CN117903684A - Polyamic acid varnish - Google Patents

Abstract

The present application provides a polyimide powder in which a conductive filler is uniformly dispersed in particles, and a polyamic acid varnish capable of realizing a polyimide molded article having excellent moldability and processability, and also excellent conductivity, tensile strength, elongation and elastic modulus due to the use of the above powder.

Description

Polyamic acid varnish

Technical Field

The present application relates to a polyamic acid varnish, a polyimide powder, a polyimide molded product, a method for preparing the polyamic acid varnish, a method for preparing the polyimide powder, and a method for preparing the polyimide molded product.

Background technique

Generally speaking, polyimide (PI) is a polymer of imide monomers formed by polymerizing dianhydride with diamine or diisocyanate solution, and has excellent mechanical properties such as strength, chemical resistance, weather resistance, and heat resistance due to the chemical stability of the imide ring. In addition, polyimide has attracted much attention as a high-functional polymer material that can be used in a wide range of industrial fields such as electronics, communications, and optics due to its excellent electrical properties such as insulation properties and low dielectric constant.

In recent years, in the semiconductor field, the demand for conductive polyimide has been increasing due to static electricity problems in production equipment. Conventionally, conductive polyimide powder is prepared by dry mixing powdered polyimide and conductive filler, and then it is appropriately molded and processed according to the application.

However, the problem with dry mixing is that polyimide powder and conductive filler are difficult to mix uniformly, resulting in frequent defects in the molding process, poor processability, and reduced expectations for physical properties such as tensile strength, elongation, and elastic modulus.

Summary of the invention

technical problem

The present application provides a polyimide powder having conductive fillers uniformly dispersed in particles and a polyamic acid varnish capable of realizing a polyimide molded product having excellent moldability and processability as well as excellent conductivity, tensile strength, elongation and elastic modulus due to being made from the above-mentioned powder.

Solutions to the problem

Among the physical properties mentioned in this specification, when measuring physical properties related to the influence of temperature, the above physical properties are physical properties measured at room temperature unless otherwise specified.

In this specification, the term room temperature is a temperature in a state without special heating or cooling, which may mean a temperature in the range of about 10°C to 30°C, for example, a temperature of 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 the present specification, the term normal pressure is a natural pressure without particular pressurization or reduction, and generally means a pressure of about 1 atm, such as atmospheric pressure.

Among the physical properties mentioned herein, when measuring physical properties related to the influence of humidity, unless otherwise specified, the above physical properties are physical properties measured at natural humidity at the above room temperature and normal pressure.

The present application relates to a polyamic acid varnish. The polyamic acid varnish according to the present invention can be a solution in which a polyimide precursor that is imidized into polyimide by thermal curing is dissolved in an organic solvent. The polyamic acid varnish according to the present application is imidized and precipitated in powder form during thermal curing, and the precipitated polyimide powder can be uniformly dispersed with conductive fillers in the particles. The polyimide powder obtained as above not only has excellent formability and processability during molding, but also can produce a polyimide molded product with excellent conductivity, tensile strength, elongation and elastic modulus.

The exemplary polyamic acid varnish according to the present application includes: polyamic acid, the polyamic acid including a diamine monomer and a dianhydride monomer as polymerization units; a conductive filler; and an organic solvent. The polyamic acid 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 polyamic acid varnish according to the present application can provide a polyimide powder in which the conductive filler is dispersed in the particles during heat curing because the conductive filler is added during the polymerization step of the polyamic acid. The polyimide powder can realize a polyimide molded product having not only excellent moldability and processability but also excellent conductivity, tensile strength, elongation and elastic modulus during molding.

The type of the organic solvent may be appropriately selected in consideration of the conductive filler and dispersibility, and as an example, the organic solvent may be an aprotic polar solvent.

For example, examples of the above-mentioned aprotic polar solvent may include: amide solvents such as N,N'-dimethylformamide (DMF), N,N'-diethylformamide (DEF), N,N'-dimethylacetamide (DMAc) or dimethylpropionamide (DMPA); phenol solvents such as p-chlorophenol, o-chlorophenol, etc.; N-methyl-pyrrolidone (NMP); γ-butyrolactone (GBL) or diethylene glycol dimethyl ether (Diglyme), etc., which can be used alone or in combination of two or more. Considering the dispersibility of the conductive filler, as the above-mentioned organic solvent, N,N'-dimethylacetamide (DMAc) or N-methyl-pyrrolidone (NMP) can be preferably used.

The method of dispersing the conductive filler in the organic solvent is not particularly limited, but in view of uniform dispersibility, ultrasonic treatment (sonication) may be preferably used. For example, the ultrasonic treatment may be performed for more than 30 minutes using VCX750 of Sonics & Materials, Inc., but is not particularly limited, and the specific conditions may vary depending on the type of solvent and conductive filler.

In addition, polyamic acid varnish according to the present invention may also include cosolvent to improve reaction efficiency.Above-mentioned cosolvent may include at least one selected from the group consisting of meta-cresol, naphtha (Naphtha), hexane, heptane, nonane, decane, benzene, toluene, dimethylbenzene, anisole, cyclohexanone, methyl ethyl ketone, tetrahydrofuran (THF), N-Methyl pyrrolidone, hexamethylphosphoramide, dioxane, tetramethylurea, triethyl phosphate, trimethyl phosphate, dimethyl formamide, dimethyl sulfoxide 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 polyamic acid varnish. For example, the content of the above-mentioned conductive filler relative to the total amount of the polyamic acid varnish can be 1 wt % to 45 wt %, 1 wt % to 40 wt %, 1 wt % to 35 wt %, 1 wt % to 30 wt %, 1 wt % to 25 wt %, 1 wt % to 20 wt %, 1 wt % to 15 wt %, 1 wt % to 10 wt %, 3 wt % to 50 wt %, 3 wt % to 45 wt %, 3 wt % to 40 wt %, 3 wt % to 35 wt %, 3 wt % to 30 wt %, 3 wt % to 25 wt %, 3 wt % to 20 wt %, 3 wt % to 15 wt %, 3 wt % to 10 wt %, 5 wt % to 50 wt %, 5 wt % to 45 wt %, 5 wt % to 40 wt %, 5 wt % to 35 wt %, 5 wt % to 30 wt %, 5 wt % to 25 wt %, 5 wt % to 20 wt %, 5 wt % to 15 wt %, or 5 wt % to 10 wt %.

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 nanotube (SWCNT), multi-walled carbon nanotube (MWCNT), graphene, graphene oxide (GO), reduced graphene oxide (rGO) or a mixture thereof. Specifically, SWCNT, MWCNT, GO or rGO is preferably used from the viewpoint of dispersibility and economy.

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 above-mentioned 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 ring group, a tetravalent heteroaliphatic ring group, a tetravalent aromatic ring group or a tetravalent heteroaromatic ring group, and the carbon atom of the carbonyl group in Chemical Formula 1 is connected to an atom constituting a ring of the above aliphatic ring group, heteroaliphatic ring group, aromatic ring group or heteroaromatic ring 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 connecting group including 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 an aliphatic cyclic group,

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 the present specification, unless otherwise specifically 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 4 hydrogen atoms from a ring of a cyclohexane ring, a cycloheptane ring, a cyclodecane ring, a cyclododecane ring, a norbornane ring, an isobornane ring, an adamantane ring, a bicyclopentane ring, and the like.

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 4 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 of the carbon atoms 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 the present specification, unless otherwise specified, the term "heteroaromatic ring group" may refer to a ring group in which at least one of the carbon atoms of the above aromatic ring group is substituted by at least one heteroatom selected from the group consisting of nitrogen, oxygen, sulfur and phosphorus. The above 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, halogen-substituted or unsubstituted alkyl having 1 to 4 carbon atoms and alkoxy having 1 to 4 carbon atoms, respectively.

In this specification, the term "fused ring" means a ring formed by two or more cyclic groups bonding in a manner of sharing two or more atoms, and means that two or more aromatic rings are bonded or connected to each other to form a polycyclic system. For example, the 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 without any atoms. For example, if X in the above chemical formula 1 is Wherein, M is a single bond, and 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 straight chain, a branched chain or a cyclic structure, and may be optionally substituted by one or more substituents. For example, the above-mentioned substituent may be a polar functional group such as 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 "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. The alkenyl group may have a straight chain, a branched chain or a 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 halogen, hydroxyl, alkoxy, thiol or thiol ether groups.

In this specification, unless otherwise specified, the term "alkynyl" may refer to an alkynyl 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 may have a straight chain, a branched chain or a 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 halogen, hydroxyl, alkoxy, thiol or thiol ether.

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 from which two hydrogen atoms are removed from different carbon atoms, and may have a straight chain, a branched chain or a cyclic structure, and may be optionally substituted with one or more substituents. For example, the above-mentioned substituent may be a polar functional group such as 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 "alkylidene" may refer to an alkylidene 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 above-mentioned alkylidene is a divalent organic group from which two hydrogen atoms are removed from a carbon atom, and may have a straight chain, a branched chain or a cyclic structure, and may be optionally substituted with one or more substituents. For example, the above-mentioned substituent may be a polar functional group such as 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 "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 above-mentioned alkoxy group may include an alkyl group having a straight chain, a branched chain or a cyclic structure, and the above-mentioned alkyl group may be optionally substituted with one or more substituents. For example, the above-mentioned substituent group may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol or thiol ether groups, etc.

In this specification, unless otherwise specified, the term "alkylamine" includes monoalkylamine (-NHR) or dialkylamine (-NR ₂ ), wherein 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 straight chain, a branched chain or a 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 "alkylamide" includes monoalkylamide (-C(O)NHR) or dialkylamide (-C(O)NR ₂ ), wherein 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 "thiol ether group" or "sulfide" may refer to -SR, wherein 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. Wherein, the above-mentioned alkyl group may include an alkyl group having a straight chain, a branched chain or a 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 "sulfoxide" may refer to -S(O)R, wherein 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. Wherein, the above-mentioned alkyl group may include an alkyl group having a straight chain, a branched chain or a cyclic structure, and may be optionally substituted with one or more substituents. For example, the above-mentioned substituent group may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol or thiol ether groups, etc.

In this specification, unless otherwise specified, the term "carbonyl" may include -C(O)R, wherein 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. Wherein, the above-mentioned alkyl group may include an alkyl group having a straight chain, a branched chain or a cyclic structure, and may be optionally substituted with one or more substituents. For example, the above-mentioned substituent group may be at least one substituent selected from the group consisting of halogen, hydroxyl, alkoxy, thiol or thiol ether groups, etc.

In this specification, unless otherwise specified, the term "ester" may include -C(O)OR or -OC(O)R, wherein 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 straight chain, a branched chain or a 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.

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-2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride (2,3,5,6-tetracarboxylic dianhydride ( -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 dicarboxylic acid dianhydride (MTDA), 3,4-dicarboxy-1,2,3,4-tetrahydro-6-fluoro-1-naphthalene succinic acid dianhydride (FTDA), 3,3,3',3'-tetramethyl-1,1'-spirobiindane-5,5',6,6'-tetracarboxylic acid anhydride (SBIDA), 4,4,4',4'-tetramethyl-3,3',4,4'-tetrahydro-2,2'-spirobi[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 acid 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), diphenyl sulfone-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 acid dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic acid 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 acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride or 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid 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 amino ( _-NH2 ), -R- _NH2 or -OR- _NH2 , the above R is substituted or unsubstituted alkylene, substituted or unsubstituted alkylidene, substituted or unsubstituted alkenylene, substituted or unsubstituted alkynylene, or substituted or unsubstituted arylene, and the rest are hydrogen; halogen; hydroxyl; carboxyl; or halogen-substituted or unsubstituted alkyl.

In addition, the diamine monomer that can be used to prepare the polyamic acid solution is an aromatic diamine, which can be classified and exemplified as follows.

1) A diamine having a benzene nucleus in the 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), has a relatively rigid structure;

2) Diaminodiphenyl ethers 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 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 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'-diamino diamines having two benzene nuclei in the structure, such as 2,4'-diaminodiphenylmethane, 4,4'-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'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide or 4,4'-diaminodiphenyl sulfoxide;

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'- A diamine having three benzene nuclei in its structure, such as bis(4-phenylphenoxy)benzophenone, 1,3-bis(3-aminophenylene sulfide)benzene, 1,3-bis(4-aminophenylene sulfide)benzene, 1,4-bis(4-aminophenylene sulfide)benzene, 1,3-bis(3-aminophenyl sulfone)benzene, 1,3-bis(4-aminophenyl sulfone)benzene, 1,4-bis(4-aminophenyl sulfone)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]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] sulfone, bis[3-(4-aminophenoxy)phenyl] sulfone, bis[4-(3-aminophenoxy)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, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl] 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 required, the above 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 polyamic acid and precipitating it in powder form during the thermal curing process of the polyamic acid varnish.

Therefore, the polyimide powder is in a particle form containing a cured product (or a thermosetting product) of the polyamic acid varnish.

For example, the polyimide powder may have a conductive filler dispersed in the particles. The polyimide powder according to the present invention may have a conductive filler dispersed in the particles because the conductive filler is added in the polymerization step of the polyamic acid. On the other hand, the existing dry mixing of polyimide powder and conductive filler may reduce the moldability and processability because the conductive filler is biased to some areas during the mixing process or the conductive filler agglomerates and is difficult to be evenly dispersed.

The present application also relates to a polyimide molded article comprising the above-mentioned polyimide powder. The above-mentioned molded article can be prepared by various molding methods using the above-mentioned polyimide powder. Examples of the above-mentioned molding method may include compression molding, injection molding, slurry molding, hollow molding, extrusion molding or spinning method, etc., and examples of the above-mentioned molded article may include plates, rods, films, sheets, pellets, strips or tubes, etc.

The above-mentioned molded product is prepared from polyimide powder in which conductive fillers are 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 ² Ω to 1.0×10 ¹³ Ω, for example, 1.0×10 ³ Ω to 1.0×10 ¹³ Ω, 1.0×10 ⁴ Ω to 1.0×10 ¹³ Ω, 1.0×10 ⁵ Ω to 1.0×10 ¹³ Ω, 1.0×10 ⁶ Ω to 1.0×10 ¹³ Ω, 1.0×10 ⁷ Ω to 1.0×10 ¹³ Ω, 1.0×10 ⁸ Ω to 1.0×10 ¹³ Ω, 1.0×10 ⁹ Ω to 1.0×10 ¹³ Ω, 1.0×10 ¹⁰ Ω to 1.0×10 ¹³ Ω, 1.0×10 ¹¹ Ω to 1.0×10 13 Ω ¹³ Ω, 1.5×10 ³ Ω to 1.0×10 ¹³ Ω, 1.5×10 ⁴ Ω to 1.0×10 ¹³ Ω, 1.5×10 ⁵ Ω to 1.0×10 ¹³ Ω, 1.5×10 ⁶ Ω to 1.0×10 ¹³ Ω, 1.5×10 ⁷ Ω to 1.0×10 ¹³ Ω, 1.5×10 ⁸ Ω to 1.0×10 ¹³ Ω, 1.5×10 ⁹ Ω to 1.0×10 ¹³ Ω, 1.5×10 ¹⁰ Ω to 1.0×10 ¹³ Ω, 1.5×10 ¹¹ Ω to 1.0×10 ¹³ Ω, 1.0×10 ³ Ω to 2.0×10 ¹² Ω, 1.0×10 ⁴ Ω to 2.0×10 ¹² Ω, 1.0×10 ⁵ Ω to 2.0×10 ¹² Ω, 1.0×10 ⁶ Ω to 2.0×10 ¹² Ω, 1.0×10 ⁷ Ω to 2.0×10 ¹² Ω, 1.0×10 ⁸ Ω to 2.0×10 ¹² Ω, 1.0×10 ⁹ Ω to 2.0×10 ¹² Ω, 1.0×10 ¹⁰ Ω to 2.0×10 ¹² Ω, 1.0×10 ¹¹ Ω to 2.0×10 ¹² Ω, 1.5×10 ³ Ω to 2.0×10 ¹² Ω, 1.5×10 ⁴ Ω to 2.0×10 ¹² Ω, 1.5×10 ⁵ Ω to 2.0×10 ¹² 10 Ω, 1.5×10 ⁶ Ω to 2.0×10 ¹² Ω, 1.5×10 ⁷ Ω to 2.0×10 ¹² Ω, 1.5×10 ⁸ Ω to 2.0×10 ¹² Ω, 1.5×10 ⁹ Ω to 2.0×10 ¹² Ω, 1.5×10 ¹⁰ Ω to 2.0×10 ¹² Ω, or 1.5×10 ¹¹ Ω to 2.0×10 ¹² Ω. The surface resistance can be measured using Advanced Energy/Trek152-1 according to ASTM D-257 method, and as its specific measurement conditions, it can be measured at 23±3°C and a source voltage of 10 V. 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 elongation of the polyimide molded article measured according to the ASTM D-1708 method may be 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, or 10% or more. The upper limit is not particularly limited, but may be 50% or less, 40% or less, 30% or less, or 20% or less.

In addition, the tensile strength of the polyimide molded article measured according to the ASTM D-1708 method may be 65 MPa or more, 68 MPa or more, 70 MPa or more, 72 MPa or more, 74 MPa or more, 76 MPa or more, 78 MPa or more, 80 MPa or more, 85 MPa or more, 90 MPa or more, 100 MPa or more, 150 MPa or more, 200 MPa or more, 250 MPa or more, 300 MPa or more, 350 MPa or more, 400 MPa or more, or 450 MPa or more. 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, and using an Instron UTM device from Instron Company using the ASTM D-1708 method.

The present application also relates to a method for preparing a polyamic acid 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 in which the conductive filler is dispersed. The polyamic acid varnish prepared by the preparation method can provide a polyimide powder in which the conductive filler is dispersed in particles when thermally cured because the conductive filler is added in the polymerization step.

The polymerization step is a step of polymerizing the dianhydride monomer and the diamine monomer by heating. The heating temperature in the polymerization step may be 30° C. to 100° C., for example, the heating temperature in the polymerization step may be 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 example, the dispersion may be performed by ultrasonic treatment. The ultrasonic treatment may be performed for more than 30 minutes using 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 about the composition of the above-mentioned polyamic acid varnish overlaps with the above-mentioned contents, the detailed description will be omitted below.

The present application relates to a method for preparing polyimide powder.

The preparation method comprises: dispersing a conductive filler in an organic solvent; polymerizing a diamine monomer and a dianhydride monomer in the organic solvent in which the conductive filler is dispersed; and thermally curing the polymer generated in the polymerization step to obtain a polyimide powder.

The above-mentioned polymerization step is a step of preparing a polyamic acid having a dianhydride monomer and a diamine monomer as polymerization units, and the polymer prepared in the polymerization step may be a polyamic acid. In the above-mentioned polymerization step, the polymerization temperature may 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, the polyamic acid is imidized to form polyimide, and its solubility in the solvent is reduced, so it can be precipitated in the form of powder. For example, the curing temperature of the thermal curing 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 hour to 10 hours, for example, 1 hour to 8 hours, 1 hour to 6 hours, 1 hour to 4 hours, or 1 hour to 3 hours.

Hereinafter, descriptions overlapping 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 product 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 product.

The above-mentioned polymerization step is a step of preparing a polyamic acid having a dianhydride monomer and a diamine monomer as polymerization units, and the polymer prepared in the polymerization step may be a polyamic acid. In the above-mentioned polymerization step, the polymerization temperature may 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 is a process of imidizing the polyamic acid into polyimide and precipitating it in the form of powder. For example, the curing temperature of the thermal curing 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 hour to 10 hours, for example, 1 hour to 8 hours, 1 hour to 6 hours, 1 hour to 4 hours, or 1 hour to 3 hours.

Examples of the above-mentioned molding may include compression molding, injection molding, slurry molding, hollow molding, extrusion molding or spinning method, and examples of the above-mentioned molded products may include plates, rods, films, sheets, pellets, belts or tubes, and the like.

Hereinafter, descriptions overlapping with the foregoing will be omitted.

Effects of the Invention

The present application provides a polyimide powder having conductive fillers uniformly dispersed in particles and a polyamic acid varnish capable of realizing a polyimide molded product having excellent moldability and processability as well as excellent conductivity, tensile strength, elongation and elastic modulus due to being made from the above-mentioned powder.

Detailed ways

Hereinafter, the present invention will be described in more detail by referring to the examples of the present invention and comparative examples not related to the present invention. However, the scope of the present invention is not limited to the following examples.

Example 1

A Dean-Stark water separator is set in a 1000ml reactor with an agitator and a nitrogen injection and discharge pipe. While injecting nitrogen, 10% by weight of carbon black as a conductive filler is added to the total amount of the polyamic acid varnish in a solvent mixed with N-methyl-2-pyrrolidone (NMP) and meta-cresol in a weight ratio of 8:2, and ultrasonic treatment is performed to disperse the conductive filler. The solvent dispersed with the conductive filler is heated to 75°C, and then 100 molar parts of 4,4'-diaminodiphenyl ether (ODA) is added and completely dissolved. Then, 80 molar parts of pyromellitic anhydride (PMDA) are added to 100 molar parts of ODA, and 20 molar parts of oxydiphthalic anhydride (OPDA) are added to 100 molar parts of ODA, and the reaction is carried out at 75°C for 2 hours to prepare a polyamic acid varnish uniformly dispersed with a conductive filler. Then, the temperature of the polyamic acid varnish was raised to 200° C. while stirring, and the mixture was heated for another 2 hours to precipitate a polyimide powder.

Example 2 to Example 6

The polyimide powder was precipitated in the same manner as in Example 1 except that the monomer components, solvent, and conductive filler were adjusted as shown in Table 1 below.

Comparative Examples 1 to 4

The polyimide powder was precipitated in the same manner as in Example 1 except that no conductive filler was used and the monomer components, solvent, and catalyst were adjusted as shown in Table 1 below.

In the following Table 1, the mixing method of the conductive filler is described as follows: "Dispersion mixing" of Examples 1 to 7 refers to a method of mixing a conductive filler in a solvent by ultrasonic treatment in the polyamic acid polymerization step as described in Example 1. "Dry mixing" of Comparative Examples 1 to 4 refers to a method of polymerizing polyamic acid without using a conductive filler, imidizing it to precipitate a polyimide powder, and then mechanically mixing the precipitated polyimide powder and the conductive filler.

Table 1

Experimental Example 1 - Processability

The molded products obtained by HCM molding the polyimide powders of the examples and comparative examples were processed into dog-bone shapes to produce each sample, and the appearance of the sample was observed with the naked eye to confirm whether cracks occurred and the number of cracks. Specifically, the case where no cracks occurred and the case where cracks occurred were divided in an area of 10 cm×10 cm in size. In the case where cracks occurred, they were divided into "few cracks" and "many cracks" according to the number of cracks as follows.

O: No cracks

△: 1 to 5 cracks (few cracks)

X: More than 5 cracks (many cracks)

Experimental Example 2-Surface Resistance

The surface resistance of the molded products obtained by HCM molding the polyimide powders of Examples and Comparative Examples was measured using Advanced Energy/Trek 152-1 according to ASTM D-257. The measurement temperature was set to 23±3° C. and the source voltage was set to 10V.

Experimental Example 3 - Elongation and Tensile Strength Measurement

The polyimide powders of Examples and Comparative Examples were HCM 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 an Instron UTM device from Instron using the ASTM D-1708 method.

Table 2

Classification Processability Surface resistance(Ω) Tensile strength(MPa) Elongation(%) Example 1 O 1.8×10 ¹² 102 7.5 Example 2 O 1.3×10 ¹² 90 6.2 Example 3 O 1.8×10 ¹⁰ 80 5.1 Example 4 O 1.0×10 ⁵ 93 6.3 Example 5 O 1.0×10 ⁴ 80 4.8 Example 6 O 1.0×10 ³ 78 5.9 Comparative Example 1 X 1.2×10 ¹⁰ 55 2.8 Comparative Example 2 X 1.1×10 ⁹ 53 1.9 Comparative Example 3 X 1.0×10 ¹² 40 1.5 Comparative Example 4 △ 1.0×10 ⁹ 60 2.4

Claims (17)

1. A polyamic acid varnish, characterized in that it comprises: Polyamic acid, wherein the polyamic acid comprises a diamine monomer and a dianhydride monomer as polymerization units; Conductive fillers; and Organic solvents. 2 . The polyamic acid varnish according to claim 1 , wherein the content of the conductive filler is 0.1 wt % to 50 wt % relative to the total amount of the polyamic acid varnish. 3 . The polyamic acid varnish according to claim 1 , wherein the conductive filler comprises at least one selected from the group consisting of carbon black, conductive carbon, graphite, conductive metal and conductive metal oxide. 4. The polyamic acid varnish according to claim 1, wherein the dianhydride monomer comprises at least one compound represented by the following chemical formula 1: [Chemical formula 1] In the above chemical formula 1, is a tetravalent aliphatic ring group, a tetravalent heteroaliphatic ring group, a tetravalent aromatic ring group or a tetravalent heteroaromatic ring group, and the carbon atom of the carbonyl group in Chemical Formula 1 is connected to an atom constituting a ring of the above aliphatic ring group, heteroaliphatic ring group, aromatic ring group or heteroaromatic ring 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 connecting group including 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. 5. The polyamic acid varnish according to claim 4, characterized in that: The above X is or an aliphatic cyclic group, 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 . 6. The polyamic acid varnish according to claim 1, characterized in that the diamine monomer comprises 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 amino ( _-NH2 ), -R- _NH2 or -OR- _NH2 , the above R is substituted or unsubstituted alkylene, substituted or unsubstituted alkylidene, substituted or unsubstituted alkenylene, substituted or unsubstituted alkynylene, or substituted or unsubstituted arylene, and the rest are hydrogen; halogen; hydroxyl; carboxyl; or halogen-substituted or unsubstituted alkyl. 7 . A polyimide powder, characterized in that it comprises a cured product of the polyimide varnish according to claim 1 . The polyimide powder according to claim 7 , wherein a conductive filler is dispersed in the particles. 9. A polyimide molded product, comprising the polyimide powder according to claim 7. 10 . The polyimide molded article according to claim 9 , wherein the surface resistance measured according to ASTM D-257 method is 1.0×10 ² Ω to 1.0×10 ¹³ Ω. 11. The polyimide molded article according to claim 9, wherein the elongation measured according to the ASTM D-1708 method is 3% or more. 12 . The polyimide molded article according to claim 9 , wherein the tensile strength measured according to ASTM D-1708 is 65 MPa or more. 13. A method for preparing a polyamic acid varnish, comprising: The step of dispersing the conductive filler in the organic solvent; and A step of polymerizing a diamine monomer and a dianhydride monomer in an organic solvent in which a conductive filler is dispersed. 14 . The method for preparing a polyamic acid varnish according to claim 13 , wherein the dispersion is carried out by ultrasonic treatment. 15. A method for preparing polyimide powder, comprising: The step of dispersing the conductive filler in the organic solvent; A step of polymerizing a diamine monomer and a dianhydride monomer in an organic solvent in which a conductive filler is dispersed; and A step of thermally curing the polymer produced in the polymerization step to obtain a polyimide powder. 16 . The method for preparing polyimide powder according to claim 15 , wherein the thermal curing is performed at a temperature of 150° C. to 300° C. for 1 hour to 10 hours. 17. A method for preparing a polyimide molded product, comprising: The step of dispersing the conductive filler in the organic solvent; A step of polymerizing a diamine monomer and a dianhydride monomer in an organic solvent in which a conductive filler is dispersed; a step of thermally curing the polymer produced in the polymerization step to obtain a polyimide powder; and The step of molding the obtained polyimide powder to produce a polyimide molded article.