阅读说明：本技术 一种高介电常数、高介电稳定性无规共聚酯和聚酯薄膜 (Random copolyester and polyester film with high dielectric constant and high dielectric stability ) 是由 黄剑 陈铸红 王红兵 张涛 张少伟 年陈瑞 丁道俊 黄昊鹏 王恒煜 张鸿翔 于 2021-07-29 设计创作，主要内容包括：本发明公开了一种高介电常数、高介电稳定性的无规共聚酯,由(Ⅰ)、(Ⅱ)、(Ⅲ)和(Ⅳ)所示的结构单元组成。本发明还公开了上述无规共聚酯的制备方法,是以对苯二甲酸、2,6-对萘二甲酸、4,6-二氨基间苯二酚、乙二醇为共聚单体,经过酯化、预缩聚、缩聚反应得到。本发明还公开了以该无规共聚酯作为原料的聚酯薄膜,具有强度高、耐热性好、热稳定性高、介电常数高、介电稳定性优异的优点,适合用作电容器用电介质材料。(The invention discloses a random copolyester with high dielectric constant and high dielectric stability, which consists of structural units shown as (I), (II), (III) and (IV). The invention also discloses a preparation method of the random copolyester, which is obtained by taking terephthalic acid, 2, 6-naphthalene dicarboxylic acid, 4, 6-diamino resorcinol and ethylene glycol as comonomers and carrying out esterification, pre-polycondensation and polycondensation reactions. The invention also discloses a polyester film using the random copolyester as a raw material, which has the advantages of high strength, good heat resistance, high thermal stability, high dielectric constant and excellent dielectric stability and is suitable for being used as a dielectric material for capacitors.)

1. A random copolyester with high dielectric constant and high dielectric stability, which is characterized by comprising the following structural units (I), (II), (III) and (IV):

2. the high dielectric constant, high dielectric stability random copolyester of claim 1, wherein the number of structural units { (I) + (II) } is 40 to 47.5% of the total structural units, the number of structural units { (III) + (IV) } is 2.5 to 10% of the total structural units, the number of structural units { (I) + (III) } is 1 to 4% of the total structural units, and the number of structural units { (II) + (IV) } is 46 to 49% of the total structural units.

3. The high dielectric constant, high dielectric stability random copolyester of claim 1, wherein the intrinsic viscosity of the random copolyester is 0.65 ± 0.04dl/g, and the melting point is 280-295 ℃.

4. A process for preparing a random copolyester with high dielectric constant and high dielectric stability as claimed in any one of claims 1 to 3, wherein said random copolyester is prepared from terephthalic acid, 2, 6-naphthalenedicarboxylic acid, 4, 6-diaminoresorcinol and ethylene glycol as comonomers through esterification, prepolycondensation and polycondensation.

5. The method for preparing high dielectric constant, high dielectric stability random copolyester according to claim 4, wherein the mole number of the comonomer satisfies: n (terephthalic acid) + n (2, 6-naphthalenedicarboxylic acid) ═ n (4, 6-diaminoresorcinol) + n (ethylene glycol); the mole number of the terephthalic acid accounts for 80-95% of the sum of the mole numbers of the terephthalic acid and the 2, 6-naphthalene dicarboxylic acid, the mole number of the 2, 6-naphthalene dicarboxylic acid accounts for 5-20% of the sum of the mole numbers of the terephthalic acid and the 2, 6-naphthalene dicarboxylic acid, the mole number of the 4, 6-diaminoresorcinol accounts for 2-8% of the sum of the mole numbers of the 4, 6-diaminoresorcinol and the ethylene glycol, and the mole number of the ethylene glycol accounts for 92-98% of the sum of the mole numbers of the 4, 6-diaminoresorcinol and the ethylene glycol.

6. A method for preparing a high dielectric constant, high dielectric stability random copolyester according to any one of claims 1 to 5, comprising the steps of: mixing terephthalic acid, 2, 6-naphthalenedicarboxylic acid, 4, 6-diaminoresorcinol, ethylene glycol, a catalyst and a stabilizer, carrying out esterification reaction under the conditions of 0.3-0.4MPa of pressure and 250 ℃ of temperature of 230-.

7. The method for preparing high dielectric constant, high dielectric stability random copolyester of claim 6, wherein the catalyst is at least one of antimony trioxide, antimony acetate, ethylene glycol antimony, tetrabutyl titanate;

the stabilizer is at least one of trimethyl phosphate, triphenyl phosphite and diphenyl phosphite.

8. A biaxially oriented polyester film with high dielectric constant and high dielectric stability, which is characterized by comprising an upper surface layer, a core layer and a lower surface layer, wherein the core layer is made of the random copolyester as claimed in any one of claims 1 to 7.

9. The biaxially oriented polyester film of claim 8, wherein the raw materials of the upper and lower surface layers are comprised of a functional polyester masterbatch and a polyester chip, and the functional polyester masterbatch is comprised of a polyester resin and an additive;

preferably, the content of the additive in the functional polyester master batch is 3300-18000 ppm;

preferably, the additive is selected from at least one of silica, barium sulfate, barium carbonate, and crosslinked PMMA;

preferably, the surface roughness Ra of the upper surface layer and the lower surface layer is 100-180nm, and the friction coefficient of the film is 0.3-0.55.

10. The high dielectric constant, high dielectric stability biaxially oriented polyester film according to claim 8 or 9, wherein the thickness of the upper surface layer is 0.5 to 0.6 μm, the thickness of the core layer is 3.0 to 3.5 μm, and the thickness of the lower surface layer is 0.5 to 0.6 μm.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to random copolyester and a polyester film with high dielectric constant and high dielectric stability.

Background

The film capacitor is a capacitor formed by winding a plastic film and a metal-plated electrode into a cylindrical shape, and is characterized by simple structure, low cost, and excellent dielectric properties such as capacity precision, withstand voltage, insulation resistance, loss tangent value and the like. The manufacture of thin film capacitors requires dielectric materials with the smallest possible dielectric loss and the largest possible dielectric constant, and with high dielectric strength, the larger the dielectric constant, the larger the charge storage capacity of the dielectric, and the larger the capacitance of the capacitor. On the other hand, the dielectric material consumes a part of electric energy in the alternating electric field to heat the medium itself, and therefore, the stability of the dielectric constant is very important.

The organic film is used as a core dielectric material of the film capacitor, and the performance of the film capacitor is determined to a great extent. BOPET films are films made of PET by a biaxial stretching process technology, have the characteristics of high strength, good transparency, excellent electrical insulation performance and the like, and have been applied to the field of film capacitors. However, the PET film has its own defects, such as easy water absorption, poor dimensional stability, etc., and the BOPET film has a relatively obvious change of dielectric constant with the temperature rise and low dielectric stability, which limits the application range.

Polyethylene naphthalate (PEN) is a homologous polyester of PET, and the chemical structure of the polyethylene naphthalate (PEN) is similar to that of PET, except that PEN in a molecular chain is replaced by naphthalene rings with higher rigidity. Compared with PET, PEN has higher physical and mechanical properties, gas barrier property, chemical stability, heat resistance, ultraviolet resistance, radiation resistance and the like due to the naphthalene ring structure, and various properties of PEN are less influenced by temperature. However, since PEN is expensive due to its high raw material cost, its development and application range are limited.

In the prior art, in order to combine the economic property of PET with the good property of PEN, many scientific research institutions at home and abroad prepare polymer alloy by melt blending of PET/PEN, so that the property of the product is improved to a certain extent. However, physical blends of PET and PEN are completely incompatible, and the properties of polyester blends are greatly affected. Therefore, the preparation of the polyester material with high dielectric constant, high dielectric stability, excellent mechanical property, high thermal stability and moderate cost has important research significance.

Disclosure of Invention

Based on the technical problems in the prior art, the invention provides random copolyester with high dielectric constant and high dielectric stability and a polyester film taking the random copolyester as a raw material.

The invention is realized by the following technical scheme:

a random copolyester with high dielectric constant and high dielectric stability, which is characterized by comprising the following structural units (I), (II), (III) and (IV):

preferably, the number of structural units { (I) + (II) } accounts for 40-47.5% of the total number of structural units, the number of structural units { (III) + (IV) } accounts for 2.5-10% of the total number of structural units, the number of structural units { (I) + (III) } accounts for 1-4% of the total number of structural units, and the number of structural units { (II) + (IV) } accounts for 46-49% of the total number of structural units.

Preferably, the random copolyester has an intrinsic viscosity of 0.65. + -. 0.04dl/g and a melting point of 280 ℃ and 295 ℃.

The preparation method of the random copolyester with high dielectric constant and high dielectric stability is characterized in that terephthalic acid, 2, 6-naphthalenedicarboxylic acid, 4, 6-diaminoresorcinol and ethylene glycol are used as comonomers, and esterification, pre-polycondensation and polycondensation are carried out to obtain the random copolyester.

Preferably, the number of moles of said comonomer is such that: n (terephthalic acid) + n (2, 6-naphthalenedicarboxylic acid) ═ n (4, 6-diaminoresorcinol) + n (ethylene glycol); the mole number of the terephthalic acid accounts for 80-95% of the sum of the mole numbers of the terephthalic acid and the 2, 6-naphthalene dicarboxylic acid, the mole number of the 2, 6-naphthalene dicarboxylic acid accounts for 5-20% of the sum of the mole numbers of the terephthalic acid and the 2, 6-naphthalene dicarboxylic acid, the mole number of the 4, 6-diaminoresorcinol accounts for 2-8% of the sum of the mole numbers of the 4, 6-diaminoresorcinol and the ethylene glycol, and the mole number of the ethylene glycol accounts for 92-98% of the sum of the mole numbers of the 4, 6-diaminoresorcinol and the ethylene glycol.

The preparation method of the random copolyester with high dielectric constant and high dielectric stability comprises the following steps: mixing terephthalic acid, 2, 6-naphthalenedicarboxylic acid, 4, 6-diaminoresorcinol, ethylene glycol, a catalyst and a stabilizer, carrying out esterification reaction under the conditions of 0.3-0.4MPa of pressure and 250 ℃ of temperature of 230-.

Preferably, the catalyst is at least one of antimony trioxide, antimony acetate, ethylene glycol antimony and tetrabutyl titanate.

The stabilizer is at least one of trimethyl phosphate, triphenyl phosphite and diphenyl phosphite.

Preferably, the mole number of the catalyst is 0.04 to 0.06% of the sum of the mole numbers of terephthalic acid and 2, 6-naphthalenedicarboxylic acid.

Preferably, the mole number of the stabilizer is 0.04 to 0.06% of the sum of the mole numbers of terephthalic acid and 2, 6-naphthalenedicarboxylic acid.

Preferably, the judgment criterion for the end of the esterification reaction is as follows: the water yield reaches more than 95 percent of the theoretical water yield.

The biaxially oriented polyester film with the high dielectric constant and the high dielectric stability is composed of an upper surface layer, a core layer and a lower surface layer, wherein the core layer is made of the random copolyester.

Preferably, the raw materials of the upper surface layer and the lower surface layer consist of a functional polyester master batch and a polyester chip, and the functional polyester master batch consists of a polyester resin and an additive.

Preferably, the content of the additive in the functional polyester master batch is 3300-18000 ppm.

Preferably, the additive is selected from at least one of silica, barium sulfate, barium carbonate, and crosslinked PMMA.

According to the invention, the additives are added into the upper surface layer and the lower surface layer of the film, so that the surface of the capacitor film has certain roughness, and the effect of preventing the film from being stuck in the winding process is achieved; preferably, the surface roughness Ra of the upper surface layer and the lower surface layer is 100-180nm, and the friction coefficient of the film is 0.3-0.55.

Preferably, the thickness of the upper surface layer is 0.5 to 0.6 μm, the thickness of the core layer is 3.0 to 3.5 μm, and the thickness of the lower surface layer is 0.5 to 0.6 μm.

The preparation method of the biaxially oriented polyester film with high dielectric constant and high dielectric stability comprises the following steps:

s1, drying the raw materials of the core layer, heating and melting in a main extruder, and filtering to obtain a core layer melt; heating and melting the raw material of the upper surface layer and the raw material of the lower surface layer in two auxiliary extruders respectively, and performing vacuum treatment to obtain an upper surface layer melt and a lower surface layer melt; filtering the core layer melt, and then converging and extruding the core layer melt, the upper surface layer melt and the lower surface layer melt in a three-layer die head to obtain a mixed melt;

s2, cooling the mixed melt through electrostatic adsorption of a cold roller to obtain a cast sheet;

and S3, sequentially carrying out longitudinal stretching, cooling and shaping, transverse stretching and heat shaping on the cast sheet to obtain the steel plate.

Preferably, in the step S1, the drying temperature is 155-190 ℃, and the drying time is 4-5 h.

Preferably, in the step S1, the die temperature is 285-290 ℃.

Preferably, in step S2, the voltage for electrostatic adsorption is 9.5-10.5kV, and the current is 10-12 mA.

Preferably, in the step S2, the cooling temperature is 25 ℃.

Preferably, in the step S3, the preheating temperature for longitudinal stretching is 70-95 ℃, the stretching temperature is 110-120 ℃, and the stretching ratio is 3.9-4.1.

Preferably, in the step S3, the temperature for cooling and shaping is 25-35 ℃.

Preferably, in the step S3, the preheating temperature for transverse stretching is 100-115 ℃, the stretching temperature is 125-135 ℃, and the stretching ratio is 3.15-3.22.

Preferably, in the step S3, the heat setting temperature is 240-.

The invention has the following beneficial effects:

(1) according to the invention, the copolyester is synthesized by terephthalic acid, 4, 6-diaminoresorcinol and ethylene glycol, on one hand, the dielectric constant and the dielectric stability of the copolyester are improved by introducing a PEN structure on a molecular chain, and the problem of poor dimensional stability and dielectric stability of a polyester material in a high-temperature environment is solved, on the other hand, by introducing a rigid rod-shaped oxazole ring into a polyester molecular structure, the mechanical property and the thermal stability of the material can be improved, and due to the planar structure of the oxazole ring, the conjugation degree of a macromolecular chain is increased, pi orbitals which are parallel to each other form delocalized molecular orbitals, and electrons can obviously improve the dielectric constant and the dielectric stability of the material under the action of the swimming polarization. The copolyester is used as a raw material, and the prepared polyester film has high tensile strength, good dielectric constant and volume resistivity, low thermal shrinkage and excellent dielectric constant stability, and is suitable for being used as a dielectric material for capacitors.

(2) The invention has simple integral preparation process, can use the existing polymerization and biaxial stretching equipment for polyester production, only needs to make process adjustment, and can directly form the film by a three-layer coextrusion process, thereby being beneficial to industrial production.

Drawings

FIG. 1 is an IR spectrum of a random copolyester of the present invention.

FIG. 2 is a graph showing the dielectric constant test of example 1 of the present invention and comparative examples 1 to 3.

Detailed Description

The technical solution of the present invention will be described in detail below with reference to specific examples.

Example 1

Adding 80mol of terephthalic acid, 20mol of 2, 6-naphthalene dicarboxylic acid, 8mol of 4, 6-diamino resorcinol, 92mol of ethylene glycol, 0.05mol of antimony trioxide catalyst and 0.05mol of triphenyl phosphate stabilizer into a polymerization reaction kettle, and filling N into the kettle₂Until the pressure is 0.3-0.4MPa, carrying out esterification reaction at the reaction temperature of 230-₂Discharging and granulating to obtain the random copolyester.

The infrared test spectrum of the random copolyester prepared in the above is shown in figure 1. Characteristic peaks of infrared in FIG. 1, 1628 and 1048cm^-1Respectively oxazole ring C ═ N and C-O stretching vibration peaks, 1598, 1560 and 1480cm^-1Is a-C ═ C-stretching vibration peak at the aromatic ring of 1250cm^-1The peak of stretching vibration of the ester group is shown. Its intrinsic viscosity is 0.653dl/g and its melting point is 293 ℃.

A biaxially oriented polyester film with high dielectric constant and high dielectric stability comprises an upper surface layer, a core layer and a lower surface layer, wherein the raw material of the core layer is the random copolyester prepared by the method; the raw materials of the upper surface layer and the lower surface layer consist of functional polyester master batch and polyester slices, wherein the functional polyester master batch is PET polyester master batch for a Korean SKC electronic grade film, and the polyester slices are PET polyester slices for the Korean SKC electronic grade film; the surface roughness Ra of the upper surface layer and the lower surface layer is 150nm, and the friction coefficient of the film is 0.35.

Wherein the thickness of the upper surface layer is 0.6 μm, the thickness of the core layer is 3.3 μm, and the thickness of the lower surface layer is 0.6 μm.

The preparation method of the biaxially oriented polyester film with high dielectric constant and high dielectric stability comprises the following steps:

s1, drying the raw materials of the core layer at the temperature of 155-190 ℃ for 4-5h, heating and melting in a main extruder, and filtering to obtain a core layer melt; heating and melting the raw material of the upper surface layer and the raw material of the lower surface layer in two auxiliary extruders respectively, and performing vacuum treatment to obtain an upper surface layer melt and a lower surface layer melt; filtering the core layer melt, converging and extruding the core layer melt, the upper surface layer melt and the lower surface layer melt in a three-layer die head to obtain a mixed melt, wherein the die head temperature is 285-290 ℃;

s2, cooling the mixed melt through electrostatic adsorption of a cold roller to obtain a cast sheet, wherein the voltage adopted by electrostatic adsorption is 9.5-10.5kV, the current is 10-12mA, and the cooling temperature is 25 ℃;

s3, sequentially carrying out longitudinal stretching, cooling and shaping, transverse stretching and heat shaping on the cast sheet to obtain a product with the longitudinal stretching preheating temperature of 70-95 ℃, the stretching temperature of 110-120 ℃ and the stretching ratio of 3.9-4.1; the temperature for cooling and shaping is 25-35 ℃; the preheating temperature of transverse stretching is 100-115 ℃, the stretching temperature is 125-135 ℃, and the stretching ratio is 3.15-3.22; the temperature of heat setting is 240-245 ℃.

Example 2

Example 2 differs from example 1 only in that: the random copolyester is different in raw material adding proportion, and specifically comprises the following components:

adding 85mol of terephthalic acid, 15mol of 2, 6-naphthalene dicarboxylic acid, 6mol of 4, 6-diamino resorcinol, 94mol of ethylene glycol, 0.05mol of antimony trioxide catalyst and 0.05mol of triphenyl phosphate stabilizer into a polymerization reaction kettle, and filling the polymerization reaction kettle with N₂To a pressure of 0.3-0.4MPa, and carrying out esterification at a reaction temperature of 230 ℃ and 250 DEG CThe esterification rate is calculated by distilling off the esterification water, when the esterification rate reaches 96 percent, the temperature is raised to 260-class 265 ℃, the vacuum is pumped until the pressure in the kettle is 300Pa, the pre-polycondensation reaction is carried out for 1h, then the temperature is slowly raised to 280-class 290 ℃ within 45min, the polycondensation reaction is carried out for 3-5h under the condition that the pressure in the kettle is less than 100Pa, N is filled₂Discharging and granulating to obtain the random copolyester.

The random copolyester prepared by the method has the intrinsic viscosity of 0.651dl/g and the melting point of 291 ℃.

The composition and preparation method of the film were the same as those of example 1, except that the random copolyester obtained in example 2 was used as the raw material for the film core layer.

Example 3

Example 3 differs from example 1 only in that: the copolyester raw materials are different in addition proportion, and specifically comprise the following components:

adding 90mol of terephthalic acid, 10mol of 2, 6-naphthalene dicarboxylic acid, 4mol of 4, 6-diamino resorcinol, 96mol of ethylene glycol, 0.05mol of antimony trioxide catalyst and 0.05mol of triphenyl phosphate stabilizer into a polymerization reaction kettle, and filling N into the kettle₂Until the pressure is 0.3-0.4MPa, carrying out esterification reaction at the reaction temperature of 230-₂Discharging and granulating to obtain the random copolyester.

The random copolyester prepared by the method has the intrinsic viscosity of 0.650dl/g and the melting point of 287 ℃.

The composition and preparation method of the film were the same as in example 1 except that the random copolyester obtained in example 3 was used as the raw material for the film core layer.

Example 4

Example 4 differs from example 1 only in that: the random copolyester raw materials have different addition proportions, and specifically comprise the following components:

95mol of terephthalic acid, 5mol of 2, 6-naphthalene dicarboxylic acid, 2mol of 4, 6-diamino resorcinol, 98mol of ethylene glycol and 0.05mol of antimony trioxideAdding a catalyst and 0.05mol of triphenyl phosphate stabilizer into a polymerization reaction kettle, and filling N into the kettle₂Until the pressure is 0.3-0.4MPa, carrying out esterification reaction at the reaction temperature of 230-₂Discharging and granulating to obtain the random copolyester.

The random copolyester obtained in the above way has an intrinsic viscosity of 0.647dl/g and a melting point of 283 ℃.

The composition and preparation method of the film were the same as in example 1, except that the random copolyester obtained in example 4 was used as the raw material for the film core layer.

Comparative example 1

The composition and preparation method of the film were the same as those of example 1, except that the raw material of the film core layer was PET chip for SKC electronic grade film in korea.

Comparative example 2

Comparative example 2 differs from example 1 only in that: the random copolyester is different in raw material adding proportion, and specifically comprises the following components:

100mol of terephthalic acid, 8mol of 4, 6-diaminoresorcinol, 92mol of ethylene glycol, 0.05mol of antimony trioxide catalyst and 0.05mol of triphenyl phosphate stabilizer are added into a polymerization reaction kettle, and N is filled in the kettle₂Until the pressure is 0.3-0.4MPa, carrying out esterification reaction at the reaction temperature of 230-₂Discharging and granulating to obtain the random copolyester.

The composition and preparation method of the film were the same as in example 1 except that the random copolyester prepared in comparative example 2 was used as the raw material for the film core layer.

Comparative example 3

Comparative example 3 differs from example 1 only in that: the random copolyester is different in raw material adding proportion, and specifically comprises the following components:

adding 80mol of terephthalic acid, 20mol of 2, 6-naphthalene dicarboxylic acid, 100mol of ethylene glycol, 0.05mol of antimony trioxide catalyst and 0.05mol of triphenyl phosphate stabilizer into a polymerization reaction kettle, and filling N into the kettle₂Until the pressure is 0.3-0.4MPa, carrying out esterification reaction at the reaction temperature of 230-₂Discharging and granulating to obtain the random copolyester.

The composition and preparation method of the film were the same as in example 1 except that the random copolyester prepared in comparative example 3 was used as the raw material for the film core layer.

Test examples

The films obtained in examples 1 to 4 and comparative examples 1 to 3 were subjected to the performance test, and the test results are shown in Table 1:

TABLE 1 film Performance test results

As can be seen from Table 1, the tensile strength of the film of the invention reaches 260-; simultaneously, the film has better dielectric constant and volume resistivity, the dielectric constant of the film can reach 5.0, and the volume resistivity can reach 4.2 multiplied by 10¹⁵Omega, m, the heat shrinkage of the film is 0-1.5%.

FIG. 2 is a graph showing the dielectric constant test of the films of example 1 and comparative examples 1 to 3. It can be seen that the dielectric constant of the film of example 1 was relatively stable up to 80 deg.C, whereas the dielectric constant of the films of comparative examples 1-3 was not stable up to 80 deg.C.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.