CN1844188A - Preparation method of special polyester for ultra-thin film for capacitor - Google Patents

Abstract

This invention is preparation of ultra-thin film polyester. It belongs to composite material. The procedure is as followings: add nano-calcium carbonate to lift roughness of surface. Modify the surface with polyoxyethylene glycols. Control the average hydraulics diameter in the range of 80~150 nanometer. Mix nano-calcium carbonate/ polyoxyethylene glycols and dimethyl terephthalate for polyreaction to get ultra-thin film polyester with good thermal property and electrical property. The product's thickness is no more than 6 micrometre. It's volume resistance is 1016Omega.m. diecoefficient(1KHz) is 3.3. Breakdown voltage is 400V/ mum. dielectric loss factor is no more than 6*10-3, coefficient of friction of rest is no more than 0.45, coefficient of dynamic friction is no more than 0.4, tensile strength is more than 150Mpa.

Description

Preparation method of special polyester for ultra-thin film for capacitor

technical field

The invention relates to a preparation method in the technical field of composite materials, in particular to a preparation method for in-situ preparation of special polyester for ultra-thin films for capacitors using nano-calcium carbonate.

technical background

With the emergence and rapid development of the information industry, especially the integration and miniaturization of components, capacitors used in these industries are developing in the direction of miniaturization and large capacity. Therefore, ultra-thin (1-6μm) ) The demand for film is increasing rapidly. Among all insulating materials suitable for capacitors, polyester materials are the most promising insulating materials for capacitors due to their superior cost performance. Compared with ordinary polyester film for packaging, as an ultra-thin polyester film for capacitors, in addition to having higher tensile strength and good heat resistance, it is also required to have a suitable surface roughness Ra, friction coefficient u _k , u _s , high breakdown voltage, high relative permittivity (that is, high electrical insulation, high volume resistance) and low dielectric loss.

Usually, in order to overcome many difficulties in the film processing process, a small amount of special "opening masterbatch" must be added in the process of polyester film drawing, but this method will cause problems due to the inorganic additives in the opening masterbatch when preparing ultra-thin films. The uneven dispersion of materials in the film drawing process leads to unavoidable problems such as high film rupture rate and many electrical weak points, which seriously affects the quality of ultra-thin polyester film for capacitors. Therefore, special raw materials for ultra-thin polyester films for capacitors The preparation technology has become a bottleneck restricting the development of microcapacitors. At present, directly adding fine inorganic particles in the polyester synthesis process is an ideal and commonly used method for preparing polyester resins for capacitor films, and how to ensure the uniform dispersion of inorganic particles in the polymer matrix is the key to preparing resins for ultra-thin capacitors. The key (that is, to ensure a certain roughness of the film, but also to improve the film strength and reduce the chance of film breakage during processing), at the same time, the addition of inorganic particles does not affect the original excellent electrical properties of the polyester film.

After searching the literature of the prior art, it is found that the Chinese patent application number is: 01804281, the preparation technology of polyester film for capacitors invented by Teijin Co., Ltd., mainly based on polyethylene 2,6-naphthalene dicarboxylate Components, calcium carbonate, plate-shaped aluminum silicate, porous silica or spherical silica are added during the polyester synthesis process, the main purpose is to improve the surface roughness of the film, and the longitudinal thermal deformation rate RMD(150) of the film at 150°C is - 1.5%≤RMD(150)≤0.0%, that is to ensure excellent insulation properties without reducing the processing properties, especially the properties in the hot pressing process, it is suitable as a dielectric for capacitors. However, this method is not suitable for processing ultra-thin capacitor insulating dielectric films due to the use of micron and submicron scale (0.1-5 μm) inorganic particles as additives. Modification will result in poor interfacial compatibility between inorganic particles and polyester and unsatisfactory dispersion stability of additives in the resin matrix.

Contents of the invention

The present invention aims at the above-mentioned problems existing in the background technology, and proposes a preparation method of special polyester for ultra-thin films for capacitors. The present invention uses nano-calcium carbonate as an additive and adopts an in-situ composite technology to prepare a special polyester for ultra-thin films for capacitors, which completely overcomes the defects of material film formation and unsatisfactory electrical properties caused by uneven dispersion of additives. Nano-scale calcium carbonate particles increase the roughness of the film surface without causing too many electrical weaknesses and affecting the electrical insulation performance of the material, so it is very suitable for processing ultra-thin films as the insulating medium of capacitors.

The present invention is achieved through the following technical solutions. The present invention first uses nano-calcium carbonate as an additive to improve the surface roughness of the film, and then uses polyethylene glycol to modify its surface so that it can be uniformly dispersed in the polyester polymerized monomer One of the bodies - ethylene glycol, and then the prepared nano-calcium carbonate/ethylene glycol slurry is processed by high-speed dispersion and circular sand milling to an average hydraulic particle size of nano-calcium carbonate of 80-150 nanometers , and finally under the catalysis of transesterification catalyst and polycondensation catalyst, transesterification reaction and polycondensation reaction with another polyester monomer - dimethyl terephthalate are carried out in situ during the polymerization process. Special polyester for ultra-thin film for capacitors with processability. The polyester film is cast and statically drawn to obtain a polyester film with a thickness of 4.5-6 microns. The volume resistance of the film is greater than 10 ¹⁶ Ω.m, the relative dielectric coefficient (1KHz) is 3.3, and the DC breakdown voltage is greater than 400V. /μm, the dielectric loss positive number is less than 6×10 ^-3 at 1KHz, the static friction coefficient of the film is less than 0.45, the dynamic friction coefficient is less than 0.4, and the tensile strength is greater than 150Mpa.

Below the method of the present invention is further described, and concrete steps are as follows:

(1) Carry out surface modification to nano-calcium carbonate, first heat the metered ethylene glycol to more than 100 degrees Celsius, then completely dissolve the metered polyethylene glycol in the above-mentioned ethylene glycol to obtain solution A, and then fresh carbonic acid Add the concentrated calcium water dispersion suspension to solution A, disperse at a high speed of 3000r/min for 30 minutes, and then use circulating sand milling for 10 minutes to 40 minutes to obtain nano-calcium carbonate/ethylene glycol dispersion slurry B with a solid content of 10% (wt%) , during the sanding process, the temperature is controlled at 60 degrees Celsius, so that the nano-calcium carbonate particles are aggregated into aggregates with an average hydraulic particle size of 80-150 nanometers, which are detected by a laser particle size analyzer.

(2) The above-mentioned dispersed slurry B through surface modification is added in the metered ethylene glycol to obtain nanometer calcium carbonate/ethylene glycol dispersed slurry C, and the addition amount of dispersed slurry B is according to the final obtained polyester. Calculation of the content of nano-calcium carbonate is required. The dispersion slurry C and another monomer of polyester --- dimethyl terephthalate are first transesterified in the presence of a transesterification catalyst, and then reacted in the presence of a polycondensation catalyst and a stable The polycondensation reaction is carried out under the condition of the presence of the agent. According to the thickness of the final processed film, the amount of modified nano-calcium carbonate added accounts for 500ppm to 10000ppm of the total polyester, and finally the special polyester for ultra-thin film for capacitors is obtained in situ.

The primary particle diameter of the nano-calcium carbonate of the present invention is 30-80 nanometers, and the shape is cube or quasi-cube. The solid content of described fresh calcium carbonate aqueous dispersion concentrated suspension is 30% (wt%), and described polyethylene glycol is macrogol 1000, macrogol 2000, macrogol 3000, polyethylene glycol One or more in ethylene glycol 4000, polyethylene glycol 5000, polyethylene glycol 6000, polyethylene glycol 7000 and polyethylene glycol 8000, the addition amount of polyethylene glycol used is 10% of nano calcium carbonate % (wt%).

The transesterification catalyst of the present invention is one or more of calcium acetate, magnesium acetate, manganese acetate, the described polycondensation catalyst is a kind of in antimony trioxide, ethylene glycol antimony, and the described stabilizer For trimethyl phosphate.

Compared with the prior art, the present invention first uses nano-calcium carbonate as an additive to increase the roughness of the film, and uses polyethylene glycol to modify its surface. On the one hand, it increases its compatibility with polyester, and on the other hand, it improves The degree of dispersion of nano-calcium carbonate in the matrix of ethylene glycol and polyester. Secondly, the present invention adopts an in-situ polymerization method to truly realize the uniform dispersion of nano-calcium carbonate particles in the matrix and ensure the uniformity of various properties of the processed ultra-thin film. At the same time, the present invention regulates the aggregate size of the nano-calcium carbonate by controlling the sanding temperature, so that the nano-calcium carbonate has a certain degree of aggregation, and when the film is processed, the film has a suitable roughness and overcomes the traditional masterbatch. A large number of additives aggregated during processing, resulting in a high rate of film breakage or even the difficulty of processing. It can be seen that this special polyester for capacitors with nano-calcium carbonate particles as an additive, because the calcium carbonate particles dispersed in the polyester matrix have a small and uniform particle size, a low rate of film breakage during processing, and few electrical weak points, it does not affect the electrical properties of the material. It is especially suitable for processing ultra-thin films with a thickness of less than 6 microns.

Detailed ways

Provide following embodiment in conjunction with content of the present invention:

Example 1

Add 667 grams of ethylene glycol into the beaker, and after adding 10 grams of polyethylene glycol 8000 into it, seal the mouth of the beaker and move it into an oil bath and control the temperature to 120 degrees. After the polyethylene glycol is completely dissolved, remove the beaker from the oil Take out in the bath and obtain solution A, add 333 grams of fresh nano-calcium carbonate (nano-calcium carbonate primary particle diameter is 30～80 nanometers) water-dispersed concentrated suspension after solution A is cooled to room temperature and be 30w% solid content, 3000r/min high-speed stirring Obtain nano-calcium carbonate/ethylene glycol dispersion slurry, add this slurry into continuous sand mill and carry out re-dispersion 40min, control sand-milling temperature to be 60 ℃, make nano-calcium carbonate aggregate to a certain extent, aggregate particle size is 150nm, finally Obtain solid content and be 10% nanometer calcium carbonate/ethylene glycol dispersion slurry B.

Get dispersion slurry B and join in 6000 grams of ethylene glycol, make the content of nano-calcium carbonate in the reaction system be 2000ppm (accounting for polyester total amount), stir and disperse to obtain dispersion material C, 9200g dimethyl terephthalate Add the ester and the above-mentioned dispersion slurry C into a 30-liter polyester polymerization kettle, use calcium acetate as a transesterification catalyst, ethylene glycol antimony as a polycondensation catalyst, and trimethyl phosphate as a polymerization stabilizer to carry out a polymerization reaction. Esterification is carried out under normal pressure, and the pressure in the kettle in the final stage of polycondensation should be kept below 80Pa. After maintaining a high vacuum for 220 minutes, the material was discharged to obtain a nano-titanium oxide/polyester composite material. The resin has a hue L value of 74.50, a hue b value of 1.60, an intrinsic viscosity of 0.680, a melting point of 261.8°C, a carboxyl content of 20mol.t ^-1 and a diethylene glycol content of 0.9%.

The above-mentioned nano-titanium oxide/polyester composite resin was dried in a vacuum oven at 150°C for 48 hours, then cast into sheets and statically drawn to make a polyester film with a thickness of 4.5 microns, and the volume resistance of the film was 10 ¹⁶ Ω. m, the relative permittivity (1KHz) is 3.3, the positive dielectric loss (1KHz) is 4×10 ^-3 , the breakdown voltage is 500V/μm, the static friction coefficient of the film is 0.35, the dynamic friction coefficient is 0.32, and the tensile strength is 180Mpa .

Example 2

According to the method described in Example 1, the difference is that the nanometer calcium carbonate consumption is 7000ppm of polyester. The surface modifier used is polyethylene glycol 4000, and the continuous sand mill time is 10 minutes. The average particle diameter of nano-calcium carbonate in the obtained dispersion slurry B is 80 nm, and the transesterification catalyst used is manganese acetate.

According to the nano-calcium carbonate/polyester composite material prepared by the method described in Example 1, the hue L value of the resin is 72.10, the hue b value is 1.30, the intrinsic viscosity is 0.660, the melting point is 260.1 ° C, and the carboxyl content is 18mol.t ^-1 , Diethylene glycol content was 1.0%.

The above-mentioned nano-titanium oxide/polyester composite resin was dried in a vacuum oven at 150°C for 48 hours, then cast into sheets and statically drawn to make a polyester film with a thickness of 6 microns, and the volume resistance of the film was 10 ¹⁶ Ω. m, the dielectric coefficient is 3.3, the breakdown voltage is 420V/μm, the positive dielectric loss (1KHz) is 5×10 ^-3 , the static friction coefficient of the film is 0.32, the dynamic friction coefficient is 0.30, and the tensile strength is 170Mpa.

Example 3

According to the method described in Example 1, the difference is that the nanometer calcium carbonate consumption is 500ppm. The polycondensation catalyst is antimony trioxide, and the average particle diameter of the nano-calcium carbonate in the dispersed slurry B is 135nm.

According to the nano-calcium carbonate/polyester composite material prepared by the method described in Example 1, the hue L value of the 0 resin is 80.10, the hue b value is 1.70, the intrinsic viscosity is 0.684, the melting point is 262.1 ° C, and the carboxyl content is 16mol.t ^-1 , Diethylene glycol content is 0.8%.

The above-mentioned nano-titanium oxide/polyester composite resin was dried in a vacuum oven at 150°C for 48 hours, then cast into sheets and statically drawn to make a polyester film with a thickness of 6 microns, and the volume resistance of the film was 10 ¹⁶ Ω. m, the relative permittivity is (1KHz) 3.3, the breakdown voltage is 600V/μm, the positive dielectric loss (1KHz) is 3×10 ^-3 , the static friction coefficient of the film is 0.45, the dynamic friction coefficient is 0.39, and the tensile strength is 184Mpa .

Example 4

According to the method described in Example 1, the difference is that the amount of nano-calcium carbonate is 10000ppm, and the modifier used is Polyethylene Glycol 1000, and the transesterification catalyst used is magnesium acetate. The particle size is 80nm.

According to the nano-calcium carbonate/polyester composite material prepared by the method described in Example 1, the hue L value of the resin is 71.10, the hue b value is 1.60, the intrinsic viscosity is 0.650, the melting point is 259.2°C, and the carboxyl content is 22mol.t ^-1 , Diethylene glycol content is 1.1%.

The above-mentioned nano-titanium oxide/polyester composite resin was dried in a vacuum oven at 150°C for 48 hours, then cast into sheets and statically drawn to make a polyester film with a thickness of 5 microns, and the volume resistance of the film was 10 ¹⁶ Ω. m, the dielectric coefficient is (1KHz) 3.3, the breakdown voltage is 400V/μm, the positive dielectric loss (1KHz) is 6×10 ^-3 , the static friction coefficient of the film is 0.30, the dynamic friction coefficient is 0.26, and the tensile strength is 150Mpa.

Claims (9)

1, a kind of preparation method of super-thin film special polyester for capacitor, it is characterized in that, at first adopt nano-calcium carbonate as the additive that improves film surface roughness, then adopt polyethylene glycol to carry out surface modification to it, make it It can be evenly dispersed in ethylene glycol, one of the monomers of polyester polymerization, and then the prepared nano-calcium carbonate/ethylene glycol slurry is processed by high-speed dispersion and circular sand grinding to the average of nano-calcium carbonate. The hydraulic particle size is less than 80-150 nanometers. Finally, under the catalysis of the transesterification catalyst and the polycondensation catalyst, the transesterification reaction and polycondensation reaction are carried out with another monomer of polyester - dimethyl terephthalate. During the polymerization process, the original A special polyester for ultra-thin film for capacitors. 2. The method for preparing special polyester for ultra-thin films for capacitors according to claim 1, characterized in that it comprises the following steps: (1) Carry out surface modification to nano-calcium carbonate, first heat the metered ethylene glycol to more than 100 degrees Celsius, then completely dissolve the metered polyethylene glycol in the above-mentioned ethylene glycol to obtain solution A, and then fresh carbonic acid Calcium water dispersion concentrated suspension was added to solution A, after 3000r/min high-speed dispersion for 30min, after 10min~40min of circular sand milling treatment, the nano calcium carbonate/ethylene glycol dispersion slurry B with a solid content of 10wt% was obtained. The temperature is controlled at 60 degrees Celsius, so that the nano-calcium carbonate particles are aggregated into aggregates with an average hydraulic particle size of 80-150 nanometers, which are detected by a laser particle size analyzer; (2) The above-mentioned dispersion slurry B through surface modification is added in the metered ethylene glycol to obtain nanometer calcium carbonate/ethylene glycol dispersion slurry C, and the addition amount of dispersion slurry B is according to the required amount in the final gained polyester Calculation of the content of nano-calcium carbonate, dispersion slurry C and another polyester monomer --- dimethyl terephthalate in the presence of a transesterification catalyst first transesterification reaction, and then in the polycondensation catalyst and stabilizer The polycondensation reaction is carried out under the condition of existence. According to the thickness of the final processed film, the amount of modified nano-calcium carbonate added accounts for 500ppm-10000ppm of the total polyester, and finally the special polyester for ultra-thin film for capacitors is obtained in situ. 3. The method for preparing polyester for ultra-thin films for capacitors according to claim 2, characterized in that the nano-calcium carbonate has a particle size of 30-80 nanometers and a shape of a cube or a cube-like shape. 4. The method for preparing special polyester for ultra-thin films for capacitors according to claim 2, characterized in that the solid content of the fresh calcium carbonate water-dispersed concentrated suspension is 30%. 5. The preparation method of special polyester for ultra-thin films for capacitors according to claim 1 or 2, wherein the polyethylene glycol is polyethylene glycol 1000, polyethylene glycol 2000, polyethylene glycol One or more of glycol 3000, polyethylene glycol 4000, polyethylene glycol 5000, polyethylene glycol 6000, polyethylene glycol 7000 and polyethylene glycol 8000. 6. The method for preparing special polyester for ultra-thin films for capacitors according to claim 1 or 2, characterized in that the amount of polyethylene glycol used is 10wt% of that of nano-calcium carbonate. 7. The method for preparing special polyester for ultra-thin films for capacitors according to claim 1 or 2, wherein the transesterification catalyst is one or more of calcium acetate, manganese acetate, and magnesium acetate . 8. The method for preparing polyester for ultra-thin films for capacitors according to claim 1 or 2, wherein the polycondensation catalyst is one of antimony trioxide and antimony ethylene glycol. 9. The method for preparing polyester for ultra-thin films for capacitors according to claim 2, characterized in that said stabilizer is trimethyl phosphate.