Method for improving breakdown field strength and mechanical property of insulation paper by mixing plant fibers and polymer fibers and insulation paper

Abstract

The invention provides a method for improving breakdown field strength and mechanical performance of insulation paper by mixing plant fibers and polymer fibers and the insulation paper. The method comprises the following steps: pulping a plant fiber pulp board to obtain plant fiber pulp; taking polymer fibers, and pulping the polymer fibers to obtain polymer fiber slurry; mixing and defibering the plant fiber pulp and the polymer fiber pulp to obtain mixed pulp; and carrying out papermaking on the mixed slurry, and then carrying out hot-pressing smoothing treatment to obtain the insulation paper. The breakdown field strength, the mechanical strength, the heat dissipation characteristic and the anti-aging characteristic of the high insulation paper can be effectively and synergistically improved.

Description

Technical Field

[0001] The invention belongs to the field of electrical insulating materials, and in particular relates to a method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers, and insulating paper. Background Art

[0002] Insulation paper is an important insulating medium in many core power equipment such as transformers, capacitors, bushings, motors, cables, etc., and plays a vital role in the stable operation and development of the power grid. At present, the insulation paper used in transformers, bushings, capacitors, and oil-filled cables is mainly plant fiber insulation paper, and plant fiber insulation paper, aramid fiber insulation paper or composite insulation paper is used in motor equipment. Insulation paper plays an important role in electrical insulation and mechanical support in power equipment, so the quality of insulation paper will directly determine the stable operation and service life of the above power equipment.

[0003] Research on multiple scales such as the chemical composition, fiber types, and paper sheet structure of insulating paper is a key link in synergistically improving the insulating performance, mechanical properties, thermal conductivity, and long-term aging resistance of insulating paper, and is a fundamental issue in ensuring the stability of the power grid system.

[0004] The technical route of plant fiber composite polymer fiber may be able to give full play to the synergistic effect of high inter-fiber bonding strength of plant fibers and high mechanical strength of polymer fibers, simple and controllable chemical composition, controllable morphology, high temperature resistance, high thermal conductivity, and good aging resistance. However, the composite method of plant fibers and polymer fibers, the type of polymer fibers used in the composite route, and the formula of polymer fibers are the key difficulties of this technical route, and the effect of this technical route on the regulation of various aspects of performance is also unknown. Summary of the invention

[0005] The purpose of the present invention is to provide a method and insulating paper for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers, so as to overcome the problems existing in the prior art. The present invention can effectively and synergistically improve the breakdown field strength, mechanical strength, heat dissipation characteristics and aging resistance of high-insulation paper.

[0006] The present invention is achieved through the following technical solutions:

[0007] The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers comprises the following steps:

[0008] Step 1: taking a plant fiber pulp board and beating it to obtain a plant fiber slurry;

[0009] Step 2: taking polymer fiber slurry obtained after pulping the polymer fiber;

[0010] Step 3: Mixing and dispersing the plant fiber slurry and the polymer fiber slurry to obtain a mixed slurry; in terms of mass percentage, the absolute dry mass of the plant fiber slurry accounts for 75-98wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polymer fiber slurry accounts for 2-25wt% of the absolute dry mass of the mixed slurry;

[0011] Step 4: Papermaking the mixed slurry, and then hot pressing and smoothing it to obtain insulating paper.

[0012] Furthermore, step 1 specifically includes: soaking the plant fiber pulp board, diluting and beating the pulp to obtain plant fiber slurry.

[0013] Furthermore, the plant fiber pulp is soaked for 12 hours, diluted to a pulp concentration of 10% by mass, and beaten to a beating degree of 65° SR.

[0014] Furthermore, step 2 specifically includes: diluting the polymer fiber with deionized water and then cutting it with a pulping machine to obtain polymer fiber slurry.

[0015] Furthermore, the polymer fibers were diluted with deionized water to a slurry concentration of 2 g / L, and cut using a Wall-E pulper to obtain a polymer fiber slurry with a weighted average fiber length of less than 2 mm.

[0016] Furthermore, the plant fiber pulp board is made of coniferous wood pulp, broadleaf wood pulp, gramineous plant pulp, straw pulp or bast pulp;

[0017] The polymer fiber is a mixture of one or more of aramid fiber, polyester fiber, polyimide fiber, glass fiber, polysulfone fiber and polyoxadiazole fiber.

[0018] Furthermore, before the plant fiber slurry and the polymer fiber slurry are mixed and decomposed, the mass concentration of the plant fiber slurry is adjusted to 4%, and the fiber is decomposed by a fiber decompressor at 15,000 revolutions to fully disperse the fibers in the deionized water system, and the decomposed plant fiber slurry is mixed and decomposed with the polymer fiber slurry.

[0019] Furthermore, before the deflaked plant fiber slurry is mixed with the polymer fiber slurry for deflaking, the mixture of the deflaked plant fiber slurry and the polymer fiber slurry is diluted to a pulp concentration of 2%, and then deflaked for 20,000 revolutions.

[0020] Further, step 4 is specifically: the mixed slurry is made into 100g / m 2 The paper sample was vacuum dried at 98°C and 1 bar to obtain an insulating paper sample, and finally the insulating paper was calendered at 120°C and 20MPa to obtain insulating paper.

[0021] An insulating paper is prepared by adopting the above method.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] The present invention selects an unbleached coniferous wood pulp as a mixed paper plant fiber component, selects aramid fiber, polyester fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber as polymer fiber components, and after pulping the coniferous wood pulp, a polymer fiber or a plurality of polymer fibers are mixed with coniferous wood fibers to prepare insulating pulp, and then wet papermaking, drying, and hot pressing are performed to obtain mixed insulating paper with different mass proportions of polymer fibers. Since the chemical composition, molecular chain structure, aggregate structure, and fiber structure of polymer fibers are significantly different from those of plant fibers, the effects of combining, winding, and filling between plant fibers and between two fibers are changed when mixed into plant fibers, so that the mixed insulating paper has better insulation performance, mechanical properties, and thermal conductivity than pure plant fiber insulating paper. At the same time, the polymer fiber does not contain components such as hemicellulose and lignin, and has higher heat resistance, which is conducive to the long-term aging resistance of insulating paper. The technical route of this application provides new ideas for the research and development of medium and high-end insulating paper for power equipment, which plays an important role in the stable operation of power equipment and the high-quality development of power grids. DETAILED DESCRIPTION

[0024] The present invention is described in detail below:

[0025] The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers comprises the following steps:

[0026] Step 1: taking a plant fiber pulp board and beating it to obtain a plant fiber pulp; the plant fiber pulp board adopts a coniferous wood pulp board, a broadleaf wood pulp board, a grass pulp board, a grass pulp board or a bast pulp board; specifically: soaking the plant fiber pulp board, diluting and beating it to obtain a plant fiber pulp, the plant fiber pulp board is soaked for 12 hours, diluted to a pulp concentration of 10% by mass concentration, and beaten to a beating degree of 65°SR;

[0027] Step 2: taking polymer fiber slurry obtained after pulping the polymer fiber; the polymer fiber is a mixture of one or more of aramid fiber, polyester fiber, polyimide fiber, glass fiber, polysulfone fiber and polyoxadiazole fiber; specifically: diluting the polymer fiber with deionized water to a slurry concentration of 2 g / L, cutting it with a Wall-E pulping machine, and obtaining a polymer fiber slurry with a weighted average fiber length of less than 2 mm;

[0028] Step 3: adjusting the mass concentration of the plant fiber slurry to 4%, using a fiber decompressor to decompress for 15,000 turns to fully disperse the fibers in a deionized water system, mixing the decompressed plant fiber slurry with the polymer fiber slurry and decompressing for 15,000 turns to obtain a mixed slurry; in terms of mass percentage, the absolute dry mass of the plant fiber slurry accounts for 75-98wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polymer fiber slurry accounts for 2-25wt% of the absolute dry mass of the mixed slurry;

[0029] Step 4: The mixed slurry is made into paper, and then hot-pressed and smoothed to obtain high-insulation paper. Specifically, the mixed slurry is made into 100g / m 2 The paper sample was vacuum dried at 98°C and 1 bar to obtain an insulating paper sample, and finally the insulating paper was calendered at 120°C and 20MPa to obtain insulating paper.

[0030] The purpose of this application is to provide a method for preparing insulating paper by mixing polymer fibers and plant fibers, thereby improving the dielectric strength, mechanical properties, thermal conductivity and aging resistance of plant fiber insulating paper to overcome the problems existing in the prior art. The present invention can synergistically improve the performance of insulating paper in various aspects.

[0031] The insulating paper of the present invention has a high breakdown field strength, which can improve the withstand voltage level of power equipment and reduce the weight of power equipment. It has a high tensile strength, which can effectively improve the equipment production efficiency and equipment operation stability. It has excellent thermal conductivity to improve the heat dissipation efficiency of the equipment, and has better aging resistance to extend the service life of the equipment.

[0032] In a possible implementation, the mass percentage of polymer fiber in the insulating paper is 2-25wt%, and the mass percentage of plant fiber in the insulating paper is 75-98wt%. In one example, the polymer fiber accounts for 2wt% of the total mass of the insulating paper, and the plant fiber accounts for 98wt% of the total mass of the insulating paper. In one example, the polymer fiber accounts for 5wt% of the total mass of the insulating paper, and the plant fiber accounts for 95wt% of the total mass of the insulating paper. In one example, the polymer fiber accounts for 12wt% of the total mass of the insulating paper, and the plant fiber accounts for 88wt% of the total mass of the insulating paper. In one example, the polymer fiber accounts for 15wt% of the total mass of the insulating paper, and the plant fiber accounts for 85wt% of the total mass of the insulating paper. In one example, the polymer fiber accounts for 19wt% of the total mass of the insulating paper, and the plant fiber accounts for 81wt% of the total mass of the insulating paper. In one example, the polymer fiber accounts for 22wt% of the total mass of the insulating paper, and the plant fiber accounts for 78wt% of the total mass of the insulating paper. In one example, the polymer fiber accounts for 25wt% of the total mass of the insulating paper, and the plant fiber accounts for 75wt% of the total mass of the insulating paper.

[0033] In this implementation, by adjusting the mass ratio of polymer fibers and plant fibers in the insulating paper, insulating paper with better overall performance can be obtained.

[0034] In a possible implementation, the polymer fiber includes any one or more combinations of aramid fiber, polyester fiber, polyimide fiber, glass fiber, polysulfone fiber paper, and polyoxadiazole fiber.

[0035] In some embodiments, an unbleached conifer pulp is selected and pulped using a PFI refiner to obtain a pulp with a beating degree of 65°SR. It should be noted that the unbleached conifer pulp listed here is only an example of the pulp used in the embodiments of the present application and does not constitute a limitation. In other embodiments, other plant fiber pulps such as broadleaf pulp, grass pulp, grass pulp, bast pulp, etc. can be used, which are not listed here one by one.

[0036] In some embodiments, the polymer fibers are cut using a Wall-E beater such that the weighted average length of the final polymer fibers is less than 2.0 mm.

[0037] In some embodiments, softwood fiber and polymer fiber are mixed according to the absolute dry weight ratio of pulp, and then the pulp concentration is adjusted to 2%, and the pulp is deflagrated by a deflagrator at 20,000 revolutions, and then left to stand for half an hour.

[0038] In some embodiments, the pulp obtained above is made into 100g / m 2 Insulation paper hand sheets.

[0039] In some embodiments, the dry paper of the copied insulating paper is subjected to hot pressing and smoothing treatment using a flat plate vulcanizer at 120° C. and 20 MPa.

[0040] Next, in conjunction with the specific embodiments shown in Table 1, the insulating paper provided in the embodiments of the present application is introduced by way of example.

[0041] Table 1 Example formulation

[0042]

[0043] The following will describe the embodiments of the present invention in detail with reference to the examples. The implementation case is a preferred embodiment of the present invention and the scope of the present invention cannot be limited thereto. In the following examples, the methods and experimental equipment used are conventional methods and instruments unless otherwise specified. In the following examples, several representative bast fibers among the above bast fibers are specifically described.

[0044] Example 1

[0045] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0046] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wally pulper to make the weighted average length of the fiber less than 2 mm. The polyester fiber pulp was then mixed with the deflaked coniferous wood fiber pulp, adjusted to a pulp concentration of 2%, and deflaked and mixed by a deflaker for 20,000 revolutions to fully mix the two fibers to obtain a mixed pulp, wherein the absolute dry mass of the coniferous wood fiber pulp accounted for 98 wt% of the absolute dry mass of the mixed pulp, and the absolute dry mass of the polyester fiber pulp accounted for 2 wt% of the absolute dry mass of the mixed pulp.

[0047] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0048] Example 2

[0049] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0050] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wall-E pulper to obtain a fiber weighted average length of less than 2 mm. The aramid fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber were pulped and cut under the same conditions, and then the aramid fiber pulp, polyester fiber pulp, polyimide fiber pulp, glass fiber pulp, polysulfone fiber pulp, and polyoxadiazole fiber pulp were mixed with the deflaked coniferous wood fiber pulp, and adjusted to a pulp concentration of 2%. The deflaker was used to deflake and mix for 20,000 revolutions to fully mix the various fibers to obtain a mixed pulp, in which the absolute dry mass of the coniferous wood fiber pulp accounted for 20% of the mixed pulp. The absolute dry mass of the mixed slurry accounts for 92wt% of the absolute dry mass, the absolute dry mass of the aramid fiber slurry accounts for 0.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyester fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyimide fiber accounts for 0.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the glass fiber accounts for 2.0wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polysulfone fiber accounts for 1.0wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polyoxadiazole fiber accounts for 0.5wt% of the absolute dry mass of the mixed slurry.

[0051] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0052] Example 3

[0053] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0054] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wall-E pulper to obtain a fiber weighted average length of less than 2 mm. The aramid fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber were pulped and cut under the same conditions, and then the aramid fiber pulp, polyester fiber pulp, polyimide fiber pulp, glass fiber pulp, polysulfone fiber pulp, and polyoxadiazole fiber pulp were mixed with the deflaked coniferous wood fiber pulp, and adjusted to a pulp concentration of 2%. The deflaker was used to deflake and mix for 20,000 revolutions to fully mix the various fibers to obtain a mixed pulp, wherein the absolute dry mass of the coniferous wood fiber pulp accounts for 20% of the mixed pulp. The absolute dry mass of the mixed slurry accounts for 88wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the aramid fiber slurry accounts for 1wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyester fiber accounts for 1.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyimide fiber accounts for 0.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the glass fiber accounts for 4.0wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polysulfone fiber accounts for 2.5wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polyoxadiazole fiber accounts for 2.5wt% of the absolute dry mass of the mixed slurry.

[0055] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0056] Example 4

[0057] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0058] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wall-E pulper to obtain a fiber weighted average length of less than 2 mm. The aramid fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber were pulped and cut under the same conditions, and then the aramid fiber pulp, polyester fiber pulp, polyimide fiber pulp, glass fiber pulp, polysulfone fiber pulp, and polyoxadiazole fiber pulp were mixed with the deflaked coniferous wood fiber pulp, and adjusted to a pulp concentration of 2%. The deflaker was used to deflake and mix for 20,000 revolutions to fully mix the various fibers to obtain a mixed pulp, in which the absolute dry mass of the coniferous wood fiber pulp accounted for 20% of the mixed pulp. The absolute dry mass of the mixed slurry accounts for 85wt% of the absolute dry mass, the absolute dry mass of the aramid fiber slurry accounts for 1.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyester fiber accounts for 1.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyimide fiber accounts for 4.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the glass fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polysulfone fiber accounts for 2.0wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polyoxadiazole fiber accounts for 2.0wt% of the absolute dry mass of the mixed slurry.

[0059] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0060] Example 5

[0061] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0062] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wall-E pulper to obtain a fiber weighted average length of less than 2 mm. The aramid fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber were pulped and cut under the same conditions, and then the aramid fiber pulp, polyester fiber pulp, polyimide fiber pulp, glass fiber pulp, polysulfone fiber pulp, and polyoxadiazole fiber pulp were mixed with the deflaked coniferous wood fiber pulp, and adjusted to a pulp concentration of 2%. The deflaker was used to deflake and mix for 20,000 revolutions to fully mix the various fibers to obtain a mixed pulp, in which the absolute dry mass of the coniferous wood fiber pulp accounted for 20% of the mixed pulp. The absolute dry mass of the mixed slurry accounts for 81wt% of the absolute dry mass, the absolute dry mass of the aramid fiber slurry accounts for 2.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyester fiber accounts for 1.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyimide fiber accounts for 2.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the glass fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polysulfone fiber accounts for 6.5wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polyoxadiazole fiber accounts for 2.5wt% of the absolute dry mass of the mixed slurry.

[0063] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0064] Example 6

[0065] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0066] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wall-E pulper to obtain a fiber weighted average length of less than 2 mm. The aramid fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber were pulped and cut under the same conditions, and then the aramid fiber pulp, polyester fiber pulp, polyimide fiber pulp, glass fiber pulp, polysulfone fiber pulp, and polyoxadiazole fiber pulp were mixed with the deflaked coniferous wood fiber pulp, and adjusted to a pulp concentration of 2%. The deflaker was used to deflake and mix for 20,000 revolutions to fully mix the various fibers to obtain a mixed pulp, in which the absolute dry mass of the coniferous wood fiber pulp accounted for 20% of the mixed pulp. The absolute dry mass of the mixed slurry accounts for 78wt% of the absolute dry mass, the absolute dry mass of the aramid fiber slurry accounts for 4.0wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyester fiber accounts for 2.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyimide fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the glass fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polysulfone fiber accounts for 3.0wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polyoxadiazole fiber accounts for 5.5wt% of the absolute dry mass of the mixed slurry.

[0067] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0068] Example 7

[0069] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0070] Afterwards, the polyester fiber was diluted with deionized water to a pulp concentration of 2 g / L, and was cut by a Wall-E pulper to obtain a fiber weighted average length of less than 2 mm. The aramid fiber, polyimide fiber, glass fiber, polysulfone fiber, and polyoxadiazole fiber were pulped and cut under the same conditions, and then the aramid fiber pulp, polyester fiber pulp, polyimide fiber pulp, glass fiber pulp, polysulfone fiber pulp, and polyoxadiazole fiber pulp were mixed with the deflaked coniferous wood fiber pulp, and adjusted to a pulp concentration of 2%. The deflaker was used to deflake and mix for 20,000 revolutions to fully mix the various fibers to obtain a mixed pulp, in which the absolute dry mass of the coniferous wood fiber pulp accounted for 20% of the mixed pulp. The absolute dry mass of the mixed slurry accounts for 75wt% of the absolute dry mass, the absolute dry mass of the aramid fiber slurry accounts for 6.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyester fiber accounts for 4.0wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polyimide fiber accounts for 2.5wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the glass fiber accounts for 3.0wt% of the absolute dry mass of the mixed slurry, the absolute dry mass of the polysulfone fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polyoxadiazole fiber accounts for 3.5wt% of the absolute dry mass of the mixed slurry.

[0071] The mixed slurry was papered using a paper machine under a deionized water system to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0072] Comparative Example

[0073] First, the commercial softwood pulp board was soaked for 12 hours, and then the fiber was beaten to a beating degree of 65°SR at a pulp concentration of 10% using a PFI refiner. The pulp concentration was then adjusted to 4%, and the fiber was deflated at 15,000 revolutions using a fiber deflagrator to allow the fiber to be fully dispersed in the deionized water system.

[0074] The debonded softwood fiber pulp was papered using a papermaking machine to produce 100 g / m 2 The paper sample was dried under vacuum at 98°C and 1 bar to obtain the insulating paper sample. Finally, the insulating paper was calendered under 120°C and 20MPa calendering conditions to obtain the insulating paper.

[0075] The performance comparison between the embodiments of the present invention and the comparative examples is shown in Table 2.

[0076] Table 2 Performance comparison between the embodiments of the present invention and the comparative examples

[0077]

[0078]

[0079] As can be seen from Table 2, the technical route of preparing insulating paper by mixing coniferous wood fiber with polymer fiber proposed in this application can improve the performance of insulating paper in various aspects to varying degrees. Among them, after mixing polymer fibers, AC breakdown can be increased by 14.21-37.56%, DC breakdown can be increased by 19.15-34.02%, tensile strength can be increased by 5.00-20.00%, and thermal conductivity can be increased by 9.00-45.45%. After 30 days of thermal aging at 120°C, the percentage of DC breakdown field strength decreases to varying degrees, which shows that the technical route of this application can improve the aging resistance of insulating paper.

[0080] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers, characterized in that: The following steps are involved: Step 1: taking a plant fiber pulp board and beating it to obtain a plant fiber slurry; Step 2: taking polymer fiber slurry obtained after pulping the polymer fiber; Step 3: Mixing and dispersing the plant fiber slurry and the polymer fiber slurry to obtain a mixed slurry; in terms of mass percentage, the absolute dry mass of the plant fiber slurry accounts for 75-98wt% of the absolute dry mass of the mixed slurry, and the absolute dry mass of the polymer fiber slurry accounts for 2-25wt% of the absolute dry mass of the mixed slurry; Step 4: Papermaking the mixed slurry, and then hot pressing and smoothing it to obtain insulating paper.

2. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 1, characterized in that: Step 1 specifically comprises: soaking the plant fiber pulp board, diluting and beating the pulp to obtain the plant fiber slurry.

3. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 2, characterized in that: The plant fiber pulp board is soaked for 12 hours, diluted to a pulp concentration of 10% by mass, and beaten to a beating degree of 65°SR.

4. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 1, characterized in that: Step 2 specifically comprises: diluting the polymer fiber with deionized water and then cutting the polymer fiber with a pulping machine to obtain polymer fiber slurry.

5. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 4, characterized in that: The polymer fibers were diluted with deionized water to a slurry concentration of 2 g / L, and cut using a Wall-E pulper to obtain a polymer fiber slurry with a weighted average fiber length of less than 2 mm.

6. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 1, characterized in that: The plant fiber pulp board is a coniferous wood pulp board, a broadleaf wood pulp board, a grass plant pulp board, a grass pulp board or a bast pulp board; The polymer fiber is a mixture of one or more of aramid fiber, polyester fiber, polyimide fiber, glass fiber, polysulfone fiber and polyoxadiazole fiber.

7. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 1, characterized in that: Before mixing and decomposing the plant fiber slurry and the polymer fiber slurry, the mass concentration of the plant fiber slurry is adjusted to 4%, and the fiber decomposing instrument is used to decompress the slurry at 15,000 revolutions to fully disperse the fibers in the deionized water system, and the decompressed plant fiber slurry is mixed and decompressed with the polymer fiber slurry.

8. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 1, characterized in that: Before the deflaked plant fiber slurry is mixed with the polymer fiber slurry for deflaking, the mixture of the deflaked plant fiber slurry and the polymer fiber slurry is diluted to a pulp concentration of 2%, and then deflaked for 20,000 revolutions.

9. The method for improving the breakdown field strength and mechanical properties of insulating paper by mixing plant fibers and polymer fibers according to claim 1, characterized in that: Step 4 is as follows: the mixed slurry is made into 100g / m 2 The paper sample was vacuum dried at 98°C and 1 bar to obtain an insulating paper sample, and finally the insulating paper was calendered at 120°C and 20MPa to obtain insulating paper.

10. An insulating paper, characterized in that: The method according to any one of claims 1 to 9 is used to prepare the product.

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