JPH04225022A - Production of liquid crystal polyester - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal polyester having high quality, especially high heat-stability in molding by charging a specific amount of raw material into a vertical-type polyester reactor furnished with stirring blades, and carrying out deacetylation polymerization of the raw material. CONSTITUTION:The objective polyester composed of the structural units of formula I, formula II, formula III and formula IV can be produced by charging raw materials such as p-hydroxybenzoic acid, 4,4'-dihydroxybiphenyl, polyethylene terephthalate, terephthalic acid and acetic anhydride into a reaction vessel 7 of a vertical-type polyester reactor furnished with stirring blades 4 and subjecting the raw materials to deacetylation polymerization reaction. The amount of the raw material is selected to get the volume of the polymerization reaction product corresponding to 50-90% of the inner volume of the reactor from the bottom to the top of the stirring blade 4, attached to the stirring shaft 1 of the above reactor.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing liquid crystalline polyester. More specifically, the present invention relates to a method for producing a liquid crystalline polyester of high quality, especially excellent thermal stability during molding, by performing efficient stirring in the melt polycondensation reaction.

0002

[Prior Art] 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. Anisotropic liquid crystalline polyester has attracted attention for its excellent fluidity and mechanical properties, and its applications are expanding to include mechanical parts, electrical, and electronic parts. As a method for producing liquid crystalline polyester, JP-A-1-
As disclosed in Japanese Patent No. 149825, when the viscosity increases, the number of stirrings is reduced to control the polymerization reaction temperature.

0003

[Problems to be Solved by the Invention] However, the polymer obtained by melt polycondensation using this method contains components with a low degree of polymerization due to insufficient mixing during polymerization, and this component is degraded due to retention during molding. It was found that this method was not sufficient for fields such as electrical and electronic components that require high quality due to problems such as gasification and foaming. Therefore, the object of the present invention is to provide a method for producing a liquid crystalline polyester that has a small amount of low polymerization degree components and has excellent thermal stability during molding.

0004

[Means for Solving the Problems] The present inventors have made extensive studies to solve the above problems, and as a result, have arrived at the present invention.

That is, the present invention provides the following (I) and (II)
), (IV) or (I), (II), (III)
In producing a liquid crystalline polyester consisting of the structural unit of (IV) by deacetic acid polymerization under melt stirring, polymerization is carried out using a vertical polyester reaction apparatus equipped with a stirring blade,
This is a method for producing liquid crystalline polyester, characterized in that the volume of the reactant at the end of polymerization is 50% to 90% of the volume up to the top of the blades attached to the stirring shaft of the apparatus, and deacetic acid polymerization is carried out.

[0006]

[C4]

[0007] (However, R1 in the formula is

[0008]

[C5]

represents one or more groups selected from R2
teeth

0010

[C6]

It represents one or more groups selected from: Also,
In the formula, X represents a hydrogen atom or a chlorine atom, and the structural unit [(
II)+(III)] and the structural unit (IV) are substantially equimolar. ) In the present invention, it is important to control the amount of contents when polymerizing polyester in the reactor, thereby creating a liquid crystalline product with less low polymerization degree components and excellent thermal stability during molding. Polyester is obtained.

The above structural unit (I) is a structural unit of polyester produced from p-hydroxybenzoic acid, and the structural unit (II) is 4,4'-dihydroxybiphenyl,
3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, phenylhydroquinone, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2
, 2-bis(4-hydroxyphenyl)propane and 4,4'-dihydroxydiphenyl ether.
The structural unit (III) is a structural unit generated from ethylene glycol, and the structural unit (IV) is a structural unit generated from terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 2,6
-naphthalene dicarboxylic acid, 1,2-bis(phenoxy)ethane-4,4'-dicarboxylic acid, 1,2-bis(2
-chlorophenoxy)ethane-4,4'-dicarboxylic acid and diphenyl ether dicarboxylic acid. Among these, if the above structural unit (III) is included, R1
but

[0013]

[C7]

70 mol% or more of the structural unit (II) is

[0015]

[Chemical formula 8]

Particularly preferred is one in which 70 mol% or more of the structural unit (IV) is:

On the other hand, when the above structural unit (III) is not included, R1 is

[0018]

[Chemical formula 9]

[0019] R2 is

[0020]

[Chemical formula 10]

##STR1## is particularly preferred.

The amount of copolymerization of the above structural units (I) to (IV) is arbitrary. However, from the viewpoint of fluidity, the following copolymerization amount is preferred.

That is, when the above structural unit (III) is included, the above structural unit [(I) + (II)] is [(I) + (I)] from the viewpoint of heat resistance, flame retardance and mechanical properties.
I) + (III)] is preferably 60 to 95 mol%,
More preferably 82 to 93 mol%. In addition, the structural unit (I
II) is [(I) + (II) + (III) ] 4
0 to 5 mol% is preferable, and 18 to 7 mol% is more preferable. Furthermore, the molar ratio of structural units (I)/(II) is preferably 75/2 from the viewpoint of the balance between heat resistance and fluidity.
5 to 95/5, more preferably 78/22 to 93
/7. Moreover, the structural unit (IV) is the structural unit [(I
I)+(III) ].

On the other hand, when the structural unit (III) is not contained, the structural unit (I) is [(
I) + (II)] is preferably 40 to 90 mol%, particularly preferably 60 to 88 mol%, and the structural unit (IV) is substantially equimolar to the structural unit (II). .

[0025] As the acetic acid depolymerization reaction in the present invention, there are methods (1) and (2), and method (2) is particularly preferred.

(1) p-acetoxybenzoic acid and 4,
Diacylated products of aromatic dihydroxy compounds such as 4'-diacetoxybiphenyl and paradiacetoxybenzene, aromatic dicarboxylic acids such as terephthalic acid, polyesters and oligomers from ethylene glycol and aromatic dicarboxylic acids, or bis of aromatic dicarboxylic acids. (β-hydroxyethyl) ester by deacetic acid polycondensation reaction.

(2) p-hydroxybenzoic acid, 4,4'
- Aromatic dihydroxy compounds such as dihydroxybiphenyl and hydroquinone, aromatic dicarboxylic acids such as acetic anhydride and terephthalic acid, and polyesters and oligomers from ethylene glycol and aromatic dicarboxylic acids, or bis(β-hydroxyethyl ) A method in which the phenolic hydroxyl group is acylated by reacting with an ester, and then the product is produced by deacetic acid polycondensation reaction.

Although the polymerization proceeds even if this acetic acid removal reaction is carried out without a catalyst, stannous acetate, tetrabutyl titanate,
In some cases, it may be preferable to add a metal compound such as potassium acetate, antimony trioxide, magnesium, or sodium acetate as a catalyst.

The amount of raw materials charged in the above production method is such that, in a normal vertical polyester reactor, the volume at the end of polymerization is 50% to 90% of the volume up to the top stage of the blade attached to the stirring shaft of the device. Yes, preferably 50% to 85
%, particularly preferably 60% to 80%. If the amount of raw materials charged is less than 50% of the volume up to the top of the blades attached to the stirring shaft of the apparatus at the end of polymerization, stirring will be inefficient and non-uniform, which is not preferred. Moreover, if it exceeds 90%, the upper part will not be sufficiently stirred due to foaming due to temperature increase and volume increase of the contents due to pressure reduction operation, resulting in non-uniformity, making it impossible to obtain a homogeneous polymer, making it impossible to achieve the object of the present invention.

The volume up to the top of the stirring blade means the volume until the top stirring blade is covered by the liquid.

[0031] In the present invention, the stirring blade is not particularly limited as long as it can substantially stir the reactants, but the shape of the stirring blade of the reaction can is preferably a helical ribbon blade. It is particularly preferable to stir in a direction in which the liquid is lowered.

The vertical reaction apparatus for polyester used in the present invention is preferably an apparatus having two or more reaction vessels in which the acetylation reaction and polycondensation reaction described in (2) above can be carried out separately, and the vertical length of the reaction vessels and Preferably, the shape has a width-to-length ratio of greater than 1 and less than 3. In addition, when polycondensing the liquid crystalline polyester of the present invention, the above structural units (I) to (I
In addition to the components constituting V), aromatic dicarboxylic acids such as 3,3'-diphenyldicarboxylic acid and 2,2'-diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. , alicyclic dicarboxylic acids such as hexahydroterephthalic acid, chlorohydroquinone, methylhydroquinone, 4,4'-
Aromatic diols such as dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxybenzophenone, 1,4-butanediol, 1,6-hexanediol neopentyl glycol, 1,4-cyclohexanediol, Aliphatic and cycloaliphatic diols such as 1,4-cyclohexanedimethanol, aromatic hydroxycarboxylic acids such as m-hydroxybenzoic acid, 2,6-hydroxynaphthoic acid, p-aminophenol, p-aminobenzoic acid, etc. Further copolymerization can be carried out within a small proportion that does not impair the purpose of the invention.

[0033]

[Examples] The present invention will be explained in more detail with reference to Examples below.

Example 1 A polymerization apparatus with an internal volume of 0.1 m3 and a length-to-width ratio of 2.5 was equipped with a stirring shaft with helical ribbon blades in the downward direction up to a height of 0.035 m3 for transesterification. Polymerization was carried out as follows using two reactors for polycondensation.

FIG. 1 is a sectional view of a vertical polyester reactor for polycondensation, which is equipped with a stirring blade 4. The stirring shaft 1 is installed vertically from the top of the reaction vessel 7, and the stirring blade 4 is used for stirring. Three stirring blade fixed rods 5 attached at right angles to the shaft 1
Fixed by Further, a scraping blade 6 is attached to the lower part of the stirring shaft 1 so that the liquid in the cone portion 3, which is the bottom of the reactor, can be refreshed. A steam outlet 2 is attached to the upper part of the reaction vessel 7. The direction of rotation is clockwise.

[0036] Here, the volume of the stirring blade up to the top stage refers to the volume until the uppermost stirring blade fixing rod is covered by the liquid.

22. p-hydroxybenzoic acid was added to reaction vessel 1.
1kg, 4,4'-dihydroxybiphenyl 2.8kg
, 4.8 kg of polyethylene terephthalate, 2.5 kg of terephthalic acid, and 21.7 kg of acetic anhydride (reactants at the end of polymerization, equivalent to 65% of the volume up to the top of the stirring blade), 130°C to 250°C The esterification reaction was carried out for 5 hours, and then the liquid was transferred to reactor 2 and reacted at 250°C to 330°C for 2 hours. The pressure of the reactor was reduced to 1.0 Torr over 2 hours, and stirring was continued for 1 hour to cause a polycondensation reaction. completed. Thereafter, the inside of the can was pressurized to 4 kg/cm2, and the polymer was discharged in the form of a strand through a mouthpiece to form pellets. A liquid crystalline polyester having the following theoretical structural formula was obtained.

[0038]

[Chemical formula 11]

k/l/m/n=80/7.5/12.5/20 Next, the obtained pellets were vacuum-dried at 150°C for one day and night, and then placed in a Sumitomo Nestal injection molding machine Promat (Sumitomo Heavy Industries, Ltd.). Machine Industry Co., Ltd.
After 10 minutes of residence time in the molding machine at a cylinder temperature of 320°C, a test piece (1/8" x 1/2" A bending test piece was molded, but the purge polymer was found to be normal.Table 1 shows the test results of the three shots of the molded bending test piece.

[0040]

[Table 1]

Example 2 Using the same reaction vessel as in Example 1, 22.1 kg of p-hydroxybenzoic acid and 4,4'-dihydroxybiphenyl 4
．． 95kg, 2,6-diacetoxynaphthalene 3.27
kg, acetic anhydride 25.03 kg and terephthalic acid 6.6 kg
5 kg (reactant at the end of polymerization, equivalent to 75% of the volume up to the top stage of the stirring blade) was polymerized and pelletized under the same conditions as in Example 1. A liquid crystalline polyester having the following theoretical structural formula was obtained.

[0042]

[Chemical formula 12]

k/l/m/n=80/13.3/6.7/20 The above polymer was molded in the same manner as in Example 1 to obtain a test piece. The results are shown in Table 1.

Comparative Example 1 Using the same reactor as in Example 1, polymerization was carried out with the same composition but with the charged amount increased as follows. p-hydroxybenzoic acid 35.4
kg, 4,4'-dihydroxybiphenyl 4.5 kg,
7.7 kg of polyethylene terephthalate, 4.0 kg of terephthalic acid, and 34.7 kg of acetic anhydride were charged (reactants at the end of polymerization, equivalent to 100% of the volume up to the top of the stirring blade), and the same procedure as in Example 1 was carried out. Polymerized. Furthermore, Example 1
Similarly, when the polymer was left in the molding machine for 10 minutes and then purged for two shots, the polymer was foamed. Thereafter, it was molded in the same manner as in Example 1, and the test results are shown in Table 1.

Comparative Example 2 Using the same reaction vessel as in Example 2, 33.2 kg of p-hydroxybenzoic acid, 7 kg of 4,4'-dihydroxybiphenyl
．． 43kg, 2,6-diacetoxynaphthalene 4.91
kg, acetic anhydride 37.5 kg and terephthalic acid 9.98 kg
kg (reactant at the end of polymerization, equivalent to 108% of the volume up to the top stage of the stirring blade), and polymerization was carried out under the same conditions as in Example 1. Further, as in Example 1, the polymer was left in the molding machine for 10 minutes and then purged for two shots, and the polymer was found to be foamed. Thereafter, it was molded in the same manner as in Example 1, and the test results are shown in Table 1.

[0046]

According to the present invention, it is possible to obtain a homogeneous liquid crystalline polyester having excellent thermal stability, which does not foam or deteriorate its physical properties even when retained in a molding machine.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a vertical polyester reaction apparatus used in Example 1.

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: A liquid crystalline polyester consisting of the following structural units (I), (II), (IV) or (I), (II), (III), and (IV) is melted and stirred by acetic acid depolymerization. During production, polymerization is performed using a vertical polyester reaction apparatus equipped with stirring blades, and the volume of the reactant at the end of polymerization is 50% to 90% of the volume up to the top stage of the blades attached to the stirring shaft of the apparatus. A method for producing liquid crystalline polyester, characterized by carrying out deacetic acid polymerization. [Chemical 1] (However, R1 in the formula represents one or more groups selected from [Chemical 2], and R2 represents one or more groups selected from [Chemical 3]. In addition, in the formula, X is hydrogen atom or chlorine atom, and the structural unit [(II)+(I
II) ] and structural unit (IV) are substantially equimolar. )