JPH0253819A - Liquid crystalline polyester containing optically active group - Google Patents

Abstract

PURPOSE:To obtain the subject polyester suitable for molding of biaxially reinforced film or sheet such as laminated structure capable of melt-molding and having excellent strength and elastic properties by copolymerizing specific monomer having optically active group. CONSTITUTION:(A) 10-90mol% monomer containing optically active group such as (s)-(+)-(6-hydroxy-2-naphthyl)propionic acid as repeating unit expressed by formula I is mixed with (B) 90-10mol% monomer of p-hydroxybenzoic acid, etc., expressed by formula II (Ar is phenyl or naphthyl, etc.) and, for instance, active esterifying agent (e.g., acetic anhydride) is added, then reacted preferably at 130-150 deg.C, thus polymerized at 180-350 deg.C to afford the aimed polyester having 0.2dl/g reduced viscosity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel optically active group-containing liquid crystal polyester that can be melt-molded and has high strength and high elasticity.

[Prior Art and Problems to be Solved by the Invention] In recent years, there has been an increasing demand for materials with excellent rigidity, heat resistance, and chemical resistance, whether for fibers, films, or molded products. Polyester is widely used for general molded products, but many polyesters have poor mechanical properties such as flexural modulus, so they are not suitable for applications that require high strength and high elasticity. In order to improve this mechanical property, it is known to mix fillers or reinforcing materials such as calcium carbonate and glass fibers, but as the specific gravity of the compound increases, the lightness, which is a characteristic of plastics, is lost. Furthermore, the molding machine is subject to severe wear during molding, which poses many practical problems.

In recent years, liquid crystalline polyester has attracted attention as a polyester that does not require reinforcing materials and is suitable for applications requiring high strength and high elasticity. Particular attention has been given to U.S. Pat.
This is after W. J. Jackson announced a thermoplastic liquid crystalline polyester consisting of polyethylene terephthalate and hydroxybenzoic acid in 1960. Since then, various research and development efforts have been conducted to develop various liquid crystalline polyesters with the aim of achieving both improved strength and rigidity and melt moldability.

However, there are still very few molded products that have been put to practical use. This is because these liquid crystalline polymers exhibit a high degree of orientation in a molten state, resulting in large anisotropy in mechanical properties.

As a means to eliminate anisotropy, W. R. Krigbaum et al. proposed a method using a cholesteric liquid crystalline polymer containing an optically active group (US Pat. No. 4,412,059). However, this method has drawbacks such as slow transesterification rate and inability to introduce all optically active units.

Furthermore, depending on the bonding mode of the structural units, there are also problems such as deterioration of physical properties and narrowing of the liquid crystal molding area.

Also, JP-A No. 62-45621. Japanese Patent Publication No. 61-19782
Publication No. 1 similarly proposes a method for producing a cholesteric liquid crystal polyester containing an optically active group. but,
These cholesteric liquid crystal polyesters have insufficient heat resistance as expected from their structures. Moreover, it is not satisfactory in terms of strength.

[Means for Solving the Problems] An object of the present invention is to provide a novel optically active group-containing liquid crystal polyester that can be melt-molded and has high strength and high elasticity.

In particular, in the present invention, it is possible to introduce any amount of optically active units into the polymer chain, and depending on the composition, nematic,
Alternatively, an optically active group-containing liquid crystal polyester such as a cholesteric liquid crystal polyester having an arbitrary cholesteric helical pitch length is provided. The optically active group-containing liquid crystalline polyester of the present invention is also characterized in that even when an optically active unit, which is a soft segment, is introduced, there is almost no effect on deterioration of the polymer physical properties.

That is, the present invention provides a repeating unit (A) represented by the following general formula.
10-90 mol% and repeating unit (B) 90-10 mol%
(B) -0-Ar-Co - (Ar represents a phenyl group, a naphthyl group, or a biphenyl group.) Using a mixed solvent of phenol/tetrachloroethane-60/40 (weight 1 ratio), 0 .5g/dρ.

The present invention relates to an optically active group-containing liquid crystal polyester having a reduced viscosity of 0.26 Ω/g or more when measured at 60°C.

The repeating unit (A) is an essential component for obtaining an optically active group-containing liquid crystal polyester, and either the D form or the L form separated from the DL racemic mixture can be used. Furthermore, since even a mixture of L exhibits optical activity if either one is present in a large amount, such a mixture can also be used. However, in this case, the efficiency of optical activation is lower than that of the pure form or the pure form. Generally, it is sufficient that the difference between the 0-isomer content and the L-isomer content is 15% or more, preferably 30% or more.

A specific example of the repeating unit (A) is (S)(+)-(
6-hydroxy-2-naphthyl)propionic acid.

The repeating unit (B) is derived from an aromatic hydroxycarboxylic acid or a derivative thereof, and its content is 90 to 10 mol%, preferably 85 to 20 mol%.

Specific examples of the repeating unit (B) include p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 4.4°-
Examples include hydroxybiphenylcarboxylic acids, which can be used alone or in combination of two or more.

When the optically active group-containing liquid crystal polyester of the present invention is gradually heated under a polarizing microscope equipped with a hot stage,
It changes from a crystalline state to a liquid crystalline state at a certain temperature. Depending on the conditions, a fingerprint texture peculiar to cholesteric liquid crystal polymers,
Alternatively, a Schlieren texture, which is characteristic of nematic liquid crystal polymers, is observed.

The optically active group-containing liquid crystalline polyester of the present invention is produced by a melt polymerization method. In this case, repeating units (A), (B)
A monomer giving the following and an active esterifying agent are mixed and heated at 130 to 150° C. for 30 minutes to 3 hours under normal pressure to effect active esterification of hydroxyl groups. After this, 18
It is heated to a temperature of about 0 to 350°C and polymerized for 2 to 6 hours. Acetic anhydride is preferred as the active esterifying agent. In order to promote the polymerization reaction, it is desirable to remove low-volatile compounds such as acetic acid produced by the transesterification reaction from the system. For this reason, in the reaction under normal pressure, it is preferable to carry out the polymerization under a nitrogen stream.

Furthermore, once the distillation of these low-volatile compounds has stopped, polymerization is continued under vacuum (e.g., below lmmHg), and the polymerization is continued when the reaction rate is approximately 100% and the degree of polymerization of the resulting polymer is sufficiently large. Terminate it.

In order to accelerate the polymerization reaction, conventionally known polyester polymerization catalysts such as alkali metal salts and Pe-Mn are used.
, Cds Mg, Bas Tis Zns Pb5C
Metal salts such as O% Sb may be used alone or in combination, but a catalyst may not be used. Further, a phosphorus compound may be added as a decomposition inhibitor. Further, although polyester is generally strengthened by heat treatment after molding, the polyester of the present invention exhibits a similar effect.

The optically active group-containing liquid crystal polyester of the present invention uses a mixed solvent of phenol/tetrachloroethane-60/40 (weight ratio), and has a concentration of 0.5 g/dρ.

The reduced viscosity measured at 60°C is 0.2 dIl/g or more, preferably 0.6 to 1.7 dIl/g. In addition, in order to adjust the molecular weight, a small amount of aromatic monocarboxylic acid, aromatic dicarboxylic acid, aromatic monool, or aromatic diol is added to the total molar ratio of repeating units (A) and (B) in a amount of 5 mo 1% or less. You may.

[Example] Examples will be described below, but these are for explanation of carrying out the present invention, and the present invention is not limited thereto.

Example 1 (s)-(+)- was placed in a glass polymerization apparatus equipped with a stirrer.
(6-hydroxy-2-naphthyl)propionic acid 40
0 g (1,85 mol), p-hydroxybenzoic acid 110 g (0,8 mol), acetic anhydride 32
After charging 3 g (3.17 mol) and purging with nitrogen, the temperature of the polymerization apparatus was raised to 150 ° C. while flowing nitrogen.
The mixture is held for 2 hours to effect active esterification of the hydroxyl groups. Thereafter, the reaction temperature was raised to 240'C over 3 hours while distilling off the by-product acetic acid. After holding for 1 hour, the pressure of the polymerization system was gradually reduced, and the pressure was held at a vacuum level of 1 μHg for 1.5 hours to complete the polymerization. After cooling the polymerization system, the polymer was taken out by destroying the glass polymerization apparatus.

As a result of thermal analysis of the polymer by DSC (heating rate: 2°C/m1n), the Tg (glass transition temperature) was 123.4.
℃, Tl11 (liquid crystal transition temperature) is 170.6℃, Ti (
The isotropic phase transition temperature) was observed at 246°C.

Also, when observed with a polarizing microscope during the heating process, 235
A fingerprint-like structure was observed at ℃.

This polymer was mixed with phenol/tetrachloroethane-60
/40 (weight ratio) mixed solvent with concentration 0, 5g/dj7
The reduced viscosity was 0.67 when dissolved at 60℃
clQ/g.

This polymer was injection molded into a flat plate with a thickness of 2 mm, and test pieces were cut out in the vertical and horizontal directions to measure mechanical properties. The results are shown in Table 1.

Example 2 (S)-(+)(
6-hydroxy-2-naphthyl)propionic acid at 86.
4 g (0.40 mol), 138 g (1, Omo 1) of p-hydroxybenzoic acid, 190 g (1, Omo 1) of 2-hydroxy-6-naphthoic acid
) and 270 g (2.65 mol) of acetic anhydride were charged, and polymerization was carried out under the same conditions as in Example 1.

DSC measurement showed a peak at 257.8°C. A fingerprint-like structure was observed at 170° C. by polarizing microscopic observation. Further, the mechanical properties are shown in Table 1.

When the reduced viscosity of this polymer was measured in the same manner as in Example 1, it was found to be 0.871! /g.

Example 3 (S)-(+)- was placed in a glass polymerization apparatus equipped with a stirrer.
(6-hydroxy-2-naphthyl)propionic acid at 32
4g (1,5mo 1), 79g (0,37m01) of 4,4'-hydroxybiphenylcarboxylic acid
, 210 g (2,06 mo I) of acetic anhydride were charged, and polymerization was carried out under the same conditions as in Example 1.

DSC measurement showed a peak at 136.9°C. Polarized light microscopy observation was performed, but the structure of the liquid crystal was not clear. Further, the mechanical properties are shown in Table 1.

The reduced viscosity of this polymer was measured in the same manner as in Example 1 and was found to be 0.41 dρ/g.

Comparative Example 1 (s) −(+)(
21.6-hydroxy-2-naphthyl)propionic acid.
6g (0,10mo 1), p-hydroxybenzoic acid 262g (1,94mo 1), acetic anhydride 2
24 g (2.2 mo 1) was charged and polymerization was carried out under the same conditions as in Example 1.

When I tried to observe this polymer under a polarizing microscope, it did not melt.

Comparative Example 2 ] 1 (s)(+)-(6
-hydroxy-2-naphthyl)propionic acid at 410.
4 g (1.9 mol), (1 p-hydroxybenzoic acid
3.8g (0.1, mol), 224g of acetic anhydride
g (2,2mo 1) was charged, and polymerization was carried out under the same conditions as in Example 1.

Tg was found to be 110°C by DSC measurement.

Nothing was observed under polarized light microscopy. This polymer was amorphous.

[Effect of the invention] The optically active group-containing liquid crystalline polyester of the present invention can be heated to 350°C.
It can be melt-molded at temperatures below, and the molded product has high mechanical properties. In addition, this polyester can be a nematic or cholesteric liquid crystal, and in particular, a cholesteric liquid crystal polymer having a rigid linear chain and an optically active monomer copolymerized in the main chain has a two-layered structure. It is expected that an axially reinforced film or sheet can be obtained, and its industrial value is high.

Claims (1)

[Claims] (1) Repeating unit (A) 10 to 9 represented by the following general formula
It consists of 0 mol% and repeating unit (B) 90 to 10 mol%, (A) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (C^* indicates optically active carbon.) (B) -O-Ar -CO- (Ar represents a phenyl group, a naphthyl group, or a biphenyl group.) Reduced viscosity measured at 0.5 g/dl at 60°C using a mixed solvent of phenol/tetrachloroethane = 60/40 (weight ratio) is 0.2dl/g or more