Polyamide varnish

Abstract

This application provides a polyimide powder in which conductive filler is uniformly dispersed within the particles, and a polyimide varnish capable of producing polyimide molded articles with excellent formability and processability due to the powder, as well as excellent conductivity, tensile strength, elongation and elastic modulus.

Description

Technical Field

[0001] The present application relates to a polyamide varnish, a polyimide powder, a polyimide molded product, a method for preparing the polyamide varnish, a method for preparing the polyimide powder, and a method for preparing the polyimide molded product. Prior Art

[0002] Generally speaking, polyimide (PI) is a polymer of imide monomers formed by solution polymerization of dianhydride with diamine or diisocyanate. Due to the chemical stability of the imide ring, it exhibits excellent mechanical properties such as strength, chemical resistance, weather resistance, and heat resistance. Furthermore, due to its excellent electrical properties, such as insulation and low dielectric constant, polyimide has attracted attention as a high-performance polymer material with applications in a wide range of industries, including electronics, communications, and optics. In recent years, demand for conductive polyimides has been increasing in the semiconductor industry due to static electricity issues in production equipment. Conventionally, conductive polyimide powders were prepared by dry-blending powdered polyimide with a conductive filler. These powders were then molded and processed appropriately for their intended use. However, the problem with dry mixing is that polyimide powder and conductive filler are difficult to mix uniformly, resulting in frequent defects during the molding process, poor processability, and lower expectations for physical properties such as tensile strength, elongation, and elastic modulus. Summary of the Invention

[0003] Problems that the invention aims to solve The present application provides a polyimide powder having a conductive filler uniformly dispersed in particles, and a polyimide varnish capable of realizing a polyimide molded article made from the above-mentioned powder having excellent moldability and processability, as well as excellent conductivity, tensile strength, elongation and elastic modulus. Technical means to solve the problem Among the physical properties mentioned in this specification, when measuring physical properties related to the influence of temperature, unless otherwise specified, the above physical properties are physical properties measured at room temperature. In this specification, the term room temperature refers to a temperature without particular heating or cooling, and may refer to a temperature within a range of about 10°C to 30°C, for example, about 15°C or higher, 18°C ​​or higher, 20°C or higher, or about 23°C or higher and about 27°C or lower. In addition, unless otherwise specified, the unit of temperature mentioned in this specification is Celsius. Among the physical properties mentioned in this article, when measuring physical properties related to the influence of pressure, unless otherwise specified, the above physical properties are physical properties measured under normal pressure. In this specification, the term normal pressure refers to a natural pressure without any particular increase or decrease in pressure, and generally means a pressure of about 1 atm, such as atmospheric pressure. Among the physical properties mentioned in this article, when measuring physical properties related to the influence of humidity, unless otherwise specified, the above physical properties are physical properties measured under natural humidity at the above room temperature and normal pressure. The present application relates to a polyamide varnish. The polyamide varnish according to the present invention can be a solution of a polyimide precursor dissolved in an organic solvent, which is imidized to form polyimide through thermal curing. During thermal curing, the polyamide varnish according to the present application undergoes imidization and precipitates as a powder. The precipitated polyimide powder can have conductive fillers uniformly dispersed within the particles. The resulting polyimide powder not only exhibits excellent formability and processability during molding, but can also produce polyimide molded products with excellent conductivity, tensile strength, elongation, and elastic modulus. An exemplary polyamide varnish according to the present application includes: a polyamide comprising a dianhydride monomer and a diamine monomer as polymerized units; a conductive filler; and an organic solvent. The polyamide varnish can be formed by polymerizing the diamine monomer and the dianhydride monomer in an organic solvent in which the conductive filler is dispersed. The polyamide varnish according to the present application, due to the addition of a conductive filler during the polyamide polymerization step, can provide a polyimide powder with the conductive filler dispersed within the particles during thermal curing. This polyimide powder, when molded, can produce polyimide molded articles that not only exhibit excellent moldability and processability, but also possess excellent conductivity, tensile strength, elongation, and elastic modulus. The type of the organic solvent may be appropriately selected in consideration of the conductive filler and dispersibility. As an example, the organic solvent may be an aprotic polar solvent. Examples of the aprotic polar solvent include: amide solvents such as N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc), or dimethylpropionamide (DMPA); phenolic solvents such as p-chlorophenol and o-chlorophenol; N-methyl-pyrrolidone (NMP); gamma-butyrolactone (GBL), or diglyme, which can be used alone or in combination of two or more. Considering the dispersibility of the conductive filler, N,N'-dimethylacetamide (DMAc) or N-methyl-pyrrolidone (NMP) is preferably used as the organic solvent. The method for dispersing the conductive filler in the organic solvent is not particularly limited, but ultrasonication is preferably used to achieve uniform dispersion. For example, the ultrasonication can be performed using a VCX750 from Sonics & Materials, Inc. for at least 30 minutes. The specific conditions vary depending on the type of solvent and conductive filler. In addition, the polyamide varnish according to the present invention may further contain a cosolvent to improve reaction efficiency. The cosolvent may include at least one selected from the group consisting of m-cresol, naphtha, hexane, heptane, nonane, decane, benzene, toluene, xylene, anisole, cyclohexanone, methyl ethyl ketone, tetrahydrofuran, N-methylpyrrolidone, hexamethylphosphatide, dioxane, tetramethylurea, triethyl phosphate, trimethyl phosphate, dimethylformamide, dimethylsulfoxide, and dimethylacetamide. In one example, the content of the conductive filler may be 1 wt % to 50 wt % relative to the total amount of the polyamide varnish. For example, the content of the conductive filler relative to the total amount of the polyamide varnish may be 1% to 45% by weight, 1% to 40% by weight, 1% to 35% by weight, 1% to 30% by weight, 1% to 25% by weight, 1% to 20% by weight, 1% to 15% by weight, 1% to 10% by weight, 3% to 50% by weight, 3% to 45% by weight, 3% to 40% by weight, 3% to 35% by weight, 3% to 30% by weight, 3% to 25% by weight, 3% to 20% by weight, 3% to 15% by weight, 3% to 10% by weight, 5% to 50% by weight, 5% to 45% by weight, 5% to 40% by weight, 5% to 35% by weight, 5% to 30% by weight, 5% to 25% by weight, 5% to 20% by weight, 5% to 15% by weight, or 5% to 10% by weight. The conductive filler may include at least one selected from the group consisting of carbon black, conductive carbon, graphite, conductive metal and conductive metal oxide. Preferably, the conductive filler may include at least one selected from the group consisting of carbon black, conductive carbon and graphite. The conductive carbon may include single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), or mixtures thereof. Specifically, SWCNTs, MWCNTs, GO, or rGO are preferred from the perspectives of dispersibility and cost-effectiveness. The conductive metal may be metal nanoparticles, metal wires or metal sheets containing silver, copper, silver-plated copper, molybdenum, zinc, tungsten, nickel, iron, palladium, platinum, tin, lead, titanium or a mixture thereof. The conductive metal oxide may include ZnO or SnO 2, etc. In one embodiment, the dianhydride monomer may be an aromatic tetracarboxylic dianhydride. For example, the dianhydride monomer may include at least one compound represented by the following Chemical Formula 1. [Chemical Formula 1] In the above chemical formula 1, is a tetravalent aliphatic cyclic group, a tetravalent heteroaliphatic cyclic group, a tetravalent aromatic cyclic group or a tetravalent heteroaromatic cyclic group, and the carbon atom of the carbonyl group in Chemical Formula 1 is connected to an atom constituting a ring of the above-mentioned aliphatic cyclic group, heteroaliphatic cyclic group, aromatic cyclic group or heteroaromatic cyclic group, The aliphatic cyclic group, the heteroaliphatic cyclic group, the aromatic cyclic group, or the heteroaromatic cyclic group is a monocyclic ring; or a condensed ring; or is connected by a linking group comprising at least one divalent substituent selected from the group consisting of a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylidene group, a substituted or unsubstituted alkenylene group, a substituted or unsubstituted alkynylene group, a substituted or unsubstituted arylene group, -O-, -S-, -C(=O)-, -S(=O)2-, and -Si(Rb)2-, wherein Rb is hydrogen or an alkyl group. Preferably, the above X is 、 or aliphatic cyclic groups, The M is at least one selected from the group consisting of a single bond, an alkylene group, an alkylidene group, O, S, C(=O) and S(=O) 2. In this specification, unless otherwise specified, the term "aliphatic cyclic group" may refer to an aliphatic cyclic group having 3 to 30 carbon atoms, 4 to 25 carbon atoms, 5 to 20 carbon atoms, and 6 to 16 carbon atoms. For example, specific examples of the tetravalent aliphatic cyclic group include groups obtained by removing four hydrogen atoms from a ring such as a cyclohexane ring, a cycloheptane ring, a cyclodecane ring, a cyclododecane ring, a norbornane ring, an isobornane ring, an adamantane ring, and a bicyclopentane ring. In this specification, unless otherwise specified, the term "aromatic ring group" may refer to an aromatic ring group having 4 to 30 carbon atoms, 5 to 25 carbon atoms, 6 to 20 carbon atoms, and 6 to 16 carbon atoms. The above aromatic ring group may be a monocyclic ring or a condensed ring. For example, examples of tetravalent aromatic hydrocarbon ring groups include groups obtained by removing four hydrogen atoms from a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, or a pyrene ring. In the present specification, the term "arylene group" may refer to a divalent organic group derived from the above-mentioned aromatic ring group. In the present specification, the term "heterocyclic group" includes a heteroaliphatic ring group and a heteroaromatic ring group. As used herein, the term "heteroaliphatic cyclic group" may refer to a cyclic group in which at least one carbon atom of the above-mentioned aliphatic cyclic group is substituted with at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and phosphorus. In this specification, unless otherwise specified, the term "heteroaromatic ring group" may refer to a ring group in which at least one carbon atom in the aromatic ring group is substituted with at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur, and phosphorus. The heteroaromatic ring group may be a monocyclic ring or a condensed ring. The above-mentioned aliphatic cyclic group, the above-mentioned heteroaliphatic cyclic group, the above-mentioned aromatic cyclic group or the above-mentioned heteroaromatic cyclic group may be substituted by at least one substituent selected from the group consisting of halogen, hydroxyl, carboxyl, alkyl having 1 to 4 carbon atoms which may be substituted or unsubstituted by halogen, and alkoxy having 1 to 4 carbon atoms. In this specification, the term "fused ring" refers to a ring formed by two or more cyclic groups bonded together to share two or more atoms, and refers to two or more aromatic rings joined or connected to form a polycyclic ring system. For example, a fused ring refers to a fused aliphatic ring, a fused aromatic ring, a fused heteroaliphatic ring, a fused heteroaromatic ring, or a combination thereof. In this specification, the term "single bond" may refer to a bond connecting two atoms in the absence of any atoms. For example, if X in the above chemical formula 1 is , where M is a single bond, then the two aromatic rings can be directly connected to each other. In this specification, unless otherwise specified, the term "alkyl" may refer to an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The above-mentioned alkyl group may have a linear, branched, or cyclic structure and may be optionally substituted with one or more substituents. For example, the above-mentioned substituents may be polar functional groups such as at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether groups. In this specification, unless otherwise specified, the term "alkenyl" may refer to an alkenyl group having 2 to 30 carbon atoms, 2 to 25 carbon atoms, 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, or 2 to 4 carbon atoms. Such alkenyl groups may have a linear, branched, or cyclic structure and may be optionally substituted with one or more substituents. For example, such substituents may be polar functional groups such as at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether groups. In this specification, unless otherwise specified, the term "alkynyl" may refer to an alkynyl group having 2 to 30 carbon atoms, 2 to 25 carbon atoms, 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 8 carbon atoms, or 2 to 4 carbon atoms. The alkynyl group may have a linear, branched, or cyclic structure and may be optionally substituted with one or more substituents. For example, the substituent may be a polar functional group such as at least one substituent selected from the group consisting of a halogen, a hydroxyl group, an alkoxy group, a thiol group, or a thiol ether group. In this specification, unless otherwise specified, the term "alkylene" may refer to an alkylene group having 2 to 30 carbon atoms, 2 to 25 carbon atoms, 2 to 20 carbon atoms, 2 to 16 carbon atoms, 2 to 12 carbon atoms, 2 to 10 carbon atoms, or 2 to 8 carbon atoms. The above-mentioned alkylene group is a divalent organic group obtained by removing two hydrogen atoms from different carbon atoms. It may have a linear, branched, or cyclic structure and may be optionally substituted with one or more substituents. For example, the above-mentioned substituents may be polar functional groups such as at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether groups. In this specification, unless otherwise specified, the term "alkylidene group" may refer to an alkylidene group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, or 1 to 8 carbon atoms. The alkylidene group is a divalent organic group obtained by removing two hydrogen atoms from a carbon atom. It may have a linear, branched, or cyclic structure and may be optionally substituted with one or more substituents. For example, the substituent may be a polar functional group such as at least one substituent selected from the group consisting of a halogen, a hydroxyl group, an alkoxy group, a thiol group, or a thiol ether group. In this specification, unless otherwise specified, the term "alkoxy" may refer to an alkoxy group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkoxy group may include an alkyl group having a linear, branched, or cyclic structure, and the alkyl group may be optionally substituted with one or more substituents. For example, the substituent may be at least one substituent selected from the group consisting of a halogen, a hydroxyl group, an alkoxy group, a thiol group, or a thiol ether group. In this specification, unless otherwise specified, the term "alkylamine" includes monoalkylamine (-NHR) or dialkylamine (-NR 2), wherein R can each independently refer to an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The above-mentioned alkyl group may include an alkyl group having a linear, branched, or cyclic structure, and may be optionally substituted with one or more substituents. For example, the above-mentioned substituent may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether. In this specification, unless otherwise specified, the term "alkylamide" includes monoalkylamide (-C(O)NHR) or dialkylamide (-C(O)NR2), where R can each independently represent an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkyl group may include an alkyl group having a linear, branched, or cyclic structure, and may be optionally substituted with one or more substituents. For example, the substituent may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether. In this specification, unless otherwise specified, the term "thiol ether group" or "sulfide" may refer to -SR, where R may each independently be an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkyl group may include a linear, branched, or cyclic alkyl group, and may be optionally substituted with one or more substituents. For example, the substituent may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether. In this specification, unless otherwise specified, the term "sulfuryl" may refer to -S(O)R, where R may each independently be an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkyl group may include a linear, branched, or cyclic alkyl group, and may optionally be substituted with one or more substituents. For example, the substituent may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether. In this specification, unless otherwise specified, the term "carbonyl" may include -C(O)R, where R may each independently refer to an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkyl group may include an alkyl group having a linear, branched, or cyclic structure, and may be optionally substituted with one or more substituents. For example, the substituent may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether. In this specification, unless otherwise specified, the term "ester" may include -C(O)OR or -OC(O)R, where R may each independently represent an alkyl group having 1 to 30 carbon atoms, 1 to 25 carbon atoms, 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms. The alkyl group may include a linear, branched, or cyclic alkyl group, and may optionally be substituted with one or more substituents. For example, the substituent may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol, or thiol ether. Examples of the aliphatic tetracarboxylic dianhydride satisfying the above Chemical Formula 1 may include 1,2,4,5-cyclohexanetetracarboxylic dianhydride (or HPMDA), bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride 2:3,5:6-dianhydride (BODA), 1,2,3,4-cyclohexanetetracarboxylic dianhydride (CHMDA), bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride 2:3,5:6-dianhydride (BHDA), butane-1,2,3,4-tetracarboxylic dianhydride (BTD), bicyclo-[2.2.2]oct-7-ene-2-exo,3-exo,5-exo,6-exo-2,3,5:6 -dianhydride (BTA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), bicyclo[4.2.0]octane-3,4,7,8-tetracarboxylic dianhydride (OTD), norbornane-2-spiro-α-cyclohexanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (ChODA), cyclopentanone bis-spiro norbornane tetracarboxylic dianhydride (CpODA), bicyclo[2.2.1]heptane-2,3,5-tricarboxylic-5-acetic dianhydride (BSDA), dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride (DCDA), dicyclohexyl-2,3'3,4'-tetracarboxylic dianhydride anhydride (HBPDA), 5,5'-oxybis(hexahydro-1,3-isobenzofurandione) (HOPDA), 5,5'-methylenebis(hexahydro-1,3-isobenzofurandione) (HMDPA), 3,3'-(1,4-piperazinediyl)bis[dihydro-2,5-furandione] (PDSA), 5-(2,5-dioxotetrahydrofurfuryl)-3-methyl-3-cyclohexane-1,2-dicarboxylic anhydride (DOCDA), 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride (TDA), 3,4-dicarboxy-1,2,3,4-tetrahydro-6-methyl-1-naphthalene butyric acid dianhydride (TDA), dianhydride (MTDA), 3,4-dicarboxy-1,2,3,4-tetrahydro-6-fluoro-1-naphthosuccinic dianhydride (FTDA), 3,3,3',3'-tetramethyl-1,1'-spirobiindane-5,5',6,6'-tetracarboxylic anhydride (SBIDA), 4,4,4',4'-tetramethyl-3,3',4,4'-tetrahydro-2,2'-spirobis[furan[3,4-g]chromene]-6,6',8,8'-tetraone (SBCDA) and 9,10-difluoro-9,10-bis(trifluoromethyl)-9,10-dihydroanthracene-2,3,6,7-tetracarboxylic dianhydride (6FDA), etc. Examples of the aromatic tetracarboxylic dianhydride satisfying the above Chemical Formula 1 may include pyromellitic dianhydride (or PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (or BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (or a-BPDA), oxyphthalic dianhydride (or OPDA), diphenylsulfonium-3,4,3',4'-tetracarboxylic dianhydride (or DSDA), bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (or BTDA), bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2 -Bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylenebis(trimellitic acid monoester anhydride), p-biphenylenebis(trimellitic acid monoester anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride or 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride (6-FDA), etc. The compound represented by the above Chemical Formula 1 is preferably an aromatic tetracarboxylic dianhydride, and in particular, the dianhydride may include pyromellitic dianhydride (or PMDA), oxyphthalic dianhydride (or OPDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (or BPDA) or 2,3,3',4'-biphenyltetracarboxylic dianhydride (or a-BPDA). As an example, the diamine monomer may include at least one compound represented by the following Chemical Formula 2. [Chemical Formula 2] In the above Chemical Formula 2, at least one of B1 to B5 is an amino group (-NH2), -R-NH2 or -OR-NH2, the above R is a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkylidene group, a substituted or unsubstituted alkenylene group, a substituted or unsubstituted alkynylene group, or a substituted or unsubstituted arylene group, and the rest are hydrogen; halogen; hydroxyl; carboxyl; or a halogen-substituted or unsubstituted alkyl group. In addition, the diamine monomers that can be used to prepare the polyamine solution are aromatic diamines, which can be classified and exemplified as follows. 1) Diamines having a benzene nucleus in their structure, such as 1,4-diaminobenzene (or p-phenylenediamine, PPD), 1,3-diaminobenzene, 2,4-diaminotoluene, 2,6-diaminotoluene or 3,5-diaminobenzoic acid (or DABA), have a relatively rigid structure; 2) Such as 4,4'-diaminodiphenyl ether (or oxydiphenylamine, ODA) and 3,4'-diaminodiphenyl ether, 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'-diamino 4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, bis(4-aminophenyl) sulfide, 4,4'-diaminobenzanilide, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine (or o-benzidine), 2,2'-dimethylbenzidine (or m-toluidine), 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether Phenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diamino-4,4'-dichlorobenzophenone, 3,3'-diamino-4,4'-dimethoxybenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diamino diamines having two benzene nuclei in their structure, such as 2,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane or 4,4'-diaminodiphenylmethane; 3) Such as 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, 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'- Diamines having three benzene nuclei in their structure, such as bis(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenyl sulfide)benzene, 1,3-bis(4-aminophenyl sulfide)benzene, 1,4-bis(4-aminophenyl sulfide)benzene, 1,3-bis(3-aminophenylsulfonate)benzene, 1,3-bis(4-aminophenylsulfonate)benzene, 1,4-bis(4-aminophenylsulfonate)benzene, 1,3-bis[2-(4-aminophenylsulfonate)benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, or 1,4-bis[2-(4-aminophenyl)isopropyl]benzene; 4) Such as 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] ketone, bis[4-(3-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]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[3-(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[3-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfide, -(4-aminophenoxy)phenyl]methane, 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, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]methane A diamine having four benzene nuclei in its structure, such as 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-hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane or 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane. As needed, the above-mentioned diamine monomers can be used alone or in combination of two or more, for example, 4,4'-diaminodiphenyl ether (or oxydiphenylamine, ODA), 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene or 4,4'-methylenediamine (MDA). Preferably, the compound represented by the above chemical formula 2 can be 4,4'-diaminodiphenyl ether (or oxydiphenylamine, ODA). The present application relates to a polyimide powder, which can be obtained by imidizing polyimide during the thermal curing process of the polyimide varnish and precipitating the polyimide in powder form. Therefore, the polyimide powder is in the form of particles containing the cured product (or thermoset product) of the polyimide varnish. For example, the polyimide powder described above may contain a conductive filler dispersed within the particles. Since the conductive filler is added during the polyamide polymerization step, the conductive filler can be dispersed within the particles of the polyimide powder according to the present invention. On the other hand, conventional dry mixing of polyimide powder and conductive filler can lead to reduced formability and processability due to the conductive filler tending to certain areas during mixing or clumping, making it difficult to evenly disperse. The present application also relates to polyimide molded articles comprising the polyimide powder. These molded articles can be prepared using the polyimide powder using various molding methods. Examples of these molding methods include compression molding, injection molding, slurry molding, hollow molding, extrusion molding, or spinning methods, and examples of these molded articles include plates, rods, films, sheets, pellets, strips, or tubes. The molded product is made from polyimide powder with conductive filler uniformly dispersed within the particles, so various physical properties can be controlled within the following numerical ranges. The surface resistance of the polyimide molded article according to the present application measured according to ASTM D257 method may be 1.0×10 2Ω to 1.0×10 13Ω, for example, 1.0×10 3Ω to 1.0×10 13Ω, 1.0×10 4Ω to 1.0×10 13Ω, 1.0×10 5Ω to 1.0×10 13Ω, 1.0×10 6Ω to 1.0×10 13Ω, 1.0×10 7Ω to 1.0×10 13Ω, 1.0×10 8Ω to 1.0×10 13Ω, 1.0×10 9Ω to 1.0×10 13Ω, 1.0×10 10Ω to 1.0×10 13Ω, 1.0×10 11Ω to 1.0×10 13Ω, 1.5×10 3Ω to 1.0×10 13Ω, 1.5×10 4Ω to 1.0×10 13Ω, 1.5×10 5Ω to 1.0×10 13Ω, 1.5×10 6Ω to 1.0×10 13Ω, 1.5×10 7Ω to 1.0×10 13Ω, 1.5×10 8Ω to 1.0×10 13Ω, 1.5×10 9Ω to 1.0×10 13Ω, 1.5×10 10Ω to 1.0×10 13Ω, 1.5×10 11Ω to 1.0×10 13Ω, 1.0×10 3Ω to 2.0×10 12Ω, 1.0×10 4Ω to 2.0×10 12Ω, 1.0×10 5Ω to 2.0×10 12Ω, 1.0×10 6Ω to 2.0×10 12Ω, 1.0×10 7Ω to 2.0×10 12Ω, 1.0×10 8Ω to 2.0×10 12Ω, 1.0×10 9Ω to 2.0×10 12Ω, 1.0×10 10Ω to 2.0×10 12Ω, 1.0×10 11Ω to 2.0×10 12Ω, 1.5×10 3Ω to 2.0×10 12Ω, 1.5×10 4Ω to 2.0×10 12Ω, 1.5×10 5Ω to 2.0×10 12Ω, 1.5×10 6Ω to 2.0×10 12Ω, 1.5×10 7Ω to 2.0×10 12Ω, 1.5×10 8Ω to 2.0×10 12Ω, 1.5×10 9Ω to 2.0×10 12Ω, 1.5×10 10Ω to 2.0×10 12Ω, or 1.5×10 11Ω to 2.0×10 12Ω. The surface resistance can be measured according to ASTM D-257 using Advanced Energy / Trek 152-1. Specifically, the measurement conditions are 23±3°C and a source voltage of 10V. When the molded article according to the present invention has a surface resistance within the above range, it can exhibit excellent conductivity, moldability, and processability. In one embodiment, the polyimide molded article may have an elongation of 3% or greater, 4% or greater, 5% or greater, 6% or greater, 7% or greater, 8% or greater, 9% or greater, or 10% or greater, as measured by ASTM D-1708. The upper limit is not particularly limited, but may be 50% or less, 40% or less, 30% or less, or 20% or less. The polyimide molded article may have a tensile strength as measured according to ASTM D-1708 of 65 MPa or greater, 68 MPa or greater, 70 MPa or greater, 72 MPa or greater, 74 MPa or greater, 76 MPa or greater, 78 MPa or greater, 80 MPa or greater, 85 MPa or greater, 90 MPa or greater, 100 MPa or greater, 150 MPa or greater, 200 MPa or greater, 250 MPa or greater, 300 MPa or greater, 350 MPa or greater, 400 MPa or greater, or 450 MPa or greater. The upper limit is not particularly limited, but may be 1000 MPa or less, 900 MPa or less, 800 MPa or less, 700 MPa or less, 600 MPa or less, or 500 MPa or less. The above elongation and tensile strength can be measured by HCM molding polyimide powder, which is then processed into a dog-bone shape with a length of 38 mm and a width of 15 mm, using Instron UTM equipment from Instron Corporation using the ASTM D-1708 method. The present application also relates to a method for preparing a polyamide varnish. The method comprises: dispersing a conductive filler in an organic solvent; and polymerizing a diamine monomer and a dianhydride monomer in the organic solvent containing the conductive filler. The polyamide varnish prepared by the method, due to the addition of the conductive filler during the polymerization step, can provide a polyimide powder with the conductive filler dispersed within the particles during thermal curing. The polymerization step is a step of polymerizing the dianhydride monomer and the diamine monomer by heating. The heating temperature in the polymerization step can be 30°C to 100°C, for example, 40°C to 100°C, 50°C to 90°C, or 60°C to 80°C. In the polymerization step, the reaction time may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours. In one embodiment, the dispersion can be performed by ultrasonic treatment. The ultrasonic treatment can be performed for more than 30 minutes using a VCX750 manufactured by Sonics & Materials, Inc., but is not particularly limited thereto, and the specific conditions may vary depending on the type of solvent and conductive filler. Since the detailed description of the composition of the above-mentioned polyamide varnish overlaps with the above-mentioned content, the detailed description will be omitted below. The present application relates to a method for preparing polyimide powder. The preparation method comprises: a step of dispersing a conductive filler in an organic solvent; a step of polymerizing a diamine monomer and a dianhydride monomer in the organic solvent in which the conductive filler is dispersed; and a step of thermally curing the polymer generated in the polymerization step to obtain a polyimide powder. The polymerization step is a step for preparing polyamide having dianhydride monomers and diamine monomers as polymerized units, and the polymer prepared in the polymerization step can be polyamide. In the polymerization step, the polymerization temperature can be 30°C to 100°C, 40°C to 100°C, 50°C to 90°C, or 60°C to 80°C. In the polymerization step, the polymerization time may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours. During the thermal curing process, the polyamic acid is imidized to form polyimide, which reduces its solubility in the solvent and precipitates as a powder. For example, the thermal curing temperature can be 150°C to 300°C, 160°C to 280°C, 170°C to 250°C, or 180°C to 200°C. The curing time of the thermal curing may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours. In the following, descriptions that overlap with the foregoing will be omitted. The present application relates to a method for preparing a polyimide molded product. The method for preparing the above-mentioned molded article includes: a step of dispersing a conductive filler in an organic solvent; a step of polymerizing a diamine monomer and a dianhydride monomer in the organic solvent in which the conductive filler is dispersed; a step of thermally curing the polymer generated in the polymerization step to obtain a polyimide powder; and a step of molding the obtained polyimide powder to prepare a polyimide molded article. The polymerization step is a step for preparing polyamide having dianhydride monomers and diamine monomers as polymerized units, and the polymer prepared in the polymerization step can be polyamide. In the polymerization step, the polymerization temperature can be 30°C to 100°C, 40°C to 100°C, 50°C to 90°C, or 60°C to 80°C. In the polymerization step, the polymerization time may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours. The thermal curing process converts the polyamide imide into polyimide and precipitates it as a powder. For example, the curing temperature can be 150°C to 300°C, 160°C to 280°C, 170°C to 250°C, or 180°C to 200°C. The curing time of the thermal curing may be 1 to 10 hours, for example, 1 to 8 hours, 1 to 6 hours, 1 to 4 hours, or 1 to 3 hours. Examples of the above-mentioned molding may include compression molding, injection molding, slurry molding, hollow molding, extrusion molding or spinning methods, and examples of the above-mentioned molded products may include plates, rods, films, sheets, pellets, belts or tubes, etc. In the following, descriptions that overlap with the foregoing will be omitted. Comparison with the effectiveness of previous technologies The present application provides a polyimide powder having a conductive filler uniformly dispersed in particles, and a polyimide varnish capable of realizing a polyimide molded article made from the above-mentioned powder having excellent moldability and processability, as well as excellent conductivity, tensile strength, elongation and elastic modulus. Implementation Method

[0004] Hereinafter, the present invention will be described in more detail by way of examples of the present invention and comparative examples not of the present invention, but the scope of the present invention is not limited by the following examples. [Example] [1] A Dean-Stark trap was installed in a 1000 ml reactor equipped with a stirrer and nitrogen inlet and outlet tubes. While nitrogen was being injected, 10% by weight of carbon black, a conductive filler, was added to a solvent consisting of a mixture of N-methyl-2-pyrrolidone (NMP) and m-cresol in a weight ratio of 8:2. Ultrasonic treatment was then performed to disperse the conductive filler. The solvent containing the conductive filler was heated to 75°C, and 100 mol parts of 4,4'-diaminodiphenyl ether (ODA) was added and completely dissolved. Next, 80 mol parts of pyromellitic dianhydride (PMDA) were added to 100 mol parts of ODA, and 20 mol parts of oxydiphthalic dianhydride (OPDA) were added to 100 mol parts of ODA. The mixture was reacted at 75°C for 2 hours to prepare a polyamide varnish in which the conductive filler was uniformly dispersed. Then, the temperature of the polyamide varnish was raised to 200°C while stirring, and heated for another 2 hours to precipitate polyimide powder. [Example] [2] [To Example] [6] [] Except for adjusting the monomer components, solvent and conductive filler as shown in Table 1 below, the polyimide powder was precipitated in the same manner as in Example 1. [Comparative Example] [1] [To Comparative Example] [4] [] Except that no conductive filler was used and the monomer composition, solvent and catalyst were adjusted as shown in Table 1 below, the polyimide powder was precipitated in the same manner as in Example 1. Table 1 below describes the mixing method for the conductive filler as follows: "Dispersion mixing" in Examples 1 to 7 refers to a method in which the conductive filler is mixed in a solvent by ultrasonic treatment during the polyamic acid polymerization step as described in Example 1. "Dry mixing" in Comparative Examples 1 to 4 refers to a method in which polyamic acid is polymerized without using a conductive filler, imidized to precipitate polyimide powder, and then mechanically mixed with the precipitated polyimide powder and the conductive filler. [Experimental example] [1-] [Processability] [] [] Samples were produced by forming the polyimide powder HCM molded articles of Examples and Comparative Examples into dog-bone shapes. The samples were visually inspected to determine the presence and number of cracks. Specifically, samples were divided into those with no cracks and those with cracks within a 10 cm x 10 cm area. In the case of cracks, the number of cracks was determined as follows: "few cracks" or "many cracks." O: No cracks △: 1 to 5 cracks (few cracks) X: More than 5 cracks (many cracks) [Experimental example] [2-] [Surface resistance] [] The surface resistivity of the polyimide powder HCM molded articles from Examples and Comparative Examples was measured using an Advanced Energy / Trek 152-1 according to ASTM D-257. The measurement temperature was set at 23±3°C and the source voltage was set at 10V. [Experimental example] [3-] [Elongation and tensile strength measurement] [] [] The polyimide powder HCM of the embodiment and comparative example was molded and then processed into a dog-bone shape with a length of 38 mm and a width of 15 mm, and the elongation and tensile strength were measured using the Instron UTM equipment of Instron Company according to the ASTM D-1708 method.

Claims

1. A method for preparing a polyamide varnish, comprising: The step of dispersing conductive fillers in organic solvents and co-solvents; The method includes a step of polymerizing diamine monomers and dianhydride monomers in an organic solvent and a co-solvent in which the conductive filler is dispersed, wherein the dispersion is performed by ultrasonic treatment, wherein the content of the conductive filler is from 1% to 50% by weight relative to the total amount of polyacrylic acid varnish, wherein the conductive filler comprises carbon black and conductive carbon, or conductive carbon, wherein the conductive carbon comprises single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), graphene, graphene oxide (GO), reduced graphene oxide (rGO), or mixtures thereof. The organic solvent is N,N'-dimethylacetamide (DMAc) or N-methyl-2-pyrrolidone (NMP), and the co-solvent comprises one or more selected from the group consisting of m-cresol, naphtha, hexane, heptane, nonane, decane, benzene, anisole, cyclohexanone, methyl ethyl ketone, tetrahydrofuran, hexamethylphosphatamine, dioxane, tetramethylurea, triethyl phosphate, trimethyl phosphate, dimethylformamide, dimethyl sulfoxide, and dimethylacetamide.

2. The method for preparing polyamide varnish as claimed in claim 1, wherein, The dianhydride monomers include pyromellitic dianhydride (PMDA), oxydiphenyl dianhydride (OPDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), or 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA).

3. The method for preparing polyamide varnish as claimed in claim 1, wherein, The diamine monomers include 4,4'-diaminodiphenyl ether (ODA), 1,4-diaminobenzene (PPD), 1,3-diaminobenzene (MPD), 2,4-diaminotoluene, 2,6-diaminotoluene, or 4,4'-methylenediamine (MDA).