JPH0319858B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel aromatic polyester that can be melt-molded at temperatures below 400°C and can provide molded articles having excellent mechanical properties and optical anisotropy. In recent years, the demand for higher performance plastics has been increasing, and many polymers with various new properties have been developed and put on the market. Among them, polymers with optical anisotropy, which is characterized by parallel arrangement of molecular chains, are particularly popular. Liquid crystal polymers have attracted attention because of their excellent mechanical properties. A typical example of this liquid crystal polymer is a wholly aromatic polyester, and for example, homopolymers and copolymers of p-hydroxybenzoic acid are known. However, p-hydroxybenzoic acid homopolymer has a too high melting point and cannot be melt-molded, and a copolyester made by copolymerizing p-hydroxybenzoic acid with, for example, terephthalic acid and hydroquinone has a softening point of about 427 It has a high temperature of ~482°C, making melt processing difficult and its mechanical properties unsatisfactory. On the other hand, optically anisotropic polyesters with improved melt moldability by lowering the melting point or softening point of such fully aromatic polyesters include polyesters made from phenylhydroquinone and terephthalic acid (for example, JP-A-53-65421). Although this polyester also has a low melting point of 350°C or lower, its mechanical properties, typified by its elastic modulus, are insufficient, and the reality is that it is desired to have an even higher elastic modulus. . Therefore, the present inventors conducted extensive research with the aim of obtaining an aromatic polyester that can be melt-molded at temperatures below 400°C and can provide molded products with excellent mechanical properties and optical anisotropy. In a polyester consisting of an acid, a part of the phenylhydroquinone is replaced with another aromatic dihydroxy compound, and all of the terephthalic acid is replaced with 4,4'-diphenyldicarboxylic acid, thereby producing a novel product that preferably meets the above objectives. It was discovered that an aromatic copolyester can be obtained, and the present invention was achieved. That is, the present invention consists of the following structural units () and (), the unit () accounts for 90 to 10 mol% of the whole, the unit () occupies 10 to 90 mol% of the whole,
The present invention provides a novel melt-mouldable aromatic copolyester characterized by a melt viscosity of 50 to 15,000 poise. (However, R in the formula is

【formula】

【formula】

【formula】 and

Indicates a group selected from [Formula]. In addition, the melt viscosity is the shear rate at the liquid crystal start temperature + 40℃.
3000 (1/sec) with a Koka type flow tester. In the aromatic copolyester of the present invention, the above structural unit () is phenylhydroquinone and 4,
The structural unit of a polyester produced from 4'-diphenyldicarboxylic acid, and the above structural unit () is the structure of a polyester produced from a specific aromatic dihydroxy compound other than phenylhydroquinone and 4,4'-diphenyldicarboxylic acid. They each mean a unit. The aromatic polyester of the present invention having such a structure has a melting point of 400°C or less, and can be molded into fibers, films, various molded products, etc. with excellent mechanical properties and optical anisotropy by ordinary melt molding. It is possible. For example, the melting point of polyethylene terephthalate is 256°C, and polyethylene
The melting point of 4,4'-diphenylcarboxylate is
355°C, a polyester consisting of 4,4'-diphenyldicarboxylic acid and phenylhydroquinone that gives a polyester with a higher melting point than terephthalic acid is, for example, terephthalic acid described in JP-A-53-65421. It is expected that the copolyester of the present invention will have a much higher melting point than the polyester made of acid and phenylhydroquinone, but the copolyester of the present invention has a relatively low melting point of 400°C or less, and has good melt fluidity, and is moreover superior to the polyester described in the above publication. It has the advantage of having a significantly higher modulus of elasticity than that of other materials, and this new effect is completely unexpected based on conventional knowledge. In the aromatic copolyester of the present invention, the aromatic dihydroxy compounds forming the structural unit () include hydroquinone, 4,4'-dihydroxybiphenyl, 2,6-dihydroxynaphthalene,
and at least one selected from chlorohydroquinone. The proportion of the structural unit () consisting of these aromatic dihydroxy compounds and phenylhydroquinone in the wholly aromatic copolyester is preferably 10 to 90 mol%, and if it is less than 10 mol%, the melting point of the resulting copolyester will be 400°C. If the amount exceeds 90 mol %, the melt fluidity and mechanical properties of the resulting copolyester will deteriorate, which is not preferable. In addition, the optimal range of the proportion occupied by the above structural unit () varies depending on the type of aromatic dihydroxy compound used;
4,4'-dihydroxybiphenyl and 2,6-
The optimal range is 10 to 50 mol % when dihydroxynaphthalene is used, and the optimal range is 15 to 85 mol % when methylhydroquinone and chlorohydroquinone are used. The aromatic copolyester of the present invention can be manufactured according to the conventional manufacturing method of copolyester, and there are no particular restrictions on the manufacturing method, but typical manufacturing methods include (1)
Diester of aromatic dihydroxy compound and 4,
(2) A method for producing from 4'-diphenyldicarboxylic acid by a monocarboxylic acid-free polycondensation reaction, and (2) a method for producing from an aromatic dihydroxy compound and a diphenyl ester of 4,4'-diphenyldicarboxylic acid by a phenol-free polycondensation reaction. There are several methods. Among these methods, the above method (1) is preferable because the polycondensation reaction proceeds without a catalyst, but the above method (2) also uses a metal compound such as stannous acetate, tetrabutyl titanate, lead acetate, or antimony trioxide as a catalyst. By using it as a compound, a desired polycondensation reaction can be achieved. In addition, when polycondensing the aromatic copolyester of the present invention, terephthalic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, etc. ,2,6-
Aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, cycloaliphatic dicarboxylic acids such as hexahydroterephthalic acid, other aromatic diols such as methylhydroquinone, 2,6-dihydroxyanthraquinone, and other aromatic dicarboxylic acids such as p-oxybenzoic acid. Oxycarboxylic acid or the like may be further copolymerized within a small proportion that does not impair the object of the present invention. Many of the aromatic copolyesters of the present invention can be measured in intrinsic viscosity in pentafluorophenol, and at a concentration of 0.1% (w/v) 60
The value measured at °C is preferably 0.35 dl/g or more, particularly preferably 0.4 to 10.0 dl/g. Further, it is necessary that the melt viscosity of the aromatic copolyester of the present invention is 50 to 15000 poise,
In particular, 100 to 5000 poise is more preferable. The melt viscosity is a value measured using a Koka type flow tester at a liquid crystal start temperature of +40° C. and a shear rate of 3000 (1/sec). The liquid crystal start temperature in the present invention is the temperature at which opalescence starts under shear stress, and is the value measured through a polarizing plate with a melting point measuring device manufactured by Yanagimoto Seisakusho Co., Ltd. The molecular weight of this aromatic copolyester that dissolves in pentafluorophenol can be measured by GPC and light scattering, and the polymer produced by the acetic acid depolymerization method has an acetyl group at the end, so it can be measured by infrared rays. Can be quantified by absorption spectroscopy or hydrolysis, and these molecular weights range from 1000 to
It is 200,000. The aromatic copolyester of the present invention thus obtained has a low melting point of 400°C or less, is optically anisotropic, and has particularly excellent mechanical properties in the uniaxial direction, and is suitable for extrusion molding,
By subjecting it to ordinary melt molding such as injection molding, compression molding, and blow molding, it can be processed into fibers, films, molded products, containers, hoses, etc. During molding, reinforcing agents such as glass fiber, carbon fiber, and asbestos, fillers, nucleating agents, flame retardants, pigments, antioxidants, stabilizers, plasticizers, lubricants, and mold release agents are added to the aromatic copolyester of the present invention during molding. Additives such as additives and other thermoplastic resins can be added to impart desired properties to the molded article. The molded article obtained from the novel aromatic polyester of the present invention has good optical anisotropy at 400° C. or lower due to its parallel molecular alignment, and has extremely excellent mechanical properties. The present invention will be further explained below with reference to Examples. Example 1 In a test tube for polymerization, 8.1 g (3 x 10 ^-2 mol) of phenylhydroquinone diacetate, 16.0 g (7 x 10 ^-2 mol) of chlorohydroquinone diacetate, 4.
24.2 g (10 x 10 ^-2 mol) of 4'-diphenyl dicarboxylic acid was charged and acetic acid depolycondensation reaction was carried out under the following conditions. First, under a nitrogen gas atmosphere at 300 to 370℃.
After reacting for 1.5 hours, the pressure was reduced to 0.6 mmHg, and further
The reaction was continued for 0.45 hours to complete the polycondensation. As a result, a theoretical amount of 12 g of acetic acid was distilled out and a brown polymer was obtained. The theoretical structural formula of the obtained aromatic copolyester is as follows, and the elemental analysis results of this polyester were in good agreement with the theoretical values as shown in Table 1.

[Table] However, O% was calculated from (100%-C%-H%-Cl%). When the infrared absorption spectrum was measured, it was 1480 cm.
^-1 , 1610 cm ^-1 , 1690 cm ^-1 , and 1720 to 1760 cm ^-1 . In addition, this polyester was placed on the sample stage of a polarizing microscope, and the temperature was raised to confirm the liquid crystal onset temperature and optical anisotropy. As a result, the liquid crystal onset temperature was 318 ° C.
It showed good optical anisotropy. Next, this copolyester was subjected to a Koka type flow tester and spun at a spinning temperature of 380°C and a spindle hole diameter of 0.3 mmφ to obtain a spun yarn of 0.2 mmφ. This spun yarn is manufactured by Toyo Baldwin Co., Ltd.
−−Using EA, frequency 110Hz, heating rate 2℃/
When the elastic modulus was measured at a distance between chucks of 40 mm, the elastic modulus was extremely high at 49 GPa at 30°C. The melt viscosity of this polymer is 358℃, shear rate 3000 (1/
seconds) and 3900 poise. Thermal properties were measured using a differential scanning calorimeter (PerkinElmer type), and the melting point was 344°C, and the cooling crystallization temperature was 295°C. For comparison, the elastic modulus of a spun yarn of a polyester made of phenylhydroquinone and terephthalic acid was polymerized according to JP-A-53-65421, and the elastic modulus was as low as 20 GPa at 30°C. Example 2 In a polymerization test tube, 18.9 g of phenylhydroquinone diacetate (7 x 10 ^-2 mol), 5.8 g of hydroquinone diacetate (3 x 10 ^-2 mol), 4,4'-
Diphenyldicarboxylic acid 24.2g (10×10 ^-2 mol)
After the reaction was carried out at 300 to 360°C for 2 hours under a nitrogen gas atmosphere, the pressure was reduced to 1 mmHg and the reaction was further carried out for 0.25 hours to complete the polycondensation reaction. As a result, 11.8 g of acetic acid, which was 98% of the theoretical amount, was distilled out to obtain a brown polymer. In addition, this copolyester was placed on the sample stage of a polarizing microscope and the temperature was raised to confirm the liquid crystal initiation temperature and optical anisotropy.As a result, the liquid crystal initiation temperature was 345℃, indicating good optical anisotropy. . The intrinsic viscosity of this polymer is 2.65, and the infrared absorption spectra are 1480 cm ^-1 , 1500 cm ^-1 , 1600 cm ^-1 ,
It had a characteristic absorption at 1730 cm ^-1 . Thermal properties were measured using a differential scanning calorimeter, and the melting point was 397°C, the cooling crystallization rate was 337°C, the temperature was 385°C, and the shear rate was 3000°C.
The melt viscosity measured at (1/sec) was 700 poise. Example 3 In place of 5.8 g (3 x 10 ^-2 mol) of hydroquinone diacetate in Example 2, 4,4'-
Diacetoxybiphenyl 8.1g (3 x 10 ^-2 mol)
or 7.3g of 2,6-diacetoxynaphthalene
(3×10 ^-2 mol) was charged and a polycondensation reaction was carried out under the same polymerization conditions as in Example 2. As a result, the theoretical amount of 96
11.5-11.8 g of ~98% acetic acid were distilled out to yield a polymer. The liquid crystal initiation temperatures of these copolyesters were 260°C and 280°C, respectively, and both exhibited good optical anisotropy. When the thermal properties of these polymers were measured using a differential scanning calorimeter, the melting points were 302°C and 314°C, respectively, and the cooling crystallization rates were 252°C and 279°C, respectively. In addition, the melt viscosity is determined at a shear rate of 3000 (1/sec)
They were 360 poise (300℃) and 510 poise (320℃).

Claims (1)

[Claims] 1 Consisting of the following structural units () and (),
Unit () accounts for 90 to 10 mol% of the total, Unit ()
accounts for 10-90 mol% of the total, and the melt viscosity is 50-90 mol%.
Melt-formable aromatic copolyester characterized by 15000 poise. (However, R in the formula represents a group selected from [Formula] [Formula] [Formula] and [Formula]. The melt viscosity is the shear rate at the liquid crystal starting temperature + 40°C.
3000 (1/sec) with a Koka type flow tester. )