and ensure the integrity of the micro-wrinkles. The ventilation volume is dynamically adjusted according to the humidity in the dryer cylinder and the drying progress of the paper.

[0043] By precisely adjusting the pressure of the calender rolls for semi-wet calendering to be 20 - 25 kN / m and matching and adjusting parameters such as the rotational speed according to the running speed of the paper, the surface of the insulating paper is decorated, making the appearance of the insulating paper more flat and smooth, and the tightness is further improved.

[0044] After semi-wet calendering, it enters the second-stage dryer cylinder. The temperature of the second-stage dryer cylinder group is set at 80 - 90 °C to further remove the bound water inside the paper, so that the paper reaches the specified drying degree, and the water content is controlled between 7% and 9%, making the tightness of the formed paper stable at 1.10 - 1.15 g / cm 3 or so.

[0045] Post-treatment stage: The formed paper is calendered in the way of four-roller and three-pressure zones. The line pressure is controlled at 35 - 40 kN / m, so that the tightness of the formed paper is stable at 1.15 - 1.20 g / cm 3 , decorating the surface of the paper to form a smooth paper surface and ensuring the surface characteristics of the paper sheet. After calendering, the paper sheet enters the rewinder for winding to form a formed paper roll.

[0046] The above content is only to illustrate the technical idea of the present invention and cannot limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A manufacturing method of a high-density micro-wrinkled insulating paper for electrical engineering, characterized in that, It includes the following steps: Using 100% unbleached softwood kraft pulp as raw material, pulp preparation and purification are carried out in sequence to obtain pulp; The pulp is wet paper - made and preliminarily dewatered to obtain a wet paper sheet, then pre - pressed and secondarily pre - pressed. Then, the wet paper sheet is subjected to micro - wrinkling treatment to form wrinkles, and then multi - stage pressing, dryer support pressing, first - stage drying, semi - wet calendering, second - stage drying, four - roll calendering and winding are carried out in sequence to obtain a high - density micro - wrinkled insulating paper for electrical engineering. Among them, the process of micro - wrinkling treatment of the wet paper sheet to form wrinkles is as follows: The wet paper is scraped off from the wrinkling cylinder by the blade of the wrinkling roll, and the angle of the blade of the wrinkling roll is 15° - 45°; and by controlling the speed difference between the receiving felt and the wrinkling cylinder, the wrinkling rate is controlled to be 5% - 15%.

2. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The pulp preparation includes pulping and refining carried out in sequence; the beating degree after pulp preparation is 30°SR - 40°SR.

3. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The wet papermaking process uses triple cylinder wire pulp feeding, and the basis weight of the pulp on the forming wire is 50 - 150 g / m 2 .

4. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The line pressure of the pre - pressing and the second - stage pre - pressing is 10 - 20 kN / m.

5. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The multi - stage pressing includes first - stage pressing and second - stage pressing carried out in sequence; the line pressure of the multi - stage pressing and the dryer support pressing is 10 - 20 kN / m; the set temperature of the dryer support pressing is 100°C - 120°C.

6. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The dryness of the wet paper after the multi-stage pressing is 40% - 50%; the dryness of the wet paper after the dryer support pressing is 50% - 60%; the dry paper density after the multi-stage pressing and the dryer support pressing is 1.0 - 1.2 g / cm 3 .

7. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that The set temperature of the first - stage drying is 120°C - 140°C; the set temperature of the second - stage drying is 80°C - 100°C.

8. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The line pressure of the semi - wet calendering is 20 - 30 kN / m; the line pressure of the four - roll calendering is 30 - 40 kN / m.

9. The manufacturing method of the high-density micro-wrinkled insulating paper for electrical engineering according to claim 1, characterized in that, The moisture content of the paper after the four - roll calendering is below 10%.

10. The high - density micro - wrinkled insulating paper for electrical engineering prepared by the manufacturing method of the high - density micro - wrinkled insulating paper for electrical engineering according to any one of claims 1 to 9.

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