Highly heat conductive electrolytic capacitor paper and method for making same

Abstract

The application discloses a high-heat-conducting electrolytic capacitor paper, which is prepared from the following components in parts by weight: paper base fiber: 40-100 parts; modified ceramic filler powder: 5-25 parts; adhesive: 1-10 parts; and auxiliary agent: 2-15 parts. The application also provides a preparation method of the high-heat-conducting electrolytic capacitor paper. The high-heat-conducting electrolytic capacitor paper has good adsorption and good insulation, and still has very low ESR in the high-frequency working process. The ceramic filler powder and the adhesive are added into the paper base fiber matrix, the ceramic filler powder greatly enhances the heat-conducting performance of the capacitor paper, and the adhesive can effectively improve the strength of the paper, so that the strength requirement of the electrolytic capacitor paper in various processing can be met. Overall, the high-heat-conducting electrolytic capacitor paper has high heat conductivity and high paper strength, and has all the excellent performances of the paper base capacitor paper.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of special paper, and particularly relates to an electrolytic capacitor paper and a preparation method thereof. BACKGROUND

[0002] At present, capacitors have been widely applied in the fields of automobile electronics, communication, rail transit, computer, industrial power supply, life lighting, large household appliances, etc. The electrolytic capacitor paper (capacitor paper), aluminum foil and electrolyte are the three major elements for producing aluminum electrolytic capacitors. The capacitor paper is mainly made of electronic-grade cellulose, such as wood pulp fiber, cotton pulp fiber, hemp pulp fiber, etc., and is an indispensable core raw material for capacitors. High-quality aluminum electrolytic capacitors require high-quality electrolytic capacitor paper, which serves as a gasket material for electrolytic capacitors, plays a role in adsorbing working electrolyte, isolating positive and negative electrode foils of the capacitor, and preventing short circuit of the two poles due to contact, and accompanies the working of the aluminum electrolytic capacitor to the end of the life of the electrolytic capacitor, and plays a decisive role in the performance of the aluminum electrolytic capacitor.

[0003] With the rapid development of high-tech fields such as 5G communication and new energy vehicles, the performance requirements of electronic components are becoming higher and higher, so the working frequency of aluminum electrolytic capacitors is also becoming higher and higher. Cellulose-based insulating paper prepared from plant fibers is one of the most widely used insulating materials in power and electrical equipment, and is often used in the internal insulation structure of transformers, generators, inductors, etc. In the process of high-frequency work, a large amount of heat is generated in the charging and discharging process of the capacitor. However, the thermal conductivity of traditional paper-based insulating materials is poor (the thermal conductivity coefficient is only 0.1-0.3 W / m·K at room temperature), which hinders the heat dissipation of the capacitor, causing the electrolyte adsorbed by the diaphragm to evaporate and dry out during the working process, greatly shortening the service life of the capacitor. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background, and to provide a high-thermal-conductivity electrolytic capacitor paper with excellent thermal conductivity and a preparation method thereof. To solve the above technical problems, the technical solution proposed by the present application is as follows:

[0005] A high-thermal-conductivity electrolytic capacitor paper, the raw materials of which include the following components in parts by weight:

[0006] Paper-based fiber: 40-100 parts;

[0007] Modified ceramic filler powder: 5-25 parts;

[0008] Binder: 1-10 parts;

[0009] Auxiliary agent: 2-15 parts.

[0010] In the above high-thermal-conductivity electrolytic capacitor paper, preferably, the raw materials thereof include the following components in parts by weight:

[0011] Paper base fiber: 70-100 parts;

[0012] Modified ceramic filler powder: 5-10 parts;

[0013] Binder: 2-5 parts;

[0014] Auxiliary agent: 2-6 parts.

[0015] In the high-thermal-conductivity electrolytic capacitor paper, preferably, the ceramic filler powder includes one or more of zinc oxide powder, aluminum oxide powder, aluminum nitride powder, boron nitride powder, and silicon carbide powder, the particle size of the ceramic filler powder is 0.1-5 μm, and the surface of the ceramic filler powder is modified by a high-molecular surfactant, the high-molecular surfactant includes one or more of polyethylene glycol, polyethylene oxide, and polyacrylamide. The ceramic filler powder is easy to be agglomerated due to electrostatic attraction, and the dispersibility is poor when directly dispersed in the slurry for papermaking, which not only affects the maximum exertion of the thermal conductivity, but also affects the pore size distribution, mechanical strength, and other properties of the capacitor paper. The application modifies the ceramic filler powder by adding a high-molecular surfactant, reduces the surface energy of the ceramic filler powder, and improves the dispersibility of the ceramic filler powder by using the steric hindrance effect, so that the thermal conductivity of the paper sheet is improved on the basis of ensuring uniform distribution. When the surface of the ceramic filler powder is modified by the high-molecular surfactant, the high-molecular surfactant can be added to the ceramic filler powder and the aqueous medium thereof for ball milling modification, and the surface-modified ceramic filler powder can be obtained. In the above surface modification, the long-chain groups of the high-molecular surfactant are firmly adsorbed on the particle surface, increase the obstacle for the re-aggregation of the particles, reduce the interfacial tension of the solid-liquid interface, increase the thermodynamic stability of the dispersion system, and form a more efficient thermal conduction network by the uniformly dispersed thermal conductive particles, thereby improving the thermal conductivity of the system, and improving the problem of diaphragm pore blocking caused by uneven particles and improving the uniformity of the diaphragm pore size.

[0016] In the high-thermal-conductivity electrolytic capacitor paper, more preferably, the ceramic filler powder is a mixed powder of boron nitride powder with a particle size of 0.1 μm and boron nitride powder with a particle size of 0.5 μm. The large boron nitride filler in the mixed filler acts as the main thermal conduction function carrier, and the small boron nitride particles increase the filling density and act as a “bridge”, forming a thermal conduction network and increasing the thermal conductivity of the diaphragm. Compared with a single component ceramic filler, the combination of the two can also reduce the ESR value.

[0017] In the high-thermal-conductivity electrolytic capacitor paper, preferably, the binder includes one or more of styrene-butadiene latex, styrene-acrylate latex, pure benzene latex, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

[0018] Preferably, the additives include a retention and drainage aid, and the retention and drainage aid includes cationic polyacrylamide and / or cationic starch. In the present application, the retention and drainage aid is added to the specific reaction system containing ceramic filler powder of the present application, which can improve the dewatering performance of the pulp, increase the retention rate of fine fibers and fillers, and improve the heat conduction effect as a papermaking additive.

[0019] Preferably, in the high-thermal-conductivity electrolytic capacitor paper, the paper base fibers include plant fibers and synthetic fibers, and the mass ratio of the plant fibers to the synthetic fibers is (30-80):(10-60).

[0020] Preferably, in the high-thermal-conductivity electrolytic capacitor paper, the plant fibers include one or more of hemp pulp, cotton pulp, wood pulp, and bamboo pulp, and the beating degree of the plant fibers is 40-85°SR.

[0021] Preferably, in the high-thermal-conductivity electrolytic capacitor paper, the synthetic fibers include one or more of Tencel fibers, polyester fibers, and polyethylene fibers, the beating degree of the Tencel fibers is 40-80°SR, the length of the polymer fibers is 0.3-5 mm, and the fineness of the polymer fibers is 0.1-2 dtex. More preferably, the beating degree of the Tencel fibers is 70-80°SR, the length of the polymer fibers is 0.5-3 mm, and the fineness of the polymer fibers is 0.3-1 dtex.

[0022] As a general technical concept, the present application also provides a preparation method of the high-thermal-conductivity electrolytic capacitor paper.

[0023] (1) The plant fibers in the paper base fibers are dispersed and defibrated after being added with water, and are beaten to obtain pulp A;

[0024] (2) The pulp A obtained in step (1), the synthetic fibers in the paper base fibers, the ceramic filler powder, and the binder are uniformly mixed to obtain mixed pulp B;

[0025] (3) The additives are added to the mixed pulp B obtained in step (2), and are diluted with water and uniformly stirred to obtain pulp C;

[0026] (4) The pulp C obtained in step (3) is wet-laid to obtain the high-thermal-conductivity electrolytic capacitor paper.

[0027] More specifically, the preparation method can include the following steps:

[0028] (1) The high-molecular surfactant is added to the ceramic filler powder and the aqueous medium thereof for ball milling modification treatment to obtain the surface-modified ceramic filler powder;

[0029] (2) the plant fiber in the paper-based fiber is dispersed and beaten after being added with water to obtain pulp A;

[0030] (3) the pulp A obtained in step (2), the synthetic fiber in the paper-based fiber, the surface modified ceramic filler powder and the adhesive are uniformly mixed to obtain mixed pulp B;

[0031] (4) the additive is added into the mixed pulp B obtained in step (3) and diluted with water, and then stirred uniformly to obtain pulp C;

[0032] (5) the pulp C obtained in step (4) is wet laid (the pulp C is formed through a long net paper machine, the forming concentration is 0.03-0.5%, and then the formed product is pressed, dried, curled, cut and post-treated), and then a high-thermal-conductivity electrolytic capacitor paper is obtained.

[0033] The high-thermal-conductivity electrolytic capacitor paper of the application is prepared by mixing the pulp of plant fiber, the pulp of synthetic fiber, the surface modified ceramic filler powder, the polymer adhesive and the retention and drainage aid and then wet laying. The ceramic material is a good thermal conductive material, and its thermal conductivity reaches 200-300 W / m·K, which is more than 2000 times of the paper-based material, and has excellent insulation performance. Therefore, the surface modified ceramic filler powder is modified by using a high molecular surfactant, the modified ceramic filler powder is added as a thermal conductive and insulating filler, the paper-based fiber is used as a raw material, the retention and drainage aid is used, and the high-thermal-conductivity electrolytic capacitor paper is prepared by using the wet papermaking technology. Meanwhile, the polymer adhesive is added to improve the strength of the diaphragm and the adhesion of the ceramic powder and the fiber, and the strength of the paper can be effectively improved. The high-thermal-conductivity electrolytic capacitor paper of the application is a high-thermal-conductivity electrolytic capacitor diaphragm with excellent performance and suitable for high-frequency work.

[0034] Compared with the prior art, the high-thermal-conductivity electrolytic capacitor paper of the application has the following advantages:

[0035] The high-thermal-conductivity electrolytic capacitor paper of the application uses the paper-based fiber as a matrix, has good adsorption and excellent insulation performance, and still has very low ESR during high-frequency work. The ceramic filler powder and the adhesive are added into the paper-based fiber matrix, the ceramic filler powder greatly enhances the thermal conductivity of the capacitor paper, and the adhesive effectively improves the strength of the paper, so that the strength requirement of the electrolytic capacitor paper during various processing can be met. Overall, the high-thermal-conductivity electrolytic capacitor paper of the application has high thermal conductivity and high paper strength, and has all the excellent performances of the paper-based capacitor paper. DETAILED DESCRIPTION

[0036] For the purpose of understanding the present application, the present application will be described herein after in further detail with reference to the preferred embodiments; however, the scope of the present application is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all terms used in the present application, as commonly used by one skilled in the art, have the same meaning. The professional terms used herein are only for the purpose of describing the specific embodiments and are not intended to limit the scope of the present application.

[0038] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by the existing method.

[0039] Example 1:

[0040] A high-thermal-conductivity electrolytic capacitor paper, comprising hemp pulp fiber, Tencel fiber, boron nitride, PVA and cationic polyacrylamide, the ratio of each substance and the preparation method of the high-thermal-conductivity electrolytic capacitor paper comprising the following steps:

[0041] The boron nitride powder with a particle size of 0.1 μm is added to the PEG aqueous solution, ultrasonic dispersion, the dispersion liquid is transferred to the ball mill tank, ball milling at 400 rpm for 10 h, vacuum filtration after ball milling, the powder obtained by filtration is dried to obtain modified boron nitride powder; the beating degree of the hemp pulp fiber after beating is 50°SR, and the pulp concentration after defibration is 1%; the beating degree of the Tencel fiber after beating is 80°SR, and the pulp concentration after defibration is 1%; the two fibers are mixed, and the pulp concentration after mixing is 1%. After the two fibers are uniformly mixed, modified boron nitride particles are added to the pulp; the adhesive PVA is added to the mixed pulp, and the concentration of PVA is 1.5%; the pulp B is obtained. Then cationic polyacrylamide is added, and the pulp C is obtained by mixing; wherein the weight ratio of hemp pulp fiber: Tencel fiber: boron nitride: PVA: cationic polyacrylamide is 72:18:5:3:2; the pulp C is formed by a cylinder paper machine (speed 100 m / min, vacuum degree-0.098 MPa), and the finished product is obtained after pressing, drying, curling and cutting.

[0042] Example 2:

[0043] A high-thermal-conductivity electrolytic capacitor paper, comprising hemp pulp fiber, Tencel fiber, boron nitride, PVA and cationic polyacrylamide, the ratio of each substance and the preparation method of the high-thermal-conductivity electrolytic capacitor paper comprising the following steps:

[0044] The boron nitride powder with particle size of 0.1 μm is added into the PEG aqueous solution, ultrasonic dispersion, the dispersion is transferred to the ball mill tank, ball milling at 400 rpm for 10 h, vacuum filtration after ball milling, the powder obtained by filtration is dried to obtain modified boron nitride powder; the beating degree of hemp pulp fiber after beating is 50°SR, the pulp concentration after defibration is 1%; the beating degree of Tencel fiber after beating is 80°SR, the pulp concentration after defibration is 1%; the two kinds of fibers are mixed, the concentration of the mixed pulp is 1%. After the two kinds of fibers are uniformly mixed, modified boron nitride particles are added into the pulp; the adhesive PVA is added into the mixed pulp, the concentration of PVA is 1.5%; the pulp B is obtained. Then cationic polyacrylamide is added, and the pulp C is obtained by mixing; the weight ratio of hemp pulp fiber: Tencel fiber: modified boron nitride: PVA: cationic polyacrylamide is 64: 16: 10: 5: 5; the pulp C is formed by the cylinder paper machine (speed 100 m / min, vacuum degree-0.098 MPa), and the finished product is obtained after pressing, drying, curling and cutting.

[0045] Example 3:

[0046] A high-thermal-conductivity electrolytic capacitor paper, comprising hemp pulp fiber, Tencel fiber, boron nitride, PVA and cationic polyacrylamide, the ratio of each substance and the preparation method of the high-thermal-conductivity electrolytic capacitor paper comprises the following steps:

[0047] The boron nitride powder with particle size of 0.5 μm is added into the PEG aqueous solution, ultrasonic dispersion, the dispersion is transferred to the ball mill tank, ball milling at 400 rpm for 10 h, vacuum filtration after ball milling, the powder obtained by filtration is dried to obtain modified boron nitride powder; the beating degree of hemp pulp fiber after beating is 50°SR, the pulp concentration after defibration is 1%; the beating degree of Tencel fiber after beating is 80°SR, the pulp concentration after defibration is 1%; the two kinds of fibers are mixed, the concentration of the mixed pulp is 1%. After the two kinds of fibers are uniformly mixed, modified boron nitride particles are added into the pulp; the adhesive PVA is added into the mixed pulp, the concentration of PVA is 1.5%; the pulp B is obtained. Then cationic polyacrylamide is added, and the pulp C is obtained by mixing; the weight ratio of hemp pulp fiber: Tencel fiber: modified boron nitride: PVA: cationic polyacrylamide is 72: 18: 5: 3: 2; the pulp C is formed by the cylinder paper machine (speed 100 m / min, vacuum degree-0.098 MPa), and the finished product is obtained after pressing, drying, curling and cutting.

[0048] Example 4:

[0049] A high-thermal-conductivity electrolytic capacitor paper, comprising hemp pulp fiber, Tencel fiber, boron nitride, PVA and cationic polyacrylamide, the ratio of each substance and the preparation method of the high-thermal-conductivity electrolytic capacitor paper comprises the following steps:

[0050] Boron nitride powder with a particle size of 0.5 μm was added to a PEG aqueous solution and ultrasonically dispersed. The dispersion was transferred to a ball mill jar and ball-milled at 400 rpm for 10 h. After ball milling, vacuum filtration was performed, and the filtered powder was dried to obtain modified boron nitride powder. The freeness of the hemp pulp fiber after beating was 50°SR, and the pulp concentration after desizing was 1%. The freeness of the Tencel fiber after beating was 80°SR, and the pulp concentration after desizing was 1%. The two fibers were mixed, and the pulp concentration after mixing was 1%. After the two fibers were mixed evenly, modified boron nitride particles were added to the pulp. The binder PVA was added to the mixed pulp, and the PVA concentration was 1.5%. Pulp B was obtained. Then cationic polyacrylamide is added and mixed to obtain pulp C; wherein the weight ratio of hemp pulp fiber: Tencel fiber: modified boron nitride: PVA: cationic polyacrylamide is 64:16:10:5:5; pulp C is formed by a cylinder paper machine (speed 100m / min, vacuum degree -0.098MPa), and after forming, it is pressed, dried, rolled and slit to obtain the finished product.

[0051] Example 5:

[0052] A high thermal conductivity electrolytic capacitor paper includes hemp pulp fiber, Tencel fiber, boron nitride, PVA and cationic polyacrylamide. The proportions of each substance and the preparation method of the high thermal conductivity electrolytic capacitor paper include the following steps:

[0053] Boron nitride powders with particle sizes of 0.1 μm and 0.5 μm were added to a PEG aqueous solution in a 1:1 ratio and ultrasonically dispersed. The dispersion was transferred to a ball mill jar and ball-milled at 400 rpm for 10 h. After ball milling, the mixture was vacuum filtered, and the resulting powder was dried to obtain modified boron nitride powder. The freeness of the hemp pulp fiber after beating was 50°SR, and the pulp concentration after desizing was 1%. The freeness of the Tencel fiber after beating was 80°SR, and the pulp concentration after desizing was 1%. The two fibers were mixed, and the resulting pulp concentration was 1%. After the two fibers were mixed evenly, modified boron nitride particles were added to the pulp. The binder PVA was added to the mixed pulp at a concentration of 1.5%, resulting in pulp B. Then cationic polyacrylamide is added and mixed to obtain pulp C; wherein the weight ratio of hemp pulp fiber: Tencel fiber: modified boron nitride: PVA: cationic polyacrylamide is 64:16:10:5:5; pulp C is formed by a cylinder paper machine (speed 100m / min, vacuum degree -0.098MPa), and after forming, it is pressed, dried, rolled and slit to obtain the finished product.

[0054] Example 6:

[0055] A high thermal conductivity electrolytic capacitor paper includes cotton pulp fiber, PET polyester fiber, boron nitride, PVA and cationic polyacrylamide. The proportions of each substance and the preparation method of the high thermal conductivity electrolytic capacitor paper include the following steps:

[0056] The boron nitride powder with a particle size of 0.1 μm is added to the PEG aqueous solution, ultrasonic dispersion, the dispersion is transferred to the ball mill tank, ball milling at 400 rpm for 10 h, vacuum filtration after ball milling, the powder obtained by filtration is dried to obtain modified boron nitride powder; the beating degree of the cotton pulp fiber after beating is 70°SR, the pulp concentration after defibration is 1%, the PET polyester fiber after dispersion, the pulp concentration is 1%, the fiber length is 5 mm, and the fineness is 1.1 dtex; the two fibers are mixed, and the pulp concentration after mixing is 1%. After the two fibers are uniformly mixed, modified boron nitride particles are added to the pulp; the adhesive PVA is added to the mixed pulp, and the concentration of PVA is 1.5%; the pulp B is obtained. Then add cationic polyacrylamide to obtain pulp C; the weight ratio of hemp pulp fiber: PET fiber: modified boron nitride: PVA: cationic polyacrylamide is 36:54:5:3:2; the pulp C is formed by the cylinder paper machine (speed 100 m / min, vacuum degree-0.098 MPa), and the finished product is obtained after pressing, drying, curling and cutting.

[0057] Example 7:

[0058] A high-thermal-conductivity electrolytic capacitor paper, comprising cotton pulp fiber, PET polyester fiber, boron nitride, PVA and cationic polyacrylamide, the ratio of each substance and the preparation method of the high-thermal-conductivity electrolytic capacitor paper comprises the following steps:

[0059] The boron nitride powder with a particle size of 0.1 μm is added to the PEG aqueous solution, ultrasonic dispersion, the dispersion is transferred to the ball mill tank, ball milling at 400 rpm for 10 h, vacuum filtration after ball milling, the powder obtained by filtration is dried to obtain modified boron nitride powder; the beating degree of the cotton pulp fiber after beating is 70°SR, the pulp concentration after defibration is 1%, the PET polyester fiber after dispersion, the pulp concentration is 1%, the fiber length is 5 mm, and the fineness is 1.1 dtex; the two fibers are mixed, and the pulp concentration after mixing is 1%. After the two fibers are uniformly mixed, modified boron nitride particles are added to the pulp; the adhesive PVA is added to the mixed pulp, and the concentration of PVA is 1.5%; the pulp B is obtained. Then add cationic polyacrylamide to obtain pulp C; the weight ratio of hemp pulp fiber: PET fiber: modified boron nitride: PVA: cationic polyacrylamide is 32:48:10:5:5; the pulp C is formed by the cylinder paper machine (speed 100 m / min, vacuum degree-0.098 MPa), and the finished product is obtained after pressing, drying, curling and cutting.

[0060] Example 8:

[0061] The application discloses a high-thermal-conductivity electrolytic capacitor paper which comprises cotton pulp fibers, PET polyester fibers, aluminum oxide, EVA and cationic starch.

[0062] The aluminum oxide powder with a particle size of 0.1 μm is added into the PEO aqueous solution and ultrasonically dispersed, the dispersion liquid is transferred into a ball mill tank and ball milled at 400 rpm for 10 h, vacuum filtration is carried out after the ball milling, the powder obtained through the vacuum filtration is dried to obtain modified aluminum oxide powder; the beating degree of the cotton pulp fibers after beating is 70°SR, the pulp concentration is 1% after defibration, the PET polyester fibers are dispersed to have a pulp concentration of 1% and a fiber length of 5 mm and a fineness of 1.1 dtex; the two kinds of fibers are mixed to have a pulp concentration of 1% after mixing; the modified aluminum oxide particles with a particle size of 0.1 μm are added into the pulp after the two kinds of fibers are uniformly mixed; the adhesive EVA is added into the mixed pulp, and the concentration of the EVA is 1.5%; the pulp B is obtained; then the cationic starch is added to obtain the pulp C; the weight ratio of the cotton pulp fibers, the PET fibers, the modified aluminum oxide, the EVA and the cationic starch is 32:48:10:5:5; the pulp C is formed through a cylinder paper machine (the speed is 100 m / min, and the vacuum degree is -0.098 MPa), and the finished product is obtained after being pressed, dried, curled and cut.

[0063] Comparative example 1

[0064] The application discloses an electrolytic capacitor paper which comprises cotton pulp fibers and PET polyester fibers, and a preparation method thereof comprises the following steps.

[0065] The beating degree of the cotton pulp fibers after beating is 50°SR, and the cotton pulp fibers are configured into 1% pulp with water after defibration; the beating degree of the Tencel fibers after beating is 80°SR, and the Tencel fibers are configured into 1% pulp with water after defibration; the two kinds of fibers are mixed, the cotton pulp fibers and the Tencel fibers account for 80% and 20% of the total dry weight of fibers respectively after mixing, and the pulp concentration is 1% after mixing; the two kinds of fibers are uniformly mixed, the pulp concentration is 0.1% when the pulp is formed through a cylinder, and then the finished product is obtained after being pressed, dried, polished, wound and cut.

[0066] Comparative example 2

[0067] The application discloses an electrolytic capacitor paper which comprises cotton pulp fibers and PET polyester fibers, and a preparation method thereof comprises the following steps.

[0068] The cotton pulp fiber has a beating degree of 70°SR after beating, and is configured into a 1% pulp slurry after defibration. The PET polyester fiber is dispersed and configured into a 1% pulp slurry after dispersion. The fiber length is 5 mm, and the fineness is 1.1 dtex. The two kinds of fibers are mixed, and the cotton pulp fiber and the PET polyester fiber account for 40% and 60% of the total dry weight of the fibers respectively after mixing. The pulp slurry concentration is 1% after mixing. After the two kinds of fibers are uniformly mixed, the pulp slurry is formed by a cylinder mold, the pulp concentration on the wire is 0.1%, and then the finished product is obtained after pressing, drying, calendering, winding and slitting.

[0069] Comparative Example 3

[0070] A high-thermal-conductivity electrolytic capacitor paper comprises hemp pulp fiber, Tencel fiber, boron nitride, PVA and cationic polyacrylamide. The ratio of each substance and the preparation method of the high-thermal-conductivity electrolytic capacitor paper comprises the following steps:

[0071] The hemp pulp fiber has a beating degree of 50°SR after beating, and the pulp concentration is 1% after defibration. The Tencel fiber has a beating degree of 80°SR after beating, and the pulp concentration is 1% after defibration. The two kinds of fibers are mixed, and the pulp slurry concentration is 1% after mixing. After the two kinds of fibers are uniformly mixed, boron nitride particles with a particle size of 0.1 μm are added to the pulp slurry. The adhesive PVA is added to the mixed pulp slurry, and the concentration of the PVA is 1.5%. A pulp slurry B is obtained. Then cationic polyacrylamide is added, and a pulp slurry C is obtained by mixing. The weight ratio of the hemp pulp fiber, the Tencel fiber, the boron nitride, the PVA and the cationic polyacrylamide is 72:18:5:3:2. The pulp slurry C is formed by a cylinder paper machine (the speed is 100 m / min, and the vacuum degree is-0.098 MPa). The finished product is obtained after pressing, drying, winding, and slitting.

[0072] Comparative Example 4

[0073] An electrolytic capacitor paper comprises hemp pulp fiber, Tencel fiber, PVA adhesive and cationic polyacrylamide. The preparation method comprises the following steps:

[0074] The hemp pulp fiber has a beating degree of 50°SR after beating, and the pulp concentration is 1% after defibration. The Tencel fiber has a beating degree of 80°SR after beating, and the pulp concentration is 1% after defibration. The two kinds of fibers are mixed, and the pulp slurry concentration is 1% after mixing. After the two kinds of fibers are uniformly mixed, the adhesive PVA is added to the mixed pulp slurry, and the concentration of the PVA is 1.5%. A pulp slurry B is obtained. Then cationic polyacrylamide is added, and a pulp slurry C is obtained by mixing. The weight ratio of the hemp pulp fiber, the Tencel fiber, the PVA and the cationic polyacrylamide is 75:20:3:2. The pulp slurry C is formed by a cylinder paper machine (the speed is 100 m / min, and the vacuum degree is-0.098 MPa). The finished product is obtained after pressing, drying, winding, and slitting.

[0075] Comparative Example 5:

[0076] A high thermal conductivity electrolytic capacitor paper includes hemp pulp fiber, Tencel fiber, boron nitride, and PVA. The proportions of each substance and the preparation method of the high thermal conductivity electrolytic capacitor paper include the following steps:

[0077] Boron nitride powders with particle sizes of 0.1 μm and 0.5 μm were added to a PEG aqueous solution in a 1:1 ratio and ultrasonically dispersed. The dispersion was transferred to a ball mill jar and ball-milled at 400 rpm for 10 h. After ball milling, the mixture was vacuum filtered, and the resulting powder was dried to obtain modified boron nitride powder. The freeness of the hemp pulp fiber after beating was 50°SR, and the pulp concentration after desizing was 1%. The freeness of the Tencel fiber after beating was 80°SR, and the pulp concentration after desizing was 1%. The two fibers were mixed, and the resulting pulp concentration was 1%. After the two fibers were mixed evenly, modified boron nitride particles were added to the pulp. The binder PVA was added to the mixed pulp at a concentration of 1.5%, resulting in pulp B. The weight ratio of hemp pulp fiber, Tencel fiber, modified boron nitride, and PVA is 66:19:10:5. The pulp C is formed by a cylinder paper machine (speed 100m / min, vacuum degree -0.098MPa). After forming, it is pressed, dried, rolled, and slit to obtain the finished product.

[0078] The electrolytic capacitor papers prepared in the examples and comparative examples were subjected to basic performance tests. The test methods for each performance data are as follows: quantitative testing of capacitor paper according to GB / T451.2-2002; thickness testing of capacitor paper according to GB / T451.3-2002; tensile strength testing of capacitor paper according to GB / T12914-2008; breakdown voltage testing of capacitor paper according to GB / T3333-1999; liquid absorption height testing of paper according to GB / T461.1-2002; ESR testing of capacitor paper using an Agilent bridge; average pore size of capacitor paper measured by bubble point method using a capillary pore size analyzer. The density (ρ, g / cm³) of capacitor paper was calculated from the thickness. 3 The specific heat capacity (Cp, J / gK) of the samples was determined using a differential scanning calorimeter; the thermal diffusivity (α, mm) of the samples was determined using a thermal conductivity meter. 2 The thermal conductivity (K, W / mK) of the material can be calculated by the formula K=α×ρ×Cp. The density is calculated by quantitative / thickness. The test results are shown in Table 1.

[0079] Table 1: Performance test data of electrolytic capacitor paper prepared in the examples and comparative examples

[0080]

[0081]

[0082] From Table 1, compared with the low-pressure type electrolytic capacitor paper prepared in Comparative Examples 1 and 2, the high-thermal-conductivity type electrolytic capacitor paper prepared in Examples 1-8 has a significantly improved thermal conductivity, and the physical properties of the capacitor paper are also improved to a certain extent, and is a high-performance thermal-conductivity electrolytic capacitor paper.

[0083] Compared with Comparative Example 1, Examples 1 and 2 improve the thermal conductivity by adding 0.1 μm boron nitride particles. With the increase of the amount of boron nitride, the thermal conductivity is significantly increased. When the amount of boron nitride is 10%, the thermal conductivity is increased by 146%. The added PVA improves the paper strength, and the tensile strength and breakdown voltage are significantly improved compared with Comparative Example 1. In addition, the addition of boron nitride particles reduces the average pore size of the paper, which is beneficial to the formation of uniform pore size with concentrated distribution. Examples 3 and 4 use 0.5 μm boron nitride particles to improve the thermal conductivity. Compared with 0.1 μm boron nitride particles, the thermal conductivity is improved more, the thermal conductivity is increased by 189%, the tensile strength and liquid absorption are reduced to a certain extent, the electric breakdown strength is improved, and the pore size is further reduced. Compared with the ESR data tested at a high frequency of 100 kHz, the ESR of the capacitor paper is improved to a certain extent after the addition of boron nitride, but the overall change is not large, which does not affect its use in high-frequency electrolytic capacitors. Example 5 uses 0.1 μm and 0.5 μm boron nitride to prepare a mixed filler in a ratio of 1:1 to improve the thermal conductivity of the diaphragm. Compared with Examples 1-4, the thermal conductivity is increased by 220%. This is because the large boron nitride filler in the mixed filler acts as the main thermal conductivity function, and the small boron nitride particles increase the packing density and play a "bridge" role, forming a thermal conductivity network and increasing the thermal conductivity of the diaphragm. At the same time, the ESR value is relatively small compared with other examples.

[0084] Compared with Comparative Example 2, Examples 6 and 7 improve the thermal conductivity by adding 0.1 μm boron nitride particles. With the increase of the amount of boron nitride, the thermal conductivity is significantly increased. When the amount of boron nitride is 10%, the thermal conductivity is increased by 197%. At the same time, the paper strength is also improved, and the liquid absorption performance is reduced compared with Comparative Example 2. Example 8 improves the thermal conductivity by adding 0.1 μm aluminum oxide particles. The thermal conductivity is reduced compared with Example 7, which is because the thermal conductivity of aluminum oxide is lower than that of boron nitride. The use of EVA as the adhesive has a certain improvement in the tensile strength, but the change is not large. The liquid absorption performance is reduced, and the ESR is increased.

[0085] Comparative Example 3 is based on Comparative Example 1, ceramic powder and PVA binder are added. Compared with Comparative Example 3 and Example 1, Example 1 uses surfactant to modify the boron nitride particles, and the thermal conductivity is higher than that of Comparative Example 3. This is because after modification, the surfactant is adsorbed on the surface of the microparticles, increasing the barrier to re-aggregation of microparticles, reducing the interfacial tension of the solid-liquid interface, increasing the thermodynamic stability of the dispersion system, and forming a more efficient thermal conduction network of uniformly dispersed thermal conductive particles, thereby improving the thermal conductivity of the system.

[0086] Comparative Example 4 is based on Comparative Example 1, PVA is added. The tightness of the separator increases, and the tensile strength improves. This is because the PVA binder contains a certain amount of hydroxyl groups in its molecular chain, so it can be adsorbed by hydrogen bonds between water molecules and the surface molecules of the fibers, thereby enhancing the surface strength of the separator. The pore size and liquid absorption height of the separator are reduced to some extent, and the ESR is improved. Compared with Comparative Example 4, the thermal conductivity of Examples 1-5 is significantly increased, and the tensile strength does not change significantly, indicating that the addition of the binder can effectively improve the strength of the separator.

[0087] The above examples show that the addition of ceramic powder particles can significantly improve the thermal conductivity of the capacitor paper, the addition of the binder can effectively enhance the strength of the paper, and the problem of powder falling off the surface of the paper caused by the addition of ceramic particles can be solved. Although the pore size of the capacitor paper is reduced to some extent, the ESR of the separator does not change significantly overall, so the reduced pore size will not affect the ion transmission rate of the capacitor paper in operation.

Claims

1. A high thermal conductivity electrolytic capacitor paper, characterized in that, Its raw materials include the following components in parts by weight: Paper-based fiber: 80 parts; Ceramic filler powder: 10 parts; Adhesive: 1-10 parts; Additives: 2-15 parts; The ceramic filler powder is a mixture of boron nitride powder with a particle size of 0.1 μm and boron nitride powder with a particle size of 0.5 μm; the surface of the ceramic filler powder is modified by a polymeric surfactant, which includes one or more of polyethylene glycol, polyethylene oxide, and polyacrylamide. The additives include retention and filtration aids, which include cationic polyacrylamide and / or cationic starch.

2. The high thermal conductivity electrolytic capacitor paper according to claim 1, characterized in that, Its raw materials include the following components in parts by weight: Paper-based fiber: 80 parts; Ceramic filler powder: 10 parts; Adhesive: 2-5 parts; Additives: 2-6 parts.

3. The high thermal conductivity electrolytic capacitor paper according to claim 1, characterized in that, The adhesive includes one or more of styrene-butadiene latex, styrene-acrylic latex, polymethyl methacrylate, polybutyl methacrylate, polyethyl acrylate, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, and polyurethane.

4. The high thermal conductivity electrolytic capacitor paper according to any one of claims 1-3, characterized in that, The paper-based fiber includes plant fiber and synthetic fiber, and the mass ratio of plant fiber to synthetic fiber is (30-80):(10-60).

5. The high thermal conductivity electrolytic capacitor paper according to claim 4, characterized in that, The plant fiber includes one or more of hemp pulp, cotton pulp, wood pulp and bamboo pulp, and the beating degree of the plant fiber is 40-85°SR.

6. The high thermal conductivity electrolytic capacitor paper according to claim 4, characterized in that, The synthetic fiber includes one or more of Tencel fiber, polyester fiber and polyethylene fiber. The Tencel fiber has a beating degree of 40-80°SR, and the polyester fiber and polyethylene fiber have a length of 0.3-5mm and a fineness of 0.1-2dtex.

7. A method for preparing high thermal conductivity electrolytic capacitor paper as described in any one of claims 1-6, characterized in that, Includes the following steps: (1) After adding water to the plant fibers in the paper base fiber, the fibers are dispersed and pulped to obtain pulp A; (2) Mix the pulp A obtained in step (1), the synthetic fiber in the paper base fiber, the ceramic filler powder and the adhesive evenly to obtain mixed pulp B; (3) Add the additive to the mixed slurry B obtained in step (2), dilute with water, stir evenly, and obtain slurry C; (4) The slurry C obtained in step (3) is wet-processed to obtain high thermal conductivity electrolytic capacitor paper.

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