Polyamic Acid Powder

Abstract

To provide a spherical polyimide precursor powder excellent in filling property to a mold, and having a diameter of a micrometer order at which, failure of a molded article hardly occurs.SOLUTION: There is provided a spherical polyimide precursor powder comprising a 50% diameter D50 of 10-3000 μm, and an imidization ratio of 50% or less. In the invention, without melting at a high temperature, the spherical polyimide precursor powder can be filled in a mold, and according to the spherical polyimide precursor powder, in a molded product, a void failure hardly occurs.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention Regarding polyamic acid powder, in particular, The present invention relates to a spherical polyamic acid powder, which is a precursor for obtaining polyimide molded products. [Background technology]

[0002] Polyimide has properties such as heat resistance, insulation, solvent resistance, low-temperature resistance, and sliding properties, and is widely used as a component material in the aerospace, semiconductor device, and electrical / electronic device fields. It is used in the form of polyimide film or polyimide molded body, but demand for polyimide powder with a particle size on the order of micrometers is increasing from the viewpoint of near-net-shape molding by pressure molding of powder filled in a mold.

[0003] Polyimide powder is generally obtained by pulverizing a film of polyamic acid varnish, which is a polyimide precursor, after baking it. However, polyimide is difficult to pulverize due to its high mechanical strength, and the pulverized polyimide has non-uniform particle size and shape.

[0004] Polyimide molded products are formed by compressing and heating polyimide powder filled into a mold. However, the more heat-resistant the polyimide, the higher the heating temperature required, making molding more difficult. Furthermore, the non-uniform shape of polyimide powder makes it difficult to fill the mold, which can lead to defects in the molded product. Furthermore, high heating temperatures are required to melt polyimide powder, making energy conservation a challenge.

[0005] One method for obtaining polyimide powder is disclosed in Patent Document 1, in which a poor solvent for polyamic acid and an aliphatic acid anhydride are added to a polyamic acid solution to chemically dehydrate and ring-close the polyimide. The method of Patent Document 1 produces a low-solubility polyimide powder with an imide ring-closure rate of 50 to 95% and a particle size of 0.1 to 10 μm. Patent Document 2 also discloses a method for obtaining a polyimide precursor powder with a particle size of 50 to 200 μm by polymerizing polyamic acid in a good solvent and mixing the resulting polyimide precursor solution with a poor solvent for precipitation. However, these polyimide resin precursors have problems, such as being difficult to mold or leaving volatile components behind, due to their high imidization rate.

[0006] A method has also been disclosed in which polyimide resin precursor powder with a sufficiently low imidization rate is obtained without using an organic solvent by pulverizing polyamic acid powder by a mechanochemical method (Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 02-18420 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-112926 [Patent Document 3] Japanese Patent Publication No. 2020-12103 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a mold that is excellent in fillability into a mold and is less likely to produce void defects in the molded polyimide. Spherical particles with a particle size of the micrometer order Polyamic acid powder to provide The purpose is to: [Means for solving the problem]

[0009] The polyamic acid powder of the present invention is a polyimide precursor powder. And The polyamic acid powder particles Non-porous It is spherical and its 50% diameter (D50) is 12 ~ 98 μm At the same time, the 10% diameter (D10) is 8 to 46 μm, and the 90% diameter (D90) is 27 to 166 μm. The imidization rate is 50% or less. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a spherical particle which has excellent filling properties into a mold and is less likely to cause void defects in the molded product. Polyamic Acid Powder Such a spherical Polyamic Acid Powder The polyamic acid varnish is diluted with a poor solvent such as alcohol, and then dropped into another poor solvent such as alcohol to precipitate spherical solids. The spherical solids have particle sizes on the order of micrometers. The resulting solid polyamic acid particles can be tightly packed into a mold and molded into a near-net shape.

[0011] In addition, the above Polyamic Acid Powder By using the above method, a polyimide molded article can be produced in a near-net shape without melting at a high temperature, which results in energy savings and improved production efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] Figure 1 shows an SEM image of solid polyamic acid particles after two-fluid atomization separation. [Figure 2] Figure 2 is a phase diagram of polyamic acid varnish, N-methyl-2-pyrrolidone, and isopropanol. A represents polyamic acid varnish (trade name: PAA-1), B represents N-methyl-2-pyrrolidone (NMP), C represents isopropanol (IPA), ◯ represents a compatible system, and × represents an incompatible system. DETAILED DESCRIPTION OF THE INVENTION

[0013] The polyimide precursor powder of the present invention is Polyamic Acid Powder This will be explained in detail. The present invention Polyamic Acid Powder is the 50% diameter ( D50 ) The thickness is 10 to 3000 μm, and the imidization rate is 50% or less. The precursor of polyimide is also called polyamic acid, which is formed by polycondensation of diamine and acid anhydride.

[0014] Polyimides are polymers obtained by imidizing (cyclodehydrating) polyamic acids and having imide bonds (-CO-NR-CO-) in the repeating units. Examples of polyimides include poly-N,N'-bisphenoxyphenyl-pyromellitimide, which is obtained by imidizing polyamic acids obtained by polycondensing pyromellitic anhydride and 4,4'-diaminodiphenyl ether, an aromatic diamine, in an aprotic polar solvent.

[0015] Aprotic polar solvents include N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAC), and N-methyl-2-pyrrolidone (NMP). These aprotic polar solvents may be used alone or in combination of two or more. Of these, N-methyl-2-pyrrolidone (NMP) is often used. Aprotic polar solvents are good solvents for polyamic acid.

[0016] The polyimide precursor powder of the present invention can be obtained by adding dropwise a polyamic acid diluted in an aprotic polar solvent (hereinafter also referred to as "polyamic acid varnish") to an excess amount of a poor solvent to precipitate spherical solid polyamic acid having a size on the order of micrometers.

[0017] To produce such fine spherical polyamic acid, a known dropping method or a liquid atomization technique such as ultrasonic atomization separation or two-fluid (liquid mixing) atomization separation is used. The following describes methods for producing polyamic acid using these atomization techniques.

[0018] The polyamic acid varnish may be a commercially available product prepared by diluting polyamic acid with N-methyl-2-pyrrolidone (NMP), such as PAA-1 (manufactured by T&K TOKA Corporation), and used as is. Alternatively, if necessary, a commercially available polyamic acid varnish may be further diluted with a small amount of NMP or an aprotic polar solvent other than NMP, such as N,N'-dimethylformamide (DMF) or N,N'-dimethylacetamide (DMAC).

[0019] Next, a poor solvent such as water, alcohol, ketone, ether, or aromatic solvent is mixed with the polyamic acid varnish. Examples of alcohols include methanol, ethanol, and isopropanol (IPA). Examples of ketones include acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone. Examples of ethers include tetrahydrofuran (THF), 1,4-dioxane, and butyl cellosolve. Examples of aromatic solvents include benzene and toluene. The amount of poor solvent added is within a range in which the polyamic acid does not precipitate, making atomization difficult. For example, when IPA is added to a polyamic acid varnish diluted with NMP, the amount is 0.5 to 2 times the weight of the polyamic acid varnish.

[0020] Figure 2 is a phase diagram of polyamic acid varnish (trade name PAA-1, manufactured by T&K TOKA Corporation), N-methyl-2-pyrrolidone (NMP), and isopropanol (IPA). In this phase diagram, when diluting polyamic acid varnish with a poor solvent, if the amount of IPA added is small, it becomes difficult to maintain a spherical shape. On the other hand, if the amount added is too large, the polyamic acid precipitates, making it difficult to maintain a uniform state.

[0021] After mixing the polyamic acid varnish with a poor solvent, atomization separation is performed. When ultrasonic atomization separation is used, atomization is performed by the tip amplitude of an ultrasonic vibrator. When two-fluid atomization separation is used, spray introduction is performed using two-fluid gas-liquid fluids at a spray pressure of 0.03 to 0.15 Pa. By performing these atomization separations, micrometer-sized droplets are formed.

[0022] Usually, the polyamic acid varnish mixed with the poor solvent is poured into the poor solvent at the same time as the atomization treatment. The poor solvent used here is the same as that described above. When the polyamic acid varnish in which droplets have been formed by atomization separation is poured into the poor solvent, the good solvent in the polyamic acid varnish diffuses into the poor solvent, and the polyamic acid spherical particles When the poor solvent becomes a non-fluid phase, the polyamic acid particles, which have a high specific gravity, settle under their own weight without agglomerating. Figure 1 shows an image taken with a scanning electron microscope (SEM) of solid polyamic acid particles after two-fluid atomization separation. The SEM image shows that spherical solid polyamic acid particles with a particle size of about 100 μm have been formed.

[0023] The solid polyamic acid particles formed in the poor solvent are filtered and dried by a known method, whereby spherical solid polyamic acid having particle sizes on the order of micrometers can be obtained.

[0024] Polyamic acid spherical solid particles have high sphericity (circularity). The solid is 50% ( D50 ) is 10 to 3000 μm, and preferably, 50% diameter ( D50 ) is 10 to 3000 μm, and 10% diameter ( D10 ) is 8 to 46 μm and 90% diameter ( D90 ) is 27 to 166 μm.

[0025] The particle size of the spherical solid polyamic acid can be adjusted by changing the spray pressure and nozzle diameter of the two-fluid atomizing spray nozzle device. Furthermore, when polyamic acid varnish is diluted with a small amount of poor solvent and then added dropwise with a Pasteur pipette, spherical solid polyamic acid having a particle size of approximately 3000 μm is obtained. In other words, the polyimide precursor powder of the present invention can be adjusted to various particle sizes, with an average particle size of 10 to 3000 μm.

[0026] The imidization rate of the polyamic acid of the present invention is 50% or less. Since the imidization proceeds by heating the polyamic acid, the imidization rate can be adjusted by heating. The imidization temperature is usually 100 to 400°C, preferably 140 to 350°C, and is carried out while removing water produced by the imidization reaction from the reaction system. Alternatively, the imidization may be carried out under reduced pressure of 0.7 to 0.01 atmospheres to an extent that water can be efficiently removed.

[0027] By producing the polyamic acid of the present invention by the above-mentioned method, the imidization rate can be reduced to 5% or less, or even 0 to 2%. The imidization rate can be determined by measuring the IR spectrum of both the polyimide and its precursor, the polyamic acid, by Fourier transform infrared spectroscopy (FT-IR) and examining the change in peak intensity. For example, in the case of aromatic polyimide, the peak derived from the aromatic ring does not change before and after heating, so the peak derived from the imide group (1775 cm -1 ) and the peak due to aromatic rings (1519 cm -1 ) and is calculated from the peak intensity ratio.

[0028] Polyimide molded articles are formed by filling a mold with spherical solid polyamic acid and compressing it. Conventional polyimide molded articles are formed by compressing and heating pulverized polyimide powder, but in order to fill the gaps between the mold and the polyimide powder, it was necessary to sinter the polyimide at high temperatures. For this reason, when non-spherical mechanically pulverized or half-imide powder produced by a mechanochemical method was used, void defects and the like were likely to occur in the molded article. On the other hand, the present invention Polyamic Acid Powderhas a particle size on the order of micrometers and a high degree of sphericity, allowing it to be tightly packed into a mold and molded into a near-net shape without the need to melt it at high temperatures and without the occurrence of void defects, etc., thereby providing highly reliable products. [Example]

[0029] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. [Example 1] 35 g of polyamic acid varnish (trade name PAA-1, manufactured by T&K TOKA Corporation) was diluted with 35 g of N-methyl-2-pyrrolidone (NMP) and 35 g of isopropanol (IPA). Next, the diluted polyamic acid varnish was subjected to two-fluid atomization separation using a two-fluid atomization spray nozzle device (product name SUJ22, manufactured by Spraying Japan Co., Ltd.) at a spray pressure of 0.15 Pa and a hydraulic pressure of 0.1 MPa, and the atomized particles of the diluted polyamic acid varnish were introduced into 1200 ml of isopropanol (IPA). The atomized particles were filtered and dried to obtain spherical solid polyamic acid particles with a 50% diameter (D50) of 98 μm (10% diameter (D10) of 46 μm to 90% diameter (D90) of 166 μm).

[0030] [Example 2] 35 g of polyamic acid varnish (trade name PAA-1, manufactured by T&K TOKA Corporation) was diluted with 35 g of N-methyl-2-pyrrolidone (NMP) and 35 g of isopropanol (IPA). Next, the diluted polyamic acid varnish was subjected to two-fluid atomization separation using a two-fluid atomization spray nozzle device (product name SV91, manufactured by Sanei Tech Co., Ltd.) at a spray pressure of 0.03 Pa and a hydraulic pressure of 0.1 MPa, and the atomized particles of the diluted polyamic acid varnish were introduced into 1000 ml of isopropanol (IPA). The atomized particles were filtered and dried to obtain spherical solid polyamic acid particles with a 50% diameter (D50) of 63 μm (10% diameter (D10) of 26 μm to 90% diameter (D90) of 143 μm).

[0031] [Example 3] 10 g of polyamic acid varnish (trade name PAA-1, manufactured by T&K TOKA Corporation) was diluted with 20 g of N-methyl-2-pyrrolidone (NMP) and 20 g of isopropanol (IPA). The diluted polyamic acid varnish was then subjected to hydraulic atomization separation at 0.05 MPa using an ultrasonic atomization spray nozzle device (product name WS40K50, manufactured by SONAER), and the atomized particles of the diluted polyamic acid varnish were introduced into 400 ml of isopropanol (IPA). The atomized particles were filtered and dried to obtain spherical solid polyamic acid particles with a 50% diameter (D50) of 12 μm (10% diameter (D10) 8 μm to 90% diameter (D90) 27 μm).

[0032] [Example 4] 10 g of polyamic acid varnish (trade name PAA-1, manufactured by T&K TOKA Corporation) was diluted with 10 g of N-methyl-2-pyrrolidone (NMP) and 10 g of isopropanol (IPA). Next, the diluted polyamic acid varnish was added dropwise to 200 ml of isopropanol (IPA) using a Pasteur pipette. The particles were filtered and dried to obtain spherical solid polyamic acid with a particle diameter of 3000 μm.

[0033] [Comparative Example 1] 137 g of polyamic acid varnish (trade name PAA-1, manufactured by T&K TOKA Corporation) was diluted with 363 g of N-methyl-2-pyrrolidone (NMP). Without atomization separation, the diluted polyamic acid varnish was added dropwise to stirred isopropanol (IPA), and the precipitate was filtered to obtain solid polyamic acid particles. The obtained solid polyamic acid particles were irregular in shape and had a 50% diameter D50 of 245 μm ((10% diameter D10) 66 μm to (50% diameter D90) 974 μm).

Claims

[Claim 1] A polyamic acid powder that is a polyimide precursor powder, The polyamic acid powder is characterized in that the particles of the polyamic acid powder are non-porous and spherical, have a 50% diameter (D50) of 12 to 98 μm, a 10% diameter (D10) of 8 to 46 μm, and a 90% diameter (D90) of 27 to 166 μm, and have an imidization rate of 50% or less.

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