JPH01153718A - Production of wholly aromatic copolyester - Google Patents

Abstract

PURPOSE:To produce a copolyester easily dischargeable from a reactor, preventing the deposition of scale, by terminating the reaction while the reaction system is still in molten state and solidifying and pulverizing the reaction product under cooling. CONSTITUTION:A wholly aromatic copolyester containing the constituent units of formulas I-IV (n and m are 0 or 1; X is H, 1-20C hydrocarbon group, O, SO2, S or CO) as essential constituent components is produced by melt- polycodensation reaction. The amount of the unit of formula I is 20-70mol.% based on the whole polymer, the ratio of unit II/(III+IV) is 0.95-1.05 and that of unit III/IV is 1/0-0.1/0.9. In the above process, the polymerization is carried out until the torque of the reaction mixture is increased to a level corresponding to 10-1,000 poise of the viscosity of the molten polymer (measured at shearing rate of 10sec<-1> at 300 deg.C), the polymer is solidified and crushed under cooling at a cooling rate of 0.5 deg.C/min-10 deg.C/min and the prepolymer taken out of the reactor is subjected to solid-phase polymerization. The copolyester can be produced e.g. by reacting 4-hydroxybenzoic acid and lower acyl ester of 4,4'- biphenol with terephthalic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a wholly aromatic copolyester.

<Conventional technology> In recent years, the demand for higher performance plastics has been increasing, and various high-performance plastics have been developed and put on the market. Thermotropic liquid crystal polymers have attracted attention because they have low melt viscosity, good processability, and excellent mechanical properties.

Fully aromatic polyester is known as this liquid crystal polymer, and polymerization methods include an interfacial polycondensation method, a solution mold clamping method, and a melt polycondensation method. Among these, the melt polycondensation method has been industrialized because it is the most simplified polymerization method in terms of process since it requires a solvent recovery step.

However, in melt polycondensation, the reaction progresses to become.

Because of this reaction behavior, the method for extracting the polymer becomes an important process issue.

Conventionally, for polyester resins, there is a method for taking out the polymer, which becomes highly viscous at the end of the reaction, in a molten state while controlling the temperature at the outlet. However, since aromatic polyester has a high reaction temperature, it easily deteriorates and the polymer remaining at the outlet mixes into the product, which is not desirable.

Also, for example, Special Publication No. 62-21808. Japanese Patent Publication No. 56-10
4932, etc., there is a method in which the reaction is carried out until the high viscosity changes to a solid phase, and after mechanically pulverizing with a high viscosity stirring device, the solid state is taken out as a powder. However, in order to crush the solid-phase-changed polymer under high shear, it was necessary to increase the power of the stirring device, and it was also necessary to change the shape of the stirring blades so that they could apply high shear force. It's coming. Furthermore, if the solid state is pulverized in this way, scale will adhere to the reactor walls and stirring blades, making cleaning difficult.

<Problems to be Solved by the Invention> An object of the present invention is to provide a method for producing a wholly aromatic copolyester by melt polycondensation, which does not cause scale adhesion and can be easily taken out. There is a particular thing.

Means for Solving Problems> That is, the present invention stops the reaction while the reaction system is in a molten state, takes out the prepolymer by solidifying and pulverizing it while cooling, and then performs solid phase polymerization. The present invention relates to a method for producing an aromatic copolyester.

More specifically, the repeating units shown below (I) to (TV) are essential components, and the unit (I) accounts for 20 to 70 of the total.
It contains mol%, and (II)/[(II)+(■)] is 0.
95-1.05, (II)/(IV) 110-0.1
When producing a fully aromatic copolyester having a molecular weight of 10.9 by melt polycondensation, the viscosity of the polymerization melt is from 10 poise to 1000 poise.
After polymerization to obtain a reactant torque comparable to Poise (shear rate 10 s-1, temperature 300°C), cooling rate 0.
The present invention relates to a method for producing a wholly aromatic copolyester by solidifying and pulverizing the prepolymer while cooling at a rate of 5°C/min to 10°C/min, followed by solid phase polymerization.

0.

(In the formula, n and m are O or 1, and X is HlC-C2
o hydrocarbon, -1o-+-3O2-.

-S-, -CO-) In cooling solidification pulverization, if the viscosity of the reaction system is lower than the viscosity corresponding to the above 10 poise, the degree of polymerization is insufficient, and the solid state polymerization step to further increase the molecular weight is performed. The polymers fuse together, making it impossible to increase the molecular weight efficiently. Further, since it takes a long time to obtain a polymer having a desired molecular weight, it has an adverse effect on the thermal stability and coloration of the polymer, which is not preferable.

When the viscosity of the reaction system is greater than the viscosity equivalent to 1000 poise, the phase changes almost immediately and it is just before solidification, resulting in uneven stirring and a load on the stirring power, resulting in poor mechanical durability. Undesirable.

After polymerization under such conditions, the scale that adheres to the reactor walls and stirring blades is hard and difficult to clean.

Furthermore, when the cooling rate is slower than 0.5° C./min, the reaction system is in a semi-molten and non-uniform state and undergoes heat history, making it impossible to obtain a homogeneous polymer. When the cooling rate is faster than 10° C./min, uniform pulverization cannot be achieved and it is also unfavorable from the viewpoint of the durability of the material. The stirring blades used in the reactor used in the present invention may be any of double helical blades, anchor blades, paddle blades, etc., but those with high viscosity are preferred. Further, during cooling pulverization, it is preferable to reduce the clearance between the stirring blade and the inner wall of the reactor in order to increase the pulverization efficiency and eliminate scale adhesion.

There are no particular limitations on the melt polycondensation method for the wholly aromatic polyconistere of the present invention, but typical production methods include, for example, 4
-Hydroxybenzoic acid, a lower acyl ester of 4°4'-biphenol, preferably an acetate, and a method of reacting terephthalic acid can be mentioned. Acyl esters can also be made in situ and used without isolation.

<Examples> The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples in any way.

Example 1 Weigh the following materials into a 50β reactor.

(a) 4-hydroxybenzoic acid 9.36 kg (67,
8 mol) (b) 4.4'-biphenol 6.3
1 bg (33,9 mol) (c) Terephthalic acid
5.63 bsr (33,9 mol) (d) Acetic anhydride
1f3.60 k+r (162,7 mol) was heated to 150°C with stirring and refluxed for 4.5 hours, then the temperature was increased to 300°C over 5 hours while distilling acetic acid from the polymerization apparatus, and then At that temperature 1.
The reaction continued for 5 hours. The melt viscosity of the reaction system was estimated from the stirring torque at that time to be 100 poise (shear rate 10 seconds-', 300°C). Solidification and pulverization was performed while cooling at a cooling rate of 3° C./min. The starting temperature of the polymer obtained was 260°C. There was almost no scale adhesion to the gas phase or liquid phase inside the reactor after pulverization, and it could be easily removed. The outflow start temperature is 10 mm in length,
Using soybeans with a diameter of 1 mm, the temperature was raised at a rate of 6° C./min under a pressure of 100 kg/min using a Koka type flow tester to a temperature that gave a melt viscosity of 48,000 poise.

After the obtained prepolymer was pulverized, it was heated to 350° C. in a nitrogen stream over 15 hours, and solid-phase polycondensation was further performed for 5 hours. The temperature at which polyester begins to flow after this heat treatment is 39
It was 0°C.

Comparative Example 1 The raw materials were the same as in Example 1, and 3 hours after the reaction time reached 300°C, the fluctuation of the stirring torque became large. The viscosity of the polymerization melt at this time is 10 seconds at a shear rate of 1,300
The torque was found to be comparable to 10,000 poise when measured at °C. From this, it was presumed that the reaction system had solidified.

After further stirring was continued until the polymer was pulverized, the mixture was cooled and the polymer was taken out. There was a lot of scale adhering to the inside of the reactor, and it was not easy to remove it.

Comparative Example 2 The raw materials were the same as in Example 1, and immediately after the reaction time reached 300°C, they were cooled and pulverized at a cooling rate of 3°C/min. There was no change in the stirring torque at that time, and the melt viscosity of the obtained polymer was measured at 300° C. at a shear rate of 10 seconds and found to be 5 poise.

The starting temperature of the polymer obtained was 200°C.

In order to increase the molecular weight of this polymer, temperature is increased from room temperature to 350°C.
Although the temperature was gradually raised to 100%, fusion occurred during the process, resulting in poor homogeneity of the product.

<Effects of the Invention> As is clear from the above description, the present invention provides a method for producing wholly aromatic polyester that can be easily removed without scale adhesion.

Claims (1)

[Claims] (1) The repeating units shown below (I) to (IV) are essential constituents, the unit (I) is contained in 20 to 70 mol% of the total, and (II)/[(III) + (IV) ] is 0.95~
1.05, (III)/(IV) is 1/0 to 0.1/0.9
When producing a wholly aromatic copolyester by melt polycondensation, the viscosity of the polymerization melt ranges from 10 poise to 1000 poise (
After polymerization until obtaining a reactant torque comparable to a shear rate of 10 s^-^1 and a temperature of 300 °C, a cooling rate of 0.5 °C
1. A method for producing a wholly aromatic copolyester, which comprises solidifying and pulverizing the prepolymer taken out while cooling at a rate of 10 DEG C./min to 10 DEG C./min and solid-phase polymerizing it. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼( IV) (where n and m are 0 or 1, X is H, C_1~
C_2_0 hydrocarbon, -O-, -SO_2-, -S-
, -CO-)