Production method of polyamic acid, polyamide imide and polyamide imide particle, and polyamide imide particle

Abstract

To solve such a problem that polyamide imide particles produced with a conventional method have large particle sizes and when used as a binder material of a powdered paint such as a fluororesin, film thickness after coating is not uniform and particle size distribution is sharp, therefore gaps are produced between polyamide imide particles and the fluororesin, the fluororesin included in a powdered paint is brought into contact with a coating object (a metal or the like) such that the bond strength is lowered.SOLUTION: In producing a polyamic acid by making an acyl chloride derivative of trimellitic acid anhydride, 4,4'-diaminodiphenyl ether and m-phenylenediamine as raw materials react with one another in an organic polar solvent, the raw materials are added so as to be 20-23 wt.% based on the reaction mixture and the polyamic acid is obtained, and subsequently polyamide imide particles are produced by ring closure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing polyamic acid and polyamide-imide particles. [Background technology]

[0002] Polyamide-imide resin has excellent heat resistance, mechanical strength, chemical resistance, and electrical properties, and is used in office automation parts such as separation claws and gears, semiconductor inspection jigs, etc. In addition, polyamide-imide resin has good adhesion to metals because it has amide groups in the polymer skeleton, and also adheres well to highly heat-resistant fluororesin (perfluoroalkoxyalkane: PFA), so it is also used as a binder for fluororesin powder paints.

[0003] Among the many polyamideimide production methods proposed to date, three representative examples are the isocyanate method, the acid chloride method, and the direct polymerization method. Of these, the acid chloride method is known to be effective in producing polyamideimide copolymers with high polymerization degrees and excellent linearity through low-temperature solution polymerization. Specific examples of this acid chloride method, i.e., a method for obtaining an organic polar solvent solution of polyamic acid by polycondensation of an acyl chloride derivative of trimellitic anhydride with an aromatic diamine in an organic polar solvent, are well known from Patent Documents 1 and 2.

[0004] As a means for precipitating polyamic acid particles from a solution of polyamic acid in an organic polar solvent, Patent Document 2 discloses a method in which the solution of polyamic acid in an organic polar solvent is reprecipitated in a large excess of stirred water.

[0005] As a method for removing impurities from polyamic acid particles precipitated after reprecipitation, Patent Documents 3 and 4 disclose a method in which the precipitated polyamic acid particles are washed several times and then soaked in distilled water overnight. Patent Document 5 discloses a method in which the polyamic acid is washed five times with ion-exchanged water after reprecipitation. Patent Document 1 discloses a method in which the polyamic acid particles are washed with distilled water after reprecipitation until the pH of the distilled water used for washing reaches 4 to 5. Patent Document 6 describes a method in which a slurry of precipitated polyamic acid particles / water is electrolyzed to reduce the chlorine content in the polyamideimide particles to 80 ppm or less.

[0006] As a method for ring-closing polyamic acid particles from which impurities have been removed to obtain polyamideimide particles, Patent Documents 6 and 7 describe a method in which the particles are dried in a hot air dryer at 150°C for 5 hours followed by drying at 220°C for 8 hours, while Patent Document 8 describes a method in which the particles are dried in a hot air dryer at 150°C for 5 hours, then at 200°C for 2 hours and then at 240°C for 4 hours. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 4,136,085 [Patent Document 2] Special Publication No. 42-15637 [Patent Document 3] U.S. Patent No. 3,748,304 [Patent Document 4] U.S. Patent No. 4,403,061 [Patent Document 5] U.S. Patent No. 4,313,868 [Patent Document 6] Japanese Patent Application Publication No. 11-49858 [Patent Document 7] Japanese Patent Application Laid-Open No. 2000-63520 [Patent Document 8] Japanese Patent Application Laid-Open No. 2007-246680 Summary of the Invention [Problem to be solved by the invention]

[0008] Polyamide-imide particles produced using conventional methods have a large particle diameter, and when used as a binder for powder coatings such as fluororesin, the film thickness after coating is not uniform. In addition, because the particle size distribution is sharp, gaps form between the polyamide-imide particles, which causes contact between the fluororesin contained in the powder coating and the object to be coated (metal, etc.), resulting in a decrease in adhesive strength. [Means for solving the problem]

[0009] The present invention is as follows. (1) A method for producing polyamic acid by reacting an acyl chloride derivative of trimellitic anhydride, 4,4'-diaminodiphenyl ether, and metaphenylenediamine as raw materials in an organic polar solvent, and adding the raw materials so that the amount of the raw materials is 20 to 23% by weight based on the reaction solution. (2) The method for producing a polyamic acid according to (1), wherein the organic polar solvent is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and cresol. (3) A method for producing polyamideimide, which comprises producing a polyamic acid by the method according to any one of (1) and (2), and then ring-closing the polyamic acid. (4) A method for producing polyamideimide particles, comprising obtaining a solution of polyamic acid in an organic polar solvent by the production method described in (1) or (2), adding the solution of polyamic acid in an organic polar solvent to a poor solvent to precipitate the polyamic acid, subjecting the precipitated polyamic acid to solid-liquid separation to obtain polyamic acid particles, and then reslurrying the obtained polyamic acid particles in hot water at 85 to 95°C to close the polyamic acid ring. (5) The method for producing polyamideimide particles according to (4), wherein when the organic polar solvent solution of polyamic acid is added to the poor solvent, the weight ratio of the organic polar solvent solution of polyamic acid to the poor solvent is 45 to 55 / 100. (6) The method for producing polyamideimide particles according to (4) or (5), wherein the pH of the reslurry liquid is 2 to 3. (7) The method for producing polyamideimide particles according to any one of (4) to (6), wherein the weight ratio of the polyamideimide particles to the warm water contained in the reslurry liquid is 19.6 or more and 21.3 or less. (8) The method for producing polyamideimide particles according to any one of (4) to (7), wherein the poor solvent contains water or an alcohol having 1 to 4 carbon atoms. (9) A method for producing polyamideimide particles according to any one of (4) to (8), comprising holding the reslurry at 85 to 95°C for 5 hours or more, subjecting the reslurry to solid-liquid separation, and drying the polyamideimide particle cake having a moisture content of 65 to 75% by weight at 180 to 230°C for 4 to 6 hours and then at 250°C for 12 to 15 hours. (10) Polyamide-imide particles having a volume-based cumulative frequency 50% diameter (median diameter: Dv50) of 30 to 65 μm and a particle size distribution dispersity ((Dv90-Dv10) / Dv50) of 3.5 to 7.0. [Effects of the Invention]

[0010] Polyamideimide particles having a small particle size can be obtained. In a more preferred embodiment, polyamideimide particles having a wide particle size distribution can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing the particle size distribution on a volume basis of the polyamideimide particles obtained in Example 1 and Comparative Example 1. [Figure 2] FIG. 2 is a graph showing the volume-based particle diameters (cumulative frequency) of the polyamideimide particles obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] The polyamideimide in the present invention includes polyamideimides having a repeating unit represented by general formula (I) as a main constituent unit and which may have polyamide and / or polyimide units having the following general formula (II) or (III):

[0013] [ka]

[0014] The polyamideimide of the general formula (I) produced in the present invention is produced by the acid chloride method, in which two types of diamines, 4,4'-diaminodiphenyl ether (general formula (IV) below), metaphenylenediamine (general formula (V) below), and an acyl chloride derivative of trimellitic anhydride (general formula (VI) below) are reacted to produce a polyamic acid, which is then ring-closed to produce the polyamideimide.

[0015] [ka]

[0016] By copolymerizing the condensation product of the two types of diamines and an acyl chloride derivative of trimellitic anhydride, a copolymer (polyamideimide) having a structural unit represented by the following general formula (VII) can be obtained.

[0017] [ka]

[0018] The values ​​of m and n in the polyamideimide are arbitrary, but it is preferable that the molar ratio of m / (m+n) is 0.6 to 0.8 from the viewpoint of a balance between heat resistance and moldability.

[0019] The reaction of an aromatic diamine with an acyl chloride derivative of trimellitic anhydride is carried out by adding the acyl chloride derivative of trimellitic anhydride to the aromatic diamine in portions under substantially anhydrous conditions, usually in the presence of an organic polar solvent, at a temperature of about 70° C. or less, preferably 40° C. or less. The reactants (acid and amine) are preferably present in an essentially equimolar ratio, and the reaction product is readily soluble in organic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N,N-dimethylsulfoxide, cresol, and the like.

[0020] The raw material concentration based on the reaction solution is preferably 20 to 23 wt%, and particularly preferably 21 to 23 wt%. By setting the raw material concentration to 21 to 23 wt%, the viscosity of the organic polar solvent solution of polyamic acid (measurement temperature: 23°C) becomes low at 0.07 to 0.12 Pa·s (approximately 2.0 Pa·s at a concentration of 31 wt%), and the dropping speed into the poor solvent increases (= the rate of supersaturation generation increases), so that nucleation becomes dominant over nucleus growth, and the precipitated particles become smaller in size.

[0021] When recovering polyamic acid particles from a solution of polyamic acid in an organic polar solvent, the polyamic acid solution can be poured into a poor solvent for the polyamic acid particles, which contains water or an alcohol having 1 to 4 carbon atoms, to precipitate (re-precipitate) the polyamic acid particles in water or methanol, and then recovered. However, from an industrial perspective, it is preferable to use water as the poor solvent.

[0022] When precipitating in water, a solution of polyamic acid in an organic polar solvent is usually added dropwise at a weight ratio of 1 to 100 / 100, but from the viewpoint of suppressing aggregation of precipitated particles, it is particularly preferable to add dropwise at a ratio of 45 to 55 / 100. The precipitated polyamic acid particles can be recovered as polyamic acid particles by solid-liquid separation through filtration or dehydration.

[0023] The recovered polyamic acid particles contain hydrogen chloride, a by-product of the polymerization reaction, coordinated to the amino terminal groups. Removal of this hydrogen chloride is preferred for reducing the amount of impurities remaining in the final product and for maintaining the polymerization and processing equipment. A common method for removing hydrogen chloride is to add the polyamic acid particles to stirred distilled water to form a reslurry solution, and then extract the hydrogen chloride into the water. The water temperature during washing is preferably 60 to 95°C, with 85 to 95°C being particularly preferred, in order to increase the extraction efficiency of hydrochloric acid. The pH of the reslurry solution is preferably 2 to 3, since a pH of 3 or higher approaches the isoelectric point of the polyamic acid particles and increases the tendency for the particles to aggregate during washing. Furthermore, the weight ratio of polyamic acid particles to warm water in the reslurry solution is preferably increased to improve the dispersibility of the polyamic acid particles and improve washing efficiency, with a ratio of warm water of 19.6 to 21.3 being particularly preferred. Furthermore, when reslurry washing is carried out at 85 to 95°C, the particles tend to become smaller in diameter due to thermal shrinkage as the washing time increases, so it is preferable to carry out reslurry washing for 5 hours or more.

[0024] The washed polyamic acid particles can be recovered as polyamic acid particles by solid-liquid separation through filtration or dehydration, in the same manner as after reprecipitation.

[0025] The recovered polyamic acid particles have a water content of approximately 65 to 75% by weight, so they are dried under vacuum conditions to evaporate the water and residual solvent and promote imide ring closure. To completely remove the water and residual solvent (vacuum degree of approximately 100 Torr or less), drying is preferably carried out at 180 to 230°C for 4 to 6 hours, and to promote imide ring closure, drying is preferably carried out at 250°C for 12 to 15 hours. Polyamide-imide particles are thus obtained. The imide ring closure rate, determined from the peak intensity ratio in the IR spectrum of the resulting polyamide-imide particles, is 70 to 95%.

[0026] The polyamideimide particles obtained in this manner have a volume-based cumulative 50% diameter (median diameter: Dv50) of 30 to 65 μm and a particle size distribution dispersity ((Dv90 - Dv10) / Dv50) of 3.5 to 7.0. Because of their fine particle size and relatively wide distribution, they are suitable for use as binders in powder coatings. The polyamideimide particles obtained by this method can also be sieved to adjust the particle size and dispersity. Here, the particle size and particle shape distribution of the polyamideimide particles were measured using a laser diffraction / scattering particle size analyzer. The particle sizes at 10%, 50%, and 90% of the cumulative curve, when the total particle volume is 100%, were defined as Dv10, Dv50, and Dv90, respectively. [Example]

[0027] The effects of the present invention will be explained more specifically below with reference to examples and comparative examples.

[0028] First, the evaluation method of the obtained polyamideimide (PAI) bulk powder will be described. The average particle size of the PAI resin microparticles was measured using a laser diffraction / scattering particle size distribution analyzer MT3000II manufactured by Nikkiso Co., Ltd., using a 0.5% by mass aqueous solution of polyoxyethylene cumyl phenyl ether (trade name: Nonal (registered trademark) 912A manufactured by Toho Chemical Industry Co., Ltd., hereinafter referred to as Nonal 912A) as the dispersion medium.

[0029] Specifically, the cumulative curve was calculated by taking the total volume of the particles obtained by analyzing the scattered light from the laser using the Microtrac method as 100%, and the particle size at the 50% point of the cumulative curve (median diameter: Dv50) was taken as the average particle size. Similarly, the dispersity (Dv90-Dv10) / Dv50 was calculated by taking the 90% point of the cumulative curve as Dv90 and the 10% point as Dv10.

[0030] Example 1 A 10-liter glass separable flask equipped with a stirrer, thermometer, and nitrogen gas inlet tube was charged with 457.1 g of 4,4'-diaminodiphenyl ether (DDE) and 105.8 g of m-phenylenediamine (MPDA), followed by 4720.7 g of anhydrous N-dimethylacetamide (DMAc) solvent and stirring to obtain a homogeneous solution. This mixture was cooled to below 10°C, and 625 g of trimellitic acid chloride (TMAC) and 67.0 g of trimellitic acid anhydride (TMA) were added in small increments at a rate that maintained the polymerization system temperature below 30°C. The raw material concentration at this time was 21 wt% based on the reaction solution. The mixture was then stirred at below 30°C for 2.5 hours to obtain a polyamic acid solution.

[0031] Next, the polymerization-terminated liquid was poured into water (2390.2 g) under high-speed stirring (polyamic acid solution / water = 50 / 100) to precipitate polyamic acid in particulate form (reprecipitation), and then the slurry was filtered, and the polyamic acid particles were dehydrated in a centrifugal dehydrator.

[0032] Approximately 4,900 g of the dehydrated polyamic acid particles were placed in a 30-liter stainless steel pot, and 21.4 kg of water was poured in (polyamideimide particles to hot water = 19.6) to produce a reslurry, which was heated to 90°C and had a pH of 2.3. The reslurry was kept at 90°C and stirred for a total of 6.5 hours.

[0033] The reslurry was then centrifuged and dehydrated, and the moisture content of the cake after dehydration was 70 to 74% by weight.

[0034] Finally, the dehydrated cake was dried in a hot air dryer at 200°C for 5 hours and then at 250°C for 12 hours to obtain polyamideimide particles. The production conditions and particle size of the obtained particles are shown in Table 1.

[0035] Comparative Example 1 A 10-liter glass separable flask equipped with a stirrer, thermometer, and nitrogen gas inlet tube was charged with 674.8 g of 4,4'-diaminodiphenyl ether (DDE) and 156.1 g of m-phenylenediamine (MPDA), followed by 4123.2 g of anhydrous N-dimethylacetamide (DMAc) solvent and stirring to obtain a homogeneous solution. This mixture was cooled to below 10°C, and 922.6 g of trimellitic acid chloride (TMAC) and 98.9 g of trimellitic acid anhydride (TMA) were added in small increments at a rate sufficient to maintain the polymerization system temperature below 30°C. The raw material concentration at this time was 31 wt% based on the reaction solution. The mixture was then stirred at below 30°C for 2.5 hours to obtain a polyamic acid solution.

[0036] Next, the polymerization-terminated liquid was poured into water (2390.2 g) under high-speed stirring (polyamic acid solution / water = 50 / 100) to precipitate polyamic acid in particulate form (reprecipitation). The slurry was then filtered, and the polyamic acid particles were dehydrated in a centrifugal dehydrator. Approximately 5,300 g of dehydrated polyamic acid particles were placed in a 30-liter stainless steel pot, and 22.4 kg of water was poured into it to produce a reslurry. The temperature was raised to 80°C (polyamideimide particles to hot water ratio = 19.6), and when the reslurry was poured in, the pH was 2.6. The reslurry was stirred and maintained at 80°C for a total of 3 hours.

[0037] The reslurry was then centrifuged and dehydrated. The moisture content of the cake after dehydration was 67 to 71% by weight. Finally, the dehydrated cake was dried in a hot air dryer at 200°C for 5 hours and then at 250°C for 12 hours to obtain polyamideimide particles. The production conditions and particle size of the obtained particles are shown in Table 1.

[0038] [Table 1]

[0039] As shown in Table 1, Figures 1 and 2, in Example 1, polyamideimide particles were obtained that had a small Dv50 of 40 µm but a large dispersity of (Dv90 - Dv10) / Dv50 = 6.05.

[0040] In Comparative Example 1, Dv50 was 203 μm, which is a practical level for coating applications (Dv50=30 to 65 μm), and the dispersity ((Dv90−Dv10) / Dv50) was 1.90. [Industrial Applicability]

[0041] The polyamideimide particles obtained by the present invention can be suitably used as a binder for fluororesin powder coatings.

Claims

1. A method for producing a polyamic acid by reacting an acyl chloride derivative of trimellitic anhydride, 4,4'-diaminodiphenyl ether, and metaphenylenediamine as raw materials in an organic polar solvent, the raw materials being added to the reaction solution so that the amount of the raw materials is 20 to 23 wt %.

2. 2. The method for producing a polyamic acid according to claim 1, wherein the organic polar solvent is at least one selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and cresol.

3. 3. A method for producing polyamideimide, comprising producing a polyamic acid by the method according to claim 1 or 2, and then ring-closing the polyamic acid.

4. A method for producing polyamide-imide particles, comprising obtaining a solution of polyamic acid in an organic polar solvent by the production method according to claim 1 or 2, adding the solution of polyamic acid in an organic polar solvent to a poor solvent to precipitate the polyamic acid, subjecting the solution to solid-liquid separation to obtain polyamic acid particles, and then reslurrying the obtained polyamic acid particles in hot water at 85 to 95°C to ring-close the polyamic acid.

5. 5. The method for producing polyamideimide particles according to claim 4, wherein when the solution of polyamic acid in an organic polar solvent is added to the poor solvent, the weight ratio of the solution of polyamic acid in an organic polar solvent to the poor solvent is 45 to 55 / 100.

6. 5. The method for producing polyamideimide particles according to claim 4, wherein the pH of the reslurry liquid is 2 to 3.

7. 5. The method for producing polyamideimide particles according to claim 4, wherein the weight ratio of the polyamideimide particles to the warm water contained in the reslurry liquid is 19.6 or more and 21.3 or less.

8. The method for producing polyamideimide particles according to claim 4, wherein the poor solvent comprises water or an alcohol having 1 to 4 carbon atoms.

9. The method for producing polyamideimide particles according to claim 4, wherein the reslurry liquid is maintained at 85 to 95°C for 5 hours or more, followed by solid-liquid separation, and the polyamideimide particle cake having a water content of 65 to 75% by weight is dried at 180 to 230°C for 4 to 6 hours and then at 250°C for 12 to 15 hours.

10. Polyamideimide particles having a volume-based cumulative frequency 50% diameter (median diameter: Dv50) of 30 to 65 μm and a particle size distribution dispersity ((Dv90-Dv10) / Dv50) of 3.5 to 7.0.

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