Polyamic acid composition and method for producing same

Abstract

The present invention relates to a polyamic acid composition and a method for producing the same. A polyimide using the polyamic acid composition according to the present invention has excellent dielectric breakdown voltage performance and corona discharge inception voltage while maintaining heat resistance and mechanical strength, and a polyimide coating produced using the polyamic acid composition according to the present invention has excellent voltage endurance characteristics.

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid composition and a method for producing the same. [Background technology]

[0002] Generally, polyimide (PI) is a polymer of imide monomer formed by solution polymerization of dianhydride and diamine or diisocyanate, and has excellent mechanical properties such as strength, chemical resistance, weather resistance, and heat resistance due to the chemical stability of the imide ring. Furthermore, polyimide has attracted attention as a highly functional polymer material applicable to a wide range of industrial fields such as electronics, communications, and optics due to its excellent electrical properties such as insulating properties and low dielectric constant.

[0003] There have been attempts to use polyimides as a coating material for conductors, taking advantage of their excellent heat resistance and low dielectric constant. That is, the insulating layer (coating) that covers a conductor must have excellent insulation properties, adhesion to the conductor, heat resistance, and mechanical strength, and polyimides can meet most of these requirements.

[0004] However, in electrical equipment requiring high voltages for insulating layers or coatings, such as motors operated at high voltages, high voltages are applied to the insulated wires that make up the electrical equipment. However, the reality is that polyimides with excellent voltage durability that can withstand such high voltages still need to be developed.

[0005] Specifically, partial discharge (corona discharge) is likely to occur on the surface of the coating to which high voltage is applied, and if corona discharge occurs, local temperature rise and generation of ozone or ions occur, causing deterioration of the coating of the insulated wire, leading to early dielectric breakdown and shortening the life of the electrical equipment. Therefore, in order to use polyimide as a coating material for conductors, especially as a coating to which high voltage is applied, improvements in voltage endurance properties such as dielectric breakdown voltage performance and corona discharge inception voltage are required. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to solve the problems and technical issues of the prior art. The present invention provides a polyamic acid composition that can be used to produce polyimides with excellent voltage endurance characteristics. The present invention can provide a polyamic acid composition and polyimides using the same that have excellent breakdown voltage performance and corona discharge inception voltage while maintaining heat resistance and mechanical strength. [Means for solving the problem]

[0007] The present invention relates to a polyamic acid composition and a method for producing the same. The polyamic acid composition can be cured to produce a polyimide. The polyimide produced using the polyamic acid composition according to the present invention may be used for a conductor coating. Thus, the present invention provides a polyimide-coated product.

[0008] The polyamic acid composition includes a polyamic acid having polymerized units derived from a dianhydride monomer component and a diamine monomer component, and a nanoparticle dispersion.

[0009] The diamine monomer component according to the present application can be classified as, for example, aromatic diamines, and examples thereof can be given below.

[0010] 1) Diamines having a relatively rigid structure, such as 1,4-diaminobenzene (or paraphenylenediamine, PDA), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene, or 3,5-diaminobenzoic acid (or DABA), which have one benzene nucleus in their structure; 2) 4,4'-diaminodiphenylmethane (methylenediamine), 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis(4-aminophenyl)sulfide, 4,4'-di Aminobenzanilide, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine (or o-tolidine), 2,2'-dimethylbenzidine (or m-tolidine), 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, (or oxydianiline, ODA), 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diamino Diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane diamines having two benzene nuclei in their structure, such as 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropene, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, or 4,4'-(1,3-propanediyl)dioxydianiline (PDDA); 3) 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis(3-aminophenoxy)benzene (or TPE-Q), 1,4-bis(4-aminophenoxy)benzene (or TPE-Q), 1,3-bis(3-aminophenoxy)-4-trifluoromethylbenzene, 3,3'-diamino-4-(4-phenyl)phenoxybenzophenone, 3,3'-diamino-4,4'-di(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenylsulfonyl) diamines having three benzene nuclei in their structure, such as 1,3-bis(4-aminophenylsulfide)benzene, 1,3-bis(4-aminophenylsulfide)benzene, 1,4-bis(4-aminophenylsulfide)benzene, 1,3-bis(3-aminophenylsulfone)benzene, 1,3-bis(4-aminophenylsulfone)benzene, 1,4-bis(4-aminophenylsulfone)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, 1,4-bis[2-(4-aminophenyl)isopropyl]benzene, or [3-(4-aminobenzoyl)oxyphenyl]4-aminobenzoate (p-BABB); 4) 3,3'-bis(3-aminophenoxy)biphenyl, 3,3'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[3-(3-aminophenoxy)phenyl]ether, bis[3-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, bis[3-(3-aminophenoxy)phenyl]ketone, bis[3-(4-aminophenoxy)phenyl] bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfone, bis[3-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[3-(3-aminophenoxy)phenyl]methane, bis[3-(4-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 2,2-bis[3-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane Diamines with four benzene nuclei in their structure, such as 2,2-bis[3-(3-aminophenoxy)phenyl]propane (BAPP), 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[3-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropene, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropene, or 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane.

[0011] For example, the diamine monomer component according to the present invention may include at least one selected from the group consisting of 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenyl ether (ODA), 4,4'-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), 2,2-dimethylbenzidine (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 1,4-bisaminophenoxybenzene (TPE-Q), bisaminophenoxybenzene (TPE-R), 2,2-bisaminophenoxyphenylpropane (BAPP), and 2,2-bisaminophenoxyphenylhexafluoropropane (HFBAPP).

[0012] Meanwhile, the dianhydride monomer component contained in the polyimide resin of the present application may be an aromatic tetracarboxylic acid dianhydride. The dianhydride monomer component may have one or more aromatic rings. The upper limit of the number of aromatic rings may be, for example, five.

[0013] The aromatic tetracarboxylic acid dianhydride component may be pyromellitic dianhydride (or PMDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA), oxydiphthalic dianhydride (ODPA), diphenylsulfone-3,4,3',4'-tetracarboxylic acid dianhydride (DSDA), bis(3,4-dicarboxylate) phenyl) sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride , p-phenylenebis(trimellitic acid monoester acid anhydride) (TAHQ), p-biphenylenebis(trimellitic acid monoester acid anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic acid dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride or 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid dianhydride (6-FDA).

[0014] For example, the dianhydride monomer component according to the present invention may comprise at least one selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), p-phenylenebis(trimellitate anhydride) (TAHQ), and 4,4-(2,2-hexafluoroisopropylidene)diphthalic anhydride (6-FDA).

[0015] In one example, the nanoparticle dispersion may be an organic solvent in which nanoparticles are dispersed. The nanoparticles are nano-sized particles and include inorganic materials such as metal oxides. For example, the nanoparticles may include silica, zirconia, or a mixture thereof. Specifically, the nanoparticles according to the present invention may be nano-sized silicon dioxide (SiO2) particles (nanosilica).

[0016] The nanoparticle dispersion may contain nanoparticles having an average particle diameter of 1 to 200 nm. For example, the average particle diameter of the nanoparticles may be 1 to 150 nm, 1 to 100 nm, 10 to 100 nm, 10 to 50 nm, 10 to 40 nm, 10 to 30 nm, or 10 to 25 nm.

[0017] The nanoparticle dispersion may also contain nanoparticles whose surfaces have been modified with a silicon-containing compound. In one example, the silicon-containing compound may contain at least one alkoxy or alkyl group having 1 to 4 carbon atoms. For example, the silicon-containing compound may contain at least one methoxy group, ethoxy group, methyl group, or ethyl group.

[0018] In yet another example, the silicon-containing compound may include nanoparticles surface-modified with an organosilane or organosiloxane.

[0019] The organic silanes include n-octyltrimethoxysilane, n-octyltriethoxysilane, isooctyltrimethoxysilane, dodecyltrimethoxysilane, octadecyltrimethoxysilane, propyltrimethoxysilane, hexyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-(methacryloxy)propyltriethoxysilane, 3-(methacryloxy)propylmethyldimethoxysilane, 3-(acryloxypropyl)methyldimethoxysilane, 3-(methacryloxy)propyldimethylethoxysilane, styrylethyltrimethoxysilane, methyl ... The vinyl triethoxysilane may contain at least one selected from the group consisting of trimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, p-tolyltriethoxysilane, vinylmethyldiacetoxysilane, vinyldimethylethoxysilane, vinylmethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriphenoxysilane, vinyltri-t-butoxysilane, vinyltris(isobutoxy)silane, vinyltriisopropenoxysilane, and vinyltris(2-methoxyethoxy)silane.

[0020] The organosilane contains at least one alkoxy group having 1 to 4 carbon atoms, and may further contain at least one substituent selected from the group consisting of an epoxy group, an amino group, an alkyl group having 1 to 4 carbon atoms, and an aryl group having 6 to 20 carbon atoms.

[0021] Specifically, the organosilane may include methoxysilane or ethoxysilane, and for example, the organosilane may include at least one selected from the group consisting of glycidoxypropyl trimethoxysilane (GPTMS), aminopropyl trimethoxysilane ((3-Aminopropyl)trimethoxysilane (APTMS), phenyltrimethoxysilane (PTMS), and phenylaminopropyl trimethoxysilane (N-Phenyl-3-aminopropyltrimethoxysilane (PAPTES)).

[0022] The organosiloxane may be a linear or cyclic compound containing an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

[0023] For example, the organosiloxane may include at least one selected from the group consisting of 1,3,5,7-tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, hexamethyldisiloxane, 1,1,2,2-tetramethyldisiloxane, and octamethyltrisiloxane.

[0024] The surface-modified nanoparticles may be produced by surface-treating nanoparticles with an organosilane or organosiloxane. For example, surface-modified nanoparticles can be obtained by treating the nanoparticles with an organosilane or organosiloxane under acidic or basic conditions at elevated temperatures for approximately 1 to 24 hours. Alternatively, surface modification can be achieved by other known methods, such as mixing an organosilane or organosiloxane with a solvent and then reacting the mixture at temperatures of 10 to 100°C or 20 to 60°C for 1 to 10 hours or 1 to 5 hours. To bond two or more compounds to the surface of nanoparticles, each of the above methods may be performed separately.

[0025] The nanoparticle dispersion may also contain nanoparticles having the following compounds (A) and (B) bound to the surface thereof: (A) a compound containing at least one aryl group having 6 to 20 carbon atoms at its terminal, and (B) A compound containing at least one amine group, hydroxy group, thiol group, or epoxy group at its terminal end.

[0026] The compound (A) may be phenyltrimethoxysilane (PTMS) or phenylaminopropyltrimethoxysilane (N-Phenyl-3-aminopropyltrimethoxysilane (PAPTES).

[0027] The compound (B) may be glycidoxypropyl trimethoxysilane (GPTMS) or aminopropyl trimethoxysilane ((3-aminopropyl)trimethoxysilane (APTMS).

[0028] As described above, when (A) a compound containing at least one aryl group having 6 to 20 carbon atoms at its terminal and (B) a compound containing at least one amine group, hydroxy group, thiol group, or epoxy group at its terminal are bound to nanoparticles, the (A) compound prevents aggregation of inorganic particles within the polyamic acid composition, and the functional group of the (B) compound can improve organic-inorganic hybridization with the solid content (polyamic acid).

[0029] The nanoparticles may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the dianhydride monomer component and the diamine monomer component combined. For example, the nanoparticle dispersion may include 2 to 30 parts by weight, 3 to 30 parts by weight, 3 to 25 parts by weight, 3 to 20 parts by weight, or 3 to 15 parts by weight of nanoparticles based on 100 parts by weight of the dianhydride monomer component and the diamine monomer component combined. By adjusting the nanoparticle content as described above, voltage endurance properties such as breakdown voltage (BVD) and partial discharge inception voltage (PDIV) can be improved while maintaining mechanical strength and thermal properties, thereby improving the voltage endurance properties of coatings using the polyamic acid composition.

[0030] The nanoparticle dispersion according to the present invention may contain metal ions at 3000 ppm or less. For example, the organic solvent may contain metal ions at 2500 ppm or less, 2000 ppm or less, 1800 ppm or less, 1500 ppm or less, 1200 ppm or less, 1000 ppm or less, 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, or 300 ppm or less. The lower limit is not particularly limited, and may be 10 ppm or more or 100 ppm or more. The metal ions may be impurities in the nanoparticles (or nanoparticle precursors) or the organic solvent raw material. For example, because of the high cost of 100% purification of the raw materials, commercially available nanoparticles (or nanoparticle precursors) and organic solvent raw materials are not 100% purified and contain a certain amount of metal ions. If the metal ions in the raw material exceed 3000 ppm, this may adversely affect voltage endurance characteristics such as breakdown voltage (BVD) and partial discharge inception voltage (PDIV).

[0031] The present invention can improve voltage endurance characteristics such as breakdown voltage (BVD) and partial discharge inception voltage (PDIV) by controlling the content of metal ions as described above, and can also improve the voltage endurance characteristics of a coating using a polyamic acid composition.

[0032] In the present invention, the nanoparticle dispersion having the above metal ion content can be prepared by removing foreign substances and impurities through filtering or by removing metal ions using an ion exchange resin.

[0033] The polyamic acid composition may have a dielectric breakdown voltage (BDV) of 170 kV / mm or more after curing, as measured according to ASTM D149 standard. The lower limit of the dielectric breakdown voltage may be 180 kV / mm or more, 190 kV / mm or more, 200 kV / mm or more, 210 kV / mm or more, 230 kV / mm or more, 240 kV / mm or more, 250 kV / mm or more, 260 kV / mm or more, 270 kV / mm or more, 280 kV / mm or more, 290 kV / mm or more, 300 kV / mm or more, or 310 kV / mm or more, and the upper limit may be, for example, 500 kV / mm or less, 400 kV / mm or less, 350 kV / mm or less, 330 kV / mm or less, or 320 kV / mm or less. The polyamic acid composition of the present invention can provide a polyimide that simultaneously satisfies low dielectric constant, heat resistance, insulating properties, adhesion, and mechanical properties at high temperatures. Therefore, when used as a wire coating, it can provide a highly reliable coating that prevents partial discharge, localized deterioration, and dielectric breakdown.

[0034] The breakdown voltage (BDV) may be measured by a method known in the art. In one example, the breakdown voltage may be measured according to the ASTM D149 standard. A specimen of an electric wire coated with the polyamic acid composition may be prepared, and a measuring device, such as PHENIX TEXNOLOGIES 6CCE50-5, may be used. The prepared specimen may be pretreated in an oven at 100°C to remove moisture, and then the specimen may be fixed in the measuring device, which is set to a room temperature atmosphere. A voltage of 10 kVAc may be applied between the upper and lower electrodes, and the AC voltage may be increased from 0 at a constant rate to measure the BDV.

[0035] The polyamic acid composition may have a partial discharge inception voltage (PDIV) of 800 Vp or more after curing, as measured according to ASTM 2275-01 standard. In a specific example, the lower limit of the partial discharge inception voltage may be 800 Vp or more, 820 Vp or more, 830 Vp or more, or 850 Vp or more, and the upper limit may be 1000 Vp or 950 Vp or less.

[0036] The partial discharge inception voltage (PDIV) may be measured by a method known in the art. For example, the partial discharge inception voltage may be measured by applying a load and twist to a pair of ends of an insulated wire specimen made using a polyamic acid composition according to ASTM 2275-01 standard to prepare a double-twisted sample, and then applying a voltage of 50 to 60 Hz at a constant rate to the threads on both ends of the sample to record the voltage at which a partial discharge (100 pC or more) occurs.

[0037] The polyamic acid composition according to the present invention may have a coefficient of thermal expansion (CTE) after curing in a range of 50 ppm / °C or less. For example, the upper limit of the CTE may be 45 ppm / °C or less, 40 ppm / °C or less, 38 ppm / °C or less, 36 ppm / °C or less, or 35 ppm / °C or less, and the lower limit may be, for example, 0.1 ppm / °C, 1 ppm / °C, 2.0 ppm / °C, 2.6 ppm / °C, 2.8 ppm / °C, 3.5 ppm / °C, or 4 ppm / °C or more. In one example, the coefficient of thermal expansion may be measured at 100 to 400°C. The CTE may be measured using a TA thermomechanical analyzer, model Q400. The polyimide is prepared into a film and cut into a width of 2 mm and a length of 10 mm. The film is heated from room temperature to 500°C at a rate of 10°C / min under a nitrogen atmosphere while applying a tension of 0.05 N, and then cooled again at a rate of 10°C / min, and the slope of the temperature gradient from 100°C to 250°C is measured.

[0038] In one example, the polyamic acid composition according to the present invention may have a glass transition temperature after curing in a range of 300°C or higher. For example, the lower limit of the glass transition temperature may be 310°C or higher, 330°C or higher, 350°C or higher, 370°C or higher, or 380°C or higher. The upper limit may be 600°C or lower. The glass transition temperature may be measured using TMA at 10°C / min for a polyimide produced by curing the polyamic acid composition.

[0039] The polyamic acid composition according to the present application may have a thermal decomposition temperature of 400°C or higher after curing at 1% by weight. The thermal decomposition temperature may be measured using a thermogravimetric analyzer (Model Q50) manufactured by TA Corporation. In a specific example, the polyimide obtained by curing the polyamic acid is heated to 150°C at a rate of 10°C / min under a nitrogen atmosphere, and then maintained at the same temperature for 30 minutes to remove moisture. The temperature may then be increased to 600°C at a rate of 10°C / min, and the temperature at which a 1% weight loss occurs may be measured. The lower limit of the thermal decomposition temperature may be, for example, 450°C or higher, 460°C or higher, 470°C or higher, or 480°C or higher. The upper limit may be, for example, 800°C or lower or 600°C or lower.

[0040] The polyamic acid composition according to the present application may have a light transmittance of 40% or more at 380 nm to 770 nm after curing. The light transmittance may be measured using an ultraviolet / visible spectrophotometer (UV-Vis spectrophotometer). For example, the light transmittance may be 42% or more, 44% or more, 50% or more, 55% or more, 60% or more, 62% or more, or 64% or more. The upper limit is not particularly limited, but may be 90% or less or 85% or less.

[0041] The polyamic acid composition of the present application may have a modulus of elasticity of 2.5 GPa or more after curing. The lower limit of the modulus of elasticity may be, for example, 3.0 GPa or more, 3.1 GPa or more, 3.3 GPa or more, or 3.5 GPa or more. The upper limit is not particularly limited, but may be 15 GPa or less or 10 GPa or less.

[0042] The polyamic acid composition may have a tensile strength of 100 MPa or more after curing. The lower limit of the tensile strength may be, for example, 110 MPa or more, 120 MPa or more, 122 MPa or more, 124 MPa or more, or 125 MPa or more, and the upper limit may be, for example, 400 MPa or less or 3500 MPa or less. The elastic modulus and tensile strength may be measured by curing the polyamic acid composition to prepare a polyimide film, cutting the film into a width of 10 mm and a length of 50 mm, and then measuring the elastic modulus and tensile strength according to ASTM D-882 using an Instron 5564 UTM instrument manufactured by Instron. The measurement may be performed at a crosshead speed of 50 mm / min.

[0043] The polyamic acid composition according to the present invention may further include a silane compound. The silane compound may be, for example, one or more compounds selected from the group consisting of epoxy-based, amino-based, and thiol-based compounds, or a mixture of two or more compounds. Specifically, the epoxy-based compound may include glycidoxypropyl trimethoxysilane (GPTMS), the amino-based compound may include aminopropyl trimethoxysilane ((3-aminopropyl)trimethoxysilane (APTMS), and the thiol-based compound may include mercaptopropyl trimethoxysilane (MPTMS), but these examples are not limited thereto. The silane compound may also include an alkoxysilane compound such as dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), or tetraethoxysilane (TEOS).

[0044] The silane compound may be contained in an amount ranging from 0.01 to 1 part by weight per 100 parts by weight of the total of the dianhydride monomer and the diamine monomer. Specifically, the content of the silane compound may be 0.03 parts by weight or more, 0.05 parts by weight or more, 0.08 parts by weight or more, 0.1 parts by weight or more, 0.15 parts by weight or more, or 0.18 parts by weight or more per 100 parts by weight of the polyamic acid, with the upper limit being, for example, 0.8 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.23 parts by weight or less, or 0.15 parts by weight or less. By including the silane compound, the present application can improve electrical properties while also improving adhesion to adherends.

[0045] The polyamic acid composition according to the present invention may have a solids content in the range of 10 to 50 wt%. The solids content may be 13 wt% or more, 15 wt% or more, 18 wt% or more, 20 wt% or more, 25 wt% or more, or 28 wt% or more, and the upper limit may be, for example, 48 wt% or less, 45 wt% or less, 43 wt% or less, 40 wt% or less, 38 wt% or less, 35 wt% or less, 33 wt% or less, or 30 wt% or less. The present invention can achieve desired physical properties and viscosity within the above ranges.

[0046] The nanoparticle dispersion according to the present invention may contain an organic solvent, and the organic solvent may be appropriately selected in consideration of the nanoparticles and dispersibility. For example, the nanoparticle dispersion may use one first organic solvent or a mixed solvent of two or more first and second organic solvents. For example, the organic solvent may be an aprotic polar solvent.

[0047] The nanoparticle dispersion may contain at least one organic solvent selected from the group consisting of N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropionamide (DMPA), p-chlorophenol, o-chlorophenol, N-methyl-pyrrolidone (NMP), γ-butyrolactone (GBL), diglyme, and naphthalene.

[0048] In one example, the mixed solvent of the present invention may be prepared by mixing a first solvent and a second solvent having a boiling point lower than that of the first solvent. The second organic solvent may be contained in an amount ranging from 0.01 to 10 wt% of the total polyamic acid composition. The lower limit of the content of the second solvent may be, for example, 0.015 wt%, 0.03 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, or 2 wt% or more, and the upper limit may be, for example, 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5.5 wt%, 5.3 wt%, 5 wt%, 4.8 wt%, 4.5 wt%, 4 wt%, 3 wt%, 2.5 wt%, 1.5 wt%, 1.2 wt%, 0.95 wt%, or 0.4 wt% or less. The first organic solvent may be contained in a range of 60 to 95 wt % of the total polyamic acid composition. The lower limit of the content of the first organic solvent may be, for example, 65 wt %, 68 wt %, 70 wt %, 73 wt %, 75 wt %, 78 wt %, or 80 wt % or more, and the upper limit may be, for example, 93 wt %, 90 wt %, 88 wt %, 85 wt %, 83 wt %, 81 wt %, or 79 wt % or less.

[0049] In one example, the first organic solvent may have a boiling point of 150°C or higher, and the second organic solvent may have a boiling point lower than that of the first organic solvent. That is, the first solvent may have a boiling point higher than that of the second solvent. The second solvent may have a boiling point in the range of 30°C or higher and lower than 150°C. The lower limit of the boiling point of the first solvent may be, for example, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, or 201°C, and the upper limit may be, for example, 500°C, 450°C, 300°C, 280°C, 270°C, 250°C, 240°C, 230°C, 220°C, 210°C, or 205°C. The lower limit of the boiling point of the second organic solvent may be, for example, 35°C, 40°C, 45°C, 50°C, 53°C, 58°C, 60°C, or 63°C or higher, and the upper limit may be, for example, 148°C, 145°C, 130°C, 120°C, 110°C, 105°C, 95°C, 93°C, 88°C, 85°C, 80°C, 75°C, 73°C, 70°C, or 68°C or lower. In the present application, polyimide with desired physical properties can be produced by using two solvents with different boiling points.

[0050] The polyamic acid composition of the present invention may be a composition having low viscosity characteristics. -1 The viscosity measured under conditions of a shear rate of 1 / s may be 10,000 cP or less, or 9,000 cP or less. The lower limit is not particularly limited, but may be 500 cP or more or 1,000 cP or more. The viscosity may be measured, for example, using a Haake Rheostress 600 under conditions of a shear rate of 1 / s, a temperature of 23°C, and a plate gap of 1 mm. By adjusting the viscosity range, the present application provides a precursor composition with excellent processability, and a coating with desired physical properties can be formed when coating a conductor wire.

[0051] A method for producing a polyamic acid composition will be described below. The method for producing a polyamic acid composition according to the present invention will be described excluding any overlapping content with the method for producing the polyamic acid composition described above, but the content described for the polyamic acid composition described above also applies to the method for producing the polyamic acid composition described below.

[0052] The method for preparing the polyamic acid composition according to the present invention includes the steps of mixing and heating a dianhydride monomer component, a diamine monomer component, a solvent, and a nanoparticle dispersion.

[0053] In the mixing and heating step, the solvent may be appropriately selected in consideration of dispersibility with the dianhydride monomer component, the diamine monomer component, and the nanoparticle dispersion. For example, the solvent may include at least one selected from the group consisting of N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropionamide (DMPA), p-chlorophenol, o-chlorophenol, N-methyl-pyrrolidone (NMP), γ-butyrolactone (GBL), diglyme, and naphthalene.

[0054] In one example, the method according to the present invention may include preparing a nanoparticle dispersion. The nanoparticle dispersion may be prepared by dispersing nanoparticles in an organic solvent.

[0055] In one example, the water content of the nanoparticle dispersion is 3 wt% or less. For example, the water content of the nanoparticle dispersion may be 2 wt% or less, 1.8 wt% or less, 1.5 wt% or less, 1 wt% or less, 0.9 wt% or less, 0.8 wt% or less, or 0.7 wt% or less. The lower limit is not particularly limited, but may be, for example, 0.1 wt% or more.

[0056] The water content of the nanoparticle dispersion can be measured by the Karl Fischer method, specifically, by quantitatively measuring the water content in a KS M 0034 sample with iodine and sulfur dioxide.

[0057] If the water content of the nanoparticle dispersion exceeds the above range, the chain length of the polymer becomes short, the viscosity formation is limited, and a high molecular weight polyimide is obtained.

[0058] The water content of the nanoparticle dispersion that satisfies the above conditions can be removed by vacuum decompression or by circulating the nanoparticle dispersion through an adsorbent such as a molecular seive.

[0059] The nanoparticle dispersion may contain metal ions at 3000 ppm or less. For example, the nanoparticle dispersion may contain metal ions at 2500 ppm or less, 2000 ppm or less, 1500 ppm or less, 1200 ppm or less, 1000 ppm or less, 900 ppm or less, 800 ppm or less, 700 ppm or less, 600 ppm or less, 500 ppm or less, 400 ppm or less, or 300 ppm or less. The lower limit is not particularly limited, but may be 10 ppm or more or 100 ppm or more.

[0060] The metal ion content of the nanoparticle dispersion may be measured by ICP and XRD, and the wavelength emitted by heating the nanoparticle dispersion may be analyzed using a spectrometer.

[0061] Nanoparticles having such a metal ion content can be prepared by removing foreign substances and impurities through filtering or by removing metal ions using an ion exchange resin.

[0062] The present invention can improve voltage endurance characteristics such as breakdown voltage (BVD) or partial discharge inception voltage (PDIV) by controlling the water content and metal ion content of the nanoparticle dispersion as described above, and can also improve the voltage endurance characteristics of a coating using a polyamic acid composition.

[0063] The organic solvent in which the nanoparticles are dispersed is the same as that described above for the polyamic acid composition.

[0064] The dianhydride monomer and the diamine monomer may be added in the form of powder, lump, or solution. Preferably, they are added in the form of powder at the beginning of the reaction, and then added in the form of solution to control the polymerization viscosity.

[0065] For example, a dianhydride monomer and a diamine monomer may be added in powder form to react with each other, and then the dianhydride may be added in solution form to react with each other until the viscosity of the polyamic acid composition reaches a certain range.

[0066] Meanwhile, the present invention provides a method for producing the polyamic acid composition, which comprises adding at least one of a dianhydride monomer and a diamine monomer to the solvent and dissolving the monomer in the solvent, and then adding the at least one of the dianhydride monomer and the diamine monomer to the solvent in two or more divided portions to polymerize the polyamic acid, followed by stirring.

[0067] The equivalent ratio of the dianhydride monomer to the diamine monomer may be adjusted by adding the dianhydride monomer and the diamine monomer in portions. Specifically, at least one of the dianhydride monomer and the diamine monomer may be added in at least two to five portions.

[0068] The heating temperature is 150 to 300°C, and may be, for example, 160 to 200°C, 170 to 200°C, 180 to 200°C, 180 to 190°C, or 185 to 195°C.

[0069] The present invention may provide a polyimide coating using a polyamic acid composition. The polyimide coating may be coated and cured on a surface of a conductor. In one embodiment, a method for manufacturing the coating may include coating a surface of a conductor with a polyamic acid composition and imidizing the polyamic acid composition coated on the surface of the conductor.

[0070] The polyimide coating may contain 1 to 40 wt % of the polyamic acid composition according to the present invention. Specifically, in the step of coating the conductor surface with the polyamic acid composition, the content of the polyamic acid composition according to the present invention relative to the total polyamic acid composition may be 1 to 40 wt %, for example, 1 to 30 wt %, 5 to 30 wt %, 10 to 30 wt %, or 10 to 20 wt %. The remainder of the polyimide coating other than the polyamic acid composition according to the present invention may be a polyamic acid composition that does not contain nanoparticles. In this case, the remaining composition may be the same except for the presence or absence of nanoparticles.

[0071] The conductor may be a copper wire made of copper or a copper alloy, but may also be a conductor made of other metal materials such as silver wire, or various metal-plated wires such as aluminum or tin-plated wire. The thickness of the conductor and coating conforms to the KS C 3107 standard. The diameter of the conductor may be within the range of 0.3 to 3.2 mm, and the standard coating thickness of the coating (average value of the maximum and minimum coating thicknesses) may be 21 to 194 μm for Type 0, 14 to 169 μm for Type 1, and 10 to 31 μm for Type 2. The cross-sectional shape of the conductor may be, but is not limited to, a circular wire, a rectangular wire, a hexagonal wire, or the like.

[0072] The polyimide coating according to the present invention may have a voltage endurance characteristic, which is the time an insulating material can withstand a constant voltage based on IEC-60851-5, of 170 minutes or more, for example, 180 minutes or more, 200 minutes or more, 220 minutes or more, or 230 minutes or more.

[0073] Specifically, the voltage endurance characteristics may be measured by a matching method under voltage conditions (700 to 2,000 V) where 100 V is added to the PDIV value, temperature conditions of 150° C., and leakage current conditions of 50 mA.

[0074] The present invention may further provide a coated electric wire including a polyimide coating prepared by coating the surface of an electric wire with the polyamic acid composition and imidizing the polyimide. In one embodiment, the coated electric wire may include an electric wire and a coating obtained by coating the surface of the electric wire with the polyimide described above and imidizing the polyimide.

[0075] The present application may also provide an electronic device including the coated electric wire. The electronic device may be, for example, an electric motor. [Effects of the Invention]

[0076] The polyamic acid composition and polyimide produced by the method for producing the same according to the present invention have excellent voltage endurance characteristics. Specifically, the polyamic acid composition and polyimide produced by the method for producing the same according to the present invention have excellent effects on breakdown voltage performance and corona discharge inception voltage while maintaining heat resistance and mechanical strength. DETAILED DESCRIPTION OF THE INVENTION

[0077] The present invention will be described in more detail below through examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited to the following examples. [Example]

[0078] <Production example> Preparation of Nanoparticles - Preparation Examples 1 to 11 Water, ethanol, ammonia water, and a nanosilica precursor (TEOS, tetraethyorthosilicate) were mixed and heated to synthesize 20 nm nanosilica. Organic solvents (NMP and DMAc) were then added, and the water and ethanol were removed under reduced pressure. Water was then removed using Molecular Seive (4Å), and metal ions were removed using an ion exchange resin to prepare a 20 wt% nanosilica dispersion in the organic solvent. The water and metal ion contents of the prepared nanosilica dispersion are shown in Table 1 below. In Table 1, the water content is expressed as a weight percent of the total mass of the nanosilica dispersion, and the metal ion content is the weight ratio of the metal ions to the weight of the nanosilica dispersion.

[0079] [Table 1]

[0080] Examples 12 to 16 A nanosilica dispersion was prepared in the same manner as in the above Preparation Example, except that the surface of the nanosilica was modified with an organosilane or organosiloxane as shown in Table 2 below before adding the organic solvent.

[0081] [Table 2]

[0082] <Example> Preparation of Polyamic Acid - Examples 1 to 20 and Comparative Examples A 1 L reactor was charged with N,N'-dimethylacetamide as a solvent under a nitrogen atmosphere.

[0083] After setting the temperature to 23 to 50°C, 100 parts by weight of pyromellitic dianhydride (PMDA) as a dianhydride monomer, 100 parts by weight of 4,4'-diaminodiphenyl ether (ODA) as a diamine monomer, and the nanosilica dispersions prepared in Preparation Examples 1 to 16 were added and dissolved to achieve the nanosilica content shown in Table 3 below, and then the PMDA and ODA were reacted at 23 to 80°C for 5 to 10 hours to gradually increase the viscosity and polymerize the polyamic acid.

[0084] The nanosilica content in Table 3 below was calculated based on 100 parts by weight of the total of the dianhydride monomer component and the diamine monomer component.

[0085] [Table 3]

[0086] Preparation of Polyimide Coatings - Examples 21 and 22 The polyamic acid composition of Example 15 prepared above was applied to a copper wire having a conductor diameter of 1 mm in a coating curing oven in the amounts shown in Table 5, with the coating thickness adjusted to between 5 and 15 μm per application. The minimum and maximum temperatures of the coating curing oven were adjusted to between 350 and 550°C, and the copper wire coating speed was adjusted to between 12 and 32 m / min, to produce polyimide coated electric wires (coated electric wires) with coating thicknesses of 33 to 35 μm. The remainder, excluding the amount of Example 15, was made from a comparative polyamic acid composition not containing the nanosilica dispersion.

[0087] The properties of the cured polyamic acid compositions are shown in Table 4 below, and the properties of the polyimide coatings are shown in Table 5 below.

[0088] <Experimental Example 1: Evaluation of Dielectric Breakdown Voltage (BDV)> The BDV values ​​of the specimens prepared in the examples and comparative examples were measured according to ASTM D149.

[0089] Measurement equipment: PHENIX TECHNOLOGIES 6CCE50-5

[0090] The prepared specimen is pretreated in an oven at 100°C to remove moisture, and then the specimen is fixed in the measuring equipment set at room temperature. A voltage of 10 KVAc is applied to the upper and lower electrodes, and the voltage is increased from 0 at a constant rate to measure the BDV.

[0091] <Experimental Example 2 - Measurement of Elastic Modulus and Tensile Strength> Polyimide films prepared by curing the polyamic acid solutions of the Examples and Comparative Examples were cut to a width of 10 mm and a length of 40 mm, and the elastic modulus and tensile strength were measured according to ASTM D-882 using an Instron 5564 UTM instrument manufactured by Instron, Inc. The measurement was performed at a cross head speed of 50 mm / min.

[0092] <Experimental Example 3 - CTE Measurement> Using a TA thermomechanical analyzer, model Q400, polyimide film was cut into a width of 2 mm and a length of 10 mm. After that, under a nitrogen atmosphere, a tension of 0.05 N was applied, and the temperature was raised from room temperature to 500°C at a rate of 10°C / min. Then, the temperature was cooled again at a rate of 10°C / min. The gradient in the temperature range from 100°C to 250°C was measured.

[0093] <Experimental Example 4 - Light transmittance> The transmittance of 10 to 20 μm polyimide films prepared by curing the polyamic acid solutions of the Examples and Comparative Examples was measured in the transmittance mode at 380 to 770 nm using a Perkin-Elmer UV-Vis Spectrophotometer, Lambda 465 model.

[0094] <Experimental Example 5 - Voltage Endurance> The voltage endurance characteristics of the polyamic acid composition (Comparative Example) not containing nanoparticles and the specimens of Examples 21 and 22 were measured based on the PDIV value using a matching method in accordance with IEC-60851-5 under conditions of a voltage of +100 V, a temperature of 150°C, and a leakage current of 50 mA. The voltage endurance characteristics of Examples 21 and 22 were shown relative to the voltage endurance characteristics of the Comparative Example, which was set to 100.

[0095] [Table 4]

[0096] [Table 5]

Claims

1. A polyamic acid having polymerized units derived from a dianhydride monomer component and a diamine monomer component, and A polyamic acid composition comprising a nanoparticle dispersion comprising nanosilica, The nanoparticle dispersion contains metal ions at 1000 ppm or less, The polyamic acid composition has a dielectric breakdown voltage (BDV) of 200 kV / mm or more after curing, as measured in accordance with ASTM D149 standard.

2. The polyamic acid composition of claim 1 , wherein the nanoparticle dispersion comprises nanoparticles that have been surface-modified with a silicon-containing compound.

3. 3. The polyamic acid composition according to claim 2, wherein the silicon-containing compound contains at least one alkoxy or alkyl group having 1 to 4 carbon atoms.

4. 3. The polyamic acid composition of claim 2, wherein the silicon-containing compound is an organosilane or an organosiloxane.

5. 5. The polyamic acid composition according to claim 4, wherein the organosilane contains at least one alkoxy group having 1 to 4 carbon atoms and further contains at least one substituent selected from the group consisting of an epoxy group, an amino group, an alkyl group having 1 to 4 carbon atoms, and an aryl group having 6 to 20 carbon atoms.

6. 5. The polyamic acid composition according to claim 4, wherein the organosiloxane is a linear or cyclic compound containing an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms.

7. The polyamic acid composition according to claim 1, wherein the nanoparticle dispersion contains nanoparticles having the following compounds (A) and (B) bonded to the surface thereof: (A) a compound containing at least one aryl group having 6 to 20 carbon atoms at its terminal; and (B) A compound containing at least one amine group, hydroxy group, thiol group, or epoxy group at its terminal end.

8. the compound (A) is phenyltrimethoxysilane (PTMS) or phenylaminopropyltrimethoxysilane (N-Phenyl-3-aminopropyltrimethoxysilane: PAPTES), 8. The polyamic acid composition according to claim 7, wherein the compound (B) is glycidoxypropyl trimethoxysilane (GPTMS) or aminopropyl trimethoxysilane ((3-aminopropyl) trimethoxysilane (APTMS).

9. 2. The polyamic acid composition according to claim 1, wherein the nanoparticle dispersion contains nanosilica having an average particle size of 1 to 200 nm.

10. 2. The polyamic acid composition according to claim 1, wherein the nanoparticle dispersion contains 1 to 30 parts by weight of nanosilica per 100 parts by weight of the total of the dianhydride monomer component and the diamine monomer component.

11. 2. The polyamic acid composition according to claim 1, wherein the dianhydride monomer component comprises at least one selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA), and p-phenylenebis(trimellitate anhydride) (TAHQ).

12. The diamine monomer components are 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminodiphenyl ether (ODA), 4,4'-methylenediamine (MDA), 4,4-diaminobenzanilide (4,4-DABA), N,N-bis(4-aminophenyl)benzene-1,4-dicarboxamide (BPTPA), and 2,2-dimethylbenzidine.

2. The polyamic acid composition according to claim 1, comprising at least one selected from the group consisting of (M-TOLIDINE), 2,2-bis(trifluoromethyl)benzidine (TFDB), 1,4-bisaminophenoxybenzene (TPE-Q), bisaminophenoxybenzene (TPE-R), 2,2-bisaminophenoxyphenylpropane (BAPP), and 2,2-bisaminophenoxyphenylhexafluoropropane (HFBAPP).

13. 2. The polyamic acid composition according to claim 1, which has a light transmittance of 40% or more in the wavelength range of 380 nm to 770 nm after curing.

14. 2. The polyamic acid composition according to claim 1, wherein the nanoparticle dispersion contains at least one organic solvent selected from the group consisting of N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), dimethylpropionamide (DMPA), p-chlorophenol, o-chlorophenol, N-methyl-pyrrolidone (NMP), γ-butyrolactone (GBL), diglyme, and naphthalene.

15. 10. A method for producing the polyamic acid composition of claim 1, comprising mixing and heating a nanoparticle dispersion containing a dianhydride monomer component, a diamine monomer component, and nanosilica.

16. A polyimide coating produced using the polyamic acid composition of claim 1.

17. The polyimide coating according to claim 16, wherein the polyimide coating comprises 1 to 40% by weight of the polyamic acid composition according to claim 1.

18. An electric wire comprising the polyimide coating of claim 16.

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