JP2564028C - - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyimide resin powder excellent in moldability and a molded article obtained therefrom. More specifically, the present invention relates to a polyimide resin powder capable of producing a polyimide molded article having excellent mechanical properties and a polyimide resin molded article having high strength and high toughness obtained by compression molding. [Prior art] In addition to excellent heat resistance, an aromatic polyimide resin molded article has abrasion resistance, chemical resistance,
Has various properties such as radiation resistance, and is widely used as mechanical parts such as sliding members, or in the fields of automobiles, office equipment, electric and electronic equipment, aerospace and nuclear power, and general industrial machinery. . However, in order to further expand the applications of polyimide resins having such excellent properties as, for example, metal substitutes and precision structural materials, it is necessary to improve mechanical properties such as strength and toughness. Ongoing efforts have been made until now. Since such a polyimide resin is generally insoluble in an organic solvent and does not melt by heating, as a method for producing a thick molded product, a polyimide resin powder is compression-molded,
In addition, a method is used in which a heat treatment is performed at the same time as the compression molding and / or after the compression molding and without pressure. As a method for producing an aromatic polyimide resin powder, for example, JP-B-39-300
No. 60, that is, an aromatic tetracarboxylic dianhydride and an aromatic diamine are reacted in an organic polar solvent to obtain a polyamic acid solution, which is then thermally dehydrated and ring-closed. Thereafter, there is a method in which the polyimide resin powder is obtained by drying with a vacuum drier and then heating at 325 ° C. for 16 hours. Also,
As disclosed in JP-B-39-9078 and JP-A-61-252228, an aromatic tetracarboxylic dianhydride and an aromatic diamine are reacted in an organic polar solvent to form a polyamic acid solution. Then, the solution is brought into contact with a poor solvent for polyamic acid such as water, toluene, hexane, etc. to obtain a polyamic acid as a powder, and heating to obtain a polyimide resin powder. As disclosed in the above publication, a method can be found in which an aromatic tetracarboxylic acid component is reacted with an aromatic diisocyanate in an organic polar solvent to directly obtain a polyimide resin powder. [Problems to be Solved by the Invention] According to these conventional methods, a polyimide resin powder having a large specific surface area and a high imidization ratio of about 100% and high crystallinity or a small specific surface area and a low imidization ratio and a low crystallinity A polyimide resin powder having properties is obtained. However, the specific surface area of the polyimide resin powder is closely related to the specific gravity and mechanical properties of the compact, and when the specific surface area is small, the cohesion between the powders in the compact becomes insufficient. The proportion of voids in the body increases, the specific gravity of the molded body,
Decreases mechanical properties. If the imidation ratio and the crystallinity of the polyimide resin powder are too high, the interaction between the powders during compression molding and during the heat treatment of the compact becomes insufficient, and the mechanical properties of the compact deteriorate. That is, in order to improve the mechanical properties of the polyimide resin molded article, it is an object to develop a polyimide resin powder having a specific surface area of not less than a certain value and an appropriate imidization ratio and crystallinity. Means for Solving the Problems The present inventors have conducted intensive studies in view of such problems, and as a result, obtained a polyimide resin powder for producing a polyimide resin molded article having both excellent heat resistance and mechanical properties, and the resin powder. To provide a polyimide resin molded article having high strength and high toughness obtained by compression molding. Specifically, it has a specific surface area of 20 m ² / g or more and 90
%, Which enables the production of essentially crystalline polyimide resin powder having an imidation ratio of less than 10%, and furthermore, by using such a polyimide resin powder, a polyimide molded article whose specific gravity, strength and toughness are greatly improved can be obtained. The inventors have found that the present invention is possible, and have reached the present invention. The present invention provides a compound represented by the general formula (I): (Wherein R ₀ is a tetravalent aromatic group having 6 to 30 carbon atoms, R ₁ is a divalent aromatic group having 6 to 30 carbon atoms, and n represents a positive integer). Aromatic polyimide resin powder comprising a powder having a specific surface area of 20 m ² / g or more, an imidization ratio of less than 90%, and being essentially crystalline. It is. Further, the present invention relates to a polyimide resin molded product obtained by compression-molding the polyimide resin powder and performing a heat treatment at the same time as the compression molding and / or after the compression molding and without pressure. . [Examples] The polyimide resin powder of the present invention has a specific surface area of at least 1 m ² / g, preferably at least 10 m ² / g, particularly preferably at least 20 m ² / g, and an imidization ratio of less than 95%. , Preferably having a characteristic value of less than 90%, being essentially crystalline and having an inherent viscosity of, for example, 30 g at a concentration of 0.5 g / 100 ml as a solution of concentrated sulfuric acid. 0.1 to 2.degree.
It has a value of 0, but is preferably at least 0.1 or more. Even if a polyimide resin powder having a value of less than 0.1 is used, a polyimide resin molded product obtained therefrom does not exhibit sufficient mechanical strength. Therefore, the polyimide resin molded article obtained by compression molding the powder of the present invention has high specific gravity, high strength and high toughness in addition to excellent heat resistance. Here, the imidation ratio refers to a ratio of the amide acid closed to the imide, and is calculated, for example, by measuring a Fourier transform infrared absorption spectrum. Specifically, first, the ratio of the absorbance of the absorption around 880 cm ^-1 in the first based on the absorption and the benzene ring in the vicinity of 720 cm ^-1 based on the imide ring (hereinafter, this ratio and r) obtained. Next, the imidation ratio of the polyamic acid was set to 0%, and a method as disclosed in JP-B-39-30060, that is, an aromatic tetracarboxylic dianhydride and an aromatic diamine were reacted in an organic polar solvent. The polyimide resin powder produced by a method of thermally dehydrating and ring-closing the polyamic acid solution was further heated at 300 ° C. for 5 hours, and the imidation ratio of the powder obtained was set to 100%. It is given as a relative value proportional to the magnitude. In the polyimide of the present invention containing a repeating unit represented by the general formula (I), R ₀
Is preferably a tetravalent aromatic group having 6 to 30 carbon atoms. Specific examples of such groups include pyromellitic acid, 3,3 ', 4,4'-biphenyltetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid, 3,3 ', 4, 4 '
-Diphenylsulfonetetracarboxylic acid, 3,3 ', 4,4'-diphenylethertetracarboxylic acid, naphthalene-1,2,5,6-tetracarboxylic acid, 2,
Examples thereof include a residue obtained by removing a carboxylic acid group from 2-hexafluoropropylidene-bisphthalic acid, and these can be used alone or as a mixture of two or more. Of these, a pyromellitic acid residue is particularly preferred. Further, R ₁ is preferably a divalent organic group containing an aromatic group having 6 to 30 carbon atoms, and a group in which a carbon atom forming an aromatic ring serves as a bond. Specific examples of such groups include 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, and 4,4'-
Diaminodiphenyl sulfide, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 2,5-diaminobenz 4-amide, bis {4- (4-aminophenoxy) phenyl} sulfone, bis {4- (
3-aminophenoxy) phenyl} sulfone, bis {4- (2-aminophenoxy) phenyl} sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,
3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenyl) benzene, bis {4- (
4-aminophenoxy) phenyl} ether, 4,4 ″ -diaminodiphenylmethane, bis (3-ethyl-4-aminophenyl) methane, bis (3-methyl-
4-aminophenyl) methane, bis (3-chloro-4-aminophenyl) methane, 4,4'-diaminobiphenyl, 4,4'-diaminooctafluorobiphenyl, 3,3'-dimethoxy-4,4'- Diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 2,2 ', 5,5'-tetrachloro-4,4' -Diaminobiphenyl, 3,3'-dicarboxy-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,4-diaminotoluene, 1,3
-Diaminobenzene, 1,4-diaminobenzene, 2,2'-bis {4- (4-
Aminophenoxy) phenyl} propane, 2,2′-bis {4- (4-aminophenoxy) phenyl} hexafluoropropane, 2,2′-bis (4-aminophenyl) propane, 2,2′-bis (4 -Aminophenyl) hexafluoropropane, 2,2'-bis (3-hydroxy-4-aminophenyl) propane, 2,
2'-bis (3-hydroxy-4-aminophenyl) hexafluoropropane,
Examples include 9,9'-bis (4-aminophenyl) -10-hydroanthracene, a residue obtained by removing an amino group from ortho-tolidine sulfone, and these can be used alone or as a mixture of two or more. Among these, a residue obtained by removing an amino group from 4,4'-diaminodiphenyl ether is preferable. The polyimide resin powder of the present invention comprises an aromatic tetracarboxylic dianhydride such as pyromellitic dianhydride and an aromatic diamine such as 4,4'-diaminodiphenyl ether, for example, pyridine, N, N -Polyamide acid solution is prepared by reacting in an organic polar solvent such as -dimethylacetamide or N, N-dimethylformamide, and then the polyamic acid solution is heated to dehydrate and ring-close the polyamic acid, followed by cooling and filtration. The obtained powder can be manufactured by a method of drying the powder at a temperature of about 200 ° C. or less. That is, the polyimide resin powder according to the present invention is essentially crystalline having both a large specific surface area and a low imidation ratio necessary for producing a molded article having excellent mechanical properties, and for example, It is characterized in that it can be produced from a polyamic acid solution by a very simple method of thermally dehydrating and ring-closing and imidizing. As a method for producing the polyimide resin molded article of the present invention from the novel polyimide resin powder of the present invention, the following methods are known techniques. For example, the resin powder filled in a mold is subjected to compression molding at a pressure of several hundreds to several thousand kg / cm ² , and simultaneously with this compression molding, in a pressurized state and / or compression molding, and In this state, after heating the polyimide resin at a temperature not lower than the glass transition temperature and not higher than the decomposition temperature, or after filling the resin powder in an elastic rubber case or the like, a CIP device (cold hydrostatic device) and And / or HIP device (hot isostatic device) at a pressure of several hundreds to several thousand kg / cm ² , and at the same time, the glass transition temperature of the polyimide resin in a pressurized state and / or a non-pressurized state after the treatment. There is a method of performing heat treatment at a temperature not lower than the decomposition temperature and the like, and the polyimide resin molded article of the present invention can be manufactured by any of these methods. Further, the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples. Example 1 4,4'-diaminodiphenyl ether (hereinafter referred to as ODA) under a nitrogen stream
After dissolving 20.02 g (0.10 mol) in a mixed solution of 250 ml of N, N-dimethylacetamide (hereinafter, referred to as DMAc) and 250 ml of pyridine (hereinafter, referred to as Py), pyromellitic acid was added under ice cooling. Anhydrous (hereinafter referred to as PMDA) 2
1.81 g (0.10 mol) of the powder was slowly added in about 30 minutes. After completion of the addition, stirring was continued for 60 minutes to obtain about 500 ml of a polyamic acid solution. Subsequently, the obtained polyamic acid solution was heated, and heating and stirring were continued. The internal temperature at this time was 110 ° C. After cooling, the filtered powder was washed with DMAc and methanol in that order, followed by filtration. Further, the powder was dried under reduced pressure at 150 ° C. for several hours, and then heat-treated at 200 ° C. in a perfect oven to obtain a completely dried state.
6 g were obtained. A part of the polyimide resin powder obtained by the above treatment was taken, and its specific surface area and imidation ratio were respectively measured by B.I. E. FIG. T. It was calculated by measuring the specific surface area using the method and measuring the infrared absorption spectrum. The diffraction intensity was measured using a wide-angle X-ray diffractometer to evaluate the crystallinity of the polyimide resin powder. As shown in the diffraction intensity curve in FIG. 1, peaks were observed at around 2 ° of 11 ° (peak 1), 14 ° (peak 2), 23 ° (peak 3), and 27 ° (peak 4). This means
This indicates that the polyimide resin powder is essentially crystalline. Thereafter, the remaining polyimide resin powder was filled in a mold, and pressed at 5,000 kg / cm ² at room temperature for 3 minutes using a hydraulic compression molding machine. Further, a heat treatment was performed at 450 ° C. for 30 minutes under a nitrogen stream under no pressure to obtain a polyimide resin molded body. With respect to the polyimide resin molded body thus obtained, specific gravity (JIS K
7112), flexural strength and flexural modulus (JIS K 7203 method), tensile rupture strength and tensile rupture elongation (JIS K 6911 method), and V-notched Izod impact strength (JIS K 7110 method). . Table 1 shows the results together with the results of the specific surface area and the imidation ratio. Example 2 Instead of DMAc used in Example 1, N, N-dimethylformamide (hereinafter referred to as D
The reaction and treatment were carried out in the same manner as in Example 1 except that 250 ml of MF was used to obtain about 36 g of the polyimide resin powder of the present invention. A part of the obtained polyimide resin powder was taken, and its specific surface area and imidation ratio were calculated in the same manner as in Example 1. Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body. The specific gravity, bending strength and elastic modulus, tensile rupture strength and tensile rupture elongation, and Izod impact strength with V notch of the polyimide resin molded article thus obtained were measured in the same manner as in Example 1. Table 1 shows the results together with the results of the specific surface area and the imidation ratio. Comparative Example 1 The polyamic acid solution obtained in the same manner as in Example 1 was heated and heated and stirred. The internal temperature at this time was 132 ° C. After cooling, the filtered powder was washed with DMAc and methanol in that order, followed by filtration. Further, the powder was dried under reduced pressure at 150 ° C. for several hours and then treated at 200 ° C. in a perfect oven to obtain about 37 g of a polyimide resin powder. A part of the obtained polyimide resin powder was taken, and its specific surface area and imidation ratio were calculated in the same manner as in Example 1. Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body. The specific gravity, flexural strength and flexural modulus, tensile rupture strength and tensile rupture elongation, and V-notched Izod impact strength of the polyimide resin molded article thus obtained were measured in the same manner as in Example 1. Table 1 shows the results together with the results of the specific surface area and the imidation ratio. Comparative Example 2 100 ml of the polyamic acid solution obtained in the same manner as in Example 1 was taken, and D was added thereto.
After adding 40 ml of MAc and stirring sufficiently, methylene chloride 1200 was added under strong stirring.
The resulting mixture was gradually added to obtain a polyamic acid powder in the form of a slurry. The obtained polyamic acid powder was washed with methylene chloride and filtered repeatedly. Further, the powder was dried under reduced pressure at 150 ° C. for several hours and then treated at 200 ° C. in a perfect oven to obtain about 7.2 g of a polyimide resin powder. A part of the obtained polyimide resin powder was taken, and its specific surface area and imidation ratio were calculated in the same manner as in Example 1. Thereafter, the remaining polyimide resin powder was treated in the same manner as in Example 1 to obtain a polyimide resin molded body. The specific gravity, flexural strength, flexural modulus, tensile rupture strength, tensile rupture elongation, and Izod impact strength with V notch of the polyimide resin molded article thus obtained were measured in the same manner as in Example 1. Table 1 shows the results together with the results of the specific surface area and the imidation ratio. According to Table 1, the polyimide resin powder obtained from Examples 1 and 2 was 20 m ² /
g and an imidation ratio of less than 90%.
The figure shows that this polyimide resin powder is essentially crystalline. A polyimide resin molded article obtained by compression-molding such a polyimide resin powder exhibits high specific gravity, high tensile strength at break and tensile elongation at break, high impact strength, and the like. [Effect of the Invention] An essentially crystalline polyimide resin powder having a large specific surface area and a low imidization ratio is obtained in the present invention. In addition, the polyimide resin molded product obtained by compression molding is extremely excellent in mechanical properties such as strength and toughness in addition to high heat resistance which is the original characteristic of aromatic polyimide resin, and it is suitable for machine parts etc. It can be used very widely and usefully.

[Brief description of the drawings]   FIG. 1 shows the wide angle X of the polyimide resin powder of the present invention obtained according to Example 1. It is a diffraction intensity curve by a line.

Claims (1)

[Claim 1] General formula (I): (Wherein, R ₀ is a tetravalent aromatic group having 6 to 30 carbon atoms, R ₁ is a divalent aromatic group having 6 to 30 carbon atoms, and n is a positive integer). An aromatic polyimide resin powder comprising a powder having a specific surface area of 20 m ² / g or more, an imidation ratio of less than 90%, and being essentially crystalline. 2. A polyimide resin molded article obtained by subjecting the polyimide resin powder according to claim 1 to compression molding, and simultaneously with and / or after compression molding, and then subjecting it to a heat treatment without pressure. .