JP2002265577A - Method of cleaning liquid crystal resin melt polymerization apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of cleaning a liquid crystal resin melt polymerization apparatus which easily removes cleaning residues and the like attached to the inner side of the liquid crystal resin melt polymerization apparatus and does not adversely affect the discharge of a liquid crystal resin after cleaning. SOLUTION: The method of cleaning a liquid crystal resin melt polymerization apparatus is characterized in cleaning the liquid crystal resin melt polymerization apparatus with the use of glycols at least once, and then cleaning it with an alkaline aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a liquid-crystalline resin melt polymerization apparatus, and more particularly to a method for cleaning a liquid-crystalline resin melt polymerization apparatus so as to easily remove a residue remaining in the melt polymerization apparatus. The present invention relates to a method for cleaning a liquid crystal resin melt polymerization apparatus that has been removed and has no adverse effect on liquid crystal resin discharge after cleaning.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher performance of plastics, and a number of polymers having various new functions have been developed and marketed. Among them, a polymer is characterized by a parallel arrangement of molecular chains. Optically anisotropic liquid crystalline resins have attracted attention because of their excellent fluidity and mechanical properties.

As such a liquid crystalline resin, a liquid crystalline resin obtained by copolymerizing p-hydroxybenzoic acid and polyethylene terephthalate (JP-B-56-18016) or p-hydroxybenzoic acid
Liquid crystalline resins having improved fluidity and heat resistance by adding an aromatic diol such as 4,4'-dihydroxybiphenyl and a copolymer component such as an aromatic dicarboxylic acid to hydroxybenzoic acid and polyethylene terephthalate (Japanese Patent Application Laid-Open No. No. 63-30523), a liquid crystalline resin obtained by copolymerizing p-hydroxybenzoic acid with 4,4′-dihydroxybiphenyl, t-butylhydroquinone and terephthalic acid (JP-A No. 62-164719), p-hydroxybenzoic acid Liquid crystalline resin obtained by copolymerizing 4,4'-dihydroxybiphenyl, isophthalic acid and terephthalic acid with an acid (Japanese Patent Publication No.
24407, JP-A-60-25046),
Liquid crystalline resin obtained by copolymerizing 6-hydroxy-2-naphthoic acid with p-hydroxybenzoic acid (JP-A-54-77691)
No. 1).

As a method for producing a liquid crystalline resin, as disclosed in Japanese Patent Application Laid-Open No. 6-192404, a raw material is charged into a reaction vessel, reacted, and then transferred to a polymerization vessel to carry out a polycondensation reaction. Using a polymerization apparatus,
JP-A-10-7780 and JP-A-10-7781 describe a production method for performing batch polymerization repeatedly with improved productivity. However, due to repeated batch polymerization, the polymer or oligomer remaining in the can undergoes thermal history and becomes foreign matter that does not melt even at a temperature equal to or higher than the melting point of the normal polymer. However, since the physical properties of the obtained liquid crystalline resin are adversely affected, it is necessary to periodically clean the inside of the can. For example, JP-A-5-295392 discloses that
As a washing method, washing with glycols is described.In particular, repeated batch polymerization or washing in a can that has been polymerized for a long time requires a very long time only with washing with glycols, It turns out that sometimes it is not enough.

[0005]

SUMMARY OF THE INVENTION In view of the background of the prior art, the present invention easily removes cleaning residue and the like adhering to a liquid crystal resin melt polymerization apparatus, and adversely affects the liquid crystal resin discharge after cleaning. It is an object of the present invention to provide a method for cleaning a liquid crystal resin melt polymerization apparatus having no defect.

[0006]

The present invention employs the following means in order to solve the above problems. That is, the method for cleaning the liquid crystal resin melt polymerization apparatus of the present invention,
Using a liquid crystal resin melt polymerization device with glycols,
After washing at least once or more, washing with an alkaline aqueous solution is performed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made to solve the above-mentioned problem, that is, it is possible to easily remove residues such as washing residue adhering to a liquid-crystalline resin melt polymerization apparatus and to obtain a liquid-crystalline resin melt which has no adverse effect on discharge of the liquid-crystalline resin after washing. The present inventors have conducted intensive studies on the method of washing the polymerization apparatus, and after washing with glycols, further washing with an alkaline aqueous solution. As a result, they have surprisingly found that such a problem can be solved all at once.

The liquid crystalline resin in the present invention is a resin capable of forming an anisotropic molten phase upon melting, and is preferably a liquid crystalline polyester, a liquid crystalline polyester amide, a liquid crystalline polyester carbonate, a liquid crystalline polyester elastomer, or the like. Among them, liquid crystalline polyester and liquid crystalline polyester amide are more preferably used.

As such a liquid crystalline polyester, a polyester which forms an anisotropic molten phase comprising a structural unit selected from an aromatic oxycarbonyl unit, an aromatic dioxy unit, an aromatic dicarbonyl unit, an ethylenedioxy unit and the like can be used. Used as the liquid crystalline polyester amide, the polyester amide forming a fusible anisotropic phase comprising the above structural unit and a structural unit selected from an aromatic iminocarbonyl unit, an aromatic diimino unit, an aromatic iminooxy unit, etc. Is preferably used.

The raw materials which can constitute the structural units of the liquid crystalline polyester or the liquid crystalline polyester amide include aromatic hydroxycarboxylic acids, dihydroxy compounds, aromatic dicarboxylic acids, polyesters comprising dioxy and dicarbonyl units, aromatic amino acids. A hydroxy compound, an aromatic aminocarboxylic acid, a derivative thereof, and the like are used, and these are obtained by appropriately combining these types and compositions and polymerizing so that the resulting polymer exhibits liquid crystallinity.

In the above, p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are preferably used as the aromatic hydroxycarboxylic acid, and 4,4'-dihydroxybiphenyl, 3 , 3 ', 5,5'-Tetramethyl-4,4'
-Dihydroxybiphenyl, hydroquinone, t-butylhydroquinone, phenylhydroquinone, methylhydroquinone, 2,6-dihydroxynaphthalene, 2,
7-dihydroxynaphthalene, 2,2-bis (4-hydroxyphenyl) propane, 4,4'-dihydroxydiphenyl ether and the like are preferably used. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis (phenoxy) ethane-4,4′-dicarboxylic acid, 2-Bis (2-chlorophenoxy) ethane-4,4'-dicarboxylic acid and diphenyl ether dicarboxylic acid are preferably used. As the polyester comprising a dioxy unit and a dicarbonyl unit, polyethylene terephthalate or an oligomer thereof is preferably used, as the aromatic aminohydroxy compound, p-aminophenol or the like is preferably used, and as the aromatic aminocarboxylic acid, p-aminophenol is used.
Aminobenzoic acid and the like are preferably used.

In addition to the above components, aromatic dicarboxylic acids such as 3,3'-diphenyldicarboxylic acid and 2,2'-diphenyldicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and dodecandioic acid. Acid, alicyclic dicarboxylic acid such as hexahydroterephthalic acid, chlorohydroquinone, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, 3,4'-dihydroxybiphenyl And aliphatic, alicyclic diols such as 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; Aromatic hydroxy such as hydroxybenzoic acid And carboxylic acid may be further copolymerized within a range that does not impair the liquid crystallinity. In particular,
It is effective for a liquid crystalline resin having a p-hydroxybenzoic acid residue, and particularly when a polyester composed of an ethylenedioxy unit and an aromatic dicarbonyl unit is used as a raw material of the liquid crystalline resin, and particularly when p-hydroxybenzoic acid is used. , Aromatic diol, aromatic dicarboxylic acid, when a liquid crystalline resin is made using the above polyester as a raw material, that is, a liquid crystalline resin comprising the following structural units (I), (II), (III) and (IV) In this case, a remarkable cleaning effect is exhibited.

[0013]

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(Where R 1 in the formula is

[0015]

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At least one group selected from the group consisting of R2
Is

[0017]

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At least one group selected from the group consisting of R3
Is

[0019]

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And represents one or more groups selected from Also,
In the formula, X represents a hydrogen atom or a chlorine atom. The structural unit (I) is selected from the group consisting of p-hydroxybenzoic acid and / or
Or a structural unit generated from 6-hydroxy-2-naphthoic acid, wherein the structural unit (II) is 4,4′-dihydroxybiphenyl, 3,3 ′, 5,5′-tetramethyl-4,
4'-dihydroxybiphenyl, hydroquinone, t-
Butylhydroquinone, phenylhydroquinone, methylhydroquinone, 2,6-dihydroxynaphthalene,
2,7-dihydroxynaphthalene, 2,2-bis (4-
Hydroxyphenyl) propane and a structural unit formed from an aromatic dihydroxy compound selected from 4,4′-dihydroxydiphenyl ether are represented by structural unit (III)
Represents a structural unit formed from ethylene glycol, and the structural unit (IV) represents terephthalic acid, isophthalic acid, 4,4′-
Diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bis (phenoxy) ethane-4,4'-
Dicarboxylic acid, 1,2-bis (2-chlorophenoxy)
The structural units generated from aromatic dicarboxylic acids selected from ethane-4,4'-dicarboxylic acid and diphenyl ether dicarboxylic acid are shown below.

The apparatus for melt-polymerizing the liquid crystalline resin is not particularly limited, such as a vertical reactor or a horizontal reactor. Specifically, a stirring blade, a stirring shaft, a baffle, a raw material, For example, a melt polymerization apparatus having a charging port, a distilling tube, a pressure reducing port, and a polymer discharging port is preferably used.

In the method for cleaning a liquid crystal resin melt polymerization apparatus of the present invention, it is important that the liquid crystal resin melt polymerization apparatus is first washed at least once with glycols. If washing with an alkaline aqueous solution (alkali washing) described later is performed without washing with glycols, a sufficient washing effect cannot be obtained, and the object of the present invention cannot be achieved.

As such glycols, ethylene glycol, tetraethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol and mixtures thereof are preferably used, but ethylene glycol, diethylene glycol, and diethylene glycol are preferred in view of the price and availability. Triethylene glycol and the like are particularly preferably used.

In washing, glycols are introduced preferably in a range of about 20 to 80% by volume of the melt polymerization apparatus. The temperature of the cleaning liquid is preferably from 150 to 300 ° C, more preferably from 200 to 280 ° C. If the temperature of the cleaning liquid is lower than 150 ° C., the cleaning effect is small,
If the temperature exceeds 0 ° C., glycols are not preferred because side reactions such as decomposition occur.

When washing is performed at a temperature higher than the boiling point of glycols, it is preferable to carry out the washing under pressure. At the time of washing, it is preferable to perform stirring with a stirrer or the like in order to enhance the washing effect. The washing time is preferably from 1 to 20 hours, more preferably from 3 to 15 hours. If the cleaning time is less than 1 hour, the cleaning effect is small.
Washing exceeding 0 hours is not preferable because the effect obtained is small compared to a long washing time and leads to a reduction in productivity.

Further, the cleaning method of the present invention is preferably performed in an atmosphere of an inert gas such as nitrogen, argon, helium, etc., and nitrogen is economically preferable. As for the number of times of washing, the larger the number, the better, but the effect obtained is reduced as compared with a long washing time. Therefore, it is preferable to perform the next step preferably once or twice, more preferably once. . Once cleaning with glycols is completed,
The glycols are discharged and then an alkali wash is performed.

In the alkali washing, an alkaline aqueous solution is generally charged into a reaction vessel in an amount of about 20 to 100% by volume of the reaction vessel. The alkali compound used in the alkaline aqueous solution is not particularly limited as long as it shows alkalinity in the aqueous solution, but an alkali metal compound and an alkaline earth metal compound showing alkalinity are preferably used, and particularly, alkali metal and alkaline earth metal water. Oxides, salts with weak acids such as acetic acid, phosphoric acid, boric acid, carbonic acid and the like are particularly preferably used. Among them, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, sodium acetate and the like are more preferably used, and sodium hydroxide is particularly preferably used from the viewpoint of economy and effects. Further, the amount of the alkali compound to be added is preferably 0.1% by weight or more and 10% by weight or less, more preferably 0.3% by weight or more and 7% by weight or less based on water. If the addition amount of the alkali compound is less than 0.1% by weight, the cleaning effect is small and long-time cleaning is required. Even if it exceeds 10 parts by weight, the cleaning effect is not remarkably improved. It is not preferable because the alkalinity increases and the amount of acid neutralized at the time of disposal increases. It is also possible to add a small amount of an organic solvent such as alcohols or glycols to an aqueous alkaline solution for washing. At the time of washing, it is preferable to perform stirring with a stirrer or the like in order to enhance the washing effect. 50-150 ° C for washing liquid temperature
It is preferably performed at 70 to 130 ° C. If necessary, it is also possible to carry out under pressure. If the temperature of the cleaning liquid is lower than 50 ° C., the cleaning effect is small, and long-time cleaning is required. If the temperature exceeds 150 ° C., a large pressure is required, which is not preferable from the viewpoint of the apparatus and safety measures. The washing time is preferably from 1 to 20 hours, more preferably from 3 to 15 hours. If the cleaning time is less than 1 hour, the cleaning effect is small, and cleaning exceeding 20 hours is not preferable because the effect obtained is small compared to a large cleaning time and leads to a decrease in productivity.

It is preferable that the alkaline cleaning be performed in an inert gas atmosphere, as in the case of cleaning with glycols. After the alkali washing, it is preferable that the washing solution is discharged, the inside of the reaction vessel is washed with water, and the remaining alkali and the like are washed.

The reason why a sufficient cleaning effect can be obtained by the cleaning method of the present invention is that a liquid crystalline resin generally contains an aromatic ester bond and is slowly decomposed by glycol.
It is thought that sufficient washing can be achieved because the liquid crystalline resin is reduced in molecular weight by glycol and washing with alkaline water in the reduced molecular weight state increases the permeability of the alkaline aqueous solution and promotes decomposition by alkali. Can be

When two or more reaction vessels are present in the liquid crystal resin melt polymerization apparatus, and they are used separately according to the reaction conditions such as the initial reaction and the polycondensation reaction, the polymerization is substantially carried out. The effect of the present invention can be sufficiently obtained by performing the cleaning method of the present invention only on the reaction vessel in which the condensation reaction is being performed.

In the method for cleaning a liquid crystalline resin melt polymerization apparatus of the present invention, when a liquid crystalline resin is produced by a continuous batch method, after repeating batch polymerization, preferably at least 20 batches, more preferably at least 30 batches, When the cleaning method of the present invention is performed, a remarkable cleaning effect is exhibited.

[0032]

The present invention will be described in more detail with reference to the following examples.

<Polymerization 1> A raw material input port, a transfer port, a condenser for condensing vapor distilled from the reaction vessel, a condensate receiving tank, an inner volume of 1.0 m ³ , an inner diameter of the can of 1.2 m,
Using a polymerization vessel of a double helical blade stirrer without a central axis having a bottom blade, polymerization was performed as follows.

221.0 kg of p-hydroxybenzoic acid,
4,4'-dihydroxybiphenyl 27.8 kg, polyethylene terephthalate 47.8 kg, terephthalic acid 2
After 4.8 kg and 211.8 kg of acetic anhydride were charged and stirred, the temperature was raised, and after reaching 130 ° C. in 0.75 hours,
The reaction was carried out at 130 ° C. for 1 hour, and the temperature was raised to 250 ° C. over 4 hours to carry out the reaction. Thereafter, the temperature was raised to 320 ° C. over 2 hours, the pressure in the polymerization vessel was reduced to 133 Pa, and stirring was continued at 320 ° C. for 2 hours to complete the polycondensation reaction. Thereafter, the inside of the polymerization can was pressurized to 0.2 MPa, and the polymer was discharged into a strand shape via a die to form a pellet.

Example 1 After 35 batches of the polymer having the above composition were repeatedly polymerized by the method of Polymerization Example 1, ethylene glycol 6 was added to the reactor.
001 (60% by volume of the polymerization vessel) was charged, the inside of the reaction vessel was replaced with nitrogen, and the pressure was increased to 0.35 MPa. Thereafter, the temperature was raised under stirring, and washing was performed at 250 ° C. for 5 hours. Thereafter, the temperature in the can was cooled to room temperature, ethylene glycol was discharged from the bottom of the polymerization can, and the glycol washing was completed. Subsequently, 800 l of a 4% aqueous sodium hydroxide solution was added to the reactor.
It was added (80% by volume of the polymerization vessel), replaced with nitrogen, and the temperature was increased while stirring at normal pressure, followed by washing at 90 ° C. for 5 hours. Thereafter, the mixture was cooled to room temperature, the alkaline aqueous solution was discharged from the bottom of the polymerization vessel, and the alkaline washing was completed. Thereafter, the polymerization can was washed with water and dried. The entire inside of the polymerization can had a metallic luster, and attached matters such as polyester and residues from washing were also removed.

After washing, the polymer having the above composition was polymerized by the method of Reference Example 1. As a result, there was no miscut due to clogging of the die, and the pelletization yield was as good as 98%. Examples 2 to 4 and Comparative Examples 1 to 5 Polymers having the above composition were produced in the number of batches shown in Table 1 by the method of Polymerization Example 1, and then washed in the same manner as in Example 1 except that the washing conditions shown in Table 1 were used. After washing, the inside of the polymerization can was observed.
Thereafter, the polymer was polymerized by the method of Polymerization Example 1, clogged with a die, and the pelletization yield was measured. Table 1 shows the results.

[0037]

[Table 1]

<Polymerization 2> The size of the baffle in the inner diameter direction of the baffle is 0 symmetrically with respect to the raw material input port, the transfer port, the condenser for condensing the vapor distilled from the reactor, the condensate receiving tank, and the inner wall of the can. With two baffles of 0.3 m
Double helical with 6 m ³ , 1.2 m inside diameter of the reaction vessel having a Faudler stirring impeller with a stirring blade diameter of 0.8 m and an inner volume of 0.8 m ³ , 1.1 m inside diameter of the can and without a central axis having a bottom impeller Polymerization was performed as follows using two polymerization cans of a blade stirrer.

In a reaction vessel, p-hydroxybenzoic acid 221.
0 kg, 4,4'-dihydroxybiphenyl 27.8 k
g, 47.8 kg of polyethylene terephthalate, 24.8 kg of terephthalic acid and 211.8 kg of acetic anhydride, and after stirring, the temperature was raised and reached 130 ° C. in 0.75 hour, then at 130 ° C. for 1 hour. The reaction was carried out, and the temperature was raised to 250 ° C. over 4 hours to carry out the reaction. Distillation rate in reactor is 85
%Met. After that, transfer to the polymerization vessel and stir 2
The temperature was raised to 320 ° C. over time, the pressure in the polymerization vessel was reduced to 133 Pa, and stirring was continued at 320 ° C. for 2 hours to complete the polycondensation reaction. Thereafter, the inside of the polymerization can was pressurized to 0.2 MPa, and the polymer was discharged into a strand shape via a die to form a pellet.

Example 5 According to the method of Polymerization Example 2, 35 batches of the polymer having the above composition were repeatedly batch-polymerized, and then ethylene glycol 5 was added to the reactor.
001 (31% by volume of the reactor) was charged, the inside of the reactor was replaced with nitrogen, and the pressure was increased to 0.35 MPa. Thereafter, the temperature was raised under stirring, and washing was performed at 250 ° C. for 5 hours. After that, the temperature in the can was cooled down to 150 ° C and returned to normal pressure.
Ethylene glycol was transferred to the polymerization vessel (63 of the polymerization vessel).
volume%). Thereafter, the polymerization vessel was replaced with nitrogen, and 0.35 MPa
Then, the temperature was raised under pressure and stirring, and washing was performed at 250 ° C. for 5 hours. After cooling to room temperature, ethylene glycol was discharged from the bottom of the polymerization vessel, and the glycol washing was completed. Subsequently, 640 l of a 4% aqueous sodium hydroxide solution was added to the reaction vessel (40% by volume of the reaction vessel), the atmosphere was replaced with nitrogen, the temperature was raised under stirring at normal pressure, and washing was performed at 90 ° C. for 5 hours. Was.
After cooling, the alkaline aqueous solution was transferred to the polymerization vessel (80% by volume of the polymerization vessel), the polymerization vessel was replaced with nitrogen, and washed at 90 ° C. for 5 hours with stirring. After cooling to room temperature, the alkaline aqueous solution was discharged from the bottom of the polymerization vessel, and the alkaline washing was completed. Thereafter, both the reaction can and the polymerization can were washed with water and dried.

The entire inside of the reaction vessel and the polymerization vessel had a metallic luster, and adhered substances such as polyester and residues from washing were removed.

After washing, the polymer having the above composition was polymerized by the method of Polymerization Example 2. As a result, there was no miscut due to clogging of the die, and a good pelletization yield of 98% was obtained.

Example 6 In Example 5, the glycol washing was carried out in the same manner, and the alkali washing was carried out under the same conditions only for the polymerization vessel. The entire inside of the reaction vessel and the polymerization vessel had a metallic luster, and adhered substances such as polyester and washing residues were also removed. After washing, the polymer having the above composition was polymerized by the method of Reference Example 2. As a result, there was no miscut due to clogging of the die, and the pelletization yield was as good as 98%.

Comparative Example 6 Washing was carried out in the same manner as in Example 5, except that alkali washing was not performed. When the inside of the polymerization can was observed, there was a deposit such as a cleaning residue on a part of the can wall. Thereafter, the polymer having the above composition was polymerized by the method of Reference Example 2. However, miscut due to clogging of the base occurred, and the pelletization yield was as low as 78%.

[0045]

According to the present invention, by performing a specific cleaning method, a cleaning residue or the like adhering to the inside of the melt polymerization apparatus can be easily removed, and the liquid crystal resin melt which has no adverse effect on the discharge of the liquid crystal resin after cleaning is obtained. The polymerization apparatus can be washed.

Claims (5)

[Claims] 1. A method for cleaning a liquid crystal resin melt polymerization apparatus, comprising washing the liquid crystal resin melt polymerization apparatus at least once with a glycol and then with an alkaline aqueous solution. (2) The glycols are ethylene glycol,
The cleaning method according to claim 1, wherein the cleaning method is at least one selected from diethylene glycol and triethylene glycol. 3. The cleaning method according to claim 1, wherein the alkaline aqueous solution is an aqueous solution obtained by adding at least one compound selected from an alkali metal compound and an alkaline earth metal compound exhibiting alkalinity. 4. The method for cleaning a liquid-crystalline resin melt polymerization apparatus according to claim 1, wherein said melt-polymerization apparatus is a liquid-crystalline resin produced after a batch-type continuous polymerization method. 5. The method for cleaning a liquid crystal resin melt polymerization apparatus according to claim 4, wherein the melt polymerization apparatus is one after manufacturing liquid crystal resin continuously for 20 batches or more.