JPH0447048B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel wholly aromatic copolyimide uniaxially oriented product that has high strength, high modulus of elasticity, and extremely excellent heat resistance. [Conventional technology] Fully aromatic copolyimide has the highest heat resistance among organic polymers, and has already been put to practical use in molded products such as films by taking advantage of this characteristic. Its mechanical properties are very ordinary, and its strength and elastic modulus are never high. As an example of obtaining polyimide molded products with high elastic modulus, in the case of fibers, a solution of polyamic acid consisting of a rigid aromatic diamine and a specific aromatic tetracarboxylic dianhydride is wet-spun, stretched, and then , a method of heating to cyclize into imide groups has been proposed, but the mechanical properties of the resulting fibers are not very good. In addition, in JP-A-60-65112, the diamine component is 3,3'-dimethylbenzidine, and the acid anhydride component is pyromellitic anhydride (A) and 3,3',4,4'-bifurinated acid anhydride. A high-strength compound consisting of a mixture of enyltetracarboxylic dianhydride (B) in a specific proportion.
High modulus fibers are disclosed. In this publication, a solution of the polyimide dissolved in a phenolic solvent is used as a stock solution, wet-spun in an ethanol coagulation bath, and then hot stretched to obtain polyimide fibers, but there are the following problems. In other words, the diamine component contains 3,
Since 3'-dimethylbenzidine is used, the polyimide produced is a nuclear methyl substituted product, and the excellent heat resistance inherent to polyimide is considerably impaired. [Problems to be Solved by the Invention] Therefore, fibers and uniaxially stretched films that have high strength, high elastic modulus, and extremely excellent heat resistance are particularly desirable. As a result of intensive research aimed at creating a uniaxially oriented product with the above characteristics, the present inventors found that
The inventors have discovered that a wholly aromatic copolyimide consisting of a specific aromatic diamine or a mixture thereof and a mixture of two specific aromatic tetracarboxylic dianhydrides is suitable for this purpose, and has thus arrived at the present invention. [Means for Solving the Problems] In the molded product of the present invention, the diamine component is p-phenylenediamine, 2-chloro-p-phenylenediamine, benzidine, 2-chlorobenzidine, and 2,2'-dichloro A wholly aromatic copolyimide consisting of at least one selected from benzidine, the acid anhydride component being pyromellitic anhydride (A) and 3,3',4,4'-biphenyltetracarboxylic dianhydride and the ratio of the above (A) in the acid anhydride component is about
This is a fully aromatic copolyimide uniaxially oriented product characterized by a content of 90 to 20 mol%. The present invention will be explained in detail below. The wholly aromatic copolyimide uniaxially oriented product of the present invention has extremely excellent mechanical properties. Taking fiber as an example, it has a strength of 15 g/d or more and an elastic modulus of 900 g/d or more. In addition, the uniaxially stretched film has a strength of 50 in the stretching direction.
Kg/mm ² or more, elastic modulus 500 Kg/mm ² or more. Also,
It also has extremely high heat resistance and chemical resistance, making it useful for many uses. The copolyimide of the present invention is disclosed in Japanese Patent Application Laid-Open No.
Unlike the one described in Publication No. 65112, there is no solvent to dissolve it once it has been formed. Therefore, first, polyamic acid, which is a precursor polymer soluble in an organic solvent, must be prepared, and after being subjected to shaping processing at that stage, it must be cyclized into an imide group using an appropriate means. Therefore, first, the method for producing polyamic acid will be explained. The aromatic diamine used in the present invention is p-phenylenediamine, 2-chloro-p-
At least one selected from phenylenediamine, benzidine, 2-chlorobenzidine and 2,2'-dichlorobenzidine. They may be used alone or in a mixture of two or more. In that case, the mixing ratio is arbitrary. On the other hand, as an acid anhydride, pyromellitic anhydride (A)
and 3,3',4,4'-biphenyltetracarboxylic dianhydride (B). The ratio of (A) in the acid anhydride component is about 90 to 20 mol%, and molded products with high performance cannot generally be obtained outside this range. for example,
A polyimide consisting of (B) alone as an acid anhydride component is inferior to the copolyimide of the present invention in terms of elastic modulus, regardless of its strength. The monomers used in the present invention are as described above, but up to about 10 mol% of other monomers may be copolymerized. Such copolymerization components include m-phenylenediamine, 4,4'-diamino-p-terphenyl, 2,1-diaminofluorene, 2,6-diaminonaphthalene, 4,4'-diaminodiphenyl ether, 3, Examples include 4'-diaminodiphenyl ether and 1,4-bis(p-aminophenoxy)benzene. In addition, as the acid anhydride component, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-
Examples include benzophenonetetracarboxylic dianhydride. A solution of polyamic acid, which is a precursor polymer, is obtained by dissolving the above diamine or a mixture thereof in an amide solvent, and then adding a mixture of the above acid anhydride in substantially equimolar amounts to the diamine component and causing polycondensation. . The intrinsic viscosity of the polyamic acid produced (the measurement method will be described later) is 0.7 or more, preferably 1.2 or more. Examples of amide solvents used in polymerization include N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and N,N-dimethylformamide. The polyamic acid solution thus obtained is then molded into fibers, films, tapes, etc. The methods can be broadly divided into wet methods and dry methods, but the wet method will be explained first. The stock solution used in the wet method may be the above-mentioned polyamic acid solution itself, but as previously proposed by the present inventors in Japanese Patent Application No. 58-27068, a part of the amic acid unit is added to the solution using a chemical cyclizing agent. It is more preferable to use a partially cyclized polymer solution which has been cyclized with . As such a cyclizing agent, acid anhydrides and aliphatic acid anhydrides such as propionic anhydride are suitable. The amount added is about 0.1 equivalent to 0.4 equivalent relative to the amic acid unit. For this chemical cyclization, an organic base such as pyridine, 3-methylpyridine, 3,5-lutidine, or quinoline may be used as a catalyst. The amount added is not particularly limited. The above polyamic acid solution or a polymer solution in which a portion of the amic acid is cyclized into imide groups is extruded into an aqueous coagulation bath through an orifice, a slit die, or the like. Alternatively, it is cast onto a flat plate and immersed in an aqueous coagulation bath. The coagulation bath may be water, an aqueous solution of a polymerization solvent, or an aqueous solution of an inorganic salt, but from the viewpoint of ease of recovery of the polymerization solvent, an aqueous solution of the same solvent is preferred. Coagulation bath temperature is 0~
50℃ is suitable. The solidified molded article may subsequently be stretched. This stretching may be carried out in water, which also serves as washing, or may be carried out in air. The stretching temperature is preferably 10 to 90°C, and the stretching ratio is 1.2 to 3.0 times. The unstretched or stretched solidified molded product is dried as it is and then subjected to thermal cyclization, or treated while swollen with a chemical cyclizing agent to close the amic acid to an imide group. The cyclizing agent and catalyst used in the latter case are the same as those used for the partial cyclization in solution, and the combination of acetic anhydride and pyridine is particularly suitable. Note that, before the solidified molded product is subjected to chemical cyclization, water in the molded product may be extracted and removed by washing with an organic solvent that does not contain active hydrogen and is miscible with water. Suitable solvents include acetone, tetrahydrofuran, dioxane, and the like. Further, other organic solvents may be used as diluents during chemical cyclization. Such diluents include dioxane, benzene, toluene, chloroform, carbon tetrachloride, acetonitrile, and the like. The treatment conditions for chemical cyclization are a temperature of 15 to 50°C, and a treatment time of 10 minutes to 1 day or more. The chemically cyclized molded article is then dried, but before drying, it may be washed with an organic solvent to remove the cyclizing agent. The above-mentioned diluents are suitable as such cleaning agents. The chemically cyclized molded product may be stretched while still wet with the cyclizing agent or cleaning agent, if there is still room for stretching. Also, NMP
It may be stretched after being immersed in a swelling agent such as. In this case, it is preferable to stretch in water to also remove the solvent, and the stretching temperature is 20 to 100°C, and the stretching ratio is 1.03 to 1.3 times. The solidified molded product, with or without chemical cyclization, is then dried. For drying, any of hot air drying, vacuum drying, or continuous drying using a heated drum or the like may be employed. The dried molded product is finally subjected to hot stretching or heat treatment. In molded products that have not been chemically cyclized, the amic acid is thermally cyclized to imide groups in this step. If polyamic acid is not stretched at the molded product stage,
Stretching must be done in this process. As the heating means, either a hot plate or a heating tube may be used. Alternatively, it may be heat-treated in batches while wound on a bobbin or drum. Further, hot stretching or heat treatment may be carried out by raising the temperature stepwise, and the final treatment temperature is preferably 400° C. or higher. Further, the atmosphere is air or an inert gas such as nitrogen. Next, dry molding will be explained. In this case as well, there are two methods: one is to use the polyamic acid solution obtained by polymerization as a stock solution, and the other is to use a polymer solution to which a chemical cyclizing agent has been added under temperature conditions (below 10°C) where cyclization does not substantially occur. be. In the latter case, after being formed into a shape such as a film, the temperature is raised to a temperature at which cyclization occurs to cause gelation and form retention. The chemical cyclizing agent used is the same as that described in the wet molding section, and the amount added is preferably 1.0 to 3.0 times the amount of amic acid equivalent. Polyamic acid solutions with or without chemical cyclizing agents can be cast onto a flat plate or extruded through a slit die onto a belt or drum to form a film.
Then, the temperature is raised to evaporate the solvent and proceed with thermal cyclization. In the case of a solution containing a chemical cyclizing agent, cyclization precedes evaporation of the solvent, as described above. Fibers can also be produced by discharging a polyamic acid solution into a hot air stream through a die.
The thus obtained molded articles, such as fibers and films, must then be stretched. Stretching may be carried out with some of the solvent remaining, or may be carried out after the solvent has been completely evaporated. Generally, the former method is easier to operate because it can be stretched at a lower temperature. The recipe for hot stretching and heat treatment is exactly the same as for the wet molded product described above. [Effects of the Invention] The fully aromatic copolyimide uniaxially oriented product of the present invention has excellent mechanical properties. In the case of fiber, the strength is 15g/
In the case of a uniaxially stretched film, the strength in the stretching direction is 50 Kg/mm ² or more and the elastic modulus is 5000 Kg/mm ² or more. It also has extremely high heat resistance and chemical resistance. Therefore, they are useful in many applications, for example the fibers can be used to reinforce rubbers, resins, etc. In addition, uniaxially stretched films can also be used as structural materials by laminating them. [Example] The present invention will be explained in more detail with the following Examples and Comparative Examples. The intrinsic viscosity (η _ioh ) of the polyamic acid in the example was measured at 25°C after diluting the polymer solution with NMP to a ratio of 0.5 g of polymer/100 ml of solvent. Further, the tensile properties were measured using Tensilon manufactured by Toyo Baldwin Co., Ltd. In the case of fibers, the sample is a single yarn with a sample length of 100 mm and a tensile speed of 10 mm/min. In addition, for film, the sample width is 5 mm, the sample length is 100 mm,
Measurement was performed at a tensile speed of 10 mm/min. Note that the influence of equipment compliance was ignored. Example 1 In this example, the diamine component was p-phenylene diamine, and the acid anhydride components were 40 mol% of pyromellitic anhydride (PMDA) and 3,3'4,4'-biphenyltetracarboxylic dianhydride. The results of spinning a copolyimide (chemical cyclization method) consisting of 60 mol% (BPDA) are shown. 4.109 g (38 mmol) of p-phenylenediamine was dissolved in 139 ml of dehydrated NMP, and 3.332 g (15.3 mmol) of PMDA and 6.742 g (22.9 mmol) of BPDA, which had been thoroughly ground and mixed in a mortar, were added and polymerized, resulting in η _ioh 3.82, a polyamic acid solution with a polymer concentration of 10.0% was obtained. This solution was diluted by adding 71 ml of NMP, cooled with ice water, and mixed with 1.56 ml of acetic anhydride while stirring.
(0.2 equivalents of amic acid units), 1.21 g of pyridine, and 2 ml of NMP were added dropwise over about 30 minutes, and the reaction was then continued at 25°C for 5 hours to form a partially cyclized polyamide with a polymer concentration of 6.5% and a solution viscosity of 500 Poise. An acid solution was obtained. Pour this solution through a 0.1mmφ, 6-hole cap.
Spun in a 25°C coagulation bath consisting of NMP/water (volume ratio 25/75) (spinning speed 10 m/min), then 25°C
It was stretched 2.0 times in water at ℃. This coagulated thread, wound around a glass bobbin, was immediately immersed in acetic anhydride/pyridine (volume ratio 70/30) and left overnight at room temperature to proceed with chemical cyclization. This chemically cyclized thread was immersed in toluene for 90 minutes, dried under vacuum at 100°C, and then placed in a 30cm long glass cylindrical tube through which nitrogen was loosely passed.
It was stretched 4.0 times at 575°C (yarn feeding speed 3.0 m/min).
The yarn quality of this hot-drawn yarn is a single yarn fineness of 1.1d and a strength of 19.6.
g/d, elongation 2.4%, and elastic modulus 980 g/d, indicating extremely high strength and high elastic modulus. Comparative Example 1 This comparative example uses p-phenylenediamine and PMDA.
The results of spinning homopolyimide (chemical cyclization method) are shown below. p-phenylenediamine and PMDA were polymerized in NMP to create a polyamic acid solution with a polymer concentration of 6.5% and η _ioh 3.58, and then acetic anhydride and pyridine in an amount of 0.2 equivalents of the amic acid unit were added, resulting in a polymer concentration of 6.3% and A partially cyclized polymer solution with a solution viscosity of 560 Poise was obtained. This solution was wet-spun using the same equipment as in Example 1,
After stretching 1.6 times in water at 25℃, acetic anhydride at room temperature/
Chemical cyclization was performed by soaking in pyridine (70/30) overnight. After further replacing with toluene, it was re-rolled and vacuum-dried. The quality of the fiber obtained by drawing this 1.1 times at 757℃ has a single yarn fineness of 2.3d, a strength of 7.3g/d, and an elongation of 0.8%.
The elastic modulus was 980 g/d, and the strength was extremely low compared to the copolyimide fiber of Example 1. Example 2 In this example, the diamine component is 2,2-dichlorobenzidine (Di-Cl-Bz), and the acid anhydride components are PMDA 80 mol% and BPDA 20 mol%. The results of forming uniaxially stretched films using the dry thermal cyclization method and the dry thermal cyclization method are shown below. Di−Cl−Bz, PMDA and BPDA in NMP
was polymerized at the above ratio, polymer concentration 14.0%, η _ioh
A polyamic acid solution of 2.85% was obtained. Next, 0.3 equivalents of amic acid units of acetic anhydride and pyridine, and an appropriate amount of NMP were added to give a polymer concentration of 9.0%.
A partially cyclized polymer solution with a solution viscosity of 5000 Poise was obtained.
This solution was wet-spun using the same recipe as in Example 1, and
It was stretched 1.4 times in water at ℃. This coagulated thread (A) was immersed overnight in acetic anhydride/pyridine (70/30) at room temperature for chemical cyclization, replaced with toluene, and then dried in vacuum. This chemically cyclized yarn was stretched 2.3 times at 450°C in nitrogen (B), and further stretched 1.1 times at 525°C (C). The yarn quality of each drawn yarn was as follows.

[Table] On the other hand, the above coagulated yarn (A) was dried in vacuum at 60℃ for 30 minutes, stretched to 1.13 times using a hot plate at 200℃, and heated in an oven at 210℃ while being wound around a glass bobbin.
Thermal cyclization was proceeded by treatment at 280°C for 10 minutes and then 30 minutes at 280°C. This thermocyclized yarn was subjected to constant length treatment at 400°C in nitrogen (D), further treated at 500°C (E), and finally constant length treatment at 525°C (F). The processing time was 6 seconds in both cases.
The fiber quality of the heat treatment system at each stage is summarized below.

[Table] Next, the results of forming the uniaxially stretched film are described. Add the above partially cyclized polymer solution to a polymer concentration of 5.5%.
After dilution, cast onto a glass plate and heat in an oven for 90
A film with a polymer concentration of 66% was obtained by heating at ℃ for 20 minutes. Peel off this film from the glass plate 135mm
After cutting to width, it was stretched 1.27 times in air at 200°C using a manual stretching machine. This uniaxially stretched film was fixed to an aluminum frame with a length of 140 mm and a width of 75 mm, and was placed in an oven at 210°C for 10 minutes, 280°C for 30 minutes, and 420°C for 3 minutes.
Heat treated for minutes. This heat treated film (9μ thickness)
The tensile properties in the stretching direction are strength 94Kg/mm ² and elongation 1.0.
%, and the elastic modulus was 10,600 Kg/mm ² , showing extremely high performance. Example 3 In this example, the diamine component was penzidine (Bz).
30 mol%, Di-Cl-BZ 70 mol%, acid anhydride components include PMDA 90 mol% and BPDA 10 mol%. BZ, Di−Cl−BZ, PMDA and
Polyamic acid with η _ioh 2.51 is produced by polymerizing BPDA at the above ratio, and then acetic anhydride and pyridine in an amount of 0.25 equivalents of the amic acid unit, and an appropriate amount of NMP are added.
was added to make the polymer concentration 8.5% and the solution viscosity 1380Poise.
A partially cyclized polymer solution was obtained. This solution was wet-spun using the same equipment as in Example 1, stretched 1.5 times in water at 25°C, and then acetic anhydride/pyridine (70/30) at room temperature.
After replacing with toluene, it was vacuum dried. This chemically cyclized yarn was drawn 3.1 times at 550°C under nitrogen, and the fiber quality was 1.3 d, strength 23.3 g/d, elongation 1.9%, and elastic modulus 1410 g/d. .

Claims (1)

[Claims] 1 The diamine component is p-phenylenediamine, 2
-Chloro-p-phenylenediamine, benzidine, 2-chlorobenzidine, and 2,2'-dichlorobenzidine, and the acid anhydride component is pyromellitic anhydride (A) and 3, A wholly aromatic copolyimide consisting of 3',4,4'-biphenyltetracarboxylic dianhydride,
A uniaxially oriented wholly aromatic copolyimide product, characterized in that the ratio of the above (A) in the acid anhydride component is 90 to 20 mol%.