Copolymerized metharamid polymer solution and resin molded product made therefrom

Abstract

The present invention provides an aramid-doped solution in which a polymer composed of a meta-aramid polymer is dissolved in an amide-based organic solvent, the inorganic salt concentration in the solution is 1% or less, and the visible light transmittance after standing for 24 hours or more at 25°C is 80% or more, and no polymer precipitation occurs. [Solution] By copolymerizing specific monomers in a specific ratio, a meta-aramid polymer and its solution can be obtained that have high stability and solubility in solution without impairing heat resistance.

Description

Technical Field

[0001] The present invention relates to a copolymerized meta-aramid polymer solution and a resin molded article having long-term stability. More specifically, it contains 1 to 25 mol% of a characteristic monomer structural unit, the inorganic salt concentration in the solution is 1% by mass or less, and the visible light transmittance after standing for 24 hours or more in a 25°C atmosphere is 80% or more, and a copolymerized meta-aramid polymer solution in which no precipitation of the polymer occurs, and a resin molded article obtained by molding the copolymerized meta-aramid polymer solution into a fiber or film form.

Background Art

[0002] Conventionally, it is well known that wholly aromatic polyamides produced from aromatic diamines and aromatic dicarboxylic acid dichlorides are excellent in heat resistance and flame retardancy. Among such wholly aromatic polyamides, fibers of meta-type wholly aromatic polyamides (hereinafter sometimes referred to as meta-aramids) represented by polymetaphenylene isophthalamide are particularly useful as heat-resistant and flame-retardant fibers.

[0003] Exhibiting these properties, meta-type wholly aromatic polyamide fibers are used, for example, in disaster prevention and safety clothing applications such as protective clothing, and industrial applications such as filters. In the field of electronics and electrical industries, films and separators having physical properties corresponding to the performance and applications required for electrical circuits, semiconductor materials, and battery materials are currently being actively developed and manufactured. In particular, mechanical properties and heat resistance that can withstand high-temperature conditions are becoming essential requirements for current materials. In such applications, aramid materials have also begun to be suitably used, and further needs are increasing.

[0004] Here, the following are the methods for meta-aramid spinning. Conventionally known dry spinning (for example, Japanese Patent Publication No. 35-14399) volatilizes and dries the solvent from the vicinity of the surface of the fibrous polymer solution spun from the spinneret to form fibers. On the other hand, in wet spinning, for example, (a) One such method is a wet spinning method (Japanese Patent Publication No. 48-17551) in which the meta-aramid polymer powder is redissolved in an amide-based solvent, and then a 15-25% by mass solution of meta-type total aromatic polyamide is spun into an aqueous coagulation bath containing 35-45% by mass of a high-concentration inorganic salt and allowed to coagulate. (b) A method of discharging a substantially salt-free metaaramid polymer solution into a solidification bath consisting of an amide solvent and water to solidify it into a fibrous material (fiber), and then stretching it in a plastic stretching bath consisting of an amide solvent and water, followed by washing with water and heat treatment (Japanese Patent Publication No. 2001-303365, Japanese Patent Publication No. 2003-301326, Japanese Patent Publication No. 2003-342832, etc.), (c) A method of forming a fibrous material by spinning a metaaramid polymer solution containing calcium chloride and water, which is produced by solution polymerization in an amide solvent and neutralization with calcium hydroxide, calcium oxide, etc., into an aqueous coagulation bath that is substantially free of inorganic salts and has an amide solvent concentration of 45-60% by mass (Japanese Patent Publication No. 2005-232598, International Publication No. 2007 / 089008, International Publication No. 2011 / 118022), Furthermore, the following are some methods for manufacturing films or separators using meta-aramid as a substrate. (d) A method of applying a meta-aramid solution containing inorganic particles to a polyethylene substrate and solidifying it by immersion in an aqueous solution consisting of an amide solvent and glycol (Japanese Patent Publication No. 2023-164113, International Publication No. 2019 / 130994), (e) A method for obtaining a film by thinning an aramid polymer solution consisting of metaphenylenediamine and terephthaloyl, then drying it and introducing it into a water bath to remove the solvent (Japanese Patent Publication No. 2024-2359).

[0005] As described above, when manufacturing fibers, films, or separators made from these meta-aramids, it is common practice to dissolve the polymer in a specific solvent and mold it using a dry or wet process.

[0006] Here, there are two methods for handling the meta-aramid polymer solution: either the solution contains inorganic salts generated during the neutralization of polymerization, or the solution is made salt-free by removing the solvent after polymerization, isolating the product, and then redissolving it in the solvent.

[0007] In the former case, the inorganic salt stabilizes the meta-aramid polymer. Therefore, if the polymer contains an inorganic salt at a certain concentration or higher relative to the polymer, it can be handled stably over a long period of time without the polymer becoming insoluble or precipitating, even at room temperature.

[0008] On the other hand, when molding polymer solutions containing high concentrations of inorganic salts using wet molding techniques, the presence of inorganic salts significantly restricts the solidification solution conditions, generally increasing the difficulty of molding. Furthermore, if inorganic salts remain after molding, it can not only affect subsequent processing equipment but also drastically degrade its performance, especially in the field of electronic materials. Therefore, when using polymer solutions containing inorganic salts, thorough cleaning after solidification is necessary, further increasing equipment constraints.

[0009] On the other hand, when using an aramid polymer solution obtained by removing the solvent after polymerization, isolating the polymer, and then redissolving it in the solvent, the aforementioned constraints are eliminated, and the molding conditions become relatively easier. However, the process becomes complicated because the polymer must be isolated. Furthermore, aramid polymer solutions that do not contain inorganic salts have the problem of very low stability at room temperature. This is due to the very strong interactions between the polymer chains of the aramid polymer. Therefore, molding processes using salt-free polymer solutions are often plagued by problems such as blockage of the system due to precipitation or gelation of the polymer solution, process abnormalities, and significant deterioration of product quality due to the presence of partially aggregated polymer during molding.

[0010] As described above, spinning and molding processes using aramid polymer solutions are constantly subject to various constraints on processability and performance due to the stability of the solution and the presence or absence of inorganic salts, and no methods to overcome these limitations have been reported to date. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Special Publication No. 35-14399 [Patent Document 2] Special Publication No. 48-17551 [Patent Document 3] Japanese Patent Publication No. 2001-303365 [Patent Document 4] Japanese Patent Publication No. 2003-301326 [Patent Document 5] Japanese Patent Publication No. 2003-342832 [Patent Document 6] Japanese Patent Publication No. 2005-232598 [Patent Document 7] International Publication No. 2007 / 089008 [Patent Document 8] International Publication No. 2011 / 118022 [Patent Document 9] Japanese Patent Publication No. 2023-164113 [Patent Document 10] International Publication No. 2019 / 130994 [Patent Document 11] Japanese Patent Publication No. 2024-2359 [Overview of the project] [Problems that the invention aims to solve]

[0012] The object of the present invention is to provide a copolymerized metaaramid polymer solution that has extremely high stability even at room temperature in a metaaramid solution that does not contain any inorganic salts, and that does not impair the inherent heat resistance of the metaaramid polymer after molding, in order to solve the aforementioned problems. [Means for solving the problem]

[0013] As a result of intensive studies to solve the above problems, the present inventor has found that a copolymerized meta-aramid polymer solution having high stability and solubility in a solution without impairing heat resistance can be obtained by copolymerizing specific monomers at a specific ratio, and has completed the present invention.

[0014] That is, according to the present invention, 1. A copolymerized meta-aramid polymer solution in which a copolymerized meta-aramid polymer containing 1 to 25 mol% of a monomer structural unit represented by the following formula (1) or (2) is dissolved in an amide organic solvent at 5 to 30% by mass, and the inorganic salt concentration in the polymer solution is 1.0% by mass or less. A copolymerized meta-aramid polymer solution characterized by the above. [Chemical formula] 2. The copolymerized meta-aramid polymer solution according to 1 above, having a visible light transmittance of 80% or more after standing in a 25°C atmosphere for 24 hours or more. And, 3. A fiber or film-shaped resin molded product formed from the copolymerized meta-aramid polymer solution according to 1 above, wherein the glass transition temperature of the resin molded product is 240 to 300°C and the melting point is 300 to 400°C. A resin molded product characterized by the above. Is provided.

Effect of the invention

[0015] The copolymerized meta-aramid polymer solution obtained in the present invention does not cause gelation or precipitation of the polymer even in a solution having an inorganic salt concentration of 1.0% by mass or less and after standing at room temperature for 24 hours or more. It can contribute to stable productivity and product quality in spinning and molding processes using aramid polymer solutions. In addition, it can be suitably used as a salt-free solution in applications of electronic materials where residual salts are a problem.

Modes for carrying out the invention

[0016] Hereinafter, the present invention will be described in detail. The copolymerized metaaramid polymer solution of the present invention is a solution of a metaaramid polymer in an amide-based organic solvent containing 5 to 30% by mass of the metaaramid polymer, with an inorganic salt concentration of 1.0% by mass or less in the solution, and is characterized by a visible light transmittance of 80% or more after standing for 24 hours or more at 25°C and no polymer precipitation occurring.

[0017] Examples of polymers constituting such polymer solutions include meta-type total aromatic polyamides (hereinafter sometimes referred to as meta-aramids), which are specifically composed of a meta-type aromatic diamine component and a meta-type aromatic dicarboxylic acid component, and are synthesized by copolymerization.

[0018] In the present invention, particularly preferred are meta-type total aromatic polyamides consisting of aramid polymers composed of a structure containing metaphenylene isophthalamide units, from the viewpoint of mechanical properties, heat resistance, and flame retardancy.

[0019] In the polymer solution of the present invention, the copolymerized metaaramid polymer is randomly copolymerized and preferably contains three types of monomer structural units consisting of metaphenylenediamine, toluenediamine, and isophthaloyl, and is a copolymer containing 1 to 25 mol% of toluenediamine. A mol% of toluenediamine of 1 to 25 mol% is essential, and 11 to 25 mol% is preferable to exhibit sufficient effect. If the mol% of toluenediamine is less than 1, the desired doping stability cannot be achieved. Also, if the mol% of toluenediamine is greater than 25, the heat resistance and strength after molding may decrease.

[0020] Furthermore, toluenediamine is preferably 2,4-toluenediamine or 2,6-toluenediamine represented by the following formula (1) or (2).

[0021] [ka]

[0022] Examples of raw materials for the aromatic dicarboxylic acid component constituting the meta-type total aromatic polyamide of the present invention include aromatic dicarboxylic acid halides such as isophthalic acid chloride and isophthalic acid bromide.

[0023] Examples of polymerization methods for the meta-type total aromatic polyamide of the present invention include, but are not limited to, methods such as: isolating a powder of polymetaphenylene isophthalamide polymer by contacting an organic solvent system (e.g., tetrahydrofuran) that is not a good solvent for the resulting polyamide containing metaphenylenediamine and isophthalic acid chloride with an aqueous solution system containing an inorganic acid acceptor and a soluble neutral salt (interfacial polymerization, Japanese Patent Publication No. 47-10863); or solution polymerization of the above diamine and acid chloride in an amide solvent followed by neutralization with calcium hydroxide, calcium oxide, etc. (solution polymerization, Japanese Patent Application Publication No. 8-074121, Japanese Patent Application Publication No. 10-88421).

[0024] Furthermore, the weight-average molecular weight of the meta-type all-aromatic polyamide copolymer (also called copolymerized meta-aramid polymer) used in the present invention must be between 400,000 and 1,000,000, according to the analytical method described later, from the viewpoint of forming molded products with a fracture strength and elongation that can withstand practical use. More preferably, it is between 500,000 and 900,000, and more preferably between 550,000 and 800,000. If the weight-average molecular weight is less than 400,000, the fracture strength will decrease significantly. Also, if the molecular weight exceeds 1,000,000, the viscosity will be too high, making it difficult to handle and requiring specialized equipment.

[0025] The polymers within the molecular weight range defined in this invention can be mixtures of low molecular weight polymers and high molecular weight polymers, and the overall molecular weight can be adjusted to stay within the defined molecular weight range. For example, if a polymer with a weight-average molecular weight of 200,000 and a polymer with a weight-average molecular weight of 800,000 are mixed, and the weight-average molecular weight of the resulting mixture is 600,000, this falls within the molecular weight range defined in this invention, and therefore there is no problem in using it.

[0026] In the present invention, as described above, the copolymerized metaaramid polymer is dissolved in an amide-based organic solvent at a concentration of 5 to 30% by mass. Examples of amide-based organic solvents used include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). Among these, NMP or DMAc is preferred from the viewpoint of solubility and handling safety. Furthermore, conventionally known methods can be employed for dissolution, such as directly adding the polymer powder to the solvent and thoroughly stirring and dissolving it with a single-screw agitator.

[0027] The copolymerized metaaramid polymer solution obtained in this manner preferably has a visible light transmittance of 80% or more after standing for 24 hours or more in a 25°C atmosphere. Here, visible light transmittance is the value measured using a haze meter NDH2000 manufactured by Nippon Denshoku Industries in accordance with JIS K 7361. When the visible light transmittance is 80% or more, precipitation and gelation of the polymer solution hardly occur, and it can be considered that no problems will occur in subsequent molding processes, etc.

[0028] Furthermore, in this invention, a fibrous or film-like resin molded product is formed from the above copolymerized meta-aramid polymer solution. For the molding method, in the case of fibers, fibrous yarns are obtained using known aramid fiber spinning methods. In the case of a film-like molded product, a thin film is formed using a doctor blade method, and the solvent is removed in a water bath to obtain a film. The resulting resin molded product has a glass transition temperature of 240-300°C and a melting point of 300-400°C. If the glass transition temperature or melting point of the resin molded product falls outside the above range, it is possible that the copolymerized meta-aramid polymer contains structures or impurities outside the specified range, which can lead to problems with the stability of the solution and the resin molded product. [Examples]

[0029] The present invention will be described in detail below with reference to examples and comparative examples, but the scope of the present invention is not limited to the following examples and comparative examples. The physical properties in the examples and comparative examples were measured by the methods described below.

[0030] [Weight-average molecular weight (Mw) and molecular weight dispersion] Analysis was performed using a high-performance liquid chromatography apparatus equipped with a size exclusion chromatography column, in accordance with JIS-K-7252, and dimethylformamide (containing 0.01 mol% lithium chloride) was used as the developing solvent. A Sigma-Aldrich polystyrene set (peak top molecular weight Mp = 400 to 2,000,000) was used as the standard molecular weight sample. Molecular weight dispersion was calculated using the weight-average molecular weight Mw / number-average molecular weight Mn.

[0031] [Single fiber fineness] Measurements were performed in accordance with JIS-L-1015, using Method A for true fineness, and the results are expressed as apparent fineness.

[0032] [Breaking strength, elongation at breaking] The tensile testing was performed using a tensile testing machine (Instron, model: 5565) in accordance with JIS-L-1015, under the following conditions. (Measurement conditions) Grip spacing: 20mm Initial load: 0.044cN (1 / 20g / dtex) Tensile speed: 20 mm / min

[0033] [Glass transition temperature and melting point of fibers] The glass transition temperature and melting point of the fibers were determined according to JIS K 7196 and JIS-K-7197 using a thermomechanical analyzer (TMA) manufactured by Hitachi High-Tech Science. The peak detected on the lower temperature side of the obtained sample was defined as the glass transition temperature. The peak temperature detected on the higher temperature side, or the temperature at which peak detection became impossible due to fiber melting, was defined as the melting point. The heating rate during measurement was 10°C / min.

[0034] [Visible light transmittance] The visible light transmittance of the polymer solution was measured using a haze meter NDH2000 manufactured by Nippon Denshoku Industries, in accordance with JIS K 7361.

[0035] [Example 1] A copolymerized aramid polymer powder was synthesized by interfacial polymerization in accordance with Japanese Patent Publication No. 47-10863, containing 75 mol% metaphenylenediamine and isophthaloyl monomer units and 25 mol% 2,6-toluenediamine units. The weight-average molecular weight was 590,000.

[0036] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. The mass concentration of the copolymerized aramid polymer was adjusted to 20% of the polymer solution. After standing the solution at 25°C for more than 24 hours, the visible light transmittance was measured to be 98%.

[0037] [Example 2] A copolymerized aramid polymer powder was synthesized by interfacial polymerization in accordance with Japanese Patent Publication No. 47-10863, containing 89 mol% metaphenylenediamine and isophthaloyl monomer units and 11 mol% 2,6-toluenediamine units. The weight-average molecular weight was 790,000.

[0038] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. The mass concentration of the copolymerized aramid polymer was adjusted to 20% of the polymer solution. After standing the solution at 25°C for more than 24 hours, the visible light transmittance was measured to be 97%.

[0039] [Example 3] The polymer solution obtained in Example 1 was heated to 85°C to serve as the spinning stock, and spun by extruding it into an 85°C coagulation bath from a spinneret with a circular discharge nozzle having a pore size of 0.1 mm and 100 pores. The composition of this coagulation bath was 43% by mass of calcium chloride, 3% by mass of NMP, and the remaining 54% by mass of water. After passing the yarn through the bath at a speed of 5.0 m / min with an immersion length (effective coagulation bath length) of 100 cm, it was withdrawn into the air.

[0040] The coagulated yarn was washed in two aqueous washing baths, with a total immersion time of 200 seconds. The water temperatures used for the two aqueous washing baths were 20°C and 30°C, respectively. The washed yarn was then stretched to 2.4 times its original length in 90°C boiling water, and subsequently immersed in 90°C warm water for 40 seconds for washing.

[0041] Next, the material was wound onto a roller with a surface temperature of 170°C and subjected to dry heat treatment, and then stretched to 1.8 times its original size on a hot plate with a surface temperature of 330°C to obtain fully aromatic polyamide fibers. The obtained fibers had a fineness of 2.5 dtex, a breaking strength of 4.7 cN / dtex, and a breaking elongation of 23%. Thermophysical properties of the obtained fibers were measured, revealing a glass transition temperature of 259°C and a melting point of 376°C.

[0042] [Example 4] The polymer solution obtained in Example 2 was used to obtain fully aromatic polyamide fibers using a method similar to that of Example 3. The obtained fibers had a fineness of 2.0 dtex, a breaking strength of 5.4 cN / dtex, and a breaking elongation of 22%. Thermophysical properties of the obtained fibers were measured, revealing a glass transition temperature of 277°C and a melting point of 367°C.

[0043] [Example 5] A copolymerized aramid polymer powder was synthesized by interfacial polymerization in accordance with Japanese Patent Publication No. 47-10863, containing 95 mol% metaphenylenediamine and isophthaloyl monomer units and 5 mol% 2,6-toluenediamine units. The weight-average molecular weight was 680,000.

[0044] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. The mass concentration of the copolymerized aramid polymer was adjusted to 20% of the polymer solution. After standing this solution at 25°C for more than 24 hours, the visible light transmittance was measured to be 81%.

[0045] [Comparative Example 1] A copolymerized aramid polymer powder was synthesized by interfacial polymerization in accordance with Japanese Patent Publication No. 47-10863, containing 99.5 mol% metaphenylenediamine and isophthaloyl monomer units and 0.5 mol% 2,6-toluenediamine units. The weight-average molecular weight was 750,000.

[0046] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. The mass concentration of the copolymerized aramid polymer was adjusted to 20% of the polymer solution. When this solution was left standing at 25°C for more than 24 hours, it became cloudy after about 12 hours, making it impossible to measure the visible light transmittance.

[0047] [Comparative Example 2] A copolymerized aramid polymer powder was synthesized by interfacial polymerization in accordance with Japanese Patent Publication No. 47-10863, containing 70 mol% metaphenylenediamine and isophthaloyl monomer units and 30 mol% 2,6-toluenediamine units. The weight-average molecular weight was 550,000.

[0048] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a transparent polymer solution. The mass concentration of the copolymerized aramid polymer was adjusted to 20% of the polymer solution. Fully aromatic polyamide fibers were obtained from this polymer solution using the method described in Example 3. The obtained fibers had a fineness of 2.2 dtex, a breaking strength of 2.0 cN / dtex, and a breaking elongation of 23%. When the thermophysical properties of the obtained fibers were measured, the glass transition temperature was 230°C and the melting point was 340°C.

[0049] [Comparative Example 3] A copolymerized aramid polymer powder was synthesized by interfacial polymerization in accordance with Japanese Patent Publication No. 47-10863, containing 85 mol% metaphenylenediamine and isophthaloyl monomer units and 15 mol% 4-chloro-1,3-phenylenediamine units. The weight-average molecular weight was 490,000.

[0050] This polymer powder was dissolved in N-methyl-2-pyrrolidone (NMP) to obtain a brown polymer solution. The mass concentration of the copolymerized aramid polymer was adjusted to 20% of the polymer solution. After standing the solution at 25°C for more than 24 hours, the visible light transmittance was measured to be 50%. No precipitation occurred, but the visible light transmittance decreased due to the coloration. [Industrial applicability]

[0051] The highly stable meta-aramid polymer obtained by this invention does not undergo gelation or precipitation even in solutions with an inorganic salt concentration of 1.0% by mass or less, and does not undergo gelation or precipitation even after standing at room temperature for 24 hours or more. Therefore, it can be suitably used in spinning and molding processes using aramid polymer solutions. In particular, it contributes to suppressing system blockage and process abnormalities due to precipitation or gelation of the polymer solution, and to preventing significant deterioration of product quality due to the presence of partially aggregated polymer during molding. Furthermore, since this aramid polymer can be used as a salt-free solution, it can be suitably used as a salt-free solution when residual salts may affect subsequent processing equipment, or especially in the field of electronic materials where residual salts significantly degrade performance. Thus, when using aramid polymers in applications requiring heat resistance, this invention demonstrates a variety of advantages.

Claims

1. A copolymerized metaaramid polymer solution comprising a copolymerized metaaramid polymer containing 1 to 25 mol% of monomer structural units represented by the following formula (1) or (2), dissolved in an amide-based organic solvent at a concentration of 5 to 30% by mass, characterized in that the inorganic salt concentration in the polymer solution is 1.0% by mass or less. 【Chemistry 1】

2. The copolymerized meta-aramid polymer solution according to claim 1, wherein the visible light transmittance after standing for 24 hours or more in a 25°C atmosphere is 80% or more.

3. A resin molded product in the form of fibers or film, formed from the copolymerized metaaramid polymer solution described in claim 1, characterized in that the resin molded product has a glass transition temperature of 240 to 300°C and a melting point of 300 to 400°C.

Images