JP7136636B2 - wholly aromatic polyester - Google Patents

Description

The present invention relates to wholly aromatic polyesters.

Among wholly aromatic polyesters, those that exhibit optical anisotropy when melted are called liquid crystalline polymers. Since it has , it is utilized as a material for various molded products as an engineering plastic.

As the wholly aromatic polyester, for example, those obtained by copolymerizing 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and optionally other monomer components are known (Patent Document 1 5). Patent Documents 1 to 4 describe wholly aromatic polyesters containing 4-hydroxybenzoic acid as a main monomer, for the purpose of improving workability, for example. Further, Patent Document 5 describes a wholly aromatic polyester containing any one of 6-hydroxy-2-naphthoic acid, 4-hydroxybenzoic acid, and 3-hydroxybenzoic acid as a main monomer, and The object is to obtain a stretchable product in

By the way, when a molded product is obtained by injection molding, if a welded portion (a confluence of flowing resins) occurs in the molded product, the mechanical strength of that portion is inferior to that of the other portion (non-welded portion). , cracks, etc. are known to occur easily. A wholly aromatic polyester, which is a liquid crystalline polymer, is highly anisotropic and has the property of being easily oriented in the direction of flow during injection molding. Therefore, during injection molding, it is difficult for the merging resins to bond with each other, and as a result, the strength tends to be low at the weld portion. In Patent Documents 1 to 5, no consideration is given to improving the strength of the weld portion, and in particular, those using 4-hydroxybenzoic acid as the main monomer generally have poor strength at the weld portion, and furthermore, decomposition gas is generated. tends to be easy.

JP-A-54-77691 JP-A-1-242619 JP-A-2004-69761 JP-A-58-89618 JP 2004-529224 A

The present invention has been devised in view of the conventional problems described above, and an object thereof is to provide a wholly aromatic polyester that generates less cracked gas during molding and has excellent weld strength.

The present inventors have found that the wholly aromatic polyester contains 6-hydroxy-2-naphthoic acid as the main monomer and 3-hydroxybenzoic acid in a predetermined ratio, so that the orientation during injection molding is lowered and the weld portion is The inventors have found that the strength is improved and the generation of cracked gas is reduced, leading to the completion of the present invention.
One aspect of the present invention for solving the above problems is as follows.

(1) Consists of the following structural units (I), (II) and (III), with 65 to 85 mol% of the following structural unit (I) and 1 to 25 mol of the following structural unit (II) relative to all structural units % , a wholly aromatic polyester containing 1 to 25 mol % of the following structural units (III) and having a total of 100 mol % of the following structural units (I) to (III).

(2) The wholly aromatic polyester according to (1) above, which has a melt viscosity of 1000 Pa·s or less at a temperature 8 to 20° C. higher than its melting point.

(3) The wholly aromatic polyester according to (1) or (2) above, which has a melt viscosity of 3 to 500 Pa·s at a temperature 8 to 20°C higher than its melting point.

(4) The wholly aromatic polyester according to any one of (1) to (3) above, which has a melting point of 380° C. or lower.

(5) The wholly aromatic polyester according to any one of (1) to (4) above, which has a melting point of 260 to 370°C.

(6) A polyester resin composition containing the wholly aromatic polyester described in any one of (1) to (5) above.

(7) A polyester molded article obtained by molding the wholly aromatic polyester described in any one of (1) to (5) above or the polyester resin composition described in (6) above.

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a wholly aromatic polyester that generates less cracked gas during molding and has excellent weld strength.

<Whole aromatic polyester>
The wholly aromatic polyester of the present embodiment consists of the following structural units (I), (II) and (III), the following structural unit (I) is 1 to 25 mol% with respect to all structural units, and the following structural unit ( II) is 65 to 85 mol %, structural unit (III) below is 1 to 25 mol %, and the total of structural units (I) to (III) below is 100 mol %.

Since the wholly aromatic polyester of the present embodiment particularly contains the structural unit (III) in a predetermined ratio, the orientation is weakened during melting, and the resins that merge during injection molding are more likely to bond. Improves strength. Moreover, since 4-hydroxybenzoic acid, which causes generation of cracked gas, is not used as the main monomer, less cracked gas is generated.

Structural unit (I) is derived from 6-hydroxy-2-naphthoic acid (hereinafter also referred to as “HNA”). The wholly aromatic polyester of the present embodiment contains 65 to 85 mol % of structural units (I) with respect to all structural units. If the content of the structural unit (I) is less than 65 mol %, the strength of the welded portion is lowered and the generation of cracked gas increases. On the other hand, when the content of the structural unit (I) exceeds 85 mol %, solidification occurs and sufficient polymerization cannot be achieved. The content of the structural unit (I) is preferably 67.5 to 85 mol%, more preferably 67.5 to 82.5 mol%, still more preferably 70 to 82.5 mol%, particularly preferably 70 to 80 in mol %.

Structural unit (II) is derived from 4-hydroxybenzoic acid (hereinafter also referred to as "pHBA"). The wholly aromatic polyester of the present embodiment contains 1 to 25 mol % of structural units (II) based on all structural units. If the content of the structural unit (II) is less than 1 mol %, the polymer will solidify in the polymerization vessel during production, resulting in insufficient polymerization. If the content of the structural unit (II) exceeds 25 mol %, the generation of cracked gas increases. The content of the structural unit (II) is preferably 1 to 22.5 mol%, more preferably 3 to 22.5 mol%, still more preferably 3 to 20 mol%, particularly preferably 5 to 20 mol%. .

Structural unit (III) is derived from 3-hydroxybenzoic acid (hereinafter also referred to as "mHBA"). The wholly aromatic polyester of the present embodiment contains 1 to 25 mol % of structural unit (III) based on all structural units. If the content of the structural unit (III) is less than 1 mol %, the orientation becomes high during melting and the strength at the welded portion decreases. When the content of the structural unit (III) exceeds 25 mol%, the liquid crystallinity is lowered. The content of the structural unit (III) is preferably 1 to 22.5 mol%, more preferably 3 to 22.5 mol%, still more preferably 3 to 20 mol%, particularly preferably 5 to 20 mol%. .

As described above, the wholly aromatic polyester of the present embodiment contains specific structural units (I) to (III) in a specific amount relative to all structural units, so that less gas is generated, and when melted, The orientation is lowered and the strength of the welded portion is increased. The wholly aromatic polyester of the present embodiment contains 100 mol % of structural units (I) to (III) in total with respect to all structural units.

Next, properties of the wholly aromatic polyester will be described. The wholly aromatic polyester of the present embodiment exhibits optical anisotropy when melted. Exhibiting optical anisotropy when melted means that the wholly aromatic polyester of the present embodiment is a liquid crystalline polymer.

In the present embodiment, the fact that the wholly aromatic polyester is a liquid crystalline polymer is an essential factor for the wholly aromatic polyester to have both thermal stability and easy processability. Some wholly aromatic polyesters composed of the structural units (I) to (III) do not form an anisotropic melt phase depending on the constituent components and the sequence distribution in the polymer. is limited to wholly aromatic polyesters that exhibit optical anisotropy when melted.

The properties of melt anisotropy can be confirmed by a conventional polarization inspection method using crossed polarizers. More specifically, melting anisotropy can be confirmed by using an Olympus polarizing microscope, melting a sample placed on a Linkcom hot stage, and observing it under a nitrogen atmosphere at a magnification of 150 times. Liquid crystalline polymers are optically anisotropic and transmit light when interposed between crossed polarizers. If the sample is optically anisotropic, polarized light will be transmitted even in the quiescent molten state, for example.

Since a nematic liquid crystalline polymer significantly lowers in viscosity above its melting point, exhibiting liquid crystallinity at a temperature equal to or above the melting point is generally an index of workability. From the viewpoint of heat resistance, the melting point is preferably as high as possible, but considering the thermal deterioration of the polymer during melt processing, the heating capacity of the molding machine, etc., 380° C. or less is a preferable standard. The melting point is preferably 260 to 370°C, more preferably 270 to 370°C, still more preferably 280 to 370°C.

The melt viscosity of the wholly aromatic polyester at a temperature 8 to 20° C. higher than the melting point of the wholly aromatic polyester of the present embodiment and at a shear rate of 1000/sec is preferably 1000 Pa s or less, more preferably 3 to It is 500 Pa·s, more preferably 3 to 250 Pa·s, and even more preferably 3 to 100 Pa·s. When the melt viscosity is within the above range, the wholly aromatic polyester itself or the composition containing the wholly aromatic polyester is easy to ensure fluidity during molding, and the filling pressure becomes excessive. Hateful. In addition, in this specification, a melt viscosity means the melt viscosity measured based on ISO11443.

Next, a method for producing the wholly aromatic polyester of the present embodiment will be described. The wholly aromatic polyester of the present embodiment is polymerized using a direct polymerization method, a transesterification method, or the like. In the polymerization, a melt polymerization method, a solution polymerization method, a slurry polymerization method, a solid phase polymerization method, or a combination of two or more thereof is used. is preferably used.

In this embodiment, in the polymerization, an acylating agent for the polymerization monomer or a terminal-activated monomer as an acid chloride derivative can be used. Acylating agents include fatty acid anhydrides such as acetic anhydride.

Various catalysts can be used for these polymerizations, and representative ones are potassium acetate, magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, antimony trioxide, tris ,4-pentanedionato)cobalt (III), and organic compound catalysts such as N-methylimidazole and 4-dimethylaminopyridine. The amount of catalyst used is generally about 0.001 to 1% by weight, preferably about 0.003 to 0.2% by weight, based on the total weight of the monomers.

[Polyester resin composition]
Various fibrous, particulate, plate-like inorganic and organic fillers can be blended into the wholly aromatic polyester of the present embodiment according to the purpose of use.

Examples of inorganic fillers to be blended in the polyester resin composition of the present embodiment include fibrous, granular, and plate-like fillers.

Examples of fibrous inorganic fillers include glass fiber, asbestos fiber, silica fiber, silica/alumina fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and silicates such as wollastonite. fibers, magnesium sulfate fibers, aluminum borate fibers, and inorganic fibrous materials such as fibrous materials of metals such as stainless steel, aluminum, titanium, copper and brass. A particularly representative fibrous filler is glass fiber.

Examples of powdery inorganic fillers include carbon black, graphite, silica, quartz powder, glass beads, milled glass fiber, glass balloons, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, and wollastonite. silicates such as night, iron oxide, titanium oxide, zinc oxide, antimony trioxide, metal oxides such as alumina, metal carbonates such as calcium carbonate and magnesium carbonate, metal sulfates such as calcium sulfate and barium sulfate Salt, other ferrite, silicon carbide, silicon nitride, boron nitride, various metal powders, and the like.

Examples of plate-like inorganic fillers include mica, glass flakes, talc, and various metal foils.

Examples of organic fillers blended in the polyester resin composition of the present embodiment include heat-resistant high-strength synthetic fibers such as aromatic polyester fibers, liquid crystalline polymer fibers, aromatic polyamide fibers, and polyimide fibers.

These inorganic and organic fillers can be used alone or in combination of two or more. Combined use of a fibrous inorganic filler and a granular or plate-like inorganic filler is a preferable combination for achieving mechanical strength, dimensional accuracy, electrical properties, and the like. Particularly preferably, glass fiber is used as the fibrous filler, and mica and talc are used as the plate-like filler. is. By combining glass fibers with mica or talc, the polyester resin composition has a particularly remarkable improvement in heat distortion temperature, mechanical properties, and the like.

When using these fillers, a sizing agent or a surface treatment agent can be used if necessary.

As described above, the polyester resin composition of the present embodiment contains, as essential components, the wholly aromatic polyester of the present embodiment and, if necessary, an inorganic or organic filler, within a range that does not impair the effects of the present embodiment. If so, other components may be included. Here, the other component may be any component, and examples thereof include additives such as other resins, antioxidants, stabilizers, pigments, and crystal nucleating agents.

Moreover, the method for producing the polyester resin composition of the present embodiment is not particularly limited, and the polyester resin composition can be prepared by a conventionally known method.

[Polyester molded product]
The polyester molded article of the present embodiment is obtained by molding the wholly aromatic polyester or polyester resin composition of the present embodiment. The molding method is not particularly limited, and a general molding method can be adopted. Examples of general molding methods include injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, and inflation molding.

The polyester molded article of the present embodiment is obtained by molding the above-described wholly aromatic polyester or polyester resin composition of the present embodiment, and thus has excellent strength at the weld portion.

In addition, the wholly aromatic polyester and polyester resin composition of the present embodiment are excellent in moldability and can be processed into various three-dimensional molded articles, fibers, films, and the like.

Preferable uses of the polyester molded article of the present embodiment having the properties as described above include connectors, CPU sockets, relay switch parts, bobbins, actuators, noise reduction filter cases, electronic circuit boards, heat fixing rolls of OA equipment, and the like. mentioned.

EXAMPLES The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[Example 1]
A polymerization vessel equipped with a stirrer, a reflux column, a monomer inlet, a nitrogen inlet, and a pressure reduction/effluent line was charged with the following raw material monomers, a fatty acid metal salt catalyst, and an acylating agent to initiate nitrogen substitution. The following (I) to (III) are monomers from which the structural units (I) to (III) are derived, respectively.
(I) 6-hydroxy-2-naphthoic acid: 1869 g (70 mol%) (HNA)
(II) 4-hydroxybenzoic acid: 196 g (10 mol%) (pHBA)
(III) 3-hydroxybenzoic acid: 392 g (20 mol%) (mHBA)
Potassium acetate catalyst 165mg
1477 g of acetic anhydride (1.02 times the total hydroxyl equivalent of HNA and HBA)
After charging the raw materials, the temperature of the reaction system was raised to 140° C., and the reaction was carried out at 140° C. for 2 hours. After that, the temperature was further raised to 340° C. over 4.1 hours, and the pressure was reduced to 10 Torr (that is, 1330 Pa) over 15 minutes to distill off acetic acid, excess acetic anhydride, and other low-boiling components. condensation was performed. After the stirring torque reached a predetermined value, nitrogen was introduced to increase the pressure from a reduced pressure state to a normal pressure state and then to a pressurized state, and the polymer was discharged from the bottom of the polymerization vessel.

<Evaluation>
The wholly aromatic polyester of Example 1 was evaluated for melting point, melt viscosity, bending strength, and cracked gas generation amount by the following methods. Table 1 shows the evaluation results.

[Melting point]
After measuring the endothermic peak temperature (Tm1) observed when the wholly aromatic polyester is heated from room temperature at a rate of 20° C./min using a differential scanning calorimeter (DSC, manufactured by PerkinElmer), (Tm1+40 ) ° C. for 2 minutes, then once cooled to room temperature at a temperature decrease rate of 20 ° C./min, and then heated again at a temperature increase rate of 20 ° C./min. ) was determined as the melting point. Table 1 shows the measurement results.

[Melt viscosity]
Using a Capilograph manufactured by Toyo Seiki Seisakusho Co., Ltd., at a temperature of 8 to 20 ° C. higher than the melting point of the wholly aromatic polyester, using an orifice with an inner diameter of 1.0 mm and a length of 20 mm, at a shear rate of 1000 / sec, ISO 11443 The melt viscosity of the wholly aromatic polyester was measured according to. Table 1 shows the measurement results.

[Bending strength]
The obtained pellets are molded under the following molding conditions using a molding machine (“SE-100DU” manufactured by Sumitomo Heavy Industries, Ltd.), and a 120 mm × 12.5 mm × 0.8 mm bending test piece having a weld part is obtained. was made. Using this test piece, bending strength was measured according to ASTM D790. Table 1 shows the measurement results.
(Molding condition)
Cylinder temperature: 370℃-370℃-360℃-350℃
Mold temperature: 80°C

[Amount of cracked gas generated]
In each example and comparative example, a thermogravimetry device (TG/DTA, manufactured by Seiko Instruments Inc.) was used, and 10 mg of wholly aromatic polyester was held at 370 ° C. under a nitrogen stream for 30 minutes. The amount of weight loss was measured and evaluated as the amount of cracked gas generated.

[Examples 2 to 7, Comparative Examples 1 to 6]
A polymer was obtained in the same manner as in Example 1, except that the types of raw material monomers and the charging ratio (% by mol) were as shown in Table 1. Then, the same evaluation as in Example 1 was performed. Table 1 shows the evaluation results.

From Table 1, it can be seen that Examples 1 to 7 all have high bending strength and excellent weld strength. In addition, the amount of cracked gas generated was small in any of the examples.
On the other hand, Comparative Examples 1 and 2, in which the amount of HNA was small, were inferior in bending strength. Moreover, in Comparative Example 3, in which the amount of HNA was large, lumps occurred and even polymerization could not be performed. Comparative Examples 4 to 6, which contained a large amount of pHBA, were inferior in bending strength and generated a large amount of cracked gas.

Claims (5)

Consisting of the following structural units (I), (II) and (III), the following structural unit (I) is 65 to 85 mol%, the following structural unit (II) is 1 to 25 mol%, and the following The structural unit (III) is 1 to 25 mol%, the total of the following structural units (I) to (III) is 100 mol%, and the melt viscosity in a specific temperature range 8 to 20 ° C. higher than the melting point is A wholly aromatic polyester of 3 to 500 Pa·s .

2. The wholly aromatic polyester according to claim 1 , which has a melting point of 380° C. or lower. 3. The wholly aromatic polyester according to claim 1 or 2 , which has a melting point of 260 to 370°C. A polyester resin composition containing the wholly aromatic polyester according to any one of claims 1 to 3 . A polyester molded article obtained by molding the wholly aromatic polyester according to any one of claims 1 to 3 or the polyester resin composition according to claim 4 .