JP2003327691A - Manufacturing method for polyamide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rational manufacturing method for synthesizing a polyamide the melting point of which is higher than the boiling point under atmospheric pressure of a diamine component being a raw material. <P>SOLUTION: When the polyamide is synthesized by directly subjecting the raw material diamine component and a dicarboxylic acid component to polycondensation reaction under pressure, a rise in the viscosity of a reaction product at the time of temperature rise in a polycondensation reaction process is suppressed to achieve the efficiency of the temperature rise and, after the temperature in the polycondensation reaction reaches a desired temperature, the polycondensation reaction is completed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel method for producing a polyamide in which a diamine component and a dicarboxylic acid component are directly subjected to a polycondensation reaction. More specifically, the present invention relates to a method for producing a polyamide by directly reacting a diamine having a boiling point lower than the melting point of the produced polyamide with a dicarboxylic acid.

[0002]

2. Description of the Related Art Generally, a polyamide synthesized from a dicarboxylic acid and a diamine uses an aqueous solution of a salt of a dicarboxylic acid and a diamine (so-called nylon salt) as a starting material. It is produced by polycondensing while distilling off. In this case, in order to remove water used as a solvent from the reaction system, not only a large amount of heat and an extremely long reaction time are required, but also the yield of polyamide obtained in one reaction is small, which is not economical. Further, since the fluctuation of the liquid level during the reaction is large, the polymer adheres to the wall surface of the reaction vessel, and the polymer is locally overheated and easily deteriorates.
There are many disadvantages to obtaining a homogeneous and good product by the conventional method.

As a method for solving these drawbacks, a method of directly polymerizing a nylon salt of dicarboxylic acid and diamine (Japanese Patent Publication No. 33-15700, Japanese Patent Publication No. 43-228).
No. 74, etc.) has been proposed. However, this method requires a step of isolating and purifying a nylon salt, and is not an efficient method. Furthermore, a method (US Pat. No. 2,240,347) in which a diamine and a dicarboxylic acid are directly mixed and polycondensation is performed under pressure is also proposed.
However, this method requires the use of an expensive horizontal stirring reactor. Further, a method in which a molten diamine containing a small amount of water is mixed with a molten dicarboxylic acid at a temperature of 220 ° C. or lower under normal pressure, and then polycondensation is carried out (JP-A-48-12).
No. 390) is also proposed. However, this method requires more time and more heat to distill off water than a method of directly polymerizing a diamine and a dicarboxylic acid, and thus cannot be said to be an efficient method.

A method for economically obtaining a polyamide by directly polycondensing only a diamine and a dicarboxylic acid under atmospheric pressure (Japanese Patent Laid-Open No. 58-1111829 and Japanese Patent Publication No. 14925).
Is proposed. In this method, a diamine is added to molten dicarboxylic acid, the polymerization temperature is raised, and finally, the addition is carried out at a temperature equal to or higher than the melting point of the polymer to carry out melt polymerization to obtain a polyamide. However, when the boiling point of the diamine component as a raw material is lower than the melting point of the obtained polyamide, the added diamine component is volatilized and a large amount is distilled out of the system by using this method. As a result, the molar ratio of the produced polyamide (diamine / dicarboxylic acid) deviates greatly from 1, and it is difficult to obtain a polyamide having a target molecular weight. Further, when the boiling point of the raw material diamine component is low with respect to the melting point of the obtained polyamide, by using a dephlegmator, although the amount of diamine distilled out of the system is reduced,
Since a large amount of diamine returned from the dephlegmator into the system lowers the temperature in the system, an extra amount of heat is required, and it is hard to say that this is an efficient method.

From the above, synthesis of polyamide having a high melting point of the obtained polyamide with respect to the boiling point of the diamine component as a raw material under normal pressure practically uses a method of using an aqueous solution of a nylon salt as a starting raw material. .

[0006]

An object of the present invention is to provide a rational production method for synthesizing a polyamide having a high melting point of the obtained polyamide with respect to the boiling point of the diamine component as a raw material under normal pressure. is there.

[0007]

Means for Solving the Problems In the polyamide having a high melting point of the obtained polyamide with respect to the boiling point of the diamine component as a raw material under normal pressure, the present inventors
In order to find a method for economically producing a polyamide in a short time by direct polycondensation reaction, we have conducted intensive studies to suppress the increase in the viscosity of the reaction product at the time of temperature increase in the polycondensation reaction process and improve the efficiency of temperature increase. The present inventors have found that the polyamide can be rationally produced by completing the polycondensation reaction after the temperature is raised to a desired temperature, and the present invention has been completed.

That is, the present invention comprises a diamine component having a lower boiling point under atmospheric pressure than the melting point of the produced polyamide,
In the method for producing a polyamide by directly polycondensing a dicarboxylic acid component, pressure in the reaction vessel is applied so that the boiling point of the diamine component is 20 ° C. or higher than the melting point of the polyamide to be produced, and the dicarboxylic acid component is melted. A method for producing a polyamide by heating to the above temperature to melt, and adding a diamine component in two stages thereto to carry out polycondensation while maintaining the molten state of the reaction mixture. In a molar ratio of diamine component / dicarboxylic acid component of 0.
The amount of total diamine components is in the range of 0.990 to 1.010 in the molar ratio, and the temperature of the reaction mixture is finally set to that of the target polyamide. The present invention relates to a method for producing a polyamide, which comprises heating to a temperature equal to or higher than the melting point and then reducing the pressure to atmospheric pressure to complete polycondensation.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In order to produce a homogeneous polyamide having a small color by the method of the present invention, the inside of the reaction vessel is sufficiently replaced with an inert gas prior to charging the dicarboxylic acid component into the reaction vessel. It is preferable. The dicarboxylic acid component may be heated to a temperature higher than its melting point in the reaction vessel to be in a molten state, charged in the reaction vessel in a molten state, or may be present in the reaction vessel in any manner.

The dicarboxylic acid component used in the present invention is
Succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid,
Α, ω-linear aliphatic dicarboxylic acids such as dodecanedioic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, aromatic dicarboxylic acids such as 4,4′-biphenyldicarboxylic acid, 1,4-cyclohexane One or more can be appropriately selected as desired from alicyclic dicarboxylic acids such as dicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decalindicarboxylic acid, tetralindicarboxylic acid, etc., and preferably contains 70 mol% or more of adipic acid. To do.

The diamine component used in the method of the present invention may be any one having a boiling point of diamine lower than the melting point of the obtained polyamide, such as tetramethylenediamine, pentamethylenediamine, hexamethylenediamine and octamethylenediamine, which are generally known. Aliphatic diamines such as methylenediamine and nonamethylenediamine, diamines having an aromatic ring such as paraxylylenediamine, paraphenylenediamine and metaxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis One or more can be appropriately selected as desired from alicyclic diamines such as (aminomethyl) cyclohexane, and preferably trans-1,4-
Bis (aminomethyl) cyclohexane 30-70 mol%
And cis-1,4-bis (aminomethyl) cyclohexane in an amount of 70 mol% or more containing a diamine mixture consisting of 70 to 30 mol% (the total of mol% is 100 mol%).

The mixture of the dicarboxylic acid component and the diamine component is kept at a temperature equal to or higher than the melting point of the dicarboxylic acid component to start the polycondensation reaction. However, in order to substantially cause the amidation reaction, it is 160 ° C. or higher. It is preferable to raise the temperature to. Furthermore, it is preferable that the oligoamide and / or polyamide produced as an intermediate is in a molten state and is set to a temperature at which the entire reaction system can maintain a uniform fluidized state.

A specific polycondensation operation is carried out by stirring a dicarboxylic acid component in a molten state in a reaction vessel, adding a diamine component thereto under pressure, and maintaining the reaction mixture at a predetermined temperature. Be seen.

In the present invention, since the diamine component having a lower boiling point under normal pressure than the melting point of the produced polyamide is used, the reaction is carried out under pressure. The pressure in the reaction vessel during the reaction is set so that the boiling point of the added diamine is higher than the melting point of the obtained polyamide by 20 ° C. or more. Preferably, the pressurization is performed so that the boiling point of the diamine to be added is 20 ° C. or more higher than the melting point of the obtained polyamide and 350 ° C. or less. The required pressure varies depending on the dicarboxylic acid component and diamine component used, but it is generally in the range of 0.1 to 0.6 MPa. Pressurization is
Nitrogen may be used, or reaction condensation water may be used.

The timing of the step of applying pressure to the reaction vessel may be from after the dicarboxylic acid component is added to the reaction vessel to a temperature 10 ° C. lower than the boiling point of the diamine component at normal pressure. Preferably, it is between the temperature after the addition of the dicarboxylic acid component to the reaction vessel and the temperature 20 ° C. lower than the boiling point of the diamine component at normal pressure. When the diamine component is added dropwise at a temperature 10 ° C. lower than the boiling point of the diamine component, the diamine component volatilizes violently, and the amount of distilling out of the system increases. As a result, the amount of diamine component in the system decreases, and it becomes difficult to obtain a polyamide having a desired molar ratio. Also, by using a decompressor,
The amount of diamine distilled out of the system can be reduced, but due to the large amount of diamine returned to the system from the dephlegmator, the temperature in the system will decrease, so an additional amount of heat will be required. Moreover, unmelted matter is generated in the obtained polyamide due to a partial temperature decrease, and it may be difficult to take it out from the reaction kettle, so it cannot be said to be an efficient method.

In the present invention, the diamine component is added in two stages. The amount of diamine component added in the first step is diamine component /
The amount of the dicarboxylic acid component is in the range of 0.700 to 0.750, and the total amount of the diamine components is 0.9.
The amount is in the range of 90 to 1.010. In the first step, the diamine component is added continuously or intermittently to the molten dicarboxylic acid component kept at the melting point of the dicarboxylic acid component or higher. The molten state of the reaction mixture is maintained by successively raising the temperature of the reaction mixture during this addition. Here, it is preferable to control the temperature within a range from the melting point of the reaction mixture to the melting point + 20 ° C. In addition, it is preferable that the first stage is terminated at a temperature 20 ° C. or lower lower than the melting point of the polyamide produced by the reaction mixture. Then, as a second step, the residual diamine component is added to the reaction mixture whose temperature has been raised, and while the molten state of the reaction mixture is maintained, the temperature of the reaction mixture is finally raised to the melting point of the intended polyamide or higher. After warming, the pressure is reduced to normal pressure to complete the polycondensation reaction,
The desired polyamide is obtained.

The addition rate of the first-stage diamine component is determined by the heat of formation of the amidation reaction, the amount of heat consumed to distill off the condensation product water, the amount of heat supplied from the heating medium through the reactor wall, the condensation product water and the raw materials. In consideration of the structures of the dephlegmator and the cooler for separating the compound from each other, the reaction temperature is selected in consideration of a predetermined reaction temperature, that is, a temperature at which the reaction system can be kept in a uniform molten state.
Usually, the time required for adding the diamine component varies depending on the scale of the reaction can, but is within the range of 0.5 hours to 5 hours. During this time, the condensed water produced as the reaction progresses,
It is distilled out of the reaction system through the partial condenser and the total condenser. Raw materials such as diamine and dicarboxylic acid that are scattered are separated by a partial condenser and returned to the reaction can again. In addition, the addition of the second-stage diamine component should be selected such that the rise in the liquid level due to foaming in the reaction can does not reach the upper part of the can and the temperature of the product is kept constant. Good. Generally, the addition of the diamine component in the second stage is performed within the range of 10 to 120 minutes.

When the method of the present invention is carried out, it is unavoidable to distill the diamine component out of the reaction system as in the case of the conventionally known aqueous solution pressure method. Therefore, a polycondensation reactor is equipped with a dephlegmator. It is necessary to prepare. The temperature of the partial condenser is controlled within the range of the boiling point of water at the pressure of the reaction vessel which is controlled to be constant and the temperature 20 ° C. higher than that temperature. By providing a partial condenser, it is possible to effectively prevent the diamine component from distilling out during the reaction, and as a result, the charging molar ratio of the diamine component to the dicarboxylic acid component containing adipic acid is 0.9.
By setting the range of 90 to 1.010, a polyamide having a constant molecular weight can be produced with good reproducibility.

The polycondensation reaction apparatus used in the method of the present invention has a pressure resistance of 0.3 MPa as compared with the apparatus used in the conventionally known aqueous solution pressurization method which requires a pressure resistance of 1.8 MPa or more.
Since ~ 1 MPa is sufficient, it can be manufactured relatively inexpensively.
In addition, in the method of the present invention, the time required for distilling off water which is the solvent required in the case of the conventionally known aqueous solution pressure method is not required at all, and therefore the time required for polycondensation can be significantly shortened. Furthermore, the conventional method does not require the amount of heat required for concentrating an aqueous solution at all, and a large amount can be charged in one reaction to improve productivity, which is extremely economical as a method for producing polyamide. Methods are provided.

[0020]

EXAMPLES Hereinafter, the method of the present invention will be specifically described by showing Examples and Comparative Examples. The measurement for evaluation in the present invention was carried out by the following method. (B) Terminal amino group concentration (μeq / g) Polyamide is precisely weighed and phenol / ethanol = 4/1
The solution was stirred and dissolved in the volumetric solution at 20 to 30 ° C. After completely dissolved, neutralization titration was performed with a 0.1 mol / liter (hereinafter, liter is referred to as "L") hydrochloric acid aqueous solution with stirring to obtain the value. (B) Terminal carboxyl group concentration (μeq / g) The polyamide was precisely weighed and melted in benzyl alcohol with stirring at 160 to 180 ° C under a nitrogen atmosphere. After completely dissolved, the mixture was cooled to 80 ° C. or lower under a nitrogen stream, 10 cc of methanol was added with stirring, and the titration was performed by neutralization titration with a 0.1 mol / L sodium hydroxide aqueous solution. (C) Number average molecular weight It was calculated from the terminal amino group concentration and terminal carboxyl group concentration by the following formula. Number average molecular weight = 2 × 106 / ({NH2} + {COO
H}) ({NH2} is the terminal amino group concentration (μeq / g), {C
OOH} represents the terminal carboxyl group concentration (μeq / g). (D) Melting point Using a DSC (manufactured by Shimadzu Corporation (DSC-50 type) DSC, the temperature was raised at a rate of 10 ° C./min under a nitrogen stream.

Example 1 A jacketed 50 L reactor equipped with a stirrer, a partial condenser, a cooler, a dropping tank, and a nitrogen gas introducing pipe (pressure resistance: 2.5).
10.00 kg (68.43 m) of adipic acid in MPa)
ol) Weighed and charged, sufficiently replaced with nitrogen, pressurized to 0.3 MPa with nitrogen, heated to 189 ° C., and adipic acid was melted uniformly. Then, while stirring the contents,
4-bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 55/45, boiling point = 241 ° C. (normal pressure), 30
3 ° C. (0.3 MPa) 6.97 kg (49.01 mo)
1) was added dropwise with stirring over 140 minutes. During this time, the internal temperature was continuously increased from 189 ° C to 279 ° C.
Subsequently, 2.71 kg of 1,4-bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 55/45)
(19.05 mol) was added dropwise with stirring over 83 minutes. During this time, the internal temperature was continuously increased from 279 ° C to 304 ° C. In the dropping step, the pressure was controlled to 0.3 MPa, and the distilled water was removed from the system through the partial condenser and the cooler. The temperature of the partial condenser was controlled in the range of 142 to 146 ° C. After the completion of dropwise addition of 1,4-bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 55/45), the mixture was stirred for 7 minutes, and the internal temperature was kept at 304 ° C during this. Then, the pressure was reduced to normal pressure in 14 minutes, and the reaction was continued for 21 minutes. The total reaction time required after the start of dropwise addition of 1,4-bis (aminomethyl) cyclohexane was 265 minutes. No solidification or precipitation of the oligomer or polyamide formed in the whole reaction process was observed, and a uniform molten state was maintained throughout. The obtained polymer has a terminal amino group concentration of 38 (μeq / g) and a terminal carboxyl group concentration of 8
0 (μeq / g), the number average molecular weight was 16900, and the melting point was 288 ° C.

Example 2 A jacketed 50 L reactor equipped with a stirrer, a partial condenser, a cooler, a dropping tank, and a nitrogen gas introducing pipe (pressure resistance: 2.5).
10.00 kg (68.43 m) of adipic acid in MPa)
ol) Weighed and charged, and after sufficiently replacing with nitrogen, the pressure was increased to 0.5 MPa with nitrogen and the temperature was raised to 189 ° C. to uniformly melt adipic acid. Then, while stirring the contents,
4-bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 65/35, boiling point = 241 ° C. (normal pressure), 33
6 ° C (0.5 MPa) 6.97 kg (49.01 mo)
1) was added dropwise with stirring over 160 minutes. During this time, the internal temperature was continuously increased from 189 ° C to 299 ° C.
Subsequently, 2.71 kg of 1,4-bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 65/35)
(19.05 mol) was added dropwise with stirring over 95 minutes. During this time, the internal temperature was continuously increased from 299 ° C to 316 ° C. In the dropping step, the pressure was controlled to 0.5 MPa, and the distilled water was removed from the system through the partial condenser and the cooler. The temperature of the partial condenser was controlled at 160 ± 2 ° C.
After the dropwise addition of 1,4-bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 65/35), the mixture was stirred for 10 minutes, and the internal temperature was kept at 316 ° C during this. afterwards,
The pressure was lowered to normal pressure in 15 minutes, and the reaction was continued for 15 minutes.
The total reaction time required after the start of dropwise addition of 1,4-bis (aminomethyl) cyclohexane was 295 minutes. No solidification or precipitation of the oligomer or polyamide formed in the whole reaction process was observed, and a uniform molten state was maintained throughout. The terminal amino group concentration of the obtained polymer is 3
3 (μeq / g), terminal carboxyl group concentration is 90 (μeq
eq / g), number average molecular weight 16300, melting point 303
It was ℃.

Comparative Example 1 Except that the temperature of the partial condenser was set to 103 to 107 ° C. under normal pressure,
When the reaction was carried out in the same manner as in Example 1, the internal temperature was 189 ° C.
It took 223 minutes to continuously elevate from 279 ° C to 279 ° C, and 158 minutes to continuously elevate from 279 ° C to 304 ° C. 1,4-
After the completion of dropwise addition of bis (aminomethyl) cyclohexane (trans isomer / cis isomer = 55/45), the mixture was stirred for 7 minutes, and the internal temperature was kept at 304 ° C during this. Then, the pressure was reduced to normal pressure in 14 minutes, and the reaction was continued for 21 minutes. The total reaction time required after the start of dropwise addition of 1,4-bis (aminomethyl) cyclohexane was 423 minutes. Further, many unmelted substances were confirmed in the polyamide at the time of taking out, and the strand die was blocked during the taking out.

[0024]

The following effects are obtained by the method for producing a polyamide of the present invention. (A) Since an aqueous solution of nylon salt is not used as a starting material, there is no step of removing water as a solvent, and the reaction time can be extremely shortened. (B) Since water is not required as a solvent, it is possible to increase the amount charged and the yield. (C) Since an aqueous solution of a nylon salt is not used as a starting material, it is possible to avoid foaming or solidification of polyamide when removing a large amount of water, and there is no energy loss for removing water as a solvent. (D) Since the molar balance of charging is accurately reproduced to the molar balance of polyamide, it becomes extremely easy to control the molar balance, that is, the degree of polymerization. (E) Since an aqueous solution of a nylon salt is not used as a starting material, it is possible to use a reaction vessel having a lower pressure resistance than a conventionally used pressure melting polymerization reaction vessel. That is, according to the method of the present invention, it is possible to directly produce a polyamide from a dicarboxylic acid and a diamine under pressure without using any solvent, which is a problem in the conventional method for producing a polyamide under pressure. As a result, the reaction time can be shortened, the energy required for distilling off water as a solvent can be saved, and the charging amount and the yield can be increased all at once.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahiro Takano             5-6 Higashi-Hachiman 5-2, Hiratsuka City, Kanagawa Prefecture             Ryogas Chemical Co., Ltd. Hiratsuka Research Center F-term (reference) 4J001 DA01 DB04 EB03 EB06 EB07                       EB08 EB14 EB36 EB37 EB46                       EC04 EC07 EC09 EC14 EC46                       EC47 EC48 FA01 FB03 FC06                       GA12 GB04 GB11

Claims (3)

[Claims] 1. A method for producing a polyamide by directly polycondensing a diamine component having a boiling point under atmospheric pressure lower than the melting point of the polyamide to be produced and a dicarboxylic acid component,
The boiling point of the diamine component is increased by 20 ° C. or more than the melting point of the polyamide to be produced, and the pressure in the reaction vessel is increased, and the dicarboxylic acid component is heated to a temperature of the melting point or higher to melt it.
This is a method for producing a polyamide in which a diamine component is added in two stages to carry out polycondensation while maintaining the molten state of the reaction mixture, and the addition amount of the diamine component in the first stage is a molar ratio of diamine component / dicarboxylic acid component. 0.700 to 0.750 by comparison
And the total amount of the diamine components is 0.
The amount is in the range of 990 to 1.010, and after the temperature of the reaction mixture is finally raised to the melting point of the target polyamide or higher, the pressure is reduced to atmospheric pressure to complete the polycondensation. Method for producing polyamide. 2. The addition of the first-stage diamine component is continuous or intermittent, and the temperature of the reaction mixture is
The method for producing a polyamide according to claim 1, wherein the molten state of the reaction mixture is maintained by controlling the temperature so as to fall within the range of the melting point of the reaction mixture to the melting point + 20 ° C. 3. The diamine component is trans-1,4-
Bis (aminomethyl) cyclohexane 30-70 mol%
And a diamine mixture consisting of 70 to 30 mol% of cis-1,4-bis (aminomethyl) cyclohexane (the total of mol% is 100 mol%) in an amount of 70 mol% or more, and the dicarboxylic acid component. Adipic acid 7
The method for producing a polyamide according to claim 1 or 2, wherein the content is 0 mol% or more.