Electrical insulation crepe paper with multi-stage crepe structure and preparation method of electrical insulation crepe paper

Abstract

The invention discloses electrical insulation crepe paper with a multi-stage wrinkle structure, which belongs to electrical insulation materials and comprises a mixed fiber matrix comprising 5-10% by mass of aramid fiber and 90-95% by mass of electronic-grade unbleached sulfate softwood pulp, the crepe paper is internally provided with tiny communicated air channels formed by closely and orderly interweaving fibers, the surface of the mixed fiber matrix is provided with a multi-stage crepe structure formed through a two-time crepe process, the crepe depth is 0.7 mm-0. 9 mm, the crepe density is 4-6 pieces / cm, the crepe structure forms a labyrinth type path, and the labyrinth type path is provided with an air inlet and an air outlet. The technical problems that traditional electrical crepe paper is high in cost and poor in heat resistance, moisture resistance and buffering and damping capacity are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical insulation materials, and particularly relates to an electrical insulation crimped paper with a multi-level crimped structure and a preparation method thereof. Background Art

[0002] In modern power systems, electrical equipment is developing towards high voltage, large capacity, and miniaturization, which poses extremely high requirements for the performance of electrical insulation materials. As one of the commonly used insulation materials, traditional electrical crimped paper exposes many performance shortcomings when facing complex operating conditions and harsh environmental conditions.

[0003] In a high-voltage environment, due to the insufficiently dense internal structure and numerous air gaps of traditional electrical crimped paper, the electric field distribution is uneven, and local electric field concentration is likely to occur, which may lead to insulation breakdown and seriously threaten the safe operation of electrical equipment. At the same time, during the operation of electrical equipment, vibrations of varying degrees will occur. The buffering and shock-absorbing ability of traditional electrical crimped paper is limited, and it cannot effectively absorb vibration energy, which makes the internal conductors and insulation layers vulnerable to mechanical damage under long-term vibration, reducing the service life of the equipment.

[0004] In addition, with the continuous increase in heat generated during equipment operation, the problem of insufficient heat dissipation performance of traditional electrical crimped paper has become increasingly prominent. If the heat cannot be dissipated in time, it will cause the equipment temperature to rise, which will in turn affect the insulation performance and accelerate material aging. In a humid environment, traditional electrical crimped paper has poor moisture barrier ability, and moisture is easily permeated into the paper interior, damaging the insulation system and causing electrical equipment failures. Therefore, developing a high-performance electrical crimped paper and its preparation method has important practical significance and urgent market demand.

[0005] Chinese Patent CN115897292A discloses an aramid crimped paper and a preparation method thereof. The crimped paper is composed of all aramid fibers and is prepared through processes such as defibration, beating, flow forming, hot pressing, and high-temperature wrinkling. The length of the aramid precipitated fibers is controlled to be 0.5 - 1.3 mm, and meta-aramid fibers and short fibers are used to ensure uniform dispersion of the fibers and high-temperature hot pressing to improve mechanical properties and electrical insulation properties. However, the aramid crimped paper of this patent is made of all aramid fibers, with a high cost, and its heat dissipation, moisture-proof, and buffering properties are still poor. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an electrical insulation crimped paper with a multi-level crimped structure and a preparation method thereof, so as to solve the technical problems of high cost, poor heat resistance, moisture-proof property, and buffering and shock-absorbing ability of traditional electrical crimped paper.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] The present invention provides an electrical insulating crepe paper with a multi-level crease structure. The crepe paper comprises a mixed fiber matrix containing 5%-10% aramid fiber and 90%-95% electronic-grade unbleached sulfate softwood pulp by mass percentage; the interior of the crepe paper has micro-connected air channels formed by the tight and orderly interweaving of fibers; the surface of the crepe paper has a multi-level crease structure formed by two creasing processes, and the crease structure constitutes a labyrinthine path. The paper thickness is 0.7 mm - 0.9 mm, and the crease density is 4 - 6 creases / cm.

[0009] Preferably, the fiber length of the electronic-grade unbleached sulfate softwood pulp is 2.5 mm - 3.5 mm, the strength is ≥30 N, and the fiber length of the aramid fiber is 1 mm - 2 mm.

[0010] The present invention also provides a preparation method of the above-mentioned electrical insulating crepe paper with a multi-level crease structure, comprising the following steps:

[0011] 1) After mixing the electronic-grade unbleached sulfate softwood pulp and aramid fiber in proportion, add cellulase for surface modification;

[0012] 2) Perform two beating treatments on the pulp prepared in step 1), control the mass percentage concentration at 10%-15%, and control the beating degree at 30 - 40°SR;

[0013] 3) Mix the pulp prepared in step 2), water and polyacrylamide in a dosage ratio of (2.5 - 3.5) g : (996.5 - 997.5) mL : (0.025 - 0.035) g to obtain a pulp with a mass percentage concentration of 0.25% - 0.35%;

[0014] 4) Wet-form the pulp prepared in step 3) to obtain paper;

[0015] 5) Perform two creasing treatments on the paper, and obtain the electrical insulating crepe paper with a multi-level crease structure after drying.

[0016] Preferably, in step 1), the cellulase modification includes adding cellulase with a mass percentage concentration of 0.5% - 1% to the electronic-grade unbleached sulfate softwood pulp and reacting at 40 - 50°C for 1 - 2 h.

[0017] Preferably, in step 2), the two beating treatments include: primary beating with a high-concentration disc refiner at a rotational speed of 1200 - 1800 r / min and a gap of 0.3 mm - 0.8 mm; secondary fine beating with a conical refiner at a rotational speed of 800 - 1200 r / min and a gap of 0.2 mm - 0.5 mm.

[0018] Preferably, in step 4), wet forming is carried out by a multi-stage vacuum suction method, with a vacuum degree of -10 kPa to -55 kPa, a temperature of 23 - 25 °C, and a humidity of 45% - 55%.

[0019] More preferably, the multi-stage vacuum suction method with a vacuum degree of -10 kPa to -55 kPa is to gradually increase the vacuum degree from -10 kPa, -20 kPa, -35 kPa, and -55 kPa levels for suction from front to back.

[0020] Preferably, wet forming treatment includes dewatering and forming the pulp within 0.5 - 1 s through the synchronous operation of a forming felt and three wire baskets.

[0021] Preferably, in step 5), the two wrinkling treatments include: the first wrinkling is to put the paper into a pressing zone composed of a pressing roll with a ceramic-coated surface, a vacuum roll, and a stainless steel grooved roll for preliminary pressing, controlling the dryness of the paper at 33 - 35%, the contact pressure between the wrinkling blade and the paper at 0.3 - 0.5 N, and the contact angle at 20 - 22°, so as to form preliminary wrinkles on the paper surface; in the second wrinkling, the temperature is controlled at 100 - 120 °C, the contact pressure between the wrinkling blade and the paper at 0.5 - 1 N, and the contact angle at 20 - 22°, so as to form multi-stage wrinkles on the paper.

[0022] The above pressing zone is a K-type pressing zone, consisting of two pressing areas composed of a pressing roll, a vacuum roll, and a stainless steel grooved roll.

[0023] Preferably, in step 5), between the first wrinkling and the second wrinkling treatments, there is also a dehydration and calendering treatment: the paper after the first wrinkling and preliminary pressing is pressed again by a pair-roll pressing method, controlling the dryness at 46% - 48%.

[0024] Preferably, in step 5), the drying includes using an infrared radiator to remove the moisture on the paper surface at 180 - 200 °C within 1 - 2 min, so that the dryness of the paper reaches 80% - 90%, and then drying with hot air at 150 - 180 °C to control the remaining moisture at 4% - 6%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The crepe paper of the present invention uses a mixed fiber matrix of 5% - 10% aramid fiber and 90% - 95% electronic-grade unbleached sulfate softwood pulp by mass percentage. The aramid fiber forms a heat-resistant skeleton, inhibiting the thermal degradation of wood pulp fibers, and effectively improving the heat resistance of the crepe paper; the aramid fiber and the wood pulp form an interpenetrating network through hydrogen bonds, and the wrinkled structure disperses stress through hierarchical buckling, enhancing the buffering ability of the crepe paper; the multi-stage wrinkled structure with a labyrinth path absorbs impact energy through elastic deformation, improving the buffering and shock-absorbing ability and moisture resistance of the crepe paper.

[0027] Furthermore, the electronic-grade unbleached softwood kraft pulp fibers with a length of 2.5 mm - 3.5 mm provide a tensile strength of ≥ 30 N. The aramid fibers with a length of 1 mm - 2 mm fill the voids, effectively enhancing the interlayer bonding force. At the same time, the short aramid fibers within this length range avoid agglomeration, improving the interfacial bonding force, and thus enhancing the mechanical strength of the crepe paper.

[0028] The present invention also provides a method for preparing the above-mentioned crepe paper. Cellulase is used to remove impurities on the fiber surface, optimize the fiber surface properties, enhance the fiber-fiber bonding force, which is beneficial to the formation of a multi-level wrinkled structure. Two-stage beating treatment increases the specific surface area of the crepe paper. The bridging effect of polyacrylamide forms covalent bonds with the hydroxyl groups on the fiber surface, enhancing the network stability and also increasing the paper strength. The dosage ratio neutralizes the negative charges of the fibers through cationic groups, inhibiting flocculation. Two-stage wrinkling treatment endows the crepe paper with a multi-level wrinkled structure with a labyrinth-like path, effectively improving the buffering and shock-absorbing ability and moisture resistance of the crepe paper.

[0029] Furthermore, cellulase with a mass percentage concentration of 0.5% - 1% is added to the electronic-grade unbleached softwood kraft pulp. The cellulase selectively hydrolyzes β-1,4 glycosidic bonds, softens the fiber cell wall, enzymatically degrades the amorphous region of the fiber, exposes the hydroxyl groups, increases the hydrogen bond density, and at the same time reduces the beating energy consumption.

[0030] Furthermore, two-stage beating enhances fibrillation through fiber-fiber friction and reduces cutting. The high-concentration disk refiner in the primary beating coarsely breaks the fiber bundles, and the conical refiner finely splits the filaments, increasing the fiber bonding area. The conical refiner in the secondary beating finely splits the filaments, increasing the fiber bonding area.

[0031] Furthermore, a multi-stage vacuum suction method is adopted to automatically adjust the vacuum degree according to the moisture content of different parts of the paper, ensuring uniform dehydration. The temperature is controlled at 23 - 25 °C, and the humidity is controlled at 45% - 55%, reducing fiber moisture absorption and static electricity phenomena, enabling the fibers to be evenly distributed and normally interwoven on the wire mesh, ensuring that the paper thickness error is controlled within ±0.03 mm, and improving the physical properties and dimensional stability of the paper. Vacuum gradient and centrifugal force cooperate to drain water, and the rotational speed difference of the wire cage induces fiber orientation.

[0032] Furthermore, a three-cylinder forming technology is adopted to replace the traditional long wire forming. During the cylinder forming process, through the synchronous operation of a forming felt and three wire cages, the pulp is quickly dehydrated within 0.5 - 1 second, improving the fiber orientation degree.

[0033] Furthermore, during the first wrinkling process, the ceramic roller reduces adhesion, the grooved roller guides the formation of wrinkles. Under pressure, the scraper gently contacts the paper surface, initially forming a wrinkled appearance, optimizing the paper's microstructure, reducing internal air gaps, improving insulation performance, laying a foundation for subsequent construction of a labyrinth path, enhancing moisture-proof performance, and at the same time improving the flexibility and cushioning performance of the paper; during the second wrinkling process, the paper forms more complex, uniform, and stable multi-level wrinkles under the condition of being heated.

[0034] Furthermore, the pair-roll pressing method makes the internal fibers of the paper arrange more closely and orderly, forming a more efficient heat conduction channel. Combining with the air convection channel formed by the paper's wrinkled structure, it significantly improves the heat dissipation efficiency. At the same time, it further enhances the binding force between fibers, improving the overall mechanical properties and insulation performance of the paper.

[0035] Furthermore, the method of combining infrared drying and hot air drying is adopted. Infrared radiation selectively heats the fiber bonding area, increasing the rate of hydrogen bond formation. The hot air temperature gradient releases internal stress and improves dimensional stability, effectively preventing shrinkage. Through a stable moisture content and a uniform drying process, the special microstructure of the paper is maintained, ensuring the stability and durability of its special properties. Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the wrinkles of ordinary crepe paper;

[0037] Figure 2 It is a schematic diagram of the wrinkles of the crepe paper of the present invention. Detailed Embodiments

[0038] To enable those skilled in the art to understand the features and effects of the present invention, the following provides only 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 conflict, the definition in this specification shall prevail.

[0039] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not in any way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0040] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges shall be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0041] In this text, unless otherwise specified, the terms "comprise", "include", "contain", "have" or similar terms cover the meanings of "consist of" and "consist essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0042] In this text, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0043] The present invention provides a method for preparing an electrical insulating crepe paper with a multi-stage wrinkled structure, comprising the following steps:

[0044] Raw material preparation: Select high-quality electronic-grade unbleached sulfate softwood pulp, and innovatively add 5%-10% aramid fiber. Adopt the enzyme pretreatment technology, add a specific cellulase with a mass percentage concentration of 0.5%-1% to the wood pulp, and react for 1-2 hours in an environment of 40-50 °C. Control the length of the wood pulp fibers between 2.5 mm and 3.5 mm, with a strength of more than 30 N, and control the length of the aramid fibers between 1 mm and 2 mm to ensure that the mixed raw materials meet the high requirements of insulating materials.

[0045] Beating: Adopt the high-consistency beating technology to increase the mass percentage concentration of the pulp to 10%-15%, and use a high-consistency disc refiner for preliminary beating. The fibers are efficiently cut and preliminarily fibrillated by the high-speed rotating disc. Subsequently, a conical refiner is introduced for secondary fine beating to further optimize the fiber morphology. During the beating process, use an on-line fiber analyzer and an intelligent control system to monitor the fiber length, fibrillation degree and beating degree in real time, and automatically adjust parameters such as the speed and gap of the disc refiner and the conical refiner according to the real-time data to ensure that the beating degree is stably controlled between 30-40 °SR, realizing the precision and intelligence of the beating process.

[0046] Pulp blending: Install a high-precision on-line concentration detector and a flow control system in the pulp blending tank. The computer accurately calculates the optimal ratio of pulp, water and polyacrylamide according to different production requirements and paper performance targets. Ensure that the mass percentage concentration of the pulp is stably controlled between 0.25%-0.35%, realizing the intelligence and precision of the pulp blending process.

[0047] Wet forming: The traditional long - wire forming is replaced by the three - cylinder forming technology. During the cylinder forming process, through the synchronous operation of a forming felt and three wire cylinders, the pulp is quickly dewatered and formed within 0.5 - 1 second. The vacuum dewatering device is optimized, adopting a multi - stage vacuum suction method, and automatically adjusting the vacuum degree according to the moisture content of different parts of the paper to ensure uniform dewatering. At the same time, a temperature and humidity control system is installed in the wet forming workshop, controlling the temperature at 23 - 25 °C and the humidity at 45% - 55%, reducing fiber moisture absorption and static electricity phenomena, enabling the fibers to be evenly distributed and normally interwoven on the wire surface, ensuring that the paper thickness error is controlled within ±0.03 mm, and improving the physical properties and dimensional stability of the paper.

[0048] Primary wrinkling: The paper after wet forming enters the K - type pressing area composed of a pressing roller with a ceramic - sprayed surface, a vacuum roller, and a stainless - steel grooved roller, accurately controlling the dryness of the paper to 33% - 35%. There is a wrinkling blade on the pressing roller with a ceramic - sprayed surface. Under the action of pressure, the blade gently contacts the paper surface, initially forming a wrinkled appearance, optimizing the paper's microstructure, reducing internal air gaps, improving insulation performance, laying a foundation for constructing a maze - like path subsequently, enhancing moisture - proof performance, and at the same time improving the flexibility and cushioning performance of the paper.

[0049] Dehydrating calendering: The paper after primary wrinkling and preliminary pressing enters the secondary pressing process equipped with an intelligent pressure control system, adopting a pair - roll pressing method to remove moisture again. The dryness of the paper reaches 45% - 48% after leaving the secondary pressing. This pressing method makes the internal fiber arrangement of the paper more compact and orderly, forming a more efficient heat conduction channel. Combining with the air convection channel formed by the wrinkled structure of the paper, it significantly improves the heat dissipation efficiency. At the same time, it further enhances the bonding force between fibers, improving the overall mechanical properties and insulation performance of the paper.

[0050] Secondary wrinkling: The paper after the previous treatment is sent to a large drying cylinder regulated by an advanced temperature control system and an intelligent wrinkling control system for wrinkling operations. The surface temperature of the large drying cylinder is accurately controlled at 100 - 120 °C. Adopting the wrinkling method with an intelligent blade device, using the intelligent blade device installed on the surface of the drying cylinder, according to the real - time state of the paper, through high - precision pressure sensors and angle sensors, the contact pressure between the blade and the paper is monitored and adjusted in real - time between 0.5 - 1 N and the angle between 15° - 30°, enabling the paper to form more complex, uniform, and stable wrinkles in the heated state.

[0051] Drying: Adopt a combination of infrared drying and hot air drying. First, use an infrared radiator to quickly remove the moisture on the paper surface within 1 - 2 minutes, making the dryness of the paper reach 80 - 90%. Then, through the hot air drying device, accurately reduce the remaining moisture to 4% - 6%. Install a multi - point temperature monitoring device and a ventilation optimization system in the drying equipment to ensure that the temperature uniformity error is controlled within ±1°C, ensure uniform heating of the paper, and maintain the special microstructure of the paper through a stable moisture content and uniform drying process, ensuring the stability and durability of its special properties.

[0052] Enhanced adaptability of insulation performance: Due to the special multi - level wrinkled structure and optimized raw material formula of the electrical engineering crepe paper of the present invention, when it adheres to the surfaces of conductors with different shapes, it can closely adhere, effectively fill the gaps, and make the electric field evenly distributed in the entire insulation area through the labyrinth - like wrinkled path.

[0053] Improved buffering and shock - absorption ability: The complex wrinkled structure and optimized fiber combination endow the electrical engineering crepe paper of the present invention with excellent buffering and shock - absorption ability, which can extend the service life of the equipment by more than 30%.

[0054] Increased heat dissipation performance: The unique wrinkled structure and tightly ordered fiber arrangement increase the surface area of the electrical engineering crepe paper of the present invention by 35%, forming numerous tiny and efficient air channels. Effectively maintain the normal working temperature of the equipment and ensure the stable performance of the equipment during long - term operation.

[0055] Improved moisture - proof performance: The labyrinth - like wrinkled path and optimized microstructure endow the electrical engineering crepe paper of the present invention with strong moisture - proof ability. Effectively protect the insulation system of electrical equipment from moisture and ensure the reliable operation of the equipment in harsh and humid environments.

[0056] By optimizing the microstructure and preparation process of the paper, the present invention significantly improves the insulation performance, buffering and shock - absorption ability, heat dissipation performance and moisture - proof performance of the electrical engineering crepe paper to meet the strict requirements of modern power systems for insulation materials of electrical equipment and ensure the safe, stable and efficient operation of electrical equipment.

[0057] The electrical engineering crepe paper of the present invention has a unique complex and delicate wrinkled structure, which promotes the tight and orderly interweaving of internal fibers of the paper, forming numerous tiny and connected air channels. These microstructural characteristics are the key to realizing its mechanical and electrical aspects and lay the foundation for improving the comprehensive performance of the electrical engineering crepe paper.

[0058] 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 not 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 also fall within the scope defined by the appended claims of this application.

[0059] In the following embodiments, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0060] Example 1

[0061] Raw material preparation: Select high-quality unbleached sulfate softwood pulp with an average fiber length of 3 mm and a strength of 35 N; add 8% aramid fiber with a fiber length controlled at 1.5 mm; add 0.8% of a specific cellulase to the pulp and react at 45 °C for 1.5 hours;

[0062] Beating: Adopt high-consistency beating technology to increase the mass percentage concentration of the pulp to 12%. First, use a high-consistency disc refiner for preliminary beating with a rotational speed set at 1500 r / min and a disc gap of 0.5 mm; then introduce a conical refiner for secondary fine beating with a rotational speed of 1000 r / min and a disc gap of 0.3 mm; during the beating process, through an on-line fiber analyzer and an intelligent control system, monitor and adjust the parameters in real time, and finally control the beating degree at 35 °SR;

[0063] Pulp blending: Blend the pulp, water, and polyacrylamide prepared above in a dosage ratio of 2.5 g: 996.5 mL: 0.025 g, and control the mass percentage concentration of the pulp at 0.3%;

[0064] Wet forming: Adopt a cylinder forming technology to dehydrate and form the pulp within 0.8 seconds; the vacuum dehydration device uses three-stage vacuum suction and automatically adjusts the vacuum degree according to the moisture content in different parts of the paper; the temperature in the wet forming workshop is controlled at 24 °C and the humidity is controlled at 50%;

[0065] Primary wrinkling: The paper after wet forming enters the K-type pressing area composed of a pressing roll with a ceramic-coated surface, a vacuum roll, and a stainless steel grooved roll. The contact pressure between the wrinkling blade and the paper is 0.4 N, and the contact angle is 21°, so that preliminary wrinkles are formed on the paper surface, and the dryness of the paper is accurately controlled to 35%;

[0066] Dehydration Calendering: The paper after one-time wrinkling and preliminary pressing is dehydrated again by means of double-roll pressing. The dryness of the paper reaches 46% after the second pressing.

[0067] Second Wrinkling: The paper after the previous treatment is sent into a large drying cylinder controlled by an advanced temperature control system and an intelligent wrinkling control system for wrinkling operation. The surface temperature of the large drying cylinder is precisely controlled at 100°C. The intelligent scraper device is used for wrinkling, and the contact pressure between the scraper and the paper is adjusted to 0.7N and the angle is 22°, so that the paper forms more complex, uniform and stable wrinkles under the heated state.

[0068] Drying: First, the surface moisture of the paper is quickly removed by an infrared radiator within 2 minutes to make the dryness of the paper reach 90%. Then, the remaining moisture is precisely reduced to 4% through a hot air drying device.

[0069] Example 2

[0070] Raw Material Preparation: Select high-quality unbleached sulfate softwood pulp with an average fiber length of 2.5mm and a strength of 30N; add 5% aramid fiber with a fiber length controlled at 1mm; add 0.5% of a specific cellulase to the wood pulp and react at 40°C for 2 hours.

[0071] Beating: High-concentration beating technology is adopted to increase the mass percentage concentration of the pulp to 10%. First, a high-concentration disc refiner is used for preliminary beating with a rotational speed set at 1200r / min and a disc gap of 0.8mm; then a conical refiner is introduced for secondary fine beating with a rotational speed of 800r / min and a disc gap of 0.5mm; the beating degree is controlled to 30°SR through an on-line monitoring system.

[0072] Pulp Blending: The pulp, water and polyacrylamide prepared in Step 2 are mixed in a dosage ratio of 3g:997mL:0.03g to obtain a pulp with a mass percentage concentration of 0.25%.

[0073] Wet Forming: The three-cylinder forming technology is adopted, and the pulp is dehydrated and formed within 0.5s. Four-stage vacuum suction (-10kPa / -20kPa / -35kPa / -55kPa) is used, and the workshop temperature is 23°C and the humidity is 45%.

[0074] First Wrinkling: The paper after wet forming is put into a K-type pressing area composed of a pressing roll with a ceramic-coated surface, a vacuum roll and a stainless steel grooved roll. The dryness of the paper is controlled at 33% in the K-type pressing area, the contact pressure of the wrinkling scraper is 0.3N, and the angle is 20° to form preliminary wrinkles.

[0075] Dehydration Calendering: The paper after one-time wrinkling and preliminary pressing is controlled to a dryness of 46% by means of double-roll pressing.

[0076] Secondary wrinkling: Feed the pre-treated paper into a large drying cylinder regulated by an advanced temperature control system and an intelligent wrinkling control system for wrinkling operation. The surface temperature of the large drying cylinder is precisely controlled at 120 °C. Adopt the method of wrinkling with an intelligent blade device, adjust the contact pressure between the blade and the paper to 0.7 N and the angle to 21°, so that the paper forms more complex, uniform and stable multi-level wrinkles under the heated state;

[0077] Drying: First, use an infrared radiator to quickly remove the moisture on the paper surface within 2 minutes to make the dryness of the paper reach 85%, and then through a hot air drying device, accurately reduce the remaining moisture to 5%; Treat with infrared radiation temperature of 185 °C for 1 minute to make the dryness reach 80%, and then dry with hot air at 150 °C until the moisture is 6%.

[0078] Example 3

[0079] Raw material preparation: Select electronic-grade unbleached sulfate softwood pulp with a fiber length of 3.5 mm and a strength of ≥30 N; Add 10% aramid fiber with the aramid fiber length controlled at 2 mm; Add 1% cellulase to the wood pulp and react for 1 h in an environment of 50 °C;

[0080] Beating: Adopt high-consistency beating technology to increase the mass percentage concentration of the pulp to 15%. First, use a high-consistency disc refiner for preliminary beating with a rotational speed set at 1800 r / min and a disc gap of 0.3 mm; Then introduce a conical refiner for secondary fine beating with a rotational speed of 1200 r / min and a disc gap of 0.2 mm; Adjust in real time through an intelligent control system, and finally control the beating degree at 40°SR;

[0081] Pulp blending: Mix the pulp, water and polyacrylamide prepared above according to the dosage ratio of 3.5 g: 997.5 mL: 0.035 g to obtain a pulp with a mass percentage concentration of 0.35%;

[0082] Wet forming: Adopt the cylinder forming technology to dehydrate and form the pulp within 1 s, adopt four-stage vacuum suction (the vacuum degree is gradually increased from -10 kPa to -55 kPa), the workshop temperature is 25 °C, and the humidity is 55%;

[0083] Primary wrinkling: The paper after wet forming enters the K-type pressing area composed of a pressing roll with a ceramic-coated surface, a vacuum roll and a stainless steel grooved roll. The contact pressure between the wrinkling blade and the paper is 0.4 N, and the contact angle is 21°, so that preliminary wrinkles are formed on the paper surface. Control the dryness of the paper at 34% in the K-type pressing area, the contact pressure of the wrinkling blade is 0.5 N, and the angle is 22°, forming uniform preliminary wrinkles;

[0084] Dehydration and calendering: The paper after primary wrinkling and preliminary pressing is dewatered again by the method of pair-roll pressing, and the dryness of the paper reaches 46% after leaving the secondary pressing;

[0085] Secondary wrinkling: Feed the pre-treated paper into a large drying cylinder regulated by an advanced temperature control system and an intelligent wrinkling control system for wrinkling operation. The surface temperature of the large drying cylinder is precisely controlled at 110°C. Adopt the wrinkling method with an intelligent blade device, adjust the contact pressure between the blade and the paper to 1 N and the angle to 20°, so that the paper forms more complex, uniform and stable wrinkles in the heated state, and form high-density wrinkles (6 pieces / cm) through an intelligent pressure feedback system.

[0086] Drying: First, use an infrared radiator to quickly remove the moisture on the paper surface within 1 minute to make the dryness of the paper reach 90%, and then use a hot air drying device at 180°C to precisely reduce the remaining moisture to 4%.

[0087] The above content is only to illustrate the technical idea of the present invention and cannot be used to 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. An electrical insulating crepe paper with a multi-level wrinkled structure, characterized in that, The crepe paper comprises a mixed fiber matrix containing 5%-10% aramid fiber and 90%-95% electronic-grade unbleached sulfate softwood pulp by mass percentage; the interior of the crepe paper has micro-connected air channels formed by tightly and orderly interwoven fibers; the surface of the crepe paper has a multi-stage fold structure formed by two creping processes, and the fold structure constitutes a labyrinth path. The paper thickness is 0.7 mm - 0.9 mm, and the fold density is 4 - 6 folds / cm.

2. The electrical insulation crinkled paper with a multi-stage wrinkled structure according to claim 1, characterized in that, The fiber length of the electronic-grade unbleached sulfate softwood pulp is 2.5 mm - 3.5 mm, the strength is ≥30 N, and the aramid fiber length is 1 mm - 2 mm.

3. The preparation method of an electrical insulating crepe paper with a multi-stage wrinkled structure according to claim 1 or 2, characterized in that, It includes the following steps: 1) After mixing the electronic-grade unbleached sulfate softwood pulp and aramid fiber in proportion, add cellulase for surface modification; 2) Perform two beating treatments on the pulp prepared in step 1), control the mass percentage concentration at 10% - 15%, and the beating degree at 30 - 40°SR; 3) Mix the pulp prepared in step 2), water, and polyacrylamide in a dosage ratio of (2.5 - 3.5) g : (996.5 - 997.5) mL : (0.025 - 0.035) g to obtain a pulp with a mass percentage concentration of 0.25% - 0.35%; 4) Wet-form the pulp prepared in step 3) to obtain paper; 5) Perform two creping treatments on the paper, and after drying, obtain the electrical insulation crepe paper with a multi-stage fold structure.

4. The preparation method of an electrical insulation crinkled paper with a multi-stage wrinkled structure according to claim 3, characterized in that, In step 1), the cellulase modification includes adding cellulase with a mass percentage concentration of 0.5% - 1% to the electronic-grade unbleached sulfate softwood pulp and reacting at 40 - 50°C for 1 - 2 h.

5. The preparation method of an electrical insulating crimped paper with a multi-stage crimped structure according to claim 3, wherein, In step 2), the two beating treatments include: primary beating with a high-concentration disc refiner at a rotational speed of 1200 - 1800 r / min and a gap of 0.3 mm - 0.8 mm; secondary fine beating with a conical refiner at a rotational speed of 800 - 1200 r / min and a gap of 0.2 mm - 0.5 mm.

6. The preparation method of an electrical insulating crimped paper with a multi-stage crimped structure according to claim 3, characterized in that, In step 4), wet forming adopts a multi-stage vacuum suction method, with a vacuum degree of -10 kPa - -55 kPa, a temperature of 23 - 25°C, and a humidity of 45% - 55%.

7. The preparation method of an electrical insulation crinkle paper with a multi-stage crinkle structure according to claim 6, characterized in that, The wet forming treatment includes dehydrating and forming the pulp within 0.5 - 1 s through the synchronous operation of a forming felt and three wire baskets.

8. The preparation method of an electrical insulating crinkled paper with a multi-stage wrinkled structure according to claim 3, characterized in that, In step 5), the two creping treatments include: the first creping is to place the paper into a pressing zone composed of a pressing roll with a ceramic-coated surface, a vacuum roll, and a stainless steel grooved roll, control the dryness of the paper at 33% - 35%, the contact pressure between the creping blade and the paper at 0.3 - 0.5 N, and the contact angle at 20 - 22° to form preliminary folds on the paper surface; in the second creping, the temperature is controlled at 100 - 120°C, the contact pressure between the creping blade and the paper at 0.5 - 1 N, and the contact angle at 20 - 22° to form multi-stage folds on the paper.

9. The preparation method of an electrical insulating crinkled paper with a multi-stage wrinkled structure according to claim 8, characterized in that, An additional dehydration and calendering treatment is also included between the first creping and the second creping treatments: re-press the paper after the first creping and preliminary pressing by means of pair-roll pressing, and control the dryness at 46% - 48%.

10. The preparation method of an electrical insulating crinkled paper with a multi-stage wrinkled structure according to claim 3, characterized in that, In step 5), the drying includes removing the moisture on the paper surface at 180 - 200°C within 1 - 2 minutes to make the dryness of the paper reach 80% - 90%, and then drying with hot air at 150 - 180°C to control the remaining moisture within 4% - 6%.

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