A capacitor paper and a method for preparing the same

Abstract

The present invention provides a capacitor paper and a preparation method thereof, comprising a first base paper layer and a polymer layer arranged in sequence, or comprising a first base paper layer, a polymer layer and a second base paper layer arranged in sequence, wherein the polymer layer is a cross-linked polymer formed by heating polyvinyl alcohol and glutaraldehyde under weak acid conditions. The capacitor paper prepared by the present invention can significantly improve the breakdown voltage resistance performance of the capacitor paper on the basis of ensuring a low ESR by coating the cross-linked polymer formed by heating polyvinyl alcohol and glutaraldehyde under weak acid conditions on the base paper layer, or by using a polymer layer synergistically cross-linked through a multi-layer composite structure.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitor paper, and in particular relates to capacitor paper with high breakdown voltage and low equivalent series resistance and a preparation method thereof. Background Art

[0002] Capacitor paper is one of the key raw materials for capacitors. With the development of the electronics industry, capacitors have higher and higher requirements for voltage resistance while maintaining their capacity and loss values ​​unchanged, which puts higher requirements on the voltage resistance performance of container paper; on the other hand, with the miniaturization and high power of electronic and electrical components, capacitors are required to generate less heat, which puts forward technical requirements for capacitor paper to have lower equivalent series resistance (ESR). Therefore, the development of capacitor paper with high voltage resistance and low ESR has become an important demand.

[0003] Chinese invention patent CN104988809A discloses a high-voltage electrolytic capacitor paper and its preparation method. The base paper pulp of the electrolytic capacitor paper disclosed in the patent is composed of the following pulps: insulating wood pulp, cotton pulp and hemp pulp; at least one of the cotton pulp and hemp pulp is selected, and the base paper is made by wet compounding with insulating wood pulp in the paper machine after papermaking with cotton pulp and / or hemp pulp, and then coating is performed on both sides of the base paper to obtain high-voltage electrolytic capacitor paper, wherein the coating liquid is PVA and PVA derivatives, PVC and its derivatives, PVDC or EVOH. The capacitor paper prepared by the method of coating with the above coating liquid has limited improvement in breakdown voltage, which cannot meet the demand for higher breakdown voltage, nor can it meet the requirement of extremely low equivalent series resistance (ESR). Summary of the invention

[0004] In order to overcome the technical problem in the prior art that capacitor paper cannot have both high breakdown voltage and low ESR value, the present invention provides a capacitor paper and a preparation method thereof, which can improve the breakdown voltage performance of the capacitor paper while ensuring a lower equivalent series resistance (ESR) value of the capacitor paper.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A first aspect of the present invention provides a capacitor paper, which includes a first base paper layer and a polymer layer arranged in sequence, or includes a first base paper layer, a polymer layer and a second base paper layer arranged in sequence, and the polymer layer is a cross-linked polymer formed by polyvinyl alcohol and glutaraldehyde.

[0007] In the present application, a double-layer composite structure including a base paper layer and a polymer is provided, or a three-layer composite structure including a first base paper layer, a polymer layer and a second base paper layer, wherein the polymer layer is a polymer formed by cross-linking polyvinyl alcohol and glutaraldehyde, and the polymer formed after cross-linking has higher electrical strength, which can greatly improve the breakdown voltage resistance performance of the capacitor paper while ensuring a lower equivalent series resistance (ESR) value.

[0008] As an optional implementation, in the capacitor paper provided by the present invention, the polymer layer is a polymer formed by cross-linking polyvinyl alcohol and glutaraldehyde under weakly acidic conditions.

[0009] In the present invention, a polymer formed by cross-linking polyvinyl alcohol and glutaraldehyde under weakly acidic conditions is used to prevent other acidic conditions from affecting the performance of capacitor paper.

[0010] As an optional embodiment, in the capacitor paper provided by the present invention, the polymer layer is a cross-linked polymer formed by heating polyvinyl alcohol and glutaraldehyde under weak acid conditions.

[0011] In the present invention, the cross-linked polymer formed by heating polyvinyl alcohol and glutaraldehyde under weak acid conditions will not be dissolved and is more stable in the application environment of capacitor paper.

[0012] As an optional embodiment, in the capacitor paper provided by the present invention, the dry coating amount of the polymer in the polymer layer is 0.01-20.0 g / m 2 .

[0013] In the present invention, coating the polymer on the first base paper layer will increase the ESR value of the capacitor paper, but will also increase the breakdown voltage of the capacitor paper. Therefore, by controlling the coating amount of the polymer, the ESR value and the breakdown voltage performance of the capacitor paper can be regulated, and the two can be kept in a relatively balanced state according to the different use requirements of the capacitor paper. The dry coating amount of the polymer in this application is set to 0.01-20.0g / m 2 , which is beneficial to improve the breakdown voltage of capacitor paper. When the polymer coating amount exceeds 20.0g / m 2 When the dry coating amount is less than 0.01 g / m, the effect of improving the breakdown voltage is no longer significant, and on the other hand, the ESR value of the capacitor paper rises sharply, which is an undesirable negative effect. 2 When the coating and lamination process is too slow, it is easy to cause poor double-layer lamination, such as local lack of glue, low bonding strength and other problems.

[0014] As an optional embodiment, in the capacitor paper provided by the present invention, the dry coating amount of the polymer in the polymer layer is 0.1-5.0 g / m 2 .

[0015] As an optional implementation manner, in the capacitor paper provided by the present invention, the thickness of the capacitor paper is 12 to 120 μm.

[0016] As an optional implementation manner, in the capacitor paper provided by the present invention, the thickness of the first base paper layer and the second base paper layer are respectively 6 to 60 μm.

[0017] In the present invention, the thickness of the single-layer capacitor paper is maintained at 6 to 60 μm. When the thickness is too low, the defects of the product increase significantly and a complete structure cannot be formed. When the thickness of the single layer exceeds 60 microns, the thickness of the composite product will exceed 120 microns, and the ESR value of the product is too high, and the capacitor made is large in size and cannot meet the requirements of practical applications.

[0018] As an optional implementation manner, in the capacitor paper provided by the present invention, the thickness of the first base paper layer and the second base paper layer is 10 to 30 μm.

[0019] As an optional embodiment, in the capacitor paper provided by the present invention, the thickness deviation of the first base paper layer is ±8% of the nominal value of the thickness of the first base paper layer, and the thickness deviation of the second base paper layer is ±8% of the nominal value of the thickness of the second base paper layer.

[0020] In the present application, the thickness deviation of the first base paper layer and the second base paper layer is limited to ±8% of the nominal value of the thickness of the corresponding layer. When the thickness deviation value is too large, the uniformity of the product is affected and the breakdown voltage fluctuates greatly. When the thickness exceeds the upper deviation, it may have an adverse effect on the assembly of the elements after winding, and even cause failure of normal assembly.

[0021] As an optional embodiment, in the capacitor paper provided by the present invention, the raw material of the first base paper layer and the second base paper layer is at least one of plant fiber, man-made fiber and synthetic fiber.

[0022] As an optional embodiment, in the capacitor paper provided by the present invention, the plant fiber is at least one of insulating wood pulp, hemp pulp, cotton pulp and straw pulp.

[0023] As an optional embodiment, in the capacitor paper provided by the present invention, the artificial fiber is a fiber that can be divided into fibrils.

[0024] As an optional embodiment, in the capacitor paper provided by the present invention, the artificial fiber is Tencel fiber.

[0025] As an optional implementation, in the capacitor paper provided by the present invention, the synthetic fiber is poly(p-phenylene benzobisoxazole) fiber or para-aramid fiber.

[0026] As an optional embodiment, in the capacitor paper provided by the present invention, the synthetic fiber is para-aramid fiber.

[0027] A second aspect of the present invention provides a method for preparing the capacitor paper, comprising the following steps:

[0028] S1. The raw material is pulped and then subjected to a refining treatment. After forming, pressing, drying and winding, a first base paper layer and / or a second base paper layer is prepared.

[0029] S2, first coating one side of the first base paper layer or the second base paper layer obtained in step S1 with a layer of polyvinyl alcohol solution, then coating the polyvinyl alcohol solution with a weak acid solution of glutaraldehyde, and heating to obtain two layers of composite capacitor paper, or first coating one side of the first base paper layer obtained in step S1 with a layer of polyvinyl alcohol solution, then coating the polyvinyl alcohol solution with a weak acid solution of glutaraldehyde, and then compounding the second base paper layer onto the coating layer of the first base paper layer, and heating to obtain three layers of composite capacitor paper.

[0030] As an optional embodiment, in the preparation method provided by the present invention, the method for setting the polymer in step S2 is at least one of coating and hot pressing bonding, and the coating method is at least one of dip coating, air knife coating, blade coating, scraper roller coating, roller coating, gravure coating, slit coating, curtain coating, rotary coating, and spray coating.

[0031] As an optional embodiment, in the preparation method provided by the present invention, the dry coating amount of the polyvinyl alcohol solution in step S2 is 0.01-20.0 g / m 2 The coating amount of the weakly acidic solution of glutaraldehyde is 0.01-20.0g / m 2 .

[0032] In the preparation method of the present invention, the coating process adopts the in-situ reaction of the polymer, and the cross-linked polymer with poor solubility can be smoothly coated on the base paper.

[0033] As an optional embodiment, in the preparation method provided by the present invention, the area of ​​the local glue deficiency in the three-layer composite capacitor paper in step S2 is ≤10mm 2 / m 2 .

[0034] The invention limits the area of ​​local glue deficiency in the three-layer composite capacitor paper to ≤10mm 2 / m 2Poor coating and lamination can lead to local glue deficiency between the two layers of paper. The breakdown voltage of the glue deficiency area is low. When the glue deficiency area is large, the edges of the two layers of capacitor paper are misaligned during the winding process of the capacitor, resulting in the capacitor being scrapped. The present invention uses a light box with a light source to inspect the possible local glue deficiency of the double-layer composite capacitor paper. Take 1m 2 The double-layer composite capacitor paper is placed flat on top of a lit light box. The surface of the paper is inspected with the naked eye. The local area with missing glue appears in a different color from the surrounding area. The outline of the area with missing glue is outlined with a pencil, and the area with missing glue is compared with a dust standard chart to read the area of ​​the area with missing glue.

[0035] As an optional embodiment, in the preparation method provided by the present invention, the area of ​​the local glue deficiency in the three-layer composite capacitor paper in step S2 is ≤1mm 2 / m 2 .

[0036] As an optional embodiment, in the preparation method provided by the present invention, the area of ​​the local glue deficiency in the three-layer composite capacitor paper in step S2 is ≤0.1mm 2 / m 2 .

[0037] As an optional embodiment, in the preparation method provided by the present invention, in step S1, the raw material is refined to 15-96° SR by a trough beater or a refiner.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The capacitor paper prepared in the present invention has a double-layer composite structure of a base paper layer and a polymer, or a three-layer composite structure including a first base paper layer, a polymer layer and a second base paper layer, and the polymer layer is a cross-linked polymer formed by polyvinyl alcohol and glutaraldehyde. The polymer layer is cross-linked through the multi-layer composite structure, and the performance of the capacitor paper's breakdown voltage resistance can be greatly improved while ensuring a low ESR.

[0040] (2) The capacitor paper prepared by the present invention has a breakdown voltage of up to 2750V and an ESR value of 0.42Ω, which has excellent performance. By adjusting the ESR value and breakdown voltage performance of the capacitor paper, the needs of different capacitors can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 This is a schematic diagram of the structure of the three-layer composite capacitor paper in Example 1 of the present invention;

[0043] Figure 2 Schematic diagram of the structure of the double-layer composite capacitor paper in Example 2 of the present invention.

[0044] Reference numerals:

[0045] 1. A layer of base paper; 2. Polymer layer; 3. B layer of base paper. DETAILED DESCRIPTION

[0046] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0047] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0048] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0049] Example 1

[0050] (1) Preparation of base paper layer: The insulating wood pulp is pulped by a pulper, and then refined by a pulper to 96°SR with a pulping concentration of 3.0%. After being formed, pressed, dried and rolled by a fourdrinier paper machine, a base paper A layer 1 with a thickness of 20.0 μm, i.e., the first base paper, is obtained. The insulating wood pulp is used to prepare a base paper B layer 2 with a thickness of 20.0 μm, i.e., the second base paper, by the same method as above.

[0051] (2) Preparation of three-layer composite capacitor paper: Add polyvinyl alcohol 1799 to ultrapure water under stirring and disperse evenly, heat to 95°C to dissolve, and prepare a solution with a mass concentration of 8% for use. Pass one side of the A-layer base paper 1 prepared in step (1) through a coating and laminating machine, first coat a layer of the aforementioned polyvinyl alcohol 1799 solution, and the dry coating amount is 0.5g / m 2Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 1 g / m 2 , and then the B layer base paper 2 prepared in step (1) is compounded onto the A layer base paper 1 with the coating layer to form a sandwich structure composite capacitor paper. After the composite capacitor paper is heated, the polyvinyl alcohol coating layer in the middle reacts with glutaraldehyde to form a cross-linked polyvinyl alcohol glutaraldehyde, which is the polymer layer 2. The composite capacitor paper is dried and trimmed to obtain the final product. The product structure diagram is shown in FIG. Figure 1 shown.

[0052] Example 2

[0053] (1) Preparation of base paper layer: A base paper layer and a base paper layer B with a thickness of 30.1 μm were prepared by the same method as in Example 1.

[0054] (2) Preparation of three-layer composite capacitor paper: Prepare polyvinyl alcohol 1799 solution as described in Example 1. Pass one side of the A-layer base paper through a coating laminating machine and first coat it with a layer of polyvinyl alcohol 1799 solution, with a dry coating amount of 0.5 g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 1 g / m 2 , and then the B layer base paper is compounded onto the coating liquid layer to form a sandwich structure. The composite capacitor paper is heated, and the middle polyvinyl alcohol coating layer and glutaraldehyde undergo an alcohol-aldehyde condensation reaction to form cross-linked polyvinyl alcohol glutaraldehyde. The composite capacitor paper is dried and trimmed to obtain the final product.

[0055] Example 3

[0056] (1) Preparation of base paper layer: After the insulating wood pulp is pulped by a pulper, it is refined by a pulper to 96°SR and the pulping concentration is 3.0%. After the Tencel fiber is de-pulped, the pulping concentration is set to 3.5%, and it is refined by a pulper to 90°SR. Then, the above-mentioned refined wood pulp and Tencel pulp are mixed in a mass ratio of 85:15, and then formed, pressed, dried and wound on a fourdrinier paper machine to obtain a base paper A layer with a thickness of 20.2 μm; after the Manila hemp pulp is de-pulped, the mass concentration is adjusted to 2.0%, and it is refined by a disc refiner to 25°SR. After forming, pressing, drying and winding on an inclined wire paper machine, a base paper B layer with a thickness of 16.2 μm is obtained.

[0057] (2) Preparation of three-layer composite capacitor paper: Prepare polyvinyl alcohol 1799 solution as described in Example 1. Pass one side of the A-layer base paper through a coating laminating machine and first coat it with a layer of polyvinyl alcohol 1799 solution, with a dry coating amount of 0.5 g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 1 g / m 2, and then compounding the B layer base paper onto the A layer base paper with the coating layer to form a sandwich structured composite capacitor paper. After the composite capacitor paper is heated, the polyvinyl alcohol coating layer in the middle reacts with glutaraldehyde to form cross-linked polyvinyl alcohol glutaraldehyde. The composite capacitor paper is dried and trimmed to obtain the final product.

[0058] Example 4

[0059] (1) Preparation of base paper layer: After the insulating wood pulp is pulped by a pulper, it is refined by a pulper to 96°SR and the pulping concentration is 3.0%. After the Tencel fiber is de-pulped, the pulping concentration is set to 3.5%, and it is refined by a pulper to 90°SR. Then, the above-mentioned refined wood pulp and Tencel pulp are mixed in a mass ratio of 85:15, and then formed, pressed, dried and wound on a fourdrinier paper machine to obtain a base paper A layer with a thickness of 20.2 μm; after the Manila hemp pulp is de-pulped, the mass concentration is adjusted to 2.0%, and it is refined by a disc refiner to 25°SR. After forming, pressing, drying and winding on an inclined wire paper machine, a base paper B layer with a thickness of 16.2 μm is obtained.

[0060] (2) Preparation of three-layer composite capacitor paper: Prepare polyvinyl alcohol 1799 solution as described in Example 1. Pass one side of the A-layer base paper through a coating laminating machine and first coat it with a layer of polyvinyl alcohol 1799 solution with a dry coating amount of 5 g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 10 g / m 2 , and then compounding the B layer base paper onto the A layer base paper with the coating layer to form a sandwich structured composite capacitor paper. After the composite capacitor paper is heated, the polyvinyl alcohol coating layer in the middle reacts with glutaraldehyde to form cross-linked polyvinyl alcohol glutaraldehyde. The composite capacitor paper is dried and trimmed to obtain the final product.

[0061] Example 5

[0062] (1) Preparation of base paper layer: Manila hemp pulp was depulped and adjusted to a mass concentration of 2.0%. The pulp was refined to 25°SR by a disc refiner. The base paper A layer with a thickness of 16.2 μm was obtained after forming, pressing, drying and winding by an inclined wire paper machine. The base paper B layer with a thickness of 16.2 μm was obtained by the same method as above.

[0063] (2) Preparation of three-layer composite capacitor paper: Prepare polyvinyl alcohol 1799 solution as described in Example 1. Pass one side of the A-layer base paper through a coating laminating machine and first coat it with a layer of polyvinyl alcohol 1799 solution with a dry coating amount of 0.5 g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the aforementioned coating layer, with a coating amount of 1 g / m 2, and then compound the B layer base paper onto the A layer base paper with the coating layer to form a sandwich structured composite capacitor paper. When the composite capacitor paper is dried and heated, the polyvinyl alcohol coating layer in the middle reacts with glutaraldehyde to form cross-linked polyvinyl alcohol glutaraldehyde, which is then dried and trimmed to obtain the final product.

[0064] Example 6

[0065] (1) Preparation of base paper layer: A base paper 1 with a thickness of 20.0 μm was prepared by the same method as in Example 1.

[0066] (2) Preparation of double-layer composite capacitor paper: Prepare polyvinyl alcohol 1799 solution as described in Example 1. Pass one side of the A-layer base paper 1 through a coating laminating machine and first coat it with a layer of polyvinyl alcohol 1799 solution, with a dry coating amount of 1 g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 2 g / m 2 , polyvinyl alcohol and glutaraldehyde undergo an aldol condensation reaction to form cross-linked polyvinyl alcohol glutaraldehyde, which is the polymer layer 2. The capacitor paper is dried and trimmed to obtain the final product. The product structure diagram is shown in the figure below. Figure 2 shown.

[0067] Comparative Example 1

[0068] Preparation of capacitor paper: A base paper with a thickness of 20.2 μm and a base paper with a thickness of 20.2 μm were prepared in the same manner as in Example 1. The two base papers were wet compounded in a press section to obtain the final product, double-layer capacitor paper.

[0069] Comparative Example 2

[0070] (1) Preparation of capacitor paper: A layer of base paper with a thickness of 20.2 μm and a layer of base paper with a thickness of 20.1 μm were prepared in the same manner as in Example 1.

[0071] (2) Add polyvinyl alcohol 1799 to ultrapure water under stirring and disperse evenly, heat to 95°C to dissolve, and prepare a solution with a mass concentration of 8% for use. Pass one side of the A-layer base paper prepared in step (1) through a coating laminating machine and first coat a layer of the polyvinyl alcohol 1799 solution, with a dry coating amount of 0.5 g / m 2 The B-layer base paper prepared in step (1) is then compounded onto the A-layer base paper with the coating layer to form a sandwich-structured composite capacitor paper. The composite capacitor paper is dried and trimmed to obtain the final product.

[0072] The difference from Example 1 is that only polyvinyl alcohol is used in the polymer layer, and no glutaraldehyde solution is used for cross-linking.

[0073] Comparative Example 3

[0074] (1) Preparation of capacitor paper: A layer of base paper with a thickness of 20.2 μm and a layer of base paper with a thickness of 20.1 μm were prepared in the same manner as in Example 1.

[0075] (2) Add polyvinyl alcohol 1799 to ultrapure water under stirring and disperse evenly, heat to 95°C to dissolve, and prepare a solution with a mass concentration of 8% for use. Pass one side of the A-layer base paper prepared in step (1) through a coating laminating machine and first coat a layer of the polyvinyl alcohol 1799 solution, with a dry coating amount of 0.5 g / m 2 Then, a weakly acidic solution of glutaraldehyde is coated on the aforementioned coating layer, with a pH value of 4 and a coating amount of 1 g / m 2 The B-layer base paper prepared in step (1) is then compounded onto the A-layer base paper with a coating layer to form a sandwich-structured composite capacitor paper. The composite capacitor paper is naturally air-dried and trimmed to obtain the final product.

[0076] The difference from Example 1 is that the weakly acidic solution of polyvinyl alcohol and glutaraldehyde is not subjected to heating treatment.

[0077] Comparative Example 4

[0078] (1) Preparation of base paper layer: The insulating wood pulp is pulped by a pulper, and then refined by a pulper to 96°SR with a pulping concentration of 3.0%. After being formed, pressed, dried and rolled by a fourdrinier paper machine, a base paper A layer with a thickness of 20.0 μm is obtained. The insulating wood pulp is used to prepare a base paper B layer with a thickness of 20.0 μm by the same method as above.

[0079] (2) Preparation of three-layer composite capacitor paper: Polyethylene glycol (Mn = 20000) was added to ultrapure water under stirring and dispersed evenly, heated to 60°C to dissolve, and prepared into a solution with a mass concentration of 8% for use. One side of the A-layer base paper prepared in step (1) was passed through a coating and laminating machine, and a layer of the aforementioned polyethylene glycol solution was first coated, and the dry coating amount was 0.5 g / m 2 The B-layer base paper prepared in step (1) is then compounded onto the A-layer base paper with the coating layer to form a sandwich-structured composite capacitor paper. The composite capacitor paper is dried and trimmed to obtain the final product.

[0080] Comparative Example 5

[0081] Preparation of capacitor paper: The same method as in Example 3 was used to prepare a base paper A layer with a thickness of 20.2 μm and a base paper B layer with a thickness of 16.2 μm. The two base papers were wet-compounded online in the press section of the paper machine to obtain the final product, double-layer capacitor paper.

[0082] Comparative Example 6

[0083] Preparation of capacitor paper: The same method as in Example 5 was used to prepare a base paper A layer with a thickness of 16.2 μm and a base paper B layer with a thickness of 16.2 μm. The two base papers were wet-compounded online in the press section of the paper machine to obtain the final product, double-layer capacitor paper.

[0084] Comparative Example 7

[0085] Preparation of capacitor paper: The insulating wood pulp is pulped by a pulper, and then refined by a pulper to 96°SR with a pulping concentration of 3.0%. After forming, pressing, drying and winding on a fourdrinier paper machine, the final product capacitor paper with a thickness of 20.2 μm is obtained.

[0086] Comparative Example 8

[0087] The same method as in Example 6 was used to prepare a base paper 1 with a thickness of 20.0 μm. A polyvinyl alcohol 1799 solution was prepared for use. One side of the base paper A was passed through a coating laminating machine and coated with a layer of polyvinyl alcohol 1799 solution. The dry coating amount was 1 g / m 2 The capacitor paper is dried and trimmed to obtain the final product.

[0088] The difference from Example 6 is that only polyvinyl alcohol is used in the polymer layer, and no glutaraldehyde solution is used for cross-linking.

[0089] Comparative Example 9

[0090] The same method as in Example 6 was used to prepare a base paper 1 with a thickness of 20.0 μm. A polyvinyl alcohol 1799 solution was prepared for use. One side of the base paper A was passed through a coating laminating machine and coated with a layer of polyvinyl alcohol 1799 solution. The dry coating amount was 1 g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 1 g / m 2 Then, a layer of polyvinyl alcohol 1799 solution is also coated on the other side of the A layer of base paper through a coating laminating machine, and the dry coating amount is 1g / m 2 Then, a weakly acidic solution of glutaraldehyde (pH 4) was applied on the above-mentioned coating layer, with a coating amount of 1 g / m 2 After heating, the polyvinyl alcohol and glutaraldehyde coated on both sides undergo an aldol condensation reaction to form cross-linked polyvinyl alcohol glutaraldehyde. The capacitor paper is dried and trimmed to obtain the final product.

[0091] The difference from Example 6 is that both sides of the A layer are coated with polymer.

[0092] 2. Performance Testing

[0093] Test environment conditions: temperature 23±2℃, relative humidity 50%±5%.

[0094] Quantitative test method: GB / T 451.2-2002; Thickness test method: GB / T 451.2-2002; Tensile strength test method: GB / T 12914-2008; Breakdown voltage test: GB / T 3333-1999; Liquid absorption height test: GB / T 461.1-2002; ESR test: After the capacitor paper is fully impregnated with capacitor electrolyte, the ESR value at 1kHz is tested using an Agilent bridge and fixture (bridge model: Agilent4285A, fixture model: 16451B, fixture diameter 38mm).

[0095] The test results of the embodiment of preparing three-layer composite capacitor paper and the corresponding comparative example are shown in Table 1:

[0096] Table 1: Test data of three-layer composite capacitor paper

[0097] Performance Standard Quantification thickness Absolutely dry tightness Tensile Strength Breakdown voltage Suction height ESR value, 25℃, EG unit <![CDATA[g / m 2 ]]> μm <![CDATA[g / cm 3 ]]> kN / m V mm / 10min Ω Example 1 37.5 39.8 0.886 4.57 2015 57 2.12 Example 2 55.5 60.0 0.865 6.63 2750 56 3.05 Comparative Example 1 36.0 39.6 0.850 4.13 1534 4 2.27 Comparative Example 2 36.5 39.8 0.857 4.24 1753 53 2.24 Comparative Example 3 37.5 39.8 0.881 4.27 1715 54 2.26 Comparative Example 4 36.5 40.1 0.851 4.16 1689 52 2.31 Example 3 25.5 36.1 0.660 4.02 1455 113 1.50 Example 4 39.0 42.3 0.862 4.31 1660 98 1.68 Comparative Example 5 24.0 36.0 0.623 3.97 1043 87 1.57 Example 5 14.5 32.2 0.421 2.01 621 116 0.42 Comparative Example 6 13.0 32.0 0.380 1.92 367 107 0.43

[0098] In Examples 1 and 2, insulating wood pulp is used as the raw material, and the prepared capacitor paper is mainly used for aluminum electrolytic capacitors with high operating voltage, which require very high breakdown voltage, while the degree of attention to the ESR value is relatively low. Compared with Comparative Examples 1, 2, 3 and 4, the breakdown voltage of Examples 1 and 2 is greatly improved, while the ESR values ​​are similar. Examples 1 and 2 have more excellent comprehensive performance.

[0099] In Examples 3 and 4, insulating wood pulp and Tencel fiber are used as the A-layer base paper, and Manila hemp pulp is used as the B-layer base paper. The prepared capacitor paper is mainly used for capacitors with high working voltage and small ESR value requirements, which require higher breakdown voltage and smaller ESR value. Compared with Comparative Example 5, the breakdown voltage of Examples 3 and 4 is significantly improved, while the ESR value is similar. Examples 3 and 4 have better comprehensive performance.

[0100] Example 5 uses Manila hemp pulp as raw material to prepare base paper. The prepared capacitor paper is mainly used for aluminum electrolytic capacitors with small ESR values, which only require extremely low ESR values ​​and a certain breakdown voltage. Compared with Comparative Example 6, the breakdown voltage of Example 5 is significantly increased, while the ESR value is similar. Example 5 has more excellent comprehensive performance.

[0101] The test results of the embodiment of preparing double-layer composite capacitor paper and the corresponding comparative example are shown in Table 2:

[0102] Table 2: Test data of double-layer composite capacitor paper capacitor paper

[0103] Performance Standard Quantification thickness Absolutely dry tightness Tensile Strength Breakdown voltage Suction height ESR value, 25℃, EG unit <![CDATA[g / m 2 ]]> μm <![CDATA[g / cm 3 ]]> kN / m V mm / 10min Ω Example 6 19.0 20.1 0.884 1.86 1014 3 1.52 Comparative Example 7 18.0 20 0.842 1.68 770 2 1.49 Comparative Example 8 19.0 20.5 0.867 1.76 909 2 1.51 Comparative Example 9 22.0 21.7 0.948 1.88 1200 1 2.39

[0104] It can be seen from Table 2 above that compared with Comparative Examples 7 and 8, Example 6 has a significant advantage in breakdown voltage, while the ESR values ​​are similar. Compared with Comparative Example 9, Example 6 has a lower ESR value and a comparable breakdown voltage level, and Example 6 has more excellent comprehensive performance.

[0105] A light box with a light source was used to inspect the capacitor papers prepared in Examples 1-5 and Comparative Examples 2, 3, and 4 for possible local glue deficiency. 2 The capacitor paper is placed flat on top of a lighted light box. The surface of the paper is inspected with the naked eye. The local area with glue deficiency presents a different color from the surrounding area. The outline of the area with glue deficiency is outlined with a pencil. The area with glue deficiency is compared with the dust standard chart. The area of ​​the area with glue deficiency is read. The test results are shown in Table 3 below:

[0106] Table 3: Test results of adhesive deficiency area of ​​capacitor papers prepared in Examples 1-5 and Comparative Examples 2, 3, and 4

[0107]

[0108]

[0109] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A method for preparing capacitor paper, characterized in that: The following steps are involved: S1, pulping the raw material, refining the raw material, forming, pressing, drying and winding the raw material to obtain a first base paper layer and / or a second base paper layer; S2, coating one side of the first base paper layer or the second base paper layer obtained in step S1 with a layer of polyvinyl alcohol solution, then coating the polyvinyl alcohol solution with a weak acid solution of glutaraldehyde, and heating to obtain two layers of composite capacitor paper, or coating one side of the first base paper layer obtained in step S1 with a layer of polyvinyl alcohol solution, then coating the polyvinyl alcohol solution with a weak acid solution of glutaraldehyde, and then compounding the second base paper layer onto the coating layer of the first base paper layer, and heating to obtain three layers of composite capacitor paper; the pH value of the weak acid solution of glutaraldehyde is 4; The capacitor paper comprises a first base paper layer and a polymer layer arranged in sequence, or comprises a first base paper layer, a polymer layer and a second base paper layer arranged in sequence, wherein the polymer layer is a polymer formed by cross-linking polyvinyl alcohol and glutaraldehyde; the polymer layer is a cross-linked polymer formed by heating polyvinyl alcohol and glutaraldehyde under weak acid conditions; the dry coating amount of the polymer in the polymer layer is 0.01-20.0 g / m 2 .

2. The method for preparing capacitor paper according to claim 1, characterized in that: The dry coating amount of the polymer in the polymer layer is 0.1-5.0 g / m 2 .

3. The method for preparing capacitor paper according to claim 1, characterized in that: The thickness of the capacitor paper is 12-120 μm.

4. The method for preparing capacitor paper according to claim 1, characterized in that: The raw materials of the first base paper layer and the second base paper layer are at least one of plant fiber, man-made fiber and synthetic fiber; the plant fiber is at least one of insulating wood pulp, hemp pulp, cotton pulp and straw pulp; the man-made fiber and synthetic fiber are fibers that can be separated into fibers, the man-made fiber is tencel fiber, and the synthetic fiber is poly(p-phenylene benzobisoxazole) fiber or para-aramid fiber.

5. The method for preparing capacitor paper according to claim 1, characterized in that: The dry coating amount of the polyvinyl alcohol solution in step S2 is 0.01-20.0 g / m 2 The coating amount of the weakly acidic solution of glutaraldehyde is 0.01-20.0g / m 2 .

6. The method for preparing capacitor paper according to claim 1, characterized in that: The area of ​​local glue deficiency in the three-layer composite capacitor paper in step S2 is ≤10mm 2 / m 2 .

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