Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/10—Esters; Ether-esters
  • C08K5/11—Esters; Ether-esters of acyclic polycarboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L79/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
  • C08L79/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
  • C08L79/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B3/00—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties
  • H01B3/18—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances
  • H01B3/30—Insulators or insulating bodies characterised by the insulating materials; Selection of materials for their insulating or dielectric properties mainly consisting of organic substances plastics; resins; waxes

Definitions

• the present disclosure relates to a resin composition, an insulated wire, and a method for producing an insulated wire.
• Patent Document 1 describes an insulating varnish that contains a coating resin and a heat-decomposable resin that decomposes at a temperature lower than the baking temperature of the coating resin, and an insulated electric wire having a heat-cured film of the insulating varnish, in which pores are formed in the heat-cured film due to the thermal decomposition of the heat-decomposable resin.
• the resin composition according to one embodiment of the present disclosure contains a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine, an organic solvent, and an aliphatic polycarboxylic acid ester, the total number of carbon atoms of which, excluding the carbon atoms of the carbonyl group, is 9 or more.
• the problem to be solved by the present disclosure is to provide a resin composition capable of forming an insulating coating having voids.
• an insulating coating having voids can be formed.
• Item 1 a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine; An organic solvent; Contains an aliphatic polycarboxylic acid ester and A resin composition in which the total number of carbon atoms in the aliphatic polycarboxylic acid ester is 9 or more, excluding the carbon atom in the carbonyl group.
• Item 2. The resin composition according to item 1, wherein the aliphatic polycarboxylic acid ester is an aliphatic dicarboxylic acid ester or an aliphatic tricarboxylic acid ester.
• Item 4. The resin composition according to any one of items 1 to 3, wherein the total number of carbon atoms in the aliphatic polycarboxylic acid ester is 19 or less, excluding the carbon atom in the carbonyl group.
• Item 5. The resin composition according to any one of items 1 to 4, wherein the content of the aliphatic polycarboxylic acid ester is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the polyimide precursor and the organic solvent combined.
• Item 7. The resin composition according to any one of items 1 to 6, further comprising thermally decomposable resin-containing particles.
• Item 8. 8. The resin composition according to any one of items 1 to 7, which is used for forming an insulating coating for an insulated wire.
• Item 9. A conductor; and an insulating coating covering the conductor. the insulating coating has a resin matrix and a plurality of pores; 9. An insulated wire, the insulating coating being formed from the resin composition according to any one of items 1 to 8.
• Item 10. 10 A method for producing an insulated wire according to claim 9, applying the resin composition to an outer peripheral surface of the conductor; and heating the resin composition applied in the applying step.
• the resin composition contains a polyimide precursor which is a reaction product of an aromatic tetracarboxylic dianhydride and an aromatic diamine, an organic solvent, and an aliphatic polycarboxylic acid ester, the total number of carbon atoms of which, excluding the carbon atoms of the carbonyl groups, is 9 or more.
• the resin composition contains an aliphatic polycarboxylic acid ester whose total number of carbon atoms, excluding the carbon atoms of the carbonyl group, is 9 or more, and thus can form an insulating film having voids.
• voids can be formed by phase separation between the polyimide precursor and the aliphatic polycarboxylic acid ester, and it is presumed that the balance between the hydrophobicity and hydrophilicity of the aliphatic polycarboxylic acid ester plays a role in whether or not voids are formed by the phase separation.
• the resin composition can be suitably used as a resin composition (resin varnish) for forming an insulating film for an insulated electric wire.
• the polyimide precursor is a reaction product obtained by a polymerization condensation reaction between an aromatic tetracarboxylic dianhydride and an aromatic diamine.
• the polyimide precursor is a compound also called polyamic acid (polyamide acid).
• the polyimide precursor forms a cyclic imide by a dehydration cyclization reaction, becoming a polyimide.
• the above aromatic tetracarboxylic dianhydrides can improve the heat resistance of the insulating film by including pyromellitic dianhydride (PMDA). This is because PMDA has a rigid and linear molecular structure.
• PMDA pyromellitic dianhydride
• the lower limit of the PMDA content relative to 100 mol% of the aromatic tetracarboxylic dianhydride may be 0 mol%, 10 mol%, 20 mol%, or 30 mol%.
• the upper limit of the PMDA content relative to 100 mol% of the aromatic tetracarboxylic dianhydride may be 100 mol%, 90 mol%, 80 mol%, or 70 mol%.
• the aromatic tetracarboxylic dianhydride may contain aromatic tetracarboxylic dianhydrides other than PMDA (hereinafter also referred to as "other aromatic tetracarboxylic dianhydrides").
• other aromatic tetracarboxylic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane ...
• Examples of the other aromatic tetracarboxylic dianhydrides include bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, and 2,3,6,7-naphthalenetetracarboxylic dianhydride.
• the other aromatic tetracarboxylic dianhydrides may be used alone or in combination of two or more.
• the content of the other aromatic tetracarboxylic dianhydrides relative to 100 mol% of the aromatic tetracarboxylic dianhydride can be appropriately determined within a range that does not impair the effects of the present disclosure.
• the upper limit of the content may be 30 mol% or 20 mol%.
• the lower limit of the content may be 0 mol% or 10 mol%.
• diaminodiphenyl ether examples include 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), 3,3'-diaminodiphenyl ether (3,3'-ODA), 2,4'-diaminodiphenyl ether (2,4'-ODA), and 2,2'-diaminodiphenyl ether (2,2'-ODA).
• 4,4'-diaminodiphenyl ether (4,4'-ODA) can improve the film elongation of the insulating film.
• the lower limit of the content of ODA relative to 100 mol% of the aromatic diamine may be 50 mol%, 60 mol%, or 70 mol%.
• the upper limit of the content of ODA relative to 100 mol% of the aromatic diamine may be 100 mol%, or 90 mol%.
• the aromatic diamine may further contain an aromatic diamine other than ODA (hereinafter, also referred to as "other aromatic diamine”).
• the other aromatic diamine include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 2,4'-diaminodiphenylsulfone, 2,2'-diamin
• the content of the other aromatic diamine relative to 100 mol% of the aromatic diamine can be appropriately determined within a range that does not impair the effects of the present disclosure.
• the upper limit of the content may be 40 mol% or 30 mol%.
• the lower limit of the content may be 0 mol% or 10 mol%.
• the polyimide precursor may have a glass transition temperature of 250°C or higher as measured by the following method.
• the lower limit of the glass transition temperature may be 280°C or 300°C. Although no limiting interpretation is desired, if the glass transition temperature is higher than 280°C, the softening of the polyimide during pore formation can be suppressed, and the porosity tends to be improved.
• the upper limit of the glass transition temperature is not particularly limited, and is, for example, 400°C.
• the glass transition temperature is a value measured by applying a thin film of the resin composition to a glass plate and heating it at 350°C for 1 hour to prepare a film-like test specimen, using a dynamic viscoelasticity measuring device under the conditions of 1 Hz and a temperature rise of 10°C/min. The glass transition temperature can be adjusted by the type of monomer constituting the polyimide precursor.
• the lower limit of the concentration of the polyimide precursor in the resin composition may be 25% by mass or 27% by mass.
• the upper limit of the concentration may be 40% by mass or 35% by mass.
• the molar ratio of the aromatic tetracarboxylic dianhydride and aromatic diamine used as raw materials for the polyimide precursor may be, for example, 95:105 or more and 105:95 or less, 97:103 or more and 103:97 or less, or 99:101 or more and 101:99 or less, from the viewpoint of ease of synthesis of the polyimide precursor.
• the aromatic tetracarboxylic dianhydride and aromatic diamine may be substantially equimolar. In this case, the molecular weight of the polyimide precursor can be easily increased.
• Substantially equimolar amount refers to a molar ratio of the aromatic tetracarboxylic dianhydride and aromatic diamine (aromatic tetracarboxylic dianhydride:aromatic diamine) in the range of 99:101 or more and 101:99 or less.
• the polyimide precursor can be obtained by the polymerization condensation reaction of the aromatic tetracarboxylic dianhydride and the aromatic diamine described above.
• the method of the polymerization condensation reaction can be the same as that of the conventional synthesis of polyimide precursors.
• a specific method of the polymerization condensation reaction can be, for example, a method of mixing an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic solvent. By this method, the aromatic tetracarboxylic dianhydride and the aromatic diamine are polymerized, and a solution in which the polyimide precursor is dissolved in the organic solvent can be obtained.
• the polymerization condensation reaction can be carried out in the presence of a reaction inhibitor to control the degree of polymerization (weight average molecular weight).
• reaction inhibitor examples include water (H 2 O) and alcohols having 1 to 15 carbon atoms.
• alcohols having 1 to 15 carbon atoms include monohydric alcohols such as ethanol, methanol, propanol, butanol, and pentanol; and polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin.
• the reaction conditions for the above polymerization can be set appropriately depending on the raw materials used, etc.
• the reaction temperature can be set to 10°C or higher and 100°C or lower
• the reaction time can be set to 0.5 hours or higher and 24 hours or lower.
• the organic solvent used in the above polymerization condensation reaction may be the same as the organic solvent described below.
• organic solvent examples include aprotic polar organic solvents such as N-methyl-2-pyrrolidone (NMP, boiling point: 202° C.), N,N-dimethylacetamide (DMAc, boiling point: 165° C.), N,N-dimethylformamide (boiling point: 153° C.), dimethylsulfoxide (boiling point: 189° C.), and ⁇ -butyrolactone (boiling point: 204° C.).
• NMP N-methyl-2-pyrrolidone
• DMAc N,N-dimethylacetamide
• N,N-dimethylformamide boiling point: 153° C.
• dimethylsulfoxide bisulfoxide
• ⁇ -butyrolactone bioiling point: 204° C.
• the organic solvent may be used alone or in combination of two or more kinds.
• the “aprotic polar organic solvent” refers to a polar organic solvent that does not have a group that releases
• the boiling point of the organic solvent is 150°C or higher, unintended drying before baking during the process of forming the insulating film can be suppressed.
• the content of the organic solvent is not particularly limited as long as it is an amount that can uniformly dissolve or disperse the aromatic tetracarboxylic dianhydride and aromatic diamine, but if the amount is too large, a large amount of the organic solvent must be volatilized when forming the insulating coating of the insulated electric wire, and it may take a long time to form the insulating coating. Therefore, the content of the organic solvent can be, for example, 100 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the total of the aromatic tetracarboxylic dianhydride and aromatic diamine.
• the total number of carbon atoms in the aliphatic polycarboxylic acid ester is 9 or more, excluding the carbon atom of the carbonyl group.
• carbon number refers to the number of carbon atoms constituting a compound or a functional group.
• aliphatic polycarboxylic acid ester refers to an ester derived from an aliphatic polycarboxylic acid.
• aliphatic polycarboxylic acid refers to an aliphatic carboxylic acid having two or more carboxy groups.
• carboxylic acid refers to a compound having a carboxy group, and includes not only carboxylic acids in the narrow sense but also carboxylic acids in the broad sense such as hydroxycarboxylic acids.
• total number of carbon atoms is 9 or more, excluding the carbon atom of the carbonyl group” refers to the carbon number obtained by subtracting the carbon atom of the carbonyl group from the total number of carbon atoms constituting the aliphatic polycarboxylic acid ester (hereinafter, also simply referred to as "total carbon number”) being 9 or more.
• the lower limit of the total carbon number is 9, and may be 10, 11, or 12.
• the upper limit of the total carbon number may be 30, 20, 19, 18, 17, or 16.
• the total carbon number is 19 or less, the balance between the hydrophobicity and hydrophilicity of the aliphatic polycarboxylic acid ester is improved, and the stability of the resin composition can be increased.
• aliphatic polycarboxylic acid esters are classified according to the number of carboxy groups, and examples of such esters include aliphatic dicarboxylic acid esters, aliphatic tricarboxylic acid esters, and aliphatic tetracarboxylic acid esters.
• aliphatic polycarboxylic acid esters are aliphatic dicarboxylic acid esters or aliphatic tricarboxylic acid esters, they have a smaller molecular weight, a lower boiling point, and a lower thermal decomposition temperature than aliphatic polycarboxylic acids having four or more carboxy groups (e.g., aliphatic tetracarboxylic acid esters), and therefore the amount of residues in the insulating film can be reduced.
• the relative dielectric constant of the insulating film can be reduced.
• the hydrophobicity of the aliphatic polycarboxylic acid ester becomes appropriate, and the dispersibility in the resin composition can be improved. Furthermore, compared to when it is derived from an aliphatic polycarboxylic acid having 9 or more carbon atoms excluding the carbon atom of the carbonyl group, the molecular weight is smaller, and the boiling point and thermal decomposition temperature are lower, so the amount of residue in the insulating coating can be reduced.
• the aliphatic polycarboxylic acid ester may, for example, be a compound represented by the following formula (1):
• R1 represents a substituted or unsubstituted n-valent aliphatic hydrocarbon group.
• R2 represents a substituted or unsubstituted monovalent aliphatic hydrocarbon group.
• n is an integer of 2 or more. However, (the number of carbon atoms in R1 ) + n ⁇ (the number of carbon atoms in R2 ) is 9 or more.
• valence of a group refers to the number of atoms to which the group is bonded.
• Aliphatic hydrocarbon groups include “chain hydrocarbon groups” and “alicyclic hydrocarbon groups”. From another perspective, “aliphatic hydrocarbon groups” include “saturated hydrocarbon groups” and “unsaturated hydrocarbon groups”.
• “Chain hydrocarbon groups” refer to hydrocarbon groups that do not contain a ring structure and are composed only of a chain structure, and include both straight-chain hydrocarbon groups and branched-chain hydrocarbon groups.
• Alicyclic hydrocarbon groups refer to hydrocarbon groups that contain only alicyclic rings as a ring structure and do not contain aromatic rings, and include both monocyclic alicyclic hydrocarbon groups and polycyclic alicyclic hydrocarbon groups. However, they do not have to be composed only of alicyclic rings, and may contain a chain structure as part of them.
• the total number of carbon atoms is the sum of the number of carbon atoms of R 1 and n times the number of carbon atoms of R 2 ((number of carbon atoms of R 1 ) + n ⁇ (number of carbon atoms of R 2 )). More specifically, for example, when the aliphatic polycarboxylic acid ester is dibutyl adipate (a compound represented by the following formula (2)), the total number of carbon atoms is 12.
• diethyl adipate (a compound represented by the following formula (3)) has a total number of carbon atoms of 8, so it does not fall under the above aliphatic polycarboxylic acid ester.
• R 1 in the above formula (1) examples include groups in which (n-1) hydrogen atoms have been removed from the monovalent aliphatic hydrocarbon group in R 2 described below.
• R2 in the above formula (1) may be a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms.
• Examples of the monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms and a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.
• Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, isobutyl, and tert-butyl; alkenyl groups such as ethenyl, propenyl, butenyl, and 2-methylprop-1-en-1-yl; and alkynyl groups such as ethynyl, propynyl, and butynyl.
• Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as cyclopentyl and cyclohexyl groups; polycyclic alicyclic saturated hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups; monocyclic alicyclic unsaturated hydrocarbon groups such as cyclopentenyl and cyclohexenyl groups; and polycyclic alicyclic unsaturated hydrocarbon groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl groups.
• the aliphatic hydrocarbon group giving R1 or R2 may have a substituent.
• substituents include a halogen atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, and an acyloxy group.
• R1 may be an n-valent aliphatic hydrocarbon group having 2 to 8 carbon atoms, or an n-valent chain hydrocarbon group having 2 to 8 carbon atoms. When R1 has 3 or more carbon atoms, the porosity of the insulating coating can be improved.
• R2 may be a monovalent aliphatic hydrocarbon group having 1 to 4 carbon atoms, a monovalent chain hydrocarbon group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms.
• n may be any number greater than or equal to 2, and may be 2, 3, or 4.
• aliphatic dicarboxylates include aliphatic dicarboxylates such as dibutyl fumarate, dibutyl succinate, diethyl sebacate, diisobutyl adipate, dibutyl adipate, dibutyl sebacate, and di(2-butoxyethyl) adipate, and citric acid esters such as triethyl citrate, triethyl O-acetyl citrate, tributyl citrate, and tributyl O-acetyl citrate.
• citric acid esters When comparing aliphatic dicarboxylates with citric acid esters, if the total number of carbon atoms is the same, citric acid esters tend to be able to form insulating films with higher porosity.
• the content of the aliphatic polycarboxylic acid ester in the resin composition can be appropriately set within the range in which the effects of the present disclosure are exhibited.
• the upper limit of the content of the aliphatic polycarboxylic acid ester may be 20 parts by mass, 18 parts by mass, 15 parts by mass, 12 parts by mass, 10 parts by mass, or 9 parts by mass, relative to 100 parts by mass of the polyimide precursor and the organic solvent in total.
• the content is 20 parts by mass or less, the insulating film formed has a good shape without foaming in appearance.
• the content is 20 parts by mass or less, the balance between the island and sea parts of the sea-island structure generated by phase separation between the polyimide precursor and the aliphatic polycarboxylic acid ester is appropriately adjusted, thereby suppressing the occurrence of poor appearance such as foaming, swelling, and peeling of the insulating film.
• the lower limit of the aliphatic polycarboxylic acid ester may be 1 part by mass, 2 parts by mass, 4 parts by mass, or 6 parts by mass, relative to 100 parts by mass of the polyimide precursor and the organic solvent in total.
• the resin composition further contains thermally decomposable resin-containing particles
• an insulating coating having a good appearance can be formed even when the porosity is high.
• the particles are gasified by the heat and form voids in the insulating film where the particles containing the thermally decomposable resin were present. In this case, the particles form islands of fine particles in the sea phase of the resin matrix that forms the insulating film. It can be distributed evenly and independent pores can be formed.
• the thermally decomposable resin contained in the thermally decomposable resin-containing particles is preferably a resin that thermally decomposes at a temperature lower than the baking temperature of the polyimide, which is the main component of the resin matrix of the insulating film.
• the baking temperature is set appropriately depending on the type of polyimide, but is usually about 200°C to 600°C.
• the thermal decomposition temperature refers to the temperature at which the mass reduction rate reaches 50% when the temperature is increased from room temperature at 10°C/min in an air atmosphere.
• the thermal decomposition temperature can be measured by measuring the thermogravimetry using a thermogravimetry-differential thermal analyzer ("TG/DTA" from SII NanoTechnology, Inc.).
• thermally decomposable resins include compounds such as polyethylene glycol and polypropylene glycol that are alkylated, (meth)acrylated, or epoxidized at one or both ends or in part; polymers of (meth)acrylic esters with alkyl groups having 1 to 6 carbon atoms, such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polypropyl (meth)acrylate, and polybutyl (meth)acrylate; polymers of modified (meth)acrylates, such as urethane oligomers, urethane polymers, urethane (meth)acrylates, epoxy (meth)acrylates, and ⁇ -caprolactone (meth)acrylate; poly(meth)acrylic acid; crosslinked products thereof; polystyrene; and crosslinked polystyrene.
• polymers of (meth)acrylic esters with alkyl groups having 1 to 6 carbon atoms such as polymethyl (meth)acrylate,
• Polymers of (meth)acrylic esters with alkyl groups having 1 to 6 carbon atoms are prone to thermal decomposition at the above baking temperature, and tend to form voids in the insulating film.
• An example of the above polymers of (meth)acrylic esters is polymethyl methacrylate (PMMA).
• PMMA polymethyl methacrylate
• (meth)acrylic acid includes both "acrylic acid” and "methacrylic acid.”
• the above-mentioned heat-decomposable resin-containing particles may be particles consisting only of the above-mentioned heat-decomposable resin, or may be particles with a core-shell structure having a core mainly composed of the above-mentioned heat-decomposable resin and a shell mainly composed of a resin having a heat decomposition temperature higher than the heat decomposition temperature of the above-mentioned heat-decomposable resin.
• particles with a core-shell structure it is possible to suppress the interconnection of pores, and to reduce the variation in pore size.
• the main component of the shell is not particularly limited as long as it is a material with a higher thermal decomposition temperature than the core, and is preferably a synthetic resin with a low dielectric constant and high heat resistance.
• examples include polystyrene, silicone, fluororesin, and polyimide. Silicone tends to increase elasticity, which in turn tends to improve the dispersion of voids in the insulating coating, resulting in excellent insulation and heat resistance.
• the resin composition may contain other components in addition to the above components.
• the other components are not particularly limited as long as they are additives that are blended into a resin varnish for forming an insulating film for an insulated electric wire, and examples of the other components include a filler, an antioxidant, a leveling agent, a curing agent, and an adhesion aid.
• the insulated wire includes a conductor and an insulating coating that covers the conductor.
• the insulated wire can be suitably used as a winding for a coil (magnet wire).
• the conductor generally contains a metal as a main component.
• the metal is not particularly limited, but if the metal is copper, a copper alloy, aluminum, or an aluminum alloy, an insulated electric wire having good workability, electrical conductivity, etc. can be obtained.
• the conductor may contain other components such as known additives in addition to the main metal component.
• the cross-sectional shape of the conductor is not particularly limited, and various shapes such as circular, square, rectangular, etc. can be adopted.
• the size of the cross-section of the conductor is also not particularly limited, and the diameter (short side width) can be, for example, 0.2 mm or more and 8.0 mm or less.
• the insulating coating is laminated on the peripheral surface of the conductor so as to cover the conductor.
• the insulating coating may cover the conductor directly or indirectly.
• indirectly covering the conductor for example, a multi-layer structure in which the covering layer of the conductor includes a layer other than the insulating coating may be mentioned.
• the insulating film is formed from the resin composition described above. Therefore, the insulating film has a number of pores.
• the average thickness of the insulating film is not particularly limited, but is usually between 2 ⁇ m and 200 ⁇ m.
• the insulated wire may further have another layer laminated on the outer surface of the insulating coating.
• Another layer is a surface lubricating layer.
• the lower limit of the porosity in the insulating coating may be 10 volume%, 15 volume%, 20 volume%, 25 volume%, or 30 volume%.
• the upper limit of the porosity may be 70 volume%, 60 volume%, 50 volume%, or 40 volume%.
• “Porosity” refers to the percentage of the volume of the pores relative to the volume of the insulating coating including the pores.
• the thermally decomposable resin-containing particles are particles with the core-shell structure
• the pores have an outer shell at their periphery that originates from the shell of the particle with the core-shell structure.
• the insulating coating may contain other components in addition to the above components.
• the other components There are no particular limitations on the other components, so long as they are additives that are blended into the insulating coating of the insulated electric wire, and examples of such components include fillers, antioxidants, leveling agents, curing agents, and adhesion aids.
• the insulated wire can be produced, for example, by a method including a step of applying the above-mentioned resin composition to the outer peripheral surface of a conductor (hereinafter referred to as the "applying step") and a step of heating the resin composition applied to the conductor (hereinafter referred to as the "heating step").
• the resin composition is applied to the outer peripheral surface of the conductor.
• One method for applying the resin composition to the outer peripheral surface of the conductor is to use a coating device equipped with a liquid composition tank that stores the resin composition and a coating die. With this coating device, the resin composition adheres to the outer peripheral surface of the conductor as the conductor passes through the liquid composition tank, and the resin composition is then applied to a uniform thickness as the conductor passes through the coating die.
• the resin composition applied to the conductor in the application step is heated. This heating causes the solvent in the resin composition to volatilize and the polyimide precursor to harden, forming polyimide.
• the apparatus used in the heating step is not particularly limited, and for example, a cylindrical baking furnace that is long in the direction in which the conductor travels can be used.
• the heating method is not particularly limited, and can be any conventionally known method such as hot air heating, infrared heating, or high-frequency heating.
• the heating temperature can be, for example, 300°C or higher and 800°C or lower.
• the heating time can be, for example, 5 seconds or higher and 1 minute or lower.
• the coating process and the heating process are usually repeated multiple times. By repeating the process multiple times, the thickness of the insulating coating can be increased.
• the hole diameter of the coating die can be adjusted appropriately according to the number of repetitions.
• Test Example 1 In Test Example 1, the influence of the type of aliphatic polycarboxylic acid ester on the formation of pores was tested.
• a film whitening test was carried out on the resin compositions No. 1 to No. 13 prepared above. Specifically, each resin composition was applied to a copper foil at intervals of 200 ⁇ m, and heated at 350° C. for 1 hour under conditions of an oxygen concentration of 1% or less to produce a film.
• the evaluation criteria for the film whitening test are as follows. A: Whitening was observed on the film. B: No whitening was observed on the film.
• the film whitening test is a simple test to check for the formation of voids. If whitening is observed in the film (the film is opaque), then voids have formed. If whitening is not observed (the film is transparent), then it can be determined that voids have not formed.
• Total carbon number means the value obtained by subtracting the number of carbon atoms in the carbonyl group from the total number of carbon atoms in the aliphatic polycarboxylic acid ester (i.e., (the number of carbon atoms in R 1 ) + n ⁇ (the number of carbon atoms in R 2) ).
• Amount blended (parts by mass) means the content of the aliphatic polycarboxylic acid ester relative to 100 parts by mass of the polyimide precursor solution in the resin composition (total of 100 parts by mass of the polyimide precursor and the organic solvent).
• “-” in the column “Porosity (volume %)” indicates that the insulated wire was not produced and the porosity was not measured.
• Table 1 shows that resin compositions No. 4, No. 7, No. 8, and No. 10 to No. 13 can actually form insulating coatings with porosities of 12 volume % or more.

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  • 2023-04-17 CN CN202380095473.1A patent/CN120731252A/zh active Pending
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