JPH03181521A - Production of polybenzobisoxazole - Google Patents

Abstract

PURPOSE:To readily obtain the subject polymer capable of providing high- strength and high-elastic fiber by dissolving a polybenzobisoxazole precursor having specific recurring units in a specified solvent, then heating and cyclizing the precursor. CONSTITUTION:The objective polymer obtained by dissolving a polybenzobisoxazole precursor having recurring units expressed by the formula [Ar is (substituted) aromatic residue] in a polyphosphoric acid component- containing solvent, then preferably heating the resultant solution at 80-140 deg.C and initiating cyclizing reaction of the aforementioned precursor expressed by the formula. Furthermore, methanesulfonic acid containing P2O5 dissolved therein is preferred as the polyphosphoric acid component-containing solvent. The precursor expressed by the formula is preferably obtained by silylating 4,6-diamino-1,3-dihydroxybenzene (salt) and subsequently polycondensing the resultant product with terephthaloyl dichloride (derivative).

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing polybenzobisoxazole, which is a rigid aromatic polymer with excellent heat resistance, mechanical properties, chemical resistance, electrical properties, etc. In particular, the present invention relates to a method for producing polybenzobisoxazole that can be made into m-fibers with high strength and high elasticity.

[Problems to be solved by conventional techniques and inventions] In recent years,
Not only light alloys such as TI and ^1, but also composite materials such as fiber-reinforced plastics (FRP) have come to be widely used for the purpose of reducing weight in aircraft, white cars, various vehicles, etc. These composite materials are also used as various structural materials, and research and development of composite materials with excellent mechanical properties is widely conducted.

Sol, which has high strength and high elasticity, is added as a reinforcing material to the base material to improve the mechanical properties of the composite material.
The use of IC is widely practiced, and glass fiber, carbon fiber, etc. are used as such fibers. Also Kevlar (DuPont product name)
5) Fully aromatic polyamides, which are referred to as aramid fibers, are also used.

Although carbon fiber exhibits extremely high elasticity, it is inferior to aramid fibers such as Kevlar in terms of loop strength and knot strength. On the other hand, aramid fibers such as Kevlar have high strength but are inferior to carbon fiber in terms of elastic modulus. Therefore, there is a need for a new fiber that combines the high elastic modulus of carbon fiber with the strength and ease of handling of aramid fibers, and research and development is underway for this new fiber.

PolyP-7benzobisthiazole (P-7) is attracting attention as a tribute that satisfies these conditions.
There are heterocycle-containing aromatic polymers such as BT) and polyP-722benzo'soxazole (hereinafter referred to as polybenzobisoxazole).

These have a structure that incorporates a heterocycle as a means of preventing low elastic modulus, and also eliminates Kevlar's drawbacks such as hygroscopicity. Furthermore, the main chain exhibits rigidity and can provide higher strength, high elasticity, and fiber penetration.

PBT and polybenzobisoxazole can be produced by the BoIJ+J acid method, which is conventionally used for the synthesis of polybarabenzimidazole and rag-polymer. Concerning PBT; well, high molecular weight products can be obtained by this acid method, but polybenzobisoxazole has an intrinsic viscosity of 771hh of 3.0J.
A polymer with a molecular weight of about 10,000 g/mol was obtained. The reason for this is not necessarily clear, but one reason is that the monomer used for the synthesis of vonobenzobisoxazole, 1.
Dihydroxybenzene (or its dihydrochloride, sulfate, etc.)
In the synthesis of , the nitro compound of the previous substance contains a trinitro compound as an impurity, and it is presumed that this causes trinitro γ honey to be produced as a by-product, causing the polymerization to increase and become fuzzy.Also, in the synthesis by the polyphosphoric acid method, Terephthalic acid and terephthalic acid chloride used in
At a temperature of around 20°C, some of the polybenzobisoxazole precursors or oligomers have already undergone a ring-closing reaction to form oxazole, so the viscosity of the reaction solution is relatively high! Second, it is thought that the polymerization reaction is complicated and complicated.

Therefore, the present inventor developed a method for producing a high molecular weight polybenzobisoxazole precursor by first silylating the amine group and hydroxyl group of an aromatic diamino dihydroxy compound and then reacting it with an aromatic dicarboxylic acid civalide. 5) I would like to apply for a patent (Japanese Patent Application No. 1-68163) This method: Since the precursor material obtained from this method has a very high molecular weight, the polybenzobisoxazole of the polymer a is formed by a ring-closing reaction. can get.

However, it has been found that if the ring-closing reaction is simply carried out by heating, it is not necessarily possible to obtain a highly molecularized polybenzobisoxazole in which all rings are closed. Furthermore, since the ring-closing reaction is caused by heating to a relatively high temperature, it has been found that there is a risk that large voids may be introduced in the pre-molding (fiber, film, etc.) due to dehydration accompanying the ring-closing reaction.

Therefore, an object of the present invention is to avoid the above-mentioned problems and to
An object of the present invention is to provide a method for easily producing polybenzobisoxazole having high strength and high elasticity.

[Means to solve the problem]

As a result of intensive research in view of the above objectives, the present inventors dissolved a precursor of polybenzobisoxazole synthesized from an aromatic diaminodihydroxy compound and an aromatic dicarboxylic acid civalide in a polyhydric acid solution, and discovered that by heating the oxazole, the oxazole ring-closing reaction occurred at a relatively low temperature, thereby making it possible to easily produce and manufacture polybenzobisoxazole with high strength and K'J l'l, and completed the present invention. Sase Buni.

That is, the method for producing polybenzobisoxazole of the present invention is a method for producing polybenzobisoxazole having a repeating unit represented by the following formula: The present invention is characterized in that a suoxazole precursor is dissolved in a solvent containing a polybenzobisoxazole component, and then heated to cause a ring-closing reaction of the precursor, thereby producing polybenzobisoxazole.

The present invention will be explained in detail below.

Production of polybenzobisoxazole precursor First, a method for producing a polybenzobisoxazole precursor will be described.

The polybenzobisoxazole@body material can be synthesized from an aromatic diaminodihydroxy compound and an aromatic dicarboxylic acid civalide.

The aromatic diaminodihydroxy compound is a compound having an amine group and a hydroxyl group on both sides of a benzene ring, respectively, as shown in the following figure. This benzene ring may have a substituent such as Cf. Further, the positional relationship between the amino group and the hydroxyl group on both sides may be symmetrical or point symmetrical with respect to the benzene ring. That is, there are the following two types of structures. Note that these hydrochlorides are also included.

110\,7-1-NH2)○(1'H2N'''-'''011'3, 4,6-diamino-1,3-dihyto'roxybenzene 1 or a salt thereof) is suitably used.

In addition, the aromatic dicarboxylic acid cybaride has the following formula: % formula % (11 (However, Ar is a substituted or unsubstituted aromatic residue,
X is a halogen group. ).

The aromatic residue ^r is not limited to a benzene ring, but may be a naphthalene ring, an anthracene ring, etc., or may be a combination of two or more benzene rings such as biphenyl. Furthermore, a substituent such as a halogen, a lower alkyl group, a lower alkoxyl group, or a phenyl group may be added to the aromatic residue Ar. By introducing such a substituent, reactivity and solubility in a solvent are improved.

Examples of such aromatic dicarboxylic acid cybalides include isophthalic acid dichloride, terephthalic acid dichloride,
4.4'-biphenyldicarboxylic acid dichloride, biphenyl ether-4,4'-dicarboxylic acid dichloride, benzophenone-4,4'-dicarboxylic acid dichloride, benzosulfone-4,4'-dicarboxylic acid dichloride, 2
-chloroterephthalic acid chloride, 2-fluoroterephthalic acid chloride, 2-methylterephthalic acid chloride, 2-
Examples include methoxyterephthalic acid chloride, 2-7enyl terephthalic acid chloride, and particularly terephthalic acid dichloride and its derivatives are preferably used. Moreover, even if these aromatic dicarboxylic acid dichlorides are used alone,
Alternatively, two or more types may be mixed and used.

To silylate the amine group and hydroxyl group of an aromatic diaminodihydroxy compound, the compound or a salt thereof,
In particular, the hydrochloride salt is treated with a nitrogen-containing silylating agent in an organic solvent at 80-140° C. for 6-18 hours.

Nitrogen-containing silylating agents useful in such silylation reactions include hexamethyldisilazane, N,N-diethylaminotrimethylsilane, N,N-diethylaminotrimethylsilane, N,0-bis(trimethylsilyl)carbamate, N-) Examples include limethylsilyl □dazole.

Further, as an organic solvent for carrying out the silylation reaction, tetrahydrofuran, carbon tetrachloride, N,N-dimethylacetamide, etc. can be used, but the organic solvent can also be omitted. If the silylation temperature is lower than 80°C, the reactivity is not sufficient, and if it is higher than 140°C, decomposition of the amine hydrochloride occurs, which is not preferable.

Note that the reaction between the silylated aromatic diaminodihydroxy compound and the aromatic dicarboxylic acid cybaride is carried out in an organic solvent.
The reaction may be carried out under substantially anhydrous conditions at -15 to 85°C for 2 to 20 hours, although this may vary somewhat depending on the solvent used. If the reaction temperature is less than -15°C, the reactivity is insufficient,
Moreover, if the temperature exceeds 85°C, there is a risk that the above-mentioned reactants will be oxidized. When the silylated aromatic diaminodihydroxy compound and the aromatic dicarboxylic acid civalide are blended in equimolar amounts, a high molecular weight polybenzobisoxazole precursor can be easily obtained.

Note that the organic solvent used here includes, for example, N,
Amide solvents such as N-dimethylformamide, %, N-dimethylacetamide, N-methyl-2-pyrrolidone,
Aromatic amine solvents such as pyridine, aromatic solvents such as dimethyl sulfoxide and tetramethyl sulfone, benzene solvents such as benzene, toluene, anisole, diphenyl ether, nitrobenzene, and benzonitrile, tetrahydrofuran, 1,4-dioxane, etc. Neutral solvents (aprotic 5
olvent).

Through this reaction, the silylated aromatic diaminodihydroxy compound and the aromatic dicarboxylic acid sybaride undergo polycondensation as shown in the reaction formula below.

Me: +5iX (wherein 6 in the formula is an aromatic residue, X is a halogen),
1e represents a methyl group. ) Next, by stirring in an alcohol such as methyl alcohol for several hours and repeating alcohol washing, a desilylation treatment is performed as illustrated in the reaction formula below.

In this way, a polybenzobisoxazole precursor is obtained.

Production of polybenzobisoxazole The method of the present invention for producing polybenzobisoxazole from the polybenzobisoxazole precursor described above will be described.

First, the solvent containing polyphosphoric acid is one that dissolves the polybenzobisoxazole precursor and
Use one in which IJ acid is soluble. Examples of such solvents include methanesulfonic acid, talolosulfonic acid, and fuming sulfuric acid, with methanesulfonic acid being particularly preferred.

As the polyphosphoric acid, it is preferable to use P2O.

The concentration of bo-IJ-IJ acid in the solvent is such that the weight ratio with the solvent such as methanesulfonic acid is 1:2 to 1:2 as a P2O5 equivalent value.
Set it so that it becomes 1:100. Weight ratio is 1:2
If it is larger (more P, 05), the viscosity of the reaction solvent will increase, which is not preferable. Also, if the weight ratio is less than 1:100 (poor P2O5), there is a risk that some amide groups in the main chain of the precursor substance will be hydrolyzed, resulting in a decrease in molecular weight, which is undesirable. . A more preferable range of this ratio is 1:10 to 1:100. Note that it is preferable to use a solvent such as methanesulfonic acid that has been sufficiently dehydrated in advance. This allows the above-mentioned hydrolysis to be kept to a minimum.

P2O5 is dissolved in a solvent such as methanesulfonic acid to obtain the above ratio and used as a reaction solvent. This dissolution operation is preferably carried out under an inert gas.

Next, the polybenzobisoxazole precursor is added to and dissolved in the reaction solvent. The polybenzobisoxazole precursor is preferably dissolved at about 25° C. under an inert gas flow while stirring.

After a homogeneous solution is obtained, it is stirred while maintaining the temperature at 80 to 140° C. under a flow of inert gas such as argon. At this stage, the polybenzobisoxazole precursor undergoes an oxazole ring-closing reaction as described below, and polybenzobisoxazole is produced.

At this time, the polyphosphoric acid component in the reaction solvent acts as a condensing agent (moves), and also removes ice generated by the oxazole ring-closing reaction, thereby promoting the reaction to proceed to the right.

As explained above, in the method for producing polybenzobisoxazole of the present invention, the oxazole ring-closing reaction of the precursor can be caused at a relatively low temperature of 80 to 140°C, and the oxazole ring-closing reaction can be carried out at a temperature of about 200°C, which was previously possible. There is no need for heating, making manufacturing easy.

[For production]

According to the present invention, a polybenzobisoxazole precursor synthesized in advance from an aromatic diaminodihydroxy compound and an aromatic dicarboxylic acid civalide is
Polybenzobisoxazole is produced by dissolving it in a solution containing the acid component and causing an oxazole ring-closing reaction in this solution, so polybenzobisoxazole can be produced at a relatively low temperature of 80 to 140℃! ! ! can be built.

This is considered to be because polyphosphoric acid acts as a condensing agent and a dehydrating agent.

Since the oxazole ring-closing reaction occurs at a relatively low temperature, the removal of water in the ring-closing reaction proceeds at a low temperature, and as a result, there are almost no voids in the polybenzobisoxazole that would be caused by the removal of water. Even if it does occur, it will be very small and the strength of the polybenzobisoxazole will improve.

In addition, by appropriately setting the concentration of boron IJ acid and the temperature of the solution, it is possible to prevent hydrolysis of the amide group in the main chain of the polybenzobisoxazole precursor. Oxazole can be produced.

〔Example〕

The present invention will be explained in further detail by the following examples.

Example 1 (1) Synthesis of poly(p-)unidinebenzobisoxazole) precursor N,N',0.0'-tetramethylsilyl-4,6-
Thoroughly dry 8.9000 g of diamitsu 1.3-benzenediol and add argon (purity 99.99%, moisture 2p).
Add 50mf of N,N-dimethylacetamide (purity 99.5% or higher, moisture 0.0099%) and heat at 25°C for about 1 hour. Dissolved. Next, terephthaloyl chloride (purity 99.1%, moisture 0°086) was added to this.
%) 4.2133g was added, and under an argon atmosphere, 2.
The reaction was carried out at 5° C. for about 6 hours while stirring at a speed of 20 rpm using a mechanical stirrer.

The resulting viscous red wine-colored transparent liquid was poured into approximately IE of methyl alcohol and left overnight.

Next, the liquid was suction-filtered, washed with methyl alcohol repeatedly, and then dried at 80° C. for 12 hours while suctioning to a pressure of 1 mmHg or less.

The resulting product was analyzed by infrared spectroscopy, and it was determined that polybenzobisoxazole 1] having a repeating unit of the following structural formula was 9 parts 1.

Incidentally, the infrared spectral analysis was performed using a PernElmer model 1750 using the KBr method.

Further, the intrinsic viscosity of the obtained polybenzobisoxazole precursor was measured using an Ubbelohde viscometer. Measurements were performed in 98% sulfuric acid at 30.0°C. Intrinsic viscosity of polybenzobisoxazole precursor η1. ．． h is 0.
It was 467 g-'.

In this example and other examples described later, the volumetric flask used to prepare the solution was placed in a desiccator in advance to prevent the solution from absorbing moisture.
It was taken out and used immediately before measurement.

(2) Production of polybenzobisoxazole from polybenzobisoxazole precursor 6.72 g of P2O was added to 67.2 g of methanesulfonic acid immediately after purification by distillation, heated to 140°C to dissolve P. The mixture was cooled to give a reaction solvent (hereinafter referred to as reaction solvent).

2.5 g of the polybenzobisoxazole precursor obtained in (1) above was added to reaction solvent A25H and dissolved at room temperature over 24 hours to obtain a brown translucent viscous liquid.

This liquid was placed in a 100-meter four-hole flask and stirred while being heated to 14.0° C. under an argon stream. After 2.5 hours, 5 hours, 7.5 hours, and 12 hours had elapsed after the start of stirring, 5 ml of each reaction solution was taken out, and each was added to 80% of distilled water and thoroughly stirred. After stirring, this was filtered, and each sample was washed for 2 hours using a Soxhlet extractor using distilled water as an extraction solvent.

After washing, each sample was dried under vacuum for 718 hours. The samples were designated as Sample B, Sample C, and Sample Sample B, Sample B, Sample C, and Sample Sample, respectively, in descending order of the time when they were collected from the solution.

Next, an infrared spectrum was measured for sample ~D. The results are shown in Figures 1 to 4, respectively. Comparing these infrared spectrum charts with the infrared spectrum of the polybenzobisoxazole precursor measured in (1) above and the infrared spectrum of polybenzobisoxazole directly synthesized from monomers or S using the polyphosphoric acid method, sample A-
It was found that the infrared spectra of D were all similar to the latter. In particular, in the spectra of samples A-D and the spectrum of polybenzobisoxazole synthesized by the polyphosphoric acid method, an absorption estimated to be based on the C=N bond of the oxazole ring was observed near 1.630 cm-'. . Also, based on the amide group observed in the spectrum of the precursor, absorption near <1640 cm-' and 1.540 c
No absorption at m−' was observed in the spectra of samples A to D.

In addition, in the spectra of Samples A and B, a faint absorption was observed at 1680co+-' that was not present in the spectrum of the precursor and the spectrum of polybenzobisoxazole synthesized by the polybenzobisoxazole method.

This absorption is thought to be based on the C-0 bond of the carboxylic acid, suggesting that there may be a slight hydrolysis of the amide bond in the sample and in B.

Next, the intrinsic viscosity of each of samples Δ to D was measured. Viscosity was measured using an Ubbelohde viscometer at 30.0°C.
The test was carried out in methanesulfonic acid under the following conditions. The measurement results are shown in Figure 5. Figure 5 shows that the products with a reaction time of 2, 5 and 5 hours (the time the polybenzobisoxazole precursor was dissolved in the reaction solvent and stirred at 140°C) had a somewhat lower viscosity; It is shown that the viscosity increases and becomes constant over a reaction time of about 7 hours. This change in viscosity is thought to be due to a change in molecular weight (change in main chain length). That is, as suggested by the results of the infrared spectra of samples A-D, a part of the main chain was once hydrolyzed by the amide group in the initial stage of the reaction, and then hydrolyzed by the action of the reaction solvent as a condensing agent. It is presumed that the removed site forms an amide group again and finally forms an oxazole ring.

Example 2.3 Reaction solvent A25 prepared in the same manner as in Example 1 (2)
2.5 g of the polybenzobisoxazole precursor W obtained in (1) of the implementation <q+ + was added to
It dissolved over time to obtain a brown semi-clear viscous liquid.

This liquid was placed in a 100 d four-bottle flask and heated at 80°C (Example 2) and 110°C (Example 3) under an argon stream.
The mixture was stirred for 12 hours while heating to .

Next, the obtained solution was filtered, washed and dried in the same manner as in Example 1 (2) to obtain a sample. Furthermore, infrared spectra were measured for each of the obtained samples.

The infrared spectra of the samples obtained in Examples 2 and 3 were both close to the infrared spectra of polybenzobisoxazole synthesized by the boron IJ IJ acid method. However, in the spectrum of Example 2, 162
A slight absorption was observed on the high wave number side shoulder of the absorption peak existing at 0 cm-', and a small absorption was also observed at 1570 cm-'l. In addition, in Example 3, the t570cm
In addition to the small absorption at -', a small absorption was also observed at l 680 cm. These absorptions were not observed in the spectrum of the polybenzobisoxazole precursor and the spectrum of polybenzobisoxazole synthesized by the polyphosphoric acid method, suggesting the presence of carboxyl groups. From the above, it appears that the main chains of the samples of Examples 2 and 3 were partially hydrolyzed, albeit slightly.

Example 4 0.2 g of P2O was added to 20 g of methanesulfonic acid that had just been purified by distillation, heated to 140°C to dissolve P2O, and cooled to room temperature to form a reaction solvent (hereinafter referred to as reaction solvent B). .

0.495 g of the polybenzobisoxazole precursor obtained in (1) of Example 1 was added to reaction solvent B51-, and the mixture was heated at room temperature.
The solution was allowed to dissolve overnight under a stream of argon.

This solution was then stirred for 12 hours while being heated to 140° C. under an argon stream.

The obtained solution was added to 100 ml of distilled water, thoroughly stirred, filtered, washed and dried in the same manner as in Example 1 (2).

When the infrared spectrum of the obtained sample was measured, it was found to be similar to the spectrum of polybenzobisoxazole synthesized by the polymeric acid method. However, 1
A small absorption believed to be based on the carboxylic acid C-0 bond was observed near 680c+n-'.

This suggests that some of the sample was slightly hydrolyzed.

From the following two examples, it can be seen that the oxazole ring-closing reaction in the polybenzobisoxazole precursor sufficiently proceeds at 80 to 140°C in a methanesulfonic acid solution containing polyphosphoric acid. Also, the concentration of the polyphosphoric acid component in methanesulfonic acid is such that the amount of P2O added to methanesulfonic acid is 1:10 to 1:1OO to methanesulfonic acid! 'i! Hydrolysis of the precursor can be better suppressed by using a concentrated solution of phosphoric acid.

〔Effect of the invention〕

According to the method of the present invention, polybenzobisoxazole is produced by dissolving a polybenzobisoxazole precursor in a solvent containing boron acid and heating it to a temperature of 80 to 140°C. be able to. In this way, polybenzobisoxazole can be produced at a relatively low temperature without heating to temperatures of around 200°C or higher, which is required in conventional polybenzobisoxazole production methods. Its manufacture becomes easy. Further, as described above, since the oxazole ring-closing reaction occurs at low temperatures, even if voids are generated due to dehydration during the ring-closing reaction, they will be very small, and the strength of the resulting polybenzobisoxazole will be improved.

Furthermore, in the method of the present invention, the reaction solvent used (PoIJ I
The solvent (containing a phosphoric acid component) can be used as it is as a dope solution for spinning. Further, the pressure required during spinning is small, and workability is good.

In the method of the present invention, a high molecular weight polybenzobisoxazole precursor synthesized from a silylated aromatic diamino dihydroxy compound and an aromatic dicarboxylic acid civalide is used, Since polybenzobisoxazole is synthesized without hydrolyzing the main chain of the precursor by appropriately setting the reaction time, the resulting polybenzobisoxazole also has a high molecular weight.

Note that the polybenzobisoxazole obtained by the method of the present invention can be easily formed into a film as well as a fiber.

[Brief explanation of drawings]

FIGS. 1 to 4 are charts showing the results of infrared spectral analysis of polybenzobisoxazole obtained in Example 1, and FIG. It is a graph showing the relationship between the reaction time when synthesizing polybenzobisoxazole from a polybenzobisoxazole precursor and the viscosity of the obtained polybenzobisoxazole. Applicant Honda Motor Co., Ltd.

Claims (4)

[Claims] (1) The following general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, in the formula, Ar is a substituted or unsubstituted aromatic residue.) Polybenzobisoxazole precursor having a repeating unit represented by A method characterized in that a substance is dissolved in a solvent containing a polyphosphoric acid component, and then heated to cause a ring-closing reaction of the precursor, thereby producing polybenzobisoxazole. (2) In the method according to claim 1, the amount of the polyphosphoric acid component in the solvent is 1:2 to 1:1 in terms of weight ratio to the solvent, when the polyphosphoric acid component is converted to P_2O_5.
00 range. (3) The method according to claim 1 or 2, wherein the solvent is methanesulfonic acid. (4) The method according to any one of claims 1 to 3, characterized in that the solution in which the polybenzobisoxazole precursor is dissolved is heated to 60°C to 150°C.