JPH0771816B2 - Melt molding method for polyester - Google Patents

Description

The present invention relates to a method for melt-molding a thermotropic liquid crystalline polyester having excellent heat resistance and moldability.

(Prior Art) As a heat-resistant polymer, thermotropic liquid crystalline polyester, which is excellent in processability, has been attracting attention, and molded articles such as fibers and films using this have been actively studied.

However, the molded product from the thermotropic liquid crystalline polyester is not only opaque but also has a very high strength and a high elastic modulus in the extrusion direction (MD direction), but it is It was decided that the direction (TD direction) had extremely low strength and low elastic modulus, so the workability during molding was poor and the anisotropy of the strength of the molded product became a problem.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned drawbacks of thermotropic liquid crystalline polyester, and provides a polyester molded article having reduced anisotropy and suitable for use at high temperature, which is suitable for operability. It is intended to provide a good manufacturing method.

(Means for Solving Problems) As a result of earnest research for achieving the above-mentioned object, the present inventors have found that a certain type of thermotropic liquid crystalline polyester has a clearing point, We have found that it is effective to perform melt molding at a temperature above the point, and have reached the present invention.

Here, the clearing point means that when the thermotropic liquid crystalline polyester is heated and melted, first,
It becomes a cloudy liquid that is optically anisotropic, but when it is heated to a higher temperature, it may become an optically isotropic transparent liquid, which is the transition point temperature.

(Depending on the type of thermotropic liquid crystalline polyester, it decomposes before reaching the clearing point.) The present invention melt-molds the thermotropic liquid crystalline polyester having a specific structural unit and having a clearing point. In this case, the gist is a polyester melt-molding method characterized by melt-molding at a temperature above the clearing point.

The polyester to which the method of the present invention is applied has a clearing point and usually has a flow initiation temperature of
It has a clearing point around 300 ℃ and around 350 ℃, and its decomposition temperature is sufficiently higher than the clearing point.

Examples of such a polyester include a thermotropic liquid crystalline random copolyester having 5 to 95 mol% of a unit represented by the following structural formula (I) with respect to the repeating unit of the polyester, particularly the following structural formula (I), ( II) and (II
(I) and (II) are substantially equivalent, and the molar ratio of (I) and (III) is 95:
A thermotropic liquid crystalline random copolyester of 5 to 5:95 is preferable, and one obtained by melt polymerization at a temperature below the clearing point is preferable.

[Ar ¹ represents a trivalent aromatic group, and Ar ² and Ar ³ represent a divalent aromatic group. However, the aromatic ring may have a substituent. In the above polyester, the amount of the unit represented by the structural formula (I) is 5 to 95 mol% based on the repeating unit of the polyester,
Preferably 25-80 mol%, more preferably 40-50 mol%
Is preferred. If this unit is too large, the strength will decrease,
If it is too small, the melting point or the flow starting temperature becomes too high.

As Ar ¹ in the structural formula (I), a benzene ring and a naphthalene ring are most preferable. In structural formula (I), the hydrogen atom of the aromatic ring is an alkyl group having 1 to 20 carbon atoms,
It may be substituted with an alkoxy group, an aryl group having 6 to 20 carbon atoms, an aryloxy group or a halogen atom.

The unit of structural formula (I) is derived from a phosphorus-containing aromatic diol component.

Specific examples of the phosphorus-containing aromatic diol include the following formula (a)
The compounds represented by formulas (d) to (d) are mentioned, and the particularly preferred ones are those represented by formula (a) and formula (b).

The unit of the structural formula (II) that forms a repeating ester unit together with the unit of the structural formula (I) is an aromatic dicarboxylic acid residue, and as the aromatic dicarboxylic acid, there are terephthalic acid (TPA) and isophthalic acid (IPA). Is preferred, TPA and IP
The molar ratio of A to 100: 0 to 0: 100, preferably 100: 0 to 50:50,
Optimally, the ratio of 80:20 to 50:50 is suitable.

The unit of the structural formula (III) forming a copolyester with the units of the structural formulas (I) and (II) is an oxycarboxylic acid such as 4-hydroxybenzoic acid residue or 6-hydroxy-2-naphthoic acid residue. It is a residue, and the aromatic ring may have a substituent as described above.

The molar ratio of the units of structural formula (I) to the units of structural formula (III) is 95: 5 to 5:95, preferably 75:25 to 20:80, optimally 40:60.
-50: 50 is preferred. If the number of units of the structural formula (III) is too small, the liquid crystallinity decreases, and if it is too large, the melting point or the flow starting temperature becomes too high.

Further, components other than the above may be copolymerized within the range of forming a good thermotropic liquid crystalline copolyester,
Such copolymerization components include hydroquinone, 4,4 '
-Dihydroxydiphenyl, naphthalic acid, 2,2-bis (4'-carboxyphenyl) propane, bis (4-carboxyphenyl) methane, bis (4-carboxyphenyl) ether, trimellitic acid, ethylene glycol, 1,4- Butanediol, 1,6-hexanediol, 2-butene-1,4-diol, cyclohexanedimethanol,
Pentaerythritol and the like can be mentioned.

As an example of a particularly preferred copolyester according to the present invention, 9,10-dihydro-9-oxa-10- (2 ', 5'-dihydroxy) whose unit represented by the structural formula (I) is represented by the above formula (a). Phenyl) phosphaphenanthrene-10-oxide (PHQ) residue, the unit represented by structural formula (I) is T
An example of a method for producing a copolyester in which the unit derived from PA / IPA and the unit represented by the structural formula (III) are units each including a 4-hydroxybenzoic acid (4HBA) residue will be described.

(A) The acid component composed of TPA / IPA, the diol component composed of the diacetate body of PHQ (PHQ-A), and the oxycarboxylic acid component composed of the acetate body of 4HBA (4HBA-A) have a hydroxy group and a carboxyl group. Equivalent amount (and preferably 0.01 to 0.25 times equivalent amount of acetic anhydride of all hydroxyl groups at the same time) or (b) acid component consisting of TPA / IPA, diol component consisting of PHQ and oxycarboxylic acid component consisting of 4HBA Was added to the reactor in an amount of 1.05 to 1.25 times equivalent to the amount of hydroxyl groups and carboxyl groups and 1.05 to 1.25 times the total amount of hydroxyl groups, and the mixture was placed in an inert atmosphere under atmospheric pressure at 150.
The esterification reaction is carried out at a temperature not exceeding ℃ for 0.5 to 4 hours. Next, in an inert atmosphere, under normal pressure, at a temperature of 150 to 300 ° C, an acid exchange reaction is performed for 0.5 to 3 hours, and then 230 to 300 ° C.
Continue the reaction at the temperature of. At that time, decompression is started according to a decompression schedule such that the time until full vacuum is one hour or more. After that, the temperature is raised sequentially to distill off acetic acid, and finally the polycondensation reaction is usually carried out at a temperature of 300 to 350 ° C. under a high reduced pressure of about 1 torr for several tens of minutes to several hours in the melt phase or solid phase. Makes it possible to produce thermotropic liquid crystalline copolyesters.

In addition, since melt viscosity becomes low under a shearing stress in a melt phase, especially at a temperature below the clearing point, it is preferable for industrial production to carry out the polycondensation reaction at a temperature below the clearing point.

Usually, a catalyst is used in the polycondensation reaction, but in the production of the copolyester in the present invention, one or more kinds of compounds selected from various metal compounds and organic sulfonic acid compounds are used.

As the metal compound, a compound such as antimony, titanium, germanium, tin, zinc, aluminum, magnesium, calcium, manganese, sodium, potassium or cobalt is used, while as the organic sulfonic acid compound, sulfosalicylic acid, o-sulfon A compound such as benzoic anhydride is used. Particularly preferred are dimethyltin maleate and o-sulfobenzoic anhydride.

The amount of the catalyst added is usually 0.1 × 10 ^{-4 to} 100 × 10 ^-4 mol, preferably 0.5 × 1 per mol of the repeating unit of polyester.
0 ^-4 to 50 x 10 ^-4 mol, optimally 1 x 10 ^-4 to 10 x 10 ^-4 mol are suitable.

The polyester in the present invention is a molded product,
The intrinsic viscosity [η] is preferably 0.3 or more, preferably 0.3 to 0.6, and most preferably 0.5 to 3.0. When [η] is smaller than this range, various physical properties such as heat resistance,
If the mechanical property value is inferior, on the other hand, if [η] is larger than this range, the melt viscosity will be too high and the fluidity will be impaired.

Therefore, when the water content in the polyester is about 100 ppm, the [η] of the polyester used for molding is usually 0.1 or more [η] higher than the above value in anticipation of a decrease in [η] during molding. It is suitable to use.
In order to obtain a water content of about 100 ppm in polyester, it may be dried under reduced pressure at a temperature of 150 to 200 ° C for about 8 to 48 hours.

The preferred thermal property value of the polyester in the present invention is that the flow initiation temperature is 330 ° C or lower, preferably 300 ° C.
℃ or less, optimally 280-230 ℃, heat distortion temperature 155 ℃ or more, preferably 180 ℃ or more, optimally 180-230 ℃. By satisfying these conditions, heat resistance and various physical and mechanical properties can be compatible.

In the present invention, the polyester thus obtained is melt-molded at a temperature above its clearing point. At the time of molding, the temperature for cooling the molten molded product,
Since the degree of anisotropy of the molded product depends on the cooling conditions such as time, rapid cooling is desirable to reduce the degree of anisotropy.

The molded product obtained by the method of the present invention is TD as well as MD direction.
Although it has sufficient strength in the direction as well, in the case of a molded product such as a fiber or a film, the strength characteristics and the like can be further improved by subjecting it to stretching and heat treatment. In particular, in the case of a film, it is desirable that the film is stretched in at least one of MD and TD by a factor of 2 to 30 times, preferably 3 to 15 times. The stretching is performed by the sequential biaxial stretching method, the tenter method or the inflation method simultaneously. It can be carried out by a known method such as a biaxial stretching method.

EXAMPLES Next, the present invention will be described in more detail with reference to examples.

The intrinsic viscosity [η] of the polymer in the examples was determined from the solution viscosity measured at 20 ° C. in an equal weight mixed solvent of phenol and ethane tetrachloride.

Thermotropic liquid crystallinity and clearing point (C
p) was confirmed with a Leitz polarization microscope with a hot stage.

For the flow start temperature (Tf), a flow tester (CFT-500 manufactured by Shimadzu Corporation) was used, a die with a diameter of 0.5 mm and a length of 2.0 mm was used, the load was 100 kg / cm ^2, and preheating was carried out at 200 ° C for 3 minutes. After that, the temperature was raised at a heating rate of 10 ° C / min, and the temperature at which the polymer began to flow out of the die was determined.

Example 1 and Comparative Example PHQ-A, 4HBA-A and acetic anhydride were added to the reactor at a molar ratio of 4.5: 5.
Charge TPA / IPA (molar ratio 60/40) equimolar to 5: 2 and PHQ, and add dimethyltin maleate as a catalyst in an amount of 4 × 10 ^-4 mol per 1 mol of the repeating unit of polyester. The esterification reaction was carried out at a temperature of 145 ℃ under pressure for 1 hour. After that, in a nitrogen atmosphere, under normal pressure, at a temperature of 200 ° C, 1
The acid exchange reaction was carried out for an hour. Then, in a nitrogen atmosphere, under normal pressure, the temperature was raised from 200 ° C to 275 ° C at a heating rate of 25 ° C / hour,
At this time, the depressurization was started according to the depressurization schedule such that it took 90 minutes to reach full vacuum (1 torr). After that, the temperature is sequentially raised to distill off acetic acid, and finally, the polycondensation reaction is carried out in the molten phase at a temperature of 320 ° C. under a reduced pressure of 1 torr for 4 hours, and [η] 0.
At 83, Tf286 ℃ and Cp377 ℃, we obtained liquid crystalline polyester with excellent color tone.

Using the J-100S type injection molding machine manufactured by Japan Steel Works, the obtained polyester was molded with pin gate and film gate molds under the molding conditions shown in Table 1, for physical properties evaluation in MD direction and in TD direction. A dumbbell No. 1 test piece specified by ASTM for physical property evaluation was obtained.

About this test piece, with an Instron tensile tester,
Tensile strength and tensile elasticity were measured at a pulling speed of 5 mm / min.

The results are shown in Table 1.

Nos. 1 to 5 are examples, and Nos. 6 to 10 are comparative examples.

Examples 2 to 6 Liquid crystalline polyesters having the characteristic values shown in Table 2 were produced by the following methods, and the same tests as in Example 1 were conducted. The results are shown in Table 2.

(Example 2) PHQ, 4HBA, and acetic anhydride were charged in a reaction apparatus at a molar ratio of 5: 5: 17 and TPA / IPA (molar ratio 70/30) at an equimolar ratio to PHQ, and dimethyltin maleate was used as a catalyst. 4 × 10 ⁻⁴ mol was added to 1 mol of the repeating unit of polyester, and esterification reaction was carried out at a temperature of 130 ° C. for 2 hours under a normal pressure in a nitrogen atmosphere. Then, the acid exchange reaction was carried out at a temperature of 220 ° C for 1 hour in a nitrogen atmosphere under normal pressure. Then, in a nitrogen atmosphere, under normal pressure, 2
The temperature was raised from 20 ° C to 280 ° C at a heating rate of 20 ° C / hour, at which time depressurization was started according to a depressurization schedule such that full vacuum (1 torr) was reached for 60 minutes. After that, the temperature was sequentially raised to distill off acetic acid, and finally, a polycondensation reaction was performed in the melt phase at a temperature of 310 ° C. under a reduced pressure of 1 torr for 2 hours to obtain a liquid crystalline polyester having an excellent color tone.

(Example 3) PHQ, hydroquinone (HQ), 4HBA and acetic anhydride were used in a reaction device in a molar ratio of 4: 1: 5: 18 and TPA in an amount equal to the sum of PHQ and HQ.
/ IPA (molar ratio 80/20) was charged, and dimethyltin maleate as a catalyst was added in an amount of 4 × 10 ^-4 mol per 1 mol of polyester repeating unit, and in a nitrogen atmosphere under atmospheric pressure at a temperature of 150 ° C. for 45 minutes. The esterification reaction was carried out. After that, the acid exchange reaction was carried out in a nitrogen atmosphere under atmospheric pressure at a temperature of 180 ° C for 3 hours.
Then, in a nitrogen atmosphere, under normal pressure, 180 ℃ to 50 ℃
The temperature was raised to 280 ° C / hour, and the depressurization was started according to the depressurization schedule such that the full vacuum (1 torr) was 90 minutes. After that, the temperature is raised sequentially to distill acetic acid,
Finally, a polycondensation reaction was carried out in the melt phase at a temperature of 325 ° C. under a reduced pressure of 1 torr for 2 hours to obtain a liquid crystalline polyester having an excellent color tone.

(Examples 4 to 6) A liquid crystalline polyester was obtained in the same manner as in Example 1 except that the phosphorus compounds (b), (c) and (d) were used instead of PHQ.

(Effect of the Invention) According to the present invention, it is possible to manufacture a polyester molded product having excellent heat resistance, physical strength, and mechanical strength and having high anisotropy and no anisotropy with good operability.

The polyester molded product obtained by the present invention is extremely useful as a material used in applications where heat resistance and strength are particularly required.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-89323 (JP, A) JP-A-61-78832 (JP, A) JP-A-60-240722 (JP, A) JP-B 4- 494 (JP, B2)

Claims (5)

[Claims] 1. A constitutional unit represented by the following structural formulas (I) to (III), wherein (I) and (II) are substantially equivalent and the moles of (I) and (III) are A method for melt-molding polyester, characterized in that when thermotropic liquid crystalline random copolyester having a ratio of 95: 5 to 5:95 is melt-molded, it is melt-molded at a temperature above a clearing point. [Ar ¹ represents a trivalent aromatic group, and Ar ² and Ar ³ represent a divalent aromatic group. However, the aromatic ring may have a substituent. ] 2. The method according to claim 1, wherein the unit represented by the structural formula (I) is represented by the following structural formula. 3. The method according to claim 1, wherein the unit represented by the structural formula (I) is represented by the following structural formula. 4. The method according to claim 1, wherein the unit represented by the structural formula (II) is a residue of terephthalic acid and / or isophthalic acid. 5. The method according to claim 1, wherein the unit represented by the structural formula (III) is a 4-hydroxybenzoic acid residue.