Crepe paper for transformer and preparation method of crepe paper

Abstract

The invention discloses crepe paper for a transformer and a preparation method of the crepe paper, and belongs to the technical field of production of auxiliary materials for manufacturing power transformers, and the preparation method comprises the following steps: adding a nonionic dispersant and reverse osmosis water into mixed pulp prepared from electrical-grade unbleached sulfate wood pulp to prepare 0.3%-0.5% outer layer pulp; mixing the mixed pulp with broke pulp and fibers, and adding polyacrylamide and reverse osmosis water to prepare inner-layer pulp with the concentration of 0.3-0.8%; the crepe paper is prepared after the outer-layer pulp and the inner-layer pulp are subjected to papermaking, squeezing, drying, wrinkling and re-drying, and the technical problems that crepe paper manufactured through an existing crepe paper production method is poor in dipping performance, electrical performance and mechanical performance are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the production of auxiliary materials for power transformer manufacturing, and particularly relates to a crimped paper for transformers and a preparation method thereof. Background Art

[0002] During the operation of power transformers, the performance of insulating materials is directly related to the stability, safety, and service life of the equipment. Traditional methods for producing crimped paper have many defects, and the crimped paper produced shows poor performance in key aspects such as impregnation performance, electrical performance, and mechanical performance. For example, during the oil immersion process of some crimped papers, due to poor impregnation performance, they cannot fully absorb insulating oil, resulting in a significant reduction in the overall insulation effect; their transverse and longitudinal elongation rates are not ideal, making it difficult to adapt to the stresses generated by factors such as temperature changes during transformer operation, and prone to cracking; in terms of electrical performance, the dielectric loss is relatively high, which not only increases the energy loss during transformer operation but also may affect the normal operation of the equipment; the mechanical performance is not strong, the tensile resistance is weak, and it is difficult to withstand various mechanical stresses under the complex working conditions of transformers. Therefore, researching and developing a new type of high-performance crimped paper and its preparation method has extremely important practical significance and market value.

[0003] 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-cut fibers are used to ensure uniform dispersion of the fibers and high-temperature hot pressing treatment to improve mechanical performance and electrical insulation performance. However, the preparation method of this crimped paper uses all aramid as raw materials and relies on synthetic fibers, resulting in high costs. Moreover, during the oil immersion process of this crimped paper, due to poor impregnation performance, it cannot fully absorb insulating oil, resulting in a significant reduction in the overall insulation effect. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a crimped paper for transformers and a preparation method thereof, so as to solve the technical problems of poor impregnation performance and high cost of the crimped paper produced by the existing crimped paper production methods.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention provides a preparation method for a crimped paper for transformers, which is characterized by including the following steps:

[0007] 1) Add a non-ionic dispersant and reverse osmosis water to the mixed pulp made from unbleached sulfate wood pulp for electrical engineering to prepare an outer layer pulp with a concentration of 0.3%-0.5%. The addition amount of the non-ionic dispersant is 0.1%-0.3% of the mass of the pulp.

[0008] 2) After mixing the mixed pulp with waste paper pulp and fibers, add polyacrylamide and reverse osmosis water to make an inner layer pulp with a concentration of 0.3%-0.8%. In the inner layer pulp, the mass percentage of waste paper pulp is 20%-40%, the mass percentage of fibers is 40%-70%, and the mass percentage of the mixed pulp is 10%-20%. The addition amount of the polyacrylamide is 0.5%-1% of the mass of the mixed pulp.

[0009] 3) After the outer layer pulp and the inner layer pulp are formed by papermaking, pressed, dried, wrinkled and dried again, the crepe paper is obtained.

[0010] Preferably, in step 1), the mixed pulp is prepared by beating an unbleached sulfate wood pulp for electrical engineering with a fiber length of 2.5 mm - 3.5 mm and an ash content < 0.5% and a composite enzyme preparation in a mass ratio of 1:(0.5 - 1), and controlling the beating degree to be 30 - 35°SR.

[0011] Preferably, the beating consistency is 3%-5%, the beating time is 30 - 45 min, and the beating energy consumption range is 150 - 200 kWh / ton.

[0012] Preferably, the composite enzyme preparation is made from cellulase and hemicellulase. Among them, the activity of cellulase is not less than 10000 U / g, and the activity of hemicellulase is not less than 5000 U / g.

[0013] Preferably, in step 1), the non-ionic dispersant is a fatty alcohol polyoxyethylene ether type.

[0014] Preferably, in step 3), a double cylinder paper machine is used to form a double-layer paper sheet with a basis weight of 70 - 80 g / m 2 The vacuum degree of the wire part is between -25 kPa and -45 kPa. After preliminary forming, it is sent to the pressing part. The pressing line pressure is controlled at 45 - 55 kN / m. After leaving the pressing part, the paper is preliminarily formed. At this time, the moisture content is controlled at 45%-48%. The drying temperature before wrinkling is 105 - 115℃.

[0015] Preferably, in step 3), the wrinkling includes setting the pressure of the wrinkling blade to 0.3 - 0.5 MPa, the wrinkling rate is 50%-100%, the drying temperature after wrinkling is 80 - 110℃, and drying until the moisture content ≤ 6%.

[0016] Preferably, after the production waste paper is disintegrated, screened and purified, waste paper pulp is obtained; the rotation speed of disintegration is 500-600 r / min, and the disintegration time is 10-15 min.

[0017] More preferably, purification includes introducing air into the pulp by using a flotation machine to generate bubbles, enabling impurities to adhere to the bubbles and smoothly float to the surface, and finally removing the impurities through a scraping device. The dosage ratio of the pulp to air is 1000 kg: 8 L. Hydrophobic impurities can be adsorbed on the surface of the bubbles, and flotation separation avoids chemical pollution.

[0018] Preferably, in step 1), the fibers are obtained by collecting and filtering white water and then recycling them. The fibers are concentrated to a concentration of 10%-15%, and the filtration pressure is maintained at 0.05-0.1 MPa.

[0019] More preferably, the disk rotation speed of the filtration equipment is controlled at 1-3 r / min.

[0020] The present invention also provides the transformer corrugated paper prepared by the above-mentioned preparation method of the transformer corrugated paper.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the preparation method of the present invention, the outer layer pulp is prepared by using unbleached sulfate wood pulp of electrical grade in combination with a non-ionic dispersant, so that the outer layer of the corrugated paper is microscopically breathable and porous, can quickly and fully absorb transformer oil, and greatly improves the stability of the insulation system. Experiments show that the impregnation time is shortened by 30% compared with traditional corrugated paper; polyacrylamide (PAM) is added to the inner layer pulp to enhance the interlayer bonding strength. The high-porosity structure of the outer layer accelerates liquid penetration, and the dense structure of the inner layer prevents excessive liquid diffusion, forming a gradient liquid absorption path, thereby avoiding impregnation delamination. Reverse osmosis water reduces conductive ions, effectively reducing the dielectric loss value (tanδ) ≤ 0.005 (traditional wood pulp paper ≥ 0.008), greatly reducing the energy loss during the operation of the transformer. The non-ionic dispersant avoids charge interference, reduces conductive impurities and free ions, blocks the leakage current path, and effectively improves the electrical performance of the corrugated paper. In addition, by using unbleached sulfate wood pulp of electrical grade as the raw material to prepare corrugated paper, expensive synthetic materials do not need to be introduced, reducing the preparation cost.

[0023] Furthermore, by using unbleached sulfate wood pulp with a fiber length of 2.5 mm - 3.5 mm and an ash content of < 0.5% and a composite enzyme preparation to prepare a mixed pulp with a beating degree of 30-35°SR, and by preparing a double-layer structure of high long fibers in the outer layer + mixed pulp in the inner layer, the fiber orientation arrangement (MD) and the corrugation structure (CD) cooperate to balance the strength and deformation ability, improving the tensile strength of the corrugated paper and thus enhancing the mechanical properties of the corrugated paper.

[0024] Furthermore, the beating consistency for beating treatment is 3% - 5%, the beating time is 30 - 45 min, and the beating energy consumption ranges from 150 - 200 kWh / ton. Medium-consistency beating balances fiber swelling and mechanical shear force, and the enzyme-mechanical synergistic effect optimizes fibrillation, thereby improving fibrillation efficiency and interfacial bonding strength.

[0025] Furthermore, cellulase and hemicellulase are used. The enzymes selectively hydrolyze the amorphous regions of fibers and retain the crystalline region structure. That is, cellulase targets and attacks the non-crystalline regions of cellulose chains, exposes microfibrils, and improves fibrillation rate. Hemicellulase removes the gelatinous layer that wraps the fibers, increases the specific surface area of the fibers, and enhances the density of hydrogen-bonding sites, thereby reducing fiber breakage, improving fibrillation efficiency, increasing the specific surface area of the fibers, and enhancing the density of bonding sites.

[0026] Furthermore, fatty alcohol polyoxyethylene ethers are used as non-ionic dispersants. The hydrophobic groups anchor on the fiber surface, and the hydrophilic EO chains form steric hindrance, inhibiting fiber flocculation and avoiding charge interference, effectively improving the electrical properties of crepe paper.

[0027] Furthermore, the vacuum degree of the wire section of the twin-wire paper machine is set between -25 kPa and -45 kPa. After preliminary forming, it is sent to the press section. The press line pressure is controlled at 45 - 55 kN / m. After leaving the press section, the paper is preliminarily formed, and at this time, the moisture content is controlled at 45% - 48%. The drying temperature is 105 - 115 °C. Gradient vacuum dewatering reduces fiber loss, high-pressure pressing closes micropores, and high-temperature drying solidifies the fiber network, making the structure of crepe paper more dense and the dewatering efficiency higher.

[0028] Furthermore, the pressure of the creping doctor blade is set at 0.3 - 0.5 MPa, and the drying temperature is 80 - 110 °C. Low-temperature creping reduces thermal stress, and the doctor blade pressure precisely controls the creping deformation. Low-temperature drying retains the fiber hydrogen bonds, thus ensuring the uniformity of creping and controlling the creping rate within 50% - 100%.

[0029] Furthermore, by adding a white water treatment process, a multi-disc filter device is used to effectively collect and utilize the fibers in the white water, improving resource utilization rate, reducing production costs, and at the same time reducing the impact on the environment. The multi-disc intercepts fibers, and low-pressure filtration at 0.05 - 0.1 MPa avoids fiber damage, and then the dynamic pressure regulation balances the recovery efficiency.

[0030] Furthermore, the rotational speed for pulping is 500 - 600 r / min, and the pulping time is 10 - 15 min. High rotational speed generates turbulent shear force, quickly separates fiber bundles, and reduces the residence time. Specific embodiments

[0031] 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 only for the terms and phrases 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 for the present invention. In case of conflict, the definition in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether right or wrong, 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.

[0033] 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 a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0034] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0035] In this article, for the sake of brevity of 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 within the scope described in this specification.

[0036] The present invention provides a method for preparing crimped paper for transformers, comprising the following steps

[0037] Step 1: Select unbleached sulfate wood pulp for electrical engineering, control its fiber length between 2.5 and 3.5 mm, and ensure that the length is uniform. At the same time, the ash content is required to be less than 0.5%, and the acid-insoluble ash content should be even less than 0.1% to ensure that the basic physical properties of the paper are not interfered by impurities.

[0038] Step 2: Collect the dry waste paper in the production process and then put it into a pulper. Set the speed of the pulper at 500 - 600 r / min. After 10 - 15 minutes of efficient pulping, the waste paper is successfully pulped into uniform small fiber fragments. Subsequently, use a special pressure screen with a pore size of 0.25 mm to preliminarily screen the pulped slurry to remove residual large impurities. Then, use an air flotation machine to accurately introduce 8 liters of air per minute per ton of slurry into the slurry, so that impurities lighter than the fibers adhere to the bubbles and float smoothly to the surface. Finally, remove them through a scraping device to further improve the purity of the slurry. Then send it to a refiner to refine the fibers to make the fibers disperse well, and store the treated waste paper in tank A.

[0039] Step 3: Collect the filtered white water generated in the fiber forming stage and introduce the white water into a multi-disc filtering device. Control the disc speed of the device at 1 - 3 r / min and maintain the filtering pressure at 0.05 - 0.1 MPa. During the filtering process, the fibers in the white water are intercepted on the filter screen surface of the disc to achieve preliminary separation of the fibers from the water. For the preliminarily separated fibers, further concentration treatment is carried out. By adjusting the concentration mechanism of the device, the fiber concentration is made to reach 10% - 15% and stored in tank B.

[0040] Step 4: First, put the unbleached sulfate wood pulp selected in Step 1 into an advanced beating device and add beating enzymes. The beating enzymes used in the present invention are a composite enzyme preparation of cellulase and hemicellulase. Among them, the activity of cellulase is not less than 10000 U / g, the activity of hemicellulase is not less than 5000 U / g, and the addition amount of the beating enzyme is 0.5 - 1 kg per ton of wood pulp. Control the pulping concentration at 3% - 5%, the pulping time at 30 - 45 min, and the pulping energy consumption range is stably controlled at 150 - 200 kWh / ton. Detect the beating degree of the fibers through an online freeness meter to ensure that the beating degree reaches 30 - 35°SR, so that the fibers are fully refined and maintain an appropriate fibrillation degree, effectively improving the strength and flexibility of the paper. The treated slurry is stored in tank C.

[0041] Step 5: Add reverse osmosis water and a non-ionic dispersant to the wood pulp in tank C in a scientific and reasonable proportion. The main component of the non-ionic dispersant is a fatty alcohol polyoxyethylene ether substance, and the addition amount is 0.1% - 0.3% of the mass of the slurry, so that the concentration of the slurry is accurately controlled between 0.3% - 0.5% to make the outer layer slurry. This dispersant is a non-ionic dispersant molecule that does not ionize ions in an aqueous solution, fully meeting the strict requirements of the subsequent papermaking process for the fluidity, fiber dispersion, and electrical insulation of the slurry.

[0042] Step 6: Mix the broke pulp in tank A, the unbleached kraft pulp in tank C, and the fibers in tank B in a certain proportion. The proportion of the broke pulp in tank A is 20%-40%, the proportion of the unbleached kraft pulp in tank C is 40%-70%, and the proportion of the fibers in tank B is 10%-20%. Then add an appropriate amount of reverse osmosis water and polyacrylamide (the addition amount is 0.5%-1% of the pulp mass) to significantly improve the paper strength. After fully stirring evenly, precisely adjust the pulp concentration to 0.3%-0.8% to make the inner layer pulp.

[0043] Step 7: Use a double cylinder paper machine for papermaking. The paper has a two-layer composite structure. Through the octopus-type equal-pressure pulp distributor of the cylinder paper machine, the outer layer pulp prepared in Step 5 and the inner layer pulp prepared in Step 6 can be evenly distributed on the wire section in sequence, and a two-layer composite wet paper sheet is quickly formed. Precisely set the paper basis weight to 70-80 g / m², precisely adjust the wire section vacuum degree of the cylinder paper machine to be between -25 kPa and -45 kPa, and send it to the pressing section after preliminary forming. The pressing line pressure is controlled at 45-55 kN / m. After leaving the pressing section, the paper is preliminarily formed, and the moisture content is controlled at 45%-48% at this time. Send it to the drying cylinder, and the temperature of the drying cylinder is 105-115 °C to dry the moisture of the paper, and the dryness reaches 58%-66%.

[0044] Step 8: Set the pressure of the wrinkling blade to 0.3-0.5 MPa. The wrinkling blade is set at the position of the outlet of the drying cylinder. Use the wrinkling blade to peel and wrinkle the paper in Step 7, and then send it to the next group of drying cylinders. The temperature is 80-110 °C, and dry it to a moisture content of less than 6%. Conduct a comprehensive inspection on the impregnation performance, electrical performance, mechanical performance, etc. of the paper. Only the paper that meets the requirements of various performance indicators can be recognized as a finished product.

[0045] The optimized papermaking and wrinkling processes of the present invention enable the crepe paper to have good elongation rates in both the transverse and longitudinal directions, can effectively adapt to the temperature changes and mechanical stresses during the operation of the transformer, significantly reduce the risk of rupture, and the transverse and longitudinal elongation rates are 25% higher than those of traditional products.

[0046] From the careful selection of raw materials to the comprehensive improvement of the production process, the present invention uses a compound of broke pulp, recycled pulp and polyacrylamide to make the inner layer pulp, comprehensively enhancing the mechanical properties and tensile resistance of the crepe paper, enabling it to withstand greater mechanical stresses, and significantly improving the reliability of the product. Under the same strict test conditions, the tensile strength is 35% higher than that of traditional products.

[0047] 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.

[0048] 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. In the following embodiments, various raw materials are used. Unless otherwise stated, commercially available products are used, and their specifications are the 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.

[0049] Example 1

[0050] Step 1: Select unbleached sulfate wood pulp for electrical engineering, with an average fiber length of 2.9 mm, a length standard deviation of 0.3 mm, an ash content of 0.38%, and an acid-insoluble ash content of 0.085%;

[0051] Step 2: Collect the dry waste paper in the production process and then put it into a pulper. Set the rotational speed of the pulper at 600 r / min. After 15 minutes of efficient pulping, the waste paper is successfully pulped into uniform small fiber fragments. Then, use a special pressure screen with a pore size of 0.25 mm to preliminarily screen the pulped slurry to remove residual large impurities. Then, use a flotation machine to introduce 8 liters of air per minute per ton of slurry into the slurry, so that the impurities with lighter specific gravity adhere to the bubbles and float to the surface smoothly. Finally, remove them through a scraping device to further improve the purity of the slurry. Then, send it to a refiner to refine the fibers to make the fibers disperse well, and store the treated waste paper in tank A;

[0052] Step 3: Collect the filtered white water generated in the fiber forming stage, introduce the white water into a multi-disc filtering device, control the rotational speed of the discs of the device at 1.5 r / min, and maintain the filtering pressure at 0.065 MPa. During the filtering process, the fibers in the white water are intercepted on the filter screen surface of the discs to achieve preliminary separation of the fibers from the water. For the preliminarily separated fibers, further concentration treatment is carried out. By adjusting the concentration mechanism of the device, the fiber concentration reaches 12% and is stored in tank B;

[0053] Step 4: First, put the unbleached sulfate wood pulp from step 1 into advanced pulping equipment and add pulping enzyme. The pulping enzyme is a composite enzyme preparation of cellulase and hemicellulase, wherein the activity of cellulase is 10,000 U / g, the activity of hemicellulase is 5,000 U / g, and the amount of pulping enzyme added is 0.8 kg per ton of wood pulp. The pulping concentration is precisely controlled at 4.5%, the pulping time is 30 minutes, and the pulping energy consumption range is stably controlled at 200 kWh / ton. The beating degree of the fiber is detected by an online beating degree meter to ensure that the beating degree reaches 32°SR, so that the fiber is fully disintegrated and maintains an appropriate degree of brooming, effectively improving the strength and flexibility of the paper, and the processed pulp is stored in tank C;

[0054] Step 5: Add reverse osmosis water and non-ionic dispersant to the wood pulp in the tank C in proportion. The main component of the non-ionic dispersant is fatty alcohol polyoxyethylene ether, and the added amount is 0.15% of the pulp mass, so that the concentration of the pulp is accurately controlled at 0.3%, to prepare the outer layer pulp;

[0055] Step 6: Mix the broken paper pulp in tank A, the unbleached kraft pulp in tank C, and the fiber in tank B in a certain proportion, with the broken paper pulp in tank A accounting for 20%, the unbleached kraft pulp in tank C accounting for 70%, and the fiber in tank B accounting for 10%. Then add appropriate amount of reverse osmosis water and polyacrylamide (the addition amount is 0.8% of the pulp mass to significantly improve the paper strength), and after fully stirring, accurately adjust the pulp concentration to 0.3% to make the inner layer pulp;

[0056] Step 7: Use a double-cylinder paper machine for papermaking, and the paper has a two-layer composite structure. Through the octopus-shaped isobaric pulp distributor of the rotary screen paper machine, the outer layer pulp configured in step 5 and the inner layer pulp configured in step 6 can be evenly distributed on the screen in turn, and two layers of composite wet paper sheets are quickly formed. The paper quantity is accurately set to 75 g / m2, and the vacuum degree of the screen of the rotary screen paper machine is accurately adjusted to -30 kPa. After initial forming, it is sent to the pressing section. The pressing line pressure is controlled at 50 kN / m. After leaving the pressing section, the paper is initially formed. At this time, the moisture content is controlled at 46%, and it is sent to the drying cylinder. The temperature of the drying cylinder is 105°C to dry the paper moisture and achieve a dryness of 63%.

[0057] Step 8: Set the pressure of the corrugating scraper to 0.3MPa. The corrugating scraper is set at the outlet of the drying cylinder. The paper in step 7 is peeled and corrugated by the corrugating scraper. Then it is sent to the next set of drying cylinders at a temperature of 110°C and dried to a moisture content of 6%. The impregnation performance, electrical performance, mechanical performance, etc. of the paper are comprehensively tested. The paper that meets the requirements of various performance indicators is the finished product.

[0058] After testing, the dipping time of the crepe paper prepared in this embodiment is ≤ 30 min, which is 30% shorter than that of traditional crepe paper. The transverse elongation rate is 15%, and the longitudinal elongation rate is 50%, which is 25% higher than that of traditional products. The dielectric loss value is ≤ 0.005, which is 20% lower than that of traditional crepe paper, greatly reducing the energy loss during the operation of the transformer. The tensile strength is ≥ 6.5 kN / m, which is 35% higher than that of traditional products.

[0059] Example 2

[0060] Step 1: Select unbleached sulfate wood pulp for electricians. The average fiber length is 2.5 mm, and the length standard deviation is 0.3 mm. The ash content is 0.38%, and the acid-insoluble ash content is 0.085%.

[0061] Step 2: Collect the dry waste paper during the production process and then put it into a pulper. Set the speed of the pulper at 500 r / min. After 10 minutes of efficient pulping, the waste paper is successfully pulped into uniform small fiber fragments. Then, use a special pressure screen with a pore size of 0.25 mm to preliminarily screen the pulped slurry to remove residual large impurities. Then, use a flotation machine to introduce 8 liters of air per minute per ton of slurry into the slurry, so that the impurities with lighter specific gravity adhere to the bubbles and float to the surface smoothly. Finally, remove them through a scraping device to further improve the purity of the slurry. Then, send it to a refiner to refine the fibers to make the fibers disperse well. Store the treated waste paper in tank A.

[0062] Step 3: Collect the filtered white water generated during the fiber forming stage and introduce the white water into a multi-disc filtration device. Control the disc speed of the device at 1 r / min and maintain the filtration pressure at 0.05 MPa. During the filtration process, the fibers in the white water are intercepted on the filter screen surface of the disc to achieve the preliminary separation of fibers and water. For the preliminarily separated fibers, further concentration treatment is carried out. By adjusting the concentration mechanism of the device, the fiber concentration reaches 10% and is stored in tank B.

[0063] Step 4: First, put the unbleached sulfate wood pulp in step 1 into an advanced beating device and add beating enzymes. The beating enzymes are a composite enzyme preparation of cellulase and hemicellulase. The activity of cellulase is 10000 U / g, the activity of hemicellulase is 5000 U / g, and the addition amount of beating enzymes is 0.5 kg per ton of wood pulp. Control the grinding concentration at 3%, the grinding time at 45 min, and the grinding energy consumption range at 150 kWh / ton. Detect the beating degree of the fibers through an online beating degree meter to ensure that the beating degree reaches 30° SR, so that the fibers are fully refined and maintain an appropriate fibrillation degree, effectively improving the strength and flexibility of the paper. Store the treated slurry in tank C.

[0064] Step 5: Add reverse osmosis water and non-ionic dispersant to the wood pulp in tank C in proportion. The main component of the non-ionic dispersant is fatty alcohol polyoxyethylene ether, and the addition amount is 0.1% of the pulp mass, so that the concentration of the pulp is accurately controlled at 0.5% to make the outer layer pulp;

[0065] Step 6: Mix the waste paper pulp in tank A, the unbleached kraft pulp in tank C, and the fibers in tank B in a certain proportion. The waste paper pulp in tank A accounts for 20%, the unbleached kraft pulp in tank C accounts for 40%, and the fibers in tank B account for 20%. Then add an appropriate amount of reverse osmosis water and polyacrylamide (the addition amount is 0.5% of the pulp mass to significantly improve the paper strength). After fully stirring evenly, accurately adjust the pulp concentration to 0.8% to make the inner layer pulp;

[0066] Step 7: Use a double-cylinder paper machine for papermaking. The paper is a two-layer composite structure. Through the octopus-type equal-pressure pulp distributor of the cylinder paper machine, the outer layer pulp prepared in Step 5 and the inner layer pulp prepared in Step 6 can be evenly distributed on the wire part in sequence, and a two-layer composite wet paper sheet is quickly formed. Accurately set the paper basis weight to 75 g / m², accurately adjust the wire part vacuum of the cylinder paper machine to -30 kPa, and send it to the pressing part after preliminary forming. The pressing line pressure is controlled at 50 kN / m. After leaving the pressing part, the paper is preliminarily formed. At this time, the moisture content is controlled at 46%, and it is sent to the drying cylinder. The temperature of the drying cylinder is 105°C to dry the paper moisture, and the dryness reaches 63%;

[0067] Step 8: Set the wrinkling blade pressure to 0.5 MPa. The wrinkling blade is set at the position of the drying cylinder outlet. Use the wrinkling blade to peel and wrinkle the paper in Step 7, and then send it to the next group of drying cylinders at a temperature of 80°C and dry it to a moisture content of 6%. Conduct a comprehensive inspection on the impregnation performance, electrical performance, mechanical performance, etc. of the paper. The paper that meets the requirements of various performance indicators is the finished product.

[0068] After testing, the impregnation time of the crepe paper prepared in this example is ≤ 25 min, the transverse elongation rate is 16%, the dielectric loss value is ≤ 0.004, and the tensile strength is ≥ 7.2 kN / m.

[0069] Example 3

[0070] Step 1: Select unbleached kraft pulp for electrical engineering, with an average fiber length of 3.5 mm and a length standard deviation of 0.3 mm. The ash content is 0.38%, of which the acid-insoluble ash content is 0.085%;

[0071] Step 2: Collect the dry damaged paper in the production process and then put it into the pulper. Set the speed of the pulper to 550r / min. After 13 minutes of efficient crushing, the damaged paper is successfully crushed into uniform small fiber fragments. Then use a special pressure screen with a pore size of 0.25 mm to preliminarily screen the crushed pulp to remove the remaining large impurities; then use an air flotation machine to pass 8 liters of air per minute per ton of pulp into the pulp, so that the lighter impurities adhere to the bubbles and float to the surface smoothly. Finally, they are removed by a scraping device to further improve the purity of the pulp, and then sent to the deflaker to deflake the fibers so that the fibers are well dispersed, and the processed damaged paper is stored in tank A;

[0072] Step 3: Collect the filtered white water generated in the fiber forming stage and introduce the white water into the multi-disc filter equipment. The disc speed of the equipment is controlled at 3r / min and the filtration pressure is maintained at 0.1MPa. During the filtration process, the fibers in the white water are trapped on the filter surface of the disc, achieving the initial separation of the fibers and water. For the fibers after the initial separation, further concentration treatment is carried out. By adjusting the concentration mechanism of the equipment, the fiber concentration reaches 10% and is stored in tank B;

[0073] Step 4: First, put the unbleached kraft wood pulp from step 1 into advanced pulping equipment and add pulping enzyme. The pulping enzyme is a composite enzyme preparation of cellulase and hemicellulase, wherein the activity of cellulase is 10000U / g, the activity of hemicellulase is 5000U / g, and the amount of pulping enzyme added is 1 kg per ton of wood pulp. Control the pulping concentration at 5%, the pulping time at 41min, and the pulping energy consumption range at 170kWh / ton. The beating degree of the fiber is tested by an online beating degree meter to ensure that the beating degree reaches 35°SR, so that the fiber is fully disintegrated and maintains an appropriate degree of brooming, effectively improving the strength and flexibility of the paper, and the processed pulp is stored in tank C;

[0074] Step 5: Add reverse osmosis water and non-ionic dispersant to the wood pulp in the tank C in proportion. The main component of the non-ionic dispersant is fatty alcohol polyoxyethylene ether, and the added amount is 0.3% of the pulp mass, so that the concentration of the pulp is accurately controlled at 0.4%, to prepare the outer layer pulp;

[0075] Step 6: Mix the broken paper pulp in tank A, the unbleached kraft pulp in tank C, and the fiber in tank B in a certain proportion, with the broken paper pulp in tank A accounting for 30%, the unbleached kraft pulp in tank C accounting for 55%, and the fiber in tank B accounting for 15%. Then add an appropriate amount of reverse osmosis water and polyacrylamide (the addition amount is 1% of the pulp mass to significantly improve the paper strength), and after sufficient stirring, accurately adjust the pulp concentration to 0.5% to make the inner layer pulp;

[0076] Step 7: Use a twin-cylinder paper machine for papermaking. The paper has a two-layer composite structure. Through an octopus-shaped isobaric pulp distributor of the cylinder paper machine, the outer layer pulp prepared in Step 5 and the inner layer pulp prepared in Step 6 can be evenly distributed on the wire section in sequence, and a two-layer composite wet paper sheet is quickly formed. Accurately set the paper basis weight to 80 g / m², precisely adjust the wire section vacuum of the cylinder paper machine to -25 kPa, and send it to the press section after preliminary forming. The press line pressure is controlled at 55 kN / m. After leaving the press section, the paper is preliminarily formed. At this time, the moisture content is controlled at 48%. Send it to the drying cylinder. The temperature of the drying cylinder is 115 °C to dry the moisture of the paper until the dryness reaches 66%;

[0077] Step 8: Set the wrinkling blade pressure to 0.4 MPa. The wrinkling blade is set at the position of the outlet of the drying cylinder. Use the wrinkling blade to peel and wrinkle the paper in Step 7, and then send it to the next group of drying cylinders. The temperature is 95 °C and it is dried until the moisture content is 6%. Conduct a comprehensive inspection on the impregnation performance, electrical performance, mechanical performance, etc. of the paper. The paper that meets the requirements of various performance indicators is the finished product.

[0078] After testing, the impregnation time of the crepe paper prepared in this example is ≤ 28 min, the transverse elongation rate is 16%, the dielectric loss value is ≤ 0.0045, and the tensile strength is ≥ 6.8 kN / m.

[0079] Example 4

[0080] Step 1: Select unbleached sulfate wood pulp for electrical engineering. The average fiber length is 3.5 mm, and the length standard deviation is 0.3 mm. The ash content is 0.38%, of which the acid-insoluble ash content is 0.085%;

[0081] Step 2: Collect the dry waste paper in the production process and then put it into a pulper. Set the rotation speed of the pulper at 550 r / min. After 13 minutes of efficient pulping, the waste paper is successfully pulped into uniform small fiber segments. Then use a special pressure screen with a pore size of 0.25 mm to preliminarily screen the pulped slurry to remove residual large impurities; then use a flotation machine to introduce 8 liters of air per ton of slurry per minute into the slurry, so that the lighter impurities adhere to the bubbles and float to the surface smoothly. Finally, use a scraping device to remove them to further improve the purity of the slurry. Then send it to a refiner to refine the fibers to make the fibers well dispersed. Store the treated waste paper in tank A;

[0082] Step 3: Collect the filtered white water generated in the fiber forming stage and introduce the white water into the multi-disc filter equipment. The disc speed of the equipment is controlled at 3r / min and the filtration pressure is maintained at 0.1MPa. During the filtration process, the fibers in the white water are trapped on the filter surface of the disc, achieving the initial separation of the fibers and water. For the fibers after the initial separation, further concentration treatment is carried out. By adjusting the concentration mechanism of the equipment, the fiber concentration reaches 15% and is stored in tank B;

[0083] Step 4: First, put the unbleached kraft wood pulp from step 1 into advanced pulping equipment and add pulping enzyme. The pulping enzyme is a composite enzyme preparation of cellulase and hemicellulase, wherein the activity of cellulase is 10000U / g, the activity of hemicellulase is 5000U / g, and the amount of pulping enzyme added is 1 kg per ton of wood pulp. Control the pulping concentration at 5%, the pulping time at 41min, and the pulping energy consumption range at 170kWh / ton. The beating degree of the fiber is tested by an online beating degree meter to ensure that the beating degree reaches 35°SR, so that the fiber is fully disintegrated and maintains an appropriate degree of brooming, effectively improving the strength and flexibility of the paper, and the processed pulp is stored in tank C;

[0084] Step 5: Add reverse osmosis water and non-ionic dispersant to the wood pulp in the tank C in proportion. The main component of the non-ionic dispersant is fatty alcohol polyoxyethylene ether, and the added amount is 0.3% of the pulp mass, so that the concentration of the pulp is accurately controlled at 0.4%, to prepare the outer layer pulp;

[0085] Step 6: Mix the broken paper pulp in tank A, the unbleached kraft pulp in tank C, and the fiber in tank B in a certain proportion, with the broken paper pulp in tank A accounting for 30%, the unbleached kraft pulp in tank C accounting for 55%, and the fiber in tank B accounting for 15%. Then add an appropriate amount of reverse osmosis water and polyacrylamide (the addition amount is 1% of the pulp mass to significantly improve the paper strength), and after sufficient stirring, accurately adjust the pulp concentration to 0.5% to make the inner layer pulp;

[0086] Step 7: Use a double-cylinder paper machine for papermaking, and the paper has a two-layer composite structure. Through the octopus-shaped isobaric pulp distributor of the rotary screen paper machine, the outer layer pulp configured in step 5 and the inner layer pulp configured in step 6 can be evenly distributed on the screen in turn, and two layers of composite wet paper sheets are quickly formed. The paper quantity is accurately set to 70 g / m2, and the vacuum degree of the screen of the rotary screen paper machine is accurately adjusted to -45kPa. After initial forming, it is sent to the pressing section. The pressing line pressure is controlled at 45kN / m. After leaving the pressing section, the paper is initially formed. At this time, the moisture content is controlled at 45%, and it is sent to the drying cylinder. The temperature of the drying cylinder is 115°C to dry the paper moisture and achieve a dryness of 58%.

[0087] Step 8: Set the pressure of the wrinkling doctor blade to 0.4 MPa. The wrinkling doctor blade is set at the outlet of the drying cylinder. Use the wrinkling doctor blade to peel and wrinkle the paper in Step 7, and then send it to the next group of drying cylinders at a temperature of 95 °C and dry it until the moisture content is 6%. Conduct a comprehensive inspection on the impregnation performance, electrical performance, mechanical performance, etc. of the paper. The paper that meets the requirements of various performance indicators is the finished product.

[0088] After testing, the impregnation time of the crepe paper prepared in this embodiment is ≤26 min, the transverse elongation rate is 15%, the dielectric loss value is ≤0.0033, and the tensile strength is ≥6.4 kN / m.

[0089] 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. A preparation method of crimped paper for transformers, characterized in that It includes the following steps: 1) Add a non-ionic dispersant and reverse osmosis water to the mixed pulp made from electrical grade unbleached sulfate wood pulp to prepare an outer layer pulp with a concentration of 0.3%-0.5%. The addition amount of the non-ionic dispersant is 0.1%-0.3% of the pulp mass. 2) After mixing the mixed pulp with broke pulp and fibers, add polyacrylamide and reverse osmosis water to make an inner layer pulp with a concentration of 0.3%-0.8%. In the inner layer pulp, the mass percentage of broke pulp is 20%-40%, the mass percentage of recycled fibers is 40%-70%, and the mass percentage of the mixed pulp is 10%-20%. The addition amount of the polyacrylamide is 0.5%-1% of the mass of the mixed pulp. 3) After the outer layer pulp and the inner layer pulp are formed by papermaking, pressed, dried, wrinkled, and dried again, the crepe paper is obtained.

2. The preparation method of the crimped paper for a transformer according to claim 1, wherein, In step 1), the mixed pulp is prepared by grinding electrical grade unbleached sulfate wood pulp with a fiber length of 2.5 mm - 3.5 mm and an ash content of <0.5% and a complex enzyme preparation in a mass ratio of 1:(0.5 - 1), and controlling the beating degree to be 30 - 35°SR.

3. A method for producing crimped paper for transformers according to claim 2, characterized in that, The grinding concentration of the grinding treatment is 3%-5%, the grinding time is 30 - 45 min, and the grinding energy consumption range is 150 - 200 kWh / ton.

4. The preparation method of a crimped paper for a transformer according to claim 2, wherein The complex enzyme preparation is made from cellulase and hemicellulase. Among them, the activity of cellulase is not less than 10000 U / g, and the activity of hemicellulase is not less than 5000 U / g.

5. A method for producing crimped paper for transformers according to claim 1, characterized in that, In step 1), the non-ionic dispersant is a fatty alcohol polyoxyethylene ether type.

6. A method for producing crimped paper for transformers according to claim 1, characterized in that, In step 3), a double-cylinder paper machine is used to form a two-layer paper sheet with a basis weight of 70 - 80 g / m 2 . The vacuum degree in the wire section is -25 kPa to -45 kPa. After preliminary forming, it is sent to the press section. The press line pressure is controlled at 45 - 55 kN / m. After leaving the press section, the paper is preliminarily formed. At this time, the moisture content is controlled at 45% - 48%. The drying temperature before wrinkling is 105 - 115 °C, and the dryness is 58% - 66%.

7. A method for producing crimped paper for transformers according to claim 1, characterized in that, In step 3), wrinkling includes setting the pressure of the wrinkling blade to 0.3 - 0.5 MPa, the wrinkling rate to 50%-100%, the drying temperature after wrinkling to 80 - 110°C, and drying until the moisture content ≤6%.

8. A method for producing crinkle paper for transformers according to claim 1, characterized in that, In step 1), the fibers are obtained by collecting and filtering white water and then concentrating the fibers to a concentration of 10%-15%, and maintaining the filtration pressure at 0.05 - 0.1 MPa.

9. A method for producing crinkle paper for transformers according to claim 1, characterized in that, In step 1), after the production dry broke is disintegrated, screened, and decontaminated, the broke pulp is obtained; the rotation speed of disintegration is 500 - 600 r / min, and the disintegration time is 10 - 15 min.

10. The transformer crepe paper prepared by the preparation method of the transformer crepe paper according to any one of claims 1 to 9.