JP2544731B2 - Wholly aromatic polyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is derived from 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, terephthalic acid and 4,4′-dihydroxydiphenyl ether derivative at 350 ° C. In the case of wholly aromatic polyesters that form an optically anisotropic molten phase at the following temperatures, various molded products with superior mechanical properties, especially toughness and impact resistance, are particularly suitable for films and injection molded products. can get.

[Conventional technology]

In recent years, polyesters that form an optically anisotropic molten phase, so-called "thermotropic liquid crystalline polyesters" have been attracting attention as materials satisfying the industrial requirements for high performance of organic polymer materials. Development is being actively expanded. Since such a polymer has a property that its molecular chain is easily oriented in one direction under shear stress, a fiber, a film, which is superior to the polymer in mechanical performance represented by strength and elastic modulus,
It is known that various molded products such as injection molded products can be obtained. Further, among the polymers, a wholly aromatic thermotropic liquid crystal polyester composed of only aromatic rings is known to exhibit extremely good heat resistance.

[Problems to be solved by the invention]

As described above, the thermotropic liquid crystal polyester is an excellent high-performance material, but some problems to be solved still remain.

Since various molded articles obtained from the polyester have a rigid molecular chain highly oriented in one direction, the mechanical performance in that direction (flow direction) is large, but the mechanical performance in the direction orthogonal to the flow direction. Is small, and the anisotropy of mechanical performance is large. Further, the elongation at break of the molded product is usually extremely small and is 5%.
It becomes the following. Further, since the rigid molecules are highly oriented in one direction, the molded product is inferior in toughness, and the impact resistance is not always sufficient.

For these reasons, thermotropic liquid crystal polyester is a very suitable material as a high-performance fiber that mainly requires unidirectional strength, but it is not necessarily satisfactory in all respects as a film or injection molded product. Not something you can do. That is, when a film is obtained from the polyester by ordinary melt extrusion, the strength in the direction orthogonal to the extrusion direction is remarkably small, so that the film has a property of easily tearing in the flow direction. Moreover, the impact resistance of the injection-molded product is not so high as to be satisfied, and the surface of the molded product has a drawback that it is very easily fibrillated. Furthermore, when the glass fiber is coexisted for injection molding in order to reduce the mechanical anisotropy, the impact resistance of the molded product is significantly lowered.

[Means for solving problems]

From the above, the present inventors have diligently studied to obtain a thermotropic liquid crystal polyester which can be easily formed into a film by melt extrusion and which gives an injection-molded article having high impact resistance. Was completed. According to the invention, it consists essentially of the following repeating units I, II, III and IV, each of the following composition: However, the molar numbers of the units III and IV are present in substantially equal amounts, and have a concentration of 0.1% by weight / volume% in pentafluorophenol and a logarithmic viscosity of 0.5 dl / g or more when measured at 60 ° C. , Wholly aromatic polyesters that form an optically anisotropic melt phase at temperatures of 350 ° C. or less.

Unit I is a 6-oxy-2-naphthoyl moiety, 6
-Derived from hydroxy-2-naphthoic acid and its derivatives. Unit I is present in the polyester in an amount within the range of 3 to 30 mol%.

Unit II is the 4-oxybenzoyl moiety and is derived from 4-hydroxybenzoic acid and its derivatives. Unit II is present in the polyester in an amount in the range 25 to 80 mol%, preferably 30 to 70 mol%.

Unit III is the terephthaloyl moiety and is derived from terephthalic acid and its derivatives. Unit III is present in the polyester in an amount in the range of 5 to 30 mol%, preferably 10 to 25 mol%.

Unit IV is the 4,4'-dioxydiphenyl ether moiety and is derived from 4,4'-dihydroxydiphenyl ether and its derivatives. Unit IV is 5 to 5 in polyester
It is present in an amount in the range 30 mol%, preferably 10 to 25 mol%. The unit III and the unit IV must be present in the polyester in substantially the same number of moles.

In each aromatic ring of units I to IV described above, at least a part of hydrogen atoms bonded to the aromatic ring is an alkyl group having 1 to 4 carbon atoms, an alkoxyl group having 1 to 4 carbon atoms,
It may be substituted with halogen or a phenyl group. However, in the usual case, it is desirable that the ring substituent is not present because the crystallinity of the resulting polyester is high and the physical properties of various molded articles obtained from the polyester are excellent.

The polyester of the present invention has units I to IV present in an amount within the range defined above, and a concentration of 0.1 wt / vol% in pentafluorophenol at 0.5 dl / g or more when measured at 60 ° C. It is necessary to form an optically anisotropic melt phase having a logarithmic viscosity and a temperature of 350 ° C. or lower. When the logarithmic viscosity is smaller than 0.5 dl / g, the mechanical properties of various molded articles obtained from the polyester are unfavorably low. Preferably, the logarithmic viscosity is 1.0 dl / g or more. The upper limit of logarithmic viscosity is usually 10 dl / g or less, preferably 7.5 d
L / g or less is desirable in terms of easiness of polymerization, easiness of molding of polyester, and physical properties of various molded articles obtained.

Confirmation of the formation of an optically anisotropic molten phase is carried out using a polarizing microscope equipped with a heating device, as is well known to those skilled in the art, under a direct light Nicol, a thin slice of a sample, preferably 5 to 20 μm.
This can be done by observing a thin piece of about m at a constant heating rate and seeing that light is transmitted at a certain temperature or higher. In this observation, polarized light transmission can be more reliably observed at high temperature by lightly applying pressure to the sample sandwiched between the cover glasses or by sliding the cover glass. In this observation, the temperature at which polarized light starts to pass is the transition temperature to the optically anisotropic molten phase. This transition temperature is the position of the endothermic peak when the behavior of the sample is observed by raising the temperature using a differential scanning calorimeter (DSC) at a constant rate of temperature increase, usually 10 to 20 ° C / min. Can also be determined by Since the endothermic peak observed by the differential scanning calorimeter of the thermootropic liquid crystal polyester of the present invention is very small compared to the crystal melting peak of the crystalline polymer into the isotropic phase, care should be taken in the measurement. You need to pay. One or more endothermic peaks may appear, but the temperature giving the largest peak may be regarded as the transition temperature.

Transition temperature determined by observation with a polarizing microscope,
In some cases, the transition temperatures measured by DSC are not the same, but in such a case, the higher temperature is regarded as the transition temperature to the anisotropic molten phase of the present invention. When this transition temperature is higher than 350 ° C., the polymerization of the polymer is not easy, the melt molding processability of the obtained polymer is poor, and the mechanical properties of various molded articles obtained are inferior.

In the present invention, it is essential that the unit I to the unit IV be present in the polyester within the range defined above, which is the only reason for the thermoforming to form an optically anisotropic molten phase at 350 ° C. or lower. A tropic liquid crystalline polyester is obtained. In particular, since the 4,4'-dioxydiphenyl ether portion of the unit IV is present in an amount of 5 to 30 mol%, the breaking elongation is larger than that of the polyester, the toughness and impact resistance are remarkably large, and the mechanical strength is high. It is possible to obtain various kinds of molded products having a small anisotropy and no surface fibril formation. When the unit IV exceeds 30 mol%, a polyester which forms an optically anisotropic melt phase at a temperature of 350 ° C. or lower cannot be obtained. Also, the unit
When IV is less than 5 mol%, a polyester which forms an optically anisotropic molten phase at 350 ° C. or below is obtained,
Various molded products obtained from the polyester, such as injection molded products, have low impact strength, high mechanical anisotropy, and remarkable surface fibrillation. Further, the presence of the unit I lowers the transition temperature of the polyester to the optically anisotropic melt phase, and also lowers the melt viscosity of the polyester, which is preferable in terms of melt moldability, and The toughness of various molded products obtained, for example, the impact resistance of injection molded products, becomes large. For example, the unit III
And notched Izod impact strength of an injection-molded article obtained from a polyester comprising 15 mol% each of unit IV and 70 mol% of unit II is extremely small, but each of unit III and unit IV is 15 mol%. An injection-molded article having extremely high impact strength can be obtained from the polyester in which 5 mol% of the unit I coexists. 6-Hydroxy-2-naphthoic acid, which is a raw material compound that gives the unit I, is usually a raw material compound of the unit II even though the unit I is present in an amount of more than 30 mol%. It is not preferable because it is more expensive than 4-hydroxybenzoic acid.

JP-A-59-62630 discloses that And a polyester that forms an anisotropic molten phase at a temperature of about 400 ° C. or lower is disclosed, and as a specific example of Ar of the aromatic dioxy component, And at the same time is a constituent of the present invention Are also illustrated. However, as Ar exemplified in the examples of the publication, The breaking elongation of the fiber obtained from the polyester is at most 1.8% in the as-spun state, and the notched Izod impact strength of the injection molded product is from 18 Kg · cm / cm to 29 K.
g · cm / cm, which is smaller than that of an injection-molded article obtained from the polyester of the present invention described later. Further, as is clear from the comparative examples below, as the dicarboxylic acid component, without using a compound having a non-linear orientation such as isophthalic acid,
When using only terephthalic acid Instead of Or When is used, a polyester that forms an anisotropic melt phase at a temperature of 350 ° C. or lower cannot be obtained. Thus, as one of several specific examples in the publication, it seems that a polymer having the same composition as that of the patent of the present application is also exemplified, but only the polyester according to the combination of the patent of the present application has a temperature of 350 ° C or lower. It is not only described that a molded product obtained from the polyester which forms an anisotropic molten phase at a temperature and has a high breaking elongation and excellent toughness and impact resistance is not only suggested but also suggested. Not not.

The British Polymer Journal December 1980 issue Jackson Jr. and Compounds such as are described as being effective in lowering the melting point of polyesters. However The mechanical performance of the injection molded product obtained from the polyester copolymerized with Compared with the case of using, the notched Izod impact strength is only 0.6ft-ld / in (3.3Kg · cm / cm).

Therefore, only by using the units I to IV within the scope of the present invention, a thermotropic liquid crystal polyester which forms an optically anisotropic molten phase at a temperature of 350 ° C. or lower can be obtained. It is not suggested from the above-mentioned documents that various molded products having better toughness than polyester can be obtained.

Although the polyester of the present invention can be produced by various ester forming reactions, it is usually produced by melt polymerization. In the usual case, the units I, II and IV are supplied in a form in which the hydroxyl groups of the starting material compounds which give them are converted into the form of a lower alkyl ester, and the polymerization is carried out by the so-called acidolysis method. The lower alkyl ester is most preferably acetic acid ester.

In the polymerization, if a known transesterification catalyst is used in an amount within the range of about 0.001 to 1% by weight, preferably about 0.005 to 0.5% by weight of the total monomer weight, preferable results are obtained in terms of the polymerization rate. . Specific examples of the transesterification catalyst include alkali or alkaline earth metal salts of carboxylic acids, alkyltin oxide, diaryltin oxide, alkylstannic acid, titanium dioxide, alkoxytitanium silicate, titanium alkoxide, Lewis acid, hydrogen halide, and the like. be able to. Melt polymerization is usually carried out in the temperature range of 200 to 375 ° C. under an atmosphere of an inert gas such as nitrogen or argon.
It is preferably carried out under the flow of the gas or under reduced pressure. Depending on the type of esterified compound of the starting hydroxy compound along with the progress of polymerization, for example, acetic acid is distilled out when an acetic acid ester is used.According to the amount of this distillate and the viscosity of the polymer, The reaction temperature is raised stepwise and the degree of vacuum is adjusted. Polymerization time is usually 1
The range is 10 hours. After the completion of melt polymerization, the polymer may be finely pulverized and further polymerized in a solid phase at a temperature equal to or lower than the melting point to increase the degree of polymerization.

The composition ratio of each repeating unit in the polyester obtained by such a method is substantially the same as the composition ratio of each raw material compound charged.

The polyester of the present invention can be processed into various molded products such as films, sheets or injection molded products by ordinary melt molding. The molded product obtained from the polyester of the present invention has a large breaking elongation and excellent toughness as compared with the molded products obtained from the thermotropic liquid crystal polyesters that have been conventionally proposed. When used as a molded product, the characteristics can be further utilized.

The polyester of the present invention is melt-molded at a temperature not lower than the transition temperature of the optically anisotropic melt phase (usually about 5 ° C. to 100 ° C. higher) to give a film of the present invention,
Sheets or injection-molded articles are obtained. The film or sheet is obtained by the conventional T-die method well known to those skilled in the art. It can also be obtained by the inflation method. The film or sheet of the present invention has a large breaking elongation as compared with the film or sheet obtained from the conventionally proposed thermotropic liquid crystal polyester, and is usually 10%.
The above is excellent in toughness. In addition, the anisotropy of mechanical properties such as strength and elastic modulus in the extrusion direction (flow direction) and the direction orthogonal thereto are smaller than those of extrusion films or sheets conventionally proposed from thermotropic liquid crystal polyester. That is also one of the characteristics of the film obtained from the polyester of the present invention.

The film or sheet obtained by melt-extruding the polyester of the present invention at a temperature equal to or higher than the transition temperature to its optically anisotropic melt phase has a breaking strength in the extrusion direction in the as-formed state. It has an initial elastic modulus of 15 kg / mm ² or more and an initial elastic modulus of 150 kg / mm ² or more.

The film or sheet thus obtained is subjected to a heat treatment under an inert gas atmosphere, at a temperature at which the film or sheet does not melt, for a certain period of time, for example, 10 minutes to 100 hours in a state where tension is not applied substantially. The strength and elastic modulus can also be increased.

The injection-molded article of the present invention can be obtained in the same manner as a usual thermoplastic polymer. As the mold, all general molds are used. Further, as the type of gate of the mold, a normal type such as a pin gate, a fan gate, a submarine gate or a film gate is used. Since the injection-molded product obtained from the polyester of the present invention has less mechanical anisotropy as compared with the conventionally proposed injection-molded product obtained from the thermotropic liquid crystal polyester, the design of the mold and the gate is relatively easy. . The mold temperature is preferably in the range of 50 to 150 ° C. The injection pressure is in the range of 150 to 1500 kg / cm ² . The injection-molded article obtained by injection-molding the polyester of the present invention at a temperature not lower than the transition temperature of the polyester to the optically anisotropic molten phase measures the notched Izod impact strength according to the method of JIS K7710. When I did,
At least 30 kg in the direction parallel to the polymer flow direction
cm / cm, usually 50 kg · cm / cm or more.

Since the polyester of the present invention has excellent toughness, it is also useful as a coating material for optical fibers. That is, since the polyester of the present invention has a larger breaking elongation than the conventionally proposed thermotropic liquid crystal polyester, by coextrusion with an optical fiber made of quartz, mechanical properties and thermal properties can be improved. An excellent coated fiber is formed.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 6-acetoxy-2 was placed in a separable flask of content 1 equipped with a stirrer, gas inlet, distillation head and condenser.
-Naphthoic acid 24.15 g (0.105 mol), 4-acetoxybenzoic acid 245.7 g (1.365 mol), terephthalic acid 52.29 g (0.3
15 mol) and 90.09 g (0.315 mol) of 4,4'-diacetoxydiphenyl ether and 0.01 g of sodium acetate as a catalyst.

The flask was then evacuated to vacuum and purged with nitrogen three times, then with a flow of dry nitrogen at a rate of about 3 / hour,
It was immersed in a bath kept at 250 ° C. After the contents of the flask began to melt and became a slurry, stirring was started and the temperature was maintained at the same temperature for 50 minutes. Then bath temperature is 280 for about 10 minutes
After the temperature was raised to ℃ and kept at the same temperature for about 50 minutes, the bath temperature was further raised to 320 ℃ and kept at the same temperature for 50 minutes. By this time 110 ml of acetic acid had distilled off. Next, the pressure in the system was gradually reduced to 20 mmHg in 10 minutes. After a while bath temperature
Polymerization was continued by raising the temperature to 340 ° C and maintaining the degree of vacuum at 0.3 mmHg. After 40 minutes from the start of depressurization, stirring was stopped, nitrogen was introduced, the pressure in the system was brought to normal pressure, and the flask was cooled. The contents were removed before the contents of the flask had completely solidified. The amount of the polymer obtained was 260 g. After crushing the polymer, 1 at 130 ℃
Vacuum dried for 0 hours. The polymer obtained showed a logarithmic viscosity of 2.72 dl / g when measured at 60 ° C. in pentafluorophenol at a concentration of 0.1% weight / volume. The logarithmic viscosity ηinh is calculated by the following equation.

to; Drop time when pentafluorophenol, which is a solvent, is measured at 60 ° C with an Ubbelohde viscometer.

t; Drop time of the solution that dissolves the sample.

c; Concentration of sample (g / dl) Micropolymer heating device for microscope made by Rincom
In TH-600, raise the temperature at a rate of 10 ° C / min under nitrogen atmosphere,
Observation with a polarizing microscope under crossed Nicols confirmed that the polymer began to transmit light at 275 ° C and the amount of transmitted light became even larger at around 290 ° C, indicating that the polymer formed an optically anisotropic molten phase. . In addition, after heat treatment with a DSC (Mettler TA 3000) at 260 ° C for 15 minutes, measurement at a temperature rising rate of 20 ° C / min showed an endothermic peak at 271 ° C.

As a result of measuring'H-NMR (JOEL GX-500) of the obtained polymer in a pentafluorophenol-trifluoroacetic acid solution, it was found that the composition ratio of each repeating unit was substantially the same as the ratio of the raw material compounds charged. Was confirmed.

When the weight reduction of this polymer was measured by a thermobalance at a heating rate of 10 ° C./min in air, the weight loss starting temperature was 412 ° C., and the weight reduction up to 500 ° C. was 5.2% by weight.

Using the obtained polymer, a small injection molding machine (TK14-IAP type) manufactured by Tabata Machinery, a cylinder temperature; 310 ° C., an injection pressure; 800 kg / cm ² , a mold having a film gate, a mold temperature; 100 Injection-molded articles were made at ° C. In addition, by devising the gate, a molded product having a size of 75 mm × 15 mm × 2 mm was obtained, in which the major axis direction was perpendicular to the flow direction of the polymer. The resulting molded product was measured for flexural strength and flexural modulus by the method according to JIS K7203, and Izod impact strength with notches by the method according to JIS K7110. The results are shown in Table 1. The product had a glossy surface and was extremely smooth, and the surface did not fibrillize.

Example 2 According to the method of Example 1, 6-acetoxy-2-naphthoic acid, 4-acetoxybenzoic acid, terephthalic acid and 4,
The molar ratio of 4'-diacetoxydiphenyl ether is 15/45.
Polymerization was carried out by charging at a ratio of / 20/20. The logarithmic viscosity of the obtained polymer was 2.65 dl / g, and it was confirmed by measurement with a polarization microscope and DSC that an optically anisotropic molten phase was formed at 271 ° C or higher.

The mechanical properties of the test pieces obtained as a result of injection molding the obtained polymer in the same manner as in Example 1 are shown in Table 1.

The resulting polymer has a slit width of 100 mm and a slit interval.
An extrusion film was prepared under the conditions of a cylinder temperature of 310 ° C. and an extrusion speed of 15 g / min using a film forming apparatus having a 0.2 mm T-die, and a film having a thickness of 60 μm was stably obtained. A test piece was prepared from this film, and a pulling test was conducted at a pulling speed of 10% / min. The following results were obtained.

The film was heat-treated at 250 ° C. for 2 hours, 260 ° C. for 5 hours, 270 ° C. for 5 hours, and then at 280 ° C. for 5 hours in a substantially relaxed state under nitrogen flow. The elastic modulus was as follows.

Examples 3 and 4 According to the method of Example 1, 6-acetoxy-2-naphthoic acid, 4-acetoxybenzoic acid, terephthalic acid and
Polymerization was carried out by charging the 4,4'-diacetoxydiphenyl ether in a molar ratio of 20/30/25/25 and 15/60 / 12.5 / 12.5, respectively. The logarithmic viscosities of the obtained polymers were 2.71 dl / g and 3.35 dl / g, respectively.
It was confirmed that an optically anisotropic molten phase having a temperature of ℃ or higher was formed.

The obtained polymer was injection-molded in the same manner as in Example 1, and the mechanical properties of the obtained test piece are shown in Table 1.

Comparative Example 1 According to the method of Example 1, 4-acetoxybenzoic acid,
Polymerization was carried out by charging terephthalic acid and 4,4'-diacetoxydiphenyl ether in a molar ratio of 70/15/15. The polymer obtained had an inherent viscosity of 2.68 dl / g. In addition, this polymer shows about
It was found to form an optically anisotropic molten phase at 325 ° C.

An injection-molded article was prepared according to Example 1 using this polymer. However, the cylinder temperature was 340 ° C. The mechanical performance of the obtained molded product is shown in Table 1. As can be seen from Table 1, the impact strength of the molded product obtained from the polyester of the present composition is extremely small.

Comparative Example 2 According to the method of Example 1, 6-acetoxy-2-naphthoic acid, 4-acetoxybenzoic acid, terephthalic acid and
The molar ratio of 4,4'-diacetoxydiphenyl ether is 10 /
Polymerization was carried out by charging at a ratio of 20/35/35. In this case, when decompression starts at 320 ° C, the viscosity in the system begins to rise significantly, and even if the bath temperature is raised to 370 ° C about 20 minutes after decompression starts, the system remains solidified and remains uniform. It was impossible to stir. The polymer obtained was extremely brittle and could not be injection molded below 400 ° C.

Comparative Examples 3 to 5 In Example 1, 4,4′-diacetoxydiphenyl ether was replaced with 4,4′-diacetoxydiphenyl-2,2-propane and 4,4′-diacetoxydiphenyl ether, respectively. Each raw material compound was charged and polymerized under exactly the same conditions except that sulfone and hydroquinone diacetate were used. As a result, in any case, the viscosity in the system rapidly increased in the latter stage of the reaction, stirring became difficult, and even if the bath temperature was raised to 375 ° C., the system did not melt but remained solidified. From this, it is understood that in these cases, the polyester forming the molten phase at 350 ° C. or lower is not formed.

EFFECTS OF THE INVENTION The present invention provides an injection-molded product having small anisotropy of mechanical properties and extremely excellent impact resistance, and a film having high elongation at break and excellent strength, which is excellent in molding processability. Tropic liquid crystal polyester is provided.

Claims (2)

(57) [Claims] 1. Repeating units I, II, III essentially as follows:
And IV (at least some of the hydrogen atoms bonded to the ring may be substituted by substituents), and each of the following compositions However, the molar numbers of units III and IV are present in substantially equal amounts, and in pentafluorophenol, 0.1% by weight / volume%
, A wholly aromatic polyester having a logarithmic viscosity of 0.5 dl / g or more when measured at 60 ° C. and forming an optically anisotropic molten phase at a temperature of 350 ° C. or less. 2. Repeating units I, II, III and IV are 3 to 30 mol%, 30 to 70 mol%, 10 to 25 mol%, and
The wholly aromatic polyester according to claim 1, which is in the range of 10 to 25 mol%.