JPH047371B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel wholly aromatic polyester that can be melt-polymerized and melt-molded and has excellent mechanical properties. In recent years, there has been an increasing demand for materials with excellent rigidity, heat resistance, and chemical resistance, whether fibers, films, or molded products. Although polyester has become widely accepted for use in general molded products, many polyesters have poor mechanical properties such as flexural modulus, so they are not suitable for applications that require high strength. In order to improve this mechanical property, it is known to blend reinforcing materials such as calcium carbonate and glass fiber, but this increases the specific gravity of the material, which reduces the lightweight advantage of plastic. During molding, the molding machine is subject to severe wear, which causes many practical problems. In recent years, polyester has been used as a material that does not require reinforcement and is suitable for applications that require high strength.
Liquid crystalline polyester has started to attract attention.
Particularly noteworthy was the Journal of Polymer Science, Polymer Chemistry Edition, Volume 14 (1976) 2043.
This was after W. J. Jackson announced a thermo-liquid crystal polymer consisting of polyethylene terephthalate and hydroxybenzoic acid on page 1. Among them, Jackson reported that this liquid crystal polymer exhibits more than 5 times the stiffness, 4 times the strength, and 25 times the impact strength of polyethylene terephthalate, opening new possibilities for high-performance resins. Indicated. Since then, JP-A-53-
65421 (DuPont), JP 54-50594 (Celanese), JP 55-21491 (ICI), JP 55-50022
(Rhône-Poulenc), JP-A-55-106220 (Fiber Industry), etc., and improved strength and rigidity,
The development of liquid crystalline polyester is continuing with the aim of achieving both melt moldability. However, although more than 100 types of liquid crystalline polyesters have been proposed, none have yet been successful as molded components.
This is because these polymers exhibit a high degree of orientation in the molten state, resulting in large anisotropy in mechanical properties. The present inventors have arrived at the present invention as a result of intensive studies aimed at alleviating the anisotropy of mechanical properties. The gist of the present invention is a structural unit represented by the following formulas (A), (B), (C) and (D). and The units (A) and (D) are present in substantially equimolar amounts, with 5 to 20 mol% of the unit (A) and 35 to 65 mol% of the unit (B).
mol%, unit (C) 15 to 45 mol% and unit (D) 5
Contains ~20 mol% and at least 0.4 dl/g
It is a wholly aromatic polyester characterized by having a logarithmic viscosity of . The wholly aromatic polyester of the present invention exhibits liquid crystallinity in a molten state, can be melt-molded, and has the characteristics of having little anisotropy in the physical properties of a molded product. The present invention will be explained in detail below. The wholly aromatic polyester of the present invention essentially consists of the above four structural units (A), (B), (C) and (D). Structural unit (A) is a terephthaloyl group and is derived from terephthalic acid or its derivatives such as alkyl esters. The unit (A) is present in a concentration of 5 to 20 mol%, preferably 8 to 15 mol% of the wholly aromatic polyester, and in an equimolar amount with the structural unit (D). Structural unit (B) is a p-oxybenzoyl group and is derived from p-hydroxybenzoic acid or a derivative thereof such as an alkyl ester. Unit (B)
is present in a concentration of 35 to 65 mol% of the wholly aromatic polyester, preferably 45 to 55 mol%. Structural unit (C) is an m-oxybenzoyl group and is derived from m-hydroxybenzoic acid or a derivative thereof such as an alkyl ester. Unit (C)
is present in a concentration of 15 to 45 mol% of the wholly aromatic polyester, preferably 25 to 35 mol%. Structural unit (D) is a 1,4-dioxynaphthyl group and is derived from 1,4-naphthalene diol or a derivative thereof such as an alkyl ester. Unit (D) is 5 to 20 mol% of the wholly aromatic polyester,
Preferably at a concentration of 8 to 15 mol% and structural units
It is present in an equimolar amount with (A). Structural units (A) and (B) are disparate substitutes, and by forming a rigid structure, they have the effect of improving the mechanical properties of the wholly aromatic polyester. On the other hand, since the molecular structure of structural units (C) and (D) exhibits asymmetrical properties with respect to the main chain of the wholly aromatic polyester, the rigidity of the molecular structure developed from units (A) and (B) is It has a relaxing effect. That is, a wholly aromatic polyester having a liquid crystal temperature range in which melt molding is possible can be produced. In particular, the m-hydroxyl group of unit (C) has the effect of bending the direction of the main chain from a straight chain to a direction of 60°, and therefore has the effect of reducing the anisotropy of the physical properties of the molded product. Therefore, by adjusting the ratio of the concentration of units (C) and (D) to the concentration of units (A) and (B) in the polymer, it is possible to obtain a polymer that is melt moldable and has high mechanical properties. A polymer with less anisotropy can be obtained. The wholly aromatic polyester of the present invention has a logarithmic viscosity of at least 0.4 dl/g (logarithmic viscosity means
It is the natural logarithm of the relative viscosity divided by the concentration of the sample solution. In this measurement, a mixed solvent of tetrachloroethane/phenol = 1/1 (weight ratio) was used as the viscosity solvent, and the measurement was performed at a concentration of 0.5 wt%. did. ), and has a logarithmic viscosity of, for example, 0.5 to 1.5 dl/g. An optical method using a polarizing microscope is suitable for determining whether or not a material can exhibit anisotropy in a molten state. That is, optical anisotropy is observed by transmission or reflection under a polarizing microscope equipped with a heat stage. When the temperature is gradually increased from room temperature, polymers that do not exhibit anisotropy are observed to immediately change to an isotropic melt at the melting point, but polymers that exhibit anisotropy generally change from a crystalline state to a certain state. It becomes a liquid crystal state at a certain temperature, and exhibits a stable liquid crystal state over a fairly wide temperature range (temperature range of 10°C or more, for example). Thereafter, the temperature increases and the melt changes to an isotropic melt. The simplest method is to determine anisotropy by observing such optical anisotropy. The wholly aromatic polyester of the present invention can be produced by a melt polymerization method. That is, terephthalic acid, p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 1,4-naphthalenediol (which may be derivatives) are mixed and melted, and the mixture is usually heated at 250° C. under normal pressure.
Polymerize by heating to a temperature of about 35°C to 35°C. In order to accelerate the polymerization reaction (to achieve 100% reaction),
It is necessary to remove by-products (acetic acid, acetic ester, etc.) from the system.For this reason, when the distillation of by-products under normal pressure has stopped, the pressure is reduced to, for example, 1 mmHg or less, and distillation of by-products is continued. The polymerization reaction is continued, and the reaction is terminated when the reaction rate is approximately 100% and the degree of polymerization of the resulting polymer has sufficiently increased. In addition,
The fully aromatic polyester of the present invention has a reaction temperature of 250
It has the advantage that it can be produced satisfactorily even at temperatures between 300°C and 300°C. The fully aromatic polyester of the present invention can be melt-molded even at temperatures below 300°C, and the molded product has high rigidity (modulus of elasticity). It is useful for materials such as electronic material parts). EXAMPLES The present invention will be specifically explained below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 and Comparative Examples 1 to 3 16.6 g of terephthalic acid, p-acetoxybenzoic acid
90.0 g, m-acetoxybenzoic acid 54.0 g, and 1,4-naphthalene diacetate 24.4 g were charged into a polymerization tube after stirring, and after purging with nitrogen three times, the polymerization tube was placed in an oil bath at 290°C. Ta. The mixture was stirred for 1 hour under a nitrogen stream, during which time most of the acetic acid was distilled off. Then after applying a vacuum of 0.5 Torr, 30
The polymerization was completed by stirring for a minute. The logarithmic viscosity of this polymer was 0.75. This polymer has a temperature range from 260°C to 350°C.
It exhibited optical anisotropy in the molten state in the temperature range up to °C. Optical anisotropy was observed using a Nikon polarizing microscope POH model equipped with a Zeiss heat stage. This polymer was made into a strand using an extruder, and its Sonic modulus (ASTM F89-68) was measured, and the results are shown in Table 1 along with the Sonic modulus values of other polymers. The Sonic Modulus value is measured using the Dynamic Modulus Tester PPM manufactured by Toyo Seiki Seisakusho Co., Ltd.
-5R was used to measure the sound velocity (ν) traveling through the strand-like polymer, and calculated from Laplace's equation E=ρν ² E: Sonic modulus ρ: density (using density gradient tube) ν: sound velocity .

【table】

[Table] Examples 2 to 14 Terephthalic acid, p-acetoxybenzoic acid, m-
Polymers were produced in the same manner as in Example 1 except that the compositions of acetoxybenzoic acid and 1,4-naphthalene diacetate were varied. The sonic modulus of the obtained wholly aromatic polyester is shown in Table 2.

[Table] Example 15 and Comparative Example 4 The polymer obtained in Example 1 was extruded to 5 mm
Make it into a φ strand, 3mm from this strand.
A corner chip was cut out and the compressive strength was measured. The compressive strength was 1 mm/sec, and the maximum load required to deform 10% of the initial thickness was divided by the cross-sectional area (ASTMD-1621). The number of test pieces is 5 in the parallel and perpendicular directions to the strands. The measuring device is Tensilon testing machine (Toyo Baldwin)
was used. Table 3 shows representative liquid crystalline polyesters (manufactured by Mitsubishi Chemical Industries, Ltd.) with an intrinsic viscosity of 0.66 (measured at 30°C at a concentration of 1 g/dl in a 50/50 (weight ratio) mixed solvent of tetrachlorethylene/phenol). ) (produced from 40 mol% polyethylene terephthalate and 60 mol% p-acetoxybenzoic acid) was measured and is also shown.

[Table] Further, the polymer obtained in Example 1 was molded into a flat plate of 80 x 80 x 3 (mm) using an injection molding machine (model AU-30, manufactured by Nissei Plastics Co., Ltd.) using a film gate. The cylinder temperature was 300-345°C. The same polymer used in Comparative Example 4 was also molded in the same manner. The cylinder temperature was set at 230-250°C. The flat plate was cut into strips in the resin flow direction (MD) and the direction perpendicular to it (TD), and the flexural modulus and flexural strength were measured (ASTMD790). The measuring device used was a Tensilon testing machine (Toyo Baldwin). Table 4 shows the results.
Shown below.

[Table] Comparative Example 6 In Example 1, using 2,6-naphthalene diacetate instead of 1,4-naphthalene diacetate, terephthalic acid: P-acetetoxybenzoic acid: m-acetoxybenzoic acid: 2,6 - Naphthalene diacetate = 10:50:30:10 (molar ratio)
Polymerization was carried out in the same manner as in Example 1, except that the ingredients were charged so as to be as follows. The obtained polymer was molded into a flat plate of 80 x 80 x 3 (mm) using an injection molding machine in the same manner as in Example 15, and cut out in the MD direction and TD direction, and the flexural modulus was measured. The results are shown in Table-5. Comparative Example 7 In Example 1, terephthalic acid: P-acetoxybenzoic acid: m-acetoxybenzoic acid: 1,4
Polymerization was carried out in the same manner as in Example 1, except that -naphthalene diacetate was charged at a molar ratio of 10:75:5:10. The obtained polymer was molded into a flat plate in the same manner as in Example 15, and the flexural modulus was measured. The results are shown in Table-5. Comparative Example 8 Polyethylene terephthalate, P-acetoxybenzoic acid, m-acetoxybenzoic acid, 1,4-naphthalene diacetate, and terephthalic acid were mixed in the ratio of the constituent units in the produced polymer: a:b:c:
Polymerization was carried out in the same manner as in Example 1 except that the molar ratio of d:e was 20:40:20:5:15. However, a to e are as follows. (e) -O-CH ₂ CH ₂ -O- The obtained polymer was molded into a flat plate in the same manner as Comparative Example 6, and the flexural modulus was measured. The results are shown in Table-5.

【table】

Claims (1)

[Claims] 1 Structural units represented by the following formulas (A), (B), (C) and (D) and The units (A) and (D) are present in substantially equimolar amounts, with 5 to 20 mol% of the unit (A) and 35 to 65 mol% of the unit (B).
mol%, unit (C) 15 to 45 mol% and unit (D) 5
Contains ~20 mol% and at least 0.4 dl/g
A wholly aromatic polyester characterized by having a logarithmic viscosity of