A high-voltage-resistant composite capacitor paper and a preparation method thereof

Abstract

The application discloses a kind of high voltage resistance composite capacitor paper, including base paper and coating layer coated on the surface of the base paper, the coating solution of the coating layer includes the following mass percentage of components: 1-10% of nano starch, 1-10% of nanocellulose, 1-10% of adhesive and 70-96% of water.The application also provides a kind of preparation method of the above-mentioned high voltage resistance composite capacitor paper.The high voltage resistance composite capacitor paper of the application includes base paper and coating layer, and the composite capacitor paper obtained after multi-layer compounding has the characteristics of high voltage resistance, high strength and low impedance.The coating layer of the high voltage resistance composite capacitor paper of the application is prepared by mixing nano starch, nanocellulose and adhesive to obtain high solid content nano coating solution, which effectively ensures the good bonding effect of coating on base paper and the uniformity of coating layer.

Description

Technical Field

[0001] This invention belongs to the field of specialty paper, and particularly relates to a capacitor paper and its preparation method. Background Technology

[0002] Capacitor paper is one of the key raw materials for capacitors. It serves as an adsorbent carrier for the electrolyte and together with the electrolyte forms the cathode of an aluminum electrolytic capacitor, while also acting as an insulator between the two electrode foils. With technological advancements, capacitors are developing towards higher withstand voltage, lower impedance, and lower heat generation, which requires capacitor paper to have higher breakdown voltage and lower equivalent series resistance (ESR).

[0003] Existing capacitor paper is mainly produced by combining a pressure-resistant layer and an absorbent layer into a double-layer paper through wet papermaking, or by bonding two layers of base paper together with adhesives to form a composite paper. For example, patent application CN109722945A discloses a breakdown-resistant composite electrolytic capacitor paper and its production method. This electrolytic capacitor paper is made by adding nanocellulose to pulp to form a pressure-resistant layer, which is then wet-laid with the absorbent layer using a long circular wire paper machine. Patent application CN109577102A discloses an electrolytic capacitor paper and its preparation method, which includes a nanofiber layer and high-pressure-resistant fiber layers composited on both sides of the nanofiber layer, with the layers bonded together by adhesives. While combining the pressure-resistant layer and absorbent layer into a double-layer paper through wet papermaking can reduce the ESR value of the capacitor paper, it also reduces the breakdown voltage and tensile strength. Bonding two layers of base paper together with adhesives to form a composite paper maintains the overall breakdown voltage or slightly increases it, but cannot meet the requirement for even lower ESR values.

[0004] As can be seen from the above, the existing capacitor paper and its preparation methods are difficult to simultaneously meet the requirements of high electrical strength and low ESR value. Therefore, it is of great significance to provide a capacitor paper with excellent comprehensive performance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a high-voltage composite capacitor paper with high electrical strength and low ESR value, and its preparation method. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0006] A high-voltage composite capacitor paper includes a base paper and a coating layer coated on the surface of the base paper. The coating liquid of the coating layer includes the following components in weight percentage: 1-10% nano starch, 1-10% nano cellulose, 1-10% adhesive and 70-96% water.

[0007] Furthermore, to ensure the effectiveness of nanocellulose and nanostarch, the ratio of their dosages needs to be controlled. Excessive use of either nanocellulose or nanostarch will result in an overly dense coating, leading to a decrease in tensile strength. Simultaneously, as the amount of nanocellulose increases, the coating porosity gradually decreases. When the impact of coating porosity on the liquid absorption of capacitor paper exceeds that of nanocellulose, the liquid absorption performance of the capacitor paper declines, and the ESR value increases. Controlling the mass ratio of nanocellulose and nanostarch is beneficial for ensuring their effective interaction.

[0008] In the aforementioned high-voltage composite capacitor paper, preferably, the nano-starch is obtained from native starch through physical, chemical, or biological methods, with an average particle size of 50-600 nm. The viscosity of the nano-starch suspension gradually increases as the particle size decreases. When the particle size decreases to 600 nm or lower, the nano-starch solution exhibits less shear thinning with increasing shear force. Under high shear rates, the viscosity stability is better, which is beneficial for enhancing the cross-linking effect with nanocellulose and improving their synergistic effect.

[0009] In the aforementioned high-voltage composite capacitor paper, preferably, the nanocellulose is obtained from cellulose fibers through physical, chemical, or biological methods, with an average length of 50-800 nm and a diameter of 10-100 nm. If the nanocellulose particle size is too large, the specific surface area is small, the molecular surface has few hydroxyl groups, and the nano-size effect is not obvious, affecting the coating uniformity; if the nanocellulose particle size is too small, the specific surface area is large, the surface energy is high, and the van der Waals forces between particles are strong, making them prone to mutual attraction and flocculation. Controlling the average length and diameter within the aforementioned range is beneficial for the coexistence of nano-starch and nanocellulose in solution, and for the synergistic effect of both.

[0010] In the above-mentioned high-voltage composite capacitor paper, preferably, the adhesive includes at least one of polyvinyl alcohol, ethylene acetate, acrylic, polyurethane and phenolic resins.

[0011] Preferably, the high-voltage composite capacitor paper also includes 0.5-2% of additives, wherein the additives include at least one of ammonium polyacrylate, polyacrylamide, and silicates.

[0012] In the above-mentioned high-voltage composite capacitor paper, preferably, the base paper is one layer, two layers or multiple layers. When the base paper is one layer, the coating layer is applied to the surface of the base paper. When the base paper is two layers or multiple layers, the coating layer is disposed between each layer of the base paper.

[0013] In the aforementioned high-voltage composite capacitor paper, preferably, when the base paper is a single layer, the thickness of the base paper is 20-50 μm; when the base paper is double-layered or multi-layered, the thickness of the base paper is 10-30 μm. If the base paper thickness is too low, the capacitor paper will have many defects and will not be able to form a complete paper sheet structure; if the thickness is too high, the ESR value of the capacitor paper will be too high and will not meet the requirements of actual capacitor production applications.

[0014] In the aforementioned high-voltage composite capacitor paper, preferably, the dry coating weight of the coating liquid is 0.1-20.0 g / m³. 2 A further preferred dry coating weight is 0.5-10.0 g / m². 2 Coating weight less than 0.1 g / m 2 When coating and laminating, problems such as localized insufficient adhesive and low bonding strength are prone to occur, especially when the coating amount exceeds 20.0 g / m². 2 At that time, the coating no longer significantly improves the breakdown voltage of the capacitor paper, and at the same time brings the negative effect of increasing the ESR value.

[0015] As a general technical concept, the present invention also provides a method for preparing the above-mentioned high-voltage composite capacitor paper, comprising the following steps:

[0016] (1) A pulping machine is used to pulp the fiber raw materials and then form paper to obtain the base paper;

[0017] (2) Stir nano starch in water to obtain nano starch solution, then disperse nano starch solution, nano cellulose, adhesive and additives evenly to obtain coating liquid;

[0018] (3) The coating liquid obtained in step (2) is applied to the original paper obtained in step (1) to obtain high voltage-resistant composite capacitor paper.

[0019] In the above preparation method, preferably, the fiber raw material includes plant fiber, man-made fiber, and synthetic fiber; the plant fiber includes at least one of insulating wood pulp, hemp pulp, cotton pulp, straw pulp, and bamboo pulp; the man-made fiber includes at least one of Tencel fiber and viscose fiber; the synthetic fiber includes at least one of polyester fiber, polyacrylonitrile fiber, polyethylene fiber, polypropylene fiber, polysulfonamide fiber, poly(p-phenylenebenzodioxazole) fiber, aromatic polyoxadiazole fiber, poly(m-phenylene isophthalamide) fiber, and poly(p-phenylene terephthalamide) fiber; the fiber raw material is pulped to 20-96°SR.

[0020] More specifically, the preparation method of this invention includes the following steps:

[0021] (1) Preparation of base paper: The fiber raw material is pulped to 20-96°SR using a pulper and then formed into A-layer base paper by paper machine or sheet forming device; the fiber raw material is pulped to 20-96°SR using a pulper and then formed into B-layer base paper by paper machine or sheet forming device.

[0022] (2) Nano starch is thoroughly stirred in ultrapure water to obtain nano starch solution, and then the nano starch solution, nano cellulose, adhesive and additives are evenly dispersed using a disperser to obtain coating liquid.

[0023] (3) A coating solution prepared by mixing nano-starch, nano-cellulose, adhesive and additives is applied to the A-layer base paper to obtain single-sided coated capacitor paper (e.g. Figure 1 (as shown); or after coating layer A, layer B is bonded to layer A to obtain double-layer composite capacitor paper (as shown). Figure 2 (As shown).

[0024] This invention primarily focuses on designing the coating liquid formulation. The resulting product, while exhibiting higher breakdown voltage and tensile strength, simultaneously reduces ESR, improves the coating liquid's adhesion, and enhances coating uniformity. Details are as follows:

[0025] This invention utilizes a coating method to prepare a nano-coating liquid by mixing nano-starch, nano-cellulose, adhesives, and additives. This liquid is then applied to a single layer of base paper, or a single layer of base paper is coated and then bonded to other base papers to obtain double-layer or multi-layer composite capacitor paper. This capacitor paper exhibits high voltage resistance and low impedance. Furthermore, different fiber types of base paper can be selected according to the production requirements of the capacitor paper. The intermediate nano-coating layer is formed through dry lamination, significantly improving the capacitor paper's ability to adsorb and retain electrolyte, thereby further reducing the ESR value of the capacitor paper.

[0026] Nano-coatings can compensate for surface defects in each layer of base paper. Furthermore, the numerous hydroxyl groups on the nanocellulose and nanostarch molecular chains allow for strong hydrogen bonding, resulting in good compatibility. Even with low nanocellulose content, the coating solution significantly improves the tensile index of capacitor paper, leading to excellent breakdown voltage and tensile strength. In addition, the combination of nanocellulose and nanostarch enhances the water retention and adhesion of the coating. By preparing a high-solids-content nano-coating solution, good adhesion and coating uniformity are effectively ensured, while simultaneously reducing the ESR value of the capacitor paper.

[0027] When using nano-starch and nano-cellulose with low particle size, the high specific surface area and surface energy of the nanoparticles make them prone to mutual attraction and aggregation. These flocculation phenomena affect the stability of the nano-coating, thereby affecting the cross-linking behavior between the two and hindering their synergistic effect. To ensure the synergistic effect of nano-cellulose and nano-starch, this invention also incorporates specific additives. By adding appropriate amounts of at least one of ammonium polyacrylate, polyacrylamide, and silicates to the coating solution, the coexistence stability of nano-starch and nano-cellulose is improved, ensuring the cross-linking effect between the nano-cellulose and nano-starch molecular chains and guaranteeing the synergistic effect.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] 1. The high-voltage composite capacitor paper of the present invention includes base paper and coating layer. After multi-layer composite, the composite capacitor paper has the characteristics of high voltage resistance, high strength and low impedance.

[0030] 2. The coating layer of the high voltage-resistant composite capacitor paper of the present invention is obtained by coating with a high solid content nano coating liquid prepared by mixing nano starch, nano cellulose and adhesive, which effectively ensures the coating has a good adhesion effect to the base paper and the uniformity of the coating. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the single-layer high-voltage composite capacitor paper structure of the present invention.

[0033] Figure 2 This is a schematic diagram of the double-layer high-voltage composite capacitor paper structure of the present invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1:

[0038] A high-voltage composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0039] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR with a pulp concentration of 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, an A-layer base paper with a thickness of 20.3μm is obtained.

[0040] Preparation of the nano-coating solution: Nano starch was thoroughly stirred in ultrapure water to obtain a nano starch solution. Then, the nano starch solution, nanocellulose, and polyvinyl alcohol were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 8%. The nano starch accounted for 4.0% of the coating solution by mass, the nanocellulose accounted for 2.0%, and the polyvinyl alcohol accounted for 2.0%.

[0041] Preparation of capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 0.5 g / m². 2 The process involves preparing coated capacitor paper, which is then dried and trimmed to obtain the final product. A schematic diagram of the specific product is shown below. Figure 1 As shown.

[0042] In this embodiment, the average particle size of the nano starch is 200-300 nm; the average length of the nanocellulose is 500-600 nm, and the diameter is 10-20 nm.

[0043] Example 2:

[0044] A high-voltage composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0045] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0046] Preparation of the nano-coating solution: Nano starch was thoroughly stirred in ultrapure water to obtain a nano starch solution. Then, the nano starch solution, nanocellulose, and polyvinyl alcohol were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 16%. The nano starch accounted for 10.0% of the coating solution by mass, the nanocellulose accounted for 4.0%, and the polyvinyl alcohol accounted for 2.0%.

[0047] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, layer B of the base paper is laminated onto layer A, which has a coating layer, to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product. A schematic diagram of the specific product is shown below. Figure 2 As shown.

[0048] In this embodiment, the average particle size of the nano starch is 200-300 nm; the average length of the nanocellulose is 500-600 nm, and the diameter is 10-20 nm.

[0049] Example 3:

[0050] A high-voltage composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0051] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0052] Preparation of the coating solution: A nano-starch solution was prepared by thoroughly stirring nano-starch in ultrapure water. Then, the nano-starch solution, nano-cellulose, and polyvinyl alcohol were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 12.0%. The nano-starch accounted for 6.0% of the coating solution by mass, the nano-cellulose accounted for 2.0%, and the polyvinyl alcohol accounted for 4.0%.

[0053] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0054] In this embodiment, the average particle size of the nano starch is 200-300 nm; the average length of the nanocellulose is 500-600 nm, and the diameter is 10-20 nm.

[0055] Example 4:

[0056] A high-voltage composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0057] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0058] Preparation of the coating solution: A nano-starch solution was prepared by thoroughly stirring nano-starch in ultrapure water. Then, the nano-starch solution, nano-cellulose, polyvinyl alcohol, and ammonium polyacrylate were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 12.5%. The nano-starch content of the coating solution was 6.0% by mass, the nano-cellulose content was 2.0% by mass, the polyvinyl alcohol content was 4.0% by mass, and the ammonium polyacrylate content was 0.5% by mass.

[0059] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0060] In this embodiment, the average particle size of the nano starch is 200-300 nm; the average length of the nanocellulose is 500-600 nm, and the diameter is 10-20 nm.

[0061] Example 5:

[0062] A high-voltage composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0063] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0064] Preparation of the coating solution: A nano-starch solution was prepared by thoroughly stirring nano-starch in ultrapure water. Then, the nano-starch solution, nano-cellulose, and polyvinyl alcohol were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 8.0%. The nano-starch accounted for 4.0% of the coating solution by mass, the nano-cellulose accounted for 2.0%, and the polyvinyl alcohol accounted for 2.0%.

[0065] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0066] In this embodiment, the average particle size of the nano starch is 200-300 nm; the average length of the nanocellulose is 500-600 nm, and the diameter is 10-20 nm.

[0067] Comparative Example 1:

[0068] A capacitor paper, comprising a base paper, is prepared by means of the following steps:

[0069] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR with a pulp concentration of 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, an A-layer base paper with a thickness of 20.3μm is obtained.

[0070] Comparative Example 2:

[0071] A capacitor paper, comprising a base paper, is prepared by means of the following steps:

[0072] Preparation of the base paper: The insulating wood pulp is pulped in a pulper, then refined to 95°SR with a pulp concentration of 3.0%. After forming, pressing, drying, and winding on a fourdrinier paper machine, a 40.5μm thick A-layer base paper is obtained.

[0073] Comparative Example 3:

[0074] A composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0075] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0076] Preparation of nano-coating solution: Polyvinyl alcohol is dispersed evenly to prepare a coating solution with a mass concentration of 10%.

[0077] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0078] Comparative Example 4:

[0079] A composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0080] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0081] Preparation of the nano-coating solution: Nano starch was thoroughly stirred in ultrapure water to obtain a nano starch solution. Then, the nano starch solution and polyvinyl alcohol were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 10.0%. The nano starch accounted for 6.0% of the coating solution by mass, and the polyvinyl alcohol accounted for 4.0% by mass.

[0082] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0083] In this comparative example, the average particle size of the nano starch was 200-300 nm.

[0084] Comparative Example 5:

[0085] A composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0086] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0087] Preparation of the nano-coating solution: Nano starch was thoroughly stirred in ultrapure water to obtain a nano starch solution. Then, the nano starch solution, nanocellulose, and polyvinyl alcohol were dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 16%. The nano starch accounted for 12.0% of the coating solution by mass, the nanocellulose accounted for 2.0%, and the polyvinyl alcohol accounted for 2.0%.

[0088] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0089] In this comparative example, the average particle size of the nano starch was 200-300 nm.

[0090] Comparative Example 6:

[0091] A composite capacitor paper includes a base paper and a coating layer applied to the surface of the base paper. Its preparation method includes the following steps:

[0092] Preparation of base paper: After the insulating wood pulp is pulped by a pulper, it is refined to 95°SR and the pulp concentration is 3.0% by a refiner. After being formed, pressed, dried and wound by a wire paper machine, a base paper with a thickness of 20.3μm is obtained. A base paper with a thickness of 20.3μm is obtained by the same method described above.

[0093] Preparation of the nano-coating solution: Nanocellulose and polyvinyl alcohol were uniformly dispersed using a disperser to prepare a coating solution with a mass concentration of 10.0%. The nanocellulose accounted for 6.0% of the mass of the coating solution, and the polyvinyl alcohol accounted for 4.0% of the mass of the coating solution.

[0094] Preparation of composite capacitor paper: One side of the A-layer base paper is coated with a coating liquid using a coating laminating machine, with a dry coating weight of 1.0 g / m². 2 Then, the B-layer base paper is laminated onto the coated A-layer base paper to form a double-layer composite capacitor paper. After drying and trimming, the composite capacitor paper is used to obtain the final product.

[0095] In this comparative example, the average length of the nanocellulose was 500-600 nm and the diameter was 10-20 nm.

[0096] The performance test data of the capacitor paper prepared in Examples 1-5 and Comparative Examples 1-5 are shown in Table 1 below.

[0097] Table 1: Performance test data of capacitor paper prepared in Examples 1-5 and Comparative Examples 1-6

[0098]

[0099]

[0100] The testing methods for the above performance data are as follows:

[0101] 1. Sample preparation and testing standards

[0102] The samples were treated and tested under standard atmospheric conditions of (23±2)℃ and (50±5)% relative humidity. This was in accordance with GB / T10739-2002, "Standard Atmospheric Conditions for the Treatment and Testing of Paper, Paperboard and Pulp Samples".

[0103] Balance graduation value: 0.0001g.

[0104] 2. Quantitative

[0105] G = M × 10. Fold five samples lengthwise to form 10 layers. Use a quantitative sampler to evenly cut 100cm samples lengthwise from the paper. 2 Five stacks of samples were prepared, and the total mass M (g) of each stack was weighed. The quantitative amount of the sample (g / m) was determined. 2 The test was conducted in accordance with GB / T451.2-2002, "Determination of basis weight of paper and paperboard".

[0106] 3. Moisture

[0107] The container containing the sample was placed in an oven at 105℃±2℃ and dried for 2 hours. The weights of the sample before and after drying were m1 and m2, respectively. The moisture content of the sample was...

[0108] 4. Absolute dryness

[0109] A single sheet of sample is stacked 10 times along the longitudinal direction. A thickness gauge is used to uniformly measure 15 points along the transverse direction of the paper. The measured value divided by 10 gives the sample thickness δ (μm). The sample's oven-dry density... The test was conducted in accordance with GB / T451.3-2002, "Determination of thickness of paper and paperboard".

[0110] 5. Breakdown voltage

[0111] A continuous, uniform voltage increase method is used to apply a power frequency voltage to the sample using a breakdown voltage meter, and the voltage value (V) at which the sample breaks down is measured. For samples with a thickness less than or equal to 60 μm, the sample consists of two layers of paper; for samples with a thickness greater than 60 μm, the sample consists of a single layer of paper. Nine effective breakdown tests are performed, and the median value of the test results is taken. For samples consisting of two layers of paper, the breakdown voltage is half of the measured value. The test follows GB / T3333-1999 "Test Method for Power Frequency Breakdown Voltage of Cable Paper".

[0112] 6. Liquid absorption height

[0113] Five samples were cut longitudinally along the paper, each sample being (15±1) mm wide and (250±10) mm long. After clamping the sample onto the paper capillary absorbance meter, the sample was vertically inserted 5 mm into distilled or deionized water. The absorbance height (mm) was read after 10 min±10 s. The result was taken as the average of the five samples, accurate to 1 mm. The test was performed according to GB / T 461.1-2002 "Determination of Capillary Absorption Height of Paper and Paperboard (Klem Method)".

[0114] 7. ESR value

[0115] After cutting the paper sample into pieces with a diameter of (30-50) mm, place them in a sealed weighing bottle containing electrolyte and soak for 18-20 hours. Then, place them flat in the LCR digital bridge fixture, ensuring the fixture electrodes are in contact with the sample. Adjust the fixture spacing to 1.0-2.0 times the paper sample thickness, and read the Rs and D values ​​displayed on the LCR digital bridge. Measure 10 parallel samples of the same sample, discarding values ​​with large deviations, and take the average of the results.

[0116] 8. Tensile strength

[0117] Ten specimens were cut using a dedicated sampler, each with a width of (15±1) mm and a length of (250±10) mm. The tensile strength (N / m) of the specimens was measured using a tensile testing machine at a tensile speed of 20 mm / min. The result was taken as the average value of the 10 specimens. The test was conducted in accordance with GB / T 12914-2018 "Determination of Tensile Strength of Paper and Paper Products - Constant Speed ​​Tensile Test (20 mm / min)".

Claims

1. A high-voltage composite capacitor paper, comprising a base paper and a coating layer applied to the surface of the base paper, characterized in that, The coating solution for the coating layer is prepared by the following method: nano starch is thoroughly stirred in ultrapure water to obtain a nano starch solution. Then, the nano starch solution, nano cellulose, polyvinyl alcohol and ammonium polyacrylate are dispersed evenly using a disperser to prepare a coating solution with a mass concentration of 12.5%, wherein the mass ratio of nano starch to coating solution is 6.0%, the mass ratio of nano cellulose to coating solution is 2.0%, the mass ratio of polyvinyl alcohol to coating solution is 4.0%, the mass ratio of ammonium polyacrylate is 0.5%, and the balance is water. The nano starch is obtained from native starch through physical, chemical or biological methods, and has an average particle size of 50-600 nm. The nanocellulose is obtained from cellulose fibers through physical, chemical or biological methods, with an average length of 50-800 nm and a diameter of 10-100 nm.

2. The high-voltage composite capacitor paper according to claim 1, characterized in that, The base paper can be one, two, or multiple layers. When the base paper is one layer, the coating layer is applied to the surface of the base paper. When the base paper is two or multiple layers, the coating layer is disposed between each layer of the base paper.

3. The high-voltage composite capacitor paper according to claim 2, characterized in that, When the base paper is a single layer, the thickness of the base paper is 20-50 μm; when the base paper is double-layered or multi-layered, the thickness of the base paper is 10-30 μm.

4. The high-voltage composite capacitor paper according to claim 1, characterized in that, The dry coating weight of the coating solution is 0.1-20.0 g / m³. 2 .

5. A method for preparing high-voltage composite capacitor paper as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) A pulping machine is used to pulp the fiber raw materials and then form paper. (2) The nano starch is stirred in water to obtain a nano starch solution, and then the nano starch solution, nano cellulose, adhesive and additives are dispersed evenly to obtain a coating liquid; (3) The coating liquid obtained in step (2) is applied to the original paper obtained in step (1) to obtain high voltage-resistant composite capacitor paper.

6. The preparation method according to claim 5, characterized in that, The fiber raw materials include plant fibers, man-made fibers, and synthetic fibers; the plant fibers include at least one of insulating wood pulp, hemp pulp, cotton pulp, straw pulp, and bamboo pulp; the man-made fibers include at least one of Tencel fiber and viscose fiber; the synthetic fibers include at least one of polyester fiber, polyacrylonitrile fiber, polyethylene fiber, polypropylene fiber, polysulfonamide fiber, poly(p-phenylenebenzodioxazole) fiber, aromatic polyoxadiazole fiber, poly(m-phenylene isophthalamide) fiber, and poly(p-phenylene terephthalamide) fiber; the fiber raw materials are pulped to 20-96°SR.

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