JPH0745566B2 - Wholly aromatic copolyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a thermotropic wholly aromatic copolyester. The copolyesters of the present invention are melt moldable and can provide molded articles with excellent mechanical properties and optical anisotropy.

<Prior art> In recent years, the demand for higher performance of plastics has been increasing, and various high-performance plastics have been developed and put on the market. Among them, they are composed of particularly rigid molecular chains and are optically anisotropic when melted. Thermotropic liquid crystal polymers exhibiting properties are attracting attention because they have a low melt viscosity, good processability, and excellent mechanical properties.

A wholly aromatic polyester is widely known as the liquid crystal polymer, and for example, homopolymers and copolymers of 4-hydroxybenzoic acid are commercially available. However, the melting point of 4-hydroxybenzoic acid homopolymer is so high that it cannot be melt-molded. Also,
A copolymer obtained by copolymerizing 4-hydroxybenzoic acid with, for example, terephthalic acid and hydroquinone or 4,4'-biphenol has considerably improved processability as described in JP-B-47-47870. Still, its softening point is extremely high at 400 ° C. or higher, making it difficult to perform melt molding and not fully expressing its original mechanical properties.

Various methods other than this have been tried as means for improving the melt processability by lowering the melting point or softening point of such wholly aromatic polyester. For example, the above publication also describes a method of using or using a meta-substituted aromatic compound such as isophthalic acid in place of the terephthalic acid component. Further, JP-B-58-40976 discloses a method of using a nuclear-substituted hydroquinone, and JP-B-56-18016,59-31530 describes a method of introducing an aliphatic component into a polymer chain. There is.

However, in these methods, even though it is possible to make the melting point of the polyester produced to be 400 ° C. or lower, the optical anisotropy is lowered during melting or, in extreme cases, disappears. It was not preferable because the remarkable deterioration of the physical properties was observed.

<Problems to be Solved by the Invention> An object of the present invention is to provide a novel thermotropic polyester which is easy to melt-process and which is made of wholly aromatic and has excellent mechanical properties.

More specifically, it is to provide a wholly aromatic copolyester which can be processed into a high-strength molded product by processing in a liquid crystal state by a thermoplastic molding method at a temperature of 400 ° C. or lower.

<Means for Solving Problems> As a result of intensive studies, the present inventors have found a wholly aromatic copolyester having a specific repeating unit that achieves the above object.

That is, 4-hydroxybenzoic acid, terephthalic acid and
In a system consisting of 4,4'-biphenol or hydroquinone, excellent melt processability and mechanical properties, especially when 4,4'-dihydroxydiphenyl sulfone is used as a dihydroxy component in combination with 4,4'-biphenol or hydroquinone. It has been found to give wholly aromatic copolyesters.

In the present invention, the repeating units represented by the following (I) to (IV) are essential constituent components, and the unit (I) is contained in an amount of 20 to 70 mol%, particularly preferably 30 to 60 mol%, (II) The molar ratio of / (III) is 95 to 5/10/90, particularly preferably 90/10 to 20/80.
And the (II + III) / (IV) molar ratio is 0.95 to 1.05.
Is a thermotropic wholly aromatic copolyester having excellent melt processability.

(In the formula, n is 0 or 1, and R ₁ , R ₂ , and R ₃ are each hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and an aryl group having 6 to 10 carbon atoms. , Or 7 to 7 carbon atoms
12 alkylaryl groups (eg phenyl and naphthyl), or halogen (preferably chlorine or bromine) groups. ) As the repeating unit (I), 4-hydroxybenzoic acid having the above-mentioned substituent, for example, 4-hydroxy-2-methylbenzoic acid, 4-hydroxy-3-methylbenzoic acid, 4-hydroxy-2-phenylbenzoic acid, 2-chloro-4-hydroxybenzoic acid and 3-chloro-4-hydroxybenzoic acid are mentioned, but unsubstituted 4-hydroxybenzoic acid is preferable from the viewpoint of mechanical properties and processability.

The amount of repeating units (I) is 20 to 70 mol%, particularly preferably 30 to 60 mol%, of the total. If the amount of the repeating unit (I) exceeds this range, the melting point of the obtained copolyester becomes high and the melt processing becomes difficult. On the other hand, if it is less than this range, the liquid crystallinity becomes insufficient and the mechanical properties of the molded product deteriorate, which is not preferable.

The repeating unit (II) is hydroquinone, 4,4'-biphenol and a compound having these substituents,
Unsubstituted 4,4'-biphenol is particularly preferable in terms of processability and mechanical properties.

The repeating unit (III) is 4,4'-dihydroxydiphenyl sulfone, and the repeating unit (IV) is terephthalic acid, isophthalic acid or a mixture thereof. If the proportion of isophthalic acid is high, the melting point of the resulting copolyester will be low and the melt processability will be improved, but the mechanical properties of the molded product will be reduced, so the molar ratio of terephthalic acid to isophthalic acid is 100 / 0- 70/30, especially 100/0 to 50/50 are preferred.

The molar ratio of repeating units (II) and (III) is 95/5 to 10/90, particularly preferably 90/10 to 20/80. If the molar ratio of (II) / (III) is out of the above range, the melting point of the obtained copolyester is high, the melt processability becomes difficult, and the mechanical properties of the molded product deteriorate, which is not preferable.

The repeating unit (II + III) / (IV) molar ratio is 0.95 to 1.05.
If it is out of this range, it is difficult to increase the molecular weight of the obtained copolyester, and the mechanical properties of the molded product are insufficient, which is not preferable.

The copolyester of the present invention can contain the above groups (I) to (IV) in a statistical distribution, in a segment, or as a block. However, regarding the chain formed from the component (I) or from (II) and (IV), if the block length is long, the melting point and the melt viscosity remarkably increase, which is not preferable.

In the aromatic copolyesters of this invention, the end groups may be optionally capped. As the capping agent, the acid terminal group has an aromatic monohydroxy compound, for example, 4-
Hydroxydiphenyl, 4-nonylphenol, β-naphthol, and hydroxy end groups include aromatic monocarboxylic acid compounds such as diphenylcarboxylic acid and naphthalenecarboxylic acid.

Intrinsic viscosity ([η] inh;
(Measured in p-chlorophenol at 45 ° C) is usually 0.2 dl / g or more by changing the polymerization conditions, but in terms of processability and mechanical properties of the molded product,
It is preferably 5 dl / g or more, particularly in the range of 1.0 to 10 dl / g.
Incidentally, the copolyester of the present invention, after undergoing solid phase polymerization by heat treatment, has a significantly large intrinsic viscosity,
Such a polyester is one embodiment of the polyester of the present invention, although it may be insoluble in the above solvent.

The aromatic copolyester of the present invention has a flow starting temperature of + 20 ° C.
10 to ¹ when measuring at a shear rate of 10 ³ sec ^-1 at a temperature of 400 ° C
Those exhibiting a melt viscosity of 0,000 poise, particularly those exhibiting a melt viscosity of 5,000 poise or less are preferable. The melt viscosity can be measured by a standard method using an Instron capillary rheometer equipped with a capillary having a length of 4 inches and an inner diameter of 0.03 inches.

The aromatic copolyester of the present invention can be produced according to the conventional polycondensation method of an aromatic copolyester, and the production method is not particularly limited, but as a typical production method, for example, 4-hydroxybenzoic acid, 4,4'-biphenol.4,
A method of reacting a lower acyl ester of 4'-dihydroxydiphenyl sulfone, preferably an acetic acid ester, with terephthalic acid can be mentioned. The acyl ester can also be made in situ and used without isolation.

More specifically showing this reaction, 4-acetoxybenzoic acid, 4,4'-diacetoxybiphenyl, or diacetoxyhydroquinone, 4,4'-diacetoxydiphenylsulfone and terephthalic acid are stirred with a stirrer, a nitrogen gas introducing pipe, A polymerization reactor equipped with a vacuum distillation apparatus is charged, and the reaction is carried out at a temperature of 160 ° C to 400 ° C, preferably 250 ° C to 350 ° C under a nitrogen stream. Since the rate of the polycondensation reaction generally increases as the temperature rises, it is preferable to carry out the polycondensation at a relatively high temperature.
However, at high temperatures, the polyester tends to decompose and higher molecular weights are advantageous for thermal stability. Therefore, it is generally desirable to start the reaction at a low temperature and continuously raise the temperature as the reaction proceeds. In addition, when the reaction rate decreases, the reaction can be performed under a reduced pressure of 0.1 to 2.0 mbar. The obtained product is preferably granular, and the secondary solid phase polycondensation reaction can be performed at a temperature of 200 to 350 ° C. under reduced pressure. This operation increases the molecular weight and significantly improves the properties of the copolyester obtained.

Further, a catalyst can be used to promote the above reaction. Catalysts of this type are known, for example Lewis acids,
Examples thereof include hydrogen halides, salts of organic acids or inorganic acids, and compounds of antimony and germanium.

The amount of catalyst is 0.001-1.0, based on the amount of all monomers used,
In particular, 0.01 to 0.2% by weight is preferable.

The thermotropic wholly aromatic copolyester of the present invention is
Since the molding temperature is as low as 400 ° C or less and the melt viscosity is relatively low, it can be used for ordinary melt molding such as injection molding, extrusion molding, compression molding, blow molding, and processed into molded products, fibers, films, etc. It is possible to Further, this copolyester provides a molded article having high strength and excellent dimensional stability because molecular orientation is achieved by the shearing force during processing. In addition, at the time of molding, the copolyester of the present invention is added to a reinforcing agent such as glass fiber or carbon fiber, a filler,
Additives such as nucleating agents, pigments, antioxidants and stabilizers and other thermoplastic resins can be added to improve the properties of the molded article.

<Examples> The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The intrinsic viscosity is 0.1% by weight.
The relative viscosity (η _rel ) of the p-chlorophenol solution of _{No. 1} at 45 ° C. was obtained by a capillary viscometer and calculated by the following formula.

[C = concentration of solution (0.1% by weight) in the formula] Also, the outflow starting temperature was 6 ° C under a pressure of 100 kg / cm ^{2 with} a high-performance flow tester using a die with a length of 10 mm and a diameter of 1 mm.
The temperature was raised at a rate of 1 / min to obtain a melt viscosity of 48,000 poise.

The anisotropy of the obtained polyester during melting was confirmed by a polarizing microscope equipped with a hot stage.

Example 1 The following substances are weighed and put into a 500 ml four-neck separable flask equipped with an induction stirrer, a nitrogen gas introduction tube and a distillation head equipped with a condenser.

(A) 4-Hydroxybenzoic acid 69.1 g (0.50 mol) (b) 4,4'-biphenol 23.3 g (0.125 mol) (c) 4,4'-dihydroxydiphenyl sulfone 31.3 g
(0.125 mol) (d) Terephthalic acid 41.5 g (0.25 mol) (e) Acetic anhydride 122.5 g (1.20 mol) The polymerization equipment was heated to 150 ° C while stirring under a nitrogen gas atmosphere.
The mixture was heated up to reflux and refluxed for 4.5 hours. Then, the temperature was raised to 300 ° C. over 5 hours while acetic acid was distilled from the polymerization apparatus, and the reaction was continued at that temperature for 0.5 hour.

Next, the polymerization apparatus was cooled to room temperature, and the obtained light brown polyester was pulverized.

The intrinsic viscosity of this polyester was 0.37 dl / g, and the polymer showed a melting endothermic peak at 284 ° C. as measured by a differential scanning calorimeter (DSC) and a heating rate of 20 ° C./min.
In thermogravimetric differential thermal analysis (TG / DTA), the thermal decomposition temperature was
It was 445 ° C. The polymer showed optical anisotropy in the molten state when observed with a polarizing microscope. Next, the polyester powder is placed under a reduced pressure of about 1 mbar for 2 hours.
After heating to 260 ° C., secondary solid phase polycondensation was performed for 10 hours. The intrinsic viscosity of the polyester after this heat treatment is 1.76 dl / g
The outflow starting temperature was 385 ° C. The melt viscosity measured at a temperature of 400 ° C and a shear rate of 10 ³ sec ^-1 was about 1600 poise.

Example 2 The following materials are weighed into the polymerization apparatus described in Example 1.

(A) 4-hydroxybenzoic acid 69.1 g (0.50 mol) (b) 4,4'-biphenol 34.9 g (0.19 mol) (c) 4,4'-dihydroxydiphenyl sulfone 75.0 g
(0.06 mol) (d) Terephthalic acid 41.5 g (0.25 mol) (e) Acetic anhydride 122.5 g (1.20 mol) Polycondensation reaction was carried out under the same conditions as in Example 1, and the obtained light brown polyester was pulverized.

This polyester is measured by a differential scanning calorimeter,
It showed a melting endotherm at 289 ° C and showed optical anisotropy in the molten state as observed by a polarizing microscope.

Next, secondary solid phase polycondensation was performed under the same conditions as in Example 1. The obtained polyester powder was insoluble in p-chlorophenol and had an outflow starting temperature of 365 ° C. Temperature 400 ℃,
Shear rate 10 ³ sec ^{-1 The} melt viscosity measured was about 1000 poise.

Example 3 The following materials are weighed into the polymerization apparatus described in Example 1.

(A) 4-Hydroxybenzoic acid 69.1 g (0.50 mol) (b) 4,4'-biphenol 11.7 g (0.06 mol) (c) 4,4'-dihydroxydiphenyl sulfone 47.6 g
(0.19 mol) (d) Terephthalic acid 41.5 g (0.25 mol) (e) Acetic anhydride 122.5 g (1.20 mol) Polycondensation reaction was carried out under the same conditions as in Example 1, and the obtained light brown polyester was pulverized.

This polyester is measured by a differential scanning calorimeter,
It showed a melting endotherm peak at 298 ° C and showed optical anisotropy in the molten state as observed by a polarizing microscope.

Next, secondary solid phase polycondensation was performed under the same conditions as in Example 1. The intrinsic viscosity of the obtained polyester was 1.84 dl / g, and the outflow starting temperature was 393 ° C. The melt viscosity measured at a temperature of 400 ° C. and a shear rate of 10 ³ sec ⁻¹ was about 2100 poise.

Comparative Example 1 The following materials are weighed into the polymerization apparatus described in Example 1.

(A) 4-Hydroxybenzoic acid 69.1 g (0.50 mol) (b) 4,4'-biphenol 23.3 g (0.125 mol) (c) Bisphenol A 28.5 g (0.125 mol) (d) Terephthalic acid 41.5 g (0.25 mol) (E) 122.5 g (1.20 mol) of acetic anhydride Polycondensation reaction was performed under the same conditions as in Example 1, and the obtained light brown polyester was pulverized.

The intrinsic viscosity of this polyester was 0.33 dl / g, and a melting endothermic peak at 286 ° C was measured by a differential scanning calorimeter. In thermogravimetric differential thermal analysis, the thermal decomposition temperature was 415 ° C. Observation with a polarization microscope showed optical anisotropy in the molten state.

Next, secondary solid phase polycondensation was performed under the same conditions as in Example 1. The intrinsic viscosity of the obtained polyester was 1.69 dl / g, and the outflow starting temperature was 387 ° C.

Comparative Example 2 The following substances are weighed and put into the polymerization apparatus described in Example 1.

(A) 4-hydroxybenzoic acid 69.1 g (0.50 mol) (b) 4,4'-dihydroxydiphenyl sulfone 62.6 g
(0.25 mol) (c) Terephthalic acid 41.5 g (0.25 mol) (d) Acetic anhydride 122.5 g (1.20 mol) Polycondensation reaction was carried out under the same conditions as in Example 1, and the obtained light brown polyester was pulverized.

The intrinsic viscosity of this polyester was 0.32 dl / g, and a melting endothermic peak at 318 ° C was measured by a differential scanning calorimeter. Observation with a polarization microscope showed no optical anisotropy.

Next, secondary solid phase polycondensation was performed under the same conditions as in Example 1. The intrinsic viscosity of the obtained polyester was 1.54 dl / g, and the outflow starting temperature was 400 ° C or higher.

Comparative Example 3 The following substances are weighed and put into the polymerization apparatus described in Example 1.

(A) 4-hydroxybenzoic acid 69.1 g (0.50 mol) (b) 4,4'-biphenol 46.6 g (0.25 mol) (c) terephthalic acid 41.5 g (0.25 mol) (d) acetic anhydride 122.5 g (1.20 mol) ) Polycondensation reaction was performed under the same conditions as in Example 1, and the obtained light brown polyester was pulverized.

This polyester has 42% by differential scanning calorimeter.
It showed a melting endotherm peak at 4 ° C and showed optical anisotropy in the molten state by observation with a polarizing microscope.

Next, secondary solid phase polycondensation was performed under the same conditions as in Example 1. The obtained polyester powder was insoluble in p-chlorophenol, and the outflow starting temperature was 400 ° C or higher.

From the above, as compared with the polyester using 4,4'-biphenol as the dihydroxy component (Comparative Example 3), 4,4 '
It can be seen that the polyester containing dihydroxydiphenyl sulfone has a low melting point and can be melt-molded at 400 ° C or lower. However, when all of the dihydroxy component was replaced with 4,4'-dihydroxididiphenyl sulfone (Comparative Example 2), it could not be melt-molded at 400 ° C or lower, and did not show optical anisotropy in the molten state, which was excellent as a liquid crystal polymer. Mechanical properties cannot be expressed. Further, the polyester using bisphenol A as the dihydroxy component (Comparative Example 1) was 4,
The thermal stability is remarkably inferior to the polyester containing 4'-dihydroxydiphenyl sulfone. Therefore, it is clear that the copolyester partially containing 4,4'-dihydroxydiphenyl sulfone in the dihydroxy component is a wholly aromatic copolyester which is easily melt-processed at 400 ° C or lower and has excellent mechanical properties.

<Effects of the Invention> As described above, the wholly aromatic polyester of the present invention is
It is a thermotropic liquid crystalline polymer that exhibits optical anisotropy when melted, and gives a molded product with low melt viscosity, good processability, and excellent mechanical properties.

Claims (1)

[Claims] 1. A repeating unit represented by the following (I) to (IV) as an essential constituent, wherein the unit (I) accounts for 20 to 70 mol% of the whole.
Included, the molar ratio of (II) / (III) is 95/5 to 10/90, (II + III) / (IV) is 0.95 to 1.05, and the flow starting temperature is + 20 ° C to 400 ° C. A wholly aromatic copolyester having a melt viscosity of 10 to 10,000 poise measured at a shear rate of 10 ³ sec ^-1 . (In the formula, n is 0 or 1, R ₁ , R ₂ and R ₃ are hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,
An aryl group having 6 to 10 carbon atoms, an alkylaryl group having 7 to 12 carbon atoms, or a halogen group. )