High dielectric constant neat polymer film

Abstract

1. A polymer film comprising residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in the form of a polymer having polymer chains comprising a salt of Formula I, where C+ is a sodium, potassium, or calcium cation, wherein the film has a thickness of about 1 to 50 micrometers and a dielectric constant of 4.5 or greater at 2 GHz in the absence of any particulate additives that increase the dielectric constant of the film, and a process for making the same.

Description

[Technical Field]

[0001] The present invention relates to polymer films with improved voltage resistance that are more suitable for handling higher voltage requirements in automobiles, electronic devices, and other applications. Specifically, the present invention relates to polymer films with high dielectric constants (also known as relative permittivity), and methods for making such films. [Background technology]

[0002] The dielectric constant or permittivity of an insulating material, such as a film, is a measure of the insulating material's or film's ability to store electrical energy in an electric field. The dielectric constant of a film is important in the design of thin-film capacitors and other devices where the film may be expected to introduce capacitance into a circuit. Films used for electrical insulation typically have low dielectric constants, but films used for their capacitance, such as in capacitors, desirably have high dielectric constants so that the films used in capacitors can be made thinner.

[0003] The present invention relates to polymer films made from polymers produced by polymerizing diamines and diacids, particularly polymer films containing residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole and aromatic diamines and aromatic diacid chlorides. Various publications have disclosed that films and other articles can be produced containing residues of paraphenylenediamine (PPD), 5(6)-amino-2-(p-aminophenyl)benzimidazole (DAPBI), and terephthaloyl dichloride (TDC). These include, for example, U.S. Patent Nos. 8,497,344 to Bos and 8,362,192 to De Vos et al.; Longbo et al. High Performance Polymers 2017, Vol. 29(I), pp. 58-67; and U.S. Patent No. 9,193,841 to Lee. Summary of the Invention [Problem to be solved by the invention]

[0004] However, none of these references disclose or provide guidance regarding polymer residues of DAPBI in which the imidazole is deprotonated and forms a salt with a cation. Polymer films containing polymers containing residues or repeating units of DAPBI in which the imidazole is deprotonated have been found to have increased dielectric constants. Polymer films with high dielectric constants are highly desired by manufacturers of automobiles and electronic devices due to their increased value per unit weight, and therefore any increase in the dielectric constant of such polymer films is highly valuable. [Means for solving the problem]

[0005] The present invention relates to a polymer film comprising residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in the form of a polymer having polymer chains comprising a salt of Formula I, where C+ is a sodium, potassium, or calcium cation, wherein the film has a thickness of about 1 to 50 micrometers and a dielectric constant of 4.5 or greater at 2 GHz in the absence of any particulate additives that increase the dielectric constant of the film. [ka]

[0006] The present invention provides a process for producing a polymeric film comprising residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in the form of a polymer having polymer chains comprising a salt of formula I, where C+ is a sodium, potassium, or calcium cation, comprising: [ka] a) forming an isotropic casting solution of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in an organic solvent in the presence of a solubilizing salt, wherein the isotropic casting solution has a polymer concentration of 1 to 5 weight percent based on the total amount of polymer, solvent, and solubilizing salt in the isotropic casting solution; b) casting a layer of an isotropic casting solution onto a surface to form a cast film; c) removing the solvent from the cast film at a temperature of 35 to 280°C, including washing the cast film with an aqueous base having a pH of 13.8 or greater to deprotonate the imidazole and form a polymer film having polymer chains comprising a polymeric imidazole salt having a basic cation; d) optionally rinsing the film with water in a second washing step; e) tension drying at a temperature of 35 to 280°C to suppress shrinkage of the film and further remove liquid from the film to form a film; The present invention also relates to a process including: [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a graph of capacitance versus dielectric constant dK for films of various thicknesses. [Figure 2] 1 is a graph showing that the relative level of in-plane dielectric constant (or dielectric constant dK) is affected by the electronic state of the imidazole groups in the polymer, and that dK is relatively stable over a wide range of frequencies. [Figure 3] Chemical structure of a 5(6)-amino-2-(p-aminophenyl)benzimidazole residue or repeat unit in a polymer chain, where the nitrogen in the benzimidazole is fully protonated in the form of a benzimidazolium salt. [Figure 4]Chemical structure of a 5(6)-amino-2-(p-aminophenyl)benzimidazole residue or repeat unit in a polymer chain, where the nitrogens in the benzimidazole are considered to be in a "neutral" state, i.e., there is no salt designation, so one of the imidazole nitrogens contains a proton and the other imidazole nitrogen has a double bond. [Figure 5] Chemical structure of a 5(6)-amino-2-(p-aminophenyl)benzimidazole residue or repeat unit in a polymer chain, where the nitrogen in the benzimidazole is considered to be in a deprotonated state, forming a benzimidazolide. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention relates to polymer films containing residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole and aromatic diamines and aromatic diacid chlorides, which have unexpectedly high dielectric constants achieved without the addition of inorganic dielectric-enhancing particles. The increase in the film's dielectric constant is achieved by the nitrogen in the benzimidazole being in a deprotonated state, forming a benzimidazolide. Specifically, as used herein, benzimidazolides are understood to be salts in which one of the nitrogens in the imidazole residue is an anion that provides a negative charge (-) to the salt, and some other species is a cation that provides a positive charge (C+) to the salt. The salts preferably contain sodium, potassium, or calcium cations.

[0009] The polymer film preferably has a thickness of 1 to 50 micrometers. Films thicker than 50 micrometers typically present manufacturing challenges in that the film is cast from a solution that has a high percentage of solvent that must be removed. Films thinner than 1 micrometer are very difficult to manufacture; thin films are difficult to handle and can easily tear. In some embodiments, the polymer film has a thickness of 1 to 12 micrometers, while in some other embodiments, the polymer film has a thickness of 1 to 5 micrometers. In still other embodiments, the polymer film has a thickness of 2 to 25 micrometers, 2 to 15 micrometers, or 2 to 5 micrometers.

[0010] The polymer film has a dielectric constant of 4.5 or greater at 2 GHz, preferably 5.0 or greater at 2 GHz, which is advantageous because a higher dielectric constant means the film has a higher capacitance. In some embodiments, the polymer film has a dielectric constant of at least 6.0 at 2 GHz. In some embodiments, the dielectric constant is 8 or less at 2 GHz.

[0011] The relationship between the dielectric constant of a film and its capacitance per area is given by the following equation:

number

[0012] Figure 1 is a graphical representation of the relationship of capacitance to dielectric constant dK for various thicknesses of an idealized film using the above equation. For any particular film with a particular dK, thinner films have higher capacitance than thicker films. As can be appreciated from Figure 1, to achieve thin films with higher capacitance, the dK of the material must be increased.

[0013] The dielectric constant (dK) of any film is conveniently measured on a 25 micrometer thick film sample, but the dielectric constant does not vary substantially over the claimed thickness range of about 1 to 50 micrometers.

[0014] The polymer of the polymer film comprises residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole and an aromatic diamine and an aromatic diacid chloride.

[0015] As used herein, the term "residue" of a chemical species refers to a moiety that is a resulting product of a chemical species in a particular reaction scheme or subsequent formulation or chemical product, regardless of whether the moiety is actually derived from the chemical species. Thus, a copolymer containing residues of paraphenylenediamine has the formula: [ka] It refers to a copolymer having one or more units of:

[0016] The copolymer having residues of terephthaloyl dichloride has the formula: [ka] It contains one or more units of:

[0017] Similarly, copolymers containing residues of DAPBI contain one or more units as shown in Figures 3-5, with the exact structure depending on the state of the imidazole group. For example, Figure 3 shows residues of DAPBI in which the nitrogens in the benzimidazole are fully protonated in the form of a benzimidazolium salt. Specifically, as used herein, a benzimidazolium salt is understood to be a salt in which one of the nitrogens in the imidazole residue is a cation, providing a positive charge (+) to the salt, and some other species is an anion (A-), providing a negative charge to the salt. This is generally the case when an imidazole polymer is treated with acid to protonate the benzimidazole and form a benzimidazolium salt.

[0018] This is also the chemical structure of the polymer immediately after polymerization of 5(6)-amino-2-(p-aminophenyl)benzimidazole and an aromatic diamine with an aromatic diacid chloride, since the polymerization produces an acid by-product. Because the diacid chloride is usually a monomer, the acid by-product is typically hydrochloric acid (HCl). Therefore, immediately after polymerization, the DAPBI residue has the chemical structure shown in Figure 3, where the anion "A-" is a chloride ion (Cl-) ionically bonded to the imidazole ring. Washing the film with water can reduce the amount of ionically bonded chloride, but it cannot remove it. This chemical structure also exists when the polymer is recovered and then dissolved in a stronger acid, such as sulfuric acid, and then cast into a film. In this case, the "A-" anion is a sulfate ion (HSO4-) ionically bonded to the imidazole ring. Washing the film with water can reduce the amount of ionically bonded sulfate, but it cannot remove it.

[0019] Figure 4 illustrates the residue of DAPBI, where the benzimidazole nitrogens are considered to be in a "neutral" state; that is, one of the imidazole nitrogens contains a proton and the other imidazole nitrogen lacks a salt designation and therefore has a double bond. This is the chemical structure of the polymer after the acid by-products generated during polymerization have been neutralized with a typical base.

[0020] Figure 5 illustrates residues of DAPBI in which the nitrogen in the benzimidazole also forms a salt; in this case, the nitrogen is considered deprotonated, forming a benzimidazolide. Specifically, as used herein, a benzimidazolide is understood to be a salt in which one of the nitrogens in the imidazole residue is an anion, providing a negative charge (-) to the salt, and some other species is a cation (C+), providing a positive charge to the salt. This is the case when an imidazole polymer is treated with a very strong base having a very high pH to deprotonate the benzimidazole and form a benzimidazolide. A very high pH of 13.8 or preferably higher is required to generate a negative charge on the imidazole. The strong base is typically sodium hydroxide, potassium hydroxide, calcium hydroxide, or a mixture thereof, so the cation (C+) on any one repeating unit can be either sodium, potassium, or calcium. Benzimidazole films such as those made from the polymer in Figure 5 were found to have a dielectric constant 15-20% higher than neutral benzimidazole (control) films with neutralized imidazole states as shown in Figure 4.

[0021] The term "polymer," as used herein, refers to a material prepared by polymerizing monomers, end-functionalized oligomers, and / or end-functionalized polymers, whether of the same or different types. The term "copolymer," as used herein, refers to a polymer prepared from at least two different monomers. For clarity, it is understood that the use of the term "polymer" as used herein can be used interchangeably with "copolymer" unless otherwise indicated. In some embodiments, all monomers can be combined and reacted at once to form a polymer. In some embodiments, monomers or varying amounts of monomers can be reacted sequentially to form an oligomer, which can be further reacted with additional monomers or oligomers to form a polymer. "Oligomer" refers to a polymer or species eluting at less than 3000 MW using a column calibrated with polyparaphenylenediamine terephthalamide homopolymer.

[0022] As used herein, "stoichiometric amount" refers to the amount of a component theoretically required to react with all of the reactive groups of a second component. For example, "stoichiometric amount" refers to the number of moles of terephthaloyl dichloride required to react with substantially all of the amine groups of the amine components (paraphenylenediamine and DAPBI). Those skilled in the art will appreciate that the term "stoichiometric amount" refers to a range of amounts that are typically within 10% of the theoretical amount. For example, the stoichiometric amount of terephthaloyl dichloride used in a polymerization reaction can be 90-110% of the amount of terephthaloyl dichloride theoretically required to react with all of the amine groups of paraphenylenediamine and DAPBI.

[0023] The term "organic solvent" as used herein is understood to include a single organic solvent or a mixture of two or more organic solvents. In some embodiments, the organic solvent is dimethylformamide, dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), or dimethyl sulfoxide. In some preferred embodiments, the organic solvent is NMP or DMAc. In some embodiments, an inorganic salt solubility enhancer is added in an appropriate amount before or during polymerization to improve the solubility of the resulting polymer in the amide polar solvent. The term "inorganic salt" refers to a single inorganic salt or a mixture of two or more inorganic salts. In some embodiments, the inorganic salt is sufficiently soluble in the solvent to liberate a halogen atom ion. In some embodiments, a preferred inorganic salt is potassium chloride (KCl), zinc chloride (ZnCl), lithium chloride (LiCl), or calcium chloride (CaCl). In certain preferred embodiments, the inorganic salt is LiCl or CaCl. "Solids" when used in conjunction with a polymer solution means the ratio of the mass of polymer (neutral basis) to the total mass of the solution, i.e., the mass of polymer and solvent.

[0024] The polymer comprises residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, in which the imidazole forms a salt with a sodium, potassium, or calcium cation; and residues of an aromatic diamine and an aromatic diacid chloride.

[0025] Suitable aromatic diamines include paraphenylenediamine, 4,4'-diaminobiphenyl, 2-methyl-paraphenylenediamine, 2-chloro-paraphenylenediamine, 2,6-naphthalenediamine, 1,5-naphthalenediamine, and 4,4'-diaminobenzanilide. In some embodiments, the preferred organic solvent is paraphenylenediamine.

[0026] Suitable aromatic diacid chlorides include terephthaloyl dichloride, 4,4'-benzyl dichloride, 2-chloroterephthaloyl dichloride, 2,5-dichloroterephthaloyl chloride, 2-methylterephthaloyl dichloride, 2,6-naphthalenedicarboxylic acid chloride, and 1,5-naphthalenedicarboxylic acid chloride. In some embodiments, the preferred aromatic diacid is terephthaloyl dichloride.

[0027] In one preferred embodiment, the polymer comprises residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole and residues of paraphenylenediamine and terephthaloyl dichloride, where the imidazole forms a salt with sodium, potassium, or calcium cations.

[0028] In some embodiments, with respect to the residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole and aromatic diamine in the polymer film, where the imidazole forms a salt with sodium, potassium, or calcium cation, the molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine is 30 / 70 to 85 / 15. In some embodiments, the molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine is 45 / 55 to 85 / 15. In still other embodiments, 5(6)-amino-2-(p-aminophenyl)benzimidazole is 50 mole percent or more of the total moles of 5(6)-amino-2-(p-aminophenyl)benzimidazole and aromatic diamine present. Preferably, the aromatic diamine is paraphenylenediamine.

[0029] Figure 2 shows that the relative levels of in-plane dielectric constant, or dK, of neat DABPI-containing films are unexpectedly affected by the electronic state of the imidazole groups in the polymer, and that dK is relatively stable over a wide range of frequencies. Figure 2 shows that the highest in-plane dielectric constants are achieved when the polymer film contains DAPBI residues that are benzimidazolides having the structure shown in Figure 5, and that the lowest in-plane dielectric constants are achieved when the polymer film contains DAPBI residues that are benzimidazolium salts having the structure shown in Figure 3. Figure 2 also shows the in-plane dielectric constants of two other sets of data for polymer films containing DAPBI residues in the neutral state, i.e., those with the structure shown in Figure 4. Two sets of data provide the in-plane dielectric constant for a polymer film having a 70 / 30 molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine (neutral 70 / 30) and a 50 / 50 molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine (neutral 50 / 50). As shown, the in-plane dielectric constant, or dK, does not change appreciably over this range of molar ratios.

[0030] The polymerization reaction of 5(6)-amino-2-(p-aminophenyl)benzimidazole, aromatic diamines, and aromatic dichlorides can be achieved by means known in the art. See, for example, PCT Patent Application No. 2005 / 054337 and U.S. Patent Application Publication No. 2010 / 0029159. Typically, one or more acid chlorides and one or more aromatic diamines are reacted in a polar amide solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, or dimethylimidazolidinone. In some embodiments, N-methyl-2-pyrrolidone is preferred.

[0031] In some embodiments, an appropriate amount of an inorganic salt solubilizer, such as lithium chloride or calcium chloride, is added before or during polymerization to improve the solubility of the resulting polymer in the amide polar solvent. After the desired degree of polymerization is achieved, the polymer exists in the form of unneutralized solid crumbs. By "crumb," we mean that the polymer is in the form of a brittle material or gel that easily separates into distinct, identifiable chunks when sheared. The unneutralized crumbs contain the polymer, polymerization solvent, solubilizer, and the by-product acid from the condensation reaction, typically hydrochloric acid (HCl). In the presence of the HCl by-product, the DAPBI residues in the polymer chain have the chemical structure shown in Figure 3, in which the imidazole is protonated.

[0032] After the polymerization reaction is complete, the unneutralized crumbs can optionally be contacted with a base, which can be a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide, or ammonium hydroxide. The basic inorganic compound can be used in aqueous solution to neutralize the HCl by-product. Optionally, the basic compound can be an organic base such as diethylamine, tributylamine, or other amines. Typically, the unneutralized copolymer crumbs are contacted with the aqueous base by washing, which converts the acidic by-products to salts (generally, sodium chloride salts when sodium hydroxide is the base and HCl is the acidic by-product) and removes a portion of the polymerization solvent. If necessary, the unneutralized copolymer crumbs can be optionally first washed one or more times with water before contacting with the basic inorganic compound to remove excess polymerization solvent. Once the acidic by-products in the polymer crumbs have been neutralized, additional water washes can be used to remove the salts and polymerization solvent. After this wash, the DAPBI residues in the polymer chains have the chemical structure shown in Figure 4, in which the imidazole is neutralized. In some embodiments, the film is cast from a polymer solution in which the imidazole is in a neutralized state.

[0033] The molecular weight of a polymer is typically monitored and correlated with one or more dilute solution viscosity measurements. Thus, the relative viscosity ("V") is typically used. rel " or "η rel " or "n rel ") and intrinsic viscosity ("V inh " or "η inh " or "n inh ") are used to monitor polymer molecular weight. The relative viscosity and intrinsic viscosity of dilute polymer solutions are related according to the following equation: V inh =ln(V rel ) / C where ln is the natural logarithm function and C is the concentration of the polymer solution. rel is a unitless ratio, so V inh is typically expressed in units of inverse concentration as deciliters per gram ("dl / g"). The polymer typically has an intrinsic viscosity of at least 3 dl / g, preferably at least 5 dl / g or greater. In some embodiments, the intrinsic viscosity can be 6 dl / g or greater.

[0034] A polymer film comprising a polymer having residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride is a) forming an isotropic casting solution comprising a polymer of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in an organic solvent in the presence of a solubilizing salt, wherein the isotropic casting solution has a polymer concentration of 1 to 5 weight percent based on the total amount of polymer, solvent, and solubilizing salt in the isotropic casting solution; b) casting a layer of an isotropic casting solution onto a surface to form a cast film; c) removing the solvent and solubilized salts from the cast film; The composition can be produced by a process comprising:

[0035] In some embodiments, the isotropic casting solution (a) can be formed by dissolving pre-formed polymer crumbs made from 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in a suitable organic solvent (a preferred solvent is DMAc). In other words, in this embodiment, preferably, 5(6)-amino-2-(p-aminophenyl)benzimidazole, para-phenylenediamine, and terephthaloyl dichloride are polymerized at a high solids content (7 weight percent or greater) in NMP / CaCl or DMAC / CaCl, followed by isolating and optionally washing the polymer crumbs, which are then dissolved in an organic solvent to form a low-solids isotropic casting solution. In some cases, using polymer crumbs in which the by-product HCl has been neutralized can reduce bubble formation when the polymer is subsequently dissolved in a strong acid such as sulfuric acid. However, neutralization of the polymer crumbs is optional. Preferably, the polymer is cast from a polymer solution that leaves no sulfur residue in the film; i.e., the final film has only trace amounts of sulfur (less than 0.05 weight percent sulfur). Preferably, the film is produced without contact with sulfuric acid or any other sulfur-containing compound.

[0036] In some other embodiments, the isotropic casting solution of a) comprises: i) polymerizing 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in an organic solvent in the presence of a solubilizing salt to form a polymer solution; ii) optionally adjusting the amount of solvent in the polymer solution by either adding or removing solvent to form an isotropic casting solution having a polymer concentration of 1 to 5 weight percent based on the total amount of polymer, solvent, and solubilizing salt in the isotropic casting solution; It can be formed by:

[0037] Regardless of the source of the polymer, the isotropic casting solution has a solid polymer concentration of 1 to 5 weight percent based on the total amount of polymer, solvent, and solubilizing salt in the isotropic casting solution. Polymer concentrations below 1 weight percent require more solvent than is typically desirable or practical in commercial processes, while polymer concentrations above 5 weight percent are considered to be at or near the upper limit of the polymer's solubility in DMAc and risk the formation of undesirable gels that are difficult to cast into films. In a preferred embodiment, the isotropic casting solution has a polymer concentration of 2 to 4 weight percent based on the amount of polymer, solvent, and solubilizing agent in the isotropic casting solution. In some preferred embodiments, the isotropic casting solution is prepared by dissolving the polymer in a DMAc / CaCl or DMAc / LiCl solvent system, with the solubilizing agent (CaCl or LiCl) having a concentration of 0.5 weight percent or greater in the solvent system. In some embodiments, a solubilizing agent concentration of 1.5 weight percent or greater in the solvent system is desirable. In some embodiments, the concentration of the solubilizing salt in the solvent system is between 2 and 5 percent by weight.

[0038] The isotropic casting solution may further contain additives such as antioxidants, lubricants, UV filters, colorants, and the like.

[0039] Step a) of forming an isotropic casting solution is then followed by step b) of casting a layer of the isotropic casting solution onto a surface to form a film. Casting the isotropic casting solution to produce a film can be achieved by a number of processes. For example, the film can be produced by casting the casting solution onto a polished metal surface and calendering it. In some methods, the film can be produced continuously, for example, by casting through a film casting die or doctor blade, or by casting the solution onto a surface such as a belt or rotating roll (or glass plate), and then optionally further doctoring the casting solution to form a cast film of desired or uniform thickness on the surface.

[0040] Once the cast film is produced, the solvent and solubilizing salts are removed from the cast film, which step includes washing the film with an aqueous base wash solution to deprotonate the imidazole in step c).

[0041] There are many methods for removing the solvent and solubilizing salts from the film, but the method and rate of solvent removal can determine the final film structure. For commercial manufacturing, the solvent removal rate needs to be as fast as practical without damaging the film. If the solvent is removed too quickly, voids may form in the film, resulting in defects and actual pinholes. These defects and holes can reduce the strength of the film and / or reduce the breakdown voltage of the film.

[0042] The rate of removal of the solvent and solubilizing salt depends on factors such as the amount of solvent and solubilizing salt present, the thickness of the film, and the driving force imposed on the film. If a nearly transparent or clear film is desired, it has been found desirable to control the rate of solvent removal in step c) to avoid creating voids in the film, which would result in undesirable opacity. The rate of solvent removal can be controlled, for example, by removing the solvent in two or more steps, where the driving force of any one step does not create voids in the film.

[0043] Neat films typically have a golden color. * , a * , b * On the scale, the approximate color value of the film falls within the following range: * (88~92);a * (-7~-11);b * (23-37) Furthermore, it has been discovered that transparent or clear (non-hazy) films can be rendered gold by controlling the removal of solvent, for example, by removing the solvent in two or more steps. Transparent or clear (non-hazy) films typically have a D65 / 10 haze percentage of 5 percent or less, preferably 2 percent or less, as measured according to ASTM D1003 Section 8, Procedure B. Lower values ​​indicate lower haze or greater clarity than higher values.

[0044] In addition, it may be advantageous to restrain the cast film during removal of the solvent in step c), for example, by using a frame that sandwiches the cast film between the frame and the surface to prevent shrinkage of the film during this step.

[0045] Removal of the solvent and solubilizing salts from the cast film in step c) can be accomplished by a number of processes: The solvent and solubilizing salts can be removed from the cast film by washing the film with an aqueous liquid in one or more steps, or by using a combination of washing and drying steps, each of which includes one or more steps.

[0046] The solvent and solubilizing salts can be removed from the cast polymer film in step c) by submerging the cast polymer film in one or more aqueous baths and / or by applying aqueous liquids to the film surface using various applicators (spray bars, troughs, etc.), preferably by washing the cast film in a countercurrent washing process using water with increasingly dilute solvent solution (less solvent in the wash water) in each stage.

[0047] Alternatively, if the solvent can be removed from the cast polymer film in step c), the drying step involves exposing the film to heat to remove the solvent from the film. In the drying step, the cast film can be exposed to heat in an oven or heated gas in a plenum chamber, each of which provides energy to remove the solvent from the cast film.

[0048] Whether the solvent is removed by washing or by the application of heat, solvent removal from the cast film can be accomplished over a wide range of temperatures, depending on how quickly the solvent needs to be removed. For example, in one embodiment of a washing process, the solvent can be removed by exposing the cast film to temperatures ranging from room temperature (20°C) or slightly above to the boiling point of the washing liquid. Alternatively, in one embodiment, the solvent can be removed from the cast polymer film by exposing the cast film to a drying step maintained at a temperature of about 35-280°C. In some embodiments, the drying step is maintained at a temperature of 80-150°C. In other embodiments, it may be desirable to perform the drying step at a temperature of 35-80°C, or to perform drying in multiple stages, each stage having a higher temperature than the previous stage.

[0049] If a drying step is used to remove the solvent, the process should further include a washing step to remove any solubilized salts left behind, as salts are undesirable in the final film.

[0050] One particularly useful process for producing films is c-1) removing at least a portion of the solvent from the cast film using heat to form an intermediate film; c-2) rinsing the intermediate film with water in a second washing step; c-3) A step of forming a film by suppressing shrinkage of the intermediate film in a tensioned drying step and further removing liquid from the intermediate film; It has been found that a step c) comprising:

[0051] Step c-1) can be carried out as previously described; i.e., the solvent can be removed from the cast polymer film by exposing the cast film to a drying step maintained at a temperature of about 35-280° C. In some embodiments, the drying step is maintained at a temperature of 80-150° C. In other embodiments, it may be desirable to carry out the drying step at a temperature of 35-80° C. or to carry out drying in multiple stages, each stage having a higher temperature than the previous stage.

[0052] Step c-1) is then followed by step c-2), in which the intermediate film is rinsed, typically by using an aqueous liquid as the rinse solution. It is contemplated that the rinse solution can be effective over a wide temperature range; the rinse solution can have a temperature ranging from room temperature (20°C) or slightly above to the boiling point of the rinse solution. In some embodiments, the rinse solution is maintained at a temperature of 80-150°C. In other embodiments, it may be desirable for the rinse solution to have a temperature of 35-80°C.

[0053] The amount of washing is determined by the process used. If it is desired to simply remove the solubilizing salts, the amount of washing is determined by the desired amount of residual solubilizing salts that will remain in the intermediate film after washing.

[0054] The result of step c-2) is a wet film, which is then followed by step c-3) to remove liquid from the washed intermediate film in a tension drying process, where the intermediate film is exposed to temperatures ranging from room temperature (20°C) to 280°C to suppress shrinkage and form the final film.

[0055] In some embodiments, it may be desirable to expose the intermediate film to a temperature of 80-150° C. in this tension drying step. In other embodiments, it may be desirable to expose the intermediate film to a temperature of 35-80° C. In this tension drying step, the intermediate film may be exposed to heat, for example, in an oven or to heated gas in a plenum chamber.

[0056] Optionally, after or during step c-3), the method for producing a polymer film can further include an optional step in which the film is further mechanically stretched either axially or biaxially. In some embodiments, the film is stretched so that the stretch ratio cross-sectional area of ​​the film is 1.2 to 8.0 percent, preferably 1.2 to 4 percent, in the axial or one direction; in some other embodiments, the film is biaxially stretched 1.2 to 8.0 percent in both directions, preferably 1.2 to 4 percent in both directions.

[0057] Neat polymer films with increased dielectric constants comprising polymers containing residues or repeating units of 5(6)-amino-2-(p-aminophenyl)benzimidazole, in which the imidazole is in a deprotonated state as shown in Figure 5, can be prepared by washing the film in step c) using an aqueous base wash solution to deprotonate the imidazole and form a polymer film having polymer chains containing polymeric imidazole salts with a cation (C+) determined by the type of base, e.g., sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. The aqueous base wash solution should have a pH of 13.8 or greater. Preferably, the aqueous base wash solution has a pH of 14; the aqueous base solution is preferably an aqueous solution containing sodium hydroxide, potassium hydroxide, calcium hydroxide, or a mixture thereof. Such suitable base wash solutions having a pH of 13.8 or greater can be prepared by dissolving an appropriate amount of base in water. The wash solution should contact the film for a sufficient time to achieve the desired chemical structure, i.e., to deprotonate one of the benzimidazole nitrogens so that the benzimidazole is in a deprotonated state and form a benzimidazolide salt with sodium, potassium, or calcium cations. Preferably, one of the nitrogens on at least 90 percent of the imidazole residue repeat units in the polymer is deprotonated, and most preferably one of the nitrogens on at least 95 percent of the imidazole residue repeat units in the polymer is deprotonated, with the anion providing a negative charge (-) to the salt, while some other species are cations providing a positive charge (C+) to the salt.

[0058] Specifically, at least 90 percent, preferably at least 95 percent, of the DAPBI residue repeat units in the polymer are salts having a structure as shown in FIG.

[0059] The films are used in electronic devices requiring higher frequencies, lower voltages, and higher currents, particularly in applications requiring smaller form factors and lower costs. It is believed that the films can provide improved electrical performance to devices, including reduced substrate size. The films have particular application in embedded capacitance applications, as well as slot liners.

[0060] Test Method The dielectric constant (relative permittivity or dK) and dissipation factor (Df or tan delta) were determined from 2 to 10 GHz (or the frequency provided using a rectangular cavity resonator according to ASTM 2520C, IPC-TM-650 2.5.5.3).

[0061] The capacitance of the film was determined with a Hioki IM3536 LCR meter using the method provided with the meter.

[0062] The breakdown voltage of the films was determined according to ASTM D-149.

[0063] Film thickness was measured using a Solartron® thickness gauge model number DR600.

[0064] Film tensile properties (film strength, modulus, and elongation at break) were measured according to ASTM D-882.

[0065] The color and clarity (haze) of the films were determined according to ASTM D1003 Section 8, Procedure B, using a Hunter Lab UltraScan® Vis spectrophotometer equipped with EasyMatch® QC and Sensor Manager and ColorCalculator® software. D65 was used as the International Commission on Illumination (CIE) standard daylight illuminant. The observer angle was measured at 10 degrees and is displayed as "D65 / 10" haze. A lower number indicates lower haze or higher clarity than a higher haze number. [Example]

[0066] Example 1 The polymer was prepared as follows. The monomers 5(6)-amino-2-(p-aminophenyl)benzimidazole (DAPBI) and paraphenylenediamine (PPD) were combined with a stoichiometric amount of terephthaloyl dichloride (TC1) in a solvent system containing N-methyl-2-pyrrolidone (NMP) solvent and 4.5 wt. % calcium chloride (CaCl) as a solubility enhancer in amounts appropriate to form a copolymer with a 70 / 30 DAPBI / PPD monomer ratio. The monomers were polymerized to form the copolymer. After polymerization was complete, the copolymer crumbs were collected, ground, and washed with sodium hydroxide to neutralize the by-product hydrochloric acid. The crumbs were then filtered and dried. The copolymer had an intrinsic viscosity of approximately 6.4 dL / g.

[0067] A polymer solution was then made from the dried polymer crumbs by mixing 3 weight percent polymer, 3 weight percent CaCl2 solubility enhancer, 2 weight percent water, and 92 weight percent dimethylacetamide (DMAc). A film approximately 6 inches by 8 inches was cast onto a glass plate using a doctor blade with a micrometer set at approximately 20 times the target dry thickness. The glass plate with the cast film was then placed in an oven operated at 100-120°C until approximately 50% of the DMAc was removed.

[0068] For the first control film, a sample of the partially dried, unwashed film on glass was placed in a first wash bath containing 3 liters of water for 30 minutes. For the comparative benzimidazolium salt film, a sample of the partially dried, unwashed film on glass was placed in a first wash bath containing 3 liters of water adjusted to pH 3 with HCl. For the inventive benzimidazolide film, the film on glass was placed in a first wash bath containing 3 liters of water adjusted to pH 14 with NaOH. Each sample was removed from the glass and placed in separate second and third aqueous wash baths for 1 hour each. Each wash bath contained 1 liter of water. Each wet film was placed on a tension frame, and while secured within the frame, the film was dried in an oven operating at 100°C for 1 hour. The film was allowed to cool to room temperature before being removed from the frame. The chloride concentration in the control film was measured to be less than 100 ppm. Similarly, a second control film was made from a copolymer with a 50 / 50 DAPBI / PPD monomer ratio using a polymer solution with 2 weight percent polymer, 6 weight percent CaCl, 2 weight percent water, and 90 weight percent DMAc. The thickness and dielectric constant of each film sample were then determined at 68-69°F and 40-42°C relative humidity. The data are summarized in Tables 1 and 2 and Figure 2.

[0069] As can be seen from the figures and tables, the benzimidazolide film samples of the present invention (benzimidazolide examples) had higher dielectric constants than the control or the benzimidazolium salt film samples (benzimidazolium salt comparisons). It was unexpected that the dielectric constant of a film could be modified by changing the state of the imidazole groups in the polymer film. For the comparative example, in which the imidazole was in the protonated state, the dielectric constant decreased by 0.5 relative to the control, whereas when the imidazole was in the deprotonated state as in the inventive examples, the dielectric constant increased by a whole unit relative to the control. This effect is useful for tailoring the dielectric constant for applications requiring a low or high dK. As can be seen from the control example, the relative amount of monomer does not appear to have a significant effect on the dielectric constant, while the state of the imidazole groups appears to have a significant effect on the dielectric constant.

[0070] Table 3 summarizes the percent difference in dielectric constant from the control sample for both the inventive benzimidazolide examples and the comparative benzimidazolium salt examples, showing an unexpectedly large increase in dielectric constant for the inventive examples. The inventive benzimidazolide examples showed consistent increases in dK of 16-20 percent over the control sample, while the comparative benzimidazolium salt examples had consistently lower dK values ​​than the control sample.

[0071] [Table 1]

[0072] [Table 2]

[0073] [Table 3]

Claims

1. Formula I, wherein C+ is a sodium, potassium, or calcium cation 【Chemical 1】 a polymer film comprising residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in the form of a polymer having polymer chains comprising a salt of The film has a thickness of about 1 to 50 micrometers and a dielectric constant of 4.5 or greater at 2 GHz in the absence of any particulate additives that increase the dielectric constant of the film.

2. 2. The polymer film of claim 1, wherein the dielectric constant is 5.0 to 6.0 at 2 GHz.

3. 3. The polymer film of claim 1, having a thickness of about 1 to 12 micrometers.

4. The polymer film according to any one of claims 1 to 3, wherein the aromatic diamine is para-phenylenediamine.

5. The polymer film according to any one of claims 1 to 4, wherein the aromatic diacid chloride is terephthaloyl dichloride.

6. 6. The polymer film of any one of claims 1 to 5, having a molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine of from 30 / 70 to 85 / 15.

7. 7. The polymer film of claim 6 having a molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine of 45 / 55 to 85 / 15.

8. 8. The polymer film of any one of claims 1 to 7, wherein the 5(6)-amino-2-(p-aminophenyl)benzimidazole is 50 mole percent or more of the total moles of 5(6)-amino-2-(p-aminophenyl)benzimidazole and aromatic diamine present.

9. The polymer film of any one of claims 1 to 8, wherein at least 90% of the imidazole residue repeat units in the polymer are salts of Formula I.

10. Formula I, wherein C+ is a sodium, potassium, or calcium cation 【Chemistry 2】 1. A method for producing a polymer film comprising residues of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in the form of a polymer having polymer chains comprising a salt of a) forming an isotropic casting solution of 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in an organic solvent in the presence of a solubilizing salt, wherein the isotropic casting solution has a polymer concentration of 1 to 5 weight percent based on the total amount of polymer, solvent, and solubilizing salt in the isotropic casting solution; b) casting a layer of an isotropic casting solution onto a surface to form a cast film; c) removing solvent from the cast film at a temperature of 35-280° C., including washing the cast film with an aqueous base having a pH of 13.8 or greater to deprotonate the imidazole and form a polymer film having polymer chains comprising a polymeric imidazole salt with a basic cation; d) optionally rinsing the film with water in a second washing step; e) tension drying at 35 to 280°C to prevent shrinkage of the film and further remove liquid from the film to form a film; A method comprising:

11. a) the isotropic casting solution i) polymerizing 5(6)-amino-2-(p-aminophenyl)benzimidazole, an aromatic diamine, and an aromatic diacid chloride in an organic solvent in the presence of a solubilizing salt to form a polymer solution; ii) optionally adjusting the amount of solvent in said polymer solution by either adding or removing solvent to form an isotropic casting solution having a polymer concentration of 1 to 5 weight percent based on the total amount of polymer, solvent, and solubilizing salt in the isotropic casting solution; The method of claim 10 , wherein the compound is formed by

12. The method according to claim 10 or 11, wherein in step c) the solvent is removed from the membrane at a temperature of 80 to 150°C.

13. 13. The method according to any one of claims 10 to 12, wherein in step c) the aqueous base has a pH of 14 or greater.

14. The method according to any one of claims 10 to 13, wherein the tension drying in step e) is carried out at a temperature of from 80°C to 150°C.

15. The method according to any one of claims 10 to 14, wherein the film is further mechanically stretched during or after step e).

16. The method of any one of claims 10 to 15, wherein the aromatic diamine is para-phenylenediamine.

17. 17. The method of any one of claims 10 to 16, wherein the aromatic diacid chloride is terephthaloyl dichloride.

18. 18. The process of any one of claims 10 to 17, having a molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine of from 30 / 70 to 85 / 15.

19. 19. The method of claim 18 having a molar ratio of 5(6)-amino-2-(p-aminophenyl)benzimidazole to aromatic diamine of from 45 / 55 to 85 / 15.

20. 20. The method of any one of claims 10 to 19, wherein the 5(6)-amino-2-(p-aminophenyl)benzimidazole is 50 mole percent or more of the total moles of 5(6)-amino-2-(p-aminophenyl)benzimidazole and aromatic diamine present.

21. 21. The method of any one of claims 10 to 20, wherein at least 90% of the imidazole residue repeat units in the polymer in the film are the salt of Formula I.

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