JPH0441697B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for producing polyester that can be melt-molded at 400° C. or lower and provides a molded article having excellent heat resistance. <Conventional technology> In recent years, the demand for higher performance plastics has been increasing, and many polymers with various new performances have been developed and put on the market. Optically anisotropic liquid crystal polymers are attracting attention because they have excellent mechanical properties. This liquid crystal polymer has 2,6 as a constituent component.
- Polyesters containing a dioxynaphthalene skeleton (for example, JP-A-54-50594) are widely known. There are various manufacturing methods for producing polyester containing this 2,6-dioxynaphthalene skeleton, but the following (1) is a typical manufacturing method.
~(4) Laws are mentioned. (1) Acylated aromatic hydroxycarboxylic acid,
A method for producing a diacylated aromatic dihydroxy compound and a dicarboxylic acid by a deacetic acid polycondensation reaction. (2) A method for producing aromatic hydroxycarboxylic acid, aromatic dihydroxy compound, dicarboxylic acid, and acetic anhydride by deacetic acid polycondensation reaction. (3) A method for producing a phenyl ester of an aromatic hydroxycarboxylic acid and a method for producing it by dephenol polycondensation from an aromatic dihydroxy compound and a diphenyl ester of a dicarboxylic acid. (4) A method for producing an aromatic hydroxycarboxylic acid, an aromatic dihydroxy compound, a dicarboxylic acid, and diphenyl carbonate by dephenol polycondensation. <Problems to be solved by the invention> Among these manufacturing methods, method (2) is the industrially cheapest manufacturing method, but the starting material is
- When using dioxynaphthalene, 2,6
- It was found that dioxynaphthalene has poor stability and is oxidized by oxygen in the atmosphere. In addition, as described in the example of JP-A No. 54-50594, the production method using method (1) requires acetylation of the starting material in advance, which increases costs and is not necessarily industrially advantageous. It turns out that there is no method. Therefore, when producing polyester using method (1), we added only the dioxynaphthalene component to the 2,6-
Using diacetoxynaphthalene not only allows the reaction to proceed uniformly and shortens the polymerization reaction time, but also
It was discovered that sublimation during polymerization of 2,6-diacetoxynaphthalene and low polymerization degree polymers can also be controlled, leading to the present invention. That is, the present invention comprises an aromatic hydroxycarboxylic acid () and/or an aromatic dihydroxy compound () having the following structural formula, acetic anhydride in an amount of 1.00 to 1.30 times the total amount of these hydroxy groups, and an aromatic or alicyclic dicarboxylic acid ( ) in the presence of 2,6-diacetoxynaphthalene (2,6-diacetoxynaphthalene). HO−R ₁ −CO ₂ H () HO−R ₂ −OH () HO ₂ C−R ₃ −CO ₂ H () (In the formula, R ₁ to _{R 2} are divalent groups consisting of one or two benzene rings, and may be nuclear-substituted with an alkyl group, a halogen atom, or a phenyl group. , these rings may be fused, or may be bonded by a single bond, or lower alkylene, lower alkylene dioxy, oxy, sulfide, or sulfone. R ₃ is one or two 2 consisting of a benzene ring
When it is a valent group or a divalent 1,4-cyclohexylene group and consists of two benzene rings, even if these rings are fused or a single bond, it is a lower alkylene, lower alkylenedioxy, It may be oxy-, sulfide- and sulfone-linked. The heat-resistant polyester of the present invention comprises a structural unit (-OR ₁ -CO-) generated from () and/or a structural unit (-OR ₂ O-) generated from (), a structural unit generated from (). Structural unit generated from (-OC-R ₃ -CO-) and ()

[Formula] The aromatic hydroxycarboxylic acids of the structural formula () include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 2,6-
These include oxynaphthoic acid, 3-chloro-4-oxybenzoic acid, 3-phenyl-4-oxybenzoic acid, and p-hydroxybenzoic acid is most preferred. In addition to hydroquinone, aromatic dihydroxy compounds of structural formula () include chlorohydroquinone, methylhydroquinone, phenylhydroquinone, t
- Nucleically substituted hydroquinones such as butylhydroquinone, 2,7-dihydroxynaphthalene, 4,
4'-dihydroxybiphenyl, 1,2-bis(4
-Hydroxyphenyl)ethane, bisphenol A, 1,2-bis(4-hydroxyphenoxy)
Ethane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfone, etc., t-butylhydroquinone, 4,4'-
Dihydroxybiphenyl and hydroquinone are preferred. Aromatic or alicyclic dicarboxylic acids of structural formula () include terephthalic acid, isophthalic acid, 2,6
-Naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 1,2-bis(4-carboxyphenyl)ethane, 1,2-bis(4-carboxyphenoxy) Ethane, 1,2-bis(2-chloro-4-carboxyphenoxy)ethane, 4,4'-dicarboxydiphenyl ether, 4,4'-dicarboxydiphenyl sulfide, 4,4'- These include dicarboxydiphenyl sulfone, and terephthalic acid and isophthalic acid are preferred. Note that a small amount of p-aminophenol, p-aminobenzoic acid, and p-phenylenediamine may be copolymerized to the extent that the object of the present invention is not impaired. The amount of acetic anhydride is determined by the structural formula ()
The amount is 1.00 to 1.30 times the mole of all hydroxyl groups represented by and/or (). If the amount is less than 1.00 times the mole, the acetylation reaction will not proceed sufficiently, and if it is more than 1.30 times the mole, excess acetic anhydride may be decomposed. This is not preferable because the color tone of the resulting polymer is poor. Moreover, the charging molar ratio of structural formula [()+()] and structural formula () is preferably 1.0 to 1.20. The aromatic polyester of the present invention thus obtained has a low melting point of 400°C or less, and can be subjected to ordinary melt molding such as extrusion molding, injection molding, compression molding, and blow molding, and can be used to make fibers, films, three-dimensional molded products,
It can be processed into containers, hoses, etc. In addition, during molding, reinforcing agents such as glass fiber, carbon fiber, and asbestos, fillers, nucleating agents, pigments, antioxidants, stabilizers, plasticizers, lubricants, mold release agents, and hardening agents are added to the aromatic polyester of the present invention. Additives such as fuel agents and other thermoplastic resins can be added to impart desired properties to the molded article. The strength of the thus obtained molded article can be increased by heat treatment, and the elastic modulus can also be increased in many cases. This heat treatment can be carried out by heat treating the molded article at a temperature below the melting point of the polymer in an inert atmosphere (e.g. nitrogen, argon helium or water vapor) or in an oxygen-containing atmosphere (e.g. air) or under reduced pressure. . This heat treatment may or may not be carried out under tension and can be carried out for several tens of minutes to several days. The molded article obtained from the novel aromatic polyester of the present invention has good optical anisotropy and heat resistance due to its parallel molecular alignment, and has extremely excellent mechanical properties and fluidity. <Examples> The present invention will be explained in more detail below using Examples. Example 1 769 g (5.76 mol) of p-oxybenzoic acid (), 124 g (7.46 x 10 ^-1 mol) of t-butylhydroquinone (), and 365 g (1.494 mol) of 2,6-diacetoxynaphthalene () were placed in the autoclave of Example 1-4.
Then, 372 g (2.24 mol) of terephthalic acid and 836 g (7.252 x 1.05 = 7.61 mol) of 93% acetic anhydride were charged and reacted at 130 to 250°C for 4 hours in a nitrogen gas atmosphere, and then heated from 250°C to 320°C for 1 hour. Raise the temperature in 15 minutes.
After reducing the pressure to 0.8 mmHg and allowing the reaction to proceed for an additional hour, the pressure was returned to normal pressure with nitrogen gas. And the gauge pressure is 3Kg/
The pressure was increased to cm ² and the discharge valve was opened to perform discharge. The obtained polymer was 1280g (95% of the theoretical amount of 1347g)
%). When the autoclave was disassembled, the amount of deposits on the autoclave and the stirring blade was 6.8 g, which was extremely small except for the polymer that remained attached to the autoclave and the stirring blade. After this sample was extracted with acetone using a Soxhlet for 5 hours, the acetone was distilled off, but no extract was obtained. In addition, the liquid crystal initiation temperature of this polymer is
258℃, logarithmic viscosity (0.1g/dl concentration, 60℃,
(measured in pentafluorophenol) is 3.20 dl/
It was hot at g. Comparative Example 1 1038 g (5.76 mol) of p-acetoxybenzoic acid () and 187 g (7.46×10 ^-1
mole), 2,6-diacetoxynaphthalene ()
365g (1.494 mol) and 372g terephthalic acid
(2.24 mol) and 250 to 320 mol under nitrogen gas atmosphere.
After reacting at °C for 4 hours, the pressure was reduced to 0.9 mmHg in 15 minutes, and after reacting for an additional 1 hour, the pressure was returned to normal pressure with nitrogen gas. Then, the pressure was increased to 3 Kg/cm ² using a gauge pressure, and the discharge valve was opened to perform discharge. The obtained polymer was 1230g (91% of the theoretical 1347g)
It was hot. When the autoclave was dismantled, yellow sublimate and low polymerization were observed in the autoclave and the top of the stirring blade, and the weight after sampling was
It was 34.6g. This sample was extracted with acetone using a Soxhlet for 5 hours, and then the acetone was distilled off to obtain 8.7 g of extract. The melting point of this extract is 172-177°C, and it is mainly composed of 2,6-diacetoxynaphthalene rather than p-acetoxybenzoic acid (194-196°C) or he-butylhydroquinone diacetate (63-65°C). I understood. Note that the logarithmic viscosity of this polymer was 3.31 dl/g. <Effects of the Present Invention> By producing the heat-resistant polyester of the present invention, melt molding is possible and molded products with good heat resistance can be obtained, so that it can be used for various purposes such as engineering plastics.

Claims (1)

[Scope of Claims] 1. An aromatic hydroxycarboxylic acid () and/or an aromatic dihydroxy compound () having the following structural formula and 1.00 to 1.30 of these total hydroxy groups.
1. A method for producing a heat-resistant polyester, which comprises polycondensing twice the amount of acetic anhydride and an aromatic or alicyclic dicarboxylic acid () in the presence of 2,6-diacetoxynaphthalene (). HO−R ₁ −CO ₂ H () HO−R ₂ −OH () HO ₂ C−R ₃ −CO ₂ H () (In the formula, R ₁ to _{R 2} are divalent groups consisting of one or two benzene rings, and may be nuclear-substituted with an alkyl group, a halogen atom, or a phenyl group. When consisting of, these rings may be fused, or may be a single bond, or may be bonded by lower alkylene, lower alkylene dioxy, oxy, sulfide, or sulfone. R ₃ is 1 or 2 2 consisting of a benzene ring of
When it is a valent group or a divalent 1,4-cyclohexylene group and consists of two benzene rings, even if these rings are fused or a single bond, it is a lower alkylene, lower alkylenedioxy, It may be oxy-, sulfide- and sulfone-linked.