JPH0729322B2 - Method for manufacturing polyester moldings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention produces a polyester molded article having excellent heat resistance, mechanical properties and flame retardancy by injection molding an aromatic copolyester containing a phosphorus atom. It is about how to do it.

(Prior Art) An aromatic polyester is known as a heat-resistant polymer, but most of the aromatic polyester is a substance that is difficult to melt-mold and its use is limited.

In recent years, thermotropic liquid crystalline polyester, which has excellent melt moldability, has been attracting attention, and molded products using this have been actively studied.

However, although aromatic polyesters are said to have excellent flame retardancy, the limiting oxygen index is at most about 40, and it is difficult to say that they have sufficient flame retardancy, and the melting point is extremely high. Since it is high and has a high melt viscosity, it must be molded at high temperature and high pressure. And, molding at high temperature and high pressure is not only economically disadvantageous, but when exposed to high temperature for a long time, polyester is decomposed to generate gas, and bubbles and silver streaks are generated on the surface of the obtained molded product. There was a problem.

The present inventors have found that an aromatic copolyester containing a specific phosphorus atom has high flame retardancy as well as good melt moldability, and previously proposed it (Japanese Patent Application No. 61-51691).
issue).

However, when injection molding this copolyester,
There is a problem that gas is generated during molding and the surface morphology of the molded product is deteriorated.

(Problems to be Solved by the Invention) The present invention provides a method for producing a polyester molded article excellent in heat resistance, mechanical properties and flame retardancy by injection molding an aromatic copolyester containing a phosphorus atom, It is an object of the present invention to provide a method for producing a polyester molded product, which is capable of producing a molded product having a good surface morphology with less generation of gas during melt molding.

(Means for Solving the Problems) As a result of earnest research to achieve the above-mentioned object, the present inventors have found that injection molding a copolyester having a low terminal acetyl group concentration is effective, The present invention has been reached.

That is, the gist of the present invention is as follows.

Injection molding of a copolyester having a unit represented by the following structural formula (I) in an amount of 5 to 95 mol% of all repeating units constituting the main chain of the polyester and having a terminal acetyl group concentration of 10 equivalents / 10 ⁶ g or less A method for producing a polyester molded article, comprising:

[Ar ¹ represents a trivalent aromatic group. However, the aromatic ring may have a substituent. The copolyester in the present invention may be any of crystalline, amorphous, and thermotropic liquid crystalline copolyester. When importance is placed on transparency, amorphous ones are preferable,
When the heat resistance is important, the melting point is high, but the crystalline one is preferable, and in order to achieve both the heat resistance and the melt moldability, the thermotropic liquid crystalline one is preferable. Particularly preferred are thermotropic liquid crystalline copolyesters having a melting point or flow initiation temperature of 330 ° C. or lower, preferably 300 ° C. or lower.

The copolyester in the present invention has 5 to 95 mol% of the unit represented by the structural formula (I) with respect to the repeating unit of the polyester, and particularly 5 units by the structural formula (I). ˜95 mol% and a unit represented by the following structural formula (II) are preferred to be 95 to 5 mol% of all repeating units constituting the main chain of the polyester.

—O—Ar ² —CO— (II) [Ar ² represents a divalent aromatic group. In the above copolyester, 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 aromatic dicarboxylic acid residue is required to be substantially equimolar to the unit of the structural formula (I), and as the aromatic dicarboxylic acid,
Terephthalic acid (TPA) and isophthalic acid (IPA) are suitable, and the molar ratio of TPA and IPA is from 100: 0 to 0: 100, preferably 10
It is suitable to use at a ratio of 0: 0 to 50:50, optimally 100: 0 to 70:30.

The unit forming the copolyester together with the unit of structural formula (I) and the unit of the aromatic dicarboxylic acid residue is
The unit I) is preferable, and specifically, it is an oxycarboxylic acid residue such as a 4-hydroxybenzoic acid residue or a 6-hydroxy-2-naphthoic acid residue, and the aromatic ring is a substituent as described above. May have.

The molar ratio of the unit of the structural formula (I) to the unit of the structural formula (II) is 95: 5 to 5:95, preferably 80:20 to 10:90. In order to obtain the thermotropic liquid crystallinity, It is good to set it from 50:50 to 10:90. When the number of units of the structural formula (I) is too large, the strength and heat resistance decrease, and when the number of the units of the structural formula (II) is too large, the melting point or the flow starting temperature becomes too high and the flame retardancy decreases.

Further, components other than the above may be copolymerized within the range of forming a copolyester exhibiting good melt moldability and flame retardancy. Examples of such copolymerization components include resorcin, hydroquinone, 4,4 ′ -Dihydroxydiphenyl, naphthalic acid, 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.

The copolyester of the present invention has an intrinsic viscosity [η] of 0.
It is preferably 5 or more, preferably 0.6 to 10.0, and most preferably 0.7 to 3.0. When [η] is smaller than this range, various physical and mechanical property values such as heat resistance are inferior, while when [η] is larger than this range, the melt viscosity becomes too high and fluidity is impaired. ， Moldability deteriorates.

Further, the copolyester in the present invention must have a terminal acetyl group concentration of 10 equivalents / 10 ⁶ g or less. If the terminal acetyl group concentration is higher than this, volatile gas is likely to be generated during melt molding, and bubbles or silver streaks are generated on the surface of the molded product.

In order to obtain a copolyester having a terminal acetyl group concentration of 10 equivalents / 10 ⁶ g or less, acetic anhydride does not become a large excess with respect to all hydroxyl groups when the copolyester is produced by the method described below. And the polycondensation reaction time should be relatively long.

Next, as an example of a particularly preferable copolyester in the present invention, 9,10-dihydro-9 represented by the above formula (a) is shown.
-Oxa-10- (2 ', 5'-dihydroxyphenyl) phosphaphenanthrene-10-oxide (PHQ), TPA / IPA
A method for producing a copolyester from 4-hydroxybenzoic acid (4HBA) will be described.

(A) TPA / IPA and PHQ diacetate (PHQ-A) and 4HBA
Of the acetate form (4HBA-A) of (4HBA-A) in an amount in which the hydroxyl group and the carboxyl group are equivalent or a slight excess of the carboxyl group (and preferably 0 to 0.1 times equivalent of acetic anhydride equivalent to the amount of all hydroxyl residues), or (B) With TPA / IPA
PHQ and 4HBA are equivalent to hydroxyl groups and carboxyl groups or an amount in which the carboxyl groups are slightly in excess, and an amount that does not result in a large excess with respect to the total amount of hydroxyl groups (preferably 0.01 to 0.10 times equivalents). (Acetic anhydride) is charged into a reactor, and an acid exchange reaction or an esterification reaction is carried out in an inert atmosphere under atmospheric pressure at a temperature of about 150 ° C. for about 2 hours. After that, the temperature is raised sequentially, acetic acid is distilled off, and then the temperature is raised to about 280 ° C. Then, the pressure is gradually reduced, and at the same time as the start of the pressure reduction or after reaching the full vacuum, the temperature is raised if necessary, and finally at a temperature of 280 to 330 ° C, usually under a high pressure of less than 1 torr for several hours to several hours. The copolyester that can be used in the present invention can be produced by performing a polycondensation reaction in the melt phase or solid phase for 10 hours, preferably 10 hours or more.

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 copolyester used for molding has a moisture content of 100 ppm.
It is desirable to keep it below the normal level, usually under reduced pressure, 150 to 20
It is dried at a temperature of 0 ℃ for about 8 to 48 hours before use.

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

The measuring methods in the examples are as follows.

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

Glass transition point (Tg) The temperature was measured with a differential scanning calorimeter (DSC-2 type manufactured by Perkin Elmer Co., Ltd.) at a heating rate of 20 ° C / min.

Flow starting temperature (Tf) Using a flow tester (CFT-500 manufactured by Shimadzu Corporation), a die with a diameter of 0.5 mm and a length of 2.0 mm, with a load of 100 kg / cm ² and 200
The temperature was raised from 10 ° C at a heating rate of 10 ° C / min, and the temperature at which the polymer began to flow out of the die was determined.

Flame-retardant The limiting oxygen index (LOI) according to JIS K 7201 was determined.

Terminal acetyl group concentration (CH ₃ CO-) Using a mass spectrometer (D-300 manufactured by JEOL Ltd.), insert 6 mg of the sample into the direct capillary and measure the direct mass spectrum to determine m / The intensity of the e = 60 mass fragment was determined by mass chromatography.

Izod impact strength (IZ) Measured with a 1/8 inch thick notched test piece according to the ASTM D256 standard.

Bending strength Measured on a 1 / 8-inch thick test piece according to the ASTM D790 standard.

Tensile strength According to ASTM D638 standard, it was measured with a dumbbell No. 1 type test piece having a thickness of 1/8 inch.

Surface morphology of molded product A disc-shaped test piece with a diameter of 100 mm and a thickness of 1/8 inch was molded and evaluated by visual observation.

G: Good S: Silver streak B: Bubbles Note: Each test piece was molded using J-100-S injection molding machine manufactured by Japan Steel Co., molding temperature 320 ℃, mold temperature 40 ℃, injection. It was carried out under the condition of a pressure of 625 kg / cm ² .

Examples 1 to 4 In the reactor, PHQ-A, 4HBA-A, AC _{2 with} the molar ratio shown in Table 1 was used.
O (acetic anhydride) TPA and IPA were charged, and dimethyltin maleate as a catalyst was added in an amount of 4 × 10 ^-4 mol per 1 mol of polyester repeating unit.
Then, the reaction was carried out while stirring for 2 hours. Then, in a nitrogen atmosphere, under normal pressure, the reaction was carried out at 200 ° C. for 2 hours and further at 280 ° C. for 2 hours. After that, decompression was started according to the decompression schedule such that it took 120 minutes to reach full vacuum, and at the same time, the heating rate was 20 ° C.
The temperature was raised at a rate of 1 hour / hour, and finally the polycondensation reaction was carried out in the melt phase at 320 ° C. under a reduced pressure of 1 Torr or less for a total of 15 hours to obtain a thermotropic liquid crystalline copolyester.

Table 1 shows the characteristic values of the obtained copolyester and a molded product obtained by injection molding of the copolyester.

Comparative Examples 1 to 4 Example 1 was repeated except that the charged amount of Ac ₂ O was increased and the depressurization was started according to the depressurization schedule such that the full vacuum was 86 minutes, and the polycondensation reaction was performed in the melt phase for a total of 8 hours. A copolyester was produced in the same manner as in 1. and the test results are shown in Table 1.

Comparative Examples 5 to 6 Copolyesters were produced in the same manner as in Example 1 except that the charged molar ratios of PHQ-A and 4HBA-A were changed as shown in Table 1.

The copolyester of Comparative Example 5 was a crystalline polyester having a melting point of 402 ° C., which was extremely brittle in terms of strength and could not be put to practical use.

Further, the copolyester of Comparative Example 6 had a very high melting point and started to decompose at 450 ° C., and injection molding was difficult.

Examples 5 to 7 The characteristic values of the copolyesters and molded products thereof obtained in substantially the same manner as in Example 1 using the phosphorus compounds shown in Table 2 instead of PHQ-A are shown in Table 2.

In addition, (b), (c) and (d) in Table 2 represent the diacetate of the organophosphorus compound having the above-described structural formulas (b), (c) and (d), respectively.

Example 8-11 reactors, a third to a molar ratio shown in Table _{PHQ, 4HBA, Ac 2 O,} TP
A and IPA were charged, 4 × 10 ⁻⁴ mol of dimethyltin maleate as a catalyst was added to 1 mol of the repeating unit of polyester, and the mixture was reacted in a nitrogen atmosphere under atmospheric pressure at 150 ° C. for 2 hours while stirring. Then, in a nitrogen atmosphere, under normal pressure, 200 ℃
Then, the mixture was reacted for 2 hours and further at 280 ° C for 2 hours. After that, decompression was started according to a decompression schedule such that it took 120 minutes to reach full vacuum, and at the same time the temperature was raised at a rate of 20 ° C / hour,
Finally, the polycondensation reaction was carried out in the melt phase at 320 ° C under a reduced pressure of less than 1 torr for a total of 16 hours to obtain a thermotropic liquid crystalline copolyester.

Table 3 shows the characteristic values of the obtained copolyester and a molded product obtained by injection molding the copolyester.

(Effect of the Invention) According to the present invention, since an aromatic copolyester containing a specific phosphorus atom having a low terminal acetyl group concentration is injection-molded, a gas generation is small during melt molding, and a molded product having a good surface morphology. Can be obtained.

Since the molded product obtained in the present invention has a specific phosphorus-containing structural unit in the side chain and is composed of a copolyester whose main chain is mainly composed of an aromatic group, it has heat resistance, mechanical properties and flame retardancy. It has excellent properties and is suitable as a molded product used in applications requiring heat resistance and high flame retardancy.

Claims (6)

[Claims] 1. A unit represented by the following structural formula (I) is 5 to 95 mol% of all repeating units constituting the main chain of polyester.
A method for producing a polyester molded article, which comprises injection-molding a copolyester having a terminal acetyl group concentration of 10 equivalents / 10 ⁶ g or less. [Ar ¹ represents a trivalent aromatic group. However, the aromatic ring may have a substituent. ] 2. The method according to claim 1, wherein the copolyester is a thermotropic liquid crystalline copolyester. 3. A copolyester having a unit represented by the following structural formula (II) in an amount of 95 to 5 mol% of all repeating units constituting the main chain of the polyester.
Method described in section. —O—Ar ² —CO— (II) [Ar ² represents a divalent aromatic group. ] 4. The method according to claim 1, wherein the unit represented by the structural formula (I) is represented by the following structural formula. 5. The method according to claim 1, wherein the unit represented by the structural formula (I) is represented by the following structural formula. 6. The method according to claim 3, wherein the unit represented by the structural formula (II) is a 4-hydroxybenzoic acid residue.